Forecast Discussions mentioning any of
"HRRR" "RAP" "RR" "RUC13" "RUC" received at GSD on 12/23/12
AREA FORECAST DISCUSSION
NWS TAUNTON MA
855 AM EST FRI DEC 21 2012
.SYNOPSIS...
LOW PRESSURE AND ITS ATTENDING OCCLUDED FRONT WILL BRING A
PERIOD OF HEAVY RAIN AND STRONG WINDS TO THE REGION TODAY. COLDER
TEMPS WILL FOLLOW FOR THE WEEKEND INTO EARLY NEXT WEEK. A WEAK
STORM COULD BRING SOME SNOW AND/OR RAIN ON CHRISTMAS DAY. A
STRONGER STORM MAY AFFECT NEW ENGLAND LATE WED INTO THU.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
855 AM UPDATE...
ONLY CHANGE TO THE FORECAST WAS TO EXPAND THE WIND ADVISORY INTO
SOUTHWEST/CENTRAL MA AND NORTHERN CT THROUGH MID AFTERNOON. ITS
MARGINAL...BUT WITH THE HEAVY RAIN AND STRONG SOUTHEAST LOW LEVEL
JET MAY SEE A BRIEF PERIOD OF WIND GUSTS AROUND 45 MPH. STILL THINK
THAT THIS WILL MAINLY BE AN ADVISORY LEVEL EVENT FOR MOST OF THE
REGION...AS SOUTHEAST LOW LEVEL JETS ARE OFTEN TOUGH TO MIX DOWN.
HOWEVER...IF WE CAN GENERATE A FINE LINE WILL HAVE TO WATCH FOR SOME
LOCALIZED STRONGER WIND GUSTS. WILL HAVE MORE IN A BIT.
PREVIOUS DISCUSSION...
A PERIOD OF STRONG WINDS AND HEAVY RAIN WILL
MOVE ACROSS SNE TODAY AS AN ANOMALOUS LOW LEVEL JET AHEAD OF A
STRONG OCCLUDED FRONT SWEEPS ACROSS THE REGION. THIS SYSTEM IS
RATHER PROGRESSIVE SO THE WORST OF THE WIND AND RAIN WILL LIKELY BE
CONFINED TO A 3-4 HOUR WINDOW...12-16Z IN THE WEST AND 16-20Z
EASTERN NEW ENG.
RAINFALL/FLOOD POTENTIAL...
STRONG LOW LEVEL JET 3-4SD AND +2SD PWAT ANOMALY WILL BRING A
PERIOD OF HEAVY RAIN TO SNE. HOWEVER...THIS SYSTEM WILL BE QUICK
MOVING LIMITING THE DURATION OF HEAVY RAIN IN ANY ONE LOCATION.
NAM IS THE MOST ROBUST WITH ELEVATED INSTABILITY PARAMETERS AND
SUGGEST POTENTIAL FOR SOME CONVECTION/THUNDER...AND HRRR IS
INDICATING A FINE LINE OF CONVECTION MOVING THROUGH.
HOWEVER...GFS AND ECMWF ARE RATHER WEAK WITH INSTABILITY. DUE TO
MIXED SIGNALS CONFIDENCE IN THUNDER AND ENHANCED RAINFALL RATES
IS LOW. EXPECTED RAINFALL IS 0.5" TO 1" WITH ISOLD AMOUNTS UP TO
1.5" ACROSS W ZONES WHICH WOULD MAINLY RESULT IN MINOR URBAN AND
POOR DRAINAGE FLOODING ISSUES. RAINFALL WILL BE EXITING THE REGION
FROM WEST TO EAST 16-21Z.
HIGH WIND THREAT...
MODEL DIFFERENCES IN THE STRENGTH OF THE LOW LEVEL JET INCREASES
FORECAST UNCERTAINTY REGARDING MAGNITUDE OF THE WIND THREAT. GFS
IS STRONGEST WITH THE JET INDICATING 80 KT AT 925 MB...BUT NAM HAS
TRENDED WEAKER WITH 70 KT AND ECMWF IS WEAKEST AT 60 KT. DESPITE
THESE DIFFERENCES...IMPRESSIVE PRESSURE FALLS ARE FORECAST
COINCIDENT WITH THE LOW LEVEL JET WHICH WILL ENHANCE WIND
ACCELERATION AND TEMPS ARE EXPECTED TO SPIKE INTO THE 50S IN THE
COASTAL PLAIN WHICH WILL INCREASE MIXING POTENTIAL. MODEL
SOUNDINGS ARE NOT VERY SUPPORTIVE OF STRONG WINDS MIXING
DOWN...BUT THE MILDER TEMPS AND ISALLOBARIC CONTRIBUTION SUPPORT
STRONG WINDS REACHING THE SURFACE. AS MENTIONED ABOVE WE ARE NOT
CONFIDENT IN A FINE LINE OF CONVECTION WHICH WOULD FURTHER INCREASE
HIGH WIND THREAT BUT WE HAVE ENOUGH CONFIDENCE TO GO WITH A HIGH
WIND WARNING FOR CAPE/ISLANDS WHERE STRONGEST LOW LEVEL WINDS ARE
EXPECTED. ELSEWHERE WE WILL GO WITH A WIND ADVISORY FOR RI AND
EASTERN MA. TIMING OF STRONGEST WINDS WILL BE 14-17Z RI AND
16-19Z E MA AND CAPE/ISLANDS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
MID LEVEL LOW MOVES INTO CENTRAL AND NORTHERN NEW ENG TONIGHT WITH
A STRONG SHORTWAVE ROTATING INTO THE REGION TOWARD MIDNIGHT. AS A
RESULT WE EXPECT SCT SNOW/RAIN SHOWERS TO REDEVELOP. BL TEMPS WILL
BE MARGINAL NEAR THE COAST WHERE ANY PRECIP MAY BE IN THE FORM OF
RAIN...BUT EXPECT MOSTLY SNOW SHOWERS ELSEWHERE. CANT RULE OUT
MINOR ACCUM IN THE HIGHER TERRAIN.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
HIGHLIGHTS...
* ARCTIC AIR MOVES IN BEHIND THE LOW PRES THROUGH THE WEEKEND
* WEAK LOW PRES MAY BRING LIGHT SNOW ON CHRISTMAS DAY
* STRONG STORM POSSIBLE WED NIGHT INTO THU
OVERVIEW AND MODEL PREFERENCES...
21/00Z MODEL GUIDANCE SUITE CONTINUES TO SHOW DECENT SYNOPTIC
SCALE AGREEMENT THROUGH THE EARLY PORTION OF THE LONG TERM BUT ARE
STRUGGLING WITH TWO DIFFERENT SYSTEMS AFFECTING THE MID AND LONG
TERM SENSIBLE WX DETAILS. ECMWF HAS COME IN LINE WITH GFS/NAM
TIMING FOR THE LOW PRES THIS WEEKEND EXITING INTO THE
MARITIMES...SO WILL CONTINUE TO BASELINE FORECAST USING GFS AS IT
HAS SHOWN MORE CONSISTENCY. THE DISAGREEMENTS BEGIN REGARDING
WITH THE E CANADA FLOW PATTERN FOR THE CHRISTMAS EVE/DAY SYSTEM. A
SPAGHETTI PLOT OF OPERATIONAL LONG RANGE GUIDANCE AND ENSEMBLES
AT H5 ARE ALL OVER THE PLACE WITH THE NRN NEW ENGLAND E CANADA
FLOW PATTERN...SO STILL NOT A LOT OF CONFIDENCE IN WHETHER OR NOT
HIGH PRES TO THE N WILL SUPPRESS LIGHT SNOW FOR CHRISTMAS EVE TO
THE S. THE LATEST ECMWF IS CLOSER TO THE SOLUTION SUGGESTED BY THE
GFS AND A FEW GEFS MEMBERS. WILL LEAN ON HPC AS FOR NOW GIVEN THE
DIFFERENCES AND ISSUES WITH UPPER LVL FLOW PATTERN. IN REGARDS TO
THE MID WEEK SYSTEM NEXT WEEK...GUIDANCE IS ACTUALLY IN DECENT
AGREEMENT WITH THE DEEPENING/SHARPENING WAVE MOVING E FROM THE
ROCKIES AGAIN...BUT GENERATE VERY DIFFERENT SFC CYCLONES. ECMWF
CONTINUES TO BE SIMILAR TO THE SYSTEM FOR TODAY AND THE WEEKEND
WHILE GFS PUSHES THE LOW NEAR THE 40/70 BENCHMARK. HPC LEANS
TOWARD THE ECENS THIS STRETCH...WHICH IS COOLER THAN THE
OPERATIONAL ECMWF...BUT WARMER THAN THE GFS...SO GIVEN THIS IS A
GOOD COMPROMISE...WILL CONTINUE TO USE IT FOR THE MID-LATE WEEK
SYSTEM.
DETAILS...
SAT INTO MON...
SLOW MOVING CUTOFF LOW PRES AND ITS WEAKENING SFC LOW WILL
GRADUALLY BE SHIFTING INTO THE MARITIMES THROUGH THE PERIOD. THIS
WILL ALLOW A MUCH COLDER AIRMASS TO MOVE IN WITH H92 TEMPS
AVERAGING THE -5C TO -8C RANGE. THEREFORE...WITH SOME REMNANT
ENERGY WRAPPING AROUND AND LOW LVL MOISTURE WRAPPING AROUND THE
LOW SAT...A FEW SNOW SHOWERS ARE LIKELY WHICH GIVEN COOLER SFC
TEMPS MAY ACCUMULATE IN SPOTS. GENERALLY AN INCH OR LESS
ACCUMULATION IS EXPECTED AT ANY GIVEN LOCATION. WITH DRY/COLD
AIRMASS SHIFTING INTO THE REGION...SUN AND MON ARE EXPECTED TO BE
MOSTLY DRY...BUT ON THE COLDER SIDE OF SEASONABLE FOR
TEMPERATURES.
MON NIGHT INTO TUE NIGHT...
GIVEN THE UNCERTAINTY HERE...THERE ARE STILL SOME QUESTIONS TO BE
ANSWERED REGARDING WEAK LOW PRES PASSING TO THE S OF SRN NEW
ENGLAND. SOUNDINGS AND DIVERGENCE FIELDS SHOW A WEAK TROWAL
WRAPPING TO THE N WITH TEMP PROFILES COOL ENOUGH FOR SNOW RIGHT TO
THE S COAST. GIVEN THE UNCERTAINTY HOWEVER...THERE COULD BE A
SHARP CUTOFF BETWEEN THOSE THAT SEE SOME OF THE WHITE FOR
CHRISTMAS AND THOSE THAT DON/T AND IT IS STILL POSSIBLE IT MAY BE
DRY ACROSS THE BOARD WITH STRONG HIGH PRES TO THE N. THE HPC STILL
FAVORS AREAS S OF THE MASS PIKE...SO WILL CONTINUE WITH THIS
SUGGESTION FOR THIS FORECAST UPDATE.
WED AND THU...
A MUCH MORE DYNAMIC SYSTEM WILL APPROACH FOR THE MID TO LATE WEEK
TIMEFRAME. GIVEN THE WIDE ENVELOPE OF SOLUTIONS FOR THIS WHICH
WILL HAVE SIGNIFICANT DIFFERENCES IN SENSIBLE WX DETAILS /GUIDANCE
RANGES FROM AN ALL RAIN TO AN ALL SNOW EVENT/. WILL TREND TOWARD
HPC WHICH IS AN ECENS BASES SOLUTION AT THIS TIME. THIS
COMPROMISES WITH SOME SNOW TO THE N AND RAIN IN THE S.
HOWEVER...NEITHER ALL SNOW OR ALL RAIN SOLUTIONS CAN/T BE RULED
OUT AND WILL HAVE TO BE MONITORED ESPECIALLY ONCE THE WAVE ITS
ASSOCIATED WITH CAN BE SAMPLED OVER LAND OBSERVING SITES.
FRI...
MODEL GUIDANCE DOES SUGGEST THAT IN ANY CASE...COOL HIGH PRES
WILL BE BUILDING IN TOWARD THE END OF THE WEEK...SO WILL LEAN
GUIDANCE IN THIS SOLUTION FOR THE EXTENDED PERIOD.
&&
.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
SHORT TERM...HIGH CONFIDENCE.
A MAINLY MVFR/IFR TO START THIS MORNING...BUT IT IS EXPECTED THAT
THE TREND WILL BE TOWARD IFR AS A BAND OF RAIN AND STRONG WINDS
MOVE THROUGH THIS MORNING AND EARLY AFTERNOON FROM WEST TO EAST.
AFTER THE RAIN MOVES OUT...COULD SEE A RAPID IMPROVEMENT TO VFR
THROUGH THE EVENING BEFORE FOG BUILDS OVER AGAIN TONIGHT WITH
VSBYS DIPPING BACK TO THE MVFR/IFR LVLS. WINDS WILL BE STRONG
TODAY OUT OF THE SE...GUSTS 30-40 IN THE INTERIOR WITH NEAR
COASTAL TERMINALS SEEING 40-50 KT GUSTS AT TIMES. WINDS RAPIDLY
SHIFT TO THE WSW AFTER RAIN MOVES OUT.
KBOS TAF...HIGH CONFIDENCE IN TRENDS...LOWER CONFIDENCE IN EXACT
TIMING IN TAFS.
TREND WILL BE TOWARD A PERIOD OF IFR THROUGH MID AFTERNOON WITH
RAIN AND LOW CIGS. WINDS WILL ALSO BE STRONG OUT OF THE SW GUSTING
AS HIGH AS 40-50 KT BY LATE MORNING/EARLY AFTERNOON. RAPID
IMPROVEMENT TO VFR AFTER WINDS DIMINISH A BIT AND SHIFT TO WSW.
LLWS MUCH OF THE EARLY PORTION OF THE DAY
KBDL TAF...HIGH CONFIDENCE IN TRENDS...LOWER CONFIDENCE IN EXACT
TIMING.
TREND WILL BE TOWARD A PERIOD OF IFR THROUGH THE EARLY AFTERNOON
WITH STRONG WINDS 16Z-19Z /GUSTS AROUND 30 KT/. ONCE WINDS SHIFT
TO THE WSW...EXPECT THEM TO DIMINISH AND FOR A LIFT TO VFR INTO
THE EVENING.
OUTLOOK...SATURDAY THROUGH TUESDAY...
SATURDAY INTO SATURDAY NIGHT...MODERATE CONFIDENCE.
MAINLY VFR. HOWEVER...OCCASIONAL RAIN AND SNOW SHOWERS COULD
REDUCE BOTH VSBYS AND CIGS TO MVFR. WINDS GUST 30-40 KT OUT OF
THE NW SAT NIGHT.
SUNDAY AND MONDAY...HIGH CONFIDENCE.
VFR. NW WINDS GUST 20-30 KT THROUGH THE DAY ON SUN.
TUESDAY...MODERATE CONFIDENCE.
MAINLY VFR....BUT LIGHT SNOW IS POSSIBLE EARLY TUESDAY ESPECIALLY
TERMINALS S OF THE MASS PIKE.
&&
.MARINE...
MODERATE TO HIGH CONFIDENCE THROUGH TONIGHT.
A BRIEF PERIOD OF STORM FORCE SE WIND GUSTS TO NEAR 50 KT IS
EXPECTED FROM WEST TO EAST 14-20Z. STORM WARNINGS CONTINUE EXCEPT
STRONG GALES FOR NARR BAY AND BOSTON HARBOR. RAIN...HEAVY AT TIMES
IMPROVING FROM WEST TO EAST DURING THE AFTERNOON.
WINDS WILL DIMINISH WITH THE WIND SHIFT TO SW LATER THIS AFTERNOON
BUT STILL EXPECT WIND GUSTS TO 30 KT TONIGHT.
OUTLOOK...SATURDAY THROUGH TUESDAY...
MODERATE TO HIGH CONFIDENCE THROUGH TUESDAY.
SAT INTO SAT NIGHT...MODERATE CONFIDENCE.
WINDS BRIEFLY DIP TO SMALL CRAFT LEVELS DURING THE DAY
SATURDAY...BUT THEN ONCE WINDS SHIFT TO THE NW EXPECT GALE FORCE
GUSTS TO RETURN ESPECIALLY SAT NIGHT INTO EARLY SUNDAY. SEAS
REMAIN ELEVATED.
SUN INTO MON...HIGH CONFIDENCE.
BOTH WINDS AND SEAS GRADUALLY DIMINISH THROUGH THE PERIOD.
ALTHOUGH EXPECTING SMALL CRAFT WINDS THROUGH SUN NIGHT. BY
MON...SEAS AND WINDS SHOULD DROP BELOW SCA THRESHOLDS.
TUE...MODERATE CONFIDENCE.
WINDS AND SEAS START BELOW SMALL CRAFT THRESHOLDS...BUT MAY SEE
25 KT GUSTS AND SEAS NEAR 5 FT OVER SRN OUTER WATERS BY TUE
AFTERNOON AS A WEAK LOW PRES PASSES S OF THE REGION.
&&
.TIDES/COASTAL FLOODING...
NOT EXPECTING ANY COASTAL FLOODING OR BEACH EROSION AS ASTRO
TIDES ARE VERY LOW.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...WIND ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR CTZ002>004.
MA...WIND ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR MAZ004>007-009-
011>021-026.
HIGH WIND WARNING UNTIL 4 PM EST THIS AFTERNOON FOR MAZ022>024.
NH...NONE.
RI...HIGH WIND WARNING UNTIL 1 PM EST THIS AFTERNOON FOR RIZ008.
WIND ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR RIZ001>007.
MARINE...STORM WARNING UNTIL 4 PM EST THIS AFTERNOON FOR ANZ231>234-250-
251-254-255.
GALE WARNING UNTIL 4 PM EST THIS AFTERNOON FOR ANZ230-236.
STORM WARNING UNTIL 1 PM EST THIS AFTERNOON FOR ANZ235-237-256.
&&
$$
SYNOPSIS...KJC/DOODY
NEAR TERM...FRANK/KJC/DOODY
SHORT TERM...KJC
LONG TERM...DOODY
AVIATION...KJC/DOODY
MARINE...KJC/DOODY
TIDES/COASTAL FLOODING...STAFF
AREA FORECAST DISCUSSION
NWS TAUNTON MA
656 AM EST FRI DEC 21 2012
.SYNOPSIS...
LOW PRESSURE AND ITS ATTENDING OCCLUDED FRONT WILL BRING A
PERIOD OF HEAVY RAIN AND STRONG WINDS TO THE REGION TODAY. COLDER
TEMPS WILL FOLLOW FOR THE WEEKEND INTO EARLY NEXT WEEK. A WEAK
STORM COULD BRING SOME SNOW AND/OR RAIN ON CHRISTMAS DAY. A
STRONGER STORM MAY AFFECT NEW ENGLAND LATE WED INTO THU.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
7 AM UPDATE...
INITIAL ISENTROPICALLY GENERATED PRECIP IS SHIFTING OFFSHORE THIS
HOUR AS NEW BAND OF RAINFALL BEGINS TO FILL IN FROM THE SW. THIS
SECOND BATCH IS ASSOCIATED WITH THE INITIAL NOSE OF A 70 KT H92
LLJ WHICH WILL BEGIN MOVING OVER THE AREA FROM W TO E THROUGH THE
MORNING. EXPECTING THE STRONG WINDS TO SHIFT TO THE E ALONG WITH
THIS JET AS WELL AS THE CHANCE FOR HEAVIEST RAINFALL. HAVE
ADJUSTED TIMING SOMEWHAT TOWARD THE LATEST RAP...WHICH HAS CAUGHT
ON WELL IN THE LAST COUPLE OF HOURS. ADJUSTED POPS/WX TOWARD THE
RAP TIMING. UPSTREAM RADARS ARE SHOWING A WEAK LINE OF LOW TOPPED
CONVECTION ASSOCIATED WITH THE TRIPLE POINT LOW AND
OCCLUSION...MAY NEED TO MONITOR THIS FOR ANY ERD MOVEMENT AS IT
COULD ENHANCE MIXING DOWN OF THE JET.
PREVIOUS DISCUSSION...
SNOW IN THE DISTANT INTERIOR HAS ACCUMULATED 1-2 INCHES. IT IS
STILL SNOWING ACROSS WESTERN AND NORTHERN MA INTO S NH WITH TEMPS
32-34 DEGREES. HOWEVER...LOW LEVEL WARMING WILL RESULT IN A QUICK
CHANGEOVER TO RAIN THROUGH 6 AM. ADDITIONAL ACCUMULATION UP TO AN
INCH IS POSSIBLE.
A PERIOD OF STRONG WINDS AND HEAVY RAIN WILL MOVE ACROSS SNE
TODAY AS AN ANOMALOUS LOW LEVEL JET AHEAD OF A STRONG OCCLUDED
FRONT SWEEPS ACROSS THE REGION. THIS SYSTEM IS RATHER PROGRESSIVE
SO THE WORST OF THE WIND AND RAIN WILL LIKELY BE CONFINED TO A 3-4
HOUR WINDOW...12-16Z IN THE WEST AND 16-20Z EASTERN NEW ENG.
RAINFALL/FLOOD POTENTIAL...
STRONG LOW LEVEL JET 3-4SD AND +2SD PWAT ANOMALY WILL BRING A
PERIOD OF HEAVY RAIN TO SNE. HOWEVER...THIS SYSTEM WILL BE QUICK
MOVING LIMITING THE DURATION OF HEAVY RAIN IN ANY ONE LOCATION.
NAM IS THE MOST ROBUST WITH ELEVATED INSTABILITY PARAMETERS AND
SUGGEST POTENTIAL FOR SOME CONVECTION/THUNDER...AND HRRR IS
INDICATING A FINE LINE OF CONVECTION MOVING THROUGH.
HOWEVER...GFS AND ECMWF ARE RATHER WEAK WITH INSTABILITY. DUE TO
MIXED SIGNALS CONFIDENCE IN THUNDER AND ENHANCED RAINFALL RATES
IS LOW. EXPECTED RAINFALL IS 0.5" TO 1" WITH ISOLD AMOUNTS UP TO
1.5" ACROSS W ZONES WHICH WOULD MAINLY RESULT IN MINOR URBAN AND
POOR DRAINAGE FLOODING ISSUES. RAINFALL WILL BE EXITING THE REGION
FROM WEST TO EAST 16-21Z.
HIGH WIND THREAT...
MODEL DIFFERENCES IN THE STRENGTH OF THE LOW LEVEL JET INCREASES
FORECAST UNCERTAINTY REGARDING MAGNITUDE OF THE WIND THREAT. GFS
IS STRONGEST WITH THE JET INDICATING 80 KT AT 925 MB...BUT NAM HAS
TRENDED WEAKER WITH 70 KT AND ECMWF IS WEAKEST AT 60 KT. DESPITE
THESE DIFFERENCES...IMPRESSIVE PRESSURE FALLS ARE FORECAST
COINCIDENT WITH THE LOW LEVEL JET WHICH WILL ENHANCE WIND
ACCELERATION AND TEMPS ARE EXPECTED TO SPIKE INTO THE 50S IN THE
COASTAL PLAIN WHICH WILL INCREASE MIXING POTENTIAL. MODEL
SOUNDINGS ARE NOT VERY SUPPORTIVE OF STRONG WINDS MIXING
DOWN...BUT THE MILDER TEMPS AND ISALLOBARIC CONTRIBUTION SUPPORT
STRONG WINDS REACHING THE SURFACE. AS MENTIONED ABOVE WE ARE NOT
CONFIDENT IN A FINE LINE OF CONVECTION WHICH WOULD FURTHER INCREASE
HIGH WIND THREAT BUT WE HAVE ENOUGH CONFIDENCE TO GO WITH A HIGH
WIND WARNING FOR CAPE/ISLANDS WHERE STRONGEST LOW LEVEL WINDS ARE
EXPECTED. ELSEWHERE WE WILL GO WITH A WIND ADVISORY FOR RI AND
EASTERN MA. TIMING OF STRONGEST WINDS WILL BE 14-17Z RI AND
16-19Z E MA AND CAPE/ISLANDS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
MID LEVEL LOW MOVES INTO CENTRAL AND NORTHERN NEW ENG TONIGHT WITH
A STRONG SHORTWAVE ROTATING INTO THE REGION TOWARD MIDNIGHT. AS A
RESULT WE EXPECT SCT SNOW/RAIN SHOWERS TO REDEVELOP. BL TEMPS WILL
BE MARGINAL NEAR THE COAST WHERE ANY PRECIP MAY BE IN THE FORM OF
RAIN...BUT EXPECT MOSTLY SNOW SHOWERS ELSEWHERE. CANT RULE OUT
MINOR ACCUM IN THE HIGHER TERRAIN.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
HIGHLIGHTS...
* ARCTIC AIR MOVES IN BEHIND THE LOW PRES THROUGH THE WEEKEND
* WEAK LOW PRES MAY BRING LIGHT SNOW ON CHRISTMAS DAY
* STRONG STORM POSSIBLE WED NIGHT INTO THU
OVERVIEW AND MODEL PREFERENCES...
21/00Z MODEL GUIDANCE SUITE CONTINUES TO SHOW DECENT SYNOPTIC
SCALE AGREEMENT THROUGH THE EARLY PORTION OF THE LONG TERM BUT ARE
STRUGGLING WITH TWO DIFFERENT SYSTEMS AFFECTING THE MID AND LONG
TERM SENSIBLE WX DETAILS. ECMWF HAS COME IN LINE WITH GFS/NAM
TIMING FOR THE LOW PRES THIS WEEKEND EXITING INTO THE
MARITIMES...SO WILL CONTINUE TO BASELINE FORECAST USING GFS AS IT
HAS SHOWN MORE CONSISTENCY. THE DISAGREEMENTS BEGIN REGARDING
WITH THE E CANADA FLOW PATTERN FOR THE CHRISTMAS EVE/DAY SYSTEM. A
SPAGHETTI PLOT OF OPERATIONAL LONG RANGE GUIDANCE AND ENSEMBLES
AT H5 ARE ALL OVER THE PLACE WITH THE NRN NEW ENGLAND E CANADA
FLOW PATTERN...SO STILL NOT A LOT OF CONFIDENCE IN WHETHER OR NOT
HIGH PRES TO THE N WILL SUPPRESS LIGHT SNOW FOR CHRISTMAS EVE TO
THE S. THE LATEST ECMWF IS CLOSER TO THE SOLUTION SUGGESTED BY THE
GFS AND A FEW GEFS MEMBERS. WILL LEAN ON HPC AS FOR NOW GIVEN THE
DIFFERENCES AND ISSUES WITH UPPER LVL FLOW PATTERN. IN REGARDS TO
THE MID WEEK SYSTEM NEXT WEEK...GUIDANCE IS ACTUALLY IN DECENT
AGREEMENT WITH THE DEEPENING/SHARPENING WAVE MOVING E FROM THE
ROCKIES AGAIN...BUT GENERATE VERY DIFFERENT SFC CYCLONES. ECMWF
CONTINUES TO BE SIMILAR TO THE SYSTEM FOR TODAY AND THE WEEKEND
WHILE GFS PUSHES THE LOW NEAR THE 40/70 BENCHMARK. HPC LEANS
TOWARD THE ECENS THIS STRETCH...WHICH IS COOLER THAN THE
OPERATIONAL ECMWF...BUT WARMER THAN THE GFS...SO GIVEN THIS IS A
GOOD COMPROMISE...WILL CONTINUE TO USE IT FOR THE MID-LATE WEEK
SYSTEM.
DETAILS...
SAT INTO MON...
SLOW MOVING CUTOFF LOW PRES AND ITS WEAKENING SFC LOW WILL
GRADUALLY BE SHIFTING INTO THE MARITIMES THROUGH THE PERIOD. THIS
WILL ALLOW A MUCH COLDER AIRMASS TO MOVE IN WITH H92 TEMPS
AVERAGING THE -5C TO -8C RANGE. THEREFORE...WITH SOME REMNANT
ENERGY WRAPPING AROUND AND LOW LVL MOISTURE WRAPPING AROUND THE
LOW SAT...A FEW SNOW SHOWERS ARE LIKELY WHICH GIVEN COOLER SFC
TEMPS MAY ACCUMULATE IN SPOTS. GENERALLY AN INCH OR LESS
ACCUMULATION IS EXPECTED AT ANY GIVEN LOCATION. WITH DRY/COLD
AIRMASS SHIFTING INTO THE REGION...SUN AND MON ARE EXPECTED TO BE
MOSTLY DRY...BUT ON THE COLDER SIDE OF SEASONABLE FOR
TEMPERATURES.
MON NIGHT INTO TUE NIGHT...
GIVEN THE UNCERTAINTY HERE...THERE ARE STILL SOME QUESTIONS TO BE
ANSWERED REGARDING WEAK LOW PRES PASSING TO THE S OF SRN NEW
ENGLAND. SOUNDINGS AND DIVERGENCE FIELDS SHOW A WEAK TROWAL
WRAPPING TO THE N WITH TEMP PROFILES COOL ENOUGH FOR SNOW RIGHT TO
THE S COAST. GIVEN THE UNCERTAINTY HOWEVER...THERE COULD BE A
SHARP CUTOFF BETWEEN THOSE THAT SEE SOME OF THE WHITE FOR
CHRISTMAS AND THOSE THAT DON/T AND IT IS STILL POSSIBLE IT MAY BE
DRY ACROSS THE BOARD WITH STRONG HIGH PRES TO THE N. THE HPC STILL
FAVORS AREAS S OF THE MASS PIKE...SO WILL CONTINUE WITH THIS
SUGGESTION FOR THIS FORECAST UPDATE.
WED AND THU...
A MUCH MORE DYNAMIC SYSTEM WILL APPROACH FOR THE MID TO LATE WEEK
TIMEFRAME. GIVEN THE WIDE ENVELOPE OF SOLUTIONS FOR THIS WHICH
WILL HAVE SIGNIFICANT DIFFERENCES IN SENSIBLE WX DETAILS /GUIDANCE
RANGES FROM AN ALL RAIN TO AN ALL SNOW EVENT/. WILL TREND TOWARD
HPC WHICH IS AN ECENS BASES SOLUTION AT THIS TIME. THIS
COMPROMISES WITH SOME SNOW TO THE N AND RAIN IN THE S.
HOWEVER...NEITHER ALL SNOW OR ALL RAIN SOLUTIONS CAN/T BE RULED
OUT AND WILL HAVE TO BE MONITORED ESPECIALLY ONCE THE WAVE ITS
ASSOCIATED WITH CAN BE SAMPLED OVER LAND OBSERVING SITES.
FRI...
MODEL GUIDANCE DOES SUGGEST THAT IN ANY CASE...COOL HIGH PRES
WILL BE BUILDING IN TOWARD THE END OF THE WEEK...SO WILL LEAN
GUIDANCE IN THIS SOLUTION FOR THE EXTENDED PERIOD.
&&
.AVIATION /11Z FRIDAY THROUGH TUESDAY/...
SHORT TERM...HIGH CONFIDENCE.
A MAINLY MVFR/IFR TO START THIS MORNING...BUT IT IS EXPECTED THAT
THE TREND WILL BE TOWARD IFR AS A BAND OF RAIN AND STRONG WINDS
MOVE THROUGH THIS MORNING AND EARLY AFTERNOON FROM WEST TO EAST.
AFTER THE RAIN MOVES OUT...COULD SEE A RAPID IMPROVEMENT TO VFR
THROUGH THE EVENING BEFORE FOG BUILDS OVER AGAIN TONIGHT WITH
VSBYS DIPPING BACK TO THE MVFR/IFR LVLS. WINDS WILL BE STRONG
TODAY OUT OF THE SE...GUSTS 30-40 IN THE INTERIOR WITH NEAR
COASTAL TERMINALS SEEING 40-50 KT GUSTS AT TIMES. WINDS RAPIDLY
SHIFT TO THE WSW AFTER RAIN MOVES OUT.
KBOS TAF...HIGH CONFIDENCE IN TRENDS...LOWER CONFIDENCE IN EXACT
TIMING IN TAFS.
TREND WILL BE TOWARD A PERIOD OF IFR THROUGH MID AFTERNOON WITH
RAIN AND LOW CIGS. WINDS WILL ALSO BE STRONG OUT OF THE SW GUSTING
AS HIGH AS 40-50 KT BY LATE MORNING/EARLY AFTERNOON. RAPID
IMPROVEMENT TO VFR AFTER WINDS DIMINISH A BIT AND SHIFT TO WSW.
LLWS MUCH OF THE EARLY PORTION OF THE DAY
KBDL TAF...HIGH CONFIDENCE IN TRENDS...LOWER CONFIDENCE IN EXACT
TIMING.
TREND WILL BE TOWARD A PERIOD OF IFR THROUGH THE EARLY AFTERNOON
WITH STRONG WINDS 16Z-19Z /GUSTS AROUND 30 KT/. ONCE WINDS SHIFT
TO THE WSW...EXPECT THEM TO DIMINISH AND FOR A LIFT TO VFR INTO
THE EVENING.
OUTLOOK...SATURDAY THROUGH TUESDAY...
SATURDAY INTO SATURDAY NIGHT...MODERATE CONFIDENCE.
MAINLY VFR. HOWEVER...OCCASIONAL RAIN AND SNOW SHOWERS COULD
REDUCE BOTH VSBYS AND CIGS TO MVFR. WINDS GUST 30-40 KT OUT OF
THE NW SAT NIGHT.
SUNDAY AND MONDAY...HIGH CONFIDENCE.
VFR. NW WINDS GUST 20-30 KT THROUGH THE DAY ON SUN.
TUESDAY...MODERATE CONFIDENCE.
MAINLY VFR....BUT LIGHT SNOW IS POSSIBLE EARLY TUESDAY ESPECIALLY
TERMINALS S OF THE MASS PIKE.
&&
.MARINE...
MODERATE TO HIGH CONFIDENCE THROUGH TONIGHT.
A BRIEF PERIOD OF STORM FORCE SE WIND GUSTS TO NEAR 50 KT IS
EXPECTED FROM WEST TO EAST 14-20Z. STORM WARNINGS CONTINUE EXCEPT
STRONG GALES FOR NARR BAY AND BOSTON HARBOR. RAIN...HEAVY AT TIMES
IMPROVING FROM WEST TO EAST DURING THE AFTERNOON.
WINDS WILL DIMINISH WITH THE WIND SHIFT TO SW LATER THIS AFTERNOON
BUT STILL EXPECT WIND GUSTS TO 30 KT TONIGHT.
OUTLOOK...SATURDAY THROUGH TUESDAY...
MODERATE TO HIGH CONFIDENCE THROUGH TUESDAY.
SAT INTO SAT NIGHT...MODERATE CONFIDENCE.
WINDS BRIEFLY DIP TO SMALL CRAFT LEVELS DURING THE DAY
SATURDAY...BUT THEN ONCE WINDS SHIFT TO THE NW EXPECT GALE FORCE
GUSTS TO RETURN ESPECIALLY SAT NIGHT INTO EARLY SUNDAY. SEAS
REMAIN ELEVATED.
SUN INTO MON...HIGH CONFIDENCE.
BOTH WINDS AND SEAS GRADUALLY DIMINISH THROUGH THE PERIOD.
ALTHOUGH EXPECTING SMALL CRAFT WINDS THROUGH SUN NIGHT. BY
MON...SEAS AND WINDS SHOULD DROP BELOW SCA THRESHOLDS.
TUE...MODERATE CONFIDENCE.
WINDS AND SEAS START BELOW SMALL CRAFT THRESHOLDS...BUT MAY SEE
25 KT GUSTS AND SEAS NEAR 5 FT OVER SRN OUTER WATERS BY TUE
AFTERNOON AS A WEAK LOW PRES PASSES S OF THE REGION.
&&
.TIDES/COASTAL FLOODING...
NOT EXPECTING ANY COASTAL FLOODING OR BEACH EROSION AS ASTRO
TIDES ARE VERY LOW.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...WIND ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR MAZ005>007-
013>021.
HIGH WIND WARNING UNTIL 4 PM EST THIS AFTERNOON FOR MAZ022>024.
NH...NONE.
RI...HIGH WIND WARNING UNTIL 1 PM EST THIS AFTERNOON FOR RIZ008.
WIND ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR RIZ001>007.
MARINE...STORM WARNING UNTIL 4 PM EST THIS AFTERNOON FOR ANZ231>234-250-
251-254-255.
GALE WARNING UNTIL 4 PM EST THIS AFTERNOON FOR ANZ230-236.
STORM WARNING UNTIL 1 PM EST THIS AFTERNOON FOR ANZ235-237-256.
&&
$$
SYNOPSIS...KJC/DOODY
NEAR TERM...KJC/DOODY
SHORT TERM...KJC
LONG TERM...DOODY
AVIATION...KJC/DOODY
MARINE...KJC/DOODY
TIDES/COASTAL FLOODING...
AREA FORECAST DISCUSSION
NWS TAUNTON MA
411 AM EST FRI DEC 21 2012
.SYNOPSIS...
LOW PRESSURE AND ITS ATTENDING OCCLUDED FRONT WILL BRING A
PERIOD OF HEAVY RAIN AND STRONG WINDS TO THE REGION TODAY. COLDER
TEMPS WILL FOLLOW FOR THE WEEKEND INTO EARLY NEXT WEEK. A WEAK
STORM COULD BRING SOME SNOW AND/OR RAIN ON CHRISTMAS DAY. A
STRONGER STORM MAY AFFECT NEW ENGLAND LATE WED INTO THU.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SNOW IN THE DISTANT INTERIOR HAS ACCUMULATED 1-2 INCHES. IT IS
STILL SNOWING ACROSS WESTERN AND NORTHERN MA INTO S NH WITH TEMPS
32-34 DEGREES. HOWEVER...LOW LEVEL WARMING WILL RESULT IN A QUICK
CHANGEOVER TO RAIN THROUGH 6 AM. ADDITIONAL ACCUMULATION UP TO AN
INCH IS POSSIBLE.
A PERIOD OF STRONG WINDS AND HEAVY RAIN WILL MOVE ACROSS SNE
TODAY AS AN ANOMALOUS LOW LEVEL JET AHEAD OF A STRONG OCCLUDED
FRONT SWEEPS ACROSS THE REGION. THIS SYSTEM IS RATHER PROGRESSIVE
SO THE WORST OF THE WIND AND RAIN WILL LIKELY BE CONFINED TO A 3-4
HOUR WINDOW...12-16Z IN THE WEST AND 16-20Z EASTERN NEW ENG.
RAINFALL/FLOOD POTENTIAL...
STRONG LOW LEVEL JET 3-4SD AND +2SD PWAT ANOMALY WILL BRING A
PERIOD OF HEAVY RAIN TO SNE. HOWEVER...THIS SYSTEM WILL BE QUICK
MOVING LIMITING THE DURATION OF HEAVY RAIN IN ANY ONE LOCATION.
NAM IS THE MOST ROBUST WITH ELEVATED INSTABILITY PARAMETERS AND
SUGGEST POTENTIAL FOR SOME CONVECTION/THUNDER...AND HRRR IS
INDICATING A FINE LINE OF CONVECTION MOVING THROUGH.
HOWEVER...GFS AND ECMWF ARE RATHER WEAK WITH INSTABILITY. DUE TO
MIXED SIGNALS CONFIDENCE IN THUNDER AND ENHANCED RAINFALL RATES
IS LOW. EXPECTED RAINFALL IS 0.5" TO 1" WITH ISOLD AMOUNTS UP TO
1.5" ACROSS W ZONES WHICH WOULD MAINLY RESULT IN MINOR URBAN AND
POOR DRAINAGE FLOODING ISSUES. RAINFALL WILL BE EXITING THE REGION
FROM WEST TO EAST 16-21Z.
HIGH WIND THREAT...
