Forecast Discussions mentioning any of "HRRR" "RR" "RUC13" "RUC" received at GSD on 12/08/11


AREA FORECAST DISCUSSION
NWS ALBANY NY
942 PM EST WED DEC 7 2011 .SYNOPSIS... A STORM SYSTEM WILL LIFT NORTHEAST FROM THE DELMARVA REGION THIS EVENING...TO THE EAST END OF LONG ISLAND AROUND MIDNIGHT...AND THEN INTO THE GULF OF MAINE THURSDAY MORNING. THIS STORM TRACK WILL RESULT IN RAIN CHANGING TO SNOW THIS EVENING ACROSS MUCH OF THE REGION WITH SIGNIFICANT SNOWFALL ACCUMULATIONS OVERNIGHT IN MANY AREAS. THE HEAVIEST SNOW IS EXPECTED TO FALL ACROSS THE NORTHERN TACONICS...EASTERN CATSKILLS...BERKSHIRES AND SOUTHERN GREEN MOUNTAINS. HEAVY RAIN WILL CONTINUE TO FALL OVERNIGHT ACROSS THE MID HUDSON VALLEY AND LITCHFIELD HILLS. && .NEAR TERM /THROUGH THURSDAY/... AS OF 930PM RADAR FSI CROSS SECTIONS AND SPOTTER REPORTS HAVE RAIN CHANGING TO SNOW AROUND THE GREATER CAPITAL DISTRICT. THIS IS RUNNING AN HOUR OR TWO BEHIND GRIDS AND MADE MINOR CHANGES. THIS PROCESS WILL RAPIDLY CHANGE RAIN OVER TO SNOW IN NEXT 1-2 HOURS. 00UTC NAM IN LINE WITH PVS QPF AND THINKING. NO DEPARTURES THERE. ONCE PCPN CHANGES OVER BURST OF SNOW FOR SEVERAL HOURS IN MASSIVE TILTED FRONTOGENESIS AS MESOSCALE BAND HAS SET UP FM SW VT TO CATSKILLS (CSTAR) WHILE PCPN MAY BE CHANGING OVER 1-2 HOURS LATER...DONT THINK IT WILL SIGNIFICANTLY ALTER CURRENT THINKING ON AMOUNTS OR HEADLINES GIVEN CHARACTER AND FORCING OF THE SNOW OVERNIGHT. ALL 3 HOUR PRESSURE MAX FALLS ARE NOW OFFSHORE NJ/DELMARVA. RAPID DEEPENING WILL OCCUR NEXT FEW HOURS AS 500HPA SHORT WAVE INTERACT WITH STRONG BAROCLINIC ZONE ALONG COAST. AS OF 7PM...NOT MAKING ANY CHANGES ATTM. AWAITING CHANGE OVER TO SNOW. ON ALB 00UTC ALB SOUNDING +4C WARM NOSE REMAINS AT 3500 MSL. FSI CROSS SECTIONS CAPPI INDICATE BRIGHT BAND LOWERING TO GROUND IN MONTGOMERY/SCHOHARIE COUNTIES...BUT ONLY ONE REPORT OF SNOW IN WEST SCHOHARIE COUNTY AN HOUR AGO. BANDLETS (CSTAR III) HAVE SET UP ACROSS RGN WITH SOME ALONG BRIGHT BAND AXISES AND OTHERS IN RN TO +RN AREAS. 18UTC NAM/GFS SHOW ALL THE RIGHT FEATURES FOR FORMATION OF A MAJOR BAND OVER FCA. 20UVM IN MAX DENDRITIC GROWN ZONE BY 03UTC...STRONG TILTED FRONTOGENESIS AND EPV. SO THE STAGE IS SET...JUST AWAITING THE ARRIVAL OF THE COLDER AIR OR ITS DYNAMIC CREATION. SFC PRES FALLS HAVE SHIFTED TO NJ-DELMARVA COAST BUT 3HR VALUES REMAIN REMAIN ON ORDER OF 4-6MB. WX WATCH CONTINUES. WINTER STORM WARNINGS ARE IN EFFECT FOR TONIGHT FOR THE EASTERN CATSKILLS...NORTHERN TACONICS...BERKSHIRES AND SOUTHERN GREEN MOUNTAINS AND WINTER WEATHER ADVISORIES IN EFFECT FOR THE SOUTHEAST ADIRONDACKS...LAKE GEORGE SARATOGA REGION...EASTERN MOHAWK VALLEY...SACANDAGA REGION...GREATER CAPITAL DISTRICT AND CENTRAL TACONICS. A FLOOD WATCH IS IN EFFECT THROUGH THURSDAY MORNING FOR THE MID HUDSON VALLEY...SOUTHERN TACONICS AND LITCHFIELD HILLS. SNOWFALL ACCUMULATIONS ARE GENERALLY EXPECTED TO BE 3 TO 8 INCHES IN THE ADVISORY AREA AND 5 TO 12 INCHES IN THE WARNING AREA EXCEPT ACROSS THE CENTRAL AND SOUTHEAST CATSKILLS...NORTHERN BERKSHIRES AND HIGHER TERRAIN OF THE SOUTHERN GREEN MOUNTAINS WHERE 8 TO 16 INCHES OF SNOW IS EXPECTED. TOTAL RAINFALL AMOUNTS IN THE FLOOD WATCH AREA ARE EXPECTED TO BE IN THE 1.75 TO 2.25 INCH RANGE. AS OF 530 PM EST...CLOUD TOPS CONTINUE TO COOL ACROSS THE FA WITH 21Z KALB SOUNDING INDICATING A WARM TONGUE OF 4C AT AROUND 875 MB WITH THE FREEZING LEVEL AT AROUND 775 MB OR 6.6 KFT. HAVE RECEIVED A REPORT OF 1 INCH OF SNOW THUS FAR IN CHARLOTTEVILLE IN SCHOHARIE COUNTY WITH HEAVY WET SNOW AND A TEMP OF 36 DEGREES AT AN ELEVATION OF AROUND 1500 FEET. EXPECT A RAPID CHANGEOVER TO SNOW THIS EVENING ACROSS MUCH OF THE FA MAINLY BETWEEN 00Z AND 03Z WITH VERY HEAVY SNOW EXPECTED TO FALL DURING MUCH OF THE NIGHT BEFORE TAPERING OFF LATE. THE ONLY AREAS WHICH ARE NOT EXPECTED TO RECEIVE MUCH SNOW ARE FAR NORTHWEST PORTIONS OF THE FA INCLUDING THE WESTERN ADIRONDACKS AND WESTERN MOHAWK VALLEY WHERE VERY LITTLE QPF EXPECTED...NORTHERN FRINGE OF PCPN SHIELD AND FAR SOUTHEAST PORTION OF FA WHICH WILL REMAIN TOO WARM FOR MUCH IN THE WAY OF SNOW MAINLY FROM THE MID HUDSON VALLEY EAST TO THE LITCHFIELD HILLS WHERE A FLOOD WATCH IS IN EFFECT. MANY FAVORABLE FACTORS FOR HEAVY SNOW ARE IN PLACE ACROSS MUCH OF THE FA WITH THE MOST SIGNIFICANT FACTORS BEING IMPRESSIVE FRONTOGENESIS H8-H7 EXTENDING FROM THE CATSKILLS NORTHEAST TO SOUTHERN VERMONT AT 00Z AND THEN SHIFTING TO AN ORIENTATION FROM JUST EAST OF THE CAPITAL DISTRICT THROUGH THROUGH THE NORTHERN BERKSHIRES INTO SOUTHERN VERMONT AT 06Z. AS THE EVENING WEARS ON THE SNOW GROWTH REGION BECOMES INCREASINGLY MORE FAVORABLE WITH THE -12 TO -18 C TEMP SLICING THROUGH A REGION OF +20 UBAR/SEC. IN ADDITION IMPRESSIVE EPV EXISTS IN LOWER LEVELS ESPECIALLY BTWN 00Z AND 06Z. THE LATEST HRRR COL MAX REFLECTIVITY ALSO INDICATES IMPRESSIVE BANDED PCPN ESPECIALLY ACROSS THE HIGHER TERRAIN IN THE WARNING AREA BETWEEN 03Z AND 06Z WITH THE BACK EDGE OF THE PCPN SHIELD EXITING THE FA FROM WEST TO EAST BETWEEN 08Z AND 10Z. EXPECT LOW TEMPS TONIGHT TO RANGE FROM THE MID 20S NORTHWEST TO MID 30S FAR SOUTHEAST. ON THURSDAY EXPECT IMPROVING CONDITIONS WITH HIGH PRESSURE MOVING IN AND MAINLY DRY CONDITIONS WITH HIGHS RANGING FROM THE UPPER 20S TO LOWER 30S NORTHWEST TO LOWER 40S FAR SOUTHEAST. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... THU NT...BACKING LOW LEVEL WINDS SHOULD ALLOW ANY LINGERING SNOW BANDS/SNOW SHOWERS TO SHIFT NORTHWARD INTO THE WESTERN ADIRONDACKS...WITH ADDITIONAL ACCUMS POSSIBLE BEFORE INVERSION HEIGHTS LOWER AND DIMINISH INTENSITY OF ANY SNOWBANDS. ELSEWHERE...INITIALLY CLEAR TO PARTLY CLOUDY SKIES SHOULD BECOME MOSTLY CLOUDY LATER AT NIGHT AS MID LEVEL ISENTROPIC LIFT INCREASES AHEAD OF NEXT APPROACHING SHORTWAVE. EXPECT MINS TO FALL INTO THE TEENS AND 20S...WARMEST ACROSS VALLEY REGIONS. FRI-SAT...UPPER LEVEL TROUGH WILL APPROACH FROM THE W...AND PASS ACROSS FRI NT. A SFC COLD FRONT ASSOCIATED WITH THIS FEATURE WILL CROSS THE REGION LATE FRI OR FRI EVE...PRECEDED AND ACCOMPANIED BY SNOW SHOWERS. THEN...BEHIND THE FRONT...BANDS OF SNOW SHOWERS AND POSSIBLE SNOW SQUALLS WILL BE POSSIBLE...INITIALLY FAVORING PORTIONS OF THE WESTERN MOHAWK VALLEY/SCHOHARIE VALLEY...THEN GRADUALLY SHIFTING NORTHWARD INTO THE WESTERN ADIRONDACKS BY SAT. THERE IS SOME POTENTIAL FOR LOCALLY HEAVY SNOWFALL AMTS WITHIN SOME OF THESE BANDS...AND WILL MENTION THIS POSSIBILITY IN THE HWO...WITH GREATEST THREAT ACROSS THE WESTERN ADIRONDACKS. EXPECT FRI MAXES TO REACH THE 30S IN MOST AREAS...EXCEPT AROUND OR INTO THE LOWER 40S WITHIN THE VALLEYS...WITH 20S ACROSS HIGHER ELEVATIONS. COLDER AIR BEHIND THE FRONT WILL MOVE IN FOR FRI NT AND SAT...WITH FRI NT MINS IN THE TEENS AND LOWER 20S...AND SAT MAXES MAINLY IN THE 30S WITHIN VALLEYS...AND 20S ACROSS HIGHER ELEVATIONS. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... THIS PERIOD WILL BE FAIRLY QUIET AS HIGH PRESSURE BUILDS INTO THE MID ATLANTIC REGION SATURDAY NIGHT AND DOMINATES OUR WEATHER INTO THE EARLY PART OF THE COMING WEEK. A CHANCE OF SOME LAKE ENHANCED SNOW SHOWERS SATURDAY NIGHT...THEN DRY UNTIL TUESDAY NIGHT WHEN A WEAK BOUNDARY BRINGS ABOUT SOME SNOW AND RAIN SHOWERS WEST OF THE HUDSON VALLEY WEDNESDAY. THE PERIOD STARTS OFF CHILLY...LOWS FROM AROUND 10 TO 20 ABOVE ON SUNDAY MORNING...WITH HIGHS SUNDAY ONLY IN THE UPPER 20S TO THE MID 30S. TEMPERATURES WILL GRADUALLY MODERATE WITH HIGHS RISING TO THE UPPER 30S AND LOWER 40S BY TUESDAY AFTERNOON. FOR THE MOST PART...USED HPC GUIDANCE TO POPULATE THE GRIDS. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... WIDESPREAD IFR CONDITIONS ARE EXPECTED THROUGH AT LEAST 08Z/THU...WITH PERHAPS JUST SOME BRIEF IMPROVEMENTS TO MVFR VSBYS AT TIMES. RAIN AND DRIZZLE WILL CONTINUE INTO THIS EVENING...WITH SOME PERIODS OF MODERATE TO HEAVY RAIN POSSIBLE. THEN...A TRANSITION TO WET SNOW IS TO OCCUR LATER THIS EVENING...ROUGHLY BETWEEN 01Z-03Z/THU AT KGFL AND KALB...AND NOT UNTIL AFTER 06Z/THU AT KPOU. THE SNOW MAY BE MODERATE TO HVY IN INTENSITY...ESP AT KALB AND POSSIBLY KPOU. PRECIPITATION SHOULD DECREASE IN INTENSITY FROM W TO E BETWEEN 07Z-09Z/THU...AND ENDING BY 11Z/THU IN ALL AREAS. FOR THU...EXPECT MAINLY VFR CONDITIONS...EXCEPT POSSIBLY SOME MVFR CIGS/VSBY IN ISOLATED SNOW SHOWERS AT KGFL AND KALB LATER IN THE AFTERNOON. WINDS WILL REMAIN FROM THE NORTH TO NORTHEAST AT 5-10 KT THIS AFTERNOON AND EARLY EVENING...THEN SHIFT INTO THE N...THEN NW AND INCREASE TO 10-20 KT AFTER 05Z/THU. WINDS WILL THEN BACK INTO THE NW TO W...AND INCREASE TO 15-25 KT AFTER 14Z/THU...WITH SOME GUSTS POSSIBLY REACHING 30-35 KT AT KALB. OUTLOOK... THU NT-SAT...MAINLY VFR...SLIGHT CHC -SHSN. BREEZY. SUN-MON...VFR...NO SIG WX. && .HYDROLOGY... A SIGNIFICANT MIXED PRECIPITATION EVENT WAS OCCURRING ACROSS THE REGION WITH STORM TOTAL LIQUID AMOUNTS FROM LESS THAN A QUARTER INCH IN NORTHERN HERKIMER COUNTY TO A LITTLE OVER TWO INCHES IN THE LOWER HUDSON VALLEY OF NEW YORK AND THE LITCHFIELD HILLS OF CONNECTICUT. OVER COOLER REGIONS SUCH AS THE HIGHER ELEVATIONS OF THE CATSKILLS...BERKSHIRES...AND GREEN MOUNTAINS OF SOUTHERN VERMONT A SUBSTANTIAL AMOUNT OF THIS PRECIPITATION IS FORECAST TO COME AS SNOW. ACROSS OUR SOUTHERNMOST COUNTIES...EASTERN ULSTER DUTCHESS...AND LITCHFIELD...MOST OF THE PRECIPITATION WILL COME AS RAIN AND LOCALLY HEAVY AMOUNTS MAY AMOUNT TO ENOUGH TO RESULT IN SOME MINOR FLOODING OF ROADS AND PARKING AREAS AND CAUSE RISES OF SEVERAL FEET ON RIVERS AND STREAMS. FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...FLOOD WATCH UNTIL 9 AM EST THURSDAY FOR CTZ001-013. NY...WINTER STORM WARNING UNTIL 6 AM EST THURSDAY FOR NYZ047-051- 054-058-063. WINTER WEATHER ADVISORY UNTIL 6 AM EST THURSDAY FOR NYZ039>043- 048>050-052-053-059>061-082>084. FLOOD WATCH UNTIL 9 AM EST THURSDAY FOR NYZ064>066. MA...WINTER STORM WARNING UNTIL 6 AM EST THURSDAY FOR MAZ001-025. VT...WINTER STORM WARNING UNTIL 6 AM EST THURSDAY FOR VTZ013-014. WINTER WEATHER ADVISORY UNTIL 6 AM EST THURSDAY FOR VTZ015. && $$ SYNOPSIS...11 NEAR TERM...11/SNYDER SHORT TERM...KL LONG TERM...RCK AVIATION...RCK HYDROLOGY...RCK
AREA FORECAST DISCUSSION
NWS ALBANY NY
703 PM EST WED DEC 7 2011 .SYNOPSIS... A STORM SYSTEM WILL LIFT NORTHEAST FROM THE DELMARVA REGION THIS EVENING...TO THE EAST END OF LONG ISLAND AROUND MIDNIGHT...AND THEN INTO THE GULF OF MAINE THURSDAY MORNING. THIS STORM TRACK WILL RESULT IN RAIN CHANGING TO SNOW THIS EVENING ACROSS MUCH OF THE REGION WITH SIGNIFICANT SNOWFALL ACCUMULATIONS OVERNIGHT IN MANY AREAS. THE HEAVIEST SNOW IS EXPECTED TO FALL ACROSS THE NORTHERN TACONICS...EASTERN CATSKILLS...BERKSHIRES AND SOUTHERN GREEN MOUNTAINS. HEAVY RAIN WILL CONTINUE TO FALL OVERNIGHT ACROSS THE MID HUDSON VALLEY AND LITCHFIELD HILLS. && .NEAR TERM /THROUGH THURSDAY/... AS OF 7PM...NOT MAKING ANY CHANGES ATTM. AWAITING CHANGE OVER TO SNOW. ON ALB 00UTC ALB SOUNDING +4C WARM NOSE REMAINS AT 3500 MSL. FSI CROSS SECTIONS CAPPI INDICATE BRIGHT BAND LOWERING TO GROUND IN MONTGOMERY/SCHOHARIE COUNTIES...BUT ONLY ONE REPORT OF SNOW IN WEST SCHOHARIE COUNTY AN HOUR AGO. BANDLETS (CSTAR III) HAVE SET UP ACROSS RGN WITH SOME ALONG BRIGHT BAND AXISES AND OTHERS IN RN TO +RN AREAS. 18UTC NAM/GFS SHOW ALL THE RIGHT FEATURES FOR FORMATION OF A MAJOR BAND OVER FCA. 20UVM IN MAX DENDRITIC GROWN ZONE BY 03UTC...STRONG TILTED FRONTOGENESIS AND EPV. SO THE STAGE IS SET...JUST AWAITING THE ARRIVAL OF THE COLDER AIR OR ITS DYNAMIC CREATION. SFC PRES FALLS HAVE SHIFTED TO NJ-DELMARVA COAST BUT 3HR VALUES REMAIN REMAIN ON ORDER OF 4-6MB. WX WATCH CONTINUES. WINTER STORM WARNINGS ARE IN EFFECT FOR TONIGHT FOR THE EASTERN CATSKILLS...NORTHERN TACONICS...BERKSHIRES AND SOUTHERN GREEN MOUNTAINS AND WINTER WEATHER ADVISORIES IN EFFECT FOR THE SOUTHEAST ADIRONDACKS...LAKE GEORGE SARATOGA REGION...EASTERN MOHAWK VALLEY...SACANDAGA REGION...GREATER CAPITAL DISTRICT AND CENTRAL TACONICS. A FLOOD WATCH IS IN EFFECT THROUGH THURSDAY MORNING FOR THE MID HUDSON VALLEY...SOUTHERN TACONICS AND LITCHFIELD HILLS. SNOWFALL ACCUMULATIONS ARE GENERALLY EXPECTED TO BE 3 TO 8 INCHES IN THE ADVISORY AREA AND 5 TO 12 INCHES IN THE WARNING AREA EXCEPT ACROSS THE CENTRAL AND SOUTHEAST CATSKILLS...NORTHERN BERKSHIRES AND HIGHER TERRAIN OF THE SOUTHERN GREEN MOUNTAINS WHERE 8 TO 16 INCHES OF SNOW IS EXPECTED. TOTAL RAINFALL AMOUNTS IN THE FLOOD WATCH AREA ARE EXPECTED TO BE IN THE 1.75 TO 2.25 INCH RANGE. AS OF 530 PM EST...CLOUD TOPS CONTINUE TO COOL ACROSS THE FA WITH 21Z KALB SOUNDING INDICATING A WARM TONGUE OF 4C AT AROUND 875 MB WITH THE FREEZING LEVEL AT AROUND 775 MB OR 6.6 KFT. HAVE RECEIVED A REPORT OF 1 INCH OF SNOW THUS FAR IN CHARLOTTEVILLE IN SCHOHARIE COUNTY WITH HEAVY WET SNOW AND A TEMP OF 36 DEGREES AT AN ELEVATION OF AROUND 1500 FEET. EXPECT A RAPID CHANGEOVER TO SNOW THIS EVENING ACROSS MUCH OF THE FA MAINLY BETWEEN 00Z AND 03Z WITH VERY HEAVY SNOW EXPECTED TO FALL DURING MUCH OF THE NIGHT BEFORE TAPERING OFF LATE. THE ONLY AREAS WHICH ARE NOT EXPECTED TO RECEIVE MUCH SNOW ARE FAR NORTHWEST PORTIONS OF THE FA INCLUDING THE WESTERN ADIRONDACKS AND WESTERN MOHAWK VALLEY WHERE VERY LITTLE QPF EXPECTED...NORTHERN FRINGE OF PCPN SHIELD AND FAR SOUTHEAST PORTION OF FA WHICH WILL REMAIN TOO WARM FOR MUCH IN THE WAY OF SNOW MAINLY FROM THE MID HUDSON VALLEY EAST TO THE LITCHFIELD HILLS WHERE A FLOOD WATCH IS IN EFFECT. MANY FAVORABLE FACTORS FOR HEAVY SNOW ARE IN PLACE ACROSS MUCH OF THE FA WITH THE MOST SIGNIFICANT FACTORS BEING IMPRESSIVE FRONTOGENESIS H8-H7 EXTENDING FROM THE CATSKILLS NORTHEAST TO SOUTHERN VERMONT AT 00Z AND THEN SHIFTING TO AN ORIENTATION FROM JUST EAST OF THE CAPITAL DISTRICT THROUGH THROUGH THE NORTHERN BERKSHIRES INTO SOUTHERN VERMONT AT 06Z. AS THE EVENING WEARS ON THE SNOW GROWTH REGION BECOMES INCREASINGLY MORE FAVORABLE WITH THE -12 TO -18 C TEMP SLICING THROUGH A REGION OF +20 UBAR/SEC. IN ADDITION IMPRESSIVE EPV EXISTS IN LOWER LEVELS ESPECIALLY BTWN 00Z AND 06Z. THE LATEST HRRR COL MAX REFLECTIVITY ALSO INDICATES IMPRESSIVE BANDED PCPN ESPECIALLY ACROSS THE HIGHER TERRAIN IN THE WARNING AREA BETWEEN 03Z AND 06Z WITH THE BACK EDGE OF THE PCPN SHIELD EXITING THE FA FROM WEST TO EAST BETWEEN 08Z AND 10Z. EXPECT LOW TEMPS TONIGHT TO RANGE FROM THE MID 20S NORTHWEST TO MID 30S FAR SOUTHEAST. ON THURSDAY EXPECT IMPROVING CONDITIONS WITH HIGH PRESSURE MOVING IN AND MAINLY DRY CONDITIONS WITH HIGHS RANGING FROM THE UPPER 20S TO LOWER 30S NORTHWEST TO LOWER 40S FAR SOUTHEAST. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... THU NT...BACKING LOW LEVEL WINDS SHOULD ALLOW ANY LINGERING SNOW BANDS/SNOW SHOWERS TO SHIFT NORTHWARD INTO THE WESTERN ADIRONDACKS...WITH ADDITIONAL ACCUMS POSSIBLE BEFORE INVERSION HEIGHTS LOWER AND DIMINISH INTENSITY OF ANY SNOWBANDS. ELSEWHERE...INITIALLY CLEAR TO PARTLY CLOUDY SKIES SHOULD BECOME MOSTLY CLOUDY LATER AT NIGHT AS MID LEVEL ISENTROPIC LIFT INCREASES AHEAD OF NEXT APPROACHING SHORTWAVE. EXPECT MINS TO FALL INTO THE TEENS AND 20S...WARMEST ACROSS VALLEY REGIONS. FRI-SAT...UPPER LEVEL TROUGH WILL APPROACH FROM THE W...AND PASS ACROSS FRI NT. A SFC COLD FRONT ASSOCIATED WITH THIS FEATURE WILL CROSS THE REGION LATE FRI OR FRI EVE...PRECEDED AND ACCOMPANIED BY SNOW SHOWERS. THEN...BEHIND THE FRONT...BANDS OF SNOW SHOWERS AND POSSIBLE SNOW SQUALLS WILL BE POSSIBLE...INITIALLY FAVORING PORTIONS OF THE WESTERN MOHAWK VALLEY/SCHOHARIE VALLEY...THEN GRADUALLY SHIFTING NORTHWARD INTO THE WESTERN ADIRONDACKS BY SAT. THERE IS SOME POTENTIAL FOR LOCALLY HEAVY SNOWFALL AMTS WITHIN SOME OF THESE BANDS...AND WILL MENTION THIS POSSIBILITY IN THE HWO...WITH GREATEST THREAT ACROSS THE WESTERN ADIRONDACKS. EXPECT FRI MAXES TO REACH THE 30S IN MOST AREAS...EXCEPT AROUND OR INTO THE LOWER 40S WITHIN THE VALLEYS...WITH 20S ACROSS HIGHER ELEVATIONS. COLDER AIR BEHIND THE FRONT WILL MOVE IN FOR FRI NT AND SAT...WITH FRI NT MINS IN THE TEENS AND LOWER 20S...AND SAT MAXES MAINLY IN THE 30S WITHIN VALLEYS...AND 20S ACROSS HIGHER ELEVATIONS. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... THIS PERIOD WILL BE FAIRLY QUIET AS HIGH PRESSURE BUILDS INTO THE MID ATLANTIC REGION SATURDAY NIGHT AND DOMINATES OUR WEATHER INTO THE EARLY PART OF THE COMING WEEK. A CHANCE OF SOME LAKE ENHANCED SNOW SHOWERS SATURDAY NIGHT...THEN DRY UNTIL TUESDAY NIGHT WHEN A WEAK BOUNDARY BRINGS ABOUT SOME SNOW AND RAIN SHOWERS WEST OF THE HUDSON VALLEY WEDNESDAY. THE PERIOD STARTS OFF CHILLY...LOWS FROM AROUND 10 TO 20 ABOVE ON SUNDAY MORNING...WITH HIGHS SUNDAY ONLY IN THE UPPER 20S TO THE MID 30S. TEMPERATURES WILL GRADUALLY MODERATE WITH HIGHS RISING TO THE UPPER 30S AND LOWER 40S BY TUESDAY AFTERNOON. FOR THE MOST PART...USED HPC GUIDANCE TO POPULATE THE GRIDS. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... WIDESPREAD IFR CONDITIONS ARE EXPECTED THROUGH AT LEAST 08Z/THU...WITH PERHAPS JUST SOME BRIEF IMPROVEMENTS TO MVFR VSBYS AT TIMES. RAIN AND DRIZZLE WILL CONTINUE INTO THIS EVENING...WITH SOME PERIODS OF MODERATE TO HEAVY RAIN POSSIBLE. THEN...A TRANSITION TO WET SNOW IS TO OCCUR LATER THIS EVENING...ROUGHLY BETWEEN 01Z-03Z/THU AT KGFL AND KALB...AND NOT UNTIL AFTER 06Z/THU AT KPOU. THE SNOW MAY BE MODERATE TO HVY IN INTENSITY...ESP AT KALB AND POSSIBLY KPOU. PRECIPITATION SHOULD DECREASE IN INTENSITY FROM W TO E BETWEEN 07Z-09Z/THU...AND ENDING BY 11Z/THU IN ALL AREAS. FOR THU...EXPECT MAINLY VFR CONDITIONS...EXCEPT POSSIBLY SOME MVFR CIGS/VSBY IN ISOLATED SNOW SHOWERS AT KGFL AND KALB LATER IN THE AFTERNOON. WINDS WILL REMAIN FROM THE NORTH TO NORTHEAST AT 5-10 KT THIS AFTERNOON AND EARLY EVENING...THEN SHIFT INTO THE N...THEN NW AND INCREASE TO 10-20 KT AFTER 05Z/THU. WINDS WILL THEN BACK INTO THE NW TO W...AND INCREASE TO 15-25 KT AFTER 14Z/THU...WITH SOME GUSTS POSSIBLY REACHING 30-35 KT AT KALB. OUTLOOK... THU NT-SAT...MAINLY VFR...SLIGHT CHC -SHSN. BREEZY. SUN-MON...VFR...NO SIG WX. && .HYDROLOGY... A SIGNIFICANT MIXED PRECIPITATION EVENT WAS OCCURRING ACROSS THE REGION WITH STORM TOTAL LIQUID AMOUNTS FROM LESS THAN A QUARTER INCH IN NORTHERN HERKIMER COUNTY TO A LITTLE OVER TWO INCHES IN THE LOWER HUDSON VALLEY OF NEW YORK AND THE LITCHFIELD HILLS OF CONNECTICUT. OVER COOLER REGIONS SUCH AS THE HIGHER ELEVATIONS OF THE CATSKILLS...BERKSHIRES...AND GREEN MOUNTAINS OF SOUTHERN VERMONT A SUBSTANTIAL AMOUNT OF THIS PRECIPITATION IS FORECAST TO COME AS SNOW. ACROSS OUR SOUTHERNMOST COUNTIES...EASTERN ULSTER DUTCHESS...AND LITCHFIELD...MOST OF THE PRECIPITATION WILL COME AS RAIN AND LOCALLY HEAVY AMOUNTS MAY AMOUNT TO ENOUGH TO RESULT IN SOME MINOR FLOODING OF ROADS AND PARKING AREAS AND CAUSE RISES OF SEVERAL FEET ON RIVERS AND STREAMS. FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...FLOOD WATCH THROUGH THURSDAY MORNING FOR CTZ001-013. NY...WINTER STORM WARNING UNTIL 6 AM EST THURSDAY FOR NYZ047-051- 054-058-063. WINTER WEATHER ADVISORY UNTIL 6 AM EST THURSDAY FOR NYZ039>043- 048>050-052-053-059>061-082>084. FLOOD WATCH THROUGH THURSDAY MORNING FOR NYZ064>066. MA...WINTER STORM WARNING UNTIL 6 AM EST THURSDAY FOR MAZ001-025. VT...WINTER STORM WARNING UNTIL 6 AM EST THURSDAY FOR VTZ013-014. WINTER WEATHER ADVISORY UNTIL 6 AM EST THURSDAY FOR VTZ015. && $$ SYNOPSIS...11 NEAR TERM...11/SNYDER SHORT TERM...KL LONG TERM...RCK AVIATION...KL HYDROLOGY...RCK
AREA FORECAST DISCUSSION
NWS ALBANY NY
655 PM EST WED DEC 7 2011 .SYNOPSIS... A STORM SYSTEM WILL LIFT NORTHEAST FROM THE DELMARVA REGION THIS EVENING...TO THE EAST END OF LONG ISLAND AROUND MIDNIGHT...AND THEN INTO THE GULF OF MAINE THURSDAY MORNING. THIS STORM TRACK WILL RESULT IN RAIN CHANGING TO SNOW THIS EVENING ACROSS MUCH OF THE REGION WITH SIGNIFICANT SNOWFALL ACCUMULATIONS OVERNIGHT IN MANY AREAS. THE HEAVIEST SNOW IS EXPECTED TO FALL ACROSS THE NORTHERN TACONICS...EASTERN CATSKILLS...BERKSHIRES AND SOUTHERN GREEN MOUNTAINS. HEAVY RAIN WILL CONTINUE TO FALL OVERNIGHT ACROSS THE MID HUDSON VALLEY AND LITCHFIELD HILLS. && .NEAR TERM /THROUGH THURSDAY/... WINTER STORM WARNINGS ARE IN EFFECT FOR TONIGHT FOR THE EASTERN CATSKILLS...NORTHERN TACONICS...BERKSHIRES AND SOUTHERN GREEN MOUNTAINS AND WINTER WEATHER ADVISORIES IN EFFECT FOR THE SOUTHEAST ADIRONDACKS...LAKE GEORGE SARATOGA REGION...EASTERN MOHAWK VALLEY...SACANDAGA REGION...GREATER CAPITAL DISTRICT AND CENTRAL TACONICS. A FLOOD WATCH IS IN EFFECT THROUGH THURSDAY MORNING FOR THE MID HUDSON VALLEY...SOUTHERN TACONICS AND LITCHFIELD HILLS. SNOWFALL ACCUMULATIONS ARE GENERALLY EXPECTED TO BE 3 TO 8 INCHES IN THE ADVISORY AREA AND 5 TO 12 INCHES IN THE WARNING AREA EXCEPT ACROSS THE CENTRAL AND SOUTHEAST CATSKILLS...NORTHERN BERKSHIRES AND HIGHER TERRAIN OF THE SOUTHERN GREEN MOUNTAINS WHERE 8 TO 16 INCHES OF SNOW IS EXPECTED. TOTAL RAINFALL AMOUNTS IN THE FLOOD WATCH AREA ARE EXPECTED TO BE IN THE 1.75 TO 2.25 INCH RANGE. AS OF 530 PM EST...CLOUD TOPS CONTINUE TO COOL ACROSS THE FA WITH 21Z KALB SOUNDING INDICATING A WARM TONGUE OF 4C AT AROUND 875 MB WITH THE FREEZING LEVEL AT AROUND 775 MB OR 6.6 KFT. HAVE RECEIVED A REPORT OF 1 INCH OF SNOW THUS FAR IN CHARLOTTEVILLE IN SCHOHARIE COUNTY WITH HEAVY WET SNOW AND A TEMP OF 36 DEGREES AT AN ELEVATION OF AROUND 1500 FEET. EXPECT A RAPID CHANGEOVER TO SNOW THIS EVENING ACROSS MUCH OF THE FA MAINLY BETWEEN 00Z AND 03Z WITH VERY HEAVY SNOW EXPECTED TO FALL DURING MUCH OF THE NIGHT BEFORE TAPERING OFF LATE. THE ONLY AREAS WHICH ARE NOT EXPECTED TO RECEIVE MUCH SNOW ARE FAR NORTHWEST PORTIONS OF THE FA INCLUDING THE WESTERN ADIRONDACKS AND WESTERN MOHAWK VALLEY WHERE VERY LITTLE QPF EXPECTED...NORTHERN FRINGE OF PCPN SHIELD AND FAR SOUTHEAST PORTION OF FA WHICH WILL REMAIN TOO WARM FOR MUCH IN THE WAY OF SNOW MAINLY FROM THE MID HUDSON VALLEY EAST TO THE LITCHFIELD HILLS WHERE A FLOOD WATCH IS IN EFFECT. MANY FAVORABLE FACTORS FOR HEAVY SNOW ARE IN PLACE ACROSS MUCH OF THE FA WITH THE MOST SIGNIFICANT FACTORS BEING IMPRESSIVE FRONTOGENESIS H8-H7 EXTENDING FROM THE CATSKILLS NORTHEAST TO SOUTHERN VERMONT AT 00Z AND THEN SHIFTING TO AN ORIENTATION FROM JUST EAST OF THE CAPITAL DISTRICT THROUGH THROUGH THE NORTHERN BERKSHIRES INTO SOUTHERN VERMONT AT 06Z. AS THE EVENING WEARS ON THE SNOW GROWTH REGION BECOMES INCREASINGLY MORE FAVORABLE WITH THE -12 TO -18 C TEMP SLICING THROUGH A REGION OF +20 UBAR/SEC. IN ADDITION IMPRESSIVE EPV EXISTS IN LOWER LEVELS ESPECIALLY BTWN 00Z AND 06Z. THE LATEST HRRR COL MAX REFLECTIVITY ALSO INDICATES IMPRESSIVE BANDED PCPN ESPECIALLY ACROSS THE HIGHER TERRAIN IN THE WARNING AREA BETWEEN 03Z AND 06Z WITH THE BACK EDGE OF THE PCPN SHIELD EXITING THE FA FROM WEST TO EAST BETWEEN 08Z AND 10Z. EXPECT LOW TEMPS TONIGHT TO RANGE FROM THE MID 20S NORTHWEST TO MID 30S FAR SOUTHEAST. ON THURSDAY EXPECT IMPROVING CONDITIONS WITH HIGH PRESSURE MOVING IN AND MAINLY DRY CONDITIONS WITH HIGHS RANGING FROM THE UPPER 20S TO LOWER 30S NORTHWEST TO LOWER 40S FAR SOUTHEAST. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... THU NT...BACKING LOW LEVEL WINDS SHOULD ALLOW ANY LINGERING SNOW BANDS/SNOW SHOWERS TO SHIFT NORTHWARD INTO THE WESTERN ADIRONDACKS...WITH ADDITIONAL ACCUMS POSSIBLE BEFORE INVERSION HEIGHTS LOWER AND DIMINISH INTENSITY OF ANY SNOWBANDS. ELSEWHERE...INITIALLY CLEAR TO PARTLY CLOUDY SKIES SHOULD BECOME MOSTLY CLOUDY LATER AT NIGHT AS MID LEVEL ISENTROPIC LIFT INCREASES AHEAD OF NEXT APPROACHING SHORTWAVE. EXPECT MINS TO FALL INTO THE TEENS AND 20S...WARMEST ACROSS VALLEY REGIONS. FRI-SAT...UPPER LEVEL TROUGH WILL APPROACH FROM THE W...AND PASS ACROSS FRI NT. A SFC COLD FRONT ASSOCIATED WITH THIS FEATURE WILL CROSS THE REGION LATE FRI OR FRI EVE...PRECEDED AND ACCOMPANIED BY SNOW SHOWERS. THEN...BEHIND THE FRONT...BANDS OF SNOW SHOWERS AND POSSIBLE SNOW SQUALLS WILL BE POSSIBLE...INITIALLY FAVORING PORTIONS OF THE WESTERN MOHAWK VALLEY/SCHOHARIE VALLEY...THEN GRADUALLY SHIFTING NORTHWARD INTO THE WESTERN ADIRONDACKS BY SAT. THERE IS SOME POTENTIAL FOR LOCALLY HEAVY SNOWFALL AMTS WITHIN SOME OF THESE BANDS...AND WILL MENTION THIS POSSIBILITY IN THE HWO...WITH GREATEST THREAT ACROSS THE WESTERN ADIRONDACKS. EXPECT FRI MAXES TO REACH THE 30S IN MOST AREAS...EXCEPT AROUND OR INTO THE LOWER 40S WITHIN THE VALLEYS...WITH 20S ACROSS HIGHER ELEVATIONS. COLDER AIR BEHIND THE FRONT WILL MOVE IN FOR FRI NT AND SAT...WITH FRI NT MINS IN THE TEENS AND LOWER 20S...AND SAT MAXES MAINLY IN THE 30S WITHIN VALLEYS...AND 20S ACROSS HIGHER ELEVATIONS. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... THIS PERIOD WILL BE FAIRLY QUIET AS HIGH PRESSURE BUILDS INTO THE MID ATLANTIC REGION SATURDAY NIGHT AND DOMINATES OUR WEATHER INTO THE EARLY PART OF THE COMING WEEK. A CHANCE OF SOME LAKE ENHANCED SNOW SHOWERS SATURDAY NIGHT...THEN DRY UNTIL TUESDAY NIGHT WHEN A WEAK BOUNDARY BRINGS ABOUT SOME SNOW AND RAIN SHOWERS WEST OF THE HUDSON VALLEY WEDNESDAY. THE PERIOD STARTS OFF CHILLY...LOWS FROM AROUND 10 TO 20 ABOVE ON SUNDAY MORNING...WITH HIGHS SUNDAY ONLY IN THE UPPER 20S TO THE MID 30S. TEMPERATURES WILL GRADUALLY MODERATE WITH HIGHS RISING TO THE UPPER 30S AND LOWER 40S BY TUESDAY AFTERNOON. FOR THE MOST PART...USED HPC GUIDANCE TO POPULATE THE GRIDS. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... WIDESPREAD IFR CONDITIONS ARE EXPECTED THROUGH AT LEAST 08Z TODAY DUE TO BOTH LOW CEILINGS AND POOR VISIBILITIES FROM A STORM SYSTEM LIFTING NORTHEAST FROM THE DELMARVA REGION MOVING ACROSS THE EASTERN OF LONG ISLAND TO THE GULF OF MAINE BY LATER THIS MORNING. PERIODS OF RAIN WILL CONTINUE THIS EVENING AND MUCH OF TONIGHT...WITH THE RAIN HEAVY AT TIMES FROM ALBANY SOUTH...WITH THE RAIN MIXING WITH AND CHANGING TO SNOW FROM NORTHWEST TO SOUTHEAST STARTING NORTHWEST OF ALBANY EARLY THIS EVENING AND GRADUALLY WORKING SOUTHWARD. THE RAIN IS EXPECTED TO MIX AND CHANGE OVER AT ALBANY AROUND 04Z...BUT NOT MIX OR CHANGE OVER AT POUGHKEEPSIE UNTIL AFTER 07Z. THE RAIN AND SNOW SHOULD PRETTY MUCH BE OVER WITH BY 10Z WITH VFR FLIGHT CONDITIONS FOR THE REST OF THE DAY ALTHOUGH SOME MVFR CIGS MAY BE ENCOUNTERED OVER THE HIGHER TERRAIN WEST OF THE HUDSON VALLEY. WINDS ACROSS THE REGION WILL GENERALLY BE NORTH OR NORTHEAST WEDNESDAY EVENING...THEN BACK AROUND TO A MORE WESTERLY DIRECTION DURING THE LATE NIGHT AND EARLY MORNING HOURS...INCREASING TO AROUND 12 KNOTS WITH GUSTS AS HIGH AS 25 KNOTS. OUTLOOK... TONIGHT-SAT...MAINLY VFR...SLIGHT CHC -SHSN. BREEZY. SUN-MON...VFR...NO SIG WX. && .HYDROLOGY... A SIGNIFICANT MIXED PRECIPITATION EVENT WAS OCCURRING ACROSS THE REGION WITH STORM TOTAL LIQUID AMOUNTS FROM LESS THAN A QUARTER INCH IN NORTHERN HERKIMER COUNTY TO A LITTLE OVER TWO INCHES IN THE LOWER HUDSON VALLEY OF NEW YORK AND THE LITCHFIELD HILLS OF CONNECTICUT. OVER COOLER REGIONS SUCH AS THE HIGHER ELEVATIONS OF THE CATSKILLS...BERKSHIRES...AND GREEN MOUNTAINS OF SOUTHERN VERMONT A SUBSTANTIAL AMOUNT OF THIS PRECIPITATION IS FORECAST TO COME AS SNOW. ACROSS OUR SOUTHERNMOST COUNTIES...EASTERN ULSTER DUTCHESS...AND LITCHFIELD...MOST OF THE PRECIPITATION WILL COME AS RAIN AND LOCALLY HEAVY AMOUNTS MAY AMOUNT TO ENOUGH TO RESULT IN SOME MINOR FLOODING OF ROADS AND PARKING AREAS AND CAUSE RISES OF SEVERAL FEET ON RIVERS AND STREAMS. FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...FLOOD WATCH THROUGH THURSDAY MORNING FOR CTZ001-013. NY...WINTER STORM WARNING UNTIL 6 AM EST THURSDAY FOR NYZ047-051- 054-058-063. WINTER WEATHER ADVISORY UNTIL 6 AM EST THURSDAY FOR NYZ039>043- 048>050-052-053-059>061-082>084. FLOOD WATCH THROUGH THURSDAY MORNING FOR NYZ064>066. MA...WINTER STORM WARNING UNTIL 6 AM EST THURSDAY FOR MAZ001-025. VT...WINTER STORM WARNING UNTIL 6 AM EST THURSDAY FOR VTZ013-014. WINTER WEATHER ADVISORY UNTIL 6 AM EST THURSDAY FOR VTZ015. && $$ SYNOPSIS...11 NEAR TERM...11/SNYDER SHORT TERM...KL LONG TERM...RCK AVIATION...RCK HYDROLOGY...RCK
AREA FORECAST DISCUSSION
NWS MOUNT HOLLY NJ
1238 PM EST TUE DEC 6 2011 .SYNOPSIS... A COLD FRONT STRETCHING FROM NORTHERN MAINE INTO LOW PRESSURE OVER WESTERN PENNSYLVANIA WILL SLOWLY SAG SOUTHEAST ACROSS OUR AREA TONIGHT. A STRONGER LOW WILL FORM OVER THE CAROLINAS WEDNESDAY AND INTENSIFY RAPIDLY AS IT PASSES CAPE COD EARLY THURSDAY. SOUTHERN PLAINS HIGH PRESSURE WILL BUILD INTO THE MID ATLANTIC STATES FRIDAY THEN BE FOLLOWED BY A COLD FRONTAL PASSAGE EARLY SATURDAY. THERE IS A CHANCE THAT LOW PRESSURE WILL FORM ON THAT FRONT TO THE EAST OF NEW JERSEY. ANOTHER SOUTHERN PLAINS HIGH PRESSURE SYSTEM WILL BUILD INTO THE MID ATLANTIC STATES NEXT SUNDAY AND MONDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A 14Z SURFACE ANALYSIS PLACED A FRONTAL BOUNDARY DRAPED FROM NORTHERN NEW ENGLAND TO WESTERN PENNSYLVANIA THEN DOWN TO THE NORTH-CENTRAL GULF OF MEXICO. A FEW WEAK AREAS OF LOW PRESSURE WERE ALONG THIS FRONT. ANOTHER MILD DAY ON TAP ACROSS THE REGION AS A SOUTHERLY FLOW IS MAINTAINED AHEAD OF A SLOWLY APPROACHING COLD FRONT. THIS BOUNDARY SHOULD TEND TO TAKE ITS TIME AS THE UPPER-LEVEL FLOW IS NEARLY PARALLEL TO IT. SOME MAINLY LIGHTER POCKETS OF RAIN HAVE BEEN MOVING ACROSS PARTS OF THE CWA THIS MORNING, WITH SOME HEAVIER SHOWERS LOCATES TO OUR SOUTHWEST OVER VIRGINIA. RAINFALL AMOUNTS TODAY ARE ANTICIPATED TO BE ON THE LIGHTER SIDE. DID RAISE QPF SLIGHTLY FOR SHOWERS MOVING FROM DOVER INTO SOUTHERN NJ IN THE NEXT FEW HOURS. LOOKING AT THE 14Z RUC AND 15Z SREF EXPECT MAJORITY OF RAINFALL TO BE NORTH OF PHILLY METRO AFTER 20Z, QPF AND POPS REFLECT THAT. AS FOR TEMPERATURES, WE MOSTLY USED AN EVENLY WEIGHTED BLEND OF THE GFS/NAM MOS. IF WE GET SOME SUNSHINE TO OCCUR, THE LOCAL TEMPERATURES ESPECIALLY ACROSS THE EASTERN/SOUTHERN AREAS COULD GET TO 70 DEGREES AS 925 MB TEMPERATURES ARE FORECAST TO BE NEAR +13C. MAXIMUM TEMPERATURES ACROSS SOUTHERN SECTIONS HAVE BEEN RAISED SLIGHTLY BASED ON 17Z METAR OBS. DEWPOINTS HAVE ALSO BEEN RAISED SLIGHTLY. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... THE FRONTAL BOUNDARY MENTIONED ABOVE WILL GRADUALLY SETTLE EASTWARD ACROSS THE REGION DURING THE NIGHT. BASED ON THE SLOW EASTWARD PROGRESSION AND THE CAA HOLDING OFF UNTIL NEAR DAYBREAK, MOST OF THE REGION WILL HAVE ANOTHER MILD NIGHT. THERE WILL BE PLENTY OF MOISTURE ACROSS THE CWA WITHIN THE SOUTHERLY FLOW AHEAD OF THE BOUNDARY. AS THE THERMAL GRADIENT STARTS TO TIGHTEN ALOFT DURING THE NIGHT, FRONTOGENETIC FORCING SHOULD RESPOND AND PRODUCE A RIBBON OF RAIN ACROSS THE AREA. THIS MAY END UP BEING FAIRLY NARROW BUT AT THIS POINT WE CONTINUED WITH CATEGORICAL POPS SLIDING SOUTHEASTWARD ACROSS THE REGION DURING THE COURSE OF THE NIGHT. OVERALL, THE RAINFALL AMOUNTS SHOULD BE ON THE LIGHTER SIDE WITH THE EXCEPTION OF A MORE FOCUSED AREA OF RAIN DEVELOPING LATE AS SOME OF THE MODEL GUIDANCE SUGGESTS /ESPECIALLY ACROSS THE CENTRAL AND SOUTHERN AREAS/. SOME OF THE MODEL PARAMETERS /I.E. SHOWALTER INDEX/ HINTS AT SOME POSSIBLE INSTABILITY DEVELOPING TONIGHT, HOWEVER FORECAST SOUNDINGS SHOW LITTLE IN THE WAY OF INSTABILITY GIVEN A RATHER SATURATED PROFILE. THEREFORE, ANY CONVECTIVE TYPE CONTRIBUTION SHOULD NOT BE DEEP ENOUGH TO PRODUCE CHARGE SEPARATION DUE TO THE RATHER LOW INSTABILITY POTENTIAL. IT APPEARS THAT THE COLD AIR LAGS FOR AWHILE, THEREFORE WE REMOVED ANY MENTION OF SNOW ACROSS THE FAR NORTHWEST. OTHERWISE, PATCHY FOG MAY ONCE AGAIN BE ACROSS THE REGION ESPECIALLY ACROSS THE HIGHER TERRAIN. HOWEVER, GIVEN THE FLOW NOT TO FAR ABOVE THE SURFACE IT WAS DECIDED TO NOT INCLUDE IT ATTM AS THE OVERALL VISIBILITIES OUTSIDE OF THE RAIN MAY NOT BE A REAL IMPACT. AS FOR TEMPERATURES, WE WENT WITH A BLEND OF THE NAM/GFS MOS TO SPLIT SOMEWHAT OF A DIFFERENCE AT SOME LOCALES. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... PATTERN ALOFT: CHARACTERIZED BY A GENERAL SENSE OF TROUGHING OVER CENTRAL NORTH AMERICA WITH SEVERAL STRONG SHORT WAVES ROLLING THROUGH THE TROUGH...ULTIMATELY SHOVING THE CURRENT PLUS 1 SD 500 MB WARM RIDGE EASTWARD INTO THE CENTRAL ATLC. THEREFORE...THE LONG PERIOD OF ABOVE NORMAL TEMPERATURES LASTING MORE THAN TWO WEEKS...WILL GIVE WAY TO SEASONABLY COOL TEMPERATURES THURSDAY AFTERNOON ONWARD THROUGH THE PERIOD. THE BEST CHANCE FOR A BELOW NORMAL DAY OR TWO IS SLATED FOR THIS COMING SUNDAY AND MONDAY. THE PRIMARY WEATHER MAKER IN THIS FCST PERIOD APPEARS TO BE WEDNESDAY AND IT MAY RESULT IN MULTIPLE HEADLINES INCLUSIVE OF ADVISORY SNOW IN E PA AND NW NJ...TO A POSSIBLE FLOOD WATCH FOR SPOTTY SMALL STREAM FLOODING ALONG THE I95 CORRIDOR TO A BRIEF NW GALE THU MORNING. THE DAILIES BELOW... WEDNESDAY...STRONG SHORT WAVE LIFTING ENE FROM THE SW USA PROMISES TO BRING HEAVY PRECIPITATION TO THE AREA...MOST OF IT RAIN BUT NEEDS TO BE CAREFULLY WATCHED FOR A MODERATE SNOW EVENT IN THE NW SECTOR OF OUR FCST AREA...PARTICULARLY READING TO ALLENTOWN TO MORRISTOWN NWWD AND ESPECIALLY HIGH TERRAIN WHICH FEATURES THE POCONOS. SUSPECT 2 TO 4 HRS OF SNOW GROWTH POTENTIAL OF 1 INCH/HR WHICH IS HIGHLIGHTED IN BOTH THE 00Z/6 GFS/NAM. DEFORMATION ZONE HEAVY PCPN IN E PA. SNOW ACCUMULATION...IF ANY SHOULD OCCUR PRIMARILY WED NIGHT. THERE IS CHC OF SPOTTY 6 INCH AMOUNTS ABOVE 1000 FT IN THE POCONOS AND POSSIBLY EXTREME NW NJ NEAR WANTAGE AND HIGH POINT. NO WATCH ATTM BUT WE MAY NEED TO ISSUE ONE LATER TODAY. TOP DOWN AND BOX WX TOOLS OFFERED ALMOST IDENTICAL WX GRIDS AS POSTED AT 315 AM THIS MORNING. THIS SYSTEM HAS A LIKELIHOOD OF PRODUCING 1 TO NEARLY 2.5 INCHES OF RAIN IN 12 HRS NEAR I95 WHERE 6 HR FFG VALUES RANGE FROM 1.6 TO 2.6 INCHES AND 12 HR HEADWATER GUIDANCE IS NEAR 2 INCHES. THIS FLAGS THE POTENTIAL OF SOME SMALL STREAM FLOODING IF 2 INCH VALUES OCCUR AND AN AFTERNOON ISSUANCE OF A FLOOD WATCH MAY BE NEEDED FOR THE ALREADY VULNERABLE LOWER FFG AREA INTO THE ILG-PHL-NE NJ METRO REGION. COLLABORATION PREFERRED TO WAIT ONE MORE FCST CYCLE. WE DO NOTE THE SREF IS AWFULLY LOW ON ITS QPF FOR THIS EVENT AND FEEL SOMETHING IS VERY WRONG WITH THE SREF WHEN THE 00Z/6 UK/EC/GGEM OP RUNS AS WELL AS THE GEFS ARE SO HEAVY. TEMPS/DEWPOINTS/WINDS WERE GENERALLY 50/50 BLENDED 00Z/6 NCEP MOS GUIDANCE EXCEPT IN THE 00Z-09Z TIME FRAME WHEN LEANED HEAVILY ON THE NAM 2M TEMPS PRESUMING PCPN WOULD BE TURNING OVER TO SNOW NW TO SE. WE COULD SEE RAIN END AS A MIX TO PHL BUT FOR NOW...MORE CONSERVATIVE. THURSDAY...P/S AND BRISK DURING THE DAY AND A MO CLEAR NIGHT. GFS MEX GUIDANCE LOOKED GOOD. FRIDAY...A CHILLY START AS HIGH PRESSURE BRIEFLY BUILDS OVERHEAD WITH LIGHT WIND. HIGH CLOUDS MAY ALREADY BE INCREASING AT DAYBREAK... AHEAD OF THE NEXT INTENSIFYING TROUGH ALOFT APPROACHING FROM THE WEST. DID NOT ADJUST POPS FROM THE 330PM KPHI MONDAY FCST SINCE MOST OF THE POP AND WX ENERGY ON THIS SHIFT WAS DEVOTED TO WEDNESDAY. SATURDAY...MAY BE BRIEFLY UNSETTLED WITH THE CFP BUT FOR NOW A CONSERVATIVE FCST. 00Z/6 MEX GUIDANCE TEMPS BLENDED WITH THE 330 PM FCST FROM YDY. THERE COULD BE A FLY IN THE OINTMENT...IN THE FORM OF A COASTAL LOW DEVELOPING WHICH IF OCCURRED WOULD REQUIRE A HEAVIER CLOUD FCST THAN NOW ISSUED AS WELL AS A CHANCE OF PCPN. FOR NOW...THE CONSERVATIVE NO CHANGE MODE BUT SOME MODEL GUIDANCE FLAGS THIS LATTER MORE UNSETTLED IDEA. SUNDAY AND MONDAY...FAIR WX AS SOUTHERN PLAINS HIGH PRESSURE ARRIVES AND DOMINATES. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. A FRONTAL BOUNDARY WILL GRADUALLY APPROACH THE AREA TODAY INTO TONIGHT AS A COUPLE OF WEAK AREA OF LOW PRESSURE SYSTEMS TRAVEL ALONG IT. A MILD AND MOIST SOUTHERLY FLOW REMAINS IN PLACE ACROSS OUR REGION AHEAD OF THIS FRONT, WHICH WILL RESULT IN WIDESPREAD CLOUDINESS THROUGH THE PERIOD. THE CEILINGS ARE EXPECTED TO LOWER AND EXPAND EASTWARD THROUGH THE DAY BECOMING MVFR ACROSS THE TAF SITES WITH SOME IFR POSSIBLE IN HEAVIER SHOWERS. AHEAD OF THE FRONTAL BOUNDARY, WE ARE EXPECTING SOME RAIN TO MOVE ACROSS A PORTION OF THE AREA AT TIMES THROUGH TONIGHT. THIS MAY BE IN THE FORM OF A FEW PERIODS OF RAIN FROM WEST TO EAST AND SHOULD BE MOSTLY ON THE LIGHTER SIDE. WE THEREFORE CONTINUED THE IDEA OF SOME RAIN AROUND AT TIMES THROUGH THE PERIOD. THE VISIBILITIES ARE PROBLEMATIC AS IT WILL MAINLY BE DEPENDENT ON THE RAIN AND THE ASSOCIATED INTENSITY. GIVEN THE AMOUNT OF MOISTURE IN THE AIR, WE FOCUSED THE REDUCTION IN THE VISIBILITY WITH THE RAIN MENTION AND THIS MAY SETTLE LOWER ESPECIALLY TONIGHT. IN SUMMARY, LOWERING CONDITIONS ARE EXPECTED THROUGH THE DAY AND TONIGHT WITH BOUTS OF RAIN AT TIMES. THE FRONT ITSELF IS EXPECTED TO GRADUALLY CROSS MOST OF THE TERMINALS TOWARD DAYBREAK WEDNESDAY WITH A SOUTHERLY WIND UP TO 10 KNOTS SHIFTING TO THE WEST. OUTLOOK... WEDNESDAY...ANY MORNING IFR MAY BECOME MVFR OR VFR CIGS FOR A TIME... MAINLY FAR N PTN OF THE AREA BEFORE DETERIORATING TO IFR IN RAIN LATE IN THE DAY FROM S TO N. A CHANGE TO 1 TO 6 HRS OF SNOW APPEARS PROBABLE IN THE KRDG/KABE REGION WED NIGHT WITH BRIEF LIFR CONDS POCONOS TO KABE WHERE A WET SNOWFALL RATE OF 1/HR IS POSSIBLE FOR A SHORT TIME. STRONGEST WINDS PROBABLY LATE WED NIGHT WHEN A WSHIFT TO NW IS EXPECTED BEHIND RAPIDLY DEEPENING AND FAST DEPARTING COASTAL LOW PRES. NW GUSTS 15 TO 25 KTS BY DAWN THU. THURSDAY...VFR. NW WIND GUSTS TO 20 OR 25 KTS BECOMING LIGHT AT NIGHT. FRIDAY...VFR. LIGHT WIND. SATURDAY...VFR THOUGH THERE MAY BE A SHORT PERIOD OF MVFR CIGS DURING THE MORNING. && .MARINE... A SOUTHERLY FLOW WILL CONTINUE TODAY AND TONIGHT AHEAD OF A SLOW MOVING COLD FRONT. THIS BOUNDARY IS NOT EXPECTED TO REACH THE WATERS UNTIL ABOUT DAYBREAK WEDNESDAY. THE FLOW AROUND 925 MB WILL INCREASE TO ABOUT 35 KNOTS THROUGH TONIGHT. GIVEN THE WAA THOUGH, THIS IS EXPECTED TO NOT MIX DOWN ALL THAT EFFICIENTLY. THEREFORE, THE WINDS ARE ANTICIPATED TO REMAIN BELOW ADVISORY CRITERIA. THE SOUTHERLY FLOW HOWEVER COULD EDGE THE SEAS UP TO 5 FEET ESPECIALLY FOR THE OFFSHORE WATERS THROUGH TONIGHT. THIS DOES NOT LOOK SOLID, THEREFORE WE HELD OFF ON AN ADVISORY FOR NOW. OUTLOOK... WED/THU...POSSIBLE SCA CONDS ON THE ATLC WATERS FOR A TIME WEDNESDAY HEADLINED A GALE WATCH FOR LATE WED NIGHT-THU MORNING WHICH WAS THE MORE IMPORTANT HEADLINE HAZARD. OTRW WIDESPREAD SCA THURSDAY MORNING WITH A LOW TO MDT PROB OF A 3 TO 6 HR PERIOD OF NW GALES IN THE 08Z-14Z THURSDAY TIME FRAME. FRI...QUIET. NO HEADLINE. SAT...A LITTLE CHOPPY WITH NEXT CFP AND CHC OF SCA CONDS DEVELOPING. && .HYDROLOGY... THIS SYSTEM HAS A LIKELIHOOD OF PRODUCING 1 TO NEARLY 2.5 INCHES OF RAIN IN 12 HRS NEAR I95 WHERE 6 HR FFG VALUES RANGE FROM 1.6 TO 2.6 INCHES AND 12 HR HEADWATER GUIDANCE IS NEAR 2 INCHES. THIS FLAGS THE POTENTIAL OF SOME SMALL STREAM FLOODING IF 2 INCH VALUES OCCUR AND AN AFTERNOON ISSUANCE OF A FLOOD WATCH MAY BE NEEDED FOR THE ALREADY VULNERABLE LOWER FFG AREA INTO THE ILG-PHL-NE NJ METRO REGION. COLLABORATION PREFERRED TO WAIT ONE MORE FCST CYCLE. WE DO NOTE THE SREF IS AWFULLY LOW ON ITS QPF FOR THIS EVENT AND FEEL SOMETHING IS VERY WRONG WITH THE SREF WHEN THE 00Z/6 UK/EC/GGEM OP RUNS AS WELL AS THE GEFS ARE SO HEAVY. && .CLIMATE... ALLENTOWN YEARLY RECORD 67.69. SOON TO BE REESTABLISHED WITH SIGNIFICANTLY HIGHER RECORD VALUES IN 2011. AS OF 5 AM...67.62. MEANWHILE THROUGH THE 5TH OF DECEMBER... KPHL 16 CONSEC DAYS ABOVE NORMAL KABE 16 CONSEC DAYS ABOVE NORMAL KTTN 16 CONSEC DAYS AT OR ABOVE NORMAL. NORMAL ON 12/3 KMPO 16 CONSEC DAYS AT OR ABOVE NORMAL. NORMAL ON 12/3 ALL OTHER CLIMO SITES NOT MENTIONED HAD A BELOW NORMAL DAY AT LEAST ON THE 3RD OF DEC. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...GALE WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY MORNING FOR ANZ450>455. && $$ SYNOPSIS...DRAG NEAR TERM...GAINES/GORSE/MEOLA SHORT TERM...GORSE LONG TERM...DRAG AVIATION...DRAG/GORSE/MEOLA MARINE...DRAG/GORSE HYDROLOGY... CLIMATE...
