Forecast Discussions mentioning any of
"HRRR" "RR" "RUC13" "RUC" received at GSD on 12/21/11
AREA FORECAST DISCUSSION
NWS NEW YORK NY
1256 PM EST MON DEC 19 2011
.SYNOPSIS...
A HIGH PRESSURE RIDGE SHIFTS OFFSHORE TODAY. A COLD FRONT WILL
MOVE THROUGH TONIGHT. HIGH PRESSURE BUILDS OVER THE AREA TUESDAY. A
WARM FRONT APPROACHES FROM THE SOUTH TUESDAY NIGHT...THEN LIFTS TO
THE NORTH WEDNESDAY...FOLLOWED BY A COLD FRONT WEDNESDAY
NIGHT...AS AN AREA OF LOW PRESSURE PASSES TO OUR NORTH. HIGH
PRESSURE THEN BUILDS IN TO OUR NORTH THURSDAY THROUGH SUNDAY...AS
A COUPLE OF LOW PRESSURE SYSTEMS PASS TO OUR SOUTH FRIDAY AND THEN
LATE NEXT WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A HIGH PRESSURE RIDGE CONTINUES TO SHIFT OFFSHORE TODAY...WITH A
RETURN FLOW OVER THE REGION. LOW PRESSURE EMBEDDED IN A STRONG
JETSTREAM ACROSS SOUTHERN CANADA IS MOVING QUICKLY TO THE EAST
ACROSS QUEBEC...DRAGGING A COLD FRONT ACROSS THE GREAT LAKES
REGION. THE PRESSURE GRADIENT WILL QUICKLY INCREASE THIS AFTERNOON
AS THE LOW PASSES TO OUR NORTH...WITH GUSTY WINDS EXPECTED.
THINKING THAT WE SHOULD JUST SEE SOME CLOUD COVER WITH THE FRONT.
WILL REMOVE ANY MENTION OF ANY PRECIPITATION WITH TOO MUCH DRY AIR
IN PLACE.
WARM AIR ADVECTION DEVELOPS WITH THE HIGH OFFSHORE...ENABLING
TEMPERATURES TO CLIMB INTO THE LOW TO MID 40S AREA WIDE. MAV/MET
GUIDANCE IN GOOD AGREEMENT...AND WERE BLENDED FOR TEMPS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/...
MODEL CONSENSUS INDICATES COLD FRONT WILL BE LOCATED OVER
WESTERN/NORTHERN NY STATE BY EARLY THIS EVENING...THEN QUICKLY SWEEP
TO THE SOUTHEAST AND MOVE THROUGH THE REGION OVERNIGHT. WITH ZONAL
FLOW ALOFT MOISTURE WILL BE LIMITED...BUT ENOUGH LAKE MOISTURE MAY
ALLOW FOR SOME SPRINKLES AND/OR FLURRIES...WITH POTENTIAL FOR LIGHT
SNOW OVER THE LOWER HUDSON VALLEY. BL TOO WARM FOR FLAKES NEAR THE
COASTS INITIALLY...BUT AS THE CWA GETS INTO THE RR QUAD OF THE H3
150 PLUS KT H3 JET AFT MIDNIGHT...A FEW FLURRIES MAY MIX IN WITH
ANY SPRINKLES HERE AS WELL.
GUSTY WINDS DIMINISH THIS EVENING AS LOW-LEVEL INVERSION
DEVELOPS...BUT GUSTS MAY REDEVELOP BY EARLY TUESDAY MORNING AS
COOLER AIR ALOFT MOVES IN BEHIND THE FRONT.
MAV/MET BLENDED AGAIN FOR LOWS TONIGHT...WHICH WILL RANGE FROM THE
UPPER 20S OVER NORTHERN SECTIONS TO THE MID 30S NEAR THE COASTS.
ON TUESDAY...HIGH PRESSURE RIDGE DROPS FROM THE GREAT LAKES INTO
THE TRI-STATE AREA. WINDS DIMINISH AS THE HIGH BUILDS IN. HIGHS
GENERALLY IN THE LOW TO MID 40S.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A PROGRESSIVE SPLIT FLOW ACROSS THE LOWER 48 GETS A BIT MORE
INTERESTING THIS WEEK AS SEVERAL SOUTHERN BRANCH LOWS INTERACT WITH
MARGINALLY COLD AIR ACROSS THE NE U.S. THE 00Z GFS AND ECMWF ARE IN
REMARKABLE AGREEMENT DURING THIS PERIOD...ALTHOUGH THERE ARE SOME
TIMING DIFFERENCES AS CAN BE EXPECTED. THE GFS IS THE MORE
PROGRESSIVE OF THE SOLUTIONS IN THE HANDLING OF EACH WAVE...WHICH
SEEMS TO MAKE SENSE BASED ON THE PROGRESSIVE NATURE OF THE UPPER
FLOW. AT THIS POINT IN TIME...IT IS TOO EARLY BE SPECIFIC WITH ANY
DETAILS...BUT THERE IS THE POTENTIAL FOR WINTRY WEATHER...
ESPECIALLY ACROSS THE INTERIOR.
THE FIRST STORM SYSTEM WILL EMERGE FROM THE MID MS VALLEY TUE NIGHT
AND TAKE A TRACK TO THE NORTH AND WEST OF THE FORECAST AREA WED.
PCPN AHEAD OF ITS WARM FRONT MAY DEVELOP IN THE OVERNIGHT HOUR TUE.
THE TIMING HERE IS CRITICAL AS THE COLD AIR WILL BE ERODING IN A
STRENGTHENING SOUTHERLY FLOW. COASTAL AREAS WILL BE ALL RAIN...BUT
THERE IS A POSSIBILITY OF A BRIEF WINTRY MIX ACROSS INLAND AREAS
PRIOR TO DAYBREAK. THE STEADIEST PCPN WILL FALL AS RAIN ON WED. THE
TRAILING COLD FRONT WILL THEN BRIEFLY DRY CONDITIONS OUT WED NIGHT
INTO THU. THE NEXT SYSTEM TAKES A TRACK FROM THE LOWER MS VALLEY
THU...NE TO OFF THE MID ATLANTIC COAST ON FRI. THIS SYSTEM TOO MAY
FEATURE A WINTRY MIX INLAND. VERTICAL TEMPERATURE PROFILES ARE
MARGINAL IN BOTH CASES WITH NO REAL GOOD SOURCE OF POLAR AIR. THE
FAST FLOW ACROSS THE NORTHERN TIER OF THE COUNTRY IS PREVENTING A
STRONG SOUTHWARD PUSH.
FINALLY...THE LAST STORM HAS THE POTENTIAL TO IMPACT THE AREA
CHRISTMAS EVE AND DAY. THE ECMWF HAS TRENDED TO A STRONGER LOW IN
COMPARISON TO THE GFS WITH A 989 MB LOW PASSING NEAR CAPE COD NEXT
SUNDAY. THE GFS IS ABOUT 20 MB WEAKER. A DECENT HIGH TO THE NORTH
FOR THIS GO AROUND MAY POSE A MORE SIGNIFICANT WINTER WEATHER
THREAT. ONCE AGAIN THOUGH...THERE WILL LIKELY BE SEVERAL CHANGES IN
THE FORECAST OUT THIS FAR. IT IS DEFINITELY WORTH KEEPING AN EYE ON.
TEMPERATURES WILL START OFF ABOVE NORMAL FOR THE MID WEEK
PERIOD...BUT THEN TRANSITION TO MORE SEASONABLE READINGS FOR THE END
OF THE WEEK INTO NEXT WEEKEND. HIGHS WILL TOP OUT IN THE LOWER 50S
WED AND THU...BUT THEN FALL TO AROUND 40 BY THE WEEKEND.
&&
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
HIGH PRESSURE MOVES EAST WITH INCREASING SW FLOW. A COLD FRONT MOVES
THROUGH THE TERMINALS LATE TONIGHT. COULD BE A FEW
FLURRIES/SPRINKLES ACCOMPANYING THE FROPA...BUT NOT EXPECTED TO
MAKE RUNWAYS WET.
VFR TODAY. INCREASING SW GUSTS TODAY...SPORADIC THROUGH 17Z. LOW
CONFIDENCE AT THIS TIME ON WHEN GUSTS WILL SUBSIDE. COLD FROPA
BETWEEN 05Z AND 09Z TONIGHT WITH WINDS BECOMING NW.
NY METRO ENHANCED AVIATION WEATHER SUPPORT...
DETAILED INFORMATION...INCLUDING HOURLY TAF WIND COMPONENT FCSTS
CAN BE FOUND AT: HTTP:/WWW.ERH.NOAA.GOV/ZNY/N90 (LOWER CASE)
KJFK FCSTER COMMENTS: AMENDMENTS POSSIBLE TO INCREASE GUST
SPEEDS. LOW CONFIDENCE ON TIMING OF GUSTS DIMINISHING...OCNL
GUSTS MAY LINGER THROUGH 03Z WHILE DIMINISHING.
KLGA FCSTER COMMENTS: AMENDMENTS POSSIBLE TO INCREASE GUST
SPEEDS. LOW CONFIDENCE ON TIMING OF GUSTS DIMINISHING...OCNL
GUSTS MAY LINGER THROUGH 03Z WHILE DIMINISHING.
KEWR FCSTER COMMENTS: AMENDMENTS POSSIBLE TO INCREASE GUST
SPEEDS. LOW CONFIDENCE ON TIMING OF GUSTS DIMINISHING...OCNL GUSTS
MAY LINGER THROUGH 03Z WHILE DIMINISHING.
KTEB FCSTER COMMENTS: AMENDMENTS POSSIBLE TO INCREASE GUST
SPEEDS. LOW CONFIDENCE ON TIMING OF GUSTS DIMINISHING...OCNL GUSTS
MAY LINGER THROUGH 03Z WHILE DIMINISHING.
KHPN FCSTER COMMENTS: AMENDMENTS POSSIBLE TO INCREASE GUST
SPEEDS. LOW CONFIDENCE ON TIMING OF GUSTS DIMINISHING...OCNL GUSTS
MAY LINGER THROUGH 03Z WHILE DIMINISHING.
KISP FCSTER COMMENTS: AMENDMENTS POSSIBLE TO INCREASE GUST
SPEEDS. LOW CONFIDENCE ON TIMING OF GUSTS DIMINISHING...OCNL GUSTS
MAY LINGER THROUGH 02Z WHILE DIMINISHING.
OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY...
TUE...VFR.
TUE NIGHT AND WED...SUB VFR IN RAIN...A WINTRY MIX POSSIBLE
INLAND TUE NIGHT. BECOMING VFR WED NIGHT.
THU...VFR.
FRI...SUB-VFR POSSIBLE.
&&
.MARINE...
GALE WARNING REMAINS UP FOR THE EASTERN TWO OCEAN ZONES. WINDS
EXPECTED TO INCREASE THIS AFTERNOON...AS THE PRESSURE GRADIENT
TIGHTENS THIS AFTERNOON AS HIGH PRESSURE MOVES EAST OF THE WATERS
AND A COLD FRONT APPROACHES FROM THE NORTHWEST. SCA CONTINUES FOR
ALL OTHER ZONES. ALSO CAN`T RULE OUT POTENTIAL FOR A FEW GALE-
FORCE GUSTS IN EASTERN LONG ISLAND SOUND AND THE WESTERN OCEAN
WATERS TODAY...AND THESE AREAS WILL NEED TO BE MONITORED.
OTHERWISE SCA CONTINUES OVER ALL WATERS NOT COVERED BY THE GALE
WARNING.
WINDS DIMINISH LATE TONIGHT BEHIND THE COLD FRONT AS HIGH PRESSURE
APPROACHES THE WATERS. SCA-LEVEL SEAS COULD LINGER INTO TUESDAY
ON THE FAR EASTERN COASTAL WATERS...OTHERWISE SUB-SCA CONDITIONS
ARE EXPECTED TUESDAY AND TUESDAY NIGHT.
THERE WILL BE POTENTIAL EPISODES OF SCA CONDITIONS THROUGHOUT THE
WEEK AS A SERIES OF LOWS IMPACT THE WATERS. THE FIRST OF WHICH WILL
SEND A COLD FRONT ACROSS THE AREA WED NIGHT WITH A STRONG WLY FLOW
ON THE BACKSIDE INTO THU MORNING. HIGH PRESSURE THEN BRIEFLY RETURNS
TO THE WATERS ON THU BEFORE LOW PRESSURE PASSES TO THE SOUTH ON FRI.
FOR NOW GOING WITH SUB-SCA CONDITIONS ON FRIDAY WITH THE COASTAL LOW
PASSING TO THE SOUTH...BUT THERE IS MUCH UNCERTAINTY IN THIS
&&
.HYDROLOGY...
DRY WEATHER EXPECTED THROUGH TUESDAY.
THERE IS THE POTENTIAL FOR AROUND A 1/4 TO 1/2 AN INCH OF LIQUID
EQUIVALENT TO FALL OVER THE REGION FROM TUESDAY NIGHT INTO WEDNESDAY
NIGHT. SOME OF THIS COULD FALL AS FROZEN PRECIPITATION ACROSS
MAINLY NORTHERN INTERIOR ZONES INTO WEDNESDAY MORNING. NO
SIGNIFICANT HYDROLOGIC IMPACT IS CURRENTLY EXPECTED.
ADDITIONAL PRECIPITATION IS EXPECTED FROM A SERIES OF LOW
PRESSURE SYSTEMS THAT WILL IMPACT THE AREA LATE IN THE WEEK AND
THE WEEKEND. NO SIGNIFICANT HYDROLOGICAL IMPACTS ARE ANTICIPATED
AT THIS TIME.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM EST TUESDAY FOR ANZ330-335-338-
340-345-355.
GALE WARNING UNTIL 1 AM EST TUESDAY FOR ANZ350-353.
&&
$$
SYNOPSIS...KCS/DW
NEAR TERM...BC/KCS
SHORT TERM...KCS
LONG TERM...DW
AVIATION...BS
MARINE...KCS/DW
HYDROLOGY...KCS/DW
AREA FORECAST DISCUSSION
NWS NEW YORK NY
1004 AM EST MON DEC 19 2011
.SYNOPSIS...
A HIGH PRESSURE RIDGE SHIFTS OFFSHORE TODAY. A COLD FRONT WILL
MOVE THROUGH TONIGHT. HIGH PRESSURE BUILDS OVER THE AREA TUESDAY. A
WARM FRONT APPROACHES FROM THE SOUTH TUESDAY NIGHT...THEN LIFTS TO
THE NORTH WEDNESDAY...FOLLOWED BY A COLD FRONT WEDNESDAY
NIGHT...AS AN AREA OF LOW PRESSURE PASSES TO OUR NORTH. HIGH
PRESSURE THEN BUILDS IN TO OUR NORTH THURSDAY THROUGH SUNDAY...AS
A COUPLE OF LOW PRESSURE SYSTEMS PASS TO OUR SOUTH FRIDAY AND THEN
LATE NEXT WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
15Z UPDATE TO MAKE JUST MINOR ADJUSTMENTS TO TEMPS AND DEW POINTS
BASED ON CURRENT OBS THIS MORNING. SOUTHWEST FLOW WILL HELP TEMPS
MODERATE ACROSS THE REGION THIS MORNING. OTHERWISE...FORECAST
GENERALLY ON TRACK.
A HIGH PRESSURE RIDGE LOCATED RIGHT ALONG THE EAST COAST EARLY
THIS MORNING WILL SHIFT OFFSHORE TODAY...ALLOWING RETURN FLOW TO
DEVELOP OVER THE REGION. LOW PRESSURE EMBEDDED IN A STRONG
JETSTREAM ACROSS SOUTHERN CANADA WILL QUICKLY SHIFT EASTWARD
ACROSS QUEBEC...DRAGGING A COLD FRONT ACROSS THE GREAT LAKES
REGION. THE PRESSURE GRADIENT WILL INCREASE QUICKLY TODAY AS THE
LOW PASSES TO OUR NORTH...WITH GUSTY WINDS DEVELOPING BY LATE
MORNING AND CONTINUING THROUGH THE AFTERNOON. 00Z NAM SUGGESTS
LIGHT PRECIP DEVELOPING OVER THE REGION BY LATE AFTERNOON WITH A
WEAK VORT MAX MOVING THROUGH...BUT SIDED WITH 00Z GFS/ECMWF WHICH
KEEP ANY PRECIP NORTH AND WEST OF THE REGION.
WARM AIR ADVECTION DEVELOPS WITH THE HIGH OFFSHORE...ENABLING
TEMPERATURES TO CLIMB INTO THE LOW TO MID 40S AREA WIDE. MAV/MET
GUIDANCE IN GOOD AGREEMENT...AND WERE BLENDED FOR TEMPS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/...
MODEL CONSENSUS INDICATES COLD FRONT WILL BE LOCATED OVER
WESTERN/NORTHERN NY STATE BY EARLY THIS EVENING...THEN QUICKLY SWEEP
TO THE SOUTHEAST AND MOVE THROUGH THE REGION OVERNIGHT. WITH ZONAL
FLOW ALOFT MOISTURE WILL BE LIMITED...BUT ENOUGH LAKE MOISTURE MAY
ALLOW FOR SOME SPRINKLES AND/OR FLURRIES...WITH POTENTIAL FOR LIGHT
SNOW OVER THE LOWER HUDSON VALLEY. BL TOO WARM FOR FLAKES NEAR THE
COASTS INITIALLY...BUT AS THE CWA GETS INTO THE RR QUAD OF THE H3
150 PLUS KT H3 JET AFT MIDNIGHT...A FEW FLURRIES MAY MIX IN WITH
ANY SPRINKLES HERE AS WELL.
GUSTY WINDS DIMINISH THIS EVENING AS LOW-LEVEL INVERSION
DEVELOPS...BUT GUSTS MAY REDEVELOP BY EARLY TUESDAY MORNING AS
COOLER AIR ALOFT MOVES IN BEHIND THE FRONT.
MAV/MET BLENDED AGAIN FOR LOWS TONIGHT...WHICH WILL RANGE FROM THE
UPPER 20S OVER NORTHERN SECTIONS TO THE MID 30S NEAR THE COASTS.
ON TUESDAY...HIGH PRESSURE RIDGE DROPS FROM THE GREAT LAKES INTO
THE TRI-STATE AREA. WINDS DIMINISH AS THE HIGH BUILDS IN. HIGHS
GENERALLY IN THE LOW TO MID 40S.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A PROGRESSIVE SPLIT FLOW ACROSS THE LOWER 48 GETS A BIT MORE
INTERESTING THIS WEEK AS SEVERAL SOUTHERN BRANCH LOWS INTERACT WITH
MARGINALLY COLD AIR ACROSS THE NE U.S. THE 00Z GFS AND ECMWF ARE IN
REMARKABLE AGREEMENT DURING THIS PERIOD...ALTHOUGH THERE ARE SOME
TIMING DIFFERENCES AS CAN BE EXPECTED. THE GFS IS THE MORE
PROGRESSIVE OF THE SOLUTIONS IN THE HANDLING OF EACH WAVE...WHICH
SEEMS TO MAKE SENSE BASED ON THE PROGRESSIVE NATURE OF THE UPPER
FLOW. AT THIS POINT IN TIME...IT IS TOO EARLY BE SPECIFIC WITH ANY
DETAILS...BUT THERE IS THE POTENTIAL FOR WINTRY WEATHER...
ESPECIALLY ACROSS THE INTERIOR.
THE FIRST STORM SYSTEM WILL EMERGE FROM THE MID MS VALLEY TUE NIGHT
AND TAKE A TRACK TO THE NORTH AND WEST OF THE FORECAST AREA WED.
PCPN AHEAD OF ITS WARM FRONT MAY DEVELOP IN THE OVERNIGHT HOUR TUE.
THE TIMING HERE IS CRITICAL AS THE COLD AIR WILL BE ERODING IN A
STRENGTHENING SOUTHERLY FLOW. COASTAL AREAS WILL BE ALL RAIN...BUT
THERE IS A POSSIBILITY OF A BRIEF WINTRY MIX ACROSS INLAND AREAS
PRIOR TO DAYBREAK. THE STEADIEST PCPN WILL FALL AS RAIN ON WED. THE
TRAILING COLD FRONT WILL THEN BRIEFLY DRY CONDITIONS OUT WED NIGHT
INTO THU. THE NEXT SYSTEM TAKES A TRACK FROM THE LOWER MS VALLEY
THU...NE TO OFF THE MID ATLANTIC COAST ON FRI. THIS SYSTEM TOO MAY
FEATURE A WINTRY MIX INLAND. VERTICAL TEMPERATURE PROFILES ARE
MARGINAL IN BOTH CASES WITH NO REAL GOOD SOURCE OF POLAR AIR. THE
FAST FLOW ACROSS THE NORTHERN TIER OF THE COUNTRY IS PREVENTING A
STRONG SOUTHWARD PUSH.
FINALLY...THE LAST STORM HAS THE POTENTIAL TO IMPACT THE AREA
CHRISTMAS EVE AND DAY. THE ECMWF HAS TRENDED TO A STRONGER LOW IN
COMPARISON TO THE GFS WITH A 989 MB LOW PASSING NEAR CAPE COD NEXT
SUNDAY. THE GFS IS ABOUT 20 MB WEAKER. A DECENT HIGH TO THE NORTH
FOR THIS GO AROUND MAY POSE A MORE SIGNIFICANT WINTER WEATHER
THREAT. ONCE AGAIN THOUGH...THERE WILL LIKELY BE SEVERAL CHANGES IN
THE FORECAST OUT THIS FAR. IT IS DEFINITELY WORTH KEEPING AN EYE ON.
TEMPERATURES WILL START OFF ABOVE NORMAL FOR THE MID WEEK
PERIOD...BUT THEN TRANSITION TO MORE SEASONABLE READINGS FOR THE END
OF THE WEEK INTO NEXT WEEKEND. HIGHS WILL TOP OUT IN THE LOWER 50S
WED AND THU...BUT THEN FALL TO AROUND 40 BY THE WEEKEND.
&&
.AVIATION /15Z MONDAY THROUGH FRIDAY/...
HIGH PRESSURE MOVES EAST WITH INCREASING SW FLOW. A COLD FRONT MOVES
THROUGH THE TERMINALS LATE TONIGHT. COULD BE A FEW
FLURRIES/SPRINKLES ACCOMPANYING THE FROPA...BUT NOT EXPECTED TO
MAKE RUNWAYS WET.
VFR TODAY. INCREASING SW GUSTS TODAY...SPORADIC THROUGH 17Z. LOW
CONFIDENCE AT THIS TIME ON WHEN GUSTS WILL SUBSIDE. COLD FROPA
BETWEEN 05Z AND 09Z TONIGHT WITH WINDS BECOMING NW.
NY METRO ENHANCED AVIATION WEATHER SUPPORT...
DETAILED INFORMATION...INCLUDING HOURLY TAF WIND COMPONENT FCSTS
CAN BE FOUND AT: HTTP:/WWW.ERH.NOAA.GOV/ZNY/N90 (LOWER CASE)
KJFK FCSTER COMMENTS: AMENDMENTS POSSIBLE TO INCREASE GUST
SPEEDS. LOW CONFIDENCE ON TIMING OF GUSTS DIMINISHING...OCNL
GUSTS MAY LINGER THROUGH 03Z WHILE DIMINISHING.
KLGA FCSTER COMMENTS: AMENDMENTS POSSIBLE TO INCREASE GUST
SPEEDS. LOW CONFIDENCE ON TIMING OF GUSTS DIMINISHING...OCNL
GUSTS MAY LINGER THROUGH 03Z WHILE DIMINISHING.
KEWR FCSTER COMMENTS: AMENDMENTS POSSIBLE TO INCREASE GUST
SPEEDS. LOW CONFIDENCE ON TIMING OF GUSTS DIMINISHING...OCNL GUSTS
MAY LINGER THROUGH 03Z WHILE DIMINISHING.
KTEB FCSTER COMMENTS: AMENDMENTS POSSIBLE TO INCREASE GUST
SPEEDS. LOW CONFIDENCE ON TIMING OF GUSTS DIMINISHING...OCNL GUSTS
MAY LINGER THROUGH 03Z WHILE DIMINISHING.
KHPN FCSTER COMMENTS: AMENDMENTS POSSIBLE TO INCREASE GUST
SPEEDS. LOW CONFIDENCE ON TIMING OF GUSTS DIMINISHING...OCNL GUSTS
MAY LINGER THROUGH 03Z WHILE DIMINISHING.
KISP FCSTER COMMENTS: AMENDMENTS POSSIBLE TO INCREASE GUST
SPEEDS. LOW CONFIDENCE ON TIMING OF GUSTS DIMINISHING...OCNL GUSTS
MAY LINGER THROUGH 02Z WHILE DIMINISHING.
OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY...
TUE...VFR.
TUE NIGHT AND WED...SUB VFR IN RAIN...A WINTRY MIX POSSIBLE
INLAND TUE NIGHT. BECOMING VFR WED NIGHT.
THU...VFR.
FRI...SUB-VFR POSSIBLE.
&&
.MARINE...
ISSUED GALE WARNING FOR EASTERN TWO OCEAN ZONES BEGINNING LATE
THIS MORNING AS CONFIDENCE INCREASES THAT GALE GUSTS WILL DEVELOP.
WINDS START LIGHT FROM THE SW THIS MORNING...BUT THE PRESSURE
GRADIENT WILL INCREASE QUICKLY AS HIGH PRESSURE MOVES EAST OF THE
WATERS AND A COLD FRONT APPROACHES FROM THE NORTHWEST. SCA
CONTINUES FOR ALL OTHER ZONES. ALSO CAN`T RULE OUT POTENTIAL FOR A
FEW GALE-FORCE GUSTS IN EASTERN LONG ISLAND SOUND AND THE WESTERN
OCEAN WATERS TODAY...AND THESE AREAS WILL NEED TO BE MONITORED.
OTHERWISE SCA CONTINUES OVER ALL WATERS NOT COVERED BY THE GALE
WARNING.
WINDS DIMINISH LATE TONIGHT BEHIND THE COLD FRONT AS HIGH PRESSURE
APPROACHES THE WATERS. SCA-LEVEL SEAS COULD LINGER INTO TUESDAY
ON THE FAR EASTERN COASTAL WATERS...OTHERWISE SUB-SCA CONDITIONS
ARE EXPECTED TUESDAY AND TUESDAY NIGHT.
THERE WILL BE POTENTIAL EPISODES OF SCA CONDITIONS THROUGHOUT THE
WEEK AS A SERIES OF LOWS IMPACT THE WATERS. THE FIRST OF WHICH WILL
SEND A COLD FRONT ACROSS THE AREA WED NIGHT WITH A STRONG WLY FLOW
ON THE BACKSIDE INTO THU MORNING. HIGH PRESSURE THEN BRIEFLY RETURNS
TO THE WATERS ON THU BEFORE LOW PRESSURE PASSES TO THE SOUTH ON FRI.
FOR NOW GOING WITH SUB-SCA CONDITIONS ON FRIDAY WITH THE COASTAL LOW
PASSING TO THE SOUTH...BUT THERE IS MUCH UNCERTAINTY IN THIS
&&
.HYDROLOGY...
TRACE AMOUNTS OF PCPN ARE POSSIBLE TONIGHT.
THERE IS THE POTENTIAL FOR AROUND A 1/4 TO 1/2 AN INCH OF LIQUID
EQUIVALENT TO FALL OVER THE REGION FROM TUESDAY NIGHT INTO WEDNESDAY
NIGHT. SOME OF THIS COULD FALL AS FROZEN PRECIPITATION ACROSS
MAINLY NORTHERN INTERIOR ZONES INTO WEDNESDAY MORNING. NO
SIGNIFICANT HYDROLOGIC IMPACT IS CURRENTLY EXPECTED.
ADDITIONAL PRECIPITATION IS EXPECTED FROM A SERIES OF LOW
PRESSURE SYSTEMS THAT WILL IMPACT THE AREA LATE IN THE WEEK AND
THE WEEKEND. NO SIGNIFICANT HYDROLOGICAL IMPACTS ARE ANTICIPATED
AT THIS TIME.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM EST TUESDAY FOR ANZ330-335-338-
340-345-355.
GALE WARNING UNTIL 1 AM EST TUESDAY FOR ANZ350-353.
&&
$$
SYNOPSIS...KCS/DW
NEAR TERM...BC/KCS
SHORT TERM...KCS
LONG TERM...DW
AVIATION...24/BS
MARINE...KCS/DW
HYDROLOGY...KCS/DW
AREA FORECAST DISCUSSION
NWS NEW YORK NY
638 AM EST MON DEC 19 2011
.SYNOPSIS...
A HIGH PRESSURE RIDGE SHIFTS OFFSHORE TODAY. A COLD FRONT WILL
MOVE THROUGH TONIGHT. HIGH PRESSURE BUILDS OVER THE AREA TUESDAY. A
WARM FRONT APPROACHES FROM THE SOUTH TUESDAY NIGHT...THEN LIFTS TO
THE NORTH WEDNESDAY...FOLLOWED BY A COLD FRONT WEDNESDAY
NIGHT...AS AN AREA OF LOW PRESSURE PASSES TO OUR NORTH. HIGH
PRESSURE THEN BUILDS IN TO OUR NORTH THURSDAY THROUGH SUNDAY...AS
A COUPLE OF LOW PRESSURE SYSTEMS PASS TO OUR SOUTH FRIDAY AND THEN
LATE NEXT WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
MINOR ADJUSTMENTS MADE TO TEMPS/SKY BASED ON CURRENT OBS EARLY
THIS MORNING. RETURN FLOW IS BEGINNING OVER THE AREA WITH SW WINDS
NOTED ON NYC METRO 11Z OBS. THIS WILL HELP TEMPS MODERATE ACROSS
THE REGION THIS MORNING. FCST GENERALLY ON TRACK.
A HIGH PRESSURE RIDGE LOCATED RIGHT ALONG THE EAST COAST EARLY
THIS MORNING WILL SHIFT OFFSHORE TODAY...ALLOWING RETURN FLOW TO
DEVELOP OVER THE REGION. LOW PRESSURE EMBEDDED IN A STRONG
JETSTREAM ACROSS SOUTHERN CANADA WILL QUICKLY SHIFT EASTWARD
ACROSS QUEBEC...DRAGGING A COLD FRONT ACROSS THE GREAT LAKES
REGION. THE PRESSURE GRADIENT WILL INCREASE QUICKLY TODAY AS THE
LOW PASSES TO OUR NORTH...WITH GUSTY WINDS DEVELOPING BY LATE
MORNING AND CONTINUING THROUGH THE AFTERNOON. 00Z NAM SUGGESTS
LIGHT PRECIP DEVELOPING OVER THE REGION BY LATE AFTERNOON WITH A
WEAK VORT MAX MOVING THROUGH...BUT SIDED WITH 00Z GFS/ECMWF WHICH
KEEP ANY PRECIP NORTH AND WEST OF THE REGION.
WARM AIR ADVECTION DEVELOPS WITH THE HIGH OFFSHORE...ENABLING
TEMPERATURES TO CLIMB INTO THE LOW TO MID 40S AREA WIDE. MAV/MET
GUIDANCE IN GOOD AGREEMENT...AND WERE BLENDED FOR TEMPS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/...
MODEL CONSENSUS INDICATES COLD FRONT WILL BE LOCATED OVER
WESTERN/NORTHERN NY STATE BY EARLY THIS EVENING...THEN QUICKLY SWEEP
TO THE SOUTHEAST AND MOVE THROUGH THE REGION OVERNIGHT. WITH ZONAL
FLOW ALOFT MOISTURE WILL BE LIMITED...BUT ENOUGH LAKE MOISTURE MAY
ALLOW FOR SOME SPRINKLES AND/OR FLURRIES...WITH POTENTIAL FOR LIGHT
SNOW OVER THE LOWER HUDSON VALLEY. BL TOO WARM FOR FLAKES NEAR THE
COASTS INITIALLY...BUT AS THE CWA GETS INTO THE RR QUAD OF THE H3
150 PLUS KT H3 JET AFT MIDNIGHT...A FEW FLURRIES MAY MIX IN WITH
ANY SPRINKLES HERE AS WELL.
GUSTY WINDS DIMINISH THIS EVENING AS LOW-LEVEL INVERSION
DEVELOPS...BUT GUSTS MAY REDEVELOP BY EARLY TUESDAY MORNING AS
COOLER AIR ALOFT MOVES IN BEHIND THE FRONT.
MAV/MET BLENDED AGAIN FOR LOWS TONIGHT...WHICH WILL RANGE FROM THE
UPPER 20S OVER NORTHERN SECTIONS TO THE MID 30S NEAR THE COASTS.
ON TUESDAY...HIGH PRESSURE RIDGE DROPS FROM THE GREAT LAKES INTO
THE TRI-STATE AREA. WINDS DIMINISH AS THE HIGH BUILDS IN. HIGHS
GENERALLY IN THE LOW TO MID 40S.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A PROGRESSIVE SPLIT FLOW ACROSS THE LOWER 48 GETS A BIT MORE
INTERESTING THIS WEEK AS SEVERAL SOUTHERN BRANCH LOWS INTERACT WITH
MARGINALLY COLD AIR ACROSS THE NE U.S. THE 00Z GFS AND ECMWF ARE IN
REMARKABLE AGREEMENT DURING THIS PERIOD...ALTHOUGH THERE ARE SOME
TIMING DIFFERENCES AS CAN BE EXPECTED. THE GFS IS THE MORE
PROGRESSIVE OF THE SOLUTIONS IN THE HANDLING OF EACH WAVE...WHICH
SEEMS TO MAKE SENSE BASED ON THE PROGRESSIVE NATURE OF THE UPPER
FLOW. AT THIS POINT IN TIME...IT IS TOO EARLY BE SPECIFIC WITH ANY
DETAILS...BUT THERE IS THE POTENTIAL FOR WINTRY WEATHER...
ESPECIALLY ACROSS THE INTERIOR.
THE FIRST STORM SYSTEM WILL EMERGE FROM THE MID MS VALLEY TUE NIGHT
AND TAKE A TRACK TO THE NORTH AND WEST OF THE FORECAST AREA WED.
PCPN AHEAD OF ITS WARM FRONT MAY DEVELOP IN THE OVERNIGHT HOUR TUE.
THE TIMING HERE IS CRITICAL AS THE COLD AIR WILL BE ERODING IN A
STRENGTHENING SOUTHERLY FLOW. COASTAL AREAS WILL BE ALL RAIN...BUT
THERE IS A POSSIBILITY OF A BRIEF WINTRY MIX ACROSS INLAND AREAS
PRIOR TO DAYBREAK. THE STEADIEST PCPN WILL FALL AS RAIN ON WED. THE
TRAILING COLD FRONT WILL THEN BRIEFLY DRY CONDITIONS OUT WED NIGHT
INTO THU. THE NEXT SYSTEM TAKES A TRACK FROM THE LOWER MS VALLEY
THU...NE TO OFF THE MID ATLANTIC COAST ON FRI. THIS SYSTEM TOO MAY
FEATURE A WINTRY MIX INLAND. VERTICAL TEMPERATURE PROFILES ARE
MARGINAL IN BOTH CASES WITH NO REAL GOOD SOURCE OF POLAR AIR. THE
FAST FLOW ACROSS THE NORTHERN TIER OF THE COUNTRY IS PREVENTING A
STRONG SOUTHWARD PUSH.
FINALLY...THE LAST STORM HAS THE POTENTIAL TO IMPACT THE AREA
CHRISTMAS EVE AND DAY. THE ECMWF HAS TRENDED TO A STRONGER LOW IN
COMPARISON TO THE GFS WITH A 989 MB LOW PASSING NEAR CAPE COD NEXT
SUNDAY. THE GFS IS ABOUT 20 MB WEAKER. A DECENT HIGH TO THE NORTH
FOR THIS GO AROUND MAY POSE A MORE SIGNIFICANT WINTER WEATHER
THREAT. ONCE AGAIN THOUGH...THERE WILL LIKELY BE SEVERAL CHANGES IN
THE FORECAST OUT THIS FAR. IT IS DEFINITELY WORTH KEEPING AN EYE ON.
TEMPERATURES WILL START OFF ABOVE NORMAL FOR THE MID WEEK
PERIOD...BUT THEN TRANSITION TO MORE SEASONABLE READINGS FOR THE END
OF THE WEEK INTO NEXT WEEKEND. HIGHS WILL TOP OUT IN THE LOWER 50S
WED AND THU...BUT THEN FALL TO AROUND 40 BY THE WEEKEND.
&&
.AVIATION /12Z MONDAY THROUGH FRIDAY/...
HIGH PRESSURE OVER THE AREA DRIFTS SOUTH AS A COLD FRONT APPROACHES.
THE FRONT MOVES THROUGH THE TERMINALS LATE TONIGHT. COULD BE A FEW
FLURRIES/SPRINKLES ACCOMPANYING THE FROPA...BUT NOT EXPECTED TO
MAKE RUNWAYS WET.
VFR. LIGHT SW WINDS WILL INCREASE AS THE DAY PROGRESSES AS A
RESULT OF A TIGHTENING PRESSURE GRADIENT. GUSTS DEVELOP AFTER 15Z
MONDAY AND PEAK IN THE EARLY TO MID AFTERNOON 20 TO 25 KT. COLD
FROPA BETWEEN 05Z AND 09Z TONIGHT WITH WINDS BECOMING NW.
NY METRO ENHANCED AVIATION WEATHER SUPPORT...
DETAILED INFORMATION...INCLUDING HOURLY TAF WIND COMPONENT FCSTS
CAN BE FOUND AT: HTTP:/WWW.ERH.NOAA.GOV/ZNY/N90 (LOWER CASE)
KJFK FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR OR SO LATER THAN
FORECAST AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. OCNL
GUSTS MAY LINGER THROUGH 03Z WHILE DIMINISHING.
KLGA FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR OR SO LATER THAN
FORECAST AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. OCNL
GUSTS MAY LINGER THROUGH 03Z WHILE DIMINISHING.
KEWR FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR OR SO LATER THAN
FORECAST AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. OCNL
GUSTS MAY LINGER THROUGH 01Z WHILE DIMINISHING.
KTEB FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR OR SO LATER THAN
FORECAST AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. OCNL
GUSTS MAY LINGER UNTIL AROUND 00Z WHILE DIMINISHING.
KHPN FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR OR SO LATER THAN
FORECAST AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. OCNL
GUSTS MAY LINGER UNTIL AROUND 00Z WHILE DIMINISHING.
KISP FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR OR SO LATER THAN
FORECAST AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. OCNL
GUSTS MAY LINGER UNTIL AROUND 00Z WHILE DIMINISHING.
OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY...
TUE...VFR.
TUE NIGHT AND WED...SUB VFR IN RAIN...A WINTRY MIX POSSIBLE
INLAND TUE NIGHT. BECOMING VFR WED NIGHT.
THU...VFR.
FRI...SUB-VFR POSSIBLE.
&&
.MARINE...
ISSUED GALE WARNING FOR EASTERN TWO OCEAN ZONES BEGINNING LATE
THIS MORNING AS CONFIDENCE INCREASES THAT GALE GUSTS WILL DEVELOP.
WINDS START LIGHT FROM THE SW THIS MORNING...BUT THE PRESSURE
GRADIENT WILL INCREASE QUICKLY AS HIGH PRESSURE MOVES EAST OF THE
WATERS AND A COLD FRONT APPROACHES FROM THE NORTHWEST. SCA
CONTINUES FOR ALL OTHER ZONES. ALSO CAN`T RULE OUT POTENTIAL FOR A
FEW GALE-FORCE GUSTS IN EASTERN LONG ISLAND SOUND AND THE WESTERN
OCEAN WATERS TODAY...AND THESE AREAS WILL NEED TO BE MONITORED.
OTHERWISE SCA CONTINUES OVER ALL WATERS NOT COVERED BY THE GALE
WARNING.
WINDS DIMINISH LATE TONIGHT BEHIND THE COLD FRONT AS HIGH PRESSURE
APPROACHES THE WATERS. SCA-LEVEL SEAS COULD LINGER INTO TUESDAY
ON THE FAR EASTERN COASTAL WATERS...OTHERWISE SUB-SCA CONDITIONS
ARE EXPECTED TUESDAY AND TUESDAY NIGHT.
THERE WILL BE POTENTIAL EPISODES OF SCA CONDITIONS THROUGHOUT THE
WEEK AS A SERIES OF LOWS IMPACT THE WATERS. THE FIRST OF WHICH WILL
SEND A COLD FRONT ACROSS THE AREA WED NIGHT WITH A STRONG WLY FLOW
ON THE BACKSIDE INTO THU MORNING. HIGH PRESSURE THEN BRIEFLY RETURNS
TO THE WATERS ON THU BEFORE LOW PRESSURE PASSES TO THE SOUTH ON FRI.
FOR NOW GOING WITH SUB-SCA CONDITIONS ON FRIDAY WITH THE COASTAL LOW
PASSING TO THE SOUTH...BUT THERE IS MUCH UNCERTAINTY IN THIS
&&
.HYDROLOGY...
TRACE AMOUNTS OF PCPN ARE POSSIBLE TONIGHT.
THERE IS THE POTENTIAL FOR AROUND A 1/4 TO 1/2 AN INCH OF LIQUID
EQUIVALENT TO FALL OVER THE REGION FROM TUESDAY NIGHT INTO WEDNESDAY
NIGHT. SOME OF THIS COULD FALL AS FROZEN PRECIPITATION ACROSS
MAINLY NORTHERN INTERIOR ZONES INTO WEDNESDAY MORNING. NO
SIGNIFICANT HYDROLOGIC IMPACT IS CURRENTLY EXPECTED.
ADDITIONAL PRECIPITATION IS EXPECTED FROM A SERIES OF LOW
PRESSURE SYSTEMS THAT WILL IMPACT THE AREA LATE IN THE WEEK AND
THE WEEKEND. NO SIGNIFICANT HYDROLOGICAL IMPACTS ARE ANTICIPATED
AT THIS TIME.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 1 AM EST
TUESDAY FOR ANZ330-335-338-340-345-355.
GALE WARNING FROM 10 AM THIS MORNING TO 1 AM EST TUESDAY FOR
ANZ350-353.
&&
$$
SYNOPSIS...KCS/DW
NEAR TERM...KCS
SHORT TERM...KCS
LONG TERM...DW
AVIATION...24
MARINE...KCS/DW
HYDROLOGY...KCS/DW
AREA FORECAST DISCUSSION
NWS NEW YORK NY
558 AM EST MON DEC 19 2011
.SYNOPSIS...
A HIGH PRESSURE RIDGE SHIFTS OFFSHORE TODAY. A COLD FRONT WILL
MOVE THROUGH TONIGHT. HIGH PRESSURE BUILDS OVER THE AREA TUESDAY. A
WARM FRONT APPROACHES FROM THE SOUTH TUESDAY NIGHT...THEN LIFTS TO
THE NORTH WEDNESDAY...FOLLOWED BY A COLD FRONT WEDNESDAY
NIGHT...AS AN AREA OF LOW PRESSURE PASSES TO OUR NORTH. HIGH
PRESSURE THEN BUILDS IN TO OUR NORTH THURSDAY THROUGH SUNDAY...AS
A COUPLE OF LOW PRESSURE SYSTEMS PASS TO OUR SOUTH FRIDAY AND THEN
LATE NEXT WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
MINOR ADJUSTMENTS MADE TO TEMPS/SKY BASED ON CURRENT OBS EARLY
THIS MORNING. RETURN FLOW IS BEGINNING OVER THE AREA WITH SW WINDS
NOTED ON NYC METRO 11Z OBS. THIS WILL HELP TEMPS MODERATE ACROSS
THE REGION THIS MORNING. FCST GENERALLY ON TRACK.
A HIGH PRESSURE RIDGE LOCATED RIGHT ALONG THE EAST COAST EARLY
THIS MORNING WILL SHIFT OFFSHORE TODAY...ALLOWING RETURN FLOW TO
DEVELOP OVER THE REGION. LOW PRESSURE EMBEDDED IN A STRONG
JETSTREAM ACROSS SOUTHERN CANADA WILL QUICKLY SHIFT EASTWARD
ACROSS QUEBEC...DRAGGING A COLD FRONT ACROSS THE GREAT LAKES
REGION. THE PRESSURE GRADIENT WILL INCREASE QUICKLY TODAY AS THE
LOW PASSES TO OUR NORTH...WITH GUSTY WINDS DEVELOPING BY LATE
MORNING AND CONTINUING THROUGH THE AFTERNOON. 00Z NAM SUGGESTS
LIGHT PRECIP DEVELOPING OVER THE REGION BY LATE AFTERNOON WITH A
WEAK VORT MAX MOVING THROUGH...BUT SIDED WITH 00Z GFS/ECMWF WHICH
KEEP ANY PRECIP NORTH AND WEST OF THE REGION.
WARM AIR ADVECTION DEVELOPS WITH THE HIGH OFFSHORE...ENABLING
TEMPERATURES TO CLIMB INTO THE LOW TO MID 40S AREA WIDE. MAV/MET
GUIDANCE IN GOOD AGREEMENT...AND WERE BLENDED FOR TEMPS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/...
MODEL CONSENSUS INDICATES COLD FRONT WILL BE LOCATED OVER
WESTERN/NORTHERN NY STATE BY EARLY THIS EVENING...THEN QUICKLY SWEEP
TO THE SOUTHEAST AND MOVE THROUGH THE REGION OVERNIGHT. WITH ZONAL
FLOW ALOFT MOISTURE WILL BE LIMITED...BUT ENOUGH LAKE MOISTURE MAY
ALLOW FOR SOME SPRINKLES AND/OR FLURRIES...WITH POTENTIAL FOR LIGHT
SNOW OVER THE LOWER HUDSON VALLEY. BL TOO WARM FOR FLAKES NEAR THE
COASTS INITIALLY...BUT AS THE CWA GETS INTO THE RR QUAD OF THE H3
150 PLUS KT H3 JET AFT MIDNIGHT...A FEW FLURRIES MAY MIX IN WITH
ANY SPRINKLES HERE AS WELL.
GUSTY WINDS DIMINISH THIS EVENING AS LOW-LEVEL INVERSION
DEVELOPS...BUT GUSTS MAY REDEVELOP BY EARLY TUESDAY MORNING AS
COOLER AIR ALOFT MOVES IN BEHIND THE FRONT.
MAV/MET BLENDED AGAIN FOR LOWS TONIGHT...WHICH WILL RANGE FROM THE
UPPER 20S OVER NORTHERN SECTIONS TO THE MID 30S NEAR THE COASTS.
ON TUESDAY...HIGH PRESSURE RIDGE DROPS FROM THE GREAT LAKES INTO
THE TRI-STATE AREA. WINDS DIMINISH AS THE HIGH BUILDS IN. HIGHS
GENERALLY IN THE LOW TO MID 40S.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A PROGRESSIVE SPLIT FLOW ACROSS THE LOWER 48 GETS A BIT MORE
INTERESTING THIS WEEK AS SEVERAL SOUTHERN BRANCH LOWS INTERACT WITH
MARGINALLY COLD AIR ACROSS THE NE U.S. THE 00Z GFS AND ECMWF ARE IN
REMARKABLE AGREEMENT DURING THIS PERIOD...ALTHOUGH THERE ARE SOME
TIMING DIFFERENCES AS CAN BE EXPECTED. THE GFS IS THE MORE
PROGRESSIVE OF THE SOLUTIONS IN THE HANDLING OF EACH WAVE...WHICH
SEEMS TO MAKE SENSE BASED ON THE PROGRESSIVE NATURE OF THE UPPER
FLOW. AT THIS POINT IN TIME...IT IS TOO EARLY BE SPECIFIC WITH ANY
DETAILS...BUT THERE IS THE POTENTIAL FOR WINTRY WEATHER...
ESPECIALLY ACROSS THE INTERIOR.
THE FIRST STORM SYSTEM WILL EMERGE FROM THE MID MS VALLEY TUE NIGHT
AND TAKE A TRACK TO THE NORTH AND WEST OF THE FORECAST AREA WED.
PCPN AHEAD OF ITS WARM FRONT MAY DEVELOP IN THE OVERNIGHT HOUR TUE.
THE TIMING HERE IS CRITICAL AS THE COLD AIR WILL BE ERODING IN A
STRENGTHENING SOUTHERLY FLOW. COASTAL AREAS WILL BE ALL RAIN...BUT
THERE IS A POSSIBILITY OF A BRIEF WINTRY MIX ACROSS INLAND AREAS
PRIOR TO DAYBREAK. THE STEADIEST PCPN WILL FALL AS RAIN ON WED. THE
TRAILING COLD FRONT WILL THEN BRIEFLY DRY CONDITIONS OUT WED NIGHT
INTO THU. THE NEXT SYSTEM TAKES A TRACK FROM THE LOWER MS VALLEY
THU...NE TO OFF THE MID ATLANTIC COAST ON FRI. THIS SYSTEM TOO MAY
FEATURE A WINTRY MIX INLAND. VERTICAL TEMPERATURE PROFILES ARE
MARGINAL IN BOTH CASES WITH NO REAL GOOD SOURCE OF POLAR AIR. THE
FAST FLOW ACROSS THE NORTHERN TIER OF THE COUNTRY IS PREVENTING A
STRONG SOUTHWARD PUSH.
FINALLY...THE LAST STORM HAS THE POTENTIAL TO IMPACT THE AREA
CHRISTMAS EVE AND DAY. THE ECMWF HAS TRENDED TO A STRONGER LOW IN
COMPARISON TO THE GFS WITH A 989 MB LOW PASSING NEAR CAPE COD NEXT
SUNDAY. THE GFS IS ABOUT 20 MB WEAKER. A DECENT HIGH TO THE NORTH
FOR THIS GO AROUND MAY POSE A MORE SIGNIFICANT WINTER WEATHER
THREAT. ONCE AGAIN THOUGH...THERE WILL LIKELY BE SEVERAL CHANGES IN
THE FORECAST OUT THIS FAR. IT IS DEFINITELY WORTH KEEPING AN EYE ON.
TEMPERATURES WILL START OFF ABOVE NORMAL FOR THE MID WEEK
PERIOD...BUT THEN TRANSITION TO MORE SEASONABLE READINGS FOR THE END
OF THE WEEK INTO NEXT WEEKEND. HIGHS WILL TOP OUT IN THE LOWER 50S
WED AND THU...BUT THEN FALL TO AROUND 40 BY THE WEEKEND.
&&
.AVIATION /12Z MONDAY THROUGH FRIDAY/...
HIGH PRESSURE OVER THE AREA DRIFTS SOUTH AS A COLD FRONT APPROACHES.
THE FRONT MOVES THROUGH THE TERMINALS LATE TONIGHT.
VFR. LIGHT AND VARIABLE WINDS EARLY THIS MORNING BECOME SOUTHWEST
AND INCREASE AS THE DAY PROGRESSES WITH A TIGHTENING PRESSURE
GRADIENT. GUSTS DEVELOP AFTER 15Z MONDAY AND PEAK IN THE EARLY TO MID
AFTERNOON 20 TO 25 KT.
NY METRO ENHANCED AVIATION WEATHER SUPPORT...
DETAILED INFORMATION...INCLUDING HOURLY TAF WIND COMPONENT FCSTS
CAN BE FOUND AT: HTTP:/WWW.ERH.NOAA.GOV/ZNY/N90 (LOWER CASE)
KJFK FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR ON EITHER SIDE OF
15Z AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. GUSTS MAY
LINGER THROUGH 03Z WHILE DIMINISHING.
KLGA FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR ON EITHER SIDE OF
15Z AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. GUSTS MAY
LINGER THROUGH 03Z WHILE DIMINISHING.
KEWR FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR ON EITHER SIDE OF
15Z AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. GUSTS MAY
LINGER THROUGH 03Z WHILE DIMINISHING.
KTEB FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR ON EITHER SIDE OF
15Z AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. GUSTS MAY
LINGER UNTIL AROUND 00Z WHILE DIMINISHING.
KHPN FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR ON EITHER SIDE OF
15Z AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. GUSTS MAY
LINGER UNTIL AROUND 00Z WHILE DIMINISHING.
KISP FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR ON EITHER SIDE OF
15Z AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. GUSTS MAY
LINGER UNTIL AROUND 00Z WHILE DIMINISHING.
OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY...
MON NIGHT...VFR. W WINDS BECMG NW BEHIND A COLD FRONT.
FLURRIES/SPRINKLES POSSIBLE.
TUE...VFR.
TUE NIGHT AND WED...SUB VFR IN RAIN...A WINTRY MIX POSSIBLE
INLAND TUE NIGHT. BECOMING VFR WED NIGHT.
THU...VFR.
FRI...SUB-VFR POSSIBLE.
&&
.MARINE...
ISSUED GALE WARNING FOR EASTERN TWO OCEAN ZONES BEGINNING LATE
THIS MORNING AS CONFIDENCE INCREASES THAT GALE GUSTS WILL DEVELOP.
WINDS START LIGHT FROM THE SW THIS MORNING...BUT THE PRESSURE
GRADIENT WILL INCREASE QUICKLY AS HIGH PRESSURE MOVES EAST OF THE
WATERS AND A COLD FRONT APPROACHES FROM THE NORTHWEST. SCA
CONTINUES FOR ALL OTHER ZONES. ALSO CAN`T RULE OUT POTENTIAL FOR A
FEW GALE-FORCE GUSTS IN EASTERN LONG ISLAND SOUND AND THE WESTERN
OCEAN WATERS TODAY...AND THESE AREAS WILL NEED TO BE MONITORED.
OTHERWISE SCA CONTINUES OVER ALL WATERS NOT COVERED BY THE GALE
WARNING.
WINDS DIMINISH LATE TONIGHT BEHIND THE COLD FRONT AS HIGH PRESSURE
APPROACHES THE WATERS. SCA-LEVEL SEAS COULD LINGER INTO TUESDAY
ON THE FAR EASTERN COASTAL WATERS...OTHERWISE SUB-SCA CONDITIONS
ARE EXPECTED TUESDAY AND TUESDAY NIGHT.
THERE WILL BE POTENTIAL EPISODES OF SCA CONDITIONS THROUGHOUT THE
WEEK AS A SERIES OF LOWS IMPACT THE WATERS. THE FIRST OF WHICH WILL
SEND A COLD FRONT ACROSS THE AREA WED NIGHT WITH A STRONG WLY FLOW
ON THE BACKSIDE INTO THU MORNING. HIGH PRESSURE THEN BRIEFLY RETURNS
TO THE WATERS ON THU BEFORE LOW PRESSURE PASSES TO THE SOUTH ON FRI.
FOR NOW GOING WITH SUB-SCA CONDITIONS ON FRIDAY WITH THE COASTAL LOW
PASSING TO THE SOUTH...BUT THERE IS MUCH UNCERTAINTY IN THIS
&&
.HYDROLOGY...
TRACE AMOUNTS OF PCPN ARE POSSIBLE TONIGHT.
THERE IS THE POTENTIAL FOR AROUND A 1/4 TO 1/2 AN INCH OF LIQUID
EQUIVALENT TO FALL OVER THE REGION FROM TUESDAY NIGHT INTO WEDNESDAY
NIGHT. SOME OF THIS COULD FALL AS FROZEN PRECIPITATION ACROSS
MAINLY NORTHERN INTERIOR ZONES INTO WEDNESDAY MORNING. NO
SIGNIFICANT HYDROLOGIC IMPACT IS CURRENTLY EXPECTED.
ADDITIONAL PRECIPITATION IS EXPECTED FROM A SERIES OF LOW
PRESSURE SYSTEMS THAT WILL IMPACT THE AREA LATE IN THE WEEK AND
THE WEEKEND. NO SIGNIFICANT HYDROLOGICAL IMPACTS ARE ANTICIPATED
AT THIS TIME.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 1 AM EST
TUESDAY FOR ANZ330-335-338-340-345-355.
GALE WARNING FROM 10 AM THIS MORNING TO 1 AM EST TUESDAY FOR
ANZ350-353.
&&
$$
SYNOPSIS...KCS/DW
NEAR TERM...KCS
SHORT TERM...KCS
LONG TERM...DW
AVIATION...24
MARINE...KCS/DW
HYDROLOGY...KCS/DW
AREA FORECAST DISCUSSION
NWS NEW YORK NY
431 AM EST MON DEC 19 2011
.SYNOPSIS...
A HIGH PRESSURE RIDGE SHIFTS OFFSHORE TODAY. A COLD FRONT WILL
MOVE THROUGH TONIGHT. HIGH PRESSURE BUILDS OVER THE AREA TUESDAY. A
WARM FRONT APPROACHES FROM THE SOUTH TUESDAY NIGHT...THEN LIFTS TO
THE NORTH WEDNESDAY...FOLLOWED BY A COLD FRONT WEDNESDAY
NIGHT...AS AN AREA OF LOW PRESSURE PASSES TO OUR NORTH. HIGH
PRESSURE THEN BUILDS IN TO OUR NORTH THURSDAY THROUGH SUNDAY...AS
A COUPLE OF LOW PRESSURE SYSTEMS PASS TO OUR SOUTH FRIDAY AND THEN
LATE NEXT WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A HIGH PRESSURE RIDGE LOCATED RIGHT ALONG THE EAST COAST EARLY THIS
MORNING WILL SHIFT OFFSHORE TODAY...ALLOWING RETURN FLOW TO DEVELOP
OVER THE REGION. LOW PRESSURE EMBEDDED IN A STRONG JETSTREAM ACROSS
SOUTHERN CANADA WILL QUICKLY SHIFT EASTWARD ACROSS QUEBEC...DRAGGING
A COLD FRONT ACROSS THE GREAT LAKES REGION. THE PRESSURE GRADIENT
WILL INCREASE QUICKLY TODAY AS THE LOW PASSES TO OUR NORTH...WITH
GUSTY WINDS DEVELOPING BY LATE MORNING AND CONTINUING THROUGH THE
AFTERNOON. 00Z NAM SUGGESTS LIGHT PRECIP DEVELOPING OVER THE REGION
BY LATE AFTERNOON WITH A WEAK VORT MAX MOVING THROUGH...BUT SIDED
WITH 00Z GFS/ECMWF WHICH KEEP ANY PRECIP NORTH AND WEST OF THE
REGION.
WARM AIR ADVECTION DEVELOPS WITH THE HIGH OFFSHORE...ENABLING
TEMPERATURES TO CLIMB INTO THE LOW TO MID 40S AREA WIDE. MAV/MET
GUIDANCE IN GOOD AGREEMENT...AND WERE BLENDED FOR TEMPS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/...
MODEL CONSENSUS INDICATES COLD FRONT WILL BE LOCATED OVER
WESTERN/NORTHERN NY STATE BY EARLY THIS EVENING...THEN QUICKLY SWEEP
TO THE SOUTHEAST AND MOVE THROUGH THE REGION OVERNIGHT. WITH ZONAL
FLOW ALOFT MOISTURE WILL BE LIMITED...BUT ENOUGH LAKE MOISTURE MAY
ALLOW FOR SOME SPRINKLES AND/OR FLURRIES...WITH POTENTIAL FOR LIGHT
SNOW OVER THE LOWER HUDSON VALLEY. BL TOO WARM FOR FLAKES NEAR THE
COASTS INITIALLY...BUT AS THE CWA GETS INTO THE RR QUAD OF THE H3
150 PLUS KT H3 JET AFT MIDNIGHT...A FEW FLURRIES MAY MIX IN WITH
ANY SPRINKLES HERE AS WELL.
GUSTY WINDS DIMINISH THIS EVENING AS LOW-LEVEL INVERSION
DEVELOPS...BUT GUSTS MAY REDEVELOP BY EARLY TUESDAY MORNING AS
COOLER AIR ALOFT MOVES IN BEHIND THE FRONT.
MAV/MET BLENDED AGAIN FOR LOWS TONIGHT...WHICH WILL RANGE FROM THE
UPPER 20S OVER NORTHERN SECTIONS TO THE MID 30S NEAR THE COASTS.
ON TUESDAY...HIGH PRESSURE RIDGE DROPS FROM THE GREAT LAKES INTO
THE TRI-STATE AREA. WINDS DIMINISH AS THE HIGH BUILDS IN. HIGHS
GENERALLY IN THE LOW TO MID 40S.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A PROGRESSIVE SPLIT FLOW ACROSS THE LOWER 48 GETS A BIT MORE
INTERESTING THIS WEEK AS SEVERAL SOUTHERN BRANCH LOWS INTERACT WITH
MARGINALLY COLD AIR ACROSS THE NE U.S. THE 00Z GFS AND ECMWF ARE IN
REMARKABLE AGREEMENT DURING THIS PERIOD...ALTHOUGH THERE ARE SOME
TIMING DIFFERENCES AS CAN BE EXPECTED. THE GFS IS THE MORE
PROGRESSIVE OF THE SOLUTIONS IN THE HANDLING OF EACH WAVE...WHICH
SEEMS TO MAKE SENSE BASED ON THE PROGRESSIVE NATURE OF THE UPPER
FLOW. AT THIS POINT IN TIME...IT IS TOO EARLY BE SPECIFIC WITH ANY
DETAILS...BUT THERE IS THE POTENTIAL FOR WINTRY WEATHER...
ESPECIALLY ACROSS THE INTERIOR.
THE FIRST STORM SYSTEM WILL EMERGE FROM THE MID MS VALLEY TUE NIGHT
AND TAKE A TRACK TO THE NORTH AND WEST OF THE FORECAST AREA WED.
PCPN AHEAD OF ITS WARM FRONT MAY DEVELOP IN THE OVERNIGHT HOUR TUE.
THE TIMING HERE IS CRITICAL AS THE COLD AIR WILL BE ERODING IN A
STRENGTHENING SOUTHERLY FLOW. COASTAL AREAS WILL BE ALL RAIN...BUT
THERE IS A POSSIBILITY OF A BRIEF WINTRY MIX ACROSS INLAND AREAS
PRIOR TO DAYBREAK. THE STEADIEST PCPN WILL FALL AS RAIN ON WED. THE
TRAILING COLD FRONT WILL THEN BRIEFLY DRY CONDITIONS OUT WED NIGHT
INTO THU. THE NEXT SYSTEM TAKES A TRACK FROM THE LOWER MS VALLEY
THU...NE TO OFF THE MID ATLANTIC COAST ON FRI. THIS SYSTEM TOO MAY
FEATURE A WINTRY MIX INLAND. VERTICAL TEMPERATURE PROFILES ARE
MARGINAL IN BOTH CASES WITH NO REAL GOOD SOURCE OF POLAR AIR. THE
FAST FLOW ACROSS THE NORTHERN TIER OF THE COUNTRY IS PREVENTING A
STRONG SOUTHWARD PUSH.
FINALLY...THE LAST STORM HAS THE POTENTIAL TO IMPACT THE AREA
CHRISTMAS EVE AND DAY. THE ECMWF HAS TRENDED TO A STRONGER LOW IN
COMPARISON TO THE GFS WITH A 989 MB LOW PASSING NEAR CAPE COD NEXT
SUNDAY. THE GFS IS ABOUT 20 MB WEAKER. A DECENT HIGH TO THE NORTH
FOR THIS GO AROUND MAY POSE A MORE SIGNIFICANT WINTER WEATHER
THREAT. ONCE AGAIN THOUGH...THERE WILL LIKELY BE SEVERAL CHANGES IN
THE FORECAST OUT THIS FAR. IT IS DEFINITELY WORTH KEEPING AN EYE ON.
TEMPERATURES WILL START OFF ABOVE NORMAL FOR THE MID WEEK
PERIOD...BUT THEN TRANSITION TO MORE SEASONABLE READINGS FOR THE END
OF THE WEEK INTO NEXT WEEKEND. HIGHS WILL TOP OUT IN THE LOWER 50S
WED AND THU...BUT THEN FALL TO AROUND 40 BY THE WEEKEND.
&&
.AVIATION /09Z MONDAY THROUGH FRIDAY/...
HIGH PRESSURE OVER THE AREA DRIFTS SOUTH AS A COLD FRONT APPROACHES.
THE FRONT MOVES THROUGH THE TERMINALS LATE TONIGHT.
VFR. LIGHT AND VARIABLE WINDS EARLY THIS MORNING BECOME SOUTHWEST
AND INCREASE AS THE DAY PROGRESSES WITH A TIGHTENING PRESSURE
GRADIENT. GUSTS DEVELOP AFTER 15Z MONDAY AND PEAK IN THE EARLY TO MID
AFTERNOON 20 TO 25 KT.
...NY METRO ENHANCED AVIATION WEATHER SUPPORT...
DETAILED INFORMATION...INCLUDING HOURLY TAF WIND COMPONENT FCSTS
CAN BE FOUND AT: HTTP://WWW.ERH.NOAA.GOV/ZNY/N90 (LOWER CASE)
KJFK FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR ON EITHER SIDE OF
15Z AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. GUSTS MAY
LINGER THROUGH 03Z WHILE DIMINISHING.
KLGA FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR ON EITHER SIDE OF
15Z AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. GUSTS MAY
LINGER THROUGH 03Z WHILE DIMINISHING.
KEWR FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR ON EITHER SIDE OF
15Z AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. GUSTS MAY
LINGER THROUGH 03Z WHILE DIMINISHING.
KTEB FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR ON EITHER SIDE OF
15Z AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. GUSTS MAY
LINGER UNTIL AROUND 00Z WHILE DIMINISHING.
KHPN FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR ON EITHER SIDE OF
15Z AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. GUSTS MAY
LINGER UNTIL AROUND 00Z WHILE DIMINISHING.
KISP FCSTER COMMENTS: GUSTS MAY BEGIN AN HOUR ON EITHER SIDE OF
15Z AND MAY BE A FEW KT HIGHER THAN FORECAST AFT 18Z. GUSTS MAY
LINGER UNTIL AROUND 00Z WHILE DIMINISHING.
OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY...
MON NIGHT...VFR. W WINDS BECMG NW BEHIND A COLD FRONT.
FLURRIES/SPRINKLES POSSIBLE.
TUE...VFR.
TUE NIGHT AND WED...SUB VFR IN RAIN...A WINTRY MIX POSSIBLE
INLAND TUE NIGHT. BECOMING VFR WED NIGHT.
THU...VFR.
FRI...SUB-VFR POSSIBLE.
&&
.MARINE...
ISSUED GALE WARNING FOR EASTERN TWO OCEAN ZONES BEGINNING LATE
THIS MORNING AS CONFIDENCE INCREASES THAT GALE GUSTS WILL DEVELOP.
WINDS START LIGHT FROM THE SW THIS MORNING...BUT THE PRESSURE
GRADIENT WILL INCREASE QUICKLY AS HIGH PRESSURE MOVES EAST OF THE
WATERS AND A COLD FRONT APPROACHES FROM THE NORTHWEST. SCA
CONTINUES FOR ALL OTHER ZONES. ALSO CAN`T RULE OUT POTENTIAL FOR A
FEW GALE-FORCE GUSTS IN EASTERN LONG ISLAND SOUND AND THE WESTERN
OCEAN WATERS TODAY...AND THESE AREAS WILL NEED TO BE MONITORED.
OTHERWISE SCA CONTINUES OVER ALL WATERS NOT COVERED BY THE GALE
WARNING.
WINDS DIMINISH LATE TONIGHT BEHIND THE COLD FRONT AS HIGH PRESSURE
APPROACHES THE WATERS. SCA-LEVEL SEAS COULD LINGER INTO TUESDAY
ON THE FAR EASTERN COASTAL WATERS...OTHERWISE SUB-SCA CONDITIONS
ARE EXPECTED TUESDAY AND TUESDAY NIGHT.
THERE WILL BE POTENTIAL EPISODES OF SCA CONDITIONS THROUGHOUT THE
WEEK AS A SERIES OF LOWS IMPACT THE WATERS. THE FIRST OF WHICH WILL
SEND A COLD FRONT ACROSS THE AREA WED NIGHT WITH A STRONG WLY FLOW
ON THE BACKSIDE INTO THU MORNING. HIGH PRESSURE THEN BRIEFLY RETURNS
TO THE WATERS ON THU BEFORE LOW PRESSURE PASSES TO THE SOUTH ON FRI.
FOR NOW GOING WITH SUB-SCA CONDITIONS ON FRIDAY WITH THE COASTAL LOW
PASSING TO THE SOUTH...BUT THERE IS MUCH UNCERTAINTY IN THIS
&&
.HYDROLOGY...
TRACE AMOUNTS OF PCPN ARE POSSIBLE TONIGHT.
THERE IS THE POTENTIAL FOR AROUND A 1/4 TO 1/2 AN INCH OF LIQUID
EQUIVALENT TO FALL OVER THE REGION FROM TUESDAY NIGHT INTO WEDNESDAY
NIGHT. SOME OF THIS COULD FALL AS FROZEN PRECIPITATION ACROSS
MAINLY NORTHERN INTERIOR ZONES INTO WEDNESDAY MORNING. NO
SIGNIFICANT HYDROLOGIC IMPACT IS CURRENTLY EXPECTED.
ADDITIONAL PRECIPITATION IS EXPECTED FROM A SERIES OF LOW
PRESSURE SYSTEMS THAT WILL IMPACT THE AREA LATE IN THE WEEK AND
THE WEEKEND. NO SIGNIFICANT HYDROLOGICAL IMPACTS ARE ANTICIPATED
AT THIS TIME.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 1 AM EST
TUESDAY FOR ANZ330-335-338-340-345-355.
GALE WARNING FROM 10 AM THIS MORNING TO 1 AM EST TUESDAY FOR
ANZ350-353.
&&
$$
SYNOPSIS...KCS/DW
NEAR TERM...KCS
SHORT TERM...KCS
LONG TERM...DW
AVIATION...24
MARINE...KCS/DW
HYDROLOGY...KCS/DW
AREA FORECAST DISCUSSION
NWS NEW YORK NY
1259 AM EST MON DEC 19 2011
.SYNOPSIS...
A HIGH PRESSURE RIDGE WILL DRIFT OVER THE REGION TONIGHT...AND
OFFSHORE ON MONDAY. A COLD FRONT WILL PASS MONDAY NIGHT. HIGH
PRESSURE BUILDS OVER THE AREA TUESDAY. A WARM FRONT APPROACHES
FROM THE SOUTH TUESDAY NIGHT...THEN LIFTS TO THE NORTH
WEDNESDAY...FOLLOWED BY A COLD FRONT WEDNESDAY NIGHT...AS AN AREA
OF LOW PRESSURE PASSES TO OUR NORTH. HIGH PRESSURE THEN BUILDS IN
TO OUR NORTH THURSDAY THROUGH SUNDAY...AS A COUPLE OF LOW PRESSURE
SYSTEMS PASS TO OUR SOUTH FRIDAY AND THEN LATE NEXT WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
HIGH PRESSURE CURRENTLY ALONG THE EAST COAST WILL CONTINUE TO
TRANSLATE SOUTH AND EAST EARLY THIS MORNING. SOME OBS IN CENTRAL
NJ REPORTING LIGHT SW WINDS...INDICATING SW FLOW WILL DEVELOP OVER
THE NEXT FEW HOURS. HIGH AND MID LEVEL CLOUDS OVER UPSTATE NY ARE
MOVING TOWARDS THE AREA BUT DUE TO THE DRY AIR IN PLACE...ONLY
HIGH CLOUDS EXPECTED EARLY THIS MORNING.
TEMP FORECAST ON TRACK WITH JUST MINOR ADJUSTMENTS MADE AT 0530Z. WITH
A SW FLOW BUILDING IN BEHIND THE HIGH PRESSURE EARLY MONDAY
MORNING...TEMPERATURES IN THE NYC METRO AREA AND ON LONG ISLAND
COULD EXPERIENCE A QUICKER WARMING THAN OTHER AREAS.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY NIGHT/...
LOW PRES OVER ONTARIO WILL RACE EWD ON MON UNDER THE INFLUENCE OF
A STRENGTHENING 120KT H3 JET. AS THE ASSOCIATED COLD FRONT
APPROACHES...THE PRES GRAD WILL TIGHTEN...ALLOWING FOR INCREASING
WSW WINDS DURING THE DAY. SUSTAINED WINDS WILL MAX OUT IN THE
15-20KT RANGE WITH SOME GUSTS TO AROUND 30KT. STRONGEST WINDS WILL
BE ALONG THE S SHORES. 12Z OKX SOUNDING INDICATED 0.14 INCHES OF
PW...SO THE FCST WILL BE KEPT DRY DURING THE DAYTIME HOURS WITH
MOISTURE TRANSPORT VECTORS NOT REACHING THE CWA TIL AROUND 00Z
TUE. TEMPS WARMER THAN SUN DUE TO BETTER MIXING ALL AREAS AND AN
ONSHORE COMPONENT ON THE COASTS.
THE COLD FRONT PASSES MON NGT. 12Z MODELS IN GOOD AGREEMENT WITH
THIS. MOISTURE REMAINS EXTREMELY LIMITED...BUT ENOUGH LAKE MOISTURE
MAY ALLOW FOR A FEW SPRINKLES AND/OR FLURRIES. HAVE RETAINED THIS
WEATHER IN THE GRIDS. BL TOO WARM FOR FLAKES NEAR THE COASTS
INITIALLY...BUT AT THE CWA GETS INTO THE RR QUAD OF THE H3 170 PLUS
KT H3 JET AFT MIDNIGHT...A FEW FLURRIES POSSIBLE POST FRONTAL ACROSS
ALL AREAS. MOS WAS IN GOOD AGREEMENT FOR TEMPS...SO A BLEND WAS
USED.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
THE GFS IS MORE PROGRESSIVE THAN THE NAM/ECMWF/SREF WITH THE SYSTEM
IMPACTING THE REGION MID WEEK...AS IS ITS BIAS...SO USED A BLEND OF
THE SLOWER SOLUTIONS TUESDAY THROUGH WEDNESDAY. WEDNESDAY NIGHT
THROUGH CHRISTMAS DAY...THERE ARE QUITE A BIT OF DIFFERENCES BETWEEN
THE GFS AND ECMWF IN HOW THEY HANDLE THE NEXT SYSTEM EJECTING FROM
THE SW U.S. AND ITS INTERACTION WITH THE NORTHERN STREAM. DUE TO
BETTER RUN TO RUN CONSISTENCY AND BETTER OVERALL VERIFICATION IN THE
LONG TERM...LEANED HEAVILY TOWARDS THE ECMWF WEDNESDAY NIGHT THROUGH
SUNDAY.
RIDGING BUILDS INTO THE AREA TUESDAY/TUESDAY NIGHT...THEN SLIDES
OFFSHORE WEDNESDAY AS A SOUTHERN STREAM TROUGH LIFTS INTO THE UPPER
OHIO RIVER VALLEY...THIS TROUGH WILL SUPPORT A SURFACE LOW TRACKING
TO OUR NORTH WEDNESDAY.
TUESDAY SHOULD BE DRY UNDERNEATH THE RIDGE BUILDING IN. OVER RUNNING
SETS UP TUESDAY NIGHT...AHEAD OF A SURFACE AND 850 HPA WARM
FRONT...EXPECT LIGHT PRECIPITATION TO GRADUALLY DEVELOP FROM SW TO
NE FROM TUESDAY NIGHT INTO WEDNESDAY MORNING. LOW LEVEL THERMAL
PROFILES SUPPORT RAIN ACROSS NYC METRO/LONG ISLAND WITH A WINTRY
MIX...INCLUDING POSSIBLY SOME FREEZING RAIN ACROSS THE
INTERIOR...BEFORE CHANGING TO ALL RAIN AS THE WARM FRONT LIFTS TO
THE NORTH WEDNESDAY MORNING. 40-50 KT LOW LEVEL JET MOVES IN BY
WEDNESDAY AFTERNOON SUPPORTING MORE WIDESPREAD RAIN.
THE AFOREMENTIONED TROUGH LIFT JUST OVER THE REGION WEDNESDAY
NIGHT...ALLOWING PRECIPITATION TO TAPER OFF FROM W TO E BY THURSDAY
MORNING - STILL CARRY SLIGHT CHANCE POPS THURSDAY MORNING AS THERE
HAS BEEN SOME UNCERTAINTY IN TIMING OF THE SYSTEM...WITH SOME
SUGGESTIONS IT COULD END UP A TAD SLOWER THAN CURRENTLY FORECAST.
RIDGING BUILDS IN THURSDAY WITH ITS AXIS SLIDING OFFSHORE THURSDAY
NIGHT. FOLLOWING THE ECMWF...IT APPEARS THAT THE SHEARING TROUGH
FORECAST TO LIFT OUT OF BAJA CA WEDNESDAY...APPROACHES BY LATE
THURSDAY NIGHT...THEN CROSSES ON FRIDAY...WITH AN ASSOCIATED
COASTAL LOW PASSING TO THE SOUTH ALONG A STALLED FRONTAL BOUNDARY.
LOW LEVEL THERMAL PROFILES SUGGEST SNOW OR RAIN/SNOW ACROSS NORTHERN
ZONES AND RAIN ACROSS SOUTHERN ZONES BY LATE THURSDAY NIGHT...WITH
PRECIPITATION TRANSITIONING TO ALL RAIN DURING THE DAY ON FRIDAY ON
THE NORTHERN TIER. THERE IS QUITE A BIT OF UNCERTAINTY WITH THIS
SYSTEM...WITH SOME POTENTIAL IT COULD END UP MISSING US ENTIRELY TO
THE SOUTH.
FRIDAY NIGHT AND SATURDAY WILL FEATURE SW FLOW ALOFT...WITH SOME
EMBEDDED SHORTWAVES. THESE WARRANT SLIGHT CHANCE POPS FOR NOW...BUT
MORE THAN LIKELY WILL BE DRY.
THE NEXT POTENTIAL SYSTEM IMPACTS THE REGION LATE CHRISTMAS
EVE/CHRISTMAS DAY...THIS TIME EJECTING FROM NEAR THE FOUR CORNERS
REGION AROUND THURSDAY. LIKE THE SYSTEM FOR FRIDAY...THE SURFACE LOW
WILL TRACK TO THE SOUTH...THE QUESTION IS HOW FAR. FOLLOWING THE
ECMWF...HAVE SLIGHT CHANCE POPS FOR LIGHT SNOW DEVELOPING ACROSS
MOST ZONES LATE SATURDAY NIGHT...AND CONTINUING INTO SUNDAY
MORNING...THEN CHANGING TO RAIN IN THE AFTERNOON. ONCE AGAIN - LOW
CONFIDENCE AT THIS TIME.
NEAR NORMAL TEMPERATURES ARE EXPECTED TUESDAY...THEN ABOVE NORMAL
TEMPERATURES TUESDAY NIGHT THROUGH THURSDAY NIGHT. NEAR NORMAL
TEMPERATURES ARE FORECAST FRIDAY-SUNDAY.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
HIGH PRESSURE OVER THE AREA DRIFTS SOUTH AS A COLD FRONT APPROACHES.
THE FRONT MOVES THROUGH THE TERMINALS LATE MONDAY NIGHT.
VFR. LIGHT AND VARIABLE WINDS BECOME SOUTHWEST LATE. GUSTS DEVELOP
AFTER 15Z MONDAY AND PEAK IN THE EARLY TO MID AFTERNOON 20 TO 25 KT.
OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY...
MONDAY NIGHT...VFR. WEST WINDS SHIFT TO NORTHWEST BEHIND A COLD
FRONT.
TUESDAY...VFR.
TUESDAY NIGHT AND WEDNESDAY...SUB VFR IN RAIN...A WINTRY MIX
POSSIBLE INLAND LATE TUESDAY NIGHT. BECOMING VFR WEDNESDAY NIGHT.
THURSDAY...VFR.
FRIDAY...SUB-VFR POSSIBLE.
&&
.MARINE...
LIGHT WINDS TNGT AS HIGH PRES BUILDS OVER THE WATERS. THE HIGH
DRIFTS E OF THE CSTL WATERS MON...ALLOWING FOR A TIGHTENING PRES
GRAD TO DEVELOP THRU THE DAY AS A COLD FRONT APPROACHES FROM THE W.
STRENGTHENING WSW WINDS WILL BE THE RESULT. SCA WILL REMAIN IN
EFFECT FOR ALL WATERS EXCEPT FOR THE ERN OCEAN...WHERE THE GALE
WATCH WILL BE RETAINED. WINDS WEAKEN INVOF THE FRONT
OVERNIGHT...THEN VEER TO THE NW BEHIND THE FRONT EARLY TUE MRNG.
SCA LEVEL SEAS COULD LINGER INTO TUESDAY ON THE FAR EASTERN COASTAL
WATERS...OTHERWISE SUB-SCA CONDITIONS ARE EXPECTED TUESDAY AND
TUESDAY NIGHT. SOUTHERLY FLOW AHEAD OF A STORM SYSTEM
WEDNESDAY...SHOULD AT LEAST BUILD SEAS ON THE COASTAL OCEAN WATERS
TO SCA LEVELS...WITH GUSTY WINDS CONTINUING THEM AT SCA LEVELS INTO
THURSDAY. THERE IS SOME POTENTIAL FOR SCA LEVEL GUSTS ON ALL WATERS
WEDNESDAY-THURSDAY...BUT NOT QUITE CONFIDENT ENOUGH TO GO WITH THIS
IN THE FORECAST AT THIS TIME.
FOR NOW GOING WITH SUB-SCA CONDITIONS ON FRIDAY WITH A COASTAL LOW
PASSING TO THE SOUTH...BUT THERE IS MUCH UNCERTAINTY IN THIS.
&&
.HYDROLOGY...
TRACE AMOUNTS OF PCPN ARE POSSIBLE MON NGT.
THERE IS THE POTENTIAL FOR AROUND A 1/4 TO 1/2 AN INCH OF LIQUID
EQUIVALENT TO FALL OVER THE REGION FROM TUESDAY NIGHT INTO WEDNESDAY
NIGHT. SOME OF THIS SHOULD FALL AS FROZEN PRECIPITATION ACROSS
MAINLY NORTHERN INTERIOR ZONES INTO WEDNESDAY MORNING. NO
SIGNIFICANT HYDROLOGIC IMPACT IS CURRENTLY EXPECTED.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 1 AM EST
TUESDAY FOR ANZ330-335-338-340-345-355.
GALE WATCH FROM 10 AM EST THIS MORNING THROUGH LATE TONIGHT
FOR ANZ350-353.
&&
$$
SYNOPSIS...JMC/MALOIT
NEAR TERM...KCS
SHORT TERM...JMC/LN
LONG TERM...MALOIT
AVIATION...MET
MARINE...JMC/MALOIT
HYDROLOGY...JMC/MALOIT
AREA FORECAST DISCUSSION
NWS NEW YORK NY
1230 AM EST MON DEC 19 2011
.SYNOPSIS...
A HIGH PRESSURE RIDGE WILL DRIFT OVER THE REGION TONIGHT...AND
OFFSHORE ON MONDAY. A COLD FRONT WILL PASS MONDAY NIGHT. HIGH
PRESSURE BUILDS OVER THE AREA TUESDAY. A WARM FRONT APPROACHES
FROM THE SOUTH TUESDAY NIGHT...THEN LIFTS TO THE NORTH
WEDNESDAY...FOLLOWED BY A COLD FRONT WEDNESDAY NIGHT...AS AN AREA
OF LOW PRESSURE PASSES TO OUR NORTH. HIGH PRESSURE THEN BUILDS IN
TO OUR NORTH THURSDAY THROUGH SUNDAY...AS A COUPLE OF LOW PRESSURE
SYSTEMS PASS TO OUR SOUTH FRIDAY AND THEN LATE NEXT WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
HIGH PRESSURE CURRENTLY OVER THE VIRGINIA COAST WILL CONTINUE TO
TRANSLATE SOUTH AND EAST OVERNIGHT. WINDS ARE CALM IN MOST
LOCATIONS WITH TEMPERATURES ALREADY IN THE TEENS TO AROUND 30 IN
THE NYC METRO AREA. DRY AIR STILL IN PLACE OVER THE AREA WITH THE
LATEST SOUNDING SHOWING PW OF 0.09 IN. HIGH AND MID LEVEL CLOUDS
OVER UPSTATE NY ARE MOVING TOWARDS THE AREA BUT DUE TO THE DRY AIR
IN PLACE...ONLY HIGH CLOUDS EXPECTED OVERNIGHT AND ARE ALREADY
MOVING IN AS OF 02Z OBS.
HAVE UPDATED TEMPERATURES AND DEW POINTS TO REFLECT THE CURRENT
CONDITIONS. WITH A SW FLOW BUILDING IN BEHIND THE HIGH PRESSURE
EARLY MONDAY MORNING...TEMPERATURES IN THE NYC METRO AREA AND ON
LONG ISLAND COULD EXPERIENCE A QUICKER WARMING THAN OTHER AREAS.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY NIGHT/...
LOW PRES OVER ONTARIO WILL RACE EWD ON MON UNDER THE INFLUENCE OF
A STRENGTHENING 120KT H3 JET. AS THE ASSOCIATED COLD FRONT
APPROACHES...THE PRES GRAD WILL TIGHTEN...ALLOWING FOR INCREASING
WSW WINDS DURING THE DAY. SUSTAINED WINDS WILL MAX OUT IN THE
15-20KT RANGE WITH SOME GUSTS TO AROUND 30KT. STRONGEST WINDS WILL
BE ALONG THE S SHORES. 12Z OKX SOUNDING INDICATED 0.14 INCHES OF
PW...SO THE FCST WILL BE KEPT DRY DURING THE DAYTIME HOURS WITH
MOISTURE TRANSPORT VECTORS NOT REACHING THE CWA TIL AROUND 00Z
TUE. TEMPS WARMER THAN SUN DUE TO BETTER MIXING ALL AREAS AND AN
ONSHORE COMPONENT ON THE COASTS.
THE COLD FRONT PASSES MON NGT. 12Z MODELS IN GOOD AGREEMENT WITH
THIS. MOISTURE REMAINS EXTREMELY LIMITED...BUT ENOUGH LAKE MOISTURE
MAY ALLOW FOR A FEW SPRINKLES AND/OR FLURRIES. HAVE RETAINED THIS
WEATHER IN THE GRIDS. BL TOO WARM FOR FLAKES NEAR THE COASTS
INITIALLY...BUT AT THE CWA GETS INTO THE RR QUAD OF THE H3 170 PLUS
KT H3 JET AFT MIDNIGHT...A FEW FLURRIES POSSIBLE POST FRONTAL ACROSS
ALL AREAS. MOS WAS IN GOOD AGREEMENT FOR TEMPS...SO A BLEND WAS
USED.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
THE GFS IS MORE PROGRESSIVE THAN THE NAM/ECMWF/SREF WITH THE SYSTEM
IMPACTING THE REGION MID WEEK...AS IS ITS BIAS...SO USED A BLEND OF
THE SLOWER SOLUTIONS TUESDAY THROUGH WEDNESDAY. WEDNESDAY NIGHT
THROUGH CHRISTMAS DAY...THERE ARE QUITE A BIT OF DIFFERENCES BETWEEN
THE GFS AND ECMWF IN HOW THEY HANDLE THE NEXT SYSTEM EJECTING FROM
THE SW U.S. AND ITS INTERACTION WITH THE NORTHERN STREAM. DUE TO
BETTER RUN TO RUN CONSISTENCY AND BETTER OVERALL VERIFICATION IN THE
LONG TERM...LEANED HEAVILY TOWARDS THE ECMWF WEDNESDAY NIGHT THROUGH
SUNDAY.
RIDGING BUILDS INTO THE AREA TUESDAY/TUESDAY NIGHT...THEN SLIDES
OFFSHORE WEDNESDAY AS A SOUTHERN STREAM TROUGH LIFTS INTO THE UPPER
OHIO RIVER VALLEY...THIS TROUGH WILL SUPPORT A SURFACE LOW TRACKING
TO OUR NORTH WEDNESDAY.
TUESDAY SHOULD BE DRY UNDERNEATH THE RIDGE BUILDING IN. OVER RUNNING
SETS UP TUESDAY NIGHT...AHEAD OF A SURFACE AND 850 HPA WARM
FRONT...EXPECT LIGHT PRECIPITATION TO GRADUALLY DEVELOP FROM SW TO
NE FROM TUESDAY NIGHT INTO WEDNESDAY MORNING. LOW LEVEL THERMAL
PROFILES SUPPORT RAIN ACROSS NYC METRO/LONG ISLAND WITH A WINTRY
MIX...INCLUDING POSSIBLY SOME FREEZING RAIN ACROSS THE
INTERIOR...BEFORE CHANGING TO ALL RAIN AS THE WARM FRONT LIFTS TO
THE NORTH WEDNESDAY MORNING. 40-50 KT LOW LEVEL JET MOVES IN BY
WEDNESDAY AFTERNOON SUPPORTING MORE WIDESPREAD RAIN.
THE AFOREMENTIONED TROUGH LIFT JUST OVER THE REGION WEDNESDAY
NIGHT...ALLOWING PRECIPITATION TO TAPER OFF FROM W TO E BY THURSDAY
MORNING - STILL CARRY SLIGHT CHANCE POPS THURSDAY MORNING AS THERE
HAS BEEN SOME UNCERTAINTY IN TIMING OF THE SYSTEM...WITH SOME
SUGGESTIONS IT COULD END UP A TAD SLOWER THAN CURRENTLY FORECAST.
RIDGING BUILDS IN THURSDAY WITH ITS AXIS SLIDING OFFSHORE THURSDAY
NIGHT. FOLLOWING THE ECMWF...IT APPEARS THAT THE SHEARING TROUGH
FORECAST TO LIFT OUT OF BAJA CA WEDNESDAY...APPROACHES BY LATE
THURSDAY NIGHT...THEN CROSSES ON FRIDAY...WITH AN ASSOCIATED
COASTAL LOW PASSING TO THE SOUTH ALONG A STALLED FRONTAL BOUNDARY.
LOW LEVEL THERMAL PROFILES SUGGEST SNOW OR RAIN/SNOW ACROSS NORTHERN
ZONES AND RAIN ACROSS SOUTHERN ZONES BY LATE THURSDAY NIGHT...WITH
PRECIPITATION TRANSITIONING TO ALL RAIN DURING THE DAY ON FRIDAY ON
THE NORTHERN TIER. THERE IS QUITE A BIT OF UNCERTAINTY WITH THIS
SYSTEM...WITH SOME POTENTIAL IT COULD END UP MISSING US ENTIRELY TO
THE SOUTH.
FRIDAY NIGHT AND SATURDAY WILL FEATURE SW FLOW ALOFT...WITH SOME
EMBEDDED SHORTWAVES. THESE WARRANT SLIGHT CHANCE POPS FOR NOW...BUT
MORE THAN LIKELY WILL BE DRY.
THE NEXT POTENTIAL SYSTEM IMPACTS THE REGION LATE CHRISTMAS
EVE/CHRISTMAS DAY...THIS TIME EJECTING FROM NEAR THE FOUR CORNERS
REGION AROUND THURSDAY. LIKE THE SYSTEM FOR FRIDAY...THE SURFACE LOW
WILL TRACK TO THE SOUTH...THE QUESTION IS HOW FAR. FOLLOWING THE
ECMWF...HAVE SLIGHT CHANCE POPS FOR LIGHT SNOW DEVELOPING ACROSS
MOST ZONES LATE SATURDAY NIGHT...AND CONTINUING INTO SUNDAY
MORNING...THEN CHANGING TO RAIN IN THE AFTERNOON. ONCE AGAIN - LOW
CONFIDENCE AT THIS TIME.
NEAR NORMAL TEMPERATURES ARE EXPECTED TUESDAY...THEN ABOVE NORMAL
TEMPERATURES TUESDAY NIGHT THROUGH THURSDAY NIGHT. NEAR NORMAL
TEMPERATURES ARE FORECAST FRIDAY-SUNDAY.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
HIGH PRESSURE OVER THE AREA DRIFTS SOUTH AS A COLD FRONT APPROACHES.
THE FRONT MOVES THROUGH THE TERMINALS LATE MONDAY NIGHT.
VFR. LIGHT AND VARIABLE WINDS BECOME SOUTHWEST LATE. GUSTS DEVELOP
AFTER 15Z MONDAY AND PEAK IN THE EARLY TO MID AFTERNOON 20 TO 25 KT.
OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY...
MONDAY NIGHT...VFR. WEST WINDS SHIFT TO NORTHWEST BEHIND A COLD
FRONT.
TUESDAY...VFR.
TUESDAY NIGHT AND WEDNESDAY...SUB VFR IN RAIN...A WINTRY MIX
POSSIBLE INLAND LATE TUESDAY NIGHT. BECOMING VFR WEDNESDAY NIGHT.
THURSDAY...VFR.
FRIDAY...SUB-VFR POSSIBLE.
&&
.MARINE...