MODEL DIFFERENCES IN THE STRENGTH OF THE LOW LEVEL JET INCREASES
FORECAST UNCERTAINTY REGARDING MAGNITUDE OF THE WIND THREAT. GFS
IS STRONGEST WITH THE JET INDICATING 80 KT AT 925 MB...BUT NAM HAS
TRENDED WEAKER WITH 70 KT AND ECMWF IS WEAKEST AT 60 KT. DESPITE
THESE DIFFERENCES...IMPRESSIVE PRESSURE FALLS ARE FORECAST
COINCIDENT WITH THE LOW LEVEL JET WHICH WILL ENHANCE WIND
ACCELERATION AND TEMPS ARE EXPECTED TO SPIKE INTO THE 50S IN THE
COASTAL PLAIN WHICH WILL INCREASE MIXING POTENTIAL. MODEL
SOUNDINGS ARE NOT VERY SUPPORTIVE OF STRONG WINDS MIXING
DOWN...BUT THE MILDER TEMPS AND ISALLOBARIC CONTRIBUTION SUPPORT
STRONG WINDS REACHING THE SURFACE. AS MENTIONED ABOVE WE ARE NOT
CONFIDENT IN A FINE LINE OF CONVECTION WHICH WOULD FURTHER INCREASE
HIGH WIND THREAT BUT WE HAVE ENOUGH CONFIDENCE TO GO WITH A HIGH
WIND WARNING FOR CAPE/ISLANDS WHERE STRONGEST LOW LEVEL WINDS ARE
EXPECTED. ELSEWHERE WE WILL GO WITH A WIND ADVISORY FOR RI AND
EASTERN MA. TIMING OF STRONGEST WINDS WILL BE 14-17Z RI AND
16-19Z E MA AND CAPE/ISLANDS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
MID LEVEL LOW MOVES INTO CENTRAL AND NORTHERN NEW ENG TONIGHT WITH
A STRONG SHORTWAVE ROTATING INTO THE REGION TOWARD MIDNIGHT. AS A
RESULT WE EXPECT SCT SNOW/RAIN SHOWERS TO REDEVELOP. BL TEMPS WILL
BE MARGINAL NEAR THE COAST WHERE ANY PRECIP MAY BE IN THE FORM OF
RAIN...BUT EXPECT MOSTLY SNOW SHOWERS ELSEWHERE. CANT RULE OUT
MINOR ACCUM IN THE HIGHER TERRAIN.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
HIGHLIGHTS...
* ARCTIC AIR MOVES IN BEHIND THE LOW PRES THROUGH THE WEEKEND
* WEAK LOW PRES MAY BRING LIGHT SNOW ON CHRISTMAS DAY
* STRONG STORM POSSIBLE WED NIGHT INTO THU
OVERVIEW AND MODEL PREFERENCES...
21/00Z MODEL GUIDANCE SUITE CONTINUES TO SHOW DECENT SYNOPTIC
SCALE AGREEMENT THROUGH THE EARLY PORTION OF THE LONG TERM BUT ARE
STRUGGLING WITH TWO DIFFERENT SYSTEMS AFFECTING THE MID AND LONG
TERM SENSIBLE WX DETAILS. ECMWF HAS COME IN LINE WITH GFS/NAM
TIMING FOR THE LOW PRES THIS WEEKEND EXITING INTO THE
MARITIMES...SO WILL CONTINUE TO BASELINE FORECAST USING GFS AS IT
HAS SHOWN MORE CONSISTENCY. THE DISAGREEMENTS BEGIN REGARDING
WITH THE E CANADA FLOW PATTERN FOR THE CHRISTMAS EVE/DAY SYSTEM. A
SPAGHETTI PLOT OF OPERATIONAL LONG RANGE GUIDANCE AND ENSEMBLES
AT H5 ARE ALL OVER THE PLACE WITH THE NRN NEW ENGLAND E CANADA
FLOW PATTERN...SO STILL NOT A LOT OF CONFIDENCE IN WHETHER OR NOT
HIGH PRES TO THE N WILL SUPPRESS LIGHT SNOW FOR CHRISTMAS EVE TO
THE S. THE LATEST ECMWF IS CLOSER TO THE SOLUTION SUGGESTED BY THE
GFS AND A FEW GEFS MEMBERS. WILL LEAN ON HPC AS FOR NOW GIVEN THE
DIFFERENCES AND ISSUES WITH UPPER LVL FLOW PATTERN. IN REGARDS TO
THE MID WEEK SYSTEM NEXT WEEK...GUIDANCE IS ACTUALLY IN DECENT
AGREEMENT WITH THE DEEPENING/SHARPENING WAVE MOVING E FROM THE
ROCKIES AGAIN...BUT GENERATE VERY DIFFERENT SFC CYCLONES. ECMWF
CONTINUES TO BE SIMILAR TO THE SYSTEM FOR TODAY AND THE WEEKEND
WHILE GFS PUSHES THE LOW NEAR THE 40/70 BENCHMARK. HPC LEANS
TOWARD THE ECENS THIS STRETCH...WHICH IS COOLER THAN THE
OPERATIONAL ECMWF...BUT WARMER THAN THE GFS...SO GIVEN THIS IS A
GOOD COMPROMISE...WILL CONTINUE TO USE IT FOR THE MID-LATE WEEK
SYSTEM.
DETAILS...
SAT INTO MON...
SLOW MOVING CUTOFF LOW PRES AND ITS WEAKENING SFC LOW WILL
GRADUALLY BE SHIFTING INTO THE MARITIMES THROUGH THE PERIOD. THIS
WILL ALLOW A MUCH COLDER AIRMASS TO MOVE IN WITH H92 TEMPS
AVERAGING THE -5C TO -8C RANGE. THEREFORE...WITH SOME REMNANT
ENERGY WRAPPING AROUND AND LOW LVL MOISTURE WRAPPING AROUND THE
LOW SAT...A FEW SNOW SHOWERS ARE LIKELY WHICH GIVEN COOLER SFC
TEMPS MAY ACCUMULATE IN SPOTS. GENERALLY AN INCH OR LESS
ACCUMULATION IS EXPECTED AT ANY GIVEN LOCATION. WITH DRY/COLD
AIRMASS SHIFTING INTO THE REGION...SUN AND MON ARE EXPECTED TO BE
MOSTLY DRY...BUT ON THE COLDER SIDE OF SEASONABLE FOR
TEMPERATURES.
MON NIGHT INTO TUE NIGHT...
GIVEN THE UNCERTAINTY HERE...THERE ARE STILL SOME QUESTIONS TO BE
ANSWERED REGARDING WEAK LOW PRES PASSING TO THE S OF SRN NEW
ENGLAND. SOUNDINGS AND DIVERGENCE FIELDS SHOW A WEAK TROWAL
WRAPPING TO THE N WITH TEMP PROFILES COOL ENOUGH FOR SNOW RIGHT TO
THE S COAST. GIVEN THE UNCERTAINTY HOWEVER...THERE COULD BE A
SHARP CUTOFF BETWEEN THOSE THAT SEE SOME OF THE WHITE FOR
CHRISTMAS AND THOSE THAT DON/T AND IT IS STILL POSSIBLE IT MAY BE
DRY ACROSS THE BOARD WITH STRONG HIGH PRES TO THE N. THE HPC STILL
FAVORS AREAS S OF THE MASS PIKE...SO WILL CONTINUE WITH THIS
SUGGESTION FOR THIS FORECAST UPDATE.
WED AND THU...
A MUCH MORE DYNAMIC SYSTEM WILL APPROACH FOR THE MID TO LATE WEEK
TIMEFRAME. GIVEN THE WIDE ENVELOPE OF SOLUTIONS FOR THIS WHICH
WILL HAVE SIGNIFICANT DIFFERENCES IN SENSIBLE WX DETAILS /GUIDANCE
RANGES FROM AN ALL RAIN TO AN ALL SNOW EVENT/. WILL TREND TOWARD
HPC WHICH IS AN ECENS BASES SOLUTION AT THIS TIME. THIS
COMPROMISES WITH SOME SNOW TO THE N AND RAIN IN THE S.
HOWEVER...NEITHER ALL SNOW OR ALL RAIN SOLUTIONS CAN/T BE RULED
OUT AND WILL HAVE TO BE MONITORED ESPECIALLY ONCE THE WAVE ITS
ASSOCIATED WITH CAN BE SAMPLED OVER LAND OBSERVING SITES.
FRI...
MODEL GUIDANCE DOES SUGGEST THAT IN ANY CASE...COOL HIGH PRES
WILL BE BUILDING IN TOWARD THE END OF THE WEEK...SO WILL LEAN
GUIDANCE IN THIS SOLUTION FOR THE EXTENDED PERIOD.
&&
.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
SHORT TERM...HIGH CONFIDENCE.
THROUGH 12Z...MAINLY MVFR IN AREAS OF LIGHT RAIN. SNOW WITH IFR
CONDITIONS IN THE INTERIOR WILL CHANGE TO RAIN 08-11Z.
AFTER 12Z...HIGH PROBABILITY FOR IFR CONDITIONS AS BAND OF
RAIN...HEAVY AT TIMES MOVES THROUGH. STRONG ESE WINDS WITH A 2-3
HOUR PERIOD OF GUSTS 40-50 KT AND LLWS MOVING EAST ACROSS COASTAL
RI AND MA 14-19Z. IFR IMPROVING TO VFR FROM WEST TO EAST DURING
THE LATE AFTERNOON AND EVENING. SCT RAIN AND SNOW SHOWERS TONIGHT
WITH AREAS OF MVFR POSSIBLE.
KBOS TAF...HIGH CONFIDENCE IN IFR CONDITIONS DEVELOPING IN RAIN
AND STRONG SE WINDS WITH GUSTS TO 45 KT. MODERATE CONFIDENCE IN
TIMING. HEAVIEST RAIN AND STRONGEST WIND 16-19Z WITH IMPROVEMENT
TO VFR TOWARD 00Z.
KBDL TAF...HIGH CONFIDENCE IN IFR CONDITIONS DEVELOPING IN RAIN
AND SE GUSTS TO 25-30 KT. MODERATE CONFIDENCE IN TIMING. HEAVIEST
RAIN AND STRONGEST WIND 13-16Z WITH IMPROVEMENT TO VFR TOWARD
21Z.
OUTLOOK...SATURDAY THROUGH TUESDAY...
SATURDAY INTO SATURDAY NIGHT...MODERATE CONFIDENCE.
MAINLY VFR. HOWEVER...OCCASIONAL RAIN AND SNOW SHOWERS COULD
REDUCE BOTH VSBYS AND CIGS TO MVFR. WINDS GUST 30-40 KT OUT OF
THE NW SAT NIGHT.
SUNDAY AND MONDAY...HIGH CONFIDENCE.
VFR. NW WINDS GUST 20-30 KT THROUGH THE DAY ON SUN.
TUESDAY...MODERATE CONFIDENCE.
MAINLY VFR....BUT LIGHT SNOW IS POSSIBLE EARLY TUESDAY ESPECIALLY
TERMINALS S OF THE MASS PIKE.
&&
.MARINE...
MODERATE TO HIGH CONFIDENCE THROUGH TONIGHT.
A BRIEF PERIOD OF STORM FORCE SE WIND GUSTS TO NEAR 50 KT IS
EXPECTED FROM WEST TO EAST 14-20Z. STORM WARNINGS CONTINUE EXCEPT
STRONG GALES FOR NARR BAY AND BOSTON HARBOR. RAIN...HEAVY AT TIMES
IMPROVING FROM WEST TO EAST DURING THE AFTERNOON.
WINDS WILL DIMINISH WITH THE WIND SHIFT TO SW LATER THIS AFTERNOON
BUT STILL EXPECT WIND GUSTS TO 30 KT TONIGHT.
OUTLOOK...SATURDAY THROUGH TUESDAY...
MODERATE TO HIGH CONFIDENCE THROUGH TUESDAY.
SAT INTO SAT NIGHT...MODERATE CONFIDENCE.
WINDS BRIEFLY DIP TO SMALL CRAFT LEVELS DURING THE DAY
SATURDAY...BUT THEN ONCE WINDS SHIFT TO THE NW EXPECT GALE FORCE
GUSTS TO RETURN ESPECIALLY SAT NIGHT INTO EARLY SUNDAY. SEAS
REMAIN ELEVATED.
SUN INTO MON...HIGH CONFIDENCE.
BOTH WINDS AND SEAS GRADUALLY DIMINISH THROUGH THE PERIOD.
ALTHOUGH EXPECTING SMALL CRAFT WINDS THROUGH SUN NIGHT. BY
MON...SEAS AND WINDS SHOULD DROP BELOW SCA THRESHOLDS.
TUE...MODERATE CONFIDENCE.
WINDS AND SEAS START BELOW SMALL CRAFT THRESHOLDS...BUT MAY SEE
25 KT GUSTS AND SEAS NEAR 5 FT OVER SRN OUTER WATERS BY TUE
AFTERNOON AS A WEAK LOW PRES PASSES S OF THE REGION.
&&
.TIDES/COASTAL FLOODING...
NOT EXPECTING ANY COASTAL FLOODING OR BEACH EROSION AS ASTRO
TIDES ARE VERY LOW.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...WIND ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR MAZ005>007-
013>021.
HIGH WIND WARNING UNTIL 4 PM EST THIS AFTERNOON FOR MAZ022>024.
NH...NONE.
RI...HIGH WIND WARNING UNTIL 1 PM EST THIS AFTERNOON FOR RIZ008.
WIND ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR RIZ001>007.
MARINE...STORM WARNING UNTIL 4 PM EST THIS AFTERNOON FOR ANZ231>234-250-
251-254-255.
GALE WARNING UNTIL 4 PM EST THIS AFTERNOON FOR ANZ230-236.
STORM WARNING UNTIL 1 PM EST THIS AFTERNOON FOR ANZ235-237-256.
&&
$$
SYNOPSIS...KJC/DOODY
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...DOODY
AVIATION...KJC/DOODY
MARINE...KJC/DOODY
TIDES/COASTAL FLOODING...STAFF
AREA FORECAST DISCUSSION
NWS TAUNTON MA
408 AM EST FRI DEC 21 2012
.SYNOPSIS...
LOW PRESSURE AND ITS ATTENDING OCCLUDED FRONT WILL BRING A
PERIOD OF HEAVY RAIN AND STRONG WINDS TO THE REGION TODAY. COLDER
TEMPS WILL FOLLOW FOR THE WEEKEND INTO EARLY NEXT WEEK. A WEAK
STORM COULD BRING SOME SNOW AND/OR RAIN ON CHRISTMAS DAY. A
STRONGER STORM MAY AFFECT NEW ENGLAND LATE WED INTO THU.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SNOW IN THE DISTANT INTERIOR HAS ACCUMULATED 1-2 INCHES. IT IS
STILL SNOWING ACROSS WESTERN AND NORTHERN MA INTO S NH WITH TEMPS
32-34 DEGREES. HOWEVER...LOW LEVEL WARMING WILL RESULT IN A QUICK
CHANGEOVER TO RAIN THROUGH 6 AM. ADDITIONAL ACCUMULATION UP TO AN
INCH IS POSSIBLE.
A PERIOD OF STRONG WINDS AND HEAVY RAIN WILL MOVE ACROSS SNE
TODAY AS AN ANOMALOUS LOW LEVEL JET AHEAD OF A STRONG OCCLUDED
FRONT SWEEPS ACROSS THE REGION. THIS SYSTEM IS RATHER PROGRESSIVE
SO THE WORST OF THE WIND AND RAIN WILL LIKELY BE CONFINED TO A 3-4
HOUR WINDOW...12-16Z IN THE WEST AND 16-20Z EASTERN NEW ENG.
RAINFALL/FLOOD POTENTIAL...
STRONG LOW LEVEL JET 3-4SD AND +2SD PWAT ANOMALY WILL BRING A
PERIOD OF HEAVY RAIN TO SNE. HOWEVER...THIS SYSTEM WILL BE QUICK
MOVING LIMITING THE DURATION OF HEAVY RAIN IN ANY ONE LOCATION.
NAM IS THE MOST ROBUST WITH ELEVATED INSTABILITY PARAMETERS AND
SUGGEST POTENTIAL FOR SOME CONVECTION/THUNDER...AND HRRR IS
INDICATING A FINE LINE OF CONVECTION MOVING THROUGH.
HOWEVER...GFS AND ECMWF ARE RATHER WEAK WITH INSTABILITY. DUE TO
MIXED SIGNALS CONFIDENCE IN THUNDER AND ENHANCED RAINFALL RATES
IS LOW. EXPECTED RAINFALL IS 0.5" TO 1" WITH ISOLD AMOUNTS UP TO
1.5" ACROSS W ZONES WHICH WOULD MAINLY RESULT IN MINOR URBAN AND
POOR DRAINAGE FLOODING ISSUES. RAINFALL WILL BE EXITING THE REGION
FROM WEST TO EAST 16-21Z.
HIGH WIND THREAT...
MODEL DIFFERENCES IN THE STRENGTH OF THE LOW LEVEL JET INCREASES
FORECAST UNCERTAINTY REGARDING MAGNITUDE OF THE WIND THREAT. GFS
IS STRONGEST WITH THE JET INDICATING 80 KT AT 925 MB...BUT NAM HAS
TRENDED WEAKER WITH 70 KT AND ECMWF IS WEAKEST AT 60 KT. DESPITE
THESE DIFFERENCES...IMPRESSIVE PRESSURE FALLS ARE FORECAST
COINCIDENT WITH THE LOW LEVEL JET WHICH WILL ENHANCE WIND
ACCELERATION AND TEMPS ARE EXPECTED TO SPIKE INTO THE 50S IN THE
COASTAL PLAIN WHICH WILL INCREASE MIXING POTENTIAL. MODEL
SOUNDINGS ARE NOT VERY SUPPORTIVE OF STRONG WINDS MIXING
DOWN...BUT THE MILDER TEMPS AND ISALLOBARIC CONTRIBUTION SUPPORT
STRONG WINDS REACHING THE SURFACE. AS MENTIONED ABOVE WE ARE NOT
CONFIDENT IN A FINE LINE OF CONVECTION WHICH WOULD FURTHER INCREASE
HIGH WIND THREAT BUT WE HAVE ENOUGH CONFIDENCE TO GO WITH A HIGH
WIND WARNING FOR CAPE/ISLANDS WHERE STRONGEST LOW LEVEL WINDS ARE
EXPECTED. ELSEWHERE WE WILL GO WITH A WIND ADVISORY FOR RI AND
EASTERN MA. TIMING OF STRONGEST WINDS WILL BE 14-17Z RI AND
16-19Z E MA AND CAPE/ISLANDS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
MID LEVEL LOW MOVES INTO CENTRAL AND NORTHERN NEW ENG TONIGHT WITH
A STRONG SHORTWAVE ROTATING INTO THE REGION TOWARD MIDNIGHT. AS A
RESULT WE EXPECT SCT SNOW/RAIN SHOWERS TO REDEVELOP. BL TEMPS WILL
BE MARGINAL NEAR THE COAST WHERE ANY PRECIP MAY BE IN THE FORM OF
RAIN...BUT EXPECT MOSTLY SNOW SHOWERS ELSEWHERE. CANT RULE OUT
MINOR ACCUM IN THE HIGHER TERRAIN.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
HIGHLIGHTS...
* ARCTIC AIR MOVES IN BEHIND THE LOW PRES THROUGH THE WEEKEND
* WEAK LOW PRES MAY BRING LIGHT SNOW ON CHRISTMAS DAY
* STRONG STORM POSSIBLE WED NIGHT INTO THU
MODELS ARE IN DECENT AGREEMENT THROUGH MUCH OF THE LONG TERM. THERE
ARE DISCREPANCIES WITH RESPECT TO THE TRACK OF A LOW PRESSURE SYSTEM
WEDNESDAY NIGHT AND THURSDAY. THE GFS DEVELOPS A LOW PRESSURE
SYSTEM IN NORTH CAROLINA OFF A PRIMARY LOW IN THE APPALACHIANS.
THIS SECONDARY LOW BECOMES THE PRIMARY AS IT MOVES UP THE EASTERN
SEABOARD MOVING OFFSHORE IN NEW JERSEY AND PASSING SOUTHERN NEW
ENGLAND JUST INSIDE THE 40/70 BENCHMARK. THE ECMWF BRINGS THE LOW
PRESSURE UP THE COAST AND THROUGH NEW YORK STATE. THE GFS KEEPS
COOLER TEMPERATURES IN THE AREA WITH POSSIBLY SOME WINTRY
PRECIPITATION WHILE THE ECMWF WOULD BE THE WARMER SOLUTION.
FRIDAY NIGHT THROUGH SATURDAY...UPPER LOW OVER NORTHERN NEW ENGLAND
WILL MOVE NORTHWARD INTO QUEBEC SATURDAY. THERE ARE DISCREPANCIES
WITH HOW QUICKLY THE UPPER TROUGH MOVES OUT OF THE NORTHEAST. THE
ECMWF IS THE SLOWEST AND KEEPS THE TROUGH OVER THE NORTHEAST THROUGH
SUNDAY. THE NAM IS SOMEWHAT MORE PROGRESSIVE AND THE GFS EVEN
FASTER...MOVING THE TROUGH INTO CANADA LATE SATURDAY. THE GFS/NAM
ARE HANDLING THE STORM SYSTEM BETTER CURRENTLY SO WILL USE A BLEND
FOR THIS TIME PERIOD. ALL MODELS INDICATE SOME LINGERING PRECIP
OVER SOUTHERN NEW ENGLAND FRIDAY NIGHT INTO SATURDAY MORNING.
EXPECT THAT AS COLD AIR STARTS TO WORK ITS WAY IN BEHIND THE FRONTAL
SYSTEM...RAIN WILL CHANGE TO SNOW FRIDAY NIGHT AND ANY LINGERING
SHOWERS/FLURRIES WILL BE AS SNOW SATURDAY. SNOW SHOULD COME TO AN
END SATURDAY AFTERNOON AND EVENING WITH DRIER AIR MOVING INTO THE
REGION. TEMPERATURES WILL DROP INTO THE UPPER TEENS TO MID 20S MOST
LOCATIONS OVERNIGHT.
SUNDAY AND MONDAY...DRY...COLD WEATHER EXPECTED AS HIGH PRESSURE
BUILDS IN OVER THE REGION. STRONG COLD AIR ADVECTION WILL BRING
COLDER AIR AND BREEZY CONDITIONS INTO SOUTHERN NEW ENGLAND SUNDAY.
HIGH TEMPERATURES SHOULD BE IN THE MID 20S TO MID 30S WHICH IS JUST
A FEW DEGREES COLDER THAN NORMAL FOR MID TO LATE DECEMBER.
CHRISTMAS DAY...LOW PRESSURE DEVELOPS OFF THE DELMARVA PENINSULA AND
MOVES OVER OR JUST SOUTH OF THE 40/70 BENCHMARK. THIS MAY BRING A
PERIOD OF LIGHT SNOW TO THE AREA. THERE IS SOME QUESTION HOW MUCH
OF AN INFLUENCE HIGH PRESSURE TO THE NORTH WILL HAVE ON PUSHING THAT
LOW FURTHER SOUTH WHICH WILL AFFECT THE NORTHWARD EXTENT OF ANY
PRECIPITATION THAT FALLS ON TUESDAY.
WEDNESDAY AND THURSDAY...THIS TIME FRAME IS THE PERIOD WITH THE MOST
MODEL DISCREPANCIES AND THAT ALL WITH THE PATH OF A LOW PRESSURE
SYSTEM MOVING OUT OF THE GULF OF MEXICO. THE ECMWF IS AN INSIDE
RUNNER BRINGING THE THE LOW UP THROUGH NEW YORK STATE AND IS THE
WARMER SOLUTION WITH MOSTLY RAIN...OR POSSIBLY SOME FREEZING
RAIN/ICE. THE GFS BRINGS THE LOW UP THE COAST AND OVER THE
BENCHMARK BRINGING COOLER TEMPERATURES AND LIKELY SNOW ACROSS MUCH
OF SOUTHERN NEW ENGLAND AND SOME RAIN ON THE CAPE AND ISLANDS.
&&
.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
SHORT TERM...HIGH CONFIDENCE.
THROUGH 12Z...MAINLY MVFR IN AREAS OF LIGHT RAIN. SNOW WITH IFR
CONDITIONS IN THE INTERIOR WILL CHANGE TO RAIN 08-11Z.
AFTER 12Z...HIGH PROBABILITY FOR IFR CONDITIONS AS BAND OF
RAIN...HEAVY AT TIMES MOVES THROUGH. STRONG ESE WINDS WITH A 2-3
HOUR PERIOD OF GUSTS 40-50 KT AND LLWS MOVING EAST ACROSS COASTAL
RI AND MA 14-19Z. IFR IMPROVING TO VFR FROM WEST TO EAST DURING
THE LATE AFTERNOON AND EVENING. SCT RAIN AND SNOW SHOWERS TONIGHT
WITH AREAS OF MVFR POSSIBLE.
KBOS TAF...HIGH CONFIDENCE IN IFR CONDITIONS DEVELOPING IN RAIN
AND STRONG SE WINDS WITH GUSTS TO 45 KT. MODERATE CONFIDENCE IN
TIMING. HEAVIEST RAIN AND STRONGEST WIND 16-19Z WITH IMPROVEMENT
TO VFR TOWARD 00Z.
KBDL TAF...HIGH CONFIDENCE IN IFR CONDITIONS DEVELOPING IN RAIN
AND SE GUSTS TO 25-30 KT. MODERATE CONFIDENCE IN TIMING. HEAVIEST
RAIN AND STRONGEST WIND 13-16Z WITH IMPROVEMENT TO VFR TOWARD
21Z.
OUTLOOK...SATURDAY THROUGH TUESDAY...
SAT...MODERATE CONFIDENCE. AREAS OF MVFR CIGS EXPECTED WITH SCT
RAIN/SNOW SHOWERS. GUSTY SW WINDS NEAR THE COAST FRI EVENING THEN
ANOTHER PULSE OF NW GUSTS TO 30 KT EXPECTED LATE SAT AND SAT
NIGHT.
SUNDAY AND MONDAY...HIGH CONFIDENCE. VFR. NW GUSTS TO 25 KT
SUN...DIMINISHING MON.
TUESDAY...MODERATE CONFIDENCE. MAINLY VFR. LIGHT SNOW POSSIBLE TUE
AFTN INTO TUE NIGHT.
&&
.MARINE...
MODERATE TO HIGH CONFIDENCE THROUGH TONIGHT.
A BRIEF PERIOD OF STORM FORCE SE WIND GUSTS TO NEAR 50 KT IS
EXPECTED FROM WEST TO EAST 14-20Z. STORM WARNINGS CONTINUE EXCEPT
STRONG GALES FOR NARR BAY AND BOSTON HARBOR. RAIN...HEAVY AT TIMES
IMPROVING FROM WEST TO EAST DURING THE AFTERNOON.
WINDS WILL DIMINISH WITH THE WIND SHIFT TO SW LATER THIS AFTERNOON
BUT STILL EXPECT WIND GUSTS TO 30 KT TONIGHT.
OUTLOOK...SATURDAY THROUGH TUESDAY...
MODERATE TO HIGH CONFIDENCE THROUGH TUESDAY.
SW SCA GUSTS TO 25-30 KT EXPECTED IN POST FRONTAL AIRMASS FRI NIGHT
INTO SAT...ESPECIALLY S COASTAL WATERS AS WINDS MAY TEMPORARILY
DIMINISH ACROSS NE MA WATERS LATE FRI NIGHT INTO SAT. ANOTHER PULSE
OF GALE FORCE WINDS EXPECTED SAT NIGHT WITH WIND SHIFT TO NW WHICH
MAY LINGER INTO SUN. WINDS WILL GRADUALLY DIMINISH SUN NIGHT INTO
MON BUT SCA GUSTS LIKELY. HAZARDOUS SEAS EXPECTED TO GRADUALLY
SUBSIDE SUN NIGHT AND MON. MON NIGHT AND TUE WINDS AND SEAS WILL
BE BELOW SCA CRITERIA.
&&
.TIDES/COASTAL FLOODING...
NOT EXPECTING ANY COASTAL FLOODING OR BEACH EROSION AS ASTRO
TIDES ARE VERY LOW.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...WIND ADVISORY FROM 7 AM THIS MORNING TO 3 PM EST THIS
AFTERNOON FOR MAZ005>007-013>021.
HIGH WIND WARNING FROM 7 AM THIS MORNING TO 4 PM EST THIS
AFTERNOON FOR MAZ022>024.
NH...NONE.
RI...HIGH WIND WARNING FROM 7 AM THIS MORNING TO 1 PM EST THIS
AFTERNOON FOR RIZ008.
WIND ADVISORY FROM 7 AM THIS MORNING TO 1 PM EST THIS
AFTERNOON FOR RIZ001>007.
MARINE...STORM WARNING UNTIL 4 PM EST THIS AFTERNOON FOR ANZ231>234-250-
251-254-255.
GALE WARNING FROM 7 AM THIS MORNING TO 4 PM EST THIS AFTERNOON
FOR ANZ230-236.
STORM WARNING UNTIL 1 PM EST THIS AFTERNOON FOR ANZ235-237-256.
&&
$$
SYNOPSIS...KJC/DOODY
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...DOODY
AVIATION...KJC/DOODY
MARINE...KJC/DOODY
TIDES/COASTAL FLOODING...
AREA FORECAST DISCUSSION
NWS MOUNT HOLLY NJ
251 AM EST FRI DEC 21 2012
.SYNOPSIS...
A POTENT AREA OF LOW PRESSURE WILL TRACK ACROSS THE GREAT LAKES AND
NORTHEAST TONIGHT AND FRIDAY, THEN ACROSS EASTERN CANADA DURING THE
WEEKEND. ITS ASSOCIATED STRONG COLD FRONT WILL SWEEP ACROSS OUR
REGION EARLY FRIDAY MORNING. A WEAK AREA OF HIGH PRESSURE THEN
BUILDS DOWN INTO OUR REGION LATE SUNDAY AND MONDAY. A WEAK LOW
PRESSURE SYSTEM MAY AFFECT OUR AREA MONDAY NIGHT INTO TUESDAY, WITH
THE POTENTIAL FOR A MUCH STRONGER STORM SET TO ARRIVE ON THURSDAY.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
STARTING IN THE POCONOS, WE ARE PLANNING ON LETTING THE ADVY
EXPIRE AT 11 PM. THE DRY AIR ALOFT HAS EVAP COOLED AND THE
FREEZING RAIN IN THE HIGHER TERRAIN HAS CHANGED TO SNOW. THE
NUMBER OF MESONET SITES BELOW FREEZING WHICH ONCE WAS AROUND 20 IS
DOWN TO 6. HRRR AND LATEST WRF-NMMB HAS EVERYONE ABOVE FREEZING BY
03Z. SOME SLIPPERY SPOTS WERE REPORTED IN THE HIGHER TERRAIN OF
MONROE COUNTY AND AROUND A QUARTER INCH OF SNOW IN PLACES.
NOW FOR THE OTHER WEATHER HAZARD, THE WIND. NOT AN EASY DECISION
BECAUSE THE SOUNDINGS ARE NEARLY ISOTHERMAL WITH POOR LAPSE RATES.
THE 00Z SOUNDINGS SUPPORTED A COMP BETWEEN THE WRF-NMMB AND GFS
FCST SPEEDS. SINCE THEN THE VWP LOOK OK AT KAKQ AND KLWX FOR THE
NEW WRF-NMMB 925MB WINDS, BUT THE MODEL IS RUNNING AROUND 5 TO
10 KTS TOO HOT AT 850MB. SO FAR THE MIXING OF STRONGER WINDS IN
THE CAROLINAS HAS BEEN SPORADIC. SO WHAT WE CAN GATHER THERE HAVE
NOT BEEN UPSIDE SURPRISES YET. THE OVERALL WIND FIELDS ARE
FORECAST THOUGH TO INTENSIFY FURTHER AS TIME GOES ON TONIGHT AND
THE MOMENTUM TRANSFER WINDS ON OCCASION ARE MIXING ADVY LEVEL WIND
GUSTS DOWN. THE MESOSCALE MODELS AND WE DONT KNOW IF THEY ARE THIS
GOOD ARE NOT FORECASTING A SINGLE NCFRB TOWARD MORNING. AFTER
COORD WITH OKX AND LOOKING AT THE 12/1/10 ANALOG THEY FOUND (WHICH
WAS AN ADVY TYPE EVENT CENTERED MAINLY IN THE ERN PART OF OUR
CWA), WE DECIDED TO ISSUE A WIND ADVY THAT COINCIDES CLOSEST WITH
THE 70KT OR GREATER ISOTACH ON THE LATEST WRF-NMMB. WE INCLUDED
ALL OF DELAWARE BAY BECAUSE OF THE SE FLOW. IF A NCFRB DOES FORM
NEAR THE JET MAX, THE ADVY MAY NEED TO BE UPGRADED OR EXPANDED.
RIGHT NOW CONFIDENCE IS TOO LOW TO ISSUE.
THE REST OF THE FCST WAS KEPT PRETTY MUCH AS IS, MOST OF THE
HEAVIEST PCPN IS EXPECTED TO FALL AFTER MIDNIGHT AND END RATHER
QUICKLY WITH THE CFP AROUND 12Z.
OTHER THAN SOME NUISANCE FLOODING, NO HYDRO ISSUES ARE EXPECTED.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/...
A THREAT OF RAIN SHOULD STILL EXIST FOR THE NORTHERN ZONES EARLY
TOMORROW MORNING. THEN WHEN THE UPPER LOW AND COLD POOL ALOFT MOVES
CLOSER, A SHOWER ANYWHERE CAN`T BE RULED OUT. TEMP PROFILES
SUGGEST SNOW SHOWERS FAR NORTH AND WEST.
TEMPS WILL HOLD STEADY OR FALL THROUGH THE 40S (30S NORTH AND WEST)
TOMORROW WITH WINDS GUSTING TO 30 OR 40 MPH.
LITTLE TO NO ACCUMULATION IS EXPECTED WHERE THE FLAKES FLY.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
A RATHER ACTIVE PATTERN LOOKS TO CONTINUE. THE OVERALL SYNOPTIC FLOW
IS COMPRISED OF A DEEP TROUGH OVER THE EAST FRIDAY NIGHT AND
SATURDAY, THEN ADDITIONAL ENERGY PUSHING INTO THE WEST ALLOWS
DOWNSTREAM RIDGING TO KICK THE TROUGH INTO CANADA WHERE IT TENDS TO
BECOME ELONGATED WEST TO EAST. A PIECE OF ENERGY ROTATING AROUND
THIS MAY ALLOW FOR A SHORT WAVE TROUGH TO SLIDE ACROSS THE GREAT
LAKES INTO THE NORTHEAST AROUND TUESDAY. A MUCH MORE PRONOUNCED
UPPER-LEVEL TROUGH THEN LOOKS TO EJECT OUT OF THE FOUR CORNERS
REGION TUESDAY NIGHT INTO WEDNESDAY. THIS FEATURE ALONG WITH A
DEEPENING SURFACE LOW IS THEN FORECAST TO MOVE THROUGH THE EAST NEXT
THURSDAY. OVERALL, THE MODEL GUIDANCE CONTINUES TO SHOW VARIABILITY
WITH TIMING AND SPACING OF EMBEDDED INDIVIDUAL FEATURES HOWEVER
CONTINUED SUPPORT FOR AN ACTIVE PATTERN. THE THERMAL GRADIENTS AND
AMPLITUDE OF THE PATTERN MAY BE PLAYING A ROLE WITH THE MODEL
VARIABILITY. IT APPEARS THERE IS AN INCREASING SIGNAL FOR AN EAST
COAST STORM DURING ABOUT THE SECOND HALF OF NEXT WEEK. OF COURSE
THIS FAR OUT, THE DETAILS ARE MUCH LESS CERTAIN AND THEREFORE MUCH
LOWER CONFIDENCE IN THE FORECAST BEYOND TUESDAY ESPECIALLY.
FOR FRIDAY NIGHT AND SATURDAY...AN INTENSE STORM IS FORECAST TO BE
IN THE SOUTHEAST CANADA AND NEW ENGLAND AREAS DURING THIS TIME
FRAME. IT WILL BE DRIVEN BY A SHARP UPPER-LEVEL TROUGH WITH A SHOT
OF MUCH COLDER AIR ALONG WITH IT. A RATHER DEEP CYCLONIC FLOW REGIME
WILL BE OCCURRING WITH THE POTENTIAL FOR SOME WRAPAROUND SNOW
SHOWERS, AND THE LAKE EFFECT SNOW MACHINE SHOULD BE IN HIGH GEAR. AS
THE CAA CONTINUES, SHORT WAVE ENERGY ROTATING AROUND THE PARENT
UPPER-LEVEL TROUGH SHOULD HELP TO MAINTAIN SOME SNOW SHOWERS INTO
OUR NORTHWEST ZONES. SOME OF THE MODEL GUIDANCE SHOWING SIGNS OF
CHANNELIZED VORTICITY ORIENTATED NORTHWEST TO SOUTHEAST. IF DEEP
ENOUGH MOISTURE CAN BE MAINTAINED AND ENOUGH LIFT/INSTABILITY CAN
OCCUR WITHIN THE NORTHWEST FLOW, SOME LOCALIZED SNOW SQUALLS MAY
OCCUR ACROSS NORTHEASTERN PENNSYLVANIA AND NORTHWESTERN NEW JERSEY.
WE WOULD LIKE TO SEE BETTER ORGANIZATION OF THE CHANNELIZED
VORTICITY TO INCREASE CONFIDENCE REGARDING LAKE EFFECT STREAMERS
REMAINING INTACT THIS FAR SOUTHEAST FROM THE LAKES. FOR NOW, WE
CARRIED LOW LIKELY POPS ACROSS THE POCONOS AND TOWARD FAR NORTHWEST
NEW JERSEY, THEN POPS TAPER WITH A SOUTHEASTWARD EXTENT. BEYOND THE
SLIGHT CHC POPS, WE CARRIED SCATTERED FLURRIES DOWN TO THE
INTERSTATE 95 CORRIDOR. SOME PLACES PARTICULARLY IN THE POCONOS
COULD PICK UP AN INCH OR TWO OF SNOW. FARTHER SOUTHEAST, WHILE A FEW
HEAVIER SNOW SHOWERS MAY BE ABLE TO OCCUR, THE DOWNSLOPING FLOW MAY
PROVIDE ENOUGH EXTRA DRYING TO ERODE THESE. THIS IS OF LOWER
CONFIDENCE THEREFORE DID NOT BRING THE SNOW SHOWER MENTION EVEN
FARTHER SOUTHEAST AND WENT WITH FLURRIES.
ANOTHER FORECAST CONCERN IS THE STRONG WIND POTENTIAL. A RATHER
TIGHT PRESSURE GRADIENT IS FORECAST TO REMAIN ACROSS OUR ENTIRE. THE
CAA COMBINED WITH THE TIGHT PRESSURE GRADIENT SHOULD KEEP THE SURFACE
WINDS GOING FRIDAY NIGHT DESPITE LESSENING VERTICAL MIXING AT TIMES.
THE VERTICAL MIXING IS MUCH MORE PRONOUNCED SATURDAY AS THE AIRMASS
IS CHILLY, THE LOW-LEVEL LAPSE RATES STEEPEN SOME MORE AND THERE IS
PLENTY OF WIND NOT TO FAR ABOVE THE SURFACE. THE FORECAST SOUNDINGS
GET CLOSE TO 40 KNOTS POTENTIALLY MIXING DOWN TO THE SURFACE,
ALTHOUGH THE GFS IS MORE ROBUST WITH THIS AS IT SUGGESTS NEARLY
50 KNOTS MIXING DOWN TO THE SURFACE. THE 925 MB WINDS ARE NOT AS
STRONG ON THE ECMWF WITH AROUND 40 KNOTS FORECAST SATURDAY
ESPECIALLY ACROSS THE SOUTHERN HALF OF OUR CWA. WE THOUGHT ABOUT
GOING WITH A HIGH WIND WATCH WITH THE GREATER CHC ACROSS ABOUT THE
SOUTHERN HALF OF THE CWA, HOWEVER THIS IS NEARLY TWO DAYS OUT. IT
MAY END UP BEING A WIND ADVISORY TYPE EVENT THEREFORE WE DECIDED TO
HOLD OFF ON ANY HEADLINES ATTM. WE HOWEVER WILL CONTINUE A
MENTION IN THE HAZARDOUS WEATHER OUTLOOK. WE INCREASED THE WINDS
SOME /ESPECIALLY GUSTS/ FOR SATURDAY FROM CONTINUITY WITH GUSTS
GENERALLY IN THE 40-45 MPH RANGE. AS FOR HIGH AND LOW TEMPERATURES,
WE GENERALLY TOOK AN EVEN BLEND OF THE NAM/GFS MOS.