AREA FORECAST DISCUSSION
NWS TALLAHASSEE FL
916 PM EST Wed Dec 7 2011 .UPDATE... Winds are diminishing this evening, and the wind advisory was allowed to expire at 00z. At least 3 stations within the forecast area measured winds gusts of at least 40 mph (KVAD, KAAF, and a Davis Vantage Pro 2 on St. George Island), and the office peaked at 39 mph on the roof of the Love Building at FSU. The focus now turns to the possibility of a light freeze tonight. Satellite imagery shows a dry slot behind the cold front with mostly clear skies over a large portion of the forecast area. The exception is across the far northwestern border where the front edge of a low cloud deck remains. This low cloud deck is fairly extensive and extends well back into Alabama and Mississippi. None of the models have a particularly good handle on these clouds with the exception of the HRRR, and the HRRR does not push this cloud cover too far into the forecast area before dissipating later tonight. The clear skies covering most of the forecast area will allow temperatures to drop more readily, and with diminishing winds, a short duration light freeze still remains possible away from the coast. The 18z MAV has low temperatures ranging from 30 to 34 across the inland locations, and this seems reasonable. The main change to the previous forecast was to tweak the sky grids to match the current satellite trends. && .AVIATION... (Through 00z Friday) The traditional MOS guidance and larger scale models are not handling the expansive area of stratus that is situated across much of Mississippi and Alabama right now. Observations show that CIGS in this stratus are 2000-3000 ft, or in the upper end of MVFR range. The HRRR (rapid refresh RUC model) has performed well through TAF issuance time, so it was used as the basis for this forecast. It gradually builds MVFR ceilings into DHN around 02z, with some FEW-SCT clouds around 2500 ft also clipping ABY and ECP late tonight. It slowly scatters out the stratus, fraying from the edges as drier air progressively works in. It`s possible that the TAFs are too optimistic at ABY and ECP, which could see some MVFR ceilings overnight, but with a lack of model support, we will handle any changes with amendments. && .MARINE... Advisory level winds and seas will continue through the night behind a cold front. Winds and seas are expected to subside by Thursday afternoon as an area of high pressure builds over the southeast states. A dry cold front is expected to move through this weekend with an increase in winds and seas to at least cautionary levels. && .PRELIMINARY POINT TEMPS/POPS... Tallahassee 32 58 35 67 42 / 0 0 0 0 0 Panama City 35 58 40 64 44 / 0 0 0 0 0 Dothan 32 56 34 62 39 / 0 0 0 0 0 Albany 32 57 34 64 39 / 0 0 0 0 0 Valdosta 32 58 37 65 41 / 0 0 0 0 0 Cross City 31 62 40 68 44 / 0 0 0 0 0 Apalachicola 38 56 39 65 46 / 0 0 0 0 0 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...Freeze Warning from 3 AM to 7 AM CST Thursday for Coffee-Dale- Geneva-Henry-Houston. GA...Freeze Warning from 4 AM to 8 AM EST Thursday for Baker-Ben Hill- Berrien-Brooks-Calhoun-Clay-Colquitt-Cook-Decatur-Dougherty- Early-Grady-Irwin-Lanier-Lee-Lowndes-Miller-Mitchell- Quitman-Randolph-Seminole-Terrell-Thomas-Tift-Turner-Worth. FL...Freeze Warning from 4 AM EST /3 AM CST/ to 8 AM EST /7 AM CST/ Thursday for Calhoun-Central Walton-Gadsden-Holmes-Inland Bay-Inland Dixie-Inland Franklin-Inland Gulf-Inland Jefferson-Inland Taylor-Inland Wakulla-Inland Walton- Jackson-Lafayette-Leon-Liberty-Madison-Washington. GM...Small Craft Advisory until 10 AM EST Thursday for Apalachee Bay- Coastal waters From Ochlockonee River to Apalachicola FL out to 20 NM-Coastal waters from Suwannee River to Keaton Beach FL out 20 NM-Coastal waters from Apalachicola to Destin FL out 20 NM-Waters from Suwannee River to Apalachicola FL from 20 to 60 NM-Waters from Apalachicola to Destin FL from 20 to 60 NM. && $$ UPDATE/MARINE...DVD AVIATION...Lamers
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1003 PM CST WED DEC 7 2011 .DISCUSSION... 856 PM CST SMALL UPDATES HAVE BEEN MADE FOR THE REMAINDER OF TONIGHTS FORECAST...WITH ATTENTION TURNING TO THURSDAY NIGHTS SNOW POTENTIAL. VARIABLE CLOUD COVERAGE BY OVERNIGHT IS MAKING IT CHALLENGING ON THE TEMPERATURE FORECAST. WITH AN INITIAL COLD FRONT CONTINUING TO LOSE DEFINITION AS IT DRAPES INTO NORTHERN IL...LOW CLOUDS HAVE DIMINISHED IN COVERAGE. SATELLITE TRENDS AND RUC SOUNDINGS ACROSS NORTHEAST IL INDICATE TEMPORARY SCATTERED CLOUDS ARE LIKELY TO CONTINUE TO PROPAGATE SOUTHEAST. CLOUDS ALONG THE MID-LEVEL BAROCLINIC ZONE SEEN AT 700 MB ON THIS EVENINGS UPPER AIR ANALYSIS WILL ALSO CONTINUE TO SLOWLY FILTER INTO THE AREA THROUGH THU MORNING. SO WILL CONTINUE TO ADJUST SKY TRENDS...BUT ALL IN ALL VARIABLE TO PARTLY CLOUDY WORDING IS PROBABLY THE BEST BET. EVEN THOUGH THE HOURLY TREND WILL DEPEND HEAVILY ON HOW ANY CLOUDS UNDULATE IN COVERAGE...LOW TEMPERATURES STILL LOOK ON TRACK. SCATTERED MID-TEENS ARE FORECAST TOWARDS ROCKFORD AND STERLING...WITH LOWER TO MID 20S TOWARDS THE LAKE AND INTO NORTHWEST IN. A LOOK AT THE LATEST GUIDANCE...08.00 NAM AND 07.21 SREF...AS WELL AS UPSTREAM TRENDS ARE STARTING TO SUPPORT THE LIKELY SCENARIO THAT A MINOR ACCUMULATING SNOW EVENT WILL BE SEEN IN THE FORECAST AREA...ESPECIALLY THE SOUTHEAST QUARTER TO THIRD. THE UPPER AIR ANALYSES THIS EVENING DEPICTED THE STRONG UPPER JET /OVER 120 KTS AT UNR/ HEADING TOWARDS THE AREA WHICH WILL PROVIDE MORE CONCENTRATED UPPER SUPPORT DURING TUE AFTERNOON AND NIGHT. SATURATION AND QG FORCING WITH THE WAVE WILL NOT ARRIVE INTO PARTS OF OUR AREA UNTIL THE NIGHT...LIKELY BY 03Z. THE NEW NAM OUTPUT INDICATES MIXING RATIOS NEAR 2 G/KG ON THE FAVORED SURFACES WHERE LIFT IS OCCURRING INTO THE FAR SOUTHEAST...AND THAT IS NEARLY COINCIDENT WITH THE DENDRITIC GROWTH AREA. WHILE TOP-DOWN METHODS ON THE NAM SOUNDINGS WARM SOME ON THE WAY DOWN...RATIOS STILL LOOK TO BE ON THE HIGHER SIDE AS INDICATED BY EVEN THE PRIOR NAM RUNS. THE SREF GUIDANCE HAS BECOME MORE FOCUSED ON ITS SNOW PROBABILITIES...INDICATING A RIBBON ACROSS THE SOUTHEAST /GIBSON CITY TO RENSSELAER/ WHERE OVER ONE INCH OF SNOW IS FORECAST BY THE MEAN OF THE MEMBERS. EVEN THE PRIOR RUNS OF THESE MODELS AND THE GFS...EC...AND NMM WRF...INDICATE THE FAR SOUTHERN TIER OF COUNTIES TO SEE SNOW...AND COULD ENVISION BASED ON RATIOS AND RECENTLY COOLED GROUND TEMPERATURES THAT ONE TO TWO INCH ACCUMULATIONS ARE POSSIBLE. MINOR ACCUMULATIONS OF A COUPLE TENTHS AS FAR NORTH AS CHICAGO CANNOT BE RULED OUT DEPENDING ON IF THE ATMOSPHERE CAN SATURATE...AND LIGHT AMOUNTS ARE FORECAST THAT FAR NORTH BY THE 18.00 NAM. WILL RE-ISSUE AN SPS TO HIGHLIGHT FOR NOW AND BRIEF THE OVERNIGHT SHIFT. MTF && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 04Z... *SLIGHT THREAT OF -SN THU EVENING. TRS //DISCUSSION...UPDATED 02Z... AREA OF MVFR STRATOCU THAT WAS OVER SOUTHERN WI AND FAR N CENTRAL IL HAS ALL BUT DISSIPATED OVER THE LAST COUPLE HRS THOUGH AN AREA OF STRATUS HAS GROWN OVER FAR NE IA AND PORTIONS OF SW IA. WITH LOSS OF ORIGINAL MVFR CLOUDS HAS DUMPED THE TEMPO MVFR CIG GROUP THAT WAS IN TIL 03Z. WHILE NEW UPSTREAM STRATUS PATCH CURRENTLY MOVING TO THE SE...FORECAST WINDS OVER LOCAL AREA HAVE MORE OF A WESTERLY COMPONENT SO EXPECT SOUTHERN EDGE OF THESE CLOUDS TO REMAIN N OF CHI AREA. SMALL POTENTIAL TO BE IN RFD VC FOR A PD THIS EVE BUT HAVE ONLY SCT020 IN RFD TAFOR FOR THIS EVE. PREVIOUS DISCUSSION...UPDATED 00Z... SFC TROF/WEAK COLD FRONT AND ASSOCIATED SLIGHT VEERING OF WINDS HAS MOVED TO JUST S OF THE WI STATE LINE AT 00Z. THE TROF PROCEEDED PATCHY AREAS OF MVFR STRATOCU CIGS SO HAVE A COUPLE HR TEMPO GROUP OF BKN022 IN THE 01Z TO 03Z WINDOW FOR CHI AREA. THEREAFTER...THESE LOWER CLOUDS MOVE OFF TO THE SSE WITH JUST SOME ALTOCUMULUS MOVING E ACROSS THE MS RIVER AHEAD OF THE SHORT WAVE ROTATING SE OVER THE NORTHERN HI PLAINS. LIGHT WINDS WINDS BACK TO WSW OVERNIGHT IN RESPONSE TO APPROACHING NORTHERN HI PLAINS SYSTEM AND ANOTHER COLD FRONT DROPPING SE ACROSS WI DURG THE DAY THU. THIS SYSTEM IS EXPECTED TO PRODUCE SOME LIGHT SNOWFALL BUT ZONE OF BEST FORCING AT THIS POINT LOOKS ALONG A NORTHERN MO...CENTRAL IL...NE IND AXIS SO THREAT OF ANY PRECIPITATION AT THE LOCAL TERMINALS QUITE SMALL. TRS //ORD AND MDW CONFIDENCE...UPDATED 04Z... *HIGH CONFIDENCE ALL FORECAST ELEMENTS. TRS //OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z... * FRIDAY...VFR. SATURDAY...VFR. SUNDAY...VFR. MONDAY...VFR INTO EVENING...SLGT CHC -SN PRODUCING MVFR CIGS AND/OR VSBYS OVERNIGHT. TUESDAY...MVFR CIGS POSSIBLE. * TRS && .MARINE... 157 PM CST A COLD FRONT MOVING ACROSS LAKE SUPERIOR AND WISCONSIN THIS AFTERNOON WILL MOVE ACROSS LAKE MICHIGAN LATER THIS AFTERNOON AND EVENING. THIS WILL HELP KEEP THE WINDS AROUND 25 TO 30 KT TONIGHT AS THE WINDS BECOME NORTHWESTERLY. A PROLONGED PERIOD OF BRISK WEST TO NORTHWESTERLY WINDS IS EXPECTED INTO SATURDAY AS HIGH PRESSURE MOVING FROM THE PLAINS EASTWARD ACROSS THE MID MISSISSIPPI VALLEY...WILL CONTINUE TO PRODUCE A DECENT PRESSURE GRADIENT ACROSS THE GREAT LAKES. LATER SATURDAY THE WINDS LOOK TO SWITCH OUT OF THE SOUTHWEST AND INCREASE TO AROUND 30 KT AGAIN AS THE SURFACE HIGH SHIFTS ACROSS THE OHIO VALLEY AND ANOTHER AREA OF LOW PRESSURE MOVES ACROSS THE PRAIRIE PROVIDENCES OF CANADA. IT APPEARS THAT THESE SOUTHWESTERLY WINDS WILL CONTINUE INTO EARLY NEXT WEEK AS THE SURFACE HIGH CONTINUES TO DOMINATE ACROSS EASTERN CONUS. THERE COULD EVEN BE A PERIOD OF LOW END GALE FORCE WINDS DURING THIS PERIOD. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO BURNS HARBOR UNTIL 10 PM THURSDAY. SMALL CRAFT ADVISORY...NEARSHORE BURNS HARBOR TO MICHIGAN CITY IN UNTIL 10 AM SATURDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
856 PM CST WED DEC 7 2011 .DISCUSSION... 856 PM CST SMALL UPDATES HAVE BEEN MADE FOR THE REMAINDER OF TONIGHTS FORECAST...WITH ATTENTION TURNING TO THURSDAY NIGHTS SNOW POTENTIAL. VARIABLE CLOUD COVERAGE BY OVERNIGHT IS MAKING IT CHALLENGING ON THE TEMPERATURE FORECAST. WITH AN INITIAL COLD FRONT CONTINUING TO LOSE DEFINITION AS IT DRAPES INTO NORTHERN IL...LOW CLOUDS HAVE DIMINISHED IN COVERAGE. SATELLITE TRENDS AND RUC SOUNDINGS ACROSS NORTHEAST IL INDICATE TEMPORARY SCATTERED CLOUDS ARE LIKELY TO CONTINUE TO PROPAGATE SOUTHEAST. CLOUDS ALONG THE MID-LEVEL BAROCLINIC ZONE SEEN AT 700 MB ON THIS EVENINGS UPPER AIR ANALYSIS WILL ALSO CONTINUE TO SLOWLY FILTER INTO THE AREA THROUGH THU MORNING. SO WILL CONTINUE TO ADJUST SKY TRENDS...BUT ALL IN ALL VARIABLE TO PARTLY CLOUDY WORDING IS PROBABLY THE BEST BET. EVEN THOUGH THE HOURLY TREND WILL DEPEND HEAVILY ON HOW ANY CLOUDS UNDULATE IN COVERAGE...LOW TEMPERATURES STILL LOOK ON TRACK. SCATTERED MID-TEENS ARE FORECAST TOWARDS ROCKFORD AND STERLING...WITH LOWER TO MID 20S TOWARDS THE LAKE AND INTO NORTHWEST IN. A LOOK AT THE LATEST GUIDANCE...08.00 NAM AND 07.21 SREF...AS WELL AS UPSTREAM TRENDS ARE STARTING TO SUPPORT THE LIKELY SCENARIO THAT A MINOR ACCUMULATING SNOW EVENT WILL BE SEEN IN THE FORECAST AREA...ESPECIALLY THE SOUTHEAST QUARTER TO THIRD. THE UPPER AIR ANALYSES THIS EVENING DEPICTED THE STRONG UPPER JET /OVER 120 KTS AT UNR/ HEADING TOWARDS THE AREA WHICH WILL PROVIDE MORE CONCENTRATED UPPER SUPPORT DURING TUE AFTERNOON AND NIGHT. SATURATION AND QG FORCING WITH THE WAVE WILL NOT ARRIVE INTO PARTS OF OUR AREA UNTIL THE NIGHT...LIKELY BY 03Z. THE NEW NAM OUTPUT INDICATES MIXING RATIOS NEAR 2 G/KG ON THE FAVORED SURFACES WHERE LIFT IS OCCURRING INTO THE FAR SOUTHEAST...AND THAT IS NEARLY COINCIDENT WITH THE DENDRITIC GROWTH AREA. WHILE TOP-DOWN METHODS ON THE NAM SOUNDINGS WARM SOME ON THE WAY DOWN...RATIOS STILL LOOK TO BE ON THE HIGHER SIDE AS INDICATED BY EVEN THE PRIOR NAM RUNS. THE SREF GUIDANCE HAS BECOME MORE FOCUSED ON ITS SNOW PROBABILITIES...INDICATING A RIBBON ACROSS THE SOUTHEAST /GIBSON CITY TO RENSSELAER/ WHERE OVER ONE INCH OF SNOW IS FORECAST BY THE MEAN OF THE MEMBERS. EVEN THE PRIOR RUNS OF THESE MODELS AND THE GFS...EC...AND NMM WRF...INDICATE THE FAR SOUTHERN TIER OF COUNTIES TO SEE SNOW...AND COULD ENVISION BASED ON RATIOS AND RECENTLY COOLED GROUND TEMPERATURES THAT ONE TO TWO INCH ACCUMULATIONS ARE POSSIBLE. MINOR ACCUMULATIONS OF A COUPLE TENTHS AS FAR NORTH AS CHICAGO CANNOT BE RULED OUT DEPENDING ON IF THE ATMOSPHERE CAN SATURATE...AND LIGHT AMOUNTS ARE FORECAST THAT FAR NORTH BY THE 18.00 NAM. WILL RE-ISSUE AN SPS TO HIGHLIGHT FOR NOW AND BRIEF THE OVERNIGHT SHIFT. MTF && PREVIOUS DISCUSSION... 820 PM CST MAIN FORECAST ISSUES ARE WITH SNOW CHANCES ACROSS THE CWA THURSDAY NIGHT INTO EARLY FRIDAY...ALTHOUGH CONFIDENCE IS LOWERING OF THIS POSSIBILITY AT THIS TIME. RATHER QUIET CONDITIONS TO START THE FORECAST PERIOD AT THIS TIME...DESPITE A MID LEVEL WAVE AND ATTENDANT SURFACE REFLECTION SHIFTING SOUTHEAST THROUGH THE REGION. PRECIPITATION IS ONCE AGAIN NOT EXPECTED AS THESE WEAK FEATURES PUSH ACROSS THE CWA LATE THIS AFTERNOON INTO THE EVENING. WHAT CAN BE EXPECTED THIS EVENING IS AN INCREASE IN CLOUD COVER. THE PARTLY CLOUDY SKIES CURRENTLY IN PLACE WILL BE REPLACED WITH A DECK OF LOW LEVEL MOISTURE ASSOCIATED WITH THIS SURFACE TROUGH. DUE EXPECT MOST OF NORTHERN ILLINOIS TO OBSERVE A PERIOD OF CLOUDY TO PARTLY CLOUDY SKIES THIS EVENING...BUT EXPECT THIS LOW LEVEL MOISTURE TO SCATTER/ERODE WITH THIS TROUGH BECOMING MORE DIFFUSE. ALTHOUGH AS THIS OCCURS UPSTREAM MID LEVEL MOISTURE TO THE WEST WILL CONTINUE TO DROP SOUTH/SOUTHEAST WITH TIME TONIGHT AND CONTINUE TO PROVIDE AT LEAST PARTLY CLOUDY SKIES. WITH A BRIEF RETURN TO ZONAL FLOW ALOFT AND SURFACE RIDGING...MOST OF THE THURSDAY APPEARS TO BE QUIET BUT WITH AN INCREASE IN CLOUD COVER AS A UPPER LEVEL TROUGH DIGS SOUTHEAST OUT OF THE NORTHERN PLAINS. OUTSIDE OF SOME PERSISTENT LAKE EFFECT SNOW SHOWERS FOR THE EASTERN HALF OF LAKE MICHIGAN AND A PERIOD OF DRIER WEATHER TONIGHT AND MOST OF THE DAY THURSDAY FOR THE CWA...CHANCES FOR SNOW WILL BEGIN TO INCREASE LATE IN THE DAY ON THURSDAY. ALTHOUGH THE CURRENT TREND OF BETTER CHANCES/HIGHER POPS ACROSS THE SOUTHERN HALF OF THE CWA REMAINS...THERE STILL REMAINS SOME UNCERTAINTY AS TO THE TIMING OF THE NEXT BIG PUSH OF COLDEST AIR ALOFT. THIS WILL THEN AFFECT THE PLACEMENT OF AN APPROACHING MID LEVEL BAROCLINIC ZONE AND RESULTANT FRONTOGENETICAL FORCING...OUT AHEAD OF A DIGGING UPPER LEVEL TROUGH. THE 12Z NAM CURRENTLY APPEARS TO THE MORE AGGRESSIVE OF THE MODELS BRINGING THIS MID LEVEL BAROCLINIC ZONE THE FURTHEST SOUTH KEEPING THE ASSOCIATED FORCING/QPF ALSO THE FURTHEST SOUTH...AND EVEN OUT OF THE CWA. WHILE THE GFS AND ECMWF HAVE THIS FORCING FURTHER NORTH. NOW FURTHER NORTH MEANING CHANCES FOR A POSSIBLE ACCUMULATING SNOW ACROSS THE SOUTHEAST PORTION OF THE CWA. IT WOULD APPEAR WITH LATEST GUIDANCE THAT CHANCES FOR ACCUMULATING SNOW ACROSS MUCH OF THE CWA IS NOT LOOKING THE GREATEST...AND POSSIBLY FOR EVEN ANY SNOWFALL AT ALL. LOOKING AT VARIOUS CROSS SECTIONS ACROSS THE REGION FOR THIS PERIOD...THE SETUP DOES NOT APPEAR THE GREATEST. OVERALL FORCING AS WELL AS ANY PERSISTENT DEFINED VERTICAL MOTION APPEARS TO MEAGER AT MOST. WITH THE AMOUNT OF DRIER AIR WHICH WILL BE IN PLACE...I WONDER IF WHATEVER FORCING WILL BE PRESENT WILL BE SPENT SATURATING THE COLUMN. IF THIS SATURATION WERE TO OCCUR...IT APPEARS THAT IT WILL BE FOR OUR FAR SOUTHEAST PORTION OF THE CWA IF NOT JUST TO THE SOUTH. ALSO...THROW IN THE FACT THAT ALL LATEST HIRES DATA IS HINTING AT THE POSSIBILITY OF A SNOW LESS THURSDAY NIGHT BY KEEPING ANY QPF JUST TO THE SOUTH OF THE CWA. WITH THIS IN MIND...HAVE STARTED THE TREND OF LOWERING POPS ACROSS MOST OF THE CWA. ALTHOUGH HAVE LEFT THE FAR SOUTHEAST AT CHANCE POPS WITH STILL SOME UNCERTAINTY AT THIS TIME. IF CURRENT TRENDS CONTINUE...POPS ACROSS THIS AREA WILL ALSO SEE THIS LOWERING TREND. IF SNOW DOES DEVELOP...ANY ACCUMULATION WILL BE AROUND THE HALF INCH MARK WITH AT MOST AN INCH AND WOULD BE CONFINED TO AREAS SOUTH OF INTERSTATE 80. ALTHOUGH CURRENT TRENDS ARE FOR A MORE SOUTHERLY TRACK OF THIS FORCING AND ASSOCIATED SNOWFALL...MODELS DO CONTINUE TO VARY FROM ONE RUN TO THE NEXT. EVEN IF THE TRACK WERE TO BE FURTHER NORTH THAN WHAT IS CURRENTLY EXPECTED WITH THE NEXT RUNS...STILL DONT FEEL IT WOULD BE FAR NORTH ENOUGH TO PROVIDE AN ACCUMULATING SNOWFALL FOR THE NORTHERN HALF OF THE CWA. RODRIGUEZ && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 02Z... * VEERING OF AOB 10KT WINDS FM WSW-W TO W-WNW DURING EARLY-MID EVENING. * STRATUS WITH BASES 010-015 FAR NE IA TO PORTIONS OF SW WI EXPANDING. * SLIGHT THREAT OF -SN THU EVENING. TRS //DISCUSSION...UPDATED 02Z... AREA OF MVFR STRATOCU THAT WAS OVER SOUTHERN WI AND FAR N CENTRAL IL HAS ALL BUT DISSIPATED OVER THE LAST COUPLE HRS THOUGH AN AREA OF STRATUS HAS GROWN OVER FAR NE IA AND PORTIONS OF SW IA. WITH LOSS OF ORIGINAL MVFR CLOUDS HAS DUMPED THE TEMPO MVFR CIG GROUP THAT WAS IN TIL 03Z. WHILE NEW UPSTREAM STRATUS PATCH CURRENTLY MOVING TO THE SE...FORECAST WINDS OVER LOCAL AREA HAVE MORE OF A WESTERLY COMPONENT SO EXPECT SOUTHERN EDGE OF THESE CLOUDS TO REMAIN N OF CHI AREA. SMALL POTENTIAL TO BE IN RFD VC FOR A PD THIS EVE BUT HAVE ONLY SCT020 IN RFD TAFOR FOR THIS EVE. PREVIOUS DISCUSSION...UPDATED 00Z... SFC TROF/WEAK COLD FRONT AND ASSOCIATED SLIGHT VEERING OF WINDS HAS MOVED TO JUST S OF THE WI STATE LINE AT 00Z. THE TROF PROCEEDED PATCHY AREAS OF MVFR STRATOCU CIGS SO HAVE A COUPLE HR TEMPO GROUP OF BKN022 IN THE 01Z TO 03Z WINDOW FOR CHI AREA. THEREAFTER...THESE LOWER CLOUDS MOVE OFF TO THE SSE WITH JUST SOME ALTOCUMULUS MOVING E ACROSS THE MS RIVER AHEAD OF THE SHORT WAVE ROTATING SE OVER THE NORTHERN HI PLAINS. LIGHT WINDS WINDS BACK TO WSW OVERNIGHT IN RESPONSE TO APPROACHING NORTHERN HI PLAINS SYSTEM AND ANOTHER COLD FRONT DROPPING SE ACROSS WI DURG THE DAY THU. THIS SYSTEM IS EXPECTED TO PRODUCE SOME LIGHT SNOWFALL BUT ZONE OF BEST FORCING AT THIS POINT LOOKS ALONG A NORTHERN MO...CENTRAL IL...NE IND AXIS SO THREAT OF ANY PRECIPITATION AT THE LOCAL TERMINALS QUITE SMALL. TRS //ORD AND MDW CONFIDENCE...UPDATED 02Z... * HIGH CONFIDENCE ALL FORECAST ELEMENTS. TRS //OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z... * FRIDAY...VFR. SATURDAY...VFR. SUNDAY...VFR. MONDAY...VFR INTO EVENING...SLGT CHC -SN PRODUCING MVFR CIGS AND/OR VSBYS OVERNIGHT. TUESDAY...MVFR CIGS POSSIBLE. * TRS && .MARINE... 157 PM CST A COLD FRONT MOVING ACROSS LAKE SUPERIOR AND WISCONSIN THIS AFTERNOON WILL MOVE ACROSS LAKE MICHIGAN LATER THIS AFTERNOON AND EVENING. THIS WILL HELP KEEP THE WINDS AROUND 25 TO 30 KT TONIGHT AS THE WINDS BECOME NORTHWESTERLY. A PROLONGED PERIOD OF BRISK WEST TO NORTHWESTERLY WINDS IS EXPECTED INTO SATURDAY AS HIGH PRESSURE MOVING FROM THE PLAINS EASTWARD ACROSS THE MID MISSISSIPPI VALLEY...WILL CONTINUE TO PRODUCE A DECENT PRESSURE GRADIENT ACROSS THE GREAT LAKES. LATER SATURDAY THE WINDS LOOK TO SWITCH OUT OF THE SOUTHWEST AND INCREASE TO AROUND 30 KT AGAIN AS THE SURFACE HIGH SHIFTS ACROSS THE OHIO VALLEY AND ANOTHER AREA OF LOW PRESSURE MOVES ACROSS THE PRAIRIE PROVIDENCES OF CANADA. IT APPEARS THAT THESE SOUTHWESTERLY WINDS WILL CONTINUE INTO EARLY NEXT WEEK AS THE SURFACE HIGH CONTINUES TO DOMINATE ACROSS EASTERN CONUS. THERE COULD EVEN BE A PERIOD OF LOW END GALE FORCE WINDS DURING THIS PERIOD. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO BURNS HARBOR UNTIL 10 PM THURSDAY. SMALL CRAFT ADVISORY...NEARSHORE BURNS HARBOR TO MICHIGAN CITY IN UNTIL 10 AM SATURDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
200 PM CST TUE DEC 6 2011 .DISCUSSION... 304 AM CST FORECAST HIGHLIGHTS TODAY INCLUDE LAKE EFFECT PRECIP TODAY...CLOUD TRENDS THROUGH TONIGHT...POTENTIAL LIGHT SNOW EVENT THURSDAY NIGHT PRIOR TO THE ARRIVAL OF SEASONS COLDEST AIR MASS LATE IN THE WEEK. VERY LITTLE CHANGE IS EXPECTED TO WINDS/STABILITY OVER THE LAKE THROUGH MIDDAY...SO GENERALLY EXPECTING A CONTINUATION OF LIGHT NUISANCE TYPE LAKE EFFECT RAIN/SNOW SHOWERS THROUGH THIS MORNING OVER NORTHEAST ILLINOIS. P-TYPE SHOULD BE MOSTLY RAIN NEAR THE LAKE WITH GREATER THREAT OF SNOW MIXTURE INLAND. EVEN WHERE PRECIP CHANGES TO ALL SNOW TEMPS SHOULD MOSTLY BE TOO WARM TO ALLOW FOR ANYTHING MORE THAN A BRIEF DUSTING AT WORST. WINDS WILL BEGIN BACKING THIS AFTERNOON SENDING THE SCATTERED LIGHT LAKE EFFECT PRECIP EASTWARD MORE INTO NW INDY THIS AFTERNOON BEFORE MOVING EAST AND OUT OF OUR CWA TOWARD EVENING. REGARDING CLOUDINESS TODAY...TIS THE SEASON FOR STRATUS AS EVENING RAOBS ACROSS THE REGION SHOWED A RATHER TEXT BOOK STRATUS SOUNDING WITH MOISTURE BENEATH A SHARP FRONTAL INVERSION. HAVE SEEN SOME BREAKS IN THE STRATUS OVER IN EASTERN WI AND COULD SEE A FEW HOLES FROM TODAY OVER MAINLY NE IL...BUT AS FLOW BACKS TO THE NORTHWEST WOULD ANTICIPATE THE STRATUS DECK TO OUR WEST TO ADVECT EASTWARD AND KEEP US FAIRLY SOCKED IN THROUGH TODAY AND INTO THIS EVENING. HAVE OPTED TO GO SOMEWHAT OPTIMISTIC WITH CLEARING TONIGHT FROM THE WEST...AND HANG ONTO CLOUDS LONGER THAN ANY GUIDANCE WOULD SUGGEST AS MODELS ARE NOTORIOUS FOR STRUGGLING WITH SHALLOW COOL SEASON STRATUS. GIVEN THE EXPECTATION OF CLOUD COVER HAVE GONE AHEAD AND RAISED LOW TEMPS TONIGHT...PARTICULARLY SOUTHEAST CWA. STRONG SHORTWAVE PASSES WELL TO OUR SOUTH WEDNESDAY AS LONG WAVE TROUGH RELOADS TO OUR NORTHWEST AND IS PREPARED TO TAKE AN ARCTIC DUMP ON US LATER THIS WEEK. PROBABLY THE MOST CONTENTIOUS PART OF THE FORECAST REVOLVES AROUND THE POTENTIAL FOR SOME ACCUMULATING SNOW THURSDAY NIGHT. GLOBAL MODELS ALL GENERALLY AGREE ON DEVELOPING A TIGHTENING LOW/MID LEVEL BAROCLINIC ZONE IN ADVANCE OF VIGOROUS SHORTWAVE MOVING INTO THE WESTERN GREAT LAKES REGION THURSDAY NIGHT. MODELS CONTINUE TO HINT AT THE DEVELOPMENT OF BAND OF LIGHT FRONTOGENTICALLY DRIVEN PRECIP IN ADVANCE OF THIS SHORTWAVE WHICH COULD BE ENOUGH TO PRODUCE A NARROW BAND OF AN INCH OR SO OF SNOW. THE DEVIL IS IN THE DETAILS HOWEVER AS THE AREA TO SEE THAT SNOWFALL WOULD LIKELY TO BE FAIRLY SMALL AND MODELS HAVE BEEN BOUNCING AROUND A BIT WITH RESPECT TO THE PLACEMENT OF THE HEAVIEST (ALBEIT STILL LIGHT) PRECIP. THE WRF-NMM AND WRF-ARW SUGGEST MOISTURE WILL BE TOO LIMITED AND FORCING TOO FAR SOUTH TO SERIOUSLY THREATEN OUR CWA WITH SUPPORT FROM THE CANADIAN MODEL. HAVING SAID ALL OF THIS...IT REALLY EQUATES TO LITTLE CHANGE FROM PREVIOUS FORECAST WITH SLIGHT CHANCE TO LOW END CHANCE POPS ACROSS THE CWA THURSDAY NIGHT. CWA WILL THEN GET SIDE-SWIPED BY A BITTERLY COLD EARLY SEASON SHOT OF ARCTIC AIR FRIDAY INTO FRIDAY NIGHT WITH H8 TEMPS PROGGED TO DROP TO -15C OR COLDER. TEMPS FRIDAY LOOK TO BE FAIRLY STEADY AND MAY EVEN FALL A BIT AS HEART OF ARCTIC AIR ARRIVES. SAVING GRACE WITH THIS COLD SNAP IS THE LACK OF SNOW COVER HERE AND UPSTREAM LIKELY ALLOWING IT TO MODIFY SOMEWHAT. EVEN SO TEMPS IN THE 20 LOOK LIKELY FRIDAY WITH LOWS IN THE TEENS FRIDAY NIGHT AWAY FROM THE CITY. PATTERN PROGGED TO REMAIN VERY PROGRESSIVE WITH BITTER COLD GETTING SHOVED QUICKLY EASTWARD OVER THE WEEKEND AS A UPPER FLOW TRANSITIONS TO MORE ZONAL. INCREASINGLY STRONG SOUTHWESTERLY WINDS SHOULD SEND TEMPS BACK TO NEAR IF NOT ABOVE NORMAL BY SUNDAY INTO MONDAY WITH LITTLE TO NO THREAT OF ANY PRECIP FRIDAY AFTERNOON THROUGH MONDAY. IZZI && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 18Z... * POTENTIAL LAKE EFFECT SNOW SHOWERS EARLY-MID AFTERNOON. * LIGHT SNOW APPROACHING FROM THE SW. * VARIABLE VFR/MVFR CIGS INTO THIS EVENING. TRS //DISCUSSION...UPDATED 18Z... AREA OF RADAR ECHOES CONTINUES TO MOVE NORTHEASTWARD OVER N CENTRAL IL AND APPROACHING METRO NE IL. LIGHT SNOW HAS BEEN REPORTED AT DVN...MLI...GBG...PIA...C75 WHERE SURFACE DEW POINT DEPRESSIONS ONLY 1 TO 3 DEG F. WITH MODELS DAMPENING OUT THE SHORT WAVE FORCING THIS -SN AS IT CONTINUES NORTHEASTWARD FROM NW MO...SE IA...W CENTRAL IL THIS AFTERNOON AND AN INCREASINGLY ANTICYCLONIC LOW LEVEL FLOW AS THE SURFACE RIDGE CONTINUES TO BUILD SOUTHEASTWARD FROM THE UPPER MIDWEST AND MID MO VALLEY...ALONG WITH MUCH DRIER LOW LEVEL AIR WITH DEW POINTS ONLY IN THE TEENS TO LOWER 20S F ACROSS NORTHERN IL DO NOT ANTICIPATE ANY OF THIS PRECIP TO REACH THE GROUND AT THE LOCAL TERMINALS. TRAJECTORY OF COLD AIR DOWN LAKE MI HAS POTENTIAL TO BRING LAKE EFFECT SNOW SHOWERS TO NE IL THIS AFTERNOON. VISIBLE SATELLITE LOOP SHOWING A LAKE EFFECT BAND HAS SPREAD SOUTHWARD FROM E OF MTW TO E OF ETB LAST COUPLE HOURS. LATEST RUNS OF RUC13 CONTINUE TO BRING LIGHT PRECIP TO THE IL SHORE 1BETWEEN 18Z AND 19Z. OTHER HIGH RESOLUTION MODELS LESS AGGRESSIVE AND ONLY SPIT OUT SPOTTY 0.01 QPF AMOUNTS OVER THE WATER. TEMPERATURE INVERSION PER FORECAST TEMPERATURE PROFILES AND VERIFIED BY ACARS DATA SHOW BASE TO BE LOCATED BETWEEN 050 AND 060 AGL WHICH WOULD BE DEEP ENOUGH FOR SOME LIGHT LAKE EFFECT THOUGH AS MENTIONED ABOVE LOW LEVEL FLOW BECOMES MORE ANTICYCLONIC WITH TIME THIS AFTERNOON AND DRY AIR IN PLACE OVER FAR NE IL AND UPSTREAM. RAC HAS HAD A PERSISTENT NNE WIND OFF THE LAKE ALL MORNING AND DEW POINT THERE HELD AT ONLY 22Z UNTIL 17Z WHEN IT DROPPED TO 20F. A LOW CHANCE OF SOME LAKE EFFECT SHOWERS REACHING VC ORD AND/OR MDW STILL EXISTS SO HAVE KEPT MENTION OF VCSH THESE SITES 20Z-23Z. REGARDING CEILINGS THIS AFTERNOON...METARS FROM NEAR THE SE WI AND NE IL SHORES SHOW THEM CONTINUING TO HOVER AROUND 030. EXPECT AT LEAST AREAS OF CIGS AROUND 030 THESE AREAS UNTIL FLOW AT CLOUD LEVEL BACKS TO N AND NW LATER AFTERNOON AND THIS EVENING. A PERSISTENT AREA OF MVFR STRATUS/STRATOCU HAS BEEN IN PLACE OVER NW WI...FARR SE MN...EASTERN IA...AND NE THROUGH SOUTHERN MO AHEAD OF THE SURFACE RIDGE AXIS. EXPECT THESE CLOUDS TO SHIFT E TO SE AS DOES THE RIDGE DURING THE AFTERNOON AND EVENING BUT BASED ON MODEL INDICATIONS AND MOS OUTPUT ANTICIPATE ONLY SCT AREAS OF MVFR WITH VFR PREVAILING THIS EVENING. SURFACE WINDS CLOSER TO THE RIDGE AXIS UPSTREAM PRETTY UNIFORMLY OUT OF THE NE AND AOB 10KT. WINDS AT LOCAL TERMINALS TO BACK DURING THE FIRST PART OF THE EVENING BOTH DIURNALLY AND AS RIDGE AXIS NEARS OVERHEAD...WITH WINDS TURNING TO OUT OF THE W TO WSW BY MIDNIGHT AS THE RIDGE AXIS SLIPS S OF THE TERMINALS. TRS //ORD AND MDW CONFIDENCE...UPDATED 18Z... * MEDIUM CONFIDENCE IN CIG TRENDS THRU THIS EVE. * LOW CONFIDENCE IN LAKE EFFECT SHOWERS IMPACTING CHI TERMINALS MID AFTERNOON-EARLY EVENING. * MEDIUM CONFIDENCE IN WIND FORECASTS THROUGH THIS EVE. TRS //OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z... * WEDNESDAY NIGHT AND THURSDAY...VFR * THURSDAY NIGHT...CHANCE OF LIGHT SNOW. MVFR POSSIBLE * FRIDAY THROUGH MONDAY...VFR SHEA && .MARINE... 158 PM CST A SURFACE RIDGE OF HIGH PRESSURE EXTENDING FROM THE PLAINS NORTHEASTWARD ACROSS THE UPPER GREAT LAKES REGION WILL SLOWLY SAG SOUTHWARD TONIGHT AS A STRONG AREA OF LOW PRESSURE MOVES INTO THE HUDSON BAY. AS THIS SURFACE RIDGE MOVES ACROSS LAKE MICHIGAN THERE WILL BE A PERIOD OF LIGHTER WINDS THIS EVENING. HOWEVER...THIS WILL BE SHORT LIVED AS THE WINDS WILL BECOME WEST SOUTHWESTERLY AND INCREASE TO NEAR 30 KT LATER TONIGHT ACROSS THE NORTHERN HALF OF THE LAKE. THESE WINDS WILL CONTINUE LAKE-WIDE DURING THE DAY ON WEDNESDAY AS A COLD FRONT MOVES SOUTH ACROSS THE LAKE. THERE COULD BE A PERIOD OF LOW END GALES AS THE COLD AIR BEGINS TO PUSH ACROSS THE LAKE WEDNESDAY NIGHT INTO THURSDAY. HOWEVER...WIDESPREAD 30 KT WITH SOME GALE FORCE GUSTS APPEARS TO BE THE MOST LIKELY AT THIS TIME. WINDS ACROSS LAKE MICHIGAN LOOK TO REMAIN IN THE 15 TO 25 KT RANGE INTO FRIDAY AS THE PRESSURE GRADIENT BETWEEN THE LOW ACROSS THE HUDSON BAY AND HIGH PRESSURE ACROSS THE PLAINS REMAINS ELEVATED. ANOTHER SURGE OF HIGHER WINDS...POTENTIALLY GALE FORCE...LOOKS TO OCCUR ON SATURDAY AS ANOTHER AREA OF LOW PRESSURE TRACKS ACROSS SOUTHERN CANADA. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 PM TUESDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1153 AM CST TUE DEC 6 2011 .DISCUSSION... 304 AM CST FORECAST HIGHLIGHTS TODAY INCLUDE LAKE EFFECT PRECIP TODAY...CLOUD TRENDS THROUGH TONIGHT...POTENTIAL LIGHT SNOW EVENT THURSDAY NIGHT PRIOR TO THE ARRIVAL OF SEASONS COLDEST AIR MASS LATE IN THE WEEK. VERY LITTLE CHANGE IS EXPECTED TO WINDS/STABILITY OVER THE LAKE THROUGH MIDDAY...SO GENERALLY EXPECTING A CONTINUATION OF LIGHT NUISANCE TYPE LAKE EFFECT RAIN/SNOW SHOWERS THROUGH THIS MORNING OVER NORTHEAST ILLINOIS. P-TYPE SHOULD BE MOSTLY RAIN NEAR THE LAKE WITH GREATER THREAT OF SNOW MIXTURE INLAND. EVEN WHERE PRECIP CHANGES TO ALL SNOW TEMPS SHOULD MOSTLY BE TOO WARM TO ALLOW FOR ANYTHING MORE THAN A BRIEF DUSTING AT WORST. WINDS WILL BEGIN BACKING THIS AFTERNOON SENDING THE SCATTERED LIGHT LAKE EFFECT PRECIP EASTWARD MORE INTO NW INDY THIS AFTERNOON BEFORE MOVING EAST AND OUT OF OUR CWA TOWARD EVENING. REGARDING CLOUDINESS TODAY...TIS THE SEASON FOR STRATUS AS EVENING RAOBS ACROSS THE REGION SHOWED A RATHER TEXT BOOK STRATUS SOUNDING WITH MOISTURE BENEATH A SHARP FRONTAL INVERSION. HAVE SEEN SOME BREAKS IN THE STRATUS OVER IN EASTERN WI AND COULD SEE A FEW HOLES FROM TODAY OVER MAINLY NE IL...BUT AS FLOW BACKS TO THE NORTHWEST WOULD ANTICIPATE THE STRATUS DECK TO OUR WEST TO ADVECT EASTWARD AND KEEP US FAIRLY SOCKED IN THROUGH TODAY AND INTO THIS EVENING. HAVE OPTED TO GO SOMEWHAT OPTIMISTIC WITH CLEARING TONIGHT FROM THE WEST...AND HANG ONTO CLOUDS LONGER THAN ANY GUIDANCE WOULD SUGGEST AS MODELS ARE NOTORIOUS FOR STRUGGLING WITH SHALLOW COOL SEASON STRATUS. GIVEN THE EXPECTATION OF CLOUD COVER HAVE GONE AHEAD AND RAISED LOW TEMPS TONIGHT...PARTICULARLY SOUTHEAST CWA. STRONG SHORTWAVE PASSES WELL TO OUR SOUTH WEDNESDAY AS LONG WAVE TROUGH RELOADS TO OUR NORTHWEST AND IS PREPARED TO TAKE AN ARCTIC DUMP ON US LATER THIS WEEK. PROBABLY THE MOST CONTENTIOUS PART OF THE FORECAST REVOLVES AROUND THE POTENTIAL FOR SOME ACCUMULATING SNOW THURSDAY NIGHT. GLOBAL MODELS ALL GENERALLY AGREE ON DEVELOPING A TIGHTENING LOW/MID LEVEL BAROCLINIC ZONE IN ADVANCE OF VIGOROUS SHORTWAVE MOVING INTO THE WESTERN GREAT LAKES REGION THURSDAY NIGHT. MODELS CONTINUE TO HINT AT THE DEVELOPMENT OF BAND OF LIGHT FRONTOGENTICALLY DRIVEN PRECIP IN ADVANCE OF THIS SHORTWAVE WHICH COULD BE ENOUGH TO PRODUCE A NARROW BAND OF AN INCH OR SO OF SNOW. THE DEVIL IS IN THE DETAILS HOWEVER AS THE AREA TO SEE THAT SNOWFALL WOULD LIKELY TO BE FAIRLY SMALL AND MODELS HAVE BEEN BOUNCING AROUND A BIT WITH RESPECT TO THE PLACEMENT OF THE HEAVIEST (ALBEIT STILL LIGHT) PRECIP. THE WRF-NMM AND WRF-ARW SUGGEST MOISTURE WILL BE TOO LIMITED AND FORCING TOO FAR SOUTH TO SERIOUSLY THREATEN OUR CWA WITH SUPPORT FROM THE CANADIAN MODEL. HAVING SAID ALL OF THIS...IT REALLY EQUATES TO LITTLE CHANGE FROM PREVIOUS FORECAST WITH SLIGHT CHANCE TO LOW END CHANCE POPS ACROSS THE CWA THURSDAY NIGHT. CWA WILL THEN GET SIDE-SWIPED BY A BITTERLY COLD EARLY SEASON SHOT OF ARCTIC AIR FRIDAY INTO FRIDAY NIGHT WITH H8 TEMPS PROGGED TO DROP TO -15C OR COLDER. TEMPS FRIDAY LOOK TO BE FAIRLY STEADY AND MAY EVEN FALL A BIT AS HEART OF ARCTIC AIR ARRIVES. SAVING GRACE WITH THIS COLD SNAP IS THE LACK OF SNOW COVER HERE AND UPSTREAM LIKELY ALLOWING IT TO MODIFY SOMEWHAT. EVEN SO TEMPS IN THE 20 LOOK LIKELY FRIDAY WITH LOWS IN THE TEENS FRIDAY NIGHT AWAY FROM THE CITY. PATTERN PROGGED TO REMAIN VERY PROGRESSIVE WITH BITTER COLD GETTING SHOVED QUICKLY EASTWARD OVER THE WEEKEND AS A UPPER FLOW TRANSITIONS TO MORE ZONAL. INCREASINGLY STRONG SOUTHWESTERLY WINDS SHOULD SEND TEMPS BACK TO NEAR IF NOT ABOVE NORMAL BY SUNDAY INTO MONDAY WITH LITTLE TO NO THREAT OF ANY PRECIP FRIDAY AFTERNOON THROUGH MONDAY. IZZI && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 18Z... * POTENTIAL LAKE EFFECT SNOW SHOWERS EARLY-MID AFTERNOON. * LIGHT SNOW APPROACHING FROM THE SW. * VARIABLE VFR/MVFR CIGS INTO THIS EVENING. TRS //DISCUSSION...UPDATED 18Z... AREA OF RADAR ECHOES CONTINUES TO MOVE NORTHEASTWARD OVER N CENTRAL IL AND APPROACHING METRO NE IL. LIGHT SNOW HAS BEEN REPORTED AT DVN...MLI...GBG...PIA...C75 WHERE SURFACE DEW POINT DEPRESSIONS ONLY 1 TO 3 DEG F. WITH MODELS DAMPENING OUT THE SHORT WAVE FORCING THIS -SN AS IT CONTINUES NORTHEASTWARD FROM NW MO...SE IA...W CENTRAL IL THIS AFTERNOON AND AN INCREASINGLY ANTICYCLONIC LOW LEVEL FLOW AS THE SURFACE RIDGE CONTINUES TO BUILD SOUTHEASTWARD FROM THE UPPER MIDWEST AND MID MO VALLEY...ALONG WITH MUCH DRIER LOW LEVEL AIR WITH DEW POINTS ONLY IN THE TEENS TO LOWER 20S F ACROSS NORTHERN IL DO NOT ANTICIPATE ANY OF THIS PRECIP TO REACH THE GROUND AT THE LOCAL TERMINALS. TRAJECTORY OF COLD AIR DOWN LAKE MI HAS POTENTIAL TO BRING LAKE EFFECT SNOW SHOWERS TO NE IL THIS AFTERNOON. VISIBLE SATELLITE LOOP SHOWING A LAKE EFFECT BAND HAS SPREAD SOUTHWARD FROM E OF MTW TO E OF ETB LAST COUPLE HOURS. LATEST RUNS OF RUC13 CONTINUE TO BRING LIGHT PRECIP TO THE IL SHORE 1BETWEEN 18Z AND 19Z. OTHER HIGH RESOLUTION MODELS LESS AGGRESSIVE AND ONLY SPIT OUT SPOTTY 0.01 QPF AMOUNTS OVER THE WATER. TEMPERATURE INVERSION PER FORECAST TEMPERATURE PROFILES AND VERIFIED BY ACARS DATA SHOW BASE TO BE LOCATED BETWEEN 050 AND 060 AGL WHICH WOULD BE DEEP ENOUGH FOR SOME LIGHT LAKE EFFECT THOUGH AS MENTIONED ABOVE LOW LEVEL FLOW BECOMES MORE ANTICYCLONIC WITH TIME THIS AFTERNOON AND DRY AIR IN PLACE OVER FAR NE IL AND UPSTREAM. RAC HAS HAD A PERSISTENT NNE WIND OFF THE LAKE ALL MORNING AND DEW POINT THERE HELD AT ONLY 22Z UNTIL 17Z WHEN IT DROPPED TO 20F. A LOW CHANCE OF SOME LAKE EFFECT SHOWERS REACHING VC ORD AND/OR MDW STILL EXISTS SO HAVE KEPT MENTION OF VCSH THESE SITES 20Z-23Z. REGARDING CEILINGS THIS AFTERNOON...METARS FROM NEAR THE SE WI AND NE IL SHORES SHOW THEM CONTINUING TO HOVER AROUND 030. EXPECT AT LEAST AREAS OF CIGS AROUND 030 THESE AREAS UNTIL FLOW AT CLOUD LEVEL BACKS TO N AND NW LATER AFTERNOON AND THIS EVENING. A PERSISTENT AREA OF MVFR STRATUS/STRATOCU HAS BEEN IN PLACE OVER NW WI...FARR SE MN...EASTERN IA...AND NE THROUGH SOUTHERN MO AHEAD OF THE SURFACE RIDGE AXIS. EXPECT THESE CLOUDS TO SHIFT E TO SE AS DOES THE RIDGE DURING THE AFTERNOON AND EVENING BUT BASED ON MODEL INDICATIONS AND MOS OUTPUT ANTICIPATE ONLY SCT AREAS OF MVFR WITH VFR PREVAILING THIS EVENING. SURFACE WINDS CLOSER TO THE RIDGE AXIS UPSTREAM PRETTY UNIFORMLY OUT OF THE NE AND AOB 10KT. WINDS AT LOCAL TERMINALS TO BACK DURING THE FIRST PART OF THE EVENING BOTH DIURNALLY AND AS RIDGE AXIS NEARS OVERHEAD...WITH WINDS TURNING TO OUT OF THE W TO WSW BY MIDNIGHT AS THE RIDGE AXIS SLIPS S OF THE TERMINALS. TRS //ORD AND MDW CONFIDENCE...UPDATED 18Z... * MEDIUM CONFIDENCE IN CIG TRENDS THRU THIS EVE. * LOW CONFIDENCE IN LAKE EFFECT SHOWERS IMPACTING CHI TERMINALS MID AFTERNOON-EARLY EVENING. * MEDIUM CONFIDENCE IN WIND FORECASTS THROUGH THIS EVE. TRS //OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z... * WEDNESDAY NIGHT AND THURSDAY...VFR * THURSDAY NIGHT...CHANCE OF LIGHT SNOW. MVFR POSSIBLE * FRIDAY THROUGH MONDAY...VFR SHEA && .MARINE... 248 AM CST HIGH PRESSURE EXTENDING FROM THE UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS WILL SLOWLY SAG ACROSS THE GREAT LAKES REGION TODAY AND TONIGHT AS A STRONG LOW PRESSURE SYSTEM MOVES ACROSS NORTHERN MANITOBA INTO THE HUDSON BAY. THIS LOW WILL DRAG A COLD FRONT ACROSS LAKE MICHIGAN WEDNESDAY. DURING THIS PERIOD...WINDS OVER THE LAKE WILL GRADUALLY SHIFT FROM NORTHERLY TO SOUTHWESTERLY. WIND SPEEDS WILL DIMINISH TO AS LOW AS TO TO 15 KT LATE TONIGHT AS THE SFC RIDGE AXIS CROSSES THE LAKE...BUT AS THE RIDGE PUSHES TO THE SOUTH AND A SFC TROUGH ASSOCIATED WITH THE COLD FRONT DROPS THROUGH THE NORTHERN PLAINS LATE TONIGHT...WINDS WILL QUICKLY INCREASE AGAIN TO AROUND 30 KT. FOLLOWING THE PASSAGE OF THE COLD FRONT...ANOTHER CANADIAN HIGH PRESSURE SYSTEM WILL DROP SOUTHEAST ACROSS THE PLAINS THURSDAY AND FRIDAY. THIS SHOULD MAINTAIN A MODERATE PRESSURE GRADIENT OVER THE GREAT LAKES. THE COMBINATION OF THE MODERATELY STRONG PRESSURE GRADIENT AND STRONG COLD ADVECTION BEHIND THE EXITING FRONT WILL KEEP WINDS AROUND 25 TO 30KT OVER THE LAKE FROM WEDNESDAY THROUGH SATURDAY. KREIN && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 PM TUESDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1105 AM CST TUE DEC 6 2011 .DISCUSSION... 