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. && $$ VISIT US AT HTTP://WWW.WEATHER.GOV/EUREKA FOLLOW US ON FACEBOOK AND TWITTER AT: HTTP://WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.EUREKA.GOV HTTP://WWW.TWITTER.COM/NWSEUREKA
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. && $$
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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