FOR SUNDAY AND MONDAY /CHRISTMAS EVE/...THE POTENT STORM IS FORECAST
TO MOVE UP THROUGH THE CANADIAN MARITIMES, HOWEVER A TIGHTENED
PRESSURE GRADIENT GENERALLY REMAINS IN PLACE. THE OVERALL FLOW
THOUGH WILL BE LESSENING, HOWEVER VERTICAL MIXING WILL PROVIDE
ENOUGH FOR A BRISK DAY ON SUNDAY. IT APPEARS THAT WITHIN THE
NORTHWESTERLY FLOW, A SHORT WAVE ROTATING AROUND THE PARENT STORM
MAY TOSS A SURFACE TROUGH OR COLD FRONT TOWARD OUR REGION. THE LAKE
EFFECT SNOW MACHINE SHOULD BE WINDING DOWN SUNDAY AS THE CAA WANES
SOME AND THE LOW-LEVEL FLOW MAY TURN MORE WESTERLY.
A SHORT WAVE TRAVERSING THE NORTHERN TIER CHRISTMAS EVE MAY ALLOW
FOR A SURFACE LOW REFLECTION TO RACE OUT AHEAD OF THE DEEPENING
TROUGH IN THE WEST. SOME MOISTURE RETURN AHEAD OF IT ALONG WITH WAA,
MAY RESULT IN AN AREA OF OVERRUNNING PRECIPITATION. THERE IS A
QUESTION REGARDING HOW DRY THE AIRMASS IS OVER OUR AREA AND THE
STRENGTH OF THE OVERALL LIFT. A LIGHT INTENSITY OF THE PRECIPITATION
MAY PLAY MORE OF A ROLE, WITH EVEN DEPENDING ON HOW THE BOUNDARY
LAYER BEHAVES. FOR NOW WE WILL FAVOR SLIGHT CHC POPS FOR A WEAK
OVERRUNNING POTENTIAL AND GO RAIN AND/OR SNOW.
FOR TUESDAY...THE AFOREMENTIONED FRONT RUNNER WEAKER SURFACE WAVE
SHOULD SCOOT OUT TO SEA EARLY TUESDAY AS THE SHORT WAVE TROUGH MAY
END UP DAMPENING OUT SOME. WHILE THERE COULD BE SOME RESIDUAL LIGHT
PRECIPITATION AROUND TO START TUESDAY, WE SIMPLY FAVORED SLIGHT CHC
POPS IN THE MORNING GIVEN LOWER CONFIDENCE ON TIMING AND OF ANY MORE
ORGANIZED LIFT.
FOR WEDNESDAY AND THURSDAY...THE PATTERN ONCE AGAIN STARTS TO REALLY
RAMP UP WEDNESDAY AS ENERGY FROM THE FOUR CORNERS REGION SLIDES
ACROSS THE PLAINS AND THEN THE TENNESSEE VALLEY. THERE IS ANOTHER
SYSTEM UP IN THE CANADIAN MARITIMES OVERALL, WHICH WOULD TEND TO
LEAD TO BLOCKING. THIS DEVELOPING PATTERN IS LOOKING MORE CONDUCIVE
FOR A COASTAL STORM TO OCCUR. IN THIS UPCOMING POTENTIAL, THE
INITIAL SURFACE LOW MAY TRACK UP THE OHIO VALLEY BUT THEN WEAKEN.
HIGH PRESSURE POSITIONED OVER EASTERN CANADA, IF IT CAN BE
MAINTAINED, MAY HELP TO WEDGE A COLDER LOW-LEVEL AIRMASS SOUTHWARD
ACROSS AT LEAST PORTIONS OF OUR AREA. THIS COLD AIR DAMMING SCENARIO
WOULD OPEN THE DOOR FOR SURFACE LOW REDEVELOPMENT NEAR THE VIRGINIA
COAST AS THE BAROCLINICITY TIGHTENS UP DUE TO THE THERMAL GRADIENT
INCREASING. THIS WOULD PROBABLY ALLOW FOR SOME WARMING ESPECIALLY
ALOFT UNTIL THE MAIN STORM GETS GOING OFF OR ALONG THE COAST.
THEREFORE, CLOUDS INCREASE WEDNESDAY AND WE WENT WITH 40-50 POPS FOR
NOW AS THE POTENTIAL IS THERE FORE A DECENT STORM. WE HELD OFF ON
GOING WITH LIKELY POPS DUE TO ENOUGH MODEL UNCERTAINTY REGARDING
TIMING AND ESPECIALLY THE DETAILS. WE WENT WITH RAIN AND/OR SNOW FOR
THE PRECIPITATION TYPE AS ANY OTHER FROZEN/FREEZING PRECIPITATION IS
MORE DEPENDENT ON THE ACTUAL THERMAL STRUCTURES.
&&
.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
THE 00Z TAFS CONTINUED THE DECENT INTO IFR AND LIFR AS THE
HEAVIER RAIN MOVES IN TONIGHT WITH THE LOWEST CONDITIONS AFTER
MIDNIGHT. WE ALSO CONTINUED THE MENTION OF LLWS. THE GRADIENT EAST
TO SOUTHEAST WIND ITSELF WILL ALSO INCREASE AND GUSTS TO AROUND 40
KTS ARE POSSIBLE AT TERMINALS AND AIRPORTS CLOSER TO THE OCEAN IN
NEW JERSEY AND DELAWARE.
THE COLD FRONT IS EXPECTED TO MOVE THROUGH FROM SOUTHWEST TO
NORTHEAST ACROSS OUR CWA WITH PASSAGE TIME PLUS OR MINUS OF 12Z
BY A COUPLE OF HOURS. RAPID IMPROVEMENT TO MVFR IF NOT VFR
CONDITIONS IS THEN FORECAST. WINDS THOUGH WILL REMAIN BLUSTERY,
BUT THIS TIME FROM THE WEST. CIGS SHOULD IMPROVE TO VFR BY LATE IN
THE MORNING. WINDS WILL REMAIN BRISK THROUGH THE DAY. PEAK GUSTS
OF AROUND 30 KTS ARE LIKELY.
OUTLOOK...
FRIDAY NIGHT AND SATURDAY...MAINLY VFR. WEST-NORTHWEST WINDS
SUSTAINED 15-25 KNOTS WITH GUSTS TO AROUND 35 KNOTS. THE STRONGER
WINDS SHOULD OCCUR DURING THE DAY SATURDAY. THERE COULD BE SOME
SUB-VFR CONDITIONS IN LOCAL/BRIEF SNOW SHOWERS ESPECIALLY FROM THE
KABE AND KRDG TERMINALS NORTH AND WEST.
SUNDAY...VFR WITH NORTHWESTERLY WINDS MAINLY 10-20 KNOTS.
MONDAY AND TUESDAY...VFR MONDAY ALTHOUGH CLOUDS SHOULD INCREASE AND
LOWER SOME. A WEAKER SYSTEM MAY MOVE THROUGH MONDAY NIGHT INTO
TUESDAY WITH THE CHANCE OF SOME LIGHT PRECIPITATION. LIGHT WINDS
MONDAY BECOME NORTHERLY NEAR 10 KNOTS TUESDAY.
&&
.MARINE...
A STRONG COLD FRONT WILL TRACK ACROSS OUR REGION EARLY TOMORROW
MORNING. GALES REMAIN IN PLACE FROM 700 PM TONIGHT, THROUGH THE
SHORT TERM PERIOD, AND INTO THE OUTLOOK PERIOD. SOUTHEAST WINDS
TONIGHT WILL BECOME SOUTHWEST TOMORROW. SEAS WILL RESPOND AND COULD
REACH DOUBLE DIGITS. RAIN OVERNIGHT TONIGHT WILL BECOME MOE SHOWERY
TOMORROW.
OUTLOOK...
A POTENT STORM IS FORECAST TO BE TO OUR NORTH FRIDAY NIGHT THROUGH
SATURDAY BEFORE SHIFTING INTO THE CANADIAN MARITIMES DURING THE
WEEKEND. A TIGHT PRESSURE GRADIENT IN COMBINATION WITH CAA WILL
ALLOW FOR STEEPER LOW-LEVEL LAPSE RATES AND EFFICIENT VERTICAL
MIXING. THE GFS 925 MB WINDS ARE MUCH STRONGER COMPARED TO THE NAM
AND ECMWF, HOWEVER ALL POINT TO GALE FORCE WINDS OCCURRING. THE GFS
WOULD SUGGEST A CHC FOR A PERIOD OF STORM FORCE GUSTS. WE ARE NOT
ALL THAT CONFIDENT REGARDING STORMS, THEREFORE WE WILL CONTINUE WITH
THE GALE WARNING THROUGH THE DAY SATURDAY. THE WINDS SHOULD START
DIMINISHING SATURDAY NIGHT, THEREFORE WE DECIDED NOT TO EXTEND THE
GALE WARNING ATTM. THERE SHOULD BE A PERIOD OF SMALL CRAFT ADVISORY
CONDITIONS FOLLOWING THE GALES INTO ABOUT SUNDAY. A WEAK SYSTEM MAY
THEN MOVE THROUGH MONDAY NIGHT INTO TUESDAY, HOWEVER THE WINDS AND
SEAS ARE ANTICIPATED TO BE BELOW ADVISORY CRITERIA.
&&
.TIDES/COASTAL FLOODING...
THE STRENGTHENING SOUTHEAST FLOW WILL ALLOW WATER TO PILE UP ALONG
THE COASTAL SECTIONS OF THE OCEAN...DELAWARE BAY AND CHESAPEAKE
BAY TONIGHT AND FRIDAY MORNING.
LOWER DELAWARE BAY AND THE SHORE...MINOR TIDAL FLOODING LEVELS
OCCURRING PRESENTLY.
UPPER DELAWARE BAY...MODERATE TIDAL FLOODING EXPECTED. DEPARTURES
ROSE SHARPLY EARLIER...BUT ARE LEVELING OFF NOW. THE HIGH TIDE AT
REEDY POINT IS AT 532 AM.
TIDAL DELAWARE...HIGH DEPARTURES EXPECTED TO CREATE MODERATE
FLOODING THIS MORNING. HIGH TIDE AT PHILADELPHIA 815 AM.
CHESAPEAKE BAY...DEPARTURES ARE CONTINUING TO INCREASE WITH THE
PRESENT CYCLE. MINOR TIDAL FLOODING WILL OCCUR OVER THE NORTHERN
PART OF THE BAY WITH THE PRESENT CYCLE...UNTIL AROUND 700 AM. THE
DEPARTURES WILL LIKELY FALL THIS AFTERNOON ONCE THE WINDS SWITCH
AROUND TO WEST OR SOUTHWEST. I HAVE EXTENDED THE CF.A THROUGH THE
NEXT CYCLE JUST IN CASE THE DEPARTURES DONT FALL ENOUGH IN TIME.
THE FLAG MATCHES UP WITH THE FLAGS ON THE OTHER SIDE OF THE BAY
ALSO.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...COASTAL FLOOD WARNING UNTIL 11 AM EST THIS MORNING FOR PAZ070-
071.
NJ...WIND ADVISORY UNTIL 9 AM EST THIS MORNING FOR NJZ001-008-010-
012>014-016-020>027.
COASTAL FLOOD ADVISORY UNTIL 8 AM EST THIS MORNING FOR
NJZ012>014-020-022>027.
COASTAL FLOOD WARNING UNTIL 8 AM EST THIS MORNING FOR NJZ016-
021.
COASTAL FLOOD WARNING UNTIL 11 AM EST THIS MORNING FOR
NJZ017>019.
DE...WIND ADVISORY UNTIL 9 AM EST THIS MORNING FOR DEZ001>004.
COASTAL FLOOD ADVISORY UNTIL 8 AM EST THIS MORNING FOR DEZ003-
004.
COASTAL FLOOD WARNING UNTIL 8 AM EST THIS MORNING FOR DEZ001-
002.
MD...WIND ADVISORY UNTIL 9 AM EST THIS MORNING FOR MDZ015-019-020.
COASTAL FLOOD ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR
MDZ008-012-015-019-020.
MARINE...GALE WARNING UNTIL 7 PM EST SATURDAY FOR ANZ430-431-450>455.
&&
$$
SYNOPSIS...GORSE
NEAR TERM...GIGI/KRUZDLO
SHORT TERM...KRUZDLO
LONG TERM...GORSE
AVIATION...GIGI/GORSE
MARINE...GORSE/KRUZDLO
TIDES/COASTAL FLOODING...
AREA FORECAST DISCUSSION
NWS MOUNT HOLLY NJ
1251 AM EST FRI DEC 21 2012
.SYNOPSIS...
A POTENT AREA OF LOW PRESSURE WILL TRACK ACROSS THE GREAT LAKES AND
NORTHEAST TONIGHT AND FRIDAY, THEN ACROSS EASTERN CANADA DURING THE
WEEKEND. ITS ASSOCIATED STRONG COLD FRONT WILL SWEEP ACROSS OUR
REGION EARLY FRIDAY MORNING. A WEAK AREA OF HIGH PRESSURE THEN
BUILDS DOWN INTO OUR REGION LATE SUNDAY AND MONDAY. A WEAK LOW
PRESSURE SYSTEM MAY AFFECT OUR AREA MONDAY NIGHT INTO TUESDAY, WITH
THE POTENTIAL FOR A MUCH STRONGER STORM SET TO ARRIVE ON THURSDAY.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
STARTING IN THE POCONOS, WE ARE PLANNING ON LETTING THE ADVY
EXPIRE AT 11 PM. THE DRY AIR ALOFT HAS EVAP COOLED AND THE
FREEZING RAIN IN THE HIGHER TERRAIN HAS CHANGED TO SNOW. THE
NUMBER OF MESONET SITES BELOW FREEZING WHICH ONCE WAS AROUND 20 IS
DOWN TO 6. HRRR AND LATEST WRF-NMMB HAS EVERYONE ABOVE FREEZING BY
03Z. SOME SLIPPERY SPOTS WERE REPORTED IN THE HIGHER TERRAIN OF
MONROE COUNTY AND AROUND A QUARTER INCH OF SNOW IN PLACES.
NOW FOR THE OTHER WEATHER HAZARD, THE WIND. NOT AN EASY DECISION
BECAUSE THE SOUNDINGS ARE NEARLY ISOTHERMAL WITH POOR LAPSE RATES.
THE 00Z SOUNDINGS SUPPORTED A COMP BETWEEN THE WRF-NMMB AND GFS
FCST SPEEDS. SINCE THEN THE VWP LOOK OK AT KAKQ AND KLWX FOR THE
NEW WRF-NMMB 925MB WINDS, BUT THE MODEL IS RUNNING AROUND 5 TO
10 KTS TOO HOT AT 850MB. SO FAR THE MIXING OF STRONGER WINDS IN
THE CAROLINAS HAS BEEN SPORADIC. SO WHAT WE CAN GATHER THERE HAVE
NOT BEEN UPSIDE SURPRISES YET. THE OVERALL WIND FIELDS ARE
FORECAST THOUGH TO INTENSIFY FURTHER AS TIME GOES ON TONIGHT AND
THE MOMENTUM TRANSFER WINDS ON OCCASION ARE MIXING ADVY LEVEL WIND
GUSTS DOWN. THE MESOSCALE MODELS AND WE DONT KNOW IF THEY ARE THIS
GOOD ARE NOT FORECASTING A SINGLE NCFRB TOWARD MORNING. AFTER
COORD WITH OKX AND LOOKING AT THE 12/1/10 ANALOG THEY FOUND (WHICH
WAS AN ADVY TYPE EVENT CENTERED MAINLY IN THE ERN PART OF OUR
CWA), WE DECIDED TO ISSUE A WIND ADVY THAT COINCIDES CLOSEST WITH
THE 70KT OR GREATER ISOTACH ON THE LATEST WRF-NMMB. WE INCLUDED
ALL OF DELAWARE BAY BECAUSE OF THE SE FLOW. IF A NCFRB DOES FORM
NEAR THE JET MAX, THE ADVY MAY NEED TO BE UPGRADED OR EXPANDED.
RIGHT NOW CONFIDENCE IS TOO LOW TO ISSUE.
THE REST OF THE FCST WAS KEPT PRETTY MUCH AS IS, MOST OF THE
HEAVIEST PCPN IS EXPECTED TO FALL AFTER MIDNIGHT AND END RATHER
QUICKLY WITH THE CFP AROUND 12Z.
OTHER THAN SOME NUISANCE FLOODING, NO HYDRO ISSUES ARE EXPECTED.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/...
A THREAT OF RAIN SHOULD STILL EXIST FOR THE NORTHERN ZONES EARLY
TOMORROW MORNING. THEN WHEN THE UPPER LOW AND COLD POOL ALOFT MOVES
CLOSER, A SHOWER ANYWHERE CAN`T BE RULED OUT. TEMP PROFILES
SUGGEST SNOW SHOWERS FAR NORTH AND WEST.
TEMPS WILL HOLD STEADY OR FALL THROUGH THE 40S (30S NORTH AND WEST)
TOMORROW WITH WINDS GUSTING TO 30 OR 40 MPH.
LITTLE TO NO ACCUMULATION IS EXPECTED WHERE THE FLAKES FLY.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
A RATHER ACTIVE PATTERN LOOKS TO CONTINUE. THE OVERALL SYNOPTIC FLOW
IS COMPRISED OF A DEEP TROUGH OVER THE EAST FRIDAY NIGHT AND
SATURDAY, THEN ADDITIONAL ENERGY PUSHING INTO THE WEST ALLOWS
DOWNSTREAM RIDGING TO KICK THE TROUGH INTO CANADA WHERE IT TENDS TO
BECOME ELONGATED WEST TO EAST. A PIECE OF ENERGY ROTATING AROUND
THIS MAY ALLOW FOR A SHORT WAVE TROUGH TO SLIDE ACROSS THE GREAT
LAKES INTO THE NORTHEAST AROUND TUESDAY. A MUCH MORE PRONOUNCED
UPPER-LEVEL TROUGH THEN LOOKS TO EJECT OUT OF THE FOUR CORNERS
REGION TUESDAY NIGHT INTO WEDNESDAY. THIS FEATURE ALONG WITH A
DEEPENING SURFACE LOW IS THEN FORECAST TO MOVE THROUGH THE EAST NEXT
THURSDAY. OVERALL, THE MODEL GUIDANCE CONTINUES TO SHOW VARIABILITY
WITH TIMING AND SPACING OF EMBEDDED INDIVIDUAL FEATURES HOWEVER
CONTINUED SUPPORT FOR AN ACTIVE PATTERN. THE THERMAL GRADIENTS AND
AMPLITUDE OF THE PATTERN MAY BE PLAYING A ROLE WITH THE MODEL
VARIABILITY. IT APPEARS THERE IS AN INCREASING SIGNAL FOR AN EAST
COAST STORM DURING ABOUT THE SECOND HALF OF NEXT WEEK. OF COURSE
THIS FAR OUT, THE DETAILS ARE MUCH LESS CERTAIN AND THEREFORE MUCH
LOWER CONFIDENCE IN THE FORECAST BEYOND TUESDAY ESPECIALLY.
FOR FRIDAY NIGHT AND SATURDAY...AN INTENSE STORM IS FORECAST TO BE
IN THE SOUTHEAST CANADA AND NEW ENGLAND AREAS DURING THIS TIME
FRAME. IT WILL BE DRIVEN BY A SHARP UPPER-LEVEL TROUGH WITH A SHOT
OF MUCH COLDER AIR ALONG WITH IT. A RATHER DEEP CYCLONIC FLOW REGIME
WILL BE OCCURRING WITH THE POTENTIAL FOR SOME WRAPAROUND SNOW
SHOWERS, AND THE LAKE EFFECT SNOW MACHINE SHOULD BE IN HIGH GEAR. AS
THE CAA CONTINUES, SHORT WAVE ENERGY ROTATING AROUND THE PARENT
UPPER-LEVEL TROUGH SHOULD HELP TO MAINTAIN SOME SNOW SHOWERS INTO
OUR NORTHWEST ZONES. SOME OF THE MODEL GUIDANCE SHOWING SIGNS OF
CHANNELIZED VORTICITY ORIENTATED NORTHWEST TO SOUTHEAST. IF DEEP
ENOUGH MOISTURE CAN BE MAINTAINED AND ENOUGH LIFT/INSTABILITY CAN
OCCUR WITHIN THE NORTHWEST FLOW, SOME LOCALIZED SNOW SQUALLS MAY
OCCUR ACROSS NORTHEASTERN PENNSYLVANIA AND NORTHWESTERN NEW JERSEY.
WE WOULD LIKE TO SEE BETTER ORGANIZATION OF THE CHANNELIZED
VORTICITY TO INCREASE CONFIDENCE REGARDING LAKE EFFECT STREAMERS
REMAINING INTACT THIS FAR SOUTHEAST FROM THE LAKES. FOR NOW, WE
CARRIED LOW LIKELY POPS ACROSS THE POCONOS AND TOWARD FAR NORTHWEST
NEW JERSEY, THEN POPS TAPER WITH A SOUTHEASTWARD EXTENT. BEYOND THE
SLIGHT CHC POPS, WE CARRIED SCATTERED FLURRIES DOWN TO THE
INTERSTATE 95 CORRIDOR. SOME PLACES PARTICULARLY IN THE POCONOS
COULD PICK UP AN INCH OR TWO OF SNOW. FARTHER SOUTHEAST, WHILE A FEW
HEAVIER SNOW SHOWERS MAY BE ABLE TO OCCUR, THE DOWNSLOPING FLOW MAY
PROVIDE ENOUGH EXTRA DRYING TO ERODE THESE. THIS IS OF LOWER
CONFIDENCE THEREFORE DID NOT BRING THE SNOW SHOWER MENTION EVEN
FARTHER SOUTHEAST AND WENT WITH FLURRIES.
ANOTHER FORECAST CONCERN IS THE STRONG WIND POTENTIAL. A RATHER
TIGHT PRESSURE GRADIENT IS FORECAST TO REMAIN ACROSS OUR ENTIRE. THE
CAA COMBINED WITH THE TIGHT PRESSURE GRADIENT SHOULD KEEP THE SURFACE
WINDS GOING FRIDAY NIGHT DESPITE LESSENING VERTICAL MIXING AT TIMES.
THE VERTICAL MIXING IS MUCH MORE PRONOUNCED SATURDAY AS THE AIRMASS
IS CHILLY, THE LOW-LEVEL LAPSE RATES STEEPEN SOME MORE AND THERE IS
PLENTY OF WIND NOT TO FAR ABOVE THE SURFACE. THE FORECAST SOUNDINGS
GET CLOSE TO 40 KNOTS POTENTIALLY MIXING DOWN TO THE SURFACE,
ALTHOUGH THE GFS IS MORE ROBUST WITH THIS AS IT SUGGESTS NEARLY
50 KNOTS MIXING DOWN TO THE SURFACE. THE 925 MB WINDS ARE NOT AS
STRONG ON THE ECMWF WITH AROUND 40 KNOTS FORECAST SATURDAY
ESPECIALLY ACROSS THE SOUTHERN HALF OF OUR CWA. WE THOUGHT ABOUT
GOING WITH A HIGH WIND WATCH WITH THE GREATER CHC ACROSS ABOUT THE
SOUTHERN HALF OF THE CWA, HOWEVER THIS IS NEARLY TWO DAYS OUT. IT
MAY END UP BEING A WIND ADVISORY TYPE EVENT THEREFORE WE DECIDED TO
HOLD OFF ON ANY HEADLINES ATTM. WE HOWEVER WILL CONTINUE A
MENTION IN THE HAZARDOUS WEATHER OUTLOOK. WE INCREASED THE WINDS
SOME /ESPECIALLY GUSTS/ FOR SATURDAY FROM CONTINUITY WITH GUSTS
GENERALLY IN THE 40-45 MPH RANGE. AS FOR HIGH AND LOW TEMPERATURES,
WE GENERALLY TOOK AN EVEN BLEND OF THE NAM/GFS MOS.
FOR SUNDAY AND MONDAY /CHRISTMAS EVE/...THE POTENT STORM IS FORECAST
TO MOVE UP THROUGH THE CANADIAN MARITIMES, HOWEVER A TIGHTENED
PRESSURE GRADIENT GENERALLY REMAINS IN PLACE. THE OVERALL FLOW
THOUGH WILL BE LESSENING, HOWEVER VERTICAL MIXING WILL PROVIDE
ENOUGH FOR A BRISK DAY ON SUNDAY. IT APPEARS THAT WITHIN THE
NORTHWESTERLY FLOW, A SHORT WAVE ROTATING AROUND THE PARENT STORM
MAY TOSS A SURFACE TROUGH OR COLD FRONT TOWARD OUR REGION. THE LAKE
EFFECT SNOW MACHINE SHOULD BE WINDING DOWN SUNDAY AS THE CAA WANES
SOME AND THE LOW-LEVEL FLOW MAY TURN MORE WESTERLY.
A SHORT WAVE TRAVERSING THE NORTHERN TIER CHRISTMAS EVE MAY ALLOW
FOR A SURFACE LOW REFLECTION TO RACE OUT AHEAD OF THE DEEPENING
TROUGH IN THE WEST. SOME MOISTURE RETURN AHEAD OF IT ALONG WITH WAA,
MAY RESULT IN AN AREA OF OVERRUNNING PRECIPITATION. THERE IS A
QUESTION REGARDING HOW DRY THE AIRMASS IS OVER OUR AREA AND THE
STRENGTH OF THE OVERALL LIFT. A LIGHT INTENSITY OF THE PRECIPITATION
MAY PLAY MORE OF A ROLE, WITH EVEN DEPENDING ON HOW THE BOUNDARY
LAYER BEHAVES. FOR NOW WE WILL FAVOR SLIGHT CHC POPS FOR A WEAK
OVERRUNNING POTENTIAL AND GO RAIN AND/OR SNOW.
FOR TUESDAY...THE AFOREMENTIONED FRONT RUNNER WEAKER SURFACE WAVE
SHOULD SCOOT OUT TO SEA EARLY TUESDAY AS THE SHORT WAVE TROUGH MAY
END UP DAMPENING OUT SOME. WHILE THERE COULD BE SOME RESIDUAL LIGHT
PRECIPITATION AROUND TO START TUESDAY, WE SIMPLY FAVORED SLIGHT CHC
POPS IN THE MORNING GIVEN LOWER CONFIDENCE ON TIMING AND OF ANY MORE
ORGANIZED LIFT.
FOR WEDNESDAY AND THURSDAY...THE PATTERN ONCE AGAIN STARTS TO REALLY
RAMP UP WEDNESDAY AS ENERGY FROM THE FOUR CORNERS REGION SLIDES
ACROSS THE PLAINS AND THEN THE TENNESSEE VALLEY. THERE IS ANOTHER
SYSTEM UP IN THE CANADIAN MARITIMES OVERALL, WHICH WOULD TEND TO
LEAD TO BLOCKING. THIS DEVELOPING PATTERN IS LOOKING MORE CONDUCIVE
FOR A COASTAL STORM TO OCCUR. IN THIS UPCOMING POTENTIAL, THE
INITIAL SURFACE LOW MAY TRACK UP THE OHIO VALLEY BUT THEN WEAKEN.
HIGH PRESSURE POSITIONED OVER EASTERN CANADA, IF IT CAN BE
MAINTAINED, MAY HELP TO WEDGE A COLDER LOW-LEVEL AIRMASS SOUTHWARD
ACROSS AT LEAST PORTIONS OF OUR AREA. THIS COLD AIR DAMMING SCENARIO
WOULD OPEN THE DOOR FOR SURFACE LOW REDEVELOPMENT NEAR THE VIRGINIA
COAST AS THE BAROCLINICITY TIGHTENS UP DUE TO THE THERMAL GRADIENT
INCREASING. THIS WOULD PROBABLY ALLOW FOR SOME WARMING ESPECIALLY
ALOFT UNTIL THE MAIN STORM GETS GOING OFF OR ALONG THE COAST.
THEREFORE, CLOUDS INCREASE WEDNESDAY AND WE WENT WITH 40-50 POPS FOR
NOW AS THE POTENTIAL IS THERE FORE A DECENT STORM. WE HELD OFF ON
GOING WITH LIKELY POPS DUE TO ENOUGH MODEL UNCERTAINTY REGARDING
TIMING AND ESPECIALLY THE DETAILS. WE WENT WITH RAIN AND/OR SNOW FOR
THE PRECIPITATION TYPE AS ANY OTHER FROZEN/FREEZING PRECIPITATION IS
MORE DEPENDENT ON THE ACTUAL THERMAL STRUCTURES.
&&
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
THE 00Z TAFS CONTINUED THE DECENT INTO IFR AND LIFR AS THE
HEAVIER RAIN MOVES IN TONIGHT WITH THE LOWEST CONDITIONS AFTER
MIDNIGHT. WE ALSO CONTINUED THE MENTION OF LLWS. THE GRADIENT EAST
TO SOUTHEAST WIND ITSELF WILL ALSO INCREASE AND GUSTS TO AROUND 40
KTS ARE POSSIBLE AT TERMINALS AND AIRPORTS CLOSER TO THE OCEAN IN
NEW JERSEY AND DELAWARE.
THE COLD FRONT IS EXPECTED TO MOVE THROUGH FROM SOUTHWEST TO
NORTHEAST ACROSS OUR CWA WITH PASSAGE TIME PLUS OR MINUS OF 12Z
BY A COUPLE OF HOURS. RAPID IMPROVEMENT TO MVFR IF NOT VFR
CONDITIONS IS THEN FORECAST. WINDS THOUGH WILL REMAIN BLUSTERY,
BUT THIS TIME FROM THE WEST. CIGS SHOULD IMPROVE TO VFR BY LATE IN
THE MORNING. WINDS WILL REMAIN BRISK THROUGH THE DAY. PEAK GUSTS
OF AROUND 30 KTS ARE LIKELY.
OUTLOOK...
FRIDAY NIGHT AND SATURDAY...MAINLY VFR. WEST-NORTHWEST WINDS
SUSTAINED 15-25 KNOTS WITH GUSTS TO AROUND 35 KNOTS. THE STRONGER
WINDS SHOULD OCCUR DURING THE DAY SATURDAY. THERE COULD BE SOME
SUB-VFR CONDITIONS IN LOCAL/BRIEF SNOW SHOWERS ESPECIALLY FROM THE
KABE AND KRDG TERMINALS NORTH AND WEST.
SUNDAY...VFR WITH NORTHWESTERLY WINDS MAINLY 10-20 KNOTS.
MONDAY AND TUESDAY...VFR MONDAY ALTHOUGH CLOUDS SHOULD INCREASE AND
LOWER SOME. A WEAKER SYSTEM MAY MOVE THROUGH MONDAY NIGHT INTO
TUESDAY WITH THE CHANCE OF SOME LIGHT PRECIPITATION. LIGHT WINDS
MONDAY BECOME NORTHERLY NEAR 10 KNOTS TUESDAY.
&&
.MARINE...
A STRONG COLD FRONT WILL TRACK ACROSS OUR REGION EARLY TOMORROW
MORNING. GALES REMAIN IN PLACE FROM 700 PM TONIGHT, THROUGH THE
SHORT TERM PERIOD, AND INTO THE OUTLOOK PERIOD. SOUTHEAST WINDS
TONIGHT WILL BECOME SOUTHWEST TOMORROW. SEAS WILL RESPOND AND COULD
REACH DOUBLE DIGITS. RAIN OVERNIGHT TONIGHT WILL BECOME MOE SHOWERY
TOMORROW.
OUTLOOK...
A POTENT STORM IS FORECAST TO BE TO OUR NORTH FRIDAY NIGHT THROUGH
SATURDAY BEFORE SHIFTING INTO THE CANADIAN MARITIMES DURING THE
WEEKEND. A TIGHT PRESSURE GRADIENT IN COMBINATION WITH CAA WILL
ALLOW FOR STEEPER LOW-LEVEL LAPSE RATES AND EFFICIENT VERTICAL
MIXING. THE GFS 925 MB WINDS ARE MUCH STRONGER COMPARED TO THE NAM
AND ECMWF, HOWEVER ALL POINT TO GALE FORCE WINDS OCCURRING. THE GFS
WOULD SUGGEST A CHC FOR A PERIOD OF STORM FORCE GUSTS. WE ARE NOT
ALL THAT CONFIDENT REGARDING STORMS, THEREFORE WE WILL CONTINUE WITH
THE GALE WARNING THROUGH THE DAY SATURDAY. THE WINDS SHOULD START
DIMINISHING SATURDAY NIGHT, THEREFORE WE DECIDED NOT TO EXTEND THE
GALE WARNING ATTM. THERE SHOULD BE A PERIOD OF SMALL CRAFT ADVISORY
CONDITIONS FOLLOWING THE GALES INTO ABOUT SUNDAY. A WEAK SYSTEM MAY
THEN MOVE THROUGH MONDAY NIGHT INTO TUESDAY, HOWEVER THE WINDS AND
SEAS ARE ANTICIPATED TO BE BELOW ADVISORY CRITERIA.
&&
.TIDES/COASTAL FLOODING...
THE STRENGTHENING SOUTHEAST FLOW WILL ALLOW WATER TO PILE UP ALONG
THE COASTAL SECTIONS OF THE OCEAN...DELAWARE BAY AND CHESAPEAKE
BAY TONIGHT AND FRIDAY MORNING.
THE LATEST NUMERICAL GUIDANCE IS SHOWING THAT REEDY POINT WILL
REACH MODERATE TIDAL FLOODING WITH THE UPCOMING HIGH TIDE...A
COASTAL FLOOD WARNING HAS BEEN ISSUED. IT DOESNT APPEAR THAT THE
HIGHEST LEVELS WILL CARRY UP INTO THE TIDAL DELAWARE RIVER AT THIS
TIME...SO THE ADVISORY WILL CONTINUE THERE.
THE HIGHER DEPARTURES HAVE COME TOO LATE FOR THE HIGH TIDE AT THE
SHORE AND THE LOWER DELAWARE BAY...SO ADVISORY TYPE WATER LEVELS
ARE EXPECTED THERE...THE ONGOING CF.A WILL CONTINUE.
AS FOR THE CHESAPEAKE BAY, CURRENT DEPARTURES ARE INCREASING...BUT
THE NEXT HIGH TIDE WILL NOT OCCUR UNTIL LATER FRIDAY MORNING INTO
THE EARLY AFTERNOON HOURS...IT APPEARS THAT THE DEPARTURES WILL BE
FALLING BY THEN. BASED ON OUR NEW ADVISORY CRITERIA OF 3.8 FEET
BOTH CAMBRIDGE AND TOLCHESTER BEACH WOULD NEED AROUND A +2.5 FOOT
DEPARTURE TO REACH THE MINOR THRESHOLD. THIS COULD BE OUT OF REACH
BY THEN. WE WILL CONTINUE TO MONITOR.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...COASTAL FLOOD ADVISORY UNTIL 11 AM EST THIS MORNING FOR PAZ070-
071.
NJ...WIND ADVISORY UNTIL 9 AM EST THIS MORNING FOR NJZ001-008-010-
012>014-016-020>027.
COASTAL FLOOD ADVISORY UNTIL 8 AM EST THIS MORNING FOR
NJZ012>014-020-022>027.
COASTAL FLOOD WARNING UNTIL 8 AM EST THIS MORNING FOR NJZ016-
021.
COASTAL FLOOD ADVISORY UNTIL 11 AM EST THIS MORNING FOR
NJZ017>019.
DE...WIND ADVISORY UNTIL 9 AM EST THIS MORNING FOR DEZ001>004.
COASTAL FLOOD ADVISORY UNTIL 8 AM EST THIS MORNING FOR DEZ003-
004.
COASTAL FLOOD WARNING UNTIL 8 AM EST THIS MORNING FOR DEZ001-
002.
MD...WIND ADVISORY UNTIL 9 AM EST THIS MORNING FOR MDZ015-019-020.
MARINE...GALE WARNING UNTIL 7 PM EST SATURDAY FOR ANZ430-431-450>455.
&&
$$
SYNOPSIS...GORSE
NEAR TERM...GIGI/KRUZDLO
SHORT TERM...KRUZDLO
LONG TERM...GORSE
AVIATION...GIGI/GORSE
MARINE...GORSE/KRUZDLO
TIDES/COASTAL FLOODING...HEAVENER/O`HARA
AREA FORECAST DISCUSSION
NWS TAMPA BAY RUSKIN FL
210 PM EST FRI DEC 21 2012
...A WINTER FEEL TO THE FORECAST THE NEXT COUPLE OF DAYS...
.SYNOPSIS...
18Z WATER VAPOR AND H4 RAP ANALYSIS CONTINUES TO SHOW A HIGHLY
AMPLIFIED UPPER LEVEL PATTERN OVER THE CONUS. PATTERN CONSISTS OF
TROUGHING BEGINNING TO MOVE ASHORE ALONG THE PACIFIC COASTLINE
FOLLOWED DOWNSTREAM BY LONGWAVE RIDGING ACROSS THE INTERMOUNTAIN
WEST AND HIGH PLAINS. THE FLOW THE SHARPLY DIPS BACK TO THE SOUTH
INTO AND IMPRESSIVE NEGATIVELY TILTED TROUGH AND CLOSED LOW FEATURE
COVERING THE EASTERN THIRD OF THE NATION. ASSOCIATED WITH THIS
PARENT ENERGY WE FIND STRONG 982MB SURFACE LOW PRESSURE OVER THE
NORTHEASTERN STATES WITH A COLD FRONT TRAILING OFF THE ATLANTIC
SEABOARD ALL THE WAY DOWN THROUGH THE BAHAMAS AND CUBA.
THIS COLD FRONT RAPIDLY PUSHED ACROSS OUR FORECAST AREA LAST NIGHT
WITH A NARROW BAND OF CONVECTION. THAT RAINFALL IS LONG GONE AS A
MUCH COLDER AND DRIER AIRMASS CONTINUES TO ARRIVE ON GUSTY NORTHWEST
WINDS. HIGH PRESSURE IS SLOWLY BUILDING EASTWARD ALONG THE NORTHERN
GULF COAST THIS AFTERNOON AND WILL BE SETTLING OVER THE REGION
DURING THE UPCOMING WEEKEND. THE STRONG NW WINDS UP TO 30 KNOTS IS
PUSHING A DECENT SWELL TOWARD THE COAST AND SURF HEIGHTS AT AREA
BEACHES HAVE REACHED 4-6 FEET PROMPTING A HIGH SURF ADVISORY THROUGH
TONIGHT. THE RIP CURRENT RISK IS ALSO HIGH AS A RESULT OF THIS SURF.
&&
.SHORT TERM (TONIGHT THROUGH SUNDAY NIGHT)...
TONIGHT...A COLD/CHILLY NIGHT ON TAP. HIGH PRESSURE WILL STILL BE
CENTERED WELL TO OUR WEST. THERE IS A RIDGE AXIS THAT EXTENDS OVER
TOWARD US...BUT THE GRADIENT WILL NOT RELAX ENOUGH OVER MUCH OF THE
AREA TO ALLOW FOR MUCH OF A RADIATIVE COMPONENT TO THE TEMPERATURE
DROP. WILL BE LOOKING AT MORE OF AN ADVECTION DROP IN TEMPS WITH
SOME COLD AIR DRAINAGE FROM THE NORTH DOWN THE PENINSULA. CURRENT
FORECAST IS LOOKING FOR WIDESPREAD LOWER TO MIDDLE 30S AWAY FROM THE
IMMEDIATE COAST...AND EVEN COLDER (MID 20S TO AROUND 30) OVER THE
INTERIOR NATURE COAST ZONES. A FREEZE WARNING REMAINS IN EFFECT FOR
THE NATURE COAST ZONES LATE TONIGHT INTO EARLY SATURDAY MORNING FOR
SEVERAL HOURS OF SUB-FREEZING TEMPS. ALTHOUGH A FREEZE WARNING IS
NOT CURRENTLY IN EFFECT FURTHER SOUTH...TEMPERATURES MAY BRIEFLY
APPROACH 32 IN SPOTS. DEWPOINT DEPRESSIONS LATE TONIGHT ARE 6-10C
WHICH ALONG WITH A LIGHT WIND SHOULD PREVENT ANY SIGNIFICANT FROST
FORMATION. AN APPROACHING UPPER LEVEL JET FROM THE NORTHWEST WILL
LIKELY BRING IN SOME THIN HIGH CLOUDS FROM THE WEST DURING THE
OVERNIGHT...HOWEVER WITH THIS NOT BEING A RADIATIONAL COOLING
EVENT...THESE HIGH CLOUDS SHOULD HAVE LITTLE IMPACT ON THE TEMP
FORECAST. THE COMBINATION OF LOW TEMPERATURES AND AT LEAST SOME WIND
STAYING UP OVERNIGHT HAS PROMPTED THE ISSUANCE OF A WIND CHILL
ADVISORY FOR ALL OF THE FORECAST AREA. THE ADVISORY CRITERIA ARE
MOST LIKELY TO BE MET AFTER MIDNIGHT INTO THE FIRST 1-2 DAYLIGHT
HOURS OF SATURDAY. STAY WARM...AND WELCOME TO OFFICIAL WINTER.