304 AM CST FORECAST HIGHLIGHTS TODAY INCLUDE LAKE EFFECT PRECIP TODAY...CLOUD TRENDS THROUGH TONIGHT...POTENTIAL LIGHT SNOW EVENT THURSDAY NIGHT PRIOR TO THE ARRIVAL OF SEASONS COLDEST AIR MASS LATE IN THE WEEK. VERY LITTLE CHANGE IS EXPECTED TO WINDS/STABILITY OVER THE LAKE THROUGH MIDDAY...SO GENERALLY EXPECTING A CONTINUATION OF LIGHT NUISANCE TYPE LAKE EFFECT RAIN/SNOW SHOWERS THROUGH THIS MORNING OVER NORTHEAST ILLINOIS. P-TYPE SHOULD BE MOSTLY RAIN NEAR THE LAKE WITH GREATER THREAT OF SNOW MIXTURE INLAND. EVEN WHERE PRECIP CHANGES TO ALL SNOW TEMPS SHOULD MOSTLY BE TOO WARM TO ALLOW FOR ANYTHING MORE THAN A BRIEF DUSTING AT WORST. WINDS WILL BEGIN BACKING THIS AFTERNOON SENDING THE SCATTERED LIGHT LAKE EFFECT PRECIP EASTWARD MORE INTO NW INDY THIS AFTERNOON BEFORE MOVING EAST AND OUT OF OUR CWA TOWARD EVENING. REGARDING CLOUDINESS TODAY...TIS THE SEASON FOR STRATUS AS EVENING RAOBS ACROSS THE REGION SHOWED A RATHER TEXT BOOK STRATUS SOUNDING WITH MOISTURE BENEATH A SHARP FRONTAL INVERSION. HAVE SEEN SOME BREAKS IN THE STRATUS OVER IN EASTERN WI AND COULD SEE A FEW HOLES FROM TODAY OVER MAINLY NE IL...BUT AS FLOW BACKS TO THE NORTHWEST WOULD ANTICIPATE THE STRATUS DECK TO OUR WEST TO ADVECT EASTWARD AND KEEP US FAIRLY SOCKED IN THROUGH TODAY AND INTO THIS EVENING. HAVE OPTED TO GO SOMEWHAT OPTIMISTIC WITH CLEARING TONIGHT FROM THE WEST...AND HANG ONTO CLOUDS LONGER THAN ANY GUIDANCE WOULD SUGGEST AS MODELS ARE NOTORIOUS FOR STRUGGLING WITH SHALLOW COOL SEASON STRATUS. GIVEN THE EXPECTATION OF CLOUD COVER HAVE GONE AHEAD AND RAISED LOW TEMPS TONIGHT...PARTICULARLY SOUTHEAST CWA. STRONG SHORTWAVE PASSES WELL TO OUR SOUTH WEDNESDAY AS LONG WAVE TROUGH RELOADS TO OUR NORTHWEST AND IS PREPARED TO TAKE AN ARCTIC DUMP ON US LATER THIS WEEK. PROBABLY THE MOST CONTENTIOUS PART OF THE FORECAST REVOLVES AROUND THE POTENTIAL FOR SOME ACCUMULATING SNOW THURSDAY NIGHT. GLOBAL MODELS ALL GENERALLY AGREE ON DEVELOPING A TIGHTENING LOW/MID LEVEL BAROCLINIC ZONE IN ADVANCE OF VIGOROUS SHORTWAVE MOVING INTO THE WESTERN GREAT LAKES REGION THURSDAY NIGHT. MODELS CONTINUE TO HINT AT THE DEVELOPMENT OF BAND OF LIGHT FRONTOGENTICALLY DRIVEN PRECIP IN ADVANCE OF THIS SHORTWAVE WHICH COULD BE ENOUGH TO PRODUCE A NARROW BAND OF AN INCH OR SO OF SNOW. THE DEVIL IS IN THE DETAILS HOWEVER AS THE AREA TO SEE THAT SNOWFALL WOULD LIKELY TO BE FAIRLY SMALL AND MODELS HAVE BEEN BOUNCING AROUND A BIT WITH RESPECT TO THE PLACEMENT OF THE HEAVIEST (ALBEIT STILL LIGHT) PRECIP. THE WRF-NMM AND WRF-ARW SUGGEST MOISTURE WILL BE TOO LIMITED AND FORCING TOO FAR SOUTH TO SERIOUSLY THREATEN OUR CWA WITH SUPPORT FROM THE CANADIAN MODEL. HAVING SAID ALL OF THIS...IT REALLY EQUATES TO LITTLE CHANGE FROM PREVIOUS FORECAST WITH SLIGHT CHANCE TO LOW END CHANCE POPS ACROSS THE CWA THURSDAY NIGHT. CWA WILL THEN GET SIDE-SWIPED BY A BITTERLY COLD EARLY SEASON SHOT OF ARCTIC AIR FRIDAY INTO FRIDAY NIGHT WITH H8 TEMPS PROGGED TO DROP TO -15C OR COLDER. TEMPS FRIDAY LOOK TO BE FAIRLY STEADY AND MAY EVEN FALL A BIT AS HEART OF ARCTIC AIR ARRIVES. SAVING GRACE WITH THIS COLD SNAP IS THE LACK OF SNOW COVER HERE AND UPSTREAM LIKELY ALLOWING IT TO MODIFY SOMEWHAT. EVEN SO TEMPS IN THE 20 LOOK LIKELY FRIDAY WITH LOWS IN THE TEENS FRIDAY NIGHT AWAY FROM THE CITY. PATTERN PROGGED TO REMAIN VERY PROGRESSIVE WITH BITTER COLD GETTING SHOVED QUICKLY EASTWARD OVER THE WEEKEND AS A UPPER FLOW TRANSITIONS TO MORE ZONAL. INCREASINGLY STRONG SOUTHWESTERLY WINDS SHOULD SEND TEMPS BACK TO NEAR IF NOT ABOVE NORMAL BY SUNDAY INTO MONDAY WITH LITTLE TO NO THREAT OF ANY PRECIP FRIDAY AFTERNOON THROUGH MONDAY. IZZI && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 16Z... * POTENTIAL LAKE EFFECT SNOW SHOWERS EARLY-MID AFTERNOON. * LIGHT SNOW APPROACHING FROM THE SW. * VARIABLE VFR/MVFR CIGS INTO THIS EVENING. TRS //DISCUSSION...UPDATED 16Z... AREA OF RADAR ECHOES CONTINUES TO MOVE NORTHEASTWARD OVER N CENTRAL IL AND APPROACHING METRO NE IL. LIGHT SNOW HAS BEEN REPORTED AT DVN...MLI...PIA...C75 WHERE SURFACE DEW POINT DEPRESSIONS 1-3 DEG F. WITH MODELS DAMPENING OUT THE SHORT WAVE FORCING THIS -SN THIS AFTERNOON AS IT CONTINUES NORTHEASTWARD FROM NW MO AND SE IA...INCREASINGLY ANTICYCLONIC LOW LEVEL FLOW AS THE SURFACE RIDGE CONTINUES TO BUILD SOUTHEASTWARD FROM THE UPPER MIDWEST AND MID MO VALLEY...AND WITH MUCH DRIER LOW LEVEL AIR WITH DEW POINTS ONLY IN THE TEENS TO LOWER 20S F ACROSS NORTHERN IL DO NOT ANTICIPATE ANY OF THIS PRECIP TO REACH THE GROUND AT THE LOCAL TERMINALS. TRAJECTORY OF COLD AIR DOWN LAKE MI HAS POTENTIAL TO BRING LAKE EFFECT SNOW SHOWERS TO NE IL THIS AFTERNOON. VISIBLY SATELLITE LOOP SHOWING A LAKE EFFECT BAND HAS SPREAD SOUTHWARD FROM E OF MTW TO E OF ETB LAST COUPLE HOURS. LATEST RUNS OF RUC13 CONTINUE TO BRING LIGHT PRECIP TO THE IL SHORE AROUND 19Z. OTHER HIGH RESOLUTION MODELS LESS AGGRESSIVE AND ONLY SPIT OUT SPOTTY 0.01 QPF AMOUNTS OVER THE WATER. BASE OF INVERSION PER FORECAST TEMPERATURE PROFILES AND VERIFIED BY ACARS DATA SHOW IT TO BE LOCATED 5500-6000 FT AGL WHICH WOULD DEEP ENOUGH FOR SOME LIGHT LAKE EFFECT THOUGH AS MENTIONED ABOVE LOW LEVEL FLOW BECOMES MORE ANTICYCLONIC WITH TIME THIS AFTERNOON AND DRY AIR IN PLACE OVER FAR NE IL AND UPSTREAM. RAC HAS HAD A PERSISTENT NNE WIND OFF THE LAKE ALL MORNING AND DEW POINT THERE STILL ONLY 22F. A LOW CHANCE OF SOME LAKE EFFECT SHOWERS REACHING VC ORD AND/OR MDW STILL EXISTS SO HAVE KEPT MENTION OF VCSH THESE SITES 18Z-21Z. REGARDING CEILINGS LATE MORNING THROUGH AFTERNOON...METARS FROM NEAR THE SE WI AND NE IL SHORES HOVER AROUND 030. EXPECT AT LEAST AREAS OF CIGS AROUND 030 THESE AREAS UNTIL FLOW AT CLOUD LEVEL BACKS TO N TO NW. A PERSISTENT AREA OF MVFR STRATUS/STRATOCU HAS BEEN IN PLACE AHEAD OF THE SURFACE RIDGE AXIS. EXPECT THESE CLOUDS TO SHIFT E TO SE AS DOES THE RIDGE THIS AFTERNOON AND EVENING BUT BASED ON MODEL INDICATIONS AND MOS OUTPUT ANTICIPATE ONLY PREVAILING SCT AREAS OF MVFR THIS EVENING. SLIGHT BACKING OF WINDS AT ORD AND MDW LAST HOUR OR TWO LIKELY IN RESPONSE TO INCREASING CONVERGENT BAND MOVING DOWN FROM MID LAKE SO HAVE KEPT WITH THIS NOTION THROUGH THE AFTERNOON AND THEN FURTHER BACKING DUE TO APPROACHING SURFACE RIDGE OCCURS THIS EVE. TRS //ORD AND MDW CONFIDENCE...UPDATED 14Z... * MEDIUM CONFIDENCE IN CIG TRENDS INTO THIS EVE. * LOW CONFIDENCE IN LAKE EFFECT SHOWERS IMPACTING CHI TERMINALS THIS AFTERNOON. * MEDIUM CONFIDENCE IN WIND FORECASTS INTO THIS EVE. TRS //OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z... * WEDNESDAY NIGHT AND THURSDAY...VFR * THURSDAY NIGHT...CHANCE OF LIGHT SNOW. MVFR POSSIBLE * FRIDAY THROUGH MONDAY...VFR SHEA && .MARINE... 248 AM CST HIGH PRESSURE EXTENDING FROM THE UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS WILL SLOWLY SAG ACROSS THE GREAT LAKES REGION TODAY AND TONIGHT AS A STRONG LOW PRESSURE SYSTEM MOVES ACROSS NORTHERN MANITOBA INTO THE HUDSON BAY. THIS LOW WILL DRAG A COLD FRONT ACROSS LAKE MICHIGAN WEDNESDAY. DURING THIS PERIOD...WINDS OVER THE LAKE WILL GRADUALLY SHIFT FROM NORTHERLY TO SOUTHWESTERLY. WIND SPEEDS WILL DIMINISH TO AS LOW AS TO TO 15 KT LATE TONIGHT AS THE SFC RIDGE AXIS CROSSES THE LAKE...BUT AS THE RIDGE PUSHES TO THE SOUTH AND A SFC TROUGH ASSOCIATED WITH THE COLD FRONT DROPS THROUGH THE NORTHERN PLAINS LATE TONIGHT...WINDS WILL QUICKLY INCREASE AGAIN TO AROUND 30 KT. FOLLOWING THE PASSAGE OF THE COLD FRONT...ANOTHER CANADIAN HIGH PRESSURE SYSTEM WILL DROP SOUTHEAST ACROSS THE PLAINS THURSDAY AND FRIDAY. THIS SHOULD MAINTAIN A MODERATE PRESSURE GRADIENT OVER THE GREAT LAKES. THE COMBINATION OF THE MODERATELY STRONG PRESSURE GRADIENT AND STRONG COLD ADVECTION BEHIND THE EXITING FRONT WILL KEEP WINDS AROUND 25 TO 30KT OVER THE LAKE FROM WEDNESDAY THROUGH SATURDAY. KREIN && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 PM TUESDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
249 AM CST TUE DEC 6 2011 .DISCUSSION... 852 PM CST A FEW CHALLENGES REVOLVING AROUND THE LAKE EFFECT PRECIPITATION THIS EVENING. RADAR IMAGERY SHOWS PRECIPITATION FROM MILWAUKEE SOUTH INTO NORTHERN WILL COUNTY. WATER VAPOR IMAGERY SHOWS DEFORMATION ZONE MOVING EAST OF THE FORECAST AREA WITH SUBSIDENCE AND MID LEVEL DRY AIR MOVING IN FROM THE SOUTHWEST. HAVE SEEN OVERALL INTENSITY OF RETURNS OFF THE LAKE DECREASE SOMEWHAT AS THIS FEATURE PROGRESSES THROUGH...BUT FORECAST SOUNDINGS SHOW LITTLE CHANGE IN THE LOW AND MID LEVELS OVERNIGHT AND SUSPECT AREA OF PRECIPITATION WILL CONTINUE THROUGH THE REMAINDER OF THE EVENING AND OVERNIGHT. SOUNDINGS DO SHOW A SLIGHT DECREASE IN THE INVERSION HEIGHTS BETWEEN 06-09Z...AND MOST OF THE HIGH-RES GUIDANCE...WITH THE RUC BEING THE EXCEPTION...SHOWS PRECIP DIMINISHING LATE TONIGHT. SUSPECT THE RUC MAY BE ONTO SOMETHING THOUGH...WITH NO REAL SENSE OF WHAT MAY CAUSE LAKE EFFECT TO SHUT OFF OVERNIGHT...THUS WILL BUMP UP POPS FOR TONIGHT. PRECIP TYPE ALSO A BIG QUESTION MARK. THE 129DM LINE ON THE 1000-850MB THICKNESS LINES UP WELL WITH CURRENT RAIN-SNOW LINE AND DOES GRADUALLY SHIFT SOUTH THROUGH COOK COUNTY TONIGHT...BUT LOCALIZED EFFECTS WITH WARM AIR OFF THE LAKE AND URBAN HEAT ISLAND WILL DELAY THE CHANGE OVER TO SNOW FOR AREAS ALONG THE LAKESHORE AND PORTIONS OF COOK COUNTY DESPITE THE GRADUAL COOL ADVECTION. HOWEVER...WET-BULBING EFFECTS UNDER THE HEAVIER SHOWERS MAY DOMINATE...AND HAS ALREADY BEEN EVIDENT ON DUAL-POL IMAGERY WITH SOME OF THE SHOWERS THAT PASSED OVER SOUTHERN DUPAGE COUNTY EARLIER TONIGHT WHERE SNOW BRIEFLY MADE ITS WAY TO THE SURFACE. SO DO EXPECT A CHANGE OVER TO SNOW AT SOME POINT...BUT HAVE VERY LOW CONFIDENCE ON PRECISE TIMING. PRECIP AMOUNT REPORTS HAVE BEEN ON THE ORDER OF A FEW HUNDREDTHS THUS FAR UNDER THE STRONGEST RETURNS...AND SEE NO REASON FOR THIS TO CHANGE OVERNIGHT NOR HAVE ANY CONCERNS FOR ACCUMULATIONS. FORECAST UPDATES TO FOLLOW SHORTLY...BMD //PREV DISCUSSION... NEAR TERM....THIS AFTERNOON THROUGH TONIGHT... VISIBLE IMAGERY CONTINUES TO SHOW A THICK STRATUS LAYER OVERHEAD. VERTICAL GROWTH OF THE CLOUD DESK REMAINS WELL SOUTH OF THE REGION OVER THE OZARKS AND WESTERN TENNESSEE. WITH THE ABUNDANT SOLAR SHIELDING...TEMPERATURES THIS AFTERNOON HAVE NOT WARMED MUCH. THUS EXPECT TEMPS TO REMAIN IN THE MID/UPR 30S. BETTER COLD AIR ADVECTION HAS CONTINUED TO OCCUR ACROSS WEST CENTRAL ILLINOIS WHERE TEMPERATURES HAVE HELD AROUND 30...AND IN THE MID 20S ACROSS CENTRAL MISSOURI. IR IMAGERY THIS AFTERNOON ALSO CONTINUES TO INDICATE MUCH THICKER CLOUD COVER OVER ILLINOIS/INDIANA. WSR-88D RADAR WAS DEPICTING PRECIPITATION PUSHING INLAND ACROSS BOTH COOK AND LAKE COUNTY ILLINOIS...AS LAKE MOISTURE SLOWLY SLIDES SOUTH/SOUTHWEST. MOISTURE REMAINS VERY SHALLOW AND MINIMAL LIFT...SUPPORTING PRECIP TO REMAIN AS LIQUID WITH PATCHY DRIZZLE. FURTHER NORTH A FEW OBSERVATIONS ACROSS WISCONSIN HAVE REPORTED LGT SN. FOR FAR NORTHEAST ILLINOIS TEMPERATURES ARE WARM ENOUGH TO MAINTAIN A LIQUID STATE OF PRECIPITATION. QUASI-STATIONARY BOUNDARY REMAINS TO OUR SOUTHEAST ACROSS THE OZARKS STRETCHING NORTHEAST THROUGH THE OHIO VALLEY. OVERNIGHT THE CHALLENGE WILL CONTINUE TO BE COVERAGE OF PRECIP...AND TEMPERATURES. GUIDANCE HAS SUGGESTED THAT TEMPERATURES WILL COOL MORE EFFICIENTLY TONIGHT WITH BETTER COLD AIR ADVECTION INTO NORTHERN IL/NORTHWEST IN...HOWEVER FEEL THIS IS TOO OVERDONE. THUS HAVE ADJUSTED OVERNIGHT LOWS UP A FEW DEGREES GIVEN THE EXPECTED THICK CLOUD COVER. WINDS START TO TURN NORTHEASTERLY THIS EVENING AND CONTINUE OVERNIGHT...WHICH SHOULD AID IN BENDING THE LAKE MOISTURE SOUTHWEST OR OVER NORTHEAST ILLINOIS. THUS HAVE MAINTAINED MENTION OF SLIGHT CHANCE WORDING. VERTICAL LIFT APPEARS TO BUMP UP A TAD OVERNIGHT...WITH SFC TEMPS PUSHING CLOSER TO FREEZING. MODEL SOUNDINGS INDICATE THAT ANY PRECIP THAT FALLS THIS EVENING WOULD START AS LIQUID...THEN POSSIBLY START TO MIX WITH LGT SNOW. AS PREVIOUSLY MENTIONED ABOUT THE MINIMAL LIFTING MECHANISM...IT IS POSSIBLE THAT PATCHY DRIZZLE COULD OCCUR BEFORE LGT SNOW WOULD OCCUR. QPF REMAINS MINIMAL...OR LESS THAN 0.05 THROUGH THE NEXT 24HRS. MORE THAN LIKELY IT IS CLOSER TO 0.01 TO 0.03. BASED ON THE EXPECTED TEMPERATURES AND MINIMAL LIFT...ANY SNOW THAT DOES FALL MAY ACCUMULATE UP TO A QUARTER OF AN INCH. ALTHOUGH THAT BEING SAID...CONFIDENCE IS LOW THAT THIS SCENARIO WOULD PAN OUT. TUESDAY THROUGH THURSDAY... A WEAK WAVE IS PROGGED TO DEVELOP ALONG THE QUASI-STATIONARY BOUNDARY AND SLIDE NORTHEAST THROUGH MISSOURI. ANTI-CYCLONIC FLOW REMAINS UPSTREAM ACROSS IOWA/MINNESOTA/WISCONSIN...WHICH SHOULD START TO TURN OFF LAKE MOISTURE SOMETIME TUE AFTN/EVE. HAVE HELD ONTO MENTION OF LGT RA/SN THRU THE MORNING HOURS. AFTN TEMPS SHOULD WARM MARGINALLY TO AROUND THE MID 30S ACROSS MOST OF THE CWFA. BY TUE AFTN/EVE THE INFLUENCE FROM THE UPSTREAM RIDGE SHOULD FINALLY ERODE THE THICK STRATUS AND ALLOW PARTLY CLOUD SKIES TO DEVELOP BY THE LATE AFTN/EVE. THIS COUPLED WITH 850MB THERMAL TROUGH OF -10 TO -12 DEG...WILL SET THE STAGE FOR OVERNIGHT LOWS IN THE TEENS TO LOWER 20S. AS WINDS SLOWLY SHIFT FROM THE NORTHWEST TO THE WEST/SOUTHWEST WED...THE LAKE MOISTURE WILL BECOME ORIENTED OVER LOWER MICHIGAN. 500MB VORT SLOWLY SLIDES EAST ALONG THE SOUTHERN STREAM...WHILE THE NORTHERN STREAM REMAINS IN PROGRESSIVE. THE FOCUS WED WILL CONTINUE TO BE ON THE ARRIVAL OF A POTENT FRONTAL BOUNDARY...THAT IS COUPLED WITH AN 850MB THERMAL TROUGH OF -20 TO -22 DEG C. THIS WILL PROVIDE THE COOLEST AIR OF THE SEASON LATER IN THE WEEK TO NORTHERN IL/NORTHWEST IN. PRIOR TO THE ARRIVAL OF THIS AIRMASS...MOISTURE IS EXPECTED TO POOL ALONG THE FRONT AS IT SLOWLY PUSHES SOUTHEAST ACROSS THE PLAINS THURSDAY. GUIDANCE HAS FLUCTUATED ON HOW THIS FEATURE WILL UNFOLD...AND IT REMAINS POSSIBLE THAT A WEAK WAVE WILL DEVELOP ALONG THE LEE-SIDE OF THE 500MB TROUGH AXIS. THIS SCENARIO COULD RESULT IN LGT SNOW OVERSPREADING NORTHERN IL/NORTHWEST IN THUR AFTN AS THE POTENT THERMAL TROUGH ARRIVES ALOFT. TEMPS THUR WILL REMAIN IN THE LOW/MID 30S. BEACHLER LONG TERM...THURSDAY NIGHT THROUGH MONDAY MAIN CONCERNS IN THE EXTENDED PORTION OF THE FORECAST ARE LIGHT SNOW POTENTIAL THURSDAY NIGHT INTO EARLY FRIDAY...FOLLOWED BY THE FIRST BLAST OF ARCTIC AIR OF THE SEASON FOR FRIDAY INTO EARLY SATURDAY. ON THURSDAY NIGHT...AS MENTIONED ABOVE...DIGGING H5 TROUGH WILL SPAWN A WEAK SURFACE LOW WHICH WILL TRACK ACROSS NORTHERN GREAT LAKES AND SEND AN ARCTIC FRONTAL BOUNDARY TOWARD AREA. MODELS HAVE BEEN CONSISTENT IN SPITTING OUT A STRIPE OF VERY LIGHT QPF NEAR OR OVER CWA IN RESPONSE TO THIS FEATURE. WITH NEGATIVE TEEN AIR AT H85 BUILDING IN FROM THE NORTH BEHIND ARCTIC FRONT...SUSPECT WAVE WILL RIDE ALONG LOW LEVEL BAROCLINIC ZONE. A PEEK AT GFS TIME HEIGHT AT ORD FOR THURSDAY NIGHT PERIOD SHOWS SATURATION AND ADEQUATE LIFT INTO -15C FAVORED SNOW GROWTH ZONE. THEREFORE...DESPITE QPF ONLY IN THE HUNDREDTHS UP TO MAYBE A TENTH OR SLIGHTLY MORE...WITH VERY COLD AIR MASS...SNOW WOULD BE HIGH RATIO AND POSSIBLY RESULT IN FIRST WIDESPREAD LIGHT ACCUMULATING SNOW OF THE SEASON FOR MANY (IF SCENARIO PANS OUT...POTENTIAL FOR AN INCH OR TWO OF SNOW). FOR NOW...HAVE BUMPED UP POPS IN GRIDS TO CHANCE ACROSS THE AREA GIVEN SOME UNCERTAINTY IN EXACTLY WHERE BEST SNOW POTENTIAL WILL OCCUR. LIGHT SNOW MAY LINGER INTO EARLY FRIDAY FOR EASTERN PORTION OF CWA BEFORE WAVE SHIFTS OFF TO THE EAST. THEREAFTER...ON FRIDAY...STRONG CAA WILL BE IN FULL FORCE WITH SHARP THERMAL TROUGH ARRIVING OVERHEAD LATE IN THE DAY. OPERATIONAL MODELS AND ENSEMBLES HAVE BACKED OFF EVER SO SLIGHTLY ON JUST HOW COLD ARCTIC AIR MASS WILL BE...BUT -15C OR SO AT H85 AND -8 TO -10 AT H95 WILL BE PLENTY COLD. TEMPERATURES WILL STRUGGLE INTO THE MID TO UPPER 20S FRIDAY AFTERNOON WITH A PERSISTENT WNW BREEZE LEADING TO LOW WIND CHILL VALUES. AXIS OF ARCTIC HIGH WILL PASS CLOSEST ON FRIDAY NIGHT...LEADING TO STRONG RADIATIONAL COOLING. IF MINOR SNOW COVER IS PRESENT...LOW TO MID TEENS...UPPER TEENS IN DOWNTOWN CHICAGO...IN GRIDS FOR LOW EARLY SATURDAY MORNING MIGHT BE A FEW DEGREES TOO HIGH. SW FLOW...STEADY WARMING ALOFT AND LIKELY FULL SUNSHINE ON SATURDAY WILL ALLOW FOR SOME RECOVERY FROM VERY COLD START TO DAY...BUT SUSPECT IT WILL BE TOUGH TO MAKE UP A LOT OF GROUND DUE TO LIMITED DAYLIGHT THIS TIME OF YEAR. THUS SHAVED OFF A DEGREE FROM MODEL BLEND FOR MAX TEMPERATURES ON SATURDAY...YIELDING HIGHS IN THE UPPER 20S TO AROUND 30 DEGREES. SUNDAY AND MONDAY LOOK TO BE MAINLY DRY WITH TEMPERATURES RETURNING TO CLOSE TO SEASONAL NORMS DUE TO SOUTHERLY FLOW AND CONTINUED WARMING OF THE COLUMN. A FRONTAL BOUNDARY MAY DROP SOUTH THROUGH THE AREA LATE MONDAY... BRINGING NEXT CHANCE FOR LIGHT PRECIP...BUT LARGE MODEL UNCERTAINTY THIS FAR OUT PRECLUDES ANYTHING MORE THAN SLIGHT POPS FOR MONDAY NIGHT. RC && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 08Z... * POTENTIAL FOR LAKE EFFECT RAIN/SNOW SHOWERS THROUGH THE AFTERNOON * PERIODS OF MVFR CIGS THROUGH TUESDAY EVENING. SHEA //DISCUSSION...UPDATED 06Z... MAIN FORECAST CONCERN AND CHALLENGE REMAINS THE LAKE EFFECT RAIN/ SNOW SHOWERS. OVERALL INTENSITY HAS DIMINISHED SOME FROM EARLIER THIS EVENING BUT STILL MANY SHOWERS FROM FAR SOUTHEAST WI INTO NORTHEAST IL. COOLER AIR SLOWLY FILTERING IN FROM THE NORTH HAS CHANGED PRECIP TO MAINLY SNOW ACROSS SOUTHEAST WI INTO FAR NORTHEAST IL...AS WELL AS LOCATIONS FARTHER INLAND...SUCH AS DPA WHERE TEMPS HAVE ALSO COOLED A FEW DEGREES. FORECAST SOUNDINGS CONTINUE TO SHOW THE INVERSION HEIGHT LOWERING SOME THROUGH THE OVERNIGHT HRS AND THIS SHOULD LIMIT THE COVERAGE AND INTENSITY OF THE LAKE EFFECT SHOWERS OVERNIGHT. WHILE THERE WILL STILL LIKELY BE PERIODS OF LIGHT RAIN AND/OR LIGHT SNOW...CONFIDENCE IN TRYING TO TIME ANY OF THIS PRECIP IS VERY LOW. AND FOR THAT REASON...HAVE GONE WITH A VICINITY MENTION...THOUGH LATER UPDATES FOR PREVAILING OR TEMPO PRECIP MAY BE NEEDED. LITTLE CHANGE TO THE AIRMASS OR LOW LEVEL PROFILES INTO TUESDAY AFTERNOON AND THERE COULD BE ADDITIONAL LAKE EFFECT SHOWERS THROUGH SUNSET...PERHAPS AIDED BY DIURNAL WARMING BY MID/LATE MORNING. CONFIDENCE VERY LOW HERE AS WELL. OUTSIDE OF PRECIP AREAS...CIGS HAVE GENERALLY LIFTED INTO LOW VFR WITH A FEW PATCHES OF HIGH MVFR CIGS. EXPECT THIS OVERALL TREND TO CONTINUE WITH MVFR POSSIBLE IN AREAS OF HEAVIER PRECIP. THOUGH AM CONCERNED THAT THERE COULD BE ANOTHER PERIOD OF MVFR CIGS TUESDAY AFTERNOON. WITH A RIDGE OF HIGH PRESSURE MOVING ACROSS THE AREA TUESDAY NIGHT...ANY MVFR CIGS MAY GET TRAPPED BELOW THE INVERSION AND COULD PERSIST WELL INTO TUESDAY NIGHT. NORTHEAST WINDS WILL SLOWLY TURN MORE NORTHERLY TUESDAY AFTERNOON THEN SHOULD FLOP WESTERLY TUESDAY EVENING AS THE ABOVE MENTIONED RIDGE BUILDS ACROSS THE AREA. WINDS COULD POTENTIALLY BECOME LIGHT AND VRB OR EVEN CALM TUESDAY EVENING. IN THE SHORT TERM...GRADIENT WILL SLOWLY RELAX OVERNIGHT AND THINK THE PREVAILING GUSTS HAVE ENDED EXCEPT AT GYY AND ALONG THE LAKE...WITH PREVAILING SPEEDS IN THE 9-13KT RANGE. CMS //ORD AND MDW CONFIDENCE...UPDATED 08Z... * LOW CONFIDENCE REGARDING PRECIP TYPE/TIMING/DURATION/INTENSITY THROUGH THE PERIOD * MEDIUM CONFIDENCE PREVAILING CIGS WILL BECOME/REMAIN VFR THROUGH TUESDAY MORNING...LOW CONFIDENCE PREVAILING MVFR CIGS MAY RETURN TUESDAY MORNING/AFTERNOON SHEA //OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z... WEDNESDAY AND THURSDAY...VFR. THURSDAY NIGHT...CHANCE OF LIGHT SNOW. MVFR POSSIBLE. FRIDAY THROUGH SUNDAY...VFR. CMS && .MARINE... 248 AM CST HIGH PRESSURE EXTENDING FROM THE UPPER MISSISSIPPI VALLEY THROUGH THE CENTRAL PLAINS WILL SLOWLY SAG ACROSS THE GREAT LAKES REGION TODAY AND TONIGHT AS A STRONG LOW PRESSURE SYSTEM MOVES ACROSS NORTHERN MANITOBA INTO THE HUDSON BAY. THIS LOW WILL DRAG A COLD FRONT ACROSS LAKE MICHIGAN WEDNESDAY. DURING THIS PERIOD...WINDS OVER THE LAKE WILL GRADUALLY SHIFT FROM NORTHERLY TO SOUTHWESTERLY. WIND SPEEDS WILL DIMINISH TO AS LOW AS TO TO 15 KT LATE TONIGHT AS THE SFC RIDGE AXIS CROSSES THE LAKE...BUT AS THE RIDGE PUSHES TO THE SOUTH AND A SFC TROUGH ASSOCIATED WITH THE COLD FRONT DROPS THROUGH THE NORTHERN PLAINS LATE TONIGHT...WINDS WILL QUICKLY INCREASE AGAIN TO AROUND 30 KT. FOLLOWING THE PASSAGE OF THE COLD FRONT...ANOTHER CANADIAN HIGH PRESSURE SYSTEM WILL DROP SOUTHEAST ACROSS THE PLAINS THURSDAY AND FRIDAY. THIS SHOULD MAINTAIN A MODERATE PRESSURE GRADIENT OVER THE GREAT LAKES. THE COMBINATION OF THE MODERATELY STRONG PRESSURE GRADIENT AND STRONG COLD ADVECTION BEHIND THE EXITING FRONT WILL KEEP WINDS AROUND 25 TO 30KT OVER THE LAKE FROM WEDNESDAY THROUGH SATURDAY. KREIN && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 PM TUESDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
201 AM CST TUE DEC 6 2011 .DISCUSSION... 852 PM CST A FEW CHALLENGES REVOLVING AROUND THE LAKE EFFECT PRECIPITATION THIS EVENING. RADAR IMAGERY SHOWS PRECIPITATION FROM MILWAUKEE SOUTH INTO NORTHERN WILL COUNTY. WATER VAPOR IMAGERY SHOWS DEFORMATION ZONE MOVING EAST OF THE FORECAST AREA WITH SUBSIDENCE AND MID LEVEL DRY AIR MOVING IN FROM THE SOUTHWEST. HAVE SEEN OVERALL INTENSITY OF RETURNS OFF THE LAKE DECREASE SOMEWHAT AS THIS FEATURE PROGRESSES THROUGH...BUT FORECAST SOUNDINGS SHOW LITTLE CHANGE IN THE LOW AND MID LEVELS OVERNIGHT AND SUSPECT AREA OF PRECIPITATION WILL CONTINUE THROUGH THE REMAINDER OF THE EVENING AND OVERNIGHT. SOUNDINGS DO SHOW A SLIGHT DECREASE IN THE INVERSION HEIGHTS BETWEEN 06-09Z...AND MOST OF THE HIGH-RES GUIDANCE...WITH THE RUC BEING THE EXCEPTION...SHOWS PRECIP DIMINISHING LATE TONIGHT. SUSPECT THE RUC MAY BE ONTO SOMETHING THOUGH...WITH NO REAL SENSE OF WHAT MAY CAUSE LAKE EFFECT TO SHUT OFF OVERNIGHT...THUS WILL BUMP UP POPS FOR TONIGHT. PRECIP TYPE ALSO A BIG QUESTION MARK. THE 129DM LINE ON THE 1000-850MB THICKNESS LINES UP WELL WITH CURRENT RAIN-SNOW LINE AND DOES GRADUALLY SHIFT SOUTH THROUGH COOK COUNTY TONIGHT...BUT LOCALIZED EFFECTS WITH WARM AIR OFF THE LAKE AND URBAN HEAT ISLAND WILL DELAY THE CHANGE OVER TO SNOW FOR AREAS ALONG THE LAKESHORE AND PORTIONS OF COOK COUNTY DESPITE THE GRADUAL COOL ADVECTION. HOWEVER...WET-BULBING EFFECTS UNDER THE HEAVIER SHOWERS MAY DOMINATE...AND HAS ALREADY BEEN EVIDENT ON DUAL-POL IMAGERY WITH SOME OF THE SHOWERS THAT PASSED OVER SOUTHERN DUPAGE COUNTY EARLIER TONIGHT WHERE SNOW BRIEFLY MADE ITS WAY TO THE SURFACE. SO DO EXPECT A CHANGE OVER TO SNOW AT SOME POINT...BUT HAVE VERY LOW CONFIDENCE ON PRECISE TIMING. PRECIP AMOUNT REPORTS HAVE BEEN ON THE ORDER OF A FEW HUNDREDTHS THUS FAR UNDER THE STRONGEST RETURNS...AND SEE NO REASON FOR THIS TO CHANGE OVERNIGHT NOR HAVE ANY CONCERNS FOR ACCUMULATIONS. FORECAST UPDATES TO FOLLOW SHORTLY...BMD //PREV DISCUSSION... NEAR TERM....THIS AFTERNOON THROUGH TONIGHT... VISIBLE IMAGERY CONTINUES TO SHOW A THICK STRATUS LAYER OVERHEAD. VERTICAL GROWTH OF THE CLOUD DESK REMAINS WELL SOUTH OF THE REGION OVER THE OZARKS AND WESTERN TENNESSEE. WITH THE ABUNDANT SOLAR SHIELDING...TEMPERATURES THIS AFTERNOON HAVE NOT WARMED MUCH. THUS EXPECT TEMPS TO REMAIN IN THE MID/UPR 30S. BETTER COLD AIR ADVECTION HAS CONTINUED TO OCCUR ACROSS WEST CENTRAL ILLINOIS WHERE TEMPERATURES HAVE HELD AROUND 30...AND IN THE MID 20S ACROSS CENTRAL MISSOURI. IR IMAGERY THIS AFTERNOON ALSO CONTINUES TO INDICATE MUCH THICKER CLOUD COVER OVER ILLINOIS/INDIANA. WSR-88D RADAR WAS DEPICTING PRECIPITATION PUSHING INLAND ACROSS BOTH COOK AND LAKE COUNTY ILLINOIS...AS LAKE MOISTURE SLOWLY SLIDES SOUTH/SOUTHWEST. MOISTURE REMAINS VERY SHALLOW AND MINIMAL LIFT...SUPPORTING PRECIP TO REMAIN AS LIQUID WITH PATCHY DRIZZLE. FURTHER NORTH A FEW OBSERVATIONS ACROSS WISCONSIN HAVE REPORTED LGT SN. FOR FAR NORTHEAST ILLINOIS TEMPERATURES ARE WARM ENOUGH TO MAINTAIN A LIQUID STATE OF PRECIPITATION. QUASI-STATIONARY BOUNDARY REMAINS TO OUR SOUTHEAST ACROSS THE OZARKS STRETCHING NORTHEAST THROUGH THE OHIO VALLEY. OVERNIGHT THE CHALLENGE WILL CONTINUE TO BE COVERAGE OF PRECIP...AND TEMPERATURES. GUIDANCE HAS SUGGESTED THAT TEMPERATURES WILL COOL MORE EFFICIENTLY TONIGHT WITH BETTER COLD AIR ADVECTION INTO NORTHERN IL/NORTHWEST IN...HOWEVER FEEL THIS IS TOO OVERDONE. THUS HAVE ADJUSTED OVERNIGHT LOWS UP A FEW DEGREES GIVEN THE EXPECTED THICK CLOUD COVER. WINDS START TO TURN NORTHEASTERLY THIS EVENING AND CONTINUE OVERNIGHT...WHICH SHOULD AID IN BENDING THE LAKE MOISTURE SOUTHWEST OR OVER NORTHEAST ILLINOIS. THUS HAVE MAINTAINED MENTION OF SLIGHT CHANCE WORDING. VERTICAL LIFT APPEARS TO BUMP UP A TAD OVERNIGHT...WITH SFC TEMPS PUSHING CLOSER TO FREEZING. MODEL SOUNDINGS INDICATE THAT ANY PRECIP THAT FALLS THIS EVENING WOULD START AS LIQUID...THEN POSSIBLY START TO MIX WITH LGT SNOW. AS PREVIOUSLY MENTIONED ABOUT THE MINIMAL LIFTING MECHANISM...IT IS POSSIBLE THAT PATCHY DRIZZLE COULD OCCUR BEFORE LGT SNOW WOULD OCCUR. QPF REMAINS MINIMAL...OR LESS THAN 0.05 THROUGH THE NEXT 24HRS. MORE THAN LIKELY IT IS CLOSER TO 0.01 TO 0.03. BASED ON THE EXPECTED TEMPERATURES AND MINIMAL LIFT...ANY SNOW THAT DOES FALL MAY ACCUMULATE UP TO A QUARTER OF AN INCH. ALTHOUGH THAT BEING SAID...CONFIDENCE IS LOW THAT THIS SCENARIO WOULD PAN OUT. TUESDAY THROUGH THURSDAY... A WEAK WAVE IS PROGGED TO DEVELOP ALONG THE QUASI-STATIONARY BOUNDARY AND SLIDE NORTHEAST THROUGH MISSOURI. ANTI-CYCLONIC FLOW REMAINS UPSTREAM ACROSS IOWA/MINNESOTA/WISCONSIN...WHICH SHOULD START TO TURN OFF LAKE MOISTURE SOMETIME TUE AFTN/EVE. HAVE HELD ONTO MENTION OF LGT RA/SN THRU THE MORNING HOURS. AFTN TEMPS SHOULD WARM MARGINALLY TO AROUND THE MID 30S ACROSS MOST OF THE CWFA. BY TUE AFTN/EVE THE INFLUENCE FROM THE UPSTREAM RIDGE SHOULD FINALLY ERODE THE THICK STRATUS AND ALLOW PARTLY CLOUD SKIES TO DEVELOP BY THE LATE AFTN/EVE. THIS COUPLED WITH 850MB THERMAL TROUGH OF -10 TO -12 DEG...WILL SET THE STAGE FOR OVERNIGHT LOWS IN THE TEENS TO LOWER 20S. AS WINDS SLOWLY SHIFT FROM THE NORTHWEST TO THE WEST/SOUTHWEST WED...THE LAKE MOISTURE WILL BECOME ORIENTED OVER LOWER MICHIGAN. 500MB VORT SLOWLY SLIDES EAST ALONG THE SOUTHERN STREAM...WHILE THE NORTHERN STREAM REMAINS IN PROGRESSIVE. THE FOCUS WED WILL CONTINUE TO BE ON THE ARRIVAL OF A POTENT FRONTAL BOUNDARY...THAT IS COUPLED WITH AN 850MB THERMAL TROUGH OF -20 TO -22 DEG C. THIS WILL PROVIDE THE COOLEST AIR OF THE SEASON LATER IN THE WEEK TO NORTHERN IL/NORTHWEST IN. PRIOR TO THE ARRIVAL OF THIS AIRMASS...MOISTURE IS EXPECTED TO POOL ALONG THE FRONT AS IT SLOWLY PUSHES SOUTHEAST ACROSS THE PLAINS THURSDAY. GUIDANCE HAS FLUCTUATED ON HOW THIS FEATURE WILL UNFOLD...AND IT REMAINS POSSIBLE THAT A WEAK WAVE WILL DEVELOP ALONG THE LEE-SIDE OF THE 500MB TROUGH AXIS. THIS SCENARIO COULD RESULT IN LGT SNOW OVERSPREADING NORTHERN IL/NORTHWEST IN THUR AFTN AS THE POTENT THERMAL TROUGH ARRIVES ALOFT. TEMPS THUR WILL REMAIN IN THE LOW/MID 30S. BEACHLER LONG TERM...THURSDAY NIGHT THROUGH MONDAY MAIN CONCERNS IN THE EXTENDED PORTION OF THE FORECAST ARE LIGHT SNOW POTENTIAL THURSDAY NIGHT INTO EARLY FRIDAY...FOLLOWED BY THE FIRST BLAST OF ARCTIC AIR OF THE SEASON FOR FRIDAY INTO EARLY SATURDAY. ON THURSDAY NIGHT...AS MENTIONED ABOVE...DIGGING H5 TROUGH WILL SPAWN A WEAK SURFACE LOW WHICH WILL TRACK ACROSS NORTHERN GREAT LAKES AND SEND AN ARCTIC FRONTAL BOUNDARY TOWARD AREA. MODELS HAVE BEEN CONSISTENT IN SPITTING OUT A STRIPE OF VERY LIGHT QPF NEAR OR OVER CWA IN RESPONSE TO THIS FEATURE. WITH NEGATIVE TEEN AIR AT H85 BUILDING IN FROM THE NORTH BEHIND ARCTIC FRONT...SUSPECT WAVE WILL RIDE ALONG LOW LEVEL BAROCLINIC ZONE. A PEEK AT GFS TIME HEIGHT AT ORD FOR THURSDAY NIGHT PERIOD SHOWS SATURATION AND ADEQUATE LIFT INTO -15C FAVORED SNOW GROWTH ZONE. THEREFORE...DESPITE QPF ONLY IN THE HUNDREDTHS UP TO MAYBE A TENTH OR SLIGHTLY MORE...WITH VERY COLD AIR MASS...SNOW WOULD BE HIGH RATIO AND POSSIBLY RESULT IN FIRST WIDESPREAD LIGHT ACCUMULATING SNOW OF THE SEASON FOR MANY (IF SCENARIO PANS OUT...POTENTIAL FOR AN INCH OR TWO OF SNOW). FOR NOW...HAVE BUMPED UP POPS IN GRIDS TO CHANCE ACROSS THE AREA GIVEN SOME UNCERTAINTY IN EXACTLY WHERE BEST SNOW POTENTIAL WILL OCCUR. LIGHT SNOW MAY LINGER INTO EARLY FRIDAY FOR EASTERN PORTION OF CWA BEFORE WAVE SHIFTS OFF TO THE EAST. THEREAFTER...ON FRIDAY...STRONG CAA WILL BE IN FULL FORCE WITH SHARP THERMAL TROUGH ARRIVING OVERHEAD LATE IN THE DAY. OPERATIONAL MODELS AND ENSEMBLES HAVE BACKED OFF EVER SO SLIGHTLY ON JUST HOW COLD ARCTIC AIR MASS WILL BE...BUT -15C OR SO AT H85 AND -8 TO -10 AT H95 WILL BE PLENTY COLD. TEMPERATURES WILL STRUGGLE INTO THE MID TO UPPER 20S FRIDAY AFTERNOON WITH A PERSISTENT WNW BREEZE LEADING TO LOW WIND CHILL VALUES. AXIS OF ARCTIC HIGH WILL PASS CLOSEST ON FRIDAY NIGHT...LEADING TO STRONG RADIATIONAL COOLING. IF MINOR SNOW COVER IS PRESENT...LOW TO MID TEENS...UPPER TEENS IN DOWNTOWN CHICAGO...IN GRIDS FOR LOW EARLY SATURDAY MORNING MIGHT BE A FEW DEGREES TOO HIGH. SW FLOW...STEADY WARMING ALOFT AND LIKELY FULL SUNSHINE ON SATURDAY WILL ALLOW FOR SOME RECOVERY FROM VERY COLD START TO DAY...BUT SUSPECT IT WILL BE TOUGH TO MAKE UP A LOT OF GROUND DUE TO LIMITED DAYLIGHT THIS TIME OF YEAR. THUS SHAVED OFF A DEGREE FROM MODEL BLEND FOR MAX TEMPERATURES ON SATURDAY...YIELDING HIGHS IN THE UPPER 20S TO AROUND 30 DEGREES. SUNDAY AND MONDAY LOOK TO BE MAINLY DRY WITH TEMPERATURES RETURNING TO CLOSE TO SEASONAL NORMS DUE TO SOUTHERLY FLOW AND CONTINUED WARMING OF THE COLUMN. A FRONTAL BOUNDARY MAY DROP SOUTH THROUGH THE AREA LATE MONDAY... BRINGING NEXT CHANCE FOR LIGHT PRECIP...BUT LARGE MODEL UNCERTAINTY THIS FAR OUT PRECLUDES ANYTHING MORE THAN SLIGHT POPS FOR MONDAY NIGHT. RC && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 08Z... * POTENTIAL FOR LAKE EFFECT RAIN/SNOW SHOWERS THROUGH THE AFTERNOON * PERIODS OF MVFR CIGS THROUGH TUESDAY EVENING. SHEA //DISCUSSION...UPDATED 06Z... MAIN FORECAST CONCERN AND CHALLENGE REMAINS THE LAKE EFFECT RAIN/ SNOW SHOWERS. OVERALL INTENSITY HAS DIMINISHED SOME FROM EARLIER THIS EVENING BUT STILL MANY SHOWERS FROM FAR SOUTHEAST WI INTO NORTHEAST IL. COOLER AIR SLOWLY FILTERING IN FROM THE NORTH HAS CHANGED PRECIP TO MAINLY SNOW ACROSS SOUTHEAST WI INTO FAR NORTHEAST IL...AS WELL AS LOCATIONS FARTHER INLAND...SUCH AS DPA WHERE TEMPS HAVE ALSO COOLED A FEW DEGREES. FORECAST SOUNDINGS CONTINUE TO SHOW THE INVERSION HEIGHT LOWERING SOME THROUGH THE OVERNIGHT HRS AND THIS SHOULD LIMIT THE COVERAGE AND INTENSITY OF THE LAKE EFFECT SHOWERS OVERNIGHT. WHILE THERE WILL STILL LIKELY BE PERIODS OF LIGHT RAIN AND/OR LIGHT SNOW...CONFIDENCE IN TRYING TO TIME ANY OF THIS PRECIP IS VERY LOW. AND FOR THAT REASON...HAVE GONE WITH A VICINITY MENTION...THOUGH LATER UPDATES FOR PREVAILING OR TEMPO PRECIP MAY BE NEEDED. LITTLE CHANGE TO THE AIRMASS OR LOW LEVEL PROFILES INTO TUESDAY AFTERNOON AND THERE COULD BE ADDITIONAL LAKE EFFECT SHOWERS THROUGH SUNSET...PERHAPS AIDED BY DIURNAL WARMING BY MID/LATE MORNING. CONFIDENCE VERY LOW HERE AS WELL. OUTSIDE OF PRECIP AREAS...CIGS HAVE GENERALLY LIFTED INTO LOW VFR WITH A FEW PATCHES OF HIGH MVFR CIGS. EXPECT THIS OVERALL TREND TO CONTINUE WITH MVFR POSSIBLE IN AREAS OF HEAVIER PRECIP. THOUGH AM CONCERNED THAT THERE COULD BE ANOTHER PERIOD OF MVFR CIGS TUESDAY AFTERNOON. WITH A RIDGE OF HIGH PRESSURE MOVING ACROSS THE AREA TUESDAY NIGHT...ANY MVFR CIGS MAY GET TRAPPED BELOW THE INVERSION AND COULD PERSIST WELL INTO TUESDAY NIGHT. NORTHEAST WINDS WILL SLOWLY TURN MORE NORTHERLY TUESDAY AFTERNOON THEN SHOULD FLOP WESTERLY TUESDAY EVENING AS THE ABOVE MENTIONED RIDGE BUILDS ACROSS THE AREA. WINDS COULD POTENTIALLY BECOME LIGHT AND VRB OR EVEN CALM TUESDAY EVENING. IN THE SHORT TERM...GRADIENT WILL SLOWLY RELAX OVERNIGHT AND THINK THE PREVAILING GUSTS HAVE ENDED EXCEPT AT GYY AND ALONG THE LAKE...WITH PREVAILING SPEEDS IN THE 9-13KT RANGE. CMS //ORD AND MDW CONFIDENCE...UPDATED 08Z... * LOW CONFIDENCE REGARDING PRECIP TYPE/TIMING/DURATION/INTENSITY THROUGH THE PERIOD * MEDIUM CONFIDENCE PREVAILING CIGS WILL BECOME/REMAIN VFR THROUGH TUESDAY MORNING...LOW CONFIDENCE PREVAILING MVFR CIGS MAY RETURN TUESDAY MORNING/AFTERNOON SHEA //OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z... WEDNESDAY AND THURSDAY...VFR. THURSDAY NIGHT...CHANCE OF LIGHT SNOW. MVFR POSSIBLE. FRIDAY THROUGH SUNDAY...VFR. CMS && .MARINE... 147 PM CST HIGH PRESSURE ACROSS THE PLAINS WILL SLOWLY SAG SOUTHWARD TUESDAY AND TUESDAY NIGHT AS A STRONG AREA OF LOW PRESSURE MOVES ACROSS NORTHERN MANITOBA INTO THE HUDSON BAY. AS A CONSEQUENCE OF THIS...WINDS ARE EXPECTED TO BECOME WEST SOUTHWESTERLY AND INCREASE TO NEAR 30 KT LATE TUESDAY NIGHT AND ON WEDNESDAY. THEN WEDNESDAY NIGHT A STRONG COLD FRONT...ASSOCIATED WITH THE LOW ACROSS NORTHERN CANADA...WILL PUSH SOUTH ACROSS LAKE MICHIGAN. WEST TO NORTHWEST WINDS WILL OCCUR IN THE WAKE OF THIS FRONT. FOLLOWING THIS FRONT...ANOTHER CANADIAN HIGH PRESSURE SYSTEM WILL DROP SOUTHEAST ACROSS THE PLAINS THURSDAY AND FRIDAY. THIS SHOULD HELP SUPPORT A DECENT PRESSURE GRADIENT ACROSS THE GREAT LAKES. THUS...IN COMBINATION WITH A VERY COLD AIR MASS OVER THE RELATIVELY WARM WATERS OF LAKE MICHIGAN...WINDS WILL LIKELY REMAIN ELEVATED IN THE 20 TO 25 KT RANGE DURING THIS PERIOD. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 PM TUESDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1101 PM CST MON DEC 5 2011 .DISCUSSION... 852 PM CST A FEW CHALLENGES REVOLVING AROUND THE LAKE EFFECT PRECIPITATION THIS EVENING. RADAR IMAGERY SHOWS PRECIPITATION FROM MILWAUKEE SOUTH INTO NORTHERN WILL COUNTY. WATER VAPOR IMAGERY SHOWS DEFORMATION ZONE MOVING EAST OF THE FORECAST AREA WITH SUBSIDENCE AND MID LEVEL DRY AIR MOVING IN FROM THE SOUTHWEST. HAVE SEEN OVERALL INTENSITY OF RETURNS OFF THE LAKE DECREASE SOMEWHAT AS THIS FEATURE PROGRESSES THROUGH...BUT FORECAST SOUNDINGS SHOW LITTLE CHANGE IN THE LOW AND MID LEVELS OVERNIGHT AND SUSPECT AREA OF PRECIPITATION WILL CONTINUE THROUGH THE REMAINDER OF THE EVENING AND OVERNIGHT. SOUNDINGS DO SHOW A SLIGHT DECREASE IN THE INVERSION HEIGHTS BETWEEN 06-09Z...AND MOST OF THE HIGH-RES GUIDANCE...WITH THE RUC BEING THE EXCEPTION...SHOWS PRECIP DIMINISHING LATE TONIGHT. SUSPECT THE RUC MAY BE ONTO SOMETHING THOUGH...WITH NO REAL SENSE OF WHAT MAY CAUSE LAKE EFFECT TO SHUT OFF OVERNIGHT...THUS WILL BUMP UP POPS FOR TONIGHT. PRECIP TYPE ALSO A BIG QUESTION MARK. THE 129DM LINE ON THE 1000-850MB THICKNESS LINES UP WELL WITH CURRENT RAIN-SNOW LINE AND DOES GRADUALLY SHIFT SOUTH THROUGH COOK COUNTY TONIGHT...BUT LOCALIZED EFFECTS WITH WARM AIR OFF THE LAKE AND URBAN HEAT ISLAND WILL DELAY THE CHANGE OVER TO SNOW FOR AREAS ALONG THE LAKESHORE AND PORTIONS OF COOK COUNTY DESPITE THE GRADUAL COOL ADVECTION. HOWEVER...WET-BULBING EFFECTS UNDER THE HEAVIER SHOWERS MAY DOMINATE...AND HAS ALREADY BEEN EVIDENT ON DUAL-POL IMAGERY WITH SOME OF THE SHOWERS THAT PASSED OVER SOUTHERN DUPAGE COUNTY EARLIER TONIGHT WHERE SNOW BRIEFLY MADE ITS WAY TO THE SURFACE. SO DO EXPECT A CHANGE OVER TO SNOW AT SOME POINT...BUT HAVE VERY LOW CONFIDENCE ON PRECISE TIMING. PRECIP AMOUNT REPORTS HAVE BEEN ON THE ORDER OF A FEW HUNDREDTHS THUS FAR UNDER THE STRONGEST RETURNS...AND SEE NO REASON FOR THIS TO CHANGE OVERNIGHT NOR HAVE ANY CONCERNS FOR ACCUMULATIONS. FORECAST UPDATES TO FOLLOW SHORTLY...BMD //PREV DISCUSSION... NEAR TERM....THIS AFTERNOON THROUGH TONIGHT... VISIBLE IMAGERY CONTINUES TO SHOW A THICK STRATUS LAYER OVERHEAD. VERTICAL GROWTH OF THE CLOUD DESK REMAINS WELL SOUTH OF THE REGION OVER THE OZARKS AND WESTERN TENNESSEE. WITH THE ABUNDANT SOLAR SHIELDING...TEMPERATURES THIS AFTERNOON HAVE NOT WARMED MUCH. THUS EXPECT TEMPS TO REMAIN IN THE MID/UPR 30S. BETTER COLD AIR ADVECTION HAS CONTINUED TO OCCUR ACROSS WEST CENTRAL ILLINOIS WHERE TEMPERATURES HAVE HELD AROUND 30...AND IN THE MID 20S ACROSS CENTRAL MISSOURI. IR IMAGERY THIS AFTERNOON ALSO CONTINUES TO INDICATE MUCH THICKER CLOUD COVER OVER ILLINOIS/INDIANA. WSR-88D RADAR WAS DEPICTING PRECIPITATION PUSHING INLAND ACROSS BOTH COOK AND LAKE COUNTY ILLINOIS...AS LAKE MOISTURE SLOWLY SLIDES SOUTH/SOUTHWEST. MOISTURE REMAINS VERY SHALLOW AND MINIMAL LIFT...SUPPORTING PRECIP TO REMAIN AS LIQUID WITH PATCHY DRIZZLE. FURTHER NORTH A FEW OBSERVATIONS ACROSS WISCONSIN HAVE REPORTED LGT SN. FOR FAR NORTHEAST ILLINOIS TEMPERATURES ARE WARM ENOUGH TO MAINTAIN A LIQUID STATE OF PRECIPITATION. QUASI-STATIONARY BOUNDARY REMAINS TO OUR SOUTHEAST ACROSS THE OZARKS STRETCHING NORTHEAST THROUGH THE OHIO VALLEY. OVERNIGHT THE CHALLENGE WILL CONTINUE TO BE COVERAGE OF PRECIP...AND TEMPERATURES. GUIDANCE HAS SUGGESTED THAT TEMPERATURES WILL COOL MORE EFFICIENTLY TONIGHT WITH BETTER COLD AIR ADVECTION INTO NORTHERN IL/NORTHWEST IN...HOWEVER FEEL THIS IS TOO OVERDONE. THUS HAVE ADJUSTED OVERNIGHT LOWS UP A FEW DEGREES GIVEN THE EXPECTED THICK CLOUD COVER. WINDS START TO TURN NORTHEASTERLY THIS EVENING AND CONTINUE OVERNIGHT...WHICH SHOULD AID IN BENDING THE LAKE MOISTURE SOUTHWEST OR OVER NORTHEAST ILLINOIS. THUS HAVE MAINTAINED MENTION OF SLIGHT CHANCE WORDING. VERTICAL LIFT APPEARS TO BUMP UP A TAD OVERNIGHT...WITH SFC TEMPS PUSHING CLOSER TO FREEZING. MODEL SOUNDINGS INDICATE THAT ANY PRECIP THAT FALLS THIS EVENING WOULD START AS LIQUID...THEN POSSIBLY START TO MIX WITH LGT SNOW. AS PREVIOUSLY MENTIONED ABOUT THE MINIMAL LIFTING MECHANISM...IT IS POSSIBLE THAT PATCHY DRIZZLE COULD OCCUR BEFORE LGT SNOW WOULD OCCUR. QPF REMAINS MINIMAL...OR LESS THAN 0.05 THROUGH THE NEXT 24HRS. MORE THAN LIKELY IT IS CLOSER TO 0.01 TO 0.03. BASED ON THE EXPECTED TEMPERATURES AND MINIMAL LIFT...ANY SNOW THAT DOES FALL MAY ACCUMULATE UP TO A QUARTER OF AN INCH. ALTHOUGH THAT BEING SAID...CONFIDENCE IS LOW THAT THIS SCENARIO WOULD PAN OUT. TUESDAY THROUGH THURSDAY... A WEAK WAVE IS PROGGED TO DEVELOP ALONG THE QUASI-STATIONARY BOUNDARY AND SLIDE NORTHEAST THROUGH MISSOURI. ANTI-CYCLONIC FLOW REMAINS UPSTREAM ACROSS IOWA/MINNESOTA/WISCONSIN...WHICH SHOULD START TO TURN OFF LAKE MOISTURE SOMETIME TUE AFTN/EVE. HAVE HELD ONTO MENTION OF LGT RA/SN THRU THE MORNING HOURS. AFTN TEMPS SHOULD WARM MARGINALLY TO AROUND THE MID 30S ACROSS MOST OF THE CWFA. BY TUE AFTN/EVE THE INFLUENCE FROM THE UPSTREAM RIDGE SHOULD FINALLY ERODE THE THICK STRATUS AND ALLOW PARTLY CLOUD SKIES TO DEVELOP BY THE LATE AFTN/EVE. THIS COUPLED WITH 850MB THERMAL TROUGH OF -10 TO -12 DEG...WILL SET THE STAGE FOR OVERNIGHT LOWS IN THE TEENS TO LOWER 20S. AS WINDS SLOWLY SHIFT FROM THE NORTHWEST TO THE WEST/SOUTHWEST WED...THE LAKE MOISTURE WILL BECOME ORIENTED OVER LOWER MICHIGAN. 