LIGHT WINDS TNGT AS HIGH PRES BUILDS OVER THE WATERS. THE HIGH
DRIFTS E OF THE CSTL WATERS MON...ALLOWING FOR A TIGHTENING PRES
GRAD TO DEVELOP THRU THE DAY AS A COLD FRONT APPROACHES FROM THE W.
STRENGTHENING WSW WINDS WILL BE THE RESULT. SCA WILL REMAIN IN
EFFECT FOR ALL WATERS EXCEPT FOR THE ERN OCEAN...WHERE THE GALE
WATCH WILL BE RETAINED. WINDS WEAKEN INVOF THE FRONT
OVERNIGHT...THEN VEER TO THE NW BEHIND THE FRONT EARLY TUE MRNG.
SCA LEVEL SEAS COULD LINGER INTO TUESDAY ON THE FAR EASTERN COASTAL
WATERS...OTHERWISE SUB-SCA CONDITIONS ARE EXPECTED TUESDAY AND
TUESDAY NIGHT. SOUTHERLY FLOW AHEAD OF A STORM SYSTEM
WEDNESDAY...SHOULD AT LEAST BUILD SEAS ON THE COASTAL OCEAN WATERS
TO SCA LEVELS...WITH GUSTY WINDS CONTINUING THEM AT SCA LEVELS INTO
THURSDAY. THERE IS SOME POTENTIAL FOR SCA LEVEL GUSTS ON ALL WATERS
WEDNESDAY-THURSDAY...BUT NOT QUITE CONFIDENT ENOUGH TO GO WITH THIS
IN THE FORECAST AT THIS TIME.
FOR NOW GOING WITH SUB-SCA CONDITIONS ON FRIDAY WITH A COASTAL LOW
PASSING TO THE SOUTH...BUT THERE IS MUCH UNCERTAINTY IN THIS.
&&
.HYDROLOGY...
TRACE AMOUNTS OF PCPN ARE POSSIBLE MON NGT.
THERE IS THE POTENTIAL FOR AROUND A 1/4 TO 1/2 AN INCH OF LIQUID
EQUIVALENT TO FALL OVER THE REGION FROM TUESDAY NIGHT INTO WEDNESDAY
NIGHT. SOME OF THIS SHOULD FALL AS FROZEN PRECIPITATION ACROSS
MAINLY NORTHERN INTERIOR ZONES INTO WEDNESDAY MORNING. NO
SIGNIFICANT HYDROLOGIC IMPACT IS CURRENTLY EXPECTED.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 1 AM EST
TUESDAY FOR ANZ330-335-338-340-345-355.
GALE WATCH FROM 10 AM EST THIS MORNING THROUGH LATE TONIGHT
FOR ANZ350-353.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
334 PM CST MON DEC 19 2011
.DISCUSSION...
333 PM CST
THE FORECAST CHALLENGES CENTER ON PRECIPITATION TYPE AND AMOUNTS
WITH THE WEATHER SYSTEM TUESDAY INTO WEDNESDAY...FOLLOWED BY
ANOTHER SYSTEM LATE IN THE WEEK.
/SHORT TERM....TONIGHT THROUGH WEDNESDAY...
SYNOPSIS...THE VIGOROUS WELL-DEFINED UPPER LOW CONTINUES TO
EVOLVE EAST INTO THE TX PANHANDLE THIS AFTERNOON. THE MOISTURE
CANOPY IS EXPANDING NORTH AND SPREADING ACROSS THE
REGION...OVERRIDING LOW-LEVEL COLD AIR ADVECTION BEHIND A FRONT
WHICH WILL STALL NEAR THE I-70 CORRIDOR. THIS FRONT SWUNG WINDS TO
THE NORTH AND DROPPED OUR ANOMALOUSLY WARM MORNING TEMPERATURES
AND HIGH DEW POINTS. THERE WAS EVEN A LAKE BREEZE WITH THE
TEMPERATURE DISCONTINUITY DESPITE THE MONTH BEING DECEMBER. THE
LOWEST TEMPERATURES IN UPSTREAM WI ARE AROUND 30...AND GIVEN THE
EXPANSIVE CLOUD COVER EXPECTED...DO NOT SEE TEMPERATURES TONIGHT
FALLING MUCH BELOW THAT ANYWHERE.
NUMERICAL GUIDANCE PREFERENCE...MODELS CONTINUE WELL CLUSTERED ON
THE SURFACE LOW TRACK WITH THIS SYSTEM. THE 19.12 NAM IS SLIGHTLY
FURTHER NORTH THAN THE GFS...BUT THE GFS IS MORE MOIST WITH THE
WARM AIR RETURN...AND THUS THEY ARE FAIRLY CLOSE WITH THE SUPPORT
FOR PRECIPITATION ON TUESDAY. WRF MODELS AND SREF PROBABILITIES
GENERALLY SUPPORT THEIR OUTPUT. SO HAVE FOLLOWED A BLEND OF THESE
TWO MODELS CLOSELY FOR FORCING...AND THE SLIGHTLY DRIER NAM FOR
FORECAST SOUNDINGS.
PRECIPITATION TONIGHT...THE ELEVATED WARM FRONT...AND THE
NORTHERN PERIPHERY OF MOISTURE TRANSPORT...WILL INCH NORTH INTO
THE SOUTHERN FORECAST AREA THIS EVENING AND SLOWLY NORTH FROM
THERE OVERNIGHT. ISENTROPIC UPGLIDE BECOMES GRADUALLY MORE ROBUST
INTO THE FAR SOUTH. DURING THE EVENING...THE COLUMN IS TOO WARM
FOR ANYTHING BUT RAIN AND AMOUNTS SHOULD GENERALLY BE LIGHT. AS
FOR OVERNIGHT...SLIGHTLY STRONGER QG FORCING MAY COOL THE COLUMN
ENOUGH TO SUPPORT SNOW LOOKING AT NAM/GFS SOUNDINGS AND THICKNESS
REGIMES. THIS WOULD SEEM MOST FAVORED ALONG THE NORTHERN
PERIPHERY OF THE PRECIPITATION SHIELD...WHICH SHOULD BE A TIGHT
GRADIENT GIVEN A STRONG DRY LAYER INDICATED NEAR 800MB ON THE NAM.
ANY SNOW AMOUNTS SHOULD BE LIGHT WITH A LOW RATIO TO WATER
EQUIVALENT.
TUESDAY...THE STRONGEST MOISTURE ADVECTION IS FOCUSED IN THE
SOUTHEAST FORECAST AREA...BUT ELEVATED UPGLIDE WITHIN GENERAL
HEIGHT FALLS WILL EVOLVE NORTH OVER THE AREA. OVER THE PAST THREE
RUNS ON THE NAM AND GFS...THE NORTHERN EXTENT OF PRECIPITATION AT
18Z ON TUESDAY HAS SLOWED DOWN. THIS WAS SOMEWHAT EXPECTED GIVEN
THE DRIER AIR IN THE LOWER LEVELS. NAM SOUNDINGS IN THE NORTHERN
PORTIONS OF THE PRECIPITATION SHIELD WOULD SUPPORT SNOW...WITH
MAXIMUM WET BULBS IN THE COLUMN ONLY AROUND ZERO. IF STRONGER
FRONTOGENETIC FORCING CAN ESTABLISH ITSELF ON THE NORTHERN
EDGE...SNOW AND OR A MIX WOULD BE MORE POSSIBLE. THE NEAR ZERO
LAYER IS PROJECTED TO BE DEEP /3000 TO 4000 FT/ FROM PONTIAC TO
RENSSELAER AT DAYBREAK AND CREEPING NORTHWARD. THIS IS EXPECTED TO
BE WITHIN 2000 FT...AND POSSIBLY ALL THE WAY TO THE SURFACE. SO
SMALL CHANCES FOR SLEET AND FREEZING RAIN STILL EXIST...ESPECIALLY
IN THE LACK OF STRONG FORCING WHICH IS THE CASE DURING THE
MORNING. CONDITIONAL SREF PROBABILITIES FOR FREEZING RAIN ON THE
19.15 SREF REMAIN NEAR 50 PERCENT AT THE NORTHERN EXTENT OF THE
RAIN SHIELD. THE KEY IS THAT THE SREF NOR THE NAM AND GFS ARE
PRODUCING MUCH FOR QPF BUT A FEW HUNDREDTHS. THE LATER THE
PRECIPITATION SPREADS INTO AN AREA DURING TUESDAY MORNING THE
LOWER CHANCE FOR IT TO BE ANYTHING FREEZING...AS THE MORNING
MINIMUM TEMPERATURES SHOULD BOTTOM OUT ONLY NEAR 30 AND THEN INCH
UP DURING THE MORNING. BY AFTERNOON...THE SURFACE TEMPERATURE
ENVELOPE IN THE GUIDANCE LOOKS HIGHLY LIKELY TO BE ABOVE FREEZING
WITH THE COLUMN SUPPORTING RAIN SOUTH OF INTERSTATE 80 AND LIKELY
RAIN WITH A CHANCE FOR A MIX TO THE NORTH. AGAIN...QPF AMOUNTS ARE
STILL GENERALLY LIGHT IN THE CORRIDOR THAT WOULD POTENTIALLY SEE
A MIX.
TUESDAY NIGHT...CONFIDENCE IN THIS PERIOD LOWERS SOME ON POPS AS
THE MAIN MOISTURE RETURN AXIS SHIFTS EAST AND THE UPPER LOW IS
STILL BACK TOWARDS KANSAS CITY AT 00Z. WITH THE AREA BEING NOT FAR
FROM THE NOSE OF THE DRY SLOT...ENOUGH DYNAMIC SUPPORT SHOULD BE
IN PLACE FOR SOME PRECIPITATION...INCLUDING POSSIBLY DRIZZLE...SO
HAVE GONE LIKELY WITH WORDING. TOWARDS THE WI STATE LINE AND
OVERNIGHT IN THE WESTERN FORECAST AREA...THERE WILL CONTINUE TO
BE A CHANCE TO MIX WITH SNOW BASED ON THE GFS SOUNDINGS AND SREF
PROBABILITIES. AGAIN ANY SNOW AMOUNTS SHOULD BE TEMPERED WITH THE
FAIRLY WARM COLUMN. SO OUTSIDE OF THE SOUTH AND EAST WHERE RAIN
AMOUNTS OVER ONE QUARTER OF AN INCH ARE ANTICIPATED...MUCH OF
THIS EVENT THROUGH TUESDAY NIGHT MAY BEST BE CHARACTERIZED BY
BEING A HIGH POP/LOW QPF EVENT.
WEDNESDAY...THE UPPER LOW WILL OPEN UP AS A WAVE AS IT PROGRESSES
OVER THE AREA ..GETTING PICKED UP BY THE NORTHERN STREAM. WITH THE
STRONG VORT...QG FORCING IS PRONOUNCED ACROSS THE AREA. HAVE
INCREASED POPS ACROSS THE EASTERN FORECAST AREA DURING THE MORNING
HOURS...AND THIS MAY NEED TO BE EXPANDED BACK WEST. THE STRONGER
DYNAMICS IF THEY MATERIALIZE WOULD LIKELY FAVOR SNOW OVER RAIN.
SOME MINOR ACCUMULATIONS UNDER AN INCH COULD BE SEEN WITH THAT.
THE COLD AIR ADVECTION IN THE LOW-LEVELS BEHIND THE SYSTEM IS
LIMITED...WITH TEMPERATURES LIKELY ONLY TO DROP SOME UNDER
PRECIPITATION DURING THE MORNING.
/LONG TERM...THURSDAY THROUGH MONDAY...
WHILE DECENT INTRA-MODEL CONSISTENCY EXISTS IN THE DAYS 3-7/HOLIDAY
WEEKEND PERIOD IN THE LARGER SCALE FEATURES (WITH TROFFING IN THE
INTERMOUNTAIN WEST AND RIDGING OVER EASTERN NORTH AMERICA) THERE ARE
HUGE DIFFERENCES IN THE SMALLER SCALE FEATURES THAT WILL DICTATE
THE SENSIBLE WEATHER FOR THE LOCAL AREA. OF PRIMARY CONCERN ARE
CHANCES OF LIGHT SNOW DURING THE FRIDAY INTO SATURDAY PERIOD SHOULD
NORTHERN AND SOUTHERN STREAMS PHASE AND AN INVERTED SFC TROF AND
CLOSED MID-LEVEL LOW SPREAD A SWATH OF LIGHT SNOW ACROSS THE
REGION.
DIFFERENCES IN MODEL SOLUTIONS REMAIN CONSIDERABLE WITH GFS THE MOST
BULLISH WITH THE ABOVE SCENARIO... HOLDING SW UPPER LOW BACK AT
FIRST AND BRINGING IT EASTWARD SLOWLY... ALLOWING ADDITIONAL
MOISTURE TO BE DRAWN NORTH AND EVENTUALLY A SURFACE LOW FORMING IN
RESPONSE TO LOWERING HEIGHTS ALOFT. THE NEW 12Z ECMWF CONTINUES TO
DEPICT BETTER FORCING ALONG A WEAK COLD FRONT THAT SAGS SOUTHEAST
ACROSS THE AREA THURSDAY NIGHT AHEAD OF ANY POSSIBLE UPPER AND THEN
SFC LOW INTERACTION THE GFS ADVERTISES... ALTHOUGH THIS LATEST EC
RUN DOES SHOW SOME SLIGHT TRENDING TOWARD THE 12Z GFS SOLUTION. THE
12Z GEM PUTS FORTH A SIGNIFICANTLY DIFFERENT SCENARIO THAT FANS OF A
WHITE CHRISTMAS WILL NOT LIKE... HOLDING THE SW UPPER LOW BACK OVER
NEW MEXICO EVEN INTO SATURDAY WITH MUCH LESS PHASING OF NORTHERN AND
SOUTHERN STREAMS. AS A RESULT... IT PROGS STRONG SURFACE RIDGING
AND ANTI-CYCLONIC FLOW DEVELOPING INTO NRN IL AND NW IN FRI NIGHT
INTO SAT.
GIVE THE ABOVE THE DAYS 3-7 FORECAST FOR THIS PACKAGE WILL BE A
COMPROMISE. THE WIDE DISPARITY IN THE MEDIUM RANGE MAY NOT BE RESOLVED
UNTIL FEATURES AND PARAMETERS MOVE INTO THE SHORT TERM. THE
RESULTING SLIGHT CHC POPS THURS NIGHT THROUGH SAT AFTERNOON IN THE
FORECAST SHOULD BE INTERPRETED THAT AS OF NOW AT LEAST ONE AND
POSSIBLY A COUPLE OF BRIEF DURATION LIGHT SNOW EVENTS ARE EXPECTED
DURING THE PERIOD. THE BEST ADVICE WE CAN GIVE THOSE TRAVELING OVER
THE BUSY HOLIDAY WEEKEND IS TO CONTINUE TO MONITOR THE FORECAST FOR
UPDATES... AS THE EVENT DRAWS NEARER WE WILL BE BETTER ABLE TO
REFINE EXACTLY WHEN AND WHERE.
MTF/ED F
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* ONGOING FROPA...MVFR CIGS BEHIND THE FRONT
* WIND SHIFT TO WEST THEN NORTHWEST...THEN NORTHEAST
* OCCNL WIND GUSTS THIS AFTERNOON
* PRECIP CHANCES/TYPE TUES MORNING
SHEA
//DISCUSSION...20Z UPDATE...
DID FURTHER TWEAKING TO THE CIG AND WIND FORECAST...EXPECT WINDS
TO CONTINUE TO FLIP AROUND TO THE NORTH AND NORTHEAST OVER THE
COURSE OF THE NEXT FEW HOURS. RUC/NAM AND HRRR GUIDANCE ALL
INDICATE IT OCCURRING IN THE 21-22Z HOUR. MKE AND RAC HAVE ALREADY
FLIPPED FROM 310 TO 350 TO 030 OVER THE COURSE OF A FEW HOURS.
EXPECT TO SEE ENW NEXT...FOLLOWED BY UGN...PWK AND THEN ORD/MDW.
CURRENTLY SEE A RARE DECEMBER LAKE BREEZE ON TORD...AND TIMING
TROUGH ORD/MDW LOOKS TO BE RIGHT IN LINE WITH EARLIER
THINKING...AND AROUND THE 2130 HOUR. OTHERWISE CIG TRENDS DO NOT
LOOK SUPPORTIVE OF LOW END MVFR...AND TRENDED THAT WAY.
SHEA
//DISCUSSION...PREVIOUS 18Z...
VFR CONDITIONS FOR THE TERMINALS WILL BE QUICKLY COMING TO A CLOSE
AS STRATUS SLIDES IN FROM THE NORTH BEHIND A FRONT THAT IS
CURRENTLY SHIFTING THROUGH THE REGION. WINDS AHEAD OF THE FRONT
WILL RANGE FROM 250-280 DEGREES...VEERING TO THE 320 TO 340 RANGE
BEHIND IT. WINDS ARE EXPECTED TO MAINTAIN THE MID TO UPPER TEEN
GUSTS THROUGH THE AFTERNOON AND INTO THE EVENING HOURS. MOST
LOCATIONS WILL SEE THE FRONT SLIDE THROUGH WITHIN THE HOUR...WITH
GYY BEING THE EXCEPTION...JUST ANOTHER HOUR BEYOND. THE MAIN PUSH
OF STRATUS FROM THE NORTH HAD BEEN PRETTY WELL TIMED TO BE AT OR
BEYOND THE 20-21Z HOUR...BUT THE LATEST VISIBLE SATELLITE IMAGERY
IS SHOWING A BIT OF AN ACCELERATION ALONG THE LEADING EDGE. MAY
NEED TO TWEAK THE TIMING OF THE MVFR CIGS SLIGHTLY FOR THE 20Z
AMD. EXPECT CIGS TO FALL INTO THE 015-018 RANGE FOR A FEW HOURS
ONCE IT MOVES THROUGH... BUT INDICATIONS POINT TOWARDS A LEVELING
OFF AND GRADUAL RISE A FEW HOURS BEHIND TO MID AND UPPER LEVEL
MVFR. NOT OVERLY CONFIDENT THAT CIGS WILL FALL TO LOW END MVFR OR
IFR RANGE...BUT THERE IS THE POSSIBILITY THAT COULD HAPPEN FOR A
VERY SHORT TIME. WINDS WILL THEN CONTINUE TO WORK AROUND THE
COMPASS DIAL...GRADUALLY REACHING NORTH...NORTHEAST AND EAST BY
TOMORROW MORNING. THE NEXT CHANCES FOR PRECIP WILL ARRIVE
TOMORROW... AS ANOTHER SYSTEM LIFTS OUT OF THE MISSISSIPPI VALLEY.
THERE ARE STILL SOME UNCERTAIN VARIABLES PERTAINING TO TIMING /AS
TRENDS HAVE BEEN SLOWING/ AS WELL AS P-TYPE.
SHEA
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* MOD-HIGH CONFIDENCE IN CIG TREND/TIMING FORECAST
** LOW CONFIDENCE ON LOW END MVFR CIG POTENTIAL
* MOD-HIGH CONFIDENCE ON WIND FORECAST
* LOW CONFIDENCE ON PRECIP TYPE/TIMING TUES MORNING
SHEA
//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...
TUESDAY NIGHT...RAIN LIKELY. MVFR/IFR CIGS.
WEDNESDAY...CHC OF RAIN AND SNOW. MVFR CIGS BECOMING VFR LATE.
THURSDAY...MAINLY VFR. SCHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...MVFR WITH A CHC OF SNOW LATE.
SATURDAY...SCHC RAIN OR SNOW THEN SCHC OF SNOW LATE. MVFR/IFR CIGS.
SUNDAY...MVFR CIGS BECOMING VFR.
JEE
&&
.MARINE...
227 PM...A COLD FRONT CONTINUES TO MOVE SOUTHEAST ACROSS THE
SOUTHERN GREAT LAKES REGION THIS AFTERNOON AND IS EXPECTED TO
DISSIPATE AS IT PUSHES SOUTH INTO THE OHIO VALLEY TONIGHT. A LARGE
RIDGE OF HIGH PRESSURE ACROSS THE NORTHERN PLAINS WILL BUILD
ACROSS THE CENTRAL LAKES TONIGHT AND AS IT DOES...THE GRADIENT IS
EXPECTED TO TIGHTEN ACROSS THE SOUTHERN HALF OR SO OF LAKE
MICHIGAN THIS EVENING. NORTHERLY WINDS 20-25KTS WILL TURN
NORTHEAST AND THEN BEGIN TO DIMINISH OVERNIGHT AS THE HIGH
CONTINUES EAST AND THE GRADIENT WEAKENS SOME. LOW PRESSURE
DEVELOPING OVER NORTHERN TEXAS WILL LIFT NORTHEAST TONIGHT AND
TUESDAY REACHING THE SOUTHERN LAKES REGION BY WEDNESDAY
MORNING...AS IT WEAKENS. ANOTHER COLD FRONT IS EXPECTED TO PUSH
SOUTH ACROSS THE LAKES REGION THURSDAY INTO THURSDAY NIGHT. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...6 PM MONDAY TO 10 AM TUESDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
227 PM CST MON DEC 19 2011
.DISCUSSION...
319 AM CST
THE MAIN FORECAST CONCERNS CENTER AROUND PRECIP TYPE AND COVERAGE
TONIGHT INTO WEDNESDAY AS LOW PRESSURE MOVES NORTHEASTWARD FROM
NORTHERN TEXAS TO NORTHERN OHIO IN CONJUNCTION WITH AN UPPER LOW.
SATELLITE MOISTURE CHANNEL IMAGERY SHOWS SEVERAL KEY FEATURES THAT
WILL DRIVE OUR WEATHER THROUGH MID-WEEK. THE FIRST IS A LOW
AMPLITUDE UPPER LEVEL TROUGH EXTENDING FROM HUDSON BAY SOUTHWESTWARD
AND MOVING TO THE EAST. A SECOND WAVE IN THE UPPER FLOW IS
POSITIONED JUST TO THE SOUTHWEST OF THE FIRST FROM CENTRAL MANITOBA
SOUTHWESTWARD INTO THE NORTHERN U.S. ROCKIES. THE NEXT AND MOST
SIGNIFICANT FEATURE IS THE CUTOFF UPPER LOW SPINNING OVER THE
ARIZONA/NEW MEXICO/MEXICO BORDER WHICH WILL LIFT NORTHEASTWARD AND BRING
US A MIX OF PRECIPITATION TUESDAY AND WEDNESDAY. AT THE
SURFACE...LOW PRESSURE JUST NORTHEAST OF LAKE SUPERIOR ASSOCIATED
WITH THE HUDSON BAY REGION TROUGH CONTINUES TO MOVE EASTWARD WITH A
COLD FRONT EXTENDING SOUTHWESTWARD ACROSS NORTHERN LAKE
HURON...SOUTHERN LAKE MICHIGAN AND BACK INTO NORTHEAST KANSAS.
PRESSURE FALLS ARE ALSO FOUND ACROSS NEW MEXICO AND WEST TEXAS IN
CONJUNCTION WITH THE APPROACHING UPPER LOW.
TODAY AND TONIGHT...MILD AND MOIST SOUTHWESTERLY LOW LEVEL FLOW
CONTINUES ACROSS THE AREA EARLY THIS MORNING AHEAD OF THE
APPROACHING FRONTAL BOUNDARY. TEMPS HAD RISEN SEVERAL DEGREES SINCE
LAST EVENING WITH BREEZY SOUTHWEST WINDS GUSTING TO AROUND 20 KT AND
AN INFLUX OF CLOUD COVER. SPEEDS HAVE STARTED TO SLACKEN SOMEWHAT AS
THE GRADIENT WEAKENS SLIGHTLY AS THE FRONTAL TROUGH APPROACHES SO
TEMPS MAY DROP A FEW DEGREES THROUGH DAYBREAK. THE FRONT WILL CROSS
THE AREA THIS MORNING SHIFTING WINDS TO THE NORTHWEST THEN NORTH.
TEMPS PROBABLY WILL NOT WARM MUCH NORTHWEST WITH MODEST COLD
ADVECTION BUILDING IN BUT SOUTHEASTERN AREAS SHOULD SEE HIGHS A FEW
DEGREES WARMER THAN MORNING TEMPS. MAY SEE TEMPS DROP A FEW DEGREES
DURING THE AFTERNOON IN THE NORTHWEST. LOW CLOUD COVER WILL BE
PERSISTENT THROUGH THE DAY BUT NORTHWEST AREAS WILL LIKELY SEE SOME
BREAKS OF SUNSHINE. FRONTAL FORCING IS WEAK BUT MOISTURE WILL
CONTINUE TO STREAM NORTHEASTWARD ACROSS THE EASTERN HALF OF THE AREA
WITH DECENT HEIGHT FALLS OCCURRING ALOFT. WILL CONTINUE SLIGHT
CHANCE FOR SPRINKLES FAR SOUTH AND EAST.
TONIGHT AND TUESDAY...HIGH PRESSURE WILL SPREAD ACROSS THE NORTHERN PLAINS
AND UPPER MISSISSIPPI RIVER VALLEY INTO THIS EVENING WITH THE
SOUTHERN PERIPHERY PUSHING INTO NORTHERN ILLINOIS. THE COOL FRONT
WILL STALL OUT FROM NORTHERN OHIO SOUTHWEST ACROSS CENTRAL ILLINOIS
AND BACK INTO NORTHEAST OKLAHOMA JOINING UP WITH DEVELOPING LOW
PRESSURE OVER THE TX/OK BORDER. A SHARP MID LEVEL BAROCLINIC ZONE
WILL SET UP FROM NORTHERN OHIO BACK ACROSS CENTRAL ILLINOIS AND
NORTHERN MISSOURI AS THE MANITOBA UPPER TROUGH TRANSLATES ACROSS THE
GREAT LAKES AND BROAD UPPER RIDGING PIVOTS EASTWARD ACROSS THE LOWER
MISSISSIPPI RIVER VALLEY AHEAD OF THE APPROACHING UPPER LOW. HIGH
THETA-E AIR WILL STREAM NORTHWARD INTO THE TEMP GRADIENT RESULTING
IN A BLOSSOMING OF PRECIPITATION ALONG IT STARTING THIS TODAY. WITH
THE HIGH SPREADING ACROSS THE UPPER MS VALLEY INTO THE GREAT LAKES
AND A NORTHEAST LOW LEVEL TRAJECTORY...DRY AIR WILL NEED TO BE
OVERCOME BEFORE PRECIP CAN SPREAD INTO THE SOUTHERN CWA TONIGHT.
EXPECT A SHARP CUTOFF TO THE PRECIP ON ITS NORTHERN FLANK AND AM
THINKING THAT PRECIP WILL ARRIVE ALONG AND SOUTH OF A
PONTIAC-KANKAKEE-RENSSELAER LINE TOWARD 06Z THEN MAKE SLOW NORTHWARD
PROGRESS THROUGH DAYBREAK. EXPECT PRECIP TYPE IN THESE AREAS TO BE
ALL RAIN BUT TYPE BECOMES MORE OF A CHALLENGE TO THE NORTH TUESDAY
MORNING. FORCING LOOKS TO BECOME LESS ORGANIZED TOWARDS INTERSTATE
80 BUT THERE WILL BE A THREAT FOR LIGHT PRECIP STARTING TUESDAY
MORNING. SURFACE TEMPS NORTH OF THE PNT-IKK-RZL LINE WILL PROBABLY
BE AT OR JUST BELOW FREEZING AND COOL SLIGHTLY NORTHWARD TOWARD
I-80. BASED ON FORECAST SOUNDINGS PRECIP WOULD LIKELY START OUT AS
SNOW BUT MAY TRANSITION TO RAIN OR FREEZING RAIN AS THE MID LEVELS
WARM BUT THE COOL/DRY NORTHEASTERLY LOW LEVEL FLOW CONTINUES
UNDERNEATH. LOW LEVEL TEMPS WILL WARM DIURNALLY HOWEVER...AND A
CHANGE OVER TO PRIMARILY RAIN IS EXPECTED TOWARD MIDDAY. LOW PRECIP
CHANCES WILL SPREAD NORTHWARD THE IL/WI BORDER INTO EARLY AFTERNOON
WITH SLIGHTLY WARMING TEMP PROFILES SUPPORTING A RAIN SNOW MIX FROM
ROUGHLY INTERSTATE 88 NORTH.
TUESDAY NIGHT AND WEDNESDAY...THE UPPER LOW WILL BE OVER NORTHEAST
KANSAS WITH THE SURFACE LOW SOMEWHERE OVER SOUTHERN OR SOUTHEAST
MISSOURI. PRETTY GOOD MODEL AGREEMENT ON A DRY PUSH OF AIR LIFTING
NORTHEASTWARD TOWARD LAKE MICHIGAN LATE TUESDAY AFTERNOON AND EARLY
TUESDAY EVENING WHICH SHOULD LIMIT PRECIP CHANCES SOMEWHAT THROUGH
THE EVENING AND POSSIBLY INTO THE EARLY OVERNIGHT. PRECIP TYPE
DURING THIS TIME SHOULD BE RAIN...EXCEPT FAR NORTHWEST WHERE RAIN
AND SNOW MAY MIX. THINGS BECOME MORE CHALLENGING OVERNIGHT AND
WEDNESDAY MORNING AS THE SURFACE LOW PASSES TO THE SOUTHEAST AND THE
UPPER LOW LIFTS NORTHEAST RIGHT ACROSS THE AREA. MID LEVEL FORCING
WILL INCREASE AS DEFORMATION DEVELOPS IN CONJUNCTION WITH Q-VECTOR
CONVERGENCE RESULTING IN ADDITIONAL BANDS OF PRECIP SPREADING IN
FROM THE SOUTHWEST AFTER MIDNIGHT THROUGH MUCH OF WEDNESDAY MORNING.
COLDER AIR WILL WRAP IN...ESPECIALLY ALOFT...LEADING TO A TOUGH
P-TYPE FORECAST. RIGHT NOW EXPECT THAT RAIN WILL MIX WITH AND
POSSIBLY CHANGE TO SNOW INTO WEDNESDAY MORNING ACROSS THE
NORTHWESTERN HALF OF THE AREA OR ROUGHLY WEST OF A CHICAGO TO
PONTIAC LINE...WITH A BETTER CHANCE FOR ALL RAIN TO THE EAST BUT A
MIX MAY OCCUR AS WELL. MODEL AGREEMENT IS SOMEWHAT LACKING IN TERMS
OF THE THERMAL PROFILE SO CONFIDENCE IS LIMITED IN THE DETAILS.
CONCEPTUALLY SPEAKING...AM ALSO CONCERNED THAT IF FORCING CAN BECOME
STRONG THEN DYNAMIC COOLING PROCESSES UNDER THE CORE OF COLDEST AIR
MAY RESULT IN A BAND OF ALL SNOW...WHICH COULD BECOME SOMEWHAT
INTENSE FOR A SHORT TIME. THIS WOULD BE FAST MOVING BUT A STRIPE OF
LOW END ACCUMULATION MAY OCCUR. COLD ADVECTION BEHIND THE DEPARTING
TROUGH IS NOT TERRIBLY STRONG GIVEN THAT WEAK UPPER RIDGING WILL
BUILD IN BEHIND IT SO WE MAY SEE SOME DIURNAL WARMING...ESPECIALLY
IF CLOUDS CAN BREAK UP.
THURSDAY THROUGH MONDAY...WEAK UPPER RIDGING WILL DAMPEN OVER THE
AREA WITH ANOTHER UPPER TROUGH SPREADING ACROSS THE FOUR CORNERS
INTO THE CENTRAL ROCKIES. THE UPPER FLOW LOOKS TO BE AT LEAST
SOMEWHAT SPLIT WITH A TROUGH ACROSS SOUTHERN CANADA. THIS MAY RESULT
IN A TIGHTENING MID LEVEL TEMP GRADIENT FROM SOUTHERN QUEBEC BACK
TOWARDS NEBRASKA THURSDAY WHICH WILL THEN SETTLE SOUTHWARD INTO THE
AREA THURSDAY NIGHT. DOES NOT APPEAR TO BE MUCH FORCING ASSOCIATED
WITH THIS BUT WILL NEED TO WATCH THE NEED FOR LOW PRECIP CHANCES.
THE SOUTHERN STREAM TROUGH WILL TRACK EAST-NORTHEASTWARD ACROSS THE
MID MISSISSIPPI RIVER VALLEY AND PUSH A SURFACE LOW NORTHEASTWARD
SOMEWHERE ACROSS THE OHIO VALLEY SATURDAY. THE ECMWF AND GFS ARE IN
REASONABLE AGREEMENT WITH THE EXISTENCE OF THESE FEATURES BUT DIFFER
ON TRACK WHICH HAS A SIGNIFICANT IMPACT ON OUR SENSIBLE WEATHER. A
WESTERLY TRACK WOULD BRING SNOW TO THE AREA FRIDAY NIGHT AND
SATURDAY. TOO EARLY FOR ANY KIND OF DETAILS BUT MOISTURE CONTENT
DOES NOT LOOK TERRIBLY HIGH SO ACCUMULATION MAY BE MINIMAL SHOULD
PRECIP OCCUR. BEYOND THAT...ANOTHER TROUGH LOOKS TO FOLLOW THE FIRST
BRINGING A PUSH OF NOTICEABLY COLDER AIR IN FOR SUNDAY BUT LARGE
SCALE RIDGING LOOKS TO QUICKLY BRING MILDER AIR BACK TO THE REGION
EARLY NEXT WEEK.
MDB
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* ONGOING FROPA...MVFR CIGS BEHIND THE FRONT
* WIND SHIFT TO WEST THEN NORTHWEST...THEN NORTHEAST
* OCCNL WIND GUSTS THIS AFTERNOON
* PRECIP CHANCES/TYPE TUES MORNING
SHEA
//DISCUSSION...20Z UPDATE...
DID FURTHER TWEAKING TO THE CIG AND WIND FORECAST...EXPECT WINDS
TO CONTINUE TO FLIP AROUND TO THE NORTH AND NORTHEAST OVER THE
COURSE OF THE NEXT FEW HOURS. RUC/NAM AND HRRR GUIDANCE ALL
INDICATE IT OCCURRING IN THE 21-22Z HOUR. MKE AND RAC HAVE ALREADY
FLIPPED FROM 310 TO 350 TO 030 OVER THE COURSE OF A FEW HOURS.
EXPECT TO SEE ENW NEXT...FOLLOWED BY UGN...PWK AND THEN ORD/MDW.
CURRENTLY SEE A RARE DECEMBER LAKE BREEZE ON TORD...AND TIMING
TROUGH ORD/MDW LOOKS TO BE RIGHT IN LINE WITH EARLIER
THINKING...AND AROUND THE 2130 HOUR. OTHERWISE CIG TRENDS DO NOT
LOOK SUPPORTIVE OF LOW END MVFR...AND TRENDED THAT WAY.
SHEA
//DISCUSSION...PREVIOUS 18Z...
VFR CONDITIONS FOR THE TERMINALS WILL BE QUICKLY COMING TO A CLOSE
AS STRATUS SLIDES IN FROM THE NORTH BEHIND A FRONT THAT IS
CURRENTLY SHIFTING THROUGH THE REGION. WINDS AHEAD OF THE FRONT
WILL RANGE FROM 250-280 DEGREES...VEERING TO THE 320 TO 340 RANGE
BEHIND IT. WINDS ARE EXPECTED TO MAINTAIN THE MID TO UPPER TEEN
GUSTS THROUGH THE AFTERNOON AND INTO THE EVENING HOURS. MOST
LOCATIONS WILL SEE THE FRONT SLIDE THROUGH WITHIN THE HOUR...WITH
GYY BEING THE EXCEPTION...JUST ANOTHER HOUR BEYOND. THE MAIN PUSH
OF STRATUS FROM THE NORTH HAD BEEN PRETTY WELL TIMED TO BE AT OR
BEYOND THE 20-21Z HOUR...BUT THE LATEST VISIBLE SATELLITE IMAGERY
IS SHOWING A BIT OF AN ACCELERATION ALONG THE LEADING EDGE. MAY
NEED TO TWEAK THE TIMING OF THE MVFR CIGS SLIGHTLY FOR THE 20Z
AMD. EXPECT CIGS TO FALL INTO THE 015-018 RANGE FOR A FEW HOURS
ONCE IT MOVES THROUGH... BUT INDICATIONS POINT TOWARDS A LEVELING
OFF AND GRADUAL RISE A FEW HOURS BEHIND TO MID AND UPPER LEVEL
MVFR. NOT OVERLY CONFIDENT THAT CIGS WILL FALL TO LOW END MVFR OR
IFR RANGE...BUT THERE IS THE POSSIBILITY THAT COULD HAPPEN FOR A
VERY SHORT TIME. WINDS WILL THEN CONTINUE TO WORK AROUND THE
COMPASS DIAL...GRADUALLY REACHING NORTH...NORTHEAST AND EAST BY
TOMORROW MORNING. THE NEXT CHANCES FOR PRECIP WILL ARRIVE
TOMORROW... AS ANOTHER SYSTEM LIFTS OUT OF THE MISSISSIPPI VALLEY.
THERE ARE STILL SOME UNCERTAIN VARIABLES PERTAINING TO TIMING /AS
TRENDS HAVE BEEN SLOWING/ AS WELL AS P-TYPE.
SHEA
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* MOD-HIGH CONFIDENCE IN CIG TREND/TIMING FORECAST
** LOW CONFIDENCE ON LOW END MVFR CIG POTENTIAL
* MOD-HIGH CONFIDENCE ON WIND FORECAST
* LOW CONFIDENCE ON PRECIP TYPE/TIMING TUES MORNING
SHEA
//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...
TUESDAY NIGHT...RAIN LIKELY. MVFR/IFR CIGS.
WEDNESDAY...CHC OF RAIN AND SNOW. MVFR CIGS BECOMING VFR LATE.
THURSDAY...MAINLY VFR. SCHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...MVFR WITH A CHC OF SNOW LATE.
SATURDAY...SCHC RAIN OR SNOW THEN SCHC OF SNOW LATE. MVFR/IFR CIGS.
SUNDAY...MVFR CIGS BECOMING VFR.
JEE
&&
.MARINE...
227 PM...A COLD FRONT CONTINUES TO MOVE SOUTHEAST ACROSS THE
SOUTHERN GREAT LAKES REGION THIS AFTERNOON AND IS EXPECTED TO
DISSIPATE AS IT PUSHES SOUTH INTO THE OHIO VALLEY TONIGHT. A LARGE
RIDGE OF HIGH PRESSURE ACROSS THE NORTHERN PLAINS WILL BUILD
ACROSS THE CENTRAL LAKES TONIGHT AND AS IT DOES...THE GRADIENT IS
EXPECTED TO TIGHTEN ACROSS THE SOUTHERN HALF OR SO OF LAKE
MICHIGAN THIS EVENING. NORTHERLY WINDS 20-25KTS WILL TURN
NORTHEAST AND THEN BEGIN TO DIMINISH OVERNIGHT AS THE HIGH
CONTINUES EAST AND THE GRADIENT WEAKENS SOME. LOW PRESSURE
DEVELOPING OVER NORTHERN TEXAS WILL LIFT NORTHEAST TONIGHT AND
TUESDAY REACHING THE SOUTHERN LAKES REGION BY WEDNESDAY
MORNING...AS IT WEAKENS. ANOTHER COLD FRONT IS EXPECTED TO PUSH
SOUTH ACROSS THE LAKES REGION THURSDAY INTO THURSDAY NIGHT. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...6 PM MONDAY TO 10 AM TUESDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
207 PM CST MON DEC 19 2011
.DISCUSSION...
319 AM CST
THE MAIN FORECAST CONCERNS CENTER AROUND PRECIP TYPE AND COVERAGE
TONIGHT INTO WEDNESDAY AS LOW PRESSURE MOVES NORTHEASTWARD FROM
NORTHERN TEXAS TO NORTHERN OHIO IN CONJUNCTION WITH AN UPPER LOW.
SATELLITE MOISTURE CHANNEL IMAGERY SHOWS SEVERAL KEY FEATURES THAT
WILL DRIVE OUR WEATHER THROUGH MID-WEEK. THE FIRST IS A LOW
AMPLITUDE UPPER LEVEL TROUGH EXTENDING FROM HUDSON BAY SOUTHWESTWARD
AND MOVING TO THE EAST. A SECOND WAVE IN THE UPPER FLOW IS
POSITIONED JUST TO THE SOUTHWEST OF THE FIRST FROM CENTRAL MANITOBA
SOUTHWESTWARD INTO THE NORTHERN U.S. ROCKIES. THE NEXT AND MOST
SIGNIFICANT FEATURE IS THE CUTOFF UPPER LOW SPINNING OVER THE
ARIZONA/NEW MEXICO/MEXICO BORDER WHICH WILL LIFT NORTHEASTWARD AND BRING
US A MIX OF PRECIPITATION TUESDAY AND WEDNESDAY. AT THE
SURFACE...LOW PRESSURE JUST NORTHEAST OF LAKE SUPERIOR ASSOCIATED
WITH THE HUDSON BAY REGION TROUGH CONTINUES TO MOVE EASTWARD WITH A
COLD FRONT EXTENDING SOUTHWESTWARD ACROSS NORTHERN LAKE
HURON...SOUTHERN LAKE MICHIGAN AND BACK INTO NORTHEAST KANSAS.
PRESSURE FALLS ARE ALSO FOUND ACROSS NEW MEXICO AND WEST TEXAS IN
CONJUNCTION WITH THE APPROACHING UPPER LOW.
TODAY AND TONIGHT...MILD AND MOIST SOUTHWESTERLY LOW LEVEL FLOW
CONTINUES ACROSS THE AREA EARLY THIS MORNING AHEAD OF THE
APPROACHING FRONTAL BOUNDARY. TEMPS HAD RISEN SEVERAL DEGREES SINCE
LAST EVENING WITH BREEZY SOUTHWEST WINDS GUSTING TO AROUND 20 KT AND
AN INFLUX OF CLOUD COVER. SPEEDS HAVE STARTED TO SLACKEN SOMEWHAT AS
THE GRADIENT WEAKENS SLIGHTLY AS THE FRONTAL TROUGH APPROACHES SO
TEMPS MAY DROP A FEW DEGREES THROUGH DAYBREAK. THE FRONT WILL CROSS
THE AREA THIS MORNING SHIFTING WINDS TO THE NORTHWEST THEN NORTH.
TEMPS PROBABLY WILL NOT WARM MUCH NORTHWEST WITH MODEST COLD
ADVECTION BUILDING IN BUT SOUTHEASTERN AREAS SHOULD SEE HIGHS A FEW
DEGREES WARMER THAN MORNING TEMPS. MAY SEE TEMPS DROP A FEW DEGREES
DURING THE AFTERNOON IN THE NORTHWEST. LOW CLOUD COVER WILL BE
PERSISTENT THROUGH THE DAY BUT NORTHWEST AREAS WILL LIKELY SEE SOME
BREAKS OF SUNSHINE. FRONTAL FORCING IS WEAK BUT MOISTURE WILL
CONTINUE TO STREAM NORTHEASTWARD ACROSS THE EASTERN HALF OF THE AREA
WITH DECENT HEIGHT FALLS OCCURRING ALOFT. WILL CONTINUE SLIGHT
CHANCE FOR SPRINKLES FAR SOUTH AND EAST.
TONIGHT AND TUESDAY...HIGH PRESSURE WILL SPREAD ACROSS THE NORTHERN PLAINS
AND UPPER MISSISSIPPI RIVER VALLEY INTO THIS EVENING WITH THE
SOUTHERN PERIPHERY PUSHING INTO NORTHERN ILLINOIS. THE COOL FRONT
WILL STALL OUT FROM NORTHERN OHIO SOUTHWEST ACROSS CENTRAL ILLINOIS
AND BACK INTO NORTHEAST OKLAHOMA JOINING UP WITH DEVELOPING LOW
PRESSURE OVER THE TX/OK BORDER. A SHARP MID LEVEL BAROCLINIC ZONE
WILL SET UP FROM NORTHERN OHIO BACK ACROSS CENTRAL ILLINOIS AND
NORTHERN MISSOURI AS THE MANITOBA UPPER TROUGH TRANSLATES ACROSS THE
GREAT LAKES AND BROAD UPPER RIDGING PIVOTS EASTWARD ACROSS THE LOWER
MISSISSIPPI RIVER VALLEY AHEAD OF THE APPROACHING UPPER LOW. HIGH
THETA-E AIR WILL STREAM NORTHWARD INTO THE TEMP GRADIENT RESULTING
IN A BLOSSOMING OF PRECIPITATION ALONG IT STARTING THIS TODAY. WITH
THE HIGH SPREADING ACROSS THE UPPER MS VALLEY INTO THE GREAT LAKES
AND A NORTHEAST LOW LEVEL TRAJECTORY...DRY AIR WILL NEED TO BE
OVERCOME BEFORE PRECIP CAN SPREAD INTO THE SOUTHERN CWA TONIGHT.
EXPECT A SHARP CUTOFF TO THE PRECIP ON ITS NORTHERN FLANK AND AM
THINKING THAT PRECIP WILL ARRIVE ALONG AND SOUTH OF A
PONTIAC-KANKAKEE-RENSSELAER LINE TOWARD 06Z THEN MAKE SLOW NORTHWARD
PROGRESS THROUGH DAYBREAK. EXPECT PRECIP TYPE IN THESE AREAS TO BE
ALL RAIN BUT TYPE BECOMES MORE OF A CHALLENGE TO THE NORTH TUESDAY
MORNING. FORCING LOOKS TO BECOME LESS ORGANIZED TOWARDS INTERSTATE
80 BUT THERE WILL BE A THREAT FOR LIGHT PRECIP STARTING TUESDAY
MORNING. SURFACE TEMPS NORTH OF THE PNT-IKK-RZL LINE WILL PROBABLY
BE AT OR JUST BELOW FREEZING AND COOL SLIGHTLY NORTHWARD TOWARD
I-80. BASED ON FORECAST SOUNDINGS PRECIP WOULD LIKELY START OUT AS
SNOW BUT MAY TRANSITION TO RAIN OR FREEZING RAIN AS THE MID LEVELS
WARM BUT THE COOL/DRY NORTHEASTERLY LOW LEVEL FLOW CONTINUES
UNDERNEATH. LOW LEVEL TEMPS WILL WARM DIURNALLY HOWEVER...AND A
CHANGE OVER TO PRIMARILY RAIN IS EXPECTED TOWARD MIDDAY. LOW PRECIP
CHANCES WILL SPREAD NORTHWARD THE IL/WI BORDER INTO EARLY AFTERNOON
WITH SLIGHTLY WARMING TEMP PROFILES SUPPORTING A RAIN SNOW MIX FROM
ROUGHLY INTERSTATE 88 NORTH.
TUESDAY NIGHT AND WEDNESDAY...THE UPPER LOW WILL BE OVER NORTHEAST
KANSAS WITH THE SURFACE LOW SOMEWHERE OVER SOUTHERN OR SOUTHEAST
MISSOURI. PRETTY GOOD MODEL AGREEMENT ON A DRY PUSH OF AIR LIFTING
NORTHEASTWARD TOWARD LAKE MICHIGAN LATE TUESDAY AFTERNOON AND EARLY
TUESDAY EVENING WHICH SHOULD LIMIT PRECIP CHANCES SOMEWHAT THROUGH
THE EVENING AND POSSIBLY INTO THE EARLY OVERNIGHT. PRECIP TYPE
DURING THIS TIME SHOULD BE RAIN...EXCEPT FAR NORTHWEST WHERE RAIN
AND SNOW MAY MIX. THINGS BECOME MORE CHALLENGING OVERNIGHT AND
WEDNESDAY MORNING AS THE SURFACE LOW PASSES TO THE SOUTHEAST AND THE
UPPER LOW LIFTS NORTHEAST RIGHT ACROSS THE AREA. MID LEVEL FORCING
WILL INCREASE AS DEFORMATION DEVELOPS IN CONJUNCTION WITH Q-VECTOR
CONVERGENCE RESULTING IN ADDITIONAL BANDS OF PRECIP SPREADING IN
FROM THE SOUTHWEST AFTER MIDNIGHT THROUGH MUCH OF WEDNESDAY MORNING.
COLDER AIR WILL WRAP IN...ESPECIALLY ALOFT...LEADING TO A TOUGH
P-TYPE FORECAST. RIGHT NOW EXPECT THAT RAIN WILL MIX WITH AND
POSSIBLY CHANGE TO SNOW INTO WEDNESDAY MORNING ACROSS THE
NORTHWESTERN HALF OF THE AREA OR ROUGHLY WEST OF A CHICAGO TO
PONTIAC LINE...WITH A BETTER CHANCE FOR ALL RAIN TO THE EAST BUT A
MIX MAY OCCUR AS WELL. MODEL AGREEMENT IS SOMEWHAT LACKING IN TERMS
OF THE THERMAL PROFILE SO CONFIDENCE IS LIMITED IN THE DETAILS.
CONCEPTUALLY SPEAKING...AM ALSO CONCERNED THAT IF FORCING CAN BECOME
STRONG THEN DYNAMIC COOLING PROCESSES UNDER THE CORE OF COLDEST AIR
MAY RESULT IN A BAND OF ALL SNOW...WHICH COULD BECOME SOMEWHAT
INTENSE FOR A SHORT TIME. THIS WOULD BE FAST MOVING BUT A STRIPE OF
LOW END ACCUMULATION MAY OCCUR. COLD ADVECTION BEHIND THE DEPARTING
TROUGH IS NOT TERRIBLY STRONG GIVEN THAT WEAK UPPER RIDGING WILL
BUILD IN BEHIND IT SO WE MAY SEE SOME DIURNAL WARMING...ESPECIALLY
IF CLOUDS CAN BREAK UP.
THURSDAY THROUGH MONDAY...WEAK UPPER RIDGING WILL DAMPEN OVER THE
AREA WITH ANOTHER UPPER TROUGH SPREADING ACROSS THE FOUR CORNERS
INTO THE CENTRAL ROCKIES. THE UPPER FLOW LOOKS TO BE AT LEAST
SOMEWHAT SPLIT WITH A TROUGH ACROSS SOUTHERN CANADA. THIS MAY RESULT
IN A TIGHTENING MID LEVEL TEMP GRADIENT FROM SOUTHERN QUEBEC BACK
TOWARDS NEBRASKA THURSDAY WHICH WILL THEN SETTLE SOUTHWARD INTO THE
AREA THURSDAY NIGHT. DOES NOT APPEAR TO BE MUCH FORCING ASSOCIATED
WITH THIS BUT WILL NEED TO WATCH THE NEED FOR LOW PRECIP CHANCES.
THE SOUTHERN STREAM TROUGH WILL TRACK EAST-NORTHEASTWARD ACROSS THE
MID MISSISSIPPI RIVER VALLEY AND PUSH A SURFACE LOW NORTHEASTWARD
SOMEWHERE ACROSS THE OHIO VALLEY SATURDAY. THE ECMWF AND GFS ARE IN
REASONABLE AGREEMENT WITH THE EXISTENCE OF THESE FEATURES BUT DIFFER
ON TRACK WHICH HAS A SIGNIFICANT IMPACT ON OUR SENSIBLE WEATHER. A
WESTERLY TRACK WOULD BRING SNOW TO THE AREA FRIDAY NIGHT AND
SATURDAY. TOO EARLY FOR ANY KIND OF DETAILS BUT MOISTURE CONTENT
DOES NOT LOOK TERRIBLY HIGH SO ACCUMULATION MAY BE MINIMAL SHOULD
PRECIP OCCUR. BEYOND THAT...ANOTHER TROUGH LOOKS TO FOLLOW THE FIRST
BRINGING A PUSH OF NOTICEABLY COLDER AIR IN FOR SUNDAY BUT LARGE
SCALE RIDGING LOOKS TO QUICKLY BRING MILDER AIR BACK TO THE REGION
EARLY NEXT WEEK.
MDB
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* ONGOING FROPA...MVFR CIGS BEHIND THE FRONT
* WIND SHIFT TO WEST THEN NORTHWEST...THEN NORTHEAST
* OCCNL WIND GUSTS THIS AFTERNOON
* PRECIP CHANCES/TYPE TUES MORNING
SHEA
//DISCUSSION...20Z UPDATE...
DID FURTHER TWEAKING TO THE CIG AND WIND FORECAST...EXPECT WINDS
TO CONTINUE TO FLIP AROUND TO THE NORTH AND NORTHEAST OVER THE
COURSE OF THE NEXT FEW HOURS. RUC/NAM AND HRRR GUIDANCE ALL
INDICATE IT OCCURRING IN THE 21-22Z HOUR. MKE AND RAC HAVE ALREADY
FLIPPED FROM 310 TO 350 TO 030 OVER THE COURSE OF A FEW HOURS.
EXPECT TO SEE ENW NEXT...FOLLOWED BY UGN...PWK AND THEN ORD/MDW.
CURRENTLY SEE A RARE DECEMBER LAKE BREEZE ON TORD...AND TIMING
TROUGH ORD/MDW LOOKS TO BE RIGHT IN LINE WITH EARLIER
THINKING...AND AROUND THE 2130 HOUR. OTHERWISE CIG TRENDS DO NOT
LOOK SUPPORTIVE OF LOW END MVFR...AND TRENDED THAT WAY.
SHEA
//DISCUSSION...PREVIOUS 18Z...
VFR CONDITIONS FOR THE TERMINALS WILL BE QUICKLY COMING TO A CLOSE
AS STRATUS SLIDES IN FROM THE NORTH BEHIND A FRONT THAT IS
CURRENTLY SHIFTING THROUGH THE REGION. WINDS AHEAD OF THE FRONT
WILL RANGE FROM 250-280 DEGREES...VEERING TO THE 320 TO 340 RANGE
BEHIND IT. WINDS ARE EXPECTED TO MAINTAIN THE MID TO UPPER TEEN
GUSTS THROUGH THE AFTERNOON AND INTO THE EVENING HOURS. MOST
LOCATIONS WILL SEE THE FRONT SLIDE THROUGH WITHIN THE HOUR...WITH
GYY BEING THE EXCEPTION...JUST ANOTHER HOUR BEYOND. THE MAIN PUSH
OF STRATUS FROM THE NORTH HAD BEEN PRETTY WELL TIMED TO BE AT OR
BEYOND THE 20-21Z HOUR...BUT THE LATEST VISIBLE SATELLITE IMAGERY
IS SHOWING A BIT OF AN ACCELERATION ALONG THE LEADING EDGE. MAY
NEED TO TWEAK THE TIMING OF THE MVFR CIGS SLIGHTLY FOR THE 20Z
AMD. EXPECT CIGS TO FALL INTO THE 015-018 RANGE FOR A FEW HOURS
ONCE IT MOVES THROUGH... BUT INDICATIONS POINT TOWARDS A LEVELING
OFF AND GRADUAL RISE A FEW HOURS BEHIND TO MID AND UPPER LEVEL
MVFR. NOT OVERLY CONFIDENT THAT CIGS WILL FALL TO LOW END MVFR OR
IFR RANGE...BUT THERE IS THE POSSIBILITY THAT COULD HAPPEN FOR A
VERY SHORT TIME. WINDS WILL THEN CONTINUE TO WORK AROUND THE
COMPASS DIAL...GRADUALLY REACHING NORTH...NORTHEAST AND EAST BY
TOMORROW MORNING. THE NEXT CHANCES FOR PRECIP WILL ARRIVE
TOMORROW... AS ANOTHER SYSTEM LIFTS OUT OF THE MISSISSIPPI VALLEY.
THERE ARE STILL SOME UNCERTAIN VARIABLES PERTAINING TO TIMING /AS
TRENDS HAVE BEEN SLOWING/ AS WELL AS P-TYPE.
SHEA
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* MOD-HIGH CONFIDENCE IN CIG TREND/TIMING FORECAST
** LOW CONFIDENCE ON LOW END MVFR CIG POTENTIAL
* MOD-HIGH CONFIDENCE ON WIND FORECAST
* LOW CONFIDENCE ON PRECIP TYPE/TIMING TUES MORNING
SHEA
//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...
TUESDAY NIGHT...RAIN LIKELY. MVFR/IFR CIGS.
WEDNESDAY...CHC OF RAIN AND SNOW. MVFR CIGS BECOMING VFR LATE.
THURSDAY...MAINLY VFR. SCHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...MVFR WITH A CHC OF SNOW LATE.
SATURDAY...SCHC RAIN OR SNOW THEN SCHC OF SNOW LATE. MVFR/IFR CIGS.
SUNDAY...MVFR CIGS BECOMING VFR.
JEE
&&
.MARINE...
206 AM CST
SOUTHWESTERLY GALES WILL CONTINUE FOR THE NEXT FEW HOURS AHEAD OF AN
APPROACHING COLD FRONT. AS THE FRONT PASSES ACROSS THE LAKE THIS
MORNING AND EARLY AFTERNOON...THE WINDS WILL VEER OUT OF THE NORTH
TO 20 TO 25 KT. A SURFACE RIDGE OF HIGH PRESSURE WILL PUSH ACROSS THE
LAKE MONDAY NIGHT INTO TUESDAY AS LOW PRESSURE TAKES SHAPE ACROSS
THE SOUTHERN PLAINS. THIS LOW WILL EVENTUALLY TRACK NORTHEASTWARD
ACROSS THE OHIO VALLEY BY WEDNESDAY.
LATER IN THE WEEK ANOTHER COLD FRONT LOOKS TO DROP SOUTH OUT OF
CANADA AND ACROSS LAKE MICHIGAN. HIGH PRESSURE BUILDING ACROSS THE
PLAINS SHOULD SET UP A DECENT GRADIENT ACROSS THE LAKE. THIS COULD
LEAD TO A PERIOD OF 15 TO 25 KT WINDS LATE THURSDAY INTO FRIDAY
BEFORE THE HIGH SHIFTS EAST ACROSS THE GREAT LAKES.
KJB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...6 PM MONDAY TO 10 AM TUESDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
133 PM CST MON DEC 19 2011
.DISCUSSION...
319 AM CST
THE MAIN FORECAST CONCERNS CENTER AROUND PRECIP TYPE AND COVERAGE
TONIGHT INTO WEDNESDAY AS LOW PRESSURE MOVES NORTHEASTWARD FROM
NORTHERN TEXAS TO NORTHERN OHIO IN CONJUNCTION WITH AN UPPER LOW.
SATELLITE MOISTURE CHANNEL IMAGERY SHOWS SEVERAL KEY FEATURES THAT
WILL DRIVE OUR WEATHER THROUGH MID-WEEK. THE FIRST IS A LOW
AMPLITUDE UPPER LEVEL TROUGH EXTENDING FROM HUDSON BAY SOUTHWESTWARD
AND MOVING TO THE EAST. A SECOND WAVE IN THE UPPER FLOW IS
POSITIONED JUST TO THE SOUTHWEST OF THE FIRST FROM CENTRAL MANITOBA
SOUTHWESTWARD INTO THE NORTHERN U.S. ROCKIES. THE NEXT AND MOST
SIGNIFICANT FEATURE IS THE CUTOFF UPPER LOW SPINNING OVER THE
ARIZONA/NEW MEXICO/MEXICO BORDER WHICH WILL LIFT NORTHEASTWARD AND BRING
US A MIX OF PRECIPITATION TUESDAY AND WEDNESDAY. AT THE
SURFACE...LOW PRESSURE JUST NORTHEAST OF LAKE SUPERIOR ASSOCIATED
WITH THE HUDSON BAY REGION TROUGH CONTINUES TO MOVE EASTWARD WITH A
COLD FRONT EXTENDING SOUTHWESTWARD ACROSS NORTHERN LAKE
HURON...SOUTHERN LAKE MICHIGAN AND BACK INTO NORTHEAST KANSAS.
PRESSURE FALLS ARE ALSO FOUND ACROSS NEW MEXICO AND WEST TEXAS IN
CONJUNCTION WITH THE APPROACHING UPPER LOW.
TODAY AND TONIGHT...MILD AND MOIST SOUTHWESTERLY LOW LEVEL FLOW
CONTINUES ACROSS THE AREA EARLY THIS MORNING AHEAD OF THE
APPROACHING FRONTAL BOUNDARY. TEMPS HAD RISEN SEVERAL DEGREES SINCE
LAST EVENING WITH BREEZY SOUTHWEST WINDS GUSTING TO AROUND 20 KT AND
AN INFLUX OF CLOUD COVER. SPEEDS HAVE STARTED TO SLACKEN SOMEWHAT AS
THE GRADIENT WEAKENS SLIGHTLY AS THE FRONTAL TROUGH APPROACHES SO
TEMPS MAY DROP A FEW DEGREES THROUGH DAYBREAK. THE FRONT WILL CROSS
THE AREA THIS MORNING SHIFTING WINDS TO THE NORTHWEST THEN NORTH.
TEMPS PROBABLY WILL NOT WARM MUCH NORTHWEST WITH MODEST COLD
ADVECTION BUILDING IN BUT SOUTHEASTERN AREAS SHOULD SEE HIGHS A FEW
DEGREES WARMER THAN MORNING TEMPS. MAY SEE TEMPS DROP A FEW DEGREES
DURING THE AFTERNOON IN THE NORTHWEST. LOW CLOUD COVER WILL BE
PERSISTENT THROUGH THE DAY BUT NORTHWEST AREAS WILL LIKELY SEE SOME
BREAKS OF SUNSHINE. FRONTAL FORCING IS WEAK BUT MOISTURE WILL
CONTINUE TO STREAM NORTHEASTWARD ACROSS THE EASTERN HALF OF THE AREA
WITH DECENT HEIGHT FALLS OCCURRING ALOFT. WILL CONTINUE SLIGHT
CHANCE FOR SPRINKLES FAR SOUTH AND EAST.
TONIGHT AND TUESDAY...HIGH PRESSURE WILL SPREAD ACROSS THE NORTHERN PLAINS
AND UPPER MISSISSIPPI RIVER VALLEY INTO THIS EVENING WITH THE
SOUTHERN PERIPHERY PUSHING INTO NORTHERN ILLINOIS. THE COOL FRONT
WILL STALL OUT FROM NORTHERN OHIO SOUTHWEST ACROSS CENTRAL ILLINOIS
AND BACK INTO NORTHEAST OKLAHOMA JOINING UP WITH DEVELOPING LOW
PRESSURE OVER THE TX/OK BORDER. A SHARP MID LEVEL BAROCLINIC ZONE
WILL SET UP FROM NORTHERN OHIO BACK ACROSS CENTRAL ILLINOIS AND
NORTHERN MISSOURI AS THE MANITOBA UPPER TROUGH TRANSLATES ACROSS THE
GREAT LAKES AND BROAD UPPER RIDGING PIVOTS EASTWARD ACROSS THE LOWER
MISSISSIPPI RIVER VALLEY AHEAD OF THE APPROACHING UPPER LOW. HIGH
THETA-E AIR WILL STREAM NORTHWARD INTO THE TEMP GRADIENT RESULTING
IN A BLOSSOMING OF PRECIPITATION ALONG IT STARTING THIS TODAY. WITH
THE HIGH SPREADING ACROSS THE UPPER MS VALLEY INTO THE GREAT LAKES
AND A NORTHEAST LOW LEVEL TRAJECTORY...DRY AIR WILL NEED TO BE
OVERCOME BEFORE PRECIP CAN SPREAD INTO THE SOUTHERN CWA TONIGHT.
EXPECT A SHARP CUTOFF TO THE PRECIP ON ITS NORTHERN FLANK AND AM
THINKING THAT PRECIP WILL ARRIVE ALONG AND SOUTH OF A
PONTIAC-KANKAKEE-RENSSELAER LINE TOWARD 06Z THEN MAKE SLOW NORTHWARD
PROGRESS THROUGH DAYBREAK. EXPECT PRECIP TYPE IN THESE AREAS TO BE
ALL RAIN BUT TYPE BECOMES MORE OF A CHALLENGE TO THE NORTH TUESDAY
MORNING. FORCING LOOKS TO BECOME LESS ORGANIZED TOWARDS INTERSTATE
80 BUT THERE WILL BE A THREAT FOR LIGHT PRECIP STARTING TUESDAY
MORNING. SURFACE TEMPS NORTH OF THE PNT-IKK-RZL LINE WILL PROBABLY
BE AT OR JUST BELOW FREEZING AND COOL SLIGHTLY NORTHWARD TOWARD
I-80. BASED ON FORECAST SOUNDINGS PRECIP WOULD LIKELY START OUT AS
SNOW BUT MAY TRANSITION TO RAIN OR FREEZING RAIN AS THE MID LEVELS
WARM BUT THE COOL/DRY NORTHEASTERLY LOW LEVEL FLOW CONTINUES
UNDERNEATH. LOW LEVEL TEMPS WILL WARM DIURNALLY HOWEVER...AND A
CHANGE OVER TO PRIMARILY RAIN IS EXPECTED TOWARD MIDDAY. LOW PRECIP
CHANCES WILL SPREAD NORTHWARD THE IL/WI BORDER INTO EARLY AFTERNOON
WITH SLIGHTLY WARMING TEMP PROFILES SUPPORTING A RAIN SNOW MIX FROM
ROUGHLY INTERSTATE 88 NORTH.
TUESDAY NIGHT AND WEDNESDAY...THE UPPER LOW WILL BE OVER NORTHEAST
KANSAS WITH THE SURFACE LOW SOMEWHERE OVER SOUTHERN OR SOUTHEAST
MISSOURI. PRETTY GOOD MODEL AGREEMENT ON A DRY PUSH OF AIR LIFTING
NORTHEASTWARD TOWARD LAKE MICHIGAN LATE TUESDAY AFTERNOON AND EARLY
TUESDAY EVENING WHICH SHOULD LIMIT PRECIP CHANCES SOMEWHAT THROUGH
THE EVENING AND POSSIBLY INTO THE EARLY OVERNIGHT. PRECIP TYPE
DURING THIS TIME SHOULD BE RAIN...EXCEPT FAR NORTHWEST WHERE RAIN
AND SNOW MAY MIX. THINGS BECOME MORE CHALLENGING OVERNIGHT AND
WEDNESDAY MORNING AS THE SURFACE LOW PASSES TO THE SOUTHEAST AND THE
UPPER LOW LIFTS NORTHEAST RIGHT ACROSS THE AREA. MID LEVEL FORCING
WILL INCREASE AS DEFORMATION DEVELOPS IN CONJUNCTION WITH Q-VECTOR
CONVERGENCE RESULTING IN ADDITIONAL BANDS OF PRECIP SPREADING IN
FROM THE SOUTHWEST AFTER MIDNIGHT THROUGH MUCH OF WEDNESDAY MORNING.
COLDER AIR WILL WRAP IN...ESPECIALLY ALOFT...LEADING TO A TOUGH
P-TYPE FORECAST. RIGHT NOW EXPECT THAT RAIN WILL MIX WITH AND
POSSIBLY CHANGE TO SNOW INTO WEDNESDAY MORNING ACROSS THE
NORTHWESTERN HALF OF THE AREA OR ROUGHLY WEST OF A CHICAGO TO
PONTIAC LINE...WITH A BETTER CHANCE FOR ALL RAIN TO THE EAST BUT A
MIX MAY OCCUR AS WELL. MODEL AGREEMENT IS SOMEWHAT LACKING IN TERMS
OF THE THERMAL PROFILE SO CONFIDENCE IS LIMITED IN THE DETAILS.
CONCEPTUALLY SPEAKING...AM ALSO CONCERNED THAT IF FORCING CAN BECOME
STRONG THEN DYNAMIC COOLING PROCESSES UNDER THE CORE OF COLDEST AIR
MAY RESULT IN A BAND OF ALL SNOW...WHICH COULD BECOME SOMEWHAT
INTENSE FOR A SHORT TIME. THIS WOULD BE FAST MOVING BUT A STRIPE OF
LOW END ACCUMULATION MAY OCCUR. COLD ADVECTION BEHIND THE DEPARTING
TROUGH IS NOT TERRIBLY STRONG GIVEN THAT WEAK UPPER RIDGING WILL
BUILD IN BEHIND IT SO WE MAY SEE SOME DIURNAL WARMING...ESPECIALLY
IF CLOUDS CAN BREAK UP.
THURSDAY THROUGH MONDAY...WEAK UPPER RIDGING WILL DAMPEN OVER THE
AREA WITH ANOTHER UPPER TROUGH SPREADING ACROSS THE FOUR CORNERS
INTO THE CENTRAL ROCKIES. THE UPPER FLOW LOOKS TO BE AT LEAST
SOMEWHAT SPLIT WITH A TROUGH ACROSS SOUTHERN CANADA. THIS MAY RESULT
IN A TIGHTENING MID LEVEL TEMP GRADIENT FROM SOUTHERN QUEBEC BACK
TOWARDS NEBRASKA THURSDAY WHICH WILL THEN SETTLE SOUTHWARD INTO THE
AREA THURSDAY NIGHT. DOES NOT APPEAR TO BE MUCH FORCING ASSOCIATED
WITH THIS BUT WILL NEED TO WATCH THE NEED FOR LOW PRECIP CHANCES.
THE SOUTHERN STREAM TROUGH WILL TRACK EAST-NORTHEASTWARD ACROSS THE
MID MISSISSIPPI RIVER VALLEY AND PUSH A SURFACE LOW NORTHEASTWARD
SOMEWHERE ACROSS THE OHIO VALLEY SATURDAY. THE ECMWF AND GFS ARE IN
REASONABLE AGREEMENT WITH THE EXISTENCE OF THESE FEATURES BUT DIFFER
ON TRACK WHICH HAS A SIGNIFICANT IMPACT ON OUR SENSIBLE WEATHER. A
WESTERLY TRACK WOULD BRING SNOW TO THE AREA FRIDAY NIGHT AND
SATURDAY. TOO EARLY FOR ANY KIND OF DETAILS BUT MOISTURE CONTENT
DOES NOT LOOK TERRIBLY HIGH SO ACCUMULATION MAY BE MINIMAL SHOULD
PRECIP OCCUR. BEYOND THAT...ANOTHER TROUGH LOOKS TO FOLLOW THE FIRST
BRINGING A PUSH OF NOTICEABLY COLDER AIR IN FOR SUNDAY BUT LARGE
SCALE RIDGING LOOKS TO QUICKLY BRING MILDER AIR BACK TO THE REGION
EARLY NEXT WEEK.
MDB
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* ONGOING FROPA...MVFR CIGS BEHIND THE FRONT
* WIND SHIFT TO WEST THEN NORTHWEST...THEN NORTHEAST
* WIND GUSTS IN THE LOW 20 KT RANGE THIS AFTERNOON
* PRECIP CHANCES/TYPE TUES MORNING
SHEA
//DISCUSSION...19Z UPDATE...
DID FURTHER TWEAKING TO THE CIG AND WIND FORECAST...EXPECT WINDS
TO CONTINUE TO FLIP AROUND TO THE NORTH AND NORTHEAST OVER THE
COURSE OF THE NEXT FEW HOURS. RUC/NAM AND HRRR GUIDANCE ALL
INDICATE IT OCCURRING IN THE 21-22Z HOUR. MKE AND RAC HAVE ALREADY
FLIPPED FROM 310 TO 350 TO 030 OVER THE COURSE OF A FEW HOURS.
EXPECT TO SEE ENW NEXT...FOLLOWED BY UGN...PWK AND THEN ORD/MDW.
SHEA
//DISCUSSION...PREVIOUS 18Z...
VFR CONDITIONS FOR THE TERMINALS WILL BE QUICKLY COMING TO A CLOSE
AS STRATUS SLIDES IN FROM THE NORTH BEHIND A FRONT THAT IS
CURRENTLY SHIFTING THROUGH THE REGION. WINDS AHEAD OF THE FRONT
WILL RANGE FROM 250-280 DEGREES...VEERING TO THE 320 TO 340 RANGE
BEHIND IT. WINDS ARE EXPECTED TO MAINTAIN THE MID TO UPPER TEEN
GUSTS THROUGH THE AFTERNOON AND INTO THE EVENING HOURS. MOST
LOCATIONS WILL SEE THE FRONT SLIDE THROUGH WITHIN THE HOUR...WITH
GYY BEING THE EXCEPTION...JUST ANOTHER HOUR BEYOND. THE MAIN PUSH
OF STRATUS FROM THE NORTH HAD BEEN PRETTY WELL TIMED TO BE AT OR
BEYOND THE 20-21Z HOUR...BUT THE LATEST VISIBLE SATELLITE IMAGERY
IS SHOWING A BIT OF AN ACCELERATION ALONG THE LEADING EDGE. MAY
NEED TO TWEAK THE TIMING OF THE MVFR CIGS SLIGHTLY FOR THE 20Z
AMD. EXPECT CIGS TO FALL INTO THE 015-018 RANGE FOR A FEW HOURS
ONCE IT MOVES THROUGH... BUT INDICATIONS POINT TOWARDS A LEVELING
OFF AND GRADUAL RISE A FEW HOURS BEHIND TO MID AND UPPER LEVEL
MVFR. NOT OVERLY CONFIDENT THAT CIGS WILL FALL TO LOW END MVFR OR
IFR RANGE...BUT THERE IS THE POSSIBILITY THAT COULD HAPPEN FOR A
VERY SHORT TIME. WINDS WILL THEN CONTINUE TO WORK AROUND THE
COMPASS DIAL...GRADUALLY REACHING NORTH...NORTHEAST AND EAST BY
TOMORROW MORNING. THE NEXT CHANCES FOR PRECIP WILL ARRIVE
TOMORROW... AS ANOTHER SYSTEM LIFTS OUT OF THE MISSISSIPPI VALLEY.
THERE ARE STILL SOME UNCERTAIN VARIABLES PERTAINING TO TIMING /AS
TRENDS HAVE BEEN SLOWING/ AS WELL AS P-TYPE.
SHEA
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* MOD-HIGH CONFIDENCE IN CIG TREND/TIMING FORECAST
** LOW CONFIDENCE ON LOW END MVFR CIG POTENTIAL
* MOD-HIGH CONFIDENCE ON WIND FORECAST
* LOW CONFIDENCE ON PRECIP TYPE/TIMING TUES MORNING
SHEA
//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...
TUESDAY NIGHT...RAIN LIKELY. MVFR/IFR CIGS.
WEDNESDAY...CHC OF RAIN AND SNOW. MVFR CIGS BECOMING VFR LATE.
THURSDAY...MAINLY VFR. SCHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...MVFR WITH A CHC OF SNOW LATE.
SATURDAY...SCHC RAIN OR SNOW THEN SCHC OF SNOW LATE. MVFR/IFR CIGS.
SUNDAY...MVFR CIGS BECOMING VFR.
JEE
&&
.MARINE...
206 AM CST
SOUTHWESTERLY GALES WILL CONTINUE FOR THE NEXT FEW HOURS AHEAD OF AN
APPROACHING COLD FRONT. AS THE FRONT PASSES ACROSS THE LAKE THIS
MORNING AND EARLY AFTERNOON...THE WINDS WILL VEER OUT OF THE NORTH
TO 20 TO 25 KT. A SURFACE RIDGE OF HIGH PRESSURE WILL PUSH ACROSS THE
LAKE MONDAY NIGHT INTO TUESDAY AS LOW PRESSURE TAKES SHAPE ACROSS
THE SOUTHERN PLAINS. THIS LOW WILL EVENTUALLY TRACK NORTHEASTWARD
ACROSS THE OHIO VALLEY BY WEDNESDAY.
LATER IN THE WEEK ANOTHER COLD FRONT LOOKS TO DROP SOUTH OUT OF
CANADA AND ACROSS LAKE MICHIGAN. HIGH PRESSURE BUILDING ACROSS THE
PLAINS SHOULD SET UP A DECENT GRADIENT ACROSS THE LAKE. THIS COULD
LEAD TO A PERIOD OF 15 TO 25 KT WINDS LATE THURSDAY INTO FRIDAY
BEFORE THE HIGH SHIFTS EAST ACROSS THE GREAT LAKES.
KJB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...6 PM MONDAY TO 10 AM TUESDAY.
&&
$$
AREA FORECAST DISCUSSION...CORRECTION TO TYPO...
NWS QUAD CITIES IA IL
315 PM CST MON DEC 19 2011
.SYNOPSIS...
12Z UA ANALYSIS HAD THE STORM SYSTEM DEVELOPING IN THE SOUTHERN
ROCKIES WITH A LLJ OF 40-50 KNOTS TRANSPORTING MOISTURE NORTH INTO
THE PLAINS AND OHIO VALLEY. AN 850MB COLD FRONT RAN FROM NORTHERN
LAKE HURON INTO NORTHEAST COLORADO. SATELLITE AND RADAR TRENDS
THROUGH MID AFTERNOON SHOWED INCREASING CLOUDS ACROSS THE AREA WITH
PRECIPITATION GENERALLY SOUTH OF A KSTJ TO KUIN LINE.
18Z SFC ANALYSIS HAD A COLD FRONT RUNNING FROM KOSC...TO KMCI...TO
AROUND KDHT. LOW PRESSURES FROM THE DEVELOPING STORM SYSTEM WERE
SOUTH OF KTCC AND NEAR KPPA. DEW POINTS WERE IN THE 40S JUST AHEAD
OF THE COLD FRONT INTO THE OHIO VALLEY WITH 50S CROSSING THE RED
RIVER INTO OKLAHOMA. DEW POINTS IN THE 20S AND 30S WERE ACROSS MUCH
OF THE NORTHERN/CENTRAL PLAINS AND UPPER MIDWEST.
&&
.SHORT TERM...TONIGHT AND TUESDAY...
THE MAIN QUESTION IS HOW LONG WILL THE DRY AIR KEEP THE
PRECIPITATION AT BAY TONIGHT INTO TUESDAY. BASED ON 12Z UA DATA...
THE WRF INITIALIZED A LITTLE BETTER THAN THE OTHER MODELS BASED ON
LOW LEVEL MOISTURE.
CONDENSATION PRESSURE DEFICITS ON EITHER STANDARD SURFACES OR THE
290-925K THETA SFC HAVE BEEN DEPICTING WELL THE AREAL COVERAGE OF
THE PRECIPITATION LATE THIS MORNING AND AFTERNOON. ALL MODELS HAVE
GENERALLY SHOWED THIS BUT THE RUC TRENDS HAVE DONE VERY WELL AND THE
RUC WILL BE USED FOR THE IMMEDIATE SHORT TERM.
BASED ON THE RUC CONDENSATION PRESSURE DEFICIT TRENDS...THE EARLY
EVENING WILL REMAIN DRY ACROSS THE ENTIRE AREA. BETWEEN 9 PM AND
MIDNIGHT PRECIPITATION WILL ADVECT/DEVELOP GENERALLY SOUTH OF A KOTM
TO KPIA LINE. FCST SOUNDINGS SHOW A TOP DOWN SATURATION TAKING PLACE
SO THERE WILL BE PLENTY OF EVAPORATIVE COOLING TAKING PLACE. THUS A
RAIN/SNOW MIX WILL DEVELOP THAT WILL LIKELY HAVE A BRIEF PERIOD OF
SLEET AS THE PRECIPITATION DEVELOPS. THERE IS A CONCERN BASED ON HOW
WARM IT HAS GOTTEN TODAY THAT PTYPE COULD BE MORE LIQUID THAN
FREEZING OR FROZEN.
AFTER MIDNIGHT...THE PRECIPITATION SHIELD WILL SLOWLY MOVE
NORTHWARD...REACHING A KOTM TO KGBG LINE AROUND 3 AM AND ROUGHLY A
KOOA TO KC75 LINE AROUND 12Z. THE I-80 CORRIDOR ON NORTH WILL REMAIN
DRY THROUGH SUNRISE. MINS TONIGHT WILL BE HIGHLY DEPENDENT ON CLOUD
COVER AND HOW THE PRECIPITATION SHIELD EVOLVES.
SNOW AMOUNTS SHOULD BE ONE HALF INCH OR LESS TONIGHT.
ON TUESDAY...THE PRECIPITATION SHIELD WILL CONTINUE MOVING NORTH AND
REACH I-80 ROUGHLY AROUND 9 AM AND SHOULD BE AROUND A VINTON TO MT
CARROLL LINE BY MID DAY. THE IMMEDIATE HWY 20 CORRIDOR IS EXPECTED
REMAIN DRY DURING THE MORNING HOURS. EVAPORATIVE COOLING WILL
CONTINUE TO PLAY SIGNIFICANTLY IN PTYPE WITH A RAIN/SNOW MIX ALONG
WITH A BRIEF PERIOD OF SLEET.
BY LATE MORNING AND INTO THE AFTERNOON HOURS...THE OVERALL FORCING
ACROSS THE AREA DECREASES. THE OVERALL PRECIPITATION INTENSITY WILL
LET UP AND A CHANGE OVER TO MAINLY RAIN IS EXPECTED EXCEPT ACROSS
ROUGHLY THE NORTHWEST THIRD OR SO OF THE CWFA WHERE A MIX IS STILL
EXPECTED. THE RAIN MAY STOP OR GO TO MORE DRIZZLE DURING THE
AFTERNOON HOURS.
SNOW AMOUNTS ON TUESDAY SHOULD BE ONE HALF INCH OR LESS. ..08..
.LONG TERM...TUESDAY NIGHT THROUGH NEXT MONDAY...
TUESDAY NIGHT AND WEDNESDAY...LATEST 12Z RUNS HAVE SHIFTED SLIGHTLY
BACK SOUTHWARD WITH RESPECT TO MAIN SFC LOW AND MID LEVEL
PROPAGATION PATHS LATER TUE THROUGH WED. WILL SIDE THE NEW 12Z RUN
ECMWF AND NAM WHICH ARE IN GOOD AGREEMENT WITH THEIR MASS FIELDS
WITH EACH OTHER AND THERE SOLUTIONS ARE IN THE MIDDLE OF THE ROAD OF
THE ENSEMBLES OF THESE FEATURES. THESE ACCEPTED SOLUTIONS SUGGEST
THAT THE SFC LOW WILL BE ACRS FAR SOUTHWEST MO AT 00Z WED...AND MOVE
NORTHEASTWARD TO THE EAST CENTRAL IL/WEST CENTRAL INDIANA BORDER
REGION BY 12Z WED WITH EYES ON THE WESTERN BASIN OF LK ERIE BY
MIDDAY WED. UPPER LOW TILTED TO THE NORTHWEST OF THE LLVL CYCLONE
WILL STILL LOOK TO PROGRESS ACRS THE SOUTHWEST HALF OF THE CWA BY
WED MORNING STILL IN A CLOSED FASHION AND THEN LOOK TO OPEN UP ON
THE WAY TO OVER THE SOUTH HALF OF LK MI BY WED AFTERNOON. ACCEPTED
THERMAL PROFILES SUGGEST LIGHT RAIN ACRS THE SOUTHEAST HALF OF THE
DVN CWA TUE EVENING WITH SOME SLEET POSSIBLY MIXED IN THE NORTHERN
FRINGE OF THE RAIN AT SFC BAND UP ALONG THE SOUTHERN I80 CORRIDOR.
WITH THE MODELS STILL SUGGESTING THE MAIN THRUST OF WARM MOIST
CONVEYOR SHUNTED OFF TO THE EAST AND SOUTHEAST OF THE AREA BY LATE
TUE...THE APPROACHING UPPER LOW WILL ONLY HAVE TO WORK WITH
SECONDARY MOISTURE FEED AND THUS ONLY A LIGHT PRECIP EVENT STILL
LOOKS ON TAP FOR TUE NIGHT FOR THE MAJORITY OF THE DVN CWA. THERMAL
PROFILES TUE EVENING ALONG AND NORTH OF A LINE FROM MT CARROLL IL...
TO CID AND SOUTHWEST OF IOWA CITY SUGGEST LIGHT SNOW AND SLEET IN
THESE AREAS TUE EVENING...AND ONLY FLURRIES ALONG AND NORTH OF THE
HWY 20 CORRIDOR. SNOW AND SLEET ACCUMS UNDER AN INCH TUE EVENING IN
THESE AREAS...BUT A CHANCE OF A NARROW SWATH OF 1-2 INCHES OF
SNOW ACCUM ON THE NORTHERN FRINGE OF RAIN/SLEET TRANSITION TO SNOW
BAND FROM WILLIAMSBURG TO CLINTON IA BY MID TUE EVENING. THEN IN-
WRAPPING MID LEVEL DRYING SHOULD SWITCH ALMOST ALL THE PRECIP TO
MAINLY DRIZZLE OR FREEZING DRIZZLE FROM MID EVENING THROUGH 12 AM-1
AM CST. AREAS OF TEMPORARY DENSE FOG POSSIBLE TOO BUT WILL LEAVE
OUT MENTION AT THIS POINT. THEN WITH THE APPROACH OF THE MID LEVEL
LOW AFTER MIDNIGHT...THE FCST SOUNDINGS SATURATE DEEPER AGAIN AND
SUPPORT A BAND OF SECONDARY DEF ZONE RAINS CLIPPING THE SOUTHEAST
THIRD OF THE CWA INTO EARLY WED MORNING WITH UP TO .3 OR .4 INCHES OF
RAIN POSSIBLE BY 8 AM CST WED. THE WESTERN FRINGE OF THIS DEF ZONE
RAIN MAY MIX WITH SNOW BY WED MORNING WITH LIGHT SLUSHY SNOW ACCUMS
UP TO AN INCH. FURTHER NORTH AND WEST OVER THE REST OF THE CWA...
LIGHT DRIZZLE OR FREEZING DRIZZLE DEPENDING ON THE SFC TEMPS WILL
LOOK TO TOP-DOWN COOL AND SATURATE INTO ALL LIGHT SNOW PARAMETERS
AFTER 1 AM WITH LIGHT ADDITIONAL SNOW ACCUMS POSSIBLE UP TO AN INCH
BY WED MORNING WHEN THE PRECIP WILL BE ON THE MOVE OUT OF THE LOCAL
FCST AREA. WILL STILL HAVE TO BE WARY OF SOME BANDED SNOWS OF AT
LEAST 1-2 INCHES AS THE UPPER LOW APPROACHES LATE TUE NIGHT IF
DYNAMICAL/TOP DOWN COOLING OCCURS QUICKER THAN CURRENTLY ANTICIPATED.
THERE STILL MAY BE A NEED FOR A WINTER WEATHER ADVISORY TUE NIGHT FOR
THE ROUNDS OF LIGHT FREEZING RAIN...FREEZING DRIZZLE...SNOW AND SLEET
MIX WITH AREAS ALONG AND NORTH OF I80 THE MOST LIKELY TARGET. THE
REST OF WED AND WED NIGHT SHOULD HAVE NO REAL WX MAKERS AND BE QUIET.
THURSDAY THROUGH FRIDAY...DEPENDING ON WHAT LIES IN THE WAKE OF THE
MID WEEK SYSTEM STREAM FLOW AND BAROCLINICITY-WISE...A RE-LOADING
SOUTHWESTERN CONUS TROF AND ACTIVE NORTHERN STREAM ACRS THE WEST
HALF OF THE CONUS HAVE ALL THE MEDIUM RANGE MODELS A FLUTTER THIS
PERIOD. MUCH UNCERTAINTY OF COURSE...BUT SIGNALS OF SOUTH-WESTERLIES
IN THE SOUTHERN STREAM REORGANIZING SOUTH AND SOUTHWEST OF THE
LOCAL AREA JUST SOUTH OF CONFLUENT FLOW MAY ALLOW SOME ELEVATED
FRONTOGENETICAL FORCING ALONG AND BEHIND A LLVL FRONT GETTING
ALIGNED PARALLEL TO THIS MEAN FLOW TO GENERATE SOME LIGHT SNOW OR
FLURRIES ACRS THE CWA EITHER LATE THU OR THU NIGHT INTO FRI
MORNING. AT THIS POINT WITH THE DRY LOOKING VERTICAL PROFILES...JUST
A DUSTING TO UNDER AN INCH WOULD ALL THAT WOULD BE POSSIBLE BY FRI
MORNING AND MAINLY FROM IOWA CITY TO FREEPORT IL AND NORTHWARD.
THE 12Z RUN UKMET...GEM AN GFS ARE EITHER DRY OR JUST HAVE FLURRIES
FOR THU NIGHT. LONGER RANGE SIGNALS SUGGEST PHASING ISSUES A PLENTY
AS THE DIGGING NORTHERN STREAM UPPER TROF OVER CENTRAL CANADA TRIES
TO INTERACT WITH THE SOUTHWEST PLAINS TROFFINESS. THE MAJORITY OF
THE LONGER RANGE MODELS HANDLE THIS PROCESS IN A WAY THAT ANY
SOUTHERN STREAM WX MAKER AND IT/S ASSOCIATED PRECIP REMAINS ALONG
OR SOUTH OF THE DVN CWA FROM FRI INTO SAT. BUT THE 12Z GFS MUCH
MORE OMINOUS AND DEVELOPED UPSTREAM. IT PHASES THE STREAMS IN A WAY
THAT A STORM SYSTEM WITH AT LEAST HIGHER END ADVISORY SNOWS/2-5+
INCHES IMPACTS THE ENTIRE CWA FRI NIGHT INTO SAT MORNING. WILL WATCH
FURTHER TRENDS OF COURSE WITH ADDITIONAL RUNS OVER THE NEXT 24-48
HRS. WILL GO WITH SEASONABLE TEMPS FOR THU THROUGH FRI FOR NOW.
SATURDAY THROUGH MONDAY...ENSEMBLES AND TELECONNECTIONS OVER THE
HOLIDAY WEEKEND SUGGEST SOME AO/ARCTIC OSCILLATION INFLUENCE AS
GENERAL L/W TROFFINESS TRIES TO ESTABLISH THIS PERIOD AND INTO EARLY
NEXT WEEK ACRS THE UPPER MIDWEST AND GRT LKS. THIS PERIOD ALSO LOOKS
GENERALLY DRY AFTER SAT WITH SOME RE-ENFORCING COOL SHOTS OUT OF
CANADA POSSIBLE FOR SEASONABLE OR SOMEWHAT BELOW TEMPS INTO NEXT
MONDAY. CAN/T RULE OUT SOME FLURRIES ON LEADING EDGES OF COOL DUMPS
OR WEAK WAVES EMBEDDED IN NORTHWESTERLY CYCLONIC FLOW...BUT WILL GO
MAINLY DRY FOR NOW. ..12..
&&
.AVIATION...
VFR WX IS GENERALLY EXPECTED THROUGH 03Z/20 WITH THE EXCEPTION OF
MVFR CIGS AT KDBQ. AFT 03Z/20 CONDITIONS WILL DETERIORATE AT KBRL
WITH MVFR CONDITIONS DVLPG WITH PRECIPITATION EXPECTED AFT 06Z/20
WHICH MAY INCLUDE PL. IFR CONDITIONS ARE POSSIBLE BEGINNING AROUND
12Z/20. AFT 12Z/20 CONDITIONS WILL DETERIORATE AT KCID/KMLI WITH MVFR
CONDITIONS DVLPG. KDBQ IS EXPECTED TO SEE MVFR CONDITIONS DVLPG ARND
18Z/20. ..08..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
08/12
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
1138 AM CST MON DEC 19 2011
.AVIATION...
DRY COLD FRONT HAS MOVED THROUGH ALL TAF SITES WHICH IS PULLING IN DRY
LOW LEVEL AIR TO THE AREA. A LAYER OF CLOUDS AROUND 2KFT AGL WILL
AFFECT KCID/KDBQ THROUGH 00Z/20. OTHERWISE...VFR WX IS EXPECTED
THROUGH 06Z/20. MVFR CONDITIONS AND PRECIP WL DVLP AT KBRL 06Z-
12Z/20 AND MAY GO TO IFR AFT 12Z/20. KCID/KMLI SHOULD SEE MVFR
CONDITIONS AND PRECIP DVLP ARND OR AFT 15Z/20 THAT MAY GO TO IFR
AFT 18Z/20.
..08..
&&
.PREV DISCUSSION... /ISSUED 1039 AM CST MON DEC 19 2011/
UPDATE...
MORNING UA ANALYSIS COMBINED WITH A 15Z SFC ANALYSIS SHOW PLENTY
OF DRY AIR MOVING SOUTH INTO THE CWFA. AS OF 15Z...THE SFC COLD
FRONT WAS INTO SOUTHERN WISCONSIN. IT RE-DEVELOPED AROUND KDBQ AND
EXTENDED SOUTHWEST TO NEAR KTOP. A PRE-FRONTAL TROF RAN FROM
SOUTHERN LAKE MICHIGAN TO AROUND KCDJ.
RUC TRENDS SHOW VERY HIGH CONDENSATION PRESSURE DEFICITS ACROSS
THE CWFA THROUGH 00Z IN THE LOW AND MID LEVELS. ON THE 290K AND
295K THETA SURFACES...THE CONDENSATION PRESSURE DEFICITS ARE EVEN
HIGHER WITH VERY LITTLE FORCING ACROSS THE AREA. FCST SOUNDINGS
FROM THE RUC IN THE FAR SOUTHERN CWFA ONLY SUGGEST A NARROW LAYER
OF MOISTURE AROUND 900MB WITH CONSIDERABLE DRY AIR ABOVE AND
SLIGHTLY DRIER AIR BELOW.