SATURDAY/SATURDAY NIGHT...
SURFACE HIGH PRESSURE CONTINUES TO BUILD EASTWARD TOWARD THE AREA
AND WILL BE DIRECTLY OVERHEAD BY SATURDAY NIGHT. SATURDAY WILL BE
ANOTHER FAIR...DRY...AND SEASONABLY COOL DAY AS TEMPERATURES
STRUGGLE INTO THE LOWER 60S NORTH AND MIDDLE 60S SOUTH. SATURDAY
EVENING AS THE SUN GOES DOWN...EXPECTING TEMPERATURES TO DROP
QUICKLY AS LIGHT WINDS AND A DRY COLUMN PROMOTE EXCELLENT
RADIATIONAL COOLING CONDITIONS. THE FREEZE WATCH REMAIN IN EFFECT
FOR THE NATURE COAST ZONES FOR SEVERAL HOURS AFTER MIDNIGHT OF
SUB-FREEZING TEMPS. CONSIDERED EXPANDING THE WATCH FURTHER
SOUTH...BUT THERE IS SOME CONCERN ABOUT THE IMPACTS OF SOME HIGHER
MOISTURE/CIRRUS MOVING IN FROM THE WEST DURING THE SECOND HALF OF
THE NIGHT. SOMETIMES THIS TYPE OF MOISTURE ADVECTION CAN HAVE THE
IMPACT OF SLOWLY THE RADIATIVE PROCESS. THIS UNCERTAINLY IN THE
DEPTH AND EXACT TIMING MAKES THE LOW TEMPERATURE FORECAST DIFFICULT.
IF THE CIRRUS HOLD OFF UNTIL DAWN...THEN TEMPS MAY BE A BIT
COOLER...BUT IF IF MOVES IN DURING THE PRE-DAWN HOURS...THEN THE
CURRENT GRIDS MIGHT BE TOO COLD. FOR NOW WILL EXPECT TO SEE GET A
FEW HOURS OF FREEZING NORTH OF I-4 AND GET TO NEAR FREEZING AWAY
FROM THE COAST FURTHER SOUTH. SMALLER DEWPOINT DEPRESSION WILL MAKE
FROST FORMATION MORE LIKELY FOR ALL AREAS DROPPING INTO THE MIDDLE
30S OR LOWER.
SUNDAY/SUNDAY NIGHT...
HIGH PRESSURE MOVES OFF TO OUR EAST WITH WINDS SLOWLY COMING AROUND
TO THE SOUTHEAST AND SOUTH WITH TIME. TEMPERATURES WILL BEGIN A
WARMING TREND BETWEEN THIS HIGH AND A COLD FRONT WELL OFF TO OUR
WEST. AT THIS TIME...NO FREEZING TEMPERATURES ARE EXPECTED SUNDAY
NIGHT.
&&
.LONG TERM (SUNDAY NIGHT-THURSDAY)...
U/L PATTERN WILL BEGIN WITH ZONAL FLOW ACROSS THE U.S. WITH A WEAK
DISTURBANCE MOVING THROUGH THE OHIO RIVER VALLEY MONDAY WITH AN
ASSOCIATED COLD FRONT DROPPING OVER THE SOUTHEAST U.S. AS THE FRONT
BECOMES PARALLEL TO THE U/L FLOW IT WILL STALL ACROSS NORTH FLORIDA
MONDAY NIGHT. A STRONG U/L DISTURBANCE WILL DIG THROUGH THE
SOUTHERN PLAINS TUESDAY WHICH WILL ENHANCE SHOWERS AND THUNDERSTORMS
ALONG THE STALLED FRONT ACROSS THE GULF COAST AND SOUTHEAST U.S.
SURFACE HIGH PRESSURE WILL PUSH EAST OF FLORIDA WITH INCREASING
SOUTHERLY FLOW AND LOW LEVEL MOISTURE ADVECTING OVER WEST CENTRAL
AND SOUTHWEST FLORIDA IN THE WARM SECTOR SOUTH OF THE FRONTAL
BOUNDARY. AN AREA OF LOW PRESSURE WILL DEVELOP OVER THE LOWER
MISSISSIPPI VALLEY AND INTENSIFY AS IT MOVES NORTHEAST TUESDAY
NIGHT. A STRONG COLD FRONT WILL MOVE ACROSS WEST CENTRAL AND
SOUTHWEST FLORIDA WEDNESDAY...HOWEVER U/L SUPPORT WILL BE LIFTING
RAPIDLY NORTH OF THE REGION. BAND OF SHOWERS AND POSSIBLE
THUNDERSTORMS WILL PUSH ACROSS THE FORECAST AREA BUT ACTIVITY WILL
WEAKEN THROUGH THE DAY. SURFACE HIGH PRESSURE WILL BUILD OVER THE
FORECAST AREA BEHIND THE FRONT WEDNESDAY NIGHT AND THURSDAY WITH
GUSTY NORTHWEST WINDS ADVECTING DRIER COOLER AIR ACROSS THE
AREA.
&&
.AVIATION...
WINDS SHOULD BECOME LESS GUSTY FROM THE NORTH-NORTHWEST TONIGHT THEN
NORTHERLY AT 9 TO 13 KNOTS ON SATURDAY. NO CEILING/VISIBILITY
RESTRICTIONS.
&&
.MARINE...
ADVISORY LEVEL CONDITIONS ARE ONGOING ACROSS THE EASTERN GULF OF
MEXICO. ANY GALE FORCE GUSTS SHOULD END BY EARLY EVENING...HOWEVER
ADVISORY CRITERIA WINDS AND SEAS WILL PERSIST THROUGH LATE TONIGHT
OR EARLY SATURDAY. THE HIGH WILL MOVE ACROSS THE REGION DURING THE
WEEKEND AND ALLOW WINDS AND SEAS TO SUBSIDE. THE NEXT COLD FRONT IS
ANTICIPATED DURING EARLY TO MID NEXT WEEK.
&&
.FIRE WEATHER...
VERY DRY AIR AND GUSTY NORTHWESTERLY WINDS ARE RESULTING IN RED FLAG
CONDITIONS THIS AFTERNOON. TEMPERATURES WILL BEGIN TO DROP RAPIDLY
TOWARD SUNSET ALLOWING WINDS TO DIMINISH AND HUMIDITIES TO RISE. IT
WILL BE VERY DRY AGAIN ON SATURDAY AND SUNDAY BUT WINDS WILL BE
LIGHTER WHICH SHOULD PRECLUDE RED FLAG CONDITIONS.
&&
.PRELIMINARY POINT TEMPS/POPS...
TPA 40 63 40 66 / 0 0 0 0
FMY 41 66 40 71 / 0 0 0 0
GIF 34 63 33 68 / 0 0 0 0
SRQ 43 63 40 66 / 0 0 0 0
BKV 30 62 28 67 / 0 0 0 0
SPG 45 62 48 66 / 0 0 0 0
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY
MORNING FOR CITRUS-HERNANDO-LEVY-PASCO-SUMTER.
RED FLAG WARNING UNTIL 6 PM EST THIS EVENING FOR CHARLOTTE-
CITRUS-DESOTO-HARDEE-HERNANDO-HIGHLANDS-HILLSBOROUGH-
LEE-LEVY-MANATEE-PASCO-PINELLAS-POLK-SARASOTA-SUMTER.
FREEZE WARNING FROM 2 AM TO 9 AM EST SATURDAY FOR CITRUS-
HERNANDO-LEVY-PASCO-SUMTER.
LAKE WIND ADVISORY UNTIL 7 PM EST THIS EVENING FOR
CHARLOTTE-CITRUS-DESOTO-HARDEE-HERNANDO-HIGHLANDS-
HILLSBOROUGH-LEE-LEVY-MANATEE-PASCO-PINELLAS-POLK-
SARASOTA-SUMTER.
WIND CHILL ADVISORY FROM 11 PM THIS EVENING TO 9 AM EST
SATURDAY FOR CHARLOTTE-CITRUS-DESOTO-HARDEE-HERNANDO-
HIGHLANDS-HILLSBOROUGH-LEE-LEVY-MANATEE-PASCO-
PINELLAS-POLK-SARASOTA-SUMTER.
HIGH SURF ADVISORY UNTIL 7 AM EST SATURDAY FOR CHARLOTTE-
HILLSBOROUGH-LEE-MANATEE-PINELLAS-SARASOTA.
GULF WATERS...SMALL CRAFT ADVISORY UNTIL 10 AM EST SATURDAY FOR BONITA
BEACH TO ENGLEWOOD OUT 20 NM-BONITA BEACH TO
ENGLEWOOD OUT 20 TO 60 NM-ENGLEWOOD TO TARPON SPRINGS
OUT 20 NM-ENGLEWOOD TO TARPON SPRINGS OUT 20 TO 60 NM-
TAMPA BAY WATERS-TARPON SPRINGS TO SUWANNEE RIVER OUT
20 NM-TARPON SPRINGS TO SUWANNEE RIVER OUT 20 TO 60
NM.
&&
$$
SYNOPSIS/SHORT TERM/MARINE...MROCZKA
AVIATION/FIRE WX...JILLSON
LONG TERM...OGLESBY
AREA FORECAST DISCUSSION
NWS TAMPA BAY RUSKIN FL
1055 AM EST FRI DEC 21 2012
...A WINTER FEEL TO THE FORECAST THE NEXT COUPLE OF DAYS...
.UPDATE...
15Z WATER VAPOR AND H4 RAP ANALYSIS CONTINUES TO SHOW A HIGHLY
AMPLIFIED UPPER LEVEL PATTERN OVER THE CONUS. PATTERN CONSISTS OF
TROUGHING BEGINNING TO MOVE ASHORE ALONG THE PACIFIC COASTLINE
FOLLOWED DOWNSTREAM BY LONGWAVE RIDGING ACROSS THE INTERMOUNTAIN
WEST AND HIGH PLAINS. THE FLOW THE SHARPLY DIPS BACK TO THE SOUTH
INTO AND IMPRESSIVE NEGATIVELY TILTED TROUGH AND CLOSED LOW FEATURE
COVERING THE EASTERN THIRD OF THE NATION. ASSOCIATED WITH THIS
PARENT ENERGY WE FIND STRONG 982MB SURFACE LOW PRESSURE OVER THE
NORTHEASTERN STATES WITH A COLD FRONT TRAILING OFF THE ATLANTIC
SEABOARD ALL THE WAY DOWN TO THE THE BAHAMAS AND CENTRAL CUBA.
THIS COLD FRONT RAPIDLY PUSHED ACROSS OUR FORECAST AREA LAST NIGHT
WITH A NARROW BAND OF CONVECTION. THAT RAINFALL IS LONG GONE AS A
MUCH COLDER AND DRIER AIRMASS IS ARRIVING ON GUSTY NORTHWEST WINDS.
TIME-HEIGHT ANALYSIS SHOWS A DEEP LAYER OF VERY DRY AIR ABOVE THE
SURFACE THROUGH THE REMAINDER OF THE DAY THAT WILL KEEP OUR SKIES
CLEAR TO MOSTLY CLEAR. DESPITE THE ABUNDANT SUNSHINE AND GOOD
MIXING...THE CAA WILL SLOW THE TEMPERATURE RISE AND EXPECT HIGH
TEMPS TO STRUGGLE TOWARD 60 NORTH OF BROOKSVILLE AND ONLY INTO THE
LOWER/MIDDLE 60S FURTHER SOUTH. THE STRONG NW WINDS UP TO 30 KNOTS
IS PUSHING A DECENT SWELL TOWARD THE COAST AND SURF HEIGHTS AT AREA
BEACHES HAVE REACHED 4-6 FEET PROMPTING A HIGH SURF ADVISORY THROUGH
THE REMAINDER OF THE AFTERNOON/EARLY EVENING. THE RIP CURRENT RISK
IS ALSO HIGH AS A RESULT OF THIS SURF.
TONIGHT...A COLD/CHILLY NIGHT ON TAP. HIGH PRESSURE WILL STILL BE
CENTERED WELL TO OUR WEST. THERE IS A RIDGE AXIS THAT EXTENDS OVER
TOWARD US...BUT THE GRADIENT WILL NOT RELAX ENOUGH OVER MUCH OF THE
AREA TO ALLOW FOR MUCH OF A RADIATIVE COMPONENT TO THE TEMPERATURE
DROP. WILL BE LOOKING AT MORE OF AN ADVECTION DROP IN TEMPS WITH
SOME COLD AIR DRAINAGE FROM THE NORTH DOWN THE PENINSULA. CURRENT
FORECAST IS LOOKING FOR WIDESPREAD LOWER TO MIDDLE 30S AWAY FROM THE
IMMEDIATE COAST...AND EVEN COLDER (MID 20S TO AROUND 30) OVER THE
INTERIOR NATURE COAST ZONES. A FREEZE WARNING REMAINS IN EFFECT FOR
THE NATURE COAST ZONES LATE TONIGHT INTO EARLY SATURDAY MORNING FOR
SEVERAL HOURS OF SUB-FREEZING TEMPS. ALTHOUGH A FREEZE WARNING IS
NOT CURRENTLY IN EFFECT FURTHER SOUTH...TEMPERATURES MAY BRIEFLY
APPROACH 32 IN SPOTS. DEWPOINT DEPRESSIONS LATE TONIGHT ARE 6-10C
WHICH ALONG WITH A LIGHT WIND SHOULD PREVENT ANY SIGNIFICANT FROST
FORMATION. AN APPROACHING UPPER LEVEL JET FROM THE NORTHWEST WILL
LIKELY BRING IN SOME THIN HIGH CLOUDS FROM THE WEST DURING THE
OVERNIGHT...HOWEVER WITH THIS NOT BEING A RADIATIONAL COOLING
EVENT...THESE HIGH CLOUDS SHOULD HAVE LITTLE IMPACT ON THE TEMP
FORECAST. WILL MAKE A FINAL DECISION BASED ON THE AFTERNOON FORECAST
PACKAGE NUMBERS...HOWEVER THE COMBINATION OF LOW TEMPERATURES AND AT
LEAST SOME WIND STAYING UP OVERNIGHT MAY REQUIRE THE ISSUANCE OF A
WIND CHILL ADVISORY FOR JUST ABOUT ALL OF THE FORECAST AREA. THE
ADVISORY CRITERIA ARE MOST LIKELY TO BE MET AFTER MIDNIGHT INTO THE
FIRST 1-2 DAYLIGHT HOURS OF SATURDAY. STAY WARM...AND WELCOME TO
OFFICIAL WINTER.
&&
.AVIATION...
STRONG COLD FRONT HAS CLEARED ALL TERMINALS NOW WITH VFR CONDITIONS
AND GUSTY NORTH TO NORTHWESTERLY WINDS EXPECTED FOR THE REMAINDER OF
THE DAY.
&&
.MARINE...
A COLD FRONT EXITED THE FORECAST WATERS EARLY THIS MORNING. ADVISORY
LEVEL CONDITIONS ARE ONGOING ACROSS THE EASTERN GULF OF MEXICO AND
PERIODS OF GALE CONDITIONS REMAIN POSSIBLE THROUGH THE AFTERNOON.
ANY GALE FORCE GUSTS SHOULD END BY EARLY EVENING...HOWEVER ADVISORY
CRITERIA WINDS AND SEAS WILL PERSIST THROUGH LATE TONIGHT OR EARLY
SATURDAY. THE HIGH WILL MOVE ACROSS THE REGION DURING THE WEEKEND
AND ALLOW WINDS AND SEAS TO SUBSIDE. THE NEXT COLD FRONT IS
ANTICIPATED DURING EARLY TO MID NEXT WEEK.
&&
.PRELIMINARY POINT TEMPS/POPS...
TPA 62 40 62 42 / 0 0 0 0
FMY 66 40 65 42 / 0 0 0 0
GIF 62 36 61 41 / 0 0 0 0
SRQ 64 41 62 43 / 0 0 0 0
BKV 61 29 60 31 / 0 0 0 0
SPG 62 49 61 48 / 0 0 0 0
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY
MORNING FOR CITRUS-HERNANDO-LEVY-PASCO-SUMTER.
LAKE WIND ADVISORY UNTIL 7 PM EST THIS EVENING FOR
CHARLOTTE-CITRUS-DESOTO-HARDEE-HERNANDO-HIGHLANDS-
HILLSBOROUGH-LEE-LEVY-MANATEE-PASCO-PINELLAS-POLK-
SARASOTA-SUMTER.
FREEZE WARNING FROM 2 AM TO 9 AM EST SATURDAY FOR CITRUS-
HERNANDO-LEVY-PASCO-SUMTER.
FIRE WEATHER WATCH SATURDAY AFTERNOON FOR CHARLOTTE-CITRUS-
DESOTO-HARDEE-HERNANDO-HIGHLANDS-HILLSBOROUGH-LEE-
LEVY-MANATEE-PASCO-PINELLAS-POLK-SARASOTA-SUMTER.
RED FLAG WARNING UNTIL 6 PM EST THIS EVENING FOR CHARLOTTE-
CITRUS-DESOTO-HARDEE-HERNANDO-HIGHLANDS-HILLSBOROUGH-
LEE-LEVY-MANATEE-PASCO-PINELLAS-POLK-SARASOTA-SUMTER.
HIGH SURF ADVISORY UNTIL 7 PM EST THIS EVENING FOR
CHARLOTTE-HILLSBOROUGH-LEE-MANATEE-PINELLAS-SARASOTA.
GULF WATERS...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 10
AM EST SATURDAY FOR ENGLEWOOD TO TARPON SPRINGS OUT 20 TO 60
NM-TARPON SPRINGS TO SUWANNEE RIVER OUT 20 TO 60 NM.
GALE WARNING UNTIL 4 PM EST THIS AFTERNOON FOR ENGLEWOOD
TO TARPON SPRINGS OUT 20 TO 60 NM-TARPON SPRINGS TO
SUWANNEE RIVER OUT 20 TO 60 NM.
SMALL CRAFT ADVISORY UNTIL 10 AM EST SATURDAY FOR BONITA
BEACH TO ENGLEWOOD OUT 20 NM-BONITA BEACH TO
ENGLEWOOD OUT 20 TO 60 NM-ENGLEWOOD TO TARPON SPRINGS
OUT 20 NM-TAMPA BAY WATERS-TARPON SPRINGS TO SUWANNEE
RIVER OUT 20 NM.
&&
$$
UPDATE/MARINE...MROCZKA
AVIATION...JILLSON
AREA FORECAST DISCUSSION
NWS CHARLESTON SC
1240 AM EST FRI DEC 21 2012
...HIGH WIND WARNING FOR LAKE MOULTRIE THROUGH 7 AM EST...
.SYNOPSIS...
A STRONG COLD FRONT WILL CROSS THE AREA OVERNIGHT. MUCH COOLER AND
DRIER WEATHER WILL FOLLOW THE FRONT AS HIGH PRESSURE BUILDS OVER THE
REGION THROUGH THE WEEKEND. UNSETTLED WEATHER WILL THEN RETURN BY
THE MIDDLE OF NEXT WEEK AS AN AREA OF LOW PRESSURE DEVELOPS TO OUR
WEST.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
THE COLD FRONT HAS PUSHED OFFSHORE AND WITH IT THE RISK FOR
MEASURABLE RAINFALL. SATELLITE SHOWS A CLEARING LINE MOVING
RAPIDLY FROM WEST-EAST WHICH WILL CLEAR THE COAST SOON. WINDY
CONDITIONS WILL PERSIST OVERNIGHT WITH 25-35 MPH WITH GUSTS TO
40-45 MPH. A WIND ADVISORY REMAINS IN EFFECT.
LAKE WINDS...WINDS AT PNOS1 ARE STEADILY INCREASING WITH THE
INITIATION OF STRONG COLD AIR ADVECTION. RAP BOUNDARY LAYER PROGS
MATCHED CURRENT OBSERVATIONS WELL AND SHOW WINDS INCREASING TO 35
KNOTS OVER THE NEXT FEW HOURS. THIS SHOULD TRANSLATE TO HIGH WIND
WARNING CRITERIA AS MIXING PROFILES IMPROVE SO HAVE HOISTED A
WARNING FOR THE LAKE THROUGH 7 AM. THE HIGH WIND WARNING
SUPERSEDES THE WIND ADVISORY FOR INLAND BERKELEY COUNTY...BUT
WARNING LEVEL WINDS WILL ONLY BE OBSERVED ON THE LAKE.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY/...
MUCH COLDER AIRMASS TO MOVE INTO THE AREA THIS PERIOD WITH
TEMPERATURES BELOW NORMAL UNTIL POSSIBLY SUNDAY. THE COMBINATION OF
STRONG COLD AIR ADVECTION AND LOW-LEVEL WINDS AS WELL AS A TIGHT
PRESSURE GRADIENT WILL LEAD TO WINDY CONDITIONS FRIDAY WHEN GUSTS
WILL BE AROUND 40 MPH. THUS...HAVE RAISED A WIND ADVISORY FOR ALL
AREAS WITH THE STRONGEST WINDS MOST LIKELY NEAR THE COAST AND ON THE
ELEVATED BRIDGES AND OVERPASSES. TEMPERATURES WILL LIKELY STRUGGLE
INTO THE MID 50S FRIDAY GIVEN THE COLD ADVECTION WITH THE COLDEST
TEMPERATURES LIKELY COMING FRIDAY NIGHT FOR MOST LOCALES WITH
FREEZING TEMPERATURES CLOSE TO THE COAST BY SATURDAY MORNING...AND
WIND CHILLS IN THE MID 20S WITH A CONTINUED BREEZE THROUGH THE
NIGHT.
SHOULD SEE SLIGHTLY WARMER TEMPERATURES SATURDAY EVEN AFTER A COLD
START WITH HIGHS IN THE MID/UPPER 50S. IT WILL LIKELY BE BREEZY
AGAIN BUT MUCH LESS SO THAN FRIDAY. ANOTHER PRETTY COLD NIGHT IS
THEN EXPECTED SATURDAY NIGHT WITH GOOD RADIATIONAL COOLING CONDITIONS
IN PLACE AS SURFACE HIGH PRESSURE SLIDES IN FROM THE WEST. SOME
INLAND LOCALES COULD GET AS COLD OR EVEN COLDER THAN FRIDAY NIGHT
WITH MOST PLACES AWAY FROM THE COAST EXPECTED TO SEE FREEZING
TEMPERATURES AGAIN. THE WARMING TREND WILL CONTINUE SUNDAY AS HIGH
PRESSURE SLIDES JUST SOUTH OF THE AREA ALLOWING TEMPERATURES TO GET
BACK CLOSER TO NORMAL...AROUND 60 DEGREES.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
COOL AND DRY CONDITIONS WILL PERSIST THROUGH MONDAY AS HIGH PRESSURE
REMAINS CENTERED OVER THE SOUTHEAST. A GRADUAL WARMING IS THEN
ANTICIPATED AS A LOW PRESSURE SYSTEM DEVELOPS OVER THE SOUTH CENTRAL
UNITED STATES. OVERALL TEMPS SHOULD WARM INTO THE LOW/MID 60S MONDAY
AND TUESDAY AS A WARM FRONT DEVELOPS AND EXTENDS EAST OVER THE DEEP
SOUTH. MOISTURE LOOKS TO INCREASE THROUGH MIDWEEK AS THE WARM FRONT
LIFTS NORTH THROUGH THE FORECAST AREA...THUS SUPPORTING A SLIGHT
CHANCE OF SHOWERS TUESDAY AFTERNOON. EXPECT TEMPS TO REACH THE UPPER
60S WITHIN THE WARM SECTOR WEDNESDAY BEFORE THE LOW PRESSURE SYSTEM
TRACKS THROUGH THE OHIO VALLEY. A SOUTHWARD EXTENDING COLD FRONT
ASSOCIATED WITH THIS SYSTEM SHOULD EVENTUALLY SWING THROUGH THE
SOUTHEASTERN UNITED STATES LATE WEDNESDAY INTO EARLY THURSDAY. A
CHANCE OF SHOWERS AND/OR THUNDERSTORMS ARE POSSIBLE AS THE FRONT
PROGRESSES TOWARDS THE ATLANTIC LATE IN THE PERIOD.
&&
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
VFR. VERY GUSTY WINDS WILL IMPACT THE TERMINALS FOR THE NEXT 18
HOURS. WINDS WILL SUBSIDE AFTER SUNSET THIS EVENING.
EXTENDED AVIATION OUTLOOK...THERE ARE NO CONCERNS AT THIS TIME.
&&
.MARINE...
TONIGHT...WINDS BECOMING WEST BEHIND THE COLD FRONT. SEAS HAVE
INCREASED SIGNIFICANTLY THIS EVENING SO ACCOUNTED FOR THAT ON THIS
UPDATE. AFTER THE COLD FRONT MOVES THROUGH CONDITIONS WILL
CONTINUE TO DETERIORATE IN THE COLD AIR ADVECTION BEHIND THE
FRONT. WITH GOOD MIXING OVER THE RELATIVELY WARM WATERS...GALE
WARNINGS ARE UP FOR ALL WATERS INCLUDING THE CHARLESTON HARBOR.
THE STRONGEST WINDS WILL OCCUR OVER THE CHARLESTON COUNTY WATERS
AND THE OUTER GEORGIA WATERS WHERE GUSTS TO 40 KTS...AND PERHAPS
EVEN 45 KTS FOR A BRIEF TIME ARE POSSIBLE. THE CHARLESTON HARBOR
MAY ALSO SEE GUSTS TO 40 KTS FOR A FEW HOURS JUST BEHIND THE
FRONT. SEAS WILL BUILD RAPIDLY TONIGHT AS WELL. EXPECT SEAS 6-9 FT
FOR THE CHARLESTON COUNTY WATERS...AND 4 TO 7 FOR ALL OTHER
NEARSHORE WATERS. THE HIGHEST SEAS WILL BE BEYOND 20 NM...IN THE
9-12 FT RANGE.
FRIDAY THROUGH TUESDAY...DANGEROUS MARINE CONDITIONS ARE EXPECTED
FRIDAY INTO FRIDAY NIGHT DUE TO THE CONTINUATION OF A TIGHT PRESSURE
GRADIENT IN PLACE ALONG WITH A FAVORABLE ENVIRONMENT TO MIX DOWN
STRONG LOW-LEVEL WINDS TO THE SURFACE...ESPECIALLY ACROSS THE WARMER
WATERS BEYOND 20 NM FROM SHORE. GALES ARE LIKELY THROUGH FRIDAY
EVENING ACROSS THE CHARLESTON COUNTY COASTAL WATERS AND THROUGH
FRIDAY NIGHT ACROSS THE OFFSHORE WATERS WITH THE POTENTIAL FOR
ANOTHER SURGE IN LOW-LEVEL WINDS. CONDITIONS SHOULD IMPROVE SATURDAY
AS THE PRESSURE GRADIENT AND COLD ADVECTION BEGIN TO WANE WITH NO
HEADLINES EXPECTED BEYOND SATURDAY AFTERNOON...ESPECIALLY ACROSS THE
NEARSHORE WATERS. FAIRLY TRANQUIL CONDITIONS THEN EXPECTED LATER IN
THE WEEKEND INTO EARLY NEXT WEEK AS HIGH PRESSURE MOVES INTO THE
AREA.
&&
.TIDES/COASTAL FLOODING...
STRONG OFFSHORE WINDS WILL RESULT IN BELOW NORMAL TIDES BEGINNING
TONIGHT. THE LOWEST TIDES WILL LIKELY OCCUR WITH LOW TIDE FRIDAY
MORNING WHERE LEVELS COULD DROP AS LOW AS -1.0 TO -2.0 MLLW.
TIDE LEVELS THIS LOW WILL LIKELY RESULT IN SOME PROBLEMS FOR
NAVIGATION..ESPECIALLY IN THE MORE TYPICAL SHALLOW AREAS. BELOW
NORMAL TIDES WILL LINGER THROUGH THE WEEKEND WITH LONG-DURATION
OFFSHORE WINDS EXPECTED.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...WIND ADVISORY UNTIL 7 PM EST THIS EVENING FOR GAZ087-088-
099>101-114>119-137>141.
SC...WIND ADVISORY UNTIL 7 PM EST THIS EVENING FOR SCZ040-042>044-
047>052.
HIGH WIND WARNING UNTIL 7 AM EST THIS MORNING FOR SCZ045.
MARINE...GALE WARNING UNTIL 5 AM EST EARLY THIS MORNING FOR AMZ330-352-
354.
GALE WARNING UNTIL MIDNIGHT EST TONIGHT FOR AMZ350.
GALE WARNING UNTIL 5 AM EST SATURDAY FOR AMZ374.
&&
$$
ST
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
134 AM EST FRI DEC 21 2012
.AVIATION...
06Z TAFS...THERMAL RIDGE WRAPPING AROUND WESTERN FRINGE OF
MID/UPPER LEVEL THROUGH ALLOWED FOR A CHANGEOVER TO RAIN AT
KSBN...AND EVEN BRIEFLY AT KFWA. PRECIP HAS SWITCHED BACK TO SNOW
AT KSBN AND EXPECTING SNOW TO PREVAIL AT BOTH TERMINALS THROUGH
THE REMAINDER OF THE NIGHT WITH ANY LINGERING RAIN OR RAIN/SNOW
MIX CONFINED CLOSER TO LAKE MICHIGAN. IFR CIGS SHOULD PREVAIL AT
TERMINALS WITH LIFR CONDITIONS POSSIBLE LATE TONIGHT AS SNOW AND
BLOWING SNOW BECOMES MORE PREVALENT OVERNIGHT AS LAKE ENHANCEMENT
INCREASES. POSSIBLE EARLY MORNING LIFR/IFR CONDITIONS SHOULD
IMPROVE TO MVFR TOWARD MIDDAY AS DEFORMATION BAND SHIFTS WELL EAST
OF THE AREA WITH LINGERING LAKE EFFECT SNOW SHOWERS PENETRATING
WELL INLAND WITH STRONG BACKGROUND WIND FIELD. IN TERMS OF
WINDS...PRESSURE RISE BUBBLE WILL CONTINUE TO TRACK ACROSS
NORTHEAST INDIANA NEXT FEW HOURS GIVING A SHORT HALF HOUR WINDOW
OF GUSTS TO 40 TO 45 KNOTS BEFORE RELAXING MORE INTO THE 35 TO 40
KNOT RANGE. WIND GUSTS TO INCREASE MID MORNING BACK INTO THE 40 TO
45 KNOT RANGE WITH EVEN SOME HIGHER GUSTS POSSIBLE AT KSBN THROUGH
MIDDAY.
&&
UPDATE...
MESOSCALE DVLPMNTS LT THIS AFTN IN COMBO W/MOST RECENT HIGHRES MODEL
GUIDANCE ALL POINTING TO SIG SNOW/WIND SPREADING EWD ACRS CWA
OVERNIGHT W/WIDESPREAD MOD-HVY SNOW NOTED OVR MUCH OF WRN/CNTRL IL. IN
FACT RECENT HRRR/RUC GUIDANCE INDICATING BRUTE WRAPPED UP MID LVL
CIRC NR KLAF HAS NOT YET PEAKED AND QUITE EVIDENT WITHIN
REINTENSIFYING DEFORMATION ZONE EXTENDING FM CNTRL IL NNE UP ACRS
WRN LK MI. IN FACT 21Z RUC DOES NOT BOTTOM H7 LOW UNTIL 12Z NR
WINDSOR ONTARIO. AS SUCH AND PER RAPID ESCALATION OF GRADIENT WINDS
WILL INITIALLY EXPAND WARNING SWD TO ENCOMPASS STARKE/MARSHALL AND
PLACE PULASKI/FULTON WITHIN HIGHER GRADED ADVISORY. FURTHER
EXPANSION OF WARNING PSBL FURTHER EAST BUT WILL CLOSELY
MONITOR CONTD EWD DVLPMNT/TRANSLATION OF DEFORMATION BAND AND
INCIPIENT LK ENHANCEMENT TWD 03-04Z ALG W/ADDNL 00Z BASED GUIDANCE
FOR CLUES.
PREV DISCUSSION... /ISSUED 404 PM EST THU DEC 20 2012/
SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT
LONGWAVE PATTERN HAS UNDERGONE TREMENDOUS AMPLIFICATION OVER THE
PAST 24 HOURS WITH POSITIVE FEEDBACK MECHANISMS FROM DEVELOPING
STORM PROMOTING STRONG RIDGING OVER THE EAST COAST. NOT TOO
SURPRISING THEN THAT THE LATEST 12Z GUIDANCE HAS TRENDED A TOUCH
FURTHER NORTHWEST WITH THE LOW TRACK...A SHIFT THAT HAS BEEN LARGELY
ANTICIPATED IN THE PAST FEW DISCUSSIONS AND REQUIRES LITTLE CHANGE
TO THE OVERALL FORECAST. LATEST SURFACE ANALYSIS SHOWS 983MB LOW
OVER CHICAGO AT PRESS TIME. LITTLE FURTHER DEEPENING IS EXPECTED AS
THE OCCLUSION PROCESS IS NOW UNDERWAY WITH A MATURE TROPOPAUSE FOLD
MOVING OVERHEAD LATER THIS EVENING. SURFACE LOW WILL CONTINUE TO
DRIFT NORTHEAST INTO LOWER MI DURING THE EVENING BEFORE CYCLONIC
SHEAR MAX PROPAGATES THROUGH THE BASE OF THE TROUGH AND FORCES
SECONDARY SURFACE LOW DEVELOPMENT OVER THE EAST COAST. MIDLEVEL DRY
SLOT HAS FILLED IN RATHER QUICKLY THIS AFTERNOON THANKS TO THE
IMPRESSIVE CVA ALOFT. EXPECT THIS TO CONTINUE AS THE LOW LEVEL
DEFORMATION AXIS PIVOTS INTO OUR CWA. TIMING OF TRANSITION TO SNOW
REMAINS A TOP CONCERN. SHARP RAIN/SNOW LINE IS CURRENTLY DRAPED OVER
CENTRAL IL WITH GOOD PUSH OF CAA FORCING A QUICK CHANGEOVER. SURFACE
WET BULBS LOOK TO REMAIN ABOVE FREEZING THROUGH ROUGHLY 03Z OVER
MOST OF OUR CWA. THIS MAY BE PARTIALLY OFFSET BY DYNAMIC COOLING
PROCESSES BUT EXPECT MOST AREAS WONT SEE ANY SNOW UNTIL ROUGHLY
01-02Z. THIS TRANSITION MAY TAKE EVEN LONGER OVER THE NORTHWEST WITH
CYCLONICALLY WRAPPED THERMAL TONGUE SLOW TO ERODE AND POSSIBLE
AIRMASS MODIFICATION NEAR THE LAKE.
STRONG WINDS WILL LIKELY BE THE BIGGEST STORY. IMPRESSIVE
ISALLOBARIC COMPONENT OVER THE REGION WILL WEAKEN SOMEWHAT AS THE
SURFACE LOW BEGINS TO FILL OVERNIGHT. HOWEVER...PROPAGATION OF THE
STILL VERY RESPECTABLE SURFACE LOW COMBINED WITH INCREASING CAA
PROMOTING DECENT LOW LEVEL INSTABILITY WILL SUPPORT STRONG WINDS.
925MB WINDS WILL BE APPROACHING 50 KTS BY TOMORROW MORNING AND THIS
SHOULD HAVE LITTLE DIFFICULTY MIXING TO THE SURFACE. EXPECT WIND
GUSTS UP TO 50 MPH LATE TONIGHT INTO TOMORROW MORNING...SUPPORTED BY
UPSTREAM OBS. IN FACT...ALREADY STARTING TO SEE SOME 40-45 MPH GUSTS
ALONG/BEHIND SURFACE BOUNDARY PASSING THROUGH THE AREA. CONTEMPLATED
GOING WITH HIGH WIND WARNING BUT HAVE ONLY SEEN A COUPLE 50+ KT
GUSTS UPSTREAM AND WHILE THIS MAY BE POSSIBLE NEAR THE
LAKESHORE...EXPECT MOST ARES TO STAY LARGELY BELOW WARNING CRITERIA.
QPF/SNOW FORECAST REMAINS TENUOUS. BEST LOW-MIDLEVEL DEFORMATION AND
ASSOCIATED FGEN RESPONSE CURRENTLY CAUSING HEAVY SNOW OVER NORTHERN
ILLINOIS AND SOUTHERN WISCONSIN WILL PASS LARGELY NORTHWEST OF OUR
AREA ALONG WITH THE TROWAL AXIS. THIS SYNOPTIC FORCING MAY CLIP OUR
NORTHWEST ZONES BUT SNOW AMOUNTS IN OUR CWA WILL BE HIGHLY DEPENDENT
ON DUBIOUS LAKE RESPONSE. PLENTY OF SYNOPTIC MOISTURE THROUGHOUT THE
COLUMN. INSTABILITY PARAMETERS ARE ALSO SUFFICIENT...AT LEAST BY
EARLY FRIDAY MORNING...WITH DELTA T`S IN THE MID TEENS AND
EQUILIBRIUM LEVELS CLIMBING TO AROUND 9 KFT BUT STRONG 850MB WINDS
REMAIN A CONCERN. NOT ONLY WILL THIS POTENTIALLY DISRUPT BAND
ORGANIZATION BUT THE MORE IMPORTANT IMPACT OF STRONG LOW LEVEL WINDS
MAY BE TREMENDOUS FRACTURING OF SNOWFLAKES...FORCING RELATIVELY LOW
SNOW RATIOS. NAM BUFR SOUNDINGS SUGGEST LAKE EFFECT SNOW WILL NOT
BEGIN IN EARNEST UNTIL AFTER 06Z TONIGHT WITH THE REAL COLD AIR PUSH
AND WILL TAPER OFF BY MIDDAY TOMORROW. QPF DURING THIS TIME LOOKS TO
BE AROUND 0.4 INCHES FOR OUR NORTHWEST COUNTIES. ASSUMING WE MANAGE
TO GET A 10:1 RATIO...THIS WILL RESULT IN MAINLY 3-5 INCHES WITH A
FEW ISOLATED HIGHER AMOUNTS. LAKE ENHANCED BANDS WILL LIKELY MAKE
FOR HIGHLY VARIABLE SNOW AMOUNTS...FURTHER EXACERBATED BY
DIFFICULTIES MEASURING SNOW IN HIGH WIND. AMOUNTS FURTHER DOWNSTREAM
WILL BE SLIGHTLY LOWER...THOUGH WITH THE VERY STRONG LOW LEVEL
FLOW...BANDS WILL LIKELY PENETRATE MUCH FURTHER INLAND THAN NORMAL.
HIGHEST SNOWFALL AMOUNTS MAY ACTUALLY END UP BEING FURTHER
DOWNSTREAM THAN THE IMMEDIATE LAKESHORE. NOT CONFIDENT ENOUGH TO
EXPAND WARNING BUT THIS IS SOMETHING THAT WILL NEED TO BE WATCHED.
STRONG WINDS WILL CERTAINLY CAUSE A FAIR AMOUNT OF BLOWING/DRIFTING.
AM A LITTLE CONCERNED THE MODEST SNOW AMOUNTS AND INITIALLY WARM
SURFACE TEMPS MAY LIMIT THE POSSIBILITY OF TRUE WHITEOUT CONDITIONS
BUT NEVERTHELESS EXPECT LARGE IMPACTS DURING THE MORNING COMMUTE AND
WILL MAINTAIN AREAWIDE WINTER WEATHER ADVISORY. SNOW AND HIGH WIND
WILL GRADUALLY TAPER OFF TOMORROW AFTERNOON AS LOW PRESSURE EXITS
THE REGION AND HIGH PRESSURE RETURNS WITH DRY AIR ADVECTION AND
SUBSIDENCE.
