Forecast Discussions mentioning any of
"HRRR" "RAP" "RR" "RUC13" "RUC" received at GSD on 12/25/12
AREA FORECAST DISCUSSION
NWS EUREKA CA
450 AM PST SUN DEC 23 2012
.SYNOPSIS...A STRONG LOW PRESSURE SYSTEM WILL BRING WIND AND RAIN
TO THE AREA THROUGH EARLY AFTERNOON. A BRIEF RIDGE OF HIGH
PRESSURE WILL BRING DRY WEATHER MONDAY BEFORE ANOTHER SYSTEMS
BRINGS ADDITIONAL WIND AND RAIN ON TUESDAY.
&&
.SHORT TERM...A STRONG LOW PRESSURE SYSTEM MOVING ONSHORE IS
CREATING A COMPLICATED SHORT TERM FORECAST. MODELS HAD BEEN
WAVERING ON THIS...BUT THE LATEST RUC AND THE 06Z NAM HAVE FINALLY
COME INTO AGREEMENT ON THE TRACK OF THE LOW.THE LOW PRESSURE IS
PROGGED TO BOTTOM OUT AT 996 MB OVER THE NORTHERN OUTER WATERS
THIS MORNING AROUND 9AM AND BEGIN TO FILL AS IT MOVES NORTHEAST
ACROSS THE ORCAL BORDER. THIS BRINGS THE STRONG WINDS FARTHER
NORTH. GUSTS TO 50 OR 55 MPH ARE POSSIBLE AS THIS LOW PRESSURE
MOVES ON SHORE THIS MORNING. THIS IS A CHANGE FROM PREVIOUS MODEL
RUNS SO HAVE MADE SOME CHANGES TO THE FORECAST. ADDED WIND
ADVISORIES FOR ZONES 1...2 AND 76 TO ACCOUNT FOR THE STRONGER
WINDS. THE WINTER STORM WARNING IN TRINITY COUNTY STILL LOOKS
GOOD...WEAVERVILLE AND TRINITY CENTER ARE BOTH STILL AT 32
DEGREES. SNOW LEVELS ARE RISING AS EXPECTED IN THE NORTH COAST
INTERIOR AND MENDOCINO COUNTY. SNOWFALL AMOUNTS LOOK TO BE FAIRLY
HIGH AT THE HIGHEST ELEVATIONS ALONG THE COAST. HEAVY RAIN IS EXPECTED
ALONG THE COASTAL AREAS WELL THIS MORNING...AMOUNTS LOOK TO BE
AROUND AN INCH WITH LOCAL AMOUNTS TO 2 INCHES IN FAVORED AREAS.
MAY NEED TO ISSUE A SMALL STREAMS FLOOD ADVISORY...THIS WILL NEED
TO BE MONITORED.
BEHIND THIS SYSTEM HIGH PRESSURE LOOKS BUILD INTO THE AREA BRIEFLY
LATE TONIGHT AND MONDAY. MOST AREAS WILL SEE PARTLY CLOUDY SKIES
FOR MUCH OF MONDAY. SOME VALLEY FOG IS POSSIBLE IN THE
MORNING...ALTHOUGH SHOWERS LOOK TO LINGER SO EXPECT AIRMASS WILL
BE TOO WELL MIXED FOR MUCH FOG. THIS WILL ALSO KEEP TEMPERATURES
FROM DROPPING TOO LOW OVERNIGHT.
THE NEXT SYSTEM LOOKS TO COME IN LATE MONDAY NIGHT INTO TUESDAY
MORNING. THE MODELS ARE IN DECENT AGREEMENT ON SLOWING THIS SYSTEM
DOWN BY A FEW HOURS SO MADE A FEW TWEAKS TO FORECAST TO ACCOUNT
FOR THAT. SNOW LEVELS WILL MAINLY BE OVER 5000 FEET WITH THIS
SYSTEM...HOWEVER ONCE AGAIN THE GFS AND NAM 12 INDICATING SOME
COLD AIR LINGERING IN EASTERN TRINITY COUNTY. WINDS WITH THIS
FRONT WILL BE FAIRLY STRONG AND AN ADVISORY MAY BE NEED NORTH OF
CAPE MENDOCINO WITH GUSTS TO 45 MPH...HOWEVER WITH THE LOW
PRESSURE FORMING WELL NORTH OF THE AREA EXPECT WINDS WILL NOT BE
MUCH STRONGER THAN THAT. BEHIND THIS SYSTEM WIDESPREAD SHOWERS ARE
EXPECTED TUESDAY NIGHT. TEMPERATURES ALOFT ONLY LOOK MARGINAL FOR
SMALL HAIL BEST SO WILL NOT HIGHLIGHT THAT THREAT. MKK
.LONG TERM...MODELS WERE IN DECENT AGREEMENT KEEPING THE REGION
IN COOL NW FLOW ALOFT WITH PERHAPS MORE SHOWER GENERATION ON WED.
OVERALL IT LOOKS LIKE THE UPPER TROUGH WILL EDGE EASTWARD ON THU
AND PUT THE AREA UNDER A RIDGE ALOFT AND LIGHT OFFSHORE FLOW. THE
MODELS BEGIN TO GO HAYWIRE ON FRI AND THROUGH NEXT WEEKEND AS THE
PROGRESSION OF STORMS START TO BREAKDOWN INTO A SPLIT TYPE FLOW.
WITH THE UNCERTAINTY IN THE FLOW PATTERN CHANGE...WHICH SEEMS
DUBIOUS...WILL GO AHEAD STAY WITH NEAR CLIMO PRECIP CHANCES.
&&
.AVIATION...A STRONG LOW PRESSURE MOVING ONSHORE NEAT THE ORCAL
BORDER THIS MORNING. LOW PRESSURE PROGGED TO BOTTOM OUT AROUND 996
OFF THE NORTH COAST. THIS WILL BEGIN TO FILL AS ITS MOVES ONSHORE
THIS MORNING. MAIN CONCERN THIS MORNING WILL BE GUSTY WINDS.
GUSTS OF 40 TO 50 MPH ARE LIKELY AT KCEC WITH WINDS NEARLY THAT
HIGH AT KACV. GUSTY WINDS ARE ALSO EXPECTED AT KUKI. THIS SYSTEM
WILL BRING PERIODS OF MODERATE TO HEAVY RAIN WHICH MAY BRING
CONDITIONS DOWN TO MVFR FOR BRIEF PERIODS. TONIGHT SHOWERS WILL
DIMINISH. SOME FOG IS POSSIBLE MONDAY MORNING...ALTHOUGH AT THIS
POINT ENVIRONMENT LOOKS AS THOUGH THERE WILL BE TOO MANY
CONVECTIVE SHOWERS STILL AROUND TO ALLOW FOG TO FORM. MKK
&&
.MARINE...A STRONG AREA OF LOW PRESSURE WILL MOVE TOWARD THE COAST
THIS MORNING BRINGING GALE FORCE SOUTHERLY WINDS TO THE SOUTHERN
WATERS. STORM FORCE GUSTS WILL BE POSSIBLE WITH THE ACTUAL FRONTAL
BOUNDARY PASSAGE AND THIS WILL BE COVERED BY SPECIAL MARINE WARNINGS
IF IT DEVELOPS. GUIDANCE INDICATES THE ACTUAL SURFACE LOW WILL MOVE
TOWARD HUMBOLDT BAY OR SLIGHTLY FARTHER NORTH...POSSIBLY BRINGING A
VERY BRIEF PERIOD OF GALE FORCE WINDS TO THE SOUTHERN PORTION OF THE
NORTHERN INNER WATERS. HOWEVER WITH HIGH UNCERTAINTY WILL STICK
WITH HIGH END SMALL CRAFTS AT THIS TIME. THE LOW WILL MOVE INLAND
AROUND NOON TODAY WITH THE FRONT LAGGING SLIGHTLY BEHIND ACROSS THE
SOUTHERN WATERS. WINDS WILL TURN OUT OF THE NORTHWEST BEHIND THE
FRONT AND DECREASE IN MAGNITUDE. AS FOR THE SEAS...A NORTHWEST SWELL
CONTINUED TO DECAY ACROSS THE WATERS THIS MORNING WHILE THE
SOUTHERLY WINDS ALLOW SHORT PERIOD SEAS TO BUILD. THESE SHORTER
PERIOD SEAS...AROUND 8 TO 10 SECONDS...WILL PEAK NEAR 15 FT AROUND
NOON ACROSS THE SOUTHERN WATERS.
SEAS AND WINDS WILL BOTH FALL BELOW SMALL CRAFT CRITERIA OVERNIGHT
INTO EARLY MONDAY AS AN UPPER LEVEL RIDGE BUILDS OVER THE WEST
COAST. HOWEVER THESE CALMER CONDITIONS WILL BE SHORT LIVED WITH
ANOTHER FRONTAL BOUNDARY APPROACHING THE WATERS MONDAY NIGHT INTO
TUESDAY. ANOTHER PERIOD OF GALE FORCE SOUTHERLY WINDS LOOKS LIKELY
WITH INCREASING SHORT PERIOD SEAS. THE FRONTAL BOUNDARY AND UPPER
TROUGH WILL MOVE EAST OF THE AREA TUESDAY AFTERNOON FOLLOWED BY A
BUILDING NORTHWEST SWELL IN THE 10 TO 14 FT RANGE REQUIRING
CONTINUED SMALL CRAFT ADVISORIES INTO MIDWEEK. RPA
&&
.HYDROLOGY...MODERATE TO HEAVY RAIN CONTINUES TO FALL ACROSS MUCH
OF THE AREA. THIS WILL CAUSE RISES ON AREA RIVERS. THE EEL RIVER
AT FERNBRIDGE REMAINS AT MONITOR STAGE. IT MAY DROP BELOW THIS
MORNING BEFORE CLIMBING AGAIN TONIGHT. THE NAVARRO RIVER IS
STILL EXPECTED TO REACH FLOOD STAGE THIS AFTERNOON SO WATCH
REMAINS IN PLACE. WILL EVAULATE THIS WITH THE NEW RFC FORECAST
THIS MORNING. MKK
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...WINTER WEATHER ADVISORY UNTIL 4 PM PST THIS AFTERNOON ABOVE 3000
FEET FOR THE CAZ003.
WINTER STORM WARNING UNTIL 4 PM PST THIS AFTERNOON ABOVE 2000
FEET FOR THE CAZ004.
WIND ADVISORY FROM 6 AM THIS MORNING TO NOON PST TODAY
CAZ001-003-076.
WIND ADVISORY UNTIL NOON PST TODAY CAZ002.
NORTHWEST CALIFORNIA COASTAL WATERS...GALE WARNING UNTIL 11 AM
PST THIS MORNING PZZ470.
GALE WARNING UNTIL 2 PM PST THIS AFTERNOON PZZ455-475.
GALE WARNING UNTIL 11 AM PST THIS MORNING PZZ450.
&&
$$
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AREA FORECAST DISCUSSION
NWS JACKSONVILLE FL
822 PM EST MON DEC 24 2012
.UPDATE...UPPER SHORT WAVE TROUGH MOVING ACROSS THE SOUTHEAST U.S.
HAS PRODUCED RAIN OVER SE GA EARLIER. 00Z JAX SOUNDING SHOWS A
MOISTENING AND STABLE AIRMASS WITH STRENGTHENING WIND FIELDS AND
LOW LEVEL WAA. CURRENTLY RAIN CONTINUES OVER NE FL MOSTLY ALONG
AND NORTH OF I-10. THE RUC MODEL HAS CORRECTLY SHOWN THE SOUTHERN
EXTENT OF PRECIP EXTENDING INTO NE FL WITH RAIN DECREASING THERE
AFTER 03Z. THIS SCENARIO LOOKS GOOD AS RADAR LOOPS SUPPORT THIS
TREND. EXPECT PRECIP TO INCREASE AGAIN TOWARDS MORNING MAINLY OVER
SE GA AS ANOTHER IMPULSE MOVES INTO THE LOWER MS RIVER VALLEY.
&&
.AVIATION...
THE UPPER LEVEL SHORT WAVE TROUGH LOOKS LIKE IT WILL EXIT THE REGION
BY MIDNIGHT TAKING THE PRECIPITATION SHIELD WITH IT. RIGHT NOW
KEEPING CONDITIONS THAT WERE REPORTED UPSTREAM IN THE VALDOSTA AREA
EARLIER THIS EVENING IN THE TEMPO GROUPS WITH BETTER PREVAILING
CONDITIONS. WITH ABUNDANT LOW LEVEL MOISTURE AND SOME LOW LEVEL
MIXING STILL THINK MOST FIELDS WILL GO DOWN IN FOG TOWARD SUNRISE.
&&
.MARINE...
STILL CONTINUING TO SEE SMALL CRAFT EXERCISE CAUTION CONDITIONS AT
THE SAINT AUGUSTINE BUOY AND WILL CONTINUE THE EXERCISE CAUTION
TROUGH THE OVERNIGHT HOURS FOR THE OFFSHORE WATERS.
RIP CURRENTS: LOW RISK EXPECTED TUESDAY.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 51 70 55 64 / 40 40 70 70
SSI 52 69 58 68 / 50 30 40 60
JAX 50 73 56 71 / 60 20 40 60
SGJ 49 72 62 73 / 30 10 30 60
GNV 48 75 56 70 / 20 10 40 60
OCF 48 75 56 72 / 20 10 40 60
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GA...NONE.
AM...NONE.
&&
$$
ZIBURA/SANDRIK/CHASE
AREA FORECAST DISCUSSION
NWS CHARLESTON SC
920 PM EST MON DEC 24 2012
.SYNOPSIS...
AN UPPER LEVEL DISTURBANCE WILL MOVE THROUGH THIS EVENING WITH A WEAK
WARM FRONT DEVELOPING OVER THE REGION TONIGHT. THE FRONT WILL
THEN LIFT NORTH THROUGH TUESDAY NIGHT AS STRONG LOW PRESSURE MOVES
THROUGH THE LOWER MISSISSIPPI RIVER VALLEY. THE LOW WILL TRACK
NORTHEAST AND WILL CROSS THE APPALACHIANS WEDNESDAY... DRIVING A
STRONG COLD FRONT THROUGH THE REGION. COOL HIGH PRESSURE WILL THEN
BUILD INTO THE AREA THURSDAY THROUGH FRIDAY. LOW PRESSURE WILL
CROSS THE REGION AND WILL PULL ANOTHER COLD FRONT THROUGH THE AREA
SATURDAY. CHILLY HIGH PRESSURE WILL BUILD OVER THE REGION SUNDAY
INTO EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
THE RADAR CONTINUES TO SHOW A DEARTH OF ANY MEANINGFUL ECHOES
DOWNSTREAM...SO I HAVE REMOVED POPS FOR PRETTY MUCH ALL COUNTIES
FOR THE OVERNIGHT PERIOD. THERE STILL MAY BE A LITTLE DRIZZLE HERE
AND THERE...BUT IT SHOULD NOT ACCUMULATE.
THE OTHER MAIN CHANGE FOR THIS LATE EVENING UPDATE WAS TO INCREASE
THE COVERAGE OF FOG OVERNIGHT. LATEST RAP AND HRRR MODELS SHOW AN
INCREASE IN COVERAGE OF VSBYS LESS THAN 1 MILE...ESPECIALLY AFTER
MIDNIGHT. IT IS POSSIBLE SOME LOCATIONS MAY GET DOWN TO 1/4
MILE...BUT I AM NOT SURE ENOUGH THAT IT WILL BE WIDESPREAD...SO
HAVE OPTED TO HOLD OFF ON AN ISSUANCE FOR A DENSE FOG ADVISORY AT
THIS TIME. STILL...THOSE WHO WILL BE TRAVELING LATE
TONIGHT...INCLUDING SLEIGH AVIATORS...WILL NEED TO BE CAREFUL.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
CHRISTMAS DAY...A VIGOROUS SHORT WAVE MOVING EASTWARD THROUGH
THE SOUTHERN PLAINS WILL TRIGGER DEEP CYCLOGENESIS OVER THE LOWER MS
VALLEY. THIS WILL GENERATE NOT ONLY A LIKELY OUTBREAK OF SEVERE
WEATHER OVER THE GULF COAST STATES...BUT ALSO A SIGNIFICANT WINTER
STORM TO ITS NORTH IN THE COLDER AIR. THE CONTINUED DEVELOPMENT OF A
WARM FRONT THAT STRETCHES EAST FROM THE SURFACE LOW WILL ALIGN
ITSELF EAST-WEST ACROSS THE FORECAST AREA. UTILIZING A CONSENSUS OF
THE VARIOUS MODELS AND PARAMETERS SUCH AS WINDS...LIFTED
INDICES...THETA-E AND LOW LEVEL THICKNESS...THE WARM FRONT WILL
TAKE SHAPE SOMEWHERE WITHIN THE CENTRAL CWFA...PROBABLY NOT TOO FAR
FROM THE SAVANNAH RIVER. VARIOUS MID LEVEL IMPULSES WILL SHIFT
QUICKLY EAST AND NW WITHIN THE FAST MOVING FLOW ALOFT...AND WILL
COMBINE WITH INCREASING ISENTROPIC LIFT TO PRODUCE OVER-RUNNING
RAINS THAT WILL SPREAD EAST AND NE THROUGH THE DAY. WE/RE NOT
ANTICIPATING MORE THAN PATCHY LIGHT RAINS/DRIZZLE AND SOME FOG IN
THE MORNING WITH ABUNDANT MOISTURE TRAPPED IN PLACE. BUT WITH THE
WARM FRONT IN THE VICINITY AND GREATER LIFT IN THE AFTERNOON...RAIN
CHANCES WILL INCREASE INTO THE 20-50 PERCENTILE IN THE AFTERNOON.
HIGHEST CHANCES WILL BE IN THE WEST...WITH LESS RISK IN THE EAST. A
FAIRLY LARGE TEMP GRADIENT WILL EXIST FROM NW TO SE...AND ONCE SOME
STEADIER RAINS DEVELOP IN THE AFTERNOON...DIABATIC RAIN-COOLING
MECHANISMS WILL LIKELY DROP PARTS OF THE NW TIER INTO THE UPPER 50S.
SOUTH OF THE FRONT WE COULD TOP OUT NEAR 70 CLOSE TO THE ALTAMAHA
RIVER.
TUESDAY NIGHT...A POWERFUL NEGATIVELY TILTED TROUGH ALOFT WILL LIFT
FROM THE LOWER MS VALLEY TO THE TN VALLEY...PULLING A DEEP
ASSOCIATED SURFACE CYCLONE TO THE NE INTO TN. THESE FEATURES ARE
BEING FED BY A 120-130 KT UPPER LEVEL JET THAT POKES INTO THE BASE
OF THE TROUGH NEAR THE NORTHERN GULF COAST. THE ASSOCIATED WARM
FRONT WILL TRACK NORTH IN RESPONSE TO THIS PATTERN...AS A SUBTLE DRY
SLOT AND THE WARM SECTOR LIFTS ACROSS MUCH OF THE REGION. THIS TAKES
THE BETTER CHANCE OF RAIN AND SHOWERS TO OUR NORTH...BUT THE
TRANSITION IS SLOW...SO POPS AS HIGH AS 30-60 PERCENT ARE WARRANTED
THROUGH MUCH OF THE NIGHT...HIGHEST NORTH AND WEST.
ADDITIONALLY...SHOWERS AND A FEW T-STORMS WILL FORM OVER THE WARMER
ATLANTIC WATERS AS THE LOW LEVEL SOUTHERLY FLOW DEVELOPS AND QUICKLY
STRENGTHENS/DEEPENS. THAT ALONG WITH AN APPROACHING 40-50 KT LOW
LEVEL JET WILL ENHANCE THE COASTAL CONVERGENCE OVER THE SC COASTAL
ZONES...ALLOWING SOME CONVECTION TO MOVE IN FROM THE OCEAN. UNLESS
THE UPSTREAM QLCS IS FASTER THAN ANTICIPATED...IT SHOULD REMAIN WEST
OF THE CWFA THROUGH 6 AM...ALTHOUGH FAST APPROACHING. TEMPS WILL
FALL LITTLE EARLY ON...THEN HOLD STEADY OR EVEN RISE IN MANY LOCALES
ONCE THE SOUTHERLY FLOW SETS IN BEHIND THE NORTHWARD LIFTING WARM
FRONT.
WEDNESDAY...THE WORST IMPACTS WILL ARRIVE DURING THIS TIME AS THE
PREVIOUSLY MENTIONED QLCS CONTINUES TO ADVANCE RAPIDLY EASTWARD...IN
ASSOCIATION WITH THE NEGATIVELY TILTED TROUGH AND ITS
DIFLUENT/DIVERGENT FLOW ALOFT THAT IS FOUND FROM THE OH VALLEY TO
THE SE STATES. STEADY HEIGHT FALLS WILL OCCUR ALOFT...AND THERE IS
SIGNIFICANT FORCING FOR ASCENT RESULTING FROM THE NOSE OF A 120-130
KT UPPER LEVEL JET AND A 45-60 KT LOW LEVEL JET THAT APPEAR TO
ARRIVE AT A SIMILAR TIME IN THE MORNING/EARLY AFTERNOON. STRONG
SHEAR IS OBVIOUSLY EVIDENT...WITH THE STRONG WIND FIELDS THROUGHOUT
THE ENTIRE TROPOSPHERE. 0-6 KM BULK SHEAR VALUES ARE 50 KT OR HIGHER
AND SOUNDINGS SHOW 50 KT AS LOW AS ABOUT 2K FT OFF THE SURFACE...SO
IT WON/T TAKE MUCH DOWNWARD TRANSFER FOR SEVERE WIND GUSTS TO BECOME
REALIZED. THUS OUR KINEMATIC PARAMETERS WILL SUPPORT A RISK FOR
DAMAGING DOWNBURST AND/OR STRAIGHT LINE WINDS...BUT GIVEN THE
MAGNITUDE OF THE SHEAR...SHOULD ANY DISCRETE SUPERCELLS FORM THERE
IS ALSO THE RISK FOR ISOLATED TORNADOES. INSTABILITY IS STILL NOT
THE GREATEST...FORTUNATELY...BUT GIVEN THE IMPRESSIVE DYNAMICS AND
SHEAR WE HAVE NO CHOICE BUT TO MAINTAIN THE RISK OF SEVERE WEATHER
IN THE HAZARDOUS WEATHER OUTLOOK. THE ONGOING QLCS IS PROGGED TO BY
KNOCKING ON THE WESTERNMOST ZONES AROUND DAYBREAK...REACHING THE
COASTAL AREAS AROUND 10 AM-1 PM...THEN INTO THE ATLANTIC THEREAFTER.
RAIN CHANCES ARE 90 PERCENT SINCE THERE ARE STILL SOME MINOR TIMING
UNCERTAINTIES WITH THIS FORECAST PACKAGE. BUT EVERYONE CAN EXPECT
RAINFALL...AND WE ANTICIPATE ABOUT 1/3 TO 2/3 INCHES OF RAIN WILL
OCCUR. TEMPS WILL CLIMB OVER EASTERN SECTIONS TO THE UPPER 60S/LOWER
70S WITH STRONG WARM ADVECTION IN ADVANCE OF THE SQUALL LINE/COLD
FRONT...BUT LOWER AND MIDDLE 60S FURTHER INLAND WILL FALL INTO THE
50S FOR THE AFTERNOON BEHIND THE FRONT AS COLD ADVECTION DEVELOPS
AND RAIN CHANCES RAPIDLY DROP FROM WEST TO EAST.
EVEN OUTSIDE OF ANY CONVECTION THERE IS A DEFINITE CONCERN FOR
STRONG GRADIENT WINDS TO OCCUR...AND A WIND ADVISORY SEEMS A
CERTAINTY FOR AT LEAST PARTS IF NOT ALL AREAS ON WEDNESDAY INTO THE
FIRST PART OF WEDNESDAY NIGHT.
WEDNESDAY NIGHT AND THURSDAY...RAPID DRYING WILL TAKE HOLD BEHIND
THE DEPARTING COLD FRONT AND THE VERTICALLY STACKED LOW
SURFACE/ALOFT AS IT MOVES TO NEAR THE DELMARVA PENINSULA WEDNESDAY
NIGHT AND TO NEAR LONG ISLAND THURSDAY. THE LARGE CYCLONIC FLOW
AROUND THE LOW WILL STILL EXTEND BACK ACROSS THE LOCAL AREA...SO A
CONTINUED INFLUX OF COLDER AIR WILL SPREAD IN ON THE WEST AND NW
WINDS. IT/LL BE ABOUT 20 DEGREES COLDER COME EARLY THURSDAY MORNING
WHEN COMPARED TO EARLY WEDNESDAY MORNING...WHILE DAYTIME HIGHS
THURSDAY WILL STRUGGLE TO REACH THE LOWER AND MIDDLE 50S DESPITE
PLENTIFUL SUNSHINE.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
HIGH PRESSURE WILL CONTINUE TO PRODUCE BELOW NORMAL TEMPERATURES AND
RELATIVELY TRANQUIL CONDITIONS FRIDAY. COMPLEX LOW PRESSURE WILL
THEN DEVELOP OVER THE GULF COAST AND WILL TRACK ACROSS THE SOUTHEAST
SATURDAY...PRODUCING RAIN AND PUSHING ANOTHER COLD FRONT THROUGH THE
AREA. HIGH PRESSURE AND ANOTHER SHOT OF CHILLY AIR WILL FOLLOW THIS
COLD FROPA INTO THE FORECAST AREA SUNDAY INTO EARLY NEXT WEEK.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
THE FORECAST FOR THE TERMINALS IS CHALLENGING THIS EVENING. RIGHT
NOW...THE CIGS A VFR LEVELS...BUT IFR CIGS ARE LURKING IN THE
MIDLANDS AS WELL AS PORTIONS OF GEORGIA...SO CONDITIONS WILL
DETERIORATE OVERNIGHT. I DO BRING THE CIGS DOWN LATER THIS
EVENING...BUT I MAY BE TOO SLOW IN BRINGING THEM TO IFR.
ANOTHER ISSUE IS THE FOG POTENTIAL. I LOWERED VSBYS IN THE EARLY
MORNING HOURS AT BOTH CHS AND SAV AS THE SET UP FOR FOG LOOKS
QUITE GOOD WITH LOW LEVEL MOISTURE TRAPPED UNDER A GOOD INVERSION.
EXTENDED AVIATION OUTLOOK...PERIODIC FLIGHT RESTRICTIONS POSSIBLE
TUESDAY AND TUESDAY NIGHT GIVEN THE INCREASE IN LOW-LEVEL
MOISTURE...THEN AGAIN WEDNESDAY AS A COMPLEX FRONTAL SYSTEM AFFECTS
THE AREA. GUSTY WINDS AND/OR LOW-LEVEL WIND SHEAR LIKELY LATE
TUESDAY NIGHT THROUGH WEDNESDAY NIGHT OR EARLY THURSDAY.
&&
.MARINE...
TONIGHT...DECENT SOUTHWEST FLOW WILL CONTINUE THIS EVENING BEFORE
A WEAK COLD FRONT APPROACHES THE AREA FROM THE NORTH LATE. THIS
WILL LEAD TO DIMINISHING WINDS WHICH WILL BE SHIFTING TO THE
WEST...ESPECIALLY ACROSS THE SC WATERS. NO HEADLINES EXPECTED BUT
THERE COULD BE SOME FOG LATE...ESPECIALLY AROUND CHARLESTON
HARBOR.
TUESDAY...A DEVELOPING WARM FRONT WILL SPLIT THE COASTAL WATERS IN
HALF NEAR THE SAVANNAH RIVER...ALLOWING FOR NE AND EAST WINDS TO
DEVELOP OVER THE SC WATERS AND SOUTHERLY WINDS ACROSS THE GA WATERS.
SPEEDS WILL BE NO MORE THAN ABOUT 8-12 KT AND SEAS NO HIGHER THAN
ABOUT 2 FT. A LITTLE FOG AND/OR DRIZZLE COULD OCCUR NORTH OF THE
WARM FRONT IN THE MORNING
TUESDAY NIGHT...THERE IS A VERY SMALL WINDOW FOR POSSIBLE SEA FOG IN
THE EVENING WITH THE CONTINUED ONSHORE FETCH...BUT GIVEN STRONG
WINDS MOVING IN OVERNIGHT THIS IS TOO LOW OF A PROBABILITY TO
INCLUDE IN ANY OF OUR GRIDS. OTHERWISE GENTLE TO MODERATE BREEZES
WILL BE ON THE RISE OVERNIGHT...AND WE/LL BE LOOKING AT SCA
CONDITIONS LATE AND WINDS/SEAS CLIMB. HOWEVER...GIVEN THAT THIS IS
THE THIRD PERIOD OF THE FORECAST...AFTER COORDINATION WITH
NEIGHBORING WFO/S JAX AND ILM WE HAVE CHOSEN NOT TO HEADLINE AT THIS
TIME.
WEDNESDAY...A SIGNIFICANT MARINE WEATHER EVENT WILL IMPACT THE
COASTAL WATERS...AS INTENSE LOW PRESSURE MOVES THROUGH THE THE TN/OH
VALLEYS AND A STRONG COLD FRONT MOVES THROUGH FROM THE WEST.
GRADIENT WINDS WILL EASILY REACH HIGH-END SCA CRITERIA OR EVEN GALES
AND WE STILL ANTICIPATE THAT GALE WATCHES AND WARNINGS WILL BE
INITIATED AT SOME POINT TUESDAY. IN ADDITION...MARINERS ARE ALERTED
TO A FAST-MOVING SQUALL LINE THAT COULD GENERATE SEVERE WINDS AS IT
TRACKS QUICKLY EAST THROUGH THE LOCAL WATERS DURING THE LATE MORNING
INTO THE EARLY OR MID-AFTERNOON.
WEDNESDAY NIGHT AND THURSDAY...STRONG COLD ADVECTION BEHIND THE COLD
FRONT WILL TRANSPIRE INTO EARLY THURSDAY...THEN WANE THE REST OF THE
DAY ON THURSDAY. GALES WILL LIKELY PERSIST INTO WEDNESDAY
NIGHT...BEFORE RAPIDLY IMPROVING CONDITIONS TAKE HOLD DURING
THURSDAY.
&&
.TIDES/COASTAL FLOODING...
HIGH SURF...STRONG SOUTH AND SW WINDS WILL LIKELY PRODUCE HIGH SURF
ALONG THE COAST...AS BREAKERS REACH 5 FEET IN THE SURF ZONE. A HIGH
SURF ADVISORY WILL LIKELY BE REQUIRED DURING THIS TIME. PLUS THE
STRONG ONSHORE FLOW ALONG WITH THE LARGE AND ROUGH SURF CONDITIONS
WILL LEAD TO A FEW AREAS OF BEACH EROSION.
BLOWOUT TIDES...IN WAKE OF THE COLD FRONT WEDNESDAY NIGHT...THE
STRONG VEERING OF WINDS TO THE WEST COULD SUPPORT BLOW-OUT TIDE
CONDITIONS WITH LEVELS DROPPING AS MUCH AS 1.25 TO 1.75 FT MLLW
BELOW PREDICTED LEVELS.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...NONE.
&&
$$
SYNOPSIS...
NEAR TERM...ALSHEIMER
SHORT TERM...
LONG TERM...SPR
AVIATION...ALSHEIMER
MARINE...RJB
TIDES/COASTAL FLOODING...
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
338 PM EST SUN DEC 23 2012
.SHORT TERM.../TONIGHT THROUGH MONDAY NIGHT/
LATEST SFC ANALYSIS HAS WEAK FRONTAL BOUNDARY JUST TO THE SOUTH
OF THE CWA EXTENDING BACK TO DEVELOPING FRONTAL WAVE IN EASTERN
OKLAHOMA. WATER VAPOR IMAGERY ALONG WITH LATEST RAP ANALYSIS
DEPICTING SPLIT FLOW PATTERN ACROSS THE EASTERN TWO THIRDS OF THE
CONUS...EACH WITH THEIR OWN WEAK DISTURBANCE THAT WILL MOVE ACROSS
THE REGION ON MONDAY. NORTHERN STREAM SHORT WAVE CURRENTLY MOVING
THROUGH THE DAKOTAS IS EXPECTED TO CONTINUE EASTWARD INTO THE
GREAT LAKES REGION WHILE SOUTHERN STREAM SHORT WAVE WILL MOVE INTO
THE TN VALLEY. MODEL TRENDS HAVE CONTINUED TOWARD A LACK OF
PHASING WITH THESE DISTURBANCES...RESULTING IN CONCERN OVER
FORCING AND AVAILABLE MOISTURE WITH PRECIP CHANCES MONDAY.
CONSENSUS FAVORS A SPLIT OVER OUR CWA IN BOTH MOISTURE AND
DYNAMICS AS WEAKER SOUTHERN STREAM MOVES QUICKLY INTO EAST TN BY
MONDAY AFTERNOON WHILE NORTHERN STREAM WAVE DIGS INTO THE CENTRAL
GREAT LAKES REGION AND WILL PROVIDE SOME DECENT FORCING IN OUR NE
CWA WITH 500MB HT FALLS OF 60-80M POSSIBLE. PROBLEM IS THAT BEST
MOISTURE WILL BE CONFINED TO THE NORTH. HAVE THEREFORE OPTED TO
KEEP POPS IN HIGH CHANCE RANGE IN EASTERN THIRD OF CWA WHERE BEST
CHANCE FOR PRECIP WILL MATERIALIZE. PRECIP TYPE WILL ALSO COME
INTO PLAY FOR THE E/SE CWA AS TEMPS EXPECTED TO REACH THE MID 30S
AND TIMING OF SYSTEM HAS BEST CHANCE FOR PRECIP AT MAX HEATING.
THIS WILL ALL ACT TO HOLD ANY ACCUMULATING SNOW IN CHECK WITH LESS
THAN AN INCH OVER THE NORTHERN CWA. SYSTEM QUICKLY EXITS THE
REGION MONDAY NIGHT...MAY GET CLIPPED WITH BRIEF LAKE EFFECT IN
ITS WAKE IN FAR NW CORNER BEFORE FLOW BECOMES MORE NE AND SHIFTS
ANY BANDS WEST OF THE AREA.&&
.LONG TERM.../TUESDAY THROUGH SATURDAY/
FOCUS OF THE EXTENDED FORECAST WILL BE ON THE POTENTIAL OF SNOWFALL
ACROSS THE AREA WEDNESDAY.
FORECAST PERIOD BEGINS TUESDAY WILL QUASI ZONAL FLOW ACROSS GREAT
LAKES REGION IN ADVANCE OF SHARPENING H5 TROF AND DEEPENING SFC LOW
ACROSS WRN TX. RAISED HI TEMPS ACROSS THE SOUTHERN 3/4THS OF THE
AREA TUESDAY SLIGHTLY...AND RAISED LOWS SLIGHTLY ON TUESDAY
NIGHT...OTHERWISE NO MAJOR CHANGES TO FORECAST. H5 CUT OFF LOW WILL
DEVELOP OVER ARKLATEX REGION LATE TUESDAY AS UPPER TROF BECOMES
NEGATIVELY TILTED AND EJECTS NORTHEASTWARD THROUGH THE MID
MISSISSIPPI VALLEY INTO THE OHIO VALLEY BY WEDNESDAY. THE EXACT
TRACK OF THE SYSTEM WILL HAVE HUGE IMPLICATIONS FOR SNOWFALL AMOUNTS
ACROSS OUR AREA.
DECENT SPREAD BETWEEN DIFFERENT MODEL SYSTEM TRACKS...NOT TO BE
UNEXPECTED 72+ HOURS OUT. 12Z NAM AND 09Z/15Z SREF ARE FURTHEST NW W/
SFC LOW TRACK INVOF CINCINNATI...WHILE THE 00Z/12Z ECMWF IS FURTHER
SE WITH A JACKSON KY TO CHARLESTON WV SFC LOW TRACK. THE 12Z
GFS/GEFS IS A NICE COMPROMISE AMONG THE SOLUTIONS...WITH A FRANKFORT
KY TO CHILLICOTHE OH TRACK. OVERALL...RECENT MODEL TRENDS HAVE
SUBTLY SHIFTED THE SYSTEM TRACK NW WITH A SLIGHTLY SLOWER
SOLUTION...WHICH IS NOT UNCOMMON WITH NEGATIVELY TILTED PANHANDLE
HOOK TYPE SYSTEMS.
A LEAN TOWARD A 12Z GFS/GEFS LOW TRACK WOULD BRING THE POTENTIAL FOR
SIGNIFICANT SNOWFALL ACROSS A PORTION OF THE AREA...WITH BROAD
SATURATED ASCENT IN THE NW QUADRANT OF THE SYSTEM. THERMAL PROFILES
WOULD BE CONDUCIVE FOR ALL SNOW WITH THE ONSET OF THE SYSTEM FOR THE
DURATION OF THE EVENT. HOWEVER...A FURTHER NW SOLUTION OR STRONGER
SYSTEM COULD WRAP WARMER AIR INTO SE PORTIONS OF THE AREA AND IN
TURN MIXED PRECIPITATION POTENTIAL. THERE IS ALSO SOME EVIDENCE FOR
HEAVIER BANDED PRECIPITATION ACROSS A PORTION OF THE AREA. STRONG
H75-H6 FRONTOGENESIS...WITH NEAR ZERO OR NEGATIVE EPV ALOFT...AND
STRONG OMEGA IMPINGING ON THE DGZ WOULD SUGGEST INGREDIENTS FOR A
POSSIBLE BAND OF HEAVY SNOWFALL...HOWEVER GIVEN UNCERTAINTIES THIS
FAR OUT...CAN NOT RESOLVE THIS IN THE FORECAST AT THIS TIME. INITIAL
THINKING IS THAT A WIDESPREAD 2-4" EVENT...WITH LOWEST AMOUNTS
WEST/NW...WITH THE POTENTIAL FOR A NARROW BAND OF 4-6" WITH LOCALLY
HIGHER AMOUNTS SOMEWHERE ACROSS THE CENTRAL TO EASTERN/SOUTHEASTERN
PORTION OF THE AREA. CONTEMPLATED A WINTER STORM WATCH WITH THIS
FCST ISSUANCE...BUT DECIDED TO DEFER TO THE NEXT SHIFT TO CAPTURE
LATEST MODEL TRENDS AND POTENTIAL INCREASED CONFIDENCE.
FORECAST WISE...INCREASED POPS WEST/NWWARD WITH GIVEN MODEL
SOLUTIONS LATE TUESDAY NIGHT THROUGH WEDNESDAY...WITH A PERIOD OF
CAT POPS FAR SE WEDNESDAY. LEFT EXPECTED PTYPE ALL SNOW AT THIS
JUNCTURE GIVEN PREFERRED MODEL SOLUTION/TRACK/INTENSITY.
SYSTEM WILL EXIT THE REGION WEDNESDAY NIGHT INTO THURSDAY. SOME
POTENTIAL FOR LIGHT LAKE EFFECT SNOW THURSDAY INTO THURSDAY NIGHT
ACROSS FAR NW PORTIONS OF THE AREA WITH NORTHERLY FLOW IN THE WAKE
OF THIS SYSTEM. OTHERWISE CONDITIONS WILL BE DRY WITH COOLER
TEMPS...ESPECIALLY EAST WITH EXPECTED FRESH SNOWPACK. LOWS THURSDAY
NIGHT COULD DROP INTO THE LOWER TEENS EAST.
NEXT SYSTEM OF INTEREST WILL ARRIVE FRIDAY NIGHT INTO SATURDAY.
ECMWF AND GFS DISAGREE WITH THE OVERALL EVOLUTION OF THE
SYSTEM...BUT BOTH HAVE THE GENERAL IDEA AND IMPACT ON OUR AREA.
ECMWF SEPARATES THE NORTHERN AND SOUTHERN STREAM ENERGY...ALLOWING
FOR SHARPENING TROUGH AND LEE CYCLOGENESIS...SIMILAR TO MIDWEEK
PANHANDLE HOOK SYSTEM. GFS HOWEVER COMBINES BOTH NORTHERN AND
SOUTHERN STREAM ENERGY WITH BROAD UPPER TROF OVER ERN CONUS AND MORE
SUBTLE SHORTWAVE. NEVERTHELESS...TEMPERATURE PROFILES SUPPORT AN ALL
SNOW TYPE EVENT.
&&
.AVIATION... /18 UTC TAFS/
WEAK SFC TROF EXTENDING JUST SOUTH OF THE CWA THIS AFTERNOON. LOW
LEVEL MOISTURE BEHIND THIS FEATURE BRINGING MVFR DECK INTO KSBN AND
LATEST VIS SAT SHOWING ADDL UPSTREAM CLOUDS WORKING DOWN THE LAKE
AND SW LWR MI SO EXPECT THIS TO PERSIST INTO THE EVENING HOURS.
MODEL INDICATIONS SHOW SOME DRYING OF THE LOW LEVELS AFTER 00Z SO
HAVE WORKED IN A PERIOD OF VFR CONDITIONS FOR KSBN BEGINNING AT 03Z.
MOISTURE AHEAD OF APPROACHING FRONTAL WAVE WILL THEN BRING MVFR CIGS
BACK INTO BOTH LOCATIONS BY MONDAY MORNING ALONG WITH WINDS VEERING
AROUND TO THE EAST BUT LT 10KTS.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&
$$
SHORT TERM...JAL
LONG TERM...NG
AVIATION...JAL
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
1134 AM CST SUN DEC 23 2012
.AVIATION...
DETERIORATING CONDITIONS AT ALL TERMINALS THE NEXT 6-12 HOURS.
LOW CLOUDS WITH BASES OF 500-1500` AGL HAVE ALREADY REACHED DBQ
TERMINAL AND WILL OVERSPREAD THE REMAINING 3 TERMINALS THIS
AFTERNOON AND EARLY EVENING. THEN...IFR TO VERY LOW MVFR CONDITIONS
WILL CONTINUE AT ALL TERMINALS INTO LATE DAY MONDAY. BETWEEN
06-17Z EXPECT CIGS AOB 500` AT DBQ AND POSSIBLY ALL TERMINALS
WITH VSBYS AOB 2 MILES AND POSSIBLY DOWN BELOW A MILE IN FOG.
SOME IMPROVEMENT TO MVFR CONDITIONS EXPECTED BY MONDAY AFTERNOON.
ISOLATED FLURRIES OR FREEZING DRIZZLE NOT OUT OF THE QUESTION
BETWEEN 06-17Z.
NICHOLS
&&
.PREV DISCUSSION...
UPDATE... /ISSUED 552 AM CST SUN DEC 23 2012/
DID A QUICK UPDATE TO FOLLOW MORE OF THE RAP TRENDS IN ALLOWING
THE CLOUDS WITH EMBEDDED FLURRIES TO SEEP SOUTH TO IMPACT THE
HIGHWAY 20 CORRIDOR BY 14-15Z OR SO THIS MORNING. THESE AREAS MAY
THEN STAY CLOUD ALL AFTERNOON AND INTO THE EVENING. WILL HAVE TO
WATCH FOR A FURTHER SOUTHWARD CREEP OF THESE CLOUDS...BUT HOPE
DIURNAL PROCESSES WELL AFTER SUNRISE-MIXING HELP HALF THE CLOUDS
FROM SINKING MUCH FURTHER SOUTH THAN HWY 30 UNTIL THIS EVENING.
TEMPS ALONG HWY 20 MAY BE HELD IN THE UPPER TEENS TO LOWER 20S IF
LOW CLOUDS HANG TOUGH. ..12..
PREV DISCUSSION... /ISSUED 335 AM CST SUN DEC 23 2012/
SYNOPSIS...
LATEST SFC ANALYSIS WAS INDICATING PASSING WEAK FRONT AND WAVE
MAINLY EAST AND SOUTH OF THE DVN CWA...WHILE CYCLOGENESIS WAS
INCREASING SOME ON THE SAME BOUNDARY OVER NORTH CENTRAL TX INTO OK.
RIDGE AXIS NOTED POKING DOWN OUT OF CANADA ACRS THE NORTHEASTERN
PLAINS AND MO RVR VALLEY. ALOFT...00Z UPPER AIR ANALYSIS AND MOISTURE
FLOW PATTERNS ON THE CURRENT WATER VAPOR IMAGERY WERE INDICATING A
FLATTENING PATTERN ACRS THE CONUS. SAME IMAGERY WAS ALSO SHOWING A
UPPER LEVEL WAVE COMPLEX CURRENTLY ACRS THE NORTHERN INTER-MOUNTAIN
REGION.
SHORT TERM...TODAY AND TONIGHT...
TODAY...MAIN CHALLENGE TODAY IS WHETHER AREAS OF LOW CLOUDS/STRATUS
LURKING ACRS WI AND PORTIONS OF MN INTO THE DAKOTAS...CAN SEEP
SOUTHWARD AND MAKE IT ACRS PORTIONS OF THE DVN CWA. LOOKING AT
VARIOUS SHORT RANGE AND HIRES MODEL LLVL RH PROGS...THEY RANGE FROM
THE NAM12 CONTINUING TO ALLOW THE LLVL CLOUDS TO SEEP DOWN INTO THE
CENTRAL PLAINS AND TOWARD SOUTHEAST WI/CHICAGO AREA WHILE THE
LOCAL CWA REMAINS MAINLY LLVL CLOUD-FREE WITH JUST PASSING ROUNDS OF
CIRRUS. OTHER PART OF THE RANGE IS THE LATEST RAP WHICH SEEPS THE
LOW CLOUDS INTO THE NORTHERN CWA THIS MORNING...THEN HOLD THEM AT
BAY OR ACTUALLY BREAKS THEM UP AS THE DAY PROGRESSES THOUGH LATE
AFTERNOON. LOOKING AT LATEST STRATUS TRENDS ON IR LOOPS...WILL SIDE
WITH THE NAM. HIGH TEMPS IN THE MID TO UPPER 20S OVER THE DEEPER SNOW
PACK AREA TAKING INTO ACCOUNT SOME POST FRONTAL CAA...TO HIGHS IN
THE LOWER 30S IN THE SOUTHEASTERN FCST AREA. WILL BANK ON THE CI
AND INCREASING NORTH FLOW INTO THE SOUTH TO LIMIT MORE WIDESPREAD
FOG IN THOSE AREAS THIS MORNING.
TONIGHT...THE ABOVE MENTIONED UPPER LEVEL VORT COMPLEX CURRENTLY
ACRS EASTERN OR/WA INTO ID...WILL LOOK TO PROPAGATE INLAND ON
NORTHERN EDGE OF DEVELOPING WESTERLIES ACRS THE CONUS TONIGHT...
MAKING ACRS THE WESTERN CWA IN DIGGING UPPER TROF FASHION BY 12Z MON
MORNING. BESIDES NICE BOUT OF LIFT THROUGH THE COLUMN TO THE LEE OF
THIS FEATURE INTO THE AREA AFTER MIDNIGHT... THE SOUTHERN PLAINS
CYCLOGENESIS TO CONTINUE TO BLOSSOM AND PROGRESS NORTHEASTWARD WITH
SFC LOW DEVELOPMENT...MAKING FOR AN ASSOCIATED INVERTED TROF POKING
ACRS THE DVN CWA FROM 06Z-12Z MON. THUS LIFT AND FOCUS THERE FOR
PRECIP FORMATION...THE QUESTION IS HOW MUCH MOISTURE AND HOW DEEP
TO ALLOW ANY SUCH PRECIP TO DEVELOP AND MAKE IT TO THE SFC. ANALYSIS
OF SEVERAL BUFKIT SOUNDINGS AND MODEL VERTICAL PROFILES SUGGEST
DEEPENING LLVL MOISTURE FROM SNOW MELT AND THE ADVECTION OF THE
ADJACENT LLVL CLOUD FIELDS TO THE WEST MOVING IN ACRS THE AREA
AND GETTING TRAPPED UNDER H85-H75 MB INVERSION. SOME LK MI STRATUS
ADVECTING TO THE WEST AN CONVERGING AROUND THE LLVL INVERTED TROF
ALSO POSSIBLE. WHILE SOME HIGH CLOUDS STREAM ACRS THE REGION AND
THICKEN...THESE PROFILES SUGGEST PLENTY OF DRY MID LEVELS HOLDING
ON THROUGH MON MORNING TO EVAPORATE ANY POTENTIAL SEEDER CRYSTALS
INTO THE LOWER MOISTURE LAYER...THUS LIGHT SNOW OR FLURRIES MAY BE
HARD TO COME BY TONIGHT. WITH THE INCREASING LIFT...THESE SAME
SOUNDINGS DO SUGGEST/ESPECIALLY THE 00Z GFS/ THAT THE BOUNDARY LAYER
MOISTURE AND TO SOMEWHAT HIGHER LEVELS RISE ENOUGH TO FUEL THE
DEVELOPMENT OF FREEZING DRIZZLE. STILL AM SKEPTICAL IF THIS SUB-
INVERSION MOISTURE CAN GET DEEP ENOUGH TO ALLOW THE LIFT TO PRODUCE
DRIZZLE...BUT IF THE LOW CLOUD DECKS CAN EVENTUALLY SEEP ACRS
PORTIONS OF THE AREA TONIGHT...THAT WOULD BE ENOUGH. FOR NOW WILL
KEEP THE SLIGHT CHC FOR LIGHT SNOW AFTER MIDNIGHT...BUT ADD THE
POTENTIAL/MENTION FOR SOME FREEZING DRIZZLE AS WELL OVER MOST OF THE
DVN CWA. WILL TOUCH UPON IN THE HWO AS WELL...BECAUSE IF THE GFS IS
CORRECT/A BIG QUESTION MARK/ THE DRIZZLE WILL BE TO AN EXTENT THAT AN
ADVISORY MAY BE NEEDED LATE TONIGHT INTO MON MORNING. WILL HAVE TO
WATCH FOR FOG DEVELOPMENT AS WELL AROUND CONVERGENT FLOW PATTERN INTO
THE INVERTED SFC TROF. ..12..
LONG TERM...MONDAY THROUGH NEXT SATURDAY...
THREE STORM SYSTEMS TO MOVE ACROSS THE MIDWEST IN THE NEXT 7
DAY...AS PART OF A CONTINUING ACTIVE PERIOD.
MONDAY THE INVERTED TROUGH THAT FORMED SUNDAY NIGHT REMAINS OVER THE
NORTHEASTERN PORTIONS OF THE FORECAST AREA...WITH PLENTY OF LOW
LEVEL CONVERGENCE AND INCREASED LOW LEVEL MOISTURE LEVELS. HAVE
SOME CONCERNS THAT THE MODELS MAY BE OVERDOING THE AMOUNT OF LOW
LEVEL MOISTURE...BUT SEEM TO BE VERIFYING FAIRLY WELL WITH THE LOW
CLOUDS OVER NORTH AND SOUTH DAKOTA THIS MORNING. THE MAIN ISSUE FOR
MONDAY IS THAT THE MOISTURE IS ALL LOW LEVEL WITH MUCH DRIER MID AND
UPPER LEVEL AIR OVER THE FORECAST AREA. WITH THE LOW LEVEL
CONVERGENCE AND THE VORT MAX MOVING OVER THE AREA THERE WILL BE
ENOUGH LIFT FOR PRECIPITATION. UNFORTUNATELY...THE SOUNDINGS ALL
SUPPORT FREEZING DRIZZLE FOR MONDAY MORNING AND EARLY AFTERNOON...
OVER MAINLY THE NORTHERN HALF TO THIRD OF THE AREA. SOME FLURRIES
ARE POSSIBLE IF SOME OF THE HIGHER LEVEL MOISTURE IS BETTER THAN THE
MODELS INDICATE...AND WE CAN GET A SEEDER FEEDER GOING.
TUESDAY AND WEDNESDAY WE GET TO WATCH THE STRONG UPPER LEVEL TROUGH
MOVE ACROSS THE SOUTHERN PLAINS AND INTO THE GULF STATES. EXPECT
THIS TO AFFECT AREAS SOUTHEAST OF THE AREA WITH PRECIPITATION.
WHILE SOME SMALL POPS ARE JUSTIFIED IN THE FAR SOUTHEAST TUESDAY
NIGHT AND WEDNESDAY...DO NOT REALLY EXPECT PRECIPITATION TO GET INTO
THE AREA. UNTIL THEN EXPECT TEMPERATURES TO BE COLDER THAN NORMAL
WITH THE CONTINUED NORTH WINDS AND COLD AIR ADVECTION. IN FACT...
WEDNESDAY NIGHT WILL BE THE COLDEST NIGHT WE HAVE HAD SO FAR WITH
SURFACE RIDGING OVERHEAD AND CLEAR SKIES. CURRENTLY HAVE MIN TEMPS
IN THE NEGATIVE SINGLE DIGITS TO NEAR 10 ABOVE...BUT EXPECT WE
COULD GO ANOTHER 5-10 DEGREES COLDER.
OUR NEXT SIGNIFICANT STORM SYSTEM IS EXPECTED TO MOVE THROUGH THE
AREA STARTING THURSDAY NIGHT...CONTINUING FRIDAY AND INTO SATURDAY.
GIVEN THE COLD AIR THAT WILL ALREADY IN PLACE...THE ENTIRE EVENT IS
EXPECTED TO PRODUCE ALL SNOW. BOTH THE GFS AND ECMWF HAVE BEEN
RELATIVELY CONSISTENT IN SHOWING THIS STORM SYSTEM FOR A SECOND DAY
NOW...THOUGH THERE ARE DIFFERENCES IN TIMING AND STRENGTH. THE
ECMWF STORM IS MUCH STRONGER AND SLOWER THAN THE GFS...AND WILL NEED
TO WATCH THIS STORM CLOSELY IN THE COMING DAYS TO SEE HOW IT
DEVELOPS.
LE
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
NICHOLS
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
752 AM CST SUN DEC 23 2012
.UPDATE...
DID A QUICK UPDATE TO FOLLOW MORE OF THE RAP TRENDS IN ALLOWING
THE CLOUDS WITH EMBEDDED FLURRIES TO SEEP SOUTH TO IMPACT THE
HIGHWAY 20 CORRIDOR BY 14-15Z OR SO THIS MORNING. THESE AREAS MAY
THEN STAY CLOUD ALL AFTERNOON AND INTO THE EVENING. WILL HAVE TO
WATCH FOR A FURTHER SOUTHWARD CREEP OF THESE CLOUDS...BUT HOPE
DIURNAL PROCESSES WELL AFTER SUNRISE-MIXING HELP HALF THE CLOUDS
FROM SINKING MUCH FURTHER SOUTH THAN HWY 30 UNTIL THIS EVENING.
TEMPS ALONG HWY 20 MAY BE HELD IN THE UPPER TEENS TO LOWER 20S IF
LOW CLOUDS HANG TOUGH. ..12..
&&
.PREV DISCUSSION... /ISSUED 552 AM CST SUN DEC 23 2012/
AVIATION...
CHALLENGING LOW CLOUD SCENARIO AT THE DBQ AND CID TERMINALS THIS
MORNING AS IFR TO LOW MVFR STRATUS ACRS MAN AND WI TRIES TO MOVE
SOUTH. CURRENT MOVEMENT WOULD HAVE THESE CLOUDS ACRS DBQ BY 15Z
THIS MORNING AND CID JUST AFTER 16Z. BUT THERE ARE SOME SIGNS OF
THIS DECK SLOWING AFTER SUNRISE AND HALTING IT/S PROGRESSION
SOUTH. DBQ HAS THE BEST CHANCE FOR THESE CLOUDS TO IMPACT AND WILL
GO TEMPO MVFR FROM MID MORNING THROUGH NOON. SOME MVFR FOG STILL
POSSIBLE AT MOST TERMINALS THROUGH 14Z THIS MORNING...THEN NORTH
TO NORTHEAST SFC WINDS TO INCREASE TODAY WITH JUST ROUNDS OF
CIRRUS. AS LOW PRESSURE MOVES ACRS MO AND TO THE MOUTH OF THE OH
RVR VALLEY TONIGHT...LIGHT CONVERGENT NORTHEAST FLOW TO FOCUS ON
THE TERMINALS. IF THE LOW CLOUDS DON/T MAKE IT ACRS THE AREA TODAY...IT
APPEARS THEY WILL TONIGHT...DOWN TO UNDER 1K FT AGL AFTER MIDNIGHT.
SOME FOG ALSO POSSIBLE TONIGHT...DOWN TO IFR LEVEL VSBYS OF AT LEAST
1-2SM. OF MORE OF AN IMPACT MAY BE THE CHANCE OF FREEZING DRIZZLE
AFTER MIDNIGHT AT ALL TERMINALS EXCEPT MAYBE BRL...IF THE LOW
CLOUDS DO INDEED FORM AND THICKEN ENOUGH. ..12..
PREV DISCUSSION... /ISSUED 335 AM CST SUN DEC 23 2012/
SYNOPSIS...
LATEST SFC ANALYSIS WAS INDICATING PASSING WEAK FRONT AND WAVE
MAINLY EAST AND SOUTH OF THE DVN CWA...WHILE CYCLOGENESIS WAS
INCREASING SOME ON THE SAME BOUNDARY OVER NORTH CENTRAL TX INTO OK.
RIDGE AXIS NOTED POKING DOWN OUT OF CANADA ACRS THE NORTHEASTERN
PLAINS AND MO RVR VALLEY. ALOFT...00Z UPPER AIR ANALYSIS AND MOISTURE
FLOW PATTERNS ON THE CURRENT WATER VAPOR IMAGERY WERE INDICATING A
FLATTENING PATTERN ACRS THE CONUS. SAME IMAGERY WAS ALSO SHOWING A
UPPER LEVEL WAVE COMPLEX CURRENTLY ACRS THE NORTHERN INTER-MOUNTAIN
REGION.
SHORT TERM...TODAY AND TONIGHT...
TODAY...MAIN CHALLENGE TODAY IS WHETHER AREAS OF LOW CLOUDS/STRATUS
LURKING ACRS WI AND PORTIONS OF MN INTO THE DAKOTAS...CAN SEEP
SOUTHWARD AND MAKE IT ACRS PORTIONS OF THE DVN CWA. LOOKING AT
VARIOUS SHORT RANGE AND HIRES MODEL LLVL RH PROGS...THEY RANGE FROM
THE NAM12 CONTINUING TO ALLOW THE LLVL CLOUDS TO SEEP DOWN INTO THE
CENTRAL PLAINS AND TOWARD SOUTHEAST WI/CHICAGO AREA WHILE THE
LOCAL CWA REMAINS MAINLY LLVL CLOUD-FREE WITH JUST PASSING ROUNDS OF
CIRRUS. OTHER PART OF THE RANGE IS THE LATEST RAP WHICH SEEPS THE
LOW CLOUDS INTO THE NORTHERN CWA THIS MORNING...THEN HOLD THEM AT
BAY OR ACTUALLY BREAKS THEM UP AS THE DAY PROGRESSES THOUGH LATE
AFTERNOON. LOOKING AT LATEST STRATUS TRENDS ON IR LOOPS...WILL SIDE
WITH THE NAM. HIGH TEMPS IN THE MID TO UPPER 20S OVER THE DEEPER SNOW
PACK AREA TAKING INTO ACCOUNT SOME POST FRONTAL CAA...TO HIGHS IN
THE LOWER 30S IN THE SOUTHEASTERN FCST AREA. WILL BANK ON THE CI
AND INCREASING NORTH FLOW INTO THE SOUTH TO LIMIT MORE WIDESPREAD
FOG IN THOSE AREAS THIS MORNING.
TONIGHT...THE ABOVE MENTIONED UPPER LEVEL VORT COMPLEX CURRENTLY
ACRS EASTERN OR/WA INTO ID...WILL LOOK TO PROPAGATE INLAND ON
NORTHERN EDGE OF DEVELOPING WESTERLIES ACRS THE CONUS TONIGHT...
MAKING ACRS THE WESTERN CWA IN DIGGING UPPER TROF FASHION BY 12Z MON
MORNING. BESIDES NICE BOUT OF LIFT THROUGH THE COLUMN TO THE LEE OF
THIS FEATURE INTO THE AREA AFTER MIDNIGHT... THE SOUTHERN PLAINS
CYCLOGENESIS TO CONTINUE TO BLOSSOM AND PROGRESS NORTHEASTWARD WITH
SFC LOW DEVELOPMENT...MAKING FOR AN ASSOCIATED INVERTED TROF POKING
ACRS THE DVN CWA FROM 06Z-12Z MON. THUS LIFT AND FOCUS THERE FOR
PRECIP FORMATION...THE QUESTION IS HOW MUCH MOISTURE AND HOW DEEP
TO ALLOW ANY SUCH PRECIP TO DEVELOP AND MAKE IT TO THE SFC. ANALYSIS
OF SEVERAL BUFKIT SOUNDINGS AND MODEL VERTICAL PROFILES SUGGEST
DEEPENING LLVL MOISTURE FROM SNOW MELT AND THE ADVECTION OF THE
ADJACENT LLVL CLOUD FIELDS TO THE WEST MOVING IN ACRS THE AREA
AND GETTING TRAPPED UNDER H85-H75 MB INVERSION. SOME LK MI STRATUS
ADVECTING TO THE WEST AN CONVERGING AROUND THE LLVL INVERTED TROF
ALSO POSSIBLE. WHILE SOME HIGH CLOUDS STREAM ACRS THE REGION AND
THICKEN...THESE PROFILES SUGGEST PLENTY OF DRY MID LEVELS HOLDING
ON THROUGH MON MORNING TO EVAPORATE ANY POTENTIAL SEEDER CRYSTALS
INTO THE LOWER MOISTURE LAYER...THUS LIGHT SNOW OR FLURRIES MAY BE
HARD TO COME BY TONIGHT. WITH THE INCREASING LIFT...THESE SAME
SOUNDINGS DO SUGGEST/ESPECIALLY THE 00Z GFS/ THAT THE BOUNDARY LAYER
MOISTURE AND TO SOMEWHAT HIGHER LEVELS RISE ENOUGH TO FUEL THE
DEVELOPMENT OF FREEZING DRIZZLE. STILL AM SKEPTICAL IF THIS SUB-
INVERSION MOISTURE CAN GET DEEP ENOUGH TO ALLOW THE LIFT TO PRODUCE
DRIZZLE...BUT IF THE LOW CLOUD DECKS CAN EVENTUALLY SEEP ACRS
PORTIONS OF THE AREA TONIGHT...THAT WOULD BE ENOUGH. FOR NOW WILL
KEEP THE SLIGHT CHC FOR LIGHT SNOW AFTER MIDNIGHT...BUT ADD THE
POTENTIAL/MENTION FOR SOME FREEZING DRIZZLE AS WELL OVER MOST OF THE
DVN CWA. WILL TOUCH UPON IN THE HWO AS WELL...BECAUSE IF THE GFS IS
CORRECT/A BIG QUESTION MARK/ THE DRIZZLE WILL BE TO AN EXTENT THAT AN
ADVISORY MAY BE NEEDED LATE TONIGHT INTO MON MORNING. WILL HAVE TO
WATCH FOR FOG DEVELOPMENT AS WELL AROUND CONVERGENT FLOW PATTERN INTO
THE INVERTED SFC TROF. ..12..
LONG TERM...MONDAY THROUGH NEXT SATURDAY...
THREE STORM SYSTEMS TO MOVE ACROSS THE MIDWEST IN THE NEXT 7
DAY...AS PART OF A CONTINUING ACTIVE PERIOD.
MONDAY THE INVERTED TROUGH THAT FORMED SUNDAY NIGHT REMAINS OVER THE
NORTHEASTERN PORTIONS OF THE FORECAST AREA...WITH PLENTY OF LOW
LEVEL CONVERGENCE AND INCREASED LOW LEVEL MOISTURE LEVELS. HAVE
SOME CONCERNS THAT THE MODELS MAY BE OVERDOING THE AMOUNT OF LOW
LEVEL MOISTURE...BUT SEEM TO BE VERIFYING FAIRLY WELL WITH THE LOW
CLOUDS OVER NORTH AND SOUTH DAKOTA THIS MORNING. THE MAIN ISSUE FOR
MONDAY IS THAT THE MOISTURE IS ALL LOW LEVEL WITH MUCH DRIER MID AND
UPPER LEVEL AIR OVER THE FORECAST AREA. WITH THE LOW LEVEL
CONVERGENCE AND THE VORT MAX MOVING OVER THE AREA THERE WILL BE
ENOUGH LIFT FOR PRECIPITATION. UNFORTUNATELY...THE SOUNDINGS ALL
SUPPORT FREEZING DRIZZLE FOR MONDAY MORNING AND EARLY AFTERNOON...
OVER MAINLY THE NORTHERN HALF TO THIRD OF THE AREA. SOME FLURRIES
ARE POSSIBLE IF SOME OF THE HIGHER LEVEL MOISTURE IS BETTER THAN THE
MODELS INDICATE...AND WE CAN GET A SEEDER FEEDER GOING.
TUESDAY AND WEDNESDAY WE GET TO WATCH THE STRONG UPPER LEVEL TROUGH
MOVE ACROSS THE SOUTHERN PLAINS AND INTO THE GULF STATES. EXPECT
THIS TO AFFECT AREAS SOUTHEAST OF THE AREA WITH PRECIPITATION.
WHILE SOME SMALL POPS ARE JUSTIFIED IN THE FAR SOUTHEAST TUESDAY
NIGHT AND WEDNESDAY...DO NOT REALLY EXPECT PRECIPITATION TO GET INTO
THE AREA. UNTIL THEN EXPECT TEMPERATURES TO BE COLDER THAN NORMAL
WITH THE CONTINUED NORTH WINDS AND COLD AIR ADVECTION. IN FACT...
WEDNESDAY NIGHT WILL BE THE COLDEST NIGHT WE HAVE HAD SO FAR WITH
SURFACE RIDGING OVERHEAD AND CLEAR SKIES. CURRENTLY HAVE MIN TEMPS
IN THE NEGATIVE SINGLE DIGITS TO NEAR 10 ABOVE...BUT EXPECT WE
COULD GO ANOTHER 5-10 DEGREES COLDER.
OUR NEXT SIGNIFICANT STORM SYSTEM IS EXPECTED TO MOVE THROUGH THE
AREA STARTING THURSDAY NIGHT...CONTINUING FRIDAY AND INTO SATURDAY.
GIVEN THE COLD AIR THAT WILL ALREADY IN PLACE...THE ENTIRE EVENT IS
EXPECTED TO PRODUCE ALL SNOW. BOTH THE GFS AND ECMWF HAVE BEEN
RELATIVELY CONSISTENT IN SHOWING THIS STORM SYSTEM FOR A SECOND DAY
NOW...THOUGH THERE ARE DIFFERENCES IN TIMING AND STRENGTH. THE
ECMWF STORM IS MUCH STRONGER AND SLOWER THAN THE GFS...AND WILL NEED
TO WATCH THIS STORM CLOSELY IN THE COMING DAYS TO SEE HOW IT
DEVELOPS.
LE
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
552 AM CST SUN DEC 23 2012
.AVIATION...
CHALLENGING LOW CLOUD SCENARIO AT THE DBQ AND CID TERMINALS THIS
MORNING AS IFR TO LOW MVFR STRATUS ACRS MAN AND WI TRIES TO MOVE
SOUTH. CURRENT MOVEMENT WOULD HAVE THESE CLOUDS ACRS DBQ BY 15Z
THIS MORNING AND CID JUST AFTER 16Z. BUT THERE ARE SOME SIGNS OF
THIS DECK SLOWING AFTER SUNRISE AND HALTING IT/S PROGRESSION
SOUTH. DBQ HAS THE BEST CHANCE FOR THESE CLOUDS TO IMPACT AND WILL
GO TEMPO MVFR FROM MID MORNING THROUGH NOON. SOME MVFR FOG STILL
POSSIBLE AT MOST TERMINALS THROUGH 14Z THIS MORNING...THEN NORTH
TO NORTHEAST SFC WINDS TO INCREASE TODAY WITH JUST ROUNDS OF
CIRRUS. AS LOW PRESSURE MOVES ACRS MO AND TO THE MOUTH OF THE OH
RVR VALLEY TONIGHT...LIGHT CONVERGENT NORTHEAST FLOW TO FOCUS ON
THE TERMINALS. IF THE LOW CLOUDS DON/T MAKE IT ACRS THE AREA TODAY...IT
APPEARS THEY WILL TONIGHT...DOWN TO UNDER 1K FT AGL AFTER MIDNIGHT.
SOME FOG ALSO POSSIBLE TONIGHT...DOWN TO IFR LEVEL VSBYS OF AT LEAST
1-2SM. OF MORE OF AN IMPACT MAY BE THE CHANCE OF FREEZING DRIZZLE
AFTER MIDNIGHT AT ALL TERMINALS EXCEPT MAYBE BRL...IF THE LOW
CLOUDS DO INDEED FORM AND THICKEN ENOUGH. ..12..
&&
.PREV DISCUSSION... /ISSUED 335 AM CST SUN DEC 23 2012/
SYNOPSIS...
LATEST SFC ANALYSIS WAS INDICATING PASSING WEAK FRONT AND WAVE
MAINLY EAST AND SOUTH OF THE DVN CWA...WHILE CYCLOGENESIS WAS
INCREASING SOME ON THE SAME BOUNDARY OVER NORTH CENTRAL TX INTO OK.
RIDGE AXIS NOTED POKING DOWN OUT OF CANADA ACRS THE NORTHEASTERN
PLAINS AND MO RVR VALLEY. ALOFT...00Z UPPER AIR ANALYSIS AND MOISTURE
FLOW PATTERNS ON THE CURRENT WATER VAPOR IMAGERY WERE INDICATING A
FLATTENING PATTERN ACRS THE CONUS. SAME IMAGERY WAS ALSO SHOWING A
UPPER LEVEL WAVE COMPLEX CURRENTLY ACRS THE NORTHERN INTER-MOUNTAIN
REGION.
SHORT TERM...TODAY AND TONIGHT...
TODAY...MAIN CHALLENGE TODAY IS WHETHER AREAS OF LOW CLOUDS/STRATUS
LURKING ACRS WI AND PORTIONS OF MN INTO THE DAKOTAS...CAN SEEP
SOUTHWARD AND MAKE IT ACRS PORTIONS OF THE DVN CWA. LOOKING AT
VARIOUS SHORT RANGE AND HIRES MODEL LLVL RH PROGS...THEY RANGE FROM
THE NAM12 CONTINUING TO ALLOW THE LLVL CLOUDS TO SEEP DOWN INTO THE
CENTRAL PLAINS AND TOWARD SOUTHEAST WI/CHICAGO AREA WHILE THE
LOCAL CWA REMAINS MAINLY LLVL CLOUD-FREE WITH JUST PASSING ROUNDS OF
CIRRUS. OTHER PART OF THE RANGE IS THE LATEST RAP WHICH SEEPS THE
LOW CLOUDS INTO THE NORTHERN CWA THIS MORNING...THEN HOLD THEM AT
BAY OR ACTUALLY BREAKS THEM UP AS THE DAY PROGRESSES THOUGH LATE
AFTERNOON. LOOKING AT LATEST STRATUS TRENDS ON IR LOOPS...WILL SIDE
WITH THE NAM. HIGH TEMPS IN THE MID TO UPPER 20S OVER THE DEEPER SNOW
PACK AREA TAKING INTO ACCOUNT SOME POST FRONTAL CAA...TO HIGHS IN
THE LOWER 30S IN THE SOUTHEASTERN FCST AREA. WILL BANK ON THE CI
AND INCREASING NORTH FLOW INTO THE SOUTH TO LIMIT MORE WIDESPREAD
FOG IN THOSE AREAS THIS MORNING.
TONIGHT...THE ABOVE MENTIONED UPPER LEVEL VORT COMPLEX CURRENTLY
ACRS EASTERN OR/WA INTO ID...WILL LOOK TO PROPAGATE INLAND ON
NORTHERN EDGE OF DEVELOPING WESTERLIES ACRS THE CONUS TONIGHT...
MAKING ACRS THE WESTERN CWA IN DIGGING UPPER TROF FASHION BY 12Z MON
MORNING. BESIDES NICE BOUT OF LIFT THROUGH THE COLUMN TO THE LEE OF
THIS FEATURE INTO THE AREA AFTER MIDNIGHT... THE SOUTHERN PLAINS
CYCLOGENESIS TO CONTINUE TO BLOSSOM AND PROGRESS NORTHEASTWARD WITH
SFC LOW DEVELOPMENT...MAKING FOR AN ASSOCIATED INVERTED TROF POKING
ACRS THE DVN CWA FROM 06Z-12Z MON. THUS LIFT AND FOCUS THERE FOR
PRECIP FORMATION...THE QUESTION IS HOW MUCH MOISTURE AND HOW DEEP
TO ALLOW ANY SUCH PRECIP TO DEVELOP AND MAKE IT TO THE SFC. ANALYSIS
OF SEVERAL BUFKIT SOUNDINGS AND MODEL VERTICAL PROFILES SUGGEST
DEEPENING LLVL MOISTURE FROM SNOW MELT AND THE ADVECTION OF THE
ADJACENT LLVL CLOUD FIELDS TO THE WEST MOVING IN ACRS THE AREA
AND GETTING TRAPPED UNDER H85-H75 MB INVERSION. SOME LK MI STRATUS
ADVECTING TO THE WEST AN CONVERGING AROUND THE LLVL INVERTED TROF
ALSO POSSIBLE. WHILE SOME HIGH CLOUDS STREAM ACRS THE REGION AND
THICKEN...THESE PROFILES SUGGEST PLENTY OF DRY MID LEVELS HOLDING
ON THROUGH MON MORNING TO EVAPORATE ANY POTENTIAL SEEDER CRYSTALS
INTO THE LOWER MOISTURE LAYER...THUS LIGHT SNOW OR FLURRIES MAY BE
HARD TO COME BY TONIGHT. WITH THE INCREASING LIFT...THESE SAME
SOUNDINGS DO SUGGEST/ESPECIALLY THE 00Z GFS/ THAT THE BOUNDARY LAYER
MOISTURE AND TO SOMEWHAT HIGHER LEVELS RISE ENOUGH TO FUEL THE
DEVELOPMENT OF FREEZING DRIZZLE. STILL AM SKEPTICAL IF THIS SUB-
INVERSION MOISTURE CAN GET DEEP ENOUGH TO ALLOW THE LIFT TO PRODUCE
DRIZZLE...BUT IF THE LOW CLOUD DECKS CAN EVENTUALLY SEEP ACRS
PORTIONS OF THE AREA TONIGHT...THAT WOULD BE ENOUGH. FOR NOW WILL
KEEP THE SLIGHT CHC FOR LIGHT SNOW AFTER MIDNIGHT...BUT ADD THE
POTENTIAL/MENTION FOR SOME FREEZING DRIZZLE AS WELL OVER MOST OF THE
DVN CWA. WILL TOUCH UPON IN THE HWO AS WELL...BECAUSE IF THE GFS IS
CORRECT/A BIG QUESTION MARK/ THE DRIZZLE WILL BE TO AN EXTENT THAT AN
ADVISORY MAY BE NEEDED LATE TONIGHT INTO MON MORNING. WILL HAVE TO
WATCH FOR FOG DEVELOPMENT AS WELL AROUND CONVERGENT FLOW PATTERN INTO
THE INVERTED SFC TROF. ..12..
LONG TERM...MONDAY THROUGH NEXT SATURDAY...
THREE STORM SYSTEMS TO MOVE ACROSS THE MIDWEST IN THE NEXT 7
DAY...AS PART OF A CONTINUING ACTIVE PERIOD.
MONDAY THE INVERTED TROUGH THAT FORMED SUNDAY NIGHT REMAINS OVER THE
NORTHEASTERN PORTIONS OF THE FORECAST AREA...WITH PLENTY OF LOW
LEVEL CONVERGENCE AND INCREASED LOW LEVEL MOISTURE LEVELS. HAVE
SOME CONCERNS THAT THE MODELS MAY BE OVERDOING THE AMOUNT OF LOW
LEVEL MOISTURE...BUT SEEM TO BE VERIFYING FAIRLY WELL WITH THE LOW
CLOUDS OVER NORTH AND SOUTH DAKOTA THIS MORNING. THE MAIN ISSUE FOR
MONDAY IS THAT THE MOISTURE IS ALL LOW LEVEL WITH MUCH DRIER MID AND
UPPER LEVEL AIR OVER THE FORECAST AREA. WITH THE LOW LEVEL
CONVERGENCE AND THE VORT MAX MOVING OVER THE AREA THERE WILL BE
ENOUGH LIFT FOR PRECIPITATION. UNFORTUNATELY...THE SOUNDINGS ALL
SUPPORT FREEZING DRIZZLE FOR MONDAY MORNING AND EARLY AFTERNOON...
OVER MAINLY THE NORTHERN HALF TO THIRD OF THE AREA. SOME FLURRIES
ARE POSSIBLE IF SOME OF THE HIGHER LEVEL MOISTURE IS BETTER THAN THE
MODELS INDICATE...AND WE CAN GET A SEEDER FEEDER GOING.
TUESDAY AND WEDNESDAY WE GET TO WATCH THE STRONG UPPER LEVEL TROUGH
MOVE ACROSS THE SOUTHERN PLAINS AND INTO THE GULF STATES. EXPECT
THIS TO AFFECT AREAS SOUTHEAST OF THE AREA WITH PRECIPITATION.
WHILE SOME SMALL POPS ARE JUSTIFIED IN THE FAR SOUTHEAST TUESDAY
NIGHT AND WEDNESDAY...DO NOT REALLY EXPECT PRECIPITATION TO GET INTO
THE AREA. UNTIL THEN EXPECT TEMPERATURES TO BE COLDER THAN NORMAL
WITH THE CONTINUED NORTH WINDS AND COLD AIR ADVECTION. IN FACT...
WEDNESDAY NIGHT WILL BE THE COLDEST NIGHT WE HAVE HAD SO FAR WITH
SURFACE RIDGING OVERHEAD AND CLEAR SKIES. CURRENTLY HAVE MIN TEMPS
IN THE NEGATIVE SINGLE DIGITS TO NEAR 10 ABOVE...BUT EXPECT WE
COULD GO ANOTHER 5-10 DEGREES COLDER.
OUR NEXT SIGNIFICANT STORM SYSTEM IS EXPECTED TO MOVE THROUGH THE
AREA STARTING THURSDAY NIGHT...CONTINUING FRIDAY AND INTO SATURDAY.
GIVEN THE COLD AIR THAT WILL ALREADY IN PLACE...THE ENTIRE EVENT IS
EXPECTED TO PRODUCE ALL SNOW. BOTH THE GFS AND ECMWF HAVE BEEN
RELATIVELY CONSISTENT IN SHOWING THIS STORM SYSTEM FOR A SECOND DAY
NOW...THOUGH THERE ARE DIFFERENCES IN TIMING AND STRENGTH. THE
ECMWF STORM IS MUCH STRONGER AND SLOWER THAN THE GFS...AND WILL NEED
TO WATCH THIS STORM CLOSELY IN THE COMING DAYS TO SEE HOW IT
DEVELOPS.
LE
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
12/LE
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
335 AM CST SUN DEC 23 2012
.SYNOPSIS...
LATEST SFC ANALYSIS WAS INDICATING PASSING WEAK FRONT AND WAVE
MAINLY EAST AND SOUTH OF THE DVN CWA...WHILE CYCLOGENESIS WAS
INCREASING SOME ON THE SAME BOUNDARY OVER NORTH CENTRAL TX INTO OK.
RIDGE AXIS NOTED POKING DOWN OUT OF CANADA ACRS THE NORTHEASTERN
PLAINS AND MO RVR VALLEY. ALOFT...00Z UPPER AIR ANALYSIS AND MOISTURE
FLOW PATTERNS ON THE CURRENT WATER VAPOR IMAGERY WERE INDICATING A
FLATTENING PATTERN ACRS THE CONUS. SAME IMAGERY WAS ALSO SHOWING A
UPPER LEVEL WAVE COMPLEX CURRENTLY ACRS THE NORTHERN INTER-MOUNTAIN
REGION.
&&
.SHORT TERM...TODAY AND TONIGHT...
TODAY...MAIN CHALLENGE TODAY IS WHETHER AREAS OF LOW CLOUDS/STRATUS
LURKING ACRS WI AND PORTIONS OF MN INTO THE DAKOTAS...CAN SEEP
SOUTHWARD AND MAKE IT ACRS PORTIONS OF THE DVN CWA. LOOKING AT
VARIOUS SHORT RANGE AND HIRES MODEL LLVL RH PROGS...THEY RANGE FROM
THE NAM12 CONTINUING TO ALLOW THE LLVL CLOUDS TO SEEP DOWN INTO THE
CENTRAL PLAINS AND TOWARD SOUTHEAST WI/CHICAGO AREA WHILE THE
LOCAL CWA REMAINS MAINLY LLVL CLOUD-FREE WITH JUST PASSING ROUNDS OF
CIRRUS. OTHER PART OF THE RANGE IS THE LATEST RAP WHICH SEEPS THE
LOW CLOUDS INTO THE NORTHERN CWA THIS MORNING...THEN HOLD THEM AT
BAY OR ACTUALLY BREAKS THEM UP AS THE DAY PROGRESSES THOUGH LATE
AFTERNOON. LOOKING AT LATEST STRATUS TRENDS ON IR LOOPS...WILL SIDE
WITH THE NAM. HIGH TEMPS IN THE MID TO UPPER 20S OVER THE DEEPER SNOW
PACK AREA TAKING INTO ACCOUNT SOME POST FRONTAL CAA...TO HIGHS IN
THE LOWER 30S IN THE SOUTHEASTERN FCST AREA. WILL BANK ON THE CI
AND INCREASING NORTH FLOW INTO THE SOUTH TO LIMIT MORE WIDESPREAD
FOG IN THOSE AREAS THIS MORNING.
TONIGHT...THE ABOVE MENTIONED UPPER LEVEL VORT COMPLEX CURRENTLY
ACRS EASTERN OR/WA INTO ID...WILL LOOK TO PROPAGATE INLAND ON
NORTHERN EDGE OF DEVELOPING WESTERLIES ACRS THE CONUS TONIGHT...
MAKING ACRS THE WESTERN CWA IN DIGGING UPPER TROF FASHION BY 12Z MON
MORNING. BESIDES NICE BOUT OF LIFT THROUGH THE COLUMN TO THE LEE OF
THIS FEATURE INTO THE AREA AFTER MIDNIGHT... THE SOUTHERN PLAINS
CYCLOGENESIS TO CONTINUE TO BLOSSOM AND PROGRESS NORTHEASTWARD WITH
SFC LOW DEVELOPMENT...MAKING FOR AN ASSOCIATED INVERTED TROF POKING
ACRS THE DVN CWA FROM 06Z-12Z MON. THUS LIFT AND FOCUS THERE FOR
PRECIP FORMATION...THE QUESTION IS HOW MUCH MOISTURE AND HOW DEEP
TO ALLOW ANY SUCH PRECIP TO DEVELOP AND MAKE IT TO THE SFC. ANALYSIS
OF SEVERAL BUFKIT SOUNDINGS AND MODEL VERTICAL PROFILES SUGGEST
DEEPENING LLVL MOISTURE FROM SNOW MELT AND THE ADVECTION OF THE
ADJACENT LLVL CLOUD FIELDS TO THE WEST MOVING IN ACRS THE AREA
AND GETTING TRAPPED UNDER H85-H75 MB INVERSION. SOME LK MI STRATUS
ADVECTING TO THE WEST AN CONVERGING AROUND THE LLVL INVERTED TROF
ALSO POSSIBLE. WHILE SOME HIGH CLOUDS STREAM ACRS THE REGION AND
THICKEN...THESE PROFILES SUGGEST PLENTY OF DRY MID LEVELS HOLDING
ON THROUGH MON MORNING TO EVAPORATE ANY POTENTIAL SEEDER CRYSTALS
INTO THE LOWER MOISTURE LAYER...THUS LIGHT SNOW OR FLURRIES MAY BE
HARD TO COME BY TONIGHT. WITH THE INCREASING LIFT...THESE SAME
SOUNDINGS DO SUGGEST/ESPECIALLY THE 00Z GFS/ THAT THE BOUNDARY LAYER
MOISTURE AND TO SOMEWHAT HIGHER LEVELS RISE ENOUGH TO FUEL THE
DEVELOPMENT OF FREEZING DRIZZLE. STILL AM SKEPTICAL IF THIS SUB-
INVERSION MOISTURE CAN GET DEEP ENOUGH TO ALLOW THE LIFT TO PRODUCE
DRIZZLE...BUT IF THE LOW CLOUD DECKS CAN EVENTUALLY SEEP ACRS
PORTIONS OF THE AREA TONIGHT...THAT WOULD BE ENOUGH. FOR NOW WILL
KEEP THE SLIGHT CHC FOR LIGHT SNOW AFTER MIDNIGHT...BUT ADD THE
POTENTIAL/MENTION FOR SOME FREEZING DRIZZLE AS WELL OVER MOST OF THE
DVN CWA. WILL TOUCH UPON IN THE HWO AS WELL...BECAUSE IF THE GFS IS
CORRECT/A BIG QUESTION MARK/ THE DRIZZLE WILL BE TO AN EXTENT THAT AN
ADVISORY MAY BE NEEDED LATE TONIGHT INTO MON MORNING. WILL HAVE TO
WATCH FOR FOG DEVELOPMENT AS WELL AROUND CONVERGENT FLOW PATTERN INTO
THE INVERTED SFC TROF. ..12..
.LONG TERM...MONDAY THROUGH NEXT SATURDAY...
THREE STORM SYSTEMS TO MOVE ACROSS THE MIDWEST IN THE NEXT 7
DAY...AS PART OF A CONTINUING ACTIVE PERIOD.
MONDAY THE INVERTED TROUGH THAT FORMED SUNDAY NIGHT REMAINS OVER THE
NORTHEASTERN PORTIONS OF THE FORECAST AREA...WITH PLENTY OF LOW
LEVEL CONVERGENCE AND INCREASED LOW LEVEL MOISTURE LEVELS. HAVE
SOME CONCERNS THAT THE MODELS MAY BE OVERDOING THE AMOUNT OF LOW
LEVEL MOISTURE...BUT SEEM TO BE VERIFYING FAIRLY WELL WITH THE LOW
CLOUDS OVER NORTH AND SOUTH DAKOTA THIS MORNING. THE MAIN ISSUE FOR
MONDAY IS THAT THE MOISTURE IS ALL LOW LEVEL WITH MUCH DRIER MID AND
UPPER LEVEL AIR OVER THE FORECAST AREA. WITH THE LOW LEVEL
CONVERGENCE AND THE VORT MAX MOVING OVER THE AREA THERE WILL BE
ENOUGH LIFT FOR PRECIPITATION. UNFORTUNATELY...THE SOUNDINGS ALL
SUPPORT FREEZING DRIZZLE FOR MONDAY MORNING AND EARLY AFTERNOON...
OVER MAINLY THE NORTHERN HALF TO THIRD OF THE AREA. SOME FLURRIES
ARE POSSIBLE IF SOME OF THE HIGHER LEVEL MOISTURE IS BETTER THAN THE
MODELS INDICATE...AND WE CAN GET A SEEDER FEEDER GOING.
TUESDAY AND WEDNESDAY WE GET TO WATCH THE STRONG UPPER LEVEL TROUGH
MOVE ACROSS THE SOUTHERN PLAINS AND INTO THE GULF STATES. EXPECT
THIS TO AFFECT AREAS SOUTHEAST OF THE AREA WITH PRECIPITATION.
WHILE SOME SMALL POPS ARE JUSTIFIED IN THE FAR SOUTHEAST TUESDAY
NIGHT AND WEDNESDAY...DO NOT REALLY EXPECT PRECIPITATION TO GET INTO
THE AREA. UNTIL THEN EXPECT TEMPERATURES TO BE COLDER THAN NORMAL
WITH THE CONTINUED NORTH WINDS AND COLD AIR ADVECTION. IN FACT...
WEDNESDAY NIGHT WILL BE THE COLDEST NIGHT WE HAVE HAD SO FAR WITH
SURFACE RIDGING OVERHEAD AND CLEAR SKIES. CURRENTLY HAVE MIN TEMPS
IN THE NEGATIVE SINGLE DIGITS TO NEAR 10 ABOVE...BUT EXPECT WE
COULD GO ANOTHER 5-10 DEGREES COLDER.
OUR NEXT SIGNIFICANT STORM SYSTEM IS EXPECTED TO MOVE THROUGH THE
AREA STARTING THURSDAY NIGHT...CONTINUING FRIDAY AND INTO SATURDAY.
GIVEN THE COLD AIR THAT WILL ALREADY IN PLACE...THE ENTIRE EVENT IS
EXPECTED TO PRODUCE ALL SNOW. BOTH THE GFS AND ECMWF HAVE BEEN
RELATIVELY CONSISTENT IN SHOWING THIS STORM SYSTEM FOR A SECOND DAY
NOW...THOUGH THERE ARE DIFFERENCES IN TIMING AND STRENGTH. THE
ECMWF STORM IS MUCH STRONGER AND SLOWER THAN THE GFS...AND WILL NEED
TO WATCH THIS STORM CLOSELY IN THE COMING DAYS TO SEE HOW IT
DEVELOPS.
LE
&&
.AVIATION...
A WEAK COLD FRONT WILL MOVE SOUTHEAST OF THE AREA THIS MORNING. WINDS
BEHIND THE FRONT HAVE SHIFTED TO THE NORTHWEST AND WILL CONTINUE
VEERING TO THE NORTHEAST AFTER SUNRISE. SOME MVFR VISIBILITIES IN FOG
ARE POSSIBLE AFTER THE FROPA. THERE IS SOME CONCERN ABOUT IFR
CONDITIONS IN FOG AND STRATUS DEVELOPING IN THE LIGHT FLOW NEAR THE
FRONT THIS MORNING AROUND KBRL. HOWEVER...WITH THE DRY LOW LEVEL AIR
IN PLACE AND CI OVER THE AREA ...THE POTENTIAL FOR FOG/STRATUS
APPEARS TO REMAIN LOW EARLY THIS MORNING. STRATUS OVER MINNESOTA
CONTINUES TO SPREAD SOUTH AND COULD MOVE INTO EAST CENTRAL IA AND
NORTHERN IL LATE THIS MORNING. HOWEVER THE CLOUDS WILL BE MOVING INTO
AN UNFAVORABLE FLOW REGIME OVER NORTHERN IOWA AND THEY SHOULD
DISSIPATE BEFORE REACHING EAST CENTRAL IA AND NORTHWEST IL. THERE IS
A BETTER CHANCE FOR MVFR CIGS MOVING IN THIS EVENING AS THE LOW LEVEL
FLOW BECOMES EASTERLY AND TAPS SOME MOISTURE OFF LAKE MICHIGAN.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
12/LE
AREA FORECAST DISCUSSION
NWS GOODLAND KS
233 AM MST SUN DEC 23 2012
.SHORT TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 150 PM MST SAT DEC 22 2012
EARLY AFTERNOON WV IMAGERY AND RUC H5 ANALYSIS SHOWS BROAD RIDGE
ACROSS THE CENTRAL US EXTENDING NORTH INTO SOUTHERN CANADA...WITH
TROUGHS UP STREAM AND DOWN STREAM ALONG THE COASTS. AT THE SURFACE A
COLD FRONT CURRENTLY EXTENDS ACROSS CENTRAL NEBRASKA...WITH A
PREFRONTAL SURFACE TROUGH ACROSS CENTRAL KANSAS.
