Forecast Discussions mentioning any of
"HRRR" "RAP" "RR" "RUC13" "RUC" received at GSD on 12/18/12
AREA FORECAST DISCUSSION...UPDATED
NWS PUEBLO CO
1130 PM MST SAT DEC 15 2012
.UPDATE...
UPDATED TO EXTEND THE WINTER WEATHER ADVISORY FOR THE EASTERN SAN
JUAN RANGE UNTIL 4 AM. THE LATEST WRF RUN AND SATELLITE ANALYSIS
INDICATES THE UPPER LEVEL STORM SYSTEM IS MOVING A BIT SLOWER THAN
EARLY MODEL SOLUTIONS. MODERATE SNOWFALL WILL CONTINUE ACROSS THE
EASTERN SAN JUANS THROUGH MUCH OF TONIGHT AS THE UPPER SYSTEM
BEGINS TO MOVE OUT OF THE AREA. AN ADDITIONAL 1 TO 3 INCHES
WITH LOCALLY HIGHER AMOUNTS ON WEST FACING SLOPES ARE POSSIBLE
OVER THE EASTERN SAN JUANS THROUGH EARLY SUNDAY MORNING. ELSEWHERE
LIGHT SNOW WILL CONTINUE OVER THE MOUNTAIN AREAS WITH A COUPLE OF
INCHES POSSIBLE OVER THE SOUTHERN SANGRE DE CRISTO RANGE. MOZLEY
&&
.PREV DISCUSSION... /ISSUED 1003 PM MST SAT DEC 15 2012/
AVIATION...
KALS...LIGHT SNOW IS CURRENTLY MOVING ACROSS THE SAN LUIS VALLEY
AND IMPACTING KALS. IT HAS REDUCED CIGS TO NEAR 1500 FEET AND VIS
TO AROUND 1SM. EXPECT PERIODS OF LIGHT SNOW TO PERSIST THROUGH
AROUND 10Z WITH VFR CONDITIONS DEVELOPING AFTER 10Z.
KCOS AND KPUB...MID AND UPPER LEVEL CLOUDS WILL SPREAD ACROSS THE
REGION TONIGHT INTO SUNDAY MORNING BUT EXPECT CONDITIONS TO REMAIN
VFR THROUGH THE NEXT 24 HOURS. 88
PREV DISCUSSION... /ISSUED 254 PM MST SAT DEC 15 2012/
SHORT TERM...
(TONIGHT AND SUNDAY)
.ROUNDS OF SNOW TO CONTINUE ALONG THE CONTINENTAL DIVIDE...
NEXT UPPER TROF ALREADY MOVING THROUGH UT TOWARDS THE 4 CORNERS
REGION AND WILL BE MOVING ACROSS SRN CO TONIGHT. STARTING TO SEE
SOME ENHANCEMENT AHEAD OF THIS FEATURE ACROSS SW UT...AND SUSPECT
THAT SNOW WILL BE PICKING UP AGAIN ACROSS THE WOLF CREEK PASS AREA
BY LATE AFTERNOON. ITS BEEN SNOWING MAJORITY OF THE DAY ALONG THE
CONTDVD...BUT BASED ON WEB CAMS AT WOLF CREEK SKI AREA AND CDOT WEB
CAMS...IT DOESN`T APPEAR AS HEAVY AS YESTERDAY. LATEST NAM12 HAS
COME IN A BIT HEAVIER WITH SNOWFALL AMOUNTS DURING THE EVENING WHEN
BRUNT OF FORCING AND DEEPER MOISTURE MOVES IN. WILL ALSO HAVE SOME
INSTABILITY TO PLAY WITH. ALL IN ALL...STILL LOOKS LIKE A SOLID
ADVISORY EVENT FOR THE EASTERN SAN JUANS WITH SNOWFALL TOTALS
RANGING FROM 5 TO 10 INCHES WITH LOCALLY UP TO A FOOT FOR THE
PEAKS. HAVE OPTED TO EXTEND THE WINTER WEATHER ADVISORY FOR ZONE 68
THROUGH 07Z...AS LATEST RUNS APPEAR A LITTLE SLOWER WITH THE
SYSTEM.
FOR THE REMAINDER OF THE REGION...HAVE ALREADY HAD ONE WAVE OF
UPGLIDE LIFT OFF TO THE NORTHEAST OF THE AREA. THIS BROUGHT SOME
ISOLATED LIGHT SHOWERS TO THE PIKES PEAK REGION RIGHT AROUND THE
NOON HOUR. AS THE NEXT WAVE APPROACHES...EXPECT ANOTHER ROUND TO
SPREAD IN DURING THE EVENING HOURS. DON`T THINK IT WILL AMOUNT TO
MUCH EAST OF THE MTS...BUT SOME AREAS ALONG MONUMENT HILL COULD PICK
UP SOME LIGHT ACCUMS RANGING FROM A TRACE TO AN INCH.
INTERESTINGLY...THE 18Z NAM HAS BACKED OFF ON SNOWFALL FOR THIS
REGION...HOWEVER RUC13 HANDLED THE EARLIER WAVE OF LIGHT SNOW
BETTER...SO WILL LEAN TOWARDS ITS SOLN AND MAINTAIN ISOLATED POPS
(SCATTERED ACROSS TELLER COUNTY/NRN EL PASO) THROUGH THE EVENING.
RUC HAS THE NEXT WAVE OF PRECIP MOVING INTO THIS AREA AROUND 01Z.
SHOULD ALSO SEE ANOTHER ROUND OF SNOW SPREAD ACROSS THE SAN LUIS
VALLEY AND INTO THE SANGRE DE CRISTO MOUNTAINS BETWEEN 03Z AND 09Z.
HAVE INCREASED POPS ACROSS THESE AREAS TO ACCOUNT FOR THIS.
ADDITIONAL ACCUMULATIONS OF 1 TO 4 INCHES WILL BE POSSIBLE FOR THE
HIGHER PEAKS. MOST OF THE SAN LUIS VALLEY SHOULD SEE LESS THAN AN
INCH...BUT SOME AREAS COULD SEE SLIGHTLY MORE...ESPECIALLY AGAINST
THE WEST SLOPES OF THE SANGRES...NEAR CRESTONE.
SYSTEM WILL EXIT EASTERN COLORADO BY EARLY SUNDAY MORNING. LIGHT
SNOW CONTINUES ALONG THE CONTINENTAL DIVIDE THROUGH THE DAY...BUT AM
ONLY GETTING ANOTHER INCH OR TWO OF ACCUMS...WHICH IS NOT ENOUGH TO
WARRANT ANY FURTHER HEADLINES AT THIS POINT. OTHERWISE...WEST TO
NORTHWEST WINDS BEHIND THE DEPARTING SYSTEM SHOULD HELP BOOST TEMPS
TO NEAR CLIMATOLOGICAL NORMALS. HAVE GONE ON THE COLDER SIDE OF
GUIDANCE FOR THE SAN LUIS VALLEY DUE TO SNOW COVER. -KT
LONG TERM...
(SUNDAY NIGHT THROUGH NEXT SATURDAY)
LONGER TERM METEOROLOGICAL CHALLENGES INCLUDE POPS...TEMPERATURES
AND GUSTY WINDS AT TIMES. RELATIVELY MOIST NORTHWESTERLY TO ZONAL
UPPER FLOW OVER THE FORECAST DISTRICT FROM SUNDAY NIGHT INTO
TUESDAY WILL ALLOW SNOW TO BE NOTED AT TIMES OVER THE SAN JUAN AND
ESPECIALLY THE CENTRAL MOUNTAINS.
AT THIS TIME...HAVE DEPICTED PERSISTENT RELATIVELY LIGHT SNOW OVER
THE CENTRAL MOUNTAINS FROM SUNDAY NIGHT INTO TUESDAY WITH INDIVIDUAL
6 HOUR SNOW AMOUNTS RARELY OVER 2 INCHES. ELSEWHERE...PROJECT THAT
BASICALLY DRY CONDITIONS WILL BE THE RULE FROM SUNDAY NIGHT INTO
TUESDAY.
FROM TUESDAY NIGHT INTO WEDNESDAY EVENING...A STRONGER UPPER WAVE
MOVES ACROSS THE FORECAST DISTRICT. THIS SYSTEM IS EXPECTED TO
ENHANCE PRECIPITATION CHANCES...GENERATE GUSTY WINDS AND PRODUCE
COOLER TEMPERATURES DURING THIS PERIOD. HAVE ADJUSTED LATEST GRIDS
AND ZONES TO REFLECT THIS TREND.
DRY UPPER RIDGING THEN BUILDING OVER SOUTHERN COLORADO FROM LATER
WEDNESDAY NIGHT INTO FRIDAY WILL ALLOW WARMER AND DRIER CONDITIONS
TO RETURN TO THE FORECAST DISTRICT WITH GRADUALLY INCREASINGLY
MOIST SOUTHWESTERLY UPPER FLOW THEN IMPINGING ON THE CWFAS WESTERN
MOUNTAINS BY NEXT SATURDAY.
WARMEST CONDITIONS OF THE LONGER TERM ARE IN STORE MONDAY AND
TUESDAY AND THEN AGAIN FRIDAY...WHILE COOLEST TEMPERATURES ARE
ANTICIPATED FROM WEDNESDAY INTO WEDNESDAY NIGHT. FINALLY...THE
STRONGEST WINDS OF THE LONGER TERM SHOULD BE NOTED AT TIMES FROM
LATER MONDAY NIGHT INTO THURSDAY...ESPECIALLY OVER EASTERN
PORTIONS OF THE FORECAST DISTRICT.
AVIATION...
ANOTHER ROUND OF HEAVIER SNOW SHOULD MOVE INTO THE SOUTHWEST AND
CENTRAL MOUNTAINS THIS EVENING. MTN OBSCURATIONS WILL CONTINUE WITH
IFR/LIFR VIS AND CIGS IN SHSN. GENERALLY VFR CONDITIONS EXPECTED AT
KCOS AND KPUB THROUGH THE NEXT 24 HOURS...THOUGH -SHSN WILL BE
POSSIBLE AT KCOS DURING THE EVENING AS THE NEXT SYSTEM APPROACHES.
CIGS WITH -SHSN COULD DROP INTO THE MVFR CATEGORY BRIEFLY...THOUGH
ANY ACCUMS SHOULD REMAIN UNDER AN INCH AND MOST LIKELY TO OCCUR TO
THE NORTH OF THE KCOS TERMINAL. KALS COULD ALSO SEE SOME MVFR TO
BRIEF IFR CIGS WITH -SHSN AFTER 01-02Z...WITH ADDITIONAL LIGHT SNOWFALL
ACCUMULATIONS OF UP TO AN INCH POSSIBLE. VFR CONDITIONS WILL
RETURN TO ALL TAF SITES BY EARLY SUNDAY MORNING AS THE SYSTEM PASSES
TO THE EAST OF THE REGION. -KT
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 4 AM MST SUNDAY FOR COZ068.
&&
$$
88/10
AREA FORECAST DISCUSSION
NWS PUEBLO CO
1003 PM MST SAT DEC 15 2012
.AVIATION...
KALS...LIGHT SNOW IS CURRENTLY MOVING ACROSS THE SAN LUIS VALLEY
AND IMPACTING KALS. IT HAS REDUCED CIGS TO NEAR 1500 FEET AND VIS
TO AROUND 1SM. EXPECT PERIODS OF LIGHT SNOW TO PERSIST THROUGH
AROUND 10Z WITH VFR CONDITIONS DEVELOPING AFTER 10Z.
KCOS AND KPUB...MID AND UPPER LEVEL CLOUDS WILL SPREAD ACROSS THE
REGION TONIGHT INTO SUNDAY MORNING BUT EXPECT CONDITIONS TO REMAIN
VFR THROUGH THE NEXT 24 HOURS. MOZLEY
&&
.PREV DISCUSSION... /ISSUED 254 PM MST SAT DEC 15 2012/
SHORT TERM...
(TONIGHT AND SUNDAY)
..ROUNDS OF SNOW TO CONTINUE ALONG THE CONTINENTAL DIVIDE...
NEXT UPPER TROF ALREADY MOVING THROUGH UT TOWARDS THE 4 CORNERS
REGION AND WILL BE MOVING ACROSS SRN CO TONIGHT. STARTING TO SEE
SOME ENHANCEMENT AHEAD OF THIS FEATURE ACROSS SW UT...AND SUSPECT
THAT SNOW WILL BE PICKING UP AGAIN ACROSS THE WOLF CREEK PASS AREA
BY LATE AFTERNOON. ITS BEEN SNOWING MAJORITY OF THE DAY ALONG THE
CONTDVD...BUT BASED ON WEB CAMS AT WOLF CREEK SKI AREA AND CDOT WEB
CAMS...IT DOESN`T APPEAR AS HEAVY AS YESTERDAY. LATEST NAM12 HAS
COME IN A BIT HEAVIER WITH SNOWFALL AMOUNTS DURING THE EVENING WHEN
BRUNT OF FORCING AND DEEPER MOISTURE MOVES IN. WILL ALSO HAVE SOME
INSTABILITY TO PLAY WITH. ALL IN ALL...STILL LOOKS LIKE A SOLID
ADVISORY EVENT FOR THE EASTERN SAN JUANS WITH SNOWFALL TOTALS
RANGING FROM 5 TO 10 INCHES WITH LOCALLY UP TO A FOOT FOR THE
PEAKS. HAVE OPTED TO EXTEND THE WINTER WEATHER ADVISORY FOR ZONE 68
THROUGH 07Z...AS LATEST RUNS APPEAR A LITTLE SLOWER WITH THE
SYSTEM.
FOR THE REMAINDER OF THE REGION...HAVE ALREADY HAD ONE WAVE OF
UPGLIDE LIFT OFF TO THE NORTHEAST OF THE AREA. THIS BROUGHT SOME
ISOLATED LIGHT SHOWERS TO THE PIKES PEAK REGION RIGHT AROUND THE
NOON HOUR. AS THE NEXT WAVE APPROACHES...EXPECT ANOTHER ROUND TO
SPREAD IN DURING THE EVENING HOURS. DON`T THINK IT WILL AMOUNT TO
MUCH EAST OF THE MTS...BUT SOME AREAS ALONG MONUMENT HILL COULD PICK
UP SOME LIGHT ACCUMS RANGING FROM A TRACE TO AN INCH.
INTERESTINGLY...THE 18Z NAM HAS BACKED OFF ON SNOWFALL FOR THIS
REGION...HOWEVER RUC13 HANDLED THE EARLIER WAVE OF LIGHT SNOW
BETTER...SO WILL LEAN TOWARDS ITS SOLN AND MAINTAIN ISOLATED POPS
(SCATTERED ACROSS TELLER COUNTY/NRN EL PASO) THROUGH THE EVENING.
RUC HAS THE NEXT WAVE OF PRECIP MOVING INTO THIS AREA AROUND 01Z.
SHOULD ALSO SEE ANOTHER ROUND OF SNOW SPREAD ACROSS THE SAN LUIS
VALLEY AND INTO THE SANGRE DE CRISTO MOUNTAINS BETWEEN 03Z AND 09Z.
HAVE INCREASED POPS ACROSS THESE AREAS TO ACCOUNT FOR THIS.
ADDITIONAL ACCUMULATIONS OF 1 TO 4 INCHES WILL BE POSSIBLE FOR THE
HIGHER PEAKS. MOST OF THE SAN LUIS VALLEY SHOULD SEE LESS THAN AN
INCH...BUT SOME AREAS COULD SEE SLIGHTLY MORE...ESPECIALLY AGAINST
THE WEST SLOPES OF THE SANGRES...NEAR CRESTONE.
SYSTEM WILL EXIT EASTERN COLORADO BY EARLY SUNDAY MORNING. LIGHT
SNOW CONTINUES ALONG THE CONTINENTAL DIVIDE THROUGH THE DAY...BUT AM
ONLY GETTING ANOTHER INCH OR TWO OF ACCUMS...WHICH IS NOT ENOUGH TO
WARRANT ANY FURTHER HEADLINES AT THIS POINT. OTHERWISE...WEST TO
NORTHWEST WINDS BEHIND THE DEPARTING SYSTEM SHOULD HELP BOOST TEMPS
TO NEAR CLIMATOLOGICAL NORMALS. HAVE GONE ON THE COLDER SIDE OF
GUIDANCE FOR THE SAN LUIS VALLEY DUE TO SNOW COVER. -KT
LONG TERM...
(SUNDAY NIGHT THROUGH NEXT SATURDAY)
LONGER TERM METEOROLOGICAL CHALLENGES INCLUDE POPS...TEMPERATURES
AND GUSTY WINDS AT TIMES. RELATIVELY MOIST NORTHWESTERLY TO ZONAL
UPPER FLOW OVER THE FORECAST DISTRICT FROM SUNDAY NIGHT INTO
TUESDAY WILL ALLOW SNOW TO BE NOTED AT TIMES OVER THE SAN JUAN AND
ESPECIALLY THE CENTRAL MOUNTAINS.
AT THIS TIME...HAVE DEPICTED PERSISTENT RELATIVELY LIGHT SNOW OVER
THE CENTRAL MOUNTAINS FROM SUNDAY NIGHT INTO TUESDAY WITH INDIVIDUAL
6 HOUR SNOW AMOUNTS RARELY OVER 2 INCHES. ELSEWHERE...PROJECT THAT
BASICALLY DRY CONDITIONS WILL BE THE RULE FROM SUNDAY NIGHT INTO
TUESDAY.
FROM TUESDAY NIGHT INTO WEDNESDAY EVENING...A STRONGER UPPER WAVE
MOVES ACROSS THE FORECAST DISTRICT. THIS SYSTEM IS EXPECTED TO
ENHANCE PRECIPITATION CHANCES...GENERATE GUSTY WINDS AND PRODUCE
COOLER TEMPERATURES DURING THIS PERIOD. HAVE ADJUSTED LATEST GRIDS
AND ZONES TO REFLECT THIS TREND.
DRY UPPER RIDGING THEN BUILDING OVER SOUTHERN COLORADO FROM LATER
WEDNESDAY NIGHT INTO FRIDAY WILL ALLOW WARMER AND DRIER CONDITIONS
TO RETURN TO THE FORECAST DISTRICT WITH GRADUALLY INCREASINGLY
MOIST SOUTHWESTERLY UPPER FLOW THEN IMPINGING ON THE CWFAS WESTERN
MOUNTAINS BY NEXT SATURDAY.
WARMEST CONDITIONS OF THE LONGER TERM ARE IN STORE MONDAY AND
TUESDAY AND THEN AGAIN FRIDAY...WHILE COOLEST TEMPERATURES ARE
ANTICIPATED FROM WEDNESDAY INTO WEDNESDAY NIGHT. FINALLY...THE
STRONGEST WINDS OF THE LONGER TERM SHOULD BE NOTED AT TIMES FROM
LATER MONDAY NIGHT INTO THURSDAY...ESPECIALLY OVER EASTERN
PORTIONS OF THE FORECAST DISTRICT.
AVIATION...
ANOTHER ROUND OF HEAVIER SNOW SHOULD MOVE INTO THE SOUTHWEST AND
CENTRAL MOUNTAINS THIS EVENING. MTN OBSCURATIONS WILL CONTINUE WITH
IFR/LIFR VIS AND CIGS IN SHSN. GENERALLY VFR CONDITIONS EXPECTED AT
KCOS AND KPUB THROUGH THE NEXT 24 HOURS...THOUGH -SHSN WILL BE
POSSIBLE AT KCOS DURING THE EVENING AS THE NEXT SYSTEM APPROACHES.
CIGS WITH -SHSN COULD DROP INTO THE MVFR CATEGORY BRIEFLY...THOUGH
ANY ACCUMS SHOULD REMAIN UNDER AN INCH AND MOST LIKELY TO OCCUR TO
THE NORTH OF THE KCOS TERMINAL. KALS COULD ALSO SEE SOME MVFR TO
BRIEF IFR CIGS WITH -SHSN AFTER 01-02Z...WITH ADDITIONAL LIGHT SNOWFALL
ACCUMULATIONS OF UP TO AN INCH POSSIBLE. VFR CONDITIONS WILL
RETURN TO ALL TAF SITES BY EARLY SUNDAY MORNING AS THE SYSTEM PASSES
TO THE EAST OF THE REGION. -KT
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR COZ068.
&&
$$
88/10
AREA FORECAST DISCUSSION
NWS MOUNT HOLLY NJ
338 PM EST SUN DEC 16 2012
.SYNOPSIS...
LOW PRESSURE WILL TRACK FROM THE GREAT LAKES REGION TO SOUTHEASTERN
CANADA INTO MONDAY AND WEAKEN. ANOTHER LOW IS FORECAST TO MOVE
ACROSS OUR AREA MONDAY NIGHT INTO TUESDAY, AND STRENGTHEN AS IT
TRACKS TOWARD NEW ENGLAND AND THE CANADIAN MARITIMES THROUGH
WEDNESDAY. HIGH PRESSURE THEN CENTERED TO OUR SOUTH BRIEFLY BUILDS
IN FOR WEDNESDAY. A STRONG LOW PRESSURE SYSTEM THEN MOVES
NORTHEASTWARD INTO THE GREAT LAKES REGION ON THURSDAY, AND ITS
ASSOCIATED STRONG COLD FRONT SWEEPS ACROSS OUR AREA EARLY FRIDAY.
THIS POTENTIALLY INTENSE STORM THEN SHIFTS INTO NEW ENGLAND AND
EASTERN CANADA DURING THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
A VERY TRICKY FCST IS IN STORE OVER THE REGION AS IT HAS BEEN ALL
DAY. A WMFRNT IS LOCATED OVER THE REGION AND IS MOVG LITTLE IN
RESPONSE TO A WAVE FORMING ON IT. THIS WAVE WILL MOVE OUT TO SEA
TONIGHT. WITH THE FRONT OVER THE AREA, EXPECT PDS OF GENLY LIGHT
RAIN FOR THE EARLY PORTION OF TONIGHT, GENLY WARM TEMPS, LIGHT WIND
AND FOG. CONFIDENCE IS LOW ON MANY DETAILS OF THE FCST SUCH AS JUST
HOW THICK AND WIDESPREAD THE FOG WILL BE. ALSO, EACH MDL HAS A
DIFFERENT SOLN ON WHERE THE MOST RAIN WILL BE. THE HRRR SEEMED TO
BE HANDLING IT BEST EARLIER, BUT IS NOW TOO DRY, EVEN THOUGH MOST OF
WHAT IS FALLING IS VERY LIGHT. MOST GUID HAS POPS INCREASING LATER
TONIGHT, AND HAVE THEREFORE, DONE SO FOR THIS FCST.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
THE WMFRNT WILL REMAIN OVER THE REGION OR MOVE A BIT NWD ON MONDAY
AND THERE COULD BE A BREAK IN ANY PRECIP DURG THE AFTN BEFORE
ANOTHER AREA OF LOW PRESSURE APPROACHES FROM THE SW LATER IN THE
DAY. AGAIN, THERE ARE VARIED SOLNS AS TO HOW MUCH AND WHAT AREAS
SEE THE MOST RAIN, AND CONFIDENCE IS LOW OVERALL. TEMPS WILL BE
QUITE WARM ON MONDAY, WITH MANY AREAS IN THE 50S, BUT A DREARY
LOOKING DAY IS IN STORE WITH LOW CLOUDS AND SOME RAIN.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
A RATHER ACTIVE PATTERN IS EXPECTED DURING THIS TIME FRAME. THE
OVERALL SYNOPTIC SETUP IS COMPRISED OF AN UPPER-LEVEL TROUGH IN THE
GREAT LAKES MONDAY NIGHT THAT SHIFTS EASTWARD. ADDITIONAL ENERGY
THEN DIVES ACROSS THE FOUR CORNERS REGION TUESDAY INTO WEDNESDAY.
THIS SECOND ENERGY LOOKS TO REALLY AMPLIFY THE PATTERN WHICH HAS A
LARGE TROUGH IN THE PLAINS THURSDAY THAT PROGRESSES INTO THE
NORTHEAST. THIS SECOND FEATURE MAY BECOME RATHER WRAPPED UP FRIDAY
AND SATURDAY. WE USED MOSTLY A MODEL BLEND APPROACH THROUGH
WEDNESDAY, BUT THEN SWITCHED TO HPC GUIDANCE FROM WEDNESDAY NIGHT
ONWARD. SOME ADDITIONAL TWEAKS WERE DONE BASED ON ADDITIONAL
COLLABORATION WITH OUR NEIGHBORING OFFICES AND ALSO TO MAINTAIN
AT LEAST SOME CONTINUITY.
FOR MONDAY NIGHT AND TUESDAY...AN UPPER-LEVEL TROUGH THAT EVENTUALLY
TAKES ON SOME NEGATIVE TILT WILL PUSH A COLD FRONT ACROSS OUR AREA
LATE MONDAY NIGHT. THE FLOW IS EXPECTED TO BE SOUTHERLY AHEAD OF
THIS FEATURE. THE COMBINATION OF STRONGER WAA AND MOISTURE ADVECTION
WILL RESULT IN ANY LINGERING DRIZZLE/FOG TRANSITIONING TO PERIODS OF
RAIN. A PLUME OF ABOUT 1.0 TO 1.25 INCHES OF PW MOVES THROUGH MONDAY
NIGHT. THIS IN COMBINATION WITH INCREASING LARGE SCALE ASCENT WILL
RESULT IN A PERIOD OF HEAVIER RAIN, WITH THE BULK OF IT FALLING
MONDAY NIGHT. THIS THEN TAPERS OFF DURING TUESDAY MORNING FROM
SOUTHWEST TO NORTHEAST. IF THE SURFACE LOW TRACKING OVER OUR AREA
CAN CONSOLIDATE SOME MORE, THERE MAY BE AN AREA OF MORE FOCUSED
HEAVIER RAINFALL. DESPITE THE RAIN, TEMPERATURES MAY START TO RISE
SOME MONDAY NIGHT. THE MODEL FORECAST SOUNDINGS HINT AT LEAST SOME
ELEVATED INSTABILITY DEVELOPING MONDAY NIGHT, HOWEVER IT MAY NOT BE
ENOUGH TO GET TRUE CHARGE SEPARATION TO OCCUR AND BE LOW-TOPPED. WE
MAINTAINED SOME CONTINUITY AND CARRIED ISOLATED THUNDER ACROSS
PORTIONS OF MARYLAND, DELAWARE AND FAR SOUTHERN NEW JERSEY FOR A
TIME MONDAY NIGHT. OUR POPS PEAK MONDAY NIGHT IN THE CATEGORICAL
RANGE, THEN DECREASE STARTING EARLY TUESDAY MORNING.
AS THE SYSTEM EXITS TO OUR NORTHEAST TUESDAY, THE MODEL CONSENSUS IS
GENERALLY FOR ANY RAIN TO TAPER OFF EARLY IN THE MORNING. HOWEVER AS
THE UPPER-LEVEL TROUGH TAKES ON MORE OF A NEGATIVE TILT, SOME
DEFORMATION TYPE FORCING ON THE WEST SIDE MAY BE STRONG ENOUGH TO
ORGANIZE AN AREA OF WRAPAROUND SHOWERS. THE FORECAST SOUNDINGS
ESPECIALLY ACROSS THE NORTHERN AREAS SUGGEST SOME INSTABILITY
DEVELOPS TUESDAY AFTERNOON AS THE MID LEVEL COLD POOL ARRIVES. THIS
COULD RESULT IN SOME LOW-TOPPED CONVECTIVE SHOWERS WITH PERHAPS
SMALL HAIL OR GRAUPEL. THE SYSTEM THEN CONTINUES TO SHIFT FARTHER
AWAY FROM OUR AREA, THEREFORE POPS LOWER THROUGH TUESDAY NIGHT. THE
COMBINATION OF SOME CAA ALOFT OCCURRING TUESDAY AND A TIGHTENING
PRESSURE GRADIENT SHOULD RESULT IN A DECENT UPTICK IN THE WINDS. THE
BOUNDARY STILL LOOKS MILD WITH THE MAIN COOLING TAKING PLACE ABOVE.
THIS SHOULD RESULT IN BREEZY TO EVEN WINDY CONDITIONS AT TIMES.
FOR WEDNESDAY AND THURSDAY...LOW PRESSURE TRACKS SOUTH OF THE
CANADIAN MARITIMES WITH A CYCLONIC FLOW REGIME OVER OUR REGION TO
START. WHILE THE AIRMASS IS NOT ALL THAT COOLER, FORECAST SOUNDINGS
SHOW ENOUGH OF A GRADIENT FOR BREEZY CONDITIONS DEVELOPING WEDNESDAY
AFTERNOON BEFORE QUICKLY DIMINISHING IN THE EVENING. THE CYCLONIC
FLOW LOOKS TO EASE UP WEDNESDAY NIGHT AND THURSDAY AS RIDGING SLIDES
EASTWARD. THIS WILL RESULT IN LIGHTER WINDS BUT THEN TURNING MORE
SOUTHEASTERLY THURSDAY.
YET ANOTHER STORM IS EXPECTED TO ARRIVE THURSDAY NIGHT AS THIS
ACTIVE PATTERN CONTINUES. THIS SYSTEM IS FORECAST TO BE MUCH MORE
AMPLIFIED AS THE OVERALL SYNOPTIC PATTERN SHIFTS INTO A STRONGER
FLOW. AS A RESULT, CLOUDS ARE EXPECTED TO QUICKLY INCREASE THURSDAY.
INCREASING LARGE SCALE ASCENT ARRIVING FROM THE WEST COMBINED WITH
AMPLE MOISTURE ADVECTION, WAA AND A STRENGTHENING WIND FIELD WILL
RESULT IN AN AREA OF SHOWERS MOVING IN TOWARD THURSDAY EVENING.
WHILE THE PRECIPITATION SHOULD BE CONVECTIVE /SHOWERY/, IT MAY END
UP BEING MORE WIDESPREAD RAIN AS THE SYSTEM PROBABLY OCCLUDES AND A
SURFACE LOW TRIES TO EVENTUALLY DEVELOP ALONG THE TRIPLE POINT.
THERE IS THE POTENTIAL FOR THUNDER AND MORE WIND ASSOCIATED WITH
THIS SYSTEM AS IT IS FORECAST TO BE MORE DYNAMIC. THE SOUTHERLY
WINDS MAY BE GUSTY IN SOME STRONGER CONVECTIVE ELEMENTS DURING THE
EVENING. GIVEN THE ROBUST WARMING OF THE AIRMASS AHEAD OF THE COLD
FRONT, ALL RAIN IS EXPECTED TO OCCUR. GIVEN SOME LINEAR LOOK TO THE
FORCING ALONG WITH A TIGHTENING 850 MB THERMAL GRADIENT MAY ALLOW
FOR THE DEVELOPMENT OF A NARROW COLD FRONTAL RAINBAND.
FOR FRIDAY AND SATURDAY...LOW PRESSURE SHOULD BE RATHER ROBUST FROM
SOUTHEASTERN CANADA AND NEW ENGLAND. A MUCH MORE PRONOUNCED COLDER
AIRMASS LOOKS TO FOLLOW THIS SYSTEM ALONG WITH POTENTIALLY WINDY
CONDITIONS ARRIVING. AS THE PRONOUNCED UPPER-LEVEL TROUGH IS
FORECAST TO BE IN THE EAST, A MUCH STRONGER CAA PATTERN UNDER A
WEST/NORTHWEST FLOW WILL OCCUR ACROSS OUR AREA. DEPENDING ON THE
SYNOPTIC SETUP UP AND DEPTH OF THE COLD AIR, SOME LAKE EFFECT SNOW
MAY RESULT AND MAKE A RUN AT OUR NORTHWEST ZONES. AS OF NOW, WE WENT
WITH SLIGHT CHC TO LOW CHC POPS FRIDAY, THEN DRY SATURDAY OTHER THAN
A MENTION OF FLURRIES ACROSS THE FAR NORTHWEST ZONES.
OF GREATER INTEREST IS THE POTENTIAL FOR STRONG WINDS FRIDAY INTO
SATURDAY. THE STRONG CAA /850 MB TEMPERATURES DOWN TO NEAR -8C/ AND
A TIGHT PRESSURE GRADIENT WILL COMBINE WITH AN 850 MB FLOW OF NEARLY
40-50 KNOTS. THIS COULD RESULT IN SURFACE GUSTS VERY CLOSE TO WIND
ADVISORY CRITERIA WHICH STARTS AT 40 KNOTS /46 MPH/. THERE SHOULD BE
EFFICIENT VERTICAL MIXING ESPECIALLY FRIDAY INTO SATURDAY AS THE
BOUNDARY LAYER COOLS WITH STRONGER CAA ABOVE. SOME SHORT WAVE ENERGY
EMBEDDED IN THE NORTHWESTERLY FLOW MAY RESULT IN A CLIPPER TYPE
SYSTEM THAT DROPS INTO OUR AREA SATURDAY NIGHT WITH ANOTHER COLD
FRONT.
FOR SUNDAY...THE UPPER-LEVEL TROUGH SHOULD BE MAINTAINED ACROSS
EASTERN CANADA AND THE NORTHEAST. THIS SHOULD RESULT IN A COLDER
AIRMASS BEING MAINTAINED ALTHOUGH ALOFT IT LOOKS TO MODIFY SOME
EARLY BEFORE PERHAPS A SECONDARY SURGE ARRIVES IN THE WAKE OF A
CLIPPER OR SECONDARY COLD FRONT. THE OVERALL FLOW STILL LOOKS ACTIVE
AS GUIDANCE SUGGESTS SIGNIFICANT ENERGY ARRIVING ON THE WEST COAST
WITH RIDGING INTO THE PLAINS, AND A TROUGH IN THE NORTHEAST. GIVEN
THIS FLOW REGIME, LAKE EFFECT SNOW MAY STILL BE ONGOING SOME OF
WHICH COULD BE INTO OUR NORTHWEST ZONES. PLENTY OF TIME TO PIN THIS
DOWN AS WIND DIRECTION IS ONE OF THE KEY FACTORS. OVERALL, WE
FOLLOWED HPC GUIDANCE MORE CLOSELY ALTHOUGH DID BUMP UP THE WINDS
SOME AS BRISK CONDITIONS MAY STILL OCCUR.
&&
.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
CONDS CONTINUE TO DETERIORATE ACRS THE AREA WITH MOST LOCATIONS MVFR
OR IFR. AS AN AREA OF LIGHT RAIN MOVED THRU MAINLY ACRS SRN NJ,
VSBYS DROPPED AND THEN CAME BACK UP. HOWEVER, THE OVERALL TREND IS
DOWNWARD, AND MOST LOCATIONS WILL BE IFR THIS EVENING AND EVEN LIFR
OVERNIGHT AS FOG DEVELOPS. CONDS WILL IMPROVE A BIT AFTER DAYBREAK
MONDAY, BUT LOW CLOUDS WILL STILL LINGER AND EXPECT IFR/MVFR FOR THE
BALANCE OF THE DAY. THE WIND IS EXPECTED TO BE VERY LIGHT WITH
SPEEDS GENLY LESS THAN 5 KTS AND IN MANY CASES CALM, WHICH IN THIS
CASE WILL NOT HELP IMPROVE THE VSBY SITUATION.
OUTLOOK...
MONDAY NIGHT...VARIABLE IFR/LIFR IN PERIODS OF RAIN AND LOW
CLOUDS/FOG. WINDS MOSTLY FROM THE SOUTHEAST AT 10 KNOTS OR LESS.
TUESDAY...ANY SUB-VFR CONDITIONS SHOULD IMPROVE TO VFR FROM
SOUTHWEST TO NORTHEAST BY MID-MORNING AS THE RAIN ENDS. WEST TO
NORTHWESTERLY WINDS INCREASE WITH GUSTS TO AROUND 25 KNOTS IN THE
AFTERNOON INTO THE EVENING. SOME WRAPAROUND SHOWERS MAY OCCUR IN THE
AFTERNOON ESPECIALLY NEAR KRDG, KABE TO KTTN.
WEDNESDAY...VFR WITH GUSTY WEST WINDS UP TO 30 KNOTS, DIMINISHING
DURING THE EVENING.
THURSDAY...VFR LOWERING TO SUB-VFR IN SHOWERS. SOUTH-SOUTHEAST WINDS
WITH GUSTS TO AROUND 20 KNOTS. THERE IS A CHANCE OF LOW-LEVEL WIND
SHEAR ESPECIALLY AT NIGHT AS A SOUTHWESTERLY LOW-LEVEL JET INCREASES
TO ABOUT 50 KNOTS NEAR 2,000 FEET.
FRIDAY...A STRONG COLD FRONT SWEEPS THROUGH EARLY WITH SHOWERS
ENDING. WINDS SHIFT TO WESTERLY AND BECOME SUSTAINED AT 15-20 KNOTS
WITH GUSTS TO AROUND 35 KNOTS.
&&
.MARINE...
A SCA HAD BEEN RAISED EARLIER FOR THE NRN WATERS AS SEAS HAD COME UP
TO OVER 6 FT AND THE WIND WAS PUSHING SCA CRITERIA. GUID SHOWED
THAT SEAS SHUD REMAIN ELEVATED THRU THE SHORT TERM PD SO THE SCA
WILL REMAIN UP. FURTHER S, SEAS WILL INCREASE A BIT AS WELL, BUT
ARE EXPECTED TO REMAIN BELOW SCA CRITERIA ATTM.
OUTLOOK...
AN AREA OF LOW PRESSURE AND A COLD FRONT MOVES THROUGH MONDAY NIGHT
WITH A PERIOD OF RAIN. A MILDER AND MOIST AIRMASS IN PLACE AHEAD OF
IT MAY RESULT IN SOME FOG, ALTHOUGH THE RAIN COULD HELP TO AIDE IN
JUST ENOUGH LOW-LEVEL MIXING.
A PERIOD OF SOME CAA OCCURS TUESDAY BEHIND THE SYSTEM, HOWEVER THIS
LOOKS TO BE SHORT IN DURATION. THE MODEL GUIDANCE SHOWS 925 MB WINDS
INCREASE TO ABOUT 30-35 KNOTS AND SOUNDINGS INDICATE THE LOW-LEVEL
LAPSE RATES STEEPEN DURING TUESDAY INTO WEDNESDAY. THIS SHOULD
RESULT IN A STRONG SMALL CRAFT ADVISORY EVENT WITH EVEN A CHANCE FOR
SOME MARGINAL GALE FORCE GUSTS. SINCE THE CAA IS NOT FORECAST TO BE
REAL ROBUST, THE OVERALL MIXING MAY BE JUST ENOUGH TO NOT ALLOW FOR
WIDESPREAD AND MORE PROLONGED GALE GUSTS.
HIGH PRESSURE CENTERED TO OUR SOUTH INFLUENCES OUR WEATHER
WEDNESDAY, THEREFORE THE WINDS ARE EXPECTED TO QUICKLY DIMINISH.
THEREFORE, SUB-SCA CONDITIONS ARE ANTICIPATED WEDNESDAY NIGHT AND
THURSDAY MORNING. A STRENGTHENING SOUTHERLY FLOW /40-55 KNOTS AT
925 MB/ THEN LATER THURSDAY AFTERNOON AND NIGHT AHEAD OF A STRONG
COLD FRONT SHOULD ALLOW WINDS AND SEAS TO EASILY REACH ADVISORY
LEVELS. THERE COULD BE ENOUGH MIXING OCCURRING WITHIN THE WAA REGIME
AND MILDER BOUNDARY LAYER TO GET SOME MARGINAL GALE GUSTS. AS THE
FRONT SWEEPS THROUGH EARLY FRIDAY MORNING, STRONGER CAA KICKS IN
WITH QUICKLY STEEPENING LOW-LEVEL LAPSE RATES. GIVEN THE STRONG CAA
PUSH COMBINED WITH 925 MB WINDS INCREASING TO 35-40 KNOTS FRIDAY
AND FRIDAY NIGHT, SHOULD RESULT IN A GOOD POTENTIAL FOR GALES
OCCURRING. FOR NOW, WE HELD OFF ON ANY HEADLINES FOR MONDAY NIGHT
AND BEYOND HOWEVER A MENTION OF THE POSSIBLE GALES IS IN THE
HAZARDOUS WEATHER OUTLOOK.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST MONDAY FOR ANZ450-451.
&&
$$
SYNOPSIS...GORSE
NEAR TERM...NIERENBERG
SHORT TERM...NIERENBERG
LONG TERM...GORSE
AVIATION...GORSE/NIERENBERG
MARINE...GORSE/NIERENBERG
AREA FORECAST DISCUSSION
NWS MIAMI FL
1233 AM EST SUN DEC 16 2012
.AVIATION...VFR CONDITIONS WILL PREVAIL THROUGH THE FORECAST WITH
A LIGHT EAST SURFACE WIND. LAND BREEZE COULD SET UP ALONG EAST
COAST WITH THE MORE INLAND TERMINALS BECOMING LIGHT WEST LESS THAN
5 KNOTS BETWEEN 06-12Z BEFORE BECOMING EAST 8-10 KNOTS. A SEA
BREEZE MAY ALSO TRY AND SET UP ALONG THE SOUTHWEST COAST BUT AT
THIS TIME HAVE LEFT OUT OF THE FORECAST FOR NOW AS IT WILL BE VERY
BRIEF LATE THIS AFTERNOON.
KOB
&&
.PREV DISCUSSION... /ISSUED 858 PM EST SAT DEC 15 2012/
UPDATE...
ALTHOUGH LATEST MIAMI SOUNDING SHOWS SLIGHTLY DRIER AIR IN THE
LOWER LEVELS, STUBBORN PATCH OF CLOUDS/SHOWERS STILL AFFECTING
PARTS OF SOUTH FLORIDA, ESPECIALLY ACROSS NORTHERN MIAMI-DADE
COUNTY. RAISED POPS FOR THE FIRST HALF OF THE NIGHT TO 20/30
PERCENT SOUTH OF ALLIGATOR ALLEY TO ACCOUNT FOR CURRENT TRENDS,
WITH LOWER POPS OVERNIGHT AS BACK EDGE OF MOISTURE SHOULD START TO
MOVE IN. ADDITIONAL CLOUDS WITH LIKELY A FEW SHOWERS DOWNWIND OVER
THE NORTHERN BAHAMAS MAY HOLD TOGETHER ENOUGH TO KEEP AN ISOLATED
SHOWER MENTION EAST COAST ALL NIGHT, BUT FOR NOW WILL REMAIN
OPTIMISTIC AND KEEP OUT OF ZONE FORECAST.
ALSO KEPT PATCHY FOG FOR INLAND AREAS OVERNIGHT AS HIGH SURFACE
MOISTURE WITH DEWPOINTS IN LOWER/MID 60S AND LIGHTER WINDS
SHOULD PROMOTE FOG DEVELOPMENT. ALL OTHER FORECAST ELEMENTS LOOK
GOOD. /MOLLEDA
PREV DISCUSSION... /ISSUED 630 PM EST SAT DEC 15 2012/
AVIATION...
MAINLY VFR CONDITIONS ARE EXPECTED THROUGH THE END OF THE TAF
PERIOD. SHOWERS ARE BEGINNING TO REDEVELOP OVER THE ATLANTIC
WATERS AND MOVING IN THE GENERAL DIRECTION OF KOPF AND KMIA. SO
WILL KEEP VCSH IN FOR THOSE TAF SITES FOR THE NEXT SEVERAL HOURS.
MVFR CONDITIONS WILL BE POSSIBLE IF A SHOWER GOES OVER ONE OF THE
TAF SITES. LIGHT EAST NORTHEAST OR EAST WINDS ARE EXPECTED
OVERNIGHT. WINDS WILL VEER TO THE SOUTHEAST DURING THE DAY ON
SUNDAY AND INCREASE TO AROUND 10 KNOTS. THERE WILL STILL BE A
CHANCE FOR LIGHT SHOWERS NEAR THE SOUTHERN HALF OF THE EAST COAST
TAF SITES ON SUNDAY...BUT LEFT OUT OF THE TAF SITES FOR NOW.
PREV DISCUSSION... /ISSUED 238 PM EST SAT DEC 15 2012/
DISCUSSION...
SCATTERED SHOWERS CONTINUE TO STREAM INTO SOUTH FLORIDA UNDER A
CONTINUED MID LEVEL INVERSION AND EAST-NORTHEASTERLY SURFACE FLOW.
LATEST HRRR DEPICTS SHOWERS DIMINISHING IN COVERAGE THROUGH THE
EVENING AND OVERNIGHT HOURS AS UPPER RIDGING BEGINS TO BUILD
ACROSS THE AREA FROM THE GULF OF MEXICO. AS RIDGING BUILDS
IN...WINDS WILL BEGIN TO DIMINISH ACROSS THE ATLANTIC WATERS
REDUCING THE RIP CURRENT THREAT SLIGHTLY INTO SUNDAY. WITH LIGHTER
WINDS OVERNIGHT AND CONTINUED LOW LEVEL MOISTURE...PLACED PATCHY
FOG ACROSS INTERIOR AREAS THROUGH THE OVERNIGHT AND EARLY MORNING
HOURS.
SUNDAY INTO MONDAY LOOK MAINLY DRY AS UPPER RIDGING DOMINATES THE
SOUTH FLORIDA PENINSULA. SURFACE WINDS WILL BECOME MORE
SOUTHEASTERLY AS A COLD FRONT APPROACHES FROM THE NORTH. BY MONDAY
NIGHT RIDGING WILL BEGIN TO BREAK DOWN AS THE FRONT PUSHES INTO
CENTRAL FLORIDA. SHOWERS AND POSSIBLE THUNDERSTORMS ARE EXPECTED
TO DEVELOP AND PUSH ACROSS SOUTH FLORIDA AS THE FRONT PASSES
THROUGH TUESDAY AFTERNOON. MODELS SEEM TO HAVE A GOOD HANDLE ON
THE TIMING OF THIS SYSTEM.
BY WEDNESDAY RIDGING RETURNS IN THE WAKE OF THE FRONT. WEDNESDAY
MORNING COULD SEE LOWS IN THE 40S ACROSS INTERIOR AREAS WITH MID
TO UPPER 50S ELSEWHERE. THE OVERALL PATTERN FOR THE LATTER HALF OF
NEXT WEEK SEEMS TO BE MUCH MORE PROGRESSIVE. SOUTHERLY FLOW
QUICKLY RETURNS OVERNIGHT WEDNESDAY INTO THURSDAY AS ANOTHER FRONT
APPROACHES THE NORTHERN GULF OF MEXICO. RAIN CHANCES RETURN FRIDAY
AS THE FRONT PUSHES INTO SOUTH FLORIDA.
MARINE...
EAST-NORTHEASTERLY WINDS ARE SLOWLY BECOMING MORE EASTERLY AND ARE
BEGINNING TO WEAKEN SLIGHTLY ACROSS THE ATLANTIC WATERS. SHOULD
STILL SEE SEAS IN THE 5 TO 6 FOOT RANGE ACROSS MAINLY THE NEAR AND
OFFSHORE WATERS OF PALM BEACH COUNTY. DECIDED TO KEEP MENTION OF
SMALL CRAFT SHOULD EXERCISE CAUTION FOR THIS AREA. ALSO EXTENDED THE
HIGH RISK OF RIP CURRENTS ACROSS THE BEACHES OF PALM BEACH COUNTY.
FIRE WEATHER...
STILL NO FIRE WEATHER CONCERNS AT THIS TIME. LOW LEVEL MOISTURE
WILL REMAIN WELL ABOVE CRITICAL THRESHOLDS ACROSS THE ENTIRE AREA
THROUGH THE PERIOD.
&&
.MFL WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
AM...NONE.
GM...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
926 PM CST MON DEC 17 2012
.DISCUSSION...
338 PM CST
PRIMARY FORECAST FOCUS AND CONCERN LIES WITH POTENTIAL HIGH IMPACT
WINTER STORM WEDNESDAY NIGHT THROUGH THURSDAY. THE THURSDAY
AFTERNOON/EVENING COMMUTE MAY BE IMPACTED BY SNOW AND HIGH WINDS
CAUSING BLOWING SNOW. NO WINTER WEATHER WATCHES WILL BE ISSUED
WITH THIS FORECAST PACKAGE...BUT WILL CONTINUE TO HIGHLIGHT THE
POTENTIAL IMPACTS WITH THIS EVENT WITH A SPECIAL WEATHER
STATEMENT.
SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT
WITH CWA ON FAR WESTERN PERIPHERY OF SHORTWAVE LIFTING NORTHEAST
FROM OHIO VALLEY THIS EVENING INTO THE FIRST PART OF TONIGHT...WILL
MAINTAIN INHERITED LOW POPS FOR SOUTHEASTERN PORTION OF CWA...THOUGH
LATEST HI RES GUIDANCE SUGGESTS THE PRECIP CURRENTLY OVER THE
SOUTHERN CWA WILL BE LARGELY PUSHING OFF TO THE EAST. DID TIGHTEN
POP GRADIENT TO KEEP ONLY THE FAR SOUTHEAST CWA WITH MENTIONABLE
POPS. FORECAST SOUNDINGS ALSO INDICATE LIFT WILL BE WEAK AT BEST BY
THIS EVENING AS UPPER WAVE DEPARTS. SOUNDING THERMAL PROFILES TODAY
HAVE BEEN TOO WARM BUT GIVEN WEAKENING UPWARD MOTION THIS
EVENING...ANY LINGERING PRECIP SHOULD BE LIGHT RAIN. FEEL LOWS
MAINLY IN THE UPPER 20S AND LOWER 30S ARE REASONABLE...THOUGH
PERSISTENT STRATUS DECK MAY KEEP THEM A BIT WARMER THAN INDICATED.
ATTENTION THEN TURNS ON POSSIBLE LIGHT SNOW CHANGING TO RAIN ON
TUESDAY WITH A WEAK SHORTWAVE QUICKLY PASSING OVER NRN IL OR ALONG
IL/WI STATELINE. OPERATIONAL MODEL RUNS WITH EXCEPTION OF 12Z
NAM...WHICH TRACKS SHORTWAVE FARTHER NORTH THROUGH SOUTHERN
WISCONSIN...SPIT OUT VERY LIGHT QPF FOR NORTHERN 1/2 TO 1/3 OF CWA
THROUGH TUES AFTERNOON. NO MAJOR CHANGES MADE TO THIS PERIOD.
THINKING THAT WHILE PRECIP IS POSSIBLE GIVEN SOME DECENT OMEGA...DRY
LAYER IN LOW LEVELS OF GFS BUFKIT SOUNDING MAKES IT QUESTIONABLE
WHETHER PRECIP WILL REACH THE GROUND. WITH THIS IN MIND...
MAINTAINED SLIGHT POPS...WITH A PROGRESSION FROM SLIGHT/LOW CHANCE
LIGHT SNOW TO LIGHT RAIN AS SURFACE WARMS INTO THE 40S BY AFTERNOON.
NO ACCUMULATION IS ANTICIPATED. FAVOR SHORTWAVE TRACK ACROSS CWA AS
OPPOSED TO FAR NORTH NAM TRACK...SO THUS THINK HIGH TEMPS WILL NOT
BE AS WARM AS NAM...WHICH BRINGS LOW 50S INTO SOUTHERN CWA.
CLOUDS WILL OVERSPREAD CWA WEDNESDAY WELL IN ADVANCE OF DEEPENING
MID LATITUDE CYCLONE. STRONG HEIGHT FALLS INVOF CYCLONE WILL FORCE
HEIGHT RISES OVER WESTERN GREAT LAKES AND THUS WARM ADVECTION AND
ANOTHER MILD DAY IN THE 40S FOR MOST OF CWA EXCEPT FAR NORTH. LIGHT
RAIN WILL NOT ARRIVE IN FAR WESTERN CWA UNTIL LATE AFTERNOON AT THE
EARLIEST...WITH SLIGHT POPS DURING THAT TIME.
WEDNESDAY NIGHT THROUGH THURSDAY
THIS PERIOD LOOKS TO POTENTIALLY BRING THE FIRST SIGNIFICANT WINTER
STORM OF THE SEASON. THERE IS STRONG MODEL CONSENSUS ON THE
STRONG/DEEPENING LOW PRESSURE AREA TO TRACK NEAR OR OVER THE CWA ON
THURSDAY. THUS THERE IS HIGH CONFIDENCE IN PRECIPITATION OCCURRING
AND THE OTHER STRONG SIGNAL CONSISTENT ACROSS ALL MODELS IS THE HIGH
WIND POTENTIAL THURSDAY AFTERNOON THROUGH THURSDAY EVENING.
THE KEY FOR THE AREA IN TERMS OF PTYPE AND QPF AMOUNTS IS THE
TRACK OF THE H5/H8 AND SURFACE LOW. NOTE THAT THE SOUTHERN STREAM
WAVE THAT WILL FORM PART OF THIS SYSTEM WAS IDENTIFIED AS BEING WEST
OF 130W ON WATER VAPOR IMAGERY AND IS NOT PROGGED TO MAKE LANDFALL
UNTIL TUESDAY MORNING ON THE CALIFORNIA COAST AND THUS WAS NOT
SAMPLED BY THE RAOB NETWORK FOR THE 12Z MODEL CYCLE. THE NORTHERN
STREAM WAVE WAS SAMPLED BY THE ALASKA RAOB NETWORK YESTERDAY
AFTERNOON...BUT WILL TRAVERSE A MORE DATA SPARSE REGION UNTIL MAKING
INROADS INTO THE PACIFIC NORTHWEST ON TUESDAY. THUS CONTINUED TRACK
DIFFERENCES AND CHANGES ARE LIKELY AMONGST THE NWP GUIDANCE UNTIL
THERE IS BETTER SAMPLING.
TRACK DIFFERENCES CONTINUE WITH TODAYS LATEST GUIDANCE...WITH THE
NAM/GFS/SREF/GEFS ALL FARTHER NORTHWEST WITH TRACK OF SURFACE LOW
THAN FOREIGN COUNTERPARTS. THIS IS ESPECIALLY THE CASE WITH 12Z
ECMWF RUN...WHICH STAYED CONSISTENT WITH A MORE SOUTHERN TRACK AND
ACTUALLY SHIFTED A HAIR SOUTH OF THE 00Z RUN. MAJOR DIFFERENCE IS IN
HANDLING OF UPPER LEVEL FEATURES...WITH NCEP MODELS PHASING THE
NORTHERN AND SOUTHERN STREAM AND CLOSING OFF AT H5 LATE WEDNESDAY
NIGHT INTO EARLY THURSDAY MORNING...WHILE THE ECMWF KEEPS THE
SOUTHERN STREAM VORT DOMINANT AND DOESNT CLOSE OFF UNTIL THURSDAY
NIGHT OVER SOUTHERN LOWER MICHIGAN.
OVERALL FAVOR THE CONSISTENCY OF THE ECMWF AND ITS ENSEMBLES DUE TO
THE EXPECTATION THAT STRONG BLOCKING RIDGE JUST NORTH OF HUDSON
BAY/A WEST BASED -NAO WILL MAKE THE FAR NORTHWEST TRACK LESS LIKELY.
DID HOWEVER GIVE A NOD TO THE REMAINDER OF THE GUIDANCE...WITH A
TRACK NOT AS FAR SOUTH AS THE EC BUT STILL SOUTHEAST OF CHICAGO ON
THURSDAY. THIS DIFFERENCE IS QUITE SIGNIFICANT IN TERMS OF SENSIBLE
WEATHER IMPACTS FOR CWA. THE NCEP SOLUTIONS WOULD RESULT IN A
PRIMARILY RAIN EVENT WELL INTO THURSDAY...BEFORE CHANGING TO SNOW ON
THE BACKSIDE OF THE DEPARTING DEEP LOW. FURTHERMORE...THE UPPER LOW
TRACK WOULD ALSO INTRODUCE DRY SLOT ISSUES...RESULTING IN LOWER
LIQUID EQUIVALENT QPF AMOUNTS. ON THE OTHER HAND...THE ECMWF STARTS
OUT WARM...ESPECIALLY IN THE SOUTHEAST CWA...BUT THE CHANGEOVER TO A
WET SNOW OCCURS MUCH QUICKER.
ALL THE CLASSIC INGREDIENTS OF AN INTENSE MID LATITUDE CYCLONE WILL
BE AT PLAY WITH THIS SYSTEM...WITH MASSIVE HEIGHT FALLS/JET STREAM
DIVERGENCE/ANOMALOUSLY STRONG WARM CONVEYOR BELT AT H85/TIGHT
THERMAL GRADIENT AND FRONTOGENESIS SUPPORTIVE OF CATEGORICAL POPS
CWA WIDE THROUGH AT LEAST THURS AFTERNOON. FURTHERMORE...UNLESS WE
GET SIGNIFICANTLY DRY SLOTTED...LIQUID EQUIVALENT QPF MAY BE CLOSE
TO 1 INCH. THE BIGGEST CONCERN IS THAT AS THICKNESSES AND
TEMPERATURES CRASH IN THE BACKSIDE DEFORMATION AXIS OF THE
SYSTEM...THE INTENSE WIND FIELD OF THE STORM WILL ALLOW FOR POSSIBLE
BLIZZARD/NEAR BLIZZARD CONDITIONS TO IMPACT THE THURSDAY PM RUSH HR.
IN FACT...WIND GUSTS FROM LATE THURSDAY AFTERNOON THROUGH THURSDAY
EVENING MAY APPROACH OR EXCEED 50 MPH. GIVEN THE COLDEST START FOR
THE NORTHWEST CWA AND VERY MILD START TO THURSDAY FOR THE
SOUTHEAST...HIGHEST SNOWFALL TOTALS WILL BE FAVORED FOR THE NW CWA
WHERE SIGNIFICANT ACCUMULATIONS ARE POSSIBLE AND TAPER TO THE FAR
SOUTHEAST...WHERE THERE LIKELY WILL BE MUCH LESS SNOW. ONE
ADDITIONAL ITEM OF NOTE IS THAT THE UNPRECEDENTED MEASURABLE SNOW
DROUGHT AT CHICAGO AND ROCKFORD HAS A GOOD SHOT OF FINALLY ENDING
WITH THIS SYSTEM.
ARCTIC AIR WILL CONTINUE TO PLUNGE INTO THE AREA THURSDAY
NIGHT...WITH STRONG GUSTY NORTHWEST WINDS CONTINUING TO PRODUCE
AREAS OF BLOWING SNOW. LOWS WILL PLUMMET INTO THE TEENS AND LOWER
20S. THE NW INDIANA LAKEFRONT..ESPECIALLY PORTER COUNTY...MAY SEE
LAKE ENHANCEMENT TO THE LINGERING SNOW ON THE BACKSIDE OF THE
SYSTEM.
RC
FOR FRIDAY INTO THE WEEKEND...
SOMEWHERE ON THE WEB YOU CAN FIND A CARTOON CALLED SNOW FOOLIN IN
WHICH THE CALENDAR TURNS FROM DEC 20 TO DEC 21 AND SUDDENLY THE
WORLD BECOMES FREEZING COLD AND COVERED WITH SNOW. THAT IS
BASICALLY THE TREND WE ARE EXPECTING THIS WEEK.
AFTER THE EVENTS OF WEDNESDAY NIGHT INTO THURSDAY...THE SUBFREEZING
HIGHS AND SINGLE DIGIT WIND CHILLS MOVE IN FRIDAY ON BRISK NORTHWEST
WINDS BETWEEN THE DEPARTING LOW AND A SKINNY RIDGE OVER THE CENTRAL
CONUS. FROM FRIDAY INTO AT LEAST CHRISTMAS EVE IT IS UNLIKELY THAT
ANYWHERE IN THE FORECAST AREA WILL RECORD ADDITIONAL HIGHS ABOVE 40
DEGREES. MORNING LOWS OVER THE WEEKEND...ESPECIALLY SATURDAY...ARE
PRESENTLY FORECAST TO DROP INTO THE TEENS BUT COULD BE EVEN COLDER
IF SKIES CLEAR OUT...WINDS TAPER OFF...AND A DECENT COVER OF SNOW IS
IN PLACE. AS FAR AS ADDITIONAL SNOW...AFTER THE MAIN STORM MOVES
OUT LATE THURSDAY...THERE REMAINS A CHANCE OF LAKE EFFECT SNOW
MAINLY ON THE LOWER MICHIGAN SIDE BUT ALSO A BIT INTO NORTHERN
INDIANA.
LENNING
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 03Z...
* BREAK IN MVFR CIGS APPEARS TO BE LINGERING...POSSIBLE TREND BACK
TO MVFR OVERNIGHT.
* N WINDS ARND 5 KT WILL SLOWLY TURN W THEN S BY DAYBREAK TUE.
* PSBL VCSH DEVELOPING DURING THE DAY TUE.
BEACHLER
//DISCUSSION...UPDATED 03Z...
IR IMAGERY INDICATES THE HOLE IN THE CLOUD COVER OVER FAR
NORTHEAST IL CONTINUES TO BE OVER ORD/MDW. IT DOES APPEAR THAT
THIS WAS TRYING TO SLIDE EAST ACROSS THE LAKE...HOWEVER CONFIDENCE
HAS BACKED OFF THAT THE MID-DECK CLOUDS WILL COME BACK OVER
ORD/MDW UNTIL LATER TONIGHT. THE RAP FORECAST GUIDANCE INDICATES
THE DRY AIR OVER ORD/MDW/DPA AIRFIELDS LINGERING THRU 06Z...THEN
SLOWLY RE-SATURATING. AT THIS TIME HAVE MADE SOME ADJUSTMENTS TO
THE GOING FORECAST TO REFLECT THE DELAY IN MVFR CIGS RETURNING TO
ORD/MDW. IT IS POSSIBLE THAT IF MVFR CIGS DO RETURN...THEY MAY END
UP BEING MARGINAL. WILL CONTINUE TO CLOSELY MONITOR THIS.
PREV DISCUSSION...UPDATED 00Z...
PRIOR TO SUNSET THE VISIBLE IMAGERY INDICATED THAT THE MOSTLY
CLOUDY SKIES CONTINUE TO HOVER OVER NORTHERN IL/NORTHWEST IN
AIRFIELDS. A FEW BREAKS WERE NOTED WELL TO THE WEST ACROSS
NORTH CENTRAL MO AND SOUTH CENTRAL IA...HOWEVER IT DOES NOT APPEAR
THIS CLEARING WILL ARRIVE ACROSS THE REGION TONIGHT OR EVEN TUE.
GUIDANCE CONTINUES TO SUGGEST THAT THE BRIEF BREAK IN THE MVFR
CIGS TO VFR WILL BE SHORT-LIVED...TRENDING BACK TOWARDS CIGS ARND
1500 FT AGL BY 04-05Z TUE. SOME DRY AIR DOES TRY TO POKE NORTHEAST
ACROSS THE AIRFIELDS ARND DAYBREAK TUE...WHICH MAY LIFT CIGS BACK
TO VFR. HOWEVER FEEL THAT SOME SCT CLOUDS ARND 1500FT AGL WILL
LINGER. IN ADDITION A WEAK WAVE WILL BE SLIDING EAST ACROSS THE
REGION TUE...AND SOME PATCHY PRECIP MAY BE ASSOCIATED WITH THIS
WAVE. AT THIS TIME ANY PRECIP SHUD BE LGT RA...BUT GIVEN THE LOW
CONFIDENCE IN COVERAGE AND TIMING WILL LEAVE THIS AS A VCSH
MENTION AT THIS TIME. THEN CIGS SHUD REMAIN VFR THRU TOMORROW
NIGHT AS THE SOUTH WINDS BECOMING WEST WINDS REMAIN ARND 10-12KT.
THE FOCUS CONTINUES TO BE ON THE APPROACHING SIGNIFICANT WEATHER
SYSTEM POISED TO ARRIVE LATE WEDNESDAY NIGHT/THURSDAY ACROSS THE
REGION. THIS WILL HAVE AN IMPACT ON THE AVIATION SECTOR ACROSS
NORTHERN IL/NORTHWEST IN AIRFIELDS.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 03Z...
* LOW/MEDIUM CONFIDENCE IN CIGS RETURNING TO MVFR ARND 06Z.
* HIGH CONFIDENCE IN THE WIND DIR/SPEED FORECAST.
* LOW CONFIDENCE IN PRECIP OF VCSH FROM 13Z TO 22Z TUE.
* HIGH CONFIDENCE IN CIGS LIFTING TO VFR CONDS ARND 10Z TUE.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...
WEDNESDAY...VFR. RAIN DEVELOPING LATE. IFR POSSIBLE.
THURSDAY...RAIN CHANGING TO SNOW. IFR/LIFR LIKELY. BECOMING VERY
WINDY WITH GUSTS 35+ KTS BY EVENING.
THURSDAY NIGHT...WINDY WITH GUSTS 35+ KT. SNOW ENDING. BLOWING
SNOW. LIFR IMPROVING TO MVFR.
FRIDAY...GUSTY NORTHWEST WINDS. VFR.
SATURDAY AND SUNDAY...VFR.
BEACHLER
&&
.MARINE...
315 PM CST
AN ACTIVE PERIOD OVER THE LAKE IS UPCOMING WEDNESDAY NIGHT THROUGH
FRIDAY. IN THE MEANTIME...A LOW PRESSURE SYSTEM WILL MOVE ACROSS
THE FAR SOUTHERN PART OF THE LAKE LATE TUESDAY AFTERNOON. WINDS
WILL NOT HAVE MUCH OF A CHANCE TO COME UP IN ADVANCE OR BEHIND
THIS SYSTEM DUE TO ITS FAST PACE. A MUCH MORE SIGNIFICANT LOW
PRESSURE ASSOCIATED WITH A WINTER STORM WILL MOVE FROM SOUTHWEST
TO NORTHEAST ACROSS THE SOUTHERN LAKES REGION ON THURSDAY. THE
PRESSURE GRADIENT WILL TIGHTEN SIGNIFICANTLY AS THE SYSTEM WILL BE
DEEPENING. WHILE THERE IS QUITE A BIT OF UNCERTAINTY IN THE EXACT
PATH...THE WIND FIELD LOOKS SUPPORTIVE OF AT LEAST GALES WITHIN
THE COLD AIR ADVECTION THURSDAY AFTERNOON THROUGH FRIDAY
MORNING. GIVEN THE FAVORED TRACK AT THIS TIME THE WIND FIELD IS
SUPPORTIVE OF STORM FORCE GUSTS. THE CIPS ANALOG GUIDANCE BASED ON
ONE OF OUR MODEL RUNS COMPARED TO 15 PAST EVENTS SHOWS THAT
ALMOST HALF OF THOSE EVENTS HAD GUSTS TO 40 KT OVER ADJACENT LAND
OF SOUTHERN LAKE MI. SO WITH STEEP LAPSE RATES OVER THE LAKE IN
THE COLD AIR PORTION OF THIS SYSTEM...IT WOULD SEEM OVER THE LAKE
EVEN HIGHER GUSTS ARE LIKELY. THUS HAVE CONTINUED MENTIONING STORM
FORCE WINDS.
MTF
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
841 PM CST MON DEC 17 2012
.DISCUSSION...
338 PM CST
PRIMARY FORECAST FOCUS AND CONCERN LIES WITH POTENTIAL HIGH IMPACT
WINTER STORM WEDNESDAY NIGHT THROUGH THURSDAY. THE THURSDAY
AFTERNOON/EVENING COMMUTE MAY BE IMPACTED BY SNOW AND HIGH WINDS
CAUSING BLOWING SNOW. NO WINTER WEATHER WATCHES WILL BE ISSUED
WITH THIS FORECAST PACKAGE...BUT WILL CONTINUE TO HIGHLIGHT THE
POTENTIAL IMPACTS WITH THIS EVENT WITH A SPECIAL WEATHER
STATEMENT.
SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT
WITH CWA ON FAR WESTERN PERIPHERY OF SHORTWAVE LIFTING NORTHEAST
FROM OHIO VALLEY THIS EVENING INTO THE FIRST PART OF TONIGHT...WILL
MAINTAIN INHERITED LOW POPS FOR SOUTHEASTERN PORTION OF CWA...THOUGH
LATEST HI RES GUIDANCE SUGGESTS THE PRECIP CURRENTLY OVER THE
SOUTHERN CWA WILL BE LARGELY PUSHING OFF TO THE EAST. DID TIGHTEN
POP GRADIENT TO KEEP ONLY THE FAR SOUTHEAST CWA WITH MENTIONABLE
POPS. FORECAST SOUNDINGS ALSO INDICATE LIFT WILL BE WEAK AT BEST BY
THIS EVENING AS UPPER WAVE DEPARTS. SOUNDING THERMAL PROFILES TODAY
HAVE BEEN TOO WARM BUT GIVEN WEAKENING UPWARD MOTION THIS
EVENING...ANY LINGERING PRECIP SHOULD BE LIGHT RAIN. FEEL LOWS
MAINLY IN THE UPPER 20S AND LOWER 30S ARE REASONABLE...THOUGH
PERSISTENT STRATUS DECK MAY KEEP THEM A BIT WARMER THAN INDICATED.
ATTENTION THEN TURNS ON POSSIBLE LIGHT SNOW CHANGING TO RAIN ON
TUESDAY WITH A WEAK SHORTWAVE QUICKLY PASSING OVER NRN IL OR ALONG
IL/WI STATELINE. OPERATIONAL MODEL RUNS WITH EXCEPTION OF 12Z
NAM...WHICH TRACKS SHORTWAVE FARTHER NORTH THROUGH SOUTHERN
WISCONSIN...SPIT OUT VERY LIGHT QPF FOR NORTHERN 1/2 TO 1/3 OF CWA
THROUGH TUES AFTERNOON. NO MAJOR CHANGES MADE TO THIS PERIOD.
THINKING THAT WHILE PRECIP IS POSSIBLE GIVEN SOME DECENT OMEGA...DRY
LAYER IN LOW LEVELS OF GFS BUFKIT SOUNDING MAKES IT QUESTIONABLE
WHETHER PRECIP WILL REACH THE GROUND. WITH THIS IN MIND...
MAINTAINED SLIGHT POPS...WITH A PROGRESSION FROM SLIGHT/LOW CHANCE
LIGHT SNOW TO LIGHT RAIN AS SURFACE WARMS INTO THE 40S BY AFTERNOON.
NO ACCUMULATION IS ANTICIPATED. FAVOR SHORTWAVE TRACK ACROSS CWA AS
OPPOSED TO FAR NORTH NAM TRACK...SO THUS THINK HIGH TEMPS WILL NOT
BE AS WARM AS NAM...WHICH BRINGS LOW 50S INTO SOUTHERN CWA.
CLOUDS WILL OVERSPREAD CWA WEDNESDAY WELL IN ADVANCE OF DEEPENING
MID LATITUDE CYCLONE. STRONG HEIGHT FALLS INVOF CYCLONE WILL FORCE
HEIGHT RISES OVER WESTERN GREAT LAKES AND THUS WARM ADVECTION AND
ANOTHER MILD DAY IN THE 40S FOR MOST OF CWA EXCEPT FAR NORTH. LIGHT
RAIN WILL NOT ARRIVE IN FAR WESTERN CWA UNTIL LATE AFTERNOON AT THE
EARLIEST...WITH SLIGHT POPS DURING THAT TIME.
WEDNESDAY NIGHT THROUGH THURSDAY
THIS PERIOD LOOKS TO POTENTIALLY BRING THE FIRST SIGNIFICANT WINTER
STORM OF THE SEASON. THERE IS STRONG MODEL CONSENSUS ON THE
STRONG/DEEPENING LOW PRESSURE AREA TO TRACK NEAR OR OVER THE CWA ON
THURSDAY. THUS THERE IS HIGH CONFIDENCE IN PRECIPITATION OCCURRING
AND THE OTHER STRONG SIGNAL CONSISTENT ACROSS ALL MODELS IS THE HIGH
WIND POTENTIAL THURSDAY AFTERNOON THROUGH THURSDAY EVENING.
THE KEY FOR THE AREA IN TERMS OF PTYPE AND QPF AMOUNTS IS THE
TRACK OF THE H5/H8 AND SURFACE LOW. NOTE THAT THE SOUTHERN STREAM
WAVE THAT WILL FORM PART OF THIS SYSTEM WAS IDENTIFIED AS BEING WEST
OF 130W ON WATER VAPOR IMAGERY AND IS NOT PROGGED TO MAKE LANDFALL
UNTIL TUESDAY MORNING ON THE CALIFORNIA COAST AND THUS WAS NOT
SAMPLED BY THE RAOB NETWORK FOR THE 12Z MODEL CYCLE. THE NORTHERN
STREAM WAVE WAS SAMPLED BY THE ALASKA RAOB NETWORK YESTERDAY
AFTERNOON...BUT WILL TRAVERSE A MORE DATA SPARSE REGION UNTIL MAKING
INROADS INTO THE PACIFIC NORTHWEST ON TUESDAY. THUS CONTINUED TRACK
DIFFERENCES AND CHANGES ARE LIKELY AMONGST THE NWP GUIDANCE UNTIL
THERE IS BETTER SAMPLING.
TRACK DIFFERENCES CONTINUE WITH TODAYS LATEST GUIDANCE...WITH THE
NAM/GFS/SREF/GEFS ALL FARTHER NORTHWEST WITH TRACK OF SURFACE LOW
THAN FOREIGN COUNTERPARTS. THIS IS ESPECIALLY THE CASE WITH 12Z
ECMWF RUN...WHICH STAYED CONSISTENT WITH A MORE SOUTHERN TRACK AND
ACTUALLY SHIFTED A HAIR SOUTH OF THE 00Z RUN. MAJOR DIFFERENCE IS IN
HANDLING OF UPPER LEVEL FEATURES...WITH NCEP MODELS PHASING THE
NORTHERN AND SOUTHERN STREAM AND CLOSING OFF AT H5 LATE WEDNESDAY
NIGHT INTO EARLY THURSDAY MORNING...WHILE THE ECMWF KEEPS THE
SOUTHERN STREAM VORT DOMINANT AND DOESNT CLOSE OFF UNTIL THURSDAY
NIGHT OVER SOUTHERN LOWER MICHIGAN.
OVERALL FAVOR THE CONSISTENCY OF THE ECMWF AND ITS ENSEMBLES DUE TO
THE EXPECTATION THAT STRONG BLOCKING RIDGE JUST NORTH OF HUDSON
BAY/A WEST BASED -NAO WILL MAKE THE FAR NORTHWEST TRACK LESS LIKELY.
DID HOWEVER GIVE A NOD TO THE REMAINDER OF THE GUIDANCE...WITH A
TRACK NOT AS FAR SOUTH AS THE EC BUT STILL SOUTHEAST OF CHICAGO ON
THURSDAY. THIS DIFFERENCE IS QUITE SIGNIFICANT IN TERMS OF SENSIBLE
WEATHER IMPACTS FOR CWA. THE NCEP SOLUTIONS WOULD RESULT IN A
PRIMARILY RAIN EVENT WELL INTO THURSDAY...BEFORE CHANGING TO SNOW ON
THE BACKSIDE OF THE DEPARTING DEEP LOW. FURTHERMORE...THE UPPER LOW
TRACK WOULD ALSO INTRODUCE DRY SLOT ISSUES...RESULTING IN LOWER
LIQUID EQUIVALENT QPF AMOUNTS. ON THE OTHER HAND...THE ECMWF STARTS
OUT WARM...ESPECIALLY IN THE SOUTHEAST CWA...BUT THE CHANGEOVER TO A
WET SNOW OCCURS MUCH QUICKER.
ALL THE CLASSIC INGREDIENTS OF AN INTENSE MID LATITUDE CYCLONE WILL
BE AT PLAY WITH THIS SYSTEM...WITH MASSIVE HEIGHT FALLS/JET STREAM
DIVERGENCE/ANOMALOUSLY STRONG WARM CONVEYOR BELT AT H85/TIGHT
THERMAL GRADIENT AND FRONTOGENESIS SUPPORTIVE OF CATEGORICAL POPS
CWA WIDE THROUGH AT LEAST THURS AFTERNOON. FURTHERMORE...UNLESS WE
GET SIGNIFICANTLY DRY SLOTTED...LIQUID EQUIVALENT QPF MAY BE CLOSE
TO 1 INCH. THE BIGGEST CONCERN IS THAT AS THICKNESSES AND
TEMPERATURES CRASH IN THE BACKSIDE DEFORMATION AXIS OF THE
SYSTEM...THE INTENSE WIND FIELD OF THE STORM WILL ALLOW FOR POSSIBLE
BLIZZARD/NEAR BLIZZARD CONDITIONS TO IMPACT THE THURSDAY PM RUSH HR.
IN FACT...WIND GUSTS FROM LATE THURSDAY AFTERNOON THROUGH THURSDAY
EVENING MAY APPROACH OR EXCEED 50 MPH. GIVEN THE COLDEST START FOR
THE NORTHWEST CWA AND VERY MILD START TO THURSDAY FOR THE
SOUTHEAST...HIGHEST SNOWFALL TOTALS WILL BE FAVORED FOR THE NW CWA
WHERE SIGNIFICANT ACCUMULATIONS ARE POSSIBLE AND TAPER TO THE FAR
SOUTHEAST...WHERE THERE LIKELY WILL BE MUCH LESS SNOW. ONE
ADDITIONAL ITEM OF NOTE IS THAT THE UNPRECEDENTED MEASURABLE SNOW
DROUGHT AT CHICAGO AND ROCKFORD HAS A GOOD SHOT OF FINALLY ENDING
WITH THIS SYSTEM.
ARCTIC AIR WILL CONTINUE TO PLUNGE INTO THE AREA THURSDAY
NIGHT...WITH STRONG GUSTY NORTHWEST WINDS CONTINUING TO PRODUCE
AREAS OF BLOWING SNOW. LOWS WILL PLUMMET INTO THE TEENS AND LOWER
20S. THE NW INDIANA LAKEFRONT..ESPECIALLY PORTER COUNTY...MAY SEE
LAKE ENHANCEMENT TO THE LINGERING SNOW ON THE BACKSIDE OF THE
SYSTEM.
RC
FOR FRIDAY INTO THE WEEKEND...
SOMEWHERE ON THE WEB YOU CAN FIND A CARTOON CALLED SNOW FOOLIN IN
WHICH THE CALENDAR TURNS FROM DEC 20 TO DEC 21 AND SUDDENLY THE
WORLD BECOMES FREEZING COLD AND COVERED WITH SNOW. THAT IS
BASICALLY THE TREND WE ARE EXPECTING THIS WEEK.
AFTER THE EVENTS OF WEDNESDAY NIGHT INTO THURSDAY...THE SUBFREEZING
HIGHS AND SINGLE DIGIT WIND CHILLS MOVE IN FRIDAY ON BRISK NORTHWEST
WINDS BETWEEN THE DEPARTING LOW AND A SKINNY RIDGE OVER THE CENTRAL
CONUS. FROM FRIDAY INTO AT LEAST CHRISTMAS EVE IT IS UNLIKELY THAT
ANYWHERE IN THE FORECAST AREA WILL RECORD ADDITIONAL HIGHS ABOVE 40
DEGREES. MORNING LOWS OVER THE WEEKEND...ESPECIALLY SATURDAY...ARE
PRESENTLY FORECAST TO DROP INTO THE TEENS BUT COULD BE EVEN COLDER
IF SKIES CLEAR OUT...WINDS TAPER OFF...AND A DECENT COVER OF SNOW IS
IN PLACE. AS FAR AS ADDITIONAL SNOW...AFTER THE MAIN STORM MOVES
OUT LATE THURSDAY...THERE REMAINS A CHANCE OF LAKE EFFECT SNOW
MAINLY ON THE LOWER MICHIGAN SIDE BUT ALSO A BIT INTO NORTHERN
INDIANA.
LENNING
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 00Z...
* BRIEF BREAK IN MVFR CIGS WILL TREND QUICKLY THIS EVENING BACK TO
MVFR CIGS ARND 1500-1900 FT AGL.
* NW WINDS ARND 6 TO 8 KT WILL SLOWLY TURN W THEN S BY DAYBREAK
TUE.
* PSBL VCSH DEVELOPING DURING THE DAY TUE.
BEACHLER
//DISCUSSION...UPDATED 02Z...
IR IMAGERY INDICATES THE HOLE IN THE CLOUD COVER OVER FAR
NORTHEAST IL CONTINUES TO BE OVER ORD/MDW. IT DOES APPEAR THAT
THIS WAS TRYING TO SLIDE EAST ACROSS THE LAKE...HOWEVER CONFIDENCE
HAS BACKED OFF THAT THE MID-DECK CLOUDS WILL COME BACK OVER
ORD/MDW UNTIL LATER TONIGHT. THE RAP FORECAST GUIDANCE INDICATES
THIS DRY AIR OVER ORD/MDW/DPA AIRFIELDS LINGERING THRU 05Z...THEN
SLOWLY RE-SATURATING. AT THIS TIME HAVE MADE SOME ADJUSTMENTS TO
THE GOING FORECAST TO REFLECT THE DELAY IN MVFR CIGS RETURNING TO
ORD/MDW. WILL CONTINUE TO CLOSELY MONITOR THIS.
PREV DISCUSSION...UPDATED 00Z...
PRIOR TO SUNSET THE VISIBLE IMAGERY INDICATED THAT THE MOSTLY
CLOUDY SKIES CONTINUE TO HOVER OVER NORTHERN IL/NORTHWEST IN
AIRFIELDS. A FEW BREAKS WERE NOTED WELL TO THE WEST ACROSS
NORTH CENTRAL MO AND SOUTH CENTRAL IA...HOWEVER IT DOES NOT APPEAR
THIS CLEARING WILL ARRIVE ACROSS THE REGION TONIGHT OR EVEN TUE.
GUIDANCE CONTINUES TO SUGGEST THAT THE BRIEF BREAK IN THE MVFR
CIGS TO VFR WILL BE SHORT-LIVED...TRENDING BACK TOWARDS CIGS ARND
1500 FT AGL BY 04-05Z TUE. SOME DRY AIR DOES TRY TO POKE NORTHEAST
ACROSS THE AIRFIELDS ARND DAYBREAK TUE...WHICH MAY LIFT CIGS BACK
TO VFR. HOWEVER FEEL THAT SOME SCT CLOUDS ARND 1500FT AGL WILL
LINGER. IN ADDITION A WEAK WAVE WILL BE SLIDING EAST ACROSS THE
REGION TUE...AND SOME PATCHY PRECIP MAY BE ASSOCIATED WITH THIS
WAVE. AT THIS TIME ANY PRECIP SHUD BE LGT RA...BUT GIVEN THE LOW
CONFIDENCE IN COVERAGE AND TIMING WILL LEAVE THIS AS A VCSH
MENTION AT THIS TIME. THEN CIGS SHUD REMAIN VFR THRU TOMORROW
NIGHT AS THE SOUTH WINDS BECOMING WEST WINDS REMAIN ARND 10-12KT.
THE FOCUS CONTINUES TO BE ON THE APPROACHING SIGNIFICANT WEATHER
SYSTEM POISED TO ARRIVE LATE WEDNESDAY NIGHT/THURSDAY ACROSS THE
REGION. THIS WILL HAVE AN IMPACT ON THE AVIATION SECTOR ACROSS
NORTHERN IL/NORTHWEST IN AIRFIELDS.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 00Z...
* MEDIUM/HIGH CONFIDENCE IN CIGS RETURNING TO MVFR ARND 04Z.
* HIGH CONFIDENCE IN THE WIND DIR/SPEED FORECAST.
* LOW CONFIDENCE IN PRECIP OF VCSH FROM 13Z TO 22Z TUE.
* HIGH CONFIDENCE IN CIGS LIFTING TO VFR CONDS ARND 10Z TUE.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...
WEDNESDAY...VFR. RAIN DEVELOPING LATE. IFR POSSIBLE.
THURSDAY...RAIN CHANGING TO SNOW. IFR/LIFR LIKELY. BECOMING VERY
WINDY WITH GUSTS 35+ KTS BY EVENING.
THURSDAY NIGHT...WINDY WITH GUSTS 35+ KT. SNOW ENDING. BLOWING
SNOW. LIFR IMPROVING TO MVFR.
FRIDAY...GUSTY NORTHWEST WINDS. VFR.
SATURDAY AND SUNDAY...VFR.
BEACHLER
&&
.MARINE...
315 PM CST
AN ACTIVE PERIOD OVER THE LAKE IS UPCOMING WEDNESDAY NIGHT THROUGH
FRIDAY. IN THE MEANTIME...A LOW PRESSURE SYSTEM WILL MOVE ACROSS
THE FAR SOUTHERN PART OF THE LAKE LATE TUESDAY AFTERNOON. WINDS
WILL NOT HAVE MUCH OF A CHANCE TO COME UP IN ADVANCE OR BEHIND
THIS SYSTEM DUE TO ITS FAST PACE. A MUCH MORE SIGNIFICANT LOW
PRESSURE ASSOCIATED WITH A WINTER STORM WILL MOVE FROM SOUTHWEST
TO NORTHEAST ACROSS THE SOUTHERN LAKES REGION ON THURSDAY. THE
PRESSURE GRADIENT WILL TIGHTEN SIGNIFICANTLY AS THE SYSTEM WILL BE
DEEPENING. WHILE THERE IS QUITE A BIT OF UNCERTAINTY IN THE EXACT
PATH...THE WIND FIELD LOOKS SUPPORTIVE OF AT LEAST GALES WITHIN
THE COLD AIR ADVECTION THURSDAY AFTERNOON THROUGH FRIDAY
MORNING. GIVEN THE FAVORED TRACK AT THIS TIME THE WIND FIELD IS
SUPPORTIVE OF STORM FORCE GUSTS. THE CIPS ANALOG GUIDANCE BASED ON
ONE OF OUR MODEL RUNS COMPARED TO 15 PAST EVENTS SHOWS THAT
ALMOST HALF OF THOSE EVENTS HAD GUSTS TO 40 KT OVER ADJACENT LAND
OF SOUTHERN LAKE MI. SO WITH STEEP LAPSE RATES OVER THE LAKE IN
THE COLD AIR PORTION OF THIS SYSTEM...IT WOULD SEEM OVER THE LAKE
EVEN HIGHER GUSTS ARE LIKELY. THUS HAVE CONTINUED MENTIONING STORM
FORCE WINDS.
MTF
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
905 PM CST MON DEC 17 2012
.UPDATE...
ONLY MINOR CHANGES TO OVERNIGHT PACKAGE. ANALYSIS AND VERIFICATION
CONFIRMS A COLDER TREND WITH A SOUTHEAST SLIDE IN SURFACE LOW
TRACK ON AMERICAN SOLUTIONS. 00Z NAM ANALYSIS SUGGESTS STILL
PLAYING CATCH UP WHICH HAS BEEN COMMON FOR A WHILE WITH THIS MODEL.
WILL BE SENDING OUT UPDATED WSW...OR WINTER STORM WATCH PRODUCT
SHORTLY WITH MENTION OF HIGHER WINDS GUSTING UP TO NEAR 50 MPH ON
BACK SIDE AND BLIZZARD TO NEAR BLIZZARDS SUPPORTED PER LOCAL STUDIES
AND TECHNIQUES. THE LOCAL IMPACTS OF WHERE THESE CONDITIONS ARE TO
OCCUR STILL TOO UNCERTAIN TO ASSESS IF AND EVEN HOW MUCH OF THE
FORECAST COULD BE IMPACTED...THIS IS LIKELY STILL 12-24 HOURS AWAY.