LONG TERM...
SATURDAY THROUGH THURSDAY...THE MAIN CHALLENGES THIS PERIOD ARE
DURING THE MIDDLE OF NEXT WEEK WHEN THERE IS THE POTENTIAL FOR
UNSETTLED WEATHER INCLUDING A CHANCE FOR MAINLY SNOW. FOR THIS
PACKAGE...OVERALL VERY POOR RUN TO RUN CONSISTENCY WITH MASS FIELDS
AMONG THE ECMWF AND GFS TENDING TO LOW CONFIDENCE IN THE FORECAST.
AT THIS POINT...FAVOR A GEM/CIPS ANALOG BLEND. THESE SOLUTIONS FAVOR
A MORE NORTHWEST TRACK OF THE SFC LOW...CLOSER TO THE UPPER LEVEL
SUPPORT. THE GFS IN THIS PATTERN TENDS TO INITIALLY TRACK THE SFC
LOW TOO FAR TO THE SOUTHEAST. THEREFORE...KEPT A HIGH CHANCE FOR
SNOW LATE WEDNESDAY INTO WEDNESDAY NIGHT. THERMAL PROFILES INDICATE
ALL SNOW DURING THIS PERIOD...SO WITH A MORE NORTHWEST TRACK AND
SUFFICIENTLY COLD TEMPERATURES ALOFT...FEEL THAT THERE IS A
REASONABLE CHANCE FOR ACCUMULATING SNOW. OTHERWISE...A WEAKER SYSTEM
WILL MOVE ACROSS THE AREA EARLY THIS WEEK WITH A CHANCE FOR A
RAIN/SNOW MIX MONDAY.
AVIATION...
18Z TAFS...DRY SLOT HAS NOW ENGULFED MOST OF THE AREA
ALTHOUGH SCATTERED SHOWERS ARE STILL BEING OBSERVED ALONG AND
AHEAD OF THE COLD FRONT LOCATED ALONG KLAF TO KIKK LINE. MAJOR
IMPACTS FOR THE REST OF THE DAY WILL BE STRONG SOUTHEASTERLY
WINDS. THESE WINDS WILL ABATE SLIGHTLY...ESPECIALLY AT KSBN...AS
THE LOW PRESSURE CENTER PASSES BY TO THE NORTHWEST. WINDS WILL
SHIFT FROM SOUTHEASTERLY TO SOUTHWESTERLY BEHIND THE FRONT...AND
EVENTUALLY NORTHWESTERLY LATER THIS EVENING AS PRECIPITATION
CHANGES OVER TO SNOW. THESE NORTHWESTERLY WINDS COULD GUST HIGHER
THAN 40 KNOTS BY FRIDAY MORNING. PRECIPITATION WILL CHANGE TO SNOW
BETWEEN 00Z AND 03Z TONIGHT. FALLING SNOW...COUPLED WITH STRONG
WINDS AND POTENTIAL FOR BLOWING SNOW WITH ANY ACCUMULATION THAT
MAY OCCUR WILL LIKELY RESULT IN SERIOUS VIS
RESTRICTIONS...ESPECIALLY BETWEEN 06Z AND 12Z TONIGHT.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR
INZ006>009-013-015>018-020-022>027-032>034.
WINTER STORM WARNING UNTIL 7 PM EST /6 PM CST/ THIS EVENING FOR
INZ003>005-012-014.
MI...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR
MIZ079>081.
WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR MIZ077-078.
OH...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR OHZ001-
002-004-005-015-016-024-025.
LM...STORM WARNING UNTIL 5 PM EST THIS AFTERNOON FOR LMZ043-046.
&&
$$
SHORT TERM...AGD
LONG TERM...SKIPPER
UPDATE...T
AVIATION...MARSILI
AREA FORECAST DISCUSSION
NWS GOODLAND KS
434 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 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 434 PM MST SAT DEC 22 2012
VFR CONDITIONS WILL PERSIST THROUGH THE NEXT 24 HOURS AT BOTH MCK
AND GLD. WEAK NORTH WINDS WILL GRADUALLY SHIFT WEST FOR MOST OF THE
PERIOD...SHIFTING TO THE NORTHWEST AGAIN TOMORROW AFTERNOON. CURRENT
SCATTERED HIGH CLOUDS WILL DIMINISH OVERNIGHT AND INCREASE
TOMORROW AFTERNOON ASSOCIATED WITH A WEAK FRONTAL PASSAGE.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...DR
LONG TERM...BULLER
AVIATION...JJM
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
613 PM EST SAT DEC 22 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 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 612 PM EST SAT DEC 22 2012
A COLD FRONT WILL MOVE ACROSS UPPER MICHIGAN THIS EVENING AND WINDS
ARE EXPECTED TO VEER TO THE NORTHWEST AND LEAD TO MVFR CEILINGS AND
LAKE EFFECT SNOW AT KCMX/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.
&&
.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 GAYLORD MI
145 AM EST FRI DEC 21 2012
.SYNOPSIS...
ISSUED AT 414 PM EST THU DEC 20 2012
STRONG LOW PRESSURE OVER THE SOUTHERN GREAT LAKES...WILL CONTINUE TO
LIFT INTO SOUTHERN MICHIGAN...GENERATING CONTINUED WINTRY WEATHER
ACROSS NORTHERN MICHIGAN THROUGH FRIDAY. PERIODS OF HEAVY SNOW IS
EXPECTED FOR AREAS OF NORTHERN MICHIGAN THROUGH FRIDAY AFTERNOON.
ANY PRECIPITATION FALLING AS RAIN OR A RAIN....SNOW MIX WILL CHANGE
OVER TO SNOW THIS EVENING. WINDS WILL INCREASE TONIGHT AND CONTINUE
THROUGH FRIDAY.
&&
.UPDATE...
ISSUED AT 135 AM EST FRI DEC 21 2012
QUITE THE STORM ON OUR HANDS. WARM NOSE/TROWAL STILL SITTING
ACROSS NE LOWER WITH RAIN AND RAIN/SNOW FROM ROUGHLY ALPENA TO
WEST BRANCH.THIS WILL CHANGE OVER TO JUST SNOW OVER THE NEXT
HANDFUL OF HOURS. MEANWHILE...DIFFLUENT UPPER AIR PATTERN WITHIN
DEFORMATION AXIS AND PERSISTENT LOW LEVEL WARM/MOIST ADVECTION
UNDERNEATH IT...WILL PROVIDE FOR ENHANCED SNOWFALL RATES FOR THE
NEXT FEW HOURS. LATEST SPENES DETAILS SUGGEST SNOWFALL RATES OF UP
TO 3"/HR FROM MISSAUKEE COUNTY THROUGH GAYLORD AND ROGERS CITY.
THIS ONLY EXACERBATES THE HEAVY (AND I MEAN HEAVY...WITH LIQUID)
SNOWS THAT HAVE ALREADY FALLEN AND SNAPPED TREE LIMBS AND TREES.
WILL INCREASE OVERNIGHT SNOWFALL AND QPF IN THIS REGION. SOME
LOCALES LIKELY TO EXCEED 20" BY DAYBREAK.
UPDATE ISSUED AT 1053 PM EST THU DEC 20 2012
WOW...VERY IMPRESSIVE STORM UNFOLDING ACROSS THE REGION WITH
SURFACE LOW NEAR GLADWIN ATTM AND SLOWLY LIFTING NORTHEAST. OVER
THE LAST HOUR...HAVE NUMEROUS REPORTS OF THUNDER...3 INCHES OF
SNOW IN ONE HOUR AT PETOSKEY...AND EXPANDING POWER OUTAGES ACROSS
NORTHERN LOWER...NOT SURPRISING GIVEN THE HEAVY NATURE OF THE SNOW
ALONG WITH NUMEROUS REPORTS OF BRANCHES/TREES DOWN. EXPECT THAT WE
HAVE ANOTHER 2-4 HOURS BEFORE RATES BEGIN TO COME DOWN...WHICH
WILL LIKELY BRING TOTALS ABOVE 15" IN A FEW SPOTS /ESP OTSEGO
COUNTY/. RAIN/SNOW LINE IS STEADILY ADVANCING EAST /NOW SNOWING AT
PZQ/..AND WILL CONTINUE TO DO SO AS THE LOW PROGRESSES EAST.
LITTLE CHANGES NECESSARY TO THE GOING FORECAST...WITH SOME UPPED
SNOW TOTALS BASED ON EVENING OBSERVATIONS. WINDS WILL GET GOING
AFTER MIDNIGHT AS WELL...UNFORTUNATELY EXACERBATING AN ALREADY
HAZARDOUS SITUATION. IF YOU MUST BE OUT...USE EXTREME CAUTION!
UPDATE ISSUED AT 834 PM EST THU DEC 20 2012
LOOKING OUT THE WINDOW HERE AT APX REVEALS MODERATE TO HEAVY
SNOW...WITH RIMED DENDRITES SUGGESTING FAIRLY "WET" SNOW TO
LIQUID RATIOS /7-10:1/...IN AGREEMENT WITH EVENING OBSERVATIONS.
NOT SURPRISINGLY...CURRENT LIGHTNING DATA SHOWS SOME IN CLOUD
FLASHES OVER AND NEAR LITTLE TRAVERSE BAY...WITH A FEW REPORTS OF
THUNDER RECEIVED AT THE OFFICE. VERY HEAVY SNOW HAS NOW DEVELOPED
ALONG A FKS-CVX-MCD LINE WITH 1 INCH+/HOUR RATES PER SPOTTERS. AT
THE SAME TIME...HEAVY SNOWS CONTINUE OVER MUCH OF INTERIOR
NORTHERN LOWER...AND EASTERN UPPER /ESP ALONG I-75 PER SPOTTERS/.
GIVEN THIS EVOLUTION...WILL LEAVE GOING HEADLINES IN PLACE AS OF
THIS TIME. PRIMARY AREA OF CONCERN /OF LESS THAN WARNING LEVEL
SNOWS OVERNIGHT/ IS FROM TVC TO MBL...WHERE A GAP IN THE ECHOES
HAVE DEVELOPED WITH THE BETTER SOUTH-NORTH MOISTURE FEED FURTHER
EAST. STILL EXPECT...HOWEVER...THAT AS WE START TO GET THE LAKE
INVOLVED LATER TONIGHT THAT THIS WILL FILL BACK IN WITH
SIGNIFICANT ACCUMS. WITH WINDS KICKING UP HERE AFTER
MIDNIGHT...EXPECT A VERY HAZARDOUS MORNING COMMUTE...AND THUS THE
WARNING WILL REMAIN.
LOW PRESSURE LOOKS TO HAVE REACHED PEAK INTENSITY WITH OBS OVER
SOUTHWEST LOWER MICHIGAN SHOWING 985MB...HAVING COME UP 1-2 MB IN
THE LAST FEW HOURS. THUS...AS THE OCCLUSION PROCESS GETS
GOING...EXPECT OUR TRANSITION TO A COOLER AIRMASS TO GO AS
EXPECTED...WITH SNOWS COLLAPSING TO THE COAST OF NORTHEAST LOWER
AFTER MIDNIGHT.
UPDATE ISSUED AT 704 PM EST THU DEC 20 2012
TERRIFIC WV SATELLITE PRESENTATION OF OUR WINTER STORM AS H5 LOW
CROSSES THROUGH NORTHERN INDIANA WITH 984 MB LOW EMERGING OVER
SOUTHWEST LOWER MICHIGAN. CLASSIC TRACK TO KEEP NEARLY ALL OF OUR
CWA IN THE DEFORMATION PRECIPITATION THROUGH THE OVERNIGHT. RECENT
TRENDS IN THE DUAL POL PRODUCTS SUGGESTS A TRANSITION BACK TO SNOW IS
COMPLETE FROM MBL TO TVC...WITH VSBY RESTRICTIONS BECOMING GREATER
AT THESE SITES AS THE SNOWFALL INTENSITY INCREASES. A RAIN/SNOW
MIX...OR JUST PLAIN RAIN CONTINUES FROM CAD TO HTL TO APN WITH
ROGERS CITY SHIFTING TO RAIN LAST HOUR. THIS LINES UP FAIRLY WELL
WITH RECENT RAP TRENDS...WITH NEW APX RAOB SHOWING THE RAP IS
ABOUT 1C TOO WARM THROUGH THE LLEVELS. THUS...HAVE ONLY NEEDED
SOME MINOR TWEAKS TO THE WEATHER GRIDS FOR THE NEXT FEW HOURS.
PRECIPITATION RATES LOOK TO REMAIN IMPRESSIVE WITH CONVECTIVE
ELEMENTS CONTINUING TO FEED THE DEFORMATION BAND.
THEREFORE...OCCASIONAL 1-2"/HOUR SNOWFALL RATES LOOK PLAUSIBLE
THROUGH AT LEAST 06Z...AND THUS OVERNIGHT SNOWFALL AMOUNTS OF 6"+
FOR FAR NORTHERN LOWER AND EASTERN UPPER STILL LOOK GOOD. A
TERRIBLE TRAVEL NIGHT FOR SURE...WITH SOME POWER OUTAGES REPORTED
/AND LIKELY TO CONTINUE AND PERHAPS EXPAND AS WINDS GET GOING
AFTER MIDNIGHT/.
UPDATE ISSUED AT 556 PM EST THU DEC 20 2012
LOW PRESSURE CROSSING SOUTHERN LAKE MICHIGAN AT THIS HOUR...NEAR
983 MB /STILL A LITTLE BELOW NEAR TERM RUC GUIDANCE/. RAIN-SNOW
LINE HAS BEEN FLIRTING WITH THE TVC-GOV-APN CORRIDOR AND THIS IS
IN GOOD AGREEMENT WITH H8 WETBULB ZERO LINE. EXPECT THAT THIS WILL
SHIFT A LITTLE FURTHER NORTH AND EAST THIS EVENING UNTIL THE LOW
REACHES OUR LONGITUDE AROUND 9-10PM...IN LINE WITH RAP
EXPECTATIONS.
PRIMARY CHANGES INCLUDE REMOVING BLOWING SNOW MENTION THROUGH THE
EVENING UNTIL WE CAN GET THE NNW WINDS TO STRENGTHEN IN
COMBINATION WITH SLOWLY COOLING BL TEMPS. HAVE ALSO ADJUSTED
WEATHER GRIDS TO ACCOUNT FOR EXPECTED MOVEMENT OF THE RAIN/SNOW
LINE. FINALLY...HAVE ADJUSTED OVERNIGHT PRECIPITATION TOTALS PER
LATEST HRRR/RAP...BUT THIS ONLY RESULTS IN A MINOR CHANGE TO
PREVIOUS GRIDDED FORECAST. STILL EXPECT SOME SPOTS OVER INTERIOR
NORTHERN LOWER AND EASTERN UPPER TO SEE UPWARDS OF 6 ADDITIONAL
INCHES OVERNIGHT. WHILE A LITTLE LESS WILL FALL AT THE COASTS...IT
WILL BE FAR MORE THAN HAS BEEN SEEN THUS FAR...THEREFORE CAUSING
TRAVEL CONDITIONS IN THESE REGIONS TO DETERIORATE RAPIDLY.
HAVE ISSUED AN SPS TO HIGHLIGHT THE CHANGING EVENING CONDITIONS.
OTHERWISE...HEADLINES LOOK GOOD. WILL REASSESS OUR FAR SOUTHEAST
FOR POTENTIAL WINTER WEATHER ADVISORY NEEDED WELL AFTER MIDNIGHT.
&&
.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 414 PM EST THU DEC 20 2012
ON THE LATEST SURFACE WEATHER MAP OF INTEREST...984 MB LOW PRESSURE
WAS CENTERED NEAR CHICAGO ILLINOIS. APX AND SURROUNDING RADARS
SHOWED MODERATE TO HEAVY PRECIPITATION ACROSS MUCH OF NORTHERN
MICHIGAN. THE FORM OF WHICH IS ALL OVER THE MAP...SOME SPOTS ACROSS
THE HIGHER TERRAIN HAS HAD 6 INCHES OR MORE...WHILE THE LOWER
ELEVATIONS HAVE HAD 2 INCHES OR LESS (IN SOME CASES NEARLY NONE AT
ALL). FORECAST CHALLENGES ARE NUMEROUS WITH CHANGEOVER TO ALL SNOW
AND ADDITIONAL ACCUMULATIONS THE MAIN ONES.
TONIGHT...STORM SYSTEM WILL CONTINUE TO TRACK NORTHEAST ACROSS LOWER
MICHIGAN TONIGHT THEN INTO WESTERN NEW YORK FRIDAY. SNOWFALL RATES
ARE EXPECTED TO PICK UP ONCE AGAIN AND AS COLDER AIR GETS PULLED
INTO THE REGION FROM THE NORTH...SNOWFALL RATES ARE EXPECTED TO
INCREASE. WATER VAPOR LOOPS DEPICT A WELL-DEFINED BAROCLINIC LEAF
STRUCTURE. ACCOMPANYING STRONG DIVERGENCE WITHIN A COUPLED UPPER JET
STRUCTURE ATOP LOW/MID-LEVEL FRONTOGENESIS WILL SUPPORT AN INCREASE
IN SNOW RATES DURING THE NEXT FEW HOURS. DEEP ASCENT THROUGH
DENDRITIC GROWTH ZONES WITHIN THE 700-500-MB LAYER WILL SUPPORT
EFFICIENT SNOW GROWTH...WITH ISOTHERMAL PROFILES IN THE 850-700-MB
LAYER YIELDING EFFICIENT SNOW AGGREGATION. SNOWFALL RATES OF 1-1.5
INCHES WILL LIKELY BECOME COMMON LATER THIS EVENING...AS ONE OR MORE
NE/SW-ORIENTED SNOW BANDS DEVELOP WHILE THE SFC LOW APPROACHES. THE
ENHANCED SFC PRESSURE GRADIENT WILL SUPPORT NNE TO ENE WINDS OF
20-25 MPH WITH GUSTS REACHING 30 TO OCCASIONALLY 35 MPH. THIS WILL
SUPPORT REDUCED VISIBILITIES TO ONE-HALF MILE IN BLOWING SNOW...AND
LOCALIZED BLIZZARD CONDITIONS MAY OCCUR. ADDITIONAL ACCUMULATIONS
WILL VARY WIDELY FROM AN INCH OR LESS NEAR THE LAKE HURON LAKE
SHORES TO BETWEEN 4 AND 8 INCHES ACROSS EASTERN UPPER AND THE HIGHER
TERRAIN OF NORTHERN LOWER. LOWS RANGING FROM THE MIDDLE 20S NORTH TO
THE LOWER 30S SOUTHEAST.
FRIDAY...WRAP AROUND SNOW SHOWERS IN THE MORNING THEN DRIER
AIR/SUBSIDENCE/RIDGING BY LATE IN THE DAY WHICH SHOULD DIMINISH
ACTIVITY. THERE IS ALSO A BIT OF OVER LAKE INSTABILITY (DELTA TS OF
ABOUT 14) WITH STRONG NORTHERLY FLOW. THIS WILL LEAD TO WIDESPREAD
BLOWING AND DRIFTING SNOW...WITH ONLY ABOUT 2 INCHES OR LESS OF
ADDITIONAL ACTUAL ACCUMULATION. HIGHS IN THE UPPER 20S NORTH TO THE
MIDDLE 30S SOUTHEAST.
.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 414 PM EST THU DEC 20 2012
FOUR WAVE NRN HEMISPHERIC PATTERN IN PLACE TODAY WITH MAJOR TROUGH
AXES OVER FAR EASTERN ASIA AND ALONG THE NOAM WEST COAST. SW
FLOW/RIDGING AND RELATIVELY MILD TEMPERATURES EXISTS DOWNSTREAM
THROUGH THE PLAINS AND THE EASTERN CONUS...WITH MUCH OF NRN MICHIGAN
JUST COLD ENOUGH TO GET IN ON THE HEAVY SNOW WITH OUR ONGOING WINTER
STORM (ACTUALLY PARTS OF THE CWA IS WITHIN THE SWEET SPOT...THE
TRANSITION ZONE FROM RAIN TO SNOW WHERE YOU GET MAXIMUM MOISTURE
INFLOW). FLOW PATTERN REMAINS SOMEWHAT PROGRESSIVE ACROSS THE CONUS
THROUGH THE UPCOMING SEVEN DAY STRETCH BUT STILL ON THE OVERALL MILD
SIDE OF THE THINGS AS THE REALLY COLD AIR REMAINS STUCK ACROSS THE
POLE INTO EASTERN ASIA...A PATTERN THAT HAS DOMINATED THIS
FALL/EARLY WINTER SEASON SO FAR. BUT FIRST...HAVE TO GET THROUGH THE
ONGOING STORM.
FRIDAY NIGHT AND SATURDAY...ONGOING STRONG SYSTEM WILL BE EXITING
EAST OF THE STATE BY FRIDAY EVENING WITH MID LEVEL RIDING/SFC HIGH
PRESSURE AND DRIER AIR NOSING INTO THE WESTERN GREAT LAKES THROUGH
THE NIGHT. NNW FLOW LAKE SNOW SHOWERS AND GUSTY WINDS WILL PERSIST
THROUGH FRIDAY EVENING BEFORE DIMINISHING SUBSTANTIALLY OVERNIGHT
INTO THE DAY SATURDAY. ACCORDINGLY...WILL START OUT WITH CATEGORICAL
NNW FLOW LAKE SNOW SHOWERS FRIDAY EVENING BEFORE DIMINISHING/ENDING
BY SATURDAY MORNING. CURR
SATURDAY NIGHT THROUGH CHRISTMAS EVE...A RELATIVE LULL IN THE
WEATHER ACTION FOR THE LATTER HALF OF THE WEEKEND THROUGH CHRISTMAS
EVE WITH BROAD HIGH PRESSURE AND WEDGE OF DRIER AIR IN THE REGION.
THAT SAID...GUIDANCE DOES DEPICT A COUPLE WAVES WITHIN THE FAST NW
FLOW ALOFT SKITING THROUGH THE NRN PART OF THE STATE...ONE SATURDAY
NIGHT AND A STRONGER ONE ON SUNDAY. SOME COLDER AIR SAGGING BACK
INTO THE REGION BEHIND THE WAVE ENOUGH TO MAINTAIN AND/OR GENERATE
SOME LAKE SNOWS OFF THE GREAT LAKES...ESPECIALLY SUNDAY AS THE
STRONGER WAVE PASSES THROUGH. BUT OVERALL NOT A BIG DEAL WITH FAIRLY
DRY AIR IN CONTROL. SUNDAY NIGHT THROUGH CHRISTMAS EVE LOOKING QUIET
AT THIS POINT WITH BROAD HIGH PRESSURE THROUGH THE REGION.
CHRISTMAS DAY THROUGH THURSDAY (EXTENDED PERIODS)...SOLUTION
DIFFERENCES AMONG THE MEDIUM RANGE GUIDANCE...AS USUAL. GEM/GFS
SOLUTIONS ARE IN ONE CAMP KEEPING THINGS ON THE QUIET SIDE FOR
CHRISTMAS DAY (ALTHOUGH THE GFS DOES HAVE A WEAK FAST MOVING WAVE
MOVING THROUGH THE REGION). ECMWF HINTING AT ANOTHER STRONGER STORM
FOR TWO RUNS NOW PUSHING UP THROUGH THE OHIO VALLEY/GREAT LAKES ON
CHRISTMAS DAY. DIFFERENCES AMONG THE GUIDANCE ARE THE RESULT OF THE
DEGREE OF PHASING BETWEEN THE NRN AND SOUTHERN STREAMS WITH OBVIOUS
BIG IMPLICATIONS. NO WAY OF KNOWING THE CORRECT SOLUTION AT THIS
JUNCTURE...BUT WILL HAVE LOWER END SNOW CHANCES ON TUESDAY FOR NOW.
ANOTHER SHOT FOR A STORM SYSTEM MAY COME WEDNESDAY NIGHT THROUGH
THURSDAY WITH THE POTENTIAL FOR YET ANOTHER STORM TO SPIN UP OFF THE
GULF AND LIFT NORTHWARD THROUGH THE EASTERN CONUS. AGAIN...BIG
DIFFERENCES ON THE TIME/TRACK OF THAT STORM (IF IT OCCURS AT ALL).
BUT WILL CARRY CHANCE POPS FOR SNOW DURING THAT TIME.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1151 PM EST THU DEC 20 2012
A COMBINATION OF IFR/MVFR CONDITIONS AT THE TAF SITES AT THE
MOMENT AS LOW PRESSURE NEAR TAWAS PUSHES EAST INTO LAKE HURON. ANY
MIX WITH RAIN IS NOW OVER AT APN...WITH SNOW THE ONLY PTYPE
THROUGH THE PERIOD. OCCASIONAL SNOWS WILL CONTINUE THROUGH
DAYBREAK WITH LIFR-IFR VSBYS/IFR CIGS POSSIBLE PARTICULARLY AT
PLN/TVC. RESTRICTIONS WILL GRADUALLY IMPROVE FOR THE DAY ON
FRIDAY...WITH MVFR CIGS/VSBYS IN LAKE EFFECT SHSN/BLOWING SNOW
WITH SOME LATE DAY/EVENING IMPROVEMENT TO VFR AT TVC/MBL.
WINDS HAVE SHIFTED NORTHERLY TO 10G20KTS ATTM AND WILL CONTINUE TO
BACK NORTHWESTERLY AND INCREASE TO 25G35KTS FOR THE DAY ON FRIDAY.
&&
.MARINE...
ISSUED AT 414 PM EST THU DEC 20 2012
MAJOR WINTER STORM LIFTING NE INTO THE GREAT LAKES THROUGH
TONIGHT...BEFORE DEPARTING FRIDAY. OVERLAKE INSTABILITY WITH
EASTERLY WINDS AT 20-35KTS TO DEVELOP AS MODERATE TO HEAVY SNOWS
(MIXED WITH OR ALL RAIN ACROSS LAKE HURON). THE SNOWS WILL BE
INCREASINGLY INTENSE THIS EVENING. WINDS WILL DECREASE SOME ACROSS A
GOOD CHUNK OF THE NEARSHORES THIS EVENING...BUT THEN RAMP BACK UP
AGAIN LATE TONIGHT AND FRIDAY WITH COLD ADVECTION FOLLOWING THE
DEPARTING SFC LOW PRESSURE. WINDS WILL GUST AS HIGH AS
50KTS...RESULTING IN STORM FORCE WINDS FOR THE NW LOWER NEARSHORES.
SOLID GALES ALL OTHER MARINE AREAS. GRADIENT GRADUALLY LOOSENS UP
OVER THE WEEKEND...BUT GALES AND OBVIOUSLY CHOPPY WAVES WILL PERSIST
THROUGH FRIDAY NIGHT.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR MIZ008-
015>029-031>034.
WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR MIZ030-
035-041.
LH...GALE WARNING UNTIL 7 AM EST SATURDAY FOR LHZ345>349.
LM...GALE WARNING UNTIL 7 AM EST SATURDAY FOR LMZ341.
STORM WARNING UNTIL 7 PM EST THIS EVENING FOR LMZ323-342-344>346.
LS...GALE WARNING UNTIL 7 AM EST SATURDAY FOR LSZ321-322.
&&
$$
UPDATE...SD
SYNOPSIS...TL
SHORT TERM...AS
LONG TERM...BA
AVIATION...JA
MARINE...AS
AREA FORECAST DISCUSSION
NWS GAYLORD MI
1158 PM EST THU DEC 20 2012
.SYNOPSIS...
ISSUED AT 414 PM EST THU DEC 20 2012
STRONG LOW PRESSURE OVER THE SOUTHERN GREAT LAKES...WILL CONTINUE TO
LIFT INTO SOUTHERN MICHIGAN...GENERATING CONTINUED WINTRY WEATHER
ACROSS NORTHERN MICHIGAN THROUGH FRIDAY. PERIODS OF HEAVY SNOW IS
EXPECTED FOR AREAS OF NORTHERN MICHIGAN THROUGH FRIDAY AFTERNOON.
ANY PRECIPITATION FALLING AS RAIN OR A RAIN....SNOW MIX WILL CHANGE
OVER TO SNOW THIS EVENING. WINDS WILL INCREASE TONIGHT AND CONTINUE
THROUGH FRIDAY.
&&
.UPDATE...
ISSUED AT 1053 PM EST THU DEC 20 2012
WOW...VERY IMPRESSIVE STORM UNFOLDING ACROSS THE REGION WITH
SURFACE LOW NEAR GLADWIN ATTM AND SLOWLY LIFTING NORTHEAST. OVER
THE LAST HOUR...HAVE NUMEROUS REPORTS OF THUNDER...3 INCHES OF
SNOW IN ONE HOUR AT PETOSKEY...AND EXPANDING POWER OUTAGES ACROSS
NORTHERN LOWER...NOT SURPRISING GIVEN THE HEAVY NATURE OF THE SNOW
ALONG WITH NUMEROUS REPORTS OF BRANCHES/TREES DOWN. EXPECT THAT WE
HAVE ANOTHER 2-4 HOURS BEFORE RATES BEGIN TO COME DOWN...WHICH
WILL LIKELY BRING TOTALS ABOVE 15" IN A FEW SPOTS /ESP OTSEGO
COUNTY/. RAIN/SNOW LINE IS STEADILY ADVANCING EAST /NOW SNOWING AT
PZQ/..AND WILL CONTINUE TO DO SO AS THE LOW PROGRESSES EAST.
LITTLE CHANGES NECESSARY TO THE GOING FORECAST...WITH SOME UPPED
SNOW TOTALS BASED ON EVENING OBSERVATIONS. WINDS WILL GET GOING
AFTER MIDNIGHT AS WELL...UNFORTUNATELY EXACERBATING AN ALREADY
HAZARDOUS SITUATION. IF YOU MUST BE OUT...USE EXTREME CAUTION!
UPDATE ISSUED AT 834 PM EST THU DEC 20 2012
LOOKING OUT THE WINDOW HERE AT APX REVEALS MODERATE TO HEAVY
SNOW...WITH RIMED DENDRITES SUGGESTING FAIRLY "WET" SNOW TO
LIQUID RATIOS /7-10:1/...IN AGREEMENT WITH EVENING OBSERVATIONS.
NOT SURPRISINGLY...CURRENT LIGHTNING DATA SHOWS SOME IN CLOUD
FLASHES OVER AND NEAR LITTLE TRAVERSE BAY...WITH A FEW REPORTS OF
THUNDER RECEIVED AT THE OFFICE. VERY HEAVY SNOW HAS NOW DEVELOPED
ALONG A FKS-CVX-MCD LINE WITH 1 INCH+/HOUR RATES PER SPOTTERS. AT
THE SAME TIME...HEAVY SNOWS CONTINUE OVER MUCH OF INTERIOR
NORTHERN LOWER...AND EASTERN UPPER /ESP ALONG I-75 PER SPOTTERS/.
GIVEN THIS EVOLUTION...WILL LEAVE GOING HEADLINES IN PLACE AS OF
THIS TIME. PRIMARY AREA OF CONCERN /OF LESS THAN WARNING LEVEL
SNOWS OVERNIGHT/ IS FROM TVC TO MBL...WHERE A GAP IN THE ECHOES
HAVE DEVELOPED WITH THE BETTER SOUTH-NORTH MOISTURE FEED FURTHER
EAST. STILL EXPECT...HOWEVER...THAT AS WE START TO GET THE LAKE
INVOLVED LATER TONIGHT THAT THIS WILL FILL BACK IN WITH
SIGNIFICANT ACCUMS. WITH WINDS KICKING UP HERE AFTER
MIDNIGHT...EXPECT A VERY HAZARDOUS MORNING COMMUTE...AND THUS THE
WARNING WILL REMAIN.
LOW PRESSURE LOOKS TO HAVE REACHED PEAK INTENSITY WITH OBS OVER
SOUTHWEST LOWER MICHIGAN SHOWING 985MB...HAVING COME UP 1-2 MB IN
THE LAST FEW HOURS. THUS...AS THE OCCLUSION PROCESS GETS
GOING...EXPECT OUR TRANSITION TO A COOLER AIRMASS TO GO AS
EXPECTED...WITH SNOWS COLLAPSING TO THE COAST OF NORTHEAST LOWER
AFTER MIDNIGHT.
UPDATE ISSUED AT 704 PM EST THU DEC 20 2012
TERRIFIC WV SATELLITE PRESENTATION OF OUR WINTER STORM AS H5 LOW
CROSSES THROUGH NORTHERN INDIANA WITH 984 MB LOW EMERGING OVER
SOUTHWEST LOWER MICHIGAN. CLASSIC TRACK TO KEEP NEARLY ALL OF OUR
CWA IN THE DEFORMATION PRECIPITATION THROUGH THE OVERNIGHT. RECENT
TRENDS IN THE DUAL POL PRODUCTS SUGGESTS A TRANSITION BACK TO SNOW IS
COMPLETE FROM MBL TO TVC...WITH VSBY RESTRICTIONS BECOMING GREATER
AT THESE SITES AS THE SNOWFALL INTENSITY INCREASES. A RAIN/SNOW
MIX...OR JUST PLAIN RAIN CONTINUES FROM CAD TO HTL TO APN WITH
ROGERS CITY SHIFTING TO RAIN LAST HOUR. THIS LINES UP FAIRLY WELL
WITH RECENT RAP TRENDS...WITH NEW APX RAOB SHOWING THE RAP IS
ABOUT 1C TOO WARM THROUGH THE LLEVELS. THUS...HAVE ONLY NEEDED
SOME MINOR TWEAKS TO THE WEATHER GRIDS FOR THE NEXT FEW HOURS.
PRECIPITATION RATES LOOK TO REMAIN IMPRESSIVE WITH CONVECTIVE
ELEMENTS CONTINUING TO FEED THE DEFORMATION BAND.
THEREFORE...OCCASIONAL 1-2"/HOUR SNOWFALL RATES LOOK PLAUSIBLE
THROUGH AT LEAST 06Z...AND THUS OVERNIGHT SNOWFALL AMOUNTS OF 6"+
FOR FAR NORTHERN LOWER AND EASTERN UPPER STILL LOOK GOOD. A
TERRIBLE TRAVEL NIGHT FOR SURE...WITH SOME POWER OUTAGES REPORTED
/AND LIKELY TO CONTINUE AND PERHAPS EXPAND AS WINDS GET GOING
AFTER MIDNIGHT/.
UPDATE ISSUED AT 556 PM EST THU DEC 20 2012
LOW PRESSURE CROSSING SOUTHERN LAKE MICHIGAN AT THIS HOUR...NEAR
983 MB /STILL A LITTLE BELOW NEAR TERM RUC GUIDANCE/. RAIN-SNOW
LINE HAS BEEN FLIRTING WITH THE TVC-GOV-APN CORRIDOR AND THIS IS
IN GOOD AGREEMENT WITH H8 WETBULB ZERO LINE. EXPECT THAT THIS WILL
SHIFT A LITTLE FURTHER NORTH AND EAST THIS EVENING UNTIL THE LOW
REACHES OUR LONGITUDE AROUND 9-10PM...IN LINE WITH RAP
EXPECTATIONS.
PRIMARY CHANGES INCLUDE REMOVING BLOWING SNOW MENTION THROUGH THE
EVENING UNTIL WE CAN GET THE NNW WINDS TO STRENGTHEN IN
COMBINATION WITH SLOWLY COOLING BL TEMPS. HAVE ALSO ADJUSTED
WEATHER GRIDS TO ACCOUNT FOR EXPECTED MOVEMENT OF THE RAIN/SNOW
LINE. FINALLY...HAVE ADJUSTED OVERNIGHT PRECIPITATION TOTALS PER
LATEST HRRR/RAP...BUT THIS ONLY RESULTS IN A MINOR CHANGE TO
PREVIOUS GRIDDED FORECAST. STILL EXPECT SOME SPOTS OVER INTERIOR
NORTHERN LOWER AND EASTERN UPPER TO SEE UPWARDS OF 6 ADDITIONAL
INCHES OVERNIGHT. WHILE A LITTLE LESS WILL FALL AT THE COASTS...IT
WILL BE FAR MORE THAN HAS BEEN SEEN THUS FAR...THEREFORE CAUSING
TRAVEL CONDITIONS IN THESE REGIONS TO DETERIORATE RAPIDLY.
HAVE ISSUED AN SPS TO HIGHLIGHT THE CHANGING EVENING CONDITIONS.
OTHERWISE...HEADLINES LOOK GOOD. WILL REASSESS OUR FAR SOUTHEAST
FOR POTENTIAL WINTER WEATHER ADVISORY NEEDED WELL AFTER MIDNIGHT.
&&
.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 414 PM EST THU DEC 20 2012
ON THE LATEST SURFACE WEATHER MAP OF INTEREST...984 MB LOW PRESSURE
WAS CENTERED NEAR CHICAGO ILLINOIS. APX AND SURROUNDING RADARS
SHOWED MODERATE TO HEAVY PRECIPITATION ACROSS MUCH OF NORTHERN
MICHIGAN. THE FORM OF WHICH IS ALL OVER THE MAP...SOME SPOTS ACROSS
THE HIGHER TERRAIN HAS HAD 6 INCHES OR MORE...WHILE THE LOWER
ELEVATIONS HAVE HAD 2 INCHES OR LESS (IN SOME CASES NEARLY NONE AT
ALL). FORECAST CHALLENGES ARE NUMEROUS WITH CHANGEOVER TO ALL SNOW
AND ADDITIONAL ACCUMULATIONS THE MAIN ONES.
TONIGHT...STORM SYSTEM WILL CONTINUE TO TRACK NORTHEAST ACROSS LOWER
MICHIGAN TONIGHT THEN INTO WESTERN NEW YORK FRIDAY. SNOWFALL RATES
ARE EXPECTED TO PICK UP ONCE AGAIN AND AS COLDER AIR GETS PULLED
INTO THE REGION FROM THE NORTH...SNOWFALL RATES ARE EXPECTED TO
INCREASE. WATER VAPOR LOOPS DEPICT A WELL-DEFINED BAROCLINIC LEAF
STRUCTURE. ACCOMPANYING STRONG DIVERGENCE WITHIN A COUPLED UPPER JET
STRUCTURE ATOP LOW/MID-LEVEL FRONTOGENESIS WILL SUPPORT AN INCREASE
IN SNOW RATES DURING THE NEXT FEW HOURS. DEEP ASCENT THROUGH
DENDRITIC GROWTH ZONES WITHIN THE 700-500-MB LAYER WILL SUPPORT
EFFICIENT SNOW GROWTH...WITH ISOTHERMAL PROFILES IN THE 850-700-MB
LAYER YIELDING EFFICIENT SNOW AGGREGATION. SNOWFALL RATES OF 1-1.5
INCHES WILL LIKELY BECOME COMMON LATER THIS EVENING...AS ONE OR MORE
NE/SW-ORIENTED SNOW BANDS DEVELOP WHILE THE SFC LOW APPROACHES. THE
ENHANCED SFC PRESSURE GRADIENT WILL SUPPORT NNE TO ENE WINDS OF
20-25 MPH WITH GUSTS REACHING 30 TO OCCASIONALLY 35 MPH. THIS WILL
SUPPORT REDUCED VISIBILITIES TO ONE-HALF MILE IN BLOWING SNOW...AND
LOCALIZED BLIZZARD CONDITIONS MAY OCCUR. ADDITIONAL ACCUMULATIONS
WILL VARY WIDELY FROM AN INCH OR LESS NEAR THE LAKE HURON LAKE
SHORES TO BETWEEN 4 AND 8 INCHES ACROSS EASTERN UPPER AND THE HIGHER
TERRAIN OF NORTHERN LOWER. LOWS RANGING FROM THE MIDDLE 20S NORTH TO
THE LOWER 30S SOUTHEAST.
FRIDAY...WRAP AROUND SNOW SHOWERS IN THE MORNING THEN DRIER
AIR/SUBSIDENCE/RIDGING BY LATE IN THE DAY WHICH SHOULD DIMINISH
ACTIVITY. THERE IS ALSO A BIT OF OVER LAKE INSTABILITY (DELTA TS OF
ABOUT 14) WITH STRONG NORTHERLY FLOW. THIS WILL LEAD TO WIDESPREAD
BLOWING AND DRIFTING SNOW...WITH ONLY ABOUT 2 INCHES OR LESS OF
ADDITIONAL ACTUAL ACCUMULATION. HIGHS IN THE UPPER 20S NORTH TO THE
MIDDLE 30S SOUTHEAST.