TONIGHT THROUGH SUNDAY...PATTERN REMAINS QUIET WITH VERY DRY AIR
MASS IN PLACE...HIGHLIGHTED BY DEWPOINT DEPRESSIONS GREATER THAN 20C
THROUGH ABOUT 400MB THROUGH SUNDAY AFTERNOON. WHILE THERE WILL BE
LARGE SCALE ASCENT ASSOCIATED WITH SHORTWAVE PASSAGE ACROSS NORTHERN
PLAINS AND ASSOCIATED COLD FRONT PASSAGE SUNDAY...I DO NOT THINK WE
WILL SEE MUCH OTHER THAN PASSING HIGH CLOUDS CONSIDERING THE DEEP
DRY AIR MASS. H85 TEMPS COOLING BY ABOUT 4-5C BY SUN MORNING WITH
MOST LOCATIONS 7-10F COOLER AND NEGATIVE VALUES POSSIBLE ACROSS THE
NORTHEAST. I DROPPED HIGH TEMPS A LITTLE SUNDAY ACROSS THE CWA
COMPARED TO THIS AFTERNOON TO ACCOUNT FOR THICKER CLOUD COVER AND
COOLER AIRMASS BEHIND FRONT. SNOWPACK CONTINUES TO MELT ACROSS THE
SW CWA AND WITH WINDS SHIFTING BACK TO THE WEST/SOUTHWEST SNOW PACK
SHOULD START TO HAVE LESS OF AN IMPACT EXCEPT IN THE FAR EAST.
.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 230 AM MST SUN DEC 23 2012
ONCE THE CHRISTMAS WEATHER SYSTEM EXITS THE REGION...EXPECT A
COUPLE DAYS OF CALM YET COLD WEATHER. A COLD ARCTIC HIGH PRESSURE
WILL SETTLE IN OVER THE PLAINS AND KEEP ANY PRECIPITATION FROM
MOVING IN FOR A COUPLE DAYS. HIGHS ON WEDNESDAY WILL BE IN THE 10S
AND 20S AND HIGHS ON THURSDAY WILL BE IN THE 20S AND 30S WITH LOWS
IN THE SINGLE DIGITS AND LOW 10S EACH NIGHT. AS THE HIGH MOVES
SLOWLY TO THE EAST...SOUTH WINDS ARE EXPECTED TO RETURN AND
POSSIBLY SOME WARMER TEMPERATURES. THAT WILL ALL DEPEND ON THE
SNOW COVER HOWEVER SINCE A WARMER AIR MASS WOULD BE MODIFIED OVER
ANY SNOW STILL PRESENT.
THE NEXT WEATHER SYSTEM WILL MOVE THROUGH THURSDAY NIGHT AND INTO
FRIDAY. MODELS ARE NOW SHOWING A WEAKER...DISORGANIZED SYSTEM. THE
GFS AND EUROPEAN ALSO NOW SHOW A SOLUTION WHERE THE BULK OF THE
UPPER LEVEL FORCING STAYS WELL TO THE SOUTH OVER TEXAS. MODELS ARE
ALSO HINTING AT SOME DRIER AIR ALOFT MOVING IN...REDUCING CHANCES OF
PRECIPITATION. COULD STILL SEE A FEW SNOW SHOWERS BUT THIS SYSTEM NO
LONGER LOOKS AS THOUGH IT COULD BE A BIGGER WEATHER MAKER. AT THIS
TIME...ONLY SLIGHT CHANCE POPS ARE WARRANTED.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 957 PM MST SAT DEC 22 2012
VFR CONDITIONS WILL CONTINUE AT KGLD AND KMCK FOR THE NEXT 24
HOURS AS HIGH PRESSURE MOVES SOUTH INTO THE REGION.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...DR
LONG TERM...RRH
AVIATION...FS
AREA FORECAST DISCUSSION
NWS GOODLAND KS
1034 PM MST SAT DEC 22 2012
.SHORT TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 150 PM MST SAT DEC 22 2012
EARLY AFTERNOON WV IMAGERY AND RUC H5 ANALYSIS SHOWS BROAD RIDGE
ACROSS THE CENTRAL US EXTENDING NORTH INTO SOUTHERN CANADA...WITH
TROUGHS UP STREAM AND DOWN STREAM ALONG THE COASTS. AT THE SURFACE A
COLD FRONT CURRENTLY EXTENDS ACROSS CENTRAL NEBRASKA...WITH A
PREFRONTAL SURFACE TROUGH ACROSS CENTRAL KANSAS.
TONIGHT THROUGH SUNDAY...PATTERN REMAINS QUIET WITH VERY DRY AIR
MASS IN PLACE...HIGHLIGHTED BY DEWPOINT DEPRESSIONS GREATER THAN 20C
THROUGH ABOUT 400MB THROUGH SUNDAY AFTERNOON. WHILE THERE WILL BE
LARGE SCALE ASCENT ASSOCIATED WITH SHORTWAVE PASSAGE ACROSS NORTHERN
PLAINS AND ASSOCIATED COLD FRONT PASSAGE SUNDAY...I DO NOT THINK WE
WILL SEE MUCH OTHER THAN PASSING HIGH CLOUDS CONSIDERING THE DEEP
DRY AIR MASS. H85 TEMPS COOLING BY ABOUT 4-5C BY SUN MORNING WITH
MOST LOCATIONS 7-10F COOLER AND NEGATIVE VALUES POSSIBLE ACROSS THE
NORTHEAST. I DROPPED HIGH TEMPS A LITTLE SUNDAY ACROSS THE CWA
COMPARED TO THIS AFTERNOON TO ACCOUNT FOR THICKER CLOUD COVER AND
COOLER AIRMASS BEHIND FRONT. SNOWPACK CONTINUES TO MELT ACROSS THE
SW CWA AND WITH WINDS SHIFTING BACK TO THE WEST/SOUTHWEST SNOW PACK
SHOULD START TO HAVE LESS OF AN IMPACT EXCEPT IN THE FAR EAST.
.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 150 PM MST SAT DEC 22 2012
FORECAST CONCERNS WILL BE STORM AT THE BEGINNING OF NEXT WEEK...
NEXT STORM TOWARD THE END OF NEXT WEEK...AND HOW COLD TO MAKE IT
NEXT WEEK. SATELLITE SHOWING AN AMPLIFIED/AMPLIFYING FLOW FROM THE
PACIFIC INTO THE ATLANTIC. IN THIS IS A COMPLEX/COLD UPPER TROUGH
ALONG THE WEST COAST OF NORTH AMERICA WHICH HAS CAUSED AN UPPER
RIDGE OVER THE CENTRAL PORTION OF COUNTRY. VERY COLD LOW LEVEL AIR
MASS/COLD FRONT NOT TOO FAR TO OUR NORTH.
MODELS AT MID AND UPPER LEVELS APPEAR TO HAVE INITIALIZED FINE.
HOWEVER BASED ON SATELLITE...WOULD FAVOR THE SLIGHTLY MORE WEST
INITIALIZATION OF THE UPPER TROUGH NEAR THE WEST COAST. THE NAM AND
ECMWF WERE DOING THE BEST ON THE LOW LEVEL SURFACE WIND/PRESSURE
FIELD. OVERALL THE CANADIAN WAS DOING A LITTLE BETTER ON THE LOW
LEVEL THERMAL FIELD.
SUNDAY NIGHT/MONDAY...MAJOR TRANSITION BEGINS ON MONDAY. MID AND
UPPER LEVEL CLOUD COVER WILL INCREASE AT THE SAME TIME A FRONT
BACKDOORS INTO THE AREA. EASTERLY UPSLOPE INCREASES DURING THE DAY.
AS A RESULT HIGH TEMPERATURES WILL END UP BEING WELL BELOW NORMAL
WITH COLDEST TEMPERATURES IN THE NORTHEAST AND THE WARMEST IN THE
SOUTHWEST. GUIDANCE WAS CLUSTERING AROUND COOLER MAXES THAN WHAT
WAS IN THERE FOR PREVIOUS FORECAST. SO REDUCED THE MAXES.
MAIN LIFT AND DEEPER MOISTURE WILL WAIT UNTIL THE NIGHT TO GET HERE.
MORE THAN ONE MODEL SHOWS THE BOUNDARY LAYER SATURATING UP WITH A
DRY MID LAYER. IT WILL BE UNUSUAL BUT IT LOOKS LIKE FOG WILL
DEVELOP IN THE AFTERNOON AND POSSIBLE SOME FREEZING DRIZZLE. SO
INSERTED THAT INTO THE GRIDS.
MONDAY NIGHT/TUESDAY...IN GENERAL MODELS AGREE ON THE EVOLUTION OF
INCOMING SYSTEM WHICH IS TO DEVELOP THE UPPER TROUGH INTO A CLOSED
OFF CIRCULATION...MAINLY AT 700 MB...AS IT DIGS/MOVES TOWARD THE
SOUTHEAST. PREVIOUS EXPERIENCE HAS SHOWN ME THAT THIS USUALLY IS NOT
THE BEST SCENARIO FOR GETTING A SIGNIFICANT AMOUNT OF SNOW. BASED ON
THE PATTERN/SATELLITE IS INDICATING/SHOWING...BELIEVE THIS SYSTEM
WILL BE COMING IN SLOWER AND FURTHER SOUTH AND WEST. THIS FITS THE
BEST WITH THE ECMWF SOLUTION AND TO A LESSER DEGREE THE CANADIAN...
UKMET...AND GFS SOLUTION. THEY DO THE SAME THING BUT FASTER.
AM CONCERNED THAT WITH THE WAY THE PATTERN IS...THAT FUTURE MODEL
RUNS WILL TAKE THE SYSTEM FURTHER SOUTHWEST AND FURTHER DIMINISH THE
AMOUNT OF SNOW. FOR THE NIGHTTIME PERIOD AS IT STANDS NOW...THE
SOUTHWEST HALF OF THE AREA LOOKS TO HAVE THE BEST CHANCE FOR SNOW.
UNTIL THE SNOW STARTS...WILL KEEP THE FOG AND DRIZZLE GOING IN THE
EVENING PER THE REASONING GIVEN ABOVE.
DURING THE DAY TUESDAY...THE BEST CHANCE FOR SNOW WILL TRANSITION
INTO THE SOUTHERN THIRD IN THE MORNING BEFORE DECREASING AND ENDING
IN THE AFTERNOON. AMOUNTS STILL LOOK IN THE 1 TO 3 INCH RANGE WITH
THE SOUTHWEST HALF HAVING THE HIGHEST AMOUNTS. COMBINATION OF
CLOUDS...PRECIPITATION...AND VERY GOOD COLD AIR ADVECTION WILL MAKE
FOR AN EXTREMELY COLD DAY WITH WELL BELOW NORMAL TEMPERATURES.
TENDED TO GO WITH THE CLUSTERING OF GUIDANCE WHICH SUPPORTED
COOLING MAXES FROM PREVIOUS FORECAST. HOWEVER...SOME GUIDANCE IS
SHOWING THAT MAXES COULD BE EVEN COLDER.
TUESDAY NIGHT THROUGH SATURDAY...QUIET WEATHER WILL OCCUR THROUGH
THURSDAY. THE NEXT SYSTEM WILL MOVE THROUGH THE REGION THURSDAY
NIGHT AND FRIDAY. MODELS ARE IN GOOD AGREEMENT WITH THE SPEED OF THE
SYSTEM MOVING THROUGH BUT DIFFER ON THE AMPLITUDE OF THE SYSTEM. THE
ECMWF IS THE OUTLIER WITH A CUTOFF SOLUTION WITH THE REMAINING
DETERMINISTIC SOLUTIONS/ENSEMBLES SUPPORTING THE OPEN WAVE
SOLUTION. LIKE WHAT THE CRH_INIT GAVE ME DUE TO THE MODEL
DIFFERENCES. RIGHT NOW IT IS SLIGHT CHANCE TO CHANCE WHICH IS
REASONABLE BUT THERE IS POTENTIAL TO GO A LITTLE HIGHER. ONE THING
FOR SURE IS THAT HIGH TEMPERATURES WILL BE COLD THROUGH THE ENTIRE
WEAK AND THE INIT TEMPERATURES LOOKED REASONABLE AND MADE LITTLE TO
NO CHANGES.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 957 PM MST SAT DEC 22 2012
VFR CONDITIONS WILL CONTINUE AT KGLD AND KMCK FOR THE NEXT 24
HOURS AS HIGH PRESSURE MOVES SOUTH INTO THE REGION.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...DR
LONG TERM...BULLER
AVIATION...FS
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
925 PM EST MON DEC 24 2012
.SYNOPSIS...
LINGERING LIGHT DRIZZLE AND FREEZING DRIZZLE WILL GIVE WAY TO
PATCHY FOG OVERNIGHT AS LOW PRESSURE EXITS NORTHEAST. AFTER A DRY
BREAK CHRISTMAS DAY...A STRONG LOW PRESSURE SYSTEM WILL COME
NORTHEAST FROM TEXAS AND BRING POTENTIALLY HEAVY AMOUNTS OF SNOW
AND ICE TO THE UPPER OHIO VALLEY WEDNESDAY.
&&
.NEAR TERM /THROUGH TUESDAY/...
PER RECENT SURFACE AND RADAR DATA...HAVE CONTINUED TREND OF
DECREASING COVERAGE OF LIGHT DRIZZLE OVERNIGHT. MAINTAINED MENTION
OF LIGHT FREEZING DRIZZLE NEAR THE MOUNTAINS WHERE TEMPERATURES
HAVE SLIPPED BELOW 32. HAVE ALSO MAINTAINED MENTION OF PATCHY FOG.
WITH RUC AND NAM MODEL PROFILES SHOWING CLOUD TOPS DECREASING AND
HENCE CLOUD TOP TEMPERATURES WARMING TO WARMER THAN -10C...THE
FALLING PRECIPITATION WILL BE LIQUID DRIZZLE. IF BY CHANCE THERE
IS ANY SNOW IT WOULD BE LIKE FINE SNOW GRAINS. EITHER WAY IT WOULD
BE OF LITTLE CONSEQUENCE.
HAVE MAINTAINED THE FREEZING RAIN ADVISORY...BUT EXPECT TO
DISCONTINUE IT BY THE MIDNIGHT HOUR.
FORECASTED TEMPERATURES TO EITHER BE STEADY OVERNIGHT OR DROP BY
NO MORE THAN 2 DEGREES. EXPECT SOME TEMPERATURE CLIMB FOR DAYTIME
CHRISTMAS...BUT RECENT GFS LAMP AND NAM MOS AND SREF MODEL OUTPUT
HAVE TRENDED WITH COOLER HIGHS THAN EARLIER GUIDANCE. STILL THE
DAY SHOULD BE DRY AND DECENT FOR TRAVEL.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
COMPACT BUT POTENT TROF THAT WILL BE YIELDING SVR WX IN THE DEEP
SOUTH WILL LIFT NEWD TUE NGT. COLD AIR WILL BE DRAWN SWD AS THE
ASSOCIATED WMFNT SHARPENS. WARM ADVCTN AT H8 WILL YIELD WDSPRD
PCPN BY WED MRNG.
FORCING FOR ASCENT WILL INCR DRAMATICALLY DURG THE DAY ON WED AS
DIFFLUENCE ALOFT STRENGTHENS AHEAD OF APRCHG UPR LOW. IT IS VERY
CLR THAT A LOT OF PCPN WILL OCCUR. THE PRIMARY FCST DIFFICULTY IS
IDENTIFYING THE NWD EXTENT OF THE H8 WARM TONGUE.
EXPECTATION IS THAT THERE WILL BE A SHARP GRADIENT FROM RAIN TO
FRZG RAIN TO SNOW ACRS FCST AREA. CONFIDENCE IS HIGH IN SNOW
MEETING WRNG CRITERION /IN EXCESS OF 6 IN PER 12 HR/ IN NRN PA
AND OH ZONES OWING TO VERY STRONG ASCENT IN DENDRITIC SNOW GROWTH
ZONE...SPCLY WED AFTN. DURG THIS TIME...SNOW RATES COULD BE QUITE
SGFNT IN I-80/I-79 CORRIDOR.
CONFIDENCE IS ALSO MDT THAT THERE WILL BE SGFNT ICE ACCUM IN MTN
ZONES...WHERE COLD AIR STAGNATES IN VLYS. ICE ACCUMS IN EXCESS OF
ONE-QUARTER INCH ARE PSBL.
FCST HAS LWR CONFIDENCE IN WHERE THE LINE BTWN RAIN AND FRZG RAIN
WILL ESTABLISH ITSELF. CLIMATOLOGY AND MODELS ALL SUGGEST THIS
LINE WILL BE NEAR AND SW FROM PITTSBURGH. ICE ACCUMS STILL XPCD IN
THESE LOCATIONS...BUT ATTM ARE XPCD TO RMN BLW WRNG THRESHOLD.
WINTER STORM WATCH HAS BEEN ISSUED FOR MUCH OF FCST AREA FROM
26/03Z TO 27/11Z. BY WED NGT...RGN WILL BE ON WRN SIDE OF THE
LOW...AND ANY PCPN WILL BE GENERATED/ENHANCED BY MODEST FLOW FROM
THE GRTLKS. ADDITIONAL ACCUMS PSBL WED NGT...BUT SHOULD BE LWR IN
MAGNITUDE THAN WED AFTN.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
HIPRES AND ASSOCIATED H5 RDG WILL MOVE ACRS FCST AREA ON FRI BUT
WILL BE TRANSIENT OWING TO APRCHG WAVES FROM NRN PLNS AND SRN
CONUS. WAVES ATTEMPT TO PHASE ON SAT/SUN...WITH ASSOCIATED PCPN
XPCD TO BE FOCUSED IN SRN ZONES. COLD AIR WILL BE SOLIDLY IN
PLACE...SO ANY PCPN WILL BE ASSOCIATED WITH SNOW.
ANOTHER WAVE XPCD TO GENERATE COASTAL LOPRES BY NEW YRS EVE.
DIFFERENCES IN AMPLITUDE OF THE UPR WAVE EXIST BTWN ECMWF AND GFS.
ATTM...ONLY LMTD IMPACT XPCD TO FCST AREA FROM THIS SYSTEM.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
PER RECENT SURFACE AND RADAR DATA...THE TREND TOWARD DECREASING
COVERAGE OF DRIZZLE WILL CONTINUE OVERNIGHT. WILL MAINTAIN MENTION
OF A CHANCE OF LIGHT FREEZING DRIZZLE WHERE TEMPERATURES ARE
COLDER THAN 32.
SATURATED SURFACE LAYER COUPLED WITH LIGHT WINDS WILL MAINTAIN
LIFR TO IFR CONDITIONS IN FOG AND LOW STRATUS THROUGH 08Z-12Z.
SLOW SURFACE LAYER DRYING SHOULD PROMOTE A TREND TOWARD MVFR AFTER
12Z.
SURFACE WINDS WILL BE LIGHT THROUGH 10Z THEN BECOME NORTHWEST NEAR
5 KTS DAYTIME TUESDAY/CHRISTMAS DAY.
.OUTLOOK.../TUESDAY NIGHT THROUGH SATURDAY/...
MVFR RESTRICTIONS ARE EXPECTED TUESDAY NIGHT...WITH IFR RESTRICTIONS
LIKELY LATE TUESDAY NIGHT AND WEDNESDAY IN FZRA/SLEET/SN. PTYPE GOES
TO ALL SN WEDNESDAY NIGHT WITH IFR WX CONTINUING INTO THU. VFR WX
RETURNS FRI...AND RESTRICTIONS WILL BE POSSIBLE AGAIN SATURDAY WITH
SNOW.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...WINTER STORM WATCH FROM TUESDAY EVENING THROUGH LATE WEDNESDAY
NIGHT FOR MDZ001.
FREEZING RAIN ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR MDZ001.
OH...WINTER STORM WATCH FROM TUESDAY EVENING THROUGH LATE WEDNESDAY
NIGHT FOR OHZ039>041-048>050-057>059.
PA...WINTER STORM WATCH FROM TUESDAY EVENING THROUGH LATE WEDNESDAY
NIGHT FOR PAZ007>009-013>016-020>023-029-073-074-076.
WV...WINTER STORM WATCH FROM TUESDAY EVENING THROUGH LATE WEDNESDAY
NIGHT FOR WVZ001>003-023-041.
FREEZING RAIN ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR WVZ023-
041.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
734 PM EST MON DEC 24 2012
.SYNOPSIS...
LINGERING LIGHT DRIZZLE AND FREEZING DRIZZLE WILL GIVE WAY TO
PATCHY FOG OVERNIGHT AS LOW PRESSURE EXITS NORTHEAST. AFTER A DRY
BREAK CHRISTMAS DAY...A STRONG LOW PRESSURE SYSTEM WILL COME
NORTHEAST FROM TEXAS AND BRING POTENTIALLY HEAVY AMOUNTS OF SNOW
AND ICE TO THE UPPER OHIO VALLEY WEDNESDAY.
&&
.NEAR TERM /THROUGH TUESDAY/...
HAVE DECREASED PRECIPITATION AMOUNTS AND FINE TUNED TEMPERATURE
AND WEATHER TYPE FORECAST BASED ON BLEND OF RECENT SURFACE AND
RADAR DATA AND RUC MODEL PROFILES.
THIS INFORMATION SHOWED CLOUD TOPS THINNING AND HENCE WARMING SO
THAT ANY REMAINING LIGHT SNOW ACROSS THE NORTH AND MOUNTAINS WILL
TRANSITION TO DRIZZLE AND FREEZING DRIZZLE BEFORE MIDNIGHT. HAVE
LIKEWISE DECREASED CHANCES OF DRIZZLE ACROSS LOWER ELEVATIONS
WEST. ADDED MENTION OF FREEZING DRIZZLE WHERE SURFACE TEMPERATURES
DIP TO THE FREEZING POINT OF 32. HAVE ALSO ADDED MENTION OF PATCHY
FOG OVERNIGHT.
WILL LEAVE FREEZING ADVISORIES AS IS...AND LIKELY WILL DISCONTINUE
THESE TOWARD MIDNIGHT.
FORECASTED TEMPERATURES TO EITHER BE STEADY OVERNIGHT OR DROP BY
NO MORE THAN 2 DEGREES. EXPECT SOME TEMPERATURE CLIMB FOR DAYTIME
CHRISTMAS...BUT RECENT GFS LAMP AND NAM MOS AND SREF MODEL OUTPUT
HAVE TRENDED WITH COOLER HIGHS THAN EARLIER GUIDANCE. STILL THE
DAY SHOULD BE DRY AND DECENT FOR TRAVEL.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
COMPACT BUT POTENT TROF THAT WILL BE YIELDING SVR WX IN THE DEEP
SOUTH WILL LIFT NEWD TUE NGT. COLD AIR WILL BE DRAWN SWD AS THE
ASSOCIATED WMFNT SHARPENS. WARM ADVCTN AT H8 WILL YIELD WDSPRD
PCPN BY WED MRNG.
FORCING FOR ASCENT WILL INCR DRAMATICALLY DURG THE DAY ON WED AS
DIFFLUENCE ALOFT STRENGTHENS AHEAD OF APRCHG UPR LOW. IT IS VERY
CLR THAT A LOT OF PCPN WILL OCCUR. THE PRIMARY FCST DIFFICULTY IS
IDENTIFYING THE NWD EXTENT OF THE H8 WARM TONGUE.
EXPECTATION IS THAT THERE WILL BE A SHARP GRADIENT FROM RAIN TO
FRZG RAIN TO SNOW ACRS FCST AREA. CONFIDENCE IS HIGH IN SNOW
MEETING WRNG CRITERION /IN EXCESS OF 6 IN PER 12 HR/ IN NRN PA
AND OH ZONES OWING TO VERY STRONG ASCENT IN DENDRITIC SNOW GROWTH
ZONE...SPCLY WED AFTN. DURG THIS TIME...SNOW RATES COULD BE QUITE
SGFNT IN I-80/I-79 CORRIDOR.
CONFIDENCE IS ALSO MDT THAT THERE WILL BE SGFNT ICE ACCUM IN MTN
ZONES...WHERE COLD AIR STAGNATES IN VLYS. ICE ACCUMS IN EXCESS OF
ONE-QUARTER INCH ARE PSBL.
FCST HAS LWR CONFIDENCE IN WHERE THE LINE BTWN RAIN AND FRZG RAIN
WILL ESTABLISH ITSELF. CLIMATOLOGY AND MODELS ALL SUGGEST THIS
LINE WILL BE NEAR AND SW FROM PITTSBURGH. ICE ACCUMS STILL XPCD IN
THESE LOCATIONS...BUT ATTM ARE XPCD TO RMN BLW WRNG THRESHOLD.
WINTER STORM WATCH HAS BEEN ISSUED FOR MUCH OF FCST AREA FROM
26/03Z TO 27/11Z. BY WED NGT...RGN WILL BE ON WRN SIDE OF THE
LOW...AND ANY PCPN WILL BE GENERATED/ENHANCED BY MODEST FLOW FROM
THE GRTLKS. ADDITIONAL ACCUMS PSBL WED NGT...BUT SHOULD BE LWR IN
MAGNITUDE THAN WED AFTN.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
HIPRES AND ASSOCIATED H5 RDG WILL MOVE ACRS FCST AREA ON FRI BUT
WILL BE TRANSIENT OWING TO APRCHG WAVES FROM NRN PLNS AND SRN
CONUS. WAVES ATTEMPT TO PHASE ON SAT/SUN...WITH ASSOCIATED PCPN
XPCD TO BE FOCUSED IN SRN ZONES. COLD AIR WILL BE SOLIDLY IN
PLACE...SO ANY PCPN WILL BE ASSOCIATED WITH SNOW.
ANOTHER WAVE XPCD TO GENERATE COASTAL LOPRES BY NEW YRS EVE.
DIFFERENCES IN AMPLITUDE OF THE UPR WAVE EXIST BTWN ECMWF AND GFS.
ATTM...ONLY LMTD IMPACT XPCD TO FCST AREA FROM THIS SYSTEM.
&&
.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
ALL SITES ARE EXPECTED TO DRY OUT BY MIDNIGHT...WITH DRIZZLE OR SNOW
THE PRIMARY PRECIPITATION TYPES EXPECTED THIS EVENING. CANNOT RULE
OUT VERY BRIEF PERIODS OF FREEZING RAIN/DRIZZLE.
HAVE CONTINUED PREVIOUS FORECAST OF IFR AT ALL SITES
OVERNIGHT...WITH SEVERAL SITES EXPECTED TO REACH LIFR CONDITIONS.
LIFR IS ALREADY IN ZZV/HLG/MGW...AND WITH SO MANY LIFR
OBSERVATIONS IN OHIO AND WEST VIRGINIA...CANNOT RULE OUT LIFR
CONDITIONS AT OTHER TERMINALS AS WELL.
HAVE PUSHED BACK A RECOVERY TO MVFR CIGS UNTIL 08Z AT THE
EARLIEST...WITH SOME SITES NEEDING MOST OF TUESDAY MORNING TO
RECOVER TO MVFR.
.OUTLOOK.../TUESDAY NIGHT THROUGH SATURDAY/...
MVFR RESTRICTIONS ARE EXPECTED TUESDAY NIGHT...WITH IFR RESTRICTIONS
LIKELY LATE TUESDAY NIGHT AND WEDNESDAY IN FZRA/SLEET/SN. PTYPE GOES
TO ALL SN WEDNESDAY NIGHT WITH IFR WX CONTINUING INTO THU. VFR WX
RETURNS FRI...AND RESTRICTIONS WILL BE POSSIBLE AGAIN SATURDAY WITH
SNOW.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...WINTER STORM WATCH FROM TUESDAY EVENING THROUGH LATE WEDNESDAY
NIGHT FOR MDZ001.
FREEZING RAIN ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR MDZ001.
OH...WINTER STORM WATCH FROM TUESDAY EVENING THROUGH LATE WEDNESDAY
NIGHT FOR OHZ039>041-048>050-057>059.
PA...WINTER STORM WATCH FROM TUESDAY EVENING THROUGH LATE WEDNESDAY
NIGHT FOR PAZ007>009-013>016-020>023-029-073-074-076.
WV...WINTER STORM WATCH FROM TUESDAY EVENING THROUGH LATE WEDNESDAY
NIGHT FOR WVZ001>003-023-041.
FREEZING RAIN ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR WVZ023-
041.
&&
$$
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
947 PM EST MON DEC 24 2012
.UPDATE...
SNOW IS QUICKLY COMING TO AN END ACROSS SOUTHEAST MICHIGAN AS THE
LAST OF THE SNOW SHOWERS IS FALLING ACROSS THE EASTERN THUMB AHEAD
OF A SHORTWAVE PUSHING THROUGH SOUTHERN LOWER MICHIGAN. WHILE MANY
LOCATIONS SAW THE ADVERTISED 0.5 TO 1 INCH OF
SNOWFALL...SEVERAL LOCATIONS GOT CLOSER TO 2 INCHES IN A SWATH
FROM LIVINGSTON TO MACOMB COUNTY. THESE AREAS WERE IN AN AREA OF
ENHANCED CONVECTION EMBEDDED IN THE MAIN SNOW BANDS WHICH PROVIDED
A QUICK BURST OF SNOWFALL AND WITH IT SLIGHTLY HIGHER TOTALS IN
THIS CORRIDOR.
THE REST OF THE NIGHT LOOKS TO BE QUIET WITH ONLY A FEW LINGERING
FLURRIES AS THE FORCING TRACKS EAST OF THE AREA. THIS RECENT ROUND
OF SNOW SHOULD OFFICIALLY BRING A WHITE CHRISTMAS TO MOST OF
SOUTHEAST MICHIGAN TOMORROW WITH THE OFFICIAL YARDSTICK FOR THIS
BEING AN INCH OF SNOW ON THE GROUND AT 7 AM.
&&
.AVIATION...ISSUED 619 PM EST MON DEC 24 2012
//DISCUSSION...
STRATUS WILL CONTINUE TO AFFECT ALL THE TAF SITES. CURRENT SATELLITE
IMAGERY IS SHOWING A BRIEF BREAK...HOWEVER THIS BREAK IS SHORT LIVED
AS MORE STATUS MOVES IN FROM THE SOUTH FROM A WEAK LOW PRESSURE
SYSTEM MOVING THROUGH THE OHIO VALLEY. SNOW FROM THIS SYSTEM WILL
WIND DOWN DURING THE FIRST FEW HOURS OF THE TAF PERIOD...LEAVING
ANYWHERE FROM A HALF OF AN INCH TO AN INCH OF SNOW FROM KFNT SOUTH
TO THE METRO AIRPORTS. VSBYS COULD DROP TO IFR AND EVEN BRIEFLY TO
LIFR BEFORE THE SNOW ENDS...THEN SETTLING BACK TO VFR ONCE THE SNOW
ENDS. ONCE THE LOW MOVES EAST A PERIOD OF QUIET WEATHER IS EXPECTED
FOR THE REST OF TONIGHT AND INTO TUESDAY AS CIGS GRADUALLY RISE TO
VFR TUESDAY AFTERNOON.
FOR DTW...UP TO AN INCH OF SNOW ACCUMULATION EXPECTED THROUGH 02Z
WITH THIS SNOW GIVEN THE EXPECTED LOWER DURATION/INTENSITY.
//DTW THRESHOLD THREATS...
* HIGH CONFIDENCE IN CEILING BELOW 5000 FT THROUGH TUESDAY MORNING.
* HIGH CONFIDENCE IN SNOW AS PRECIPITATION TYPE.
&&
.PREV DISCUSSION...ISSUED 337 PM EST MON DEC 24 2012
SHORT TERM...THIS EVENING AND TONIGHT
UPSTREAM LIGHT SNOW AND VIRGA HAVE BEEN STEADILY PUSHING INTO THE
AREA AHEAD OF THE COMPACT MID-LEVEL SHORTWAVE ROTATING ACROSS THE
LOWER PENINSULA THIS AFTERNOON. FOR SEVERAL HOURS NOW, A PERIOD OF
VIRGA HAS PRECEDED A RATHER BRIEF PERIOD OF LIGHT TO MODERATE
SNOWFALL.
ANALYSIS OF OBSERVATIONS AND SHORT TERM MODEL DATA INDICATE THAT THE
ONGOING SNOWFALL/VIRGA IS STRONGLY TIED TO TWO SEPARATE FEATURES.
THE FIRST, AND PRIMARY TO AFFECT SOUTHEAST MICHIGAN, IS THE BROAD
CORRIDOR OF ASCENT ASSOCIATED WITH DCVA PRECEDING THE WAVE ITSELF.
THE SECOND, MAINLY AFFECTING LOCATIONS SOUTH OF THE BORDER...PERHAPS
AS FAR NORTH AS THE I-94 CORRIDOR...IS A DEEP FRONTOLYTIC
CIRCULATION LEADING THE NOSE OF THE ASSOCIATED 80-KT JET STREAK.
THIS REGION OF FORCED COLD ASCENT HAS ALSO DRAWN UPON A POCKET OF WEAK
MID-LEVEL INSTABILITY TO PRODUCE A STRONGER CONVECTIVE RESPONSE TO
THE SOUTH AND OCCASIONAL ECHOES OF 40DBZ OVER NORTHERN IN.
THE NORTHWARD MIGRATION OF THE ELEVATED FRONTAL ZONE/THETA-E RIDGE
AS WELL AS SUB-850 EASTERLY MOISTURE ADVECTION WILL HELP TO ERODE
THE H85-H7 DRY LAYER APPARENT ON THIS MORNING`S 12Z DTX SOUNDING AND
ALLOW FOR A SUBSEQUENT EXPANSION OF LIGHT SNOW AND DECREASE IN VIRGA
OVER THE NEXT FEW HOURS. RECENT RADAR TRENDS CONFIRM THESE
EXPECTATIONS (AND YESTERDAY`S NMM CORE SOLUTIONS). RUC ANALYSIS
SUGGESTS THAT WHILE A BRIEF PERIOD OF CONVECTIVE PRECIP WILL BE
POSSIBLE ACROSS THE SOUTHERN CWA, THE BULK OF THE EVENT WILL LIKELY
TAKE PLACE ACROSS THE HEART OF THE FORECAST AREA AND WILL BE
CHARACTERIZED BY A FEW HOURS OF LIGHT SNOW WITH EMBEDDED MODERATE
BANDING OWING TO BOTH A VERY WEAKLY STATICALLY STABLE ATMOSPHERE
ABOVE THE LOW-LEVEL FRONT AND MARGINAL MID-LEVEL INSTABILITY. THE
FORECAST HAS THEREFORE BEEN AMENDED TO REFLECT A HIGHER POP SCENARIO
FROM APPROXIMATELY LIVINGSTON TO TO LAPEER COUNTIES WHERE A
WIDESPREAD HALF INCH OR SO IS STILL POSSIBLE. LOCATIONS AFFECTED BY
SAID BANDING WILL SEE A PORTION OF THE SNOW ACCUMULATE MORE QUICKLY
AS VSBYS FALL TO 1-2 MILES PER UPSTREAM OBS...RESULTING IN THE
POTENTIAL FOR A FEW ISOLATED 1" ACCUMS.
LONG TERM...
CHRISTMAS DAY WILL BE ON THE TRANQUIL SIDE OVERALL AROUND SE
MICHIGAN LEADING INTO AN ACTIVE PERIOD OF WINTER WEATHER AFTER THE
HOLIDAY. HIGHER END ADVISORY CRITERIA SNOWFALL AMOUNTS AND RATES ARE
ANTICIPATED FOR SE MICHIGAN WEDNESDAY THROUGH WEDNESDAY NIGHT WITH
THE TIMING ON THE DAY AFTER CHRISTMAS AND POTENTIAL TRAVEL IMPACTS
BEING THE NOTABLE ASPECT OF THE EVENT.
THE WEDNESDAY LOW PRESSURE SYSTEM WILL BE PRECEDED BY SOME LAKE
EFFECT SNOW SHOWERS MAKING INLAND PROGRESS OFF LAKE HURON DURING
CHRISTMAS DAY. INLAND PROGRESS COULD BE AS FAR SOUTH AS I-69 AND
WEST TO I-75 ON A SCATTERED BASIS WITH GREATER COVERAGE IN THE THUMB
CLOSER TO THE LAKE. INSTABILITY WILL BE MODEST WITH LAKE TO 850
DELTA-T RUNNING AROUND 15C BUT WITH INVERSION HEIGHT BOOSTED BY SOME
SEEDING FROM MID LEVEL MOISTURE TRAILING TODAY`S WAVE. THE BROAD
INVERTED SURFACE TROUGH WILL PROVIDE A FAVORABLE LOW LEVEL WIND
FIELD FOR FOCUSING NORTHERLY FLOW INTO THE THUMB FOR A FEW HOURS
BEFORE FILLING AND DRYING TOWARD EVENING.
THE MAIN CONCERN IN THE FORECAST REMAINS THE EVOLUTION OF A LARGE
LOW PRESSURE SYSTEM SET TO IMPACT MUCH OF THE COUNTRY EAST OF THE
MISSISSIPPI WEDNESDAY INTO THURSDAY. THIS SYSTEM IS EXPECTED TO
NEGATIVELY IMPACT POST HOLIDAY TRAVEL ACROSS THE REGION WITH
MODERATE SNOW ACCUMULATION REMAINING THE PRIMARY EXPECTATION IN SE
MICHIGAN. SUBJECT UPPER LEVEL ENERGY WAS MORE FULLY INLAND FROM THE
WEST COAST FOR THE MORNING UPPER AIR ANALYSIS, SO IT IS A GOOD SIGN
THAT THE 12Z MODEL CYCLE HAS NOT SHIFTED MUCH OFF OF EARLIER
SOLUTIONS AS THE SYSTEM DEVELOPS OVER THE WESTERN GULF COAST DURING
CHRISTMAS DAY AND DEEPENS INTO THE TENNESSEE VALLEY BY WEDNESDAY
MORNING. AGREEMENT BETWEEN THE NAM, GFS, ECMWF, AND LOCAL WRF GLOBAL
IS EXCELLENT BY THEN ON THE POSITION AND INTENSITY OF THE LARGE
SCALE FEATURES ASSOCIATED WITH THE SYSTEM. THE CANADIAN REMAINS
FASTER/FARTHER EAST IN THE SOLUTION SPACE PERHAPS REPRESENTING THE
STRONG INFLUENCE ON TRACK AND STRENGTH BY THE SOUTHWARD POSITION OF
THE UPPER JET AXIS FROM SOUTHERN CALIFORNIA TO THE CENTRAL GULF
COAST. THERE IS ALSO CONSIDERABLE LOW LEVEL BAROCLINICITY, GULF
MOISTURE, AND WARM SECTOR INSTABILITY IN ADVANCE OF THE WAVE FROM
THE TENNESSEE VALLEY TO THE MID ATLANTIC STATES. ALL OF THIS, ALONG
WITH A NEW ROUND OF UPPER LEVEL HEIGHT FALLS OVER THE WEST COAST,
FAVORS PROGRESSION AND THE TRANSFER OF CYCLOGENESIS TO THE EAST
COAST DURING WEDNESDAY.
CONFIDENCE IN THE MODEL SOLUTIONS ON THE BULK FEATURES DOES NOT GET
US OUT OF THE WOODS ON A WINTER EVENT OR SIMPLIFY THE FORECAST FOR
OUR AREA DURING WEDNESDAY INTO WEDNESDAY NIGHT AS A CONSIDERABLE
AMOUNT OF MOISTURE REMAINS ADVERTISED FOR THE REGION. WITH AN EASY
CALL ON ALL SNOW AS THE PRECIPITATION TYPE, THE QUESTION OF AMOUNT
REMAINS TIED TO THE CHARACTER AND DURATION OF MAX FORCING AND
MICROPHYSICAL ASPECTS OF THE SNOW OVER SE MICHIGAN DURING THE PEAK
OF THE EVENT WEDNESDAY AFTERNOON THROUGH WEDNESDAY EVENING. THE
TRANSFER OF CYCLOGENESIS TO THE MID ATLANTIC COAST WILL SIPHON AT
LEAST SOME ENERGY AND MOISTURE OUT OF THE GREAT LAKES BUT A WELL
ORGANIZED TROWAL IS SHOWN TO BE IN PLACE OVER OUR AREA WITH A STRONG
HYBRID ATLANTIC/GULF MOISTURE CONVEYOR FEEDING INTO THE NORTH FLANK
OF THE SYSTEM. MODEL FIELDS OF SPECIFIC HUMIDITY INDICATE MORE THAN
ADEQUATE AMOUNTS OF 2-3 G/KG IN THE 850 TO 700 MB LAYER ASSOCIATED
WITH THE TROWAL AXIS. THIS LEAVES DURATION AS THE LIMITING FACTOR AS
FIELDS OF THETA-E INDICATE THE TROWAL SHRINKING EASTWARD QUICKLY BY
MIDNIGHT WEDNESDAY NIGHT. WILDCARDS TO CONSIDER THAT COULD SKEW
AMOUNTS HIGHER INCLUDE THE ACTUAL TIMING OF EAST COAST TRANSFER,
MESOSCALE BANDS WITHIN THE TROWAL, AND LAKE ENHANCEMENT. THE
POTENTIAL FOR LAKE ENHANCEMENT WILL BE THE MOST LIKELY EXTRA
CONTRIBUTOR BUT THAT WILL TEND TO STRETCH THE EVENT WELL INTO
THURSDAY AS SYNOPTIC FORCING WANES. THIS WILL CONTINUE TO BE
EVALUATED BUT THE PREPONDERANCE OF EVIDENCE FOR THIS FORECAST
PACKAGE, ALONG WITH MODEL SOUNDING DERIVED SNOW RATIO AVERAGING
11:1, SUGGESTS STORM TOTALS WILL REMAIN MOSTLY BELOW 6 INCHES DURING
THE 12 TO 18 HOUR EVENT ENDING BY SUNRISE THURSDAY.
AFTER A BREAK DURING THURSDAY AND MOST OF FRIDAY, THE ACTIVE LARGE
SCALE PATTERN WILL CONTINUE WITH THE NEXT PACIFIC SYSTEM REACHING
THE GREAT LAKES TO START THE WEEKEND. EARLY INDICATIONS ARE THIS
SYSTEM WILL BE LESS ORGANIZED AS IT MOVES THROUGH THE GREAT LAKES
BEFORE GAINING STRENGTH ALONG THE EAST COAST TOWARD SUNDAY.
MARINE...
LIGHT NORTHERLY WINDS TONIGHT OF 15 KNOTS OR LESS WILL TURN EASTERLY
AND BEGIN TO INCREASE ON TUESDAY NIGHT AS A STRONG LOW PRESSURE
SYSTEM LIFTS TOWARD THE REGION FROM THE SOUTH. THE PROLONGED PERIOD
OF ONSHORE FLOW WILL FAVOR ELEVATED WAVE CONDITIONS FOR ALL
NEARSHORE ZONES BETWEEN WEDNESDAY AND THURSDAY MORNING IN ADDITION
TO POTENTIAL FUNNELING INTO SAGINAW BAY. SMALL CRAFT ADVISORIES
APPEAR LIKELY AT THIS TIME. BY WEDNESDAY AFTERNOON INTO WEDNESDAY
NIGHT...GUSTS TO NEAR GALES WILL BE POSSIBLE ACROSS AREA WATERS.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
UPDATE.......KURIMSKI
AVIATION.....KURIMSKI
SHORT TERM...JVC
LONG TERM....BT
MARINE.......JVC
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
619 PM EST MON DEC 24 2012
.AVIATION...
//DISCUSSION...
STRATUS WILL CONTINUE TO AFFECT ALL THE TAF SITES. CURRENT SATELLITE
IMAGERY IS SHOWING A BRIEF BREAK...HOWEVER THIS BREAK IS SHORT LIVED
AS MORE STATUS MOVES IN FROM THE SOUTH FROM A WEAK LOW PRESSURE
SYSTEM MOVING THROUGH THE OHIO VALLEY. SNOW FROM THIS SYSTEM WILL
WIND DOWN DURING THE FIRST FEW HOURS OF THE TAF PERIOD...LEAVING
ANYWHERE FROM A HALF OF AN INCH TO AN INCH OF SNOW FROM KFNT SOUTH
TO THE METRO AIRPORTS. VSBYS COULD DROP TO IFR AND EVEN BRIEFLY TO
LIFR BEFORE THE SNOW ENDS...THEN SETTLING BACK TO VFR ONCE THE SNOW
ENDS. ONCE THE LOW MOVES EAST A PERIOD OF QUIET WEATHER IS EXPECTED
FOR THE REST OF TONIGHT AND INTO TUESDAY AS CIGS GRADUALLY RISE TO
VFR TUESDAY AFTERNOON.
FOR DTW...UP TO AN INCH OF SNOW ACCUMULATION EXPECTED THROUGH 02Z
WITH THIS SNOW GIVEN THE EXPECTED LOWER DURATION/INTENSITY.
//DTW THRESHOLD THREATS...
* HIGH CONFIDENCE IN CEILING BELOW 5000 FT THROUGH TUESDAY MORNING.
* HIGH CONFIDENCE IN SNOW AS PRECIPITATION TYPE.
&&
.PREV DISCUSSION...ISSUED 337 PM EST MON DEC 24 2012
SHORT TERM...THIS EVENING AND TONIGHT
UPSTREAM LIGHT SNOW AND VIRGA HAVE BEEN STEADILY PUSHING INTO THE
AREA AHEAD OF THE COMPACT MID-LEVEL SHORTWAVE ROTATING ACROSS THE
LOWER PENINSULA THIS AFTERNOON. FOR SEVERAL HOURS NOW, A PERIOD OF
VIRGA HAS PRECEDED A RATHER BRIEF PERIOD OF LIGHT TO MODERATE
SNOWFALL.
ANALYSIS OF OBSERVATIONS AND SHORT TERM MODEL DATA INDICATE THAT THE
ONGOING SNOWFALL/VIRGA IS STRONGLY TIED TO TWO SEPARATE FEATURES.
THE FIRST, AND PRIMARY TO AFFECT SOUTHEAST MICHIGAN, IS THE BROAD
CORRIDOR OF ASCENT ASSOCIATED WITH DCVA PRECEDING THE WAVE ITSELF.
THE SECOND, MAINLY AFFECTING LOCATIONS SOUTH OF THE BORDER...PERHAPS
AS FAR NORTH AS THE I-94 CORRIDOR...IS A DEEP FRONTOLYTIC
CIRCULATION LEADING THE NOSE OF THE ASSOCIATED 80-KT JET STREAK.
THIS REGION OF FORCED COLD ASCENT HAS ALSO DRAWN UPON A POCKET OF WEAK
MID-LEVEL INSTABILITY TO PRODUCE A STRONGER CONVECTIVE RESPONSE TO
THE SOUTH AND OCCASIONAL ECHOES OF 40DBZ OVER NORTHERN IN.
THE NORTHWARD MIGRATION OF THE ELEVATED FRONTAL ZONE/THETA-E RIDGE
AS WELL AS SUB-850 EASTERLY MOISTURE ADVECTION WILL HELP TO ERODE
THE H85-H7 DRY LAYER APPARENT ON THIS MORNING`S 12Z DTX SOUNDING AND
ALLOW FOR A SUBSEQUENT EXPANSION OF LIGHT SNOW AND DECREASE IN VIRGA
OVER THE NEXT FEW HOURS. RECENT RADAR TRENDS CONFIRM THESE
EXPECTATIONS (AND YESTERDAY`S NMM CORE SOLUTIONS). RUC ANALYSIS
SUGGESTS THAT WHILE A BRIEF PERIOD OF CONVECTIVE PRECIP WILL BE
POSSIBLE ACROSS THE SOUTHERN CWA, THE BULK OF THE EVENT WILL LIKELY
TAKE PLACE ACROSS THE HEART OF THE FORECAST AREA AND WILL BE
CHARACTERIZED BY A FEW HOURS OF LIGHT SNOW WITH EMBEDDED MODERATE
BANDING OWING TO BOTH A VERY WEAKLY STATICALLY STABLE ATMOSPHERE
ABOVE THE LOW-LEVEL FRONT AND MARGINAL MID-LEVEL INSTABILITY. THE
FORECAST HAS THEREFORE BEEN AMENDED TO REFLECT A HIGHER POP SCENARIO
FROM APPROXIMATELY LIVINGSTON TO TO LAPEER COUNTIES WHERE A
WIDESPREAD HALF INCH OR SO IS STILL POSSIBLE. LOCATIONS AFFECTED BY
SAID BANDING WILL SEE A PORTION OF THE SNOW ACCUMULATE MORE QUICKLY
AS VSBYS FALL TO 1-2 MILES PER UPSTREAM OBS...RESULTING IN THE
POTENTIAL FOR A FEW ISOLATED 1" ACCUMS.
LONG TERM...
CHRISTMAS DAY WILL BE ON THE TRANQUIL SIDE OVERALL AROUND SE
MICHIGAN LEADING INTO AN ACTIVE PERIOD OF WINTER WEATHER AFTER THE
HOLIDAY. HIGHER END ADVISORY CRITERIA SNOWFALL AMOUNTS AND RATES ARE
ANTICIPATED FOR SE MICHIGAN WEDNESDAY THROUGH WEDNESDAY NIGHT WITH
THE TIMING ON THE DAY AFTER CHRISTMAS AND POTENTIAL TRAVEL IMPACTS
BEING THE NOTABLE ASPECT OF THE EVENT.
THE WEDNESDAY LOW PRESSURE SYSTEM WILL BE PRECEDED BY SOME LAKE
EFFECT SNOW SHOWERS MAKING INLAND PROGRESS OFF LAKE HURON DURING
CHRISTMAS DAY. INLAND PROGRESS COULD BE AS FAR SOUTH AS I-69 AND
WEST TO I-75 ON A SCATTERED BASIS WITH GREATER COVERAGE IN THE THUMB
CLOSER TO THE LAKE. INSTABILITY WILL BE MODEST WITH LAKE TO 850
DELTA-T RUNNING AROUND 15C BUT WITH INVERSION HEIGHT BOOSTED BY SOME
SEEDING FROM MID LEVEL MOISTURE TRAILING TODAY`S WAVE. THE BROAD
INVERTED SURFACE TROUGH WILL PROVIDE A FAVORABLE LOW LEVEL WIND
FIELD FOR FOCUSING NORTHERLY FLOW INTO THE THUMB FOR A FEW HOURS
BEFORE FILLING AND DRYING TOWARD EVENING.
THE MAIN CONCERN IN THE FORECAST REMAINS THE EVOLUTION OF A LARGE
LOW PRESSURE SYSTEM SET TO IMPACT MUCH OF THE COUNTRY EAST OF THE
MISSISSIPPI WEDNESDAY INTO THURSDAY. THIS SYSTEM IS EXPECTED TO
NEGATIVELY IMPACT POST HOLIDAY TRAVEL ACROSS THE REGION WITH
MODERATE SNOW ACCUMULATION REMAINING THE PRIMARY EXPECTATION IN SE
MICHIGAN. SUBJECT UPPER LEVEL ENERGY WAS MORE FULLY INLAND FROM THE
WEST COAST FOR THE MORNING UPPER AIR ANALYSIS, SO IT IS A GOOD SIGN
THAT THE 12Z MODEL CYCLE HAS NOT SHIFTED MUCH OFF OF EARLIER
SOLUTIONS AS THE SYSTEM DEVELOPS OVER THE WESTERN GULF COAST DURING
CHRISTMAS DAY AND DEEPENS INTO THE TENNESSEE VALLEY BY WEDNESDAY
MORNING. AGREEMENT BETWEEN THE NAM, GFS, ECMWF, AND LOCAL WRF GLOBAL
IS EXCELLENT BY THEN ON THE POSITION AND INTENSITY OF THE LARGE
SCALE FEATURES ASSOCIATED WITH THE SYSTEM. THE CANADIAN REMAINS
FASTER/FARTHER EAST IN THE SOLUTION SPACE PERHAPS REPRESENTING THE
STRONG INFLUENCE ON TRACK AND STRENGTH BY THE SOUTHWARD POSITION OF
THE UPPER JET AXIS FROM SOUTHERN CALIFORNIA TO THE CENTRAL GULF
COAST. THERE IS ALSO CONSIDERABLE LOW LEVEL BAROCLINICITY, GULF
MOISTURE, AND WARM SECTOR INSTABILITY IN ADVANCE OF THE WAVE FROM
THE TENNESSEE VALLEY TO THE MID ATLANTIC STATES. ALL OF THIS, ALONG
WITH A NEW ROUND OF UPPER LEVEL HEIGHT FALLS OVER THE WEST COAST,
FAVORS PROGRESSION AND THE TRANSFER OF CYCLOGENESIS TO THE EAST
COAST DURING WEDNESDAY.
CONFIDENCE IN THE MODEL SOLUTIONS ON THE BULK FEATURES DOES NOT GET
US OUT OF THE WOODS ON A WINTER EVENT OR SIMPLIFY THE FORECAST FOR
OUR AREA DURING WEDNESDAY INTO WEDNESDAY NIGHT AS A CONSIDERABLE
AMOUNT OF MOISTURE REMAINS ADVERTISED FOR THE REGION. WITH AN EASY
CALL ON ALL SNOW AS THE PRECIPITATION TYPE, THE QUESTION OF AMOUNT
REMAINS TIED TO THE CHARACTER AND DURATION OF MAX FORCING AND
MICROPHYSICAL ASPECTS OF THE SNOW OVER SE MICHIGAN DURING THE PEAK
OF THE EVENT WEDNESDAY AFTERNOON THROUGH WEDNESDAY EVENING. THE
TRANSFER OF CYCLOGENESIS TO THE MID ATLANTIC COAST WILL SIPHON AT
LEAST SOME ENERGY AND MOISTURE OUT OF THE GREAT LAKES BUT A WELL
ORGANIZED TROWAL IS SHOWN TO BE IN PLACE OVER OUR AREA WITH A STRONG
HYBRID ATLANTIC/GULF MOISTURE CONVEYOR FEEDING INTO THE NORTH FLANK
OF THE SYSTEM. MODEL FIELDS OF SPECIFIC HUMIDITY INDICATE MORE THAN
ADEQUATE AMOUNTS OF 2-3 G/KG IN THE 850 TO 700 MB LAYER ASSOCIATED
WITH THE TROWAL AXIS. THIS LEAVES DURATION AS THE LIMITING FACTOR AS
FIELDS OF THETA-E INDICATE THE TROWAL SHRINKING EASTWARD QUICKLY BY
MIDNIGHT WEDNESDAY NIGHT. WILDCARDS TO CONSIDER THAT COULD SKEW
AMOUNTS HIGHER INCLUDE THE ACTUAL TIMING OF EAST COAST TRANSFER,
MESOSCALE BANDS WITHIN THE TROWAL, AND LAKE ENHANCEMENT. THE
POTENTIAL FOR LAKE ENHANCEMENT WILL BE THE MOST LIKELY EXTRA
CONTRIBUTOR BUT THAT WILL TEND TO STRETCH THE EVENT WELL INTO
THURSDAY AS SYNOPTIC FORCING WANES. THIS WILL CONTINUE TO BE
EVALUATED BUT THE PREPONDERANCE OF EVIDENCE FOR THIS FORECAST
PACKAGE, ALONG WITH MODEL SOUNDING DERIVED SNOW RATIO AVERAGING
11:1, SUGGESTS STORM TOTALS WILL REMAIN MOSTLY BELOW 6 INCHES DURING
THE 12 TO 18 HOUR EVENT ENDING BY SUNRISE THURSDAY.
AFTER A BREAK DURING THURSDAY AND MOST OF FRIDAY, THE ACTIVE LARGE
SCALE PATTERN WILL CONTINUE WITH THE NEXT PACIFIC SYSTEM REACHING
THE GREAT LAKES TO START THE WEEKEND. EARLY INDICATIONS ARE THIS
SYSTEM WILL BE LESS ORGANIZED AS IT MOVES THROUGH THE GREAT LAKES
BEFORE GAINING STRENGTH ALONG THE EAST COAST TOWARD SUNDAY.
MARINE...
LIGHT NORTHERLY WINDS TONIGHT OF 15 KNOTS OR LESS WILL TURN EASTERLY
AND BEGIN TO INCREASE ON TUESDAY NIGHT AS A STRONG LOW PRESSURE
SYSTEM LIFTS TOWARD THE REGION FROM THE SOUTH. THE PROLONGED PERIOD
OF ONSHORE FLOW WILL FAVOR ELEVATED WAVE CONDITIONS FOR ALL
NEARSHORE ZONES BETWEEN WEDNESDAY AND THURSDAY MORNING IN ADDITION
TO POTENTIAL FUNNELING INTO SAGINAW BAY. SMALL CRAFT ADVISORIES
APPEAR LIKELY AT THIS TIME. BY WEDNESDAY AFTERNOON INTO WEDNESDAY
NIGHT...GUSTS TO NEAR GALES WILL BE POSSIBLE ACROSS AREA WATERS.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....KURIMSKI
SHORT TERM...JVC
LONG TERM....BT
MARINE.......JVC
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
607 PM EST MON DEC 24 2012
.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 434 PM EST MON DEC 24 2012
WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL LOW OVER NRN
ONTARIO WITH A TROUGH EXTENDING INTO THE WESTERN GREAT LAKES. A
SHORTWAVE TROUGH WAS LOCATED OVER LOWER MI WHILE UPSTREAM A WEAKER
SHRTWV EXTENDED FROM THE SRN END OF JAMES BAY TO NEAR KINL. ALTHOUGH THE
STRONGEST 700-300 MB QVECTOR CONV REMAINED SOUTHEAST OF UPPER MI
WHILE...SOME WEAK TO MODERATE FORCING LINGERING OVER THE AREA
SUPPORTED AREAS OF LIGHT SNOW WITH VISIBILITIES GENERALLY AT OR
ABOVE 5SM. NW LOW LEVEL WINDS WITH 850 MB TEMPS AROUND -15C ALSO
SUPPORTED SOME LIGHT LES BANDS. A SIGNIFICANT LIMITING FACTOR FOR
LES INTENSITY WAS LOW INVERSION HEIGHTS AROUND 4K FT AND INFLUX OF
DRIER AIR BELOW THE INVERSION.
TONIGHT...INCREASING LOW-LVL CONVERGENCE AIDED BY DEVELOPING LAND
BREEZES SHOULD PROVIDE ADDITIONAL FOCUS FOR LES INTO ERN ALGER/NRN
SCHOOLCRAFT AND PERHAPS OVER THE PORCUPINE MOUNTAINS OVER THE WEST.
THE DRY AIR UPSTREAM AND LOW INVERSION HEIGHTS WILL LIMIT
AMOUNTS...ESPECIALLY OVER THE WEST...TO GENERALLY AN INCH OR LESS.
GREATER POPS WERE INCLUDED OVER THE ERN CWA WHERE THE LONGER FETCH
WILL HELP KEEP INVERSION HEIGHTS IN THE 5K-7K FT RANGE AND CLOUD
SUPPORT SLIGHTLY GREATER SNOWFALL AMOUNTS OF AN INCH OR TWO.
LES WILL CONTINUE INTO CHRISTMAS DAY AS 850 MB TEMPS REMAIN NEAR
-14C BUT SHOULD DIMINISH AS WINDS BACK TO WNW WITH SLOWLY LOWERING
INVERSION HEIGHTS AND MORE ANTICYCLONIC/DIVERGENT LOW LEVEL FLOW.
SNOWFALL INTENSITY/AMOUNTS WILL REMAIN GREATEST OVER THE EAST WHERE
AN ADDITIONAL INCH MAY ACCUMULATE.
.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 434 PM EST MON DEC 24 2012
NOT A LOT OF EXCITING WEATHER TO GO IN DEPTH ABOUT FOR THE LONG TERM
PERIOD /TUESDAY NIGHT THROUGH NEXT MONDAY/. WE WILL BE DOMINATED BY
NORTHERLY WINDS FOR MUCH OF THE PERIOD WITH SLIGHT TO LOW CHANCE
POPS NEAR LAKE SUPERIOR...AS THE STORM TRACK CONTINUES TO BE WELL TO
OUR S.
TUESDAY NIGHT SHOULD BE ONE OF THE COLDEST IN A WHILE...WITH A FEW
LOCATIONS OVER INTERIOR W PORTIONS OF UPPER MI FALLING BELOW 0
THANKS TO A POCKET OF CLEARING NOTED BY SOME OF THE SMALLER SCALE
MODELS.
DID INCREASE THE FCST MODEL CONSENSUS POPS FOR SATURDAY NIGHT
THROUGH MONDAY...HEDGING THE FCST CLOSER TO THE ECMWF AND SLIGHTLY
HIGHER CONFIDENCE IN COLD AIR ROTATING IN ON MAINLY NW WINDS. THE
OUTLIER WAS THE GFS...PARTICULARLY FROM SUNDAY ON AS IT BROUGHT A
SFC LOW FROM CENTRAL CANADA TO ONTARIO SUNDAY NIGHT. A WEAKENING SFC
TROUGH CONTINUED FOR THE GFS...EXTENDING W FROM THE EXITING LOW OFF
THE COAST OF MAINE. THE ECMWF HAD FAIRLY STEADY 850MB TEMPS OF -15
TO -20C FROM SATURDAY NIGHT THROUGH MONDAY...WITH AT LEAST LIMITED
MOISTURE TO BRING IN A GOOD CHANCE OF SNOW SHOWERS.
&&
.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 606 PM EST MON DEC 24 2012
WITH A STRONG INVERSION OVER THE AREA...THE STRATUS CLOUDS WILL
PERSIST THROUGH THE FORECAST PERIOD EXCEPT AT IWD WHICH WILL HAVE A
SW WIND WHICH WILL PUSH THE LAKE EFFECT CLOUDS NORTH OF THEM ON TUE
AFTERNOON. OTHWERWISE...A NW FLOW WILL BRING SOME OCCASIONAL LIGHT
LAKE EFFECT SNOW TO THE TAF SITES BUT VSBYS SHOULD NOT BE RESTRICTED
BY IT. SO...EXPECT MVFR CIGS AT BOTH KCMX AND KSAW THROUGH THE FCST
PERIOD.
&&
.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 434 PM EST MON DEC 24 2012
A HIGH PRESSURE RIDGE BUILDING IN FROM THE CANADIAN PRAIRIES TODAY
AND TONIGHT WILL LINGER THROUGH MUCH OF THE WEEK...KEEPING WINDS
AT OR BELOW 25 KNOTS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...JLB
LONG TERM...KF
AVIATION...07
MARINE...JLB
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
352 PM EST SUN DEC 23 2012
.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 350 PM EST SUN DEC 23 2012
WV IMAGERY AND RUC ANALYSIS INDICATED CONFLUENT WNW MID/UPPER LEVEL
FLOW THROUGH THE NRN GREAT LAKES BETWEEN A TROUGH FROM JAMES BAY
INTO QUEBEC AND A RIDGE INTO THE UPPER MS VALLEY. AN UPSTREAM
SHORTWAVE TROUGH OVER NORTH DAKOTA SUPPORTED AN AREA OF SNOW OVER
WRN AND NRN ND. NW FLOW LES HAD DIMINISHED OVER CNTRL UPPER MI AS A
SFC RIDGE BUILDS INTO THE AREA WITH DRY ADVECTION...LOWERING
INVERSION HEIGHTS...BACKING WINDS AND INCREASING ACYC FLOW. FARTHER
EAST...LES LINGERED INTO THE EAST(ERY/ANJ) WITH VSBY STILL IN THE
2-4SM RANGE.
DEVELOPING LAND BREEZES TONIGHT COULD PROVIDE FOCUS FOR LES BANDS
OVER SHORELINE AREAS EAST OF MUNISING IN WNW FLOW...BUT WILL ONLY
MAINTAIN SLIGHT CHANCE POPS GIVEN MARGINAL INSTABILITY WITH LAKE 850
MB TEMPS NEAR -12C AND DRY LOW-LVL AIR BLO LOW INVERSION HEIGHTS OF
4K FT.
LATE TONIGHT AND MONDAY...AS THE ND SHRTWV MOVES THROUGH UPPER MS
VALLEY TONIGHT INTO WI ON MONDAY...THE STRONGEST 700-300 MB QVECTOR
CONV IS EXPECTED TO REMAIN TO THE SOUTH WITH THE MOST FAVORABLE
MOISTURE PROFILE FOR PCPN THROUGH NRN WI AND FAR SRN UPPER MI. MODELS
CONSENSUS QPF AND FAVORS CONTINUATION OF HIGHEST POPS THROUGH THE
SRN TIER OF COUNTIES. EVEN THOUGH PCPN AMOUNTS OF ONLY AROUND 0.05
INCH OR SNOWFALL OF AN INCH OR LESS IS EXPECTED...POPS WERE BOOSTED
INTO THE 50-65 RANGE OVER THE SOUTH. WITH 850 MB TEMPS TO NEAR
-14C...SOME ADDITIONAL LES WILL BE POSSIBLE FOR NW FLOW FAVORED
LOCATIONS DOWNWIND OF LAKE SUPERIOR. LOW INVERSION HEIGHTS AOB 4K FT
AND AN UPSTREAM 850-800 MB DRY LAYER WILL LIMIT LES INTENSITY AND
ONLY CHANCE POPS WERE MENTIONED.
.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 350 PM EST SUN DEC 23 2012
CHRISTMAS EVE NIGHT/CHRISTMAS/CHRISTMAS NIGHT...WAVE THAT BRINGS LGT
SNOW TO PORTIONS OF THE AREA ON MONDAY EXITS CHRISTMAS EVE EVENING.
H85-H6 MOISTURE LINGERS OVER EASTERN CWA MONDAY EVENING BUT THERE
REALLY IS NOT MUCH LIFT WITHIN THE DEEPER MOISTURE. NORTHWEST WINDS
RESULT IN POTENTIAL LK EFFECT ALONG LK SUPERIOR. SOUNDINGS A BIT
MORE FAVORABLE OVER ALGER/NORTHERN SCHOOLCRAFT DUE TO SLIGHTLY
HIGHER INVERSION AROUND 5KFT AND TEMPS AT INVERSION TOP AROUND -16C.
NAM AT MUNISING/P53 SHOWS LAKE INDUCED CAPES OVER 300 J/KG WITH
PORTION OF LAKE CLOUD LAYER IN DGZ. WITH EXPECTED SFC WINDS FAVORING
ENAHNCED CONVERGENCE...INCREASED POPS TO LIKELY OVR ALGER AND
NORTHERN SCHOOLCRAFT INTO TUESDAY MORNING. ACCUMS WILL MAINLY BE
LIGHT BUT THERE COULD BE A FEW INCHES OF SNOW. DESPITE BEING LK
EFFECT...SLR/S STAY MORE TOWARD 15:1. LOWER INVERSIONS FCST IN THE
WEST AND NOT AS MUCH MOISTURE WILL LIMIT LK EFFECT OVER THE WEST. BY
LATER ON CHRISTMAS DAY WINDS BACK TO MORE OF A WEST NORTHWEST
DIRECTION. KEPT POPS IN THE HIGH CHANCE/LOWER LIKELY RANGE BUT
ADJUSTED BASED ON EXPECTED LOW-LEVEL WIND DIRECTION. AWAY FM THE LK
EFFECT CONCERNS...A MORE WEST WIND INITIALLY TUESDAY NIGHT WILL
ALLOWS INTERIOR AREAS TO HAVE CHANCE OF FALLING BLO ZERO FOR MIN
TEMPS. WINDS TURN MORE NORTHERLY LATE...BUT GIVEN LIGHT SYNOPTIC
WINDS AND PWATS BLO 50 PCT OF NORMAL...TEMPS OVER INLAND AREAS COULD
STILL FALL OFF VERY QUICKLY IN THE EVENING. INTRODUCED SOME SUB ZERO
LOWS ALONG WI BORDER...BUT WHERE SKIES ARE MOSTLY CLEAR...COULD SEE
READINGS THIS LOW CLOSER TO LK SUPERIOR AND OVER INTERIOR EAST AS
WELL.
WEDNESDAY THROUGH THURSDAY...LATEST RUN OF GFS REMAINS CONSISTENT IN
INDICATING SOUTHERN PLAINS INTO LOWER MISSISSIPPI RIVER VALLEY
SNOWSTORM TRACKING FARTHER WEST AS IT HEADS TOWARD GREAT LAKES
MIDWEEK. LATEST GFS BRINGS SFC LOW JUST SOUTHEAST OF DETROIT
WEDNESDAY AFTN AS DOES THE NAM. HPC GUIDANCE INDICATES SEVERAL
INCHES OF SNOW OVER SOUTHEAST LOWER MICHIGAN WITH THIS STORM. GFS
ALSO ALLOWS ENOUGH OF CONNECTION OF NORTHERN AND SOUTHERN BRANCH
WAVES TO RESULT IN STRONGER INVERTED TROUGH ACROSS THE UPPER GREAT
LAKES REGION THROUGH THURSDAY MORNING. RESULT IS SYNOPTIC SNOW
SHIELD GRAZING EASTERN CWA WEDNESDAY AFTN AND PUSHING AS FAR WEST AS
ESC/MNM/SAW WEDNESDAY NIGHT. ECMWF AND GEM-NHEM FARTHER TO THE
EAST...AS ARE ENSEMBLES OF GFS/ECMWF AND CANADIAN. FARTHER WEST IDEA
ALSO HAS BEARING ON ONGOING LK EFFECT. GFS DOES NOT SHOW ALL THAT
MUCH RESPONSE FOR THE NORTHEAST FLOW LK EFFECT AS INVERSION HEIGHTS
STAY BLO 5KFT INTO THURSDAY. COULD SEE GFS IDEA SUPPORTING SEEDER
FEEDER ENHANCED SNOW ALONG LK SUPERIOR. LITTLE CHANGE IN
INVERSION/LAKE INSTABILITY...SO WENT FOR SIMILAR LOOK TO LK EFFECT
POPS AS IS IN THE FORECAST FOR MONDAY NIGHT THROUGH TUESDAY NIGHT.
DEPENDING ON THE LOW-LEVEL WINDS...ISOLD SPOTS MAY PICK UP A FEW
MORE INCHES OF LK EFFECT SNOW. EVENTUALLY... LK EFFECT SHOULD BECOME
MORE DISORGANIZED LATER THURSDAY/THURSDAY NIGHT AS SFC-H85 WINDS
SHOW MORE SHEAR AND ARE NOT AGREED UPON WELL BY ECMWF OR GFS. WILL
CONTINUE PREVIOUS SHIFTS IDEA OF TRENDING DOWN THE LK EFFECT BY
THURSDAY.
FRIDAY THROUGH NEXT WEEKEND...RECENT RUNS OF ECMWF HAD BEEN
INDICATING PHASING OF SOUTHERN BRANCH AND NORTHERN BRANCH WAVES
HELPING TO PUSH SFC LOW INTO CNTRL GREAT LAKES FOR SATURDAY WITH
SYNOPTIC SNOW OVER UPR MICHIGAN. 00Z ECMWF WAS SLIGHTLY FARTHER
SOUTH WITH MID-LEVEL/SFC LOWS AND SLOWER WITH ARRIVAL OF SNOW. 12Z
ECMWF CONTINUES THAT TREND AND NOW LOOKS MORE LIKE OTHER GUIDANCE
INCLUDING GFS/GEM/ECMWF ENSEMBLES BY SHOWING LESS PHASING AND A MORE
SUPRESSED SFC LOW MOVING FROM SOUTHERN PLAINS ACROSS OHIO VALLEY
FRIDAY AND TOWARD EAST COAST ON SATURDAY. SHORTWAVE TROUGH THAT WILL
BE RESPONSIBLE FOR THIS SYSTEM IS STILL OVER PACIFIC SOUTH OF THE
ALLUTIAN ISLANDS...SO OBVIOUSLY PLENTY OF TIME FOR CHANGES TO OCCUR.
LOW CHANCE CONSENSUS POPS WORK FOR NOW GIVEN THE UNCERTAINTY WITH
THE SYSTEM AND POSSIBLE LK EFFECT ALONG LK SUPERIOR.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1239 PM EST SUN DEC 23 2012
EXPECT LAKE EFFECT CLOUDS/FLURRIES TO PERSIST WITH MVFR CIGS AND VFR
VSBY INTO THIS AFTERNOON. WITH A STRONG INVERSION OVER THE AREA...THE
CLOUDS AND MVFR CIG WILL PERSIST TONIGHT INTO MONDAY.
HOWEVER...THERE MAY BE A PERIOD LATE THIS AFTERNOON AND EVENING WITH
VFR CONDITIONS AT SAW AND IWD AS DRIER MOVES IN AND WINDS BACK
SLIGHTLY. THERE WAS STILL ENOUGH UNCERTAINTY SO THAT NO CHANGE WAS
MADE TO PREVAILING MVFR FCST. A SHORTWAVE TROUGH MOVING TOWARD THE
REGION MONDAY WILL BRING THE POTENTIAL FOR MORE WIDESPREAD SNOW WITH
MVFR VISIBILITIES IN LIGHT SNOW.
&&
.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 350 PM EST SUN DEC 23 2012
A TIGHT PRES GRADIENT BTWN A RIDGE INTO THE UPPER MS VALLEY AND LOW
PRESSURE OVER HUDSON BAY RESULTING NORTHWEST WINDS TO 30 KNOTS OVER
EASTERN LAKE SUPERIOR WILL WEAKEN THIS EVENING ALLOWING WINDS TO
DIMINISH. A HIGH PRESSURE RIDGE FROM THE CANADIAN PRAIRIES WILL
BUILD INTO THE UPPER GREAT LAKES FROM TONIGHT INTO THE MIDDLE OF
NEXT WEEK...KEEPING WINDS AT OR BELOW 25 KNOTS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...JLB
LONG TERM...JLA
AVIATION...JLB
MARINE...JLB
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1240 PM EST SUN DEC 23 2012
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 520 AM EST SUN DEC 23 2012
WV IMAGERY AND RUC ANALYSIS REVEAL THE SHORTWAVE WHICH MOVED ACROSS
LAKE SUPERIOR LAST EVENING AND PUSHED A COLD FRONT SOUTH OF THE
AREA. A NW FLOW OF 850 MB TEMPS AROUND -15C ASSOC WITH THIS
SHORTWAVE/FRONTAL SYSTEM HAS HELPED GENERATE SOME LIGHT LES BANDS
OVER NCNTRL COUNTIES EARLY THIS MORNING.
LES SHOULD DIMINISH FROM WEST TO EAST BY MIDDAY TODAY AS HIGH PRES
FROM NW OF LAKE SUPERIOR BUILDS INTO THE REGION AND INVERSION HGTS
LOWER TO AROUND 3K FT UNDER INCREASINGLY ANTICYCLONIC/DIVERGENT LOW
LEVEL FLOW.
DEVELOPING LAND BREEZES TONIGHT COULD PROVIDE FOCUS FOR LES BANDS
OVER SHORELINE AREAS EAST OF MUNISING IN WNW FLOW...BUT WL ONLY
MAINTAIN SLIGHT CHC POPS GIVEN MARGINAL INSTABILITY WITH LAKE
DELTA-T 13-14C AND DRY LOW-LVL AIR BLO LOW INVERSION HGTS OF 4KFT.
EXPECT INCREASING CLOUDS LATE TONIGHT FROM THE WEST AS WELL-DEFINED
SHORTWAVE APPROACHES FROM THE NRN PLAINS. MODEL SNDGS SHOW TOP-DOWN
MOISTENING DUE TO INCREASING Q-VECT CONV AND ISENTROPIC ASCENT WHICH
COULD GENERATE SOME FLURRIES OR LIGHT SNOW OVER FAR WEST LATE
TONIGHT.
.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 520 AM EST SUN DEC 23 2012
A GENERALLY QUIET LONG TERM PERIOD...WITH WITH NO SIGNIFICANT
SYSTEMS POISED TO AFFECT UPPER MICHIGAN.
ON MONDAY...A SHORTWAVE WILL BE SLIDING SOUTHEAST FROM MINNESOTA
AND THROUGH WISCONSIN AND EVENTUALLY LOWER MICHIGAN. THE BEST
FORCING AND HEIGHT FALLS FROM THIS SYSTEM LOOK TO STAY TO THE SOUTH
OF THE AREA...BUT DECENT HEIGHT FALLS AND H700-300 Q-VECTOR
CONVERGENCE MOVE ACROSS THE SOUTHERN HALF OF UPPER MICHIGAN TO
SUPPORT SOME SNOW SHOWERS. THERE IS A POCKET OF DRY H900-800 AIR TO
OVERCOME TO START ON MONDAY MORNING...WHICH IS ENOUGH TO KEEP
FROM GOING LIKELY WITH POPS. OVER THE NORTH...MODELS NOT INDICATING
THAT BECOMING MOIST...SO DON/T THINK THE NORTH HALF WOULD HAVE MUCH
SYNOPTIC CHANCES ALTHOUGH THERE COULD BE LIGHT LAKE EFFECT WITH
COLDER H850 TEMPS SPILLING IN DURING THE AFTERNOON HOURS. FAVORABLE
COND PRES DEF ON 275-295K SURFACES AND H800-700 FGEN STREAM RIGHT
ALONG THE WISCONSIN AND UPPER MICHIGAN BORDER...SO WOULD EXPECT AN
WEST-EAST BAND OF SNOW SHOWERS RUNNING ALONG THAT LOCATION ON
MONDAY. DID BUMP POPS UP 10-20 PERCENT WITH THE BETTER MODEL
SIGNALS AND EXPECT AROUND AN INCH OF SNOW NEAR THE WI BORDER.
BEHIND THE SYNOPTIC SYSTEM...UPPER LOW SPINNING IN NORTHERN ONTARIO
WILL THROW A COUPLE OF WEAK SHORTWAVES ACROSS LAKE SUPERIOR THROUGH
WEDNESDAY. WITH GENERALLY NORTHWEST TO NORTHERLY FLOW AND H850
TEMPS AROUND -14C DURING THIS PERIOD...EXPECT LAKE EFFECT TO BE THE
NORM. IN ADDITION...WITH THE INVERSION SETTING UP OVER MUCH OF THE
CWA...ANY CLOUDS THAT BECOME TRAPPED BELOW THE INVERSION WILL
LIKELY STAY IN PLACE. THUS...WILL GO WITH MORE OF A PESSIMISTIC
CLOUD FORECAST FOR MONDAY NIGHT INTO TUESDAY NIGHT. DON/T EXPECT
ANY SIGNIFICANT LAKE EFFECT SNOW DURING THIS PERIOD...JUST A
PERSISTENT DUSTING TO AN INCH OR TWO EVERY 12 HOURS.
THEN ON WEDNESDAY...A LOW THAT DEPARTED TEXAS ON TUESDAY WILL SHIFT
NORTHEAST THROUGH THE OHIO RIVER VALLEY AND INTO THE MID ATLANTIC
STATES. AT THIS POINT...IT SHOULD STAY FAR ENOUGH THE SOUTHEAST TO
ONLY BRUSH THE FAR SOUTHEAST CWA WITH HIGH CLOUDS. BUT THE LOW
LEVEL RESPONSE IN THE WIND FIELDS WILL FOCUS THE LAKE EFFECT TO
MORE NORTHEAST WIND FAVORED LOCATIONS. AS HAS BEEN THE CASE FOR
MOST OF THE LONG TERM PERIOD...INVERSION HEIGHTS OF 4-5KFT SHOULD
LIMIT THE INTENSITY OF THE LAKE EFFECT SNOW SHOWERS EVEN THOUGH
DELTA-T VALUES ARE AROUND 18 AND LAKE INDUCED CAPSE ARE AROUND
200-300 J/KG.
UNCERTAINTY GROWS QUICKLY AFTER WEDNESDAY NIGHT...AS MODELS HAVE
HIGH PRESSURE RIDGE FROM HIGH IN ONTARIO MOVE OVER THE AREA FOR
THURSDAY AND THURSDAY NIGHT AND THEN A POTENTIAL SYSTEM DEVELOPING
IN THE CENTRAL PLAINS AND MOVING THROUGH THE GREAT LAKES. THIS
ENTIRE PERIOD LARGELY DEPENDS ON WHETHER THE LOW DEVELOPS OVER THE
CENTRAL PLAINS...AS THAT CONTROLS THE LOW/MID LEVEL WIND FIELDS
CONTROLLING LAKE EFFECT POTENTIAL ON THURSDAY AND THEN SNOW ON
FRIDAY/SATURDAY. GIVEN THE CONSISTENCY IN THE ECMWF OVER THE LAST 4
RUNS AND IT/S SUPERIOR LONG RANGE VERIFICATION/PERFORMANCE...HARD
TO ARGUE AGAINST THE IDEA OF A LOW MOVING THROUGH THE GREAT LAKES.
MEANWHILE...00Z GFS AND 00Z GEM ENSEMBLE MEAN SHOW THE SIMILAR UPPER
TROUGH BUT KEEP THE SURFACE FEATURE AS AN ELONGATED TROUGH
STRETCHING FROM THE GREAT LAKES THROUGH THE OHIO RIVER VALLEY. AT
LEAST BOTH IDEAS HAVE THE POTENTIAL FOR SOME SNOWFALL...SO WILL
CONTINUE TO MENTION CHANCE POPS FOR FRIDAY NIGHT AND INTO SATURDAY.
BEFORE THAT...THE DIFFERING WIND FIELDS AND GENERALLY LIGHT/VARIABLE
LOW LEVEL WINDS WOULD SUGGEST LIMITED CONFIDENCE LAKE EFFECT AND
WILL DIMINISH CHANCES THURSDAY INTO FRIDAY AS WINDS LIKELY TURN TO
THE SOUTH.
AS FOR TEMPS DURING THE PERIOD...LOOKS TO BE VERY SEASONABLE AFTER
THE FIFTH WARMEST DECEMBER 1ST-22ND AT NWS MARQUETTE. SHOULD SEE
HIGHS MOST DAYS BETWEEN THE UPPER TEENS AND MIDDLE 20S.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1239 PM EST SUN DEC 23 2012
EXPECT LAKE EFFECT CLOUDS/FLURRIES TO PERSIST WITH MVFR CIGS AND VFR
VSBY INTO THIS AFTERNOON. WITH A STRONG INVERSION OVER THE AREA...THE
CLOUDS AND MVFR CIG WILL PERSIST TONIGHT INTO MONDAY.
HOWEVER...THERE MAY BE A PERIOD LATE THIS AFTERNOON AND EVENING WITH
VFR CONDITIONS AT SAW AND IWD AS DRIER MOVES IN AND WINDS BACK
SLIGHTLY. THERE WAS STILL ENOUGH UNCERTAINTY SO THAT NO CHANGE WAS
MADE TO PREVAILING MVFR FCST. A SHORTWAVE TROUGH MOVING TOWARD THE
REGION MONDAY WILL BRING THE POTENTIAL FOR MORE WIDESPREAD SNOW WITH
MVFR VISIBILITIES IN LIGHT SNOW.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 520 AM EST SUN DEC 23 2012
NORTHWEST WINDS UP TO 30 KNOTS ARE EXPECTED TODAY OVER NCNTRL AND
ERN LAKE SUPERIOR IN THE WAKE OF A COLD FRONT. A FEW GALE GUSTS TO
35 ARE POSSIBLE EARLY THIS MORNING. A HIGH PRESSURE RIDGE FROM THE
CANADIAN PRAIRIES WILL THEN BUILD INTO THE UPPER GREAT LAKES FROM
TONIGHT INTO THE MIDDLE OF NEXT WEEK...KEEPING WINDS AT OR BELOW
25 KNOTS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...VOSS
LONG TERM...SRF
AVIATION...JLB
MARINE...VOSS
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
642 AM EST SUN DEC 23 2012
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 520 AM EST SUN DEC 23 2012
WV IMAGERY AND RUC ANALYSIS REVEAL THE SHORTWAVE WHICH MOVED ACROSS
LAKE SUPERIOR LAST EVENING AND PUSHED A COLD FRONT SOUTH OF THE
AREA. A NW FLOW OF 850 MB TEMPS AROUND -15C ASSOC WITH THIS
SHORTWAVE/FRONTAL SYSTEM HAS HELPED GENERATE SOME LIGHT LES BANDS
OVER NCNTRL COUNTIES EARLY THIS MORNING.
LES SHOULD DIMINISH FROM WEST TO EAST BY MIDDAY TODAY AS HIGH PRES
FROM NW OF LAKE SUPERIOR BUILDS INTO THE REGION AND INVERSION HGTS
LOWER TO AROUND 3K FT UNDER INCREASINGLY ANTICYCLONIC/DIVERGENT LOW
LEVEL FLOW.
DEVELOPING LAND BREEZES TONIGHT COULD PROVIDE FOCUS FOR LES BANDS
OVER SHORELINE AREAS EAST OF MUNISING IN WNW FLOW...BUT WL ONLY
MAINTAIN SLIGHT CHC POPS GIVEN MARGINAL INSTABILITY WITH LAKE
DELTA-T 13-14C AND DRY LOW-LVL AIR BLO LOW INVERSION HGTS OF 4KFT.
EXPECT INCREASING CLOUDS LATE TONIGHT FROM THE WEST AS WELL-DEFINED
SHORTWAVE APPROACHES FROM THE NRN PLAINS. MODEL SNDGS SHOW TOP-DOWN
MOISTENING DUE TO INCREASING Q-VECT CONV AND ISENTROPIC ASCENT WHICH
COULD GENERATE SOME FLURRIES OR LIGHT SNOW OVER FAR WEST LATE
TONIGHT.
.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 520 AM EST SUN DEC 23 2012
A GENERALLY QUIET LONG TERM PERIOD...WITH WITH NO SIGNIFICANT
SYSTEMS POISED TO AFFECT UPPER MICHIGAN.
ON MONDAY...A SHORTWAVE WILL BE SLIDING SOUTHEAST FROM MINNESOTA
AND THROUGH WISCONSIN AND EVENTUALLY LOWER MICHIGAN. THE BEST
FORCING AND HEIGHT FALLS FROM THIS SYSTEM LOOK TO STAY TO THE SOUTH
OF THE AREA...BUT DECENT HEIGHT FALLS AND H700-300 Q-VECTOR
CONVERGENCE MOVE ACROSS THE SOUTHERN HALF OF UPPER MICHIGAN TO
SUPPORT SOME SNOW SHOWERS. THERE IS A POCKET OF DRY H900-800 AIR TO
OVERCOME TO START ON MONDAY MORNING...WHICH IS ENOUGH TO KEEP
FROM GOING LIKELY WITH POPS. OVER THE NORTH...MODELS NOT INDICATING
THAT BECOMING MOIST...SO DON/T THINK THE NORTH HALF WOULD HAVE MUCH
SYNOPTIC CHANCES ALTHOUGH THERE COULD BE LIGHT LAKE EFFECT WITH
COLDER H850 TEMPS SPILLING IN DURING THE AFTERNOON HOURS. FAVORABLE
COND PRES DEF ON 275-295K SURFACES AND H800-700 FGEN STREAM RIGHT
ALONG THE WISCONSIN AND UPPER MICHIGAN BORDER...SO WOULD EXPECT AN
WEST-EAST BAND OF SNOW SHOWERS RUNNING ALONG THAT LOCATION ON
MONDAY. DID BUMP POPS UP 10-20 PERCENT WITH THE BETTER MODEL
SIGNALS AND EXPECT AROUND AN INCH OF SNOW NEAR THE WI BORDER.
BEHIND THE SYNOPTIC SYSTEM...UPPER LOW SPINNING IN NORTHERN ONTARIO
WILL THROW A COUPLE OF WEAK SHORTWAVES ACROSS LAKE SUPERIOR THROUGH
WEDNESDAY. WITH GENERALLY NORTHWEST TO NORTHERLY FLOW AND H850
TEMPS AROUND -14C DURING THIS PERIOD...EXPECT LAKE EFFECT TO BE THE
NORM. IN ADDITION...WITH THE INVERSION SETTING UP OVER MUCH OF THE
CWA...ANY CLOUDS THAT BECOME TRAPPED BELOW THE INVERSION WILL
LIKELY STAY IN PLACE. THUS...WILL GO WITH MORE OF A PESSIMISTIC
CLOUD FORECAST FOR MONDAY NIGHT INTO TUESDAY NIGHT. DON/T EXPECT
ANY SIGNIFICANT LAKE EFFECT SNOW DURING THIS PERIOD...JUST A
PERSISTENT DUSTING TO AN INCH OR TWO EVERY 12 HOURS.
THEN ON WEDNESDAY...A LOW THAT DEPARTED TEXAS ON TUESDAY WILL SHIFT
NORTHEAST THROUGH THE OHIO RIVER VALLEY AND INTO THE MID ATLANTIC
STATES. AT THIS POINT...IT SHOULD STAY FAR ENOUGH THE SOUTHEAST TO
ONLY BRUSH THE FAR SOUTHEAST CWA WITH HIGH CLOUDS. BUT THE LOW
LEVEL RESPONSE IN THE WIND FIELDS WILL FOCUS THE LAKE EFFECT TO
MORE NORTHEAST WIND FAVORED LOCATIONS. AS HAS BEEN THE CASE FOR
MOST OF THE LONG TERM PERIOD...INVERSION HEIGHTS OF 4-5KFT SHOULD
LIMIT THE INTENSITY OF THE LAKE EFFECT SNOW SHOWERS EVEN THOUGH
DELTA-T VALUES ARE AROUND 18 AND LAKE INDUCED CAPSE ARE AROUND
200-300 J/KG.
UNCERTAINTY GROWS QUICKLY AFTER WEDNESDAY NIGHT...AS MODELS HAVE
HIGH PRESSURE RIDGE FROM HIGH IN ONTARIO MOVE OVER THE AREA FOR
THURSDAY AND THURSDAY NIGHT AND THEN A POTENTIAL SYSTEM DEVELOPING
IN THE CENTRAL PLAINS AND MOVING THROUGH THE GREAT LAKES. THIS
ENTIRE PERIOD LARGELY DEPENDS ON WHETHER THE LOW DEVELOPS OVER THE
CENTRAL PLAINS...AS THAT CONTROLS THE LOW/MID LEVEL WIND FIELDS
CONTROLLING LAKE EFFECT POTENTIAL ON THURSDAY AND THEN SNOW ON
FRIDAY/SATURDAY. GIVEN THE CONSISTENCY IN THE ECMWF OVER THE LAST 4
RUNS AND IT/S SUPERIOR LONG RANGE VERIFICATION/PERFORMANCE...HARD
TO ARGUE AGAINST THE IDEA OF A LOW MOVING THROUGH THE GREAT LAKES.
MEANWHILE...00Z GFS AND 00Z GEM ENSEMBLE MEAN SHOW THE SIMILAR UPPER
TROUGH BUT KEEP THE SURFACE FEATURE AS AN ELONGATED TROUGH
STRETCHING FROM THE GREAT LAKES THROUGH THE OHIO RIVER VALLEY. AT
LEAST BOTH IDEAS HAVE THE POTENTIAL FOR SOME SNOWFALL...SO WILL
CONTINUE TO MENTION CHANCE POPS FOR FRIDAY NIGHT AND INTO SATURDAY.