COMPRESSIONAL HEATING WITH THE TROF AND FRONT ARE RAISING
TEMPERATURES HIGHER THAN FCST AS WELL. THE CAA BEHIND THE FRONT IS
NOT OVERLY STRONG. HOWEVER...THE WEAK SUN STRENGTH COMBINED WITH
INCOMING CLOUDS SHOULD PREVENT MUCH OF AN ADDITIONAL RISE THIS
AFTERNOON. TEMPERATURES WILL LIKELY DO A SLOW FALL THROUGH THE
AFTERNOON IN THE NORTH AND NORTHWEST PARTS OF THE CWFA.
AN UPDATE TO THE FCST WILL BE AVAILABLE BY 1045 AM.
.08..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
1039 AM CST MON DEC 19 2011
.UPDATE...
MORNING UA ANALYSIS COMBINED WITH A 15Z SFC ANALYSIS SHOW PLENTY
OF DRY AIR MOVING SOUTH INTO THE CWFA. AS OF 15Z...THE SFC COLD
FRONT WAS INTO SOUTHERN WISCONSIN. IT RE-DEVELOPED AROUND KDBQ AND
EXTENDED SOUTHWEST TO NEAR KTOP. A PRE-FRONTAL TROF RAN FROM
SOUTHERN LAKE MICHIGAN TO AROUND KCDJ.
RUC TRENDS SHOW VERY HIGH CONDENSATION PRESSURE DEFICITS ACROSS
THE CWFA THROUGH 00Z IN THE LOW AND MID LEVELS. ON THE 290K AND
295K THETA SURFACES...THE CONDENSATION PRESSURE DEFICITS ARE EVEN
HIGHER WITH VERY LITTLE FORCING ACROSS THE AREA. FCST SOUNDINGS
FROM THE RUC IN THE FAR SOUTHERN CWFA ONLY SUGGEST A NARROW LAYER
OF MOISTURE AROUND 900MB WITH CONSIDERABLE DRY AIR ABOVE AND
SLIGHTLY DRIER AIR BELOW.
COMPRESSIONAL HEATING WITH THE TROF AND FRONT ARE RAISING
TEMPERATURES HIGHER THAN FCST AS WELL. THE CAA BEHIND THE FRONT IS
NOT OVERLY STRONG. HOWEVER...THE WEAK SUN STRENGTH COMBINED WITH
INCOMING CLOUDS SHOULD PREVENT MUCH OF AN ADDITIONAL RISE THIS
AFTERNOON. TEMPERATURES WILL LIKELY DO A SLOW FALL THROUGH THE
AFTERNOON IN THE NORTH AND NORTHWEST PARTS OF THE CWFA.
AN UPDATE TO THE FCST WILL BE AVAILABLE BY 1045 AM.
..08..
&&
.PREV DISCUSSION... /ISSUED 555 AM CST MON DEC 19 2011/
AVIATION...
THE COLD FRONT WILL MOVE THROUGH ALL TAF SITES SHIFTING WINDS TO THE
NORTHWEST BY EARLY AFTERNOON. VFR CONDITIONS ARE EXPECTED BOTH
AHEAD OF AND BEHIND THE FRONT FOR MUCH OF THE DAY. THERE WILL BE
SOME CIGS BASED AROUND 4KFT ALONG AND EAST OF THE MISSISSIPPI
RIVER THIS MORNING. BEHIND THE FRONT SOME CLOUDS BASED AROUND
2KFT MAY MOVE INTO THE KCID/KDBQ AREA BY LATE THIS AFTERNOON.
THESE CLOUDS WILL BE BREAKING UP AS THE REACH EAST CENTRAL
IOWA...SO THEY MAY ONLY RESULT IN A SCATTERED LAYER. VFR
CONDITIONS WILL REMAIN OVER KCID/KDBQ AREAS FOR THE OVERNIGHT
HOURS WITH SURFACE WINDS BECOMING NORTHEASTERLY. EXPECT
DETERIORATING CONDITIONS IN THE SOUTH INCLUDING KBRL AS RAIN
SPREADS IN FROM THE SOUTH LATE THIS AFTERNOON. A RAIN/SNOW/SLEET
MIX WITH MVFR CIGS/VSBYS IS EXPECTED THE REST OF THE NIGHT. KMLI
WILL BE ON THE NORTHERN FRINGE OF THE PRECIPITATION TONIGHT.
EXPECT CIGS/VSBYS REMAIN IN THE VFR CATEGORY WITH A LOW POTENTIAL
FOR SOME LIGHT SNOW OR SLEET ESPECIALLY AFTER 06Z.
PREV DISCUSSION... /ISSUED 419 AM CST MON DEC 19 2011/
SYNOPSIS...
SPLIT MID LEVEL FLOW CONTINUES TO DOMINATE THE CONUS THIS MORNING.
A NORTHERN STREAM S/W TROF WAS DROPPING SOUTHEAST THROUGH THE
NORTHERN ROCKIES WITH FLAT ZONAL FLOW EAST OF THE TROF ACROSS THE
REST OF THE NORTHERN TIER OF STATE. THE SOUTHERN STREAM CUTOFF LOW
WAS MOVING EAST ALONG THE AZ/MEXICAN BORDER. S/W RIDGING AHEAD OF
THE UPPER LOW EXTENDED FROM THE CENTRAL GULF COAST NORTHWEST THROUGH
THE CENTRAL PLAINS. AT THE SURFACE A COLD FRONT WAS LOCATED FROM
NORTHERN WI THROUGH SOUTHEAST MN AND NORTHWEST IA AT MIDNIGHT. NO
PRECIP WAS OCCURRING WITH THE BOUNDARY...BUT AN EXTENSIVE STRATUS
FIELD WAS LOCATED IN THE COLD AIR...BUT LAGGING THE SURFACE FRONT.
IN THE WARM SECTOR UNSEASONABLY MILD EARLY MORNING TEMPERATURES WERE
OCCURRING. AN AREA OF STRATUS WITH ITS WESTERN EDGE ALONG THE
MISSISSIPPI RIVER WAS CO-LOCATED WITH THE LOW LEVEL MOIST FEED.
TEMPERATURES UNDER THIS CLOUD DECK WERE STILL IN THE UPPER 40S EARLY
THIS MORNING WITH MID/UPPER 30S UNDER CLEAR SKIES WEST OF THE
RIVER.
SHORT TERM...TODAY AND TONIGHT...
SHORT RANGE MODELS WERE IN CLOSE AGREEMENT WITH THE OVERALL SYNOPTIC
PATTERN FOR TODAY AND TONIGHT. THE SURFACE COLD FRONT IS PROGGED TO
MOVE THROUGH THE CWFA TODAY AND SHOULD EXIT THE SOUTHERN COUNTIES BY
MID AFTERNOON. THE SOUTHERN STREAM CUTOFF UPPER LOW IS PROGGED TO
BE OVER SOUTHERN NM THIS MORNING AND IS EXPECTED TO LIFT NORTHEAST
INTO TX/OK PANHANDLES BY TUESDAY MORNING. MODEL QPF FIELDS ARE
SIMILAR IN BREAKING OUT/EXPANDING PRECIPITATION OVER THE SOUTHERN
PLAINS THIS MORNING AS GULF MOISTURE WORKS NORTH AND INTERACTS WITH
THE UPPER SYSTEM. THE PRECIPITATION IS PROGGED TO SPREAD NORTHEAST
UNTIL IT ENCOUNTERS DRY LOW LEVEL AIR OVER SOUTHERN IA CAUSING IT TO
STALL OVERNIGHT.
FOR TODAY THE BIG CHALLENGE WILL BE THE COLD AIR STRATUS OVER MN/SD
EARLY THIS MORNING. MODEL LOW RH PROGS SHOW THE STRATUS BREAKING UP
AS IT MOVES SOUTHEAST. CONCEPTUALLY THIS MAKES SENSE AS WINDS IN
THE CLOUD BEARING LAYER OVER SD/NE BECOME MORE NORTHEASTERLY THIS
MORNING AS LOW PRESSURE DEVELOPS OVER THE SOUTHERN PLAINS. WINDS
OVER THE GREAT LAKES REMAIN NORTHERLY CAUSING DIFFLUENT POST FRONTAL FLOW
OVER IA. THIS SHOULD KEEP THE BULK OF THE STRATUS FROM REACHING THE
CWFA...SO PARTLY TO MOSTLY SUNNY SKIES ARE EXPECTED OVER THE WESTERN
CWFA THIS MORNING WITH CLEARING OCCURRING OVER THE NORTHEAST AS THE
WARM SECTOR STRATUS IS PUSHED EAST WITH THE COLD FRONT. MID/HIGH
CLOUDS SHOULD SPREAD BACK INTO THE SOUTHERN CWFA LATE THIS MORNING
AND THIS AFTERNOON AHEAD OF THE SOUTHERN STREAM UPPER LOW. LESS
CLOUDS TODAY SUPPORTS SLIGHTLY WARMER TEMPERATURES ESPECIALLY IN THE
NW WHERE SUNSHINE SHOULD OFFSET SOME OF THE COLD AIR ADVECTION.
SOME LOW CHANCE POPS WERE MAINTAINED IN THE FAR SOUTH LATE THIS
MORNING AND THIS AFTERNOON. TEMPERATURES INITIALLY SUPPORT ALL
RAIN. IF THE RAIN MAKES AS FAR NORTH AS HIGHWAY 34...THEN SOME SLEET
COULD MIX IN WITH THERMAL PROFILES SHOWING SOME REFREEZING IS
POSSIBLE NEAR THE SURFACE.
TONIGHT PRECIPITATION CHANCES WILL INCREASE OVER THE SOUTH WITH THE
NORTHERN EXTENT OF THE PRECIPITATION EXPECTED TO BE NEAR INTERSTATE
80. WILL GO WITH CATEGORICAL POPS IN THE FAR SOUTH TAPERING OFF TO
SLIGHTS NEAR THE INTERSTATE. A MIX WAS ALSO MENTIONED ACROSS THE
SOUTH TONIGHT. THERMAL PROFILES SUPPORT A RAIN/SNOW MIX WITH A LOW
POTENTIAL FOR SLEET. FURTHER NORTH IT LOOKS MORE LIKE A SNOW/SLEET
MIX. FREEZING RAIN WAS NOT MENTIONED SINCE SURFACE TEMPERATURES IN
THE FAR SOUTH ARE EXPECTED TO STAY JUST ABOVE FREEZING.
PRECIPITATION AMOUNTS BY TUESDAY MORNING ARE EXPECTED TO BE LESS
THAN A HALF INCH. THERE MAY BE SOME ACCUMULATION OF SNOW SOUTH
OF HIGHWAY 34 BUT WITH THE EXPECTED MIXED PRECIPITATION...SNOW
AMOUNTS WERE KEPT UNDER ONE HALF INCH. ..DLF..
LONG TERM...TUESDAY THROUGH SUNDAY...
TUESDAY THROUGH WEDNESDAY...THE MAIN FORECAST CONCERNS ARE WITH THE
DETAILS OF THE SURFACE LOW TRACK AND ASSOCIATED PRECIPITATION
TYPE/S. THE FORECAST MODELS ARE IN GOOD OVERALL AGREEMENT...ALTHOUGH
THERE ARE SOME SLIGHT DIFFERENCES IN THE THERMAL AND MOISTURE
DETAILS WHICH MAKE ALL THE DIFFERENCE IN WHAT PRECIPITATION TYPE/S
WILL OCCUR.
AS THE CLOSED UPPER LOW SLOWLY EJECTS NORTHEAST...THE SURFACE LOW IS
FORECAST TO TRACK ACROSS SOUTHEAST MISSOURI AND CENTRAL ILLINOIS
ON TUESDAY. ALTHOUGH THE BULK OF PRECIPITATION FROM THIS SYSTEM
MAY FALL BY TUESDAY MORNING...GENERALLY LIGHT PRECIPITATION IS
EXPECTED TO AFFECT PORTIONS OF THE FORECAST AREA THROUGH AT LEAST
TUESDAY NIGHT. THE PRECIPITATION TO START THE DAY TUESDAY WILL BE
ASSOCIATED WITH THE WARM MOIST CONVEYOR REGION ON THE NORTHWEST SIDE
OF THE SURFACE LOW TRACK. FORECAST THERMAL PROFILES ARE NOT CLEAR
CUT...AS TEMPERATURES HOVER NEAR THE CRITICAL THRESHOLDS FOR
FREEZING/FROZEN PRECIPITATION. MIXED PRECIPITATION IN THE FORM OF
SNOW AND/OR SLEET IS LIKELY THROUGH THE MORNING TUESDAY...WITH THE
SOUTHERN THIRD OR SO OF THE FORECAST AREA THE MOST LIKELY TO SEE
RAIN AS ONE OF THE PRECIPITATION TYPES. AS THE DEEPER MOISTURE WITH
THIS SYSTEM IS FORECAST TO BE SHUNTED TO THE SOUTHEAST...THE THERMAL
PROFILES SUGGEST THERE MAY BE LIMITED MOISTURE IN THE ICE GROWTH
LAYER...ESPECIALLY AS THE DAY PROGRESSES ON TUESDAY. THIS WOULD MEAN
THAT THE DOMINANT PRECIPITATION TYPE MAY BE RAIN OR DRIZZLE. SURFACE
TEMPERATURES ARE EXPECTED TO BE ABOVE FREEZING FOR MUCH OF THE
DAY...OTHERWISE WHERE TEMPERATURES MIGHT BE BELOW FREEZING FOR A
TIME...THE RAIN OR DRIZZLE COULD BECOME FREEZING RAIN OR DRIZZLE.
THIS MAY BE MORE OF A CONCERN AS TEMPERATURES DIURNALLY FALL TUESDAY
NIGHT...AT WHICH TIME THE AREA IS FORECAST TO BE AFFECTED BY
PRECIPITATION ASSOCIATED WITH THE SYSTEMS DEFORMATION ZONE.
ONE POSITIVE IN ALL OF THESE QUESTIONS ABOUT PRECIPITATION TYPE IS
THAT PRECIPITATION AMOUNTS LOOK TO BE ON THE LIGHTER SIDE. LIQUID
PRECIPITATION TOTALS FROM DAYBREAK TUESDAY THROUGH WEDNESDAY MORNING
ARE FORECAST TO BE UP TO A QUARTER OF AN INCH ACROSS THE SOUTHERN
FORECAST AREA AND TAPER OFF TO AROUND A TENTH OF AN INCH TOWARD THE
NORTHERN FORECAST SECTIONS.
AN ACTIVE WEATHER PATTERN IS FORECAST TO CONTINUE BEYOND
WEDNESDAY...AS SHORTWAVES COME ACROSS FROM THE PACIFIC NORTHWEST.
THE AMOUNT OF PHASING BEFORE THE SHORTWAVES EJECT ACROSS THE CONUS
CONTINUES TO BE THE CHALLENGE. GENERALLY SPEAKING...NEAR TO SLIGHTLY
ABOVE NORMAL TEMPERATURES ARE EXPECTED TO CONTINUE THROUGH THE WEEK.
LOW PRECIPITATION CHANCES WERE CARRIED FROM FRIDAY INTO SATURDAY AS
ONE OF THE UPPER WAVES IS FORECAST TO KICK OUT ACROSS THE CENTRAL
CONUS. CONFIDENCE IN THIS PRECIPITATION SCENARIO REMAINS LOW FOR
NOW. ..STOFLET..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS TOPEKA KS
552 PM CST TUE DEC 20 2011
...UPDATE TO AVIATION...
.DISCUSSION...
SHORT RANGE (TONIGHT AND WEDNESDAY)...
20Z WATER VAPOR IMAGERY AND ASSOCIATED RUC ANALYSIS CONTINUES TO
SHOW THE 500 MB TROUGH MOVING SLOWLY TO THE NORTHEAST ACROSS EASTERN
KANSAS. CURRENTLY IT IS SITTING OVER SOUTH CENTRAL KANSAS AND SHOULD
PUSH THROUGH THE AREA BY TONIGHT. RADAR TRENDS SHOW PRECIPITATION
ENDING ACROSS CENTRAL KANSAS...AND THIS TREND SHOULD CONTINUE
THROUGH THE REST OF THE EVENING AS THE BETTER LIFT ASSOCIATED WITH
THIS SYSTEM PUSHES EAST. ANOTHER SHIELD OF LIGHT PRECIPITATION IS
MOVING NORTHEASTWARD ALONG THE KANSAS TURNPIKE AND WILL LIKELY BRING
ANOTHER ROUND OF MIXED PRECIPITATION TO AREAS EAST OF THE TURNPIKE.
CURRENTLY KUKL INDICATES 36 DEGREES AS DOES KOJC...SO EXPECT THE
BULK OF THE REMAINING PRECIP TO FALL IN THE FORM OF A RAIN/SNOW MIX
FOR THE REMAINDER OF THE EVENING ALONG THE NEWLY FORMED DEFORMATION
BAND. EXPECT THE BEST LIFT WITH THIS ROUND OF SHOWERS TO MOVE OFF TO
THE EAST BY LATE THIS EVENING THUS ENDING ALL PRECIP FOR OUR
FORECAST AREA. SHOULD THERE BE ANY SNOW ASSOCIATED WITH THIS
EVENINGS PRECIP DON`T EXPECT MUCH MORE THAN A DUSTING OF SNOW ON
GRASSY SURFACES. SINCE ROADWAYS ARE WET FROM THE ONGOING PRECIP AND
OVERNIGHT LOWS WILL DROP INTO THE TEENS TO TWENTIES THERE IS A
POTENTIAL FOR SLICK SPOTS ON ROADWAYS...ESPECIALLY ONCE TEMPS DIP
BELOW 32 DEGREES. SKIES WILL GRADUALLY CLEAR BEHIND THE DEPARTING
SYSTEM...FIRST ACROSS CENTRAL AND NORTH CENTRAL KANSAS...THEN BY 12Z
ACROSS FAR EASTERN KANSAS. AS A RESULT OF THE NEWLY FALLEN SNOW
ACROSS C/NC KANSAS AND THE CLEARING SKIES EXPECT LOW TEMPS TO REACH
INTO THE MID TEENS TONIGHT...AND INTO THE LOWER TO MID 20S FURTHER
EAST WHERE NO SNOW FELL AND SKIES WILL BE SLOWER TO CLEAR. WEDNESDAY
WILL BRING A MILD DAY ACROSS NORTHEAST KANSAS AS TEMPS WILL REACH
INTO THE LOWER TO MID 40S WHERE NO NEW SNOW FELL...BUT WILL ONLY
REACH THE MID 30S OVER THE SNOW PACK IN C/NC KANSAS. JL
THURS-TUES...AFTER A BREAK FROM THE CLOUDS AND
PRECIPITATION...THE NEXT UPPER TROF APPROACHES THE STATE FROM THE
NORTH AND NORTHWEST THURSDAY AND THROUGH FRIDAY. AT THIS TIME MAIN
PIECE OF ENERGY AND DYNAMICS STAYS TO THE WEST...LEAVING THE LEAD
SHEAR VORTICITY AHEAD OF THE NORTHERN WAVE TO SLIDE ACROSS KANSAS.
ENOUGH LIFT WITH THIS AND COUPLED WITH SOME FRONTOGENETIC FORCING
TO BRING A CHANCE OF SNOW THROUGH FRIDAY. NOT MUCH MOISTURE TO
WORK WITH SO DONT EXPECT MUCH FOR ACCUMULATIONS DESPITE HIGHER
SNOW TO LIQUID RATIOS THAN THE PREVIOUS STORM. STILL VARIATIONS IN
THE GUIDANCE AS TO HOW TO HANDLE THE WESTERN PORTION OF THIS
SYSTEM WITH EC/NAM TRENDING A SOUTHWARD SLOWER TRACK AND GFS MORE
PROGRESSIVE ACROSS AND OUT OF OUR AREA. EC IS THEREFORE COOLER IN
THE EXTENDED WHILE GFS IS WARMER IN MORE WESTERLY FLOW. HAVE DRY
CONDITIONS BEYOND FRIDAY WITH A SLOW WARMING TREND...AND WILL HAVE
TO WATCH EVOLUTION OF THAT UPPER PATTERN FOR CHANGES. 67
&&
.AVIATION...
CIGS WILL REMAIN IFR IN KTOP/KFOE TERMINALS UNTIL AROUND
03Z...THEN MVFR CIGS BEFORE IMPROVING TO VFR BY 06Z. WILL KEEP
FCST DRY THROUGH THE PERIOD AT KMHK...BUT SOME LINGERING -RASNPL
IS STILL POSSIBLE BENEATH UPPER LOW UNTIL 01Z AT KTOP/KFOE. ALL
SITES WILL GO CLEAR WEST TO EAST BETWEEN 06-12Z WITH SOME PATCHY
FOG POSSIBLE WITH THE LIGHT WINDS.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS TOPEKA KS
358 PM CST MON DEC 19 2011
.DISCUSSION...
THE FOCUS OF THIS FORECAST REMAINS ON THE POTENT STORM SYSTEM WHICH
WILL MOVE OFF THE HIGH PLAINS AND BRING RAIN AND SNOW TO ALL OF
NORTHEAST AND EAST CENTRAL KANSAS TONIGHT AND TOMORROW.
20Z WATER VAPOR IMAGERY AND ASSOCIATED RUC ANALYSIS SHOWING THE 500
MB TROUGH MAKING A NORTHEAST TURN AS IT TAKES ON A NEGATIVE TILT
OVER FAR WESTERN TEXAS. STRONG ISENTROPIC LIFT CAUSING A WIDE SHIELD
OF PRECIPITATION MAINLY IN THE FORM OF RAIN TO MOVE NORTHWARD ACROSS
THE AREA. SOME ELEVATED INSTABILITY HAS ALLOWED FOR SOME WEAK
CONVECTION WITHIN THE AREA OF PRECIP ALLOWING FOR A FEW RUMBLES OF
THUNDER. WITH WARM LOW LEVEL TEMPERATURES ACROSS FAR EASTERN KANSAS
THE PRECIPITATION HAS FALLEN AS RAIN THROUGHOUT THE DAY. FURTHER TO
THE WEST COOLER AIR IN THE LOWER TO MID LEVELS HAS FACILITATED A
GRADUAL CHANGE OVER TO A MIX OF RAIN AND SNOW WITH SOME SLEET.
ACROSS CENTRAL AND SOUTHWEST KANSAS WHERE THE COLD AIR IS EVEN
DEEPER PRECIP HAS CHANGED COMPLETELY OVER TO SNOW. THE AREA WITH THE
BIGGEST CONCERN FOR THIS SYSTEM WILL BE ACROSS CENTRAL AND NORTH
CENTRAL KANSAS WHERE SNOW AMOUNTS COULD BE THE HIGHEST. BEST
FRONTOGENETICAL LIFT AND ASSOCIATED HIGHEST OMEGA LOOKS TO PERSIST
ACROSS THE AREA BETWEEN 00Z AND 12Z TONIGHT...AND THIS WILL LIKELY
BRING THE HEAVIEST SNOW...ESPECIALLY TO AREAS OF CENTRAL KANSAS.
GOOD LIFT THROUGH THE -8 TO -14 C DENDRITIC GROWTH LAYER WILL LIKELY
KEEP ALL PRECIP WEST AND NORTH OF A HIAWATHA TO COUNCIL GROVE LINE.
SNOW COULD RAPIDLY INCREASE WITH SNOW RATES APPROACHING 3 TO 5
INCHES OVER A 6 TO 10 HOUR PERIOD ACROSS THAT AREA. COMPLICATING THE
CONDITIONS WILL BE STRONG WINDS ACROSS CENTRAL KANSAS
OVERNIGHT...LEADING TO REDUCED VISIBILITIES AND DANGEROUS TRAVEL
CONDITIONS...ESPECIALLY ALONG INTERSTATE 70. VERY TRICKY PRECIP TYPE
FORECAST FOR AREAS ALONG AND EAST OF THE KANSAS TURNPIKE. FORECAST
SOUNDINGS INDICATE ICE CRYSTALS INTRODUCED INTO THE ATMOSPHERIC
COLUMN...BUT WARMER 850 MB TEMPS COULD TEMPER THE ABILITY OF SNOW TO
REACH THE SURFACE. HOWEVER WITH REAL TIME TEMPS RUNNING A BIT COOLER
THAN MODEL TEMPS...MAY NEED TO CALIBRATE MODELS WITH REAL TIME INFO
AND LEAN TOWARD A SLIGHTLY COOLER SOLUTION...FOR PRECIP TYPES AND
SNOW AMOUNTS ACROSS THE EASTERN COUNTIES. SHOULD PRECIP BE ABLE TO
CHANGE OVER TO SNOW BY 01 TO 03Z EAST OF THE AFOREMENTIONED HIAWATHA
TO COUNCIL GROVE LINE...MAY NEED TO BUMP UP SNOW
AMOUNTS...ESPECIALLY FOR THE TOPEKA AREA. AROUND 12Z TUESDAY MORNING
DRY MID LEVEL AIR WILL PUSH INTO THE AREA WHICH WILL REMOVE ICE
CRYSTALS FROM THE COLUMN FOR A FEW HOURS TUESDAY MORNING. DURING
THIS TIME EXPECT PRECIP TO GO FROM A LIGHT SNOW TO A LIGHT DRIZZLE
OR FREEZING DRIZZLE ACROSS AREAS WHERE TEMPS ARE BELOW FREEZING. BY
LATE TUESDAY AFTERNOON THE MID LEVEL TROWAL WILL SET UP NEAR THE
INTERSTATE 70 CORRIDOR WHICH COULD BRING ANOTHER ROUND OF LIGHT SNOW
FOR TUESDAY AFTERNOON AS THE ATMOSPHERIC COLUMN SHOULD BE COOL
ENOUGH ACROSS THE ENTIRE FORECAST AREA.
WILL NOT MAKE ANY MAJOR CHANGES TO THE ONGOING WARNING/ADVISORY
LOCATIONS AS COUNTIES CURRENTLY UNDER THE WINTER STORM WARNING ARE
STILL ON TRACK TO ACCUMULATE 6 TO 8 INCHES OF SNOW. THE COUNTIES
FURTHEST NORTH AND EAST CONTAIN LESSER CONFIDENCE IN REACHING THE 6
TO 8 INCH RANGE...BUT COUNTIES ALONG INTERSTATE 70 AND WEST OF THE
KANSAS TURNPIKE SHOULD EXPECT AT LEAST 4 TO 6 INCHES OF SNOW...WITH
HIGHER AMOUNTS ACROSS CENTRAL KANSAS. ALSO STRONG WINDS ALONG
INTERSTATE 70 WILL COMPLICATE TRAVEL CONDITIONS AS THEY WILL
COINCIDE WITH THE HEAVY SNOW OVERNIGHT TO BRING LOWERED VISIBILITY
AND DANGEROUS TRAVEL CONDITIONS.
EXPECT LIGHT SNOW TO GRADUALLY COME TO AN END BY EARLY WEDNESDAY
MORNING AS THE UPPER TROUGH EXITS COMPLETELY OUT OF THE AREA WITH
CLEARING SKIES AND SEASONABLE TEMPS.
ANOTHER SYSTEM SWINGS INTO THE PLAINS THURSDAY INTO FRIDAY BUT
WITH A NORTHERLY TRAJECTORY AND MORE LIMITED MOISTURE WILL CARRY
CHANCE TO SLIGHT CHANCE POPS AT THIS TIME. CONDITIONS CLEAR OUT
FOR SATURDAY WITH ANOTHER PUSH OF COLDER AIR SATURDAY NIGHT INTO
SUNDAY.
&&
.AVIATION...
EXPECT MVFR CONDITIONS OVER TERMINALS THROUGH AT LEAST 0Z AS
RADAR SHOWS WIDESPREAD RAINFALL TRACKING NORTHWARD OVER TERMINALS.
NORTHERLY WINDS INCREASE BEHIND PASSAGE OF COLD FRONT FROM 10 TO
20 KTS SUSTAINED THROUGH FORECAST PERIOD. AS COLDER AIR FILTERS
SOUTHWARD...EXPECT A TRANSITION TO IFR AFTER 00Z AT KMHK AND 05Z
AT KTOP/KFOE AS RAIN TRANSITIONS TO SNOW AND VISIBILITIES/CIGS
LOWER. THE HEAVIEST SNOW IS FORECAST TO OCCUR AROUND 03Z AND
THEREAFTER AT KMHK WHERE CONDITIONS MAY REACH LIFR IN THE HEAVIER
SNOW BANDS. KTOP AND KFOE MAY SEE A MIXTURE OF LIGHT FREEZING
DRIZZLE WITH THE LIGHT SNOW TUESDAY MORNING.
BOWEN
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 6 PM CST TUESDAY FOR KSZ009>011-
020>023-034>036.
WINTER WEATHER ADVISORY UNTIL 6 PM CST TUESDAY FOR KSZ008-012-
024-026-037>039.
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM CST
TUESDAY FOR KSZ040-054-055.
&&
$$
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
320 PM CST MON DEC 19 2011
.SYNOPSIS...
THE OVERALL SYNOPSIS FROM THE 12Z...250MB CHART SHOWED A 80-KNOT
JET STREAK OF WIND FROM SOUTHWEST TEXAS THROUGH SOUTHWEST KANSAS
TO SOUTHERN IOWA. A STRONGER 110KT NORTHWEST JET WAS ENTERING BAHA
CALIFORNIA (W. MEXICO), WHILE A 120-KNOT JET STRETCHED FROM
NORTHERN MINNESOTA TO SOUTHWEST QUEBEC. THE 500MB CHART AT 12Z HAD
A LARGE UPPER LOW PRESSURE SYSTEM OVER EXTREME WESTERN TEXAS, WITH
MOISTURE FLOWING NORTHEASTWARD INTO KANSAS. THE 500MB TEMPERATURE
AT DDC WAS AT 17C. THE 700 MB CHART LOOKED SIMILAR TO THE 500MB
CHART PATTERN, BUT WITH THE H7 LOW PRESSURE OVER SOUTH CENTRAL NEW
MEXICO. A COLD FRONT WAS EVIDENT AT 12Z AT THE 850MB LEVEL ACROSS
NORTH CENTRAL KANSAS, WITH LBF AT -04C AND DDC AT +10C.
&&
.DISCUSSION...
DAYS 1-2...
THE UPPER STORM SYSTEM MOVING ACROSS NEW MEXICO AND TEXAS, AND
INTO NORTHERN OKLAHOMA, WAS BRINGING WINTER-LIKE WEATHER TO MOST
OF SOUTHWESTERN KANSAS THIS AFTERNOON. THERE WAS A BAND OF RAIN,
SOME MODERATE, THAT MOVED NORTH FROM FROM OKLAHOMA MORNING LAID
DOWN 0.02 TO 0.50 INCH OF RAIN ACROSS MUCH OF OUR SOUTHERN CWA.
THIS SOAKED UPPER LAYER OF SURFACE GROUND WILL DELAY TO ONSET OF
ACCUMULATING SNOW, BUT SNOW RATES OF .5 TO 1.0-INCH PER HOUR AT
TIMES WILL LEAD TO A QUICK ACCUMULATION. FURTHERMORE, PER THE
FORECAST SOUNDINGS FROM THE NAM AND RUC MODELS BOTH SHOWED A WARM
ELEVATED LAYER OF +2 DEGREES, INDICATING THERE MAY BE SOME SLEET
OR LIGHT FREEZING RAIN BEFORE THE EASTERN PART OF THE CWA CHANGES
TO ALL SNOW, SO WILL MENTION THAT. A SURFACE COLD FRONT WAS
WORKING SOUTH THROUGH THE CWA TODAY, AND CLEARED THE SOUTHEAST
PART OF OUR FORECAST AREA BETWEEN 20 AND 21Z. WHERE THE
OVERRIDING COLD AIR WILL MEET THE BEST LIFT OVER THE ELEVATED
FRONT IS WHERE A HEAVY BAND OF SNOW SHOULD SET UP...FROM
APPROXIMATELY LAKIN TO GARDEN CITY TO NESS CITY...WHERE 10 TO 11
INCHES OF SNOW IS POSSIBLE BY TUESDAY AFTERNOON. SOUTHEAST OF THAT
ZONE, IN THE LIBERAL TO DODGE CITY TO KINSLEY TO SAINT JOHN ZONE...I
STILL THINK THERE COULD BE SOME BANDS OF HEAVY SNOW TONIGHT...WITH
LESS DURATION THAN NORTH OF THERE, AND 5 TO 8 INCHES OF SNOW IS
EXPECTED THERE BY TUESDAY AFTERNOON. IN BOTH THESE ZONES...STRONG
NORTH WINDS OF 20 TO 35 MPH WITH GUSTS TO NEAR 45 MPH WILL COMBINE
WITH THE SNOW TO CREATE LOW VISIBILITIES IN BLOWING AND DRIFTING
SNOW. WITH A FEW AREAS IN OUR EXTREME WEST SUCH AS TRB AND 3K3
ALREADY REPORTING M1/4SM +SN...THINK THIS COLD AIR AND STRONG
WINDS WILL WRAP TO THE EAST TONIGHT. THEREFORE, THE BLIZZARD
WARNING WILL CONTINUE THROUGH NOON TUESDAY, NORTHWEST OF A LINE
FROM COLDWATER TO PRATT. A WINTER WEATHER ADVISORY FOR 3 TO 5
INCHES OF SNOW AND BLOWING SNOW WILL ALSO CONTINUE THROUGH NOON
TUESDAY FOR PRATT, BARBER AND COMANCHE COUNTIES.
AS FOR TEMPS, THINK OVERNIGHT THAT LOWER DEW POINTS WILL BE
FILTERING IN FROM THE NORTH ON THE STRONG FLOW. STAYED PRETTY
CLOSE TO THE PREVIOUS FORECAST OF MIN T`S FROM AROUND 17F IN EHA
TO 23F IN P28. TOMORROW WILL SEE THICK CLOUDS AROUND ALONG WITH
EARLY SNOW. THE TEMPERATURE WILL NOT RISE MUCH AND SHOULD TOP OUT
IN THE 27F TO 30F DEGREE RANGE. CLOUDS WILL CLEAR OUT FROM WEST TO
EAST TUESDAY EVENING, AND WITH FRESH SNOW COVER EXPECTED AND LIGHT
WEST WINDS, THE TEMPERATURE SHOULD PLUMMET. LOWS TUESDAY NIGHT
WILL BE QUITE COLD, RANGING FROM A VERY COLD 5F IN EHA TO 14F IN
P28. WEDNESDAY, WE WILL STILL BE IN THE GRIP OF COLD ARCTIC AIR
CENTERED TO OUR NORTHEAST, BUT NOT MUCH WARMER THAN TUESDAY IN
MOST SPOTS. HAVE WENT WITH A MAX T FORECAST FOR WEDNESDAY IN THE
27F DEGREE RANGE NEAR LBL, EHA, GCK AND DDC, RANGING UP TO 33F AT P28.
DAYS 3-7...
A NORTHERN BRANCH SHORTWAVE TROUGH WILL DIG TO NEAR THE FOUR CORNERS
ON THURSDAY WITH SOME LIGHT SNOW EXPECTED MOSTLY IN THE AFTERNOON
ACROSS WESTERN KANSAS. THE TROUGH THEN WILL MOVE INTO THE PLAINS ON
FRIDAY WITH LIGHT SNOW ENDING FROM WEST TO EAST ON FRIDAY MORNING.
EXPECT LESS THAN AN INCH ACCUMULATION. ANOTHER LONGER WAVE TROUGH
WILL MOVE ACROSS THE CENTRAL CONUS ON SUNDAY WITH MAINLY DRY
CONDITIONS AND LESS MOISTURE TO WORK WITH. THE GFS AND NEW ECMWF ARE
DIFFERENT WITH ONE SHOWING A SHORTWAVE RIDGE AND THE OTHER A
SHORTWAVE TROUGH BUT LOOKS TO DRY FOR ANY PRECIPITATION.
A COLD FRONT WILL MOVE INTO THE CENTRAL PLAINS WITH HIGH PRESSURE
AND LOWS IN THE TEENS TO LOW 20S ON THURSDAY MORNING AND HIGHS FROM
THE UPPER 20S NORTH TO AROUND 34 SOUTHEAST FA ON THURSDAY. A RIDGE
OF COLD HIGH PRESSURE MOVES INTO THE PLAINS ON FRIDAY WITH LOWS IN
THE TEENS AND HIGHS ONLY IN THE MID 20S. SATURDAY MORNING LOOKS THE
COLDEST WITH LIGHT WINDS AND LOWS IN THE SINGLE DIGITS. FOR SATURDAY
HIGHS SHOULD BE AROUND 30 TO 35. ON CHRISTMAS DAY SUNDAY MORNING
LOWS WILL BE MAINLY IN THE TEENS AND HIGHS AROUND 30 TO 35 WITH
MOSTLY CLEAR SKIES. ON MONDAY MORNING LOWS WILL BE COLD AGAIN WITH
CLEAR SKIES AROUND 10 TO 15 DEGREES AND HIGHS MONDAY WITH WARMING
SOUTHWEST WINDS AND HIGHS FROM THE MID 30S TO LOWER 40S.
&&
.AVIATION...
FOR THE 18Z TAF ISSUANCE...
PRIMARILY IFR CONDITIONS WILL PREVAIL AT ALL TAF SITES THROUGH
TONIGHT AS LIGHT TO MODERATE RAIN CONTINUES TO SPREAD NORTH
ACROSS WESTERN KANSAS. RAIN WILL SWITCH OVER TO SNOW TONIGHT AT
ALL TAF SITES WHILE CIGS LOWER. STRONG NORTH TO NORTHEASTERLY
WINDS DEVELOPING BEHIND THE COLD FRONT WILL CAUSE BLOWING SNOW
CONDITIONS OVERNIGHT RESTRICTING VISIBILITIES THROUGH TUESDAY
MORNING. AS A RESULT, EXPECT IFR CIGS/VSBYS DURING PERIODS OF
HEAVIER SNOW AND BLOWING SNOW.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 20 27 9 27 / 100 80 0 0
GCK 19 27 6 27 / 100 70 0 0
EHA 17 28 5 27 / 100 60 0 0
LBL 19 28 6 27 / 100 60 0 0
HYS 20 27 6 28 / 100 100 0 0
P28 23 30 14 33 / 100 90 10 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
BLIZZARD WARNING UNTIL NOON CST /11 AM MST/ TUESDAY FOR KSZ030-
031-043>046-061>066-074>080-084>088.
WINTER WEATHER ADVISORY UNTIL NOON CST TUESDAY FOR KSZ081-089-
090.
&&
$$
FN12/07/35
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
1141 AM EST MON DEC 19 2011
.SYNOPSIS...
A COLD FRONT ACROSS LAKE MICHIGAN WILL PUSH INTO THE OHIO VALLEY
AND BECOME STATIONARY TONIGHT AND TUESDAY...BRINGING A MIXTURE OF
RAIN AND SNOW. LOW PRESSURE MOVING ALONG THIS BOUNDARY WILL BRING
RAIN TUESDAY NIGHT AND WEDNESDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
UPDATE FOR THE AFTERNOON TO AGAIN MOVES TEMPERATURES UP MAINLY IN
EASTERN OHIO. ONLY MINOR CHANGES TO REMAINDER OF THIS AFTERNOON.
A FRONTAL BOUNDARY CROSSING THE GREAT LAKES WILL INCREASE CLOUDS
AND RAIN CHANCES THROUGH THE EVENING. SOUTHWEST FLOW WILL PUSH
AFTERNOON TEMPERATURES INTO THE 40S WITH GUSTY SOUTHWEST WINDS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/...
LATEST MODEL RUNS CONTINUE TO SHOW SURFACE BOUNDARY BECOMING
STATIONARY ACROSS THE SOUTHERN HALF OF THE FORECAST AREA LATE
TONIGHT. TEMPERATURE PROFILES FROM BUFKIT STILL SUGGEST THAT
MUCH OF THE REGION MAINLY NORTH OF THE MASON-DIXON LINE WILL HAVE
A RAIN/SNOW MIXTURE LATE TONIGHT INTO EARLY TUESDAY MORNING. QPF
AMOUNTS WILL BE LIGHT THROUGH TUESDAY. AREAS NORTH OF PITTSBURGH
TOWARD THE I-80 CORRIDOR WILL LIKELY CHANGE TO ALL SNOW MONDAY
NIGHT BUT ANY ACCUMULATION WILL BE LESS THAN AN INCH.
PRECIPITATION WILL CHANGE TO ALL RAIN BY TUESDAY AFTERNOON AS
TEMPERATURES RISE INTO THE UPPER 30S TO MID 40S.
A SHORT WAVE TROUGH WILL MOVE NORTHEAST FROM THE SOUTHERN PLAINS
WITH ITS ASSOCIATED SURFACE LOW TRACKING ACROSS THE OHIO VALLEY
WEDNESDAY. THIS SYSTEM WILL BRING PERIODS OF RAIN TUESDAY NIGHT
THROUGH LATE WEDNESDAY.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
WEAK SURFACE RIDGE WILL GIVE A GENERALLY DRY FORECAST THURSDAY. A
WEAK DISTURBANCE WILL BRING THE CHANCE FOR SHOWERS FRIDAY WITH
ABOVE NORMAL TEMPERATURES FOLLOWED BY HIGH PRESSURE AND SEASONABLE
TEMPERATURES SATURDAY. A COLD FRONT WILL BRING A CHANCE FOR RAIN
OR SNOW SHOWERS CHRISTMAS DAY. OVERALL LONG TERM FORECAST WAS A
MODIFIED VERSION OF THE HPC GRIDS.
&&
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
NOT ALOT TO CHANGE FOR THIS TAF ISSUANCE AS MODEL BUFKIT PROFILES
AND RUC DATA CONTINUE TO SUGGEST WIND SHEAR ALOFT OVERNIGHT.
MAINTAINED WIND SHEAR OF WS010/23040KT THROUGH 16Z AS VERTICAL
MIXING BEGINS TO TAKE PLACE OUT AHEAD OF THE BOUNDARY PROGGED TO
BRING PRECIP TO ALL TERMINALS STARTING AROUND 19Z. SURFACE WINDS
WILL BECOME SOUTHWEST 10-15 KTS WITH GUSTS TO 20-25 KTS BY MIDDAY
MONDAY. CURRENT LAMP AND MAV GUIDANCE SUGGESTS RESTRICTIONS WILL
START OUT AT MVFR AS THE COLD FRONT DROPS SOUTHEASTWARD.
OUTLOOK...MONDAY NIGHT THROUGH FRIDAY...
STALLING COLD FRONTAL PRECIPITATION BAND WILL CAUSE FREQUENT IFR
PERIODS MONDAY NIGHT INTO WEDNESDAY. ENSUING WINTRY MIX MAY CAUSE
ADDED THE AVIATION HAZARD OF LOW LEVEL ICING TUESDAY. COLD POOL
STRATOCUMULUS MAY PROVIDE LINGERING RESTRICTIONS, MAINLY IN THE
MVFR RANGE THURSDAY. A NORTHEAST MOVING LOW PRESSURE SYSTEM MAY
PROVIDE MIXED PRECIPITATION AND IFR RESTRICTIONS FRIDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
1001 AM EST MON DEC 19 2011
.SYNOPSIS...
A COLD FRONT WILL PUSH INTO THE OHIO VALLEY AND BECOME STATIONARY
MONDAY NIGHT AND TUESDAY...BRINGING A MIXTURE OF RAIN AND SNOW.
LOW PRESSURE MOVING ALONG THIS BOUNDARY WILL BRING RAIN TUESDAY
NIGHT AND WEDNESDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
ONLY MINOR CHANGES TO BRINGS IN SCATTERED POPS A BIT SOONER THIS
MORNING ACROSS OHIO INTO NORTHWEST PA AND BRING CLOUDS TO THE
RIDGES MORE QUICKLY. RAISED MAX TEMPS A COUPLE DEGREES BASED ON
CURRENT READINGS. A FRONTAL BOUNDARY CROSSING THE GREAT LAKES WILL
INCREASE CLOUDS AND RAIN CHANCES THROUGH THE EVENING. SOUTHWEST
FLOW WILL PUSH AFTERNOON TEMPERATURES INTO THE 40S WITH GUSTY
SOUTHWEST WINDS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/...
LATEST MODEL RUNS CONTINUE TO SHOW SURFACE BOUNDARY BECOMING
STATIONARY ACROSS THE SOUTHERN HALF OF THE FORECAST AREA LATE
TONIGHT. TEMPERATURE PROFILES FROM BUFKIT STILL SUGGEST THAT
MUCH OF THE REGION MAINLY NORTH OF THE MASON-DIXON LINE WILL HAVE
A RAIN/SNOW MIXTURE LATE TONIGHT INTO EARLY TUESDAY MORNING. QPF
AMOUNTS WILL BE LIGHT THROUGH TUESDAY. AREAS NORTH OF PITTSBURGH
TOWARD THE I-80 CORRIDOR WILL LIKELY CHANGE TO ALL SNOW MONDAY
NIGHT BUT ANY ACCUMULATION WILL BE LESS THAN AN INCH.
PRECIPITATION WILL CHANGE TO ALL RAIN BY TUESDAY AFTERNOON AS
TEMPERATURES RISE INTO THE UPPER 30S TO MID 40S.
A SHORT WAVE TROUGH WILL MOVE NORTHEAST FROM THE SOUTHERN PLAINS
WITH ITS ASSOCIATED SURFACE LOW TRACKING ACROSS THE OHIO VALLEY
WEDNESDAY. THIS SYSTEM WILL BRING PERIODS OF RAIN TUESDAY NIGHT
THROUGH LATE WEDNESDAY.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
WEAK SURFACE RIDGE WILL GIVE A GENERALLY DRY FORECAST THURSDAY. A
WEAK DISTURBANCE WILL BRING THE CHANCE FOR SHOWERS FRIDAY WITH
ABOVE NORMAL TEMPERATURES FOLLOWED BY HIGH PRESSURE AND SEASONABLE
TEMPERATURES SATURDAY. A COLD FRONT WILL BRING A CHANCE FOR RAIN
OR SNOW SHOWERS CHRISTMAS DAY. OVERALL LONG TERM FORECAST WAS A
MODIFIED VERSION OF THE HPC GRIDS.
&&
.AVIATION /15Z MONDAY THROUGH FRIDAY/...
NOT ALOT TO CHANGE FOR THIS TAF ISSUANCE AS MODEL BUFKIT PROFILES
AND RUC DATA CONTINUE TO SUGGEST WIND SHEAR ALOFT OVERNIGHT.
MAINTAINED WIND SHEAR OF WS010/23040KT THROUGH 16Z AS VERTICAL
MIXING BEGINS TO TAKE PLACE OUT AHEAD OF THE BOUNDARY PROGGED TO
BRING PRECIP TO ALL TERMINALS STARTING AROUND 19Z. SURFACE WINDS
WILL BECOME SOUTHWEST 10-15 KTS WITH GUSTS TO 20-25 KTS BY MIDDAY
MONDAY. CURRENT LAMP AND MAV GUIDANCE SUGGESTS RESTRICTIONS WILL
START OUT AT MVFR AS THE COLD FRONT DROPS SOUTHEASTWARD.
OUTLOOK...MONDAY NIGHT THROUGH FRIDAY...
STALLING COLD FRONTAL PRECIPITATION BAND WILL CAUSE FREQUENT IFR
PERIODS MONDAY NIGHT INTO WEDNESDAY. ENSUING WINTRY MIX MAY CAUSE
ADDED THE AVIATION HAZARD OF LOW LEVEL ICING TUESDAY. COLD POOL
STRATOCUMULUS MAY PROVIDE LINGERING RESTRICTIONS, MAINLY IN THE
MVFR RANGE THURSDAY. A NORTHEAST MOVING LOW PRESSURE SYSTEM MAY
PROVIDE MIXED PRECIPITATION AND IFR RESTRICTIONS FRIDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
714 AM EST MON DEC 19 2011
.SYNOPSIS...
A COLD FRONT WILL PUSH INTO THE OHIO VALLEY AND BECOME STATIONARY
MONDAY NIGHT AND TUESDAY...BRINGING A MIXTURE OF RAIN AND SNOW.
LOW PRESSURE MOVING ALONG THIS BOUNDARY WILL BRING RAIN TUESDAY
NIGHT AND WEDNESDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
ONLY MINOR CHANGES TO NEAR TERM. OVERSPREAD CLOUDS A BIT QUICKER
THIS MORNING AND MADE A FEW TWEAKS TO MORNING TEMPERATURE RISE.
PRECIPITATION PROBABILITIES WILL INCREASE WEST TO EAST BY THIS
AFTERNOON AHEAD OF A FRONTAL BOUNDARY CROSSING THE GREAT LAKES.
SOUTHWEST FLOW WILL PUSH AFTERNOON TEMPERATURES INTO THE 40S.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/...
LATEST MODEL RUNS CONTINUE TO SHOW SURFACE BOUNDARY BECOMING
STATIONARY ACROSS THE SOUTHERN HALF OF THE FORECAST AREA LATE
TONIGHT. TEMPERATURE PROFILES FROM BUFKIT STILL SUGGEST THAT
MUCH OF THE REGION MAINLY NORTH OF THE MASON-DIXON LINE WILL HAVE
A RAIN/SNOW MIXTURE LATE TONIGHT INTO EARLY TUESDAY MORNING. QPF
AMOUNTS WILL BE LIGHT THROUGH TUESDAY. AREAS NORTH OF PITTSBURGH
TOWARD THE I-80 CORRIDOR WILL LIKELY CHANGE TO ALL SNOW MONDAY
NIGHT BUT ANY ACCUMULATION WILL BE LESS THAN AN INCH.
PRECIPITATION WILL CHANGE TO ALL RAIN BY TUESDAY AFTERNOON AS
TEMPERATURES RISE INTO THE UPPER 30S TO MID 40S.
A SHORT WAVE TROUGH WILL MOVE NORTHEAST FROM THE SOUTHERN PLAINS
WITH ITS ASSOCIATED SURFACE LOW TRACKING ACROSS THE OHIO VALLEY
WEDNESDAY. THIS SYSTEM WILL BRING PERIODS OF RAIN TUESDAY NIGHT
THROUGH LATE WEDNESDAY.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
WEAK SURFACE RIDGE WILL GIVE A GENERALLY DRY FORECAST THURSDAY. A
WEAK DISTURBANCE WILL BRING THE CHANCE FOR SHOWERS FRIDAY WITH
ABOVE NORMAL TEMPERATURES FOLLOWED BY HIGH PRESSURE AND SEASONABLE
TEMPERATURES SATURDAY. A COLD FRONT WILL BRING A CHANCE FOR RAIN
OR SNOW SHOWERS CHRISTMAS DAY. OVERALL LONG TERM FORECAST WAS A
MODIFIED VERSION OF THE HPC GRIDS.
&&
.AVIATION /12Z MONDAY THROUGH FRIDAY/...
NOT ALOT TO CHANGE FOR THIS TAF ISSUANCE AS MODEL BUFKIT PROFILES
AND RUC DATA CONTINUE TO SUGGEST WIND SHEAR ALOFT OVERNIGHT.
MAINTAINED WIND SHEAR OF WS010/23040KT THROUGH 16Z AS VERTICAL
MIXING BEGINS TO TAKE PLACE OUT AHEAD OF THE BOUNDARY PROGGED TO
BRING PRECIP TO ALL TERMINALS STARTING AROUND 19Z. SURFACE WINDS
WILL BECOME SOUTHWEST 10-15 KTS WITH GUSTS TO 20-25 KTS BY MIDDAY
MONDAY. CURRENT LAMP AND MAV GUIDANCE SUGGESTS RESTRICTIONS WILL
START OUT AT MVFR AS THE COLD FRONT DROPS SOUTHEASTWARD.
OUTLOOK...MONDAY NIGHT THROUGH FRIDAY...
STALLING COLD FRONTAL PRECIPITATION BAND WILL CAUSE FREQUENT IFR
PERIODS MONDAY NIGHT INTO WEDNESDAY. ENSUING WINTRY MIX MAY CAUSE
ADDED THE AVIATION HAZARD OF LOW LEVEL ICING TUESDAY. COLD POOL
STRATOCUMULUS MAY PROVIDE LINGERING RESTRICTIONS, MAINLY IN THE
MVFR RANGE THURSDAY. A NORTHEAST MOVING LOW PRESSURE SYSTEM MAY
PROVIDE MIXED PRECIPITATION AND IFR RESTRICTIONS FRIDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
408 AM EST MON DEC 19 2011
.SYNOPSIS...
A COLD FRONT WILL PUSH INTO THE OHIO VALLEY AND BECOME STATIONARY
MONDAY NIGHT AND TUESDAY...BRINGING A MIXTURE OF RAIN AND SNOW.
LOW PRESSURE MOVING ALONG THIS BOUNDARY WILL BRING RAIN TUESDAY
NIGHT AND WEDNESDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
MAINLY CLEAR SKIES WILL CONTINUE THROUGH MID MORNING AS SURFACE
HIGH DEPARTS. CLOUD COVER AND PRECIPITATION PROBABILITIES WILL
INCREASE WEST TO EAST BY THIS AFTERNOON AHEAD OF A FRONTAL
BOUNDARY CROSSING THE GREAT LAKES. SOUTHWEST FLOW WILL PUSH
AFTERNOON TEMPERATURES INTO THE 40S.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/...
LATEST MODEL RUNS CONTINUE TO SHOW SURFACE BOUNDARY BECOMING
STATIONARY ACROSS THE SOUTHERN HALF OF THE FORECAST AREA LATE
TONIGHT. TEMPERATURE PROFILES FROM BUFKIT STILL SUGGEST THAT
MUCH OF THE REGION MAINLY NORTH OF THE MASON-DIXON LINE WILL HAVE
A RAIN/SNOW MIXTURE LATE TONIGHT INTO EARLY TUESDAY MORNING. QPF
AMOUNTS WILL BE LIGHT THROUGH TUESDAY. AREAS NORTH OF PITTSBURGH
TOWARD THE I-80 CORRIDOR WILL LIKELY CHANGE TO ALL SNOW MONDAY
NIGHT BUT ANY ACCUMULATION WILL BE LESS THAN AN INCH.
PRECIPITATION WILL CHANGE TO ALL RAIN BY TUESDAY AFTERNOON AS
TEMPERATURES RISE INTO THE UPPER 30S TO MID 40S.
A SHORT WAVE TROUGH WILL MOVE NORTHEAST FROM THE SOUTHERN PLAINS
WITH ITS ASSOCIATED SURFACE LOW TRACKING ACROSS THE OHIO VALLEY
WEDNESDAY. THIS SYSTEM WILL BRING PERIODS OF RAIN TUESDAY NIGHT
THROUGH LATE WEDNESDAY.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
WEAK SURFACE RIDGE WILL GIVE A GENERALLY DRY FORECAST THURSDAY. A
WEAK DISTURBANCE WILL BRING THE CHANCE FOR SHOWERS FRIDAY WITH
ABOVE NORMAL TEMPERATURES FOLLOWED BY HIGH PRESSURE AND SEASONABLE
TEMPERATURES SATURDAY. A COLD FRONT WILL BRING A CHANCE FOR RAIN
OR SNOW SHOWERS CHRISTMAS DAY. OVERALL LONG TERM FORECAST WAS A
MODIFIED VERSION OF THE HPC GRIDS.
&&
.AVIATION /08Z MONDAY THROUGH FRIDAY/...
NOT ALOT TO CHANGE FOR THIS TAF ISSUANCE AS MODEL BUFKIT PROFILES
AND RUC DATA CONTINUE TO SUGGEST WIND SHEAR ALOFT OVERNIGHT.
MAINTAINED WIND SHEAR OF WS010/23040KT THROUGH 16Z AS VERTICAL
MIXING BEGINS TO TAKE PLACE OUT AHEAD OF THE BOUNDARY PROGGED TO
BRING PRECIP TO ALL TERMINALS STARTING AROUND 19Z. SURFACE WINDS
WILL BECOME SOUTHWEST 10-15 KTS WITH GUSTS TO 20-25 KTS BY MIDDAY
MONDAY. CURRENT LAMP AND MAV GUIDANCE SUGGESTS RESTRICTIONS WILL
START OUT AT MVFR AS THE COLD FRONT DROPS SOUTHEASTWARD.
OUTLOOK...MONDAY NIGHT THROUGH FRIDAY...
STALLING COLD FRONTAL PRECIPITATION BAND WILL CAUSE FREQUENT IFR
PERIODS MONDAY NIGHT INTO WEDNESDAY. ENSUING WINTRY MIX MAY CAUSE
ADDED THE AVIATION HAZARD OF LOW LEVEL ICING TUESDAY. COLD POOL
STRATOCUMULUS MAY PROVIDE LINGERING RESTRICTIONS, MAINLY IN THE
MVFR RANGE THURSDAY. A NORTHEAST MOVING LOW PRESSURE SYSTEM MAY
PROVIDE MIXED PRECIPITATION AND IFR RESTRICTIONS FRIDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
1256 AM EST MON DEC 19 2011
.SYNOPSIS...
A COLD FRONT WILL PUSH SOUTH AND BECOME STATIONARY OVER THE
REGION MONDAY NIGHT AND TUESDAY...BRINGING A CHANCE OF RAIN AND
SNOW. LOW PRESSURE MOVING ALONG THIS BOUNDARY WILL BRING RAIN
TUESDAY NIGHT AND WEDNESDAY.
&&
.NEAR TERM /THROUGH TODAY/...
EXPECT MAINLY CLEAR SKIES OVERNIGHT BUT LITTLE DROP IN
TEMPERATURES AS SOUTHERLY FLOW INCREASES.
MORNING SUNSHINE SHALL FADE BEHIND A CANOPY OF MID LEVEL CLOUDS
AHEAD OF A BAROCLINIC ZONE CROSSING THROUGH THE GREAT LAKES. RAIN
CHANCES WILL INCREASE BY AFTERNOON AND TEMPERATURES WILL PEAK IN
THE 40S.
&&
.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
AS COLD FRONT BECOMES STATIONARY SOUTH OF THE MASON DIXON LINE
MONDAY NIGHT MODEL PROFILES AND THICKNESS VALUES SUGGEST THAT MUCH
OF THE REGION WILL HAVE A RAIN-SNOW MIX INTO THE FIRST HALF OF
TUESDAY. AREAS NORTH OF PITTSBURGH TOWARD THE I-80 CORRIDOR WILL
BE ALL SNOW FOR A TIME BUT ANY ACCUMULATION WILL BE A COATING OR
LESS THAN AN INCH. BY TUESDAY AFTERNOON PRECIP WILL BECOME ALL
RAIN AS LOW PRESSURE MOVES ACROSS THE LOWER OHIO VALLEY. MILD
TEMPERATURES AND CONTINUED RAIN SHOWERS INTO WEDNESDAY AS THE
SURFACE LOW MOVES TO THE EASTERN GREAT LAKES AND PUSHES A WEAK
COLD FRONT ACROSS AREA BY LATE DAY.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
WEAK SURFACE RIDGE WILL GIVE A GENERALLY DRY FORECAST THURSDAY. A
WEAK DISTURBANCE WILL BRING THE CHANCE FOR SHOWERS FRIDAY WITH
ABOVE NORMAL TEMPERATURES FOLLOWED BY HIGH PRESSURE AND SEASONABLE
TEMPERATURES SATURDAY. A COLD FRONT WILL BRING A CHANCE FOR RAIN
OR SNOW SHOWERS CHRISTMAS DAY. OVERALL LONG TERM FORECAST WAS A
MODIFIED VERSION OF THE HPC GRIDS.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
NOT ALOT TO CHANGE FOR THIS TAF ISSUANCE AS MODEL BUFKIT PROFILES
AND RUC DATA CONTINUE TO SUGGEST WIND SHEAR ALOFT OVERNIGHT.
MAINTAINED WIND SHEAR OF WS010/23040KT THROUGH 16Z AS VERTICAL
MIXING BEGINS TO TAKE PLACE OUT AHEAD OF THE BOUNDARY PROGGED TO
BRING PRECIP TO ALL TERMINALS STARTING AROUND 19Z. SURFACE WINDS
WILL BECOME SOUTHWEST 10-15 KTS WITH GUSTS TO 20-25 KTS BY MIDDAY
MONDAY. CURRENT LAMP AND MAV GUIDANCE SUGGESTS RESTRICTIONS WILL
START OUT AT MVFR AS THE COLD FRONT DROPS SOUTHEASTWARD.
OUTLOOK...MONDAY NIGHT THROUGH FRIDAY...
STALLING COLD FRONTAL PRECIPITATION BAND WILL CAUSE FREQUENT IFR
PERIODS MONDAY NIGHT INTO WEDNESDAY. ENSUING WINTRY MIX MAY CAUSE
ADDED THE AVIATION HAZARD OF LOW LEVEL ICING TUESDAY. COLD POOL
STRATOCUMULUS MAY PROVIDE LINGERING RESTRICTIONS, MAINLY IN THE
MVFR RANGE THURSDAY. A NORTHEAST MOVING LOW PRESSURE SYSTEM MAY
PROVIDE MIXED PRECIPITATION AND IFR RESTRICTIONS FRIDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
107 PM EST MON DEC 19 2011
UPDATED AVIATION DISCUSSION FOR THE 18Z TAFS
.DISCUSSION /TODAY THROUGH SUNDAY/... ISSUED AT 407 AM EST
997MB LOW PRESSURE SYSTEM LOCATED OVER EASTERN ONTARIO WILL CONTINUE
E INTO SRN QUEBEC THIS MORNING. COLD FRONT CURRENTLY SWEEPING
THROUGH CNTRL/ERN UPPER MI...WITH ONLY SCT CLOUDS ASSOCIATED WITH
IT/S PASSING. BEHIND THE FRONT...A LARGE AREA OF LOW CLOUDS OVER NRN
MN...SW ONTARIO AND MANITOBA WOULD INDICATE THAT MOISTURE MAY BE
BETTER THAN INDICATED BY THE 00Z NAM. 00Z GFS AND LATEST RUC RUNS
SEEM TO BE DOING A LITTLE BETTER ON PICKING UP THE LOW CLOUDS AND
WILL FOLLOW THAT FOR THE TODAY FORECAST /WHICH IS A LITTLE MORE
PESSIMISTIC/.
COLD AIR STILL LAGGING BEHIND THE FRONT...AND WITH THE AREA OF LOW
CLOUDS CURRENTLY WORKING INTO WRN UPPER MI...EXPECT SOME PCPN TO
START OVER THE NEXT COUPLE OF HOURS OVER THE UPSLOPE HIGHER TERRAIN.
H850-700 DRY AIR AND SUBSIDENCE WILL HELP KEEP INVERSION HEIGHTS AT
3KFT. DRY NEAR SFC AIR WILL KEEP CLOUD DEPTHS LIMITED /ONLY AROUND
1.5-2KFT/ SO HAVE LIMITED CONF ON MUCH PCPN OCCURRING. THIS COULD
CREATE SOME P-TYPE ISSUES INITIALLY...AS BUFKIT SOUNDINGS SHOW CLOUD
TEMPS ARE ONLY IN THE -4 TO -7C RANGE...LIMITING ICE CRYSTALS.
SHOULD BE A QUICK TRANSITION FROM W TO E THROUGH THE EARLY MORNING
HOURS WITH THE H850 TEMPS FALLING TO -11C BY 15Z. THEREFORE...WILL
CONTINUE MENTION OF DZ/FZDZ THROUGH 12Z OVER THE W AND JUST DZ
THROUGH 15Z OVER THE E DUE TO WARMER SFC TEMPS. THE COLDER H850
TEMPS WILL LIKELY LEAD TO SOME LIGHT LES DEVELOPMENT THIS
MORNING...BUT INVERSION HEIGHTS WILL LIMIT INTENSITY. WITH THE
LONGER FETCH...THINK THE LES WILL CONTINUE THROUGH THE AFTN EVEN
THOUGH THE LOWER INVERSION HEIGHTS MAY END UP LEADING TO MAINLY
CLOUDS. OTHERWISE...TRANSITIONED TO MORE OF A -SHSN/FLURRIES IN THE
AFTN OVER THE W BEFORE DECREASING CLOUDS LATE IN THE AFTN DUE TO THE
WARMING H850 TEMPS AND DRIER AIR FINALLY ARRIVING WITH THE
APPROACHING SFC RIDGE.
HIGH PRESSURE RIDGE SLIDES OVER THE AREA TONIGHT...BRINGING AN END
TO THE LES OVER THE E AND THE LK CLOUDS OVER THE REST OF THE AREA.
WITH THE DECREASING CLOUDS AND WINDS...SHOULD BE A COLD NIGHT OVER
THE INTERIOR LOCATIONS. PWATS AROUND 35 PERCENT OF NORMAL WILL HELP
ENHANCE RADIATIONAL COOLING AND HAVE LOWS IN THE MID SINGLE DIGITS
ABOVE ZERO OVER THE INTERIOR W/CNTRL. WINDS WILL INCREASE SOME OVER
THE FAR W LATE IN THE NIGHT AHEAD OF THE NEXT WAVE...WHICH COULD
LEAD TO A RISE IN TEMPS LATE THERE.
NEXT SHORTWAVE AND ASSOCIATED LOW WILL BE MOVING THROUGH THE NRN
STREAM ON TUES...BUT WITH IT BEING LOCATED MUCH FARTHER N /OVER NRN
ONTARIO AND HUDSON BAY/ EXPECT IT TO HAVE LIMITED AFFECT ON THE
WEATHER OTHER THAN INCREASING THE WSW WINDS. SHOULD BE ANOTHER ABOVE
NORMAL TEMP DAY WITH A MOSTLY SUNNY SKY.
MODELS HAVE CONTINUED THE FASTER TREND WITH MERGING THE SRN STREAM
UPPER LOW CURRENTLY OVER THE SWRN CONUS WITH THE NRN STREAM ON WED
OVER THE LOWER GREAT LKS. WITH THE APPROACHING NRN STREAM WAVE STILL
OVER MANITOBA/SASK...AREA SHOULD BE BETWEEN SYSTEMS AND UNDER WEAK
HIGH PRESSURE TUES NIGHT AND WED MORNING. WILL GO WITH PARTLY CLOUDY
TO MOSTLY CLEAR SKIES FOR NOW...WITH CLOUDS JUST TO THE NW AND SE OF
THE CWA...BUT WILL BE CONTINGENT ON LOW CLOUDS HINTED AT BY THE NAM
NOT STICKING AROUND TOO LONG. THEN WITH SFC TROUGH TO THE
NW...ASSOCIATED WITH LOW OVER HUDSON BAY...NEARING THE CWA IN THE
AFTN AND MOVING THROUGH WED NIGHT...HAVE INCREASED CLOUDS FROM THE
AFTN ON. MOISTURE/FORCING IS WEAK WITH THE PASSAGE OF THE
TROUGH...SO WILL CONTINUE MENTION OF SLIGHTS OVER WRN LK SUPERIOR IN
THE AFTN AND SLIGHTS/LOW CHANCES ALONG THE FRONT WED NIGHT.
UPPER TROUGH THEN SWEEPS ACROSS THE AREA LATE WED NIGHT INTO
FRI...BRINGING A BETTER CHANCE FOR SNOW BEHIND THE FRONT. SOME
DIFFERENCES IN THE H850 TEMPS WITH THE 00Z GFS AND 12Z ECMWF...BUT
OVERALL IDEA IS AROUND -12C...WHICH WOULD CREATE LARGE ENOUGH
DELTA-T VALUES FOR LES. AS IS THE CASE TODAY...H800-650 SUBSIDENCE
AND DRY AIR WILL LIMIT THE INVERSION HEIGHTS TO 4KFT. SHOULD BE
DECENT LLVL MOISTURE TO WORK WITH BELOW THE INVERSION...SO AM
CONFIDENT ENOUGH TO GO WITH CHANCE POPS. WITH THE FORCING BELOW THE
DGZ /CLOUD TOPS ONLY REACH -15C ON THE COLDER GFS/ EXPECT SNOW
RATIOS TO BE IN THE LOW TEENS AND WILL LIKELY ONLY SEE A LIGHT
DUSTING FOR AREAS FAVORED BY A NNW WIND.
UPPER TROUGH STARTS TO SHIFT E ON FRI AS SFC HIGH BEGINS TO PUSH
OVER THE AREA. DRIER AIR ASSOCIATED WITH THE HIGH WILL LEAD TO
DIMINISHING LES POPS THURS NIGHT WEST AND DURING THE DAY FRI
EAST...AS WINDS BECOME ANTICYCLONIC. MAY SEE WEAK UPPER RIDGING ON
SAT...AHEAD OF THE NEXT NRN STREAM TROUGH TO AFFECT THE AREA SAT
NIGHT INTO SUN. ONCE AGAIN...FORCING/MOISTURE LIMITED ALONG THE
FRONT AND THE BEST POTENTIAL FOR PCPN WILL COME ON SUN WITH LES...AS
H850 TEMPS FALL TOWARDS -13C.
&&
.AVIATION /FOR THE 18Z TAF ISSUANCE/...
NW FLOW WILL KEEP MVFR STRATUS DECK OVER UPR MI INTO THIS EVENING.
EXPECT SKIES TO CLEAR THIS EVENING AT KIWD AND KSAW AS SFC HIGH PRES
RIDGE AXIS DROPS SE THRU THE AREA AND WINDS SHIFT WSW. WINDS WILL
CLEAR LATER TONIGHT AT KCMX AS WINDS WILL STAY ONSHORE LONGER THERE.
SW GRADIENT WINDS WILL INCREASE TUESDAY WITH GUSTS APPROACHING 25 KT
AT KIWD AND KSAW BY LATE MORNING/EARLY AFTERNOON.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
IN THE WAKE OF A COLD FRONT MOVING SE ACROSS LAKE SUPERIOR...A
PERIOD OF GALE FORCE GUSTS SHOULD OCCUR OVER THE E HALF OF THE LAKE
EARLY THIS MORNING IN ADVANCE OF 5MB/3HR PRES RISES. SINCE CORE OF
PRES RISES WILL SHIFT E OF LAKE SUPERIOR BY MID MORNING...GALE
WARNING WILL MOST LIKELY BE CANCELLED BY NEXT SCHEDULED FCST
ISSUANCE. OTHERWISE...WINDS WILL DIMINISH W TO E TODAY/TONIGHT AS
HIGH PRES QUICKLY APPROACHES AND THEN PASSES ACROSS THE GREAT LAKES.
DEEP LOW PRES MOVING E TO HUDSON BAY EARLY TUE WILL LIKELY BRING
ANOTHER ROUND OF SW GALES TO PORTIONS OF LAKE SUPERIOR...MAINLY THE
W HALF. SW WIND DIRECTION WILL FAVOR THE AREA BTWN THE KEWEENAW AND
ISLE ROYALE FOR STRONGEST WINDS TUE (GUSTS TO AROUND 40KT). GALES
WILL END TUE NIGHT AS PRES GRADIENT WEAKENS. WINDS WILL BE BLO 25KT
WED THRU FRI.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...
GALE WARNING UNTIL 1 PM EST THIS AFTERNOON FOR LSZ250-251-266-
267.
GALE WATCH FROM TUESDAY MORNING THROUGH LATE TUESDAY NIGHT FOR
LSZ162-263-264.
GALE WARNING UNTIL 7 AM EST THIS MORNING FOR LSZ264.
LAKE MICHIGAN...NONE.
&&
$$
DISCUSSION...SRF
AVIATION...VOSS
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
735 AM EST MON DEC 19 2011
UPDATED AVIATION DISCUSSION FOR THE 12Z TAFS
.DISCUSSION /TODAY THROUGH SUNDAY/... ISSUED AT 407 AM EST
997MB LOW PRESSURE SYSTEM LOCATED OVER EASTERN ONTARIO WILL CONTINUE
E INTO SRN QUEBEC THIS MORNING. COLD FRONT CURRENTLY SWEEPING
THROUGH CNTRL/ERN UPPER MI...WITH ONLY SCT CLOUDS ASSOCIATED WITH
IT/S PASSING. BEHIND THE FRONT...A LARGE AREA OF LOW CLOUDS OVER NRN
MN...SW ONTARIO AND MANITOBA WOULD INDICATE THAT MOISTURE MAY BE
BETTER THAN INDICATED BY THE 00Z NAM. 00Z GFS AND LATEST RUC RUNS
SEEM TO BE DOING A LITTLE BETTER ON PICKING UP THE LOW CLOUDS AND
WILL FOLLOW THAT FOR THE TODAY FORECAST /WHICH IS A LITTLE MORE
PESSIMISTIC/.
COLD AIR STILL LAGGING BEHIND THE FRONT...AND WITH THE AREA OF LOW
CLOUDS CURRENTLY WORKING INTO WRN UPPER MI...EXPECT SOME PCPN TO
START OVER THE NEXT COUPLE OF HOURS OVER THE UPSLOPE HIGHER TERRAIN.
H850-700 DRY AIR AND SUBSIDENCE WILL HELP KEEP INVERSION HEIGHTS AT
3KFT. DRY NEAR SFC AIR WILL KEEP CLOUD DEPTHS LIMITED /ONLY AROUND
1.5-2KFT/ SO HAVE LIMITED CONF ON MUCH PCPN OCCURRING. THIS COULD
CREATE SOME P-TYPE ISSUES INITIALLY...AS BUFKIT SOUNDINGS SHOW CLOUD
TEMPS ARE ONLY IN THE -4 TO -7C RANGE...LIMITING ICE CRYSTALS.
SHOULD BE A QUICK TRANSITION FROM W TO E THROUGH THE EARLY MORNING
HOURS WITH THE H850 TEMPS FALLING TO -11C BY 15Z. THEREFORE...WILL
CONTINUE MENTION OF DZ/FZDZ THROUGH 12Z OVER THE W AND JUST DZ
THROUGH 15Z OVER THE E DUE TO WARMER SFC TEMPS. THE COLDER H850
TEMPS WILL LIKELY LEAD TO SOME LIGHT LES DEVELOPMENT THIS
MORNING...BUT INVERSION HEIGHTS WILL LIMIT INTENSITY. WITH THE
LONGER FETCH...THINK THE LES WILL CONTINUE THROUGH THE AFTN EVEN
THOUGH THE LOWER INVERSION HEIGHTS MAY END UP LEADING TO MAINLY
CLOUDS. OTHERWISE...TRANSITIONED TO MORE OF A -SHSN/FLURRIES IN THE
AFTN OVER THE W BEFORE DECREASING CLOUDS LATE IN THE AFTN DUE TO THE
WARMING H850 TEMPS AND DRIER AIR FINALLY ARRIVING WITH THE
APPROACHING SFC RIDGE.
HIGH PRESSURE RIDGE SLIDES OVER THE AREA TONIGHT...BRINGING AN END
TO THE LES OVER THE E AND THE LK CLOUDS OVER THE REST OF THE AREA.
WITH THE DECREASING CLOUDS AND WINDS...SHOULD BE A COLD NIGHT OVER
THE INTERIOR LOCATIONS. PWATS AROUND 35 PERCENT OF NORMAL WILL HELP
ENHANCE RADIATIONAL COOLING AND HAVE LOWS IN THE MID SINGLE DIGITS
ABOVE ZERO OVER THE INTERIOR W/CNTRL. WINDS WILL INCREASE SOME OVER
THE FAR W LATE IN THE NIGHT AHEAD OF THE NEXT WAVE...WHICH COULD
LEAD TO A RISE IN TEMPS LATE THERE.
NEXT SHORTWAVE AND ASSOCIATED LOW WILL BE MOVING THROUGH THE NRN
STREAM ON TUES...BUT WITH IT BEING LOCATED MUCH FARTHER N /OVER NRN
ONTARIO AND HUDSON BAY/ EXPECT IT TO HAVE LIMITED AFFECT ON THE
WEATHER OTHER THAN INCREASING THE WSW WINDS. SHOULD BE ANOTHER ABOVE
NORMAL TEMP DAY WITH A MOSTLY SUNNY SKY.
MODELS HAVE CONTINUED THE FASTER TREND WITH MERGING THE SRN STREAM
UPPER LOW CURRENTLY OVER THE SWRN CONUS WITH THE NRN STREAM ON WED
OVER THE LOWER GREAT LKS. WITH THE APPROACHING NRN STREAM WAVE STILL
OVER MANITOBA/SASK...AREA SHOULD BE BETWEEN SYSTEMS AND UNDER WEAK
HIGH PRESSURE TUES NIGHT AND WED MORNING. WILL GO WITH PARTLY CLOUDY
TO MOSTLY CLEAR SKIES FOR NOW...WITH CLOUDS JUST TO THE NW AND SE OF
THE CWA...BUT WILL BE CONTINGENT ON LOW CLOUDS HINTED AT BY THE NAM
NOT STICKING AROUND TOO LONG. THEN WITH SFC TROUGH TO THE
NW...ASSOCIATED WITH LOW OVER HUDSON BAY...NEARING THE CWA IN THE
AFTN AND MOVING THROUGH WED NIGHT...HAVE INCREASED CLOUDS FROM THE
AFTN ON. MOISTURE/FORCING IS WEAK WITH THE PASSAGE OF THE
TROUGH...SO WILL CONTINUE MENTION OF SLIGHTS OVER WRN LK SUPERIOR IN
THE AFTN AND SLIGHTS/LOW CHANCES ALONG THE FRONT WED NIGHT.
UPPER TROUGH THEN SWEEPS ACROSS THE AREA LATE WED NIGHT INTO
FRI...BRINGING A BETTER CHANCE FOR SNOW BEHIND THE FRONT. SOME
DIFFERENCES IN THE H850 TEMPS WITH THE 00Z GFS AND 12Z ECMWF...BUT
OVERALL IDEA IS AROUND -12C...WHICH WOULD CREATE LARGE ENOUGH
DELTA-T VALUES FOR LES. AS IS THE CASE TODAY...H800-650 SUBSIDENCE
AND DRY AIR WILL LIMIT THE INVERSION HEIGHTS TO 4KFT. SHOULD BE
DECENT LLVL MOISTURE TO WORK WITH BELOW THE INVERSION...SO AM
CONFIDENT ENOUGH TO GO WITH CHANCE POPS. WITH THE FORCING BELOW THE
DGZ /CLOUD TOPS ONLY REACH -15C ON THE COLDER GFS/ EXPECT SNOW
RATIOS TO BE IN THE LOW TEENS AND WILL LIKELY ONLY SEE A LIGHT
DUSTING FOR AREAS FAVORED BY A NNW WIND.
UPPER TROUGH STARTS TO SHIFT E ON FRI AS SFC HIGH BEGINS TO PUSH
OVER THE AREA. DRIER AIR ASSOCIATED WITH THE HIGH WILL LEAD TO
DIMINISHING LES POPS THURS NIGHT WEST AND DURING THE DAY FRI
EAST...AS WINDS BECOME ANTICYCLONIC. MAY SEE WEAK UPPER RIDGING ON
SAT...AHEAD OF THE NEXT NRN STREAM TROUGH TO AFFECT THE AREA SAT
NIGHT INTO SUN. ONCE AGAIN...FORCING/MOISTURE LIMITED ALONG THE
FRONT AND THE BEST POTENTIAL FOR PCPN WILL COME ON SUN WITH LES...AS
H850 TEMPS FALL TOWARDS -13C.
&&
.AVIATION /FOR THE 12Z TAF ISSUANCE/...
STRATUS WITH MVFR CIGS HAS SPREAD INTO UPPER MI. GIVEN THE EXTENSIVE
NATURE OF THE STRATUS (EXTENDS WELL NW INTO SE MANITOBA)...THIS FCST
ISSUANCE WILL TREND MUCH MORE PESSIMISTIC BY HOLDING MVFR CIGS
(MOSTLY BLO 2K FT) THRU THE DAY TODAY AT KIWD/KCMX/KSAW. AT SOME
POINT TONIGHT...SKIES WILL CLEAR AS SFC HIGH PRES RIDGE AXIS DROPS
SE THRU THE AREA AND WINDS SHIFT SW.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
IN THE WAKE OF A COLD FRONT MOVING SE ACROSS LAKE SUPERIOR...A
PERIOD OF GALE FORCE GUSTS SHOULD OCCUR OVER THE E HALF OF THE LAKE
EARLY THIS MORNING IN ADVANCE OF 5MB/3HR PRES RISES. SINCE CORE OF
PRES RISES WILL SHIFT E OF LAKE SUPERIOR BY MID MORNING...GALE
WARNING WILL MOST LIKELY BE CANCELLED BY NEXT SCHEDULED FCST
ISSUANCE. OTHERWISE...WINDS WILL DIMINISH W TO E TODAY/TONIGHT AS
HIGH PRES QUICKLY APPROACHES AND THEN PASSES ACROSS THE GREAT LAKES.
DEEP LOW PRES MOVING E TO HUDSON BAY EARLY TUE WILL LIKELY BRING
ANOTHER ROUND OF SW GALES TO PORTIONS OF LAKE SUPERIOR...MAINLY THE
W HALF. SW WIND DIRECTION WILL FAVOR THE AREA BTWN THE KEWEENAW AND
ISLE ROYALE FOR STRONGEST WINDS TUE (GUSTS TO AROUND 40KT). GALES
WILL END TUE NIGHT AS PRES GRADIENT WEAKENS. WINDS WILL BE BLO 25KT
WED THRU FRI.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...
GALE WARNING UNTIL 1 PM EST THIS AFTERNOON FOR LSZ250-251-266-
267.
GALE WATCH FROM TUESDAY MORNING THROUGH LATE TUESDAY NIGHT FOR
LSZ162-263-264.
GALE WARNING UNTIL 7 AM EST THIS MORNING FOR LSZ264.
LAKE MICHIGAN...NONE.
&&
$$
DISCUSSION...SRF
AVIATION...ROLFSON
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
407 AM EST MON DEC 19 2011
.DISCUSSION /TODAY THROUGH SUNDAY/...
997MB LOW PRESSURE SYSTEM LOCATED OVER EASTERN ONTARIO WILL CONTINUE
E INTO SRN QUEBEC THIS MORNING. COLD FRONT CURRENTLY SWEEPING
THROUGH CNTRL/ERN UPPER MI...WITH ONLY SCT CLOUDS ASSOCIATED WITH
IT/S PASSING. BEHIND THE FRONT...A LARGE AREA OF LOW CLOUDS OVER NRN
MN...SW ONTARIO AND MANITOBA WOULD INDICATE THAT MOISTURE MAY BE
BETTER THAN INDICATED BY THE 00Z NAM. 00Z GFS AND LATEST RUC RUNS
SEEM TO BE DOING A LITTLE BETTER ON PICKING UP THE LOW CLOUDS AND
WILL FOLLOW THAT FOR THE TODAY FORECAST /WHICH IS A LITTLE MORE
PESSIMISTIC/.
COLD AIR STILL LAGGING BEHIND THE FRONT...AND WITH THE AREA OF LOW
CLOUDS CURRENTLY WORKING INTO WRN UPPER MI...EXPECT SOME PCPN TO
START OVER THE NEXT COUPLE OF HOURS OVER THE UPSLOPE HIGHER TERRAIN.
H850-700 DRY AIR AND SUBSIDENCE WILL HELP KEEP INVERSION HEIGHTS AT
3KFT. DRY NEAR SFC AIR WILL KEEP CLOUD DEPTHS LIMITED /ONLY AROUND
1.5-2KFT/ SO HAVE LIMITED CONF ON MUCH PCPN OCCURRING. THIS COULD
CREATE SOME P-TYPE ISSUES INITIALLY...AS BUFKIT SOUNDINGS SHOW CLOUD
TEMPS ARE ONLY IN THE -4 TO -7C RANGE...LIMITING ICE CRYSTALS.
SHOULD BE A QUICK TRANSITION FROM W TO E THROUGH THE EARLY MORNING
HOURS WITH THE H850 TEMPS FALLING TO -11C BY 15Z. THEREFORE...WILL
CONTINUE MENTION OF DZ/FZDZ THROUGH 12Z OVER THE W AND JUST DZ
THROUGH 15Z OVER THE E DUE TO WARMER SFC TEMPS. THE COLDER H850
TEMPS WILL LIKELY LEAD TO SOME LIGHT LES DEVELOPMENT THIS
MORNING...BUT INVERSION HEIGHTS WILL LIMIT INTENSITY. WITH THE
LONGER FETCH...THINK THE LES WILL CONTINUE THROUGH THE AFTN EVEN
THOUGH THE LOWER INVERSION HEIGHTS MAY END UP LEADING TO MAINLY
CLOUDS. OTHERWISE...TRANSITIONED TO MORE OF A -SHSN/FLURRIES IN THE
AFTN OVER THE W BEFORE DECREASING CLOUDS LATE IN THE AFTN DUE TO THE
WARMING H850 TEMPS AND DRIER AIR FINALLY ARRIVING WITH THE
APPROACHING SFC RIDGE.
HIGH PRESSURE RIDGE SLIDES OVER THE AREA TONIGHT...BRINGING AN END
TO THE LES OVER THE E AND THE LK CLOUDS OVER THE REST OF THE AREA.
WITH THE DECREASING CLOUDS AND WINDS...SHOULD BE A COLD NIGHT OVER
THE INTERIOR LOCATIONS. PWATS AROUND 35 PERCENT OF NORMAL WILL HELP
ENHANCE RADIATIONAL COOLING AND HAVE LOWS IN THE MID SINGLE DIGITS
ABOVE ZERO OVER THE INTERIOR W/CNTRL. WINDS WILL INCREASE SOME OVER
THE FAR W LATE IN THE NIGHT AHEAD OF THE NEXT WAVE...WHICH COULD
LEAD TO A RISE IN TEMPS LATE THERE.
NEXT SHORTWAVE AND ASSOCIATED LOW WILL BE MOVING THROUGH THE NRN
STREAM ON TUES...BUT WITH IT BEING LOCATED MUCH FARTHER N /OVER NRN
ONTARIO AND HUDSON BAY/ EXPECT IT TO HAVE LIMITED AFFECT ON THE
WEATHER OTHER THAN INCREASING THE WSW WINDS. SHOULD BE ANOTHER ABOVE
NORMAL TEMP DAY WITH A MOSTLY SUNNY SKY.
MODELS HAVE CONTINUED THE FASTER TREND WITH MERGING THE SRN STREAM
UPPER LOW CURRENTLY OVER THE SWRN CONUS WITH THE NRN STREAM ON WED
OVER THE LOWER GREAT LKS. WITH THE APPROACHING NRN STREAM WAVE STILL
OVER MANITOBA/SASK...AREA SHOULD BE BETWEEN SYSTEMS AND UNDER WEAK
HIGH PRESSURE TUES NIGHT AND WED MORNING. WILL GO WITH PARTLY CLOUDY
TO MOSTLY CLEAR SKIES FOR NOW...WITH CLOUDS JUST TO THE NW AND SE OF
THE CWA...BUT WILL BE CONTINGENT ON LOW CLOUDS HINTED AT BY THE NAM
NOT STICKING AROUND TOO LONG. THEN WITH SFC TROUGH TO THE
NW...ASSOCIATED WITH LOW OVER HUDSON BAY...NEARING THE CWA IN THE
AFTN AND MOVING THROUGH WED NIGHT...HAVE INCREASED CLOUDS FROM THE
AFTN ON. MOISTURE/FORCING IS WEAK WITH THE PASSAGE OF THE
TROUGH...SO WILL CONTINUE MENTION OF SLIGHTS OVER WRN LK SUPERIOR IN
THE AFTN AND SLIGHTS/LOW CHANCES ALONG THE FRONT WED NIGHT.
UPPER TROUGH THEN SWEEPS ACROSS THE AREA LATE WED NIGHT INTO
FRI...BRINGING A BETTER CHANCE FOR SNOW BEHIND THE FRONT. SOME
DIFFERENCES IN THE H850 TEMPS WITH THE 00Z GFS AND 12Z ECMWF...BUT
OVERALL IDEA IS AROUND -12C...WHICH WOULD CREATE LARGE ENOUGH
DELTA-T VALUES FOR LES. AS IS THE CASE TODAY...H800-650 SUBSIDENCE
AND DRY AIR WILL LIMIT THE INVERSION HEIGHTS TO 4KFT. SHOULD BE
DECENT LLVL MOISTURE TO WORK WITH BELOW THE INVERSION...SO AM
CONFIDENT ENOUGH TO GO WITH CHANCE POPS. WITH THE FORCING BELOW THE
DGZ /CLOUD TOPS ONLY REACH -15C ON THE COLDER GFS/ EXPECT SNOW
RATIOS TO BE IN THE LOW TEENS AND WILL LIKELY ONLY SEE A LIGHT
DUSTING FOR AREAS FAVORED BY A NNW WIND.
UPPER TROUGH STARTS TO SHIFT E ON FRI AS SFC HIGH BEGINS TO PUSH
OVER THE AREA. DRIER AIR ASSOCIATED WITH THE HIGH WILL LEAD TO
DIMINISHING LES POPS THURS NIGHT WEST AND DURING THE DAY FRI
EAST...AS WINDS BECOME ANTICYCLONIC. MAY SEE WEAK UPPER RIDGING ON
SAT...AHEAD OF THE NEXT NRN STREAM TROUGH TO AFFECT THE AREA SAT
NIGHT INTO SUN. ONCE AGAIN...FORCING/MOISTURE LIMITED ALONG THE
FRONT AND THE BEST POTENTIAL FOR PCPN WILL COME ON SUN WITH LES...AS
H850 TEMPS FALL TOWARDS -13C.
&&
.AVIATION /FOR THE 06Z TAF ISSUANCE/...
A TROUGH/COLD FRONT SAGGING INTO UPPER MICHIGAN BEHIND LOW PRES
MOVING EAST THROUGH NRN ONTARIO WILL PUSH WINDS TO A MORE NW
DIRECTION...AS WELL AS INCREASED LOW LEVEL MOISTURE AND PLENTY OF
COLD AIR. EXPECT MVFR CIGS BEHIND THE COLD FRONT...LOWEST AT CMX AND
IWD...GIVEN THE FAVORABLE NW UPSLOPE WINDS OFF LAKE SUPERIOR.
CONDITIONS SHOULD IMPROVE TO VFR BY LATE MORNING AS DRIER AIR MOVES
IN.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
IN THE WAKE OF A COLD FRONT MOVING SE ACROSS LAKE SUPERIOR...A
PERIOD OF GALE FORCE GUSTS SHOULD OCCUR OVER THE E HALF OF THE LAKE
EARLY THIS MORNING IN ADVANCE OF 5MB/3HR PRES RISES. SINCE CORE OF
PRES RISES WILL SHIFT E OF LAKE SUPERIOR BY MID MORNING...GALE
WARNING WILL MOST LIKELY BE CANCELLED BY NEXT SCHEDULED FCST
ISSUANCE. OTHERWISE...WINDS WILL DIMINISH W TO E TODAY/TONIGHT AS
HIGH PRES QUICKLY APPROACHES AND THEN PASSES ACROSS THE GREAT LAKES.
DEEP LOW PRES MOVING E TO HUDSON BAY EARLY TUE WILL LIKELY BRING
ANOTHER ROUND OF SW GALES TO PORTIONS OF LAKE SUPERIOR...MAINLY THE
W HALF. SW WIND DIRECTION WILL FAVOR THE AREA BTWN THE KEWEENAW AND
ISLE ROYALE FOR STRONGEST WINDS TUE (GUSTS TO AROUND 40KT). GALES
WILL END TUE NIGHT AS PRES GRADIENT WEAKENS. WINDS WILL BE BLO 25KT
WED THRU FRI.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
GALE WARNING UNTIL 1 PM EST THIS AFTERNOON FOR LSZ250-251-266-
267.
GALE WATCH FROM TUESDAY MORNING THROUGH LATE TUESDAY NIGHT FOR
LSZ162-263-264.
GALE WARNING UNTIL 7 AM EST THIS MORNING FOR LSZ264.
LAKE MICHIGAN...
NONE.
&&
$$
DISCUSSION...SRF
AVIATION...JLB
MARINE...ROLFSON
AREA FORECAST DISCUSSION...UPDATED
NWS DULUTH MN
1205 PM CST MON DEC 19 2011
.AVIATION...12/19/18Z ISSUANCE...
MVFR IN LOW CLOUDS ACROSS THE AREA...WITH PATCHY LIGHT SNOW AND
FREEZING DRIZZLE MOSTLY IN AND AROUND THE IRON RANGE INTO EARLY
EVENING. CLOUDS WILL SLOWLY ERODE FROM WEST TO EAST DURING THE
EVENING WITH VFR CLEAR FOLLOWING LATE TONIGHT.