.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 414 PM EST THU DEC 20 2012
FOUR WAVE NRN HEMISPHERIC PATTERN IN PLACE TODAY WITH MAJOR TROUGH
AXES OVER FAR EASTERN ASIA AND ALONG THE NOAM WEST COAST. SW
FLOW/RIDGING AND RELATIVELY MILD TEMPERATURES EXISTS DOWNSTREAM
THROUGH THE PLAINS AND THE EASTERN CONUS...WITH MUCH OF NRN MICHIGAN
JUST COLD ENOUGH TO GET IN ON THE HEAVY SNOW WITH OUR ONGOING WINTER
STORM (ACTUALLY PARTS OF THE CWA IS WITHIN THE SWEET SPOT...THE
TRANSITION ZONE FROM RAIN TO SNOW WHERE YOU GET MAXIMUM MOISTURE
INFLOW). FLOW PATTERN REMAINS SOMEWHAT PROGRESSIVE ACROSS THE CONUS
THROUGH THE UPCOMING SEVEN DAY STRETCH BUT STILL ON THE OVERALL MILD
SIDE OF THE THINGS AS THE REALLY COLD AIR REMAINS STUCK ACROSS THE
POLE INTO EASTERN ASIA...A PATTERN THAT HAS DOMINATED THIS
FALL/EARLY WINTER SEASON SO FAR. BUT FIRST...HAVE TO GET THROUGH THE
ONGOING STORM.
FRIDAY NIGHT AND SATURDAY...ONGOING STRONG SYSTEM WILL BE EXITING
EAST OF THE STATE BY FRIDAY EVENING WITH MID LEVEL RIDING/SFC HIGH
PRESSURE AND DRIER AIR NOSING INTO THE WESTERN GREAT LAKES THROUGH
THE NIGHT. NNW FLOW LAKE SNOW SHOWERS AND GUSTY WINDS WILL PERSIST
THROUGH FRIDAY EVENING BEFORE DIMINISHING SUBSTANTIALLY OVERNIGHT
INTO THE DAY SATURDAY. ACCORDINGLY...WILL START OUT WITH CATEGORICAL
NNW FLOW LAKE SNOW SHOWERS FRIDAY EVENING BEFORE DIMINISHING/ENDING
BY SATURDAY MORNING. CURR
SATURDAY NIGHT THROUGH CHRISTMAS EVE...A RELATIVE LULL IN THE
WEATHER ACTION FOR THE LATTER HALF OF THE WEEKEND THROUGH CHRISTMAS
EVE WITH BROAD HIGH PRESSURE AND WEDGE OF DRIER AIR IN THE REGION.
THAT SAID...GUIDANCE DOES DEPICT A COUPLE WAVES WITHIN THE FAST NW
FLOW ALOFT SKITING THROUGH THE NRN PART OF THE STATE...ONE SATURDAY
NIGHT AND A STRONGER ONE ON SUNDAY. SOME COLDER AIR SAGGING BACK
INTO THE REGION BEHIND THE WAVE ENOUGH TO MAINTAIN AND/OR GENERATE
SOME LAKE SNOWS OFF THE GREAT LAKES...ESPECIALLY SUNDAY AS THE
STRONGER WAVE PASSES THROUGH. BUT OVERALL NOT A BIG DEAL WITH FAIRLY
DRY AIR IN CONTROL. SUNDAY NIGHT THROUGH CHRISTMAS EVE LOOKING QUIET
AT THIS POINT WITH BROAD HIGH PRESSURE THROUGH THE REGION.
CHRISTMAS DAY THROUGH THURSDAY (EXTENDED PERIODS)...SOLUTION
DIFFERENCES AMONG THE MEDIUM RANGE GUIDANCE...AS USUAL. GEM/GFS
SOLUTIONS ARE IN ONE CAMP KEEPING THINGS ON THE QUIET SIDE FOR
CHRISTMAS DAY (ALTHOUGH THE GFS DOES HAVE A WEAK FAST MOVING WAVE
MOVING THROUGH THE REGION). ECMWF HINTING AT ANOTHER STRONGER STORM
FOR TWO RUNS NOW PUSHING UP THROUGH THE OHIO VALLEY/GREAT LAKES ON
CHRISTMAS DAY. DIFFERENCES AMONG THE GUIDANCE ARE THE RESULT OF THE
DEGREE OF PHASING BETWEEN THE NRN AND SOUTHERN STREAMS WITH OBVIOUS
BIG IMPLICATIONS. NO WAY OF KNOWING THE CORRECT SOLUTION AT THIS
JUNCTURE...BUT WILL HAVE LOWER END SNOW CHANCES ON TUESDAY FOR NOW.
ANOTHER SHOT FOR A STORM SYSTEM MAY COME WEDNESDAY NIGHT THROUGH
THURSDAY WITH THE POTENTIAL FOR YET ANOTHER STORM TO SPIN UP OFF THE
GULF AND LIFT NORTHWARD THROUGH THE EASTERN CONUS. AGAIN...BIG
DIFFERENCES ON THE TIME/TRACK OF THAT STORM (IF IT OCCURS AT ALL).
BUT WILL CARRY CHANCE POPS FOR SNOW DURING THAT TIME.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1151 PM EST THU DEC 20 2012
A COMBINATION OF IFR/MVFR CONDITIONS AT THE TAF SITES AT THE
MOMENT AS LOW PRESSURE NEAR TAWAS PUSHES EAST INTO LAKE HURON. ANY
MIX WITH RAIN IS NOW OVER AT APN...WITH SNOW THE ONLY PTYPE
THROUGH THE PERIOD. OCCASIONAL SNOWS WILL CONTINUE THROUGH
DAYBREAK WITH LIFR-IFR VSBYS/IFR CIGS POSSIBLE PARTICULARLY AT
PLN/TVC. RESTRICTIONS WILL GRADUALLY IMPROVE FOR THE DAY ON
FRIDAY...WITH MVFR CIGS/VSBYS IN LAKE EFFECT SHSN/BLOWING SNOW
WITH SOME LATE DAY/EVENING IMPROVEMENT TO VFR AT TVC/MBL.
WINDS HAVE SHIFTED NORTHERLY TO 10G20KTS ATTM AND WILL CONTINUE TO
BACK NORTHWESTERLY AND INCREASE TO 25G35KTS FOR THE DAY ON FRIDAY.
&&
.MARINE...
ISSUED AT 414 PM EST THU DEC 20 2012
MAJOR WINTER STORM LIFTING NE INTO THE GREAT LAKES THROUGH
TONIGHT...BEFORE DEPARTING FRIDAY. OVERLAKE INSTABILITY WITH
EASTERLY WINDS AT 20-35KTS TO DEVELOP AS MODERATE TO HEAVY SNOWS
(MIXED WITH OR ALL RAIN ACROSS LAKE HURON). THE SNOWS WILL BE
INCREASINGLY INTENSE THIS EVENING. WINDS WILL DECREASE SOME ACROSS A
GOOD CHUNK OF THE NEARSHORES THIS EVENING...BUT THEN RAMP BACK UP
AGAIN LATE TONIGHT AND FRIDAY WITH COLD ADVECTION FOLLOWING THE
DEPARTING SFC LOW PRESSURE. WINDS WILL GUST AS HIGH AS
50KTS...RESULTING IN STORM FORCE WINDS FOR THE NW LOWER NEARSHORES.
SOLID GALES ALL OTHER MARINE AREAS. GRADIENT GRADUALLY LOOSENS UP
OVER THE WEEKEND...BUT GALES AND OBVIOUSLY CHOPPY WAVES WILL PERSIST
THROUGH FRIDAY NIGHT.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER STORM WARNING UNTIL 7 PM EST FRIDAY FOR MIZ008-015>029-
031>034.
WINTER WEATHER ADVISORY UNTIL 7 PM EST FRIDAY FOR MIZ030-035-041.
LH...GALE WARNING UNTIL 7 AM EST SATURDAY FOR LHZ345>349.
LM...GALE WARNING UNTIL 7 AM EST SATURDAY FOR LMZ341.
STORM WARNING UNTIL 7 PM EST FRIDAY FOR LMZ323-342-344>346.
LS...GALE WARNING UNTIL 7 AM EST SATURDAY FOR LSZ321-322.
&&
$$
UPDATE...ARNOTT
SYNOPSIS...TL
SHORT TERM...AS
LONG TERM...BA
AVIATION...JA
MARINE...AS
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
555 PM CST SAT DEC 22 2012
.UPDATED FOR 00Z AVIATION DISCUSSION BELOW...
.DISCUSSION...
CDFNT NOW JUST W OF MSP AND CONTG TO PUSH EAST WITH NICE AREA OF SFC
PRESSURE RISES ACROSS THE DKTS INTO W MN. NOT MUCH CLOUD COVER IN
WAKE OF FNT WITH MAIN AREA OF CLDS AND --SN PUSHING ESE ACROSS N MN
WITH WEAK UPPER AIR DISTURBANCE NOW PUSHING ACRS NW MN.
EXPANSIVE HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE AREA OUT OF
CANADA KEEPING KEEPING TEMPS COOL THRU THE WEEK. A PIECE OF ENERGY
FROM STRONG NW COAST TROUGH WILL PUSH ACROSS THE NORTHERN ROCKIES
TONIGHT AND THEN ACRS OUR AREA SUNDAY NIGHT/MONDAY. LOOKING PRETTY
GUD FOR A PERIOD OF -SN WITH FAIRLY STRONG UPPER TROF MOVING THRU
AREA...BUT MOISTURE PRETTY LIMITED. UPPED POPS A BIT FOR UP TO AN
INCH OF SNOW. BEST CHC FOR ANY ACCUM SEEMS TO BE ACRS N CWA NEAR
PATH OF MID LEVEL LOW.
ECMWF IN PARTICULAR REMAINS AGGRESSIVE ON POSSIBLE SNOW EVENT FOR
LATE FRIDAY INTO SATURDAY BRINGING MORE OF A SW WAVE INTO AREA AND
ASSOCIATED DEEP SURFACE LOW PRESSURE. MAINTAINED POPS IN THE MID
CHC RANGE AS IN PREVIOUS PACKAGE.
&&
.AVIATION.../00Z TAF ISSUANCE/
LARGE AREA OF STRATUS HAS FORMED OVER NORTHERN MN IS MOVING SOUTH
AROUND 13 KTS. THIS WOULD BRING THEM INTO THE KAXN/KSTC REGION
THROUGH 02Z AND KRNH/KMSP AREA THROUGH 06Z. VARIOUS MODELS DRY THIS
LAYER OUT AS IF MOVES SOUTH THIS EVENING. ONLY THE RAP WAS
INDICATING MAKING IT AS FAR SOUTH AS KMSP-KRWF AS A CEILING. WILL
MENTION SCT015 OVER CENTRAL AREAS AND MENTION THE MVFR CEILINGS
DEVELOPING OVER THE NORTH AND FAR EAST. THIS FORECAST TO DROP SOUTH
OVERNIGHT SO DO EXPECT SOME CLEARING AFTER 06Z FROM THE
NORTH....REMAINING LONGEST IN THE KEAU AREA. SOME HIGH CLOUDS
AROUND INTO EARLY SUNDAY WITH LOWERING MID CLOUD DECK INTO THE
AFTERNOON AHEAD OF NEXT SHORT WAVE FOR SUNDAY NIGHT. NORTHWEST TO
NORTH WINDS TONIGHT BECOMING MORE NORTH/NORTHEAST INTO SUNDAY. MOST
AREAS SHOULD REMAIN BELOW 10 KNOTS..BUT MAY BE A BIT STRONG THIS
EVENING OVER THE FAR WEST WITH CAA AND GRADIENT BEHIND COLD FRONT.
KMSP...SOME MVFR CEILING THREAT IN THE 05Z-09Z PERIOD. WILL KEEP IT
SCT015 FOR NOW AND MONITOR CLOUD TRENDS THIS EVENING. MODELS
TRENDING DRIER WITH THE NARRE-TL INDICATING ANY MVFR CEILING
REMAINING NORTH AND EAST. SFC WINDS NORTHWEST/NORTH OVERNIGHT
BECOMING MORE NORTHEAST INTO SUNDAY. SHOULD REMAIN BELOW 10 KNOTS
THROUGH THE PERIOD. LOWERING MID CLOUD DECK INTO SUNDAY
AFTERNOON/EVENING AND BELIEVE IT WILL REMAIN DRY THROUGH 06Z SUNDAY.
/OUTLOOK FOR KMSP/
MON...MVFR CIGS/VSBYS IN -SN POSSIBLE EARLY...THEN VFR.
WINDS N 6 TO 8 KTS.
TUE...VFR. NW 6 TO 8 KTS.
WED...VFR. WINDS NW 5 KTS.
&&
MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
$$
BAP/DE
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
1155 AM CST FRI DEC 21 2012
.UPDATE...
18Z AVIATION DISCUSSION ADDED BELOW.
&&
.DISCUSSION...
/ISSUED 424 AM CST FRI DEC 21 2012/
SINCE THE WORLD HAS NOT ENDED...DOWN TO BUSINESS. THE IMPRESSIVE
SYSTEM THAT BROUGHT INCREDIBLE AMOUNTS OF SNOW AND BLIZZARD
CONDITIONS JUST SOUTH AND EAST OF THE AREA IS STILL SPINNING AWAY
OVER LOWER MICHIGAN. A RIDGE QUICKLY TOOK ITS PLACE ACROSS WRN MN
YESTERDAY AND HAS REMAINED NEARLY STATIONARY SINCE. THE PRESSURE
GRADIENT IS BEGINNING TO RELAX...ESPECIALLY UNDER THE RIDGE WHERE
TEMPERATURES HAVE FALLEN A COUPLE DEGREES BELOW ZERO. FURTHER
EAST...TEENS ABOVE ZERO WERE COMMON EAST OF I-35. SOME WIND CHILL
READINGS WILL APPROACH -20F THIS MORNING NEAR THE SD BORDER WITH
WINDS REMAINING 5 OR 6 KTS.
A BATCH OF STRATUS OVER NWRN MN AND ERN ND HAS BEEN CREEPING SOUTH
OVERNIGHT. RAP FORECAST SOUNDINGS AND RH FIELDS SHOW THIS STRATUS
SPREADING SOUTH ACROSS WEST CENTRAL MN THIS MORNING. CANNOT ARGUE
THIS BASED ON SATELLITE TRENDS AND A STEEP INVERSION ALLOWING THIS
STRATUS TO CONTINUE ADVECTING SWD WITH THE MEAN WIND. NOT SURE HOW
IT WILL EVOLVE THIS AFTERNOON...IT VERY WELL MAY JUST STAY IN
PLACE INTO TONIGHT. FOR NOW...EXTRAPOLATED THAT BANK OF CLOUDS
SOUTH THROUGH THE MORNING WITH A GRADUAL DISSIPATING TREND THIS
AFTERNOON. FLURRIES HAVE ALSO BEEN REPORTED WITH THIS STRATUS
SINCE THE DGZ IS PRACTICALLY AT OR JUST ABOVE THE SURFACE SO ALSO
INCLUDED A CHC OF FLURRIES THROUGH EARLY AFTERNOON WHERE CLOUDS
ARE FORECAST TO BE THICKEST.
OTHERWISE...THE RIDGE WILL REMAIN JUST ABOUT OVERHEAD THROUGH
TONIGHT BEFORE A WEAK COLD FRONT PUSHES SOUTHEAST ACROSS MN AND WI
SATURDAY. DEPENDING ON CLOUD COVER TONIGHT WHICH IS STILL
UNCERTAIN...COULD SEE LOWS TANK IN SOME AREAS. WAS NOT CONFIDENT
TO FORECAST WHERE THIS MAY HAPPEN...SO USED A MODEL BLEND TO
OBTAIN SINGLE DIGITS ABOVE ACROSS THE WHOLE CWA.
THE FRONT WILL COME THROUGH DRY SATURDAY WITH A STRONG SURFACE
RIDGE BUILDING SOUTHEAST FROM WESTERN CANADA. AN UPPER LEVEL
DISTURBANCE WILL SLIDE SOUTHEAST ON THE PERIPHERY OF THE SURFACE
RIDGE MONDAY...BUT A LOT OF DRY AIR SHOULD BE IN PLACE WITH A
NORTHEAST FLOW SO NOT ANTICIPATING MUCH SNOW WITH THIS SYSTEM.
MODELS HAVE ALSO BACKED OFF ON THE AMOUNT OF QPF. REDUCED POPS TO
SCHC...BUT THEY COULD BE TAKEN OUT ALL TOGETHER AT SOME POINT.
THE SURFACE RIDGE WILL NOT REALLY BUDGE NEXT WEEK WITH DRY AND
SEASONABLY COLD WEATHER EXPECTED. A HIGHLY AMPLIFIED UPPER
PATTERN WITH DEEP TROUGHS TRAVERSING THE COUNTRY WILL LARGELY KEEP
THE STORM TRACK WELL TO THE SOUTH. CHRISTMAS EVE AND CHRISTMAS DAY
ARE EXPECTED TO BE QUITE ACTIVE WITH SNOW AND ICE LIKELY ACROSS
THE SOUTHERN PLAINS/MID SOUTH/OHIO VALLEY.
&&
.AVIATION.../18Z TAF ISSUANCE/
FEW WEATHER CONCERNS THIS TAF PERIOD AS HIGH PRESSURE SLOWLY WORKS
ACROSS THE AREA THROUGH TONIGHT. TOWARD THE END OF THE PERIOD...A
WEAK COLD WILL BE APPROACHING CENTRAL MN...WHICH WILL HELP FORCE
WINDS OVER TO THE SOUTH OVERNIGHT. SPEEDS WILL BE UNDER 10 KTS
WITH CLOUD COVER BEING NOTHING MORE THAN VARYING AMOUNTS OF
CIRRUS.
KMSP...HIGH CONFIDENCE TAF OVERALL. SHOULD BE GOOD TO HOLD A 30/35
OPERATION THROUGH THE REST OF THE DAY...WITH WINDS SATURDAY COMING
OUT OF THE SOUTH...THOUGH UNDER 7 KTS.
/OUTLOOK FOR KMSP/
SUN...IFR CIGS POSSIBLE EARLY...OTHERWISE VFR. WINDS NE 5 KTS.
MON...VFR...SMALL CHANCE FOR MVFR WITH LIGHT SNOW. NE 5 KNOTS.
TUE...VFR. WINDS N 5 TO 10 KTS.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
BORGHOFF/MPG
AREA FORECAST DISCUSSION...UPDATED
NWS TWIN CITIES/CHANHASSEN MN
548 AM CST FRI DEC 21 2012
.UPDATE...
UPDATED FOR THE 12Z AVIATION DISCUSSION BELOW.
.DISCUSSION...
SINCE THE WORLD HAS NOT ENDED...DOWN TO BUSINESS. THE IMPRESSIVE
SYSTEM THAT BROUGHT INCREDIBLE AMOUNTS OF SNOW AND BLIZZARD
CONDITIONS JUST SOUTH AND EAST OF THE AREA IS STILL SPINNING AWAY
OVER LOWER MICHIGAN. A RIDGE QUICKLY TOOK ITS PLACE ACROSS WRN MN
YESTERDAY AND HAS REMAINED NEARLY STATIONARY SINCE. THE PRESSURE
GRADIENT IS BEGINNING TO RELAX...ESPECIALLY UNDER THE RIDGE WHERE
TEMPERATURES HAVE FALLEN A COUPLE DEGREES BELOW ZERO. FURTHER
EAST...TEENS ABOVE ZERO WERE COMMON EAST OF I-35. SOME WIND CHILL
READINGS WILL APPROACH -20F THIS MORNING NEAR THE SD BORDER WITH
WINDS REMAINING 5 OR 6 KTS.
A BATCH OF STRATUS OVER NWRN MN AND ERN ND HAS BEEN CREEPING SOUTH
OVERNIGHT. RAP FORECAST SOUNDINGS AND RH FIELDS SHOW THIS STRATUS
SPREADING SOUTH ACROSS WEST CENTRAL MN THIS MORNING. CANNOT ARGUE
THIS BASED ON SATELLITE TRENDS AND A STEEP INVERSION ALLOWING THIS
STRATUS TO CONTINUE ADVECTING SWD WITH THE MEAN WIND. NOT SURE HOW
IT WILL EVOLVE THIS AFTERNOON...IT VERY WELL MAY JUST STAY IN
PLACE INTO TONIGHT. FOR NOW...EXTRAPOLATED THAT BANK OF CLOUDS
SOUTH THROUGH THE MORNING WITH A GRADUAL DISSIPATING TREND THIS
AFTERNOON. FLURRIES HAVE ALSO BEEN REPORTED WITH THIS STRATUS
SINCE THE DGZ IS PRACTICALLY AT OR JUST ABOVE THE SURFACE SO ALSO
INCLUDED A CHC OF FLURRIES THROUGH EARLY AFTERNOON WHERE CLOUDS
ARE FORECAST TO BE THICKEST.
OTHERWISE...THE RIDGE WILL REMAIN JUST ABOUT OVERHEAD THROUGH
TONIGHT BEFORE A WEAK COLD FRONT PUSHES SOUTHEAST ACROSS MN AND WI
SATURDAY. DEPENDING ON CLOUD COVER TONIGHT WHICH IS STILL
UNCERTAIN...COULD SEE LOWS TANK IN SOME AREAS. WAS NOT CONFIDENT
TO FORECAST WHERE THIS MAY HAPPEN...SO USED A MODEL BLEND TO
OBTAIN SINGLE DIGITS ABOVE ACROSS THE WHOLE CWA.
THE FRONT WILL COME THROUGH DRY SATURDAY WITH A STRONG SURFACE
RIDGE BUILDING SOUTHEAST FROM WESTERN CANADA. AN UPPER LEVEL
DISTURBANCE WILL SLIDE SOUTHEAST ON THE PERIPHERY OF THE SURFACE
RIDGE MONDAY...BUT A LOT OF DRY AIR SHOULD BE IN PLACE WITH A
NORTHEAST FLOW SO NOT ANTICIPATING MUCH SNOW WITH THIS SYSTEM.
MODELS HAVE ALSO BACKED OFF ON THE AMOUNT OF QPF. REDUCED POPS TO
SCHC...BUT THEY COULD BE TAKEN OUT ALL TOGETHER AT SOME POINT.
THE SURFACE RIDGE WILL NOT REALLY BUDGE NEXT WEEK WITH DRY AND
SEASONABLY COLD WEATHER EXPECTED. A HIGHLY AMPLIFIED UPPER
PATTERN WITH DEEP TROUGHS TRAVERSING THE COUNTRY WILL LARGELY KEEP
THE STORM TRACK WELL TO THE SOUTH. CHRISTMAS EVE AND CHRISTMAS DAY
ARE EXPECTED TO BE QUITE ACTIVE WITH SNOW AND ICE LIKELY ACROSS
THE SOUTHERN PLAINS/MID SOUTH/OHIO VALLEY.
&&
.AVIATION.../12Z TAF ISSUANCE/
ONE LONE ISSUE IS AN AREA OF STRATUS DROPPING SOUTH ACROSS WESTERN
MN. INCLUDED IFR CEILINGS AT KAXN FOR A FEW HOURS LATE THIS
MORNING...BUT THAT SHOULD BE ABOUT THE EXTENT OF THE CLOUDS. HAVE
A LOT OF DOUBT IT WILL MAKE TO EITHER KSTC OR KRWF. THERE WILL BE
A GRADUAL WIND SHIFT TO THE WEST...SOUTHWEST...THEN SOUTH THIS
EVENING.
KMSP...
VFR AT THE AIRPORT TODAY AND TONIGHT. THERE WILL BE A WIND SHIFT
FROM THE CURRENT NORTHWEST DIRECTION TO SOUTHWEST AND EVENTUALLY
SOUTH THIS EVENING AS A HIGH PRESSURE PASSES THROUGH THE AREA. THE
WIND SHIFT WILL OCCUR GRADUALLY AND NO ABRUPT CHANGE IN DIRECTION
IS EXPECTED.
/OUTLOOK FOR KMSP/
SAT...VFR. S 5 KNOTS.
SUN...VFR. NE 5 KNOTS.
MON...VFR...SMALL CHANCE FOR MVFR WITH LIGHT SNOW. NE 5 KNOTS.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
BB/CLF
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
424 AM CST FRI DEC 21 2012
.DISCUSSION...
SINCE THE WORLD HAS NOT ENDED...DOWN TO BUSINESS. THE IMPRESSIVE
SYSTEM THAT BROUGHT INCREDIBLE AMOUNTS OF SNOW AND BLIZZARD
CONDITIONS JUST SOUTH AND EAST OF THE AREA IS STILL SPINNING AWAY
OVER LOWER MICHIGAN. A RIDGE QUICKLY TOOK ITS PLACE ACROSS WRN MN
YESTERDAY AND HAS REMAINED NEARLY STATIONARY SINCE. THE PRESSURE
GRADIENT IS BEGINNING TO RELAX...ESPECIALLY UNDER THE RIDGE WHERE
TEMPERATURES HAVE FALLEN A COUPLE DEGREES BELOW ZERO. FURTHER
EAST...TEENS ABOVE ZERO WERE COMMON EAST OF I-35. SOME WIND CHILL
READINGS WILL APPROACH -20F THIS MORNING NEAR THE SD BORDER WITH
WINDS REMAINING 5 OR 6 KTS.
A BATCH OF STRATUS OVER NWRN MN AND ERN ND HAS BEEN CREEPING SOUTH
OVERNIGHT. RAP FORECAST SOUNDINGS AND RH FIELDS SHOW THIS STRATUS
SPREADING SOUTH ACROSS WEST CENTRAL MN THIS MORNING. CANNOT ARGUE
THIS BASED ON SATELLITE TRENDS AND A STEEP INVERSION ALLOWING THIS
STRATUS TO CONTINUE ADVECTING SWD WITH THE MEAN WIND. NOT SURE HOW
IT WILL EVOLVE THIS AFTERNOON...IT VERY WELL MAY JUST STAY IN
PLACE INTO TONIGHT. FOR NOW...EXTRAPOLATED THAT BANK OF CLOUDS
SOUTH THROUGH THE MORNING WITH A GRADUAL DISSIPATING TREND THIS
AFTERNOON. FLURRIES HAVE ALSO BEEN REPORTED WITH THIS STRATUS
SINCE THE DGZ IS PRACTICALLY AT OR JUST ABOVE THE SURFACE SO ALSO
INCLUDED A CHC OF FLURRIES THROUGH EARLY AFTERNOON WHERE CLOUDS
ARE FORECAST TO BE THICKEST.
OTHERWISE...THE RIDGE WILL REMAIN JUST ABOUT OVERHEAD THROUGH
TONIGHT BEFORE A WEAK COLD FRONT PUSHES SOUTHEAST ACROSS MN AND WI
SATURDAY. DEPENDING ON CLOUD COVER TONIGHT WHICH IS STILL
UNCERTAIN...COULD SEE LOWS TANK IN SOME AREAS. WAS NOT CONFIDENT
TO FORECAST WHERE THIS MAY HAPPEN...SO USED A MODEL BLEND TO
OBTAIN SINGLE DIGITS ABOVE ACROSS THE WHOLE CWA.
THE FRONT WILL COME THROUGH DRY SATURDAY WITH A STRONG SURFACE
RIDGE BUILDING SOUTHEAST FROM WESTERN CANADA. AN UPPER LEVEL
DISTURBANCE WILL SLIDE SOUTHEAST ON THE PERIPHERY OF THE SURFACE
RIDGE MONDAY...BUT A LOT OF DRY AIR SHOULD BE IN PLACE WITH A
NORTHEAST FLOW SO NOT ANTICIPATING MUCH SNOW WITH THIS SYSTEM.
MODELS HAVE ALSO BACKED OFF ON THE AMOUNT OF QPF. REDUCED POPS TO
SCHC...BUT THEY COULD BE TAKEN OUT ALL TOGETHER AT SOME POINT.
THE SURFACE RIDGE WILL NOT REALLY BUDGE NEXT WEEK WITH DRY AND
SEASONABLY COLD WEATHER EXPECTED. A HIGHLY AMPLIFIED UPPER
PATTERN WITH DEEP TROUGHS TRAVERSING THE COUNTRY WILL LARGELY KEEP
THE STORM TRACK WELL TO THE SOUTH. CHRISTMAS EVE AND CHRISTMAS DAY
ARE EXPECTED TO BE QUITE ACTIVE WITH SNOW AND ICE LIKELY ACROSS
THE SOUTHERN PLAINS/MID SOUTH/OHIO VALLEY.
&&
.AVIATION... /06Z TAF ISSUANCE/
AREAS OF LOW END MVFR TO IFR CEILINGS REMAIN OVER THE AREA THIS
EVENING. FARTHER TO THE NORTHWEST AREA OF LOW LEVEL MOISTURE
REMAINS TRAPPED UNDER SUBSIDENCE INVERSION LOCATED BENEATH THE
SURFACE RIDGE OVER THE EASTERN DAKOTAS. SOME EXPANSION TO THE
SOUTH NOTED WITH THIS AREA. FURTHER WEST...SOME ICE FOG DEVELOPING
OVER EASTERN SOUTH DAKOTA. NEW NAM AND LATEST HRRR SHOWING SOME
POSSIBILITY OF LOWER CLOUDS AND ICE FOG DEVELOPING UNDER THE
RIDGE...BUT APPEARS BEST CHANCE WILL REMAIN OVER THE EASTERN
DAKOTAS. THE IFR CEILINGS AT KRWF REMAIN ASSOCIATED WITH ELEVATED
SNOW LAYER ALONG THE MN RIVER VALLEY DUE TO EARLIER BLSN. THIS WILL
GRADUALLY DISSIPATE AFTER 06Z AS WIND SUBSIDES. WILL HAVE TO HOLD
ONTO THE POSSIBILITY OF SOME LOW END MVFR CEILING FARTHER EAST INTO
WISCONSIN IN THE WAKE OF THE STORM...AS NARRE-TL INDICATED SOME HIGH
PROBABILITIES FOR THIS OCCURRING. SHOULD SEE SKC/VFR DEVELOPING INTO THE
MORNING FRIDAY...LASTING THROUGH FRIDAY NIGHT.
GUSTY NORTHWEST WINDS WILL DIMINISH OVER THE EASTERN AREAS LATER
TONIGHT/FRIDAY MORNING AND SURFACE WINDS WILL EVENTUALLY TURN
SOUTHERLY LATE FRIDAY AFTERNOON OVER THE WEST AS THE HIGH PRESSURE
RIDGE MOVES THROUGH.
KMSP...CONFIDENCE NOT HIGH ON VFR CONDITIONS REMAINING THROUGH THE
NIGHT. STILL SEE SOME BKN-OVC010-015 NORTHWEST OF THE AREA AND STILL
MAY WORK TO THE SOUTHEAST THROUGH THE EARLY MORNING. WILL HOLD ONTO
SOME FEW-SCT013 OVERNIGHT ANYWAY. SHOULD SEE VFR THEN DEVELOPING
FRIDAY MORNING LASTING FRIDAY NIGHT AS THE HIGH MOVES THROUGH.
NORTHWEST WINDS DIMINISHING OVERNIGHT AND THEN BECOMING MORE
SOUTHWEST LATE AFTERNOON AND SOUTHERLY AFTER 00Z SAT.
/OUTLOOK FOR KMSP/
FRI...VFR. NW 5 TO 10 KNOTS.
SAT...VFR. S 5 KNOTS.
SUN...VFR. NE 5 KNOTS.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
BORGHOFF/DWE
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
1035 PM CST THU DEC 20 2012
.AVIATION... /06Z TAF ISSUANCE/
AREAS OF LOW END MVFR TO IFR CEILINGS REMAIN OVER THE AREA THIS
EVENING. FARTHER TO THE NORTHWEST AREA OF LOW LEVEL MOISTURE
REMAINS TRAPPED UNDER SUBSIDENCE INVERSION LOCATED BENEATH THE
SURFACE RIDGE OVER THE EASTERN DAKOTAS. SOME EXPANSION TO THE
SOUTH NOTED WITH THIS AREA. FURTHER WEST...SOME ICE FOG DEVELOPING
OVER EASTERN SOUTH DAKOTA. NEW NAM AND LATEST HRRR SHOWING SOME
POSSIBILITY OF LOWER CLOUDS AND ICE FOG DEVELOPING UNDER THE
RIDGE...BUT APPEARS BEST CHANCE WILL REMAIN OVER THE EASTERN
DAKOTAS. THE IFR CEILINGS AT KRWF REMAIN ASSOCIATED WITH ELEVATED
SNOW LAYER ALONG THE MN RIVER VALLEY DUE TO EARLIER BLSN. THIS WILL
GRADUALLY DISSIPATE AFTER 06Z AS WIND SUBSIDES. WILL HAVE TO HOLD
ONTO THE POSSIBILITY OF SOME LOW END MVFR CEILING FARTHER EAST INTO
WISCONSIN IN THE WAKE OF THE STORM...AS NARRE-TL INDICATED SOME HIGH
PROBABILITIES FOR THIS OCCURRING. SHOULD SEE SKC/VFR DEVELOPING INTO THE
MORNING FRIDAY...LASTING THROUGH FRIDAY NIGHT.
GUSTY NORTHWEST WINDS WILL DIMINISH OVER THE EASTERN AREAS LATER
TONIGHT/FRIDAY MORNING AND SURFACE WINDS WILL EVENTUALLY TURN
SOUTHERLY LATE FRIDAY AFTERNOON OVER THE WEST AS THE HIGH PRESSURE
RIDGE MOVES THROUGH.
KMSP...CONFIDENCE NOT HIGH ON VFR CONDITIONS REMAINING THROUGH THE
NIGHT. STILL SEE SOME BKN-OVC010-015 NORTHWEST OF THE AREA AND STILL
MAY WORK TO THE SOUTHEAST THROUGH THE EARLY MORNING. WILL HOLD ONTO
SOME FEW-SCT013 OVERNIGHT ANYWAY. SHOULD SEE VFR THEN DEVELOPING
FRIDAY MORNING LASTING FRIDAY NIGHT AS THE HIGH MOVES THROUGH.
NORTHWEST WINDS DIMINISHING OVERNIGHT AND THEN BECOMING MORE
SOUTHWEST LATE AFTERNOON AND SOUTHERLY AFTER 00Z SAT.
/OUTLOOK FOR KMSP/
FRI...VFR. NW 5 TO 10 KNOTS.
SAT...VFR. S 5 KNOTS.
SUN...VFR. NE 5 KNOTS.
&&
.DISCUSSION... /ISSUED 214 PM CST THU DEC 20 2012/
THE TOP WEATHER CONCERNS THIS FORECAST PERIOD ARE LOW TEMPERATURES
TONIGHT AND SNOWFALL CHANCES FOR CHRISTMAS EVE DAY.
LIGHT SNOW OVER WEST CENTRAL WISCONSIN WILL CONTINUE TO TAPER OFF
DURING THE LATE AFTERNOON AND EARLY EVENING HOURS. WIND SPEEDS WILL
ALSO BE ON THE DOWNWARD TREND AND AREAS OF BLOWING SNOW WILL
GRADUALLY SUBSIDE ACCORDINGLY. WHILE MODELS MIGHT BE A BIT
OPTIMISTIC ON THE CLEARING TONIGHT GIVEN THE CYCLONIC FLOW AND
COLD AIR ADVECTION...THINK MOST OF THE CWA SHOULD SEE CLEAR SKIES
BY 06Z-09Z. HAVE LEANED TOWARD THE COLDER END OF NUMERICAL
GUIDANCE OVER THE NORTHWEST...WHERE LOWS SHOULD SNEAK INTO THE
SINGLE DIGITS BELOW ZERO GIVEN THE LONGER PERIOD OF CLEAR SKIES.
EAST AND SOUTH CENTRAL MN SHOULD SEE LOWS IN THE SINGLE DIGITS
ABOVE ZERO...WITH READINGS AROUND OR JUST ABOVE 10 DEGREES FROM
EAU CLAIRE TOWARD LADYSMITH WHERE CLOUDS ARE EXPECTED TO LINGER
LONGER.
A RATHER BENIGN WEATHER PATTERN SETS IN FOR FRIDAY THROUGH THE
WEEKEND...AS WEAK RIDGING DOMINATES. DRY WEATHER AND BELOW NORMAL
HIGH TEMPERATURES WILL PREVAIL.
BY SUNDAY NIGHT...THE LARGE SCALE REGIME WILL TRANSITION TO THAT
OF A MORE ZONAL NATURE...AND MODELS HAVE BEEN FAIRLY CONSISTENT IN
DROPPING A NORTHERN STREAM SHORTWAVE ACROSS THE AREA ON THE 24TH
INTO THE 25TH. LOOKS LIKE THE WAVE COULD PRODUCE A QUICK INCH OF
SNOW ACROSS MUCH OF THE FORECAST AREA.
COOL CANADIAN HIGH PRESSURE SETTLES IN TO THE NORTH CENTRAL CONUS
FROM CHRISTMAS THROUGH MOST OF NEXT WEEK. HIGH TEMPERATURES WILL
AVERAGE BETWEEN 5 AND 15 DEGREES BELOW NORMAL...WHICH TRANSLATES
TO HIGHS FROM THE SINGLE DIGITS /WEST/ TO AROUND 20 ABOVE /EAST/.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
LS/DWE
AREA FORECAST DISCUSSION...UPDATED
NWS NORTH PLATTE NE
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...UPDATED
NWS NORTH PLATTE NE
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...CDC
AVIATION...CDC
AREA FORECAST DISCUSSION
NWS OMAHA/VALLEY NE
512 PM CST SAT DEC 22 2012
.AVIATION...
00Z TAFS FOR KOFK...KLNK AND KOMA.
MVFR CIGS NEAR FL012 ARE EXPECTED TO MOVE/DEVELOP SOUTH INTO
NORTHEAST NEBRASKA BY 11Z...THEN TO KOMA AND KLNK BY 14Z. A PERIOD
OF IFR CIGS AND MVFR VSBYS IN FOG IS POSSIBLE BEFORE 18Z...WITH
CIGS BETWEEN FL010 AND FL020 REMAINING IN PLACE THROUGH 00Z.
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.
&&
$$
AREA FORECAST DISCUSSION
NWS BINGHAMTON NY
956 PM EST SAT DEC 22 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 SUNDAY NIGHT/...
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 /MONDAY 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 /03Z 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 SUNDAY FOR NYZ009.
&&
$$
SYNOPSIS...MLJ
NEAR TERM...DJP/MLJ
SHORT TERM...HEDEN
LONG TERM...HEDEN
AVIATION...PVN
AREA FORECAST DISCUSSION
NWS NEWPORT/MOREHEAD CITY NC
1236 AM EST FRI DEC 21 2012
.SYNOPSIS...
A STRONG COLD FRONT WILL MOVE OFFSHORE BY EARLY FRIDAY MORNING.
HIGH PRESSURE WILL SLOWLY BUILD INTO THE AREA FROM THE SOUTHWEST
FRIDAY THROUGH SUNDAY. A WARM FRONT WILL MOVE INTO THE AREA MONDAY
AND BECOME STATIONARY THROUGH WEDNESDAY.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
AS OF 1230 AM FRIDAY...STRONG COLD FRONT NOW MOVING INTO THE MHX
CWA ALTHOUGH AXIS OF LOWER DEWPOINTS STILL ABOUT 50 MILES OR SO
BEHIND THE ACTUAL FRONT. THE SURFACE LOW IS RAPIDLY DEEPENING WITH
3 HOURLY PRESSURE FALLS OF CLOSE TO 10 MB OVER CENTRAL VIRGINIA.
STRONG GUSTY WINDS WILL ACCOMPANY THE FRONTAL PASSAGE WITH
OBSERVATIONS AND WIND PROFILE DATA SHOWING THE POTENTIAL FOR GUSTS
TO AROUND 45 KNOTS. CONVECTIVE PARAMETERS SHOW THE BEST SEVERE
POTENTIAL REMAINING OFFSHORE...BUT SOME HEAVIER SHOWERS WILL
CERTAINLY MIX DOWN GUSTY WINDS OVER THE NEXT 3 TO 5 HOURS OR SO.