BEFORE THAT...THE DIFFERING WIND FIELDS AND GENERALLY LIGHT/VARIABLE
LOW LEVEL WINDS WOULD SUGGEST LIMITED CONFIDENCE LAKE EFFECT AND
WILL DIMINISH CHANCES THURSDAY INTO FRIDAY AS WINDS LIKELY TURN TO
THE SOUTH.
AS FOR TEMPS DURING THE PERIOD...LOOKS TO BE VERY SEASONABLE AFTER
THE FIFTH WARMEST DECEMBER 1ST-22ND AT NWS MARQUETTE. SHOULD SEE
HIGHS MOST DAYS BETWEEN THE UPPER TEENS AND MIDDLE 20S.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 641 AM EST SUN DEC 23 2012
KIWD AND KCMX...MVFR CEILINGS AND OCCASIONAL FLURRIES WILL LIKELY
CONTINUE THROUGH FCST PD IN A NW FLOW.
KSAW...EXPECT MVFR CIGS/LES FLURRIES TO LIFT BY EARLY AFTERNOON AS
FLOW BACKS FROM NNW TO NW. LOOK FOR VFR CONDITIONS TO CONTINUE FROM
THIS AFTERNOON THROUGH TONIGHT UNDER NW TO WNW FLOW. MID LVL CLOUDS
WILL MOVE IN THIS EVENING AND LOWER THROUGH THE NIGHT AS NEXT SYSTEM
APPROACHES FROM THE NRN PLAINS.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 520 AM EST SUN DEC 23 2012
NORTHWEST WINDS UP TO 30 KNOTS ARE EXPECTED TODAY OVER NCNTRL AND
ERN LAKE SUPERIOR IN THE WAKE OF A COLD FRONT. A FEW GALE GUSTS TO
35 ARE POSSIBLE EARLY THIS MORNING. A HIGH PRESSURE RIDGE FROM THE
CANADIAN PRAIRIES WILL THEN BUILD INTO THE UPPER GREAT LAKES FROM
TONIGHT INTO THE MIDDLE OF NEXT WEEK...KEEPING WINDS AT OR BELOW
25 KNOTS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...VOSS
LONG TERM...SRF
AVIATION...VOSS
MARINE...VOSS
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
521 AM EST SUN DEC 23 2012
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 520 AM EST SUN DEC 23 2012
WV IMAGERY AND RUC ANALYSIS REVEAL THE SHORTWAVE WHICH MOVED ACROSS
LAKE SUPERIOR LAST EVENING AND PUSHED A COLD FRONT SOUTH OF THE
AREA. A NW FLOW OF 850 MB TEMPS AROUND -15C ASSOC WITH THIS
SHORTWAVE/FRONTAL SYSTEM HAS HELPED GENERATE SOME LIGHT LES BANDS
OVER NCNTRL COUNTIES EARLY THIS MORNING.
LES SHOULD DIMINISH FROM WEST TO EAST BY MIDDAY TODAY AS HIGH PRES
FROM NW OF LAKE SUPERIOR BUILDS INTO THE REGION AND INVERSION HGTS
LOWER TO AROUND 3K FT UNDER INCREASINGLY ANTICYCLONIC/DIVERGENT LOW
LEVEL FLOW.
DEVELOPING LAND BREEZES TONIGHT COULD PROVIDE FOCUS FOR LES BANDS
OVER SHORELINE AREAS EAST OF MUNISING IN WNW FLOW...BUT WL ONLY
MAINTAIN SLIGHT CHC POPS GIVEN MARGINAL INSTABILITY WITH LAKE
DELTA-T 13-14C AND DRY LOW-LVL AIR BLO LOW INVERSION HGTS OF 4KFT.
EXPECT INCREASING CLOUDS LATE TONIGHT FROM THE WEST AS WELL-DEFINED
SHORTWAVE APPROACHES FROM THE NRN PLAINS. MODEL SNDGS SHOW TOP-DOWN
MOISTENING DUE TO INCREASING Q-VECT CONV AND ISENTROPIC ASCENT WHICH
COULD GENERATE SOME FLURRIES OR LIGHT SNOW OVER FAR WEST LATE
TONIGHT.
.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 520 AM EST SUN DEC 23 2012
A GENERALLY QUIET LONG TERM PERIOD...WITH WITH NO SIGNIFICANT
SYSTEMS POISED TO AFFECT UPPER MICHIGAN.
ON MONDAY...A SHORTWAVE WILL BE SLIDING SOUTHEAST FROM MINNESOTA
AND THROUGH WISCONSIN AND EVENTUALLY LOWER MICHIGAN. THE BEST
FORCING AND HEIGHT FALLS FROM THIS SYSTEM LOOK TO STAY TO THE SOUTH
OF THE AREA...BUT DECENT HEIGHT FALLS AND H700-300 Q-VECTOR
CONVERGENCE MOVE ACROSS THE SOUTHERN HALF OF UPPER MICHIGAN TO
SUPPORT SOME SNOW SHOWERS. THERE IS A POCKET OF DRY H900-800 AIR TO
OVERCOME TO START ON MONDAY MORNING...WHICH IS ENOUGH TO KEEP
FROM GOING LIKELY WITH POPS. OVER THE NORTH...MODELS NOT INDICATING
THAT BECOMING MOIST...SO DON/T THINK THE NORTH HALF WOULD HAVE MUCH
SYNOPTIC CHANCES ALTHOUGH THERE COULD BE LIGHT LAKE EFFECT WITH
COLDER H850 TEMPS SPILLING IN DURING THE AFTERNOON HOURS. FAVORABLE
COND PRES DEF ON 275-295K SURFACES AND H800-700 FGEN STREAM RIGHT
ALONG THE WISCONSIN AND UPPER MICHIGAN BORDER...SO WOULD EXPECT AN
WEST-EAST BAND OF SNOW SHOWERS RUNNING ALONG THAT LOCATION ON
MONDAY. DID BUMP POPS UP 10-20 PERCENT WITH THE BETTER MODEL
SIGNALS AND EXPECT AROUND AN INCH OF SNOW NEAR THE WI BORDER.
BEHIND THE SYNOPTIC SYSTEM...UPPER LOW SPINNING IN NORTHERN ONTARIO
WILL THROW A COUPLE OF WEAK SHORTWAVES ACROSS LAKE SUPERIOR THROUGH
WEDNESDAY. WITH GENERALLY NORTHWEST TO NORTHERLY FLOW AND H850
TEMPS AROUND -14C DURING THIS PERIOD...EXPECT LAKE EFFECT TO BE THE
NORM. IN ADDITION...WITH THE INVERSION SETTING UP OVER MUCH OF THE
CWA...ANY CLOUDS THAT BECOME TRAPPED BELOW THE INVERSION WILL
LIKELY STAY IN PLACE. THUS...WILL GO WITH MORE OF A PESSIMISTIC
CLOUD FORECAST FOR MONDAY NIGHT INTO TUESDAY NIGHT. DON/T EXPECT
ANY SIGNIFICANT LAKE EFFECT SNOW DURING THIS PERIOD...JUST A
PERSISTENT DUSTING TO AN INCH OR TWO EVERY 12 HOURS.
THEN ON WEDNESDAY...A LOW THAT DEPARTED TEXAS ON TUESDAY WILL SHIFT
NORTHEAST THROUGH THE OHIO RIVER VALLEY AND INTO THE MID ATLANTIC
STATES. AT THIS POINT...IT SHOULD STAY FAR ENOUGH THE SOUTHEAST TO
ONLY BRUSH THE FAR SOUTHEAST CWA WITH HIGH CLOUDS. BUT THE LOW
LEVEL RESPONSE IN THE WIND FIELDS WILL FOCUS THE LAKE EFFECT TO
MORE NORTHEAST WIND FAVORED LOCATIONS. AS HAS BEEN THE CASE FOR
MOST OF THE LONG TERM PERIOD...INVERSION HEIGHTS OF 4-5KFT SHOULD
LIMIT THE INTENSITY OF THE LAKE EFFECT SNOW SHOWERS EVEN THOUGH
DELTA-T VALUES ARE AROUND 18 AND LAKE INDUCED CAPSE ARE AROUND
200-300 J/KG.
UNCERTAINTY GROWS QUICKLY AFTER WEDNESDAY NIGHT...AS MODELS HAVE
HIGH PRESSURE RIDGE FROM HIGH IN ONTARIO MOVE OVER THE AREA FOR
THURSDAY AND THURSDAY NIGHT AND THEN A POTENTIAL SYSTEM DEVELOPING
IN THE CENTRAL PLAINS AND MOVING THROUGH THE GREAT LAKES. THIS
ENTIRE PERIOD LARGELY DEPENDS ON WHETHER THE LOW DEVELOPS OVER THE
CENTRAL PLAINS...AS THAT CONTROLS THE LOW/MID LEVEL WIND FIELDS
CONTROLLING LAKE EFFECT POTENTIAL ON THURSDAY AND THEN SNOW ON
FRIDAY/SATURDAY. GIVEN THE CONSISTENCY IN THE ECMWF OVER THE LAST 4
RUNS AND IT/S SUPERIOR LONG RANGE VERIFICATION/PERFORMANCE...HARD
TO ARGUE AGAINST THE IDEA OF A LOW MOVING THROUGH THE GREAT LAKES.
MEANWHILE...00Z GFS AND 00Z GEM ENSEMBLE MEAN SHOW THE SIMILAR UPPER
TROUGH BUT KEEP THE SURFACE FEATURE AS AN ELONGATED TROUGH
STRETCHING FROM THE GREAT LAKES THROUGH THE OHIO RIVER VALLEY. AT
LEAST BOTH IDEAS HAVE THE POTENTIAL FOR SOME SNOWFALL...SO WILL
CONTINUE TO MENTION CHANCE POPS FOR FRIDAY NIGHT AND INTO SATURDAY.
BEFORE THAT...THE DIFFERING WIND FIELDS AND GENERALLY LIGHT/VARIABLE
LOW LEVEL WINDS WOULD SUGGEST LIMITED CONFIDENCE LAKE EFFECT AND
WILL DIMINISH CHANCES THURSDAY INTO FRIDAY AS WINDS LIKELY TURN TO
THE SOUTH.
AS FOR TEMPS DURING THE PERIOD...LOOKS TO BE VERY SEASONABLE AFTER
THE FIFTH WARMEST DECEMBER 1ST-22ND AT NWS MARQUETTE. SHOULD SEE
HIGHS MOST DAYS BETWEEN THE UPPER TEENS AND MIDDLE 20S.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY MORNING) ISSUED AT
444 AM EST SUN DEC 23 2012
A COLD FRONT WILL CONTINUE TO MOVE THROUGH THE AREA OVERNIGHT WITH
NORTHWEST WINDS CONTINUING. MVFR CEILINGS AND LAKE EFFECT SNOW WILL
CONTINUE AT KCMX/KIWD. WITH A NORTHWEST UPSLOPE WIND...CIGS WILL
TEMPORARILY BE IFR AT KIWD. NOT OVERLY CONFIDENT ON AMOUNT OF
VISIBILITY RESTRICTIONS AND OPTED TO MENTION HIGH END MVFR AT THIS
POINT. EVEN THOUGH KSAW IS LESS LIKELY TO SEE LAKE EFFECT SNOW WITH
THE GENERALLY NORTHWEST WINDS...CIGS INTO THE MVFR RANGE ARE STILL
EXPECTED. PERSISTENCE LOOKS TO BE THE WAY TO GO WITH THIS FORECAST
AND ONCE THE MVFR CIGS SET IN...THEY WILL STAY THROUGH THE END OF
THE FORECAST PERIOD EXCEPT AT SAW WHERE A WEST WIND WILL CLEAR THEM
BACK OUT BY LATE SUN AFTERNOON.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 520 AM EST SUN DEC 23 2012
NORTHWEST WINDS UP TO 30 KNOTS ARE EXPECTED TODAY OVER NCNTRL AND
ERN LAKE SUPERIOR IN THE WAKE OF A COLD FRONT. A FEW GALE GUSTS TO
35 ARE POSSIBLE EARLY THIS MORNING. A HIGH PRESSURE RIDGE FROM THE
CANADIAN PRAIRIES WILL THEN BUILD INTO THE UPPER GREAT LAKES FROM
TONIGHT INTO THE MIDDLE OF NEXT WEEK...KEEPING WINDS AT OR BELOW
25 KNOTS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...VOSS
LONG TERM...SRF
AVIATION...07
MARINE...VOSS
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
445 AM EST SUN DEC 23 2012
.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 341 PM EST SAT DEC 22 2012
WV IMAGERY AND RUC ANALYSIS INDICATED NW MID/UPPER LEVEL FLOW
BETWEEN A TROUGH OVER JAMES BAY INTO QUEBEC AND A RIDGE OVER THE
WESTERN PLAINS. A SHORTWAVE TROUGH WAS LOCATED OVER NW ONTARIO
BETWEEN LAKE WINNIPEG AND THUNDER BAY ONTARIO. THE SHRTWV AND AN
ASSOCIATED COLD FRONT INTO NRN MN SUPPORTED SOME LIGHT SNOW OR
FLURRIES INTO FAR NRN WITH VISIBILITIES GENERALLY AT OR ABOVE 5SM.
VIS SATELLITE LOOP SHOWED MAINLY JUST MID CLOUDS SPREADING ACROSS
UPPER MI ASSOCIATED WITH 285K-295K ISENTROPIC LIFT AHEAD OF THE
TROUGH.
AS THE SHRTWV DIVES TO THE ESE AND PULLS THE COLD FRONT THROUGH
UPPER MI...WINDS WILL VEER FROM W TO NNW. 925-850 MB MOISTURE WILL
ALSO QUICKLY INCREASE ACROSS THE AREA. DESPITE THE RELATIVELY
SHALLOW COLD AIR MASS WITH INVERSION HEIGHTS OF ONLY 4K-5K
FT...EXPECT LES TO INCREASE THIS EVENING AND PEAK LATE TONIGHT AND
EARLY SUNDAY. LAKE INDUCED CAPES BUILD INTO THE 200-300 J/KG RANGE
BUT THE CLOUD LAYER REMAINS MAINLY BELOW THE DGZ. SO...ONLY INCLUDED
SCT/CHANCE POPS WITH ANY ACCUMULATIONS AT OR BELOW A HALF INCH.
LES SHOULD DIMINISH FROM WEST TO EAST BY MIDDAY INTO SUNDAY
AFTERNOON AS HIGH PRES BUILDS INTO THE REGION WITH LOWERING
INVERSION HEIGHTS TO AROUND 3K FT AND INCREASINGLY
ANTICYCLONIC/DIVERGENT LOW LEVEL FLOW.
.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 341 PM EST SAT DEC 22 2012
SPLIT FLOW IN PLACE TO START THE LONG TERM. SUBTROPICAL H2 JET IS
ALONG SOUTHERN TIER OF CONUS WHILE NORTHERN STREAM H4-H3 JET RIDES
ACROSS CANADA WITH BROAD UPPER LOW FM HUDSON BAY ACROSS QUEBEC. CORE
OF LOW-LEVEL COLD AIR BENEATH THAT LOW...BUT DEVELOPING NW WINDS IN
WAKE OF FRONT THAT PASSES ACROSS TONIGHT...RESULTS IN ENOUGH OVER
WATER INSTABILITY WITH LAKE-900MB DELTA T/S AOA 15C FOR LK EFFECT SNOW
SHOWERS. AS MENTIONED IN THE SHORT TERM DISCUSSION...INVERSIONS LESS
THAN 5KFT RESULTING FM LARGE SCALE RISING HEIGHTS/SUBSIDENCE AND
ANTICYCLONIC FLOW WILL BE LIMITING FACTORS FOR ANYTHING OTHER THAN
LIGHT SNOW ACCUMS...MAINLY UNDER 1 INCH.
LATER SUNDAY NIGHT AND INTO MONDAY COUPLE OF SHORTWAVES EMERGE
ACROSS MIDDLE CONUS...ONE DIGGING FROM WYOMING TO NORTHERN ILLINOIS
AND THE OTHER SLIDING FROM OK/TX PANHANDLE TO TENNESSEE. OVERALL
MODELS HAVE TRENDED STRONGER WITH NORTHERN WAVE. GFS/NAM/UKMET
STRONGER WITH NORTHERN ONE INITIALLY BUT LAST COUPLE RUNS OF ECMWF
ALSO SHOW SOME IMPACT FOR UPR MICHIGAN ON CHRISTMAS EVE DAY. HAVE
LOW CHANCE POPS EVERYWHERE DUE TO SYSTEM SNOW AND/OR LK EFFECT.
IF TRENDS CONTINUE...POPS MAY NEED INCREASING FOR HIGH POP/LOW QPF
SETUP. MOISTURE IS LIMITED WITH NORTHERN END OF SYSTEM SO ANY SNOW
AMOUNTS WILL BE LESS THAN AN INCH. LK EFFECT AREAS MAY SEE A BIT
MORE SNOW DUE TO WEAK LAKE ENHANCEMENT...THOUGH GFS/NAM SOUNDINGS
REALLY DO NOT SHOW MUCH LAKE RESPONSE FROM THE SYSTEM IN TERMS OF A
HIGHER INVERSION.
LK EFFECT MAY PICK UP SLIGHTLY IN WAKE OF SYSTEM MOVING THROUGH
ON MONDAY AS ECMWF/GFS/NAM INDICATE H85 TEMPS FALLING TO AROUND -15C
MONDAY NIGHT AND TUESDAY. INVERSIONS REMAIN LOWER THAN 5KFT THOUGH
WHICH WILL LIMIT SNOW ACCUMS TO JUST A FEW INCHES. VERY LITTLE
CHANGES IN LARGE SCALE/MESOSCALE PATTERN THROUGH THURSDAY SO EXPECT
PERSISTENT/STEADY STATE LIGHT LK EFFECT ALONG LK SUPERIOR. LATEST
GFS/ECMWF RUNS IN GOOD AGREEMENT WITH TRACK OF SFC LOW LIFTING FM
TENNESSEE RIVER VALLEY ACROSS THE NORTHEAST CONUS WEDNESDAY INTO
THURSDAY. SYNOPTIC SNOW ON NORTHWEST PERIFERY OF SYSTEM STAYS MAINLY
TO THE EAST OF UPR MICHIGAN. 12Z GFS FARTHER NORTHWEST...GRAZING
EASTERN CWA WITH LGT QPF ON WEDNESDAY. GFS IS AN OUTLIER COMPARED TO
ECMWF/GEM-NHEM AND EVEN PREVIOUS RUNS OF GFS. WILL JUST STICK WITH
SCATTERED POPS FOR NORTH-NORTHWEST FLOW LK EFFECT. NUDGED POPS UP
SOME ALONG LK SUPERIOR OVER THE CONSENSUS WITH EXPECTED LK EFFECT.
NEXT CHANCE OF WIDESPREAD SYNOPTIC SNOW COULD BE FRIDAY NIGHT INTO
NEXT SATURDAY IF ECMWF IS CORRECT. ECMWF REMAINS CONSISTENT SHOWING
ACTIVE SOUTHERN STREAM SENDING ANOTHER UPR TROUGH/SFC LOW OUT OF THE
PLAINS ACROSS THE WESTERN GREAT LAKES. NORTHERN STREAM WAVE DIGGING
INTO THE NORTH SIDE SYSTEM AS WELL. GEM-NHEM SIMILAR THROUGH 12Z
FRIDAY BUT GFS IS STUBBORNLY NOT DEVELOPING THE SYSTEM AS IT IS NOT
AS WRAPPED UP WITH SOUTHERN STREAM WAVE COMPARED TO ECMWF AND IT
ALSO HAS MORE SEPARATION BTWN THE NORTHERN AND SOUTHERN BRANCH
STREAMS THROUGH SATURDAY. GIVEN PAST TRACK RECORD IN DAYS 4-7...A
FEW CONSECUTIVE RUNS OF ECMWF SHOWING SOMETHING IS GOOD ENOUGH TO
INCLUDE IT IN EXTENDED. CONSENSUS POPS WERE NOT TOO BAD BUT DID
INCREASE THEM SLIGHTLY ON SATURDAY SO CHANCE FOR SNOW IS IN THERE
FOR ALL CWA. COLDER AIR BEHIND THE SYSTEM MAY RESULT IN PROLONGED LK
EFFECT EVENT JUST BEYOND DAY 7. CERTAINLY NO THAWS IN STORE FOR LAST
WEEK OF 2012 WITH DAYTIME HIGHS IN THE TEENS/20S AND NIGHTIME LOWS
IN SINGLE DIGITS TO TEENS. RECENTLY DEPOSITED SNOW WILL STAY AROUND
UNTIL FURTHER NOTICE.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY MORNING) ISSUED AT
444 AM EST SUN DEC 23 2012
A COLD FRONT WILL CONTINUE TO MOVE THROUGH THE AREA OVERNIGHT WITH
NORTHWEST WINDS CONTINUING. MVFR CEILINGS AND LAKE EFFECT SNOW WILL
CONTINUE AT KCMX/KIWD. WITH A NORTHWEST UPSLOPE WIND...CIGS WILL
TEMPORARILY BE IFR AT KIWD. NOT OVERLY CONFIDENT ON AMOUNT OF
VISIBILITY RESTRICTIONS AND OPTED TO MENTION HIGH END MVFR AT THIS
POINT. EVEN THOUGH KSAW IS LESS LIKELY TO SEE LAKE EFFECT SNOW WITH
THE GENERALLY NORTHWEST WINDS...CIGS INTO THE MVFR RANGE ARE STILL
EXPECTED. PERSISTENCE LOOKS TO BE THE WAY TO GO WITH THIS FORECAST
AND ONCE THE MVFR CIGS SET IN...THEY WILL STAY THROUGH THE END OF
THE FORECAST PERIOD EXCEPT AT SAW WHERE A WEST WIND WILL CLEAR THEM
BACK OUT BY LATE SUN AFTERNOON.
&&
.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 341 PM EST SAT DEC 22 2012
WINDS ARE EXPECTED TO INCREASE UP TO 30 KNOTS OUT OF THE NORTHWEST
TONIGHT INTO SUNDAY AS A COLD FRONT SWEEPS SOUTHEAST ACROSS LAKE
SUPERIOR. A HIGH PRESSURE RIDGE FROM THE CANADIAN PRAIRIES WILL THEN
BUILD INTO THE UPPER GREAT LAKES FROM SUNDAY NIGHT INTO THE
THE FIRST HALF OF NEXT WEEK...KEEPING WINDS AT OR BELOW 25 KNOTS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...JLB
LONG TERM...JLA
AVIATION...07
MARINE...JLB
AREA FORECAST DISCUSSION
NWS HASTINGS NE
1150 AM CST SUN DEC 23 2012
.AVIATION...18Z TAF. A FEW CIRRUS ARE MOVING THROUGH THE KGRI
TERMINAL AREA WITH JUST A FEW LOWER CLOUDS THAT SHOULD DISSIPATE
EARLY THIS AFTERNOON. LIGHT WINDS WILL BECOME WESTERLY BUT REMAIN
FAIRLY LIGHT.
&&
.PREV DISCUSSION... /ISSUED 428 AM CST SUN DEC 23 2012/
SHORT TERM...TODAY THROUGH CHRISTMAS. THE BIG FORECAST CHALLENGE
WILL CONTINUE TO CENTER AROUND THE CHANCE OF A LITTLE LIGHT SNOW ON
CHRISTMAS EVE INTO CHRISTMAS DAY. TEMPERATURES WILL ALSO BE VERY
CHALLENGING GIVEN THE FORECAST MODELS OVER EMPHASIS OF SNOW COVER ON
SFC TEMPERATURES.
TODAY...LOW CLOUDS HAVE BEEN SLIDING SOUTHWARD INTO NORTHERN
PORTIONS OF OUR CWA EARLY THIS MORNING. THE RAP MODEL RH VALUES AT
925MB SEEM TO HAVE THE BEST HANDLE ON THESE LOW CLOUDS. THE NAM LOW
LEVEL RH FIELDS CONTINUE TO BE TOO HEAVILY SATURATED...LIKELY DUE
TO HOW THE MODEL IS HANDLING OUR SNOW COVER. WILL CONTINUE TO KEEP
A GOOD DEAL OF CLOUD COVER IN THE FORECAST TODAY ACROSS NEBRASKA
ZONES...BUT AM NOT OVERLY CONFIDENT IN HOW THE LOW CLOUDS WILL PLAY
OUT. KANSAS ZONES SHOULD SEE MORE SUNSHINE. TEMPERATURES WILL LIKELY
BE BACK BELOW FREEZING FOR HIGHS ACROSS MOST AREAS...ESPECIALLY OVER
SNOW COVERED AREAS DUE TO CLOUDS AND COLD SHALLOW AIR SLOWLY
FILTERING INTO THE REGION FROM THE NORTH.
CHRISTMAS EVE/MONDAY...A LEAD SHORT WAVE WILL TRACK FROM THE DAKOTAS
SUNDAY NIGHT INTO THE GREAT LAKES ON MONDAY. THERE WILL BE GOOD COLD
AIR ADVECTION BEHIND THIS SYSTEM ACROSS OUR FORECAST AREA.
THEREFORE...HIGH TEMPERATURES WILL LIKELY BE EVEN COLDER AND WE
SHOULD BE STUCK IN THE TEENS FROM AROUND THE TRI CITIES NORTHEAST
WITH LOWER 20S ACROSS OUR KANSAS ZONES. THE DAYTIME HOURS SHOULD
BE DRY...BUT AN UPPER LOW WILL BE DIGGING ACROSS THE ROCKIES WITH
LIGHT SNOW SPREADING ACROSS THE FRONT RANGE OF THE ROCKIES BY
EARLY EVENING. THIS UPPER LOW WILL QUICKLY SLIDE SOUTH SOUTHEAST
ALONG THE HIGH PLAINS MONDAY NIGHT/CHRISTMAS EVE INTO NORTH TEXAS
BY SUNRISE ON CHRISTMAS. FORECAST MODELS CONTINUE TO SHOW GOOD
AGREEMENT IN LIGHT SNOW MONDAY NIGHT FOR AREAS WEST OF HIGHWAY
281. THERE IS MORE UNCERTAINTY WITH REGARD TO SEEING SNOW FOR
AREAS EAST OF HIGHWAY 281 WITH SOME MODELS DRY AND OTHERS SHOWING
VERY LIGHT SNOW. PREVIOUS POPS RANGING FROM LIKELY SNOW IN OUR
WEST TO LOW END CHANCE IN OUR EAST...SEEM RIGHT ON TARGET AND MADE
LITTLE IF ANY CHANGES.
CHRISTMAS DAY...LIGHT SNOW WILL CONTINUE TO BE POSSIBLE ESPECIALLY
IN THE MORNING AND ESPECIALLY FOR AREAS WEST OF HIGHWAY 281. WHEN
IT IS ALL SAID AND DONE BY LATER IN THE AFTERNOON THIS CURRENTLY
APPEARS TO BE A 1 TO 2 INCH SNOW EVENT FOR AREAS WEST OF HIGHWAY
281...AND 1 INCH OR LESS FOR AREAS EAST OF HIGHWAY 281. IT WILL BE
SO COLD THAT SNOW TO LIQUID RATIOS COULD BE AROUND 20:1 MAKING FOR
A VERY LIGHT AND FLUFFY SNOW. THE WIND WILL CERTAINLY BE MUCH
LIGHTER THAN WHAT WE EXPERIENCED WITH OUR LAST SYSTEM...BUT WILL
STILL BE A BIT BREEZY AT 15 TO 20 MPH...WHICH COULD RESULT IN SOME
BLOWING SNOW AND REDUCED VISIBILITIES AT TIMES. IT SHOULD ALSO BE
POINTED OUT THAT THIS WILL BE A VERY COLD CHRISTMAS WITH HIGHS
ONLY IN THE LOWER TEENS AND WIND CHILL VALUES REMAINING BELOW ZERO
ALL DAY LONG. ACTUAL LOW TEMPERATURES CHRISTMAS NIGHT WILL RANGE
FROM -1 TO -6 WITH WIND CHILL VALUES OF AROUND -15F.
LONG TERM...WEDNESDAY THROUGH SATURDAY. PRIMARY FORECAST CONCERNS
LIE WITH TEMPERATURES...AND END OF THE WEEK PRECIPITATION
CHANCES.
THE START OF THE LONG TERM PERIOD SHOWS MODELS IN GOOD
AGREEMENT...WITH SHARP NORTHWESTERLY FLOW IN PLACE IN THE UPPER
LEVELS...AS LOW PRESSURE SHIFTS INTO THE MIDWEST AND ANOTHER TROUGH
MOVES ONTO THE WEST COAST. THROUGH THE REMAINDER OF THE DAY ON
WEDNESDAY AND INTO WEDNESDAY NIGHT...SHORTWAVE UPPER LEVEL RIDGING
SLIDE OUT OF THE ROCKIES AND ONTO THE PLAINS...KEEPING DRY
CONDITIONS IN PLACE. GENERALLY LIGHT WINDS ARE EXPECTED...BECOMING
MORE SOUTHERLY THROUGH THE DAY...AS A SURFACE RIDGE AXIS SLIDES
THROUGH AND EAST OF THE CWA. STILL PLENTY OF COLD AIR IN
PLACE...AND EVEN THOUGH THERE SHOULD BE MORE IN THE WAY OF
SUN...HIGH TEMPERATURES ONLY EXPECTED TO TOP OUT IN THE LOWER/MID
TEENS.
THURSDAY AND FRIDAY...THE NEXT SYSTEM WHICH WILL BRING PRECIPITATION
CHANCES MOVES IN. OVERALL CONFIDENCE IS NOT THE HIGHEST...WITH
PLENTY OF DIFFERENCES BETWEEN MODELS STILL IN PLACE. AT 12Z
THURSDAY...AN UPPER LEVEL TROUGH IS EXPECTED TO BE SPREAD OVER THE
ROCKIES...WITH THE MAIN LOW LOCATED SOMEWHERE OVER WY. THROUGH THE
DAY ON THURSDAY...THIS SYSTEM WILL MAKE A LITTLE EASTWARD
PROGRESS...ENDING UP ROUGHLY OVER WRN SD/NEB BY EVENING. THURSDAY
NIGHT AND ESP INTO FRIDAY IS WHEN MORE OF THE MODEL DIFFERENCES
ARISE...WITH THE GFS TAKING THE SYSTEM GENERALLY OVER NRN NEB...BUT
THE 00Z ECMWF SWINGS ANOTHER PIECE OF ENERGY DOWN INTO THE SRN
PLAINS. WHILE NEITHER MODELS DEPICTS A LOT OF QPF OVER THE
CWA...THE LATEST RUN OF THE ECMWF MAINLY CLIPS THE NORTH THEN TAKES
THE BRUNT OF THE ACTION TO THE SOUTH WITH THAT SECOND SYSTEM. SO
WITH THESE DIFFERENCES...LEFT THE POPS GENERALLY AS IS...IN THE LOW
CHANCE CATEGORY. FOR SATURDAY...THE DRY FORECAST RETURNS WITH THE
CWA SITTING IN NORTHWESTERLY UPPER LEVEL FLOW IN THE WAKE OF THIS
LATEST SYSTEM. HIGH TEMPERATURES IN THE THURS-SAT TIME FRAME ARE
EXPECTED TO RANGE FROM THE MID TEENS TO MID 20S...WITH OVERNIGHT
LOWS CONTINUING IN THE SINGLE DIGITS TO MID TEENS.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS HASTINGS NE
526 AM CST SUN DEC 23 2012
.AVIATION...12Z TAF. MAIN AREA OF CONCERN...AND LOW
CONFIDENCE...IS WITH THE SKY COVER. AS STATED IN PREVIOUS TAF
DISCUSSION...THE RAP HAS HAD THE BEST HANDLE THIS MORNING ON THE
LOW LEVEL STRATUS...WHICH HAS REMAINED OUT OF THE TERMINAL
AREA...SO FAR. THE CURRENT RUN SHOWS THIS NARROW BAND OF STRATUS
GENERALLY HANGING AROUND IN THE SAME VICINITY...AND NOT EVER
MAKING A SOLID PUSH TOWARD THE TERMINAL. BUT...IT IS AFFECTING
LOCATIONS NEAR THE TERMINAL...WITH ODX AND EAR BOTH SHOWING LOWER
CEILINGS/VISIBILITIES. DECIDED TO KEEP A TEMPO GROUP GOING THROUGH
MID MORNING WITH THE TERMINAL RIDING ON THAT EASTERN EDGE OF LOWER
CATEGORY CONDITIONS. OTHERWISE KEPT THE REMAINDER OF THE TAF
PERIOD SIMPLE...WITH NORTHWESTERLY WINDS DEVELOPING THIS AFTERNOON
BEHIND A SURFACE BOUNDARY PASSING THROUGH.
&&
.PREV DISCUSSION... /ISSUED 428 AM CST SUN DEC 23 2012/
SHORT TERM...TODAY THROUGH CHRISTMAS. THE BIG FORECAST CHALLENGE
WILL CONTINUE TO CENTER AROUND THE CHANCE OF A LITTLE LIGHT SNOW ON
CHRISTMAS EVE INTO CHRISTMAS DAY. TEMPERATURES WILL ALSO BE VERY
CHALLENGING GIVEN THE FORECAST MODELS OVER EMPHASIS OF SNOW COVER ON
SFC TEMPERATURES.
TODAY...LOW CLOUDS HAVE BEEN SLIDING SOUTHWARD INTO NORTHERN
PORTIONS OF OUR CWA EARLY THIS MORNING. THE RAP MODEL RH VALUES AT
925MB SEEM TO HAVE THE BEST HANDLE ON THESE LOW CLOUDS. THE NAM LOW
LEVEL RH FIELDS CONTINUE TO BE TOO HEAVILY SATURATED...LIKELY DUE
TO HOW THE MODEL IS HANDLING OUR SNOW COVER. WILL CONTINUE TO KEEP
A GOOD DEAL OF CLOUD COVER IN THE FORECAST TODAY ACROSS NEBRASKA
ZONES...BUT AM NOT OVERLY CONFIDENT IN HOW THE LOW CLOUDS WILL PLAY
OUT. KANSAS ZONES SHOULD SEE MORE SUNSHINE. TEMPERATURES WILL LIKELY
BE BACK BELOW FREEZING FOR HIGHS ACROSS MOST AREAS...ESPECIALLY OVER
SNOW COVERED AREAS DUE TO CLOUDS AND COLD SHALLOW AIR SLOWLY
FILTERING INTO THE REGION FROM THE NORTH.
CHRISTMAS EVE/MONDAY...A LEAD SHORT WAVE WILL TRACK FROM THE DAKOTAS
SUNDAY NIGHT INTO THE GREAT LAKES ON MONDAY. THERE WILL BE GOOD COLD
AIR ADVECTION BEHIND THIS SYSTEM ACROSS OUR FORECAST AREA.
THEREFORE...HIGH TEMPERATURES WILL LIKELY BE EVEN COLDER AND WE
SHOULD BE STUCK IN THE TEENS FROM AROUND THE TRI CITIES NORTHEAST
WITH LOWER 20S ACROSS OUR KANSAS ZONES. THE DAYTIME HOURS SHOULD
BE DRY...BUT AN UPPER LOW WILL BE DIGGING ACROSS THE ROCKIES WITH
LIGHT SNOW SPREADING ACROSS THE FRONT RANGE OF THE ROCKIES BY
EARLY EVENING. THIS UPPER LOW WILL QUICKLY SLIDE SOUTH SOUTHEAST
ALONG THE HIGH PLAINS MONDAY NIGHT/CHRISTMAS EVE INTO NORTH TEXAS
BY SUNRISE ON CHRISTMAS. FORECAST MODELS CONTINUE TO SHOW GOOD
AGREEMENT IN LIGHT SNOW MONDAY NIGHT FOR AREAS WEST OF HIGHWAY
281. THERE IS MORE UNCERTAINTY WITH REGARD TO SEEING SNOW FOR
AREAS EAST OF HIGHWAY 281 WITH SOME MODELS DRY AND OTHERS SHOWING
VERY LIGHT SNOW. PREVIOUS POPS RANGING FROM LIKELY SNOW IN OUR
WEST TO LOW END CHANCE IN OUR EAST...SEEM RIGHT ON TARGET AND MADE
LITTLE IF ANY CHANGES.
CHRISTMAS DAY...LIGHT SNOW WILL CONTINUE TO BE POSSIBLE ESPECIALLY
IN THE MORNING AND ESPECIALLY FOR AREAS WEST OF HIGHWAY 281. WHEN
IT IS ALL SAID AND DONE BY LATER IN THE AFTERNOON THIS CURRENTLY
APPEARS TO BE A 1 TO 2 INCH SNOW EVENT FOR AREAS WEST OF HIGHWAY
281...AND 1 INCH OR LESS FOR AREAS EAST OF HIGHWAY 281. IT WILL BE
SO COLD THAT SNOW TO LIQUID RATIOS COULD BE AROUND 20:1 MAKING FOR
A VERY LIGHT AND FLUFFY SNOW. THE WIND WILL CERTAINLY BE MUCH
LIGHTER THAN WHAT WE EXPERIENCED WITH OUR LAST SYSTEM...BUT WILL
STILL BE A BIT BREEZY AT 15 TO 20 MPH...WHICH COULD RESULT IN SOME
BLOWING SNOW AND REDUCED VISIBILITIES AT TIMES. IT SHOULD ALSO BE
POINTED OUT THAT THIS WILL BE A VERY COLD CHRISTMAS WITH HIGHS
ONLY IN THE LOWER TEENS AND WIND CHILL VALUES REMAINING BELOW ZERO
ALL DAY LONG. ACTUAL LOW TEMPERATURES CHRISTMAS NIGHT WILL RANGE
FROM -1 TO -6 WITH WIND CHILL VALUES OF AROUND -15F.
LONG TERM...WEDNESDAY THROUGH SATURDAY. PRIMARY FORECAST CONCERNS
LIE WITH TEMPERATURES...AND END OF THE WEEK PRECIPITATION
CHANCES.
THE START OF THE LONG TERM PERIOD SHOWS MODELS IN GOOD
AGREEMENT...WITH SHARP NORTHWESTERLY FLOW IN PLACE IN THE UPPER
LEVELS...AS LOW PRESSURE SHIFTS INTO THE MIDWEST AND ANOTHER TROUGH
MOVES ONTO THE WEST COAST. THROUGH THE REMAINDER OF THE DAY ON
WEDNESDAY AND INTO WEDNESDAY NIGHT...SHORTWAVE UPPER LEVEL RIDGING
SLIDE OUT OF THE ROCKIES AND ONTO THE PLAINS...KEEPING DRY
CONDITIONS IN PLACE. GENERALLY LIGHT WINDS ARE EXPECTED...BECOMING
MORE SOUTHERLY THROUGH THE DAY...AS A SURFACE RIDGE AXIS SLIDES
THROUGH AND EAST OF THE CWA. STILL PLENTY OF COLD AIR IN
PLACE...AND EVEN THOUGH THERE SHOULD BE MORE IN THE WAY OF
SUN...HIGH TEMPERATURES ONLY EXPECTED TO TOP OUT IN THE LOWER/MID
TEENS.
THURSDAY AND FRIDAY...THE NEXT SYSTEM WHICH WILL BRING PRECIPITATION
CHANCES MOVES IN. OVERALL CONFIDENCE IS NOT THE HIGHEST...WITH
PLENTY OF DIFFERENCES BETWEEN MODELS STILL IN PLACE. AT 12Z
THURSDAY...AN UPPER LEVEL TROUGH IS EXPECTED TO BE SPREAD OVER THE
ROCKIES...WITH THE MAIN LOW LOCATED SOMEWHERE OVER WY. THROUGH THE
DAY ON THURSDAY...THIS SYSTEM WILL MAKE A LITTLE EASTWARD
PROGRESS...ENDING UP ROUGHLY OVER WRN SD/NEB BY EVENING. THURSDAY
NIGHT AND ESP INTO FRIDAY IS WHEN MORE OF THE MODEL DIFFERENCES
ARISE...WITH THE GFS TAKING THE SYSTEM GENERALLY OVER NRN NEB...BUT
THE 00Z ECMWF SWINGS ANOTHER PIECE OF ENERGY DOWN INTO THE SRN
PLAINS. WHILE NEITHER MODELS DEPICTS A LOT OF QPF OVER THE
CWA...THE LATEST RUN OF THE ECMWF MAINLY CLIPS THE NORTH THEN TAKES
THE BRUNT OF THE ACTION TO THE SOUTH WITH THAT SECOND SYSTEM. SO
WITH THESE DIFFERENCES...LEFT THE POPS GENERALLY AS IS...IN THE LOW
CHANCE CATEGORY. FOR SATURDAY...THE DRY FORECAST RETURNS WITH THE
CWA SITTING IN NORTHWESTERLY UPPER LEVEL FLOW IN THE WAKE OF THIS
LATEST SYSTEM. HIGH TEMPERATURES IN THE THURS-SAT TIME FRAME ARE
EXPECTED TO RANGE FROM THE MID TEENS TO MID 20S...WITH OVERNIGHT
LOWS CONTINUING IN THE SINGLE DIGITS TO MID TEENS.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
SHORT...WESELY
LONG/AVIATION...ADO
AREA FORECAST DISCUSSION
NWS HASTINGS NE
428 AM CST SUN DEC 23 2012
.SHORT TERM...TODAY THROUGH CHRISTMAS. THE BIG FORECAST CHALLENGE
WILL CONTINUE TO CENTER AROUND THE CHANCE OF A LITTLE LIGHT SNOW ON
CHRISTMAS EVE INTO CHRISTMAS DAY. TEMPERATURES WILL ALSO BE VERY
CHALLENGING GIVEN THE FORECAST MODELS OVER EMPHASIS OF SNOW COVER ON
SFC TEMPERATURES.
TODAY...LOW CLOUDS HAVE BEEN SLIDING SOUTHWARD INTO NORTHERN
PORTIONS OF OUR CWA EARLY THIS MORNING. THE RAP MODEL RH VALUES AT
925MB SEEM TO HAVE THE BEST HANDLE ON THESE LOW CLOUDS. THE NAM LOW
LEVEL RH FIELDS CONTINUE TO BE TOO HEAVILY SATURATED...LIKELY DUE
TO HOW THE MODEL IS HANDLING OUR SNOW COVER. WILL CONTINUE TO KEEP
A GOOD DEAL OF CLOUD COVER IN THE FORECAST TODAY ACROSS NEBRASKA
ZONES...BUT AM NOT OVERLY CONFIDENT IN HOW THE LOW CLOUDS WILL PLAY
OUT. KANSAS ZONES SHOULD SEE MORE SUNSHINE. TEMPERATURES WILL LIKELY
BE BACK BELOW FREEZING FOR HIGHS ACROSS MOST AREAS...ESPECIALLY OVER
SNOW COVERED AREAS DUE TO CLOUDS AND COLD SHALLOW AIR SLOWLY
FILTERING INTO THE REGION FROM THE NORTH.
CHRISTMAS EVE/MONDAY...A LEAD SHORT WAVE WILL TRACK FROM THE DAKOTAS
SUNDAY NIGHT INTO THE GREAT LAKES ON MONDAY. THERE WILL BE GOOD COLD
AIR ADVECTION BEHIND THIS SYSTEM ACROSS OUR FORECAST AREA.
THEREFORE...HIGH TEMPERATURES WILL LIKELY BE EVEN COLDER AND WE
SHOULD BE STUCK IN THE TEENS FROM AROUND THE TRI CITIES NORTHEAST
WITH LOWER 20S ACROSS OUR KANSAS ZONES. THE DAYTIME HOURS SHOULD
BE DRY...BUT AN UPPER LOW WILL BE DIGGING ACROSS THE ROCKIES WITH
LIGHT SNOW SPREADING ACROSS THE FRONT RANGE OF THE ROCKIES BY
EARLY EVENING. THIS UPPER LOW WILL QUICKLY SLIDE SOUTH SOUTHEAST
ALONG THE HIGH PLAINS MONDAY NIGHT/CHRISTMAS EVE INTO NORTH TEXAS
BY SUNRISE ON CHRISTMAS. FORECAST MODELS CONTINUE TO SHOW GOOD
AGREEMENT IN LIGHT SNOW MONDAY NIGHT FOR AREAS WEST OF HIGHWAY
281. THERE IS MORE UNCERTAINTY WITH REGARD TO SEEING SNOW FOR
AREAS EAST OF HIGHWAY 281 WITH SOME MODELS DRY AND OTHERS SHOWING
VERY LIGHT SNOW. PREVIOUS POPS RANGING FROM LIKELY SNOW IN OUR
WEST TO LOW END CHANCE IN OUR EAST...SEEM RIGHT ON TARGET AND MADE
LITTLE IF ANY CHANGES.
CHRISTMAS DAY...LIGHT SNOW WILL CONTINUE TO BE POSSIBLE ESPECIALLY
IN THE MORNING AND ESPECIALLY FOR AREAS WEST OF HIGHWAY 281. WHEN
IT IS ALL SAID AND DONE BY LATER IN THE AFTERNOON THIS CURRENTLY
APPEARS TO BE A 1 TO 2 INCH SNOW EVENT FOR AREAS WEST OF HIGHWAY
281...AND 1 INCH OR LESS FOR AREAS EAST OF HIGHWAY 281. IT WILL BE
SO COLD THAT SNOW TO LIQUID RATIOS COULD BE AROUND 20:1 MAKING FOR
A VERY LIGHT AND FLUFFY SNOW. THE WIND WILL CERTAINLY BE MUCH
LIGHTER THAN WHAT WE EXPERIENCED WITH OUR LAST SYSTEM...BUT WILL
STILL BE A BIT BREEZY AT 15 TO 20 MPH...WHICH COULD RESULT IN SOME
BLOWING SNOW AND REDUCED VISIBILITIES AT TIMES. IT SHOULD ALSO BE
POINTED OUT THAT THIS WILL BE A VERY COLD CHRISTMAS WITH HIGHS
ONLY IN THE LOWER TEENS AND WIND CHILL VALUES REMAINING BELOW ZERO
ALL DAY LONG. ACTUAL LOW TEMPERATURES CHRISTMAS NIGHT WILL RANGE
FROM -1 TO -6 WITH WIND CHILL VALUES OF AROUND -15F.
.LONG TERM...WEDNESDAY THROUGH SATURDAY. PRIMARY FORECAST CONCERNS
LIE WITH TEMPERATURES...AND END OF THE WEEK PRECIPITATION
CHANCES.
THE START OF THE LONG TERM PERIOD SHOWS MODELS IN GOOD
AGREEMENT...WITH SHARP NORTHWESTERLY FLOW IN PLACE IN THE UPPER
LEVELS...AS LOW PRESSURE SHIFTS INTO THE MIDWEST AND ANOTHER TROUGH
MOVES ONTO THE WEST COAST. THROUGH THE REMAINDER OF THE DAY ON
WEDNESDAY AND INTO WEDNESDAY NIGHT...SHORTWAVE UPPER LEVEL RIDGING
SLIDE OUT OF THE ROCKIES AND ONTO THE PLAINS...KEEPING DRY
CONDITIONS IN PLACE. GENERALLY LIGHT WINDS ARE EXPECTED...BECOMING
MORE SOUTHERLY THROUGH THE DAY...AS A SURFACE RIDGE AXIS SLIDES
THROUGH AND EAST OF THE CWA. STILL PLENTY OF COLD AIR IN
PLACE...AND EVEN THOUGH THERE SHOULD BE MORE IN THE WAY OF
SUN...HIGH TEMPERATURES ONLY EXPECTED TO TOP OUT IN THE LOWER/MID
TEENS.
THURSDAY AND FRIDAY...THE NEXT SYSTEM WHICH WILL BRING PRECIPITATION
CHANCES MOVES IN. OVERALL CONFIDENCE IS NOT THE HIGHEST...WITH
PLENTY OF DIFFERENCES BETWEEN MODELS STILL IN PLACE. AT 12Z
THURSDAY...AN UPPER LEVEL TROUGH IS EXPECTED TO BE SPREAD OVER THE
ROCKIES...WITH THE MAIN LOW LOCATED SOMEWHERE OVER WY. THROUGH THE
DAY ON THURSDAY...THIS SYSTEM WILL MAKE A LITTLE EASTWARD
PROGRESS...ENDING UP ROUGHLY OVER WRN SD/NEB BY EVENING. THURSDAY
NIGHT AND ESP INTO FRIDAY IS WHEN MORE OF THE MODEL DIFFERENCES
ARISE...WITH THE GFS TAKING THE SYSTEM GENERALLY OVER NRN NEB...BUT
THE 00Z ECMWF SWINGS ANOTHER PIECE OF ENERGY DOWN INTO THE SRN
PLAINS. WHILE NEITHER MODELS DEPICTS A LOT OF QPF OVER THE
CWA...THE LATEST RUN OF THE ECMWF MAINLY CLIPS THE NORTH THEN TAKES
THE BRUNT OF THE ACTION TO THE SOUTH WITH THAT SECOND SYSTEM. SO
WITH THESE DIFFERENCES...LEFT THE POPS GENERALLY AS IS...IN THE LOW
CHANCE CATEGORY. FOR SATURDAY...THE DRY FORECAST RETURNS WITH THE
CWA SITTING IN NORTHWESTERLY UPPER LEVEL FLOW IN THE WAKE OF THIS
LATEST SYSTEM. HIGH TEMPERATURES IN THE THURS-SAT TIME FRAME ARE
EXPECTED TO RANGE FROM THE MID TEENS TO MID 20S...WITH OVERNIGHT
LOWS CONTINUING IN THE SINGLE DIGITS TO MID TEENS.
&&
.AVIATION...06Z TAF. PRIMARY CONCERN WITH THIS TAF FORECAST LIES
WITH THE POTENTIAL FOR LOW LEVEL STRATUS. KEPT THINGS ON THE
PESSIMISTIC SIDE...WITH MVFR CONDITIONS POSSIBLE THROUGH THE REST
OF THE OVERNIGHT HOURS INTO EARLY SUN MORNING...BUT CONFIDENCE IS
NOT OVERLY HIGH. CURRENT RUN OF THE RAP SHOWING 900MB RH FIELDS
HAVING A GOOD HANDLE ON CURRENT CONDITIONS...BUT DEPICTS THE
STRATUS FIELD NOT MAKING IT ALL THE WAY DOWN TO THE TERMINAL AREA
AS WINDS HELPING DRIVE THE CLOUDS SWITCH FROM THE NORTH MORE TO
THE EAST/SOUTHEAST...STOPPING ITS SOUTHWARD PROGRESS. CURRENTLY
STILL HAVE A COUPLE FINGERS OF SUB-1000FT CEILINGS IN THE
AREA...AND WILL AT LEAST KEEP A TEMPO GROUP GOING. WILL HAVE TO
MONITOR THE MAIN AREA OF LOW LEVEL STRATUS CURRENTLY ACROSS MN
OVER THE NEXT COUPLE OF HOURS...AND WILL ADJUST THE FORECAST AS
NECESSARY.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
SHORT...WESELY
LONG/AVIATION...ODER
AREA FORECAST DISCUSSION
NWS HASTINGS NE
1137 PM CST SAT DEC 22 2012
.AVIATION...06Z TAF. PRIMARY CONCERN WITH THIS TAF FORECAST LIES
WITH THE POTENTIAL FOR LOW LEVEL STRATUS. KEPT THINGS ON THE
PESSIMISTIC SIDE...WITH MVFR CONDITIONS POSSIBLE THROUGH THE REST
OF THE OVERNIGHT HOURS INTO EARLY SUN MORNING...BUT CONFIDENCE IS
NOT OVERLY HIGH. CURRENT RUN OF THE RAP SHOWING 900MB RH FIELDS
HAVING A GOOD HANDLE ON CURRENT CONDITIONS...BUT DEPICTS THE
STRATUS FIELD NOT MAKING IT ALL THE WAY DOWN TO THE TERMINAL AREA
AS WINDS HELPING DRIVE THE CLOUDS SWITCH FROM THE NORTH MORE TO
THE EAST/SOUTHEAST...STOPPING ITS SOUTHWARD PROGRESS. CURRENTLY
STILL HAVE A COUPLE FINGERS OF SUB-1000FT CEILINGS IN THE
AREA...AND WILL AT LEAST KEEP A TEMPO GROUP GOING. WILL HAVE TO
MONITOR THE MAIN AREA OF LOW LEVEL STRATUS CURRENTLY ACROSS MN
OVER THE NEXT COUPLE OF HOURS...AND WILL ADJUST THE FORECAST AS
NECESSARY.
&&
PREV DISCUSSION... /ISSUED 328 PM CST SAT DEC 22 2012/
SHORT TERM...TONIGHT AND SUNDAY. MAIN FORECAST CONCERNS WILL BE
CLOUD COVER AND TEMPERATURES.
SATELLITE SHOWS SOME CIRRUS MOVING THROUGH THE AREA THIS
AFTERNOON. SURFACE ANALYSIS SHOWS THE COLD FRONT HAS MADE IT
THROUGH THE FORECAST AREA. EVEN BEHIND THE COLD FRONT TEMPERATURES
HAVE BEEN WARMING ACROSS THE AREA AND MOST LOCATIONS HAVE MADE IT
ABOVE FREEZING.
A SURFACE HIGH PRESSURE SYSTEM SETTLES INTO THE FORECAST AREA
TONIGHT BEHIND THE COLD FRONT THAT MOVED THROUGH THE AREA EARLIER
TODAY. COOLER AIR MOVES INTO THE AREA DURING THE NIGHT. THE
CONCERN IS THAT THERE IS ALSO SOME LOW LEVEL MOISTURE THAT IS
SHOWING UP AT 925MB THAT MOVES INTO THE AREA. MODELS ALL SHOW SOME
LOW LEVEL MOISTURE MOVING INTO THE AREA...BUT WHERE IT IS SUPPOSED
TO CURRENTLY BE HAS LITTLE TO NO LOW LEVEL STRATUS. EXPECT THE
CLOUDS WILL DEVELOP TONIGHT AS THE TEMPERATURES FALL OFF. THEN THE
NEXT QUESTION IS HOW FAR WILL THE TEMPERATURES FALL OFF BEFORE THE
CLOUDS DEVELOP/MOVE INTO THE AREA. EXPECT THAT THE TEMPERATURES
WILL BE A BIT WARMER THAN NUMERICAL GUIDANCE FOR TONIGHT...BUT
WILL STILL BE WELL BELOW NORMAL.
MODELS ALSO INDICATE THAT THE LOW LEVEL MOISTURE WILL CONTINUE
INTO SUNDAY. WITH MOSTLY CLOUDY SKIES TEMPERATURES WILL LIKELY NOT
RISE MUCH BUT SHOULD MANAGE TO GET INTO THE 20S.
LONG TERM...STARTING 00Z MONDAY. GUIDANCE FROM THE
NAM...OPERATIONAL GFS...EC AND SREF-MEAN ALL SUGGEST A MID LEVEL
SHORT WAVE WILL PUSH ACROSS THE NORTHERN PLAINS SUNDAY NIGHT. ANY
OMEGA IN ASSOCIATION WITH THIS SYSTEM APPEARS AS THOUGH IT WILL
REMAIN NORTH/NORTHEAST OF OUR AREA AND AS A RESULT...DRY
CONDITIONS WERE MAINTAINED IN THE FORECAST FOR SUNDAY NIGHT. AN
OVERALL LACK IN KINEMATIC FORCING SHOULD ALSO PRESENT DRY
CONDITIONS TO OUR AREA DURING THE DAY MONDAY. THE
NAM...OPERATIONAL GFS...EC...AND SREF-MEAN ALL CONTINUE TO
INDICATE A MID LEVEL SHORT WAVE WILL MOVE ACROSS THE CENTRAL ROCKY
MOUNTAIN RANGE MONDAY NIGHT...AND THEN SOUTHEAST ACROSS PORTIONS
OF THE CENTRAL AND SOUTHERN PLAINS DURING THE DAY TUESDAY....WITH
SNOWFALL CURRENTLY FORECAST ACROSS MUCH OF THE CWA MONDAY NIGHT
INTO TUESDAY. ALTHOUGH THIS SYSTEM IS EXPECTED TO REMAIN OPEN AT
500MB...MODEL GUIDANCE DOES SUGGEST A CLOSE 700MB LOW WILL
DEVELOP...WITH A RESULTANT AXIS OF MID LEVEL DEFORMATION
DEVELOPING TO THE NORTH OF THE 700MB LOW. MID LEVEL THERMAL
ADVECTION AHEAD OF THE MID LEVEL TROUGH AXIS MAY BRING THE INITIAL
SHOT OF PRECIPITATION TO OUR AREA MONDAY EVENING...HOWEVER THE
BULK OF THE PRECIPITATION APPEARS IT WILL RESULT FROM THE
AFOREMENTIONED AXIS OF MID LEVEL DEFORMATION WHICH IS EXPECTED TO
PUSH OVER OUR AREA MONDAY NIGHT INTO TUESDAY. GIVEN THE MODEL
AGREEMENT...AND MODEL CONSISTENCY...THROUGH THE PAST SEVERAL
DAYS...OPTED TO RAISE POPS ACROSS MUCH OF THE CWA...BUT ESPECIALLY
ACROSS OUR WEST WHERE LIKELY POPS ARE NOW IN EXISTENCE. QPF FIELDS
FROM THE SREF-MEAN...NAM...OPERATIONAL GFS SUGGEST STORM-TOTAL
LIQUID PRECIPITATION AMOUNTS APPROACHING 0.25" ACROSS OUR EXTREME
WEST...WITH LIQUID PRECIPITATION AMOUNTS REMAINING UNDER 0.10"
GENERALLY EAST OF HIGHWAY 281. GIVEN THAT THIS IS GOING TO BE A
PROGRESSIVE SYSTEM IN NORTHWESTERLY FLOW WITH LIMITED LOWER
TROPOSPHERIC MOISTURE...OPTED TO UNDERCUT PRECIPITATION AMOUNTS
SOMEWHAT FROM WHAT GUIDANCE OFFERS. THE OFFICIAL FORECAST
GENERALLY HAS 0.05"-0.15" STORM-TOTAL LIQUID PRECIPITATION ACROSS
THE CWA...WITH THE HIGHEST AMOUNTS ACROSS OUR WEST. BIGGEST
CONCERN WITH THIS UPCOMING SYSTEM IS THE VERY DRY/COLD LOW LEVEL
AIRMASS IN PLACE...WHICH WILL UNDOUBTEDLY PROMOTE HIGH SNOW-WATER
RATIOS. WITH SURFACE TEMPERATURES GENERALLY RANGING BETWEEN 10 AND
15 DEGREES F THROUGH MUCH OF THE EVENT...A SNOW-WATER RATIO IN
EXCESS OF 20:1 IS NOT OUT OF THE QUESTION. NOT YET READY TO GO ALL
OUT WITH SNOWFALL ACCUMULATIONS HOWEVER...MOSTLY BECAUSE THIS IS
STILL A CLIPPER SYSTEM AND HIGH SNOWFALL ACCUMULATIONS ARE VERY
HARD TO COME BY WITH THESE SYSTEMS. AS A RESULT...STAYED CLOSER TO
A 20:1 SNOW-WATER RATIO...WHICH PRESENTS STORM TOTAL SNOWFALL
ACCUMULATIONS GENERALLY IN THE 1-3 INCH RANGE. ONE OTHER CONCERN
WITH THIS UPCOMING SYSTEM IS THE POTENTIAL FOR VISIBILITY
RESTRICTIONS IN BLOWING SNOW. THE NAM AND OPERATIONAL GFS BOTH
SUGGEST AN INCREASING LOW LEVEL PRESSURE GRADIENT WILL PROMOTE AN
INCREASING LOW LEVEL WIND FIELD MONDAY NIGHT AND TUESDAY. WITH
SNOW EXPECTED TO BE VERY DRY AND FLUFFY...VISIBILITY RESTRICTIONS
WILL BE EASY TO COME BY AS THE SUSTAINED WIND REMAINS NEAR 15KTS.
UPPER LEVEL RIDGING AND A RESULTANT OVERALL LACK IN KINEMATIC
FORCING IS EXPECTED TO BRING DRY CONDITIONS TO THE AREA TUESDAY
NIGHT THROUGH MUCH OF THURSDAY. BY LATE THURSDAY HOWEVER YET
ANOTHER MID LEVEL SHORT WAVE IS EXPECTED TO BRING A CHANCE FOR
PRECIPITATION. OPTED TO STAY CLOSE TO WHAT ALLBLEND PRESENTED FOR
THIS TIME PERIOD...WHICH IS 20-30% POPS ACROSS MUCH OF THE CWA
THURSDAY NIGHT INTO FRIDAY. DRY CONDITIONS ARE CURRENTLY FORECAST
SATURDAY AS SUBSIDENCE SETTLES INTO THE REGION BEHIND THE
DEPARTING MID LEVEL SHORT WAVE.
A LOW LEVEL BAROCLINIC ZONE IS EXPECTED TO PUSH ACROSS THE AREA
SUNDAY NIGHT INTO MONDAY IN ASSOCIATION WITH THE NORTHERN PLAINS
MID LEVEL SHORT WAVE...WITH HIGHS ON MONDAY LIKELY REMAINING IN
THE TEENS AND 20S. A REINFORCING SHOT OF LOW LEVEL COLD AIR
ADVECTION IS THEN EXPECTED TO INFILTRATE THE REGION BEHIND THE MID
LEVEL SHORT WAVE MONDAY NIGHT INTO TUESDAY...WITH A ~1030MB
SURFACE RIDGE EXPECTED TO SET UP SHOP OVER THE CENTRAL PLAINS
TUESDAY THROUGH WEDNESDAY. THIS WILL SET THE STAGE FOR SOME OF THE
COLDEST WEATHER WE HAVE SEEN IN A LONG TIME...WITH LOWS NEAR OR
BELOW ZERO ACROSS MUCH OF THE CWA TUESDAY NIGHT AND WEDNESDAY
NIGHT...AND HIGHS STRUGGLING THROUGH THE SINGLE DIGITS AND TEENS
ABOVE ZERO TUESDAY AND WEDNESDAY. A SLIGHT WARMING TREND IS THEN
EXPECTED TO FINISH OUT THE FORECAST PERIOD AS WEAK LOW LEVEL WARM
ADVECTION OVERTAKES THE AREA.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS OMAHA/VALLEY NE
1130 PM CST SAT DEC 22 2012
.AVIATION...
06Z TAFS FOR KOFK...KLNK AND KOMA.
VSBYS NEAR 5SM IN FOG ARE LIKELY OVERNIGHT UNDER SCATTERED HIGH
CLOUDS. MVFR CIGS AT FL015 ARE EXPECTED TO DEVELOP BETWEEN 10Z AND
14Z AT ALL EASTERN NEBRASKA TAF SITES...WITH THOSE CIGS LINGERING
PAST 18Z. A GRADUAL IMPROVEMENT TO VFR SHOULD OCCUR BY 00Z AS
ANOTHER COLD FRONT SLIPS THROUGH THE REGION. WINDS WILL BE FAIRLY
LIGHT THROUGH THE TAF PERIOD.
DERGAN
&&
.PREV DISCUSSION... /ISSUED 341 PM CST SAT DEC 22 2012/
SHORT TERM...TONIGHT THROUGH CHRISTMAS DAY.
THE FORECAST CONCERNS IN THE SHORT TERM WILL BE THE CLOUDS...POTENTIAL
FOR FLURRIES OR LIGHT SNOW WITH A NORTHERN STREAM WAVE SUNDAY
NIGHT AND THE SOUTHERN STREAM WAVE CHRISTMAS EVE AND CHRISTMAS
DAY...AND TEMPERATURES.
SUNSHINE AND WARM H85 TEMPERATURES HAVE TRANSLATED INTO READINGS IN
THE 30S AND A FEW 40S FOR MUCH OF THE FORECAST AREA. THE SURFACE
WINDSHIFT TO THE NORTHWEST HAD MADE TO THE VALLEY NWS BY 130PM AND
COOLING IN TEMPERATURES WERE NOTICED FROM YANKTON TO ONEILL.
THE STORM SYSTEM OF INTEREST FOR OUR WEATHER LATER THIS WEEKEND AND
EARLY NEXT WEEK IS JUST STARTING TO BECOME SAMPLED BY THE WEST COAST
STATIONS IN THE 12Z RUNS. AT THIS POINT...THERE IS GOOD AGREEMENT
IN THE SHORT RANGE MODELS THAT LEAD ENERGY FROM THIS SYSTEM WILL
MOVES ACROSS THE NORTHERN ROCKIES...INTO THE PLAINS TONIGHT AND
SUNDAY...FLATTENING THE MID LEVEL RIDGE AND ALLOWING VERY COLD AIR
FROM CANADA TO MOVE SOUTHWARD ACROSS THE DAKOTAS...MINNESOTA...AND
IOWA...WITH SOMEWHAT OF A GLANCING BLOW LOCALLY. AT THIS
TIME...THERE IS AN AREA OF STRATUS AND FLURRIES ACROSS NORTHERN
NORTH DAKOTA. A LOOK AT THE 18Z STLT AND THE 18Z PROJECTIONS FOR
NAM/GFS AND MOST RECENT HRRR SEEM TO BE OVERDOING THE LOW LEVEL RH.
THE 12Z EC SEEMS TO HAVE A BETTER HANDLE ON THE LOW LEVEL RH.
THE WATER VAPOR SATELLITE IMAGERY AND A LOOK AT WINDS ALOFT AND
HEIGHTS SHOW ONE JET SEGMENT WEST OF THE TROF OFF THE WEST COAST AND
ANOTHER JET SEGMENT OVER THE SOUTHWEST U.S. WITH MOISTURE FROM THE
TROPICS STREAMING INTO THE SOUTHERN ROCKIES AND SOUTHERN PLAINS.
HIGH LEVEL CLOUDS WILL BE ON THE INCREASE DURING THE OVERNIGHT HOURS
AND CONTINUE INTO SUNDAY. STRATUS DEVELOPMENT IS LESS CERTAIN...AND
FOR NOW THE BEST CHANCE FOR STRATUS APPEARS TO BE INTO NORTH CENTRAL
NEBRASKA OVERNIGHT WITH SOME STRATUS DEVELOPING OVER PARTS OF THE
FORECAST AREA SUNDAY. THERE IS GOOD MID LEVEL WARM AIR ADVECTION
WELL TO THE NORTH OF THE AREA AND THERE COULD BE SOME FLURRIES IN
THE FAR NORTH/NORTHEAST TOWARD MACY AND MAPLETON WITH THE CLOUDS AND
ALSO AS THE SHORTWAVE IS TRACKING FROM THE DAKOTAS INTO IOWA.
TONIGHT...SURFACE HIGH PRESSURE WILL BUILD IN AND HAVE LOWS IN THE
SINGLE DIGITS AND TEENS. HIGHS SUNDAY SHOULD BE COLDER...ONLY IN
THE TEENS AND 20S. THE SHORTWAVE TROF SUNDAY NIGHT BRINGS A
WINDSHIFT THRU AND MUCH COLDER TEMPERATURES. HIGHS MONDAY SHOULD
MAINLY BE IN THE TEENS.
THE NEXT STRONGER...LARGER STORM SYSTEM JUST MOVING ONTO THE WEST
COAST IS FORECAST TO TRACK ACROSS THE ROCKIES INTO THE PLAINS
CHRISTMAS EVE AND CHRISTMAS DAY. THE SURFACE LOW TRACKS WELL TO THE
SOUTH OVER TEXAS...AND THE BETTER LIFT IS ALSO WELL TO THE SOUTH.
THERE IS SOME BROAD MID AND UPPER LEVEL LIFT AND WITH THE COLD
AIRMASS IS IN PLACE THERE MAY BE SOME FLURRIES OR LIGHT SNOW. FOR
NOW HAVE SOME CHANCE PROB OF PRECIPITATION TOWARD
ALBION...COLUMBUS...AND SEWARD...WITH SLIGHT CHANCE FOR LIGHT SNOW
AND CHANCE OF FLURRIES MENTIONED ACROSS PARTS OF . HIGHS MONDAY
AND TUESDAY LOOK TO HOLD IN THE TEENS.
ZAPOTOCNY
LONG TERM...TUESDAY NIGHT THROUGH SATURDAY.
NEW MEDIUM RANGE MODELS INDICATING GOING FCST IS IN GOOD
SHAPE...THUS ONLY MINOR ADJUSTMENT MADE. LARGE SCALE FLOW IS
ADVERISED TO BE RATHER PROGRESSIVE THRU THE EXTENDED PDS.
MODELS PROG A LONGWAVE TROF EXITING EWD OF THE REGION TUESDAY NIGHT
WITH ITS AXIS PRETTY MUCH CUTTING DOWN THE MS VLY. MEANWHILE...
UPSTREAM SHORTWAVE TROF OFF THE PAC NW COAST WILL BE THE NEXT SYSTEM
OF INTEREST FOR POSSIBLE ACTIVE WX. THE ECM CONTINUES TO BE THE MOST
ROBUST PUSHING THE SYSTEM ACROSS CA INTO THE INTERMOUNTAIN WEST WED
NIGHT/THURS MORNING WITH 500 MB HGT FALLS AROUND 160M AND INCREASING
DPVA INDUCING SFC CYCLOGENESIS NEAR THE OK PANHANDLE. SYNOPTIC LIFT
INCREASES INTO THURSDAY NIGHT AS NARROW CHANNEL OF VORTICIY ROUNDS
THE BASE OF THE TROF. THIS IN COMBINATION WITH A RELATIVELY WEAK
LOW/MID LYR FRONTOGENETIC CIRCULATION AND MODEST 280K ISENTROPIC
UPGLIDE...THE ECM FOCUSES PCPN INITIATION FROM ABOUT SWRN SD TO NERN
CO THEN PUSHES IT EWD THRU THE DAY ON FRIDAY. AM INCLINED AT THIS
POINT TO FAVOR ECM SOLUTION OVER THE GFS. THEREFORE WILL MAINTAIN
SMALL SNOW POPS THURSDAY NIGHT AND FRIDAY. FRIDAY EVENING...ANY SNOW
ACTIVITY SHOULD BE COMING TO A QUICK END AS CAA/SUBSIDENCE
SUPPRESSES ANY DYNAMIC FORCING. OTHERWISE...BOTH ECM MOS AND MEX
ADVERTISING WELL BELOW NORMAL TEMPS DAYS 4-7.
DEE
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
IA...NONE.
&&
$$
99/99
AREA FORECAST DISCUSSION...UPDATED
NWS NORTH PLATTE NE
1127 PM CST SAT DEC 22 2012
.UPDATE...
.AVIATION...
THE ARCTIC FRONT AND MVFR/IFR/LIFR CIGS HAS SLIPPED THROUGH KVTN. THE
RAP MODELS BRINGS THE FRONT WEST AND SOUTH OVERNIGHT BUT KEEPS THE
FRONT NORTH OF KLBF AND EAST OF KMHN. LOW PRESSURE WILL TRACK
ALONG THE FRONT SUNDAY CAUSING IT TO RETREAT NORTH AND EAST A BIT IN
THE LATE MORNING AND AFTERNOON. ONCE THE LOW GOES BY LATE IN THE
AFTERNOON...MVFR/IFR/LIFR CIGS CAN RETURN...MOST LIKELY AFTER
SUNSET. STILL VFR CONTINUES AT KLBF AND AREAS WEST OF KLBF...NORTH
THROUGH KIEN.
NOTE THAT NONE OF THE MODELS ARE HANDLING THIS FRONT VERY WELL.
THE RAP IS STRUGGLING SO LOOK FOR UPDATES AS WARRANTED.
&&
.PREV DISCUSSION... /ISSUED 808 PM CST SAT DEC 22 2012/
UPDATE...
DISCUSSION...
LOW PRESSURE FORMING NEAR THE BLACK HILLS...HIGH LEVEL
CLOUDINESS AND MIXING AHEAD OF A WEAK ARCTIC BOUNDARY SHOULD KEEP
MIN TEMPS WARMER TONIGHT. SO A NEW MULTI MODEL TEMPERATURE FORECAST IS IN
PLACE. THE MET AND MAV HAVE BEEN SHOWING 2 TO 3 DEGREE COLD BIAS
LATELY.
PREV DISCUSSION... /ISSUED 632 PM CST SAT DEC 22 2012/
UPDATE...
AVIATION...
AN ARCTIC FRONT WILL DROP THROUGH NCNTL NEB OVERNIGHT. IT IS
BELIEVED THAT THE FRONT WILL REMAIN EAST OF HIGHWAY 83 TONIGHT AND
SUNDAY. MVFR AND PERHAPS IFR CIGS/VSBY WILL DEVELOP FROM KANW EAST.
THE LATEST RAP MODEL SUGGESTS THE FRONT WILL REACH CLOSE TO KVTN
BUT NOT THROUGH KVTN. THUS A BRIEF PERIOD OF IFR CIGS MAY DEVELOP
TOWARD MORNING. LOW PRESSURE ACROSS THE CNTL/NRN HIGH PLAINS
SUNDAY WILL LIFT THE FRONT NORTH AND EAST A BIT BUT AREAS ALONG
AND EAST OF 183 SHOULD REMAIN IN IFR/MVFR THROUGHOUT THE DAY
SUNDAY AND PERHAPS BEYOND.
NOTE THAT EVERY ARCTIC FRONT BEHAVES A LITTLE DIFFERENT. SOME
PRODUCE WIDESPREAD FOG OTHERS FOG JUST ON THE LEADING EDGE AND YET OTHERS
PRODUCE NO FOG AT ALL...JUST LOW CIGS. SO LOOK FOR UPDATES AT KLBF
AND KVTN AS WARRANTED. THE FRONT IS EXPECTED TO BECOME STATIONARY
NORTH AND EAST OF KLBF TONIGHT.
VFR IS EXPECTED WEST OF HIGHWAY 83 OVERNIGHT AND THROUGHOUT THE
DAY SUNDAY.
PREV DISCUSSION... /ISSUED 322 AM CST SAT DEC 22 2012/
SYNOPSIS...H5 ANALYSIS THIS MORNING HAS LOW PRESSURE OVER SRN
QUEBEC...AND OFF THE COAST OF BRITISH COLUMBIA. A DEEP TROUGH OF LOW
PRESSURE EXTENDED SOUTH FROM THE EASTERN LOW INTO NEW ENGLAND AND
THE WESTERN ATLANTIC...WHILE THE WRN TROUGH EXTENDED OFF THE COAST
OF OREGON AND NRN CALIFORNIA. ACROSS THE CENTRAL CONUS...LOW
AMPLITUDE RIDGING WAS PRESENT. AT THE SURFACE...THE LEADING EDGE OF
ARCTIC AIR...HAS PUSHED INTO SRN SD AND FAR NRN NEBRASKA THIS
AFTERNOON. TEMPERATURES HAVE FLAT LINED AROUND NOONTIME AS COLD
ARCTIC AIR BEGINS TO SEEP INTO NRN NEBRASKA. FURTHER SOUTH...TEMPS
AS OF 2 PM CST RANGED FROM 34 BEHIND THE ARCTIC FRONT AT ONEILL...TO
44 AT THEDFORD.
DISCUSSION...
SHORT RANGE...TONIGHT THROUGH TUESDAY...MAIN FORECASTING CHALLENGE
THROUGH MONDAY LIES WITH TEMPERATURES AND HIGHS SUNDAY AND
MONDAY...AND HOW FAR CAN THE ARCTIC FRONT PUSH INTO SOUTHWESTERN AND
WESTERN NEBRASKA. AFTER MONDAY...PRECIPITATION CHANCES...AND SNOW
ACCUMULATIONS MONDAY NIGHT INTO TUESDAY BECOME THE FORECAST
CHALLENGE AS A DISTURBANCE TRACKS SOUTHEAST ACROSS THE HIGH PLAINS
AND EASTERN SLOPES OF THE ROCKIES.
FOR TONIGHT THROUGH SUNDAY NIGHT...AS MENTIONED
ABOVE...TEMPERATURES/CLOUD COVER WILL BE TRICKY AS AN ARCTIC FRONT
WILL BACK INTO THE FORECAST AREA TONIGHT INTO SUNDAY. TIME SECTIONS
ARE INDICATIVE OF A VERY SHALLOW ARCTIC AIR MASS WITH H925 TEMPS
REACHING -14C AT KONL BY 12Z SUNDAY...ALONG WITH VERY SHALLOW
MOISTURE FROM THE SFC UP TO H900. WITH TEMPS ABOVE FREEZING IN THE
H85 TO H800 LAYER...AND SOME WEAK LIFT...AM A LITTLE CONCERNED ABOUT
THE POTENTIAL FOR FZDZ IN MY NORTHEAST. HOWEVER...GIVEN THE
SHALLOWNESS OF THE MOIST LAYER AND LACK OF IT UPSTREAM IN THE
DAKOTAS...WILL FORGO MENTION AT THIS TIME. ON SUNDAY...THE FRONT WILL PUSH
EAST INTO THE CENTRAL CWA...ALLOWING HIGHS TO REACH NEAR 40 IN THE
EASTERN PANHANDLE. FURTHER EAST...HIGHS WILL STRUGGLE TO REACH THE
UPPER TEENS IN THE NORTHEASTERN CWA. A SECOND...REINFORCING SHOT OF
ARCTIC AIR WILL PUSH INTO THE FORECAST AREA SUNDAY NIGHT AS AN UPPER
LEVEL TROUGH OF LOW PRESSURE TRACKS ACROSS THE DAKOTAS. AT THIS
TIME...THE BEST MOISTURE AND LIFT WITHIN THE DENDRITIC LAYER WILL BE
OFF TO THE NORTHEAST OF THE FORECAST AREA...SO A DRY FCST CONTINUES.
ON MONDAY AND MONDAY NIGHT...ARCTIC HIGH PRESSURE WILL BUILD INTO
THE NORTHERN AND CENTRAL PLAINS MONDAY FORCING A THIRD AND STRONGER
ARCTIC FRONT INTO THE CWA. EASTERLY WINDS WILL BEGIN TO INCREASE
MONDAY AFTERNOON AS HIGH PRESSURE BUILDS INTO THE NORTHERN
PLAINS...INCREASING UPSLOPE FLOW ACROSS THE WESTERN HALF OF THE
FORECAST AREA. BY MONDAY AFTERNOON...ISENTROPIC LIFT WILL INCREASE
ACROSS THE PANHANDLE AND BEGIN TO SPREAD EAST INTO WESTERN NEBRASKA
MONDAY EVENING. DECIDED TO INCREASE PRECIPITATION CHANCES IN THE
WEST FOR MONDAY NIGHT WITH DECENT AGREEMENT NOTED BETWEEN THE NAM
AND GFS SOLNS. AS IT STANDS...THE BEST CHANCES FOR ACCUMULATING SNOW
IS WEST OF A LINE FROM VALENTINE TO BROKEN BOW...WITH THE HIGHEST
ACCUMS POSSIBLE IN THE EASTERN PANHANDLE AND SWRN NEBRASKA...WHERE
ISENTROPIC LIFT IS MOST PRONOUNCED IN THE DENDRITIC LAYER MONDAY
NIGHT. IN THESE AREAS...2 TO 4 INCHES OF SNOW IS POSSIBLE WITH 1 TO
2 INCHES POSSIBLE IN PORTIONS OF CENTRAL NEBRASKA INTO THE CENTRAL
SANDHILLS. FOR NORTH PLATTE...AROUND 2 INCHES IS POSSIBLE...WITH
AROUND AN INCH POSSIBLE FOR VALENTINE. LIFT WILL BEGIN TO WEAKEN
SIGNIFICANTLY TUESDAY MORNING AS THE UPPER LEVEL LOW DROPS INTO THE
SRN PLAINS. SINCE THIS IS A HEAVY TRAVEL DAY...WILL BE ISSUING A
SPECIAL WEATHER STATEMENT WITH THIS PACKAGE.
LONG RANGE...TUESDAY NIGHT THROUGH SATURDAY...BITTERLY COLD
TEMPERATURES WILL PUSH INTO THE HIGH PLAINS TUESDAY NIGHT AS ARCTIC
HIGH PRESSURE BUILDS INTO THE DAKOTAS AND NEBRASKA. LOWS TUESDAY
NIGHT WERE TRENDED DOWNWARD TO THE SINGLE DIGITS BELOW ZERO. THIS
WAS A CONSERVATIVE ADJUSTMENT AS THE LATEST MEX HAS -19 FOR KLBF
WEDS MORNING...WITH A HIGH OF JUST 11. ARCTIC AIR WILL REMAIN
ENTRENCHED ACROSS THE FORECAST AREA THROUGH THE END OF THE WEEK WITH
HIGHS STRUGGLING TO REACH THE MID 20S FRIDAY AND SATURDAY.
FINALLY...A SECOND UPPER LEVEL TROUGH OF LOW PRESSURE WILL CROSS THE
INTERMOUNTAIN WEST FRIDAY INTO SATURDAY WITH AN INCREASED THREAT OF
SNOW. ATTM...SOME SIGNIFICANT TIMING...TRACK AND STRENGTH
DIFFERENCES ARE NOTED BETWEEN THE EURO AND GFS MODEL SOLNS. WITH
THIS IN MIND...WILL KEEP THE INHERITED LOW POPS IN THE FCST AND NOT
INCREASE FURTHER.
AVIATION...A VERY SHALLOW ARCTIC FRONT WAS LOCATED JUST NORTH OF
THE SOUTH DAKOTA/NEBRASKA BORDER AT 19Z FROM ROUGHLY KRAP TO KICR TO
KYKN. STRATUS WAS OBSERVED ACROSS NORTH DAKOTA AND IS EXPECTED TO
EXPAND SOUTH TONIGHT INTO NORTH CENTRAL AND CENTRAL NEBRASKA. THIS
SHOULD DROP CEILINGS TO MVFR LATE TONIGHT AT KVTN. EXPECT THE
STRATUS TO HANG AROUND WELL INTO THE MORNING AND PERHAPS INTO THE
AFTERNOON. THE STRATUS LOOKS TO BE VERY SHALLOW...BUT IF THE DEPTH IS
ENOUGH...COULD GET SOME FLURRIES TO THE EAST OF KVTN. AT KLBF...IT
APPEARS THE VEIL OF STRATUS WILL STAY JUST TO THE EAST.
HOWEVER...WITH WINDS BECOMING LIGHT AND VARIABLE...BELIEVE LOCAL
TOPOGRAPHY WILL SWITCH WINDS TO THE SOUTHEAST AND COULD BRING
MOISTURE UP THE VALLEY. ACCOMPANIED WITH THE COLD AIR
DRAINAGE...COULD SEE SOME 4SM TO 6SM IN VERY SHALLOW FOG.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM/EXTENDED...TAYLOR
AVIATION...CDC
AREA FORECAST DISCUSSION
NWS BINGHAMTON NY
117 AM EST SUN DEC 23 2012
.SYNOPSIS...
A SLOW MOVING STORM OVER QUEBEC...WILL REMAIN OUR DOMINANT
FEATURE THROUGH TODAY. A MOIST NORTHWEST FLOW ASSOCIATED WITH THIS
SYSTEM...WILL CAUSE A LAKE EFFECT SNOW BAND TO DEVELOP LATE
EARLY THIS MORNING AND TODAY ACROSS UPSTATE NEW YORK...WITH
LIGHTER SNOW SHOWERS AND FLURRIES FARTHER SOUTH. HIGH PRESSURE
WILL BRIEFLY BUILD IN TONIGHT INTO MONDAY, WITH MAINLY DRY
CONDITIONS. A FAST MOVING STORM WILL MOVE INTO THE MID ATLANTIC
REGION BY LATE MONDAY, WITH A QUICK SHOT OF SNOW POSSIBLE
CHRISTMAS EVE, INTO CHRISTMAS MORNING.
&&
.NEAR TERM /THROUGH TODAY/...
UPDATE 1230 AM...LES BAND HAS INTENSIFIED DURING THE PAST COUPLE
OF HOURS ACROSS NRN ONONDAGA COUNTY, NRN MADISON AND WESTERN
ONEIDA COUNTY. H5 SHORT WAVE MOVING THROUGH SOUTHERN ONTARIO WILL
BACK THE LOW LEVEL FLOW DURING THE EARLY MORNING HOURS AND
GRADUALLY LIFT THE BAND JUST INTO ONEIDA COUNTY. MADE SHORT TERM
POPS ADJ AND INCREASED SHORT TERM SNOW ACCUMS ACROSS NRN ONONDAGA
AND NRN MADISON COUNTY INTO THE 1-3 INCH RANGE. ALSO SPREAD MORE
SNOWFALL ACROSS NRN ONEIDA COUNTY AS BAND WILL LINGER THERE
THROUGH AT LEAST MIDDAY.
PREVIOUS DISC...
LATEST RAP SOUNDINGS IN BUFKIT SUGGEST THE LES BAND WILL REMAIN
MORE OR LESS ALONG THE NORTHERN ONODAGA - MADISON COUNTY BORDER
FOR THE NEXT SEVERAL HOURS. THE SNOW BAND IS EXPECTED TO SHIFT
INTO THE ADVISORY AREA LATE OVERNIGHT...PERHAPS NOT UNTIL AFTER 2
AM.
WITH THIS IN MIND...HAVE INCREASED POPS AND SNOW AMOUNTS WITHIN
THE CURRENT BAND, AND SLIGHTLY REDUCED THE SNOW AMOUNTS IN THE
ADVISORY STATEMENT. ALSO SIGNIFICANTLY DELAYED TIMING OF MAIN BAND
SHIFT.
7 PM UPDATE...
REMOVED REMAINING WSW SEGMENTS FROM EARLIER, AS BLOWING AND
DRIFTING OF SNOW HAS LESSENED IN LIGHTER WINDS. RE-TIMED LES BAND
TO ARRIVE BETWEEN 10 PM AND MIDNIGHT.
NEEDED TO INCREASE NEAR TERM TEMPS, AS THERE HAS BEEN VERY LITTLE
MOVEMENT RECENTLY DUE TO THE THICK CLOUD COVER.
3 PM UPDATE...
STEADY SYNOPTIC/LAKE-ENHANCED SNOWFALL IS FINALLY WINDING DOWN
LATE THIS AFTN ACRS OUR ERN ZNS...AND IT SHOULD BE OVER BY
21-23Z...OTHER THAN SOME RESIDUAL -SHSN/FLRYS. SXNS OF
ONEIDA/ONONDAGA/CORTLAND/MADISON/CHENANGO CNTYS APPEARED TO
RECEIVE MAX SNOWFALL WITH THIS EVENT (LOCALLY 10-12"+).
THE NEXT CONCERN IS LES POTENTIAL LTR TNT AND SUN. BASED ON
NAM12/LOCAL WRF/4 KM ARW OUTPUT...AS WELL AS COLLAB WITH
SURROUNDING OFFICES...WE`VE DECIDED TO HOIST A LAKE SNOW ADVSY IN
NRN ONEIDA. THE BRUNT OF THE LES BAND SHOULD STAY JUST N OF NRN
ONONDAGA/NRN MADISON CNTYS...AND WE`LL THUS LEAVE THESE ZONES OUT.
WE`LL START THE LES ADVSY AFTER THE EXISTING WINTER STM WRNG
EXPIRES THIS EVE...ASSUMING IT EVEN STAYS IN TACT THIS LONG...AND
THEN CARRY IT THROUGH THE DAY SUN. A NICE GEO BAY CONNECTION
SHOULD BE IN PLAY...ALG WITH DECENT DZ MECHANICS. THUS...DESPITE
THE SLOW NWD DRIFT ANTICIPATED OVER TIME WITH GRADUALLY BACKING
WINDS...WE FELT THE ADVSY WAS WARRANTED (BRIEF SNOWFALL RATES OF
1"+ PER HOUR). OUTSIDE OF THE MAIN LES BAND...ONLY HIT AND MISS
-SHSN AND FLRYS ARE FORESEEN THROUGH SUN.
SUN NGT...THE COLUMN DRIES OUT...AND LOW-LVL WINDS BECOME FAIRLY
LGT. AS A RESULT...ONLY A FEW RESIDUAL FLRYS ARE EXPECTED IN THE
SRN TUG HILL RGN...WITH DRY WX AND PTL CLEARING ELSEWHERE.
PREV DISC... 12 NOON UPDATE... ONCE AGN...BASED ON RECENT
REPORTS/RADAR TRENDS...WE`VE UPPED TOTALS A BIT IN NWRN
ONEIDA...WRN MADISON...AND PTNS OF CORTLAND AND CHENANGO. CENTERED
ARND THE HIGH TERRAIN LOCALES IN THIS PARTICULAR RGN...IT
APPEARS WE`LL HAVE A SOLID AREA OF 10"+ TOTALS...WITH A FEW PLACES
OVER A FOOT. THE GRADIENT APPEARS TO BE RATHER TIGHT IN CHENANGO
(NW TO SE)...SO WE`LL KEEP AN ADVSY FOR THIS CNTY. IN FACT...NO
CHGS TO OUR WRNG OR ADVSY AREAS ATTM...WE JUST UPDATED THE SNOW
TOTALS MAP.
WATER VAPOR IMAGERY AND SFC OBS INDICATE THAT HVYR SNOW IS
TAPERING OFF FROM W TO E...AS A NARROW DRY SLOT ALOFT ROTATES IN
FROM WRN NY EARLY THIS AFTN. DESPITE A SHALLOWER DEPTH OF
MOISTURE...VSBL SAT IMAGERY STILL SHOWS A DISCERNIBLE CONNECTION
TO GEO BAY...SO WE`LL SIMPLY SHOW STEADY...OCNLY HVY
SNOW...TAPERING OFF TO OCNL...SOMEWHAT LGTR SNOW SHWRS UP N. FOR
THE TWIN TIERS AND NE PA...SNOW SHOULD BECOME LIGHTER AND MORE
SPOTTY WITH TIME THIS AFTN.
AS FOR THE WINDS...WE`RE STILL SEEING GUSTS IN THE 35-40 KT RANGE
ATTM...SO THE WIND ADVSY WILL REMAIN UP AS WELL.
&&
.SHORT TERM /TONIGHT THROUGH TUESDAY/...
4 PM UPDATE...
ACTIVE PATTERN CONTINUES THROUGH THE WEEK WITH TWO CHANCES AT
STORMS...THE FIRST BEING ALL SNOW AND THE SECOND TRENDING TOWARD
MORE QUESTION MARKS IN TERMS OF PTYPE. FIRST THE STORM FOR
CHRISTMAS EVE INTO CHRISTMAS DAY.
MONDAY...LINGERING LAKE EFFECT IS POSSIBLE EARLY IN THE MORNING
WITH 850 TEMPS STILL AROUND -10C/-12C ON A NORTHWEST FLOW. THIS
SHOULD BE LIMITED TO CNY AND JUST A FEW FLURRIES AS WE BEGIN TO
SEE DRIER AIR MOVE INTO THE AREA BY MIDDAY. AFTER A BRIEF BREAK
THROUGH MOST OF THE DAY...WE WILL TURN OUR ATTENTION TOWARD LATE
IN THE DAY WITH SNOW BREAKING OUT ACROSS NEPA INTO THE SOUTHERN
TIER BY EVENING. MAIN WEATHER PLAYERS ARE NOW MOVING THROUGH THE
WESTERN US...WITH UPPER LEVEL ENERGY MOVING INTO THE PACIFIC
NORTHWEST...AND A WEAK WAVE MOVING TOWARD WESTERN TEXAS. THE WEAK
WAVE MOVING TOWARD TEXAS WILL FORM A SURFACE LOW OVER THE
TENNESSEE VALLEY BY 12Z MONDAY AND THIS WILL TRACK OFF THE MID-
ATLANTIC COAST BY TUESDAY. MORE IMPORTANTLY FOR OUR AREA WILL BE
WHAT HAPPENS TO THE ENERGY MOVING INTO THE PACIFIC NORTHWEST
NOW...AS THIS TRACKS EAST ACROSS THE UPPER MIDWEST MONDAY. IT WILL
BE THIS NORTHERN SYSTEM (THE DISTURBANCE IN THE JET STREAM WINDS
ALOFT) THAT WILL BRING OUR SHOT AT SNOW CHRISTMAS EVE NIGHT. READ
ON.