&&
.PREV DISCUSSION... /ISSUED 1143 AM CST MON DEC 19 2011/
UPDATE...LARGE STRATUS CLOUD FIELD WILL REMAIN ANCHORED OVER MOST
OF CWA TODAY WITH SOME BREAKS AROUND SWRN CORNER OF CWA. HAVE
INCREASED SKY COVERAGE IN GRIDS/ZFP. FLURRIES OVER IRON
RANGE....APPEAR TO BE MOVING SE TOWARDS TWIN PORTS. HAVE ADDED
FLURRIES TO MOST OF AREA THROUGH DAY. ALSO...SOME BRIEF ZL REPORTED
NEAR KHIB AND A REPORT FROM PUBLIC NEAR PAYNE AS WELL. WILL NOT
ADD TO GRIDS/ZFP THIS TIME AS IT IS VERY LIGHT AND LIMITED IN AREAL
COVERAGE. WILL MONITOR FOR POTENTIAL UPDATE.
WILL NEED TO REASSESS OVERNIGHT FCST FOR POSSIBLE CHANGES TO
SKY/TEMP GRIDS.
PREV DISCUSSION... /ISSUED 402 AM CST MON DEC 19 2011/
SHORT TERM...TODAY THROUGH TUESDAY...
SURFACE COLD FRONT CONTINUES TO PUSH STEADILY SOUTHWARD THROUGH
WISCONSIN EARLY THIS MORNING IN WAKE OF CLIPPER SYSTEM THAT PASSED
TO OUR NORTH YDAY. THE AIRMASS BEHIND THE COLD FRONT IS NOT
TERRIBLY COLD BY MID DECEMBER STANDARDS FOR THIS PART OF THE WORLD
WITH TEMPS IN THE TEENS TO LOWER 20S..BUT IS ALSO CHARACTERIZED BY
A VERY EXPANSIVE STRATOCUMULUS DECK THAT COVERS ALMOST THE ENTIRE
DULUTH CWA AS OF 330 AM AND EXTENDS SEVERAL HUNDRED MILES TO OUR
NORTH. THE EVOLUTION AND EVENTUAL DISSIPATION OF THIS CLOUD DECK
IS KEY TO THE FORECAST FOR TODAY AND TONIGHT. MOST OF THE SHORT
RANGE MODEL GUIDANCE HAS BEEN INSISTENT FOR MANY MODEL RUNS THAT
THE CLOUDS WILL BREAK UP VERY RAPIDLY THIS MORNING WITH THE HRRR
AND RUC BEING THE OUTLIERS WITH A MUCH MORE SLOW BREAK UP
SOLUTION. GIVEN THE SATELLITE APPEARANCE AND MID DECEMBER
CLIMATOLOGY..WE ARE MUCH LESS OPTIMISTIC THAT CLOUDS WILL BE ABLE
TO BREAK UP AS RAPIDLY AS MUCH OF THE MODEL GUIDANCE SUGGESTS AND
WE HAVE TRENDED TOWARD THE HRRR/RUC SOLUTIONS WHICH CALL FOR
GENERALLY CLOUDY SKIES UNTIL THIS EVENING. NORTHWEST WINDS WILL
CONTINUE TO BE GUSTY THIS MORNING AS 5 MB/3 HR PRESSURE RISE
CENTER CONTINUES TO TRANSLATE ACROSS NRN LAKE SUPERIOR WITH TIGHT
GRADIENT. HOWEVER..WINDS SHUD SLACKEN CONSIDERABLY BY AFTERNOON
WITH LOSS OF ISALLOBARIC COMPONENT AND WEAKENING GRADIENT.
HIGH PRESSURE WILL THEN BUILD INTO THE REGION TONIGHT AND LEAVE
THE AREA LARGELY IN BETWEEN THE BIG SYSTEM COMING OUT ONTO THE
PLAINS TO OUR SOUTH AND THE STRONG WNW FLOW ALOFT ACROSS CANADA.
S/SW FLOW WILL RETURN ON TUESDAY AS RIDGE MOVES TO OUR SOUTH AND
NEXT LOW AMPLITUDE WAVE APPROACHES FROM THE NORTHWEST. THIS
SYSTEM..ON SCHEDULE FOR TUE/TUE NITE..APPEARS TO BE SIMILAR TO
THE ONE THAT JUST PASSED BY WITH A BRIEF SURGE OF WARM AIR
FOLLOWED BY ANOTHER PACIFIC TYPE COLD FRONT TUE NIGHT.
LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
THE PERIOD SHOULD BEGIN INCREASING CLOUD COVER AS A COLD FRONT IN
MANITOBA AND ONTARIO APPROACHES THE CANADIAN BORDER TUESDAY NIGHT.
THE COLD FRONT WILL LIKELY MOVE THROUGH THE NORTHLAND
WEDNESDAY...RESULTING IN CLOUDY CONDITIONS AND POSSIBLE LIGHT SNOW
ACROSS THE NORTHERN FA. BOTH THE GFS AND ECMWF BRING 850 HPA
TEMPERATURES OF -8 TO -12 CELSIUS OVER WESTERN LAKE SUPERIOR
WEDNESDAY NIGHT AND THURSDAY IN THE WAKE OF THE COLD FRONT.
CONSIDERING THE LAKE SURFACE TEMPERATURE IS AROUND 4 DEGREES
CELSIUS...THAT RESULTS IN SURFACE TO 850 HPA TEMPERATURE DIFFERENCES
AROUND 12 TO 16 DEGREES. THE NORTHERLY WINDS THAT DEVELOP WEDNESDAY
NIGHT AND THURSDAY COULD THEREFORE RESULT IN LAKE EFFECT SNOW ACROSS
THE PARTS OF THE SOUTH SHORE. THE MODELS BRING HIGH PRESSURE INTO
THE UPPER MIDWEST THURSDAY AND FRIDAY...RESULTING IN CLEARING SKIES.
A WARMING TREND LOOKS LIKELY FRIDAY INTO SATURDAY AS SOUTHERLY WINDS
INCREASE AHEAD OF AN APPROACHING COLD FRONT FROM THE WEST. SUNDAY
LOOKS COLDER AND CLOUDY IN THE WAKE OF THE COLD FRONT. THERE MAY BE
SOME LIGHT SNOW.
&&
.POINT TEMPS/POPS...
DLH 27 12 25 16 / 0 0 0 0
INL 23 9 29 18 / 10 0 10 10
BRD 30 11 28 15 / 0 0 0 0
HYR 32 11 26 16 / 10 0 0 0
ASX 32 16 29 20 / 20 0 0 0
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...SMALL CRAFT ADVISORY UNTIL 4 PM CST THIS AFTERNOON FOR LSZ146-
147.
&&
$$
SHORT TERM...CANNON
LONG TERM....EOM
AVIATION...EOM
AREA FORECAST DISCUSSION...UPDATED
NWS DULUTH MN
1143 AM CST MON DEC 19 2011
.UPDATE...LARGE STRATUS CLOUD FIELD WILL REMAIN ANCHORED OVER MOST
OF CWA TODAY WITH SOME BREAKS AROUND SWRN CORNER OF CWA. HAVE
INCREASED SKY COVERAGE IN GRIDS/ZFP. FLURRIES OVER IRON
RANGE....APPEAR TO BE MOVING SE TOWARDS TWIN PORTS. HAVE ADDED
FLURRIES TO MOST OF AREA THROUGH DAY. ALSO...SOME BRIEF ZL REPORTED
NEAR KHIB AND A REPORT FROM PUBLIC NEAR PAYNE AS WELL. WILL NOT
ADD TO GRIDS/ZFP THIS TIME AS IT IS VERY LIGHT AND LIMITED IN AREAL
COVERAGE. WILL MONITOR FOR POTENTIAL UPDATE.
WILL NEED TO REASSESS OVERNIGHT FCST FOR POSSIBLE CHANGES TO
SKY/TEMP GRIDS.
&&
.PREV DISCUSSION... /ISSUED 542 AM CST MON DEC 19 2011/
AVIATION...12Z TAF ISSUANCE
A LARGE MVFR STRATUS DECK COVERS MANITOBA/ONTARIO/NORTHERN
MN/NORTHWESTERN WI THIS MORNING. MANY MODELS INDICATE THIS LAYER
WILL QUICKLY DISSIPATE THIS MORNING...BUT AM BETTING AGAINST THE
MODELS AND THINK IT WILL BE DIFFICULT FOR THIS STRATUS DECK TO
DISSIPATE. THEREFORE...FORECASTING MVFR CIGS AT ALL TAF SITES
THROUGH AT LEAST THE EARLY AFTERNOON WITH CLEARING BY THIS EVENING.
EXPECT NORTHWEST WINDS AROUND 10 TO 15 KNOTS WHICH WILL RELAX LATE
THIS AFTERNOON AND BECOME VERY LIGHT OVERNIGHT. WIND GUSTS OF 15 TO
25 KNOTS ARE POSSIBLE AT KDLH/KHIB/KINL/KBRD THROUGH MID
MORNING...AND THEN WINDS WILL BECOME LESS GUSTY BY AFTERNOON. LIGHT
SOUTHWEST WINDS WILL BEGIN TO DEVELOP LATE TONIGHT. WIND SHEAR MAY
BE AN ISSUE AT KINL LATE TONIGHT.
PREV DISCUSSION... /ISSUED 402 AM CST MON DEC 19 2011/
SHORT TERM...TODAY THROUGH TUESDAY...
SURFACE COLD FRONT CONTINUES TO PUSH STEADILY SOUTHWARD THROUGH
WISCONSIN EARLY THIS MORNING IN WAKE OF CLIPPER SYSTEM THAT PASSED
TO OUR NORTH YDAY. THE AIRMASS BEHIND THE COLD FRONT IS NOT
TERRIBLY COLD BY MID DECEMBER STANDARDS FOR THIS PART OF THE WORLD
WITH TEMPS IN THE TEENS TO LOWER 20S..BUT IS ALSO CHARACTERIZED BY
A VERY EXPANSIVE STRATOCUMULUS DECK THAT COVERS ALMOST THE ENTIRE
DULUTH CWA AS OF 330 AM AND EXTENDS SEVERAL HUNDRED MILES TO OUR
NORTH. THE EVOLUTION AND EVENTUAL DISSIPATION OF THIS CLOUD DECK
IS KEY TO THE FORECAST FOR TODAY AND TONIGHT. MOST OF THE SHORT
RANGE MODEL GUIDANCE HAS BEEN INSISTENT FOR MANY MODEL RUNS THAT
THE CLOUDS WILL BREAK UP VERY RAPIDLY THIS MORNING WITH THE HRRR
AND RUC BEING THE OUTLIERS WITH A MUCH MORE SLOW BREAK UP
SOLUTION. GIVEN THE SATELLITE APPEARANCE AND MID DECEMBER
CLIMATOLOGY..WE ARE MUCH LESS OPTIMISTIC THAT CLOUDS WILL BE ABLE
TO BREAK UP AS RAPIDLY AS MUCH OF THE MODEL GUIDANCE SUGGESTS AND
WE HAVE TRENDED TOWARD THE HRRR/RUC SOLUTIONS WHICH CALL FOR
GENERALLY CLOUDY SKIES UNTIL THIS EVENING. NORTHWEST WINDS WILL
CONTINUE TO BE GUSTY THIS MORNING AS 5 MB/3 HR PRESSURE RISE
CENTER CONTINUES TO TRANSLATE ACROSS NRN LAKE SUPERIOR WITH TIGHT
GRADIENT. HOWEVER..WINDS SHUD SLACKEN CONSIDERABLY BY AFTERNOON
WITH LOSS OF ISALLOBARIC COMPONENT AND WEAKENING GRADIENT.
HIGH PRESSURE WILL THEN BUILD INTO THE REGION TONIGHT AND LEAVE
THE AREA LARGELY IN BETWEEN THE BIG SYSTEM COMING OUT ONTO THE
PLAINS TO OUR SOUTH AND THE STRONG WNW FLOW ALOFT ACROSS CANADA.
S/SW FLOW WILL RETURN ON TUESDAY AS RIDGE MOVES TO OUR SOUTH AND
NEXT LOW AMPLITUDE WAVE APPROACHES FROM THE NORTHWEST. THIS
SYSTEM..ON SCHEDULE FOR TUE/TUE NITE..APPEARS TO BE SIMILAR TO
THE ONE THAT JUST PASSED BY WITH A BRIEF SURGE OF WARM AIR
FOLLOWED BY ANOTHER PACIFIC TYPE COLD FRONT TUE NIGHT.
LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
THE PERIOD SHOULD BEGIN INCREASING CLOUD COVER AS A COLD FRONT IN
MANITOBA AND ONTARIO APPROACHES THE CANADIAN BORDER TUESDAY NIGHT.
THE COLD FRONT WILL LIKELY MOVE THROUGH THE NORTHLAND
WEDNESDAY...RESULTING IN CLOUDY CONDITIONS AND POSSIBLE LIGHT SNOW
ACROSS THE NORTHERN FA. BOTH THE GFS AND ECMWF BRING 850 HPA
TEMPERATURES OF -8 TO -12 CELSIUS OVER WESTERN LAKE SUPERIOR
WEDNESDAY NIGHT AND THURSDAY IN THE WAKE OF THE COLD FRONT.
CONSIDERING THE LAKE SURFACE TEMPERATURE IS AROUND 4 DEGREES
CELSIUS...THAT RESULTS IN SURFACE TO 850 HPA TEMPERATURE DIFFERENCES
AROUND 12 TO 16 DEGREES. THE NORTHERLY WINDS THAT DEVELOP WEDNESDAY
NIGHT AND THURSDAY COULD THEREFORE RESULT IN LAKE EFFECT SNOW ACROSS
THE PARTS OF THE SOUTH SHORE. THE MODELS BRING HIGH PRESSURE INTO
THE UPPER MIDWEST THURSDAY AND FRIDAY...RESULTING IN CLEARING SKIES.
A WARMING TREND LOOKS LIKELY FRIDAY INTO SATURDAY AS SOUTHERLY WINDS
INCREASE AHEAD OF AN APPROACHING COLD FRONT FROM THE WEST. SUNDAY
LOOKS COLDER AND CLOUDY IN THE WAKE OF THE COLD FRONT. THERE MAY BE
SOME LIGHT SNOW.
&&
.POINT TEMPS/POPS...
DLH 27 12 25 16 / 0 0 0 10
INL 23 9 29 18 / 10 0 10 10
BRD 30 11 28 15 / 0 0 0 10
HYR 32 11 26 16 / 10 0 0 0
ASX 32 16 29 20 / 20 0 0 0
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...SMALL CRAFT ADVISORY UNTIL 4 PM CST THIS AFTERNOON FOR LSZ146-
147.
&&
$$
SHORT TERM...CANNON
AREA FORECAST DISCUSSION...UPDATED
NWS DULUTH MN
542 AM CST MON DEC 19 2011
.AVIATION...12Z TAF ISSUANCE
A LARGE MVFR STRATUS DECK COVERS MANITOBA/ONTARIO/NORTHERN
MN/NORTHWESTERN WI THIS MORNING. MANY MODELS INDICATE THIS LAYER
WILL QUICKLY DISSIPATE THIS MORNING...BUT AM BETTING AGAINST THE
MODELS AND THINK IT WILL BE DIFFICULT FOR THIS STRATUS DECK TO
DISSIPATE. THEREFORE...FORECASTING MVFR CIGS AT ALL TAF SITES
THROUGH AT LEAST THE EARLY AFTERNOON WITH CLEARING BY THIS EVENING.
EXPECT NORTHWEST WINDS AROUND 10 TO 15 KNOTS WHICH WILL RELAX LATE
THIS AFTERNOON AND BECOME VERY LIGHT OVERNIGHT. WIND GUSTS OF 15 TO
25 KNOTS ARE POSSIBLE AT KDLH/KHIB/KINL/KBRD THROUGH MID
MORNING...AND THEN WINDS WILL BECOME LESS GUSTY BY AFTERNOON. LIGHT
SOUTHWEST WINDS WILL BEGIN TO DEVELOP LATE TONIGHT. WIND SHEAR MAY
BE AN ISSUE AT KINL LATE TONIGHT.
&&
.PREV DISCUSSION... /ISSUED 402 AM CST MON DEC 19 2011/
SHORT TERM...TODAY THROUGH TUESDAY...
SURFACE COLD FRONT CONTINUES TO PUSH STEADILY SOUTHWARD THROUGH
WISCONSIN EARLY THIS MORNING IN WAKE OF CLIPPER SYSTEM THAT PASSED
TO OUR NORTH YDAY. THE AIRMASS BEHIND THE COLD FRONT IS NOT
TERRIBLY COLD BY MID DECEMBER STANDARDS FOR THIS PART OF THE WORLD
WITH TEMPS IN THE TEENS TO LOWER 20S..BUT IS ALSO CHARACTERIZED BY
A VERY EXPANSIVE STRATOCUMULUS DECK THAT COVERS ALMOST THE ENTIRE
DULUTH CWA AS OF 330 AM AND EXTENDS SEVERAL HUNDRED MILES TO OUR
NORTH. THE EVOLUTION AND EVENTUAL DISSIPATION OF THIS CLOUD DECK
IS KEY TO THE FORECAST FOR TODAY AND TONIGHT. MOST OF THE SHORT
RANGE MODEL GUIDANCE HAS BEEN INSISTENT FOR MANY MODEL RUNS THAT
THE CLOUDS WILL BREAK UP VERY RAPIDLY THIS MORNING WITH THE HRRR
AND RUC BEING THE OUTLIERS WITH A MUCH MORE SLOW BREAK UP
SOLUTION. GIVEN THE SATELLITE APPEARANCE AND MID DECEMBER
CLIMATOLOGY..WE ARE MUCH LESS OPTIMISTIC THAT CLOUDS WILL BE ABLE
TO BREAK UP AS RAPIDLY AS MUCH OF THE MODEL GUIDANCE SUGGESTS AND
WE HAVE TRENDED TOWARD THE HRRR/RUC SOLUTIONS WHICH CALL FOR
GENERALLY CLOUDY SKIES UNTIL THIS EVENING. NORTHWEST WINDS WILL
CONTINUE TO BE GUSTY THIS MORNING AS 5 MB/3 HR PRESSURE RISE
CENTER CONTINUES TO TRANSLATE ACROSS NRN LAKE SUPERIOR WITH TIGHT
GRADIENT. HOWEVER..WINDS SHUD SLACKEN CONSIDERABLY BY AFTERNOON
WITH LOSS OF ISALLOBARIC COMPONENT AND WEAKENING GRADIENT.
HIGH PRESSURE WILL THEN BUILD INTO THE REGION TONIGHT AND LEAVE
THE AREA LARGELY IN BETWEEN THE BIG SYSTEM COMING OUT ONTO THE
PLAINS TO OUR SOUTH AND THE STRONG WNW FLOW ALOFT ACROSS CANADA.
S/SW FLOW WILL RETURN ON TUESDAY AS RIDGE MOVES TO OUR SOUTH AND
NEXT LOW AMPLITUDE WAVE APPROACHES FROM THE NORTHWEST. THIS
SYSTEM..ON SCHEDULE FOR TUE/TUE NITE..APPEARS TO BE SIMILAR TO
THE ONE THAT JUST PASSED BY WITH A BRIEF SURGE OF WARM AIR
FOLLOWED BY ANOTHER PACIFIC TYPE COLD FRONT TUE NIGHT.
LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
THE PERIOD SHOULD BEGIN INCREASING CLOUD COVER AS A COLD FRONT IN
MANITOBA AND ONTARIO APPROACHES THE CANADIAN BORDER TUESDAY NIGHT.
THE COLD FRONT WILL LIKELY MOVE THROUGH THE NORTHLAND
WEDNESDAY...RESULTING IN CLOUDY CONDITIONS AND POSSIBLE LIGHT SNOW
ACROSS THE NORTHERN FA. BOTH THE GFS AND ECMWF BRING 850 HPA
TEMPERATURES OF -8 TO -12 CELSIUS OVER WESTERN LAKE SUPERIOR
WEDNESDAY NIGHT AND THURSDAY IN THE WAKE OF THE COLD FRONT.
CONSIDERING THE LAKE SURFACE TEMPERATURE IS AROUND 4 DEGREES
CELSIUS...THAT RESULTS IN SURFACE TO 850 HPA TEMPERATURE DIFFERENCES
AROUND 12 TO 16 DEGREES. THE NORTHERLY WINDS THAT DEVELOP WEDNESDAY
NIGHT AND THURSDAY COULD THEREFORE RESULT IN LAKE EFFECT SNOW ACROSS
THE PARTS OF THE SOUTH SHORE. THE MODELS BRING HIGH PRESSURE INTO
THE UPPER MIDWEST THURSDAY AND FRIDAY...RESULTING IN CLEARING SKIES.
A WARMING TREND LOOKS LIKELY FRIDAY INTO SATURDAY AS SOUTHERLY WINDS
INCREASE AHEAD OF AN APPROACHING COLD FRONT FROM THE WEST. SUNDAY
LOOKS COLDER AND CLOUDY IN THE WAKE OF THE COLD FRONT. THERE MAY BE
SOME LIGHT SNOW.
&&
.POINT TEMPS/POPS...
DLH 23 8 25 16 / 0 0 0 0
INL 21 9 28 18 / 10 0 10 10
BRD 25 10 27 15 / 0 0 0 0
HYR 26 9 25 16 / 0 0 0 0
ASX 28 14 28 20 / 20 0 0 0
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...SMALL CRAFT ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR LSZ146-
147.
&&
$$
AVIATION...GROCHOCINSKI
AREA FORECAST DISCUSSION
NWS DULUTH MN
402 AM CST MON DEC 19 2011
.SHORT TERM...TODAY THROUGH TUESDAY...
SURFACE COLD FRONT CONTINUES TO PUSH STEADILY SOUTHWARD THROUGH
WISCONSIN EARLY THIS MORNING IN WAKE OF CLIPPER SYSTEM THAT PASSED
TO OUR NORTH YDAY. THE AIRMASS BEHIND THE COLD FRONT IS NOT
TERRIBLY COLD BY MID DECEMBER STANDARDS FOR THIS PART OF THE WORLD
WITH TEMPS IN THE TEENS TO LOWER 20S..BUT IS ALSO CHARACTERIZED BY
A VERY EXPANSIVE STRATOCUMULUS DECK THAT COVERS ALMOST THE ENTIRE
DULUTH CWA AS OF 330 AM AND EXTENDS SEVERAL HUNDRED MILES TO OUR
NORTH. THE EVOLUTION AND EVENTUAL DISSIPATION OF THIS CLOUD DECK
IS KEY TO THE FORECAST FOR TODAY AND TONIGHT. MOST OF THE SHORT
RANGE MODEL GUIDANCE HAS BEEN INSISTENT FOR MANY MODEL RUNS THAT
THE CLOUDS WILL BREAK UP VERY RAPIDLY THIS MORNING WITH THE HRRR
AND RUC BEING THE OUTLIERS WITH A MUCH MORE SLOW BREAK UP
SOLUTION. GIVEN THE SATELLITE APPEARANCE AND MID DECEMBER
CLIMATOLOGY..WE ARE MUCH LESS OPTIMISTIC THAT CLOUDS WILL BE ABLE
TO BREAK UP AS RAPIDLY AS MUCH OF THE MODEL GUIDANCE SUGGESTS AND
WE HAVE TRENDED TOWARD THE HRRR/RUC SOLUTIONS WHICH CALL FOR
GENERALLY CLOUDY SKIES UNTIL THIS EVENING. NORTHWEST WINDS WILL
CONTINUE TO BE GUSTY THIS MORNING AS 5 MB/3 HR PRESSURE RISE
CENTER CONTINUES TO TRANSLATE ACROSS NRN LAKE SUPERIOR WITH TIGHT
GRADIENT. HOWEVER..WINDS SHUD SLACKEN CONSIDERABLY BY AFTERNOON
WITH LOSS OF ISALLOBARIC COMPONENT AND WEAKENING GRADIENT.
HIGH PRESSURE WILL THEN BUILD INTO THE REGION TONIGHT AND LEAVE
THE AREA LARGELY IN BETWEEN THE BIG SYSTEM COMING OUT ONTO THE
PLAINS TO OUR SOUTH AND THE STRONG WNW FLOW ALOFT ACROSS CANADA.
S/SW FLOW WILL RETURN ON TUESDAY AS RIDGE MOVES TO OUR SOUTH AND
NEXT LOW AMPLITUDE WAVE APPROACHES FROM THE NORTHWEST. THIS
SYSTEM..ON SCHEDULE FOR TUE/TUE NITE..APPEARS TO BE SIMILAR TO
THE ONE THAT JUST PASSED BY WITH A BRIEF SURGE OF WARM AIR
FOLLOWED BY ANOTHER PACIFIC TYPE COLD FRONT TUE NIGHT.
&&
.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
THE PERIOD SHOULD BEGIN INCREASING CLOUD COVER AS A COLD FRONT IN
MANITOBA AND ONTARIO APPROACHES THE CANADIAN BORDER TUESDAY NIGHT.
THE COLD FRONT WILL LIKELY MOVE THROUGH THE NORTHLAND
WEDNESDAY...RESULTING IN CLOUDY CONDITIONS AND POSSIBLE LIGHT SNOW
ACROSS THE NORTHERN FA. BOTH THE GFS AND ECMWF BRING 850 HPA
TEMPERATURES OF -8 TO -12 CELSIUS OVER WESTERN LAKE SUPERIOR
WEDNESDAY NIGHT AND THURSDAY IN THE WAKE OF THE COLD FRONT.
CONSIDERING THE LAKE SURFACE TEMPERATURE IS AROUND 4 DEGREES
CELSIUS...THAT RESULTS IN SURFACE TO 850 HPA TEMPERATURE DIFFERENCES
AROUND 12 TO 16 DEGREES. THE NORTHERLY WINDS THAT DEVELOP WEDNESDAY
NIGHT AND THURSDAY COULD THEREFORE RESULT IN LAKE EFFECT SNOW ACROSS
THE PARTS OF THE SOUTH SHORE. THE MODELS BRING HIGH PRESSURE INTO
THE UPPER MIDWEST THURSDAY AND FRIDAY...RESULTING IN CLEARING SKIES.
A WARMING TREND LOOKS LIKELY FRIDAY INTO SATURDAY AS SOUTHERLY WINDS
INCREASE AHEAD OF AN APPROACHING COLD FRONT FROM THE WEST. SUNDAY
LOOKS COLDER AND CLOUDY IN THE WAKE OF THE COLD FRONT. THERE MAY BE
SOME LIGHT SNOW.
&&
.AVIATION...06Z TAF ISSUANCE...
CEILINGS ANYWHERE FROM 700FT TO 2500FT WERE ADVANCING SOUTH
THROUGH THE MOST OF NORTHERN MINNESOTA AS OF 0530Z...AND WILL
OVERTAKE NORTHERN WISCONSIN OVER THE NEXT FEW HOURS. WINDS HAD
SWITCHED OUT OF THE NORTHWEST OVER NORTHERN MINNESOTA...AND WILL
BE SWITCHING OVER THE NEXT FEW HOURS OVER NORTHERN WISCONSIN.
STRONG CAA WILL CONTINUE TONIGHT...AND MAY PRODUCE SOME
FLURRIES...WITH SOME SNOW SHOWERS LATE OVER SNOWBELT OF NORTHERN
WISCONSIN. ANY ACCUMULATION WILL BE LIGHT. DRYING IS EXPECTED
MONDAY MORNING...AND MODELS AND NUMERICAL GUIDANCE SUGGESTS MUCH
OF THE CLOUD WILL CLEAR DURING THE MORNING. CURRENT SATELLITE
SHOWS A SMALL BREAK IN FAR WESTERN MINNESOTA...WITH CLOUDS COVER
MUCH OF NORTHWEST ONTARIO/SOUTHEAST MANITOBA. WE WENT SCATTERED AT
MOST TAFS SITES AROUND 16Z.
&&
.POINT TEMPS/POPS...
DLH 23 8 25 16 / 0 0 0 0
INL 21 9 28 18 / 10 0 10 10
BRD 25 10 27 15 / 0 0 0 0
HYR 26 9 25 16 / 0 0 0 0
ASX 28 14 28 20 / 20 0 0 0
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...SMALL CRAFT ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR LSZ146-
147.
&&
$$
MILLER/GROCHOCINSKI
AREA FORECAST DISCUSSION
NWS HASTINGS NE
349 PM CST MON DEC 19 2011
.SHORT TERM...MORNING UPPER AIR ANALYSIS AND WATER VAPOR IMAGERY
INDICATE A MID AND UPPER LEVEL LOW OVER WEST TEXAS...MOVING NORTHEAST
INTO THE CENTRAL CONUS. WATER VAPOR IMAGERY ALSO INDICATES A MID
LEVEL DRY INTRUSION MOVING NORTHEASTWARD INTO NORTHERN TEXAS AND
PORTIONS OF OKLAHOMA. AT THE SURFACE AN AREA OF LOW PRESSURE EXISTS OVER
THE PANHANDLE OF TEXAS AND A SURFACE FRONT EXTENDS NORTHEAST FROM
THE SURFACE LOW INTO WESTERN AND NORTHERN OKLAHOMA...AS WELL AS
EASTERN KANSAS. KUEX INDICATES INCOMING PRECIPITATION OVER NORTH
CENTRAL KANSAS IN A ZONE OF LOW LEVEL THERMAL ADVECTION AND
RESULTANT ISENTROPIC UPGLIDE AND SATURATION. ADDITIONAL FORCING
THROUGH A ZONE OF MID LEVEL DIFFLUENCE IS ALSO HELPING PROMOTE
PRECIPITATION OVER AREAS NORTHEAST OF THE MID LEVEL LOW. SNOW IS
ALREADY IN PROGRESS AT NATOMA AS A RESULT.
THE LOW LEVEL BAROCLINIC ZONE CLEARED OUR CWA EARLIER TODAY AND
THE LOW LEVEL WIND FIELD ACROSS OUR CWA REMAINS FROM THE
NORTH/NORTHEAST AS A RESULT. SURFACE TEMPERATURES HAVE BEEN AT A
NEAR STANDSTILL IF NOT FALLING SOMEWHAT TODAY...WITH TEMPERATURES
AS OF MID AFTERNOON GENERALLY IN THE LOWER 30S. SHORT TERM GUIDANCE
CONTINUES TO SUGGEST THE MID LEVEL LOW WILL MOVE NORTHEAST ACROSS
THE SOUTHERN AND CENTRAL PLAINS TONIGHT AND TUESDAY. LOW LEVEL
THERMAL ADVECTION...WORKING IN CONCERT WITH MID LEVEL DIFFLUENCE AND
DEFORMATION TO THE NORTH AND NORTHEAST OF THE MID LEVEL LOW...WILL CONTINUE
PROMOTING PRECIPITATION PRODUCTION OVER THE AREA TONIGHT.
PRECIPITATION IS ALSO EXPECTED DURING THE DAY TUESDAY AS MID LEVEL
DEFORMATION TO THE NORTH AND NORTHWEST OF THE MID LEVEL LOW CLEARS
THE AREA.
MOISTURE THROUGH THE LOWER HALF OF THE TROPOSPHERIC COLUMN IS
EXPECTED TO REMAIN QUITE HIGH THROUGH THE NEXT 24 HOURS WITH 500MB
DEW POINTS IN EXCESS OF -25 DEGREES C AND 700MB DEW POINTS IN
EXCESS OF -10 DEGREES C ACROSS OUR SOUTH/SOUTHEAST. THESE MOISTURE
LEVELS...WORKING IN CONCERT WITH THE AFOREMENTIONED KINEMATIC
FORCING...SHOULD BE MORE THAN SUFFICIENT FOR SIGNIFICANT
PRECIPITATION PRODUCTION ACROSS OUR SOUTH AND SOUTHEAST TONIGHT AND
TOMORROW. QPF FIELDS FROM THE NAM...OPERATIONAL GFS...EC AND SREF-
MEAN ALL SUGGEST STORM TOTAL LIQUID PRECIPITATION AMOUNTS IN
EXCESS OF 0.80" ACROSS OUR SOUTH AND SOUTHEAST. SURFACE
TEMPERATURES WILL LIKELY FALL INTO THE UPPER AND MID 20S THROUGH
THE REMAINDER OF THE EVENT AND AS A RESULT WILL GO AHEAD AND
ASSUME A 10:1 SNOW-WATER RATIO TO START THE EVENT...WITH RATIOS
CLIMBING TO NEAR 13:1 BY TONIGHT AND TOMORROW. THIS YIELDS STORM
TOTAL SNOWFALL ACCUMULATIONS ON THE ORDER OF 5-12 INCHES ACROSS
OUR EXTREME SOUTH...AND STORM TOTAL SNOWFALL ACCUMULATIONS IN THE
1-5 INCH RANGE FARTHER NORTH.
LOW LEVEL PRESSURE RISES POST-FROPA HAVE PROMOTED AN INCREASED LOW
LEVEL PRESSURE GRADIENT TODAY...WITH SUSTAINED WINDS NEAR 20KTS
ACROSS MUCH OF THE CWA AS OF MID AFTERNOON. THESE CONDITIONS ARE EXPECTED
TO CONTINUE THROUGH THIS EVENING...WITH DIMINISHING WINDS EXPECTED
BY MIDNIGHT AS THE LOW LEVEL PRESSURE GRADIENT RELAXES. AS A
RESULT...THESE WINDS SHOULD REMAIN WELL BELOW BLIZZARD CRITERIA.
ALL THAT BEING SAID...THE INHERITED WINTER STORM WARNING FOR
ROOKS...OSBORNE AND MITCHELL COUNTIES...ALONG WITH THE WINTER
WEATHER ADVISORY FOR PHILLIPS...SMITH AND JEWELL COUNTIES...APPEAR
TO BE RIGHT ON...BUT DID GO AHEAD AND START THE WINTER STORM
WARNING NOW GIVEN SNOWFALL IS ALREADY OCCURRING AT NATOMA.
JUST A FEW THINGS TO CONSIDER AS WE HEAD INTO THIS STORM. THE
CONTRAST BETWEEN MOIST AIR AND DRY AIR...AS WELL AS BETWEEN STRONG
KINEMATIC FORCING AND NEXT TO NO FORCING...IS EXPECTED TO BE RATHER
SHARP THUS RESULTING IN A VERY TIGHT GRADIENT OF STORM TOTAL
SNOWFALL ACCUMULATIONS. ALTHOUGH CONFIDENCE REMAINS HIGH REGARDING
ACTUAL STORM TOTAL SNOWFALL ACCUMULATIONS...THE AXIS OF HEAVIEST
SNOW COULD SHIFT DRAMATICALLY IN RESPONSE TO VERY SMALL DEVIATIONS
IN STORM PATH. THANKFULLY...GUIDANCE HAS REMAINED FAIRLY
CONSISTENT WITH RESPECT TO STORM PATH...A TREND WHICH WE HOPE WILL
CONTINUE. FINALLY...GUIDANCE DOES SUGGEST THE MID LEVEL DRY
INTRUSION WILL INFILTRATE MUCH OF KANSAS BY TUESDAY MORNING...THUS
DRYING OUT THE DENDRITIC LAYER AND LIKELY LEADING TO A PERIOD OF
FREEZING DRIZZLE. AT THIS TIME IT APPEARS THIS MID LEVEL DRY
INTRUSION SHOULD REMAIN SOUTH AND SOUTHEAST OF OUR AREA AND AS A
RESULT...LEFT ANY MENTION OF FREEZING DRIZZLE OUT OF THE FORECAST.
.LONG TERM...TUESDAY NIGHT THROUGH MONDAY. THE UPPER LOW WILL
CONTINUE TO MOVE NORTHEAST AND AWAY FROM THE AREA TUESDAY NIGHT.
THE MAJORITY OF MODEL SOLUTIONS SUGGESTS THE SNOW SHOULD BE DONE BY
TUESDAY NIGHT...AND WILL CONTINUE TO CARRY A DRY FORECAST.
A BRIEF H5 RIDGE BUILDS IN TUESDAY NIGHT INTO WEDNESDAY...WHICH
SHOULD KEEP IT DRY THROUGH WEDNESDAY...HOWEVER ANOTHER UPPER
TROUGH/LOW BEGINS TO APPROACH THE REGION WEDNESDAY NIGHT. THE
NAM/GFS/ECMWF ALL AGREE THAT MOST OF WEDNESDAY EVENING SHOULD REMAIN
DRY...HOWEVER LIGHT SNOW COULD BEGIN TO APPROACH FAR NORTH AND WEST
PORTIONS OF THE FORECAST AREA BY LATE EVENING. THE SNOW CHANCES
WILL THEN SPREAD ACROSS THE FORECAST AREA OVERNIGHT WEDNESDAY INTO
THURSDAY. THE NAM/GFS DEPICT THE STRONGEST LIFT/FORCING ACROSS
ROUGHLY THE SOUTHERN HALF OF THE CWA LATE WEDNESDAY NIGHT INTO
THURSDAY...AND HAVE INCREASED POPS FOR THAT AREA...ESPECIALLY FOR
THURSDAY. SNOW AMOUNTS ARE STILL UNCERTAIN...AND SREF 12 HOUR SNOW
PROBABILITIES FOR AN INCH OR MORE OF SNOW ARE NOT VERY HIGH...THOUGH
THE HIGHER PROBABILITIES ARE SHOWN IN THE SOUTH AND WEST.
ONE CONCERN IS THE POTENTIAL FOR HIGHER SNOW RATIOS WITH THE CARIBOU
SNOW TECHNIQUE SUGGESTING RATIOS CLIMBING TO NEAR 18 TO 1 FOR
THURSDAY AFTERNOON. FOR NOW...WILL GO WITH A GENERAL HALF INCH TO
INCH AND A HALF...WITH THE HIGHER AMOUNTS IN THE SOUTH AND WEST.
THERE IS STILL PLENTY OF TIME TO REFINE AMOUNTS AS THIS NEXT SYSTEM
GETS CLOSER.
OVERALL...THE CHRISTMAS HOLIDAY WEEKEND LOOKS TO BE FAIRLY QUIET.
ANOTHER WAVE COULD MOVE ACROSS THE REGION SATURDAY NIGHT INTO
CHRISTMAS DAY...BUT MOISTURE IS LACKING SO IT SHOULD PASS THROUGH
DRY. TEMPERATURES ARE EXPECTED TO BE FAIRLY SEASONABLE WITH HIGHS
PRIMARILY IN THE 30S.
&&
PREV DISCUSSION... /ISSUED 1120 AM CST MON DEC 19 2011/
AVIATION...18Z TAF. IFR CEILINGS HAVE MOVED INTO PARTS OF SOUTH
CENTRAL NEBRASKA BEHIND A COLD FRONT THAT TRAVELED ACROSS THE
AREA EARLIER TODAY. THE GENERAL TREND HAS BEEN FOR THE IFR
CEILINGS TO LIFT TO MVFR...AND THIS IS ALSO SHOWN BY THE LATEST
NAM PROXIMITY SOUNDINGS..SO WILL ONLY CARRY THE LOWER CEILINGS IN
A BRIEF TEMPO GROUP. PROXIMITY SOUNDINGS ALSO SHOW THE MVFR
CEILINGS IMPROVING THIS AFTERNOON...THOUGH THE RUC IS FASTER IN
LIFTING THE CEILINGS THAN THE NAM. WILL AIM FOR MORE OF A
COMPROMISE SOLUTION AND GO WITH 21Z AS A START. WINDS WILL REMAIN
GUSTY AND FROM THE NORTH MOST OF THE AFTERNOON...BUT THEY SHOULD
DIMINISH THIS EVENING. THERE WILL BE CHANCES OF SNOW SOUTH OF
KGRI AS A STORM SYSTEM MOVES ACROSS THE CENTRAL AND SOUTHERN
PLAINS...BUT THINK THAT THE CHANCES WILL STAY FAR ENOUGH SOUTH TO
KEEP THE MENTION OUT OF THE FORECAST AT KGRI.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...WINTER WEATHER ADVISORY UNTIL 6 PM CST TUESDAY FOR KSZ005>007.
WINTER STORM WARNING UNTIL 6 PM CST TUESDAY FOR KSZ017>019.
&&
$$
SHORT TERM...BRYANT
AREA FORECAST DISCUSSION
NWS HASTINGS NE
1237 PM CST MON DEC 19 2011
.UPDATE...MORNING UPPER AIR ANALYSIS AND WATER VAPOR IMAGERY
INDICATE A MID AND UPPER LEVEL LOW OVER NEW MEXICO BEGINNING TO
MOVE NORTHEAST INTO THE CENTRAL CONUS. WATER VAPOR IMAGERY ALSO
INDICATES A MID LEVEL DRY INTRUSION MOVING NORTHEASTWARD ACROSS
WEST TEXAS. AT THE SURFACE AN AREA OF LOW PRESSURE EXISTS OVER THE
PANHANDLE OF TEXAS AND A SURFACE FRONT EXTENDS NORTHEAST FROM THE
SURFACE LOW INTO WESTERN AND NORTHERN OKLAHOMA AS WELL AS EASTERN
KANSAS. RADAR DATA FROM SITES ACROSS KANSAS...AS WELL AS
KUEX...INDICATE INCOMING PRECIPITATION ACROSS THE SOUTHERN TWO-
THIRDS OF KANSAS IN A ZONE OF LOW LEVEL THERMAL ADVECTION AND
RESULTANT ISENTROPIC UPGLIDE AND SATURATION. ADDITIONAL FORCING
THROUGH A ZONE OF DIFFLUENCE IS ALSO HELPING PROMOTE PRECIPITATION
OVER AREAS NORTHEAST OF THE MID LEVEL LOW.
THE LOW LEVEL BAROCLINIC ZONE CLEARED OUR CWA EARLIER TODAY AND THE LOW
LEVEL WIND FIELD ACROSS OUR CWA REMAINS FROM THE NORTH/NORTHEAST
AS A RESULT. SURFACE TEMPERATURES HAVE BEEN AT A NEAR STANDSTILL
IF NOT FALLING SOMEWHAT THROUGH THE MORNING HOURS...WITH
TEMPERATURES AT MIDDAY GENERALLY IN THE LOWER 30S. SHORT TERM
GUIDANCE CONTINUES TO SUGGEST THE MID LEVEL LOW WILL MOVE
NORTHEAST ACROSS THE SOUTHERN AND CENTRAL PLAINS TONIGHT AND
TUESDAY. LOW LEVEL THERMAL ADVECTION WORKING IN CONCERT WITH MID
LEVEL DIFFLUENCE AND DEFORMATION TO THE NORTH AND NORTHEAST OF THE
MID LEVEL LOW WILL ALSO CONTINUE PROMOTING PRECIPITATION
PRODUCTION ACROSS THE REGION...WITH PRECIPITATION EXPECTED OVER
SOUTH AND SOUTHEASTERN PORTIONS OF OUR CWA STARTING LATE THIS
AFTERNOON. PRECIPITATION SHOULD THEN CONTINUE OVER THE AREA
TONIGHT AS LOW LEVEL THERMAL ADVECTION AND MID LEVEL DIFFLUENCE
AND DEFORMATION ALSO CONTINUE OVER THE AREA...WITH PRECIPITATION
ALSO EXPECTED DURING THE DAY TUESDAY AS MID LEVEL DEFORMATION TO
THE NORTH AND NORTHWEST OF THE MID LEVEL LOW CLEARS THE AREA.
MOISTURE THROUGH THE LOWER HALF OF THE TROPOSPHERIC COLUMN IS
EXPECTED TO REMAIN QUITE HIGH THROUGH THE NEXT 24 HOURS WITH 500MB
DEW POINTS IN EXCESS OF -25 DEGREES C AND 700MB DEW POINTS IN
EXCESS OF -10 DEGREES C ACROSS OUR SOUTH/SOUTHEAST. THESE MOISTURE
LEVELS...WORKING IN CONCERT WITH THE AFOREMENTIONED KINEMATIC
FORCING...SHOULD BE MORE THAN SUFFICIENT FOR SIGNIFICANT
PRECIPITATION PRODUCTION ACROSS OUR SOUTH AND SOUTHEAST TONIGHT AND
TOMORROW. QPF FIELDS FROM THE NAM...OPERATIONAL GFS...EC AND SREF-
MEAN ALL SUGGEST STORM TOTAL LIQUID PRECIPITATION AMOUNTS IN
EXCESS OF 0.80" ACROSS OUR SOUTH/SOUTHEAST. SURFACE TEMPERATURES
SHOULD START THE EVENT NEAR 30...BUT WILL LIKELY FALL INTO THE
UPPER 20S AND MID 20S THROUGH THE REMAINDER OF THE EVENT. GIVEN
THIS...WILL GO AHEAD AND ASSUME A 10:1 SNOW-WATER RATIO TO START
THE EVENT...WITH RATIOS CLIMBING TO NEAR 13:1 BY TONIGHT AND
TOMORROW. THIS YIELDS STORM TOTAL SNOWFALL ACCUMULATIONS ON THE
ORDER OF 5-12 INCHES ACROSS OUR EXTREME SOUTH...WITH STORM TOTAL
SNOWFALL ACCUMULATIONS IN THE 1-5 INCH RANGE FARTHER NORTH.
LOW LEVEL PRESSURE RISES POST-FROPA HAVE PROMOTED AN INCREASED LOW
LEVEL PRESSURE GRADIENT THIS MORNING...WITH SUSTAINED WINDS
ALREADY IN EXCESS OF 20KTS ACROSS MUCH OF THE CWA. THESE
CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THIS AFTERNOON AND
INTO THIS EVENING...WITH DIMINISHING WINDS EXPECTED BY MIDNIGHT AS
THE LOW LEVEL PRESSURE GRADIENT RELAXES. THE STRONGEST LOW LEVEL
PRESSURE RISES ARE SUPPOSE TO BE OCCURRING NOW BASED ON SHORT TERM
GUIDANCE...THUS DO NOT ANTICIPATE THE NEED FOR A WIND ADVISORY FOR
THIS AFTERNOON. ADDITIONALLY...THESE WINDS SHOULD REMAIN WELL
BELOW BLIZZARD CRITERIA THUS DO NOT ANTICIPATE A BLIZZARD WARNING
WILL BE NEEDED FOR TONIGHT OR TOMORROW.
ALL THAT BEING SAID...THE INHERITED WINTER STORM WARNING FOR
ROOKS...OSBORNE AND MITCHELL COUNTIES...ALONG WITH THE WINTER
WEATHER ADVISORY FOR PHILLIPS...SMITH AND JEWELL COUNTIES...APPEAR
TO BE RIGHT ON AND NO CHANGES TO THE HEADLINES ARE CURRENTLY ANTICIPATED.
JUST A FEW THINGS TO CONSIDER AS WE HEAD INTO THIS STORM. THE
CONTRAST BETWEEN MOIST AIR AND DRY AIR...AS WELL AS BETWEEN STRONG
KINEMATIC FORCING AND NEXT TO NO FORCING...IS EXPECTED TO BE RATHER
SHARP THUS RESULTING IN A VERY TIGHT GRADIENT OF STORM TOTAL
SNOWFALL ACCUMULATIONS. ALTHOUGH CONFIDENCE REMAINS HIGH REGARDING
ACTUAL STORM TOTAL SNOWFALL ACCUMULATIONS...THE AXIS OF HEAVIEST
SNOW COULD SHIFT DRAMATICALLY IN RESPONSE TO VERY SMALL DEVIATIONS
IN STORM PATH. THANKFULLY...GUIDANCE HAS REMAINED FAIRLY
CONSISTENT WITH RESPECT TO STORM PATH...A TREND WHICH WE HOPE WILL
CONTINUE. FINALLY...GUIDANCE DOES SUGGEST THE MID LEVEL DRY
INTRUSION WILL INFILTRATE MUCH OF KANSAS LATER THIS EVENING...THUS
DRYING OUT THE DENDRITIC LAYER AND LIKELY LEADING TO A PERIOD OF
FREEZING DRIZZLE. AT THIS TIME IT APPEARS THIS MID LEVEL DRY
INTRUSION SHOULD REMAIN SOUTH/SOUTHEAST OF OUR AREA AND AS A
RESULT...LEFT ANY MENTION OF FREEZING DRIZZLE OUT OF THE FORECAST.
&&
.PREV DISCUSSION... /ISSUED 1120 AM CST MON DEC 19 2011/
AVIATION...18Z TAF. IFR CEILINGS HAVE MOVED INTO PARTS OF SOUTH
CENTRAL NEBRASKA BEHIND A COLD FRONT THAT TRAVELED ACROSS THE
AREA EARLIER TODAY. THE GENERAL TREND HAS BEEN FOR THE IFR
CEILINGS TO LIFT TO MVFR...AND THIS IS ALSO SHOWN BY THE LATEST
NAM PROXIMITY SOUNDINGS..SO WILL ONLY CARRY THE LOWER CEILINGS IN
A BRIEF TEMPO GROUP. PROXIMITY SOUNDINGS ALSO SHOW THE MVFR
CEILINGS IMPROVING THIS AFTERNOON...THOUGH THE RUC IS FASTER IN
LIFTING THE CEILINGS THAN THE NAM. WILL AIM FOR MORE OF A
COMPROMISE SOLUTION AND GO WITH 21Z AS A START. WINDS WILL REMAIN
GUSTY AND FROM THE NORTH MOST OF THE AFTERNOON...BUT THEY SHOULD
DIMINISH THIS EVENING. THERE WILL BE CHANCES OF SNOW SOUTH OF
KGRI AS A STORM SYSTEM MOVES ACROSS THE CENTRAL AND SOUTHERN
PLAINS...BUT THINK THAT THE CHANCES WILL STAY FAR ENOUGH SOUTH TO
KEEP THE MENTION OUT OF THE FORECAST AT KGRI.
PREV DISCUSSION... /ISSUED 511 AM CST MON DEC 19 2011/
SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT. PRIMARY FORECAST
CONCERN LIES WITH PRECIPITATION CHANCES TODAY THROUGH TUESDAY.
SEEING THE RELATIVE QUIET BEFORE THE STORM EARLY THIS
MORNING...BUT THE NEXT SYSTEM OF INTEREST IS QUITE EVIDENT ON
SATELLITE IMAGERY. THE MAIN UPPER LEVEL LOW PRESSURE SYSTEM TAKING
AIM ON THE PLAINS IS CURRENTLY SPINNING OVER SRN NEW
MEXICO...WHILE THE NORTHERN STREAM SHORTWAVE TROUGH ALSO AFFECTING
THE REGION CONTINUES TO SHIFT SOUTHEAST OUT OF CENTRAL CANADA AND
INTO THE DAKOTAS. AT THE SURFACE...THE COLD FRONT HAS BEEN MAKING
ITS WAY SOUTH OVERNIGHT...AND CURRENTLY IS DRAPED THROUGH THE
CENTRAL PORTIONS OF THE CWA...BRINGING NORTHWESTERLY WINDS BEHIND
IT...BUT THE MORE GUSTY WINDS ARE FOR THE TIME BEING LAGGING JUST
A BIT FURTHER NORTH. THE CWA IS ALSO SEEING INCREASED LOW TO MID
LEVEL MOISTURE AND CLOUD COVER STREAM NORTH FROM THE MAIN STORM
SYSTEM...WHILE LOW LEVEL STRATUS ACCOMPANYING THE SURFACE COLD
FRONT CONTINUES TO PUSH SOUTH AND WILL BE POKING INTO THE NORTHERN
CWA WITHIN THE NEXT HOUR.
THE MOST ACTIVE PERIOD IN THE SHORT TERM CONTINUES TO LIE ROUGHLY
BETWEEN MIDDAY TODAY THROUGH MIDDAY TUESDAY. THE NORTHERN STREAM
SHORTWAVE TROUGH MOVING THROUGH THE DAKOTAS WILL CONTINUE TO PUSH
THE SURFACE COLD FRONT FURTHER SOUTH INTO CENTRAL PORTIONS OF
KANSAS BY MIDDAY. THE UPPER LEVEL LOW PRESSURE SYSTEM WILL
CONTINUE TO PUSH EAST THROUGH NEW MEXICO THROUGH THE DAY...AND BY
LATE THIS EVENING IS EXPECTED TO BE CENTERED OVER THE PANHANDLE OF
TEXAS. THROUGH THE REMAINDER OF THE OVERNIGHT HOURS AND THROUGH
TUESDAY...THE SYSTEM WILL CONTINUE ITS NORTHEASTWARD
TREK...CROSSING THROUGH SOUTH CENTRAL AND EASTERN KANSAS...AND
LOOKS TO END UP NEAR THE KANSAS CITY AREA BY TUESDAY EVENING.
ISENTROPIC LIFT RAMPING UP OUT AHEAD OF THE SYSTEM WILL BRING
INCREASING PRECIPITATION CHANCES...ESPECIALLY STARTING THIS
AFTERNOON...WITH CHANCES CONTINUING OVERNIGHT AND INTO TUESDAY
WITH BETTER FRONTOGENETICAL FORCING AND WITH THE SYSTEM ITSELF
PASSES THROUGH THE REGION. MAIN CHANGES MADE TO THE FORECAST WERE
TO INCREASE POPS...MAINLY ACROSS NC KS. HOWEVER...EVEN THIS CLOSE
TO THE EVENT...SOME UNCERTAINTY EXISTS BECAUSE OF INCONSISTENCIES
BETWEEN MODELS. THE 00Z RUNS OF MANY MODELS DEPICTED A SLIGHT
NORTHWARD TREND TO THINGS...WHICH WAS CONCERNING FOR MORE OF THE
CWA...ONLY TO SEE THE 06Z RUNS STARTING TO PUSH THINGS BACK CLOSER
TO WHERE THEY WERE LAST NIGHT. BECAUSE OF THIS...DIDNT MAKE
SIGNIFICANT CHANGES TO POPS IN SC NEB...THOUGH CONFIDENCE IS NOT
HIGH IN JUST HOW FAR NORTH SNOW WILL ACTUALLY FALL. IF TRENDS FROM
CURRENT MODEL RUNS HOLD...FORECAST POPS ARE TOO FAR NORTH...BUT AT
THIS POINT DO HAVE LIGHT ACCUMULATIONS ALONG AND JUST NORTH OF
HIGHWAY 6.
DECIDED TO UPGRADE THE WATCH ACROSS THE SRN 3 COUNTIES TO A WINTER
STORM WARNING...THERE HAS BEEN MORE CONSISTENCY WITH MODELS
SHOWING THE GREATER QPF IN THOSE AREAS AND TO THE SOUTH...AND
FEEL THAT SOUTHERN PORTIONS OF THOSE COUNTIES COULD END UP SEEING
ARND 8 INCHES OF SNOW. STILL EXPECTING A SHARP GRADIENT WITH
PRECIPITATION AMOUNTS AS ONE GOES FURTHER NORTH...BUT THERE IS
STILL THE POTENTIAL FOR PHILLIPS/SMITH/JEWELL COUNTIES TO SEE 2 TO
6 INCHES OF SNOW /THE HIGHER AMOUNTS ARE EXPECTED TO BE IN JEWELL
COUNTY/...SO A WINTER WX ADV WAS ISSUED FOR THOSE COUNTIES.
CONSIDERED THROWING NUCKOLLS/THAYER IN AS WELL...BUT CURRENT
FORECAST TOTALS WERE ONLY IN THE 1 TO 3 RANGE. DAY SHIFT WILL HAVE
TO ASSESS 12Z RUNS TO SEE IF THEY DO NEED TO BE ADDED.
SOMETHING ELSE TO ADD TO THE SNOW CONCERN IS THE EXPECTED INCREASE
IN WINDS. WHILE THE MAIN FRONT WILL SHIFT SOUTH OF THE CWA...THE
APPROACHING STORM FROM THE SW WILL PREVENT IT FROM COMPLETELY
CLEARING THE AREA...AND WITH HIGH PRESSURE BUILDING IN FROM THE
NORTHWEST...IT WILL LEAD TO A TIGHTENING PRESSURE GRADIENT. THERE
IS EXPECTED TO BE AN INCREASE IN WINDS ACROSS THE CWA WITH THE
INITIAL FRONTAL PASSAGE...WITH THAT TIGHTER GRADIENT SETTING UP
THIS AFTERNOON AND EVENING. SPEEDS INCREASING TO 20 TO 30 MPH WITH
HIGHER GUSTS WILL BE COMMON ACROSS THE CWA...BUT NORTHERN AREAS
WILL START TO SEE SPEEDS TAPER OFF SOONER THAN SOUTHERN AREAS.
THESE SPEEDS STICKING AROUND LONGER IN THE SOUTH CORRESPONDS WITH
THE ONSET OF THE PRECIPITATION LATER TODAY/TONIGHT...WHICH WILL
RESULT IN SOME TRAVEL DIFFICULTIES DUE TO VISIBILITY RESTRICTIONS.
AS WE GET INTO TOMORROW...WILL START TO SEE PRECIPITATION
BEGINNING TO WIND DOWN...ESPECIALLY TOWARD MIDDAY AND INTO THE
AFTERNOON HOURS. WHILE SOUTHEASTERN AREAS COULD SEE ADDITIONAL
LIGHT ACCUMULATIONS...THE HEAVIEST SNOWFALL WILL HAVE ENDED. DID
LOWER POPS DURING THE AFTERNOON...BUT IT IS POSSIBLE THEY WILL
NEED TO BE LOWER EVEN MORE WITH A QUICKER EXIT OF PRECIPITATION.
DRY CONDITIONS REMAIN TUESDAY EVENING AND INTO WEDNESDAY IN THE
WAKE OF THIS LATEST SYSTEM...BUT IT IS A BRIEF BREAK IN THE
ACTION. CHANCES FOR SNOW MAKE A RETURN TO NORTHERN PORTIONS OF THE
CWA LATE WEDNESDAY NIGHT...AS A LOW PRESSURE SYSTEM SWINGS SOUTH
INTO THE CENTRAL ROCKIES WITH A TROUGH AXIS EXTENDING NORTHEAST
THROUGH WRN NEB AND THE DAKOTAS. ANY SNOWFALL WOULD LIKELY BE ON
THE LIGHT SIDE.
AS FAR AS TEMPERATURES GO...BETWEEN THE INCREASING CLOUD COVER AND
COOLER AIR FILTERING IN WITH BEHIND THE FRONT...NOT EXPECTING
BIG CHANGES THROUGH THE MORNING HOURS TODAY...AND SHOULD SEE HIGHS
BEFORE/NEAR MIDDAY BEFORE STARTING TO SEE TEMPS FALL OFF DURING
THE AFTERNOON. INTO TUESDAY...EVEN THOUGH PRECIPITATION WILL BE
COMING TO AN END DURING THE AFTERNOON...COOLER AIR REMAINING IN
PLACE IS EXPECTED TO KEEP HIGHS IN THE UPPER 20S TO LOWER 30S. AND
DEPENDING ON THE ACTUAL SNOWFALL THAT FALLS WITH THIS STORM
SYSTEM...SOME AREAS MAY NEED A DOWNWARD ADJUSTMENT. SHOULD SEE A
BUMP UP IN TEMPS ON WED WITH A MORE DOWNSLOPING COMPONENT TO THE
WINDS...WITH SNOW FREE AREAS POSSIBLY REACHING NEAR 40...WHILE
SOUTHEASTERN AREAS MAY STRUGGLE TO GET INTO THE MID 30S.
LONG TERM...THURSDAY THROUGH SUNDAY. AT THE ONSET OF THE EXTENDED
ON THURSDAY...COLD AIR WILL CONTINUE TO FILTER SOUTH FOLLOWING
COLD FRONTAL PASSAGE AS UPPER TROUGH CROSSES THE CENTRAL PLAINS.
FRONTOGENETIC FORCING AND LIFT IN UPPER DYNAMICS AS TROUGH SWINGS
THROUGH WILL PROVIDE CHCS FOR LIGHT SNOW NW/SE THURSDAY INTO
FRIDAY MORNING...AND HAVE FOLLOWED CLOSER TO OPEN WAVE ECMWF
SOLUTION VS GFS WHICH CLOSES THE LOW IN NORTHEAST KS THURSDAY
NIGHT. CONDITIONS STILL LOOK TO DRY OUT FOR THE HOLIDAY WEEKEND
WITH A BRIEF PERIOD OF HEIGHT RISES FRIDAY NIGHT/SATURDAY BEHIND
DEPARTING TROUGH. ANOTHER CLIPPER SYSTEM BRINGS IN ANOTHER ROUND
OF COLD AIR FOR CHRISTMAS DAY...WHILE A 100+KT JET DIVES ALONG THE
ROCKY MOUNTAIN REGION FURTHER CARVING A TROUGH ACROSS THE CENTRAL
PLAINS. GFS IS COLDER WITH TEMP PROFILE FOR CHRISTMAS THAN ECMWF
AND SUGGESTS HIGHS MAY ONLY BE IN THE 20S...BUT GIVEN UNCERTAINTY
ON DEGREE OF COLD AIR WILL FOLLOW CLOSER TO ENSEMBLE SOLUTIONS
WITH HIGHS DURING THROUGH THE EXTENDED PERIODS AVERAGING IN THE
LOWER 30S WITH LOWS MAINLY IN THE TEENS.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM CST
TUESDAY FOR KSZ005>007.
WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST TUESDAY
FOR KSZ017>019.
&&
$$
UPDATE...BRYANT
SHORT TERM...ADO
LONG TERM...CF
AREA FORECAST DISCUSSION
NWS HASTINGS NE
1120 AM CST MON DEC 19 2011
.AVIATION...18Z TAF. IFR CEILINGS HAVE MOVED INTO PARTS OF SOUTH
CENTRAL NEBRASKA BEHIND A COLD FRONT THAT TRAVELED ACROSS THE
AREA EARLIER TODAY. THE GENERAL TREND HAS BEEN FOR THE IFR
CEILINGS TO LIFT TO MVFR...AND THIS IS ALSO SHOWN BY THE LATEST
NAM PROXIMITY SOUNDINGS..SO WILL ONLY CARRY THE LOWER CEILINGS IN
A BRIEF TEMPO GROUP. PROXIMITY SOUNDINGS ALSO SHOW THE MVFR
CEILINGS IMPROVING THIS AFTERNOON...THOUGH THE RUC IS FASTER IN
LIFTING THE CEILINGS THAN THE NAM. WILL AIM FOR MORE OF A
COMPROMISE SOLUTION AND GO WITH 21Z AS A START. WINDS WILL REMAIN
GUSTY AND FROM THE NORTH MOST OF THE AFTERNOON...BUT THEY SHOULD
DIMINISH THIS EVENING. THERE WILL BE CHANCES OF SNOW SOUTH OF
KGRI AS A STORM SYSTEM MOVES ACROSS THE CENTRAL AND SOUTHERN
PLAINS...BUT THINK THAT THE CHANCES WILL STAY FAR ENOUGH SOUTH TO
KEEP THE MENTION OUT OF THE FORECAST AT KGRI.
&&
.PREV DISCUSSION... /ISSUED 511 AM CST MON DEC 19 2011/
SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT. PRIMARY FORECAST
CONCERN LIES WITH PRECIPITATION CHANCES TODAY THROUGH TUESDAY.
SEEING THE RELATIVE QUIET BEFORE THE STORM EARLY THIS
MORNING...BUT THE NEXT SYSTEM OF INTEREST IS QUITE EVIDENT ON
SATELLITE IMAGERY. THE MAIN UPPER LEVEL LOW PRESSURE SYSTEM TAKING
AIM ON THE PLAINS IS CURRENTLY SPINNING OVER SRN NEW
MEXICO...WHILE THE NORTHERN STREAM SHORTWAVE TROUGH ALSO AFFECTING
THE REGION CONTINUES TO SHIFT SOUTHEAST OUT OF CENTRAL CANADA AND
INTO THE DAKOTAS. AT THE SURFACE...THE COLD FRONT HAS BEEN MAKING
ITS WAY SOUTH OVERNIGHT...AND CURRENTLY IS DRAPED THROUGH THE
CENTRAL PORTIONS OF THE CWA...BRINGING NORTHWESTERLY WINDS BEHIND
IT...BUT THE MORE GUSTY WINDS ARE FOR THE TIME BEING LAGGING JUST
A BIT FURTHER NORTH. THE CWA IS ALSO SEEING INCREASED LOW TO MID
LEVEL MOISTURE AND CLOUD COVER STREAM NORTH FROM THE MAIN STORM
SYSTEM...WHILE LOW LEVEL STRATUS ACCOMPANYING THE SURFACE COLD
FRONT CONTINUES TO PUSH SOUTH AND WILL BE POKING INTO THE NORTHERN
CWA WITHIN THE NEXT HOUR.
THE MOST ACTIVE PERIOD IN THE SHORT TERM CONTINUES TO LIE ROUGHLY
BETWEEN MIDDAY TODAY THROUGH MIDDAY TUESDAY. THE NORTHERN STREAM
SHORTWAVE TROUGH MOVING THROUGH THE DAKOTAS WILL CONTINUE TO PUSH
THE SURFACE COLD FRONT FURTHER SOUTH INTO CENTRAL PORTIONS OF
KANSAS BY MIDDAY. THE UPPER LEVEL LOW PRESSURE SYSTEM WILL
CONTINUE TO PUSH EAST THROUGH NEW MEXICO THROUGH THE DAY...AND BY
LATE THIS EVENING IS EXPECTED TO BE CENTERED OVER THE PANHANDLE OF
TEXAS. THROUGH THE REMAINDER OF THE OVERNIGHT HOURS AND THROUGH
TUESDAY...THE SYSTEM WILL CONTINUE ITS NORTHEASTWARD
TREK...CROSSING THROUGH SOUTH CENTRAL AND EASTERN KANSAS...AND
LOOKS TO END UP NEAR THE KANSAS CITY AREA BY TUESDAY EVENING.
ISENTROPIC LIFT RAMPING UP OUT AHEAD OF THE SYSTEM WILL BRING
INCREASING PRECIPITATION CHANCES...ESPECIALLY STARTING THIS
AFTERNOON...WITH CHANCES CONTINUING OVERNIGHT AND INTO TUESDAY
WITH BETTER FRONTOGENETICAL FORCING AND WITH THE SYSTEM ITSELF
PASSES THROUGH THE REGION. MAIN CHANGES MADE TO THE FORECAST WERE
TO INCREASE POPS...MAINLY ACROSS NC KS. HOWEVER...EVEN THIS CLOSE
TO THE EVENT...SOME UNCERTAINTY EXISTS BECAUSE OF INCONSISTENCIES
BETWEEN MODELS. THE 00Z RUNS OF MANY MODELS DEPICTED A SLIGHT
NORTHWARD TREND TO THINGS...WHICH WAS CONCERNING FOR MORE OF THE
CWA...ONLY TO SEE THE 06Z RUNS STARTING TO PUSH THINGS BACK CLOSER
TO WHERE THEY WERE LAST NIGHT. BECAUSE OF THIS...DIDNT MAKE
SIGNIFICANT CHANGES TO POPS IN SC NEB...THOUGH CONFIDENCE IS NOT
HIGH IN JUST HOW FAR NORTH SNOW WILL ACTUALLY FALL. IF TRENDS FROM
CURRENT MODEL RUNS HOLD...FORECAST POPS ARE TOO FAR NORTH...BUT AT
THIS POINT DO HAVE LIGHT ACCUMULATIONS ALONG AND JUST NORTH OF
HIGHWAY 6.
DECIDED TO UPGRADE THE WATCH ACROSS THE SRN 3 COUNTIES TO A WINTER
STORM WARNING...THERE HAS BEEN MORE CONSISTENCY WITH MODELS
SHOWING THE GREATER QPF IN THOSE AREAS AND TO THE SOUTH...AND
FEEL THAT SOUTHERN PORTIONS OF THOSE COUNTIES COULD END UP SEEING
ARND 8 INCHES OF SNOW. STILL EXPECTING A SHARP GRADIENT WITH
PRECIPITATION AMOUNTS AS ONE GOES FURTHER NORTH...BUT THERE IS
STILL THE POTENTIAL FOR PHILLIPS/SMITH/JEWELL COUNTIES TO SEE 2 TO
6 INCHES OF SNOW /THE HIGHER AMOUNTS ARE EXPECTED TO BE IN JEWELL
COUNTY/...SO A WINTER WX ADV WAS ISSUED FOR THOSE COUNTIES.
CONSIDERED THROWING NUCKOLLS/THAYER IN AS WELL...BUT CURRENT
FORECAST TOTALS WERE ONLY IN THE 1 TO 3 RANGE. DAY SHIFT WILL HAVE
TO ASSESS 12Z RUNS TO SEE IF THEY DO NEED TO BE ADDED.
SOMETHING ELSE TO ADD TO THE SNOW CONCERN IS THE EXPECTED INCREASE
IN WINDS. WHILE THE MAIN FRONT WILL SHIFT SOUTH OF THE CWA...THE
APPROACHING STORM FROM THE SW WILL PREVENT IT FROM COMPLETELY
CLEARING THE AREA...AND WITH HIGH PRESSURE BUILDING IN FROM THE
NORTHWEST...IT WILL LEAD TO A TIGHTENING PRESSURE GRADIENT. THERE
IS EXPECTED TO BE AN INCREASE IN WINDS ACROSS THE CWA WITH THE
INITIAL FRONTAL PASSAGE...WITH THAT TIGHTER GRADIENT SETTING UP
THIS AFTERNOON AND EVENING. SPEEDS INCREASING TO 20 TO 30 MPH WITH
HIGHER GUSTS WILL BE COMMON ACROSS THE CWA...BUT NORTHERN AREAS
WILL START TO SEE SPEEDS TAPER OFF SOONER THAN SOUTHERN AREAS.
THESE SPEEDS STICKING AROUND LONGER IN THE SOUTH CORRESPONDS WITH
THE ONSET OF THE PRECIPITATION LATER TODAY/TONIGHT...WHICH WILL
RESULT IN SOME TRAVEL DIFFICULTIES DUE TO VISIBILITY RESTRICTIONS.
AS WE GET INTO TOMORROW...WILL START TO SEE PRECIPITATION
BEGINNING TO WIND DOWN...ESPECIALLY TOWARD MIDDAY AND INTO THE
AFTERNOON HOURS. WHILE SOUTHEASTERN AREAS COULD SEE ADDITIONAL
LIGHT ACCUMULATIONS...THE HEAVIEST SNOWFALL WILL HAVE ENDED. DID
LOWER POPS DURING THE AFTERNOON...BUT IT IS POSSIBLE THEY WILL
NEED TO BE LOWER EVEN MORE WITH A QUICKER EXIT OF PRECIPITATION.
DRY CONDITIONS REMAIN TUESDAY EVENING AND INTO WEDNESDAY IN THE
WAKE OF THIS LATEST SYSTEM...BUT IT IS A BRIEF BREAK IN THE
ACTION. CHANCES FOR SNOW MAKE A RETURN TO NORTHERN PORTIONS OF THE
CWA LATE WEDNESDAY NIGHT...AS A LOW PRESSURE SYSTEM SWINGS SOUTH
INTO THE CENTRAL ROCKIES WITH A TROUGH AXIS EXTENDING NORTHEAST
THROUGH WRN NEB AND THE DAKOTAS. ANY SNOWFALL WOULD LIKELY BE ON
THE LIGHT SIDE.
AS FAR AS TEMPERATURES GO...BETWEEN THE INCREASING CLOUD COVER AND
COOLER AIR FILTERING IN WITH BEHIND THE FRONT...NOT EXPECTING
BIG CHANGES THROUGH THE MORNING HOURS TODAY...AND SHOULD SEE HIGHS
BEFORE/NEAR MIDDAY BEFORE STARTING TO SEE TEMPS FALL OFF DURING
THE AFTERNOON. INTO TUESDAY...EVEN THOUGH PRECIPITATION WILL BE
COMING TO AN END DURING THE AFTERNOON...COOLER AIR REMAINING IN
PLACE IS EXPECTED TO KEEP HIGHS IN THE UPPER 20S TO LOWER 30S. AND
DEPENDING ON THE ACTUAL SNOWFALL THAT FALLS WITH THIS STORM
SYSTEM...SOME AREAS MAY NEED A DOWNWARD ADJUSTMENT. SHOULD SEE A
BUMP UP IN TEMPS ON WED WITH A MORE DOWNSLOPING COMPONENT TO THE
WINDS...WITH SNOW FREE AREAS POSSIBLY REACHING NEAR 40...WHILE
SOUTHEASTERN AREAS MAY STRUGGLE TO GET INTO THE MID 30S.
LONG TERM...THURSDAY THROUGH SUNDAY. AT THE ONSET OF THE EXTENDED
ON THURSDAY...COLD AIR WILL CONTINUE TO FILTER SOUTH FOLLOWING
COLD FRONTAL PASSAGE AS UPPER TROUGH CROSSES THE CENTRAL PLAINS.
FRONTOGENETIC FORCING AND LIFT IN UPPER DYNAMICS AS TROUGH SWINGS
THROUGH WILL PROVIDE CHCS FOR LIGHT SNOW NW/SE THURSDAY INTO
FRIDAY MORNING...AND HAVE FOLLOWED CLOSER TO OPEN WAVE ECMWF
SOLUTION VS GFS WHICH CLOSES THE LOW IN NORTHEAST KS THURSDAY
NIGHT. CONDITIONS STILL LOOK TO DRY OUT FOR THE HOLIDAY WEEKEND
WITH A BRIEF PERIOD OF HEIGHT RISES FRIDAY NIGHT/SATURDAY BEHIND
DEPARTING TROUGH. ANOTHER CLIPPER SYSTEM BRINGS IN ANOTHER ROUND
OF COLD AIR FOR CHRISTMAS DAY...WHILE A 100+KT JET DIVES ALONG THE
ROCKY MOUNTAIN REGION FURTHER CARVING A TROUGH ACROSS THE CENTRAL
PLAINS. GFS IS COLDER WITH TEMP PROFILE FOR CHRISTMAS THAN ECMWF
AND SUGGESTS HIGHS MAY ONLY BE IN THE 20S...BUT GIVEN UNCERTAINTY
ON DEGREE OF COLD AIR WILL FOLLOW CLOSER TO ENSEMBLE SOLUTIONS
WITH HIGHS DURING THROUGH THE EXTENDED PERIODS AVERAGING IN THE
LOWER 30S WITH LOWS MAINLY IN THE TEENS.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 PM CST
TUESDAY FOR KSZ005>007.
WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST TUESDAY
FOR KSZ017>019.
&&
$$
AREA FORECAST DISCUSSION
NWS BUFFALO NY
1025 PM EST TUE DEC 20 2011
.SYNOPSIS...
HIGH PRESSURE ACROSS NEW YORK STATE WILL MOVE TO THE EAST OF THE
REGION TONIGHT. MEANWHILE...LOW PRESSURE MOVING OUT OF THE SOUTHERN
PLAINS WILL PUSH A WARM FRONT NORTH TOWARD THE LOWER LAKES LATER
TONIGHT AND WEDNESDAY. THE SOUTHERLY WINDS TO THE WEST OF THE HIGH
PRESSURE CENTER AND THE PASSAGE OF THE WARM FRONT WILL BRING WARMER
TEMPERATURES AND RAIN... WHICH COULD BEGIN AS A WINTRY MIX OF
PRECIPITATION ACROSS THE TUG HILL REGION.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
THE 00Z BUF SOUNDING SHOWS AN 850 MB TEMP OF -5C...WHICH IS 3
DEGREES C COLDER THAN NEARLY ALL MODEL GUIDANCE. THIS IS LIKELY
DUE TO THE SHARPNESS OF THE BOUNDARY ALOFT...WHICH IS NOT BEING
SUFFICIENTLY RESOLVED BY THE MODELS. AT 1000 PM...RADAR SHOWS A
LINE LIFTING ACROSS CHAUTAUQUA COUNTY. THIS IS LIKELY THE LEADING
EDGE OF SIGNIFICANT WARM AIR ADVECTION.
BASED ON THIS...EXPECT THIS LINE IS IS WHAT WILL WARM TEMPERATURES
ALOFT ENOUGH TO SUPPORT RAIN. RETURNS ON THIS ARE QUITE
MEAGER...AND HAVE OPTED TO DOWNGRADE THIS TO JUST FLURRIES AS THIS
MOVES THROUGH SINCE IT IS LESS LIKELY TO BE MEASURABLE. THE 00Z BUFFALO
SOUNDING SUGGESTS PRECIPITATION WILL START AS A BRIEF PERIOD OF
SNOW OR SNOW AND RAIN MIXED. BEHIND THIS...TEMPERATURES ALOFT
WILL BE TOO WARM TO SUPPORT SNOW...WITH THIS LINE EXPECTED TO
CONTINUE TO LIFT NORTHWARD OVERNIGHT.
DESPITE THE BRIEF PERIOD OF MIXED PRECIPITATION AT THE ONSET...IT
DOES APPEAR SURFACE TEMPERATURES WILL CONTINUE TO GRADUALLY WARM
OVERNIGHT. WILL CONTINUE TO WATCH THIS CLOSELY...BECAUSE AS THIS
LIGHT BAND MOVES ACROSS...TEMPERATURES ARE FORECAST TO BE JUST A
COUPLE DEGREES ABOVE FREEZING...WHICH IS A TAD CLOSE FOR COMFORT.
EAST OF LAKE ONTARIO CLEARED OUT THIS EVENING...WHICH ALLOWED
TEMPERATURES TO DROP INTO THE UPPER TEENS IN MANY SPOTS. BECAUSE
OF THIS...NOW HAVE THE ADVISORY FOR JEFFERSON COUNTY AS WELL...AND
UNTIL 1000 AM. FROZEN QPFS WILL NOT BE MUCH. LOOKING FOR JUST A
LIGHT GLAZE OF ICE IF ANYTHING...BUT IT DOES NOT TAKE MUCH ICE TO
MAKE THINGS SLICK.
OTHERWISE...EXPECT AREAS OF FOG TO DEVELOP BEHIND THIS...WITH JHW
ALREADY DOWN TO A HALF MILE. FOG WILL SPREAD ACROSS ALL OF THE
SOUTHERN TIER...BUT THE SE DOWNSLOPE FLOW SHOULD LIMIT FOG NORTH
OF THE I-90 THRUWAY.
WARM AIR OVERSPREADS THE ENTIRE FORECAST AREA BY MID MORNING ON
WEDNESDAY AND THE STEADIER RAINS WILL FOLLOW CLOSELY. RAINFALL
TOTALS WILL RANGE FROM A THIRD TO A HALF INCH FROM LATE MORNING
THROUGH WEDNESDAY EVENING. THIS SAID...LOCALIZED AMOUNTS TO AN
INCH ARE POSSIBLE...ESPECIALLY SOUTH OF THE THRUWAY...WHERE BOTH
THE NAM AND HRRR BRING IN THE BEST QPFS. WOULD NOT BE SURPRISED TO
HEAR A RUMBLE OF THUNDER...GIVEN A MODEST AMOUNT OF ELEVATED CAPE.
WITH NO LIGHTNING STRIKES UPSTREAM...CARRY ONLY ISOLATED THUNDER
IN PORTIONS OF THE SOUTHERN TIER WEDNESDAY MORNING.
TEMPS WILL TOP OUT IN THE LOWER TO MID 40S ACROSS THE EASTERN LAKE
ONTARIO REGION WITH MID 40S TO LOW 50S FOR THE REMAINDER OF THE
FORECAST AREA.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
A SPLIT FLOW WILL REMAIN IN PLACE ACROSS THE COUNTRY DURING THIS
PERIOD WITH OUR FORECAST AREA GENERALLY BEING DOMINATED BY THE
SOUTHERN BRANCH. THIS WILL TRANSLATE INTO CONTINUED ABOVE NORMAL
TEMPERATURES WITH LITTLE (IF ANY) IN THE WAY OF SNOWFALL. SAME OL`
SAME OL`. WHILE THERE WILL BE ONE SIZE-ABLE SHORTWAVE OF NOTE DURING
THIS STRETCH...GUIDANCE HAS BEEN VERY CONSISTENT WITH KEEPING THE
BULK OF ITS AFFECTS TO OUR SOUTH. OUR REGION WILL BE MORE INFLUENCED
BY MORE SUBTLE FEATURES. THE DETAILS...
A POTENT SHORTWAVE WILL RACE ACROSS OUR FORECAST AREA WEDNESDAY
NIGHT. THIS WILL BE A `WARM` PCPN EVENT WITH WIDESPREAD RAIN IN THE
EVENING TAPERING OFF DURING THE COURSE OF THE OVERNIGHT. THE RAIN
EARLY ON WILL BE ENHANCED BY SOME DECENT JET INDUCED LIFT SO THAT
TOTAL RAINFALL FROM THE SYSTEM WILL AVERAGE A QUARTER...TO AT MOST
ONE HALF INCH. AS THE SHORTWAVE EXITS ACROSS NEW ENGLAND LATE
WEDNESDAY NIGHT...BROAD BASED RIDGING WILL BUILD IN FROM THE WEST.
ON THURSDAY...A LOW AMPLITUDE H5 RIDGE AND ASSOCIATED WEAK SFC HIGH
WILL MOVE ACROSS OUR FORECAST AREA. THIS WILL SUPPORT FAIR DRY
WEATHER WITH AFTERNOON TEMPERATURES RANGING FROM THE UPPER 30S
ACROSS PARTS OF THE NORTH COUNTRY TO THE MID AND UPPER 40S IN THE
GENESEE VALLEY AND SOUTH SHORE OF LAKE ONTARIO.
FAIR WEATHER SHOULD PERSIST ACROSS MOST OF THE REGION THURSDAY
NIGHT...ALTHOUGH A WEAK COLD FRONT SAGGING SOUTH FROM QUEBEC COULD
HELP TO PRODUCE SOME FLURRIES AND VERY LIGHT SNOW SHOWERS. A
CONFLUENT FLOW ALOFT SHOULD MINIMIZE ANY CHANCE FOR ACCUMULATING
SNOW.
FOR FRIDAY...THE AFOREMENTIONED WEAK COLD FRONT WILL PUSH ACROSS OUR
FORECAST AREA. WILL KEEP THE LOW CHC POPS IN PLAY FROM CONTINUITY...
BUT WILL ADD THE MENTION OF RAIN SHOWERS (ALONG WITH THE SNOW
SHOWERS) AS A VERY LIMITED SNOW GROWTH WILL BE IN PLACE. FORCING
FROM THE FRONT WILL BE VERY WEAK THOUGH...SO EVEN THE LOW CHC POPS
MAY BE TOO PESSIMISTIC.
WHILE THE NEXT POTENT SHORTWAVE WILL BE HEADING OUR WAY FROM THE
UPPER GREAT LAKES FRIDAY NIGHT...LINGERING SFC HIGH PRESSURE SHOULD
KEEP THE NIGHT MAINLY PCPN FREE.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
A SOMEWHAT AMPLIFIED +PNA PATTERN ACROSS THE LOWER 48 AT THE START
OF THIS PERIOD WILL QUICKLY BREAK DOWN INTO A LOW AMPLITUDE PACIFIC
FLOW AS MID LATITUDE BLOCKING WILL GENERALLY REMAIN ABSENT ACROSS
THE NORTHERN HEMISPHERE. MEDIUM RANGE GUIDANCE WAS SUGGESTING THAT
SOME BLOCKING COULD DEVELOP IN PREVIOUS MODEL RUNS...BUT THAT TREND
HAS SINCE BEEN REVERSED. THIS WILL RESULT IN TEMPERATURES AVERAGING
NEAR TO ABOVE NORMAL...ALTHOUGH THERE WILL BE BRIEF PERIODS WHEN IT
WILL BE SEASONABLY CHILLY.
THE BIGGEST QUESTION FOR MANY DURING THIS PERIOD IS...WILL THERE
ENOUGH SNOW FOR A WHITE CHRISTMAS? THAT MAY LARGELY DEPEND ON YOUR
SPECIFIC DEFINITION OF A WHITE CHRISTMAS...AS SIGNIFICANT SNOWFALL
FOR OUR REGION IS NOT CURRENTLY IN THE MAKING.
FOR SATURDAY...A POTENT SHORTWAVE IN THE NORTHERN BRANCH WILL BRUSH
BY TO OUR NORTH. THIS WILL BRING US THE CHANCE FOR SOME LIGHT SNOW
SHOWERS...BUT WITH A HIGHLY SHEAR AIRMASS IN ITS WAKE...ASSISTANCE
FROM THE LAKES (IE. LAKE EFFECT) IS NOT ANTICIPATED. THIS SHOULD
KEEP THE SNOW FROM MEASURING MORE THAN A COVERING.
THE MOST SIGNIFICANT WEATHER FEATURE OF THIS PERIOD WILL THEN TAKE
AIM ON THE MID ATLANTIC AND NORTHEAST COAST FOR CHRISTMAS DAY AND
NIGHT. THE MEDIUM RANGE GUIDANCE PACKAGES HAVE NOT BEEN IN SYNC WITH
THIS FEATURE FOR THE PAST SEVERAL RUNS...AND THAT FACT REMAINS THE
SAME AS THE GFS NEVER REALLY GENERATES ANYTHING AT THE SFC WHILE THE
USUALLY MORE TRUSTWORTHY ECMWF DEPICTS A COASTAL LOW. IT IS THIS
LATTER SOLUTION THAT SUGGESTS THE BACK-EDGE OF THE SYNOPTIC SNOW
SHIELD WILL LIFT UP ACROSS OUR AREA SUNDAY NIGHT. WILL RAISE POPS TO
40 TO COVER FOR THIS POTENTIAL. IF THE STORM SYSTEM WORKS OUT
EXACTLY AS DEPICTED...THEN THERE COULD BE SUB-ADVISORY CRITERIA SNOW
ACCUMS SOUTH AND EAST OF BUFFALO...BUT FROM THIS RANGE IT WOULD NOT
BE PRUDENT TO PUT A LOT OF CONFIDENCE INTO THAT.
A SEASONABLY COLD NORTHWEST FLOW IN ITS WAKE WILL COMBINE WITH A H5
TROUGH TO BRING US THE CHANCE FOR SNOW SHOWERS AND SOME LAKE
ENHANCEMENT MONDAY AND MONDAY NIGHT...THEN WARMING ALOFT AND THE
PROGRESSION OF A H5 RIDGE SHOULD ENCOURAGE FAIR AND MILDER WEATHER
FOR TUESDAY INTO MID WEEK.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
THE LEADING EDGE OF WARM AIR ADVECTION ALOFT IS GRADUALLY
APPROACHING FROM THE SOUTHWEST...WITH THIS JUST ABOUT TO CROSS JHW
AT 02Z. WHILE THERE MAY BE A BRIEF IMPROVEMENT IN CIGS JUST AHEAD
OF THIS...FOLLOWING ITS PASSAGE...CIGS HAVE GENERALLY LOWERED
CONSIDERABLY BEHIND IT IN NE OH AND NW PA...WHERE 200 TO 400 CIGS
ARE COMMONPLACE. EXPECT JHW TO LOWER QUITE QUICKLY OVER THE NEXT
COUPLE HOURS.
THE SE DOWNSLOPE FLOW SHOULD KEEP BUF/IAG/ROC MAINLY MVFR INTO WEDNESDAY
MORNING. PRECIPITATION MAY START AS A VERY BRIEF PERIOD OF
SNOW...HOWEVER RADAR AND MODEL TRENDS SUGGESTING THIS SHOULD BE
VERY LIGHT...AND LARGELY SHOULD NOT HAVE TOO MUCH OF AN IMPACT ON
TAF LOCATIONS.
WHILE THERE MAY BE PATCHY AREAS OF MIXED PRECIPITATION EAST OF
LAKE ONTARIO...EXPECT PRECIPITATION AT THE TAF SITES TO BE RAIN.
INTRODUCED A BRIEF PERIOD OF LLWS AT JHW/ROC ON WEDNESDAY...WHERE AN AREA
OF MID-LEVEL WARM AIR ADVECTION WILL CROSS ALOFT BUT STRUGGLE TO
MIX TO THE SURFACE.
OUTLOOK...
WEDNESDAY NIGHT...MVFR/IFR WITH RAIN.
THURSDAY...MAINLY VFR.
THURSDAY NIGHT...CHC LIGHT SNOW OR RAIN ESPECIALLY TOWARDS THE
SOUTH AND EAST.
FRIDAY AND SATURDAY...MAINLY VFR CHC SNOW SHOWERS.
SUNDAY...MAINLY VFR IN SCTD SNOW SHOWERS.
&&
.MARINE...
HIGH PRESSURE ACROSS NEW YORK STATE TODAY WILL MOVE TO THE EAST OF
THE REGION TONIGHT. SOUTHERLY WINDS WILL INCREASE TONIGHT AND
WEDNESDAY AS A WARM FRONT LIFTS NORTH TOWARD THE LOWER LAKES...THE
ATTENDANT LOW AND COLD FRONT WILL CROSS THE LAKES ON WEDNESDAY NIGHT
WITH INCREASING WESTERLY WINDS AND WAVES BUILDING TO SMALL CRAFT
ADVISORY CRITERIA GENERALLY FROM WEDNESDAY EVENING THROUGH MID
MORNING ON THURSDAY.
&&
.CLIMATE...
THE WINTER OF 2011-12 HAS STARTED SLOW IN THE SNOWFALL CATEGORY
ACROSS WESTERN AND CENTRAL NEW YORK. THROUGH DECEMBER 19TH...THE
CURRENT SNOW THIS SEASON OF 3.0 INCHES (BUFFALO) AND 2.1
INCHES(ROCHESTER) ARE WELL BELOW NORMAL THUS FAR. THERE HAVE BEEN
SEVERAL YEARS THAT HAVE HAD SIMILAR STARTS THOUGH. BELOW IS A LIST
OF THE TOP LEAST AMOUNT OF SNOW IN BOTH CITIES...MEASURED AT THE
RESPECTIVE AIRPORTS...THROUGH AND INCLUDING CHRISTMAS EVE.
BUFFALO
1 3.0 2011
2 3.1 1998
3 3.3 1931
4 3.6 1896
5 4.3 1918
...
10 6.5 1888
15 7.8 1891
***NORMAL THROUGH DECEMBER 24TH 29.1***
ROCHESTER
1 2.1 2011
2 2.6 1939
3 3.7 2001
4 3.8 1877
5 4.2 2006
...
10 6.2 1998
15 7.8 1940
***NORMAL THROUGH DECEMBER 24TH 23.5***
SNOWFALL RECORDS GO BACK TO THE WINTER OF 1884-85.
&&
.BUF WATCHES/WARNINGS/ADVISORIES...
NY...WINTER WEATHER ADVISORY FROM 3 AM TO 10 AM EST WEDNESDAY FOR
NYZ006>008.
MARINE...SMALL CRAFT ADVISORY FROM 8 PM WEDNESDAY TO 8 AM EST THURSDAY
FOR LEZ040-041.
SMALL CRAFT ADVISORY FROM MIDNIGHT WEDNESDAY NIGHT TO
8 AM EST THURSDAY FOR LOZ042-043.
SMALL CRAFT ADVISORY FROM MIDNIGHT WEDNESDAY NIGHT TO 10
AM EST THURSDAY FOR LOZ044-045.
&&
$$
SYNOPSIS...WCH
NEAR TERM...APFFEL/WCH
SHORT TERM...RSH
LONG TERM...RSH
AVIATION...APFFEL
MARINE...APFFEL/WCH
CLIMATE...THOMAS
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
842 PM EST TUE DEC 20 2011
.SYNOPSIS...
A COLD FRONT WILL SLOWLY APPROACH THE AREA WEDNESDAY AND THURSDAY
...THEN STALL ACROSS THE AREA THROUGH THE WEEKEND. WAVES OF LOW
PRESSURE WILL RIDE ALONG THIS FRONT...RESULTING WITH INCREASING
CHANCES FOR PRECIPITATION. THE PROSPECTS FOR MEASURABLE RAINFALL
WILL INCREASE AS THE WEEK PROGRESSES WITH THE BEST CHANCE EARLY IN
THE WEEKEND. HIGH PRESSURE WILL FINALLY REACH THE AREA EARLY IN THE
NEW WORK WEEK.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
AS OF 840 PM TUESDAY...HAVE INCREASED CLOUD COVER ACROSS ALL OF THE
ILM CWA. THIS BASED ON LATEST SAT IMAGERY TRENDS AND THE LATEST 18Z
MODEL RUNS. LATEST HRRR KEEPS THE MAJORITY OF THE PCPN TONIGHT WEST
OF THE ILM CWA. THE BEST PCPN CHANCES ACROSS THE ILM CWA WILL OCCUR
WEST OF THE I-95 CORRIDOR. 5H S/W TROF AND ASSOCIATED UVVS MOVING
NE-WARD...WILL PASS IN CLOSE PROXIMITY TO WARRANT LOW CHANCE POPS
WELL INLAND. EAST OF I-95 AND TO THE COAST...ISOLATED -SHRA AT BEST.