WHAT IS CERTAIN IS THE STRONG WINDS WITH THE SNOW AND CERTAIN NEAR
BLIZZARD CONDITIONS TO POSSIBLY BLIZZARD CONDITIONS IN THE COLD
DEFORMATION ZONE IN RURAL AND OPEN AREAS AT A MINIMUM. THE UPDATED
WSW PRODUCT SHOULD BE OUT WITHIN THE NEXT HALF HOUR.
NICHOLS
&&
.PREV DISCUSSION... /ISSUED 553 PM CST MON DEC 17 2012/
AVIATION...
STRATUS AND PATCHY FOG WILL LIKELY REMAIN IN PLACE TONIGHT...WITH
INTERVALS OF PARTIAL CLEARING POSSIBLE. LIGHT SNOW OR FLURRIES MAY
IMPACT CID...DBQ AND POSSIBLY MLI TOWARD DAWN TUESDAY UNTIL MID
DAY. LINGERING LOW LEVEL MOISTURE AND LIGHT WINDS WILL CONTINUE
IFR AND POSSIBLE LIFR CONDITIONS DUE TO LOW CIGS AND POSSIBLY FOG
THROUGH THE NIGHT...MAINLY AT DBQ AND POSSIBLY AT CID TERMINALS.
BRL AND MLI TERMINALS ARE MORE FAVORED FOR MVFR CONDITIONS TONIGHT. `
A FAST MOVING LOW PRESSURE SYSTEM MOVING OUT OF THE ROCKIES WILL
PASS NEAR HIGHWAY 30 CORRIDOR TUESDAY AFTERNOON WITH VFR CONDITIONS
AND PARTLY CLOUDY SKIES AT BRL...MLI AND PROBABLY CID TERMINALS.
DBQ TERMINAL SHOULD IMPROVE TO MVFR BY LATE TUESDAY AFTERNOON.
NICHOLS
PREV DISCUSSION... /ISSUED 330 PM CST MON DEC 17 2012/
SYNOPSIS...
LIGHT WINDS AND LINGERING LOW LEVEL MOISTURE HAS KEPT LOW CLOUDS AND
LIGHT FOG IN PLACE TODAY ACROSS THE FORECAST AREA. AS A RESULT...
TEMPERATURES HAVE STRUGGLED TO CLIMB...HAVING ONLY REACHED THE UPPER
20S NORTH TO MID 30S SOUTH THIS AFTERNOON. MSAS ANALYSIS INDICATED A
RIDGE OF HIGH PRESSURE REACHED FROM TX TO MN...FLANKED BY LOW
PRESSURE MOVING ALONG A COLD FRONT IN NORTHERN KY TO THE SE...AND A
LEE TROUGH REACHING FROM NORTHERN MT TO EASTERN CO. IN THE UPPER
LEVELS...A TROUGH AXIS REACHED FROM THE EASTERN DAKOTAS TO THE MO
BOOTHEEL REGION. UPSTREAM...12Z ANALYSIS INDICATED A 160 KT JET AT
300 MT MOVING IN THE STRONG...NEARLY ZONAL FLOW...ACROSS NORTHERN CA
INTO THE GREAT BASIN REGION. AN UPPER LOW WAS OFF THE NORTHERN BC
COAST WITH A TROUGH AXIS EXTENDING S-SW INTO THE PACIFIC.
SHORT TERM...TONIGHT AND TUESDAY...
DEVELOPING ACTIVE PATTERN WILL SEND ANOTHER ROUND OF PRECIPITATION
THROUGH THE REGION TONIGHT INTO EARLY TUESDAY. FORECAST CHALLENGES
CENTER ON THIS PRECIPITATION LATE TONIGHT INTO TUESDAY...ALONG WITH
LOW CLOUDS AND FOG.
LATEST VISIBLE SATELLITE IMAGES SHOW AN AREA OF CLOUDS OVER NORTH
CENTRAL MO INTO SOUTHERN IA...SLOWLY MIGRATING EASTWARD WITH THE
UPPER LEVEL TROUGH. AS THIS EXTENDS EASTWARD INTO THE SOUTHERN THIRD
OF THE FORECAST AREA AROUND SUNSET...THERE WILL BE A POTENTIAL FOR
THICKENING OF THE FOG THAT HAS LINGERED OVER SE IA AND ADJACENT
AREAS OF MO AND IL THIS EVENING. BASED ON LATEST RAP LOW LEVEL
MOISTURE FIELDS...STRATUS WILL LIKELY REMAIN IN PLACE THROUGH THE
NIGHT OVER THE REMAINDER OF THE FORECAST AREA...AND LIKELY FILL BACK
IN ANY HOLES THAT DEVELOP ACROSS THE SOUTH. WILL GO WITH PATCHY FOG
WORDING FOR NOW AND MONITOR THE SOUTH THIS EVENING FOR POSSIBLE
UPDATES TO MORE DENSE OR WIDESPREAD COVERAGE. A STRIKE AGAINST FOG
TONIGHT WILL BE THE INCOMING SUBSIDENCE BEHIND THE UPPER LEVEL WAVE
AND INCREASING WINDS TOWARD MORNING AS A SURFACE LOW APPROACHES.
AS SEEN TODAY...CLOUDS...LINGERING MOISTURE AND WEAK WINDS WILL
LIMIT DIURNAL TEMPERATURE CURVES AND HAVE KEPT MINS CLOSE TO CURRENT
DEWPOINTS...FROM THE MID 20S NORTH TO LOWER 30S SOUTH.
THE FOCUS THEN TURNS TO AN IMPULSE IN THE FAST ZONAL FLOW ALOFT THAT
WAS MOVING ACROSS CENTRAL ID AT MIDDAY. MODELS DEVELOP THIS INTO A
CLIPPER LIKE LOW PRESSURE SYSTEM AS THE ENERGY MOVES OVER THE LEE
TROUGH TONIGHT. THIS FAST MOVING LOW DEVELOPS OVER NEB LATE
TONIGHT...THEN HEADS EASTWARD OVER THE FORECAST AREA DURING THE
DAY TUESDAY. HAVE GENERALLY FOLLOWED A BLEND OF THE GFS/ECMWF AND
GEM WITH THIS FEATURE...WHICH DEVELOPS A NW TO SE ORIENTED WARM
ADVECTION WING OF LIGHT SNOW OVER THE CENTRAL PART OF THE FORECAST
AREA BETWEEN 06Z AND 12Z AND HAVE KEPT CHANCE POPS THERE. THE
POTENTIAL FOR LIGHT SNOW OR FLURRIES SHOULD THEN SHIFT TO THE FAR
NORTH AND NORTHEAST BY AFTERNOON AS THE LOW MOVES TOWARD CHICAGO.
WITH LIMITED MOISTURE AND RAPID PROGRESSION...SNOWFALL AMOUNTS
SHOULD BE WELL BELOW AN INCH IN MOST LOCATIONS WITH THE BEST CHANCES
OF A LIGHT COATING NORTH OF THE HIGHWAY 30 CORRIDOR. HAVE TRENDED
SOME PARTIAL CLEARING FROM SW TO NE IN THE AFTERNOON...BUT THIS MAY
END UP BEING TOO OPTIMISTIC DUE TO THE LINGERING MOISTURE AND
CYCLONIC FLOW THROUGH THE AFTERNOON. BRISK WESTERLY WINDS IN THE FAR
SOUTH MAY ALLOW TEMPERATURES TO REACH THE UPPER 40S...WHILE HIGHS IN
THE NORTH ARE KEPT IN THE UPPER 30S.
SHEETS
LONG TERM...TUESDAY NIGHT THROUGH NEXT MONDAY...
ALL LONG TERM FCST ENERGY INTO HANDLING MIDWEEK STORM SYSTEM...WITH
THE WEEKEND LOOKING IN BETWEEN SYSTEMS AND RATHER BENIGN/SEASONABLE
ANYWAY THROUGH EARLY MONDAY. ASSESSING THE LATEST 12Z MEDIUM RANGE
MODEL RUNS AS WELL AS THE NAM...SURPRISINGLY GOOD AGREEMENT WITH
GENERAL SFC LOW AND MID LEVEL LOW PATHS BUT WITH SOME TRACKING
SPEED AND STRENGTH VARIANCES. THIS TAKING INTO ACCOUNT BULK OF WAVE
ENERGY THAT WILL DRIVE THE STORM STILL OFF THE PACIFIC NORTHWEST
COAST AND SOUTH OF THE GULF OF AK. ALL MODELS BUT THE 12Z ECMWF THAT
IS. WHILE THE OTHERS HAVE TRENDED FURTHER NORTH AND WEST WITH THEIR
LATEST 12Z RUNS WHICH MAKE FOR MORE OF A PRECIP TYPE/AMOUNT CHALLENGE
FOR THE DVN CWA...THE CONSISTENT ECMWF WOULD STILL IMPACT MOST OF THE
LOCAL FCST AREA WITH A QUICKER SWITCH OVER TO SNOW AND MORE AREAS
STARTING OFF AS SNOW TO BEGIN WITH. THE ENSEMBLE SFC LOW TRACK OF
THE 12Z GFS/NAM/UKMET/GEM ALL HOOK THE DEVELOPING LOW FROM THE OK
PANHANDLE ON WED UP THROUGH NORTHEAST MO/WEST CENTRAL IL LATE WED
NIGHT...TO A NORTH CENTRAL IL POSITION BY THU MORNING...AND THEN
BOMB IT OUT ACRS LOWER MI INTO THU EVENING. THE 12Z EURO MAINTAINS
A TRACK FURTHER TO THE SOUTHEAST OF THE ENSEMBLE PATH...SOUTHWEST MO
TO NEAR THE STL AREA BY THU MORNING AND THEN OFF TO WEST CENTRAL
INDIANA BY EARLY THU AFTERNOON. THE ENSEMBLE OF SOLUTIONS BESIDES THE
ECMWF WOULD GENERALLY SUGGEST MUCH OF THE SOUTHEAST HALF TO TWO
THIRDS OF THE FCST AREA TO BE RAIN OR EVEN EXPERIENCE SOME
CONVECTION THROUGH MIDNIGHT WED NIGHT...WHILE THE NORTHWEST THIRD
MIXES AND DYNAMICALLY COOLS INTO WET ACCUMULATING SNOW AFTER 03Z
THU. AS DEF ZONE CONTINUES TO FORM AND LLVL COLD CONVEYOR IN-WRAPS
AND INCREASES...THESE MODELS GENERALLY SUGGEST THE SWITCH OVER TO
WET SNOW TO CONTINUE FROM WEST-NORTHWEST TO THE EAST AFTER MIDNIGHT
AND INTO EARLY THU MORNING ACRS THE DVN CWA. 3-7 INCHES POSSIBLE BY
12Z THU ALONG AND WEST OF A LINE FROM SIGOURNEY IA...TO EAST OF
CEDAR RAPIDS AND TO WEST OF DBQ. SOME ADDITIONAL ACCUMS OF 1-2
INCHES IN THESE AREAS POSSIBLE THROUGH 18Z THU...BUT BULK OF
ACCUMULATING SNOW TO SWITCH EASTWARD ACRS THE REST OF THE CWA WITH 3-
6 INCHES POSSIBLE ALONG AND NORTH OF A LINE FROM MT PLEASANT IA...TO
THE QUAD CITIES..AND TO STERLING IL.
WHILE THE NORTHWEST THIRD AND NORTH CENTRAL PORTIONS OF THE DVN CWA
MAY EVENTUALLY GET 4-8+ INCHES BY THU EVENING...THE ENSEMBLES MINUS
THE ECMWF SUGGEST THE HIGHEST SNOWFALL TOTALS OF 8-12+ INCHES OCCUR
WEST AND NORTH OF THE DVN CWA ACRS SOUTH CENTRAL IA...UP THROUGH
NORTHEASTERN IA INTO SW/CENTRAL WI. EXTENT OF BOMBING CYCLONE TO THE
EAST STILL INDICATED BY BULK OF THE MODEL RUNS TO DRIVE VERY STRONG
NORTH BECOMING NORTHWEST WINDS LATE WED NIGHT AND ESPECIALLY ON
THU...SUSTAINED 25 TO 35 MPH WITH GUSTS TO AT LEAST 45 MPH. GRAVITY
WAVE PHENOMENA WEST OF RAPIDLY DEEPENING CYCLONE COULD ALSO PRODUCE
ISOLATED GUSTS OVER 50 MPH AT MAX DEEPENING STAGE ON THU. THUS WHERE
ACCUMULATING SNOWS OCCUR...NEAR BLIZZARD OR BLIZZARD CONDITIONS VERY
POSSIBLE. BACK TO THE ECMWF...IT/S TRACK WOULD MEAN MORE OF A DIRECT
HIT UPON THE LOCAL AREA AND HIGHER SNOW AMOUNTS FURTHER EAST AND
SOUTH...ESPECIALLY TAKING INTO ACCOUNT SOME FUJI-WARA EFFECT OF
SECONDARY VORT INTERACTING IN TROF BASE AND ENHANCING DEF ZONE SNOWS
ACRS THE LOCAL AREA ON THU. DESPITE ONGOING MODEL UNCERTAINTY AND
THE SYSTEM TO BE BETTER SAMPLED FOR THE 00Z RUNS TONIGHT AND
ESPECIALLY 12Z TUE...WILL ISSUE A WINTER STORM WATCH FOR ROUGHLY THE
NORTHWEST HALF OF THE DVN CWA FOR WED NIGHT AND THU GIVING A NOD
SOMEWHAT TO THE ENSEMBLE TRACK. THE STRONG WINDS LOOK TO BE A LARGE
IMPACT EVEN FOR ADVISORY LEVEL OR SLIGHTLY LESS SNOW AMOUNTS. DO FEEL
THE CWA WILL HAVE TO EVENTUALLY BE DIVIDED INTO WINTER STORM WARNING
AND ADVISORY AREAS...BUT WHERE AN WHEN STILL UP IN THE AIR. A
WATCHFUL EYE WILL ALSO NEED TO BE OPEN FOR TRENDS ON THE NEXT 1-2
MODEL RUNS BACK CLOSER TO THE CONSISTENT ECMWF...WHICH WOULD THEN
WARRANT THE NEED OF EXPANDING THE WATCH SOUTH AND EAST. ..12..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR BENTON-BUCHANAN-CEDAR-CLINTON-DELAWARE-
DUBUQUE-HENRY IA-IOWA-JACKSON-JEFFERSON-JOHNSON-JONES-
KEOKUK-LINN-LOUISA-MUSCATINE-SCOTT-VAN BUREN-WASHINGTON.
IL...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR JO DAVIESS-ROCK ISLAND.
MO...NONE.
&&
$$
NICHOLS
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
553 PM CST MON DEC 17 2012
.AVIATION...
STRATUS AND PATCHY FOG WILL LIKELY REMAIN IN PLACE TONIGHT...WITH
INTERVALS OF PARTIAL CLEARING POSSIBLE. LIGHT SNOW OR FLURRIES MAY
IMPACT CID...DBQ AND POSSIBLY MLI TOWARD DAWN TUESDAY UNTIL MID
DAY. LINGERING LOW LEVEL MOISTURE AND LIGHT WINDS WILL CONTINUE
IFR AND POSSIBLE LIFR CONDITIONS DUE TO LOW CIGS AND POSSIBLY FOG
THROUGH THE NIGHT...MAINLY AT DBQ AND POSSIBLY AT CID TERMINALS.
BRL AND MLI TERMINALS ARE MORE FAVORED FOR MVFR CONDITIONS TONIGHT. `
A FAST MOVING LOW PRESSURE SYSTEM MOVING OUT OF THE ROCKIES WILL
PASS NEAR HIGHWAY 30 CORRIDOR TUESDAY AFTERNOON WITH VFR CONDITIONS
AND PARTLY CLOUDY SKIES AT BRL...MLI AND PROBABLY CID TERMINALS.
DBQ TERMINAL SHOULD IMPROVE TO MVFR BY LATE TUESDAY AFTERNOON.
NICHOLS
&&
.PREV DISCUSSION... /ISSUED 330 PM CST MON DEC 17 2012/
SYNOPSIS...
LIGHT WINDS AND LINGERING LOW LEVEL MOISTURE HAS KEPT LOW CLOUDS AND
LIGHT FOG IN PLACE TODAY ACROSS THE FORECAST AREA. AS A RESULT...
TEMPERATURES HAVE STRUGGLED TO CLIMB...HAVING ONLY REACHED THE UPPER
20S NORTH TO MID 30S SOUTH THIS AFTERNOON. MSAS ANALYSIS INDICATED A
RIDGE OF HIGH PRESSURE REACHED FROM TX TO MN...FLANKED BY LOW
PRESSURE MOVING ALONG A COLD FRONT IN NORTHERN KY TO THE SE...AND A
LEE TROUGH REACHING FROM NORTHERN MT TO EASTERN CO. IN THE UPPER
LEVELS...A TROUGH AXIS REACHED FROM THE EASTERN DAKOTAS TO THE MO
BOOTHEEL REGION. UPSTREAM...12Z ANALYSIS INDICATED A 160 KT JET AT
300 MT MOVING IN THE STRONG...NEARLY ZONAL FLOW...ACROSS NORTHERN CA
INTO THE GREAT BASIN REGION. AN UPPER LOW WAS OFF THE NORTHERN BC
COAST WITH A TROUGH AXIS EXTENDING S-SW INTO THE PACIFIC.
SHORT TERM...TONIGHT AND TUESDAY...
DEVELOPING ACTIVE PATTERN WILL SEND ANOTHER ROUND OF PRECIPITATION
THROUGH THE REGION TONIGHT INTO EARLY TUESDAY. FORECAST CHALLENGES
CENTER ON THIS PRECIPITATION LATE TONIGHT INTO TUESDAY...ALONG WITH
LOW CLOUDS AND FOG.
LATEST VISIBLE SATELLITE IMAGES SHOW AN AREA OF CLOUDS OVER NORTH
CENTRAL MO INTO SOUTHERN IA...SLOWLY MIGRATING EASTWARD WITH THE
UPPER LEVEL TROUGH. AS THIS EXTENDS EASTWARD INTO THE SOUTHERN THIRD
OF THE FORECAST AREA AROUND SUNSET...THERE WILL BE A POTENTIAL FOR
THICKENING OF THE FOG THAT HAS LINGERED OVER SE IA AND ADJACENT
AREAS OF MO AND IL THIS EVENING. BASED ON LATEST RAP LOW LEVEL
MOISTURE FIELDS...STRATUS WILL LIKELY REMAIN IN PLACE THROUGH THE
NIGHT OVER THE REMAINDER OF THE FORECAST AREA...AND LIKELY FILL BACK
IN ANY HOLES THAT DEVELOP ACROSS THE SOUTH. WILL GO WITH PATCHY FOG
WORDING FOR NOW AND MONITOR THE SOUTH THIS EVENING FOR POSSIBLE
UPDATES TO MORE DENSE OR WIDESPREAD COVERAGE. A STRIKE AGAINST FOG
TONIGHT WILL BE THE INCOMING SUBSIDENCE BEHIND THE UPPER LEVEL WAVE
AND INCREASING WINDS TOWARD MORNING AS A SURFACE LOW APPROACHES.
AS SEEN TODAY...CLOUDS...LINGERING MOISTURE AND WEAK WINDS WILL
LIMIT DIURNAL TEMPERATURE CURVES AND HAVE KEPT MINS CLOSE TO CURRENT
DEWPOINTS...FROM THE MID 20S NORTH TO LOWER 30S SOUTH.
THE FOCUS THEN TURNS TO AN IMPULSE IN THE FAST ZONAL FLOW ALOFT THAT
WAS MOVING ACROSS CENTRAL ID AT MIDDAY. MODELS DEVELOP THIS INTO A
CLIPPER LIKE LOW PRESSURE SYSTEM AS THE ENERGY MOVES OVER THE LEE
TROUGH TONIGHT. THIS FAST MOVING LOW DEVELOPS OVER NEB LATE
TONIGHT...THEN HEADS EASTWARD OVER THE FORECAST AREA DURING THE
DAY TUESDAY. HAVE GENERALLY FOLLOWED A BLEND OF THE GFS/ECMWF AND
GEM WITH THIS FEATURE...WHICH DEVELOPS A NW TO SE ORIENTED WARM
ADVECTION WING OF LIGHT SNOW OVER THE CENTRAL PART OF THE FORECAST
AREA BETWEEN 06Z AND 12Z AND HAVE KEPT CHANCE POPS THERE. THE
POTENTIAL FOR LIGHT SNOW OR FLURRIES SHOULD THEN SHIFT TO THE FAR
NORTH AND NORTHEAST BY AFTERNOON AS THE LOW MOVES TOWARD CHICAGO.
WITH LIMITED MOISTURE AND RAPID PROGRESSION...SNOWFALL AMOUNTS
SHOULD BE WELL BELOW AN INCH IN MOST LOCATIONS WITH THE BEST CHANCES
OF A LIGHT COATING NORTH OF THE HIGHWAY 30 CORRIDOR. HAVE TRENDED
SOME PARTIAL CLEARING FROM SW TO NE IN THE AFTERNOON...BUT THIS MAY
END UP BEING TOO OPTIMISTIC DUE TO THE LINGERING MOISTURE AND
CYCLONIC FLOW THROUGH THE AFTERNOON. BRISK WESTERLY WINDS IN THE FAR
SOUTH MAY ALLOW TEMPERATURES TO REACH THE UPPER 40S...WHILE HIGHS IN
THE NORTH ARE KEPT IN THE UPPER 30S.
SHEETS
LONG TERM...TUESDAY NIGHT THROUGH NEXT MONDAY...
ALL LONG TERM FCST ENERGY INTO HANDLING MIDWEEK STORM SYSTEM...WITH
THE WEEKEND LOOKING IN BETWEEN SYSTEMS AND RATHER BENIGN/SEASONABLE
ANYWAY THROUGH EARLY MONDAY. ASSESSING THE LATEST 12Z MEDIUM RANGE
MODEL RUNS AS WELL AS THE NAM...SURPRISINGLY GOOD AGREEMENT WITH
GENERAL SFC LOW AND MID LEVEL LOW PATHS BUT WITH SOME TRACKING
SPEED AND STRENGTH VARIANCES. THIS TAKING INTO ACCOUNT BULK OF WAVE
ENERGY THAT WILL DRIVE THE STORM STILL OFF THE PACIFIC NORTHWEST
COAST AND SOUTH OF THE GULF OF AK. ALL MODELS BUT THE 12Z ECMWF THAT
IS. WHILE THE OTHERS HAVE TRENDED FURTHER NORTH AND WEST WITH THEIR
LATEST 12Z RUNS WHICH MAKE FOR MORE OF A PRECIP TYPE/AMOUNT CHALLENGE
FOR THE DVN CWA...THE CONSISTENT ECMWF WOULD STILL IMPACT MOST OF THE
LOCAL FCST AREA WITH A QUICKER SWITCH OVER TO SNOW AND MORE AREAS
STARTING OFF AS SNOW TO BEGIN WITH. THE ENSEMBLE SFC LOW TRACK OF
THE 12Z GFS/NAM/UKMET/GEM ALL HOOK THE DEVELOPING LOW FROM THE OK
PANHANDLE ON WED UP THROUGH NORTHEAST MO/WEST CENTRAL IL LATE WED
NIGHT...TO A NORTH CENTRAL IL POSITION BY THU MORNING...AND THEN
BOMB IT OUT ACRS LOWER MI INTO THU EVENING. THE 12Z EURO MAINTAINS
A TRACK FURTHER TO THE SOUTHEAST OF THE ENSEMBLE PATH...SOUTHWEST MO
TO NEAR THE STL AREA BY THU MORNING AND THEN OFF TO WEST CENTRAL
INDIANA BY EARLY THU AFTERNOON. THE ENSEMBLE OF SOLUTIONS BESIDES THE
ECMWF WOULD GENERALLY SUGGEST MUCH OF THE SOUTHEAST HALF TO TWO
THIRDS OF THE FCST AREA TO BE RAIN OR EVEN EXPERIENCE SOME
CONVECTION THROUGH MIDNIGHT WED NIGHT...WHILE THE NORTHWEST THIRD
MIXES AND DYNAMICALLY COOLS INTO WET ACCUMULATING SNOW AFTER 03Z
THU. AS DEF ZONE CONTINUES TO FORM AND LLVL COLD CONVEYOR IN-WRAPS
AND INCREASES...THESE MODELS GENERALLY SUGGEST THE SWITCH OVER TO
WET SNOW TO CONTINUE FROM WEST-NORTHWEST TO THE EAST AFTER MIDNIGHT
AND INTO EARLY THU MORNING ACRS THE DVN CWA. 3-7 INCHES POSSIBLE BY
12Z THU ALONG AND WEST OF A LINE FROM SIGOURNEY IA...TO EAST OF
CEDAR RAPIDS AND TO WEST OF DBQ. SOME ADDITIONAL ACCUMS OF 1-2
INCHES IN THESE AREAS POSSIBLE THROUGH 18Z THU...BUT BULK OF
ACCUMULATING SNOW TO SWITCH EASTWARD ACRS THE REST OF THE CWA WITH 3-
6 INCHES POSSIBLE ALONG AND NORTH OF A LINE FROM MT PLEASANT IA...TO
THE QUAD CITIES..AND TO STERLING IL.
WHILE THE NORTHWEST THIRD AND NORTH CENTRAL PORTIONS OF THE DVN CWA
MAY EVENTUALLY GET 4-8+ INCHES BY THU EVENING...THE ENSEMBLES MINUS
THE ECMWF SUGGEST THE HIGHEST SNOWFALL TOTALS OF 8-12+ INCHES OCCUR
WEST AND NORTH OF THE DVN CWA ACRS SOUTH CENTRAL IA...UP THROUGH
NORTHEASTERN IA INTO SW/CENTRAL WI. EXTENT OF BOMBING CYCLONE TO THE
EAST STILL INDICATED BY BULK OF THE MODEL RUNS TO DRIVE VERY STRONG
NORTH BECOMING NORTHWEST WINDS LATE WED NIGHT AND ESPECIALLY ON
THU...SUSTAINED 25 TO 35 MPH WITH GUSTS TO AT LEAST 45 MPH. GRAVITY
WAVE PHENOMENA WEST OF RAPIDLY DEEPENING CYCLONE COULD ALSO PRODUCE
ISOLATED GUSTS OVER 50 MPH AT MAX DEEPENING STAGE ON THU. THUS WHERE
ACCUMULATING SNOWS OCCUR...NEAR BLIZZARD OR BLIZZARD CONDITIONS VERY
POSSIBLE. BACK TO THE ECMWF...IT/S TRACK WOULD MEAN MORE OF A DIRECT
HIT UPON THE LOCAL AREA AND HIGHER SNOW AMOUNTS FURTHER EAST AND
SOUTH...ESPECIALLY TAKING INTO ACCOUNT SOME FUJI-WARA EFFECT OF
SECONDARY VORT INTERACTING IN TROF BASE AND ENHANCING DEF ZONE SNOWS
ACRS THE LOCAL AREA ON THU. DESPITE ONGOING MODEL UNCERTAINTY AND
THE SYSTEM TO BE BETTER SAMPLED FOR THE 00Z RUNS TONIGHT AND
ESPECIALLY 12Z TUE...WILL ISSUE A WINTER STORM WATCH FOR ROUGHLY THE
NORTHWEST HALF OF THE DVN CWA FOR WED NIGHT AND THU GIVING A NOD
SOMEWHAT TO THE ENSEMBLE TRACK. THE STRONG WINDS LOOK TO BE A LARGE
IMPACT EVEN FOR ADVISORY LEVEL OR SLIGHTLY LESS SNOW AMOUNTS. DO FEEL
THE CWA WILL HAVE TO EVENTUALLY BE DIVIDED INTO WINTER STORM WARNING
AND ADVISORY AREAS...BUT WHERE AN WHEN STILL UP IN THE AIR. A
WATCHFUL EYE WILL ALSO NEED TO BE OPEN FOR TRENDS ON THE NEXT 1-2
MODEL RUNS BACK CLOSER TO THE CONSISTENT ECMWF...WHICH WOULD THEN
WARRANT THE NEED OF EXPANDING THE WATCH SOUTH AND EAST. ..12..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR BENTON-BUCHANAN-CEDAR-CLINTON-DELAWARE-
DUBUQUE-HENRY IA-IOWA-JACKSON-JEFFERSON-JOHNSON-JONES-
KEOKUK-LINN-LOUISA-MUSCATINE-SCOTT-VAN BUREN-WASHINGTON.
IL...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR JO DAVIESS-ROCK ISLAND.
MO...NONE.
&&
$$
NICHOLS
AREA FORECAST DISCUSSION
NWS DES MOINES IA
549 PM CST MON DEC 17 2012
...SIGNIFICANT WINTER STORM TO IMPACT THE MIDWEST AND PLAINS
WEDNESDAY AND THURSDAY...
.SHORT TERM /TONIGHT/...
LOW PRESSURE OVER NORTHEAST WYOMING WILL SHIFT EAST ACROSS SOUTH
DAKOTA AND NEBRASKA AND REACH NORTHWEST IOWA LATE TONIGHT. AN
ASSOCIATED UPPER LEVEL SHORT WILL SPREAD INCREASING QG FORCING
ACROSS CENTRAL IOWA. IN ADDITION...STRONG THETA-E ADVECTION WILL
ARRIVE AFTER MIDNIGHT THROUGH CENTRAL AND NORTHWEST IOWA. THE BEST
COMBINATION OF FORCING IS OVER CENTRAL IA NEAR DES MOINES AND AMES
BETWEEN 3 AM TO 6 AM HOWEVER THE DEEPER MOISTURE WILL BE FARTHER
NORTH. TYPICALLY THIS TIME OF YEAR FORCING TRUMPS DEEP MOISTURE
THEREFORE CERTAINLY SHOULD HAVE PRECIPITATION FARTHER SOUTH THAN
WHAT MOST MODEL GUIDANCE PRECIPITATION FIELDS WOULD SUGGEST. WARM
ADVECTION IN THE LOW LEVELS IS EXPECTED AS WELL OVERNIGHT RESULTING
IN NON-DIURNAL TEMPERATURES. THIS COULD SWITCH PRECIPITATION TYPE TO
RAIN ON THE SOUTHERN FRINGES. NOT CONFIDENT IN POTENTIAL OF FREEZING
RAIN WITH UNCERTAINTY IN ARRIVAL OF WARMER AIR ALOFT...THOUGH CAN
NOT TOTALLY DISCOUNT. POTENTIAL AS WELL FOR POCKETS OF LOWER
VISIBILITIES DUE TO FOG THOUGH LOW LEVEL WARM ADVECTION SHOULD LIMIT
AREAL COVERAGE OF VISIBILITIES BELOW 2SM.
.LONG TERM /TUESDAY THROUGH MONDAY/...
WILL SEE SOME LINGERING POPS IN THE NORTH ON TUESDAY MORNING AS THE
SYSTEM GRADUALLY DEPARTS TO THE EAST. SOME LIGHT ACCUMULATIONS WILL
STILL BE POSSIBLE AROUND MASON CITY BEFORE MIDDAY BUT PCPN IS
EXPECTED TO END BY MIDDAY. THE WEATHER WILL BE TRANQUIL FROM TUESDAY
AFTERNOON INTO EARLY WEDNESDAY MORNING BEFORE MAJOR SYSTEM BEGINS TO
AFFECT THE FORECAST AREA.
THIS MAJOR STORM IS CURRENTLY OFF THE WEST COAST AND WILL COME
ASHORE LATE TONIGHT INTO TUESDAY. THEREFORE...THERE IS LITTLE
RESOLUTION OF THE SYSTEM BY THE UPPER AIR NETWORK WHICH IS LIKELY
CAUSING SOME OF THE DIFFERENCES SEEN IN THE MODEL RUNS. INITIALLY
ON WEDNESDAY...RIDGE AXIS WILL BE IN PLACE ACROSS THE NORTHEAST WITH
RELATIVELY QUITE WEATHER. HOWEVER...BY MIDDAY...FORCING WILL
RAPIDLY INCREASE AS ISENTROPIC LIFT BEGINS IN EARNEST. STRONG
FRONTOGENETICAL FORCING ALSO ARRIVES ACROSS CENTRAL INTO NORTHERN
IOWA BY LATE AFTERNOON WHICH WILL LIKELY ENHANCE PCPN RATES IN THOSE
LOCATIONS. PCPN WILL BREAK OUT DURING THE AFTERNOON AND INCREASE IN
BOTH COVERAGE AND INTENSITY AS THE AFTERNOON PROGRESSES. SNOW IS
EXPECTED ALONG AND NORTH OF AN ATLANTIC TO WATERLOO LINE WITH A BAND
OF MIXED PCPN OF 50 MILES WIDE OR SO SOUTH OF THE SNOW. RAIN IS
EXPECTED ALONG THE MISSOURI BORDER AS READINGS REMAIN ABOVE
FREEZING.
CONDITIONS DETERIORATE RAPIDLY ON WEDNESDAY NIGHT AS COLD ADVECTION
INTENSIFIES ACROSS THE STATE. UPPER SYSTEM WILL EJECT FROM SOUTHERN
PLAINS AND RACE NORTHEAST TO NEAR QUINCY ILLINOIS BY DAYBREAK.
SYSTEM WILL BE DEEPENING AND BECOMING NEGATIVELY TILTED WITH TIME AS
SURFACE LOW STRENGTHENS. PCPN ACRS THE FORECAST AREA WILL BECOME
ALL SNOW BY MIDNIGHT AS COLD AIR IS DRAWN SOUTHWARD. WINDS ARE
LIKELY TO BECOME A VERY SERIOUS ISSUE AFTER MIDNIGHT AND CERTAINLY
BY DAYBREAK ON THURSDAY. 925MB WINDS WILL BE NEAR OR EVEN SLIGHTLY
ABOVE 50KTS WITH MOS OUTPUT SHOWING SUSTAINED WINDS OF 30KTS IN MANY
LOCATIONS IN CENTRAL IOWA. THIS EVENT MAY BECOME MORE OF A BLIZZARD
INTO THURSDAY MORNING AS THE WINDS INCREASE AND WILL HAVE TO BE
MONITORED CLOSELY. SNOW ON WEDNESDAY NIGHT WILL BE HEAVIEST IN THE
EVENING AS MID LEVEL FORCING IS MAXIMIZED. SOME CONVECTIVE SNOW
WILL BE POSSIBLE AS WELL WITH NEGATIVE EPV ACROSS MUCH OF THE STATE
WITH DECENT MID LEVEL LAPSE RATES. CONDITIONS WILL BE POOR ON
THURSDAY MORNING WITH VERY STRONG WINDS DESPITE THE SNOWFALL
ENDING. GIVEN ALL OF THIS...HAVE ISSUED A WINTER STORM WATCH FOR
MUCH OF CENTRAL IOWA FROM MIDDAY WEDNESDAY INTO THURSDAY FOR THE
POTENTIAL OF HEAVY SNOWFALL AND VERY STRONG WINDS. AN UPGRADE TO
BLIZZARD WATCH MAY BE NEEDED SHOULD FORECAST WINDS REMAIN STRONG OR
INCREASE.
THE WEATHER BEYOND THURSDAY IS RELATIVELY QUIET WITH LITTLE CHANGE
IN THE FORECAST. MAIN CONCERN IS THAT TEMPERATURES WOULD BE TOO
WARM GIVEN THE FRESH SNOW COVER ACROSS THE AREA.
&&
.AVIATION...18/00Z
SOMEWHAT LOW CONFIDENCE THIS SET WITH VARIABLE CONDITIONS STATEWIDE
AT 00Z...VFR/MVFR EAST DOWN TO MVFR/LIFR WEST. WEAK FRONTAL
BOUNDARY ALSO NOTED ALONG KSUX/KDSM/KMLI LINE. LATEST RAP SEEMS TO
HAVE BEST HANDLE ON REALITY RIGHT NOW AND WILL BE FOLLOWED FOR
GUIDANCE...WHICH IS NOT DISSIMILAR TO PREVIOUS FORECAST. THIS
RESULTS IN AT LEAST IFR CONDITIONS OVER MOST LOCATIONS AS THEY
SPREAD EASTWARD. LOW LEVEL MOISTURE REMAINS TRAPPED IN LIGHT SELY
WINDS. CONDITIONS SHOULD IMPROVE BY MIDDAY CENTRAL AND SOUTH BUT
MAY REMAIN AT LEAST MVFR NORTH...NORTH OF FRONTAL BOUNDARY WHERE
THERE COULD ALSO BE SOME LIGHT SNOW OVERNIGHT. WINDS WILL ALSO
INCREASE SOMEWHAT BY TUE AFTERNOON.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
AFTERNOON FOR ADAIR-ADAMS-APPANOOSE-AUDUBON-BLACK HAWK-BOONE-
BREMER-BUTLER-CALHOUN-CARROLL-CASS-CLARKE-CRAWFORD-DALLAS-DAVIS-
DECATUR-FRANKLIN-GREENE-GRUNDY-GUTHRIE-HAMILTON-HARDIN-JASPER-LUCAS-
MADISON-MAHASKA-MARION-MARSHALL-MONROE-POLK-POWESHIEK-RINGGOLD-SAC-
STORY-TAMA-TAYLOR-UNION-WAPELLO-WARREN-WAYNE-WEBSTER-WRIGHT
&&
$$
SHORT TERM...DONAVON
LONG TERM...COGIL
AVIATION...AVIATION
AREA FORECAST DISCUSSION
NWS DES MOINES IA
307 PM CST SUN DEC 16 2012
.SHORT TERM /TONIGHT/...
CHALLENGING FORECAST ESPECIALLY FROM A FOG AND LOW CLOUDS
PERSPECTIVE. FOG AND LOW CLOUDS HAVE BEEN STUBBORN IN LIFTING TODAY
ESPECIALLY ACROSS THE SOUTHERN...CENTRAL AND EASTERN CWA. AND IN THE
NORTHWESTERN CWA WHERE THE FOG AND LOW CLOUDS DID LIFT...ANOTHER
AREA OF LOW CLOUDS HAS BEEN MOVING SOUTHEAST FROM SOUTH DAKOTA AND
MINNESOTA.
HAVE TAKEN A SOMEWHAT PESSIMISTIC APPROACH TO THE LOW CLOUDS AND FOG
FOR TONIGHT. ALTHOUGH BUFKIT NAM SOUNDINGS ARE OPTIMISTIC...THE
BUFKIT RAP SOUNDINGS ARE QUITE PESSIMISTIC. THE FORECAST TENDS TO
SPLIT THE DIFFERENCE WITH A LEAN TOWARD THE LOW CLOUDS AND FOG BEING
STUBBORN. LOW LEVEL MOISTURE IS EXPECTED TO REMAIN PLENTIFUL
OVERNIGHT ESPECIALLY IN THOSE AREAS THAT STILL HAVE LOW CLOUDS AND
FOG. WITH WIND SPEEDS DECREASING OVERNIGHT...MIXING WILL DIMINISH
AND THE FOG IS EXPECTED TO COME BACK. THUS HAVE GONE WITH PATCHY FOG
WORDING IN MANY AREAS FOR TONIGHT/S FCST GRIDS. IN THE NORTHWESTERN
CWA...HAVE BROUGHT THE CLOUDS BACK IN ALONG WITH THE POSSIBILITY OF
PATCHY FOG THERE AS WELL. THE LOWEST VISIBILITIES IN THE FOG ARE
EXPECTED TO BE IN THE NORTHEASTERN CWA.
ON A DIFFERENT NOTE...SOME WEAK FRONTOGENETICAL FORCING HAS LED TO
AN AREA OF ECHOES ON THE RADAR MAINLY ACROSS THE WESTERN CWA TODAY.
OVER TIME THE ECHOES HAVE SPREAD EASTWARD...INDICATING THAT THE
FORCING IS TRANSLATING EASTWARD...WHICH IS SUPPORTED BY MODEL CROSS
SECTIONS. SINCE THE PRECIP IS NOT EXPECTED TO REACH THE GROUND
MUCH...IF AT ALL...HAVE GONE ONLY WITH SLIGHT CHANCE POPS ACROSS THE
SOUTHERN CWA INTO THIS EVE. THERE IS A DRY ENOUGH LAYER BETWEEN THE
LAYER OF FORCING AND THE LOWER LEVEL MOISTURE THAT THE PRECIP IS NOT
EXPECTED TO MAKE IT THROUGH THAT DRIER LAYER.
.LONG TERM /MONDAY THROUGH SUNDAY/...
A PAIR OF SUCCESSIVE 500 MB SHORTWAVES WILL MOVE ACROSS NORTHERN
IOWA...THE FIRST ON MONDAY AND THE SECOND ON TUESDAY MORNING. AT THE
SURFACE A HIGH PRESSURE RIDGE WILL CROSS THE AREA ON MONDAY...WITH
THE MID-LEVEL SHORTWAVE GENERATING CLOUDS BUT FORECAST SOUNDINGS
INDICATING TOO MUCH DRY AIR IN THE LOWER LEVELS TO RESULT IN
PRECIPITATION. ON MONDAY NIGHT HOWEVER THE RIDGE WILL MOVE OFF TO
THE EAST...AND A SURFACE LOW WILL DEVELOP AROUND THE BLACK HILLS
AHEAD OF THE APPROACHING SECOND WAVE AND MOVE QUICKLY EASTWARD
TOWARD IOWA. THIS WILL CAUSE SURFACE WINDS TO COME AROUND QUICKLY TO
SOUTH BY EARLY TUESDAY MORNING WITH AN INCREASE IN ATMOSPHERIC
MOISTURE. AS THE WAVE AND LOW CROSS THE AREA ON TUESDAY MORNING IT
WILL PROVIDE A BRIEF OPPORTUNITY FOR SOME LIGHT SNOW ACROSS OUR FAR
NORTH BEFORE THE SYSTEM CLEARS OUT RAPIDLY TO THE EAST. AT THIS TIME
WILL STICK WITH JUST SLIGHT POPS ROUGHLY NORTH OF HIGHWAY 20 ON
TUESDAY MORNING...AND LITTLE IF ANY ACCUMULATION IS ANTICIPATED.
THE BIGGEST POTENTIAL WEATHER IMPACT OF THE SEVEN DAY FORECAST WILL
COME FROM A LONGWAVE 500 MB TROUGH COMING ASHORE OVER THE PACIFIC
U.S. COAST LATE ON TUESDAY. IT STILL APPEARS THAT THIS TROUGH WILL
NOT BE FULLY PHASED...AND THAT MOST OF THE ENERGY WILL DIG INTO THE
SOUTHERN STREAM WITH A NORTHERN STREAM WAVE TRAILING SLIGHTLY
BEHIND. AS THE OVERALL SYSTEM MOVES EASTWARD TOWARD THE CENTRAL U.S.
AND IOWA THE COMPLICATED EVOLUTION OF THE TWO INTERTWINED WAVES WILL
HAVE DRAMATIC IMPACTS ON THE DETAILS OF THEIR ASSOCIATED SENSIBLE
WEATHER. THE SOUTHERN STREAM WAVE WILL GENERATE A STRONG SURFACE LOW
PRESSURE CENTER OVER THE SOUTHERN HIGH PLAINS ON TUESDAY NIGHT/EARLY
WEDNESDAY...WHICH WILL SUBSEQUENTLY MOVE EAST NORTHEAST ACROSS
MISSOURI AND ILLINOIS...WITH A LARGE SWATH OF SNOW SPREADING ALONG
THE NORTHWESTERN FLANK OF THE TRACK. HOWEVER THE PHASING
ISSUES...COMBINED WITH THE FACT THAT THE ENTIRE SYSTEM IS STILL WELL
OFFSHORE AND NOT BEING SAMPLED BY THE UPPER AIR NETWORK...ARE
WREAKING HAVOC WITH THE FORECAST OF THE STORM TRACK BEING OUTPUT BY
THE VARIOUS PROGNOSTIC MODELS. A SHIFT OF 50 OR 100 MILES ONE WAY OR
ANOTHER WILL MAKE THE DIFFERENCE BETWEEN THE HEAVIER SNOW SWATH
FALLING ACROSS CENTRAL IOWA...SOUTHEASTERN IOWA...OR NORTHEASTERN
MISSOURI. GIVEN THE INHERENT UNCERTAINTY IN THIS SCENARIO AND POOR
CONSISTENCY AMONG THE MODELS HAVE OPTED TO KEEP THE FORECAST VERY
CLOSE TO PREVIOUS ISSUANCES...WITH LIKELY TO CATEGORICAL POPS ACROSS
ABOUT THE SOUTHEASTERN HALF OR TWO THIRDS OF THE CWA. IT IS STILL
TOO EARLY TO MAKE ANY FORECAST OF SNOWFALL AMOUNTS...BUT SEVERAL
INCHES OF SNOWFALL ARE LIKELY TO THE NORTHWEST OF THE LOW AND
PROBABLY SOMEWHERE IN THE SOUTHEASTERN HALF OF OUR AREA. THIS WILL
BE CLOSELY MONITORED OVER THE NEXT SEVERAL DAYS.
THE MIDWEEK SYSTEM WILL CLEAR OUT QUICKLY LATE THURSDAY AND THURSDAY
NIGHT...AFTER WHICH QUIET AND DRY WEST NORTHWESTERLY 500 MB FLOW
WILL BE ESTABLISHED. THIS WILL LEAD TO COOLER WEATHER...ESPECIALLY
IF A SNOW PACK IS IN PLACE AFTER THE WEDNESDAY/THURSDAY STORM...WITH
NO ADDITIONAL PRECIPITATION IN THE FORECAST.
&&
.AVIATION...16/18Z
LOW CONFIDENCE FCST AT ALL TERMINALS DUE MAINLY TO STUBBORN FOG AND
STRATUS. SOME FCST GUIDANCE IS OPTIMISTIC AT THE FOG AND STRATUS
LIFTING THIS AFTN/EVENING...WHILE OTHER GUIDANCE KEEPS IT AROUND
LONGER AND BRINGS IT BACK TONIGHT. FOR NOW HAVE GONE MIDDLE OF THE
ROAD AT ALL TERMINALS...AND WILL MONITOR WX TRENDS FOR UPDATES.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...ZOGG
LONG TERM...LEE
AVIATION...ZOGG
AREA FORECAST DISCUSSION
NWS TOPEKA KS
1151 AM CST SUN DEC 16 2012
...UPDATE TO AVIATION...
.UPDATE...
AFTER MAKING SOME CALLS ACROSS EAST CENTRAL KS...IT APPEARS AS
THOUGH THE HIGH CLOUDS HAVE NOT DIMINISHED THE DENSE FOG. NOW THAT
SKIES ARE CLEARING OUT AGAIN...VISIBILITIES ARE LIKELY TO REMAIN
DOWN TO A QUARTER OF A MILE...AND WE HAVE ISSUED A DENSE FOG
ADVISORY THROUGH MID MORNING.
&&
.DISCUSSION...
09Z WATER VAPOR IMAGERY SHOWS A COMPACT SHORTWAVE OVER THE NM/CO
ROCKIES. A SECOND SHORTWAVE WAS NOTED OVER THE PACIFIC NORTHWEST. AT
THE SURFACE...WEAK RIDGING WAS SEEN FROM THE NORTHERN PLAINS INTO
NORTHERN KS.
FOR TODAY THROUGH MONDAY...A RATHER DISORGANIZED CYCLONIC FLOW IS
PROGGED TO AFFECT THE AREA WITH THE SHORTWAVES NOTED ON WATER VAPOR
TRAVERSING THE AREA. INITIALLY FORECAST SOUNDINGS FROM THE RAP AND
NAM SHOW SOME MID LEVEL DRY AIR THAT HAS TO BE OVERCOME WITH THE
BETTER MID LEVEL SATURATION REMAINING JUST NORTH OF THE STATE LINE.
WITH THIS IN MIND AND THE MODELS SHOWING THE SHORTWAVE OVER NM/CO
WEAKENING AS IT MOVES EAST...WILL MAINTAIN THE MENTION OF FLURRIES
AND OR SPRINKLES ACROSS THE FAR NORTHERN COUNTIES THINKING THAT ANY
PRECIP WILL NOT BE MEASURABLE. IT SEEMS THAT DRY LOW LEVELS FOR
TONIGHT AND MONDAY MORNING WILL ALSO LIMIT PRECIP CHANCES AS THE
WAVE OVER THE PACIFIC NORTHWEST KICKS THE LONGWAVE TROUGH EAST. WITH
WEAK COLD AIR ADVECTION AND INCREASING CLOUDS...TEMPS SHOULD BE
COOLER TODAY WITH HIGHS GENERALLY IN THE 40S. LOW LEVEL WINDS ARE
EXPECTED TO TURN BACK FROM THE SOUTH AND SOUTHWEST FOR MONDAY...SO
TEMPS SHOULD BEGIN TO MODERATE.
THE NEXT CHANCE FOR MEASURABLE PRECIP CONTINUES TO LOOK LIKE IT WILL
OCCUR WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT...AND WE MAY END UP
SEEING THE FIRST SNOWFALL OF THE WINTER. THE GFS AND ECMWF APPEAR TO
BE CONVERGING ON A PROGRESSIVE SYSTEM MOVING ACROSS THE PLAINS AS
THE NEXT SHORTWAVE TROUGH PROPAGATES ACROSS NORTH AMERICA. WHILE THE
GFS IS NOTABLY FASTER WITH THE SURFACE LOW...THE TRACKS OF THE
SYSTEM ARE SIMILAR FROM BOTH MODEL SOLUTIONS. ALSO BECAUSE OF THE
PROGRESSIVE NATURE OF THE SYSTEM AND BOTH MODELS DEEPENING THE
SURFACE LOW AS IT PASSES SOUTHEAST OF THE FORECAST AREA...THE COLD
AIR IS QUICKER TO PUSH SOUTH DURING THE AFTERNOON WEDNESDAY WITH
TEMPS POTENTIALLY FALLING DURING THE AFTERNOON. THERE APPEARS TO BE
DECENT QG VECTOR CONVERGENCE WITH THE SYSTEM AND MODELS SHOW GOOD
MID LEVEL FRONTOGENESIS NORTHWEST OF THE SURFACE LOW TRACK. GIVEN
THE TEMP PROFILES RAPIDLY COOLING AND THE MESOSCALE FORCING...THINK
THERE COULD BE A BAND OF SNOW FORM LATE WEDNESDAY AFTERNOON AND
THROUGH THE NIGHT. CROSS SECTIONS FROM THE GFS AND ECMWF SUGGEST THE
STRONGER VERTICAL MOTION WILL OCCUR BETWEEN 00 AND 06Z THUR WITH DRY
AIR AND SUBSIDENCE QUICKLY FILLING IN TOWARDS 12Z. BECAUSE OF THE
PROGRESSIVE NATURE OF THE SYSTEM...SNOW AMOUNTS LOOK TO BE ON THE
ORDER OF A COUPLE INCHES.
SOMEWHAT ZONAL FLOW DEVELOPS IN THE WAKE OF THE WEDNESDAY NIGHT
SYSTEM...WITH THE UPPER LEVEL JET SETTING UP ACROSS THE SOUTHERN
HALF OF THE COUNTRY. THIS SHOULD KEEP A DRY AND COOL AIRMASS OVER
THE PLAINS FOR THURSDAY NIGHT THROUGH SATURDAY.
WOLTERS
&&
.AVIATION...
MAIN CONCERN WILL BE HOW LONG IFR/LIFR CONDITIONS PERSIST ACROSS THE
TAF SITES. DAY TIME HEATING SHOULD INCREASE TEMPERATURES ENOUGH TO
IMPROVE THE VSBY TO MVFR THIS AFTERNOON AROUND 20Z. THE CEILINGS
SHOULD ALSO IMPROVE TO MVFR SOMETIME THIS EVENING WHICH WILL
REMAIN ENTRENCHED ACROSS THE TAF SITES THROUGH TONIGHT. DEPENDING
ON WHEN THE STRATUS CLEARS OUT FOG MAY DEVELOP AGAIN TONIGHT BUT
WILL LET LATER SHIFTS MONITOR THE SITUATION.
SANDERS
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
1146 AM CST SUN DEC 16 2012
...UPDATED AVIATION SECTION FOR 18Z TAFS...
.UPDATE...
ISSUED AT 944 AM CST SUN DEC 16 2012
THE DENSE FOG ADVISORY WAS UPDATED TO REFLECT THE SOUTHWEST
ADVECTION OF THE FOG DOWN INTO THE LIBERAL AND MEADE AREAS. HRRR
AND RAP MODELS SUGGEST VISIBLITIES WILL STAY DOWN UNTIL AROUND
17Z...WITH ONLY SLOW IMPROVEMENT IN VISIBILITY AND CEILING THROUGH
MIDDAY/EARLY AFTERNOON. THIS WILL IMPACT TEMPERATURES TODAY AND
HAVE HAD TO DRASTICALLY LOWER THE TEMPERATURES FOR TODAY FROM THE
ARKANSAS RIVER SOUTH TO THE OKLAHOMA BORDER AS MESOSCALE LOW WILL
TRAVEL ALONG THE KS-OK BORDER TODAY KEEPING COOL, MOIST NORTHEAST
WINDS IN PLACE PRETTY MUCH ALL DAY.
&&
.SHORT TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 341 AM CST SUN DEC 16 2012
THE COLORADO SHORTWAVE HAS BEEN PROGRESSING STEADILY EASTWARD PER
SATELLITE LOOPS. EXTRAPOLATING IT AT ITS CURRENT SPEED WOULD PUT IT
OVER SOUTH CENTRAL KANSAS BY 18Z. THE 00Z NAM HAS A PRETTY GOOD
HANDLE ON THIS. THIS MODEL ALSO KEEPS ANY PRECIPITATION ASSOCIATED
WITH THIS WAVE OVER FAR NORTHERN KANSAS THIS MORNING. THE LATEST
RUNS OF THE RUC13 ARE ALSO DRY BUT IT DOES TRY TO DEVELOP SOME
LIGHT PRECIPITATION OVER SOUTH CENTRAL KANSAS TOWARD MIDDAY. BASED
ON CURRENT RADAR TRENDS, HAVE OPTED TO LOWER POPS ACROSS WEST
CENTRAL KANSAS THIS MORNING AND REMOVE THE MENTION OF SPRINKLES
FROM THE FORECAST. THIS WILL HAVE TO BE WATCHED FOR THE NEXT FEW
HOURS FOR ANY CHANGES IN THE CURRENT RADAR TRENDS.
ONCE THE FIRST WAVE MOVES OUT OF WESTERN KANSAS, WE SHOULD SEE AN
INCREASE IN SUNSHINE FOR A WHILE UNTIL CIRRUS ASSOCIATED WITH THE
NEXT WAVE BEGINS TO MOVE IN FROM THE WEST. THIS COULD HELP BOOST
TEMPERATURES UP A LITTLE THIS AFTERNOON AND HAVE ADJUSTED TODAY`S
HIGH TEMPERATURES UP A BIT ESPECIALLY OVER CENTRAL KANSAS.
THE NEXT WAVE WILL MOVE OUT OVER THE CENTRAL HIGH PLAINS THIS
EVENING AND SHOULD BE EAST OF THE AREA BY MIDNIGHT. AM NOT
EXPECTING ANY SIGNIFICANT PRECIPITATION WITH THIS WAVE AS WELL.
HAVE LOWERED SUNDAY NIGHTS LOW TEMPERATURES A FEW DEGREES CLOSER
TO THE NAM MOS NUMBERS.
.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 403 AM CST SUN DEC 16 2012
THE MAJOR ADJUSTMENTS TO THE EXTENDED FORECAST OCCURRED IN THE
WEDNESDAY AND WEDNESDAY NIGHT TIMEFRAME, WHEN THE POTENTIAL FOR A
DYNAMIC LOW TO DEVELOP OVER THE HIGH PLAINS, BRINGING GOOD POTENTIAL
FOR WINDY AND SNOWY CONDITIONS.
THE RELATIVELY MILD TEMPERATURES WILL CONTINUE ON MONDAY AND
TUESDAY, AS A FAST MOVING PACIFIC JET SPREADS INTO THE NATIONS
INTERIOR, FORMING A PROGRESSIVE FLAT RIDGE THAT LIFTS INTO THE
EASTERN HALF OF THE NATION BY WEDNESDAY. THE POSITION OF THE JET AND
THE RELATIVE HUMIDITY FIELDS OF MODEL LOWER AND MID TROPOSPHERIC
LAYERS SUGGEST MOSTLY SUNNY CONDITIONS SHOULD BE EXPERIENCED ACROSS
WESTERN KANSAS MONDAY AND TUESDAY. EARLY IN THE PERIOD LIGHT NORTHERLY
WINDS ASSOCIATED WITH THE RETREATING NORTHERN PLAINS HIGH WILL
BECOME MORE SOUTHWESTERLY BY TUESDAY AS SURFACE TROUGHING DEVELOPS
ACROSS THE DAKOTAS. MODEL CONSENSUS CONTINUES TO SUPPORT HIGHS
REACHING THE 50S. TUESDAY MAY BE AROUND 5 DEGREES WARMER WITH
TEMPERATURES REACHING AROUND 60 DEGREES WITH WEAK DOWNSLOPING
SURFACE WINDS, ESPECIALLY ACROSS SOUTH CENTRAL KANSAS.
THE UPPER FLOW WILL BE RAPIDLY DEVELOPING INTO A STRONGLY AMPLIFIED
UPPER TROUGH EARLY WEDNESDAY, AND DRIVE A COLD FRONT THROUGH WESTERN
KANSAS WEDNESDAY MORNING. BOTH THE ECMWF AND GFS DEVELOP A SURFACE
TO 700 LOW POLEWARD TILTED FROM NORTHERN OKLAHOMA INTO KANSAS. THIS
SHOULD PRODUCE A PERIOD OF MID LEVEL FRONTOGENETIC FORCING WITH COLD
ENOUGH AIR FOR SNOW ACCUMULATION TO DEVELOP BEHIND THE SURFACE COLD
FRONT. THE INTENSITY AND LOCATIONS ARE HOWEVER STILL MUCH OF AN
UNCERTAINTY AT THIS TIME. REGARDLESS, WE`VE INCREASED POPS IN THE
WEDNESDAY TIMEFRAME AND FOLLOWED THE COLDER MODEL TRENDS FOR
TEMPERATURES INTO THURSDAY AND THURSDAY NIGHT. WE USED A SLIGHTLY
DOWNWARD ADJUSTED ECMWF QPF FORECAST. BASED ON TEMPERATURES NOT
EXPECTED TO BE EXCEEDING COLD WEDNESDAY, AND WINDY CONDITIONS BEHIND
THE BOUNDARY, A CONSERVATIVE 8:1 SNOW RATIO WAS USED FOR THE SNOW
ACCUMULATION. THAT PRODUCES SNOWFALL AMOUNTS RANGING FROM AROUND A
HALF INCH TO AN INCH AN A HALF. ADDITIONAL MODEL RUNS MAY SHED MORE
INSIGHT ON WHETHER SIGNIFICANT IMPACTS MAY OCCUR, BUT WITH THESE
KIND OF SNOW TOTALS AND WIND SPEEDS, HEADLINES DON`T APPEAR LIKELY
AT THIS TIME.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1145 AM CST SUN DEC 16 2012
THE REMAINDER OF THE AFTERNOON WILL SEE VFR CONDITIONS AFTER THE
MORNING DENSE FOG EVENT. SURFACE WINDS NORTHWEST OF THE DEPARTING
SMALL SCALE LOW WILL REMAIN LIGHT, MAINLY OUT OF THE
NORTH/NORTHEAST, AND RESIDUAL MOISTURE WILL HANG AROUND THIS
EVENING, PARTICULARLY AT DDC. DRY AIR ADVECTION WILL INCREASE LATE
TONIGHT ACROSS THE WEST. WILL CARRY 3 MILES VISIBILITY IN THE
FORECAST FOR DDC TERMINAL 06-12Z MONDAY MORNING BUT KEEP VFR
CONDITIONS THROUGHOUT AT GCK AND HYS. A REPEAT OF THE DENSE FOG
EVENT TOMORROW MORNING IS UNLIKELY WITH AFOREMENTIONED DOWNSLOPE
FLOW INCREASING BY DAYBREAK MONDAY.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 42 24 54 29 / 10 10 0 0
GCK 44 22 52 28 / 10 10 0 0
EHA 43 25 54 31 / 10 0 0 0
LBL 39 22 54 29 / 10 10 0 0
HYS 44 24 52 28 / 10 10 0 0
P28 43 29 57 30 / 10 0 0 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...UMSCHEID
SHORT TERM...GERARD
LONG TERM...RUSSELL
AVIATION...UMSCHEID
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
948 AM CST SUN DEC 16 2012
.UPDATE...
ISSUED AT 944 AM CST SUN DEC 16 2012
THE DENSE FOG ADVISORY WAS UPDATED TO REFLECT THE SOUTHWEST
ADVECTION OF THE FOG DOWN INTO THE LIBERAL AND MEADE AREAS. HRRR
AND RAP MODELS SUGGEST VISIBLITIES WILL STAY DOWN UNTIL AROUND
17Z...WITH ONLY SLOW IMPROVEMENT IN VISIBILITY AND CEILING THROUGH
MIDDAY/EARLY AFTERNOON. THIS WILL IMPACT TEMPERATURES TODAY AND
HAVE HAD TO DRASTICALLY LOWER THE TEMPERATURES FOR TODAY FROM THE
ARKANSAS RIVER SOUTH TO THE OKLAHOMA BORDER AS MESOSCALE LOW WILL
TRAVEL ALONG THE KS-OK BORDER TODAY KEEPING COOL, MOIST NORTHEAST
WINDS IN PLACE PRETTY MUCH ALL DAY.
&&
.SHORT TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 341 AM CST SUN DEC 16 2012
THE COLORADO SHORTWAVE HAS BEEN PROGRESSING STEADILY EASTWARD PER
SATELLITE LOOPS. EXTRAPOLATING IT AT ITS CURRENT SPEED WOULD PUT IT
OVER SOUTH CENTRAL KANSAS BY 18Z. THE 00Z NAM HAS A PRETTY GOOD
HANDLE ON THIS. THIS MODEL ALSO KEEPS ANY PRECIPITATION ASSOCIATED
WITH THIS WAVE OVER FAR NORTHERN KANSAS THIS MORNING. THE LATEST
RUNS OF THE RUC13 ARE ALSO DRY BUT IT DOES TRY TO DEVELOP SOME
LIGHT PRECIPITATION OVER SOUTH CENTRAL KANSAS TOWARD MIDDAY. BASED
ON CURRENT RADAR TRENDS, HAVE OPTED TO LOWER POPS ACROSS WEST
CENTRAL KANSAS THIS MORNING AND REMOVE THE MENTION OF SPRINKLES
FROM THE FORECAST. THIS WILL HAVE TO BE WATCHED FOR THE NEXT FEW
HOURS FOR ANY CHANGES IN THE CURRENT RADAR TRENDS.
ONCE THE FIRST WAVE MOVES OUT OF WESTERN KANSAS, WE SHOULD SEE AN
INCREASE IN SUNSHINE FOR A WHILE UNTIL CIRRUS ASSOCIATED WITH THE
NEXT WAVE BEGINS TO MOVE IN FROM THE WEST. THIS COULD HELP BOOST
TEMPERATURES UP A LITTLE THIS AFTERNOON AND HAVE ADJUSTED TODAY`S
HIGH TEMPERATURES UP A BIT ESPECIALLY OVER CENTRAL KANSAS.
THE NEXT WAVE WILL MOVE OUT OVER THE CENTRAL HIGH PLAINS THIS
EVENING AND SHOULD BE EAST OF THE AREA BY MIDNIGHT. AM NOT
EXPECTING ANY SIGNIFICANT PRECIPITATION WITH THIS WAVE AS WELL.
HAVE LOWERED SUNDAY NIGHTS LOW TEMPERATURES A FEW DEGREES CLOSER
TO THE NAM MOS NUMBERS.
.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 403 AM CST SUN DEC 16 2012
THE MAJOR ADJUSTMENTS TO THE EXTENDED FORECAST OCCURRED IN THE
WEDNESDAY AND WEDNESDAY NIGHT TIMEFRAME, WHEN THE POTENTIAL FOR A
DYNAMIC LOW TO DEVELOP OVER THE HIGH PLAINS, BRINGING GOOD POTENTIAL
FOR WINDY AND SNOWY CONDITIONS.
THE RELATIVELY MILD TEMPERATURES WILL CONTINUE ON MONDAY AND
TUESDAY, AS A FAST MOVING PACIFIC JET SPREADS INTO THE NATIONS
INTERIOR, FORMING A PROGRESSIVE FLAT RIDGE THAT LIFTS INTO THE
EASTERN HALF OF THE NATION BY WEDNESDAY. THE POSITION OF THE JET AND
THE RELATIVE HUMIDITY FIELDS OF MODEL LOWER AND MID TROPOSPHERIC
LAYERS SUGGEST MOSTLY SUNNY CONDITIONS SHOULD BE EXPERIENCED ACROSS
WESTERN KANSAS MONDAY AND TUESDAY. EARLY IN THE PERIOD LIGHT NORTHERLY
WINDS ASSOCIATED WITH THE RETREATING NORTHERN PLAINS HIGH WILL
BECOME MORE SOUTHWESTERLY BY TUESDAY AS SURFACE TROUGHING DEVELOPS
ACROSS THE DAKOTAS. MODEL CONSENSUS CONTINUES TO SUPPORT HIGHS
REACHING THE 50S. TUESDAY MAY BE AROUND 5 DEGREES WARMER WITH
TEMPERATURES REACHING AROUND 60 DEGREES WITH WEAK DOWNSLOPING
SURFACE WINDS, ESPECIALLY ACROSS SOUTH CENTRAL KANSAS.
THE UPPER FLOW WILL BE RAPIDLY DEVELOPING INTO A STRONGLY AMPLIFIED
UPPER TROUGH EARLY WEDNESDAY, AND DRIVE A COLD FRONT THROUGH WESTERN
KANSAS WEDNESDAY MORNING. BOTH THE ECMWF AND GFS DEVELOP A SURFACE
TO 700 LOW POLEWARD TILTED FROM NORTHERN OKLAHOMA INTO KANSAS. THIS
SHOULD PRODUCE A PERIOD OF MID LEVEL FRONTOGENETIC FORCING WITH COLD
ENOUGH AIR FOR SNOW ACCUMULATION TO DEVELOP BEHIND THE SURFACE COLD
FRONT. THE INTENSITY AND LOCATIONS ARE HOWEVER STILL MUCH OF AN
UNCERTAINTY AT THIS TIME. REGARDLESS, WE`VE INCREASED POPS IN THE
WEDNESDAY TIMEFRAME AND FOLLOWED THE COLDER MODEL TRENDS FOR
TEMPERATURES INTO THURSDAY AND THURSDAY NIGHT. WE USED A SLIGHTLY
DOWNWARD ADJUSTED ECMWF QPF FORECAST. BASED ON TEMPERATURES NOT
EXPECTED TO BE EXCEEDING COLD WEDNESDAY, AND WINDY CONDITIONS BEHIND
THE BOUNDARY, A CONSERVATIVE 8:1 SNOW RATIO WAS USED FOR THE SNOW
ACCUMULATION. THAT PRODUCES SNOWFALL AMOUNTS RANGING FROM AROUND A
HALF INCH TO AN INCH AN A HALF. ADDITIONAL MODEL RUNS MAY SHED MORE
INSIGHT ON WHETHER SIGNIFICANT IMPACTS MAY OCCUR, BUT WITH THESE
KIND OF SNOW TOTALS AND WIND SPEEDS, HEADLINES DON`T APPEAR LIKELY
AT THIS TIME.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 544 AM CST SUN DEC 16 2012
NORTHEAST UPSLOPE FLOW ACROSS CENTRAL KANSAS IS CREATING WIDESPREAD
DENSE FOG, EXPANDING WESTWARD THIS MORNING. OBSERVATIONS FROM GREAT
BEND AND SURROUNDING LOCATIONS CONFIRMED THE LOW VISIBILITIES, AND
THE AREA OF EXPANSIVE FOG CAN BE SEEN ON THE 11-3.9 MICRON SATELLITE
CHANNEL. THIS FOG WILL LIKELY AFFECT THE KDDC TERMINAL PERHAPS
THROUGH MID MORNING. LESS CONFIDENCE EXIST OF THE SAME IMPACTS AT
KGCK AT THIS TIME.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 42 24 54 29 / 10 10 0 0
GCK 44 22 52 28 / 10 10 0 0
EHA 43 25 54 31 / 10 0 0 0
LBL 39 22 54 29 / 10 10 0 0
HYS 44 24 52 28 / 10 10 0 0
P28 43 29 57 30 / 10 0 0 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 11 AM CST THIS MORNING FOR KSZ046-
064>066-076>081-086>090.
&&
$$
UPDATE...UMSCHEID
SHORT TERM...GERARD
LONG TERM...RUSSELL
AVIATION...RUSSELL
AREA FORECAST DISCUSSION
NWS TOPEKA KS
626 AM CST SUN DEC 16 2012
...UPDATE TO AVIATION...
.UPDATE...
AFTER MAKING SOME CALLS ACROSS EAST CENTRAL KS...IT APPEARS AS
THOUGH THE HIGH CLOUDS HAVE NOT DIMINISHED THE DENSE FOG. NOW THAT
SKIES ARE CLEARING OUT AGAIN...VISIBILITIES ARE LIKELY TO REMAIN
DOWN TO A QUARTER OF A MILE...AND WE HAVE ISSUED A DENSE FOG
ADVISORY THROUGH MID MORNING.
&&
.DISCUSSION...
09Z WATER VAPOR IMAGERY SHOWS A COMPACT SHORTWAVE OVER THE NM/CO
ROCKIES. A SECOND SHORTWAVE WAS NOTED OVER THE PACIFIC NORTHWEST. AT
THE SURFACE...WEAK RIDGING WAS SEEN FROM THE NORTHERN PLAINS INTO
NORTHERN KS.
FOR TODAY THROUGH MONDAY...A RATHER DISORGANIZED CYCLONIC FLOW IS
PROGGED TO AFFECT THE AREA WITH THE SHORTWAVES NOTED ON WATER VAPOR
TRAVERSING THE AREA. INITIALLY FORECAST SOUNDINGS FROM THE RAP AND
NAM SHOW SOME MID LEVEL DRY AIR THAT HAS TO BE OVERCOME WITH THE
BETTER MID LEVEL SATURATION REMAINING JUST NORTH OF THE STATE LINE.
WITH THIS IN MIND AND THE MODELS SHOWING THE SHORTWAVE OVER NM/CO
WEAKENING AS IT MOVES EAST...WILL MAINTAIN THE MENTION OF FLURRIES
AND OR SPRINKLES ACROSS THE FAR NORTHERN COUNTIES THINKING THAT ANY
PRECIP WILL NOT BE MEASURABLE. IT SEEMS THAT DRY LOW LEVELS FOR
TONIGHT AND MONDAY MORNING WILL ALSO LIMIT PRECIP CHANCES AS THE
WAVE OVER THE PACIFIC NORTHWEST KICKS THE LONGWAVE TROUGH EAST. WITH
WEAK COLD AIR ADVECTION AND INCREASING CLOUDS...TEMPS SHOULD BE
COOLER TODAY WITH HIGHS GENERALLY IN THE 40S. LOW LEVEL WINDS ARE
EXPECTED TO TURN BACK FROM THE SOUTH AND SOUTHWEST FOR MONDAY...SO
TEMPS SHOULD BEGIN TO MODERATE.
THE NEXT CHANCE FOR MEASURABLE PRECIP CONTINUES TO LOOK LIKE IT WILL
OCCUR WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT...AND WE MAY END UP
SEEING THE FIRST SNOWFALL OF THE WINTER. THE GFS AND ECMWF APPEAR TO
BE CONVERGING ON A PROGRESSIVE SYSTEM MOVING ACROSS THE PLAINS AS
THE NEXT SHORTWAVE TROUGH PROPAGATES ACROSS NORTH AMERICA. WHILE THE
GFS IS NOTABLY FASTER WITH THE SURFACE LOW...THE TRACKS OF THE
SYSTEM ARE SIMILAR FROM BOTH MODEL SOLUTIONS. ALSO BECAUSE OF THE
PROGRESSIVE NATURE OF THE SYSTEM AND BOTH MODELS DEEPENING THE
SURFACE LOW AS IT PASSES SOUTHEAST OF THE FORECAST AREA...THE COLD
AIR IS QUICKER TO PUSH SOUTH DURING THE AFTERNOON WEDNESDAY WITH
TEMPS POTENTIALLY FALLING DURING THE AFTERNOON. THERE APPEARS TO BE
DECENT QG VECTOR CONVERGENCE WITH THE SYSTEM AND MODELS SHOW GOOD
MID LEVEL FRONTOGENESIS NORTHWEST OF THE SURFACE LOW TRACK. GIVEN
THE TEMP PROFILES RAPIDLY COOLING AND THE MESOSCALE FORCING...THINK
THERE COULD BE A BAND OF SNOW FORM LATE WEDNESDAY AFTERNOON AND
THROUGH THE NIGHT. CROSS SECTIONS FROM THE GFS AND ECMWF SUGGEST THE
STRONGER VERTICAL MOTION WILL OCCUR BETWEEN 00 AND 06Z THUR WITH DRY
AIR AND SUBSIDENCE QUICKLY FILLING IN TOWARDS 12Z. BECAUSE OF THE
PROGRESSIVE NATURE OF THE SYSTEM...SNOW AMOUNTS LOOK TO BE ON THE
ORDER OF A COUPLE INCHES.
SOMEWHAT ZONAL FLOW DEVELOPS IN THE WAKE OF THE WEDNESDAY NIGHT
SYSTEM...WITH THE UPPER LEVEL JET SETTING UP ACROSS THE SOUTHERN
HALF OF THE COUNTRY. THIS SHOULD KEEP A DRY AND COOL AIRMASS OVER
THE PLAINS FOR THURSDAY NIGHT THROUGH SATURDAY.
WOLTERS
&&
.AVIATION...
PRIMARILY MVFR CONDITIONS WILL PERSIST AT TAF SITES THROUGH AROUND
15Z AS REDUCED VISIBILITIES AND LOW STRATUS MOVE IN FROM THE NORTH.
TOP/FOE MAY REMAIN IN LOW CEILINGS LONGER AND EVENTUALLY IMPROVE
BY 18Z...WHEN ALL TAF SITES ARE ANTICIPATED TO BE VFR.
BLAIR
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM CST THIS MORNING FOR KSZ054>056-
058-059.
&&
$$
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
545 AM CST SUN DEC 16 2012
...UPDATED FOR AVIATION...
.SYNOPSIS...
ISSUED AT 341 AM CST SUN DEC 16 2012
THE 00Z UPPER AIR ANALYSIS SHOWED A SOMEWHAT SPLIT FLOW PATTERN
OVER WESTERN NORTH AMERICA. IN THE NORTH, SHORTWAVE TROUGHS WERE
MOVING OVER THE CENTRAL CANADIAN PRAIRIE AND INTO BRITISH COLUMBIA.
FARTHER SOUTH, THE SHORTWAVE TROUGH THAT MOVED OUT OF THE CENTRAL
HIGH PLAINS SUNDAY MORNING WAS OVER THE GREAT LAKES REGION. FARTHER
WEST, A COMPACT SHORTWAVE WAS MOVING ACROSS SOUTHERN COLORADO WHILE
ANOTHER WAVE WAS ON ITS HEELS OVER THE GREAT BASIN INTO ARIZONA.
THE REGIONAL RADAR MOSAIC SHOWS A SMALL AREA OF LIGHT TO MODERATE
SNOW OVER FAR SOUTHWEST NEBRASKA, WHICH APPEARS TO BE FORCED BY
SOME MID LEVEL FRONTOGENESIS. RADAR RETURNS OVER SOUTHERN COLORADO
HAVE BEEN FAIRLY LIGHT SO FAR THIS MORNING.
&&
.SHORT TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 341 AM CST SUN DEC 16 2012
THE COLORADO SHORTWAVE HAS BEEN PROGRESSING STEADILY EASTWARD PER
SATELLITE LOOPS. EXTRAPOLATING IT AT ITS CURRENT SPEED WOULD PUT IT
OVER SOUTH CENTRAL KANSAS BY 18Z. THE 00Z NAM HAS A PRETTY GOOD
HANDLE ON THIS. THIS MODEL ALSO KEEPS ANY PRECIPITATION ASSOCIATED
WITH THIS WAVE OVER FAR NORTHERN KANSAS THIS MORNING. THE LATEST
RUNS OF THE RUC13 ARE ALSO DRY BUT IT DOES TRY TO DEVELOP SOME
LIGHT PRECIPITATION OVER SOUTH CENTRAL KANSAS TOWARD MIDDAY. BASED
ON CURRENT RADAR TRENDS, HAVE OPTED TO LOWER POPS ACROSS WEST
CENTRAL KANSAS THIS MORNING AND REMOVE THE MENTION OF SPRINKLES
FROM THE FORECAST. THIS WILL HAVE TO BE WATCHED FOR THE NEXT FEW
HOURS FOR ANY CHANGES IN THE CURRENT RADAR TRENDS.
ONCE THE FIRST WAVE MOVES OUT OF WESTERN KANSAS, WE SHOULD SEE AN
INCREASE IN SUNSHINE FOR A WHILE UNTIL CIRRUS ASSOCIATED WITH THE
NEXT WAVE BEGINS TO MOVE IN FROM THE WEST. THIS COULD HELP BOOST
TEMPERATURES UP A LITTLE THIS AFTERNOON AND HAVE ADJUSTED TODAY`S
HIGH TEMPERATURES UP A BIT ESPECIALLY OVER CENTRAL KANSAS.
THE NEXT WAVE WILL MOVE OUT OVER THE CENTRAL HIGH PLAINS THIS
EVENING AND SHOULD BE EAST OF THE AREA BY MIDNIGHT. AM NOT
EXPECTING ANY SIGNIFICANT PRECIPITATION WITH THIS WAVE AS WELL.
HAVE LOWERED SUNDAY NIGHTS LOW TEMPERATURES A FEW DEGREES CLOSER
TO THE NAM MOS NUMBERS.
.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 403 AM CST SUN DEC 16 2012
THE MAJOR ADJUSTMENTS TO THE EXTENDED FORECAST OCCURRED IN THE
WEDNESDAY AND WEDNESDAY NIGHT TIMEFRAME, WHEN THE POTENTIAL FOR A
DYNAMIC LOW TO DEVELOP OVER THE HIGH PLAINS, BRINGING GOOD POTENTIAL
FOR WINDY AND SNOWY CONDITIONS.
THE RELATIVELY MILD TEMPERATURES WILL CONTINUE ON MONDAY AND
TUESDAY, AS A FAST MOVING PACIFIC JET SPREADS INTO THE NATIONS
INTERIOR, FORMING A PROGRESSIVE FLAT RIDGE THAT LIFTS INTO THE
EASTERN HALF OF THE NATION BY WEDNESDAY. THE POSITION OF THE JET AND
THE RELATIVE HUMIDITY FIELDS OF MODEL LOWER AND MID TROPOSPHERIC
LAYERS SUGGEST MOSTLY SUNNY CONDITIONS SHOULD BE EXPERIENCED ACROSS
WESTERN KANSAS MONDAY AND TUESDAY. EARLY IN THE PERIOD LIGHT NORTHERLY
WINDS ASSOCIATED WITH THE RETREATING NORTHERN PLAINS HIGH WILL
BECOME MORE SOUTHWESTERLY BY TUESDAY AS SURFACE TROUGHING DEVELOPS
ACROSS THE DAKOTAS. MODEL CONSENSUS CONTINUES TO SUPPORT HIGHS
REACHING THE 50S. TUESDAY MAY BE AROUND 5 DEGREES WARMER WITH
TEMPERATURES REACHING AROUND 60 DEGREES WITH WEAK DOWNSLOPING
SURFACE WINDS, ESPECIALLY ACROSS SOUTH CENTRAL KANSAS.
THE UPPER FLOW WILL BE RAPIDLY DEVELOPING INTO A STRONGLY AMPLIFIED
UPPER TROUGH EARLY WEDNESDAY, AND DRIVE A COLD FRONT THROUGH WESTERN
KANSAS WEDNESDAY MORNING. BOTH THE ECMWF AND GFS DEVELOP A SURFACE
TO 700 LOW POLEWARD TILTED FROM NORTHERN OKLAHOMA INTO KANSAS. THIS
SHOULD PRODUCE A PERIOD OF MID LEVEL FRONTOGENETIC FORCING WITH COLD
ENOUGH AIR FOR SNOW ACCUMULATION TO DEVELOP BEHIND THE SURFACE COLD
FRONT. THE INTENSITY AND LOCATIONS ARE HOWEVER STILL MUCH OF AN
UNCERTAINTY AT THIS TIME. REGARDLESS, WE`VE INCREASED POPS IN THE
WEDNESDAY TIMEFRAME AND FOLLOWED THE COLDER MODEL TRENDS FOR
TEMPERATURES INTO THURSDAY AND THURSDAY NIGHT. WE USED A SLIGHTLY
DOWNWARD ADJUSTED ECMWF QPF FORECAST. BASED ON TEMPERATURES NOT
EXPECTED TO BE EXCEEDING COLD WEDNESDAY, AND WINDY CONDITIONS BEHIND
THE BOUNDARY, A CONSERVATIVE 8:1 SNOW RATIO WAS USED FOR THE SNOW
ACCUMULATION. THAT PRODUCES SNOWFALL AMOUNTS RANGING FROM AROUND A
HALF INCH TO AN INCH AN A HALF. ADDITIONAL MODEL RUNS MAY SHED MORE
INSIGHT ON WHETHER SIGNIFICANT IMPACTS MAY OCCUR, BUT WITH THESE
KIND OF SNOW TOTALS AND WIND SPEEDS, HEADLINES DON`T APPEAR LIKELY
AT THIS TIME.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 544 AM CST SUN DEC 16 2012
NORTHEAST UPSLOPE FLOW ACROSS CENTRAL KANSAS IS CREATING WIDESPREAD
DENSE FOG, EXPANDING WESTWARD THIS MORNING. OBSERVATIONS FROM GREAT
BEND AND SURROUNDING LOCATIONS CONFIRMED THE LOW VISIBILITIES, AND
THE AREA OF EXPANSIVE FOG CAN BE SEEN ON THE 11-3.9 MICRON SATELLITE
CHANNEL. THIS FOG WILL LIKELY AFFECT THE KDDC TERMINAL PERHAPS
THROUGH MID MORNING. LESS CONFIDENCE EXIST OF THE SAME IMPACTS AT
KGCK AT THIS TIME.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 47 24 54 29 / 10 10 0 0
GCK 47 22 52 28 / 10 10 0 0
EHA 49 25 54 31 / 10 0 0 0
LBL 50 22 54 29 / 10 10 0 0
HYS 42 24 52 28 / 10 10 0 0
P28 51 29 57 30 / 10 0 0 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 10 AM CST THIS MORNING FOR KSZ031-045-
046-064>066-078>081-089-090.
&&
$$
SYNOPSIS...GERARD
SHORT TERM...GERARD
LONG TERM...RUSSELL
AVIATION...RUSSELL
AREA FORECAST DISCUSSION...UPDATED
NWS TOPEKA KS
420 AM CST SUN DEC 16 2012
.UPDATE...
AFTER MAKING SOME CALLS ACROSS EAST CENTRAL KS...IT APPEARS AS
THOUGH THE HIGH CLOUDS HAVE NOT DIMINISHED THE DENSE FOG. NOW THAT
SKIES ARE CLEARING OUT AGAIN...VISIBILITIES ARE LIKELY TO REMAIN
DOWN TO A QUARTER OF A MILE...AND WE HAVE ISSUED A DENSE FOG
ADVISORY THROUGH MID MORNING.
&&
.DISCUSSION...
09Z WATER VAPOR IMAGERY SHOWS A COMPACT SHORTWAVE OVER THE NM/CO
ROCKIES. A SECOND SHORTWAVE WAS NOTED OVER THE PACIFIC NORTHWEST. AT
THE SURFACE...WEAK RIDGING WAS SEEN FROM THE NORTHERN PLAINS INTO
NORTHERN KS.
FOR TODAY THROUGH MONDAY...A RATHER DISORGANIZED CYCLONIC FLOW IS
PROGGED TO AFFECT THE AREA WITH THE SHORTWAVES NOTED ON WATER VAPOR
TRAVERSING THE AREA. INITIALLY FORECAST SOUNDINGS FROM THE RAP AND
NAM SHOW SOME MID LEVEL DRY AIR THAT HAS TO BE OVERCOME WITH THE
BETTER MID LEVEL SATURATION REMAINING JUST NORTH OF THE STATE LINE.
WITH THIS IN MIND AND THE MODELS SHOWING THE SHORTWAVE OVER NM/CO
WEAKENING AS IT MOVES EAST...WILL MAINTAIN THE MENTION OF FLURRIES
AND OR SPRINKLES ACROSS THE FAR NORTHERN COUNTIES THINKING THAT ANY
PRECIP WILL NOT BE MEASURABLE. IT SEEMS THAT DRY LOW LEVELS FOR
TONIGHT AND MONDAY MORNING WILL ALSO LIMIT PRECIP CHANCES AS THE
WAVE OVER THE PACIFIC NORTHWEST KICKS THE LONGWAVE TROUGH EAST. WITH
WEAK COLD AIR ADVECTION AND INCREASING CLOUDS...TEMPS SHOULD BE
COOLER TODAY WITH HIGHS GENERALLY IN THE 40S. LOW LEVEL WINDS ARE
EXPECTED TO TURN BACK FROM THE SOUTH AND SOUTHWEST FOR MONDAY...SO
TEMPS SHOULD BEGIN TO MODERATE.
THE NEXT CHANCE FOR MEASURABLE PRECIP CONTINUES TO LOOK LIKE IT WILL
OCCUR WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT...AND WE MAY END UP
SEEING THE FIRST SNOWFALL OF THE WINTER. THE GFS AND ECMWF APPEAR TO
BE CONVERGING ON A PROGRESSIVE SYSTEM MOVING ACROSS THE PLAINS AS
THE NEXT SHORTWAVE TROUGH PROPAGATES ACROSS NORTH AMERICA. WHILE THE
GFS IS NOTABLY FASTER WITH THE SURFACE LOW...THE TRACKS OF THE
SYSTEM ARE SIMILAR FROM BOTH MODEL SOLUTIONS. ALSO BECAUSE OF THE
PROGRESSIVE NATURE OF THE SYSTEM AND BOTH MODELS DEEPENING THE
SURFACE LOW AS IT PASSES SOUTHEAST OF THE FORECAST AREA...THE COLD
AIR IS QUICKER TO PUSH SOUTH DURING THE AFTERNOON WEDNESDAY WITH
TEMPS POTENTIALLY FALLING DURING THE AFTERNOON. THERE APPEARS TO BE
DECENT QG VECTOR CONVERGENCE WITH THE SYSTEM AND MODELS SHOW GOOD
MID LEVEL FRONTOGENESIS NORTHWEST OF THE SURFACE LOW TRACK. GIVEN
THE TEMP PROFILES RAPIDLY COOLING AND THE MESOSCALE FORCING...THINK
THERE COULD BE A BAND OF SNOW FORM LATE WEDNESDAY AFTERNOON AND
THROUGH THE NIGHT. CROSS SECTIONS FROM THE GFS AND ECMWF SUGGEST THE
STRONGER VERTICAL MOTION WILL OCCUR BETWEEN 00 AND 06Z THUR WITH DRY
AIR AND SUBSIDENCE QUICKLY FILLING IN TOWARDS 12Z. BECAUSE OF THE
PROGRESSIVE NATURE OF THE SYSTEM...SNOW AMOUNTS LOOK TO BE ON THE
ORDER OF A COUPLE INCHES.