500MB VORT SLOWLY SLIDES EAST ALONG THE SOUTHERN STREAM...WHILE THE NORTHERN STREAM REMAINS IN PROGRESSIVE. THE FOCUS WED WILL CONTINUE TO BE ON THE ARRIVAL OF A POTENT FRONTAL BOUNDARY...THAT IS COUPLED WITH AN 850MB THERMAL TROUGH OF -20 TO -22 DEG C. THIS WILL PROVIDE THE COOLEST AIR OF THE SEASON LATER IN THE WEEK TO NORTHERN IL/NORTHWEST IN. PRIOR TO THE ARRIVAL OF THIS AIRMASS...MOISTURE IS EXPECTED TO POOL ALONG THE FRONT AS IT SLOWLY PUSHES SOUTHEAST ACROSS THE PLAINS THURSDAY. GUIDANCE HAS FLUCTUATED ON HOW THIS FEATURE WILL UNFOLD...AND IT REMAINS POSSIBLE THAT A WEAK WAVE WILL DEVELOP ALONG THE LEE-SIDE OF THE 500MB TROUGH AXIS. THIS SCENARIO COULD RESULT IN LGT SNOW OVERSPREADING NORTHERN IL/NORTHWEST IN THUR AFTN AS THE POTENT THERMAL TROUGH ARRIVES ALOFT. TEMPS THUR WILL REMAIN IN THE LOW/MID 30S. BEACHLER LONG TERM...THURSDAY NIGHT THROUGH MONDAY MAIN CONCERNS IN THE EXTENDED PORTION OF THE FORECAST ARE LIGHT SNOW POTENTIAL THURSDAY NIGHT INTO EARLY FRIDAY...FOLLOWED BY THE FIRST BLAST OF ARCTIC AIR OF THE SEASON FOR FRIDAY INTO EARLY SATURDAY. ON THURSDAY NIGHT...AS MENTIONED ABOVE...DIGGING H5 TROUGH WILL SPAWN A WEAK SURFACE LOW WHICH WILL TRACK ACROSS NORTHERN GREAT LAKES AND SEND AN ARCTIC FRONTAL BOUNDARY TOWARD AREA. MODELS HAVE BEEN CONSISTENT IN SPITTING OUT A STRIPE OF VERY LIGHT QPF NEAR OR OVER CWA IN RESPONSE TO THIS FEATURE. WITH NEGATIVE TEEN AIR AT H85 BUILDING IN FROM THE NORTH BEHIND ARCTIC FRONT...SUSPECT WAVE WILL RIDE ALONG LOW LEVEL BAROCLINIC ZONE. A PEEK AT GFS TIME HEIGHT AT ORD FOR THURSDAY NIGHT PERIOD SHOWS SATURATION AND ADEQUATE LIFT INTO -15C FAVORED SNOW GROWTH ZONE. THEREFORE...DESPITE QPF ONLY IN THE HUNDREDTHS UP TO MAYBE A TENTH OR SLIGHTLY MORE...WITH VERY COLD AIR MASS...SNOW WOULD BE HIGH RATIO AND POSSIBLY RESULT IN FIRST WIDESPREAD LIGHT ACCUMULATING SNOW OF THE SEASON FOR MANY (IF SCENARIO PANS OUT...POTENTIAL FOR AN INCH OR TWO OF SNOW). FOR NOW...HAVE BUMPED UP POPS IN GRIDS TO CHANCE ACROSS THE AREA GIVEN SOME UNCERTAINTY IN EXACTLY WHERE BEST SNOW POTENTIAL WILL OCCUR. LIGHT SNOW MAY LINGER INTO EARLY FRIDAY FOR EASTERN PORTION OF CWA BEFORE WAVE SHIFTS OFF TO THE EAST. THEREAFTER...ON FRIDAY...STRONG CAA WILL BE IN FULL FORCE WITH SHARP THERMAL TROUGH ARRIVING OVERHEAD LATE IN THE DAY. OPERATIONAL MODELS AND ENSEMBLES HAVE BACKED OFF EVER SO SLIGHTLY ON JUST HOW COLD ARCTIC AIR MASS WILL BE...BUT -15C OR SO AT H85 AND -8 TO -10 AT H95 WILL BE PLENTY COLD. TEMPERATURES WILL STRUGGLE INTO THE MID TO UPPER 20S FRIDAY AFTERNOON WITH A PERSISTENT WNW BREEZE LEADING TO LOW WIND CHILL VALUES. AXIS OF ARCTIC HIGH WILL PASS CLOSEST ON FRIDAY NIGHT...LEADING TO STRONG RADIATIONAL COOLING. IF MINOR SNOW COVER IS PRESENT...LOW TO MID TEENS...UPPER TEENS IN DOWNTOWN CHICAGO...IN GRIDS FOR LOW EARLY SATURDAY MORNING MIGHT BE A FEW DEGREES TOO HIGH. SW FLOW...STEADY WARMING ALOFT AND LIKELY FULL SUNSHINE ON SATURDAY WILL ALLOW FOR SOME RECOVERY FROM VERY COLD START TO DAY...BUT SUSPECT IT WILL BE TOUGH TO MAKE UP A LOT OF GROUND DUE TO LIMITED DAYLIGHT THIS TIME OF YEAR. THUS SHAVED OFF A DEGREE FROM MODEL BLEND FOR MAX TEMPERATURES ON SATURDAY...YIELDING HIGHS IN THE UPPER 20S TO AROUND 30 DEGREES. SUNDAY AND MONDAY LOOK TO BE MAINLY DRY WITH TEMPERATURES RETURNING TO CLOSE TO SEASONAL NORMS DUE TO SOUTHERLY FLOW AND CONTINUED WARMING OF THE COLUMN. A FRONTAL BOUNDARY MAY DROP SOUTH THROUGH THE AREA LATE MONDAY... BRINGING NEXT CHANCE FOR LIGHT PRECIP...BUT LARGE MODEL UNCERTAINTY THIS FAR OUT PRECLUDES ANYTHING MORE THAN SLIGHT POPS FOR MONDAY NIGHT. RC && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 06Z... * POTENTIAL FOR LAKE EFFECT RAIN/SNOW SHOWERS THROUGH TUESDAY AFTERNOON. * PERIODS OF MVFR CIGS THROUGH TUESDAY EVENING. CMS //DISCUSSION...UPDATED 06Z... MAIN FORECAST CONCERN AND CHALLENGE REMAINS THE LAKE EFFECT RAIN/ SNOW SHOWERS. OVERALL INTENSITY HAS DIMINISHED SOME FROM EARLIER THIS EVENING BUT STILL MANY SHOWERS FROM FAR SOUTHEAST WI INTO NORTHEAST IL. COOLER AIR SLOWLY FILTERING IN FROM THE NORTH HAS CHANGED PRECIP TO MAINLY SNOW ACROSS SOUTHEAST WI INTO FAR NORTHEAST IL...AS WELL AS LOCATIONS FARTHER INLAND...SUCH AS DPA WHERE TEMPS HAVE ALSO COOLED A FEW DEGREES. FORECAST SOUNDINGS CONTINUE TO SHOW THE INVERSION HEIGHT LOWERING SOME THROUGH THE OVERNIGHT HRS AND THIS SHOULD LIMIT THE COVERAGE AND INTENSITY OF THE LAKE EFFECT SHOWERS OVERNIGHT. WHILE THERE WILL STILL LIKELY BE PERIODS OF LIGHT RAIN AND/OR LIGHT SNOW...CONFIDENCE IN TRYING TO TIME ANY OF THIS PRECIP IS VERY LOW. AND FOR THAT REASON...HAVE GONE WITH A VICINITY MENTION...THOUGH LATER UPDATES FOR PREVAILING OR TEMPO PRECIP MAY BE NEEDED. LITTLE CHANGE TO THE AIRMASS OR LOW LEVEL PROFILES INTO TUESDAY AFTERNOON AND THERE COULD BE ADDITIONAL LAKE EFFECT SHOWERS THROUGH SUNSET...PERHAPS AIDED BY DIURNAL WARMING BY MID/LATE MORNING. CONFIDENCE VERY LOW HERE AS WELL. OUTSIDE OF PRECIP AREAS...CIGS HAVE GENERALLY LIFTED INTO LOW VFR WITH A FEW PATCHES OF HIGH MVFR CIGS. EXPECT THIS OVERALL TREND TO CONTINUE WITH MVFR POSSIBLE IN AREAS OF HEAVIER PRECIP. THOUGH AM CONCERNED THAT THERE COULD BE ANOTHER PERIOD OF MVFR CIGS TUESDAY AFTERNOON. WITH A RIDGE OF HIGH PRESSURE MOVING ACROSS THE AREA TUESDAY NIGHT...ANY MVFR CIGS MAY GET TRAPPED BELOW THE INVERSION AND COULD PERSIST WELL INTO TUESDAY NIGHT. NORTHEAST WINDS WILL SLOWLY TURN MORE NORTHERLY TUESDAY AFTERNOON THEN SHOULD FLOP WESTERLY TUESDAY EVENING AS THE ABOVE MENTIONED RIDGE BUILDS ACROSS THE AREA. WINDS COULD POTENTIALLY BECOME LIGHT AND VRB OR EVEN CALM TUESDAY EVENING. IN THE SHORT TERM...GRADIENT WILL SLOWLY RELAX OVERNIGHT AND THINK THE PREVAILING GUSTS HAVE ENDED EXCEPT AT GYY AND ALONG THE LAKE...WITH PREVAILING SPEEDS IN THE 9-13KT RANGE. CMS //ORD AND MDW CONFIDENCE...UPDATED 06Z... * LOW CONFIDENCE REGARDING PRECIP TYPE/TIMING/DURATION/INTENSITY THROUGH THE PERIOD. * MEDIUM CONFIDENCE PREVAILING CIGS WILL BECOME/REMAIN VFR THROUGH TUESDAY MORNING...LOW CONFIDENCE PREVAILING MVFR CIGS MAY RETURN TUESDAY MORNING/AFTERNOON. CMS //OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z... WEDNESDAY AND THURSDAY...VFR. THURSDAY NIGHT...CHANCE OF LIGHT SNOW. MVFR POSSIBLE. FRIDAY THROUGH SUNDAY...VFR. CMS && .MARINE... 147 PM CST HIGH PRESSURE ACROSS THE PLAINS WILL SLOWLY SAG SOUTHWARD TUESDAY AND TUESDAY NIGHT AS A STRONG AREA OF LOW PRESSURE MOVES ACROSS NORTHERN MANITOBA INTO THE HUDSON BAY. AS A CONSEQUENCE OF THIS...WINDS ARE EXPECTED TO BECOME WEST SOUTHWESTERLY AND INCREASE TO NEAR 30 KT LATE TUESDAY NIGHT AND ON WEDNESDAY. THEN WEDNESDAY NIGHT A STRONG COLD FRONT...ASSOCIATED WITH THE LOW ACROSS NORTHERN CANADA...WILL PUSH SOUTH ACROSS LAKE MICHIGAN. WEST TO NORTHWEST WINDS WILL OCCUR IN THE WAKE OF THIS FRONT. FOLLOWING THIS FRONT...ANOTHER CANADIAN HIGH PRESSURE SYSTEM WILL DROP SOUTHEAST ACROSS THE PLAINS THURSDAY AND FRIDAY. THIS SHOULD HELP SUPPORT A DECENT PRESSURE GRADIENT ACROSS THE GREAT LAKES. THUS...IN COMBINATION WITH A VERY COLD AIR MASS OVER THE RELATIVELY WARM WATERS OF LAKE MICHIGAN...WINDS WILL LIKELY REMAIN ELEVATED IN THE 20 TO 25 KT RANGE DURING THIS PERIOD. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 9 PM TUESDAY. && $$
AREA FORECAST DISCUSSION
NWS TOPEKA KS
1139 AM CST TUE DEC 6 2011 ...UPDATE TO AVIATION... && .AVIATION... VFR CONDITIONS EXPECTED THROUGH THE PERIOD. NORTH WINDS BECOME VARIABLE OVERNIGHT AND SHIFT AROUND TO THE SOUTHWEST ON WEDNESDAY. SPEEDS REMAIN BELOW 12 KTS. 67 && .PREV DISCUSSION... /ISSUED 536 AM CST TUE DEC 6 2011/ SHORT RANGE FORECAST (TODAY AND WEDNESDAY)... 8Z WATER VAPOR IMAGERY AND ASSOCIATED 500 MB RUC ANALYSIS SHOWS A HIGHLY AMPLIFIED POSITIVELY TILTED TROUGH OVER THE CENTRAL PLAINS WITH ITS AXIS EXTENDING FROM LAKE SUPERIOR AND RUNNING SOUTHWESTWARD THROUGH NEBRASKA AND INTO THE FOUR CORNER REGION. CURRENTLY TEMPERATURES ACROSS CENTRAL NEBRASKA ARE BELOW ZERO AS THE SURFACE RIDGE OF HIGH PRESSURE IS CENTERED OVER NEBRASKA. THE COLDEST LOCATION REMAINS KBBW WHERE THE TEMP AT 9Z WAS -11. ACROSS NORTHEAST KANSAS TEMPERATURES REMAIN IN THE MID TEENS WITH WIND CHILLS IN THE SINGLE DIGITS. ACROSS SOUTHEAST KANSAS MEAGER FRONTOGENETICAL AND ISENTROPIC LIFT HAS BROUGHT SOME LIGHT SNOW...MAINLY IN THE FORM OF NON-ACCUMULATING FLURRIES. BY MID-DAY ON TUESDAY EXPECT THE LOW/MID LEVEL LIFT AND SATURATED CONDITIONS TO MOVE OFF THE EAST OF THE FORECAST AREA ALLOWING A GRADUAL BREAKDOWN OF THE STRATUS DECK. EXPECT VERY LIGHT COLD AIR ADVECTION TO PERSIST THROUGHOUT THE DAY AS WINDS STAY FROM THE NORTH WHERE THE SURFACE HIGH WILL RESIDE. AS A RESULT OF THE COLD AIR ADVECTION AND THE ABBREVIATED DURATION OF CLEAR SKIES EXPECT TEMPS ON TUESDAY TO REMAIN IN THE MID TO UPPER 20S ACROSS AREAS NORTH OF THE KANSAS TURNPIKE...WITH TEMPS SOUTH AND EAST OF THE TURNPIKE REACHING THE LOWER 30S. FOR TUESDAY NIGHT THE SURFACE HIGH MOVES EASTWARD AND CENTERS OVER NORTHEAST KANSAS. EXPECT SKIES TO CLEAR OUT AND WINDS TO GO CALM OVERNIGHT. EXPECT TUESDAY NIGHT/WED MORNING TO BE THE COLDEST PERIOD FOR THIS FORECAST PACKAGE AS TEMPS WILL DROP TO THE LOWER TEENS ACROSS THE ENTIRE AREA...WITH THE LOWER TERRAIN OF RIVER VALLEYS PERHAPS DROPPING INTO THE SINGLE DIGITS. BY WEDNESDAY THE ARCTIC AIRMASS WHICH BROUGHT THE FRIGID TEMPS FOR THE EARLY PART OF THE WEEK WILL SHIFT EAST AND WARMER AIR WILL ADVECT INTO THE AREA...ALLOWING WEDNESDAY`S TEMPS TO REACH THE UPPER 30S TO LOWER 40S. MID-RANGE AND EXTENDED FORECAST (THURSDAY THROUGH MONDAY)... FAIRLY INACTIVE WEATHER PATTERN SHAPING UP FOR THE MIDDLE TO LATE PART OF THE WEEK AND INTO THE WEEKEND...AS NO REAL MID OR UPPER LEVEL FORCING ENTERS THE AREA. ALTHOUGH THE DAY TIME HOURS WILL BE SLIGHTLY WARMER FOR THE MIDDLE TO LATE PART OF THE WEEK OVERNIGHT LOWS WILL STILL DROP TO THE MID TEENS TO UPPER 20S AS ANOTHER MASS OF COLD AIR DIPS INTO THE AREA. PERHAPS THE ONLY WEATHER TO AFFECT NORTHEAST KANSAS WILL BE LATE IN THE WEEK AS AN UPPER LEVEL LOW DIGS SOUTHWARD THROUGH NEBRASKA BUT ITS SOUTHWARD PROGRESS STOPS IN SOUTHERN NEBRASKA BEFORE IT EJECTS EASTWARD. WITH LITTLE MOISTURE FOR THE SYSTEM TO WORK WITH EXPECT ONLY A FEW FLURRIES ACROSS AREAS NORTH OF HIGHWAY 24 THURSDAY NIGHT/FRIDAY MORNING. THEREAFTER EXPECT A DRY FORECAST FOR THE REST OF THE WEEK AND THROUGH THE WEEKEND WITH DAYTIME HIGHS IN THE 40S AND OVERNIGHT LOWS IN THE UPPER 20S TO LOWER 30S. JL && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS TOPEKA KS
536 AM CST TUE DEC 6 2011 ...UPDATE TO AVIATION... .DISCUSSION... SHORT RANGE FORECAST (TODAY AND WEDNESDAY)... 8Z WATER VAPOR IMAGERY AND ASSOCIATED 500 MB RUC ANALYSIS SHOWS A HIGHLY AMPLIFIED POSITIVELY TILTED TROUGH OVER THE CENTRAL PLAINS WITH ITS AXIS EXTENDING FROM LAKE SUPERIOR AND RUNNING SOUTHWESTWARD THROUGH NEBRASKA AND INTO THE FOUR CORNER REGION. CURRENTLY TEMPERATURES ACROSS CENTRAL NEBRASKA ARE BELOW ZERO AS THE SURFACE RIDGE OF HIGH PRESSURE IS CENTERED OVER NEBRASKA. THE COLDEST LOCATION REMAINS KBBW WHERE THE TEMP AT 9Z WAS -11. ACROSS NORTHEAST KANSAS TEMPERATURES REMAIN IN THE MID TEENS WITH WIND CHILLS IN THE SINGLE DIGITS. ACROSS SOUTHEAST KANSAS MEAGER FRONTOGENETICAL AND ISENTROPIC LIFT HAS BROUGHT SOME LIGHT SNOW...MAINLY IN THE FORM OF NON-ACCUMULATING FLURRIES. BY MID-DAY ON TUESDAY EXPECT THE LOW/MID LEVEL LIFT AND SATURATED CONDITIONS TO MOVE OFF THE EAST OF THE FORECAST AREA ALLOWING A GRADUAL BREAKDOWN OF THE STRATUS DECK. EXPECT VERY LIGHT COLD AIR ADVECTION TO PERSIST THROUGHOUT THE DAY AS WINDS STAY FROM THE NORTH WHERE THE SURFACE HIGH WILL RESIDE. AS A RESULT OF THE COLD AIR ADVECTION AND THE ABBREVIATED DURATION OF CLEAR SKIES EXPECT TEMPS ON TUESDAY TO REMAIN IN THE MID TO UPPER 20S ACROSS AREAS NORTH OF THE KANSAS TURNPIKE...WITH TEMPS SOUTH AND EAST OF THE TURNPIKE REACHING THE LOWER 30S. FOR TUESDAY NIGHT THE SURFACE HIGH MOVES EASTWARD AND CENTERS OVER NORTHEAST KANSAS. EXPECT SKIES TO CLEAR OUT AND WINDS TO GO CALM OVERNIGHT. EXPECT TUESDAY NIGHT/WED MORNING TO BE THE COLDEST PERIOD FOR THIS FORECAST PACKAGE AS TEMPS WILL DROP TO THE LOWER TEENS ACROSS THE ENTIRE AREA...WITH THE LOWER TERRAIN OF RIVER VALLEYS PERHAPS DROPPING INTO THE SINGLE DIGITS. BY WEDNESDAY THE ARCTIC AIRMASS WHICH BROUGHT THE FRIGID TEMPS FOR THE EARLY PART OF THE WEEK WILL SHIFT EAST AND WARMER AIR WILL ADVECT INTO THE AREA...ALLOWING WEDNESDAY`S TEMPS TO REACH THE UPPER 30S TO LOWER 40S. MID-RANGE AND EXTENDED FORECAST (THURSDAY THROUGH MONDAY)... FAIRLY INACTIVE WEATHER PATTERN SHAPING UP FOR THE MIDDLE TO LATE PART OF THE WEEK AND INTO THE WEEKEND...AS NO REAL MID OR UPPER LEVEL FORCING ENTERS THE AREA. ALTHOUGH THE DAY TIME HOURS WILL BE SLIGHTLY WARMER FOR THE MIDDLE TO LATE PART OF THE WEEK OVERNIGHT LOWS WILL STILL DROP TO THE MID TEENS TO UPPER 20S AS ANOTHER MASS OF COLD AIR DIPS INTO THE AREA. PERHAPS THE ONLY WEATHER TO AFFECT NORTHEAST KANSAS WILL BE LATE IN THE WEEK AS AN UPPER LEVEL LOW DIGS SOUTHWARD THROUGH NEBRASKA BUT ITS SOUTHWARD PROGRESS STOPS IN SOUTHERN NEBRASKA BEFORE IT EJECTS EASTWARD. WITH LITTLE MOISTURE FOR THE SYSTEM TO WORK WITH EXPECT ONLY A FEW FLURRIES ACROSS AREAS NORTH OF HIGHWAY 24 THURSDAY NIGHT/FRIDAY MORNING. THEREAFTER EXPECT A DRY FORECAST FOR THE REST OF THE WEEK AND THROUGH THE WEEKEND WITH DAYTIME HIGHS IN THE 40S AND OVERNIGHT LOWS IN THE UPPER 20S TO LOWER 30S. JL && .AVIATION... STRATUS WITH MVFR CEILINGS...AROUND 1600 FT...WERE OBSERVED AT THE TAF SITES THIS MORNING. ISENTROPIC DOWN-GLIDE WILL INCREASE THROUGH MID MORNING AND SHOULD SCATTER OUT THE MVFR CEILINGS BY 16Z. EXPECT VFR CONDITIONS THROUGH THE REMAINDER OF THE TAF PERIOD. NORTH WINDS OF 8 TO 12 KTS WILL SLOWLY DIMINISH THROUGH THE DAY. GARGAN && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS TOPEKA KS
339 AM CST TUE DEC 6 2011 .DISCUSSION... SHORT RANGE FORECAST (TODAY AND WEDNESDAY)... 8Z WATER VAPOR IMAGERY AND ASSOCIATED 500 MB RUC ANALYSIS SHOWS A HIGHLY AMPLIFIED POSITIVELY TILTED TROUGH OVER THE CENTRAL PLAINS WITH ITS AXIS EXTENDING FROM LAKE SUPERIOR AND RUNNING SOUTHWESTWARD THROUGH NEBRASKA AND INTO THE FOUR CORNER REGION. CURRENTLY TEMPERATURES ACROSS CENTRAL NEBRASKA ARE BELOW ZERO AS THE SURFACE RIDGE OF HIGH PRESSURE IS CENTERED OVER NEBRASKA. THE COLDEST LOCATION REMAINS KBBW WHERE THE TEMP AT 9Z WAS -11. ACROSS NORTHEAST KANSAS TEMPERATURES REMAIN IN THE MID TEENS WITH WIND CHILLS IN THE SINGLE DIGITS. ACROSS SOUTHEAST KANSAS MEAGER FRONTOGENETICAL AND ISENTROPIC LIFT HAS BROUGHT SOME LIGHT SNOW...MAINLY IN THE FORM OF NON-ACCUMULATING FLURRIES. BY MID-DAY ON TUESDAY EXPECT THE LOW/MID LEVEL LIFT AND SATURATED CONDITIONS TO MOVE OFF THE EAST OF THE FORECAST AREA ALLOWING A GRADUAL BREAKDOWN OF THE STRATUS DECK. EXPECT VERY LIGHT COLD AIR ADVECTION TO PERSIST THROUGHOUT THE DAY AS WINDS STAY FROM THE NORTH WHERE THE SURFACE HIGH WILL RESIDE. AS A RESULT OF THE COLD AIR ADVECTION AND THE ABBREVIATED DURATION OF CLEAR SKIES EXPECT TEMPS ON TUESDAY TO REMAIN IN THE MID TO UPPER 20S ACROSS AREAS NORTH OF THE KANSAS TURNPIKE...WITH TEMPS SOUTH AND EAST OF THE TURNPIKE REACHING THE LOWER 30S. FOR TUESDAY NIGHT THE SURFACE HIGH MOVES EASTWARD AND CENTERS OVER NORTHEAST KANSAS. EXPECT SKIES TO CLEAR OUT AND WINDS TO GO CALM OVERNIGHT. EXPECT TUESDAY NIGHT/WED MORNING TO BE THE COLDEST PERIOD FOR THIS FORECAST PACKAGE AS TEMPS WILL DROP TO THE LOWER TEENS ACROSS THE ENTIRE AREA...WITH THE LOWER TERRAIN OF RIVER VALLEYS PERHAPS DROPPING INTO THE SINGLE DIGITS. BY WEDNESDAY THE ARCTIC AIRMASS WHICH BROUGHT THE FRIGID TEMPS FOR THE EARLY PART OF THE WEEK WILL SHIFT EAST AND WARMER AIR WILL ADVECT INTO THE AREA...ALLOWING WEDNESDAY`S TEMPS TO REACH THE UPPER 30S TO LOWER 40S. MID-RANGE AND EXTENDED FORECAST (THURSDAY THROUGH MONDAY)... FAIRLY INACTIVE WEATHER PATTERN SHAPING UP FOR THE MIDDLE TO LATE PART OF THE WEEK AND INTO THE WEEKEND...AS NO REAL MID OR UPPER LEVEL FORCING ENTERS THE AREA. ALTHOUGH THE DAY TIME HOURS WILL BE SLIGHTLY WARMER FOR THE MIDDLE TO LATE PART OF THE WEEK OVERNIGHT LOWS WILL STILL DROP TO THE MID TEENS TO UPPER 20S AS ANOTHER MASS OF COLD AIR DIPS INTO THE AREA. PERHAPS THE ONLY WEATHER TO AFFECT NORTHEAST KANSAS WILL BE LATE IN THE WEEK AS AN UPPER LEVEL LOW DIGS SOUTHWARD THROUGH NEBRASKA BUT ITS SOUTHWARD PROGRESS STOPS IN SOUTHERN NEBRASKA BEFORE IT EJECTS EASTWARD. WITH LITTLE MOISTURE FOR THE SYSTEM TO WORK WITH EXPECT ONLY A FEW FLURRIES ACROSS AREAS NORTH OF HIGHWAY 24 THURSDAY NIGHT/FRIDAY MORNING. THEREAFTER EXPECT A DRY FORECAST FOR THE REST OF THE WEEK AND THROUGH THE WEEKEND WITH DAYTIME HIGHS IN THE 40S AND OVERNIGHT LOWS IN THE UPPER 20S TO LOWER 30S. JL && .AVIATION... FORECAST SOUNDINGS AND SATELLITE TRENDS SUGGEST MVFR CIGS TO REMAIN OVER THE TERMINALS THROUGH 12Z OR SO. EXPECT MHK TO BREAK OUT EARLIER WITH TOP AND FOE TO FOLLOW AS SUBSIDENCE ERODES THE CLOUDS BY 18Z. WINDS CONTINUE NORTH NEAR 10 KTS THEN DECREASE AS SURFACE HIGH MOVES EAST. 53 && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS GOODLAND KS
1020 PM MST MON DEC 5 2011 .UPDATE... 850 PM MDT MON DEC 5 2011 LATEST RUC HRRR HAS A BIT BETTER HANDLE ON COLDER TEMPS PRESENTLY AND THROUGH THE REST OF THE OVERNIGHT REALLY TANKS TEMPS IN AREAS SUCH AS MCCOOK AND NORTON WITH READINGS IN THE -10F TO -14F RANGE AFTER 12Z. 00Z MET GUIDANCE FOR KMCK SHOWING -9F. KMCK DROPPED TO -1F 2 MORNINGS AGO. HAVE UPDATED MINS TO DROP THEM TO AROUND -11F WHILE IN NORTON HAVE LOWERED THEM TO THE -10F RANGE. FOR NORTON COUNTY COMBINATION OF THE 10F FORECAST AND WEST WIND OF 5 MPH OR LESS PUTS THEM IN WIND CHILL ADVISORY CRITERIA. WILL CONTINUE TO MONITOR 03Z RUN OF THE HRRR AND SEE WHAT IT DOES FOR TEMPS AND WINDS. 007 && .DISCUSSION... 221 PM MST MON DEC 5 2011 EARLY AFTERNOON WV IMAGERY AND RUC H5 ANALYSIS SHOW LARGE SCALE TROUGH EXTENDING FROM GREAT LAKES REGION...ACROSS CENTRAL COLORADO...WITH BASE OF TROUGH OVER SOUTHERN ARIZONA/NEW MEXICO. THROUGH TONIGHT...SURFACE HIGH PRESSURE WILL CONTINUE TO BUILD OVER THE CENTRAL HIGH PLAINS AS A WEAK SHORTWAVE TROUGH CONTINUES TO PUSH AWAY FROM THE FORECAST AREA. COMBINATION OF CLEARING SKY...VERY LIGHT WINDS AND WIDESPREAD SNOW COVER WILL CONTRIBUTE TO VERY COLD TEMPERATURES OVERNIGHT. AMBIENT TEMPERATURES WILL FALL BELOW ZERO FOR ALL BUT THE FAR SOUTHEAST PORTION OF THE FORECAST AREA WHICH WILL REMAIN AT OR SLIGHTLY ABOVE ZERO. DESPITE THE LIGHT WINDS...WIND CHILL READINGS WILL FALL TO AS LOW AS 20 BELOW ZERO FOR A PERIOD OF TIME PRIMARILY OVER THE NORTHWEST HALF OF THE FORECAST AREA. AS SUCH...WILL ISSUE A WIND CHILL ADVISORY. FOLTZ TUESDAY-WEDNESDAY...SHORTWAVE RIDGING WILL BUILD OVER THE CWA TUESDAY QUICKLY FOLLOWED BY WESTERLY FLOW ALOFT WEDNESDAY...WHICH WILL FAVOR DRY CONDITIONS OVER CWA. SHALLOW COLD AIR MASS WILL BEGIN TO MODERATE...WITH HIGH/LOW TEMP FORECAST COMPLICATED BY LINGERING SNOW PACK. CONTINUED TO UNDERCUT GUIDANCE THROUGH THESE PERIODS....NOT EXPECTING TEMPS TO MAKE IT ABOVE FREEZING UNTIL WED AFTERNOON. WEDNESDAY NIGHT-THURSDAY NIGHT...COLD FRONT PUSHES SOUTH ACROSS CWA WEDNESDAY NIGHT...WITH SHORTWAVE TROUGH PASSING NORTH OF CWA THURSDAY/THURSDAY NIGHT. BEST LIFT/MOISTURE LOOKS TO REMAIN OVER CENTRAL NEBRASKA...HOWEVER MODEL POINT SOUNDINGS DO SHOW DENDRITIC LAYER BEGINNING TO SATURATE IN EXTREME NORTHERN PART OF CWA IN THE 21Z-00Z TIME FRAME. WENT AHEAD AND ADDED SLIGHT CHANCE POPS TO SW NEBRASKA COUNTIES 18Z-00Z WHERE A DUSTING COULDNT BE RULED OUT. ALSO EXPANDED FLURRIES FURTHER SOUTH...AND MADE CONDITIONS DRY AFTER 06Z. FRIDAY-MONDAY...WARMING TREND WILL START UP AGAIN FRIDAY...AND CONTINUE THROUGH THE WEEKEND WITH SHORTWAVE RIDGING ACROSS WESTERN CONUS THROUGH SATURDAY. TEMPERATURES SHOULD MODERATE TO NEAR NORMAL VALUES IN THE UPPER 30S/LOW 40S SAT/SUN. CLOSED LOW BEGINS TO DEVELOP OVER SW CONUS BY SUNDAY NIGHT/MONDAY WITH W/SW FLOW DEVELOPING OVER CWA AHEAD OF THIS FEATURE. GUIDANCE IN GENERAL AGREEMENT ON ARRIVAL OF COLD FRONT SUN NIGHT/MON...WHICH SHOULD SUPPORT A RETURN TO BELOW NORMAL TEMPERATURES EARLY NEXT WEEK. NOT EXPECTING ANY PRECIP THROUGH EXTENDED PERIODS...WITH DRY AIR MASS IN PLACE OVER CWA. DR && .AVIATION... 1020 PM MST MON DEC 5 2011 FOR THE 06Z TAFS...VFR THROUGH THE PERIOD AT BOTH KGLD AND KMCK. SFC HIGH OVER THE AREA PRODUCING SOUTHEST WINDS OF 5 TO 10 KTS. THESE WINDS WILL CONTINUE THROUGH THE DAY TUESDAY BEFORE BECOMING WEST TOWARD THE END OF THE PERIOD WITH AN INCREASE IN MID LEVEL CLOUDS AS WELL. 007 && .GLD WATCHES/WARNINGS/ADVISORIES... KS...WIND CHILL ADVISORY UNTIL 8 AM MST /9 AM CST/ TUESDAY FOR KSZ001>003-013-014-027. NE...WIND CHILL ADVISORY UNTIL 8 AM MST /9 AM CST/ TUESDAY FOR NEZ079>081. CO...WIND CHILL ADVISORY UNTIL 8 AM MST TUESDAY FOR COZ090>092. && $$
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
1113 PM CST MON DEC 5 2011 .AVIATION... FOR THE 06Z TAF ISSUANCE. VFR CONDITIONS WILL PREVAIL AT ALL TAF SITES THROUGH LATE TUESDAY AFTERNOON. SURFACE HIGH PRESSURE WILL PREVAIL ACROSS THE NORTHERN ROCKIES LATE TONIGHT INFLUENCING NORTHERLY WINDS 5 TO 10KT THROUGH EARLY TUESDAY MORNING. A LEE SIDE TROUGH OF LOW PRESSURE WILL DEVELOP ACROSS EASTERN COLORADO TUESDAY MORNING TURNING WINDS WESTERLY 5 TO 10KT BY EARLY TUESDAY AFTERNOON. && .PREV DISCUSSION... /ISSUED 500 PM CST MON DEC 5 2011/ SYNOPSIS... THE 15.12Z 250 HPA MAP CONTINUED TO SHOW A LARGE TROUGH BISECTING THE CONUS WITH A STRONG 100 KT JET EXTENDING SOUTHWARD FROM SASKATCHEWAN AND ACROSS MONTANA. AN EVEN FASTER JET NEAR 150 KT WAS MOVING ACROSS SE CANADA WITH AN EXTENSION OF THIS JET, ALBEIT WEAKER WINDS, TOWARDS KANSAS. AT 500 HPA, VERY COLD AIR OF -40 DEG C WAS OBSERVED AT KABR WITH -30S DEG C SOUTHWARD ACROSS COLORADO. THE ARCTIC AIR AT 700 HPA WITH TEMPERATURES AT LEAST -20 DEG C EXTENDED ACROSS THE NORTHERN PLAINS. 5 DEGREES OF COOLING WAS NOTED BETWEEN THE 00Z AND 12Z RAOB FOR KDDC AT 850 HPA. AT THE SURFACE, ARCTIC AIR EXTENDED ACROSS THE PLAINS WITH TEENS AND 20S DEG F CONTINUING AT 21Z ACROSS THE SUNFLOWER STATE. -SUGDEN DISCUSSION... DAYS 1-2... TONIGHT: THE VERY SHORT TERM CONCERN FOR THIS EVENING IS THE SNOW POTENTIAL ACROSS THE CENTRAL AND SOUTHERN HALF OF THE CWFA WITH A MORE APPRECIABLE CHANCE FOR "HEAVIER" SNOW ACROSS THE SE CWFA. THE SATELLITE WATER VAPOR CHANNEL SHOWS A WEAK DISTURBANCE MOVING NEW MEXICO AT THE BASE OF AN UPPER LEVEL TROUGH. A PV ANOMALY ASSOCIATED WITH THE PASSAGE OF THE UPPER LEVEL TROUGH AND ISENTROPIC LIFT IN THE 290-295K THETA LAYER WILL PROVIDE ENOUGH LIFT FOR SOME SNOW SHOWERS, PARTICULARLY ACROSS THE SE FA. AS A RESULT, HAVE INCREASED POPS UP TO CHANCE AND UPPED SNOWFALL AMOUNTS TO 0.6-1.0 INCHES TOWARDS MEDICINE LODGE. HRRR ALSO IS SHOWING SOME ACCUMULATIONS WHICH AGREES WITH THE QPF OUTPUT FROM THE THE NAM, GFS, GEM, ECMWF, ARW, AND NMM...WHICH ALL PAINT A LITTLE QPF IN THIS REGION. OTHERWISE, MID AND LOW LEVEL CLOUDS WILL EVENTUALLY CLEAR TONIGHT AS THE COLD SURFACE HIGH PRESSURE CENTER SETTLES ACROSS KANSAS AND THE TROF CONTINUES EAST. THIS WILL RESULT IN WEAKENING OF WINDS AND ALLOW TEMPERATURES TO PLUMMET. I HAVE -2 TO -4 DEG F TO THE NORTHWEST AND AROUND 16 DEG F SE AS THE NW WILL HAVE WEAKER WINDS AND LESS CLOUD COVER THAN COMPARED TO THE SE. HAVE CONTINUED THE TREND OF HIGHLIGHTING THE LOW WIND CHILL VALUES IN THE HWO. THESE VALUES ARE NOT EXPECTED TO REACH WIND CHILL ADVISORY CRITERIA. TUESDAY: HAVE ZERO POPS IN TUESDAY AS THE CWFA WILL BE ON THE BACKSIDE (SUBSIDENCE) OF THE UPPER LEVEL TROUGH AND HIGH PRESSURE WILL CONTINUE AT THE SURFACE. THINK THE NAM MODEL IS BEING TOO INFLUENCED BY THE SNOWFIELD ACROSS WEST CENTRAL AND NORTHWEST KANSAS SO HAVE STEERED AWAY FROM THIS RUN. TEMPERATURES WILL SLIGHTLY MODERATE COMPARED TO MONDAYS HIGHS AND BE IN THE 20S DEG F. BY TOMORROW EVENING, A WEAK LEE SURFACE TROUGH WILL DEVELOP ACROSS EASTERN COLORADO WHICH WILL TURN OUR WINDS MORE SOUTHWESTERLY TO WESTERLY. SKIES SHOULD BE CLEAR WITH A DRY AIRMASS OVERHEAD. WEDNESDAY: THE DAY WILL START COLD WITH SINGLE DIGITS TO LOW TEENS DEG F DURING THE MORNING. DURING THE DAY, THE WEAK LEE SIDE TROUGH WILL MOVE EASTWARDS ACROSS WESTERN KANSAS USHERED BY A SHORTWAVE TROUGH MOVING ACROSS THE NORTHERN PLAINS. THIS WILL TURN OUR WINDS MORE NORTHWESTERLY SO WE COULD SEE SOME DOWNSLOPE CONDITIONS AND RESULT WARMER TEMPERATURES. MEX GUIDANCE HAS KDDC IN THE 40S AND THE ECMWF IS PARTICULARLY WARM WITH MID 40S DEG F ACROSS THE CENTRAL AND SE FA. HAVE NOT WARMED TEMPERATURES UP TO THIS BUT DID TWEAK THEM UP HIGHER WEDNESDAY. -SUGDEN DAYS 3-7... A SPLIT JET STREAM IS EXPECTED TO PREVAIL ACROSS THE CONUS WITH BENIGN WEATHER AS A RESULT THROUGH THE EXTENDED FORECAST. WEDNESDAY NIGHT THROUGH FRIDAY: A NORTHWEST TO SOUTHEAST ORIENTED SURFACE HIGH WILL MOVE THROUGH THE NORTHERN PLAINS THURSDAY AS A SHORTWAVE TROUGH IN THE NORTHERN BRANCH OF THE JET SWINGS SOUTHEASTWARD AROUND THE SOUTHERN EDGE OF THE LARGER HUDSON BAY . ANY NORTHWEST FLOW FRONTOGENESIS AND ATTENDANT SNOW TIED TO THIS FEATURE WILL BE NORTH AND EAST OF THE SOUTHWEST KANSAS REGION SO NO POPS ARE IN THE FORECAST. A GLANCING BLOW OF ARCTIC AIR WILL ONLY RESULT IN A MINIMAL IMPACT ON TEMPERATURES WITH HIGHS GENERALLY IN THE UPPER 30S FOR BOTH THURSDAY AND FRIDAY. SATURDAY THROUGH MONDAY: THE NORTHERN POLAR JET WILL BE SHIFTED NORTH DURING THIS TIME FRAME WITH VERY WEAK FLOW IN THE MID AND UPPER LEVELS OVER THE CENTRAL ROCKIES AND GREAT PLAINS. MEANWHILE...THE SOUTHERN JET WILL REMAIN ALONG AN AXIS FROM THE NORTHERN BAJA OF CALIFORNIA THROUGH SOUTHWEST TEXAS TO THE GULF COAST REGION. THE DETERMINISTIC GFS AND ECMWF MODELS BOTH SHOW A MINOR SHORTWAVE TROUGH WITHIN THE SOUTHERN JET MOVING ACROSS SOUTHERN CALIFORNIA/NORTHERN BAJA CALIFORNIA ENTERING THE DESERT SOUTHWEST REGION. A JET STREAM IN THE NORTHERN POLAR JET IS EXPECTED TO DIG SOUTHWARD DOWN THE WEST COAST AROUND SUNDAY...WHICH WILL BECOME INVOLVED WITH THE SOUTHERN JET IN SOME FASHION. INTERACTION OF SOUTHERN AND NORTHERN BRANCHES OF THE JET IS SOMETHING THAT MODELS WILL STRUGGLE WITH AT THIS TIME FRAME...SO THERE IS A LOT OF UNCERTAINTY GOING INTO LATE WEEKEND/EARLY NEXT WEEK CONCERNING HOW A POTENTIAL MEAN TROUGH IN THE WEST WILL EVOLVE...AND JUST HOW IT WILL IMPACT SOUTHWEST KANSAS WEATHER AS A RESULT. -UMSCHEID && .PRELIMINARY POINT TEMPS/POPS... DDC 8 27 10 41 / 20 0 0 0 GCK 4 24 8 39 / 10 0 0 0 EHA 6 25 9 41 / 20 0 0 0 LBL 8 27 9 41 / 20 0 0 0 HYS 7 24 9 37 / 10 0 0 0 P28 16 30 14 42 / 40 0 0 0 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ FN12/99/99
AREA FORECAST DISCUSSION
NWS LOUISVILLE KY
945 PM EST WED DEC 07 2011 ...Forecast Update... Did a minor update to account for current temperature and sky trends. The remaining forecast is on track. Updated products have been issued. Dry air continues to migrate into the forecast area. Current T/Td spreads of generally 6-9 degrees yields relative humidity values in the 70 to low 80 percent range. Latest guidance, particularly LAMP data, handle the current conditions well and keep a 4-5 degree spread through the morning hours. With this T/Td spread and westerly wind speeds in the 3-5 mph range overnight, believe it will be difficult for fog formation. Additionally, the gusty northwest winds this afternoon across much of the forecast area actually aided in drying the surface a bit. At this time, the only potential location for fog formation would be confined to the water surfaces of rivers and lakes in the form of steam fog (also known as evaporation fog), as this cold airmass works over slightly warmer river/lake waters. Once again, this would be localized to very near the water surface, if fog were to form. && .Short Term (Tonight and Thursday)... First off, snow band was not as impressive as the HRRR earlier today made it out to be. County officials in our Lake Cumberland region have all indicated very little snow stuck. Webcams from that area also look mostly just wet and not white. Had some pictures with snow from the LEX-area webcams in a brief band that went through their in the last couple of hours, but likewise nothing has accumulated. Surface temperatures are just too warm, in the mid 30s along with the still wet grounds from the rain earlier in the week. Sunshine is poking out some in cloud cover west of a KLEX to Scottsville line. With any heating though, additional low clouds are developing. These clouds may yet produce some scattered very light flurries across central KY, but temperatures will not be cool enough where these clouds are to promote lots of snow. With the cloud cover, temperatures are holding to around 40 degrees at most. Skies should clear out overnight as deep dry air moves into the region. High pressure will move in south of the region, so expect a general westerly wind through the night. Expect temperatures to fall into the 20s areawide overnight under these clear skies. Sheltered locations may see the low 20s. High pressure will be centered over the Appalachians during the day Thursday. Thus expect a southwesterly flow. Clear skies should allow us to reach the low/mid 40s areawide, roughly 5 degrees below normal. .Long term (Thursday night - Wednesday)... A digging shortwave will dive from the northern plains into the lower Great Lakes on Friday. Moisture return ahead of this system will be limited and therefore continued to only mention flurries in the forecast early Friday morning across southern Indiana, gradually working eastward across north central Kentucky and the Bluegrass through the day. Temperatures ahead of the front will likely warm enough for just sprinkles in the late morning and afternoon. In the morning and the evening, moisture to about 700 mb should yield some potential for ice crystals as temps at this level will be around -10 C. No impacts from these flurries are anticipated. Otherwise, cold frontal boundary moves through Friday afternoon and evening with a cold airmass lurking for the weekend. Lows Friday night are expected to drop into the lower 20 in most spots, with a few upper teens possible across southern Indiana and perhaps the Bluegrass. High temperatures on Saturday will struggle, only making it to the low and mid 30s. Saturday night will bring more temperatures right around the 20 degree mark. Sunday into the middle of next week, mid level flow will gradually transition from a progressive zonal flow then try to head back toward the classic La Nina pattern we have been seeing which would yield southwest flow aloft with a ridge to our southeast and a developing trough over the western CONUS. Will keep forecast through Wednesday dry, although some signs point to another potent system tracking into the region possibly Thursday or Friday. Although this is pretty far out, confidence in the recent pattern supported by teleconnections could lead to another substantial precipitation event across the Ohio Valley. Stay tuned. Highs through the first half of next week will gradually moderate toward the mid 40s, with upper 40s and low 50s ahead of the next system possible on Wednesday. Lows each night will be in the 20s, warming to the low 30s by Wednesday morning. && .Aviation (00Z TAF Issuance)... Expect VFR conditions through the TAF period as our latest weather system departs the region to the east. Skies will continue to clear from west to east overnight. Additionally, dry air is filtering into the area. The T/Td spread should be large enough to limit fog formation overnight. Current guidance and trends in the observations are illustrating this as well. Surface winds will become southwesterly by morning as surface high pressure builds across the Appalachians. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...NONE. KY...NONE. $$ Update...........MJP Short Term.......RJS Long Term........BJS Aviation.........MJP
AREA FORECAST DISCUSSION
NWS CARIBOU ME