TEMPERATURES WILL HOLD STEADY FOR NEXT 3 OR 4 HOURS BEFORE FALLING
WITH THE ARRIVAL OF THE DEWPOINT FRONT. THE LATEST RAP IS A BIT
FASTER MOVING MOST OF THE PRECIPITATION OFFSHORE BETWEEN 10Z AND
12Z.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 AM SATURDAY/...
AS OF 400 PM THURSDAY...STRONG CAA IN WAKE OF FRONT ALONG WITH GOOD
MOMENTUM TRANSPORT WITH SHRT WV MOVING ACROSS WILL PRODUCE STRONG
WESTERLY WINDS...WITH GUSTS TO 40 MPH PSBL INLAND AND POSSIBLY UP TO
45 MPH COAST. THIS IS JUST BELOW WIND ADVSY CRITERIA AND PER COORD
WITH SURROUNDING OFFICES HAVE ISSUED SPS AND WILL LET OVERNIGHT
SHIFT LOOK AT NEXT MODEL RUN. SOME COLD AIR SCU LIKELY DURING AFTN
SPREADING IN FROM NW. MOS BLEND SUPPORTS PREVIOUS FCST MAX TEMPS IN
LOW-MID 50S.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
AS OF 330 PM THURSDAY...COLD FRONT WILL BE WELL OFFSHORE FRIDAY
NIGHT...BUT STILL REMAIN A TIGHT SURFACE PRESSURE GRADIENT. MODELS
CONTINUE TO BE A GOOD AGREEMENT FOR THIS WEEKEND WITH A TIGHT
SURFACE PRESSURE GRADIENT TO REMAIN UNTIL SATURDAY. HIGH PRESSURE
WILL SLOWLY BUILD IN OVER THE WEEKEND...WITH WEAK FRONT TO MOVE
THROUGH MONDAY THIS FRONT WILL BECOME STATIONARY OVER NC...BRING AN
INCREASE OF MOISTURE TO THE AREA. THE STATIONARY FRONT WILL LIFT
NORTH AS AN APPROACHING LOW PRESSURE SYS MOVES TO OUR WEST OF
EASTERN NC BRINGING ITS ASSOCIATED COLD FRONT ACROSS NC APROX
THURSDAY. BOTH THE GFS AND ECMWF DO NOT HAVE A GOOD HANDLE OF THIS
NEXT SYSTEM...SO HAVE GONE WITH HPC GUIDANCE.
&&
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
SHORT TERM /THROUGH FRIDAY/...
AS OF 1230 AM FRIDAY...SOME MVFR CEILINGS WITH A FEW PERIODS OF
IFR ARE LIKELY THROUGH ABOUT 08Z OR 09Z AS FRONTAL BOUNDARY
ADVANCES QUICKLY ACROSS THE REGION. PRECIPITATION SHOULD EXIT THE
COAST BY 12Z BUT GUSTY W/WNW WILL CONTINUE BEHIND THE FRONT INTO
THE EVENING HOURS. WITH STEEP LAPSE RATES...WOULD EXPECT SOME
BROKEN STRATOCUMULUS TO DEVELOP DURING THE AFTERNOON...ALTHOUGH
MODEL SOUNDINGS KEEP CEILINGS ABOVE 3000 FT AND IN THE VFR RANGE.
.
LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 330 PM THURSDAY...EXPECT VFR CONDITIONS TO CONTINUE THROUGHOUT
THE WEEKEND WITH BREEZY CONDITIONS THROUGH SATURDAY AS HIGH PRESSURE
BUILDS IN FROM THE SOUTH.
&&
.MARINE...
SHORT TERM /THROUGH FRIDAY/...
AS OF 1235 AM FRIDAY...GALE CONDITIONS OCCURRING OVER THE SOUTHERN
WATERS WITH GUSTS TO 39 KNOTS AT CAPE LOOKOUT AND 41 KNOTS AT THE
BUOY 30 MILES SOUTHEAST OF NEW RIVER INLET. EXPECT ADDITIONAL GALE
FORCE WINDS TO OCCUR AS STRONG SURFACE FRONT EDGES ACROSS THE CWA
EARLY THIS MORNING. SEAS ALREADY IN THE 6 TO 10 FOOT RANGE AT THIS
TIME. NO MAJOR CHANGES NEEDED TO CURRENT MARINE FORECAST.
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 330 PM THURSDAY...COLD FRONT WILL BE WELL OFFSHORE...BUT
STILL REMAINS A TIGHT SURFACE PRESSURE GRADIENT BEHIND THE FRONT.
WINDS WILL REMAIN FROM THE WEST IN GALE FORCE UNTIL SATURDAY
AFTERNOON. WINDS WILL CONTINUE TO SUBSIDE SATURDAY AFTERNOON AS
HIGH PRESSURE BUILDS IN FROM THE SOUTH. EXPECT...SEAS TO CONTINUE
TO SUBSIDE FRIDAY NIGHT THROUGH SATURDAY.
&&
.TIDES/COASTAL FLOODING...
AS OF 300 PM THURSDAY...GUSTY WESTERLY WINDS 25 TO 35 MPH WILL
DEVELOP FRIDAY AND PERSIST INTO SATURDAY...WITH EXTRATROPICAL STORM
SURGE GDNC INDICATING WATER LEVEL RISES OF 1 TO 2 FEET SOUNDSIDE OF
OUTER BANKS. COASTAL FLOOD ADVISORY ISSUED ACCORDINGLY.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...WIND ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR NCZ095-103-
104.
COASTAL FLOOD ADVISORY FROM 7 AM THIS MORNING TO 7 PM EST
SATURDAY FOR NCZ103-104.
MARINE...GALE WARNING UNTIL 1 PM EST SATURDAY FOR AMZ130-135-150-152-
154-156-158.
&&
$$
SYNOPSIS...JBM
NEAR TERM...CTC
SHORT TERM...JBM/BM
LONG TERM...BM
AVIATION...CTC/BM
MARINE...CTC/BM
TIDES/COASTAL FLOODING...JBM
AREA FORECAST DISCUSSION...UPDATED
NWS GRAND FORKS ND
1011 AM CST FRI DEC 21 2012
.DISCUSSION...CLOUDS AND CLEARING TRENDS CONTINUE TO BE A
CHALLENGE. 16Z SATELLITE IMAGERY INDICATES A CLEAR AREA ACROSS
WEST CENTRAL MINNESOTA...WITH LOW CLOUDS TO THE WEST AND
NORTH...AND HIGH CLOUDS ACROSS THE FAR WESTERN FA. THE FAR WESTERN
FA DOES HAVE SOME FOG ISSUES AS WELL. TEMPERATURES ARE IN THE
5F TO 10F RANGE UNDER THE LOW CLOUDS...-5F TO 0F RANGE UNDER CLEAR
SKY...AND AROUND 0F WHERE THERE IS FOG. THE LOW CLOUDS APPEAR TO
BE SLOWLY MOVING EAST AND ERODING ALONG THE EDGES. 925MB WINDS
BECOME SOUTH AND INCREASE TODAY...SO EXPECT THIS TREND TO
CONTINUE. NOT MUCH CHANGE NEEDED TO THE FORECAST FOR TODAY...WITH
ONLY MINOR TWEAKS TO SKY AND TEMPERATURE BASED ON LATEST
OBSERVATIONS.
&&
.AVIATION...MVFR/IFR STRATUS DECK WILL MOVE VERY SLOWLY TO THE
EAST THROUGH THE DAY. IMPROVING CEILINGS NOT EXPECTED AT KFAR/KGFK
UNTIL 18 UTC OR LATER AND 21 UTC OR LATER AT KTVF/KBJI. SCATTERED
FLURRIES ARE POSSIBLE WITH CLOUD COVER WITH AN INFREQUENT
REDUCTION IN VISIBILITY TO 5 SM. LIGHT AND VARIABLE WIND WILL
INCREASE FROM THE SOUTH FROM WEST TO EAST AS SURFACE HIGH MOVES
INTO EASTERN MN.
&&
.PREV DISCUSSION... /ISSUED 338 AM CST FRI DEC 21 2012/
SHORT TERM...TODAY THROUGH SUNDAY NIGHT
CHALLENGE WILL BE CLOUD COVER AND TEMPERATURES TODAY AND THEN
PRECIPITATION CHANCES SUNDAY NIGHT. MODELS ARE IN GOOD AGREEMENT...
BUT WILL FOCUS ON 925 HPA RH OUTPUT FROM THE HIGH RESOLUTION RAP
FOR NEAR TERM CLOUD TRENDS.
09 UTC SATELLITE LOOP SHOWS A WEDGE OF LOW STRATUS ENCOMPASSING
ALL OF THE FORECAST AREA EXCEPT FOR EXTREME SOUTHEAST ND INTO
ADJACENT PORTIONS OF WEST CENTRAL MN. THIS AREA OF CLOUDS IS
SAGGING TO THE SOUTH AROUND 10 KTS WITH VERY LITTLE EAST-WEST
MOVEMENT. RAP SUGGESTS CLOUDS WILL MOVE VERY SLOWLY TO THE EAST
THROUGH THE DAY AS SOUTHERLY RETURN FLOW DEVELOPS ON BACKSIDE OF
DEPARTING SURFACE RIDGE. MIXING WITHIN THE RIDGE ITSELF IS ALMOST
NON-EXISTENT...SO SEE NO REASON WHY CLOUDS WOULD BREAK-UP EARLY.
FOR THIS...INCREASED SKY COVER THROUGH THE DAY ALONG AND EAST OF
THE VALLEY. THINK THERE SHOULD BE SOME CLEARING ALONG THE VALLEY
BY THIS AFTERNOON...BUT NOT UNTIL AFTER SUNSET ACROSS MUCH OF
NORTHWEST MN. DESPITE MODEST LOW-MID LEVEL WARM AIR ADVECTION...
DO NOT EXPECT MUCH TEMPERATURE RECOVERY UNDER CLOUDS..SO DECREASED
AFTERNOON HIGHS INTO THE LOW TO MID TEENS MOST LOCATIONS. SOME
SCATTERED FLURRIES ARE POSSIBLE THROUGH THE DAY...BUT NO REAL
ACCUMULATION IS EXPECTED. ALSO COULD SEE SOME PATCHY FOG EARLY
THIS MORNING ALONG THE WESTERN FLANK OF THE STRATUS DECK.
A DRY COLD FRONT WILL DROP SOUTH FROM CANADA TONIGHT AND SATURDAY.
DO NOT EXPECT ANY SNOW...BUT WINDS WILL SHIFT TO THE NORTHWEST
WITH A REINFORCING SHOT OF LOW CLOUDS. AFTERNOON HIGHS ON SATURDAY
WILL RANGE FROM 10 ABOVE ACROSS THE DEVILS LAKE BASIN TO NEAR 20
DEGREES ACROSS LAKES COUNTRY OF WEST CENTRAL MN. ANOTHER COOL...
BUT DRY DAY ON SUNDAY WITH LIGHT NORTHERLY WIND. HIGHS ACROSS
EASTERN ND INTO PORTIONS OF NORTHWEST MN NOT LIKELY TO BREAK OUT
OF THE SINGLE DIGITS.
ATTENTION TURNS TO SUNDAY NIGHT AS 700 HPA LOW MOVES INTO THE
CENTRAL VALLEY. MID-LEVEL FRONTOGENESIS AND UPPER LEVEL DYNAMIC
SUPPORT IS LACKING...BUT CONVERGENCE ALONG THE TRACK OF THE MID-
LEVEL CIRCULATION COMBINED WITH SOME WARM AIR ADVECTION INDUCED
LIFT SHOULD RESULT IN SOME LIGHT SNOW MAINLY ALONG AND NORTH OF
THE HIGHWAY TWO CORRIDOR. INCREASED POPS INTO THE 30 TO 40 PERCENT
RANGE...BUT ACCUMULATIONS SHOULD BE LIGHT...GENERALLY 1-2 INCHES
OR LESS.
LONG TERM...MONDAY THROUGH THURSDAY NIGHT
THE PATTERN WILL BEGIN WITH MAINLY ZONAL FLOW AND A CHANCE FOR
SOME LIGHT SNOW CHRISTMAS EVE WITH A SHORTWAVE. THEREAFTER...SFC
RIDGING WILL BUILD SOUTH FROM CANADA...AND RESULT IN DRY WEATHER
TUE-THU AND TEMPS BELOW NORMAL. THERE ARE SOME INDICATIONS THAT
MORE OF AN ACTIVE SW FLOW ALOFT MAY DEVELOP THU NIGHT AND FRI...
AND THE POTENTIAL FOR SOME SORT OF STORM SYSTEM...SO SOMETHING TO
MONITOR.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...NONE.
MN...NONE.
&&
$$
TG
AREA FORECAST DISCUSSION
NWS GRAND FORKS ND
338 AM CST FRI DEC 21 2012
.SHORT TERM...TODAY THROUGH SUNDAY NIGHT
CHALLENGE WILL BE CLOUD COVER AND TEMPERATURES TODAY AND THEN
PRECIPITATION CHANCES SUNDAY NIGHT. MODELS ARE IN GOOD AGREEMENT...
BUT WILL FOCUS ON 925 HPA RH OUTPUT FROM THE HIGH RESOLUTION RAP
FOR NEAR TERM CLOUD TRENDS.
09 UTC SATELLITE LOOP SHOWS A WEDGE OF LOW STRATUS ENCOMPASSING
ALL OF THE FORECAST AREA EXCEPT FOR EXTREME SOUTHEAST ND INTO
ADJACENT PORTIONS OF WEST CENTRAL MN. THIS AREA OF CLOUDS IS
SAGGING TO THE SOUTH AROUND 10 KTS WITH VERY LITTLE EAST-WEST
MOVEMENT. RAP SUGGESTS CLOUDS WILL MOVE VERY SLOWLY TO THE EAST
THROUGH THE DAY AS SOUTHERLY RETURN FLOW DEVELOPS ON BACKSIDE OF
DEPARTING SURFACE RIDGE. MIXING WITHIN THE RIDGE ITSELF IS ALMOST
NON-EXISTENT...SO SEE NO REASON WHY CLOUDS WOULD BREAK-UP EARLY.
FOR THIS...INCREASED SKY COVER THROUGH THE DAY ALONG AND EAST OF
THE VALLEY. THINK THERE SHOULD BE SOME CLEARING ALONG THE VALLEY
BY THIS AFTERNOON...BUT NOT UNTIL AFTER SUNSET ACROSS MUCH OF
NORTHWEST MN. DESPITE MODEST LOW-MID LEVEL WARM AIR ADVECTION...
DO NOT EXPECT MUCH TEMPERATURE RECOVERY UNDER CLOUDS..SO DECREASED
AFTERNOON HIGHS INTO THE LOW TO MID TEENS MOST LOCATIONS. SOME
SCATTERED FLURRIES ARE POSSIBLE THROUGH THE DAY...BUT NO REAL
ACCUMULATION IS EXPECTED. ALSO COULD SEE SOME PATCHY FOG EARLY
THIS MORNING ALONG THE WESTERN FLANK OF THE STRATUS DECK.
A DRY COLD FRONT WILL DROP SOUTH FROM CANADA TONIGHT AND SATURDAY.
DO NOT EXPECT ANY SNOW...BUT WINDS WILL SHIFT TO THE NORTHWEST
WITH A REINFORCING SHOT OF LOW CLOUDS. AFTERNOON HIGHS ON SATURDAY
WILL RANGE FROM 10 ABOVE ACROSS THE DEVILS LAKE BASIN TO NEAR 20
DEGREES ACROSS LAKES COUNTRY OF WEST CENTRAL MN. ANOTHER COOL...
BUT DRY DAY ON SUNDAY WITH LIGHT NORTHERLY WIND. HIGHS ACROSS
EASTERN ND INTO PORTIONS OF NORTHWEST MN NOT LIKELY TO BREAK OUT
OF THE SINGLE DIGITS.
ATTENTION TURNS TO SUNDAY NIGHT AS 700 HPA LOW MOVES INTO THE
CENTRAL VALLEY. MID-LEVEL FRONTOGENESIS AND UPPER LEVEL DYNAMIC
SUPPORT IS LACKING...BUT CONVERGENCE ALONG THE TRACK OF THE MID-
LEVEL CIRCULATION COMBINED WITH SOME WARM AIR ADVECTION INDUCED
LIFT SHOULD RESULT IN SOME LIGHT SNOW MAINLY ALONG AND NORTH OF
THE HIGHWAY TWO CORRIDOR. INCREASED POPS INTO THE 30 TO 40 PERCENT
RANGE...BUT ACCUMULATIONS SHOULD BE LIGHT...GENERALLY 1-2 INCHES
OR LESS.
.LONG TERM...MONDAY THROUGH THURSDAY NIGHT
THE PATTERN WILL BEGIN WITH MAINLY ZONAL FLOW AND A CHANCE FOR
SOME LIGHT SNOW CHRISTMAS EVE WITH A SHORTWAVE. THEREAFTER...SFC
RIDGING WILL BUILD SOUTH FROM CANADA...AND RESULT IN DRY WEATHER
TUE-THU AND TEMPS BELOW NORMAL. THERE ARE SOME INDICATIONS THAT
MORE OF AN ACTIVE SW FLOW ALOFT MAY DEVELOP THU NIGHT AND FRI...
AND THE POTENTIAL FOR SOME SORT OF STORM SYSTEM...SO SOMETHING TO
MONITOR.
&&
.AVIATION...
MVFR/IFR STRATUS DECK WILL MOVE VERY SLOWLY TO THE EAST THROUGH
THE DAY. IMPROVING CEILINGS NOT EXPECTED AT KFAR/KGFK UNTIL 18 UTC
OR LATER AND 21 UTC OR LATER AT KTVF/KBJI. SCATTERED FLURRIES ARE
POSSIBLE WITH CLOUD COVER WITH AN INFREQUENT REDUCTION IN
VISIBILITY TO 5 SM. LIGHT AND VARIABLE WIND WILL INCREASE FROM THE
SOUTH FROM WEST TO EAST AS SURFACE HIGH MOVES INTO EASTERN MN.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...NONE.
MN...NONE.
&&
$$
ROGERS/DK
AREA FORECAST DISCUSSION
NWS WILMINGTON OH
401 PM EST FRI DEC 21 2012
.SYNOPSIS...
A STRONG LOW PRESSURE SYSTEM OVER NEW ENGLAND WILL SLOWLY MOVE
NORTHEAST AWAY FROM THE REGION TONIGHT. A RIDGE OF HIGH PRESSURE
WILL BUILD ACROSS THE REGION ON SATURDAY AND SATURDAY NIGHT. THE
HIGH WILL THEN MOVE EAST ON SUNDAY AS A COLD FRONT APPROACHES THE
AREA FROM THE NORTHWEST.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
STRONG LOW PRESSURE NEAR NRN NEW YORK STATE THIS AFTERNOON WILL
PIVOT SLOWLY NORTHEAST AWAY FROM THE REGION OVERNIGHT.
MOSAIC RADAR CONTINUED TO SHOW CONSIDERABLE SNOW SHOWER ACTIVITY
ACROSS PARTS OF THE NRN AND ERN ZONES. MUCH OF THIS ACTIVITY
APPEARS TO BE LINKED TO A 900-850 MB FRONTOGENETIC AXIS AS
DEPICTED BY THE LATEST RAP MODEL. THE RAP MODEL GRADUALLY SHIFTS
THIS AXIS ESE AND EVENTUALLY WEAKEN IT AS IT DOES SO. THUS...WILL
FORECAST CAT POPS IN THE NRN AND EASTERN SECTIONS INTO THE EVENING
HOURS...AND THEN GRADUALLY TAPER OFF THE POPS TOWARD MIDNIGHT.
HAVE CONTINUED THE WINTER WEATHER ADVISORY UNTIL 10 PM FOR
LOCATIONS THAT WERE ALREADY IN IT AND WHERE LIKELY POPS WERE STILL
FORECAST. WILL ASSESS THE SITUATION BEFORE 6 PM TO SEE IF SOME OF
THE WESTERN COUNTIES IN THE WINTER ADVISORY ADVISORY MAY BE
DROPPED BY THEN. AS FOR THE WINDS...WE COULD SEE AN ISOLATED GUST
NEAR WIND ADVISORY CRITERIA THROUGH THE EARLY EVENING...BUT FOR
THE MOST PART...WIND GUSTS SHOULD STAY BELOW THE CRITERIA
THRESHOLD...SO HAVE ALLOWED THIS TO EXPIRE. WINDS WILL SLOWLY
DIMINISH FROM SW TO NE THROUGH THE OVERNIGHT HOURS AS LOW PRESSURE
CONTINUES TO PULL SLOWLY AWAY.
OTHERWISE...SKIES WILL BE MOSTLY CLOUDY TO CLOUDY THIS EVENING.
CLOUD COVER IS A BIT TRICKY OVERNIGHT. NAM AND GFS CONTINUE TO
DEPICTED MOISTURE AROUND 925 MB PUSHING SE AGAIN INTO THE REGION
OVERNIGHT. AS SUCH HAVE KEPT MOST LOCATIONS MOSTLY CLOUDY EXCEPT
FOR THE SW WHERE IT MAY GO MOSTLY CLEAR. OVERNIGHT LOWS WILL BE
CLOUD DEPENDENT AND WIND DEPENDENT BUT SHOULD RANGE FROM THE UPPER
TEENS SW TO THE MID 20S NORTHEAST.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
LOW PRESSURE WILL CONTINUE TO MOVE ENE ON SATURDAY AS A SFC RIDGE
OF HIGH PRESSURE BUILDS INTO THE OHIO VALLEY FROM THE WEST.
AGAIN...MODELS ARE HOLDING ON TO LOW LEVEL MOISTURE ACRS THE NRN
AND ERN SECTIONS THROUGH A GOOD PART OF THE DAY...SO HAVE GONE
PARTLY TO MOSTLY CLOUDY HERE. WE SHOULD GRADUALLY SEE IMPROVEMENT
THROUGH THE DAY SO THAT ALL LOCATIONS SHOULD BE MOSTLY CLEAR BY
SATURDAY EVENING. SKIES SHOULD REMAIN MOSTLY CLEAR SATURDAY NIGHT.
FOR SUNDAY INTO SUNDAY NIGHT...SURFACE HIGH PRESSURE RIDGE WILL
SLIP TO THE EAST. MEANWHILE...A COLD FRONT WILL DROP INTO THE
REGION SUNDAY NIGHT. MOISTURE AND LIFT ARE MEAGER TO START
WITH...SO HAVE ALLOWED FOR CLOUDS TO INCREASE OVERNIGHT...BUT LEFT
CHANCES OF PCPN UNTIL MONDAY MORNING.
AS FOR TEMPS...THEY SHOULD RANGE FROM THE LOWER TO UPPER 30S ON
SATURDAY. A MODIFYING AIRMASS AND RETURN FLOW WILL BRING
TEMPERATURES FROM THE UPPER 30S NORTH TO THE UPPER 40S SOUTH ON
SUNDAY. OVERNIGHT LOWS SATURDAY NIGHT SHOULD BE SOMEWHAT SUBDUED
WITH AN INCREASING SOUTHERLY FLOW. LOWS SUNDAY NIGHT WILL BE CLOUD
DEPENDENT BUT HAVE THEM RANGING FROM THE MID 20S NORTH TO THE
LOWER 30S SOUTH.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
AN ACTIVE WEATHER PATTERN WILL EVOLVE DURING THE LONG TERM FORECAST.
WEAK LOW PRESSURE WILL BRING SPREAD PRECIPITATION ACROSS THE OHIO
VALLEY ON MONDAY. THE ONSET TIMING OF SHOWER ACTIVITY IS STILL IN
QUESTION AND WILL HELP TO DETERMINE IF WE SEE A WINTRY MIX MONDAY
MORNING...OR AN ALL RAIN EVENT DURING THE DAY MONDAY. COLDER AIR ON
THE NORTH AND EASTERN SIDE OF THE LOW WILL BRING ABOUT A CHANGEOVER
TO A RAIN/SNOW MIX AND PERHAPS A BRIEF TIME OF LIGHT SNOW MONDAY
EVENING BEFORE PRECIPITATION EXITS THE AREA. BASED ON CURRENT TIMING
OF CHANGEOVER IN THE EVENING AND LIGHT QPF AMOUNTS...DO NOT EXPECT
MUCH IN THE WAY OF ANY SNOW ACCUMULATION FROM THIS SYSTEM.
CHRISTMAS DAY LOOKS TO HAVE FAIR WEATHER WITH SEASONABLE
TEMPERATURES. THE ATTENTION THEN TURNS TO A STORM SYSTEM THAT MAY
AFFECT THE AREA CHRISTMAS NIGHT THROUGH THURSDAY MORNING. FOR THE
PAST FEW DAYS MODELS HAVE BEEN ADJUSTING THEIR FORECAST POSITIONS ON
A DEVELOPING SURFACE LOW IN THE SOUTH CENTRAL PORTIONS OF THE CONUS
AHEAD OF A DEEP TROUGH EXITING THE SOUTHERN ROCKIES ON CHRISTMAS
DAY. THE 12Z ECMWF AND GFS ARE SUGGESTING THAT THIS STORM WILL TRACK
ACROSS THE OHIO VALLEY ON WEDNESDAY. THERE ARE STILL LARGE
DIFFERENCES AMONGST THE FORECAST MODELS FOR THE EXACT LOW TRACK AND
HOW COLD TEMPERATURES WILL BE ALOFT WITH THIS LOW. WENT WITH A ECMWF
WEIGHTED CONSENSUS BLEND FOR POPS AND TEMPERATURES DURING THIS TIME
PERIOD. THE TRACK FORECAST WILL LIKELY CONTINUE TO SHIFT FROM RUN TO
RUN AS WE ARE STILL 5 DAYS OUT. WENT LIKELY FOR POPS DURING THE MOST
CONFIDENT TIME PERIOD THAT THE SYSTEM WOULD AFFECT OUR AREA.
THIS SYSTEM SHOULD EXIT THE REGION THURSDAY WITH HIGH PRESSURE
BUILDING IN FOR FRIDAY.
&&
.AVIATION /21Z FRIDAY THROUGH WEDNESDAY/...
MVFR CIGS TO CONTINUE WITH CIGS IN THE 1.5-2.5 KFT RANGE THRU THE
AFTERNOON. IN CYCLONIC FLOW AROUND SFC LOW MOVG THRU THE EASTERN
GREAT LAKES...SNOW SHOWERS WILL CONTINUE TO REDUCE VSBYS TO 2-5
MILES. A FEW IFR CIGS WILL BE PSBL IN HEAVIER SNOW SHOWERS
EXPECTED ACRS KDAY AND KCMH/KLCK. PRECIP WILL END FROM SW TO NE AND
CIGS TO IMPROVE THIS EVENING. NUMERICAL MODELS SHOWING LOW LEVEL
MSTR REDEVELOPING LATE TNGT AND HAVE RE-INTRODUCED MVFR CIGS AT
KDAY/KILN. KEPT MVFR CIGS GOING AT KCMH THRU THE NIGHT ALTHOUGH
THERE MAY BE A BREAK LATE THIS EVENING PRIOR TO THE REDEVELOPMENT.
HAVE JUST BROUGHT SCTD CLOUDS BACK TO KCVG/KLUK AS THIS MOISTURE
LOOKS TO STAY TO THE NE OF THE SRN TAF SITES.
IN VERY TIGHT PRESSURE GRADIENT AROUND DEEP SFC LOW...WEST WINDS
WILL BE 25-30 KT SUSTAINED WITH GUSTS UP TO 40 KTS THIS AFTN. HIGH
PRESSURE WILL BUILD OVER THE MIDWEST TONIGHT AND WINDS WILL
GRADUALLY DIE DOWN FROM THEIR DAYTIME MAXIMA BUT STILL BE 10-15KT
GUSTING TO 25KT.
OUTLOOK...MVFR CEILINGS AND VSBYS ARE POSSIBLE MONDAY.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR
OHZ026-035-043>046-051>056-061>065-072-074.
KY...NONE.
IN...NONE.
&&
$$
SYNOPSIS...HICKMAN
NEAR TERM...HICKMAN
SHORT TERM...HICKMAN
LONG TERM...LATTO
AVIATION...AR
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
1246 AM EST FRI DEC 21 2012
.SYNOPSIS...
STRONG COLD FRONT PLOWS THROUGH THIS EVENING. SNOW SHOWERS BEHIND
LOW PRESSURE TONIGHT INTO SATURDAY. HIGH PRESSURE PASSES SUNDAY. LOW
PRESSURE CHRISTMAS EVE AND AGAIN MIDWEEK.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
1230 AM UPDATE...
COLDER AIR A BIT SLOWER TO ARRIVE...BUT GRAUPEL WAS OCCURRING A
LITTLE BIT AGO AT THE OFFICE AND HTS JUST CHANGED OVER TO -SN AT
THE 05Z OB...SO THE TRANSITION FROM RAIN TO SNOW STILL GENERALLY
ON TRACK.
PREVIOUS DISCUSSION FOLLOWS...
INITIAL PRECIP FROM THIS MORNING HAS MOSTLY LIFTED TO THE
NORTH...WITH THE NEXT BATCH ALREADY WELL INTO WESTERN CWA. HAVE
GOTTEN SOME REPORTS OF LIGHT SNOW FALLING ACROSS HIGHER TERRAIN IN
NORTHERN WV MOUNTAINS. THIS IS TIED TO A SMALL COLD POOL STILL IN
PLACE...BUT AS WINDS SHIFT AROUND TO MORE S THEN SW...THIS COLD POOL
SHOULD BE CLEARED OUT WITH A RETURN TO RAIN UNTIL TONIGHT. ALL THIS
CURRENT PRECIP IS STILL WELL PRE-FRONTAL...WITH THE COLD FRONT
CURRENTLY RUNNING FROM THE LOW IN NORTHEASTERN IL...THROUGH SW
IN...AND CENTRAL KY/TN. AT 19Z...FRONT SHOWING UP WELL ON RADAR IN
KY...RUNNING FROM ROUGHLY KGLW TO KSDF. PRE-FRONTAL PRECIP SHOULD
WRAP UP BEFORE THE FRONT...WITH A THIN LINE OF SHOWERS RIGHT ALONG
THE FRONT. IN GENERAL PRE-FRONTAL WIND GUSTS HAVE BEEN 20-35
KTS...WITH THE STRONGER GUSTS BEHIND THE FRONT. CONSIDERED STARTING
WIND ADVISORY EARLIER...BUT NOT SEEING ANY OBS WITH CRITERIA OPTED
TO LEAVE AS IS...WAITING FOR THOSE STRONGER GUSTS BEHIND THE FRONT.
MODELS STILL SHOWING A PRETTY GOOD DRY SLOT BEHIND THE FRONT...SO
TRANSITION AN AREA OF LOW SLIGHT CHANCE POPS ACROSS THE CWA FROM
ABOUT 03Z TO 06Z...THEN HAVE WRAP AROUND MOISTURE SURGING BACK IN.
INITIALLY...COLD AIR WILL STILL BE LAGGING BEHIND THE FRONT OF THE
PRECIP SHIELD...SO WRAP AROUND SHOULD START AS RAIN SHOWERS. THEN AS
COLD AIR SURGES IN WILL SEE A TRANSITION FROM RAIN TO SNOW IN THE
MOUNTAINS AND ALSO MOVING ACROSS THE LOWLANDS FROM WEST TO EAST.
WITH THE WRAP AROUND...COORDINATED WITH SHORT TERM FORECASTER ON A
WINTER WEATHER ADVISORY STARTING AT 06Z FROM PERRY COUNTY OHIO EAST
TO THE ALREADY IN PLACE ADVISORY IN WV.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH SATURDAY NIGHT/...
SIGNIFICANT UPSLOPE SNOW EVENT IMPACTS THE AREA THIS PERIOD.
WRAP AROUND ARRIVES FROM THE W RIGHT AT THE START OF THE PERIOD.
MODELS INCLUDING NEAR TERM HIRES SUGGESTS THIS IMPACTS MID SE OHIO
BEFORE LIFTING THROUGH FAR NORTHERN WV AND ON INTO PA FRI. GENERAL
UPSLOPE FLOW ALSO SETS UP RIGHT AT THE START OF THE PERIOD AND
PERSISTS INTO SAT BEFORE WINDING DOWN SAT AFTERNOON AND EVENING.
AS COMMA / WRAP AROUND TAIL LIFTS OUT FRI...SECOND PLUME OFF LAKE
MICHIGAN MAY SET UP FOR A TIME...PERHAPS A LITTLE S OF WHERE THE
INITIAL WRAP AROUND OCCURS. IT THEN WILL EITHER DRIFT INTO THE SAME
AREA AFFECTED BY THE INITIAL RAP AROUND OR SIMPLY FADE IN PLACE LATE
FRI.
THE WESTERN SLOPES OF THE MOUNTAINS EXPERIENCE STRONG UPSLOPE
WINDS AS THE HIGH SPEEDS SOMEWHAT MAKE UP THE THE LESS THAN
PERPENDICULAR ANGLE PER W FLOW. AIR MASS IS COLD ENOUGH AND
MOISTURE DEPTH GREAT ENOUGH TO EASILY SUPPORT FAVORED DENDRITIC
GROWTH MOST OF THE TIME AND THUS SIGNIFICANT SNOW ACCUMULATIONS.
LEFT WARNINGS AND ADVISORIES AS IS EXCEPT TO EXPAND THE ADVISORY W
ACROSS OUR FAR NORTHERN WV COUNTIES AND ON BACK THROUGH MID SE OHIO
WHERE INITIAL WRAP AROUND SETS UP. SNOW AMOUNTS FARTHER S AND W ARE
ONLY A LITTLE LOWER THOUGH AND REMAINING COUNTIES NOT WARNED OR
ADVISED WILL STILL HAVE WINTRY IMPACTS.
ENTERTAINED BLIZZARD WARNINGS NORTHERN MOUNTAINS BUT RECKONED 3 HRS
OF 1/4SM SN BLSN WOULD BE HARD TO REALIZE SAVE MAYBE FOR THE HIGHEST
WINDWARD SLOPES. SIMILAR DEAL ON HIGH WIND WARNING AS ONLY A FEW
LOCATIONS WILL EXPERIENCE BRIEF GUSTS PAST 50 KTS. 60-65 KTS FLOW
SHOWN AT H85 FRI NT PER NOCTURNAL JET BUT THIS WILL NOT BE REALIZED
AT SURFACE...CLOSE ONLY ACROSS THE HIGHEST EXPOSED RIDGES.
MAINTAINED AREA WIDE WIND ADVISORY.
SNOWS AND WINDS WIND DOWN AND CLEARING COMMENCES SW TO NE SAT MIDDAY
THROUGH SAT NT AS HEIGHTS RISE AND WEAK LOW-MID LEVEL WARM ADVECTION
COMMENCES.
USED A HIRES/NAM/MOS COMBINATION ON TEMPERATURES THROUGH FRI NT
WHICH REFLECTS CORE OF THE COLD AIR CROSSING FRI MIDDAY AND
AFTERNOON. HAVE SUBFREEZING TEMPERATURES EVERYWHERE DURING THAT
TIME WHICH...TOGETHER WITH THE WINTER SOLSTICE...WILL FAVOR DAYTIME
ACCUMULATIONS. TEMPERATURES SAT AND SAT NT NEEDED NOTHING MORE THAN
MINOR EDITS IN LIGHT OF LATEST OF GUIDANCE / ON LOW SIDE / ...AS
SYSTEM SLOWLY PULLS OUT.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
THIS WILL BE A VERY UNSETTLED WEATHER PATTERN WITH CHANGEABLE
TEMPERATURES...IN WHICH TWO LOW PRESSURE SYSTEMS WILL AFFECT THE
AREA. THE MODELS ARE NOT IN GOOD AGREEMENT WITH THE STRENGTH AND
TIMING OF THESE SYSTEMS. RELYING MORE ON THE ENSEMBLES TO MITIGATE
THE DIFFERENCES WILL BE THE WAY TO GO...SO HPC GUIDANCE WITH THE
BLEND OF MODEL DATA WAS FOLLOWED CLOSELY.
EXPECT A DRY AND CHILLY DAY SUNDAY UNDER HIGH PRESSURE.
THE FIRST SYSTEM MONDAY AND MONDAY NIGHT WILL BE ON THE FLAT SIDE
WITH A WEAK LOW PRESSURE SYSTEM TRACKING ACROSS ALONG THE OHIO
RIVER. THIS WILL PUT US ON THE MILD SIDE WITH MAINLY RAIN
MONDAY...EXCEPT POSSIBLY SNOW IN THE NORTHERN
MOUNTAINS...TRANSITIONING TO SOME LIGHT SNOW ON THE BACK SIDE ACROSS
THE NORTH MONDAY NIGHT.
KEPT LOW LIQUID POPS SOUTH TUESDAY WITH FRONTAL SYSTEM TO OUR
SOUTH...BUT MOST OF THE AREA WILL BE DRY AND CHILLY WITH WEAK HIGH
PRESSURE.
SECOND SYSTEM LOOKS TO BE MUCH STRONGER AS IT TRACKS NORTHEASTWARD
TO THE WEST OF OUR AREA...BRINGING A GOOD SHOT OF MILD AIR AND
SIGNIFICANT RAIN WEDNESDAY. AS THE LOW PASSES WEDNESDAY
NIGHT...EXPECT A GENERAL TRANSITION TO SNOW WEDNESDAY NIGHT INTO
THURSDAY MORNING.
&&
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
EXPECT DEVELOPMENT OF WIDESPREAD MVFR CONDITIONS AND LOCAL IFR
CONDITIONS...WHICH WILL REMAIN FOR MUCH OF THE TAF PERIOD.
PERIODIC IFR CONDITIONS AND UNDER WILL OCCUR AT TIMES ON FRIDAY IN
HEAVIER SNOW SHOWERS.
IN ADDITION...VERY STRONG WINDS WILL DEVELOP BEHIND THE COLD
FRONT. EXPECT WIND GUSTS OF UP TO 40 KTS ACROSS THE
LOWLANDS...AND UP TO 50 KTS ACROSS THE HIGHER TERRAIN BEHIND THE
FRONTAL PASSAGE FOR MUCH OF THE VALID PERIOD.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z SATURDAY...
FORECAST CONFIDENCE: MEDIUM.
ALTERNATE SCENARIOS: TIMING OF PRECIPITATION AND LOWER CLOUDS COULD
VARY.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
DATE FRI 12/21/12
UTC 1HRLY 06 07 08 09 10 11 12 13 14 15 16 17
EST 1HRLY 01 02 03 04 05 06 07 08 09 10 11 12
CRW CONSISTENCY L L L M M M M M L L M M
HTS CONSISTENCY M L L L L M M L L L L L
BKW CONSISTENCY L L M M M M M M M M M M
EKN CONSISTENCY L M M M M M M M M M M M
PKB CONSISTENCY L L L M M M M L L L L L
CKB CONSISTENCY L L L M M M M M L L L M
AFTER 06Z SATURDAY...
IFR POSSIBLE INTO SATURDAY DUE TO SNOW SHOWERS...ESPECIALLY IN
THE MOUNTAINS. IFR CONDITIONS MAY LINGER ACROSS THE HIGHER TERRAIN
INTO SUNDAY.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...WIND ADVISORY UNTIL 10 PM EST THIS EVENING FOR WVZ005>011-
013>020-024>034-039-040.
WIND ADVISORY UNTIL 7 AM EST SATURDAY FOR WVZ035>038-046-047.
WINTER STORM WARNING UNTIL 2 PM EST SATURDAY FOR WVZ036>038-
046-047.
WINTER WEATHER ADVISORY UNTIL 2 PM EST SATURDAY FOR WVZ027-028-
035-039-040.
WINTER WEATHER ADVISORY UNTIL 7 AM EST SATURDAY FOR WVZ015-016-
018-025-026-029>034.
WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR
WVZ008>011-017-019-020.
OH...WIND ADVISORY UNTIL 10 PM EST THIS EVENING FOR OHZ066-067-075-
076-083>087.
WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR
OHZ066-067-075-076-085.
KY...WIND ADVISORY UNTIL 10 PM EST THIS EVENING FOR KYZ101>103-105.
VA...WIND ADVISORY UNTIL 10 PM EST THIS EVENING FOR VAZ003-004.