SOMEWHAT ZONAL FLOW DEVELOPS IN THE WAKE OF THE WEDNESDAY NIGHT
SYSTEM...WITH THE UPPER LEVEL JET SETTING UP ACROSS THE SOUTHERN
HALF OF THE COUNTRY. THIS SHOULD KEEP A DRY AND COOL AIRMASS OVER
THE PLAINS FOR THURSDAY NIGHT THROUGH SATURDAY.
WOLTERS
&&
.AVIATION...
MOSTLY CLEAR SKIES ACROSS THE TERMINALS HAS LED TO MVFR/IFR FOG TO
DEVELOP OVER THE PAST HOUR EXCEPT IN KTOP. WITH LIGHT WINDS...EXPECT
MORE IFR/VLIFR FOG TO DEVELOP NEXT 1-3 HOURS. HOWEVER...AFT 08-09Z
SOME MID AND HIGH CLOUDS MAY BE OFFSETTING FACTOR ALONG WITH DRY AIR
JUST ABOVE THE FOG...SO HAVE INCREASED VSBYS AFT THAT TIME THROUGH
ON THRU 14Z. BEYOND 14Z HAVE CONTINUED VFR CONDITIONS WITH LIGHT
NORTH/NORTHEAST WINDS AND MID LEVEL AC DECK AROUND 12 KFT.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY FOR KSZ054>056-058-059 UNTIL 9 AM TODAY.
&&
$$
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
404 AM CST SUN DEC 16 2012
.SYNOPSIS...
ISSUED AT 341 AM CST SUN DEC 16 2012
THE 00Z UPPER AIR ANALYSIS SHOWED A SOMEWHAT SPLIT FLOW PATTERN
OVER WESTERN NORTH AMERICA. IN THE NORTH, SHORTWAVE TROUGHS WERE
MOVING OVER THE CENTRAL CANADIAN PRAIRIE AND INTO BRITISH COLUMBIA.
FARTHER SOUTH, THE SHORTWAVE TROUGH THAT MOVED OUT OF THE CENTRAL
HIGH PLAINS SUNDAY MORNING WAS OVER THE GREAT LAKES REGION. FARTHER
WEST, A COMPACT SHORTWAVE WAS MOVING ACROSS SOUTHERN COLORADO WHILE
ANOTHER WAVE WAS ON ITS HEELS OVER THE GREAT BASIN INTO ARIZONA.
THE REGIONAL RADAR MOSAIC SHOWS A SMALL AREA OF LIGHT TO MODERATE
SNOW OVER FAR SOUTHWEST NEBRASKA, WHICH APPEARS TO BE FORCED BY
SOME MID LEVEL FRONTOGENESIS. RADAR RETURNS OVER SOUTHERN COLORADO
HAVE BEEN FAIRLY LIGHT SO FAR THIS MORNING.
&&
.SHORT TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 341 AM CST SUN DEC 16 2012
THE COLORADO SHORTWAVE HAS BEEN PROGRESSING STEADILY EASTWARD PER
SATELLITE LOOPS. EXTRAPOLATING IT AT ITS CURRENT SPEED WOULD PUT IT
OVER SOUTH CENTRAL KANSAS BY 18Z. THE 00Z NAM HAS A PRETTY GOOD
HANDLE ON THIS. THIS MODEL ALSO KEEPS ANY PRECIPITATION ASSOCIATED
WITH THIS WAVE OVER FAR NORTHERN KANSAS THIS MORNING. THE LATEST
RUNS OF THE RUC13 ARE ALSO DRY BUT IT DOES TRY TO DEVELOP SOME
LIGHT PRECIPITATION OVER SOUTH CENTRAL KANSAS TOWARD MIDDAY. BASED
ON CURRENT RADAR TRENDS, HAVE OPTED TO LOWER POPS ACROSS WEST
CENTRAL KANSAS THIS MORNING AND REMOVE THE MENTION OF SPRINKLES
FROM THE FORECAST. THIS WILL HAVE TO BE WATCHED FOR THE NEXT FEW
HOURS FOR ANY CHANGES IN THE CURRENT RADAR TRENDS.
ONCE THE FIRST WAVE MOVES OUT OF WESTERN KANSAS, WE SHOULD SEE AN
INCREASE IN SUNSHINE FOR A WHILE UNTIL CIRRUS ASSOCIATED WITH THE
NEXT WAVE BEGINS TO MOVE IN FROM THE WEST. THIS COULD HELP BOOST
TEMPERATURES UP A LITTLE THIS AFTERNOON AND HAVE ADJUSTED TODAY`S
HIGH TEMPERATURES UP A BIT ESPECIALLY OVER CENTRAL KANSAS.
THE NEXT WAVE WILL MOVE OUT OVER THE CENTRAL HIGH PLAINS THIS
EVENING AND SHOULD BE EAST OF THE AREA BY MIDNIGHT. AM NOT
EXPECTING ANY SIGNIFICANT PRECIPITATION WITH THIS WAVE AS WELL.
HAVE LOWERED SUNDAY NIGHTS LOW TEMPERATURES A FEW DEGREES CLOSER
TO THE NAM MOS NUMBERS.
.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 403 AM CST SUN DEC 16 2012
THE MAJOR ADJUSTMENTS TO THE EXTENDED FORECAST OCCURRED IN THE
WEDNESDAY AND WEDNESDAY NIGHT TIMEFRAME, WHEN THE POTENTIAL FOR A
DYNAMIC LOW TO DEVELOP OVER THE HIGH PLAINS, BRINGING GOOD POTENTIAL
FOR WINDY AND SNOWY CONDITIONS.
THE RELATIVELY MILD TEMPERATURES WILL CONTINUE ON MONDAY AND
TUESDAY, AS A FAST MOVING PACIFIC JET SPREADS INTO THE NATIONS
INTERIOR, FORMING A PROGRESSIVE FLAT RIDGE THAT LIFTS INTO THE
EASTERN HALF OF THE NATION BY WEDNESDAY. THE POSITION OF THE JET AND
THE RELATIVE HUMIDITY FIELDS OF MODEL LOWER AND MID TROPOSPHERIC
LAYERS SUGGEST MOSTLY SUNNY CONDITIONS SHOULD BE EXPERIENCED ACROSS
WESTERN KANSAS MONDAY AND TUESDAY. EARLY IN THE PERIOD LIGHT NORTHERLY
WINDS ASSOCIATED WITH THE RETREATING NORTHERN PLAINS HIGH WILL
BECOME MORE SOUTHWESTERLY BY TUESDAY AS SURFACE TROUGHING DEVELOPS
ACROSS THE DAKOTAS. MODEL CONSENSUS CONTINUES TO SUPPORT HIGHS
REACHING THE 50S. TUESDAY MAY BE AROUND 5 DEGREES WARMER WITH
TEMPERATURES REACHING AROUND 60 DEGREES WITH WEAK DOWNSLOPING
SURFACE WINDS, ESPECIALLY ACROSS SOUTH CENTRAL KANSAS.
THE UPPER FLOW WILL BE RAPIDLY DEVELOPING INTO A STRONGLY AMPLIFIED
UPPER TROUGH EARLY WEDNESDAY, AND DRIVE A COLD FRONT THROUGH WESTERN
KANSAS WEDNESDAY MORNING. BOTH THE ECMWF AND GFS DEVELOP A SURFACE
TO 700 LOW POLEWARD TILTED FROM NORTHERN OKLAHOMA INTO KANSAS. THIS
SHOULD PRODUCE A PERIOD OF MID LEVEL FRONTOGENETIC FORCING WITH COLD
ENOUGH AIR FOR SNOW ACCUMULATION TO DEVELOP BEHIND THE SURFACE COLD
FRONT. THE INTENSITY AND LOCATIONS ARE HOWEVER STILL MUCH OF AN
UNCERTAINTY AT THIS TIME. REGARDLESS, WE`VE INCREASED POPS IN THE
WEDNESDAY TIMEFRAME AND FOLLOWED THE COLDER MODEL TRENDS FOR
TEMPERATURES INTO THURSDAY AND THURSDAY NIGHT. WE USED A SLIGHTLY
DOWNWARD ADJUSTED ECMWF QPF FORECAST. BASED ON TEMPERATURES NOT
EXPECTED TO BE EXCEEDING COLD WEDNESDAY, AND WINDY CONDITIONS BEHIND
THE BOUNDARY, A CONSERVATIVE 8:1 SNOW RATIO WAS USED FOR THE SNOW
ACCUMULATION. THAT PRODUCES SNOWFALL AMOUNTS RANGING FROM AROUND A
HALF INCH TO AN INCH AN A HALF. ADDITIONAL MODEL RUNS MAY SHED MORE
INSIGHT ON WHETHER SIGNIFICANT IMPACTS MAY OCCUR, BUT WITH THESE
KIND OF SNOW TOTALS AND WIND SPEEDS, HEADLINES DON`T APPEAR LIKELY
AT THIS TIME.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1209 AM CST SUN DEC 16 2012
AN UPPER LEVEL DISTURBANCE WILL MOVE OUT OF SOUTHERN COLORADO ACROSS
SOUTHERN KANSAS LATE TONIGHT THROUGH SUNDAY MORNING. THIS WILL BRING
SCATTERED TO OCCASIONALLY BROKEN MID TO HIGH LEVEL CLOUDS, ALONG
WITH POSSIBLE SPRINKLES, ACROSS WESTERN KANSAS THROUGH THE FIRST
PART OF THE PERIOD. THERE IS A VERY SMALL CHANCE FOR A BRIEF PERIOD
OF IFR CIGS AT GARDEN CITY AND DODGE CITY BETWEEN 12Z AND 15Z BUT
CONFIDENCE IS TOO LOW TO ADD IT TO THE TAFS AT THIS TIME.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 47 24 54 29 / 10 10 0 0
GCK 47 22 52 28 / 10 10 0 0
EHA 49 25 54 31 / 10 0 0 0
LBL 50 22 54 29 / 10 10 0 0
HYS 42 24 52 28 / 10 10 0 0
P28 51 29 57 30 / 10 0 0 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...GERARD
SHORT TERM...GERARD
LONG TERM...RUSSELL
AVIATION...GERARD
AREA FORECAST DISCUSSION...UPDATED
NWS TOPEKA KS
346 AM CST SUN DEC 16 2012
.DISCUSSION...
09Z WATER VAPOR IMAGERY SHOWS A COMPACT SHORTWAVE OVER THE NM/CO
ROCKIES. A SECOND SHORTWAVE WAS NOTED OVER THE PACIFIC NORTHWEST. AT
THE SURFACE...WEAK RIDGING WAS SEEN FROM THE NORTHERN PLAINS INTO
NORTHERN KS.
FOR TODAY THROUGH MONDAY...A RATHER DISORGANIZED CYCLONIC FLOW IS
PROGGED TO AFFECT THE AREA WITH THE SHORTWAVES NOTED ON WATER VAPOR
TRAVERSING THE AREA. INITIALLY FORECAST SOUNDINGS FROM THE RAP AND
NAM SHOW SOME MID LEVEL DRY AIR THAT HAS TO BE OVERCOME WITH THE
BETTER MID LEVEL SATURATION REMAINING JUST NORTH OF THE STATE LINE.
WITH THIS IN MIND AND THE MODELS SHOWING THE SHORTWAVE OVER NM/CO
WEAKENING AS IT MOVES EAST...WILL MAINTAIN THE MENTION OF FLURRIES
AND OR SPRINKLES ACROSS THE FAR NORTHERN COUNTIES THINKING THAT ANY
PRECIP WILL NOT BE MEASURABLE. IT SEEMS THAT DRY LOW LEVELS FOR
TONIGHT AND MONDAY MORNING WILL ALSO LIMIT PRECIP CHANCES AS THE
WAVE OVER THE PACIFIC NORTHWEST KICKS THE LONGWAVE TROUGH EAST. WITH
WEAK COLD AIR ADVECTION AND INCREASING CLOUDS...TEMPS SHOULD BE
COOLER TODAY WITH HIGHS GENERALLY IN THE 40S. LOW LEVEL WINDS ARE
EXPECTED TO TURN BACK FROM THE SOUTH AND SOUTHWEST FOR MONDAY...SO
TEMPS SHOULD BEGIN TO MODERATE.
THE NEXT CHANCE FOR MEASURABLE PRECIP CONTINUES TO LOOK LIKE IT WILL
OCCUR WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT...AND WE MAY END UP
SEEING THE FIRST SNOWFALL OF THE WINTER. THE GFS AND ECMWF APPEAR TO
BE CONVERGING ON A PROGRESSIVE SYSTEM MOVING ACROSS THE PLAINS AS
THE NEXT SHORTWAVE TROUGH PROPAGATES ACROSS NORTH AMERICA. WHILE THE
GFS IS NOTABLY FASTER WITH THE SURFACE LOW...THE TRACKS OF THE
SYSTEM ARE SIMILAR FROM BOTH MODEL SOLUTIONS. ALSO BECAUSE OF THE
PROGRESSIVE NATURE OF THE SYSTEM AND BOTH MODELS DEEPENING THE
SURFACE LOW AS IT PASSES SOUTHEAST OF THE FORECAST AREA...THE COLD
AIR IS QUICKER TO PUSH SOUTH DURING THE AFTERNOON WEDNESDAY WITH
TEMPS POTENTIALLY FALLING DURING THE AFTERNOON. THERE APPEARS TO BE
DECENT QG VECTOR CONVERGENCE WITH THE SYSTEM AND MODELS SHOW GOOD
MID LEVEL FRONTOGENESIS NORTHWEST OF THE SURFACE LOW TRACK. GIVEN
THE TEMP PROFILES RAPIDLY COOLING AND THE MESOSCALE FORCING...THINK
THERE COULD BE A BAND OF SNOW FORM LATE WEDNESDAY AFTERNOON AND
THROUGH THE NIGHT. CROSS SECTIONS FROM THE GFS AND ECMWF SUGGEST THE
STRONGER VERTICAL MOTION WILL OCCUR BETWEEN 00 AND 06Z THUR WITH DRY
AIR AND SUBSIDENCE QUICKLY FILLING IN TOWARDS 12Z. BECAUSE OF THE
PROGRESSIVE NATURE OF THE SYSTEM...SNOW AMOUNTS LOOK TO BE ON THE
ORDER OF A COUPLE INCHES.
SOMEWHAT ZONAL FLOW DEVELOPS IN THE WAKE OF THE WEDNESDAY NIGHT
SYSTEM...WITH THE UPPER LEVEL JET SETTING UP ACROSS THE SOUTHERN
HALF OF THE COUNTRY. THIS SHOULD KEEP A DRY AND COOL AIRMASS OVER
THE PLAINS FOR THURSDAY NIGHT THROUGH SATURDAY.
WOLTERS
&&
.AVIATION...
MOSTLY CLEAR SKIES ACROSS THE TERMINALS HAS LED TO MVFR/IFR FOG TO
DEVELOP OVER THE PAST HOUR EXCEPT IN KTOP. WITH LIGHT WINDS...EXPECT
MORE IFR/VLIFR FOG TO DEVELOP NEXT 1-3 HOURS. HOWEVER...AFT 08-09Z
SOME MID AND HIGH CLOUDS MAY BE OFFSETTING FACTOR ALONG WITH DRY AIR
JUST ABOVE THE FOG...SO HAVE INCREASED VSBYS AFT THAT TIME THROUGH
ON THRU 14Z. BEYOND 14Z HAVE CONTINUED VFR CONDITIONS WITH LIGHT
NORTH/NORTHEAST WINDS AND MID LEVEL AC DECK AROUND 12 KFT.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
342 AM CST SUN DEC 16 2012
...UPDATED SYNOPSIS AND SHORT TERM DISCUSSION...
.SYNOPSIS...
ISSUED AT 341 AM CST SUN DEC 16 2012
THE 00Z UPPER AIR ANALYSIS SHOWED A SOMEWHAT SPLIT FLOW PATTERN
OVER WESTERN NORTH AMERICA. IN THE NORTH, SHORTWAVE TROUGHS WERE
MOVING OVER THE CENTRAL CANADIAN PRAIRIE AND INTO BRITISH COLUMBIA.
FARTHER SOUTH, THE SHORTWAVE TROUGH THAT MOVED OUT OF THE CENTRAL
HIGH PLAINS SUNDAY MORNING WAS OVER THE GREAT LAKES REGION. FARTHER
WEST, A COMPACT SHORTWAVE WAS MOVING ACROSS SOUTHERN COLORADO WHILE
ANOTHER WAVE WAS ON ITS HEELS OVER THE GREAT BASIN INTO ARIZONA.
THE REGIONAL RADAR MOSAIC SHOWS A SMALL AREA OF LIGHT TO MODERATE
SNOW OVER FAR SOUTHWEST NEBRASKA, WHICH APPEARS TO BE FORCED BY
SOME MID LEVEL FRONTOGENESIS. RADAR RETURNS OVER SOUTHERN COLORADO
HAVE BEEN FAIRLY LIGHT SO FAR THIS MORNING.
&&
.SHORT TERM...(TODAY THROUGH TONIGHT)
ISSUED AT 341 AM CST SUN DEC 16 2012
THE COLORADO SHORTWAVE HAS BEEN PROGRESSING STEADILY EASTWARD PER
SATELLITE LOOPS. EXTRAPOLATING IT AT ITS CURRENT SPEED WOULD PUT IT
OVER SOUTH CENTRAL KANSAS BY 18Z. THE 00Z NAM HAS A PRETTY GOOD
HANDLE ON THIS. THIS MODEL ALSO KEEPS ANY PRECIPITATION ASSOCIATED
WITH THIS WAVE OVER FAR NORTHERN KANSAS THIS MORNING. THE LATEST
RUNS OF THE RUC13 ARE ALSO DRY BUT IT DOES TRY TO DEVELOP SOME
LIGHT PRECIPITATION OVER SOUTH CENTRAL KANSAS TOWARD MIDDAY. BASED
ON CURRENT RADAR TRENDS, HAVE OPTED TO LOWER POPS ACROSS WEST
CENTRAL KANSAS THIS MORNING AND REMOVE THE MENTION OF SPRINKLES
FROM THE FORECAST. THIS WILL HAVE TO BE WATCHED FOR THE NEXT FEW
HOURS FOR ANY CHANGES IN THE CURRENT RADAR TRENDS.
ONCE THE FIRST WAVE MOVES OUT OF WESTERN KANSAS, WE SHOULD SEE AN
INCREASE IN SUNSHINE FOR A WHILE UNTIL CIRRUS ASSOCIATED WITH THE
NEXT WAVE BEGINS TO MOVE IN FROM THE WEST. THIS COULD HELP BOOST
TEMPERATURES UP A LITTLE THIS AFTERNOON AND HAVE ADJUSTED TODAY`S
HIGH TEMPERATURES UP A BIT ESPECIALLY OVER CENTRAL KANSAS.
THE NEXT WAVE WILL MOVE OUT OVER THE CENTRAL HIGH PLAINS THIS
EVENING AND SHOULD BE EAST OF THE AREA BY MIDNIGHT. AM NOT
EXPECTING ANY SIGNIFICANT PRECIPITATION WITH THIS WAVE AS WELL.
HAVE LOWERED SUNDAY NIGHTS LOW TEMPERATURES A FEW DEGREES CLOSER
TO THE NAM MOS NUMBERS.
.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 318 PM CST SAT DEC 15 2012
TRANQUIL WEATHER IS ANTICIPATED SUNDAY NIGHT THROUGH TUESDAY NIGHT
MID TO UPPER LEVEL RIDGING BUILDS ACROSS THE ROCKIES AND PLAINS AND
HIGH PRESSURE POSITIONS ITSELF ACROSS THE SOUTHERN ROCKIES. THE
ATMOSPHERIC COLUMN WILL BE FAIRLY DRY BRINGING PARTLY CLOUDY SKIES
AND DRY CONDITIONS TO SOUTHWEST KANSAS. WINDS WILL GENERALLY BE FROM
THE WEST MONDAY INTO TUESDAY THEN SHIFTING MORE OF A SOUTHERLY
DIRECTION TUESDAY NIGHT. LOWS MONDAY MORNING WILL BE IN THE 20S
WITH HIGHS MONDAY AFTERNOON REACHING TO THE LOWER 50S. LOWS TUESDAY
MORNING ARE FORECASTED TO RANGE FROM THE UPPER 20S TO AROUND 30
DEGREES WITH HIGHS TUESDAY AFTERNOON IN THE MID TO UPPER 50S. LOWS
BY SUNRISE WEDNESDAY ARE FORECASTED TO BE IN THE LOWER 30S.
THE NEXT STORM SYSTEM STARTS TO AFFECT WESTERN KANSAS ON WEDNESDAY
AS AN UPPER LEVEL SHORTWAVE AND STRONG UPPER LEVEL JET MOVES INTO
THE CENTRAL ROCKIES. MID LEVEL MOISTURE ADVECTS INTO THE AREA AS THE
DAY PROGRESSES BRINGING AN INCREASE IN CLOUDINESS. MEDIUM RANGE
MODELS DIFFER SLIGHTLY ON THE SPEED OF THIS SYSTEM WITH THE GFS
BEING THE FASTEST AND THE ECMWF SLIGHTLY SLOWER. NEVERTHELESS, THE
MODELS DEPICT A STATIONARY FRONT MOVING INTO WEST CENTRAL KANSAS
WEDNESDAY AFTERNOON WITH AN INCREASE IN PRECIPITATION CHANCES ACROSS
THE SAME AREA WEDNESDAY EVENING. PRECIPITATION CHANCES THEN SPREAD
ACROSS THE REMAINDER OF SOUTHWEST KANSAS WEDNESDAY NIGHT WITH A COLD
FRONT MOVING THROUGH WESTERN KANSAS. WINDS SHIFT TO THE NORTH BEHIND
THIS FRONT. IT IS TOO FAR OUT TO PIN POINT PRECIPITATION TYPE BUT
FIRST GUESS HAS PRECIPITATION STARTING OUT AS RAIN WEDNESDAY EVENING
CHANGING OVER TO ALL SNOW AFTER MIDNIGHT. THIS SYSTEM THEN MOVES OUT
OF THE AREA BY THURSDAY MORNING WITH DECREASING CLOUDINESS FROM WEST
TO EAST. WITH CLOUDINESS AND COOLER TEMPERATURES BEHIND THE FRONT,
WEDNESDAY`S HIGHS ARE FORECASTED TO RANGE FROM THE LOWER 40S ACROSS
WEST CENTRAL KANSAS TO UPPER 50S ACROSS THE KS/OK BORDER. LOWS
THURSDAY MORNING ARE FORECASTED TO DIP INTO THE 20S.
ZONAL WEST TO EAST ZONAL FLOW DEVELOPS THURSDAY INTO THE WEEKEND
WITH HIGH PRESSURE BEING THE DOMINATE FEATURE ACROSS THE SOUTHERN
PLAINS AT THE SURFACE. THIS WILL SUPPRESS ANY ACTIVITY ACROSS
WESTERN KANSAS BRINGING MOSTLY CLEAR SKIES AND DRY CONDITIONS. HIGHS
ARE FORECASTED TO BE IN THE UPPER 30S AND LOWER 40S THURSDAY THEN IN
THE 40S FRIDAY. LOWS FRIDAY AND SATURDAY MORNING WILL GENERALLY BE
IN THE LOWER TO MID 20S.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1209 AM CST SUN DEC 16 2012
AN UPPER LEVEL DISTURBANCE WILL MOVE OUT OF SOUTHERN COLORADO ACROSS
SOUTHERN KANSAS LATE TONIGHT THROUGH SUNDAY MORNING. THIS WILL BRING
SCATTERED TO OCCASIONALLY BROKEN MID TO HIGH LEVEL CLOUDS, ALONG
WITH POSSIBLE SPRINKLES, ACROSS WESTERN KANSAS THROUGH THE FIRST
PART OF THE PERIOD. THERE IS A VERY SMALL CHANCE FOR A BRIEF PERIOD
OF IFR CIGS AT GARDEN CITY AND DODGE CITY BETWEEN 12Z AND 15Z BUT
CONFIDENCE IS TOO LOW TO ADD IT TO THE TAFS AT THIS TIME.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 47 24 54 29 / 10 10 0 0
GCK 47 22 52 28 / 10 10 0 0
EHA 49 25 54 31 / 10 0 0 0
LBL 50 22 54 29 / 10 10 0 0
HYS 42 24 52 28 / 10 10 0 0
P28 51 29 57 30 / 10 0 0 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...GERARD
SHORT TERM...GERARD
LONG TERM...HOVORKA_42
AVIATION...GERARD
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
955 PM EST MON DEC 17 2012
.SYNOPSIS...
LOW PRESSURE WILL LIFT NORTHEAST OF THE UPPER OHIO VALLEY
OVERNIGHT AND PULL A COLD FRONT ACROSS THE REGION TUESDAY. THIS
WILL BRING RAIN SHOWERS TO THE AREA UNTIL TUESDAY EVENING.
&&
.NEAR TERM /THROUGH TUESDAY/...
03Z ENHANCED SHORT TERM FORECAST UPDATE HAS BEEN ISSUED TO REMOVE
THUNDERSTORM WORDING AND TO MAKE ADJUSTMENTS TO POP GRIDS BASED
ON RECENT RADAR TRENDS.
THE LATEST RAP MID-LEVEL ANALYSIS INDICATES A BROAD 500MB TROUGH
EXTENDING FROM THE NORTHERN PLAINS TO THE GREAT LAKES. AT THE
SURFACE...A 1001MB LOW IS CENTERED NEAR BEAVER FALLS. A LINE OF
CONVECTION FROM EARLIER HAS DIMINISHED TO AN AREA OF SHOWERS
MOVING INTO WESTERN PA. NUMEROUS SHOWERS ASSOCIATED WITH THE MID-
LEVEL TROUGH ARE UPSTREAM IN WESTERN OHIO.
TONIGHT...THE SURFACE LOW WILL SHIFT NORTHEASTWARD INTO
WESTERN NY AND THE MID-LEVEL TROUGH WILL SLIDE INTO THE UPPER OHIO
VALLEY. FORCING FROM THE TROUGH WILL ALLOW FOR NUMEROUS SHOWERS TO
CROSS THE AREA OVERNIGHT. CAA WILL BE LIMITED DESPITE WINDS SHIFTING
TO NORTHERLY IN THE WAKE OF THE LOW. LOWS ARE FAIRLY CLOSE TO LAMP
GUIDANCE...ONLY DROPPING TO NEAR 40 ACROSS MUCH OF THE AREA BY
DAWN.
TUESDAY...SHOWERS WILL DIMINISH WEST TO EAST AS DEEP MOISTURE IS
SHUNTED EAST DURING THE DAY. COLD ADVECTION AT 850MB WILL BEGIN
MIDDAY BUT TEMPERATURES NOT NEARLY COLD ENOUGH FOR ANY LAKE
POTENTIAL. TEMPERATURES WILL BE MILD FIRST HALF OF NIGHT THEN
BEGIN TO FALL OFF LATE WITH FROPA. LITTLE RECOVERY EXPECTED FOR
MAX TEMPS TUESDAY.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
BUILDING HIGH PRESSURE WILL END SHOWERS TUESDAY NIGHT. MAY BE A
FEW STRAY SNOW SHOWERS TUESDAY EVENING IN THE RIDGES BUT NOTHING
OF SIGNIFICANCE. A DRY WEDNESDAY WITH WARM ADVECTION HOLDING
TEMPS ABOVE THE SEASONAL AVERAGES. LITTLE DROP OFF IN
TEMPERATURES WEDNESDAY NIGHT IN STRENGTHENING SOUTHERLY FLOW AHEAD
OF APPROACHING STORM SYSTEM FOR THURSDAY.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
LOW PRESSURE OVER ILLINOIS THURSDAY MORNING WILL MOVE OVER LOWER
MICHIGAN BY THURSDAY EVENING AND ONTARIO BY FRIDAY MORNING.
ASSOCIATED FRONT WILL MOVE ACROSS THE REGION DURING THAT TIME
PERIOD. HAVE INCREASED POPS TO CATEGORICAL CONSIDERING AGREEMENT
FROM DETERMINISTIC/ENSEMBLE MODELS. BULK OF THE RAIN WITH THE FRONT
ITSELF WILL FALL DURING THE DAYTIME AS RAIN WITH THURSDAY HIGH
TEMPERATURES IN THE 40S AND 50S...ALTHOUGH PRECIPITATION WILL CHANGE
OVER TO SNOW THURSDAY NIGHT. WITH THE LOW MAKING SLOW PROGRESS TO
THE EAST...WRAPAROUND/LAKE EFFECT SNOW WILL CONTINUE INTO
FRIDAY...AS TEMPERATURES WILL STRUGGLE TO REACH FREEZING. MODELS
CONTINUE TO INDICATE POSSIBILITY OF STRONG WIND GUSTS IN THE 40-50
MPH RANGE...POSSIBLY IN ADVANCE OF THE COLD FRONT BUT MORE LIKELY
AFTER THE FRONTAL PASSAGE THURSDAY NIGHT AND FRIDAY. WILL CONTINUE
MENTION IN THE HWO FOR HIGHER ELEVATIONS...WHICH HAVE THE GREATEST
CHANCE OF REALIZING THESE WIND GUSTS.
MODEL DIFFERENCES BEGIN TO DEVELOP BY FRIDAY NIGHT...WITH 12Z GFS
SHOWING STACKED LOW MOVING OFFSHORE MORE QUICKLY THAN THE ECMWF.
SPEED OF THE DEPARTING LOW WILL DETERMINE HOW LONG FAVORABLE FETCH
WILL PERSIST OFF LAKE ERIE. FOR NOW...HAVE GONE WITH SLOW DECLINE IN
POPS THROUGH THE WEEKEND. EXPECT LITTLE RECOVERY IN
TEMPERATURES...WITH HIGHS A COUPLE OF DEGREES BELOW NORMAL.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
REMNANTS OF EARLIER CONVECTIVE ACTIVITY CONTINUE TO PUSH
NORTHEASTWARD FROM A KBVI TO KMGW LINE AS OF 255Z. THESE WILL
BRING CIGS BACK DOWN FOR A PERIOD...HOWEVER WEAK MIXING BEHIND
THEM SHOULD BRING CIGS BACK UP TEMPORARILY. IFR OR LOWER CIGS
SHOULD AGAIN DEVELOP OVERNIGHT WITH LINGERING LOW LEVEL MOISTURE
AND VERY POOR MIXING. STRONGER MOMENTUM IS SET TO MOVE IN BY
TUESDAY WHEN CIGS WILL RISE AS GUSTS END UP SURFACING ACROSS THE
AREA DURING THE AFTERNOON. FRIES
.OUTLOOK.../TUESDAY NIGHT THROUGH SATURDAY/...
MVFR RESTRICTIONS SHOULD DIMINISH TUESDAY NIGHT WITH LOW PRESSURE.
WEDNESDAY AND WEDNESDAY NIGHT WILL HAVE VFR CONDITIONS...BUT ANOTHER
LOW PRESSURE SYSTEM WILL BRING SHOWERS AND RESTRICTIONS TO ALL SITES
THURSDAY...WITH RAIN CHANGING TO SNOW THURSDAY NIGHT. LAKE EFFECT
SNOW SHOWERS AND RESTRICTIONS ARE EXPECTED TO CONTINUE FRIDAY AND
SATURDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
701 PM EST MON DEC 17 2012
.SYNOPSIS...
LOW PRESSURE WILL LIFT NORTHEAST OF THE UPPER OHIO VALLEY
OVERNIGHT AND PULL A COLD FRONT ACROSS THE REGION TUESDAY. THIS
WILL BRING RAIN SHOWERS TO THE AREA UNTIL TUESDAY EVENING.
&&
.NEAR TERM /THROUGH TUESDAY/...
00Z ENHANCED SHORT TERM FORECAST UPDATE HAS BEEN ISSUED TO REDUCE
THUNDER CHANCES AND PIN DOWN COVERAGE OF SHOWERS OVERNIGHT.
THE LATEST RAP MID-LEVEL ANALYSIS INDICATES A BROAD 500MB TROUGH
EXTENDING FROM THE NORTHERN PLAINS TO THE GREAT LAKES. THE LATEST
SURFACE ANALYSIS INDICATES A 1000MB LOW CENTERED NEAR ZANESVILLE.
A FRONTAL BOUNDARY EXTENDS NORTHEAST OF THE LOW TOWARD ERIE, PA.
WITH THE LOW...A LINE OF CONVECTION IS PUSHING INTO EASTERN
OHIO...BRINGING SUB-SEVERE WIND GUSTS THUS FAR. THIS HAS BEEN DUE
TO THE LACK OF AVAILABLE INSTABILITY DESPITE STRONG SHEAR.
TONIGHT...THE SURFACE LOW WILL SHIFT NORTHEASTWARD INTO WESTERN NY
AND THE MID-LEVEL TROUGH WILL SLIDE INTO THE UPPER OHIO VALLEY.
FORCING FROM THE TROUGH WILL ALLOW FOR NUMEROUS SHOWERS TO CONTINUE
THROUGH MUCH OF THE NIGHT. CAA WILL BE LIMITED DESPITE WINDS
SHIFTING TO NORTHERLY IN THE WAKE OF THE LOW. LOWS ARE FAIRLY
CLOSE TO LAMP GUIDANCE...ONLY DROPPING TO NEAR 40 ACROSS MUCH OF
THE AREA BY DAWN.
TUESDAY...SHOWERS WILL DIMINISH WEST TO EAST AS DEEP MOISTURE IS
SHUNTED EAST DURING THE DAY. COLD ADVECTION AT 850MB WILL BEGIN
MIDDAY BUT TEMPERATURES NOT NEARLY COLD ENOUGH FOR ANY LAKE
POTENTIAL. TEMPERATURES WILL BE MILD FIRST HALF OF NIGHT THEN
BEGIN TO FALL OFF LATE WITH FROPA. LITTLE RECOVERY EXPECTED FOR
MAX TEMPS TUESDAY.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
BUILDING HIGH PRESSURE WILL END SHOWERS TUESDAY NIGHT. MAY BE A
FEW STRAY SNOW SHOWERS TUESDAY EVENING IN THE RIDGES BUT NOTHING
OF SIGNIFICANCE. A DRY WEDNESDAY WITH WARM ADVECTION HOLDING
TEMPS ABOVE THE SEASONAL AVERAGES. LITTLE DROP OFF IN
TEMPERATURES WEDNESDAY NIGHT IN STRENGTHENING SOUTHERLY FLOW AHEAD
OF APPROACHING STORM SYSTEM FOR THURSDAY.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
LOW PRESSURE OVER ILLINOIS THURSDAY MORNING WILL MOVE OVER LOWER
MICHIGAN BY THURSDAY EVENING AND ONTARIO BY FRIDAY MORNING.
ASSOCIATED FRONT WILL MOVE ACROSS THE REGION DURING THAT TIME
PERIOD. HAVE INCREASED POPS TO CATEGORICAL CONSIDERING AGREEMENT
FROM DETERMINISTIC/ENSEMBLE MODELS. BULK OF THE RAIN WITH THE FRONT
ITSELF WILL FALL DURING THE DAYTIME AS RAIN WITH THURSDAY HIGH
TEMPERATURES IN THE 40S AND 50S...ALTHOUGH PRECIPITATION WILL CHANGE
OVER TO SNOW THURSDAY NIGHT. WITH THE LOW MAKING SLOW PROGRESS TO
THE EAST...WRAPAROUND/LAKE EFFECT SNOW WILL CONTINUE INTO
FRIDAY...AS TEMPERATURES WILL STRUGGLE TO REACH FREEZING. MODELS
CONTINUE TO INDICATE POSSIBILITY OF STRONG WIND GUSTS IN THE 40-50
MPH RANGE...POSSIBLY IN ADVANCE OF THE COLD FRONT BUT MORE LIKELY
AFTER THE FRONTAL PASSAGE THURSDAY NIGHT AND FRIDAY. WILL CONTINUE
MENTION IN THE HWO FOR HIGHER ELEVATIONS...WHICH HAVE THE GREATEST
CHANCE OF REALIZING THESE WIND GUSTS.
MODEL DIFFERENCES BEGIN TO DEVELOP BY FRIDAY NIGHT...WITH 12Z GFS
SHOWING STACKED LOW MOVING OFFSHORE MORE QUICKLY THAN THE ECMWF.
SPEED OF THE DEPARTING LOW WILL DETERMINE HOW LONG FAVORABLE FETCH
WILL PERSIST OFF LAKE ERIE. FOR NOW...HAVE GONE WITH SLOW DECLINE IN
POPS THROUGH THE WEEKEND. EXPECT LITTLE RECOVERY IN
TEMPERATURES...WITH HIGHS A COUPLE OF DEGREES BELOW NORMAL.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
A LINE OF SHOWERS WITH A BIT OF EMBEDDED THUNDER WILL MOVE NE FROM
NEAR KZZV AS OF 2330Z TOWARD KHLG AND KPIT BETWEEN 02 AND 03Z
LIKELY. THIS WILL BRING A SWITCH TO WSW WIND WITH SOME LIGHT GUST
POTENTIAL AT THESE SITES. OTHERWISE...THE FIRST SHIELD OF RAINFALL
IS MOVING NORTHEAST OUT OF THE KPIT AND KMGW AREAS...WITH A BREAK
AND EVEN POSSIBLE VFR CONDITIONS FOR AN HOUR OR TWO BEFORE THE
NEXT LINE OF SHOWERS ARRIVES. CIGS/VIS SHOULD FALL TO IFR MOST
EVERYWHERE OVERNIGHT. CONDITIONS ONLY IMPROVE WHEN SOME WESTERLY
WIND GUSTS ARRIVE BY TUESDAY AFTERNOON. FRIES
.OUTLOOK.../TUESDAY NIGHT THROUGH SATURDAY/...
MVFR RESTRICTIONS SHOULD DIMINISH TUESDAY NIGHT WITH LOW PRESSURE.
WEDNESDAY AND WEDNESDAY NIGHT WILL HAVE VFR CONDITIONS...BUT ANOTHER
LOW PRESSURE SYSTEM WILL BRING SHOWERS AND RESTRICTIONS TO ALL SITES
THURSDAY...WITH RAIN CHANGING TO SNOW THURSDAY NIGHT. LAKE EFFECT
SNOW SHOWERS AND RESTRICTIONS ARE EXPECTED TO CONTINUE FRIDAY AND
SATURDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
324 PM EST SUN DEC 16 2012
.SYNOPSIS...
LOW PRESSURE DRIFTING EASTWARD ACROSS THE GREAT LAKES WILL PROVIDE
THE UPPER OHIO VALLEY WITH MILD CLOUDY CONDITIONS AND ISOLATED
LIGHT SHOWERS INTO MONDAY MORNING. THEN LOW PRESSURE FORMING NEAR
ARKANSAS TONIGHT WILL MOVE NORTHEASTWARD WITH MORE NUMEROUS
SHOWERS LATER MONDAY INTO MIDDAY TUESDAY. A STRONG COLD FRONT LATE
THURSDAY WILL BRING NOTICEABLY COLDER TEMPERATURES FOR THE
WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
BLEND OF RECENT SURFACE SATELLITE AND RADAR DATA COUPLED WITH
RECENT RAP WRF-NMM AND SREF MODEL OUTPUT SHOW CLOUDY MILD
CONDITIONS CONTINUING ACROSS THE UPPER OHIO VALLEY WITH NO MORE
THAN ISOLATED LIGHT SHOWERS INTO EARLY TONIGHT.
MODELS CONTINUE TO SUGGEST THERE CAN BE AN INCREASE IN SHOWER
CHANCES SOUTH OF THE I-70 CORRIDOR LATE TONIGHT. LIFT MAY BECOME
MORE ORGANIZED JUST SOUTH OF THE OHIO RIVER...DUE TO INCREASED
CONVERGENCE ASSOCIATED WITH AN INCREASED LOW LEVEL JET DEVELOPING
AHEAD OF THE LOW PRESSURE CENTER DEVELOPING NEAR ARKANSAS.
FORECASTED TEMPERATURES TO REMAIN MILD THROUGH TONIGHT WITH
MINIMAL NIGHTTIME COOLING...SO THIS HIGHS THIS AFTERNOON AND
LOWS TONIGHT CAN BE MORE THAN 20 DEGREES WARMER THAN NORMAL.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/...
RECENT SREF MODEL OUTPUT...WITH DETAILS FROM NAM GFS AND WRF-
NMM...SHOW SHOWERS...ASSOCIATED WITH LOW PRESSURE CENTER TRACKING
NORTHEASTWARD ALONG THE APPALACHIAN MOUNTAINS...SPREADING SOUTH TO
NORTH ACROSS THE UPPER OHIO VALLEY MONDAY AND MONDAY NIGHT.
SHOWERS WILL EXIT EAST AS THE LOW PRESSURE CENTER EXITS PAST NEW
ENGLAND TUESDAY AFTERNOON.
ENSUING COLD POOL IS NOT THAT COLD OR DEEP...SO INSTABILITY
FOR SHOWERS WILL LIKEWISE BE WEAK. SO IT APPEARS LIKELY THAT MOST
POST SYSTEM SHOWERS WILL HAVE ENDED FOR MOST LOCATIONS BEFORE ANY
CHANGE OVER TO LIGHT OR WET SNOW OCCURS LATE TUESDAY AFTERNOON.
CONSENSUS OF GFS AND NAM MOS PLUS SREF MEAN VALUES SHOW TEMPERATURES
COOLING WITH THE SHOWERS AND LOW PRESSURE PASSAGE MONDAY NIGHT AND
TUESDAY...BUT STILL BE GENERALLY UP TO 10 DEGREES WARMER THAN NORMAL.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
WEAK HIGH PRESSURE RIDGE WILL BUILD IN TUESDAY NIGHT BEHIND
DEPARTING LOW PRESSURE. THINK THAT SHOWERS WILL DISSIPATE QUICKLY
TUESDAY EVENING AS INVERSION HEIGHTS FALL RAPIDLY. SKIES WILL REMAIN
AT LEAST PARTLY CLOUDY THROUGH MUCH OF TUESDAY NIGHT AND
WEDNESDAY...ALTHOUGH FLOW WILL INCLUDE A SOUTHERLY COMPONENT AND NOT
ALLOW FOR LAKE EFFECT.
MODELS ARE THEN IN GENERAL AGREEMENT ABOUT LOW PRESSURE MOVING
NORTHEAST ACROSS THE CENTRAL PLAINS INTO ONTARIO BY FRIDAY MORNING.
SLIGHTLY INCREASED THE LIKELY POPS THAT WERE ALREADY IN THE FORECAST
WITH SOLID CONSENSUS FROM DETERMINISTIC/ENSEMBLE MODELS.
TEMPERATURES WILL SURGE INTO THE LOWER 50S AHEAD OF THE FRONT ON
THURSDAY...WITH A STRONG DROPOFF AS THE FRONT MOVES THROUGH. IN
FACT...HIGHS ON FRIDAY MAY ONLY BE A COUPLE DEGREES HIGHER THAN
THURSDAY NIGHT LOWS. ALL PRECIPITATION SHOULD CHANGE OVER FROM RAIN
TO SNOW AFTER MIDNIGHT ON THURSDAY...WITH LAKE EFFECT MACHINE
STARTING UP AT THAT TIME.
ANOTHER CONCERN ON FRIDAY WILL BE WIND GUSTS...WITH LAST 2 GFS RUNS
SHOWING 40-45 KT POTENTIAL WIND GUSTS IN BUFKIT AND CIPS ANALOG
GUIDANCE SUGGESTING THAT ABOUT HALF OF PREVIOUS CLIMATOLOGY EVENTS
HAD WIND GUSTS OVER 40 KTS. 12Z GFS/ECMWF SHOW SOME DISAGREEMENT AS
TO HOW LONG LAKE EFFECT WILL PERSIST...BUT DECIDED TO KEEP AT LEAST
SLIGHT CHANCE POPS UP NORTH THROUGH THE REST OF THE FORECAST.
TEMPERATURES WILL STRUGGLE TO CLIMB ABOVE FREEZING FRIDAY THROUGH
SUNDAY.
&&
.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
RECENT SURFACE AND SATELLITE DATA SHOW STRATOCUMULUS CEILINGS
ACROSS THE UPPER OHIO VALLEY WILL BE MAINLY MVFR INTO TONIGHT.
ANY SHOWERS WILL BE ISOLATED IN COVERAGE AND LIGHT IN INTENSITY
AND SHOULD NOT ADD TO ANY RESTRICTIONS.
AS LOW PRESSURE CENTER FROM ARKANSAS MOVES NORTHEASTWARD ALONG THE
APPALACHIAN MOUNTAINS MONDAY...SHOWERS AND RESTRICTIONS WILL
LIKEWISE SPREAD SOUTH TO NORTH ACROSS THE UPPER OHIO VALLEY
DAYTIME MONDAY. AT THIS JUNCTURE HAVE NOT FORECASTED LOWER THAN
MVFR...BUT IFR CANNOT BE RULED OUT BY LATE MONDAY AFTERNOON.
SURFACE WINDS WILL BE FROM THE SOUTH AND SOUTHEAST AT 5 TO 15 KTS
INTO MONDAY.
.OUTLOOK.../MONDAY NIGHT THROUGH FRIDAY/...
IFR RESTRICTIONS CAN OCCUR MONDAY NIGHT INTO TUESDAY MORNING DUE
TO SHOWERS WITH NORTHEASTWARD PASSAGE OF LOW PRESSURE CENTER. SOME
MVFR RESTRICTIONS MAY REMAIN TUESDAY AFTERNOON INTO WEDNESDAY DUE
TO LINGERING POST SYSTEM COLD POOL STRATOCUMULUS. ANOTHER LOW
PRESSURE SYSTEM WILL BRING SHOWERS AND RESTRICTIONS THURSDAY INTO
FRIDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
225 PM EST SUN DEC 16 2012
.SYNOPSIS...
LOW PRESSURE DRIFTING EASTWARD ACROSS THE GREAT LAKES WILL PROVIDE
THE UPPER OHIO VALLEY WITH MILD CLOUDY CONDITIONS AND ISOLATED
LIGHT SHOWERS INTO MONDAY MORNING. THEN LOW PRESSURE FORMING NEAR
ARKANSAS TONIGHT WILL MOVE NORTHEASTWARD WITH MORE NUMEROUS
SHOWERS LATER MONDAY INTO MIDDAY TUESDAY. A STRONG COLD FRONT LATE
THURSDAY WILL BRING NOTICEABLY COLDER TEMPERATURES FOR THE
WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
BLEND OF RECENT SURFACE SATELLITE AND RADAR DATA COUPLED WITH
RECENT RAP WRF-NMM AND SREF MODEL OUTPUT SHOW CLOUDY MILD
CONDITIONS CONTINUING ACROSS THE UPPER OHIO VALLEY WITH NO MORE
THAN ISOLATED LIGHT SHOWERS INTO EARLY TONIGHT.
MODELS CONTINUE TO SUGGEST THERE CAN BE AN INCREASE IN SHOWER
CHANCES SOUTH OF THE I-70 CORRIDOR LATE TONIGHT. LIFT MAY BECOME
MORE ORGANIZED JUST SOUTH OF THE OHIO RIVER...DUE TO INCREASED
CONVERGENCE ASSOCIATED WITH AN INCREASED LOW LEVEL JET DEVELOPING
AHEAD OF THE LOW PRESSURE CENTER DEVELOPING NEAR ARKANSAS.
FORECASTED TEMPERATURES TO REMAIN MILD THROUGH TONIGHT WITH
MINIMAL NIGHTTIME COOLING...SO THIS HIGHS THIS AFTERNOON AND
LOWS TONIGHT CAN BE MORE THAN 20 DEGREES WARMER THAN NORMAL.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY/...
RECENT SREF MODEL OUTPUT...WITH DETAILS FROM NAM GFS AND WRF-
NMM...SHOW SHOWERS...ASSOCIATED WITH LOW PRESSURE CENTER TRACKING
NORTHEASTWARD ALONG THE APPALACHIAN MOUNTAINS...SPREADING SOUTH TO
NORTH ACROSS THE UPPER OHIO VALLEY MONDAY AND MONDAY NIGHT.
SHOWERS WILL EXIT EAST AS THE LOW PRESSURE CENTER EXITS PAST NEW
ENGLAND TUESDAY AFTERNOON.
ENSUING COLD POOL IS NOT THAT COLD OR DEEP...SO INSTABILITY
FOR SHOWERS WILL LIKEWISE BE WEAK. SO IT APPEARS LIKELY THAT MOST
POST SYSTEM SHOWERS WILL HAVE ENDED FOR MOST LOCATIONS BEFORE ANY
CHANGE OVER TO LIGHT OR WET SNOW OCCURS LATE TUESDAY AFTERNOON.
CONSENSUS OF GFS AND NAM MOS PLUS SREF MEAN VALUES SHOW TEMPERATURES
COOLING WITH THE SHOWERS AND LOW PRESSURE PASSAGE MONDAY NIGHT AND
TUESDAY...BUT STILL BE GENERALLY UP TO 10 DEGREES WARMER THAN NORMAL.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
HIGH PRES RIDGING WL BUILD IN WED...WITH WAA KICKING IN AS THE
RIDGE AXIS PASSES EAST. MODELS WERE TRENDING MUCH WARMER WED AND
WED NT THAN EARLIER...SO INCREASED TEMPS DURING DURING THAT TIME.
NO OTHER MAJOR CHANGES TO THE LONG TERM PERIOD WERE MADE.
PREVIOUS...
THE NEXT STORM SYSTEM WILL DEVELOP IN THE PLAINS AND
BEGIN TO AFFECT THE REGION THURSDAY. WITH GOOD AGREEMENT FROM 12Z
GFS/ECMWF AND 00Z NAEFS...HAVE BUMPED UP POPS TO LIKELY THURSDAY
AFTERNOON AND EVENING AS BULK OF PRECIPITATION WILL COME THROUGH
WITH COLD FRONT.
LOW CENTER WILL THEN MEANDER ACROSS THE EASTERN GREAT LAKES ON
FRIDAY. THE LOW WILL PUMP COLD AIR INTO THE AREA ON FRIDAY...AND
TEMPERATURES MAY DECREASE THROUGHOUT THE ENTIRE DAY. COLD AIR AND
ADDITIONAL MOISTURE WILL ALLOW FOR A GOOD CHANCE OF LAKE
EFFECT/UPSLOPE SNOW SHOWERS FRIDAY AND SATURDAY.
ABOVE NORMAL TEMPERATURES WEDNESDAY AND THURSDAY WILL TUMBLE
BELOW NORMAL FOR FRIDAY AND SATURDAY BEHIND THE COLD FRONT.
&&
.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
RECENT SURFACE AND SATELLITE DATA SHOW STRATOCUMULUS CEILINGS
ACROSS THE UPPER OHIO VALLEY WILL BE MAINLY MVFR INTO TONIGHT.
ANY SHOWERS WILL BE ISOLATED IN COVERAGE AND LIGHT IN INTENSITY
AND SHOULD NOT ADD TO ANY RESTRICTIONS.
AS LOW PRESSURE CENTER FROM ARKANSAS MOVES NORTHEASTWARD ALONG THE
APPALACHIAN MOUNTAINS MONDAY...SHOWERS AND RESTRICTIONS WILL
LIKEWISE SPREAD SOUTH TO NORTH ACROSS THE UPPER OHIO VALLEY
DAYTIME MONDAY. AT THIS JUNCTURE HAVE NOT FORECASTED LOWER THAN
MVFR...BUT IFR CANNOT BE RULED OUT BY LATE MONDAY AFTERNOON.
SURFACE WINDS WILL BE FROM THE SOUTH AND SOUTHEAST AT 5 TO 15 KTS
INTO MONDAY.
.OUTLOOK.../MONDAY THROUGH FRIDAY/...
IFR RESTRICTIONS CAN OCCUR MONDAY NIGHT INTO TUESDAY MORNING DUE
TO SHOWERS WITH NORTHEASTWARD PASSAGE OF LOW PRESSURE CENTER. SOME
MVFR RESTRICTIONS MAY REMAIN TUESDAY AFTERNOON INTO WEDNESDAY DUE
TO LINGERING POST SYSTEM COLD POOL STRATOCUMULUS. ANOTHER LOW
PRESSURE SYSTEM WILL BRING SHOWERS AND RESTRICTIONS THURSDAY INTO
FRIDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
123 PM EST SUN DEC 16 2012
.SYNOPSIS...
LOW PRESSURE DRIFTING EASTWARD ACROSS THE GREAT LAKES WILL PROVIDE
THE UPPER OHIO VALLEY WITH MILD CLOUDY CONDITIONS AND ISOLATED
LIGHT SHOWERS INTO MONDAY MORNING. THEN LOW PRESSURE FORMING NEAR
ARKANSAS TONIGHT WILL MOVE NORTHEASTWARD WITH MORE NUMEROUS
SHOWERS LATER MONDAY INTO MIDDAY TUESDAY. A STRONG COLD FRONT LATE
THURSDAY WILL BRING NOTICEABLY COLDER TEMPERATURES FOR THE
WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
BLEND OF RECENT SURFACE SATELLITE AND RADAR DATA COUPLED WITH
RECENT RAP WRF-NMM AND SREF MODEL OUTPUT SHOW CLOUDY MILD
CONDITIONS CONTINUING ACROSS THE UPPER OHIO VALLEY WITH NO MORE
THAN ISOLATED LIGHT SHOWERS INTO EARLY TONIGHT.
MODELS CONTINUE TO SUGGEST THERE CAN BE AN INCREASE IN SHOWER
CHANCES SOUTH OF THE I-70 CORRIDOR LATE TONIGHT...AS LIFT MAY
BECOME MORE ORGANIZED ALONG AN INCREASED LOW LEVEL JET AHEAD OF
THE LOW PRESSURE CENTER DEVELOPING NEAR ARKANSAS.
FORECASTED TEMPERATURES TO REMAIN MILD THROUGH TONIGHT WITH
MINIMAL NIGHTTIME COOLING...SO THIS HIGHS THIS AFTERNOON AND
LOWS TONIGHT CAN BE MORE THAN 20 DEGREES WARMER THAN NORMAL.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY/...
RECENT SREF MODEL OUTPUT...WITH DETAILS FROM NAM GFS AND WRF-
NMM...SHOW SHOWERS...ASSOCIATED WITH LOW PRESSURE CENTER TRACKING
NORTHEASTWARD ALONG THE APPALACHIAN MOUNTAINS...SPREADING SOUTH TO
NORTH ACROSS THE UPPER OHIO VALLEY MONDAY AND MONDAY NIGHT.
SHOWERS WILL EXIT EAST AS THE LOW PRESSURE CENTER EXITS PAST NEW
ENGLAND TUESDAY AFTERNOON.
ENSUING COLD POOL IS NOT THAT COLD OR DEEP...SO INSTABILITY
FOR SHOWERS WILL LIKEWISE BE WEAK. SO IT APPEARS LIKELY SHOWERS
WILL HAVE ENDED FOR MOST LOCATIONS BEFORE ANY CHANGE TO SNOW
OCCURS LATE TUESDAY AFTERNOON.
CONSENSUS OF GFS AND NAM MOS PLUS SREF MEAN VALUES SHOW TEMPERATURES
COOLING WITH THE SHOWERS AND LOW PRESSURE PASSAGE...BUT STILL BE
GENERALLY UP TO 10 DEGREES WARMER THAN NORMAL.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
HIGH PRES RIDGING WL BUILD IN WED...WITH WAA KICKING IN AS THE
RIDGE AXIS PASSES EAST. MODELS WERE TRENDING MUCH WARMER WED AND
WED NT THAN EARLIER...SO INCREASED TEMPS DURING DURING THAT TIME.
NO OTHER MAJOR CHANGES TO THE LONG TERM PERIOD WERE MADE.
PREVIOUS...
THE NEXT STORM SYSTEM WILL DEVELOP IN THE PLAINS AND
BEGIN TO AFFECT THE REGION THURSDAY. WITH GOOD AGREEMENT FROM 12Z
GFS/ECMWF AND 00Z NAEFS...HAVE BUMPED UP POPS TO LIKELY THURSDAY
AFTERNOON AND EVENING AS BULK OF PRECIPITATION WILL COME THROUGH
WITH COLD FRONT.
LOW CENTER WILL THEN MEANDER ACROSS THE EASTERN GREAT LAKES ON
FRIDAY. THE LOW WILL PUMP COLD AIR INTO THE AREA ON FRIDAY...AND
TEMPERATURES MAY DECREASE THROUGHOUT THE ENTIRE DAY. COLD AIR AND
ADDITIONAL MOISTURE WILL ALLOW FOR A GOOD CHANCE OF LAKE
EFFECT/UPSLOPE SNOW SHOWERS FRIDAY AND SATURDAY.
ABOVE NORMAL TEMPERATURES WEDNESDAY AND THURSDAY WILL TUMBLE
BELOW NORMAL FOR FRIDAY AND SATURDAY BEHIND THE COLD FRONT.
&&
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
RECENT SURFACE AND SATELLITE DATA SHOW STRATOCUMULUS CEILINGS
ACROSS THE UPPER OHIO VALLEY WILL VARY BETWEEN MVFR AND VFR INTO
TONIGHT. ANY SHOWERS WILL BE ISOLATED IN COVERAGE AND LIGHT IN
INTENSITY AND SHOULD NOT ADD TO ANY RESTRICTIONS.
AS LOW PRESSURE CENTER FROM ARKANSAS MOVES NORTHEASTWARD ALONG THE
APPALACHIAN MOUNTAINS MONDAY...SHOWERS AND RESTRICTIONS WILL
LIKEWISE SPREAD SOUTH TO NORTH ACROSS THE UPPER OHIO VALLEY
DAYTIME MONDAY. AT THIS JUNCTURE HAVE NOT FORECASTED LOWER THAN
MVFR...BUT IFR CANNOT BE RULED OUT BY LATE MONDAY AFTERNOON.
SURFACE WINDS WILL BE FROM THE SOUTH AND SOUTHEAST AT 5 TO 15 KTS
INTO MONDAY.
.OUTLOOK.../MONDAY THROUGH FRIDAY/...
IFR RESTRICTIONS CAN OCCUR MONDAY NIGHT INTO TUESDAY MORNING DUE
TO SHOWERS WITH NORTHEASTWARD PASSAGE OF LOW PRESSURE CENTER. SOME
MVFR RESTRICTIONS MAY REMAIN TUESDAY AFTERNOON INTO WEDNESDAY
LINGERING POST SYSTEM COLD POOL STRATOCUMULUS. ANOTHER LOW
PRESSURE SYSTEM WILL BRING RAIN AND SNOW SHOWERS AND RESTRICTIONS
THURSDAY INTO FRIDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
856 AM EST SUN DEC 16 2012
.SYNOPSIS...
LOW PRESSURE DRIFTING EASTWARD ACROSS THE GREAT LAKES WILL PROVIDE
THE UPPER OHIO VALLEY WITH MILD CLOUDY CONDITIONS AND ISOLATED
LIGHT SHOWERS INTO MONDAY MORNING. THEN LOW PRESSURE FORMING NEAR
ARKANSAS TONIGHT WILL MOVE NORTHEASTWARD WITH MORE NUMEROUS
SHOWERS LATER MONDAY INTO EARLY TUESDAY. A STRONG COLD FRONT LATE
THURSDAY WILL BRING NOTICEABLY COLDER TEMPERATURES FOR THE WEEKEND.
&&
.NEAR TERM /THROUGH MONDAY/...
BLEND OF RECENT SURFACE SATELLITE AND RADAR DATA COUPLED WITH
RECENT RAP WRF-NMM AND SREF MODEL OUTPUT SHOW CLOUDY MILD
CONDITIONS CONTINUING ACROSS THE UPPER OHIO VALLEY WITH NO MORE
THAN ISOLATED LIGHT SHOWERS THE REST OF TODAY AND TONIGHT.
SURFACE LAYER MOISTURE WILL BE INCREASING BUT LIFTING MECHANISMS
WILL REMAIN WEAK IN THE SOUTHERLY FLOW FEEDING THE LOW PRESSURE
CENTER DRIFTING EASTWARD ACROSS THE GREAT LAKES.
HOWEVER SREF AND NAM MODEL OUTPUT SHOW THAT WITH LOW PRESSURE
FORMING NEAR ARKANSAS TONIGHT...AND THEN MOVING NORTHEASTWARD
TOWARD THE UPPER OHIO VALLEY MONDAY...SHOWERS WILL BECOME MORE
NUMEROUS SOUTH TO NORTH ACROSS THE UPPER OHIO VALLEY MONDAY
AFTERNOON.
FORECASTED TEMPERATURES TO REMAIN MILD WITH VALUES ABOUT 20
DEGREES WARMER THAN NORMAL.
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
RECENT SREF MODEL OUTPUT SHOWS SHOWERS ACROSS THE UPPER OHIO
VALLEY MONDAY NIGHT INTO TUESDAY AS LOW PRESSURE CENTER TRACKS NORTHEASTWARD
ALONG THE APPALACHIAN MOUNTAINS...EXITING PAST NEW ENGLAND TUESDAY
AFTERNOON.
ENSUING COLD POOL IS NOT THAT COLD OR DEEP...SO INSTABILITY
FOR SHOWERS WILL LIKEWISE BE WEAK. SO IT APPEARS LIKELY SHOWERS
WILL HAVE ENDED FOR MOST LOCATIONS BEFORE ANY CHANGE TO SNOW
OCCURS.
TEMPERATURES WILL NOT BE AS WARM...BUT STILL BE GENERALLY MORE
THAN 10 DEGREES WARMER THAN NORMAL.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
HIGH PRES RIDGING WL BUILD IN WED...WITH WAA KICKING IN AS THE
RIDGE AXIS PASSES EAST. MODELS WERE TRENDING MUCH WARMER WED AND
WED NT THAN EARLIER...SO INCREASED TEMPS DURING DURING THAT TIME.
NO OTHER MAJOR CHANGES TO THE LONG TERM PERIOD WERE MADE.
PREVIOUS...
THE NEXT STORM SYSTEM WILL DEVELOP IN THE PLAINS AND
BEGIN TO AFFECT THE REGION THURSDAY. WITH GOOD AGREEMENT FROM 12Z
GFS/ECMWF AND 00Z NAEFS...HAVE BUMPED UP POPS TO LIKELY THURSDAY
AFTERNOON AND EVENING AS BULK OF PRECIPITATION WILL COME THROUGH
WITH COLD FRONT.
LOW CENTER WILL THEN MEANDER ACROSS THE EASTERN GREAT LAKES ON
FRIDAY. THE LOW WILL PUMP COLD AIR INTO THE AREA ON FRIDAY...AND
TEMPERATURES MAY DECREASE THROUGHOUT THE ENTIRE DAY. COLD AIR AND
ADDITIONAL MOISTURE WILL ALLOW FOR A GOOD CHANCE OF LAKE
EFFECT/UPSLOPE SNOW SHOWERS FRIDAY AND SATURDAY.
ABOVE NORMAL TEMPERATURES WEDNESDAY AND THURSDAY WILL TUMBLE
BELOW NORMAL FOR FRIDAY AND SATURDAY BEHIND THE COLD FRONT.
&&
.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
RECENT SURFACE AND SATELLITE DATA SHOW STRATOCUMULUS CEILINGS
ACROSS THE UPPER OHIO VALLEY WILL VARY BETWEEN MVFR AND VFR INTO
TONIGHT. ANY SHOWERS WILL BE ISOLATED IN COVERAGE AND LIGHT IN
INTENSITY AND SHOULD NOT ADD TO ANY RESTRICTIONS.
SURFACE WINDS WILL BE FROM THE SOUTH AND SOUTHEAST AT 5 TO 10 KTS
INTO TONIGHT.
.OUTLOOK.../MONDAY THROUGH THURSDAY/...
IFR RESTRICTIONS CAN OCCUR LATE MONDAY INTO TUESDAY DUE TO SHOWERS
WITH NORTHEASTWARD PASSAGE OF LOW PRESSURE CENTER. SOME MVFR RESTRICTIONS
MAY REMAIN TUESDAY NIGHT INTO WEDNESDAY NIGHT WITH SOME PARTIAL
CLEARING. ANOTHER LOW PRESSURE SYSTEM WILL BRING RAIN/SNOW SHOWERS
AND RESTRICTIONS THURSDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS WAKEFIELD VA
143 AM EST SUN DEC 16 2012
.SYNOPSIS...
LOW PRESSURE WILL MOVE FROM PLAINS STATES INTO THE GREAT LAKES
REGION TONIGHT THROUGH SUNDAY...PUSHING A WARM FRONT THROUGH THE
AREA. ANOTHER AREA OF LOW PRESSURE MOVES FROM THE OHIO VALLEY TO
THE NORTHEASTERN STATES MONDAY...WITH THE TRAILING COLD FRONT
CROSSING THE REGION EARLY TUESDAY.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
LONGWAVE IR IMAGERY SHOWS COOLING CLOUD TOPS INDICATIVE OF AN
EMBEDDED IMPULSE OVER EASTERN TN. THIS WAVE IS EXPECTED TO
INTERACT WITH INCREASING WAA AS A WARM FRONT LIFTS N ACROSS THE
CAROLINA COASTAL PLAIN. THE LATEST RUC PROGS RATHER STRONG LOW/MID
LEVEL LIFT LATE TONIGHT INTO EARLY SUNDAY MORNING ACROSS SE VA AND
NE NC. POPS HAVE BEEN INCREASED TO LIKELY INTO SUNDAY
MORNING...GIVEN THE SATELLITE TRENDS AND LATEST RUC SOLUTIONS. AT
THIS POINT ANTECEDENT DRY CONDITIONS ARE STILL EXPECTED DELAY THE
ONSET OF ANY RAIN...BUT KRAX AND KAKQ RADARS ARE INDICATING AN
INCREASE IN LOW-LEVEL MOISTURE BY SHOWING LIGHT ECHOES FROM
CENTRAL NC TO THE TIDEWATER. GENERALLY QPF AMOUNTS SHOULD
GENERALLY RANGE BETWEEN 0.1-0.2IN ACROSS EXTREME SE VA AND COASTAL
NE NC...BUT THERE IS SOME INDICATION OF POTENTIAL ELEVATED
CONVECTIVE ELEMENTS THAT COULD RESULT IN UP TO 0.2-0.3IN.
OTHERWISE...ONLY SLIGHT CHANCE/CHANCE POPS ARE FORECAST ELSEWHERE.
OVERNIGHT MINIMA ARE LIKELY OCCURRING THIS EVENING...ESPECIALLY
ACROSS THE SE WHERE LOWS FROM THE MID 30S TO LOW 40S WILL RISE TO
THE UPPER 40S TO LOW 50S BY MORNING. ELSEWHERE...TEMPERATURES
SHOULD BE STEADY IN THE LOW TO MID 40S.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY/...
WARM FRONT LIFTS NORTH ACROSS THE REGION SUNDAY MORNING, WITH A BIT
OF A LULL IN ACCUMULATING PCPN EXPECTED SUN MORN. SHORTWAVE TROUGH
IS PROGGED TO FOLLOW SW FLOW ALOFT, PUSHING ACROSS THE REGION LATER
SUNDAY. THUS, RAIN CHANCES INCREASE AGAIN BY LATE SUNDAY MORNING
INTO EARLY EVENING. CONTINUE TO ORIENT HIGHEST (LIKELY) RAIN CHANCES
ACROSS ROUGHLY ALONG AND NORTH OF I-64, WITH LOWER CHCS FOR RAIN, OR
A FEW SHRAS OVER SE VA AND NE NC. TEMPERATURES FAIRLY MILD AS FA
REMAINS IN WARM SECTOR AHEAD OF APPROACHING COLD FRONT. HIGHS A BIT
OF A CHALLENGE GIVEN CONTINUED SIGNIFICANT CLOUD COVER. LOOKING FOR
M-U50S NORTH TO L-M60S SOUTH.
FIRST SLUG OF MOISTURE/SHORTWAVE KICKS OFF THE DELMARVA COAST SUNDAY
NIGHT. MIDLVL DRY OUT A BIT, WHICH WOULD TEND TO FAVOR SOME PATCHY
DZ/FOG RATHER THAN ACCUMULATING PCPN LATE SUN NIGHT/ERY MONDAY
MORNING. GIVEN ONSHORE FLOW/WAA AND CONSIDERABLE CLOUDINESS, WENT
AOA WARMER MET GUIDANCE. LOWS ~50-55.
MONDAY...
BRIEF LULL IN PCPN MONDAY MORNING AHEAD OF SECOND SHORTWAVE, WHICH
IS EXPECTED TO BEGIN TO CROSS THE LOCAL AREA MIDDAY MONDAY INTO MON
NIGHT. HAVE AGAIN ORIENTED BEST POPS IN THE AFTN/EVE TIME FRAME
MONDAY. DESPITE INCREASINGLY MOIST AIRMASS, QPF VALUES APPEAR RATHER
MEAGER WITH BETTER FORCING ONCE AGAIN OFF TO OUR NORTH (FROM THE OH
VLY INTO THE NORTHEAST) AND TO OUR SOUTH. STILL, QPF OF AN
ADDITIONAL ONE TO TWO-TENTHS ON AVERAGE APPEARS REASONABLE. DESPITE
SHRAS AND CONSIDERABLE CLOUDS, RATHER MILD W/ CONTINUED WAA. LOOK
FOR HIGHS INTO THE U50S-NR 60 ACROSS THE PIEDMONT, L-M60S ELSEWHERE.
MONDAY NIGHT/TUESDAY...
SECOND SHORTWAVE PIVOTS NE/OFFSHORE LATE MON. UPPER LOW
DAMPENS/WEAKENS A BIT AS IT MOVES FROM THE MIDDLE MS VALLEY MON
NIGHT NE TO THE EASTERN GREAT LAKES BY TUESDAY MORNING...PUSHING
THE ATTENDANT SFC FRONT EAST AS WELL. NUMERICAL GUIDANCE HAS
SLOWED SLIGHTLY WITH FRONTAL TIMING. NEW 12Z SUITE OF DATA LOOKS
TO BRING FRONT THROUGH BY/SHORTLY AFTER DAWN TUESDAY MORNING.
GIVEN WEAK FRONTAL FORCING, EXPECT THIS TIMING TO CONTINUE TO SLOW
SLIGHTLY WITH SUBSEQUENT RUNS. THUS, GIVEN THIS SLOWER TIMING AND
WITH SIG CAA LIKELY TO LAG BEHIND FROPA, HV KEPT MAXIMA IN THE
U50S/NR 60 WEST, M-U60S SE.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
TRENDED EXTENDED PERIOD FORECAST TOWARD THE LATEST EUROPEAN MODEL,
AS A STORM SYSTEM BRINGS WET CONDITIONS AND COOL TEMPS TO THE MID
ATLANTIC STATES TOWARD THE END OF NEXT WEEK.
UPPER/SFC LOW WILL CONTINUE TO PUSH OFFSHORE WED MORNING AS COOL
MID/UPPER LEVEL TROUGH LOCATES OVER THE INTERMOUNTAIN WEST.
UPPER/SFC HIGH PRESSURE WILL BUILD INTO THE REGION WEDS AS DEEP WLY
FLOW BRINGS SUNNY TO PARTLY SUNNY SKIES. AS THE BEST COLD AIR WILL
REMAIN NORTH OF THE REGION...850 TEMPS ONLY EXPECTED TO FALL TO
RIGHT AROUND FREEZING. THUS...HAVE TRENDED TEMPS WEDS A FEW DEGS
WARMER INTO THE MID/UPPER 50S.
SFC HIGH PRESSURE WILL DRIFT OFF THE SE COAST THURSDAY MORNING AS
THE MID LEVEL RIDGE AXIS MOVES EAST OF THE REGION LATE THURSDAY
MORNING. DEPARTING LOW PRESSURE FROM EARLIER IN THE WEEK WILL PHASE
WITH STRONG LOW OVER THE NORTHERN ATLANTIC...HELPING AMPLIFY THE
EAST COAST RIDGE. THIS WILL RESULT IN INCREASED SWLY FLOW AND
MOISTURE ADVECTION INTO THE REGION. CLOUDS WILL ALSO BE ON THE
INCREASE WITH MOSTLY CLOUDY/CLOUDY SKIES EXPECTED BY THURSDAY
AFTERNOON. WHILE HEIGHTS/THICKNESS VALUES INCREASE...CLOUD COVER AND
WEAK MIXING WILL LIMIT AFTERNOON WARMING WITH TEMPS ONLY EXPECTED IN
THE LOW/MID 50S N TO MID/UPPER 50S S.
WHILE SPATIAL AND TIMING DIFFERENCES EXIST WITH THE COLD FRONT IN
EACH RUN...FRONT IS EXPECTED TO REACH THE FA THURS NIGHT AND CROSS
THE REGION THROUGH FRIDAY MORNING. BEST FORCING FOR ASCENT LOOKS TO
BE OVER THE REGION AS VORT MAX AND PV ANOMALY...AS WELL AS COUPLING
SUBTROPICAL/POLAR JET INCREASE DIVERGENCE ALOFT. COULD SEE A GOOD
CHANCE AT WIDESPREAD BENEFICIAL RAIN SHOWERS. COLD POLAR CONTINENTAL
AIR WILL RUSH IN BEHIND THE SYSTEM WITH TEMPS EXPECTED IN THE MID
40S NE TO MID 50S SW FRIDAY AFTERNOON (TEMPS MAY FALL DURING THE DAY
DEPENDING ON FRONTAL TIMING). TEMPS WILL FALL INTO THE MID/UPPER 20S
SATURDAY MORNING ONLY TO REBOUND INTO THE LOW/MID 40S SATURDAY
AFTERNOON...POSSIBLY COLDER. MOST OF THE PRECIP WILL BE TIED TO THE
FRONT AND BEATING THE POLAR AIR...TEMPS WILL BE WARM ENOUGH TO
SQUASH ANY WINTRY MIX FRIDAY MORNING.
AS OMEGA BLOCKING IS FORECAST TO OCCUR OVER THE NORTHERN ATLANTIC
THROUGH NEXT WEEKEND...COLD WEATHER IS LIKELY TO CONTINUE THROUGH
THE WEEKEND AS ANOTHER SHORTWAVE REINFORCES THE COLD AIR.
HOWEVER...DRY CONDITIONS WILL PREVAIL.
&&
.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
CONTD INCRS IN MOISTURE/LWRG OF CLDNS IN THE NEXT 24-36 HRS. KEPT
CIGS IN MVFR CAT (ALG W/ SCT -RA) INTO TNGT...W/ LO PROB FOR IFR
(CIGS AND/OR VSBY). ADDITIONAL -RA PSBL TNGT/MON W/ A HIGHER PROB
FOR IFR CIGS/VSBYS...ESP AFT MDNGT TNGT/MON MRNG. GRADUAL
IMPROVEMENT MON NGT...THEN VFR CONDS W/ GUSTY WNW WNDS TUE INTO
WED. A CHANCE OF SHOWERS BY LT THU.
&&
.MARINE...
SFC HIGH PRESSURE HAS ALLOWED FOR CALM WINDS AOB 10 KT OVER THE
WATERS THIS AFTERNOON WITH SEAS GENERALLY 2 TO 3 FT. HIGH PRESSURE
WILL SHIFT OFFSHORE THIS EVENING AS A WEAK COASTAL LOW LIFTS UP
THE SE COAST TONIGHT BRINGING LIGHT RAIN AND S/SE WINDS ALONG THE
COAST. LOW PRESSURE WILL THEN LIFT OUT OF THE MIDWEST
MONDAY...WITH A SECONDARY AREA OF LOW PRESSURE DEVELOPING JUST
NORTH OF THE WATERS MONDAY NIGHT/TUESDAY. WINDS WILL BACK TO THE
S/SW MONDAY AFTERNOON (5 TO 10 KT). WITH HIGH PRESSURE LOCATED
OFFSHORE...THE PRESSURE GRADIENT WILL TIGHTEN ALLOWING FOR
INCREASINGLY SLY WINDS OVER THE WATERS BEGINNING MONDAY EVENING. A
WEAK COLD FRONT WILL CROSS THE WATERS MONDAY NIGHT INTO
TUESDAY...BACKING THE WINDS TO THE W/NW AND ALLOWING FOR STRONGER
CAA ALOFT. SEAS WILL BEGIN TO BUILD 4 TO 5 FT TUESDAY
AFTERNOON...THUS SCA HEADLINES WILL LIKELY BE NEEDED AT LEAST OVER
THE NORTHERN COASTAL ZONES. STRONGEST CAA WILL OCCUR TUESDAY NIGHT
INTO WEDNESDAY...WHICH WILL LEAD TO LIKELY SCA CONDITIONS OVER THE
WATERS.
WINDS/SEAS WILL BEGIN TO SUBSIDE WEDS AFTERNOON AS HIGH PRESSURE
BUILDS IN FROM THE SOUTH. ANOTHER STRONGER LOW PRESSURE SYSTEM
WILL IMPACT THE REGION TOWARD THE END OF NEXT WEEK WITH SCA
CONDITIONS LIKELY.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...MAM
NEAR TERM...AJZ/MAS/MAM
SHORT TERM...MAM
LONG TERM...MPR/SAM
AVIATION...ALB
MARINE...MAS/SAM
AREA FORECAST DISCUSSION
NWS WAKEFIELD VA
1204 AM EST SUN DEC 16 2012
.SYNOPSIS...
LOW PRESSURE WILL MOVE FROM PLAINS STATES INTO THE GREAT LAKES
REGION TONIGHT THROUGH SUNDAY...PUSHING A WARM FRONT THROUGH THE
AREA. ANOTHER AREA OF LOW PRESSURE MOVES FROM THE OHIO VALLEY TO
THE NORTHEASTERN STATES MONDAY...WITH THE TRAILING COLD FRONT
CROSSING THE REGION EARLY TUESDAY.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
LONGWAVE IR IMAGERY SHOWS COOLING CLOUD TOPS INDICATIVE OF AN
EMBEDDED IMPULSE OVER EASTERN TN. THIS WAVE IS EXPECTED TO
INTERACT WITH INCREASING WAA AS A WARM FRONT LIFTS N ACROSS THE
CAROLINA COASTAL PLAIN. THE LATEST RUC PROGS RATHER STRONG LOW/MID
LEVEL LIFT LATE TONIGHT INTO EARLY SUNDAY MORNING ACROSS SE VA AND
NE NC. POPS HAVE BEEN INCREASED TO LIKELY INTO SUNDAY
MORNING...GIVEN THE SATELLITE TRENDS AND LATEST RUC SOLUTIONS. AT
THIS POINT ANTECEDENT DRY CONDITIONS ARE STILL EXPECTED DELAY THE
ONSET OF ANY RAIN...BUT KRAX AND KAKQ RADARS ARE INDICATING AN
INCREASE IN LOW-LEVEL MOISTURE BY SHOWING LIGHT ECHOES FROM
CENTRAL NC TO THE TIDEWATER. GENERALLY QPF AMOUNTS SHOULD
GENERALLY RANGE BETWEEN 0.1-0.2IN ACROSS EXTREME SE VA AND COASTAL
NE NC...BUT THERE IS SOME INDICATION OF POTENTIAL ELEVATED
CONVECTIVE ELEMENTS THAT COULD RESULT IN UP TO 0.2-0.3IN.
OTHERWISE...ONLY SLIGHT CHANCE/CHANCE POPS ARE FORECAST ELSEWHERE.
OVERNIGHT MINIMA ARE LIKELY OCCURRING THIS EVENING...ESPECIALLY
ACROSS THE SE WHERE LOWS FROM THE MID 30S TO LOW 40S WILL RISE TO
THE UPPER 40S TO LOW 50S BY MORNING. ELSEWHERE...TEMPERATURES
SHOULD BE STEADY IN THE LOW TO MID 40S.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
WARM FRONT LIFTS NORTH ACROSS THE REGION SUNDAY MORNING, WITH A BIT
OF A LULL IN ACCUMULATING PCPN EXPECTED SUN MORN. SHORTWAVE TROUGH
IS PROGGED TO FOLLOW SW FLOW ALOFT, PUSHING ACROSS THE REGION LATER
SUNDAY. THUS, RAIN CHANCES INCREASE AGAIN BY LATE SUNDAY MORNING
INTO EARLY EVENING. CONTINUE TO ORIENT HIGHEST (LIKELY) RAIN CHANCES
ACROSS ROUGHLY ALONG AND NORTH OF I-64, WITH LOWER CHCS FOR RAIN, OR
A FEW SHRAS OVER SE VA AND NE NC. TEMPERATURES FAIRLY MILD AS FA
REMAINS IN WARM SECTOR AHEAD OF APPROACHING COLD FRONT. HIGHS A BIT
OF A CHALLENGE GIVEN CONTINUED SIGNIFICANT CLOUD COVER. LOOKING FOR
M-U50S NORTH TO L-M60S SOUTH.
FIRST SLUG OF MOISTURE/SHORTWAVE KICKS OFF THE DELMARVA COAST SUNDAY
NIGHT. MIDLVL DRY OUT A BIT, WHICH WOULD TEND TO FAVOR SOME PATCHY
DZ/FOG RATHER THAN ACCUMULATING PCPN LATE SUN NIGHT/ERY MONDAY
MORNING. GIVEN ONSHORE FLOW/WAA AND CONSIDERABLE CLOUDINESS, WENT
AOA WARMER MET GUIDANCE. LOWS ~50-55.
MONDAY...
BRIEF LULL IN PCPN MONDAY MORNING AHEAD OF SECOND SHORTWAVE, WHICH
IS EXPECTED TO BEGIN TO CROSS THE LOCAL AREA MIDDAY MONDAY INTO MON
NIGHT. HAVE AGAIN ORIENTED BEST POPS IN THE AFTN/EVE TIME FRAME
MONDAY. DESPITE INCREASINGLY MOIST AIRMASS, QPF VALUES APPEAR RATHER
MEAGER WITH BETTER FORCING ONCE AGAIN OFF TO OUR NORTH (FROM THE OH
VLY INTO THE NORTHEAST) AND TO OUR SOUTH. STILL, QPF OF AN
ADDITIONAL ONE TO TWO-TENTHS ON AVERAGE APPEARS REASONABLE. DESPITE
SHRAS AND CONSIDERABLE CLOUDS, RATHER MILD W/ CONTINUED WAA. LOOK
FOR HIGHS INTO THE U50S-NR 60 ACROSS THE PIEDMONT, L-M60S ELSEWHERE.
MONDAY NIGHT/TUESDAY...
SECOND SHORTWAVE PIVOTS NE/OFFSHORE LATE MON. UPPER LOW
DAMPENS/WEAKENS A BIT AS IT MOVES FROM THE MIDDLE MS VALLEY MON
NIGHT NE TO THE EASTERN GREAT LAKES BY TUESDAY MORNING...PUSHING
THE ATTENDANT SFC FRONT EAST AS WELL. NUMERICAL GUIDANCE HAS
SLOWED SLIGHTLY WITH FRONTAL TIMING. NEW 12Z SUITE OF DATA LOOKS
TO BRING FRONT THROUGH BY/SHORTLY AFTER DAWN TUESDAY MORNING.
GIVEN WEAK FRONTAL FORCING, EXPECT THIS TIMING TO CONTINUE TO SLOW
SLIGHTLY WITH SUBSEQUENT RUNS. THUS, GIVEN THIS SLOWER TIMING AND
WITH SIG CAA LIKELY TO LAG BEHIND FROPA, HV KEPT MAXIMA IN THE
U50S/NR 60 WEST, M-U60S SE.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
TRENDED EXTENDED PERIOD FORECAST TOWARD THE LATEST EUROPEAN MODEL,
AS A STORM SYSTEM BRINGS WET CONDITIONS AND COOL TEMPS TO THE MID
ATLANTIC STATES TOWARD THE END OF NEXT WEEK.
UPPER/SFC LOW WILL CONTINUE TO PUSH OFFSHORE WED MORNING AS COOL
MID/UPPER LEVEL TROUGH LOCATES OVER THE INTERMOUNTAIN WEST.
UPPER/SFC HIGH PRESSURE WILL BUILD INTO THE REGION WEDS AS DEEP WLY
FLOW BRINGS SUNNY TO PARTLY SUNNY SKIES. AS THE BEST COLD AIR WILL
REMAIN NORTH OF THE REGION...850 TEMPS ONLY EXPECTED TO FALL TO
RIGHT AROUND FREEZING. THUS...HAVE TRENDED TEMPS WEDS A FEW DEGS
WARMER INTO THE MID/UPPER 50S.
SFC HIGH PRESSURE WILL DRIFT OFF THE SE COAST THURSDAY MORNING AS
THE MID LEVEL RIDGE AXIS MOVES EAST OF THE REGION LATE THURSDAY
MORNING. DEPARTING LOW PRESSURE FROM EARLIER IN THE WEEK WILL PHASE
WITH STRONG LOW OVER THE NORTHERN ATLANTIC...HELPING AMPLIFY THE
EAST COAST RIDGE. THIS WILL RESULT IN INCREASED SWLY FLOW AND
MOISTURE ADVECTION INTO THE REGION. CLOUDS WILL ALSO BE ON THE
INCREASE WITH MOSTLY CLOUDY/CLOUDY SKIES EXPECTED BY THURSDAY
AFTERNOON. WHILE HEIGHTS/THICKNESS VALUES INCREASE...CLOUD COVER AND
WEAK MIXING WILL LIMIT AFTERNOON WARMING WITH TEMPS ONLY EXPECTED IN
THE LOW/MID 50S N TO MID/UPPER 50S S.
WHILE SPATIAL AND TIMING DIFFERENCES EXIST WITH THE COLD FRONT IN
EACH RUN...FRONT IS EXPECTED TO REACH THE FA THURS NIGHT AND CROSS
THE REGION THROUGH FRIDAY MORNING. BEST FORCING FOR ASCENT LOOKS TO
BE OVER THE REGION AS VORT MAX AND PV ANOMALY...AS WELL AS COUPLING
SUBTROPICAL/POLAR JET INCREASE DIVERGENCE ALOFT. COULD SEE A GOOD
CHANCE AT WIDESPREAD BENEFICIAL RAIN SHOWERS. COLD POLAR CONTINENTAL
AIR WILL RUSH IN BEHIND THE SYSTEM WITH TEMPS EXPECTED IN THE MID
40S NE TO MID 50S SW FRIDAY AFTERNOON (TEMPS MAY FALL DURING THE DAY
DEPENDING ON FRONTAL TIMING). TEMPS WILL FALL INTO THE MID/UPPER 20S
SATURDAY MORNING ONLY TO REBOUND INTO THE LOW/MID 40S SATURDAY
AFTERNOON...POSSIBLY COLDER. MOST OF THE PRECIP WILL BE TIED TO THE
FRONT AND BEATING THE POLAR AIR...TEMPS WILL BE WARM ENOUGH TO
SQUASH ANY WINTRY MIX FRIDAY MORNING.