MONDAY NIGHT...BOTH THE GFS/NAM/EURO ALL IN GOOD AGREEMENT WITH
SNOW DURING THIS PERIOD AND WILL GO LIKELY POPS ALL AREAS EXCEPT
NORTH OF I-90 AS THE UPPER LOW MENTIONED ABOVE TRACK RIGHT OVER
OUR AREA. IN REALITY EVEN THESE AREAS SHOULD GET INTO THE SNOW BUT
CONFIDENCE JUST SLIGHTLY LOWER WITH THE GFS SHOWING A NORTHERN
EDGE TO THE PRECIP...WHILE THE NAM AND EURO BRING QPF TO THE
ENTIRE CWA. WITH QPF AMOUNTS BETWEEN .15 AND .25"...LOOKING AT A
WIDESPREAD 2" TO 4" SNOW. AMOUNTS MAY BE SLIGHTLY LESS THAN THIS
OVER THE FAR NORTH IF THE GFS VERIFIES...WITH AMOUNTS CLOSER TO 5"
ALONG THE NY/PA POSSIBLE ESPECIALLY IF SNOW GROWTH IS AS DECENT AS
SOME OF THE MODELS SUGGEST. AMOUNTS WOULD BE BORDERLINE FOR AN
ADVISORY (CRITERIA IS 4" OR GREATER) BUT WILL MENTION IN THE HWO
GIVEN THE TRAVEL PLANS MANY HAVE CHRISTMAS EVE. THIS IS ESPECIALLY
TRUE SINCE OUR CONFIDENCE ON A WIDESPREAD SNOW IS HIGH GIVEN THE
MODEL CONSISTENCY.
TUESDAY...ANY LINGERING SNOW EARLY TUESDAY SHOULD BE QUICK TO
DIMINISH BY LATE MORNING. DESPITE COLD AIR ON THE BACKSIDE OF THE
SYSTEM...FLOW LOOKS A BIT TOO NORTHERLY OR NORTHEASTERLY FOR MORE
THAN A MENTION OF FLURRIES DURING THE AFTERNOON.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
4 PM UPDATE...
WEDNESDAY/THURSDAY...BOTH THE 12Z EURO AND GFS HAVE TRENDED MORE
INLAND AND THUS WARMER WITH THE MID-WEEK STORM. WE ARE STILL COLD
ENOUGH FOR MAINLY SNOW THROUGH THE DAYLIGHT HOURS OF
WEDNESDAY...EVEN WITH THE WARMER TREND. WILL INTRODUCE A WINTRY
MIX FROM BINGHAMTON SOUTH AND EAST WEDNESDAY NIGHT...WITH BOTH
MODELS SHOWING MID LEVEL WARMING AND P-TYPE ISSUES ABOUND. WILL
NOT GET ANY MORE SPECIFIC THAN THIS AS TRENDS CAN AND WILL CHANGE
THIS FAR OUT. WRAP AROUND SNOWS POSSIBLE ON THURSDAY...ESPECIALLY
ON THE EURO.
FRIDAY/SATURDAY...LOW CONFIDENCE FORECAST AT THE END OF NEXT WEEK
WITH BOTH THE EURO AND GFS SHOWING A NORTHWEST FLOW BUT DIFFER ON
THE AMOUNT OF COLD AIR (EURO WARMER THAN THE GFS). WILL PLAY
FLURRIES OVER NEPA TO A CHANCE OF SNOW SHOWERS OVER CNY FOR NOW.
&&
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
1230 AM UPDATE...
A BAND OF LAKE EFFECT SNOW ACROSS SYR AND RME WILL CONTINUE EARLY
THIS MORNING WITH IFR CONDITIONS AND MAYBE ALTERNATE MINIMUMS
MOSTLY DUE TO VSBYS BELOW 2 MILES. THE BAND WILL SLOWLY LIFT THE
NEXT FEW HOURS CAUSING A LOWERING AT RME BY 8Z. ROME WILL CONTINUE
WITH IFR VSBYS IN SNOW UNTIL 16Z. RME WILL BE MVFR THIS AFTN AND
EVE AS THE FLOW CONTINUES FROM THE WEST. SYR WILL BECOME MVFR BY
10Z THEN VFR BY 15Z...BUT MAY LOWER BACK TO MVFR DURING THE
EVENING WITH A RETURN OF WEAK SNOW SHOWERS.
ELM ITH BGM WILL BE MOSTLY MVFR UNTIL AROUND 15Z. SOME FLURRIES
BUT MVFR MOSTLY BECAUSE OF A 2500 FT CIG. AVP SHOULD BE FAR ENOUGH
SOUTH THAT A TEMPO THERE WILL COVER IT.
LAKE EFFECT MOISTURE WANES LATE TODAY SO SKIES MAY BECOME SCT AT
ELM AND AVP.
W WINDS AT 10 KTS EARLY THIS MORNING THROUGH THE DAY. SOME GUSTS
THIS AFTERNOON TO 20 KTS THEN DROPPING TO 5 TO 10 KTS THIS
EVENING.
OUTLOOK...
SUN OVERNGT/MON...MAINLY VFR.
MON NGT/TUE AM...MVFR/IFR POSSIBLE IN LIGHT SNOW.
TUE PM/TUE NGT...VFR.
WED/THUR...MVFR/IFR POSSIBLE IN SNOW OR A WINTRY MIX.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NY...LAKE EFFECT SNOW ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR
NYZ009.
&&
$$
SYNOPSIS...MLJ
NEAR TERM...DJP/MLJ/RRM
SHORT TERM...HEDEN
LONG TERM...HEDEN
AVIATION...TAC
AREA FORECAST DISCUSSION
NWS BINGHAMTON NY
1230 AM EST SUN DEC 23 2012
.SYNOPSIS...
A SLOW MOVING STORM OVER QUEBEC...WILL REMAIN OUR DOMINANT
FEATURE THROUGH SUNDAY. A MOIST NORTHWEST FLOW ASSOCIATED WITH
THIS SYSTEM...WILL CAUSE A LAKE-EFFECT SNOW BAND TO DEVELOP LATE
TONIGHT AND SUNDAY ACROSS UPSTATE NEW YORK...WITH LIGHTER SNOW
SHOWERS AND FLURRIES FARTHER SOUTH. HIGH PRESSURE WILL BRIEFLY
BUILD IN SUNDAY NIGHT INTO MONDAY...WITH MAINLY DRY CONDITIONS. A
FAST MOVING STORM WILL MOVE INTO THE MID-ATLANTIC REGION BY LATE
MONDAY...WITH A QUICK SHOT OF SNOW POSSIBLE CHRISTMAS EVE...INTO
EARLY CHRISTMAS MORNING.
&&
.NEAR TERM /THROUGH TODAY/...
UPDATE 1230 AM...LES BAND HAS INTENSIFIED DURING THE PAST COUPLE
OF HOURS ACROSS NRN ONONDAGA COUNTY, NRN MADISON AND WESTERN
ONEIDA COUNTY. H5 SHORT WAVE MOVING THROUGH SOUTHERN ONTARIO WILL
BACK THE LOW LEVEL FLOW DURING THE EARLY MORNING HOURS AND
GRADUALLY LIFT THE BAND JUST INTO ONEIDA COUNTY. MADE SHORT TERM
POPS ADJ AND INCREASED SHORT TERM SNOW ACCUMS ACROSS NRN ONONDAGA
AND NRN MADISON COUNTY INTO THE 1-3 INCH RANGE. ALSO SPREAD MORE
SNOWFALL ACROSS NRN ONEIDA COUNTY AS BAND WILL LINGER THERE
THROUGH AT LEAST MIDDAY.
PREVIOUS DISC...
LATEST RAP SOUNDINGS IN BUFKIT SUGGEST THE LES BAND WILL REMAIN
MORE OR LESS ALONG THE NORTHERN ONODAGA - MADISON COUNTY BORDER
FOR THE NEXT SEVERAL HOURS. THE SNOW BAND IS EXPECTED TO SHIFT
INTO THE ADVISORY AREA LATE OVERNIGHT...PERHAPS NOT UNTIL AFTER 2
AM.
WITH THIS IN MIND...HAVE INCREASED POPS AND SNOW AMOUNTS WITHIN
THE CURRENT BAND, AND SLIGHTLY REDUCED THE SNOW AMOUNTS IN THE
ADVISORY STATEMENT. ALSO SIGNIFICANTLY DELAYED TIMING OF MAIN BAND
SHIFT.
7 PM UPDATE...
REMOVED REMAINING WSW SEGMENTS FROM EARLIER, AS BLOWING AND
DRIFTING OF SNOW HAS LESSENED IN LIGHTER WINDS. RE-TIMED LES BAND
TO ARRIVE BETWEEN 10 PM AND MIDNIGHT.
NEEDED TO INCREASE NEAR TERM TEMPS, AS THERE HAS BEEN VERY LITTLE
MOVEMENT RECENTLY DUE TO THE THICK CLOUD COVER.
3 PM UPDATE...
STEADY SYNOPTIC/LAKE-ENHANCED SNOWFALL IS FINALLY WINDING DOWN
LATE THIS AFTN ACRS OUR ERN ZNS...AND IT SHOULD BE OVER BY
21-23Z...OTHER THAN SOME RESIDUAL -SHSN/FLRYS. SXNS OF
ONEIDA/ONONDAGA/CORTLAND/MADISON/CHENANGO CNTYS APPEARED TO
RECEIVE MAX SNOWFALL WITH THIS EVENT (LOCALLY 10-12"+).
THE NEXT CONCERN IS LES POTENTIAL LTR TNT AND SUN. BASED ON
NAM12/LOCAL WRF/4 KM ARW OUTPUT...AS WELL AS COLLAB WITH
SURROUNDING OFFICES...WE`VE DECIDED TO HOIST A LAKE SNOW ADVSY IN
NRN ONEIDA. THE BRUNT OF THE LES BAND SHOULD STAY JUST N OF NRN
ONONDAGA/NRN MADISON CNTYS...AND WE`LL THUS LEAVE THESE ZONES OUT.
WE`LL START THE LES ADVSY AFTER THE EXISTING WINTER STM WRNG
EXPIRES THIS EVE...ASSUMING IT EVEN STAYS IN TACT THIS LONG...AND
THEN CARRY IT THROUGH THE DAY SUN. A NICE GEO BAY CONNECTION
SHOULD BE IN PLAY...ALG WITH DECENT DZ MECHANICS. THUS...DESPITE
THE SLOW NWD DRIFT ANTICIPATED OVER TIME WITH GRADUALLY BACKING
WINDS...WE FELT THE ADVSY WAS WARRANTED (BRIEF SNOWFALL RATES OF
1"+ PER HOUR). OUTSIDE OF THE MAIN LES BAND...ONLY HIT AND MISS
-SHSN AND FLRYS ARE FORESEEN THROUGH SUN.
SUN NGT...THE COLUMN DRIES OUT...AND LOW-LVL WINDS BECOME FAIRLY
LGT. AS A RESULT...ONLY A FEW RESIDUAL FLRYS ARE EXPECTED IN THE
SRN TUG HILL RGN...WITH DRY WX AND PTL CLEARING ELSEWHERE.
PREV DISC... 12 NOON UPDATE... ONCE AGN...BASED ON RECENT
REPORTS/RADAR TRENDS...WE`VE UPPED TOTALS A BIT IN NWRN
ONEIDA...WRN MADISON...AND PTNS OF CORTLAND AND CHENANGO. CENTERED
ARND THE HIGH TERRAIN LOCALES IN THIS PARTICULAR RGN...IT APPEARS
WE`LL HAVE A SOLID AREA OF 10"+ TOTALS...WITH A FEW PLACES OVER A
FOOT. THE GRADIENT APPEARS TO BE RATHER TIGHT IN CHENANGO (NW TO
SE)...SO WE`LL KEEP AN ADVSY FOR THIS CNTY. IN FACT...NO CHGS TO
OUR WRNG OR ADVSY AREAS ATTM...WE JUST UPDATED THE SNOW TOTALS
MAP.
WATER VAPOR IMAGERY AND SFC OBS INDICATE THAT HVYR SNOW IS TAPERING
OFF FROM W TO E...AS A NARROW DRY SLOT ALOFT ROTATES IN FROM WRN
NY EARLY THIS AFTN. DESPITE A SHALLOWER DEPTH OF MOISTURE...VSBL
SAT IMAGERY STILL SHOWS A DISCERNIBLE CONNECTION TO GEO BAY...SO
WE`LL SIMPLY SHOW STEADY...OCNLY HVY SNOW...TAPERING OFF TO
OCNL...SOMEWHAT LGTR SNOW SHWRS UP N. FOR THE TWIN TIERS AND NE
PA...SNOW SHOULD BECOME LIGHTER AND MORE SPOTTY WITH TIME THIS
AFTN.
AS FOR THE WINDS...WE`RE STILL SEEING GUSTS IN THE 35-40 KT RANGE
ATTM...SO THE WIND ADVSY WILL REMAIN UP AS WELL.
&&
.SHORT TERM /TONIGHT THROUGH TUESDAY/...
4 PM UPDATE...
ACTIVE PATTERN CONTINUES THROUGH THE WEEK WITH TWO CHANCES AT
STORMS...THE FIRST BEING ALL SNOW AND THE SECOND TRENDING TOWARD
MORE QUESTION MARKS IN TERMS OF PTYPE. FIRST THE STORM FOR
CHRISTMAS EVE INTO CHRISTMAS DAY.
MONDAY...LINGERING LAKE EFFECT IS POSSIBLE EARLY IN THE MORNING WITH 850
TEMPS STILL AROUND -10C/-12C ON A NORTHWEST FLOW. THIS SHOULD BE
LIMITED TO CNY AND JUST A FEW FLURRIES AS WE BEGIN TO SEE DRIER AIR
MOVE INTO THE AREA BY MIDDAY. AFTER A BRIEF BREAK THROUGH MOST OF
THE DAY...WE WILL TURN OUR ATTENTION TOWARD LATE IN THE DAY WITH
SNOW BREAKING OUT ACROSS NEPA INTO THE SOUTHERN TIER BY EVENING.
MAIN WEATHER PLAYERS ARE NOW MOVING THROUGH THE WESTERN US...WITH
UPPER LEVEL ENERGY MOVING INTO THE PACIFIC NORTHWEST...AND A WEAK
WAVE MOVING TOWARD WESTERN TEXAS. THE WEAK WAVE MOVING TOWARD TEXAS
WILL FORM A SURFACE LOW OVER THE TENNESSEE VALLEY BY 12Z MONDAY
AND THIS WILL TRACK OFF THE MID-ATLANTIC COAST BY TUESDAY. MORE
IMPORTANTLY FOR OUR AREA WILL BE WHAT HAPPENS TO THE ENERGY MOVING
INTO THE PACIFIC NORTHWEST NOW...AS THIS TRACKS EAST ACROSS THE
UPPER MIDWEST MONDAY. IT WILL BE THIS NORTHERN SYSTEM (THE
DISTURBANCE IN THE JET STREAM WINDS ALOFT) THAT WILL BRING OUR
SHOT AT SNOW CHRISTMAS EVE NIGHT. READ ON.
MONDAY NIGHT...BOTH THE GFS/NAM/EURO ALL IN GOOD AGREEMENT WITH SNOW
DURING THIS PERIOD AND WILL GO LIKELY POPS ALL AREAS EXCEPT NORTH OF
I-90 AS THE UPPER LOW MENTIONED ABOVE TRACK RIGHT OVER OUR AREA. IN
REALITY EVEN THESE AREAS SHOULD GET INTO THE SNOW BUT CONFIDENCE
JUST SLIGHTLY LOWER WITH THE GFS SHOWING A NORTHERN EDGE TO THE
PRECIP...WHILE THE NAM AND EURO BRING QPF TO THE ENTIRE CWA. WITH
QPF AMOUNTS BETWEEN .15 AND .25"...LOOKING AT A WIDESPREAD 2" TO
4" SNOW. AMOUNTS MAY BE SLIGHTLY LESS THAN THIS OVER THE FAR NORTH
IF THE GFS VERIFIES...WITH AMOUNTS CLOSER TO 5" ALONG THE NY/PA
POSSIBLE ESPECIALLY IF SNOW GROWTH IS AS DECENT AS SOME OF THE
MODELS SUGGEST. AMOUNTS WOULD BE BORDERLINE FOR AN ADVISORY
(CRITERIA IS 4" OR GREATER) BUT WILL MENTION IN THE HWO GIVEN THE
TRAVEL PLANS MANY HAVE CHRISTMAS EVE. THIS IS ESPECIALLY TRUE
SINCE OUR CONFIDENCE ON A WIDESPREAD SNOW IS HIGH GIVEN THE MODEL
CONSISTENCY.
TUESDAY...ANY LINGERING SNOW EARLY TUESDAY SHOULD BE QUICK TO
DIMINISH BY LATE MORNING. DESPITE COLD AIR ON THE BACKSIDE OF THE
SYSTEM...FLOW LOOKS A BIT TOO NORTHERLY OR NORTHEASTERLY FOR MORE
THAN A MENTION OF FLURRIES DURING THE AFTERNOON.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
4 PM UPDATE...
WEDNESDAY/THURSDAY...BOTH THE 12Z EURO AND GFS HAVE TRENDED MORE
INLAND AND THUS WARMER WITH THE MID-WEEK STORM. WE ARE STILL COLD
ENOUGH FOR MAINLY SNOW THROUGH THE DAYLIGHT HOURS OF
WEDNESDAY...EVEN WITH THE WARMER TREND. WILL INTRODUCE A WINTRY MIX
FROM BINGHAMTON SOUTH AND EAST WEDNESDAY NIGHT...WITH BOTH MODELS
SHOWING MID LEVEL WARMING AND P-TYPE ISSUES ABOUND. WILL NOT GET ANY
MORE SPECIFIC THAN THIS AS TRENDS CAN AND WILL CHANGE THIS FAR OUT.
WRAP AROUND SNOWS POSSIBLE ON THURSDAY...ESPECIALLY ON THE EURO.
FRIDAY/SATURDAY...LOW CONFIDENCE FORECAST AT THE END OF NEXT WEEK
WITH BOTH THE EURO AND GFS SHOWING A NORTHWEST FLOW BUT DIFFER ON
THE AMOUNT OF COLD AIR (EURO WARMER THAN THE GFS). WILL PLAY
FLURRIES OVER NEPA TO A CHANCE OF SNOW SHOWERS OVER CNY FOR NOW.
&&
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
00Z UPDATE...
SNOW IS WINDING DOWN AT THIS TIME WITH ALL TERMINALS GOING VFR AT
THIS TIME, THOUGH SOME MVFR CIGS MAY STILL EXIST AT KRME FOR THE
NEXT TWO HOURS. ANOTHER LAKE BAND WILL SET UP ACROSS FAR NORTHERN
TERMINALS AFTER 04Z TONIGHT WITH POTENTIAL IFR EXISTING AT KSYR
AND KRME THROUGH 10Z-12Z. ELSEWHERE EXPECT TERMINALS TO, AT WORST,
DIP DOWN TO MVFR CIGS OVERNIGHT. ALL SITES EXPECTED TO BECOME VFR
AFTER 14Z SUNDAY.
WINDS WILL REMAIN OUT OF THE NORTHWEST EARLY AROUND 10-15KTS WITH
GUSTS APPROACHING 20-30KTS. WINDS WILL GRADUALLY BECOME MORE WSW
AFTER 10Z AROUND 10KTS.
OUTLOOK...
SUN NGT/MON...MAINLY VFR.
MON NGT/TUE...MVFR/IFR POSSIBLE IN LIGHT SNOW.
WED/THUR...MVFR/IFR POSSIBLE IN SNOW OR A WINTRY MIX.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NY...LAKE EFFECT SNOW ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR
NYZ009.
&&
$$
SYNOPSIS...MLJ
NEAR TERM...DJP/MLJ/RRM
SHORT TERM...HEDEN
LONG TERM...HEDEN
AVIATION...PVN
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA...UPDATED
NWS SIOUX FALLS SD
1139 AM CST SUN DEC 23 2012
.AVIATION /DISCUSSION FOR 18Z TAFS/...
VFR CONDITIONS ARE EXPECTED IN THE EARLY HOURS OF THE TAF PD.
BETTER SIGNALS TODAY FROM NAM/GFS AS FAR AS STRATUS DEVELOPMENT AT
THE TAF SITES LATER TONIGHT. WILL KEEP VFR UNTIL AROUND 03Z-04Z AT
KFSD AND KSUX AND 00Z-02Z AT KHON. SOME FLURRIES MAY MATERIALIZE
AT KHON BUT SIGNIFICANT RESTRICTION TO VISIBILITY IS NOT EXPECTED.
/SALLY
&&
.PREV DISCUSSION... /ISSUED 1043 AM CST SUN DEC 23 2012/
UPDATE...
UPDATED SKY COVER TO REFLECT CURRENT TRENDS WITH LESS SKY COVER
ROUGHLY WEST OF 1-29 AND MCLDY IN AND JUST AROUND THE BUFFALO
RIDGE AREA. TEMPS ARE ON TRACK SO NO ADJUSTMENTS MADE THERE.
/SALLY
PREV DISCUSSION... /ISSUED 540 AM CST SUN DEC 23 2012/
DISCUSSION.../ISSUED AT 330 AM CST/
PROBABLY ONE OF THE BIGGEST CHALLENGES OVER THE NEXT FEW DAYS IS
FIGURING OUT SKY COVER. AND THAT CERTAINLY IS THE CHALLENGE IN THE
SHORTER TERM TODAY ALSO. STRATUS EXISTS IN MINNESOTA...CURRENTLY
EDGING INTO OUR EASTERN ZONES AS IT MOVES SOUTH TO SOUTHWEST. IN
ADDITION...STRATUS ALSO EXISTS ON THE WESTERN EDGE OF OUR FORECAST
AREA. THE STRATUS IN MINNESOTA HAS NOT BEEN PICKED UP BY THE MODELS
EXCEPT FOR MAYBE THE RAP. HOWEVER THE RAP HAS STRATUS NEARLY
EVERYWHERE AT THIS TIME. THE STRATUS ON OUR WESTERN EDGE WAS BETTER
FORECAST BY THE MODELS. IT HAS BEEN TRYING TO TREND WESTWARD ALONG A
LOW LEVEL WIND WHICH IS OUT OF THE NORTHEAST...BUT IT IS ALSO
EXPANDING INTO CENTRAL NEBRASKA. SO WHAT TO DO. FIRST OF ALL...HIGH
LEVEL CLOUDINESS...AT LEAST OF THE OFF AND ON VARIETY...SHOULD BE
ABUNDANT TODAY. SO OVERALL SKY COVER SHOULD NOT BE REAL PRISTINE
ANYWHERE IN OUR FORECAST AREA. THE WESTERN STRATUS MAY TRY TO
RETREAT A BIT WESTWARD THIS MORNING. HOWEVER IT THEN MAY TRY TO
SNEAK BACK IN THIS AFTERNOON DEEPER INTO OUR SOUTHWEST ZONES AS
WINDS OFF THE SURFACE BACK A BIT TO THE NORTH/NORTHWEST IN THAT
AREA. THE EASTERN PLAINS STRATUS IS MORE PROBLEMATIC. THIS STRATUS
VERY LIKELY HAS A SHALLOWER DEPTH. AND AT LEAST ON THE SATELLITE
PICTURE IT LOOKS AS THOUGH IT IS GETTING FRAGMENTED A BIT IN CENTRAL
AND NORTHERN MN UNDER SUBSIDENCE. NONETHELESS...IT WILL LIKELY
IMPACT SOME OF OUR EASTERN ZONES THIS MORNING...BEFORE POSSIBLY
DISSIPATING SOME THIS AFTERNOON. TEMPERATURES IN THAT STRATUS LAYER
ARE VERY EFFICIENT FOR SNOW MAKING...SO WOULD NOT EVEN RULE OUT AN
ISOLATED FLURRY THIS MORNING IN MUCH OF OUR EAST. FOR TEMPERATURES...
DID NOT NEED TO ALTER THEM MUCH AT ALL FROM THE PREVIOUS FORECAST.
MAX READINGS SHOULD BE IN THE TEENS...WITH SOME 20S IN OUR FAR
SOUTHWEST ZONES.
A SHORT WAVE THEN MOVES EASTWARD ACROSS OUR AREA LATE THIS AFTERNOON
AND TONIGHT. UPPER QG FORCING BOTH OFF THE NAM AND GFS SHOWS THE
MAIN WAVE JUST TO THE NORTH OF OUR FORECAST AREA. HOWEVER THE
MOISTURE DEPTH IS DEEP ENOUGH IN OUR NORTHERN ZONES...COUPLED WITH
EFFICIENT -10C TO -15C AIR JUST OFF THE SURFACE AND ISENTROPIC
LIFT...THAT LIGHT SNOW OR FLURRIES IS STILL A THREAT. BEHIND
TONIGHTS WAVE...COLD AIR ADVECTION BEGINS TO POUR IN AGAIN WHICH
WILL KEEP THE NORTHERLY WINDS STIRRED UP SOME. HOWEVER DUE TO
ANTICIPATED CLOUD COVER...THE LOWS SHOULD NOT BOTTOM OUT HORRIBLY
BAD FOR THIS TIME OF YEAR.
SUBTLE UPPER RIDGING IS IN PLACE ON A COLD MONDAY IN BETWEEN TWO
WAVES. SKY COVER IS A REAL CHALLENGE. STRATUS MAY LINGER IN OUR
EASTERN ZONES WITH THE COLD AIR ADVECTION. HOWEVER ONE WORRIES ABOUT
SUBSIDENCE BREAKING IT APART SOONER THAN CURRENTLY FORECAST. IN COLD
AIR...MODEL LOW LEVEL HUMIDITY FIELDS AND CONDENSATION PRESSURE
DEFICITS CAN BE WAY OVERDONE SOMETIMES MAKING IT LESS THAN
TRUSTWORTHY. OUR WESTERN ZONES MAY SEE SOME PARTIAL CLEARING BEFORE
THE UPPER TROUGH IN THE ROCKIES MOVES CLOSER TO OUR AREA CASTING
SOME MID AND UPPER CLOUDINESS IN THOSE AREAS. AGAIN...MAX
TEMPERATURES STILL LOOK GOOD FROM YESTERDAYS FORECAST WITH READINGS
A FEW DEGREES EITHER SIDE OF 10. COUPLED WITH A BRISK COLD AIR
ADVECTION WIND...WIND CHILL READINGS WILL BE SUB ZERO.
THE COLD AIR ADVECTION CONTINUES TO DRAIN DOWN MONDAY NIGHT AND
TUESDAY FROM A LARGE SURFACE HIGH IN WESTERN AND SOUTHERN CANADA.
THEREFORE THE NORTHERLY WINDS WILL CONTINUE TO STAY RATHER BRISK.
LOWS SHOULD BE MOSTLY SUB ZERO MONDAY NIGHT EXCEPT POSSIBLY IN OUR
FAR SOUTHERN ZONES...AND MANY LOCATIONS WILL NOT GET OUT OF THE
SINGLE DIGITS ON CHRISTMAS. THE AFOREMENTIONED ROCKY MOUNTAIN UPPER
WAVE IS DIVING TO THE SOUTH...LARGELY NOT AFFECTING OUR FORECAST
AREA EXCEPT FOR POSSIBLY GIVING MID AND HIGH LEVEL CLOUDINESS. ONE
AREA OF MAJOR CONCERN IS MONDAY NIGHT...CONCERNING LOWS IN OUR
EASTERN ZONES. SOME INDICATIONS ARE THAT CLOUD COVER IN THAT AREA
WILL BE THIN...AS THE THICKER CLOUDS MOVE SOUTHWARD WITH THE UPPER
WAVE. IF THIS HAPPENS...LOWS COULD BE COLDER THAN FORECAST DESPITE
SOME WIND. THIS IS MENTIONED BECAUSE WE ARE ALREADY FORECASTING WIND
CHILL ADVISORY CRITERIA MONDAY NIGHT AND TUESDAY MORNING FOR ALL
AREAS EXCEPT THE MISSOURI RIVER VALLEY. WIND CHILL READINGS LOOK TO
BE COMMONLY -20F TO -25F. SO ANY COLDER LOWS IN OUR EAST MAY PRESS
WIND CHILL WARNING CRITERIA.
FINALLY ON TUESDAY NIGHT...KEPT THE PREVIOUS LOWS GOING WHICH ARE
MUCH COLDER THEN ALL CONSENSUS GUIDANCES. JUST NOT BUYING THE AMOUNT
OF CLOUD COVER THE MODELS ARE TRYING TO KICK OUT...AND WINDS WILL
FINALLY SLACKEN OFF. COLD CANADIAN HIGH PRESSURE EXTENDS ALL THE WAY
FROM CANADA TO SOUTH TEXAS BY THIS TIME...WITH THE SURFACE RIDGE
MOVING CLOSE TO THE I 29 CORRIDOR. THEREFORE LOWS SHOULD RANGE FROM
AROUND -12F IN OUR FAR NORTHERN ZONES...TO NEAR -5F IN OUR FAR
SOUTH. /MJF
FOR WED THROUGH SAT...THE MAIN FOCUS IS ON THE POTENTIAL FOR SNOW ON
FROM THURSDAY THROUGH FRIDAY. THE 00Z ECMWF HAS TRENDED TOWARD THE
OPERATIONAL 00Z GFS WITH BOTH MODELS NOW SHOWING THE POLAR VORTEX
CENTERED NEAR 100 W IN CANADA. THIS PREVENTS AS MUCH AMPLIFICATION
OF THE RIDGE AS WOULD BE EXPECTED WITH A DEEPENING EAST COAST
CYCLONE. THIS RESULTS IN A FASTER PROGRESSION OF THE WAVE AS WELL AS
LESS FOCUSED ASCENT. THE 00Z CANADIAN GEM ALSO SUPPORTS THIS
SOLUTION WHICH FITS THE MEAN GFS ENSEMBLE. THEREFORE...HAVE RAISED
POPS A BIT ON THURSDAY NIGHT WHILE LOWERING/REMOVING POPS ON FRIDAY
NIGHT WEST OF I29.
ALL MODELS AGREE THE RIDGE WILL HANG OVER SW MN AND NW IA
THROUGH WED NIGHT AND WITH SOME CLEARING AND LIGHT WINDS. THIS WILL
KEEP IT WELL BELOW NORMAL ON WEDNESDAY WITH HIGHS FROM 5 TO 15
ABOVE. AND...WHILE NOT COMPLETELY CONFIDENT YET...SEEMS AS IF THIS
SHOULD BE A GOOD RADIATION NIGHT AND HAVE LOWERED MINS TO -5 TO -10
EAST OF I29. INCREASING SOUTHEAST FLOW WILL KEEP TEMPS ABOVE ZERO
WEST OF I29. DESPITE WARM ADVECTION THURSDAY AND FRIDAY...IT WILL
REMAIN BELOW NORMAL AS MOST OF THE WARM ADVECTION GOES TO LARGE
SCALE ASCENT AND CLOUDS OVERSPREAD THE AREA. HAVE A SLIGHT CHANCE OF
SNOW THURSDAY WITH A CHANCE OF SNOW FOR THE ENTIRE AREA THURSDAY
NIGHT AND FRIDAY. THE DURATION OF ANY ACCUMULATING SNOW WILL LIKELY
BE LESS THAN 12 HOURS BUT AT THIS POINT IT IS MOSTLY LIKELY GOING TO
STRADDLE 12Z. AT THIS POINT...SNOWFALL WITH THIS EVENT LOOKS TO BE
RATHER LIGHT. COLD AIR AND FAIRLY STRONG NORTHWEST WINDS WILL SPREAD
OVER THE AREA FRIDAY NIGHT AND SATURDAY WITH HIGHS SATURDAY BACK
BETWEEN 10 AND 15 ABOVE...WITH THE POTENTIAL TO BE EVEN COLDER.
/SCHUMACHER
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
MN...NONE.
NE...NONE.
SD...NONE.
&&
$$
99/99/99
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA...UPDATED
NWS SIOUX FALLS SD
1043 AM CST SUN DEC 23 2012
.UPDATE...
UPDATED SKY COVER TO REFLECT CURRENT TRENDS WITH LESS SKY COVER
ROUGHLY WEST OF 1-29 AND MCLDY IN AND JUST AROUND THE BUFFALO
RIDGE AREA. TEMPS ARE ON TRACK SO NO ADJUSTMENTS MADE THERE.
/SALLY
&&
.PREV DISCUSSION... /ISSUED 540 AM CST SUN DEC 23 2012/
DISCUSSION.../ISSUED AT 330 AM CST/
PROBABLY ONE OF THE BIGGEST CHALLENGES OVER THE NEXT FEW DAYS IS
FIGURING OUT SKY COVER. AND THAT CERTAINLY IS THE CHALLENGE IN THE
SHORTER TERM TODAY ALSO. STRATUS EXISTS IN MINNESOTA...CURRENTLY
EDGING INTO OUR EASTERN ZONES AS IT MOVES SOUTH TO SOUTHWEST. IN
ADDITION...STRATUS ALSO EXISTS ON THE WESTERN EDGE OF OUR FORECAST
AREA. THE STRATUS IN MINNESOTA HAS NOT BEEN PICKED UP BY THE MODELS
EXCEPT FOR MAYBE THE RAP. HOWEVER THE RAP HAS STRATUS NEARLY
EVERYWHERE AT THIS TIME. THE STRATUS ON OUR WESTERN EDGE WAS BETTER
FORECAST BY THE MODELS. IT HAS BEEN TRYING TO TREND WESTWARD ALONG A
LOW LEVEL WIND WHICH IS OUT OF THE NORTHEAST...BUT IT IS ALSO
EXPANDING INTO CENTRAL NEBRASKA. SO WHAT TO DO. FIRST OF ALL...HIGH
LEVEL CLOUDINESS...AT LEAST OF THE OFF AND ON VARIETY...SHOULD BE
ABUNDANT TODAY. SO OVERALL SKY COVER SHOULD NOT BE REAL PRISTINE
ANYWHERE IN OUR FORECAST AREA. THE WESTERN STRATUS MAY TRY TO
RETREAT A BIT WESTWARD THIS MORNING. HOWEVER IT THEN MAY TRY TO
SNEAK BACK IN THIS AFTERNOON DEEPER INTO OUR SOUTHWEST ZONES AS
WINDS OFF THE SURFACE BACK A BIT TO THE NORTH/NORTHWEST IN THAT
AREA. THE EASTERN PLAINS STRATUS IS MORE PROBLEMATIC. THIS STRATUS
VERY LIKELY HAS A SHALLOWER DEPTH. AND AT LEAST ON THE SATELLITE
PICTURE IT LOOKS AS THOUGH IT IS GETTING FRAGMENTED A BIT IN CENTRAL
AND NORTHERN MN UNDER SUBSIDENCE. NONETHELESS...IT WILL LIKELY
IMPACT SOME OF OUR EASTERN ZONES THIS MORNING...BEFORE POSSIBLY
DISSIPATING SOME THIS AFTERNOON. TEMPERATURES IN THAT STRATUS LAYER
ARE VERY EFFICIENT FOR SNOW MAKING...SO WOULD NOT EVEN RULE OUT AN
ISOLATED FLURRY THIS MORNING IN MUCH OF OUR EAST. FOR TEMPERATURES...
DID NOT NEED TO ALTER THEM MUCH AT ALL FROM THE PREVIOUS FORECAST.
MAX READINGS SHOULD BE IN THE TEENS...WITH SOME 20S IN OUR FAR
SOUTHWEST ZONES.
A SHORT WAVE THEN MOVES EASTWARD ACROSS OUR AREA LATE THIS AFTERNOON
AND TONIGHT. UPPER QG FORCING BOTH OFF THE NAM AND GFS SHOWS THE
MAIN WAVE JUST TO THE NORTH OF OUR FORECAST AREA. HOWEVER THE
MOISTURE DEPTH IS DEEP ENOUGH IN OUR NORTHERN ZONES...COUPLED WITH
EFFICIENT -10C TO -15C AIR JUST OFF THE SURFACE AND ISENTROPIC
LIFT...THAT LIGHT SNOW OR FLURRIES IS STILL A THREAT. BEHIND
TONIGHTS WAVE...COLD AIR ADVECTION BEGINS TO POUR IN AGAIN WHICH
WILL KEEP THE NORTHERLY WINDS STIRRED UP SOME. HOWEVER DUE TO
ANTICIPATED CLOUD COVER...THE LOWS SHOULD NOT BOTTOM OUT HORRIBLY
BAD FOR THIS TIME OF YEAR.
SUBTLE UPPER RIDGING IS IN PLACE ON A COLD MONDAY IN BETWEEN TWO
WAVES. SKY COVER IS A REAL CHALLENGE. STRATUS MAY LINGER IN OUR
EASTERN ZONES WITH THE COLD AIR ADVECTION. HOWEVER ONE WORRIES ABOUT
SUBSIDENCE BREAKING IT APART SOONER THAN CURRENTLY FORECAST. IN COLD
AIR...MODEL LOW LEVEL HUMIDITY FIELDS AND CONDENSATION PRESSURE
DEFICITS CAN BE WAY OVERDONE SOMETIMES MAKING IT LESS THAN
TRUSTWORTHY. OUR WESTERN ZONES MAY SEE SOME PARTIAL CLEARING BEFORE
THE UPPER TROUGH IN THE ROCKIES MOVES CLOSER TO OUR AREA CASTING
SOME MID AND UPPER CLOUDINESS IN THOSE AREAS. AGAIN...MAX
TEMPERATURES STILL LOOK GOOD FROM YESTERDAYS FORECAST WITH READINGS
A FEW DEGREES EITHER SIDE OF 10. COUPLED WITH A BRISK COLD AIR
ADVECTION WIND...WIND CHILL READINGS WILL BE SUB ZERO.
THE COLD AIR ADVECTION CONTINUES TO DRAIN DOWN MONDAY NIGHT AND
TUESDAY FROM A LARGE SURFACE HIGH IN WESTERN AND SOUTHERN CANADA.
THEREFORE THE NORTHERLY WINDS WILL CONTINUE TO STAY RATHER BRISK.
LOWS SHOULD BE MOSTLY SUB ZERO MONDAY NIGHT EXCEPT POSSIBLY IN OUR
FAR SOUTHERN ZONES...AND MANY LOCATIONS WILL NOT GET OUT OF THE
SINGLE DIGITS ON CHRISTMAS. THE AFOREMENTIONED ROCKY MOUNTAIN UPPER
WAVE IS DIVING TO THE SOUTH...LARGELY NOT AFFECTING OUR FORECAST
AREA EXCEPT FOR POSSIBLY GIVING MID AND HIGH LEVEL CLOUDINESS. ONE
AREA OF MAJOR CONCERN IS MONDAY NIGHT...CONCERNING LOWS IN OUR
EASTERN ZONES. SOME INDICATIONS ARE THAT CLOUD COVER IN THAT AREA
WILL BE THIN...AS THE THICKER CLOUDS MOVE SOUTHWARD WITH THE UPPER
WAVE. IF THIS HAPPENS...LOWS COULD BE COLDER THAN FORECAST DESPITE
SOME WIND. THIS IS MENTIONED BECAUSE WE ARE ALREADY FORECASTING WIND
CHILL ADVISORY CRITERIA MONDAY NIGHT AND TUESDAY MORNING FOR ALL
AREAS EXCEPT THE MISSOURI RIVER VALLEY. WIND CHILL READINGS LOOK TO
BE COMMONLY -20F TO -25F. SO ANY COLDER LOWS IN OUR EAST MAY PRESS
WIND CHILL WARNING CRITERIA.
FINALLY ON TUESDAY NIGHT...KEPT THE PREVIOUS LOWS GOING WHICH ARE
MUCH COLDER THEN ALL CONSENSUS GUIDANCES. JUST NOT BUYING THE AMOUNT
OF CLOUD COVER THE MODELS ARE TRYING TO KICK OUT...AND WINDS WILL
FINALLY SLACKEN OFF. COLD CANADIAN HIGH PRESSURE EXTENDS ALL THE WAY
FROM CANADA TO SOUTH TEXAS BY THIS TIME...WITH THE SURFACE RIDGE
MOVING CLOSE TO THE I 29 CORRIDOR. THEREFORE LOWS SHOULD RANGE FROM
AROUND -12F IN OUR FAR NORTHERN ZONES...TO NEAR -5F IN OUR FAR
SOUTH. /MJF
FOR WED THROUGH SAT...THE MAIN FOCUS IS ON THE POTENTIAL FOR SNOW ON
FROM THURSDAY THROUGH FRIDAY. THE 00Z ECMWF HAS TRENDED TOWARD THE
OPERATIONAL 00Z GFS WITH BOTH MODELS NOW SHOWING THE POLAR VORTEX
CENTERED NEAR 100 W IN CANADA. THIS PREVENTS AS MUCH AMPLIFICATION
OF THE RIDGE AS WOULD BE EXPECTED WITH A DEEPENING EAST COAST
CYCLONE. THIS RESULTS IN A FASTER PROGRESSION OF THE WAVE AS WELL AS
LESS FOCUSED ASCENT. THE 00Z CANADIAN GEM ALSO SUPPORTS THIS
SOLUTION WHICH FITS THE MEAN GFS ENSEMBLE. THEREFORE...HAVE RAISED
POPS A BIT ON THURSDAY NIGHT WHILE LOWERING/REMOVING POPS ON FRIDAY
NIGHT WEST OF I29.
ALL MODELS AGREE THE RIDGE WILL HANG OVER SW MN AND NW IA
THROUGH WED NIGHT AND WITH SOME CLEARING AND LIGHT WINDS. THIS WILL
KEEP IT WELL BELOW NORMAL ON WEDNESDAY WITH HIGHS FROM 5 TO 15
ABOVE. AND...WHILE NOT COMPLETELY CONFIDENT YET...SEEMS AS IF THIS
SHOULD BE A GOOD RADIATION NIGHT AND HAVE LOWERED MINS TO -5 TO -10
EAST OF I29. INCREASING SOUTHEAST FLOW WILL KEEP TEMPS ABOVE ZERO
WEST OF I29. DESPITE WARM ADVECTION THURSDAY AND FRIDAY...IT WILL
REMAIN BELOW NORMAL AS MOST OF THE WARM ADVECTION GOES TO LARGE
SCALE ASCENT AND CLOUDS OVERSPREAD THE AREA. HAVE A SLIGHT CHANCE OF
SNOW THURSDAY WITH A CHANCE OF SNOW FOR THE ENTIRE AREA THURSDAY
NIGHT AND FRIDAY. THE DURATION OF ANY ACCUMULATING SNOW WILL LIKELY
BE LESS THAN 12 HOURS BUT AT THIS POINT IT IS MOSTLY LIKELY GOING TO
STRADDLE 12Z. AT THIS POINT...SNOWFALL WITH THIS EVENT LOOKS TO BE
RATHER LIGHT. COLD AIR AND FAIRLY STRONG NORTHWEST WINDS WILL SPREAD
OVER THE AREA FRIDAY NIGHT AND SATURDAY WITH HIGHS SATURDAY BACK
BETWEEN 10 AND 15 ABOVE...WITH THE POTENTIAL TO BE EVEN COLDER.
/SCHUMACHER
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
MN...NONE.
NE...NONE.
SD...NONE.
&&
$$
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
540 AM CST SUN DEC 23 2012
.DISCUSSION.../ISSUED AT 330 AM CST/
PROBABLY ONE OF THE BIGGEST CHALLENGES OVER THE NEXT FEW DAYS IS
FIGURING OUT SKY COVER. AND THAT CERTAINLY IS THE CHALLENGE IN THE
SHORTER TERM TODAY ALSO. STRATUS EXISTS IN MINNESOTA...CURRENTLY
EDGING INTO OUR EASTERN ZONES AS IT MOVES SOUTH TO SOUTHWEST. IN
ADDITION...STRATUS ALSO EXISTS ON THE WESTERN EDGE OF OUR FORECAST
AREA. THE STRATUS IN MINNESOTA HAS NOT BEEN PICKED UP BY THE MODELS
EXCEPT FOR MAYBE THE RAP. HOWEVER THE RAP HAS STRATUS NEARLY
EVERYWHERE AT THIS TIME. THE STRATUS ON OUR WESTERN EDGE WAS BETTER
FORECAST BY THE MODELS. IT HAS BEEN TRYING TO TREND WESTWARD ALONG A
LOW LEVEL WIND WHICH IS OUT OF THE NORTHEAST...BUT IT IS ALSO
EXPANDING INTO CENTRAL NEBRASKA. SO WHAT TO DO. FIRST OF ALL...HIGH
LEVEL CLOUDINESS...AT LEAST OF THE OFF AND ON VARIETY...SHOULD BE
ABUNDANT TODAY. SO OVERALL SKY COVER SHOULD NOT BE REAL PRISTINE
ANYWHERE IN OUR FORECAST AREA. THE WESTERN STRATUS MAY TRY TO
RETREAT A BIT WESTWARD THIS MORNING. HOWEVER IT THEN MAY TRY TO
SNEAK BACK IN THIS AFTERNOON DEEPER INTO OUR SOUTHWEST ZONES AS
WINDS OFF THE SURFACE BACK A BIT TO THE NORTH/NORTHWEST IN THAT
AREA. THE EASTERN PLAINS STRATUS IS MORE PROBLEMATIC. THIS STRATUS
VERY LIKELY HAS A SHALLOWER DEPTH. AND AT LEAST ON THE SATELLITE
PICTURE IT LOOKS AS THOUGH IT IS GETTING FRAGMENTED A BIT IN CENTRAL
AND NORTHERN MN UNDER SUBSIDENCE. NONETHELESS...IT WILL LIKELY
IMPACT SOME OF OUR EASTERN ZONES THIS MORNING...BEFORE POSSIBLY
DISSIPATING SOME THIS AFTERNOON. TEMPERATURES IN THAT STRATUS LAYER
ARE VERY EFFICIENT FOR SNOW MAKING...SO WOULD NOT EVEN RULE OUT AN
ISOLATED FLURRY THIS MORNING IN MUCH OF OUR EAST. FOR TEMPERATURES...
DID NOT NEED TO ALTER THEM MUCH AT ALL FROM THE PREVIOUS FORECAST.
MAX READINGS SHOULD BE IN THE TEENS...WITH SOME 20S IN OUR FAR
SOUTHWEST ZONES.
A SHORT WAVE THEN MOVES EASTWARD ACROSS OUR AREA LATE THIS AFTERNOON
AND TONIGHT. UPPER QG FORCING BOTH OFF THE NAM AND GFS SHOWS THE
MAIN WAVE JUST TO THE NORTH OF OUR FORECAST AREA. HOWEVER THE
MOISTURE DEPTH IS DEEP ENOUGH IN OUR NORTHERN ZONES...COUPLED WITH
EFFICIENT -10C TO -15C AIR JUST OFF THE SURFACE AND ISENTROPIC
LIFT...THAT LIGHT SNOW OR FLURRIES IS STILL A THREAT. BEHIND
TONIGHTS WAVE...COLD AIR ADVECTION BEGINS TO POUR IN AGAIN WHICH
WILL KEEP THE NORTHERLY WINDS STIRRED UP SOME. HOWEVER DUE TO
ANTICIPATED CLOUD COVER...THE LOWS SHOULD NOT BOTTOM OUT HORRIBLY
BAD FOR THIS TIME OF YEAR.
SUBTLE UPPER RIDGING IS IN PLACE ON A COLD MONDAY IN BETWEEN TWO
WAVES. SKY COVER IS A REAL CHALLENGE. STRATUS MAY LINGER IN OUR
EASTERN ZONES WITH THE COLD AIR ADVECTION. HOWEVER ONE WORRIES ABOUT
SUBSIDENCE BREAKING IT APART SOONER THAN CURRENTLY FORECAST. IN COLD
AIR...MODEL LOW LEVEL HUMIDITY FIELDS AND CONDENSATION PRESSURE
DEFICITS CAN BE WAY OVERDONE SOMETIMES MAKING IT LESS THAN
TRUSTWORTHY. OUR WESTERN ZONES MAY SEE SOME PARTIAL CLEARING BEFORE
THE UPPER TROUGH IN THE ROCKIES MOVES CLOSER TO OUR AREA CASTING
SOME MID AND UPPER CLOUDINESS IN THOSE AREAS. AGAIN...MAX
TEMPERATURES STILL LOOK GOOD FROM YESTERDAYS FORECAST WITH READINGS
A FEW DEGREES EITHER SIDE OF 10. COUPLED WITH A BRISK COLD AIR
ADVECTION WIND...WIND CHILL READINGS WILL BE SUB ZERO.
THE COLD AIR ADVECTION CONTINUES TO DRAIN DOWN MONDAY NIGHT AND
TUESDAY FROM A LARGE SURFACE HIGH IN WESTERN AND SOUTHERN CANADA.
THEREFORE THE NORTHERLY WINDS WILL CONTINUE TO STAY RATHER BRISK.
LOWS SHOULD BE MOSTLY SUB ZERO MONDAY NIGHT EXCEPT POSSIBLY IN OUR
FAR SOUTHERN ZONES...AND MANY LOCATIONS WILL NOT GET OUT OF THE
SINGLE DIGITS ON CHRISTMAS. THE AFOREMENTIONED ROCKY MOUNTAIN UPPER
WAVE IS DIVING TO THE SOUTH...LARGELY NOT AFFECTING OUR FORECAST
AREA EXCEPT FOR POSSIBLY GIVING MID AND HIGH LEVEL CLOUDINESS. ONE
AREA OF MAJOR CONCERN IS MONDAY NIGHT...CONCERNING LOWS IN OUR
EASTERN ZONES. SOME INDICATIONS ARE THAT CLOUD COVER IN THAT AREA
WILL BE THIN...AS THE THICKER CLOUDS MOVE SOUTHWARD WITH THE UPPER
WAVE. IF THIS HAPPENS...LOWS COULD BE COLDER THAN FORECAST DESPITE
SOME WIND. THIS IS MENTIONED BECAUSE WE ARE ALREADY FORECASTING WIND
CHILL ADVISORY CRITERIA MONDAY NIGHT AND TUESDAY MORNING FOR ALL
AREAS EXCEPT THE MISSOURI RIVER VALLEY. WIND CHILL READINGS LOOK TO
BE COMMONLY -20F TO -25F. SO ANY COLDER LOWS IN OUR EAST MAY PRESS
WIND CHILL WARNING CRITERIA.
FINALLY ON TUESDAY NIGHT...KEPT THE PREVIOUS LOWS GOING WHICH ARE
MUCH COLDER THEN ALL CONSENSUS GUIDANCES. JUST NOT BUYING THE AMOUNT
OF CLOUD COVER THE MODELS ARE TRYING TO KICK OUT...AND WINDS WILL
FINALLY SLACKEN OFF. COLD CANADIAN HIGH PRESSURE EXTENDS ALL THE WAY
FROM CANADA TO SOUTH TEXAS BY THIS TIME...WITH THE SURFACE RIDGE
MOVING CLOSE TO THE I 29 CORRIDOR. THEREFORE LOWS SHOULD RANGE FROM
AROUND -12F IN OUR FAR NORTHERN ZONES...TO NEAR -5F IN OUR FAR
SOUTH. /MJF
FOR WED THROUGH SAT...THE MAIN FOCUS IS ON THE POTENTIAL FOR SNOW ON
FROM THURSDAY THROUGH FRIDAY. THE 00Z ECMWF HAS TRENDED TOWARD THE
OPERATIONAL 00Z GFS WITH BOTH MODELS NOW SHOWING THE POLAR VORTEX
CENTERED NEAR 100 W IN CANADA. THIS PREVENTS AS MUCH AMPLIFICATION
OF THE RIDGE AS WOULD BE EXPECTED WITH A DEEPENING EAST COAST
CYCLONE. THIS RESULTS IN A FASTER PROGRESSION OF THE WAVE AS WELL AS
LESS FOCUSED ASCENT. THE 00Z CANADIAN GEM ALSO SUPPORTS THIS
SOLUTION WHICH FITS THE MEAN GFS ENSEMBLE. THEREFORE...HAVE RAISED
POPS A BIT ON THURSDAY NIGHT WHILE LOWERING/REMOVING POPS ON FRIDAY
NIGHT WEST OF I29.
ALL MODELS AGREE THE RIDGE WILL HANG OVER SW MN AND NW IA
THROUGH WED NIGHT AND WITH SOME CLEARING AND LIGHT WINDS. THIS WILL
KEEP IT WELL BELOW NORMAL ON WEDNESDAY WITH HIGHS FROM 5 TO 15
ABOVE. AND...WHILE NOT COMPLETELY CONFIDENT YET...SEEMS AS IF THIS
SHOULD BE A GOOD RADIATION NIGHT AND HAVE LOWERED MINS TO -5 TO -10
EAST OF I29. INCREASING SOUTHEAST FLOW WILL KEEP TEMPS ABOVE ZERO
WEST OF I29. DESPITE WARM ADVECTION THURSDAY AND FRIDAY...IT WILL
REMAIN BELOW NORMAL AS MOST OF THE WARM ADVECTION GOES TO LARGE
SCALE ASCENT AND CLOUDS OVERSPREAD THE AREA. HAVE A SLIGHT CHANCE OF
SNOW THURSDAY WITH A CHANCE OF SNOW FOR THE ENTIRE AREA THURSDAY
NIGHT AND FRIDAY. THE DURATION OF ANY ACCUMULATING SNOW WILL LIKELY
BE LESS THAN 12 HOURS BUT AT THIS POINT IT IS MOSTLY LIKELY GOING TO
STRADDLE 12Z. AT THIS POINT...SNOWFALL WITH THIS EVENT LOOKS TO BE
RATHER LIGHT. COLD AIR AND FAIRLY STRONG NORTHWEST WINDS WILL SPREAD
OVER THE AREA FRIDAY NIGHT AND SATURDAY WITH HIGHS SATURDAY BACK
BETWEEN 10 AND 15 ABOVE...WITH THE POTENTIAL TO BE EVEN COLDER.
/SCHUMACHER
&&
.AVIATION.../FOR 12Z TAF ISSUANCE/
LARGE AREA OF STRATUS OVER MN AND NORTHEAST SD CONTINUES TO ADVECT
SOUTHWEST AT 15 TO 20 KTS. BASED UPON CURRENT TRAJECTORY...STRATUS
WILL REACH KFSD BETWEEN 1200 AND 1230 UTC...AND KHON AROUND 1300Z.
BECAUSE OF CIRRUS COVERING UP STRATUS IN SD...THERE IS A BIT MORE
UNCERTAINTY ON TIMING OF STRATUS THERE. AT THE LEADING EDGE OF
STRATUS IS SOME LIGHT SNOW OR FOG...LIKELY DUE TO HIGHER MOISTURE
INTERACTING WITH COLDER AIR AHEAD OF STRATUS. THIS WILL BRING AN
HOUR OR TWO OF VSBYS FROM 3 TO 5 SM ALTHOUGH THERE MAY BE A BRIEF
PERIOD OF 2SM VSBYS. THE REAL QUESTION THE REST OF THE DAY IS HOW
LONG THE STRATUS STAYS AROUND AND IF IT REACH KSUX. WITH FLOW
BECOMING EASTERLY THROUGH THE MORNING AND LITTLE IN WAY OF
SUBSIDENCE...REALLY DO NOT EXPECT TO STRATUS TO COMPLETELY DISSIPATE
ALTHOUGH IT APPEARS THIN IN PLACES ON SATELLITE SO SOME BREAKS ARE
POSSIBLE. DECIDED TO BE PESSIMISTIC IN BOTH KFSD AND KHON AND KEEP
STRATUS IN THROUGH THE DAY. AS FOR KSUX...THE EDGE OF THE STRATUS
MAY JUST GET THERE BEFORE FLOW TURNS EAST OR EVEN ESE SO HAVE A
COUPLE OF HOURS OF LOW CIGS LATE THIS MORNING BEFORE GOING SCATTERED
THIS AFTERNOON. FLOW THEN TURNS NW TONIGHT AND THAT SHOULD REMOVE
THIS BATCH OF STRATUS ONLY TO BE REPLACED BY ANOTHER BATCH FROM THE
NORTHWEST. THIS STRATUS SHOULD BE HIGHER UP...AROUND 2000 FT. WHILE
THERE IS A CHANCE OF FLURRIES OR LIGHT SNOW OVERNIGHT BY KHON AND
KFSD...PROBABILITY IS TOO LOW TO PUT IN TAF AT THIS TIME.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
MN...NONE.
NE...NONE.
SD...NONE.
&&
$$
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
330 AM CST SUN DEC 23 2012
.DISCUSSION.../ISSUED AT 330 AM CST/
PROBABLY ONE OF THE BIGGEST CHALLENGES OVER THE NEXT FEW DAYS IS
FIGURING OUT SKY COVER. AND THAT CERTAINLY IS THE CHALLENGE IN THE
SHORTER TERM TODAY ALSO. STRATUS EXISTS IN MINNESOTA...CURRENTLY
EDGING INTO OUR EASTERN ZONES AS IT MOVES SOUTH TO SOUTHWEST. IN
ADDITION...STRATUS ALSO EXISTS ON THE WESTERN EDGE OF OUR FORECAST
AREA. THE STRATUS IN MINNESOTA HAS NOT BEEN PICKED UP BY THE MODELS
EXCEPT FOR MAYBE THE RAP. HOWEVER THE RAP HAS STRATUS NEARLY
EVERYWHERE AT THIS TIME. THE STRATUS ON OUR WESTERN EDGE WAS BETTER
FORECAST BY THE MODELS. IT HAS BEEN TRYING TO TREND WESTWARD ALONG A
LOW LEVEL WIND WHICH IS OUT OF THE NORTHEAST...BUT IT IS ALSO
EXPANDING INTO CENTRAL NEBRASKA. SO WHAT TO DO. FIRST OF ALL...HIGH
LEVEL CLOUDINESS...AT LEAST OF THE OFF AND ON VARIETY...SHOULD BE
ABUNDANT TODAY. SO OVERALL SKY COVER SHOULD NOT BE REAL PRISTINE
ANYWHERE IN OUR FORECAST AREA. THE WESTERN STRATUS MAY TRY TO
RETREAT A BIT WESTWARD THIS MORNING. HOWEVER IT THEN MAY TRY TO
SNEAK BACK IN THIS AFTERNOON DEEPER INTO OUR SOUTHWEST ZONES AS
WINDS OFF THE SURFACE BACK A BIT TO THE NORTH/NORTHWEST IN THAT
AREA. THE EASTERN PLAINS STRATUS IS MORE PROBLEMATIC. THIS STRATUS
VERY LIKELY HAS A SHALLOWER DEPTH. AND AT LEAST ON THE SATELLITE
PICTURE IT LOOKS AS THOUGH IT IS GETTING FRAGMENTED A BIT IN CENTRAL
AND NORTHERN MN UNDER SUBSIDENCE. NONETHELESS...IT WILL LIKELY
IMPACT SOME OF OUR EASTERN ZONES THIS MORNING...BEFORE POSSIBLY
DISSIPATING SOME THIS AFTERNOON. TEMPERATURES IN THAT STRATUS LAYER
ARE VERY EFFICIENT FOR SNOW MAKING...SO WOULD NOT EVEN RULE OUT AN
ISOLATED FLURRY THIS MORNING IN MUCH OF OUR EAST. FOR TEMPERATURES...
DID NOT NEED TO ALTER THEM MUCH AT ALL FROM THE PREVIOUS FORECAST.
MAX READINGS SHOULD BE IN THE TEENS...WITH SOME 20S IN OUR FAR
SOUTHWEST ZONES.
A SHORT WAVE THEN MOVES EASTWARD ACROSS OUR AREA LATE THIS AFTERNOON
AND TONIGHT. UPPER QG FORCING BOTH OFF THE NAM AND GFS SHOWS THE
MAIN WAVE JUST TO THE NORTH OF OUR FORECAST AREA. HOWEVER THE
MOISTURE DEPTH IS DEEP ENOUGH IN OUR NORTHERN ZONES...COUPLED WITH
EFFICIENT -10C TO -15C AIR JUST OFF THE SURFACE AND ISENTROPIC
LIFT...THAT LIGHT SNOW OR FLURRIES IS STILL A THREAT. BEHIND
TONIGHTS WAVE...COLD AIR ADVECTION BEGINS TO POUR IN AGAIN WHICH
WILL KEEP THE NORTHERLY WINDS STIRRED UP SOME. HOWEVER DUE TO
ANTICIPATED CLOUD COVER...THE LOWS SHOULD NOT BOTTOM OUT HORRIBLY
BAD FOR THIS TIME OF YEAR.
SUBTLE UPPER RIDGING IS IN PLACE ON A COLD MONDAY IN BETWEEN TWO
WAVES. SKY COVER IS A REAL CHALLENGE. STRATUS MAY LINGER IN OUR
EASTERN ZONES WITH THE COLD AIR ADVECTION. HOWEVER ONE WORRIES ABOUT
SUBSIDENCE BREAKING IT APART SOONER THAN CURRENTLY FORECAST. IN COLD
AIR...MODEL LOW LEVEL HUMIDITY FIELDS AND CONDENSATION PRESSURE
DEFICITS CAN BE WAY OVERDONE SOMETIMES MAKING IT LESS THAN
TRUSTWORTHY. OUR WESTERN ZONES MAY SEE SOME PARTIAL CLEARING BEFORE
THE UPPER TROUGH IN THE ROCKIES MOVES CLOSER TO OUR AREA CASTING
SOME MID AND UPPER CLOUDINESS IN THOSE AREAS. AGAIN...MAX
TEMPERATURES STILL LOOK GOOD FROM YESTERDAYS FORECAST WITH READINGS
A FEW DEGREES EITHER SIDE OF 10. COUPLED WITH A BRISK COLD AIR
ADVECTION WIND...WIND CHILL READINGS WILL BE SUB ZERO.
THE COLD AIR ADVECTION CONTINUES TO DRAIN DOWN MONDAY NIGHT AND
TUESDAY FROM A LARGE SURFACE HIGH IN WESTERN AND SOUTHERN CANADA.
THEREFORE THE NORTHERLY WINDS WILL CONTINUE TO STAY RATHER BRISK.
LOWS SHOULD BE MOSTLY SUB ZERO MONDAY NIGHT EXCEPT POSSIBLY IN OUR
FAR SOUTHERN ZONES...AND MANY LOCATIONS WILL NOT GET OUT OF THE
SINGLE DIGITS ON CHRISTMAS. THE AFOREMENTIONED ROCKY MOUNTAIN UPPER
WAVE IS DIVING TO THE SOUTH...LARGELY NOT AFFECTING OUR FORECAST
AREA EXCEPT FOR POSSIBLY GIVING MID AND HIGH LEVEL CLOUDINESS. ONE
AREA OF MAJOR CONCERN IS MONDAY NIGHT...CONCERNING LOWS IN OUR
EASTERN ZONES. SOME INDICATIONS ARE THAT CLOUD COVER IN THAT AREA
WILL BE THIN...AS THE THICKER CLOUDS MOVE SOUTHWARD WITH THE UPPER
WAVE. IF THIS HAPPENS...LOWS COULD BE COLDER THAN FORECAST DESPITE
SOME WIND. THIS IS MENTIONED BECAUSE WE ARE ALREADY FORECASTING WIND
CHILL ADVISORY CRITERIA MONDAY NIGHT AND TUESDAY MORNING FOR ALL
AREAS EXCEPT THE MISSOURI RIVER VALLEY. WIND CHILL READINGS LOOK TO
BE COMMONLY -20F TO -25F. SO ANY COLDER LOWS IN OUR EAST MAY PRESS
WIND CHILL WARNING CRITERIA.
FINALLY ON TUESDAY NIGHT...KEPT THE PREVIOUS LOWS GOING WHICH ARE
MUCH COLDER THEN ALL CONSENSUS GUIDANCES. JUST NOT BUYING THE AMOUNT
OF CLOUD COVER THE MODELS ARE TRYING TO KICK OUT...AND WINDS WILL
FINALLY SLACKEN OFF. COLD CANADIAN HIGH PRESSURE EXTENDS ALL THE WAY
FROM CANADA TO SOUTH TEXAS BY THIS TIME...WITH THE SURFACE RIDGE
MOVING CLOSE TO THE I 29 CORRIDOR. THEREFORE LOWS SHOULD RANGE FROM
AROUND -12F IN OUR FAR NORTHERN ZONES...TO NEAR -5F IN OUR FAR
SOUTH. /MJF
FOR WED THROUGH SAT...THE MAIN FOCUS IS ON THE POTENTIAL FOR SNOW ON
FROM THURSDAY THROUGH FRIDAY. THE 00Z ECMWF HAS TRENDED TOWARD THE
OPERATIONAL 00Z GFS WITH BOTH MODELS NOW SHOWING THE POLAR VORTEX
CENTERED NEAR 100 W IN CANADA. THIS PREVENTS AS MUCH AMPLIFICATION
OF THE RIDGE AS WOULD BE EXPECTED WITH A DEEPENING EAST COAST
CYCLONE. THIS RESULTS IN A FASTER PROGRESSION OF THE WAVE AS WELL AS
LESS FOCUSED ASCENT. THE 00Z CANADIAN GEM ALSO SUPPORTS THIS
SOLUTION WHICH FITS THE MEAN GFS ENSEMBLE. THEREFORE...HAVE RAISED
POPS A BIT ON THURSDAY NIGHT WHILE LOWERING/REMOVING POPS ON FRIDAY
NIGHT WEST OF I29.
ALL MODELS AGREE THE RIDGE WILL HANG OVER SW MN AND NW IA
THROUGH WED NIGHT AND WITH SOME CLEARING AND LIGHT WINDS. THIS WILL
KEEP IT WELL BELOW NORMAL ON WEDNESDAY WITH HIGHS FROM 5 TO 15
ABOVE. AND...WHILE NOT COMPLETELY CONFIDENT YET...SEEMS AS IF THIS
SHOULD BE A GOOD RADIATION NIGHT AND HAVE LOWERED MINS TO -5 TO -10
EAST OF I29. INCREASING SOUTHEAST FLOW WILL KEEP TEMPS ABOVE ZERO
WEST OF I29. DESPITE WARM ADVECTION THURSDAY AND FRIDAY...IT WILL
REMAIN BELOW NORMAL AS MOST OF THE WARM ADVECTION GOES TO LARGE
SCALE ASCENT AND CLOUDS OVERSPREAD THE AREA. HAVE A SLIGHT CHANCE OF
SNOW THURSDAY WITH A CHANCE OF SNOW FOR THE ENTIRE AREA THURSDAY
NIGHT AND FRIDAY. THE DURATION OF ANY ACCUMULATING SNOW WILL LIKELY
BE LESS THAN 12 HOURS BUT AT THIS POINT IT IS MOSTLY LIKELY GOING TO
STRADDLE 12Z. AT THIS POINT...SNOWFALL WITH THIS EVENT LOOKS TO BE
RATHER LIGHT. COLD AIR AND FAIRLY STRONG NORTHWEST WINDS WILL SPREAD
OVER THE AREA FRIDAY NIGHT AND SATURDAY WITH HIGHS SATURDAY BACK
BETWEEN 10 AND 15 ABOVE...WITH THE POTENTIAL TO BE EVEN COLDER.
/SCHUMACHER
&&
.AVIATION.../FOR 06Z TAF ISSUANCE/
LOW STRATUS SEEN ON THE LATEST SATELLITE LOOP OVER NORTHERN
MINNESOTA AND EASTERN NORTH DAKOTA IS DROPPING SOUTH SOUTHWEST. THE
QUESTION IS HOW FAR WEST AND SOUTH THIS WILL SPREAD WITH LIGHT
NORTHEAST FLOW. IT SEEMS LIKELY THAT THIS BAND WILL MOVE INTO THE
KFSD AREA AROUND DAYBREAK WITH A BIT MORE UNCERTAINTY FURTHER SOUTH
INTO KSUX...WHILE THE WESTERN EDGE OF THIS BAND IS MORE OBSCURED AND
FRAGMENTED WITH HIGHER CLOUDS. MODELS QUIET UNCERTAIN...WITH THE RAP
INDICATING THAT KFSD WILL BE IN STRATUS WELL INTO SUNDAY. HAVE ADDED
BKN010 LAYER TO KFSD BUT WILL ONLY HINT AT POTENTIAL AT OTHER SITES
FOR NOW. SHOULD SEE SOME BREAKING OUT LATER ON SATURDAY BUT LOW
CLOUDS COULD BECOME A HAZARD FOR THE BETTER PART OF THE DAY.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
MN...NONE.
NE...NONE.
SD...NONE.
&&
$$
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
1055 PM CST SAT DEC 22 2012
.DISCUSSION.../ISSUED AT 957 PM CST/
SEVERAL INTERESTING SUBTLETIES FOR THE EVENING UPDATE...PRIMARILY
FOCUSED AROUND THE ADVANCING STRATUS FIELD MOVING SOUTH THROUGH
EASTERN NORTH DAKOTA AND CENTRAL MINNESOTA...AS WELL AS THE SMALLER
STRATUS PATCHES WEST OF THE JAMES RIVER. ADVECTIVE TRENDS WOULD
SUGGEST THAT STRATUS WILL BE A PROBLEM STARTING AFTER 08-09Z...
SPREADING SOUTH AND THEN A BIT WEST OF SOUTH AT THE LOW LEVEL WINDS
FIELDS PICK UP AN EASTERLY COMPONENT. RAP SEEMS TO BE THE ONLY
GUIDANCE THAT IS PICKING UP ON POTENTIAL TO ACCEPTABLE DEGREE...
AND THIS WOULD BE EVEN MORE PESSIMISTIC THAN THE CHANGES THAT WERE
MADE. WITH TEMPERATURES IN THE CLOUD BEARING LEVEL VERY COMFORTABLY
DENDRITIC...WOULD EXPECT A FEW FLURRIES TO ACCOMPANY THE CLOUDS AS
WELL. CARRIED FLURRIES INTO SUNDAY MORNING AS WELL...AND IF RAP IS
RIGHT COULD BE EVEN LONGER INTO THE DAY.
INCREASE IN HIGHER CLOUDS AS WELL AS THE ADVANCING LOWER CLOUDS
SHOULD HELP TO SLOW OR LIMIT THE TEMPERATURE FALL...AND AS A RESULT
DID RAISE THE LOW TEMPERATURES SOMEWHAT FOR THE NORTHEAST AREAS.
/CHAPMAN
&&
.AVIATION.../FOR 06Z TAF ISSUANCE/
LOW STRATUS SEEN ON THE LATEST SATELLITE LOOP OVER NORTHERN
MINNESOTA AND EASTERN NORTH DAKOTA IS DROPPING SOUTH SOUTHWEST. THE
QUESTION IS HOW FAR WEST AND SOUTH THIS WILL SPREAD WITH LIGHT
NORTHEAST FLOW. IT SEEMS LIKELY THAT THIS BAND WILL MOVE INTO THE
KFSD AREA AROUND DAYBREAK WITH A BIT MORE UNCERTAINTY FURTHER SOUTH
INTO KSUX...WHILE THE WESTERN EDGE OF THIS BAND IS MORE OBSCURED AND
FRAGMENTED WITH HIGHER CLOUDS. MODELS QUIET UNCERTAIN...WITH THE RAP
INDICATING THAT KFSD WILL BE IN STRATUS WELL INTO SUNDAY. HAVE ADDED
BKN010 LAYER TO KFSD BUT WILL ONLY HINT AT POTENTIAL AT OTHER SITES
FOR NOW. SHOULD SEE SOME BREAKING OUT LATER ON SATURDAY BUT LOW
CLOUDS COULD BECOME A HAZARD FOR THE BETTER PART OF THE DAY.
&&
.PREV DISCUSSION.../ISSUED AT 233 PM CST/
SHORT TERM ISSUES REVOLVE AROUND SKY COVER LATE TONIGHT INTO
TOMORROW AND ITS AFFECT ON TEMPS. NAM/GFS/SREF ALL VERY SIMILAR SO
USED A BLEND.
BOTH NAM/GFS/SREF SHOW INCREASING MID-HIGH LEVEL MOISTURE IN
TIME/HEIGHT SECTIONS AS H5 RIDGE MOVES EAST ACROSS THE NORTHERN
PLAINS TONIGHT AND TOMORROW. WEAK SHWV SLIDES EAST TONIGHT WITH
INCREASING HIGH CLOUDS THE MAIN RESULT. DID NOT CUT OVERNIGHT LOWS
MUCH AS CLOUD COVER WILL HELP KEEP TEMPS FROM DROPPING SIGNIFICANTLY
BUT WILL STILL BE COLDER THAN LAST NIGHT.
H85 COLD ADVECTION CONTINUES ON SUNDAY AS HIGH PRESS MOVES SOUTH
FROM CANADA. CLOUDY AND COLD CONDITIONS CAN BE EXPECTED TOMORROW
WITH HIGHS ONLY IN THE TEENS AS H85 TEMPS DROP FROM AROUND +4C TO
+6C TODAY TO -4C TO 0C ON SUNDAY. /SP
LATE SUNDAY AFTERNOON THROUGH SUNDAY EVENING MODELS STILL CONSISTENT
ON SWINGING THROUGH UPPER LEVEL SUPPORT WHICH WILL DRAG DOWN A
REINFORCING SHOT OF COLD AIR. ANTECEDENT CONDITIONS ARE VERY DRY
WITH SATURATION NOT OCCURRING UNTIL PASSAGE OF THE MAIN FORCING.
THERE IS VERY LITTLE IN THE WAY OF THE PRE EXISTING THERMAL GRADIENT
EITHER. THERE IS SOME MODERATE FORCING WITHIN THE DENDRITIC
LAYER...THE STRONGEST FROM ABOUT 21Z THROUGH 6Z OVER THE EASTERN
HALF OF THE CWA...CENTERED OVER SOUTHWEST MINNESOTA ABOUT 3Z. BUT
WITH THE DENDRITIC LAYER RELATIVE HUMIDITY VALUES OF 40 TO 70
PERCENT DURING THE BETTER FORCING SOME CONCERN ABOUT BEING ABLE TO
PRODUCE ANY SNOWFLAKES. AS STATED EARLIER...FORCING...MOISTURE AND
SOME INSTABILITY DO COME TOGETHER OVER PARTS OF SOUTHWEST MINNESOTA
SUNDAY EVENING FROM ABOUT 3Z THROUGH 6Z SO WILL NEED TO INCREASE
POPS A BIT AS THESE SMALLER WEAKER WAVES HAVE CREATED SOME PROBLEMS
THE PAST WEEK OR SO. LOOKING AT A HALF AN INCH TO AN INCH OF
POTENTIAL AS FORCING MOVES THROUGH FAIRLY QUICKLY BUT WITH LIGHT
WINDS AND A RELATIVELY DEEP DENDRITIC LAYER SNOW COULD ACCUMULATE
MORE EASILY SO WILL NEED TO WATCH TRENDS ON THIS SYSTEM.
MODELS HAVE COME IN A LITTLE COLDER ON MONDAY THAN PREVIOUS
RUNS...ABOUT 2 DEGREES C AT 925MB. THIS REINFORCED COLD AIR ON
MONDAY WILL LEAD TOWARDS A VERY COLD DAY WITH HIGHS FROM THE SINGLE
DIGITS NORTH OF INTERSTATE 90 TO 10 TO 15 SOUTH. WITH A 10 TO 15 MPH
NORTH WIND WIND CHILLS WILL BE ABOUT 5 BELOW TO 15 BELOW THROUGH THE
DAY. ALSO LOWERED LOWS JUST A TOUCH ON MONDAY NIGHT BUT WITH A NORTH
WIND AROUND 10 MPH THROUGH THE NIGHT NEED TO BE CAREFUL AND NOT GO
TOO COLD. ALSO SOME CONCERN ABOUT CLOUD COVER WIT THE GFS A LITTLE
MORE BOISTEROUS ON SPREADING SOME HIGH LEVEL CLOUDS.
IN THE LATTER PERIODS(WED/SAT)...MAIN CONCERNS DURING THIS TIME
FRAME CONTINUE TO FOCUS AROUND THE THURSDAY NIGHT/FRIDAY MORNING
SYSTEM. THE MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE TIMING OF
THE SYSTEM BUT STRENGTH DOES SHOW SOME DIFFERENCES. THE ECMWF IS THE
STRONGEST WITH A STRONGER POST WAVE RIDGE BUILDING NORTHWEST WHILE
ALL MODELS DO INDICATE A QUASI BLOCKING/SLOW MOVING LOW PRESSURE
JUST OFF THE NORTHEAST COAST OF THE U.S. WHICH SHOULD ALLOW FOR A
LITTLE DIGGING/STRENGTHENING. THUS...WILL ALSO INCREASE POPS A BIT
THURSDAY NIGHT INTO FRIDAY AS THIS ALSO APPEARS TO BE A MORE BROAD
OVERRUNNING TYPE EVENT WHICH BRINGS A BETTER CHANCE THAT MORE
LOCATIONS WILL GET MEASURABLE SNOWFALL. BEHIND THIS SYSTEM FRIDAY
NIGHT INTO SATURDAY...COLD AIR NEAR THE SURFACE SHOULD REMAIN LOCKED
IN PLACE WITH A RIDGE OF HIGH PRESSURE NOSING SOUTH DOWN THE WESTERN
HIGH PLAINS. MEN STATISTICAL GUIDANCE ALSO SUGGESTS STAYING COLD
WITH MEX FORECAST HIGHS ABOUT 10 DEGREES BELOW CLIMATOLOGY AND THE
MEN FORECAST VALUES EVEN COLDER...STRAYING FARTHER FROM CLIMATOLOGY.
WILL REMAIN BELOW GUIDANCE FRIDAY AND SATURDAY. ALSO GOING COLD ON
WEDNESDAY MORNING WITH HIGH PRESSURE EXTENDING SOUTH DOWN SOUTHWEST
MINNESOTA INTO THE BIG SIOUX RIVER VALLEY. /08
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
MN...NONE.
NE...NONE.
SD...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS FORT WORTH TX
912 PM CST MON DEC 24 2012
.UPDATE...
WE HAVE ANALYZED THE 00Z UPPER AIR DATA AND HAVE WATCHED THE
SURFACE OBS CLOSELY FOR SIGNS OF ANY DISCREPANCIES BETWEEN THEM
AND THE MODEL DATA. THE BIG THING THAT STANDS OUT ARE THAT THE
SURFACE LOW IN NORTHEAST NEW MEXICO AT 6PM WAS ABOUT 80 MILES
FARTHER SOUTH THAN ALL OF THE MODELS HAD FORECAST 24 HOURS AGO.
WHEN DEALING WITH A SWINGING/DIGGING UPPER LEVEL SYSTEM...THE
SURFACE PRESSURE PATTERN AND PRESSURE TENDENCIES OFFER ENORMOUS
CLUES ON THE FUTURE TRACK OF A POTENTIAL VORTICITY ANOMALY BEFORE
IT CLOSES OFF TO BECOME A FULL FLEDGED UPPER LOW. THE 3PM AND 6PM
SURFACE ANALYSIS SHOWED A LARGE REGION OF PRESSURE FALLS ACROSS
NEW MEXICO AND WEST TEXAS IN ADVANCE OF THE SYSTEM. GIVEN THE
ORIENTATION OF THE PRESSURE FALLS AND LOCATION OF THE SURFACE
LOW...IT CAN BE DETERMINED WITHOUT EVEN LOOKING AT A FORECAST
MODEL THAT THE UPPER LOW HAS NOT FINISHED DIGGING SOUTH. THE BIG
QUESTION IS HOW FAR SOUTH WILL THE UPPER LOW MAKE IT BEFORE IT
BEGINS TO SWING BACK TO THE NORTHEAST. AT THIS HOUR PRESSURE FALLS
CONTINUE IN THE REGION FROM LUBBOCK TO MIDLAND...WITH ANOTHER
PRESSURE FALL AREA DEVELOPING IN SOUTHEAST TEXAS. EXTRAPOLATING
SUGGESTS THE UPPER LOW WILL TRACK JUST SOUTH OF LUBBOCK BY SUNRISE
AND TO NEAR WACO BY SUNSET. AS THE LOW APPROACHES WACO...A WARM
FRONT WILL BE ORGANIZING OUT OF THE WEAK STATIONARY FRONT
CURRENTLY ANALYZED FROM SAN ANTONIO TO HOUSTON. BAROCLINIC QG
THEORY SUGGESTS THAT ONCE LOW LEVEL WARM ADVECTION BEGINS IN
EARNEST ACROSS SOUTHEAST TEXAS BY MORNING...IT WILL INDUCE HEIGHT
RISES TO THE SOUTHEAST OF OUR UPPER LOW WHICH WILL CAUSE THE LOW
TO CLOSE OFF AND FINISH DIGGING SOUTH...AND START ITS GRADUAL
TURN TO THE NORTHEAST. TOMORROW EVENING I WOULD EXPECT THE LOW TO
TRACK FROM NEAR WACO TO NEAR SHREVEPORT. IN SUMMARY THE USUAL
MEDIUM RANGE MODELS APPEAR TO BE A LITTLE TOO FAR NORTH WITH THE
TRACK OF THE UPPER LOW. OUR EXPECTATIONS FOR THE TRACK OF THE LOW
ALIGN WELL WITH THE RAP FORECAST WHICH IS TO THE SOUTH OF ALL
OTHER MODELS...SO WE WILL USE THE RAP HEAVILY.
OUR FORECAST HAS BEEN ON THE SOUTHERLY SIDE AND SNOWIER SIDE OF
THE MODEL GUIDANCE. SO ALTHOUGH WE ARE SEEING AN EVEN MORE
SOUTHERLY TRACK COME TO FRUITION...THIS DOES NOT NECESSARILY
MEAN THE FORECAST SNOW AMOUNTS NEED TO BE AMENDED MUCH. THIS IS IN
PART DUE TO THE DIFFICULTY IN GETTING THE COLDER/SUBFREEZING AIR
FARTHER SOUTH BEFORE THE PRECIPITATION ENDS. THE EXCEPTION IS THE
NORTHWEST ZONES WHERE THE MORE SOUTHERLY TRACK SUGGESTS MORE
PRECIP WILL FALL IN SUBFREEZING AIR. DUE TO THE TERRAIN EFFECTS
HERE...COLD AIR HAS AN EASY TIME GETTING INTO OUR NORTHWEST ZONES
WHEN WE HAVE A NORTH/NORTHEAST SURFACE WIND. HAVE EXPANDED THE
SNOW ADVISORY TO INCLUDE YOUNG/JACK/WISE COUNTIES...AND HAVE
INCREASED SNOW TOTALS TO THE 2-4 INCH RANGE FROM BOWIE TO SHERMAN.
THE NORTHEAST ZONES LIKELY WONT SWITCH TO SNOW UNTIL LATE
AFTERNOON...AS COLD AIR WILL HAVE TROUBLE MOVING IN AT THE SURFACE
DUE TO THE LEE SHADOW WARMING EFFECT OF THE OZARK PLATEAU. MOST OF
THE SNOW THAT OCCURS THERE WILL BE AFTER 6 PM AND WILL BE HIGHLY
DEPENDENT ON WHETHER MESOSCALE BANDING CAN SET UP IN THE WAKE OF
THE UPPER LOW. THE NEW NAM HAS FINALLY FORECAST SOME SIGNIFICANT
BANDING TO OCCUR...THUS WILL LEAVE THE ADVISORY ALONE IN THIS
AREA...BUT CONFIDENCE IS A LITTLE LOWER IN THE NORTHEAST ZONES FOR
2+ INCHES OF SNOW.
FARTHER TO THE SOUTH OF THE ADVISORY...FOR THE I-20 CORRIDOR AND
INCLUDING THE METROPLEX...THERE IS NOW HIGH CONFIDENCE THAT SNOW
WILL OCCUR. HOWEVER ALL INDICATIONS ARE THAT IT WILL STILL BE A
BRIEF 1-3 HOUR EVENT WITH NOT ENOUGH TIME TO GET ACCUMULATIONS
OVER AN INCH. IT MUST BE STRESSED THAT WITH TEMPERATURES FALLING
INTO THE 20S BY SUNSET...ANY APPRECIABLE MOISTURE REMAINING ON
BRIDGES...OVERPASSES AND EVEN SURFACE STREETS WILL LIKELY RE-
FREEZE INTO BLACK ICE. ALTHOUGH WE ARE USING 1+ INCH AS CRITERIA
FOR THE COUNTIES IN THE WINTER WEATHER ADVISORY AREA...WE MAY
EXPAND THE ADVISORY SOUTH INTO THE METROPLEX OVERNIGHT DUE SOLELY
TO TRAVEL IMPACTS.
FINALLY CONCERNING THE SEVERE WEATHER THREAT. WITH A MORE SOUTHERLY
TRACK OF THE UPPER LOW...THIS MEANS THERE IS LESS OF A CHANCE OF THE
WARM FRONT MAKING IT INTO THE SOUTHEAST CWA TONIGHT AS IT WILL
LIKELY STAY SOUTHEAST OF THE AREA. ELEVATED THUNDERSTORMS ARE STILL
EXPECTED TO RAPIDLY INCREASE IN COVERAGE AFTER 3 AM...WITH ELEVATED
INSTABILITY HIGH ENOUGH FOR A FEW SEVERE HAIL STORMS SOUTH OF I-20.
HAVE TONED DOWN THE DAMAGING WIND AND TORNADO THREAT FROM OUR
PRODUCTS...BUT WE WILL CONTINUE TO ADVERTISE HAIL STORMS POSSIBLE
LATE TONIGHT AND EARLY TOMORROW MORNING.
TR.92
&&
.AVIATION...
/00Z TAFS/
CONCERNS...THREAT FOR THUNDER LATE TONIGHT AND EARLY TUESDAY
MORNING. CHANGE OVER TO SNOW IN THE DFW METROPLEX TUESDAY
AFTERNOON. STRONG AND GUSTY NORTHWEST WINDS TUESDAY AFTERNOON.
VFR CONDITIONS WILL PREVAIL THIS EVENING BUT CONDITIONS WILL
DETERIORATE DURING THE OVERNIGHT HOURS. SHOWERS AND THUNDERSTORMS
WILL SPREAD ACROSS THE REGION OVERNIGHT BEGINNING AROUND 09Z/3 AM
CST. THERE IS THE POTENTIAL THAT SOME STORMS AROUND KACT WILL BE
SEVERE WITH A HAIL THREAT. THE THREAT FOR RAIN AND THUNDER WILL
CONTINUE INTO THE EARLY MORNING HOURS AND THEN LAPSE RATES WEAKEN
SUGGESTING A TRANSITION TO SHOWERS CAN BE EXPECTED FOR THE
REMAINDER OF THE MORNING HOURS. AS THE RAIN BEGINS
OVERNIGHT...MVFR CONDITIONS WILL GRADUALLY DEVELOP...BUT NEAR IFR
CONDITIONS CAN BE EXPECTED TUESDAY MORNING AS THE RAIN CONTINUES.
A STRONG COLD FRONT WILL SWEEP ACROSS THE TAF SITES AROUND MIDDAY.
THIS WILL RESULT IN VERY STRONG WINDS FROM THE NORTHWEST AT
25G35KTS FOR MUCH OF THE AFTERNOON HOURS. CROSSWIND IMPACTS ON
NORTH-SOUTH RUNWAYS WILL BE MODERATE AT WINDS THESE STRONG.
AROUND 21Z...THE RAIN WILL TRANSITION TO SNOW IN THE METROPLEX AND
THEN END IN THE EARLY EVENING HOURS. SOME LIGHT ACCUMULATIONS ARE
POSSIBLE. THE TIMING OF THE TRANSITION TO ALL SNOW IS DEPENDENT ON
HOW FAST THE SUB-FREEZING TEMPERATURES ARRIVE IN THE METROPLEX. AT
THIS TIME...MOST OF THE MODELS HAVE THE FREEZING AIR ARRIVING IN
THE MIDDLE OF THE AFTERNOON...BUT AT LEAST ONE MODEL SUGGESTS THIS
TRANSITION COULD OCCUR A FEW HOURS EARLIER. THE LOCATION OF THE
FREEZING TEMPERATURES NEEDS TO BE CLOSELY WATCHED TOMORROW FOR ANY
CHANGES TO THE TIMING OF THE TRANSITION TO SNOW. ONCE THE SNOW
CLEARS...CEILINGS WILL LIFT SOME TO AROUND 2000 FEET BUT WILL
REMAIN MVFR THROUGH THE END OF THIS TAF PERIOD.
AT KACT...THE RAIN WILL END AROUND MIDDAY AS DRY AIR MOVES IN FROM
THE WEST. NO WINTER PRECIPITATION IS EXPECTED AT THIS TIME.
CEILINGS WILL LIKELY BRIEFLY IMPROVE AS THE RAIN SHIFTS TO THE
EAST...BUT WRAP AROUND MVFR CIGS BEHIND THIS STORM SYSTEM WILL
QUICKLY MOVE IN DURING THE EARLY AFTERNOON HOURS.
82/JLD
&&
.PREV UPDATE...
.UPDATE...
UPDATING ZONE TO INCLUDE A WINTER WEATHER ADVISORY FOR CHRISTMAS
AFTERNOON AND EVENING. 75
&&
.PREV DISCUSSION... /ISSUED 301 PM CST MON DEC 24 2012/
OUR CHRISTMAS DAY/NIGHT WINTER STORM IS TAKING SHAPE OVER THE
INTERIOR WEST THIS AFTERNOON. IT WILL MOVE SOUTHEAST OVERNIGHT AND
SHOULD DEVELOP A CLOSED CIRCULATION AS IT ENTERS THE SOUTHWESTERN
PANHANDLE BY DAYBREAK CHRISTMAS. ALTHOUGH TODAY/S MODEL SOLUTIONS
CONTINUE TO SHOW SLIGHT TIMING AND TRACKING DIFFERENCES...THE
AGREEMENT AND CONSENSUS BETWEEN THE GFS AND THE ECMWF HAVE BEEN
AND CONTINUE TO BE THE PREFERRED SOLUTION FOR THIS STORM. THE
500MB CENTER SHOULD TRACK ALONG I-20 BETWEEN ABILENE AND DFW THEN
JUST SOUTH OF I-30 FROM DFW TO TEXARKANA. IF THE TRACK IS 30 MILES
SOUTH OR NORTH OF OUR FORECAST THEN IMPACTS WILL ALSO SHIFT ACCORDINGLY.