858 AM EST TUE DEC 6 2011 .SYNOPSIS... A COLD FRONT WILL MOVE OFF THE COAST LATE TODAY WITH A SERIES OF WEAK LOW PRESSURE SYSTEMS TRACKING ALONG THE FRONT TONIGHT INTO WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/... UPDATE: USING HRRR MODEL WILL END PRECIPITATION FROM WEST TO EAST ACROSS THE REGION THIS AFTERNOON. REGION WILL START OUT PRECIP FREE THIS EVENING THEN NEXT LOW PRESSURE MOVING ALONG STATIONARY FRONT OVER THE GULF OF MAINE WILL BRING PRECIP BACK ACROSS THE AREA LATER TONIGHT. A COLD FRONT IS EXPECTED TO MOVE THROUGH THE STATE DURING THE DAY TODAY. CURRENT GUIDANCE APPEARS TO MOVE THIS FRONTAL SYSTEM TOO FAST AND EXPECT THE FRONT TO REMAIN STATIONARY DURING THE EARLY MORNING AS A WAVE MOVES NORTHEASTWARD ALONG THE FRONT. AFTER THE WAVE MOVES OFF TO THE NORTHEAST THE COLD AIR SHOULD MOVE IN DURING THE MID MORNING. HAVE USED THE NAM12 AND GFS40 TO INITIALIZE THE POP GRIDS THEN HAVE MANUALLY ADJUSTED TO BETTER FIT THE TIMING OF THE COLD FRONT. HAVE ALSO INCREASE THE POPS TO NEAR 100 PERCENT IN THE VICINITY OF THE FRONT. BY LATE IN THE AFTERNOON AND EARLY EVENING THE FRONT SHOULD BE CLEARING THE COAST. ANOTHER LOW IS EXPECTED TO DEVELOP ALONG THE FRONT TO THE SOUTH LATER TONIGHT AND AS A RESULT PRECIPITATION WILL SPREAD BACK INTO SOUTH TOWARDS WEDNESDAY MORNING. HAVE USED A BLEND OF NAM12 AND GMOS FOR WIND AND USED THE NAM12 FOR TEMPERATURE AND DEW POINT. ALSO BLENDED NAM12 AND GFS40 FOR QPF WITH SOME MANUAL ADJUSTMENTS. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY/... AN INTERESTING FORECAST IN STORE FOR THIS TERM. A SECOND WAVE OF LOW PRES IS EXPECTED TO MOVE ALONG THE STALLED FRONTAL BOUNDARY AND PASS THROUGH THE COAST ON WEDNESDAY. DECIDED TO USE THE SREF POPS BLENDED IN W/THE GFS FOR EARLY WEDNESDAY WHICH SHOWED 60-80% POPS ACROSS THE NORTHERN AND EASTERN AREAS W/. BLYR TEMPERATURES DO LOOK TO BE COLD ENOUGH ACROSS THE NORTHERN AND NORTHWESTERN AREAS FOR ALL SNOW WHILE CENTRAL AND DOWNEAST AREAS WILL SEE MAINLY RAIN. THE PRECIP WILL WIND DOWN BY THE AFTERNOON W/COLDER AIR SLOWLY SEEPING SOUTHWARD. QPF IS A BLEND OF HPC/GFS AND THE NAM WHICH SHOWS .05 TO .15". ANY SNOWFALL ACCUMULATIONS WILL BE ACROSS THE FAR NORTH AND NORTHWEST W/UP TO AN INCH OF ADDITIONAL ACCUMULATION. THE TEMPERATURES WERE ADJUSTED UPWARD USING A BLEND OF THE BCGMOS AND NAM12 GIVEN THE PROXIMITY OF THE FRONT AND HOW THE COLD AIR HAS BEEN HELD BACK THIS MORNING AS DISCUSSED ABOVE IN NEAR TERM SECTION. A BRIEF BREAK IN THINGS AS SOME WEAK RIDGING IS SHOWN TO WORK ACROSS THE CWA FOR WEDNESDAY NIGHT W/SOME PARTIAL CLEARING AND COLDER TEMPERATURES ESPECIALLY ACROSS THE NORTHERN 3RD OF THE CWA. ONCE AGAIN, PREVIOUS MINS WERE RAISED DUE TO SLOWER PROGRESSION OF THE COLD AIR. NOW THE ATTENTION TURNS TO THURSDAY W/THE APCH OF LOW PRES FROM THE MID ATLC REGION. THE 00Z RUN OF THE ECMWF ALONG THE 5 OUT 10 GFS ENSEMBLE MEMBERS SHOW THE LOW FURTHER W AND PASSING THROUGH THE GULF OF MAINE AND THEN ACROSS NOVA SCOTIA. THE ECMWF IS THE FURTHEST WEST BRINGING THE LOW THROUGH THE BAY OF FUNDY WHICH WOULD MEAN A SIGNIFICANT SNOWSTORM FOR JUST ABOUT THE ENTIRE CWA. THE 00Z RUN OF THE NAM WAS FURTHER EAST AND BRINGS THE HEAVIEST QPF INTO THE DOWNEAST AND THE COAST. THE CANADIAN HEMISPHERIC IS CLOSER TO THE NAM AND OPERATIONAL RUN OF THE GFS W/A TRACK ACROSS NOVA SCOTIA. SINCE THE TRENDS HAVE BEEN A MORE WESTERN TRACK ESPECIALLY FROM THE ECMWF AND THE GFS ENSEMBLE, CONFIDENCE IS BUILDING TO RAISE THE BAR AND BRING LIKELY POPS INTO THE DOWNEAST AND COAST ON THURSDAY AND CHC POPS UP INTO NORTHERN MAINE. THE CONFIDENCE IS NOT HIGH ENOUGH THOUGH TO BRING HIGHER PERCENTAGES FURTHER NORTH AS SHOWN BY THE ECMWF. IT WILL BE INTERESTING TO SEE HOW THE LATER MODEL RUNS HANDLE THIS SYSTEM. TEMPERATURES DO LOOK LIKE THEY COULD BE COLD ENOUGH FOR SNOW EVEN AS FAR SOUTH AS BANGOR AND PERHAPS BAR HARBOR. DECIDED TO BLEND THE GMOS AND BCGMOS FOR MAX TEMPERATURES ON THURSDAY WHICH SHOW LOW TO MID 30S. WE WILL ADD A SECTION TO THE HWO ADDRESSING THIS POTENTIAL STORM. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... THE STORM SYSTEM APPEARS TO BE A FAST MOVER PULLING THROUGH THE MARITIMES W/MUCH COLDER AIR SET TO POUR INTO THE REGION THROUGH THE WEEKEND. INITIALIZED THE LONGER TERM W/THE GMOS AND THEN ADJUSTED MAINLY FOR THE POPS AND WINDS. A DISTURBANCE IS SHOWN BY THE GFS AND THE ECMWF TO AFFECT THE CWA ON SATURDAY W/THE POSSIBILITY OF LIGHT SNOW AND MINOR ACCUMULATIONS. AFTER THIS SYSTEM PULLS THROUGH SATURDAY EVENING, MUCH COLDER AIR IS SHOWN TO PUSH INTO THE REGION W/SOME OF THE COLDEST TEMPERATURES OF THE SEASON SO FAR. GMOS TEMPERATURES LOOKED TO BE HANDLING THIS WELL AND SO NO REASON TO DEVIATE FROM THEM. THE PRECIP CHCS LOOKED OVERDONE ON SUNDAY AND DECIDED TO DROP THEM BACK W/HIGH PRES SHOWN TO RIDGE ACROSS THE REGION. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... NEAR TERM: EXPECT MVFR/IFR CONDITIONS TODAY AND TONIGHT. SHORT TERM: IFR/MVFR LOOKS TO BE THE GOING RATE FOR WEDNESDAY W/SNOW ACROSS THE NORTHERN TERMINALS ESPECIALLY KCAR AND KPQI. A BREAK TO MVFR AND EVEN VFR POSSIBLE FOR KBGR AND KBHB WEDNESDAY EVENING W/MVFR HOLDING FOR THE NORTHERN TERMINALS. THERE IS THE POTENTIAL FOR CIGS AND VSBYS TO DROP BACK TO IFR AND EVEN LIFR COME THURSDAY FOR ALL THE TAF SITES AS A STORM SYSTEM APCHS FROM THE SOUTH. && .MARINE... NEAR TERM: HAVE USED A BLEND OF THE NAM12 AND GFS40 FOR WINDS. FOR WAVES USED SWAN/NAM. LONG PERIOD INCOMING WAVE APPEARS TO BE 1 FOOT OR LESS BASED ON BUOY SPECTRAL AND WNA SPECTRAL BULLETIN...SO MOST OF COMBINED SEA RESULTING FROM LOCAL WINDS. SWAN BRING SEAS CLOSE TO SCA AGAIN LATER TODAY. MY THINKING IS THAT WAVE HEIGHT WILL TOP OFF JUST UNDER 5 FEET SO WILL NOT ISSUE SCA AT THIS TIME. SHORT TERM: THERE IS POTENTIAL FOR SCA CONDITIONS ON THURSDAY INTO THURSDAY NIGHT AS LOW PRES INTENSIFIES AS IS IT MOVES THROUGH THE GULF OF MAINE INTO THE MARITIMES. BLENDED THE GEM/NAM12 AND GFS FOR WEDNESDAY INTO WEDNESDAY NIGHT AND THEN FOLLOWED W/THE GFS AND GMOS FROM THURSDAY ONWARD. THEREFORE, WINDS WERE BROUGHT UP TO 20 TO 25 KTS FOR AFOREMENTIONED TIME-FRAME AND THEN SPEEDS COME DOWN AS HIGH PRES RIDGES IN FOR FRIDAY. WNAWAVE AND THE SWAN GUIDANCE WAS USED FOR WAVES WHICH KEEP HEIGHTS AOB 5 FT. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...NONE. MARINE...NONE. && $$ NEAR TERM...FOSTER/MIGNONE SHORT TERM...HEWITT LONG TERM...HEWITT AVIATION...FOSTER/MIGNONE MARINE...FOSTER/MIGNONE/HEWITT
AREA FORECAST DISCUSSION
NWS CARIBOU ME
1227 AM EST TUE DEC 6 2011 .SYNOPSIS... A SLOW MOVING COLD FRONT WILL MOVE ACROSS THE STATE BY LATE TONIGHT. THE FRONT WILL MOVE OFF THE COAST LATER TUESDAY WITH A SERIES OF WEAK LOW PRESSURES TRACKING ALONG THE COASTAL FRONT TUESDAY NIGHT INTO WEDNESDAY. && .NEAR TERM /THROUGH TUESDAY/... HAVE ADJUSTED TEMPERATURE...POP AND WEATHER GRIDS. THE HRRR MODEL DOES NOT BRING THE NEXT SURGE BACK INTO NORTHERN MAINE UNTIL EARLY THIS EVENING SO WILL START OUT WITH LOWER POPS ACROSS THE NORTH AND THEN GRADUALLY INCREASE POPS BACK TO CATEGORICAL THIS EVENING. AS THE COLD FRONT CROSSES NORTHERN MAINE AFTER MIDNIGHT, RAIN WILL MIX WITH SNOW AND THEN CHANGE TO ALL SNOW ACROSS MAINLY NORTHERN AROOSTOOK COUNTY. SNOW WILL CONTINUE INTO THE MORNING HOURS BUT EXPECT SNOW TO BE LIGHT. AT THIS TIME STILL EXPECTING 1 TO 3 INCHES OF SNOW ACROSS NORTHERN SECTIONS WITH THE HIGHEST VALUES ACROSS THE ST. JOHN VALLEY. EXPECT RAIN TO MOVE INTO CENTRAL REGIONS AFTER MIDNIGHT AND THEN INTO DOWNEAST JUST BEFORE SUNRISE TUESDAY. RAIN WILL CONTINUE FOR MOST OF THE DAY OVER DOWNEAST AS LOW PRESSURE MOVES ALONG THE FRONT AS IT SLIDES OFF THE COAST. HIGH TEMPERATURES ON TUESDAY WILL ONLY RISE 1 TO 3 DEGREES FROM THE MORNING LOWS AS COLDER AIR MOVES IN WITH THE NORTH WINDS BEHIND THE COLD FRONT. FOR RAINFALL AMOUNTS EXPECTING BETWEEN A QUARTER TO HALF AN INCH ACROSS THE REGION BY TUESDAY AFTERNOON. && .SHORT TERM /TUESDAY NIGHT THROUGH FRIDAY/... THE UNSETTLED PATTERN WILL CONTINUE THROUGH THE SHORT TERM. A COLD FRONT WILL BE STRETCHED ACROSS THE GULF OF MAINE TUESDAY NIGHT WITH A WAVE OF LOW PRESSURE POSITIONED NEAR NOVA SCOTIA TUESDAY EVENING. PRECIPITATION...MOSTLY IN THE FORM OF SNOW THOUGH MIXED WITH RAIN DOWNEAST AND ESPECIALLY ALONG THE COAST... WILL BEGIN TO WIND DOWN OVERNIGHT AS THIS LOW CONTINUES TO TREK TO THE EAST. HOWEVER ANOTHER WEAK WAVE...THIS ONE FURTHER SOUTH...WILL KEEP AT LEAST THE SLIGHT CHANCE OF RAIN/SNOW SHOWERS ACROSS THE REGION THROUGH WEDNESDAY MORNING. HIGH PRESSURE WILL FINALLY BE ABLE TO TAKE HOLD WEDNESDAY NIGHT...BUT YET ANOTHER LOW WILL MOVE TO THE SOUTH OF THE GULF OF MAINE THURSDAY. THE 12Z ECMWF IS THE MOST AGGRESSIVE AND THE FURTHEST NORTH WITH THIS SYSTEM AND INDICATES THAT MUCH OF DOWNEAST MAINE WOULD SEE A RAIN/SNOW MIX. THE 12Z NAM AND GFS MEANWHILE KEEP THE LOW SOUTH AND ONLY BRUSH THE COAST WITH PRECIPITATION. HAVE GONE WITH SLIGHT CHANCE POPS FOR NOW. ALSO KEPT SLIGHT CHANCE POPS ACROSS THE NORTH AS A COLD FRONT APPROACHES FROM CANADA. DAYTIME TEMPERATURES WEDNESDAY AND THURSDAY WILL RANGE FROM THE LOWER 30S NORTH TO AROUND 40 SOUTH WHILE THE NIGHTS DIP DOWN INTO THE 20S.&& && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... THE START OF THE LONG TERM FINDS THE GFS AND THE ECMWF WITH A SIMILAR SOLUTION...HOWEVER THE GFS APPEARS ABOUT 6HRS BEHIND THE ECMWF ON MOVEMENT OF THE MAIN LOW. A LOW PRESSURE (GFS) IN THE N ATLANTIC SE OF NOVA SCOTIA...A DEEP COLD CORE LOW OVER HUDSON BAY WITH A TROUGH EXTENDING S THROUGH THE CENTRAL GREAT LAKES REGION. A CANADIAN HIGH PRESSURE RIDGE THAT DUG INTO THE SOUTHERN STATES WILL BEGIN TO SPREAD TOWARDS NEW ENGLAND. THE ECMWF THE PRIMARY LOW IS FARTHER NORTH INTO THE CANADIAN MARITIMES. AND THE BUILDING RIDGE EXTEND FARTHER NORTH INTO SOUTHERN NEW ENGLAND. BY FRIDAY MORNING THE HIGH MOVES INTO THE ATLANTIC... THE GFS DIGS THE TROUGH ACROSS THE GREAT LAKE FARTHER SOUTH. THE ECMWF DEVELOPS A WEAK LOW OVER EASTERN ILLINOIS. BY FRIDAY EVENING BOTH MODELS ARE INDICATING A LOW OVER THE NORTHERN GREAT LAKES...WITH A TROUGH OF LOWER PRESSURE EXTENDING SOUTH ALONG THE EASTERN SEABOARD. BY EARLY SATURDAY MORNING BOTH MODELS MOVES THE LOW EAST...THE GFS TO NRN MAINE...THE ECMWF TO SRN QUEBEC. BY SATURDAY MORNING THE GFS MOVES THE LOW AND FRONT EAST OF THE AREA...THE ECMWF TO ERN MAINE. BY SATURDAY EVENING THE LOW WILL BE WELL EAST AND A HIGH PRESSURE RIDGE WILL BUILD IN. HIGHER PRESSURE WILL BUILD IN THROUGH THE END OF THE PERIOD...HOWEVER THE COLD LOW OVER HUDSON BAY WILL REMAIN THROUGH THE PERIOD AND WILL PERIODICALLY KICK OFF SHORT WAVES THAT WILL MOVE THROUGH NORTHERN AND CENTRAL MAINE THROUGH THE END OF THE PERIOD. LOADED GMOS...WITH SOME HAND SMOOTHING. PLUS 15 PERCENT FOR GUST OVER LAND 20 PERCENT OVER WATER. NAWAVE 4 FOR SEAS IN THE COASTAL WATERS. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... NEAR TERM: VFR CONDITIONS ACROSS THE NORTH WILL LOWER TO MVFR THIS EVENING AND THEN IFR BY LATER TONIGHT AND REMAIN IFR THROUGH TUESDAY. VFR CONDITIONS ACROSS DOWNEAST WILL LOWER TO IFR AFTER SUNRISE TUESDAY AND REMAIN IFR FOR THE REMAINDER OF THE DAY. SHORT TERM: WIDESPREAD IFR IN SNOW /MIXED WITH RAIN SOUTH/ EXPECTED INTO WEDNESDAY MORNING...THEN GRADUALLY IMPROVING CONDITIONS FROM NORTH TO SOUTH WEDNESDAY AFTERNOON AS HIGH PRESSURE BUILDS OVER THE REGION. CLOUDS WILL INCREASE LATE WEDNESDAY NIGHT AND THURSDAY AS A COLD FRONT APPROACHES FROM CANADA AND A LOW PRESSURE SYSTEM MOVES TO THE SOUTH OF THE GULF OF MAINE. THERE IS A SLIGHT CHANCE THAT THESE SYSTEMS WILL BRING SNOW AND MVFR/IFR CONDITIONS TO THE REGION THURSDAY. MORE RAIN/SNOW IS POSSIBLE FRIDAY AND FRIDAY NIGHT AS ANOTHER LOW MOVES ACROSS NORTHERN MAINE. && .MARINE... NEAR TERM: WINDS AND SEAS WILL REMAIN BELOW SCA CRITERIA THROUGH TUESDAY. A COLD FRONT WILL APPROACH FROM THE NORTH TONIGHT AND TUESDAY AND THEN CROSS THE WATERS BY TUESDAY EVENING. SHORT TERM: NO HEADLINES EXPECTED OVER THE WATERS AS WINDS REMAIN BELOW 25 KT AND WAVES LESS THAN 5 FT. THE WEATHER WILL BE UNSETTLED HOWEVER AS A SERIES OF LOW PRESSURE WAVES MOVE OVER OR JUST TO THE SOUTH OF THE GULF OF MAINE THROUGH MID WEEK. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...NONE. MARINE...NONE. && $$ NEAR TERM...MIGNONE
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
429 PM EST TUE DEC 6 2011 .SYNOPSIS... COLDER AIR WILL ENTER THE UPPER OHIO VALLEY IN THE WAKE OF A SLOWLY MOVING COLD FRONT. A LOW PRESSURE CENTER WILL DEEPEN OVER THE WESTERN CAROLINAS WEDNESDAY MORNING AND CAUSE PRECIPITATION TO LINGER LONG ENOUGH ACROSS THE MOUNTAINS, FOR RAIN TO CHANGE TO HEAVY WET SNOW WEDNESDAY AFTERNOON INTO EARLY THURSDAY. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... PER RECENT SURFACE AND RADAR DATA AND HRRR AND NAM MODEL OUTPUT, MAINTAINED SHOWERS SOUTHEAST OF PITTSBURGH THIS PERIOD. EXPECT DRIZZLE NORTH AND WEST OF PITTSBURGH AND AREAS OF FOG ACROSS THE MOUNTAINS OVERNIGHT. FORECASTED LOWS USING BLEND OF GFS AND NAM MOS VALUES. MOST SPOTS WILL REMAIN ABOVE FREEZING OVERNIGHT, AND WITH THE GROUND STILL WARM, IT SEEMED UNLIKELY ANY OF THIS LIQUID PRECIPITATION WOULD FREEZE. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/... RECENT MODEL SUITE CONTINUES TO SHOW A LOW PRESSURE CENTER DEEPENING OVER THE WESTERN CAROLINAS EARLY WEDNESDAY AND THEN MOVING NORTHEAST PAST THE DELMARVA PENINSULA EARLY THURSDAY. THIS WILL MAINTAIN PRECIPITATION ACROSS THE MOUNTAINS INTO EARLY THURSDAY, WITH RAIN CHANGING TO SNOW DUE TO THE COOLING TEMPERATURES. THE PRECIPITATION, CHANGING TO SNOW, CAN BECOME HEAVY MIDDAY WEDNESDAY INTO THE WEE HOURS OF THURSDAY ACROSS THE WV-MD MOUNTAINS. HENCE HAVE UPGRADED THE WINTER STORM WATCH TO A WINTER STORM WARNING AS SNOW AMOUNTS CAN EXCEED 6 INCHES. THE DENSITY OF THE SNOW CAN HAVE THE ADDED IMPACT OF CAUSING DOWNED TREES AND POWER LINES. COLD WEST WINDS ACROSS THE LAKE ERIE COUPLED WITH A SECONDARY COLD FRONT MAY CAUSE SNOW SHOWERS ACROSS THE I-80 CORRIDOR THURSDAY. ISOLATED SNOW SHOWERS CAN REDEVELOP ACROSS THE HIGHER MOUNTAINS DUE TO THE RESULTING UPSLOPE FLOW. PASSING HIGH PRESSURE SHOULD PROVIDE A DRY BREAK THURSDAY NIGHT AND MOST OF FRIDAY. FORECASTED TEMPERATURE DETAILS USING BLEND OF GFS AND NAM MOS WHICH SHOWED VALUES ABOUT 5 DEGREES COLDER THAN NORMAL. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... THE MODELS ARE IN A GENERAL AGREEMENT FOR THE START OF THE LONG TERM PERIOD WITH A WAVE DROPPING THROUGH THE GREAT LAKES SPAWNING SOME SNOW SHOWERS ON SATURDAY AND REINFORCING THE COLD AIR ACROSS THE REGION THROUGH THE WEEKEND. 850HPA TEMPS OF -16C ACCOMPANY THIS TROUGH SO KEPT TEMPERATURES BELOW NORMAL FOR THE FIRST HALF OF THE LONG TERM PERIOD... MODERATING A FEW DEGREES EACH DAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES A HOLD OVER THE EAST COAST. KEPT CLOSE TO HPC GUIDANCE FOR THE LATTER HALF OF THE PERIOD DUE TO LOW END MODEL CONFIDENCE. && .AVIATION /21Z TUESDAY THROUGH SUNDAY/... NORTHWEST FLOW BEHIND A VERY SLOW MOVING FRONTAL BOUNDARY WILL KEEP IFR CONDITIONS THROUGH A MAJORITY OF THE 24-30 HOUR TAF PERIOD. SINCE BUFKIT SOUNDINGS SUGGEST THAT MANY OF THE PORTS WILL IMPROVE TO AT LEAST LOW-END MVFR FOR A FEW HOURS THIS AFTERNOON AND UPSTREAM OBSERVATIONS INDICATE THIS IMPROVEMENT...DECIDED TO MENTION THIS IN MOST OF THE TAF LOCATIONS. THE SITES CLOSER TO THE FRONTAL BOUNDARY...MGW AND LBE...MAY NOT EXPERIENCE THIS TEMPORARY IMPROVEMENT. CONDITIONS SHOULD DETERIORATE BACK TO IFR FOR THE REST OF THE OVERNIGHT PERIOD INTO WEDNESDAY AS NORTHWEST FLOW AT THE SURFACE AND SOUTHWEST FLOW ALOFT HOLD STRATUS IN PLACE. A SHORTWAVE MOVING THROUGH THE UPPER LEVEL FLOW WILL BRING THE CHANCE FOR ADDITIONAL SHOWERS TOMORROW. OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY... RESTRICTIONS WILL BE POSSIBLE THROUGH WED NIGHT BEFORE HIGH PRESSURE BUILDS IN FOR THURSDAY AND FRIDAY. NEXT CHANCE FOR RESTRICTIONS WILL BE WITH THE SHORTWAVE PASSAGE SATURDAY. VFR WILL RETURN SUNDAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...WINTER STORM WARNING FROM 11 AM WEDNESDAY TO 4 AM EST THURSDAY FOR MDZ001. OH...NONE. PA...NONE. WV...WINTER STORM WARNING FROM 11 AM WEDNESDAY TO 4 AM EST THURSDAY FOR WVZ023-041. && $$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
1106 AM EST TUE DEC 6 2011 .SYNOPSIS... COLDER AIR WILL ENTER THE UPPER OHIO VALLEY IN THE WAKE OF A SLOWLY MOVING COLD FRONT. PRECIPITATION WILL LINGER LONG ENOUGH ACROSS THE MOUNTAINS FOR RAIN TO CHANGE TO SNOW WEDNESDAY INTO EARLY THURSDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... PER RECENT SURFACE AND RADAR DATA AND HRRR AND NAM MODEL OUTPUT, MAINTAINED SHOWERS SOUTHEAST OF PITTSBURGH THIS PERIOD, WHILE ADJUSTING TEMPERATURES SLIGHTLY LOWER. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/... CONTINUE TO EXPECT COLDER THAN NORMAL TEMPERATURES TO SWEEP ACROSS THE UPPER OHIO VALLEY THIS PERIOD. HAVE MAINTAINED WINTER STORM WATCH ACROSS THE WV-MD MOUNTAINS WEDNESDAY INTO THURSDAY. TRAILING SURFACE LOW PRESSURE CENTER ALONG SLOW EASTBOUND COLD FRONT WILL CAUSE PRECIPITATION TO LINGER ACROSS THE WV-MD MOUNTAINS, WHERE IT CAN CHANGE FROM RAIN TO WET SNOW DURING WEDNESDAY. STILL UNCERTAINTY REGARDING PRECIPITATION AMOUNTS AND TEMPERATURES DETAILS, WHICH WILL VARY BY ELEVATION. HENCE HAVE HELD OFF ON MORE SPECIFIC WINTER WEATHER ISSUANCES. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... ANOTHER TROUGH WILL CROSS THE AREA ON FRIDAY, SERVING TO INSTIGATE A CHANCE OF SNOW SHOWERS THROUGH FRIDAY NIGHT AND PROVIDE A REINFORCING SHOT OF COLD AIR. AFTERWARD, FORECAST IS CLOSEST TO THE ECMWF ENSEMBLE MEAN. A STRONG AREA OF HIGH PRESSURE WILL BUILD INTO THE AREA AND KEEP THE FORECAST DRY FOR THE WEEKEND INTO MONDAY. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/... EXPECT COLD NORTH TO NORTHWEST WINDS TO MAINTAIN IFR STRATUS ACROSS MUCH OF THE UPPER OHIO VALLEY INTO AFTERNOON. THERE MAY BE TEMPORARY IMPROVEMENT TO MVFR LATER THIS AFTERNOON. HOWEVER, DETERIORATION BACK TO IFR IS EXPECTED TNGT AS FRONT/POOLED MSTR IS NOT EXPECTED TO MAKE MUCH SWD PROGRESS UNDER SWLY FLOW ALOFT. OUTLOOK...WEDNESDAY THROUGH SATURDAY... A SHORTWV IS FORECAST TO MOVE THRU THE SW FLOW OVR THE REGION AND SPAWN SOME PCPN IN MGW AREA ON WED. CIG RESTRICTIONS ARE POSSIBLE FOR MUCH OF WED AT OTHER TERMINALS. THEREAFTER...A BROAD UPR TROUGH IS FORECAST TO DEVELOP OVR THE GREAT LAKES. PERIODIC RESTRICTIONS AND SOME SHSN SHOULD BE ANTICIPATED IN THE COLD FLOW OVR THE REGION. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY NIGHT FOR MDZ001. OH...NONE. PA...NONE. WV...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY NIGHT FOR WVZ023-041. && $$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
625 PM EST WED DEC 7 2011 UPDATED AVIATION DISCUSSION FOR 00Z TAFS .SYNOPSIS /ISSUED AT 354 PM/... WV IMAGERY AND RUC ANALYSIS INDICATED CYCLONIC MID/UPPER LEVEL FLOW AROUND A VORTEX OVER HUDSON BAY BRINGING NRN STREAM WNW FLOW FROM SRN CANADA INTO THE UPPER GREAT LAKES. AN UPSTREAM SHORTWAVE TROUGH WAS MOVING THROUGH SRN MANITOBA WITH ANOTHER TRAILING SHRTWV OVER NRN SASK. AT THE SFC...WINDS WERE VEERING W TO WNW BEHIND A TROUGH/FRONT THAT MOVED THROUGH THIS MORNING. A TRAILING ARCTIC FRONT NEAR LAKE WINNIPEG WAS DROPPING TOWARD THE AREA WITH MUCH COLDER AIR BEHIND IT WITH TEMPERATURES FROM -5 TO 5F OVER NORTHERN MANITOBA/SASK. VIS LOOP INDICATED CLEARING SKIES OVER THE WEST HALF OF THE CWA AS DRIER AIR MOVES INTO THE REGION. EVEN WITH 850 MB TEMPS AROUND -11C...SKIES HAD CLEARED OVER MUCH OF WRN LAKE SUPERIOR. && .SHORT TERM...TONIGHT AND THURSDAY CLOUDS AND SCT LIGHT LAKE EFFECT SNOW SHOWERS ARE EXPECTED TO REDEVELOP OVER WRN LAKE SUPERIOR INTO WRN UPPER MI THIS EVENING AS GREATER LOW LEVEL MOISTURE MOVES TOWARD THE AREA...PER VIS LOOP. PASSAGE OF THE SASK SHRTWV AND ARCTIC FRONT THU MORNING WITH INCREASING 850-700 MB MOISTURE AND INVERSION HEIGHTS CLIMBING AROUND 8K FT WILL PROVIDE A SIGNIFICANT BOOST TO THE LAKE EFFECT SNOW. SNOW GROWTH ALSO LOOKS FAVORABLE AS THE DGZ WILL BE RIGHT IN THE BEST OMEGA/UPWARD MOTION. GIVEN MODEL QPF AND SNOW/WATER RATIOS APPROACHING 30/1 WOULD NOT BE SURPRISED TO SEE PERIODS OF MODERATE TO HEAVY SNOWFALL. THE MOST PERSISTENT LOW LEVEL CONV AND CHANCE FOR GREATEST ACCUMULATION IS EXPECTED FROM FAR NE ONTONAGON COUNTY INTO CENTRAL HOUGHTON COUNTY...FROM GREENLAND TO TWIN LAKES. INCREASINGLY CONVERGENT WRLY FLOW. INCREASING WINDS GUSTING TO NEAR 30 MPH AT TIMES ON THURSDAY WILL ALSO SHARPLY REDUCE VSBYS IN BLOWING SNOW AS WELL AND CAUSE DRIFTING SNOW ACROSS THE ROADS. SO...WITH THE LIKELIHOOD OF AN EXTENDED PERIOD OF LES...HEAVY SNOW AT TIMES...A LAKE EFFECT SNOW WARNING WAS ISSUED. CONFIDENCE IN ACCUMULATIONS BY LATE THURSDAY IS LIMITED BY UNCERTAINTY ON WHERE THE HEAVIER BANDS WILL DEVELOP AND HOW LONG THEY WILL PERSIST. SNOWFALL GENERALLY FROM 3 TO 7 INCHES IS LIKELY WITH SOME HIGHER LCL AMOUNTS. LOCATIONS NEAR LAKE SUPERIOR EAST OF MUNISING...FROM GRAND MARAIS TO TWO HEART MAY ALSO SEE A PERIOD OF HEAVIER LES IF THE EXPECTED DOMINANT BAND SAGS SOUTHWARD WITH SLIGHTLY VEERING WINDS THU. UNCERTAINTY REMAINS WHETHER THE HEAVIER SNOW WILL REMAIN OFFSHORE OR MOVE INLAND...SO NO HEADLINES WERE ISSUED AT THIS TIME. .LONG TERM /THURSDAY NIGHT THROUGH NEXT WEDNESDAY/... SIGNIFICANT LAKE EFFECT SNOW IS THE MAIN CONCERN FOR THE INITIAL PORTION OF THE LONG TERM. LARGE SCALE TROUGH WITH COLDEST AIR OF SEASON THUS FAR TO PUSH INTO THE AREA SETTLES OVER MUCH OF THE EASTERN CONUS TO END THE WEEK. NOT MUCH IN THE WAY OF LARGER SCALE SHORTWAVES THAT WILL BRING WIDESPREAD SNOW TO THE AREA...BUT SIGNIFICANT LK EFFECT FOR WEST FLOW AREAS IS LIKELY AS H85 TEMPS TUMBLE TO AROUND -18C BY FRIDAY. MODEL SOUNDINGS INDICATE LAKE INDUCED CAPES AOA 600J/KG WHILE LAKE EQUIBRIUM LEVELS ARE OVR 10 KFT AGL. HIGHER OVERWATER INSTABILITY IS SUPPLEMENTED BY STRONG LOW-LEVEL (SFC-H95) CONVERGENCE. MODELS ARE ACTUALLY IN VERY GOOD AGREEMENT WITH OVERALL SCENARIO THOUGH SUBTLE SHIFTS IN BLYR WINDS MAKE ALL THE DIFFERENCE AS TO THE LOCATIONS THAT END UP WITH THE HIGHEST SNOW AMOUNTS. BY LATE THURSDAY AND INTO THURSDAY NIGHT...SHEAR WITHIN THE SFC-H8 LAYER IS QUITE LOW...LEADING TO BETTER CHANCE THAT DOMINANT BANDS CAN ORGANIZE. WINDS BECOMING WESTERLY AT 925MB WITH WSW OR SW SFC WINDS OVR UPR MI (ENHANCED BY NIGHTTIME LAND BREEZES) WOULD FAVOR STRONGEST CONVERGENCE/HEAVIER SNOW BANDS OVR WESTERN UPR MI FM ONTONAGON THROUGH TWIN LAKES/PAINESDALE. WARNING WILL CONTINUE FOR THOSE AREAS THROUGH LATE FRIDAY FOR THIS PROLONGED HEAVY LAKE EFFECT SNOW EVENT. STORM TOTALS OVER A FOOT SEEM PRETTY LIKELY IF THE PRIMARY SNOW BAND STAYS STATIONARY FOR REASONABLE AMOUNT OF TIME. HIGHER TERRAIN AREAS OF REST OF HOUGHTON COUNTY WILL ALSO SEE OFF-AND-ON HEAVIER SNOW SHOWERS. ALSO EXPECT SOME HEAVIER SNOW TO OCCUR OVR SOUTHERN PORTIONS OF HOUGHTON COUNTY...MAINLY NORTH OF M-38. ADVY WILL COVER THIS POSSIBILITY. EXPECT VERY LITTLE IF ANY SNOW TOWARD KENTON/SIDNAW ALONG M-28. KEWEENAW COUNTY IS MORE OF A QUESTION MARK AS THE MORE WNW BLYR WINDS THERE ARE NOT AS FAVORABLE. STILL THOUGH...DEGREE OF INSTABILITY AND SUFFICIENT MOISTURE PRESENT COULD LEAD TO LOCALIZED HEAVY AMOUNTS OVR HIGHER TERRAIN THERE AS WELL. AN ADVISORY WILL HANDLE THIS FOR NOW...THOUGH LATER UPGRADE COULD BE NEEDED. EXPECT QUIET WEATHER FOR REST OF THE CWA THURSDAY NIGHT INTO FRIDAY. TEMPS WILL BE ON THE CHILLY SIDE THOUGH WITH NIGHTTIME LOWS THURSDAY NIGHT TOWARD THE ZERO MARK OVR INTERIOR SW UPR MI AND HIGHS ON FRIDAY MAINLY STAYING IN THE TEENS. BY LATE FRIDAY...WEAKER TROUGH FCST TO SLIDE THROUGH THE AREA MAY VEER WINDS TO MORE NW LEADING TO INCREASED CHANCES OF LAKE EFFECT SNOW SHOWERS INTO FAR EASTERN SECTION OF CWA...MAINLY EAST OF MUNISING AND WELL NORTH OF NEWBERRY. LAKE EFFECT SNOW PARAMETER DEVELOPED BY NWS GAYLORD WHICH INCORPORATES 1000-850MB SHEAR/850-700MB RH/H85 TEMPS INDICATES FAVORABLE SETUP FOR HEAVY SNOW RATES IN THOSE EASTERN AREAS FRIDAY AFTN/FRIDAY EVENING. SNOWFALL RATES UP TO 2 INCHES PER HOUR COULD OCCUR IN THOSE AREAS AND HEADLINES MAY BE NEEDED AT SOME POINT. HOWEVER...WILL LEAVE THOSE DECISIONS TO LATER SHIFTS AS EXPECT VERY LITTLE SNOWFALL IN THOSE AREAS THROUGH FRIDAY MORNING. TROUGH AND COLDER AIR SFC-H85 SLOWLY HEAD INTO LOWER GREAT LAKES FRIDAY NIGHT INTO SATURDAY. WARM AIR ADVECTION STARTS UP BY SATURDAY LEADING TO A PUSH OF ISENTROPIC ASCENT 285-290K (750-650MB) ACROSS MUCH OF THE CWA. UVM IN THE LAYER FAIRLY STRONG...BUT TROUBLE IS THERE IS DRY AIR LINGERING BLO H85 THRU THE DAY. COULD BE SOME FLURRIES OR LIGHT SNOW SHOWERS...BUT BETTER SATURATION WILL KEEP THE GREATER CHANCE OF ACCUMULATING SNOWS MORE INTO ONTARIO. GUSTY SW WINDS WILL ADD CHILL TO THE AIR DESPITE SFC TEMPS REBOUNDING INTO LOWER TO MIDDLE 20S. FOR THE EXTENDED...TROUGH THAT WAS OVER THE AREA FOR MUCH OF THIS WEEK IS FCST TO EASE INTO EASTERN CANADA LEADING TO MORE OF A ZONAL FLOW PATTERN/WARMING TREND BY EARLY NEXT WEEK. WEAK SHORTWAVE/WARM FRONT SLIDES ACROSS UPR LAKES MONDAY BUT MOISTURE IS MINIMAL SO DO NOT EXPECT A WHOLE LOT OF PRECIPITIATON. BETTER CHANCE OF PRECIPITATION WOULD BE FARTHER NORTH CLOSER TO H85-H7 FRONTOGENESIS AND RIGHT ENTRANCE REGION OF UPR JET OVR ONTARIO. ANOTHER TROUGH FORMING OVR SCNTRL CANADA IS FCST TO MOVE ACROSS THE UPR GREAT LAKES LATE TUESDAY INTO WEDNESDAY. DIFFERENCES BEGIN TO APPEAR WITH REGARD TO DEPTH OF TROUGH BY WEDNESDAY. LAST TWO RUNS OF GFS CLOSED THE TROUGH OFF OVR UPR MISSISSIPPI RIVER VALLEY/UPR LAKES. MEANWHILE... RECENT RUNS OF THE ECMWF AND PREVIOUS RUNS OF GFS INDICATED MORE OF A PROGRESSIVE SYSTEM...WITH DEEPER SYSTEM FORMING OVR CNTRL PLAINS MID-LATE NEXT WEEK. ENSEMBLES FM GFS/ECMWF/CANADIAN SHED LITTLE LIGHT ON THE SUBJECT WITH MIXED SIGNALS IN TERMS OF STRENGTH AND MOVEMENT OF THE TROUGHS. DOES SEEM THAT AT LEAST ECMWF WOULD SUPPORT BETTER CHANCE OF ORGANIZED PRECIPITATION IN THE MIDWEEK TIME FRAME. WILL NOT PUT TOO MUCH EMPHASIS ON THIS YET THOUGH AS SUPPORT FOR THAT IDEA REMAINS LIMITED SUPPORT LOOKING AT OTHER AVILABLE GUIDANCE AND ENSEMBLES. && .AVIATION /FOR THE 00Z TAF ISSUANCE/... EXPECT VFR CONDITIONS THIS EVNG WITH WEAK HI PRES RDG/DRY AIR WEDGE DOMINATING UPR MI. ARRIVAL OF THE FIRST IN A SERIES OF LO PRES TROFS WL BRING DETERIORATING CONDITIONS TOWARD MIDNGT AT LEAST TO THE MORE EXPOSED CMX LOCATION...WHERE LK MOISTENING/DESTABILIZATION WL BE MORE SGNFT. THE SECOND LO PRES TROF IS DUE TO ARRIVE MID MRNG ON THU. THIS DEEPER TROF WL BE FOLLOWED BY STRONGER W WINDS THAT WL CAUSE GUSTS AS HI AS 30 KT OVER THE EXPOSED KEWEENAW/CMX. THE COMBINATION OF FALLING LK EFFECT SN AND BLSN WHIPPED UP BY THESE STRONG WINDS WL LIKELY LEAD TO LIFR CONDITIONS AT THAT SITE. THE DRY NATURE OF THE ARCTIC AIRMASSES WL LIMIT DETERIORATION AT IWD AND ESPECIALLY SAW...WHERE THE PREVAILING WLY WIND COMPONENT WL DOWNSLOPE/DRY AND RESULT IN PREDOMINANT VFR CONDITIONS. && .MARINE /FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE/... WINDS MAINLY OUT OF A WESTERLY DIRECTION OVER 20KTS WILL PREVAIL THROUGH MUCH OF THE PERIOD. THE WINDS/WAVES ALONG WITH PLENTY OF COLD AIR WILL RESULT IN THE POTENTIAL FOR FREEZING SPRAY TONIGHT INTO FRIDAY. WESTERLY GALES ARE EXPECTED TO RETURN AROUND SUNRISE THURSDAY BEHIND AN ARCTIC FRONT OVER THE WEST HALF...BEFORE EXTENDING THROUGH CENTRAL AND EASTERN LS THROUGH EARLY THURSDAY EVENING. EXPECT STRONG HIGH PRESSURE ACROSS SW CANADA TO WEAKEN ACROSS THE PLAINS STATES FRIDAY...WHILE EXTENDING A RIDGE ACROSS LS BY FRIDAY NIGHT. LOW PRESSURE OVER MANITOBA SATURDAY MORNING WILL SLIDE ACROSS ONTARIO SATURDAY AFTERNOON AND EVENING...WHILE DRAGGING A TROUGH OVER LS. A PERIOD OF SW GALES IS POSSIBLE SATURDAY AHEAD OF THE LOW. ANOTHER LOW PRESSURE SYSTEM...OVER THE DAKOTAS SUNDAY MORNING...WILL LIKELY FILTER ACROSS LAKE SUPERIOR SUNDAY NIGHT. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... LAKE EFFECT SNOW WARNING FROM 1 AM THURSDAY TO 7 PM EST FRIDAY FOR MIZ002-003. LAKE EFFECT SNOW ADVISORY FROM 1 AM THURSDAY TO 7 PM EST FRIDAY FOR MIZ001-084. LAKE SUPERIOR... GALE WARNING FROM 7 AM THURSDAY TO 1 AM EST FRIDAY FOR LSZ263>267. LAKE MICHIGAN... NONE. && $$ SYNOPSIS...JLB SHORT TERM...JLB LONG TERM...JLA AVIATION...KC MARINE...JLB
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
415 PM EST TUE DEC 6 2011 .SYNOPSIS... WV IMAGERY AND RUC ANALYSIS INDICATED A SHEARED MID/UPPER LEVEL TROUGH FROM NRN ONTARIO THROUGH NW WI AND IA INTO THE CNTRL PLAINS. AN UPSTREAM SHORTWAVE TROUGH WAS MOVING THROUGH CNTRL MANITOBA. AT THE SFC...SW FLOW WAS INCREASING OVER WRN LAKE SUPERIOR AND W UPPER MI BTWN A DEPARTING RIDGE FROM QUEBEC INTO EAST UPPER MI AND A TROUGH OVER MANITOBA. ALTHOUGH THE BACKING WINDS HAVE PUSHED THE LAKE CLOUDS OFFSHORE OVER THE CNTRL AND WEST CWA...LOWER LEVEL MOISTURE OVER WRN WI WAS STREAMING BACK INTO THE WEST...PER VIS LOOP. MID LEVEL CLOUDS WERE ADVANCING THROUGH NW ONTARIO AND NRN MN ASSOCIATED WITH WAA/295K ISENTROPIC LIFT AHEAD OF THE TROUGH. && .SHORT TERM...TONIGHT AND WEDNESDAY MAIN FCST CONCERN IS LES POTENTIAL WITH THE FRONT/TROUGH MOVING THROUGH THE AREA. SATELLITE TRENDS AND NAM/RUC 925-900 MB RH FCST SUGGESTS THAT THE LOWER CLOUDS WILL CONTINUE TO SPREAD TO THE EAST THIS EVENING AND THEN MOVE OUT OVERNIGHT AS WINDS BEGIN TO VEER MORE TO THE WNW. MODERATE MID LEVEL QVECTOR CONV ASSOCIATED WITH THE TROUGH MOVING INTO THE AREA WED MORNING WILL BRING AN INCREASE IN 850-700 MB MOISTURE. WITH WINDS VEERING WRLY AND 850 MB TEMPS TO AROUND -11C...CONDITIONS WILL BECOME MORE FAVORABLE FOR LES INTO THE KEWEENAW LATE TONIGHT INTO WED MORNING. CAA DROPS 850 MB TEMPS TO AROUND -14C DURING THE AFTERNOON...BUT THE DEEPER MOISTURE IS EXPECTED TO DEPART. SINCE THE PERIOD WITH THE COMBINATION OF LOW LEVEL CONV AND 850-700 MB MOISTURE IS BRIEF...ANY LES ACCUMULATIONS ARE EXPECTED TO BE LIGHT...GENERALLY AN INCH OR LESS. SCT -SHSN WILL ALSO AFFECT LOCATIONS E OF MUNISING DURING THE AFTERNOON BUT AGAIN ACCUMULATIONS SHOULD BE LIGHT. .LONG TERM /WED NIGHT THROUGH NEXT TUESDAY/... COLD FRONT THAT WILL START THE COOLING TREND WILL BE EAST OF THE AREA AT THE START OF THE PERIOD...WHICH WILL PRODUCED A PROLONGED LAKE EFFECT SNOW PERIOD FOR PORTIONS OF UPPER MICHIGAN. EXPECT SFC LOW TO BE STATIONED OVER HUDSON BAY THROUGH SAT...WHILE A SFC HIGH SHIFTS FROM THE NRN PLAINS ON THURS TO THE OHIO RIVER VALLEY BY FRI NIGHT. THIS WILL LEAD TO WINDS OUT OF A WNW DIRECTION ON WED NIGHT INTO THURS...THEN BACKING TO THE W FOR THURS NIGHT INTO FRI NIGHT. THIS A LITTLE MORE WESTERLY THAN SHOWN YESTERDAY AND WILL LIKELY FOCUS PCPN OVER THE ERN CWA TO BE FROM GRAND MARAIS EASTWARD...RIGHT ALONG THE SHORELINE. THINK LAND BREEZES WILL HELP FOCUS A DOMINATE BAND EITHER RIGHT ALONG THE SHORELINE OR JUST OFFSHORE AT TIMES DURING THE PERIOD. OVER THE WEST...FAVORABLE LOCATIONS WILL BE FROM ROCKLAND THROUGH COPPER HARBOR...ESPECIALLY OVER THE HIGHER TERRAIN. EXPECT LES TO BE ONGOING AT THE START OF THE PERIOD...BUT WILL REALLY BEGIN TO RAMP UP OVERNIGHT WED INTO THURS MORNING...AS SHORTWAVE AND SECONDARY SFC TROUGH SWEEP ACROSS THE AREA. THIS WILL INCREASE MID LVL MOISTURE AND START A DOWNWARD TREND IN H850 TEMPS FROM -14C /DELTA-T OF 19/ TO -20C OVER THE W AND -18C OVER THE E. THESE VALUES DON/T LOOK AS COLD AS YESTERDAY FOR THE THURS/FRI TIME FRAME...WHICH WILL BE MORE FAVORABLE FOR THE LES POTENTIAL...AS THE DGZ WILL BE RIGHT IN THE BEST OMEGA. IN ADDITION...MODELS SHOWING A MORE MOIST LLVL...WITH LESS SUB CLOUD LAYER DRY AIR. THIS ALLOWS THE BEST LK INDUCED FORCING TO BE LOCATED DIRECTLY IN OR THE TOP HALF OF THE DGZ AND AID FOR FASTER ACCUMULATION. THUS...HAVE BUMPED UP SLR UP SLIGHTLY INTO THE LOW/MID 20S...ALTHOUGH NOT QUITE AS HIGH AS SEEN ON SOME OF THE CARIBOU SLR VALUES. MIGHT BE A LITTLE LULL IN LES OVER THE WEST ON THURS AFTN...AS DRIER AIR ABOVE H800 MOVES THROUGH AND LOWERS THE INVERSION HEIGHTS. THIS WILL BE SHORT LIVED AS NEXT WAVE OF DEEPER MOISTURE MOVES IN AND INVERSION HEIGHTS RISE ON THURS NIGHT WITH THE UPPER TROUGH MOVING OVERHEAD. EVEN WITH THIS LULL...THERE WILL STILL BE GUSTY WINDS THAT WILL CREATE BLOWING/DRIFTING SNOW ALONG THE LK SUPERIOR SHORELINE WITH THE FAIRLY FLUFFY SNOW THAT WILL HAVE FALLEN WED NIGHT INTO THURS MORNING. FRI DEEPER MOISTURE STARTS TO DEPART THE WEST DURING THE DAY...STARTING TO DIMINISH LES INSTENSITY...BUT WILL STILL BE ONGOING THROUGH FRI NIGHT. WITH WINDS SHIFTING MORE OUT OF THE WSW...EXPECT BEST BANDS TO BE OVER THE KEWEENAW AND OFFSHORE OVER THE E /ALTHOUGH A WEAK TROUGH COULD SLIDE THE BAND BACK ONSHORE FRI NIGHT/. AS FOR SNOWFALL AMOUNTS...LES PARAMETER EXCEEDS 2 FOR MUCH OF THE PERIOD...WHICH ALONG WITH LK INDUCED CAPE VALUES EXCEEDING 700 J/KG AND EQL/S IN THE 9-12KFT RANGE...THE POTENTIAL IS THERE FOR HEAVY SNOWFALL ACCUMULATIONS. CURRENT FCST FROM 6Z THURS TO 6Z SAT HAS 12-20 INCHES OVER THE HIGHER TERRAIN FROM ROCKLAND TO CALUMET AND SIMILAR TOTALS RIGHT ALONG THE LK SUPERIOR SHORELINE E OF GRAND MARAIS. WILL LIKELY SEE A COUPLE PERIODS WHERE OUR 8IN/12HR WARN CRITERIA WILL BE REACHED OVER THE WEST...SO HAVE PUT OUT A LES WATCH FOR ONTONAGON THROUGH KEWEENAW COUNTIES. HAVE LIMITED CONFIDENCE IN THE EAST WITH BAND LOCATION DUE TO THE LITTLE MORE WRLY WINDS AND SOME LIKELY WANDERING OF THE BAND ON/OFF SHORE THROUGH THE PERIOD...SO HELD OFF ON A WATCH FOR TIME BEING. DAYS 4 THROUGH 7 /FRI NIGHT THROUGH NEXT TUESDAY/... EXPECT LES TO COME TO AN END ON SAT...AS A CLIPPER SYSTEM DROPS THROUGH SOUTHERN ONTARIO AND SHIFTS WINDS TO THE SW AND PRODUCES WAA ALOFT. FINE DETAILS BECOME A LITTLE MORE MUDDLED FOR SUN THROUGH TUES...AS NO MAJOR DISTURBANCES OR FEATURES AFFECT THE REGION. THIS LEAVES THE AREA UNDER ZONAL FLOW ALOFT FOR SUN...AHEAD OF A SHORTWAVE MOVING ACROSS THE AREA MON INTO MON NIGHT. WITH H850 TEMPS AROUND -1C ON SUN...EXPECT TEMPS TO BE SLIGHTLY ABOVE NORMAL WITH HIGHS IN THE LOWER 30S. SUN NIGHT INTO MON NIGHT SHOULD SEE A SFC TROUGH NEAR THE UPPER GREAT LKS REGION...BUT WITH HOW WEAK IT APPEARS TO BE WITH THE ZONAL FLOW...HAVE LIMITED CONFIDENCE ON PCPN. THUS...WILL GO WITH A MOSTLY CLOUDY PERIOD...ALTHOUGH THE BEST CHANCE FOR PCPN WILL BE MON INTO MON NIGHT. THESE CLOUDS WILL KEEP OVERNIGHT LOWS FROM BEING TOO COLD AND KEEP TEMPS NEAR NORMAL FOR MON INTO TUES. && .AVIATION /FOR THE 18Z TAF ISSUANCE/ ANY LEFTOVER MVFR CIGS WITH LAKE EFFECT CLOUDS ARE EXPECTED TO MOVE OUT BY MID TO LATE AFTERNOON AS WINDS BACK TO THE SW. SW GRADIENT WINDS INCREASING THIS EVENING AHEAD OF APPROACHING COLD FRONT WILL SUPPORT LLWS AT ALL TAF SITES TONIGHT. WINDS VEERING WRLY LATE TONIGHT BEHIND THE FRONT SHOULD BRING MVFR CIGS BACK INTO KIWD AND KCMX. FAVORABLE WRLY FLOW AT KCMX MAY RESULT IN WIND GUSTS AOA 30 KTS AS WELL AS POSSIBLE LAKE EFFECT SNOW SHOWERS. && .MARINE /FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE/... SW WINDS ARE EXPECTED TO INCREASE TO GALE FORCE TONIGHT INTO EARLY WED...MAINLY OVER WESTERN AND NCNTRL LAKE SUPERIOR AHEAD OF A TROUGH MOVING TOWARD THE REGION. AS WINDS VEER NW BEHIND THE TROUGH...WINDS ARE EXPECTED TO DIMINISH INTO THE 20-30 KT RANGE. A WINTRY PATTERN OF W-NW WINDS WILL THEN PERSIST THRU LATE WEEK WITH LAKE EFFECT SNOW SHOWERS. GIVEN ARCTIC AIR PASSING OVER THE LAKE AND EFFICIENT MIXING...EXPECT WINDS CONSISTENTLY 20-30 KT WITH ANOTHER PERIOD OF GALES POSSIBLE AGAIN LATE WED NIGHT AND THURSDAY. COMBINATION OF ARCTIC AIR AND STRONG WIND SHOULD RESULT IN FREEZING SPRAY WED NIGHT INTO FRIDAY. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... LAKE EFFECT SNOW WATCH FROM LATE WEDNESDAY NIGHT THROUGH LATE FRIDAY NIGHT FOR MIZ001>003. LAKE SUPERIOR... GALE WARNING UNTIL 10 AM EST WEDNESDAY FOR LSZ266. GALE WARNING UNTIL 7 AM EST /6 AM CST/ WEDNESDAY FOR LSZ162. GALE WARNING UNTIL 10 AM EST WEDNESDAY FOR LSZ263-264. LAKE MICHIGAN... NONE. && $$ SYNOPSIS...JLB SHORT TERM...JLB LONG TERM...SRF AVIATION...JLB MARINE...JLB
AREA FORECAST DISCUSSION...UPDATED FOR 06Z TAFS
NWS MARQUETTE MI