AS OMEGA BLOCKING IS FORECAST TO OCCUR OVER THE NORTHERN ATLANTIC
THROUGH NEXT WEEKEND...COLD WEATHER IS LIKELY TO CONTINUE THROUGH
THE WEEKEND AS ANOTHER SHORTWAVE REINFORCES THE COLD AIR.
HOWEVER...DRY CONDITIONS WILL PREVAIL.
&&
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
LOW CONFIDENCE FORECAST FOR SUNDAY AS WARM ADVECTION STRATUS
DEVELOPS OVER THE REGION. USED A MIXTURE OF GUIDANCE WITH NAM
SEEMING TO LOW. EXPECT LOWEST BASES WILL BE OVER NRN AREAS. A FEW
HOURS OF LIGHT RAIN IS EXPECTED THROUGH MID MRNG. KEPT IFR OUT
OF THE FCST AT ORF AND ECG. LOW CLOUDS BASES EXPECTED TO ONLY
IMPROVE A LITTLE DURING THE LATE MRNG AND EARLY AFTN. MOST GUIDANCE
BRINGS IFR BACK TO THE TAF SITES BY LATE AFTN BUT DID NOT INCLUDE IT
THIS FAR OUT.
IN THE SHORT TERM...SINCE PUTTING OUT THE TAF...MVFR VSBYS HAVE
DEVELOPED AT PHF AND ORF AS T/TD SPREAD HAS DECREASED UNDER A THIN
PARTIAL CLOUD COVER. WILL MONITOR BUT DO NOT SEE INDICATION OF
WIDESPREAD IFR AT THIS TIME AS CLOUDS INCREASE ACROSS THE AREA.
OUTLOOK...PERIODS OF IFR ALONG WITH PCPN ARE EXPECTED THROUGH MONDAY
NIGHT. CONDITIONS IMPROVE TUESDAY WITH DRY WEATHER FORECAST THROUGH
WEDNESDAY. A CHANCE FOR SHOWERS RETURNS THURSDAY.
&&
.MARINE...
SFC HIGH PRESSURE HAS ALLOWED FOR CALM WINDS AOB 10 KT OVER THE
WATERS THIS AFTERNOON WITH SEAS GENERALLY 2 TO 3 FT. HIGH PRESSURE
WILL SHIFT OFFSHORE THIS EVENING AS A WEAK COASTAL LOW LIFTS UP
THE SE COAST TONIGHT BRINGING LIGHT RAIN AND S/SE WINDS ALONG THE
COAST. LOW PRESSURE WILL THEN LIFT OUT OF THE MIDWEST
MONDAY...WITH A SECONDARY AREA OF LOW PRESSURE DEVELOPING JUST
NORTH OF THE WATERS MONDAY NIGHT/TUESDAY. WINDS WILL BACK TO THE
S/SW MONDAY AFTERNOON (5 TO 10 KT). WITH HIGH PRESSURE LOCATED
OFFSHORE...THE PRESSURE GRADIENT WILL TIGHTEN ALLOWING FOR
INCREASINGLY SLY WINDS OVER THE WATERS BEGINNING MONDAY EVENING. A
WEAK COLD FRONT WILL CROSS THE WATERS MONDAY NIGHT INTO
TUESDAY...BACKING THE WINDS TO THE W/NW AND ALLOWING FOR STRONGER
CAA ALOFT. SEAS WILL BEGIN TO BUILD 4 TO 5 FT TUESDAY
AFTERNOON...THUS SCA HEADLINES WILL LIKELY BE NEEDED AT LEAST OVER
THE NORTHERN COASTAL ZONES. STRONGEST CAA WILL OCCUR TUESDAY NIGHT
INTO WEDNESDAY...WHICH WILL LEAD TO LIKELY SCA CONDITIONS OVER THE
WATERS.
WINDS/SEAS WILL BEGIN TO SUBSIDE WEDS AFTERNOON AS HIGH PRESSURE
BUILDS IN FROM THE SOUTH. ANOTHER STRONGER LOW PRESSURE SYSTEM
WILL IMPACT THE REGION TOWARD THE END OF NEXT WEEK WITH SCA
CONDITIONS LIKELY.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...MAM
NEAR TERM...AJZ/MAS/MAM
SHORT TERM...MAM
LONG TERM...MPR/SAM
AVIATION...LSA
MARINE...MAS/SAM
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1208 PM EST SUN DEC 16 2012
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 521 AM EST SUN DEC 16 2012
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW SPLIT FLOW ACROSS
NAMERICA WITH NRN BRANCH FLOW CONFINED TO CANADA. ACTIVE SRN BRANCH
FLOW OVER THE CONUS FEATURES A TROF OVER THE ROCKIES UPSTREAM OF A
RDG ALONG THE E COAST. SHRTWV EMBEDDED IN THE WSW FLOW ALF BTWN
THESE LARGER SCALE FEATURES IS RIPPLING THRU THE GREAT LKS BUT
WEAKENING AS IT MOVES INTO THE LARGER SCALE UPR RDG. THIS
DISTURBANCE WAS RESPONSIBLE FOR THE RA/SN MIX THAT IMPACTED UPR MI
ON SAT...BUT LATEST IR IMAGERY INDICATES CLOUD TOP TEMPS ARE WARMING
OVER THE AREA UNDER LARGER SCALE H85-5 QVECTOR DVGC LEFT IN THE WAKE
OF THIS WEAKENING SHRTWV DESPITE DEEP MSTR SHOWN ON THE LOCAL 00Z
RAOBS. LINGERNIG PCPN IS ON THE LIGHT SIDE AND CONSISTS OF MAINLY
SCT -SHSNRA OVER THE E HALF OF THE CWA CLOSER TO THE DEPARTING
SHRTWV. SFC TEMPS REMAIN WELL ABV NORMAL...MAINLY 34 TO 39 AT 09Z.
SOME FOG HAS FORMED AS WELL UNDER THE UPR SUBSIDENCE/DRYING. JUST TO
THE W THERE IS ANOTHER AREA OF COLDER CLOUD TOPS OVER MN ASSOCIATED
WITH ANOTHER WEAKER SHRTWV NEAR MPX AND A NRN BRANCH DISTURBANCE
NEAR LK WINNIPEG. UNDER THE BAND OF HIER RADAR REFLECTIVIES...MANY
LOCATIONS OVER THE E HALF OF MN ARE REPORTING SOME -SN...MIXED WITH
-RA AT A FEW SPOTS.
FCST CONCERNS IN THE SHORT TERM REVOLVE ARND LINGERING PCPN
CHCS/PTYPE ASSOCIATED WITH DEPARTING DISTURBANCE AND THEN ON TIMING/
PTYPE OF POPS ASSOCIATED WITH PAIR OF SHRTWVS TO THE W.
TODAY...EXPECT LINGERING PCPN OVER MAINLY THE E HALF ASSOCIATED WITH
FIRST SHRTWV TO FADE THIS MRNG AND PERHAPS GIVE WAY TO SOME
-DZ/-FZDZ IN UPSLOPE AREAS IMPACTED BY LLVL SE FLOW AS THE
DISTURBANCE/ACCOMPANYING FORCING SHIFTS TO THE E AND DEEP QVECTOR
DVGC/SUBSIDENCE/UPR DRYING TAKES HOLD. BUT STRIPE OF PCPN TO THE W
WL BEGIN TO SHIFT E INTO THE WRN CWA BY 12Z AS THE PAIR OF SHRTWVS/
ACCOMPANYING H7-3 QVECTOR CNVGC MOVE TO THE E. HOWEVER...MODELS SHOW
THE QVECTOR CNVGC WEAKENING WITH TIME...PROBABLY BECAUSE OF
INCREASING CAD IN THE WAKE OF H85 LO SHIFTING THRU THE UPR LKS. SO
SUSPECT PCPN AMOUNTS ASSOCIATED WITH THE INCOMING BAND OF SN MIXED
WITH RA WL BE GREATEST OVER THE W BUT STILL ON THE LIGHT SIDE.
TONIGHT...LINGERING PCPN WL TRANSITION TO LES AS PAIR OF SHRTWVS TO
THE W FADE AND THE WNW FLOW IN THE WAKE OF H85 LO MOVING NE THRU
ONTARIO ADVECTS COLDER AIR INTO THE UPR LKS UNDER MID LVL DRYING.
HOWEVER...FCST H85 TEMPS FCST NO LOWER THAN -8 TO -9C /COMPARED TO
WATER TEMPS IN THE 4-5C RANGE/ AS WELL AS PLACEMENT OF THE DGZ ABV
THE LLVL MSTR SUGGEST THIS LES SHOULD BE RELATIVELY LIGHT.
MAINTAINED THE HIER LIKELY POPS OVER THE NW CWA WITH MORE FVRBL LLVL
CNVGC/UPSLOPE WIND COMPONENT/GREATER THERMAL INSTABILITY. BUT EVEN
THERE...ANY SN ACCUM SHOULD BE AOB 2 INCHES.
.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 521 AM EST SUN DEC 16 2012
MONDAY...THE WEAK SFC LOW PRES WILL ONLY SLOWLY LIFT TO THE
NORTHEAST OF THE AREA AS THE MID/UPPER LEVEL TROUGH FROM NW ONTARIO
AND MANITOBA INTO THE NRN GREAT LAKES PERSISTS. WITH LITTLE OR NO
LARGE SCALE FORCING OVER THE AREA AND 850 MB TEMPS ONLY TO AROUND
-8C...LAKE INDUCED CAPE/INSTABILITY FOR ANY LES WILL ONLY BE
MARGINAL. THERE WILL STILL BE ENOUGH 850-750 MB MOISTURE OVER THE
AREA (INVERSION HEIGHTS NEAR 7K FT) FOR SCT/NMRS -SHSN EARLY MONDAY
INTO THE KEWEENAW AND FOR AREAS FROM MUNSING EASTWARD. HOWEVER...ONLY
LIGHT SNOWFALL AMOUNT OF AN INCH OR LESS ARE EXPECTED.
MONDAY NIGHT INTO TUE...WITH WINDS BACKING TO THE WEST AND BECOMING
LIGHT/ANTICYLONIC ALONG WITH FALLING INVERSION HEIGHTS AS A WEAK
RIDGE BUILD INTO THE AREA...ANY LINGERING LES WILL DIMINISH AND END
MON NIGHT WITH LITTLE OR NO ADDITIONAL ACCUMULATION. ONLY WEAK
FORCING WITH A SHORTWAVE TROUGH BRUSHING THE LATE MON NIGHT INTO TUE
WILL NOT BE ENOUGH TO SUPPORT ANY ADDITIONAL PCPN. A SHRTWV AND
ASSOCIATED BAND OF 285K-290K ISENTROPIC LIFT MOVING OUT OF THE
PLAINS INTO WI LATE TUE INTO TUE NIGHT COULD BRING SOME PATCHY LIGHT
SNOW INTO WEST UPPER MI.
WED-SAT...MODELS CONTINUE TO ADVERTISE POTENTIAL FOR A MAJOR WINTER
STORM SYSTEM MOVING OUT OF THE SOUTHERN PLAINS INTO THE CENTRAL
GREAT LAKES. THE MODELS HAVE COME INTO BETTER AGREEMENT WITH THE
TRACK OF THE SYSTEM WITH CONSENSUS BRINGING THE SFC LOW THROUGH LOWER
MI. HOWEVER...SIGNFICANT UNCERTAINTY REMAINS WITH THE EVENTUAL TRACK
AND STRENGTH AT THIS TIME FRAME. THE MAIN CLUSTER OF SOLUTIONS FROM THE
GFS ENSEMBLES AND OPERATIONAL GFS/ECMWF/UKMET WOULD BRING THE SYSTEM
CLOSE ENOUGH TO UPPER MI FOR SIGNFICANT SYNOPTIC SNOW ACROSS THE EAST
HALF OF THE CWA THU INTO THU NIGHT. UNLESS THE STORM AND DEEPER
MOISTURE MOVE TOO FAR TO THE SOUTH...A SIGNFICANT LAKE ENHANCED SNOW
TRANSITIONING TO PURE LES WOULD ALSO BE LIKELY FOR NORTH WIND FAVORED
SNOWBELTS INTO FRI. WITH A DEEP LOW PRES SYSTEM LIKELY...THERE WILL
BE THE POTENTIAL FOR VERY DIFFICULT TRAVEL CONDITIONS WITH SN/BLSN.
ADDITIONAL LES FOR N TO NW SNOWBELTS IS ALSO POSSIBLE INTO SATURDAY.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1208 PM EST SUN DEC 16 2012
EXPECT IFR/LIFR CONDITIONS TO PREDOMINATE THRU THIS AFTERNOON AT ALL
3 SITES WITH LINGERING LLVL MSTR ACCOMPANYING PASSAGE OF A SFC LO
PRESSURE TROF. SOME VLIFR CONDITIONS ARE LIKELY EARLY AT CMX AS
WELL. CONDITIONS ARE LIKELY TO IMPROVE TO MVFR TNGT AT IWD/SAW WITH
W FLOW IN THE WAKE OF THE TROF PASSAGE BRINGING A BIT DRIER LLVL AIR
AS WELL A DOWNSLOPE WIND COMPONENT TO SAW. IFR CONDITIONS ARE LIKELY
TO PERSIST THE ENTIRE PERIOD AT CMX WITH UPSLOPE WIND ALSO MOISTENED
BY PASSAGE OVER LK SUP.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 521 AM EST SUN DEC 16 2012
AS A LO PRES TROF SHIFTS E ACROSS THE LAKE TODAY...EXPECT
DIMINISHING SE WINDS OVER THE E. ALLOWED GOING GALE WARNING FOR THE
FAR E TO EXPIRE AT 09Z AS SCHEDULED. FOLLOWING THE TROF PASSAGE THRU
TONIGHT...PLAN ON A WIND SHIFT TO THE WNW W TO E. BUT A FAIRLY WEAK
PRES GRADIENT THRU TONIGHT SHOULD KEEP THESE WINDS NO HIER THAN
15-25 KTS.
NORTH GALES ARE POSSIBLE LATE THURSDAY INTO FRIDAY AS A DEEPENING LOW
PRESSURE SYSTEM MOVES FROM THE MID MISSISSIPPI VALLEY INTO THE
CENTRAL GREAT LAKES.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...KC
LONG TERM...JLB
AVIATION...07
MARINE...KC/JLB
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
629 AM EST SUN DEC 16 2012
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 521 AM EST SUN DEC 16 2012
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW SPLIT FLOW ACROSS
NAMERICA WITH NRN BRANCH FLOW CONFINED TO CANADA. ACTIVE SRN BRANCH
FLOW OVER THE CONUS FEATURES A TROF OVER THE ROCKIES UPSTREAM OF A
RDG ALONG THE E COAST. SHRTWV EMBEDDED IN THE WSW FLOW ALF BTWN
THESE LARGER SCALE FEATURES IS RIPPLING THRU THE GREAT LKS BUT
WEAKENING AS IT MOVES INTO THE LARGER SCALE UPR RDG. THIS
DISTURBANCE WAS RESPONSIBLE FOR THE RA/SN MIX THAT IMPACTED UPR MI
ON SAT...BUT LATEST IR IMAGERY INDICATES CLOUD TOP TEMPS ARE WARMING
OVER THE AREA UNDER LARGER SCALE H85-5 QVECTOR DVGC LEFT IN THE WAKE
OF THIS WEAKENING SHRTWV DESPITE DEEP MSTR SHOWN ON THE LOCAL 00Z
RAOBS. LINGERNIG PCPN IS ON THE LIGHT SIDE AND CONSISTS OF MAINLY
SCT -SHSNRA OVER THE E HALF OF THE CWA CLOSER TO THE DEPARTING
SHRTWV. SFC TEMPS REMAIN WELL ABV NORMAL...MAINLY 34 TO 39 AT 09Z.
SOME FOG HAS FORMED AS WELL UNDER THE UPR SUBSIDENCE/DRYING. JUST TO
THE W THERE IS ANOTHER AREA OF COLDER CLOUD TOPS OVER MN ASSOCIATED
WITH ANOTHER WEAKER SHRTWV NEAR MPX AND A NRN BRANCH DISTURBANCE
NEAR LK WINNIPEG. UNDER THE BAND OF HIER RADAR REFLECTIVIES...MANY
LOCATIONS OVER THE E HALF OF MN ARE REPORTING SOME -SN...MIXED WITH
-RA AT A FEW SPOTS.
FCST CONCERNS IN THE SHORT TERM REVOLVE ARND LINGERING PCPN
CHCS/PTYPE ASSOCIATED WITH DEPARTING DISTURBANCE AND THEN ON TIMING/
PTYPE OF POPS ASSOCIATED WITH PAIR OF SHRTWVS TO THE W.
TODAY...EXPECT LINGERING PCPN OVER MAINLY THE E HALF ASSOCIATED WITH
FIRST SHRTWV TO FADE THIS MRNG AND PERHAPS GIVE WAY TO SOME
-DZ/-FZDZ IN UPSLOPE AREAS IMPACTED BY LLVL SE FLOW AS THE
DISTURBANCE/ACCOMPANYING FORCING SHIFTS TO THE E AND DEEP QVECTOR
DVGC/SUBSIDENCE/UPR DRYING TAKES HOLD. BUT STRIPE OF PCPN TO THE W
WL BEGIN TO SHIFT E INTO THE WRN CWA BY 12Z AS THE PAIR OF SHRTWVS/
ACCOMPANYING H7-3 QVECTOR CNVGC MOVE TO THE E. HOWEVER...MODELS SHOW
THE QVECTOR CNVGC WEAKENING WITH TIME...PROBABLY BECAUSE OF
INCREASING CAD IN THE WAKE OF H85 LO SHIFTING THRU THE UPR LKS. SO
SUSPECT PCPN AMOUNTS ASSOCIATED WITH THE INCOMING BAND OF SN MIXED
WITH RA WL BE GREATEST OVER THE W BUT STILL ON THE LIGHT SIDE.
TONIGHT...LINGERING PCPN WL TRANSITION TO LES AS PAIR OF SHRTWVS TO
THE W FADE AND THE WNW FLOW IN THE WAKE OF H85 LO MOVING NE THRU
ONTARIO ADVECTS COLDER AIR INTO THE UPR LKS UNDER MID LVL DRYING.
HOWEVER...FCST H85 TEMPS FCST NO LOWER THAN -8 TO -9C /COMPARED TO
WATER TEMPS IN THE 4-5C RANGE/ AS WELL AS PLACEMENT OF THE DGZ ABV
THE LLVL MSTR SUGGEST THIS LES SHOULD BE RELATIVELY LIGHT.
MAINTAINED THE HIER LIKELY POPS OVER THE NW CWA WITH MORE FVRBL LLVL
CNVGC/UPSLOPE WIND COMPONENT/GREATER THERMAL INSTABILITY. BUT EVEN
THERE...ANY SN ACCUM SHOULD BE AOB 2 INCHES.
.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 521 AM EST SUN DEC 16 2012
MONDAY...THE WEAK SFC LOW PRES WILL ONLY SLOWLY LIFT TO THE
NORTHEAST OF THE AREA AS THE MID/UPPER LEVEL TROUGH FROM NW ONTARIO
AND MANITOBA INTO THE NRN GREAT LAKES PERSISTS. WITH LITTLE OR NO
LARGE SCALE FORCING OVER THE AREA AND 850 MB TEMPS ONLY TO AROUND
-8C...LAKE INDUCED CAPE/INSTABILITY FOR ANY LES WILL ONLY BE
MARGINAL. THERE WILL STILL BE ENOUGH 850-750 MB MOISTURE OVER THE
AREA (INVERSION HEIGHTS NEAR 7K FT) FOR SCT/NMRS -SHSN EARLY MONDAY
INTO THE KEWEENAW AND FOR AREAS FROM MUNSING EASTWARD. HOWEVER...ONLY
LIGHT SNOWFALL AMOUNT OF AN INCH OR LESS ARE EXPECTED.
MONDAY NIGHT INTO TUE...WITH WINDS BACKING TO THE WEST AND BECOMING
LIGHT/ANTICYLONIC ALONG WITH FALLING INVERSION HEIGHTS AS A WEAK
RIDGE BUILD INTO THE AREA...ANY LINGERING LES WILL DIMINISH AND END
MON NIGHT WITH LITTLE OR NO ADDITIONAL ACCUMULATION. ONLY WEAK
FORCING WITH A SHORTWAVE TROUGH BRUSHING THE LATE MON NIGHT INTO TUE
WILL NOT BE ENOUGH TO SUPPORT ANY ADDITIONAL PCPN. A SHRTWV AND
ASSOCIATED BAND OF 285K-290K ISENTROPIC LIFT MOVING OUT OF THE
PLAINS INTO WI LATE TUE INTO TUE NIGHT COULD BRING SOME PATCHY LIGHT
SNOW INTO WEST UPPER MI.
WED-SAT...MODELS CONTINUE TO ADVERTISE POTENTIAL FOR A MAJOR WINTER
STORM SYSTEM MOVING OUT OF THE SOUTHERN PLAINS INTO THE CENTRAL
GREAT LAKES. THE MODELS HAVE COME INTO BETTER AGREEMENT WITH THE
TRACK OF THE SYSTEM WITH CONSENSUS BRINGING THE SFC LOW THROUGH LOWER
MI. HOWEVER...SIGNFICANT UNCERTAINTY REMAINS WITH THE EVENTUAL TRACK
AND STRENGTH AT THIS TIME FRAME. THE MAIN CLUSTER OF SOLUTIONS FROM THE
GFS ENSEMBLES AND OPERATIONAL GFS/ECMWF/UKMET WOULD BRING THE SYSTEM
CLOSE ENOUGH TO UPPER MI FOR SIGNFICANT SYNOPTIC SNOW ACROSS THE EAST
HALF OF THE CWA THU INTO THU NIGHT. UNLESS THE STORM AND DEEPER
MOISTURE MOVE TOO FAR TO THE SOUTH...A SIGNFICANT LAKE ENHANCED SNOW
TRANSITIONING TO PURE LES WOULD ALSO BE LIKELY FOR NORTH WIND FAVORED
SNOWBELTS INTO FRI. WITH A DEEP LOW PRES SYSTEM LIKELY...THERE WILL
BE THE POTENTIAL FOR VERY DIFFICULT TRAVEL CONDITIONS WITH SN/BLSN.
ADDITIONAL LES FOR N TO NW SNOWBELTS IS ALSO POSSIBLE INTO SATURDAY.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 628 AM EST SUN DEC 16 2012
EXPECT IFR/LIFR CONDITIONS TO PREDOMINATE THRU TODAY AT ALL 3 SITES
WITH LINGERING LLVL MSTR ACCOMPANYING PASSAGE OF SFC LO PRES TROF.
SOME VLIFR CONDITIONS ARE LIKELY EARLY AT CMX AS WELL. CONDITIONS
ARE LIKELY TO IMPROVE TO MVFR TNGT AT IWD/SAW WITH W FLOW IN THE
WAKE OF THE TROF PASSAGE BRINGING A BIT DRIER LLVL AIR AS WELL A
DOWNSLOPE WIND COMPONENT TO SAW. IFR CONDITIONS ARE LIKELY TO
PERSIST THE ENTIRE PERIOD AT CMX WITH UPSLOPE WIND ALSO MOISTENED BY
PASSAGE OVER LK SUP.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 521 AM EST SUN DEC 16 2012
AS A LO PRES TROF SHIFTS E ACROSS THE LAKE TODAY...EXPECT
DIMINISHING SE WINDS OVER THE E. ALLOWED GOING GALE WARNING FOR THE
FAR E TO EXPIRE AT 09Z AS SCHEDULED. FOLLOWING THE TROF PASSAGE THRU
TONIGHT...PLAN ON A WIND SHIFT TO THE WNW W TO E. BUT A FAIRLY WEAK
PRES GRADIENT THRU TONIGHT SHOULD KEEP THESE WINDS NO HIER THAN
15-25 KTS.
NORTH GALES ARE POSSIBLE LATE THURSDAY INTO FRIDAY AS A DEEPENING LOW
PRESSURE SYSTEM MOVES FROM THE MID MISSISSIPPI VALLEY INTO THE
CENTRAL GREAT LAKES.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...KC
LONG TERM...JLB
AVIATION...KC
MARINE...KC/JLB
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
527 AM EST SUN DEC 16 2012
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 521 AM EST SUN DEC 16 2012
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW SPLIT FLOW ACROSS
NAMERICA WITH NRN BRANCH FLOW CONFINED TO CANADA. ACTIVE SRN BRANCH
FLOW OVER THE CONUS FEATURES A TROF OVER THE ROCKIES UPSTREAM OF A
RDG ALONG THE E COAST. SHRTWV EMBEDDED IN THE WSW FLOW ALF BTWN
THESE LARGER SCALE FEATURES IS RIPPLING THRU THE GREAT LKS BUT
WEAKENING AS IT MOVES INTO THE LARGER SCALE UPR RDG. THIS
DISTURBANCE WAS RESPONSIBLE FOR THE RA/SN MIX THAT IMPACTED UPR MI
ON SAT...BUT LATEST IR IMAGERY INDICATES CLOUD TOP TEMPS ARE WARMING
OVER THE AREA UNDER LARGER SCALE H85-5 QVECTOR DVGC LEFT IN THE WAKE
OF THIS WEAKENING SHRTWV DESPITE DEEP MSTR SHOWN ON THE LOCAL 00Z
RAOBS. LINGERNIG PCPN IS ON THE LIGHT SIDE AND CONSISTS OF MAINLY
SCT -SHSNRA OVER THE E HALF OF THE CWA CLOSER TO THE DEPARTING
SHRTWV. SFC TEMPS REMAIN WELL ABV NORMAL...MAINLY 34 TO 39 AT 09Z.
SOME FOG HAS FORMED AS WELL UNDER THE UPR SUBSIDENCE/DRYING. JUST TO
THE W THERE IS ANOTHER AREA OF COLDER CLOUD TOPS OVER MN ASSOCIATED
WITH ANOTHER WEAKER SHRTWV NEAR MPX AND A NRN BRANCH DISTURBANCE
NEAR LK WINNIPEG. UNDER THE BAND OF HIER RADAR REFLECTIVIES...MANY
LOCATIONS OVER THE E HALF OF MN ARE REPORTING SOME -SN...MIXED WITH
-RA AT A FEW SPOTS.
FCST CONCERNS IN THE SHORT TERM REVOLVE ARND LINGERING PCPN
CHCS/PTYPE ASSOCIATED WITH DEPARTING DISTURBANCE AND THEN ON TIMING/
PTYPE OF POPS ASSOCIATED WITH PAIR OF SHRTWVS TO THE W.
TODAY...EXPECT LINGERING PCPN OVER MAINLY THE E HALF ASSOCIATED WITH
FIRST SHRTWV TO FADE THIS MRNG AND PERHAPS GIVE WAY TO SOME
-DZ/-FZDZ IN UPSLOPE AREAS IMPACTED BY LLVL SE FLOW AS THE
DISTURBANCE/ACCOMPANYING FORCING SHIFTS TO THE E AND DEEP QVECTOR
DVGC/SUBSIDENCE/UPR DRYING TAKES HOLD. BUT STRIPE OF PCPN TO THE W
WL BEGIN TO SHIFT E INTO THE WRN CWA BY 12Z AS THE PAIR OF SHRTWVS/
ACCOMPANYING H7-3 QVECTOR CNVGC MOVE TO THE E. HOWEVER...MODELS SHOW
THE QVECTOR CNVGC WEAKENING WITH TIME...PROBABLY BECAUSE OF
INCREASING CAD IN THE WAKE OF H85 LO SHIFTING THRU THE UPR LKS. SO
SUSPECT PCPN AMOUNTS ASSOCIATED WITH THE INCOMING BAND OF SN MIXED
WITH RA WL BE GREATEST OVER THE W BUT STILL ON THE LIGHT SIDE.
TONIGHT...LINGERING PCPN WL TRANSITION TO LES AS PAIR OF SHRTWVS TO
THE W FADE AND THE WNW FLOW IN THE WAKE OF H85 LO MOVING NE THRU
ONTARIO ADVECTS COLDER AIR INTO THE UPR LKS UNDER MID LVL DRYING.
HOWEVER...FCST H85 TEMPS FCST NO LOWER THAN -8 TO -9C /COMPARED TO
WATER TEMPS IN THE 4-5C RANGE/ AS WELL AS PLACEMENT OF THE DGZ ABV
THE LLVL MSTR SUGGEST THIS LES SHOULD BE RELATIVELY LIGHT.
MAINTAINED THE HIER LIKELY POPS OVER THE NW CWA WITH MORE FVRBL LLVL
CNVGC/UPSLOPE WIND COMPONENT/GREATER THERMAL INSTABILITY. BUT EVEN
THERE...ANY SN ACCUM SHOULD BE AOB 2 INCHES.
.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 521 AM EST SUN DEC 16 2012
MONDAY...THE WEAK SFC LOW PRES WILL ONLY SLOWLY LIFT TO THE
NORTHEAST OF THE AREA AS THE MID/UPPER LEVEL TROUGH FROM NW ONTARIO
AND MANITOBA INTO THE NRN GREAT LAKES PERSISTS. WITH LITTLE OR NO
LARGE SCALE FORCING OVER THE AREA AND 850 MB TEMPS ONLY TO AROUND
-8C...LAKE INDUCED CAPE/INSTABILITY FOR ANY LES WILL ONLY BE
MARGINAL. THERE WILL STILL BE ENOUGH 850-750 MB MOISTURE OVER THE
AREA (INVERSION HEIGHTS NEAR 7K FT) FOR SCT/NMRS -SHSN EARLY MONDAY
INTO THE KEWEENAW AND FOR AREAS FROM MUNSING EASTWARD. HOWEVER...ONLY
LIGHT SNOWFALL AMOUNT OF AN INCH OR LESS ARE EXPECTED.
MONDAY NIGHT INTO TUE...WITH WINDS BACKING TO THE WEST AND BECOMING
LIGHT/ANTICYLONIC ALONG WITH FALLING INVERSION HEIGHTS AS A WEAK
RIDGE BUILD INTO THE AREA...ANY LINGERING LES WILL DIMINISH AND END
MON NIGHT WITH LITTLE OR NO ADDITIONAL ACCUMULATION. ONLY WEAK
FORCING WITH A SHORTWAVE TROUGH BRUSHING THE LATE MON NIGHT INTO TUE
WILL NOT BE ENOUGH TO SUPPORT ANY ADDITIONAL PCPN. A SHRTWV AND
ASSOCIATED BAND OF 285K-290K ISENTROPIC LIFT MOVING OUT OF THE
PLAINS INTO WI LATE TUE INTO TUE NIGHT COULD BRING SOME PATCHY LIGHT
SNOW INTO WEST UPPER MI.
WED-SAT...MODELS CONTINUE TO ADVERTISE POTENTIAL FOR A MAJOR WINTER
STORM SYSTEM MOVING OUT OF THE SOUTHERN PLAINS INTO THE CENTRAL
GREAT LAKES. THE MODELS HAVE COME INTO BETTER AGREEMENT WITH THE
TRACK OF THE SYSTEM WITH CONSENSUS BRINGING THE SFC LOW THROUGH LOWER
MI. HOWEVER...SIGNFICANT UNCERTAINTY REMAINS WITH THE EVENTUAL TRACK
AND STRENGTH AT THIS TIME FRAME. THE MAIN CLUSTER OF SOLUTIONS FROM THE
GFS ENSEMBLES AND OPERATIONAL GFS/ECMWF/UKMET WOULD BRING THE SYSTEM
CLOSE ENOUGH TO UPPER MI FOR SIGNFICANT SYNOPTIC SNOW ACROSS THE EAST
HALF OF THE CWA THU INTO THU NIGHT. UNLESS THE STORM AND DEEPER
MOISTURE MOVE TOO FAR TO THE SOUTH...A SIGNFICANT LAKE ENHANCED SNOW
TRANSITIONING TO PURE LES WOULD ALSO BE LIKELY FOR NORTH WIND FAVORED
SNOWBELTS INTO FRI. WITH A DEEP LOW PRES SYSTEM LIKELY...THERE WILL
BE THE POTENTIAL FOR VERY DIFFICULT TRAVEL CONDITIONS WITH SN/BLSN.
ADDITIONAL LES FOR N TO NW SNOWBELTS IS ALSO POSSIBLE INTO SATURDAY.
&&
.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 730 PM EST SAT DEC 15 2012
IFR/LIFR CONDITIONS WL PREDOMINATE THIS FCST PERIOD AS LOW-LVL
MOISTURE PERSISTS FROM THE ARRIVAL OF A LOW PRESSURE SYSTEM MOVING
THROUGH THE GREAT LAKES. VLIFR CONDITIONS ARE EXPECTED LATE TONIGHT
INTO SUNDAY MORNING...ESPECIALLY AT KCMX AND POSSIBLY KSAW IN
PREVAILING LIGHT E-SE UPSLOPE FLOW AND DRYING CONDITIONS ALOFT.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 521 AM EST SUN DEC 16 2012
AS A LO PRES TROF SHIFTS E ACROSS THE LAKE TODAY...EXPECT
DIMINISHING SE WINDS OVER THE E. ALLOWED GOING GALE WARNING FOR THE
FAR E TO EXPIRE AT 09Z AS SCHEDULED. FOLLOWING THE TROF PASSAGE THRU
TONIGHT...PLAN ON A WIND SHIFT TO THE WNW W TO E. BUT A FAIRLY WEAK
PRES GRADIENT THRU TONIGHT SHOULD KEEP THESE WINDS NO HIER THAN
15-25 KTS.
NORTH GALES ARE POSSIBLE LATE THURSDAY INTO FRIDAY AS A DEEPENING LOW
PRESSURE SYSTEM MOVES FROM THE MID MISSISSIPPI VALLEY INTO THE
CENTRAL GREAT LAKES.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...KC
LONG TERM...JLB
AVIATION...VOSS
MARINE...KC
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
514 AM CST SUN DEC 16 2012
.UPDATE...FOR 12Z AVIATION DISCUSSION BELOW
&&
.DISCUSSION.../ISSUED 235 AM CST SUN DEC 16 2012/
THERE ARE A FEW MINOR WEATHER ISSUES WITH
WHICH TO CONTEND OVER THE UPCOMING WEEK... BUT THE BIG STORY WILL
LIKELY BE A STRONG WINTER STORM OVER THE CENTRAL AND EASTERN CONUS
THE SECOND HALF OF THE WEEK. WE LOOK TO MISS OUT ON THAT SYSTEM
UNLESS THINGS CHANGE DRAMATICALLY... BUT WITH MODELS CONTINUING TO
TREND EAST IT APPEARS ONLY THE EASTERN PORTION OF THE AREA WILL
HAVE ANY CHANCE OF SEEING SNOWFALL... AND EVEN THOSE LOCATIONS
COULD SEE LITTLE OR NOTHING. IN THE BIG PICTURE... THE AMPLIFIED
UPPER LEVEL PATTERN LOOKS TO REMAIN IN PLACE THROUGH THE WEEK...
WITH TROUGHING OVER OUR AREA THROUGH MIDWEEK GIVING WAY TO UPPER
RIDGING BY WEEK/S END AS UPPER TROUGHS SETUP AS BOOKENDS ALONG THE
WEST AND EAST COASTS.
IN THE SHORT TERM... PCPN CURRENTLY OVER THE EASTERN PORTION OF
THE AREA WILL CONTINUE TO MOVE EAST THIS MORNING AS THE SURFACE
LOW OVER WISCONSIN MOVES INTO UPPER MICHIGAN BY THIS EVENING.
HOWEVER... THERE WILL BE ENOUGH LINGERING MOISTURE AND CYCLONIC
FLOW... AS WELL AS A WEAK SHORTWAVE MOVING THROUGH... TO KEEP SOME
LIGHT PCPN GOING THROUGH AT LEAST THE MORNING HOURS. COLDER
TEMPERATURES CONTINUE TO WORK INTO THE AREA... SO THE EXPECTATION
IS THAT ANY REMAINING PCPN SHOULD BE IN THE FORM OF SNOW BY 12Z.
HOWEVER... SHOULD THE DEEPER MOISTURE EXIT TOO QUICKLY THERE COULD
BE SOME PATCHY DRIZZLE OR FREEZING DRIZZLE... SO THAT WILL NEED TO
BE MONITORED. KEPT SOME LOW POPS OVER THE FAR EAST INTO THIS
AFTERNOON... ALTHOUGH ANYTHING THAT REMAINS SHOULD BE PATCHY AND
VERY LIGHT. A WEAK SURFACE RIDGE WILL WORK ACROSS THE AREA TONIGHT
THROUGH MONDAY... BUT IT PROBABLY WON/T DO MUCH TO SCOUR OUT CLOUD
COVER BASED ON THE NAM AND GFS 925-850MB MOISTURE PROFILES AS WELL
AS CURRENT UPSTREAM OBSERVATIONS AND 11-3.9 MICRON SATELLITE
IMAGERY. SO... KEPT MOSTLY CLOUDY CONDITIONS IN PLACE THROUGH
MONDAY WITH A DRY FORECAST. SOME WEAK ISENTROPIC LIFT AND
850-700MB FRONTOGENESIS WILL LIFT ACROSS THE AREA ON TUESDAY AS A
WEAK SURFACE LOW MOVES THROUGH THE REGION. THE BEST COMBINATION OF
FORCING AND DEEP LAYER SATURATION LOOKS TO OCCUR TO OUR NORTH...
BUT WE STILL LOOK TO HAVE ENOUGH COMING TOGETHER FOR AT LEAST
CHANCE POPS AT THIS POINT. COULD EVENTUALLY SEE SOME LIGHT
ACCUMULATIONS DEPENDING ON WHERE THE AXIS OF PCPN SETS UP... BUT
BY NO MEANS DOES IT APPEAR TO BE A SIGNIFICANT ISSUE AT THIS POINT.
SHORTWAVE RIDGING WILL OCCUR ACROSS OUR AREA TUESDAY NIGHT INTO
WEDNESDAY AHEAD OF THE MAJOR SYSTEM THAT WILL AFFECT LOCATIONS
MAINLY SOUTH/EAST OF US. THAT SYSTEM LOOKS TO GET ORGANIZED IN THE
LEE OF THE SOUTHERN ROCKIES WEDNESDAY MORNING... THEN LIFT
NORTHEAST ACROSS MISSOURI AND ILLINOIS WEDNESDAY NIGHT AND INTO
LOWER MICHIGAN BY THURSDAY AFTERNOON. THE EASTERN HALF OF THE CWFA
COULD GET CLIPPED BY SOME OF THE PCPN... ALTHOUGH THE ECMWF...
GFS... AND FIM CONTINUE TO SUGGEST ALL BUT THE FAR EASTERN PORTION
OF THE AREA WILL ENTIRELY MISS OUT ON PCPN. FOR NOW... KNOCKED
DOWN POPS FROM WHAT CONSENSUS GUIDANCE SUGGESTED... BUT KEPT SOME
CHANCE POPS FOR ROUGHLY THE SOUTHEAST HALF OF THE FORECAST AREA.
HOWEVER... IF TRENDS CONTINUE THEN LATER FORECASTS SHOULD BE ABLE
TO LOWER POPS FURTHER AND PERHAPS ONLY KEEP A MENTION FOR THE
EASTERN TIER OR TWO OF COUNTIES. GOOD UPPER RIDGING LOOKS TO WORK
INTO THE AREA BEHIND THE SYSTEM... WITH DRY WEATHER ACROSS THE
ENTIRE AREA FOR THE END OF THE WEEK.
&&
.AVIATION.../12Z TAF ISSUANCE/
EXPECT IFR CIGS TO PREVAIL AT THE TAF SITES TODAY. A SLIVER OF
CLEAR SKIES DEVELOPED OVERNIGHT OVER WEST CENTRAL AND SOUTHWEST
MN...EBUT XPECT STRATUS TO FILL BACK IN PER 16.09Z RAP 925MB RH
PROGS. VSBYS WILL TINKER BETWEEN LOW-END VFR AND HIGH-END
MVFR...BUT SHOULD IMPROVE TO AROUND 4SM OR BETTER THIS MORNING
WITH THE EXIT OF THE TROUGH AND PRECIP. GRADUAL IMPROVEMENT IS
EXPECTED FROM WESTERN TOWARD CENTRAL MN BY THIS EVENING...BUT MOST
SITES SHOULD NOT IMPROVE TO VFR UNTIL BETWEEN 06Z AND 12Z
MONDAY...WITH THE EXCEPTION OF KRWF. PREVALENT NORTHWEST WINDS
THROUGH THE PERIOD...WITH SPEEDS AROUND 10 KTS DECREASE TO BELOW 5
KTS SUNDAY EVE.
KMSP...IFR CIGS EXPECTED THROUGH THIS MORNING...IMPROVING TO MVFR
LATE THIS EVENING. CONFIDENCE ON IMPROVEMENT TO MVFR IS RATHER
LOW. ALSO EXPECT SOME MIST THIS MORNING WITH VSBYS AROUND
6SM...BUT SHOULD SEE AN UNRESTRICTED VSBY BY THIS AFTERNOON.
NORTHWEST WINDS OF 7 TO 10 KTS TODAY DECREASE BELOW 5 KTS BY 06Z MONDAY.
/OUTLOOK FOR KMSP/
MON...VFR WITH MVFR CIGS POSSIBLE. WINDS NW AT 5KTS.
TUE...MVFR WITH -SN POSSIBLE. WINDS SE BECOMING W AT 5KTS LATE.
WED...VFR. WINDS WNW AT 5-10KTS.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
TRH/LS
AREA FORECAST DISCUSSION
NWS JACKSON MS
412 PM CST SUN DEC 16 2012
.DISCUSSION...
A LARGE RAIN SHIELD CONTINUES OVER MUCH OF THE ARKLAMISS AS OF LATE
AFTERNOON AND THIS MAKES CONFIDENCE IN REDEVELOPMENT OF THE SEVERE
WEATHER POTENTIAL A LITTLE SHAKY FOR THIS EVENING AND OVERNIGHT.
HOWEVER...MOST GUIDANCE REMAINS CONVINCING IN THE STORM REDEVELOPMENT
SCENARIO AS STRONGER LIFT IS FORECAST TO DEVELOP WITH THE APPROACH
OF A STRONG MID LEVEL SHORTWAVE TROUGH AND HEIGHT FALL CENTER (500 MB
> 80M) AND ACCESS TO 330K+ THETAE.
WE ARE FOLLOWING THE COURSE AND CONTINUE TO MENTION THE POSSIBILITY
FOR SEVERE WEATHER OVER ABOUT THE SOUTHEAST HALF OF THE ARKLAMISS
AFTER 900 PM. THERE IS SOME DISAGREEMENT AMONG THE MODELS ABOUT WHEN
EXACTLY STORMS WILL RE- INITIATE IN OUR AREA...AND IT COULD BE LATER
GIVEN STRONGER STABILIZATION FROM THE CURRENT RAIN SHIELD. THE MOST
RECENT RUN OF THE HRRR IS ACTUALLY LESS EMPHATIC WITH
DEVELOPMENT...SO THE POSSIBILITY EXISTS THAT REDEVELOPMENT WILL NOT
OCCUR AT ALL. IF THE 12Z GFS PANS OUT...WE WILL SEE A RETURN OF MIXED
LAYER CAPE ~500 J/KG AND BACKING LOW LEVEL SHEAR VECTORS WITH
CONTINUED STRONG DEEP LAYER SHEAR. THIS WOULD SUPPORT A FEW SEVERE
STORMS AND WILL CONTINUE THE MENTION IN THE HWO/GRAPHICS.
DEPENDING ON REDEVELOPMENT OF STORMS TONIGHT...WE WILL NEED TO
CONTINUE A CLOSE MONITOR FOR HEAVY RAINFALL WITH ABUNDANT MOISTURE
STILL AVAILABLE AND WITH A CONTINUED SET-UP FOR TRAINING OF
STORMS...PARTICULARLY OVER SOUTHEAST PORTIONS OF THE FORECAST AREA.
TSTMS COULD LINGER MONDAY MORNING ALONG THE I-59 CORRIDOR BEFORE THE
COLD FRONT/DRY LINE CAN PASS THROUGH. OTHERWISE...EXPECT A DRY
WEATHER REGIME TO TAKE HOLD BY MONDAY AFTERNOON WITH ABOVE CLIMATIC
NORMAL TEMPERATURES. /EC/
TUESDAY THROUGH SUNDAY...
SURFACE HIGH PRESSURE WILL SHIFT OFF TO OUR EAST ON TUE BRINGING
BACK RETURN FLOW OFF THE GULF. UNSEASONABLY WARM CONDITIONS CAN BE
EXPECTED TUE AND WED AS A RESULT/ESPECIALLY WED WHERE HIGHS IN THE
LOW TO MID 70S WILL COME IN SOME 15 DEGREES ABOVE NORMAL FOR MID
DEC. THE WARMTH WILL NOT LAST LONG THOUGH AS A POTENT COLD FRONT IS
PROGGED TO CROSS THE REGION STARTING EARLY THU MORNING.
THE UPPER WAVE ASSOC WITH THIS NEXT SYSTEM WILL CROSS INTO THE
CENTRAL PLAINS WED EVENING INDUCING A DEEP SURFACE LOW OVER THE
OKLAHOMA PANHANDLE THAT WILL TRACK EAST NORTHEAST ACROSS SOUTHERN MO
AND EVENTUALLY THE GREAT LAKES. THE SYNOPTIC SETUP OFFERED BY THE
MODELS WITH THIS SYSTEM IS QUITE IMPRESSIVE...AND AT FIRST GLANCE IT
WOULD APPEAR THAT SEVERE WEATHER FOR THE ARKLAMISS WOULD BE A SLAM
DUNK. HOWEVER THE DETAILS OFFER A DIFFERENT STORY...AT LEAST FOR
NOW. WHILE ROBUST WIND FIELDS JUST AHEAD OF THE FRONT DRAW UP AMPLE
AMOUNTS OF MOISTURE/DEW POINTS CLIMBING NEAR OR ABOVE 65 DEG FOR A
GOOD PORTION OF THE AREA AND PW VALUES RISING ABOVE 1.5 IN/
TEMPERATURES ALOFT ARE RATHER WARM(H5 TEMPS -10 TO -11) WHICH
SIGNIFICANTLY REDUCES MID LEVEL LAPSE RATES AND RESULTANT
INSTABILITY. WE WILL HAVE TO KEEP AN EYE ON THIS TO SEE IF THE
MODELS TREND COOLER ALOFT BECAUSE IF THEY DO...AND THE SYNOPTIC
SETUP REMAINS SIMILAR...WE COULD BE LOOKING AT DECENT SEVERE WEATHER
POTENTIAL LATE WED INTO THU MORNING. FOR NOW...WILL OMIT MENTION OF
ANY SEVERE WEATHER IN THE HWO/GRAPHICS.
MUCH COOLER AIR WILL FILTER ACROSS THE REGION IN WAKE OF THE FRONT
WITH TEMPERATURES LIKELY FALLING THROUGH THE DAYLIGHT HOURS THU.
STRONG MIXING WILL ALLOW WINDY CONDITIONS TO DEVELOP THU AND ITS
FEASIBLE A WIND ADVISORY MAY BECOME NECESSARY FOR AT LEAST THE
DELTA...IF NOT AREAS FURTHER SOUTH AND EAST AS WELL. HIGH PRESSURE
WILL TRANSIT THE DEEP SOUTH FRI INTO THE FIRST PART OF THE WEEKEND
BEFORE RAIN CHANCES RETURN EARLY NEXT WEEK. /BK/
&&
.AVIATION...
CEILINGS SHOULD RAIN IN MVFR-IFR CONDITIONS ALONG WITH
MVFR/IFR IN RAIN AND THUNDERSTORM CONDITIONS THROUGH THE NIGHT. THE
BEST CHANCE OF THUNDERSTORMS WILL AFFECT THE SOUTHERN THIRD OF THE
REGION. WINDS WILL BE FROM THE SOUTH AT 10 TO 15 KNOTS WITH SOME HIGHER
GUSTS...THEN TURN SOUTHWEST AROUND 5 TO 10 KNOTS ON MONDAY MORNING.
THE RAINS AND CLOUDS WILL BE DECREASING FROM THE NORTHWEST ON MONDAY...THUS
VFR CONDITIONS WILL PREVAIL BY LATE MORNING INTO THE AFTERNOON./17/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 57 71 38 70 / 70 17 6 0
MERIDIAN 58 74 37 68 / 83 22 7 0
VICKSBURG 57 69 35 71 / 50 11 5 0
HATTIESBURG 62 74 41 70 / 91 31 7 0
NATCHEZ 60 67 38 69 / 69 11 5 0
GREENVILLE 56 64 41 69 / 27 9 4 0
GREENWOOD 55 69 38 70 / 44 11 5 0
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
EC/BK/17/
AREA FORECAST DISCUSSION
NWS JACKSON MS
1058 AM CST SUN DEC 16 2012
.UPDATE...
...RISK FOR HEAVY RAINFALL AND STRONG TO SEVERE STORMS CONTINUES...
A LARGE CONVECTIVE SYSTEM IS STEADILY TRACKING ESE ACROSS THE ARKLAMISS
LATE THIS MORNING. 12Z JAN/LIX SOUNDINGS REVEALED WEAK LAPSE RATES...
AND CURRENT ANALYSES INIDICATE MIXED LAYER CAPE ONLY ~200 J/KG AHEAD
OF THE SYSTEM. LATEST DGX VAD WIND PROFILE SHOWS A DISRUPTED LOOKING
SHEAR PROFILE WITH WESTERLY WIND COMPONENTS IN THE 2000-4000 FT RANGE
YIELDING 0-1KM SHEAR VECTORS VEERED TO NEARLY PARALLEL WITH CONVECTIVE
LINE.
SO THE STRONG/SEVERE STORM POTENTIAL IS AT LEAST TEMPORARILY IN
A LULL...BUT THE CONCERN FOR HEAVY RAIN CONTINUES. THERE IS PLENTY
OF MOISTURE TRANSPORT WITH PRECIPITABLE WATER NEAR 1.6 INCHES AND A
VERY MOIST BOUNDARY LAYER WITH DEWPOINTS REACHING THE MID 60S. FLASH
FLOOD GUIDANCE IS HIGH FOR THIS TIME OF THE YEAR AND THUS FAR THE
MCS HAS BEEN PROGRESSIVE ENOUGH TO LIMIT FLOODING CONCERNS...BUT WILL
KEEP A CLOSE EYE ON BACKING LOW LEVEL WINDS AHEAD OF MESOSCALE
CONVECTIVE VORTICES PROPAGATING ALONG THE LINE WHICH COULD SLOW THE
LINE DOWN AND AT LEAST TEMPORARILY RAISE FF CONCERNS. ALSO...WILL
MONITOR FOR INCREASING BOUNDARY LAYER MOISTURE AND INSTABILITY IN THE
WARM SECTOR WHICH COULD ELEVATE THE STRONG/SVR STORM POTENTIAL THIS
AFTERNOON. /EC/
&&
.PREV DISCUSSION... /ISSUED 406 AM CST SUN DEC 16 2012/
..HEAVY RAIN/FEW SEVERE STORMS POSSIBLE TODAY INTO TONIGHT...
SHORT TERM...(TODAY THROUGH MONDAY NIGHT)...
MAIN CONVECTIVE BAND ACROSS N MS INTO SRN AR STEADILY EXPANDING/
GETTING STRONGER PAST SEVERAL HOURS. OTHERWISE...ISOLATED LIGHT SHRA
CONTINUE TO CROSS N AND W PORTIONS OF THE CWFA WITH LOW STRATUS
ELSEWHERE. STALLED FRONTAL BOUNDARY STILL HANGING BACK NEAR A KJBR-
KTYR LINE AS AN UPSTREAM S/WV OVER THE SRN ROCKIES TO THE TX BIG BEND
MOVES EWD AT 40KTS TOWARD THE OZARKS. A POWERFUL UPPER JET WITH EPAC
CONNECTIONS WILL AID IN RAINFALL PRODUCTION GETTING RAMPED UP TODAY
WITH CONTINUED EXPANSION OF THE PRE-FRONTAL CONVECTION. LIKELY
TRAINING OF CONVECTION IN THIS SCENARIO DURING THE DAYLIGHT HOURS
COULD GENERATE AN AXIS OF 2-4 INCHES RATHER EASILY. MODEL CONSENSUS
PLACES THE HEAVIEST RAINFALL FROM AROUND NATCHEZ TO MERIDIAN BETWEEN
NOON AND MIDNIGHT...SOME RISK FOR LOCALIZED FLASH FLOODING WILL EXIST
BUT WILL HOLD OFF A FLASH FLOOD WATCH UNTIL THE AXIS BECOMES MORE
DEFINED SINCE 3HR FFG STILL ABOVE 3 INCHES MOST AREAS.
UNTIL THE DIURNAL INSTABILITY GETS ADDED TO THE MIX...LOOK FOR THE
EXPANDING RAIN BAND TO PUSH TO NEAR A WINNSBORO TO JACKSON TO
COLUMBUS AXIS BY ABOUT NOON...PER LATEST RUC PROGS. THEN THE RISK
FOR A FEW STRONG/SEVERE STORMS WILL BE INCREASING S OF THAT AXIS
THROUGH THE EVENING HOURS FUELED BY PWATS RISING NEAR 1.5 INCHES...
0-3KM HELICITIES OF 200-300M*M/S*S...6.5C 7-500MB LAPSE RATES...
INCREASINGLY COUPLED 850-200MB DIFFERENTIAL DIVERGENCE...850MB THETA
E AXIS OF 334K AND LEFT EXIT REGION OF A 65KT 500MB JET STREAK.
AT THIS POINT IT LOOKS LIKE THE AREA WITH THE GREATEST SEVERE
WEATHER RISK WILL BE ACROSS THE SERN HALF OF THE CWA WHERE THE BEST
COMBINATION OF SHEAR AND INSTABILITY WILL BE CO-LOCATED. EVEN A
DECENT TORNADO RISK COULD DEVELOP FOR SERN MS FROM 00-06Z AS A LAYER
OF MARINE GULF AIR OF 65-68F DEWPTS ATTEMPTS TO SURGE NWD...REF NEW
SPC DAY ONE OUTLOOK FOR UPDATES.
PRIMARY ASCENT PUSHES OFF TO OUR E MONDAY MORNING WITH DEVELOPING
UNIDIRECTIONAL FLOW FROM THE WSW BY MIDDAY. DRYING PWATS DROP TO
NEAR ONE HALF INCH BY MIDDAY ACROSS I-55...AND CLOSER TO ONE THIRD
INCH BY MIDNIGHT MONDAY NIGHT WHEN BEST CLEARING EXPECTED OF THE
REMAINING CLOUD COVER. DUE TO THE BEST RAINFALL AXIS POSITION LYING
ALONG OR S OF I-20 DURING SUNDAY...HAVE ADDED PATCHY FOG TO SRN HALF
OF CWFA LATE MONDAY NIGHT WHERE WET GROUNDS AND COOLER L40S TEMPS
EXIST UNDER NEAR CALM SURFACE WIND/CLEAR SKY CONDITIONS.
AS FOR TEMPS/POPS...RAISED GFS MOS POPS TODAY FOR NWRN HALF BEFORE
NOON AND THE SERN HALF DURING THE AFTERNOON THROUGH OVERNIGHT
PERIODS. MOS TEMP RANGE SEEMED A BIT HIGH SO NARROWED THE HIGH/LOW
RANGE A BIT THROUGH MONDAY WHILE ACCEPTING GUIDANCE FOR MONDAY
NIGHT. /40/
LONG TERM...(TUESDAY THROUGH SUNDAY)...
SURFACE HIGH PRESSURE WILL SHIFT OFF TO OUR EAST ON TUE BRINGING
BACK RETURN FLOW OFF THE GULF. UNSEASONABLY WARM CONDITIONS CAN BE
EXPECTED TUE AND WED AS A RESULT/ESPECIALLY WED WHERE HIGHS IN THE
LOW TO MID 70S WILL COME IN SOME 15 DEGREES ABOVE NORMAL FOR MID
DEC. THE WARMTH WILL NOT LAST LONG THOUGH AS A POTENT COLD FRONT IS
PROGGED TO CROSS THE REGION STARTING EARLY THU MORNING.
THE UPPER WAVE ASSOC WITH THIS NEXT SYSTEM WILL CROSS INTO THE
CENTRAL PLAINS WED EVENING INDUCING A DEEP SURFACE LOW OVER THE
OKLAHOMA PANHANDLE THAT WILL TRACK EAST NORTHEAST ACROSS SOUTHERN MO
AND EVENTUALLY THE GREAT LAKES. THE SYNOPTIC SETUP OFFERED BY THE
MODELS WITH THIS SYSTEM IS QUITE IMPRESSIVE...AND AT FIRST GLANCE IT
WOULD APPEAR THAT SEVERE WEATHER FOR THE ARKLAMISS WOULD BE A SLAM
DUNK. HOWEVER THE DETAILS OFFER A DIFFERENT STORY...AT LEAST FOR
NOW. WHILE ROBUST WIND FIELDS JUST AHEAD OF THE FRONT DRAW UP AMPLE
AMOUNTS OF MOISTURE/DEW POINTS CLIMBING NEAR OR ABOVE 65 DEG FOR A
GOOD PORTION OF THE AREA AND PW VALUES RISING ABOVE 1.5 IN/
TEMPERATURES ALOFT ARE RATHER WARM(H5 TEMPS -10 TO -11) WHICH
SIGNIFICANTLY REDUCES MID LEVEL LAPSE RATES AND RESULTANT
INSTABILITY. WE WILL HAVE TO KEEP AN EYE ON THIS TO SEE IF THE
MODELS TREND COOLER ALOFT BECAUSE IF THEY DO...AND THE SYNOPTIC
SETUP REMAINS SIMILAR...WE COULD BE LOOKING AT DECENT SEVERE WEATHER
POTENTIAL LATE WED INTO THU MORNING. FOR NOW...WILL OMIT MENTION OF
ANY SEVERE WEATHER IN THE HWO/GRAPHICS.
MUCH COOLER AIR WILL FILTER ACROSS THE REGION IN WAKE OF THE FRONT
WITH TEMPERATURES LIKELY FALLING THROUGH THE DAYLIGHT HOURS THU.
STRONG MIXING WILL ALLOW WINDY CONDITIONS TO DEVELOP THU AND ITS
FEASIBLE A WIND ADVISORY MAY BECOME NECESSARY FOR AT LEAST THE
DELTA...IF NOT AREAS FURTHER SOUTH AND EAST AS WELL. HIGH PRESSURE
WILL TRANSIT THE DEEP SOUTH FRI INTO THE FIRST PART OF THE WEEKEND
BEFORE RAIN CHANCES RETURN EARLY NEXT WEEK. /BK/
&&
.AVIATION...
MVFR-IFR CEILINGS SHOULD DETERIORATE TO FREQUENTLY IFR
CONDITIONS IN ADVANCING RAIN/TSRA BAND SAGGING SWD THROUGH THE TAF
SITES. SSWLY SFC WINDS WL BECOME A LITTLE GUSTY AHEAD OF THE
PRECIPITATION THRU THE AFTN BEFORE WEAKENING THIS EVENING. SHRA AND
TSRA ACTIVITY WILL BE STRONGEST/HEAVIEST ACROSS THE I-20 CORRIDOR
AND SWD BY THIS AFTERNOON WHILE IT ALL WILL GRADUALLY END FROM NW TO
SE LATER TONIGHT FOR THE DELTA REGION AND DURING MONDAY MORNING FOR
OUR ERN/SRN SITES. A GRADUAL SHIFT TO WSWLY LOW LEVEL FLOW WILL
RETURN VFR CONDITIONS AND WILL HELP THE RAINS ON MONDAY WITH
CLEARING SKIES MONDAY EVENING. 17/40/
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS JACKSON MS
406 AM CST SUN DEC 16 2012
...HEAVY RAIN/FEW SEVERE STORMS POSSIBLE TODAY INTO TONIGHT...
.SHORT TERM...(TODAY THROUGH MONDAY NIGHT)...
MAIN CONVECTIVE BAND ACROSS N MS INTO SRN AR STEADILY EXPANDING/
GETTING STRONGER PAST SEVERAL HOURS. OTHERWISE...ISOLATED LIGHT SHRA
CONTINUE TO CROSS N AND W PORTIONS OF THE CWFA WITH LOW STRATUS
ELSEWHERE. STALLED FRONTAL BOUNDARY STILL HANGING BACK NEAR A KJBR-
KTYR LINE AS AN UPSTREAM S/WV OVER THE SRN ROCKIES TO THE TX BIG BEND
MOVES EWD AT 40KTS TOWARD THE OZARKS. A POWERFUL UPPER JET WITH EPAC
CONNECTIONS WILL AID IN RAINFALL PRODUCTION GETTING RAMPED UP TODAY
WITH CONTINUED EXPANSION OF THE PRE-FRONTAL CONVECTION. LIKELY
TRAINING OF CONVECTION IN THIS SCENARIO DURING THE DAYLIGHT HOURS
COULD GENERATE AN AXIS OF 2-4 INCHES RATHER EASILY. MODEL CONSENSUS
PLACES THE HEAVIEST RAINFALL FROM AROUND NATCHEZ TO MERIDIAN BETWEEN
NOON AND MIDNIGHT...SOME RISK FOR LOCALIZED FLASH FLOODING WILL EXIST
BUT WILL HOLD OFF A FLASH FLOOD WATCH UNTIL THE AXIS BECOMES MORE
DEFINED SINCE 3HR FFG STILL ABOVE 3 INCHES MOST AREAS.
UNTIL THE DIURNAL INSTABILITY GETS ADDED TO THE MIX...LOOK FOR THE
EXPANDING RAIN BAND TO PUSH TO NEAR A WINNSBORO TO JACKSON TO
COLUMBUS AXIS BY ABOUT NOON...PER LATEST RUC PROGS. THEN THE RISK
FOR A FEW STRONG/SEVERE STORMS WILL BE INCREASING S OF THAT AXIS
THROUGH THE EVENING HOURS FUELED BY PWATS RISING NEAR 1.5 INCHES...
0-3KM HELICITIES OF 200-300M*M/S*S...6.5C 7-500MB LAPSE RATES...
INCREASINGLY COUPLED 850-200MB DIFFERENTIAL DIVERGENCE...850MB THETA
E AXIS OF 334K AND LEFT EXIT REGION OF A 65KT 500MB JET STREAK.
AT THIS POINT IT LOOKS LIKE THE AREA WITH THE GREATEST SEVERE
WEATHER RISK WILL BE ACROSS THE SERN HALF OF THE CWA WHERE THE BEST
COMBINATION OF SHEAR AND INSTABILITY WILL BE CO-LOCATED. EVEN A
DECENT TORNADO RISK COULD DEVELOP FOR SERN MS FROM 00-06Z AS A LAYER
OF MARINE GULF AIR OF 65-68F DEWPTS ATTEMPTS TO SURGE NWD...REF NEW
SPC DAY ONE OUTLOOK FOR UPDATES.
PRIMARY ASCENT PUSHES OFF TO OUR E MONDAY MORNING WITH DEVELOPING
UNIDIRECTIONAL FLOW FROM THE WSW BY MIDDAY. DRYING PWATS DROP TO
NEAR ONE HALF INCH BY MIDDAY ACROSS I-55...AND CLOSER TO ONE THIRD
INCH BY MIDNIGHT MONDAY NIGHT WHEN BEST CLEARING EXPECTED OF THE
REMAINING CLOUD COVER. DUE TO THE BEST RAINFALL AXIS POSITION LYING
ALONG OR S OF I-20 DURING SUNDAY...HAVE ADDED PATCHY FOG TO SRN HALF
OF CWFA LATE MONDAY NIGHT WHERE WET GROUNDS AND COOLER L40S TEMPS
EXIST UNDER NEAR CALM SURFACE WIND/CLEAR SKY CONDITIONS.
AS FOR TEMPS/POPS...RAISED GFS MOS POPS TODAY FOR NWRN HALF BEFORE
NOON AND THE SERN HALF DURING THE AFTERNOON THROUGH OVERNIGHT
PERIODS. MOS TEMP RANGE SEEMED A BIT HIGH SO NARROWED THE HIGH/LOW
RANGE A BIT THROUGH MONDAY WHILE ACCEPTING GUIDANCE FOR MONDAY
NIGHT. /40/
.LONG TERM...(TUESDAY THROUGH SUNDAY)...
SURFACE HIGH PRESSURE WILL SHIFT OFF TO OUR EAST ON TUE BRINGING
BACK RETURN FLOW OFF THE GULF. UNSEASONABLY WARM CONDITIONS CAN BE
EXPECTED TUE AND WED AS A RESULT/ESPECIALLY WED WHERE HIGHS IN THE
LOW TO MID 70S WILL COME IN SOME 15 DEGREES ABOVE NORMAL FOR MID
DEC. THE WARMTH WILL NOT LAST LONG THOUGH AS A POTENT COLD FRONT IS
PROGGED TO CROSS THE REGION STARTING EARLY THU MORNING.
THE UPPER WAVE ASSOC WITH THIS NEXT SYSTEM WILL CROSS INTO THE
CENTRAL PLAINS WED EVENING INDUCING A DEEP SURFACE LOW OVER THE
OKLAHOMA PANHANDLE THAT WILL TRACK EAST NORTHEAST ACROSS SOUTHERN MO
AND EVENTUALLY THE GREAT LAKES. THE SYNOPTIC SETUP OFFERED BY THE
MODELS WITH THIS SYSTEM IS QUITE IMPRESSIVE...AND AT FIRST GLANCE IT
WOULD APPEAR THAT SEVERE WEATHER FOR THE ARKLAMISS WOULD BE A SLAM
DUNK. HOWEVER THE DETAILS OFFER A DIFFERENT STORY...AT LEAST FOR
NOW. WHILE ROBUST WIND FIELDS JUST AHEAD OF THE FRONT DRAW UP AMPLE
AMOUNTS OF MOISTURE/DEW POINTS CLIMBING NEAR OR ABOVE 65 DEG FOR A
GOOD PORTION OF THE AREA AND PW VALUES RISING ABOVE 1.5 IN/
TEMPERATURES ALOFT ARE RATHER WARM(H5 TEMPS -10 TO -11) WHICH
SIGNIFICANTLY REDUCES MID LEVEL LAPSE RATES AND RESULTANT
INSTABILITY. WE WILL HAVE TO KEEP AN EYE ON THIS TO SEE IF THE
MODELS TREND COOLER ALOFT BECAUSE IF THEY DO...AND THE SYNOPTIC
SETUP REMAINS SIMILAR...WE COULD BE LOOKING AT DECENT SEVERE WEATHER
POTENTIAL LATE WED INTO THU MORNING. FOR NOW...WILL OMIT MENTION OF
ANY SEVERE WEATHER IN THE HWO/GRAPHICS.
MUCH COOLER AIR WILL FILTER ACROSS THE REGION IN WAKE OF THE FRONT
WITH TEMPERATURES LIKELY FALLING THROUGH THE DAYLIGHT HOURS THU.
STRONG MIXING WILL ALLOW WINDY CONDITIONS TO DEVELOP THU AND ITS
FEASIBLE A WIND ADVISORY MAY BECOME NECESSARY FOR AT LEAST THE
DELTA...IF NOT AREAS FURTHER SOUTH AND EAST AS WELL. HIGH PRESSURE
WILL TRANSIT THE DEEP SOUTH FRI INTO THE FIRST PART OF THE WEEKEND
BEFORE RAIN CHANCES RETURN EARLY NEXT WEEK. /BK/
&&
.AVIATION...WIDESPREAD MVFR CEILINGS AT DAYBREAK SHOULD DETERIORATE
TO FREQUENTLY IFR CONDITIONS IN ADVANCING RAIN/TSRA BAND SAGGING SWD
THROUGH THE TAF SITES. SSWLY SFC WINDS WL BECOME A LITTLE GUSTY
AHEAD OF THE PRECIPITATION THRU THE AFTN BEFORE WEAKENING THIS
EVENING. SHRA AND TSRA ACTIVITY WILL BE STRONGEST/HEAVIEST ACROSS
THE I-20 CORRIDOR AND SWD BY THIS AFTERNOON WHILE IT ALL WILL
GRADUALLY END FROM NW TO SE LATER TONIGHT FOR THE DELTA REGION AND
DURING MONDAY MORNING FOR OUR ERN/SRN SITES. A GRADUAL SHIFT TO
WSWLY LOW LEVEL FLOW WILL RETURN VFR CONDITIONS AND WILL HELP THE
RAINS ON MONDAY WITH CLEARING SKIES MONDAY EVENING. /40/
&&
.PRELIMINARY POINT TEMPS/POPS...
JACKSON 69 56 69 41 / 97 70 17 5
MERIDIAN 70 58 69 39 / 97 83 22 7
VICKSBURG 68 56 66 36 / 97 50 11 4
HATTIESBURG 73 61 72 42 / 80 91 31 6
NATCHEZ 69 57 68 40 / 98 69 11 4
GREENVILLE 69 53 65 40 / 92 27 9 4
GREENWOOD 68 53 65 42 / 97 44 11 5
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...NONE.
LA...NONE.
AR...NONE.
&&
$$
40/BK
AREA FORECAST DISCUSSION
NWS HASTINGS NE
337 PM CST SUN DEC 16 2012
.SHORT TERM...TONIGHT AND TOMORROW.
UPPER LEVEL SATELLITE DATA HAS SHOW A FEW SMALL DISTURBANCES
SHIFTING ACROSS THE PLAINS TODAY...ONE OF WHICH BROUGHT SOME LIGHT
SNOW TO PORTIONS OF THE CWA THIS MORNING. TRACE AMOUNTS UP NEAR
A HALF OF AN INCH WERE REPORTED...AND BY MIDDAY PRECIPITATION
TRENDS HAD FALLEN BACK TO JUST A FEW SCATTERED FLURRIES IN
NORTHEASTERN PORTIONS OF THE CWA. CLOUD COVER HAS BEEN
ANNOYING...THE NORTHEASTERN HALF OF THE CWA HAS BEEN STUCK UNDER
STUBBORN LOW LEVEL STRATUS...VS THE WESTERN HALF WHICH HAS SEEN
PLENTY OF SUN. SURFACE ANALYSIS SHOWS A RIDGE AXIS EXTENDING
THROUGH THE CENTRAL/EASTERN PORTIONS OF THE REGION...KEEPING WINDS
GENERALLY ON THE LIGHT AND AT TIMES VARIABLE SIDE. THANKS TO THE
CLOUD COVER...EASTERN LOCATIONS HAVE HUNG AROUND THE LOW 30S THIS
AFTERNOON...OUT WEST HAS REACHED INTO THE LOWER 40S.
KEPT THE FORECAST TONIGHT DRY...THOUGH MODELS ARE SHOWING ANOTHER
WEAK DISTURBANCE SWINGING THOUGH THE REGION...POTENTIALLY BRINGING
SOME ADDITIONAL LIGHT PRECIPITATION. AT THIS POINT...SHOULD ANY
PRECIPITATION FALL...IT LOOKS TO REMAIN JUST OFF TO THE
SOUTH/SOUTHWEST OF THE CWA. AT THE SURFACE...A WEAK TROUGH AXIS
GETS PUSHED THROUGH AS THE DISTURBANCE CROSSES...EVENTUALLY
BRINGING A WESTERLY COMPONENT TO THE WINDS. AHEAD OF THAT
SWITCH...CONCERNED ABOUT THE POTENTIAL FOR SOME PATCHY FOG
DEVELOPMENT...AS THE WINDS REMAIN LIGHT/CALM WITH NOT AS MUCH IN
THE WAY OF CLOUD COVER EXPECTED. WITH THE NAM/SREF BOTH SHOWING
REDUCED VISIBILITIES AND THE RAP NOT TOO FAR OUTSIDE THE CWA
BOUNDARY...DECIDED TO INSERT A PATCHY FOG MENTION ACROSS PORTIONS
OF SC NEB.
INTO MONDAY...EXPECTING TO SEE WEAK SHORTWAVE UPPER LEVEL RIDGING
OVER THE REGION...KEEPING CONDITIONS QUIET. SHOULD SEE VARIABLE
SKY COVER THROUGH THE DAY WITH UPPER LEVEL CLOUDS STREAMING IN.
AT THE SURFACE...THE CWA IS COMING UNDER INCREASING INFLUENCE OF
LOW PRESSURE DEVELOPING OVER THE HIGH PLAINS...RESULTING IN WINDS
BECOMING MORE SOUTHERLY WITH TIME. AFTER LOW TEMPERATURES TONIGHT
EXPECTED IN THE TEENS TO LOWER 20S...HIGHS ON MONDAY LOOK TO REACH
INTO THE LOWER 40S TO NEAR 50.
.LONG TERM...MONDAY NIGHT THROUGH SUNDAY.
MAIN CHALLENGE REMAINS DETERMINING CHANCES AND TIMING OF SNOW FOR
WEDNESDAY/WEDNESDAY NIGHT.
WE BEGIN THE LONG TERM FORECAST MONDAY NIGHT WITH ZONAL FLOW. THE
FLOW REMAINS QUITE PROGRESSIVE AS A SIGNIFICANT TROUGH DEVELOPS IN
THE WESTERN UNITED STATES BY TUESDAY. AS A RESPONSE TO THIS
DEEPENING TROUGH TO THE WEST...PLENTY OF WARM AIR WILL ARRIVE ON
TUESDAY AND PLACE OUR HIGH TEMPERATURES WELL ABOVE NORMAL BY ABOUT
15 DEGREES OR SO. THIS ABOVE NORMAL WEATHER WILL MOST CERTAINLY
NOT LAST AS THE TROUGH PROGRESSES QUICKLY TO THE EAST AND AN
ASSOCIATED COLD FRONT SWINGS IN FROM THE NORTHWEST VERY LATE
TUESDAY NIGHT INTO WEDNESDAY. A SHARP COOL DOWN WILL ENSUE.
THE TIMELINE FOR THIS NEXT WAVE IS TRENDING TOWARD A SOONER ARRIVAL
AND SOONER EXIT. ISENTROPIC LIFT BEGINS EARLY WEDNESDAY MORNING
BEHIND A QUICKLY MOVING COLD FRONT...WITH THIS FORCING GIVING WAY
TO MID-LEVEL FRONTOGENETIC FORCING LATER IN THE DAY.
ALSO...LARGER SCALE SYNOPTIC FORCING BECOMES STRONGER AS THE DAY
WEARS ON AND IS FORECAST TO BE RESPECTABLE FOR A SHORT
TIME...ADDING ANOTHER LAYER OF FORCING TO AID IN SNOW PRODUCTION.
THE ECMWF INDICATES THAT SYNOPTIC FORCING WILL PEAK NEAR 00Z
THURSDAY. THIS WAVE IS A QUICK HITTER...HOWEVER...WITH MOST IF NOT
ALL FORCING EAST OF THE CWA BY MIDNIGHT WEDNESDAY NIGHT...WHICH
WILL ALSO END ANY SNOW PRODUCTION. WITH THIS WAVE BEING SUCH A
QUICK HITTER...SNOW AMOUNTS ARE STILL ON TRACK FOR UP TO 4 INCHES
OR SO FOR SOMEBODY NEARBY...BUT THIS PROBABLY WOULD NOT BE A
UBIQUITOUS SNOW AMOUNT. IF THIS SYSTEM SLOWS DOWN JUST A
BIT...THIS COULD MEAN MORE SNOW WITH LARGER SNOW AMOUNTS AND
PLENTY OF WIND TO CREATE DRIFTING SNOW POTENTIAL. WIND ALOFT FOR
WEDNESDAY AFTERNOON AND EVENING IS QUITE STRONG AND BLOWING SNOW
WILL BE A POTENTIAL ISSUE. THERE IS ALSO SOME DISCREPANCY AMONG
MODELS WHERE THE TRACK OF THE 700 MB CLOSED LOW WILL BE AS THE NAM
DRAGS THIS LOW ACROSS THE CENTRAL CWA...WHILE THE ECMWF TAKES THE
700 MB LOW ACROSS CENTRAL KANSAS. THE GFS DOES NOT CLOSE THE LOW
OFF...BUT DOES FAVOR A SOLUTION CLOSER TO THE ECMWF. NO QUESTION
ABOUT PRECIPITATION TYPE SO FAR...AS SOUNDINGS INDICATE ALL SNOW
WITH THIS EVENT. WE TEND TO FAVOR A MORE SOUTHERN TRACK WITH THESE
PACIFIC SYSTEMS. ALSO WEDNESDAY MAY BE A TRICKY DAY FOR HOURLY
TEMPERATURES DEPENDING ON THE TIMING OF THE COLD FRONT. WE COULD
REACH HIGHS MORE TOWARD LATE MORNING RATHER THEN IN THE AFTERNOON.
ANYWAY...TEMPERATURES WILL PROBABLY GO ALMOST NOWHERE FROM THE
LOWS ON TUESDAY NIGHT. I CONTINUED TO GO COLDER THAN ALLBLEND FOR
TEMPERATURES FOR WEDNESDAY NIGHT AND BEYOND CONSIDERING POTENTIAL
SNOW COVER.
&&
.AVIATION...18Z TAF. LOOKING TO SEE SOME CLOUDS RIGHT ON THE
VFR/MVFR BRINK HANGING AROUND FOR AT LEAST A LITTLE WHILE THIS
AFTERNOON...ASSOCIATED WITH A WEAK DISTURBANCE AND SOME LINGERING
FLURRIES GRADUALLY SHIFTING EAST. OTHERWISE...VFR CONDITIONS ARE
CURRENTLY EXPECTED. SURFACE HIGH PRESSURE CURRENTLY IN PLACE OVER
THE REGION IS KEEPING WINDS ON THE LIGHT AND AT TIMES VARIABLE
SIDE...WHICH IS EXPECTED TO CONTINUE THROUGH THE AFTERNOON. MORE
WESTERLY WINDS WILL DEVELOP LATER TONIGHT AND CONTINUE THROUGH THE
END OF THE TAF PERIOD AS LOW PRESSURE SETS UP OVER THE HIGH
PLAINS...BUT SPEEDS EXPECTED TO REMAIN BELOW 10KTS.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
SHORT/AVIATION...ADO
LONG...HEINLEIN
AREA FORECAST DISCUSSION
NWS HASTINGS NE
1137 AM CST SUN DEC 16 2012
.AVIATION...18Z TAF. LOOKING TO SEE SOME CLOUDS RIGHT ON THE
VFR/MVFR BRINK HANGING AROUND FOR AT LEAST A LITTLE WHILE THIS
AFTERNOON...ASSOCIATED WITH A WEAK DISTURBANCE AND SOME LINGERING
FLURRIES GRADUALLY SHIFTING EAST. OTHERWISE...VFR CONDITIONS ARE
CURRENTLY EXPECTED. SURFACE HIGH PRESSURE CURRENTLY IN PLACE OVER
THE REGION IS KEEPING WINDS ON THE LIGHT AND AT TIMES VARIABLE
SIDE...WHICH IS EXPECTED TO CONTINUE THROUGH THE AFTERNOON. MORE
WESTERLY WINDS WILL DEVELOP LATER TONIGHT AND CONTINUE THROUGH THE
END OF THE TAF PERIOD AS LOW PRESSURE SETS UP OVER THE HIGH
PLAINS...BUT SPEEDS EXPECTED TO REMAIN BELOW 10KTS.
&&
.PREV DISCUSSION... /ISSUED 906 AM CST SUN DEC 16 2012/
UPDATE...MADE SOME CHANGES TO WEDNESDAY AND WEDNESDAY NIGHT
FORECAST. ADJUSTED THE GRADIENT FOR CHANCES OF PRECIPITATION ON
WEDNESDAY AND INCREASED CHANCES OF PRECIPITATION CENTRAL/SOUTH A
BIT. ALSO BROKE UP WEATHER AND CHANCES OF PRECIPITATION INTO 6
HOUR BLOCKS WEDNESDAY AND WEDNESDAY NIGHT...AS BOTH WEDNESDAY
MORNING AND LATE WEDNESDAY NIGHT APPEAR TO HAVE MUCH LOWER CHANCES
OF SNOW COMPARED TO WEDNESDAY AFTERNOON AND EVENING. ALSO ADJUSTED
SKY COVER TO BE COMPLETELY CLOUDY FOR WEDNESDAY AFTERNOON AND
EVENING.
PREV DISCUSSION... /ISSUED 433 AM CST SUN DEC 16 2012/
SHORT TERM...THROUGH 12Z WEDNESDAY. EVENING UPPER AIR ANALYSIS
INDICATES A LONGWAVE TROUGH OVER THE WESTERN HALF OF THE CONUS
WITH QUASI- ZONAL FLOW ACROSS THE EAST. MID AND UPPER LEVEL JET
ENERGY EXTENDS FROM WEST-TEXAS...EAST/NORTHEAST INTO THE SOUTHERN
PLAINS AND LOWER MISSISSIPPI VALLEY...AND THEN FARTHER EAST INTO
THE SOUTHEASTERN CONUS. MID AND UPPER LEVEL TROPOSPHERIC FLOW OVER
OUR AREA REMAINS FAIRLY WEAK AS A RESULT...MAXING OUT AT AROUND
60KTS NEAR 200MB PER 00Z SOUNDING DATA FROM KLBF. WATER VAPOR
IMAGERY SHOWS PLENTY OF MID LEVEL MOISTURE ADVANCING
EAST/NORTHEAST ALONG THE MID TO UPPER LEVEL JET AXIS ACROSS THE
SOUTH AND SOUTHEASTERN CONUS...WITH DRIER MID LEVEL AIR NOTED
FARTHER NORTH. WATER VAPOR IMAGERY ALSO INDICATES A COMPACT MID
LEVEL SHORT WAVE OVER COLORADO...BEGINNING TO EJECT OUT FROM THE
MAIN LONGWAVE TROUGH. AT THE SURFACE A RIDGE OF HIGH PRESSURE IS
NOTED EXTENDING FROM THE NORTHERN HIGH PLAINS...SOUTH/SOUTHEAST
INTO THE CENTRAL PLAINS. A COLD FRONT IS ALSO NOTED EXTENDING FROM
SOUTHWEST TO NORTHEAST ACROSS KANSAS...SOUTHWESTERN MISSOURI AND
IOWA. THE LOW LEVEL WIND FIELD ACROSS OUR AREA REMAINS FROM THE
NORTHWEST AS A RESULT. RADAR DATA FROM KUEX...KLNX AND KGLD
CONTINUE TO SHOW PRECIPITATION OVER SOUTHWESTERN NEBRASKA AND
NORTHWESTERN KANSAS...WITH SNOW BEING REPORTED OVER SOME AREAS AS
WELL. FOR LOCATIONS ACROSS OUR WESTERN CWA...WHERE KUEX HAS
INDICATED PRECIPITATION FOR THE PAST FEW HOURS...PRECIPITATION AT
THE SURFACE HAS YET TO BE REPORTED AS THE LOWER TROPOSPHERE STILL
APPEARS TOO DRY FOR SUCH ACTIVITY TO BE REALIZED.
GUIDANCE FROM THE NAM...OPERATIONAL GFS...EC AND SREF-MEAN ALL
SUGGEST THE MID LEVEL SHORT WAVE...APPROACHING OUR AREA FROM
COLORADO...WILL CONTINUE PUSHING ACROSS THE CENTRAL PLAINS DURING
THE DAY TODAY. DPVA AND WEAK MID LEVEL THERMAL ADVECTION AHEAD OF
THE MID LEVEL TROUGH AXIS...WORKING IN CONCERT WITH AN AXIS OF
FRONTOGENESIS NEAR 700MB...SHOULD SUSTAIN PRECIPITATION PRODUCTION
OVER NORTHWESTERN KANSAS AND SOUTHWESTERN NEBRASKA THROUGH THE
NEXT FEW HOURS...WITH PRECIPITATION PERHAPS MAKING IT TO THE
SURFACE ACROSS WESTERN PORTIONS OF OUR AREA AS WELL. FORECAST
PROXIMITY SOUNDINGS FROM ACROSS MUCH OF OUR CWA...PER THE NAM AND
OPERATIONAL GFS...SUGGEST THE LOWER TROPOSPHERE WILL HAVE TO DO
QUITE A BIT OF SATURATING FARTHER EAST BEFORE PRECIPITATION IS
REALIZED AT THE SURFACE...THUS CONFIDENCE IS NOT ALL THAT HIGH
THAT ANY MEASURABLE PRECIPITATION WILL BE REALIZED EAST OF HIGHWAY
183. BUT FARTHER WEST ACROSS THE AREA...WHERE MID LEVEL
PRECIPITATION HAS BEEN ONGOING FOR SEVERAL HOURS NOW AND CEILINGS
ARE LOWERING CLOSER TO 2000FT AGL..CONFIDENCE IS SOMEWHAT HIGHER
OF PRECIPITATION BEING REALIZED AT THE SURFACE. GIVEN ALL
THIS...WENT AHEAD WITH CHANCE POPS ACROSS OUR FAR WEST...ROUGHLY
WEST OF HIGHWAY 183...WITH SLIGHT CHANCE POPS FARTHER EAST. THE
RAP...NAM AND OPERATIONAL GFS ALL SUGGEST THE MID LEVEL TROUGH
AXIS WILL BEGIN CLEARING THE AREA BY 15Z...THUS ALLOWING THE BULK
OF THE OMEGA AND MID LEVEL FRONTOGENESIS TO ALSO PUSH EAST OF OUR
AREA BY LATE MORNING OR MIDDAY. QPF FIELDS FROM VARIOUS MODELS
SUGGEST VERY LIGHT PRECIPITATION MAY STILL BE REALIZED OVER
PORTIONS OF OUR AREA BEYOND 15Z...BUT GIVEN THE LIMITED FORCING BY
THIS TIME OPTED TO ONLY GO WITH 20% POPS 15-18Z...AND ISOLATED
FLURRIES AND SPRINKLES AFTER 18Z.
ALTHOUGH A FEW LOCATIONS ACROSS SOUTHWESTERN NEBRASKA AND
NORTHWESTERN KANSAS HAVE REPORTED RECEIVING ONE OR TWO INCHES OF
SNOW SINCE 06Z...CURRENT RETURNS FROM KUEX...KLNX AND KGLD ALL
SUGGEST THE ONGOING PRECIPITATION IS FAIRLY LIGHT AT THIS HOUR AND
CURRENTLY DO NOT EXPECT THIS TREND TO CHANGE AS THIS ACTIVITY
WORKS INTO OUR AREA. GIVEN ALL THIS...WILL GO AHEAD AND PRESENT A
COUPLE TENTHS OF AN INCH OF SNOWFALL TO MOST LOCATIONS WEST OF
HIGHWAY 183...WITH A FEW LOCATIONS ACROSS WESTERN DAWSON...WESTERN
GOSPER AND WESTERN FURNAS COUNTIES CLOSER TO A HALF INCH.
IT IS WORTH NOTING THAT FORECAST PROXIMITY SOUNDINGS FROM OUR
EAST/NORTHEASTERN CWA PER THE NAM AND RAP SUGGEST AND ELEVATED
WARM LAYER NEAR 850MB COULD PRESENT TEMPERATURES SLIGHTLY ABOVE
FREEZING THROUGH 15Z WHILE SURFACE TEMPERATURES REMAIN BELOW
FREEZING. 850MB TEMPERATURES FOR ALL SITES ACROSS OUR CWA ARE
EXPECTED TO FALL BELOW FREEZING BY NO LATER THAN 15Z HOWEVER...PER
THE NAM AND RAP...AND GIVEN THE LOW CONFIDENCE/VERY LOW CHANCE OF
MEASURABLE PRECIPITATION ACTUALLY BEING OBSERVED THAT FAR EAST
BEFORE 15Z...OPTED TO KEEP ANY MENTION OF -ZR OUT OF THE FORECAST.