LAST NIGHTS FRONT IS LOCATED FROM NORTH OF HOUSTON TO NEAR SAN ANTONIO
TO AROUND FORT STOCKTON. SURFACE CYCLOGENESIS WILL BEGIN OVERNIGHT
ALONG THIS FRONT AND TRACK EAST ALONG THE FRONT. WE ARE EXPECTING
A WARM FRONT TO LIFT THROUGH THE SOUTHERN AND SOUTHEAST COUNTIES
LATE TONIGHT AND THROUGH THE EAST-CENTRAL COUNTIES EARLY CHRISTMAS
MORNING AS THE SURFACE LOW SLIDES EAST. CONVECTION WILL BEGIN
OVERNIGHT AS THE ELEVATED WARM FRONT PUSHES NORTHWARD. STRONG
UPPER DYNAMICS AND MID LEVEL INSTABILITY WILL LEAD TO SOME STRONG
TO SEVERE THUNDERSTORMS BEFORE AND AFTER DAYBREAK. HAIL WILL BE
THE MAIN THREAT BUT DAMAGING WIND CAN BE EXPECTED ALONG AND SOUTH
OF THE SURFACE BOUNDARY. AS FOR TORNADOES...STORMS MOVING OVER THE
SURFACE BOUNDARY WILL EXPERIENCE AN INCREASE IN STORM-RELATIVE
HELICITY AND BRIEF TORNADOES ARE POSSIBLE. THE SEVERE WEATHER
THREAT SHOULD MOVE INTO EAST TEXAS BY LATE MORNING.
COLD ARCTIC AIR HAS BEEN BUILDING OVER THE NORTHERN AND CENTRAL
PLAINS AND WILL SURGE INTO NORTH TEXAS BEHIND THE EXITING
SURFACE LOW. THIS WILL RESULT IN RAIN TRANSITIONING TO SNOW WEST
TO EAST ALONG AND NORTH OF I-20 FROM LATE MORNING (NW) THROUGH
MID AFTERNOON (NE). WE STILL EXPECT 1-3 INCHES OVER THE NORTHERN
TWO ROWS OF COUNTIES WITH THE HIGHEST AMOUNTS GENERALLY EAST OF A
SHERMAN TO GREENVILLE LINE. WOULD NOT BE SURPRISED IF A BAND OF
HEAVIER SNOW OCCURRED OVER THE NORTHEAST COUNTIES AROUND PARIS
WHERE THE 700MB FRONTOGENESIS IS MORE LIKELY TO ENHANCE THE
WRAP-AROUND BANDING. THE SNOW IS EXPECTED TO END OVER THE
NORTHEAST BY MIDNIGHT. SNOW ACROSS OKLAHOMA AND WESTERN ARKANSAS
COULD TOTAL 4-8 INCHES...AND TRAVEL NORTH OF THE RED RIVER OR INTO
WESTERN ARKANSAS WILL BE TREACHEROUS CHRISTMAS DAY THROUGH
WEDNESDAY.
A WIND ADVISORY WILL BE NEEDED CHRISTMAS AFTERNOON AND NIGHT AS
NORTH WINDS BLOW 20-30 MPH WITH GUSTS TO 40MPH. BLOWING SNOW WILL
BE POSSIBLE IN THE AFTERNOON AND OVERNIGHT HOURS WHERE SNOW HAS
OCCURRED. IT WILL BE BITTERLY COLD ON CHRISTMAS NIGHT WITH WIND
CHILLS IN THE LOWER SINGLE DIGITS AND TEENS. ALSO ANY MOISTURE
REMAINING ON ROADWAYS CHRISTMAS EVENING WILL FREEZE OVERNIGHT SO
WEDNESDAY MORNING COMMUTERS NEED TO BE ALERT FOR ICY SPOTS.
COLD AND DRY FOR WEDNESDAY. TEMPERATURES MODERATE ON THURSDAY AS
WINDS RETURN SOUTH. ANOTHER COLD FRONT WILL MOVE THROUGH THE
REGION FRIDAY WITH A CHANCE OF SHOWERS OVER THE CENTRAL AND
EASTERN COUNTIES. TEMPERATURES BEHIND THIS FRONT WILL NOT BE AS
COLD...BUT WILL KEEP HIGHS/LOWS BELOW NORMAL OVER THE WEEKEND.
75
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 44 46 21 35 21 / 50 70 10 5 5
WACO, TX 45 53 23 42 18 / 60 50 10 5 5
PARIS, TX 42 43 21 31 15 / 50 80 40 10 5
DENTON, TX 40 42 20 31 17 / 50 80 10 5 5
MCKINNEY, TX 43 43 22 31 16 / 50 80 20 10 5
DALLAS, TX 45 46 22 36 23 / 50 70 10 5 5
TERRELL, TX 45 48 24 35 18 / 50 80 20 10 5
CORSICANA, TX 46 52 23 40 21 / 60 70 10 5 5
TEMPLE, TX 49 56 23 43 20 / 70 40 10 5 5
MINERAL WELLS, TX 40 41 17 35 18 / 50 60 10 5 5
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM NOON TO 9 PM CST TUESDAY FOR
TXZ091>095-103>107.
&&
$$
/
FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION
VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP (ALL LOWER CASE)
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
507 PM CST MON DEC 24 2012
UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE
.SHORT TERM...TONIGHT AND TUESDAY.
LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A SHORTWAVE
TROUGH EXTENDING FROM NE WISCONSIN TO SOUTHERN LOWER MICHIGAN EARLY
THIS AFTERNOON. COMMA HEAD PRECIP WITH A LITTLE HELP FROM A LIGHT
LAKE EFFECT COMPONENT PRODUCED AREAS OF LIGHT SNOW THAT LINGERED
ACROSS NORTHEAST AND EAST-CENTRAL WISCONSIN THROUGH MID-AFTERNOON
BUT IS CURRENTLY EXITING TO THE EAST. WILL SHOW MOST OF THE PRECIP
ENDING BY 00Z THIS EVENING. IMPROVING CONDITIONS ARE OCCURRING OVER
CENTRAL AND NORTH-CENTRAL WISCONSIN WHERE BREAKS IN THE OVERCAST ARE
GROWING LARGER. HIGH PRESSURE IS BUILDING SOUTHWARD ACROSS THE
NORTHERN PLAINS WHERE SKIES ARE MOSTLY CLEAR AND COLD. THE MAIN
FORECAST CONCERNS INCLUDE THE TIMING OF THE END OF THE PRECIP AND
CLEARING TRENDS TONIGHT.
TONIGHT...THE SHORTWAVE TROUGH WILL BE WELL EAST OF THE REGION OVER
LOWER MICHIGAN AT THE START OF THE PERIOD. RESIDUAL MOISTURE WILL
TAKE AWHILE TO PUSH OUT OF THE REGION...SO WILL START THE EVENING
WITH MOSTLY CLOUDY CONDITIONS WITH A CHANCE OF FLURRIES OVER NE
WISCONSIN. BUT STRONG DRY AIR ADVECTION OVER NORTHWEST WISCONSIN
WILL SLOWLY MOVE SOUTHEAST THROUGH THE NIGHT AND GRADUALLY CLEAR OUT
THE SKIES ACROSS THE MAJORITY OF THE REGION. THE LONE EXCEPTION
WILL BE OVER N-C WISCONSIN WHERE LIGHT NW FLOW WILL CONTINUE TO
GENERATE LAKE EFFECT CLOUDS AND LIGHT SNOW SHOWERS. TEMPS WILL FALL
TO NEAR ZERO OVER THE COLD SPOTS OF LINCOLN COUNTY WHERE SKIES WILL
CLEAR FIRST TO THE MIDDLE TEENS NEAR LAKE MICHIGAN WHERE CLOUDS WILL
CLEAR LAST.
TUESDAY...CANADIAN HIGH PRESSURE WILL BUILD SOUTHEAST ACROSS THE
NORTHERN PLAINS AND NOSE ITS WAY ACROSS THE WESTERN GREAT LAKES.
LIGHT NORTHWEST FLOW WILL CONTINUE OFF LAKE SUPERIOR INTO N-C
WISCONSIN THROUGH THE MORNING...WHICH WILL KEEP SCT FLURRIES...AND
PARTLY TO MOSTLY CLOUDY CONDITIONS THERE. ELSEWHERE...MOSTLY SUNNY
CONDITIONS SHOULD PREVAIL. HIGHS RANGING FROM THE MID TEENS WEST TO
THE MID 20S EAST.
.LONG TERM...TUESDAY NIGHT THRU NEXT SUNDAY.
OVERALL...NO SIGNIFICANT CHANGES TO THE LONG TERM FORECAST. MAIN
FOCUS WAS TO TRY ADD A BIT MORE DETAIL REGARDING LES POTENTIAL
FOR LAKE MICHIGAN COUNTIES FOR WEDNESDAY.
MODELS CONTINUE TO BE IN FAIRLY GOOD AGREEMENT ON OVERALL TRACK OF
SOUTHERN STORM SYSTEM FORECAST TO TRACK TO THE OHIO VALLEY ON
WEDNESDAY. AS PREVIOUSLY FORECAST...THE NORTHERN FRINGE OF STRATIFORM
PRECIPITATION SHIELD WILL JUST CLIP EXTREME SOUTHEAST WISCONSIN
AND THE SOUTHERN PORTION OF LAKE MICHIGAN LATE WEDNESDAY. OTHER
THAN MIDDLE TO HIGH-LEVEL CLOUDS...THE MAIN IMPACT OF THIS SYSTEM
WILL BE TO CREATE A DEEP NORTHEASTERLY WIND FLOW EXTENDING FROM
THE SURFACE UP TO NEAR 700 MB. MAXIMUM OVERWATER BOUNDARY LAYER
FETCH ALSO IN PLACE BY 12Z WEDNESDAY. EXAMINATION OF MODIFIED
FORECAST GFS/NAM SOUNDINGS OVER LAKESHORE COUNTIES INDICATE A
FAIRLY DEEP MOIST AND UNSTABLE LAYER...WITH INVERSION HEIGHTS
APPROACHING 7000 FT AGL OVER WESTERN LAKE MICHIGAN. NAM/GFS ALSO
SUGGEST THAT MOIST LAYER MAY GROW DEEP ENOUGH TO PENETRATE INTO
FAVORABLE DENDRITIC GROWTH ZONE. WATER SURFACE TO 850 DELTA T
VALUES ON THE ORDER OF -16C TO -18C BY 12Z WEDNESDAY OVER THE
NORTHERN HALF OF LAKE MICHIGAN. GFS HAS BEEN FAIRLY CONSISTENT
LAST FEW RUNS...SPITTING OUT AREA OF QPF OVER NORTHERN LAKE
MICHIGAN AFTER 06Z WEDNESDAY AND BRINGING IT ONSHORE BY 12Z
WEDNESDAY. GIVEN OVERALL SYNOPTIC SETUP...NO REASON TO DISCOUNT
SIGNAL FROM GFS. BOTTOM LINE IS FAIRLY DECENT SET-UP FOR LAKE
EFFECT OVER MANITOWOC AND KEWAUNEE COUNTIES STARTING AROUND
DAYBREAK WEDNESDAY AND PERHAPS CONTINUING FOR MUCH OF THE DAY.
GIVEN BOUNDARY LAYER WINDS SPEEDS...WOULD EXPECT MULTIPLE AND SOMEWHAT
LES ORGANIZED LES BANDS RATHER THAN A SINGLE BAND. GIVEN THE
MESOSCALE NATURE OF LES PRECIPITATION WILL LET LATER SHIFTS TRY TO
REFINE THE DETAILS. FELT CONFIDENT ENOUGH AT THIS POINT TO AT
LEAST ADJUST POPS UPWARD INTO THE CHANCE CATEGORY ON WEDNESDAY.
FINALLY...GIVEN DEEP AND PERSISTENT NORHEASTERLY FLOW...ANY LES
BANDS THAT DEVELOP MAY BE ABLE TO PENETRATE AS FAR WEST AS THE FOX
RIVER VALLEY BEFORE WEAKNING. AS OHIO VALLEY STORM SYSTEM
CONTINUES TO MOVE NORTHEAST TO THE EASTERN SEABOARD...BOUNDARY
LAYER WINDS WILL BACK TO OFFSHORE WEDNESDAY NIGHT PUSHING ANY LES
BAND SOUTHWARD. FAIRLY TRANQUIL DAY ON THURSDAY AS WEAK HIGH
PRESSURE RIDGE MOVES ACROSS THE FORTECAST AREA.
THEN BY FRIDAY...SOUTHERN AND NORTHERN STREAM ENERGY BEGIN TO
APPROACH THE CENTRAL PLAINS AND UPPER MISSISSIPPI VALLEY.
UNCERTAINTY REMAINS AS TO HOW THESE FEATURES WILL INTERACT...WITH
CONCENSUS OF GUIDANCE SUGGESTING PERHAPS SOME PHASING OVER THE
OHIO VALLEY FRIDAY NIGHT. REGARDLESS...COMBINATION OF THESE
FEATURES SHOULD BE ABLE TO CREATE WAA ADVECTION REGIME AND DRAW
ADEQUATE MOISTURE NORTHWARD TOWARD THE FORECAST AREA TO GENERATE
BROAD AND GENERALLY LIGHT AREA OF QPF LIKELY TO SPREAD INTO THE
FORECAST AREA LATE ON FRIDAY INTO SATURDAY. LEANING MORE TOWARD
SOMEWHAT LESS ORGANIZED INVERTED TROUGH LOOK OF THE ECMWF AND
OPERATIONAL GFS FOR FRIDAY SYSTEM. INVERTED TROUGH AND CYCLONIC
FLOW MAY HANG BACK ACROSS THE WESTERN GREAT LAKES INTO
SATURDAY...THUS CONTINUE CHANCE POPS UNTIL THEN AS PER PREVIOUS
FORECAST.
DAYTIME TEMPERATURES SHOULD GRADUALLY MODERATE BY THE END OF THE
WEEK TO NEAR OF PERHAPS SLIGHTLY ABOVE NORMAL.
&&
.AVIATION...PATCHY MVFR CIGS WILL CONTINUE DISSIPATE THIS EVENING.
EVENTUALLY VFR CONDITIONS TO PREVAIL OVERNIGHT INTO TUESDAY WITH
THE EXCEPTION OF PATCHY MVFR CIGS NEAR THE GREAT LAKES.
TDH
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
236 PM CST SUN DEC 23 2012
.SHORT TERM...TONIGHT AND MONDAY
THE LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW ARCTIC HIGH
PRESSURE STRETCHING FROM NORTHERN ALBERTA TO THE WESTERN GREAT LAKES
EARLY THIS AFTERNOON. LOW LEVEL STRATO-CU RAPIDLY DISSIPATED LATE
THIS MORNING ACROSS ALL BUT FAR NORTH-CENTRAL WISCONSIN. MEANWHILE
UPSTREAM...A SHORTWAVE TROUGH IS MOVING EAST OVER NORTH-DAKOTA WHERE
IT IS PRODUCING 1-3SM IN LIGHT SNOW. MID AND HIGH CLOUDS ARE
ALREADY ENTERING WESTERN WISCONSIN AHEAD OF THIS SYSTEM. AS THE
SHORTWAVE CONTINUES TO MOVE EAST THROUGH THE REGION LATE TONIGHT AND
TOMORROW...PRECIP CHANCES ARE THE MAIN FORECAST CONCERN.
TONIGHT...HIGH PRESSURE WILL BE IN PLACE FOR THE FIRST PART OF THE
EVENING WITH ONLY LIGHT NORTHWEST FLOW CREATING LOW STRATO-CU OVER
FAR N-C WISCONSIN. HOWEVER...MID AND HIGH CLOUDS WILL BE ON THE
INCREASE AND LOWERING THROUGH THE NIGHT AHEAD OF A SHORTWAVE TROUGH
MOVING EAST OVER THE NORTHERN PLAINS. THIS WAVE WILL BE APPROACHING
THE NORTHERN MISSISSIPPI VALLEY LATE TONIGHT...AND WILL PUSH DECENT
MID AND UPPER FORCING INTO THE REGION. 850MB LOW AND SURFACE
INVERTED TROUGH WILL HANG BACK OVER NE IOWA AND SOUTHEAST MINNESOTA
WHERE LOW LEVEL MOISTURE ARRIVES BY 12Z MONDAY. AS A
RESULT...PROGGED SOUNDINGS INDICATE A PROMINENT DRY WEDGE BETWEEN
925 AND 700MB THAT WILL HAVE TO SATURATE BEFORE PRECIP ARRIVES.
KEPT A SMALL CHANCE OF LIGHT SNOW OVER N-C WISCONSIN WHERE LOW
STRATO-CU COULD BECOME SEEDED BY THE LOWERING MID-DECK LATE. BUT THINK
THE REMAINING PART OF THE CWA WILL HAVE TO WAIT UNTIL MONDAY MORNING
FOR PRECIP CHANCES. LOWS IN THE MIDDLE SINGLE DIGITS NORTH TO THE
MID TEENS SOUTH.
MONDAY...THE SHORTWAVE TROUGH WILL MOVE ACROSS THE STATE THROUGH
ABOUT MID-AFTERNOON BEFORE DEPARTING TO THE EAST. WILL SEE
INCREASING AMOUNTS OF LOW AND MID-LEVEL MOISTURE...AND THE DRY WEDGE
IN THE SOUNDINGS ERODES OVER THE COURSE OF THE MORNING. DESPITE THE
850MB LOW AND INVERTED SURFACE TROUGH PASSING BY TO OUR
SOUTH...THINK WILL HAVE ENOUGH LIFT ABOVE 700MB FOR AT LEAST A
CHANCE OF LIGHT SNOW EVERYWHERE. THE BEST CHANCES WILL REMAIN OVER
N-C WISCONSIN AND THE LAKE MICHIGAN SHORELINE DUE TO THE AID OF A
SMALL LAKE EFFECT COMPONENT. THOUGH THE FORCING WILL EXIT THE STATE
DURING THE AFTERNOON...IT SEEMS THAT ENOUGH LOW LEVEL MOISTURE WILL
LINGER TO KEEP SKIES CLOUDY WITH SCATTERED FLURRY ACTIVITY. WILL
SHOW A HALF INCH TO AN INCH OF ACCUMULATION OVER N-C AND FAR NE
WISCONSIN. HIGHS MAINLY IN THE LOW TO MID 20S.
.LONG TERM...MONDAY NIGHT THROUGH SATURDAY.
WESTERN GREAT LAKES REGION LOOKS TO REMAIN ON THE NORTHERN
PERIPHERY OF RATHER ACTIVE SOUTHERN STREAM. OTHER THAN SOME
LINGERING LIGHT SNOW OR FLURRIES ACROSS THE FAR EASTERN SECTION OF
THE FORECAST AREA MONDAY EVENING WITH DEPARTING DISTURBANCE...GENERALLY
BENIGN WEATHER EXPECTED OVER THE FORECAST AREA THROUGH MOST OF THE
WORK WEEK. EXCEPTION WILL BE SOME MARGINAL LAKE EFFECT SNOW
CHANCES ALONG THE LAKE MICHIGAN SHORELINE AND THE TRADITIONAL LAKE
SUPERIOR SNOW BELT REGION. DAYTIME TEMPERATURES WILL START OUT A
FEW DEGREES BELOW NORMAL EARLY IN THE WEEK THEN GRADUALLY REBOUND
TO NEAR OR SLIGHTLY ABOVE NORMAL BY THE END OF THE WEEK.
MODELS CONTINUE TO MAINTAIN THAT AN IMPRESSIVE STORM SYSTEM WILL
TAKE SHAPE OVER THE SOUTHERN MISSISSIPPI VALLEY TUESDAY NIGHT THEN
HEAD NORTHEAST ACROSS THE OHIO VALLEY. SYSTEM WILL LIKELY GET
CLOSE ENOUGH TO BRING MID-HIGH CLOUDS INTO THE AREA LATE TUESDAY
NIGHT INTO WEDNESDAY. LIGHT STRATIFORM PRECIPITATION MAY CLIP
SOUTHEAST CORNER OF WISCONSIN...BUT SHOULD STAY SOUTH OF THE
FORECAST AREA. HOWEVER...WILL NEED TO KEEP AN EYE ON THIS SYSTEM
AS A SLIGHT JOG TO THE WEST COULD BRING A LITTLE LIGHT SNOW INTO
FAR SOUTHEAST PORTION OF THE FORECAST AREA. IN ADDITION...WEAK
NORTHERN STREAM DISTURBANCE IS ALSO FORECAST TO APPROACH THE
FORECAST AREA LATE WEDNESDAY AND POSSIBLY PHASE WITH MAIN SYSTEM
OVER LOWER MICHIGAN. THIS WEAK DISTURBANCE COULD ALSO BRING A
LITTLE LIGHT SNOW OR FLURRIES OVER EASTERN WISCONSIN LATE ON
WEDNESDAY. FINALLY...A PERIPHERAL EFFECT OF SYSTEM MOVING ACROSS
THE OHIO VALLEY WILL BE THAT A DEEP LAYER OF NORTHEAST WINDS WILL
DEVELOP AFTER 06Z WEDNESDAY AND PERSIST UNTIL ABOUT 06Z THURSDAY.
DESPITE A SOMEWHAT FAVORABLE OVERWATER FETCH...LOW-LEVEL
INSTABLITY NOT IMPRESSIVE. LOOKS LIKE THE MOST FAVORABLE WINDOW
FOR MARGINAL LES WOULD BE FROM 06Z TO 18Z WEDNESDAY. MAINTAINED
LOW CHANCE POPS ALONG THE LAKESHORE ESPECIALLY FROM KEWAUNEE
SOUTHWARD.
MEDIUM RANGE MODELS STILL HINTING AT ANOTHER SOUTHERN STREAM SYSTEM
TO EVOLVE OVER THE SOUTHERN MISSISSIPPI VALLEY FRIDAY...IN ADDITION
TO ANOTHER WEAKER PEICE OF NORTHERN STREAM ENERGY FORECAST TO
WORK ACROSS THE NORTHERN PLAINS. ALTHOUGH CONFIDENCE STILL LOW
WITH RESPECT ANY INTERACTION WITH THESE FEATURES...IT APPEARS THAT
A BROAD WAA REGIME DOWNSTREAM MAY GENERATE SOME LIGHT SNOW OVER
THE CENTRAL MISSISSIPPI VALLEY THAT COULD SPREAD INTO WISCONSIN
SOMETIME ON FRIDAY. FOR NOW...MAINTAINED CHANCE POPS FRIDAY INTO
SATURDAY.
&&
.AVIATION...MVFR CIGS ARE RAPIDLY ERODING LATE THIS MORNING...WHICH
SHOULD LEAVE VFR CONDITIONS ACROSS MOST OF THE REGION BY EARLY THIS
AFTERNOON. THEREAFTER...MID AND HIGH CLOUDS WILL BE INCREASING THIS
EVENING AND LOWERING OVERNIGHT AHEAD OF THE NEXT DISTURBANCE. LIGHT
SNOW CHANCES WILL INCREASE ON MONDAY MORNING...AND THE BEST CHANCE
WILL OCCUR OVER NORTH-CENTRAL WISCONSIN...AND ALSO NEAR THE LAKE
MICHIGAN SHORELINE WHERE LIGHT NORTHEAST WINDS MAY GENERATE LIGHT
LAKE EFFECT SNOW SHOWERS. MVFR TO IFR CONDITIONS ARE LIKELY OVER
N-C WISCONSIN BENEATH THE MOST PERSISTENT LIGHT SNOW ACTIVITY DURING
THE MORNING...BUT MVFR CIGS COULD BECOME WIDESPREAD IN THE AFTERNOON.
MPC
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
MPC/ESB
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1148 AM CST SUN DEC 23 2012
.SHORT TERM...TODAY THROUGH TUESDAY NIGHT
258 AM CST SUN DEC 23 2012
MAIN FORECAST CONCERNS ARE ON LIGHT PRECIPITATION TONIGHT INTO
MONDAY...INCLUDING POTENTIAL NOW FOR SOME FREEZING DRIZZLE SOUTH OF
I-90.
CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED TROUGHING OVER THE NORTHEAST PACIFIC INTO THE PACIFIC
NORTHWEST...A SHORTWAVE TROUGH CROSSING IDAHO...RIDGING OVER THE
PLAINS...AND A SHORTWAVE OVER EASTERN LAKE SUPERIOR. ACCOMPANYING
THE EASTERN LAKE SUPERIOR SHORTWAVE WAS A SERIES OF TWO COLD FRONTS
PER SURFACE ANALYSIS. THE FIRST EXTENDED FROM LAKE HURON TO ST
LOUIS...WHILE THE SECOND STRETCHED FROM NORTHERN LAKE MICHIGAN TO
RED WING MINNESOTA. A MASS OF LOW STRATUS WAS PRESENT ALONG AND
BEHIND THE SECOND COLD FRONT...WHICH STRETCHED ALMOST UP TO THE
INTERNATIONAL BORDER. SOME FLURRIES WERE OCCURRING AS WELL WITH THE
STRATUS DECK OVER NORTHERN WI AND MN WHERE IT INTERSECTED THE
DENDRITIC GROWTH ZONE. 00Z INL AND ABR SOUNDINGS REPRESENTED THE
STRATUS DECK WELL WITH SATURATION AROUND 900MB WHERE A FAIRLY STRONG
INVERSION WAS PRESENT. CHILLY AIR TOO ACCOMPANYING THE SECOND COLD
FRONT...NOTED BY 925MB TEMPS OF -4C AT MPX COMPARED TO -14C AT ABR
AND -16C AT INL FROM 00Z SOUNDING DATA. TO THE NORTHWEST...CANADIAN
HIGH PRESSURE WAS NOSING DOWN FROM NORTHERN SASKATCHEWAN INTO
MINNESOTA. TEMPERATURES WERE WELL BELOW ZERO OVER SOUTH CENTRAL
CANADA UNDER THE CORE OF THE SURFACE HIGH. LASTLY...FARTHER TO THE
WEST...MID AND HIGH CLOUDS WERE ON THE INCREASE OVER THE NORTHERN
PLAINS...DOWNSTREAM OF THE IDAHO SHORTWAVE.
TODAY...THE UPPER RIDGING SEEN OVER THE PLAINS WILL SHIFT OVER THE
FORECAST AREA...PUSHED BY THE TROUGH OVER IDAHO MARCHING EAST...
PROVIDING CONTINUED SUBSIDENCE FROM ALOFT. BIGGEST CONCERN IS IF THE
LOW CLOUDS MARCHING SOUTH INTO NORTHERN PORTIONS OF THE AREA AT THIS
TIME WILL: 1. OVERSPREAD THE AREA AND 2. NOT DISSIPATE BECAUSE OF
THE SUBSIDENCE STRENGTHENING THE LOW LEVEL INVERSION. THE RAP MODEL
APPEARS TO HAVE THE BEST HANDLE ON THE STRATUS SITUATION...BUT IS
VERY INTERESTING TO LOOK AT. IF ONE USES THE 900MB OR 925MB RH
PROGS...WHICH MATCH UP WELL WITH 00Z SOUNDING DATA WHERE THE STRATUS
WAS VERTICALLY...IT WOULD SUGGEST THAT THE STRATUS MAY TEND TO BREAK
UP IN THE 10-14Z TIME FRAME...THOUGH LINGER OVER NORTHEAST WISCONSIN
WITH THE AIDED LAKE EFFECT OFF SUPERIOR. HOWEVER...MODEL SOUNDINGS
SHOW THAT THE INVERSION LOWERS THROUGH THE DAY...PUSHING THE STRATUS
LOWER VERTICALLY...SUCH THAT A 950MB RH PROG IS MORE REPRESENTATIVE.
THE LOWERING INVERSION MAKES SENSE GIVEN THE UPPER RIDGING MOVING
OVERHEAD. GIVEN THE TIME OF YEAR WHICH FAVORS STRATUS NOT WANTING TO
DISSIPATE...HAVE FOLLOWED THE MORE PESSIMISTIC 950MB RH PROG...WHICH
BASICALLY MEANS LOW CLOUDS ENCOMPASS THE AREA BY 13Z OR SO AND STICK
AROUND THROUGH THE DAY. THE ONE THING THE LOWERING INVERSION DOES IS
GET THE STRATUS OUT OF THE DENDRITIC GROWTH ZONE...SO THE FLURRIES
SHOULD STOP. THE CLOUD DEPTH BECOMES TOO SMALL AND AIRMASS TOO
SUBSIDENT TO WORRY ABOUT A FREEZING DRIZZLE THREAT. A COLDER DAY IS
DEFINITELY IN STORE WITH THE CLOUDS AROUND AND 925MB TEMPS FALLING
TO -6 TO -10C BY 18Z.
TONIGHT INTO MONDAY...FOCUS IS ON THE SHORTWAVE TROUGH CROSSING
IDAHO. MODELS COMPARED TO YESTERDAY AT THIS TIME HAVE TRENDED TO THE
MORE POTENT IDEA...BUT ARE DEFINITELY FARTHER NORTH. BY 12Z
MONDAY...THE SHORTWAVE TROUGH IS PROGGED TO STRETCH FROM CENTRAL
MINNESOTA INTO NORTHERN IOWA. AS THE TROUGH APPROACHES TONIGHT...WE
SHOULD SEE A RAPID INCREASE IN MID AND HIGH CLOUDS...NOTED BY
CONDENSATION PRESSURE DEFICITS AS WELL AS LIFT ON THE 285-300K
SURFACES. DESPITE THE IMPRESSIVE LOOK OF THE SHORTWAVE TROUGH AT
500MB IN THE MODELS...QPF IS VERY HARD TO COME BY PRIOR TO 12Z IN
THE 23.00Z GFS/NAM/UKMET. ONLY THE 23.00Z CANADIAN PRODUCES SOME QPF
AND THAT IS ONLY A COUPLE HUNDREDTHS AT MOST. IT APPEARS MUCH OF THE
FORCING IS HAVING TO GO INTO MOISTENING THE LOW TO MID-LEVELS...
GIVEN THE PRE-EXISTING DRY AIRMASS WHICH CAN BE SEEN ON THE 00Z MPX
AND ABR SOUNDINGS. STILL FEEL CONFIDENT TO HAVE AT LEAST A 20-30
PERCENT CHANCE IN THE 09-12Z PERIOD TONIGHT GIVEN ALL THE FORCING.
EVEN HEADING INTO THE 12-18Z TIME WINDOW...WHEN THE SHORTWAVE TROUGH
IS CROSSING THE AREA...MODELS ARE STRUGGLING TO PRODUCE MUCH IF ANY
QPF WITH THE 23.00Z CANADIAN THE MOST BULLISH. HOWEVER...DIGGING
INTO THE HIRES ARW AND NMM MODELS...THEY ALL SHOW A BAND OF SNOW
CROSSING ALONG AND NORTH OF I-94 BETWEEN 12-18Z. GIVEN THE STRENGTH
OF THE TROUGH...THESE HIRES MODELS AND THE BULLISH CANADIAN...
INCREASED PRECIPITATION CHANCES TOWARDS 60 UP IN TAYLOR COUNTY.
CHANCES DECREASE TO THE SOUTH GIVEN THE FARTHER NORTH TRACK.
MEANWHILE...ANOTHER INTERESTING THING HAS SHOWN UP. THIS SHORTWAVE
TROUGH IS STRONG ENOUGH TO PRODUCE AN INVERTED SURFACE TROUGH...
WHICH WAS ALWAYS KNOWN. HOWEVER...THE NAM...CANADIAN...HIRES
NMM AND 23.03Z SREF ALL PRODUCE SOME VERY LIGHT QPF ALONG THE
INVERTED TROUGH LATE TONIGHT INTO THE DAY MONDAY. SOUNDINGS SOUTH OF
I-90 SHOW PROBLEMS WITH ICE IN THE CLOUDS...THUS VERY CONCERNED
OF FREEZING DRIZZLE AND AS SUCH ADDED IT TO THE FORECAST. IF THE
SREF IS RIGHT...WHICH ALBEIT IS 2/3 DOMINATED BY NAM RELATED
MEMBERS...THE AREA ACROSS FAR SOUTHWEST WISCONSIN INTO CLAYTON
COUNTY EVENTUALLY WOULD NEED AN ADVISORY FOR FREEZING DRIZZLE. MOST
OF THE PRECIPITATION SHOULD PUSH EAST OF THE AREA FOR THE AFTERNOON
AS THE SHORTWAVE TROUGH SHIFTS EAST TO LAKE MICHIGAN. IN THE WAKE OF
THE SHORTWAVE TROUGH...WE GET A REINFORCING SHOT OF COLD AIR FROM
THE SOUTH CENTRAL CANADIAN HIGH...NOTED BY 925MB TEMPS DROPPING TO
-8 TO -12C.
MONDAY NIGHT THROUGH TUESDAY NIGHT...MUCH OF THE CURRENT NORTHEAST
PACIFIC TROUGH IS SLATED TO DIG DOWN INTO THE FOUR CORNERS REGION ON
MONDAY...DIVE SOUTH INTO TEXAS ON TUESDAY AND TURN NEUTRAL TO
NEGATIVE TILT AS IT LIFTS INTO THE TENNESSEE VALLEY BY 12Z
WEDNESDAY. AN INTENSIFYING LOW PRESSURE SYSTEM IS EXPECTED TO
ACCOMPANY THE TROUGH...WHICH FOLLOWING THE CLASSIC CYCLONE
DEVELOPMENT WILL HAVE A DEFORMATION/COLD CONVEYOR BELT OF
PRECIPITATION. MODELS OVERALL HAVE BEEN VERY CONSISTENT ON THE TRACK
OF THIS TROUGH AND SYSTEM THE PAST COUPLE DAYS...WHICH KEEPS ALL THE
DEFORMATION PRECIPITATION WELL SOUTHEAST OF THE AREA. IN FACT...THE
BULK OF THE MID AND HIGH CLOUDS LOOK TO STAY TO THE SOUTHEAST. THE
ONLY SYNOPTIC ITEM OF WORRY WOULD BE A NORTHERN STREAM TYPE TROUGH
CROSSING THE DAKOTAS TUESDAY NIGHT...SPREADING SOME MID AND HIGH
CLOUDS ACROSS MINNESOTA. OTHERWISE...THE FORECAST AREA IS DOMINATED
BY THE CANADIAN HIGH OVER SOUTH CENTRAL CANADA BEGINNING TO DROP
SOUTH INTO THE NORTHERN PLAINS. 925MB TEMPS COOL EVEN MORE AS THE
HIGH DROPS SOUTH...DOWN TO -10 TO -14C BY 12Z TUESDAY AND HOLDING
STEADY THROUGH TUESDAY NIGHT. THE BIG QUESTION THEN BECOMES IF LOW
STRATUS THAT IS HANGING AROUND FROM MONDAY CAN CLEAR OUT...SINCE THE
COOLING 925MB TEMPS...SNOW COVER AND OVERALL LIGHT WINDS AT THE
SURFACE WOULD BE FAVORABLE FOR SOME CHILLY NIGHTS. GFS SOUNDINGS
SUGGEST THAT SKIES SHOULD CLEAR MONDAY NIGHT...BUT CONFIDENCE IS
SOMEWHAT LOW GIVEN THE CURRENT STRATUS SITUATION. NAM SOUNDINGS ARE
MORE PESSIMISTIC WITH LOW LEVEL MOISTURE PRESENT AND MAY BE THE
WAY TO GO. THUS...HAVE WENT MORE CLOUDY WHICH TO SOME DEGREE WILL
HELP LIMIT THE TEMPERATURE FALL AS WELL AS RISE DURING THE DAY
TUESDAY. STILL...IT IS GOING TO BE COOL GIVEN THE COLD ADVECTION
PATTERN.
.LONG TERM...WEDNESDAY THROUGH SATURDAY NIGHT
258 AM CST SUN DEC 23 2012
23.00Z MODELS ARE IN GOOD AGREEMENT THROUGH THURSDAY WITH REGARDS TO
THE UPPER AND SURFACE PATTERNS...THEN BEGIN TO DIFFER FOR FRIDAY AND
INTO THE WEEKEND ON HANDLING TROUGHING COMING OUT OF THE WESTERN
U.S..
THE BEGINNING OF THE PERIOD STARTS OFF WITH THE POTENT TROUGH AND
STORM SYSTEM OVER THE TENNESSEE VALLEY...WHICH LIFTS NORTHEAST INTO
THE NORTHEASTERN U.S. ON THURSDAY. AGAIN...THIS SYSTEM IS TOO FAR
AWAY FROM US TO BRING ANY PRECIPITATION. INSTEAD...THE FORECAST AREA
REMAINS DOMINATED BY THE CANADIAN HIGH PRESSURE AREA...WHICH REMAINS
FORECAST TO MOVE INTO THE AREA WEDNESDAY NIGHT INTO THURSDAY. THIS
HIGH WILL KEEP CONDITIONS SEASONABLY COOL AND DRY. FOCUS THEN TURNS
TO A DEEP TROUGH FORMING OVER THE WESTERN U.S. DURING THE DAY
THURSDAY. MODELS SHIFT THIS TROUGH EAST INTO THE PLAINS FOR
FRIDAY...THOUGH MORE IMPORTANTLY IS WHAT HAPPENS TO THE MAIN CORE
SHORTWAVE AT THE BASE OF THE TROUGH. THE GFS/CANADIAN ARE QUITE
PROGRESSIVE...SHEARING IT OUT AND SENDING IT EASTWARD TOWARDS
TENNESSEE BY 00Z SATURDAY. MEANWHILE...THE ECMWF RUNS AND TO SOME
DEGREE THE UKMET CONTINUE TO INDICATE A MUCH DEEPER SCENARIO...
LIFTING THE SHORTWAVE UP INTO INDIANA AND OHIO ON SATURDAY. THIS
LATTER SOLUTION WOULD YIELD SOME DEFORMATION SNOW FOR THE AREA ON
SATURDAY...BEING PRECEDED BY SOME LIGHT WARM ADVECTION SNOW FOR
FRIDAY AND FRIDAY NIGHT. FOR NOW HAVE CONTINUED TO FOLLOW A
CONSENSUS APPROACH...YIELDING 30-40 PERCENT CHANCES OF SNOW AND
SLIGHTLY WARMER CONDITIONS. STILL RIGHT NOW IT DOES NOT APPEAR WE
WOULD BE DEALING WITH ANY SIGNIFICANT SNOW...BUT SOMETHING
CERTAINLY TO WATCH.
&&
.AVIATION...THIS AFTERNOON THROUGH MONDAY
1148 AM CST SUN DEC 23 2012
NORTHEAST DOWNSLOPE FLOW OFF THE NORTHERN WI HIGHLANDS HAS PRODUCED
SUBSIDENCE IN/UNDER THE STRONG SFC-850MB INVERSION. PILOT REPORTS
INDICATED THE LOW LEVEL MOISTURE/STRATUS CLOUDS ARE ONLY ABOUT 1K FT
THICK...ALLOWING FOR THE SUBSIDENCE/DOWNSLOPE FLOW TO BREAK/ERODE
THEM. HAVE TRENDED TAFS FOR THIS AFTERNOON/EVENING TOWARD VFR WITH
SCT STRATO-CU AROUND 1K FT AND CIRRUS ABOVE. MID LEVEL MOISTURE/
LIFT INCREASE TONIGHT AS A VIGOROUS SHORTWAVE APPROACHES WITH CIGS
LOWERING INTO THE 8K TO 10K FT RANGE AFTER MIDNIGHT. MUCH OF THE
LIFT GOES INTO SATURATING THE COLUMN...WHICH NOW LOOKS LIKE IT
EVENTUALLY OCCURS VERY LATE TONIGHT AND FOR MON MORNING. INTRODUCED
SOME MVFR VSBYS IN -SN/BR AS THIS WAVE PASSES. CIGS TO GO BACK TO
BKN/OVC IFR/MVFR WITH THE PASSING WAVE AND THE -SN.
FORCING/LIFT MOVE OFF TO THE EAST FOR THE AFTERNOON BUT PLENTY OF
SFC-850MB MOISTURE...TRAPPED IN/UNDER A SFC-800MB INVERSION...
REMAINS OVER THE AREA IN ITS WAKE. VSBYS SHOULD GO BACK TO VFR FOR
MON AFTERNOON BUT LOOKING LIKE MVFR/LCL IFR CIGS TO PERSIST THRU MON
INTO MON EVENING.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
258 AM CST SUN DEC 23 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...AJ
LONG TERM....AJ
AVIATION.....RRS
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
531 AM CST SUN DEC 23 2012
.SHORT TERM...TODAY THROUGH TUESDAY NIGHT
258 AM CST SUN DEC 23 2012
MAIN FORECAST CONCERNS ARE ON LIGHT PRECIPITATION TONIGHT INTO
MONDAY...INCLUDING POTENTIAL NOW FOR SOME FREEZING DRIZZLE SOUTH OF
I-90.
CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED TROUGHING OVER THE NORTHEAST PACIFIC INTO THE PACIFIC
NORTHWEST...A SHORTWAVE TROUGH CROSSING IDAHO...RIDGING OVER THE
PLAINS...AND A SHORTWAVE OVER EASTERN LAKE SUPERIOR. ACCOMPANYING
THE EASTERN LAKE SUPERIOR SHORTWAVE WAS A SERIES OF TWO COLD FRONTS
PER SURFACE ANALYSIS. THE FIRST EXTENDED FROM LAKE HURON TO ST
LOUIS...WHILE THE SECOND STRETCHED FROM NORTHERN LAKE MICHIGAN TO
RED WING MINNESOTA. A MASS OF LOW STRATUS WAS PRESENT ALONG AND
BEHIND THE SECOND COLD FRONT...WHICH STRETCHED ALMOST UP TO THE
INTERNATIONAL BORDER. SOME FLURRIES WERE OCCURRING AS WELL WITH THE
STRATUS DECK OVER NORTHERN WI AND MN WHERE IT INTERSECTED THE
DENDRITIC GROWTH ZONE. 00Z INL AND ABR SOUNDINGS REPRESENTED THE
STRATUS DECK WELL WITH SATURATION AROUND 900MB WHERE A FAIRLY STRONG
INVERSION WAS PRESENT. CHILLY AIR TOO ACCOMPANYING THE SECOND COLD
FRONT...NOTED BY 925MB TEMPS OF -4C AT MPX COMPARED TO -14C AT ABR
AND -16C AT INL FROM 00Z SOUNDING DATA. TO THE NORTHWEST...CANADIAN
HIGH PRESSURE WAS NOSING DOWN FROM NORTHERN SASKATCHEWAN INTO
MINNESOTA. TEMPERATURES WERE WELL BELOW ZERO OVER SOUTH CENTRAL
CANADA UNDER THE CORE OF THE SURFACE HIGH. LASTLY...FARTHER TO THE
WEST...MID AND HIGH CLOUDS WERE ON THE INCREASE OVER THE NORTHERN
PLAINS...DOWNSTREAM OF THE IDAHO SHORTWAVE.
TODAY...THE UPPER RIDGING SEEN OVER THE PLAINS WILL SHIFT OVER THE
FORECAST AREA...PUSHED BY THE TROUGH OVER IDAHO MARCHING EAST...
PROVIDING CONTINUED SUBSIDENCE FROM ALOFT. BIGGEST CONCERN IS IF THE
LOW CLOUDS MARCHING SOUTH INTO NORTHERN PORTIONS OF THE AREA AT THIS
TIME WILL: 1. OVERSPREAD THE AREA AND 2. NOT DISSIPATE BECAUSE OF
THE SUBSIDENCE STRENGTHENING THE LOW LEVEL INVERSION. THE RAP MODEL
APPEARS TO HAVE THE BEST HANDLE ON THE STRATUS SITUATION...BUT IS
VERY INTERESTING TO LOOK AT. IF ONE USES THE 900MB OR 925MB RH
PROGS...WHICH MATCH UP WELL WITH 00Z SOUNDING DATA WHERE THE STRATUS
WAS VERTICALLY...IT WOULD SUGGEST THAT THE STRATUS MAY TEND TO BREAK
UP IN THE 10-14Z TIME FRAME...THOUGH LINGER OVER NORTHEAST WISCONSIN
WITH THE AIDED LAKE EFFECT OFF SUPERIOR. HOWEVER...MODEL SOUNDINGS
SHOW THAT THE INVERSION LOWERS THROUGH THE DAY...PUSHING THE STRATUS
LOWER VERTICALLY...SUCH THAT A 950MB RH PROG IS MORE REPRESENTATIVE.
THE LOWERING INVERSION MAKES SENSE GIVEN THE UPPER RIDGING MOVING
OVERHEAD. GIVEN THE TIME OF YEAR WHICH FAVORS STRATUS NOT WANTING TO
DISSIPATE...HAVE FOLLOWED THE MORE PESSIMISTIC 950MB RH PROG...WHICH
BASICALLY MEANS LOW CLOUDS ENCOMPASS THE AREA BY 13Z OR SO AND STICK
AROUND THROUGH THE DAY. THE ONE THING THE LOWERING INVERSION DOES IS
GET THE STRATUS OUT OF THE DENDRITIC GROWTH ZONE...SO THE FLURRIES
SHOULD STOP. THE CLOUD DEPTH BECOMES TOO SMALL AND AIRMASS TOO
SUBSIDENT TO WORRY ABOUT A FREEZING DRIZZLE THREAT. A COLDER DAY IS
DEFINITELY IN STORE WITH THE CLOUDS AROUND AND 925MB TEMPS FALLING
TO -6 TO -10C BY 18Z.
TONIGHT INTO MONDAY...FOCUS IS ON THE SHORTWAVE TROUGH CROSSING
IDAHO. MODELS COMPARED TO YESTERDAY AT THIS TIME HAVE TRENDED TO THE
MORE POTENT IDEA...BUT ARE DEFINITELY FARTHER NORTH. BY 12Z
MONDAY...THE SHORTWAVE TROUGH IS PROGGED TO STRETCH FROM CENTRAL
MINNESOTA INTO NORTHERN IOWA. AS THE TROUGH APPROACHES TONIGHT...WE
SHOULD SEE A RAPID INCREASE IN MID AND HIGH CLOUDS...NOTED BY
CONDENSATION PRESSURE DEFICITS AS WELL AS LIFT ON THE 285-300K
SURFACES. DESPITE THE IMPRESSIVE LOOK OF THE SHORTWAVE TROUGH AT
500MB IN THE MODELS...QPF IS VERY HARD TO COME BY PRIOR TO 12Z IN
THE 23.00Z GFS/NAM/UKMET. ONLY THE 23.00Z CANADIAN PRODUCES SOME QPF
AND THAT IS ONLY A COUPLE HUNDREDTHS AT MOST. IT APPEARS MUCH OF THE
FORCING IS HAVING TO GO INTO MOISTENING THE LOW TO MID-LEVELS...
GIVEN THE PRE-EXISTING DRY AIRMASS WHICH CAN BE SEEN ON THE 00Z MPX
AND ABR SOUNDINGS. STILL FEEL CONFIDENT TO HAVE AT LEAST A 20-30
PERCENT CHANCE IN THE 09-12Z PERIOD TONIGHT GIVEN ALL THE FORCING.
EVEN HEADING INTO THE 12-18Z TIME WINDOW...WHEN THE SHORTWAVE TROUGH
IS CROSSING THE AREA...MODELS ARE STRUGGLING TO PRODUCE MUCH IF ANY
QPF WITH THE 23.00Z CANADIAN THE MOST BULLISH. HOWEVER...DIGGING
INTO THE HIRES ARW AND NMM MODELS...THEY ALL SHOW A BAND OF SNOW
CROSSING ALONG AND NORTH OF I-94 BETWEEN 12-18Z. GIVEN THE STRENGTH
OF THE TROUGH...THESE HIRES MODELS AND THE BULLISH CANADIAN...
INCREASED PRECIPITATION CHANCES TOWARDS 60 UP IN TAYLOR COUNTY.
CHANCES DECREASE TO THE SOUTH GIVEN THE FARTHER NORTH TRACK.
MEANWHILE...ANOTHER INTERESTING THING HAS SHOWN UP. THIS SHORTWAVE
TROUGH IS STRONG ENOUGH TO PRODUCE AN INVERTED SURFACE TROUGH...
WHICH WAS ALWAYS KNOWN. HOWEVER...THE NAM...CANADIAN...HIRES
NMM AND 23.03Z SREF ALL PRODUCE SOME VERY LIGHT QPF ALONG THE
INVERTED TROUGH LATE TONIGHT INTO THE DAY MONDAY. SOUNDINGS SOUTH OF
I-90 SHOW PROBLEMS WITH ICE IN THE CLOUDS...THUS VERY CONCERNED
OF FREEZING DRIZZLE AND AS SUCH ADDED IT TO THE FORECAST. IF THE
SREF IS RIGHT...WHICH ALBEIT IS 2/3 DOMINATED BY NAM RELATED
MEMBERS...THE AREA ACROSS FAR SOUTHWEST WISCONSIN INTO CLAYTON
COUNTY EVENTUALLY WOULD NEED AN ADVISORY FOR FREEZING DRIZZLE. MOST
OF THE PRECIPITATION SHOULD PUSH EAST OF THE AREA FOR THE AFTERNOON
AS THE SHORTWAVE TROUGH SHIFTS EAST TO LAKE MICHIGAN. IN THE WAKE OF
THE SHORTWAVE TROUGH...WE GET A REINFORCING SHOT OF COLD AIR FROM
THE SOUTH CENTRAL CANADIAN HIGH...NOTED BY 925MB TEMPS DROPPING TO
-8 TO -12C.
MONDAY NIGHT THROUGH TUESDAY NIGHT...MUCH OF THE CURRENT NORTHEAST
PACIFIC TROUGH IS SLATED TO DIG DOWN INTO THE FOUR CORNERS REGION ON
MONDAY...DIVE SOUTH INTO TEXAS ON TUESDAY AND TURN NEUTRAL TO
NEGATIVE TILT AS IT LIFTS INTO THE TENNESSEE VALLEY BY 12Z
WEDNESDAY. AN INTENSIFYING LOW PRESSURE SYSTEM IS EXPECTED TO
ACCOMPANY THE TROUGH...WHICH FOLLOWING THE CLASSIC CYCLONE
DEVELOPMENT WILL HAVE A DEFORMATION/COLD CONVEYOR BELT OF
PRECIPITATION. MODELS OVERALL HAVE BEEN VERY CONSISTENT ON THE TRACK
OF THIS TROUGH AND SYSTEM THE PAST COUPLE DAYS...WHICH KEEPS ALL THE
DEFORMATION PRECIPITATION WELL SOUTHEAST OF THE AREA. IN FACT...THE
BULK OF THE MID AND HIGH CLOUDS LOOK TO STAY TO THE SOUTHEAST. THE
ONLY SYNOPTIC ITEM OF WORRY WOULD BE A NORTHERN STREAM TYPE TROUGH
CROSSING THE DAKOTAS TUESDAY NIGHT...SPREADING SOME MID AND HIGH
CLOUDS ACROSS MINNESOTA. OTHERWISE...THE FORECAST AREA IS DOMINATED
BY THE CANADIAN HIGH OVER SOUTH CENTRAL CANADA BEGINNING TO DROP
SOUTH INTO THE NORTHERN PLAINS. 925MB TEMPS COOL EVEN MORE AS THE
HIGH DROPS SOUTH...DOWN TO -10 TO -14C BY 12Z TUESDAY AND HOLDING
STEADY THROUGH TUESDAY NIGHT. THE BIG QUESTION THEN BECOMES IF LOW
STRATUS THAT IS HANGING AROUND FROM MONDAY CAN CLEAR OUT...SINCE THE
COOLING 925MB TEMPS...SNOW COVER AND OVERALL LIGHT WINDS AT THE
SURFACE WOULD BE FAVORABLE FOR SOME CHILLY NIGHTS. GFS SOUNDINGS
SUGGEST THAT SKIES SHOULD CLEAR MONDAY NIGHT...BUT CONFIDENCE IS
SOMEWHAT LOW GIVEN THE CURRENT STRATUS SITUATION. NAM SOUNDINGS ARE
MORE PESSIMISTIC WITH LOW LEVEL MOISTURE PRESENT AND MAY BE THE
WAY TO GO. THUS...HAVE WENT MORE CLOUDY WHICH TO SOME DEGREE WILL
HELP LIMIT THE TEMPERATURE FALL AS WELL AS RISE DURING THE DAY
TUESDAY. STILL...IT IS GOING TO BE COOL GIVEN THE COLD ADVECTION
PATTERN.
.LONG TERM...WEDNESDAY THROUGH SATURDAY NIGHT
258 AM CST SUN DEC 23 2012
23.00Z MODELS ARE IN GOOD AGREEMENT THROUGH THURSDAY WITH REGARDS TO
THE UPPER AND SURFACE PATTERNS...THEN BEGIN TO DIFFER FOR FRIDAY AND
INTO THE WEEKEND ON HANDLING TROUGHING COMING OUT OF THE WESTERN
U.S..
THE BEGINNING OF THE PERIOD STARTS OFF WITH THE POTENT TROUGH AND
STORM SYSTEM OVER THE TENNESSEE VALLEY...WHICH LIFTS NORTHEAST INTO
THE NORTHEASTERN U.S. ON THURSDAY. AGAIN...THIS SYSTEM IS TOO FAR
AWAY FROM US TO BRING ANY PRECIPITATION. INSTEAD...THE FORECAST AREA
REMAINS DOMINATED BY THE CANADIAN HIGH PRESSURE AREA...WHICH REMAINS
FORECAST TO MOVE INTO THE AREA WEDNESDAY NIGHT INTO THURSDAY. THIS
HIGH WILL KEEP CONDITIONS SEASONABLY COOL AND DRY. FOCUS THEN TURNS
TO A DEEP TROUGH FORMING OVER THE WESTERN U.S. DURING THE DAY
THURSDAY. MODELS SHIFT THIS TROUGH EAST INTO THE PLAINS FOR
FRIDAY...THOUGH MORE IMPORTANTLY IS WHAT HAPPENS TO THE MAIN CORE
SHORTWAVE AT THE BASE OF THE TROUGH. THE GFS/CANADIAN ARE QUITE
PROGRESSIVE...SHEARING IT OUT AND SENDING IT EASTWARD TOWARDS
TENNESSEE BY 00Z SATURDAY. MEANWHILE...THE ECMWF RUNS AND TO SOME
DEGREE THE UKMET CONTINUE TO INDICATE A MUCH DEEPER SCENARIO...
LIFTING THE SHORTWAVE UP INTO INDIANA AND OHIO ON SATURDAY. THIS
LATTER SOLUTION WOULD YIELD SOME DEFORMATION SNOW FOR THE AREA ON
SATURDAY...BEING PRECEDED BY SOME LIGHT WARM ADVECTION SNOW FOR
FRIDAY AND FRIDAY NIGHT. FOR NOW HAVE CONTINUED TO FOLLOW A
CONSENSUS APPROACH...YIELDING 30-40 PERCENT CHANCES OF SNOW AND
SLIGHTLY WARMER CONDITIONS. STILL RIGHT NOW IT DOES NOT APPEAR WE
WOULD BE DEALING WITH ANY SIGNIFICANT SNOW...BUT SOMETHING
CERTAINLY TO WATCH.
&&
.AVIATION...TODAY AND TONIGHT
522 AM CST SUN DEC 23 2012
NORTH/NORTHEAST AIRFLOW OFF LAKE SUPERIOR WILL CONTINUE TO PRODUCE
AN EXPANSIVE DECK OF LOW MVFR/IFR STRATUS CLOUD COVER TODAY INTO
TONIGHT. LOOKING FURTHER....A TROUGH OF LOW PRESSURE MOVING OUT OF
THE DAKOTAS WILL BRING SOME LIGHT SNOW INTO PORTIONS OF CENTRAL MN
BY 12Z AND THEN INTO THE TAF SITES AFTER 12Z. WILL HAVE TO WATCH
FOR THE POSSIBILITY OF PATCHY FREEZING DRIZZLE AS WELL. WILL BRIEF
THE DAYSHIFT ABOUT THIS POSSIBILITY AND HAVE THEM ASSESS FOR THE
18Z TAF PACKAGE.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
258 AM CST SUN DEC 23 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...AJ
LONG TERM...AJ
AVIATION...DAS
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
258 AM CST SUN DEC 23 2012
.SHORT TERM...TODAY THROUGH TUESDAY NIGHT
258 AM CST SUN DEC 23 2012
MAIN FORECAST CONCERNS ARE ON LIGHT PRECIPITATION TONIGHT INTO
MONDAY...INCLUDING POTENTIAL NOW FOR SOME FREEZING DRIZZLE SOUTH OF
I-90.
CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED TROUGHING OVER THE NORTHEAST PACIFIC INTO THE PACIFIC
NORTHWEST...A SHORTWAVE TROUGH CROSSING IDAHO...RIDGING OVER THE
PLAINS...AND A SHORTWAVE OVER EASTERN LAKE SUPERIOR. ACCOMPANYING
THE EASTERN LAKE SUPERIOR SHORTWAVE WAS A SERIES OF TWO COLD FRONTS
PER SURFACE ANALYSIS. THE FIRST EXTENDED FROM LAKE HURON TO ST
LOUIS...WHILE THE SECOND STRETCHED FROM NORTHERN LAKE MICHIGAN TO
RED WING MINNESOTA. A MASS OF LOW STRATUS WAS PRESENT ALONG AND
BEHIND THE SECOND COLD FRONT...WHICH STRETCHED ALMOST UP TO THE
INTERNATIONAL BORDER. SOME FLURRIES WERE OCCURRING AS WELL WITH THE
STRATUS DECK OVER NORTHERN WI AND MN WHERE IT INTERSECTED THE
DENDRITIC GROWTH ZONE. 00Z INL AND ABR SOUNDINGS REPRESENTED THE
STRATUS DECK WELL WITH SATURATION AROUND 900MB WHERE A FAIRLY STRONG
INVERSION WAS PRESENT. CHILLY AIR TOO ACCOMPANYING THE SECOND COLD
FRONT...NOTED BY 925MB TEMPS OF -4C AT MPX COMPARED TO -14C AT ABR
AND -16C AT INL FROM 00Z SOUNDING DATA. TO THE NORTHWEST...CANADIAN
HIGH PRESSURE WAS NOSING DOWN FROM NORTHERN SASKATCHEWAN INTO
MINNESOTA. TEMPERATURES WERE WELL BELOW ZERO OVER SOUTH CENTRAL
CANADA UNDER THE CORE OF THE SURFACE HIGH. LASTLY...FARTHER TO THE
WEST...MID AND HIGH CLOUDS WERE ON THE INCREASE OVER THE NORTHERN
PLAINS...DOWNSTREAM OF THE IDAHO SHORTWAVE.
TODAY...THE UPPER RIDGING SEEN OVER THE PLAINS WILL SHIFT OVER THE
FORECAST AREA...PUSHED BY THE TROUGH OVER IDAHO MARCHING EAST...
PROVIDING CONTINUED SUBSIDENCE FROM ALOFT. BIGGEST CONCERN IS IF THE
LOW CLOUDS MARCHING SOUTH INTO NORTHERN PORTIONS OF THE AREA AT THIS
TIME WILL: 1. OVERSPREAD THE AREA AND 2. NOT DISSIPATE BECAUSE OF
THE SUBSIDENCE STRENGTHENING THE LOW LEVEL INVERSION. THE RAP MODEL
APPEARS TO HAVE THE BEST HANDLE ON THE STRATUS SITUATION...BUT IS
VERY INTERESTING TO LOOK AT. IF ONE USES THE 900MB OR 925MB RH
PROGS...WHICH MATCH UP WELL WITH 00Z SOUNDING DATA WHERE THE STRATUS
WAS VERTICALLY...IT WOULD SUGGEST THAT THE STRATUS MAY TEND TO BREAK
UP IN THE 10-14Z TIME FRAME...THOUGH LINGER OVER NORTHEAST WISCONSIN
WITH THE AIDED LAKE EFFECT OFF SUPERIOR. HOWEVER...MODEL SOUNDINGS
SHOW THAT THE INVERSION LOWERS THROUGH THE DAY...PUSHING THE STRATUS
LOWER VERTICALLY...SUCH THAT A 950MB RH PROG IS MORE REPRESENTATIVE.
THE LOWERING INVERSION MAKES SENSE GIVEN THE UPPER RIDGING MOVING
OVERHEAD. GIVEN THE TIME OF YEAR WHICH FAVORS STRATUS NOT WANTING TO
DISSIPATE...HAVE FOLLOWED THE MORE PESSIMISTIC 950MB RH PROG...WHICH
BASICALLY MEANS LOW CLOUDS ENCOMPASS THE AREA BY 13Z OR SO AND STICK
AROUND THROUGH THE DAY. THE ONE THING THE LOWERING INVERSION DOES IS
GET THE STRATUS OUT OF THE DENDRITIC GROWTH ZONE...SO THE FLURRIES
SHOULD STOP. THE CLOUD DEPTH BECOMES TOO SMALL AND AIRMASS TOO
SUBSIDENT TO WORRY ABOUT A FREEZING DRIZZLE THREAT. A COLDER DAY IS
DEFINITELY IN STORE WITH THE CLOUDS AROUND AND 925MB TEMPS FALLING
TO -6 TO -10C BY 18Z.
TONIGHT INTO MONDAY...FOCUS IS ON THE SHORTWAVE TROUGH CROSSING
IDAHO. MODELS COMPARED TO YESTERDAY AT THIS TIME HAVE TRENDED TO THE
MORE POTENT IDEA...BUT ARE DEFINITELY FARTHER NORTH. BY 12Z
MONDAY...THE SHORTWAVE TROUGH IS PROGGED TO STRETCH FROM CENTRAL
MINNESOTA INTO NORTHERN IOWA. AS THE TROUGH APPROACHES TONIGHT...WE
SHOULD SEE A RAPID INCREASE IN MID AND HIGH CLOUDS...NOTED BY
CONDENSATION PRESSURE DEFICITS AS WELL AS LIFT ON THE 285-300K
SURFACES. DESPITE THE IMPRESSIVE LOOK OF THE SHORTWAVE TROUGH AT
500MB IN THE MODELS...QPF IS VERY HARD TO COME BY PRIOR TO 12Z IN
THE 23.00Z GFS/NAM/UKMET. ONLY THE 23.00Z CANADIAN PRODUCES SOME QPF
AND THAT IS ONLY A COUPLE HUNDREDTHS AT MOST. IT APPEARS MUCH OF THE
FORCING IS HAVING TO GO INTO MOISTENING THE LOW TO MID-LEVELS...
GIVEN THE PRE-EXISTING DRY AIRMASS WHICH CAN BE SEEN ON THE 00Z MPX
AND ABR SOUNDINGS. STILL FEEL CONFIDENT TO HAVE AT LEAST A 20-30
PERCENT CHANCE IN THE 09-12Z PERIOD TONIGHT GIVEN ALL THE FORCING.
EVEN HEADING INTO THE 12-18Z TIME WINDOW...WHEN THE SHORTWAVE TROUGH
IS CROSSING THE AREA...MODELS ARE STRUGGLING TO PRODUCE MUCH IF ANY
QPF WITH THE 23.00Z CANADIAN THE MOST BULLISH. HOWEVER...DIGGING
INTO THE HIRES ARW AND NMM MODELS...THEY ALL SHOW A BAND OF SNOW
CROSSING ALONG AND NORTH OF I-94 BETWEEN 12-18Z. GIVEN THE STRENGTH
OF THE TROUGH...THESE HIRES MODELS AND THE BULLISH CANADIAN...
INCREASED PRECIPITATION CHANCES TOWARDS 60 UP IN TAYLOR COUNTY.
CHANCES DECREASE TO THE SOUTH GIVEN THE FARTHER NORTH TRACK.
MEANWHILE...ANOTHER INTERESTING THING HAS SHOWN UP. THIS SHORTWAVE
TROUGH IS STRONG ENOUGH TO PRODUCE AN INVERTED SURFACE TROUGH...
WHICH WAS ALWAYS KNOWN. HOWEVER...THE NAM...CANADIAN...HIRES
NMM AND 23.03Z SREF ALL PRODUCE SOME VERY LIGHT QPF ALONG THE
INVERTED TROUGH LATE TONIGHT INTO THE DAY MONDAY. SOUNDINGS SOUTH OF
I-90 SHOW PROBLEMS WITH ICE IN THE CLOUDS...THUS VERY CONCERNED
OF FREEZING DRIZZLE AND AS SUCH ADDED IT TO THE FORECAST. IF THE
SREF IS RIGHT...WHICH ALBEIT IS 2/3 DOMINATED BY NAM RELATED
MEMBERS...THE AREA ACROSS FAR SOUTHWEST WISCONSIN INTO CLAYTON
COUNTY EVENTUALLY WOULD NEED AN ADVISORY FOR FREEZING DRIZZLE. MOST
OF THE PRECIPITATION SHOULD PUSH EAST OF THE AREA FOR THE AFTERNOON
AS THE SHORTWAVE TROUGH SHIFTS EAST TO LAKE MICHIGAN. IN THE WAKE OF
THE SHORTWAVE TROUGH...WE GET A REINFORCING SHOT OF COLD AIR FROM
THE SOUTH CENTRAL CANADIAN HIGH...NOTED BY 925MB TEMPS DROPPING TO
-8 TO -12C.
MONDAY NIGHT THROUGH TUESDAY NIGHT...MUCH OF THE CURRENT NORTHEAST
PACIFIC TROUGH IS SLATED TO DIG DOWN INTO THE FOUR CORNERS REGION ON
MONDAY...DIVE SOUTH INTO TEXAS ON TUESDAY AND TURN NEUTRAL TO
NEGATIVE TILT AS IT LIFTS INTO THE TENNESSEE VALLEY BY 12Z
WEDNESDAY. AN INTENSIFYING LOW PRESSURE SYSTEM IS EXPECTED TO
ACCOMPANY THE TROUGH...WHICH FOLLOWING THE CLASSIC CYCLONE
DEVELOPMENT WILL HAVE A DEFORMATION/COLD CONVEYOR BELT OF
PRECIPITATION. MODELS OVERALL HAVE BEEN VERY CONSISTENT ON THE TRACK
OF THIS TROUGH AND SYSTEM THE PAST COUPLE DAYS...WHICH KEEPS ALL THE
DEFORMATION PRECIPITATION WELL SOUTHEAST OF THE AREA. IN FACT...THE
BULK OF THE MID AND HIGH CLOUDS LOOK TO STAY TO THE SOUTHEAST. THE
ONLY SYNOPTIC ITEM OF WORRY WOULD BE A NORTHERN STREAM TYPE TROUGH
CROSSING THE DAKOTAS TUESDAY NIGHT...SPREADING SOME MID AND HIGH
CLOUDS ACROSS MINNESOTA. OTHERWISE...THE FORECAST AREA IS DOMINATED
BY THE CANADIAN HIGH OVER SOUTH CENTRAL CANADA BEGINNING TO DROP
SOUTH INTO THE NORTHERN PLAINS. 925MB TEMPS COOL EVEN MORE AS THE
HIGH DROPS SOUTH...DOWN TO -10 TO -14C BY 12Z TUESDAY AND HOLDING
STEADY THROUGH TUESDAY NIGHT. THE BIG QUESTION THEN BECOMES IF LOW
STRATUS THAT IS HANGING AROUND FROM MONDAY CAN CLEAR OUT...SINCE THE
COOLING 925MB TEMPS...SNOW COVER AND OVERALL LIGHT WINDS AT THE
SURFACE WOULD BE FAVORABLE FOR SOME CHILLY NIGHTS. GFS SOUNDINGS
SUGGEST THAT SKIES SHOULD CLEAR MONDAY NIGHT...BUT CONFIDENCE IS
SOMEWHAT LOW GIVEN THE CURRENT STRATUS SITUATION. NAM SOUNDINGS ARE
MORE PESSIMISTIC WITH LOW LEVEL MOISTURE PRESENT AND MAY BE THE
WAY TO GO. THUS...HAVE WENT MORE CLOUDY WHICH TO SOME DEGREE WILL
HELP LIMIT THE TEMPERATURE FALL AS WELL AS RISE DURING THE DAY
TUESDAY. STILL...IT IS GOING TO BE COOL GIVEN THE COLD ADVECTION
PATTERN.
.LONG TERM...WEDNESDAY THROUGH SATURDAY NIGHT
258 AM CST SUN DEC 23 2012
23.00Z MODELS ARE IN GOOD AGREEMENT THROUGH THURSDAY WITH REGARDS TO
THE UPPER AND SURFACE PATTERNS...THEN BEGIN TO DIFFER FOR FRIDAY AND
INTO THE WEEKEND ON HANDLING TROUGHING COMING OUT OF THE WESTERN
U.S..
THE BEGINNING OF THE PERIOD STARTS OFF WITH THE POTENT TROUGH AND
STORM SYSTEM OVER THE TENNESSEE VALLEY...WHICH LIFTS NORTHEAST INTO
THE NORTHEASTERN U.S. ON THURSDAY. AGAIN...THIS SYSTEM IS TOO FAR
AWAY FROM US TO BRING ANY PRECIPITATION. INSTEAD...THE FORECAST AREA
REMAINS DOMINATED BY THE CANADIAN HIGH PRESSURE AREA...WHICH REMAINS
FORECAST TO MOVE INTO THE AREA WEDNESDAY NIGHT INTO THURSDAY. THIS
HIGH WILL KEEP CONDITIONS SEASONABLY COOL AND DRY. FOCUS THEN TURNS
TO A DEEP TROUGH FORMING OVER THE WESTERN U.S. DURING THE DAY
THURSDAY. MODELS SHIFT THIS TROUGH EAST INTO THE PLAINS FOR
FRIDAY...THOUGH MORE IMPORTANTLY IS WHAT HAPPENS TO THE MAIN CORE
SHORTWAVE AT THE BASE OF THE TROUGH. THE GFS/CANADIAN ARE QUITE
PROGRESSIVE...SHEARING IT OUT AND SENDING IT EASTWARD TOWARDS
TENNESSEE BY 00Z SATURDAY. MEANWHILE...THE ECMWF RUNS AND TO SOME
DEGREE THE UKMET CONTINUE TO INDICATE A MUCH DEEPER SCENARIO...
LIFTING THE SHORTWAVE UP INTO INDIANA AND OHIO ON SATURDAY. THIS
LATTER SOLUTION WOULD YIELD SOME DEFORMATION SNOW FOR THE AREA ON
SATURDAY...BEING PRECEDED BY SOME LIGHT WARM ADVECTION SNOW FOR
FRIDAY AND FRIDAY NIGHT. FOR NOW HAVE CONTINUED TO FOLLOW A
CONSENSUS APPROACH...YIELDING 30-40 PERCENT CHANCES OF SNOW AND
SLIGHTLY WARMER CONDITIONS. STILL RIGHT NOW IT DOES NOT APPEAR WE
WOULD BE DEALING WITH ANY SIGNIFICANT SNOW...BUT SOMETHING
CERTAINLY TO WATCH.
&&
.AVIATION...
1020 PM CST SAT DEC 22 2012
LOW CLOUDS ARE MAKING STEADY ADVANCEMENT SOUTHWARD...PER FOG/STRATUS
SATELLITE IMAGERY...WITH TRENDS BRINGING IT INTO KRST BY 08Z OR SO.
RAP13 IS RATHER AGGRESSIVE WITH ITS SOUTHWARD MOVEMENT...AND WOULD
SUGGEST MVFR CIGS AT KRST/KLSE FROM 08-10Z THROUGH ABOUT 14Z.
HOWEVER...THE RAP ALSO APPEARS TOO MOIST AT THE MOMENT...COMPARING
ITS SOUNDING WITH THE LAPS AT KRST. ALSO...00Z SOUNDINGS AT DVN/MPX
DO POINT OUT TO A GOOD AMOUNT OF DRY AIR TO BATTLE AS THE CLOUDS
PUSH SOUTH. STILL...SATELLITE IS HARD TO ARGUE WITH...SO WILL
INCREASE THE CLOUDS FOR THE EARLY MORNING HOURS...WITH A FEW HOUR
PERIOD OF MVFR CIGS.
HIGH CLOUDS WILL BE THE INCREASE SUN AFTERNOON...AHEAD OF AN
APPROACHING UPPER LEVEL SHORTWAVE TROUGH. THE CLOUDS WILL GRADUALLY
THICKEN...WITH SOME LOWERING BY MONDAY MORNING. S-- LOOKS LIKE A
GOOD BET LATE SUN NIGHT/MON MORNING...BUT MINIMAL IF ANY
ACCUMULATION. BUFKIT SOUNDINGS SUGGEST MVFR/IFR CIGS WILL RETURN BY
MONDAY MORNING...WHICH COULD HANG AROUND FOR MUCH OF THE DAY.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
258 AM CST SUN DEC 23 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...AJ
LONG TERM...AJ
AVIATION.....RIECK
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
1216 AM CST SUN DEC 23 2012
UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE
.SHORT TERM...TONIGHT AND SUNDAY.
LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A COUPLE WEAK
SHORTWAVES...ONE OVER SOUTHEAST SOUTH DAKOTA AND ANOTHER OVER
SOUTHWEST ONTARIO...AND THEY ARE PUSHING AN EQUALLY WEAK COLD FRONT
OVER NORTHWEST WISCONSIN EARLY THIS AFTERNOON. WIDELY SCT FLURRY
ACTIVITY WAS REPORTED IN THE OBS EARLIER TODAY OVER EASTERN NORTH
DAKOTA AND NORTHERN MINNESOTA...BUT NOTHING SO FAR CLOSER TO
WISCONSIN. OTHERWISE...JUST HAVE SOME CIRRUS PASSING OVER CENTRAL
AND SOUTHERN PORTIONS OF THE STATE...AND A BATCH OF MID CLOUDS OVER
NORTHERN WISCONSIN AND THE UPPER PENINSULA. THE MAIN FORECAST
CONCERNS ARE CLOUDS AND LAKE EFFECT SNOW SHOWERS AS WINDS SHIFT TO
THE NORTHWEST FOLLOWING THE PASSAGE OF THE COLD FRONT.
TONIGHT...THE WEAK COLD FRONT WILL PASS ACROSS THE REGION THIS
EVENING WHICH WILL SHIFT WINDS BACK TO THE NORTH-NORTHWEST. THIN
RIBBON OF MID-LEVEL MOISTURE WILL GET STRETCHED OUT ALONG THE FRONT
THIS EVENING WHICH SHOULD LEAVE MOSTLY CLEAR TO PARTLY CLOUDY
CONDITIONS ACROSS THE REGION. BEHIND THE FRONT...A SHALLOW ARCTIC
AIRMASS WILL FILTER SOUTHEAST ACROSS THE NORTHERN WISCONSIN.
STEEPENING LOW LEVEL LAPSE RATES BENEATH A SHARP INVERSION WILL
PROMOTE THE ADVECTION OF LAKE EFFECT CLOUDS OFF LAKE SUPERIOR INTO
NORTHERN WISCONSIN. CAN SEE FLURRIES OR LIGHT SNOW SHOWERS
IMPACTING THE VILAS AND NORTHERN PARTS OF ONEIDA AND FOREST
COUNTY...MAINLY AFTER MIDNIGHT WITH ONLY VERY SMALL ACCUMULATIONS
EXPECTED. THE CLOUDS MAY MAKE A RUN AT WAUSAU/SHAWANO AND CRIVITZ
LATE. LOW LEVEL WINDS OF 15-20 KTS IS MARGINAL FOR DECOUPLING...BUT
CLOUDS ACROSS THE NORTH SHOULD KEEP THEM WARMER THAN LAST NIGHT.
WILL GO WITH LOWS FROM THE MID-SINGLE DIGITS OVER CENTRAL
WISCONSIN...TO THE LOWER 20S NEAR THE LAKE MICHIGAN SHORELINE.
SUNDAY...CANADIAN HIGH PRESSURE WILL GRADUALLY BUILD INTO THE REGION
THROUGH THE DAY. MVFR STRATO-CU WILL LIKELY CREATE A PARTLY TO
MOSTLY CLOUDY START TO THE DAY NORTHWEST OF A AUW TO MNM LINE AS
FLOW WILL REMAIN OUT OF THE NW FOR A GOOD CHUNK OF THE DAY. AM
COUNTING ON WEAK MIXING TO FORCE THE LOW CLOUDS TO RETREAT SOMEWHAT
DURING THE AFTERNOON BUT WILL KEEP PARTLY SUNNY TO MOSTLY CLOUDY
WORDING IN THE GRIDS OVER N-C WISCONSIN. THE RIGHT REAR QUAD OF A JET
STREAK THEN SHIFTS EAST FROM THE NORTHERN PLAINS AND ACROSS THE
STATE DURING THE AFTERNOON. PLENTY OF DRY AIR IN THE MID-LEVELS
WILL KEEP THE AREA PRECIP FREE...BUT SHOULD SEE A DECENT CIRRUS
SHIELD ARRIVE. TEMPS WILL FALL ABOUT 5 DEGREES UP NORTH COMPARED TO
TODAY...PLACING HIGHS IN THE LOW TO MID 20S ACROSS THE REGION.
.LONG TERM...SUNDAY NIGHT THROUGH NEXT SATURDAY.
MODELS SHOWED A MORE ACTIVE WEATHER PATTERN DURING THE PERIOD WITH
LOW AMPLITUDE UPPER LEVEL FLOW THROUGH EARLY NEXT WEEK BEFORE A
WEST COAST TROUGH PUSHES EASTWARD. MODELS WERE IN GOOD AGREEMENT
IN TAKING A 500MB TROUGH THROUGH THE WESTERN GREAT LAKES REGION ON
MONDAY...BUT MOST OF THE ENERGY WITH THAT SHORT WAVE REMAINS SOUTH
OF THE FORECAST AREA. HAVE INCLUDED SOME LOW END CHANCE POPS TO
COVER THAT EVENT. NOT SO MUCH AGREEMENT ON THE PATH OF A STRONGER
SYSTEM THAT WILL BE MOVING NORTHEAST OUT OF THE SOUTHERN PLAINS
MIDWEEK. 12Z ECMWF WOULD HAVE IT MISS THE AREA WHILE THE 12Z GFS
BRINGS QPF TO THE SOUTHEAST 1/3 TO 1/2 OF THE AREA. THERE IS
SLIGHTLY BETTER AGREEMENT IN TAKING A TROUGH ACROSS THE REGION AT
THE END OF THE PERIOD. SO HAVE CHANCE POPS FRIDAY NIGHT AND SATURDAY.
TEMPERATURES SHOULD START THE PERIOD SLIGHTLY BELOW NORMAL BUT
WARM TO NEAR NORMAL BY NEXT WEEKEND.
&&
.AVIATION...A WEAK COLD FRONT WILL DROP SOUTH ACROSS THE AREA
OVERNIGHT AND BRING MVFR CIGS TO MOST PLACES BY DAYBREAK. IFR CIGS
OF 700 TO 1000` POSSIBLE OVER THE FAR NORTH. THE CLOUDS WILL ERODE
NEAR THE LAKE AND BAY SUNDAY BUT REMAIN OVER THE REST OF THE REGION.
RDM
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1020 PM CST SAT DEC 22 2012
.SHORT TERM...
920 PM CST SAT DEC 22 2012
AREA OF LOW CLOUDS MAKING STEADY PROGRESS SOUTHWARD ACROSS MN AT MID
EVENING...WITH SATELLITE TRENDS PLACING THE LEADING EDGE AT
ROCHESTER BY 08Z. THE NAM12/RAP13 CAPTURE THE CLOUDS IN THE THEIR
LOW LEVEL RH FIELDS...BUT THE RAP IS THE MOST AGGRESSIVE BRINGING IT
SOUTH...PERHAPS TOO AGGRESSIVE. COMPARING THE RAP SOUNDINGS WITH
LAPS SHOWS THE RAP TO BE TOO MOIST UNDER THE LOW LEVEL INVERSION.
00Z SOUNDINGS AT ABR SHOWS THE LOW CLOUD VERY WELL...BUT IT GETS
PROGRESSIVE DRIER TO THE SOUTHEAST...COMPARING THE MPX AND DVN 00Z
UPPER AIR SOUNDINGS. SO...HAVE UPDATED THE FORECAST TO BRING THE
CLOUDS DOWN INTO THE AREA...BUT HAVE ELECTED TO ADD SOME DRYING ON
THE LEADING EDGE OF THE CLOUDS FOR NOW. HAVE ALSO ADDED SOME
FLURRIES...AS EVIDENCED BY SFC OBS IN CENTRAL/NORTHERN MN. CLOUDS
MAY HAVE TO BE INCREASED FOR THE EARLY MORNINGS HOURS IF THE
MOISTURE COMPLETELY WINS OUT OVER THE DRIER AIR.
.LONG TERM...TUESDAY NIGHT THROUGH SATURDAY
247 PM CST SAT DEC 22 2012
22.12 MEDIUM RANGE MODELS ARE IN REASONABLE AGREEMENT TUESDAY NIGHT
INTO WEDNESDAY SHOWING THE SOUTHERN STREAM TROUGH LIFTING NORTH INTO
THE OHIO RIVER VALLEY AND CLOSING INTO AN UPPER LOW. THIS SYSTEM IS
EXPECTED TO REMAIN WELL TO THE EAST OF THE AREA AS IT LIFTS INTO NEW
ENGLAND WEDNESDAY NIGHT INTO THURSDAY. HIGH PRESSURE WILL MAINTAIN
COOL AND QUIET WEATHER THROUGH THURSDAY WITH HIGHS IN THE TEENS AND
LOWS RANGING FROM THE SINGLE DIGITS BELOW ZERO TO SINGLE DIGITS
ABOVE ZERO. ANOTHER TROUGH WILL CROSS THE ROCKIES ONT THURSDAY AND
MOVE INTO THE PLAINS DURING THE DAY ON FRIDAY. FORECAST MODELS START
TO DIVERGE FRIDAY INTO SATURDAY ON THE EVOLUTION OF THIS TROUGH. THE
ECMWF CONTINUES TO WRAP THIS SYSTEM INTO AN UPPER LOW AS IT LIFTS
INTO THE GREAT LAKES AND MERGES WITH A TROUGH MOVING SOUTHEAST
ACROSS SOUTHERN ALBERTA/SASKATCHEWAN. THE ECMWF SOLUTION WOULD BRING
A PROLONGED PERIOD OF LIGHT SNOW TO THE FORECAST AREA. THE GFS KEEPS
THESE TWO SYSTEMS FROM MERGING AND BRINGS THE NORTHERN STREAM TROUGH
ACROSS THE FORECAST AREA DURING THE DAY ON SATURDAY. GIVEN THE
VARYING MODEL SOLUTIONS DECIDED TO LEAN TOWARD A MODEL CONSENSUS
BLEND APPROACH WITH CHANCES FOR LIGHT SNOW FRIDAY THROUGH
SATURDAY.
&&
.AVIATION...
1020 PM CST SAT DEC 22 2012
LOW CLOUDS ARE MAKING STEADY ADVANCEMENT SOUTHWARD...PER FOG/STRATUS
SATELLITE IMAGERY...WITH TRENDS BRINGING IT INTO KRST BY 08Z OR SO.
RAP13 IS RATHER AGGRESSIVE WITH ITS SOUTHWARD MOVEMENT...AND WOULD
SUGGEST MVFR CIGS AT KRST/KLSE FROM 08-10Z THROUGH ABOUT 14Z.
HOWEVER...THE RAP ALSO APPEARS TOO MOIST AT THE MOMENT...COMPARING
ITS SOUNDING WITH THE LAPS AT KRST. ALSO...00Z SOUNDINGS AT DVN/MPX
DO POINT OUT TO A GOOD AMOUNT OF DRY AIR TO BATTLE AS THE CLOUDS
PUSH SOUTH. STILL...SATELLITE IS HARD TO ARGUE WITH...SO WILL
INCREASE THE CLOUDS FOR THE EARLY MORNING HOURS...WITH A FEW HOUR
PERIOD OF MVFR CIGS.
HIGH CLOUDS WILL BE THE INCREASE SUN AFTERNOON...AHEAD OF AN
APPROACHING UPPER LEVEL SHORTWAVE TROUGH. THE CLOUDS WILL GRADUALLY
THICKEN...WITH SOME LOWERING BY MONDAY MORNING. S-- LOOKS LIKE A
GOOD BET LATE SUN NIGHT/MON MORNING...BUT MINIMAL IF ANY
ACCUMULATION. BUFKIT SOUNDINGS SUGGEST MVFR/IFR CIGS WILL RETURN BY
MONDAY MORNING...WHICH COULD HANG AROUND FOR MUCH OF THE DAY.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
247 PM CST SAT DEC 22 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...RIECK
LONG TERM....WETENKAMP
AVIATION.....RIECK
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
149 AM EST TUE DEC 25 2012
.SYNOPSIS...
LINGERING LIGHT DRIZZLE AND FREEZING DRIZZLE WILL GIVE WAY TO
PATCHY FOG OVERNIGHT AS LOW PRESSURE EXITS NORTHEAST. AFTER A DRY
BREAK CHRISTMAS DAY...A STRONG LOW PRESSURE SYSTEM WILL COME
NORTHEAST FROM TEXAS AND BRING POTENTIALLY HEAVY AMOUNTS OF SNOW
AND ICE TO THE UPPER OHIO VALLEY WEDNESDAY.
&&
.NEAR TERM /THROUGH TODAY/...
PER RECENT SURFACE AND RADAR DATA...HAVE CONTINUED TREND OF
DECREASING COVERAGE OF LIGHT DRIZZLE OVERNIGHT. MAINTAINED MENTION
OF LIGHT FREEZING DRIZZLE NEAR THE MOUNTAINS WHERE TEMPERATURES
HAVE SLIPPED BELOW 32. HAVE ALSO MAINTAINED MENTION OF PATCHY FOG.
WITH RUC AND NAM MODEL PROFILES SHOWING CLOUD TOPS DECREASING AND
HENCE CLOUD TOP TEMPERATURES WARMING TO WARMER THAN -10C...THE
FALLING PRECIPITATION WILL BE LIQUID DRIZZLE. IF BY CHANCE THERE
IS ANY SNOW IT WOULD BE LIKE FINE SNOW GRAINS. EITHER WAY IT WOULD
BE OF LITTLE CONSEQUENCE.
HAVE MAINTAINED THE FREEZING RAIN ADVISORY...BUT EXPECT TO
DISCONTINUE IT BY THE MIDNIGHT HOUR.
FORECASTED TEMPERATURES TO EITHER BE STEADY OVERNIGHT OR DROP BY
NO MORE THAN 2 DEGREES. EXPECT SOME TEMPERATURE CLIMB FOR DAYTIME
CHRISTMAS...BUT RECENT GFS LAMP AND NAM MOS AND SREF MODEL OUTPUT
HAVE TRENDED WITH COOLER HIGHS THAN EARLIER GUIDANCE. STILL THE
DAY SHOULD BE DRY AND DECENT FOR TRAVEL.
&&
.SHORT TERM /TONIGHT THROUGH THURSDAY/...
COMPACT BUT POTENT TROF THAT WILL BE YIELDING SVR WX IN THE DEEP
SOUTH WILL LIFT NEWD TUE NGT. COLD AIR WILL BE DRAWN SWD AS THE
ASSOCIATED WMFNT SHARPENS. WARM ADVCTN AT H8 WILL YIELD WDSPRD
PCPN BY WED MRNG.
FORCING FOR ASCENT WILL INCR DRAMATICALLY DURG THE DAY ON WED AS
DIFFLUENCE ALOFT STRENGTHENS AHEAD OF APRCHG UPR LOW. IT IS VERY
CLR THAT A LOT OF PCPN WILL OCCUR. THE PRIMARY FCST DIFFICULTY IS
IDENTIFYING THE NWD EXTENT OF THE H8 WARM TONGUE.
EXPECTATION IS THAT THERE WILL BE A SHARP GRADIENT FROM RAIN TO
FRZG RAIN TO SNOW ACRS FCST AREA. CONFIDENCE IS HIGH IN SNOW
MEETING WRNG CRITERION /IN EXCESS OF 6 IN PER 12 HR/ IN NRN PA
AND OH ZONES OWING TO VERY STRONG ASCENT IN DENDRITIC SNOW GROWTH
ZONE...SPCLY WED AFTN. DURG THIS TIME...SNOW RATES COULD BE QUITE
SGFNT IN I-80/I-79 CORRIDOR.
CONFIDENCE IS ALSO MDT THAT THERE WILL BE SGFNT ICE ACCUM IN MTN
ZONES...WHERE COLD AIR STAGNATES IN VLYS. ICE ACCUMS IN EXCESS OF
ONE-QUARTER INCH ARE PSBL.
FCST HAS LWR CONFIDENCE IN WHERE THE LINE BTWN RAIN AND FRZG RAIN
WILL ESTABLISH ITSELF. CLIMATOLOGY AND MODELS ALL SUGGEST THIS
LINE WILL BE NEAR AND SW FROM PITTSBURGH. ICE ACCUMS STILL XPCD IN
THESE LOCATIONS...BUT ATTM ARE XPCD TO RMN BLW WRNG THRESHOLD.
WINTER STORM WATCH HAS BEEN ISSUED FOR MUCH OF FCST AREA FROM
26/03Z TO 27/11Z. BY WED NGT...RGN WILL BE ON WRN SIDE OF THE
LOW...AND ANY PCPN WILL BE GENERATED/ENHANCED BY MODEST FLOW FROM
THE GRTLKS. ADDITIONAL ACCUMS PSBL WED NGT...BUT SHOULD BE LWR IN
MAGNITUDE THAN WED AFTN.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
HIPRES AND ASSOCIATED H5 RDG WILL MOVE ACRS FCST AREA ON FRI BUT
WILL BE TRANSIENT OWING TO APRCHG WAVES FROM NRN PLNS AND SRN
CONUS. WAVES ATTEMPT TO PHASE ON SAT/SUN...WITH ASSOCIATED PCPN
XPCD TO BE FOCUSED IN SRN ZONES. COLD AIR WILL BE SOLIDLY IN
PLACE...SO ANY PCPN WILL BE ASSOCIATED WITH SNOW.
ANOTHER WAVE XPCD TO GENERATE COASTAL LOPRES BY NEW YRS EVE.
DIFFERENCES IN AMPLITUDE OF THE UPR WAVE EXIST BTWN ECMWF AND GFS.
ATTM...ONLY LMTD IMPACT XPCD TO FCST AREA FROM THIS SYSTEM.
&&
.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
DRIZZLE COVER HAS CONTINUED TO DECLINE INTO THE EARLY AM
HOURS...WITH NO SITE NOW REPORTING IT. OTERHWISE...LIFR STRATUS
CONTINUES ACROSS THE ENTIRE AREA...THOUGH SOME IMPROVEMENT IN
VISIBILITY HAS BEEN NOTED. STATISTICAL GUIDANCE SUGGESTS
VISIBILITIES SHOULD COME UP A BIT AS DEEPER SURFACE LAYER MOISTURE
STARTS TO EXIT THE AREA. ADDITIONALLY...AFTER SUNRISE...MODEL TIME
HEIGHT SECTIONS INDICATE SOME BREAKUP OF THE STRATUS. MOST SITES
SHOULD TREND TOWARD MVFR BY AFTERNOON WITH RATHER LIGHT WINDS
THROUGHOUT.
.OUTLOOK.../TUESDAY NIGHT THROUGH SATURDAY/...