&&
$$
SYNOPSIS...TRM/JMV/MZ
NEAR TERM...MZ/50
SHORT TERM...TRM
LONG TERM...JMV
AVIATION...50
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
959 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 00Z TAF ISSUANCE/
VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. COULD SEE A BRIEF
DIP IN VISIBILITY TO MVFR AROUND SUNRISE...HOWEVER THIS SHOULD ONLY
LAST AN HOUR OR TWO.
&&
.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 LA CROSSE WI
920 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...
500 PM CST SAT DEC 22 2012
THE CONCERN TONIGHT IS FOR THE POTENTIAL OF A LOW STRATUS LAYER.
RAP13/NAM12 SHOW AN AREA OF LOW LEVEL SATURATION ACROSS THE
DAKOTAS/NORTHWEST MN...BRINGING THIS SOUTH THROUGH THE NIGHT. THE
RAP13 IS MORE AGGRESSIVE IN ITS EASTWARD EXTENT ON THE STRATUS...AND
WOULD HAVE IT IMPACT KRST OVERNIGHT. SOME SFC OBS OVER WESTERN MN
INDICATE CIGS AROUND 1 KFT...ALTHOUGH NOTHING SEEN ON FOG/STRATUS
SATELLITE IMAGERY. A CLOSER LOOK AT VSBY DURING THE DAYLIGHT HOURS
DOES SHOW SOME VERY SHALLOW CLOUDS STREETS THAT COULD BE RESPONSIBLE
FOR THE OBS. OR...IT COULD ALSO BE SUSPENDED ICE CRYSTALS IN THE
COLDER AIR. BUFKIT SOUNDINGS HAVE A LOW LEVEL INVERSION INTO SUN
MORNING. IF ANY MOISTURE COULD POOL UNDER THAT...STRATUS AND
POSSIBLY SOME BR COULD DEVELOP. CONFIDENCE NOT OVERLY HIGH AT THE
MOMENT THOUGH...AND WILL KEEP ANY CIGS WEST OF THE KRST/KLSE
TONIGHT.
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 LA CROSSE WI
1130 AM CST FRI DEC 21 2012
.SHORT TERM...TODAY THROUGH SUNDAY NIGHT
240 AM CST FRI DEC 21 2012
MAIN FORECAST CONCERNS TO BEGIN THE FIRST DAY OF WINTER ARE ON
TEMPERATURES TONIGHT...ANY LOW CLOUD POTENTIAL SATURDAY NIGHT INTO
SUNDAY...AND ANY PRECIPITATION POTENTIAL SUNDAY NIGHT.
CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED DEEP TROUGHING OFF THE WEST COAST OF THE U.S....RIDGING
BUILDING ALONG THE LEE OF THE ROCKIES INTO SOUTH CENTRAL CANADA...
AND DEEP TROUGHING FROM THE GREAT LAKES INTO THE SOUTHEASTERN U.S..
THE LATTER DEEP TROUGHING CONTAINS THE STRONG STORM SYSTEM THAT
BROUGHT THE SNOW AND STRONG WINDS TO THE FORECAST AREA YESTERDAY.
ROADS STILL REMAIN HAZARDOUS TOO...ESPECIALLY OVER THE SOUTHEASTERN
PORTION OF THE FORECAST AREA. WINDS REMAIN BRISK...DUE TO A TIGHT
PRESSURE GRADIENT BETWEEN 987MB LOW PRESSURE NEAR DETROIT AND A
1025MB HIGH PRESSURE RIDGE OVER THE EASTERN DAKOTAS. WITH THE
FORECAST AREA EXPERIENCING RISING HEIGHTS AT 500MB...ABOUT 40 METERS
SINCE 00Z ACCORDING TO THE RAP...SUBSIDENCE HAS BEEN ON THE
INCREASE. DRY ADVECTION WAS ALSO OCCURRING...NOTED BY THE
PRECIPITABLE WATER DROPPING AT MPX FROM 0.33 INCHES AT 12Z ON THE
20TH TO 0.16 INCHES AT 00Z. THE COMBINATION OF SUBSIDENCE AND DRYING
HAS LED TO CLEARING SKIES IN THE WAKE OF THE STORM SYSTEM. CLEARING
LINE STRETCHED FROM EAU CLAIRE TO LA CROSSE AND DUBUQUE. COLDER AIR
ALSO ACCOMPANYING THE SUBSIDENCE AND DRYING...REFLECTED BY SURFACE
TEMPERATURES IN THE SINGLE DIGITS ACROSS WESTERN PORTIONS OF
MINNESOTA AND IOWA...AND IN THE SINGLE DIGITS BELOW ZERO OVER THE
EASTERN DAKOTAS UNDER THE SURFACE RIDGE. 925MB TEMPS AT MPX AT 00Z
WERE -10C...ABOUT 3 COLDER THAN 12 HOURS EARLIER.
TODAY AND TONIGHT...THE UPPER RIDGING ALONG THE LEE OF THE ROCKIES
WILL SHIFT EASTWARD INTO THE PLAINS BY TONIGHT IN RESPONSE TO THE
DEEP EAST PACIFIC TROUGH APPROACHING THE WESTERN U.S. COAST. WITH
THE UPPER RIDGING TRYING TO PUSH INTO THE FORECAST AREA...MID LEVEL
HEIGHTS WILL CONTINUE TO CLIMB...MAINTAINING THE SUBSIDENCE. IN
ADDITION...THE SHIFT EAST IN THE UPPER PATTERN OCCURS AT THE SURFACE
AS WELL...WITH THE HIGH PRESSURE RIDGE SHIFTING EAST OVER THE
FORECAST AREA AROUND MIDNIGHT. WITH THE SUBSIDENCE AND DRYING
PATTERN IN PLACE...EXPECT A DRY PERIOD. IN FACT...OTHER THAN A FEW
HIGH CLOUDS AFTER MIDNIGHT TONIGHT CROSSING THE UPPER RIDGE...SKIES
SHOULD BE MAINLY CLEAR. DESPITE THE PLENTIFUL SUNSHINE TODAY...
BREEZY NORTHWEST WINDS COMBINED WITH 925MB TEMPS IN THE -6 TO -10C
RANGE AND FRESH SNOW COVER WILL LIMIT HEATING. HIGHS SHOULD TOP OUT
FROM THE MID TEENS TO MID 20S...COLDEST OVER THE HIGHER ALBEDO
PRESENT WEST OF THE MISSISSIPPI RIVER. CONCERN FOR TEMPERATURES
PLUMMETING TONIGHT GIVEN THE COOLER DAY TODAY...DECOUPLING WINDS AND
MOSTLY CLEAR SKIES. HAVE LEANED TOWARDS THE COLD SIDE OF GUIDANCE AS
A RESULT.
SATURDAY AND SATURDAY NIGHT...MODELS ARE POINTING TO A SHORTWAVE
CURRENTLY IN SOUTHEAST BRITISH COLUMBIA TOPPING THE RIDGE AND MOVING
THROUGH EASTERN LAKE SUPERIOR SATURDAY NIGHT. ALTHOUGH THIS
SHORTWAVE IS FAR FROM US...A COLD FRONT ACCOMPANIES THE SHORTWAVE
WHICH SLIDES THROUGH THE FORECAST AREA SATURDAY NIGHT. AHEAD OF THE
FRONT...WE SEE SOME 925MB WARMING...PROGGED TO CLIMB TO -2C OR SO
BY 18Z SATURDAY. 850MB TEMPS ARE EVEN WARMER...0-3C OR SO...BUT
THERE IS NO WAY OF MIXING UP TO THIS DUE TO BEING NOW AT THE
SHORTEST DAY LENGTH AND HAVING THE FRESH SNOW. NEVERTHELESS...
COMBINATION OF SUN THROUGH SOME HIGH CLOUDS AND SOUTHWEST WINDS
PICKING UP A BIT SHOULD ALLOW TEMPERATURES TO CLIMB INTO THE 20S
EVERYWHERE. SOME VALLEY LOCATIONS COULD PUSH 30. NOT ANTICIPATING
ANY PRECIPITATION TO ACCOMPANY THE FRONTAL PASSAGE...DUE TO
PLENTIFUL DRY AIR AND ALL FORCING WELL NORTHEAST OF THE AREA.
HOWEVER...AFTER THE FRONTAL PASSAGE...CONCERNED THERE MAY BE AN
INCREASE OF LOW CLOUDS AS SUGGESTED BY 21.00Z GFS 925MB RH FIELDS.
THE 21.00Z NAM AND ECMWF 925MB RH FIELD ARE NOT NEARLY AS
PESSIMISTIC AND THUS WILL CONTINUE WITH THE PREVIOUS MOSTLY CLEAR
FORECAST. COMBINATION OF COLD ADVECTION IN THE WAKE OF THE FRONT AND
RADIATIONAL COOLING ARE EXPECTED TO SEND TEMPERATURES BACK DOWN INTO
THE SINGLE DIGITS AND TEENS.
SUNDAY AND SUNDAY NIGHT...SOME OF THE CURRENT EASTERN PACIFIC TROUGH
IS PROGGED BY ALL MODELS TO HEAD EAST INTO THE PLAINS SUNDAY NIGHT.
ASSOCIATED WITH THIS UPPER TROUGHING IS A NORTHWEST TO SOUTHEAST
ORIENTED INVERTED TROUGH AT THE SURFACE...WHICH BY 12Z MONDAY SHOULD
HAVE REACHED AT LEAST SIOUX FALLS PER MODEL CONSENSUS. GIVEN THE
APPROACH OF THE UPPER AND INVERTED SURFACE TROUGH...ONE WOULD EXPECT
AN ISENTROPIC LIFT PATTERN...WHICH INDEED EXISTS. HOWEVER...ANY
ISENTROPIC LIFT IS ROOTED ON THE 290-300K SURFACES WHICH PUTS IT AT
A PRESSURE LEVEL OF 700MB OR HIGHER...AND MORE TOWARDS 12Z.
THEREFORE...NOT SURE IF ANY PRECIPITATION CAN MAKE IT TO THE
SURFACE. THE 21.00Z NAM/GFS ARE BOTH DRY FOR SUNDAY NIGHT. AS
SUCH...HAVE KEPT A DRY FORECAST GOING. LOW CLOUD COVER CONCERN STILL
EXISTS HERE FOR SUNDAY AND SUNDAY NIGHT...ESPECIALLY IF SOME MOVE IN
BEHIND THE SATURDAY NIGHT COLD FRONT. SHOULD LOW CLOUDS MOVE
IN...LIKELY SUNDAY AND SUNDAY NIGHT WILL END UP CLOUDY. CLOUDS ARE
GOING TO INCREASE ANYWAY...ESPECIALLY SUNDAY NIGHT ASSOCIATED WITH
THE ISENTROPIC LIFT REGIME AHEAD OF THE UPPER TROUGH. GIVEN THE
UNCERTAINTY SURROUNDING CLOUD COVER ON SUNDAY...WENT WITH A BLEND OF
GUIDANCE FOR HIGHS. THE BLEND OF GUIDANCE LOOKS GOOD TOO FOR LOWS
SUNDAY NIGHT AS IT HANDLES THE CLOUD COVER INCREASE FINE.
.LONG TERM...MONDAY THROUGH THURSDAY
240 AM CST FRI DEC 21 2012
21.00Z ECMWF/GFS/CANADIAN/UKMET ARE IN FAIRLY GOOD AGREEMENT BOTH
WITH THE UPPER AND SURFACE PATTERNS THROUGHOUT THE LONG TERM PERIOD.
MAIN STORM TRACK THROUGHOUT THE LONG TERM IS SOUTH OF THE FORECAST
AREA...WHERE THERE APPEARS TO BE A STORM SYSTEM THAT CROSSES THE
SOUTHERN PLAINS INTO THE MID-ATLANTIC REGION INTO NEW ENGLAND
BETWEEN TUESDAY THROUGH THURSDAY. TRENDS CONTINUE SOUTH WITH THIS
SYSTEM...THUS ALL PRECIPITATION STAYS AWAY FROM THE FORECAST AREA.
THE ONLY SYSTEM REALLY TO DEAL WITH IS THAT UPPER TROUGH AND
INVERTED TROUGH APPROACHING THE FORECAST AREA SUNDAY NIGHT. MODELS
SUGGEST THE UPPER TROUGH IS ACTUALLY SPLIT INTO TWO PARTS...WITH THE
MAIN FEATURE/SHORTWAVE IN IT TRACKING ACROSS THE OHIO RIVER VALLEY.
WE HAVE THE NORTHERN PART OF THE TROUGH CROSSING THE FORECAST
AREA MONDAY INTO MONDAY NIGHT...BUT ALL THE BETTER MOISTURE IS WITH
THE SOUTHERN SHORTWAVE. THE 21.00Z ECMWF BASICALLY CAME IN DRY WITH
THE NORTHERN PART OF THE TROUGH AND THE 21.00Z GFS ONLY HAS SOME
VERY LIGHT QPF. GIVEN THE LACK OF MOISTURE...ESPECIALLY BELOW
700MB...ONLY HAVE 20 PERCENT CHANCES OF PRECIPITATION IN THE
FORECAST FOR MONDAY AND MONDAY NIGHT. IF TRENDS CONTINUE...THESE
COULD BE PULLED IN LATER FORECASTS.
WITH A STORM TRACK MORE TO THE SOUTH OF THE FORECAST AREA...THIS
MEANS NO WARM UPS ARE IN STORE. IN FACT...THE BULK OF THE PERIOD
SHOULD AVERAGE BELOW NORMAL AS 925MB TEMPS COOL TO -10 TO -12C FOR
TUESDAY AND WEDNESDAY BEHIND THE INVERTED TROUGH. SOME SLIGHT
WARMING SHOULD OCCUR FOR THURSDAY. SOMETHING TO WATCH IS IF WE END
UP WITH CLEAR SKIES AND LIGHT WINDS AT NIGHT...SINCE SNOW COVER IS
VERY FAVORABLE FOR HAVING TEMPERATURES PLUMMET.
&&
.AVIATION...THROUGH 18Z SATURDAY
1130 AM CST FRI DEC 21 2012
A SURFACE RIDGE OF HIGH PRESSURE OVER THE CENTRAL AND NORTHERN
PLAINS WILL SLIDE EASTWARD ACROSS THE AREA TONIGHT. EXCEPT FOR A
FEW HIGH CLOUDS ON ITS BACKSIDE LATER THIS EVENING...SKIES WILL BE
CLEAR. A FEW GUSTS TO NEAR 20 KNOTS ARE POSSIBLE THROUGH 21Z TODAY
BEFORE WINDS DIMINISH TO LESS THAN 10 KNOTS AFTER 21-22Z THIS AFTERNOON.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
240 AM CST FRI DEC 21 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...AJ
LONG TERM...AJ
AVIATION...RABERDING
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
531 AM CST FRI DEC 21 2012
.SHORT TERM...TODAY THROUGH SUNDAY NIGHT
240 AM CST FRI DEC 21 2012
MAIN FORECAST CONCERNS TO BEGIN THE FIRST DAY OF WINTER ARE ON
TEMPERATURES TONIGHT...ANY LOW CLOUD POTENTIAL SATURDAY NIGHT INTO
SUNDAY...AND ANY PRECIPITATION POTENTIAL SUNDAY NIGHT.
CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED DEEP TROUGHING OFF THE WEST COAST OF THE U.S....RIDGING
BUILDING ALONG THE LEE OF THE ROCKIES INTO SOUTH CENTRAL CANADA...
AND DEEP TROUGHING FROM THE GREAT LAKES INTO THE SOUTHEASTERN U.S..
THE LATTER DEEP TROUGHING CONTAINS THE STRONG STORM SYSTEM THAT
BROUGHT THE SNOW AND STRONG WINDS TO THE FORECAST AREA YESTERDAY.
ROADS STILL REMAIN HAZARDOUS TOO...ESPECIALLY OVER THE SOUTHEASTERN
PORTION OF THE FORECAST AREA. WINDS REMAIN BRISK...DUE TO A TIGHT
PRESSURE GRADIENT BETWEEN 987MB LOW PRESSURE NEAR DETROIT AND A
1025MB HIGH PRESSURE RIDGE OVER THE EASTERN DAKOTAS. WITH THE
FORECAST AREA EXPERIENCING RISING HEIGHTS AT 500MB...ABOUT 40 METERS
SINCE 00Z ACCORDING TO THE RAP...SUBSIDENCE HAS BEEN ON THE
INCREASE. DRY ADVECTION WAS ALSO OCCURRING...NOTED BY THE
PRECIPITABLE WATER DROPPING AT MPX FROM 0.33 INCHES AT 12Z ON THE
20TH TO 0.16 INCHES AT 00Z. THE COMBINATION OF SUBSIDENCE AND DRYING
HAS LED TO CLEARING SKIES IN THE WAKE OF THE STORM SYSTEM. CLEARING
LINE STRETCHED FROM EAU CLAIRE TO LA CROSSE AND DUBUQUE. COLDER AIR
ALSO ACCOMPANYING THE SUBSIDENCE AND DRYING...REFLECTED BY SURFACE
TEMPERATURES IN THE SINGLE DIGITS ACROSS WESTERN PORTIONS OF
MINNESOTA AND IOWA...AND IN THE SINGLE DIGITS BELOW ZERO OVER THE
EASTERN DAKOTAS UNDER THE SURFACE RIDGE. 925MB TEMPS AT MPX AT 00Z
WERE -10C...ABOUT 3 COLDER THAN 12 HOURS EARLIER.
TODAY AND TONIGHT...THE UPPER RIDGING ALONG THE LEE OF THE ROCKIES
WILL SHIFT EASTWARD INTO THE PLAINS BY TONIGHT IN RESPONSE TO THE
DEEP EAST PACIFIC TROUGH APPROACHING THE WESTERN U.S. COAST. WITH
THE UPPER RIDGING TRYING TO PUSH INTO THE FORECAST AREA...MID LEVEL
HEIGHTS WILL CONTINUE TO CLIMB...MAINTAINING THE SUBSIDENCE. IN
ADDITION...THE SHIFT EAST IN THE UPPER PATTERN OCCURS AT THE SURFACE
AS WELL...WITH THE HIGH PRESSURE RIDGE SHIFTING EAST OVER THE
FORECAST AREA AROUND MIDNIGHT. WITH THE SUBSIDENCE AND DRYING
PATTERN IN PLACE...EXPECT A DRY PERIOD. IN FACT...OTHER THAN A FEW
HIGH CLOUDS AFTER MIDNIGHT TONIGHT CROSSING THE UPPER RIDGE...SKIES
SHOULD BE MAINLY CLEAR. DESPITE THE PLENTIFUL SUNSHINE TODAY...
BREEZY NORTHWEST WINDS COMBINED WITH 925MB TEMPS IN THE -6 TO -10C
RANGE AND FRESH SNOW COVER WILL LIMIT HEATING. HIGHS SHOULD TOP OUT
FROM THE MID TEENS TO MID 20S...COLDEST OVER THE HIGHER ALBEDO
PRESENT WEST OF THE MISSISSIPPI RIVER. CONCERN FOR TEMPERATURES
PLUMMETING TONIGHT GIVEN THE COOLER DAY TODAY...DECOUPLING WINDS AND
MOSTLY CLEAR SKIES. HAVE LEANED TOWARDS THE COLD SIDE OF GUIDANCE AS
A RESULT.
SATURDAY AND SATURDAY NIGHT...MODELS ARE POINTING TO A SHORTWAVE
CURRENTLY IN SOUTHEAST BRITISH COLUMBIA TOPPING THE RIDGE AND MOVING
THROUGH EASTERN LAKE SUPERIOR SATURDAY NIGHT. ALTHOUGH THIS
SHORTWAVE IS FAR FROM US...A COLD FRONT ACCOMPANIES THE SHORTWAVE
WHICH SLIDES THROUGH THE FORECAST AREA SATURDAY NIGHT. AHEAD OF THE
FRONT...WE SEE SOME 925MB WARMING...PROGGED TO CLIMB TO -2C OR SO
BY 18Z SATURDAY. 850MB TEMPS ARE EVEN WARMER...0-3C OR SO...BUT
THERE IS NO WAY OF MIXING UP TO THIS DUE TO BEING NOW AT THE
SHORTEST DAY LENGTH AND HAVING THE FRESH SNOW. NEVERTHELESS...
COMBINATION OF SUN THROUGH SOME HIGH CLOUDS AND SOUTHWEST WINDS
PICKING UP A BIT SHOULD ALLOW TEMPERATURES TO CLIMB INTO THE 20S
EVERYWHERE. SOME VALLEY LOCATIONS COULD PUSH 30. NOT ANTICIPATING
ANY PRECIPITATION TO ACCOMPANY THE FRONTAL PASSAGE...DUE TO
PLENTIFUL DRY AIR AND ALL FORCING WELL NORTHEAST OF THE AREA.
HOWEVER...AFTER THE FRONTAL PASSAGE...CONCERNED THERE MAY BE AN
INCREASE OF LOW CLOUDS AS SUGGESTED BY 21.00Z GFS 925MB RH FIELDS.
THE 21.00Z NAM AND ECMWF 925MB RH FIELD ARE NOT NEARLY AS
PESSIMISTIC AND THUS WILL CONTINUE WITH THE PREVIOUS MOSTLY CLEAR
FORECAST. COMBINATION OF COLD ADVECTION IN THE WAKE OF THE FRONT AND
RADIATIONAL COOLING ARE EXPECTED TO SEND TEMPERATURES BACK DOWN INTO
THE SINGLE DIGITS AND TEENS.
SUNDAY AND SUNDAY NIGHT...SOME OF THE CURRENT EASTERN PACIFIC TROUGH
IS PROGGED BY ALL MODELS TO HEAD EAST INTO THE PLAINS SUNDAY NIGHT.
ASSOCIATED WITH THIS UPPER TROUGHING IS A NORTHWEST TO SOUTHEAST
ORIENTED INVERTED TROUGH AT THE SURFACE...WHICH BY 12Z MONDAY SHOULD
HAVE REACHED AT LEAST SIOUX FALLS PER MODEL CONSENSUS. GIVEN THE
APPROACH OF THE UPPER AND INVERTED SURFACE TROUGH...ONE WOULD EXPECT
AN ISENTROPIC LIFT PATTERN...WHICH INDEED EXISTS. HOWEVER...ANY
ISENTROPIC LIFT IS ROOTED ON THE 290-300K SURFACES WHICH PUTS IT AT
A PRESSURE LEVEL OF 700MB OR HIGHER...AND MORE TOWARDS 12Z.
THEREFORE...NOT SURE IF ANY PRECIPITATION CAN MAKE IT TO THE
SURFACE. THE 21.00Z NAM/GFS ARE BOTH DRY FOR SUNDAY NIGHT. AS
SUCH...HAVE KEPT A DRY FORECAST GOING. LOW CLOUD COVER CONCERN STILL
EXISTS HERE FOR SUNDAY AND SUNDAY NIGHT...ESPECIALLY IF SOME MOVE IN
BEHIND THE SATURDAY NIGHT COLD FRONT. SHOULD LOW CLOUDS MOVE
IN...LIKELY SUNDAY AND SUNDAY NIGHT WILL END UP CLOUDY. CLOUDS ARE
GOING TO INCREASE ANYWAY...ESPECIALLY SUNDAY NIGHT ASSOCIATED WITH
THE ISENTROPIC LIFT REGIME AHEAD OF THE UPPER TROUGH. GIVEN THE
UNCERTAINTY SURROUNDING CLOUD COVER ON SUNDAY...WENT WITH A BLEND OF
GUIDANCE FOR HIGHS. THE BLEND OF GUIDANCE LOOKS GOOD TOO FOR LOWS
SUNDAY NIGHT AS IT HANDLES THE CLOUD COVER INCREASE FINE.
.LONG TERM...MONDAY THROUGH THURSDAY
240 AM CST FRI DEC 21 2012
21.00Z ECMWF/GFS/CANADIAN/UKMET ARE IN FAIRLY GOOD AGREEMENT BOTH
WITH THE UPPER AND SURFACE PATTERNS THROUGHOUT THE LONG TERM PERIOD.
MAIN STORM TRACK THROUGHOUT THE LONG TERM IS SOUTH OF THE FORECAST
AREA...WHERE THERE APPEARS TO BE A STORM SYSTEM THAT CROSSES THE
SOUTHERN PLAINS INTO THE MID-ATLANTIC REGION INTO NEW ENGLAND
BETWEEN TUESDAY THROUGH THURSDAY. TRENDS CONTINUE SOUTH WITH THIS
SYSTEM...THUS ALL PRECIPITATION STAYS AWAY FROM THE FORECAST AREA.
THE ONLY SYSTEM REALLY TO DEAL WITH IS THAT UPPER TROUGH AND
INVERTED TROUGH APPROACHING THE FORECAST AREA SUNDAY NIGHT. MODELS
SUGGEST THE UPPER TROUGH IS ACTUALLY SPLIT INTO TWO PARTS...WITH THE
MAIN FEATURE/SHORTWAVE IN IT TRACKING ACROSS THE OHIO RIVER VALLEY.
WE HAVE THE NORTHERN PART OF THE TROUGH CROSSING THE FORECAST
AREA MONDAY INTO MONDAY NIGHT...BUT ALL THE BETTER MOISTURE IS WITH
THE SOUTHERN SHORTWAVE. THE 21.00Z ECMWF BASICALLY CAME IN DRY WITH
THE NORTHERN PART OF THE TROUGH AND THE 21.00Z GFS ONLY HAS SOME
VERY LIGHT QPF. GIVEN THE LACK OF MOISTURE...ESPECIALLY BELOW
700MB...ONLY HAVE 20 PERCENT CHANCES OF PRECIPITATION IN THE
FORECAST FOR MONDAY AND MONDAY NIGHT. IF TRENDS CONTINUE...THESE
COULD BE PULLED IN LATER FORECASTS.
WITH A STORM TRACK MORE TO THE SOUTH OF THE FORECAST AREA...THIS
MEANS NO WARM UPS ARE IN STORE. IN FACT...THE BULK OF THE PERIOD
SHOULD AVERAGE BELOW NORMAL AS 925MB TEMPS COOL TO -10 TO -12C FOR
TUESDAY AND WEDNESDAY BEHIND THE INVERTED TROUGH. SOME SLIGHT
WARMING SHOULD OCCUR FOR THURSDAY. SOMETHING TO WATCH IS IF WE END
UP WITH CLEAR SKIES AND LIGHT WINDS AT NIGHT...SINCE SNOW COVER IS
VERY FAVORABLE FOR HAVING TEMPERATURES PLUMMET.
&&
.AVIATION...TODAY AND TONIGHT
531 AM CST FRI DEC 21 2012
GUSTY NORTHWEST WINDS WILL CONTINUE THROUGH THIS MORNING...THEN
SLOWLY SUBSIDE THIS AFTERNOON. OTHERWISE...MOSTLY CLEAR/VFR CONDITIONS
EXPECTED AT KRST/KLSE TAF SITES THROUGH TONIGHT AS A RIDGE OF HIGH
PRESSURE DRIFTS ACROSS THE UPPER MISSISSIPPI RIVER REGION.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
240 AM CST FRI DEC 21 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...AJ
LONG TERM...AJ
AVIATION...DAS
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
240 AM CST FRI DEC 21 2012
.SHORT TERM...TODAY THROUGH SUNDAY NIGHT
240 AM CST FRI DEC 21 2012
MAIN FORECAST CONCERNS TO BEGIN THE FIRST DAY OF WINTER ARE ON
TEMPERATURES TONIGHT...ANY LOW CLOUD POTENTIAL SATURDAY NIGHT INTO
SUNDAY...AND ANY PRECIPITATION POTENTIAL SUNDAY NIGHT.
CURRENTLY AS OF 08Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED DEEP TROUGHING OFF THE WEST COAST OF THE U.S....RIDGING
BUILDING ALONG THE LEE OF THE ROCKIES INTO SOUTH CENTRAL CANADA...
AND DEEP TROUGHING FROM THE GREAT LAKES INTO THE SOUTHEASTERN U.S..
THE LATTER DEEP TROUGHING CONTAINS THE STRONG STORM SYSTEM THAT
BROUGHT THE SNOW AND STRONG WINDS TO THE FORECAST AREA YESTERDAY.
ROADS STILL REMAIN HAZARDOUS TOO...ESPECIALLY OVER THE SOUTHEASTERN
PORTION OF THE FORECAST AREA. WINDS REMAIN BRISK...DUE TO A TIGHT
PRESSURE GRADIENT BETWEEN 987MB LOW PRESSURE NEAR DETROIT AND A
1025MB HIGH PRESSURE RIDGE OVER THE EASTERN DAKOTAS. WITH THE
FORECAST AREA EXPERIENCING RISING HEIGHTS AT 500MB...ABOUT 40 METERS
SINCE 00Z ACCORDING TO THE RAP...SUBSIDENCE HAS BEEN ON THE
INCREASE. DRY ADVECTION WAS ALSO OCCURRING...NOTED BY THE
PRECIPITABLE WATER DROPPING AT MPX FROM 0.33 INCHES AT 12Z ON THE
20TH TO 0.16 INCHES AT 00Z. THE COMBINATION OF SUBSIDENCE AND DRYING
HAS LED TO CLEARING SKIES IN THE WAKE OF THE STORM SYSTEM. CLEARING
LINE STRETCHED FROM EAU CLAIRE TO LA CROSSE AND DUBUQUE. COLDER AIR
ALSO ACCOMPANYING THE SUBSIDENCE AND DRYING...REFLECTED BY SURFACE
TEMPERATURES IN THE SINGLE DIGITS ACROSS WESTERN PORTIONS OF
MINNESOTA AND IOWA...AND IN THE SINGLE DIGITS BELOW ZERO OVER THE
EASTERN DAKOTAS UNDER THE SURFACE RIDGE. 925MB TEMPS AT MPX AT 00Z
WERE -10C...ABOUT 3 COLDER THAN 12 HOURS EARLIER.
TODAY AND TONIGHT...THE UPPER RIDGING ALONG THE LEE OF THE ROCKIES
WILL SHIFT EASTWARD INTO THE PLAINS BY TONIGHT IN RESPONSE TO THE
DEEP EAST PACIFIC TROUGH APPROACHING THE WESTERN U.S. COAST. WITH
THE UPPER RIDGING TRYING TO PUSH INTO THE FORECAST AREA...MID LEVEL
HEIGHTS WILL CONTINUE TO CLIMB...MAINTAINING THE SUBSIDENCE. IN
ADDITION...THE SHIFT EAST IN THE UPPER PATTERN OCCURS AT THE SURFACE
AS WELL...WITH THE HIGH PRESSURE RIDGE SHIFTING EAST OVER THE
FORECAST AREA AROUND MIDNIGHT. WITH THE SUBSIDENCE AND DRYING
PATTERN IN PLACE...EXPECT A DRY PERIOD. IN FACT...OTHER THAN A FEW
HIGH CLOUDS AFTER MIDNIGHT TONIGHT CROSSING THE UPPER RIDGE...SKIES
SHOULD BE MAINLY CLEAR. DESPITE THE PLENTIFUL SUNSHINE TODAY...
BREEZY NORTHWEST WINDS COMBINED WITH 925MB TEMPS IN THE -6 TO -10C
RANGE AND FRESH SNOW COVER WILL LIMIT HEATING. HIGHS SHOULD TOP OUT
FROM THE MID TEENS TO MID 20S...COLDEST OVER THE HIGHER ALBEDO
PRESENT WEST OF THE MISSISSIPPI RIVER. CONCERN FOR TEMPERATURES
PLUMMETING TONIGHT GIVEN THE COOLER DAY TODAY...DECOUPLING WINDS AND
MOSTLY CLEAR SKIES. HAVE LEANED TOWARDS THE COLD SIDE OF GUIDANCE AS
A RESULT.
SATURDAY AND SATURDAY NIGHT...MODELS ARE POINTING TO A SHORTWAVE
CURRENTLY IN SOUTHEAST BRITISH COLUMBIA TOPPING THE RIDGE AND MOVING
THROUGH EASTERN LAKE SUPERIOR SATURDAY NIGHT. ALTHOUGH THIS
SHORTWAVE IS FAR FROM US...A COLD FRONT ACCOMPANIES THE SHORTWAVE
WHICH SLIDES THROUGH THE FORECAST AREA SATURDAY NIGHT. AHEAD OF THE
FRONT...WE SEE SOME 925MB WARMING...PROGGED TO CLIMB TO -2C OR SO
BY 18Z SATURDAY. 850MB TEMPS ARE EVEN WARMER...0-3C OR SO...BUT
THERE IS NO WAY OF MIXING UP TO THIS DUE TO BEING NOW AT THE
SHORTEST DAY LENGTH AND HAVING THE FRESH SNOW. NEVERTHELESS...
COMBINATION OF SUN THROUGH SOME HIGH CLOUDS AND SOUTHWEST WINDS
PICKING UP A BIT SHOULD ALLOW TEMPERATURES TO CLIMB INTO THE 20S
EVERYWHERE. SOME VALLEY LOCATIONS COULD PUSH 30. NOT ANTICIPATING
ANY PRECIPITATION TO ACCOMPANY THE FRONTAL PASSAGE...DUE TO
PLENTIFUL DRY AIR AND ALL FORCING WELL NORTHEAST OF THE AREA.
HOWEVER...AFTER THE FRONTAL PASSAGE...CONCERNED THERE MAY BE AN
INCREASE OF LOW CLOUDS AS SUGGESTED BY 21.00Z GFS 925MB RH FIELDS.
THE 21.00Z NAM AND ECMWF 925MB RH FIELD ARE NOT NEARLY AS
PESSIMISTIC AND THUS WILL CONTINUE WITH THE PREVIOUS MOSTLY CLEAR
FORECAST. COMBINATION OF COLD ADVECTION IN THE WAKE OF THE FRONT AND
RADIATIONAL COOLING ARE EXPECTED TO SEND TEMPERATURES BACK DOWN INTO
THE SINGLE DIGITS AND TEENS.
SUNDAY AND SUNDAY NIGHT...SOME OF THE CURRENT EASTERN PACIFIC TROUGH
IS PROGGED BY ALL MODELS TO HEAD EAST INTO THE PLAINS SUNDAY NIGHT.
ASSOCIATED WITH THIS UPPER TROUGHING IS A NORTHWEST TO SOUTHEAST
ORIENTED INVERTED TROUGH AT THE SURFACE...WHICH BY 12Z MONDAY SHOULD
HAVE REACHED AT LEAST SIOUX FALLS PER MODEL CONSENSUS. GIVEN THE
APPROACH OF THE UPPER AND INVERTED SURFACE TROUGH...ONE WOULD EXPECT
AN ISENTROPIC LIFT PATTERN...WHICH INDEED EXISTS. HOWEVER...ANY
ISENTROPIC LIFT IS ROOTED ON THE 290-300K SURFACES WHICH PUTS IT AT
A PRESSURE LEVEL OF 700MB OR HIGHER...AND MORE TOWARDS 12Z.
THEREFORE...NOT SURE IF ANY PRECIPITATION CAN MAKE IT TO THE
SURFACE. THE 21.00Z NAM/GFS ARE BOTH DRY FOR SUNDAY NIGHT. AS
SUCH...HAVE KEPT A DRY FORECAST GOING. LOW CLOUD COVER CONCERN STILL
EXISTS HERE FOR SUNDAY AND SUNDAY NIGHT...ESPECIALLY IF SOME MOVE IN
BEHIND THE SATURDAY NIGHT COLD FRONT. SHOULD LOW CLOUDS MOVE
IN...LIKELY SUNDAY AND SUNDAY NIGHT WILL END UP CLOUDY. CLOUDS ARE
GOING TO INCREASE ANYWAY...ESPECIALLY SUNDAY NIGHT ASSOCIATED WITH
THE ISENTROPIC LIFT REGIME AHEAD OF THE UPPER TROUGH. GIVEN THE
UNCERTAINTY SURROUNDING CLOUD COVER ON SUNDAY...WENT WITH A BLEND OF
GUIDANCE FOR HIGHS. THE BLEND OF GUIDANCE LOOKS GOOD TOO FOR LOWS
SUNDAY NIGHT AS IT HANDLES THE CLOUD COVER INCREASE FINE.
.LONG TERM...MONDAY THROUGH THURSDAY
240 AM CST FRI DEC 21 2012
21.00Z ECMWF/GFS/CANADIAN/UKMET ARE IN FAIRLY GOOD AGREEMENT BOTH
WITH THE UPPER AND SURFACE PATTERNS THROUGHOUT THE LONG TERM PERIOD.
MAIN STORM TRACK THROUGHOUT THE LONG TERM IS SOUTH OF THE FORECAST
AREA...WHERE THERE APPEARS TO BE A STORM SYSTEM THAT CROSSES THE
SOUTHERN PLAINS INTO THE MID-ATLANTIC REGION INTO NEW ENGLAND
BETWEEN TUESDAY THROUGH THURSDAY. TRENDS CONTINUE SOUTH WITH THIS
SYSTEM...THUS ALL PRECIPITATION STAYS AWAY FROM THE FORECAST AREA.
THE ONLY SYSTEM REALLY TO DEAL WITH IS THAT UPPER TROUGH AND
INVERTED TROUGH APPROACHING THE FORECAST AREA SUNDAY NIGHT. MODELS
SUGGEST THE UPPER TROUGH IS ACTUALLY SPLIT INTO TWO PARTS...WITH THE
MAIN FEATURE/SHORTWAVE IN IT TRACKING ACROSS THE OHIO RIVER VALLEY.
WE HAVE THE NORTHERN PART OF THE TROUGH CROSSING THE FORECAST
AREA MONDAY INTO MONDAY NIGHT...BUT ALL THE BETTER MOISTURE IS WITH
THE SOUTHERN SHORTWAVE. THE 21.00Z ECMWF BASICALLY CAME IN DRY WITH
THE NORTHERN PART OF THE TROUGH AND THE 21.00Z GFS ONLY HAS SOME
VERY LIGHT QPF. GIVEN THE LACK OF MOISTURE...ESPECIALLY BELOW
700MB...ONLY HAVE 20 PERCENT CHANCES OF PRECIPITATION IN THE
FORECAST FOR MONDAY AND MONDAY NIGHT. IF TRENDS CONTINUE...THESE
COULD BE PULLED IN LATER FORECASTS.
WITH A STORM TRACK MORE TO THE SOUTH OF THE FORECAST AREA...THIS
MEANS NO WARM UPS ARE IN STORE. IN FACT...THE BULK OF THE PERIOD
SHOULD AVERAGE BELOW NORMAL AS 925MB TEMPS COOL TO -10 TO -12C FOR
TUESDAY AND WEDNESDAY BEHIND THE INVERTED TROUGH. SOME SLIGHT
WARMING SHOULD OCCUR FOR THURSDAY. SOMETHING TO WATCH IS IF WE END
UP WITH CLEAR SKIES AND LIGHT WINDS AT NIGHT...SINCE SNOW COVER IS
VERY FAVORABLE FOR HAVING TEMPERATURES PLUMMET.
&&
.AVIATION...
1100 PM CST THU DEC 20 2012
TIGHT PRESSURE GRADIENT PERSISTS THROUGH FRI MORNING...BUT WILL
SLACKEN LATER IN THE DAY AS HIGH PRESSURE BUILDS IN FROM THE WEST.
STRONG WINDS SHOULD STILL RESULT IN A FEW HOURS OF BLSN
OVERNIGHT...WITH MINOR REDUCTION IN VSBY. COULD BE SOME IMPACTS ON
RUNWAY CLEARING DUE TO THE BLOWING/DRIFTING SNOW.
LOW CIGS ARE EXPECTED TO CLEAR OVERNIGHT ALSO...ALTHOUGH LATEST
FOG/STRATUS SATELLITE IMAGERY SHOWS ANOTHER BATCH OF LOW STRATUS
SINKING SOUTHWARD ACROSS NORTHERN MN. RAP13/NAM12 TRENDS ARE TO KEEP
THE BULK OF THIS CLOUDINESS TO THE WEST/NORTHWEST...WITH SOME
DISSIPATION DURING THE DAY. KRST COULD BE IMPACTED THOUGH. WILL
LEAVE SKC-SCT FOR NOW...BUT UPDATES COULD BE NEEDED IF THE CLOUDS
TREND MORE EAST.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
240 AM CST FRI DEC 21 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...AJ
LONG TERM...AJ
AVIATION.....RIECK
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 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
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
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 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 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 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 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 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 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
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 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 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 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 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.
&&
$$
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
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