THE NAM...OPERATIONAL GFS...EC AND SREF-MEAN ALL SUGGEST YET
ANOTHER MID LEVEL SHORT WAVE WILL PUSH OVER THE CENTRAL PLAINS
TONIGHT. FORECAST PROXIMITY SOUNDINGS FROM ACROSS THE CWA PER THE
NAM AND OPERATIONAL GFS SUGGEST HOWEVER THAT TROPOSPHERIC MOISTURE
WILL BE TOO LACKING FOR PRECIPITATION PRODUCTION AND AS A
RESULT...LEFT TONIGHT DRY. SUBTLE MID AND UPPER LEVEL RIDGING IS
EXPECTED TO MOVE INTO THE CENTRAL CONUS MONDAY THROUGH TUESDAY
NIGHT. THE RESULTANT LACK IN OVERALL KINEMATIC FORCING SHOULD THEN
PRESENT DRY CONDITIONS TO FINISH OUT THE SHORT TERM FORECAST
PERIOD.
WEAK LOW LEVEL COLD AIR ADVECTION ACROSS THE REGION TODAY SHOULD
PRESENT SLIGHTLY COOLER TEMPERATURES TODAY WHEN COMPARED TO
YESTERDAY...WITH AFTERNOON HIGHS IN THE 30S AND 40S CURRENTLY
FORECAST. WEAK LOW LEVEL WARM AIR ADVECTION AND A DOWN-SLOPING
COMPONENT TO THE LOW LEVEL WIND FIELD SHOULD THEN PRESENT A SUBTLE
WARMING TREND TO FINISH OUT THE SHORT TERM FORECAST PERIOD...WITH
HIGHS IN THE 40S AND 50S EXPECTED MONDAY AND TUESDAY.
LONG TERM...WEDNESDAY THROUGH SATURDAY
THE MAIN STORY: WED CONTINUES TO THREATEN SOME WINTRY WX AND
SLIPPERY TRAVEL FOR PART OF THE FCST AREA WITH TEMPS AVERAGING
SEASONABLY COLD THROUGH THE PERIOD.
PATTERN: THE HEMISPHERIC HGT ANOMALIES ARE LIKELY TO MAINTAIN
-NAO/ -PNA CONFIGURATION...ESSENTIALLY WORKING AGAINST EACH OTHER
TO BRING ANY REAL ARCTIC COLD DEEP INTO THE CONUS. HOWEVER...THE E
PACIFIC LONGWAVE TROF WILL CONTINUE TO DELIVER OCCASIONAL PCPN
THREATS. THE FIRST OCCURRED WITH THIS PAST FRI NIGHT`S RAINFALL
/WHICH BROUGHT WIDESPREAD 0.5 TO 0.75"/. THE NEXT ARRIVES WED AND
THE PATTERN LOOKS FAVORABLE FOR ANOTHER DURING THE WEEK OF
CHRISTMAS.
HAZARDS: WE CONTINUE TO SEE POTENTIAL FOR SOME ACCUMULATING SNOW
WED-WED EVE. THE THREAT CONTINUES HIGHLIGHTED IN THE HWO.
PCPN: WED-WED EVE CONFIDENCE IS HIGH FOR A LIGHT SNOWFALL EVENT.
CONFIDENCE IS AVERAGE FOR A MODERATE SNOWFALL...PROBABLY S AND E
OF HASTINGS "IF" IT WAS TO OCCUR.
THE DAILY DETAILS...
LOW TEMPS ALL PERIODS WERE LOWERED TO BIAS CORRECTED ALL-BLEND
GUIDANCE. THIS COORDINATED WITH LBF SINCE THIS LOWERED TEMPS MOST
OVER OUR NW COUNTIES. WED HIGH TEMPS WERE ALSO LOWERED TO MEX
TEMPS AND WAS COORDINATED WITH ALL SURROUNDING OFFICES.
DETERMINISTIC MODELS AND NAEFS/EC ENSEMBLE MEANS CONTINUE TO
SUGGEST HIGH CONFIDENCE IN LEE CYCLOGENESIS WED...WITH THE LOW
EJECTING ACROSS KS /OR NRN OK?/ INTO THE MID MS VALLEY.
HOWEVER...ENSEMBLE SPREAD OF 8-10 MB EXISTS NW OF THE MEAN SFC LOW
POSITION... SUGGESTING DIFFERENCES IN TIMING/LOCATION AMONG THE
VARIOUS POSSIBLE OUTCOMES IN THE GUIDANCE ENVELOPE.
THERE ARE A COUPLE GFS ENSEMBLE MEMBERS THAT OFFER 0.5" OF COMMA-
HEAD QPF IN VICINITY OF HWY 81...SIMILAR TO THE 00Z/15 EC. SO
ALTHO IT/S A LOW PROBABILITY...SOME POTENTIAL CONTINUES FOR
WARNING SNOWFALL AMOUNTS OVER OR SOMEWHERE NEARBY OUR FCST AREA.
FOR NOW GFS ENSEMBLE PROBABILITIES ARE HIGH /70 PERCENT/ FOR 0.1"
IN 24 HRS ALONG AND E OF HWY 281.
REGARDLESS OF HOW MUCH SNOW FALLS...WED IS LIKELY TO BE A RAW
NASTY DAY WITH A SHARP N WIND AND FALLING AFTERNOON TEMPS.
FCST FOR WED IS ESSENTIALLY CLOUDY IN CAA WITH -SN DEVELOPING IN
INCREASINGLY GUSTY NE WINDS. NOT SURE IT SNOWS EVERYWHERE. TRACK
DEPENDENT. BEST GUESS AT THIS POINT IS LOWEST CHANCE FOR
MEASURABLE SNOW IS N AND W OF GRI. TEMPS PROBABLY RISE LITTLE FROM
MORNING LOWS AND THEN FALL AFTER MIDDAY.
WED NGT: ANY SNOW ENDS PROBABLY BY MIDNIGHT. CLEARING FROM THE SW.
A BLUSTERY NIGHT WITH WIND CHILLS AS LOW AS -5F AT TIMES.
WINDS WERE INCREASED ABOVE GUIDANCE 12 PM WED TO 12 PM THU.
THU: UPPER TROF TRANSITIONS TO NW FLOW. SUNNY. BLUSTERY N WINDS
EVENTUALLY SUBSIDE AS SFC RIDGE MOVES IN LATE. NEAR NORMAL TEMPS
BUT IT WILL FEEL COLD GIVEN THE MILD DEC THUS FAR...ESPECIALLY
WITH A BITING N WIND AND WIND CHILLS NEAR ZERO IN THE
MRNG...ESPECIALLY N AND W OF GRI.
FRI: SUNNY AND PROBABLY 5F ABOVE NORMAL WITH LIGHT SW WINDS.
SAT: QUITE A BIT OF SPREAD WITH AMPLITUDE/POSITION OF THE RIDGE
BUT MOST MODELS/ENSEMBLE MEMBERS SUGGEST A DRY COLD FRONTAL
PASSAGE. FOR NOW SEASONABLY COLD TEMPS.
ARCTIC COLD: WE/VE NOTICED VARIOUS RUNS OF THE GFS/EC HAVE
THREATENED TO BRING DOWN SOME BITTER ARCTIC COLD THE LAST WEEK OF
DEC. THE GFS ENSEMBLES CONTINUE TO HINT AT A POSSIBLE 2-3 DAY
SPELL OF COLD TEMPS IN THIS TIMEFRAME. THE DETERMINISTIC 5-DAY
MEANS FROM THE LAST COUPLE RUNS OF THE GFS/EC WANT TO DEVELOP A
HUDSON BAY LOW UPSTREAM OF THE GREENLAND BLOCK. WOULD LIKE TO SEE
MORE ENSEMBLE SUPPORT BEFORE GETTING HOPES US. HOWEVER...WE WOULD
NEED SOME HELP EITHER VIA A TRANSITION TO A +PNA /WRN N AMERICA
RIDGING/ OR SOME HIGH- LATITUDE RIDGING OVER AK. THERE ARE SOME
HINTS OF THIS IN THE ENSEMBLES.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
AVIATION...ADO
UPDATE...HEINLEIN
SHORT...BRYANT
LONG...HALBLAUB
AREA FORECAST DISCUSSION
NWS HASTINGS NE
906 AM CST SUN DEC 16 2012
.UPDATE...MADE SOME CHANGES TO WEDNESDAY AND WEDNESDAY NIGHT
FORECAST. ADJUSTED THE GRADIENT FOR CHANCES OF PRECIPITATION ON
WEDNESDAY AND INCREASED CHANCES OF PRECIPITATION CENTRAL/SOUTH A
BIT. ALSO BROKE UP WEATHER AND CHANCES OF PRECIPITATION INTO 6
HOUR BLOCKS WEDNESDAY AND WEDNESDAY NIGHT...AS BOTH WEDNESDAY
MORNING AND LATE WEDNESDAY NIGHT APPEAR TO HAVE MUCH LOWER CHANCES
OF SNOW COMPARED TO WEDNESDAY AFTERNOON AND EVENING. ALSO ADJUSTED
SKY COVER TO BE COMPLETELY CLOUDY FOR WEDNESDAY AFTERNOON AND
EVENING.
&&
.PREV DISCUSSION... /ISSUED 514 AM CST SUN DEC 16 2012/
AVIATION...12Z KGRI TAF. VFR CONDITIONS EXPECTED THROUGH THE NEXT
24 HOURS. STRATUS IS NOTED ON SATELLITE IMAGERY...WITH SURFACE
OBSERVATIONS REPORTING VISIBILITY RESTRICTIONS IN FOG...FROM
EASTERN NEBRASKA INTO EASTERN AND CENTRAL KANSAS. THIS AREA OF
STRATUS AND FOG IS PIVOTING AROUND SOUTH CENTRAL NEBRASKA AND IS
NOT EXPECTED TO IMPACT THE TERMINAL. LOW TO MID LEVEL CLOUDS ARE
HOWEVER MOVING INTO THE TERMINAL FROM THE WEST/SOUTHWEST. THE
MAJORITY OF GUIDANCE SUGGESTS THE TERMINAL WILL REMAIN AT VFR
LEVELS WITH CEILINGS DROPPING NO LOWER THAN 4000 OR 3500 FT AGL.
THAT BEING SAID IT IS WORTH NOTING THAT ONE SET OF GUIDANCE DOES
SUGGEST MVFR CONDITIONS COULD BE REALIZED BY LATE MORNING. THERE
ARE SOME MVFR CEILINGS OVER SOUTHWESTERN NEBRASKA...BUT IT IS
CURRENTLY BELIEVED THAT A RELATIVELY DRY LOWER TROPOSPHERE WILL
PREVENT THESE CEILINGS FROM BEING REALIZED AT KGRI. GIVEN ALL
THIS...WENT AHEAD WITH CEILINGS NO LOWER THAN 3500FT AGL FOR KGRI.
THE SURFACE WIND WILL REMAIN LIGHT AND VARIABLE DURING THE TAF
PERIOD AND AS HINTED AT EARLIER...VISIBILITY RESTRICTIONS ARE NOT
EXPECTED THROUGH THE NEXT 24 HOURS.
PREV DISCUSSION... /ISSUED 433 AM CST SUN DEC 16 2012/
SHORT TERM...THROUGH 12Z WEDNESDAY. EVENING UPPER AIR ANALYSIS
INDICATES A LONGWAVE TROUGH OVER THE WESTERN HALF OF THE CONUS
WITH QUASI- ZONAL FLOW ACROSS THE EAST. MID AND UPPER LEVEL JET
ENERGY EXTENDS FROM WEST-TEXAS...EAST/NORTHEAST INTO THE SOUTHERN
PLAINS AND LOWER MISSISSIPPI VALLEY...AND THEN FARTHER EAST INTO
THE SOUTHEASTERN CONUS. MID AND UPPER LEVEL TROPOSPHERIC FLOW OVER
OUR AREA REMAINS FAIRLY WEAK AS A RESULT...MAXING OUT AT AROUND
60KTS NEAR 200MB PER 00Z SOUNDING DATA FROM KLBF. WATER VAPOR
IMAGERY SHOWS PLENTY OF MID LEVEL MOISTURE ADVANCING
EAST/NORTHEAST ALONG THE MID TO UPPER LEVEL JET AXIS ACROSS THE
SOUTH AND SOUTHEASTERN CONUS...WITH DRIER MID LEVEL AIR NOTED
FARTHER NORTH. WATER VAPOR IMAGERY ALSO INDICATES A COMPACT MID
LEVEL SHORT WAVE OVER COLORADO...BEGINNING TO EJECT OUT FROM THE
MAIN LONGWAVE TROUGH. AT THE SURFACE A RIDGE OF HIGH PRESSURE IS
NOTED EXTENDING FROM THE NORTHERN HIGH PLAINS...SOUTH/SOUTHEAST
INTO THE CENTRAL PLAINS. A COLD FRONT IS ALSO NOTED EXTENDING FROM
SOUTHWEST TO NORTHEAST ACROSS KANSAS...SOUTHWESTERN MISSOURI AND
IOWA. THE LOW LEVEL WIND FIELD ACROSS OUR AREA REMAINS FROM THE
NORTHWEST AS A RESULT. RADAR DATA FROM KUEX...KLNX AND KGLD
CONTINUE TO SHOW PRECIPITATION OVER SOUTHWESTERN NEBRASKA AND
NORTHWESTERN KANSAS...WITH SNOW BEING REPORTED OVER SOME AREAS AS
WELL. FOR LOCATIONS ACROSS OUR WESTERN CWA...WHERE KUEX HAS
INDICATED PRECIPITATION FOR THE PAST FEW HOURS...PRECIPITATION AT
THE SURFACE HAS YET TO BE REPORTED AS THE LOWER TROPOSPHERE STILL
APPEARS TOO DRY FOR SUCH ACTIVITY TO BE REALIZED.
GUIDANCE FROM THE NAM...OPERATIONAL GFS...EC AND SREF-MEAN ALL
SUGGEST THE MID LEVEL SHORT WAVE...APPROACHING OUR AREA FROM
COLORADO...WILL CONTINUE PUSHING ACROSS THE CENTRAL PLAINS DURING
THE DAY TODAY. DPVA AND WEAK MID LEVEL THERMAL ADVECTION AHEAD OF
THE MID LEVEL TROUGH AXIS...WORKING IN CONCERT WITH AN AXIS OF
FRONTOGENESIS NEAR 700MB...SHOULD SUSTAIN PRECIPITATION PRODUCTION
OVER NORTHWESTERN KANSAS AND SOUTHWESTERN NEBRASKA THROUGH THE
NEXT FEW HOURS...WITH PRECIPITATION PERHAPS MAKING IT TO THE
SURFACE ACROSS WESTERN PORTIONS OF OUR AREA AS WELL. FORECAST
PROXIMITY SOUNDINGS FROM ACROSS MUCH OF OUR CWA...PER THE NAM AND
OPERATIONAL GFS...SUGGEST THE LOWER TROPOSPHERE WILL HAVE TO DO
QUITE A BIT OF SATURATING FARTHER EAST BEFORE PRECIPITATION IS
REALIZED AT THE SURFACE...THUS CONFIDENCE IS NOT ALL THAT HIGH
THAT ANY MEASURABLE PRECIPITATION WILL BE REALIZED EAST OF HIGHWAY
183. BUT FARTHER WEST ACROSS THE AREA...WHERE MID LEVEL
PRECIPITATION HAS BEEN ONGOING FOR SEVERAL HOURS NOW AND CEILINGS
ARE LOWERING CLOSER TO 2000FT AGL..CONFIDENCE IS SOMEWHAT HIGHER
OF PRECIPITATION BEING REALIZED AT THE SURFACE. GIVEN ALL
THIS...WENT AHEAD WITH CHANCE POPS ACROSS OUR FAR WEST...ROUGHLY
WEST OF HIGHWAY 183...WITH SLIGHT CHANCE POPS FARTHER EAST. THE
RAP...NAM AND OPERATIONAL GFS ALL SUGGEST THE MID LEVEL TROUGH
AXIS WILL BEGIN CLEARING THE AREA BY 15Z...THUS ALLOWING THE BULK
OF THE OMEGA AND MID LEVEL FRONTOGENESIS TO ALSO PUSH EAST OF OUR
AREA BY LATE MORNING OR MIDDAY. QPF FIELDS FROM VARIOUS MODELS
SUGGEST VERY LIGHT PRECIPITATION MAY STILL BE REALIZED OVER
PORTIONS OF OUR AREA BEYOND 15Z...BUT GIVEN THE LIMITED FORCING BY
THIS TIME OPTED TO ONLY GO WITH 20% POPS 15-18Z...AND ISOLATED
FLURRIES AND SPRINKLES AFTER 18Z.
ALTHOUGH A FEW LOCATIONS ACROSS SOUTHWESTERN NEBRASKA AND
NORTHWESTERN KANSAS HAVE REPORTED RECEIVING ONE OR TWO INCHES OF
SNOW SINCE 06Z...CURRENT RETURNS FROM KUEX...KLNX AND KGLD ALL
SUGGEST THE ONGOING PRECIPITATION IS FAIRLY LIGHT AT THIS HOUR AND
CURRENTLY DO NOT EXPECT THIS TREND TO CHANGE AS THIS ACTIVITY
WORKS INTO OUR AREA. GIVEN ALL THIS...WILL GO AHEAD AND PRESENT A
COUPLE TENTHS OF AN INCH OF SNOWFALL TO MOST LOCATIONS WEST OF
HIGHWAY 183...WITH A FEW LOCATIONS ACROSS WESTERN DAWSON...WESTERN
GOSPER AND WESTERN FURNAS COUNTIES CLOSER TO A HALF INCH.
IT IS WORTH NOTING THAT FORECAST PROXIMITY SOUNDINGS FROM OUR
EAST/NORTHEASTERN CWA PER THE NAM AND RAP SUGGEST AND ELEVATED
WARM LAYER NEAR 850MB COULD PRESENT TEMPERATURES SLIGHTLY ABOVE
FREEZING THROUGH 15Z WHILE SURFACE TEMPERATURES REMAIN BELOW
FREEZING. 850MB TEMPERATURES FOR ALL SITES ACROSS OUR CWA ARE
EXPECTED TO FALL BELOW FREEZING BY NO LATER THAN 15Z HOWEVER...PER
THE NAM AND RAP...AND GIVEN THE LOW CONFIDENCE/VERY LOW CHANCE OF
MEASURABLE PRECIPITATION ACTUALLY BEING OBSERVED THAT FAR EAST
BEFORE 15Z...OPTED TO KEEP ANY MENTION OF -ZR OUT OF THE FORECAST.
THE NAM...OPERATIONAL GFS...EC AND SREF-MEAN ALL SUGGEST YET
ANOTHER MID LEVEL SHORT WAVE WILL PUSH OVER THE CENTRAL PLAINS
TONIGHT. FORECAST PROXIMITY SOUNDINGS FROM ACROSS THE CWA PER THE
NAM AND OPERATIONAL GFS SUGGEST HOWEVER THAT TROPOSPHERIC MOISTURE
WILL BE TOO LACKING FOR PRECIPITATION PRODUCTION AND AS A
RESULT...LEFT TONIGHT DRY. SUBTLE MID AND UPPER LEVEL RIDGING IS
EXPECTED TO MOVE INTO THE CENTRAL CONUS MONDAY THROUGH TUESDAY
NIGHT. THE RESULTANT LACK IN OVERALL KINEMATIC FORCING SHOULD THEN
PRESENT DRY CONDITIONS TO FINISH OUT THE SHORT TERM FORECAST
PERIOD.
WEAK LOW LEVEL COLD AIR ADVECTION ACROSS THE REGION TODAY SHOULD
PRESENT SLIGHTLY COOLER TEMPERATURES TODAY WHEN COMPARED TO
YESTERDAY...WITH AFTERNOON HIGHS IN THE 30S AND 40S CURRENTLY
FORECAST. WEAK LOW LEVEL WARM AIR ADVECTION AND A DOWN-SLOPING
COMPONENT TO THE LOW LEVEL WIND FIELD SHOULD THEN PRESENT A SUBTLE
WARMING TREND TO FINISH OUT THE SHORT TERM FORECAST PERIOD...WITH
HIGHS IN THE 40S AND 50S EXPECTED MONDAY AND TUESDAY.
LONG TERM...WEDNESDAY THROUGH SATURDAY
THE MAIN STORY: WED CONTINUES TO THREATEN SOME WINTRY WX AND
SLIPPERY TRAVEL FOR PART OF THE FCST AREA WITH TEMPS AVERAGING
SEASONABLY COLD THROUGH THE PERIOD.
PATTERN: THE HEMISPHERIC HGT ANOMALIES ARE LIKELY TO MAINTAIN
-NAO/ -PNA CONFIGURATION...ESSENTIALLY WORKING AGAINST EACH OTHER
TO BRING ANY REAL ARCTIC COLD DEEP INTO THE CONUS. HOWEVER...THE E
PACIFIC LONGWAVE TROF WILL CONTINUE TO DELIVER OCCASIONAL PCPN
THREATS. THE FIRST OCCURRED WITH THIS PAST FRI NIGHT`S RAINFALL
/WHICH BROUGHT WIDESPREAD 0.5 TO 0.75"/. THE NEXT ARRIVES WED AND
THE PATTERN LOOKS FAVORABLE FOR ANOTHER DURING THE WEEK OF
CHRISTMAS.
HAZARDS: WE CONTINUE TO SEE POTENTIAL FOR SOME ACCUMULATING SNOW
WED-WED EVE. THE THREAT CONTINUES HIGHLIGHTED IN THE HWO.
PCPN: WED-WED EVE CONFIDENCE IS HIGH FOR A LIGHT SNOWFALL EVENT.
CONFIDENCE IS AVERAGE FOR A MODERATE SNOWFALL...PROBABLY S AND E
OF HASTINGS "IF" IT WAS TO OCCUR.
THE DAILY DETAILS...
LOW TEMPS ALL PERIODS WERE LOWERED TO BIAS CORRECTED ALL-BLEND
GUIDANCE. THIS COORDINATED WITH LBF SINCE THIS LOWERED TEMPS MOST
OVER OUR NW COUNTIES. WED HIGH TEMPS WERE ALSO LOWERED TO MEX
TEMPS AND WAS COORDINATED WITH ALL SURROUNDING OFFICES.
DETERMINISTIC MODELS AND NAEFS/EC ENSEMBLE MEANS CONTINUE TO
SUGGEST HIGH CONFIDENCE IN LEE CYCLOGENESIS WED...WITH THE LOW
EJECTING ACROSS KS /OR NRN OK?/ INTO THE MID MS VALLEY.
HOWEVER...ENSEMBLE SPREAD OF 8-10 MB EXISTS NW OF THE MEAN SFC LOW
POSITION... SUGGESTING DIFFERENCES IN TIMING/LOCATION AMONG THE
VARIOUS POSSIBLE OUTCOMES IN THE GUIDANCE ENVELOPE.
THERE ARE A COUPLE GFS ENSEMBLE MEMBERS THAT OFFER 0.5" OF COMMA-
HEAD QPF IN VICINITY OF HWY 81...SIMILAR TO THE 00Z/15 EC. SO
ALTHO IT/S A LOW PROBABILITY...SOME POTENTIAL CONTINUES FOR
WARNING SNOWFALL AMOUNTS OVER OR SOMEWHERE NEARBY OUR FCST AREA.
FOR NOW GFS ENSEMBLE PROBABILITIES ARE HIGH /70 PERCENT/ FOR 0.1"
IN 24 HRS ALONG AND E OF HWY 281.
REGARDLESS OF HOW MUCH SNOW FALLS...WED IS LIKELY TO BE A RAW
NASTY DAY WITH A SHARP N WIND AND FALLING AFTERNOON TEMPS.
FCST FOR WED IS ESSENTIALLY CLOUDY IN CAA WITH -SN DEVELOPING IN
INCREASINGLY GUSTY NE WINDS. NOT SURE IT SNOWS EVERYWHERE. TRACK
DEPENDENT. BEST GUESS AT THIS POINT IS LOWEST CHANCE FOR
MEASURABLE SNOW IS N AND W OF GRI. TEMPS PROBABLY RISE LITTLE FROM
MORNING LOWS AND THEN FALL AFTER MIDDAY.
WED NGT: ANY SNOW ENDS PROBABLY BY MIDNIGHT. CLEARING FROM THE SW.
A BLUSTERY NIGHT WITH WIND CHILLS AS LOW AS -5F AT TIMES.
WINDS WERE INCREASED ABOVE GUIDANCE 12 PM WED TO 12 PM THU.
THU: UPPER TROF TRANSITIONS TO NW FLOW. SUNNY. BLUSTERY N WINDS
EVENTUALLY SUBSIDE AS SFC RIDGE MOVES IN LATE. NEAR NORMAL TEMPS
BUT IT WILL FEEL COLD GIVEN THE MILD DEC THUS FAR...ESPECIALLY
WITH A BITING N WIND AND WIND CHILLS NEAR ZERO IN THE
MRNG...ESPECIALLY N AND W OF GRI.
FRI: SUNNY AND PROBABLY 5F ABOVE NORMAL WITH LIGHT SW WINDS.
SAT: QUITE A BIT OF SPREAD WITH AMPLITUDE/POSITION OF THE RIDGE
BUT MOST MODELS/ENSEMBLE MEMBERS SUGGEST A DRY COLD FRONTAL
PASSAGE. FOR NOW SEASONABLY COLD TEMPS.
ARCTIC COLD: WE/VE NOTICED VARIOUS RUNS OF THE GFS/EC HAVE
THREATENED TO BRING DOWN SOME BITTER ARCTIC COLD THE LAST WEEK OF
DEC. THE GFS ENSEMBLES CONTINUE TO HINT AT A POSSIBLE 2-3 DAY
SPELL OF COLD TEMPS IN THIS TIMEFRAME. THE DETERMINISTIC 5-DAY
MEANS FROM THE LAST COUPLE RUNS OF THE GFS/EC WANT TO DEVELOP A
HUDSON BAY LOW UPSTREAM OF THE GREENLAND BLOCK. WOULD LIKE TO SEE
MORE ENSEMBLE SUPPORT BEFORE GETTING HOPES US. HOWEVER...WE WOULD
NEED SOME HELP EITHER VIA A TRANSITION TO A +PNA /WRN N AMERICA
RIDGING/ OR SOME HIGH- LATITUDE RIDGING OVER AK. THERE ARE SOME
HINTS OF THIS IN THE ENSEMBLES.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
LONG TERM UPDATE...HEINLEIN
AVIATION/SHORT TERM...BRYANT
LONG TERM...HALBLAUB
AREA FORECAST DISCUSSION
NWS HASTINGS NE
433 AM CST SUN DEC 16 2012
.SHORT TERM...THROUGH 12Z WEDNESDAY. EVENING UPPER AIR ANALYSIS
INDICATES A LONGWAVE TROUGH OVER THE WESTERN HALF OF THE CONUS
WITH QUASI- ZONAL FLOW ACROSS THE EAST. MID AND UPPER LEVEL JET
ENERGY EXTENDS FROM WEST-TEXAS...EAST/NORTHEAST INTO THE SOUTHERN
PLAINS AND LOWER MISSISSIPPI VALLEY...AND THEN FARTHER EAST INTO
THE SOUTHEASTERN CONUS. MID AND UPPER LEVEL TROPOSPHERIC FLOW OVER
OUR AREA REMAINS FAIRLY WEAK AS A RESULT...MAXING OUT AT AROUND
60KTS NEAR 200MB PER 00Z SOUNDING DATA FROM KLBF. WATER VAPOR
IMAGERY SHOWS PLENTY OF MID LEVEL MOISTURE ADVANCING
EAST/NORTHEAST ALONG THE MID TO UPPER LEVEL JET AXIS ACROSS THE
SOUTH AND SOUTHEASTERN CONUS...WITH DRIER MID LEVEL AIR NOTED
FARTHER NORTH. WATER VAPOR IMAGERY ALSO INDICATES A COMPACT MID
LEVEL SHORT WAVE OVER COLORADO...BEGINNING TO EJECT OUT FROM THE
MAIN LONGWAVE TROUGH. AT THE SURFACE A RIDGE OF HIGH PRESSURE IS
NOTED EXTENDING FROM THE NORTHERN HIGH PLAINS...SOUTH/SOUTHEAST
INTO THE CENTRAL PLAINS. A COLD FRONT IS ALSO NOTED EXTENDING FROM
SOUTHWEST TO NORTHEAST ACROSS KANSAS...SOUTHWESTERN MISSOURI AND
IOWA. THE LOW LEVEL WIND FIELD ACROSS OUR AREA REMAINS FROM THE
NORTHWEST AS A RESULT. RADAR DATA FROM KUEX...KLNX AND KGLD
CONTINUE TO SHOW PRECIPITATION OVER SOUTHWESTERN NEBRASKA AND
NORTHWESTERN KANSAS...WITH SNOW BEING REPORTED OVER SOME AREAS AS
WELL. FOR LOCATIONS ACROSS OUR WESTERN CWA...WHERE KUEX HAS
INDICATED PRECIPITATION FOR THE PAST FEW HOURS...PRECIPITATION AT
THE SURFACE HAS YET TO BE REPORTED AS THE LOWER TROPOSPHERE STILL
APPEARS TOO DRY FOR SUCH ACTIVITY TO BE REALIZED.
GUIDANCE FROM THE NAM...OPERATIONAL GFS...EC AND SREF-MEAN ALL
SUGGEST THE MID LEVEL SHORT WAVE...APPROACHING OUR AREA FROM
COLORADO...WILL CONTINUE PUSHING ACROSS THE CENTRAL PLAINS DURING
THE DAY TODAY. DPVA AND WEAK MID LEVEL THERMAL ADVECTION AHEAD OF
THE MID LEVEL TROUGH AXIS...WORKING IN CONCERT WITH AN AXIS OF
FRONTOGENESIS NEAR 700MB...SHOULD SUSTAIN PRECIPITATION PRODUCTION
OVER NORTHWESTERN KANSAS AND SOUTHWESTERN NEBRASKA THROUGH THE
NEXT FEW HOURS...WITH PRECIPITATION PERHAPS MAKING IT TO THE
SURFACE ACROSS WESTERN PORTIONS OF OUR AREA AS WELL. FORECAST
PROXIMITY SOUNDINGS FROM ACROSS MUCH OF OUR CWA...PER THE NAM AND
OPERATIONAL GFS...SUGGEST THE LOWER TROPOSPHERE WILL HAVE TO DO
QUITE A BIT OF SATURATING FARTHER EAST BEFORE PRECIPITATION IS
REALIZED AT THE SURFACE...THUS CONFIDENCE IS NOT ALL THAT HIGH
THAT ANY MEASURABLE PRECIPITATION WILL BE REALIZED EAST OF HIGHWAY
183. BUT FARTHER WEST ACROSS THE AREA...WHERE MID LEVEL
PRECIPITATION HAS BEEN ONGOING FOR SEVERAL HOURS NOW AND CEILINGS
ARE LOWERING CLOSER TO 2000FT AGL..CONFIDENCE IS SOMEWHAT HIGHER
OF PRECIPITATION BEING REALIZED AT THE SURFACE. GIVEN ALL
THIS...WENT AHEAD WITH CHANCE POPS ACROSS OUR FAR WEST...ROUGHLY
WEST OF HIGHWAY 183...WITH SLIGHT CHANCE POPS FARTHER EAST. THE
RAP...NAM AND OPERATIONAL GFS ALL SUGGEST THE MID LEVEL TROUGH
AXIS WILL BEGIN CLEARING THE AREA BY 15Z...THUS ALLOWING THE BULK
OF THE OMEGA AND MID LEVEL FRONTOGENESIS TO ALSO PUSH EAST OF OUR
AREA BY LATE MORNING OR MIDDAY. QPF FIELDS FROM VARIOUS MODELS
SUGGEST VERY LIGHT PRECIPITATION MAY STILL BE REALIZED OVER
PORTIONS OF OUR AREA BEYOND 15Z...BUT GIVEN THE LIMITED FORCING BY
THIS TIME OPTED TO ONLY GO WITH 20% POPS 15-18Z...AND ISOLATED
FLURRIES AND SPRINKLES AFTER 18Z.
ALTHOUGH A FEW LOCATIONS ACROSS SOUTHWESTERN NEBRASKA AND
NORTHWESTERN KANSAS HAVE REPORTED RECEIVING ONE OR TWO INCHES OF
SNOW SINCE 06Z...CURRENT RETURNS FROM KUEX...KLNX AND KGLD ALL
SUGGEST THE ONGOING PRECIPITATION IS FAIRLY LIGHT AT THIS HOUR AND
CURRENTLY DO NOT EXPECT THIS TREND TO CHANGE AS THIS ACTIVITY
WORKS INTO OUR AREA. GIVEN ALL THIS...WILL GO AHEAD AND PRESENT A
COUPLE TENTHS OF AN INCH OF SNOWFALL TO MOST LOCATIONS WEST OF
HIGHWAY 183...WITH A FEW LOCATIONS ACROSS WESTERN DAWSON...WESTERN
GOSPER AND WESTERN FURNAS COUNTIES CLOSER TO A HALF INCH.
IT IS WORTH NOTING THAT FORECAST PROXIMITY SOUNDINGS FROM OUR
EAST/NORTHEASTERN CWA PER THE NAM AND RAP SUGGEST AND ELEVATED
WARM LAYER NEAR 850MB COULD PRESENT TEMPERATURES SLIGHTLY ABOVE
FREEZING THROUGH 15Z WHILE SURFACE TEMPERATURES REMAIN BELOW
FREEZING. 850MB TEMPERATURES FOR ALL SITES ACROSS OUR CWA ARE
EXPECTED TO FALL BELOW FREEZING BY NO LATER THAN 15Z HOWEVER...PER
THE NAM AND RAP...AND GIVEN THE LOW CONFIDENCE/VERY LOW CHANCE OF
MEASURABLE PRECIPITATION ACTUALLY BEING OBSERVED THAT FAR EAST
BEFORE 15Z...OPTED TO KEEP ANY MENTION OF -ZR OUT OF THE FORECAST.
THE NAM...OPERATIONAL GFS...EC AND SREF-MEAN ALL SUGGEST YET
ANOTHER MID LEVEL SHORT WAVE WILL PUSH OVER THE CENTRAL PLAINS
TONIGHT. FORECAST PROXIMITY SOUNDINGS FROM ACROSS THE CWA PER THE
NAM AND OPERATIONAL GFS SUGGEST HOWEVER THAT TROPOSPHERIC MOISTURE
WILL BE TOO LACKING FOR PRECIPITATION PRODUCTION AND AS A
RESULT...LEFT TONIGHT DRY. SUBTLE MID AND UPPER LEVEL RIDGING IS
EXPECTED TO MOVE INTO THE CENTRAL CONUS MONDAY THROUGH TUESDAY
NIGHT. THE RESULTANT LACK IN OVERALL KINEMATIC FORCING SHOULD THEN
PRESENT DRY CONDITIONS TO FINISH OUT THE SHORT TERM FORECAST
PERIOD.
WEAK LOW LEVEL COLD AIR ADVECTION ACROSS THE REGION TODAY SHOULD
PRESENT SLIGHTLY COOLER TEMPERATURES TODAY WHEN COMPARED TO
YESTERDAY...WITH AFTERNOON HIGHS IN THE 30S AND 40S CURRENTLY
FORECAST. WEAK LOW LEVEL WARM AIR ADVECTION AND A DOWN-SLOPING
COMPONENT TO THE LOW LEVEL WIND FIELD SHOULD THEN PRESENT A SUBTLE
WARMING TREND TO FINISH OUT THE SHORT TERM FORECAST PERIOD...WITH
HIGHS IN THE 40S AND 50S EXPECTED MONDAY AND TUESDAY.
.LONG TERM...WEDNESDAY THROUGH SATURDAY
THE MAIN STORY: WED CONTINUES TO THREATEN SOME WINTRY WX AND
SLIPPERY TRAVEL FOR PART OF THE FCST AREA WITH TEMPS AVERAGING
SEASONABLY COLD THROUGH THE PERIOD.
PATTERN: THE HEMISPHERIC HGT ANOMALIES ARE LIKELY TO MAINTAIN
-NAO/ -PNA CONFIGURATION...ESSENTIALLY WORKING AGAINST EACH OTHER
TO BRING ANY REAL ARCTIC COLD DEEP INTO THE CONUS. HOWEVER...THE E
PACIFIC LONGWAVE TROF WILL CONTINUE TO DELIVER OCCASIONAL PCPN
THREATS. THE FIRST OCCURRED WITH THIS PAST FRI NIGHT`S RAINFALL
/WHICH BROUGHT WIDESPREAD 0.5 TO 0.75"/. THE NEXT ARRIVES WED AND
THE PATTERN LOOKS FAVORABLE FOR ANOTHER DURING THE WEEK OF
CHRISTMAS.
HAZARDS: WE CONTINUE TO SEE POTENTIAL FOR SOME ACCUMULATING SNOW
WED-WED EVE. THE THREAT CONTINUES HIGHLIGHTED IN THE HWO.
PCPN: WED-WED EVE CONFIDENCE IS HIGH FOR A LIGHT SNOWFALL EVENT.
CONFIDENCE IS AVERAGE FOR A MODERATE SNOWFALL...PROBABLY S AND E
OF HASTINGS "IF" IT WAS TO OCCUR.
THE DAILY DETAILS...
LOW TEMPS ALL PERIODS WERE LOWERED TO BIAS CORRECTED ALL-BLEND
GUIDANCE. THIS COORDINATED WITH LBF SINCE THIS LOWERED TEMPS MOST
OVER OUR NW COUNTIES. WED HIGH TEMPS WERE ALSO LOWERED TO MEX
TEMPS AND WAS COORDINATED WITH ALL SURROUNDING OFFICES.
DETERMINISTIC MODELS AND NAEFS/EC ENSEMBLE MEANS CONTINUE TO
SUGGEST HIGH CONFIDENCE IN LEE CYCLOGENESIS WED...WITH THE LOW
EJECTING ACROSS KS /OR NRN OK?/ INTO THE MID MS VALLEY.
HOWEVER...ENSEMBLE SPREAD OF 8-10 MB EXISTS NW OF THE MEAN SFC LOW
POSITION... SUGGESTING DIFFERENCES IN TIMING/LOCATION AMONG THE
VARIOUS POSSIBLE OUTCOMES IN THE GUIDANCE ENVELOPE.
THERE ARE A COUPLE GFS ENSEMBLE MEMBERS THAT OFFER 0.5" OF COMMA-
HEAD QPF IN VICINITY OF HWY 81...SIMILAR TO THE 00Z/15 EC. SO
ALTHO IT/S A LOW PROBABILITY...SOME POTENTIAL CONTINUES FOR
WARNING SNOWFALL AMOUNTS OVER OR SOMEWHERE NEARBY OUR FCST AREA.
FOR NOW GFS ENSEMBLE PROBABILITIES ARE HIGH /70 PERCENT/ FOR 0.1"
IN 24 HRS ALONG AND E OF HWY 281.
REGARDLESS OF HOW MUCH SNOW FALLS...WED IS LIKELY TO BE A RAW
NASTY DAY WITH A SHARP N WIND AND FALLING AFTERNOON TEMPS.
FCST FOR WED IS ESSENTIALLY CLOUDY IN CAA WITH -SN DEVELOPING IN
INCREASINGLY GUSTY NE WINDS. NOT SURE IT SNOWS EVERYWHERE. TRACK
DEPENDENT. BEST GUESS AT THIS POINT IS LOWEST CHANCE FOR
MEASURABLE SNOW IS N AND W OF GRI. TEMPS PROBABLY RISE LITTLE FROM
MORNING LOWS AND THEN FALL AFTER MIDDAY.
WED NGT: ANY SNOW ENDS PROBABLY BY MIDNIGHT. CLEARING FROM THE SW.
A BLUSTERY NIGHT WITH WIND CHILLS AS LOW AS -5F AT TIMES.
WINDS WERE INCREASED ABOVE GUIDANCE 12 PM WED TO 12 PM THU.
THU: UPPER TROF TRANSITIONS TO NW FLOW. SUNNY. BLUSTERY N WINDS
EVENTUALLY SUBSIDE AS SFC RIDGE MOVES IN LATE. NEAR NORMAL TEMPS
BUT IT WILL FEEL COLD GIVEN THE MILD DEC THUS FAR...ESPECIALLY
WITH A BITING N WIND AND WIND CHILLS NEAR ZERO IN THE
MRNG...ESPECIALLY N AND W OF GRI.
FRI: SUNNY AND PROBABLY 5F ABOVE NORMAL WITH LIGHT SW WINDS.
SAT: QUITE A BIT OF SPREAD WITH AMPLITUDE/POSITION OF THE RIDGE
BUT MOST MODELS/ENSEMBLE MEMBERS SUGGEST A DRY COLD FRONTAL
PASSAGE. FOR NOW SEASONABLY COLD TEMPS.
ARCTIC COLD: WE/VE NOTICED VARIOUS RUNS OF THE GFS/EC HAVE
THREATENED TO BRING DOWN SOME BITTER ARCTIC COLD THE LAST WEEK OF
DEC. THE GFS ENSEMBLES CONTINUE TO HINT AT A POSSIBLE 2-3 DAY
SPELL OF COLD TEMPS IN THIS TIMEFRAME. THE DETERMINISTIC 5-DAY
MEANS FROM THE LAST COUPLE RUNS OF THE GFS/EC WANT TO DEVELOP A
HUDSON BAY LOW UPSTREAM OF THE GREENLAND BLOCK. WOULD LIKE TO SEE
MORE ENSEMBLE SUPPORT BEFORE GETTING HOPES US. HOWEVER...WE WOULD
NEED SOME HELP EITHER VIA A TRANSITION TO A +PNA /WRN N AMERICA
RIDGING/ OR SOME HIGH- LATITUDE RIDGING OVER AK. THERE ARE SOME
HINTS OF THIS IN THE ENSEMBLES.
&&
.PREV DISCUSSION... /ISSUED 1107 PM CST SAT DEC 15 2012/
AVIATION...06Z KGRI TAF. VFR CONDITIONS EXPECTED THROUGH THE NEXT
24 HOURS. CEILINGS BETWEEN 4000FT AGL AND 8000FT AGL WILL PERSIST
AT THE TERMINAL THROUGH SUNDAY AFTERNOON...WITH HIGH LEVEL CLOUDS
EXPECTED THEREAFTER. THE SURFACE WIND WILL REMAIN FROM THE
NORTHWEST TONIGHT BEFORE BECOMING LIGHT AND VARIABLE DURING THE
DAY SUNDAY. VISIBILITY RESTRICTIONS ARE NOT EXPECTED THROUGH THE
NEXT 24 HOURS.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
SHORT TERM/AVIATION...BRYANT
LONG TERM...HALBLAUB
AREA FORECAST DISCUSSION
NWS NORTH PLATTE NE
1129 PM CST SAT DEC 15 2012
.AVIATION...
A WEAK STORM SYSTEM WILL AFFECT WESTERN NEBRASKA TONIGHT WITH
BKN100 CEILINGS LOWERING THROUGH MVFR CEILINGS OVER SOUTHWEST NEBRASKA.
LIGHT SNOW WILL CONTINUE OVER SOUTHWEST NEBRASKA BETWEEN KOGA AND
KIML. CONFIDENCE NOT HIGH FOR SNOW TOO IMPACT KLBF SO HAVE LEFT
OUT OF THE TAF FOR NOW. CIGS MAY LOWER INTO IFR OVER SOUTHWEST
NEBRASKA SUNDAY MORNING.
&&
.PREV DISCUSSION... /ISSUED 356 PM CST SAT DEC 15 2012/
UPDATE...
DISCUSSION...
JUST A QUICK REFRESH ON THE POPS AND QPF ACROSS SWRN NEB. NO REAL
CHANGE BUT QPF PLUMES SUGGEST HIGHER CONFIDENCE FORM KOGA SOUTH
THROUGH KIML SO POPS ARE UP SLIGHTLY AND MEASUREABLE QPF IS FCST A
BIT FARTHER NORTH.
PREV DISCUSSION... /ISSUED 301 PM CST SAT DEC 15 2012/
DISCUSSION...
THE AREA OF WEAK DEFORMATION ACROSS NERN COLO WILL DRIFT EAST
NORTHEAST AND DECAY THIS EVENING. THUS FAR NO SNOW OR RAIN HAS
REACHED THE GROUND DESPITE THE PERSISTENT RADAR RETURNS. LATER
TONIGHT...A SECOND IMPULSE...CURRENTLY ACROSS THE SRN ROCKIES...WILL
LIFT NORTHEAST FORMING A SECOND AREA OF WEAK DEFORMATION WHICH
COULD DRIFT ACROSS SRN NEB AFTER MIDNIGHT PRODUCING LIGHT SNOW.
THE MODELS ARE HAVING A HARD TIME WITH SOME SOLNS SHOWING
DEFORMATION ACROSS THE SAND HILLS AND OTHERS ACROSS SRN NEB.
THE CONSENSUS OF SOLNS SUPPORTS LIGHT SNOW ACROSS SRN NEB. CHANCE
POPS ARE IN PLACE WITH ACCUMULATIONS LESS THAN AN INCH. HPC
SUGGESTED LITTLE OR NO ACCUMULATION ACROSS SWRN NEB. THE ECM
SHOWED 2 INCHES NEAR KOGA...THE GFS SHOWED 5 INCHES NEAR
KIML...THE GEM SHOWED 2 INCHES NEAR KIML AND THE NAM SHOWED AN
INCH ALL OVER THE PLACE. THE RAP HAS BEEN WOBBLING 1 TO 2 INCHES
NORTH AND SOUTH...GENERALLY NEAR OR SOUTH OF INTERSTATE 80.
IT WOULD BE BEST TO WAIT FOR THE RADAR AND SFC OBSERVATIONS TO
LIGHT UP AND THEN GET MORE SPECIFIC WITH POPS AND SNOW AMOUNTS SINCE
THIS IS A FAIRLY COMPACT AREA OF SNOW THE MODELS ARE FORECASTING
TO DEVELOP. THE MODELS ARE SHOWING A WEAK AREA OF ARCTIC HIGH PRESSURE
BUILDING DOWN TONIGHT AND THE PROGRESS OF THAT AIR COULD HAVE A
LOT TO DO WITH THE LOCATION OF THE SNOWFALL. ALSO...THE NAN AND
RUC SHOW RAIN THIS EVENING AHEAD OF THE FRONT..THEN SNOW WHILE THE
GFS IS ALL SNOW.
THIS SYSTEM WILL EXIT THE FCST AREA LATE IN THE DAY SUNDAY MAKING
FOR A COOL DAY AS THE ARCTIC HIGH DRIFTS EAST...LOW PRESSURE
REFORMS ACROSS THE CNTL HIGH PLAINS AND SOUTH WINDS DEVELOP
RECYCLING COLD AIR NORTH.
THE NEXT WEATHER SYSTEM OF INTEREST CROSSES THE FCST AREA TUESDAY
NIGHT THROUGH WEDNESDAY NIGHT. THERE ARE TWO SCENARIOS SHOWN IN THE
MODELS. THE ECM SUGGESTS A MORE SOUTHERLY ROUTE TAKING A LEAD
SHORT WAVE AND DEFORMATION ZONE THROUGH NORTHWEST NEBRASKA
FOLLOWED BY THE MAIN FORCING THROUGH SRN NEB AND KANSAS...MOSTLY
SOUTH AND EAST OF THE FCST AREA. THE GEM AND GFS SUGGEST A MORE
CLASSIC DISTURBANCE CRIS CROSSING THE COLD FRONT PRODUCING LIGHT
SNOW THROUGHOUT THE FCST AREA. THE FCST USED 50 PERCENT OF THE ECM
AND 25 PERCENT OF THE OTHER TWO MODELS. ALL MODELS SHOW WEAK
FRONTOGENESIS ACROSS NW NEB TUESDAY NIGHT. THE ECM QUICKLY DECAYS
THAT FEATURE WHILE THE GEM AND GFS CARRY THAT ACROSS THE FCST
AREA. EITHER WAY...BY THURSDAY MORNING H10-5 THICKNESSES FALL TO
BELOW 520 DM AND H850 TEMPERATURES ARE AROUND MINUS 7C.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM/EXTENDED...CDC
AVIATION...POWER
AREA FORECAST DISCUSSION
NWS GRAND FORKS ND
1016 AM CST SUN DEC 16 2012
.DISCUSSION...
MAIN CHANGE FOR THE MORNING UPDATE WAS TO BUMP UP CLOUD COVER FOR
THE REST OF THE DAY. LOTS OF LOW LEVEL MOISTURE TRAPPED UNDER THE
SUBSIDENCE INVERSION WITH HIGH PRESSURE AND SAT LOOPS SHOW NO BIG
BREAKS IN THE CLOUDS UNTIL NORTH OF LAKE WINNIPEG. HRRR AND LAV
GUIDANCE SEEM TO SUPPORT A PRETTY CLOUDY DAY FOR THE REST OF THE
DAY...SO BUMPED UP CLOUDS. LOW LEVEL WARM AIR ADVECTION WILL MOVE
SOUTH OF THE AREA AND WEAK COLD AIR ADVECTION MOVING IN. THINK
THAT TEMPS WILL STEADY OFF AND THEN SLOWLY START TO DROP...WITH
THE EXCEPTION OF THE FAR SOUTHEASTERN COUNTIES. PATCHY FOG HAS
TAKEN OVER NORTH CENTRAL ND...BUT MOST OF IT HAS STAYED WEST OF
OUR COUNTIES. STILL...WILL INCLUDE A PATCHY MENTION IN THE FAR
NORTHWESTERN COUNTIES FOR THE REST OF THE MORNING AS WEB CAMS SHOW
SOME FOG ALONG THE CENTER OF THE SFC HIGH.
&&
.AVIATION...
MOST LOCATIONS HAVE STAYED IFR OR LOWER UNDER AN EXTENSIVE STRATUS
DECK. A FEW LOCATIONS COULD RECOVER TO MVFR FOR A TIME THIS
AFTERNOON...BUT CONDITIONS WILL STAY PRETTY CLOUDY. CEILINGS WILL
COME DOWN AGAIN AND RETURN TO IFR OR LOWER AFTER SUNSET. NORTHERLY
WINDS AT LESS THAN 10 KTS WILL BECOME LIGHT AND VARIABLE.
&&
.PREV DISCUSSION... /ISSUED 331 AM CST SUN DEC 16 2012/
SHORT TERM...
CHALLENGES FOR THE FORECAST INCLUDE CLOUD COVER AND ITS IMPACTS ON
TEMPS ALONG WITH AREAL COVERAGE AND POPS FOR LIGHT SNOW TUESDAY.
MODELS IN FAIR AGREEMENT AND WILL USE A BLEND FOR THE FORECAST.
WATER VAPOR IMAGERY SHOWS AN UPPER LEVEL TROUGH SLOWLY SLIDING
ACROSS MANITOBA THIS MORNING. MODELS IN AGREEMENT WITH THIS
FEATURE CUTTING OFF AND LINGERING ACROSS SOUTHERN CANADA AS THE
300MB FLOW REMAINS SPLIT ACROSS THE NORTHERN PLAINS. AT THE SFC
RELATIVELY WEAK HIGH PRESSURE IS CENTERED OVER W ND AND W
MANITOBA. STRATUS DECK ACROSS THE FA AND UNDER THE HIGH WILL BE
SLOW TO ERODE WITH LITTLE MIXING AND A RELATIVELY MOIST LOW LEVEL.
MODEL SOUNDINGS SHOW A STRONG INVERSION WITH A DRY LAYER ABOVE THE
LOW LEVEL RH. EXPECTING LITTLE IN THE WAY OF SOLAR TODAY WITH
TEMPS NEARLY STEADY AS CURRENT READINGS IN THE TEENS AND LOW 20S
PERSIST FOR MUCH OF THE DAY.
AFOREMENTIONED SFC HIGH TO DRIFT SLOWLY EAST AND IS PROGGED TO BE
CENTERED OVER THE FA ON MON 12Z. THERMAL PROFILE REMAINS UNCHANGED
THOUGH CLOUD COVER TO IMPACT TEMPS...ANY HOLES OR CLEARING IN THE
STRATUS DECK WILL ALLOW THE SFC TO RADIATE OUT AND TEMPS TO FALL
QUICKLY. GIVEN THE UNCERTAINTY OF CLEARING AND LOW LEVEL RH
THINKING MORE CLOUDS THAN NOT WITH TEMPS IN THE SINGLE DIGITS
FORECASTED FOR MON MORNING LOWS. HIGHS MONDAY A BIT LOWER AS A
COOLER START WITH LITTLE SOLAR AND MIXING TO LIMIT TEMP RISE.
SFC HIGH SLOWLY MOVES EAST WITH RETURN FLOW SETTING UP MONDAY
NIGHT INTO TUESDAY AS ZONAL FLOW ALOFT BRINGS IN A WEAK WAVE WITH
MODELS INDICATING SOME WAA PRECIP ON TUESDAY. THE NAM CONTINUES TO
BE MUCH QUICKER WITH THE BAND OF PRECIP LIFTING FROM SW TO NE
ACROSS THE FA THAN THE OTHER MODELS THOUGH ITS PLACEMENT OF THE
SFC LOW ON 18Z TUESDAY IS SIMILAR...IN THE MT/ND/SASK AREA. KEPT
THE CHC/SCHC POPS TUESDAY.
LONG TERM (WEDNESDAY-SATURDAY)...
A FAIRLY QUIET PERIOD APPEARS TO BE IN STORE. THERE WILL BE A SLIGHT
CHANCE FOR LIGHT SNOW ON WEDNESDAY WITH AN UPPER TROUGH MOVING THROUGH
THE REGION...OTHERWISE EXPECT RIDGING TO DOMINATE. ENERGY FROM THE
NORTHERN STREAM WILL BRIEFLY FLATTEN THE UPPER RIDGE FRIDAY-
SATURDAY...BUT SHOULD REMAIN NORTH OF THE INTERNATIONAL BORDER.
OVERALL...TEMPERATURES WILL BE NEAR OR SLIGHTLY BELOW NORMAL.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...NONE.
MN...NONE.
&&
$$
JR
AREA FORECAST DISCUSSION
NWS WILMINGTON OH
706 PM EST MON DEC 17 2012
.SYNOPSIS...
LOW PRESSURE WILL MOVE NORTHEAST THROUGH THE REGION THIS EVENING. HIGH
PRESSURE WILL BUILD IN FOR TUESDAY AND WEDNESDAY. A STRONG COLD
FRONT WILL SWEEP THROUGH THE AREA ON THURSDAY...BRINGING
PRECIPITATION AND WINDY CONDITIONS.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
AN AREA OF LOW PRESSURE WILL CONTINUE TRACKING NORTHEAST THROUGH
THE ILN CWA THIS EVENING...EVENTUALLY MOVING INTO PENNSYLVANIA AS
A SURFACE COLD FRONT BEGINS ITS PROGRESSION THROUGH THE REGION. ON
THE SOUTH SIDE OF THIS BOUNDARY...WEAK SURFACE BASED INSTABILITY
HAS BEEN ABLE TO JUST NUDGE INTO THE FAR SOUTHERN ILN
COUNTIES...WITH SOME ELEVATED INSTABILITY EXTENDING THROUGH THE
SOUTHERN 1/3 TO 1/2 OF THE CWA. ATMOSPHERIC TEMPERATURE LEVELS ARE
QUITE LOW COMPARED TO A MORE TYPICAL SPRING OR SUMMER SEVERE
EVENT...WHICH HAS FAVORED THE PRODUCTION OF LARGE AMOUNTS OF SMALL
HAIL. MOST OF THE STORMS HAVE STRUGGLED TO GROW TALL ENOUGH TO
GENERATE LARGE HAIL...EVEN AS SHEAR SEEMS SUFFICIENT TO SUPPORT
SOME ORGANIZATION.
A WEAKENING TREND IS EXPECTED TONIGHT...BUT WITH RAP AND NAM12
RUNS INDICATING SOME WEAK INSTABILITY WILL PERSIST IN SOUTHERN
OHIO / NORTHEAST KENTUCKY FOR SEVERAL HOURS. SO...THUNDER WILL BE
KEPT IN THE FORECAST. IN ADDITION...CATEGORICAL POPS WILL BE USED
AS EXTRAPOLATED FROM THE CURRENT BAND OF PRECIPITATION...BEFORE
TAPERING TO LIKELY OVERNIGHT AS THE FORCING MOVES FURTHER AWAY.
NEAR THE BASE OF THE MID-LEVEL TROUGH...AND ON THE BACK SIDE OF
THE SURFACE LOW...ADDITIONAL (GENERALLY LIGHT) PRECIPITATION IS
EXPECTED TO CONTINUE OVERNIGHT ON A WSW-ENE AXIS ACROSS THE
NORTHERN PORTIONS OF THE CWA. TEMPERATURES WILL BE COOLING DOWN
JUST ENOUGH TO ALLOW FOR A WET MIX OF RAIN AND SNOW NEAR THE END
OF THE PRECIPITATION. NO ACCUMULATIONS ARE EXPECTED.
COLD ADVECTION WILL HELP TEMPS APPROACH FREEZING IN THE NORTHWEST
CWA OVERNIGHT...WITH A GRADIENT THAT EXTENDS TO THE LOWER 40S IN
THE SOUTHEAST CORNER.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/...
THE SURFACE PRESSURE PATTERN WILL REMAIN COMPLICATED THROUGH THE
SHORT TERM...AS A NARROW RIDGE OF HIGH PRESSURE BUILDS IN
TUESDAY...BEFORE LOW PRESSURE MOVES EAST THROUGH THE SOUTHERN
GREAT LAKES TUESDAY NIGHT. IN THE MID LEVELS...A RIDGE WILL BUILD
OVER THE OHIO VALLEY AND SOUTHERN STATES THROUGH WEDNESDAY. DRY
WEATHER WILL CHARACTERIZE THE PERIOD...WITH FLOW REMAINING
GENERALLY SOUTHWESTERLY. TEMPERATURES WILL INCREASE A BIT FROM
TUESDAY TO WEDNESDAY...ESPECIALLY IN THE SOUTHERN COUNTIES. ON THE
OTHER HAND...LIGHTER WINDS AND CLEARING SKIES SHOULD MAKE TUESDAY
NIGHT COOLER THAN MONDAY NIGHT.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
FOR THE PERIOD WEDNESDAY NIGHT INTO THURSDAY NIGHT...A DEEPENING MID
LEVEL TROF AND DEEPENING SFC LOW PRESSURE SYSTEM WILL PULL NORTHEAST
FROM THE SRN PLAINS TO THE GREAT LAKES/OHIO VALLEY REGION. THE TRACK
OF THE SFC LOW CONTINUES TO BE NW OF THE REGION...SO ANY MAJOR
WINTER WEATHER WILL STAY TO OUR NW. THE LOW WILL BE ASSOCIATED WITH
A STRONG COLD FRONT. DEEP MOISTURE COMBINED WITH STRONG SYNOPTIC
SCALE FORCING WILL SPREAD SHOWERS INTO THE WESTERN PARTS OF THE AREA
LATE WEDNESDAY NIGHT...AND WILL CONTINUE TO PUSH EAST INTO
THURSDAY. TEMPERATURES WILL WARM INTO THE LOWER AND MID 50S ON
THURSDAY FOLLOWED BY FALLING TEMPERATURES LATE IN THE DAY INTO
THURSDAY NIGHT. COLD AIR ADVECTION IN THE WAKE OF THE LOW AND FRONT
WILL BRING SOME WRAP AROUND AND LAKE INDUCED SNOW SHOWERS LATE
THURSDAY INTO THURSDAY NIGHT. RIGHT NOW...ANY SNOW ACCUMULATION
SHOULD BE MINOR. WINDY CONDITIONS ARE FORECAST DUE TO A TIGHTENING
PRESSURE GRADIENT AND MOMENTUM TRANSFER IN THE STRONG COLD AIR
ADVECTION BEHIND FRONTAL PASSAGE THURSDAY INTO THURSDAY NIGHT. WILL
CONTINUE TO MENTION THE POSSIBILITY OF 40 MPH TO 50 MPH WIND GUSTS
IN THE HWO PRODUCT.
FOR FRIDAY INTO FRIDAY NIGHT...UPR LVL TROF WILL HAVE CLOSED OFF TO
OUR NORTH AND NORTHEAST...AND WILL MOVE AWAY FROM OUR REGION. CLOUDS
AND LINGERING SNOW SHOWERS ON FRIDAY WILL TAPER OFF FROM SW TO NE
THROUGH THE DAY...FOLLOWED BY CLEARING SKIES FRIDAY NIGHT. HIGHS ON
FRIDAY WILL STRUGGLE TO WARM INTO THE LOWER AND MID 30S.
FOR THE PERIOD SATURDAY THROUGH MONDAY...MODELS CONTINUE TO DISAGREE
WHETHER UPR LVL CLOSED LOW TO OUR NE WILL ROTATE BACK TO THE
SOUTHWEST AND ALLOW COLDER AIR TO INFILTRATE FROM THE NORTH. IF THIS
OCCURS...THERE WILL BE MORE CLOUDS ACRS OUR NORTHERN ZONES WITH LAKE
EFFECT SNOW SHOWERS STAYING DOWNWIND OF THE GREAT LAKES. FOR
NOW...HAVE KEPT THE FORECAST DRY WITH SURFACE HIGH PRESSURE AT LEAST
IN PLACE AT THE SURFACE. HAVE NOT GONE AS COLD AS THE LATEST 17.12Z
ECMWF...AND HAVE RESORTED TO A BLEND OF THIS WITH HPC GUIDANCE.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
SFC LOW JUST NORTH OF HTS AND SLOWLY PROGRESSING ENE. PLENTY OF LL
MOISTURE...IN THAT MVFR TO IFR CIGS EXPECTED THROUGH MOST OF THE
NIGHT FOR NEARLY ALL LOCATIONS. THE QUESTION IS WHETHER LIFR CIGS
MAY SNEAK IN AT SOME LOCATIONS. CURRENTLY NOT FORECASTING LIFR
CIGS...THOUGH IF ANY LOCATIONS WOULD INCUR THIS..WOULD LIKELY BE
KCVG/KLUK/KDAY. SLIGHT IMPROVEMENT TO MVFR IN THE 12-14Z
TIMEFRAME...WHEN WINDS BEGIN TO BECOME SWERLY AS THE CENTER OF THE
RIDGE JUST SOUTH OF THE REGION BEGINS TO TREK EAST. VFR CIGS AFTER
ABOUT 14-15Z.
OUTLOOK...MVFR CONDITIONS ARE POSSIBLE THURSDAY. WIND GUSTS FROM
35 TO 45 KTS POSSIBLE THURSDAY AFTERNOON AND NIGHT.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.
&&
$$
SYNOPSIS...HATZOS
NEAR TERM...HATZOS
SHORT TERM...HATZOS
LONG TERM...HICKMAN
AVIATION...JDR
AREA FORECAST DISCUSSION
NWS WILMINGTON OH
1233 PM EST SUN DEC 16 2012
.SYNOPSIS...
A WEAK COLD FRONT WILL SLIDE INTO THE AREA THIS AFTERNOON AND
EVENING. LOW PRESSURE WILL DEVELOP ALONG THIS FRONT AND MOVE
ACROSS THE AREA MONDAY. HIGH PRESSURE WILL BUILD IN TUESDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
LOW LEVEL MOISTURE WILL REMAIN IN PLACE ACROSS THE CWA TODAY.
CEILINGS HAVE BEGUN TO LIFT SLIGHTLY THIS MORNING...AND RADAR
ECHOES HAVE DIMINISHED IN COVERAGE AS WELL. A SLIGHT CHANCE OF
SHOWERS WILL BE KEPT IN THE FORECAST...MAINLY IN THE EAST AND JUST
FOR THE NEXT FEW HOURS...BEFORE LIMITING ANY CHANCE OF
PRECIPITATION TO THE FAR SOUTHEAST THROUGH THE AFTERNOON HOURS.
THE LATEST HRRR RUNS ARE SHOWING THAT ANY CONVECTION THAT DEVELOPS
WILL OCCUR NEAR OR AFTER 00Z AND WILL LIKELY BE LIMITED TO THE
SOUTH AND SOUTHEAST. GIVEN THE REMAINING UNCERTAINTY IN BOTH
FORCING AND INSTABILITY...THERE APPEARS TO BE NO REASON TO
INCREASE POPS THIS EVENING (THOUGH A SLIGHTLY HIGHER CHANCE WILL
EXIST LATER IN THE OVERNIGHT HOURS).
TEMPERATURES WERE MOSTLY ON TRACK...WITH SOME SLIGHT UPWARD
ADJUSTMENTS MADE IN THE SOUTH. WARM ADVECTION WILL DOMINATE THE
TEMPERATURE CURVE TODAY...WITH ESSENTIALLY ZERO DIRECT SUNLIGHT
EXPECTED.
PREVIOUS DISCUSSION >
SOUTHERLY FLOW WILL CONTINUE ACROSS THE REGION TODAY. PLENTY OF
LOW LEVEL MOISTURE IN PLACE ALTHOUGH THERE SHOULD BE SOME BREAKS
IN THE CLOUDS ESPECIALLY LATER IN THE DAY. A WEAK COLD FRONT WILL
PUSH INTO THE REGION LATE THIS AFTERNOON. AND THERE WILL BE A WEAK
MID LEVEL IMPULSE TRACKING ACROSS THE AREA. BUT OVERALL FORCING IS
MINIMAL. SO ONLY KEPT SLIGHT CHANCE POPS IN FOR TODAY.
TEMPERATURES WILL BE WELL ABOVE NORMAL WITH A MOS BLEND USED AS A
BASE FOR HIGHS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
BOUNDARY WILL WORK FURTHER INTO THE FORECAST AREA TONIGHT BEFORE
STALLING AS LOW PRESSURE DEVELOPS ALONG THE FRONT OFF TO THE
SOUTHWEST. AS THE LOW APPROACHES LATE TONIGHT EXPECT SHOWERS TO
DEVELOP IN THE SOUTHERN COUNTIES. THE LOW WILL CONTINUE TO TRAVEL
ALONG THE FRONT AND ACROSS THE REGION ON MONDAY. MODELS ARE
TRENDING TOWARDS A LESS DEVELOPED LOW WHICH SHOULD KEEP THE
GREATER COVERAGE OF SHOWERS FROM SPREADING TOO FAR NORTHWEST. BUT
STILL ENOUGH UNCERTAINTY TO KEEP CHANCE POPS GOING ALL THE WAY
INTO WEST CENTRAL OHIO. THERE WILL BE SOME INSTABILITY ALONG AND
SOUTH OF THE FRONT SO DID INCLUDE A CHANCE OF THUNDERSTORMS THERE.
A SHORT WAVE WILL TRAVEL ACROSS THE REGION MONDAY NIGHT AND WITH
MOISTURE STILL LINGERING IN THE AREA THAT MAY GENERATE SOME
ADDITIONAL SHOWERS AREA WIDE. AFTER IT PASSES RIDGING WILL
TEMPORARILY MOVE IN ALLOWING FOR SOME DRYING.
WARMER GUIDANCE LOOKED MORE REASONABLE FOR TONIGHT BUT A BLEND WAS
USED MONDAY NIGHT. LEANED TOWARDS COOLER GUIDANCE FOR HIGH
TEMPERATURES BOTH DAYS.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
UPPER RIDGING WILL CONTINUE INTO WEDNESDAY AHEAD OF AN APPROACHING
DEEPENING TROUGH. SO EXPECT DRY AND UNSEASONABLY WARM CONDITIONS
ONCE AGAIN. AS THE UPPER SYSTEM PIVOTS NORTHEAST TOWARDS THE
REGION THE ASSOCIATED SURFACE LOW WILL PUSH A WARM FRONT THROUGH
THE AREA WEDNESDAY NIGHT. THIS WILL LEAD TO STEADY OR RISING
TEMPERATURES OVERNIGHT. SHOWERS WILL SPREAD IN FROM THE WEST LATE
WEDNESDAY NIGHT AND SWEEP ACROSS THE REGION ON THURSDAY. WITH WEAK
INSTABILITY FORECAST AT THIS POINT BUT FAIRLY STRONG DYNAMICS...
CANNOT RULE OUT SOME THUNDER ALTHOUGH IT IS NOT INCLUDED IN THE
FORECAST YET. THE LOW WILL LIFT NORTH OF THE AREA BUT AFTER A
STRONG COLD FRONT SWEEPS THROUGH THE TEMPERATURES WILL FALL IN THE
AFTERNOON.
00Z GUIDANCE HAS COME INTO AGREEMENT IN KEEPING THIS SYSTEM
PROGRESSIVE. SO THERE WILL ONLY BE A BRIEF WINDOW FOR WRAP AROUND
AND LAKE ENHANCED SNOW SHOWERS TO AFFECT THE REGION THURSDAY NIGHT
AND FRIDAY. HIGH PRESSURE WILL BUILD IN WITH TEMPERATURES AT OR
SLIGHTLY BELOW SEASONAL NORMALS.
&&
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
WITH PLENTY OF VARIABLE CONDITIONS EXPECTED IN THE NEXT 24
HOURS...THIS SET OF TAFS WAS DIFFICULT...AND CONFIDENCE IN
SPECIFICS IS NOT ESPECIALLY HIGH.
LOW LEVEL MOISTURE WILL CONTINUE ACROSS THE REGION THROUGH THE
PERIOD. CLOUDS HAVE GENERALLY BEEN ON A LIFTING TREND THROUGH THE
MORNING...AND VFR CEILINGS ARE EXPECTED TO BE MORE PREVALENT INTO
THE AFTERNOON. HOWEVER...SOME MVFR CONDITIONS ARE STILL
POSSIBLE...ESPECIALLY IN THE FIRST FEW HOURS OF THE VALID TAFS.
SSW WINDS HAVE BEEN OCCASIONALLY GUSTY (AROUND 18-24 KNOTS) BUT
SOMETIMES MORE CALM. THE TAFS WILL INCLUDE THE GUSTS...BUT THEY
MAY NOT OCCUR AT ALL TIMES.
SHOWERS AND POSSIBLY THUNDERSTORMS ARE EXPECTED TO DEVELOP
TONIGHT...THOUGH THE HIGHEST CONCENTRATION SHOULD REMAIN SOUTH OF
THE TAF SITES. VCSH WITH TEMPO -SHRA HAS BEEN ADDED TO ACCOUNT FOR
THIS ACTIVITY AFTER SUNSET...THOUGH CONFIDENCE IN THUNDER
AFFECTING A TAF SITE IS EXTREMELY LOW. CEILINGS WILL ALSO LOWER
AGAIN DURING THE OVERNIGHT...WITH MVFR VISIBILITIES AND CEILINGS
IN THE LOW MVFR RANGE. THOUGH NOT SPECIFICALLY FORECAST...SOME IFR
CEILINGS ARE POSSIBLE NEAR SUNRISE.
LOW PRESSURE MOVING NORTHEAST THROUGH THE OHIO VALLEY WILL BRING
ANOTHER CHANCE FOR PRECIPITATION ON MONDAY. THIS LOOKS TO BEGIN
NEAR THE END OF THE TAF PERIOD...AND MVFR CONDITIONS ARE EXPECTED
TO BE PREVAILING. LATE IN THE PERIOD...WINDS WILL BEGIN A SHIFT
FROM SOUTHERLY TO WESTERLY.
OUTLOOK...MVFR CEILINGS AND VISIBILITIES WILL BE POSSIBLE FROM
MONDAY THROUGH TUESDAY. MVFR CONDITIONS ARE AGAIN EXPECTED ON
THURSDAY.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.
&&
$$
SYNOPSIS...
NEAR TERM...HATZOS
SHORT TERM...
LONG TERM...
AVIATION...HATZOS
AREA FORECAST DISCUSSION
NWS WILMINGTON OH
923 AM EST SUN DEC 16 2012
.SYNOPSIS...
A WEAK COLD FRONT WILL SLIDE INTO THE AREA THIS AFTERNOON AND
EVENING. LOW PRESSURE WILL DEVELOP ALONG THIS FRONT AND MOVE
ACROSS THE AREA MONDAY. HIGH PRESSURE WILL BUILD IN TUESDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
LOW LEVEL MOISTURE WILL REMAIN IN PLACE ACROSS THE CWA TODAY.
CEILINGS HAVE BEGUN TO LIFT SLIGHTLY THIS MORNING...AND RADAR
ECHOES HAVE DIMINISHED IN COVERAGE AS WELL. A SLIGHT CHANCE OF
SHOWERS WILL BE KEPT IN THE FORECAST...MAINLY IN THE EAST AND JUST
FOR THE NEXT FEW HOURS...BEFORE LIMITING ANY CHANCE OF
PRECIPITATION TO THE FAR SOUTHEAST THROUGH THE AFTERNOON HOURS.
THE LATEST HRRR RUNS ARE SHOWING THAT ANY CONVECTION THAT DEVELOPS
WILL OCCUR NEAR OR AFTER 00Z AND WILL LIKELY BE LIMITED TO THE
SOUTH AND SOUTHEAST. GIVEN THE REMAINING UNCERTAINTY IN BOTH
FORCING AND INSTABILITY...THERE APPEARS TO BE NO REASON TO
INCREASE POPS THIS EVENING (THOUGH A SLIGHTLY HIGHER CHANCE WILL
EXIST LATER IN THE OVERNIGHT HOURS).
TEMPERATURES WERE MOSTLY ON TRACK...WITH SOME SLIGHT UPWARD
ADJUSTMENTS MADE IN THE SOUTH. WARM ADVECTION WILL DOMINATE THE
TEMPERATURE CURVE TODAY...WITH ESSENTIALLY ZERO DIRECT SUNLIGHT
EXPECTED.
PREVIOUS DISCUSSION >
SOUTHERLY FLOW WILL CONTINUE ACROSS THE REGION TODAY. PLENTY OF
LOW LEVEL MOISTURE IN PLACE ALTHOUGH THERE SHOULD BE SOME BREAKS
IN THE CLOUDS ESPECIALLY LATER IN THE DAY. A WEAK COLD FRONT WILL
PUSH INTO THE REGION LATE THIS AFTERNOON. AND THERE WILL BE A WEAK
MID LEVEL IMPULSE TRACKING ACROSS THE AREA. BUT OVERALL FORCING IS
MINIMAL. SO ONLY KEPT SLIGHT CHANCE POPS IN FOR TODAY.
TEMPERATURES WILL BE WELL ABOVE NORMAL WITH A MOS BLEND USED AS A
BASE FOR HIGHS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
BOUNDARY WILL WORK FURTHER INTO THE FORECAST AREA TONIGHT BEFORE
STALLING AS LOW PRESSURE DEVELOPS ALONG THE FRONT OFF TO THE
SOUTHWEST. AS THE LOW APPROACHES LATE TONIGHT EXPECT SHOWERS TO
DEVELOP IN THE SOUTHERN COUNTIES. THE LOW WILL CONTINUE TO TRAVEL
ALONG THE FRONT AND ACROSS THE REGION ON MONDAY. MODELS ARE
TRENDING TOWARDS A LESS DEVELOPED LOW WHICH SHOULD KEEP THE
GREATER COVERAGE OF SHOWERS FROM SPREADING TOO FAR NORTHWEST. BUT
STILL ENOUGH UNCERTAINTY TO KEEP CHANCE POPS GOING ALL THE WAY
INTO WEST CENTRAL OHIO. THERE WILL BE SOME INSTABILITY ALONG AND
SOUTH OF THE FRONT SO DID INCLUDE A CHANCE OF THUNDERSTORMS THERE.
A SHORT WAVE WILL TRAVEL ACROSS THE REGION MONDAY NIGHT AND WITH
MOISTURE STILL LINGERING IN THE AREA THAT MAY GENERATE SOME
ADDITIONAL SHOWERS AREA WIDE. AFTER IT PASSES RIDGING WILL
TEMPORARILY MOVE IN ALLOWING FOR SOME DRYING.
WARMER GUIDANCE LOOKED MORE REASONABLE FOR TONIGHT BUT A BLEND WAS
USED MONDAY NIGHT. LEANED TOWARDS COOLER GUIDANCE FOR HIGH
TEMPERATURES BOTH DAYS.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
UPPER RIDGING WILL CONTINUE INTO WEDNESDAY AHEAD OF AN APPROACHING
DEEPENING TROUGH. SO EXPECT DRY AND UNSEASONABLY WARM CONDITIONS
ONCE AGAIN. AS THE UPPER SYSTEM PIVOTS NORTHEAST TOWARDS THE
REGION THE ASSOCIATED SURFACE LOW WILL PUSH A WARM FRONT THROUGH
THE AREA WEDNESDAY NIGHT. THIS WILL LEAD TO STEADY OR RISING
TEMPERATURES OVERNIGHT. SHOWERS WILL SPREAD IN FROM THE WEST LATE
WEDNESDAY NIGHT AND SWEEP ACROSS THE REGION ON THURSDAY. WITH WEAK
INSTABILITY FORECAST AT THIS POINT BUT FAIRLY STRONG DYNAMICS...
CANNOT RULE OUT SOME THUNDER ALTHOUGH IT IS NOT INCLUDED IN THE
FORECAST YET. THE LOW WILL LIFT NORTH OF THE AREA BUT AFTER A
STRONG COLD FRONT SWEEPS THROUGH THE TEMPERATURES WILL FALL IN THE
AFTERNOON.
00Z GUIDANCE HAS COME INTO AGREEMENT IN KEEPING THIS SYSTEM
PROGRESSIVE. SO THERE WILL ONLY BE A BRIEF WINDOW FOR WRAP AROUND
AND LAKE ENHANCED SNOW SHOWERS TO AFFECT THE REGION THURSDAY NIGHT
AND FRIDAY. HIGH PRESSURE WILL BUILD IN WITH TEMPERATURES AT OR
SLIGHTLY BELOW SEASONAL NORMALS.
&&
.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
MVFR AND VFR CIGS WILL BE AROUND THE AREA TAF SITES THIS MORNING
BEFORE VFR CONDITIONS GRADUALLY RETURN TO THE AREA THIS
AFTERNOON. SOME DRIZZLE OR LIGHT SHOWER ACTIVITY WILL ALSO BE
PRESENT ACROSS THE AREA THIS MORNING BEFORE MOVING OUT OF THE TAF
SITES. WINDS WILL PICK UP THIS AFTERNOON WITH SOME WIND GUSTS
AROUND 20 KNOTS POSSIBLE. WINDS WILL DECREASE ACROSS THE TAF SITES
THIS EVENING AND CIGS WILL LOWER AS AN AREA OF LOW PRESSURE
APPROACHES THE REGION FROM THE SOUTH. AS THIS AREA OF LOW PRESSURE
NEARS THE REGION TONIGHT RAIN SHOWERS WILL MOVE INTO THE SOUTHERN
TAF SITES. IN ADDITION...CIGS AND VSBYS WILL LOWER ACROSS THE
AREA.
OUTLOOK...MVFR CEILINGS AND VISIBILITIES POSSIBLE MONDAY INTO
TUESDAY AND THEN AGAIN ON THURSDAY.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.
&&
$$
SYNOPSIS...
NEAR TERM...HATZOS/
SHORT TERM...
LONG TERM...
AVIATION...NOVAK
AREA FORECAST DISCUSSION
NWS WILMINGTON OH
1257 AM EST SUN DEC 16 2012
.SYNOPSIS...
LOW PRESSURE WILL MOVE INTO THE GREAT LAKES THROUGH SUNDAY...WITH
A COLD FRONT MOVING INTO THE OHIO VALLEY THROUGH SUNDAY NIGHT. AN
AREA OF LOW PRESSURE WILL THEN DEVELOP ON MONDAY...WITH ANOTHER
COLD FRONT FOLLOWING ON MONDAY NIGHT.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
GOING FORECAST PRETTY MUCH ON TARGET RIGHT NOW. UPDATED TO STOP
ANY MORE FALL IN TEMPS...THE WARM SECTOR CONTINUES TO SLOWLY
ESTABLISH ITSELF OVER THE FORECAST AREA...AND WITH THE
THICK/EXPANSIVE/LOWERING STRATUS AND INCREASING SWLY BOUNDARY
LAYER FLOW IT WILL BE TOUGH FOR TEMPS TO DROP FROM CURRENT VALUES.
MAINTAINED THE LOW SHOWER CHANCE TONIGHT - BUT THOUGHT HEAVILY
ABOUT PULLING IT COMPLETELY IN LIEU OF LOW RAIN CHANCES JUST FOR
MEASURABLE DRIZZLE. DEEP MOISTURE /PER EVENING SATELLITE LOOPS AND
16.00Z KILN SOUNDING/ IS ABSENT SO HAVE THE FEELING THE
LIGHT/SPECKLED QPF SEEN ON MANY DETERMINISTIC 15.18Z DATASETS IS
PROBABLY REFLECTION OF THE DRIZZLE THAT HAS BEEN SEEN IN HIT/MISS
FASHION TO OUR WEST. THAT SAID...RADAR ECHO OVER CNTL/NRN IND DOES
HAVE SHOWERY LOOK TO IT AT TIMES SO KEPT MENTION OF BOTH DRIZZLE
AND SHOWERS OVERNIGHT BUT THINK AREAS OF DRIZZLE PROBABLY WIN OUT
IN TERMS OF WHAT/S MORE PREVALENT. IN TERMS OF DRIZZLE...THE
16.00Z NAM AND RECENT 16.XXZ RUNS OF RAP INDICATE THE 0-2KM
RH WILL CONTINUE TO EXPAND/INCREASE THROUGH THE NIGHT SO WE SHOULD
SEE AREAS OF -DZ INCREASE ESP AFTER 06Z. WINDS WILL CONTINUE TO
VEER/SLOWLY INCREASE THROUGH THE NIGHT AS WEAK LOW MEANDERS
THROUGH WISCONSIN AND INTO NRN LOWER MICH.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH MONDAY NIGHT/...
THE BASIC PREMISE OF THE SHORT TERM FORECAST HAS COME INTO BETTER
AGREEMENT WITH THE 12Z MODEL CYCLE...BUT MANY OF THE DETAILS
REMAIN SOMEWHAT UNCERTAIN.
AS CLOUDS GRADUALLY LIFT ON SUNDAY MORNING...DRIZZLE IS EXPECTED
TO COME TO AN END. A SLOW MOVING AND ILL-DEFINED FRONT WILL BE
MOVING INTO THE REGION FROM THE NORTH...ASSOCIATED WITH THE GREAT
LAKES SURFACE LOW. THE TIMING OF THIS FEATURE HAS SLOWED...AND
ONLY THE HIGH-RESOLUTION OF THE NAM12 SHOWS AN INDICATION OF THE
FRONT ACTIVATING IN ANY SIGNIFICANT WAY. MARGINAL INSTABILITY WILL
BE ABLE TO BUILD AHEAD OF THE FRONT...BUT THE FORCING IS NOT
PARTICULARLY STRONG. A SLIGHT CHANCE OF THUNDER HAS BEEN
MAINTAINED IN THE SOUTH AND SOUTHEASTERN PORTIONS OF THE FORECAST
AREA.
A SURFACE LOW IS EXPECTED TO DEVELOP NEAR THE OHIO/MISSISSIPPI
RIVER CONFLUENCE BY MONDAY MORNING...AHEAD OF AN ENERGETIC TROUGH
MOVING THROUGH THE MIDDLE OF THE COUNTRY. SUBTRACTING THE NAM
SOLUTION...MODELS SEEM TO BE AGREEING ON A CINCINNATI-TO-ERIE
TRACK FOR THIS LOW...WITH INCREASED CONFIDENCE IN MEASURABLE
PRECIPITATION ACROSS THE FORECAST AREA. A SIGNIFICANT UPWARD
ADJUSTMENT WAS MADE TO BRING THE ENTIRE CWA TO LIKELY POPS ON
MONDAY. THERE IS AN INDICATION OF SOME WEAK INSTABILITY
DEVELOPING...BUT THIS MAINLY SEEMS TO FOLLOW BEHIND THE GREATER
CHANCES OF PRECIPITATION. THUNDER WAS NOT INCLUDED IN THE FORECAST.
THE STRENGTH OF THE MID LEVEL WAVE WILL HAVE AN IMPACT ON HOW LONG
THE PRECIPITATION IS ABLE TO PERSIST ON EARLY TUESDAY MORNING.
TEMPERATURES BEHIND THE LOW (AND ASSOCIATED COLD FRONT) WILL COOL
OFF ENOUGH TO SUPPORT SNOW AT THE END OF THE FORECAST PERIOD...BUT
WITH PRECIPITATION EXPECTED TO BE MOVING OUT...LITTLE MORE THAN A
RAIN/SNOW MIX WITH NO ACCUMULATION CAN BE FORECAST AT THIS TIME.
WITH THE BOUNDARY AND LOW IN THE AREA DURING THIS PART OF THE
FORECAST...TEMPERATURE GRADIENTS ARE A BIT SHARPER THAN NORMAL FOR
BOTH MAXES AND MINS. WITH THIS IN MIND...AND THE WAY THAT ANY
SMALL MODEL DIFFERENCES COULD CHANGE THE TEMPERATURE FORECAST BY
SEVERAL DEGREES...A BLENDED APPROACH NEAR THE MEDIAN OF THE MODEL
SPECTRUM WAS USED.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
ALTHOUGH THE OPERATIONAL MODELS ARE LATCHING ON TO THE MAIN SYNOPTIC
FEATURES IN THE EXTENDED PERIOD...THERE CONTINUES TO BE CONSIDERABLE
SPREAD IN TERMS OF STRENGTH...TIMING AND A PLACEMENT OF THESE
FEATURES. AS A RESULT...HAVE LEANED MORE ON THE 15.12Z ECMWF AND
BLENDED IT WITH HPC GUIDANCE. THE 15.12Z ECMWF WAS USED DUE TO THE
FACT THAT IT TENDS TO PERFORM BETTER THAN THE GFS IN THE EXTENDED
AND OFTEN LATCHES ON TO A PATTERN A DAY AHEAD OF THE GFS.
ON TUESDAY...LOW PRESSURE WILL CONTINUE TO PUSH NE OF THE REGION AS
A WEAK SURFACE RIDGE BUILDS INTO THE OHIO VALLEY. ANY LINGERING PCPN
IN THE EAST WILL COME TO AN END BY AFTERNOON...FOLLOWED BY PARTIAL
CLEARING. TEMPERATURES WILL REMAIN MILD WITH HIGHS MAINLY IN THE 40S.
FOR TUESDAY NIGHT INTO WEDNESDAY...WEAK SURFACE RIDGE WILL MOVE EAST
AS A MID LEVEL RIDGE BUILDS ACRS THE OHIO VALLEY REGION IN ADVANCE
OF THE NEXT WEATHER SYSTEM. MID AND HIGH LEVEL CLOUDINESS CAN BE
EXPECTED ALONG WITH CONTINUE MILD TEMPERATURES. HIGHS ON WEDNESDAY
WILL RANGE FROM THE LOWER 40S NORTH TO THE LOWER 50S SOUTH.