1118 PM EST MON DEC 5 2011 .SYNOPSIS... WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL TROUGH FROM HUDSON BAY AND NRN ONTARIO THROUGH THE NRN PLAINS TO THE SRN ROCKIES. LITTLE LOW OR MID LEVEL FORCING WAS ASSOCIATED WITH THE TROUGH IN THE VERY DRY AIRMASS UPSTREAM. AT THE SFC...A RIDGE EXTENDED FROM NRN ONTARIO INTO THE NRN PLAINS RESULTING IN WEAK NRLY LOW LEVEL FLOW ACROSS LAKE SUPERIOR INTO UPPER MI. RADAR INDICATED LIGHT DISORGANIZED LES INTO UPPER MI. ACYC FLOW INTO THE REGION AND SHEAR WITHIN THE SFC-850 MB LAYER HAS LIMITED INTENSITY WITH GENERALLY LIGHT ACCUMULATIONS OF AN INCH OR LESS OBSERVED IN WEST AND NORTH CENTRAL UPPER MI. SNOW RATIO HAS BEEN HIGH...TYPICAL OF MOST LES...WITH THE CLOUD LAYER IN THE 2K-6K FT DGZ. && .SHORT TERM...TONIGHT AND TUESDAY SOME INCREASE IN LES INTENSITY MAY BE POSSIBLE THIS EVENING AS THE MID LEVEL TROUGH MOVES INTO THE AREA AND 850 MB TEMPS DROP SLIGHTLY TO NEAR -15C. HOWEVER...THE CBL FLOW WILL ALSO BECOME INCREASINGLY ANTICYCLONIC AS THE SFC RIDGE AXIS SHIFTS OVER THE AREA. THIS WILL ALLOW THE WINDS TO BACK OVERNIGHT WHICH WILL SHIFT THE BEST SNOWFALL BY MORNING TO THE ONTONAGON TO THE KEWEENAW AS WELL AS ALGER COUNTY. DESPITE THE FAVORABLE INSTABILITY AND MOISTURE...THE SHEAR COMBINED WITH THE SHIFTING NATURE OF THE BANDS SHOULD LIMIT SNOWFALL TO 1-2 INCHES...MAINLY FROM IWD-CMX AND FROM MQT-P53. THE LIGHT WINDS MAY ALLOW THE DEVELOPMENT OF A BAND ALONG THE SHORELINE INTO THE WEST ANE NEAR MARQUETTE AS THE LAND BREEZE STRENGTHENS...PER HIGH RES WRF/ARW BUT CONFIDENCE IN DETAILS FOR LES BAND EVOLUTION IN THE LIGHT WIND REGIME IS LOW. A BRIEF PERIOD OF HEAVIER SNOW WOULD BE POSSIBLE IF SUCH A BAND DEVELOPS. ANY LES ACROSS THE KEWEENAW AND EAST OF MARQUETTE SHOULD RAPIDLY SHIFT OFFSHORE ON TUESDAY AS THE RIDGE AXIS MOVES SOUTHEAST. CONDITIONS SHOULD BE MORE PLEASANT BY AFTERNOON WITH SOME SUNSHINE OVER THE AREA ALONG WITH RELATIVELY LIGHT SW WINDS. .LONG TERM /TUES NIGHT THROUGH NEXT MONDAY/... AT THE START OF THE PERIOD...AN ELONGATED UPPER TROUGH WILL BE STRETCHING FROM JAMES BAY TO THE SRN PLAINS AND QUICKLY SHIFTING E OF THE AREA. THIS WILL ALLOW A WEAK RIDGE...AHEAD OF THE MAIN UPPER LOW TO AFFECT THE AREA DURING THE LONG TERM OVER THE NW TERRITORIES OF CANADA. THIS WEAK UPPER RIDGE WILL CAUSE SFC RIDGE TO SLIDE E ACROSS THE CWA TUES EVENING. MIGHT SEE A QUICK COOL DOWN TUES EVENING WITH THE CLEAR SKIES AND LIGHT WINDS...ESPECIALLY OVER THE CNTRL/ERN CWA...BUT INCREASING SWRLY FLOW AND MID LEVEL CLOUDS AHEAD OF THE NEXT FRONT WILL LEVEL TEMPS OFF AND MAY EVEN CAUSE THEM TO RISE SOME OVER THE WRN CWA. WITH THE DEEPER MOISTURE AND H850-700 Q-VECTOR CONV ARRIVING LATE TUES NIGHT...COULD SEE A FEW SNOW SHOWERS LATE TUES NIGHT OVER THE KEWEENAW. BUT WITH THE BEST FORCING/MOISTURE OVER NRN LK SUPERIOR...WILL KEEP THE CHANCES THERE. STRONGER PRESSURE GRADIENT AHEAD OF THE FRONT WILL LIKELY LEAD TO SOME GALES OVER LK SUPERIOR TUES NIGHT. EVEN WITH THE WAA ALOFT...LLVL WINDS BELOW THE INVERSION LOOK TO BE IN THE 30-40KT RANGE AND WILL LIKELY ALSO LEAD TO A GUSTY OVERNIGHT FOR THE HIGHER TERRAIN OF KEWEENAW PENINSULA. WILL CONTINUE THE GALE WATCH OVER W/CNTRL LK SUPERIOR. COLD FRONT MOVING THROUGH ON WED AND WILL USHER IN THE COLDEST AIR OF THE SEASON. EXPECT THE MID LVL FORCING/MOISTURE TO BE THROUGH THE AREA BY WED AFTN...AND WILL MOVE UP THE POP TIMING FROM THE PREVIOUS SHIFT TO BE MORE IN THE MORNING FROM THE AFTN. MAY TAKE A LITTLE WHILE FOR THE LES TO GET GOING BEHIND THE FRONT...AS INVERSION HEIGHTS FALL TO 4.5-5.5KFT AND LLVL DRY AIR LIMITS ANY POTENTIAL CLOUD DEPTH. THUS...WILL GO WITH SLIGHTS OVER THE WNW WIND FAVORED LOCATIONS OVER THE WEST AND KEEP CHANCES OVER THE EAST WHERE THE LOW-MID LVL MOISTURE WILL TRY TO LINGER LONGER. THINK THESE LIMITED CONDITIONS WILL CONTINUE INTO THE EVENING HOURS BEFORE REALLY INTENSIFYING THROUGH THE NIGHT. THIS INTENSIFICATION WILL LARGELY BE DUE TO A SHORTWAVE MOVING THROUGH ON WED NIGHT...WHICH WILL INCREASE THE LOW-MID LVL MOISTURE AND PULL EVEN COLDER H850 TEMPS OVER THE AREA /STEADILY FALLING TO NEAR -20C BY THURS EVENING/. THIS WILL INCREASE DELTA-T/S TO SOME FAIRLY IMPRESSIVE VALUES /LOW-MID 20S BY THURS EVENING/. IN ADDITION...WITH INVERSION HEIGHTS RISING TO 7-10KFT AND LK INDUCED CAPES IN THE 500-700 J/KG RANGE...LOOKS TO BE A GOOD POTENTIAL FOR AREAS TO RECEIVE MOD/HEAVY LES LATE WED NIGHT INTO THURS. LAKE EFFECT SNOW PARAMATER SUPPORTS THIS POTENTIAL...RISING ABOVE 2...WHICH SUPPORTS A HIGH POTENTIAL FOR HEAVY SNOWFALL RATES...OVER THE W WED NIGHT AND THE E ON THURS. WINDS LOOK TO BE OUT OF THE WNW WED NIGHT INTO THURS...SO HAVE THE HIGHEST POPS IN THOSE FAVORED LOCATIONS. ONE ITEM TO NOTE ON WIND DIRECTIONS IS THAT THE NAM/GEM HINTING AT A MESO LOW FORMING OVER ERN LK SUPERIOR ON THURS...WHICH COULD END UP FORCING WINDS MORE TO THE NW OVER THE WRN CWA. OVER THE E...THIS COULD CAUSE A DOMINATE BAND TO SETUP SOMEWHERE OVER THE SERN LAKE...POTENTIALLY RIGHT ALONG THE SHORELINE E OF GRAND MARAIS DUE TO THE WSW WINDS AROUND THE MESO LOW. FINALLY...COULD BE A SLIGHT LULL OVER THE W IN THE AFTN...AS SLIGHTLY DRIER AIR MOVES THROUGH...AND HAVE SLIGHTLY LOWERED POPS FOR THAT TIMEFRAME. DAYS 4 THROUGH 7 /THURS NIGHT THROUGH NEXT MONDAY/... ARCTIC TROUGH DROPPING SE ACROSS THE AREA THURS NIGHT INTO SAT WILL PROVIDE REINFORCING COLD AIR TO THE AREA AND CONTINUE THE LES. EXPECT THE -16 TO -20C H850 TEMPS TO CONTINUE THURS NIGHT INTO FRI NIGHT AS BL WINDS ARE FROM THE WNW THURS NIGHT INTO FRI AND THEN START TO SHIFT TO THE WSW FRI NIGHT. WITH THE ABUNDANT LOW-MID LVL MOISTURE UNDER THE UPPER TROUGH...THE INGREDIENTS ARE COMING TOGETHER FOR A POTENTIALLY SIGNIFICANT LES PERIOD THURS NIGHT INTO FRI FOR WNW WIND FAVORED LOCATIONS. AS MENTIONED PREVIOUSLY...LES PARAMETER CONTINUES TO HIGHLIGHT THE HEAVY SNOW POTENTIAL...VALUES ABOVE 2...THROUGH FRI FOR WNW WIND LOCATIONS. THIS IS ALSO SEEN IN BUFKIT LK INDUCED CAPE VALUES EXCEEDING 700 J/KG AND EQL LVLS BETWEEN 7-10KFT. IT IS A WAYS OUT...BUT BUFKIT SOUNDINGS ARE SHOWING THE CLOUD BASES TO BE AT OR ABOVE THE DGZ AND LIMIT DENDRITES. EITHER WAY...SHOULD SEE A HIGH SLR VALUE AND ALLOW FOR EASY BLOWING/DRIFTING FOR AREAS NEAR LK SUPERIOR WHERE THE WINDS WILL BE STRONGEST. IN ADDITION...THIS DRIER AIR IN THE LLVLS COULD ALSO LEAD TO A COUPLE MAIN/DOMINATE BANDS. WILL STICK TO OUR LES CLIMO POP/SKY GRIDS FOR THIS TIME FRAME AND WILL CONTINUE TO MENTION THE HEAVY SNOW POTENTIAL IN THE HWO. WITH THE WINDS SHIFTING TO THE SW AND WAA DEVELOPING ON SAT...EXPECT THE LES TO DIMINISH. THIS WAA IS DUE TO A WEAK SHORTWAVE AND CLIPPER SYSTEM SLIDES THROUGH SOUTHERN ONTARIO...WITH THE MAIN ENERGY/MOISTURE STAYING N OF THE CWA. UPPER FLOW TRANSITIONS TO MORE ZONAL NRN STREAM ALONG THE U.S./CANADA BORDER FOR SUN INTO MON. THIS ALLOWS WARMER H850 TEMPS...AROUND -1 TO 1C...TO MOVE OVER THE AREA AND LEAD TO A PERIOD OF SLIGHTLY ABOVE NORMAL TEMPERATURES WITH HIGHS IN THE UPPER 20S AND LOWER 30S. MODELS CONSISTENT ON SFC TROUGH SETTLING OVER THE AREA SUN NIGHT INTO MON...AS SFC HIGHS ARE SETUP OVER THE NRN PLAINS AND OHIO VALLEY. LIMITED UPPER LVL FORCING...SO HAVE KEPT THE FCST DRY FOR NOW. && .AVIATION /FOR THE 06Z TAF ISSUANCE/ FOR EARLY IN THIS FCST PERIOD...WEATHER AT TAF SITES WILL BE DOMINATED BY LAKE EFFECT CLOUDS/SNOW SHOWERS WITH PREDOMINANT MVFR CIGS. AS IS TYPICAL FOR LAKE EFFECT SNOW SHOWERS...VSBY WILL BE QUITE VARIABLE...GENERALLY RANGING FROM MVFR TONIGHT. SOME IMPROVEMENT IN VIS IS EXPECTED TUE MORNING AS WINDS BACK MORE WNW AHEAD OF BUILDING HIGH PRES RDG DIMINISHING SHSN. VFR CONDITIONS WILL OCCUR IN THE LATE MORNING TO EARLY AFTERNOON AT ALL SITES. COULD BE SOME STRONGER WINDS AND LLWS IN THE LATER PERIODS AT ALL SITES...BUT THAT IS WAY OUT THERE AND CONFIDENCE IN PUTTING IT INTO FORECAST IS PRETTY LOW AT THIS TIME. && .MARINE /FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE/... EXPECT WINDS MOSTLY IN THE 10-20 KT RANGE INTO TUE MORNING AS A HIGH PRES RIDGE OVER NORTHERN ONTARIO AND THE NRN PLAINS SLOWLY BUILDS ACROSS LAKE SUPERIOR. AS THE RIDGE SLIPS SE OF THE LAKE AND A COLD FRONT APPROACHES...SW WINDS ARE EXPECTED TO INCREASE TO GALE FORCE TUE NIGHT INTO EARLY WED...MAINLY OVER WESTERN AND NCNTRL LAKE SUPERIOR. A WINTRY PATTERN OF W-NW WINDS WILL THEN PERSIST THRU LATE WEEK WITH LAKE EFFECT SNOW SHOWERS. GIVEN ARCTIC AIR PASSING OVER THE LAKE...EFFICIENT MIXING WITH 20-30 KT AND SOME GALE FORCE GUSTS AT TIMES LATE IN THE WEEK. WITH ARCTIC AIRMASS INTO THE AREA SOME FREEZING SPRAY MAY ALSO DEVELOP. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... NONE. LAKE SUPERIOR... GALE WARNING FROM 7 PM TUESDAY TO 10 AM EST WEDNESDAY FOR LSZ266. GALE WARNING FROM 5 PM EST /4 PM CST/ TUESDAY TO 7 AM EST / 6 AM CST WEDNESDAY FOR LSZ162. GALE WATCH FROM 5 PM EST TUESDAY TO 10 AM EST WEDNESDAY FOR LSZ263-264. LAKE MICHIGAN... NONE. && $$ SYNOPSIS...JLB SHORT TERM...JLB LONG TERM...SRF AVIATION...07 MARINE...JLB
AREA FORECAST DISCUSSION
NWS KANSAS CITY/PLEASANT HILL MO
357 AM CST Tue Dec 6 2011 .DISCUSSION... Water vapor imagery early this morning shows us that Kansas and Missouri remain under the direct influence of a large, positively tilled and shearing, trough. It is evident that a dry wedge, that rotated under the base of the trough early Monday, has quickly stretched northeast, effectively detaching the moisture feed of the Pineapple Express from much of the dynamics of the slowly shearing trough. Which, is not to say moisture isn`t available, just that there will be less to work with in the coming days. Otherwise, of note is a subtle shortwave that has rounded the base of the trough, and is heading towards central Missouri via south central Kansas. Light snow has been observed with this features in Wichita, with a few tenths of an inch of accumulation this morning. For today, of primary concern is the shortwave and potential for snow. Upper air sounding from Monday evening in Topeka shows a nice dry layer between 900mb and 700mb, which any snow will have to overcome in order to reach the surface. But, a variety of models advertise that this should not be much of a problem as the top-down seeder-feeder process gets to work as the shortwave moves through central Missouri this morning. Current snow observations noted at Wichita, and now Springfield and Columbia, back this idea up. Still, lack of quality deep layer moisture, and the limited residency time of the shortwave, should limit accumulations to something around or under one inch. As for location, best potential for any accumulation looks to be along a line from Clinton northeast through Moberly, where the shearing vorticity axis of the shortwave is expected to traverse. Some flurries will be possible father north and west, think Kansas City to Bethany line. Have continued to highlight snow across central Missouri by inserting likely POPs for this morning. After todays fleeting snow flakes stop falling, our next potential shot at snow will arrive across the Missouri-Iowa border Thursday night. The longwave polar low, currently in the process of shifting across northern Canada towards the Hudson Bay, will send another reinforcing cold shot of air south into the Plains States starting Wednesday, which will insure that temperatures stay well below normal through the remainder of the work week. However, looking at Thursday nights precipitation potential, the entrance region to the jet streak rounding the base of the mean trough, carved out by the polar low across the central plains, would be coincident with enough moisture to squeeze some flakes out along the Iowa border. As for the weekend, currently it looks dry, and like a warming trend will prevail, though we will only be warming back to around normal. As Saturday arrives a ridge across the west coast will be shifting farther east. This should allow for temperatures to moderate a bit through the weekend as synoptic level height gains, and a modest south wind on the back side of a surface high to our east, take the edge off the cold temperatures. CUTTER && .AVIATION... For the 06Z TAFs, MVFR cigs are likely to persist through the night and probably Tuesday morning. Since the NAM and to a lesser extent the GFS have shown to be unreliable on handling the cold air stratocu deck have relied on the RUC and AVNFPS climatology. An approaching mid level shortwave will pass just south of the terminals but can`t rule out scattered flurries from time to time. But lacking definite timing and they not likely to be an obscuration to visibilities will not mention in the TAFs. Passage of shortwave trough axis should see clearing skies in the afternoon with VFR conditions. MJ && .EAX WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ WFO EAX
AREA FORECAST DISCUSSION
NWS KANSAS CITY/PLEASANT HILL MO
1137 PM CST MON DEC 5 2011 ...UPDATED AVIATION DISCUSSION... .DISCUSSION... /943 PM CST MON DEC 5 2011/ Have raised snow chances a bit overnight, mainly over the far southern counties and for later in the night. However, did increase snow chances markedly over the eastern 1/4 of the CWA on Tuesday. Mid/upper level system ejecting out of NM tonight. Latest RUC is a bit stronger and further north with the 700mb vorticity center. Looks like a seeded-feeder setup to start out where a snow from a higher level of clouds falls into a lower cloud deck and "seed" it resulting in light snow and/or flurries. However, increasing dynamics, weak frontogenetic forcing and weak isentropic lift could generate areas/bands of light snow towards sunrise tomorrow. A better bet for measurable snow will occur Tuesday morning when the drier sub-cloud regions have become saturated. Initial thoughts are a tenth of an inch of snow is possible across the far southern counties, but possibly enough to make roads slick as this will be a dry/fluffy snow. Have a bit of concern that a region of upward vertical motion progged just above a nearly saturated layer dendritic snow growth region between 12-z15z over the far eastern counties could yield more than the current half inch of snow currently forecast. Since confidence in models has been low of late on how they have handled the cloud structures of late will go the conservative route and let the mid shift make any changes. MJ && .PREV DISCUSSION... /318 PM CST Mon Dec 5 2011/ Brisk northerly winds continues to advect colder air into Missouri with chilly temperatures the next couple of days. The main concern is a shortwave in southern New Mexico, south of the Four Corners Low. Short term high resolution models (NAM and RUC) are indicating that this wave will progress northeast into west central Missouri on Tuesday. light to moderate snow has been occurring in the TX panhandle, aided by upslope, with development toward the northeast. The models are showing very weak isentropic upglide along with weak deformation ahead of a weak 700 mb low in eastern Kansas late tonight and early Tuesday. Moisture is quite limited but have inserted sct snow showers for much of the area late tonight and Tuesday. Cannot rule out a narrow band of more persistent snow, producing very light accumulations. Later shifts will have to monitor the progress of this system. Otherwise, the trough axis will pass late Tuesday and Wednesday with dry conditions. DB Medium Range (Thursday through Monday)... Operational and ensemble members are in good agreement through the majority of the period depicting primarily stagnant longwave features over the western hemisphere. Most notable are a seasonably deep polar vortex centered across northern Hudson Bay and the Nunavut archipelago and an equally intense ridge through the Gulf of Alaska (both features in the 1-2 normalized standard deviations away from average range). This scenario will result in broad nwly/quasi-zonal flow for locations east of the Rockies with largely dry conditions and temperature slightly below average into the weekend. By the end of the period, models also indicate energy spilling over the top of the western ridge, causing a slight retrogressive phase, placing much of the central and southern plains into a warming, swly flow regime. There is naturally uncertainty into the depth and positioning of swrn conus energy late in the period, however the effect on weather through the forecast area would not be felt until after this valid period. Only real potential sensible weather during this medium range period still appears to be very light snow/snow flurries Thursday night into Friday morning across far northern Missouri. 21 && .AVIATION... For the 06Z TAFs, MVFR cigs are likely to persist through the night and probably Tuesday morning. Since the NAM and to a lesser extent the GFS have shown to be unreliable on handling the cold air stratocu deck have relied on the RUC and AVNFPS climatology. An approaching mid level shortwave will pass just south of the terminals but can`t rule out scattered flurries from time to time. But lacking definite timing and they not likely to be an obscuration to visibilities will not mention in the TAFs. Passage of shortwave trough axis should see clearing skies in the afternoon with VFR conditions. MJ && .EAX WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ WFO EAX
AREA FORECAST DISCUSSION
NWS BUFFALO NY
730 PM EST WED DEC 7 2011 .SYNOPSIS... LOW PRESSURE TRACKING ALONG A STALLED EAST COAST FRONT WILL BRING LIGHT SNOW TO PARTS OF WESTERN AND CENTRAL NEW YORK THIS AFTERNOON AND EVENING. AS THE LOW SLIDES OFF THE NEW ENGLAND COAST TONIGHT...THE LIGHT SNOW WILL TAPER OFF...THEN GIVE WAY TO LIMITED LAKE EFFECT SNOW SHOWERS LATER TONIGHT INTO THURSDAY MORNING. HIGH PRESSURE WILL THEN BRING DRIER AND BREEZY CONDITIONS THURSDAY AFTERNOON...BEFORE POTENTIALLY SIGNIFICANT LAKE EFFECT SNOW SETS UP EAST OF THE LAKES THURSDAY NIGHT AND FRIDAY. && .NEAR TERM /THROUGH THURSDAY/... THROUGH 700 PM...PRECIPITATION ASSOCIATED WITH INTENSIFYING LOW PRESSURE TRACKING ALONG THE ATLANTIC SEABOARD IS LARGELY REMAINING TO THE EAST. THE BACK EDGE OF THIS HAS NUDGED SLIGHTLY EASTWARD...LEAVING ONLY FLURRIES IN ALL BUT EASTERN PORTIONS OF LEWIS COUNTY. THIS TREND WILL CONTINUE...EXITING EAST IN THE NEXT COUPLE HOURS. AS COLDER AIR DEEPENS BEHIND THE LOW LATER TONIGHT...SOME LAKE EFFECT SNOW SHOWERS ARE EXPECTED TO SET UP SOUTHEAST OF BOTH LAKES. 850 MB TEMPERATURES WILL DROP TO AROUND -10C OVERNIGHT...RESULTING IN MODERATE INSTABILITY IN A NW TO W FLOG. THE 18Z RUN OF THE NAM AND 21Z RUN OF THE RUC BOTH SHOW A VERY SHALLOW LAYER OF MOISTURE EAST OF LAKE ERIE. WHILE THERE MAY BE SOME LIGHT PRECIPITATION...THE LACK OF DENDRITIC SNOW GROWTH WILL LIKELY RESULT IN A SNOW/DRIZZLE MIX OR FLURRIES WHICH SHOULD STRUGGLE TO ACCUMULATE. EAST OF LAKE ONTARIO LOOKS A BIT MORE INTERESTING. THE LONGER FETCH ACROSS THE LAKE SHOULD ALLOW FOR A BIT MORE MOISTURE TO BUILD OR MAINTAIN. AS THE INITIAL NW FLOW SHIFTS MORE WESTERLY...THERE MAY BE A NARROW OPPORTUNITY FOR A LAKE EFFECT BAND TO DEVELOP BETWEEN MIDNIGHT AND DAYBREAK AS NIGHTTIME ENHANCES CONVERGENCE ON THE LAKE. BASED ON THIS...DID NUDGE UP POPS...AND MENTION AN INCH OR TWO OF SNOW POSSIBLE IN OSWEGO COUNTY. THIS SAID...CONFIDENCE REMAINS FAIRLY LOW GIVEN THE NARROW OPPORTUNITY FOR DEVELOPMENT. ON THURSDAY...HIGH PRESSURE WILL RIDGE NORTH FROM THE MIDDLE ATLANTIC STATES AND CAUSE THE BOUNDARY LAYER WINDS TO BACK TO THE SOUTHWEST. AT THE SAME TIME...THE MODELS SHOW NOTICEABLY DRIER AIR ADVECTING EAST ACROSS THE AREA AS THE DAY WEARS ON. AS A RESULT...LINGERING SNOW SHOWERS OFF LAKE ONTARIO WILL CONTINUE TO WEAKEN WHILE LIFTING SLOWLY TO THE NORTH. THE SNOW SHOWERS OFF LAKE ERIE SHOULD END AROUND DAYBREAK THURSDAY. THE PRESSURE GRADIENT BETWEEN THE DEPARTING LOW AND MIDDLE ATLANTIC SURFACE RIDGE WILL RESULT IN BREEZY TO WINDY CONDITIONS LATE THURSDAY MORNING INTO THE AFTERNOON...ESPECIALLY DOWNWIND OF THE LAKES. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... LAKE EFFECT SNOW WATCHES WILL BE ISSUED FOR DOWNWIND AREAS OF THE LAKES FOR THIS PERIOD. ALTHOUGH THIS DOES NOT APPEAR TO BE A CLASSIC SIGNIFICANT LAKE SNOW EVENT...IT WILL BE THE FIRST MODERATE ACCUMULATING SNOW EVENT OF THE WINTER SEASON FOR THE BUFFALO METRO AREA AND WATERTOWN. A POLAR VORTEX OVER HUDSON BAY WILL SEND A SERIES OF SHORTWAVES SOUTHWARD ALONG WITH SUFFICIENTLY COLD AIR ALOFT. LAKE PROCESSES WILL TAKE CENTER STAGE DURING THIS PERIOD AS OVER-LAKE INSTABILITY INCREASES. IT CONTINUES TO LOOK LIKE ACCUMULATING LAKE SNOWS WILL BEGIN LATER THURSDAY NIGHT WITH THE ARRIVAL PACIFIC BASED MOISTURE AHEAD OF A STRONG MID LEVEL SHORTWAVE. WINDS BACKING TO SOUTHWEST WILL LIKELY AIM A CONSOLIDATED SINGLE LAKE SNOW BAND TOWARDS THE BUFFALO/NIAGARA FALLS AREA OFF LAKE ERIE AS WELL AS WATERTOWN OFF LAKE ONTARIO...PARTICULARLY AFTER MIDNIGHT. THERE STILL LOOKS TO BE A FEW UNCERTAINTIES WITH THE OVERALL LAKE EFFECT SETUP. SOME DISCREPANCIES REMAIN IN LOW LEVEL STEERING FLOW WITH GFS/CMC SUGGESTING STEERING FLOW JUST A BIT MORE BACKED THAN THE NAM PLACING HEAVIEST BAND A BIT FARTHER TO THE NORTH...AT LEAST INITIALLY. MODEL CONSENSUS DOES SUGGEST THAT THE BUF/IAG/ART AREAS WILL BE THE PRIME TARGET AREAS FROM LATE THURSDAY NIGHT THROUGH AT LEAST THE FIRST HALF OF FRIDAY. SOME SHEAR SHOWING UP IN THE MODEL PROFILES MAY KEEP MOST INTENSE BAND FROM SITTING IN ONE AREA TOO LONGER WHICH MAY LIMIT PROLONGED SNOWFALL RATES. MODEL SUGGESTION IS THAT THERE WILL BE A SEVERAL HOUR PERIOD LIKELY CENTERED AROUND 8 AM FRIDAY MORNING WHERE SNOWFALL RATES UP TO AN INCH WILL BE POSSIBLE...ESPECIALLY IF A DOMINATE BAND DOES INDEED SET UP. GRADUALLY VEERING LOW LEVEL FLOW WILL DRIVE THE LAKE SNOWS SLOWLY SOUTHWARD THROUGH THE DAY EVENTUALLY SETTLING SOUTH OF THE BUFFALO AND WATERTOWN AREAS...INTO THE SOUTHERN TIER ALONG THE CHAUTAUQUA RIDGE AND THE TUG HILL BY FRIDAY NIGHT. INCREASING SHEAR ALOFT AND DRIER AIR WILL WORK IN AT THE SAME TIME AND WE MAY SEE A SIGNIFICANT DECREASE IN THE LAKE EFFECT ACTIVITY FRIDAY NIGHT... ESPECIALLY OFF LAKE ERIE. LAKE EFFECT MAY LINGER EAST OF LAKE ONTARIO THROUGH THE DAY SATURDAY AS MOISTURE INCREASES AHEAD OF APPROACHING WEAK CLIPPER. ANY LAKE SNOWS SHOULD COMPLETELY END EARLY SATURDAY AS SUBSIDENCE AND DRIER AIR CONTINUE TO WORK IN. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... THIS PORTION OF THE FORECAST LOOKS RELATIVELY QUIET. THE REGION LOOKS TO STAY IN BETWEEN WEAK NORTHERN STREAM CLIPPER SYSTEM SUNDAY AND BROAD HIGH PRESSURE RIDGED JUST TO THE SOUTH OF THE REGION. NORTHERN STREAM SYSTEM LOOKS MOISTURE STARVED AT THIS POINT AND MAY JUST RESULT IN SOME INCREASING CLOUDS FOR NORTHERN TIER AREAS BUT PRECIPITATION CHANCES LOOK LIMITED. HIGH PRESSURE THEN BECOME ESTABLISHED OVER THE AREA MONDAY..SLIDING EAST THROUGH MID WEEK. A COLD FRONT WORKS THROUGH BY MID WEEK..INCREASING SYNOPTIC SCALE MOISTURE WITH THE SUGGESTION OF ENOUGH COLD AIR BEHIND IT TO POTENTIALLY THINK ABOUT LAKE INFLUENCES RETURNING. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... LARGELY MVFR CONDITIONS SHOULD IMPROVE TONIGHT AS DRIER AIR BUILDS IN FROM THE WEST. LINGERING IFR CONDITIONS AT JHW/ART ARE POSSIBLE THROUGH 03Z. OTHERWISE...MVFR/VFR SHOULD PREDOMINATE...DEPENDING ON FLOW OFF THE LAKES. WINDS WILL BE GUSTY THURSDAY...BUT THESE STRONGER WINDS WILL LIKELY HELP LIMIT CLOUDS TO FORM AS A RESULT OF THE LAKES...THOUGH PATCHY BKN MVFR CIGS ARE POSSIBLE DURING MUCH OF THE DAY. OUTLOOK... THURSDAY NIGHT...MAINLY VFR. LOCAL MVFR/IFR EAST OF THE LAKES IN LAKE EFFECT SNOW SHOWERS. FRIDAY...MVFR/IFR WITH SNOW SHOWERS. LOCALLY HEAVIER LAKE EFFECT SNOW EAST AND NORTHEAST OF THE LAKES. SATURDAY...MAINLY VFR WITH AREAS OF MVFR IN SNOW SHOWERS SOUTHEAST OF THE LAKES. SUNDAY AND MONDAY...VFR. && .MARINE... A RELATIVE WEAK PRESSURE GRADIENT OVER THE LOWER LAKES WILL STRENGTHEN LATER THIS EVENING AND TONIGHT AS A DEVELOPING LOW HEADS NORTHEAST UP THE NEW ENGLAND COAST. A BRISK WEST TO SOUTHWEST FLOW WILL REMAIN IN PLACE THURSDAY AND FRIDAY...RESULTING IN A HIGH LIKELIHOOD OF SMALL CRAFT ADVISORY CONDITIONS. SCA WILL ALSO BE ISSUED FOR THE NIAGARA RIVER AND ST LAWRENCE RIVER FOR THURSDAY. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...LAKE EFFECT SNOW WATCH FROM LATE THURSDAY NIGHT THROUGH LATE FRIDAY NIGHT FOR NYZ006>008. LAKE EFFECT SNOW WATCH FROM LATE THURSDAY NIGHT THROUGH FRIDAY AFTERNOON FOR NYZ001-010>012-085. MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM EST FRIDAY FOR LEZ040-041. SMALL CRAFT ADVISORY FROM NOON TO 7 PM EST THURSDAY FOR LEZ020. SMALL CRAFT ADVISORY FROM 1 PM TO 10 PM EST THURSDAY FOR LOZ030. SMALL CRAFT ADVISORY FROM 2 AM THURSDAY TO 1 PM EST FRIDAY FOR LOZ043-044. SMALL CRAFT ADVISORY FROM 2 AM THURSDAY TO 9 AM EST FRIDAY FOR LOZ042. SMALL CRAFT ADVISORY FROM 2 AM THURSDAY TO 4 PM EST FRIDAY FOR LOZ045. SMALL CRAFT ADVISORY FROM 1 PM TO 10 PM EST THURSDAY FOR SLZ022. && $$ SYNOPSIS...TJP NEAR TERM...APFFEL/TJP SHORT TERM...TMA LONG TERM...TMA AVIATION...APFFEL MARINE...TJP
AREA FORECAST DISCUSSION
NWS GRAND FORKS ND
1043 AM CST TUE DEC 6 2011 .DISCUSSION... CONCERN FOR THE UPDATE IS THE WIND SPEED. ALL INDICATIONS ARE THE LOW LEVEL INVERSION WILL HOLD PREVENTING 40KT - 45KT 925MB WIND FROM MIXING DOWN. HRRR HAS BEEN CONSISTENT IN DEVELOPING SFC GUSTS TO 40KTS OVER NORTH RRV AND NORTHWEST MINNESOTA COUNTIES 18Z-23Z. RUC13 AND NAM12 LAPSE RATES REMAIN STRONGLY NEGATIVE...YET MOMENTUM TRANSFER WILL PROBABLY PUSH TRANSIENT GUSTS TO THE SURFACE. PLAN TO UP THE WIND GUSTS MORE IN LINE WITH THE HRRR BUT NOT QUITE AS STRONG. OTRW THE PREVIOUS FORECAST IS IN GOOD SHAPE. WILL HOLD OFF ON WIND ADVISORY ALTHOUGH IT COULD BE CLOSE PARTICULARLY IN THE HIGHER TERRAIN FAVORED AREAS OF THE DEVILS LAKE BASIN AND NORTHWEST MINNESOTA. && .AVIATION...MAIN CONCERN FOR TODAY WILL BE WIND SPEEDS. BUMPED UP WINDS PER PUBLIC FCST COORDINATION. EXPECT SOUTHWEST WINDS WITH GUSTS UP TO 35 KNOTS. CIRRUS EXPECTED INTO TONIGHT. PROBABILITY FOR MVFR CIGS INCREASE BY WEDNESDAY MORNING ALONG COLD FRONT. && .PREV DISCUSSION... /ISSUED 337 AM CST TUE DEC 6 2011/ SHORT TERM...CHALLENGES INCLUDE WINDS TODAY ALONG WITH CLOUD COVER AND TEMPERATURES THROUGH THE PERIOD. 00Z MODELS IN DECENT AGREEMENT AND WILL USE A BLEND FOR DETAILS. TODAY-TONIGHT...STRONG SYSTEM WILL PROPAGATE ACROSS CANADA...WELL NORTH OF THE REGION. SOUTHWEST WINDS WILL INCREASE INTO THE AFTERNOON HOURS. MODEL SOUNDINGS SUGGEST MIXING TO 925MB...WITH 30-40KNTS AVAILABLE TO MIX...WITH 20-30 DEGREE DIFFERENCE FROM THE SFC TO 925MB. CONSIDERING THESE FACTORS SUSTAINED WINDS WILL LIKELY BE JUST BELOW ADVISORY CRITERIA. STRONGEST WINDS EXPECTED IN FAVORABLE CROOKSTON TO HALLOCK AREA. SIMILAR SITUATION LAST FRIDAY PROVED MOST TEMPERATURE GUIDANCE TOO COLD...WITH ECMWF VERIFYING BEST. FOLLOWING ECMWF...INCREASED MAX TEMPS 3-6F. 850MB THERMAL RIDGE WILL PROPAGATE THROUGH THE FA 00Z-06Z WED...AND COLD FROPA THROUGH THE REGION BY 12Z. LIKELY WILL BE SOME SORT OF NON-DIURNAL TEMPERATURE TREND. INCREASED SKY COVER AS MODEL GUIDANCE SUGGESTING LOW-LEVEL STRATUS IN COLD AIR ADVECTION JUST AHEAD OF UPPER WAVE. VERY LIGHT PRECIP ALSO POSSIBLE ACROSS NE FA. MODEL SOUNDINGS SUGGEST FZDZ POSSIBLE. LOW-LEVEL SATURATED LAYER AVERAGE TEMP WILL BE AROUND -8C WITH DRY LAYER ABOVE SUGGESTING SUPERCOOLED WATER DROPLETS. INCLUDED FLURRY/FZDZ AFT 06Z. WED-THUR NIGHT...UPPER FLOW BECOMES NORTHWEST WITH MULTIPLE WEAK/FAST MOVING SYSTEMS. COLDER AIRMASS SHOULD CONTINUE TO FILTER INTO THE REGION WITH COLDEST AIRMASS ON THUR. THERE WILL LIKELY BE PARTLY CLOUDY PERIODS...BUT BEGINNING TO THINK THAT MUCH OF THIS PERIOD WILL BE CLOUDY (ESPECIALLY THE NE HALF OF THE FA WHERE COLDEST 850MB TEMPS WILL BE LOCATED)...AND INCREASED SKY COVER ACROSS THE NE HALF OF THE FA. DID NOT INSERT PRECIP...BUT WOULD NOT BE SURPRISED TO SEE PERIODIC FLURRIES. BREEZY WINDS LIKELY. LONG TERM (FRIDAY-MONDAY)... MODELS IN THE EXTENDED ARE IN GOOD AGREEMENT AS UPPER LEVEL NW FLOW DOMINATES THE WEATHER PATTERN. CONTINUED DRY WEATHER WITH TEMPERATURES REBOUNDING TO ABOVE NORMAL FOR THE WEEKEND WITH HIGHER THICKNESSES BUILDING INTO THE NORTHERN PLAINS. AVIATION...MAIN CONCERN FOR TODAY WILL BE WIND SPEEDS. EXPECT SOUTHWEST WINDS WITH GUSTS UP TO 25 KNOTS. CIRRUS EXPECTED INTO TONIGHT. PROBABILITY FOR MVFR CIGS INCREASE BY WEDNESDAY MORNING ALONG COLD FRONT. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...NONE. MN...NONE. && $$ EWENS
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
1247 PM EST TUE DEC 6 2011 .SYNOPSIS... A SLOW MOVING COLD FRONT WILL GRADUALLY SLIDE EASTWARD TODAY. STRONG SYSTEM BRINGS RAIN WEDNESDAY...CHANGING TO SNOW WEDNESDAY NIGHT. HIGH PRESSURE THURSDAY. CLIPPER FRIDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... EARLY MORNING RADAR TRENDS INDICATE TWO POINTS OF FOCUS FOR PRECIPITATION. COLD FRONT JUST EAST OF OH RIVER VALLEY HAS BEEN THE IMPETUS FOR SCT SHOWERS OVERNIGHT INTO THE EARLY MORNING. NOT EXPECTING THIS TO CHANGE MUCH...SAVE FOR THE EVENTUAL EASTWARD CREEP OF THE FRONTAL BOUNDARY. SECOND FOCUS IS A WAVE RIDING NORTH ALONG THE FRONT...CURRENTLY LOCATED IN EAST-CENTRAL TN. EXPECTING SHOWERS ASSOCIATED WITH THIS FEATURE TO BE A LITTLE MORE ORGANIZED AS THEY ENTER OUR SW VA AND WV MOUNTAIN COUNTIES IN THE COMING HOURS. HRRR HAS HANDLED ONGOING PRECIPITATION TRENDS THE BEST...STICKING WITH THIS SOLUTION THIS MORNING. LOW CIGS AND VSBYS HAVE BEEN REPORTED ALONG THE FRONT AS IT MADE IT SLOW JOURNEY THROUGH SE OHIO...EXPECTING THIS TREND TO CONTINUE IN CRW AND CKB VICINITIES BEFORE ANY DAYTIME MIXING CAN IMPROVE CONDITIONS. LOW STRATUS SHOULD HANG AROUND CWA THROUGH AT LEAST MIDDAY WITH THE GREATEST IMPACT EVIDENT IN MOUNTAIN COUNTIES. TEMPS REMAIN COOLER THAN MOS WEST OF TROF AXIS...TWEAKED TEMPS TO ACCOUNT FOR THIS. GOING WITH A NEAR NON-DIURNAL TREND TO HIGH TEMPS WITH COLD FRONT STILL IN THE REGION. KEEPING WITH THE TREND OF AOA MOS TEMPS IN WV MNTS TODAY...WHILE AOB MOS IN THE LOWLANDS. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... MUCH BETTER CONSENSUS IN THE MODELS TONIGHT COMPARED TO THE RUNS LAST NIGHT REGARDING THE VIGOROUS SYSTEM SLATED FOR WEDNESDAY AND WEDNESDAY NIGHT. MOISTURE WILL HAVE ALREADY OVERSPREAD THE AREA SOUTH OF THE OHIO RIVER BY 12Z WEDNESDAY...AND EXPECT STEADY RAIN THROUGH THE FIRST PART OF THAT TIME PERIOD. THE ENTIRE KEY TO THIS FORECAST IS THE RATE OF THE COLD AIR ADVECTION AND THE SURFACE TEMPERATURES FALLING BELOW FREEZING. THIS WILL OCCUR FIRST IN THE HIGHEST ELEVATIONS WHERE THE MOST SIGNIFICANT ACCUMULATIONS ARE LIKELY. 925MB TEMPERATURE GRADIENT WILL TIGHTEN UP OVER THE EASTERN MOUNTAINS AND FINALLY KICK THROUGH AFTER AROUND 21Z WEDNESDAY...WHICH WILL SUBSEQUENTLY ALLOW THE CHANGE OVER TO SNOW FOR THE REMAINDER OF THE MOUNTAINS. WHILE THE OPERATIONAL MODELS GO EASY ON THE SPEED OF THE COLD AIR ADVECTION...STRENGTH OF THE DYNAMICS IN PLAY DO LEAVE SOME QUESTION AS TO WHETHER THIS PARAMETER IS BEING REPRESENTED WELL BY THESE MODELS...OR IF THERE WILL BE AN EARLIER TRANSITION TIME TO COME OVER THE NEXT COUPLE OF RUNS. SYSTEM WILL BE EFFICIENT WHEN IT COMES TO CREATING PRECIPITATION. JET STREAK OVER 140KTS EXISTS OVER SOUTHEAST OHIO WEDNESDAY...AND THE 500MB WAVE INDICATES A SHIFT TO A NEGATIVE TILT UPON PASSAGE THROUGH THE CENTRAL AND SOUTHERN APPALACHIANS. ROBUST FRONTOGENETIC FORCING WILL COUPLE WITH Q VECTOR CONVERGENCE IN THE UPPER LEVELS...CREATING ENHANCED OMEGA THROUGH THE DENDRITIC GROWTH LAYERS...WITH SATURATION OF THE COLUMN EXTENDING FROM THE SURFACE TO ABOVE 500MB. THE 03Z RUN OF THE SREF BRINGS PROBABILITIES OF SNOW EXCEEDING 4 INCHES AT ABOUT THE 30 TO 40 PERCENT RANGE FOR POCAHONTAS COUNTY. CURRENT STATE OF THE FORECAST GRIDS DOES BRING AROUND 4 TO 8 INCHES TOTAL SNOW ACCUMULATION...RELEGATED TO THE HIGHEST PEAKS OF THE CWA...ABOVE ROUGHLY 4000FT. WITH THE SLOWER CHANGE OVER TO SNOW IN THE MOUNTAINS BELOW 4000FT...ABOUT 2 TO 4 INCHES OF SNOW ARE IN THE FORECAST FOR THIS ISSUANCE. ANOTHER VARIABLE IN THIS OVERALL EQUATION IS THE MILD AIR THAT HAS BEEN IN PLACE...THE RAIN THAT WILL PRECEDE THE SNOW...AND THE LENGTH OF TIME NECESSARY FOR THE SNOW TO ACCUMULATE. GIVEN THE FACT THAT THIS IS A LATE 3RD PERIOD TO EARLY 4TH PERIOD EVENT...WILL NOT COMMIT TO THE WATCH FOR NOW. ANY VARIABILITY IN THE TIMING OF THE BELOW FREEZING AIR COULD ALTER THE SNOWFALL TOTAL FORECAST SIGNIFICANTLY...IN EITHER DIRECTION. NOT COMFORTABLE WITH THIS POTENTIAL VOLATILITY TO THE FORECAST AND WILL DRAW ATTENTION TO THIS SYSTEM IN THE HWO AND RWS TEXT PRODUCTS. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... A SHARP AMPLIFYING TROF WILL BE THE MAIN FEATURE EARLY IN THE EXTENDED. THIS TROF WILL SETTLE INTO EASTERN CONUS...ADVERTISED BY A CLIPPER FOR FRI NIGHT. BEST LIFT WITH THIS FEATURE WILL SKIRT BY MAINLY TO NORTH. HOWEVER...GIVEN SOME MOISTURE AND MAGNITUDE OF COLD AIR BEHIND IT...CANT RULE OUT SOME FLURRIES ABOUT ANYWHERE WITH FROPA. WILL MENTION FLURRIES IN WX GRIDS FOR LOWLANDS AND CARRY CHC POPS NORTHERN MTNS. H85 TEMPS COME DOWN TO ARND -10C BY SAT MORNING. NOT MUCH IN THE WAY OF UPSLOPE AS ATMOSPHERIC COLUMN WILL QUICKLY DRY OUT AND NW FLOW MEAGER. WILL DRY THINGS OUT QUICKLY SAT...WITH A RETURN TO SUNSHINE FOR ALL BY AFTN...ALBEIT COLD. DESPITE THE SUNSHINE...THINK 40F WILL BE HARD TO COME BY IN THE LOWLANDS...WITH GUIDANCE SUGGESTING MID 30S IS ABOUT IT...WITH 20S IN THE MTNS. UPR TROF DOESNT STICK ARND IN THIS PROGRESSIVE PATTERN...AS WAA QUICKLY ALLOWS H85 TEMPS TO RECOVER. HOWEVER...COLD NIGHT WILL BE ON TAP SAT WITH SFC HIGH BUILDING OVERHEAD. WILL GO WITH AN EARLY LOW HIGHEST ELEVATIONS AND LEVEL OFF OR SLIGHTLY REBOUND BY SUN MORNING...WITH LOWLANDS DIPPING DOWN INTO LWR 20S. TOOK TYPICAL COLD SPOTS INTO TEENS...IE NORTHERN MTN VALLEYS/NE KY. MODERATING TEMPS WILL CARRY THE WAY EARLY NEXT WEEK...THOUGH STILL REMAINING ON THE CHILLY SIDE. SHOULD STAY DRY THROUGH TUES. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... A COLD FRONT CURRENTLY LOCATED JUST WEST OF BKW AND EKN IS VERY SLOWLY MOVING EASTWARD. LIFR/IFR CONDITIONS CAN BE EXPECTED WEST OF THE FRONT...WITH VFR/MVFR EAST OF THE FRONT. A LOW WILL FORM ALONG THIS FRONT AND MOVE NORTHWARD LATE TONIGHT AND WEDNESDAY. THIS WILL BRING MORE RAIN TO THE AREA. WITH THE REGION ON THE WEST SIDE OF THE FRONT...EXPECT LIFR/IFR CONDITIONS. COLD AIR ON THE BACK SIDE OF THIS SYSTEM COULD CAUSE A BURST OF SNOW LATE WEDNESDAY. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z WEDNESDAY... FORECAST CONFIDENCE: HIGH WEST OF THE FRONT...LOW FOR TIMING OF FRONT IN THE EAST. ALTERNATE SCENARIOS: TIMING OF THE FRONT CONTROLS THE COLLAPSE OF CEILINGS IN THE EASTERN COUNTIES. THIS TIMING 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. UTC 1HRLY 18 19 20 21 22 23 00 01 02 03 04 05 EST 1HRLY 13 14 15 16 17 18 19 20 21 22 23 00 CRW CONSISTENCY M M M M M M M M M L L L HTS CONSISTENCY H H H H H L L L L M M M BKW CONSISTENCY M L M M M L L L M L L L EKN CONSISTENCY L M M M M M M L L L L L PKB CONSISTENCY M H H M M L L L L M M M CKB CONSISTENCY M H H H H H H H H L L L AFTER 18Z WEDNESDAY... IFR IN PERIODS OF PRECIPITATION AND FOG INTO WEDNESDAY NIGHT. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...26/TAX NEAR TERM...TAX SHORT TERM...26 LONG TERM...30 AVIATION...RPY
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