MVFR RESTRICTIONS ARE EXPECTED TUESDAY NIGHT...WITH IFR RESTRICTIONS
LIKELY BY WEDNESDAY MORNING IN SN/+SN. SOME AREAS SOUTH OF KPIT
MAY MIX WITH OR CHANGE TO ZR/IP...HOWEVER BEHIND THE SNOW
BAND...DZ/FZDZ MAY BE THE PREDOMINANT WEATHER TYPE. DURATION OF
+SN SHOULD BE LONGEST FROM NORTH OF KZZV TO KPHD...KFKL...AND
KDUJ. FRIES
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...WINTER STORM WATCH FROM THIS EVENING THROUGH LATE WEDNESDAY
NIGHT FOR MDZ001.
OH...WINTER STORM WATCH FROM THIS EVENING THROUGH LATE WEDNESDAY
NIGHT FOR OHZ039>041-048>050-057>059.
PA...WINTER STORM WATCH FROM THIS EVENING THROUGH LATE WEDNESDAY
NIGHT FOR PAZ007>009-013>016-020>023-029-073-074-076.
WV...WINTER STORM WATCH FROM THIS EVENING THROUGH LATE WEDNESDAY
NIGHT FOR WVZ001>003-023-041.
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1242 AM EST TUE DEC 25 2012
.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 434 PM EST MON DEC 24 2012
WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL LOW OVER NRN
ONTARIO WITH A TROUGH EXTENDING INTO THE WESTERN GREAT LAKES. A
SHORTWAVE TROUGH WAS LOCATED OVER LOWER MI WHILE UPSTREAM A WEAKER
SHRTWV EXTENDED FROM THE SRN END OF JAMES BAY TO NEAR KINL. ALTHOUGH THE
STRONGEST 700-300 MB QVECTOR CONV REMAINED SOUTHEAST OF UPPER MI
WHILE...SOME WEAK TO MODERATE FORCING LINGERING OVER THE AREA
SUPPORTED AREAS OF LIGHT SNOW WITH VISIBILITIES GENERALLY AT OR
ABOVE 5SM. NW LOW LEVEL WINDS WITH 850 MB TEMPS AROUND -15C ALSO
SUPPORTED SOME LIGHT LES BANDS. A SIGNIFICANT LIMITING FACTOR FOR
LES INTENSITY WAS LOW INVERSION HEIGHTS AROUND 4K FT AND INFLUX OF
DRIER AIR BELOW THE INVERSION.
TONIGHT...INCREASING LOW-LVL CONVERGENCE AIDED BY DEVELOPING LAND
BREEZES SHOULD PROVIDE ADDITIONAL FOCUS FOR LES INTO ERN ALGER/NRN
SCHOOLCRAFT AND PERHAPS OVER THE PORCUPINE MOUNTAINS OVER THE WEST.
THE DRY AIR UPSTREAM AND LOW INVERSION HEIGHTS WILL LIMIT
AMOUNTS...ESPECIALLY OVER THE WEST...TO GENERALLY AN INCH OR LESS.
GREATER POPS WERE INCLUDED OVER THE ERN CWA WHERE THE LONGER FETCH
WILL HELP KEEP INVERSION HEIGHTS IN THE 5K-7K FT RANGE AND CLOUD
SUPPORT SLIGHTLY GREATER SNOWFALL AMOUNTS OF AN INCH OR TWO.
LES WILL CONTINUE INTO CHRISTMAS DAY AS 850 MB TEMPS REMAIN NEAR
-14C BUT SHOULD DIMINISH AS WINDS BACK TO WNW WITH SLOWLY LOWERING
INVERSION HEIGHTS AND MORE ANTICYCLONIC/DIVERGENT LOW LEVEL FLOW.
SNOWFALL INTENSITY/AMOUNTS WILL REMAIN GREATEST OVER THE EAST WHERE
AN ADDITIONAL INCH MAY ACCUMULATE.
.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 434 PM EST MON DEC 24 2012
NOT A LOT OF EXCITING WEATHER TO GO IN DEPTH ABOUT FOR THE LONG TERM
PERIOD /TUESDAY NIGHT THROUGH NEXT MONDAY/. WE WILL BE DOMINATED BY
NORTHERLY WINDS FOR MUCH OF THE PERIOD WITH SLIGHT TO LOW CHANCE
POPS NEAR LAKE SUPERIOR...AS THE STORM TRACK CONTINUES TO BE WELL TO
OUR S.
TUESDAY NIGHT SHOULD BE ONE OF THE COLDEST IN A WHILE...WITH A FEW
LOCATIONS OVER INTERIOR W PORTIONS OF UPPER MI FALLING BELOW 0
THANKS TO A POCKET OF CLEARING NOTED BY SOME OF THE SMALLER SCALE
MODELS.
DID INCREASE THE FCST MODEL CONSENSUS POPS FOR SATURDAY NIGHT
THROUGH MONDAY...HEDGING THE FCST CLOSER TO THE ECMWF AND SLIGHTLY
HIGHER CONFIDENCE IN COLD AIR ROTATING IN ON MAINLY NW WINDS. THE
OUTLIER WAS THE GFS...PARTICULARLY FROM SUNDAY ON AS IT BROUGHT A
SFC LOW FROM CENTRAL CANADA TO ONTARIO SUNDAY NIGHT. A WEAKENING SFC
TROUGH CONTINUED FOR THE GFS...EXTENDING W FROM THE EXITING LOW OFF
THE COAST OF MAINE. THE ECMWF HAD FAIRLY STEADY 850MB TEMPS OF -15
TO -20C FROM SATURDAY NIGHT THROUGH MONDAY...WITH AT LEAST LIMITED
MOISTURE TO BRING IN A GOOD CHANCE OF SNOW SHOWERS.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1241 AM EST TUE DEC 25 2012
WITH A STRONG INVERSION OVER THE AREA...THE STRATUS CLOUDS WILL
PERSIST THROUGH THE FORECAST PERIOD EXCEPT AT IWD WHERE A DEVELOPING
SW WIND WILL PUSH THE LAKE EFFECT CLOUDS NORTH OF THEM ON TUE
AFTERNOON. OTHERWISE...A NW FLOW WILL BRING SOME OCCASIONAL LIGHT
LAKE EFFECT SNOW TO THE TAF SITES BUT VSBYS SHOULD NOT BE RESTRICTED
BY IT. SO...EXPECT MVFR CIGS AT BOTH KCMX AND KSAW THROUGH THE FCST
PERIOD. &&
.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 434 PM EST MON DEC 24 2012
A HIGH PRESSURE RIDGE BUILDING IN FROM THE CANADIAN PRAIRIES TODAY
AND TONIGHT WILL LINGER THROUGH MUCH OF THE WEEK...KEEPING WINDS
AT OR BELOW 25 KNOTS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...JLB
LONG TERM...KF
AVIATION...07
MARINE...JLB
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
1143 PM EST MON DEC 24 2012
.AVIATION...
//DISCUSSION...
SNOW AND LOW STRATUS HAVE PULLED OUT FOR THE MOST PART OVER THE TAF
SITES. ALTHOUGH THERE IS ADDITIONAL STRATUS UPSTREAM...OBSERVATIONS
DO NOT SHOW THIS STRATUS MAKING A BEELINE FOR THE TAF SITES
OVERNIGHT. AT THIS POINT WILL KEEP CIGS VFR WITH A TEMPO GROUP EARLY
ON FOR LINGERING STRATUS. THERE ARE SOME BREAKS IN THE CLOUDS
UPSTREAM...HOWEVER WITH A CONTINUED FEED OF MOISTURE OFF THE GREAT
LAKES THERE IS NOT ENOUGH CONFIDENCE TO CLEAR THE CLOUDS OUT AT THIS
POINT. A PERIOD OF QUIET WEATHER IS EXPECTED FOR THE REST OF TUESDAY
AS DAYTIME SNOW SHOWERS STAY TO THE EAST OF THE TAF SITES WITH
MOISTURE COMING IN OFF LAKE HURON.
//DTW THRESHOLD THREATS...
* MEDIUM CONFIDENCE IN CEILINGS BELOW 5000 FT THROUGH THE TAF
PERIOD.
&&
.PREV DISCUSSION...ISSUED 947 PM EST MON DEC 24 2012
UPDATE...
SNOW IS QUICKLY COMING TO AN END ACROSS SOUTHEAST MICHIGAN AS THE
LAST OF THE SNOW SHOWERS IS FALLING ACROSS THE EASTERN THUMB AHEAD
OF A SHORTWAVE PUSHING THROUGH SOUTHERN LOWER MICHIGAN. WHILE MANY
LOCATIONS SAW THE ADVERTISED 0.5 TO 1 INCH OF
SNOWFALL...SEVERAL LOCATIONS GOT CLOSER TO 2 INCHES IN A SWATH
FROM LIVINGSTON TO MACOMB COUNTY. THESE AREAS WERE IN AN AREA OF
ENHANCED CONVECTION EMBEDDED IN THE MAIN SNOW BANDS WHICH PROVIDED
A QUICK BURST OF SNOWFALL AND WITH IT SLIGHTLY HIGHER TOTALS IN
THIS CORRIDOR.
THE REST OF THE NIGHT LOOKS TO BE QUIET WITH ONLY A FEW LINGERING
FLURRIES AS THE FORCING TRACKS EAST OF THE AREA. THIS RECENT ROUND
OF SNOW SHOULD OFFICIALLY BRING A WHITE CHRISTMAS TO MOST OF
SOUTHEAST MICHIGAN TOMORROW WITH THE OFFICIAL YARDSTICK FOR THIS
BEING AN INCH OF SNOW ON THE GROUND AT 7 AM.
PREV DISCUSSION...ISSUED 337 PM EST MON DEC 24 2012
SHORT TERM...THIS EVENING AND TONIGHT
UPSTREAM LIGHT SNOW AND VIRGA HAVE BEEN STEADILY PUSHING INTO THE
AREA AHEAD OF THE COMPACT MID-LEVEL SHORTWAVE ROTATING ACROSS THE
LOWER PENINSULA THIS AFTERNOON. FOR SEVERAL HOURS NOW, A PERIOD OF
VIRGA HAS PRECEDED A RATHER BRIEF PERIOD OF LIGHT TO MODERATE
SNOWFALL.
ANALYSIS OF OBSERVATIONS AND SHORT TERM MODEL DATA INDICATE THAT THE
ONGOING SNOWFALL/VIRGA IS STRONGLY TIED TO TWO SEPARATE FEATURES.
THE FIRST, AND PRIMARY TO AFFECT SOUTHEAST MICHIGAN, IS THE BROAD
CORRIDOR OF ASCENT ASSOCIATED WITH DCVA PRECEDING THE WAVE ITSELF.
THE SECOND, MAINLY AFFECTING LOCATIONS SOUTH OF THE BORDER...PERHAPS
AS FAR NORTH AS THE I-94 CORRIDOR...IS A DEEP FRONTOLYTIC
CIRCULATION LEADING THE NOSE OF THE ASSOCIATED 80-KT JET STREAK.
THIS REGION OF FORCED COLD ASCENT HAS ALSO DRAWN UPON A POCKET OF WEAK
MID-LEVEL INSTABILITY TO PRODUCE A STRONGER CONVECTIVE RESPONSE TO
THE SOUTH AND OCCASIONAL ECHOES OF 40DBZ OVER NORTHERN IN.
THE NORTHWARD MIGRATION OF THE ELEVATED FRONTAL ZONE/THETA-E RIDGE
AS WELL AS SUB-850 EASTERLY MOISTURE ADVECTION WILL HELP TO ERODE
THE H85-H7 DRY LAYER APPARENT ON THIS MORNING`S 12Z DTX SOUNDING AND
ALLOW FOR A SUBSEQUENT EXPANSION OF LIGHT SNOW AND DECREASE IN VIRGA
OVER THE NEXT FEW HOURS. RECENT RADAR TRENDS CONFIRM THESE
EXPECTATIONS (AND YESTERDAY`S NMM CORE SOLUTIONS). RUC ANALYSIS
SUGGESTS THAT WHILE A BRIEF PERIOD OF CONVECTIVE PRECIP WILL BE
POSSIBLE ACROSS THE SOUTHERN CWA, THE BULK OF THE EVENT WILL LIKELY
TAKE PLACE ACROSS THE HEART OF THE FORECAST AREA AND WILL BE
CHARACTERIZED BY A FEW HOURS OF LIGHT SNOW WITH EMBEDDED MODERATE
BANDING OWING TO BOTH A VERY WEAKLY STATICALLY STABLE ATMOSPHERE
ABOVE THE LOW-LEVEL FRONT AND MARGINAL MID-LEVEL INSTABILITY. THE
FORECAST HAS THEREFORE BEEN AMENDED TO REFLECT A HIGHER POP SCENARIO
FROM APPROXIMATELY LIVINGSTON TO TO LAPEER COUNTIES WHERE A
WIDESPREAD HALF INCH OR SO IS STILL POSSIBLE. LOCATIONS AFFECTED BY
SAID BANDING WILL SEE A PORTION OF THE SNOW ACCUMULATE MORE QUICKLY
AS VSBYS FALL TO 1-2 MILES PER UPSTREAM OBS...RESULTING IN THE
POTENTIAL FOR A FEW ISOLATED 1" ACCUMS.
LONG TERM...
CHRISTMAS DAY WILL BE ON THE TRANQUIL SIDE OVERALL AROUND SE
MICHIGAN LEADING INTO AN ACTIVE PERIOD OF WINTER WEATHER AFTER THE
HOLIDAY. HIGHER END ADVISORY CRITERIA SNOWFALL AMOUNTS AND RATES ARE
ANTICIPATED FOR SE MICHIGAN WEDNESDAY THROUGH WEDNESDAY NIGHT WITH
THE TIMING ON THE DAY AFTER CHRISTMAS AND POTENTIAL TRAVEL IMPACTS
BEING THE NOTABLE ASPECT OF THE EVENT.
THE WEDNESDAY LOW PRESSURE SYSTEM WILL BE PRECEDED BY SOME LAKE
EFFECT SNOW SHOWERS MAKING INLAND PROGRESS OFF LAKE HURON DURING
CHRISTMAS DAY. INLAND PROGRESS COULD BE AS FAR SOUTH AS I-69 AND
WEST TO I-75 ON A SCATTERED BASIS WITH GREATER COVERAGE IN THE THUMB
CLOSER TO THE LAKE. INSTABILITY WILL BE MODEST WITH LAKE TO 850
DELTA-T RUNNING AROUND 15C BUT WITH INVERSION HEIGHT BOOSTED BY SOME
SEEDING FROM MID LEVEL MOISTURE TRAILING TODAY`S WAVE. THE BROAD
INVERTED SURFACE TROUGH WILL PROVIDE A FAVORABLE LOW LEVEL WIND
FIELD FOR FOCUSING NORTHERLY FLOW INTO THE THUMB FOR A FEW HOURS
BEFORE FILLING AND DRYING TOWARD EVENING.
THE MAIN CONCERN IN THE FORECAST REMAINS THE EVOLUTION OF A LARGE
LOW PRESSURE SYSTEM SET TO IMPACT MUCH OF THE COUNTRY EAST OF THE
MISSISSIPPI WEDNESDAY INTO THURSDAY. THIS SYSTEM IS EXPECTED TO
NEGATIVELY IMPACT POST HOLIDAY TRAVEL ACROSS THE REGION WITH
MODERATE SNOW ACCUMULATION REMAINING THE PRIMARY EXPECTATION IN SE
MICHIGAN. SUBJECT UPPER LEVEL ENERGY WAS MORE FULLY INLAND FROM THE
WEST COAST FOR THE MORNING UPPER AIR ANALYSIS, SO IT IS A GOOD SIGN
THAT THE 12Z MODEL CYCLE HAS NOT SHIFTED MUCH OFF OF EARLIER
SOLUTIONS AS THE SYSTEM DEVELOPS OVER THE WESTERN GULF COAST DURING
CHRISTMAS DAY AND DEEPENS INTO THE TENNESSEE VALLEY BY WEDNESDAY
MORNING. AGREEMENT BETWEEN THE NAM, GFS, ECMWF, AND LOCAL WRF GLOBAL
IS EXCELLENT BY THEN ON THE POSITION AND INTENSITY OF THE LARGE
SCALE FEATURES ASSOCIATED WITH THE SYSTEM. THE CANADIAN REMAINS
FASTER/FARTHER EAST IN THE SOLUTION SPACE PERHAPS REPRESENTING THE
STRONG INFLUENCE ON TRACK AND STRENGTH BY THE SOUTHWARD POSITION OF
THE UPPER JET AXIS FROM SOUTHERN CALIFORNIA TO THE CENTRAL GULF
COAST. THERE IS ALSO CONSIDERABLE LOW LEVEL BAROCLINICITY, GULF
MOISTURE, AND WARM SECTOR INSTABILITY IN ADVANCE OF THE WAVE FROM
THE TENNESSEE VALLEY TO THE MID ATLANTIC STATES. ALL OF THIS, ALONG
WITH A NEW ROUND OF UPPER LEVEL HEIGHT FALLS OVER THE WEST COAST,
FAVORS PROGRESSION AND THE TRANSFER OF CYCLOGENESIS TO THE EAST
COAST DURING WEDNESDAY.
CONFIDENCE IN THE MODEL SOLUTIONS ON THE BULK FEATURES DOES NOT GET
US OUT OF THE WOODS ON A WINTER EVENT OR SIMPLIFY THE FORECAST FOR
OUR AREA DURING WEDNESDAY INTO WEDNESDAY NIGHT AS A CONSIDERABLE
AMOUNT OF MOISTURE REMAINS ADVERTISED FOR THE REGION. WITH AN EASY
CALL ON ALL SNOW AS THE PRECIPITATION TYPE, THE QUESTION OF AMOUNT
REMAINS TIED TO THE CHARACTER AND DURATION OF MAX FORCING AND
MICROPHYSICAL ASPECTS OF THE SNOW OVER SE MICHIGAN DURING THE PEAK
OF THE EVENT WEDNESDAY AFTERNOON THROUGH WEDNESDAY EVENING. THE
TRANSFER OF CYCLOGENESIS TO THE MID ATLANTIC COAST WILL SIPHON AT
LEAST SOME ENERGY AND MOISTURE OUT OF THE GREAT LAKES BUT A WELL
ORGANIZED TROWAL IS SHOWN TO BE IN PLACE OVER OUR AREA WITH A STRONG
HYBRID ATLANTIC/GULF MOISTURE CONVEYOR FEEDING INTO THE NORTH FLANK
OF THE SYSTEM. MODEL FIELDS OF SPECIFIC HUMIDITY INDICATE MORE THAN
ADEQUATE AMOUNTS OF 2-3 G/KG IN THE 850 TO 700 MB LAYER ASSOCIATED
WITH THE TROWAL AXIS. THIS LEAVES DURATION AS THE LIMITING FACTOR AS
FIELDS OF THETA-E INDICATE THE TROWAL SHRINKING EASTWARD QUICKLY BY
MIDNIGHT WEDNESDAY NIGHT. WILDCARDS TO CONSIDER THAT COULD SKEW
AMOUNTS HIGHER INCLUDE THE ACTUAL TIMING OF EAST COAST TRANSFER,
MESOSCALE BANDS WITHIN THE TROWAL, AND LAKE ENHANCEMENT. THE
POTENTIAL FOR LAKE ENHANCEMENT WILL BE THE MOST LIKELY EXTRA
CONTRIBUTOR BUT THAT WILL TEND TO STRETCH THE EVENT WELL INTO
THURSDAY AS SYNOPTIC FORCING WANES. THIS WILL CONTINUE TO BE
EVALUATED BUT THE PREPONDERANCE OF EVIDENCE FOR THIS FORECAST
PACKAGE, ALONG WITH MODEL SOUNDING DERIVED SNOW RATIO AVERAGING
11:1, SUGGESTS STORM TOTALS WILL REMAIN MOSTLY BELOW 6 INCHES DURING
THE 12 TO 18 HOUR EVENT ENDING BY SUNRISE THURSDAY.
AFTER A BREAK DURING THURSDAY AND MOST OF FRIDAY, THE ACTIVE LARGE
SCALE PATTERN WILL CONTINUE WITH THE NEXT PACIFIC SYSTEM REACHING
THE GREAT LAKES TO START THE WEEKEND. EARLY INDICATIONS ARE THIS
SYSTEM WILL BE LESS ORGANIZED AS IT MOVES THROUGH THE GREAT LAKES
BEFORE GAINING STRENGTH ALONG THE EAST COAST TOWARD SUNDAY.
MARINE...
LIGHT NORTHERLY WINDS TONIGHT OF 15 KNOTS OR LESS WILL TURN EASTERLY
AND BEGIN TO INCREASE ON TUESDAY NIGHT AS A STRONG LOW PRESSURE
SYSTEM LIFTS TOWARD THE REGION FROM THE SOUTH. THE PROLONGED PERIOD
OF ONSHORE FLOW WILL FAVOR ELEVATED WAVE CONDITIONS FOR ALL
NEARSHORE ZONES BETWEEN WEDNESDAY AND THURSDAY MORNING IN ADDITION
TO POTENTIAL FUNNELING INTO SAGINAW BAY. SMALL CRAFT ADVISORIES
APPEAR LIKELY AT THIS TIME. BY WEDNESDAY AFTERNOON INTO WEDNESDAY
NIGHT...GUSTS TO NEAR GALES WILL BE POSSIBLE ACROSS AREA WATERS.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....KURIMSKI
UPDATE.......KURIMSKI
SHORT TERM...JVC
LONG TERM....BT
MARINE.......JVC
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS HASTINGS NE
358 AM CST TUE DEC 25 2012
.SHORT TERM...TODAY THROUGH THURSDAY NIGHT. PRIMARY FORECAST
CONCERN LIES WITH PRECIPITATION CHANCES TODAY AND AGAIN
THURSDAY/THURSDAY NIGHT.
UPPER LEVEL SATELLITE IMAGERY SHOWING THE LOW PRESSURE SYSTEM OF
INTEREST STARTING TO EMERGE FROM THE ROCKIES...ENDING UP ROUGHLY
OVER THE PANHANDLES OF TX/OK BY SUNRISE THIS MORNING. INCREASING
LIFT ASSOCIATED WITH THIS SYSTEM IS GRADUALLY BUILDING NORTH INTO
THE CWA...AND WRN LOCATIONS HAVE JUST RECENTLY STARTED REPORTING
SOME -SN. NO SURPRISES WITH THE SURFACE PATTERN...THE MAIN LOW IS
WELL TO THE SOUTH OF THE CWA...WITH HIGHER PRESSURE SET UP OVER
THE DAKOTAS...RESULTING IN AT TIMES GUSTY NORTHERLY WINDS.
THROUGH THE REST OF THE DAYTIME HOURS...REALLY NO SIGNIFICANT
CHANGES MADE. MODELS CONTINUE TO BE IN GOOD AGREEMENT SHOWING THE
MAIN UPPER LEVEL SLIDING ACROSS THE SRN PLAINS...ALONG/JUST SOUTH
OF THE OK/TX BORDER. THE BETTER CHANCES FOR PRECIPITATION
REMAINS GENERALLY ALONG AND WEST OF HIGHWAY 183...BUT DID MAKE
SOME ADJUSTMENTS TO THE AREAL COVERAGE OF THE POPS. LATEST RUNS OF
MANY OF THE MODELS ARE SHOWING A SLIGHT SOUTHWARD SHIFT TO SOME OF
THE HIGHER QPF VALUES...BRINGING INCREASED SNOWFALL POTENTIAL TO
PORTIONS OF OUR NC KS...AND ADJUSTED THE POPS ACCORDINGLY.
OTHERWISE...THE TIMING REMAINS BASICALLY THE SAME WITH THE MAIN
CHANCES COMING DURING THE MORNING HOURS...AND OVERALL AMOUNTS
DIDNT CHANGE MUCH. THIS AFTERNOON...EXPECTING A QUICK DOWNWARD
TREND IN PRECIPITATION...WITH ANY CHANCES CONFINED TO THE WRN
FRINGE OF THE CWA. AS FAR AS ACCUMULATIONS GO...AREAS WEST OF
HIGHWAY 183 STILL LOOKING AT THE POTENTIAL OF GENERALLY ARND 1-1.5
INCHES...A FEW LOCATIONS COULD POSSIBLY CREEP NEAR 2 INCHES.
BETWEEN HIGHWAY 183 AND 281...A COUPLE TENTHS OF AN INCH /EAST/ UP
TO AN INCH /WEST/ ARE POSSIBLE. EAST OF HIGHWAY 281...NOT
EXPECTING MUCH MORE THAN SOME FLURRIES TO PERHAPS A TENTH OF AN
INCH OR SO. HIGHS FOR TODAY STILL LOOKING TO TOP OUT IN THE
LOWER/MID TEENS...AND WIND SPEED WILL RANGE FROM 10-15 MPH IN THE
NORTH TO 15-20 WITH GUSTS NEAR 25MPH IN THE SOUTH CLOSER TO THE
SFC LOW. CURRENT OBS WHERE SNOW IS STARTING TO FALL ARE SHOWING
THE ADDITION OF WIND IS BRINGING VISIBILITIES DOWN NEAR 2 MILES AT
TIMES...AND THAT TREND WILL REMAIN THE CASE THROUGH THE MORNING
ANYWHERE SNOW FALLS. BRIEF PERIODS OF VISIBILITIES CLOSER TO A MILE
OR LESS WILL BE POSSIBLE...JUST WILL BE DEPENDENT ON HOW MUCH SNOW
IS COMING DOWN.
PRECIPITATION TODAY IS EXPECTED TO COME TO AN END BY THIS
EVENING...WITH DRY CONDITIONS THEN THROUGH THE OVERNIGHT HOURS. A
SURFACE RIDGE AXIS WILL GRADUALLY BUILD INTO THE REGION...AND IS
EXPECTED TO SETTLE IN RIGHT OVER THE CWA BY 12Z
WEDNESDAY...BRINGING LIGHT/VARIABLE TO AT TIMES CALM WINDS. THE
MAIN QUESTION FOR TONIGHT LIES WITH HOW COLD TEMPERATURES ARE
GOING TO GET. LITTLE CONCERNED ABOUT SKIES NOT CLEARING AS MUCH AS
THOUGHT EVEN 24 HOURS AGO...WHICH WOULD KEEP TEMPS FROM FALLING AS
MUCH. DID END UP TRENDING OVERNIGHT LOW TEMPERATURES CLOSER TO THE
MET/MAV GUIDANCE...AND STILL REMAINS BELOW RAW MODEL OUTPUT. THIS
WILL BE SOMETHING FOR THE DAY SHIFT TO LOOK INTO WITH THE NEW
MODELS RUNS...PERHAPS SOME ADDITIONAL UPWARD ADJUSTMENTS MAY BE
NEEDED.
INTO WEDNESDAY...THE DRY FORECAST REMAINS IN PLACE...AS UPPER
LEVEL SHORTWAVE RIDGING SLIDES EAST ONTO AND THROUGH THE PLAINS
BETWEEN SYSTEMS. WILL BE SEEING AN INCREASE IN CLOUD COVER THROUGH
THE DAY AS THE NEXT UPPER LEVEL SYSTEM APPROACHES...AND WINDS WILL
START THE DAY LIGHT WITH THAT SFC RIDGE AXIS IN PLACE...BUT WILL
BECOME MORE SOUTHERLY AS IT SLIDES OFF TO THE EAST. UNFORTUNATELY
NOT GOING TO BE SEEING A BREAK FROM THE BELOW AVERAGE
TEMPERATURES...WITH HIGHS ONLY LOOKING TO TOP OUT IN THE MID/UPPER
TEENS.
LOOKING TOWARD WEDNESDAY NIGHT...AND ESPECIALLY THURSDAY AND
THURSDAY NIGHT...ANOTHER CHANCE FOR ACCUMULATING SNOWFALL COMES TO
THE CWA. AS THE UPPER LEVEL LOW PRESSURE SYSTEM AND TROUGH MOVE
EAST THROUGH THE ROCKIES...MORE SOUTHWESTERLY FLOW DEVELOPS OVER
THE CENTRAL PLAINS. AT THIS POINT...MODELS REMAIN IN DECENT
AGREEMENT KEEPING THINGS DRY PRIOR TO 12Z THURSDAY...BUT IT
WOULDNT TAKE MUCH OF A SHIFT TO END UP NEEDING TO ADD POPS LATE
WEDNESDAY NIGHT. THE BETTER CHANCES REMAIN DURING THE DAYTIME
HOURS THURSDAY AND INTO AT LEAST THE FIRST HALF OF THURSDAY NIGHT.
AT 12Z THURSDAY...THERE REMAIN SOME DIFFERENCES BETWEEN
MODELS...BUT THE LOW LOOKS TO BE OVER OR MOVING INTO THE PANHANDLE
OF NEBRASKA REGION. THROUGH THE DAYTIME HOURS...THE LOW TAKES AN
EASTWARD PATH...AND THE MODEL DIFFERENCES CONTINUE...BUT IN
GENERAL THE LOW SHOULD BE CROSSING THE NORTHERN HALF OF NEBRASKA.
THE MAIN CHANGE MADE TO THE FORECAST WAS TO INCREASE POPS ACROSS
THE NORTHERN HALF OF THE CWA...WITH LIKELY POPS I-80 AND NORTH.
THIS IS ANOTHER PROGRESSIVE SYSTEM...BUT SNOWFALL ACCUMULATIONS OF
ARND 2 INCHES LOOKS POSSIBLE...MAINLY NORTH OF HIGHWAY 92.
PRECIPITATION IS EXPECTED TO COME TO AN END BY 12Z FRIDAY.
.LONG TERM...FRIDAY THROUGH MONDAY. TEMPERATURES WILL BE THE MAIN
CHALLENGE THROUGH THIS PERIOD.
SHORTWAVE UPPER LEVEL RIDGING WILL DEVELOP ACROSS THE CENTRAL
PLAINS FRIDAY AND THROUGH WEEKEND. THIS SHOULD GIVE US PLENTY OF
SUNSHINE FOR THE PERIOD AND DRY CONDITIONS. RETURN SOUTHWEST FLOW
BY LATER SATURDAY WILL HELP MODERATE DAYTIME TEMPERATURES INTO THE
20S...STILL BELOW NORMAL BUT A NICE RESPITE FROM THE CURRENT COLD
SPELL. THE RIDGE IS REPLACED BY A WEAK SHORTWAVE WORKING SOUTH
FROM CANADA ON MONDAY. WHILE SOME FLURRIES MAY BE POSSIBLE...TOO
EARLY TO THINK MEASURABLE PRECIPITATION. THE MAIN INFLUENCE WILL
BE ANOTHER REINFORCING SHOT OF AN ARCTIC AIR MASS FOR
MONDAY/TUESDAY. HIGH TEMPERATURES MAY SLIP BACK A BIT...AND THAT
IS THE TREND DEPICTED IN MONDAY/S HIGH TEMPERATURES...SUGGESTING 3
TO 5 DEGREES COOLER THAN SUNDAY.
AFTER A CHILLY START TO NEXT WEEK...SIGNS ARE SHOWING THAT A
WARMING CHINOOK WIND MAY DEVELOP IN CENTRAL CANADA AS UPPER
LEVEL RIDGING PUSHES INTO THAT AREA. THIS COULD SPELL A DEVELOPING
WESTERLY BREEZE WORKING ITS WAY SOUTH FROM THE CANADIAN PROVINCES.
THIS WOULD SETTLE INTO THE AREA NEXT WEDNESDAY/THURSDAY
POTENTIALLY...AND GIVE US OUR BEST SHOT AT SOME MELTING IN THE
NEAR FUTURE. IT APPEARS TEMPERATURES WILL BE NEAR NORMAL IN THE 10
TO 15 DAY PERIOD...TEMPERED SOME BY CURRENT SNOWPACK.
&&
.AVIATION...06Z TAF. THE ENTIRE FORECAST PERIOD WILL HAVE MID
LEVEL CEILINGS RANGING FROM 3500 FEET TO 12K FEET. STARTING TO
SEE EVIDENCE OF SECOND SNOW AREA DEVELOPING ON RADAR TO THE
SOUTHWEST OF KGRI...SIMILAR TO TRENDS ON THE HRRR AND WRF MODELS.
THIS SHOULD EVENTUALLY BE GRAND ISLAND/S SNOW MAKER..ALBEIT VERY
LIGHT. EXPECTING THE SNOW TO DEVELOP PRIOR TO SUNRISE AND LINGER
THROUGH LATE MORNING...WITH POSSIBLY SOME BRIEF PERIODS OF MVFR
VISIBILITIES. ANY SNOW ACCUMULATIONS WILL BE IN THE RANGE OF A
SKIFF OR SO. A STEADY NORTH NORTHEAST WILL DROP OFF AROUND SUNSET
AS CEILINGS SLOWLY LIFT AS WELL.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS HASTINGS NE
1115 PM CST MON DEC 24 2012
.AVIATION...06Z TAF. THE ENTIRE FORECAST PERIOD WILL HAVE MID
LEVEL CEILINGS RANGING FROM 3500 FEET TO 12K FEET. STARTING TO
SEE EVIDENCE OF SECOND SNOW AREA DEVELOPING ON RADAR TO THE
SOUTHWEST OF KGRI...SIMILAR TO TRENDS ON THE HRRR AND WRF MODELS.
THIS SHOULD EVENTUALLY BE GRAND ISLAND/S SNOW MAKER..ALBEIT VERY
LIGHT. EXPECTING THE SNOW TO DEVELOP PRIOR TO SUNRISE AND LINGER
THROUGH LATE MORNING...WITH POSSIBLY SOME BRIEF PERIODS OF MVFR
VISIBILITIES. ANY SNOW ACCUMULATIONS WILL BE IN THE RANGE OF A
SKIFF OR SO. A STEADY NORTH NORTHEAST WILL DROP OFF AROUND SUNSET
AS CEILINGS SLOWLY LIFT AS WELL.
&&
.PREV DISCUSSION... /ISSUED 551 PM CST MON DEC 24 2012/
AVIATION...00Z KGRI TAF...CIGS ARE EXPECTED TO LOWER AT THE
TERMINAL OVERNIGHT WITH NORTHEASTERLY WINDS BECOMING MORE
NORTHERLY BY MIDNIGHT. THERE IS A SMALL PROBABILITY FOR SOME MVFR
CIGS/VSBYS IN -SN AFT ABOUT 25/09Z...BUT KEPT IN A PROB30 GROUP
FOR NOW AS BETTER CHANCES FOR SOME LIGHT SNOWFALL APPEARS FURTHER
WEST...WITH MAINLY FLURRIES AND NO VISIBILITY RESTRICTIONS
EXPECTED AT THE TERMINAL FOR THE TIME BEING.
PREV DISCUSSION... /ISSUED 342 PM CST MON DEC 24 2012/
SHORT TERM...CHRISTMAS EVE THROUGH CHRISTMAS DAY
MAIN STORY: CLOUDY THIS CHRISTMAS EVE WITH LIGHT SNOW DEVELOPING
LATE AND CONTINUING INTO CHRISTMAS DAY...MAINLY W OF THE TRI-
CITIES. AN INTENSIFYING STORM TO THE S WILL COMBINE WITH BITTER
COLD TO RESULT IN NASTY WIND CHILLS AND THE COLDEST CHRISTMAS IN
16 YRS!
ZFP/AFM/PFM AND UPDATED HWO HAVE ALL POSTED.
UPPER-LEVELS: SHORT-WAVE TROF AND ASSOCIATED 130 KT TROPOPAUSE JET
IS MOVING THRU THE 4 CORNERS ATTM. THIS WILL INITIATE LEE
CYCLOGENESIS...BUT SFC LOW WILL TRACK FAR TO THE S OVER TX.
HOWEVER...THE TROF/JET WILL INDUCE UPSLOPE AS MID-LEVEL
CIRCULATION CLOSES OFF. THIS WILL RESULT IN SOME -SN LATE TNGT
INTO CHRISTMAS DAY...ENHANCING THE HOLIDAY FEEL BUT THREATENING
SOME SLIPPERY TRAVEL.
REST OF THIS AFTN: M/CLOUDY WITH AREAS S OF HWY 24 OVER N-CNTRL KS
FLIRTING WITH P/CLOUDY. ANOTHER COLD DAY WITH TEMPS NEARLY 20F
BELOW NORMAL.
TONIGHT: BECOMING CLOUDY FOR ANY AREAS NOT COMPLETELY OVC BY SUNSET.
POSSIBLY SOME -SN MOVING IN W OF HWY 283 AFTER MIDNIGHT. NE WINDS
GRADUALLY INCREASE TO 10-20 MPH BY MIDNIGHT AND 15-25 MPH AFTER 3
AM.
LOW TEMPS ARE A 67/33 BLEND OF MAV/MET MOS. THEN NUDGED UP ORD AND
SURROUNDING AREAS 2F. COULD GET BURNED ON THIS IN NE ADVECTION BUT
HARD TO BELIEVE ORD IS COLDER TNGT THAN WHAT THE LOW WAS THIS AM.
CHRISTMAS DAY: CLOUDY AND BITTERLY COLD WITH A BITING NE WIND AS
LOW DEVELOPS WELL S OF THE FCST AREA. PERIODS OF -SN MAINLY ALONG
AND W OF HWY 183. USED 09Z SREF TO ASSIST WITH POPS.
COULD SEE FLURRIES OR A TOUCH OF -SN FROM THE TRI-CITIES E.
SNOW: CURRENT EXPECTATION IS AROUND 1" ALONG AND W OF HWY 283. LESS
THAN 1" BETWEEN HWY 283 AND 183. THEN JUST A DUSTING POSSIBLE AS FAR
E AS ORD-KEARNEY-SMITH CTR KS-OSBORNE KS.
SNOW RATIO: LOW CONFIDENCE. STAYED CLOSE TO CLIMO BUT FEELING IS
THAT IT WILL BE LOWER. LIFT IS MOSTLY ABOVE THE DGZ PER CROSS
SECTIONS...AND VERY WEAK IN THE DENDRITIC GROWTH ZONE /DGZ/. THIS
SUGGESTS PRIMARILY PLATE HABITS OR SMALL DENDRITES. INCREASED FLAKE
DENSITY SUPPORTS A LOWER RATIO.
WHERE CAN THIS FCST BREAK DOWN: HOW FAR E WILL SNOW FALL? AND HOW
FAR E WILL 1" OCCUR? THE 12Z NAM-ARW IS THE FARTHEST E WITH ITS .1
QPF...TO KEARNEY/SMITH CTR. NOT TO SAY IT CAN/T HAPPEN BUT SREF
PROBS FOR AT LEAST .1 ARE GREATEST W OF HWY 283. SO THIS FCST IS
CONSERVATIVE. MAY NOT BE FAR ENOUGH E. HIGHEST SREF PROBS FOR 1" OF
ACCUM IS OVER EXTREME WRN DAWSON COUNTY BUT THIS IS PROBABLY TOO
CONSERVATIVE.
WIND CHILLS: 0 TO -10F TNGT. -7 TO -10F CHRISTMAS DAY.
DRESS VERY WARMLY IF YOU HAVE PLANS TO CAROL OUTSIDE OR TRAVEL TO
HOLIDAY PARTIES. THIS KIND OF COLD WILL BE DANGEROUS!
CLIMATE: FOR THOSE INTERESTED OUR FCST TEMPS FOR TOMORROW ARE AN
INTERESTING COMPARISON WITH PREVIOUS CHRISTMAS EXTREMES. PLEASE SEE
THE EXCELLENT WEB STORY ON CHRISTMAS CLIMO ON OUR TOP NEWS OF THE
DAY FOR THE DETAILS. BOTTOM LINE...THIS WILL BE AMONG THE TOP TEN
COLDEST CHRISTMAS DAYS ON RECORD FOR THE HIGH TEMP AND DAILY AVG
TEMP. THE GRI HIGH TEMP CHRISTMAS 1996 WAS ONLY 11F. WE ARE
CURRENTLY FCSTG 11F. IF THIS FCST IS CORRECT THIS WILL TIE FOR THE
4TH COLDEST CHRISTMAS ON RECORD AT GRI.
LONG TERM...CHRISTMAS DAY NIGHT THROUGH MONDAY/NEW YEARS EVE. AS A
LIGHT SNOW EVENT RAPIDLY WRAPS UP CHRISTMAS DAY...FOCUS IS ON THE
NEXT ROUND OF SNOW MOVING IN ON THURSDAY. STARTING WITH CHRISTMAS
DAY NIGHT...BOTH THE SOUTHERN PLAINS CLOSED SYSTEM AND WEAKER
NORTHERN STREAK TROUGH TREK EASTWARD CHRISTMAS DAY NIGHT. UNDER
MORE INFLUENCE OF THE NORTHERN STREAM TROUGH...THE MID/UPPER TROUGH AXIS
DOES NOT PASS TO OUR EAST UNTIL OVERNIGHT AND WOULD NOT BE SURPRISED
TO SEE A FEW FLURRIES LINGERING BRIEFLY INTO THE EVENING...HOWEVER
AS AXIS SHIFTS EASTWARD INTO DRIER AIR...ANY LINGERING FLURRIES
SHOULD WIND DOWN RATHER QUICKLY.
LITTLE CHANGE IN THE FRIGID ARCTIC AIRMASS ON WEDNESDAY...WITH DRY
CONDITIONS IN SHORTWAVE RIDGING...BUT UNDER THE INFLUENCE OF A
1030MB SURFACE HIGH PRESSURE SYSTEM. TEMPS WILL STRUGGLE WITH JUST
TEENS FORECAST FOR HIGHS...OVERNIGHT WIND CHILLS IN THE TEENS BELOW
ZERO...AND DAYTIME WIND CHILLS IN THE SINGLE DIGITS. WEDNESDAY
NIGHT INTO THURSDAY...THE SURFACE RIDGE SHIFTS EASTWARD WITH SFC LOW
PRESSURE DEEPENING ALONG THE HIGH PLAINS WHILE UPSTREAM UPPER LOW
MOVES FURTHER INTO THE NORTHERN/CENTRAL ROCKIES. A 130KT JET ROUNDS
BASE OF TROUGH AND NOSES NORTH ONTO THE CENTRAL PLAINS WITH
DIVERGENCE ALOFT INCREASING BY THURSDAY MORNING. ISENTROPIC LIFT AS
INDICATED ON THE 290K SURFACE IS ALSO ON THE INCREASE
THURSDAY...ESPECIALLY ACROSS OUR NORTHERN ZONES AHEAD OF THE
APPROACHING CLOSED UPPER LOW SYSTEM. SNOW IS EXPECTED TO DEVELOP
DURING THE DAY ON THURSDAY...AND CONTINUE INTO THURSDAY NIGHT AS THE
SYSTEM TRACKS ACROSS NEBRASKA. BASED ON THE CURRENT TRACK OF THE
SYSTEM...THE BEST SNOW CHCS FAVOR LOCATIONS IN
NEBRASKA...PARTICULARLY NORTH OF INTERSTATE 80. GIVEN THE COLD
AIRMASS...SNOW RATIOS WILL BE RATHER HIGH AND SNOW ACCUMULATIONS
LOOK LIKELY. WILL AIM FOR SNOW AMOUNTS OF AN INCH OR TWO IN OUR FAR
NORTHERN ZONES ON THURSDAY...WITH LESSER AMOUNTS TO THE SOUTH.
THE UPPER LOW EXITS THE CENTRAL PLAINS TO THE UPPER MIDWEST REGION
THURSDAY NIGHT/FRIDAY WITH SNOWFALL ENDING W/E. STILL UNDER
INFLUENCE OF AN UPPER TROUGH FRIDAY AND WITH THE NEW SNOWFALL...COLD
AIRMASS IN PLACE...TEMPS WILL CONTINUE TO STRUGGLE. UPPER TROUGH
FINALLY DEPARTS HEADING INTO THE WEEKEND ALLOWING FOR HEIGHTS TO
RISE WITH UPPER RIDGING PROGGED ACROSS THE CENTRAL PLAINS FOR THE
WEEKEND. THE ARCTIC AIR BEGINS TO DISLODGE AND TEMPS IN THE 20S
LOOK PROBABLE FOR HIGHS. ALTHOUGH JUST BEYOND THE EXTENDED...ECMWF
ADVERTISES ANOTHER SURGE OF ARCTIC AIR TO ARRIVE IN TIME FOR NEW
YEARS DAY WITH A 1037MB SURFACE HIGH SETTLING IN.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS WILMINGTON OH
454 AM EST TUE DEC 25 2012
.SYNOPSIS...
LOW PRESSURE WILL TRACK FROM TEXAS TODAY AND SKIM THE SOUTHERN
OHIO VALLEY AS IT MOVES NORTHEAST ON WEDNESDAY. HIGH PRESSURE OVER
THE MIDWEST WILL BUILD FOR THE LATTER PART OF THE WEEK AND SETTLE
OVER THE OHIO VALLEY ON FRIDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
RADAR RETURNS HAVE NOT MATERIALIZED INTO ANY ADDITIONAL FREEZING
DRIZZLE EARLY THIS MORNING OVER THE NORTHWEST PORTIONS OF CWA.
EXPECT CLOUDY SKIES TO SEE SOME BREAKS THIS AFTERNOON AND THEN
HAVE THE SOUTHWESTERN SYSTEM BEGIN TO OVERSPREAD THE REGION LATE
TODAY. TEMPERATURES WILL RISE INTO THE MID AND UPPER 30S FOR MUCH
OF THE REGION. AREAS SOUTH OF THE OHIO COULD TOP OUT IN THE LOW
40S TODAY.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
PRECIPITATION SHIELD WILL OVERSPREAD THE OHIO VALLEY TONIGHT.
MODELS AND NUMERICAL GUIDANCE WERE ALL 2-3 DEGREES COOLER ON LOW
TEMPERATURES THAN THEIR 3 HOURLY VALUES AND I BLENDED GUIDANCE
WITH CURRENT FORECAST AND THEN BUMPED UP VALUES A DEGREE OR TWO
ACROSS THE BOARD. A 3 DEGREE DEPARTURE FROM STATED 3 HOURLY
TEMPERATURES IS TOO MUCH...ESPECIALLY GIVEN THAT THE 0Z TO 12Z
TIME ONLY HAD A 2 OR 3 DEGREE TEMPERATURE DIFFERENCE FOR ANY SITE
FOR BOTH THE MAV AND MET GUIDANCE.
THIS WARMER START PLAYS INTO THE FORECAST AS THE RAIN WILL BE
OVERSPREADING THE AREA AND COULD BEGIN AS FREEZING RAIN FOR
PRIMARILY COLDER DRAINAGE AREAS. A WARM CORE OF AIR WILL BE FOUND
OVER SOUTHEASTERN CWA AND NOSE INTO THE I-71 CORRIDOR EARLY
WEDNESDAY. SNOW ALONG THE I-71 CORRIDOR MAY MIX WITH RAIN AT TIMES
AND THIS COULD CUT DOWN SIGNIFICANT SNOWFALL TOTALS HERE. A LOT OF
THIS REMAINS TO BE SEEN AND THAT IS WHY THE WATCH OVER
BUTLER/WARREN COUNTIES WAS CONTINUED AND THE OLD WATCH UPGRADED TO
A WARNING WHERE 6" OR BETTER OF SNOWFALL IS EXPECTED. WITH THE
UNCERTAINTY OF THESE TOTALS MIXING WITH RAIN AND THE POTENTIAL OF
FREEZING RAIN HERE...A TIER OF COUNTIES IN OHIO AND A NUMBER OF
COUNTIES OVER INDIANA HAVE BEEN ADDED. IN KY...IT ONLY INCLUDES
THOSE IN THE I-71 CORRIDOR.
THE SYSTEM IS FAIRLY PROGRESSIVE AND ANY RAIN SHOULD BE CHANGING
TO SNOW BY SUNSET WEDNESDAY. THIS TIME WILL ALSO MARK THE END OF
ANY LINGERING HEAVY SNOWFALL AND A TRANSITION TO LIGHT SNOW AND
FLURRIES. THIS LIGHT SNOW WILL LIKELY TURN OFF DURING THE
OVERNIGHT HOURS AS THE UPPER LEVEL DYNAMICS MOVE EAST AND RIDGING
BUILDS IN. THE DOWNWARD MOTION FROM ALOFT WILL NOT PERMIT
LINGERING FLURRIES TO PERSIST MUCH PAST MIDNIGHT OR SO.
COOLER TEMPERATURES WILL PREVAIL BEYOND WEDNESDAY AS NORTH WINDS
PULL COLD AIR TO THE REGION. CLOUD COVER WILL NOT PERMIT RUNAWAY
RADIATIONAL COOLING TO BE A FACTOR THROUGH THIS TIME.
HOWEVER...BEYOND THIS...ANY CLEARING AT NIGHT WILL COMBINE WITH
FRESH SNOW COVER TO LET TEMPERATURES DROP SIGNIFICANTLY.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
DEPARTING WINTER STORM WILL LEAVE DRY CONDITIONS AND SEASONABLE
TEMPERATURES AS SHORTWAVE RIDGING BUILDS IN OVER THE OHIO
VALLEY...DOWNSTREAM INTERMOUNTAIN WEST SHORTWAVE RIDGING. THIS
ENERGY ROTATING THROUGH A VERY BROAD LONGWAVE TROUGH CENTERED OVER
THE CONUS WILL LARGELY EJECT NORTH OF THE AREA INTO SATURDAY.
HOWEVER... THE BASE OF THE TROUGH WILL INTERACT WITH A DEEP MOISTURE
POOL OVER THE WESTERN GULF AND SEND AN ENHANCED STREAM OF MOISTURE
INTO THE OHIO VALLEY...WITH WEAK SFC LOW DEVELOPMENT OVER THE
SOUTHEAST.
HAVE KEPT MUCH OF THURSDAY /RESIDUAL SNOW SHOWER CHANCE MAINLY
EARLY/ DRY AND INTO FRIDAY AS WELL...AND THEN SPREAD SNOW CHANCES
BACK IN FRIDAY NIGHT AND THROUGH THE DAY SATURDAY. TEMP PROFILES
SUGGEST MAJORITY OF THIS HAS A BETTER SNOW CHANCE THAN RAIN
CHANCE...BUT ENSEMBLE PERSPECTIVE SUGGESTS THERE IS ENOUGH CHANCE AT
THIS TIME RANGE TO BRING A THREAT OF EITHER RAIN OR SNOW INTO PARTS
OF THE AREA ON SATURDAY...THOUGH RIGHT NOW IT APPEARS A BETTER SNOW
THREAT...WITH LIGHT ACCUMULATIONS...AND HAVE SET UP GRIDDED FORECAST
THAT WAY FOR NOW.
SYSTEM SHOULD BE TRANSIENT THUS DIMINISHING THREATS OF SNOW ON
SUNDAY AS TEMPERATURES REMAIN NEAR/SLIGHTLY BELOW NORMAL.
&&
.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
NLY FLOW ON THE BACKSIDE OF LOW PRESSURE IS KEEPING IFR/MVFR ST
ACROSS THE TAFS. AS THE LOW CONTINUES TO MOVE E...WEAK HIGH
PRESSURE RIDGE WILL SLOWLY BUILD INTO THE REGION. MODELS DIFFER IN
THEIR HANDLING OF THE LOW LEVEL MOISTURE AND HOW MUCH IT CLEARS.
THE RAP MODEL KEEPS THE LOW LEVEL TRAPPED ACROSS THE REGION THE
ENTIRE DAY. THE NAM SCOURS IT OUT AROUND 12Z. THE GFS IS KIND OF
THE COMPROMISE AND KEEPS SOME MOISTURE ACROSS THE TAFS BUT LIFTS
AND BREAKS ITS UP A LITTLE. THIS LAST SOLUTION SEEMS THE MOST
REASONABLE...SO ALLOWED THE CIGS TO RISE TO AROUND 2500 FT AND GO
BROKEN. CIGS SHOULD RISE TO VFR AS THE LOW LOW LEVEL MOISTURE
WAINS.
THE EFFECTS OF THE MAJOR WINTER STORM START TO AFFECT CVG IN THE
EXTENDED PORTION OF THE 30 HR TAF. BROUGHT THE PCPN IN AS S THERE
AND DROPPED CIGS DOWN TO IFR AFT 06Z.
OUTLOOK...IFR CEILINGS AND VISIBILITIES OVERSPREADING THE REGION
TUESDAY NIGHT...CONTINUING WEDNESDAY INTO WEDNESDAY NIGHT.
CONDITIONS WILL LIFT TO MVFR ON THURSDAY. MVFR/IFR CEILINGS AND
VISIBILITIES POSSIBLE SATURDAY.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...WINTER STORM WARNING FROM 1 AM WEDNESDAY TO 1 AM EST THURSDAY
FOR OHZ026-034-035-042>046-051>056-060>062.
WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE WEDNESDAY
NIGHT FOR OHZ063>065-070>072-077.
KY...WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE WEDNESDAY
NIGHT FOR KYZ089>091.
IN...WINTER STORM WARNING FROM 1 AM WEDNESDAY TO 1 AM EST THURSDAY
FOR INZ050-058-059-066.
WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE WEDNESDAY
NIGHT FOR INZ073>075-080.
&&
$$
SYNOPSIS...FRANKS
NEAR TERM...
SHORT TERM...FRANKS
LONG TERM...BINAU
AVIATION...SITES
AREA FORECAST DISCUSSION
NWS WILMINGTON OH
110 AM EST TUE DEC 25 2012
.SYNOPSIS...
MOSTLY CLOUDY WEATHER IS EXPECTED TONIGHT AS WEAK LOW PRESSURE
MOVES EAST. AFTER A DRY CHRISTMAS DAY DUE TO WEAK HIGH
PRESSURE...A MAJOR WINTER STORM TRACKING FROM THE LOWER
MISSISSIPPI VALLEY TO THE CENTRAL APPALACHIANS WILL IMPACT THE
REGION CHRISTMAS NIGHT THROUGH WEDNESDAY NIGHT. A RIDGE OF HIGH
PRESSURE SHOULD BRING DRY CONDITIONS FOR THURSDAY AND FRIDAY.
ANOTHER LOW WILL PROVIDE MORE WINTRY PRECIPITATION ON SATURDAY.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
LATEST RUN OF THE FORECAST HAD ME INTRODUCE DRIZZLE AND FREEZING
DRIZZLE FOR OUR NORTHWEST 1/4 TO 1/3 OF CWA THROUGH DAYBREAK.
TEMPERATURES RIGHT AT THAT MAGICAL 32 OR ZERO DEPENDING ON YOUR
INCLINATION ARE PRETTY UNIFORM OVER MUCH OF THE REGION AT THIS
MOMENT IN TIME. NORTHWEST WINDS WILL TURN NORTH IN FAIRLY SHORT
ORDER AND HELP CEASE ANY FURTHER EASTWARD PROGRESSION TO ANY
DRIZZLE EARLY THIS MORNING.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY NIGHT/...
WEAK RIDGE BETWEEN LOWS WILL KEEP CONDITIONS DRY ON CHRISTMAS DAY.
PARTIAL SUNSHINE WILL ALLOW TEMPERATURES TO RISE CLOSE TO
NORMAL...IN THE UPPER 30S AND LOW 40S.
WEATHER WILL DETERIORATE RAPIDLY TUESDAY NIGHT AS LOW PRESSURE
SPINS UP AND MOVES TO TENNESSEE. THIS LOW WILL LIFT GULF MOISTURE
OVER A COLD AIRMASS IN LOWER LEVELS TO PRODUCE HEAVY WINTRY
PRECIPITATION. WENT CLOSER TO THE ECMWF SOLUTION WHICH HAS BEEN
QUITE CONSISTENT FOR SEVERAL DAYS IN BRINGING TEMPERATURE PROFILES
CONDUCIVE FOR WINTER PRECIP ACROSS MUCH OF THE ILN AREA. BASED ON
THAT LATEST GUIDANCE...HAVE EXPANDED OUR WINTER STORM WATCH
FARTHER SOUTH TO INCLUDE COLUMBUS AND DAYTON. EXPECT HEAVY SNOW OF
AROUND 6 INCHES THE WATCH AREA...WITH PERHAPS 1 TO 3 INCHES AT
LOCATIONS SOUTH OF THE WATCH AREA INCLUDING CINCINNATI...WHERE
WARMER AIR IS FORECAST TO FILTER IN AND ALLOW RAIN TO MIX IN ON
WEDNESDAY. SLEET ALSO MAY MIX IN FOR A TIME ON WEDNESDAY WHEN
MODEL SOUNDINGS INDICATE PARTIAL MELTING AND REFREEZING OF
HYDROMETEORS.
A LARGE PART OF THE IMPACT FROM THIS SYSTEM WILL INVOLVE WINDS
ASSOCIATED WITH THE TIGHT PRESSURE GRADIENT EVIDENT ON THE
NORTHWEST QUADRANT THE LOW CENTER. IN THE WATCH AREA...WINDS FROM
THE NORTHEAST ARE FORECAST TO BE AROUND 20 MPH SUSTAINED WITH
GUSTS AROUND 30 MPH. THOSE WINDS COMBINING WITH A BAND OF MODERATE
SNOW WILL PRODUCE CONSIDERABLE BLOWING AND DRIFTING...WHICH WILL
CAUSE OCCASIONAL WHITEOUTS THAT WILL MAKE POST-CHRISTMAS TRAVEL
ALL THE MORE DIFFICULT.
SNOW WILL TAPER OFF FROM WEST TO EAST ON WEDNESDAY NIGHT AS THE
LOW DEPARTS TO THE EAST COAST.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
DEPARTING WINTER STORM WILL LEAVE DRY CONDITIONS AND SEASONABLE
TEMPERATURES AS SHORTWAVE RIDGING BUILDS IN OVER THE OHIO
VALLEY...DOWNSTREAM INTERMOUNTAIN WEST SHORTWAVE RIDGING. THIS
ENERGY ROTATING THROUGH A VERY BROAD LONGWAVE TROUGH CENTERED OVER
THE CONUS WILL LARGELY EJECT NORTH OF THE AREA INTO SATURDAY.
HOWEVER... THE BASE OF THE TROUGH WILL INTERACT WITH A DEEP MOISTURE
POOL OVER THE WESTERN GULF AND SEND AN ENHANCED STREAM OF MOISTURE
INTO THE OHIO VALLEY...WITH WEAK SFC LOW DEVELOPMENT OVER THE
SOUTHEAST.
HAVE KEPT MUCH OF THURSDAY /RESIDUAL SNOW SHOWER CHANCE MAINLY
EARLY/ DRY AND INTO FRIDAY AS WELL...AND THEN SPREAD SNOW CHANCES
BACK IN FRIDAY NIGHT AND THROUGH THE DAY SATURDAY. TEMP PROFILES
SUGGEST MAJORITY OF THIS HAS A BETTER SNOW CHANCE THAN RAIN
CHANCE...BUT ENSEMBLE PERSPECTIVE SUGGESTS THERE IS ENOUGH CHANCE AT
THIS TIME RANGE TO BRING A THREAT OF EITHER RAIN OR SNOW INTO PARTS
OF THE AREA ON SATURDAY...THOUGH RIGHT NOW IT APPEARS A BETTER SNOW
THREAT...WITH LIGHT ACCUMULATIONS...AND HAVE SET UP GRIDDED FORECAST
THAT WAY FOR NOW.
SYSTEM SHOULD BE TRANSIENT THUS DIMINISHING THREATS OF SNOW ON
SUNDAY AS TEMPERATURES REMAIN NEAR/SLIGHTLY BELOW NORMAL.
&&
.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
NLY FLOW ON THE BACKSIDE OF LOW PRESSURE IS KEEPING IFR/MVFR ST
ACROSS THE TAFS. AS THE LOW CONTINUES TO MOVE E...WEAK HIGH
PRESSURE RIDGE WILL SLOWLY BUILD INTO THE REGION. MODELS DIFFER IN
THEIR HANDLING OF THE LOW LEVEL MOISTURE AND HOW MUCH IT CLEARS.
THE RAP MODEL KEEPS THE LOW LEVEL TRAPPED ACROSS THE REGION THE
ENTIRE DAY. THE NAM SCOURS IT OUT AROUND 12Z. THE GFS IS KIND OF
THE COMPROMISE AND KEEPS SOME MOISTURE ACROSS THE TAFS BUT LIFTS
AND BREAKS ITS UP A LITTLE. THIS LAST SOLUTION SEEMS THE MOST
REASONABLE...SO ALLOWED THE CIGS TO RISE TO AROUND 2500 FT AND GO
BROKEN. CIGS SHOULD RISE TO VFR AS THE LOW LOW LEVEL MOISTURE
WAINS.
THE EFFECTS OF THE MAJOR WINTER STORM START TO AFFECT CVG IN THE
EXTENDED PORTION OF THE 30 HR TAF. BROUGHT THE PCPN IN AS S THERE
AND DROPPED CIGS DOWN TO IFR AFT 06Z.
OUTLOOK...IFR CEILINGS AND VISIBILITIES OVERSPREADING THE REGION
TUESDAY NIGHT...CONTINUING WEDNESDAY INTO WEDNESDAY NIGHT.
CONDITIONS WILL LIFT TO MVFR ON THURSDAY. MVFR/IFR CEILINGS AND
VISIBILITIES POSSIBLE SATURDAY.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE WEDNESDAY
NIGHT FOR OHZ026-034-035-042>046-051>056-060>062-070-071.
KY...NONE.
IN...WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE WEDNESDAY
NIGHT FOR INZ050-058-059-066.
&&
$$
SYNOPSIS...CONIGLIO
NEAR TERM...FRANKS/HICKMAN
SHORT TERM...CONIGLIO
LONG TERM...BINAU
AVIATION...SITES
AREA FORECAST DISCUSSION...UPDATED
NWS SAN ANGELO TX
334 AM CST TUE DEC 25 2012
.SHORT TERM...
THE COMBINATION OF STRONG WINDS AND SNOW WILL REDUCE VISIBILITIES
AND MAKE TRAVEL DIFFICULT ACROSS THE NORTHERN BIG COUNTRY AFTER 9
AM. STRONG WINDS AND FREEZING TEMPERATURES WILL ALSO RESULT IN WIND
CHILL VALUES LOWERING INTO THE SINGLE DIGITS BY EARLY EVENING.
WINTER WEATHER ADVISORY IS IN EFFECT FOR THROCKMORTON TODAY FOR 1-3
INCHES OF SNOW...WINTER WEATHER ADVISORY WILL BE ISSUED SHORTLY FOR
HASKELL...JONES...AND SHACKELFORD COUNTIES FOR 1 TO 2 INCHES OF
SNOW. A WIND ADVISORY IS ALSO IN EFFECT FOR STRONG NORTH WINDS.
LATEST RUC MODEL IS SHOWING THE BEST SNOWFALL ACCUMULATIONS ACROSS
THROCKMORTON COUNTY...AND THIS COUNTY WILL BE HAVE TO BE WATCHED
CLOSELY FOR A POSSIBLE UPGRADE TO WINTER STORM WARNING IF SNOWFALL
TOTALS ARE EXPECTED TO EXCEED 4 INCHES.
AS THE UPPER LEVEL LOW DIGS A LITTLE FURTHER SOUTH...IT SHOULD TRACK
SOUTHEAST ACROSS THE NORTHERN BIG COUNTRY TODAY. THE BEST CHANCE
FOR SNOW WILL BE FROM 9AM THROUGH 6PM WHEN TEMPERATURES ARE EXPECTED
TO PLUNGE BELOW FREEZING AND SOUNDINGS PROG THE BEST SNOW
POTENTIAL. THE NORTHERN BIG COUNTRY...MAINLY FROM ROTAN TO ALBANY
AND NORTH IS THE AREA THAT HAS THE BEST CHANCE OF RECEIVING SNOW
TODAY SINCE THIS REGION IS LOCATED TO THE NORTHWEST OF THE SURFACE
LOW THAT WILL TRACK FROM FAR WEST TEXAS...TO CENTRAL TEXAS AND THEN
INTO SOUTHEAST TEXAS TODAY.
COULD SEE LIGHT SNOWFALL ACCUMULATIONS FROM A DUSTING TO LESS THAN
AN INCH ALONG THE I20 CORRIDOR COMMUNITIES OF SWEETWATER...ABILENE
AND BAIRD. A FEW SHOWERS ARE POSSIBLE THIS MORNING ACROSS MOST OF
THE AREA IN THE WARM AIR ADVECTION IN ADVANCE OF THE UPPER LOW. A
FEW THUNDERSTORMS ARE ALSO POSSIBLE ACROSS THE EASTERN COUNTIES.
THE SNOW SHOULD END BY 6PM AS THE UPPER LOW PRESSURE SYSTEM
DEPARTS. AS SKIES CLEAR TONIGHT...LOW TEMPERATURES WILL DROP OFF
QUICKLY ESPECIALLY ACROSS THE SNOW COVERED FIELDS OF THE NORTHERN
BIG COUNTRY.
26
.LONG TERM...
UPPER RIDGE WILL BUILD OVER THE FORECAST AREA IN THE WAKE OF THE
DEPARTING UPPER LOW...THEN QUICKLY BACK TO THE SOUTHWEST BY THURSDAY
IN RESPONSE TO A DEVELOPING UPPER LOW OVER THE SOUTHWEST. COLD
POSTFRONTAL HIGHS ON WEDNESDAY WILL ONLY BE IN THE LOW TO MID 30S
OVER THE BIG COUNTRY WITH UPPER 30S TO MID 40S SOUTH OF INTERSTATE
20. AFTER ANOTHER COLD MORNING ON THURSDAY WITH LOWS IN THE MID
TEENS TO THE LOWER 20S...WILL SEE AFTERNOON HIGHS ON THURSDAY IN THE
LOWER TO UPPER 50S.
BOTH ECMWF AND GFS MOVE THE NEXT UPPER LOW OVER THE CENTRAL PLAINS
BY LATE THURSDAY...PUSHING THE NEXT COLD FRONT THROUGH THE FORECAST
AREA DURING THE DAY ON FRIDAY. A SERIES OF FRONTAL PASSAGES INTO THE
BEGINNING OF THE COMING WEEK WILL KEEP AFTERNOON HIGHS AT OR BELOW
SEASONAL NORMS.
AS WE APPROACH THE NEW YEAR...THINGS GET A LITTLE COMPLICATED. THE
GFS ENSEMBLE IS CHAOTIC WITH THE PREFERRED SOLUTION ELUDING TO A
CLOSED LOW OVER THE BAJA MONDAY THROUGH MID-WEEK. THIS SCENARIO
INTRODUCES RAINFALL OVER THE FORECAST AREA EARLY MONDAY AND KEEPS A
CHANCE OF RAINFALL THROUGH MID-WEEK AS A SOUTHWEST FLOW ALOFT
CONTINUES OVER THE AREA. THE ECMWF OPENS AN UPPER TROUGH OVER THE
BAJA EARLY MONDAY AND THEN CLOSES AN UPPER LOW OVER THE BAJA ON
TUESDAY...WITH THE BEST CHANCE OF RAINFALL OVER OUR AREA LATE
TUESDAY. WILL GO WITH THE GFS WHICH INTRODUCES MOISTURE OVER THE CWA
DURING THE DAY ON MONDAY. WILL KEEP MOISTURE OVER THE AREA THROUGH
THE END OF THE EXTENDED AS BOTH MODELS SHOW PRECIP ON TUESDAY. WITH
KEEP PRECIP TYPE LIGHT RAIN AT THIS TIME BUT AS WILL GET FURTHER
DOWN THE ROAD...THERE MAY BE A CHANCE FOR FROZEN PRECIP ENCROACHING
ON NORTHWESTERN COUNTIES LATER INTO THE WEEK.
15
&&
.PRELIMINARY POINT TEMPS/POPS...
ABILENE 39 15 31 22 53 / 40 5 0 0 0
SAN ANGELO 48 18 41 23 58 / 30 0 0 0 0
JUNCTION 58 22 45 19 59 / 20 0 0 0 0
&&
.SJT WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FROM 10 AM THIS MORNING TO 8 PM CST THIS EVENING
FOR THE FOLLOWING ZONES: BROWN...CALLAHAN...COKE...COLEMAN...
CONCHO...CROCKETT...FISHER...HASKELL...IRION...JONES...KIMBLE...
MASON...MCCULLOCH...MENARD...NOLAN...RUNNELS...SAN SABA...
SCHLEICHER...SHACKELFORD...STERLING...SUTTON...TAYLOR...
THROCKMORTON...TOM GREEN.
WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 6 PM CST THIS
EVENING FOR THE FOLLOWING ZONES:
HASKELL...JONES...SHACKELFORD...THROCKMORTON.
&&
$$
15
AREA FORECAST DISCUSSION...UPDATED
NWS FORT WORTH TX
1150 PM CST MON DEC 24 2012
.AVIATION...
/06Z TAFS/
CONCERNS...THREAT FOR THUNDER OVERNIGHT AND EARLY TUESDAY
MORNING. CHANGE OVER TO SNOW IN THE DFW METROPLEX TUESDAY
AFTERNOON. STRONG AND GUSTY NORTHWEST WINDS TUESDAY AFTERNOON
THROUGH THE OVERNIGHT HOURS.
WIDESPREAD LIGHT SHOWERS ARE ALREADY DEVELOPING ACROSS THE REGION
AND MVFR STRATUS IS SPREADING NORTH INTO WACO. THE METROPLEX TAF
SITES WILL REMAIN VFR UNTIL THE PRECIPITATION INCREASES BY 08-09Z
BUT WACO WILL CONTINUE IN MVFR THROUGH THE NIGHT. EXPECT SHOWERS
AND SCATTERED THUNDERSTORMS TO OCCUR THROUGH THE OVERNIGHT HOURS
WITH REDUCED VISIBILITIES AND MVFR CIGS. THE POTENTIAL FOR THUNDER
IS HIGHER AT WACO AND SOME SEVERE STORMS ARE POSSIBLE AROUND THE
WACO AREA AS WELL...WITH A THREAT FOR HAIL. LATEST GUIDANCES
SUGGEST THE SHOWER ACTIVITY COULD BECOME HEAVIER CLOSER TO
DAYBREAK AS AN UPPER LEVEL LOW GETS CLOSER TO THE REGION AND LIFT
INCREASES. THIS COULD RESULT IN TEMPORARY IFR CONDITIONS AT ALL
TAF SITES DURING PERIODS OF HEAVY SHOWERS AND/OR THUNDERSTORMS.
THE PRECIPITATION WILL CONTINUE FOR MOST OF THE DAY WITH A
CHANGE OVER TO SNOW IN THE DFW METROPLEX IN THE EARLY TO MID
AFTERNOON HOURS. THERE COULD ALSO BE A BRIEF WINDOW OF SLEET MIXED
IN AS WELL BEFORE THE CHANGE OVER TO ALL SNOW. THE SNOW WILL LAST
FOR A FEW HOURS AND ACCUMULATIONS UP TO AN INCH ARE POSSIBLE. AT
THIS SAME TIME...A STRONG FRONT WILL SWEEP ACROSS THE METROPLEX
RESULTING IN VERY STRONG NORTHWEST WINDS. THE WINDS COULD CAUSE
BLOWING SNOW THAT COULD REDUCE VISIBILITIES. CONDITIONS OVERALL
SHOULD INCREASE IN THE EVENING HOURS AS THE SYSTEM MOVES
EAST...BUT THE STRONG WINDS WILL CONTINUE OVERNIGHT.
AT KACT...THE PRECIPITATION IS EXPECTED TO REMAIN ALL LIQUID...
ENDING DURING THE AFTERNOON HOURS. THE FRONT WILL ARRIVE AROUND
MIDDAY. THERE IS A SMALL CHANCE FOR SOME FLURRIES BUT THE
POTENTIAL IS FAIRLY LOW.
CEILINGS SHOULD IMPROVE AT ALL SITES TUESDAY EVENING BUT THERE IS
A POTENTIAL THAT THE MVFR CIGS BEHIND THIS SYSTEM COULD HOLD IN
LONGER THAN IS IN THE CURRENT TAF FORECAST.
82/JLD
&&
.UPDATE...
WE HAVE ANALYZED THE 00Z UPPER AIR DATA AND HAVE WATCHED THE
SURFACE OBS CLOSELY FOR SIGNS OF ANY DISCREPANCIES BETWEEN THEM
AND THE MODEL DATA. THE BIG THING THAT STANDS OUT ARE THAT THE
SURFACE LOW IN NORTHEAST NEW MEXICO AT 6PM WAS ABOUT 80 MILES
FARTHER SOUTH THAN ALL OF THE MODELS HAD FORECAST 24 HOURS AGO.
WHEN DEALING WITH A SWINGING/DIGGING UPPER LEVEL SYSTEM...THE
SURFACE PRESSURE PATTERN AND PRESSURE TENDENCIES OFFER ENORMOUS
CLUES ON THE FUTURE TRACK OF A POTENTIAL VORTICITY ANOMALY BEFORE
IT CLOSES OFF TO BECOME A FULL FLEDGED UPPER LOW. THE 3PM AND 6PM
SURFACE ANALYSIS SHOWED A LARGE REGION OF PRESSURE FALLS ACROSS
NEW MEXICO AND WEST TEXAS IN ADVANCE OF THE SYSTEM. GIVEN THE
ORIENTATION OF THE PRESSURE FALLS AND LOCATION OF THE SURFACE
LOW...IT CAN BE DETERMINED WITHOUT EVEN LOOKING AT A FORECAST
MODEL THAT THE UPPER LOW HAS NOT FINISHED DIGGING SOUTH. THE BIG
QUESTION IS HOW FAR SOUTH WILL THE UPPER LOW MAKE IT BEFORE IT
BEGINS TO SWING BACK TO THE NORTHEAST. AT THIS HOUR PRESSURE FALLS
CONTINUE IN THE REGION FROM LUBBOCK TO MIDLAND...WITH ANOTHER
PRESSURE FALL AREA DEVELOPING IN SOUTHEAST TEXAS. EXTRAPOLATING
SUGGESTS THE UPPER LOW WILL TRACK JUST SOUTH OF LUBBOCK BY SUNRISE
AND TO NEAR WACO BY SUNSET. AS THE LOW APPROACHES WACO...A WARM
FRONT WILL BE ORGANIZING OUT OF THE WEAK STATIONARY FRONT
CURRENTLY ANALYZED FROM SAN ANTONIO TO HOUSTON. BAROCLINIC QG
THEORY SUGGESTS THAT ONCE LOW LEVEL WARM ADVECTION BEGINS IN
EARNEST ACROSS SOUTHEAST TEXAS BY MORNING...IT WILL INDUCE HEIGHT
RISES TO THE SOUTHEAST OF OUR UPPER LOW WHICH WILL CAUSE THE LOW
TO CLOSE OFF AND FINISH DIGGING SOUTH...AND START ITS GRADUAL
TURN TO THE NORTHEAST. TOMORROW EVENING I WOULD EXPECT THE LOW TO
TRACK FROM NEAR WACO TO NEAR SHREVEPORT. IN SUMMARY THE USUAL
MEDIUM RANGE MODELS APPEAR TO BE A LITTLE TOO FAR NORTH WITH THE
TRACK OF THE UPPER LOW. OUR EXPECTATIONS FOR THE TRACK OF THE LOW
ALIGN WELL WITH THE RAP FORECAST WHICH IS TO THE SOUTH OF ALL
OTHER MODELS...SO WE WILL USE THE RAP HEAVILY.
OUR FORECAST HAS BEEN ON THE SOUTHERLY SIDE AND SNOWIER SIDE OF
THE MODEL GUIDANCE. SO ALTHOUGH WE ARE SEEING AN EVEN MORE
SOUTHERLY TRACK COME TO FRUITION...THIS DOES NOT NECESSARILY
MEAN THE FORECAST SNOW AMOUNTS NEED TO BE AMENDED MUCH. THIS IS IN
PART DUE TO THE DIFFICULTY IN GETTING THE COLDER/SUBFREEZING AIR
FARTHER SOUTH BEFORE THE PRECIPITATION ENDS. THE EXCEPTION IS THE
NORTHWEST ZONES WHERE THE MORE SOUTHERLY TRACK SUGGESTS MORE
PRECIP WILL FALL IN SUBFREEZING AIR. DUE TO THE TERRAIN EFFECTS
HERE...COLD AIR HAS AN EASY TIME GETTING INTO OUR NORTHWEST ZONES
WHEN WE HAVE A NORTH/NORTHEAST SURFACE WIND. HAVE EXPANDED THE
SNOW ADVISORY TO INCLUDE YOUNG/JACK/WISE COUNTIES...AND HAVE
INCREASED SNOW TOTALS TO THE 2-4 INCH RANGE FROM BOWIE TO SHERMAN.
THE NORTHEAST ZONES LIKELY WONT SWITCH TO SNOW UNTIL LATE
AFTERNOON...AS COLD AIR WILL HAVE TROUBLE MOVING IN AT THE SURFACE
DUE TO THE LEE SHADOW WARMING EFFECT OF THE OZARK PLATEAU. MOST OF
THE SNOW THAT OCCURS THERE WILL BE AFTER 6 PM AND WILL BE HIGHLY
DEPENDENT ON WHETHER MESOSCALE BANDING CAN SET UP IN THE WAKE OF
THE UPPER LOW. THE NEW NAM HAS FINALLY FORECAST SOME SIGNIFICANT
BANDING TO OCCUR...THUS WILL LEAVE THE ADVISORY ALONE IN THIS
AREA...BUT CONFIDENCE IS A LITTLE LOWER IN THE NORTHEAST ZONES FOR
2+ INCHES OF SNOW.
FARTHER TO THE SOUTH OF THE ADVISORY...FOR THE I-20 CORRIDOR AND
INCLUDING THE METROPLEX...THERE IS NOW HIGH CONFIDENCE THAT SNOW
WILL OCCUR. HOWEVER ALL INDICATIONS ARE THAT IT WILL STILL BE A
BRIEF 1-3 HOUR EVENT WITH NOT ENOUGH TIME TO GET ACCUMULATIONS
OVER AN INCH. IT MUST BE STRESSED THAT WITH TEMPERATURES FALLING
INTO THE 20S BY SUNSET...ANY APPRECIABLE MOISTURE REMAINING ON
BRIDGES...OVERPASSES AND EVEN SURFACE STREETS WILL LIKELY RE-
FREEZE INTO BLACK ICE. ALTHOUGH WE ARE USING 1+ INCH AS CRITERIA
FOR THE COUNTIES IN THE WINTER WEATHER ADVISORY AREA...WE MAY
EXPAND THE ADVISORY SOUTH INTO THE METROPLEX OVERNIGHT DUE SOLELY
TO TRAVEL IMPACTS.
FINALLY CONCERNING THE SEVERE WEATHER THREAT. WITH A MORE SOUTHERLY
TRACK OF THE UPPER LOW...THIS MEANS THERE IS LESS OF A CHANCE OF THE
WARM FRONT MAKING IT INTO THE SOUTHEAST CWA TONIGHT AS IT WILL
LIKELY STAY SOUTHEAST OF THE AREA. ELEVATED THUNDERSTORMS ARE STILL
EXPECTED TO RAPIDLY INCREASE IN COVERAGE AFTER 3 AM...WITH ELEVATED
INSTABILITY HIGH ENOUGH FOR A FEW SEVERE HAIL STORMS SOUTH OF I-20.
HAVE TONED DOWN THE DAMAGING WIND AND TORNADO THREAT FROM OUR
PRODUCTS...BUT WE WILL CONTINUE TO ADVERTISE HAIL STORMS POSSIBLE
LATE TONIGHT AND EARLY TOMORROW MORNING.
TR.92
&&
.PREV DISCUSSION... /ISSUED 301 PM CST MON DEC 24 2012/
OUR CHRISTMAS DAY/NIGHT WINTER STORM IS TAKING SHAPE OVER THE
INTERIOR WEST THIS AFTERNOON. IT WILL MOVE SOUTHEAST OVERNIGHT AND
SHOULD DEVELOP A CLOSED CIRCULATION AS IT ENTERS THE SOUTHWESTERN
PANHANDLE BY DAYBREAK CHRISTMAS. ALTHOUGH TODAY/S MODEL SOLUTIONS
CONTINUE TO SHOW SLIGHT TIMING AND TRACKING DIFFERENCES...THE
AGREEMENT AND CONSENSUS BETWEEN THE GFS AND THE ECMWF HAVE BEEN
AND CONTINUE TO BE THE PREFERRED SOLUTION FOR THIS STORM. THE
500MB CENTER SHOULD TRACK ALONG I-20 BETWEEN ABILENE AND DFW THEN
JUST SOUTH OF I-30 FROM DFW TO TEXARKANA. IF THE TRACK IS 30 MILES
SOUTH OR NORTH OF OUR FORECAST THEN IMPACTS WILL ALSO SHIFT ACCORDINGLY.
LAST NIGHTS FRONT IS LOCATED FROM NORTH OF HOUSTON TO NEAR SAN ANTONIO
TO AROUND FORT STOCKTON. SURFACE CYCLOGENESIS WILL BEGIN OVERNIGHT
ALONG THIS FRONT AND TRACK EAST ALONG THE FRONT. WE ARE EXPECTING
A WARM FRONT TO LIFT THROUGH THE SOUTHERN AND SOUTHEAST COUNTIES
LATE TONIGHT AND THROUGH THE EAST-CENTRAL COUNTIES EARLY CHRISTMAS
MORNING AS THE SURFACE LOW SLIDES EAST. CONVECTION WILL BEGIN
OVERNIGHT AS THE ELEVATED WARM FRONT PUSHES NORTHWARD. STRONG
UPPER DYNAMICS AND MID LEVEL INSTABILITY WILL LEAD TO SOME STRONG
TO SEVERE THUNDERSTORMS BEFORE AND AFTER DAYBREAK. HAIL WILL BE
THE MAIN THREAT BUT DAMAGING WIND CAN BE EXPECTED ALONG AND SOUTH
OF THE SURFACE BOUNDARY. AS FOR TORNADOES...STORMS MOVING OVER THE
SURFACE BOUNDARY WILL EXPERIENCE AN INCREASE IN STORM-RELATIVE
HELICITY AND BRIEF TORNADOES ARE POSSIBLE. THE SEVERE WEATHER
THREAT SHOULD MOVE INTO EAST TEXAS BY LATE MORNING.
COLD ARCTIC AIR HAS BEEN BUILDING OVER THE NORTHERN AND CENTRAL
PLAINS AND WILL SURGE INTO NORTH TEXAS BEHIND THE EXITING
SURFACE LOW. THIS WILL RESULT IN RAIN TRANSITIONING TO SNOW WEST
TO EAST ALONG AND NORTH OF I-20 FROM LATE MORNING (NW) THROUGH
MID AFTERNOON (NE). WE STILL EXPECT 1-3 INCHES OVER THE NORTHERN
TWO ROWS OF COUNTIES WITH THE HIGHEST AMOUNTS GENERALLY EAST OF A
SHERMAN TO GREENVILLE LINE. WOULD NOT BE SURPRISED IF A BAND OF
HEAVIER SNOW OCCURRED OVER THE NORTHEAST COUNTIES AROUND PARIS
WHERE THE 700MB FRONTOGENESIS IS MORE LIKELY TO ENHANCE THE
WRAP-AROUND BANDING. THE SNOW IS EXPECTED TO END OVER THE
NORTHEAST BY MIDNIGHT. SNOW ACROSS OKLAHOMA AND WESTERN ARKANSAS
COULD TOTAL 4-8 INCHES...AND TRAVEL NORTH OF THE RED RIVER OR INTO
WESTERN ARKANSAS WILL BE TREACHEROUS CHRISTMAS DAY THROUGH
WEDNESDAY.
A WIND ADVISORY WILL BE NEEDED CHRISTMAS AFTERNOON AND NIGHT AS
NORTH WINDS BLOW 20-30 MPH WITH GUSTS TO 40MPH. BLOWING SNOW WILL
BE POSSIBLE IN THE AFTERNOON AND OVERNIGHT HOURS WHERE SNOW HAS
OCCURRED. IT WILL BE BITTERLY COLD ON CHRISTMAS NIGHT WITH WIND
CHILLS IN THE LOWER SINGLE DIGITS AND TEENS. ALSO ANY MOISTURE
REMAINING ON ROADWAYS CHRISTMAS EVENING WILL FREEZE OVERNIGHT SO
WEDNESDAY MORNING COMMUTERS NEED TO BE ALERT FOR ICY SPOTS.
COLD AND DRY FOR WEDNESDAY. TEMPERATURES MODERATE ON THURSDAY AS
WINDS RETURN SOUTH. ANOTHER COLD FRONT WILL MOVE THROUGH THE
REGION FRIDAY WITH A CHANCE OF SHOWERS OVER THE CENTRAL AND
EASTERN COUNTIES. TEMPERATURES BEHIND THIS FRONT WILL NOT BE AS
COLD...BUT WILL KEEP HIGHS/LOWS BELOW NORMAL OVER THE WEEKEND.
75
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 42 46 21 35 21 / 50 70 10 5 5
WACO, TX 43 53 23 42 18 / 60 50 10 5 5
PARIS, TX 40 43 21 31 15 / 50 80 40 10 5
DENTON, TX 38 42 20 31 17 / 50 80 10 5 5
MCKINNEY, TX 41 43 22 31 16 / 50 80 20 10 5
DALLAS, TX 43 46 22 36 23 / 50 70 10 5 5
TERRELL, TX 43 48 24 35 18 / 50 80 20 10 5
CORSICANA, TX 44 52 23 40 21 / 60 70 10 5 5
TEMPLE, TX 47 56 23 43 20 / 70 40 10 5 5
MINERAL WELLS, TX 38 41 17 35 18 / 50 60 10 5 5
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM NOON TO 9 PM CST TUESDAY FOR
TXZ091>095-100>107.
&&
$$
82/92
AREA FORECAST DISCUSSION...UPDATED
NWS LUBBOCK TX
1017 PM CST MON DEC 24 2012
.UPDATE...
THE AFD YOU HAVE WAITED FOR IS READY BEFORE THE STORM
ALTHOUGH THE FORM IS WEIRD AND LANGUAGE NOT THE NORM.
THE STORM THAT IS ARRIVING IS BECOMING MORE CLEAR...
A FEW SCENARIOS ARE POSSIBLE WITH THE EVENT DRAWING NEAR.
WATER VAPOR SATELLITE SHOWS THE STORM STILL COMING OUR WAY...
SOUTHEAST OF THE FOUR CORNERS IT SPINS TO ARRIVE CHRISTMAS DAY.
THE RAP AND NAM ARE BREAKING OUT SNOW ACROSS THE NORTHWEST
AS EARLY AS 08 TO 10Z WHICH IS WHAT THEY HAVE GUESSED.
285K ISENTROPIC LIFT AND MOISTURE INCREASE BY LATE MORNING...
THE RAP AND NAM SHOW SNOW AMOUNTS THAT MAY WARRANT A WARNING.
MOST FAVORED AREA ARE ACROSS NORTHERN COUNTIES INTO THE PLAINS...
SNOW BANDING IS HINTED AS THE MODELS LOOSE THE REINS.
TEMPERATURE PROFILES ARE STILL EXPECTED TO FALL BELOW FREEZING
WHICH CONCERNS OF A MIX OF RAIN AND SNOW STILL ARE EASING.
THE DEPTH OF COLD AIR INCREASES RAPIDLY AFTER SUNRISE...
STRONG NORTH WINDS COMBINED WITH SNOW COULD BE BLINDING WE ADVISE.
THE BANDS EASE EARLY MORNING AND MORE SNOW LOOKS TO FORM...
ISENTROPIC LIFT KICKS IN NEAR CHILDRESS AND EAST OF THE STORM.
THE AMOUNTS BECOME TRICKY AND THERE IS QUITE A RANGE AS THE LIFT
STARTS TO WEAKEN AND MOISTURE LEVELS START TO CHANGE.
WITH SNOW STARTING OUT WEST AND RAPIDLY MOVING TO THE EAST...
THE LOCATION/RATE OF THE SNOW WILL BE IMPORTANT TO SAY THE LEAST.
IF THE MOST OPTIMISTIC MODELS TURN OUT TO BE CORRECT...
SOME LOCATIONS MAY SEE 4 TO 6 INCHES WHICH WE CANNOT NEGLECT.
WILL HOLD OFF WITH UPGRADING THE ADVISORY TO A WARNING
BUT IT MAY BE REQUIRED WHICH MAY HAPPEN EARLY TUESDAY MORNING.
AS IT STANDS RIGHT NOW THE HUB CITY MAY TURN WHITE
WITH ONE OF THE BANDS APPROACHING CHANCES ARE BETTER THAN SLIGHT.
TRAVEL REMAINS HIGHLY DISCOURAGED IF YOU WANT TO GO NORTH...
ONCE THE SNOW STARTS TO FALL AND THE WIND BLOWS THENCEFORTH.
WE WILL HOLD OUR BREATHS AS WE FINALLY HEAD OUT THE DOOR...
AND ANOTHER SHIFT WILL ARRIVE OUT HERE ON THE OPERATIONS FLOOR.
THE POTENTIAL IS THERE FOR THIS STORM TO CHANGE IT/S MIND...
IF THINGS DRASTICALLY CHANGE THEN THE FORECAST IS IN A BIND.
HOWEVER OUR CONFIDENCE IS INCREASING THAT THE SNOW WILL SOON FALL
WATCHING...OBSERVING...AND FORECAST IN CASE OF A CURVE BALL.
STAY TUNED TO YOUR FAVORITE SOURCES OF WEATHER INFORMATION...
THE SITUATION IS FLUID...CHANGING...AND ALWAYS IN TRANSLATION.
THIS FORECAST SHIFT WILL LEAVE IN A BIT LESS THAN TWO HOURS
HOPING TO WAKE UP TO SEE VERIFICATION IN THE FORM OF SNOW SHOWERS.
FROM THIS FORECASTER TO YOU WHO TRUST US FOR YOUR FORECAST...
I HOPE THIS AFD HELPS YOU AND INFORMS YOU...WITHOUT BEING AGHAST.
MY PURPOSE IS SOLELY TO SHOW YOU WE CARE
AND TO BE METEOROLGICALLY SOUND AND DO IT WITH FLAIR.
TOMORROW SOON WILL ARRIVE AND IT COULD POSSIBLY BE WHITE
SO MERRY CHRISTMAS TO YALL AND TO ALL A GOOD NIGHT!
JORDAN/WFO LUBBOCK
&&
.PREV DISCUSSION... /ISSUED 543 PM CST MON DEC 24 2012/
AVIATION...
CURRENT VFR CONDITIONS WILL GRADUALLY DECREASE INTO MVFR RANGE
TOMORROW MORNING AS A STRONG COLD FRONT PUSHES INTO THE REGION. AT
THE SAME TIME...A STORM SYSTEM WILL MOVE OVER THE REGION RESULTING
IN WINTER PRECIPITATION.
FOR KCDS...MAIN IMPACT WILL BE LOW VISIBILITIES IN BLOWING SNOW
THAT WILL LAST MUCH OF THE MORNING THROUGH AFTERNOON HOURS.
VISIBILITIES WILL DROP INTO MVFR TO IFR RANGE WITH CEILINGS IN THE
MVFR RANGE. FRONT WILL ARRIVE BEFORE SUNRISE/11Z AND INCREASE WIND
SPEEDS FROM THE NORTH AT 25 TO 35 KNOTS AND GUSTS APPROACHING 40
KNOTS. STORM SYSTEM WILL HAVE PUSHED EAST BY MID-DAY BUT
PRECIPITATION WILL SLOWLY END AFTER IT PASSES. CONDITIONS WILL
RETURN BACK TO MVFR TO VFR RANGE AROUND SUNSET.