FOR THE PERIOD WEDNESDAY NIGHT INTO FRIDAY...MODELS CONTINUE TO SHOW
A PATTERN CHANGE IN THE OFFING WITH THE UPR LVL FLOW BECOMING MORE
AMPLIFIED THROUGH THE PERIOD. A VIGOROUS S/WV WILL PIVOT FROM THE
SRN PLAINS TO THE GREAT LAKES REGION THROUGH THE PERIOD. THIS UPR
LVL SUPPORT WILL PERTURB DEEPENING LOW PRESSURE WHICH WILL PUSH A
STRONG COLD FRONT THROUGH THE REGION SOMETIME THURSDAY INTO THURSDAY
NIGHT. IT APPEARS THE SFC LOW WILL TRACK NW OF THE REGION WHICH
WOULD KEEP HEAVIER WINTER PCPN TO THE NW OF THE TRACK AND OUT OF OUR
AREA. DEEP MOISTURE RETURN AND DYNAMICS WILL SPREAD SHOWERS ALONG
AND AHEAD OF A COLD FRONT WEDNESDAY NIGHT INTO THURSDAY. COLDER AIR
IS FORECAST TO SPILL INTO THE REGION THURSDAY NIGHT INTO FRIDAY IN
THE WAKE OF THE LOW/COLD FRONT. THIS WILL CHANGE ANY LIQUID PCPN TO
SNOW SHOWERS WHILE TEMPERATURES DROP. HAVE LIMITED SNOW SHOWERS TO
THE CHANCE CATEGORY THURSDAY NIGHT INTO FRIDAY DUE TO WRAP AROUND
MOISTURE AND COLDER AIR MOVING ACROSS THE WARMER WATER OF THE GREAT
LAKES. ANY SNOW ACCUMULATION SHOULD BE MINOR BUT WILL DEPEND ON THE
EXACT TRACK AND CLOSING OF MID LVL S/WV INTO A MID LEVEL
CIRCULATION. AGAIN...WAY TOO EARLY TO KNOW AT THIS POINT GIVEN THE
MODEL SPREAD MENTIONED. TEMPERATURES WILL DROP TO BELOW NORMAL
READINGS ON FRIDAY IN THE CAA PATTERN.
FOR FRIDAY NIGHT INTO SATURDAY...MODELS ARE IN DISAGREEMENT ON HOW
FAST UPR LVL LOW WILL PULL NE AND WHETHER IT WILL ROTATE BACK TOWARD
THE SOUTHWEST INTO EARLY NEXT WEEK. HAVE GONE WITH PARTLY CLOUDY
SKIES AT THIS POINT WITH A SMALL CHANCE OF SNOW SHOWERS DOWN WIND OF
THE GREAT LAKES...MAINLY ACROSS OUR NRN AND ERN LOCATIONS.
TEMPERATURES ARE EXPECTED TO BE BELOW NORMAL.
&&
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
MVFR CIGS HAVE WORKED INTO KCVG AND KLUK. THERE IS SOME
UNCERTAINTY WITH HOW LOW CIGS WILL GET ACROSS THE TAF SITES
OVERNIGHT AND INTO THE EARLY DAYTIME HOURS ON SUNDAY. GENERALLY
EXPECT LOWER CIGS ACROSS THE WESTERN TAF SITES WITH IFR CIGS
POSSIBLE. CIGS ACROSS THE EAST AT KCMH AND KLCK SHOULD REMAIN
HIGHER AND ONLY DROP DOWN INTO THE MVFR CATEGORY.
THERE ARE SOME LIGHT RETURNS ON RADAR HOWEVER NOT MUCH IS SHOWING
UP IN THE WAY OF PRECIPITATION YET WITH THE OBS. AS THE NIGHT
PROGRESSES EXPECT THERE TO BE SOME DRIZZLE ACROSS THE TAF SITES
AND THIS WILL HELP TO REDUCE VSBYS TO THE MVFR CATEGORY. CIGS AND
VSBYS WILL GRADUALLY IMPROVE THROUGH THE DAY ON SUNDAY WITH ANY
PRECIPITATION COMING TO AN END ACROSS THE AREA.
SUNDAY NIGHT A LOW PRESSURE SYSTEM BEGINS TO NEAR THE AREA FROM
THE SOUTH AND CIGS WILL START TO LOWER AGAIN AT THE SOUTHERN TAF
SITES. BEGAN TO BRING IN SOME SHOWER ACTIVITY TO THE AREA AT KCVG
AND KLUK BY THE END OF THE TAF PERIOD.
OUTLOOK...MVFR CEILINGS AND VISIBILITIES POSSIBLE SUNDAY NIGHT
INTO TUESDAY AND THEN AGAIN ON THURSDAY.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.
&&
$$
SYNOPSIS...HATZOS
NEAR TERM...BINAU
SHORT TERM...HATZOS
LONG TERM...HICKMAN
AVIATION...NOVAK
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NWS RAPID CITY SD
705 PM MST MON DEC 17 2012
.DISCUSSION...CURRENT SURFACE MAP SHOWS WARM FRONT ACROSS EASTERN
MONTANA INTO FAR WESTERN SOUTH DAKOTA...WITH WEAK LOW ALONG THE
FRONT NEAR THE BLACK HILLS. BAND OF CONVECTIVE SNOW HAS DEVELOPED
FROM NEAR GILLETTE TO THE NORTHERN BLACK HILLS. 18Z NAM/00Z RUC
SPREAD THIS CONVECTIVE SNOW ACROSS NORTHWEST SOUTH DAKOTA
OVERNIGHT. 00Z RAP IS GIVING 0.25-0.50 INCHES OF QPF ACROSS
NORTHWEST SOUTH DAKOTA OVERNIGHT...WITH UP TO 6 INCHES OF SNOW.
18Z NAM A LITTLE MORE REALISTIC WITH NARROW BAND OF 1-2 INCHES OF
SNOW. 00Z NAM IS COMING IN AND KEEPS THE ACCUMULATING SNOW
CONFINED TO THE BLACK HILLS.
FORECAST UPDATED TO INCREASE POPS THROUGH EARLY TUESDAY MORNING.
WILL LIMIT SNOWFALL ACCUMULATIONS TO 1-2 INCHES...MAINLY OVER THE
NORTHERN BLACK HILLS AND PLAINS JUST NORTH OF THE BLACK HILLS.
WITH EASTERLY WINDS ACROSS THE EASTERN PORTION OF THE FORECAST
AREA...LOW STRATUS/FZFG HAS BEEN MOVING WESTWARD. AS WARM FRONT
SHIFTS EAST OVERNIGHT...STRATUS/FOG WILL BEGIN TO DISSIPATE FROM
WEST TO EAST.
&&
.AVIATION...00Z TAF UPDATE
IFR CIGS/VSBY WILL SPREAD ACROSS PORTIONS OF NORTHEAST WYOMING AND
NORTHWEST SOUTH DAKOTA THIS EVENING WITH NUMEROUS SNOW SHOWERS.
LIFR CIGS/VSBY WITH STRATUS/FZFG OVER CENTRAL SOUTH DAKOTA WILL
BACK INTO WESTERN SOUTH DAKOTA THIS EVENING...AND WILL BE LOCATED
ALONG AND EAST A LINE FROM KHEI-KPHP-KVTN. CONDITIONS WILL FROM
WEST TO EAST AFTER MIDNIGHT.
&&
.PREV DISCUSSION... /ISSUED 248 PM MST MON DEC 17 2012/
DISCUSSION...UPPER LEVEL ANALYSIS HAS FLAT RIDGE ACROSS THE
SOUTHWEST CONUS WITH WEAK TROFFING ACROSS THE PACIFIC NORTHWEST.
21Z SURFACE ANALYSIS PLACES LOW OVER SOUTHERN ALBERTA WHILE A
STATIONERY BOUNDARY BISECTS THE CWA. TEMPERATURES ARE IN THE 20S
AND LOWER 30S NORTH OF THE BOUNDARY...AND IN THE UPPER 30S AND 40S
SOUTH.
FOR TONIGHT...WEAK UPPER RIDGE PUSHES EAST TONIGHT AS THE ALBERTA
SURFACE LOW SLIDES INTO SOUTHERN SASKATCHEWAN. STATIONERY BOUNDARY
SLOWLY LIFTS NORTHEAST AS WESTERLY BOUNDARY LAYER FLOW INCREASES.
SHOULD BE A BREEZY NIGHT FOR MANY WESTERN AREAS WHERE BOUNDARY
LAYER REMAINS COUPLED. SOME FOG MAY REDEVELOP ACROSS CENTRAL
PORTIONS OF SOUTH DAKOTA THIS EVENING...BEFORE BOUNDARY FINALLY
LIFTS TO THE NORTH. LOWS WILL VARY FROM THE LOW TEENS IN DEEPER
DECOUPLED AREAS...TO THE 20S WHERE ATMOSPHERE STAYS COUPLED. WEAK
ENERGY CROSSING THE NORTHERN TIER MAY PRODUCE SOME SNOW SHOWERS
ACROSS NORTHWEST SOUTH DAKOTA THIS EVENING.
ON TUESDAY...TEMPERATURES WILL BE COOLER AS WEAK UPPER RIDGE
PUSHES EAST AND WESTERN TROF MOVES INTO THE NORTHERN ROCKIES.
HIGHS WILL BE CLOSER TO AVERAGE...IN THE 30S TO AROUND 40 DEGREES.
UPPER TROF DIGS INTO THE CENTRAL AND SOUTHERN ROCKIES TUESDAY
NIGHT WITH SURFACE LOW DEVELOPING OVER SOUTHERN COLORADO. LIGHT
WESTERLY FLOW WILL CONTINUE OVER THE AREA WITH LOWS FALLING INTO
THE TEENS AND 20S.
FOR WEDNESDAY...SURFACE LOW MOVES EAST ALONG THE KANSAS/OKLAHOMA
BORDER AS BASE OF UPPER TROF MOVES INTO WESTERN KANSAS. BROAD
AREA OF PRECIP WILL SLIDE ACROSS SOUTHEASTERN WYOMING INTO WESTERN
NEBRASKA...AND POSSIBLY GRAZE THE VERY SOUTHERN EDGE OF THE
FORECAST AREA. SOME OF THE MODEL GUIDANCE KEEPS PRECIP JUST TO THE
SOUTH OF THE AREA...SO WILL CONTINUE LOW POPS ACROSS FAR SOUTHERN
SOUTH DAKOTA. SYSTEM SHIFTS EAST WEDNESDAY NIGHT AS SURFACE RIDGE
SLIDES INTO THE AREA. TEMPERATURES WILL REMAIN CLOSE TO SEASONAL
AVERAGES.
EXTENDED...AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL BUILD OVER THE
INTERMOUNTAIN WEST ON THURSDAY...AS THE UPPER LEVEL TROF SHIFTS EAST
OF THE GREAT PLAINS. A FAIRLY FLAT RIDGE WILL THEN BECOME CENTERED
OVER THE NORTHERN PLAINS THROUGH THE WEEKEND...RESULTING IN A NEARLY
ZONAL FLOW PATTERN AND DRY WEATHER. EXPECT SLIGHTLY WARMER THAN
NORMAL TEMPERATURES THROUGH THE EXTENDED PERIOD WITH AN EXCEPTION
OVER THE NORTHEASTERN PART OF THE FORECAST AREA WHERE THE GFS
CONTINUES TO SHOW COOLER AIR BACKING INTO THE REGION. EXTENDED
MODELS SHOW ANOTHER UPPER TROUGH BRINGING A CHANCE OF SNOW TO PARTS
OF THE AREA ON MONDAY...BUT THEY STILL DIFFER GREATLY IN THE
STRENGTH AND PLACEMENT OF THE SURFACE LOW.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
SHORT TERM...07
LONG TERM....WFO UNR
AVIATION...07
AREA FORECAST DISCUSSION
NWS NASHVILLE TN
1124 PM CST SAT DEC 15 2012
.UPDATE...FOR 06Z AVIATION FORECAST
&&
.AVIATION...
SHOWERS AND ISOLATED THUNDERSTORMS ARE HEADING INTO SOUTHWEST
MIDDLE TENENSSEE AT THIS TIME. EXPECT THIS TREND TO CONTINUE IN
THE OVERNGIHT WITH SHOWERS MORE CONCENTRATED OVER SOUTHERN AND
EASTERN AREAS OF THE MID STATE. ALSO...LOOK FOR CEILINGS AND VSBYS TO
LOWER IN THE OVERNIGHT. ALTHOUGH SOME SCATTERED SHOWERS ARE
EXPECTED OVER THE NORTHWEST THEY WILL BE FEWER IN NUMBER.
BOYD
&&
.PREV DISCUSSION... /ISSUED 834 PM CST SAT DEC 15 2012/
UPDATE...
FORECAST FOR TONIGHT APPEARS ON TRACK AND ONLY MINOR TWEAKS WERE
MADE. WAA CONTINUES TO INCREASE OVER THE MID STATE WITH DEWPOINTS
NOW IN THE MID 40S TO MID 50S. TEMPERATURES HAVE ALSO BEGUN RISING
OVER THE WESTERN HALF AND RAISED LOW TEMPS OVER THAT REGION.
HOWEVER...HAD TO LOWER MINS ON THE PLATEAU WHERE TEMPS ARE
ALREADY NEAR/BELOW FORECAST LOWS...BUT TEMPS SHOULD REMAIN STEADY
OR SLOWLY RISE THERE THE REMAINDER OF THE NIGHT AS WELL.
CURRENT RADAR IMAGERY INDICATES AN AREA OF RAIN WITH A COUPLE OF
THUNDERSTORMS OVER THE PLATEAU. ADDITIONAL ACTIVITY IS FORMING
OVER THE LOWER MISSISSIPPI VALLEY...AND SHORT TERM GUIDANCE
INDICATES THIS WILL SPREAD ACROSS THE MID STATE OVERNIGHT.
ANTICIPATING SOME STRONGER CONVECTION AFTER MIDNIGHT PER 00Z NAM
AND 23Z HRRR RUNS...AND CANNOT RULE OUT AN ISOLATED STRONG OR
MARGINALLY SEVERE STORM OVER SOUTHERN AND EASTERN ZONES. WITH
ACTIVITY ELEVATED ABOVE THE SURFACE INVERSION PER 00Z OHX
SOUNDING...MAIN THREATS WOULD BE GUSTY WINDS OR HAIL DUE TO THE
INTENSE LOW LEVEL SHEAR.
PREV DISCUSSION... /ISSUED 745 PM CST SAT DEC 15 2012/
UPDATE...FOR AVIATION FORECAST
AVIATION...
ELEVATED SHOWER ACTIVITY IS ON-GOING OVER EASTERN AND SOUTHERN SECTIONS
OF THE MID STATE WITH AN OCCASIONAL LIGHTNING STRIKE IN SOME OF THE
STRONGER RETURNS. THIS ACTIVITY REMAINS ELEVATED AND WILL CONTINUE
TO MOVE QUICKLY TOWARD THE NORTHEAST AS WIND FIELDS WILL REMAIN
STRONG ABOVE SURFACE. THERE IS NEWLY DEVELOPED ACTIVITY OVER
NORTHWEST MISSISSIPPI AT 01Z THIS EVENING THAT WILL BE MOVING THIS
WAY ALONG WITH ACTIVITY THAT HAS FIRED FARTHER TO THE SOUTHWEST
OVER NORTHERN LOUISIANA DURING THE PAST HOUR. SREF KEEPS THE BULK
OF THIS ACTIVITY OVER THE SOUTHEAST HALF OF MIDDLE TENNESSEE...GENERALLY
SOUTH AND EAST OF NASHVILLE THROUGH 12Z SUNDAY. AFTER 12Z SUNDAY
ACTIVITY WILL BECOME MORE NUMEROUS ACROSS MIDDLE TENNESSEE EXCEPT
FOR FAR NORTHWEST WHERE IT WILL BE SCATTERED. MARGINALLY SEVERE
STORM OR TWO POSSIBLE ON SUNDAY...ESPECIALLY NEAR ALABAMA BORDER.
WILL UPDATE AVIATION FORECAST AND TWEAK TIMING FOR CONVECTION.
BOYD
PREV DISCUSSION... /ISSUED 617 PM CST SAT DEC 15 2012/
UPDATE...FOR 00Z AVIATION FORECAST
AVIATION...
STILL A RATHER TIGHT SURFACE PRESSURE GRADIENT ACROSS THE TENNESSEE
VALLEY WITH SURFACE GEOSTROPHIC WINDS ON THE ORDER OF 45 TO 50 KNOTS
AT THE TOP OF THE BOUNDARY LAYER. LOW LEVEL JET CURRENTLY PUNCHING
ACROSS EASTERN ARKANSAS AND UP THROUGH WESTERN TENNESSEE AND
KENTUCKY WITH A 160 KNOT UPPER LEVEL JET FROM OKLAHOMA EASTWARD
THROUGH THE OHIO/TENNESSEE VALLEYS. TOTAL TOTALS THIS EVENING ARE
HIGHER TO OUR SOUTH ACROSS NORTHERN ALABAMA/MISSISSIPPI. BUFKIT
SOUNDINGS OFF GFS SHOWING GOOD INVERSION OFF SURFACE DURING MUCH
OF THE OVERNIGHT HOURS SO ANY CONVECTION SHOULD REMAIN ELEVATED
AND ZIP ALONG AT A PRETTY GOOD SPEED OFF TOWARD THE NORTHEAST.
BASICALLY KEPT WHAT THE DAYSHIFT HAD AS FAR AS AVIATION FORECASTS
BUT WILL TAKE CLOSER WHEN NEWER GUIDANCE ARRIVES AND UPDATE
PACKAGE IF NEED BE DURING THE EVENING.
BOYD
PREV DISCUSSION... /ISSUED 254 PM CST SAT DEC 15 2012/
DISCUSSION...
SURFACE ENERGY TO CONTINUE TO PULL NORTH THROUGH THIS AFTERNOON AND
TONIGHT. HOWEVER...SOUTHWESTERLY FLOW ALOFT TO BECOME MORE ACTIVE AS
A SERIES OF IMPULSES RIDES NORTHEAST WITHIN THE FLOW. MOISTURE LEVELS
TO REMAIN WITH SOME ENHANCEMENT EXPECTED OVERNIGHT AND INTO SUNDAY.
A RELATIVELY WEAK FRONTAL BOUNDARY WILL HEAD OUR WAY WITH THE FROPA
EXPECTED ON MONDAY.
PRESSURE GRADIENTS TO REMAIN ON THE TIGHT SIDE THROUGH MONDAY. 10-20
MPH WINDS WITH SOME HIGHER GUSTS TO LIKELY PREVAIL.
OVERALL FOR THE SHORT TERM...RAINFALL CHANCES WILL BE GREATEST
TONIGHT AND SUNDAY WITH THE ACTIVE SOUTHWESTERLY UPPER FLOW. THE
TRAJECTORY AND IMPACT OF THE IMPULSES WILL BE GREATEST ACROSS
SOUTHERN MIDDLE TN AND THE PLATEAU. FOR SUNDAY NIGHT AND
MONDAY...MOISTURE LEVELS WILL DROP BUT THE APPROACHING WEAK FRONTAL
BOUNDARY WILL PROVIDE GENERALLY LOW RAINFALL CHANCES.
IN TERMS OF TSTM POTENTIAL...SHOWALTERS ARE NEAR ZERO WITH LIMITED
SFC CAPE VALUES. WILL STILL INCLUDE ISOL/SCT TSTMS FOR EACH PERIOD.
FOR THE NEAR TERM TEMPS...WARM PATTERN WITH THE MOIST SOUTHERN
DIRECTIONALLY UNIFORM FLOW. SLIGHTLY COOLER FOR MONDAY NIGHT BEHIND
THE FROPA BUT STILL ABOVE NORMAL. REPLACING AIRMASS WILL FEATURE A
SFC HIGH THAT WILL BUILD SLIGHTLY NORTHWARD FROM THE GULF. SO MILD
CONDITIONS TO CONTINUE BEHIND THE FROPA.
IN THE EXTENDED FCST...TUESDAY AND WEDNESDAY WILL FEATURE MOSTLY
SUNNY AND MILD CONDITIONS. THEN... A STRONG COLD FRONT WILL GAIN
STRENGTH AND PUSH ACROSS THE AREA ON THURSDAY. SHOWERS AND TSTMS
LOOK LIKE A GOOD BET FOR THURSDAY AS THE EURO AND GFS SOLUTIONS
MATCH UP QUITE WELL. LOOKS LIKE UP TO AN INCH OF RAINFALL POSSIBLE.
INSTABILITIES ARE JUST STRONG ENOUGH TO WARRANT ISOL TSTMS AS WELL.
COLDER CONDITIONS TO RETURN BEHIND THE FRONT. VERSUS THE MEX...WILL
UNDERCUT RATHER AGGRESSIVELY FOR FRIDAY AND SATURDAY.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
01
AREA FORECAST DISCUSSION
NWS SAN ANGELO TX
1049 PM CST SAT DEC 15 2012
.DISCUSSION...
/SEE BELOW FOR AVIATION DISCUSSION/
&&
.AVIATION...
VFR NEXT 24 HOURS. DRY WESTERLY WINDS PICK UP LATE MORNING AS A
SURFACE TROUGH MOVES EAST THROUGH OKLAHOMA. A FEW GUSTS OF 23-25
KTS POSSIBLE AT KSJT AND KABI...WITH LIGHTER WINDS FARTHER SOUTH.
&&
.PREV DISCUSSION... /ISSUED 512 PM CST SAT DEC 15 2012/
DISCUSSION...
/SEE BELOW FOR AVIATION DISCUSSION/
AVIATION...
VFR NEXT 24 HOURS. MID AND UPPER LEVEL HIGH CLOUDINESS ASSOCIATED
WITH THE SUBTROPICAL JET WILL PERSIST OVERNIGHT AND INTO SUNDAY
MORNING. GUSTY WINDS OF 25-28 KTS TOWARD NOON AT KSJT AND KABI AS
A SURFACE LOW MOVES EAST ACROSS THE TEXAS AND OKLAHOMA PANHANDLES.
04
PREV DISCUSSION... /ISSUED 306 PM CST SAT DEC 15 2012/
SHORT TERM...
TEMPERATURES THIS AFTERNOON RANGE FROM THE LOWER 60S ACROSS THE
NORTHERN BIG COUNTRY TO THE MID 70S ACROSS THE NORTHWEST HILL
COUNTRY. THE GUSTY WEST WINDS THAT WERE FORECAST FOR TODAY NEVER
REALLY MATERIALIZED DUE...IN LARGER PART...TO THE THICK MID/HIGH
CLOUD COVER THAT MOVED IN FROM THE SOUTH AND WEST. THIS IS IN
RESPONSE TO A 150 KT H25 SUBTROPICAL JET STREAK ORIENTED FROM
NORTHWEST MEXICO INTO SOUTHWEST OK. THIS JET AXIS IS PROGGED TO
SLIDE JUST TO OUR SOUTHEAST OVER THE NEXT 24 HOURS WHICH WOULD HELP
ELIMINATE MUCH OF THE HIGH CLOUDS OVER OUR CWA. IN THE MEANTIME...
WE CAN EXPECT MOSTLY CLOUDY SKIES OVERNIGHT WHICH GENERALLY MEANS
WARMER TEMPS THAN THOSE SUGGESTED BY GUIDANCE. I INCREASED MINS
ACROSS THE I-10 CORRIDOR WHERE THE THICKEST CLOUD COVER IS EXPECTED.
OTHERWISE...GUIDANCE LOOKED GOOD WITH LOW 40S. THE RAP WAS
GENERATING LIGHT QPF TONIGHT BUT IT REMAINS AN OUTLIER AND LOOKS
SUSPICIOUS AT BEST.
I EXPECT AT LEAST PARTIAL CLEARING SUNDAY AFTERNOON. THIS SHOULD
ALLOW SOME OF THE STRONGER WINDS ALOFT TO MIX DOWN TO THE SURFACE
AND PROVIDE A FEW HOURS OF GUSTY WEST WINDS. I STILL THINK WIND
SPEEDS WILL REMAIN IN THE 15-20 MPH RANGE ACROSS THE BIG COUNTRY AND
CONCHO VALLEY /LIGHTER ELSEWHERE/ DESPITE TODAY/S HUMBLING EXAMPLE.
THE ENHANCED DOWNSLOPE SHOULD HELP PUSH TEMPS BACK INTO THE UPPER
60S TO LOWER 70S AS H85 TEMPS ARE ONLY PROGGED TO COOL BY AROUND 1C
BY 00Z MONDAY.
JOHNSON
LONG TERM...
THE EXTENDED FORECAST IS CHARACTERIZED BY GENERALLY ABOVE NORMAL
TEMPERATURES AND LITTLE TO NO CHANCE OF PRECIPITATION. AN UPPER
LEVEL TROUGH WILL MOVE ACROSS THE PLAINS ON MONDAY...WITH THE ONLY
REAL AFFECT ON WEST CENTRAL TEXAS BEING AN INCREASE IN WINDS. EXPECT
WEST NORTHWEST WINDS OF 15 TO 20 MPH...WITH TEMPERATURES RANGING
FROM THE MID 60S TO LOWER 70S. A STEADY WARM UP IS FORECAST ON
TUESDAY AND WEDNESDAY AHEAD OF THE NEXT UPPER LEVEL TROUGH. HIGH
TEMPERATURES WILL BE RUNNING 15 TO 20 DEGREES ABOVE SEASONAL
NORMALS...GENERALLY IN THE LOWER TO MID 70S. THE MAIN WEATHER
CONCERN WILL BE THE POTENTIAL FOR STRONG WINDS ON WEDNESDAY. A
FAIRLY POTENT UPPER LEVEL TROUGH WILL APPROACH THE AREA ON
WEDNESDAY...WITH A 994MB SURFACE LOW DEVELOPING OVER THE TEXAS
PANHANDLE. A TIGHT SURFACE PRESSURE GRADIENT WILL DEVELOP ACROSS THE
REGION...RESULTING IN WEST WINDS OF 20 TO 30 MPH...WITH HIGHER
GUSTS...ACROSS MUCH OF THE BIG COUNTRY AND CONCHO VALLEY. FARTHER
SOUTH WINDS SHOULD REMAIN IN THE 15 TO 25 MPH RANGE.
AS THE AFOREMENTIONED UPPER LEVEL TROUGH SWINGS ACROSS THE
PLAINS...A COLD FRONT WILL QUICKLY MOVE THROUGH THE AREA WEDNESDAY
NIGHT. NORTH WINDS OF 15 TO 20 MPH AND COOLER TEMPERATURES CAN BE
EXPECTED BEHIND THE FRONT. I LOWERED HIGH TEMPERATURES BY A FEW
DEGREES FOR THURSDAY...GENERALLY IN THE MID AND UPPER 50S. A CHILLY
MORNING IS FORECAST FRIDAY. SKIES WILL BE MOSTLY CLEAR...DEWPOINTS
WILL BE IN THE SINGLE DIGITS AND SKIES WILL BECOME LIGHT. THE
CURRENT FORECAST HAS LOW TEMPERATURES RANGING FROM THE MID TO UPPER
20S...AND THESE MAY NEED TO LOWERED SLIGHTLY ON FUTURE SHIFTS. A
SLOW WARM UP WILL ENSUE THROUGH NEXT WEEKEND...WITH NO CHANCE OF
PRECIPITATION.
DANIELS
&&
.PRELIMINARY POINT TEMPS/POPS...
ABILENE 44 69 38 66 36 / 0 0 0 0 0
SAN ANGELO 41 71 37 68 35 / 0 0 0 0 0
JUNCTION 43 74 36 71 31 / 5 0 0 0 0
&&
.SJT WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
99/99/04
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
903 PM CST MON DEC 17 2012
UPDATE...
LOW-LEVEL CLOUDS ARE STUBBORN TO BREAK UP. WEAK LOW-LEVEL FLOW WITH
WEAK SURFACE HIGH PRESSURE WILL NOT BE ENOUGH TO BREAK THE CLOUDS
UP. AFTER SOME MID AND UPPER LEVEL CLOUDS MOVE EAST...RADIATIONAL
COOLING DURING LONG NIGHT SHOULD ENSURE CLOUD DECK REMAINS. THERE
ISA HOLD OVER SOUTHEAST WISCONSIN...BUT THIS SHOULD CLOSE UP. RADAR
SHOWS SOME RETURNS OVER SOUTHERN WISCONSIN...SO WILL THROW IN SOME
FLURRIES.
&&
.AVIATION/06Z TAFS/...
EXPECT MVFR CONDITIONS TO CONTINUE OVERNIGHT DUE TO WEAK FLOW
ASSOCIATED WITH SURFACE HIGH PRESSURE RIDGE. WEAKENING LOW PRESSURE
MOVING ACROSS NORTHERN ILLINOIS WILL BRING CHANCES OF LIGHT RAIN OR
SNOW TUESDAY. WILL KEEP MVFR CONDITIONS GOING TUESDAY.
&&
PREVIOUS DISCUSSION FROM MONDAY AFTERNOON...
.TONIGHT AND TUESDAY...FORECAST CONFIDENCE...MEDIUM
STUBBORN LOW CLOUD DECK CONTINUES ACROSS SOUTHERN WISCONSIN. BULK OF
MODELS CONTINUE TO SUGGEST IT WILL SCATTER OUT LATE AFTERNOON AND
EVENING...BUT MODELS ORIGINALLY HAD THE SUN POKING OUT THIS MORNING.
GIVEN EXTENT OF THIS STRATUS DECK AND RECENT MODEL PERFORMANCE...
KEPT OVERCAST SKIES THROUGH THE NIGHT. THIS IS SIMILAR TO THE LATEST
RAP...WHICH SEEMS TO HAVE A DECENT HANDLE ON THINGS. STAYED AWAY
FROM COLDEST MODELS FOR LOWS AGAIN TONIGHT...WITH THE CLOUDS
EXPECTED TO HANG AROUND.
BIG ISSUE TOMORROW IS WEAK SHORTWAVE AND SFC LOW EXPECTED TO SLIDE
THROUGH THE AREA. MODELS ARE IN BETTER AGREEMENT WITH THE TRACK OF
THIS SYSTEM...BUT THE NAM CONTINUES WITH A FARTHER NORTH SOLUTION
THAN OTHER MODELS. LEANED TOWARD THE SOUTHERN SOLUTION...BUT DID
LEAVE A LITTLE INFLUENCE FROM NAM POSSIBILITY. LATEST NAM HAS
SHIFTED A BIT SOUTH...WHICH IS ENCOURAGING THAT MAYBE SOUTHERN
SOLUTION...OR AT LEAST A BLEND OF SOLUTIONS...WAS THE WAY TO GO.
EITHER WAY...DOES NOT LOOK LIKE A TON OF PRECIP WITH THIS ONE. WILL
PROBABLY BE ALL SNOW IN THE MORNING WITH COLDER TEMPS...POSSIBLY
MIXING WITH RAIN IN THE AFTERNOON AS IT WARMS UP A BIT. NOT
EXPECTING MUCH MORE THAN A COUPLE TENTHS OF AN INCH OF SNOW. THE
BEST CHANCE FOR MEASURABLE WILL BE FROM MADISON WESTWARD WHERE IT
WILL BE COLDER WHEN THE PRECIP MOVES IN.
.TUESDAY NIGHT THROUGH WEDNESDAY...FORECAST CONFIDENCE IS HIGH.
QUIET THIS PERIOD AS WE WAIT FOR THE ARRIVAL OF THE WINTER STORM
FOR THE WESTERN GREAT LAKES. THE LOW DRIFTING THROUGH ON TUESDAY
MAY STILL HAVE SOME LIGHT RAIN/SNOW LINGERING NORTH OF PORT
WASHINGTON AS IT PEELS OFF TO THE EAST EARLY IN THE EVENING.
THE GFS IS THE FASTEST WITH THE ARRIVAL OF PRECIP AHEAD OF THE
STORM ON WEDNESDAY...SPREADING IT ACROSS THE ENTIRE CWA BY 6PM ON
WEDNESDAY. THIS IS AN OUTLIER AND WILL LIMIT ANY AFTERNOON PRECIP
CHANCES TO THE AREA SOUTHWEST OF MADISON.
.WEDNESDAY NIGHT INTO THURSDAY NIGHT...FORECAST CONFIDENCE IS
MEDIUM TO HIGH.
WE ISSUED A WINTER STORM WATCH EARLIER IN THE DAY FOR THE AREA WE
HAD THE HIGHEST CONFIDENCE OF HEAVY SNOW. THIS AREA IS WITHIN THE
OVERLAP REGION OF MOST OF THE THE MODEL SOLUTIONS. I WOULD EXPECT
ADJUSTMENTS TO THIS WATCH OVER THE NEXT FEW FORECAST CYCLES AS THE
MODELS BEGIN TO SETTLE DOWN AND HONE IN ON A CONSENSUS SOLUTION.
HERE/S THE LATEST ON OUR MODEL SUITE THAT CAME IN THIS MORNING.
THE NAM TOOK A 160 MILE SHIFT SOUTH WITH THE 12Z RUN..GOING FROM
THE MOST NORTHERN AND WARM SOLUTION...TO ONE VERY SIMILAR TO THE
GFS. THE GFS DIDN/T CHANGE VERY MUCH...IF ANYTHING IT MOVED A
NOTCH NORTH AND LOOKS WARMER IN IT/S CRITICAL 0-5000FT THERMAL
PROFILE. THE GEM /CANADIAN/ HAS PICKED UP SPEED AND DOESN/T
INTENSIFY UNTIL IT GETS EAST OF US. THE TRACK IS MORE OR LESS
UNCHANGED. AND FINALLY...THE ECMWF /EUROPEAN/ IS STEADY AS CAN
BE...NOT BUDGING MUCH AT ALL IN ITS TRACK. THE ECMWF IS THE MODEL
WITH THE MOST SOUTHERN SOLUTION. IT WOULD BRING MORE SNOW TO THE
SOUTHEAST FORECAST AREA COMPARED TO THE WESTERN AREA.
THE DYNAMIC/FORCING PROFILE HASN/T CHANGED FROM THE OVERNIGHT
INTERPRETATION. THE UPPER SYSTEM IS STILL GOING NEGATIVE TILT AND
INTENSIFYING AS IT MOVES INTO WISCONSIN. THIS WILL CAUSE THE
SURFACE LOW TO DEEPEN RAPIDLY AS IT MOVES INTO NORTHERN
ILLINOIS...VS INTENSIFYING EAST OF US. THIS MAKES THE STORM EVEN
MORE UNTRUSTWORTHY AND DANGEROUS. COLUMN COOLING CAN HAPPEN MUCH
FASTER THAN EXPECTED. THE OMEGA FORCING WITHIN THE DENDRITE
REGION...CROSS-HAIRS...EXPLODES FOR A TIME...HIGHLIGHTING SOME
PRETTY HEAVY SNOW POTENTIAL CENTERED AROUND 12Z THURSDAY MORNING.
THE POTENTIAL FOR THUNDER SNOW IS LOOKING VERY GOOD. QEPV CHARTS
AND SOUNDING ANALYSIS ARE SHOWING LOTS OF POTENTIAL FROM 750MB UP
THROUGH 500MB. PRETTY STEEP LAPSE RATES FOR THIS TIME OF YEAR.
PRECIPITABLE WATER VALUES OFF THE NAM AND THE GFS ARE ALMOST TOO
HIGH...REACHING ABOUT .75 INCH...WHICH IS ABOUT 2 STANDARD
DEVIATIONS ABOVE CLIMO. TYPICAL BIG SNOWSTORMS IN DECEMBER HAVE A
PW OF AROUND .4 TO .5. THIS SPEAKS TO THE WARMTH OF THE NAM AND
GFS. QPF AMOUNTS ARE STILL AROUND 1 INCH. SO...WHERE IT WILL BE ALL
SNOW...THIS MEANS WE COULD SEE SNOW ACCUMS PUSHING 12 INCHES NORTH
AND WEST OF MADISON. BUT...THIS IS FOLLOWING MORE OF A NAM/GFS/EC
BLEND. IF THE MODELS COME IN CLOSER TO THE ECMWF SOUTHERN
SOLUTION...EXPECT MORE SNOW TO THE SOUTHEAST.
WINDS WILL CRANK UP BY LATE MORNING ON THURSDAY WITH GUSTS
POSSIBLY HITTING 35 MPH. THIS COULD LEAD TO BLIZZARD OR NEAR
BLIZZARD CONDITIONS.
EXPECT THE SNOW TO BEGIN WINDING DOWN FROM WEST TO EAST THURSDAY
AFTERNOON INTO THE EVENING. EXPECT WINDS TO STAY UP INTO THE
EVENING...THEN SLOWLY DIMINISH.
.FRIDAY THROUGH MONDAY...FORECAST CONFIDENCE IS HIGH.
COLD HIGH PRESSURE SETTLES IN. LOOKS PRETTY QUIET AND CHILLY THIS
PERIOD.
&&
.AVIATION/00Z TAFS/...
MAINLY MVFR CIGS CONTINUE ACROSS SOUTHERN WISCONSIN. MODELS CONTINUE
TO TRY AND SCATTER THINGS OUT...BUT JUST IS NOT HAPPENING.
CONSIDERING KEEPING THE MVFR STRATUS GOING RIGHT THROUGH THE NIGHT
PER THE LATEST RAP RUN.
LOW PRESSURE WILL SLIDE THROUGH SOUTHERN WISCONSIN
TOMORROW...BRINGING A CHANCE FOR RAIN/SNOW SHOWERS. IF CONDITIONS
HAVE ACTUALLY IMPROVED BY THEN...MAY SEE CIGS GO BACK DOWN AS THE
LOW SLIDES THROUGH. NOT EXPECTING MUCH IN THE WAY OF SNOW
ACCUMULATIONS...BUT COULD SEE A COUPLE TENTHS OF AN INCH. BEST
CHANCE FOR ANY ACCUMULATION WOULD BE FROM MADISON WESTWARD...AS IT
WILL BE COLDER THERE WHEN THE PRECIP MOVES IN.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR WIZ046-047-051-056>058-062-063-067.
LM...NONE.
&&
$$
TONIGHT/TUESDAY AND AVIATION/MARINE...DDV
TUESDAY NIGHT THROUGH MONDAY...DAVIS
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
848 PM CST MON DEC 17 2012
UPDATE...
LOW-LEVEL CLOUDS ARE STUBBORN TO BREAK UP. WEAK LOW-LEVEL FLOW WITH
WEAK SURFACE HIGH PRESSURE WILL NOT BE ENOUGH TO BREAK THE CLOUDS
UP. AFTER SOME MID AND UPPER LEVEL CLOUDS MOVE EAST...RADIATIONAL
COOLING DURING LONG NIGHT SHOULD ENSURE CLOUD DECK REMAINS. THERE
ISA HOLD OVER SOUTHEAST WISCONSIN...BUT THIS SHOULD CLOSE UP. RADAR
SHOWS SOME RETURNS OVER SOUTHERN WISCONSIN...BUT SURFACE OBS HAVE
DRY CONDITIONS...SO JUST VIRGA.
&&
.AVIATION/06Z TAFS/...
EXPECT MVFR CONDITIONS TO CONTINUE OVERNIGHT DUE TO WEAK FLOW
ASSOCIATED WITH SURFACE HIGH PRESSURE RIDGE. WEAKENING LOW PRESSURE
MOVING ACROSS NORTHERN ILLINOIS WILL BRING CHANCES OF LIGHT RAIN OR
SNOW TUESDAY. WILL KEEP MVFR CONDITIONS GOING TUESDAY.
&&
PREVIOUS DISCUSSION FROM MONDAY AFTERNOON...
.TONIGHT AND TUESDAY...FORECAST CONFIDENCE...MEDIUM
STUBBORN LOW CLOUD DECK CONTINUES ACROSS SOUTHERN WISCONSIN. BULK OF
MODELS CONTINUE TO SUGGEST IT WILL SCATTER OUT LATE AFTERNOON AND
EVENING...BUT MODELS ORIGINALLY HAD THE SUN POKING OUT THIS MORNING.
GIVEN EXTENT OF THIS STRATUS DECK AND RECENT MODEL PERFORMANCE...
KEPT OVERCAST SKIES THROUGH THE NIGHT. THIS IS SIMILAR TO THE LATEST
RAP...WHICH SEEMS TO HAVE A DECENT HANDLE ON THINGS. STAYED AWAY
FROM COLDEST MODELS FOR LOWS AGAIN TONIGHT...WITH THE CLOUDS
EXPECTED TO HANG AROUND.
BIG ISSUE TOMORROW IS WEAK SHORTWAVE AND SFC LOW EXPECTED TO SLIDE
THROUGH THE AREA. MODELS ARE IN BETTER AGREEMENT WITH THE TRACK OF
THIS SYSTEM...BUT THE NAM CONTINUES WITH A FARTHER NORTH SOLUTION
THAN OTHER MODELS. LEANED TOWARD THE SOUTHERN SOLUTION...BUT DID
LEAVE A LITTLE INFLUENCE FROM NAM POSSIBILITY. LATEST NAM HAS
SHIFTED A BIT SOUTH...WHICH IS ENCOURAGING THAT MAYBE SOUTHERN
SOLUTION...OR AT LEAST A BLEND OF SOLUTIONS...WAS THE WAY TO GO.
EITHER WAY...DOES NOT LOOK LIKE A TON OF PRECIP WITH THIS ONE. WILL
PROBABLY BE ALL SNOW IN THE MORNING WITH COLDER TEMPS...POSSIBLY
MIXING WITH RAIN IN THE AFTERNOON AS IT WARMS UP A BIT. NOT
EXPECTING MUCH MORE THAN A COUPLE TENTHS OF AN INCH OF SNOW. THE
BEST CHANCE FOR MEASURABLE WILL BE FROM MADISON WESTWARD WHERE IT
WILL BE COLDER WHEN THE PRECIP MOVES IN.
.TUESDAY NIGHT THROUGH WEDNESDAY...FORECAST CONFIDENCE IS HIGH.
QUIET THIS PERIOD AS WE WAIT FOR THE ARRIVAL OF THE WINTER STORM
FOR THE WESTERN GREAT LAKES. THE LOW DRIFTING THROUGH ON TUESDAY
MAY STILL HAVE SOME LIGHT RAIN/SNOW LINGERING NORTH OF PORT
WASHINGTON AS IT PEELS OFF TO THE EAST EARLY IN THE EVENING.
THE GFS IS THE FASTEST WITH THE ARRIVAL OF PRECIP AHEAD OF THE
STORM ON WEDNESDAY...SPREADING IT ACROSS THE ENTIRE CWA BY 6PM ON
WEDNESDAY. THIS IS AN OUTLIER AND WILL LIMIT ANY AFTERNOON PRECIP
CHANCES TO THE AREA SOUTHWEST OF MADISON.
.WEDNESDAY NIGHT INTO THURSDAY NIGHT...FORECAST CONFIDENCE IS
MEDIUM TO HIGH.
WE ISSUED A WINTER STORM WATCH EARLIER IN THE DAY FOR THE AREA WE
HAD THE HIGHEST CONFIDENCE OF HEAVY SNOW. THIS AREA IS WITHIN THE
OVERLAP REGION OF MOST OF THE THE MODEL SOLUTIONS. I WOULD EXPECT
ADJUSTMENTS TO THIS WATCH OVER THE NEXT FEW FORECAST CYCLES AS THE
MODELS BEGIN TO SETTLE DOWN AND HONE IN ON A CONSENSUS SOLUTION.
HERE/S THE LATEST ON OUR MODEL SUITE THAT CAME IN THIS MORNING.
THE NAM TOOK A 160 MILE SHIFT SOUTH WITH THE 12Z RUN..GOING FROM
THE MOST NORTHERN AND WARM SOLUTION...TO ONE VERY SIMILAR TO THE
GFS. THE GFS DIDN/T CHANGE VERY MUCH...IF ANYTHING IT MOVED A
NOTCH NORTH AND LOOKS WARMER IN IT/S CRITICAL 0-5000FT THERMAL
PROFILE. THE GEM /CANADIAN/ HAS PICKED UP SPEED AND DOESN/T
INTENSIFY UNTIL IT GETS EAST OF US. THE TRACK IS MORE OR LESS
UNCHANGED. AND FINALLY...THE ECMWF /EUROPEAN/ IS STEADY AS CAN
BE...NOT BUDGING MUCH AT ALL IN ITS TRACK. THE ECMWF IS THE MODEL
WITH THE MOST SOUTHERN SOLUTION. IT WOULD BRING MORE SNOW TO THE
SOUTHEAST FORECAST AREA COMPARED TO THE WESTERN AREA.
THE DYNAMIC/FORCING PROFILE HASN/T CHANGED FROM THE OVERNIGHT
INTERPRETATION. THE UPPER SYSTEM IS STILL GOING NEGATIVE TILT AND
INTENSIFYING AS IT MOVES INTO WISCONSIN. THIS WILL CAUSE THE
SURFACE LOW TO DEEPEN RAPIDLY AS IT MOVES INTO NORTHERN
ILLINOIS...VS INTENSIFYING EAST OF US. THIS MAKES THE STORM EVEN
MORE UNTRUSTWORTHY AND DANGEROUS. COLUMN COOLING CAN HAPPEN MUCH
FASTER THAN EXPECTED. THE OMEGA FORCING WITHIN THE DENDRITE
REGION...CROSS-HAIRS...EXPLODES FOR A TIME...HIGHLIGHTING SOME
PRETTY HEAVY SNOW POTENTIAL CENTERED AROUND 12Z THURSDAY MORNING.
THE POTENTIAL FOR THUNDER SNOW IS LOOKING VERY GOOD. QEPV CHARTS
AND SOUNDING ANALYSIS ARE SHOWING LOTS OF POTENTIAL FROM 750MB UP
THROUGH 500MB. PRETTY STEEP LAPSE RATES FOR THIS TIME OF YEAR.
PRECIPITABLE WATER VALUES OFF THE NAM AND THE GFS ARE ALMOST TOO
HIGH...REACHING ABOUT .75 INCH...WHICH IS ABOUT 2 STANDARD
DEVIATIONS ABOVE CLIMO. TYPICAL BIG SNOWSTORMS IN DECEMBER HAVE A
PW OF AROUND .4 TO .5. THIS SPEAKS TO THE WARMTH OF THE NAM AND
GFS. QPF AMOUNTS ARE STILL AROUND 1 INCH. SO...WHERE IT WILL BE ALL
SNOW...THIS MEANS WE COULD SEE SNOW ACCUMS PUSHING 12 INCHES NORTH
AND WEST OF MADISON. BUT...THIS IS FOLLOWING MORE OF A NAM/GFS/EC
BLEND. IF THE MODELS COME IN CLOSER TO THE ECMWF SOUTHERN
SOLUTION...EXPECT MORE SNOW TO THE SOUTHEAST.
WINDS WILL CRANK UP BY LATE MORNING ON THURSDAY WITH GUSTS
POSSIBLY HITTING 35 MPH. THIS COULD LEAD TO BLIZZARD OR NEAR
BLIZZARD CONDITIONS.
EXPECT THE SNOW TO BEGIN WINDING DOWN FROM WEST TO EAST THURSDAY
AFTERNOON INTO THE EVENING. EXPECT WINDS TO STAY UP INTO THE
EVENING...THEN SLOWLY DIMINISH.
.FRIDAY THROUGH MONDAY...FORECAST CONFIDENCE IS HIGH.
COLD HIGH PRESSURE SETTLES IN. LOOKS PRETTY QUIET AND CHILLY THIS
PERIOD.
&&
.AVIATION/00Z TAFS/...
MAINLY MVFR CIGS CONTINUE ACROSS SOUTHERN WISCONSIN. MODELS CONTINUE
TO TRY AND SCATTER THINGS OUT...BUT JUST IS NOT HAPPENING.
CONSIDERING KEEPING THE MVFR STRATUS GOING RIGHT THROUGH THE NIGHT
PER THE LATEST RAP RUN.
LOW PRESSURE WILL SLIDE THROUGH SOUTHERN WISCONSIN
TOMORROW...BRINGING A CHANCE FOR RAIN/SNOW SHOWERS. IF CONDITIONS
HAVE ACTUALLY IMPROVED BY THEN...MAY SEE CIGS GO BACK DOWN AS THE
LOW SLIDES THROUGH. NOT EXPECTING MUCH IN THE WAY OF SNOW
ACCUMULATIONS...BUT COULD SEE A COUPLE TENTHS OF AN INCH. BEST
CHANCE FOR ANY ACCUMULATION WOULD BE FROM MADISON WESTWARD...AS IT
WILL BE COLDER THERE WHEN THE PRECIP MOVES IN.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR WIZ046-047-051-056>058-062-063-067.
LM...NONE.
&&
$$
TONIGHT/TUESDAY AND AVIATION/MARINE...DDV
TUESDAY NIGHT THROUGH MONDAY...DAVIS
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
529 PM CST MON DEC 17 2012
.SHORT TERM...TONIGHT THROUGH THURSDAY
303 PM CST MON DEC 17 2012
MAIN FORECAST CONCERNS ARE ON BRIEF LIGHT SNOW EVENT TOMORROW AND
THE POSSIBLE WINTER STORM LATE WEDNESDAY INTO THURSDAY.
CURRENTLY AS OF 21Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED TROUGHING FROM THE GULF OF ALASKA TO OFF THE PACIFIC
NORTHWEST...A RELATIVELY POTENT SHORTWAVE CROSSING THE NORTHERN
ROCKIES...A WEAK NORTH TO SOUTH ORIENTED SHORTWAVE OVER THE FAR
EASTERN DAKOTAS AND A WEAK RIDGE SANDWICHED IN-BETWEEN THESE
SHORTWAVES. MID LEVEL CLOUDS WERE ASSOCIATED AHEAD OF THE DAKOTAS
SHORTWAVE...WITH A FEW FLURRIES FALLING OUT OF THESE OVER SOUTHWEST
MINNESOTA AND NORTHWEST IOWA. OVER THE FORECAST AREA...STRATUS
PERSISTS...BURIED UNDERNEATH A SUBSIDENCE INVERSION SEEN ON THE 12Z
MPX...GRB AND DVN SOUNDINGS. HAVING LIGHT WINDS ASSOCIATED WITH HIGH
PRESSURE AT THE SURFACE COMBINED WITH BEING AT THE BOTTOM OF THE
DAYLIGHT CYCLE HAS NOT HELPED EITHER TO GET RID OF THE STRATUS.
TEMPERATURES AS A RESULT HAVE NOT CLIMBED A WHOLE LOT FROM MORNING
LOWS. THE STRATUS ACTUALLY EXTENDS WEST ALL THE WAY INTO THE CENTRAL
DAKOTAS. FARTHER WEST...LEE TROUGHING HAS FORMED DOWNSTREAM OF THE
NORTHERN ROCKIES SHORTWAVE...ALSO AIDED BY A 130KT JET NEAR THE
TROPOPAUSE ON THE SOUTH SIDE OF THE SHORTWAVE. THERE HAS BEEN QUITE
A BIT OF PRECIPITATION ACROSS THE NORTHERN ROCKIES AS WELL AS THE
UPPER JET DRIVES IN PACIFIC MOISTURE.
TONIGHT AND TUESDAY...FOCUS IS ON THAT NORTHERN ROCKIES SHORTWAVE.
MODELS ARE IN REALLY GOOD AGREEMENT BRING THE SHORTWAVE INTO
SOUTHERN SOUTH DAKOTA BY 06Z...NEAR SIOUX CITY IOWA BY 12Z...NEAR
DUBUQUE BY 18Z AND CHICAGO BY 00Z. THIS TRACK IS A BIT FARTHER SOUTH
THAN SUGGESTED OVER THE PAST FEW DAYS...WITH PERHAPS THE CANADIAN
AND ECMWF DOING THE BEST JOB ON IT. THE SHORTWAVE AND THE ASSOCIATED
UPPER JET SOUTH OF IT ARE STRONG ENOUGH THAT OUT OF THE CURRENT LEE
TROUGHING A SURFACE LOW IS SUGGESTED TO DEVELOP. THIS LOW OF COURSE
ENDS UP TRACKING WITH THE SHORTWAVE...RESULTING IN A LOW TO
MID-LEVEL FRONTOGENESIS ZONE ON THE NORTH SIDE OF IT. MOISTURE
INITIALLY IS LIMITED...NOTED BY THE CURRENT LACK OF MID-CLOUDS
ACROSS MUCH OF THE PLAINS. HOWEVER...AS WE GO THROUGH TONIGHT...
CONDENSATION PRESSURE DEFICITS ON THE 285-290K SURFACES DECREASE AS
THE LIFT HELPS TO SATURATE THE MID-LEVELS OF THE ATMOSPHERE. SHOULD
SEE A BAND OF LIGHT SNOW BREAK OUT ACROSS SOUTH DAKOTA INTO SOUTHERN
MINNESOTA AND NORTHERN IOWA BY LATE TONIGHT...ON THE NORTH SIDE OF
THE LOW. PERHAPS SOME OF THIS SNOW SQUEAKS INTO WESTERN PORTIONS OF
THE FORECAST AREA TOWARDS 12Z. WITH THE TREND FARTHER SOUTH WITH THE
SHORTWAVE TRACK...HAVE LEANED THE FORECAST MORE TOWARDS THE 17.12Z
GFS/ECMWF IDEA VERSUS THE FARTHER NORTH BUT TRENDING SOUTH 17.12Z
NAM FOR TUESDAY. THE FRONTOGENESIS BAND OF SNOW SHOULD AFFECT MAINLY
I-90 SOUTH AND RAISED PRECIPITATION CHANCES TOWARDS 60 IN THIS AREA.
LIMITED MOISTURE NOTED BY MIXING RATIOS OF 2-3 G/KG ON THE 285-290K
SURFACES WILL KEEP QPF AMOUNTS DOWN TO AT MOST A 0.10 OF AN INCH
TOTAL LIQUID EQUIVALENT. THE LIFT IS PRIMARILY CENTERED BELOW THE
DENDRITIC GROWTH ZONE...KEEPING SNOW TO WATER RATIOS DOWN NEAR 10 TO
1...THUS ONLY UP TO AN INCH OF SNOW IS ANTICIPATED. CONCERN THOUGH
IS THAT THE SNOW IS COMING AT MORNING COMMUTE TIME...SO HAVE ISSUED
AN SPS TO ACCOUNT FOR THIS. PLENTY OF CLOUDS LOOK TO PERSIST THROUGH
THIS PERIOD THUS AGAIN TEMPERATURES IMPACTED BY ADVECTION. WITH THE
FARTHER SOUTH TRACK OF THE LOW...HAVE COOLED HIGHS DOWN FOR TUESDAY.
TUESDAY NIGHT THROUGH THURSDAY...ALL ATTENTION IS ON THE WINTER
STORM POTENTIAL...WHICH RELATES TO THE CURRENT TROUGH OFF THE
PACIFIC NORTHWEST. THAT TROUGH IS COMPOSED OF 2 PARTS...A POTENT
SHORTWAVE NEAR 42N 140 W...AND A COLD SHORTWAVE NEAR THE NORTHERN
BRITISH COLUMBIA COAST. 500MB TEMPS WERE AROUND -40C WITH THE COLD
SHORTWAVE...AND JUST AHEAD OF IT OVER NORTHERN BRITISH COLUMBIA
850MB TEMPS ARE IN THE -15 TO -25C RANGE. THE IDEA SHOWN FOR THE
PAST MANY DAYS IS THAT THESE TWO PARTS ARE EVENTUALLY GOING TO PHASE
UP AFTER CROSSING THE WESTERN U.S....RESULTING IN A DEEPENING WINTER
STORM FROM THE CENTRAL PLAINS INTO THE GREAT LAKES. THE QUESTION HAS
BEEN WHERE DOES THE PHASING OCCUR WITH RESPECT TO OUR LONGITUDE TO
HELP DETERMINE THE EXACT TRACK AND SPEED. THE ANSWER STILL IS NOT
THERE YET...HOWEVER...THE DETERMINISTIC MODEL SPREAD IS SHRINKING
AND SHOULD CONTINUE TO DO SO OVER THE NEXT FEW DAYS AS THE TROUGH
COMES INTO THE WESTERN U.S.. WITH THE 17.12Z MODEL GUIDANCE...TRACK
SPREAD RANGES FROM THE NORTHWEST SOLUTION OF THE NAM TO THE
SOUTHEAST SOLUTION OF THE ECMWF. THE GFS...UKMET AND CANADIAN LIE
IN-BETWEEN. THE NAM HAS BEEN TRENDING SOUTHEAST...THE GFS NORTHWEST
AND THE CANADIAN/ECMWF STAYING FAIRLY CLOSE. THE FORECAST FOLLOWS A
BLEND OF THE GFS...CANADIAN AND ECMWF SCENARIOS SINCE THESE SEEM TO
BE THE MOST LIKELY TO OCCUR GIVEN TRENDS. FOR WHAT ITS WORTH...THE
PAST 4 SREF RUNS ARE VERY CONSISTENT ON A FARTHER NORTHWEST TRACK
CLOSE TO OR EVEN MORE NORTHWEST THAN THE NAM. NEEDLESS TO SAY...
STILL PLENTY OF UNCERTAINTY.
SOME DETAILS...TUESDAY NIGHT INTO WEDNESDAY MORNING SHOULD STAY DRY
AS WE ARE IN-BETWEEN SYSTEMS. BIG QUESTION MARK IS IF WE CAN CLEAR.
MOST MODELS SAY WE CAN...BUT HAVING SNOW ON TUESDAY COMBINED WITH
MODELS NOT DOING THE GREATEST ON THE CURRENT STRATUS YIELDS A MORE
PESSIMISTIC VIEW. AS SUCH...HAVE INCREASED CLOUD COVER AND FURTHER
INCREASES MAY BE NECESSARY. AS THE STORM SYSTEM DEEPENS IN THE
SOUTHERN PLAINS ON WEDNESDAY...A BAND OF FRONTOGENESIS
DEVELOPS/STRENGTHENS UP INTO OUR REGION. THE GFS AND CANADIAN
PRODUCE PRECIPITATION IN THE AFTERNOON AS THEY ARE QUICKER TO
SATURATE THE LOW LEVELS AND TO BRING IN THE FORCING...COMPARED TO
THE ECMWF/NAM/UKMET. HARD TO SAY WHICH GROUP MAY BE MORE CORRECT AT
THIS POINT...THOUGH THE MORE CONSISTENT SIGNAL HAS BEEN TO WAIT
UNTIL WEDNESDAY EVENING TO BRING THE PRECIPITATION IN. THUS...FOR
NOW JUST INCLUDED 20-40 PERCENT CHANCES FROM I-90 SOUTH FOR THE
AFTERNOON. THE MAJORITY OF THE FORECAST AREA SHOULD SEE
PRECIPITATION WEDNESDAY NIGHT INTO THURSDAY MORNING...NO MATTER WHAT
MODEL SOLUTION IS FOLLOWED. IF THERE IS ANYWHERE OF CONCERN DURING
THIS PERIOD THAT MAY NOT SEE PRECIPITATION IT IS OUR FAR NORTHWEST
AS INDICATED BY THE ECMWF. THUS...HIGHEST CHANCES UP AT OR NEAR 100
ARE CONFINED TO THE SOUTHEAST HALF. PRECIPITATION SHOULD START TO
DIMINISH THURSDAY AFTERNOON AS THE SYSTEM HEADS OFF INTO LOWER
MICHIGAN.
IMPACTS/CONCERNS TO WORRY ABOUT WITH THIS WINTER STORM INCLUDE:
1. HEAVY SNOW...PRETTY GOOD MODEL CONSENSUS EXISTS THAT THE TIME
PERIOD WOULD BE WEDNESDAY NIGHT INTO THURSDAY MORNING. EXACT
PLACEMENT OF HEAVIEST SNOW IS STILL UNCERTAIN...BUT FOLLOWING THE
AFOREMENTIONED GFS/ECMWF/CANADIAN BLEND PLACES IT IN THE
SOUTHEASTERN HALF OF THE FORECAST AREA. WITH MAYBE 100 MB OF
DENDRITIC GROWTH AT MOST AND FAIRLY HIGH UP SAY BETWEEN
550-650MB...THE SNOW TO WATER RATIOS SHOULD BE TYPICAL...IN THE
10-15 TO 1 RANGE.
2. MIXED PRECIPITATION TYPES...MODEL CONSENSUS HAS BEEN TO KEEP THE
SYSTEM OFF TO OUR SOUTHEAST...KEEPING OUR AREA IN THE DEEPER COLD
AIR AND THUS SNOW AS THE MAJORITY PRECIPITATION TYPE. HOWEVER...THE
GFS SUGGESTS THAT IF THE SYSTEM CAN WRAP UP ENOUGH...EVEN GRANT AND
CLAYTON COUNTIES COULD END UP WITH SLEET OR RAIN FOR A TIME.
3. BLOWING SNOW/WIND...AS THE SYSTEM DEEPENS ON ITS WAY UP THROUGH
ILLINOIS WEDNESDAY NIGHT AND BEGINS TO PULL AWAY FROM THE AREA ON
THURSDAY...THE PRESSURE GRADIENT TIGHTENS...CAUSING NORTHWEST WINDS
TO INCREASE. THESE WINDS COULD EASILY REACH THE 15-25KT RANGE WITH
HIGHER GUSTS. COMBINING THESE WITH FALLING OR ALREADY ON THE GROUND
SNOW WOULD YIELD BLOWING SNOW...ESPECIALLY ACROSS NORTHEAST IOWA
WHICH HAS THE MOST EXPOSED TERRAIN.
WITH THE NARROWING MODEL SPREAD...ENOUGH CONFIDENCE EXISTED EARLIER
TODAY TO ISSUE A WINTER STORM WATCH FOR ABOUT THE SOUTHEASTERN HALF
OF THE FORECAST AREA. NOTE THAT THE WATCH AREA MAY NOT END UP BEING
THE FINAL WARNING AREA...THUS THE PHRASE WATCH. FURTHER REFINEMENTS
MAY OCCUR...ESPECIALLY ONCE CONFIDENCE INCREASES ENOUGH TO CHANGE
THE WATCHES TO ADVISORIES/WARNINGS.
.LONG TERM...THURSDAY NIGHT THROUGH MONDAY
303 PM CST MON DEC 17 2012
MAIN FORECAST CONCERNS ARE TEMPERATURES THROUGH FORECAST PERIOD.
THE DETERMINISTIC 17.12Z GFS/ECMWF/GEM ARE IN GOOD AGREEMENT WITH
UPPER LEVEL TROUGH OVER THE NORTHEASTERN UNITED STATES AND UPPER
LEVEL RIDGE OVER THE EASTERN ROCKY MOUNTAINS THROUGH 18Z
SATURDAY...THEN THE MODELS BEGIN TO DIVERGE ON STRENGTH OF THE
UPPER LEVEL TROUGH OVER THE NORTHEASTERN UNITED STATES AND UPPER
LEVEL RIDGE OVER THE ROCKY MOUNTAINS. THE 17.12Z ECMWF IS MORE
AMPLIFIED WITH THE UPPER LEVEL TROUGH SATURDAY NIGHT INTO MONDAY
THAN THE 17.12Z GFS/GEM. IF THIS OCCURS...THE UPPER MIDWEST AND
GREAT LAKES REGION WILL REMAIN UNDER NORTHERLY FLOW ALOFT AND A
COLDER AIRMASS WILL FILTER INTO THE AREA. THIS WILL HAVE IMPACTS
ON TEMPERATURES...ESPECIALLY SATURDAY NIGHT INTO MONDAY. THE
17.12Z GFS INDICATES WEST TO EAST ZONAL FLOW ACROSS THE UNITED
STATES AND SLIGHTLY WARMER TEMPERATURES THAN THE 17.12Z ECMWF.
THIS WOULD RESULT IN NEAR NORMAL TEMPERATURES ACROSS FORECAST
AREA. AT THIS TIME...WILL CONTINUE WITH A CONSENSUS BLEND OF
TEMPERATURES...BASED ON THE LOW CONFIDENCE OF UPPER LEVEL FLOW
PATTERN AFTER 18Z SATURDAY.
NO REAL INDICATION OF ANY PRECIPITATION OCCURRING AS THE UPPER
FLOW PATTERN PROGGED IS MOSTLY SUBSIDENT...FAVORING HIGH PRESSURE
AT THE SURFACE.
&&
.AVIATION...TONIGHT AND TUESDAY
529 PM CST MON DEC 17 2012
INFRARED SATELLITE IMAGERY CONTINUES TO SHOW AN EXTENSIVE AREA OF
IFR STRATUS ACROSS THE REGION...WITH LOWER END MVFR CEILINGS
ACROSS WISCONSIN. THESE CONDITIONS WILL PERSIST THROUGH THE NIGHT
WITH PERHAPS A FEW BREAKS IN THE LOWER CEILINGS...BUT THESE WILL
BE SHORT LIVED. EXPECT LIGHT SNOW TO BREAK OUT AT THE TAF SITES
BETWEEN 12Z-14Z WITH IFR VISIBILITIES LIKELY OF 1-2SM. THERE COULD
BE A NARROWER BAND WITH LOWER VISIBILITIES...BUT STILL TO EARLY TO
DEFINE WHERE THIS COULD SET UP. EXPECT THE LIGHT SNOW TO CONTINUE
INTO THE AFTERNOON...BUT WILL TAPER OFF AT KRST WITH VISIBILITIES
LIFTING INTO THE MVFR CATEGORY.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
303 PM CST MON DEC 17 2012
WI...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR WIZ034-041>044-053>055-061.
MN...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR MNZ096.
IA...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR IAZ010-011-019-029-030.
&&
$$
SHORT TERM...AJ
LONG TERM...DTJ/AJ
AVIATION...RABERDING
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
238 PM CST SUN DEC 16 2012
.SHORT TERM...TONIGHT THROUGH WEDNESDAY
238 PM CST SUN DEC 16 2012
MAIN FORECAST CONCERNS ARE ON PRECIPITATION CHANCES AND TYPE FOR
TUESDAY AND WEDNESDAY.
CURRENTLY AS OF 20Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED A POTENT SHORTWAVE TROUGH APPROACHING THE PACIFIC NORTHWEST
AND BROAD TROUGHING ENCOMPASSING MUCH OF THE CENTRAL U.S. INTO THE
WESTERN GREAT LAKES. WITHIN THIS BROAD TROUGHING...THERE ARE VERY
FEW SHORTWAVES THAT LOOK TO HAVE ANY IMPACT ON OUR FORECAST AREA
DURING THE NEXT FEW DAYS. THE ONLY SHORTWAVE REALLY OF NOTE WAS OVER
WESTERN PORTIONS OF MONTANA AND WYOMING. AT THE SURFACE...LOW
PRESSURE WAS OVER UPPER MICHIGAN WHILE HIGH PRESSURE COVERED THE
DAKOTAS INTO WESTERN MINNESOTA. IN-BETWEEN THE TWO...NORTHERLY WINDS
ARE DRIVING COLDER LOW LEVEL AIR INTO THE FORECAST AREA. SURFACE
TEMPERATURES HAVE FALLEN INTO THE 20S OVER PORTIONS OF SOUTHEAST
MINNESOTA WHILE THE REST OF THE AREA REMAINS MOSTLY IN THE 30S. THE
COLD AIR EXTENDS UP TO 850MB WITH 12Z SOUNDINGS FROM BIS...ABR AND
MPX SHOWING -4C TEMPERATURES. ALONG WITH THE COLDER AIR...EXTENSIVE
LOW STRATUS EXISTS FROM THE DAKOTAS INTO THE FORECAST AREA...TRAPPED
BELOW A COLD FRONTAL/SUBSIDENCE INVERSION SHOWN ON THE
AFOREMENTIONED SOUNDINGS. AS THE COLD AIR HAS BEEN FLOWING IN...SOME
FOG HAS DEVELOPED...DUE TO RECENT RAIN AND MELTING SNOW.
VISIBILITIES DROPPED EVEN DOWN TO 1/4SM MILE IN SOME PLACES IN
SOUTHEAST MINNESOTA. LAST ITEM TO NOTE IS A QUICK SNOW DEPTH
COMPARISON TO OBSERVED. THE 16.12Z NAM HAS WAY TOO MUCH SNOW ALONG
AND SOUTH OF I-90...AS ITS SNOW DEPTH INFORMATION HAS NOT UPDATED
SINCE 00Z ON THE 15TH.
TONIGHT AND MONDAY...WEAK UPPER RIDGING WITHIN THE BROAD TROUGH IS
FORECAST TO BUILD INTO THE AREA FOR TONIGHT AND MUCH OF MONDAY...
AHEAD OF THAT SHORTWAVE OVER WESTERN MONTANA AND WYOMING. GOOD MODEL
AGREEMENT EXISTS THAT THE SHORTWAVE WILL REACH WESTERN MINNESOTA BY
00Z TUESDAY. THE WEAK UPPER RIDGING BUILDING IN COMBINED WITH THE
SURFACE RIDGING COMING IN AT THE SURFACE FAVORS DRY CONDITIONS
THROUGH MONDAY. THE BIGGEST QUESTION IS IF THIS STRATUS CAN
DISSIPATE AT ALL. TOUGH TO USE THE NAM...PARTICULARLY ALONG AND
SOUTH OF I-90...SINCE IT HAS TOO MUCH SNOW AND THIS IS INFLUENCING
ITS HANDLING OF BOUNDARY LAYER. HOWEVER...BOTH GFS AND RAP SOUNDINGS
WHICH HAVE A BETTER HANDLE ON THE SNOW DEPTH SITUATION SUGGEST THE
STRATUS WILL DEFINITELY STAY IN PLACE TONIGHT. LOOKS LIKE THERE IS
ENOUGH STIRRING OF THE BOUNDARY LAYER TO PREVENT MORE THAN PATCHY
FOG. PERHAPS THERE IS A SHOT OF DIURNAL MIXING OUT THE STRATUS
TOMORROW...THOUGH MID AND HIGH CLOUDS WILL INCREASE AHEAD OF THE
APPROACHING SHORTWAVE. AS A RESULT...MAINLY CLOUDY CONDITIONS WILL
PREVAIL. THIS MEANS TEMPERATURES FOR THE MOST PART ARE GOING TO BE
INFLUENCED BY ADVECTION. A BLEND OF GUIDANCE SEEMED REASONABLE FOR
BOTH LOWS AND HIGHS.
MONDAY NIGHT AND TUESDAY...THE SHORTWAVE OVER WESTERN MINNESOTA AT
00Z TUESDAY IS SLATED TO CROSS THE AREA MONDAY NIGHT...BUT IT LOOKS
LIKE IT WILL COME THROUGH WITH LITTLE FANFARE OUTSIDE OF SOME
MID/HIGH CLOUDS. THIS IS BECAUSE OF PLENTIFUL DRY AIR IN-BETWEEN
THESE MID/HIGH CLOUDS AND A POSSIBLE HANGING AROUND VERY LOW STRATUS
DECK. OF MORE SIGNIFICANCE IS LATE IN THE NIGHT AND HEADING INTO THE
DAY TUESDAY...WHEN WARM ADVECTION IMPACTS FROM THE POTENT TROUGH
APPROACHING THE PACIFIC NORTHWEST CURRENTLY BEGIN TO MOVE IN. AT 12Z
TUESDAY...MODELS SHOW THE POTENT TROUGH...ALBEIT IN A MUCH WEAKER
STATE AFTER CROSSING THE NORTHERN ROCKIES...STRETCHED FROM THE
DAKOTAS INTO NORTHWEST IOWA. THIS TROUGH SLIDES EAST THROUGH MUCH OF
THE AREA ON TUESDAY...IN RESPONSE TO BUILDING 500MB HEIGHTS
DOWNSTREAM OF DEEP TROUGHING COMING INTO CALIFORNIA. MODELS HAVE
COME INTO GOOD AGREEMENT SHOWING A BAND OF ISENTROPIC LIFT/MID-LEVEL
FRONTOGENESIS ACCOMPANYING THIS TROUGH PASSAGE...YIELDING A BAND OF
QPF LIFTING NORTHWARD THROUGH THE FORECAST AREA DURING THE DAY
TUESDAY. PRECIPITATION COULD DEVELOP AS EARLY AS AFTER MIDNIGHT
MONDAY NIGHT AS SUGGESTED BY THE 16.12Z GFS AND SOME OF THE 16.09Z
SREF ENSEMBLES. HAVE CONFINED A 20 PERCENT CHANCE FOR MONDAY NIGHT
TO SOUTHEAST MINNESOTA. GIVEN THE GOOD AGREEMENT FOR TUESDAY...
INCREASED CHANCES UP TOWARDS 50...HIGHEST NORTH OF I-90 WHERE THE
BEST CONSENSUS EXISTS. HIGHER CHANCES MAY BE NECESSARY IN FUTURE
FORECASTS. AMOUNTS DO NOT LOOK LIKE A WHOLE LOT...BETWEEN THE BAND
LIFTING NORTH AND LIFT THAT IS QUALITATIVELY MODERATE AT BEST.
PRECIPITATION TYPE COULD BE AN ISSUE...WITH THE 16.12Z NAM SHOWING A
WARM NOSE AROUND 2C AROUND 2000 FT AGL ACCOMPANYING THE BAND. THE
GFS SUGGESTS ALL SNOW AND WILL PLAY THAT ROUTE FOR NOW AS IT SEEMS
THAT THE WARM NOSE SHOULD ACTUALLY COME IN SOUTH OF THE BAND. AFTER
THE PASSAGE OF THE BAND...THE GFS AND NAM SHOWS SKIES CLEARING OUT.
THIS MAY OCCUR AND IF IT DOES...TEMPERATURES SOUTH OF I-90 COULD POP
INTO THE 40S. FOR NOW TAKING A CONSENSUS APPROACH AS THE ECMWF
SUGGESTS A SLOWER LIFT NORTH OF THE BAND.
TUESDAY NIGHT AND WEDNESDAY...ATTENTION BEGINS TO SHIFT TO THE
TROUGHING OVER CALIFORNIA AT 00Z WEDNESDAY. GOOD MODEL AGREEMENT
EXISTS OF IT SLIDING ACROSS ARIZONA AND NEW MEXICO DURING THIS
PERIOD...RESULTING IN DEEPENING LOW PRESSURE ACROSS THE OKLAHOMA AND
TEXAS PANHANDLES. DOWNSTREAM...500MB HEIGHTS CONTINUE TO RISE...
PARTICULARLY ACROSS THE LOWER AND MID-MISSISSIPPI RIVER VALLEY. THIS
IN TURN SETS UP A STRENGTHENING MID-LEVEL FRONTOGENESIS ZONE
INITIALLY ACROSS COLORADO...THEN SPREADING UP THROUGH KANSAS...
EASTERN NEBRASKA AND EVENTUALLY IOWA BY WEDNESDAY AFTERNOON. THE
16.12Z NAM APPEARS TO BE AN OUTLIER IN EJECTING THE SURFACE SYSTEM
NORTH TO KANSAS CITY BY 00Z THURSDAY...COMPARED TO THE
GFS/ECMWF/UKMET/CANADIAN WHICH ALL HOLD IT BACK OVER OKLAHOMA. THE
FASTER EJECTING NAM WOULD ALLOW WARMER AIR TO ENTER SOUTHERN
SECTIONS OF THE FORECAST AREA ON WEDNESDAY AS WELL AS PRECIP INTO
SOUTH CENTRAL MINNESOTA. THE LATTER MORE FAVORED GROUP REQUIRES
HAVING SOME CHANCES OF PRECIPITATION...SNOW OR RAIN/SNOW MIX...TO
SOUTHERN SECTIONS OF THE FORECAST AREA WEDNESDAY AFTERNOON.
OTHERWISE...THE REST OF THE PERIOD IS DRY. WEAK PRESSURE GRADIENT
AFTER MIDNIGHT TUESDAY NIGHT PLUS POSSIBLE CLEARING WOULD
RESULT IN GOOD RADIATIONAL COOLING CONDITIONS...THOUGH THE EXTENT OF
CLEARING IS UNCERTAIN AT THIS TIME. PLUS...MID/HIGH CLOUDS MAY
ALREADY BE APPROACHING THE AREA ASSOCIATED WITH THE FRONTOGENESIS
TUESDAY NIGHT...THICKENING OVER THE AREA ON WEDNESDAY. THUS HAVE
STAYED TOWARD A GUIDANCE BLEND FOR BOTH HIGHS AND LOWS.
.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY
238 PM CST SUN DEC 16 2012
FOCUS CONTINUES TO BE ON THE DEEP TROUGHING COMING OUT OF NEW MEXICO
AND THE ASSOCIATED SURFACE SYSTEM IN OKLAHOMA.
ECMWF/CANADIAN/GFS/UKMET AND GFS ENSEMBLES ALL STILL SUGGEST PHASING
OF THIS TROUGHING AND A NORTHERN STREAM TROUGH DROPPING DOWN INTO
THE NORTHERN PLAINS. HOWEVER...TRENDS OF THE ABOVE MODELS ARE ALL
SHOWING THIS PHASING TAKING PLACE FARTHER EAST WITH THE TRACKS NOW
MAINLY GOING UP THROUGH INDIANA. THIS TREND IS GETTING CONCERNING
FOR PRECIPITATION FOR WEDNESDAY NIGHT AND THURSDAY...ESPECIALLY
OVER THE NORTHWEST 1/3 OR SO WHERE IT COULD END UP DRY. CERTAINLY
PLENTY OF TIME FOR ADJUSTMENTS FOR THE TRACK GIVEN THAT THE DEEP
TROUGH PORTION IS STILL SOUTH OF THE ALEUTIANS. ADJUSTED THE
PRECIPITATION CHANCES SLIGHTLY DOWNWARD FOR WEDNESDAY NIGHT AND
THURSDAY TO ACCOUNT FOR THE SOUTHEAST TREND...BUT AT LEAST AT THIS
TIME THE SOUTHEAST HALF OF THE FORECAST AREA STILL LOOKS GOOD TO
PICK UP SOME ACCUMULATING SNOW.
AFTER THE WEDNESDAY NIGHTTHURSDAY SYSTEM...THE PATTERN LOOKS QUIET
WITH UPPER RIDGING DOMINATING THE WESTERN HALF OF THE U.S. OR SO AND
THE FORECAST AREA IN WEST TO NORTHWEST FLOW AND HIGH PRESSURE AT THE
SURFACE. CERTAINLY SOME COLDER AIR WILL COME DOWN IN THE WAKE OF THE
SYSTEM...SENDING TEMPERATURES DOWN TO NEAR OR JUST BELOW NORMAL...
BUT IT APPEARS THIS WILL BE SHORT-LIVED AS 500MB HEIGHTS RISE.
&&
.AVIATION...THIS AFTERNOON THROUGH MONDAY
1200 PM CST SUN DEC 16 2012
MVFR/IFR CIGS/VSBYS WILL PERSIST ACROSS MUCH OF THE AREA THRU
TONIGHT AND MONDAY. CONSIDERABLE MOISTURE REMAINS TRAPPED ACROSS THE
REGION...IN/UNDER A SFC-800MB INVERSION. AREA SOUNDINGS SHOW THIS
MOISTURE TO BE SOME 3K-4K FT DEEP OVER MUCH OF MN/IA/WI. WITH WEAK
GRADIENTS AND A WEAK RIDGE OF HIGH PRESSURE TO BUILD OVER THE AREA
TONIGHT...LITTLE IN THE WAY OF ADVECTION LOOKS TO OCCUR PLUS THERE
IS PLENTY OF MOISTURE UPSTREAM OVER THE DAKOTAS/NORTHERN MN. THE
HIGH HOLDS THE INVERSION IN PLACE AS WELL. THUS...CONTINUED IFR
CIGS/VSBYS AT KRST THRU THE TAF PERIOD. KLSE A LITTLE BETTER BEING
IN THE VALLEY WITH CIGS AROUND 1K FT AND VFR OR MVFR VSBYS. THE
STRATUS BLANKET AND SOME WEAK NORTHWEST GRADIENT FLOW SHOULD KEEP
THE FOG FROM BECOMING DENSE AGAIN TONIGHT.
ANY IMPROVEMENT MONDAY LOOKS TO BE SLOW WITH WARM ADVECTION AND AN
INCREASE OF MOISTURE SPREADING INTO THE AREA AHEAD OF A WEAK
SHORTWAVE TROUGH MOVING ACROSS THE UPPER MIDWEST.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
238 PM CST SUN DEC 16 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...AJ
LONG TERM...AJ
AVIATION.....RRS
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1200 PM CST SUN DEC 16 2012
.SHORT TERM...TODAY THROUGH TUESDAY NIGHT
305 AM CST SUN DEC 16 2012
THE MAIN FOCUS OVER THE NEXT FEW DAYS IS ON THE DEPARTING
PRECIPITATION TODAY FOLLOWED BY THE CHANCE FOR SNOW ON TUESDAY.
LIGHT RAIN/DRIZZLE AND LIGHT SNOW WILL COME TO AN END FROM WEST TO
EAST TODAY AS A MID LEVEL SHORTWAVE TROUGH PROPAGATES TO THE NORTHEAST
INTO THE GREAT LAKES. AS OF 2 AM...SURFACE OBS AND DUAL POL RADAR
SHOWED THE RAIN/SNOW LINE FROM JUST WEST OF EAU CLAIRE WISCONSIN
DOWN TO WINONA MINNESOTA AND DECORAH IOWA. THE TRANSITION TO LIGHT
SNOW WILL BE RATHER BRIEF AND THEREFORE ANY SNOW ACCUMULATIONS
WILL BE ON THE LIGHT SIDE. EARLIER RUNS OF THE RAP HAD SHOWN THE
POSSIBILITY OF SOME FREEZING DRIZZLE OCCURRING AS THE SNOW CAME TO
AN END...BUT OBSERVATIONS/RADAR UPSTREAM IS NOT SHOWING ANY OF
THIS. DENSE FOG FORMED ACROSS MUCH OF THE REGION OVERNIGHT AS A
RESULT OF HIGH LOW LEVEL MOISTURE DUE TO RECENT RAIN AND SNOW MELT
ALONG WITH THE CORE OF A SURFACE LOW OVERHEAD WHICH PROVIDED
LIGHT TO CALM WINDS. AS THE COLD FRONT EXTENDING SOUTH FROM THE
LOW MOVES THROUGH...WINDS WILL PICK UP AND THE DENSE FOG WILL MIX
OUT WITH VISIBILITY IMPROVING. WITH VISIBILITY STILL LESS THAN A
QUARTER MILE IN NORTH CENTRAL WISCONSIN...WILL LET THE ADVISORY
ROLL FOR NOW WITH IT EXPIRING AT 6 AM...BUT MAY BE ABLE TO CLEAR
IT EARLY.
NOT THE CLEAREST OF WEATHER PATTERNS EXPECTED THROUGH THE NEXT FEW
DAYS WITH SUBTLE SYSTEMS MOVING INTO THE REGION THROUGH THE
SOUTHWEST-WESTERLY FLOW ALOFT. A WEAK MID LEVEL TROUGH WILL MOVE
THROUGH TODAY...BUT WILL ONLY ADD CLOUD COVER TO THE REGION.
16.00Z NAM/GFS SOUNDINGS SHOW THAT THE FORCING IS NOT VERY STRONG
AND THE DRY LAYER IS TOO DEEP FOR SEEDER FEEDER TO PRODUCE SOME
SNOW. A SURFACE RIDGE OF HIGH PRESSURE WILL THEN MOVE THROUGH THE
REGION TONIGHT INTO MONDAY BEFORE THE NEXT SYSTEM TAKES SHAPE IN
THE NORTHERN PLAINS. MUCH OF THE FORCING FOR THIS SYSTEM WILL BE
FROM THE LOW LEVEL WARM AIR ADVECTION...BUT THERE ALSO IS A MID
LEVEL TROUGH THAT ROTATES NORTHWARD INTO SOUTHERN CANADA OVER THE
SAME TIME FRAME. THE 16.00Z ECMWF IS THE STRONGEST WITH HAVING A
SURFACE LOW MOVE THROUGH...BUT OVERALL QPF REMAINS ON THE LIGHT
SIDE AT LESS THAN A TENTH OF AN INCH. PRECIPITATION TYPE WILL
MAINLY BE LIGHT SNOW WITH ANY ACCUMULATIONS LIKELY LESS THAN AN
INCH.
.LONG TERM...WEDNESDAY THROUGH SATURDAY
305 AM CST SUN DEC 16 2012
THE FOCUS FROM MID WEEK INTO NEXT WEEKEND CONTINUES TO BE WITH THE
POTENTIAL FOR A WINTER STORM WEDNESDAY NIGHT INTO THURSDAY. WHILE
THE SUITE OF 16.00Z GUIDANCE STILL ADVERTISES THIS DEEPENING
SURFACE LOW MOVING INTO SOUTHERN LAKE MICHIGAN BY THURSDAY
MORNING...THE TREND IS FOR THE MAJOR IMPACTS FROM THIS SYSTEM TO
BE MORE SO FELT TO THE SOUTH AND EAST OF THE FORECAST AREA. THE
FURTHER EAST THAT THIS SYSTEM CONTINUES TO MOVE...THE LOWER OUR
CHANCES BECOME OF SEEING THE HEAVIEST SNOW BAND OCCUR IN THE
FORECAST AREA. BASED ON 16.00Z GUIDANCE...THE WESTERN EDGE OF THE
SNOW APPEARS TO RUN FROM CENTRAL IOWA THROUGH SOUTHEAST MINNESOTA
AND NORTHWEST WISCONSIN. WHILE THE HEAVIEST SNOW BAND MAY BE TO THE
EAST OF THE FORECAST AREA...THE CHANCES FOR SNOW ACROSS THE REGION
STILL LOOK GOOD...SO HAVE BUMPED UP THE PRECIPITATION PROBABILITIES
WEDNESDAY NIGHT INTO THURSDAY. THIS SYSTEM IS CURRENTLY UP NEAR
THE ALEUTIAN ISLANDS WEST OF ALASKA AND WILL BE INTO CALIFORNIA BY
TUESDAY WHICH IS WHEN WE SHOULD HAVE A BETTER HANDLE ON THE
SYSTEMS TRACK.
BEHIND THIS SYSTEM...COLDER AIR WILL GET PULLED DOWN FROM SOUTHERN
CANADA...BUT IT APPEARS TO BE A FAIRLY SHORT LIVED COLD BURST
BEFORE LOW LEVEL WARM AIR ADVECTION STRENGTHENS OUT OF THE
SOUTHWEST ON SATURDAY. DUE TO THIS...HAVE TRENDED SLIGHTLY WARMER
FOR TEMPERATURES INTO THE WEEKEND.