WIDESPREAD 50S FOR LOWS LOOK GOOD EARLY IN THE NIGHT...WITH TEMPS
EITHER STEADY OR INCREASING SLIGHTLY AFTER MIDNIGHT DUE TO
WAA...LITE PCPN AND THE CLOUD COVER.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
AS OF 3 PM TUESDAY...A LARGE AREA OF HIGH PRESSURE WILL BE CENTERED
ACROSS THE WESTERN ATLANTIC. THE WESTERN PERIPHERY OF THIS HIGH WILL
HANG ON ACROSS THE EASTERN CAROLINAS THROUGH THE MID-TERM. AT THE
SAME TIME...A VERY DEEP TROUGH WILL CARVE OUT ACROSS THE WESTERN
UNITED STATES. ONE AREA OF LOW PRESSURE WILL PASS WELL N OF THE AREA
ON WED AS ANOTHER AREA OF LOW PRESSURE EJECTS OUT OF THE FOUR
CORNERS REGION AND PASSES JUST N OF THE AREA THU AND THU NIGHT. AS
EACH ONE OF THESE SYSTEMS RIDE OVER THE TOP OF THE RIDGE THEY WILL
AID IN FLATTENING IT OUT...SETTING UP THE STAGE FOR PERHAPS SOME
MEANINGFUL RAIN JUST BEYOND THIS FORECAST PERIOD.
A DEEP AND WARM SW FLOW WILL KEEP CONDITIONS UNSETTLED THIS PERIOD
WITH CLOUDS DOMINATING THE SKY. WHILE MEASURABLE RAINFALL CAN NOT BE
RULED OUT AT ANY TIME DURING THIS PERIOD...AT THIS POINT IT IS VERY
DIFFICULT TO HONE IN ON A TIME WHEN THE CHANCE FOR SHOWERS WILL BE
HIGHEST. HOWEVER...WE WILL CARRY THE HIGHEST POPS LATER THU AND THU
NIGHT AS FOUR CORNERS LOW MAKES ITS CLOSEST APPROACH. HOWEVER...
AGAIN...TIMING IS VERY UNCERTAIN AT THIS POINT.
GIVEN DEWPOINTS IN THE LOWER TO MID 60S WILL BE ADVECTING
NORTHWARD...WE DO EXPECT PATCHY SEA FOG TO DEVELOP. GIVEN THE
TRAJECTORIES...SOME OF THIS FOG SHOULD SKIRT THE COASTAL AREAS...
ESPECIALLY ACROSS BRUNSWICK COUNTY. INTRODUCED PATCHY FOG ALONG THE
COAST FOR LATER WED S...SPREADING UP THE COAST WED NIGHT AND THU.
THIS FOG MAY EVENTUALLY GROW MORE WIDESPREAD AND DENSE AT THE COAST
AS WARM AND MOIST FLOW PERSISTS ACROSS THE COOL SHELF WATERS.
DAYTIME HIGHS AND LOWS WILL BE WELL ABOVE NORMAL THROUGH THE PERIOD.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 3 PM TUESDAY...MUCH OF THE PERIOD REMAINS UNSETTLED. A COLD
FRONT...LAYING PARALLEL TO FLOW ALOFT...WILL BE STALLED OVER THE
AREA FRI AND THEN JUST OFF THE COAST SAT/SUN. SEVERAL WEAK
SURFACE WAVES WILL TRAVEL NORTHEAST ALONG THE BOUNDARY. ADDITIONALLY
THERE WILL BE WEAK SHORTWAVES TRAVELING UP THE WESTERN SIDE OF THE
5H RIDGE DURING THE FIRST HALF OF THE PERIOD. TIMING THESE SUBTLE
FEATURES IS DIFFICULT AT BEST SO DID NOT MAKE A LOT OF CHANGES TO
POP GRIDS.
SUN INTO MON THE MEDIUM RANGE GUIDANCE STARTS TO DIVERGE. THE GFS
SHOWS A MORE PROGRESSIVE ZONAL PATTERN DEVELOPING WHILE THE
ECMWF/CANADIAN SHOW MORE AMPLIFICATION. THE RESULT OF THIS IS THE
GFS WANTS TO BRING IN ANOTHER SYSTEM BEFORE THE END OF THE PERIOD
WHILE THE ECMWF/CANADIAN SOLUTIONS DO NOT. THE SLOWER ECMWF SOLUTION
IS FAVORED WHICH KEEPS THE END OF THE PERIOD DRY.
TEMPERATURES ABOVE TO WELL ABOVE CLIMO CONTINUE INTO THE WEEKEND
DESPITE CLOUD COVER AND THREAT OF PRECIP. ONCE THE FRONT PUSHES OFF
THE COAST...SUN INTO MON...TEMPERATURES WILL DROP BELOW CLIMO
THROUGH THE END OF THE PERIOD.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AS OF 00Z...MOISTURE WILL BE ON THE INCREASE AS A COLD FRONT SLOWLY
APPROACHES THE REGION. MODERATE UNCERTAINTY WITH RESPECT TO CEILING
HEIGHTS OVERNIGHT. THE NAM IS THE MOST PESSIMISTIC...WITH IFR
PREDOMINATE AFTER MIDNIGHT. THINK THIS MAY BE OVERDONE...GIVEN THAT
IT ALSO SHOWING LOW VISIBILITIES. WILL GO WITH A LOW MVFR
CEILING...MAINLY AT THE INLAND TERMINALS.
DEEP MOISTURE MOVES INTO THE WESTERN CWA BY MIDDAY WEDNESDAY...WITH
A DECENT CHANCE FOR PRECIPITATION. ANY RAIN WILL LIKELY BY
LIGHT...WITH LITTLE REDUCTION IN VISIBILITY. LIKEWISE CEILINGS WILL
REMAIN MVFR TO VFR...WITH A LOT OF 4K CEILINGS NEAR THE SUBSIDENCE
INVERSION. SOUTHERLY GRADIENT WILL INCREASE...WITH GUSTY WINDS
EXPECTED BY LATE MORNING.
EXTENDED OUTLOOK...LOW CONFIDENCE IN MORNING FOG THURSDAY. MORE RAIN
WITH ASSOCIATED RESTRICTIONS POSSIBLE FRIDAY/SATURDAY. VFR EXPECTED
SUNDAY.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 840 PM TUESDAY...WAA UNDER S-SW WINDS WILL RULE TONIGHT.
LATEST NAM INDICATES WINDS AT 925MB INCREASING TO 25-30 KT AFTER
MIDNIGHT THROUGH DAYBREAK WEDNESDAY. WITH SSTS ACROSS THE SHELF
WATERS IN THE 50S...THE HIGHER WINDS ALOFT WILL HAVE A DIFFICULT
TIME MIXING TO THE OCEAN SFC. WATER TEMPS IN THE UPPER 60S RESIDE
JUST OFFSHORE FROM THE ILM WATERS...PER LATEST SSTS FROM
41036...41037 AND 41013. AS A RESULT...WILL INDICATE S-SW WINDS
INCREASING ONLY TO 10-15 KT OVERNIGHT. SEAS 2 TO 3 FT...WILL
INCREASE TO 2 TO 4 FT...EXCEPT UP TO 5 FT ACROSS THE OUTER WATERS
OFF CAPE FEAR. THE INCREASE IN SEAS OVERNIGHT WILL MAINLY COME FROM
THE HIGHER RESULTANT SEAS JUST OFFSHORE...BLEEDING INTO THE COASTAL
WATERS. AN UNDERLYING 2 FOOT EASTERLY GROUND SWELL AT 10-12 SECOND
PERIODS WILL DOMINATE THE SIG. SEAS EARLY ON. WIND DRIVEN SHORT
PERIOD WAVES WILL BECOME A FACTOR TO SIG. SEAS AFTER MIDNIGHT.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 3 PM TUESDAY...WINDS WILL BE FROM THE SW THROUGH THE PERIOD.
SW FLOW ALOFT WILL BE ROBUST WITH JETTING AT TIMES INCREASING WINDS
TO 40+ KT ALOFT. HOWEVER...THESE WINDS WILL NOT EFFICIENTLY MIX DOWN
GIVEN THE COOL WATER TEMPS...THUS WINDS THROUGH THE PERIOD SHOULD
NOT EXCEED 15 TO 20 KT. SEAS WILL NOT EXCEED 3 TO 5 FT.
AS DEWPOINTS IN THE LOWER TO MID 60S ADVECT ACROSS THE WATERS...
PATCHY SEA FOG IS EXPECTED TO DEVELOP ACROSS THE SOUTHERN WATERS WED
AFTERNOON AND THEN SPREAD N THROUGH THU. THE COVERAGE OF FOG MAY
INCREASE WITH TIME AND GROW DENSER AS WARM AND MOIST FLOW PERSISTS
ACROSS THE COOL SHELF WATERS.
LONG TERM /FRIDAY THROUGH SUNDAY/...
AS OF 3 PM TUESDAY...STALLED FRONT IN THE VICINITY WILL KEEP WIND
DIRECTION FORECAST THROUGH THE PERIOD QUITE TRICKY. FRI THE FRONT
WILL BE WEST OF THE WATERS WITH SOUTHWEST FLOW IN PLACE. FRONT
SHIFTS OFFSHORE FRI NIGHT INTO SAT WITH LIGHT NORTHERLY FLOW
DEVELOPING. FRONT REMAINS STALLED JUST OFF THE COAST THROUGH THE
END OF THE PERIOD...WITH SPEEDS 10 TO 15 KT. SEAS WILL RUN 3 TO 5
FT THROUGH THE PERIOD.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...NONE.
&&
$$
NEAR TERM...DCH
SHORT TERM...RJD
LONG TERM...III
AVIATION...43
AREA FORECAST DISCUSSION
NWS GRAND FORKS ND
1021 AM CST MON DEC 19 2011
.DISCUSSION...
THE CHALLENGE TODAY WILL BE CLOUD TRENDS AND TEMPS. A FAIRLY
EXPANSIVE CLOUD BAND WILL HANG TOUGH ACROSS NW MN AND NE ND
THROUGH TODAY...BEFORE SLOWLY DISSIPATING THIS EVENING AND
OVERNIGHT. THIS COUPLED WITH LIMITED MIXING SHOULD MEAN TEMPS
WON/T RISE TOO MUCH TODAY. EXPECT TEMPS TO WARM THE MOST IN THE SW
WHERE MORE SUNSHINE IS EXPECTED. WILL INCREASE SKY COVER...AND
TWEAK TEMPS UP A BIT MAINLY IN MN WHERE TEMPS ARE AT PROJECTED
HIGHS. OTHERWISE...THE REST OF THE FORECAST IS IN GOOD SHAPE
TODAY.
&&
.AVIATION...
MVFR STRATUS DECK EXTENDS WELL NORTH INTO CENTRAL MANITOBA AND WILL
CONTINUE TO SLIDE SOUTH-SOUTHEASTWARD THROUGH THE AFTERNOON. VALLEY
AIRFIELDS MAY BE NEAR THE CLEARING EDGE FOR MUCH OF THE AFTERNOON
WITH BRIEF PERIODS OF SCATTERED CEILINGS POSSIBLE. HOWEVER...A
RETURN TO PROLONGED VFR CONDITIONS NOT EXPECTED UNTIL MID-LATE
AFTERNOON AT THE EARLIEST FOR KGFK/KFAR AND AFTER 00 UTC AT KBJI.
LIGHT NORTHWEST WIND WILL SLOWLY SHIFT TO THE SOUTH OVERNIGHT.
&&
.PREV DISCUSSION... /ISSUED 235 AM CST MON DEC 19 2011/
DISCUSSION...FORECAST CHALLENGE CONCERNS MAINLY TEMPERATURES.
MODELS IN GOOD AGREEMENT. FOR PERSISTENCE WILL FOLLOW GFS FOR
DETAILS.
COLD ADVECTION CONTINUES EARLY THIS MORNING LEVELING OFF TOWARDS
LATE MORNING. COOLING HAS BEEN OFFSET BY MIXING AND CLOUD COVER.
CLOUDS LIKELY TO HOLD MINIMUMS UP THIS MORNING BUT WHEN CLOUDS BREAK
UP WILL DETERMINE HOW MUCH RECOVERY TODAY. RUC HOLDING IN LAYERED RH
THROUGH 18Z WITH GFS DRYING COLUMN DURING THE AFTERNOON AS HIGH
PRESSURE BUILDS IN. WILL BE RAISING MAX TEMPERATURES TODAY BASED ON
ANTICIPATED WARMER START. WITH LACK OF SNOW COVER AND LEVELING OFF
OF COLD ADVECTION ANY CLOUD BREAKS THIS AFTERNOON WILL ALLOW FOR A
MINOR TEMPERATURE RECOVERY.
HIGH PRESSURE WILL SAG SOUTH AND EAST OVERNIGHT INTO TUESDAY. THIS
WILL EVENTUALLY SET UP RETURN FLOW AND MODEST WARM ADVECTION FOR
TUESDAY. SKIES SHOULD CLEAR OFF ALONG WITH DIMINISHING WIND TONIGHT.
AGAIN LACK OF SNOW COVER WILL AFFECT MINIMUM TEMPERATURES AND STAY
WARMER THAN GUIDANCE. TRENDS CONTINUE TUESDAY WILL MAINTAIN MAXIMUM
TEMPERATURES WELL ABOVE GUIDANCE WITH LACK OF ANY SNOW COVER AND
ANTICIPATED SOLAR.
WEAK SURFACE TROUGH WILL CROSS FA TUESDAY NIGHT HOWEVER MOISTURE
LOOKS LIMITED SO WILL DROP LOW END POPS.
MID LEVEL FLOW REMAINS SPLIT WITH UPPER LOW CURRENTLY ACROSS DESERT
SW TRACKING EAST WELL SOUTH OF FA ON WEDNESDAY. ANY NORTHERN STREAM
MID LEVEL SUPPORT LOOKS WEAK HOWEVER WITH BAROCLINIC ZONE DROPPING
THROUGH FA COULD SEE SOME PATCHY -SN OR FLURRIES. WITH SPOTTY NATURE
OF MODEL QPF WILL NOT MAKE ANY MODIFICATIONS TO CURRENT SLIGHT
CHANCE POPS.
LONG TERM (THU-SUN)...
MODELS IN GOOD AGREEMENT WITH THE EXTENDED PATTERN... INDICATING
LITTLE CHANGE TO THE ONGOING OVERALL DRY PATTERN WITH WIDE
TEMPERATURE SWINGS AS SHORT WAVES TRAVERSE THE REGION. A SEASONABLY
COOL AIRMASS IN PLACE ON THURSDAY WILL LEAD TO NEAR NORMAL HIGHS AND
TRANSITION QUICKLY AS 500MB RIDGING BUILDS INTO THE NORTHERN PLAINS
WITH WAA OCCURS DURING THE DAY FRIDAY AND THE FIRST HALF OF
SATURDAY. THE ONLY PRECIP IN THE EXTENDED LOOKS TO BE FROM A COLD
FRONT SATURDAY NIGHT THAT MAY BRING A DUSTING OF SNOW TO THE AREA.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...NONE.
MN...NONE.
&&
$$
DK
AREA FORECAST DISCUSSION
NWS GRAND FORKS ND
235 AM CST MON DEC 19 2011
.DISCUSSION...FORECAST CHALLENGE CONCERNS MAINLY TEMPERATURES.
MODELS IN GOOD AGREEMENT. FOR PERSISTENCE WILL FOLLOW GFS FOR
DETAILS.
COLD ADVECTION CONTINUES EARLY THIS MORNING LEVELING OFF TOWARDS
LATE MORNING. COOLING HAS BEEN OFFSET BY MIXING AND CLOUD COVER.
CLOUDS LIKELY TO HOLD MINIMUMS UP THIS MORNING BUT WHEN CLOUDS BREAK
UP WILL DETERMINE HOW MUCH RECOVERY TODAY. RUC HOLDING IN LAYERED RH
THROUGH 18Z WITH GFS DRYING COLUMN DURING THE AFTERNOON AS HIGH
PRESSURE BUILDS IN. WILL BE RAISING MAX TEMPERATURES TODAY BASED ON
ANTICIPATED WARMER START. WITH LACK OF SNOW COVER AND LEVELING OFF
OF COLD ADVECTION ANY CLOUD BREAKS THIS AFTERNOON WILL ALLOW FOR A
MINOR TEMPERATURE RECOVERY.
HIGH PRESSURE WILL SAG SOUTH AND EAST OVERNIGHT INTO TUESDAY. THIS
WILL EVENTUALLY SET UP RETURN FLOW AND MODEST WARM ADVECTION FOR
TUESDAY. SKIES SHOULD CLEAR OFF ALONG WITH DIMINISHING WIND TONIGHT.
AGAIN LACK OF SNOW COVER WILL AFFECT MINIMUM TEMPERATURES AND STAY
WARMER THAN GUIDANCE. TRENDS CONTINUE TUESDAY WILL MAINTAIN MAXIMUM
TEMPERATURES WELL ABOVE GUIDANCE WITH LACK OF ANY SNOW COVER AND
ANTICIPATED SOLAR.
WEAK SURFACE TROUGH WILL CROSS FA TUESDAY NIGHT HOWEVER MOISTURE
LOOKS LIMITED SO WILL DROP LOW END POPS.
MID LEVEL FLOW REMAINS SPLIT WITH UPPER LOW CURRENTLY ACROSS DESERT
SW TRACKING EAST WELL SOUTH OF FA ON WEDNESDAY. ANY NORTHERN STREAM
MID LEVEL SUPPORT LOOKS WEAK HOWEVER WITH BAROCLINIC ZONE DROPPING
THROUGH FA COULD SEE SOME PATCHY -SN OR FLURRIES. WITH SPOTTY NATURE
OF MODEL QPF WILL NOT MAKE ANY MODIFICATIONS TO CURRENT SLIGHT
CHANCE POPS.
.LONG TERM (THU-SUN)...
MODELS IN GOOD AGREEMENT WITH THE EXTENDED PATTERN... INDICATING
LITTLE CHANGE TO THE ONGOING OVERALL DRY PATTERN WITH WIDE
TEMPERATURE SWINGS AS SHORT WAVES TRAVERSE THE REGION. A SEASONABLY
COOL AIRMASS IN PLACE ON THURSDAY WILL LEAD TO NEAR NORMAL HIGHS AND
TRANSITION QUICKLY AS 500MB RIDGING BUILDS INTO THE NORTHERN PLAINS
WITH WAA OCCURS DURING THE DAY FRIDAY AND THE FIRST HALF OF
SATURDAY. THE ONLY PRECIP IN THE EXTENDED LOOKS TO BE FROM A COLD
FRONT SATURDAY NIGHT THAT MAY BRING A DUSTING OF SNOW TO THE AREA.
&&
.AVIATION...
SOME BINOVC SHOWING UP FROM VALLEY WEST BUT OVERALL EXPECT MVFR/VFR
CIGS TO PERSIST INTO EARLY AFTERNOON. VFR TO MVFR CIGS SPOTTY AND
VERY DIFFICULT TO PINPOINT WITH FORECAST WITH LOWEST CIGS EAST OF
VALLEY.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...NONE.
MN...NONE.
&&
$$
VOELKER/JIMMY K
AREA FORECAST DISCUSSION
NWS NORMAN OK
536 PM CST TUE DEC 20 2011
.AVIATION...PRECIPITATION HAD ENDED THIS AFTERNOON. CEILINGS
REMAIN IN PLACE...MAINLY MVFR. KOKC AND KOUN SHOULD IMPROVE TO
MVFR NEAR THE BEGINNING OF THE PERIOD. SUBSTANTIAL HEIGHT RISES IN
THE WAKE OF THE DEPARTING STORM SYSTEM...SUPPORT THE MODELED
NOTION THAT CLOUD COVER WILL THIN AND BREAK UP FROM WEST TO EAST
THIS EVENING. WE USED THE HRRR CEILING FORECAST...BUT HELD ONTO
CIGS AN HOUR OR TWO LONGER THAN THE MODEL FOR GOOD MEASURE. SOME
LIGHT VISIBILITY RESTRICTION IS POSSIBLE BY MORNING...BUT
WEDNESDAY SHOULD SEE SUN AND A LIGHT DOWNSLOPE WIND FROM THE SOUTHWEST.
&&
.PREV DISCUSSION... /ISSUED 334 PM CST TUE DEC 20 2011/
DISCUSSION...
AS ONE STORM SYSTEM DEPARTS TO THE NORTHEAST...ANOTHER IS LINED UP
TO MOVE INTO THE SOUTHERN PLAINS LATE WEDNESDAY NIGHT INTO
THURSDAY...FOLLOWED BY YET ANOTHER SYSTEM FRIDAY NIGHT AND
POSSIBLY SATURDAY.
THE NEARLY SOLID OVERCAST CLOUDS WILL DISSIPATE FROM WEST TO EAST
LATE TONIGHT AS SUBSIDENCE ERODES THE MOISTURE LAYER. THAT SHOULD
PROVIDE A SEASONALLY MILD AND MAINLY SUNNY DAY TOMORROW. THERE MAY
BE A FEW PATCHES OF LIGHT FOG OVERNIGHT...MOST LIKELY IN AREAS
THAT RECEIVED SNOW OR SLEET TODAY...AND ESPECIALLY WHERE CLEARING
OCCURS CLOSER TO SUNRISE. AT THIS POINT...LOCATIONS AND
SIGNIFICANCE OF ANY FOG ARE TOO UNCERTAIN TO WARRANT INCLUSION IN
THE FORECAST.
THE NEXT STORM SYSTEM WILL ARRIVE FROM THE NORTHWEST AS A SHORT
WAVE PASSES THROUGH THE LARGE UPPER TROUGH OVER THE ROCKIES. A
REINFORCEMENT OF COLD AIR WILL ARRIVE ON THURSDAY...AND MOISTURE
WILL BE LOFTED OVER THE SURFACE COLD AIR WITH THE USUAL RESULT. AT
THIS POINT...VERTICAL TEMPERATURE PROFILES SUGGEST MAINLY RAIN AND
SNOW...BUT OTHER FORMS OF PRECIPITATION ARE ALMOST ALWAYS A
POSSIBILITY IN THIS PART OF THE COUNTRY. ACCUMULATIONS SHOULD BE
RATHER LIGHT...BUT SOME ACCUMULATIONS ARE LIKELY TO OCCUR OVER
PARTS OF CENTRAL AND NORTHERN OKLAHOMA.
THE SAME UPPER-LEVEL WAVE THAT WILL BRING THE COOLER WEATHER AND
PRECIPITATION ON THURSDAY WILL THEN SWING EAST FOR FRIDAY NIGHT
AND SATURDAY...BRINGING A CHANCE FOR RAIN AND SNOW TO SOUTHERN
OKLAHOMA AND PERHAPS WESTERN NORTH TEXAS. AGAIN...AMOUNTS ARE
CURRENTLY EXPECTED TO BE LIGHT.
&&
.PRELIMINARY POINT TEMPS/POPS...
OKLAHOMA CITY OK 25 50 31 46 / 0 10 10 10
HOBART OK 24 50 30 43 / 0 0 0 10
WICHITA FALLS TX 27 55 34 51 / 0 10 10 10
GAGE OK 20 40 20 34 / 0 0 0 20
PONCA CITY OK 23 47 25 44 / 10 10 10 20
DURANT OK 30 52 36 54 / 0 10 10 10
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...NONE.
TX...NONE.
&&
$$
11/22/22
AREA FORECAST DISCUSSION
NWS HOUSTON/GALVESTON TX
350 PM CST MON DEC 19 2011
.DISCUSSION...
A STRONG UPPER LEVEL LOW PRESSURE SYSTEM CONTINUES PUSHING
NORTHEASTWARD INTO THE TEXAS PANHANDLE THIS AFTERNOON. AHEAD OF
THIS SYSTEM SHOWERS AND THUNDERSTORMS CONTINUE TO INCREASE IN
COVERAGE ACROSS CENTRAL AND NORTH TEXAS...WITH THIS ACTIVITY
EXTENDING SOUTHWARD INTO OUR NORTHWESTERN COUNTIES. THIS ACTIVITY
SHOULD CONTINUE TO INCREASE IN COVERAGE ACROSS OUR WESTERN
COUNTIES THIS AFTERNOON BEFORE A BROKEN LINE OF THUNDERSTORMS
PUSHES EASTWARD THROUGH THE REGION THIS EVENING. LATEST RUNS OF
THE HRRR AND LOCAL WRF MODELS CONTINUE TO SUGGEST THE STRONGEST
ACTIVITY WILL DEVELOP ACROSS OUR NORTHERN COUNTIES LATER THIS
EVENING AND PUSH EASTWARD OUT OF THE REGION BY AROUND MIDNIGHT.
SCATTERED SHOWERS AND THUNDERSTORMS MAY LINGER ACROSS OUR EASTERN
AND COASTAL COUNTIES THROUGH DAYBREAK ON TUESDAY BEFORE THE
PACIFIC COLD FRONT PUSHES THROUGH THE REGION. OUR NEXT CHANCE FOR
RAIN WILL COME WEDNESDAY NIGHT INTO THURSDAY MORNING AS ANOTHER
UPPER LEVEL TROUGH MOVES THROUGH THE PANHANDLE. STRONG ISENTROPIC
LIFT WILL EXIST ACROSS THE REGION ALONG WITH UPPER LEVEL SUPPORT
IN THE FORM OF A RIGHT ENTRANCE REGION OF THE UPPER JET.
PRECIPITATION SHOULD COME TO AN END FAIRLY EARLY THURSDAY
AFTERNOON AS THE SYSTEM MOVES RAPIDLY OUT OF THE REGION.
MODELS CONTINUE TO HAVE SOME DIFFICULTY WITH THE TIMING OF THE
NEXT WEATHER SYSTEM WHICH WILL AFFECT THE REGION OVER THE HOLIDAY
WEEKEND. LATEST MODEL RUNS HAVE TRENDED DRIER FOR THE WEEKEND BUT
AM HESITANT TO REMOVE POPS WITH THE UPPER TROUGH AXIS REMAINING TO
OUR WEST. WILL KEEP SLIGHT CHANCE POPS IN PLACE FOR CHRISTMAS DAY
FOR NOW. 38
&&
.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL) 71 53 61 38 60 / 50 80 10 10 10
HOUSTON (IAH) 72 62 68 43 62 / 20 80 20 10 10
GALVESTON (GLS) 71 63 70 50 62 / 20 60 30 10 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL 9 PM CST THIS EVENING
FOR THE FOLLOWING ZONES: MATAGORDA BAY...WATERS FROM
FREEPORT TO THE MATAGORDA SHIP CHANNEL OUT 20 NM.
SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL MIDNIGHT CST TONIGHT
FOR THE FOLLOWING ZONES: GALVESTON BAY...WATERS FROM HIGH
ISLAND TO FREEPORT OUT 20 NM.
SMALL CRAFT ADVISORY UNTIL 6 AM CST TUESDAY FOR THE FOLLOWING
ZONES: WATERS FROM HIGH ISLAND TO FREEPORT 20 TO 60 NM.
SMALL CRAFT ADVISORY UNTIL 9 PM CST THIS EVENING FOR THE
FOLLOWING ZONES: WATERS FROM FREEPORT TO THE MATAGORDA SHIP
CHANNEL 20 NM TO 60 NM.
&&
$$
DISCUSSION...38
AVIATION/MARINE...45
AREA FORECAST DISCUSSION...UPDATED
NWS FORT WORTH TX
1152 AM CST MON DEC 19 2011
.AVIATION...
18Z TAF CONCERNS...
TIMING OF MAIN BAND OF TSRA AND CIG TRENDS...AS WELL AS WIND
SHIFTS REGARDING SURFACE TROUGH...THEN COLD FRONT TUES MORNING.
PER LATEST MODEL SOUNDINGS...MID AFTERNOON THROUGH SUNSET FOR THE
MAIN BAND OF STORMS TO MOVE THROUGH. WILL SKEW EASTERN METRO TAFS
AN HOUR LATER FROM WESTERN METRO TAFS ON TIMING TSRA/CIGS/AND
ARRIVAL OF SURFACE BOUNDARIES THROUGH TONIGHT. WACO TIMING WILL BE
SIMILAR TO WESTERN METRO AIRPORTS WITH PREVAILING MVFR AND SOONER
ARRIVAL OF SHRA/TSRA.
SHOULD SEE SURFACE TROUGH ARRIVE MID-LATE EVENING WITH WINDS
VEERING AND SPEEDS LOWERING WITH VFR CONDITIONS. COLD FRONT
ARRIVES IN MID-LATE MORNING PERIOD TUESDAY WITH WINDS VEERING WNW
15G25 KTS. WRAP AROUND MVFR CIGS FOR D/FW AIRPORTS TUES
MORNING...SLOWLY RISING TO LOW VFR WITH DEEPENING COLD AIR
ADVECTION BY MIDDAY TUES/AFTER.
05/
&&
.UPDATE...
LATEST WATER VAPOR IMAGERY SHOWS THE LARGE UPPER LOW CONTINUING TO
SLOWLY MOVE EAST THIS MORNING AND MAY NOW BE STARTING TO SHIFT TO
THE NORTH. THIS CONTINUED EASTWARD MOVEMENT OVERNIGHT WASNT
FORECASTED BY THE MODELS AND THE OVERALL TRACK OF THE UPPER LOW
AND SUBSEQUENT SURFACE LOW WILL BE A BIT FURTHER SOUTH THAN
ANTICIPATED. A LEAD VORTICITY LOBE HAS DETACHED FROM THIS TROUGH
AND A BAND OF THUNDERSTORMS HAVE DEVELOPED WITHIN THIS SMALL AREA
OF ENHANCED LIFT THIS MORNING JUST WEST OF THE FORECAST AREA.
EXPECT THIS AREA OF SHOWERS AND THUNDERSTORMS TO CONTINUE TO MOVE
TO THE NE AND IT COULD AFFECT OUR NORTHWESTERN ZONES LATER THIS
MORNING.
16Z SURFACE ANALYSIS CONTINUES TO SHOW MOISTURE STREAMING
NORTHWARD. 60 DEWPOINTS ARE NOW JUST SOUTHWEST OF THE CWA AND
SHOULD SEE THESE VALUES IN OUR CWA SHORTLY. A WARM FRONT IS
ANALYZED ACROSS THE SOUTHWESTERN ZONES AND THIS BOUNDARY IS
EXPECTED TO MOVE NORTHEAST WITH THE SURFACE LOW.
THE SET UP FOR SEVERE WEATHER THIS AFTERNOON AND EVENING CONTINUES
TO COME TOGETHER...BUT THERE ARE STILL SEVERAL FACTORS THAT HAVE
TO PLAY OUT IN THE NEXT 4-6 HOURS TO DETERMINE THE OVERALL CHANCES
FOR SEVERE THUNDERSTORMS. THE LARGE AREA OF PRECIP TO OUR WEST
CONTINUES TO SLOWLY MOVE TO THE EAST AND WOULDNT BE SURPRISED TO
SEE SCATTERED SHOWERS AND THUNDERSTORMS WEST OF INTERSTATE 35 IN
THE LATE MORNING AND EARLY AFTERNOON HOURS AS THE LEAD IMPULSE
MOVES NEAR THE AREA. EXPECT THAT WE WOULD HAVE SOME TIME BETWEEN
THIS LEAD PRECIP AND WHEN THE LINE OF THUNDERSTORMS MOVES THROUGH
THE AREA IN THE LATE AFTERNOON AND EVENING HOURS. WITH A 50-60
KNOT LOW LEVEL JET IN PLACE...THE AIRMASS SHOULD BE ABLE TO
QUICKLY RECOVER FROM ANY LINGERING EFFECTS OF PRECIPITATION.
THE SECOND FACTOR WILL BE THE AVAILABLE INSTABILITY IN PLACE THIS
AFTERNOON. THE 12Z NAM SEEMS TO HAVE THE BEST HANDLE REGARDING
SURFACE T/TD AND INSTABILITY VALUES. EXPECT THE 60 DEWPOINT
ISODROSOTHERM TO BE AS FAR NORTH AS HILL COUNTY BY 21Z AND INTO
THE METROPLEX BY 00Z THIS EVENING. WE SHOULD SEE SOME SURFACE CAPE
WITH THE 60 DEWPOINTS...BUT HIGHER VALUES NEAR 1000 J/KG WILL BE
CONFINED TO AREAS WITH 63+ DEWPOINTS...LOCATED TO THE SOUTH OF
WACO. THESE LOCATIONS WILL SEE THE BEST CHANCES OF SEVERE
WEATHER.
THE THIRD FACTOR WILL BE THE STORM MODE. LATEST HIGH RESOLUTION
MODEL OUTPUT FORMS A SOLID LINE OF CONVECTION IN OUR WESTERN ROW OF
COUNTIES NEAR 19Z OR 1 PM AS STRONG FRONTOGENETICAL FORCING
DEVELOPS ALONG THE EASTWARD MOVING FRONTAL BOUNDARY. THERE ARE
SOME HINTS IN THE MODEL OUTPUT THAT AS THE LINE MOVES EAST THERE
MAY BE SOME BREAKS IN THE LINE AND SEPARATE STORM SEGMENTS WOULD
BE THE DOMINANT MODE. IF THIS WERE TO OCCUR...THE POTENTIAL
FOR TORNADOES WOULD INCREASE AS THESE SEGMENTS WOULD LIKELY BE
SUPERCELLS GIVEN THE STRONG SHEAR IN PLACE. LOCATIONS SOUTH AND
EAST OF A KILLEEN TO DFW TO PALESTINE LINE HAVE THE BEST CHANCES
FOR A TORNADO TODAY PER LATEST SPC DAY 1 OUTLOOK. THESE LOCATIONS
WILL HAVE THE BEST LOW-LEVEL INSTABILITY THIS AFTERNOON...BUT
AGAIN...THE FURTHER SOUTH YOU ARE...THE BETTER CHANCE FOR A
TORNADO. TEMPERATURE/DEWPOINT FIELDS WILL NEED TO BE WATCHED
CLOSELY TODAY AS A FEW DEGREES OFF OF FORECASTED VALUES EITHER WAY
COULD HAVE A BIG IMPACT ON THE SEVERE/TORNADO POTENTIAL.
85/NH
&&
.PREV DISCUSSION... /ISSUED 412 AM CST MON DEC 19 2011/
POWERFUL UPPER LEVEL LOW NEAR EL PASO WILL BEGIN TO CURVE NORTH
AND TRACK ACROSS THE TX PANHANDLE TONIGHT. STORM SYSTEM WILL BE
RESPONSIBLE FOR BLIZZARD CONDITIONS OVER THE SOUTHERN HIGH PLAINS
AND A ROUND OF STORMS WITH A POTENTIAL FOR SEVERE WEATHER HERE.
THIS UPPER LOW IS VERY STRONG AND HAS SIMILARITIES TO THE DEC 29
2006 SYSTEM THAT PRODUCED 22 TORNADOES IN OUR CWA. ALTHOUGH WE DO
NOT EXPECT AN EVENT OF THAT MAGNITUDE THIS TIME DUE TO A FARTHER
NORTH POSITION OF THE WARM FRONT AND LESS UNSTABLE AIR OVER OUR
REGION...IT DOES HEIGHTEN OUR AWARENESS FOR SEVERE WEATHER.
SUBSTANTIAL HEIGHT FALLS ARE ALREADY RESULTING IN 3HR PRESSURE
FALLS OF 3-5 MB ACROSS MUCH OF WEST TX. SOUTHERLY WINDS THROUGH
THE TROPOSPHERE ARE INCREASING...AND WILL CONTINUE TO DO SO DURING
THE DAY. WIND SHEAR WILL BECOME VERY STRONG WITH 0-6KM SHEAR NEAR
60KT AND 0-3KM HELICITY AT OR ABOVE 500 M2/S2. SOUTHERLY 850 MB
WINDS ARE EXPECTED TO REACH 60KT BY NOON...AIDING IN THE TRANSPORT
OF WARM/MOIST AIR INTO THE CWA. RAPID AIR MASS MODIFICATION IS
EXPECTED DURING THE NEXT 12 HOURS...WITH DEWPOINTS LIKELY RISING
INTO THE LOW 60S...WITH SOME MID 60S ACROSS THE SOUTH CENTRAL CWA.
STRONG MOISTURE ADVECTION SHOULD KEEP SKIES CLOUDY...AND HIGH
TEMPS SHOULD BE HELD IN THE MID-UPPER 60S...HELPING TO LIMIT
INSTABILITY. THE PRIMARY INHIBITING FACTOR FOR SEVERE WEATHER AND
THE MOST UNCERTAIN PART OF THIS FORECAST IS THE INSTABILITY. GIVEN
THE NATURE OF THIS DYNAMIC SYSTEM AND ANALOGS TO PAST COOL SEASON
SEVERE WEATHER PRODUCING SYSTEMS...WILL CONTINUE TO FAVOR THE NAM
WHICH IS MOST AGGRESSIVE WITH INSTABILITY. EXPECT SB CAPE TO REACH
1000 J/KG OVER THE SOUTH CENTRAL ZONES...WITH VALUES TAPERING OFF
TO 500 J/KG NEAR THE I-20 CORRIDOR. IT IS IMPORTANT TO NOTE THAT
ABOUT 250 J/KG OF THE TOTAL CAPE RESIDES BELOW 3KM...WHICH IS VERY
HIGH FOR ANYTIME OF THE YEAR...AND INCREASES THE POTENTIAL FOR
VORTEX STRETCHING NEAR THE GROUND AND TORNADOGENESIS.
MOST OF THE STORMS WILL FORM ALONG A NORTH-SOUTH ORIENTED COLD
FRONT THAT WILL REACH THE WESTERN CWA IN THE EARLY AFTERNOON.
AHEAD OF THE FRONT...THERE WILL BE SOME WARM ADVECTION SHOWERS
STREAMING UP FROM THE SOUTH. CONVECTION AHEAD OF THE FRONT MAY BE
DISCRETE...BUT INSTABILITY MAY NOT YET BE HIGH ENOUGH FOR ANYTHING
MORE THAN SHOWERS UNTIL FRONTOGENETIC FORCING ARRIVES WITH THE
FRONT. STORM MOTION IS EXPECTED TO BE AT 45KT AND THIS SUGGESTS
DAMAGING WINDS WILL BE THE PRIMARY SEVERE WEATHER THREAT DUE TO
DOWNWARD MOMENTUM TRANSPORT. BECAUSE STORMS SHOULD FORM INTO A
LINE ALONG THE FRONT...TORNADO POTENTIAL SHOULD BE LIMITED...BUT
CONDITIONS ARE STILL FAVORABLE FOR ISOLATED BRIEF SPIN-UPS WITHIN
THE LINE. SEVERE WEATHER THREAT EXISTS JUST ABOUT EVERYWHERE...BUT
WILL BE HIGHEST ALONG THE I-35 CORRIDOR SOUTH OF I-20 WHERE BAND
OF INSTABILITY WILL BE HIGHEST. THERE IS SOME UNCERTAINTY WITH THE
TIMING...AS THE HRRR IS THE QUICKEST...AND THE NAM ABOUT 5 HOURS
SLOWER. THE ECMWF OFFERS A GOOD COMPROMISE AND EXPECT THE SQUALL
LINE TO IMPACT THE WESTERN ZONES 2-6PM...THE I-35 CORRIDOR
4-8PM...AND MOVE OUT OF THE EASTERN ZONES BY 12AM.
WINDY AND COLDER CONDITIONS ARE EXPECTED TUESDAY AS COLD AIR POURS
IN BEHIND THE CYCLONE. SOME WRAP AROUND CLOUDS WILL AFFECT THE
NORTHERN ZONES. WINDS DIMINISH TUESDAY NIGHT...WITH SUBFREEZING
TEMPS OVER MOST OF THE CWA. NEXT UPPER LEVEL SHORTWAVE WILL
APPROACH WEDNESDAY...WITH INCREASING MID-HIGH CLOUDS. MOISTURE
APPEARS SUFFICIENT FOR A LOW CHANCE OF RAIN OVER THE SOUTHEAST
HALF OF THE AREA WED NIGHT AND THURSDAY MORNING. ONCE THIS IMPULSE
MOVES THROUGH...ANOTHER COLD FRONT WILL ARRIVE THURSDAY EVENING.
EXTENDED FORECAST REMAINS OF VERY LOW CONFIDENCE DUE TO WIDESPREAD
DISAGREEMENT IN HOW SEVERAL VORT LOBES INTERACT WITH EACH OTHER.
REGARDLESS OF THE DETAILS...THE SYNOPTIC PATTERN SUGGESTS WITH
HIGH CONFIDENCE THAT IT WILL BE COLD FOR THE HOLIDAY WEEKEND. WILL
NEED BETTER INTER-MODEL AND RUN-TO-RUN CONSISTENCY BEFORE
ENTERTAINING THE POTENTIAL FOR PRECIPITATION.
TR.92
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 63 44 50 31 53 / 100 90 5 0 5
WACO, TX 67 43 53 29 54 / 90 90 5 0 10
PARIS, TX 62 49 56 30 51 / 50 100 10 0 5
DENTON, TX 62 42 47 27 52 / 100 80 10 0 5
MCKINNEY, TX 63 44 49 28 52 / 90 100 10 0 5
DALLAS, TX 64 45 51 33 53 / 90 100 5 0 5
TERRELL, TX 65 47 53 32 52 / 80 100 5 0 5
CORSICANA, TX 68 47 55 33 54 / 70 100 10 0 10
TEMPLE, TX 68 43 55 31 55 / 90 90 5 0 10
MINERAL WELLS, TX 61 39 46 26 53 / 100 40 10 0 5
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
05/85
AREA FORECAST DISCUSSION...UPDATED
NWS CORPUS CHRISTI TX
1108 AM CST MON DEC 19 2011
.DISCUSSION...PACIFIC FRONT CURRENTLY ENTERING EXTREME NW CWA.
CLEARING SKIES ACROSS REST OF S TX ARE ALLOWING FOR STRONG MIXING
OF UNSEASONABLY STRONG 45 TO 55 KT LLJ TO MIX TO SFC. GUSTS OVER
40 MPH HAVE ALREADY OCCURRED AT ALICE AND BEEVILLE AND HAVE
EXPANDED WIND ADVISORY FOR REST OF EASTERN HALF OF CWA. HAVE ALSO
INCREASED HIGHS ACROSS THE BOARD DUE TO ADDITIONAL SUNSHINE AND
STRONG SRLY WINDS. HAVE REMOVED MENTION OF WX ACROSS MOST ZONES
UNTIL LATE THIS AFTERNOON. LATEST HRRR AND 4KM WRF INDICATE NARROW
BAND OF PRECIP MAY DEVELOP ACROSS EASTERN ZONES BY MID TO LATE
AFTERNOON AND THEN INTENSIFY OVER MARINE AREAS. STRONGEST CONVECTION
MAY REMAIN TO THE NORTHEAST OF CWA.
&&
.PRELIMINARY POINT TEMPS/POPS...
CORPUS CHRISTI 79 60 68 44 62 / 30 40 20 10 10
VICTORIA 76 56 64 39 61 / 50 50 10 10 10
LAREDO 76 50 66 44 65 / 10 10 0 0 10
ALICE 83 57 67 43 64 / 20 30 10 10 10
ROCKPORT 74 61 68 47 61 / 40 50 20 10 10
COTULLA 75 45 65 39 64 / 20 10 0 0 10
KINGSVILLE 82 58 69 44 64 / 20 30 20 10 10
NAVY CORPUS 76 62 67 49 62 / 30 40 20 10 10
&&
.CRP WATCHES/WARNINGS/ADVISORIES...
TX...WIND ADVISORY UNTIL 4 PM CST THIS AFTERNOON FOR THE FOLLOWING
ZONES: ARANSAS...BEE...CALHOUN...GOLIAD...JIM WELLS...
KLEBERG...LIVE OAK...NUECES...REFUGIO...SAN PATRICIO...
VICTORIA.
GM...SMALL CRAFT ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR THE
FOLLOWING ZONES: COASTAL WATERS FROM BAFFIN BAY TO PORT
ARANSAS OUT 20 NM...COASTAL WATERS FROM PORT ARANSAS TO
MATAGORDA SHIP CHANNEL OUT 20 NM...WATERS FROM BAFFIN BAY
TO PORT ARANSAS FROM 20 TO 60 NM...WATERS FROM PORT ARANSAS
TO MATAGORDA SHIP CHANNEL FROM 20 TO 60 NM.
SMALL CRAFT ADVISORY FOR WINDS UNTIL 6 PM CST THIS EVENING FOR
THE FOLLOWING ZONES: BAYS AND WATERWAYS FROM BAFFIN BAY TO
PORT ARANSAS...BAYS AND WATERWAYS FROM PORT ARANSAS TO PORT
O`CONNOR.
&&
$$
UPDATE...HART/79
AREA FORECAST DISCUSSION...UPDATED
NWS FORT WORTH TX
931 AM CST MON DEC 19 2011
.AVIATION...
15Z AMEND UPDATE AND CONCERNS...
TIMING OF ANY MULTI-CELLULAR SHRA/TSRA THROUGH MIDDAY WITH FIRST
SHORTWAVE AND LOWERING OF CIGS.
FIRST SHORTWAVE NOW LIFTING NNE WITH LINEAR BAND OF SHRA/EMBEDDED
TSRA LIFTING NNE AROUND 50 KTS BETWEEN ABILENE AND BRECKENRIDGE...WITH
LINE ITSELF MOVING EAST NEAR 25 KTS. THINKING IS SOME STRONG
ELEVATED/MIXED WARMER AIR NEAR I-35 CORRIDOR SHOULD DIMINISH THE
INTENSITY OF THIS BAND BEFORE IT GETS TO D/FW TERMINALS...BUT
ENOUGH TO SPEED UP A VCTS/CB WORDING AT TERMINALS STARTING AT 18Z.
WILL LEAVE TEMPO GROUP FOR MORE STRONG-SEVERE BAND OF TSRA AS IS
FOR NOW WITH TIMING BEING DURING THE MID-LATE AFTERNOON HOURS.
HOWEVER...A FEW MODELS SHOW SLOWER TIMING.
ONLY OTHER ADJUSTMENT IS WITH NEAR 60 KTS SOUTHERLY LLJ MIXING IN
THE NEXT FEW HOURS...HAVE INSERTED SSE SUSTAINED WINDS NEAR 15 KTS
WITH GUSTS AT OR EXCEEDING 25 KTS.
WE WILL CONTINUE TO FINE TUNE TIMING OF CONVECTION AND LOWERING OF
CIGS INTO MVFR/IFR CATEGORY AS WE APPROACH THE ISSUANCE OF THE 18Z
TAFS.
05/
&&
.PREV DISCUSSION... /ISSUED 412 AM CST MON DEC 19 2011/
POWERFUL UPPER LEVEL LOW NEAR EL PASO WILL BEGIN TO CURVE NORTH
AND TRACK ACROSS THE TX PANHANDLE TONIGHT. STORM SYSTEM WILL BE
RESPONSIBLE FOR BLIZZARD CONDITIONS OVER THE SOUTHERN HIGH PLAINS
AND A ROUND OF STORMS WITH A POTENTIAL FOR SEVERE WEATHER HERE.
THIS UPPER LOW IS VERY STRONG AND HAS SIMILARITIES TO THE DEC 29
2006 SYSTEM THAT PRODUCED 22 TORNADOES IN OUR CWA. ALTHOUGH WE DO
NOT EXPECT AN EVENT OF THAT MAGNITUDE THIS TIME DUE TO A FARTHER
NORTH POSITION OF THE WARM FRONT AND LESS UNSTABLE AIR OVER OUR
REGION...IT DOES HEIGHTEN OUR AWARENESS FOR SEVERE WEATHER.
SUBSTANTIAL HEIGHT FALLS ARE ALREADY RESULTING IN 3HR PRESSURE
FALLS OF 3-5 MB ACROSS MUCH OF WEST TX. SOUTHERLY WINDS THROUGH
THE TROPOSPHERE ARE INCREASING...AND WILL CONTINUE TO DO SO DURING
THE DAY. WIND SHEAR WILL BECOME VERY STRONG WITH 0-6KM SHEAR NEAR
60KT AND 0-3KM HELICITY AT OR ABOVE 500 M2/S2. SOUTHERLY 850 MB
WINDS ARE EXPECTED TO REACH 60KT BY NOON...AIDING IN THE TRANSPORT
OF WARM/MOIST AIR INTO THE CWA. RAPID AIR MASS MODIFICATION IS
EXPECTED DURING THE NEXT 12 HOURS...WITH DEWPOINTS LIKELY RISING
INTO THE LOW 60S...WITH SOME MID 60S ACROSS THE SOUTH CENTRAL CWA.
STRONG MOISTURE ADVECTION SHOULD KEEP SKIES CLOUDY...AND HIGH
TEMPS SHOULD BE HELD IN THE MID-UPPER 60S...HELPING TO LIMIT
INSTABILITY. THE PRIMARY INHIBITING FACTOR FOR SEVERE WEATHER AND
THE MOST UNCERTAIN PART OF THIS FORECAST IS THE INSTABILITY. GIVEN
THE NATURE OF THIS DYNAMIC SYSTEM AND ANALOGS TO PAST COOL SEASON
SEVERE WEATHER PRODUCING SYSTEMS...WILL CONTINUE TO FAVOR THE NAM
WHICH IS MOST AGGRESSIVE WITH INSTABILITY. EXPECT SB CAPE TO REACH
1000 J/KG OVER THE SOUTH CENTRAL ZONES...WITH VALUES TAPERING OFF
TO 500 J/KG NEAR THE I-20 CORRIDOR. IT IS IMPORTANT TO NOTE THAT
ABOUT 250 J/KG OF THE TOTAL CAPE RESIDES BELOW 3KM...WHICH IS VERY
HIGH FOR ANYTIME OF THE YEAR...AND INCREASES THE POTENTIAL FOR
VORTEX STRETCHING NEAR THE GROUND AND TORNADOGENESIS.
MOST OF THE STORMS WILL FORM ALONG A NORTH-SOUTH ORIENTED COLD
FRONT THAT WILL REACH THE WESTERN CWA IN THE EARLY AFTERNOON.
AHEAD OF THE FRONT...THERE WILL BE SOME WARM ADVECTION SHOWERS
STREAMING UP FROM THE SOUTH. CONVECTION AHEAD OF THE FRONT MAY BE
DISCRETE...BUT INSTABILITY MAY NOT YET BE HIGH ENOUGH FOR ANYTHING
MORE THAN SHOWERS UNTIL FRONTOGENETIC FORCING ARRIVES WITH THE
FRONT. STORM MOTION IS EXPECTED TO BE AT 45KT AND THIS SUGGESTS
DAMAGING WINDS WILL BE THE PRIMARY SEVERE WEATHER THREAT DUE TO
DOWNWARD MOMENTUM TRANSPORT. BECAUSE STORMS SHOULD FORM INTO A
LINE ALONG THE FRONT...TORNADO POTENTIAL SHOULD BE LIMITED...BUT
CONDITIONS ARE STILL FAVORABLE FOR ISOLATED BRIEF SPIN-UPS WITHIN
THE LINE. SEVERE WEATHER THREAT EXISTS JUST ABOUT EVERYWHERE...BUT
WILL BE HIGHEST ALONG THE I-35 CORRIDOR SOUTH OF I-20 WHERE BAND
OF INSTABILITY WILL BE HIGHEST. THERE IS SOME UNCERTAINTY WITH THE
TIMING...AS THE HRRR IS THE QUICKEST...AND THE NAM ABOUT 5 HOURS
SLOWER. THE ECMWF OFFERS A GOOD COMPROMISE AND EXPECT THE SQUALL
LINE TO IMPACT THE WESTERN ZONES 2-6PM...THE I-35 CORRIDOR
4-8PM...AND MOVE OUT OF THE EASTERN ZONES BY 12AM.
WINDY AND COLDER CONDITIONS ARE EXPECTED TUESDAY AS COLD AIR POURS
IN BEHIND THE CYCLONE. SOME WRAP AROUND CLOUDS WILL AFFECT THE
NORTHERN ZONES. WINDS DIMINISH TUESDAY NIGHT...WITH SUBFREEZING
TEMPS OVER MOST OF THE CWA. NEXT UPPER LEVEL SHORTWAVE WILL
APPROACH WEDNESDAY...WITH INCREASING MID-HIGH CLOUDS. MOISTURE
APPEARS SUFFICIENT FOR A LOW CHANCE OF RAIN OVER THE SOUTHEAST
HALF OF THE AREA WED NIGHT AND THURSDAY MORNING. ONCE THIS IMPULSE
MOVES THROUGH...ANOTHER COLD FRONT WILL ARRIVE THURSDAY EVENING.
EXTENDED FORECAST REMAINS OF VERY LOW CONFIDENCE DUE TO WIDESPREAD
DISAGREEMENT IN HOW SEVERAL VORT LOBES INTERACT WITH EACH OTHER.
REGARDLESS OF THE DETAILS...THE SYNOPTIC PATTERN SUGGESTS WITH
HIGH CONFIDENCE THAT IT WILL BE COLD FOR THE HOLIDAY WEEKEND. WILL
NEED BETTER INTER-MODEL AND RUN-TO-RUN CONSISTENCY BEFORE
ENTERTAINING THE POTENTIAL FOR PRECIPITATION.
TR.92
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 63 44 50 31 53 / 100 90 5 0 5
WACO, TX 67 43 53 29 54 / 90 90 5 0 10
PARIS, TX 62 49 56 30 51 / 50 100 10 0 5
DENTON, TX 62 42 47 27 52 / 100 80 10 0 5
MCKINNEY, TX 63 44 49 28 52 / 90 100 10 0 5
DALLAS, TX 64 45 51 33 53 / 90 100 5 0 5
TERRELL, TX 65 47 53 32 52 / 80 100 5 0 5
CORSICANA, TX 68 47 55 33 54 / 70 100 10 0 10
TEMPLE, TX 68 43 55 31 55 / 90 90 5 0 10
MINERAL WELLS, TX 61 39 46 26 53 / 100 40 10 0 5
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
05/92
AREA FORECAST DISCUSSION...UPDATED
NWS FORT WORTH TX
528 AM CST MON DEC 19 2011
.AVIATION...
CONCERNS...STRONG TO SEVERE THUNDERSTORMS LATE THIS AFTERNOON.
A STRONG WINTER STORM WILL MOVE OUT OF THE SOUTHERN ROCKIES THIS
MORNING AND MOVE ACROSS KANSAS/OKLAHOMA ON TUESDAY. AS THIS
CYCLONE WINDS UP...MVFR CIGS...SCATTERED SHOWERS AND A FEW
THUNDERSTORMS IN THE WARM SECTOR WILL AFFECT THE TAF SITES
THROUGH MIDDAY. COME LATE THIS AFTERNOON...STRONG TO SEVERE LINEAR
CONVECTION OCCURRING ALONG A COLD FRONT TO THE WEST WILL PUSH
THROUGH THE I-35 CORRIDOR AND ACROSS THE TAF SITES 22-01Z. THE
POTENTIAL EXISTS FOR BRIEF IFR CIGS/VIS DURING THE STRONGER
THUNDERSTORMS. SKIES SHOULD GO VFR AFTER 02Z AS A DRY SLOT MOVES
OVER THE REGION AHEAD OF WRAP-AROUND CLOUDINESS THAT INVADES
NORTH TEXAS ON TUESDAY.
WILL PUSH CIGS DOWN TO MVFR 2500FT EARLY THIS MORNING AND TO
1500FT BY LATE MORNING AS SCATTERED SHOWERS MOVE NORTH AT 50+KTS.
CIGS BECOME VFR QUICKLY THIS EVENING BEHIND THE COLD FRONT.
AIRPORT WEATHER WARNING FOR KDFW IS LIKELY DURING THE AFTERNOON
HOURS FOR LIGHTNING...AND LATE AFTERNOON THROUGH EARLY EVENING
FOR LIGHTNING AND/OR WIND GUSTS 35+KTS. 75
&&
.PREV DISCUSSION... /ISSUED 412 AM CST MON DEC 19 2011/
POWERFUL UPPER LEVEL LOW NEAR EL PASO WILL BEGIN TO CURVE NORTH
AND TRACK ACROSS THE TX PANHANDLE TONIGHT. STORM SYSTEM WILL BE
RESPONSIBLE FOR BLIZZARD CONDITIONS OVER THE SOUTHERN HIGH PLAINS
AND A ROUND OF STORMS WITH A POTENTIAL FOR SEVERE WEATHER HERE.
THIS UPPER LOW IS VERY STRONG AND HAS SIMILARITIES TO THE DEC 29
2006 SYSTEM THAT PRODUCED 22 TORNADOES IN OUR CWA. ALTHOUGH WE DO
NOT EXPECT AN EVENT OF THAT MAGNITUDE THIS TIME DUE TO A FARTHER
NORTH POSITION OF THE WARM FRONT AND LESS UNSTABLE AIR OVER OUR
REGION...IT DOES HEIGHTEN OUR AWARENESS FOR SEVERE WEATHER.
SUBSTANTIAL HEIGHT FALLS ARE ALREADY RESULTING IN 3HR PRESSURE
FALLS OF 3-5 MB ACROSS MUCH OF WEST TX. SOUTHERLY WINDS THROUGH
THE TROPOSPHERE ARE INCREASING...AND WILL CONTINUE TO DO SO DURING
THE DAY. WIND SHEAR WILL BECOME VERY STRONG WITH 0-6KM SHEAR NEAR
60KT AND 0-3KM HELICITY AT OR ABOVE 500 M2/S2. SOUTHERLY 850 MB
WINDS ARE EXPECTED TO REACH 60KT BY NOON...AIDING IN THE TRANSPORT
OF WARM/MOIST AIR INTO THE CWA. RAPID AIR MASS MODIFICATION IS
EXPECTED DURING THE NEXT 12 HOURS...WITH DEWPOINTS LIKELY RISING
INTO THE LOW 60S...WITH SOME MID 60S ACROSS THE SOUTH CENTRAL CWA.
STRONG MOISTURE ADVECTION SHOULD KEEP SKIES CLOUDY...AND HIGH
TEMPS SHOULD BE HELD IN THE MID-UPPER 60S...HELPING TO LIMIT
INSTABILITY. THE PRIMARY INHIBITING FACTOR FOR SEVERE WEATHER AND
THE MOST UNCERTAIN PART OF THIS FORECAST IS THE INSTABILITY. GIVEN
THE NATURE OF THIS DYNAMIC SYSTEM AND ANALOGS TO PAST COOL SEASON
SEVERE WEATHER PRODUCING SYSTEMS...WILL CONTINUE TO FAVOR THE NAM
WHICH IS MOST AGGRESSIVE WITH INSTABILITY. EXPECT SB CAPE TO REACH
1000 J/KG OVER THE SOUTH CENTRAL ZONES...WITH VALUES TAPERING OFF
TO 500 J/KG NEAR THE I-20 CORRIDOR. IT IS IMPORTANT TO NOTE THAT
ABOUT 250 J/KG OF THE TOTAL CAPE RESIDES BELOW 3KM...WHICH IS VERY
HIGH FOR ANYTIME OF THE YEAR...AND INCREASES THE POTENTIAL FOR
VORTEX STRETCHING NEAR THE GROUND AND TORNADOGENESIS.
MOST OF THE STORMS WILL FORM ALONG A NORTH-SOUTH ORIENTED COLD
FRONT THAT WILL REACH THE WESTERN CWA IN THE EARLY AFTERNOON.
AHEAD OF THE FRONT...THERE WILL BE SOME WARM ADVECTION SHOWERS
STREAMING UP FROM THE SOUTH. CONVECTION AHEAD OF THE FRONT MAY BE
DISCRETE...BUT INSTABILITY MAY NOT YET BE HIGH ENOUGH FOR ANYTHING
MORE THAN SHOWERS UNTIL FRONTOGENETIC FORCING ARRIVES WITH THE
FRONT. STORM MOTION IS EXPECTED TO BE AT 45KT AND THIS SUGGESTS
DAMAGING WINDS WILL BE THE PRIMARY SEVERE WEATHER THREAT DUE TO
DOWNWARD MOMENTUM TRANSPORT. BECAUSE STORMS SHOULD FORM INTO A
LINE ALONG THE FRONT...TORNADO POTENTIAL SHOULD BE LIMITED...BUT
CONDITIONS ARE STILL FAVORABLE FOR ISOLATED BRIEF SPIN-UPS WITHIN
THE LINE. SEVERE WEATHER THREAT EXISTS JUST ABOUT EVERYWHERE...BUT
WILL BE HIGHEST ALONG THE I-35 CORRIDOR SOUTH OF I-20 WHERE BAND
OF INSTABILITY WILL BE HIGHEST. THERE IS SOME UNCERTAINTY WITH THE
TIMING...AS THE HRRR IS THE QUICKEST...AND THE NAM ABOUT 5 HOURS
SLOWER. THE ECMWF OFFERS A GOOD COMPROMISE AND EXPECT THE SQUALL
LINE TO IMPACT THE WESTERN ZONES 2-6PM...THE I-35 CORRIDOR
4-8PM...AND MOVE OUT OF THE EASTERN ZONES BY 12AM.
WINDY AND COLDER CONDITIONS ARE EXPECTED TUESDAY AS COLD AIR POURS
IN BEHIND THE CYCLONE. SOME WRAP AROUND CLOUDS WILL AFFECT THE
NORTHERN ZONES. WINDS DIMINISH TUESDAY NIGHT...WITH SUBFREEZING
TEMPS OVER MOST OF THE CWA. NEXT UPPER LEVEL SHORTWAVE WILL
APPROACH WEDNESDAY...WITH INCREASING MID-HIGH CLOUDS. MOISTURE
APPEARS SUFFICIENT FOR A LOW CHANCE OF RAIN OVER THE SOUTHEAST
HALF OF THE AREA WED NIGHT AND THURSDAY MORNING. ONCE THIS IMPULSE
MOVES THROUGH...ANOTHER COLD FRONT WILL ARRIVE THURSDAY EVENING.
EXTENDED FORECAST REMAINS OF VERY LOW CONFIDENCE DUE TO WIDESPREAD
DISAGREEMENT IN HOW SEVERAL VORT LOBES INTERACT WITH EACH OTHER.
REGARDLESS OF THE DETAILS...THE SYNOPTIC PATTERN SUGGESTS WITH
HIGH CONFIDENCE THAT IT WILL BE COLD FOR THE HOLIDAY WEEKEND. WILL
NEED BETTER INTER-MODEL AND RUN-TO-RUN CONSISTENCY BEFORE
ENTERTAINING THE POTENTIAL FOR PRECIPITATION.
TR.92
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 63 44 50 31 53 / 100 90 5 0 5
WACO, TX 67 43 53 29 54 / 90 90 5 0 10
PARIS, TX 62 49 56 30 51 / 50 100 10 0 5
DENTON, TX 62 42 47 27 52 / 100 80 10 0 5
MCKINNEY, TX 63 44 49 28 52 / 90 100 10 0 5
DALLAS, TX 64 45 51 33 53 / 90 100 5 0 5
TERRELL, TX 65 47 53 32 52 / 80 100 5 0 5
CORSICANA, TX 68 47 55 33 54 / 70 100 10 0 10
TEMPLE, TX 68 43 55 31 55 / 90 90 5 0 10
MINERAL WELLS, TX 61 39 46 26 53 / 100 40 10 0 5
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
75/
AREA FORECAST DISCUSSION
NWS FORT WORTH TX
412 AM CST MON DEC 19 2011
.DISCUSSION...
POWERFUL UPPER LEVEL LOW NEAR EL PASO WILL BEGIN TO CURVE NORTH
AND TRACK ACROSS THE TX PANHANDLE TONIGHT. STORM SYSTEM WILL BE
RESPONSIBLE FOR BLIZZARD CONDITIONS OVER THE SOUTHERN HIGH PLAINS
AND A ROUND OF STORMS WITH A POTENTIAL FOR SEVERE WEATHER HERE.
THIS UPPER LOW IS VERY STRONG AND HAS SIMILARITIES TO THE DEC 29
2006 SYSTEM THAT PRODUCED 22 TORNADOES IN OUR CWA. ALTHOUGH WE DO
NOT EXPECT AN EVENT OF THAT MAGNITUDE THIS TIME DUE TO A FARTHER
NORTH POSITION OF THE WARM FRONT AND LESS UNSTABLE AIR OVER OUR
REGION...IT DOES HEIGHTEN OUR AWARENESS FOR SEVERE WEATHER.
SUBSTANTIAL HEIGHT FALLS ARE ALREADY RESULTING IN 3HR PRESSURE
FALLS OF 3-5 MB ACROSS MUCH OF WEST TX. SOUTHERLY WINDS THROUGH
THE TROPOSPHERE ARE INCREASING...AND WILL CONTINUE TO DO SO DURING
THE DAY. WIND SHEAR WILL BECOME VERY STRONG WITH 0-6KM SHEAR NEAR
60KT AND 0-3KM HELICITY AT OR ABOVE 500 M2/S2. SOUTHERLY 850 MB
WINDS ARE EXPECTED TO REACH 60KT BY NOON...AIDING IN THE TRANSPORT
OF WARM/MOIST AIR INTO THE CWA. RAPID AIR MASS MODIFICATION IS
EXPECTED DURING THE NEXT 12 HOURS...WITH DEWPOINTS LIKELY RISING
INTO THE LOW 60S...WITH SOME MID 60S ACROSS THE SOUTH CENTRAL CWA.
STRONG MOISTURE ADVECTION SHOULD KEEP SKIES CLOUDY...AND HIGH
TEMPS SHOULD BE HELD IN THE MID-UPPER 60S...HELPING TO LIMIT
INSTABILITY. THE PRIMARY INHIBITING FACTOR FOR SEVERE WEATHER AND
THE MOST UNCERTAIN PART OF THIS FORECAST IS THE INSTABILITY. GIVEN
THE NATURE OF THIS DYNAMIC SYSTEM AND ANALOGS TO PAST COOL SEASON
SEVERE WEATHER PRODUCING SYSTEMS...WILL CONTINUE TO FAVOR THE NAM
WHICH IS MOST AGGRESSIVE WITH INSTABILITY. EXPECT SB CAPE TO REACH
1000 J/KG OVER THE SOUTH CENTRAL ZONES...WITH VALUES TAPERING OFF
TO 500 J/KG NEAR THE I-20 CORRIDOR. IT IS IMPORTANT TO NOTE THAT
ABOUT 250 J/KG OF THE TOTAL CAPE RESIDES BELOW 3KM...WHICH IS VERY
HIGH FOR ANYTIME OF THE YEAR...AND INCREASES THE POTENTIAL FOR
VORTEX STRETCHING NEAR THE GROUND AND TORNADOGENESIS.
MOST OF THE STORMS WILL FORM ALONG A NORTH-SOUTH ORIENTED COLD
FRONT THAT WILL REACH THE WESTERN CWA IN THE EARLY AFTERNOON.
AHEAD OF THE FRONT...THERE WILL BE SOME WARM ADVECTION SHOWERS
STREAMING UP FROM THE SOUTH. CONVECTION AHEAD OF THE FRONT MAY BE
DISCRETE...BUT INSTABILITY MAY NOT YET BE HIGH ENOUGH FOR ANYTHING
MORE THAN SHOWERS UNTIL FRONTOGENETIC FORCING ARRIVES WITH THE
FRONT. STORM MOTION IS EXPECTED TO BE AT 45KT AND THIS SUGGESTS
DAMAGING WINDS WILL BE THE PRIMARY SEVERE WEATHER THREAT DUE TO
DOWNWARD MOMENTUM TRANSPORT. BECAUSE STORMS SHOULD FORM INTO A
LINE ALONG THE FRONT...TORNADO POTENTIAL SHOULD BE LIMITED...BUT
CONDITIONS ARE STILL FAVORABLE FOR ISOLATED BRIEF SPIN-UPS WITHIN
THE LINE. SEVERE WEATHER THREAT EXISTS JUST ABOUT EVERYWHERE...BUT
WILL BE HIGHEST ALONG THE I-35 CORRIDOR SOUTH OF I-20 WHERE BAND
OF INSTABILITY WILL BE HIGHEST. THERE IS SOME UNCERTAINTY WITH THE
TIMING...AS THE HRRR IS THE QUICKEST...AND THE NAM ABOUT 5 HOURS
SLOWER. THE ECMWF OFFERS A GOOD COMPROMISE AND EXPECT THE SQUALL
LINE TO IMPACT THE WESTERN ZONES 2-6PM...THE I-35 CORRIDOR
4-8PM...AND MOVE OUT OF THE EASTERN ZONES BY 12AM.
WINDY AND COLDER CONDITIONS ARE EXPECTED TUESDAY AS COLD AIR POURS
IN BEHIND THE CYCLONE. SOME WRAP AROUND CLOUDS WILL AFFECT THE
NORTHERN ZONES. WINDS DIMINISH TUESDAY NIGHT...WITH SUBFREEZING
TEMPS OVER MOST OF THE CWA. NEXT UPPER LEVEL SHORTWAVE WILL
APPROACH WEDNESDAY...WITH INCREASING MID-HIGH CLOUDS. MOISTURE
APPEARS SUFFICIENT FOR A LOW CHANCE OF RAIN OVER THE SOUTHEAST
HALF OF THE AREA WED NIGHT AND THURSDAY MORNING. ONCE THIS IMPULSE
MOVES THROUGH...ANOTHER COLD FRONT WILL ARRIVE THURSDAY EVENING.
EXTENDED FORECAST REMAINS OF VERY LOW CONFIDENCE DUE TO WIDESPREAD
DISAGREEMENT IN HOW SEVERAL VORT LOBES INTERACT WITH EACH OTHER.
REGARDLESS OF THE DETAILS...THE SYNOPTIC PATTERN SUGGESTS WITH
HIGH CONFIDENCE THAT IT WILL BE COLD FOR THE HOLIDAY WEEKEND. WILL
NEED BETTER INTER-MODEL AND RUN-TO-RUN CONSISTENCY BEFORE
ENTERTAINING THE POTENTIAL FOR PRECIPITATION.
TR.92
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 63 44 50 31 53 / 100 90 5 0 5
WACO, TX 67 43 53 29 54 / 90 90 5 0 10
PARIS, TX 62 49 56 30 51 / 50 100 10 0 5
DENTON, TX 62 42 47 27 52 / 100 80 10 0 5
MCKINNEY, TX 63 44 49 28 52 / 90 100 10 0 5
DALLAS, TX 64 45 51 33 53 / 90 100 5 0 5
TERRELL, TX 65 47 53 32 52 / 80 100 5 0 5
CORSICANA, TX 68 47 55 33 54 / 70 100 10 0 10
TEMPLE, TX 68 43 55 31 55 / 90 90 5 0 10
MINERAL WELLS, TX 61 39 46 26 53 / 100 40 10 0 5
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION...UPDATED
NWS FORT WORTH TX
1137 PM CST SUN DEC 18 2011
.AVIATION...
AN UPPER LEVEL LOW CURRENTLY OVER SOUTHEASTERN ARIZONA...WILL
MOVE EAST ACROSS THE SOUTHERN PLAINS IN THE NEXT 24 TO 36 HOURS.
INCREASING LOW LEVEL MOISTURE HAS BROUGHT MVFR CEILINGS MAINLY
WEST OF I-35 AS OF 05Z...AND THESE CEILINGS WILL SPREAD ACROSS
THE REST OF THE TAF SITES BETWEEN 06Z AND 09Z. MVFR CEILINGS
SHOULD THEN HOLD IN FOR MOST...IF NOT...ALL OF THE DAY MONDAY. AN
INITIAL BAND OF SHOWERS AND THUNDERSTORMS BETWEEN ABILENE AND
WICHITA FALLS AS OF 05Z...WILL MOVE OFF TO THE NORTHEAST AND NOT
AFFECT THE AREA AIRPORTS. CAN NOT RULE OUT A CHANCE OF
SHOWERS/THUNDERSTORMS MID TO LATE MORNING AT THE TAF SITES BUT
UNCERTAINTY IS TOO HIGH TO MENTION AT THIS TIME. A LINE OF
THUNDERSTORMS IS EXPECTED TO DEVELOP ACROSS WEST TEXAS BY MIDDAY
MONDAY AND MOVE EAST ACROSS NORTH TEXAS DURING THE AFTERNOON AND
EVENING HOURS. FOR NOW HAVE PLACED 6SM -TSRA FOR THE MOST LIKELY
PERIOD OF 22Z-02Z...THOUGH SOME EARLIER ACTIVITY MAY OCCUR AHEAD
OF THE MAIN LINE OF THUNDERSTORMS. WINDS SHOULD SHIFT TO
SOUTHWEST 02-04Z.
58
&&
.UPDATE...
IMPRESSIVE UPPER LEVEL STORM SYSTEM IS SHOWING GOOD WV SATELLITE
STRUCTURE AS IT CHURNS ALONG OVER SOUTHEASTERN AZ AND APPROACHES
TEXAS FROM THE WEST. ISOLATED CONVECTION CONTINUES NEAR THE COLD
CENTER OF THE LOW...AND HAS ALSO DEVELOPED JUST WEST OF THE
FORECAST AREA IN ZONE OF INCREASING ASCENT AND MOISTURE RETURN
AHEAD OF THE FEATURE. STILL EXPECT PRECIPITATION TO REMAIN
ISOLATED AND MOSTLY WEST OF THE INTERSTATE 35 CORRIDOR THROUGH
EARLY MONDAY MORNING. SHOWERS AND THUNDERSTORMS WILL THEN INCREASE
RAPIDLY LATE TOMORROW MORNING AND INTENSIFY DURING THE AFTERNOON
HOURS AS THE SYSTEM BARRELS INTO THE AREA WITH A NEGATIVELY TILTED
AXIS...IMPRESSIVE DYNAMICS...AND FAIRLY GOOD INSTABILITY FOR THIS
TIME OF YEAR.
FOR THIS UPDATE WILL ADD MENTION OF ISOLATED THUNDER WEST OF I
35/35W WHERE A FEW STRIKES MAY OCCUR BETWEEN MIDNIGHT AND 6 AM
FRIDAY. OTHERWISE FORECAST IS ON TRACK.
30
&&
.PREV DISCUSSION... /ISSUED 407 PM CST SUN DEC 18 2011/
12Z UPPER AIR ANALYSIS INDICATED THAT A CUT OFF LOW REMAINED IN
PLACE OVER FAR SOUTHERN CA WITH RIDGING OVER THE GULF OF MEXICO.
THIS LEFT SOUTHWEST FLOW ALOFT OVER THE SOUTHERN PLAINS OUT AHEAD
OF THE UPPER LOW. SOUTHWEST FLOW ALOFT HAD LED TO THE ADVECTION OF
STEEP LAPSE RATES INTO WEST TX THIS MORNING WITH A TEMPERATURE
DIFFERENCE IN THE H700 TO H500 LAYER OF 22 DEG C. A POOL OF 10 DEG
C DEW POINTS WAS OBSERVED AT THE H850 LEVEL OVER FAR SOUTH TX AND
THE EFFECTS OF LEE SIDE CYCLOGENESIS WERE BECOMING EVIDENT WITH
THE DEVELOPMENT OF A CYCLONIC CIRCULATION OVER FAR WEST TX. 21Z
SFC ANALYSIS INDICATED THAT A MOISTURE WAS RAPIDLY RETURNING TO
WESTERN AND CENTRAL TX WITH 45 DEG F DEW POINTS OBSERVED AS VAR
NORTH AS CHILDRESS.
TONIGHT THROUGH TUESDAY...AFTERNOON WATER VAPOR IMAGERY INDICATED
THAT THE CUT OFF LOW AS ALREADY BEGINNING TO MOVE EAST AND THE
CENTER OF CIRCULATION HAD JUST CROSSED OVER THE SOUTHERN AZ BORDER
AS OF 21Z. A PLUME OF PACIFIC MOISTURE HAS ALREADY BEEN ADVECTED
OVER MUCH OF THE SOUTHERN PLAINS...AND SOUTHWEST FLOW ALOFT
CONTINUES THIS TRANSPORT OF MID TO UPPER TROPOSPHERIC MOISTURE
INTO THE REGION. THE PROGRESSION OF SURFACE DEW POINTS WAS THE
MOST INTERESTING PIECE OF INFORMATION THAT COULD BE OBSERVED ABOUT
THE POTENTIAL THERMODYNAMIC ENVIRONMENT THIS AFTERNOON AHEAD OF
THIS UPPER LOW. BASED ON 12Z GUIDANCE...THE NAM WAS THE ONLY MODEL
TO SUFFICIENTLY HANDLE THE RAPID INFLUX OF LOW LEVEL MOISTURE INTO
TX. THE NAM HAD ROUGHLY AN ACCURATE REPRESENTATION OF 21Z DEW
POINTS ACROSS TX WITH THE GFS LAGGING BEHIND BY 6 HRS AND THE
ECMWF COMING IN A FEW DEG F TOO LOW FOR ITS 00Z FORECAST THIS
EVENING. EVEN THE 18Z INITIALIZATION OF THE RUC IS SLOW ON THIS
MOISTURE TRANSPORT WHICH POINTS TO A POTENTIALLY SIGNIFICANT
SOURCE OF ERROR WITH REGARDS TO HANDLING THE THERMODYNAMIC
ENVIRONMENT THAT WILL SET UP OVER NORTH TX TOMORROW.
DID NOT CHANGE MUCH WITH REGARDS TO THE TIMING OF EXPECTED
PRECIPITATION ACROSS NORTH TX WITH THIS FORECAST PACKAGE. THE
UPPER LEVEL SYSTEM AND ASSOCIATED FRONTAL BOUNDARIES ARE EXPECTED
TO MOVE THRU NORTH TX AT ROUGHLY THE SAME TIME AS THE PREVIOUS
FORECAST INDICATED. THE UPPER LOW IS EXPECTED TO MOVE INTO THE
SOUTHERN PLAINS TOMORROW EVENING AND THEN BECOME NEGATIVELY TILTED
AS IT MOVES NORTHEAST OVER NORTH CENTRAL TX AND OVER OK MONDAY
NIGHT. STRONG LARGE SCALE FORCING FOR ASCENT WILL SPREAD OVER
NORTH TX AHEAD OF THIS UPPER LOW...WITH MAXIMUM ASCENT SPREADING
OVER THE FORECAST AREA FROM 21Z MONDAY TO 06Z TUESDAY. THE
FORECAST STRENGTH OF THE UPPER LOW AS IT MOVES OVER THE SOUTHERN
PLAINS IS HIGH WITH H500 HEIGHTS REGISTERING AS A -2.5 STANDARD
DEVIATION ANOMALY PER HPCS ANALYSIS OF THE 12Z GFS. PRECIPITABLE
WATER VALUES CONTINUE TO BE FORECAST TO HOLD IN THE 99TH
PERCENTILE OVER NORTH TX FOR DECEMBER. THE 0 TO 6 KM BULK SHEAR
MAGNITUDE IS EXPECTED TO BE IN EXCESS OF 55 KTS DURING THE PERIOD
OF MAXIMUM FORCING FOR ASCENT WHICH SPEAKS TO THE STRENGTH OF THE
WIND FIELDS OUT AHEAD OF THIS SYSTEM. INSTABILITY CONTINUES TO BE
THE MOST DIFFICULT PARAMETER TO FORECAST...AND THE DEGREE OF
INSTABILITY WILL LARGELY DETERMINE OUR SEVERE WEATHER CHANCES AND
COVERAGE TOMORROW AFTERNOON.
BASED ON 21Z SURFACE OBS...THE NAM APPEARS TO HAVE THE BEST HANDLE
ON LOW LEVEL MOISTURE MOISTURE RETURN OUT AHEAD OF THIS SYSTEM.
MOISTURE TRANSPORT IS EXPECTED TO INCREASE IN INTENSITY TONIGHT
AND DURING THE DAY MONDAY AS THE UPPER LEVEL LOW MOVES OVER THE
SOUTHERN PLAINS. THE LOW LEVEL JET IS FORECAST TO INCREASE TO AT
LEAST 50 KTS OVER NORTH TX TOMORROW...WITH OUR LOCAL 4 KM WRF
INDICATING A POTENTIAL JET CORE OF 60 KTS AFTER 21Z. STRATUS IS
STILL EXPECTED TO BE IN PLACE OVER MOST OF THE OPEN WARM SECTOR
TOMORROW WHICH WILL BE A LIMITING FACTOR FOR LOW LEVEL
DESTABILIZATION. HOWEVER WITH MOISTURE TRANSPORT LIKELY
UNDERESTIMATED IN MOST OPERATIONAL GUIDANCE...THINK THAT SURFACE
BASED INSTABILITY IS LIKEWISE UNDERESTIMATED. 12Z MOS GUIDANCE IS
NOW CONSISTENT WITH MID 60S HIGHS FOR DFW TOMORROW. MOS GUIDANCE
ALSO INDICATES HIGHS IN THE UPPER 60S TO LOWER 70S FOR WACO
TOMORROW. THIS IS A FEW DEGREES WARMER THAN HIGHS WERE EXPECTED TO
CLIMB FROM YESTERDAYS FORECAST.
CONFIDENCE IN THESE HIGHER TEMPERATURES IS INCREASING DUE TO
SIGNIFICANT BREAKS IN CLOUD COVER OVER NORTH TX AND THE TX GULF
COAST. WARMER AFTERNOON TEMPERATURES TODAY WILL THEORETICALLY LEAD
TO WARMER OVERNIGHT LOWS ONCE CLOUD COVER BUILDS BACK IN TONIGHT.
THIS WOULD MEAN THAT LESS HEATING IS NECESSARY TO REACH HIGHER
TEMPERATURES TOMORROW AFTERNOON. THE 12 AND 18Z NAM RUNS BOTH
CONTINUE TO AGGRESSIVELY ADVERTISE FREE CONVECTION POTENTIAL
TOMORROW AFTERNOON AND EVENING. WITH THE NAM HAVING THE BEST
HANDLE ON LOW LEVEL MOISTURE AND HIGH TEMPERATURES LIKELY CLIMBING
A FEW DEGREES HIGHER TOMORROW THAN PREVIOUS EXPECTED...CONFIDENCE
IN THE NAMS THERMODYNAMIC SOLUTION HAS INCREASED SUBSTANTIALLY.
THE NAM ADVERTISES A CORRIDOR OF SURFACE BASED CAPE OF 1000 J/KG
EXTENDING FROM THE METROPLEX SOUTH...NEAR THE INTERSTATE 35
CORRIDOR BY 00Z TUE OR TOMORROW AT 6 PM.
AS PREVIOUS FORECAST MENTIONED...LOW LCL HEIGHTS INDICATE THAT A
SIGNIFICANT PORTION OF THE FREE CONVECTION POTENTIAL ENERGY /CAPE/
WILL LIE IN THE LOWEST 3 KMS. 0 TO 3 KM CAPE VALUES ARE FORECAST
TO BE IN EXCESS OF 200 J/KG WITHIN THIS SAME GENERAL CORRIDOR.
THESE VALUES ARE QUITE HIGH EVEN FOR A SPRING SEVERE WEATHER
EPISODE...AND HIGH LOW LEVEL CAPE VALUES SPEAK TO THE POTENTIAL
FOR LOW LEVEL STRETCHING AND TILTING OF HORIZONTAL VORTICITY INTO
THE VERTICAL. LOW LEVEL WIND PROFILES CONTINUE TO VEER WITH HEIGHT
AND CONTAIN SIGNIFICANT SPEED SHEAR DUE TO THE PRESENCE OF THE
STRONG LOW LEVEL JET. 0-1 KM HELICITY VALUES IN EXCESS OF 200
M2/S2 ARE PRESENT WITHIN THE CORRIDOR OF HIGH LOW LEVEL CAPE. THIS
COMBINATION OF PARAMETERS INDICATES THAT ANY UPDRAFT WILL HAVE A
STRONG LIKELIHOOD TO INGEST HORIZONTAL VORTICITY WHICH GREATLY
INCREASES THE SEVERE WEATHER THREAT TOMORROW AFTERNOON. THE
GENERAL STORM MODE IS STILL EXPECTED TO BE LINEAR WITH SIGNIFICANT
FORCING FOR ASCENT EXPECTED ALONG A PACIFIC TYPE COLD FRONT THAT
WILL MOVE TROUGH NORTH TX JUST AHEAD OF THE CORE OF THE UPPER LOW.
THIS NORTH/SOUTH ORIENTED FRONT IS ORIENTED NEARLY PARALLEL TO THE
0-6 KM BULK SHEAR VECTORS WHICH GENERALLY FAVORS SHARED COLD POOLS
LEADING TO A LINEAR STORM MODE.
EVEN WITH A LINEAR STORM MODE STRETCHING AND TILTING OF HORIZONTAL
VORTICITY INTO THE VERTICAL CAN LEAD TO THE DEVELOPMENT OF
MESOVORTICIES CAPABLE OF PRODUCING STRONG LOCALIZED WIND
DAMAGE...AND TO THE DEVELOPMENT OF BRIEF TORNADOES. ANY DISCRETE
STORMS OUT AHEAD OF LINE SEGMENT CONVECTION WILL LIKELY BE IN THE
FORM OF LOW-TOPPED AND VERY FAST MOVING SUPERCELLS. ANY LOW-TOPPED
SUPERCELL AWAY FROM THE MAIN LINE OF CONVECTION WILL BE CAPABLE OF
PRODUCING A TORNADO...ESPECIALLY SOUTH OF THE METROPLEX TOMORROW
AFTERNOON. THE MOST WIDESPREAD SEVERE WEATHER HAZARD IS THOUGHT
TO BE IN THE FORM OF STRAIGHT LINE WIND DAMAGE...AND THIS IS
MOSTLY DUE TO THE POTENTIAL FOR STRONG ENVIRONMENTAL WINDS TO BE
DRIVEN DOWN TO THE SURFACE. DEEP MOISTURE MEANS THAT THERE IS
LITTLE THETA-E DIFFERENCE WITH HEIGHT...AND THEREFORE LITTLE
POTENTIAL FOR ENHANCED DOWNDRAFT SPEEDS OR MICROBURSTS.
OVERALL CONFIDENCE IN AN ORGANIZED STORM MODE IS HIGH NOW FOR
TOMORROW AFTERNOON. DAMAGING STRAIGHT LINE WINDS WITH A HIGH
POTENTIAL FOR LOCALLY ENHANCED DAMAGE IS THE MOST PREVALENT SEVERE
WEATHER HAZARD. THERE IS AN ATTENDANT TORNADO THREAT TOMORROW
AFTERNOON...ESPECIALLY IF ANY DISCRETE STORMS ARE ABLE TO DEVELOP
OUT AHEAD OF THE SQUALL LINE/PACIFIC FRONT. 99TH PERCENTILE PWATS
ALWAYS RAISE THE POTENTIAL FOR LOCALIZED FLOODING ISSUES...HOWEVER
THE VERY FAST STORM MOTION IS EXPECTED TO MITIGATE SIGNIFICANT
FLOODING CONCERNS.
THE PACIFIC TYPE COLD FRONT IS EXPECTED TO MOVE EAST THRU MOST OF
NORTH TX BY MIDNIGHT /06Z TUE/ MONDAY NIGHT. THE ATTENDANT SQUALL
LINE WILL LIKELY BE JUST EXITING THE FORECAST AREA AT THIS TIME
SO HAVE LINGERED HIGH POPS OVER THE FAR EASTERN CWA AFTER
MIDNIGHT. BY TUESDAY MORNING THERE IS SOME LOW END POTENTIAL FOR
LIGHT RAIN ASSOCIATED WITH MOISTURE WRAPPED AROUND THE UPPER
LOW...ESPECIALLY AS SOME RESIDUAL FRONTOGENETIC FORCING BUILDS
INTO THE NORTHERN CWA AS THE CANADIAN AIRMASS RESPONSIBLE FOR THE
BLIZZARD PORTION OF THIS SYSTEM /OVER THE SOUTHERN HIGH PLAINS/
MOVES SOUTH INTO NORTH TX. NO WINTRY PRECIPITATION IS EXPECTED AT
THIS TIME AS THERE WILL BE VERY LITTLE MOISTURE LEFT TO WORK WITH
AND TEMPERATURES WILL GENERALLY REMAIN ABOVE FREEZING EARLY
TUESDAY MORNING BEHIND THE FRONT.
EXTENDED...NO SIGNIFICANT CHANGES MADE TO THE EXTENDED AT THIS
TIME. KEPT THE LOW END RAIN CHANCES OVER THE SOUTHEASTERN PORTION
OF THE CWA ON THURSDAY AS ANOTHER SHORTWAVE TROUGH MOVES OVER
NORTH TX. THE 12Z ECMWF WAS THE MOST AGGRESSIVE WITH PRECIPITATION
BECAUSE IT BRINGS THE WAVE OVER NORTH TX THE FURTHEST NORTH AND
STRONGER THAN THE GFS ADVERTISES. EITHER WAY LIMITED MOISTURE WILL
PREVENT SIGNIFICANT COVERAGE OF RAIN OVER NORTH TX ON THURSDAY.
MAINTAINED A DRY FORECAST FOR THE HOLIDAY WEEKEND AS RUN TO RUN
AND MODEL TO MODEL CONSISTENCY EVEN ON LARGE SCALE FLOW REMAINS
POOR AT THIS TIME. GENERAL CONSENSUS IS THAT TEMPERATURES WILL BE
BELOW NORMAL...SO FOR NOW A COOL AND DRY HOLIDAY WEEKEND IS
EXPECTED.
CAVANAUGH
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 51 64 45 50 31 / 10 80 100 5 5
WACO, TX 52 67 44 53 28 / 10 70 100 5 5
PARIS, TX 44 63 47 54 30 / 10 50 100 10 10
DENTON, TX 52 61 43 46 27 / 10 90 100 10 5
MCKINNEY, TX 48 62 45 50 30 / 10 80 100 5 5
DALLAS, TX 51 64 46 50 31 / 10 80 100 5 5
TERRELL, TX 48 64 49 53 31 / 10 50 100 5 5
CORSICANA, TX 48 66 47 55 32 / 10 50 100 5 5
TEMPLE, TX 50 66 43 55 29 / 10 70 100 5 5
MINERAL WELLS, TX 53 64 39 46 25 / 20 100 80 10 5
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
58/30
AREA FORECAST DISCUSSION
NWS FORT WORTH TX
1037 PM CST SUN DEC 18 2011
.UPDATE...
IMPRESSIVE UPPER LEVEL STORM SYSTEM IS SHOWING GOOD WV SATELLITE
STRUCTURE AS IT CHURNS ALONG OVER SOUTHEASTERN AZ AND APPROACHES
TEXAS FROM THE WEST. ISOLATED CONVECTION CONTINUES NEAR THE COLD
CENTER OF THE LOW...AND HAS ALSO DEVELOPED JUST WEST OF THE
FORECAST AREA IN ZONE OF INCREASING ASCENT AND MOISTURE RETURN
AHEAD OF THE FEATURE. STILL EXPECT PRECIPITATION TO REMAIN
ISOLATED AND MOSTLY WEST OF THE INTERSTATE 35 CORRIDOR THROUGH
EARLY MONDAY MORNING. SHOWERS AND THUNDERSTORMS WILL THEN INCREASE
RAPIDLY LATE TOMORROW MORNING AND INTENSIFY DURING THE AFTERNOON
HOURS AS THE SYSTEM BARRELS INTO THE AREA WITH A NEGATIVELY TILTED
AXIS...IMPRESSIVE DYNAMICS...AND FAIRLY GOOD INSTABILITY FOR THIS
TIME OF YEAR.
FOR THIS UPDATE WILL ADD MENTION OF ISOLATED THUNDER WEST OF I
35/35W WHERE A FEW STRIKES MAY OCCUR BETWEEN MIDNIGHT AND 6 AM
FRIDAY. OTHERWISE FORECAST IS ON TRACK.
30
&&
.AVIATION...
CONCERNS...MVFR CEILINGS DEVELOPING 09-12Z. POSSIBLE
THUNDERSTORMS MONDAY AFTERNOON/EVENING.
AN UPPER LEVEL LOW CURRENTLY OVER SOUTHWESTERN ARIZONA...WILL
MOVE EAST ACROSS THE SOUTHERN PLAINS IN THE NEXT 24 TO 36 HOURS.
INCREASING SOUTHERLY LOW LEVEL FLOW WILL BRING SOME MVFR CEILINGS
NORTHWARD INTO WACO AROUND 09Z...AND INTO THE METROPLEX AROUND
12Z. MVFR CEILINGS SHOULD THEN HOLD IN FOR MOST...IF NOT...ALL OF
THE DAY. A LINE OF THUNDERSTORMS IS EXPECTED TO DEVELOP ACROSS
WEST TEXAS BY MIDDAY MONDAY AND MOVE EAST ACROSS NORTH TEXAS
DURING THE AFTERNOON AND EVENING HOURS. FOR NOW HAVE PLACED 6SM
-TSRA STARTING AT 21Z AT ALL OF THE TAF SITES...THOUGH SOME
EARLIER ACTIVITY MAY OCCUR AHEAD OF THE MAIN LINE OF
THUNDERSTORMS. WINDS SHOULD SHIFT TO SOUTHWEST AFTER 03Z.