519 AM EST TUE DEC 6 2011 .SYNOPSIS... LIGHT RAIN SHOWERS EXPECTED TO LINGER THIS MORNING WITH A SLOW MOVING COLD FRONT IN THE VICINITY. STRONG SYSTEM BRINGS RAIN AND SNOW WEDNESDAY AND WEDNESDAY NIGHT. HIGH PRESSURE THURSDAY. CLIPPER FRIDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... EARLY MORNING RADAR TRENDS INDICATE TWO POINTS OF FOCUS FOR PRECIPITATION. COLD FRONT JUST EAST OF OH RIVER VALLEY HAS BEEN THE IMPETUS FOR SCT SHOWERS OVERNIGHT INTO THE EARLY MORNING. NOT EXPECTING THIS TO CHANGE MUCH...SAVE FOR THE EVENTUAL EASTWARD CREEP OF THE FRONTAL BOUNDARY. SECOND FOCUS IS A WAVE RIDING NORTH ALONG THE FRONT...CURRENTLY LOCATED IN EAST-CENTRAL TN. EXPECTING SHOWERS ASSOCIATED WITH THIS FEATURE TO BE A LITTLE MORE ORGANIZED AS THEY ENTER OUR SW VA AND WV MNT COUNTIES IN THE COMING HOURS. HRRR HAS HANDLED ONGOING PRECIPITATION TRENDS THE BEST...STICKING WITH THIS SOLN THIS MORNING. LOW CIGS AND VSBYS HAVE BEEN REPORTED ALONG THE FRONT AS IT MADE IT SLOW JOURNEY THROUGH SE OHIO...EXPECTING THIS TREND TO CONTINUE IN CRW AND CKB VICINITIES BEFORE ANY DAYTIME MIXING CAN IMPROVE CONDITIONS. LOW STRATUS SHOULD HANG AROUND CWA THROUGH AT LEAST MIDDAY WITH THE GREATEST IMPACT EVIDENT IN MNT COUNTIES. TEMPS REMAIN COOLER THAN MOS WEST OF TROF AXIS...TWEAKED TEMPS TO ACCOUNT FOR THIS. GOING WITH A NEAR NON-DIURNAL TREND TO HIGH TEMPS WITH COLD FRONT STILL IN THE REGION. KEEPING WITH THE TREND OF AOA MOS TEMPS IN WV MNTS TODAY...WHILE AOB MOS IN THE LOWLANDS. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... MUCH BETTER CONSENSUS IN THE MODELS TONIGHT COMPARED TO THE RUNS LAST NIGHT REGARDING THE VIGOROUS SYSTEM SLATED FOR WEDNESDAY AND WEDNESDAY NIGHT. MOISTURE WILL HAVE ALREADY OVERSPREAD THE AREA SOUTH OF THE OHIO RIVER BY 12Z WEDNESDAY...AND EXPECT STEADY RAIN THROUGH THE FIRST PART OF THAT TIME PERIOD. THE ENTIRE KEY TO THIS FORECAST IS THE RATE OF THE COLD AIR ADVECTION AND THE SURFACE TEMPERATURES FALLING BELOW FREEZING. THIS WILL OCCUR FIRST IN THE HIGHEST ELEVATIONS WHERE THE MOST SIGNIFICANT ACCUMULATIONS ARE LIKELY. 925MB TEMPERATURE GRADIENT WILL TIGHTEN UP OVER THE EASTERN MOUNTAINS AND FINALLY KICK THROUGH AFTER AROUND 21Z WEDNESDAY...WHICH WILL SUBSEQUENTLY ALLOW THE CHANGE OVER TO SNOW FOR THE REMAINDER OF THE MOUNTAINS. WHILE THE OPERATIONAL MODELS GO EASY ON THE SPEED OF THE COLD AIR ADVECTION...STRENGTH OF THE DYNAMICS IN PLAY DO LEAVE SOME QUESTION AS TO WHETHER THIS PARAMETER IS BEING REPRESENTED WELL BY THESE MODELS...OR IF THERE WILL BE AN EARLIER TRANSITION TIME TO COME OVER THE NEXT COUPLE OF RUNS. SYSTEM WILL BE EFFICIENT WHEN IT COMES TO CREATING PRECIPITATION. JET STREAK OVER 140KTS EXISTS OVER SOUTHEAST OHIO WEDNESDAY...AND THE 500MB WAVE INDICATES A SHIFT TO A NEGATIVE TILT UPON PASSAGE THROUGH THE CENTRAL AND SOUTHERN APPALACHIANS. ROBUST FRONTOGENETIC FORCING WILL COUPLE WITH Q VECTOR CONVERGENCE IN THE UPPER LEVELS...CREATING ENHANCED OMEGA THROUGH THE DENDRITIC GROWTH LAYERS...WITH SATURATION OF THE COLUMN EXTENDING FROM THE SURFACE TO ABOVE 500MB. THE 03Z RUN OF THE SREF BRINGS PROBABILITIES OF SNOW EXCEEDING 4 INCHES AT ABOUT THE 30 TO 40 PERCENT RANGE FOR POCAHONTAS COUNTY. CURRENT STATE OF THE FORECAST GRIDS DOES BRING AROUND 4 TO 8 INCHES TOTAL SNOW ACCUMULATION...RELEGATED TO THE HIGHEST PEAKS OF THE CWA...ABOVE ROUGHLY 4000FT. WITH THE SLOWER CHANGE OVER TO SNOW IN THE MOUNTAINS BELOW 4000FT...ABOUT 2 TO 4 INCHES OF SNOW ARE IN THE FORECAST FOR THIS ISSUANCE. ANOTHER VARIABLE IN THIS OVERALL EQUATION IS THE MILD AIR THAT HAS BEEN IN PLACE...THE RAIN THAT WILL PRECEDE THE SNOW...AND THE LENGTH OF TIME NECESSARY FOR THE SNOW TO ACCUMULATE. GIVEN THE FACT THAT THIS IS A LATE 3RD PERIOD TO EARLY 4TH PERIOD EVENT...WILL NOT COMMIT TO THE WATCH FOR NOW. ANY VARIABILITY IN THE TIMING OF THE BELOW FREEZING AIR COULD ALTER THE SNOWFALL TOTAL FORECAST SIGNIFICANTLY...IN EITHER DIRECTION. NOT COMFORTABLE WITH THIS POTENTIAL VOLATILITY TO THE FORECAST AND WILL DRAW ATTENTION TO THIS SYSTEM IN THE HWO AND RWS TEXT PRODUCTS. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... A SHARP AMPLIFYING TROF WILL BE THE MAIN FEATURE EARLY IN THE EXTENDED. THIS TROF WILL SETTLE INTO EASTERN CONUS...ADVERTISED BY A CLIPPER FOR FRI NIGHT. BEST LIFT WITH THIS FEATURE WILL SKIRT BY MAINLY TO NORTH. HOWEVER...GIVEN SOME MOISTURE AND MAGNITUDE OF COLD AIR BEHIND IT...CANT RULE OUT SOME FLURRIES ABOUT ANYWHERE WITH FROPA. WILL MENTION FLURRIES IN WX GRIDS FOR LOWLANDS AND CARRY CHC POPS NORTHERN MTNS. H85 TEMPS COME DOWN TO ARND -10C BY SAT MORNING. NOT MUCH IN THE WAY OF UPSLOPE AS ATMOSPHERIC COLUMN WILL QUICKLY DRY OUT AND NW FLOW MEAGER. WILL DRY THINGS OUT QUICKLY SAT...WITH A RETURN TO SUNSHINE FOR ALL BY AFTN...ALBEIT COLD. DESPITE THE SUNSHINE...THINK 40F WILL BE HARD TO COME BY IN THE LOWLANDS...WITH GUIDANCE SUGGESTING MID 30S IS ABOUT IT...WITH 20S IN THE MTNS. UPR TROF DOESNT STICK ARND IN THIS PROGRESSIVE PATTERN...AS WAA QUICKLY ALLOWS H85 TEMPS TO RECOVER. HOWEVER...COLD NIGHT WILL BE ON TAP SAT WITH SFC HIGH BUILDING OVERHEAD. WILL GO WITH AN EARLY LOW HIGHEST ELEVATIONS AND LEVEL OFF OR SLIGHTLY REBOUND BY SUN MORNING...WITH LOWLANDS DIPPING DOWN INTO LWR 20S. TOOK TYPICAL COLD SPOTS INTO TEENS...IE NORTHERN MTN VALLEYS/NE KY. MODERATING TEMPS WILL CARRY THE WAY EARLY NEXT WEEK...THOUGH STILL REMAINING ON THE CHILLY SIDE. SHOULD STAY DRY THROUGH TUES. && .AVIATION /10Z TUESDAY THROUGH SATURDAY/... COLD FRONT CURRENTLY JUST EAST OF HTS AND PKB AND SHOULD CONTINUE TO SLOWLY MOVE EAST THIS MORNING. IFR/LIFR CONDITIONS ALONG THE FRONT...WITH IMPROVEMENT TO MVFR/IFR BEHIND THE FRONT IN LOW STRATUS DECK. CONDITIONS SHOULD IMPROVE TO PREDOMINANTLY MVFR CONDITONS BASED ON CIGS. EXPECTING ADDITIONAL SHRA TODAY ALONG THE FRONT AND IN MNT COUNTIES. POSSIBLE IFR CONDITIONS COULD EXIST IN ANY SHOWERS THAT OCCUR WITH LOWERED VSBYS. RAIN WILL EVENTUALLY TAPER OFF FROM W TO E TUES AFTERNOON THIS SHOULD ALLOW VSBYS TO IMPROVE WHILE CIGS WILL BE SLOWER TO RESPOND. EXPECTING CONDITIONS TO DETERIORATE AGAIN TONIGHT WITH MVFR CIGS AND VSBYS...PRIMARILY IN THE MOUNTAINS. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z WEDNESDAY... FORECAST CONFIDENCE: MEDIUM. ALTERNATE SCENARIOS: CONDITIONS ALONG THE FRONT HAVE CAUSED BOUNCING CIGS AND VSBYS TO LESS THAN FORECAST...ANY VARIANCE IN TIMING COULD CAUSE TIMING CHANGES OF WORSENING CONDITIONS. DEGREE AND TIMING OF IMPROVEMENT TODAY COULD ALSO 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 TUE 12/06/11 UTC 1HRLY 08 09 10 11 12 13 14 15 16 17 18 19 EST 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14 CRW CONSISTENCY M M L L M M M L M M M M HTS CONSISTENCY L M M M M M L L M H H H BKW CONSISTENCY M M L M M M M M L L L L EKN CONSISTENCY H L L L L L L L M M M M PKB CONSISTENCY M M M M M M L L H M H H CKB CONSISTENCY L L L L M M M M M M M M AFTER 12Z WEDNESDAY... IFR IN PERIODS OF RAIN INTO WEDS...ALSO WITH SNOW EXPECTED IN THE MOUNTAINS. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...26/TAX NEAR TERM...TAX SHORT TERM...26 LONG TERM...30 AVIATION...TAX
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
403 AM EST TUE DEC 6 2011 .SYNOPSIS... LIGHT RAIN SHOWERS EXPECTED TO LINGER THIS MORNING WITH A SLOW MOVING COLD FRONT IN THE VICINITY. STRONG SYSTEM BRINGS RAIN AND SNOW WEDNESDAY AND WEDNESDAY NIGHT. HIGH PRESSURE THURSDAY. CLIPPER FRIDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... 330 AM UPDATE... MAIN CHANGE WITH THIS ISSUANCE IS THE UPDATE TO POPS BASED ON REGIONAL RADAR TRENDS. HRRR MODEL APPEARS TO BE HANDLING THE CURRENT SITUATION WELL...WILL BE STICKING WITH THIS SOLN FOR NEXT WAVE THAT IS TRAVELING ALONG THE FRONT...CURRENTLY IN EAST CENTRAL TN. 1230 AM UPDATE... TWEAKED POPS TO BE MORE REPRESENTATIVE OF RADAR ECHOES...HEAVIEST PRECIPITATION HAS MOVED JUST EAST OF CWA WITH LIGHT SHOWERS LINGERING BACK ALONG THE COLD FRONT. HEAVIEST RATES SEEM TO BE .10 TO .20 IN/HR...SO NO CONCERN WITH WATER PROBLEMS. LOW STRATUS DECK APPEARING RIGHT ON TIME BEHIND THE COLD FRONT...EXPECTING STRATUS TO CONTINUE CREEPING EAST THROUGH THE EARLY MORNING. PREV DISCN... MODELS IN FAIRLY GOOD AGREEMENT WITH FRONTAL BOUNDARY PUSHING THROUGH THE REGION EARLY TUESDAY. LOW TEMPERATURES DEPEND ON PERFECT TIMING OF THE FRONT. LOOKING AT CURRENT TEMPERATURES AROUND THE FRONT...WILL GO WITH COOLER MOS IN THE FAR WEST...AND WARMER MOS IN THE FAR EAST. EXPECTING A LOW STRATUS DECK BEHIND THE FRONT ON TUESDAY. WITH SUCH A SHALLOW LAYER OF COLD AIR...DO NOT THINK THE MOS GUIDANCE IS HANDLING IT WELL. THEREFORE...WILL GO ON THE LOWER SIDE OF MOS GUIDANCE FOR HIGHS. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... MUCH BETTER CONSENSUS IN THE MODELS TONIGHT COMPARED TO THE RUNS LAST NIGHT REGARDING THE VIGOROUS SYSTEM SLATED FOR WEDNESDAY AND WEDNESDAY NIGHT. MOISTURE WILL HAVE ALREADY OVERSPREAD THE AREA SOUTH OF THE OHIO RIVER BY 12Z WEDNESDAY...AND EXPECT STEADY RAIN THROUGH THE FIRST PART OF THAT TIME PERIOD. THE ENTIRE KEY TO THIS FORECAST IS THE RATE OF THE COLD AIR ADVECTION AND THE SURFACE TEMPERATURES FALLING BELOW FREEZING. THIS WILL OCCUR FIRST IN THE HIGHEST ELEVATIONS WHERE THE MOST SIGNIFICANT ACCUMULATIONS ARE LIKELY. 925MB TEMPERATURE GRADIENT WILL TIGHTEN UP OVER THE EASTERN MOUNTAINS AND FINALLY KICK THROUGH AFTER AROUND 21Z WEDNESDAY...WHICH WILL SUBSEQUENTLY ALLOW THE CHANGE OVER TO SNOW FOR THE REMAINDER OF THE MOUNTAINS. WHILE THE OPERATIONAL MODELS GO EASY ON THE SPEED OF THE COLD AIR ADVECTION...STRENGTH OF THE DYNAMICS IN PLAY DO LEAVE SOME QUESTION AS TO WHETHER THIS PARAMETER IS BEING REPRESENTED WELL BY THESE MODELS...OR IF THERE WILL BE AN EARLIER TRANSITION TIME TO COME OVER THE NEXT COUPLE OF RUNS. SYSTEM WILL BE EFFICIENT WHEN IT COMES TO CREATING PRECIPITATION. JET STREAK OVER 140KTS EXISTS OVER SOUTHEAST OHIO WEDNESDAY...AND THE 500MB WAVE INDICATES A SHIFT TO A NEGATIVE TILT UPON PASSAGE THROUGH THE CENTRAL AND SOUTHERN APPALACHIANS. ROBUST FRONTOGENETIC FORCING WILL COUPLE WITH Q VECTOR CONVERGENCE IN THE UPPER LEVELS...CREATING ENHANCED OMEGA THROUGH THE DENDRITIC GROWTH LAYERS...WITH SATURATION OF THE COLUMN EXTENDING FROM THE SURFACE TO ABOVE 500MB. THE 03Z RUN OF THE SREF BRINGS PROBABILITIES OF SNOW EXCEEDING 4 INCHES AT ABOUT THE 30 TO 40 PERCENT RANGE FOR POCAHONTAS COUNTY. CURRENT STATE OF THE FORECAST GRIDS DOES BRING AROUND 4 TO 8 INCHES TOTAL SNOW ACCUMULATION...RELEGATED TO THE HIGHEST PEAKS OF THE CWA...ABOVE ROUGHLY 4000FT. WITH THE SLOWER CHANGE OVER TO SNOW IN THE MOUNTAINS BELOW 4000FT...ABOUT 2 TO 4 INCHES OF SNOW ARE IN THE FORECAST FOR THIS ISSUANCE. ANOTHER VARIABLE IN THIS OVERALL EQUATION IS THE MILD AIR THAT HAS BEEN IN PLACE...THE RAIN THAT WILL PRECEDE THE SNOW...AND THE LENGTH OF TIME NECESSARY FOR THE SNOW TO ACCUMULATE. GIVEN THE FACT THAT THIS IS A LATE 3RD PERIOD TO EARLY 4TH PERIOD EVENT...WILL NOT COMMIT TO THE WATCH FOR NOW. ANY VARIABILITY IN THE TIMING OF THE BELOW FREEZING AIR COULD ALTER THE SNOWFALL TOTAL FORECAST SIGNIFICANTLY...IN EITHER DIRECTION. NOT COMFORTABLE WITH THIS POTENTIAL VOLATILITY TO THE FORECAST AND WILL DRAW ATTENTION TO THIS SYSTEM IN THE HWO AND RWS TEXT PRODUCTS. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... A SHARP AMPLIFYING TROF WILL BE THE MAIN FEATURE EARLY IN THE EXTENDED. THIS TROF WILL SETTLE INTO EASTERN CONUS...ADVERTISED BY A CLIPPER FOR FRI NIGHT. BEST LIFT WITH THIS FEATURE WILL SKIRT BY MAINLY TO NORTH. HOWEVER...GIVEN SOME MOISTURE AND MAGNITUDE OF COLD AIR BEHIND IT...CANT RULE OUT SOME FLURRIES ABOUT ANYWHERE WITH FROPA. WILL MENTION FLURRIES IN WX GRIDS FOR LOWLANDS AND CARRY CHC POPS NORTHERN MTNS. H85 TEMPS COME DOWN TO ARND -10C BY SAT MORNING. NOT MUCH IN THE WAY OF UPSLOPE AS ATMOSPHERIC COLUMN WILL QUICKLY DRY OUT AND NW FLOW MEAGER. WILL DRY THINGS OUT QUICKLY SAT...WITH A RETURN TO SUNSHINE FOR ALL BY AFTN...ALBEIT COLD. DESPITE THE SUNSHINE...THINK 40F WILL BE HARD TO COME BY IN THE LOWLANDS...WITH GUIDANCE SUGGESTING MID 30S IS ABOUT IT...WITH 20S IN THE MTNS. UPR TROF DOESNT STICK ARND IN THIS PROGRESSIVE PATTERN...AS WAA QUICKLY ALLOWS H85 TEMPS TO RECOVER. HOWEVER...COLD NIGHT WILL BE ON TAP SAT WITH SFC HIGH BUILDING OVERHEAD. WILL GO WITH AN EARLY LOW HIGHEST ELEVATIONS AND LEVEL OFF OR SLIGHTLY REBOUND BY SUN MORNING...WITH LOWLANDS DIPPING DOWN INTO LWR 20S. TOOK TYPICAL COLD SPOTS INTO TEENS...IE NORTHERN MTN VALLEYS/NE KY. MODERATING TEMPS WILL CARRY THE WAY EARLY NEXT WEEK...THOUGH STILL REMAINING ON THE CHILLY SIDE. SHOULD STAY DRY THROUGH TUES. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... COLD FRONT CURRENTLY JUST WEST OF HTS AND PKB AND SHOULD CONTINUE TO SLOWLY MOVE EAST OVERNIGHT. SHRA AHEAD OF FRONT MAY CAUSE BORDERLINE MVFR CONDITIONS...BUT FOR THE MOST PART VFR STILL PREDOMINANT EAST OF OHIO RIVER. ONCE THE FRONT PASSES...CIGS DROP TO MVFR IN LOW STRATUS DECK. BY DAWN...IFR CIGS AND VSBY WILL BE COMMON IN WIDESPREAD RAIN. THE RAIN WILL TAPER OFF FROM W TO E TUE...ALLOWING VSBY TO IMPROVE TO VFR IN THE LOWLANDS AND MVFR IN THE MOUNTAINS BY AFTERNOON. HOWEVER...CIGS WILL STRUGGLE TO CLIMB TO LOW MVFR ION THE LOWLANDS. IN THE MOUNTAINS...IT WILL TAKE UNTIL ABOUT DAWN FOR CIGS TO GET DOWN TO IFR BUT THEN CIGS WILL REMAIN IFR OR CLOSE TO IT THROUGH THE DAY TUE. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z WEDNESDAY... FORECAST CONFIDENCE: MEDIUM. ALTERNATE SCENARIOS: TIMING OF THE FRONT COULD VARY...CAUSING TIMING OF IFR/LIFR CONDITIONS TO VARY. DENSITY OF THE FOG TONIGHT COULD ALSO VARY. TIMING AND DEGREE OF IMPROVEMENT TUE ALSO 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 TUE 12/06/11 UTC 1HRLY 08 09 10 11 12 13 14 15 16 17 18 19 EST 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14 CRW CONSISTENCY M M L L M M M L M M M M HTS CONSISTENCY L M M M M M L L M H H H BKW CONSISTENCY M M L M M M M M L L L L EKN CONSISTENCY H L L L L L L L M M M M PKB CONSISTENCY M M M M M M L L H M H H CKB CONSISTENCY L L L L M M M M M M M M AFTER 06Z WEDNESDAY... IFR IN PERIODS OF RAIN INTO TUE NT...AND IN THE MOUNTAINS IN SNOW WED NT. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...26/TAX NEAR TERM...RPY/TAX SHORT TERM...26 LONG TERM...30 AVIATION...TAX
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
344 AM EST TUE DEC 6 2011 .SYNOPSIS... LIGHT RAIN SHOWERS EXPECTED TO LINGER THIS MORNING WITH A SLOW MOVING COLD FRONT IN THE VICINITY. COLDER WEDNESDAY WITH TROUGH AXIS ALOFT CROSSING WEDNESDAY NIGHT. HIGH PRESSURE THURSDAY. CLIPPER FRIDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... 330 AM UPDATE... MAIN CHANGE WITH THIS ISSUANCE IS THE UPDATE TO POPS BASED ON REGIONAL RADAR TRENDS. HRRR MODEL APPEARS TO BE HANDLING THE CURRENT SITUATION WELL...WILL BE STICKING WITH THIS SOLN FOR NEXT WAVE THAT IS TRAVELING ALONG THE FRONT...CURRENTLY IN EAST CENTRAL TN. 1230 AM UPDATE... TWEAKED POPS TO BE MORE REPRESENTATIVE OF RADAR ECHOES...HEAVIEST PRECIPITATION HAS MOVED JUST EAST OF CWA WITH LIGHT SHOWERS LINGERING BACK ALONG THE COLD FRONT. HEAVIEST RATES SEEM TO BE .10 TO .20 IN/HR...SO NO CONCERN WITH WATER PROBLEMS. LOW STRATUS DECK APPEARING RIGHT ON TIME BEHIND THE COLD FRONT...EXPECTING STRATUS TO CONTINUE CREEPING EAST THROUGH THE EARLY MORNING. PREV DISCN... MODELS IN FAIRLY GOOD AGREEMENT WITH FRONTAL BOUNDARY PUSHING THROUGH THE REGION EARLY TUESDAY. LOW TEMPERATURES DEPEND ON PERFECT TIMING OF THE FRONT. LOOKING AT CURRENT TEMPERATURES AROUND THE FRONT...WILL GO WITH COOLER MOS IN THE FAR WEST...AND WARMER MOS IN THE FAR EAST. EXPECTING A LOW STRATUS DECK BEHIND THE FRONT ON TUESDAY. WITH SUCH A SHALLOW LAYER OF COLD AIR...DO NOT THINK THE MOS GUIDANCE IS HANDLING IT WELL. THEREFORE...WILL GO ON THE LOWER SIDE OF MOS GUIDANCE FOR HIGHS. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY/... RECENT MODEL RUNS HAVE COME INTO BETTER AGREEMENT IN THE SHORT TERM PERIOD. PROGRESSION OF SURFACE FRONT ACROSS THE CWA HAS BEEN TRENDING SLOWER. NAM EVEN APPEARS TO HANG UP THE FRONT OVER THE MOUNTAINS WEDNESDAY...WITH SEVERAL WAVES RIDING ALONG THE FRONT...WHILE GFS FOR EXAMPLE...APPEARS TO CLEAR THE SURFACE FRONT EAST OF THE MOUNTAINS LATE TUESDAY NIGHT OR WEDNESDAY. MUCH OF THE INITIAL PRECIPITATION IN THE SHORT TERM WILL START OUT AS RAIN...BUT BY WEDNESDAY NIGHT/THURSDAY...A MORE SIGNIFICANT SHORTWAVE TROUGH WILL APPROACH FROM THE WEST. STILL SOME DIFFERENCES IN THE EXACT TRACK...TIMING...AND THUS NORTHWARD EXTEND OF THE PRECIPITATION SHIELD ASSOCIATED WITH THIS...SO FOR NOW...KIND OF WENT WITH A SPLIT BETWEEN THE 12Z NAM AND 12Z GFS. THINKING ENOUGH COLD AIR WILL BE IN PLACE LATE WEDNESDAY NIGHT/EARLY THURSDAY FOR PRECIPITATION TO GRADUALLY CHANGE OVER TO SNOW CWA WIDE. WITH 1000-500MB THICKNESSES HOVERING AROUND 540 AND RATHER MOIST SOUNDINGS WITH MUCH OF THE SOUNDING NEAR 0C...EXPECTING A HEAVIER...WET SNOW. ACCUMULATIONS ARE STILL UP IN THE AIR A BIT...BUT REALLY ONLY EXPECTING ACCUMULATIONS IN THE HIGHER TERRAIN...PARTICULARLY NORTHERN MOUNTAIN ZONES. ANY SNOW IN THE LOWLANDS WILL LIKELY NOT ACCUMULATE DUE TO WARM GROUND. FOR NOW...DECIDED TO BE CONSERVATIVE ON SNOWFALL ACCUMULATIONS...AND HAVE GENERALLY 2-4 INCHES IN THE NORTHERN MOUNTAIN ZONES...WITH GENERALLY 1-3 INCHES IN SURROUNDING HIGHER TERRAIN COUNTIES. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... A SHARP AMPLIFYING TROF WILL BE THE MAIN FEATURE EARLY IN THE EXTENDED. THIS TROF WILL SETTLE INTO EASTERN CONUS...ADVERTISED BY A CLIPPER FOR FRI NIGHT. BEST LIFT WITH THIS FEATURE WILL SKIRT BY MAINLY TO NORTH. HOWEVER...GIVEN SOME MOISTURE AND MAGNITUDE OF COLD AIR BEHIND IT...CANT RULE OUT SOME FLURRIES ABOUT ANYWHERE WITH FROPA. WILL MENTION FLURRIES IN WX GRIDS FOR LOWLANDS AND CARRY CHC POPS NORTHERN MTNS. H85 TEMPS COME DOWN TO ARND -10C BY SAT MORNING. NOT MUCH IN THE WAY OF UPSLOPE AS ATMOSPHERIC COLUMN WILL QUICKLY DRY OUT AND NW FLOW MEAGER. WILL DRY THINGS OUT QUICKLY SAT...WITH A RETURN TO SUNSHINE FOR ALL BY AFTN...ALBEIT COLD. DESPITE THE SUNSHINE...THINK 40F WILL BE HARD TO COME BY IN THE LOWLANDS...WITH GUIDANCE SUGGESTING MID 30S IS ABOUT IT...WITH 20S IN THE MTNS. UPR TROF DOESNT STICK ARND IN THIS PROGRESSIVE PATTERN...AS WAA QUICKLY ALLOWS H85 TEMPS TO RECOVER. HOWEVER...COLD NIGHT WILL BE ON TAP SAT WITH SFC HIGH BUILDING OVERHEAD. WILL GO WITH AN EARLY LOW HIGHEST ELEVATIONS AND LEVEL OFF OR SLIGHTLY REBOUND BY SUN MORNING...WITH LOWLANDS DIPPING DOWN INTO LWR 20S. TOOK TYPICAL COLD SPOTS INTO TEENS...IE NORTHERN MTN VALLEYS/NE KY. MODERATING TEMPS WILL CARRY THE WAY EARLY NEXT WEEK...THOUGH STILL REMAINING ON THE CHILLY SIDE. SHOULD STAY DRY THROUGH TUES. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... COLD FRONT CURRENTLY JUST WEST OF HTS AND PKB AND SHOULD CONTINUE TO SLOWLY MOVE EAST OVERNIGHT. SHRA AHEAD OF FRONT MAY CAUSE BORDERLINE MVFR CONDITIONS...BUT FOR THE MOST PART VFR STILL PREDOMINANT EAST OF OHIO RIVER. ONCE THE FRONT PASSES...CIGS DROP TO MVFR IN LOW STRATUS DECK. BY DAWN...IFR CIGS AND VSBY WILL BE COMMON IN WIDESPREAD RAIN. THE RAIN WILL TAPER OFF FROM W TO E TUE...ALLOWING VSBY TO IMPROVE TO VFR IN THE LOWLANDS AND MVFR IN THE MOUNTAINS BY AFTERNOON. HOWEVER...CIGS WILL STRUGGLE TO CLIMB TO LOW MVFR ION THE LOWLANDS. IN THE MOUNTAINS...IT WILL TAKE UNTIL ABOUT DAWN FOR CIGS TO GET DOWN TO IFR BUT THEN CIGS WILL REMAIN IFR OR CLOSE TO IT THROUGH THE DAY TUE. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z WEDNESDAY... FORECAST CONFIDENCE: MEDIUM. ALTERNATE SCENARIOS: TIMING OF THE FRONT COULD VARY...CAUSING TIMING OF IFR/LIFR CONDITIONS TO VARY. DENSITY OF THE FOG TONIGHT COULD ALSO VARY. TIMING AND DEGREE OF IMPROVEMENT TUE ALSO 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 TUE 12/06/11 UTC 1HRLY 08 09 10 11 12 13 14 15 16 17 18 19 EST 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14 CRW CONSISTENCY M M L L M M M L M M M M HTS CONSISTENCY L M M M M M L L M H H H BKW CONSISTENCY M M L M M M M M L L L L EKN CONSISTENCY H L L L L L L L M M M M PKB CONSISTENCY M M M M M M L L H M H H CKB CONSISTENCY L L L L M M M M M M M M AFTER 06Z WEDNESDAY... IFR IN PERIODS OF RAIN INTO TUE NT...AND IN THE MOUNTAINS IN SNOW WED NT. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...SL/30/TAX NEAR TERM...RPY/TAX SHORT TERM...SL LONG TERM...30 AVIATION...TAX
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
509 AM EST TUE DEC 6 2011 .SYNOPSIS... A MOIST SOUTHWEST FLOW ALOFT WILL INTERACT WITH A SLOW MOVING WAVY FRONTAL BOUNDARY TO BRING UNSETTLED CONDITIONS TO THE AREA THROUGH MID WEEK. UPPER LEVEL ENERGY MIGRATING FROM THE ROCKIES EASTWARD ACROSS THE CENTRAL PLAINS STATES INTO THE APPALACHIANS SHOULD INDUCE A MORE DEFINED AREA OF LOW PRESSURE OVER THE CAROLINAS BY WEDNESDAY NIGHT. THIS SYSTEM MAY SPREAD A SWATH OF LIGHT TO MODERATE SNOW ACROSS SOUTHERN AND EASTERN PENNSYLVANIA AS IT TRACKS NORTHEAST NEAR THE MID-ATLANTIC COAST. SEASONABLY COLD AND BRISK BUT MAINLY DRY WEATHER IS ANTICIPATED FROM LATER THIS WEEK INTO THE FIRST PART OF THE WEEKEND...WITH SOME MODERATION IN TEMPERATURES LIKELY HEADING INTO EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AT 0530Z THE SFC COLD FRONT WAS LOCATED JUST E OF A JHW-YNG-ZZV LINE. RDR SHOWS GREATEST CVRG OR LGT/MOD RNFL MOVG ACRS THE NW AND NCNTRL MTNS. MDL AND CIWS DATA SUGGEST PCPN WILL BECOME DISORGANIZED THROUGH THE PREDAWN HOURS AS BEST MID/UPPER FORCING SLIDES OFF TO THE NORTH AND FNTL WAVE LIFTS NEWD FM SW PA. WV/IR SATL DATA ALSO SHOWS DRY SLOT SURGING NEWD INTO THE UPPER OH VLY WHICH SHOULD ALSO HELP TO CUT OFF PCPN TO SOME EXTENT. AN UNSEASONABLY MILD EARLY DEC NIGHT WILL CONTINUE OVR MUCH OF THE CWA WITH READINGS IN THE MID 40S TO MID 50S. THE EXCEPTION WILL BE OVR THE FAR NW AS COLDER AIR WRAPS IN FM THE NORTH. MARGINAL BL AND LLVL WET BULBS SUGGEST A LOW CHANCE FOR RA/SN MIX WITH SFC TEMPS BOTTOMING OUT IN THE MID TO UPPER 30S. PREVIOUS DISC FROM 1059 PM... SFC COLD FRONT HAS STALLED OUT TEMPORARILY THIS EVENING...JUST TO THE SE OF INTERSTATE 90 IN FAR NWRN PENN. 03Z SFC OBS...AND THE 02Z RUC DISPLAY A VERY TIGHT...MEAN SFC-925 MB TEMP GRADIENT FROM KERI...SW TO KCMH. RUC INDICATES THAT THIS BOUNDARY WILL CRAWL EAST TO NEAR A KELZ...TO KDUJ AND KPIT LINE BY THE 10-12Z TUESDAY TIMEFRAME. THE RAIN AREA /THAT HAS BEEN STREAMING NE AND CONFINED NEAR...AND JUST IN THE WAKE OF THE FRONT/ HAS STARTED TO QUICKLY EXPAND EAST AHEAD OF THIS BOUNDARY /NEARING KUNV ATTM AND LIKELY BEGINNING IN KIPT BY 05Z/...AS THE NOSE OF A STRENGTHENING 50-55KT/850 MB SWRLY JET MOVES NORTH ACROSS THE ALLEGHENY PLATEAU. THIS LLJ ENERGY WILL BE AIDED BY INCREASING 850-700 UVVEL BENEATH PULSES OF UPPER LEVEL DIVERGENCE BENEATH THE RIGHT ENTRANCE REGION OF A 110 KT JET LIFTING INTO NEW YORK STATE TOWARD DAYBREAK. RUC AND SREF MEAN...12-HOUR QPF IS AROUND 0.50 OF AN INCH ACROSS OUR FAR NW ZONES /NEAR KBFD/...AND BETWEEN 0.10 AND 0.25 OF AN INCH THROUGHOUT THE CENTRAL COUNTIES. RAINFL AMOUNTS OVER MUCH OF THE LOWER SUSQUEHANNA VALLEY REGION WILL STAY AOB 0.10 IF AN INCH THROUGH 12Z TUESDAY. LATEST NAM/HRRR SPREADS THE PRECIP GRADUALLY TO THE EAST ACROSS THE REST OF THE SCENT MTNS AND SUSQ VALLEY THROUGH THE PREDAWN HOURS. TIMING OF HIGHEST CHCS FOR PRECIP IS BETWEEN 05-10Z TUES ACROSS THE NW HALF OF THE CWA...AND DURING THE MID TO LATE MORNING IN THE SE ZONES. RUC 925 MB WET BULB TEMPS SINK TO A MIN OF ABOUT PLUS 1-2C ACROSS THE FAR NW BY 12Z TUESDAY...SO A CHANG-OVER TO SLEET/WET SNOW IS NOT EXPECTED AS FAR EAST AS WARREN OR KBFD. POPS WILL DECREASE AROUND OR SHORTLY AFTER DAYBREAK TUESDAY IN THE FAR NW. THE EXTENSIVE CLOUD COVER AND CONTINUED LIGHT SOUTH TO SOUTHEAST SFC WINDS ACROSS MOST OF THE AREA SHOULD KEEP TEMPS FROM FALLING VERY MUCH TONIGHT. TEMPS WILL FALL AN ADDITIONAL SEVERAL DEG F ACROSS THE HIGHER TERRAIN OF THE NORTH AND WEST...BUT WILL BE STEADY OR FALL JUST A FEW DEGREES ELSEWHERE AS MOISTURE BUILDS AND CLOUDS LOWER SUBSTANTIALLY. WILL JUST MENTION PATCHY 2-3SM FOG IN THE WHOLE AREA FOR THE TIME BEING. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... A FAIRLY PROGRESSIVE AND DYNAMIC H5/H7 SHORTWAVE TROUGH WILL STREAK EWD FM THE LWR MS VLY ACRS THE SRN APPALACHIANS TO THE MID- ATLC SEABOARD WED/WED NGT INTO EARLY THURS. AS THE MID/UPPER LEVEL TROUGH TAKES ON A NEGATIVE TILT...STRONG HEIGHT FALLS AND UPPER LEVEL DIVERGENCE WILL INDUCE SFC LOW DEVELOPMENT INVOF THE CAROLINAS/VA VCNTY WED NGT. THE DEEP LAYER ASCENT AND FAVORABLE JET DYNAMICS WILL LEAD TO LOWERING SNOW LEVELS AS COLD AIR WRAPS INTO THE SYS AS IT ROTATES UP ACRS ERN NY INTO NEW ENGLAND. GUID INDICATES DECENT CLUSTERING WITH THE SFC LOW BUT LINGERING TIMING AND TRACK UNCERTAINTY STILL REMAINS...ALTHOUGH THE SPREADS HAVE NARROWED CONSIDERABLY FROM 24 HOURS AGO. THE PREFERENCE IS STILL TWD A FASTER PROGRESSION OF THE SYS OVERALL AND THE SREF AND GEFS MEANS APPEAR TO BE ADJUSTING IN THIS DIRECTION. WHILE THERE IS A MODEST INCREASE IN FORECASTER CONFIDENCE IN LIGHT OF THE NARROWING SPREADS AND GENERAL TREND TWD A CONSENSUS SOLN...THE RECENT POOR CONTINUITY AND LINGERING UNCERTAINTY /ESPECIALLY IN THE TRACK OF THE LOW/ LEADS TO BELOW AVG CONFIDENCE. IT APPEARS THAT A 12-HR PD OF MOD TO PERHAPS HVY PCPN WILL BE POSSIBLE OVR THE SRN AND ERN ZONES IN THE DEFORMATION ZONE AND COMMA HEAD LOCATED ON THE NW EDGE OF THE EVENTUAL SFC LOW TRACK. PCPN SHOULD CHANGEOVER FROM RAIN TO SNOW AS COLD AIR FILLS IN ON THE BACKSIDE OF THE DEEPENING SYS. THE GFS SFC LOW TRACK IS FURTHER EAST/OFFSHORE COMPARED TO THE NAM/ECMWF/CAN/GEFS...THUS BRINGING THE THREAT OF LESS SNOW COMPARED TO THE OTHER GUID...WHICH IS INDICATING A SOLID 0.50 TO 1 INCH OF LIQUID IN 12 HRS OVR MUCH OF SERN PA ENDING 12Z THURS. THE LOWER ELEVATIONS/VALLEYS WILL LKLY START AS RAIN AND TRANSITION OVR TO SNOW WHICH COULD LIMIT ACCUMS. MEANWHILE HIGHER ELEVATIONS SHOULD SEE HIGH PROBABILITIES FOR MORE SIGNIFICANT ACCUMS GIVEN LONGER DURATION. OVERALL... CONFIDENCE DID NOT QUITE MEET THE WATCH ISSUANCE THRESHOLD ALTHOUGH CONSIDERED ISSUING WSW WITH COLLABORATION FROM LWX AND PHI. FOR NOW WILL KEEP MENTION IN THE HWO MENTIONING LIGHT TO MODERATE ACCUMS POSSIBLE. IT SHOULD BE NOTED THAT MOD TO HVY ACCUMS IN EXCESS OF 6 INCHES ARE ALSO POSSIBLE GIVEN MDL QPFS...WITH A LOWER RISK/PROBABILITY OUTCOME DUE TO THE AFOREMENTIONED UNCERTAINTY IN THE TRACK/TIMING AND THERMAL PROFILES/ELEVATION DEPENDENCE. THE LOW WILL MOVE OFF THE SOUTHERN NEW ENGLAND COAST BY DAYBREAK THURS WITH A BRISK AND COLD WLY FLOW REGIME PREVAILING OVR CNTRL PA DURING THE DAY. THIS SHOULD TRANSLATE INTO A BRIEF PD OF MTN SNOW SHOWERS EARLY GIVEN FAVORABLE DOWNWIND LAKE TRAJECTORIES AND COLD CYC FLOW ALOFT. THE LLVL FLOW WILL BACK MORE TO THE WSW THURS NGT INTO FRI AS A NRN STREAM TROUGH ROTATES INTO THE UPPER MIDWEST AROUND THE BASE OF HUDSON BAY VORTEX. && .LONG TERM /FRIDAY THROUGH MONDAY/... A MSTR-STARVED COLD FNT MARKING THE LEADING EDGE OF THE UPPER MIDWEST H5 TROUGH AND ACCOMPANYING SEASONABLY COLD /-12 TO -14C AT 850MB/ AIR ALOFT WILL CROSS THE AREA FRI NGT...WITH LITTLE FANFARE OTHER THAN SOME LAKE ENHANCED/UPSLOPE SNOW SHOWERS ALONG THE ALLEGHENIES. TEMPERATURES SHOULD BOTTOM ON SATURDAY AS THE CORE UPPER TROUGH AXIS MOVES OVERHEAD. HIGH PRES WILL OVERSPREAD THE REGION ON SUN AND DOMINATE THE PATTERN INTO EARLY NEXT WEEK. RETURN FLOW AROUND THE HIGH SHOULD LEAD TO MODERATING TEMPS WITH FAIR WEATHER PERSISTING THROUGH MONDAY. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... A COLD FRONT...LOCATED EXTENDING ACROSS THE WESTERN HALF OF PA AT 07Z...WILL PUSH SLOWLY SOUTHEAST ACROSS PENNSYLVANIA LATE TONIGHT...ACCOMPANIED BY OCNL LGT RAIN. CURRENT ANALYSIS SHOWS IFR CONDS CONFINED TO NW PA...BEHIND FRONT. HOWEVER...AS THE FRONT PUSHES EAST...EXPECT DETERIORATING FLYING CONDS TO SPREAD OVER THE REST OF PA. SHORT RANGE MDL DATA SUPPORTS IFR CONDS BECOMING WIDESPREAD ACROSS THE REST OF CENTRAL PA AFTER 09Z. MODEST IMPROVEMENT IS EXPECTED BY TUESDAY AFTN...AS FRONT BEGINS TO PUSH EAST OF THE REGION. MANY LOCATIONS WILL LIKELY IMPROVE TO MVFR CONDS. HOWEVER...RESIDUAL MOISTURE ASCENDING THE W MTNS COULD LEAD TO LINGERING IFR CIGS AT JST AND BFD THRU TUE NIGHT. OUTLOOK... WED...AM LOW CIGS POSSIBLE W MTNS. WED NIGHT...RAIN/SNOW AND LOW CIGS POSSIBLE SOUTHEAST. THU...NO SIG WX EXPECTED. FRI...PM SHSN POSSIBLE NW MTNS. SAT...NO SIG WX EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...STEINBUGL NEAR TERM...LAMBERT/STEINBUGL SHORT TERM...STEINBUGL LONG TERM...STEINBUGL AVIATION...FITZGERALD/CERU
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
229 AM EST TUE DEC 6 2011 .SYNOPSIS... A MOIST SOUTHWEST FLOW ALOFT WILL INTERACT WITH A SLOW MOVING WAVY FRONTAL BOUNDARY TO BRING UNSETTLED CONDITIONS TO THE AREA THROUGH MID WEEK. UPPER LEVEL ENERGY MIGRATING FROM THE ROCKIES EASTWARD ACROSS THE CENTRAL PLAINS STATES INTO THE APPALACHIANS SHOULD INDUCE A MORE DEFINED AREA OF LOW PRESSURE OVER THE SOUTHERN MID-ATLANTIC REGION BY WEDNESDAY NIGHT BEFORE LIFTING NORTHEAST OFF THE SOUTHERN NEW ENGLAND COAST EARLY THURSDAY MORNING. COLD AND BRISK WEATHER IS ANTICIPATED FROM LATER THIS WEEK INTO THE FIRST PART OF THE WEEKEND...WITH SOME MODERATION IN TEMPERATURES LIKELY HEADING INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 8 AM THIS MORNING/... AT 0530Z THE SFC COLD FRONT WAS LOCATED JUST E OF A JHW-YNG-ZZV LINE. RDR SHOWS GREATEST CVRG OR LGT/MOD RNFL MOVG ACRS THE NW AND NCNTRL MTNS. MDL AND CIWS DATA SUGGEST PCPN WILL BECOME DISORGANIZED THROUGH THE PREDAWN HOURS AS BEST MID/UPPER FORCING SLIDES OFF TO THE NORTH AND FNTL WAVE LIFTS NEWD FM SW PA. WV/IR SATL DATA ALSO SHOWS DRY SLOT SURGING NEWD INTO THE UPPER OH VLY WHICH SHOULD ALSO HELP TO CUT OFF PCPN TO SOME EXTENT. AN UNSEASONABLY MILD EARLY DEC NIGHT WILL CONTINUE OVR MUCH OF THE CWA WITH READINGS IN THE MID 40S TO MID 50S. THE EXCEPTION WILL BE OVR THE FAR NW AS COLDER AIR WRAPS IN FM THE NORTH. MARGINAL BL AND LLVL WET BULBS SUGGEST A LOW CHANCE FOR RA/SN MIX WITH SFC TEMPS BOTTOMING OUT IN THE MID TO UPPER 30S. PREVIOUS DISC FROM 1059 PM... SFC COLD FRONT HAS STALLED OUT TEMPORARILY THIS EVENING...JUST TO THE SE OF INTERSTATE 90 IN FAR NWRN PENN. 03Z SFC OBS...AND THE 02Z RUC DISPLAY A VERY TIGHT...MEAN SFC-925 MB TEMP GRADIENT FROM KERI...SW TO KCMH. RUC INDICATES THAT THIS BOUNDARY WILL CRAWL EAST TO NEAR A KELZ...TO KDUJ AND KPIT LINE BY THE 10-12Z TUESDAY TIMEFRAME. THE RAIN AREA /THAT HAS BEEN STREAMING NE AND CONFINED NEAR...AND JUST IN THE WAKE OF THE FRONT/ HAS STARTED TO QUICKLY EXPAND EAST AHEAD OF THIS BOUNDARY /NEARING KUNV ATTM AND LIKELY BEGINNING IN KIPT BY 05Z/...AS THE NOSE OF A STRENGTHENING 50-55KT/850 MB SWRLY JET MOVES NORTH ACROSS THE ALLEGHENY PLATEAU. THIS LLJ ENERGY WILL BE AIDED BY INCREASING 850-700 UVVEL BENEATH PULSES OF UPPER LEVEL DIVERGENCE BENEATH THE RIGHT ENTRANCE REGION OF A 110 KT JET LIFTING INTO NEW YORK STATE TOWARD DAYBREAK. RUC AND SREF MEAN...12-HOUR QPF IS AROUND 0.50 OF AN INCH ACROSS OUR FAR NW ZONES /NEAR KBFD/...AND BETWEEN 0.10 AND 0.25 OF AN INCH THROUGHOUT THE CENTRAL COUNTIES. RAINFL AMOUNTS OVER MUCH OF THE LOWER SUSQUEHANNA VALLEY REGION WILL STAY AOB 0.10 IF AN INCH THROUGH 12Z TUESDAY. LATEST NAM/HRRR SPREADS THE PRECIP GRADUALLY TO THE EAST ACROSS THE REST OF THE SCENT MTNS AND SUSQ VALLEY THROUGH THE PREDAWN HOURS. TIMING OF HIGHEST CHCS FOR PRECIP IS BETWEEN 05-10Z TUES ACROSS THE NW HALF OF THE CWA...AND DURING THE MID TO LATE MORNING IN THE SE ZONES. RUC 925 MB WET BULB TEMPS SINK TO A MIN OF ABOUT PLUS 1-2C ACROSS THE FAR NW BY 12Z TUESDAY...SO A CHANG-OVER TO SLEET/WET SNOW IS NOT EXPECTED AS FAR EAST AS WARREN OR KBFD. POPS WILL DECREASE AROUND OR SHORTLY AFTER DAYBREAK TUESDAY IN THE FAR NW. THE EXTENSIVE CLOUD COVER AND CONTINUED LIGHT SOUTH TO SOUTHEAST SFC WINDS ACROSS MOST OF THE AREA SHOULD KEEP TEMPS FROM FALLING VERY MUCH TONIGHT. TEMPS WILL FALL AN ADDITIONAL SEVERAL DEG F ACROSS THE HIGHER TERRAIN OF THE NORTH AND WEST...BUT WILL BE STEADY OR FALL JUST A FEW DEGREES ELSEWHERE AS MOISTURE BUILDS AND CLOUDS LOWER SUBSTANTIALLY. WILL JUST MENTION PATCHY 2-3SM FOG IN THE WHOLE AREA FOR THE TIME BEING. && .SHORT TERM /8 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... FRONT INCHES IT/S WAY ACROSS THE REST OF CENTRAL/ERN PENN ON TUES. NO SIGNIFICANT WAVES DEVELOP ALONG IT...SO GENERALLY SCT SHRA WILL FALL THROUGH THE DAY ON TUESDAY. LIKELIHOOD OF SHOWERS FAIRLY HIGH DURING THE WHOLE DAY...AND PINNING A TIME FOR HIGHEST POPS NOT EASY. WILL PAINT THE HIGHER POPS IN THE AFTN AS PRESSURE LOWER ON THE FRONT SLIGHTLY. THE MORE-ORGANIZED SHOWERS AND HIGHER POPS SHOULD BE IN THE SERN HALF OF THE FORECAST AREA. UPPER TROUGH STAYS HIGHLY POSITIVE AND DRAGS ALONG. THUS...LITTLE CHANGE IN THE SFC PATTERN AND FORCING IS SEEN FOR EARLY TUES NIGHT. HOWEVER...THE SFC BOUNDARY DOES SEEM TO CLEAR THE FORECAST AREA TUES NIGHT...AND WILL LOWER POPS OVER MUCH OF THE AREA IN THE SECOND HALF OF THE NIGHT. UPSLOPE IN THE WEST COULD FORCE ENOUGH MOISTURE UP INTO THE HILLS TO GENERATE SHOWERS...BUT P-TYPE IS QUESTIONABLE. 8H TEMPS ARE ABOVE FZG THROUGH 06-09Z IN THE WRN HIGHLANDS...BUT SFC TEMPS SHOULD FOLLOW ALONG IN LOCK STEP AND GET INTO THE 20S NW AND NEAR FZG IN THE LAURELS. WILL THEREFORE MENTION SHSN MIXING IN TO THE SCT SHRA IN THE W AFTER MIDNIGHT. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... A POSITIVE TILTED LONG WAVE TROUGH EXTENDING FROM THE GREAT LAKES INTO TX ON WED WILL BRING DEEP BROAD SWLY FLOW ALOFT. NAM/EC AND GEFS MODEL/ENSEMBLE GUIDANCE HAS TRENDED TOWARD GOOD AGREEMENT FOR A WAVE OF LOW PRESSURE TO DEVELOP OVER THE SE STATES WEDNESDAY /ALONG THE STALLED OUT FRONT THAT/S PROGGED TO EXTEND NE TO THE NEW JERSEY COAST/. GFS /WHICH SEVERAL RUNS AGO...DISPLAYED PRACTICALLY THE LONE CHC OF A LIGHT TO MODERATE WINTER WEATHER EVENT ACROSS OUR SE AND PERHAPS CENTRAL CWA/ HAS BECOME ONE OF THE FEW OUTLIER SOLUTIONS. /THE OTHER BEING THE 12Z CANADIAN GEM MODEL/. 12Z EC...18Z GEFS...AND THE 18Z/00Z NAM ARE IN PRETTY GOOD AGREEMENT AND INDICATE THE POTENTIAL FOR A FEW TO SVRL INCHES OF WET SNOW NEAR THE I-81 CORRIDOR. THE 21Z SREF HASN/T CHANGED MUCH FROM THE 15Z VERSION...WITH THE NW EDGE OF ITS 0.25 INCH STORM TOTAL LEQ QPF CONTOUR FROM KMRB...TO NEAR KMUI AND KABE. THE COMPACT...OPEN /AND PERHAPS SLIGHTLY NEG TILT/ UPPER SHORTWAVE THAT WILL BE LIFTING QUICKLY NE OUT OF THE SOUTHERN U.S. WILL NOT HAVE A CHANCE TO AMPLIFY SIGNIFICANTLY...CONSIDERING THE DEEP VORTEX DRIFTING OVER HUDSON BAY...WITH A FAST WESTERLY UPPER FLOW ACROSS THE NRN U.S. AND UPPER GLAKES REGION. HOWEVER...THE WELL- DEFINED ENTRANCE REGION OF A POTENT 140 KT UPPER JET FROM PENN TO SRN NEW ENGLAND WILL HELP TO CREATE A POTENTIAL PERIOD OF MODERATE TO STRONG UVVEL AS JET MAX WITH THE LIFTING SHORTWAVE LINKS UP. BUMPED UP POPS TO LIKELY ACROSS THE FAR SE WITH A TIGHT POP GRADIENT BETWEEN I-81 AND A KAOO...KUNV AND KIPT LINE. PRECIP TYPE WILL LIKELY START AS A COLD LIGHT RAIN IN THE SOUTH...WITH SOME AREAS OF LIGHT RAIN/WET SNOW DEVELOPING FROM THE HIGHER MID CLOUD BASE ACROSS THE REGION NORTHWEST OF I-81 BY LATE EVENING. MENTIONED THE CHC FOR A LIGHT TO MDT WET SNOW FOR OUR SE ZONES IN THE HAZ WEATHER OUTLOOK. MODELS REBOUND WITH BETTER CONSENSUS AFTER THIS SYSTEM HEADED INTO THE WEEKEND. A NORTHERN STREAM COLD FRONT MOVES THROUGH FRI TURNING FLOW WESTERLY AND BRINGING COLD AND BRISK CONDITIONS TO START THE WEEKEND. TEMPS WILL BE ABOUT 5F BELOW NORMAL /WHICH WILL BE NOTICEABLE AFTER OUR RUN OF RELATIVELY MILD TEMPS/ AND LAKE EFFECT/OROGRAPHIC SNOW SHOWERS WILL DEVELOP FRI NIGHT INTO SAT...MAINLY CONFINED TO THE NW MTNS. HIGH PRES RETURNS FOR SUNDAY/MONDAY WHICH WILL ALLOW TEMPERATURES TO GRADUALLY MODERATE WITH FAIR WEATHER. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... A COLD FRONT...LOCATED EXTENDING ACROSS THE WESTERN HALF OF PA AT 07Z...WILL PUSH SLOWLY SOUTHEAST ACROSS PENNSYLVANIA LATE TONIGHT...ACCOMPANIED BY OCNL LGT RAIN. CURRENT ANALYSIS SHOWS IFR CONDS CONFINED TO NW PA...BEHIND FRONT. HOWEVER...AS THE FRONT PUSHES EAST...EXPECT DETERIORATING FLYING CONDS TO SPREAD OVER THE REST OF PA. SHORT RANGE MDL DATA SUPPORTS IFR CONDS BECOMING WIDESPREAD ACROSS THE REST OF CENTRAL PA AFTER 09Z. MODEST IMPROVEMENT IS EXPECTED BY TUESDAY AFTN...AS FRONT BEGINS TO PUSH EAST OF THE REGION. MANY LOCATIONS WILL LIKELY IMPROVE TO MVFR CONDS. HOWEVER...RESIDUAL MOISTURE ASCENDING THE W MTNS COULD LEAD TO LINGERING IFR CIGS AT JST AND BFD THRU TUE NIGHT. OUTLOOK... WED...AM LOW CIGS POSSIBLE W MTNS. WED NIGHT...RAIN/SNOW AND LOW CIGS POSSIBLE SOUTHEAST. THU...NO SIG WX EXPECTED. FRI...PM SHSN POSSIBLE NW MTNS. SAT...NO SIG WX EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT/STEINBUGL NEAR TERM...LAMBERT/STEINBUGL SHORT TERM...DANGELO/LAMBERT LONG TERM...LAMBERT/RXR/STEINBUGL AVIATION...FITZGERALD/CERU
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