&&
.AVIATION...THIS AFTERNOON THROUGH MONDAY
1200 PM CST SUN DEC 16 2012
MVFR/IFR CIGS/VSBYS WILL PERSIST ACROSS MUCH OF THE AREA THRU
TONIGHT AND MONDAY. CONSIDERABLE MOISTURE REMAINS TRAPPED ACROSS THE
REGION...IN/UNDER A SFC-800MB INVERSION. AREA SOUNDINGS SHOW THIS
MOISTURE TO BE SOME 3K-4K FT DEEP OVER MUCH OF MN/IA/WI. WITH WEAK
GRADIENTS AND A WEAK RIDGE OF HIGH PRESSURE TO BUILD OVER THE AREA
TONIGHT...LITTLE IN THE WAY OF ADVECTION LOOKS TO OCCUR PLUS THERE
IS PLENTY OF MOISTURE UPSTREAM OVER THE DAKOTAS/NORTHERN MN. THE
HIGH HOLDS THE INVERSION IN PLACE AS WELL. THUS...CONTINUED IFR
CIGS/VSBYS AT KRST THRU THE TAF PERIOD. KLSE A LITTLE BETTER BEING
IN THE VALLEY WITH CIGS AROUND 1K FT AND VFR OR MVFR VSBYS. THE
STRATUS BLANKET AND SOME WEAK NORTHWEST GRADIENT FLOW SHOULD KEEP
THE FOG FROM BECOMING DENSE AGAIN TONIGHT.
ANY IMPROVEMENT MONDAY LOOKS TO BE SLOW WITH WARM ADVECTION AND AN
INCREASE OF MOISTURE SPREADING INTO THE AREA AHEAD OF A WEAK
SHORTWAVE TROUGH MOVING ACROSS THE UPPER MIDWEST.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
541 AM CST SUN DEC 16 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...HALBACH
LONG TERM....HALBACH
AVIATION.....RRS
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
542 AM CST SUN DEC 16 2012
.SHORT TERM...TODAY THROUGH TUESDAY NIGHT
305 AM CST SUN DEC 16 2012
THE MAIN FOCUS OVER THE NEXT FEW DAYS IS ON THE DEPARTING
PRECIPITATION TODAY FOLLOWED BY THE CHANCE FOR SNOW ON TUESDAY.
LIGHT RAIN/DRIZZLE AND LIGHT SNOW WILL COME TO AN END FROM WEST TO
EAST TODAY AS A MID LEVEL SHORTWAVE TROUGH PROPAGATES TO THE NORTHEAST
INTO THE GREAT LAKES. AS OF 2 AM...SURFACE OBS AND DUAL POL RADAR
SHOWED THE RAIN/SNOW LINE FROM JUST WEST OF EAU CLAIRE WISCONSIN
DOWN TO WINONA MINNESOTA AND DECORAH IOWA. THE TRANSITION TO LIGHT
SNOW WILL BE RATHER BRIEF AND THEREFORE ANY SNOW ACCUMULATIONS
WILL BE ON THE LIGHT SIDE. EARLIER RUNS OF THE RAP HAD SHOWN THE
POSSIBILITY OF SOME FREEZING DRIZZLE OCCURRING AS THE SNOW CAME TO
AN END...BUT OBSERVATIONS/RADAR UPSTREAM IS NOT SHOWING ANY OF
THIS. DENSE FOG FORMED ACROSS MUCH OF THE REGION OVERNIGHT AS A
RESULT OF HIGH LOW LEVEL MOISTURE DUE TO RECENT RAIN AND SNOW MELT
ALONG WITH THE CORE OF A SURFACE LOW OVERHEAD WHICH PROVIDED
LIGHT TO CALM WINDS. AS THE COLD FRONT EXTENDING SOUTH FROM THE
LOW MOVES THROUGH...WINDS WILL PICK UP AND THE DENSE FOG WILL MIX
OUT WITH VISIBILITY IMPROVING. WITH VISIBILITY STILL LESS THAN A
QUARTER MILE IN NORTH CENTRAL WISCONSIN...WILL LET THE ADVISORY
ROLL FOR NOW WITH IT EXPIRING AT 6 AM...BUT MAY BE ABLE TO CLEAR
IT EARLY.
NOT THE CLEAREST OF WEATHER PATTERNS EXPECTED THROUGH THE NEXT FEW
DAYS WITH SUBTLE SYSTEMS MOVING INTO THE REGION THROUGH THE
SOUTHWEST-WESTERLY FLOW ALOFT. A WEAK MID LEVEL TROUGH WILL MOVE
THROUGH TODAY...BUT WILL ONLY ADD CLOUD COVER TO THE REGION.
16.00Z NAM/GFS SOUNDINGS SHOW THAT THE FORCING IS NOT VERY STRONG
AND THE DRY LAYER IS TOO DEEP FOR SEEDER FEEDER TO PRODUCE SOME
SNOW. A SURFACE RIDGE OF HIGH PRESSURE WILL THEN MOVE THROUGH THE
REGION TONIGHT INTO MONDAY BEFORE THE NEXT SYSTEM TAKES SHAPE IN
THE NORTHERN PLAINS. MUCH OF THE FORCING FOR THIS SYSTEM WILL BE
FROM THE LOW LEVEL WARM AIR ADVECTION...BUT THERE ALSO IS A MID
LEVEL TROUGH THAT ROTATES NORTHWARD INTO SOUTHERN CANADA OVER THE
SAME TIME FRAME. THE 16.00Z ECMWF IS THE STRONGEST WITH HAVING A
SURFACE LOW MOVE THROUGH...BUT OVERALL QPF REMAINS ON THE LIGHT
SIDE AT LESS THAN A TENTH OF AN INCH. PRECIPITATION TYPE WILL
MAINLY BE LIGHT SNOW WITH ANY ACCUMULATIONS LIKELY LESS THAN AN
INCH.
.LONG TERM...WEDNESDAY THROUGH SATURDAY
305 AM CST SUN DEC 16 2012
THE FOCUS FROM MID WEEK INTO NEXT WEEKEND CONTINUES TO BE WITH THE
POTENTIAL FOR A WINTER STORM WEDNESDAY NIGHT INTO THURSDAY. WHILE
THE SUITE OF 16.00Z GUIDANCE STILL ADVERTISES THIS DEEPENING
SURFACE LOW MOVING INTO SOUTHERN LAKE MICHIGAN BY THURSDAY
MORNING...THE TREND IS FOR THE MAJOR IMPACTS FROM THIS SYSTEM TO
BE MORE SO FELT TO THE SOUTH AND EAST OF THE FORECAST AREA. THE
FURTHER EAST THAT THIS SYSTEM CONTINUES TO MOVE...THE LOWER OUR
CHANCES BECOME OF SEEING THE HEAVIEST SNOW BAND OCCUR IN THE
FORECAST AREA. BASED ON 16.00Z GUIDANCE...THE WESTERN EDGE OF THE
SNOW APPEARS TO RUN FROM CENTRAL IOWA THROUGH SOUTHEAST MINNESOTA
AND NORTHWEST WISCONSIN. WHILE THE HEAVIEST SNOW BAND MAY BE TO THE
EAST OF THE FORECAST AREA...THE CHANCES FOR SNOW ACROSS THE REGION
STILL LOOK GOOD...SO HAVE BUMPED UP THE PRECIPITATION PROBABILITIES
WEDNESDAY NIGHT INTO THURSDAY. THIS SYSTEM IS CURRENTLY UP NEAR
THE ALEUTIAN ISLANDS WEST OF ALASKA AND WILL BE INTO CALIFORNIA BY
TUESDAY WHICH IS WHEN WE SHOULD HAVE A BETTER HANDLE ON THE
SYSTEMS TRACK.
BEHIND THIS SYSTEM...COLDER AIR WILL GET PULLED DOWN FROM SOUTHERN
CANADA...BUT IT APPEARS TO BE A FAIRLY SHORT LIVED COLD BURST
BEFORE LOW LEVEL WARM AIR ADVECTION STRENGTHENS OUT OF THE
SOUTHWEST ON SATURDAY. DUE TO THIS...HAVE TRENDED SLIGHTLY WARMER
FOR TEMPERATURES INTO THE WEEKEND.
&&
.AVIATION...TODAY AND TONIGHT
541 AM CST SUN DEC 16 2012
THE RAIN AND SNOW HAS ALREADY MOVED OUT OF KRST AND IT WILL MOVE
OUT OF KLSE BY 16.14Z. LOOKING AT THE RADAR RETURNS...IT LOOKS
LIKE THE RAIN AND SNOW WILL NOT CAUSE ANY VISIBILITY RESTRICTIONS.
MEANWHILE THE BR AT KRST SHOULD DISSIPATE BY 16.18Z. BR WILL ONCE
AGAIN DEVELOP AT KRST AROUND 17.02Z AND THEN LINGER THROUGH THE
NIGHT.
WITH THE LOW LEVEL CLOUDS BEING TRAPPED BY A SUBSIDENCE
INVERSION THROUGH THIS TIME PERIOD...KRST WILL REMAIN LIFR/IFR AND
KLSE WILL CONTINUE TO SEE MVFR CEILINGS.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
541 AM CST SUN DEC 16 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...HALBACH
LONG TERM...HALBACH
AVIATION...BOYNE
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
305 AM CST SUN DEC 16 2012
.SHORT TERM...TODAY THROUGH TUESDAY NIGHT
305 AM CST SUN DEC 16 2012
THE MAIN FOCUS OVER THE NEXT FEW DAYS IS ON THE DEPARTING
PRECIPITATION TODAY FOLLOWED BY THE CHANCE FOR SNOW ON TUESDAY.
LIGHT RAIN/DRIZZLE AND LIGHT SNOW WILL COME TO AN END FROM WEST TO
EAST TODAY AS A MID LEVEL SHORTWAVE TROUGH PROPAGATES TO THE NORTHEAST
INTO THE GREAT LAKES. AS OF 2 AM...SURFACE OBS AND DUAL POL RADAR
SHOWED THE RAIN/SNOW LINE FROM JUST WEST OF EAU CLAIRE WISCONSIN
DOWN TO WINONA MINNESOTA AND DECORAH IOWA. THE TRANSITION TO LIGHT
SNOW WILL BE RATHER BRIEF AND THEREFORE ANY SNOW ACCUMULATIONS
WILL BE ON THE LIGHT SIDE. EARLIER RUNS OF THE RAP HAD SHOWN THE
POSSIBILITY OF SOME FREEZING DRIZZLE OCCURRING AS THE SNOW CAME TO
AN END...BUT OBSERVATIONS/RADAR UPSTREAM IS NOT SHOWING ANY OF
THIS. DENSE FOG FORMED ACROSS MUCH OF THE REGION OVERNIGHT AS A
RESULT OF HIGH LOW LEVEL MOISTURE DUE TO RECENT RAIN AND SNOW MELT
ALONG WITH THE CORE OF A SURFACE LOW OVERHEAD WHICH PROVIDED
LIGHT TO CALM WINDS. AS THE COLD FRONT EXTENDING SOUTH FROM THE
LOW MOVES THROUGH...WINDS WILL PICK UP AND THE DENSE FOG WILL MIX
OUT WITH VISIBILITY IMPROVING. WITH VISIBILITY STILL LESS THAN A
QUARTER MILE IN NORTH CENTRAL WISCONSIN...WILL LET THE ADVISORY
ROLL FOR NOW WITH IT EXPIRING AT 6 AM...BUT MAY BE ABLE TO CLEAR
IT EARLY.
NOT THE CLEAREST OF WEATHER PATTERNS EXPECTED THROUGH THE NEXT FEW
DAYS WITH SUBTLE SYSTEMS MOVING INTO THE REGION THROUGH THE
SOUTHWEST-WESTERLY FLOW ALOFT. A WEAK MID LEVEL TROUGH WILL MOVE
THROUGH TODAY...BUT WILL ONLY ADD CLOUD COVER TO THE REGION.
16.00Z NAM/GFS SOUNDINGS SHOW THAT THE FORCING IS NOT VERY STRONG
AND THE DRY LAYER IS TOO DEEP FOR SEEDER FEEDER TO PRODUCE SOME
SNOW. A SURFACE RIDGE OF HIGH PRESSURE WILL THEN MOVE THROUGH THE
REGION TONIGHT INTO MONDAY BEFORE THE NEXT SYSTEM TAKES SHAPE IN
THE NORTHERN PLAINS. MUCH OF THE FORCING FOR THIS SYSTEM WILL BE
FROM THE LOW LEVEL WARM AIR ADVECTION...BUT THERE ALSO IS A MID
LEVEL TROUGH THAT ROTATES NORTHWARD INTO SOUTHERN CANADA OVER THE
SAME TIME FRAME. THE 16.00Z ECMWF IS THE STRONGEST WITH HAVING A
SURFACE LOW MOVE THROUGH...BUT OVERALL QPF REMAINS ON THE LIGHT
SIDE AT LESS THAN A TENTH OF AN INCH. PRECIPITATION TYPE WILL
MAINLY BE LIGHT SNOW WITH ANY ACCUMULATIONS LIKELY LESS THAN AN
INCH.
.LONG TERM...WEDNESDAY THROUGH SATURDAY
305 AM CST SUN DEC 16 2012
THE FOCUS FROM MID WEEK INTO NEXT WEEKEND CONTINUES TO BE WITH THE
POTENTIAL FOR A WINTER STORM WEDNESDAY NIGHT INTO THURSDAY. WHILE
THE SUITE OF 16.00Z GUIDANCE STILL ADVERTISES THIS DEEPENING
SURFACE LOW MOVING INTO SOUTHERN LAKE MICHIGAN BY THURSDAY
MORNING...THE TREND IS FOR THE MAJOR IMPACTS FROM THIS SYSTEM TO
BE MORE SO FELT TO THE SOUTH AND EAST OF THE FORECAST AREA. THE
FURTHER EAST THAT THIS SYSTEM CONTINUES TO MOVE...THE LOWER OUR
CHANCES BECOME OF SEEING THE HEAVIEST SNOW BAND OCCUR IN THE
FORECAST AREA. BASED ON 16.00Z GUIDANCE...THE WESTERN EDGE OF THE
SNOW APPEARS TO RUN FROM CENTRAL IOWA THROUGH SOUTHEAST MINNESOTA
AND NORTHWEST WISCONSIN. WHILE THE HEAVIEST SNOW BAND MAY BE TO THE
EAST OF THE FORECAST AREA...THE CHANCES FOR SNOW ACROSS THE REGION
STILL LOOK GOOD...SO HAVE BUMPED UP THE PRECIPITATION PROBABILITIES
WEDNESDAY NIGHT INTO THURSDAY. THIS SYSTEM IS CURRENTLY UP NEAR
THE ALEUTIAN ISLANDS WEST OF ALASKA AND WILL BE INTO CALIFORNIA BY
TUESDAY WHICH IS WHEN WE SHOULD HAVE A BETTER HANDLE ON THE
SYSTEMS TRACK.
BEHIND THIS SYSTEM...COLDER AIR WILL GET PULLED DOWN FROM SOUTHERN
CANADA...BUT IT APPEARS TO BE A FAIRLY SHORT LIVED COLD BURST
BEFORE LOW LEVEL WARM AIR ADVECTION STRENGTHENS OUT OF THE
SOUTHWEST ON SATURDAY. DUE TO THIS...HAVE TRENDED SLIGHTLY WARMER
FOR TEMPERATURES INTO THE WEEKEND.
&&
.AVIATION...THROUGH 06Z MONDAY
1126 PM CST SAT DEC 15 2012
SURFACE LOW NOW OVER WESTERN WISCONSIN WILL CONTINUE TO PULL
NORTHEAST TONIGHT. WRAP AROUND MOISTURE ON ITS BACK SIDE WAS
PUSHING THROUGH SOUTHEAST MINNESOTA AND WILL PASS ACROSS THE TAF
SITES THROUGH THE OVERNIGHT HOURS. VISIBILITIES HAVE IMPROVED AT
KRST DUE TO THE WIND SHIFT AND LIGHT PRECIPITATION. EXPECT THIS TO
OCCUR AT KLSE AROUND 08Z. THE TRANSITION FROM LIQUID TO SNOW WILL
OCCUR AT KRST BETWEEN 06Z-08Z AND AT KLSE BETWEEN 10Z-12Z. ONE
CONCERN IS RAP AND NAM BUFKIT SOUNDINGS SHOWING A LOSS OF ICE AND
THUS MAYBE SOME LIGHT FZDZ FOR A PERIOD OF TIME LATER THIS MORNING
BEFORE THE PRECIPITATION ENDS AND DID INCLUDE A TEMPO GROUP AT
BOTH SITES. OTHERWISE...CEILINGS WILL REMAIN IFR THROUGH AT LEAST
18Z AND MAY RISE INTO THE LOWER MVFR CATEGORY FOR THE AFTERNOON.
WITH THE MOISTURE TRAPPED UNDER THE INVERSION...SOME CONCERN AS TO
LOWERING CEILINGS/VISIBILITIES ONCE AGAIN AFTER 00Z AS COLUMN
COOLS.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
305 AM CST SUN DEC 16 2012
WI...DENSE FOG ADVISORY UNTIL 6 AM CST EARLY THIS MORNING FOR WIZ017-
029-034-042>044.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...HALBACH
LONG TERM...HALBACH
AVIATION...RABERDING
AREA FORECAST DISCUSSION
NWS DENVER/BOULDER CO
949 PM MST MON DEC 17 2012
.UPDATE...
&&
.SHORT TERM...NO CHANGES NEEDED THIS EVENING. WELL ORGANIZED
SHOWER BAND WILL DROP SOUTH ACROSS OUR AREA OVER THE NEXT 6 HOURS.
A LITTLE BIT OF THIS WAS GETTING EAST OF THE MOUNTAINS IN WYOMING
WITH A BRIEF SHOWER AT CHEYENNE...BUT STRONGER DESCENT OFF OF THE
HIGHER MOUNTAINS OF THE FRONT RANGE WILL LIKELY REDUCE THIS AS THE
BAND DROPS SOUTHWARD. CURRENT LOW POPS FOR LARIMER COUNTY IS ALL
WE HAVE ON THE PLAINS AND THAT LOOKS FINE. FOR THE MOUNTAINS THIS
BAND WILL ENHANCE SNOWFALL FOR A FEW HOURS AS IT
PASSES...AMOUNTS IN THE FORECAST LOOK PRETTY GOOD.
&&
.AVIATION...VFR WITH SOUTH WINDS THROUGH TUESDAY MORNING...WINDS
BECOMING MORE EASTERLY AND POSSIBLY EVEN NORTHEAST BY LATE TUESDAY
AFTERNOON WITH A SLIGHT CHANCE OF CEILINGS LOWERING ENOUGH FOR
INSTRUMENT APPROACHES TO KDEN IN THE LATE AFTERNOON. MORE LIKELY
THESE CONDITIONS WILL WAIT UNTIL EVENING WITH SNOW DEVELOPING
AFTER MIDNIGHT TUESDAY NIGHT.
&&
.PREV DISCUSSION... /ISSUED 334 PM MST MON DEC 17 2012/
SHORT TERM...WEB CAMS SHOWING SNOW ACROSS MOUNTAINS
CONTINUING...THOUGH A BIT IMPROVEMENT IN THE LAST FEW HOURS. ALSO
SOME GUSTS AROUND 50 MPH ALONG THE DIVIDE...WHICH HAS BEEN
CREATING AREAS OF BLOWING AND DRIFTING SNOW. LATEST SNOTEL OBS
SUGGESTING ABOUT 6 INCHES OF SNOW HAD FALLEN ACROSS ZONE 31 IN THE
LAST 6 HOURS...WITH PERHAPS 2 TO 4 INCHES FOR ZONES 33 AND 34.
ACROSS FOOTHILLS AND ALONG URBAN CORRIDOR...WESTERLY WINDS GUSTING
IN THE 30-40 MPH RANGE MOST AREAS. STRONG PACIFIC JET STILL
EXPECTED TO MOVE ACROSS NORTHERN COLORADO DURING THE EVENING AND
OVERNIGHT WITH STRONGER WINDS LOWERING TO NEAR MOUNTAIN TOP. MODEL
CROSS SECTIONS INDICATING INCREASING LAPSE RATES ALONG WITH MID
LEVEL ASCENT. SHOULD SEE MOUNTAIN SNOW BEGIN TO INCREASE AGAIN
DURING THE EVENING AS THE LIFT INCREASES. LOCAL SNOW MODEL STILL
YIELDING ROUGHLY 5-10 INCHES ACROSS ZONE 31 TONIGHT...WITH AROUND
4-8 INCHES FOR ZONES 33 AND 34. THIS LOOKS REASONABLE BUT MAY NEED
TO ADD A FEW INCHES FOR THE DYNAMICS. FEEL CURRENT WARNING FOR
ZONE 31 AND ADVISORY FOR 33 STILL ON TRACK. BUT WILL ALSO INCLUDE
ZONE 34 IN THE ADVISORY...THOUGH AMOUNTS MAY NOT MEET CRITERIA
THERE WILL BE SUFFICIENT BLOWING SNOW. ACROSS PLAINS SHOULD SEE
WINDS BEGIN TO DECOUPLE THOUGH WILL REMAIN A BIT GUSTY NEAR THE
FOOTHILLS. LATEST RUC SHOWS SOME LIGHT PRECIP ACROSS ZONE 38 THIS
EVENING...STILL LOOKS REASONABLE WITH THE APPROACHING LIFT. ON
TUESDAY...FLOW ALOFT WEAKENS A BIT AS THE JET CORE HEADS EAST AND
BECOMES MORE SOUTHWEST AS AN UPPER TROUGH APPROACHES THE GREAT
BASIN. WILL STILL BE A BIT GUSTY ACROSS THE RIDGES. SOUTHWEST FLOW
NOT FAVORABLE FOR DECENT MOUNTAIN SNOWFALL. MID LEVEL QG ACENT
ALSO DECREASES. WOULD EXPECT SNOW TO CONTINUE WITH FAIRLY GOOD
MOISTURE...BUT SHOULD BE LIGHT. WILL NOT EXTEND HILITES BEYOND
12Z. ACROSS PLAINS...SURFACE WINDS TO BECOME EASTERLY WITH THE
DEVELOPMENT OF AN ANTICYCLONE. LATEST GFS AND ECMWF SHOWS SOME
LIGHT QPF DURING THE AFTERNOON...MAY BE A BIT OVERDONE AS LOW
LEVEL STILL LOOK DRY.
LONG TERM...MODELS CONTINUE TO ADVERTISE A SIGNIFICANT WINTER
WEATHER EVENT ACROSS THE FORECAST AREA ON WEDNESDAY. FROM TUESDAY
EVENING THROUGH WEDNESDAY EVENING AN UPPER TROUGH WILL BE MOVING
OVER THE STATE WHILE A SURFACE LOW OVER SOUTHEAST COLORADO
UNDERGOES STRONG CYCLOGENESIS. A STRONG COLD FRONT WILL MOVE OVER
NORTHERN COLORADO...INCLUDING THE MOUNTAINS...TUESDAY EVENING.
UPSLOPE WINDS WILL THEN CONTINUE THROUGH THE PRE-DAWN HOURS AND
STRENGTHEN THROUGH THE DAY WEDNESDAY. THE UPPER TROUGH WILL
CONTAIN PLENTY OF DYNAMICS ACCORDING TO THE Q-G DIAGNOSTICS
PACKAGE. THE PRESENCE OF THE STRONG UPPER LEVEL JET OVER THE PAST
FEW DAYS MAKE THE MODEL SOLUTIONS VERY BELIEVABLE. THE NAM QPF
AMOUNTS ARE A FAIR AMOUNT HIGHER THAN THE GFS AND ECMWF SOLUTIONS
CONCERNING HOW MUCH SNOW WE GET ON WEDNESDAY. ALL MODELS AGREE
QUITE A BIT OF WIND DEVELOPING. WITH THE THREAT OF SIGNIFICANT
BLOWING SNOW BECAUSE OF THE WIND...WILL ISSUE A WINTER STORM WATCH
ACROSS THE PLAINS. SNOW AMOUNTS OF 3 TO 6 INCHES WILL BE TOO LIGHT
IF THE NAM IS RIGHT. WIND GUSTS OF 25 TO 40 MPH MIGHT BE COMMON AT
THE HEIGHT OF THE STORM. PERIODS OF SNOW WILL BE ONGOING IN THE
MOUNTAINS DUE TO THE DYNAMICS OVER THE STATE.
THE UPPER TROUGH WILL BE MOVING EAST OF COLORADO BY WEDNESDAY
EVENING WHICH WILL BRING A RAPID END TO THE SNOW EVENT. LINGERING
SHOWERS IN THE EVENING WILL COME TO AN END OVERNIGHT. FOR THE
PERIOD THURSDAY THROUGH SUNDAY...STRONG UPPER RIDGING WILL BE OVER
THE STATE WITH DRY WEATHER FROM THE MOUNTAINS EASTWARD WITH
TEMPERATURES TRENDING TOWARD SEASONAL NORMALS.
EARLY NEXT WEEK LOOKS LIKE ANOTHER TROUGH MAY BE APPROACHING THE
STATE IF THE ECMWF IS CORRECT. FOR THE TIME BEING WILL JUST
MENTION AN INCREASING CHANCE OF SNOW IN THE MOUNTAINS AS THE STATE
COMES UNDER THE SOUTHWESTERLY FLOW AHEAD OF THE TROUGH.
AVIATION...WESTERLY WINDS TO CONTINUE ACROSS THE DENVER
AREA THROUGH 02Z...WITH SOME GUSTS TO TO 35 KTS. WINDS TO DECREASE
AT DEN AND APA AND BECOME SOUTHWESTERLY DURING THE EVENING BUT
SHOULD REMAIN WESTERLY AND GUSTY AT BJC. AFTER 15Z TUESDAY...
MODELS SHOW THE DEVELOPMENT OF AN ANTICYCLONE IN THE DENVER
AREA...WITH WIND BECOMING EASTERLY. VFR TO CONTINUE WITH NO
PRECIPITATION EXPECTED.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY
AFTERNOON FOR COZ038>051.
WINTER WEATHER ADVISORY UNTIL 5 AM MST TUESDAY FOR COZ033-034.
WINTER STORM WARNING UNTIL 5 AM MST TUESDAY FOR COZ031.
&&
$$
SHORT TERM...D-L
LONG TERM....DANKERS
AVIATION/UPDATE...GIMMESTAD
AREA FORECAST DISCUSSION
NWS DES MOINES IA
345 AM CST TUE DEC 18 2012
...SIGNIFICANT WINTER STORM TO IMPACT THE MIDWEST AND PLAINS
WEDNESDAY AND THURSDAY...
.SHORT TERM /TODAY/...
LOW CLOUDS CONTINUE OVER MUCH OF THE AREA THIS MORNING DUE TO
STRATUS THAT HAS DEVELOPED OVER THE PAST 24 TO 36 HOURS WITH HIGH
PRESSURE OFF TO EAST AND WEAK LOW PRESSURE ALOFT. ANOTHER WAVE IS
CURRENTLY DROPPING SOUTHEAST AND IS LOCATED NEAR THE SOUTH DAKOTA
AND NEBRASKA BORDER THIS MORNING. A WARM FRONT IS DEVELOPING OVER
IOWA NOW AND AT H850-H700 FORCING IS INCREASING ACROSS NORTHWEST
IOWA NOW WITH LIGHT SNOW BEGINNING TO SHOW UP ON RADAR. THE AREA IS
LIFTING TO THE EAST WITH TIME AND SHOULD AFFECT MAINLY FOLKS ALONG
AND NORTH OF HIGHWAY 20 WITH SOME LIGHT PRECIPITATION POSSIBLE TO
HIGHWAY 30. RIGHT ALONG THE IA AND MN BORDER UP TO AN INCH OF SNOW
MAY FALL THROUGH MIDDAY BEFORE THE WEAK SYSTEM AND FORCING MOVES
EAST. OVER THE SOUTH THE BACK EDGE OF THE STRATUS EXTENDS TO NEAR
OMAHA BUT IS ERODING ON THE SOUTH EDGE AS WARM AIR ADVECTION
INCREASES EARLY TODAY. BY THE NOON HOUR THERE WILL BE SOME BREAKS
ACROSS THE SOUTH WHICH SHOULD HELP PUSH AFTERNOON HIGHS BACK INTO
THE LOWER 40S. ACROSS THE NORTH THE CLOUDS WILL HOLD ON LONGER AND
KEEP HIGHS IN THE MID 30S. WINDS WILL BE LIGHT ACROSS THE REGION
TODAY FROM THE SOUTHEAST AND THEN SWITCHING TO THE NORTHWEST BY
AFTERNOON AND EVENING.
.LONG TERM /TONIGHT THROUGH MONDAY/...
MAIN FOCUS IS ON THE MAJOR WINTER STORM TO IMPACT CENTRAL IOWA
WEDNESDAY NIGHT AND THURSDAY. THE STORM IS JUST COMING ONSHORE NOW
AND WILL PUSH INTO THE AREA WEDNESDAY NIGHT AND THURSDAY. SOUNDINGS
SHOW THE WEST SATURATING QUICKLY WEDNESDAY AFTERNOON THEN MOISTURE
SPREADS EAST/NORTHEASTWARD. COLD AIR WRAPS QUICKLY INTO THIS
SYSTEM SO PRECIP SHOULD QUICKLY CHANGE OVER TO SNOW CWA WIDE BY
EVENING. SNOW RATIOS WILL BE FAIRLY HIGH WITH THIS SYSTEM AS WELL
GIVEN THE AMOUNT OF COLD AIR. FORCING IS VERY IMPRESSIVE WITH THIS
SYSTEM AND THIS WILL PRODUCE HIGHER PRECIP RATES. THE EURO AND GFS
DO BOTH HAVE A BAND OF HIGHER QPF IN THE CORRIDOR OF BETTER FORCING
FROM ROUGHLY WATERLOO TO AUDUBON SO I TRIED TO ADJUST SNOWFALL IN
THIS AREA.
I WAS LOOKING AT WHETHER OR NOT TO KICK TO WATCH UP A NOTCH TO A
BLIZZARD WATCH GIVEN THE STRONG NORTH WINDS THAT WILL ACCOMPANY THIS
STORM. SUSTAINED WINDS OF 30 TO 40 MPH ARE QUITE LIKELY WITH SOME
POTENTIAL OF GUSTS 40+ MPH. AT THIS POINT HOWEVER WE HAVE NO SNOW
ON THE GROUND AND I RECALL THAT TO GET REDUCED VISIBILITY FOR A
SUSTAINED PERIOD OF TIME THERE SHOULD BE SOME EXISTING SNOW COVER.
HOWEVER...I DO EXPECT SNOW TO BEGIN IN EARNEST IN THE EVENING AND
THE STRONGEST WINDS TO NOT IMPACT THE AREA UNTIL BETWEEN 09Z AND 12Z
SO WITH 6 TO 9 HOURS OF SNOWFALL PRIOR TO THE ONSET OF THE WIND...WE
SHOULD HAVE A SUFFICIENT BLANKET ON THE GROUND. CONFIDENCE BETWEEN
OFFICES STILL NOT HIGH ENOUGH TO GO BLIZZARD WATCH AS WE ARE STILL
TRYING TO DEFINE WHERE THE HEAVIEST SNOW BAND WILL SET UP. AS A
RESULT WE WILL LEAVE THE WATCH A WINTER STORM WATCH AND HAVE A LOOK
AT ONE MORE MODEL RUN BEFORE MAKING THAT DECISION.
FOR THE REMAINDER OF THE EXTENDED I GENERALLY LOWERED TEMPS IN
ANTICIPATION OF A SNOW PACK THAT WILL KEEP TEMPS LOWER. MOST OF THE
REMAINDER OF THE EXTENDED LOOKS QUIET WITH TEMPS SLOWLY RECOVERING.
THERE IS POTENTIAL FOR ANOTHER SYSTEM TO AFFECT THE AREA NEXT
TUESDAY INTO WEDNESDAY BUT WITH MODEL DISCREPANCIES AND THE
IMPENDING STORM THIS WEEK...I HAVE JUST PLACED POPS IN THE GRIDS
DURING THE TIMEFRAME MOST LIKELY TO SEE PRECIP.
&&
.AVIATION...18/06Z
SOMEWHAT LOW CONFIDENCE THIS SET WITH VARIABLE CONDITIONS STATEWIDE
AT 0530Z...MVFR/IFR EAST DOWN TO IFR/LIFR WEST. WEAK FRONTAL
BOUNDARY THROUGH CENTRAL IA BECOMING SOMEWHAT DIFFUSE THAN NOTED
EARLIER. LATEST RAP SEEMS TO HAVE BEST HANDLE ON REALITY RIGHT NOW
WITH HIGHER LOW LEVEL MOISTURE AND WILL BE FOLLOWED FOR GUIDANCE.
THIS RESULTS IN IFR CONDITIONS OVER MOST LOCATIONS OVERNIGHT AS LOW
LEVEL MOISTURE REMAINS TRAPPED IN LIGHT SELY WINDS. CONDITIONS
SHOULD IMPROVE SOMEWHAT BY MIDDAY CENTRAL AND SOUTH BUT MAY REMAIN
AT LEAST MVFR NORTH...NORTH OF FRONTAL BOUNDARY WHERE THERE COULD
ALSO BE SOME LIGHT SNOW EARLY THIS MORNING. WINDS WILL ALSO
INCREASE SOMEWHAT BY TUE AFTERNOON...BUT NOT AS MUCH AS PREVIOUSLY
ANTICIPATED.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
AFTERNOON FOR ADAIR-ADAMS-APPANOOSE-AUDUBON-BLACK HAWK-BOONE-
BREMER-BUTLER-CALHOUN-CARROLL-CASS-CLARKE-CRAWFORD-DALLAS-DAVIS-
DECATUR-FRANKLIN-GREENE-GRUNDY-GUTHRIE-HAMILTON-HARDIN-JASPER-LUCAS-
MADISON-MAHASKA-MARION-MARSHALL-MONROE-POLK-POWESHIEK-RINGGOLD-SAC-
STORY-TAMA-TAYLOR-UNION-WAPELLO-WARREN-WAYNE-WEBSTER-WRIGHT
&&
$$
SHORT TERM...DONAVON
LONG TERM...COGIL
AVIATION...SMALL
AREA FORECAST DISCUSSION
NWS DES MOINES IA
1135 PM CST MON DEC 17 2012
...SIGNIFICANT WINTER STORM TO IMPACT THE MIDWEST AND PLAINS
WEDNESDAY AND THURSDAY...
.SHORT TERM /TONIGHT/...
LOW PRESSURE OVER NORTHEAST WYOMING WILL SHIFT EAST ACROSS SOUTH
DAKOTA AND NEBRASKA AND REACH NORTHWEST IOWA LATE TONIGHT. AN
ASSOCIATED UPPER LEVEL SHORT WILL SPREAD INCREASING QG FORCING
ACROSS CENTRAL IOWA. IN ADDITION...STRONG THETA-E ADVECTION WILL
ARRIVE AFTER MIDNIGHT THROUGH CENTRAL AND NORTHWEST IOWA. THE BEST
COMBINATION OF FORCING IS OVER CENTRAL IA NEAR DES MOINES AND AMES
BETWEEN 3 AM TO 6 AM HOWEVER THE DEEPER MOISTURE WILL BE FARTHER
NORTH. TYPICALLY THIS TIME OF YEAR FORCING TRUMPS DEEP MOISTURE
THEREFORE CERTAINLY SHOULD HAVE PRECIPITATION FARTHER SOUTH THAN
WHAT MOST MODEL GUIDANCE PRECIPITATION FIELDS WOULD SUGGEST. WARM
ADVECTION IN THE LOW LEVELS IS EXPECTED AS WELL OVERNIGHT RESULTING
IN NON-DIURNAL TEMPERATURES. THIS COULD SWITCH PRECIPITATION TYPE TO
RAIN ON THE SOUTHERN FRINGES. NOT CONFIDENT IN POTENTIAL OF FREEZING
RAIN WITH UNCERTAINTY IN ARRIVAL OF WARMER AIR ALOFT...THOUGH CAN
NOT TOTALLY DISCOUNT. POTENTIAL AS WELL FOR POCKETS OF LOWER
VISIBILITIES DUE TO FOG THOUGH LOW LEVEL WARM ADVECTION SHOULD LIMIT
AREAL COVERAGE OF VISIBILITIES BELOW 2SM.
.LONG TERM /TUESDAY THROUGH MONDAY/...
WILL SEE SOME LINGERING POPS IN THE NORTH ON TUESDAY MORNING AS THE
SYSTEM GRADUALLY DEPARTS TO THE EAST. SOME LIGHT ACCUMULATIONS WILL
STILL BE POSSIBLE AROUND MASON CITY BEFORE MIDDAY BUT PCPN IS
EXPECTED TO END BY MIDDAY. THE WEATHER WILL BE TRANQUIL FROM TUESDAY
AFTERNOON INTO EARLY WEDNESDAY MORNING BEFORE MAJOR SYSTEM BEGINS TO
AFFECT THE FORECAST AREA.
THIS MAJOR STORM IS CURRENTLY OFF THE WEST COAST AND WILL COME
ASHORE LATE TONIGHT INTO TUESDAY. THEREFORE...THERE IS LITTLE
RESOLUTION OF THE SYSTEM BY THE UPPER AIR NETWORK WHICH IS LIKELY
CAUSING SOME OF THE DIFFERENCES SEEN IN THE MODEL RUNS. INITIALLY
ON WEDNESDAY...RIDGE AXIS WILL BE IN PLACE ACROSS THE NORTHEAST WITH
RELATIVELY QUITE WEATHER. HOWEVER...BY MIDDAY...FORCING WILL
RAPIDLY INCREASE AS ISENTROPIC LIFT BEGINS IN EARNEST. STRONG
FRONTOGENETICAL FORCING ALSO ARRIVES ACROSS CENTRAL INTO NORTHERN
IOWA BY LATE AFTERNOON WHICH WILL LIKELY ENHANCE PCPN RATES IN THOSE
LOCATIONS. PCPN WILL BREAK OUT DURING THE AFTERNOON AND INCREASE IN
BOTH COVERAGE AND INTENSITY AS THE AFTERNOON PROGRESSES. SNOW IS
EXPECTED ALONG AND NORTH OF AN ATLANTIC TO WATERLOO LINE WITH A BAND
OF MIXED PCPN OF 50 MILES WIDE OR SO SOUTH OF THE SNOW. RAIN IS
EXPECTED ALONG THE MISSOURI BORDER AS READINGS REMAIN ABOVE
FREEZING.
CONDITIONS DETERIORATE RAPIDLY ON WEDNESDAY NIGHT AS COLD ADVECTION
INTENSIFIES ACROSS THE STATE. UPPER SYSTEM WILL EJECT FROM SOUTHERN
PLAINS AND RACE NORTHEAST TO NEAR QUINCY ILLINOIS BY DAYBREAK.
SYSTEM WILL BE DEEPENING AND BECOMING NEGATIVELY TILTED WITH TIME AS
SURFACE LOW STRENGTHENS. PCPN ACRS THE FORECAST AREA WILL BECOME
ALL SNOW BY MIDNIGHT AS COLD AIR IS DRAWN SOUTHWARD. WINDS ARE
LIKELY TO BECOME A VERY SERIOUS ISSUE AFTER MIDNIGHT AND CERTAINLY
BY DAYBREAK ON THURSDAY. 925MB WINDS WILL BE NEAR OR EVEN SLIGHTLY
ABOVE 50KTS WITH MOS OUTPUT SHOWING SUSTAINED WINDS OF 30KTS IN MANY
LOCATIONS IN CENTRAL IOWA. THIS EVENT MAY BECOME MORE OF A BLIZZARD
INTO THURSDAY MORNING AS THE WINDS INCREASE AND WILL HAVE TO BE
MONITORED CLOSELY. SNOW ON WEDNESDAY NIGHT WILL BE HEAVIEST IN THE
EVENING AS MID LEVEL FORCING IS MAXIMIZED. SOME CONVECTIVE SNOW
WILL BE POSSIBLE AS WELL WITH NEGATIVE EPV ACROSS MUCH OF THE STATE
WITH DECENT MID LEVEL LAPSE RATES. CONDITIONS WILL BE POOR ON
THURSDAY MORNING WITH VERY STRONG WINDS DESPITE THE SNOWFALL
ENDING. GIVEN ALL OF THIS...HAVE ISSUED A WINTER STORM WATCH FOR
MUCH OF CENTRAL IOWA FROM MIDDAY WEDNESDAY INTO THURSDAY FOR THE
POTENTIAL OF HEAVY SNOWFALL AND VERY STRONG WINDS. AN UPGRADE TO
BLIZZARD WATCH MAY BE NEEDED SHOULD FORECAST WINDS REMAIN STRONG OR
INCREASE.
THE WEATHER BEYOND THURSDAY IS RELATIVELY QUIET WITH LITTLE CHANGE
IN THE FORECAST. MAIN CONCERN IS THAT TEMPERATURES WOULD BE TOO
WARM GIVEN THE FRESH SNOW COVER ACROSS THE AREA.
&&
.AVIATION...18/06Z
SOMEWHAT LOW CONFIDENCE THIS SET WITH VARIABLE CONDITIONS STATEWIDE
AT 0530Z...MVFR/IFR EAST DOWN TO IFR/LIFR WEST. WEAK FRONTAL
BOUNDARY THROUGH CENTRAL IA BECOMING SOMEWHAT DIFFUSE THAN NOTED
EARLIER. LATEST RAP SEEMS TO HAVE BEST HANDLE ON REALITY RIGHT NOW
WITH HIGHER LOW LEVEL MOISTURE AND WILL BE FOLLOWED FOR GUIDANCE.
THIS RESULTS IN IFR CONDITIONS OVER MOST LOCATIONS OVERNIGHT AS LOW
LEVEL MOISTURE REMAINS TRAPPED IN LIGHT SELY WINDS. CONDITIONS
SHOULD IMPROVE SOMEWHAT BY MIDDAY CENTRAL AND SOUTH BUT MAY REMAIN
AT LEAST MVFR NORTH...NORTH OF FRONTAL BOUNDARY WHERE THERE COULD
ALSO BE SOME LIGHT SNOW EARLY THIS MORNING. WINDS WILL ALSO
INCREASE SOMEWHAT BY TUE AFTERNOON...BUT NOT AS MUCH AS PREVIOUSLY
ANTICIPATED.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
AFTERNOON FOR ADAIR-ADAMS-APPANOOSE-AUDUBON-BLACK HAWK-BOONE-
BREMER-BUTLER-CALHOUN-CARROLL-CASS-CLARKE-CRAWFORD-DALLAS-DAVIS-
DECATUR-FRANKLIN-GREENE-GRUNDY-GUTHRIE-HAMILTON-HARDIN-JASPER-LUCAS-
MADISON-MAHASKA-MARION-MARSHALL-MONROE-POLK-POWESHIEK-RINGGOLD-SAC-
STORY-TAMA-TAYLOR-UNION-WAPELLO-WARREN-WAYNE-WEBSTER-WRIGHT
&&
$$
SHORT TERM...DONAVON
LONG TERM...COGIL
AVIATION...SMALL
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
1123 PM CST MON DEC 17 2012
.AVIATION...
STRATUS AND PATCHY FOG WILL LIKELY REMAIN IN PLACE OVERNIGHT...WITH
INTERVALS OF PARTIAL CLEARING POSSIBLE. LIGHT SNOW OR FLURRIES MAY
IMPACT CID...DBQ POSSIBLY TOWARD DAWN TUESDAY UNTIL MID DAY. LINGERING
LOW LEVEL MOISTURE AND LIGHT WINDS WILL CONTINUE IFR AND POSSIBLE
LIFR CONDITIONS DUE TO LOW CIGS AND POSSIBLY FOG THROUGH THE
LATE MORNING...MAINLY AT DBQ AND POSSIBLY AT CID TERMINALS. BRL AND
MLI TERMINALS ARE MORE FAVORED FOR MVFR CONDITIONS. A FAST MOVING
LOW PRESSURE SYSTEM MOVING OUT OF THE ROCKIES WILL PASS NEAR
HIGHWAY 30 CORRIDOR TUESDAY AFTERNOON WITH VFR CONDITIONS AND
PARTLY CLOUDY SKIES AT BRL...MLI AND PROBABLY CID TERMINALS. DBQ
TERMINAL SHOULD IMPROVE TO MVFR BY LATE TUESDAY AFTERNOON.
NICHOLS
&&
.PREV DISCUSSION... /ISSUED 905 PM CST MON DEC 17 2012/
UPDATE...
ONLY MINOR CHANGES TO OVERNIGHT PACKAGE. ANALYSIS AND VERIFICATION
CONFIRMS A COLDER TREND WITH A SOUTHEAST SLIDE IN SURFACE LOW
TRACK ON AMERICAN SOLUTIONS. 00Z NAM ANALYSIS SUGGESTS STILL
PLAYING CATCH UP WHICH HAS BEEN COMMON FOR A WHILE WITH THIS MODEL.
WILL BE SENDING OUT UPDATED WSW...OR WINTER STORM WATCH PRODUCT
SHORTLY WITH MENTION OF HIGHER WINDS GUSTING UP TO NEAR 50 MPH ON
BACK SIDE AND BLIZZARD TO NEAR BLIZZARDS SUPPORTED PER LOCAL STUDIES
AND TECHNIQUES. THE LOCAL IMPACTS OF WHERE THESE CONDITIONS ARE TO
OCCUR STILL TOO UNCERTAIN TO ASSESS IF AND EVEN HOW MUCH OF THE
FORECAST COULD BE IMPACTED...THIS IS LIKELY STILL 12-24 HOURS AWAY.
WHAT IS CERTAIN IS THE STRONG WINDS WITH THE SNOW AND CERTAIN NEAR
BLIZZARD CONDITIONS TO POSSIBLY BLIZZARD CONDITIONS IN THE COLD
DEFORMATION ZONE IN RURAL AND OPEN AREAS AT A MINIMUM. THE UPDATED
WSW PRODUCT SHOULD BE OUT WITHIN THE NEXT HALF HOUR.
NICHOLS
PREV DISCUSSION...
SYNOPSIS...
LIGHT WINDS AND LINGERING LOW LEVEL MOISTURE HAS KEPT LOW CLOUDS AND
LIGHT FOG IN PLACE TODAY ACROSS THE FORECAST AREA. AS A RESULT...
TEMPERATURES HAVE STRUGGLED TO CLIMB...HAVING ONLY REACHED THE UPPER
20S NORTH TO MID 30S SOUTH THIS AFTERNOON. MSAS ANALYSIS INDICATED A
RIDGE OF HIGH PRESSURE REACHED FROM TX TO MN...FLANKED BY LOW
PRESSURE MOVING ALONG A COLD FRONT IN NORTHERN KY TO THE SE...AND A
LEE TROUGH REACHING FROM NORTHERN MT TO EASTERN CO. IN THE UPPER
LEVELS...A TROUGH AXIS REACHED FROM THE EASTERN DAKOTAS TO THE MO
BOOTHEEL REGION. UPSTREAM...12Z ANALYSIS INDICATED A 160 KT JET AT
300 MT MOVING IN THE STRONG...NEARLY ZONAL FLOW...ACROSS NORTHERN CA
INTO THE GREAT BASIN REGION. AN UPPER LOW WAS OFF THE NORTHERN BC
COAST WITH A TROUGH AXIS EXTENDING S-SW INTO THE PACIFIC.
SHORT TERM...TONIGHT AND TUESDAY...
DEVELOPING ACTIVE PATTERN WILL SEND ANOTHER ROUND OF PRECIPITATION
THROUGH THE REGION TONIGHT INTO EARLY TUESDAY. FORECAST CHALLENGES
CENTER ON THIS PRECIPITATION LATE TONIGHT INTO TUESDAY...ALONG WITH
LOW CLOUDS AND FOG.
LATEST VISIBLE SATELLITE IMAGES SHOW AN AREA OF CLOUDS OVER NORTH
CENTRAL MO INTO SOUTHERN IA...SLOWLY MIGRATING EASTWARD WITH THE
UPPER LEVEL TROUGH. AS THIS EXTENDS EASTWARD INTO THE SOUTHERN THIRD
OF THE FORECAST AREA AROUND SUNSET...THERE WILL BE A POTENTIAL FOR
THICKENING OF THE FOG THAT HAS LINGERED OVER SE IA AND ADJACENT
AREAS OF MO AND IL THIS EVENING. BASED ON LATEST RAP LOW LEVEL
MOISTURE FIELDS...STRATUS WILL LIKELY REMAIN IN PLACE THROUGH THE
NIGHT OVER THE REMAINDER OF THE FORECAST AREA...AND LIKELY FILL BACK
IN ANY HOLES THAT DEVELOP ACROSS THE SOUTH. WILL GO WITH PATCHY FOG
WORDING FOR NOW AND MONITOR THE SOUTH THIS EVENING FOR POSSIBLE
UPDATES TO MORE DENSE OR WIDESPREAD COVERAGE. A STRIKE AGAINST FOG
TONIGHT WILL BE THE INCOMING SUBSIDENCE BEHIND THE UPPER LEVEL WAVE
AND INCREASING WINDS TOWARD MORNING AS A SURFACE LOW APPROACHES.
AS SEEN TODAY...CLOUDS...LINGERING MOISTURE AND WEAK WINDS WILL
LIMIT DIURNAL TEMPERATURE CURVES AND HAVE KEPT MINS CLOSE TO CURRENT
DEWPOINTS...FROM THE MID 20S NORTH TO LOWER 30S SOUTH.
THE FOCUS THEN TURNS TO AN IMPULSE IN THE FAST ZONAL FLOW ALOFT THAT
WAS MOVING ACROSS CENTRAL ID AT MIDDAY. MODELS DEVELOP THIS INTO A
CLIPPER LIKE LOW PRESSURE SYSTEM AS THE ENERGY MOVES OVER THE LEE
TROUGH TONIGHT. THIS FAST MOVING LOW DEVELOPS OVER NEB LATE
TONIGHT...THEN HEADS EASTWARD OVER THE FORECAST AREA DURING THE
DAY TUESDAY. HAVE GENERALLY FOLLOWED A BLEND OF THE GFS/ECMWF AND
GEM WITH THIS FEATURE...WHICH DEVELOPS A NW TO SE ORIENTED WARM
ADVECTION WING OF LIGHT SNOW OVER THE CENTRAL PART OF THE FORECAST
AREA BETWEEN 06Z AND 12Z AND HAVE KEPT CHANCE POPS THERE. THE
POTENTIAL FOR LIGHT SNOW OR FLURRIES SHOULD THEN SHIFT TO THE FAR
NORTH AND NORTHEAST BY AFTERNOON AS THE LOW MOVES TOWARD CHICAGO.
WITH LIMITED MOISTURE AND RAPID PROGRESSION...SNOWFALL AMOUNTS
SHOULD BE WELL BELOW AN INCH IN MOST LOCATIONS WITH THE BEST CHANCES
OF A LIGHT COATING NORTH OF THE HIGHWAY 30 CORRIDOR. HAVE TRENDED
SOME PARTIAL CLEARING FROM SW TO NE IN THE AFTERNOON...BUT THIS MAY
END UP BEING TOO OPTIMISTIC DUE TO THE LINGERING MOISTURE AND
CYCLONIC FLOW THROUGH THE AFTERNOON. BRISK WESTERLY WINDS IN THE FAR
SOUTH MAY ALLOW TEMPERATURES TO REACH THE UPPER 40S...WHILE HIGHS IN
THE NORTH ARE KEPT IN THE UPPER 30S.
SHEETS
LONG TERM...TUESDAY NIGHT THROUGH NEXT MONDAY...
ALL LONG TERM FCST ENERGY INTO HANDLING MIDWEEK STORM SYSTEM...WITH
THE WEEKEND LOOKING IN BETWEEN SYSTEMS AND RATHER BENIGN/SEASONABLE
ANYWAY THROUGH EARLY MONDAY. ASSESSING THE LATEST 12Z MEDIUM RANGE
MODEL RUNS AS WELL AS THE NAM...SURPRISINGLY GOOD AGREEMENT WITH
GENERAL SFC LOW AND MID LEVEL LOW PATHS BUT WITH SOME TRACKING
SPEED AND STRENGTH VARIANCES. THIS TAKING INTO ACCOUNT BULK OF WAVE
ENERGY THAT WILL DRIVE THE STORM STILL OFF THE PACIFIC NORTHWEST
COAST AND SOUTH OF THE GULF OF AK. ALL MODELS BUT THE 12Z ECMWF THAT
IS. WHILE THE OTHERS HAVE TRENDED FURTHER NORTH AND WEST WITH THEIR
LATEST 12Z RUNS WHICH MAKE FOR MORE OF A PRECIP TYPE/AMOUNT CHALLENGE
FOR THE DVN CWA...THE CONSISTENT ECMWF WOULD STILL IMPACT MOST OF THE
LOCAL FCST AREA WITH A QUICKER SWITCH OVER TO SNOW AND MORE AREAS
STARTING OFF AS SNOW TO BEGIN WITH. THE ENSEMBLE SFC LOW TRACK OF
THE 12Z GFS/NAM/UKMET/GEM ALL HOOK THE DEVELOPING LOW FROM THE OK
PANHANDLE ON WED UP THROUGH NORTHEAST MO/WEST CENTRAL IL LATE WED
NIGHT...TO A NORTH CENTRAL IL POSITION BY THU MORNING...AND THEN
BOMB IT OUT ACRS LOWER MI INTO THU EVENING. THE 12Z EURO MAINTAINS
A TRACK FURTHER TO THE SOUTHEAST OF THE ENSEMBLE PATH...SOUTHWEST MO
TO NEAR THE STL AREA BY THU MORNING AND THEN OFF TO WEST CENTRAL
INDIANA BY EARLY THU AFTERNOON. THE ENSEMBLE OF SOLUTIONS BESIDES THE
ECMWF WOULD GENERALLY SUGGEST MUCH OF THE SOUTHEAST HALF TO TWO
THIRDS OF THE FCST AREA TO BE RAIN OR EVEN EXPERIENCE SOME
CONVECTION THROUGH MIDNIGHT WED NIGHT...WHILE THE NORTHWEST THIRD
MIXES AND DYNAMICALLY COOLS INTO WET ACCUMULATING SNOW AFTER 03Z
THU. AS DEF ZONE CONTINUES TO FORM AND LLVL COLD CONVEYOR IN-WRAPS
AND INCREASES...THESE MODELS GENERALLY SUGGEST THE SWITCH OVER TO
WET SNOW TO CONTINUE FROM WEST-NORTHWEST TO THE EAST AFTER MIDNIGHT
AND INTO EARLY THU MORNING ACRS THE DVN CWA. 3-7 INCHES POSSIBLE BY
12Z THU ALONG AND WEST OF A LINE FROM SIGOURNEY IA...TO EAST OF
CEDAR RAPIDS AND TO WEST OF DBQ. SOME ADDITIONAL ACCUMS OF 1-2
INCHES IN THESE AREAS POSSIBLE THROUGH 18Z THU...BUT BULK OF
ACCUMULATING SNOW TO SWITCH EASTWARD ACRS THE REST OF THE CWA WITH 3-
6 INCHES POSSIBLE ALONG AND NORTH OF A LINE FROM MT PLEASANT IA...TO
THE QUAD CITIES..AND TO STERLING IL.
WHILE THE NORTHWEST THIRD AND NORTH CENTRAL PORTIONS OF THE DVN CWA
MAY EVENTUALLY GET 4-8+ INCHES BY THU EVENING...THE ENSEMBLES MINUS
THE ECMWF SUGGEST THE HIGHEST SNOWFALL TOTALS OF 8-12+ INCHES OCCUR
WEST AND NORTH OF THE DVN CWA ACRS SOUTH CENTRAL IA...UP THROUGH
NORTHEASTERN IA INTO SW/CENTRAL WI. EXTENT OF BOMBING CYCLONE TO THE
EAST STILL INDICATED BY BULK OF THE MODEL RUNS TO DRIVE VERY STRONG
NORTH BECOMING NORTHWEST WINDS LATE WED NIGHT AND ESPECIALLY ON
THU...SUSTAINED 25 TO 35 MPH WITH GUSTS TO AT LEAST 45 MPH. GRAVITY
WAVE PHENOMENA WEST OF RAPIDLY DEEPENING CYCLONE COULD ALSO PRODUCE
ISOLATED GUSTS OVER 50 MPH AT MAX DEEPENING STAGE ON THU. THUS WHERE
ACCUMULATING SNOWS OCCUR...NEAR BLIZZARD OR BLIZZARD CONDITIONS VERY
POSSIBLE. BACK TO THE ECMWF...IT/S TRACK WOULD MEAN MORE OF A DIRECT
HIT UPON THE LOCAL AREA AND HIGHER SNOW AMOUNTS FURTHER EAST AND
SOUTH...ESPECIALLY TAKING INTO ACCOUNT SOME FUJI-WARA EFFECT OF
SECONDARY VORT INTERACTING IN TROF BASE AND ENHANCING DEF ZONE SNOWS
ACRS THE LOCAL AREA ON THU. DESPITE ONGOING MODEL UNCERTAINTY AND
THE SYSTEM TO BE BETTER SAMPLED FOR THE 00Z RUNS TONIGHT AND
ESPECIALLY 12Z TUE...WILL ISSUE A WINTER STORM WATCH FOR ROUGHLY THE
NORTHWEST HALF OF THE DVN CWA FOR WED NIGHT AND THU GIVING A NOD
SOMEWHAT TO THE ENSEMBLE TRACK. THE STRONG WINDS LOOK TO BE A LARGE
IMPACT EVEN FOR ADVISORY LEVEL OR SLIGHTLY LESS SNOW AMOUNTS. DO FEEL
THE CWA WILL HAVE TO EVENTUALLY BE DIVIDED INTO WINTER STORM WARNING
AND ADVISORY AREAS...BUT WHERE AN WHEN STILL UP IN THE AIR. A
WATCHFUL EYE WILL ALSO NEED TO BE OPEN FOR TRENDS ON THE NEXT 1-2
MODEL RUNS BACK CLOSER TO THE CONSISTENT ECMWF...WHICH WOULD THEN
WARRANT THE NEED OF EXPANDING THE WATCH SOUTH AND EAST. ..12..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR BENTON-BUCHANAN-CEDAR-CLINTON-DELAWARE-
DUBUQUE-HENRY IA-IOWA-JACKSON-JEFFERSON-JOHNSON-JONES-
KEOKUK-LINN-LOUISA-MUSCATINE-SCOTT-VAN BUREN-WASHINGTON.
IL...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR JO DAVIESS-ROCK ISLAND.
MO...NONE.
&&
$$
NICHOLS
AREA FORECAST DISCUSSION
NWS NORTH PLATTE NE
1136 PM CST MON DEC 17 2012
.AVIATION...
VISUAL FLIGHT RULES FOR KLBF TERMINAL THROUGH 19/06Z WEDNESDAY.
THE LOW STRATUS NEAR KONL WILL CONTINUE TO MOVE SLOWLY EAST
OVERNIGHT AS A SURFACE LOW CURRENTLY NEAR KVTN MOVES EAST NORTHEAST
INTO SOUTHEASTERN SOUTH DAKOTA TOWARD 12Z. THIS WILL BRING A
BACKING WIND TO THE NORTHWEST NEAR 10KTS FOR KVTN...ALONG WITH THE
POTENTIAL FOR MVFR CEILINGS IN WRAP AROUND FROM 10Z-14Z. LATEST
NAM AND RAP MODELS FAVOR A CEILING AOA 3500 FEET WHICH IS WHAT
GOING FORECAST HAS. OTHERWISE SCATTERED CLOUD HEIGHTS AOA 8 KFT
WITH INCREASING MID/HIGH CLOUDS TOWARD 00Z/19TH AS UPSTREAM WINTER
STORM TAKES AIM ON THE CENTRAL ROCKIES.
&&
.PREV DISCUSSION... /ISSUED 349 PM CST MON DEC 17 2012/
DISCUSSION...
THE STORM OF INTEREST IS RAPIDLY APPROACHING THE PACIFIC NORTHWEST COAST.
MODELS AND TIMING TOOLS INDICATE THE DISTURBANCE IS MOVING EAST
SOUTHEAST AT 30KTS AND WILL CONTINUE SO THROUGH WEDNESDAY NIGHT.
SOME MODEL SOLNS ARE SOUTH...NORTH...WETTER AND DRIER. THE ECMWF
HAS BEEN THE MOST CONSISTENT FOCUSING THE BEST FORCING ACROSS SWRN
NEB SOUTH OF INTERSTATE 80. THE GFS...NAM AND GEM HAVE BEEN
WOBBLING NORTH AND SOUTH. THE ECM IS ALSO ABOUT 6 HOURS SLOWER
THAN THE OTHER MODELS AND SHOWS THE DRIEST BOUNDARY LAYER MOISTURE
AND PRODUCES THE LEAST QPF. THE GFS ENSEMBLE H700MB LOW TRACK AND
QPF IS A REASONABLE COMPROMISE IN TERMS OF TIMING AND CAPTURING
AREAS SOUTH OF NEBRASKA HIGHWAY 2 WITH SNOW.
THE FEATURE OF INTEREST APPEARS TO BE VERY STRONG BUT FAST MOVING
MID LEVEL FRONTOGENESIS AND DEFORMATION ALONG AND JUST NORTH OF
THE H700MB LOW. IT IS STRONGLY TILTED POSITIVELY. THIS SHOULD
PRODUCE A RELATIVELY NARROW BAND OF LIGHT TO MODERATE SNOW. THE
NAM IS SHOWING HEAVY SNOW AS TEMPERATURES ARE VERY FAVORABLE FOR
GROWTH AND THE DENDRITIC LAYER WILL BE DESCENDING AS COLD AIR
FILLS IN BEHIND THE H7 LOW. THE QUICK MOTION OF THE STORM MAKES
HEAVY SNOW LESS LIKELY.
ONE THING ALL MODELS AGREE ON ARE WIND SPEEDS. A NRN STREAM
DISTURBANCE MOVING THROUGH THE NRN PLAINS TUESDAY WILL TAP SOME
ARCTIC AIR AND THIS WILL DROP SOUTH WEDNESDAY MORNING AND GET
CAUGHT UP IN THE SFC CYCLONE. WIND SPEEDS WEDNESDAY AFTN SHOULD
INCREASE TO 15 TO 25 MPH WITH SPEEDS APPROACHING 30 MPH ACROSS FAR
SWRN NEB. MOST OF THE SNOW SHOULD BE OVER BY TIME THE WINDS COME
UP BUT THATS PERFECT FOR BLOWING SNOW.
THURSDAY THROUGH SATURDAY...A ZONAL FLOW TAKES OVER ALOFT PRODUCING
CLEAR SKIES A GRADUAL MODERATION IN TEMPERATURES. THE WEATHER MAY
BE QUIET IN NEBRASKA BUT A LARGE UPPER LEVEL RIDGE WILL BUILD
ACROSS ALASKA SUPPORTING THE DEVELOPMENT OF A VERY LARGE ARCTIC
HIGH PRESSURE SYSTEM. THIS HIGH WILL EVENTUALLY DROP SOUTH AND THE
MODELS ARE HAVING TROUBLE TIMING THE EVENTUAL ARCTIC FRONTAL
PASSAGE INTO NEBRASKA. TODAYS MODEL RUNS SUGGEST THE FRONT WILL
DROP IN MONDAY...A DAY OR SO LATER THAN YESTERDAYS MODEL SOLNS. SO
THERE IS A CHANCE OF SNOW MONDAY FOR UPSLOPE CONDITIONS.
OTHERWISE THE FCST IS STRAIGHT FORWARD. THE ARCTIC DRAPE ACROSS
NORTHEAST NEBRASKA WHILL REMAIN IN PLACE TONIGHT THROUGH 14Z
TUESDAY ACCORDING TO THE RUC. SFC LOW PRESSURE WILL DROP SOUTHEAST
ALONG THE FRONT TONIGHT. IT MAY EVEN REMAIN ON TUESDAY BUT THATS
NOT INDICATED BY ANY MODEL. THE TANDEM EFFECT OF THE NRN STREAM
LOW AND THE LOW DROPPING THROUGH NEB TONIGHT SHOULD LIFT THE
ARCTIC FRONT AND CLOUDS NORTH TUESDAY.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...WINTER STORM WATCH FROM WEDNESDAY
MORNING THROUGH WEDNESDAY EVENING FOR NEZ058-069>071.
&&
$$
SHORT TERM/EXTENDED...NWS
AVIATION...ROBERG
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NWS RAPID CITY SD
1051 PM MST MON DEC 17 2012
.AVIATION...06Z TAFS
MVFR CIGS/IFR VSBY WILL BE FOUND ACROSS THE AREA WITH SCATTERED
SNOW SHOWERS...MAINLY FROM THE BLACK HILLS INTO CENTRAL SOUTH
DAKOTA. LIFR CIGS/VSBY WITH STRATUS/FZFG OVER CENTRAL SOUTH
DAKOTA WILL LINGER THROUGH THE NIGHT ALONG AND EAST A LINE FROM
KHEI-KPHP-KVTN. CONDITIONS WILL FROM WEST TO EAST LATE TONIGHT.
&&
.PREV DISCUSSION... /ISSUED 705 PM MST MON DEC 17 2012/
DISCUSSION...CURRENT SURFACE MAP SHOWS WARM FRONT ACROSS EASTERN
MONTANA INTO FAR WESTERN SOUTH DAKOTA...WITH WEAK LOW ALONG THE
FRONT NEAR THE BLACK HILLS. BAND OF CONVECTIVE SNOW HAS DEVELOPED
FROM NEAR GILLETTE TO THE NORTHERN BLACK HILLS. 18Z NAM/00Z RUC
SPREAD THIS CONVECTIVE SNOW ACROSS NORTHWEST SOUTH DAKOTA
OVERNIGHT. 00Z RAP IS GIVING 0.25-0.50 INCHES OF QPF ACROSS
NORTHWEST SOUTH DAKOTA OVERNIGHT...WITH UP TO 6 INCHES OF SNOW.
18Z NAM A LITTLE MORE REALISTIC WITH NARROW BAND OF 1-2 INCHES OF
SNOW. 00Z NAM IS COMING IN AND KEEPS THE ACCUMULATING SNOW
CONFINED TO THE BLACK HILLS.
FORECAST UPDATED TO INCREASE POPS THROUGH EARLY TUESDAY MORNING.
WILL LIMIT SNOWFALL ACCUMULATIONS TO 1-2 INCHES...MAINLY OVER THE
NORTHERN BLACK HILLS AND PLAINS JUST NORTH OF THE BLACK HILLS.
WITH EASTERLY WINDS ACROSS THE EASTERN PORTION OF THE FORECAST
AREA...LOW STRATUS/FZFG HAS BEEN MOVING WESTWARD. AS WARM FRONT
SHIFTS EAST OVERNIGHT...STRATUS/FOG WILL BEGIN TO DISSIPATE FROM
WEST TO EAST.
PREV DISCUSSION... /ISSUED 248 PM MST MON DEC 17 2012/
DISCUSSION...UPPER LEVEL ANALYSIS HAS FLAT RIDGE ACROSS THE
SOUTHWEST CONUS WITH WEAK TROFFING ACROSS THE PACIFIC NORTHWEST.
21Z SURFACE ANALYSIS PLACES LOW OVER SOUTHERN ALBERTA WHILE A
STATIONERY BOUNDARY BISECTS THE CWA. TEMPERATURES ARE IN THE 20S
AND LOWER 30S NORTH OF THE BOUNDARY...AND IN THE UPPER 30S AND 40S
SOUTH.
FOR TONIGHT...WEAK UPPER RIDGE PUSHES EAST TONIGHT AS THE ALBERTA
SURFACE LOW SLIDES INTO SOUTHERN SASKATCHEWAN. STATIONERY BOUNDARY
SLOWLY LIFTS NORTHEAST AS WESTERLY BOUNDARY LAYER FLOW INCREASES.
SHOULD BE A BREEZY NIGHT FOR MANY WESTERN AREAS WHERE BOUNDARY
LAYER REMAINS COUPLED. SOME FOG MAY REDEVELOP ACROSS CENTRAL
PORTIONS OF SOUTH DAKOTA THIS EVENING...BEFORE BOUNDARY FINALLY
LIFTS TO THE NORTH. LOWS WILL VARY FROM THE LOW TEENS IN DEEPER
DECOUPLED AREAS...TO THE 20S WHERE ATMOSPHERE STAYS COUPLED. WEAK
ENERGY CROSSING THE NORTHERN TIER MAY PRODUCE SOME SNOW SHOWERS
ACROSS NORTHWEST SOUTH DAKOTA THIS EVENING.
ON TUESDAY...TEMPERATURES WILL BE COOLER AS WEAK UPPER RIDGE
PUSHES EAST AND WESTERN TROF MOVES INTO THE NORTHERN ROCKIES.
HIGHS WILL BE CLOSER TO AVERAGE...IN THE 30S TO AROUND 40 DEGREES.
UPPER TROF DIGS INTO THE CENTRAL AND SOUTHERN ROCKIES TUESDAY
NIGHT WITH SURFACE LOW DEVELOPING OVER SOUTHERN COLORADO. LIGHT
WESTERLY FLOW WILL CONTINUE OVER THE AREA WITH LOWS FALLING INTO
THE TEENS AND 20S.
FOR WEDNESDAY...SURFACE LOW MOVES EAST ALONG THE KANSAS/OKLAHOMA
BORDER AS BASE OF UPPER TROF MOVES INTO WESTERN KANSAS. BROAD
AREA OF PRECIP WILL SLIDE ACROSS SOUTHEASTERN WYOMING INTO WESTERN
NEBRASKA...AND POSSIBLY GRAZE THE VERY SOUTHERN EDGE OF THE
FORECAST AREA. SOME OF THE MODEL GUIDANCE KEEPS PRECIP JUST TO THE
SOUTH OF THE AREA...SO WILL CONTINUE LOW POPS ACROSS FAR SOUTHERN
SOUTH DAKOTA. SYSTEM SHIFTS EAST WEDNESDAY NIGHT AS SURFACE RIDGE
SLIDES INTO THE AREA. TEMPERATURES WILL REMAIN CLOSE TO SEASONAL
AVERAGES.
EXTENDED...AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL BUILD OVER THE
INTERMOUNTAIN WEST ON THURSDAY...AS THE UPPER LEVEL TROF SHIFTS EAST
OF THE GREAT PLAINS. A FAIRLY FLAT RIDGE WILL THEN BECOME CENTERED
OVER THE NORTHERN PLAINS THROUGH THE WEEKEND...RESULTING IN A NEARLY
ZONAL FLOW PATTERN AND DRY WEATHER. EXPECT SLIGHTLY WARMER THAN
NORMAL TEMPERATURES THROUGH THE EXTENDED PERIOD WITH AN EXCEPTION
OVER THE NORTHEASTERN PART OF THE FORECAST AREA WHERE THE GFS
CONTINUES TO SHOW COOLER AIR BACKING INTO THE REGION. EXTENDED
MODELS SHOW ANOTHER UPPER TROUGH BRINGING A CHANCE OF SNOW TO PARTS
OF THE AREA ON MONDAY...BUT THEY STILL DIFFER GREATLY IN THE
STRENGTH AND PLACEMENT OF THE SURFACE LOW.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
SHORT TERM...07
LONG TERM....WFO UNR
AVIATION...07
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1129 PM CST MON DEC 17 2012
.SHORT TERM...TONIGHT THROUGH THURSDAY
303 PM CST MON DEC 17 2012
MAIN FORECAST CONCERNS ARE ON BRIEF LIGHT SNOW EVENT TOMORROW AND
THE POSSIBLE WINTER STORM LATE WEDNESDAY INTO THURSDAY.
CURRENTLY AS OF 21Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED TROUGHING FROM THE GULF OF ALASKA TO OFF THE PACIFIC
NORTHWEST...A RELATIVELY POTENT SHORTWAVE CROSSING THE NORTHERN
ROCKIES...A WEAK NORTH TO SOUTH ORIENTED SHORTWAVE OVER THE FAR
EASTERN DAKOTAS AND A WEAK RIDGE SANDWICHED IN-BETWEEN THESE
SHORTWAVES. MID LEVEL CLOUDS WERE ASSOCIATED AHEAD OF THE DAKOTAS
SHORTWAVE...WITH A FEW FLURRIES FALLING OUT OF THESE OVER SOUTHWEST
MINNESOTA AND NORTHWEST IOWA. OVER THE FORECAST AREA...STRATUS
PERSISTS...BURIED UNDERNEATH A SUBSIDENCE INVERSION SEEN ON THE 12Z
MPX...GRB AND DVN SOUNDINGS. HAVING LIGHT WINDS ASSOCIATED WITH HIGH
PRESSURE AT THE SURFACE COMBINED WITH BEING AT THE BOTTOM OF THE
DAYLIGHT CYCLE HAS NOT HELPED EITHER TO GET RID OF THE STRATUS.
TEMPERATURES AS A RESULT HAVE NOT CLIMBED A WHOLE LOT FROM MORNING
LOWS. THE STRATUS ACTUALLY EXTENDS WEST ALL THE WAY INTO THE CENTRAL
DAKOTAS. FARTHER WEST...LEE TROUGHING HAS FORMED DOWNSTREAM OF THE
NORTHERN ROCKIES SHORTWAVE...ALSO AIDED BY A 130KT JET NEAR THE
TROPOPAUSE ON THE SOUTH SIDE OF THE SHORTWAVE. THERE HAS BEEN QUITE
A BIT OF PRECIPITATION ACROSS THE NORTHERN ROCKIES AS WELL AS THE
UPPER JET DRIVES IN PACIFIC MOISTURE.
TONIGHT AND TUESDAY...FOCUS IS ON THAT NORTHERN ROCKIES SHORTWAVE.
MODELS ARE IN REALLY GOOD AGREEMENT BRING THE SHORTWAVE INTO
SOUTHERN SOUTH DAKOTA BY 06Z...NEAR SIOUX CITY IOWA BY 12Z...NEAR
DUBUQUE BY 18Z AND CHICAGO BY 00Z. THIS TRACK IS A BIT FARTHER SOUTH
THAN SUGGESTED OVER THE PAST FEW DAYS...WITH PERHAPS THE CANADIAN
AND ECMWF DOING THE BEST JOB ON IT. THE SHORTWAVE AND THE ASSOCIATED
UPPER JET SOUTH OF IT ARE STRONG ENOUGH THAT OUT OF THE CURRENT LEE
TROUGHING A SURFACE LOW IS SUGGESTED TO DEVELOP. THIS LOW OF COURSE
ENDS UP TRACKING WITH THE SHORTWAVE...RESULTING IN A LOW TO
MID-LEVEL FRONTOGENESIS ZONE ON THE NORTH SIDE OF IT. MOISTURE
INITIALLY IS LIMITED...NOTED BY THE CURRENT LACK OF MID-CLOUDS
ACROSS MUCH OF THE PLAINS. HOWEVER...AS WE GO THROUGH TONIGHT...
CONDENSATION PRESSURE DEFICITS ON THE 285-290K SURFACES DECREASE AS
THE LIFT HELPS TO SATURATE THE MID-LEVELS OF THE ATMOSPHERE. SHOULD
SEE A BAND OF LIGHT SNOW BREAK OUT ACROSS SOUTH DAKOTA INTO SOUTHERN
MINNESOTA AND NORTHERN IOWA BY LATE TONIGHT...ON THE NORTH SIDE OF
THE LOW. PERHAPS SOME OF THIS SNOW SQUEAKS INTO WESTERN PORTIONS OF
THE FORECAST AREA TOWARDS 12Z. WITH THE TREND FARTHER SOUTH WITH THE
SHORTWAVE TRACK...HAVE LEANED THE FORECAST MORE TOWARDS THE 17.12Z
GFS/ECMWF IDEA VERSUS THE FARTHER NORTH BUT TRENDING SOUTH 17.12Z
NAM FOR TUESDAY. THE FRONTOGENESIS BAND OF SNOW SHOULD AFFECT MAINLY
I-90 SOUTH AND RAISED PRECIPITATION CHANCES TOWARDS 60 IN THIS AREA.
LIMITED MOISTURE NOTED BY MIXING RATIOS OF 2-3 G/KG ON THE 285-290K
SURFACES WILL KEEP QPF AMOUNTS DOWN TO AT MOST A 0.10 OF AN INCH
TOTAL LIQUID EQUIVALENT. THE LIFT IS PRIMARILY CENTERED BELOW THE
DENDRITIC GROWTH ZONE...KEEPING SNOW TO WATER RATIOS DOWN NEAR 10 TO
1...THUS ONLY UP TO AN INCH OF SNOW IS ANTICIPATED. CONCERN THOUGH
IS THAT THE SNOW IS COMING AT MORNING COMMUTE TIME...SO HAVE ISSUED
AN SPS TO ACCOUNT FOR THIS. PLENTY OF CLOUDS LOOK TO PERSIST THROUGH
THIS PERIOD THUS AGAIN TEMPERATURES IMPACTED BY ADVECTION. WITH THE
FARTHER SOUTH TRACK OF THE LOW...HAVE COOLED HIGHS DOWN FOR TUESDAY.
TUESDAY NIGHT THROUGH THURSDAY...ALL ATTENTION IS ON THE WINTER
STORM POTENTIAL...WHICH RELATES TO THE CURRENT TROUGH OFF THE
PACIFIC NORTHWEST. THAT TROUGH IS COMPOSED OF 2 PARTS...A POTENT
SHORTWAVE NEAR 42N 140 W...AND A COLD SHORTWAVE NEAR THE NORTHERN
BRITISH COLUMBIA COAST. 500MB TEMPS WERE AROUND -40C WITH THE COLD
SHORTWAVE...AND JUST AHEAD OF IT OVER NORTHERN BRITISH COLUMBIA
850MB TEMPS ARE IN THE -15 TO -25C RANGE. THE IDEA SHOWN FOR THE
PAST MANY DAYS IS THAT THESE TWO PARTS ARE EVENTUALLY GOING TO PHASE
UP AFTER CROSSING THE WESTERN U.S....RESULTING IN A DEEPENING WINTER
STORM FROM THE CENTRAL PLAINS INTO THE GREAT LAKES. THE QUESTION HAS
BEEN WHERE DOES THE PHASING OCCUR WITH RESPECT TO OUR LONGITUDE TO
HELP DETERMINE THE EXACT TRACK AND SPEED. THE ANSWER STILL IS NOT
THERE YET...HOWEVER...THE DETERMINISTIC MODEL SPREAD IS SHRINKING
AND SHOULD CONTINUE TO DO SO OVER THE NEXT FEW DAYS AS THE TROUGH
COMES INTO THE WESTERN U.S.. WITH THE 17.12Z MODEL GUIDANCE...TRACK
SPREAD RANGES FROM THE NORTHWEST SOLUTION OF THE NAM TO THE
SOUTHEAST SOLUTION OF THE ECMWF. THE GFS...UKMET AND CANADIAN LIE
IN-BETWEEN. THE NAM HAS BEEN TRENDING SOUTHEAST...THE GFS NORTHWEST
AND THE CANADIAN/ECMWF STAYING FAIRLY CLOSE. THE FORECAST FOLLOWS A
BLEND OF THE GFS...CANADIAN AND ECMWF SCENARIOS SINCE THESE SEEM TO
BE THE MOST LIKELY TO OCCUR GIVEN TRENDS. FOR WHAT ITS WORTH...THE
PAST 4 SREF RUNS ARE VERY CONSISTENT ON A FARTHER NORTHWEST TRACK
CLOSE TO OR EVEN MORE NORTHWEST THAN THE NAM. NEEDLESS TO SAY...
STILL PLENTY OF UNCERTAINTY.
SOME DETAILS...TUESDAY NIGHT INTO WEDNESDAY MORNING SHOULD STAY DRY
AS WE ARE IN-BETWEEN SYSTEMS. BIG QUESTION MARK IS IF WE CAN CLEAR.
MOST MODELS SAY WE CAN...BUT HAVING SNOW ON TUESDAY COMBINED WITH
MODELS NOT DOING THE GREATEST ON THE CURRENT STRATUS YIELDS A MORE
PESSIMISTIC VIEW. AS SUCH...HAVE INCREASED CLOUD COVER AND FURTHER
INCREASES MAY BE NECESSARY. AS THE STORM SYSTEM DEEPENS IN THE
SOUTHERN PLAINS ON WEDNESDAY...A BAND OF FRONTOGENESIS
DEVELOPS/STRENGTHENS UP INTO OUR REGION. THE GFS AND CANADIAN
PRODUCE PRECIPITATION IN THE AFTERNOON AS THEY ARE QUICKER TO
SATURATE THE LOW LEVELS AND TO BRING IN THE FORCING...COMPARED TO
THE ECMWF/NAM/UKMET. HARD TO SAY WHICH GROUP MAY BE MORE CORRECT AT
THIS POINT...THOUGH THE MORE CONSISTENT SIGNAL HAS BEEN TO WAIT
UNTIL WEDNESDAY EVENING TO BRING THE PRECIPITATION IN. THUS...FOR
NOW JUST INCLUDED 20-40 PERCENT CHANCES FROM I-90 SOUTH FOR THE
AFTERNOON. THE MAJORITY OF THE FORECAST AREA SHOULD SEE
PRECIPITATION WEDNESDAY NIGHT INTO THURSDAY MORNING...NO MATTER WHAT
MODEL SOLUTION IS FOLLOWED. IF THERE IS ANYWHERE OF CONCERN DURING
THIS PERIOD THAT MAY NOT SEE PRECIPITATION IT IS OUR FAR NORTHWEST
AS INDICATED BY THE ECMWF. THUS...HIGHEST CHANCES UP AT OR NEAR 100
ARE CONFINED TO THE SOUTHEAST HALF. PRECIPITATION SHOULD START TO
DIMINISH THURSDAY AFTERNOON AS THE SYSTEM HEADS OFF INTO LOWER
MICHIGAN.
IMPACTS/CONCERNS TO WORRY ABOUT WITH THIS WINTER STORM INCLUDE:
1. HEAVY SNOW...PRETTY GOOD MODEL CONSENSUS EXISTS THAT THE TIME
PERIOD WOULD BE WEDNESDAY NIGHT INTO THURSDAY MORNING. EXACT
PLACEMENT OF HEAVIEST SNOW IS STILL UNCERTAIN...BUT FOLLOWING THE
AFOREMENTIONED GFS/ECMWF/CANADIAN BLEND PLACES IT IN THE
SOUTHEASTERN HALF OF THE FORECAST AREA. WITH MAYBE 100 MB OF
DENDRITIC GROWTH AT MOST AND FAIRLY HIGH UP SAY BETWEEN
550-650MB...THE SNOW TO WATER RATIOS SHOULD BE TYPICAL...IN THE
10-15 TO 1 RANGE.
2. MIXED PRECIPITATION TYPES...MODEL CONSENSUS HAS BEEN TO KEEP THE
SYSTEM OFF TO OUR SOUTHEAST...KEEPING OUR AREA IN THE DEEPER COLD
AIR AND THUS SNOW AS THE MAJORITY PRECIPITATION TYPE. HOWEVER...THE
GFS SUGGESTS THAT IF THE SYSTEM CAN WRAP UP ENOUGH...EVEN GRANT AND
CLAYTON COUNTIES COULD END UP WITH SLEET OR RAIN FOR A TIME.
3. BLOWING SNOW/WIND...AS THE SYSTEM DEEPENS ON ITS WAY UP THROUGH
ILLINOIS WEDNESDAY NIGHT AND BEGINS TO PULL AWAY FROM THE AREA ON
THURSDAY...THE PRESSURE GRADIENT TIGHTENS...CAUSING NORTHWEST WINDS
TO INCREASE. THESE WINDS COULD EASILY REACH THE 15-25KT RANGE WITH
HIGHER GUSTS. COMBINING THESE WITH FALLING OR ALREADY ON THE GROUND
SNOW WOULD YIELD BLOWING SNOW...ESPECIALLY ACROSS NORTHEAST IOWA
WHICH HAS THE MOST EXPOSED TERRAIN.
WITH THE NARROWING MODEL SPREAD...ENOUGH CONFIDENCE EXISTED EARLIER
TODAY TO ISSUE A WINTER STORM WATCH FOR ABOUT THE SOUTHEASTERN HALF
OF THE FORECAST AREA. NOTE THAT THE WATCH AREA MAY NOT END UP BEING
THE FINAL WARNING AREA...THUS THE PHRASE WATCH. FURTHER REFINEMENTS
MAY OCCUR...ESPECIALLY ONCE CONFIDENCE INCREASES ENOUGH TO CHANGE
THE WATCHES TO ADVISORIES/WARNINGS.
.LONG TERM...THURSDAY NIGHT THROUGH MONDAY
303 PM CST MON DEC 17 2012
MAIN FORECAST CONCERNS ARE TEMPERATURES THROUGH FORECAST PERIOD.
THE DETERMINISTIC 17.12Z GFS/ECMWF/GEM ARE IN GOOD AGREEMENT WITH
UPPER LEVEL TROUGH OVER THE NORTHEASTERN UNITED STATES AND UPPER
LEVEL RIDGE OVER THE EASTERN ROCKY MOUNTAINS THROUGH 18Z
SATURDAY...THEN THE MODELS BEGIN TO DIVERGE ON STRENGTH OF THE
UPPER LEVEL TROUGH OVER THE NORTHEASTERN UNITED STATES AND UPPER
LEVEL RIDGE OVER THE ROCKY MOUNTAINS. THE 17.12Z ECMWF IS MORE
AMPLIFIED WITH THE UPPER LEVEL TROUGH SATURDAY NIGHT INTO MONDAY
THAN THE 17.12Z GFS/GEM. IF THIS OCCURS...THE UPPER MIDWEST AND
GREAT LAKES REGION WILL REMAIN UNDER NORTHERLY FLOW ALOFT AND A
COLDER AIRMASS WILL FILTER INTO THE AREA. THIS WILL HAVE IMPACTS
ON TEMPERATURES...ESPECIALLY SATURDAY NIGHT INTO MONDAY. THE
17.12Z GFS INDICATES WEST TO EAST ZONAL FLOW ACROSS THE UNITED
STATES AND SLIGHTLY WARMER TEMPERATURES THAN THE 17.12Z ECMWF.
THIS WOULD RESULT IN NEAR NORMAL TEMPERATURES ACROSS FORECAST
AREA. AT THIS TIME...WILL CONTINUE WITH A CONSENSUS BLEND OF
TEMPERATURES...BASED ON THE LOW CONFIDENCE OF UPPER LEVEL FLOW
PATTERN AFTER 18Z SATURDAY.
NO REAL INDICATION OF ANY PRECIPITATION OCCURRING AS THE UPPER
FLOW PATTERN PROGGED IS MOSTLY SUBSIDENT...FAVORING HIGH PRESSURE
AT THE SURFACE.
&&
.AVIATION...THROUGH 06Z WEDNESDAY
1129 PM CST MON DEC 17 2012
EXTENSIVE STRATUS STILL REMAINS ACROSS THE REGION...BUT THERE WERE
HOLES WHERE CEILINGS ROSE INTO THE VFR CATEGORY. MODEL SOUNDINGS
CONTINUE TO SHOW MOISTURE TRAPPED UNDER THE INVERSION WITH THE LOW
STRATUS CONTINUING. HOWEVER...BASED ON METARS WILL LIKELY SEE
HOLES WITH VFR CONDITIONS FOR A SHORT TIME. THIS VERY DIFFICULT TO
TIME IN THE TAFS AND WILL KEEP A TEMPO GROUP TO ACCOUNT FOR THIS.