FOR KLBB...HEAVIEST SNOW IS EXPECTED TO REMAIN NORTH OF THE
REGION HOWEVER BRIEF PERIODS OF SNOW WILL BE POSSIBLE. CONFIDENCE
IS LOW AT THIS TIME AND WILL NOT INCLUDE IN THE TAF AT THIS TIME.
STRONG COLD FRONT WILL ARRIVE AROUND 11Z AND INCREASE THE WIND
SPEED ALSO TO THE 20 TO 30 KNOT RANGE WITH GUSTS APPROACHING 40
KNOTS. DRY CONDITIONS AND STRONG WINDS WILL RESULT IN PERIODS OF
BLOWING DUST THAT WILL REDUCE VISIBILITY SOMEWHAT...HOWEVER IT
SHOULD REMAIN IN THE VFR RANGE. CONDITIONS WILL IMPROVE LATE IN
THE DAY AS WIND SPEEDS DECREASE.
JORDAN
PREV DISCUSSION... /ISSUED 310 PM CST MON DEC 24 2012/
SHORT TERM...
HIGH IMPACT WINTER STORM WILL DEVELOP ACROSS THE PANHANDLE OVERNIGHT
AND MOVE EAST-SOUTHEAST INTO OK ON CHRISTMAS DAY. 12Z AND 18Z MODEL
RUNS CONTINUE FAIRLY GOOD CONTINUITY WITH THE MID-LEVEL TROUGH
DIGGING ACROSS UT THIS AFTERNOON CLOSING OFF AND DEEPENING NORTH OF
LUB BY 12Z TUE. THE SYSTEM THEN EJECTS ALONG OR SOUTH OF THE RED
RIVER CHRISTMAS DAY. THE FAST MOVEMENT OF THE SYSTEM SHOULD LIMIT
THE OVERALL AFFECTS OF ACCUMULATING PRECIP YET THERE IS STILL ENOUGH
LIFT AND INITIAL MOISTURE TRANSPORT INTO THE DEEPENING SYSTEM TO
CAUSE SOME CONCERN.
EXPECT PRECIP TO BREAK OUT NEAR THE NM STATE LINE AFTER MIDNIGHT AS
JET ENERGY DIVES TOWARD THE BASE OF THE TROUGH. THE PRECIP SHIELD
SHOULD BROADEN AND MOVE EAST ACROSS THE NORTHERN SOUTH PLAINS AND
PANHANDLE THROUGH THE MORNING TUE. THE TRACK OF THE UPPER LOW WOULD
PLACE THE FAVORED LOCATION FOR THE HEAVIEST PRECIP NORTH OF A LINE
FROM HEREFORD TO CHILDRESS BUT WITH THE TENDENCY FOR A FEW MODELS TO
CONTINUE TO DIG THE SYSTEM FURTHER SOUTH HAVE BROADENED THE AREA OF
ON INCH OR GREATER SNOW TO INCLUDE THE FAR NORTHERN SOUTH PLAINS.
WHILE THE WESTERN PORTION OF THE WINTER WEATHER ADVISORY AREA MAY
SEE LIMITED SNOW TOTALS...STRONG NORTH WINDS IN THE WAKE OF THE
CANADIAN FRONT WILL CREATE AREAS OF BLOWING SNOW WITH NEAR WHITE-OUT
CONDITIONS EXPECTED FOR THE MAJOR ROADS HEADING INTO THE PANHANDLE.
THE NAM IS FORECASTING 3HR PRESSURE RISES NEAR 10MB ACROSS EASTERN
NM BY 12 TUE SO WIND SPEEDS ARE EXPECTED TO BE ON THE UPPER END OF
THE RANGE PERHAPS PUSHING ADVISORY LEVEL AT TIMES IN THE EARLY
AFTERNOON. THE TRANSITION OF PRECIPITATION FROM RAIN TO SNOW SHOULD
BE VERY QUICK GIVEN THE STRONG DYNAMICAL COOLING AND WET-BULBING
FROM A RELATIVE DRY LOW LEVEL AIRMASS. STILL SIGNIFICANT WARM
ADVECTION IN THE LOW LEVELS WILL BE ONGOING AHEAD OF THE SYSTEM AND
THERE WILL BE A WARM NOSE TO OVERCOME. WOULD NOT BE SURPRISED TO SEE
SOME SLEET OR RAIN SHOWERS AHEAD OF THE MAIN PRECIP IN THE ROLLING
PLAINS VERY EARLY IN THE DAY. AS A RESULT HAVE LEFT A BRIEF WINDOW
OF RA/SN OR PL/SN AHEAD OF THE UPPER LOW AS IT TRACKS EAST BETWEEN
12Z AND 15Z TUE. PRECIP WILL TRANSITION TO ALL SNOW THEN COME TO AN
END RATHER QUICKLY TUE AFTERNOON FROM I-27 EASTWARD BUT ANY
REMAINING MESOSCALE SNOW BANDS ON BACK SIDE OF SYSTEM WILL CONTINUE
TO CREATE AREAS OF VERY LOW VISIBILITY. WE HAVE EXTENDED THE WINTER
WEATHER ADVISORY THROUGH 00Z TO ACCOUNT FOR ANY SLOWER MOVEMENT.
A VERY LOW DIURNAL TEMPERATURE RANGE IS EXPECTED CHRISTMAS DAY WITH
SOME LOCATIONS POSSIBLY REMAINING IN THE TEENS FAR NORTHWEST WITH
STEADY OR DROPPING TEMPERATURES ELSEWHERE. WIND CHILL VALUES COULD
BE NEAR OR SLIGHTLY BELOW ZERO IN A FEW LOCATIONS EARLY IN THE
MORNING.
LONG TERM...
UPPER LOW PRODUCING A WIDE RANGE OF INCLEMENT WEATHER ACROSS THE
SOUTHERN CONUS ON CHRISTMAS DAY PROGGED TO BE ALL THE WAY TO THE
ARKLATEX BY 26/00Z. THIS WILL RESULT IN RAPIDLY IMPROVING CONDITIONS
ACROSS THE FORECAST AREA THROUGH THE EARLY CHRISTMAS EVENING HOURS.
ANY LINGERING SNOWFALL OVER THE SOUTHEAST PANHANDLE OR NORTHERN
ROLLING PLAINS WILL END WHILE CLOUDS AND WINDS WILL ALSO BE ON THE
DECREASE AS A SURFACE PRESSURE RIDGE SETTLES SOUTH ACROSS WEST
TEXAS. THIS WILL LEAD TO A VERY COLD NIGHT ACROSS THE REGION WITH
WEDNESDAY MORNING LOWS FALLING INTO THE 5 TO 15 DEGREE RANGE ACROSS
ALL OF THE FORECAST AREA PER MOS GUIDANCE.
GFS/ECMWF DETERMINISTIC RUNS INDICATE A CONTINUATION OF THE
PROGRESSIVE PATTERN THROUGH THE 7 DAY PERIOD. HIGHLIGHTS WILL BE
ANOTHER UPPER LOW TRANSLATING ACROSS THE MIDWEST BY THE END OF THE
WEEK AND ANOTHER RATHER POTENT LOOKING CLOSED LOW SOMEWHERE ACROSS
THE SW CONUS BY EARLY NEXT WEEK. THE MID WEEK SYSTEM WILL PASS
MAINLY NORTH OF THE FORECAST AREA AND PROBABLY ONLY RESULT IN A
TIGHTENING OF LOWER HEIGHT GRADIENTS TO RESULT IN BREEZY CONDITIONS
ACROSS THE EXTREME SOUTHERN PANHANDLE ON THURSDAY. TEMPERATURES WILL
MODERATE SOME BY THURSDAY WITH SURFACE WINDS BACK AROUND TO THE
SOUTH AND WEST BUT ANOTHER COLD FRONT SHOULD KNOCK OFF AROUND 10
DEGREES OR SO FOR FRIDAY. SHORT WAVE RIDGING WILL THEN ENSUE FOR THE
UPCOMING WEEKEND WITH TEMPERATURES WARMING ONCE AGAIN. SHOULD REMAIN
DRY THROUGH THE LONG TERM PERIOD.
THE LATTER UPPER LOW SHOWN BY BOTH GFS/ECMWF WOULD BE INTERESTING
SHOULD ANY SEMBLANCE OF IT ACTUALLY PAN OUT. BOTH MODELS CLOSE OFF A
LOW AND ADVECT IT TOWARD WEST TEXAS AROUND OR SHORTLY AFTER NEW
YEARS DAY AND BOTH LOOK VERY WET FOR A LARGE PART OF THE SOUTHWEST
US. OF COURSE...WE WILL ONLY BE MONITORING THE MODEL SOLUTIONS FOR
NOW TO SEE IF THIS TREND CONTINUES AND WHAT...IF ANY...IMPACTS THIS
LOW MAY EVENTUALLY HOLD FOR THE FORECAST AREA. JW
&&
.PRELIMINARY POINT TEMPS/POPS...
FRIONA 17 20 7 39 18 / 70 80 10 0 0
TULIA 20 22 8 36 16 / 60 80 10 0 0
PLAINVIEW 21 24 8 38 18 / 50 80 10 0 0
LEVELLAND 27 29 13 39 18 / 40 20 0 0 0
LUBBOCK 24 28 10 39 19 / 30 30 10 0 0
DENVER CITY 35 35 15 41 19 / 10 10 0 0 0
BROWNFIELD 30 32 13 40 19 / 10 10 0 0 0
CHILDRESS 28 28 10 28 16 / 30 80 10 0 0
SPUR 27 29 12 37 19 / 10 30 10 0 0
ASPERMONT 30 30 13 35 19 / 10 40 10 0 0
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 PM CST TUESDAY FOR THE FOLLOWING
ZONES: TXZ021>032.
&&
$$
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
1019 PM CST MON DEC 24 2012
UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE
.SHORT TERM...TONIGHT AND TUESDAY.
LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A SHORTWAVE
TROUGH EXTENDING FROM NE WISCONSIN TO SOUTHERN LOWER MICHIGAN EARLY
THIS AFTERNOON. COMMA HEAD PRECIP WITH A LITTLE HELP FROM A LIGHT
LAKE EFFECT COMPONENT PRODUCED AREAS OF LIGHT SNOW THAT LINGERED
ACROSS NORTHEAST AND EAST-CENTRAL WISCONSIN THROUGH MID-AFTERNOON
BUT IS CURRENTLY EXITING TO THE EAST. WILL SHOW MOST OF THE PRECIP
ENDING BY 00Z THIS EVENING. IMPROVING CONDITIONS ARE OCCURRING OVER
CENTRAL AND NORTH-CENTRAL WISCONSIN WHERE BREAKS IN THE OVERCAST ARE
GROWING LARGER. HIGH PRESSURE IS BUILDING SOUTHWARD ACROSS THE
NORTHERN PLAINS WHERE SKIES ARE MOSTLY CLEAR AND COLD. THE MAIN
FORECAST CONCERNS INCLUDE THE TIMING OF THE END OF THE PRECIP AND
CLEARING TRENDS TONIGHT.
TONIGHT...THE SHORTWAVE TROUGH WILL BE WELL EAST OF THE REGION OVER
LOWER MICHIGAN AT THE START OF THE PERIOD. RESIDUAL MOISTURE WILL
TAKE AWHILE TO PUSH OUT OF THE REGION...SO WILL START THE EVENING
WITH MOSTLY CLOUDY CONDITIONS WITH A CHANCE OF FLURRIES OVER NE
WISCONSIN. BUT STRONG DRY AIR ADVECTION OVER NORTHWEST WISCONSIN
WILL SLOWLY MOVE SOUTHEAST THROUGH THE NIGHT AND GRADUALLY CLEAR OUT
THE SKIES ACROSS THE MAJORITY OF THE REGION. THE LONE EXCEPTION
WILL BE OVER N-C WISCONSIN WHERE LIGHT NW FLOW WILL CONTINUE TO
GENERATE LAKE EFFECT CLOUDS AND LIGHT SNOW SHOWERS. TEMPS WILL FALL
TO NEAR ZERO OVER THE COLD SPOTS OF LINCOLN COUNTY WHERE SKIES WILL
CLEAR FIRST TO THE MIDDLE TEENS NEAR LAKE MICHIGAN WHERE CLOUDS WILL
CLEAR LAST.
TUESDAY...CANADIAN HIGH PRESSURE WILL BUILD SOUTHEAST ACROSS THE
NORTHERN PLAINS AND NOSE ITS WAY ACROSS THE WESTERN GREAT LAKES.
LIGHT NORTHWEST FLOW WILL CONTINUE OFF LAKE SUPERIOR INTO N-C
WISCONSIN THROUGH THE MORNING...WHICH WILL KEEP SCT FLURRIES...AND
PARTLY TO MOSTLY CLOUDY CONDITIONS THERE. ELSEWHERE...MOSTLY SUNNY
CONDITIONS SHOULD PREVAIL. HIGHS RANGING FROM THE MID TEENS WEST TO
THE MID 20S EAST.
.LONG TERM...TUESDAY NIGHT THRU NEXT SUNDAY.
OVERALL...NO SIGNIFICANT CHANGES TO THE LONG TERM FORECAST. MAIN
FOCUS WAS TO TRY ADD A BIT MORE DETAIL REGARDING LES POTENTIAL
FOR LAKE MICHIGAN COUNTIES FOR WEDNESDAY.
MODELS CONTINUE TO BE IN FAIRLY GOOD AGREEMENT ON OVERALL TRACK OF
SOUTHERN STORM SYSTEM FORECAST TO TRACK TO THE OHIO VALLEY ON
WEDNESDAY. AS PREVIOUSLY FORECAST...THE NORTHERN FRINGE OF STRATIFORM
PRECIPITATION SHIELD WILL JUST CLIP EXTREME SOUTHEAST WISCONSIN
AND THE SOUTHERN PORTION OF LAKE MICHIGAN LATE WEDNESDAY. OTHER
THAN MIDDLE TO HIGH-LEVEL CLOUDS...THE MAIN IMPACT OF THIS SYSTEM
WILL BE TO CREATE A DEEP NORTHEASTERLY WIND FLOW EXTENDING FROM
THE SURFACE UP TO NEAR 700 MB. MAXIMUM OVERWATER BOUNDARY LAYER
FETCH ALSO IN PLACE BY 12Z WEDNESDAY. EXAMINATION OF MODIFIED
FORECAST GFS/NAM SOUNDINGS OVER LAKESHORE COUNTIES INDICATE A
FAIRLY DEEP MOIST AND UNSTABLE LAYER...WITH INVERSION HEIGHTS
APPROACHING 7000 FT AGL OVER WESTERN LAKE MICHIGAN. NAM/GFS ALSO
SUGGEST THAT MOIST LAYER MAY GROW DEEP ENOUGH TO PENETRATE INTO
FAVORABLE DENDRITIC GROWTH ZONE. WATER SURFACE TO 850 DELTA T
VALUES ON THE ORDER OF -16C TO -18C BY 12Z WEDNESDAY OVER THE
NORTHERN HALF OF LAKE MICHIGAN. GFS HAS BEEN FAIRLY CONSISTENT
LAST FEW RUNS...SPITTING OUT AREA OF QPF OVER NORTHERN LAKE
MICHIGAN AFTER 06Z WEDNESDAY AND BRINGING IT ONSHORE BY 12Z
WEDNESDAY. GIVEN OVERALL SYNOPTIC SETUP...NO REASON TO DISCOUNT
SIGNAL FROM GFS. BOTTOM LINE IS FAIRLY DECENT SET-UP FOR LAKE
EFFECT OVER MANITOWOC AND KEWAUNEE COUNTIES STARTING AROUND
DAYBREAK WEDNESDAY AND PERHAPS CONTINUING FOR MUCH OF THE DAY.
GIVEN BOUNDARY LAYER WINDS SPEEDS...WOULD EXPECT MULTIPLE AND SOMEWHAT
LES ORGANIZED LES BANDS RATHER THAN A SINGLE BAND. GIVEN THE
MESOSCALE NATURE OF LES PRECIPITATION WILL LET LATER SHIFTS TRY TO
REFINE THE DETAILS. FELT CONFIDENT ENOUGH AT THIS POINT TO AT
LEAST ADJUST POPS UPWARD INTO THE CHANCE CATEGORY ON WEDNESDAY.
FINALLY...GIVEN DEEP AND PERSISTENT NORHEASTERLY FLOW...ANY LES
BANDS THAT DEVELOP MAY BE ABLE TO PENETRATE AS FAR WEST AS THE FOX
RIVER VALLEY BEFORE WEAKNING. AS OHIO VALLEY STORM SYSTEM
CONTINUES TO MOVE NORTHEAST TO THE EASTERN SEABOARD...BOUNDARY
LAYER WINDS WILL BACK TO OFFSHORE WEDNESDAY NIGHT PUSHING ANY LES
BAND SOUTHWARD. FAIRLY TRANQUIL DAY ON THURSDAY AS WEAK HIGH
PRESSURE RIDGE MOVES ACROSS THE FORTECAST AREA.
THEN BY FRIDAY...SOUTHERN AND NORTHERN STREAM ENERGY BEGIN TO
APPROACH THE CENTRAL PLAINS AND UPPER MISSISSIPPI VALLEY.
UNCERTAINTY REMAINS AS TO HOW THESE FEATURES WILL INTERACT...WITH
CONCENSUS OF GUIDANCE SUGGESTING PERHAPS SOME PHASING OVER THE
OHIO VALLEY FRIDAY NIGHT. REGARDLESS...COMBINATION OF THESE
FEATURES SHOULD BE ABLE TO CREATE WAA ADVECTION REGIME AND DRAW
ADEQUATE MOISTURE NORTHWARD TOWARD THE FORECAST AREA TO GENERATE
BROAD AND GENERALLY LIGHT AREA OF QPF LIKELY TO SPREAD INTO THE
FORECAST AREA LATE ON FRIDAY INTO SATURDAY. LEANING MORE TOWARD
SOMEWHAT LESS ORGANIZED INVERTED TROUGH LOOK OF THE ECMWF AND
OPERATIONAL GFS FOR FRIDAY SYSTEM. INVERTED TROUGH AND CYCLONIC
FLOW MAY HANG BACK ACROSS THE WESTERN GREAT LAKES INTO
SATURDAY...THUS CONTINUE CHANCE POPS UNTIL THEN AS PER PREVIOUS
FORECAST.
DAYTIME TEMPERATURES SHOULD GRADUALLY MODERATE BY THE END OF THE
WEEK TO NEAR OF PERHAPS SLIGHTLY ABOVE NORMAL.
&&
.AVIATION...EVENING GRB RAOB SHOWS PLENTY OF MOISTURE IN THE LOWER
LEVELS TONIGHT. SUPPORTS EVENING TREND OF LINGERING MVFR CIGS
ACROSS MUCH OF THE STATE TONIGHT AND EVEN INTO TUESDAY. HAVE
ALREADY TRENDED MORE PESSIMISTIC WITH THE CLOUDS TONIGHT.
TDH
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS GOODLAND KS
838 AM MST TUE DEC 25 2012
.UPDATE...
ISSUED AT 821 AM MST TUE DEC 25 2012
AFTER CLOSER EXAMINATION OF LATEST RUC AND NAM DATA...CONCERNED
ABOUT POCKET OF NEGATIVE EPV* VALUES GRADUALLY MOVING INTO THE
AREA FROM THE EAST. THIS AREA OF POTENTIAL INSTABILITY CORRELATES
WELL WITH AREA OF ENHANCED REFLECTIVITY ACROSS THE CENTER OF THE
CWA WHICH HAS HAD SEVERAL LOCATIONS REPORTING 1/2SM IN SNOW. THIS
WILL GRADUALLY SHIFT SOUTH AND DIMINISH AS LARGE SCALE FORCING ENDS.
WHILE I DO NOT EXPECT TO SEE LARGE SNOW AMOUNTS DUE TO THE SHORT
EXPECTED DURATION...WITH POTENTIALLY UNSTABLE CONDITIONS HAVE
CONCERNS THAT THERE WILL BE A FEW POCKETS OF LOCALLY HIGH AMOUNTS
AROUND 4 INCHES. WHILE 4 INCH AMOUNTS ARE NOT EXPECTED TO BE
WIDESPREAD...THINK CURRENT DATA SUPPORTS WINTER WEATHER ADVISORY
FOR THE REST OF THE DAY. WHILE CONDITIONS ARE MARGINAL...THINK
WITH MANY PEOPLE TRAVELING SOMEWHAT RELAXED CRITERIA WARRANTED.
UPDATE ISSUED AT 639 AM MST TUE DEC 25 2012
BASED ON VERY HIGH SNOW TO LIQUID RATIOS OBSERVED AT OFFICE...HAVE
UPPED SNOW AMOUNTS TO BE MORE IN LINE WITH HIGHER RATIOS. STILL
KEEPS FORECAST IN 1 TO 3 INCH RANGE...BUT DID RESULT IN ABOUT AN
INCH HIGHER AMOUNTS FORECAST ACROSS NORTHEAST CWA.
&&
.SHORT TERM...(TODAY THROUGH THURSDAY NIGHT)
ISSUED AT 404 AM MST TUE DEC 25 2012
LIGHT SNOW WILL CONTINUE TO SPREAD ACROSS THE FORECAST AREA THIS
MORNING BEFORE DIMINISHING RAPIDLY BY LATE AFTERNOON AS THE LOW
PRESSURE SYSTEM MOVES THROUGH TEXAS AND COLD SURFACE HIGH
PRESSURE PUSHES FURTHER SOUTH INTO THE CENTRAL AND SOUTHERN HIGH
PLAINS BY LATE TODAY. STILL EXPECT ONE TO THREE INCHES OF
ACCUMULATIONS ACROSS THE FORECAST AREA.
COLD AND DRY CONDITIONS ARE EXPECTED TONIGHT AND WEDNESDAY WITH
THE COLD AREA OF HIGH PRESSURE AT THE SURFACE MOVING FURTHER
EAST...ALLOWING THE WESTERN SECTIONS OF THE FORECAST AREA TO BEGIN
WARMING AS SHORT WAVE RIDGING MOVES OVER THE REGION.
THE INITIAL SHORT WAVE TROUGH AT THE LEADING EDGE OF THE MAIN
UPPER TROUGH DEEPENING OVER THE WESTERN UNITED STATES MOVES EAST
ACROSS THE CENTRAL HIGH PLAINS ON THURSDAY. ANOTHER ROUND OF LIGHT
SNOW IS POSSIBLE WITH THE PRIMARY ACCUMULATIONS OCCURRING MAINLY
OVER THE NORTHERN SECTIONS OF THE FORECAST AREA.
.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 1222 AM MST TUE DEC 25 2012
THE PERIOD BEGINS WITH A TROUGH AXIS ACROSS THE CENTRAL PLAINS ON
FRIDAY. HOWEVER MOISTURE WILL BE LACKING DUE TO DEEP WESTERLY FLOW
AND THE MAIN ENERGY WITH THE SYSTEM WILL BE TO THE SOUTH...SO LEFT
IT DRY. SHORTWAVE RIDGING WILL FOLLOW FOR THE WEEKEND WITH
CONTINUED DRY CONDITIONS. ANOTHER SHORTWAVE TROUGH APPROACHES FOR
EARLY NEXT WEEK...HOWEVER A SPLIT UPPER FLOW SUGGESTS MINIMAL
PRECIPITATION CHANCES WITH IT AS WELL. TEMPERATURES FOR THE PERIOD
WILL HAVE SOME MINOR FLUCTUATIONS...BUT GENERALLY BE AROUND 10
DEGREES BELOW NORMAL.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 404 AM MST TUE DEC 25 2012
CONDITIONS WILL VARY BETWEEN IFR AND MVFR AT MCK AND GLD THROUGH
THE MORNING AS LIGHT SNOW CONTINUES TO FALL ACROSS THE CENTRAL
HIGH PLAINS REGION. LIGHT SNOW WILL DIMINISH FROM WEST TO EAST
THROUGH THE AFTERNOON. AFTER 21Z...CONDITIONS AT GLD WILL BECOME
MVFR WITH VFR CONDITIONS EXPECTED AFTER 06Z. MCK WILL TRANSITION
TO VFR BETWEEN 21Z AND 00Z WITH A POSSIBLE RETURN OF MVFR
CONDITIONS AFTER 09Z WITH FOG AND LOW CEILINGS.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...WINTER WEATHER ADVISORY UNTIL 5 PM MST /6 PM CST/ THIS AFTERNOON
FOR KSZ001>003-013>015-027>029-041-042.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...JRM
SHORT TERM...LOCKHART
LONG TERM...024
AVIATION...LOCKHART
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1100 AM EST TUE DEC 25 2012
.UPDATE...
ISSUED AT 1100 AM EST TUE DEC 25 2012
INCREASED CLOUD COVER...AS MUCH OF THE CWA REMAINS UNDER A THICK
LAYER OF CLOUDS. THE ONLY SIGNIFICANT POCKETS OF CLEARING ARE OVER S
CENTRAL AND OVER FAR W LAKE SUPERIOR. ALSO INCREASED POPS N CENTRAL
GIVEN THE SLOWER THAN ANTICIPATED CLEARING AND RADAR ESTIMATED
SNOWFALL OF A QUARTER TO HALF AN INCH NEAR SAW OVER THE PAST HOUR.
&&
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 509 AM EST TUE DEC 25 2012
LATEST 09Z WV IMAGERY AND RUC ANALYSIS SHOWS A SHORTWAVE TROUGH
EXITING EAST OF THE UPPER GREAT LAKES. THIS SHORTWAVE LIKELY
PROVIDED SOME WEAK ENHANCEMENT TO LES BANDS OVER ALGER COUNTY
EARLIER THIS MORNING. LATEST MQT RADAR LOOP SHOWS AN ILL-DEFINED
DOMINANT LES BAND NEAR SHOT POINT BUT OTHERWISE RETURNS ON RADAR
WOULD JUST SUGGEST LITTLE MORE THAN FLURRIES ACROSS THE REST OF THE
NCNTRL FCST AREA.
LES SHOULD CONTINUE TO BE ON THE WANE THIS CHRISTMAS DAY AS FLOW
BCMS INCREASINGLY ANTICYCLONIC AND INCREASING SUBSIDENCE LOWERS
INVERSION HGTS TO BLO 4KFT. HAVE THIS WELL DEPICTED WITH DECREASING
TREND IN POP GRIDS THRU THE DAY. SNOWFALL INTENSITY/AMOUNTS WILL
REMAIN GREATEST OVER THE EAST WHERE AN ADDITIONAL INCH MAY
ACCUMULATE. MAY ALSO SEE AN ADDITIONAL INCH NEAR TWIN LAKES AREA IN
HOUGHTON COUNTY WHERE FOCUSED LOW-LVL CONVERGENCE COULD PROVIDE
LOCALIZED BOOST IN SNOW AMOUNTS.
LARGE SCALE ANTICYCLONIC FLOW...LOW INVERSION HGTS AOB 4KFT AND
INFLUX OF DRY AIR BLO INVERSION WILL ALL WORK TO KEEP LES AMOUNTS IN
CHECK TONIGHT. AGAIN THERE COULD BE SOME LOCALIZED ONE INCH
ACCUMULATIONS OVER ALGER AND NRN LUCE COUNTIES AND NEAR TWIN LAKES
IN HOUGHTON COUNTY WHERE DEVELOPING LAND BREEZES WILL AID LOW-LVL
CONVERGENCE. TAKING ALL FACTORS INTO CONSIDERATION...ONLY LOW CHC
POPS WILL BE JUSTIFIED.
TONIGHT SHOULD BE ONE OF THE COLDEST IN A WHILE...WITH A FEW
LOCATIONS OVER INTERIOR W PORTIONS OF UPPER MI FALLING BELOW ZERO
THANKS TO SHORTWAVE RDGG AND ASSOC INCREASING SUBSIDENCE/Q-VECT DIV
ALLOWING FOR LOW CLOUDS TO CLEAR OUT OVER INTERIOR LOCATIONS.
.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 509 AM EST TUE DEC 25 2012
NO BIG STORMS ARE ON THE HORIZON THROUGH THE END OF THE YEAR. WITH
85H TEMPS IN THE -10 TO -12 C RANGE...LIGHT NORTH NORTHEASTERLY
WINDS BETWEEN HIGH PRESSURE OVER ONTARIO AND SURFACE LOW MOVING UP
THE NORTHEAST COAST...AND INVERSION HEIGHTS GENERALLY AROUND
5KFT...EXPECT LIGHT LAKE EFFECT SNOW SHOWERS TO PERSIST NEAR LAKE
SUPERIOR THOUGH THURSDAY.
NORTHERN STREAM SHORTWAVE ENERGY WILL CARVE OUT AN UPPER TROUGH OVER
THE UPPER GREAT LAKES THIS WEEKEND. NET RESULT WILL BE A CHANCE FOR
SOME VERY LIGHT SYNOPTIC SNOW FRIDAY INTO SATURDAY AS SURFACE LOW
MOVES NORTH OF LAKES SUPERIOR. THEN...LOWERING 85H TEMPS WILL BRING
PERSISTENT LIGHT LAKE EFFECT SNOW SHOWERS TO NORTHWESTERLY WIND
FAVORED AREAS THROUGH THE END OF THE YEAR.
DAYTIME TEMPS WILL BE CLOSE TO NORMAL THROUGH THE END OF THE WEEK
BUT WITH PERSISTENT CLOUD COVER...ESPECIALLY NEAR LAKE SUPERIOR...
OVERNIGHT LOWS WILL CONTINUE TO RUN ABOVE NORMAL.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 635 AM EST TUE DEC 25 2012
WRLY FLOW AT KIWD AND KCMX WILL MAINTAIN IFR CIGS/FLURRIES INTO LATE
MORNING AND MVFR CIGS THEREAFTER INTO TONIGHT. NW FLOW SHIFTING TO
WNW LATE THIS AFTERNOON AT KSAW WILL ALLOW MVFR CIGS/FLURRIES TO
DISSIPATE AS VFR CONDITIONS TAKE HOLD UNTIL LATE TONIGHT. AS WINDS
VEER NNW LATE TONIGHT...LOOK FOR MVFR LAKE CLOUDS/FLURRIES TO MOVE
BACK IN AGAIN.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 509 AM EST TUE DEC 25 2012
A HIGH PRESSURE RIDGE CONTINUING TO BUILD IN FROM THE CANADIAN
PRAIRIES WILL PERSIST THROUGH MUCH OF THE WEEK...KEEPING WINDS AT OR
BELOW 25 KNOTS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
UPDATE...KF
SHORT TERM...VOSS
LONG TERM...MZ
AVIATION...VOSS
MARINE...VOSS
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
636 AM EST TUE DEC 25 2012
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 509 AM EST TUE DEC 25 2012
LATEST 09Z WV IMAGERY AND RUC ANALYSIS SHOWS A SHORTWAVE TROUGH
EXITING EAST OF THE UPPER GREAT LAKES. THIS SHORTWAVE LIKELY
PROVIDED SOME WEAK ENHANCEMENT TO LES BANDS OVER ALGER COUNTY
EARLIER THIS MORNING. LATEST MQT RADAR LOOP SHOWS AN ILL-DEFINED
DOMINANT LES BAND NEAR SHOT POINT BUT OTHERWISE RETURNS ON RADAR
WOULD JUST SUGGEST LITTLE MORE THAN FLURRIES ACROSS THE REST OF THE
NCNTRL FCST AREA.
LES SHOULD CONTINUE TO BE ON THE WANE THIS CHRISTMAS DAY AS FLOW
BCMS INCREASINGLY ANTICYCLONIC AND INCREASING SUBSIDENCE LOWERS
INVERSION HGTS TO BLO 4KFT. HAVE THIS WELL DEPICTED WITH DECREASING
TREND IN POP GRIDS THRU THE DAY. SNOWFALL INTENSITY/AMOUNTS WILL
REMAIN GREATEST OVER THE EAST WHERE AN ADDITIONAL INCH MAY
ACCUMULATE. MAY ALSO SEE AN ADDITIONAL INCH NEAR TWIN LAKES AREA IN
HOUGHTON COUNTY WHERE FOCUSED LOW-LVL CONVERGENCE COULD PROVIDE
LOCALIZED BOOST IN SNOW AMOUNTS.
LARGE SCALE ANTICYCLONIC FLOW...LOW INVERSION HGTS AOB 4KFT AND
INFLUX OF DRY AIR BLO INVERSION WILL ALL WORK TO KEEP LES AMOUNTS IN
CHECK TONIGHT. AGAIN THERE COULD BE SOME LOCALIZED ONE INCH
ACCUMULATIONS OVER ALGER AND NRN LUCE COUNTIES AND NEAR TWIN LAKES
IN HOUGHTON COUNTY WHERE DEVELOPING LAND BREEZES WILL AID LOW-LVL
CONVERGENCE. TAKING ALL FACTORS INTO CONSIDERATION...ONLY LOW CHC
POPS WILL BE JUSTIFIED.
TONIGHT SHOULD BE ONE OF THE COLDEST IN A WHILE...WITH A FEW
LOCATIONS OVER INTERIOR W PORTIONS OF UPPER MI FALLING BELOW ZERO
THANKS TO SHORTWAVE RDGG AND ASSOC INCREASING SUBSIDENCE/Q-VECT DIV
ALLOWING FOR LOW CLOUDS TO CLEAR OUT OVER INTERIOR LOCATIONS.
.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 509 AM EST TUE DEC 25 2012
NO BIG STORMS ARE ON THE HORIZON THROUGH THE END OF THE YEAR. WITH
85H TEMPS IN THE -10 TO -12 C RANGE...LIGHT NORTH NORTHEASTERLY
WINDS BETWEEN HIGH PRESSURE OVER ONTARIO AND SURFACE LOW MOVING UP
THE NORTHEAST COAST...AND INVERSION HEIGHTS GENERALLY AROUND
5KFT...EXPECT LIGHT LAKE EFFECT SNOW SHOWERS TO PERSIST NEAR LAKE
SUPERIOR THOUGH THURSDAY.
NORTHERN STREAM SHORTWAVE ENERGY WILL CARVE OUT AN UPPER TROUGH OVER
THE UPPER GREAT LAKES THIS WEEKEND. NET RESULT WILL BE A CHANCE FOR
SOME VERY LIGHT SYNOPTIC SNOW FRIDAY INTO SATURDAY AS SURFACE LOW
MOVES NORTH OF LAKES SUPERIOR. THEN...LOWERING 85H TEMPS WILL BRING
PERSISTENT LIGHT LAKE EFFECT SNOW SHOWERS TO NORTHWESTERLY WIND
FAVORED AREAS THROUGH THE END OF THE YEAR.
DAYTIME TEMPS WILL BE CLOSE TO NORMAL THROUGH THE END OF THE WEEK
BUT WITH PERSISTENT CLOUD COVER...ESPECIALLY NEAR LAKE SUPERIOR...
OVERNIGHT LOWS WILL CONTINUE TO RUN ABOVE NORMAL.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 635 AM EST TUE DEC 25 2012
WRLY FLOW AT KIWD AND KCMX WILL MAINTAIN IFR CIGS/FLURRIES INTO LATE
MORNING AND MVFR CIGS THEREAFTER INTO TONIGHT. NW FLOW SHIFTING TO
WNW LATE THIS AFTERNOON AT KSAW WILL ALLOW MVFR CIGS/FLURRIES TO
DISSIPATE AS VFR CONDITIONS TAKE HOLD UNTIL LATE TONIGHT. AS WINDS
VEER NNW LATE TONIGHT...LOOK FOR MVFR LAKE CLOUDS/FLURRIES TO MOVE
BACK IN AGAIN.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 509 AM EST TUE DEC 25 2012
A HIGH PRESSURE RIDGE CONTINUING TO BUILD IN FROM THE CANADIAN
PRAIRIES WILL PERSIST THROUGH MUCH OF THE WEEK...KEEPING WINDS AT OR
BELOW 25 KNOTS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...VOSS
LONG TERM...MZ
AVIATION...VOSS
MARINE...VOSS
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
510 AM EST TUE DEC 25 2012
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 509 AM EST TUE DEC 25 2012
LATEST 09Z WV IMAGERY AND RUC ANALYSIS SHOWS A SHORTWAVE TROUGH
EXITING EAST OF THE UPPER GREAT LAKES. THIS SHORTWAVE LIKELY
PROVIDED SOME WEAK ENHANCEMENT TO LES BANDS OVER ALGER COUNTY
EARLIER THIS MORNING. LATEST MQT RADAR LOOP SHOWS AN ILL-DEFINED
DOMINANT LES BAND NEAR SHOT POINT BUT OTHERWISE RETURNS ON RADAR
WOULD JUST SUGGEST LITTLE MORE THAN FLURRIES ACROSS THE REST OF THE
NCNTRL FCST AREA.
LES SHOULD CONTINUE TO BE ON THE WANE THIS CHRISTMAS DAY AS FLOW
BCMS INCREASINGLY ANTICYCLONIC AND INCREASING SUBSIDENCE LOWERS
INVERSION HGTS TO BLO 4KFT. HAVE THIS WELL DEPICTED WITH DECREASING
TREND IN POP GRIDS THRU THE DAY. SNOWFALL INTENSITY/AMOUNTS WILL
REMAIN GREATEST OVER THE EAST WHERE AN ADDITIONAL INCH MAY
ACCUMULATE. MAY ALSO SEE AN ADDITIONAL INCH NEAR TWIN LAKES AREA IN
HOUGHTON COUNTY WHERE FOCUSED LOW-LVL CONVERGENCE COULD PROVIDE
LOCALIZED BOOST IN SNOW AMOUNTS.
LARGE SCALE ANTICYCLONIC FLOW...LOW INVERSION HGTS AOB 4KFT AND
INFLUX OF DRY AIR BLO INVERSION WILL ALL WORK TO KEEP LES AMOUNTS IN
CHECK TONIGHT. AGAIN THERE COULD BE SOME LOCALIZED ONE INCH
ACCUMULATIONS OVER ALGER AND NRN LUCE COUNTIES AND NEAR TWIN LAKES
IN HOUGHTON COUNTY WHERE DEVELOPING LAND BREEZES WILL AID LOW-LVL
CONVERGENCE. TAKING ALL FACTORS INTO CONSIDERATION...ONLY LOW CHC
POPS WILL BE JUSTIFIED.
TONIGHT SHOULD BE ONE OF THE COLDEST IN A WHILE...WITH A FEW
LOCATIONS OVER INTERIOR W PORTIONS OF UPPER MI FALLING BELOW ZERO
THANKS TO SHORTWAVE RDGG AND ASSOC INCREASING SUBSIDENCE/Q-VECT DIV
ALLOWING FOR LOW CLOUDS TO CLEAR OUT OVER INTERIOR LOCATIONS.
.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 509 AM EST TUE DEC 25 2012
NO BIG STORMS ARE ON THE HORIZON THROUGH THE END OF THE YEAR. WITH
85H TEMPS IN THE -10 TO -12 C RANGE...LIGHT NORTH NORTHEASTERLY
WINDS BETWEEN HIGH PRESSURE OVER ONTARIO AND SURFACE LOW MOVING UP
THE NORTHEAST COAST...AND INVERSION HEIGHTS GENERALLY AROUND
5KFT...EXPECT LIGHT LAKE EFFECT SNOW SHOWERS TO PERSIST NEAR LAKE
SUPERIOR THOUGH THURSDAY.
NORTHERN STREAM SHORTWAVE ENERGY WILL CARVE OUT AN UPPER TROUGH OVER
THE UPPER GREAT LAKES THIS WEEKEND. NET RESULT WILL BE A CHANCE FOR
SOME VERY LIGHT SYNOPTIC SNOW FRIDAY INTO SATURDAY AS SURFACE LOW
MOVES NORTH OF LAKES SUPERIOR. THEN...LOWERING 85H TEMPS WILL BRING
PERSISTENT LIGHT LAKE EFFECT SNOW SHOWERS TO NORTHWESTERLY WIND
FAVORED AREAS THROUGH THE END OF THE YEAR.
DAYTIME TEMPS WILL BE CLOSE TO NORMAL THROUGH THE END OF THE WEEK
BUT WITH PERSISTENT CLOUD COVER...ESPECIALLY NEAR LAKE SUPERIOR...
OVERNIGHT LOWS WILL CONTINUE TO RUN ABOVE NORMAL.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1241 AM EST TUE DEC 25 2012
WITH A STRONG INVERSION OVER THE AREA...THE STRATUS CLOUDS WILL
PERSIST THROUGH THE FORECAST PERIOD EXCEPT AT IWD WHERE A DEVELOPING
SW WIND WILL PUSH THE LAKE EFFECT CLOUDS NORTH OF THEM ON TUE
AFTERNOON. OTHERWISE...A NW FLOW WILL BRING SOME OCCASIONAL LIGHT
LAKE EFFECT SNOW TO THE TAF SITES BUT VSBYS SHOULD NOT BE RESTRICTED
BY IT. SO...EXPECT MVFR CIGS AT BOTH KCMX AND KSAW THROUGH THE FCST
PERIOD.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 509 AM EST TUE DEC 25 2012
A HIGH PRESSURE RIDGE CONTINUING TO BUILD IN FROM THE CANADIAN
PRAIRIES WILL PERSIST THROUGH MUCH OF THE WEEK...KEEPING WINDS AT OR
BELOW 25 KNOTS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...VOSS
LONG TERM...MZ
AVIATION...07
MARINE...VOSS
AREA FORECAST DISCUSSION
NWS RALEIGH NC
945 AM EST TUE DEC 25 2012
.SYNOPSIS...
WEAK HIGH PRESSURE WILL EXTEND ACROSS THE REGION TODAY THEN SHIFT
OFFSHORE BY SUNSET. A WARM FRONT AND A DEEPENING LOW PRESSURE SYSTEM
WILL APPROACH FROM THE SOUTHWEST TONIGHT. THE STRONG STORM SYSTEM
AND ACCOMPANYING COLD FRONT WILL SWEEP ACROSS THE AREA WEDNESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 945 AM TUESDAY...
WHILE FOG AND LOW CLOUDS HAVE SCOURED ACROSS MUCH OF THE CENTRAL AND
EASTERN CWA...DENSE FOG IS STILL REPORTED IN THE TRIAD...AND TRAFFIC
CAMERAS IN THE AREA SHOW MURKY CONDITIONS ALONG THE I-40 CORRIDOR.
VISIBILITIES HAVE IMPROVED IN RANDOLPH AND DAVIDSON COUNTIES...AND
THERE IS STILL A COUPLE MORE HOURS FOR THE FOG AND STRATUS TO MIX
OUT BEFORE HIGH CLOUDS BEGIN TO POUR BACK IN AHEAD OF THE STORMS
SYSTEM DEVELOPING OVER THE GULF COAST. RAP FORECAST
SOUNDINGS...WHICH SHOW MORE LOW LEVEL MOISTURE THAN WAS OBSERVED ON
THE MORNING RAOBS....SHOW THE LOW CLOUDS SCOURING IN THE TRIAD BY
AROUND NOON. WILL INCREASE CLOUD COVER IN THE NORTHWEST PIEDMONT
AND TRIM OFF A COUPLE DEGREES ON HIGHS SINCE CIRRUS WILL BE STEADILY
INCREASING EVEN AFTER THE LOW CLOUDS BURN OFF. OTHERWISE..THE
FORECAST APPEARS TO BE IN GOOD SHAPE THROUGH 00Z. HIGHS 52-61
NORTHWEST TO SOUTHEAST. -SMITH
TONIGHT...A WARM FRONT WILL DEVELOP ACROSS SC THIS EVENING IN
RESPONSE TO A POWERFUL LOW PRESSURE SYSTEM LIFTING ACROSS THE LOWER
MS VALLEY. SLY WINDS A FEW THOUSAND FEET ABOVE THE SURFACE WILL
ADVECT WARM MOIST AIR UP AND OVER THE COOL STABLE SURFACE LAYER
RESIDING OVER CENTRAL NC. THIS WILL LEAD TO THE DEVELOPMENT OF LOW
CLOUDS...EXPANDING SW-NE IN THE EVENING. ISENTROPIC LIFT WILL
INCREASE LATE THIS EVENING INTO THE OVERNIGHT CAUSING AN EXPANSIVE
AREA OF MODERATE RAINFALL TO DEVELOP. THE GREATEST RAINFALL AMOUNTS
SHOULD FALL OVER THE WESTERN PIEDMONT WHERE BEST LIFT PROJECTED TO
BE FOCUS. TEMPS WILL INITIALLY FALL WITH ONSET OF THE RAIN DUE TO
EVAPORATIVE COOLING IN THE SUB-CLOUD LAYER AFTERWHICH TEMPS WILL
STABILIZE AND MAY ACTUALLY RISE IN THE PRE-DAWN HOURS ACROSS THE
SOUTH AS THE WARM FRONT APPROACHES FROM THE SOUTH. MIN TEMPS NEAR 40
FAR NORTH TO THE MID 40S SOUTH.
&&
.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
AS OF 320 AM TUESDAY...
...AN ACTIVE WEATHER DAY SHAPING UP WEDNESDAY FOR CENTRAL NC WITH A
HIGH LIKELIHOOD OF STRONG TO SEVERE THUNDERSTORMS....
THE SC WARM FRONT PROJECTED TO LIFT NWD ACROSS A LARGE PART OF THE
FORECAST AREA WED AM INTO THE AFTERNOON. THE RAINFALL IN THE WEST
LATE TONIGHT MAY ESTABLISH AN INSITU OR HYBRID CAD AIR MASS OVER THE
NW PIEDMONT. THUS BY MID DAY..MAY SEE A DISTINCT AIR MAS ACROSS THE
REGION WITH COOL STABLE AIR (TEMPS INT EH 40S TO NEAR 50) OVER THE
TRIAD REGION WHILE THE REST OF THE REGION...ESPECIALLY THE SANDHILLS
AND A LARGE PART OF THE COASTAL PLAIN...IN A WARM MOIST UNSTABLE AIR
MASS WITH TEMPS IN THE UPPER 50S AND 60S.
THE STRONG LOW PRESSURE SYSTEM WILL LIFT ENE FROM THE TN VALLEY INTO
THE MID ATLANTIC WED. A STRONG SUB-TROPICAL JET ROUNDING THE BASE OF
THE TROUGH WILL CAUSE THE UPPER TROUGH TO ATTAIN A NEGATIVE TILT
WHICH WILL SPREAD COLDER AIR ALOFT OVER THE WARM MOIST AIR IN THE
LOWER LAYERS OF THE ATMOSPHERE. THIS WILL RESULT IN AN UNSTABLE
ATMOSPHERE ACROSS CENTRAL NC WITH MID LEVEL LAPSE RATES UP TO 7.5
DEGREES. IN ADDITION...THE LOW PRESSURE SYSTEM WILL SPAWN A STRONG
LOW LEVEL JET THAT WILL LIFT ACROSS THE REGION IN THE AFTERNOON.
THIS STRONG LLJ INTERACTING WITH SURFACE BOUNDARY/WARM FRONT WILL
GREATLY ENHANCE THE LOW LEVEL HELICITY SUPPORTIVE OF STORMS WITH
ROTATING UPDRAFTS. THUS...WITH A STRONG WIND FIELD IN PLACE
INTERACTING WITH AN INCREASINGLY MOIST AND UNSTABLE (FOR WINTER) AIR
MASS...STRONG TO SEVERE STORMS APPEAR QUITE LIKELY.
AT THIS TIME...IT APPEARS A NEAR SOLID LINE OF STORMS WILL OCCUR
AHEAD OF A STRONG COLD FRONT THAT WILL CROSS THE REGION IN THE
AFTERNOON. OUT AHEAD OF THE LINE...THE AIR MASS WILL BE SUPPORTIVE
OF A FEW SUPERCELL THUNDERSTORMS. WHILE THE PRIMARY SEVERE WEATHER
THREAT WILL BE DAMAGING STRAIGHT-LINE WINDS ASSOCIATED WITH THE LINE
OF CONVECTION...THE ISOLATED THUNDERSTORMS THAT OCCUR AHEAD OF THE
LINE WILL HAVE THE POTENTIAL TO PRODUCE A FEW TORNADOES.
CURRENT INDICATIONS SUGGEST THAT THE SEVERE WEATHER THREAT MAY
START AS EARLY 10-11 AM IN THE SOUTHERN COUNTIES THEN EXPAND N-NE
TO COVER THE REST OF THE REGION DURING THE AFTERNOON HOURS AS A
SURFACE LOW MOVES ALONG THE NWD MOVING WARM FRONT. THE SEVERE
WEATHER THREAT BEGINS TO DECREASE IN THE WEST BY LATE AFTERNOON AND
IN THE EAST SHORTLY AFTER SUNSET.
WEDNESDAY NIGHT...THE SURFACE COLD FRONT WILL EXIT THE REGION EARLY.
W-NW WINDS BEHIND THE FRONT WILL BE QUITE STRONG WITH GUSTS 25-30MPH
PROBABLE. THESE WINDS WILL ALSO USHER MUCH COOLER AND DRIER AIR INTO
THE REGION. THIS DRIER AIR SHOULD QUICKLY DISSIPATE CLOUD COVERAGE
ACROSS THE AREA...LEADING TO CLEAR SKIES BY MIDNIGHT. MUCH COOLER
WITH MIN TEMPS IN THE LOW-MID 30S.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 255 AM TUESDAY...
FOR THURSDAY THROUGH FRIDAY NIGHT: THE DEPARTING STORM IS EXPECTED
TO BE CENTERED JUST OFF NYC THURSDAY MORNING. THE MSLP GRADIENT OVER
NC REMAINS SUFFICIENTLY STRONG FOR CONTINUED BRISK WINDS...
SUSTAINED OVER 15 MPH AND GUSTS UP TO 30-35 MPH THROUGH AT LEAST THE
EARLY PART OF THE AFTERNOON. HIGHLY STABLE AND WARMING MID LEVELS
WITH 120-150 METER HEIGHT RISES SHOULD STAVE OFF MOST CLOUDS...
ALTHOUGH A FEW FLAT STRATOCU ARE LIKELY IN THE AFTERNOON AS THE
REMAINING BOUNDARY LAYER MOISTURE GETS TRAPPED BENEATH THE
SUBSIDENCE INVERSION ALOFT... AND VERY HIGH THIN CLOUDS WILL STREAK
OVER THE AREA AS WELL WITH AN ELONGATED 125+ KT JET CORE PASSING
OVERHEAD. THE SHALLOW MIXED LAYER SUPPORTS HIGHS THURSDAY OF
46-52... VERY CLOSE TO EXISTING FORECAST. GOOD RADIATIONAL COOLING
THURSDAY NIGHT AS SURFACE HIGH PRESSURE DRIFTS OVERHEAD WITH FAIR TO
MOSTLY CLEAR SKIES. LOWS 26-30. THE HIGH SLIPS OFF THE SOUTHEAST
COAST BY LATE FRIDAY... AND HIGH CLOUDS WILL BE INCREASING SLOWLY AS
THE ANTICYCLONIC MID LEVEL FLOW FLATTENS TO SOUTHWESTERLY AND
STRENGTHENS... IN ADVANCE OF OUR NEXT STORM SYSTEM DIGGING OVER THE
SRN PLAINS. WITH LITTLE CHANGE IN AIR MASS OR VERTICAL THERMAL
STRUCTURE... EXPECT HIGHS TO BE MINIMALLY HIGHER FRIDAY... 48-53.
SKIES WILL TREND TO CLOUDY SOUTH TO NORTH AS THE LONGWAVE TROUGH
AXIS SWINGS TOWARD THE MISS VALLEY... RESULTING IN THICKENING AND
LOWERING MID CLOUDS. GFS FORECAST SOUNDINGS SHOW THE SURFACE-BASED
STABLE POOL HOLDING FIRM DESPITE THE INCREASING SOUTHERLY FLOW AND
MOIST UPGLIDE FROM 950 MB UP (PARTICULARLY 285K-290K)... DRAWING LOW
LEVEL ATLANTIC MOISTURE INTO THE SOUTHERN AND EASTERN PORTIONS OF
THE FORECAST AREA... AND THIS FLOW WILL INCREASE TOWARD MORNING AS
SURFACE LOW PRESSURE IS EXPECTED TO STRENGTHEN OVER THE GULF COAST
BETWEEN NEW ORLEANS AND MOBILE. THE LATEST GFS/ECMWF RUNS SUPPORT
DELAYING THE DEEP LAYER LIFT AND THE RESULTING CHANCE OF MEASURABLE
RAIN UNTIL CLOSE TO SUNRISE SATURDAY MORNING... SO WILL SLOW THE
ARRIVAL OF RAIN CHANCES BY A FEW HOURS LATE FRIDAY NIGHT. LOWS
30-38.
FOR SATURDAY/SATURDAY NIGHT: ANOTHER STRONG STORM SYSTEM WILL AFFECT
NC EARLY IN THE WEEKEND. THE LATEST ECMWF INITIALIZED AT 00Z
SUPPORTS AND EXTENDS RECENT MODEL TRENDS TOWARD A MILLER TYPE-A
(SINGLE-LOW) CYCLOGENESIS PATTERN... WITH THE SURFACE LOW MOVING
EASTWARD ACROSS SRN GA BEFORE TRACKING UP THE COAST OF THE
CAROLINAS. MOISTURE SHOULD BE PLENTIFUL WITH FEEDS FROM BOTH THE
ATLANTIC AND GULF... AND FORCING FOR ASCENT IS LIKELY TO BE RAPIDLY
STRENGTHENING SATURDAY. 12-HR PROJECTED MID LEVEL HEIGHT FALLS ARE
150 M TO AS MUCH AS 200 M OVER NC IN CONJUNCTION WITH INCREASING
(BUT NOT OVERLY INTENSE) UPPER DIVERGENCE AND STRENGTHENING LOW
LEVEL MASS CONVERGENCE MAINLY IN OUR SOUTH AND EAST. WILL MAINTAIN
SOME CAUTION BUT DECENT MODEL AGREEMENT WITHIN THIS ACTIVE PATTERN
SUPPORTS AN UPTICK OF RAIN CHANCES ESPECIALLY IN THE SOUTH AND EAST.
HIGHS FROM 45 IN THE COOL STABLE AIR IN THE NORTHWEST CWA RANGING TO
56 SOUTHEAST. RAIN SHOULD TAPER TO SPOTTY DRIZZLE GIVEN THE DRYING
ALOFT SATURDAY EVENING... BEFORE ENDING ENTIRELY AFTER MIDNIGHT.
LOWS 29-35.
FOR SUNDAY/MONDAY: QUIET WEATHER BEHIND THIS SYSTEM WITH SURFACE
HIGH PRESSURE BUILDING OVERHEAD FROM THE WEST. THE AIR MASS SHOULD
BE SOMEWHAT MODIFIED PARTICULARLY WITH HEIGHTS RISING QUICKLY ALOFT
AS NEW LONGWAVE TROUGHING DIGS OVER THE ROCKIES. EXPECT BELOW NORMAL
TEMPS SUNDAY TRENDING UP CLOSER TO NORMAL MONDAY... WITH DRY
WEATHER. -GIH
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
AS OF 645 AM TUESDAY...
MERRY CHRISTMAS!
WIDESPREAD MVFR/IFR CEILINGS WILL GRADUALLY LIFT AND DISSIPATE
THROUGH 10 AM AS DRIER MORE STABLE AIR OVERSPREADS THE REGION FROM
THE NE. LOCALIZED THICK FOG WITH VISIBILITIES AT OR BELOW A HALF
MILE ARE CONFINED TO SECTIONS OF THE WESTERN PIEDMONT AND SANDHILLS.
THE FOG WILL ALSO LIFT AND DISSIPATE PRIOR TO 9 AM.
FOR THE REMINDER OF CHRISTMAS MORNING INTO CHRISTMAS AFTERNOON
EXPECT VFR CONDITIONS AND SURFACE WINDS GRADUALLY VEERING FROM A NNE
DIRECTION IN THE MORNING TO AN ELY COMPONENT BY MID AFTERNOON.
A POWERFUL STORM SYSTEM OVER THE LOWER MS VALLEY LATER TODAY AND
TONIGHT WILL LIFT NE INTO THE TN VALLEY BY WEDNESDAY MORNING. THIS
SYSTEM WILL CAUSE A WARM FRONT TO DEVELOP OVER SC BY WEDNESDAY
MORNING. SLY FLOW ABOVE THIS FEATURE WILL CAUSE WIDESPREAD RAIN AND
LOW CLOUDS TO ENVELOPE CENTRAL NC FROM THE SW LATE TONIGHT INTO
WEDNESDAY MORNING. THIS WILL LEAD TO AN EXTENDED PERIOD OF MVFR/IFR
CONDITIONS. WHILE NEAR SURFACE WINDS EARLY WEDNESDAY MORNING WILL BE
ELY...WINDS AT AND ABOVE 3000FT WILL BE SLY AND INCREASING TO NEAR
35KTS. THIS SLY WINDS WILL GRADUALLY LOWER TO NEAR 1500FT BY
MID-LATE WEDNESDAY MORNING...POSSIBLY CREATING LLWS CONDITIONS UNTIL
EARLY AFTERNOON.
AS THE STORM SYSTEM LIFTS ENE INTO THE MID ATLANTIC BY WEDNESDAY
EVENING...A STRONG COLD FRONT WILL CROSS CENTRAL NC WEDNESDAY
AFTERNOON. AHEAD OF THIS FRONT...EXPECT GUSTY SLY WINDS WITH GUSTS
NEAR 30 KTS POSSIBLE. SHOWERS AND A FEW STRONG-SEVERE STORMS WILL
CROSS THE REGION WEDNESDAY AFTERNOON...ENDING BY EARLY WEDNESDAY
EVENING.
IMPROVING AVIATION CONDITIONS EXPECTED WEDNESDAY NIGHT WITH VFR
CONDITIONS ANTICIPATED LATE WEDNESDAY NIGHT THROUGH FRIDAY. SURFACE
WINDS WILL BE BRISK IN WAKE OF THE FRONT WEDNESDAY NIGHT INTO EARLY
THURSDAY WITH GUSTS AROUND 30KTS LIKELY. THE NEXT SHOT AT ADVERSE
AVIATION WEATHER CONDITIONS IS EXPECTED LATE FRIDAY NIGHT INTO
SATURDAY.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...WSS
NEAR TERM...WSS/SMITH
SHORT TERM...WSS
LONG TERM...HARTFIELD
AVIATION...WSS
AREA FORECAST DISCUSSION
NWS PEACHTREE CITY GA
309 PM EST TUE DEC 25 2012
...SEVERE STORMS INCLUDING A FEW TORNADOES LIKELY LATE TUES
NIGHT/WED MORNING...
.SHORT TERM /TONIGHT THROUGH THURSDAY/...
INGREDIENTS STILL COMING TOGETHER FOR NOCTURNAL SEVERE WEATHER EVENT
AFTER MIDNIGHT TONIGHT. 12Z RUNS HAVE CONTINUED TREND OF MORE
FAVORABLE PARAMETERS. 0-1KM BULK SHEAR OF 45-55KT NOW IN BOTH NAM
AND GFS...THOUGH THESE ARE SOMEWHAT EAST OF BEST MOISTURE/CAPE AXIS.
IN SPITE OF THIS...FCST SIG TOR PARAMETER VALUES ARE NOW 1.5-2.5 IN
GFS AND 4-5 WITH THE NAM. TORNADO THREAT IS QUITE HIGH FOR A COOL
SEASON QLCS EVENT.
TIMING ON GFS AND ECMWF HAS SHIFTED SLIGHTLY BACK TO BETTER MATCH
THE SLOWER NAM. LATEST HRRR NOW SIMILAR TO GFS TIMING. DUE TO
UNCERTAINTY IN MODELS AND WHETHER ANY PREFRONTAL STORM ACTIVITY WILL
DEVELOP...HAVE NOT TWEAKED TIMING BACK TOO MUCH. TOTAL RAINFALL
STILL HARD PRESSED TO EXCEED 2 INCHES. NO SIGNIFICANT FLOODING
PROBLEMS EXPECTED.
AFTER FRONT PASSES...PRECIP SHOULD END QUICKLY. WILL BE ISSUING A
WIND ADVISORY FOR THE ENTIRE AREA BUT STARTING A LITTLE SOONER IN
THE MOUNTAINS AS LOW LEVEL FLOW OF 50KTS COULD MIX DOWN TO HIGHER
ELEVATIONS. ALSO HAVE CONTINUED SLT CHC/CHC RAIN/SNOW SHOWER MIX
OVER PARTS OF FAR NE GA WED NIGHT. SHOULD NOT SEE ANY ACCUMULATION.
REST OF FCST LOOKS GOOD. WE WILL CONTINUE TO MONITOR THE SITUATION.
SNELSON
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
THE LONG TERM PORTION OF THE FORECAST BEGINS WITH WRAP AROUND
MOISTURE FROM THE BACK SIDE OF THE EXITING LOW PRESSURE SYSTEM
ACROSS N GA. COOLER AIR WILL ALSO BE FILTERING INTO THE STATE BUT IT
LOOKS LIKE THE BETTER MOISTURE WILL STAY FAR ENOUGH NORTH THAT IT
SHOULD NOT CAUSE ANY WINTER PRECIP ACROSS THE N GA MOUNTAINS THU
NIGHT/FRIDAY MORNING. HIGH PRESSURE BUILDS IN THURSDAY WITH MOISTURE
BEGINNING TO RETURN TO THE REGION FRIDAY. MOISTURE BEGINS PUSHING IN
AHEAD OF NEXT SYSTEM WHICH WILL BRING ANOTHER ROUND OF PRECIP TO THE
STATE FRIDAY NIGHT/SATURDAY. THIS NEXT SYSTEM DOES NOT LOOK AS
STRONG AS THE ONE THAT WILL MOVE THROUGH TONIGHT...SO WILL CONTINUE
WITH ONLY SHOWERS FOR NOW. THE MODELS SHOW THIS SECOND SYSTEM MOVING
THROUGH THE AREA VERY FAST WITH THE RAIN MOVING INTO W GA AROUND 06Z
SAT AND THE ENTIRE SYSTEM EXITING THE EAST SIDE OF THE STATE BY 18Z
SAT. A STRONG HIGH PRESSURE RIDGE BUILDS IN BEHIND THIS SECOND
SYSTEM AND IT LOOKS TO KEEP NORTH AND CENTRAL GEORGIA DRY SUNDAY AND
MONDAY.
01
&&
.HYDROLOGY...
FLASH FLOOD GUIDANCE REMAINS IN THE 1.5/2.5/3.0 FOR 1H 3H 6H
GUIDANCE RESPECTIVELY. THESE ARE SLIGHTLY REDUCED VALUES WITH RECENT
RAINS BUT LIKELY NOT SUFFICIENT FOR SIGNIFICANT FLOODING CONCERNS
GIVEN INITIAL LIGHT TO MODERATE RAIN AHEAD OF SYSTEM AND THEN
RAPID MOVEMENT OF COLD FRONT ONCE CONVECTIVELY ENHANCED BANDS SET
UP. STILL WILL BE CLOSELY MONITORING THE NEXT 24 HOUR FOR ANY
SHORT FUSE RIVER AND STREAM WARNINGS PRIMARILY.
&&
.AVIATION...
18Z UPDATE...
LIFR CIGS/VSBYS HAVE BEEN SLOW TO IMPROVE TODAY. AREA OF RAIN
SPREADING NORTH THIS AFTERNOON MAY HELP IMPROVE CONDITIONS BUT
NOT MUCH. SCT SHRA LIKELY TONIGHT AFTER INITIAL ROUND OF RAIN
BEFORE MAIN LINE OF SHRA/TSRA MOVES IN FROM THE WEST. HAVE ADDED
PREVAILING TSRA FROM 08-12Z TO TAFS TO PROVIDE CLARITY AND
CONFIDENCE IN FCST. A FEW STORMS COULD BE STRONG. SFC WINDS WILL
SWITCH TO SW THEN W AFTER THE STORMS MOVE THRU AND WILL GUST TO
30KTS IN THE AFTERNOON.
//ATL CONFIDENCE...18Z UPDATE...
MEDIUM CONFIDENCE ON TIMING OF CIGS/VSBYS TODAY AND TSRA TONIGHT.
HIGH CONFIDENCE ON ALL OTHER ELEMENTS.
SNELSON
&&
.PRELIMINARY POINT TEMPS/POPS...
ATHENS 49 52 31 51 / 100 80 0 5
ATLANTA 49 49 30 49 / 100 20 0 5
BLAIRSVILLE 46 48 28 45 / 100 80 20 5
CARTERSVILLE 49 50 31 46 / 100 20 0 5
COLUMBUS 50 51 33 53 / 100 20 0 5
GAINESVILLE 47 50 31 48 / 100 60 0 5
MACON 55 55 33 54 / 100 60 0 5
ROME 48 49 32 47 / 100 20 5 5
PEACHTREE CITY 49 49 31 50 / 100 20 0 5
VIDALIA 59 60 36 56 / 80 80 0 0
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FROM 10 AM TO 10 PM EST WEDNESDAY FOR THE
FOLLOWING ZONES: BALDWIN...BANKS...BARROW...BARTOW...BIBB...
BLECKLEY...BUTTS...CARROLL...CHATTAHOOCHEE...CHEROKEE...CLARKE...
CLAYTON...COBB...COWETA...CRAWFORD...CRISP...DAWSON...DEKALB...
DODGE...DOOLY...DOUGLAS...EMANUEL...FAYETTE...FLOYD...FORSYTH...
GLASCOCK...GREENE...GWINNETT...HALL...HANCOCK...HARALSON...
HARRIS...HEARD...HENRY...HOUSTON...JACKSON...JASPER...
JEFFERSON...JOHNSON...JONES...LAMAR...LAURENS...MACON...
MADISON...MARION...MERIWETHER...MONROE...MONTGOMERY...MORGAN...
MUSCOGEE...NEWTON...NORTH FULTON...OCONEE...OGLETHORPE...
PAULDING...PEACH...PICKENS...PIKE...POLK...PULASKI...PUTNAM...
ROCKDALE...SCHLEY...SOUTH FULTON...SPALDING...STEWART...SUMTER...
TALBOT...TALIAFERRO...TAYLOR...TELFAIR...TOOMBS...TREUTLEN...
TROUP...TWIGGS...UPSON...WALTON...WARREN...WASHINGTON...
WEBSTER...WHEELER...WILCOX...WILKES...WILKINSON.
WIND ADVISORY FROM 1 AM TO 10 PM EST WEDNESDAY FOR THE FOLLOWING
ZONES: CATOOSA...CHATTOOGA...DADE...FANNIN...GILMER...GORDON...
LUMPKIN...MURRAY...TOWNS...UNION...WALKER...WHITE...WHITFIELD.
&&
$$
SHORT TERM...SNELSON
LONG TERM....01
AVIATION...SNELSON
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
406 PM EST TUE DEC 25 2012
.SHORT TERM...
TONIGHT THROUGH WEDNESDAY NIGHT...
SIGNIFICANT WINTER STORM TO IMPACT MUCH OF THE CWA IN THE SHORT
TERM. WATER VAPOR IMAGERY SHOWING POTENT UPPER LOW DIGGING THROUGH
TEXAS. 12Z RAOB AND LATEST RAP ANALYSIS HAS 100KT+ UPPER JET COMING
INTO THE BASE OF THE TROUGH. ASSOCIATED SFC LOW NEAR TX/LA BORDER AT
18Z AND IS EXPECTED TO LIFT NE INTO THE CENTRAL TN VALLEY BY 12Z
WED. GOOD ISENT ASCENT AHEAD OF THIS SYSTEM ALONG THE 290-295K SFC
IS EXPECTED TO INITIATE PRECIP IN THE FAR SOUTHERN CWA AFTER
MIDNIGHT TONIGHT WITH LARGE SCALE FORCING TO INTENSIFY PRECIP TO
MOD-HVY SNOW AFTER 12Z. DESPITE A TREND TO A MORE SE TRACK...GOOD
DEFORMATION AXIS STILL SETS UP OVER SE CWA ALONG WITH SUBSTANTIAL
HEIGHT FALLS IN A DEEP MOISTURE COLUMN TO SUPPORT A WINDOW OF
OPPORTUNITY FOR WARNING CRITERIA SNOWFALL. STRONG GRADIENT BRINGING
15 TO 25 MPH WINDS WITH GUSTS TO 30 MPH LENDS FURTHER CREDENCE IN
MAINTAINING WINTER STORM WARNING. HAD TRANSITIONED REMAINING
COUNTIES IN THE WATCH OVER TO AN ADVISORY WITH GENERALLY 1-3/2-4
INCH AMOUNTS BUT ALSO ACCOMPANIED BY GUSTY WINDS FOR BLOWING SNOW.
POTENTIAL FOR MOD-HVY SNOW WILL BE SHORT-LIVED HOWEVER AS SYSTEM
WILL QUICKLY EXIT TOWARD THE EAST COAST WEDNESDAY NIGHT.
&&
.LONG TERM...
THURSDAY THROUGH TUESDAY...THE CHALLENGES THIS PERIOD INCLUDE
CHANCES FOR SNOW WITH THE PASSAGE OF A WEAK UPPER TROF LATE THIS
WEEK. ALSO...HIGH AND LOW TEMPERATURES WITH AN EXTENDED PERIOD OF
COLD AIR AND SNOW COVER OVER AT LEAST PART OF THE FORECAST AREA WILL
PROVIDE ADDITIONAL CHALLENGES. FOR THIS PACKAGE...FAVORED THE GFS.
THE GFS HAS AT LEAST AS GOOD OF RUN TO RUN CONSISTENCY AS THE ECMWF
AND APPEARS TO BE HANDLING THIS PATTERN REASONABLY WELL. THE GFS
TIMING OF THE SYSTEM LATE THIS WEEK HAS ALSO BEEN CONSISTENT FOR THE
PAST 8 RUNS AND APPEARS ON TRACK. ALSO...THE OPERATION MOS AND
ENSEMBLE MOS HAS BEEN RELATIVELY STABLE IN ITS OUTPUT FOR SEVERAL
DAYS AND APPEARS IN LINE. HAVE MODIFIED HIGH AND LOW TEMPS GIVEN
SNOW FIELD CONSIDERATIONS.
AT THE START OF THE PERIOD...DOWNWARD MOTION WILL HAVE INCREASED
SIGNIFICANTLY AS EVIDENCE OF NET ISENTROPIC ADIABATIC OMEGA WITH A
DRYING OF THE MID LEVELS. AS A RESULT...HAVE REMOVED LINGERING
FLURRIES THURSDAY OVER NW OHIO. FOR THE REST OF THE PERIOD...TRIED
TO PUT SOME DETAIL IN THE TIMING OF THE UPPER LEVEL TROF THIS
WEEKEND AND SUBSEQUENT LAKE EFFECT SNOW SHOWERS. THERE IS LITTLE
MOISTURE TO WORK WITH AND FORCING IS WEAK...SO ANY SNOW AMOUNTS
SHOULD BE LIGHT. LAKE EFFECT PARAMETERS ARE VERY MARGINAL WITH A
LIMITED FETCH. DELTA T VALUES GENERALLY SHOULD BE 10 TO 14 WITH LOW
INVERSION HEIGHTS. REMOVED THE CHANCE FOR SNOW SUNDAY AND SUNDAY
NIGHT. GFS BUFKIT PROFILE SUPPORTS FREEZING DRIZZLE OVER SNOW GIVEN
THE LACK OF ICE INDUCED IN THE CLOUD LAYER. TEMPERATURES IN A DEEP
LAYER WARM ABOVE -10C. NOT OPTIMISTIC ABOUT SNOW CHANCES MONDAY...
BUT FOR THE SAKE OF CONSISTENCY AND LINGERING UNCERTAINTY ABOUT
EARLY NEXT WEEK...LEFT LAKE EFFECT SNOW SHOWERS IN THE FORECAST
MONDAY.
&&
.AVIATION...
12Z TAFS...DRIER LOW LEVEL AIR HAS WORKED INTO MUCH OF NORTH
CENTRAL INDIANA RESULTING IN SCATTERING OF LOW CLOUDS AT KSBN.
SATELLITE TRENDS SUGGEST THIS CLEARING MAY REACH KFWA OVER NEXT
FEW HOURS BUT CONFIDENCE IN ANY SUSTAINED BREAKS IS LOW AS
NORTHEAST FLOW TRAJECTORIES OFF SOUTHERN LAKE HURON/LAKE ERIE
MAY ACT TO MAINTAIN STRATOCU THROUGH THE DAY. WILL KEEP VFR
CONDITIONS AT KFWA FOR NOW BUT WILL NEED TO MONITOR TRENDS FOR
POSSIBLE MVFR AMENDMENTS. NORTH WINDS WILL BECOME NORTHEAST TODAY
WITH SPEEDS GENERALLY 10 KNOTS OR LESS. NORTHEAST WINDS TO
STRENGTHEN TONIGHT AS SFC LOW PRESSURE DEEPENS TO THE SOUTH IN
ASSOCIATION WITH STORM SYSTEM TO IMPACT THE AREA FOR WEDNESDAY. A
LIGHT SNOW MENTION WAS ADDED TO KFWA TOWARD THE END OF THE
PERIOD...BUT CONDITIONS WILL DETERIORATE RAPIDLY AT KFWA JUST
BEYOND THIS FORECAST PERIOD AS HEAVIER SNOW MOVES IN FROM THE SOUTH.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WINTER STORM WARNING FROM 7 AM WEDNESDAY TO 1 AM EST THURSDAY
FOR INZ009.
WINTER STORM WARNING FROM 4 AM TO 10 PM EST WEDNESDAY FOR INZ018-
025>027-032>034.
WINTER WEATHER ADVISORY FROM 7 AM WEDNESDAY TO 1 AM EST THURSDAY
FOR INZ005>008.
WINTER WEATHER ADVISORY FROM 4 AM TO 10 PM EST WEDNESDAY FOR
INZ015>017-020-022>024.
MI...WINTER WEATHER ADVISORY FROM 7 AM WEDNESDAY TO 1 AM EST THURSDAY
FOR MIZ079>081.
OH...WINTER STORM WARNING FROM 7 AM WEDNESDAY TO 1 AM EST THURSDAY
FOR OHZ001-002-004-005.
WINTER STORM WARNING FROM 4 AM TO 10 PM EST WEDNESDAY FOR OHZ015-
016-024-025.
LM...SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 7 PM EST THURSDAY
FOR LMZ043-046.
&&
$$
SHORT TERM...JAL
LONG TERM...SKIPPER
AVIATION...JAL
AREA FORECAST DISCUSSION
NWS GOODLAND KS
1045 AM MST TUE DEC 25 2012
.UPDATE...
ISSUED AT 821 AM MST TUE DEC 25 2012
AFTER CLOSER EXAMINATION OF LATEST RUC AND NAM DATA...CONCERNED
ABOUT POCKET OF NEGATIVE EPV* VALUES GRADUALLY MOVING INTO THE
AREA FROM THE EAST. THIS AREA OF POTENTIAL INSTABILITY CORRELATES
WELL WITH AREA OF ENHANCED REFLECTIVITY ACROSS THE CENTER OF THE
CWA WHICH HAS HAD SEVERAL LOCATIONS REPORTING 1/2SM IN SNOW. THIS
WILL GRADUALLY SHIFT SOUTH AND DIMINISH AS LARGE SCALE FORCING ENDS.
WHILE I DO NOT EXPECT TO SEE LARGE SNOW AMOUNTS DUE TO THE SHORT
EXPECTED DURATION...WITH POTENTIALLY UNSTABLE CONDITIONS HAVE
CONCERNS THAT THERE WILL BE A FEW POCKETS OF LOCALLY HIGH AMOUNTS
AROUND 4 INCHES. WHILE 4 INCH AMOUNTS ARE NOT EXPECTED TO BE
WIDESPREAD...THINK CURRENT DATA SUPPORTS WINTER WEATHER ADVISORY
FOR THE REST OF THE DAY. WHILE CONDITIONS ARE MARGINAL...THINK
WITH MANY PEOPLE TRAVELING SOMEWHAT RELAXED CRITERIA WARRANTED.
UPDATE ISSUED AT 639 AM MST TUE DEC 25 2012
BASED ON VERY HIGH SNOW TO LIQUID RATIOS OBSERVED AT OFFICE...HAVE
UPPED SNOW AMOUNTS TO BE MORE IN LINE WITH HIGHER RATIOS. STILL
KEEPS FORECAST IN 1 TO 3 INCH RANGE...BUT DID RESULT IN ABOUT AN
INCH HIGHER AMOUNTS FORECAST ACROSS NORTHEAST CWA.
&&
.SHORT TERM...(TODAY THROUGH THURSDAY NIGHT)
ISSUED AT 404 AM MST TUE DEC 25 2012
LIGHT SNOW WILL CONTINUE TO SPREAD ACROSS THE FORECAST AREA THIS
MORNING BEFORE DIMINISHING RAPIDLY BY LATE AFTERNOON AS THE LOW
PRESSURE SYSTEM MOVES THROUGH TEXAS AND COLD SURFACE HIGH
PRESSURE PUSHES FURTHER SOUTH INTO THE CENTRAL AND SOUTHERN HIGH
PLAINS BY LATE TODAY. STILL EXPECT ONE TO THREE INCHES OF
ACCUMULATIONS ACROSS THE FORECAST AREA.
COLD AND DRY CONDITIONS ARE EXPECTED TONIGHT AND WEDNESDAY WITH
THE COLD AREA OF HIGH PRESSURE AT THE SURFACE MOVING FURTHER
EAST...ALLOWING THE WESTERN SECTIONS OF THE FORECAST AREA TO BEGIN
WARMING AS SHORT WAVE RIDGING MOVES OVER THE REGION.
THE INITIAL SHORT WAVE TROUGH AT THE LEADING EDGE OF THE MAIN
UPPER TROUGH DEEPENING OVER THE WESTERN UNITED STATES MOVES EAST
ACROSS THE CENTRAL HIGH PLAINS ON THURSDAY. ANOTHER ROUND OF LIGHT
SNOW IS POSSIBLE WITH THE PRIMARY ACCUMULATIONS OCCURRING MAINLY
OVER THE NORTHERN SECTIONS OF THE FORECAST AREA.
.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 1222 AM MST TUE DEC 25 2012
THE PERIOD BEGINS WITH A TROUGH AXIS ACROSS THE CENTRAL PLAINS ON
FRIDAY. HOWEVER MOISTURE WILL BE LACKING DUE TO DEEP WESTERLY FLOW
AND THE MAIN ENERGY WITH THE SYSTEM WILL BE TO THE SOUTH...SO LEFT
IT DRY. SHORTWAVE RIDGING WILL FOLLOW FOR THE WEEKEND WITH
CONTINUED DRY CONDITIONS. ANOTHER SHORTWAVE TROUGH APPROACHES FOR
EARLY NEXT WEEK...HOWEVER A SPLIT UPPER FLOW SUGGESTS MINIMAL
PRECIPITATION CHANCES WITH IT AS WELL. TEMPERATURES FOR THE PERIOD
WILL HAVE SOME MINOR FLUCTUATIONS...BUT GENERALLY BE AROUND 10
DEGREES BELOW NORMAL.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1040 AM MST TUE DEC 25 2012
CONDITIONS CONTINUE TO VARY BETWEEN HIGH MVFR/VFR TO IFR CONDITIONS
AS PERIODS OF SNOW CONTINUE TO IMPACT BOTH TAF SITES. GIVEN
OVERALL RADAR PATTERN AND EXPECTED CHANGES TO FORCING FOR THE NEXT
FEW HOURS EXPECT THIS TREND TO CONTINUE AT KGLD WHILE CONDITIONS
AS SNOW CONTINUES TO DIMINISH AT MCK. SNOW SHOULD GENERALLY END
AROUND 21Z WITH CIGS RAISING THROUGH THE EARLY EVENING. POINT
SOUNDINGS INDICATE POTENTIAL FOR FOG OVERNIGHT AS WINDS BECOME
LIGHT AND STRONG SUBSIDENCE MAY BRING A PERIOD OF CLEARING. NOT
SURE IF THIS IS JUST MODELS RESPONDING TO CURRENT SNOW FIELD BUT
IF SOUNDINGS VERIFY WE MAY NOT ONLY SEE FOG BUT PERSISTENT
FLURRIES/ICE CRYSTALS THROUGH THE NIGHT.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...WINTER WEATHER ADVISORY UNTIL 5 PM MST /6 PM CST/ THIS AFTERNOON
FOR KSZ001>003-013>015-027>029-041-042.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...JRM
SHORT TERM...LOCKHART
LONG TERM...024
AVIATION...JRM
AREA FORECAST DISCUSSION
NWS PADUCAH KY
319 PM CST TUE DEC 25 2012
.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
ISSUED AT 318 PM CST TUE DEC 25 2012
IN THE NEAR TERM...AN INTENSIFYING BAND OF MIXED PRECIPITATION IS
LIFTING NORTHWARD FROM NORTHERN ARKANSAS AS OF 20Z. THIS BAND IS
ASSOCIATED WITH STRONG WARM ADVECTION ON EASTERLY FLOW IN THE
850/700 MB LAYER. RUC MODEL BRINGS THE ZONE OF STRONG MID LEVEL
WARM ADVECTION AND ASSOCIATED PRECIP INTO SOUTHEAST MISSOURI BY
00Z. PRECIP TYPE WILL GRADUALLY CHANGE TO SNOW BY MID EVENING IN
SE MISSOURI...ONCE THE WARM ADVECTION DIMINISHES AND FRONTOGENETIC
FORCING TAKES OVER. INTERESTING TO NOTE THAT RUC MODEL THERMAL
PROFILES ARE SOMEWHAT COLDER THAN GFS/NAM PROFILES THIS EVENING.
LATER IN THE EVENING...IN THE 03Z TO 06Z TIME FRAME...RUC
INDICATES THE MAIN FORCING MECHANISM WILL BECOME MID LEVEL
FRONTOGENESIS /850 TO 700 MB LAYER/. THIS WILL RESULT IN LOCALLY
HEAVY PRECIPITATION ACQUIRING MORE OF A BANDED CHARACTER AS IT
OVERSPREADS THE REMAINDER OF THE FORECAST AREA.
LOOKING AT THE 12Z MODEL SUITE...MODELS ARE ALMOST IN LOCKSTEP AS
THE EVENT IS NOW WITHIN THE NEXT 24 HOURS. THE PRIMARY ISSUES ARE
PRECIPITATION TYPE AND LOCATION OF THE DEFORMATION ZONE /HEAVIEST
QPF/.
THE SWATH OF HEAVIEST QPF IS EXPECTED TO OCCUR UNDER THE DEFORMATION
ZONE TO THE NORTHWEST OF THE MID LEVEL LOW. AN INTENSE/COMPACT 500
MB LOW WILL TRACK EAST/NORTHEAST ACROSS TENNESSEE TONIGHT AND
WEDNESDAY. THE ASSOCIATED DEFORMATION ZONE WILL BE ACROSS SE
MISSOURI AND ROUGHLY ALONG AND NORTHWEST OF THE OHIO RIVER. THIS IS
EVIDENT IN THE 12Z GFS...WHICH SHOWS PRONOUNCED MID LEVEL
FRONTOGENETICAL FORCING AND HEAVY QPF COLOCATED WITH EACH OTHER. MOST
OTHER MODEL QPF GUIDANCE INDICATES THE DEFORMATION ZONE LOCATION
IN THE SAME AREA. THEREFORE...EXPECT THE SWATH OF HEAVIEST
SNOWFALL TO OCCUR WITHIN THAT AREA...MAINLY NW OF A KEVV/KPAH LINE.
ONE MAJOR CAVEAT IS PRECIP TYPE. THE MODELS HAVE ACTUALLY WARMED
SOMEWHAT IN THE 800 TO 900 MB LAYER TONIGHT DUE TO PRONOUNCED
EASTERLY FLOW AT 850 MB. ABOVE FREEZING AIR IS FORECAST TO WRAP
WESTWARD AROUND THE TOP OF THE 850 MB LOW...WHICH WILL DELAY THE
CHANGEOVER TO SNOW ALONG AND EAST OF THE KEVV/KPAH CORRIDOR. BASED
ON A BLEND OF SREF/NAM/GFS THERMAL PROFILES...THE CHANGEOVER TO SNOW
FROM KPAH TO KEVV WOULD BE IN THE 07Z TO 11Z TIME FRAME. THIS WOULD
CUT DOWN SIGNIFICANTLY ON FORECAST SNOWFALL AMOUNTS...THOUGH A FEW
HOURS OF HEAVY WET SNOW AND BLIZZARD CONDITIONS ARE STILL EXPECTED.
MODEL BOUNDARY LAYER AND 850 MB TEMPS IN THE FAR SOUTHEAST DO NOT
SUPPORT MUCH SNOW IN THE KHOP AREA...AND THE WINTER STORM WATCH
HAS BEEN DISCONTINUED FOR THAT AREA.
WHERE THE BULK OF THE PRECIPITATION IS ALL SNOW NORTH AND WEST OF
THE KEVV/KPAH CORRIDOR...THERE IS HIGH CONFIDENCE IN A CRIPPLING
BLIZZARD. SNOWFALL AMOUNTS WITHIN THE DEFORMATION ZONE AXIS SHOULD
REACH A FOOT OR SO. LOOKING AT BUFKIT MOMENTUM TRANSFER...BOTH THE
NAM AND GFS INDICATE A HIGH POTENTIAL FOR GUSTS TO AT LEAST 35
KNOTS. THE SREF SHOWS A 50 PERCENT CHANCE OF SUSTAINED WINDS OVER 25
KNOTS IN SE MISSOURI. DESPITE THE HEAVY WET NATURE OF THE
SNOW...DRIFTS WILL BE MEASURED IN FEET IN THE SWATH OF HEAVIEST
SNOW. THE COMBINATION OF HEAVY WET SNOW AND WIND WILL LIKELY CAUSE
SOME POWER OUTAGES.
AS FOR THE TIMING OF THE EVENT...PRECIP WILL SPREAD NORTH ACROSS
THE ENTIRE FORECAST AREA THROUGH 06Z. THE HEAVIEST PRECIP WILL
OCCUR ROUGHLY FROM 03Z TO 12Z. THE DEFORMATION ZONE WILL LIFT OUT
WEDNESDAY MORNING...BUT WINDS WILL NOT BEGIN TO DIMINISH UNTIL AT
LEAST 18Z. THE STRONG WINDS WILL CONTINUE TO RESULT IN EXTENSIVE
BLOWING AND DRIFTING IN THE HEAVY SNOW AREA.
.LONG TERM /THURSDAY THROUGH NEXT TUESDAY NIGHT/...
ISSUED AT 318 PM CST TUE DEC 25 2012
IN THE EXTENDED FORECAST PERIOD...SHORTWAVE RIDGING ALOFT WILL
DOMINATE DURING FROM THURSDAY THROUGH THE EARLY MORNING HOURS ON
FRIDAY. ALTHOUGH THERE WILL BE A LITTLE MORE INSOLATION /SUNSHINE/
AVAILABLE...THERE WILL STILL BE WEAK COLD AIR ADVECTION OVER THE
EXPECTED SNOW FIELD FROM THE TUESDAY NIGHT/WEDNESDAY MORNING WINTER
STORM. WITH THIS IN MIND...LOWERED TEMPERATURES 3 TO 5 DEGREES FROM
LIKELY HIGH TEMPERATURES DUE TO CLOUDS...WINDS AND SNOW COVER. THIS
ADJUSTMENT WAS MAINLY DONE OVER AREAS WHERE TWO OR MORE INCHES WERE
EXPECTED IN THE STORM TOTAL SNOWFALL GRIDDED FORECAST ACROSS THE WFO
PAH FORECAST AREA.
BY FRIDAY AFTERNOON...BOTH 12Z ECMWF AND GFS DETERMINISTIC MODEL
GUIDANCE INDICATE SOME ENHANCEMENT OF THE SHORTWAVE TROUGH MOVING
INTO THE WFO PAH FORECAST AREA IN THE SOUTHWESTERLY FLOW BEHIND THE
AFOREMENTIONED SHORTWAVE RIDGE. THE LIFT ASSOCIATED WITH THIS
FEATURE...COMBINED WITH A RESURGENCE OF CANADIAN POLAR AIR /AS WELL
AS ANY ANTECEDENT SNOW COVER/ SHOULD FORCE THE DEVELOPMENT OF LIGHT
WINTRY MIX LATE FRIDAY NIGHT. WITH THIS IN MIND...ATTEMPTED TO LIMIT
AN MEASURABLE SNOW/SLEET POTENTIAL WHERE THERE WAS NOT A MIX WITH
RAIN. AN INITIAL STAB AT SNOW/SLEET AMOUNTS WOULD LEAD TO AMOUNTS
LESS THAN ONE INCH OVER SOUTHEAST MO...SOUTHERN IL....SOUTHWEST IN
AND WESTERN KY ALONG THE OHIO RIVER. SHOULD THE COLDER AIR FILTER IN
FASTER...MAXIMUM AMOUNTS MAY BE CLOSER TO 1.5 INCHES.
SINCE THIS WEATHER SYSTEM LOOKS FOCUSED WITH MORE ISENTROPIC
LIFT...LEFT THE PRECIPITATION ON THE LIGHTER SIDE IN TERMS OF
INTENSITY AND SHORTER IN OVERALL DURATION OF MEASURABLE
PRECIPITATION.
BEYOND SATURDAY...RIDGING ALOFT WILL BUILD BACK INTO THE AREA WITH
SURFACE HIGH PRESSURE AT THE SURFACE. THIS SCENARIO...WITH ANY
ANTECEDENT SNOW COVER...WILL LEAD TOWARD SLIGHTLY COOLER
TEMPERATURES THAN NORMAL OVER SOUTHERN ILLINOIS AND SOUTHWEST
INDIANA THROUGH NEXT TUESDAY.
THERE IS SOME DIFFERENCE IN TIMING OF THE NEXT SOUTHWEST LOW MOVING
TOWARD THE AREA NEXT TUESDAY/WEDNESDAY...WITH THE ECMWF BEING COOLER
AND FASTER AND THE GFS SLOWER AND WARMER. FOR NOW...WILL KEEP THINGS
DRY THROUGH THE REMAINDER OF THIS FORECAST PACKAGE.
&&
.AVIATION...