58
&&
.PREV DISCUSSION... /ISSUED 407 PM CST SUN DEC 18 2011/
12Z UPPER AIR ANALYSIS INDICATED THAT A CUT OFF LOW REMAINED IN
PLACE OVER FAR SOUTHERN CA WITH RIDGING OVER THE GULF OF MEXICO.
THIS LEFT SOUTHWEST FLOW ALOFT OVER THE SOUTHERN PLAINS OUT AHEAD
OF THE UPPER LOW. SOUTHWEST FLOW ALOFT HAD LED TO THE ADVECTION OF
STEEP LAPSE RATES INTO WEST TX THIS MORNING WITH A TEMPERATURE
DIFFERENCE IN THE H700 TO H500 LAYER OF 22 DEG C. A POOL OF 10 DEG
C DEW POINTS WAS OBSERVED AT THE H850 LEVEL OVER FAR SOUTH TX AND
THE EFFECTS OF LEE SIDE CYCLOGENESIS WERE BECOMING EVIDENT WITH
THE DEVELOPMENT OF A CYCLONIC CIRCULATION OVER FAR WEST TX. 21Z
SFC ANALYSIS INDICATED THAT A MOISTURE WAS RAPIDLY RETURNING TO
WESTERN AND CENTRAL TX WITH 45 DEG F DEW POINTS OBSERVED AS VAR
NORTH AS CHILDRESS.
TONIGHT THROUGH TUESDAY...AFTERNOON WATER VAPOR IMAGERY INDICATED
THAT THE CUT OFF LOW AS ALREADY BEGINNING TO MOVE EAST AND THE
CENTER OF CIRCULATION HAD JUST CROSSED OVER THE SOUTHERN AZ BORDER
AS OF 21Z. A PLUME OF PACIFIC MOISTURE HAS ALREADY BEEN ADVECTED
OVER MUCH OF THE SOUTHERN PLAINS...AND SOUTHWEST FLOW ALOFT
CONTINUES THIS TRANSPORT OF MID TO UPPER TROPOSPHERIC MOISTURE
INTO THE REGION. THE PROGRESSION OF SURFACE DEW POINTS WAS THE
MOST INTERESTING PIECE OF INFORMATION THAT COULD BE OBSERVED ABOUT
THE POTENTIAL THERMODYNAMIC ENVIRONMENT THIS AFTERNOON AHEAD OF
THIS UPPER LOW. BASED ON 12Z GUIDANCE...THE NAM WAS THE ONLY MODEL
TO SUFFICIENTLY HANDLE THE RAPID INFLUX OF LOW LEVEL MOISTURE INTO
TX. THE NAM HAD ROUGHLY AN ACCURATE REPRESENTATION OF 21Z DEW
POINTS ACROSS TX WITH THE GFS LAGGING BEHIND BY 6 HRS AND THE
ECMWF COMING IN A FEW DEG F TOO LOW FOR ITS 00Z FORECAST THIS
EVENING. EVEN THE 18Z INITIALIZATION OF THE RUC IS SLOW ON THIS
MOISTURE TRANSPORT WHICH POINTS TO A POTENTIALLY SIGNIFICANT
SOURCE OF ERROR WITH REGARDS TO HANDLING THE THERMODYNAMIC
ENVIRONMENT THAT WILL SET UP OVER NORTH TX TOMORROW.
DID NOT CHANGE MUCH WITH REGARDS TO THE TIMING OF EXPECTED
PRECIPITATION ACROSS NORTH TX WITH THIS FORECAST PACKAGE. THE
UPPER LEVEL SYSTEM AND ASSOCIATED FRONTAL BOUNDARIES ARE EXPECTED
TO MOVE THRU NORTH TX AT ROUGHLY THE SAME TIME AS THE PREVIOUS
FORECAST INDICATED. THE UPPER LOW IS EXPECTED TO MOVE INTO THE
SOUTHERN PLAINS TOMORROW EVENING AND THEN BECOME NEGATIVELY TILTED
AS IT MOVES NORTHEAST OVER NORTH CENTRAL TX AND OVER OK MONDAY
NIGHT. STRONG LARGE SCALE FORCING FOR ASCENT WILL SPREAD OVER
NORTH TX AHEAD OF THIS UPPER LOW...WITH MAXIMUM ASCENT SPREADING
OVER THE FORECAST AREA FROM 21Z MONDAY TO 06Z TUESDAY. THE
FORECAST STRENGTH OF THE UPPER LOW AS IT MOVES OVER THE SOUTHERN
PLAINS IS HIGH WITH H500 HEIGHTS REGISTERING AS A -2.5 STANDARD
DEVIATION ANOMALY PER HPCS ANALYSIS OF THE 12Z GFS. PRECIPITABLE
WATER VALUES CONTINUE TO BE FORECAST TO HOLD IN THE 99TH
PERCENTILE OVER NORTH TX FOR DECEMBER. THE 0 TO 6 KM BULK SHEAR
MAGNITUDE IS EXPECTED TO BE IN EXCESS OF 55 KTS DURING THE PERIOD
OF MAXIMUM FORCING FOR ASCENT WHICH SPEAKS TO THE STRENGTH OF THE
WIND FIELDS OUT AHEAD OF THIS SYSTEM. INSTABILITY CONTINUES TO BE
THE MOST DIFFICULT PARAMETER TO FORECAST...AND THE DEGREE OF
INSTABILITY WILL LARGELY DETERMINE OUR SEVERE WEATHER CHANCES AND
COVERAGE TOMORROW AFTERNOON.
BASED ON 21Z SURFACE OBS...THE NAM APPEARS TO HAVE THE BEST HANDLE
ON LOW LEVEL MOISTURE MOISTURE RETURN OUT AHEAD OF THIS SYSTEM.
MOISTURE TRANSPORT IS EXPECTED TO INCREASE IN INTENSITY TONIGHT
AND DURING THE DAY MONDAY AS THE UPPER LEVEL LOW MOVES OVER THE
SOUTHERN PLAINS. THE LOW LEVEL JET IS FORECAST TO INCREASE TO AT
LEAST 50 KTS OVER NORTH TX TOMORROW...WITH OUR LOCAL 4 KM WRF
INDICATING A POTENTIAL JET CORE OF 60 KTS AFTER 21Z. STRATUS IS
STILL EXPECTED TO BE IN PLACE OVER MOST OF THE OPEN WARM SECTOR
TOMORROW WHICH WILL BE A LIMITING FACTOR FOR LOW LEVEL
DESTABILIZATION. HOWEVER WITH MOISTURE TRANSPORT LIKELY
UNDERESTIMATED IN MOST OPERATIONAL GUIDANCE...THINK THAT SURFACE
BASED INSTABILITY IS LIKEWISE UNDERESTIMATED. 12Z MOS GUIDANCE IS
NOW CONSISTENT WITH MID 60S HIGHS FOR DFW TOMORROW. MOS GUIDANCE
ALSO INDICATES HIGHS IN THE UPPER 60S TO LOWER 70S FOR WACO
TOMORROW. THIS IS A FEW DEGREES WARMER THAN HIGHS WERE EXPECTED TO
CLIMB FROM YESTERDAYS FORECAST.
CONFIDENCE IN THESE HIGHER TEMPERATURES IS INCREASING DUE TO
SIGNIFICANT BREAKS IN CLOUD COVER OVER NORTH TX AND THE TX GULF
COAST. WARMER AFTERNOON TEMPERATURES TODAY WILL THEORETICALLY LEAD
TO WARMER OVERNIGHT LOWS ONCE CLOUD COVER BUILDS BACK IN TONIGHT.
THIS WOULD MEAN THAT LESS HEATING IS NECESSARY TO REACH HIGHER
TEMPERATURES TOMORROW AFTERNOON. THE 12 AND 18Z NAM RUNS BOTH
CONTINUE TO AGGRESSIVELY ADVERTISE FREE CONVECTION POTENTIAL
TOMORROW AFTERNOON AND EVENING. WITH THE NAM HAVING THE BEST
HANDLE ON LOW LEVEL MOISTURE AND HIGH TEMPERATURES LIKELY CLIMBING
A FEW DEGREES HIGHER TOMORROW THAN PREVIOUS EXPECTED...CONFIDENCE
IN THE NAMS THERMODYNAMIC SOLUTION HAS INCREASED SUBSTANTIALLY.
THE NAM ADVERTISES A CORRIDOR OF SURFACE BASED CAPE OF 1000 J/KG
EXTENDING FROM THE METROPLEX SOUTH...NEAR THE INTERSTATE 35
CORRIDOR BY 00Z TUE OR TOMORROW AT 6 PM.
AS PREVIOUS FORECAST MENTIONED...LOW LCL HEIGHTS INDICATE THAT A
SIGNIFICANT PORTION OF THE FREE CONVECTION POTENTIAL ENERGY /CAPE/
WILL LIE IN THE LOWEST 3 KMS. 0 TO 3 KM CAPE VALUES ARE FORECAST
TO BE IN EXCESS OF 200 J/KG WITHIN THIS SAME GENERAL CORRIDOR.
THESE VALUES ARE QUITE HIGH EVEN FOR A SPRING SEVERE WEATHER
EPISODE...AND HIGH LOW LEVEL CAPE VALUES SPEAK TO THE POTENTIAL
FOR LOW LEVEL STRETCHING AND TILTING OF HORIZONTAL VORTICITY INTO
THE VERTICAL. LOW LEVEL WIND PROFILES CONTINUE TO VEER WITH HEIGHT
AND CONTAIN SIGNIFICANT SPEED SHEAR DUE TO THE PRESENCE OF THE
STRONG LOW LEVEL JET. 0-1 KM HELICITY VALUES IN EXCESS OF 200
M2/S2 ARE PRESENT WITHIN THE CORRIDOR OF HIGH LOW LEVEL CAPE. THIS
COMBINATION OF PARAMETERS INDICATES THAT ANY UPDRAFT WILL HAVE A
STRONG LIKELIHOOD TO INGEST HORIZONTAL VORTICITY WHICH GREATLY
INCREASES THE SEVERE WEATHER THREAT TOMORROW AFTERNOON. THE
GENERAL STORM MODE IS STILL EXPECTED TO BE LINEAR WITH SIGNIFICANT
FORCING FOR ASCENT EXPECTED ALONG A PACIFIC TYPE COLD FRONT THAT
WILL MOVE TROUGH NORTH TX JUST AHEAD OF THE CORE OF THE UPPER LOW.
THIS NORTH/SOUTH ORIENTED FRONT IS ORIENTED NEARLY PARALLEL TO THE
0-6 KM BULK SHEAR VECTORS WHICH GENERALLY FAVORS SHARED COLD POOLS
LEADING TO A LINEAR STORM MODE.
EVEN WITH A LINEAR STORM MODE STRETCHING AND TILTING OF HORIZONTAL
VORTICITY INTO THE VERTICAL CAN LEAD TO THE DEVELOPMENT OF
MESOVORTICIES CAPABLE OF PRODUCING STRONG LOCALIZED WIND
DAMAGE...AND TO THE DEVELOPMENT OF BRIEF TORNADOES. ANY DISCRETE
STORMS OUT AHEAD OF LINE SEGMENT CONVECTION WILL LIKELY BE IN THE
FORM OF LOW-TOPPED AND VERY FAST MOVING SUPERCELLS. ANY LOW-TOPPED
SUPERCELL AWAY FROM THE MAIN LINE OF CONVECTION WILL BE CAPABLE OF
PRODUCING A TORNADO...ESPECIALLY SOUTH OF THE METROPLEX TOMORROW
AFTERNOON. THE MOST WIDESPREAD SEVERE WEATHER HAZARD IS THOUGHT
TO BE IN THE FORM OF STRAIGHT LINE WIND DAMAGE...AND THIS IS
MOSTLY DUE TO THE POTENTIAL FOR STRONG ENVIRONMENTAL WINDS TO BE
DRIVEN DOWN TO THE SURFACE. DEEP MOISTURE MEANS THAT THERE IS
LITTLE THETA-E DIFFERENCE WITH HEIGHT...AND THEREFORE LITTLE
POTENTIAL FOR ENHANCED DOWNDRAFT SPEEDS OR MICROBURSTS.
OVERALL CONFIDENCE IN AN ORGANIZED STORM MODE IS HIGH NOW FOR
TOMORROW AFTERNOON. DAMAGING STRAIGHT LINE WINDS WITH A HIGH
POTENTIAL FOR LOCALLY ENHANCED DAMAGE IS THE MOST PREVALENT SEVERE
WEATHER HAZARD. THERE IS AN ATTENDANT TORNADO THREAT TOMORROW
AFTERNOON...ESPECIALLY IF ANY DISCRETE STORMS ARE ABLE TO DEVELOP
OUT AHEAD OF THE SQUALL LINE/PACIFIC FRONT. 99TH PERCENTILE PWATS
ALWAYS RAISE THE POTENTIAL FOR LOCALIZED FLOODING ISSUES...HOWEVER
THE VERY FAST STORM MOTION IS EXPECTED TO MITIGATE SIGNIFICANT
FLOODING CONCERNS.
THE PACIFIC TYPE COLD FRONT IS EXPECTED TO MOVE EAST THRU MOST OF
NORTH TX BY MIDNIGHT /06Z TUE/ MONDAY NIGHT. THE ATTENDANT SQUALL
LINE WILL LIKELY BE JUST EXITING THE FORECAST AREA AT THIS TIME
SO HAVE LINGERED HIGH POPS OVER THE FAR EASTERN CWA AFTER
MIDNIGHT. BY TUESDAY MORNING THERE IS SOME LOW END POTENTIAL FOR
LIGHT RAIN ASSOCIATED WITH MOISTURE WRAPPED AROUND THE UPPER
LOW...ESPECIALLY AS SOME RESIDUAL FRONTOGENETIC FORCING BUILDS
INTO THE NORTHERN CWA AS THE CANADIAN AIRMASS RESPONSIBLE FOR THE
BLIZZARD PORTION OF THIS SYSTEM /OVER THE SOUTHERN HIGH PLAINS/
MOVES SOUTH INTO NORTH TX. NO WINTRY PRECIPITATION IS EXPECTED AT
THIS TIME AS THERE WILL BE VERY LITTLE MOISTURE LEFT TO WORK WITH
AND TEMPERATURES WILL GENERALLY REMAIN ABOVE FREEZING EARLY
TUESDAY MORNING BEHIND THE FRONT.
EXTENDED...NO SIGNIFICANT CHANGES MADE TO THE EXTENDED AT THIS
TIME. KEPT THE LOW END RAIN CHANCES OVER THE SOUTHEASTERN PORTION
OF THE CWA ON THURSDAY AS ANOTHER SHORTWAVE TROUGH MOVES OVER
NORTH TX. THE 12Z ECMWF WAS THE MOST AGGRESSIVE WITH PRECIPITATION
BECAUSE IT BRINGS THE WAVE OVER NORTH TX THE FURTHEST NORTH AND
STRONGER THAN THE GFS ADVERTISES. EITHER WAY LIMITED MOISTURE WILL
PREVENT SIGNIFICANT COVERAGE OF RAIN OVER NORTH TX ON THURSDAY.
MAINTAINED A DRY FORECAST FOR THE HOLIDAY WEEKEND AS RUN TO RUN
AND MODEL TO MODEL CONSISTENCY EVEN ON LARGE SCALE FLOW REMAINS
POOR AT THIS TIME. GENERAL CONSENSUS IS THAT TEMPERATURES WILL BE
BELOW NORMAL...SO FOR NOW A COOL AND DRY HOLIDAY WEEKEND IS
EXPECTED.
CAVANAUGH
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 51 64 45 50 31 / 10 80 100 5 5
WACO, TX 52 67 44 53 28 / 10 70 100 5 5
PARIS, TX 44 63 47 54 30 / 10 50 100 10 10
DENTON, TX 52 61 43 46 27 / 10 90 100 10 5
MCKINNEY, TX 48 62 45 50 30 / 10 80 100 5 5
DALLAS, TX 51 64 46 50 31 / 10 80 100 5 5
TERRELL, TX 48 64 49 53 31 / 10 50 100 5 5
CORSICANA, TX 48 66 47 55 32 / 10 50 100 5 5
TEMPLE, TX 50 66 43 55 29 / 10 70 100 5 5
MINERAL WELLS, TX 53 64 39 46 25 / 20 100 80 10 5
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
58/30
AREA FORECAST DISCUSSION
NWS SPOKANE WA
323 PM PST Tue Dec 20 2011
.SYNOPSIS...A cold front will sweep through the inland northwest
from the north this evening. This system is not expected to carry
much snow, but it will bring decidedly cooler temperatures to the
region as well as improving ventilation conditions. An active
winter weather pattern is expected to continue through the holiday
weekend and into the first part of next week.
&&
.DISCUSSION...
Tonight...Satellite imagery indicates an upper level trough over
British Columbia dropping southeast towards Eastern Washington and
North Idaho. Instability in the mid levels of the atmosphere will
increase significantly this evening as 500mb temps fall to near
-36C and 850-500mb lapse rates increase to 7-8 C/KM. However
moisture is limited with this trough, and with 850mb winds of
15-25 knots out of the west to northwest significant down slope
flow off the higher terrain of Northern Washington and British
Columbia is likely. This should keep the best chances for snow
showers over the Cascades, Central Panhandle Mountains, Blue
Mountains, and Camas Prairie. Low level up slope flow into the
Palouse may also result in a brief light accumulation. An area of
lift from a passing vort max will also increase chances for snow
showers in these areas. The Camas Prairie looks to be the most
favored in this flow pattern but even here models only generate
one to two tenths of liquid precipitation so snow accumulations
were kept near 2 inches with no highlights needed at this time.
The cool and dry advection tonight with this trough will weaken
the inversion and will bring erosion of the stratus layer
especially over the northern valleys...and down the Okanogan
Valley into the western Columbia Basin. Patchy fog may form once
stratus clears but with the boundary layer drying out confidence
is not high so for now left mention of the forecast. JW
Wednesday through Friday...Through this portion of the forecast an
upper level low will pass out of the forecast area Wednesday morning,
then the weather will be dominated by a flat ridge of high
pressure through Thursday after. This will be followed by a
weakening/splitting weather disturbance Thursday night and Friday.
Challenges through this portion of the forecast will be the
probably of fog/stratus development with high pressure over the
region. Also, while model guidance all show a weakening frontal
system Thursday night the GFS/SREF show some weakening and a
slower solution than the NAM/EC/GEM. So far this season slower and
splitting weather systems have been the way and will lean in that
direction, what ever solution verifies confidence is not high
that there will be much snow.
Wednesday through Thursday northwest-north flow will keep some
snow showers over the southeast zones through about mid day
Wednesday, otherwise a dry and cool flow will result in a dry
forecast. The northerly flow and resultant cold air advection
should me enough to mix out the surface inversion and the
fog/stratus that has been going with it. There will most likely be
some regeneration of the fog along warmer water sources Thursday
morning, but expect this to be shallow and patchy. Temperatures
will cool by several degrees and be just on the cool side of normal.
Thursday night and Friday upper level moisture ahead of the
upstream weather system will move over the ridge. This should help
inhibit radiational cooling and keep the inversion from
strengthening any further. Model guidance is showing differing
solutions, but this trough passage is far from impressive. Some
isentropic ascent and upper level moisture is expected to track
through southern BC and will bring some light snow to the Cascade
crest and the northern mountains. Up-sloping will increase the
lift over the panhandle mountains, but with little moisture to
work with any snow accumulations will be very light. The following
cold front is almost non-existent at the surface but may be marginally
successful in keeping the boundary layer mixed. /Tobin
Fri Nt through Tues: Significant challenges still exist as a
result of major guidance timing disagreements beginning Christmas
eve and lasting through Tues. Consensus is to stay with the less
progressive somewhat drier ECMWF, which delays the cold front
passage the GFS has for Christmas day until Christmas night. Even
so, the ECMWF still begins to produce light stratiform snows along
a developing...or in-situ...warm frontal boundary bisecting Ern
Wa and N Id more or less west to east well in advance of its
offshore cold front that the GFS already has past Spokane by
midday Christmas. With Christmas five days out, its essential that
we trend in the direction of the most consistent guidance and try
to give the major population centers more attention. That said,
and based on the above mentioned guidance trends, it still looks
like Spokane will see some snow on Christmas. This will be
particularly true if the aforementioned stationary east-west
frontal boundary sets up farther south than expected. It is this
boundary that will be the primary source of isentropic lift that
will produce the initial snow on Christmas. Due to the quick approach
of the upper low, snow amnts should not be heavy. However, the
highest amnts will fall across Nrn Wa and the N Id Panhandle Christmas.
A note of significance: Once the upper low crosses the Cascades
Christmas night and crosses N Id Mon (assuming this timing is
correct), N Id (and especially the Mtns of N Id) will enter a very
favorable pattern for convective snows as the post frontal lapse
rates steepen and the flow veers to westerly and takes on a much
more favorable upslope component. This is a heavy snow pattern for
the mtns of N Id. Gusty winds still look possible Monday. bz
&&
.AVIATION...
18Z TAFs: Low stratus will continue to impact the majority of the
TAF sites this afternoon. The exception will be KPUW and KLWS where
a drier boundary layer from south-southeast winds should result in
VFR conditions persisting. A tough forecast in general for the
KGEG-KSFF-KCOE corridor as models indicate stratus hanging up in
this area with clearing to the south and stratus remaining locked in
to the north. Will rely on current trends and HRRR guidance for
this area. As winds switch to the southwest ahead of a cold front
late this afternoon and evening this will favor stratus advecting east
from the basin into the KGEG-KSFF-KCOE corridor as well as KPUW and
eventually KLWS. But then as drier advection moves in after 06z
behind the cold front should see some erosion of the stratus
especially KMWH/KEAT and probably KGEG and KSFF based on drying in
the boundary layer indicated by the NAM. Stratus will probably hang
in longer at KCOE/KPUW/KLWS with west-northwest winds favoring
stratus hanging up in these areas. A brief period of -SN may also
occur in these areas with the cold front especially KPUW.
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 22 28 16 26 19 30 / 20 0 0 0 0 20
Coeur d`Alene 21 29 15 29 15 33 / 20 0 0 0 0 30
Pullman 25 30 15 30 21 34 / 40 10 0 0 0 10
Lewiston 30 33 20 35 22 37 / 50 10 0 0 0 10
Colville 21 29 10 30 18 32 / 20 0 0 0 0 10
Sandpoint 22 29 11 29 16 31 / 30 10 0 0 0 30
Kellogg 24 29 18 30 21 32 / 70 10 10 0 0 30
Moses Lake 22 33 14 31 18 32 / 0 0 0 0 0 10
Wenatchee 24 33 17 33 24 33 / 0 0 0 0 0 10
Omak 19 29 9 29 18 31 / 10 0 0 0 0 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&
$$
AREA FORECAST DISCUSSION...UPDATED
NWS SPOKANE WA
316 PM PST Tue Dec 20 2011
.SYNOPSIS...A COLD FRONT WILL SWEEP THROUGH THE INLAND NORTHWEST FROM
THE NORTH LATE THIS AFTERNOON AND THIS EVENING. THIS SYSTEM IS NOT
EXPECTED TO CARRY MUCH SNOW, BUT IT WILL BRING DECIDEDLY COOLER
TEMPERATURES TO THE REGION AS WELL AS IMPROVING VENTILATION
CONDITIONS. AN ACTIVE WINTER WEATHER PATTERN IS EXPECTED TO
CONTINUE THROUGH THE HOLIDAY WEEKEND AND INTO THE FIRST PART OF
NEXT WEEK.
&&
.DISCUSSION...
Tonight...Satellite imagery indicates an upper level trough over
British Columbia dropping southeast towards Eastern Washington and
North Idaho. Instability in the mid levels of the atmosphere will
increase significantly this evening as 500mb temps fall to near
-36C and 850-500mb lapse rates increase to 7-8 C/KM. However
moisture is limited with this trough, and with 850mb winds of
15-25 knots out of the west to northwest significant down slope
flow off the higher terrain of Northern Washington and British
Columbia is likely. This should keep the best chances for snow
showers over the Cascades, Central Panhandle Mountains, Blue
Mountains, and Camas Prairie. Low level up slope flow into the
Palouse may also result in a brief light accumulation. An area of
lift from a passing vort max will also increase chances for snow
showers in these areas. The Camas Prairie looks to be the most
favored in this flow pattern but even here models only generate
one to two tenths of liquid precipitation so snow accumulations
were kept near 2 inches with no highlights needed at this time.
The cool and dry advection tonight with this trough will weaken
the inversion and will bring erosion of the stratus layer
especially over the northern valleys...and down the Okanogan
Valley into the western Columbia Basin. Patchy fog may form once
stratus clears but with the boundary layer drying out confidence
is not high so for now left mention of the forecast. JW
Wednesday through Friday...Through this portion of the forecast an
upper level low will pass out of the forecast area Wednesday morning,
then the weather will be dominated by a flat ridge of high
pressure through Thursday after. This will be followed by a
weakening/splitting weather disturbance Thursday night and Friday.
Challenges through this portion of the forecast will be the
probably of fog/stratus development with high pressure over the
region. Also, while model guidance all show a weakening frontal
system Thursday night the GFS/SREF show some weakening and a
slower solution than the NAM/EC/GEM. So far this season slower and
splitting weather systems have been the way and will lean in that
direction, what ever solution verifies confidence is not high
that there will be much snow.
Wednesday through Thursday northwest-north flow will keep some
snow showers over the southeast zones through about mid day
Wednesday, otherwise a dry and cool flow will result in a dry
forecast. The northerly flow and resultant cold air advection
should me enough to mix out the surface inversion and the
fog/stratus that has been going with it. There will most likely be
some regeneration of the fog along warmer water sources Thursday
morning, but expect this to be shallow and patchy. Temperatures
will cool by several degrees and be just on the cool side of normal.
Thursday night and Friday upper level moisture ahead of the
upstream weather system will move over the ridge. This should help
inhibit radiational cooling and keep the inversion from
strengthening any further. Model guidance is showing differing
solutions, but this trough passage is far from impressive. Some
isentropic ascent and upper level moisture is expected to track
through southern BC and will bring some light snow to the Cascade
crest and the northern mountains. Up-sloping will increase the
lift over the panhandle mountains, but with little moisture to
work with any snow accumulations will be very light. The following
cold front is almost non-existent at the surface but may be marginally
successful in keeping the boundary layer mixed. /Tobin
FRI NT THROUGH TUES: SIGNIFICANT CHALLENGES STILL EXIST AS A RESULT
OF MAJOR GUIDANCE TIMING DISAGREEMENTS BEGINNING CHRISTMAS EVE
AND LASTING THROUGH TUES. CONSENSUS IS TO STAY WITH THE LESS
PROGRESSIVE AND SOMEWHAT DRIER ECMWF, WHICH DELAYS THE COLD FRONT
PASSAGE THE GFS HAS FOR CHRISTMAS DAY UNTIL CHRISTMAS NIGHT. EVEN
SO, THE ECMWF STILL BEGINS TO PRODUCE LIGHT STRATIFORM SNOWS ALONG
A DEVELOPING...OR IN-SITU...WARM FRONTAL BOUNDARY BISECTING ERN WA
AND N ID MORE OR LESS WEST TO EAST WELL IN ADVANCE OF ITS OFFSHORE
COLD FRONT THAT THE GFS ALREADY HAS PAST SPOKANE BY MIDDAY
CHRISTMAS. WITH CHRISTMAS FIVE DAYS OUT, IT`S ESSENTIAL THAT WE
TREND IN THE DIRECTION OF THE MOST CONSISTANT GUIDANCE AND TRY TO
GIVE THE MAJOR POPULATION CENTERS MORE ATTENTION. THAT SAID, AND
BASED ON THE ABOVE MENTIONED GUIDANCE TRENDS, IT STILL LOOKS LIKE
SPOKANE WILL SEE SOME SNOW ON CHRISTMAS. THIS WILL BE ESPECIALLY
TRUE IF THE AFOREMENTIONED STATIONARY EAST-WEST FRONTAL BOUNDARY
SETS UP FARTHER SOUTH THAN EXPECTED. IT IS THIS BOUNDARY THAT WILL
BE THE PRIMARY SOURCE OF ISENTROPIC LIFT THAT WILL PRODUCE THE
INITIAL SNOW ON CHRISTMAS. DUE TO THE QUICK APPROACH OF THE UPPER
LOW, SNOW AMNTS SHOULDER NOT BE HEAVY. HOWEVER, THE HIGHEST AMNTS
WILL FALL ACROSS NRN WA AND N ID CHRISTMAS. A NOTE OF SIGNIFICANCE:
ONCE THE UPPER LOW CROSSES THE CASCADES CHRISTMAS NIGHT AND
CROSSES N ID MON (ASSUMING THIS TIMING IS CORRECT), N ID (AND
ESPECIALLY THE MTNS) WILL ENTER A VERY FAVORABLE PATTERN FOR
CONVECTIVE SNOWS AS THE POST FRONTAL LAPSE RATES STEEPEN AND THE
FLOW VEERS TO WESTERLY AND TAKES ON A MUCH MORE FAVORABLE UPSLOPE
COMPONENT. GUSTY WINDS STILL LOOK POSSIBLE INTO MONDAY.BZ
&&
.AVIATION...
18Z TAFs: Low stratus will continue to impact the majority of the
TAF sites this afternoon. The exception will be KPUW and KLWS where
a drier boundary layer from south-southeast winds should result in
VFR conditions persisting. A tough forecast in general for the
KGEG-KSFF-KCOE corridor as models indicate stratus hanging up in
this area with clearing to the south and stratus remaining locked in
to the north. Will rely on current trends and HRRR guidance for
this area. As winds switch to the southwest ahead of a cold front
late this afternoon and evening this will favor stratus advecting east
from the basin into the KGEG-KSFF-KCOE corridor as well as KPUW and
eventually KLWS. But then as drier advection moves in after 06z
behind the cold front should see some erosion of the stratus
especially KMWH/KEAT and probably KGEG and KSFF based on drying in
the boundary layer indicated by the NAM. Stratus will probably hang
in longer at KCOE/KPUW/KLWS with west-northwest winds favoring
stratus hanging up in these areas. A brief period of -SN may also
occur in these areas with the cold front especially KPUW.
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 22 28 16 26 19 30 / 20 0 0 0 0 20
Coeur d`Alene 21 29 15 29 15 33 / 20 0 0 0 0 30
Pullman 25 30 15 30 21 34 / 40 10 0 0 0 10
Lewiston 30 33 20 35 22 37 / 50 10 0 0 0 10
Colville 21 29 10 30 18 32 / 20 0 0 0 0 10
Sandpoint 22 29 11 29 16 31 / 30 10 0 0 0 30
Kellogg 24 29 18 30 21 32 / 70 10 10 0 0 30
Moses Lake 22 33 14 31 18 32 / 0 0 0 0 0 10
Wenatchee 24 33 17 33 24 33 / 0 0 0 0 0 10
Omak 19 29 9 29 18 31 / 10 0 0 0 0 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&
$$
AREA FORECAST DISCUSSION
NWS SPOKANE WA
314 PM PST Tue Dec 20 2011
.SYNOPSIS...A COLD FRONT WILL SWEEP THROUGH THE INLAND NORTHWEST FROM
THE NORTH LATE THIS AFTERNOON AND THIS EVENING. THIS SYSTEM IS NOT
EXPECTED TO CARRY MUCH SNOW, BUT IT WILL BRING DECIDEDLY COOLER
TEMPERATURES TO THE REGION AS WELL AS IMPROVING VENTILATION
CONDITIONS. AN ACTIVE WINTER WEATHER PATTERN IS EXPECTED TO
CONTINUE THROUGH THE HOLIDAY WEEKEND AND INTO THE FIRST PART OF
NEXT WEEK.
&&
.DISCUSSION...
Tonight...Satellite imagery indicates an upper level trough over
British Columbia dropping southeast towards Eastern Washington and
North Idaho. Instability in the mid levels of the atmosphere will
increase significantly this evening as 500mb temps fall to near
-36C and 850-500mb lapse rates increase to 7-8 C/KM. However
moisture is limited with this trough, and with 850mb winds of
15-25 knots out of the west to northwest significant down slope
flow off the higher terrain of Northern Washington and British
Columbia is likely. This should keep the best chances for snow
showers over the Cascades, Central Panhandle Mountains, Blue
Mountains, and Camas Prairie. Low level up slope flow into the
Palouse may also result in a brief light accumulation. An area of
lift from a passing vort max will also increase chances for snow
showers in these areas. The Camas Prairie looks to be the most
favored in this flow pattern but even here models only generate
one to two tenths of liquid precipitation so snow accumulations
were kept near 2 inches with no highlights needed at this time.
The cool and dry advection tonight with this trough will weaken
the inversion and will bring erosion of the stratus layer
especially over the northern valleys...and down the Okanogan
Valley into the western Columbia Basin. Patchy fog may form once
stratus clears but with the boundary layer drying out confidence
is not high so for now left mention of the forecast. JW
Wednesday through Friday...Through this portion of the forecast an
upper level low will pass out of the forecast area Wednesday morning,
then the weather will be dominated by a flat ridge of high
pressure through Thursday after. This will be followed by a
weakening/splitting weather disturbance Thursday night and Friday.
Challenges through this portion of the forecast will be the
probably of fog/stratus development with high pressure over the
region. Also, while model guidance all show a weakening frontal
system Thursday night the GFS/SREF show some weakening and a
slower solution than the NAM/EC/GEM. So far this season slower and
splitting weather systems have been the way and will lean in that
direction, what ever solution verifies confidence is not high
that there will be much snow.
Wednesday through Thursday northwest-north flow will keep some
snow showers over the southeast zones through about mid day
Wednesday, otherwise a dry and cool flow will result in a dry
forecast. The northerly flow and resultant cold air advection
should me enough to mix out the surface inversion and the
fog/stratus that has been going with it. There will most likely be
some regeneration of the fog along warmer water sources Thursday
morning, but expect this to be shallow and patchy. Temperatures
will cool by several degrees and be just on the cool side of normal.
Thursday night and Friday upper level moisture ahead of the
upstream weather system will move over the ridge. This should help
inhibit radiational cooling and keep the inversion from
strengthening any further. Model guidance is showing differing
solutions, but this trough passage is far from impressive. Some
isentropic ascent and upper level moisture is expected to track
through southern BC and will bring some light snow to the Cascade
crest and the northern mountains. Up-sloping will increase the
lift over the panhandle mountains, but with little moisture to
work with any snow accumulations will be very light. The following
cold front is almost non-existent at the surface but may be marginally
successful in keeping the boundary layer mixed. /Tobin
FRI NT THROUGH TUES: SIGNIFICANT CHALLENGES STILL EXIST AS A RESULT
OF MAJOR GUIDANCE TIMING DISAGREEMENTS BEGINNING CHRISTMAS EVE
AND LASTING THROUGH TUES. CONSENSUS IS TO STAY WITH THE LESS
PROGRESSIVE AND SOMEWHAT DRIER ECMWF, WHICH DELAYS THE COLD FRONT
PASSAGE THE GFS HAS FOR CHRISTMAS DAY UNTIL CHRISTMAS NIGHT. EVEN
SO, THE ECMWF STILL BEGINS TO PRODUCE LIGHT STRATIFORM SNOWS ALONG
A DEVELOPING...OR IN-SITU...WARM FRONTAL BOUNDARY BISECTING ERN WA
AND N ID MORE OR LESS WEST TO EAST WELL IN ADVANCE OF ITS OFFSHORE
COLD FRONT THAT THE GFS ALREADY HAS PAST SPOKANE BY MIDDAY
CHRISTMAS. WITH CHRISTMAS FIVE DAYS OUT, IT`S ESSENTIAL THAT WE
TREND IN THE DIRECTION OF THE MOST CONSISTANT GUIDANCE AND TRY TO
GIVE THE MAJOR POPULATION CENTERS MORE ATTENTION. THAT SAID, AND
BASED ON THE ABOVE MENTIONED GUIDANCE TRENDS, IT STILL LOOKS LIKE
SPOKANE WILL SEE SOME SNOW ON CHRISTMAS. THIS WILL BE ESPECIALLY
TRUE IF THE AFOREMENTIONED STATIONARY EAST-WEST FRONTAL BOUNDARY
SETS UP FARTHER SOUTH THAN EXPECTED. IT IS THIS BOUNDARY THAT WILL
BE THE PRIMARY SOURCE OF ISENTROPIC LIFT THAT WILL PRODUCE THE
INITIAL SNOW ON CHRISTMAS. DUE TO THE QUICK APPROACH OF THE UPPER
LOW, SNOW AMNTS SHOULDER NOT BE HEAVY. HOWEVER, THE HIGHEST AMNTS
WILL FALL ACROSS NRN WA AND N ID CHRISTMAS. A NOTE OF SIGNIFICANCE:
ONCE THE UPPER LOW CROSSES THE CASCADES CHRISTMAS NIGHT AND
CROSSES N ID MON (ASSUMING THIS TIMING IS CORRECT), N ID (AND
ESPECIALLY THE MTNS) WILL ENTER A VERY FAVORABLE PATTERN FOR
CONVECTIVE SNOWS AS THE POST FRONTAL LAPSE RATES STEEPEN AND THE
FLOW VEERS TO WESTERLY AND TAKES ON A MUCH MORE FAVORABLE UPSLOPE
COMPONENT. GUSTY WINDS STILL LOOK POSSIBLE INTO MONDAY.BZ
&&
.AVIATION...
18Z TAFs: Low stratus will continue to impact the majority of the
TAF sites this afternoon. The exception will be KPUW and KLWS where
a drier boundary layer from south-southeast winds should result in
VFR conditions persisting. A tough forecast in general for the
KGEG-KSFF-KCOE corridor as models indicate stratus hanging up in
this area with clearing to the south and stratus remaining locked in
to the north. Will rely on current trends and HRRR guidance for
this area. As winds switch to the southwest ahead of a cold front
late this afternoon and evening this will favor stratus advecting east
from the basin into the KGEG-KSFF-KCOE corridor as well as KPUW and
eventually KLWS. But then as drier advection moves in after 06z
behind the cold front should see some erosion of the stratus
especially KMWH/KEAT and probably KGEG and KSFF based on drying in
the boundary layer indicated by the NAM. Stratus will probably hang
in longer at KCOE/KPUW/KLWS with west-northwest winds favoring
stratus hanging up in these areas. A brief period of -SN may also
occur in these areas with the cold front especially KPUW.
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 22 28 16 26 19 30 / 20 0 0 0 0 20
Coeur d`Alene 21 29 15 29 15 33 / 20 0 0 0 0 30
Pullman 25 30 15 30 21 34 / 40 10 0 0 0 10
Lewiston 30 33 20 35 22 37 / 50 10 0 0 0 10
Colville 21 29 10 30 18 32 / 20 0 0 0 0 10
Sandpoint 22 29 11 29 16 31 / 30 10 0 0 0 30
Kellogg 24 29 18 30 21 32 / 70 10 10 0 0 30
Moses Lake 22 33 14 31 18 32 / 0 0 0 0 0 10
Wenatchee 24 33 17 33 24 33 / 0 0 0 0 0 10
Omak 19 29 9 29 18 31 / 10 0 0 0 0 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&
$$
AREA FORECAST DISCUSSION...CORRECTED
NWS SPOKANE WA
303 PM PST TUE DEC 20 2011
.SYNOPSIS...A COLD FRONT WILL SWEEP THROUGH THE INLAND NORTHWEST FROM
THE NORTH LATE THIS AFTERNOON AND THIS EVENING. THIS SYSTEM IS NOT
EXPECTED TO CARRY MUCH SNOW, BUT IT WILL BRING DECIDEDLY COOLER
TEMPERATURES TO THE REGION AS WELL AS IMPROVING VENTILATION
CONDITIONS. AN ACTIVE WINTER WEATHER PATTERN IS EXPECTED TO
CONTINUE THROUGH THE HOLIDAY WEEKEND AND INTO THE FIRST PART OF
NEXT WEEK.
&&
.DISCUSSION...
TONIGHT...SATELLITE IMAGERY INDICATES AN UPPER LEVEL TROUGH OVER
BRITISH COLUMBIA DROPPING SOUTHEAST TOWARDS EASTERN WASHINGTON AND
NORTH IDAHO. INSTABILITY IN THE MID LEVELS OF THE ATMOSPHERE WILL
INCREASE SIGNIFICANTLY THIS EVENING AS 500MB TEMPS FALL TO NEAR
-36C AND 850-500MB LAPSE RATES INCREASE TO 7-8 C/KM. HOWEVER
MOISTURE IS LIMITED WITH THIS TROUGH, AND WITH 850MB WINDS OF
15-25 KNOTS OUT OF THE WEST TO NORTHWEST SIGNIFICANT DOWN SLOPE
FLOW OFF THE HIGHER TERRAIN OF NORTHERN WASHINGTON AND BRITISH
COLUMBIA IS LIKELY. THIS SHOULD KEEP THE BEST CHANCES FOR SNOW
SHOWERS OVER THE CASCADES, CENTRAL PANHANDLE MOUNTAINS, BLUE
MOUNTAINS, AND CAMAS PRAIRIE. LOW LEVEL UP SLOPE FLOW INTO THE
PALOUSE MAY ALSO RESULT IN A BRIEF LIGHT ACCUMULATION. AN AREA OF
LIFT FROM A PASSING VORT MAX WILL ALSO INCREASE CHANCES FOR SNOW
SHOWERS IN THESE AREAS. THE CAMAS PRAIRIE LOOKS TO BE THE MOST
FAVORED IN THIS FLOW PATTERN BUT EVEN HERE MODELS ONLY GENERATE
ONE TO TWO TENTHS OF LIQUID PRECIPITATION SO SNOW ACCUMULATIONS
WERE KEPT NEAR 2 INCHES WITH NO HIGHLIGHTS NEEDED AT THIS TIME.
THE COOL AND DRY ADVECTION TONIGHT WITH THIS TROUGH WILL WEAKEN
THE INVERSION AND WILL BRING EROSION OF THE STRATUS LAYER
ESPECIALLY OVER THE NORTHERN VALLEYS...AND DOWN THE OKANOGAN
VALLEY INTO THE WESTERN COLUMBIA BASIN. PATCHY FOG MAY FORM ONCE
STRATUS CLEARS BUT WITH THE BOUNDARY LAYER DRYING OUT CONFIDENCE
IS NOT HIGH SO FOR NOW LEFT MENTION OF THE FORECAST. JW
WEDNESDAY THROUGH FRIDAY...THROUGH THIS PORTION OF THE FORECAST AN
UPPER LEVEL LOW WILL PASS OUT OF THE FORECAST AREA WEDNESDAY MORNING,
THEN THE WEATHER WILL BE DOMINATED BY A FLAT RIDGE OF HIGH
PRESSURE THROUGH THURSDAY AFTER. THIS WILL BE FOLLOWED BY A
WEAKENING/SPLITTING WEATHER DISTURBANCE THURSDAY NIGHT AND FRIDAY.
CHALLENGES THROUGH THIS PORTION OF THE FORECAST WILL BE THE
PROBABLY OF FOG/STRATUS DEVELOPMENT WITH HIGH PRESSURE OVER THE
REGION. ALSO, WHILE MODEL GUIDANCE ALL SHOW A WEAKENING FRONTAL
SYSTEM THURSDAY NIGHT THE GFS/SREF SHOW SOME WEAKENING AND A
SLOWER SOLUTION THAN THE NAM/EC/GEM. SO FAR THIS SEASON SLOWER AND
SPLITTING WEATHER SYSTEMS HAVE BEEN THE WAY AND WILL LEAN IN THAT
DIRECTION, WHAT EVER SOLUTION VERIFIES CONFIDENCE IS NOT HIGH
THAT THERE WILL BE MUCH SNOW.
WEDNESDAY THROUGH THURSDAY NORTHWEST-NORTH FLOW WILL KEEP SOME
SNOW SHOWERS OVER THE SOUTHEAST ZONES THROUGH ABOUT MID DAY
WEDNESDAY, OTHERWISE A DRY AND COOL FLOW WILL RESULT IN A DRY
FORECAST. THE NORTHERLY FLOW AND RESULTANT COLD AIR ADVECTION
SHOULD ME ENOUGH TO MIX OUT THE SURFACE INVERSION AND THE
FOG/STRATUS THAT HAS BEEN GOING WITH IT. THERE WILL MOST LIKELY BE
SOME REGENERATION OF THE FOG ALONG WARMER WATER SOURCES THURSDAY
MORNING, BUT EXPECT THIS TO BE SHALLOW AND PATCHY. TEMPERATURES
WILL COOL BY SEVERAL DEGREES AND BE JUST ON THE COOL SIDE OF NORMAL.
THURSDAY NIGHT AND FRIDAY UPPER LEVEL MOISTURE AHEAD OF THE
UPSTREAM WEATHER SYSTEM WILL MOVE OVER THE RIDGE. THIS SHOULD HELP
INHIBIT RADIATIONAL COOLING AND KEEP THE INVERSION FROM
STRENGTHENING ANY FURTHER. MODEL GUIDANCE IS SHOWING DIFFERING
SOLUTIONS, BUT THIS TROUGH PASSAGE IS FAR FROM IMPRESSIVE. SOME
ISENTROPIC ASCENT AND UPPER LEVEL MOISTURE IS EXPECTED TO TRACK
THROUGH SOUTHERN BC AND WILL BRING SOME LIGHT SNOW TO THE CASCADE
CREST AND THE NORTHERN MOUNTAINS. UP-SLOPING WILL INCREASE THE
LIFT OVER THE PANHANDLE MOUNTAINS, BUT WITH LITTLE MOISTURE TO
WORK WITH ANY SNOW ACCUMULATIONS WILL BE VERY LIGHT. THE FOLLOWING
COLD FRONT IS ALMOST NON-EXISTENT AT THE SURFACE BUT MAY BE MARGINALLY
SUCCESSFUL IN KEEPING THE BOUNDARY LAYER MIXED. /TOBIN
FRI NT THROUGH TUES: SIGNIFICANT CHALLENGES STILL EXIST AS A
RESULT OF MAJOR GUIDANCE TIMING DISAGREEMENTS BEGINNING CHRISTMAS
EVE AND LASTING THROUGH TUES. CONSENSUS IS TO STAY WITH THE LESS
PROGRESSIVE SOMEWHAT DRIER ECMWF, WHICH DELAYS THE COLD FRONT
PASSAGE THE GFS HAS FOR CHRISTMAS DAY UNTIL CHRISTMAS NIGHT. EVEN
SO, THE ECMWF STILL BEGINS TO PRODUCE LIGHT STRATIFORM SNOWS ALONG
A DEVELOPING...OR IN-SITU...WARM FRONTAL BOUNDARY BISECTING ERN
WA AND N ID MORE OR LESS WEST TO EAST WELL IN ADVANCE OF ITS
OFFSHORE COLD FRONT THAT THE GFS ALREADY HAS PAST SPOKANE BY
MIDDAY CHRISTMAS. WITH CHRISTMAS FIVE DAYS OUT, ITS ESSENTIAL THAT
WE TREND IN THE DIRECTION OF THE MOST CONSISTENT GUIDANCE AND TRY
TO GIVE THE MAJOR POPULATION CENTERS MORE ATTENTION. THAT SAID,
AND BASED ON THE ABOVE MENTIONED GUIDANCE TRENDS, IT STILL LOOKS
LIKE SPOKANE WILL SEE SOME SNOW ON CHRISTMAS. THIS WILL BE
PARTICULARLY TRUE IF THE AFOREMENTIONED STATIONARY EAST-WEST
FRONTAL BOUNDARY SETS UP FARTHER SOUTH THAN EXPECTED. IT IS THIS
BOUNDARY THAT WILL BE THE PRIMARY SOURCE OF ISENTROPIC LIFT THAT
WILL PRODUCE THE INITIAL SNOW ON CHRISTMAS. DUE TO THE QUICK APPROACH
OF THE UPPER LOW, SNOW AMNTS SHOULD NOT BE HEAVY. HOWEVER, THE
HIGHEST AMNTS WILL FALL ACROSS NRN WA AND THE N ID PANHANDLE CHRISTMAS.
A NOTE OF SIGNIFICANCE: ONCE THE UPPER LOW CROSSES THE CASCADES
CHRISTMAS NIGHT AND CROSSES N ID MON (ASSUMING THIS TIMING IS
CORRECT), N ID (AND ESPECIALLY THE MTNS OF N ID) WILL ENTER A VERY
FAVORABLE PATTERN FOR CONVECTIVE SNOWS AS THE POST FRONTAL LAPSE
RATES STEEPEN AND THE FLOW VEERS TO WESTERLY AND TAKES ON A MUCH
MORE FAVORABLE UPSLOPE COMPONENT. THIS IS A HEAVY SNOW PATTERN FOR
THE MTNS OF N ID. GUSTY WINDS STILL LOOK POSSIBLE MONDAY. BZ
&&
.AVIATION...
18Z TAFS: LOW STRATUS WILL CONTINUE TO IMPACT THE MAJORITY OF THE
TAF SITES THIS AFTERNOON. THE EXCEPTION WILL BE KPUW AND KLWS WHERE
A DRIER BOUNDARY LAYER FROM SOUTH-SOUTHEAST WINDS SHOULD RESULT IN
VFR CONDITIONS PERSISTING. A TOUGH FORECAST IN GENERAL FOR THE
KGEG-KSFF-KCOE CORRIDOR AS MODELS INDICATE STRATUS HANGING UP IN
THIS AREA WITH CLEARING TO THE SOUTH AND STRATUS REMAINING LOCKED IN
TO THE NORTH. WILL RELY ON CURRENT TRENDS AND HRRR GUIDANCE FOR
THIS AREA. AS WINDS SWITCH TO THE SOUTHWEST AHEAD OF A COLD FRONT
LATE THIS AFTERNOON AND EVENING THIS WILL FAVOR STRATUS ADVECTING EAST
FROM THE BASIN INTO THE KGEG-KSFF-KCOE CORRIDOR AS WELL AS KPUW AND
EVENTUALLY KLWS. BUT THEN AS DRIER ADVECTION MOVES IN AFTER 06Z
BEHIND THE COLD FRONT SHOULD SEE SOME EROSION OF THE STRATUS
ESPECIALLY KMWH/KEAT AND PROBABLY KGEG AND KSFF BASED ON DRYING IN
THE BOUNDARY LAYER INDICATED BY THE NAM. STRATUS WILL PROBABLY HANG
IN LONGER AT KCOE/KPUW/KLWS WITH WEST-NORTHWEST WINDS FAVORING
STRATUS HANGING UP IN THESE AREAS. A BRIEF PERIOD OF -SN MAY ALSO
OCCUR IN THESE AREAS WITH THE COLD FRONT ESPECIALLY KPUW.
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 22 28 16 26 19 30 / 20 0 0 0 0 20
COEUR D`ALENE 21 29 15 29 15 33 / 20 0 0 0 0 30
PULLMAN 25 30 15 30 21 34 / 40 10 0 0 0 10
LEWISTON 30 33 20 35 22 37 / 50 10 0 0 0 10
COLVILLE 21 29 10 30 18 32 / 20 0 0 0 0 10
SANDPOINT 22 29 11 29 16 31 / 30 10 0 0 0 30
KELLOGG 24 29 18 30 21 32 / 70 10 10 0 0 30
MOSES LAKE 22 33 14 31 18 32 / 0 0 0 0 0 10
WENATCHEE 24 33 17 33 24 33 / 0 0 0 0 0 10
OMAK 19 29 9 29 18 31 / 10 0 0 0 0 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
939 PM CST TUE DEC 20 2011
.UPDATE...
SATELLITE IMAGERY SHOWS A TIGHT CIRCULATION WITH THE MID LEVEL
CLOSED LOW AND VORTICITY CENTER MOVING THROUGH NORTHWEST
MISSOURI THIS EVENING. THIS GUY LIFTS NORTHEAST INTO LOWER
MICHIGAN AND BECOMES AND OPEN WAVE BY 18Z ON WEDNESDAY. AREA
RADARS ARE SHOWING A GRADUAL FILLING IN AS LIGHT/STEADY ISENTROPIC
ASCENT IS CAUSING A DEEPER LOW LEVEL SATURATION. THIS IS COUPLED
WITH THE INFLUENCE OF THE Q-VECTOR CONVERGENCE WITH THE
APPROACHING MID LEVEL SYSTEM. THE RUC SEEMS TO HAVE THE BEST
HANDLE ON TEMPS...KEEPING MUCH OF THE AREA JUST ABOVE THE FREEZING
MARK. TEMPS HAVE RISEN A FEW DEGREES THROUGH THE EVENING AS THE
MOISTURE MOVES IN. SO...GENERALLY LOOKING AT ALL LIQUID WITH THE
PRECIP OVERNIGHT. CAN/T RULE OUT SOME SPOTTING FREEZING
PRECIP...BUT NOT ENOUGH CONFIDENCE TO PUT IT IN ANYWHERE. WE/LL
KEEP AN EYE ON THE FAR NORTH/NORTHWEST WHERE TEMPS ARE CLOSER TO
FREEZING. BUT THE MAIN PRECIP AREA SHOULD STAY SOUTH OF THERE.
THINGS SHOULD BEGIN TO CLEAR FROM WEST TO EAST BY MID MORNING ON
WEDNESDAY.
&&
.AVIATION/06Z TAFS/...
EXPECTING WIDESPREAD IFR CONDITIONS FOR THE SOUTHEAST WISCONSIN
TAFS OVERNIGHT AND INTO WEDNESDAY MORNING...PROBABLY THROUGH
15-17Z WEDNESDAY. LIGHT PRECIPITATION SHOULD EXPAND THROUGH THE
EVENING AND CONTINUE OVERNIGHT AS A LOW PRESSURE SYSTEM PASSES
JUST TO THE SOUTH THROUGH WEDNESDAY MORNING. TEMPS LOOK LIKE THEY
WILL STAY JUST ABOVE FREEZING MOST AREAS...SO FREEZING PRECIP
ISN/T EXPECTED TO BE A PROBLEM. KMSN MAY NOT GET INTO THE IFR
CIGS...BUT WIDESPREAD MVFR CIGS/VSBYS EXPECTED THROUGH WEDNESDAY
MORNING.
&&
.PREV DISCUSSION... /ISSUED 325 PM CST TUE DEC 20 2011/
VERY SHORT TERM...TONIGHT AND WEDNESDAY.
BAND OF LIGHT RAIN/LIGHT SNOW SHOWERS CURRENTLY IN FAR NORTHERN
ILLINOIS SHOULD PUSH INTO THE FAR SOUTHERN COUNTIES THROUGH THE REST
OF THE AFTERNOON. ROCKFORD ASOS REPORTED A PERIOD OF RAIN AND SNOW
WITH THIS BAND...WITH RUC FORECAST SOUNDINGS IN THE AREA SHOWING WEB
BULB NEAR FREEZING. THIS AREA BEING DRIVEN BY LOW LEVEL WARM AIR
ADVECTION AND MID LEVEL FRONTOGENESIS RESPONSE. THIS AREA OF
PRECIPITATION BEING SLOWED IN ITS ADVANCE BY DRIER AIR PUSHING
SOUTHEAST INTO THE AREA.
LOCAL HIGH RESOLUTION MODELS NOT DOING A GOOD JOB WITH CAPTURING
THIS BAND. THINKING FOR THE REST OF THE AFTERNOON WOULD BE TO
MENTION LIGHT RAIN SHOWERS/SNOW SHOWERS IN THE FAR SOUTHERN
COUNTIES. WARM AIR ADVECTION SHIFTS EAST BY 00Z WEDNESDAY...SO THINK
THIS BAND WILL WEAKEN AND DISSIPATE BY THEN. WILL HAVE TO KEEP AN
EYE ON IT INTO THE EARLY EVENING...AS IT MAY AFFECT ROADS WITH A
DUSTING OF SNOW INTO THE EARLY EVENING IN THIS AREA.
ONCE THIS DISSIPATES BY EARLY EVENING...NEXT ISSUE WILL BE DRIZZLE
AND VERY LIGHT RAIN WITH PASSING UPPER LEVEL LOW TONIGHT AND EARLY
WEDNESDAY. WEAK LOW LEVEL FRONTOGENESIS RESPONSE CLIPS THE FAR
SOUTHERN AND SOUTHEASTERN COUNTIES THIS EVENING...EXITING THE
SOUTHEAST BY EARLY WEDNESDAY MORNING. UPPER LOW TRACKS NORTHEAST TO
FAR EASTERN IOWA BY 12Z WEDNESDAY...WITH DIFFERENTIAL CYCLONIC
VORTICITY ADVECTION INTO THE FORECAST AREA AHEAD OF IT.
AREA FORECAST SOUNDINGS SATURATE IN THE LOW LEVELS FROM SOUTHEAST TO
NORTHEAST ACROSS THE SOUTHERN PORTIONS OF THE FORECAST AREA THIS
EVENING...REMAINING SO INTO WEDNESDAY MORNING. SOUNDINGS SUPPORT
VERY LIGHT RAIN/DRIZZLE ACROSS THE SOUTHEAST AND FAR SOUTHERN
COUNTIES TONIGHT. POTENTIAL FOR LIGHT FREEZING DRIZZLE REMAINS IN
AREAS MAINLY SOUTH AND SOUTHWEST OF MADISON...WHERE TEMPERATURES ARE
EXPECTED TO DIP BELOW FREEZING.
PRECIPITATION SHOULD CLEAR THE FAR SOUTHEAST BY LATE WEDNESDAY
MORNING. DRIER AIR WORKING INTO THE LOW LEVELS SHOULD THEN BRING
QUIET WEATHER THROUGH THE AFTERNOON...WITH CLOUDS GRADUALLY MIXING
OUT FROM WEST TO EAST.
SHORT TERM...WEDNESDAY NIGHT THROUGH FRIDAY.
FOCUS OF THIS PERIOD ON INCREASING THREAT FOR LIGHT PRECIPITATION
WEDNESDAY NIGHT INTO THURSDAY. SHORT TERM GUIDANCE IN REASONABLE
AGREEMENT ON WEAK ISENTROPIC FORCING SPREADING ACROSS PORTIONS OF
SOUTH CENTRAL WI LATER WED NIGHT INTO THU. WEAK ISENTROPIC FORCING
ON 295 THETA SFC ENHANCED BY RIGHT ENTRANCE REGION OF 300H JET
MOVING TO THE EAST ACROSS THE NORTHERN GTLAKES. HENCE WL ADD LOW
CHANCE POPS ACROSS NRN CWA. BEST FORCING SLIDES TO THE EAST THU
MRNG. WL CONT SCHC WORDING AS WEAK ISENTROPIC OMEGA AND WEAK 700H
WAVE SLIDES ACROSS SRN WI.
LOW LEVEL FLOW TURNS TO THE NORTH THU NIGHT. LOW LEVEL WINDS REMAIN
MORE NORTHERLY ON NAM WHILE GFS MORE NORTHEAST. WITH DELTA-T AROUND
15C...GFS WOULD HINT AT POSSIBLY PERIOD OF -SHSN OVER LAKESHORE
COUNTIES THU EVE. INITIAL MOISTURE QUESTIONABLE...AND LOW LEVELS
GRADUALLY DRY OUT THU NIGHT...SO WEAK LAKE EFFECT THREAT DIMINISHES
AFT MIDNIGHT. FOR NOW...DUE TO UNCERTAINTY IN LOW LEVEL WINDS...WL
HAVE SCHC WORDING DURING THE EVE. COLDER AIR IN PLACE ON FRIDAY AS
HIGH PRESSURE RIDGING PASSES THROUGH SRN WI.
LONG TERM...FRIDAY NIGHT THROUGH TUESDAY.
UNCERTAINTIES APPEAR RIGHT AWAY IN THE EXTENDED PERIOD AS BOTH ECMWF
AND GFS HAVING DIFFICULTIES DETERMINING STRENGTH OF SPLIT FLOW
ACROSS CONUS AND WESTERLIES ACROSS UPPER MIDWEST. EXTENDED GUIDANCE
NOW TRENDING TOWARD STRONGER WEST TO NORTHWEST FLOW ACROSS NORTHERN
CONUS INCLUDING WRN GTLAKES FOR DURATION OF PERIOD...HENCE
INCREASING CONFIDENCE. GFS ENSEMBLE MEMBERS ALSO SHOWING BETTER
AGREEMENT FOR THIS PATTERN AS WELL. THIS SCENARIO RESULTS IN DEEP
MOISTURE REMAINING WELL SOUTH OF AREA...AVAILABLE TO TAP INTO FOR
MORE UNSETTLED FLOW ACROSS SRN CONUS.
WITH MOSTLY ZONAL TO WNW FLOW AND DEEP MOISTURE TO THE
SOUTH...EXTENDED PERIOD FOR SRN WI LOOKING FAIRLY QUIET WITH
TEMPERATURES AVERAGING OUT NEAR OR SLIGHTLY ABOVE NORMAL DUE TO LACK
OF SNOW COVER. BOTH ECMWF AND GFS INDICATE LONG WAVE TROUGH MOVING
THRU WRN GTLAKES LATE IN THE HOLIDAY WEEKEND. ECMWF INCLUDES A
STRONGER SHORT WAVE SLIDING SOUTHWARD AND DEEPENING IN LONG WAVE
TROUGH. MOISTURE WILL BE MINIMAL AND NEITHER GEM OR GFS SHOWING
THIS STRONGER FEATURE. MEDIUM RANGE ENSEMBLE POPS ALSO REMAIN LESS
THAN 10 PERCENT. HENCE WL CONTINUE DRY FORECAST FOR NOW THROUGH THE
HOLIDAY WEEKEND.
WL NEED TO KEEP ONE EYE ON DEVELOPING LOW PRESSURE OVER SOUTHEAST
CONUS XMAS EVE AS IT TRACKS NORTHEAST ON XMAS DAY...HOWEVER
PREDOMINANT WEST TO NORTHWEST FLOW OVER NORTHERN CONUS SHOULD KEEP
THIS SYSTEM WELL TO THE SOUTHEAST.
LONG WAVE TROUGH CONTINUES ITS TREK EWD LATE IN THE WEEKEND AND
EARLY MONDAY...WITH ZONAL FLOW RETURNING FOR THE FIRST PART OF THE
WEEK. GFS 5DAY 500H MEANS INDICATES THIS FLOW WL CONTINUE THROUGH
THE LAST DAYS OF THE YEAR WITH GRADUALLY LOWERING HEIGHTS. EXPECT
WEAK SHORT WAVES TRAVERSING WESTERLIES TO OCCASIONALLY THREATEN SRN
WI WITH LIGHT PRECIP DURING THIS PD.
AVIATION /00Z TAFS/...BAND OF LIGHT RAIN AND LIGHT SNOW SHOWERS
WILL AFFECT KENOSHA UNTIL AROUND 00Z WEDNESDAY. QUESTIONABLE IF IT
WILL MAKE IT TO MILWAUKEE...WAUKESHA AND MADISON WITH DRIER AIR TO
THE NORTH SLOWING ITS ADVANCE. FOR NOW...WILL MENTION VICINITY IN
TAFS BUT NOT PREVAILING. SOME MVFR CEILINGS AND VISIBILITIES
POSSIBLE IN THIS BAND...ALONG WITH A DUSTING OF SNOW ON RUNWAYS.
MVFR CEILINGS AND VISIBILITIES ARE EXPECTED TO SHIFT NORTHWARD TO
TAF SITES DURING THE EVENING. LIGHT DRIZZLE IS EXPECTED AT THE
EASTERN SITES BETWEEN 03Z TO 15Z WEDNESDAY...WITH LIGHT RAIN
POSSIBLE AT KENOSHA. PATCHY LIGHT FREEZING DRIZZLE IS POSSIBLE AT
MADISON BETWEEN 09Z AND 13Z WEDNESDAY...BUT WILL LEAVE OUT OF TAFS
FOR NOW DUE TO SOME UNCERTAINTY WITH HOW FAR NORTHWEST THE DRIZZLE
WILL REACH.
VFR CONDITIONS SHOULD RETURN BY 15Z TO 16Z WEDNESDAY ACROSS TAF
SITES...AND REMAIN THROUGH THE REST OF THE DAY. LIGHT SOUTH WINDS
TODAY WILL BECOME VARIABLE TONIGHT...THEN SOUTHWEST TO WEST BY
MIDDAY WEDNESDAY.
CONFIDENCE...
TONIGHT AND WEDNESDAY...MEDIUM.
WEDNESDAY NIGHT AND THURSDAY...LOW TO MEDIUM.
THURSDAY NIGHT AND FRIDAY...MEDIUM TO HIGH.
FRIDAY NIGHT THROUGH TUESDAY...MEDIUM.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&
$$
UPDATE...DAVIS
TONIGHT/WEDNESDAY AND AVIATION/MARINE...WOOD
WEDNESDAY NIGHT THROUGH TUESDAY...MBK
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
246 PM CST MON DEC 19 2011
.SHORT TERM...THROUGH WEDNESDAY NIGHT
246 PM CST MON DEC 19 2011
MAIN FORECAST CONCERN IS WITH THE PRECIPITATION CHANCES AND TYPES
TUESDAY AND TUESDAY NIGHT.
SURFACE ANALYSIS THIS AFTERNOON SHOWS A NEARLY STATIONARY FRONT
FROM LOWER MICHIGAN TO AN AREA OF LOW PRESSURE OVER EASTERN NEW
MEXICO. HIGH PRESSURE WAS CENTERED OVER THE WESTERN DAKOTAS AND
EASTERN MONTANA.
STRATUS CLOUDS HAVE COME IN BEHIND THE COLD FRONT AND COVERED
ALMOST THE ENTIRE AREA THIS AFTERNOON. VISIBLE SATELLITE DOES
SHOW QUITE A FEW HOLES IN THE CLOUD FIELD AND THE CLOUDS ALSO
APPEAR TO BE THINNING OUT. THE 19.12Z NAM BUFKIT SOUNDINGS WOULD
SUGGEST THE CLOUDS SHOULD SCATTER OUT THIS EVENING WHILE SEVERAL
RUNS NOW OF THE RUC DO NOT SCATTER THE CLOUDS OUT UNTIL THE
OVERNIGHT HOURS. HAVE TRIED TO BALANCE THESE MODEL TRENDS WITH THE
CURRENT SATELLITE TRENDS TO SHOW CLEARING THROUGH THE EVENING FOR
MOST OF THE AREA. THIS WILL ALSO HAVE A BIG IMPACT ON THE
TEMPERATURES. HAVE BUMPED THE TEMPERATURES UP SOME...ESPECIALLY
ACROSS THE NORTH WHERE THE CLOUDS MAY HOLD ON THE LONGEST...BUT IF
THEY CLEAR OUT EARLIER THAN EXPECTED...THESE WILL HAVE TO BE MOVED
DOWN.
THE STORM SYSTEM OVER THE SOUTHWEST WILL BE EJECTING NORTHEAST
TOWARD THE OHIO RIVER VALLEY AND EASTERN GREAT LAKES FOR TUESDAY
THROUGH WEDNESDAY. AFTER A NORTHWARD JOG IN THE TRACK OF THIS
SYSTEM WITH YESTERDAY/S MODELS...ALL THE 19.12Z MODELS HAVE
SETTLED BACK SOUTH WITH THE TRACK. IT ONCE AGAIN APPEARS THAT THE
SOUTHERN PARTS OF THE AREA WILL EITHER GET BRUSHED WITH THIS SYSTEM
OR IT WILL JUST MISS TO THE SOUTH. THE NAM AND GFS STILL SHOW
DECENT FORCING WITH THIS SYSTEM JUST GOING BY TO THE SOUTH.
BETWEEN 4 AND 8 PVU/S OF VORTICITY ADVECTION IN THE 500-300 MB
LAYER PASSES BY TUESDAY AFTERNOON AND NIGHT. THE BEST QG
CONVERGENCE IS EXPECTED TO MISS THE AREA WITH JUST SOME WEAK
CONVERGENCE IN THE 700-500 MB LAYER COMING THROUGH TUESDAY NIGHT.
STILL EXPECTING TO SEE SOME WEAK FRONTOGENESIS IN THE 850-500 MB
LAYER AS WELL. ONE THING THAT HAS NOT CHANGED IN THE MODELS...IS
WHETHER THERE WILL BE ICE PRESENT IN THE CLOUDS. BUFKIT SOUNDINGS
ACROSS THE FAR SOUTH CONTINUE TO SUGGEST CLOUD TOP TEMPERATURES
ONLY AROUND -10C WHICH COULD LEAD TO MORE LIQUID INSTEAD OF SNOW.
HAVE CONTINUED WITH THE MIX OF FREEZING RAIN/RAIN AND SNOW BUT
WITH ONLY LIGHT PRECIPITATION AMOUNTS ANTICIPATED...ANY SNOW OR
ICE ACCUMULATIONS WILL BE VERY LIGHT.
ONCE THIS SYSTEM GOES BY...A NORTHERN STREAM SHORT WAVE TROUGH
WILL MOVE ALONG THE CANADIAN BORDER WEDNESDAY NIGHT. THIS WAVE
WILL PUSH A COLD FRONT INTO THE AREA THAT COULD POSSIBLY PRODUCE
SOME LIGHT SNOW AND HAVE CONTINUED WITH THE LOW END SNOW CHANCES
ACROSS THE NORTH WITH THIS SYSTEM.
.LONG TERM...THURSDAY THROUGH MONDAY
246 PM CST MON DEC 19 2011
THE COLD FRONT WILL CONTINUE TO PUSH SOUTH ACROSS THE REMAINDER OF
THE AREA THURSDAY AND COULD STILL BE PRODUCING SOME LIGHT SNOW.
ADDED IN SOME LOW END SNOW CHANCES TO HANDLE THIS POSSIBILITY.
ONCE THIS SYSTEM GOES BY...THE REMAINDER OF THE PERIOD LOOKS TO BE
PRETTY QUIET. ANOTHER NORTHERN STREAM WAVE COULD BRUSH THE UPPER
MIDWEST CHRISTMAS DAY AND HAVE CONTINUED WITH THE LOW SNOW CHANCES
ACROSS THE NORTHERN PART OF THE FORECAST AREA AS THE BEST FORCING
WITH THIS WAVE LOOKS TO REMAIN TO THE NORTH OF THE AREA.
&&
.AVIATION...THROUGH 18Z TUESDAY
1141 AM CST MON DEC 19 2011
EXPANSIVE FIELD OF POST-FRONTAL MVFR STRATOCUMULUS IN PLACE ACROSS
THE REGION. LATEST MODELS INDICATE THIS CLOUDS COVER SHOULD BREAK
UP/SCATTER OUT AROUND 00Z AS A RIDGE OF HIGH PRESSURE SETTLES
OVERHEAD. LIGHT/VARIABLE WINDS OVERNIGHT AND RADIATIONAL COOLING
COMBINED WITH A SOMEWHAT MOIST LOWER BOUNDARY LAYER MAY LEAD TO
SOME 3-5SM BR AT THE KRST/KLSE TAF SITE IN THE 11-14Z TIME FRAME.
CIRRUS/HIGHER LEVEL ALTOCUMULUS SHIELD LOOKS TO MOVE INTO PORTIONS
OF NORTHEAST IA/FAR SOUTHWEST WISCONSIN THROUGH THE REMAINDER OF
TUESDAY...BUT REMAINING VFR AT KLSE/KRST.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
246 PM CST MON DEC 19 2011
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...04
LONG TERM...04
AVIATION...DAS
AREA FORECAST DISCUSSION...UPDATED
NWS MILWAUKEE/SULLIVAN WI
1159 AM CST MON DEC 19 2011
.UPDATE...MOSTLY CLEAR SKIES IN FAR SOUTH AND SOUTHEAST PARTS OF
CWA HAVE ALLOWED TEMPS TO RISE INTO THE 40S. SURFACE OBS SHOW
STEADY OR SLIGHTLY FALLING TEMPS UNDER STRATUS DECK GRADUALLY
ENTERING SOUTHERN WISCONSIN. EXPECT FURTHER WARMING TO BE OFFSET
BY COLD AIR ADVECTION IN WAKE OF EARLIER FROPA...AND GIVEN THE
TEMP TRENDS UPSTREAM...THINK TEMPS HAVE PEAKED IN THE
NORTHWEST...AND WILL PEAK AT MIDDAY SOUTH AND EAST.
&&
.AVIATION/18Z TAFS/...LARGE AREA OF STRATUS IS CURRENTLY PUSHING
SOUTHEAST THROUGH THE FORECAST AREA BEHIND THE EXITING COLD FRONT.
STRATUS SHOULD REACH ILLINOIS BORDER BY MID AFTERNOON...WITH
CLOUDS THEN LINGERING THROUGH AT LEAST EVENING. THE FLOW WILL TURN
ONSHORE LATER TODAY...WITH SFC TO 850 MB DELTA T VALUES INCREASING
TO AROUND 14C. THUS EXPECTING LOW CLOUDS TO STICK AROUND IN THE
EAST THROUGH THE NIGHT. FARTHER WEST...MODELS SHOWING SOME DRYING
IN THE LOW LEVELS...SO WENT BACK TO VFR AT MSN TOWARD MIDNIGHT.
STRATUS FIELD IS QUITE EXPANSIVE THOUGH...SO WILL HAVE TO WATCH
SATELLITE TRENDS. WOULD NOT BE SURPRISED IF CLOUDS HANG ON IN THE
WEST LONGER THAN CURRENTLY EXPECTED.
UNLESS THE STRATUS IS STILL LINGERING...SHOULD SEE MAINLY HIGH
CLOUDS TUESDAY LOWERING THROUGH THE AFTERNOON AS LOW PRESSURE
APPROACHES FROM THE SOUTHWEST. MAY SEE SOME LIGHT RAIN OR SNOW
APPROACH THE IL/WI BORDER BY EVENING...BUT MOST MODELS KEEP PRECIP
SOUTH OF THE BORDER UNTIL LATER IN THE EVENING OR OVERNIGHT.
&&
.PREV DISCUSSION... /ISSUED 327 AM CST MON DEC 19 2011/
TODAY AND TONIGHT...FORECAST CONFIDENCE MEDIUM TO HIGH.
MID/UPPER JET MAX ACROSS THE NORTHERN GREAT LAKES TAKES THE MID
LEVEL SHORTWAVE AND ASSOCIATED LOW NORTHEAST OF LAKE
SUPERIOR...OFF TO THE EAST THIS MORNING...WITH A WEAK MID LEVEL
TROUGH AXIS PUSHING DOWN ACROSS SOUTHERN WISCONSIN TONIGHT.
850MB THERMAL RIDGE WILL EXTEND ACROSS SOUTHERN WISCONSIN EARLY
THIS MORNING. RUC SOUNDINGS INDICATE THAT THE 4 THSD FT LOW CLOUD
SHIELD PUSHING NORTHEAST SHOULD ONLY BRIEFLY AFFECT MAINLY THE FAR
SOUTHEAST BEFORE HEADING OFF TO THE EAST. RUC AND NAM SATURATE THE
LOWER LEVELS LATER THIS MORNING ON THE RUC VERSUS THIS AFTERNOON
ON THE NAM. CURRENT TRENDS ON SATELLITE SUPPORT THE SLOWER NAM
WITH LOW CLOUDS FARTHER BEHIND THE COLD FRONT. NAM THEN DISSIPATES
THIS CLOUD LAYER WITH COLD AIR ADVECTION AND DRYING LATER TONIGHT.
HOWEVER MODELS TEND TO OVERDO THE DRYING SO WILL DELAY THE
CLEARING A LITTLE.
SHORT TERM...TUESDAY THROUGH WEDNESDAY NIGHT...FORECAST CONFIDENCE
MEDIUM.
NAM/CANADIAN AND GFS/ECMWF SHOWING DIFFERENT PATHS FOR THE SURFACE
LOW FOR TUESDAY INTO WEDNESDAY. THE NAM/CANADIAN SHOWS IT SHIFTING
FROM EAST CENTRAL OKLAHOMA TO SOUTHWEST MISSOURI TUESDAY...THEN TO
NORTH CENTRAL ILLINOIS TUESDAY NIGHT...THEN NORTHEAST INTO LAKE
HURON WEDNESDAY. THIS PATH BRINGS QPF INTO THE AREA TUESDAY
AFTERNOON AND EVENING...THEN ANOTHER SHOT ON WEDNESDAY.
GFS/ECMWF SHOWS THE LOW MOVING FROM EAST CENTRAL OKLAHOMA TO FAR
SOUTHERN MISSOURI TUESDAY...THEN TO NORTHERN INDIANA/NORTHWEST
OHIO TUESDAY NIGHT..BEFORE SHIFTING INTO THE NORTHEASTERN UNITED
STATES WEDNESDAY. THIS PATH BRINGS QPF INTO FAR SOUTHERN PORTIONS
OF THE AREA TUESDAY AFTERNOON...THEN TO THE SOUTHEAST HALF OF THE
AREA TUESDAY NIGHT. MOST QPF SHIFTS EAST ON WEDNESDAY.
ALL MODELS SHOWING WARM AIR ADVECTION TUESDAY AFTERNOON ACROSS THE
AREA...WITH IT CONTINUING TUESDAY NIGHT ON THE NAM/CANADIAN. THE
GFS/ECMWF KEEP THE WARM AIR ADVECTION MAINLY EAST OF THE AREA
TUESDAY NIGHT. MODELS ALSO BRING UPPER LOW TO EASTERN KANSAS
TUESDAY...THEN INTO NORTHERN ILLINOIS TUESDAY NIGHT...BEFORE
SHIFTING EAST WEDNESDAY.
AREA FORECAST SOUNDINGS ON THE NAM AND GFS INDICATED THAT ANY
PRECIPITATION ON TUESDAY WOULD BEGIN AS A LIGHT RAIN AND LIGHT
SNOW MIX...BEFORE THE ICE CRYSTAL INTRODUCTION IN THE SATURATED
PORTION OF THE AIR COLUMN DIMINISHES BY 00Z WEDNESDAY.
THEN...POTENTIAL FOR LIGHT FREEZING RAIN COMES INTO THE AREA AND
LASTS TUESDAY NIGHT...PERHAPS INTO EARLY WEDNESDAY. AREAS IN THE
FAR EAST MAY WARM ENOUGH TO BRING A MIX OF LIGHT FREEZING RAIN AND
LIGHT RAIN...OR ALL LIGHT RAIN. TUESDAY NIGHT INTO EARLY WEDNESDAY
MAY HAVE TO BE WATCHED FOR A FREEZING RAIN ADVISORY IF THESE
CONDITIONS LINGER IN THE MODELS IN SUBSEQUENT RUNS. SOME
UNCERTAINTY EXISTS...WITH BETTER SHOT BEING WITH THE STRONGER
SURFACE LOW IN THE NAM/CANADIAN MODELS THAN WEAKER LOW WITH THE
GFS/ECMWF.
NAM/CANADIAN SEEM TO SHOW AN ENHANCED AREA OF QPF ACROSS
SOUTHEASTERN SECTIONS OF THE AREA FOR THE 6 HOURS ENDING AT 18Z
WEDNESDAY. THIS SEEMS TO BE DRIVEN BY Q VECTOR CONVERGENCE.
GFS/ECMWF NOT SHOWING THIS...AND HAVE BEST LIFT EAST OF THE
REGION. AREA FORECAST SOUNDINGS SHOWING SUPPORT IN THE MORNING FOR
LIGHT FREEZING RAIN/LIGHT SNOW/LIGHT RAIN MIX IN THE WEST...WITH
MORE LIGHT RAIN IN THE FAR EAST WITH MILDER TEMPERATURES.
CONTINUED TO MENTION POPS IN THIS PERIOD...WITH SOME UNCERTAINTY
ON PRECIPITATION TYPES GIVEN THE MODEL DIFFERENCES. MILD
TEMPERATURES OVERALL CONTINUE FOR TUESDAY THROUGH WEDNESDAY.
QUIET WEATHER RETURNS FOR WEDNESDAY NIGHT...AHEAD OF ADVANCING
COLD FRONT. MILD TEMPERATURES ARE EXPECTED TO CONTINUE.
LONG TERM...THURSDAY THROUGH CHRISTMAS DAY...FORECAST CONFIDENCE
MEDIUM.
GFS/ECMWF BOTH SHOW A COLD FRONT SHIFTING SOUTHEAST THROUGH THE
REGION THURSDAY. ECMWF HINTING AT SOME LIGHT QPF WITH THIS
FEATURE...WITH THE GFS SHOWING LITTLE TO NONE. FOR NOW...LEANED
TOWARD THE CONSENSUS FORECAST AND LEFT LOW POPS FOR LIGHT SNOW
SHOWERS. MILD TEMPERATURES SHOULD LINGER.
MODELS THEN SHOW SIMILAR AND DIFFERENT TRENDS THURSDAY NIGHT
THROUGH CHRISTMAS DAY ACROSS THE REGION. THEY BOTH DO SHOW HIGH
PRESSURE PASSING TO THE NORTH OF THE REGION THURSDAY NIGHT AND
FRIDAY...WITH ITS RIDGE AXIS SHIFTING INTO THE AREA SATURDAY. THE
ECMWF TRIES TO KEEP AN INTACT SHORTWAVE TROUGH EXTENDING FROM THE
WESTERN GREAT LAKES TO THE CENTRAL AND SOUTHERN PLAINS STATES
FRIDAY. THE GFS KEEPS MORE OF A NORTHERN AND SOUTHERN STREAM
SEPARATELY...WITH AN UPPER LOW MOVING TOWARD THE AREA FRIDAY INTO
FRIDAY NIGHT.
THE GFS IS MUCH FURTHER SOUTH WITH THE BASE OF THE SHORTWAVE
TROUGH FRIDAY NIGHT. ANOTHER SHORTWAVE TROUGH THEN MOVES INTO THE
REGION FOR SATURDAY NIGHT INTO CHRISTMAS DAY. NOT MUCH QPF IN
MODELS WITH THIS FEATURE.
FOR NOW...WILL USE CONSENSUS APPROACH TO GRIDS GIVEN THE
DISAGREEMENT WITH FEATURES. THIS SHOULD KEEP THE FORECAST DRY FOR
NOW...WITH TEMPERATURES NEAR SEASONAL NORMALS.
AVIATION/12Z TAFS/...
THE WIND SHEAR POTENTIAL EARLY THIS MORNING ENDS AS THE 850MB JET
MAX OF 50 KNOTS PUSHES EAST INTO THE EASTERN GREAT LAKES.
THEN MAIN QUESTION IS STRATUS POTENTIAL. 4 THSD FT LOW CLOUDS MOVE
OFF WITH THE LOW LEVEL JET EARLY THIS MORNING. RUC AND NAM
SATURATE THE LOWER LEVELS LATER THIS MORNING ON THE RUC...WHICH
WOULD IMPLY IFR CIGS...VS THIS AFTERNOON ON THE NAM WHICH WOULD
MORE LIKELY BE MVFR CIGS. CURRENT TRENDS ON SATELLITE SUPPORT THE
SLOWER NAM WITH MVFR CIGS AFTER THE COLD FRONT. NAM SOUNDINGS THEN
DISSIPATES THE LOW LEVEL CLOUDS WITH COLD AIR ADVECTION AND DRYING
LATER TONIGHT. HOWEVER MODELS TEND TO OVERDO THE DRYING.
MARINE...
LOW PRESSURE NORTHEAST OF LAKE SUPERIOR WILL MOVE EAST. SMALL
CRAFT ADVISORY SOUTHWEST WINDS SHOULD DIMINISH THIS MORNING.
NORTH TO NORTHEAST WINDS MAY APPROACH SMALL CRAFT LEVELS THIS
AFTERNOON AND INTO THE EVENING BEHIND A TRAILING COLD FRONT. THIS
WILL HAVE TO BE WATCHED FOR ANOTHER POSSIBLE SMALL CRAFT ADVISORY.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&
$$
UPDATE...WIMBERLEY/DDV
TODAY/TONIGHT AND AVIATION/MARINE...HENTZ
TUESDAY THROUGH SUNDAY...WOOD
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
337 AM CST MON DEC 19 2011
.SHORT TERM...TODAY THROUGH WEDNESDAY
337 AM CST MON DEC 19 2011
MAIN FORECAST CONCERNS REMAIN ON STORM SYSTEM MOVING THROUGH THE
REGION TUESDAY AFTERNOON THROUGH EARLY WEDNESDAY...WITH THE
POTENTIAL FOR LIGHT FREEZING RAIN/SNOW.
CURRENT SURFACE OBSERVATIONS SHOWED A COLD FRONT EXTENDING FROM
EASTERN LAKE SUPERIOR...SOUTHWEST INTO NORTHEAST NEBRASKA...MOVING
SOUTHEAST TOWARD THE FORECAST AREA.
THE COLD FRONT WILL MOVE ACROSS THE AREA EARLY THIS MORNING WITH
STRATUS MOVING IN FROM NORTHWEST TO SOUTHEAST. LOOK FOR TEMPERATURES
TO FALL THROUGH THE DAY IN THE WAKE OF THE COLD FRONT...FROM THE MID
30S THIS MORNING TO THE MID TO UPPER 20S BY LATE THIS AFTERNOON. THE
NAM IS SHOWING SOME FRONTOGENESIS IN THE 850 THROUGH 700 MB LEVELS IN
THE 12 TO 15Z TIMEFRAME THIS MORNING. HOWEVER...THESE LEVEL ARE VERY
DRY WITH RH VALUES AROUND 50 PERCENT AT 12Z...FALLING TO AROUND 13
PERCENT BY 18Z. FORECAST SOUNDINGS ARE SHOWING THE CLOUD LAYER FROM
950-900 MB...WITH WEAK OMEGA THROUGH THIS LAYER. WILL HAVE TO WATCH
FOR FREEZING DRIZZLE POTENTIAL THIS MORNING. HAVE NOT SEEN ANY
VISIBILITY RESTRICTIONS OR LIGHT PRECIP REPORTS UPSTREAM THIS
MORNING AND THINKING THAT LIFT WILL BE TOO WEAK TO PRODUCE DRIZZLE.
NORTHWEST WINDS WILL INCREASE BEHIND THE FRONT TODAY. ACROSS THE
OPEN AREAS OF SOUTHEAST MINNESOTA AND NORTHEAST IOWA...LOOK FOR
WINDS TO INCREASE INTO THE 15 TO 25 MPH RANGE TODAY WITH GUSTS TO
AROUND 30 MPH POSSIBLE. RIDGE TOPS ACROSS WESTERN WISCONSIN MAY ALSO
SEE A FEW GUSTS IN THE 25 TO 30 MPH RANGE...OTHERWISE PLAN ON
NORTHWEST WINDS AT 10 TO 15 MPH ACROSS WESTERN WISCONSIN. WIND
CHILLS ARE EXPECTED TO FALL INTO THE TEENS THIS AFTERNOON. THE
STRATUS WILL LINGER ACROSS THE FORECAST AREA THROUGH EARLY EVENING
BEFORE SURFACE HIGH PRESSURE MOVES IN. PLAN ON GRADUALLY
DECREASING CLOUDS TONIGHT WITH LOWS FALLING INTO THE TEENS TO
LOWER 20S.
19.00 MODELS ARE IN AGREEMENT SHOWING A LOW PRESSURE SYSTEM MOVING
FROM SOUTHERN NEW MEXICO/TEXAS PAN HANDLE...NORTHEAST INTO THE
CENTRAL PLAINS. THE COLD FRONT THAT MOVES THROUGH THE REGION
TODAY...WILL PUSH SOUTH TONIGHT AND BECOME STATIONARY EXTENDING
FROM NORTHERN MISSOURI...EAST INTO THE OHIO RIVER VALLEY REGION.
THE FRONT WILL ACT AS A BAROCLINIC ZONE FOR THE LOW MOVING ACROSS
THE CENTRAL PLAINS. THE FRONT WILL LIFT NORTHWARD AS A WARM FRONT
LATE TONIGHT INTO TUESDAY AS THE LOW MOVES FROM
NEBRASKA...NORTHEAST INTO NORTHERN MISSOURI/SOUTHERN IOWA. THE
WARM FRONT IS EXPECTED TO MOVE INTO NORTHEAST IOWA/SOUTHERN
WISCONSIN TUESDAY AFTERNOON WITH A LIGHT RAIN/SNOW MIX SPREAD INTO
NORTHEAST IOWA AND FAR SOUTHWEST WISCONSIN. THE STRONGEST
ISENTROPIC LIFT ON THE 280 THROUGH 290 K SURFACES WILL BE FOCUSED
MAINLY ALONG AND SOUTH OF A WEST UNION TO BOSCOBEL WISCONSIN LINE
ON TUESDAY INTO TUESDAY NIGHT...SO THESE AREAS WILL HAVE THE BEST
CHANCE OF SEEING PRECIPITATION. FORECAST SOUNDINGS ARE SHOWING ICE
BEING LOST ALOFT LATE TUESDAY AFTERNOON INTO TUESDAY
EVENING...WITH RAIN/SNOW SWITCHING OVER TO LIGHT FREEZING RAIN AS
SURFACE TEMPERATURES COOL BELOW FREEZING. TWO WAVES OF POTENTIAL
VORTICITY ADVECTION OF 14 PVU/S LOOK TO MOVE ACROSS NORTHEAST IOWA
AND FAR SOUTHWEST WISCONSIN TUESDAY AFTERNOON AND AGAIN LATE
TUESDAY NIGHT. THE PRECIPITATION SHOULD REMAIN SOUTH OF INTERSTATE
90 THROUGH TUESDAY NIGHT. THERE IS THE POTENTIAL FOR A BRIEF
PERIOD OF SLEET ACROSS PORTIONS OF NORTHEAST IOWA AND FAR
SOUTHWEST WISCONSIN WHERE 19.00 FORECAST SOUNDINGS SHOW A WARM
LAYER PUSHING INTO THE AREA IN THE 09Z TO 12Z TIMEFRAME WITH MAX
TEMPERATURES ALOFT AROUND 3 DEGREES C. THE 19.06 NAM FORECAST
SOUNDINGS HAVE SHIFTED THE WARM LAYER SOUTH OF THIS AREA...SO ITS
LOOKING LIKE FREEZING RAIN WILL BE THE PRIMARY CONCERN THROUGH
TUESDAY NIGHT INTO EARLY WEDNESDAY MORNING. THE LOW IS EXPECTED TO
LIFT INTO SOUTHERN LOWER MICHIGAN BY LATE WEDNESDAY MORNING. LIGHT
RAIN/SNOW MAY LINGER ACROSS FAR SOUTHWEST WISCONSIN INTO THE LATE
MORNING HOURS. CLOUDS WILL BE ON THE DECREASE WEDNESDAY AFTERNOON
AS THE SYSTEM EXITS THE REGION. LOOK FOR HIGH TEMPERATURES TO
RANGE FROM THE LOWER 30S ACROSS NORTH CENTRAL WISCONSIN TO THE MID
30S ACROSS NORTHEAST IOWA.
.LONG TERM...THURSDAY THROUGH SUNDAY
337 AM CST MON DEC 19 2011
19.00 MODELS ARE GENERATING SOME LIGHT SNOW ACROSS NORTHWEST
SECTIONS OF THE FORECAST AREA ON WEDNESDAY NIGHT AS A WEAK FRONTAL
BOUNDARY MOVES THROUGH. THE NAM AND ECMWF ALONG WITH FORECAST
SOUNDINGS SUPPORT SATURATION AND WEAK LIFT ACROSS SOUTHEAST
MINNESOTA THROUGH NORTH CENTRAL WISCONSIN. HAVE ADDED A SLIGHT
CHANCE OF PRECIPITATION TO THESE AREAS. WILL HAVE TO KEEP A CLOSE
WATCH ON THE NEXT FEW MODEL RUNS...WITH THE POTENTIAL TO EXPAND
PRECIPITATION CHANCES TO THE SOUTHEAST ON THURSDAY. THE NEXT
SYSTEM IS EXPECTED TO APPROACH THE REGION LATE FRIDAY INTO
SATURDAY...THE MODELS ARE SHOWING DIFFERING SOLUTIONS. THE GFS
BRINGS AN UPPER LOW FROM THE CENTRAL ROCKIES THURSDAY NIGHT...INTO
NORTHERN MISSOURI AND NORTHERN ILLINOIS FRIDAY NIGHT INTO EARLY
SATURDAY. THE ECMWF TAKES THE TROUGH ACROSS THE SOUTHERN PLAINS
AND INTO THE APPALACHIANS. WILL HAVE TO CLOSELY MONITOR THE NEXT
FEW MODEL RUNS...THIS WILL BE OUR LAST REAL SHOT OF SEEING SNOW
FOR THE WEEKEND. FOR FRIDAY THROUGH SUNDAY...PLAN ON HIGHS IN THE
MID 20S TO LOWER 30S...WITH LOWS IN THE TEENS TO AROUND 20. AN
UPPER TROUGH IS EXPECTED TO MOVE ACROSS NORTHERN WISCONSIN ON
SUNDAY BRINGING A SLIGHT CHANCE OF SNOW TO LOCATIONS ACROSS NORTH
CENTRAL WISCONSIN.