OTHERWISE...CEILINGS WILL BE IN THE IFR TO LOWER END VFR CATEGORY. NEXT
SYSTEM THEN MOVES ACROSS IOWA...WITH SNOW BREAKING OUT TUESDAY
MORNING BETWEEN 12Z-15Z. 18.00Z GFS AND NAM SHOWING MAIN BAND TO
MOVE JUST SOUTH OF THE TAF SITES...BUT STILL LOOKS LIKE 2-3 MILE
VISIBILITIES IN THE LIGHT SNOW INTO THE AFTERNOON HOURS. EXPECT
CEILINGS IN THE IFR TO LOWER MVFR IN THE SNOW...RISING TO MVFR
AFTER THE SNOW ENDS AND THROUGH THE END OF THE TAF PERIOD.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
303 PM CST MON DEC 17 2012
WI...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR WIZ034-041>044-053>055-061.
MN...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR MNZ096.
IA...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
AFTERNOON FOR IAZ010-011-019-029-030.
&&
$$
SHORT TERM...AJ
LONG TERM...DTJ/AJ
AVIATION...RABERDING
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
757 AM EST TUE DEC 18 2012
.SYNOPSIS...
SHOWERS WILL END TODAY AS LOW PRESSURE EXITS TO THE NORTHEAST.
HIGH PRESSURE WILL FOLLOW WITH DRY MILD CONDITIONS WEDNESDAY.
LOW PRESSURE COMING FROM CALIFORNIA WILL STRENGTHEN AS IT PICKS
UP COLDER AIR CROSSING THE PLAINS...TO PROVIDE US WITH SHOWERS
THURSDAY...BLUSTERY CONDITIONS FRIDAY... AND A COLDER WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
BLEND OF RECENT SURFACE RADAR AND SATELLITE DATA COUPLED WITH
RECENT RAP AND SREF MODEL OUTPUT SHOWS SHOWERS DECREASING WEST TO
EAST ACROSS THE UPPER OHIO VALLEY THIS MORNING AND PRETTY MUCH
ENDING THIS AFTERNOON.
NAM MODEL PROFILES SHOW CLOUDS CAN LINGER
INTO TONIGHT. SURFACE WINDS WILL BE FROM THE WEST WITH GUSTS UP
TO 25 MPH.
FORECASTED TEMPERATURES TODAY WILL BE FAIRLY STEADY...BASED ON
RECENT RAP AND SREF MODEL OUTPUT. LOWS TONIGHT WILL BE MAINLY IN
THE LOWER 30S...WHICH IS STILL NEARLY 10 DEGREES WARMER THAN
NORMAL.
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
THAT BUILDING HIGH PRES WL PROVIDE FOR A DRY WEDNESDAY WITH WARM
ADVECTION DRIVING TEMPS FURTHER ABOVE THE SEASONAL AVERAGES. WARM
READINGS CAN BE EXPECTED INTO THURSDAY AS THAT ADVCTN REGIME
STRENGTHENS IN ADVN OF LOW PRES DEEPENING/DIGGING TWD THE GREAT
LAKES.
RAIN CHCS ARE ALSO ON THE RISE IN THE THURSDAY FORECAST AND THE
POPS INCRS TO CATEGORICAL NMBRS BY AFTN HAS BEEN
MAINTAINED...ALTHOUGH TIMING HAS BEEN ADJUSTED FORWARD BASED ON
THE LATEST DETERMINISTIC MDL TRENDS. IN ADDITION...THE TIGHTENING
PRES GRADIENT WL STRENGTHEN THE WIND FIELD...AND ADVISORY-LVL
GUSTS ARE POSSIBLE...ESPECIALLY OVR THE RIDGE ZONES. THE HAZARDOUS
WEATHER OUTLOOK HAS BEEN UPDATED FOR THAT POTENTIAL...WHICH WL
PERSIST INTO FRIDAY AS THE LOW DIGS ACRS THE ERN LAKES.
FINALLY...STRONG COLD ADVCTN FOLLOWING FRONTAL PASSAGE IS EXPECTED
TO CHANGE RAIN SHOWERS TO SNOW ON THURSDAY NGT...AND SOME LIGHT
ACCUMULATION WL BE POSSIBLE THROUGH FRIDAY. THE BTR CHC OF THAT
POTENTIAL IS FOR COUNTIES IN LEE OF THE LAKES...AND FOR THE RIDGE
ZONES.
SHORT TERM TEMPERATURES WERE FORECAST USING A BLEND OF THE WARMER GUIDANCE.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
MODEL DIFFERENCES ARE INDICATED BY FRIDAY NIGHT...WITH THE GFS
SHOWING THE MATURE LOW MOVING OFFSHORE MORE QUICKLY THAN THE
ECMWF. SPEED OF THE DEPARTING LOW WILL DETERMINE HOW LONG
FAVORABLE FETCH WILL PERSIST OFF LAKE ERIE. FOR NOW...HAVE GONE
WITH SLOW DECLINE IN POPS THROUGH THE WEEKEND. EXPECT LITTLE
RECOVERY IN TEMPERATURES...WITH HIGHS A COUPLE OF DEGREES BELOW
NORMAL.
&&
.AVIATION /13Z TUESDAY THROUGH SATURDAY/...
SHOWERS AND RESTRICTIONS WILL CONTINUE FOR MUCH OF THE MORNING
BEFORE A GRADUAL IMPROVEMENT IN BOTH CIGS AND VSBYS IS EXPECTED.
IFR CLOUD DECK SHOULD BEGIN TO LIFT...WITH BETTER MIXING AS THE
COLD FRONT AND LOW SHIFT NORTHEASTWARD. BUFKIT SOUNDINGS SUGGEST THAT
MID LEVEL SUBSIDENCE WILL HELP TO SCATTER OUT THE CLOUD DECK LATE
TODAY. WHILE CONFIDENCE IN THIS ISN`T EXTREMELY HIGH...AND WILL
DEPEND ON THE UPPER LEVEL FLOW...TRIED TO HINT AT THIS
IMPROVEMENT.
WINDS OUT AHEAD OF AND SOUTH OF THE LOW WILL GENERALLY REMAIN E-SE
SHIFTING TO SW-W BY MORNING. WINDS SHOULD INCREASE TO 10KTS WITH
GUSTS TO 20KTS POSSIBLE FOR THE REMAINDER OF TUESDAY.
.OUTLOOK.../TONIGHT THROUGH SATURDAY/...
GUIDANCE SUGGESTS A RETURN OF SOME RESTRICTIONS IN COLD POOL
STRATOCUMULUS TUESDAY NIGHT/WEDNESDAY MORNING...ESPECIALLY NORTH
OF I-80. OTHERWISE...VFR EXPECTED IN HIGH PRESSURE BEFORE YET
ANOTHER LOW PRESSURE SYSTEM APPROACHES THURSDAY AFTERNOON.
RESTRICTIONS WILL THEN BE PROBABLE FROM THURSDAY ONWARD WITH THIS
STRONGER LOW PRESSURE/COLD FRONT PASSAGE. STRONG WIND GUSTS MAY
ALSO BE OF CONCERN THURSDAY NIGHT/FRIDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS BUFFALO NY
746 AM EST TUE DEC 18 2012
.SYNOPSIS...
LOW PRESSURE WILL LIFT ACROSS NEW YORK THIS MORNING AND THEN EXIT
INTO SOUTHERN NEW ENGLAND THIS AFTERNOON. RAIN WILL CONTINUE THIS
MORNING...THEN TAPER OFF FROM WEST TO EAST THIS AFTERNOON...ENDING
AS SNOW ACROSS HIGHER TERRAIN AND EAST OF LAKE ONTARIO. HIGH
PRESSURE WILL BRING FAIR AND MILD WEATHER MID WEEK BEFORE A STRONGER
SYSTEM BRINGS RAIN ON THURSDAY AND MORE WINTRY WEATHER AND WIND TO
THE REGION BY FRIDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AT 700 AM...A WEAK AREA OF LOW PRESSURE WAS CENTERED ACROSS
CENTRAL NEW YORK. EVEN THOUGH THE SURFACE LOW IS ONLY 998 MB...IT
IS FAIRLY WELL DEVELOPED ALOFT AND CLOSED OFF TO 700 MB WITH A
SHARP 500 MB TROF TO THE WEST. ASSOCIATED WITH THIS LOW IS A LARGE
AREA OF RAIN ACROSS WESTERN NEW YORK. THE MAIN FOCUS FOR LIFT WITH
THIS IS WARM AIR ADVECTION WRAPPING AROUND THE 850MB LOW IN A
TROWAL- LIKE FEATURE ON THE BACK SIDE OF THE LOW.
OVERALL MODEL GUIDANCE HAS A GOOD HANDLE ON THIS...THOUGH A
CONSENSUS OF THE 00Z NAM/RGEM AND THE 21Z SREF TENDS TO BE A BIT TOO
SLOW IN ENDING RAIN EAST OF LAKE ONTARIO WHEN COMPARED WITH
RADAR TRENDS. THE HRRR SEEMS TO HAVE A GOOD HANDLE ON THIS
FEATURE. QPF FORECAST HAVE BEEN GOOD...WITH ADDITIONAL RAIN LIKELY
TO AVERAGE AROUND A QUARTER INCH TODAY...WITH AN ADDITIONAL TENTH
OR SO EAST OF LAKE ONTARIO TONIGHT. RAIN WILL SLOWLY END FROM WEST
TO EAST...TAPERING OFF WEST OF ROCHESTER AROUND EARLY
AFTERNOON...AND ENDING LATE AFTERNOON BETWEEN ROCHESTER AND SYRACUSE.
OUTSIDE OF THE NOTABLY DREARY CONDITIONS ACROSS THE REGION...THIS
SYSTEM WILL NOT HAVE A MAJOR IMPACT ON MOST OF WESTERN NEW
YORK...SINCE PRECIPITATION SHOULD FALL PRIMARILY AS RAIN. THIS
SAID...COLDER AIR MOVING IN FROM THE WEST THIS AFTERNOON WILL CAUSE
RAIN TO MIX WITH AND CHANGE TO SNOW ACROSS HIGHER TERRAIN IN THE
SOUTHERN TIER...EXTENDING INTO THE BOSTON HILLS. EXPECT A SLIGHTLY
LATER CHANGEOVER EAST OF LAKE ONTARIO...AGAIN HIGHER TERRAIN SUCH AS
THE TUG HILL TRANSITIONING FIRST. COLDER AIR WILL CONTINUE TO WORK
IN THIS EVENING...WHEN MOST LINGERING PRECIPITATION SHOULD FALL
PRIMARILY AS SNOW.
ONE IMPORTANT NOTE IN TERMS OF PRECIPITATION TYPE IS THAT BECAUSE
THIS IS SYNOPTIC INSTEAD OF LAKE EFFECT...OUR USUAL -6C AT 850MB
RAIN/SNOW LINE WILL NOT APPLY. NAM/GFS BUFKIT FORECAST SOUNDINGS
BOTH SUPPORT A CHANGEOVER ONCE 850MB TEMPERATURES REACH ABOUT
-3C...WHICH SEEMS REASONABLE CONSIDERING THIS WILL BE IN THE
NORTHWESTERN SECTOR OF THE LOW. USED A CONSENSUS OF THE
SREF/RGEM/NAM TO TIME THIS...WHICH IS A BIT SLOWER THAN THE 00Z NAM
WHICH SEEMS TO BE ON THE COLDEST END OF GUIDANCE.
OTHERWISE...DRIER AIR WILL WORK IN FROM THE WEST THIS EVENING...WITH
A PARTIAL CLEARING FROM BUFFALO TO ROCHESTER. EXPECT MINIMAL
ACCUMULATIONS OF AN INCH OR LESS IN WESTERN PORTIONS OF THE
SOUTHERN TIER THIS AFTERNOON...AND THIS MAINLY ACROSS HIGHER
TERRAIN. SOME MODELS SUGGEST LIGHT QPF IN THE SOUTHERN TIER THIS
EVENING...BUT EXPECT NO ADDITIONAL ACCUMULATION THIS EVENING.
THERE WILL BE MORE MOISTURE EAST OF LAKE ONTARIO...WHICH IS CLOSER
TO THE UPPER LOW. THUS EXPECT SLIGHTLY MORE SIGNIFICANT AMOUNTS
EAST OF LAKE ONTARIO...WHERE A GENERAL 1 TO 3 INCHES THROUGH
TONIGHT.
TEMPERATURES WILL HOLD STEADY OR SLOWLY DROP TODAY...AS THE FLOW
BECOMES MORE NORTHWESTERLY. MORNING HIGHS IN THE LOWER 40S CAN BE
EXPECTED IN MOST LOCATIONS. TONIGHT WILL BE COOLER...BUT LINGERING
WINDS AND CLOUD COVER SHOULD KEEP TEMPERATURES TOO DRASTICALLY...MAINLY
IN THE LOWER 30S.
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
LINGERING LIGHT SNOW SHOWERS POSSIBLE EAST OF LAKE ONTARIO WEDNESDAY
MORNING...BEFORE MOISTURE PULLS EASTWARD. HIGH PRESSURE BOTH AT THE
SURFACE AND ALOFT WILL THEN BUILD IN FOR THE REMAINDER OF THE DAY
AND MAINTAIN ITSELF ACROSS THE REGION THROUGH WEDNESDAY NIGHT. THIS
WILL RESULT IN A PERIOD OF QUIET CONDITIONS...BEFORE WE DEAL WITH
THE SIGNIFICANT STORM SYSTEM IN THE LONGER TERM. MODEL CROSS
SECTIONS WOULD SUGGEST A FAIR AMOUNT OF SUNSHINE DEVELOPING
WEDNESDAY...ALTHOUGH A HINT OF SOME LAKE CLOUDINESS PERSISTING
SOUTHEAST OF THE LAKES IN A GENERAL NORTHWEST FLOW. TEMPERATURES
WILL STILL BE MILD FOR MID DECEMBER...WITH HIGHS IN THE LOWER 40S
ACROSS THE LOWER ELEVATIONS AND UPPER 30S FOR THE HIGHER TERRAIN.
HIGH PRESSURE WILL BEGIN TO SHIFT EAST OF THE AREA WEDNESDAY NIGHT
ALLOWING A STRENGTHENING WARM AIR ADVECTION PATTERN TO SET UP. THERE
SHOULD BE A GRADUALLY WEST TO EAST INCREASE IN CLOUD COVER
OVERNIGHT. TEMPERATURES LIKELY TO REMAIN IN THE 30S OR EVEN RISE
ACROSS THE WEST WITH 20S FARTHER TO THE EAST.
BY THURSDAY...OUR ATTENTION TURNS TO A SIGNIFICANT STORM SYSTEM THAT
WILL BE PROGRESSING EAST ACROSS THE NATION. A MODEL CONSENSUS
CONTINUES TO FAVOR A DEEPENING CENTRAL ILLINOIS TO SOUTHERN MICHIGAN
SURFACE LOW TRACK. THIS FORECAST TRACK WOULD EASILY PLACE WESTERN
AND CENTRAL NEW YORK IN THE WARM AIR IN ADVANCE OF THE MID LATITUDE
CYCLONE...SUPPORTING A RAIN EVENT WITHIN THE INITIAL THETA-E AND
ISENTROPIC ASCENT SURGE THURSDAY AFTERNOON AND THURSDAY EVENING. THE
DEEP SOUTHERLY FLOW WILL RESULT IN A MILD DAY THURSDAY WITH HIGHS IN
THE 50S ACROSS THE LOWER ELEVATIONS AND 40S ELSEWHERE.
AS THE SOUTHERN STREAM PV ANOMALY ATTEMPTS TO TAKE ON A NEGATIVE
TILT THURSDAY NIGHT...SHARPLY COLDER AIR WILL BE USHERED IN BEHIND
THE SURFACE COLD FRONT. IMPRESSIVE WIND FIELDS WITHIN THE MID LEVEL
DRY SLOT WILL MATERIALIZE IN WAKE OFF THE FRONT...WITH A POTENTIAL
SHORT PERIOD OF HIGH WINDS. THE DRY SLOT WILL ALSO DIMINISH THE RAIN
RAPIDLY BEHIND THE FRONT. WE MAY SEE SNOW DEVELOP AS EARLY AS LATE
THURSDAY NIGHT ACROSS THE FAR WEST...ESPECIALLY THE HIGHER
ELEVATIONS OF THE SOUTHERN TIER.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
FRIDAY THE PRIMARY SURFACE LOW IS FORECAST TO TRACK OVER OR JUST
NORTH OF LAKE ONTARIO. MODEL DIFFERENCES STILL REVOLVE AROUND HOW
MUCH SECONDARY CYCLOGENESIS WILL TAKE PLACE ON THE TRIPLE POINT OF
THE LOW ALONG THE EAST COAST FRIDAY. THE ECMWF REMAINS THE MOST
AGGRESSIVE...ALLOWING THIS SECONDARY LOW TO TAKE OVER BY MIDDAY
FRIDAY...THEN MAKE A LOOP THROUGH WESTERN NEW ENGLAND AND BACK INTO
NORTHERN NEW YORK FRIDAY NIGHT. THE GFS AND CANADIAN GEM ALSO HAVE
SOME SECONDARY CYCLOGENESIS...BUT A LITTLE WEAKER AND SLOWER...WHICH
ALLOWS THE SURFACE LOW TO LIFT INTO SOUTHERN QUEBEC FRIDAY NIGHT AND
ALSO ALLOWS IT TO PULL OUT FASTER OVER THE WEEKEND...WHILE THE ECMWF
HANGS THE SURFACE LOW AND MID LEVEL CLOSED LOW BACK LONGER.
THE DETAILS OF THE SYNOPTIC EVOLUTION AND TRACK WILL PLAY AN
IMPORTANT ROLE IN WHERE THE HEAVIEST SNOW WILL BE...AND IT WILL
PROBABLY STILL BE A FEW DAYS BEFORE WE HAVE A MORE PRECISE MODEL
CONSENSUS GIVEN THE COMPLEXITY OF THE PATTERN EVOLUTION. IN A
GENERAL SENSE...EXPECT SNOW DEVELOPING FROM WEST TO EAST FRIDAY
MORNING AS THE WRAP AROUND/COMMA HEAD ARRIVES. SNOW SHOULD CONTINUE
FRIDAY THROUGH MUCH OF SATURDAY...WITH INTENSITY DEPENDING ON
EXACTLY WHERE THE MID LEVEL CUTOFF AND SURFACE LOW END UP STALLING.
IT IS LOOKING MORE AND MORE LIKELY WE WILL SEE AT LEAST SOME
ACCUMULATING SNOW EVERYWHERE...WITH CURRENT INDICATIONS SUGGESTING
THE HEAVIEST WILL BE SOUTHEAST OF THE LAKES AND ACROSS HIGHER
TERRAIN WITH SOME HELP FROM LAKE ENHANCEMENT AND UPSLOPE FLOW.
FROM SUNDAY INTO EARLY NEXT WEEK THE AREA WILL REMAIN UNDER THE
INFLUENCE OF THE CUTOFF UPPER LEVEL LOW...ALTHOUGH TO WHAT EXTENT
STILL DEPENDS ON WHERE IT ENDS UP STALLING. FOR NOW WILL JUST RUN
WITH A CHANCE OF SNOW SHOWERS EVERYWHERE...WITH THE BEST CHANCES
SOUTHEAST OF THE LAKES WITH SOME NORTHWEST FLOW LAKE EFFECT.
TEMPERATURES WILL BE BACK TO WHERE THEY SHOULD BE FOR THIS TIME OF
YEAR OVER THE WEEKEND...AND MAYBE EVEN BELOW AVERAGE IF THE COLDER
ECMWF SOLUTION VERIFIES.
&&
.AVIATION /13Z TUESDAY THROUGH SATURDAY/...
LOW PRESSURE ACROSS CENTRAL NEW YORK AT 12Z WILL SLOWLY LIFT TO THE
NORTHEAST. THERE IS LOTS OF LOW LEVEL MOISTURE AND RAIN ASSOCIATED
WITH THIS LOW...WITH LOW CIGS AND VSBY MAINLY DEPENDENT ON
LOCALIZED FLOWS. AHEAD OF THE LOW...A SE FLOW HAS DOWNSLOPED...AND
KEPT CONDITIONS MAINLY VFR. HOWEVER...NOW ALL TAF SITES ARE IN A
NORTHERLY FLOW TO THE NORTH OF THE SYSTEM...WITH WIDESPREAD IFR OR
LOWER CONDITIONS. HOWEVER...DRIER AIR SITS JUST TO THE WEST...SO AS
WINDS BECOME MORE WESTERLY AND INCREASE...CIGS SHOULD START IMPROVING FROM
W-E THIS MORNING AND INTO THIS AFTERNOON...WITH MAINLY MVFR CONDITIONS
LIKELY BY LATE AFTERNOON.
RAIN WILL TAPER OFF FROM WEST TO EAST AS WELL...BUT WILL PROBABLY
MIX WITH OR TURN TO SNOW AT JHW/ART. MINIMAL ACCUMULATIONS ARE
POSSIBLE AT ART.
DRIER AIR WILL CONTINUE TO BUILD INTO THE REGION TONIGHT...WITH LIFTING
CIGS AND A GRADUAL IMPROVEMENT TO VFR EXPECTED.
OUTLOOK...
WEDNESDAY...MAINLY VFR.
THURSDAY...DETERIORATING TO MVFR WITH SHOWERS LIKELY IN THE
AFTERNOON.
THURSDAY NIGHT...MVFR WITH RAIN SHOWERS CHANGING TO SNOW. GUSTY WINDS.
FRIDAY...IFR WITH SNOW LIKELY. GUSTY WINDS.
SATURDAY...MVFR/IFR SNOW SHOWERS LIKELY.
&&
.MARINE...
WEAK LOW PRESSURE EXITING TO THE EAST WILL RESULT IN A NORTHWESTERLY
FLOW DEVELOPING THIS AFTERNOON AND TONIGHT. WHILE THE LOW IS QUITE
WEAK...THE GRADIENT BETWEEN THIS AND HIGH PRESSURE TO THE WEST SHOULD
BE ENOUGH TO PRODUCE SMALL CRAFT CONDITIONS ON THE WATERS. THESE
WILL LAST LONGEST ON EASTERN LAKE ONTARIO...WHERE THE FLOW WILL BE
STRONGEST AND MOST CONDUCIVE TO WAVE BUILDING.
AFTER THIS...HIGH PRESSURE WILL BUILD ACROSS THE WATERS WEDNESDAY
NIGHT.
A STRONGER STORM SYSTEM IS FORECAST TO MOVE INTO THE VICINITY OF THE
LOWER LAKES BY THURSDAY AND FRIDAY. THIS WILL BRING A PERIOD OF
STRONGER WINDS...AND GREATER WAVE HEIGHTS. THIS SYSTEM HAS THE
POTENTIAL TO BRING GALE FORCE WINDS...DEPENDING ON THE TRACK AND
STRENGTH.
&&
.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR LEZ040-041.
SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO NOON
EST WEDNESDAY FOR LOZ043.
SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 5 AM EST
WEDNESDAY FOR LOZ042.
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 6 PM EST
WEDNESDAY FOR LOZ044-045.
&&
$$
SYNOPSIS...APFFEL
NEAR TERM...APFFEL
SHORT TERM...TMA
LONG TERM...HITCHCOCK
AVIATION...APFFEL
MARINE...APFFEL/TMA
AREA FORECAST DISCUSSION
NWS GRAND FORKS ND
944 AM CST TUE DEC 18 2012
.DISCUSSION...
ADJUSTED POPS/WX FOR A SLOWER PROGRESSION OF THE PRECIP BAND
THROUGH THE CWA. RADAR HAS SOME LIGHT RETURNS FROM DEVILS LAKE
BASIN TO SHEYENNE VALLEY...BUT WEB CAMS AND SFC OBS SHOW NOT MUCH
IS REACHING THE GROUND YET. VALLEY CITY AND COOPERSTOWN OBS
SHOWING SOME 1/4MI VIS...BUT THIS IS FAIRLY PATCHY AND THINK IT
WILL BE SHORT LIVED SO WILL COVER WITH NOWCASTS AND NOT INCLUDE AN
ADVISORY. BETTER RADAR RETURNS AND CHANCES FOR ACCUMULATING SNOW
ARE FURTHER WEST NEAR THE SFC TROUGH AXIS. NAM AND RAP ARE IN
PRETTY GOOD AGREEMENT ON BRINGING MEASURABLE PRECIP INTO THE
WESTERN COUNTIES DURING THE LATE MORNING/EARLY AFTERNOON...AND
INTO THE RED RIVER VALLEY DURING THE 21Z TO 00Z TIME FRAME.
RAISED HIGHS A COUPLE OF DEGREES IN THE SOUTHWESTERN CWA AS SOME
LOCATIONS HAVE ALREADY HIT THEIR AFTERNOON HIGH OF 25. DO NOT
THINK THEY WILL WARM A LARGE AMOUNT DUE TO EXTENSIVE CLOUD
COVER...BUT THINK THEY SHOULD CONTINUE TO RISE A FEW DEGREES TO
TOP OUT IN THE UPPER 20S.
&&
.AVIATION...
EXPECT MAINLY IFR CONDITIONS TO PERSIST THROUGH THE PERIOD...WITH
LIGHT SNOW OVERSPREADING THE AREA FROM WEST TO EAST TODAY. THE MVFR
CIGS IN THE EASTERN TAF SITES WILL FALL INTO THE IFR RANGE DURING
THE LATE MORNING AND EARLY AFTERNOON. WINDS SHOULD REMAIN
LIGHT...UNDER 10KT GENERALLY FROM THE SE.
&&
.PREV DISCUSSION... /ISSUED 244 AM CST TUE DEC 18 2012/
SHORT TERM...
THE MAIN CHALLENGE WILL BE LIGHT SNOW BAND THAT WILL MOVE FROM
WEST TO EAST TODAY AND TONIGHT. MODELS ARE IN GOOD AGREEMENT WITH
THIS LIGHT SNOW...WITH SLIGHT TIMING DIFFERENCES. IT SEEMS THE
SLIGHTLY SLOWER PROGRESSION OF THE LIGHT SNOW IS PREFERRED...WITH
THE LATEST RUNS PICKING UP ON THIS.
FOR TODAY AND TONIGHT...EXPECT AN AREA OF ISENTROPIC LIFT AND DEEPER
LAYERED SATURATION TO MOVE SLOWLY FROM WEST TO EAST THROUGH THE
DAY. THE BEST THREAT FOR ACCUMULATING SNOW SHOULD OCCUR IN THE RED
RIVER VALLEY...WHERE UP TO AN INCH OR PERHAPS A BIT MORE IS
POSSIBLE THROUGH TONIGHT. AN UPPER LEVEL TROUGH SHOULD MOVE INTO
CENTRAL ND AROUND 00Z WED...AND THIS SHOULD ENHANCE LARGER SCALE
LIFT PER Q VECTOR AND OMEGA FIELDS. THERE WILL ALSO BE A WEAK BAND
OF MID LEVEL FGEN THAT WILL ALSO HELP VERTICAL MOTION AND SNOW
PRODUCTION. WINDS WILL REMAIN FAIRLY LIGHT FROM THE SOUTHEAST...SO
NO BLOWING SNOW ISSUES AT ALL TO WORRY ABOUT. TEMPS SHOULD WARM
SOME TODAY FROM WEAK LOW LEVEL WAA AND WON/T FALL TOO MUCH
OVERNIGHT WITH COLDER AIR JUST NORTH OF THE CANADIAN BORDER.
ON WED...EXPECT SOME LINGERING LIGHT SNOW ACROSS THE NORTH...WITH
FLURRIES POSSIBLE IN ALL AREAS BY EVENING. LOW LEVEL COLD AIR
ADVECTION WILL MOVE INTO THE NW BY AFTERNOON...AND TEMPS COULD
FALL SOME HERE BY AFTERNOON...WITH NORTHERLY WINDS INCREASING SOME
IN ALL AREAS BY 00Z THU.
ON THU...EXPECT A DRY AND COOL DAY WITH SFC HIGH PRESSURE CONTROLLING
THE WEATHER PATTERN. THERE SHOULD BE SOME SUNSHINE BY THE
AFTERNOON WITH DRIER AIR AND SUBSIDENCE ADVECTING IN FROM THE
NORTH. TEMPS SHOULD BE IN THE SINGLE DIGITS ABOVE NORTH TO AROUND
10 IN MOST OTHER AREAS.
LONG TERM (FRI-MON)...
MODELS IN GOOD AGREEMENT IN THE EXTENDED TIME FRAME WITH OVERALL DRY
WEATHER EXPECTED. UPPER LEVEL RIDGE WILL BRING THE QUIET PATTERN TOT
THE REGION THOUGH CANADIAN HIGH PRESSURE AT THE SFC WILL KEEP A COLD
AIR MASS ANCHORED ACROSS THE NORTHERN PLAINS. THIS WILL GIVE BELOW
NORMAL TEMPS THROUGH THE PERIOD. THE RIDGE WILL SLOWLY GIVE WAY TO
SOUTHWEST FLOW ALOFT AND BRING A CHC OF -SN FOR CHRISTMAS EVE.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...NONE.
MN...NONE.
&&
$$
JR
AREA FORECAST DISCUSSION
NWS BISMARCK ND
619 AM CST TUE DEC 18 2012
.DISCUSSION...QUICK UPDATE TO RAISE POPS IN THE SOUTH CENTRAL THIS
MORNING. BAND OF SNOW FROM BEULAH AND CENTER SOUTHEAST THROUGH
BISMARCK TO CANNONBALL...LINTON AND STRASBURG CONTINUES TO SLIDE
SOUTHEAST AND COULD DUMP UP TO AN INCH OF SNOW EARLY THIS MORNING.
LATEST RAP SHOWS THE BAND HOLDING TOGETHER AS IT MOVES ACROSS
SOUTH CENTRAL NORTH DAKOTA SO RAISED POPS TO LIKELY ALONG AND
EAST OF THIS BAND. OTHERWISE NO UPDATES OTHER THAN TO POPULATE
WITH THE LATEST SENSIBLE WEATHER.
&&
.AVIATION...LOW PRESSURE OVER SOUTHWEST SASKATCHEWAN AT 12 UTC
WITH A WARM FRONT EXTENDING INTO WESTERN NORTH DAKOTA. THE SURFACE
LOW WILL MOVE INTO NORTHWEST NORTH DAKOTA THIS MORNING AND INTO
NORTHEAST NORTH DAKOTA BY MID EVENING...LIFTING INTO SOUTHERN
MANITOBA BY 12 UTC WEDNESDAY. CURRENTLY...IFR CEILINGS OVER
CENTRAL NORTH DAKOTA INCLUDING MINOT BISMARCK AND JAMESTOWN.
CEILINGS ARE EXPECTED TO IMPROVE AT BISMARCK AND MINOT BY MID TO
LATE MORNING AND AT JAMESTOWN BY EARLY AFTERNOON AS THE SURFACE
LOW TRACKS ACROSS NORTHERN NORTH DAKOTA AND A DRIER WESTERLY
SURFACE FLOW MOVES WEST TO EAST ACROSS THE LOCAL AREA. MVFR-IFR
CEILINGS WILL LINGER AT OR JUST NORTH OF WILLISTON AND MINOT
TODAY...THEN DROP SOUTH LATER TONIGHT AS THE SURFACE LOW MOVES
EAST AND FLOW TURNS MORE NORTHWEST. THERE WILL BE ISOLATED TO
SCATTERED SNOW SHOWERS TODAY...MOST PREVALENT ACROSS THE NORTH.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
TWH
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
743 AM EST TUE DEC 18 2012
.SYNOPSIS...
LOW PRESSURE WILL TRACK NORTHEAST ACROSS SOUTHWESTERN NEW YORK AND
THE FINGER LAKES REGION THIS MORNING. A SOUTHWARD TRAILING COLD
FRONT WILL PUSH EAST ACROSS THE STATE THROUGH EARLY THIS AFTERNOON.
BRISK WEST WINDS AND DRIER AIR WILL FOLLOW THIS FRONT ACROSS THE
CENTRAL AND EASTERN VALLEYS...WHILE RAIN SHOWERS CHANGE TO
OCCASIONAL SNOW SHOWERS ACROSS THE NORTHERN AND WESTERN MOUNTAINS.
A RIDGE OF HIGH PRESSURE WILL DRIFT ACROSS THE REGION ON WEDNESDAY
ACCOMPANIED BY FAIR WEATHER. ANOTHER SIGNIFICANT LOW PRESSURE SYSTEM
AND ATTENDANT COLD FRONT WILL IMPACT THE LOCAL WEATHER WITH
RAIN...FOLLOWED BY SNOW SHOWERS AND GUSTY WEST TO NORTHWEST WINDS
LATE THIS WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
430 AM UPDATE...
997 MB SFC LOW WAS LOCATED NEAR KBFD AND MOVING NORTHEAST. A FEW
MID/UPPER LEVEL VORT CENTERS INVOF OF THIS LOW WERE HELPING TO
PRODUCE AREAS OF STEADIER LIGHT TO MDT RAIN ACROSS...AND ABOUT 50NM
INLAND FROM THE SE SHORE OF LAKE ERIE.
THE COLD FRONT TRAILING SOUTH FROM THE LOW WILL MOVE STEADILY EAST
ACROSS THE REGION THIS MORNING...EXITING THE SUSQ VALLEY BY EARLY
THIS AFTERNOON.
AREAS OF FOG NEAR AND JUST TO THE NE OF A SFC WARM FRONT /THAT WAS
LIFTING SLOWLY NEWRD ACROSS THE SUSQ VALLEY/ WILL PERSIST THROUGH
ABOUT 13Z. THE DENSE FOG ADVISORY...PREVIOUSLY IN EFFECT UNTIL 11Z
TODAY...WAS RECENTLY CANCELLED.
VSBYS WILL LIKELY DIP TO BETWEEN 1/4 AND 1/2SM AT TIMES THROUGH
ABOUT 13Z...BUT WIDESPREAD DENSE FOG IS NOT LIKELY AS THE LIGHT AND
VARIABLE WINDS QUICKLY FRESHEN TO 10-15 KTS FROM THE WEST-SOUTHWEST
JUST AHEAD OF THE CFRONT THIS MORNING.
LATEST RUC AND SREF GUIDANCE SHOWS THE RAIN SHOWERS BECOMING/STAYING
ISOLATED TO SCATTERED ACROSS MUCH OF CENTRAL AND SERN PENN...WHILE
THE MORE FREQUENT RAIN SHOWERS CHANGE TO MAINLY SNOW SHOWERS AFTER
15Z AS THE FREEZING LEVEL QUICKLY DESCENDS FROM SVRL KFT AGL...DOWN
TO NEAR THE SFC FOR THE MIDDAY AND AFTERNOON HOURS.
A FEW INTERVALS OF SUNSHINE DEVELOPING THROUGH THE LIFTING STRATO CU
CLOUD BASES WILL HELP TO BOOST TEMPS INTO THE 40S AND LOWER 50S
THROUGHOUT THE CENTRAL AND SE VALLEY FOR A MIDDAY HIGH BEFORE LLVL
COLD ADVECTION STRENGTHENS TO TRIM TEMPS GRADUALLY DOWNWARD FROM 18Z
ON.
A LIGHT COATING OF SNOW /TO PERHAPS ONE INCH/ COULD ACCUMULATE ON
THE RIDGE TOPS OF THE LAURELS AND NW MTNS LATER THIS AFTERNOON AND
EVENING AS TEMPS DIP INTO THE LOWER 30S.
IN ADDITION...WEST TO NORTHWEST WINDS WILL INCREASE LATE THIS
MORNING AND SHOULD GUST BETWEEN 30-35 MPH THIS AFTERNOON.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
WEST-NORTHWEST WINDS WILL STAY GUSTY THIS EVENING WITH SNOW SHOWERS
DIMINISHING...BEFORE THE BASE OF THE SUBSIDENCE INVERSION GRADUALLY
LOWERS. THE RELATIVELY SHALLOW AND WARM CLOUD TEMPS OF -3C TO -6C
WILL SUPPORT JUST SOME LIGHT SNOW GRAINS OR PATCHY FREEZING DRIZZLE
ACROSS THE WESTERN MTNS TONIGHT.
ELSEWHERE PARTLY TO MOSTLY CLOUDY SKIES WILL BE FOUND ACROSS THE
CENTRAL RIDGE AND VALLEY REGION...AND SUSQ VALLEY.
MIN TEMPS TONIGHT WILL VARY FROM THE U20S TO AROUND 32F ACROSS THE
MTNS...TO THE LOWER AND MID 30S ELSEWHERE.
A RIDGE OF HIGH PRESSURE AT THE SFC AND ALOFT WILL DRIFT EAST ACROSS
THE STATE WEDNESDAY...ACCOMPANIED BY PARTLY...TO MOSTLY CLOUDY SKIES
CENTRAL AN NW...AND MOSTLY SUNNY SKIES IN THE SOUTHEAST.
VERTICAL MIXING UP TO 2-3 KFT AGL...COMBINED WITHE THE TAIL END OF
THE 925-850MB THERMAL TROUGH AND NW FLOW ALOFT WILL YIELD 10-15 KT
NW WINDS FOR THE MIDDAY AND AFTERNOON HOURS.
MAX TEMPS IN THE U30S TO LOWER 40S ACROSS THE MTNS...AND NEAR 50F
THROUGHOUT THE LOWER AND MIDDLE SUSQ VALLEY...WILL BE NEARLY 10F
ABOVE NORMAL.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
MEDIUM RANGE MODEL AND ENSEMBLE GUIDANCE REMAINS IN PRETTY GOOD
AGREEMENT WITH RESPECT TO THE LARGE SCALE PATTERN FROM THE SECOND
HALF OF THE WEEK THROUGH THE WEEKEND. A DEEPENING CYCLONE WILL MOVE
OUT OF THE MID-MS VALLEY INTO THE GREAT LAKES BY 00Z FRI...AND THEN
OCCLUDE INTO NORTHERN NEW ENGLAND AS IT SLOWS AMID AMPLIFYING FLOW.
THE GFS/GEFS REMAIN A BIT QUICKER THAN THE ECMWF/ECENS WITH THE
PROGRESSION OF THIS SYSTEM...INCLUDING THE TRAILING/SHARP COLD
FRONT. IT APPEARS SECONDARY SFC WAVE DEVELOPMENT IS LKLY ALONG THE
COLD FRONT INVOF NJ AS EMPHASIZED MORE-SO BY THE DETERMINISTIC
/NON-NCEP/ OPER ECMWF AND CANADIAN GEM. STG SLY LLJ +3-4SD AHEAD OF
THE COLD FRONT WILL TRANSPORT ABOVE NORMAL MSTR/PWAT NWD ALONG THE
FRONT. DIFFLUENT FLOW ALOFT ASSOC WITH 100KT SWLY UPPER JET ALONG
WITH STG HEIGHT FALL CENTER CROSSING THE LWR LAKES WILL SUPPORT A
BAND OF MOD FRONTAL RAINS. DESPITE STG SLY FLOW/WAA JUST OFF THE
DECK...MESO MODEL DATA INDICATES MUCH OF THE CWA /ESP THE NRN MTNS/
MAY BE CAD IN RESPONSE TO STG LLVL AGEO WINDS OUT OF THE ENE. HAVE
NOT LOOKED CLOSELY BUT THE LG SCALE PATTERN DOES SEEM TO SUPPORT A
LOW-TOPPED NCFRB. MAY ALSO NEED TO WATCH FOR STG PRES FALL/RISE
COUPLET WHICH MAY LEAD TO A BRIEF PERIOD OF POST-FRONTAL HIGH
WINDS/GUSTS.
COLD AIR WILL RUSH INTO THE AREA IN THE WAKE OF A SHARP COLD
FROPA...AND MAY CATCH-UP TO THE BACKSIDE OF THE DEPARTING
SYNOPTIC PCPN SHIELD...CHANGING RAIN OVER THE SNOW AT THE END OF
THE EVENT. THIS KIND OF DETAIL WILL NEED TO BE RESOLVED AT SHORTER
RANGES. A PROLONGED PERIOD OF SEASONABLY COLD AND BLUSTERY
NORTHWEST/CYCLONIC FLOW WILL PREVAIL FROM FRIDAY INTO THE UPCOMING
WEEKEND...WHICH WILL SUPPORT A PROLONGED PERIOD OF LAKE
EFFECT/UPSLOPE SNOW EVENT OVER THE NORTHWEST MTNS AND LAUREL
HIGHLANDS. THERE ARE STRONG INDICATIONS FROM THE MODELS AND
ENSEMBLES THAT SEVERAL INCHES OF SNOW IS POSSIBLE - IF NOT LKLY -
PARTICULARLY IN THE NW MTNS. WILL NEED TO ADD THIS WINTER WX
THREAT INTO THE HWO...WITH MEDIUM TO RELATIVELY HIGH CONFIDENCE
EVEN AT THIS RANGE.
SEASONABLY COLD...WINTERTIME TEMPERATURES SHOULD PERSIST INTO EARLY
NEXT WEEK. EVEN THOUGH TEMPS WILL BE NEAR NORMAL...IT WILL FEEL
MUCH COLDER GIVEN THE MILD DECEMBER THUS FAR. CYCLONIC FLOW ALOFT
SHOULD LOSE ITS GRIP ON THE NERN CONUS BY EARLY NEXT WEEK...AS
GEFS AND ECENS BOTH SHOW A TROUGH DEVELOPING OVER THE CENTRAL U.S.
BY CHRISTMAS DAY.
&&
.AVIATION /13Z TUESDAY THROUGH SATURDAY/...
LOW PRESSURE WILL TRACK NORTHEAST ACROSS SOUTHWESTERN NEW YORK AND
THE FINGER LAKES REGION THIS MORNING. THIS WILL KEEP MAINLY IFR
CONDITIONS ACROSS CENTRAL PA FOR SEVERAL MORE HOURS. A STEADIER
RAIN WILL IMPACT KBFD WHILE SCATTERED TO NUMEROUS SHOWERS AND
AREAS OF DRIZZLE SLIDE ACROSS REMAINDER OF NORTHERN AND CENTRAL
MTNS. WINDS WILL TURN WESTERLY THROUGH MID MORNING.
A COLD FRONT WILL CROSS THE STATE EARLY TODAY...WHICH WILL BRING
CHANGES. WESTERLY WINDS WILL PICK UP THIS AFTERNOON...GUSTING UP
TO 35-40 MPH. WITH DOWNSLOPE COMPONENT TO THE WIND...THE LOWER
SUSQ WILL SEE CONDITIONS IMPROVE TO VFR. CENTRAL MTNS WILL IMPROVE
TO MVFR...BUT WESTERN AND NORTHERN HIGHER TERRAIN WILL REMAIN IFR
AS COLD POOL ALOFT MOVES THROUGH IN ADDITION TO FORCED UPSLOPE
FLOW OF COOL/MOIST AIR AT LOW LEVELS TO KEEP LOW CLOUDS IN PLACE.
PRECIP WILL TURN TO SNOW SHOWERS BY LATE MORNING FROM KBFD-
KJST...AND LOCAL RESTRICTIONS WILL BE LIKELY.
EXPECT PARTIAL CLEARING ACROSS THE RIDGE AND VALLEY REGION OF PA
TONIGHT. THE COLD AIR AND NORTHWESTERLY FLOW SHOULD ALLOW FOR
BANDS OF LAKE ENHANCED SNOW AT BFD AND JST INTO EARLY
TONIGHT...FOLLOWED BY SOME IMPROVEMENT TO MVFR LATE. GUSTY NW
WINDS UP TO 35KTS POSSIBLE EARLY TONIGHT...BEFORE GRADUALLY
SUBSIDING.
OUTLOOK...
WED...BREEZY NW WIND. MVFR POSS NRN AND WESTERN MTNS...AND MAINLY VFR
ELSEWHERE.
THU...RAIN SHOWERS LIKELY. MAINLY VFR WITH MVFR POSS LATE.
FRI...TURNING COLDER. RAIN/SNOW SHOWERS BECOMING ALL SNOW...ESP
NW IN IFR/MVFR. BREEZY WEST WINDS RETURN.
SAT...BREEZY. LAKE EFFECT SNOWS IN NW MTNS WITH MVFR/IFR
CONDITIONS. MVFR POSS CENTRAL. VFR SE.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT
LONG TERM...LAMBERT/STEINBUGL
AVIATION...RXR
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
445 AM EST TUE DEC 18 2012
.SYNOPSIS...
LOW PRESSURE WILL TRACK NORTHEAST ACROSS SOUTHWESTERN NEW YORK AND
THE FINGER LAKES REGION THIS MORNING. A SOUTHWARD TRAILING COLD
FRONT WILL PUSH EAST ACROSS THE STATE THROUGH EARLY THIS AFTERNOON.
BRISK WEST WINDS AND DRIER AIR WILL FOLLOW THIS FRONT ACROSS THE
CENTRAL AND EASTERN VALLEYS...WHILE RAIN SHOWERS CHANGE TO
OCCASIONAL SNOW SHOWERS ACROSS THE NORTHERN AND WESTERN MOUNTAINS.
A RIDGE OF HIGH PRESSURE WILL DRIFT ACROSS THE REGION ON WEDNESDAY
ACCOMPANIED BY FAIR WEATHER. ANOTHER SIGNIFICANT LOW PRESSURE SYSTEM
AND ATTENDANT COLD FRONT WILL IMPACT THE LOCAL WEATHER WITH
RAIN...FOLLOWED BY SNOW SHOWERS AND GUSTY WEST TO NORTHWEST WINDS
LATE THIS WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
430 AM UPDATE...
997 MB SFC LOW WAS LOCATED NEAR KBFD AND MOVING NORTHEAST. A FEW
MID/UPPER LEVEL VORT CENTERS INVOF OF THIS LOW WERE HELPING TO
PRODUCE AREAS OF STEADIER LIGHT TO MDT RAIN ACROSS...AND ABOUT 50NM
INLAND FROM THE SE SHORE OF LAKE ERIE.
THE COLD FRONT TRAILING SOUTH FROM THE LOW WILL MOVE STEADILY EAST
ACROSS THE REGION THIS MORNING...EXITING THE SUSQ VALLEY BY EARLY
THIS AFTERNOON.
AREAS OF FOG NEAR AND JUST TO THE NE OF A SFC WARM FRONT /THAT WAS
LIFTING SLOWLY NEWRD ACROSS THE SUSQ VALLEY/ WILL PERSIST THROUGH
ABOUT 13Z. THE DENSE FOG ADVISORY...PREVIOUSLY IN EFFECT UNTIL 11Z
TODAY...WAS RECENTLY CANCELLED.
VSBYS WILL LIKELY DIP TO BETWEEN 1/4 AND 1/2SM AT TIMES THROUGH
ABOUT 13Z...BUT WIDESPREAD DENSE FOG IS NOT LIKELY AS THE LIGHT AND
VARIABLE WINDS QUICKLY FRESHEN TO 10-15 KTS FROM THE WEST-SOUTHWEST
JUST AHEAD OF THE CFRONT THIS MORNING.
LATEST RUC AND SREF GUIDANCE SHOWS THE RAIN SHOWERS BECOMING/STAYING
ISOLATED TO SCATTERED ACROSS MUCH OF CENTRAL AND SERN PENN...WHILE
THE MORE FREQUENT RAIN SHOWERS CHANGE TO MAINLY SNOW SHOWERS AFTER
15Z AS THE FREEZING LEVEL QUICKLY DESCENDS FROM SVRL KFT AGL...DOWN
TO NEAR THE SFC FOR THE MIDDAY AND AFTERNOON HOURS.
A FEW INTERVALS OF SUNSHINE DEVELOPING THROUGH THE LIFTING STRATO CU
CLOUD BASES WILL HELP TO BOOST TEMPS INTO THE 40S AND LOWER 50S
THROUGHOUT THE CENTRAL AND SE VALLEY FOR A MIDDAY HIGH BEFORE LLVL
COLD ADVECTION STRENGTHENS TO TRIM TEMPS GRADUALLY DOWNWARD FROM 18Z
ON.
A LIGHT COATING OF SNOW /TO PERHAPS ONE INCH/ COULD ACCUMULATE ON
THE RIDGE TOPS OF THE LAURELS AND NW MTNS LATER THIS AFTERNOON AND
EVENING AS TEMPS DIP INTO THE LOWER 30S.
IN ADDITION...WEST TO NORTHWEST WINDS WILL INCREASE LATE THIS
MORNING AND SHOULD GUST BETWEEN 30-35 MPH THIS AFTERNOON.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
WEST-NORTHWEST WINDS WILL STAY GUSTY THIS EVENING WITH SNOW SHOWERS
DIMINISHING...BEFORE THE BASE OF THE SUBSIDENCE INVERSION GRADUALLY
LOWERS. THE RELATIVELY SHALLOW AND WARM CLOUD TEMPS OF -3C TO -6C
WILL SUPPORT JUST SOME LIGHT SNOW GRAINS OR PATCHY FREEZING DRIZZLE
ACROSS THE WESTERN MTNS TONIGHT.
ELSEWHERE PARTLY TO MOSTLY CLOUDY SKIES WILL BE FOUND ACROSS THE
CENTRAL RIDGE AND VALLEY REGION...AND SUSQ VALLEY.
MIN TEMPS TONIGHT WILL VARY FROM THE U20S TO AROUND 32F ACROSS THE
MTNS...TO THE LOWER AND MID 30S ELSEWHERE.
A RIDGE OF HIGH PRESSURE AT THE SFC AND ALOFT WILL DRIFT EAST ACROSS
THE STATE WEDNESDAY...ACCOMPANIED BY PARTLY...TO MOSTLY CLOUDY SKIES
CENTRAL AN NW...AND MOSTLY SUNNY SKIES IN THE SOUTHEAST.
VERTICAL MIXING UP TO 2-3 KFT AGL...COMBINED WITHE THE TAIL END OF
THE 925-850MB THERMAL TROUGH AND NW FLOW ALOFT WILL YIELD 10-15 KT
NW WINDS FOR THE MIDDAY AND AFTERNOON HOURS.
MAX TEMPS IN THE U30S TO LOWER 40S ACROSS THE MTNS...AND NEAR 50F
THROUGHOUT THE LOWER AND MIDDLE SUSQ VALLEY...WILL BE NEARLY 10F
ABOVE NORMAL.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
MEDIUM RANGE MODEL AND ENSEMBLE GUIDANCE REMAINS IN PRETTY GOOD
AGREEMENT WITH RESPECT TO THE LARGE SCALE PATTERN FROM THE SECOND
HALF OF THE WEEK THROUGH THE WEEKEND. A DEEPENING CYCLONE WILL MOVE
OUT OF THE MID-MS VALLEY INTO THE GREAT LAKES BY 00Z FRI...AND THEN
OCCLUDE INTO NORTHERN NEW ENGLAND AS IT SLOWS AMID AMPLIFYING FLOW.
THE GFS/GEFS REMAIN A BIT QUICKER THAN THE ECMWF/ECENS WITH THE
PROGRESSION OF THIS SYSTEM...INCLUDING THE TRAILING/SHARP COLD
FRONT. IT APPEARS SECONDARY SFC WAVE DEVELOPMENT IS LKLY ALONG THE
COLD FRONT INVOF NJ AS EMPHASIZED MORE-SO BY THE DETERMINISTIC
/NON-NCEP/ OPER ECMWF AND CANADIAN GEM. STG SLY LLJ +3-4SD AHEAD OF
THE COLD FRONT WILL TRANSPORT ABOVE NORMAL MSTR/PWAT NWD ALONG THE
FRONT. DIFFLUENT FLOW ALOFT ASSOC WITH 100KT SWLY UPPER JET ALONG
WITH STG HEIGHT FALL CENTER CROSSING THE LWR LAKES WILL SUPPORT A
BAND OF MOD FRONTAL RAINS. DESPITE STG SLY FLOW/WAA JUST OFF THE
DECK...MESO MODEL DATA INDICATES MUCH OF THE CWA /ESP THE NRN MTNS/
MAY BE CAD IN RESPONSE TO STG LLVL AGEO WINDS OUT OF THE ENE. HAVE
NOT LOOKED CLOSELY BUT THE LG SCALE PATTERN DOES SEEM TO SUPPORT A
LOW-TOPPED NCFRB. MAY ALSO NEED TO WATCH FOR STG PRES FALL/RISE
COUPLET WHICH MAY LEAD TO A BRIEF PERIOD OF POST-FRONTAL HIGH
WINDS/GUSTS.
COLD AIR WILL RUSH INTO THE AREA IN THE WAKE OF A SHARP COLD
FROPA...AND MAY CATCH-UP TO THE BACKSIDE OF THE DEPARTING
SYNOPTIC PCPN SHIELD...CHANGING RAIN OVER THE SNOW AT THE END OF
THE EVENT. THIS KIND OF DETAIL WILL NEED TO BE RESOLVED AT SHORTER
RANGES. A PROLONGED PERIOD OF SEASONABLY COLD AND BLUSTERY
NORTHWEST/CYCLONIC FLOW WILL PREVAIL FROM FRIDAY INTO THE UPCOMING
WEEKEND...WHICH WILL SUPPORT A PROLONGED PERIOD OF LAKE
EFFECT/UPSLOPE SNOW EVENT OVER THE NORTHWEST MTNS AND LAUREL
HIGHLANDS. THERE ARE STRONG INDICATIONS FROM THE MODELS AND
ENSEMBLES THAT SEVERAL INCHES OF SNOW IS POSSIBLE - IF NOT LKLY -
PARTICULARLY IN THE NW MTNS. WILL NEED TO ADD THIS WINTER WX
THREAT INTO THE HWO...WITH MEDIUM TO RELATIVELY HIGH CONFIDENCE
EVEN AT THIS RANGE.
SEASONABLY COLD...WINTERTIME TEMPERATURES SHOULD PERSIST INTO EARLY
NEXT WEEK. EVEN THOUGH TEMPS WILL BE NEAR NORMAL...IT WILL FEEL
MUCH COLDER GIVEN THE MILD DECEMBER THUS FAR. CYCLONIC FLOW ALOFT
SHOULD LOSE ITS GRIP ON THE NERN CONUS BY EARLY NEXT WEEK...AS
GEFS AND ECENS BOTH SHOW A TROUGH DEVELOPING OVER THE CENTRAL U.S.
BY CHRISTMAS DAY.
&&
.AVIATION /10Z TUESDAY THROUGH SATURDAY/...
THE HEAVIEST SHOWERS SHOWERS CONTINUE TO MOVE EASTWARD...WITH MAINLY
AREAS OF LIGHT RAIN/DRIZZLE IN CENTRAL PA AT THIS TIME.
LOW PRESSURE NEAR KYNG WILL CONTINUE TO TRACK NORTHEAST...AND INTO
THROUGH WESTERN AND CENTRAL NEW YORK STATE LATE THIS MORNING.
WIDESPREAD IFR TO LIFR CIGS...WITH MVFR TO IFR VSBYS WILL CONTINUE
THROUGH THE MID MORNING HOURS BEFORE A COLD FRONT CROSSES THE STATE
AND BRINGS SOME IMPROVEMENT TO CIGS AND VSBYS ACRS THE CENTRAL AND
ERN VALLEYS DURING THE MIDDAY AND AFTERNOON HOURS AS THE LLVL FLOW
SHIFTS TO WESTERLY.
THE WEST WINDS WILL GUST BETWEEN 28-33KTS DURING THE LATE MORNING
AND AFTERNOON HOURS TODAY.
POOR IFR TO LIFR FLYING CONDITIONS AND UNSETTLED WEATHER CONTINUES
ACRS THE WESTERN AND NRN MTNS FOR MUCH OF TODAY AS THE ORTHOGONAL
FLOW OF COLDER/MOIST AIR ASCENDS THE RIDGES. A CHANGEOVER FROM RAIN
TO SNOW IS EXPECTED FROM KJST TO KFIG AND KBFD LATE THIS MORNING.
EXPECT PARTIAL CLEARING ACROSS THE RIDGE AND VALLEY REGION OF PENN
TONIGHT. THE COLD AIR AND NORTHWESTERLY FLOW SHOULD ALLOW FOR BANDS
OF LAKE ENHANCED SNOW AT BFD AND JST INTO EARLY TONIGHT...FOLLOWED
BY SOME IMPROVEMENT TO MVFR LATE. GUSTY NW WINDS UP TO 35KTS
POSSIBLE EARLY TONIGHT...BEFORE GRADUALLY SUBSIDING.
OUTLOOK...
WED...BREEZY NW WIND. MVFR POSS NRN AND WESTERN MTNS...AND MAINLY VFR
ELSEWHERE.
THU...RAIN SHOWERS LIKELY. MAINLY VFR WITH MVFR POSS LATE.
FRI...TURNING COLDER. RAIN/SNOW SHOWERS BECOMING ALL SNOW...ESP
NW. BREEZY WEST WINDS RETURN.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT
LONG TERM...LAMBERT/STEINBUGL
AVIATION...LAMBERT/RXR
AREA FORECAST DISCUSSION
NWS DENVER/BOULDER CO
342 PM MST TUE DEC 18 2012
.SHORT TERM...MOUNTAIN WEB CAMS SHOW SNOW HAS DECREASED MOST AREAS
AS FLOW ALOFT BECOMES SOUTHWEST AHEAD OF APPROACHING TROUGH.
ELSEWHERE...MID AND HIGH LEVEL CLOUDS ON THE INCREASE AS MOISTURE
SPREADS INTO REGION. MODELS SIMILAR IN BRINGING TROUGH ACROSS
GREAT BASIN THIS EVENING WITH INCREASING MID LEVEL ASCENT AND
INSTABILITY. SHOULD BEGIN TO SEE SNOW INCREASE ONCE AGAIN...
ESPECIALLY AFTER MIDNIGHT WHEN 700 MB LOW MOVES INTO WESTERN
COLORADO AND FLOW ALOFT BECOMES WESTERLY. SHOULD SEE A GOOD SHOT
OF SNOW WITH THE INCREASING ASCENT AND FAVORABLE LAPSE RATES. WILL
ISSUE AN ADVISORY FOR SNOW FOR THE MOUNTAINS...BEGINNING AT
MIDNIGHT. ACROSS PLAINS...SURFACE LOW TO DEEPEN TONIGHT AHEAD THE
APPROACHING LOW WITH WINDS BECOMING NORTHERLY AFTER 06Z. AIRMASS
TO GRADUALLY MOISTEN AS DEEPER MOISTURE SPREADS INTO AREA.
BEGINNING TO SEE SOME ECHOES ACROSS LARIMER AND NORTHWESTERN WELD
COUNTIES. LATEST MODELS SHOW MOST OF THE SNOW DEVELOPING AFTER
06Z..THOUGH THE RAP HOLDING OFF UNTIL AFTER 09Z WHICH MAY BE A BIT
SLOW. AS WINDS BECOME NORTHERLY...SHOULD SEE SNOW COVERAGE
INCREASE AND BEGIN TO SPREAD SOUTH BY 12Z. UPPER LOW TO MOVE
ACROSS THE STATE DURING THE MORNING WITH GOOD QG VERTICAL
VELOCITIES AND INCREASING LAPSE RATES. LATEST MODELS HAVE BEEN
INDICATING LESS SNOW FOR THE PLAINS...BUT MAY BE OVERDONE GIVEN
THE MID LEVEL ASCENT. A FEW LOCATIONS COULD SEE SNOW FALL RATES OF
1/2 TO 1 INCH PER HOUR DURING THE PERIOD OF GREATEST ASCENT DURING
THE MORNING. WILL UPGRADE THE WINTER STORM WATCH TO A SNOW AND
BLOWING SNOW ADVISORY FOR MUCH OF THE PLAINS. WILL BEGIN THIS
HILITES AT 08Z...MAINLY TO ACCOUNT FOR THE MORNING RUSH. WILL ALSO
ISSUE A SNOW ADVISORY FOR THE FOOTHILLS BEGINNING AT 08Z AS
MODELS SHOW DEEP UPSLOPE TO AROUND 600 MB. ACROSS THE FAR EASTERN
PLAINS...BEST CHANCE FOR SNOW TO BE AROUND 15Z. THOUGH SNOW
AMOUNTS MAY BE A BIT LIGHT...THE GUSTY WINDS WILL PROVIDE FOR
BLIZZARD CONDITIONS FOR ZONES 46..47 AND 49 WITH LIMITED
VISIBILITES. WILL ISSUE A BLIZZARD WARNING FOR THOSE ZONES
BEGINNING AT 15Z. WILL ALSO INCLUDE ZONES 48..50..51 AS WELL AS
41. SOME ROAD CLOSURES WILL CERTAINLY BE POSSIBLE. ACROSS THE
MOUNTAINS...WILL CONTINUE THE ADVISORY THROUGH THE AFTERNOON. SNOW
WILL PROBABLY BE ON THE DECREASE AS MOISTURE AND DYNAMICS
DECREASE. TOTAL SNOW ACCUMULATIONS LOOK TO BE FROM 3 TO 8 INCHES
ACROSS THE PLAINS AND FOOTHILLS...HIGHEST NEAR THE WYOMING
BORDER. ACROSS THE MOUNTAINS...6 TO 14 INCHES CAN BE EXPECTED.
.LONG TERM...MODELS SHOW THE UPPER TROUGH AXIS OVER THE EASTERN
BORDER AT 00Z WEDNESDAY EVENING. STRONG NORTHWESTERLY FLOW ALOFT
IS PROGGED WEDNESDAY NIGHT. ON THURSDAY AND THURSDAY NIGHT...AN UPPER
RIDGE IS PROGGED TO MOVE ACROSS COLORADO WITH FAIRLY STRONG WEST-
NORTHWESTERLY FLOW ALOFT. THURSDAY NIGHT AND FRIDAY ARE PROGGED
TO HAVE FAIRLY WEAK ZONAL FLOW ALOFT. BY FRIDAY NIGHT...THE FLOW
ALFOT IS WEST-SOUTHWESTERLY IN DIRECTION. THE QG VERTICAL VELOCITY
FIELDS HAVE DOWNWARD SYNOPTIC SCALE ENERGY PROGGED FOR THE CWA
WEDNESDAY NIGHT INTO THURSDAY EVENING. THE REST OF THE THURSDAY
NIGHT THROUGH FRIDAY NIGHT...THE ENERGY IS BENIGN. THE LOW LEVEL
WIND AND PRESSURE FIELDS SHOW THE BOUNDARY LAYER FLOW TO BECOME
DOWNSLOPING EARLY WEDNESDAY EVENING. BY 06Z WEDNESDAY NIGHT...
WESTERLY WINDS PREVAIL OVER THE MOUNTAINS...FOOTHILLS AND WESTERN
PLAINS...WITH FAIRLY STRONG NORTHWESTERLIES THE FURTHER EAST TO GO
TO THE COLORADO BORDER. DOWNSLOPING IS PROGGED TO CONTINUE
THURSDAY AND FRIDAY...BUT AT LESSER SPEEDS. FOR MOISTURE...THERE
IS STILL SOME OVER THE EASTERN FORECAST AREA EARLY THURSDAY
EVENING...BUT ALL THE MODELS DRY THINGS OUT RAPIDLY AND BY 06Z
WEDNESDAY NIGHT...PRECIPATION SHOULD BE OVER EVERYWHERE. MOISTURE
IS QUITE SPARSE THURSDAY THROUGH FRIDAY NIGHT. THERE IS NO
MEASURABLE PRECIPITATION NOTED ON THE QPF FIELDS WEDNESDAY NIGHT
THROUGH FRIDAY NIGHT...ALL FIVE PERIODS. FOR POPS...WILL DECREASE
EVERYTHING RAPIDLY WEDNESDAY EVENING...THEN NO POPS FROM 06Z
WEDNESDAY NIGHT THROUGH FRIDAY. WILL LINGER SOME BLOWING SNOW OVER
APPROPRIATE AREAS WEDNESDAY NIGHT. AS FAR AS HIGHLIGHTS GO...
WILL GO WITH THE SHORT TERM FORECASTER. FOR TEMPERATURES...
THURSDAY HIGHS ARE 6-9 C WARMER THAN WEDNESDAY`S. MOS GUIDANCE
VALUES MAY BE TO HIGH...ESPECIALLY FIGURING WE WILL LIKELY HAVE A
SNOW COVER IN PLACE OVER MUCH OF THE CWA. FRIDAYS`S HIGH COME UP
ANOTHER 2-4 C FROM THURSDAY`S. FOR THE LATER DAYS...SATURDAY
THROUGH TUESDAY...MODELS HAVE WEST-SOUTHWESTERLY FLOW ALOFT OVER
THE CWA SATURDAY INTO MONDAY. THE ECMWF BRINGS AN UPPER TROUGH
ACROSS LATE MONDAY AND MONDAY NIGHT. THE GFS IS MUCH SLOWER WITH
THE SYSTEM. BOTH MODELS HAVE LITTLE MOISTURE OVER THE WEEKEND. BUT
BY SUNDAY NIGHT...MOISTURE IS ON THE INCREASE. BOTH MODELS DO
SHOW A PRETTY COLD AIRMASS TO MOVE INTO COLORADO WITH THE UPPER
TROUGH MONDAY OR TUESDAY...DEPENDING. THERE IS ALSO UPSLOPE FOR
THE PLAINS AND FOOTHILLS. WILL GO WITH MINOR POPS RIGHT NOW AND
CONTINUE TO WATCH THE EVOLUTION OF THIS FEATURE.
&&
.AVIATION...EASTERLY WINDS TO SHIFT TO THE NORTH AROUND 06Z AS A
COLD FRONT MOVES SOUTH ACROSS THE PLAINS. SHOULD SEE CEILINGS
GRADUALLY LOWER...WITH CEILINGS AROUND 6000 FEET POSSIBLE. NOT
EXPECTING SNOW TO DEVELOP UNTIL AFTER 06Z WITH MVFR CONDITIONS
BY 09Z. IFR CONDITIONS TO FROM 12Z TO 19Z DUE TO SNOW AND BLOWING
SNOW AS WELL AS LOW CEILINGS. SNOW TO DECREASE AFTER 19Z BUT GUSTY
WINDS TO CONTINUE. MVFR CONDITIONS TO PREVAIL WITH OCCASIONAL IFR
CONDITIONS. TOTAL SNOW ACCUMULATIONS OF 2 TO 4 INCHES
EXPECTED...MAINLY DURING THE 12Z TO 18Z TIME FRAME.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
BLIZZARD WARNING FROM 8 AM TO 8 PM MST WEDNESDAY FOR COZ041-
046>051.
WINTER WEATHER ADVISORY FROM 3 AM TO 5 PM MST WEDNESDAY FOR
COZ035-036.
WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 5 PM MST
WEDNESDAY FOR COZ031-033-034.
WINTER WEATHER ADVISORY FROM 3 AM TO 8 PM MST WEDNESDAY FOR
COZ038>040-042>045.
&&
$$
SHORT TERM...D-L
LONG TERM....RJK
AVIATION...D-L
AREA FORECAST DISCUSSION
NWS GRAND JUNCTION CO
258 PM MST TUE DEC 18 2012
.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 218 PM MST TUE DEC 18 2012
THIS LATE AFTERNOON THE FORECAST AREA IS DIVIDED INTO TWO REGIMES
DIVIDED BY THE COLD FRONT LAYING ALONG THE ROAN-TAVAPUTS PLATEAU
INTO THE FLATTOPS. ALONG AND NORTH OF THE FRONT...HEAVY SNOW HAS
BEEN FALLING. STATE PATROL REPORTS AROUND 6 INCHES IN CRAIG THOUGH
ONLY HALF AND INCH IN VERNAL. CROSHO AND BUFFALO PARK SNOTELS REPORT 15
INCHES OF NEW SNOW. SOUTH OF THE FRONT SNOWFALL HAS BEEN MUCH MORE
SKETCHY...MAINLY ALONG SW FACING SLOPES.
A STRONG WEST TO EAST ORIENTED JET STREAK ALONG THE WYOMING
BORDER THIS MORNING HAS LIFTED OFF TO THE NE TODAY. IN RESPONSE
THE MID-UPPER FLOW HAS BACKED TO SSW TODAY PRODUCING WARM
ADVECTION. THIS WARM OVER-RUNNING HAS HELPED TO PRODUCE THE HEAVY
SNOWFALL ALONG THE STATIONARY FRONT. SOUTH OF THE
FRONT...AFTERNOON SURFACE TEMPERATURES CLIMBED SEVERAL DEGREES
ABOVE GUIDANCE. STRONG ISENTROPIC UPGLIDE WILL CONTINUE INTO THIS
EVENING. THIS STABILIZING PATTERN CAN BE SEEN ON RADAR WITH MTN
WAVE BANDING SEEN TO THE NORTH OF THE RADAR TRANSMITTER.
WET BULB ZERO AND 700MB TEMPS SUPPORT SNOW DOWN TO 4500FT SO ANY
SHOWERS WILL QUICKLY TURN TO SNOW.
THE UPPER LEVEL TROUGH MOTION...THROUGH THE GREAT BASIN TONIGHT...
HAS GOOD MODEL CONTINUITY. YET THE 18Z NAM AND RAP BOTH SUPPORT A
LATER FRONTAL ADVANCE HOWEVER...NOW INTO THE I-70 CORRIDOR AROUND
MIDNIGHT TONIGHT. THIS PUTS THE CENTRAL VALLEY WARNINGS IN DOUBT
BUT DOES NOT REMOVE THE POTENTIAL TO GET UP TO 6 INCHES OF
SNOWFALL THERE. BASED ON THIS AND IN COORDINATION WITH THE SLC
OFFICE... HAVE KEPT THE WARNINGS IN PLACE AND SLOWED THE WORDING
TO EMPHASIZE THE PERIOD BETWEEN MIGHT AND SUNRISE.
THE SOUTHERN ZONES TOO WILL SEE IMPRESSIVE FRONTAL FORCING AFTER
MIDNIGHT INTO WEDNESDAY MORNING. IN THE COLD SECTOR OF THE STORM
LATE TONIGHT THROUGH WEDNESDAY...700MB TEMPERATURES WILL DROP
RIGHT THROUGH THE DENDRITIC CRYSTAL GROWTH REGIME TO -17C BY
WEDNESDAY AFTERNOON. THIS WILL VERY EFFICIENTLY EEK OUT ALL
AVAILABLE MOISTURE. ONLY NW-FACING SLOPES WILL CONTINUE THROUGH
WEDNESDAY AFTERNOON WITH ALL SHOWERS SHUTTING DOWN BY SUNSET. A
VERY COLD NIGHT IS IN STORE FOR WEDNESDAY NIGHT.
.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY) ISSUED AT 430 AM
MST TUE DEC 18 2012
DRIER NORTHWESTERLY FLOW ALOFT OVERHEAD WEDNESDAY NIGHT AS THE STORM
SYSTEM CONTINUES TO MOVE EAST. A RIDGE OF HIGH PRESSURE WILL MOVE
EAST OVER THE REGION AND REMAIN DOMINATE DURING THE END OF THE WEEK.
WITH SNOW ON THE GROUND...THE COLD AIR MASS BEHIND THE FRONT AND HIGH
PRESSURE EXPECT VALLEY INVERSIONS. TEMPERATURES SHOULD REMAIN COLD
IN THE VALLEYS. THEREFORE WENT BELOW GUIDANCE FOR THESE LOCATIONS.
THE COLDEST MORNING SHOULD BE THURSDAY WHICH SHOULD ALSO BE THE
COLDEST OF THE SEASON. BY THE END OF THE WEEK TEMPERATURES SHOULD BE
MODIFIED SLIGHTLY BUT THIS WILL BE A SLOW PROCESS DUE TO THE
PREVIOUSLY MENTIONED RIDGE OF HIGH PRESSURE.
THE RIDGE WILL SLIDE EASTWARD ALLOWING THE NEXT STORM SYSTEM INTO
THE AREA BY MONDAY ALTHOUGH THE TIMING AND PLACEMENT VARIES BETWEEN
MODELS. INCREASED THE PRECIPITATION FORECAST SLIGHTLY TO HIGHLIGHT
THAT A STORM IS ON THE HORIZON. THAT SAID THERE ARE MANY VARIABLES
STILL NOT WORKED OUT YET SO MUCH UNCERTAINTY WITH TIMING AND
STRENGTH.
&&
.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 1030 AM MST TUE DEC 18 2012
WIDESPREAD MODERATE TO STRONG MECHANICAL TURBULENCE EXPECTED THIS
EVENING ALONG AND NORTH OF AREA RIDGES AND MTNS. WRN COLORADO TAF
SITES...DETERIORATING CONDITIONS TONIGHT WITH LOWERING CIGS AFTER
03Z...BECOMING WIDESPREAD IFR FOR ALL TAF SITES AFTER 06Z.
WIDESPREAD 1 1/2SM -SN BR CIGS VV002 IS EXPECTED INTO WEDNESDAY MORNING.
AREAS OF MODERATE SN OVER NW COLORADO TODAY WILL SPREAD
SOUTHWARD OVERNIGHT.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER STORM WARNING UNTIL NOON MST WEDNESDAY FOR COZ003-006>008-
011-014-020-022-023.
WINTER STORM WARNING UNTIL 6 AM MST WEDNESDAY FOR COZ001-002.
WINTER STORM WARNING UNTIL 6 PM MST WEDNESDAY FOR COZ004-005-009-
010-012-013-017>019.
WINTER WEATHER ADVISORY UNTIL NOON MST WEDNESDAY FOR COZ021.
UT...WINTER STORM WARNING UNTIL NOON MST WEDNESDAY FOR UTZ025.
WINTER WEATHER ADVISORY UNTIL 6 AM MST WEDNESDAY FOR UTZ024.
WINTER STORM WARNING UNTIL 8 AM MST WEDNESDAY FOR UTZ027.
WINTER STORM WARNING UNTIL 6 AM MST WEDNESDAY FOR UTZ023.
WINTER WEATHER ADVISORY UNTIL 8 AM MST WEDNESDAY FOR UTZ029.
WINTER STORM WARNING UNTIL 6 PM MST WEDNESDAY FOR UTZ028.
&&
$$
SHORT TERM...JOE
LONG TERM...AS
AVIATION...PF/JOE
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
459 PM EST TUE DEC 18 2012
.SYNOPSIS...
BRISK AND DRIER CONDITIONS WILL PREVAIL ACROSS THE COMMONWEALTH
TONIGHT. SOME LAKE EFFECT SNOW SHOWERS AND FLURRIES WILL AFFECT
NORTHWEST SECTIONS. A MOISTURE LIMITED UPPER AIR DISTURBANCE AND
ASSOCIATED WEAK SURFACE LOW PRESSURE WILL PRODUCE SOME LIGHT SNOW
SHOWERS FROM EASTERN OHIO THROUGH THE LAUREL HIGHLANDS EARLY
WEDNESDAY MORNING...RESULTING IN A LIGHT COATING OF SNOW IN SOME
LOCATIONS. OTHERWISE...DRY CONDITIONS WILL PREVAIL UNTIL THURSDAY
AS A RIDGE OF HIGH PRESSURE DRIFTS ACROSS THE REGION ON WEDNESDAY.
ANOTHER SIGNIFICANT LOW PRESSURE SYSTEM AND ASSOCIATED COLD FRONT
WILL IMPACT THE LOCAL WEATHER WITH RAIN...FOLLOWED BY SNOW SHOWERS
AND GUSTY WEST TO NORTHWEST WINDS LATE THIS WEEK INTO THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
21Z RADAR LOOP SHOWING RAIN/SNOW SHOWERS RAPIDLY DIMINISHING FROM
WEST TO EAST ACROSS THE AREA...AS UPPER LVL TROF AND ASSOC
DEFORMATION BAND/DEEP LYR MOISTURE SHIFTS EAST. BASED ON LATEST
RADAR TRENDS AND RAP OUTPUT...WILL REMOVE MENTION OF PRECIP OVR
THE N MTNS BY ARND 00Z. GUSTY WEST WINDS CONTINUE TO BUFFET AREA
AS OF 21Z. HOWEVER...EXPECT THEM TO SUBSIDE OVERNIGHT AS SFC
RIDGING BUILDS INTO THE AREA.
NEXT UPSTREAM SHORTWAVE...OVR CHICAGO AT 21Z...WILL TRACK INTO
WESTERN PA LATE TONIGHT...WITH ASSOCIATED WEAK SFC LOW PRESSURE
PUSHING INTO EASTERN OHIO BEFORE GETTING ABSORBED INTO THE STRONG
PRESSURE GRADIENT ACROSS THE REGION. THIS COULD PRODUCE SOME
TRACE TO COATING AMOUNTS OF SNOW ACROSS THE LAUREL HIGHLANDS LATE
TONIGHT. LITTLE IF ANY ACCUMS EXPECTED THIS EVENING OVER WARREN
AND MCKEAN COUNTIES. SOME UNCERTAINTY WITH REGARDS TO PTYPE...AS
LYR OF MOISTURE WILL BE RELATIVELY SHALLOW AND MAY NOT BE DEEP
ENOUGH TO SUPPORT ICE CRYSTALS. WILL REEVALUATE THIS EVENING AND
MAY MENTION THE POSSIBILITY OF FZDZ/DZ IN ADDITION TO SHSN.
SOME PARTIAL CLEARING REACHING INTO THE WEST CENTRAL MOUNTAINS
AND LAURELS THIS EVENING...THEN CLOUDS INCREASE AGAIN LATER ON AS
THE AFOREMENTIONED DISTURBANCE APPROACHES. MIN TEMPS WILL BE
TRICKY AS A RESULT OVER THE WEST...BUT EXPECT READINGS TO FALL
BELOW FREEZING FROM THE LAURELS NORTHWARD TO THE NORTHWEST
MOUNTAINS AND EASTWARD THROUGH THE ENDLESS MOUNTAIN REGION. LOWS
FROM THE CENTRAL MOUNTAINS TO THE LOWER SUSQ ARE LIKELY TO BE IN
THE L/M 30S.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
SHORTWAVE RIDGING ALOFT AND BUILDING SFC HIGH PRESSURE WILL
PROVIDE A DECENT DAY ACROSS CENTRAL PA ON WEDNESDAY...AFTER ANY
AM -SHSN/-FZDZ DISSIPATE WITH THE EXIT OF THE WEAKENING LO PRE
SYSTEM.
PARTLY TO MOSTLY CLOUDY SKIES CENTRAL AND NW AREAS...AND MOSTLY SUNNY
SKIES ARE EXPECTED IN THE SOUTHEAST. VERTICAL MIXING UP TO 2-3
KFT AGL...COMBINED WITH THE TAIL END OF THE 925-850MB THERMAL
TROUGH AND NW FLOW ALOFT WILL YIELD 10-15 KT NW WINDS FOR THE
MIDDAY AND AFTERNOON HOURS. HIGH TEMPS SHOULD REACH THE UPPER 30S
TO LOWER 40S OVER THE MOUNTAINS...AND APPROACH 50F THROUGH THE
LOWER AND MIDDLE SUSQ RIVER VALLEY AIDED BY DOWNSLOPING FLOW. THIS
WILL STILL BE NEARLY 10F ABOVE NORMAL FOR THIS TIME OF YEAR.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
***ACTIVE WINTER PATTERN IN STORE LATE THIS WEEK INTO THE WEEKEND***
A SPLIT FLOW UPPER TROUGH ALIGNED ALONG THE FRONT RANGE OF THE
ROCKIES WITH A VERY POTENT SRN STREAM SHORT WAVE OVER THE FOUR
CORNERS REGION WILL EJECT OUT INTO THE CENTRAL/SRN PLAINS AND REACH
THE MID MS VLY BY 12Z THU. THE SRN STREAM TROUGH WILL DEEPEN AND
INTENSIFY WHILE ATTEMPTING TO PHASE WITH THE NRN STREAM FEATURE.
THIS WILL ALLOW A LEE SURFACE WAVE TO DEVELOP NEAR THE TX/OK
PANHANDLES...WITH INTENSIFICATION EXPECTED AS IT TRACKS ENEWD THRU
MO INTO CENTRAL IL BY THE END OF DAY2. THE SURFACE LOW WILL COMPLETE
CYCLOGENESIS ON DAY 3...CONTINUING TO DEEPEN AS IT LIFTS NEWD AND
OCCLUDES NEAR THE THUMB OF LOWER MI. WITH THE EXCEPTION OF THE
NAM...THE 18/12Z MODELS HAVE SHIFTED WEST...A BIT SLOWER...WITH
THE SFC LOW FCST TO TRACK NEWD FROM OKLAHOMA INTO THE GREAT LAKES
REGION. MEANWHILE...ITS ASSOCIATED POWERFUL/SHARP COLD FRONT WILL
SWEEP EWD AND CROSS THE APPLCHNS THUR NIGHT AND REACH THE MID-
ATL/SOUTHEAST COAST BY 12Z FRI. A TRIPLE POINT/SECONDARY LOW WILL
FORM OVER THE VA PIEDMONT AND TRACK NEWD TOWARD THE
POCONOS/CATSKILLS...AS THE MID-UPPER TROUGH GOES NEGATIVE TILT.
THE DEEP LOW EVENTUALLY BECOMES VERTICALLY STACKED INVOF UPSTATE
NY BY 00Z SAT.
INTENSE MID LEVEL HEIGHT FALLS...ON THE ORDER OF 200-250 M IN 12
HR...WILL SHIFT EWD FROM THE OH VLY ACROSS CENTRAL PA THUR NIGHT.
THE EXIT REGION OF A 100KT JET MAX ROUNDING THE BASE OF THE UPPER
LOW/MID LEVEL HEIGHT FALL CENTER WILL PROVIDE AMPLE LG SCALE
LIFT/DIVERGENCE ALOFT...WHILE VERY STRONG +3-5 SIGMA /50-60KT/ SLY
850MB LLJ WILL DRAW A NARROW RIBBON OF MODEST PWATS NWD ALONG THE
SHARP COLD FRONTAL BOUNDARY. THE DEEP-LAYER FORCING AND STRONG
DYNAMICS WILL SUPPORT A BAND OF MODERATE FRONTAL PCPN...WHICH MAY
TAKE ON THE FORM OF A NARROW COLD-FRONTAL RAIN BAND /NCFRB/. DAY 3
QPF AMTS RANGE BTWN 0.50-0.75 INCHES...WITH A MAX AROUND 1 INCH
INTO ERN PA NEAR THE TRIPLE POINT LOW TRACK. A BLEND OF
NAM/GFS/SREF HR THERMAL PROFILES ALLOWS FOR A PTYPE CHANGEOVER
FROM RAIN TO SNOW ON THE BACKSIDE OF THE FRONTAL PCPN BAND...AS
STRONG DYNAMIC COOLING AND LLVL CAA RAPIDLY DROPS TEMPS IN THE COLUMN.
THIS SUGGESTS A LGT SNOW ACCUM IS POSSIBLE LATE THU NIGHT INTO
EARLY FRI...ESPECIALLY OVR THE N-CNTRL AND NERN ZONES. IN
ADDITION...A LOW PROB FOR -FZRA WILL EXIST OVR THE NRN MTNS EARLY
THU AT THE ONSET OF PCPN...AS STG LLVL NE AGEO WINDS KEEPS COLD AIR
ENTRENCHED ALONG AND EAST OF THE ALLEGHENIES. THERE ARE STRONG
INDICATIONS FOR CAD ON THU...SO DESPITE THE STG WAA TEMPS MAY
STRUGGLE TO GET MUCH ABOVE 40F ESP IN THE NRN TIER. WILL BE A
TRICKY TEMP FCST...WITH HIGHS POSSIBLY OCCURRING JUST AFTER
FROPA/WIND SHIFT AND BEFORE THE COLD AIR RUSHES IN FROM THE WEST.
THE MID-LATE DECEMBER PATTERN STABILIZES TO SOME EXTENT HEADING
INTO THE WEEKEND...AS THE DEEP SFC/UPPER SYSTEM SHOULD PROVE SLOW
TO EXIT NRN NEW ENGLAND AND THE CANADIAN MARITIMES WORKING INTO
BLOCKED HIGH LATITUDE FLOW. THIS WILL OPEN THE DOOR FOR A
PERSISTENT...SEASONABLY COLD AND BLUSTERY NW FLOW TO MAINTAIN NEAR
TO BELOW NORMAL TEMPERATURES THROUGH THE WEEKEND AND PERHAPS INTO
EARLY NEXT WEEK. MORE IMPORTANTLY...THIS WILL LIKELY LEAD TO A
PROTRACTED LAKE EFFECT SNOW EVENT FROM FRIDAY-SUNDAY...WITH
SIGNIFICANT SNOW ACCUMULATIONS POSSIBLE OVER THE NW MTNS AND
ALLEGHENY RIDGES/LAUREL HIGHLANDS. WILL CONTINUE TO MENTION THE
HEAVY LAKE EFFECT SNOW THREAT IN THE HWO WITH ABOVE AVG
CONFIDENCE.
THE BROAD CYCLONIC FLOW ALOFT/LAKE EFFECT SNOW REGIME SHOULD LOSE
ITS GRIP ON THE AREA BY EARLY NEXT WEEK. THE 18/12Z ECENS AND
GEFS SHOW A TROUGH DEVELOPING IN THE NATIONS MIDSECTION WHICH
SHOULD FORCE HEIGHTS TO RISE DOWNSTREAM. A PACIFIC SYSTEM IS FCST
TO EMERGE INTO THE CENTRAL US NEXT TUE WHERE SRN PLAINS
CYCLOGENESIS/GULF INFLOW/DEVELOPING PCPN COULD OCCUR TUCKED
UNDERNEATH A MID-HIGHER LATITUDE DOME OF COLDER HIGH PRESSURE TO
THE NORTH. THIS SYSTEM MAY BRING A WINTRY MIXTURE OF PCPN TO THE
REGION AROUND DEC 26TH /NEXT WED/ AS IT LIFTS NEWD THRU THE LWR
MS/TN/OH VLYS AND INTO THE NORTHEAST STATES.
&&
.AVIATION /22Z TUESDAY THROUGH SUNDAY/...
VFR CONDS WILL PREVAIL ACROSS THE LOWER SUSQ...WITH MVFR CONDS
ACROSS THE CENTRAL MOUNTAINS. WESTERN AND NORTHERN HIGH TERRAIN
WILL MVFR TO LCL IFR DUE TO UPSLOPE FLOW AND SCT -SHSN. COLD AIR
AND NORTHWESTERLY FLOW WILL MAINTAIN SNOW SHOWERS AT BFD AND JST
INTO EARLY TONIGHT...FOLLOWED BY SOME IMPROVEMENT TO MVFR LATE.
GUSTY NW WINDS UP TO 35KTS POSSIBLE EARLY TONIGHT...BEFORE
GRADUALLY SUBSIDING. UPPER AIR DISTURBANCE WILL SPREAD MVFR CIGS
AND SCT -SHSN INTO THE LAUREL HIGHLANDS AND VCNTY KJST EARLY
FRIDAY MORNING.
OUTLOOK...
WED...BREEZY NW WIND. MVFR AND -SHSN/FLURRIES POSS NRN AND
WESTERN MTNS...AND MAINLY VFR ELSEWHERE.
THU...RAIN SHOWERS LIKELY. MAINLY VFR WITH MVFR POSS LATE.
FRI...TURNING COLDER. RAIN/SNOW SHOWERS BECOMING ALL SNOW...ESP
NW IN IFR/MVFR. BREEZY WEST WINDS RETURN.
SAT...BREEZY. LAKE EFFECT SNOWS IN NW MTNS WITH MVFR/IFR
CONDITIONS. MVFR POSS CENTRAL. VFR SE.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...DEVOIR
NEAR TERM...DEVOIR/FITZGERALD
SHORT TERM...DEVOIR
LONG TERM...STEINBUGL
AVIATION...DEVOIR/RXR