ISSUED AT 1200 PM CST TUE DEC 25 2012
OR THE 18Z TAF ISSUANCE...PRIMARILY MOVE FROM VFR/MVFR VISIBILITIES
DUE TO CONTINUED MOISTENING OF BOUNDARY LAYER CANADIAN POLAR AIRMASS
ENGULFING THE TAF SITES. FOR THE PERIOD FROM 00Z TO 06Z...MOVE
QUICKLY TOWARD LOW MVFR TO LOWER IFR CATEGORY CEILINGS AS THE
WEATHER SYSTEM SHARPENS AND DEEPENS NEAR KCGI/KPAH TAF SITES. WITH
THE DEFORMATION ZONE NEARBY KCGI/KPAH...DECIDED TO GO WITH HIGH
SUSTAINED WINDS/WIND GUSTS...AS SURFACE WIND GRADIENT WILL BE
LOCALLY HIGHER. AS A CARRYOVER FROM THE 12Z TAFS...KEPT A TEMPORARY
MENTION OF LIFR/VLIFR CEILINGS AND VISIBILITIES...DURING THE MAXIMUM
STORM INTENSITY OVER THESE SITES. FOR THE KEVV AND KOWB TAF
SITES...GIVEN THE SHARP GRADIENT IN PRECIPITATION TYPE...KEPT THESE
LOCATIONS IN MVFR VISIBILITY RAIN THROUGH AT LEAST 09Z DECEMBER
26TH...THEN RAPIDLY CHANGE TO IFR/LIFR CONDITIONS THROUGH 13Z...WITH
A SLOW IMPROVEMENT TO IFR CONDITIONS THROUGH 18Z TUESDAY.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
KY...BLIZZARD WARNING FROM 6 PM THIS EVENING TO NOON CST WEDNESDAY
FOR KYZ001.
WINTER WEATHER ADVISORY FROM 6 AM TO NOON CST WEDNESDAY FOR
KYZ012-017-021-022.
BLIZZARD WARNING FROM MIDNIGHT TONIGHT TO NOON CST WEDNESDAY FOR
KYZ002>011-013>016-018>020.
MO...BLIZZARD WARNING FROM 6 PM THIS EVENING TO NOON CST WEDNESDAY
FOR MOZ076-086-087-100-107>112-114.
IL...BLIZZARD WARNING FROM 6 PM THIS EVENING TO NOON CST WEDNESDAY
FOR ILZ075>078-080>089-092-093.
BLIZZARD WARNING FROM MIDNIGHT TONIGHT TO NOON CST WEDNESDAY FOR
ILZ090-091-094.
IN...BLIZZARD WARNING FROM MIDNIGHT TONIGHT TO NOON CST WEDNESDAY FOR
INZ081-082-085>088.
&&
$$
SHORT TERM...MY
LONG TERM....SMITH
AVIATION...SMITH
AREA FORECAST DISCUSSION
NWS PADUCAH KY
1205 PM CST TUE DEC 25 2012
.UPDATE...
ISSUED AT 1205 PM CST TUE DEC 25 2012
PRELIMINARY THOUGHTS INCORPORATING 12Z NAM/GFS...
MODELS ARE ALMOST IN LOCKSTEP AS THE EVENT IS NOW WITHIN THE NEXT
24 HOURS. THE PRIMARY ISSUES ARE PRECIPITATION TYPE AND LOCATION
OF THE DEFORMATION ZONE /HEAVIEST QPF/.
THE SWATH OF HEAVIEST QPF IS EXPECTED TO OCCUR UNDER THE DEFORMATION
ZONE TO THE NORTHWEST OF THE MID LEVEL LOW. AN INTENSE/COMPACT 500
MB LOW WILL TRACK EAST/NORTHEAST ACROSS TENNESSEE TONIGHT AND
WEDNESDAY. THE ASSOCIATED DEFORMATION ZONE WILL BE ACROSS SE
MISSOURI AND ROUGHLY ALONG AND NORTHWEST OF THE OHIO RIVER. THIS IS
EVIDENT IN THE 12Z GFS...WHICH SHOWS PRONOUNCED MID LEVEL
FRONTOGENETICAL FORCING AND HEAVY QPF COLOCATED WITH EACH OTHER. MOST
OTHER MODEL QPF GUIDANCE INDICATES THE DEFORMATION ZONE LOCATION
IN THE SAME AREA. THEREFORE...EXPECT THE SWATH OF HEAVIEST
SNOWFALL TO OCCUR WITHIN THAT AREA...MAINLY NW OF A KEVV/KPAH LINE.
ONE MAJOR CAVEAT IS PRECIP TYPE. THE MODELS HAVE ACTUALLY WARMED
SOMEWHAT IN THE 800 TO 900 MB LAYER TONIGHT DUE TO PRONOUNCED
EASTERLY FLOW AT 850 MB. ABOVE FREEZING AIR IS FORECAST TO WRAP
WESTWARD AROUND THE TOP OF THE 850 MB LOW...WHICH WILL DELAY THE
CHANGEOVER TO SNOW ALONG AND EAST OF THE KEVV/KPAH CORRIDOR. BASED
ON A BLEND OF SREF/NAM/GFS THERMAL PROFILES...THE CHANGEOVER TO SNOW
FROM KPAH TO KEVV WOULD BE IN THE 07Z TO 11Z TIME FRAME. THIS WOULD
CUT DOWN SIGNIFICANTLY ON FORECAST SNOWFALL AMOUNTS...THOUGH A FEW
HOURS OF HEAVY WET SNOW AND BLIZZARD CONDITIONS ARE STILL EXPECTED.
MODEL BOUNDARY LAYER TEMPS IN THE FAR SOUTHEAST DO NOT SUPPORT MUCH
IF ANY SNOW IN THE KHOP AREA...AND THE WINTER STORM WATCH WILL BE
DISCONTINUED FOR THAT AREA.
WHERE THE BULK OF THE PRECIPITATION IS ALL SNOW NORTH AND WEST OF
THE KEVV/KPAH CORRIDOR...THERE IS HIGH CONFIDENCE IN A CRIPPLING
BLIZZARD. SNOWFALL AMOUNTS WITHIN THE DEFORMATION ZONE AXIS SHOULD
REACH A FOOT OR SO. LOOKING AT BUFKIT MOMENTUM TRANSFER...BOTH THE
NAM AND GFS INDICATE A HIGH POTENTIAL FOR GUSTS TO AT LEAST 35
KNOTS. THE SREF SHOWS A 50 PERCENT CHANCE OF SUSTAINED WINDS OVER 25
KNOTS IN SE MISSOURI. DESPITE THE HEAVY WET NATURE OF THE
SNOW...DRIFTS WILL BE MEASURED IN FEET IN THE SWATH OF HEAVIEST
SNOW. THE COMBINATION OF HEAVY WET SNOW AND WIND WILL LIKELY CAUSE
SOME POWER OUTAGES.
AS FOR THE TIMING OF THE EVENT...RADAR TRENDS AND HRRR GUIDANCE
INDICATE A LIGHT RAIN/SNOW MIX WILL SPREAD NORTHWARD INTO THE KPOF
AREA FROM 21Z TO 00Z. THE PRECIP WILL SPREAD NORTH ACROSS THE ENTIRE
FORECAST AREA IN THE 00Z TO 06Z TIMEFRAME. THE HEAVIEST PRECIP WILL
OCCUR ROUGHLY FROM 03Z TO 12Z. THE DEFORMATION ZONE WILL LIFT OUT
WEDNESDAY MORNING...BUT WINDS WILL NOT BEGIN TO DIMINISH UNTIL AT
LEAST 18Z. THE STRONG WINDS WILL CONTINUE TO RESULT IN EXTENSIVE
BLOWING AND DRIFTING IN THE HEAVY SNOW AREA.
&&
.SHORT TERM.../THROUGH WEDNESDAY NIGHT/...
ISSUED AT 411 AM CST TUE DEC 25 2012
THE MODELS HAVE SHIFTED FARTHER SOUTH WITH THE PATH OF THE WINTER
STORM SYSTEM CURRENTLY TAKING SHAPE OVER NORTHWEST TEXAS. IT WILL
MOVE TO THE ARKLATEX REGION BY 00Z WEDNESDAY AND SHIFT EAST
NORTHEAST THROUGH MIDDLE TENNESSEE WEDNESDAY MORNING. GIVEN THE SHIFT
TO THE SOUTH...THE ONSET OF PRECIPITATION MAY BE A BIT DELAYED TIL
00Z WED OR A BIT LATER. IN ADDITION...THE 00Z ECMWF AND NAM ARE LEADING
THE WAY IN HOLDING SIGNIFICANT SNOWS ACROSS MUCH OF THE AREA FROM
THE MISSISSIPPI RIVER COUNTIES OF SOUTHEAST MISSOURI EASTWARD
THROUGH THE REMAINDER OF THE AREA INTO WEDNESDAY MORNING. TRIED
TO PUSH THE GRIDS TOWARD THESE TRENDS.
LOW CLOUDS CURRENTLY COVER THE ENTIRE AREA...AND THE LAMP
GUIDANCE INDICATES THAT THEY WILL BE PERSISTENT THROUGH THE DAY
TODAY. THIS WILL LIKELY HOLD TEMPERATURES DOWN A FEW DEGREES FROM
PREVIOUS FORECAST LEVELS. THIS COULD LEAD TO A FREEZING RAIN
THREAT AT THE ONSET OF THE EVENT. BUT...A LOOK AT MODEL SOUNDINGS
INDICATES THAT THE WARM LAYER OVER MUCH OF THE AREA PRIOR TO THE
ONSET OF PRECIPITATION WILL NOT LIKELY SURVIVE THE SATURATION
PROCESS...AND SATURATION AND A CHANGE OVER TO SNOW SHOULD OUTPACE
THE FREEZING LINE EASTWARD ACROSS THE AREA. AREAS TO THE WEST OF
I-57 SHOULD BE ALL SNOW AFTER 00Z...AND THE FAR EASTERN PORTION OF
THE AREA WILL BECOME ALL SNOW AROUND 12Z WEDNESDAY.
USING HPC QPF AND A 12 TO 1 SNOW TO LIQUID RATIO WHEN AND WHERE
THERE IS PURE SNOW...AND A RATIO WELL UNDER 10 TO 1 WHERE THE
TRANSITION IS OCCURRING...NETTED A LARGE AREA OF 4 TO 10 INCH
STORM TOTAL SNOWFALL AMOUNTS. QPF IS LOWER OVER CARTER AND RIPLEY
COUNTIES...AND PORTIONS OF THOSE COUNTIES MAY STRUGGLE TO GET 4
INCHES...BUT IT WILL BE CLOSE ENOUGH. OVER CHRISTIAN...MUHLENBERG
AND TODD COUNTIES IT SPITS OUT ABOUT 4 INCHES...BUT CONFIDENCE IS
NOT AS HIGH IN THE TIMING OF THE CHANGE OVER. SO WARNING LEVEL
SNOWS ARE LIKELY ALL AREAS.
AM NOT OVERLY OPTIMISTIC ABOUT HITTING BLIZZARD WIND LEVELS OF 35
MPH...BUT SOME GUSTS TO THAT LEVEL WILL BE POSSIBLE. MEG AND LZK
HAVE DECIDED TO GO WITH A BLIZZARD WARNING...SO SEE NO REASON NOT
TO JOIN IN ON THAT PARTY. EVEN IF THE WINDS DO NOT QUITE GET
THERE...THE IMPACT WILL BE SUCH THAT THE BLIZZARD WARNING WILL BE
WARRANTED OVER MUCH OF THE AREA. WILL KEEP THE SAME TIMES AS FOR
THE WATCH...BUT IT MAY NEED TO BE EXTENDED INTO THE AFTERNOON
ACROSS THE EVANSVILLE TRI STATE AREA...ESPECIALLY IF BLOWING SNOW
DEVELOPS AS SUSPECTED.
WILL BE ISSUING THE WARNING FOR ALL BUT THE 3 SOUTHEASTERNMOST
COUNTIES. IT MAY BE NEEDED THERE...BUT AM CONCERNED BOTH ABOUT
SNOW AMOUNTS REACHING 4 INCHES...AND WINDS REACHING
CRITERIA WITH THE SURFACE LOW NOT FAR TO THE SOUTHEAST OF THAT
AREA. WILL ISSUE A WINTER STORM WATCH FOR THOSE 3 COUNTIES FROM
06Z-18Z WED...AND LET THE DAY SHIFT RE-CONSIDER IT LATER TODAY.
ANY ISSUES IN THOSE AREAS WILL HOLD OFF UNTIL THE VERY END OF THE
SECOND PERIOD.
DID NOT SEE MUCH EVIDENCE OF INSTABILITY TO SUPPORT THUNDER...SO
REMOVED THE THUNDER MENTION FROM THE FORECAST. HOWEVER...DO SEE
EVIDENCE OF POTENTIAL BANDING WITHIN THE DEFORMATION ZONE. THIS
COULD LEAD TO SOME LOCALLY VERY INTENSE SNOWFALL RATES AND
DEFINITE WHITE OUT CONDITIONS. DEFINITELY A FUN NIGHT IN STORE FOR
THE REGION.
.LONG TERM.../THURSDAY THROUGH MONDAY/...
ISSUED AT 411 AM CST TUE DEC 25 2012
NOT MUCH CHANGE IN THE EXTENDED. CONTINUED TO TREND COOLER WITH
TEMPS A FEW DEGREES BELOW ALLBLEND AND CLOSER TO THE ECMWF OUTPUT.
THIS WILL ALSO BE SUPPORTED BY THE SNOW COVER KEEPING THINGS A
LITTLE COOLER THAN MODELS WOULD INDICATE. SO ANY CHANGES TO TEMPS IN
THE FUTURE WOULD BE TO THE COLDER AND NOT WARMER. SIMILAR WITH DEW
POINTS AS WELL. WE HAVE NORTH THEN EAST WINDS AND INCREASE DEW
POINTS FROM THE MID TEENS TO THE MID 20S AND THATS DIFFICULT TO DO
WITH THE AFOREMENTIONED WIND DIRECTION. WE ARE STILL ON COURSE FOR
ANOTHER SNOW STORM FRIDAY NIGHT THAT LOOKS LIKE ANOTHER INCH
POSSIBLE WITH THIS SYSTEM. HOWEVER SOUTH OF THE OHIO RIVER THERE
COULD BE MIXING WITH RAIN THEN CHANGING OVER TO ALL RAIN SOUTH OF
THE RIVER BEFORE ENDING SATURDAY AFTN. HOWEVER IF THE SNOW FIELDS
COOL US A GOOD DEAL MORE THAN MODELS WOULD INDICATE THIS SECOND
STORM SYSTEM COULD BE ALL SNOW BUT STILL WOULD NOT PRODUCE MORE THAN
A COUPLE INCHES WITH CURRENT LIQUID EQUIVALENT AND RATIOS.
&&
.AVIATION...
ISSUED AT 1200 PM CST TUE DEC 25 2012
OR THE 18Z TAF ISSUANCE...PRIMARILY MOVE FROM VFR/MVFR VISIBILITIES
DUE TO CONTINUED MOISTENING OF BOUNDARY LAYER CANADIAN POLAR AIRMASS
ENGULFING THE TAF SITES. FOR THE PERIOD FROM 00Z TO 06Z...MOVE
QUICKLY TOWARD LOW MVFR TO LOWER IFR CATEGORY CEILINGS AS THE
WEATHER SYSTEM SHARPENS AND DEEPENS NEAR KCGI/KPAH TAF SITES. WITH
THE DEFORMATION ZONE NEARBY KCGI/KPAH...DECIDED TO GO WITH HIGH
SUSTAINED WINDS/WIND GUSTS...AS SURFACE WIND GRADIENT WILL BE
LOCALLY HIGHER. AS A CARRYOVER FROM THE 12Z TAFS...KEPT A TEMPORARY
MENTION OF LIFR/VLIFR CEILINGS AND VISIBILITIES...DURING THE MAXIMUM
STORM INTENSITY OVER THESE SITES. FOR THE KEVV AND KOWB TAF
SITES...GIVEN THE SHARP GRADIENT IN PRECIPITATION TYPE...KEPT THESE
LOCATIONS IN MVFR VISIBILITY RAIN THROUGH AT LEAST 09Z DECEMBER
26TH...THEN RAPIDLY CHANGE TO IFR/LIFR CONDITIONS THROUGH 13Z...WITH
A SLOW IMPROVEMENT TO IFR CONDITIONS THROUGH 18Z TUESDAY.
NOTE...A CORRECTION WAS SENT SHORTLY AFTER THE ROUTINE ISSUANCE TIME
TO REFLECT BLOWING SNOW DURING THE LOWEST CEILINGS AND VISIBILITIES.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
KY...BLIZZARD WARNING FROM 6 PM THIS EVENING TO NOON CST WEDNESDAY
FOR KYZ001>016-018>020.
WINTER STORM WATCH FROM LATE TONIGHT THROUGH WEDNESDAY MORNING
FOR KYZ017-021-022.
MO...BLIZZARD WARNING FROM 6 PM THIS EVENING TO NOON CST WEDNESDAY
FOR MOZ076-086-087-100-107>112-114.
IL...BLIZZARD WARNING FROM 6 PM THIS EVENING TO NOON CST WEDNESDAY
FOR ILZ075>078-080>094.
IN...BLIZZARD WARNING FROM 6 PM THIS EVENING TO NOON CST WEDNESDAY
FOR INZ081-082-085>088.
&&
$$
UPDATE...MY
SHORT TERM...DRS
LONG TERM....KH
AVIATION...SMITH
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
125 PM EST TUE DEC 25 2012
.UPDATE...
ISSUED AT 1100 AM EST TUE DEC 25 2012
INCREASED CLOUD COVER...AS MUCH OF THE CWA REMAINS UNDER A THICK
LAYER OF CLOUDS. THE ONLY SIGNIFICANT POCKETS OF CLEARING ARE OVER S
CENTRAL AND OVER FAR W LAKE SUPERIOR. ALSO INCREASED POPS N CENTRAL
GIVEN THE SLOWER THAN ANTICIPATED CLEARING AND RADAR ESTIMATED
SNOWFALL OF A QUARTER TO HALF AN INCH NEAR SAW OVER THE PAST HOUR.
&&
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 509 AM EST TUE DEC 25 2012
LATEST 09Z WV IMAGERY AND RUC ANALYSIS SHOWS A SHORTWAVE TROUGH
EXITING EAST OF THE UPPER GREAT LAKES. THIS SHORTWAVE LIKELY
PROVIDED SOME WEAK ENHANCEMENT TO LES BANDS OVER ALGER COUNTY
EARLIER THIS MORNING. LATEST MQT RADAR LOOP SHOWS AN ILL-DEFINED
DOMINANT LES BAND NEAR SHOT POINT BUT OTHERWISE RETURNS ON RADAR
WOULD JUST SUGGEST LITTLE MORE THAN FLURRIES ACROSS THE REST OF THE
NCNTRL FCST AREA.
LES SHOULD CONTINUE TO BE ON THE WANE THIS CHRISTMAS DAY AS FLOW
BCMS INCREASINGLY ANTICYCLONIC AND INCREASING SUBSIDENCE LOWERS
INVERSION HGTS TO BLO 4KFT. HAVE THIS WELL DEPICTED WITH DECREASING
TREND IN POP GRIDS THRU THE DAY. SNOWFALL INTENSITY/AMOUNTS WILL
REMAIN GREATEST OVER THE EAST WHERE AN ADDITIONAL INCH MAY
ACCUMULATE. MAY ALSO SEE AN ADDITIONAL INCH NEAR TWIN LAKES AREA IN
HOUGHTON COUNTY WHERE FOCUSED LOW-LVL CONVERGENCE COULD PROVIDE
LOCALIZED BOOST IN SNOW AMOUNTS.
LARGE SCALE ANTICYCLONIC FLOW...LOW INVERSION HGTS AOB 4KFT AND
INFLUX OF DRY AIR BLO INVERSION WILL ALL WORK TO KEEP LES AMOUNTS IN
CHECK TONIGHT. AGAIN THERE COULD BE SOME LOCALIZED ONE INCH
ACCUMULATIONS OVER ALGER AND NRN LUCE COUNTIES AND NEAR TWIN LAKES
IN HOUGHTON COUNTY WHERE DEVELOPING LAND BREEZES WILL AID LOW-LVL
CONVERGENCE. TAKING ALL FACTORS INTO CONSIDERATION...ONLY LOW CHC
POPS WILL BE JUSTIFIED.
TONIGHT SHOULD BE ONE OF THE COLDEST IN A WHILE...WITH A FEW
LOCATIONS OVER INTERIOR W PORTIONS OF UPPER MI FALLING BELOW ZERO
THANKS TO SHORTWAVE RDGG AND ASSOC INCREASING SUBSIDENCE/Q-VECT DIV
ALLOWING FOR LOW CLOUDS TO CLEAR OUT OVER INTERIOR LOCATIONS.
.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 509 AM EST TUE DEC 25 2012
NO BIG STORMS ARE ON THE HORIZON THROUGH THE END OF THE YEAR. WITH
85H TEMPS IN THE -10 TO -12 C RANGE...LIGHT NORTH NORTHEASTERLY
WINDS BETWEEN HIGH PRESSURE OVER ONTARIO AND SURFACE LOW MOVING UP
THE NORTHEAST COAST...AND INVERSION HEIGHTS GENERALLY AROUND
5KFT...EXPECT LIGHT LAKE EFFECT SNOW SHOWERS TO PERSIST NEAR LAKE
SUPERIOR THOUGH THURSDAY.
NORTHERN STREAM SHORTWAVE ENERGY WILL CARVE OUT AN UPPER TROUGH OVER
THE UPPER GREAT LAKES THIS WEEKEND. NET RESULT WILL BE A CHANCE FOR
SOME VERY LIGHT SYNOPTIC SNOW FRIDAY INTO SATURDAY AS SURFACE LOW
MOVES NORTH OF LAKES SUPERIOR. THEN...LOWERING 85H TEMPS WILL BRING
PERSISTENT LIGHT LAKE EFFECT SNOW SHOWERS TO NORTHWESTERLY WIND
FAVORED AREAS THROUGH THE END OF THE YEAR.
DAYTIME TEMPS WILL BE CLOSE TO NORMAL THROUGH THE END OF THE WEEK
BUT WITH PERSISTENT CLOUD COVER...ESPECIALLY NEAR LAKE SUPERIOR...
OVERNIGHT LOWS WILL CONTINUE TO RUN ABOVE NORMAL.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 124 PM EST TUE DEC 25 2012
PLENTY OF MOISTURE AND LIGHT WINDS AOB 5KTS UNDER A STRONG INVERSION
AROUND 4KFT LATE TONIGHT THROUGH WEDNESDAY MORNING COULD RESULT IN
LOWER VIS BR/SHSN CENTERED AROUND DAYBREAK AT CMX. HOWEVER...WILL
NOT JUMP ON THIS FCST QUITE YET...GIVEN THE LOW
PROBABILITY/PREDICTABILITY. MVFR CEILINGS AND OCCASIONAL VIS WILL BE
THE RULE FOR MUCH OF THE PERIOD THANKS TO THE LIKE NW FLOW OFF LAKE
SUPERIOR. SAW MAY BREAK OUT TO SCT BY THIS EVENING AS DRY AIR
CONTINUES TO WORK IN FROM S CENTRAL UPPER MI...WITH MVFR CEILINGS
RETURNING AGAIN BEFORE DAYBREAK. WINDS WILL BECOME LIGHT AND NNE
OVER W LAKE SUPERIOR BY WEDNESDAY MORNING...CUTTING OFF/ENDING MUCH
OF THE SNOW SHOWERS OVER CMX AND IWD...BUT WITH LOWERED CEILINGS/VIS
AND SAW THANKS TO UPSLOPE SNOW SHOWERS AND FLURRIES.
&&
.MARINE...(FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 509 AM EST TUE DEC 25 2012
A HIGH PRESSURE RIDGE CONTINUING TO BUILD IN FROM THE CANADIAN
PRAIRIES WILL PERSIST THROUGH MUCH OF THE WEEK...KEEPING WINDS AT OR
BELOW 25 KNOTS.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
UPDATE...KF
SHORT TERM...VOSS
LONG TERM...MZ
AVIATION...KF
MARINE...VOSS
AREA FORECAST DISCUSSION
NWS BURLINGTON VT
328 PM EST TUE DEC 25 2012
.SYNOPSIS...
HIGH PRESSURE MOVES INTO THE NORTH COUNTRY WEDNESDAY. A NOREASTER
WILL IMPACT THE REGION WEDNESDAY NIGHT THROUGH THURSDAY NIGHT WITH
THE FIRST SIGNFICANT SNOW STORM OF THE YEAR. MAINLY SNOW FOR
NORTHERN NEW YORK AND NORTHERN VERMONT WITH A POSSIBLE WINTRY MIX AT
TIMES FOR SOUTHERN AND EASTERN VERMONT. SNOW AND SNOW SHOWERS WILL
CONTINUE THROUGH FRIDAY MORNING IN THE NORTHERN MOUNTAINS.
&&
.NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/...
AS OF 323 PM EST TUESDAY...GRADUAL CLEARING WILL CONT THIS EVENING AND
OVERNIGHT WITH DEWPOINTS IN THE SINGLE NUMBERS AND FRESH SNOW
COVER..MIN T WILL BE MAINLY SINGLE NUMBERS AND MAY HAVE NOT GONE
COLD ENUF FOR ADRNDKS/NE VT...ALL BASED ON CLD COVER.
&&
.SHORT TERM /7 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
AS OF 323 PM EST TUESDAY... RIDGE OF HIGH PRESSURE ACROSS QUEBEC
AND ONTARIO NOSING INTO THE NORTH COUNTRY WILL RETREAT SLIGHTLY
DURING WEDNESDAY.
A STRONG CUT-OFF SHORTWAVE LIFTS NE ACROSS OHIO RIVER VALLEY WED
NGT AND OVER NEW ENGLAND ON THU IN A NEG TILT ORIENTATION. SFC LOW
PRESSURE MOVES FROM TENNESSEE VALLEY WED TO ALG OR JUST OFFSHORE OF
NEW JERSEY THU MRNG AND THEN NEAR OR OVER CAPE COD THU. H7 LOW IN
FAVORABLE TRACK FOR MAJOR SNOWFALL ACRS FA BUT SOMEWHAT
MARGINAL/MILDER TEMPERATURES JUST S/E ALG WITH FLOW OFF THE
ATLANTIC TRIES TO INTRODUCE SOME LOW-MID LVL WARMING FOR SRN/ERN
VT.
NWP MODELS ALL IN GOOD AGREEMENT WITH NAM12 THE MILDER MODEL BUT
EVEN WENT COOLER ON THE 12Z RUN. PRIMARILY A HEAVY SNOWFALL EVENT
WITH SOME MIX OR BRIEF CHANGE TO SLEET FOR SRN HALF OF VT AND ERN
VT AS WELL.
STRONG H8 JET (70KTS) MOVING ACRS FA WITH ITS CORE ACRS SRN AND ERN
VT WILL ALLOW FOR SOME SHADOWING AND UPSLOPE EFFECTS WHICH MAY
ACCOUNT FOR WIDE RANGES IN SNOWFALL AMTS. H925 JET OF 40-45 KTS
MAINLY ACRS SRN VT WILL RAISE SOME CONCERNS OF SOME DOWNSLOPING
WINDS BUT THE INVERSION APPEARS JUST ABOVE MOUNTAIN RIDGES.
ATTM...SCNDRY THREAT THAT CAN BE FOCUSED IN LATER FCSTS BUT WIND
GUSTS 35-40 MPH FOR A BRIEF PERIOD POSSIBLE.
AGAIN...TRIED TO INCORPORATE UPSLOPE/DOWNSLOPE CONSIDERATIONS AND A
BLEND OF NAM12/SREF/GFS/ECMWF. SOME OF THE MDLS ARE PERSISTENT WITH
MUCH HEAVIER QPF IN ST LWRNC VLY (1.5-2 INCHES) BUT HAVE ADJUSTED
DOWN. IN THE END...GENERALLY AROUND AN INCH OF QPF WITH THE
FOLLOWING EXCEPTIONS...LOWER (0.6-0.8) IN SRN WESTERN SLOPES AND NE
VT ALONG WITH SOME DOWNSLOPING IN WRN ADRNDKS WHILE HIGHER QPF
(1-1.25) ALONG ERN SLOPES OF SRN GREENS AND SE ADRNDKS.
I/M HANGING ONTO PCPN FOR NRN MTNS THU NGT AND GRADUALLY ENDING FRI
MRNG. THE MAIN ACCUM PRIOR TO 00Z FRI BUT ADDTNL UPSLOPE FOR WRN
SLOPES OF GREENS AND NE VT WHERE WILL HAVE EXPERIENCED ERLR
SHADOWING.
IN THE END...GENERAL 10-15 INCHES WITH SLIGHT LOWER FOR NE VT...ST
LWRNC VLY AND SRN GREENS WITH THE HIGHER AMTS AS MENTIONED ERLR IN
FAVORED SE UPSLOPE REGIONS.
OF NOTE...IT HAS BEEN 658 DAYS SINCE THE LAST 6+" SNOWSTORM AT BTV
(3/7/11) AND THIS WILL LIKELY BREAK THAT STREAK.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 350 PM EST TUESDAY...OVERALL ACTIVE WX PATTERN CONTS WITH
ADDITIONAL CHCS FOR SNOW OVER THE WKND INTO EARLY NEXT WK.
HOWEVER...LATEST TRENDS IN GUIDANCE SHOW LIMITED PHASING FOR
WEEKEND SYSTEM...WHICH WL KEEP BEST DEEP LAYER MOISTURE/LIFT TO
OUR SOUTH AND EAST...ASSOCIATED WITH SFC LOW TRACKING SOUTHEAST OF
THE BENCHMARK. STILL PLENTY OF UNCERTAINTY AS S/W ENERGY EJECTS
FROM WESTERN TROF...AS MODELS TEND TO PERFORM POORLY IN THE
WESTERN MTNS IN THE DAY 4 THRU 6 PERIOD. STILL ANTICIPATING SOME
LIGHT SNOW ASSOCIATED WITH MID/UPPER LVL TROF AND LEFTOVER 850 TO
500MB RH IN TROF AXIS FOR LATE SAT INTO SUN. OTHERWISE...DEEP
CYCLONIC FLW DEVELOPS AS LOW PRES INTENSIFIES ACRS THE CANADIAN
MARITIMES. THIS WL PUSH MUCH COLDER TEMPS ACRS OUR CWA FOR EARLY
NEXT WEEK...ALONG WITH A CHC FOR MAINLY MTN SNOW SHOWERS. BASED ON
EXPECTED FRESH SNOW COVER AND COOL NORTHERLY FLW...WL CUT MACHINE
NUMBERS BY SEVERAL DEGREES THRU THE PERIOD. THINKING MAINLY 20S
FOR THE WEEKEND...BUT HIGHS FALLING BACK INTO THE TEENS AND LOWER
20S NEXT WK...WITH LOWS NEAR NORMAL.
&&
.AVIATION /21Z TUESDAY THROUGH SUNDAY/...
THROUGH 18Z WEDNESDAY...AVIATION CHALLENGE THRU 18Z WEDS WL
POTENTIAL FOR LOW CLOUDS AND IFR CONDITIONS AT BTV/MPV/SLK/RUT.
SFC ANALYSIS SHOWS LIGHT SNOW FROM THIS MORNING...QUICKLY
DISSIPATING WITH SFC HIGH PRES BUILDING INTO OUR NORTHERN TAF
SITES. THIS HAS RESULTED IN CLRING SKIES AND DRIER AIR TO ADVECT
INTO THE REGION WITH SFC DWPTS IN THE SINGLE DIGITS. QUESTION
TONIGHT WL BE AMOUNT OF LLVL MOISTURE IN MODIFIED ARCTIC AIRMASS
AND POTENTIAL FOR CLOUDS. NAM12 AND RAP SOUNDINGS SHOW LLVL RH
DEVELOPING ACRS BTV/SLK/MPV THIS EVENING...WITH POTENTIAL FOR IFR
CIGS. GIVEN SOME CLOUDS UPSTREAM AND SOUNDINGS SHOWING GOOD RH
BTWN SFC AND 800MB...EXPECT SOME LOW CLOUDS WITH A FEW FLURRIES
POSSIBLE AT MPV/SLK/BTV...WL USE TEMPO GROUP TO COVER MVFR TO
POTENTIALLY IFR CONDITIONS OVERNIGHT...ESPECIALLY AT SLK.
OTHERWISE...MSS/RUT/PBG SHOULD STAY VFR THRU 18Z WEDS.
OUTLOOK 18Z WEDNESDAY THROUGH SATURDAY...
SIGNIFICANT STORM WL HAVE MAJOR IMPACTS ON THE AVIATION COMMUNITY
FROM 06Z THURS THRU 12Z FRIDAY WITH LONG DURATIONS OF IFR/LIFR IN
PERIODS OF MODERATE TO HEAVY SNOW AND LOW CIGS. SOME SLEET WL BE
POSSIBLE AT RUT/MPV ON THURSDAY...WITH EASTERLY WIND GUSTS TO 45
MPH POSSIBLE AT RUT. THESE GUSTY WINDS WL CREATE AREAS OF BLOWING
SNOW AND TURBULENCE AT ALL SITES...ESPECIALLY ON THURSDAY ASSOCIATED
WITH A LLVL JET OF 40 TO 60 KNTS. FLYING CONDITIONS WL SLOWLY
IMPROVE ON FRIDAY AFTN...WITH VFR CONDITIONS LIKELY BY FRIDAY
NIGHT AND SATURDAY.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...WINTER STORM WARNING FROM 7 PM WEDNESDAY TO 7 AM EST FRIDAY
FOR VTZ001>012-016>019.
NY...WINTER STORM WARNING FROM 7 PM WEDNESDAY TO 7 AM EST FRIDAY
FOR NYZ026>031-034-035-087.
&&
$$
SYNOPSIS...SLW
NEAR TERM...SLW
SHORT TERM...SLW
LONG TERM...TABER
AVIATION...TABER
AREA FORECAST DISCUSSION
NWS BURLINGTON VT
323 PM EST TUE DEC 25 2012
.SYNOPSIS...
A WEAK UPPER LEVEL DISTURBANCE WILL BRING SOME LIGHT SNOW TO
PORTIONS OF THE NORTH COUNTRY ON THIS CHRISTMAS MORNING. FAIR AND
SEASONABLY COLD CONDITIONS ARE EXPECTED TONIGHT AND WEDNESDAY. A
NOR EASTER WILL AFFECT THE REGION WITH HEAVY SNOW WEDNESDAY NIGHT
AND THURSDAY. THIS WILL RESULT IN SIGNIFICANT TRAVEL IMPACTS WITH
SNOW COVERED ROADS AND LOW VISIBILITY...AND THE POTENTIAL FOR
HEAVY SNOW ACCUMULATION ACROSS THE NORTH COUNTRY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 942 AM EST TUESDAY...VERY SIMILAR TO LAST UPDATE.
FORECAST PRETTY MUCH ON TRACK. WITH LATEST UPDATE...ONLY MINOR
ADJUSTMENTS TO HOURLY PARAMETERS FOR THIS MORNING TO REFLECT
LATEST CONDITIONS AND TRENDS. SOME LIGHT SNOW FALLING ACROSS
PORTIONS OF THE FORECAST AREA ON THIS CHRISTMAS MORNING. RADAR
LOOKS A BIT MORE OMINOUS THAN WHAT IS BEING REPORTED ON OBS...AS
LOW LEVELS QUITE DRY IN ADVANCE OF THE PRECIPITATION. STILL
LOOKING AT ONLY LIGHT ACCUMULATIONS WITH A DUSTING TO 2 INCHES
EXPECTED...MAINLY SOUTH.
PREVIOUS DISCUSSION...
AN UPPER LEVEL DISTURBANCE MOVING EAST FROM THE GREAT LAKES WILL
BRING SOME LIGHT SNOW TO PORTIONS OF THE FORECAST AREA THIS
MORNING. WEAK SURFACE LOW ASSOCIATED WITH THE DISTURBANCE WILL
PASS SOUTH OF NEW ENGLAND THROUGH MIDDAY. BEST CHANCE FOR SEEING
AN INCH OR TWO OF SNOW ACCUMULATION WILL BE OVER SOUTHERN PORTIONS
OF THE AREA...WHILE JUST A DUSTING IS EXPECTED ACROSS THE FAR
NORTHERN TIER OF ZONES. AS BOTH THE UPPER LEVEL SHORTWAVE AND
SURFACE DISTURBANCE MOVE EAST OF THE REGION THIS AFTERNOON...THE
CHANCES FOR LIGHT SNOW WILL DIMINISH...ALTHOUGH SKIES WILL REMAIN
GENERALLY CLOUDY. MAX TEMPS EXPECTED TO BE IN MOSTLY IN THE 20S.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
AS OF 502 AM EST TUESDAY...SHORT-TERM PERIOD BEGINS QUIET...BUT ENDS
WITH THE A SIGNIFICANT NOR`EASTER WHICH IS LIKELY TO BRING A HEAVY
SNOWFALL TO THE REGION BEGINNING WEDNESDAY NIGHT.
A RIDGE OF HIGH PRESSURE BUILDS INTO THE REGION FROM THE NORTHWEST
TONIGHT AND THRU THE DAY WEDNESDAY BRINGING DRY WEATHER AND
SEASONABLY COLD TEMPERATURES TO THE NORTH COUNTRY. AMOUNT OF
CLEARING WE SEE TONIGHT IS IN QUESTION...AS SOME MODEL SOUNDINGS
INDICATING AN ABUNDANCE OF LOW LEVEL MOISTURE OVER THE REGION.
HAVE GONE WITH A FORECAST OF PARTLY CLOUDY...AND RAISED TEMPS A
FEW DEGREES FROM MOS GUIDANCE NUMBERS. EXPECT LOWS IN THE SINGLE
NUMBERS AND TEENS. LOOK FOR A CONTINUATION OF PARTLY CLOUDY SKIES
DURING WEDNESDAY...ALTHOUGH AN INCREASE IN CLOUDS CAN BE EXPECTED
LATER IN THE DAY.
NWP MODELS ALL IN GOOD AGREEMENT WITH LOW PRESSURE OVER THE
TENNESSEE VALLEY WEDNESDAY REDEVELOPING ALONG MID-ATLANTIC COAST
AT 00Z THURSDAY...LIFTING NNEWD ALONG THE NEW JERSEY COAST BY 12Z
THURSDAY. STRONG NEGATIVE TILT 500MB WAVE DRAWS SIGNIFICANT MOISTURE
NORTHWARD INTO THE FORECAST AREA WITH STRONG SYNOPTIC ASCENT
BEGINNING AFTER MIDNIGHT. ONCE SNOW DEVELOPS...IT APPEARS FROM MODEL
SOUNDINGS THAT INTENSITY WILL INCREASE QUICKLY WITH SNOW BECOMING
HEAVY AT TIMES WITH STRONG UVV AND DENDRITE SNOW GROWTH. HAVE
CONTINUED WITH PREVIOUS THINKING OF HEAVY SNOW DEVELOPING LATE
WEDNESDAY NIGHT...WITH SEVERAL INCHES OF SNOW ON THE GROUND BY
DAYBREAK THURSDAY. PERIOD OF HEAVIEST PRECIPITATION CONTINUES
THROUGH ABOUT 18Z THURSDAY...THEN BEGINS TO DIMINISH AS SURFACE LOW
REACHES GULF OF MAINE BY THURSDAY EVENING. BY NIGHTFALL...EXPECT
SNOW ACCUMULATIONS OF 8 TO 13 INCHES ACROSS MUCH OF THE REGION.
HAVE GONE WITH 12:1-14:1 SNOW RATIO...WHICH IS COMMON FOR THESE
TYPES OF SYSTEMS WITH E-SE 850MB FETCH ACROSS THE REGION.
ALTHOUGH MOST MODELS ARE IN GOOD AGREEMENT REGARDING THE STORM
TRACK...IT SHOULD BE NOTED THAT THE NAM HAS CONTINUED WITH A TRACK A
BIT FURTHER WEST...WHICH IF PROVEN CORRECT COULD POSE SOME PROBLEMS.
THE RESULT WOULD BE POTENTIALLY STRONG GUSTY WINDS...ESPECIALLY
ALONG THE WEST WESTERN SLOPES OF THE GREEN MOUNTAINS. IT WOULD
ALSO ALLOW FOR MORE MIXED PRECIPITATION ACROSS MUCH OF VERMONT.
THE MIXTURE COMBINED WITH SHADOWING WOULD LIKELY REDUCE SNOW
AMOUNTS SIGNIFICANTLY FROM THE GOING FORECAST. SO CONFIDENCE NOT
THE GREATEST IN THE FORECAST DETAILS...ESPECIALLY FOR SOUTHERN AND
EASTERN VERMONT. IN ANY EVENT THOUGH...IT WILL BE A SIGNIFICANT
STORM WITH MAJOR IMPACTS TO THE ENTIRE FORECAST AREA.
OF NOTE...IT HAS BEEN 658 DAYS SINCE THE LAST 6+" SNOWSTORM AT BTV
(3/7/11) AND THIS WILL LIKELY BREAK THAT STREAK.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 350 PM EST TUESDAY...OVERALL ACTIVE WX PATTERN CONTS WITH
ADDITIONAL CHCS FOR SNOW OVER THE WKND INTO EARLY NEXT WK.
HOWEVER...LATEST TRENDS IN GUIDANCE SHOW LIMITED PHASING FOR
WEEKEND SYSTEM...WHICH WL KEEP BEST DEEP LAYER MOISTURE/LIFT TO
OUR SOUTH AND EAST...ASSOCIATED WITH SFC LOW TRACKING SOUTHEAST OF
THE BENCHMARK. STILL PLENTY OF UNCERTAINTY AS S/W ENERGY EJECTS
FROM WESTERN TROF...AS MODELS TEND TO PERFORM POORLY IN THE
WESTERN MTNS IN THE DAY 4 THRU 6 PERIOD. STILL ANTICIPATING SOME
LIGHT SNOW ASSOCIATED WITH MID/UPPER LVL TROF AND LEFTOVER 850 TO
500MB RH IN TROF AXIS FOR LATE SAT INTO SUN. OTHERWISE...DEEP
CYCLONIC FLW DEVELOPS AS LOW PRES INTENSIFIES ACRS THE CANADIAN
MARITIMES. THIS WL PUSH MUCH COLDER TEMPS ACRS OUR CWA FOR EARLY
NEXT WEEK...ALONG WITH A CHC FOR MAINLY MTN SNOW SHOWERS. BASED ON
EXPECTED FRESH SNOW COVER AND COOL NORTHERLY FLW...WL CUT MACHINE
NUMBERS BY SEVERAL DEGREES THRU THE PERIOD. THINKING MAINLY 20S
FOR THE WEEKEND...BUT HIGHS FALLING BACK INTO THE TEENS AND LOWER
20S NEXT WK...WITH LOWS NEAR NORMAL.
&&
.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
THROUGH 18Z WEDNESDAY...AVIATION CHALLENGE THRU 18Z WEDS WL
POTENTIAL FOR LOW CLOUDS AND IFR CONDITIONS AT BTV/MPV/SLK/RUT.
SFC ANALYSIS SHOWS LIGHT SNOW FROM THIS MORNING...QUICKLY
DISSIPATING WITH SFC HIGH PRES BUILDING INTO OUR NORTHERN TAF
SITES. THIS HAS RESULTED IN CLRING SKIES AND DRIER AIR TO ADVECT
INTO THE REGION WITH SFC DWPTS IN THE SINGLE DIGITS. QUESTION
TONIGHT WL BE AMOUNT OF LLVL MOISTURE IN MODIFIED ARCTIC AIRMASS
AND POTENTIAL FOR CLOUDS. NAM12 AND RAP SOUNDINGS SHOW LLVL RH
DEVELOPING ACRS BTV/SLK/MPV THIS EVENING...WITH POTENTIAL FOR IFR
CIGS. GIVEN SOME CLOUDS UPSTREAM AND SOUNDINGS SHOWING GOOD RH
BTWN SFC AND 800MB...EXPECT SOME LOW CLOUDS WITH A FEW FLURRIES
POSSIBLE AT MPV/SLK/BTV...WL USE TEMPO GROUP TO COVER MVFR TO
POTENTIALLY IFR CONDITIONS OVERNIGHT...ESPECIALLY AT SLK.
OTHERWISE...MSS/RUT/PBG SHOULD STAY VFR THRU 18Z WEDS.
OUTLOOK 18Z WEDNESDAY THROUGH SATURDAY...
SIGNIFICANT STORM WL HAVE MAJOR IMPACTS ON THE AVIATION COMMUNITY
FROM 06Z THURS THRU 12Z FRIDAY WITH LONG DURATIONS OF IFR/LIFR IN
PERIODS OF MODERATE TO HEAVY SNOW AND LOW CIGS. SOME SLEET WL BE
POSSIBLE AT RUT/MPV ON THURSDAY...WITH EASTERLY WIND GUSTS TO 45
MPH POSSIBLE AT RUT. THESE GUSTY WINDS WL CREATE AREAS OF BLOWING
SNOW AND TURBULENCE AT ALL SITES...ESPECIALLY ON THURSDAY ASSOCIATED
WITH A LLVL JET OF 40 TO 60 KNTS. FLYING CONDITIONS WL SLOWLY
IMPROVE ON FRIDAY AFTN...WITH VFR CONDITIONS LIKELY BY FRIDAY
NIGHT AND SATURDAY.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...WINTER STORM WARNING FROM 7 PM WEDNESDAY TO 7 AM EST FRIDAY
FOR VTZ001>012-016>019.
NY...WINTER STORM WARNING FROM 7 PM WEDNESDAY TO 7 AM EST FRIDAY
FOR NYZ026>031-034-035-087.
&&
$$
SYNOPSIS...RJS
NEAR TERM...RJS/SLW
SHORT TERM...RJS
LONG TERM...TABER
AVIATION...TABER
AREA FORECAST DISCUSSION
NWS BURLINGTON VT
1254 PM EST TUE DEC 25 2012
.SYNOPSIS...
A WEAK UPPER LEVEL DISTURBANCE WILL BRING SOME LIGHT SNOW TO
PORTIONS OF THE NORTH COUNTRY ON THIS CHRISTMAS MORNING. FAIR AND
SEASONABLY COLD CONDITIONS ARE EXPECTED TONIGHT AND WEDNESDAY. A
NOR EASTER WILL AFFECT THE REGION WITH HEAVY SNOW WEDNESDAY NIGHT
AND THURSDAY. THIS WILL RESULT IN SIGNIFICANT TRAVEL IMPACTS WITH
SNOW COVERED ROADS AND LOW VISIBILITY...AND THE POTENTIAL FOR
HEAVY SNOW ACCUMULATION ACROSS THE NORTH COUNTRY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 942 AM EST TUESDAY...VERY SIMILAR TO LAST UPDATE.
FORECAST PRETTY MUCH ON TRACK. WITH LATEST UPDATE...ONLY MINOR
ADJUSTMENTS TO HOURLY PARAMETERS FOR THIS MORNING TO REFLECT
LATEST CONDITIONS AND TRENDS. SOME LIGHT SNOW FALLING ACROSS
PORTIONS OF THE FORECAST AREA ON THIS CHRISTMAS MORNING. RADAR
LOOKS A BIT MORE OMINOUS THAN WHAT IS BEING REPORTED ON OBS...AS
LOW LEVELS QUITE DRY IN ADVANCE OF THE PRECIPITATION. STILL
LOOKING AT ONLY LIGHT ACCUMULATIONS WITH A DUSTING TO 2 INCHES
EXPECTED...MAINLY SOUTH.
PREVIOUS DISCUSSION...
AN UPPER LEVEL DISTURBANCE MOVING EAST FROM THE GREAT LAKES WILL
BRING SOME LIGHT SNOW TO PORTIONS OF THE FORECAST AREA THIS
MORNING. WEAK SURFACE LOW ASSOCIATED WITH THE DISTURBANCE WILL
PASS SOUTH OF NEW ENGLAND THROUGH MIDDAY. BEST CHANCE FOR SEEING
AN INCH OR TWO OF SNOW ACCUMULATION WILL BE OVER SOUTHERN PORTIONS
OF THE AREA...WHILE JUST A DUSTING IS EXPECTED ACROSS THE FAR
NORTHERN TIER OF ZONES. AS BOTH THE UPPER LEVEL SHORTWAVE AND
SURFACE DISTURBANCE MOVE EAST OF THE REGION THIS AFTERNOON...THE
CHANCES FOR LIGHT SNOW WILL DIMINISH...ALTHOUGH SKIES WILL REMAIN
GENERALLY CLOUDY. MAX TEMPS EXPECTED TO BE IN MOSTLY IN THE 20S.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
AS OF 502 AM EST TUESDAY...SHORT-TERM PERIOD BEGINS QUIET...BUT ENDS
WITH THE A SIGNIFICANT NOR`EASTER WHICH IS LIKELY TO BRING A HEAVY
SNOWFALL TO THE REGION BEGINNING WEDNESDAY NIGHT.
A RIDGE OF HIGH PRESSURE BUILDS INTO THE REGION FROM THE NORTHWEST
TONIGHT AND THRU THE DAY WEDNESDAY BRINGING DRY WEATHER AND
SEASONABLY COLD TEMPERATURES TO THE NORTH COUNTRY. AMOUNT OF
CLEARING WE SEE TONIGHT IS IN QUESTION...AS SOME MODEL SOUNDINGS
INDICATING AN ABUNDANCE OF LOW LEVEL MOISTURE OVER THE REGION.
HAVE GONE WITH A FORECAST OF PARTLY CLOUDY...AND RAISED TEMPS A
FEW DEGREES FROM MOS GUIDANCE NUMBERS. EXPECT LOWS IN THE SINGLE
NUMBERS AND TEENS. LOOK FOR A CONTINUATION OF PARTLY CLOUDY SKIES
DURING WEDNESDAY...ALTHOUGH AN INCREASE IN CLOUDS CAN BE EXPECTED
LATER IN THE DAY.
NWP MODELS ALL IN GOOD AGREEMENT WITH LOW PRESSURE OVER THE
TENNESSEE VALLEY WEDNESDAY REDEVELOPING ALONG MID-ATLANTIC COAST
AT 00Z THURSDAY...LIFTING NNEWD ALONG THE NEW JERSEY COAST BY 12Z
THURSDAY. STRONG NEGATIVE TILT 500MB WAVE DRAWS SIGNIFICANT MOISTURE
NORTHWARD INTO THE FORECAST AREA WITH STRONG SYNOPTIC ASCENT
BEGINNING AFTER MIDNIGHT. ONCE SNOW DEVELOPS...IT APPEARS FROM MODEL
SOUNDINGS THAT INTENSITY WILL INCREASE QUICKLY WITH SNOW BECOMING
HEAVY AT TIMES WITH STRONG UVV AND DENDRITE SNOW GROWTH. HAVE
CONTINUED WITH PREVIOUS THINKING OF HEAVY SNOW DEVELOPING LATE
WEDNESDAY NIGHT...WITH SEVERAL INCHES OF SNOW ON THE GROUND BY
DAYBREAK THURSDAY. PERIOD OF HEAVIEST PRECIPITATION CONTINUES
THROUGH ABOUT 18Z THURSDAY...THEN BEGINS TO DIMINISH AS SURFACE LOW
REACHES GULF OF MAINE BY THURSDAY EVENING. BY NIGHTFALL...EXPECT
SNOW ACCUMULATIONS OF 8 TO 13 INCHES ACROSS MUCH OF THE REGION.
HAVE GONE WITH 12:1-14:1 SNOW RATIO...WHICH IS COMMON FOR THESE
TYPES OF SYSTEMS WITH E-SE 850MB FETCH ACROSS THE REGION.
ALTHOUGH MOST MODELS ARE IN GOOD AGREEMENT REGARDING THE STORM
TRACK...IT SHOULD BE NOTED THAT THE NAM HAS CONTINUED WITH A TRACK A
BIT FURTHER WEST...WHICH IF PROVEN CORRECT COULD POSE SOME PROBLEMS.
THE RESULT WOULD BE POTENTIALLY STRONG GUSTY WINDS...ESPECIALLY
ALONG THE WEST WESTERN SLOPES OF THE GREEN MOUNTAINS. IT WOULD
ALSO ALLOW FOR MORE MIXED PRECIPITATION ACROSS MUCH OF VERMONT.
THE MIXTURE COMBINED WITH SHADOWING WOULD LIKELY REDUCE SNOW
AMOUNTS SIGNIFICANTLY FROM THE GOING FORECAST. SO CONFIDENCE NOT
THE GREATEST IN THE FORECAST DETAILS...ESPECIALLY FOR SOUTHERN AND
EASTERN VERMONT. IN ANY EVENT THOUGH...IT WILL BE A SIGNIFICANT
STORM WITH MAJOR IMPACTS TO THE ENTIRE FORECAST AREA.
OF NOTE...IT HAS BEEN 658 DAYS SINCE THE LAST 6+" SNOWSTORM AT BTV
(3/7/11) AND THIS WILL LIKELY BREAK THAT STREAK.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 350 AM EST TUESDAY...SURFACE LOW PRESSURE WILL BE LOCATED
JUST NORTHEAST OF CAPE COD BY 00Z FRIDAY...SHIFTING NORTHEAST
INTO THE GULF OF MAINE THROUGH THE NIGHT. THE COMBINATION OF
ABUNDANT LOW LEVEL MOISTURE AND SURFACE/MID-LEVEL WINDS SHIFTING
TO THE NORTH/NORTHWEST WILL CREATE A FAVORABLE ENVIRONMENT FOR
CONTINUED MODERATE SNOW ACROSS THE REGION...ESPECIALLY ACROSS THE
FAVORED UPSLOPE LOCALES ALONG THE WESTERN SLOPES OF THE NORTHERN
GREEN MOUNTAINS AND NORTHERN ADIRONDACKS. ADDITIONAL SNOWFALL
AMOUNTS OF 2-3" ARE LIKELY THURSDAY NIGHT...WITH STORM TOTALS
ACROSS THE REGION LOOKING TO BE IN THE 10-16" RANGE BY FRIDAY
MORNING WITH LOCALIZED HIGHER AMOUNTS ACROSS THE HIGHER
ELEVATIONS.
12-18Z FRIDAY...SURFACE LOW RACES NORTHEAST TO THE GULF OF SAINT
LAWRENCE AND OVER NEWFOUNDLAND DRAGGING THE BULK OF LOW/MID LEVEL
MOISTURE ALONG WITH IT. THUS...SOME LINGERING SNOW SHOWERS ARE
POSSIBLE ACROSS NORTHEAST PORTIONS OF THE AREA...BUT SHOULD BE
FAIRLY LIGHT AND TAPERING OFF BY THE AFTERNOON AS SURFACE HIGH
PRESSURE BEGINS TO BUILD INTO THE NORTHEAST. THIS SURFACE HIGH
REMAINS OVER THE REGION THROUGH SATURDAY WITH GENERALLY DRY
CONDITIONS EXPECTED. UPPER FLOW REMAINS FAIRLY ZONAL THROUGH THIS
PERIOD WITH SEVERAL WEAK EMBEDDED VORTS MOVING THROUGH THE FLOW SO
WHILE HIGH PRESSURE WILL BE OVER THE REGION AT THE SURFACE...EXPECT
SKIES TO REMAIN PRETTY CLOUDY THROUGH THIS TIME-FRAME.
NEXT SYSTEM IN LINE TO AFFECT THE NORTHEAST COMES SATURDAY NIGHT AS
A POTENT UPPER TROUGH MOVING OUT OF THE MIDWEST DEVELOPS SURFACE LOW
PRESSURE OFF THE CAROLINA COAST. LATEST LONG RANGE MODELS OF THE
ECMWF AND GFS ARE IN GOOD AGREEMENT SHOWING THIS LOW STAYING SOUTH
OF THE FORECAST AREA THOUGH...AND MAINLY AFFECTING THE MID-
ATLANTIC STATES WITH MAYBE SOME LIGHT SNOW ACCUMULATIONS ACROSS
FAR SOUTHERN VERMONT.
BEYOND THE WEEKEND...LARGE SCALE TROUGH REMAINS OVER THE REGION WITH
BELOW NORMAL TEMPERATURES AND A CHANCE FOR SNOW SHOWERS EXPECTED.
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
THROUGH 18Z WEDNESDAY...AVIATION CHALLENGE THRU 18Z WEDS WL
POTENTIAL FOR LOW CLOUDS AND IFR CONDITIONS AT BTV/MPV/SLK/RUT.
SFC ANALYSIS SHOWS LIGHT SNOW FROM THIS MORNING...QUICKLY
DISSIPATING WITH SFC HIGH PRES BUILDING INTO OUR NORTHERN TAF
SITES. THIS HAS RESULTED IN CLRING SKIES AND DRIER AIR TO ADVECT
INTO THE REGION WITH SFC DWPTS IN THE SINGLE DIGITS. QUESTION
TONIGHT WL BE AMOUNT OF LLVL MOISTURE IN MODIFIED ARCTIC AIRMASS
AND POTENTIAL FOR CLOUDS. NAM12 AND RAP SOUNDINGS SHOW LLVL RH
DEVELOPING ACRS BTV/SLK/MPV THIS EVENING...WITH POTENTIAL FOR IFR
CIGS. GIVEN SOME CLOUDS UPSTREAM AND SOUNDINGS SHOWING GOOD RH
BTWN SFC AND 800MB...EXPECT SOME LOW CLOUDS WITH A FEW FLURRIES
POSSIBLE AT MPV/SLK/BTV...WL USE TEMPO GROUP TO COVER MVFR TO
POTENTIALLY IFR CONDITIONS OVERNIGHT...ESPECIALLY AT SLK.
OTHERWISE...MSS/RUT/PBG SHOULD STAY VFR THRU 18Z WEDS.
OUTLOOK 18Z WEDNESDAY THROUGH SATURDAY...
SIGNIFICANT STORM WL HAVE MAJOR IMPACTS ON THE AVIATION COMMUNITY
FROM 06Z THURS THRU 12Z FRIDAY WITH LONG DURATIONS OF IFR/LIFR IN
PERIODS OF MODERATE TO HEAVY SNOW AND LOW CIGS. SOME SLEET WL BE
POSSIBLE AT RUT/MPV ON THURSDAY...WITH EASTERLY WIND GUSTS TO 45
MPH POSSIBLE AT RUT. THESE GUSTY WINDS WL CREATE AREAS OF BLOWING
SNOW AND TURBULENCE AT ALL SITES...ESPECIALLY ON THURSDAY ASSOCIATED
WITH A LLVL JET OF 40 TO 60 KNTS. FLYING CONDITIONS WL SLOWLY
IMPROVE ON FRIDAY AFTN...WITH VFR CONDITIONS LIKELY BY FRIDAY
NIGHT AND SATURDAY.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH FRIDAY
MORNING FOR VTZ001>012-016>019.
NY...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH FRIDAY
MORNING FOR NYZ026>031-034-035-087.
&&
$$
SYNOPSIS...RJS
NEAR TERM...RJS/SLW
SHORT TERM...RJS
LONG TERM...LAHIFF
AVIATION...TABER
AREA FORECAST DISCUSSION
NWS RALEIGH NC
300 PM EST TUE DEC 25 2012
.SYNOPSIS...
WEAK HIGH PRESSURE WILL EXTEND ACROSS THE REGION TODAY THEN SHIFT
OFFSHORE BY SUNSET. A WARM FRONT AND A DEEPENING LOW PRESSURE SYSTEM
WILL APPROACH FROM THE SOUTHWEST TONIGHT. THE STRONG STORM SYSTEM
AND ACCOMPANYING COLD FRONT WILL SWEEP ACROSS THE AREA WEDNESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 945 AM TUESDAY...
WHILE FOG AND LOW CLOUDS HAVE SCOURED ACROSS MUCH OF THE CENTRAL AND
EASTERN CWA...DENSE FOG IS STILL REPORTED IN THE TRIAD...AND TRAFFIC
CAMERAS IN THE AREA SHOW MURKY CONDITIONS ALONG THE I-40 CORRIDOR.
VISIBILITIES HAVE IMPROVED IN RANDOLPH AND DAVIDSON COUNTIES...AND
THERE IS STILL A COUPLE MORE HOURS FOR THE FOG AND STRATUS TO MIX
OUT BEFORE HIGH CLOUDS BEGIN TO POUR BACK IN AHEAD OF THE STORMS
SYSTEM DEVELOPING OVER THE GULF COAST. RAP FORECAST
SOUNDINGS...WHICH SHOW MORE LOW LEVEL MOISTURE THAN WAS OBSERVED ON
THE MORNING RAOBS....SHOW THE LOW CLOUDS SCOURING IN THE TRIAD BY
AROUND NOON. WILL INCREASE CLOUD COVER IN THE NORTHWEST PIEDMONT
AND TRIM OFF A COUPLE DEGREES ON HIGHS SINCE CIRRUS WILL BE STEADILY
INCREASING EVEN AFTER THE LOW CLOUDS BURN OFF. OTHERWISE..THE
FORECAST APPEARS TO BE IN GOOD SHAPE THROUGH 00Z. HIGHS 52-61
NORTHWEST TO SOUTHEAST. -SMITH
TONIGHT...A WARM FRONT WILL DEVELOP ACROSS SC THIS EVENING IN
RESPONSE TO A POWERFUL LOW PRESSURE SYSTEM LIFTING ACROSS THE LOWER
MS VALLEY. SLY WINDS A FEW THOUSAND FEET ABOVE THE SURFACE WILL
ADVECT WARM MOIST AIR UP AND OVER THE COOL STABLE SURFACE LAYER
RESIDING OVER CENTRAL NC. THIS WILL LEAD TO THE DEVELOPMENT OF LOW
CLOUDS...EXPANDING SW-NE IN THE EVENING. ISENTROPIC LIFT WILL
INCREASE LATE THIS EVENING INTO THE OVERNIGHT CAUSING AN EXPANSIVE
AREA OF MODERATE RAINFALL TO DEVELOP. THE GREATEST RAINFALL AMOUNTS
SHOULD FALL OVER THE WESTERN PIEDMONT WHERE BEST LIFT PROJECTED TO
BE FOCUS. TEMPS WILL INITIALLY FALL WITH ONSET OF THE RAIN DUE TO
EVAPORATIVE COOLING IN THE SUB-CLOUD LAYER AFTERWHICH TEMPS WILL
STABILIZE AND MAY ACTUALLY RISE IN THE PRE-DAWN HOURS ACROSS THE
SOUTH AS THE WARM FRONT APPROACHES FROM THE SOUTH. MIN TEMPS NEAR 40
FAR NORTH TO THE MID 40S SOUTH.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY/...
AS OF 300 PM TUESDAY...
THE STORM WILL BE OFF THE JERSEY COAST THURSDAY MORNING WITH A
STRONG PRESSURE GRADIENT PRODUCING BRISK NORTHWEST BREEZE AT AROUND
15 MPH WITH GUSTS TO PERHAPS 30 MPH. ENSUING DRY AND COLD AIR
ADVECTION WILL LIMIT HIGHS TO THE MID 40S IN THE NORTHWEST TO
PERHAPS SOME LOWER 50S ACROSS THE SOUTH. WEAKENING GRADIENT WITH
SURFACE HIGH PRESSURE BUILDING IN THURSDAY NIGHT...CLEAR SKIES WILL
PRODUCE OPTIMAL RADIATIONAL COOLING WITH MINS MOSTLY IN THE UPPER
20S. THE SURFACE HIGH WILL BE OVERHEAD BRIEFLY ON FRIDAY...ALLOWING
ONLY A MODEST INCREASE IN HIGH TEMPS...MOSTLY LOWER 50S. HIGH
CLOUDINESS WILL BE ON THE INCREASE AS A 130+ KT SOUTHERLY JET
FLATTENS THE UPPER RIDGING AND TAKES AIM INTO THE MID ATLANTIC.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 300 PM TUESDAY...
MOISTURE ADVECTION WILL BE UNDERWAY IN BACKING WINDS AHEAD OF OUR
NEXT APPROACHING SYSTEM ON FRIDAY NIGHT. ISENTROPIC LIFT WILL BE
MAXIMIZED LATE FRIDAY NIGHT...AND WILL SMEAR SLIGHT CHANCE POPS
ACROSS MAINLY THE WEST AND SOUTH BY MORNING. MINS WILL BE TEMPERED
BY INCREASING CLOUDINESS AND WEAK WARM AIR ADVECTION...LOW TO MID
30S.
THE SYSTEM TRANSLATES ACROSS THE AREA QUICKLY ON SATURDAY WITH
STRENTHENING DELAYED UNTIL IT IS WELL CLEAR OF THE MID ATLANTIC
COAST. EXPECT A RAPID MOISTURE ADVECTION CUTOFF AS THE LOW LEVEL
FLOW VEERS WEST ACROSS THE GULF STATES BY EARLY AFTERNOON. WILL
CONTINUE LIKELY POPS ACROSS THE WEST IN THE MORNING AND IN THE EAST
IN THE AFTERNOON...ALTHOUGH RAINFALL AMOUNTS WILL BE ON THE LIGHT
SIDE DUE TO THE SPEED AND LIMITED MOISTURE. THE QUICK SHUTOFF OF
WARM AIR ADVECTION AND EVAPORATIVE COOLING WILL LIMIT HIGHS TO
MOSTLY MID AND UPPER 40S.
UNSEASONABLY COOL HIGH PRESSURE BUILDS IN BEHIND THIS SYSTEM...WITH
TRANQUIL WEATHER FOR THE REMAINDER OF THE FORECAST. HIGHS WILL TOP
OUT IN THE LOW TO MID 40S ON SUNDAY AFTER A COOL MORNING START IN
THE UPPER 20S. HIGH OVERHEAD SUNDAY NIGHT WILL ALLOW STRONG
RADIATIONAL COOLING...MINS IN THE MID...PERHAPS LOWER...20S. NEXT
UPPER TROF DIGGING INTO THE SOUTHERN ROCKIES WILL PRODUCE RISING
HEIGHTS ON MONDAY AND HIGHS 45 TO 50...AND 50 TO 55 TUESDAY.
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
AS OF 100 PM TUESDAY...
A POWERFUL STORM SYSTEM OVER THE LOWER MS VALLEY THIS AFTERNOON WILL
LIFT NE INTO THE TENNESSEE VALLEY BY WEDNESDAY MORNING. A WARM FRONT
ASSOCIATED WITH THIS SYSTEM WILL LIFT NORTH WITH WIDESPREAD RAIN AND
LOW CLOUDINESS SPREADING ACROSS CENTRAL NORTH CAROLINA FROM AROUND
MIDNIGHT TONIGHT THROUGH MID DAY WEDNESDAY. IFR CONDITIONS WILL BE
PREVALENT WITH LIGHT TO MODERATE RAIN. COOL AIR IN PLACE OVER THE
AREA WILL PROVIDE A ZONE OF LOW LEVEL WIND SHEAR WITH WINDS ABOVE
1000 FEET STRENGTHENING LATER TONIGHT INTO MID WEDNESDAY MORNING.
EASTERLY SURFACE WINDS WILL INCREASE RAPIDLY TO 35 TO 40 KNOTS AND
SHIFTING MORE SOUTHEASTERLY.
AS THE STORM LIFTS NE INTO THE MID ATLANTIC WEDNESDAY EVENING...A
STRONG COLD FRONT WILL CROSS CENTRAL NC WEDNESDAY AFTERNOON. AHEAD
OF THIS FRONT...SOUTHERLY WINDS WILL POTENTIALLY GUST TO 30 KTS.
SHOWERS AND A FEW STRONG TO EVEN SEVERE THUNDERSTORMS ARE EXPECTED
FROM MID MORNING IN THE WEST INTO THE EARLY AFTERNOON IN THE
EAST...ENDING BY EARLY WEDNESDAY EVENING.
IMPROVING AVIATION CONDITIONS ARE EXPECTED WEDNESDAY NIGHT WITH VFR
CONDITIONS FROM LATE WEDNESDAY NIGHT THROUGH FRIDAY. SURFACE WINDS
WILL BE INITIALLY BRISK IN WAKE OF THE FRONT WEDNESDAY NIGHT INTO
EARLY THURSDAY WITH GUSTS TO AROUND 30KTS. THE NEXT SHOT AT
ADVERSE AVIATION WEATHER CONDITIONS IS EXPECTED LATE FRIDAY NIGHT
INTO SATURDAY. HIGH PRESSURE WILL BUILD IN ON SUNDAY WITH VFR
CONDITIONS EXPECTED.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...WSS
NEAR TERM...WSS/SMITH
SHORT TERM...MLM
LONG TERM...MLM
AVIATION...MLM
AREA FORECAST DISCUSSION
NWS RALEIGH NC
115 PM EST TUE DEC 25 2012
.SYNOPSIS...
WEAK HIGH PRESSURE WILL EXTEND ACROSS THE REGION TODAY THEN SHIFT
OFFSHORE BY SUNSET. A WARM FRONT AND A DEEPENING LOW PRESSURE SYSTEM
WILL APPROACH FROM THE SOUTHWEST TONIGHT. THE STRONG STORM SYSTEM
AND ACCOMPANYING COLD FRONT WILL SWEEP ACROSS THE AREA WEDNESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 945 AM TUESDAY...
WHILE FOG AND LOW CLOUDS HAVE SCOURED ACROSS MUCH OF THE CENTRAL AND
EASTERN CWA...DENSE FOG IS STILL REPORTED IN THE TRIAD...AND TRAFFIC
CAMERAS IN THE AREA SHOW MURKY CONDITIONS ALONG THE I-40 CORRIDOR.
VISIBILITIES HAVE IMPROVED IN RANDOLPH AND DAVIDSON COUNTIES...AND
THERE IS STILL A COUPLE MORE HOURS FOR THE FOG AND STRATUS TO MIX
OUT BEFORE HIGH CLOUDS BEGIN TO POUR BACK IN AHEAD OF THE STORMS
SYSTEM DEVELOPING OVER THE GULF COAST. RAP FORECAST
SOUNDINGS...WHICH SHOW MORE LOW LEVEL MOISTURE THAN WAS OBSERVED ON
THE MORNING RAOBS....SHOW THE LOW CLOUDS SCOURING IN THE TRIAD BY
AROUND NOON. WILL INCREASE CLOUD COVER IN THE NORTHWEST PIEDMONT
AND TRIM OFF A COUPLE DEGREES ON HIGHS SINCE CIRRUS WILL BE STEADILY
INCREASING EVEN AFTER THE LOW CLOUDS BURN OFF. OTHERWISE..THE
FORECAST APPEARS TO BE IN GOOD SHAPE THROUGH 00Z. HIGHS 52-61
NORTHWEST TO SOUTHEAST. -SMITH
TONIGHT...A WARM FRONT WILL DEVELOP ACROSS SC THIS EVENING IN
RESPONSE TO A POWERFUL LOW PRESSURE SYSTEM LIFTING ACROSS THE LOWER
MS VALLEY. SLY WINDS A FEW THOUSAND FEET ABOVE THE SURFACE WILL
ADVECT WARM MOIST AIR UP AND OVER THE COOL STABLE SURFACE LAYER
RESIDING OVER CENTRAL NC. THIS WILL LEAD TO THE DEVELOPMENT OF LOW
CLOUDS...EXPANDING SW-NE IN THE EVENING. ISENTROPIC LIFT WILL
INCREASE LATE THIS EVENING INTO THE OVERNIGHT CAUSING AN EXPANSIVE
AREA OF MODERATE RAINFALL TO DEVELOP. THE GREATEST RAINFALL AMOUNTS
SHOULD FALL OVER THE WESTERN PIEDMONT WHERE BEST LIFT PROJECTED TO
BE FOCUS. TEMPS WILL INITIALLY FALL WITH ONSET OF THE RAIN DUE TO
EVAPORATIVE COOLING IN THE SUB-CLOUD LAYER AFTERWHICH TEMPS WILL
STABILIZE AND MAY ACTUALLY RISE IN THE PRE-DAWN HOURS ACROSS THE
SOUTH AS THE WARM FRONT APPROACHES FROM THE SOUTH. MIN TEMPS NEAR 40
FAR NORTH TO THE MID 40S SOUTH.
&&
.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
AS OF 320 AM TUESDAY...
...AN ACTIVE WEATHER DAY SHAPING UP WEDNESDAY FOR CENTRAL NC WITH A
HIGH LIKELIHOOD OF STRONG TO SEVERE THUNDERSTORMS....
THE SC WARM FRONT PROJECTED TO LIFT NWD ACROSS A LARGE PART OF THE
FORECAST AREA WED AM INTO THE AFTERNOON. THE RAINFALL IN THE WEST
LATE TONIGHT MAY ESTABLISH AN INSITU OR HYBRID CAD AIR MASS OVER THE
NW PIEDMONT. THUS BY MID DAY..MAY SEE A DISTINCT AIR MAS ACROSS THE
REGION WITH COOL STABLE AIR (TEMPS INT EH 40S TO NEAR 50) OVER THE
TRIAD REGION WHILE THE REST OF THE REGION...ESPECIALLY THE SANDHILLS
AND A LARGE PART OF THE COASTAL PLAIN...IN A WARM MOIST UNSTABLE AIR
MASS WITH TEMPS IN THE UPPER 50S AND 60S.
THE STRONG LOW PRESSURE SYSTEM WILL LIFT ENE FROM THE TN VALLEY INTO
THE MID ATLANTIC WED. A STRONG SUB-TROPICAL JET ROUNDING THE BASE OF
THE TROUGH WILL CAUSE THE UPPER TROUGH TO ATTAIN A NEGATIVE TILT
WHICH WILL SPREAD COLDER AIR ALOFT OVER THE WARM MOIST AIR IN THE
LOWER LAYERS OF THE ATMOSPHERE. THIS WILL RESULT IN AN UNSTABLE
ATMOSPHERE ACROSS CENTRAL NC WITH MID LEVEL LAPSE RATES UP TO 7.5
DEGREES. IN ADDITION...THE LOW PRESSURE SYSTEM WILL SPAWN A STRONG
LOW LEVEL JET THAT WILL LIFT ACROSS THE REGION IN THE AFTERNOON.
THIS STRONG LLJ INTERACTING WITH SURFACE BOUNDARY/WARM FRONT WILL
GREATLY ENHANCE THE LOW LEVEL HELICITY SUPPORTIVE OF STORMS WITH
ROTATING UPDRAFTS. THUS...WITH A STRONG WIND FIELD IN PLACE
INTERACTING WITH AN INCREASINGLY MOIST AND UNSTABLE (FOR WINTER) AIR
MASS...STRONG TO SEVERE STORMS APPEAR QUITE LIKELY.
AT THIS TIME...IT APPEARS A NEAR SOLID LINE OF STORMS WILL OCCUR
AHEAD OF A STRONG COLD FRONT THAT WILL CROSS THE REGION IN THE
AFTERNOON. OUT AHEAD OF THE LINE...THE AIR MASS WILL BE SUPPORTIVE
OF A FEW SUPERCELL THUNDERSTORMS. WHILE THE PRIMARY SEVERE WEATHER
THREAT WILL BE DAMAGING STRAIGHT-LINE WINDS ASSOCIATED WITH THE LINE
OF CONVECTION...THE ISOLATED THUNDERSTORMS THAT OCCUR AHEAD OF THE
LINE WILL HAVE THE POTENTIAL TO PRODUCE A FEW TORNADOES.
CURRENT INDICATIONS SUGGEST THAT THE SEVERE WEATHER THREAT MAY
START AS EARLY 10-11 AM IN THE SOUTHERN COUNTIES THEN EXPAND N-NE
TO COVER THE REST OF THE REGION DURING THE AFTERNOON HOURS AS A
SURFACE LOW MOVES ALONG THE NWD MOVING WARM FRONT. THE SEVERE
WEATHER THREAT BEGINS TO DECREASE IN THE WEST BY LATE AFTERNOON AND
IN THE EAST SHORTLY AFTER SUNSET.
WEDNESDAY NIGHT...THE SURFACE COLD FRONT WILL EXIT THE REGION EARLY.
W-NW WINDS BEHIND THE FRONT WILL BE QUITE STRONG WITH GUSTS 25-30MPH
PROBABLE. THESE WINDS WILL ALSO USHER MUCH COOLER AND DRIER AIR INTO
THE REGION. THIS DRIER AIR SHOULD QUICKLY DISSIPATE CLOUD COVERAGE
ACROSS THE AREA...LEADING TO CLEAR SKIES BY MIDNIGHT. MUCH COOLER
WITH MIN TEMPS IN THE LOW-MID 30S.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 255 AM TUESDAY...
FOR THURSDAY THROUGH FRIDAY NIGHT: THE DEPARTING STORM IS EXPECTED
TO BE CENTERED JUST OFF NYC THURSDAY MORNING. THE MSLP GRADIENT OVER
NC REMAINS SUFFICIENTLY STRONG FOR CONTINUED BRISK WINDS...
SUSTAINED OVER 15 MPH AND GUSTS UP TO 30-35 MPH THROUGH AT LEAST THE
EARLY PART OF THE AFTERNOON. HIGHLY STABLE AND WARMING MID LEVELS
WITH 120-150 METER HEIGHT RISES SHOULD STAVE OFF MOST CLOUDS...
ALTHOUGH A FEW FLAT STRATOCU ARE LIKELY IN THE AFTERNOON AS THE
REMAINING BOUNDARY LAYER MOISTURE GETS TRAPPED BENEATH THE
SUBSIDENCE INVERSION ALOFT... AND VERY HIGH THIN CLOUDS WILL STREAK
OVER THE AREA AS WELL WITH AN ELONGATED 125+ KT JET CORE PASSING
OVERHEAD. THE SHALLOW MIXED LAYER SUPPORTS HIGHS THURSDAY OF
46-52... VERY CLOSE TO EXISTING FORECAST. GOOD RADIATIONAL COOLING
THURSDAY NIGHT AS SURFACE HIGH PRESSURE DRIFTS OVERHEAD WITH FAIR TO
MOSTLY CLEAR SKIES. LOWS 26-30. THE HIGH SLIPS OFF THE SOUTHEAST
COAST BY LATE FRIDAY... AND HIGH CLOUDS WILL BE INCREASING SLOWLY AS
THE ANTICYCLONIC MID LEVEL FLOW FLATTENS TO SOUTHWESTERLY AND
STRENGTHENS... IN ADVANCE OF OUR NEXT STORM SYSTEM DIGGING OVER THE
SRN PLAINS. WITH LITTLE CHANGE IN AIR MASS OR VERTICAL THERMAL
STRUCTURE... EXPECT HIGHS TO BE MINIMALLY HIGHER FRIDAY... 48-53.
SKIES WILL TREND TO CLOUDY SOUTH TO NORTH AS THE LONGWAVE TROUGH
AXIS SWINGS TOWARD THE MISS VALLEY... RESULTING IN THICKENING AND
LOWERING MID CLOUDS. GFS FORECAST SOUNDINGS SHOW THE SURFACE-BASED
STABLE POOL HOLDING FIRM DESPITE THE INCREASING SOUTHERLY FLOW AND
MOIST UPGLIDE FROM 950 MB UP (PARTICULARLY 285K-290K)... DRAWING LOW
LEVEL ATLANTIC MOISTURE INTO THE SOUTHERN AND EASTERN PORTIONS OF
THE FORECAST AREA... AND THIS FLOW WILL INCREASE TOWARD MORNING AS
SURFACE LOW PRESSURE IS EXPECTED TO STRENGTHEN OVER THE GULF COAST
BETWEEN NEW ORLEANS AND MOBILE. THE LATEST GFS/ECMWF RUNS SUPPORT
DELAYING THE DEEP LAYER LIFT AND THE RESULTING CHANCE OF MEASURABLE
RAIN UNTIL CLOSE TO SUNRISE SATURDAY MORNING... SO WILL SLOW THE
ARRIVAL OF RAIN CHANCES BY A FEW HOURS LATE FRIDAY NIGHT. LOWS
30-38.
FOR SATURDAY/SATURDAY NIGHT: ANOTHER STRONG STORM SYSTEM WILL AFFECT
NC EARLY IN THE WEEKEND. THE LATEST ECMWF INITIALIZED AT 00Z
SUPPORTS AND EXTENDS RECENT MODEL TRENDS TOWARD A MILLER TYPE-A
(SINGLE-LOW) CYCLOGENESIS PATTERN... WITH THE SURFACE LOW MOVING
EASTWARD ACROSS SRN GA BEFORE TRACKING UP THE COAST OF THE
CAROLINAS. MOISTURE SHOULD BE PLENTIFUL WITH FEEDS FROM BOTH THE
ATLANTIC AND GULF... AND FORCING FOR ASCENT IS LIKELY TO BE RAPIDLY
STRENGTHENING SATURDAY. 12-HR PROJECTED MID LEVEL HEIGHT FALLS ARE
150 M TO AS MUCH AS 200 M OVER NC IN CONJUNCTION WITH INCREASING
(BUT NOT OVERLY INTENSE) UPPER DIVERGENCE AND STRENGTHENING LOW
LEVEL MASS CONVERGENCE MAINLY IN OUR SOUTH AND EAST. WILL MAINTAIN
SOME CAUTION BUT DECENT MODEL AGREEMENT WITHIN THIS ACTIVE PATTERN
SUPPORTS AN UPTICK OF RAIN CHANCES ESPECIALLY IN THE SOUTH AND EAST.
HIGHS FROM 45 IN THE COOL STABLE AIR IN THE NORTHWEST CWA RANGING TO
56 SOUTHEAST. RAIN SHOULD TAPER TO SPOTTY DRIZZLE GIVEN THE DRYING
ALOFT SATURDAY EVENING... BEFORE ENDING ENTIRELY AFTER MIDNIGHT.
LOWS 29-35.
FOR SUNDAY/MONDAY: QUIET WEATHER BEHIND THIS SYSTEM WITH SURFACE
HIGH PRESSURE BUILDING OVERHEAD FROM THE WEST. THE AIR MASS SHOULD
BE SOMEWHAT MODIFIED PARTICULARLY WITH HEIGHTS RISING QUICKLY ALOFT
AS NEW LONGWAVE TROUGHING DIGS OVER THE ROCKIES. EXPECT BELOW NORMAL
TEMPS SUNDAY TRENDING UP CLOSER TO NORMAL MONDAY... WITH DRY
WEATHER. -GIH
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
AS OF 100 PM TUESDAY...
A POWERFUL STORM SYSTEM OVER THE LOWER MS VALLEY THIS AFTERNOON WILL
LIFT NE INTO THE TENNESSEE VALLEY BY WEDNESDAY MORNING. A WARM FRONT
ASSOCIATED WITH THIS SYSTEM WILL LIFT NORTH WITH WIDESPREAD RAIN AND
LOW CLOUDINESS SPREADING ACROSS CENTRAL NORTH CAROLINA FROM AROUND
MIDNIGHT TONIGHT THROUGH MID DAY WEDNESDAY. IFR CONDITIONS WILL BE
PREVALENT WITH LIGHT TO MODERATE RAIN. COOL AIR IN PLACE OVER THE
AREA WILL PROVIDE A ZONE OF LOW LEVEL WIND SHEAR WITH WINDS ABOVE
1000 FEET STRENGTHENING LATER TONIGHT INTO MID WEDNESDAY MORNING.
EASTERLY SURFACE WINDS WILL INCREASE RAPIDLY TO 35 TO 40 KNOTS AND
SHIFTING MORE SOUTHEASTERLY.
AS THE STORM LIFTS NE INTO THE MID ATLANTIC WEDNESDAY EVENING...A
STRONG COLD FRONT WILL CROSS CENTRAL NC WEDNESDAY AFTERNOON. AHEAD
OF THIS FRONT...SOUTHERLY WINDS WILL POTENTIALLY GUST TO 30 KTS.
SHOWERS AND A FEW STRONG TO EVEN SEVERE THUNDERSTORMS ARE EXPECTED
FROM MID MORNING IN THE WEST INTO THE EARLY AFTERNOON IN THE
EAST...ENDING BY EARLY WEDNESDAY EVENING.
IMPROVING AVIATION CONDITIONS ARE EXPECTED WEDNESDAY NIGHT WITH VFR
CONDITIONS FROM LATE WEDNESDAY NIGHT THROUGH FRIDAY. SURFACE WINDS
WILL BE INITIALLY BRISK IN WAKE OF THE FRONT WEDNESDAY NIGHT INTO
EARLY THURSDAY WITH GUSTS TO AROUND 30KTS. THE NEXT SHOT AT
ADVERSE AVIATION WEATHER CONDITIONS IS EXPECTED LATE FRIDAY NIGHT
INTO SATURDAY. HIGH PRESSURE WILL BUILD IN ON SUNDAY WITH VFR
CONDITIONS EXPECTED.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...WSS
NEAR TERM...WSS/SMITH
SHORT TERM...WSS
LONG TERM...HARTFIELD
AVIATION...MLM
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
225 PM CST TUE DEC 25 2012
.SHORT TERM...TONIGHT AND WEDNESDAY.
LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW ARCTIC HIGH
PRESSURE CENTERED OVER THE NORTHERN GREAT PLAINS AND NOSING ACROSS
THE WESTERN GREAT LAKES. CLOUDS AND FLURRIES HAVE RETREATED NORTH
OF THE UPPER PENINSULA BORDER EARLY THIS AFTERNOON AND ARE NO LONGER
IMPACTING N-C WISCONSIN. MEANWHILE...LIGHT NE LOW LEVEL FLOW HAS
ALREADY STARTED TO DEVELOP OVER NORTHEAST WISCONSIN AND LAKE CLOUDS
ARE ALREADY PUSHING ACROSS THE FOX VALLEY. SNOW FLURRIES ARE
SHOWING UP ON RADAR JUST OFFSHORE THE KEWAUNEE COAST...AND EVEN WHAT
LOOKS LIKE A MID-LAKE BAND HAS BEEN MOVING EAST OVER CENTRAL LAKE
MICHIGAN. AS DEEPER AND STRONGER NE FLOW DEVELOPS LATER TONIGHT AND
WEDNESDAY...LAKE EFFECT SNOW CHANCES AND AMOUNTS ARE THE MAIN
FORECAST CONCERNS.
TONIGHT...SURFACE HIGH PRESSURE RIDGE AXIS WILL BE EXTENDING ACROSS
NORTHERN WISCONSIN AND LAKE MICHIGAN AT THE START OF THE
EVENING...BUT WILL SHIFT NORTHWARD THROUGH THE NIGHT. AS STRONG LOW
PRESSURE MOVES OVER THE SOUTHERN OHIO VALLEY...WIND DIRECTION WILL
BECOME NORTHEASTERLY FROM THE SURFACE UP TO 700MB. 12Z GRB SOUNDING WAS
PRETTY DRY ABOVE 900MB THIS MORNING...BUT ONCE THE NE FLOW BECOMES
ESTABLISHED...OUR AIR WILL BE COMING FROM NORTHERN LAKE MICHIGAN
WHERE THE 12Z APX SOUNDING WAS CONSIDERABLY MORE SATURATED...UP TO
825MB. SINCE AMPLE CLOUD COVER ALREADY EXISTS OVER NORTHERN LAKE
MICHIGAN...AND SHOWING NO SIGNS OF DISSIPATING...SEE NO REASON WHY
THE LAKE CLOUDS COULD NOT CONTINUE TO PUSH ACROSS THE WESTERN FOX
VALLEY AND POSSIBLY EXPAND INTO CENTRAL WISCONSIN. LAKE EFFECT SNOW
POTENTIAL WILL IMPROVE THROUGH THE NIGHT WHEN 1000-850MB FLOW
STRENGTHENS TO 15 KTS. COMBINED WITH LENGTHENING FETCHES AND DELTA
T/S AROUND 16C...LAKE EFFECT SNOW SHOWERS LOOK LIKELY LATE TONIGHT
OVER E-C AND NE WISCONSIN. THINK IT WILL TAKE AWHILE FOR THE
MULTIPLE BANDS TO DEVELOP WITH WINDS LIGHT THIS EVENING. SO WILL
SHOW ACCUMS UP TO AN INCH OVER E-C WISCONSIN...MAINLY AFTER
MIDNIGHT. ELSEWHERE...CIRRUS WILL INCREASE FROM THE SW AFTER
MIDNIGHT AHEAD OF A NORTHERN STREAM SHORTWAVE. LOWS SLIGHTLY BELOW
ZERO OVER N-C WISCONSIN...TO THE UPPER TEENS NEAR LAKE MICHIGAN.
WEDNESDAY...NORTHEAST FLOW WILL CONTINUE UNABATED FOR THE ENTIRE
DAY. WITH A CIRRUS SHIELD OVERHEAD...DELTA T/S WILL REMAIN AROUND
15C WITH GREAT FETCH LENGTHS AND 1000-850MB WINDS BETWEEN 15-20KTS.
IN ADDITION...AN INCOMING SHORTWAVE TROUGH WILL LIFT INVERSION
HEIGHTS TO NEAR 800MB (PROBABLY UNDERESTIMATED DUE TO LAKE MICHIGAN
MODIFICATIONS) AND CREATE LARGE-SCALE ASCENT...WHICH WILL SUBTLY IMPROVE
LES POTENTIAL. WENT A LITTLE MORE BULLISH WILL SNOWFALL POTENTIAL
DUE TO THESE FACTORS...AND WILL SHOW 1-2 INCHES IN THE FORECAST. AM
CONCERNED THAT THE LONG FETCH LENGTHS AND A PERSISTENT WIND
DIRECTION WILL LEAD TO HIGHER AMOUNTS SINCE THIS COULD LEAD TO
ORGANIZED BANDING. ELSEWHERE...PLENTY OF CIRRUS OVERHEAD WILL CREATE
TO PARTLY SUNNY TO MOSTLY CLOUDY CONDITIONS. HIGHS MAINLY IN THE LOW
TO MID 20S.
.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY.
LAKE EFFECT SNOW SHOWERS WILL BE DIMINISHING EARLY IN THE PERIOD
AS LOW-LEVEL WINDS BACK AND SURFACE HIGH PRESSURE MOVES IN.
PACIFIC ENERGY MOVES ON SHORE WED AND QUICKLY MOVES INTO MIDWEST
BY LATE IN WEEK. ASSOCIATED SHORTWAVE TROF AND SURFACE WAVE MOVE
ACROSS REGION ON FRIDAY. ENOUGH MOISTURE ASSOCIATED WITH SYSTEM
TO PRODUCE LIGHT COATING OF SNOW ACROSS AT LEAST THE SOUTHERN
THIRD OR SO OF FORECAST AREA.
SEASONAL TEMPS DURING PERIOD AS ARCTIC AIR...FOR THE MOST PART...
REMAINS BOTTLE UP IN CANADA...NORTH AND NORTHEAST OF WI.
&&
.AVIATION...GOOD FLYING CONDITIONS ACROSS MOST OF THE REGION THROUGH
THE REST OF THE AFTERNOON. MVFR CIGS/VSBYS IN LIGHT SNOW OVER N-C
WISCONSIN WILL RETREAT TO THE UPPER PENINSULA BY MID-AFTERNOON.
MVFR STRATUS OVER THE LAKE MICHIGAN SHORELINE IS NOT AS CLEAR CUT.
DESPITE INCOMING HIGH PRESSURE...LIGHT WINDS AND AMPLE INSTABILITY
SEEM TO BE ENOUGH TO SUSTAIN BKN CONDITIONS. AS LIGHT WINDS TURN NE
THIS EVENING...EXPECT THE BKN CIGS TO SURGE ACROSS ALL OF NE
WISCONSIN INCLUDING THE FOX VALLEY. LIGHT FLURRIES WILL LIKELY
GRADUALLY PICK UP IN INTENSITY LATE TONIGHT THROUGH WEDNESDAY
MORNING. SOME MINOR ACCUMULATIONS ARE POSSIBLE BY THE END OF THE
TAF PERIOD...BUT THE SNOW WILL BE LIGHT AND FLUFFY AND EASILY BLOWN
OFF THE RUNWAYS AND AIRCRAFT.
MPC
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
MPC/JKL