&&
.AVIATION...THROUGH 06Z TUESDAY
1123 PM CST SUN DEC 18 2011
THE MAIN FOCUS CONTINUES TO BE ON THE COLD FRONT PASSAGE TIMING
AND WHEN THE LOW STRATUS DECK GETS INTO THE TAF REGION.
CURRENTLY...THIS COLD FRONT EXTENDS FROM JUST SOUTH OF LAKE
SUPERIOR DOWN TO SIOUX FALLS SOUTH DAKOTA. THIS STRATUS DECK IS
LAGGING BEHIND THE FRONTAL PASSAGE AND IS MAINLY MVFR BETWEEN 1KFT
TO 2KFT THOUGH A FEW OBS HAVE BEEN REPORTING 800FT CEILINGS. BASED
ON THESE TRENDS AND 19.03Z RUC SOUNDINGS FROM LSE/RST...HAVE
BACKED OUT OF THE IFR CEILING FORECAST AND BROUGHT THEM UP TO LOW
END MVFR TOWARD 10/11Z. WITH A LITTLE DEEPER MIXING AS THE DAY
PROGRESSES...WOULD EXPECT THESE CEILINGS TO GRADUALLY CLIMB THOUGH
STAY MVFR. WHEN/IF SKIES CLEAR OUT IS THE NEXT QUESTIONS WITH MUCH
OF THE FORECAST GUIDANCE SUGGESTING THAT THE CLOUDS WILL CLEAR BY
MID AFTERNOON. THIS MAY BE QUITE OPTIMISTIC THOUGH WITH A SHALLOW
INVERSION HOLDING ON INTO TOMORROW NIGHT. THUS...HAVE KEPT CIGS
AROUND THROUGH THE REST OF THE FORECAST PERIOD BUT ENDED THE
HIGHER GUSTS BY DUSK.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
337 AM CST MON DEC 19 2011
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...WETENKAMP
LONG TERM....WETENKAMP
AVIATION.....HALBACH
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
327 AM CST MON DEC 19 2011
.TODAY AND TONIGHT...FORECAST CONFIDENCE MEDIUM TO HIGH.
MID/UPPER JET MAX ACROSS THE NORTHERN GREAT LAKES TAKES THE MID
LEVEL SHORTWAVE AND ASSOCIATED LOW NORTHEAST OF LAKE
SUPERIOR...OFF TO THE EAST THIS MORNING...WITH A WEAK MID LEVEL
TROUGH AXIS PUSHING DOWN ACROSS SOUTHERN WISCONSIN TONIGHT.
850MB THERMAL RIDGE WILL EXTEND ACROSS SOUTHERN WISCONSIN EARLY
THIS MORNING. RUC SOUNDINGS INDICATE THAT THE 4 THSD FT LOW CLOUD
SHIELD PUSHING NORTHEAST SHOULD ONLY BRIEFLY AFFECT MAINLY THE FAR
SOUTHEAST BEFORE HEADING OFF TO THE EAST. RUC AND NAM SATURATE THE
LOWER LEVELS LATER THIS MORNING ON THE RUC VERSUS THIS AFTERNOON
ON THE NAM. CURRENT TRENDS ON SATELLITE SUPPORT THE SLOWER NAM
WITH LOW CLOUDS FARTHER BEHIND THE COLD FRONT. NAM THEN DISSIPATES
THIS CLOUD LAYER WITH COLD AIR ADVECTION AND DRYING LATER TONIGHT.
HOWEVER MODELS TEND TO OVERDO THE DRYING SO WILL DELAY THE
CLEARING A LITTLE.
.SHORT TERM...TUESDAY THROUGH WEDNESDAY NIGHT...FORECAST CONFIDENCE
MEDIUM.
NAM/CANADIAN AND GFS/ECMWF SHOWING DIFFERENT PATHS FOR THE SURFACE
LOW FOR TUESDAY INTO WEDNESDAY. THE NAM/CANADIAN SHOWS IT SHIFTING
FROM EAST CENTRAL OKLAHOMA TO SOUTHWEST MISSOURI TUESDAY...THEN TO
NORTH CENTRAL ILLINOIS TUESDAY NIGHT...THEN NORTHEAST INTO LAKE
HURON WEDNESDAY. THIS PATH BRINGS QPF INTO THE AREA TUESDAY
AFTERNOON AND EVENING...THEN ANOTHER SHOT ON WEDNESDAY.
GFS/ECMWF SHOWS THE LOW MOVING FROM EAST CENTRAL OKLAHOMA TO FAR
SOUTHERN MISSOURI TUESDAY...THEN TO NORTHERN INDIANA/NORTHWEST
OHIO TUESDAY NIGHT..BEFORE SHIFTING INTO THE NORTHEASTERN UNITED
STATES WEDNESDAY. THIS PATH BRINGS QPF INTO FAR SOUTHERN PORTIONS
OF THE AREA TUESDAY AFTERNOON...THEN TO THE SOUTHEAST HALF OF THE
AREA TUESDAY NIGHT. MOST QPF SHIFTS EAST ON WEDNESDAY.
ALL MODELS SHOWING WARM AIR ADVECTION TUESDAY AFTERNOON ACROSS THE
AREA...WITH IT CONTINUING TUESDAY NIGHT ON THE NAM/CANADIAN. THE
GFS/ECMWF KEEP THE WARM AIR ADVECTION MAINLY EAST OF THE AREA
TUESDAY NIGHT. MODELS ALSO BRING UPPER LOW TO EASTERN KANSAS
TUESDAY...THEN INTO NORTHERN ILLINOIS TUESDAY NIGHT...BEFORE
SHIFTING EAST WEDNESDAY.
AREA FORECAST SOUNDINGS ON THE NAM AND GFS INDICATED THAT ANY
PRECIPITATION ON TUESDAY WOULD BEGIN AS A LIGHT RAIN AND LIGHT
SNOW MIX...BEFORE THE ICE CRYSTAL INTRODUCTION IN THE SATURATED
PORTION OF THE AIR COLUMN DIMINISHES BY 00Z WEDNESDAY.
THEN...POTENTIAL FOR LIGHT FREEZING RAIN COMES INTO THE AREA AND
LASTS TUESDAY NIGHT...PERHAPS INTO EARLY WEDNESDAY. AREAS IN THE
FAR EAST MAY WARM ENOUGH TO BRING A MIX OF LIGHT FREEZING RAIN AND
LIGHT RAIN...OR ALL LIGHT RAIN. TUESDAY NIGHT INTO EARLY WEDNESDAY
MAY HAVE TO BE WATCHED FOR A FREEZING RAIN ADVISORY IF THESE
CONDITIONS LINGER IN THE MODELS IN SUBSEQUENT RUNS. SOME
UNCERTAINTY EXISTS...WITH BETTER SHOT BEING WITH THE STRONGER
SURFACE LOW IN THE NAM/CANADIAN MODELS THAN WEAKER LOW WITH THE
GFS/ECMWF.
NAM/CANADIAN SEEM TO SHOW AN ENHANCED AREA OF QPF ACROSS
SOUTHEASTERN SECTIONS OF THE AREA FOR THE 6 HOURS ENDING AT 18Z
WEDNESDAY. THIS SEEMS TO BE DRIVEN BY Q VECTOR CONVERGENCE.
GFS/ECMWF NOT SHOWING THIS...AND HAVE BEST LIFT EAST OF THE
REGION. AREA FORECAST SOUNDINGS SHOWING SUPPORT IN THE MORNING FOR
LIGHT FREEZING RAIN/LIGHT SNOW/LIGHT RAIN MIX IN THE WEST...WITH
MORE LIGHT RAIN IN THE FAR EAST WITH MILDER TEMPERATURES.
CONTINUED TO MENTION POPS IN THIS PERIOD...WITH SOME UNCERTAINTY
ON PRECIPITATION TYPES GIVEN THE MODEL DIFFERENCES. MILD
TEMPERATURES OVERALL CONTINUE FOR TUESDAY THROUGH WEDNESDAY.
QUIET WEATHER RETURNS FOR WEDNESDAY NIGHT...AHEAD OF ADVANCING
COLD FRONT. MILD TEMPERATURES ARE EXPECTED TO CONTINUE.
.LONG TERM...THURSDAY THROUGH CHRISTMAS DAY...FORECAST CONFIDENCE
MEDIUM.
GFS/ECMWF BOTH SHOW A COLD FRONT SHIFTING SOUTHEAST THROUGH THE
REGION THURSDAY. ECMWF HINTING AT SOME LIGHT QPF WITH THIS
FEATURE...WITH THE GFS SHOWING LITTLE TO NONE. FOR NOW...LEANED
TOWARD THE CONSENSUS FORECAST AND LEFT LOW POPS FOR LIGHT SNOW
SHOWERS. MILD TEMPERATURES SHOULD LINGER.
MODELS THEN SHOW SIMILAR AND DIFFERENT TRENDS THURSDAY NIGHT
THROUGH CHRISTMAS DAY ACROSS THE REGION. THEY BOTH DO SHOW HIGH
PRESSURE PASSING TO THE NORTH OF THE REGION THURSDAY NIGHT AND
FRIDAY...WITH ITS RIDGE AXIS SHIFTING INTO THE AREA SATURDAY. THE
ECMWF TRIES TO KEEP AN INTACT SHORTWAVE TROUGH EXTENDING FROM THE
WESTERN GREAT LAKES TO THE CENTRAL AND SOUTHERN PLAINS STATES
FRIDAY. THE GFS KEEPS MORE OF A NORTHERN AND SOUTHERN STREAM
SEPARATELY...WITH AN UPPER LOW MOVING TOWARD THE AREA FRIDAY INTO
FRIDAY NIGHT.
THE GFS IS MUCH FURTHER SOUTH WITH THE BASE OF THE SHORTWAVE
TROUGH FRIDAY NIGHT. ANOTHER SHORTWAVE TROUGH THEN MOVES INTO THE
REGION FOR SATURDAY NIGHT INTO CHRISTMAS DAY. NOT MUCH QPF IN
MODELS WITH THIS FEATURE.
FOR NOW...WILL USE CONSENSUS APPROACH TO GRIDS GIVEN THE
DISAGREEMENT WITH FEATURES. THIS SHOULD KEEP THE FORECAST DRY FOR
NOW...WITH TEMPERATURES NEAR SEASONAL NORMALS.
&&
.AVIATION/12Z TAFS/...
THE WIND SHEAR POTENTIAL EARLY THIS MORNING ENDS AS THE 850MB JET
MAX OF 50 KNOTS PUSHES EAST INTO THE EASTERN GREAT LAKES.
THEN MAIN QUESTION IS STRATUS POTENTIAL. 4 THSD FT LOW CLOUDS MOVE
OFF WITH THE LOW LEVEL JET EARLY THIS MORNING. RUC AND NAM
SATURATE THE LOWER LEVELS LATER THIS MORNING ON THE RUC...WHICH
WOULD IMPLY IFR CIGS...VS THIS AFTERNOON ON THE NAM WHICH WOULD
MORE LIKELY BE MVFR CIGS. CURRENT TRENDS ON SATELLITE SUPPORT THE
SLOWER NAM WITH MVFR CIGS AFTER THE COLD FRONT. NAM SOUNDINGS THEN
DISSIPATES THE LOW LEVEL CLOUDS WITH COLD AIR ADVECTION AND DRYING
LATER TONIGHT. HOWEVER MODELS TEND TO OVERDO THE DRYING.
&&
.MARINE...
LOW PRESSURE NORTHEAST OF LAKE SUPERIOR WILL MOVE EAST. SMALL
CRAFT ADVISORY SOUTHWEST WINDS SHOULD DIMINISH THIS MORNING.
NORTH TO NORTHEAST WINDS MAY APPROACH SMALL CRAFT LEVELS THIS
AFTERNOON AND INTO THE EVENING BEHIND A TRAILING COLD FRONT. THIS
WILL HAVE TO BE WATCHED FOR ANOTHER POSSIBLE SMALL CRAFT ADVISORY.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 8 AM CST THIS MORNING FOR LMZ643>646.
&&
$$
TODAY/TONIGHT AND AVIATION/MARINE...HENTZ
TUESDAY THROUGH SUNDAY...WOOD
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1123 PM CST SUN DEC 18 2011
.SHORT TERM...THROUGH TUESDAY NIGHT
227 PM CST SUN DEC 18 2011
MAIN FORECAST CONCERN IS WITH THE PRECIPITATION CHANCES AND TYPES
TUESDAY AND TUESDAY NIGHT.
SURFACE ANALYSIS THIS AFTERNOON SHOWS AN AREA OF LOW PRESSURE OVER
SOUTHWEST ONTARIO WITH A COLD FRONT EXTENDING SOUTHWEST THROUGH
NORTH DAKOTA.
THE COLD FRONT WILL SLIDE ACROSS THE REGION OVERNIGHT. AS IT
DOES...THE 18.12Z NAM AND 18.18Z RUC SUGGEST THERE WILL BE A
RIBBON OF LOW LEVEL MOISTURE BEHIND THE FRONT THAT SHOULD BE
SUFFICIENT TO ALLOW SATURATION TO OCCUR. THIS SHOULD RESULT IN A
BAND OF STRATUS CLOUDS DEVELOPING ACROSS THE REGION AND HAVE
RAISED THE CLOUD COVER TO HANDLE THIS. OBSERVATIONS ACROSS
SASKATCHEWAN AND MANITOBA DO INDICATE THE EXISTENCE OF THIS
STRATUS ALREADY. THE NAM BUFKIT SOUNDINGS INDICATE SOME VERTICAL
MOTION THROUGH THIS SATURATED LAYER SUGGESTING THE POTENTIAL FOR
SOME DRIZZLE. HOWEVER...THE RUC DOES NOT SHOW THIS AND WILL LEAVE
OUT THE MENTION OF ANY DRIZZLE.
THE FRONT WILL BECOME STATIONARY SOUTH OF THE AREA MONDAY NIGHT AS
THE UPPER LEVEL LOW OVER THE SOUTHWEST STARTS TO EJECT OUT TO THE
NORTHEAST. AS THIS SYSTEM COMES OUT...BOTH THE NAM AND GFS BRING
BETWEEN 4 AND 8 PVU/S OF VORTICITY ADVECTION IN THE 500-300 MB
LAYER ACROSS THE SOUTHERN PARTS OF THE FORECAST AREA TUESDAY AND
TUESDAY NIGHT. THIS IS EXPECTED TO RESULT IN WEAK TO MODERATE QG
CONVERGENCE OCCURRING ACROSS THE FAR SOUTHERN PARTS OF THE
FORECAST AREA. THERE SHOULD ALSO BE SOME WEAK FRONTOGENESIS IN THE
850-500 MB LAYER OF THE SAME AREA. THERE IS ENOUGH OF A CONSENSUS
IN ALL THE MODELS TO BRING THE PRECIPITATION CHANCES TO ABOUT THE
INTERSTATE 90 CORRIDOR TUESDAY AFTERNOON AND NIGHT. BUFKIT
SOUNDINGS FROM BOTH THE NAM AND GFS SUGGEST THERE MAY NOT BE A LOT
OF ICE PRESENT IN THE CLOUDS AS THIS SYSTEM COMES THROUGH. THE
SOUNDINGS SUGGEST CLOUD TOP TEMPERATURES MAY BE IN THE -10 TO -12C
RANGE AND THERE COULD ALSO BE A BIT OF A WARM LAYER ALOFT AT TIMES
AS WELL. HAVE THUS ADDED IN SOME PROBABILITIES OF FREEZING RAIN
AND WILL HAVE A MIXTURE OF RAIN...SNOW AND FREEZING RAIN. ACTUAL
PRECIPITATION AMOUNTS SHOULD BE VERY LIGHT AND ANY SNOW OR ICE
ACCUMULATIONS THAT OCCUR SHOULD NOT AMOUNT TO MUCH.
.LONG TERM...WEDNESDAY THROUGH SUNDAY
227 PM CST SUN DEC 18 2011
AS THE SYSTEM PULLS AWAY FROM THE AREA WEDNESDAY...THERE COULD
STILL BE A LITTLE BIT OF LINGERING PRECIPITATION ACROSS THE FAR
SOUTHEASTERN PARTS OF THE FORECAST AREA. THE NEXT NORTHERN STREAM
SHORT WAVE TROUGH IS EXPECTED TO COME ACROSS THE UPPER MIDWEST
WEDNESDAY NIGHT AND THURSDAY. MODELS HAVE BEEN INCONSISTENT ON
WHETHER THIS WILL BE ENOUGH TO PRODUCE SOME LIGHT SNOW AS THE WEAK
COLD FRONT COMES THROUGH. FOR NOW...WILL STAY WITH THE CURRENT
MODEL CONSENSUS GRIDS SHOWING THE SNOW CHANCES FARTHER NORTH
CLOSER TO THE SHORT WAVE TROUGH...BUT COULD SEE LATER FORECASTS
ADDING IN SOME SNOW CHANCES FOR THIS SYSTEM. ANOTHER WAVE WILL BE
DROPPING INTO THE UPPER MIDWEST NEXT SUNDAY AND WILL HAVE SOME
SMALL SNOW CHANCES ACROSS THE NORTH WITH THIS SYSTEM.
&&
.AVIATION...THROUGH 06Z TUESDAY
1123 PM CST SUN DEC 18 2011
THE MAIN FOCUS CONTINUES TO BE ON THE COLD FRONT PASSAGE TIMING
AND WHEN THE LOW STRATUS DECK GETS INTO THE TAF REGION.
CURRENTLY...THIS COLD FRONT EXTENDS FROM JUST SOUTH OF LAKE
SUPERIOR DOWN TO SIOUX FALLS SOUTH DAKOTA. THIS STRATUS DECK IS
LAGGING BEHIND THE FRONTAL PASSAGE AND IS MAINLY MVFR BETWEEN 1KFT
TO 2KFT THOUGH A FEW OBS HAVE BEEN REPORTING 800FT CEILINGS. BASED
ON THESE TRENDS AND 19.03Z RUC SOUNDINGS FROM LSE/RST...HAVE
BACKED OUT OF THE IFR CEILING FORECAST AND BROUGHT THEM UP TO LOW
END MVFR TOWARD 10/11Z. WITH A LITTLE DEEPER MIXING AS THE DAY
PROGRESSES...WOULD EXPECT THESE CEILINGS TO GRADUALLY CLIMB THOUGH
STAY MVFR. WHEN/IF SKIES CLEAR OUT IS THE NEXT QUESTIONS WITH MUCH
OF THE FORECAST GUIDANCE SUGGESTING THAT THE CLOUDS WILL CLEAR BY
MID AFTERNOON. THIS MAY BE QUITE OPTIMISTIC THOUGH WITH A SHALLOW
INVERSION HOLDING ON INTO TOMORROW NIGHT. THUS...HAVE KEPT CIGS
AROUND THROUGH THE REST OF THE FORECAST PERIOD BUT ENDED THE
HIGHER GUSTS BY DUSK.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
227 PM CST SUN DEC 18 2011
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...04
LONG TERM...04
AVIATION...HALBACH
AREA FORECAST DISCUSSION
NWS CHEYENNE WY
910 AM MST MON DEC 19 2011
.UPDATE...DURING THE PAST HOUR...HAVE RECEIVED NUMEROUS REPORTS OF
VEHICLE ROLLOVERS IN PLATTE AND GOSHEN COUNTIES DUE TO BLACK ICE
FROM FREEZING DRIZZLE AND FOG. FOG HAS BEEN LOCALLY DENSE WITH
VISIBILITIES REDUCED TO A QUARTER MILE OR LESS FROM CHEYENNE NORTH
THROUGH WHEATLAND AND BORDEAUX. THE WINTER WEATHER ADVISORY WAS
ISSUED AT 851 AM AND REMAINS IN EFFECT UNTIL NOON FOR LARAMIE...
GOSHEN...PLATTE AND EASTERN ALBANY COUNTIES.
&&
.PREV DISCUSSION... /ISSUED 416 AM MST MON DEC 19 2011/
AVIATION...12Z TAFS
STRATUS CONTINUES TO MAKE ITS WAY SOUTH ACROSS THE NORTHERN
NEBRASKA PANHANDLE THIS MORNING. AM SEEING THE BACK EDGE THOUGH ON
STRATUS SATELLITE IMAGERY APPROACHING THE NORTHERN PANHANDLE...SO
KEPT CHADRON MVFR LATEST HRRR FORECAST LOOKS PRETTY GOOD ON TIMING
OF IFR/LIFR ONSET FOR AIRPORTS ALONG AND EAST OF THE LARAMIE RANGE
AND CONTINUE FOLLOWING ITS GUIDANCE. FOR KLAR AND KRWL...BELIEVE
THESE TWO AIRPORTS WILL COME DOWN IN LIGHT SNOW LATER THIS
MORNING. EVENTUALLY...BY MID AFTERNOON...AM EXPECTING STRATUS TO
BREAK UP AS WINDS SHIFT WESTERLY.
CLAYCOMB
PREV DISCUSSION... /ISSUED 250 AM MST MON DEC 19 2011/
SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT.
TODAY...COLD FRONT QUICKLY PASSED SOUTHWARD ACROSS OUR COUNTIES
EARLIER TONIGHT WITH DECENT COLD AIR ADVECTION ONGOING WITH 2-4 MB 3
HOURLY PRESSURE RISES IN THE WAKE OF THE COLD FRONT. AS INPUT BY DAY
SHIFT FORECAST...WILL MAINTAIN PATCHY FREEZING DRIZZLE ACROSS OUR
PANHANDLE COUNTIES SOUTH OF SCOTTSBLUFF TO ALLIANCE AS THE
ATMOSPHERE SUGGEST FAVORABLE CONDITIONS. LOW AND MID LEVELS WILL
CONTINUE TO SATURATE THIS MORNING AND WITH FAVORABLE NORTHEAST TO
EAST UPSLOPE...AND DYNAMICS FROM PASSING SHORTWAVE TROUGH
ALOFT...WILL INCLUDE 60 TO 100 PERCENT POPS FOR SNOW THIS MORNING
ALONG AND JUST EAST OF THE LARAMIE RANGE WITH LESSER POPS FURTHER
EAST AND WEST DUE TO DRY AIR AT LOW LEVELS AND DOWNSLOPING EAST
WINDS WEST OF THE MOUNTAINS AND SNOW SHADOW EFFECTS. AREAS OF FOG
DEVELOP AS THE TEMPERATURE AND DEWPOINT SPREADS NARROW. SNOWFALL
ACCUMULATIONS LESS THAN 2 INCHES DUE TO PROGRESSIVE NATURE OF THE
SYSTEM AND LIMITED QPF. CHANCES FOR SNOW DECREASE SIGNIFICANTLY THIS
AFTERNOON...THOUGH REMAIN HIGH ACROSS THE SOUTHERN LARAMIE RANGE DUE
TO PERSISTENT EASTERLY UPSLOPE. MUCH COLDER THAN SUNDAY WITH CLOUDS
AND IN THE COLD AIRMASS BEHIND THE FRONT.
TONIGHT...DECREASING CLOUDS AND LIGHT WINDS WILL MAKE FOR A CHILLY
NIGHT WITH COLDEST CONDITIONS ACROSS THE LARAMIE VALLEY. WEAK LEE
TROUGHING DEVELOPS BUT SHOULD NOT HAVE MUCH EFFECT ON LOW
TEMPERATURES.
TUESDAY...SLOW WARMING TREND IN BETWEEN SYSTEMS. WITH SOME SUNSHINE
AND SURFACE LEE TROUGHING INDUCING DOWNSLOPE WARMING...WILL SEE HIGH
TEMPERATURES IN THE 20S WEST AND 30S EAST.
TUESDAY NIGHT...NOT AS COLD AS MONDAY NIGHT AS MID AND HIGH CLOUDS
INCREASE IN ADVANCE OF THE NEXT STRONGER SHORTWAVE TROUGH ALOFT
APPROACHING FROM IDAHO AND WESTERN MONTANA.
WEDNESDAY...RATHER IMPRESSIVE SHORTWAVE TROUGH ALOFT CONTINUES TO
DIG ACROSS IDAHO AND WESTERN WYOMING SENDING ANOTHER COLD FRONT
ACROSS OUR COUNTIES IN THE AFTERNOON. THE NAM SHOWS A DEEPLY
SATURATED LAYER DEVELOPING IN THE AFTERNOON ACROSS OUR COUNTIES IN
THE WAKE OF THE COLD FRONT WHILE THE GFS IS SLOWER IN THE
EVOLVEMENT. NAM TENDS TO DO BETTER IN THESE SITUATIONS AND THUS WILL
FOLLOW ITS SOLUTION BRINGING CHANCE OF SNOW ACROSS ALL OUR COUNTIES
IN THE AFTERNOON...WITH 50 TO 100 PERCENT POPS NORTH OF A RAWLINS TO
CHADRON LINE WITH DEEPLY SATURATED AIRMASS LIFTED BY DYNAMICS AND
OROGRAPHICS.
WEDNESDAY NIGHT...SHORTWAVE TROUGH ALOFT MOVES ACROSS WESTERN
COLORADO WITH DYNAMICS AND OROGRAPHICS PROVIDING THE LIFT OF OUR
SATURATED AIRMASS TO PRODUCE FAIRLY WIDESPREAD LIGHT SNOW OVER OUR
COUNTIES...WITH MOST COVERAGE OVER THE FAVORED UPSLOPE LOCATIONS
NEAR THE SOUTHERN LARAMIE RANGE OF WESTERN LARAMIE COUNTY.
LONG TERM...THURSDAY THROUGH MONDAY
19/00Z ECMWF AND GFS MODEL RUNS IN VERY GOOD AGREEMENT ON TRACK OF
LOW OVER UTAH THURSDAY MORNING POSITIONING OF PRECIPITATION OVER
WYOMING. GFS MORE BULLISH ON QPFS WITH EC MORE CONSERVATIVE. AM
BECOMING A LITTLE CONCERNED THOUGH WITH ACCUMULATING SNOWFALL AS
THIS TRACK IS A FAVORABLE PATTERN FOR US TO SEE SIGNIFICANT
SNOWFALL. LATER SHIFTS WILL NEED TO WATCH TO SEE IF THE LOW SLOWS
DOWN OR SHIFTS SLIGHTLY NORTH OF ITS CURRENT FORECAST TRACK.
LATEST TRACK ON BOTH THE GFS AND ECMWF HAS THE LOW TRACKING FROM
CENTRAL UTAH INTO SOUTHERN COLORADO AND FINALLY INTO NORTHERN NEW
MEXICO THURSDAY AFTERNOON. FOR NOW...HAVE SNOW ACCUMULATIONS OF 3
TO 5 INCHES FROM WEDNESDAY NIGHT THROUGH THURSDAY FOR MUCH OF THE
CWA WITH 10 TO 14 INCHES IN THE SNOWY AND SIERRA MADRE RANGES.
SNOW COMES TO AN END THURSDAY AFTERNOON WITH RIDGING MOVING INTO
THE AREA FROM THE NORTH. WESTERLY WINDS RETURN FRIDAY WITH 700MB
TEMPERATURES INCREASING FROM -14C THURSDAY AFTERNOON TO AROUND -6C
FRIDAY AFTERNOON. TEMPERATURES WILL BE TRICKY FRIDAY AND DEPENDS A
LOT ON RESIDING SNOW FROM THURSDAYS STORM. KEPT TEMPERATURES FAIRLY
COOL WITH LOW 30S FOR HIGHS EAST OF THE LARAMIE RANGE AND LOW 20S WEST.
LOOKS LIKE ANOTHER WEAK SHORTWAVE AND SURFACE COLD FRONT TO TRACK
THROUGH SOUTHEAST WYOMING SATURDAY. 700MB WINDS REALLY INCREASE
WITH THIS SYSTEM WITH GFS FORECASTING WINDS OF 50+ KT FRIDAY
AFTERNOON INTO SATURDAY MORNING. 700MB CRAIG TO CASPER HGT
GRADIENT AROUND 60 METERS AS WELL ON THE GFS DURING THAT TIME. DID
GO AHEAD AND INCREASE WIND SPEEDS FROM THURSDAY NIGHT THROUGH
FRIDAY NIGHT WITH THIS SYSTEM AND LATER SHIFTS WILL NEED TO WATCH
FOR WIND HIGHLIGHTS...ESPECIALLY FOR OUR WIND PRONE AREAS. WILL
ADD HIGH WIND POTENTIAL IN THIS MORNINGS HWO AS WELL.
PRETTY COLD WEEKEND AS 700MB TEMPERATURES FALL BACK DOWN TO -14 TO
-18C. LOOKING PROBABLY AT SINGLE DIGIT LOWS AND HIGHS STRUGGLING
TO GET ABOVE FREEZING. COULD BE COLDER DEPENDING ON ANY EXISTING
SNOW PACK FROM THURSDAYS STORM AS WELL.
FIRE WEATHER...
NO FIRE WEATHER CONCERNS. HIGHER MINIMUM AFTERNOON
RELATIVE HUMIDITIES TODAY IN THE WAKE OF THE COLD FRONT.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER WEATHER ADVISORY UNTIL NOON MONDAY FOR WYZ106-WYZ107-
WYZ108-WYZ117-WYZ118-WYZ119.
NE...NONE.
&&
$$
SHORT TERM/FIRE WEATHER...RUBIN
LONG TERM/AVIATION...CLAYCOMB
UPDATE...JAMSKI
AREA FORECAST DISCUSSION
NWS CHEYENNE WY
416 AM MST MON DEC 19 2011
.AVIATION...12Z TAFS
STRATUS CONTINUES TO MAKE ITS WAY SOUTH ACROSS THE NORTHERN
NEBRASKA PANHANDLE THIS MORNING. AM SEEING THE BACK EDGE THOUGH ON
STRATUS SATELLITE IMAGERY APPROACHING THE NORTHERN PANHANDLE...SO
KEPT CHADRON MVFR LATEST HRRR FORECAST LOOKS PRETTY GOOD ON TIMING
OF IFR/LIFR ONSET FOR AIRPORTS ALONG AND EAST OF THE LARAMIE RANGE
AND CONTINUE FOLLOWING ITS GUIDANCE. FOR KLAR AND KRWL...BELIEVE
THESE TWO AIRPORTS WILL COME DOWN IN LIGHT SNOW LATER THIS
MORNING. EVENTUALLY...BY MID AFTERNOON...AM EXPECTING STRATUS TO
BREAK UP AS WINDS SHIFT WESTERLY.
CLAYCOMB
&&
.PREV DISCUSSION... /ISSUED 250 AM MST MON DEC 19 2011/
SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT.
TODAY...COLD FRONT QUICKLY PASSED SOUTHWARD ACROSS OUR COUNTIES
EARLIER TONIGHT WITH DECENT COLD AIR ADVECTION ONGOING WITH 2-4 MB 3
HOURLY PRESSURE RISES IN THE WAKE OF THE COLD FRONT. AS INPUT BY DAY
SHIFT FORECAST...WILL MAINTAIN PATCHY FREEZING DRIZZLE ACROSS OUR
PANHANDLE COUNTIES SOUTH OF SCOTTSBLUFF TO ALLIANCE AS THE
ATMOSPHERE SUGGEST FAVORABLE CONDITIONS. LOW AND MID LEVELS WILL
CONTINUE TO SATURATE THIS MORNING AND WITH FAVORABLE NORTHEAST TO
EAST UPSLOPE...AND DYNAMICS FROM PASSING SHORTWAVE TROUGH
ALOFT...WILL INCLUDE 60 TO 100 PERCENT POPS FOR SNOW THIS MORNING
ALONG AND JUST EAST OF THE LARAMIE RANGE WITH LESSER POPS FURTHER
EAST AND WEST DUE TO DRY AIR AT LOW LEVELS AND DOWNSLOPING EAST
WINDS WEST OF THE MOUNTAINS AND SNOW SHADOW EFFECTS. AREAS OF FOG
DEVELOP AS THE TEMPERATURE AND DEWPOINT SPREADS NARROW. SNOWFALL
ACCUMULATIONS LESS THAN 2 INCHES DUE TO PROGRESSIVE NATURE OF THE
SYSTEM AND LIMITED QPF. CHANCES FOR SNOW DECREASE SIGNIFICANTLY THIS
AFTERNOON...THOUGH REMAIN HIGH ACROSS THE SOUTHERN LARAMIE RANGE DUE
TO PERSISTENT EASTERLY UPSLOPE. MUCH COLDER THAN SUNDAY WITH CLOUDS
AND IN THE COLD AIRMASS BEHIND THE FRONT.
TONIGHT...DECREASING CLOUDS AND LIGHT WINDS WILL MAKE FOR A CHILLY
NIGHT WITH COLDEST CONDITIONS ACROSS THE LARAMIE VALLEY. WEAK LEE
TROUGHING DEVELOPS BUT SHOULD NOT HAVE MUCH EFFECT ON LOW
TEMPERATURES.
TUESDAY...SLOW WARMING TREND IN BETWEEN SYSTEMS. WITH SOME SUNSHINE
AND SURFACE LEE TROUGHING INDUCING DOWNSLOPE WARMING...WILL SEE HIGH
TEMPERATURES IN THE 20S WEST AND 30S EAST.
TUESDAY NIGHT...NOT AS COLD AS MONDAY NIGHT AS MID AND HIGH CLOUDS
INCREASE IN ADVANCE OF THE NEXT STRONGER SHORTWAVE TROUGH ALOFT
APPROACHING FROM IDAHO AND WESTERN MONTANA.
WEDNESDAY...RATHER IMPRESSIVE SHORTWAVE TROUGH ALOFT CONTINUES TO
DIG ACROSS IDAHO AND WESTERN WYOMING SENDING ANOTHER COLD FRONT
ACROSS OUR COUNTIES IN THE AFTERNOON. THE NAM SHOWS A DEEPLY
SATURATED LAYER DEVELOPING IN THE AFTERNOON ACROSS OUR COUNTIES IN
THE WAKE OF THE COLD FRONT WHILE THE GFS IS SLOWER IN THE
EVOLVEMENT. NAM TENDS TO DO BETTER IN THESE SITUATIONS AND THUS WILL
FOLLOW ITS SOLUTION BRINGING CHANCE OF SNOW ACROSS ALL OUR COUNTIES
IN THE AFTERNOON...WITH 50 TO 100 PERCENT POPS NORTH OF A RAWLINS TO
CHADRON LINE WITH DEEPLY SATURATED AIRMASS LIFTED BY DYNAMICS AND
OROGRAPHICS.
WEDNESDAY NIGHT...SHORTWAVE TROUGH ALOFT MOVES ACROSS WESTERN
COLORADO WITH DYNAMICS AND OROGRAPHICS PROVIDING THE LIFT OF OUR
SATURATED AIRMASS TO PRODUCE FAIRLY WIDESPREAD LIGHT SNOW OVER OUR
COUNTIES...WITH MOST COVERAGE OVER THE FAVORED UPSLOPE LOCATIONS
NEAR THE SOUTHERN LARAMIE RANGE OF WESTERN LARAMIE COUNTY.
LONG TERM...THURSDAY THROUGH MONDAY
19/00Z ECMWF AND GFS MODEL RUNS IN VERY GOOD AGREEMENT ON TRACK OF
LOW OVER UTAH THURSDAY MORNING POSITIONING OF PRECIPITATION OVER
WYOMING. GFS MORE BULLISH ON QPFS WITH EC MORE CONSERVATIVE. AM
BECOMING A LITTLE CONCERNED THOUGH WITH ACCUMULATING SNOWFALL AS
THIS TRACK IS A FAVORABLE PATTERN FOR US TO SEE SIGNIFICANT
SNOWFALL. LATER SHIFTS WILL NEED TO WATCH TO SEE IF THE LOW SLOWS
DOWN OR SHIFTS SLIGHTLY NORTH OF ITS CURRENT FORECAST TRACK.
LATEST TRACK ON BOTH THE GFS AND ECMWF HAS THE LOW TRACKING FROM
CENTRAL UTAH INTO SOUTHERN COLORADO AND FINALLY INTO NORTHERN NEW
MEXICO THURSDAY AFTERNOON. FOR NOW...HAVE SNOW ACCUMULATIONS OF 3
TO 5 INCHES FROM WEDNESDAY NIGHT THROUGH THURSDAY FOR MUCH OF THE
CWA WITH 10 TO 14 INCHES IN THE SNOWY AND SIERRA MADRE RANGES.
SNOW COMES TO AN END THURSDAY AFTERNOON WITH RIDGING MOVING INTO
THE AREA FROM THE NORTH. WESTERLY WINDS RETURN FRIDAY WITH 700MB
TEMPERATURES INCREASING FROM -14C THURSDAY AFTERNOON TO AROUND -6C
FRIDAY AFTERNOON. TEMPERATURES WILL BE TRICKY FRIDAY AND DEPENDS A
LOT ON RESIDING SNOW FROM THURSDAYS STORM. KEPT TEMPERATURES FAIRLY
COOL WITH LOW 30S FOR HIGHS EAST OF THE LARAMIE RANGE AND LOW 20S WEST.
LOOKS LIKE ANOTHER WEAK SHORTWAVE AND SURFACE COLD FRONT TO TRACK
THROUGH SOUTHEAST WYOMING SATURDAY. 700MB WINDS REALLY INCREASE
WITH THIS SYSTEM WITH GFS FORECASTING WINDS OF 50+KTS FRIDAY
AFTERNOON INTO SATURDAY MORNING. 700MB CRAIG TO CASPER HGT
GRADIENT AROUND 60 METERS AS WELL ON THE GFS DURING THAT TIME. DID
GO AHEAD AND INCREASE WIND SPEEDS FROM THURSDAY NIGHT THROUGH
FRIDAY NIGHT WITH THIS SYSTEM AND LATER SHIFTS WILL NEED TO WATCH
FOR WIND HIGHLIGHTS...ESPECIALLY FOR OUR WIND PRONE AREAS. WILL
ADD HIGH WIND POTENTIAL IN THIS MORNINGS HWO AS WELL.
PRETTY COLD WEEKEND AS 700MB TEMPERATURES FALL BACK DOWN TO -14 TO
-18C. LOOKING PROBABLY AT SINGLE DIGIT LOWS AND HIGHS STRUGGLING
TO GET ABOVE FREEZING. COULD BE COLDER DEPENDING ON ANY EXISTING
SNOW PACK FROM THURSDAYS STORM AS WELL.
&&
FIRE WEATHER...
NO FIRE WEATHER CONCERNS. HIGHER MINIMUM AFTERNOON
RELATIVE HUMIDITIES TODAY IN THE WAKE OF THE COLD FRONT.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
SHORT TERM/FIRE WEATHER...RUBIN
LONG TERM/AVIATION...CLAYCOMB
AREA FORECAST DISCUSSION
NWS CHEYENNE WY
250 AM MST MON DEC 19 2011
.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT.
TODAY...COLD FRONT QUICKLY PASSED SOUTHWARD ACROSS OUR COUNTIES
EARLIER TONIGHT WITH DECENT COLD AIR ADVECTION ONGOING WITH 2-4 MB 3
HOURLY PRESSURE RISES IN THE WAKE OF THE COLD FRONT. AS INPUT BY DAY
SHIFT FORECAST...WILL MAINTAIN PATCHY FREEZING DRIZZLE ACROSS OUR
PANHANDLE COUNTIES SOUTH OF SCOTTSBLUFF TO ALLIANCE AS THE
ATMOSPHERE SUGGEST FAVORABLE CONDITIONS. LOW AND MID LEVELS WILL
CONTINUE TO SATURATE THIS MORNING AND WITH FAVORABLE NORTHEAST TO
EAST UPSLOPE...AND DYNAMICS FROM PASSING SHORTWAVE TROUGH
ALOFT...WILL INCLUDE 60 TO 100 PERCENT POPS FOR SNOW THIS MORNING
ALONG AND JUST EAST OF THE LARAMIE RANGE WITH LESSER POPS FURTHER
EAST AND WEST DUE TO DRY AIR AT LOW LEVELS AND DOWNSLOPING EAST
WINDS WEST OF THE MOUNTAINS AND SNOW SHADOW EFFECTS. AREAS OF FOG
DEVELOP AS THE TEMPERATURE AND DEWPOINT SPREADS NARROW. SNOWFALL
ACCUMULATIONS LESS THAN 2 INCHES DUE TO PROGRESSIVE NATURE OF THE
SYSTEM AND LIMITED QPF. CHANCES FOR SNOW DECREASE SIGNIFICANTLY THIS
AFTERNOON...THOUGH REMAIN HIGH ACROSS THE SOUTHERN LARAMIE RANGE DUE
TO PERSISTENT EASTERLY UPSLOPE. MUCH COLDER THAN SUNDAY WITH CLOUDS
AND IN THE COLD AIRMASS BEHIND THE FRONT.
TONIGHT...DECREASING CLOUDS AND LIGHT WINDS WILL MAKE FOR A CHILLY
NIGHT WITH COLDEST CONDITIONS ACROSS THE LARAMIE VALLEY. WEAK LEE
TROUGHING DEVELOPS BUT SHOULD NOT HAVE MUCH EFFECT ON LOW
TEMPERATURES.
TUESDAY...SLOW WARMING TREND IN BETWEEN SYSTEMS. WITH SOME SUNSHINE
AND SURFACE LEE TROUGHING INDUCING DOWNSLOPE WARMING...WILL SEE HIGH
TEMPERATURES IN THE 20S WEST AND 30S EAST.
TUESDAY NIGHT...NOT AS COLD AS MONDAY NIGHT AS MID AND HIGH CLOUDS
INCREASE IN ADVANCE OF THE NEXT STRONGER SHORTWAVE TROUGH ALOFT
APPROACHING FROM IDAHO AND WESTERN MONTANA.
WEDNESDAY...RATHER IMPRESSIVE SHORTWAVE TROUGH ALOFT CONTINUES TO
DIG ACROSS IDAHO AND WESTERN WYOMING SENDING ANOTHER COLD FRONT
ACROSS OUR COUNTIES IN THE AFTERNOON. THE NAM SHOWS A DEEPLY
SATURATED LAYER DEVELOPING IN THE AFTERNOON ACROSS OUR COUNTIES IN
THE WAKE OF THE COLD FRONT WHILE THE GFS IS SLOWER IN THE
EVOLVEMENT. NAM TENDS TO DO BETTER IN THESE SITUATIONS AND THUS WILL
FOLLOW ITS SOLUTION BRINGING CHANCE OF SNOW ACROSS ALL OUR COUNTIES
IN THE AFTERNOON...WITH 50 TO 100 PERCENT POPS NORTH OF A RAWLINS TO
CHADRON LINE WITH DEEPLY SATURATED AIRMASS LIFTED BY DYNAMICS AND
OROGRAPHICS.
WEDNESDAY NIGHT...SHORTWAVE TROUGH ALOFT MOVES ACROSS WESTERN
COLORADO WITH DYNAMICS AND OROGRAPHICS PROVIDING THE LIFT OF OUR
SATURATED AIRMASS TO PRODUCE FAIRLY WIDESPREAD LIGHT SNOW OVER OUR
COUNTIES...WITH MOST COVERAGE OVER THE FAVORED UPSLOPE LOCATIONS
NEAR THE SOUTHERN LARAMIE RANGE OF WESTERN LARAMIE COUNTY.
.LONG TERM...THURSDAY THROUGH MONDAY
19/00Z ECMWF AND GFS MODEL RUNS IN VERY GOOD AGREEMENT ON TRACK OF
LOW OVER UTAH THURSDAY MORNING POSITIONING OF PRECIPITATION OVER
WYOMING. GFS MORE BULLISH ON QPFS WITH EC MORE CONSERVATIVE. AM
BECOMING A LITTLE CONCERNED THOUGH WITH ACCUMULATING SNOWFALL AS
THIS TRACK IS A FAVORABLE PATTERN FOR US TO SEE SIGNIFICANT
SNOWFALL. LATER SHIFTS WILL NEED TO WATCH TO SEE IF THE LOW SLOWS
DOWN OR SHIFTS SLIGHTLY NORTH OF ITS CURRENT FORECAST TRACK.
LATEST TRACK ON BOTH THE GFS AND ECMWF HAS THE LOW TRACKING FROM
CENTRAL UTAH INTO SOUTHERN COLORADO AND FINALLY INTO NORTHERN NEW
MEXICO THURSDAY AFTERNOON. FOR NOW...HAVE SNOW ACCUMULATIONS OF 3
TO 5 INCHES FROM WEDNESDAY NIGHT THROUGH THURSDAY FOR MUCH OF THE
CWA WITH 10 TO 14 INCHES IN THE SNOWY AND SIERRA MADRE RANGES.
SNOW COMES TO AN END THURSDAY AFTERNOON WITH RIDGING MOVING INTO
THE AREA FROM THE NORTH. WESTERLY WINDS RETURN FRIDAY WITH 700MB
TEMPERATURES INCREASING FROM -14C THURSDAY AFTERNOON TO AROUND -6C
FRIDAY AFTERNOON. TEMPERATURES WILL BE TRICKY FRIDAY AND DEPENDS A
LOT ON RESIDING SNOW FROM THURSDAYS STORM. KEPT TEMPERATURES FAIRLY
COOL WITH LOW 30S FOR HIGHS EAST OF THE LARAMIE RANGE AND LOW 20S WEST.
LOOKS LIKE ANOTHER WEAK SHORTWAVE AND SURFACE COLD FRONT TO TRACK
THROUGH SOUTHEAST WYOMING SATURDAY. 700MB WINDS REALLY INCREASE
WITH THIS SYSTEM WITH GFS FORECASTING WINDS OF 50+KTS FRIDAY
AFTERNOON INTO SATURDAY MORNING. 700MB CRAIG TO CASPER HGT
GRADIENT AROUND 60 METERS AS WELL ON THE GFS DURING THAT TIME. DID
GO AHEAD AND INCREASE WIND SPEEDS FROM THURSDAY NIGHT THROUGH
FRIDAY NIGHT WITH THIS SYSTEM AND LATER SHIFTS WILL NEED TO WATCH
FOR WIND HIGHLIGHTS...ESPECIALLY FOR OUR WIND PRONE AREAS. WILL
ADD HIGH WIND POTENTIAL IN THIS MORNINGS HWO AS WELL.
PRETTY COLD WEEKEND AS 700MB TEMPERATURES FALL BACK DOWN TO -14 TO
-18C. LOOKING PROBABLY AT SINGLE DIGIT LOWS AND HIGHS STRUGGLING
TO GET ABOVE FREEZING. COULD BE COLDER DEPENDING ON ANY EXISTING
SNOW PACK FROM THURSDAYS STORM AS WELL.
&&
.AVIATION...06Z TAFS
LATEST STRATUS SATELLITE IMAGERY SHOWING BAND OF LOW CLOUDS
RAPIDLY MOVING SOUTH OUT OF SOUTH DAKOTA AND NORTHEASTERN WYOMING.
LATEST HRRR FORECAST SHOWS LIFR CONDITIONS INTO THE NORTHERN
PANHANDLE BY 08Z...QUICKLY MOVING SOUTH TO COVER THE ENTIRE
PANHANDLE BY 11Z. UPSLOPING WINDS WILL BRING IFR/LIFR CONDITIONS
INTO CHEYENNE SHORTLY THEREAFTER. STRATUS LOOKS TO STAY IN AT
LEAST UNTIL THIS AFTERNOON AND COULD HOLD ON INTO THIS EVENING
ACROSS THE PANHANDLE AND AT KCYS. WEST WINDS RETURN LATE THIS
EVENING AND STRATUS SHOULD BREAK OUT COMPLETELY AT THAT TIME.
&&
.FIRE WEATHER...
NO FIRE WEATHER CONCERNS. HIGHER MINIMUM AFTERNOON
RELATIVE HUMIDITIES TODAY IN THE WAKE OF THE COLD FRONT.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
SHORT TERM/FIRE WEATHER...RUBIN
LONG TERM/AVIATION...CLAYCOMB
AREA FORECAST DISCUSSION
NWS CHEYENNE WY
1022 PM MST SUN DEC 18 2011
.AVIATION...06Z TAFS
LATEST STRATUS SATELLITE IMAGERY SHOWING BAND OF LOW CLOUDS
RAPIDLY MOVING SOUTH OUT OF SOUTH DAKOTA AND NORTHEASTERN WYOMING.
LATEST HRRR FORECAST SHOWS LIFR CONDITIONS INTO THE NORTHERN
PANHANDLE BY 08Z...QUICKLY MOVING SOUTH TO COVER THE ENTIRE
PANHANDLE BY 11Z. UPSLOPING WINDS WILL BRING IFR/LIFR CONDITIONS
INTO CHEYENNE SHORTLY THEREAFTER. STRATUS LOOKS TO STAY IN AT
LEAST UNTIL THIS AFTERNOON AND COULD HOLD ON INTO THIS EVENING
ACROSS THE PANHANDLE AND AT KCYS. WEST WINDS RETURN LATE THIS
EVENING AND STRATUS SHOULD BREAK OUT COMPLETELY AT THAT TIME.
CLAYCOMB
&&
PREV DISCUSSION.../ISSUED 303 PM MST SUN DEC 18 2011/
SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT...
PRIMARY FORECAST CHALLENGE WILL CENTER AROUND A COLD FRONTAL
PASSAGE AND ITS RESULTANT IMPACT AS IT PUSHES THROUGH THE CWA
LATER TONIGHT THROUGH EARLY MONDAY AFTERNOON. THE SPLIT FLOW
PATTERN WILL CONTINUE THROUGH THE PERIOD AS A NORTHERN STREAM
SHORTWAVE KICKS THE CLOSED LOW CURRENTLY OVR SW ARIZONA INTO THE
SOUTHERN PLAINS LATER MONDAY AND TUESDAY. FORTUNATELY THE IMPACT
OF THE THIS SOUTHERN STREAM SYSTEM WILL BE CONFINED WELL SOUTH OF
THE CWA. THAT SAID...THE NRN STREAM SHORTWAVE WILL DRAG A COLD
FRONT FROM NORTH TO SOUTH THROUGH THE AREA LATER TONIGHT. SFC
ANALYSIS AT 20Z SHOWS THE SFC COLD FRONT EXTENDING FROM CENTRAL
NORTH DAKOTA INTO CENTRAL MONTANA AND BEING PUSHED SOUTH BY 5MB
3-HOURLY PRESSURE PRESSURE RISES. MODELS ARE CONSISTENT IN PUSHING
THIS COLD FRONT INTO EAST CENTRAL WYOMING/NRN NEBRASKA PANHANDLE
BY AROUND SUNSET AND CLEARING THE ENTIRE CWA BY AROUND MIDNIGHT.
WINDS WILL TURN NORTH/NORTHEASTERLY IN THE WAKE OF THE COLD FRONT.
SO EXPECT PERIOD OF FAVORABLE OROGRAPHIC ASCENT FOR LARAMIE RANGE
AND ADJACENT EAST/NORTH PLAINS LOCATIONS. HAVE ALSO SPREAD
PRECIPITATION CHANCES A BIT FURTHER EAST INTO THE PANHANDLE AS
WELL...ESPECIALLY FOR FAVORED AREAS NORTH OF THE PINE RIDGE. PROGD
WRN NEBRASKA BUFKIT RAOBS SHOW A NEARLY SATURATED POST-FRONTAL
PBL...WITH DRY CONDITIONS ABOVE. SO HAVE INTRODUCED PATCHY
FREEZING DRIZZLE ACROSS THE WESTERN NEBRASKA PANHANDLE LATER
TONIGHT/EARLY MONDAY MORNING. HAVE ALSO TRENDED SNOW CHANCES
UPWARDS SOME ESPECIALLY ALONG THE LARAMIE RANGE AND THE
INTERSTATE 25 CORRIDOR. UPPER-LEVEL SUPPORT WILL BE LACKING WITH
THIS SYSTEM KEEPING SNOW RATES WEAK AND ACCUMULATIONS LIGHT. IN
GENERAL...EXPECT UP TO AN INCH OF NEW SNOW BELOW 7500 FEET WITH 1
TO 3 INCHES ABOVE BY MONDAY AFTERNOON. LARGE SCALE SUBSIDENCE
BENEATH A BUILDING 1032MB SFC HIGH WILL EFFECTIVELY SHUT OFF ANY
SNOW CHANCES BY MONDAY AFTERNOON. A MUCH DRIER AIR MASS WILL
RESULT IN BENIGN CONDITIONS FOR MONDAY NIGHT THROUGH TUESDAY
NIGHT.
AFTER AN UNSEASONABLY WARM WEEKEND...TEMPERATURES WILL TURN
ABRUPTLY COLDER BEHIND TONIGHTS COLD FRONT. H7 TEMPERATURES OF
AROUND 3C TODAY WILL FALL TO AROUND -10C BY MONDAY AFTERNOON. SO
HIGHS WILL ONLY CLIMB INTO THE 20S AND LOW 30S. WARM AIR ADVECTION
WILL RESULT IN HIGH TEMPERATURES THAT WILL MODERATE BACK INTO THE
30S AND LOW 40S FOR TUESDAY.
LONG TERM...WEDNESDAY THROUGH CHRISTMAS DAY...
THE MAIN CONCERN OVER THE EXTENDED PERIOD IS THE WINTER STORM
FORECASTED TO AFFECT THE AREA LATE WEDNESDAY THROUGH THURSDAY. THE
MEDIUM RANGE MODELS HAVE COME INTO BETTER AGREEMENT...SHOWING A
MIDLEVEL TROUGH AMPLIFYING AND DIGGING SOUTHEAST OVER IDAHO AND
UTAH ON WEDNESDAY. THE MIDLEVEL TROUGH ATTEMPTS TO CLOSE OFF NORTH
OF THE FOUR CORNERS REGION ON WEDNESDAY NIGHT...WITH LARGE SCALE
LIFT AND MIDLEVEL Q-VECTOR CONVERGENCE OVER SOUTHEAST WYOMING. IN
THE LOWER LEVELS...850-700 MB WINDS ARE PROGGED TO TURN EASTERLY
WITH A GOOD PERIOD OF UPSLOPE FROM 00Z TO 12Z THURSDAY ALONG THE
LARAMIE RANGE. HIGHS WILL STRUGGLE TO GET OUT OF THE MID 20S EAST
OF THE LARAMIE RANGE ON THURSDAY WITH CLOUD COVER...SFC
UPSLOPE...AND COLD AIR ADVECTION. THE GFS AND ECMWF CLOSE OFF THE
SYSTEM MORE COMPARED TO THE CANADIAN...HOWEVER ALL MODELS SHOW THE
TROUGH PUSHING OFF TO THE SOUTHEAST BY LATE THURSDAY. WITH THE
INCREASE IN MODEL AGREEMENT OVER THE EVOLUTION OF THIS
SYSTEM...THE MAIN CHANGE IN THIS FORECAST PACKAGE WAS TO INCREASE
POPS OVER THE PLAINS AND ESPECIALLY OVER THE HIGHER
ELEVATIONS/FOOTHILLS FROM LATE WEDNESDAY THROUGH MIDDAY THURSDAY.
SOME MODERATE ACCUMULATIONS LOOK INCREASINGLY POSSIBLE WITH THIS
STORM SYSTEM. CONDITIONS WILL DRY OUT BEHIND THE TROUGH ON
FRIDAY...HOWEVER SFC TEMPERATURES THROUGH SUNDAY WILL BE BELOW
NORMAL WITH 700 MB TEMPERATURES AROUND -12C.
&&
FIRE WEATHER...
NO FIRE WEATHER CONCERNS THROUGH THE WEEK. AFTER A DRY AND
UNSEASONABLY WARM SUNDAY...A COLD FRONT WILL DROP SOUTH THROUGH
THE DISTRICT THIS EVENING TURNING TEMPERATURES SHARPLY COOLER FOR
MONDAY. ALSO ANTICIPATE CLOUDY CONDITIONS ALONG WITH A PERIOD OF
SNOW OR FREEZING DRIZZLE ACROSS THE AREA LATE TONIGHT THROUGH
MONDAY MORNING. THIS PRECIPITATION WILL WANE BY LATE
MONDAY...GIVING WAY TO DRY CONDITIONS AND MODERATING TEMPERATURES
ON TUESDAY. ANOTHER STORM SYSTEM WILL BRING ADDITIONAL SNOW
CHANCES ON WEDNESDAY NIGHT AND THURSDAY.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
SHORT TERM/FIRE WEATHER...HAHN
LONG TERM/AVIATION...FINCH
AREA FORECAST DISCUSSION...UPDATED
NWS TOPEKA KS
1123 PM CST TUE DEC 20 2011
...UPDATE TO AVIATION...
.DISCUSSION...
SHORT RANGE (TONIGHT AND WEDNESDAY)...
20Z WATER VAPOR IMAGERY AND ASSOCIATED RUC ANALYSIS CONTINUES TO
SHOW THE 500 MB TROUGH MOVING SLOWLY TO THE NORTHEAST ACROSS EASTERN
KANSAS. CURRENTLY IT IS SITTING OVER SOUTH CENTRAL KANSAS AND SHOULD
PUSH THROUGH THE AREA BY TONIGHT. RADAR TRENDS SHOW PRECIPITATION
ENDING ACROSS CENTRAL KANSAS...AND THIS TREND SHOULD CONTINUE
THROUGH THE REST OF THE EVENING AS THE BETTER LIFT ASSOCIATED WITH
THIS SYSTEM PUSHES EAST. ANOTHER SHIELD OF LIGHT PRECIPITATION IS
MOVING NORTHEASTWARD ALONG THE KANSAS TURNPIKE AND WILL LIKELY BRING
ANOTHER ROUND OF MIXED PRECIPITATION TO AREAS EAST OF THE TURNPIKE.
CURRENTLY KUKL INDICATES 36 DEGREES AS DOES KOJC...SO EXPECT THE
BULK OF THE REMAINING PRECIP TO FALL IN THE FORM OF A RAIN/SNOW MIX
FOR THE REMAINDER OF THE EVENING ALONG THE NEWLY FORMED DEFORMATION
BAND. EXPECT THE BEST LIFT WITH THIS ROUND OF SHOWERS TO MOVE OFF TO
THE EAST BY LATE THIS EVENING THUS ENDING ALL PRECIP FOR OUR
FORECAST AREA. SHOULD THERE BE ANY SNOW ASSOCIATED WITH THIS
EVENINGS PRECIP DON`T EXPECT MUCH MORE THAN A DUSTING OF SNOW ON
GRASSY SURFACES. SINCE ROADWAYS ARE WET FROM THE ONGOING PRECIP AND
OVERNIGHT LOWS WILL DROP INTO THE TEENS TO TWENTIES THERE IS A
POTENTIAL FOR SLICK SPOTS ON ROADWAYS...ESPECIALLY ONCE TEMPS DIP
BELOW 32 DEGREES. SKIES WILL GRADUALLY CLEAR BEHIND THE DEPARTING
SYSTEM...FIRST ACROSS CENTRAL AND NORTH CENTRAL KANSAS...THEN BY 12Z
ACROSS FAR EASTERN KANSAS. AS A RESULT OF THE NEWLY FALLEN SNOW
ACROSS C/NC KANSAS AND THE CLEARING SKIES EXPECT LOW TEMPS TO REACH
INTO THE MID TEENS TONIGHT...AND INTO THE LOWER TO MID 20S FURTHER
EAST WHERE NO SNOW FELL AND SKIES WILL BE SLOWER TO CLEAR. WEDNESDAY
WILL BRING A MILD DAY ACROSS NORTHEAST KANSAS AS TEMPS WILL REACH
INTO THE LOWER TO MID 40S WHERE NO NEW SNOW FELL...BUT WILL ONLY
REACH THE MID 30S OVER THE SNOW PACK IN C/NC KANSAS. JL
THURS-TUES...AFTER A BREAK FROM THE CLOUDS AND
PRECIPITATION...THE NEXT UPPER TROF APPROACHES THE STATE FROM THE
NORTH AND NORTHWEST THURSDAY AND THROUGH FRIDAY. AT THIS TIME MAIN
PIECE OF ENERGY AND DYNAMICS STAYS TO THE WEST...LEAVING THE LEAD
SHEAR VORTICITY AHEAD OF THE NORTHERN WAVE TO SLIDE ACROSS KANSAS.
ENOUGH LIFT WITH THIS AND COUPLED WITH SOME FRONTOGENETIC FORCING
TO BRING A CHANCE OF SNOW THROUGH FRIDAY. NOT MUCH MOISTURE TO
WORK WITH SO DONT EXPECT MUCH FOR ACCUMULATIONS DESPITE HIGHER
SNOW TO LIQUID RATIOS THAN THE PREVIOUS STORM. STILL VARIATIONS IN
THE GUIDANCE AS TO HOW TO HANDLE THE WESTERN PORTION OF THIS
SYSTEM WITH EC/NAM TRENDING A SOUTHWARD SLOWER TRACK AND GFS MORE
PROGRESSIVE ACROSS AND OUT OF OUR AREA. EC IS THEREFORE COOLER IN
THE EXTENDED WHILE GFS IS WARMER IN MORE WESTERLY FLOW. HAVE DRY
CONDITIONS BEYOND FRIDAY WITH A SLOW WARMING TREND...AND WILL HAVE
TO WATCH EVOLUTION OF THAT UPPER PATTERN FOR CHANGES. 67
&&
.AVIATION...
LAST ROUND OF SNOW EXITING THE TERMINALS...SO EXPECT REMAINDER OF
THE FCST TO BE DRY...ALTHOUGH WILL STILL TAKE A FEW HOURS
FOR MVFR CIGS TO CLEAR OUT. BEYOND THE ONSET OF CLEARING...POTENTIAL
FOR GROUND FOG THROUGH SUNRISE WITH THE WET/SNOWCOVERED GROUND WILL
BE THE FOCUS OF CONCERN IN THE TERMINALS UNTIL AROUND 14Z...OTHERWISE
SKC WITH SOUTHWEST WINDS GENERALLY UNDER 10KTS REMAINDER OF THE FCST.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
359 AM EST WED DEC 21 2011
.SYNOPSIS...
A SERIES OF STORM SYSTEMS WILL BRING RAIN TO THE AREA THROUGH
EARLY FRIDAY. TEMPERATURES WILL REMAIN ABOVE NORMAL THROUGH THE
END OF THE WORK WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
LOW PRESSURE WILL MOVE INTO THE UPPER OHIO VALLEY THIS AFTERNOON.
WARMER AIR AND MOISTURE WILL SURGE NORTHWARD, AHEAD OF THE SURFACE
SYSTEM. THIS WILL MEAN A DAY OF WELL ABOVE NORMAL TEMPS AND
WIDESPREAD RAIN. LATEST HRRR RUN IS SHOWING THE FIRST AREA OF RAIN
MOVING ACROSS THE NORTH AND WEST THROUGH MID-MORNING AND THEN
FILLING IN ACROSS THE REST OF THE REGION THERE AFTER.
MODELS ARE ALSO SHOWING SOME INSTABILITY RIGHT ALONG THE
ASSOCIATED COLD FRONT, WHICH WILL PASS THROUGH LATE THIS
AFTERNOON. IT IS POSSIBLE AN ISO STORM COULD DEVELOP LATE TODAY
WITH THE PASSAGE OF THE FRONT.
A STRONG LL JET, AHEAD OF THE SYSTEM, COULD PROVIDE SOME STRONGER
GUSTS TODAY. THE LIMITING FACTOR WILL BE THAT THE AREA WILL BE IN
THE WARM SECTOR, WHICH WILL INHIBIT MOST OF THE STRONGER WINDS
FROM MIXING DOWN. HOWEVER, IF CONVECTION DEVELOPS, THERE WILL BE A
THREAT FOR STRONG GUSTS WITH THE STORMS. THIS WILL NEED TO BE
MONITORED AS THE DAY PROGRESSES.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
SFC LOW WILL MOVE QUICKLY INTO NEW ENGLAND THIS EVENING AND THE
COLD FRONT WILL MOVE INTO E PA. THIS WILL BRING AN END TO THE
SHOWERS, HOWEVER, THERE COULD BE A BRIEF PERIOD OF GUSTY WINDS
RIGHT BEHIND THE FRONT. MODELS ARE CONTINUING TO SHOW A STRONG LL
JET BEHIND THE FRONT THIS EVENING, AND IN THE CAA, IT IS POSSIBLE
THAT WINDS COULD MIX DOWN. LATEST NAM RUN IS SHOWING PRESSURE RISES
OF UP TO 5MB RIGHT BEHIND THE SFC BOUNDARY.
COLDER AIR WILL SETTLE INTO THE AREA TONIGHT AND THROUGH MOST OF
THURSDAY. THERE WILL BE A PERIOD OF DRY WEATHER THROUGH AT LEAST
THE FIRST HALF OF THU.
MODELS ARE IN GOOD AGREEMENT DEVELOPING ANOTHER SFC LOW WHICH WILL
MOVE UP THE APPALACHIANS THURSDAY AFTERNOON AND TURN TOWARD THE
EAST COAST THURSDAY NIGHT. WITH THE CURRENT FORECAST TRACK OF THE
SFC LOW, WARMER AIR WILL SURGE NORTHWARD AND KEEP THIS A RAIN
EVENT. HOWEVER, IF THE LOW WOULD TAKE A TRACK FURTHER TO THE EAST,
OR SHIFT TO THE EAST FASTER, LOCATIONS ACROSS THE FAR NORTH COULD
SEE MIXED PRECIPITATION.
THE SFC LOW WILL QUICKLY EXIT THE EAST COAST EARLY FRIDAY AND
COLDER AIR WILL WRAP IN BEHIND THE EXITING LOW. THERE MAY BE SOME
LINGER SHOWERS/SNOW SHOWERS IN THE CAA BEHIND THE LOW.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
VERY LOW CONFIDENCE IN THE LONG TERM, AS MEDIUM RANGE OP MODELS
ARE SHOWING LARGE VARIANCES BEGINNING ON SUNDAY.
12Z ECMWF IS SHOWING ANOTHER LARGE SFC LOW DEVELOPING OVER THE
GULF COAST SAT NIGHT AND RUSHING NORTHWARD ON SUNDAY.
HOWEVER, THE 00Z GFS DOES NOT DEVELOP THIS SFC SYSTEM, RATHER IT
BRINGS A WEAK COLD FRONT THROUGH ON SUNDAY. THE 12Z GEFS, 12Z
ECMWF ENSEMBLES, AND 12Z CMC ARE ALL SHOWING SOLUTIONS CLOSER TO
THAT OF THE GFS. SO FOR THE WEEKEND WILL LEAN CLOSER TO THE 00Z
GFS SOLUTION. THIS WOULD MEAN A COLDER AND DRIER FORECAST.
LOW CONFIDENCE CONTINUES FOR THE REMAINDER OF THE THE LONG TERM.
&&
.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
PER BLEND OF RECENT SURFACE AND RADAR DATA ALONG WITH SUITE OF HIGH
RESOLUTION MODELS, EXPECT FREQUENT SHOWERS WITH IFR RESTRICTIONS AT
TIMES TODAY, AS STRONG NORTHEASTWARD MOVING LOW PRESSURE CENTER
PASSES THROUGH OHIO THIS AFTERNOON. SHOWERS SHOULD END ABRUPTLY THIS
EVENING.
NAM MODEL PROFILES SHOW INSTABILITY CAN DEVELOP ACROSS THE UPPER
OHIO VALLEY THIS AFTERNOON AS IN THE SO-CALLED WARM SECTOR OF THE
SYSTEM. SO WILL MENTION POSSIBLE THUNDER, WHICH CONCURS WITH SPC
GUIDANCE.
NAM MODEL PROFILES LIKEWISE SHOW FAST WINDS 2-4 KFT AGL TODAY. DID
NOT THINK WINDS QUITE FAST ENOUGH TO MENTION LOW LEVEL WIND SHEAR
THIS MORNING. DID ADD WIND GUSTS TO 20-25 KTS LATER TODAY, BUT MAY
HAVE TO MAKE HIGHER. LIKEWISE, POST-SYSTEM STRONG PRESSURE RISES MAY
CAUSE A PERIOD OF GUSTY WINDS TONIGHT.
POST SYSTEM STRATOCUMULUS SHOULD YIELD MVFR CEILINGS LATE TONIGHT,
AND PERHAPS A PERIOD OF IFR.
OUTLOOK...THURSDAY THROUGH SUNDAY...
MVFR STRATOCUMULUS CEILINGS CAN LINGER INTO DAYTIME THURSDAY. A
SERIES OF PASSING SYSTEMS WILL ALSO PROVIDE PERIODS OF PRECIPITATION
AND RESTRICTIONS THURSDAY NIGHT INTO MONDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS BUFFALO NY
328 AM EST WED DEC 21 2011
.SYNOPSIS...
HIGH PRESSURE ACROSS NEW YORK STATE WILL MOVE TO THE EAST OF THE
REGION TONIGHT. MEANWHILE...LOW PRESSURE MOVING OUT OF THE SOUTHERN
PLAINS WILL PUSH A WARM FRONT NORTH TOWARD THE LOWER LAKES LATER
TONIGHT AND WEDNESDAY. THE SOUTHERLY WINDS TO THE WEST OF THE HIGH
PRESSURE CENTER AND THE PASSAGE OF THE WARM FRONT WILL BRING WARMER
TEMPERATURES AND RAIN... WHICH COULD BEGIN AS A WINTRY MIX OF
PRECIPITATION ACROSS THE TUG HILL REGION.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE 00Z BUF SOUNDING SHOWS AN 850 MB TEMP OF -5C...WHICH IS 3
DEGREES C COLDER THAN NEARLY ALL MODEL GUIDANCE. THIS IS LIKELY
DUE TO THE SHARPNESS OF THE BOUNDARY ALOFT...WHICH IS NOT BEING
SUFFICIENTLY RESOLVED BY THE MODELS. AT 1000 PM...RADAR SHOWS A
LINE LIFTING ACROSS CHAUTAUQUA COUNTY. THIS IS LIKELY THE LEADING
EDGE OF SIGNIFICANT WARM AIR ADVECTION.
BASED ON THIS...EXPECT THIS LINE IS IS WHAT WILL WARM TEMPERATURES
ALOFT ENOUGH TO SUPPORT RAIN. RETURNS ON THIS ARE QUITE
MEAGER...AND HAVE OPTED TO DOWNGRADE THIS TO JUST FLURRIES AS THIS
MOVES THROUGH SINCE IT IS LESS LIKELY TO BE MEASURABLE. THE 00Z BUFFALO
SOUNDING SUGGESTS PRECIPITATION WILL START AS A BRIEF PERIOD OF
SNOW OR SNOW AND RAIN MIXED. BEHIND THIS...TEMPERATURES ALOFT
WILL BE TOO WARM TO SUPPORT SNOW...WITH THIS LINE EXPECTED TO
CONTINUE TO LIFT NORTHWARD OVERNIGHT.
DESPITE THE BRIEF PERIOD OF MIXED PRECIPITATION AT THE ONSET...IT
DOES APPEAR SURFACE TEMPERATURES WILL CONTINUE TO GRADUALLY WARM
OVERNIGHT. WILL CONTINUE TO WATCH THIS CLOSELY...BECAUSE AS THIS
LIGHT BAND MOVES ACROSS...TEMPERATURES ARE FORECAST TO BE JUST A
COUPLE DEGREES ABOVE FREEZING...WHICH IS A TAD CLOSE FOR COMFORT.
EAST OF LAKE ONTARIO CLEARED OUT THIS EVENING...WHICH ALLOWED
TEMPERATURES TO DROP INTO THE UPPER TEENS IN MANY SPOTS. BECAUSE
OF THIS...NOW HAVE THE ADVISORY FOR JEFFERSON COUNTY AS WELL...AND
UNTIL 1000 AM. FROZEN QPFS WILL NOT BE MUCH. LOOKING FOR JUST A
LIGHT GLAZE OF ICE IF ANYTHING...BUT IT DOES NOT TAKE MUCH ICE TO
MAKE THINGS SLICK.
OTHERWISE...EXPECT AREAS OF FOG TO DEVELOP BEHIND THIS...WITH JHW
ALREADY DOWN TO A HALF MILE. FOG WILL SPREAD ACROSS ALL OF THE
SOUTHERN TIER...BUT THE SE DOWNSLOPE FLOW SHOULD LIMIT FOG NORTH
OF THE I-90 THRUWAY.
WARM AIR OVERSPREADS THE ENTIRE FORECAST AREA BY MID MORNING ON
WEDNESDAY AND THE STEADIER RAINS WILL FOLLOW CLOSELY. RAINFALL
TOTALS WILL RANGE FROM A THIRD TO A HALF INCH FROM LATE MORNING
THROUGH WEDNESDAY EVENING. THIS SAID...LOCALIZED AMOUNTS TO AN
INCH ARE POSSIBLE...ESPECIALLY SOUTH OF THE THRUWAY...WHERE BOTH
THE NAM AND HRRR BRING IN THE BEST QPFS. WOULD NOT BE SURPRISED TO
HEAR A RUMBLE OF THUNDER...GIVEN A MODEST AMOUNT OF ELEVATED CAPE.
WITH NO LIGHTNING STRIKES UPSTREAM...CARRY ONLY ISOLATED THUNDER
IN PORTIONS OF THE SOUTHERN TIER WEDNESDAY MORNING.
TEMPS WILL TOP OUT IN THE LOWER TO MID 40S ACROSS THE EASTERN LAKE
ONTARIO REGION WITH MID 40S TO LOW 50S FOR THE REMAINDER OF THE
FORECAST AREA.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
THE POTENT UPPER WAVE SHIFTS TO THE EAST AT THE START OF THE
PERIOD...AS WEAK SHORTWAVE RIDGING DEVELOPS ACROSS WESTERN NEW
YORK. THIS SHOULD PROVIDE A BRIEF BREAK IN PRECIPITATION FOR MOST
OF THE AREA. MILD DAY EXPECTED THURSDAY AFTERNOON WITH TEMPERATURES
RANGING FROM THE UPPER 30S ACROSS PARTS OF THE NORTH COUNTRY TO
THE MID AND UPPER 40S IN THE GENESEE VALLEY AND SOUTH SHORE OF
LAKE ONTARIO.
LATEST MODELS ARE IN SIMILAR AGREEMENT DEVELOPING ANOTHER SURFACE
WAVE WHICH WILL MOVE UP THE APPALACHIANS THURSDAY AFTERNOON AND
TURN TOWARD THE EAST COAST THURSDAY NIGHT. THIS FORECAST TRACK
WOULD FAVOR KEEPING THE REGION WELL INTO THE COLD AIR WITH THE
NORTHERN FRINGE OF PRECIPITATION MORE THAN LIKELY FALLING AS SNOW
IN THE THURSDAY NIGHT THROUGH FRIDAY TIME FRAME. THERMAL PROFILES
WOULD SUGGEST THAT PRECIPITATION ONSET COULD BE IN THE FORM OF
RAIN BEFORE ATMOSPHERIC COLUMN COMPLETELY COOLS. TIME HEIGHT
CROSS SECTIONS REVEALING DEEP SATURATION AMID THE STRONG FORCING.
295K ISENTROPIC SURFACE SHOWS BEST LIFT FROM THE SOUTHERN TIER
SOUTHWARD INTO PENNSYLVANIA. THE HIGH SPOTS ALONG THE SOUTHERN
TIER LIKELY HAVE THE BEST POTENTIAL FOR ACCUMULATING SNOWS. A 1-3
INCH POTENTIAL LOOKS REASONABLE BASED ON CURRENT FORECAST TRACK OF
THE SURFACE WAVE.
THE SURFACE WAVE WILL PUSH EAST OF THE AREA BY LATE FRIDAY WITH
COLDER AIR WRAPPING IN BRINGING THE POTENTIAL FOR SOME LIMITED
LAKE RESPONSE.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
A SOMEWHAT AMPLIFIED +PNA PATTERN ACROSS THE LOWER 48 AT THE START
OF THIS PERIOD WILL QUICKLY BREAK DOWN INTO A LOW AMPLITUDE PACIFIC
FLOW AS MID LATITUDE BLOCKING WILL GENERALLY REMAIN ABSENT ACROSS
THE NORTHERN HEMISPHERE. MEDIUM RANGE GUIDANCE WAS SUGGESTING THAT
SOME BLOCKING COULD DEVELOP IN PREVIOUS MODEL RUNS...BUT THAT TREND
HAS SINCE BEEN REVERSED. THIS WILL RESULT IN TEMPERATURES AVERAGING
NEAR TO ABOVE NORMAL...ALTHOUGH THERE WILL BE BRIEF PERIODS WHEN IT
WILL BE SEASONABLY CHILLY.
THE BIGGEST QUESTION FOR MANY DURING THIS PERIOD IS...WILL THERE
ENOUGH SNOW FOR A WHITE CHRISTMAS? THAT MAY LARGELY DEPEND ON YOUR
SPECIFIC DEFINITION OF A WHITE CHRISTMAS...AS SIGNIFICANT SNOWFALL
FOR OUR REGION IS NOT CURRENTLY IN THE MAKING.
FOR SATURDAY...A POTENT SHORTWAVE IN THE NORTHERN BRANCH WILL BRUSH
BY TO OUR NORTH. THIS WILL BRING US THE CHANCE FOR SOME LIGHT SNOW
SHOWERS...BUT WITH A HIGHLY SHEAR AIRMASS IN ITS WAKE...ASSISTANCE
FROM THE LAKES (IE. LAKE EFFECT) IS NOT ANTICIPATED. THIS SHOULD
KEEP THE SNOW FROM MEASURING MORE THAN A COVERING.
THE MOST SIGNIFICANT WEATHER FEATURE OF THIS PERIOD WILL THEN TAKE
AIM ON THE MID ATLANTIC AND NORTHEAST COAST FOR CHRISTMAS DAY AND
NIGHT. THE MEDIUM RANGE GUIDANCE PACKAGES HAVE NOT BEEN IN SYNC WITH
THIS FEATURE FOR THE PAST SEVERAL RUNS...AND THAT FACT REMAINS THE
SAME AS THE GFS NEVER REALLY GENERATES ANYTHING AT THE SFC WHILE THE
USUALLY MORE TRUSTWORTHY ECMWF DEPICTS A COASTAL LOW. IT IS THIS
LATTER SOLUTION THAT SUGGESTS THE BACK-EDGE OF THE SYNOPTIC SNOW
SHIELD WILL LIFT UP ACROSS OUR AREA SUNDAY NIGHT. WILL RAISE POPS TO
40 TO COVER FOR THIS POTENTIAL. IF THE STORM SYSTEM WORKS OUT
EXACTLY AS DEPICTED...THEN THERE COULD BE SUB-ADVISORY CRITERIA SNOW
ACCUMS SOUTH AND EAST OF BUFFALO...BUT FROM THIS RANGE IT WOULD NOT
BE PRUDENT TO PUT A LOT OF CONFIDENCE INTO THAT.
A SEASONABLY COLD NORTHWEST FLOW IN ITS WAKE WILL COMBINE WITH A H5
TROUGH TO BRING US THE CHANCE FOR SNOW SHOWERS AND SOME LAKE
ENHANCEMENT MONDAY AND MONDAY NIGHT...THEN WARMING ALOFT AND THE
PROGRESSION OF A H5 RIDGE SHOULD ENCOURAGE FAIR AND MILDER WEATHER
FOR TUESDAY INTO MID WEEK.
&&
.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
THE LEADING EDGE OF WARM AIR ADVECTION ALOFT IS GRADUALLY
CROSSING BUF AT 05Z. THIS MAY CAUSE A PERIOD OF LOWER CIGS...BUT
UPSTREAM OBS SUGGEST THIS WILL BE TEMPORARY. THE SE DOWNSLOPE
FLOW SHOULD KEEP BUF/IAG/ROC MAINLY MVFR TIL WEDNESDAY MORNING.
THE STEADY MODERATE TO POSSIBLY HEAVY RAIN WILL ENTER FROM SW TO
NE WEDNESDAY MORNING. THIS WILL LOWER CIGS...WITH A FAIR PERIOD OF
LIFR-IFR CONDITIONS EXPECTED. CONDITIONS WILL NOT IMPROVE UNTIL
THE LOW LIFTS ACROSS THE LAKES AND INCREASES WINDS AND
MIXING...WHICH WILL EVENTUALLY DRY THINGS OUT.
OUTLOOK...
WEDNESDAY NIGHT...MVFR/IFR WITH RAIN.
THURSDAY...MAINLY VFR.
THURSDAY NIGHT...CHC LIGHT SNOW OR RAIN
ESPECIALLY TOWARDS THE SOUTH AND EAST.
FRIDAY AND SATURDAY...MAINLY VFR CHC SNOW SHOWERS.
SUNDAY...MAINLY VFR IN SCTD SNOW SHOWERS.
&&
.MARINE...
HIGH PRESSURE ACROSS NEW YORK STATE TODAY WILL MOVE TO THE EAST OF
THE REGION TONIGHT. SOUTHERLY WINDS WILL INCREASE TONIGHT AND
WEDNESDAY AS A WARM FRONT LIFTS NORTH TOWARD THE LOWER LAKES...THE
ATTENDANT LOW AND COLD FRONT WILL CROSS THE LAKES ON WEDNESDAY NIGHT
WITH INCREASING WESTERLY WINDS AND WAVES BUILDING TO SMALL CRAFT
ADVISORY CRITERIA GENERALLY FROM WEDNESDAY EVENING THROUGH MID
MORNING ON THURSDAY.
&&
.CLIMATE...
THE WINTER OF 2011-12 HAS STARTED SLOW IN THE SNOWFALL CATEGORY
ACROSS WESTERN AND CENTRAL NEW YORK. THROUGH DECEMBER 19TH...THE
CURRENT SNOW THIS SEASON OF 3.0 INCHES (BUFFALO) AND 2.1
INCHES(ROCHESTER) ARE WELL BELOW NORMAL THUS FAR. THERE HAVE BEEN
SEVERAL YEARS THAT HAVE HAD SIMILAR STARTS THOUGH. BELOW IS A LIST
OF THE TOP LEAST AMOUNT OF SNOW IN BOTH CITIES...MEASURED AT THE
RESPECTIVE AIRPORTS...THROUGH AND INCLUDING CHRISTMAS EVE.
BUFFALO
1 3.0 2011
2 3.1 1998
3 3.3 1931
4 3.6 1896
5 4.3 1918
...
10 6.5 1888
15 7.8 1891
***NORMAL THROUGH DECEMBER 24TH 29.1***
ROCHESTER
1 2.1 2011
2 2.6 1939
3 3.7 2001
4 3.8 1877
5 4.2 2006
...
10 6.2 1998
15 7.8 1940
***NORMAL THROUGH DECEMBER 24TH 23.5***
SNOWFALL RECORDS GO BACK TO THE WINTER OF 1884-85.
&&
.BUF WATCHES/WARNINGS/ADVISORIES...
NY...WINTER WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR
NYZ006>008.
MARINE...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 4 AM EST
THURSDAY FOR LEZ020-040-041.
SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 10 AM
EST THURSDAY FOR LOZ043>045.
SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 8 AM EST
THURSDAY FOR LOZ042.
&&
$$
SYNOPSIS...WCH
NEAR TERM...APFFEL/WCH
SHORT TERM...TMA
LONG TERM...RSH
AVIATION...APFFEL
MARINE...APFFEL/WCH
CLIMATE...THOMAS
AREA FORECAST DISCUSSION
NWS BUFFALO NY
1156 PM EST TUE DEC 20 2011
.SYNOPSIS...
HIGH PRESSURE ACROSS NEW YORK STATE WILL MOVE TO THE EAST OF THE
REGION TONIGHT. MEANWHILE...LOW PRESSURE MOVING OUT OF THE SOUTHERN
PLAINS WILL PUSH A WARM FRONT NORTH TOWARD THE LOWER LAKES LATER
TONIGHT AND WEDNESDAY. THE SOUTHERLY WINDS TO THE WEST OF THE HIGH
PRESSURE CENTER AND THE PASSAGE OF THE WARM FRONT WILL BRING WARMER
TEMPERATURES AND RAIN... WHICH COULD BEGIN AS A WINTRY MIX OF
PRECIPITATION ACROSS THE TUG HILL REGION.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
THE 00Z BUF SOUNDING SHOWS AN 850 MB TEMP OF -5C...WHICH IS 3
DEGREES C COLDER THAN NEARLY ALL MODEL GUIDANCE. THIS IS LIKELY
DUE TO THE SHARPNESS OF THE BOUNDARY ALOFT...WHICH IS NOT BEING
SUFFICIENTLY RESOLVED BY THE MODELS. AT 1000 PM...RADAR SHOWS A
LINE LIFTING ACROSS CHAUTAUQUA COUNTY. THIS IS LIKELY THE LEADING
EDGE OF SIGNIFICANT WARM AIR ADVECTION.
BASED ON THIS...EXPECT THIS LINE IS IS WHAT WILL WARM TEMPERATURES
ALOFT ENOUGH TO SUPPORT RAIN. RETURNS ON THIS ARE QUITE
MEAGER...AND HAVE OPTED TO DOWNGRADE THIS TO JUST FLURRIES AS THIS
MOVES THROUGH SINCE IT IS LESS LIKELY TO BE MEASURABLE. THE 00Z BUFFALO
SOUNDING SUGGESTS PRECIPITATION WILL START AS A BRIEF PERIOD OF
SNOW OR SNOW AND RAIN MIXED. BEHIND THIS...TEMPERATURES ALOFT
WILL BE TOO WARM TO SUPPORT SNOW...WITH THIS LINE EXPECTED TO
CONTINUE TO LIFT NORTHWARD OVERNIGHT.
DESPITE THE BRIEF PERIOD OF MIXED PRECIPITATION AT THE ONSET...IT
DOES APPEAR SURFACE TEMPERATURES WILL CONTINUE TO GRADUALLY WARM
OVERNIGHT. WILL CONTINUE TO WATCH THIS CLOSELY...BECAUSE AS THIS
LIGHT BAND MOVES ACROSS...TEMPERATURES ARE FORECAST TO BE JUST A
COUPLE DEGREES ABOVE FREEZING...WHICH IS A TAD CLOSE FOR COMFORT.
EAST OF LAKE ONTARIO CLEARED OUT THIS EVENING...WHICH ALLOWED
TEMPERATURES TO DROP INTO THE UPPER TEENS IN MANY SPOTS. BECAUSE
OF THIS...NOW HAVE THE ADVISORY FOR JEFFERSON COUNTY AS WELL...AND
UNTIL 1000 AM. FROZEN QPFS WILL NOT BE MUCH. LOOKING FOR JUST A
LIGHT GLAZE OF ICE IF ANYTHING...BUT IT DOES NOT TAKE MUCH ICE TO
MAKE THINGS SLICK.
OTHERWISE...EXPECT AREAS OF FOG TO DEVELOP BEHIND THIS...WITH JHW
ALREADY DOWN TO A HALF MILE. FOG WILL SPREAD ACROSS ALL OF THE
SOUTHERN TIER...BUT THE SE DOWNSLOPE FLOW SHOULD LIMIT FOG NORTH
OF THE I-90 THRUWAY.
WARM AIR OVERSPREADS THE ENTIRE FORECAST AREA BY MID MORNING ON
WEDNESDAY AND THE STEADIER RAINS WILL FOLLOW CLOSELY. RAINFALL
TOTALS WILL RANGE FROM A THIRD TO A HALF INCH FROM LATE MORNING
THROUGH WEDNESDAY EVENING. THIS SAID...LOCALIZED AMOUNTS TO AN
INCH ARE POSSIBLE...ESPECIALLY SOUTH OF THE THRUWAY...WHERE BOTH
THE NAM AND HRRR BRING IN THE BEST QPFS. WOULD NOT BE SURPRISED TO
HEAR A RUMBLE OF THUNDER...GIVEN A MODEST AMOUNT OF ELEVATED CAPE.
WITH NO LIGHTNING STRIKES UPSTREAM...CARRY ONLY ISOLATED THUNDER
IN PORTIONS OF THE SOUTHERN TIER WEDNESDAY MORNING.
TEMPS WILL TOP OUT IN THE LOWER TO MID 40S ACROSS THE EASTERN LAKE
ONTARIO REGION WITH MID 40S TO LOW 50S FOR THE REMAINDER OF THE
FORECAST AREA.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
A SPLIT FLOW WILL REMAIN IN PLACE ACROSS THE COUNTRY DURING THIS
PERIOD WITH OUR FORECAST AREA GENERALLY BEING DOMINATED BY THE
SOUTHERN BRANCH. THIS WILL TRANSLATE INTO CONTINUED ABOVE NORMAL
TEMPERATURES WITH LITTLE (IF ANY) IN THE WAY OF SNOWFALL. SAME OL`
SAME OL`. WHILE THERE WILL BE ONE SIZE-ABLE SHORTWAVE OF NOTE DURING
THIS STRETCH...GUIDANCE HAS BEEN VERY CONSISTENT WITH KEEPING THE
BULK OF ITS AFFECTS TO OUR SOUTH. OUR REGION WILL BE MORE INFLUENCED
BY MORE SUBTLE FEATURES. THE DETAILS...
A POTENT SHORTWAVE WILL RACE ACROSS OUR FORECAST AREA WEDNESDAY
NIGHT. THIS WILL BE A `WARM` PCPN EVENT WITH WIDESPREAD RAIN IN THE
EVENING TAPERING OFF DURING THE COURSE OF THE OVERNIGHT. THE RAIN
EARLY ON WILL BE ENHANCED BY SOME DECENT JET INDUCED LIFT SO THAT
TOTAL RAINFALL FROM THE SYSTEM WILL AVERAGE A QUARTER...TO AT MOST
ONE HALF INCH. AS THE SHORTWAVE EXITS ACROSS NEW ENGLAND LATE
WEDNESDAY NIGHT...BROAD BASED RIDGING WILL BUILD IN FROM THE WEST.
ON THURSDAY...A LOW AMPLITUDE H5 RIDGE AND ASSOCIATED WEAK SFC HIGH
WILL MOVE ACROSS OUR FORECAST AREA. THIS WILL SUPPORT FAIR DRY
WEATHER WITH AFTERNOON TEMPERATURES RANGING FROM THE UPPER 30S
ACROSS PARTS OF THE NORTH COUNTRY TO THE MID AND UPPER 40S IN THE
GENESEE VALLEY AND SOUTH SHORE OF LAKE ONTARIO.
FAIR WEATHER SHOULD PERSIST ACROSS MOST OF THE REGION THURSDAY
NIGHT...ALTHOUGH A WEAK COLD FRONT SAGGING SOUTH FROM QUEBEC COULD
HELP TO PRODUCE SOME FLURRIES AND VERY LIGHT SNOW SHOWERS. A
CONFLUENT FLOW ALOFT SHOULD MINIMIZE ANY CHANCE FOR ACCUMULATING
SNOW.
FOR FRIDAY...THE AFOREMENTIONED WEAK COLD FRONT WILL PUSH ACROSS OUR
FORECAST AREA. WILL KEEP THE LOW CHC POPS IN PLAY FROM CONTINUITY...
BUT WILL ADD THE MENTION OF RAIN SHOWERS (ALONG WITH THE SNOW
SHOWERS) AS A VERY LIMITED SNOW GROWTH WILL BE IN PLACE. FORCING
FROM THE FRONT WILL BE VERY WEAK THOUGH...SO EVEN THE LOW CHC POPS
MAY BE TOO PESSIMISTIC.
WHILE THE NEXT POTENT SHORTWAVE WILL BE HEADING OUR WAY FROM THE
UPPER GREAT LAKES FRIDAY NIGHT...LINGERING SFC HIGH PRESSURE SHOULD
KEEP THE NIGHT MAINLY PCPN FREE.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
A SOMEWHAT AMPLIFIED +PNA PATTERN ACROSS THE LOWER 48 AT THE START
OF THIS PERIOD WILL QUICKLY BREAK DOWN INTO A LOW AMPLITUDE PACIFIC
FLOW AS MID LATITUDE BLOCKING WILL GENERALLY REMAIN ABSENT ACROSS
THE NORTHERN HEMISPHERE. MEDIUM RANGE GUIDANCE WAS SUGGESTING THAT
SOME BLOCKING COULD DEVELOP IN PREVIOUS MODEL RUNS...BUT THAT TREND
HAS SINCE BEEN REVERSED. THIS WILL RESULT IN TEMPERATURES AVERAGING
NEAR TO ABOVE NORMAL...ALTHOUGH THERE WILL BE BRIEF PERIODS WHEN IT
WILL BE SEASONABLY CHILLY.
THE BIGGEST QUESTION FOR MANY DURING THIS PERIOD IS...WILL THERE
ENOUGH SNOW FOR A WHITE CHRISTMAS? THAT MAY LARGELY DEPEND ON YOUR
SPECIFIC DEFINITION OF A WHITE CHRISTMAS...AS SIGNIFICANT SNOWFALL
FOR OUR REGION IS NOT CURRENTLY IN THE MAKING.
FOR SATURDAY...A POTENT SHORTWAVE IN THE NORTHERN BRANCH WILL BRUSH
BY TO OUR NORTH. THIS WILL BRING US THE CHANCE FOR SOME LIGHT SNOW
SHOWERS...BUT WITH A HIGHLY SHEAR AIRMASS IN ITS WAKE...ASSISTANCE
FROM THE LAKES (IE. LAKE EFFECT) IS NOT ANTICIPATED. THIS SHOULD
KEEP THE SNOW FROM MEASURING MORE THAN A COVERING.
THE MOST SIGNIFICANT WEATHER FEATURE OF THIS PERIOD WILL THEN TAKE
AIM ON THE MID ATLANTIC AND NORTHEAST COAST FOR CHRISTMAS DAY AND
NIGHT. THE MEDIUM RANGE GUIDANCE PACKAGES HAVE NOT BEEN IN SYNC WITH
THIS FEATURE FOR THE PAST SEVERAL RUNS...AND THAT FACT REMAINS THE
SAME AS THE GFS NEVER REALLY GENERATES ANYTHING AT THE SFC WHILE THE
USUALLY MORE TRUSTWORTHY ECMWF DEPICTS A COASTAL LOW. IT IS THIS
LATTER SOLUTION THAT SUGGESTS THE BACK-EDGE OF THE SYNOPTIC SNOW
SHIELD WILL LIFT UP ACROSS OUR AREA SUNDAY NIGHT. WILL RAISE POPS TO
40 TO COVER FOR THIS POTENTIAL. IF THE STORM SYSTEM WORKS OUT
EXACTLY AS DEPICTED...THEN THERE COULD BE SUB-ADVISORY CRITERIA SNOW
ACCUMS SOUTH AND EAST OF BUFFALO...BUT FROM THIS RANGE IT WOULD NOT
BE PRUDENT TO PUT A LOT OF CONFIDENCE INTO THAT.
A SEASONABLY COLD NORTHWEST FLOW IN ITS WAKE WILL COMBINE WITH A H5
TROUGH TO BRING US THE CHANCE FOR SNOW SHOWERS AND SOME LAKE
ENHANCEMENT MONDAY AND MONDAY NIGHT...THEN WARMING ALOFT AND THE
PROGRESSION OF A H5 RIDGE SHOULD ENCOURAGE FAIR AND MILDER WEATHER
FOR TUESDAY INTO MID WEEK.
&&
.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
THE LEADING EDGE OF WARM AIR ADVECTION ALOFT IS GRADUALLY
CROSSING BUF AT 05Z. THIS MAY CAUSE A PERIOD OF LOWER CIGS...BUT
UPSTREAM OBS SUGGEST THIS WILL BE TEMPORARY. THE SE DOWNSLOPE
FLOW SHOULD KEEP BUF/IAG/ROC MAINLY MVFR TIL WEDNESDAY MORNING.
THE STEADY MODERATE TO POSSIBLY HEAVY RAIN WILL ENTER FROM SW TO
NE WEDNESDAY MORNING. THIS WILL LOWER CIGS...WITH A FAIR PERIOD OF
LIFR-IFR CONDITIONS EXPECTED. CONDITIONS WILL NOT IMPROVE UNTIL
THE LOW LIFTS ACROSS THE LAKES AND INCREASES WINDS AND
MIXING...WHICH WILL EVENTUALLY DRY THINGS OUT.
OUTLOOK...
WEDNESDAY NIGHT...MVFR/IFR WITH RAIN.
THURSDAY...MAINLY VFR.
THURSDAY NIGHT...CHC LIGHT SNOW OR RAIN
ESPECIALLY TOWARDS THE SOUTH AND EAST.
FRIDAY AND SATURDAY...MAINLY VFR CHC SNOW SHOWERS.
SUNDAY...MAINLY VFR IN SCTD SNOW SHOWERS.
&&
.MARINE...
HIGH PRESSURE ACROSS NEW YORK STATE TODAY WILL MOVE TO THE EAST OF
THE REGION TONIGHT. SOUTHERLY WINDS WILL INCREASE TONIGHT AND
WEDNESDAY AS A WARM FRONT LIFTS NORTH TOWARD THE LOWER LAKES...THE
ATTENDANT LOW AND COLD FRONT WILL CROSS THE LAKES ON WEDNESDAY NIGHT
WITH INCREASING WESTERLY WINDS AND WAVES BUILDING TO SMALL CRAFT
ADVISORY CRITERIA GENERALLY FROM WEDNESDAY EVENING THROUGH MID
MORNING ON THURSDAY.
&&
.CLIMATE...
THE WINTER OF 2011-12 HAS STARTED SLOW IN THE SNOWFALL CATEGORY
ACROSS WESTERN AND CENTRAL NEW YORK. THROUGH DECEMBER 19TH...THE
CURRENT SNOW THIS SEASON OF 3.0 INCHES (BUFFALO) AND 2.1
INCHES(ROCHESTER) ARE WELL BELOW NORMAL THUS FAR. THERE HAVE BEEN
SEVERAL YEARS THAT HAVE HAD SIMILAR STARTS THOUGH. BELOW IS A LIST
OF THE TOP LEAST AMOUNT OF SNOW IN BOTH CITIES...MEASURED AT THE
RESPECTIVE AIRPORTS...THROUGH AND INCLUDING CHRISTMAS EVE.
BUFFALO
1 3.0 2011
2 3.1 1998
3 3.3 1931
4 3.6 1896
5 4.3 1918
...
10 6.5 1888
15 7.8 1891
***NORMAL THROUGH DECEMBER 24TH 29.1***
ROCHESTER
1 2.1 2011
2 2.6 1939
3 3.7 2001
4 3.8 1877
5 4.2 2006
...
10 6.2 1998
15 7.8 1940
***NORMAL THROUGH DECEMBER 24TH 23.5***
SNOWFALL RECORDS GO BACK TO THE WINTER OF 1884-85.
&&
.BUF WATCHES/WARNINGS/ADVISORIES...
NY...WINTER WEATHER ADVISORY FROM 3 AM TO 10 AM EST WEDNESDAY FOR
NYZ006>008.
MARINE...SMALL CRAFT ADVISORY FROM 8 PM WEDNESDAY TO 8 AM EST THURSDAY
FOR LEZ040-041.
SMALL CRAFT ADVISORY FROM MIDNIGHT WEDNESDAY NIGHT TO
8 AM EST THURSDAY FOR LOZ042-043.
SMALL CRAFT ADVISORY FROM MIDNIGHT WEDNESDAY NIGHT TO 10
AM EST THURSDAY FOR LOZ044-045.
&&
$$
SYNOPSIS...WCH
NEAR TERM...APFFEL/WCH
SHORT TERM...RSH
LONG TERM...RSH
AVIATION...APFFEL
MARINE...APFFEL/WCH
CLIMATE...THOMAS
AREA FORECAST DISCUSSION
NWS DENVER CO
901 AM MST WED DEC 21 2011
.UPDATE...STRONG TROUGH IS CURRENTLY OVER SOUTHWEST MONTANA WILL
CONTINUE TO DIG SOUTH TODAY. A SOUTHWEST JET AHEAD OF THIS TROUGH IS
PRODUCING AN AREA OF LIGHT SNOW FROM NORTH CENTRAL COLORADO TO
SOUTHERN WYOMING. THIS AREA OF SNOW WILL SINK SOUTH THROUGH THE DAY
AS THE SYSTEM MOVES SOUTH. MODELS SHOWING THIS WILL WEAKEN AS IT
MOVE INTO COLORADO. SO IF ANY SNOW FALL IT WILL BE LIGHT. WILL ADD
SOME LOW POPS TO THE FORECAST TO COVER THIS. MAIN STORM IS STILL
OVER SOUTHERN MONTANA AND NORTHERN WYOMING. WIDESPREAD SNOW IS ON
TRACK TO START THIS EVENING. BEST LIFT AND STRONGEST UPSLOPE WILL
OCCUR AFTER MIDNIGHT...THUS THE HEAVIEST SNOW WILL FALL DURING THIS
TIME FRAME.
CURRENT WINTER WEATHER HIGHLIGHTS LOOK ON TRACK...WILL ADD THE
MOUNTAIN VALLEYS TO THE ADVISORY WHERE IT APPEARS 3 TO 6 INCHES WILL
FALL. ONLY OTHER CHANGE TO THE FORECAST WILL BE TO ADD A COUPLE OF
INCHES OF SNOW TO THE WINTER STORM WARNING. MODELS HAVE BEEN
CONSISTENT IN FORECASTING 0.40 TO 0.75 INCHES OF LIQUID WITH THIS
STORM FOR THE URBAN CORRIDOR. USING A 15 TO 1 RATIO...THIS WOULD
LEAD TO ABOUT 6 TO 11 INCHES. WOULD EXPECT A LITTLE MORE ACROSS
FAVORED UPSLOPE AREAS IN AND NEAR THE FOOTHILLS.
&&
.AVIATION...HIGH CLOUDS WILL INCREASE TODAY AS THE WINTER STORM
NEARS THE COLORADO. CEILINGS WILL REMAIN ABOVE 10000 THROUGH 21Z
THEN FALL THROUGH THE AFTERNOON AND EVENING. CEILINGS AND
VISIBILITIES SHOULD TANK FAIRLY RAPIDLY DURING THE 00Z TO 03Z TIME
FRAME WITH SNOW AND REMAIN DOWN THROUGH THE NIGHT. WINDS WILL
TRANSITION TO LIGHT NORTH/NORTHEAST DURING THE AFTERNOON WITH A
GRADUAL INCREASE INTO THE EVENING HOURS. SUSTAINED SPEEDS IN THE 10
TO 15 KNOT RANGE SHOULD BE COMMON AFTER ABOUT 00Z...CONTINUING
THROUGH 12Z WITH GUSTS TO THE LOWER 20S...STRONGEST AT KDEN.
HEAVIEST SNOW WILL OCCUR 06-12Z. EXPECTING SNOW ACCUMULATION AT
KDEN TO BE 6-8 INCHES...WITH 7-10 INCHES POSSIBLE AT KAPA AND
KBJC.
&&
.PREV DISCUSSION... /ISSUED 427 AM MST WED DEC 21 2011/
SHORT TERM...FORECAST IN PRETTY GOOD SHAPE AND MODELS IN GOOD
AGREEMENT WITH THE UPCOMING STORM. VERY WEAK QG ASCENT IS ALREADY
UNDERWAY OVER THE CWA PER LATEST RUC ANALYSES AND IT WILL BE ON
THE INCREASE THROUGHOUT THE SHORT TERM. THE HEART OF IT IS OVER
CENTRAL COLORADO BY 12Z THURSDAY WITH AT LEAST MODEST VALUES
THROUGHOUT THE ENTIRE CWA BY THEN. AT THE SURFACE UPSLOPE WILL
ALSO BE INCREASING THROUGH THE PERIOD WITH SOME MINOR AND PROBABLY
NOT TERRIBLY SIGNIFICANT TIMING DIFFERENCES AMONGST THE MODELS.
CONTRARY TO SOME OF THE EARLIER STORMS THIS YEAR A DECENT QG
ANALLOBARIC CENTER IS FORECAST TO DEVELOP OVER THE AREA BY 12Z
WHICH MAY ENHANCE THE UPSLOPE INTO THE FRONT RANGE AND AID IN
SNOWFALL IN AND NEAR THE FOOTHILLS. ALL IN ALL THIS LOOKS TO BE A
FAIRLY TYPICAL EARLY WINTER STORM FOR NORTHEAST AND NORTH CENTRAL
COLORADO.
LONG TERM...AN UPPER LEVEL LOW WILL BE OVER SWRN CO THU MORNING AND
WILL MOVE SLOWLY SSE INTO NWRN NEW MEXICO BY THU NIGHT.
CROSS-SECTIONS SHOW FAVORABLE UPSLOPE FLOW AND DECENT QG ASCENT THRU
18Z WITH A GRADUAL WEAKENING IN BOTH UPSLOPE FLOW AND QG ASCENT
DURING THE AFTN HOURS. THUS SHOULD SEE PERIODS OF MDT TO HEAVY SNOW
IN THE FOOTHILLS AND ERN FACING SLOPES OF THE MTNS. AT LOWER
ELEVATIONS APPEARS BEST CHC OF HEAVY SNOWS WILL BE FM BOULDER TO
DENVER SOUTHWARD ACROSS THE PALMER DIVIDE SO WILL CONTINUE WITH A
WARNING IN THESE AREAS THRU 18Z. FURTHER NORTH CLOSER TO TO THE
CO-WY BORDER APPEARS SNOW AMOUNTS WILL NOT BE QUITE AS HEAVY SO WILL
HAVE AN ADVISORY IN THOSE AREAS THRU 18Z. OVER THE PLAINS WILL HAVE
ADVISORIES FM EAST OF DENVER TO LIMON THRU MIDDAY. WINDS WILL BE
GUSTY IN THE MORNING AS WELL ESPECIALLY ALONG AND EAST OF I-25 SO
WILL SEE SOME BLOWING SNOW AND POOR VISIBILITIES AS WELL.
BY AFTN SHOULD SEE SNOWFALL GRADUALLY DECREASE FM NORTH TO SOUTH
ALTHOUGH ACROSS THE SRN FOOTHILLS AND PALMER DIVIDE ITS POSSIBLE MDT
SNOWFALL MAY LINGER THRU THE LATE AFTN HOURS. AS FOR TOTAL AMOUNTS
WILL HAVE 6 TO 12 INCHES IN THE MTNS...8 TO 16 INCHES IN THE
FOOTHILLS...5 TO 10 INCHES FM DENVER SOUTH TO THE PALMER DIVIDE WITH
3 TO 6 INCHES NEAR THE CO-WY BORDER. OVER THE PLAINS AMOUNTS WILL
RANGE FROM 2 TO 4 INCHES OVER THE FAR NERN CORNER WITH 3 TO 6 INCHES
ELSEWHERE. HIGHS ON THU WILL STRUGGLE TO GET ABOVE 20 DEGREES OVER
MUCH OF NERN CO AS COLD SFC HIGH PRESSURE BUILDS SOUTHWARD INTO THE
AREA.
FOR THU NIGHT INTO FRI THE STORM SYSTEM WILL CONTINUE TO MOVE SE
AWAY FM THE AREA WITH SNOW ENDING IN ALL AREAS BY EARLY THU
EVENING. CLEARING SKIES THU NIGHT COMBINED WITH FRESH SNOW COVER
MAY ALLOW FOR LOWS TO DROP BLO ZERO ACROSS MUCH OF NERN CO BY FRI
MORNING. ON FRI DRY NNE MID LEVEL FLOW WILL BE OVER THE AREA WITH
MO PCPN EXPECTED. HIGHS ON FRI WILL LIKELY BE AFFECTED BY SNOW
COVER OVER NERN CO AS INVERSIONS WILL HAVE A HARD TIME BREAKING SO
WILL KEEP HIGHS IN THE 25 TO 30 DEGREE RANGE.
FOR SAT LOOKS LIKE A WEAK WEATHER DISTURBANCE MAY TRACK ACROSS NRN
CO HOWEVER CROSS-SECTIONS SHOW VERY LITTLE MOISTURE WITH THIS
FEATURE SO WILL ONLY MENTION A SLIGHT CHC OF SNOW IN THE MTNS NORTH
OF -70. AS FOR HIGHS LATEST GFS IS REALLY STARTING TO WRM TEMPS
HOWEVER BELIEVE LINGERING SNOW PACK COMBINED WITH LACK OF DOWNSLOPE
COMPONENT WILL PROBABLY KEEP HIGHS IN THE 30S ACROSS NERN CO INSTEAD
OF THE 40S AS SHOWN BY THE GFS. BY CHRISTMAS AN UPPER LEVEL RIDGE
WILL BE OVER THE AREA WITH CROSS-SECTIONS SHOWING A DRY AIRMASS IN
PLACE SO WILL KEEP FCST DRY. ONCE AGAIN LATEST GFS IS SHOWING QUITE
A BIT OF WARMING ON SUN WITH HIGHS IN THE 50S ACROSS NERN CO AS LOW
LEVEL WINDS ARE FCST TO BECOME WEAK SWLY. FOR NOW WILL KEEP
READINGS IN THE UPPER 30S TO MID 40S DUE TO LINGERING SNOW COVER.
FOR MON THE FLOW ALOFT WILL INCREASE AND BECOME MORE WLY WHICH
SHOULD ALLOW FOR BETTER DOWNSLOPE WARMING AND ALLOW HIGHS TO RISE
WELLS INTO 40S. WITH THE INCREASING FLOW ALOFT WINDS WILL BECOME
GUSTY IN THE MTNS AND FOOTHILLS. BY TUE THE ECMWF AND GFS DIVERGE
SOMEWHAT AS THE GFS HAS MAINLY DRY WNW FLOW ALOFT WHILE THE ECMWF
SHOWS AN UPPER LEVEL ROUGH MOVING QUICKLY ACROSS THE AREA WITH A CHC
OF SNOW IN THE MTNS.
AVIATION...VFR CONDITIONS ARE EXPECTED THROUGH AT LEAST EARLY
AFTERNOON WITH A THREAT OF SCT-BKN060 BY MID AFTERNOON. CEILINGS
AND VISIBILITIES SHOULD TANK FAIRLY RAPIDLY DURING THE 00Z TO 03Z
TIME FRAME WITH SNOW AND REMAIN DOWN THROUGH THE NIGHT. WINDS WILL
TRANSITION TO LIGHT NORTH/NORTHEAST DURING THE DAY WITH A GRADUAL
INCREASE INTO THE EVENING HOURS. SUSTAINED SPEEDS IN THE 10 TO 15
KNOT RANGE SHOULD BE COMMON AFTER ABOUT 00Z...CONTINUING THROUGH
12Z WITH GUSTS TO THE LOWER 20S...STRONGEST AT KDEN. THE WIND WILL
CAUSE SOME BLOWING SNOW AS WELL.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 5 PM THIS AFTERNOON TO 11 AM MST
THURSDAY FOR COZ030>034-037-038-042>046.
WINTER STORM WARNING FROM 5 PM THIS AFTERNOON TO 11 AM MST
THURSDAY FOR COZ035-036-039>041.
&&
$$
SHORT TERM...RPK
LONG TERM....ET
UPDATE/AVIATION...MEIER
AREA FORECAST DISCUSSION
NWS DENVER CO
427 AM MST WED DEC 21 2011
.SHORT TERM...FORECAST IN PRETTY GOOD SHAPE AND MODELS IN GOOD
AGREEMENT WITH THE UPCOMING STORM. VERY WEAK QG ASCENT IS ALREADY
UNDERWAY OVER THE CWA PER LATEST RUC ANALYSES AND IT WILL BE ON
THE INCREASE THROUGHOUT THE SHORT TERM. THE HEART OF IT IS OVER
CENTRAL COLORADO BY 12Z THURSDAY WITH AT LEAST MODEST VALUES
THROUGHOUT THE ENTIRE CWA BY THEN. AT THE SURFACE UPSLOPE WILL
ALSO BE INCREASING THROUGH THE PERIOD WITH SOME MINOR AND PROBABLY
NOT TERRIBLY SIGNIFICANT TIMING DIFFERENCES AMONGST THE MODELS.
CONTRARY TO SOME OF THE EARLIER STORMS THIS YEAR A DECENT QG
ANALLOBARIC CENTER IS FORECAST TO DEVELOP OVER THE AREA BY 12Z
WHICH MAY ENHANCE THE UPSLOPE INTO THE FRONT RANGE AND AID IN
SNOWFALL IN AND NEAR THE FOOTHILLS. ALL IN ALL THIS LOOKS TO BE A
FAIRLY TYPICAL EARLY WINTER STORM FOR NORTHEAST AND NORTH CENTRAL
COLORADO.
.LONG TERM...AN UPPER LEVEL LOW WILL BE OVER SWRN CO THU MORNING AND
WILL MOVE SLOWLY SSE INTO NWRN NEW MEXICO BY THU NIGHT.
CROSS-SECTIONS SHOW FAVORABLE UPSLOPE FLOW AND DECENT QG ASCENT THRU
18Z WITH A GRADUAL WEAKENING IN BOTH UPSLOPE FLOW AND QG ASCENT
DURING THE AFTN HOURS. THUS SHOULD SEE PERIODS OF MDT TO HEAVY SNOW
IN THE FOOTHILLS AND ERN FACING SLOPES OF THE MTNS. AT LOWER
ELEVATIONS APPEARS BEST CHC OF HEAVY SNOWS WILL BE FM BOULDER TO
DENVER SOUTHWARD ACROSS THE PALMER DIVIDE SO WILL CONTINUE WITH A
WARNING IN THESE AREAS THRU 18Z. FURTHER NORTH CLOSER TO TO THE
CO-WY BORDER APPEARS SNOW AMOUNTS WILL NOT BE QUITE AS HEAVY SO WILL
HAVE AN ADVISORY IN THOSE AREAS THRU 18Z. OVER THE PLAINS WILL HAVE
ADVISORIES FM EAST OF DENVER TO LIMON THRU MIDDAY. WINDS WILL BE
GUSTY IN THE MORNING AS WELL ESPECIALLY ALONG AND EAST OF I-25 SO
WILL SEE SOME BLOWING SNOW AND POOR VISIBILITIES AS WELL.
BY AFTN SHOULD SEE SNOWFALL GRADUALLY DECREASE FM NORTH TO SOUTH
ALTHOUGH ACROSS THE SRN FOOTHILLS AND PALMER DIVIDE ITS POSSIBLE MDT
SNOWFALL MAY LINGER THRU THE LATE AFTN HOURS. AS FOR TOTAL AMOUNTS
WILL HAVE 6 TO 12 INCHES IN THE MTNS...8 TO 16 INCHES IN THE
FOOTHILLS...5 TO 10 INCHES FM DENVER SOUTH TO THE PALMER DIVIDE WITH
3 TO 6 INCHES NEAR THE CO-WY BORDER. OVER THE PLAINS AMOUNTS WILL
RANGE FROM 2 TO 4 INCHES OVER THE FAR NERN CORNER WITH 3 TO 6 INCHES
ELSEWHERE. HIGHS ON THU WILL STRUGGLE TO GET ABVE 20 DEGREES OVER
MUCH OF NERN CO AS COLD SFC HIGH PRESSURE BUILDS SOUTHWARD INTO THE
AREA.
FOR THU NIGHT INTO FRI THE STORM SYSTEM WILL CONTINUE TO MOVE SE
AWAY FM THE AREA WITH SNOW ENDING IN ALL AREAS BY EARLY THU
EVENING. CLEARING SKIES THU NIGHT COMBINED WITH FRESH SNOW COVER
MAY ALLOW FOR LOWS TO DROP BLO ZERO ACROSS MUCH OF NERN CO BY FRI
MORNING. ON FRI DRY NNE MID LEVEL FLOW WILL BE OVER THE AREA WITH
MO PCPN EXPECTED. HIGHS ON FRI WILL LIKELY BE AFFECTED BY SNOW
COVER OVER NERN CO AS INVERSIONS WILL HAVE A HARD TIME BREAKING SO
WILL KEEP HIGHS IN THE 25 TO 30 DEGREE RANGE.
FOR SAT LOOKS LIKE A WEAK WEATHER DISTURBANCE MAY TRACK ACROSS NRN
CO HOWEVER CROSS-SECTIONS SHOW VERY LITTLE MOISTURE WITH THIS
FEATURE SO WILL ONLY MENTION A SLIGHT CHC OF SNOW IN THE MTNS NORTH
OF -70. AS FOR HIGHS LATEST GFS IS REALLY STARTING TO WRM TEMPS
HOWEVER BELIEVE LINGERNG SNOW PACK COMBINED WITH LACK OF DOWNSLOPE
COMPONENT WILL PROBABLY KEEP HIGHS IN THE 30S ACROSS NERN CO INSTEAD
OF THE 40S AS SHOWN BY THE GFS. BY CHRISTMAS AN UPPER LEVEL RIDGE
WILL BE OVER THE AREA WITH CROSS-SECTIONS SHOWING A DRY AIRMASS IN
PLACE SO WILL KEEP FCST DRY. ONCE AGAIN LATEST GFS IS SHOWING QUITE
A BIT OF WARMING ON SUN WITH HIGHS IN THE 50S ACROSS NERN CO AS LOW
LEVEL WINDS ARE FCST TO BECOME WEAK SWLY. FOR NOW WILL KEEP
READINGS IN THE UPPER 30S TO MID 40S DUE TO LINGERING SNOW COVER.
FOR MON THE FLOW ALOFT WILL INCREASE AND BECOME MORE WLY WHICH
SHOULD ALLOW FOR BETTER DOWNSLOPE WARMING AND ALLOW HIGHS TO RISE
WELLS INTO 40S. WITH THE INCREASING FLOW ALOFT WINDS WILL BECOME
GUSTY IN THE MTNS AND FOOTHILLS. BY TUE THE ECMWF AND GFS DIVERGE
SOMEWHAT AS THE GFS HAS MAINLY DRY WNW FLOW ALOFT WHILE THE ECMWF
SHOWS AN UPPER LEVEL ROUGH MOVING QUICKLY ACROSS THE AREA WITH A CHC
OF SNOW IN THE MTNS.
&&
.AVIATION...VFR CONDITIONS ARE EXPECTED THROUGH AT LEAST EARLY
AFTERNOON WITH A THREAT OF SCT-BKN060 BY MID AFTERNOON. CEILINGS
AND VISIBILITIES SHOULD TANK FAIRLY RAPIDLY DURING THE 00Z TO 03Z
TIME FRAME WITH SNOW AND REMAIN DOWN THROUGH THE NIGHT. WINDS WILL
TRANSITION TO LIGHT NORTH/NORTHEAST DURING THE DAY WITH A GRADUAL
INCREASE INTO THE EVENING HOURS. SUSTAINED SPEEDS IN THE 10 TO 15
KNOT RANGE SHOULD BE COMMON AFTER ABOUT 00Z...CONTINUING THROUGH
12Z WITH GUSTS TO THE LOWER 20S...STRONGEST AT KDEN. THE WIND WILL
CAUSE SOME BLOWING SNOW AS WELL.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 5 PM THIS AFTERNOON TO 11 AM MST
THURSDAY FOR COZ031-033-034-037-038-042>046.
WINTER STORM WARNING FROM 5 PM THIS AFTERNOON TO 11 AM MST
THURSDAY FOR COZ035-036-039>041.
&&
$$
SHORT TERM...ET
LONG TERM....RPK
AVIATION...ET
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
1048 AM EST WED DEC 21 2011
.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL LIFT FROM THE OHIO VALLEY INTO THE
EASTERN GREAT LAKES TODAY, BRINGING RAIN AND UNSEASONABLY WARM
TEMPERATURES TO THE AREA. HIGH PRESSURE WILL THEN BRIEFLY BRING A
BREAK FROM SHOWERS TONIGHT INTO EARLY THURSDAY. THE NEXT LOW WILL
APPROACH FROM THE SOUTHWEST AND RETURN SHOWERS TO THE AREA FOR
THURSDAY NIGHT.
&&
.NEAR TERM /THROUGH TONIGHT/...
15Z ENHANCED SHORT TERM FORECAST UPDATE HAS BEEN ISSUED TO PIN DOWN
THE MAIN PRE-FRONTAL PRECIPITATION SHIELD AS IT MOVES INTO THE UPPER
OHIO VALLEY LATE THIS MORNING INTO THE AFTERNOON HOURS. IN ADDITION,
TEMPS HAVE BEEN INCREASED, ESPECIALLY SOUTH OF PITTSBURGH.
THE LATEST RUC MID-LEVEL ANALYSIS INDICATES A CLOSED LOW ACROSS
ILLINOIS WITH THE UPPER OHIO VALLEY IN A SOUTHWESTERLY FLOW AHEAD OF
THIS FEATURE. A SATURATED AREA OF 1000-500MB LAYER IS ADVECTING
ACROSS THE UPPER OHIO VALLEY WITH MID-LEVEL DRY AIR ADVECTION FROM
INDIANA INTO WESTERN OHIO. 850MB TEMPS OF 8C-10C ARE INDICATIVE OF
THE WARM AIR ALOFT THAT HAS BUILT IN WITH THE WARM SECTOR. AT THE
SURFACE, A 1004MB LOW IS LOCATED IN NW OHIO WITH A WARM FRONT
EXTENDING NORTHEAST OF THIS FEATURE ACROSS LAKE ERIE. MEANWHILE, A
COLD FRONT EXTENDS SOUTH OF THE LOW INTO THE CENTRAL GULF STATES.
AN AXIS OF PRE-FRONTAL RAIN IS SHIFTING INTO WESTERN PA AHEAD OF
THE LOW. BEHIND THIS AXIS THERE IS SOME CLEARING IN A DRY SWATH
AHEAD OF THE COLD FRONT.
TODAY...THE SURFACE LOW WILL TRANSVERSE NORTHEASTWARD, PROGGED TO BE
ACROSS LAKE ERIE BY 21Z. NAM12/RUC13 700MB OMEGA FIELDS INDICATE A
BROAD AREA OF FORCING FOR ASCENT ASSOCIATED WITH THE PRE-FRONTAL
AXIS OF RAIN MOVING MOSTLY EAST OF THE AREA BY THE LATE AFTERNOON.
AS RAIN MOVES THROUGH, A HALF OF AN INCH TO THREE QUARTERS OF AN
INCH OF PRECIPITATION CAN BE EXPECTED. WINDS WILL GUST THIS
AFTERNOON AT 20 TO 25 MPH AS PRESSURE GRADIENT TIGHTENS AND WINDS
BRIEFLY MIX DOWN WITH BREAKS IN CLOUD COVERAGE. WARM AIR ADVECTION
WILL BE ONGOING IN A STRONG SOUTHERLY FLOW AHEAD OF THE COLD
FRONT. THUS, HIGHS TODAY ARE A FEW DEGREES WARMER THAN A MAV/MET
BLEND, ESPECIALLY SOUTH OF PITTSBURGH. HIGHS TODAY WILL RANGE FROM
THE LOWER TO MID 60S ACROSS NORTH-CENTRAL WV TO THE MID 50S ALONG
THE I-80 CORRIDOR.
BEHIND THE INITIAL PRECIP SHIELD, MID-LEVEL DRYING WILL DIMINISH THE
COVERAGE OF SHOWERS. HRRR/WRF-NMM SUPPORT SCATTERED LOW-TOPPED
CONVECTION DEVELOPING IN THIS AREA FOR THE LATE AFTERNOON AND
EARLY EVENING. WEAK SBCAPE (<500 J/KG) AND STRONG 0-6KM SHEAR
(70KT) AHEAD OF A COLD FRONT APPROACHING THE AREA CONTINUE TO
SUPPORT THE CHANCE OF ISOLATED THUNDERSTORMS. NOT OF THE QUESTION
CONVECTION COULD BRING DOWN SOME STRONGER GUSTS LATER THIS
AFTERNOON. CONCUR WITH THE STORM PREDICTION CENTER WHICH HAS THE
AREA HIGHLIGHTED IN ITS GENERAL THUNDERSTORM OUTLOOK.
TONIGHT...THE SURFACE LOW WILL PUSH INTO THE NORTHEAST AND ITS
ASSOCIATED COLD FRONT WILL SLIDE EAST OF THE AREA. ANY CONVECTION
WILL QUICKLY DIMINISH AND PUSH EAST OF THE AREA AFTER 00Z. THUS,
FORECAST IS DRY ACROSS THE AREA BY 03Z. COLD AIR ADVECTION WILL BE
WEAK IN THE WAKE OF THE FRONT, WITH A ZONAL MID-LEVEL FLOW IN THE
BEHIND THE LAGGING 500MB TROUGH. OVERNIGHT LOWS ARE A MAV/MET BLEND,
RANGING RANGE FROM THE UPPER 30S ACROSS THE I-80 CORRIDOR TO THE LOWER
40S ELSEWHERE.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY/...
COLDER AIR WILL SETTLE INTO THE AREA THROUGH MOST OF THURSDAY.
THERE WILL BE A PERIOD OF DRY WEATHER THROUGH AT LEAST THE FIRST
HALF OF THU.
MODELS ARE IN GOOD AGREEMENT DEVELOPING ANOTHER SFC LOW WHICH WILL
MOVE UP THE APPALACHIANS THURSDAY AFTERNOON AND TURN TOWARD THE
EAST COAST THURSDAY NIGHT. WITH THE CURRENT FORECAST TRACK OF THE
SFC LOW, WARMER AIR WILL SURGE NORTHWARD AND KEEP THIS A RAIN
EVENT. HOWEVER, IF THE LOW WOULD TAKE A TRACK FURTHER TO THE EAST,
OR SHIFT TO THE EAST FASTER, LOCATIONS ACROSS THE FAR NORTH COULD
SEE MIXED PRECIPITATION.
THE SFC LOW WILL QUICKLY EXIT THE EAST COAST EARLY FRIDAY AND
COLDER AIR WILL WRAP IN BEHIND THE EXITING LOW. THERE MAY BE SOME
LINGER SHOWERS/SNOW SHOWERS IN THE CAA BEHIND THE LOW.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
VERY LOW CONFIDENCE IN THE LONG TERM, AS MEDIUM RANGE OP MODELS
ARE SHOWING LARGE VARIANCES BEGINNING ON SUNDAY.
12Z ECMWF IS SHOWING ANOTHER LARGE SFC LOW DEVELOPING OVER THE
GULF COAST SAT NIGHT AND RUSHING NORTHWARD ON SUNDAY.
HOWEVER, THE 00Z GFS DOES NOT DEVELOP THIS SFC SYSTEM, RATHER IT
BRINGS A WEAK COLD FRONT THROUGH ON SUNDAY. THE 12Z GEFS, 12Z
ECMWF ENSEMBLES, AND 12Z CMC ARE ALL SHOWING SOLUTIONS CLOSER TO
THAT OF THE GFS. SO FOR THE WEEKEND WILL LEAN CLOSER TO THE 00Z
GFS SOLUTION. THIS WOULD MEAN A COLDER AND DRIER FORECAST.
LOW CONFIDENCE CONTINUES FOR THE REMAINDER OF THE THE LONG TERM.
&&
.AVIATION /16Z WEDNESDAY THROUGH SUNDAY/...
AREA OF RAIN MOVING RAPIDLY EAST. BACK EDGE OF STEADY RAIN JUST
EAST OF ZZV AND SHOULD REACH PIT 1700-1730Z AND TO THE RIDGES
SHORTLY AFTER 18Z. RAIN IS FOLLOWED BY AREA OF MVFR STRATUS WITH
AREAS OF IFR CIGS. DRY SLOT WITH POSSIBLE CONVECTION REACHES ZZV
AROUND 18Z AND PIT BY 21Z. EXPECT FRONTAL PASSAGE AT AT ZZV AROUND
21Z, PIT AROUND 00Z AND TO THE RIDGES BY 03Z. MVFR CIGS WILL
OVERSPREAD AREA AFTER FRONTAL PASSAGE.
NAM MODEL PROFILES LIKEWISE SHOW FAST WINDS 1-4 KFT AGL TODAY. SO
HAVE ADDED LOW LEVEL WIND SHEAR THROUGH MID MORNING. AFTER THAT,
EXPECT SUFFICIENT VERTICAL MIXING IN THE SURFACE LAYER TO HAVE
THESE FAST WINDS PRODUCE GUSTS TO 20-25 KTS MIDDAY INTO EARLY
AFTERNOON. POST-SYSTEM STRONG PRESSURE RISES MAY CAUSE A PERIOD OF
WIND GUSTS TO ABOUT 30 KTS LATE THIS AFTERNOON INTO EARLY EVENING.
OUTLOOK...THURSDAY THROUGH SUNDAY...
MVFR STRATOCUMULUS CEILINGS CAN LINGER INTO DAYTIME THURSDAY. A
SERIES OF PASSING SYSTEMS WILL ALSO PROVIDE PERIODS OF PRECIPITATION
AND RESTRICTIONS THURSDAY NIGHT INTO MONDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
953 AM EST WED DEC 21 2011
.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL LIFT FROM THE OHIO VALLEY INTO THE
EASTERN GREAT LAKES TODAY, BRINGING RAIN AND UNSEASONABLY WARM
TEMPERATURES TO THE AREA. HIGH PRESSURE WILL THEN BRIEFLY BRING A
BREAK FROM SHOWERS TONIGHT INTO EARLY THURSDAY. THE NEXT LOW WILL
APPROACH FROM THE SOUTHWEST AND RETURN SHOWERS TO THE AREA FOR
THURSDAY NIGHT.
&&
.NEAR TERM /THROUGH TONIGHT/...
15Z ENHANCED SHORT TERM FORECAST UPDATE HAS BEEN ISSUED TO PIN DOWN
THE MAIN PRE-FRONTAL PRECIPITATION SHIELD AS IT MOVES INTO THE UPPER
OHIO VALLEY LATE THIS MORNING INTO THE AFTERNOON HOURS. IN ADDITION,
TEMPS HAVE BEEN INCREASED, ESPECIALLY SOUTH OF PITTSBURGH.
THE LATEST RUC MID-LEVEL ANALYSIS INDICATES A CLOSED LOW ACROSS
ILLINOIS WITH THE UPPER OHIO VALLEY IN A SOUTHWESTERLY FLOW AHEAD OF
THIS FEATURE. A SATURATED AREA OF 1000-500MB LAYER IS ADVECTING
ACROSS THE UPPER OHIO VALLEY WITH MID-LEVEL DRY AIR ADVECTION FROM
INDIANA INTO WESTERN OHIO. 850MB TEMPS OF 8C-10C ARE INDICATIVE OF
THE WARM AIR ALOFT THAT HAS BUILT IN WITH THE WARM SECTOR. AT THE
SURFACE, A 1004MB LOW IS LOCATED IN NW OHIO WITH A WARM FRONT
EXTENDING NORTHEAST OF THIS FEATURE ACROSS LAKE ERIE. MEANWHILE, A
COLD FRONT EXTENDS SOUTH OF THE LOW INTO THE CENTRAL GULF STATES.
AN AXIS OF PRE-FRONTAL RAIN IS SHIFTING INTO WESTERN PA AHEAD OF
THE LOW. BEHIND THIS AXIS THERE IS SOME CLEARING IN A DRY SWATH
AHEAD OF THE COLD FRONT.
TODAY...THE SURFACE LOW WILL TRANSVERSE NORTHEASTWARD, PROGGED TO BE
ACROSS LAKE ERIE BY 21Z. NAM12/RUC13 700MB OMEGA FIELDS INDICATE A
BROAD AREA OF FORCING FOR ASCENT ASSOCIATED WITH THE PRE-FRONTAL
AXIS OF RAIN MOVING MOSTLY EAST OF THE AREA BY THE LATE AFTERNOON.
AS RAIN MOVES THROUGH, A HALF OF AN INCH TO THREE QUARTERS OF AN
INCH OF PRECIPITATION CAN BE EXPECTED. WINDS WILL GUST THIS
AFTERNOON AT 20 TO 25 MPH AS PRESSURE GRADIENT TIGHTENS AND WINDS
BRIEFLY MIX DOWN WITH BREAKS IN CLOUD COVERAGE. WARM AIR ADVECTION
WILL BE ONGOING IN A STRONG SOUTHERLY FLOW AHEAD OF THE COLD
FRONT. THUS, HIGHS TODAY ARE A FEW DEGREES WARMER THAN A MAV/MET
BLEND, ESPECIALLY SOUTH OF PITTSBURGH. HIGHS TODAY WILL RANGE FROM
THE LOWER TO MID 60S ACROSS NORTH-CENTRAL WV TO THE MID 50S ALONG
THE I-80 CORRIDOR.
BEHIND THE INITIAL PRECIP SHIELD, MID-LEVEL DRYING WILL DIMINISH THE
COVERAGE OF SHOWERS. HRRR/WRF-NMM SUPPORT SCATTERED LOW-TOPPED
CONVECTION DEVELOPING IN THIS AREA FOR THE LATE AFTERNOON AND
EARLY EVENING. WEAK SBCAPE (<500 J/KG) AND STRONG 0-6KM SHEAR
(70KT) AHEAD OF A COLD FRONT APPROACHING THE AREA CONTINUE TO
SUPPORT THE CHANCE OF ISOLATED THUNDERSTORMS. NOT OF THE QUESTION
CONVECTION COULD BRING DOWN SOME STRONGER GUSTS LATER THIS
AFTERNOON. CONCUR WITH THE STORM PREDICTION CENTER WHICH HAS THE
AREA HIGHLIGHTED IN ITS GENERAL THUNDERSTORM OUTLOOK.
TONIGHT...THE SURFACE LOW WILL PUSH INTO THE NORTHEAST AND ITS
ASSOCIATED COLD FRONT WILL SLIDE EAST OF THE AREA. ANY CONVECTION
WILL QUICKLY DIMINISH AND PUSH EAST OF THE AREA AFTER 00Z. THUS,
FORECAST IS DRY ACROSS THE AREA BY 03Z. COLD AIR ADVECTION WILL BE
WEAK IN THE WAKE OF THE FRONT, WITH A ZONAL MID-LEVEL FLOW IN THE
BEHIND THE LAGGING 500MB TROUGH. OVERNIGHT LOWS ARE A MAV/MET BLEND,
RANGING RANGE FROM THE UPPER 30S ACROSS THE I-80 CORRIDOR TO THE LOWER
40S ELSEWHERE.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY/...
COLDER AIR WILL SETTLE INTO THE AREA THROUGH MOST OF THURSDAY.
THERE WILL BE A PERIOD OF DRY WEATHER THROUGH AT LEAST THE FIRST
HALF OF THU.
MODELS ARE IN GOOD AGREEMENT DEVELOPING ANOTHER SFC LOW WHICH WILL
MOVE UP THE APPALACHIANS THURSDAY AFTERNOON AND TURN TOWARD THE
EAST COAST THURSDAY NIGHT. WITH THE CURRENT FORECAST TRACK OF THE
SFC LOW, WARMER AIR WILL SURGE NORTHWARD AND KEEP THIS A RAIN
EVENT. HOWEVER, IF THE LOW WOULD TAKE A TRACK FURTHER TO THE EAST,
OR SHIFT TO THE EAST FASTER, LOCATIONS ACROSS THE FAR NORTH COULD
SEE MIXED PRECIPITATION.
THE SFC LOW WILL QUICKLY EXIT THE EAST COAST EARLY FRIDAY AND
COLDER AIR WILL WRAP IN BEHIND THE EXITING LOW. THERE MAY BE SOME
LINGER SHOWERS/SNOW SHOWERS IN THE CAA BEHIND THE LOW.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
VERY LOW CONFIDENCE IN THE LONG TERM, AS MEDIUM RANGE OP MODELS
ARE SHOWING LARGE VARIANCES BEGINNING ON SUNDAY.
12Z ECMWF IS SHOWING ANOTHER LARGE SFC LOW DEVELOPING OVER THE
GULF COAST SAT NIGHT AND RUSHING NORTHWARD ON SUNDAY.
HOWEVER, THE 00Z GFS DOES NOT DEVELOP THIS SFC SYSTEM, RATHER IT
BRINGS A WEAK COLD FRONT THROUGH ON SUNDAY. THE 12Z GEFS, 12Z
ECMWF ENSEMBLES, AND 12Z CMC ARE ALL SHOWING SOLUTIONS CLOSER TO
THAT OF THE GFS. SO FOR THE WEEKEND WILL LEAN CLOSER TO THE 00Z
GFS SOLUTION. THIS WOULD MEAN A COLDER AND DRIER FORECAST.
LOW CONFIDENCE CONTINUES FOR THE REMAINDER OF THE THE LONG TERM.
&&
.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
PER BLEND OF RECENT SURFACE AND RADAR DATA ALONG WITH SUITE OF HIGH
RESOLUTION MODELS, EXPECT FREQUENT SHOWERS WITH IFR RESTRICTIONS AT
TIMES TODAY, AS STRONG NORTHEASTWARD MOVING LOW PRESSURE CENTER
PASSES THROUGH OHIO THIS AFTERNOON. SHOWERS SHOULD END ABRUPTLY THIS
EVENING.
NAM MODEL PROFILES SHOW INSTABILITY CAN DEVELOP ACROSS THE UPPER
OHIO VALLEY THIS AFTERNOON, AS THE VALLEY WILL BE IN THE SO-CALLED
WARM SECTOR OF THE SYSTEM. SO WILL MENTION POSSIBLE THUNDER, WHICH
CONCURS WITH SPC GUIDANCE.
NAM MODEL PROFILES LIKEWISE SHOW FAST WINDS 1-4 KFT AGL TODAY. SO
HAVE ADDED LOW LEVEL WIND SHEAR THROUGH MID MORNING. AFTER THAT,
EXPECT SUFFICIENT VERTICAL MIXING IN THE SURFACE LAYER TO HAVE THESE
FAST WINDS PRODUCE GUSTS TO 20-25 KTS MIDDAY INTO EARLY AFTERNOON.
POST-SYSTEM STRONG PRESSURE RISES MAY CAUSE A PERIOD OF WIND GUSTS
TO ABOUT 30 KTS LATE THIS AFTERNOON INTO EARLY EVENING.
POST SYSTEM STRATOCUMULUS SHOULD YIELD MAINLY MVFR CEILINGS
TONIGHT, WITH PERHAPS A PERIOD OF IFR.
OUTLOOK...THURSDAY THROUGH SUNDAY...
MVFR STRATOCUMULUS CEILINGS CAN LINGER INTO DAYTIME THURSDAY. A
SERIES OF PASSING SYSTEMS WILL ALSO PROVIDE PERIODS OF PRECIPITATION
AND RESTRICTIONS THURSDAY NIGHT INTO MONDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS GREENVILLE-SPARTANBURG SC
958 AM EST WED DEC 21 2011
.SYNOPSIS...
AN UNSETTLED WEATHER PATTERN WILL PERSIST THROUGH THE REMAINDER OF
THE WEEK AND INTO THE HOLIDAY WEEKEND. A COLD FRONT WILL PUSH TOWARD
THE WESTERN CAROLINAS WEDNESDAY AND BECOME STATIONARY. MEANWHILE...A
LOW PRESSURE SYSTEM WILL FORM ACROSS THE GULF OF MEXICO THURSDAY AND
MOVE ALONG THE STATIONARY FRONT INTO FRIDAY. YET ANOTHER AREA OF LOW
PRESSURE WILL LIKELY AFFECT THE REGION LATE SATURDAY THROUGH
CHRISTMAS DAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AT 945 AM...THUNDER CHANCES HAVE BEEN INCREASED SLIGHTLY ALONG THE
SPINE OF THE SRN APPALACHIANS AS DEWPOINTS CONTINUE TO SURGE NWD
AHEAD OF THE FRONT. POPS HAVE ALSO BEEN INCREASED THROUGH MID AFTN
IN THE ERN PIEDMONT AS THE BEST COMBINATION OF LOW LEVEL WARM
ADVECTION AND UPPER JET DIVERGENCE IS PROVIDING GOOD FORCING IN THE
MOIST AIRMASS. TEMPS HAVE BEEN TRIMMED A DEGREE OR TWO
THROUGHOUT...ESPECIALLY IN SW SECTIONS.
OTHERWISE...THE MAIN LOW PRES SYSTEM TO THE NW CONTINUES TO LIFT NE
FROM IL TO THE GREAT LAKES TODAY. LOW LEVEL FLOW WILL VEER SLIGHTLY
TO DIMINISH THE WARM ADVECTION LIFT ACROSS OUR AREA...BUT SHOWERS
WILL BE SLOW TO DIMINISH FROM W TO E LATE TODAY AS THE BOUNDARY
SLOWLY SLIPS INTO THE FORECAST AREA.
TONIGHT...SHOWER ACTIVITY WILL CONTINUE TO DIMINISH...AS LOW LEVEL
FLOW VEERS IN RESPONSE TO CYCLONE LIFTING RAPIDLY INTO NEW
ENGLAND...AND MUCH DRIER AIR BEGINS TO PUSH IN ALOFT. WITH THE
FRONTAL BOUNDARY TAKING ON AN INCREASINGLY ZONAL ORIENTATION...IT
WILL SLOW DRAMATICALLY AND EVEN HANG UP OVER THE THE AREA TONIGHT.
THIS COULD RESULT IN A FEW SHOWERS PERSISTING INTO THE OVERNIGHT...
SO POPS NEVER ACTUALLY FALL BELOW SLIGHT CHANCE. OTHERWISE...WITH NO
APPRECIABLE CHANGE IN THE LOW LEVEL AIR MASS...MIN TEMPS WILL BE
WELL ABOVE NORMAL...IN FACT THEY WILL BE VERY CLOSE TO THE NORMAL
HIGH TEMPS FOR THIS TIME OF YEAR.
&&
.SHORT TERM /THURSDAY THROUGH SATURDAY/...
AS OF 230 AM WEDNESDAY...THERE IS A CONSENSUS AMONG THE MODEL
GUIDANCE FOR KICKING OUT A SHORT WAVE OVER NORTHERN MEXICO AND TEXAS
ON THURSDAY. AT THE START OF THE PERIOD...CYCLOGENESIS WILL ALREADY
BE UNDERWAY ACROSS THE NW GULF ALONG THE STALLED FRONTAL BOUNDARY.
MOISTURE FLUX FROM THE GULF NEVER REALLY GOES AWAY INTO THURSDAY
MORNING ALTHO IT SEEMS THAT A LULL WILL PROBABLY DEVELOP BEFORE THIS
NEXT SYSTEM APPROACHES...AND HOPEFULLY A LULL CAN BE ENGINEERED INTO
THE FCST GRIDS BY LATER SHIFTS. AT ANY RATE...LOW LEVEL FORCING
COMES ROARING BACK ALONG THE OLD FRONT ON THURSDAY...SO EXPECT
PRECIP TO BREAK OUT QUICKLY FROM THE SW AS WE WORK THROUGH THE DAY.
GENERALLY FOLLOWED THE SREF WITH RAMPING THE POP ALL THE WAY UP TO
CATEGORICAL ACROSS THE MTNS AND FOOTHILLS BY THE END OF THE
DAY...WITH LIKELY ACROSS THE PIEDMONT. A PREFERENCE FOR THE ECMWF
WOULD BRING THE SURFACE LOW PAST THROUGH THE GREAT VALLEY OF TN
THURSDAY EVENING...SO EXPECT CONTINUED WARM ADVECTION/UPGLIDE ACROSS
MOST OF THE FCST AREA THROUGH THE EVENING. THE LOW SHOULD PULL AWAY
TO THE N OR NE EARLY FRIDAY MORNING...DRAGGING THE SURFACE FRONT
BEHIND IT AND ACROSS THE FCST AREA IN THE PRE-DAWN HOURS. THUS...AS
QUICKLY AS THE POP RAMPED UP...IT RAMPS BACK DOWN...FAVORING ONLY A
CHANCE OVER THE PIEDMONT BY SUNRISE FRIDAY. THAT PRECIP CHANCE
CONTINUES TO TAIL OFF TO SLIGHT CHANCE IN THE AFTERNOON E OF I-85 IN
CASE THE FRONT DOES NOT MAKE AS MUCH EASTWARD PROGRESS AS EXPECTED.
HIGH TEMPS HAVE BEEN NUDGED UPWARD A DEGREE OR TWO TOWARD THE
GUIDANCE BLEND.
CONFIDENCE PLUMMETS THEREAFTER. THE FRIDAY NIGHT AND SATURDAY PART
OF THE FCST HAS BEEN VEXING BECAUSE OF POOR CONTINUITY AND
CONSISTENCY IN THE MODEL GUIDANCE. FOR THIS CYCLE...THERE IS GOOD
AGREEMENT AMONG THE OPERATIONAL MODELS THAT THE FRONT WILL MAKE IT
OFFSHORE BY FRIDAY NIGHT AND WE WILL DRY OUT FROM THE NW AT LEAST
BRIEFLY. THE NEW 03Z SREF AGREES...GIVING US ESSENTIALLY A DRY FCST
FRIDAY NIGHT AND SATURDAY. THIS FLIES IN THE FACE OF THE PREVIOUS
FCST GUIDANCE...WHICH WAS HIGH CHANCE TO LIKELY FOR SATURDAY.
AGAIN...A LULL BETWEEN SYSTEMS MAKES SENSE. HOWEVER...WITH SUCH POOR
CONSISTENCY OF LATE...IF WE COMPLETELY ELIMINATE PRECIP CHANCES WE
MIGHT BE BACK IN THE POSITION OF HAVING TO ADD THEM ONCE AGAIN IN
THE NEXT CYCLE. SO...AFTER SOME BRIEF DRYING FRIDAY NIGHT...THE
COMPROMISE WILL BE TO LOWER THE POP TO THE SLIGHT CHANCE RANGE FOR
SATURDAY...WITH THE HOPE THAT CONFIDENCE WILL INCREASE AND ALLOW IT
TO BE ELIMINATED LATER TODAY.
&&
.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
AS OF 320 AM WEDNESDAY...A COMPLICATED WX PATTERN REMAINS IN STORE
FOR THE EXT RANGE. THE LATEST OP MODELS ARE HAVING VARYING IDEAS ON
HOW TO HANDLE THE UPPER SPLIT FLOW...THE AMOUNT OF NRN STREAM
ENHANCING ENERGY MOVING SOUTH AND THE BREAKDOWN AND ALIGNMENT OF THE
SUBTROP HIGH. THERE ARE OTHER DIFFERENCES INCLUDING THE
CONFIGURATION OF THE H3 JET ENTRANCE/EXIT REGIONS...BUT SUFFICE TO
SAY ALL THIS DOESN/T TRANSLATE TO GOOD CONFIDENCE WRT TO THE LLVL
FEATURES NOR THE EXPECTED TIMING AND CHARACTER OF THE SENSIBLE WX.
THE PREVIOUS FCST WAS THUS GIVEN MUCH WEIGHT AND THE BIGGEST CHANGES
MADE WERE TO THE POP GRIDS SAT NIGHT INTO MON. STILL THINK THERE IS
A GOOD CHANCE OF A RELATIVELY WEAK WEDGE IN PLACE BEGINNING SAT
NIGHT AND STRONGER FLOW ASSOCIATED WITH THE MORE AMPLIFIED ECMWF
BRINGS IN A MOIST GOM AIR MASS EARLY...WHILE THE 00Z GFS IS ABOUT 12
HRS LATER WITH MEASURABLE PRECIP REACHING THE WRN ZONES BY 12Z SUN.
THERE IS SOME TOKEN SUPPORT FOR THE GFS SOLN BY THE SLOWEST 00Z CMC
AND THE LATEST STATISTICAL GUIDANCE HAS MADE SIGNIFICANT CHANGES IN
12 HR POPS...SO THE POP GRIDS WERE ADJUSTED DOWN EARLY...WHICH
MATCHES WELL WITH THE SHORT RANGE THINKING...THEN BROUGHT UP TO HIGH
END CHANCE BY SUN AFTERNOON.
PARTIAL THICKNESSES SUGGEST A MARGINAL P/TYPE ISSUE ACROSS THE NC
MTNS SAT NIGHT...BUT FOR NOW IT DOESN/T LOOK LIKE MOISTURE WILL BE
DEEP ENOUGH FOR MUCH IF ANY ACCUM SNOW BELOW 3.5 KFT AS SFC
TEMPS/TDS DONT SUPPORT IT. UP HIGHER...SNOW MAY REACH ADVISORY
LEVELS BY SUN NIGHT...BUT IT REALLY IS TOO EARLY TO TELL SINCE MODEL
THERMAL CONSENSUS IS HIGHLY LACKING.
EXPECT MAX TEMPS TO BE THE COLDEST SUN WITH CLOUDS AND N/LY OR
PERHAPS NE/LY WEDGE TYPE FLOW KEEPING HIGHS A COUPLE DEGREES BELOW
NORMAL. A SLOW AND WEAK WARM UP TO AROUND NORMAL IS PROBABLE MON AND
TUE AS THE SYSTEM MOVES EAST OF THE AREA AND INSOLATION INCREASES.
THE LATTER PART OF THE EXT RANGE REMAINS DRY AND WARMER...BUT THIS
COULD CHANGE TO MORE OF A WET AND COLD PATTERN SINCE THERE IS
EVIDENCE OF ANOTHER SRN STREAM OR A GOM SYSTEM IMPINGING ON THE AREA
WED AND THU.
&&
.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...WIDESPREAD LIGHT TO MODERATE SHOWERS WILL CONTINUE THROUGH
AT LEAST MID AFTERNOON BETWEEN WARM ADVECTION AND UPPER JET
DIVERGENCE FORCING. VERY LITTLE RECOVERY THROUGH IFR IS THUS
EXPECTED FOR THE REMAINDER OF THE DAY SO WILL REMOVE THE IMPROVEMENT
TO MVFR PREVIOUSLY ADVERTISED FOR LATE THIS AFTN AND THIS EVENING.
THE RUC PROFILES HAVE BACKED OFF ON LOW LEVEL WIND SHEAR FOR THE
AFTN...WILL LIKELY ALLOW THE CURRENT MENTION TO EXPIRE AT 19Z AS S
TO SW SFC WINDS CONTINUE TO INCREASE. LIFR CONDITIONS WILL LIKELY
RETURN OVERNIGHT AS MID AND UPPER DRYING OCCURS BUT THE BL REMAINS
VERY MOIST.
ELSEWHERE...MOIST SRLY FLOW CONTINUES TO COMBINE WITH WARM ADVECTION
AT LOW LEVELS AND IMPROVING JET DIVERGENCE ALOFT TO KEEP LIGHT
PRECIP GOING AT ALL TAF LOCATIONS. THE BEST THUNDER CHANCES SHOULD
REMAIN WEST OF KAVL AND S OF KAND THROUGH THE AFTN. VERY LITTLE
IMPROVEMENT IS EXPECTED THROUGH IFR TODAY...AND A RETURN TO
LIFR/VLIFR IS NOW EXPECTED THROUGHOUT OVERNIGHT. S TO SW FLOW WILL
STEADILY INCREASE TOWARD 10KT THIS AFTN...BUT WILL NOT FEATURE ANY
GUSTS.
OUTLOOK...LOW CIGS/POOR VSBY WILL CONTINUE INTO EARLY THU...
WITH RAIN EXPECTED TO REDEVELOP OVER THE AREA BY AFTERNOON.
OTHERWISE...VERY UNSETTLED CONDITIONS WILL PERSIST INTO EARLY NEXT
WEEK...AS A FRONT STALLS IN THE VICINITY AND ADDITIONAL WAVES OF LOW
PRESSURE RIPPLE NE ALONG THE FRONTAL ZONE. RESTRICTIONS WILL BE
POSSIBLE JUST ABOUT ANYTIME THROUGH THE OUTLOOK PERIOD.
AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE
PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE
CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)...
WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.
&&
$$
SYNOPSIS...SBK
NEAR TERM...HG/JDL
SHORT TERM...PM
LONG TERM...SBK
AVIATION...HG/JDL
AREA FORECAST DISCUSSION...UPDATED
NWS COLUMBIA SC
500 PM EST WED DEC 21 2011
.SYNOPSIS...
A SLOW MOVING FRONTAL SYSTEM WILL REMAIN NEAR THE FORECAST AREA
THROUGH THE CHRISTMAS WEEKEND. A SERIES OF LOW PRESSURE SYSTEMS WILL
MOVE NORTHEASTWARD ALONG THE FRONT.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
WARM ADVECTION PATTERN PERSISTS ACROSS THE FORECAST THIS AFTERNOON
WITH ADEQUATE MOISTURE EVIDENT ON THE 21Z RUC ANALYSIS SOUNDING.
PRECIPITABLE WATER VALUES ARE MAXIMIZED ACROSS THE MIDLANDS WITH
VALUES AROUND 1.5 INCHES...HOWEVER THE BEST MOISTURE TRANSPORT IS
SHIFTING NORTHEAST OF THE FORECAST AREA. THIS CAN BE SEEN IN THE
REGIONAL RADAR MOSAIC WHERE A CLUSTER OF RAIN IS LIFTING OUT OF
THE NORTHEASTERN PART OF THE FORECAST AREA WITH MAINLY FEW TO
SCATTERED SHOWERS REMAINING ACROSS THE AREA.
HAVE UPDATED THE POP FORECAST TO MORE ACCURATELY DEPICT THE
CURRENT ACTIVITY AND EXPECT THE COVERAGE SHOULD CONTINUE TO
DIMINISH INTO THE EVENING AND OVERNIGHT HOURS AS THE 850MB JET
SHIFTS EAST AND MOISTURE TRANSPORT CONTINUES TO WANE. EXPECT
TEMPERATURES TO MOVE LITTLE OVER THE NEXT SEVERAL HOURS WITH
OVERCAST SKIES AND LOW DEWPOINT DEPRESSIONS AND A WELL MIXED
BOUNDARY LAYER. LOWS TONIGHT WILL BE QUITE MILD AND COULD POSSIBLE
SET A RECORD WARMEST LOW AT COLUMBIA.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/...
CONVERGENCE AND MOISTURE ASSOCIATED WITH THE SLOW MOVING FRONT WILL
SUPPORT A CONTINUED SHOWER CHANCE. THE GREATER CHANCE MAY BE
THURSDAY NIGHT ASSOCIATED WITH STRONGER CONVERGENCE AHEAD OF THE
FRONT. THE NAM AND GFS SHOW SOME DRYING DEVELOPING FRIDAY AS THE
FRONT PUSHES A LITTLE FARTHER SOUTHEASTWARD. THERE HAVE BEEN
INCONSISTENCIES WITH PREVIOUS RUNS WITH THE TIMING OF THE FRONT
AND A SERIES OF MID-LEVEL SHORTWAVE TROUGHS. USED THE GUIDANCE
CONSENSUS FOR THE POP FORECAST.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
THE GFS SHOWED THE FRONT LINGERING NEAR THE FORECAST AREA THROUGH
CHRISTMAS DAY WITH DRYING MONDAY. THE MODEL SHOWED ANOTHER WAVE
DEVELOPING AND PUSHING HIGHER MOISTURE BACK INTO THE FORECAST AREA
MONDAY NIGHT AND TUESDAY. RIDGING APPEARED TO BECOME DOMINATE
WEDNESDAY. THE GFS AND ECMWF HAVE TRENDED INTO BETTER AGREEMENT WITH
HIGH MOISTURE CHRISTMAS DAY. THE GFS ENSEMBLES CONTINUED TO DISPLAY
HIGH SPREAD ASSOCIATED WITH THE COMPLEX SPLIT FLOW PATTERN.
CONFIDENCE REMAINED LOW WITH THE FORECAST THROUGH THE EXTENDED
PERIOD. LEANED TOWARD THE GFS ENSEMBLE MEAN POPS.
&&
.AVIATION /22Z WEDNESDAY THROUGH MONDAY/...
SCATTERED AREAS OF LIGHT RAIN HAVE DIMINISHED ACROSS THE AREA OVER
THE PAST FEW HOURS. WILL KEEP MENTION OF VCSH IN THE TAFS UNTIL 00Z.
EXPECT MVFR/IFR CONDITIONS TO DEVELOP BY 00Z WITH PATCHY FOG DURING
THE OVERNIGHT HOURS. CONDITIONS WILL SLOWLY IMPROVE AFTER 16Z
THURSDAY WITH IFR CIGS AND MVFR VSBYS.
EXTENDED AVIATION OUTLOOK...PERIODS OF CIG/VSBY RESTRICTIONS
EXPECTED THROUGH SATURDAY AS A SERIES OF WEATHER SYSTEMS CROSS THE
REGION.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.
&&
$$
NEAR TERM...HC
AVIATION...CL
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
420 PM EST WED DEC 21 2011
.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL LIFT FROM THE OHIO VALLEY INTO THE
EASTERN GREAT LAKES THIS EVENING, BRINGING SHOWERS AND
UNSEASONABLY WARM TEMPERATURES TO THE AREA. HIGH PRESSURE WILL
THEN BRIEFLY BRING A BREAK FROM SHOWERS TONIGHT INTO EARLY
THURSDAY. THE NEXT LOW WILL APPROACH FROM THE SOUTHWEST AND RETURN
SHOWERS TO THE AREA FOR THURSDAY NIGHT.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
QUICK UPDATE TO BUMP UP WIND GUSTS AND ADD STRONGER THUNDERSTORM
WORDING ACROSS SOUTHEASTERN COUNTIES. EVEN OUTSIDE OF
SHOWERS...MANY LOCATIONS COULD SEE SOME 30-40 MPH WIND GUSTS AS
COLD FRONT APPROACHES FROM THE WEST. IN ADDITION...A LINE OF HEAVY
SHOWERS WITH ISOLATED THUNDERSTORMS HAS CONTINUED TO MOVE
EAST...AND CURRENTLY EXTENDS FROM IDI SOUTHWEST BACK TOWARDS HLG.
PREVIOUS DISCUSSION FOLLOWS.
THE LATEST RUC MID-LEVEL ANALYSIS INDICATES A TROUGH WITH ITS
AXIS CENTERED ACROSS MICHIGAN. THE UPPER OHIO VALLEY IS IN A
SOUTHWESTERLY FLOW AHEAD OF THIS FEATURE. A PUNCH OF DRY MID-
LEVEL AIR IS ADVECTING THE AREA WITH THE 1000-850MB LAYER REMAINING
SATURATED. 850MB TEMPS OF AROUND 8C ARE INDICATIVE OF THE WARM AIR
ALOFT THAT HAS BUILT IN WITH THE WARM SECTOR. AT THE SURFACE, A
999MB LOW IS LOCATED ACROSS SOUTHERN ONTARIO WITH A WARM FRONT EXTENDING
EAST OF THIS FEATURE ACROSS LAKE ONTARIO. MEANWHILE, A COLD FRONT EXTENDS
SOUTHWEST OF THE LOW INTO THE CENTRAL GULF STATES. VIS AND WV SAT
IMAGERY INDICATE THE DRY SWATH IN OHIO AHEAD OF THE COLD FRONT. A
FEW NARROW LINE SEGMENTS OF SHALLOW CONVECTION HAVE DEVELOPED AND
ARE MOVING ACROSS EASTERN OHIO INTO WESTERN PA.
THIS EVENING...THE SURFACE LOW WILL MOVE NORTHEASTWARD, PROGGED TO
BE ACROSS LAKE ONTARIO BY 00Z. WINDS WILL GUST THIS AFTERNOON UP
TO 25 MPH AS THE PRESSURE GRADIENT TIGHTENS AND WINDS BRIEFLY MIX
DOWN WITH BREAKS IN CLOUD COVERAGE. WARM AIR ADVECTION WILL BE
ONGOING IN A STRONG SOUTHERLY FLOW AHEAD OF THE COLD FRONT. THUS,
HIGHS TODAY ARE A FEW DEGREES WARMER THAN LAMP GUIDANCE,
ESPECIALLY SOUTH OF PITTSBURGH. HIGHS TODAY WILL RANGE FROM THE
LOWER TO MID 60S ACROSS NORTH-CENTRAL WV TO THE MID 50S ALONG THE
I-80 CORRIDOR.
HRRR/WRF-NMM SUPPORT SCATTERED LOW- TOPPED CONVECTION IN OHIO
MOVING ACROSS THE AREA THROUGH THE EARLY EVENING. WEAK SBCAPE
(<500 J/KG) AND STRONG 0-6KM SHEAR (80KT) AHEAD OF A COLD FRONT
APPROACHING THE AREA CONTINUE TO SUPPORT THE CHANCE OF ISOLATED
THUNDERSTORMS. NOT OUT OF THE QUESTION SHOWERS OR THUNDERSTORMS
COULD BRING DOWN SOME STRONGER GUSTS TO THE SURFACE LATER THROUGH
00Z. THE STORM PREDICTION CENTER HAS PORTIONS OF EASTERN OHIO,
WESTERN PA, AND NORTH- CENTRAL WV IN A SLIGHT RISK INTO THE EARLY
EVENING.
TONIGHT...THE SURFACE LOW WILL PUSH INTO THE NORTHEAST AND ITS
ASSOCIATED COLD FRONT WILL SLIDE EAST OF THE AREA. ANY CONVECTION
WILL QUICKLY DIMINISH AND PUSH EAST OF THE AREA AFTER 00Z. THUS,
FORECAST IS DRY ACROSS THE AREA BY 03Z. COLD AIR ADVECTION WILL BE
WEAK IN THE WAKE OF THE FRONT, WITH A ZONAL MID-LEVEL FLOW IN THE
BEHIND THE LAGGING 500MB TROUGH. OVERNIGHT LOWS ARE A MAV/MET BLEND,
RANGING RANGE FROM THE UPPER 30S ACROSS THE I-80 CORRIDOR TO THE LOWER
40S ELSEWHERE.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
THERE IS NAM/GFS/ECMWF AGREEMENT THAT HIGH PRESSURE CENTERED ACROSS
WEST VIRGINIA EARLY ON THURSDAY WILL SHIFT EASTWARD OFF THE
MID-ATLANTIC COAST. A SURFACE LOW WILL MOVE FROM THE WESTERN GULF
INTO THE CENTRAL APPALACHIANS, RETURNING THE CHANCE OF RAIN SHOWERS
FOR AREAS SOUTH AND WEST OF PITTSBURGH BY THE LATE AFTERNOON
HOURS. SHOWERS WILL BECOME LIKELY THURSDAY NIGHT AS THE LOW MOVES
UP THE APPALACHIANS AND OFF THE JERSEY COAST BY FRIDAY MORNING. WITH
A SOUTHWESTERLY MID-LEVEL FLOW ALOFT, AND THE LOW ADVECTING WARMER
AIR INTO THE AREA, TEMPERATURES WILL BE AROUND 10 DEGREES ABOVE
NORMAL.
FRIDAY INTO SATURDAY...AS THE SURFACE LOW PULLS EAST OF THE AREA,
THE LOW-LEVEL FLOW WILL BECOME NORTHWESTERLY ON FRIDAY. COLD AIR
ADVECTION WILL PULL THE 1000-500MB 5400M THICKNESS LINE SOUTHWARD
WITH LINGERING RAIN AND SNOW SHOWER POSSIBLE FRIDAY MORNING BEFORE
1000-850MB MOISTURE SHIFTS EAST OF THE AREA. LIGHT ACCUMULATIONS OF
LESS THAN AN INCH HAVE BEEN INCLUDED FOR FOREST COUNTY. HIGH
PRESSURE WILL BEGIN TO BUILD IN FRIDAY AFTERNOON INTO CHRISTMAS
EVE, ALLOWING FOR A DRY FORECAST ACROSS MOST OF THE AREA THROUGH THIS
PERIOD. TEMPERATURES WILL BE AROUND 5 DEGREES ABOVE NORMAL.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
GENERALLY WENT WITH HPC GUIDANCE. KEPT LOW CHANCE POPS ACROSS WV ON
CHRISTMAS DAY WITH WEAK STORM MOVING THROUGH THE MID ATLANTIC
STATES. WEAK FRONT AND SHOT OF COLD AIR MOVING THROUGH THE GREAT
LAKES LATE CHRISTMAS DAY POSES CHANCE OF SNOW SHOWERS ACROSS
NORTHERN ZONES AND RIDGES LATE SUNDAY INTO EARLY MONDAY.
HIGH PRESSURE BUILDS ACROSS THE REGION MONDAY AND TUESDAY WITH
MODERATING TEMPERATURES. GFS AND ECMWF DIFFER SIGNIFICANTLY IN
SURFACE FEATURES BY WEDNESDAY...BUT BOTH HAVE SOMETHING MOVING
THROUGH THE REGION SO CHANCE OF PRECIP SEEMS REASONABLE. SHOULD BE
RAIN INITIALLY...POSSIBLY MIXING WITH SNOW LATE IN THE DAY.
&&
.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
ALTHOUGH WIDESPREAD RAIN HAS MOVED EAST OF THE FORECAST
AREA...LINE OF HEAVIER SHOWERS HAS GONE THROUGH PIT...AGC...AND
HLG. EFFECTS WILL SOON BE FELT AT LBE AND MGW. EXPECT A BRIEF
PERIOD OF HEAVY RAIN AND GUSTY WINDS. THERE IS A SMALL GAP OF
ABOUT 100 MILES ACROSS EASTERN OHIO AND WESTERN PENNSYLVANIA WHERE
CEILINGS WILL SCATTER OUT...BEFORE MVFR STRATOCUMULUS MOVES BACK.
GUSTY SOUTHWEST WINDS TO 20KTS AHEAD OF FRONT WITH POSSIBLE GUST
TO 25 OR 30KTS WITH FRONTAL PASSAGE. WINDS WILL DIMINISH RAPIDLY
AFTER FRONTAL PASSAGE. STRATOCU MOVES OVER REGION AND REMAINS
THROUGH THURSDAY.
OUTLOOK...FRIDAY THROUGH MONDAY...
THE NEXT THE SERIES MOVES THROUGH THE UPPER OHIO VALLEY THURSDAY
NIGHT AND EARLY FRIDAY SPREADING RAIN AND IFR CONDITIONS ACROSS THE
REGION THURSDAY EVENING THROUGH EARLY FRIDAY MORNING. RAIN SHOULD BE
ENDING BY DAYBREAK FRIDAY WITH CONDITIONS IMPROVING TO MVFR FRIDAY
MORNING AND VFR DURING THE AFTERNOON. VFR CONDITIONS CONTINUE
THROUGH SATURDAY.
NEXT WAVE MOVES SOUTH OF THE REGION ON CHRISTMAS DAY WITH MVFR
CONDITIONS IN RAIN OR SNOW ACROSS WV CHRISTMAS DAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
328 PM EST WED DEC 21 2011
.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL LIFT FROM THE OHIO VALLEY INTO THE
EASTERN GREAT LAKES THIS EVENING, BRINGING SHOWERS AND
UNSEASONABLY WARM TEMPERATURES TO THE AREA. HIGH PRESSURE WILL
THEN BRIEFLY BRING A BREAK FROM SHOWERS TONIGHT INTO EARLY
THURSDAY. THE NEXT LOW WILL APPROACH FROM THE SOUTHWEST AND RETURN
SHOWERS TO THE AREA FOR THURSDAY NIGHT.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
THE LATEST RUC MID-LEVEL ANALYSIS INDICATES A TROUGH WITH ITS
AXIS CENTERED ACROSS MICHIGAN. THE UPPER OHIO VALLEY IS IN A
SOUTHWESTERLY FLOW AHEAD OF THIS FEATURE. A PUNCH OF DRY MID-
LEVEL AIR IS ADVECTING THE AREA WITH THE 1000-850MB LAYER REMAINING
SATURATED. 850MB TEMPS OF AROUND 8C ARE INDICATIVE OF THE WARM AIR
ALOFT THAT HAS BUILT IN WITH THE WARM SECTOR. AT THE SURFACE, A
999MB LOW IS LOCATED ACROSS SOUTHERN ONTARIO WITH A WARM FRONT EXTENDING
EAST OF THIS FEATURE ACROSS LAKE ONTARIO. MEANWHILE, A COLD FRONT EXTENDS
SOUTHWEST OF THE LOW INTO THE CENTRAL GULF STATES. VIS AND WV SAT
IMAGERY INDICATE THE DRY SWATH IN OHIO AHEAD OF THE COLD FRONT. A
FEW NARROW LINE SEGMENTS OF SHALLOW CONVECTION HAVE DEVELOPED AND
ARE MOVING ACROSS EASTERN OHIO INTO WESTERN PA.
THIS EVENING...THE SURFACE LOW WILL TRANSVERSE NORTHEASTWARD,
PROGGED TO BE ACROSS LAKE ONTARIO BY 00Z. WINDS WILL GUST THIS
AFTERNOON UP TO 25 MPH AS THE PRESSURE GRADIENT TIGHTENS AND WINDS
BRIEFLY MIX DOWN WITH BREAKS IN CLOUD COVERAGE. WARM AIR ADVECTION
WILL BE ONGOING IN A STRONG SOUTHERLY FLOW AHEAD OF THE COLD
FRONT. THUS, HIGHS TODAY ARE A FEW DEGREES WARMER THAN LAMP
GUIDANCE, ESPECIALLY SOUTH OF PITTSBURGH. HIGHS TODAY WILL RANGE
FROM THE LOWER TO MID 60S ACROSS NORTH-CENTRAL WV TO THE MID 50S
ALONG THE I-80 CORRIDOR.
HRRR/WRF-NMM SUPPORT SCATTERED LOW- TOPPED CONVECTION IN OHIO
MOVING ACROSS THE AREA THROUGH THE EARLY EVENING. WEAK SBCAPE
(<500 J/KG) AND STRONG 0-6KM SHEAR (80KT) AHEAD OF A COLD FRONT
APPROACHING THE AREA CONTINUE TO SUPPORT THE CHANCE OF ISOLATED
THUNDERSTORMS. NOT OUT OF THE QUESTION SHOWERS OR THUNDERSTORMS
COULD BRING DOWN SOME STRONGER GUSTS TO THE SURFACE LATER THROUGH
00Z. THE STORM PREDICTION CENTER HAS PORTIONS OF EASTERN OHIO,
WESTERN PA, AND NORTH- CENTRAL WV IN A SLIGHT RISK INTO THE EARLY
EVENING.
TONIGHT...THE SURFACE LOW WILL PUSH INTO THE NORTHEAST AND ITS
ASSOCIATED COLD FRONT WILL SLIDE EAST OF THE AREA. ANY CONVECTION
WILL QUICKLY DIMINISH AND PUSH EAST OF THE AREA AFTER 00Z. THUS,
FORECAST IS DRY ACROSS THE AREA BY 03Z. COLD AIR ADVECTION WILL BE
WEAK IN THE WAKE OF THE FRONT, WITH A ZONAL MID-LEVEL FLOW IN THE
BEHIND THE LAGGING 500MB TROUGH. OVERNIGHT LOWS ARE A MAV/MET BLEND,
RANGING RANGE FROM THE UPPER 30S ACROSS THE I-80 CORRIDOR TO THE LOWER
40S ELSEWHERE.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
THERE IS NAM/GFS/ECMWF AGREEMENT THAT HIGH PRESSURE CENTERED ACROSS
WEST VIRGINIA EARLY ON THURSDAY WILL SHIFT EASTWARD OFF THE
MID-ATLANTIC COAST. A SURFACE LOW WILL MOVE FROM THE WESTERN GULF
INTO THE CENTRAL APPALACHIANS, RETURNING THE CHANCE OF RAIN SHOWERS
FOR AREAS SOUTH AND WEST OF PITTSBURGH BY THE LATE AFTERNOON
HOURS. SHOWERS WILL BECOME LIKELY THURSDAY NIGHT AS THE LOW MOVES
UP THE APPALACHIANS AND OFF THE JERSEY COAST BY FRIDAY MORNING. WITH
A SOUTHWESTERLY MID-LEVEL FLOW ALOFT, AND THE LOW ADVECTING WARMER
AIR INTO THE AREA, TEMPERATURES WILL BE AROUND 10 DEGREES ABOVE
NORMAL.
FRIDAY INTO SATURDAY...AS THE SURFACE LOW PULLS EAST OF THE AREA,
THE LOW-LEVEL FLOW WILL BECOME NORTHWESTERLY ON FRIDAY. COLD AIR
ADVECTION WILL PULL THE 1000-500MB 5400M THICKNESS LINE SOUTHWARD
WITH LINGERING RAIN AND SNOW SHOWER POSSIBLE FRIDAY MORNING BEFORE
1000-850MB MOISTURE SHIFTS EAST OF THE AREA. LIGHT ACCUMULATIONS OF
LESS THAN AN INCH HAVE BEEN INCLUDED FOR FOREST COUNTY. HIGH
PRESSURE WILL BEGIN TO BUILD IN FRIDAY AFTERNOON INTO CHRISTMAS
EVE, ALLOWING FOR A DRY FORECAST ACROSS MOST OF THE AREA THROUGH THIS
PERIOD. TEMPERATURES WILL BE AROUND 5 DEGREES ABOVE NORMAL.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
GENERALLY WENT WITH HPC GUIDANCE. KEPT LOW CHANCE POPS ACROSS WV ON
CHRISTMAS DAY WITH WEAK STORM MOVING THROUGH THE MID ATLANTIC
STATES. WEAK FRONT AND SHOT OF COLD AIR MOVING THROUGH THE GREAT
LAKES LATE CHRISTMAS DAY POSES CHANCE OF SNOW SHOWERS ACROSS
NORTHERN ZONES AND RIDGES LATE SUNDAY INTO EARLY MONDAY.
HIGH PRESSURE BUILDS ACROSS THE REGION MONDAY AND TUESDAY WITH
MODERATING TEMPERATURES. GFS AND ECMWF DIFFER SIGNIFICANTLY IN
SURFACE FEATURES BY WEDNESDAY...BUT BOTH HAVE SOMETHING MOVING
THROUGH THE REGION SO CHANCE OF PRECIP SEEMS REASONABLE. SHOULD BE
RAIN INITIALLY...POSSIBLY MIXING WITH SNOW LATE IN THE DAY.
&&
.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
AREA OF RAIN MOVING RAPIDLY EAST. BACK EDGE OF STEADY RAIN HAS MOVED
OUT OF OHIO AND WILL BE EAST OF CWA BETWEEN 18Z-19Z. RAIN IS
FOLLOWED BY AREA OF MVFR STRATUS. DRY SLOT WITH POSSIBLE CONVECTION
REACHES ZZV AROUND 18Z AND PIT BY 21Z. ISOLD SHOWERS ARE DEVELOPING
IN THE CLEARING AREA...BUT EXPECT THEY WILL DIE OUT FOR THE MOST
PART WITH LOSS OF DIURNAL HEATING BY THE TIME THEY REACH THE
MAJORITY OF TERMINALS IN CWA. POSSIBLE EXCEPTION WOULD BE ZZV.
GUSTY SOUTHWEST WINDS TO 20KTS AHEAD OF FRONT WITH POSSIBLE GUST TO
25 OR 30KTS WITH FRONTAL PASSAGE. WINDS WILL DIMINISH RAPIDLY AFTER
FRONTAL PASSAGE. STRATOCU MOVES OVER REGION AND REMAINS THROUGH
THURSDAY.
OUTLOOK...FRIDAY THROUGH MONDAY...
THE NEXT THE SERIES MOVES THROUGH THE UPPER OHIO VALLEY THURSDAY
NIGHT AND EARLY FRIDAY SPREADING RAIN AND IFR CONDITIONS ACROSS THE
REGION THURSDAY EVENING THROUGH EARLY FRIDAY MORNING. RAIN SHOULD BE
ENDING BY DAYBREAK FRIDAY WITH CONDITIONS IMPROVING TO MVFR FRIDAY
MORNING AND VFR DURING THE AFTERNOON. VFR CONDITIONS CONTINUE
THROUGH SATURDAY.
NEXT WAVE MOVES SOUTH OF THE REGION ON CHRISTMAS DAY WITH MVFR
CONDITIONS IN RAIN OR SNOW ACROSS WV CHRISTMAS DAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
107 PM EST WED DEC 21 2011
.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL LIFT FROM THE OHIO VALLEY INTO THE
EASTERN GREAT LAKES THIS AFTERNOON, BRINGING SHOWERS AND
UNSEASONABLY WARM TEMPERATURES TO THE AREA. HIGH PRESSURE WILL
THEN BRIEFLY BRING A BREAK FROM SHOWERS TONIGHT INTO EARLY
THURSDAY. THE NEXT LOW WILL APPROACH FROM THE SOUTHWEST AND RETURN
SHOWERS TO THE AREA FOR THURSDAY NIGHT.
&&
.NEAR TERM /THROUGH TONIGHT/...
18Z ENHANCED SHORT TERM FORECAST UPDATE HAS BEEN ISSUED TO ACCOUNT
FOR THE LATEST TEMP TRENDS AND TO TIME SCATTERED CONVECTION
DEVELOPING IN OHIO AS IT CROSSES THE AREA.
THE LATEST RUC MID-LEVEL ANALYSIS INDICATES A TROUGH WITH ITS AXIS
CENTERED ACROSS MICHIGAN. THE UPPER OHIO VALLEY IS IN A
SOUTHWESTERLY FLOW AHEAD OF THIS FEATURE. A PUNCH OF DRY MID-
LEVEL AIR IS ADVECTING THE AREA WITH 1000-850MB REMAINING
SATURATED. 850MB TEMPS OF AROUND 8C ARE INDICATIVE OF THE WARM AIR
ALOFT THAT HAS BUILT IN WITH THE WARM SECTOR. AT THE SURFACE, A
1000MB LOW IS LOCATED ACROSS EASTERN MICHIGAN WITH A WARM FRONT
EXTENDING EAST OF THIS FEATURE ACROSS LAKE ERIE. MEANWHILE, A COLD
FRONT EXTENDS SOUTHWEST OF THE LOW INTO THE CENTRAL GULF STATES.
VIS AND WV SAT IMAGERY INDICATE THE DRY SWATH IN OHIO AHEAD OF THE
COLD FRONT. A FEW NARROW LINE SEGMENTS OF SHALLOW CONVECTION ARE
DEVELOPING IN THIS AREA OF CLEARING.
THIS AFTERNOON...THE SURFACE LOW WILL TRANSVERSE NORTHEASTWARD,
PROGGED TO BE ACROSS LAKE ONTARIO BY 00Z. WINDS WILL GUST THIS
AFTERNOON UP TO 25 MPH AS THE PRESSURE GRADIENT TIGHTENS AND WINDS
BRIEFLY MIX DOWN WITH BREAKS IN CLOUD COVERAGE. WARM AIR ADVECTION
WILL BE ONGOING IN A STRONG SOUTHERLY FLOW AHEAD OF THE COLD
FRONT. THUS, HIGHS TODAY ARE A FEW DEGREES WARMER THAN LAMP
GUIDANCE, ESPECIALLY SOUTH OF PITTSBURGH. HIGHS TODAY WILL RANGE
FROM THE LOWER TO MID 60S ACROSS NORTH-CENTRAL WV TO THE MID 50S
ALONG THE I-80 CORRIDOR.
BEHIND THE INITIAL PRECIP SHIELD, MID-LEVEL DRYING HAS DIMINISHED
THE COVERAGE OF SHOWERS. HRRR/WRF-NMM SUPPORT SCATTERED LOW-
TOPPED CONVECTION IN OHIO SHIFTING EASTWARD INTO THE AREA FOR THE
LATE AFTERNOON AND EARLY EVENING. WEAK SBCAPE (<500 J/KG) AND
STRONG 0-6KM SHEAR (80KT) AHEAD OF A COLD FRONT APPROACHING THE
AREA CONTINUE TO SUPPORT THE CHANCE OF ISOLATED THUNDERSTORMS.
WITH THE SHALLOW NATURE OF THE CONVECTION, AM NOT ANTICIPATING
MUCH LIGHTNING. NOT OF THE QUESTION STRONGER SHOWERS OR
THUNDERSTORMS COULD BRING DOWN SOME STRONGER GUSTS TO THE SURFACE
LATER THIS AFTERNOON. THE STORM PREDICTION CENTER HAS UPGRADED
PORTIONS OF EASTERN OHIO, WESTERN PA, AND NORTH-CENTRAL WV TO A
SLIGHT RISK FOR THIS AFTERNOON.
TONIGHT...THE SURFACE LOW WILL PUSH INTO THE NORTHEAST AND ITS
ASSOCIATED COLD FRONT WILL SLIDE EAST OF THE AREA. ANY CONVECTION
WILL QUICKLY DIMINISH AND PUSH EAST OF THE AREA AFTER 00Z. THUS,
FORECAST IS DRY ACROSS THE AREA BY 03Z. COLD AIR ADVECTION WILL BE
WEAK IN THE WAKE OF THE FRONT, WITH A ZONAL MID-LEVEL FLOW IN THE
BEHIND THE LAGGING 500MB TROUGH. OVERNIGHT LOWS ARE A MAV/MET BLEND,
RANGING RANGE FROM THE UPPER 30S ACROSS THE I-80 CORRIDOR TO THE LOWER
40S ELSEWHERE.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY/...
COLDER AIR WILL SETTLE INTO THE AREA THROUGH MOST OF THURSDAY.
THERE WILL BE A PERIOD OF DRY WEATHER THROUGH AT LEAST THE FIRST
HALF OF THU.
MODELS ARE IN GOOD AGREEMENT DEVELOPING ANOTHER SFC LOW WHICH WILL
MOVE UP THE APPALACHIANS THURSDAY AFTERNOON AND TURN TOWARD THE
EAST COAST THURSDAY NIGHT. WITH THE CURRENT FORECAST TRACK OF THE
SFC LOW, WARMER AIR WILL SURGE NORTHWARD AND KEEP THIS A RAIN
EVENT. HOWEVER, IF THE LOW WOULD TAKE A TRACK FURTHER TO THE EAST,
OR SHIFT TO THE EAST FASTER, LOCATIONS ACROSS THE FAR NORTH COULD
SEE MIXED PRECIPITATION.
THE SFC LOW WILL QUICKLY EXIT THE EAST COAST EARLY FRIDAY AND
COLDER AIR WILL WRAP IN BEHIND THE EXITING LOW. THERE MAY BE SOME
LINGER SHOWERS/SNOW SHOWERS IN THE CAA BEHIND THE LOW.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
VERY LOW CONFIDENCE IN THE LONG TERM, AS MEDIUM RANGE OP MODELS
ARE SHOWING LARGE VARIANCES BEGINNING ON SUNDAY.
12Z ECMWF IS SHOWING ANOTHER LARGE SFC LOW DEVELOPING OVER THE
GULF COAST SAT NIGHT AND RUSHING NORTHWARD ON SUNDAY.
HOWEVER, THE 00Z GFS DOES NOT DEVELOP THIS SFC SYSTEM, RATHER IT
BRINGS A WEAK COLD FRONT THROUGH ON SUNDAY. THE 12Z GEFS, 12Z
ECMWF ENSEMBLES, AND 12Z CMC ARE ALL SHOWING SOLUTIONS CLOSER TO
THAT OF THE GFS. SO FOR THE WEEKEND WILL LEAN CLOSER TO THE 00Z
GFS SOLUTION. THIS WOULD MEAN A COLDER AND DRIER FORECAST.
LOW CONFIDENCE CONTINUES FOR THE REMAINDER OF THE THE LONG TERM.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AREA OF RAIN MOVING RAPIDLY EAST. BACK EDGE OF STEADY RAIN HAS MOVED
OUT OF OHIO AND WILL BE EAST OF CWA BETWEEN 18Z-19Z. RAIN IS
FOLLOWED BY AREA OF MVFR STRATUS. DRY SLOT WITH POSSIBLE CONVECTION
REACHES ZZV AROUND 18Z AND PIT BY 21Z. ISOLD SHOWERS ARE DEVELOPING
IN THE CLEARING AREA...BUT EXPECT THEY WILL DIE OUT FOR THE MOST
PART WITH LOSS OF DIURNAL HEATING BY THE TIME THEY REACH THE
MAJORITY OF TERMINALS IN CWA. POSSIBLE EXCEPTION WOULD BE ZZV.
GUSTY SOUTHWEST WINDS TO 20KTS AHEAD OF FRONT WITH POSSIBLE GUST TO
25 OR 30KTS WITH FRONTAL PASSAGE. WINDS WILL DIMINISH RAPIDLY AFTER
FRONTAL PASSAGE. STRATOCU MOVES OVER REGION AND REMAINS THROUGH
THURSDAY.
OUTLOOK...FRIDAY THROUGH MONDAY...
THE NEXT THE SERIES MOVES THROUGH THE UPPER OHIO VALLEY THURSDAY
NIGHT AND EARLY FRIDAY SPREADING RAIN AND IFR CONDITIONS ACROSS THE
REGION THURSDAY EVENING THROUGH EARLY FRIDAY MORNING. RAIN SHOULD BE
ENDING BY DAYBREAK FRIDAY WITH CONDITIONS IMPROVING TO MVFR FRIDAY
MORNING AND VFR DURING THE AFTERNOON. VFR CONDITIONS CONTINUE
THROUGH SATURDAY.
NEXT WAVE MOVES SOUTH OF THE REGION ON CHRISTMAS DAY WITH MVFR
CONDITIONS IN RAIN OR SNOW ACROSS WV CHRISTMAS DAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$