1254 AM EST TUE DEC 6 2011 .SYNOPSIS... A MOIST SOUTHWEST FLOW ALOFT WILL INTERACT WITH A SLOW MOVING WAVY FRONTAL BOUNDARY TO BRING UNSETTLED CONDITIONS TO THE AREA THROUGH MID WEEK. UPPER LEVEL ENERGY MIGRATING FROM THE ROCKIES EASTWARD ACROSS THE CENTRAL PLAINS STATES INTO THE APPALACHIANS SHOULD INDUCE A MORE DEFINED AREA OF LOW PRESSURE OVER THE SOUTHERN MID-ATLANTIC REGION BY WEDNESDAY NIGHT BEFORE LIFTING NORTHEAST OFF THE SOUTHERN NEW ENGLAND COAST EARLY THURSDAY MORNING. COLD AND BRISK WEATHER IS ANTICIPATED FROM LATER THIS WEEK INTO THE FIRST PART OF THE WEEKEND...WITH SOME MODERATION IN TEMPERATURES LIKELY HEADING INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 8 AM THIS MORNING/... AT 0530Z THE SFC COLD FRONT WAS LOCATED JUST E OF A JHW-YNG-ZZV LINE. RDR SHOWS GREATEST CVRG OR LGT/MOD RNFL MOVG ACRS THE NW AND NCNTRL MTNS. MDL AND CIWS DATA SUGGEST PCPN WILL BECOME DISORGANIZED THROUGH THE PREDAWN HOURS AS BEST MID/UPPER FORCING SLIDES OFF TO THE NORTH AND FNTL WAVE LIFTS NEWD FM SW PA. WV/IR SATL DATA ALSO SHOWS DRY SLOT SURGING NEWD INTO THE UPPER OH VLY WHICH SHOULD ALSO HELP TO CUT OFF PCPN TO SOME EXTENT. AN UNSEASONABLY MILD EARLY DEC NIGHT WILL CONTINUE OVR MUCH OF THE CWA WITH READINGS IN THE MID 40S TO MID 50S. THE EXCEPTION WILL BE OVR THE FAR NW AS COLDER AIR WRAPS IN FM THE NORTH. MARGINAL BL AND LLVL WET BULBS SUGGEST A LOW CHANCE FOR RA/SN MIX WITH SFC TEMPS BOTTOMING OUT IN THE MID TO UPPER 30S. PREVIOUS DISC FROM 1059 PM... SFC COLD FRONT HAS STALLED OUT TEMPORARILY THIS EVENING...JUST TO THE SE OF INTERSTATE 90 IN FAR NWRN PENN. 03Z SFC OBS...AND THE 02Z RUC DISPLAY A VERY TIGHT...MEAN SFC-925 MB TEMP GRADIENT FROM KERI...SW TO KCMH. RUC INDICATES THAT THIS BOUNDARY WILL CRAWL EAST TO NEAR A KELZ...TO KDUJ AND KPIT LINE BY THE 10-12Z TUESDAY TIMEFRAME. THE RAIN AREA /THAT HAS BEEN STREAMING NE AND CONFINED NEAR...AND JUST IN THE WAKE OF THE FRONT/ HAS STARTED TO QUICKLY EXPAND EAST AHEAD OF THIS BOUNDARY /NEARING KUNV ATTM AND LIKELY BEGINNING IN KIPT BY 05Z/...AS THE NOSE OF A STRENGTHENING 50-55KT/850 MB SWRLY JET MOVES NORTH ACROSS THE ALLEGHENY PLATEAU. THIS LLJ ENERGY WILL BE AIDED BY INCREASING 850-700 UVVEL BENEATH PULSES OF UPPER LEVEL DIVERGENCE BENEATH THE RIGHT ENTRANCE REGION OF A 110 KT JET LIFTING INTO NEW YORK STATE TOWARD DAYBREAK. RUC AND SREF MEAN...12-HOUR QPF IS AROUND 0.50 OF AN INCH ACROSS OUR FAR NW ZONES /NEAR KBFD/...AND BETWEEN 0.10 AND 0.25 OF AN INCH THROUGHOUT THE CENTRAL COUNTIES. RAINFL AMOUNTS OVER MUCH OF THE LOWER SUSQUEHANNA VALLEY REGION WILL STAY AOB 0.10 IF AN INCH THROUGH 12Z TUESDAY. LATEST NAM/HRRR SPREADS THE PRECIP GRADUALLY TO THE EAST ACROSS THE REST OF THE SCENT MTNS AND SUSQ VALLEY THROUGH THE PREDAWN HOURS. TIMING OF HIGHEST CHCS FOR PRECIP IS BETWEEN 05-10Z TUES ACROSS THE NW HALF OF THE CWA...AND DURING THE MID TO LATE MORNING IN THE SE ZONES. RUC 925 MB WET BULB TEMPS SINK TO A MIN OF ABOUT PLUS 1-2C ACROSS THE FAR NW BY 12Z TUESDAY...SO A CHANG-OVER TO SLEET/WET SNOW IS NOT EXPECTED AS FAR EAST AS WARREN OR KBFD. POPS WILL DECREASE AROUND OR SHORTLY AFTER DAYBREAK TUESDAY IN THE FAR NW. THE EXTENSIVE CLOUD COVER AND CONTINUED LIGHT SOUTH TO SOUTHEAST SFC WINDS ACROSS MOST OF THE AREA SHOULD KEEP TEMPS FROM FALLING VERY MUCH TONIGHT. TEMPS WILL FALL AN ADDITIONAL SEVERAL DEG F ACROSS THE HIGHER TERRAIN OF THE NORTH AND WEST...BUT WILL BE STEADY OR FALL JUST A FEW DEGREES ELSEWHERE AS MOISTURE BUILDS AND CLOUDS LOWER SUBSTANTIALLY. WILL JUST MENTION PATCHY 2-3SM FOG IN THE WHOLE AREA FOR THE TIME BEING. && .SHORT TERM /8 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... FRONT INCHES IT/S WAY ACROSS THE REST OF CENTRAL/ERN PENN ON TUES. NO SIGNIFICANT WAVES DEVELOP ALONG IT...SO GENERALLY SCT SHRA WILL FALL THROUGH THE DAY ON TUESDAY. LIKELIHOOD OF SHOWERS FAIRLY HIGH DURING THE WHOLE DAY...AND PINNING A TIME FOR HIGHEST POPS NOT EASY. WILL PAINT THE HIGHER POPS IN THE AFTN AS PRESSURE LOWER ON THE FRONT SLIGHTLY. THE MORE-ORGANIZED SHOWERS AND HIGHER POPS SHOULD BE IN THE SERN HALF OF THE FORECAST AREA. UPPER TROUGH STAYS HIGHLY POSITIVE AND DRAGS ALONG. THUS...LITTLE CHANGE IN THE SFC PATTERN AND FORCING IS SEEN FOR EARLY TUES NIGHT. HOWEVER...THE SFC BOUNDARY DOES SEEM TO CLEAR THE FORECAST AREA TUES NIGHT...AND WILL LOWER POPS OVER MUCH OF THE AREA IN THE SECOND HALF OF THE NIGHT. UPSLOPE IN THE WEST COULD FORCE ENOUGH MOISTURE UP INTO THE HILLS TO GENERATE SHOWERS...BUT P-TYPE IS QUESTIONABLE. 8H TEMPS ARE ABOVE FZG THROUGH 06-09Z IN THE WRN HIGHLANDS...BUT SFC TEMPS SHOULD FOLLOW ALONG IN LOCK STEP AND GET INTO THE 20S NW AND NEAR FZG IN THE LAURELS. WILL THEREFORE MENTION SHSN MIXING IN TO THE SCT SHRA IN THE W AFTER MIDNIGHT. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... A POSITIVE TILTED LONG WAVE TROUGH EXTENDING FROM THE GREAT LAKES INTO TX ON WED WILL BRING DEEP BROAD SWLY FLOW ALOFT. NAM/EC AND GEFS MODEL/ENSEMBLE GUIDANCE HAS TRENDED TOWARD GOOD AGREEMENT FOR A WAVE OF LOW PRESSURE TO DEVELOP OVER THE SE STATES WEDNESDAY /ALONG THE STALLED OUT FRONT THAT/S PROGGED TO EXTEND NE TO THE NEW JERSEY COAST/. GFS /WHICH SEVERAL RUNS AGO...DISPLAYED PRACTICALLY THE LONE CHC OF A LIGHT TO MODERATE WINTER WEATHER EVENT ACROSS OUR SE AND PERHAPS CENTRAL CWA/ HAS BECOME ONE OF THE FEW OUTLIER SOLUTIONS. /THE OTHER BEING THE 12Z CANADIAN GEM MODEL/. 12Z EC...18Z GEFS...AND THE 18Z/00Z NAM ARE IN PRETTY GOOD AGREEMENT AND INDICATE THE POTENTIAL FOR A FEW TO SVRL INCHES OF WET SNOW NEAR THE I-81 CORRIDOR. THE 21Z SREF HASN/T CHANGED MUCH FROM THE 15Z VERSION...WITH THE NW EDGE OF ITS 0.25 INCH STORM TOTAL LEQ QPF CONTOUR FROM KMRB...TO NEAR KMUI AND KABE. THE COMPACT...OPEN /AND PERHAPS SLIGHTLY NEG TILT/ UPPER SHORTWAVE THAT WILL BE LIFTING QUICKLY NE OUT OF THE SOUTHERN U.S. WILL NOT HAVE A CHANCE TO AMPLIFY SIGNIFICANTLY...CONSIDERING THE DEEP VORTEX DRIFTING OVER HUDSON BAY...WITH A FAST WESTERLY UPPER FLOW ACROSS THE NRN U.S. AND UPPER GLAKES REGION. HOWEVER...THE WELL- DEFINED ENTRANCE REGION OF A POTENT 140 KT UPPER JET FROM PENN TO SRN NEW ENGLAND WILL HELP TO CREATE A POTENTIAL PERIOD OF MODERATE TO STRONG UVVEL AS JET MAX WITH THE LIFTING SHORTWAVE LINKS UP. BUMPED UP POPS TO LIKELY ACROSS THE FAR SE WITH A TIGHT POP GRADIENT BETWEEN I-81 AND A KAOO...KUNV AND KIPT LINE. PRECIP TYPE WILL LIKELY START AS A COLD LIGHT RAIN IN THE SOUTH...WITH SOME AREAS OF LIGHT RAIN/WET SNOW DEVELOPING FROM THE HIGHER MID CLOUD BASE ACROSS THE REGION NORTHWEST OF I-81 BY LATE EVENING. MENTIONED THE CHC FOR A LIGHT TO MDT WET SNOW FOR OUR SE ZONES IN THE HAZ WEATHER OUTLOOK. MODELS REBOUND WITH BETTER CONSENSUS AFTER THIS SYSTEM HEADED INTO THE WEEKEND. A NORTHERN STREAM COLD FRONT MOVES THROUGH FRI TURNING FLOW WESTERLY AND BRINGING COLD AND BRISK CONDITIONS TO START THE WEEKEND. TEMPS WILL BE ABOUT 5F BELOW NORMAL /WHICH WILL BE NOTICEABLE AFTER OUR RUN OF RELATIVELY MILD TEMPS/ AND LAKE EFFECT/OROGRAPHIC SNOW SHOWERS WILL DEVELOP FRI NIGHT INTO SAT...MAINLY CONFINED TO THE NW MTNS. HIGH PRES RETURNS FOR SUNDAY/MONDAY WHICH WILL ALLOW TEMPERATURES TO GRADUALLY MODERATE WITH FAIR WEATHER. && .AVIATION /05Z TUESDAY THROUGH SATURDAY/... A COLD FRONT...LOCATED OVER NW PA AT 03Z...WILL PUSH SLOWLY SOUTHEAST ACROSS PENNSYLVANIA LATE TONIGHT...ACCOMPANIED BY OCNL LGT RAIN. CURRENT ANALYSIS SHOWS IFR CONDS CONFINED TO NW PA...BEHIND FRONT. HOWEVER...AS THE FRONT PUSHES EAST...EXPECT DETERIORATING FLYING CONDS TO SPREAD OVER THE REST OF PA. SHORT RANGE MDL DATA SUPPORTS IFR CONDS DEVELOPING AT BFD BY 06Z...THEN BECOMING WIDESPREAD ACROSS THE REST OF CENTRAL PA TOWARDS DAWN. MODEST IMPROVEMENT IS EXPECTED BY TUESDAY AFTN...AS FRONT BEGINS TO PUSH EAST OF THE REGION. MANY LOCATIONS WILL LIKELY IMPROVE TO MVFR CONDS. HOWEVER...RESIDUAL MOISTURE ASCENDING THE W MTNS COULD LEAD TO LINGERING IFR CIGS AT JST AND BFD THRU TUE NIGHT. OUTLOOK... WED...AM LOW CIGS POSSIBLE W MTNS. WED NIGHT...RAIN/SNOW AND LOW CIGS POSSIBLE SOUTHEAST. THU...NO SIG WX EXPECTED. FRI...PM SHSN POSSIBLE NW MTNS. SAT...NO SIG WX EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT/STEINBUGL NEAR TERM...LAMBERT/STEINBUGL SHORT TERM...DANGELO/LAMBERT LONG TERM...LAMBERT/RXR/STEINBUGL AVIATION...FITZGERALD
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
1152 PM EST MON DEC 5 2011 .SYNOPSIS... A MOIST SOUTHWEST FLOW ALOFT WILL INTERACT WITH A SLOW MOVING FRONTAL BOUNDARY AND ONE OR MORE WAVES OF LOW PRESSURE TO BRING UNSETTLED CONDITIONS TO THE AREA THROUGH MID WEEK. COLD AND BRISK WEATHER IS ANTICIPATED FROM LATER THIS WEEK INTO THE WEEKEND. && .NEAR TERM /UNTIL 8 AM TUESDAY MORNING/... SFC COLD FRONT HAS STALLED OUT TEMPORARILY THIS EVENING...JUST TO THE SE OF INTERSTATE 90 IN FAR NWRN PENN. 03Z SFC OBS...AND THE 02Z RUC DISPLAY A VERY TIGHT...MEAN SFC-925 MB TEMP GRADIENT FROM KERI...SW TO KCMH. RUC INDICATES THAT THIS BOUNDARY WILL CRAWL EAST TO NEAR A KELZ...TO KDUJ AND KPIT LINE BY THE 10-12Z TUESDAY TIMEFRAME. THE RAIN AREA /THAT HAS BEEN STREAMING NE AND CONFINED NEAR...AND JUST IN THE WAKE OF THE FRONT/ HAS STARTED TO QUICKLY EXPAND EAST AHEAD OF THIS BOUNDARY /NEARING KUNV ATTM AND LIKELY BEGINNING IN KIPT BY 05Z/...AS THE NOSE OF A STRENGTHENING 50-55KT/850 MB SWRLY JET MOVES NORTH ACROSS THE ALLEGHENY PLATEAU. THIS LLJ ENERGY WILL BE AIDED BY INCREASING 850-700 UVVEL BENEATH PULSES OF UPPER LEVEL DIVERGENCE BENEATH THE RIGHT ENTRANCE REGION OF A 110 KT JET LIFTING INTO NEW YORK STATE TOWARD DAYBREAK. RUC AND SREF MEAN...12-HOUR QPF IS AROUND 0.50 OF AN INCH ACROSS OUR FAR NW ZONES /NEAR KBFD/...AND BETWEEN 0.10 AND 0.25 OF AN INCH THROUGHOUT THE CENTRAL COUNTIES. RAINFL AMOUNTS OVER MUCH OF THE LOWER SUSQUEHANNA VALLEY REGION WILL STAY AOB 0.10 IF AN INCH THROUGH 12Z TUESDAY. LATEST NAM/HRRR SPREADS THE PRECIP GRADUALLY TO THE EAST ACROSS THE REST OF THE SCENT MTNS AND SUSQ VALLEY THROUGH THE PREDAWN HOURS. TIMING OF HIGHEST CHCS FOR PRECIP IS BETWEEN 05-10Z TUES ACROSS THE NW HALF OF THE CWA...AND DURING THE MID TO LATE MORNING IN THE SE ZONES. RUC 925 MB WET BULB TEMPS SINK TO A MIN OF ABOUT PLUS 1-2C ACROSS THE FAR NW BY 12Z TUESDAY...SO A CHANG-OVER TO SLEET/WET SNOW IS NOT EXPECTED AS FAR EAST AS WARREN OR KBFD. POPS WILL DECREASE AROUND OR SHORTLY AFTER DAYBREAK TUESDAY IN THE FAR NW. THE EXTENSIVE CLOUD COVER AND CONTINUED LIGHT SOUTH TO SOUTHEAST SFC WINDS ACROSS MOST OF THE AREA SHOULD KEEP TEMPS FROM FALLING VERY MUCH TONIGHT. TEMPS WILL FALL AN ADDITIONAL SEVERAL DEG F ACROSS THE HIGHER TERRAIN OF THE NORTH AND WEST...BUT WILL BE STEADY OR FALL JUST A FEW DEGREES ELSEWHERE AS MOISTURE BUILDS AND CLOUDS LOWER SUBSTANTIALLY. WILL JUST MENTION PATCHY 2-3SM FOG IN THE WHOLE AREA FOR THE TIME BEING. && .SHORT TERM /8 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... FRONT INCHES IT/S WAY ACROSS THE REST OF CENTRAL/ERN PENN ON TUES. NO SIGNIFICANT WAVES DEVELOP ALONG IT...SO GENERALLY SCT SHRA WILL FALL THROUGH THE DAY ON TUESDAY. LIKELIHOOD OF SHOWERS FAIRLY HIGH DURING THE WHOLE DAY...AND PINNING A TIME FOR HIGHEST POPS NOT EASY. WILL PAINT THE HIGHER POPS IN THE AFTN AS PRESSURE LOWER ON THE FRONT SLIGHTLY. THE MORE-ORGANIZED SHOWERS AND HIGHER POPS SHOULD BE IN THE SERN HALF OF THE FORECAST AREA. UPPER TROUGH STAYS HIGHLY POSITIVE AND DRAGS ALONG. THUS...LITTLE CHANGE IN THE SFC PATTERN AND FORCING IS SEEN FOR EARLY TUES NIGHT. HOWEVER...THE SFC BOUNDARY DOES SEEM TO CLEAR THE FORECAST AREA TUES NIGHT...AND WILL LOWER POPS OVER MUCH OF THE AREA IN THE SECOND HALF OF THE NIGHT. UPSLOPE IN THE WEST COULD FORCE ENOUGH MOISTURE UP INTO THE HILLS TO GENERATE SHOWERS...BUT P-TYPE IS QUESTIONABLE. 8H TEMPS ARE ABOVE FZG THROUGH 06-09Z IN THE WRN HIGHLANDS...BUT SFC TEMPS SHOULD FOLLOW ALONG IN LOCK STEP AND GET INTO THE 20S NW AND NEAR FZG IN THE LAURELS. WILL THEREFORE MENTION SHSN MIXING IN TO THE SCT SHRA IN THE W AFTER MIDNIGHT. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... A POSITIVE TILTED LONG WAVE TROUGH EXTENDING FROM THE GREAT LAKES INTO TX ON WED WILL BRING DEEP BROAD SWLY FLOW ALOFT. NAM/EC AND GEFS MODEL/ENSEMBLE GUIDANCE HAS TRENDED TOWARD GOOD AGREEMENT FOR A WAVE OF LOW PRESSURE TO DEVELOP OVER THE SE STATES WEDNESDAY /ALONG THE STALLED OUT FRONT THAT/S PROGGED TO EXTEND NE TO THE NEW JERSEY COAST/. GFS /WHICH SEVERAL RUNS AGO...DISPLAYED PRACTICALLY THE LONE CHC OF A LIGHT TO MODERATE WINTER WEATHER EVENT ACROSS OUR SE AND PERHAPS CENTRAL CWA/ HAS BECOME ONE OF THE FEW OUTLIER SOLUTIONS. /THE OTHER BEING THE 12Z CANADIAN GEM MODEL/. 12Z EC...18Z GEFS...AND THE 18Z/00Z NAM ARE IN PRETTY GOOD AGREEMENT AND INDICATE THE POTENTIAL FOR A FEW TO SVRL INCHES OF WET SNOW NEAR THE I-81 CORRIDOR. THE 21Z SREF HASN/T CHANGED MUCH FROM THE 15Z VERSION...WITH THE NW EDGE OF ITS 0.25 INCH STORM TOTAL LEQ QPF CONTOUR FROM KMRB...TO NEAR KMUI AND KABE. THE COMPACT...OPEN /AND PERHAPS SLIGHTLY NEG TILT/ UPPER SHORTWAVE THAT WILL BE LIFTING QUICKLY NE OUT OF THE SOUTHERN U.S. WILL NOT HAVE A CHANCE TO AMPLIFY SIGNIFICANTLY...CONSIDERING THE DEEP VORTEX DRIFTING OVER HUDSON BAY...WITH A FAST WESTERLY UPPER FLOW ACROSS THE NRN U.S. AND UPPER GLAKES REGION. HOWEVER...THE WELL- DEFINED ENTRANCE REGION OF A POTENT 140 KT UPPER JET FROM PENN TO SRN NEW ENGLAND WILL HELP TO CREATE A POTENTIAL PERIOD OF MODERATE TO STRONG UVVEL AS JET MAX WITH THE LIFTING SHORTWAVE LINKS UP. BUMPED UP POPS TO LIKELY ACROSS THE FAR SE WITH A TIGHT POP GRADIENT BETWEEN I-81 AND A KAOO...KUNV AND KIPT LINE. PRECIP TYPE WILL LIKELY START AS A COLD LIGHT RAIN IN THE SOUT...WITH SOME AREAS OF LIGHT RAIN/WET SNOW DEVELOPING FROM THE HIGHER MID CLOUD BASE ACROSS THE REGION NORTHWEST OF I-81 BY LATE EVENING. MENTIONED THE CHC FOR A LIGHT TO MDT WET SNOW FOR OUR SE ZONES IN THE HAZ WEATHER OUTLOOK. MODELS REBOUND WITH BETTER CONSENSUS AFTER THIS SYSTEM HEADED INTO THE WEEKEND. A NORTHERN STREAM COLD FRONT MOVES THROUGH FRI TURNING FLOW WESTERLY AND BRINGING COLD AND BRISK CONDITIONS TO START THE WEEKEND. TEMPS WILL BE ABOUT 5F BELOW NORMAL /WHICH WILL BE NOTICEABLE AFTER OUR RUN OF RELATIVELY MILD TEMPS/ AND LAKE EFFECT/OROGRAPHIC SNOW SHOWERS WILL DEVELOP FRI NIGHT INTO SAT...MAINLY CONFINED TO THE NW MTNS. HIGH PRES RETURNS FOR SUNDAY/MONDAY WHICH WILL ALLOW TEMPERATURES TO GRADUALLY MODERATE WITH FAIR WEATHER. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... A COLD FRONT...LOCATED OVER NW PA AT 03Z...WILL PUSH SLOWLY SOUTHEAST ACROSS PENNSYLVANIA LATE TONIGHT...ACCOMPANIED BY OCNL LGT RAIN. CURRENT ANALYSIS SHOWS IFR CONDS CONFINED TO NW PA...BEHIND FRONT. HOWEVER...AS THE FRONT PUSHES EAST...EXPECT DETERIORATING FLYING CONDS TO SPREAD OVER THE REST OF PA. SHORT RANGE MDL DATA SUPPORTS IFR CONDS DEVELOPING AT BFD BY 06Z...THEN BECOMING WIDESPREAD ACROSS THE REST OF CENTRAL PA TOWARDS DAWN. MODEST IMPROVEMENT IS EXPECTED BY TUESDAY AFTN...AS FRONT BEGINS TO PUSH EAST OF THE REGION. MANY LOCATIONS WILL LIKELY IMPROVE TO MVFR CONDS. HOWEVER...RESIDUAL MOISTURE ASCENDING THE W MTNS COULD LEAD TO LINGERING IFR CIGS AT JST AND BFD THRU TUE NIGHT. OUTLOOK... WED...AM LOW CIGS POSSIBLE W MTNS. WED NIGHT...RAIN/SNOW AND LOW CIGS POSSIBLE SOUTHEAST. THU...NO SIG WX EXPECTED. FRI...PM SHSN POSSIBLE NW MTNS. SAT...NO SIG WX EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...DANGELO/LAMBERT LONG TERM...LAMBERT/RXR/STEINBUGL AVIATION...FITZGERALD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
756 PM CST WED DEC 7 2011 .DISCUSSION... WENT AHEAD AND INCREASE LOWS ABOUT 5 TO 8 DEGREES IN MOST SPOTS AS CLOUD COVER NOW SEEMS TO BE LOCKED IN FOR THE NIGHT...ESPECIALLY WITH THE APPROACH OF THE UPPER LEVEL WAVE IN THE NORTHERN ROCKIES. SO...BASICALLY LOOKING AT TEMPERATURES RANGING FROM AROUND THE MID TEENS TO LOWER 20S. DID ADD SOME FLURRIES AND A SLIGHT CHANCE FOR LIGHT SNOW IN THE FAR SOUTHERN CWA FRO 9-12Z AS THE RUC AND HRRR CONTINUE TO INDICATE THAT SOME SNOWFALL MAY GET SQUEEZED OUT OF THE MID LEVEL DECK MOVING SOUTHWARD. THIS DOES NOT SEEM COMPLETELY OUT OF THE QUESTION SINCE THE THERMAL PROFILE BECOMES MORE DENDRITIC IN THE STRONGER FORCING AT THIS TIME AND OUR LOWEST LEVELS ARE NOT COMPLETELY DRY SO COULD SEE SOME FLAKES WITH THE BETTER CHANCES NEAR THE MISSOURI RIVER FROM ABOUT 9Z THROUGH 15Z. /08 && .PREV DISCUSSION.../ISSUED AT 252 PM CST/ FRONTAL BOUNDARY CONTINUES TO DROP SOUTHWARD ACROSS THE REGION THIS AFTERNOON...AND WILL EXIT THE AREA BY THIS EVENING. MAIN CHALLENGE TONIGHT WILL BE IN TEMPERATURES...WITH STRONG COLD AIR ADVECTION BEHIND THE FRONT...MUTED BY CLOUD COVER EXPECTED TO BE OVER MUCH OF THE AREA DURING THE OVERNIGHT HOURS. WITH BREAKS IN THE CLOUDS...WILL SEE TEMPERATURES FLUCTUATE DEPENDING ON THE CLOUD COVER...THOUGH WILL SEE A GENERAL DOWNWARD TREND THROUGH THE NIGHT WITH LOWS JUST UNDER 10 THROUGH THE HURON TO BROOKINGS CORRIDOR...TO THE MID TEENS ALONG THE MISSOURI RIVER CORRIDOR WHERE CLOUDS WILL BE MORE DOMINANT. MODELS CONTINUING SLIGHT SOUTHWARD TREND WITH PRECIP CHANCES ON THURSDAY...AS NORTHERN STREAM WAVE DROPS SOUTHEAST INTO THE NORTHERN PLAINS. 700MB FRONTOGENESIS STILL HUGS THE MISSOURI RIVER VALLEY... HOWEVER MOST MODELS SHOWING A DRY LAYER IN THE ATMOSPHERE NORTH OF THE RIVER THAT WILL LIMIT NORTHWARD EXTENT OF ACCUMULATING PRECIP. HAVE SCALED POPS BACK TO JUST OUR FAR SOUTHERN AREAS...GENERALLY SOUTH OF LAKE ANDES/KYKN/KSLB LINE...WITH JUST A FEW TENTHS OF SNOW AT BEST IN THESE AREAS. 850MB BAROCLINIC ZONE LINGERS FROM NORTH CENTRAL NEBRASKA INTO SOUTHWEST SOUTH DAKOTA INTO THE EVENING AS THE MAIN WAVE DROPS THROUGH THE DAKOTAS....AND THIS COULD KEEP SOME LIGHT SNOW OR FLURRIES GOING JUST TO OUR SOUTHWEST INTO THURSDAY EVENING. WILL KEEP IT DRY IN OUR AREA...THOUGH SOME MID CLOUDS WILL LIKELY HANG AROUND IN THE WESTERN PORTIONS OF THE MISSOURI RIVER VALLEY THROUGH 06Z BEFORE DRIER MID LEVEL AIR PUSHES SOUTH WITH THE WAVE. FOCUS FOR THE REMAINDER OF THE WEEK AND INTO THE WEEKEND WILL BE ON TEMPERATURES...WITH POTENTIAL FOR SOME DECENT RADIATIONAL NIGHTTIME COOLING. SURFACE RIDGE AXIS SHIFTS INTO NEBRASKA SO WILL LIKELY NOT SEE WINDS GO COMPLETELY CALM EXCEPT IN MORE SHELTERED AREAS. HOWEVER EVEN WITH RELATIVELY LIGHT WEST-SOUTHWEST WINDS EXPECTED OVER THE SNOWPACK AREAS...SHOULD SEE QUICK EVENING DROPS IN TEMPERATURES ACROSS OUR SOUTHEAST THURSDAY AND FRIDAY NIGHTS...WITH NON-DIURNAL RISE IN TEMPERATURES EXPECTED LATER FRIDAY NIGHT AS WINDS/CLOUDS INCREASE AHEAD OF WARM FRONT. DAYTIME TEMPERATURES SHOULD SEE GRADUAL DECREASE IN EFFECT OF SNOWPACK ON READINGS...THOUGH COULD STILL HOLD HIGHS BACK A FEW DEGREES ON FRIDAY WITH FULL SUNSHINE AND LIMITED MIXING. LONGER RANGE STILL LOOKS RELATIVELY DRY THROUGH TUESDAY...WITH MODELS SHOWING DECENT AGREEMENT DIGGING YET ANOTHER WAVE INTO THE SOUTHWEST CONUS WHILE SEPARATE NORTHERN STREAM TROUGH SLIDES EAST ACROSS THE CANADIAN BORDER. WEAK WAVE SEEN EJECTING OUT OF SOUTHWEST SYSTEM INTO THE MIDDLE MISSOURI VALLEY ON MONDAY. FORECAST SOUNDINGS QUITE SPARSE ON MOISTURE ABOVE 850MB...BUT SIMILAR IN SHOWING STRONG NORTHWARD PUSH OF LOW LEVEL MOISTURE/STRATUS AHEAD OF COLD FRONT IN THE LATE NIGHT/MORNING HOURS. MOISTURE PROFILES FROM ALL MODELS ARE REMINISCENT OF DRIZZLE SOUNDINGS...WITH LACK OF MOISTURE IN CRITICAL ICE-BEARING LAYER ALOFT...BUT TOUGH TO PINPOINT THREAT OF POTENTIAL FREEZING PRECIP AT DAY 4-5 RANGE SO WILL JUST GO WITH MENTION OF LIGHT RAIN/SNOW WITH SLIGHT CHANCE POPS IN OUR FAR SOUTHEAST DURING THE DAY MONDAY. GREATER DIFFERENCES IN THE MODELS ARISE BY THE MIDDLE OF NEXT WEEK IN HANDLING OF NORTHERN STREAM TROUGH AS IT MOVES ACROSS THE GREAT LAKES AND EASTERN CANADA...AS WELL AS SOUTHWEST CONUS CUTOFF. GFS STRONGER/SLOWER WITH NORTHERN STREAM TROUGH WHILE ALSO MAINTAINING STRONGER SOUTHWEST SYSTEM...WITH ANOTHER RELATIVELY WEAK WAVE LIFTING NORTHEAST THROUGH THE PLAINS MIDWEEK. ECMWF ON THE OTHER HAND IS SLIGHTLY WEAKER/FASTER WITH THE NORTHERN STREAM TROUGH... ALLOWING STRONGER CHUNK OF ENERGY TO LIFT NORTHEAST INTO THE PLAINS ON WEDNESDAY. EITHER SCENARIO GIVES AT LEAST SOUTHERN PARTS OF OUR AREA A CHANCE OF PRECIP LATE IN THE FORECAST PERIOD. MAIN DIFFERENCE IS STRONGER ECMWF SPREADS THE PRECIP MUCH FARTHER NORTHEAST THAN THE GFS. IN EITHER CASE...SEEMS SOME CHANCE POPS ARE WARRANTED FOR THE DAY 7 TIMEFRAME AT THIS TIME. AFOREMENTIONED DIFFERENCES ALSO RESULT IN DRASTICALLY DIFFERENT LOW LEVEL TEMPERATURE PROFILES...WITH ECMWF PULLING WARMER AIR MUCH FARTHER NORTH THAN GFS WHERE NORTHERN STREAM REMAINS DOMINANT. WITH RIDE WITH BLEND OF THE TWO SOLUTIONS AND KEEP PRECIP TYPE AS ALL SNOW FOR NOW...BUT WARMER ECMWF COULD BRING A THREAT OF LIQUID PRECIP INTO THE MIX AND WILL KEEP A CLOSE EYE ON TRENDS FOR THIS OVER THE NEXT FEW DAYS. && .AVIATION.../FOR THE 00Z TAF ISSUANCE/ GENERAL VFR CONDITIONS EXPECTED THROUGH 00Z FRI. VERY SMALL THREAT FOR MARGINAL MVFR STRATUS LATE TONIGHT AND EARLY MORNING BEHIND COLD FRONT...BUT BELOW MENTIONABLE THRESHOLD...AT WHICH TIME A FEW FLURRIES AT BEST FOR KSUX AREA...WHICH SHOULD NOT BREACH VFR IF THEY EVEN CAN SURVIVE THE LOW LEVEL DRY AIR. /CHAPMAN && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. NE...NONE. IA...NONE. && $$
AREA FORECAST DISCUSSION
NWS BROWNSVILLE TX
1158 AM CST TUE DEC 6 2011 .DISCUSSION...SEE THE AVIATION SEGMENT BELOW FOR THE DISCUSSION OF THE 18Z TAF ISSUANCE. && .AVIATION...THE 12Z BRO SOUNDING SHOWS THAT THE CURRENT ATMS IS PRETTY SATURATED AND A FAIRLY STRONG INVERSION IS EVIDENT AT AND BELOW THE 850 MB LEVEL. AS A RESULT VSBL IMAGERY OVER DEEP SOUTH TX SHOWS AN LARGE AREA OF OVC CLD DECKS. HOWEVER A LARGE HOLE IN THE LOW CLD DECKS IS EVIDENT OVER SOUTH CENTRAL TX AND APPEARS TO BE MOVING S-SE AT A PRETTY GOOD CLIP. THE LATEST RUC AND NAM12 RH FIELDS SHOWS MUCH DRIER AIR FILTERING IN OVER THE REGION THROUGHOUT THE EVENING AND OVERNIGHT HOURS WHICH WILL RESULT IN THE LIFTING OF THE CEILINGS THROUGHOUT THE UPCOMING TAF PERIOD. ACCORDINGLY EXPECT VFR VSBYS AND CEILINGS THROUGH 18Z TOMORROW WITH LIGHT TO MODERATE NORTHERLY SURFACE FLOW PERSISTING AS THE SURFACE RIDGING SPREADS OVER THE REGION. && .PREV DISCUSSION... /ISSUED 427 AM CST TUE DEC 6 2011/ SHORT TERM /TODAY THROUGH WEDNESDAY/...THE UPPER TROUGH AXIS CURRENTLY EXTENDING TO THE DESERT SOUTHWEST WILL LIFT OUT ACROSS NORTH TEXAS LATE TUESDAY NIGHT. WEAK ISENTROPIC LIFT AHEAD OF THE UPPER TROUGH WILL RESULT IN CLOUDY SKIES...COOL TEMPERATURES...AND A SLIGHT CHANCE OF LIGHT RAIN/SPRINKLES THIS MORNING THROUGH EARLY THIS AFTERNOON. CLOUDS WILL BEGIN TO DECREASE LATER THIS AFTERNOON AND TONIGHT AS THE UPPER TROUGH LIFTS OUT OVER THE SOUTHERN PLAINS. SURFACE HIGH PRESSURE WILL SETTLE INTO DEEP SOUTH TEXAS LATE TONIGHT THROUGH WEDNESDAY. THE MAIN CHALLENGE WILL BE HOW LOW THE TEMPERATURES DROP TONIGHT/WEDNESDAY MORNING. LIGHT WINDS... CLEARING SKIES...AND MUCH DRIER AIR FILTERING INTO THE AREA WOULD SUGGEST A COLD NIGHT IN DEEP SOUTH TEXAS AND IN THE RIO GRANDE VALLEY. CURRENT MODEL DATA CONSENSUS IS ALSO INDICATING A COLD NIGHT ACROSS THE AREA. THE ONLY CONCERN IS THAT THE WINDS MAY NOT DROP OFF AS QUICKLY AS THE MODEL GUIDANCE IS INDICATING. AFTER A LONG IN OFFICE DISCUSSION...PONDERING OVER THE AVAILABLE GUIDANCE ONE LAST TIME...AND COORDINATING WITH WFO CRP...HAVE DECIDED TO ISSUE A FREEZE WATCH FOR A GOOD PORTION OF THE CWA. THE FREEZE WATCH WILL INCLUDE ALL OF THE COUNTIES OF BRO CWA EXCEPT FOR HIDALGO AND CAMERON COUNTIES AND THE COASTAL PORTION OF WILLACY COUNTY. WIDESPREAD TEMPERATURES ARE EXPECTED TO BE IN THE UPPER 20S TO LOWER 30S ACROSS DEEP SOUTH TEXAS AND THE VALLEY WEDNESDAY MORNING. PLEASE REFER TO THE NPW BRO PRODUCT. THANKS WFO CORPUS CHRISTI FOR THE COORDINATION REGARDING THE FREEZE WATCH. LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...CLEAR SKIES WILL COMBINE WITH LIGHT WINDS AND DRIER AIR TO PRODUCE ANOTHER ROUND OF FREEZING TEMPERATURES ACROSS MOST OF DEEP SOUTH TEXAS AND THE RIO GRANDE VALLEY LATE WEDNESDAY NIGHT THROUGH EARLY THURSDAY MORNING .AND A FREEZE WARNING MAY BE NEEDED FOR THAT TIME. PLEASANT AND DRY WEATHER WITH MODERATING TEMPERATURES IS EXPECTED THURSDAY AND THURSDAY NIGHT AS SURFACE HIGH PRESSURE YIELDS TO AN INVERTED SURFACE TROUGH OF LOW PRESSURE DEVELOPING OVER THE WESTERN GULF OF MEXICO. ISOLATED TO SCATTERED AREAS OF RAIN WITH OVERCAST SKIES WILL THEN PREVAIL FOR FRIDAY THROUGH EARLY NEXT WEEK AS THE TROUGH INTENSIFIES AND PERSISTS. TEMPERATURES WILL BE HELD AT BELOW NORMAL LEVELS FROM FRIDAY THROUGH SUNDAY DUE TO THE INCREASED CLOUD COVER AND FLOW FROM THE NORTHEAST AND EAST...HOWEVER TEMPERATURES WILL BEGIN TO RECOVER ON MONDAY AS THE FLOW SHIFTS FROM OUT OF THE SOUTHEAST. MARINE...TODAY THROUGH WEDNESDAY...OBS AT BUOY 020 CURRENTLY REFLECT NNW WINDS AT AROUND 19 KNOTS WITH HIGHER GUSTS AND WAVE HEIGHTS AROUND 7 FEET WITH A 5 SECOND PERIOD. STRONG WINDS WILL PERSIST TODAY AS HIGH PRESSURE CONTINUES TO SURGE ACROSS THE LOWER TEXAS COAST. THE SMALL CRAFT ADVISORY ON THE BAY IS IN EFFECT UNTIL 1 PM TODAY AND MAY LIKELY BE EXTENDED THROUGH LATE THIS AFTERNOON OR INTO EARLY THIS EVENING. A SMALL CRAFT ADVISORY HAS BEEN EXTENDED ON THE GULF WATERS THROUGH 6 AM WEDNESDAY. LITTLE CHANGE IS OTHERWISE EXPECTED IN THE SHORT TERM MARINE FORECAST. WEDNESDAY NIGHT THROUGH MONDAY...MARINE CONDITIONS ARE EXPECTED TO STEADILY IMPROVE WEDNESDAY NIGHT THROUGH FRIDAY...WITH SMALL CRAFT ADVISORIES NOT ANTICIPATED TO BE NEEDED...AS SURFACE HIGH PRESSURE SHIFTS EAST FROM THE TEXAS COASTLINE TO THE MID-ATLANTIC REGION. WINDS AND SEAS WILL THEN INCREASE FOR FRIDAY NIGHT THROUGH EARLY NEXT WEEK...WITH SMALL CRAFT ADVISORIES INCREASINGLY POSSIBLE...AS THE HIGH PRESSURE SYSTEM INTERACTS WITH LOW PRESSURE OVER THE BAY OF CAMPECHE AND SOUTHERN GULF OF MEXICO. && .BRO WATCHES/WARNINGS/ADVISORIES... TX...FREEZE WATCH FROM LATE TONIGHT THROUGH WEDNESDAY MORNING FOR TXZ248>252-254. GM...SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM CST THIS AFTERNOON FOR GMZ130-132-135. SMALL CRAFT ADVISORY UNTIL 6 AM CST WEDNESDAY FOR GMZ150-155-170- 175. && $$ THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT: HTTP://WWW.WEATHER.GOV/BROWNSVILLE SHORT TERM...60 LONG TERM...54 GRAPHICAST/UPPER AIR...VEGA
AREA FORECAST DISCUSSION...UPDATED
NWS LUBBOCK TX
1141 PM CST MON DEC 5 2011 .AVIATION... UNCERTAINTY REMAINS HIGH AS TO WHEN SNOW WILL END AT KLBB AND WHAT CEILINGS WILL DO ONCE THE SNOW ENDS. OCCASIONAL PERIODS OF SNOW CONTINUE AT KLBB AS BANDS REDEVELOP NEAR THE TERMINAL BUT CEILINGS HAVE BEEN FAIRLY CONSISTENT. ALL INDICATIONS ARE THAT MVFR CONDITIONS WILL CONTINUE THROUGH THE OVERNIGHT HOURS AND SNOW SHOULD FINALLY SHUT OFF A FEW HOURS AFTER MIDNIGHT LOCAL TIME. EXPECT TO SEE VFR CEILINGS DEVELOP BY MID-MORNING TUESDAY AND CONTINUE THROUGH THE END OF THIS TAF CYCLE. JORDAN && .PREV DISCUSSION... /ISSUED 604 PM CST MON DEC 5 2011/ AVIATION... SNOW HAS LET UP AT KLBB AND CEILINGS HAVE GONE VFR BRIEFLY... HOWEVER EXPECT THAT WE WILL CONTINUE TO SEE PERIODS OF SNOW AT KLBB AND CEILINGS BOUNCING AROUND MVFR TO VFR THROUGH THE OVERNIGHT HOURS. IFR CONDITIONS ARE HARD TO FIGURE OUT RIGHT NOW AT KLBB BUT FEEL THE CEILINGS SHOULD REMAIN ABOVE THIS. EXPECT SNOW TO END AT KLBB BEFORE MIDNIGHT ALTHOUGH PERIODS OF LIGHT FLURRIES MAY PERSIST INTO TUESDAY MORNING. KCDS SHOULD REMAIN VFR WITH NO PRECIPITATION ALTHOUGH THERE MAY BE BRIEF PERIODS OF MVFR THROUGH THE OVERNIGHT HOURS. EXPECT VFR CONDITIONS BY LATE TOMORROW MORNING INTO EARLY TUESDAY AFTERNOON FOR KLBB. JORDAN PREV DISCUSSION... /ISSUED 334 PM CST MON DEC 5 2011/ SHORT TERM... THE MAIN FOCUS FOR THE SHORT TERM WILL CONTINUE TO BE THE WINTER WEATHER IMPACTS ASSOCIATED WITH A STRONG UPPER-LOW PRESSURE SYSTEM STILL PUSHING THROUGH THE FOUR CORNERS REGION. OVER THE COURSE OF THE DAY...LIGHT SNOW SHOWERS HAVE PERSISTED ACROSS THE CAPROCK...THOUGH VERY MINOR ACCUMULATIONS HAVE OCCURRED SINCE THE MID-MORNING HOURS. HOWEVER...CURRENT OBS...SATELLITE AND RADAR IMAGERY AND MODEL PROJECTIONS ARE SHOWING THE POTENTIAL FOR SOME ADDITIONAL AREAS OF LIGHT SNOWFALL TO MOVE INTO THE AREA LATE THIS AFTERNOON AND THIS EVENING AS ANOTHER LOBE OF ENERGY FROM THE AFOREMENTIONED UPPER-LOW ROTATES OVER THE REGION. MOST OF THE QPF SIGNALS SHOWN ARE FAIRLY LIGHT...BUT THE TTU WRF AND THE HRRR BOTH SHOW SOME ENHANCED PRECIPITATION BANDS DEVELOPING ACROSS THE NORTHWESTERN ZONES THIS EVENING. THIS THINKING SEEMS TO BE PLAUSIBLE AS IR SATELLITE DATA IS INDICATING A BAND OF COLDER CLOUD TOPS PUSHING INTO THE WESTERN PANHANDLE...WITH SURFACE OBS AT CLOVIS DROPPING DOWN TO 1-2 SM DUE TO SNOW. THUS...SOME LOCALIZED BURSTS OF MODERATE SNOW WILL BE POSSIBLE /PARTICULARLY ACROSS THE SW PANHANDLE/ WHERE AN ADDITIONAL INCH OF SNOW MAY BE POSSIBLE TONIGHT. HAVE INCREASED POPS TO LIKELY TO CHANCE ACROSS MUCH OF THE AREA THIS EVENING...BEFORE LOWERING THEM AFTER MIDNIGHT AS PRECIPITATION BEGINS TO WANE. THE OTHER BIG CONCERN FOR THIS EVENING WILL BE THE BRISK NORTHERLY WINDS AND STRONG COLD AIR ADVECTION OCCURRING...WHICH WILL DROP TEMPERATURES INTO THE SINGLE DIGITS ACROSS THE SW PANHANDLE AND INTO THE TEENS ACROSS THE REST OF THE AREA. GIVEN THE BITTERLY COLD TEMPERATURES AND WINDS THAT SHOULD REMAIN ABOVE 10 MPH OVERNIGHT SOME LOW WIND CHILLS WILL DEVELOP AFTER SUNSET. GIVEN THE POTENTIAL FOR SOME DANGEROUSLY COLD WINDS CHILLS AT OR AROUND -5 DEGREES OCCURRING LATER TONIGHT ACROSS THE NORTHWEST ZONES...HAVE PLACED THAT AREA IN A WIND CHILL ADVISORY THROUGH 15Z TOMORROW. GIVEN THE POTENTIAL FOR SOME ADDITIONAL /ALBEIT GENERALLY LIGHT/ SNOWFALL ACCUMULATIONS ON THE CAPROCK THIS EVENING AND ALREADY HAZARDOUS DRIVING CONDITIONS FROM BLACK ICE AND SNOW ON AREA ROADWAYS...HAVE OPTED TO EXTEND THE WINTER WEATHER ADVISORY ON THE CAPROCK UNTIL 12Z. TOMORROW WILL BE A BITTERLY COLD DAY ACROSS THE AREA...AS HIGHS WILL GENERALLY REMAIN WELL BELOW FREEZING IN THE 20S DUE TO VERY LOW THICKNESS VALUES AND A CONTINUED NORTHERLY WIND. LONG TERM... AMPLIFIED PATTERN THROUGHOUT THE CONUS WILL SLOWLY RELAX BY MIDWEEK RESULTING IN BRIEFLY ZONAL FLOW AND SLIGHTLY MILDER TEMPS ON THE SOUTH PLAINS. THIS PATTERN HOWEVER STILL LOOKS TO BREAK DOWN ON FRIDAY YIELDING BROADLY CYCLONIC FLOW COURTESY OF A DEEP POLAR VORTEX TAKING RESIDENCE IN THE HUDSON BAY. JUST A GLANCING BLOW FROM THIS BROAD TROUGH WILL YIELD A DRY POLAR FRONT LATE THU NIGHT/EARLY FRI SERVING TO KNOCK HIGHS ON FRI 15-20 DEG BELOW CLIMO. MEDIUM RANGE MODELS INSIST ON DEEPER WEST OR SWLY FLOW BY THE WEEKEND INDICATIVE OF MORE SEASONABLE TEMPS. GREATEST FORECAST CHALLENGE THIS PERIOD INVOLVES LO TEMPS TUE NIGHT AS STRATUS CLEARS AND WINDS SLACKEN WITHIN AN ELONGATED SURFACE RIDGE. CHOSE NOT TO LOWER INHERITED MIN TEMPS MUCH BELOW GUIDANCE FOR NOW AS ALL NUMERICAL DATA INDICATE LIGHT WESTERLY FLOW OVERNIGHT. SHOULD THESE LIGHT WINDS VEER MORE NLY IN LATER FORECASTS...THEN THE RECORD DAILY LOW AT LBB /8 SET IN 2005/ MAY BE IN JEOPARDY. && .PRELIMINARY POINT TEMPS/POPS... FRIONA 8 21 7 40 17 / 60 10 0 0 0 TULIA 12 22 11 41 18 / 50 10 0 0 0 PLAINVIEW 13 23 10 40 18 / 50 10 0 0 0 LEVELLAND 13 22 9 40 19 / 50 10 0 0 0 LUBBOCK 15 25 11 40 19 / 40 10 0 0 0 DENVER CITY 14 26 16 40 20 / 50 10 0 0 0 BROWNFIELD 14 26 13 40 20 / 50 10 0 0 0 CHILDRESS 20 30 17 42 21 / 20 10 0 0 0 SPUR 20 30 15 44 20 / 30 10 0 0 0 ASPERMONT 21 33 20 45 22 / 20 10 10 0 0 && .LUB WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 6 AM CST TUESDAY FOR THE FOLLOWING ZONES: TXZ021>024-027>030-033>036-039>042. WIND CHILL ADVISORY UNTIL 9 AM CST TUESDAY FOR THE FOLLOWING ZONES: TXZ021>023-027-028. && $$ 99/99/99
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
541 PM CST WED DEC 7 2011 .SHORT TERM...THROUGH SATURDAY 254 PM CST WED DEC 7 2011 A QUIET PERIOD OF BELOW NORMAL TEMPERATURES THROUGH FRIDAY...THE COLDEST AIR OF THE SEASON THUS FAR. THE FORECAST WAS ON TRACK WITH ONLY MINOR CHANGES MADE. CURRENTLY MONITORING THE NORTHEAST TO SOUTHWEST ORIENTED LOWER CLOUDS /2 KFT/ MOVING THROUGH IN WARM ADVECTION IN THE LOWER LEVELS. COLD FRONT AT THE SURFACE IS REALLY NOT DETECTABLE WITH FULL SUN IN MN MESSING WITH TEMPERATURES. FRONT IS REALLY NOT THAT STRONG NEAR THE SURFACE. THE CLOUDS ARE MAKING STEADY PROGRESS THROUGH NORTH CENTRAL WI BUT HAVE SLOWED OVER SERN MN...BUT ARE SLOWLY SHIFTING SOUTHEAST. MID-CLOUDS EXTEND FROM THE DAKOTAS INTO SRN MN AND IOWA AS WELL...BUT THOSE ARE A BIT THINNER. OTHERWISE...LARGE AREA OF CLEARING IS EVIDENT OVER MOST OF MN AND THIS SHOULD WORK INTO THE AREA NORTH OF THE MID-CLOUDS OVERNIGHT. LOW-LEVEL TEMPERATURE WAVE MOVING THROUGH WITH GOOD WARM ADVECTION SHIFTING EAST /KMPX WARMED 7C OVERNIGHT AT 850MB/ AND NOW COLD ADVECTION BEGINNING. KINL WAS -12C THIS MORNING AT 850MB AND THE PAS /N OF LAKE WINNIPEG/ WAS -19C WITH NORTHWEST WINDS AT 40 KTS. THIS IS THE COLD POOL SURGING IN THROUGH FRIDAY. WITH LITTLE WEATHER...THE CONSENSUS OF THE MODELS IS REALLY CLOSE ON THE OUTCOMES AND FORECAST USED A NAM/GFS/ECMWF/GEM BLEND. COLD AIR ADVECTION IN NORTHWEST FLOW BEGINS THIS EVENING AREA-WIDE AND WILL CONTINUE THROUGH FRIDAY. SECOND COLD SURGE COMES IN THURSDAY EVENING PULLING OUR 925 MB TEMPERATURES DOWN TO -12C /CURRENTLY ABOUT -4C/. WITH ABOUT 7-10 MPH WINDS FRIDAY MORNING...BUS STOPS WILL BE COLD WITH WIND CHILLS -15 TO -20F OVER SERN MN AND IN NORTH CENTRAL WI. DO NOT SEE THIS BECOMING AN ADVISORY EVENT FOR WIND CHILL. WARM ADVECTION THEN BEGINS LATE FRIDAY NIGHT AS MAJOR RIDGE BUILDING OCCURS IN THE CENTRAL U.S. HOWEVER...HAVE LOWERED THE CENTRAL WISCONSIN LOW TEMPERATURES BASED ON MOSTLY CLEAR SKIES AND THE RIDGE AXIS PASSING OVERHEAD PER CONSENSUS OF MODELS. THIS USUALLY DECOUPLES THE BOUNDARY LAYER IN WI...ESPECIALLY CENTRAL...IN THE FAVORED COLD SPOTS. ALSO HAVE CONTINUED THE TREND OF WARMING THE TEMPERATURES AFTER MIDNIGHT IN THE WESTERN AREAS AS THE SOUTHERLY WINDS KICK IN. HAVE NOT CHANGED MUCH FOR THE HIGHS ON SATURDAY...STILL IN THE UPPER 20S. BUT THE PRESSURE GRADIENT SUGGESTS WINDS NEEDED TO BE INCREASED INTO THE 15-25 MPH RANGE WHICH KEEPS THE WIND CHILLS IN THE LOWER TEENS. SO...UNLIKELY PEOPLE WILL THINK THIS IS A WARMER DAY THAN FRIDAY EVEN THOUGH HIGH TEMPERATURES RISE 12-15F. .LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY 254 PM CST WED DEC 7 2011 THE 07.00Z AND 07.12Z ECMWF...GEM...AND GFS ARE IN GOOD AGREEMENT THROUGH MONDAY BUT THEN DIVERGE ON HOW THE DETAILS OF THE LARGE SCALE PATTERN WILL EMERGE. THE WARM ADVECTION CONTINUES THROUGH SUNDAY WITH PEOPLE FINALLY GETTING SOME OF THAT WARM FEELING. THERE IS GOOD CONSENSUS IN THE MODELS ON THE NEXT SHORTWAVE SHIFTING THROUGH WITH A DRIZZLE/SHOWERY/LIGHT PRECIPITATION EVENT MONDAY AND MONDAY NIGHT. WITH SOME COLD ADVECTION SUGGESTED...POSSIBLY JUST FROM THE PRECIPITATION COOLING PROCESS...SOME AREAS MAY BE NEAR FREEZING WITH SUPERCOOLED LIQUID AN ISSUE. WILL HAVE TO MONITOR THE EVOLUTION OF THIS SYSTEM FOR POSSIBLE FREEZING DRIZZLE. TOWARD MIDWEEK THE 07.06Z AND 07.12Z GFS HAVE PROVIDED AN OUTLIER AGAINST THEIR LIKE ECMWF AND GEM RUNS. THE ECMWF HAS A NEGATIVELY TILTED STRONG...WARM WEATHER SYSTEM SHIFTING OUT OF THE SWRN LARGE SCALE TROUGH THROUGH THE AREA WEDNESDAY. THIS WOULD BE A RAIN SYSTEM WITH 40S AREA-WIDE PER ECMWF SOLUTION. THE GFS HOLDS MORE ENERGY IN THE NORTHERN STREAM WITH A COLDER/SLOWER SOLUTION. IT SEEMS TO BE THE OUTLIER. IN ANY CASE...RIGHT NOW WE ARE RAMPING UP THE WEATHER FOR THAT PERIOD AND HAVE KEPT A S/RS/S MIX OF PRECIPITATION. WOULD THINK THE TREND WILL BE WARMER WITH FUTURE FORECASTS FOR MID-WEEK. && .AVIATION...TONIGHT AND THURSDAY 541 PM CST WED DEC 7 2011 A BAND OF MVFR CLOUDS OVER BOTH TAF SITES SHOULD MOVE EAST OF THE REGION THIS EVENING. THE 07.21Z RUC SEEMS TO HAVE A GOOD HANDLE ON THIS MOISTURE FIELD AROUND 925 MB AND MOVES IT OUT OF KRST RIGHT AROUND 00Z AND OUT OF KLSE AROUND 02Z AND HAVE USED THIS AS TIMING. AFTER THAT...IT LOOKS AS IF SOME MID TO HIGH LEVEL CLOUDS WILL MOVE IN AND OUT OF THE REGION THROUGH THE REMAINDER OF THE NIGHT INTO THURSDAY MORNING. COULD EVEN SEE SOME OCCASIONAL CEILINGS FROM THESE CLOUDS BUT IF THAT DOES OCCUR...THEY WILL BE HIGH VFR CEILINGS. && .ARX WATCHES/WARNINGS/ADVISORIES... 254 PM CST WED DEC 7 2011 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM...BAUMGARDT LONG TERM...BAUMGARDT AVIATION...04
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
219 PM CST TUE DEC 6 2011 .SYNOPSIS...SEASONABLY COLD AND VERY QUIET FOR THE EARLY PART OF DECEMBER. AMPLIFIED LNGWV PATTERN IN PLACE...WITH LARGE SCALE FLOW DOMINATED BY MASSIVE RIDGE OVER THE ERN PAC. THE FLOW DOWNSTREAM WAS SOMEWHAT SPLIT...WITH NRN STREAM MUCH STRONGER THAN THE SRN...AND WITH TROFFING OVER ERN NOAM. THE TREND DURING THE FIRST PART OF THE FCST PERIOD WL BE FOR BROAD ERN NOAM TROF TO EXPAND SWD FM VORTEX IN THE HUDSON BAY RGN. THE SAME FEATURES SHOULD REMAIN IN PLACE FOR THE LATTER HALF OF THE PERIOD...BUT WITH A GRADUAL DECR IN AMPLITUDE. TEMPS ACRS THE AREA HAVE COOLED TO NR NORMAL...AND WL CONT THE DOWNSLIDE TO SOMEWHAT BLO NORMAL LEVELS AS THE UPR TROF DEEPENS OVER THE RGN. ALTHOUGH THE N NOW HAS A DECENT SNOWCOVER...THE LACK OF A WIDESPREAD DEEP SNOWCOVER ACRS THE ENTIRE REGION WL PREVENT THIS FROM TURNING INTO A VERY COLD PERIOD. READINGS SHOULD REBOUND DURING THE LATTER PART OF THE PERIOD AS UPR FLOW BECOMES MORE WLY. GULF MOISTURE WL REMAIN TRAPPED WELL S OF THE AREA...AND DON/T SEE ANY STG SYSTEMS IN THE FAST NWLY/WNWLY FLOW EITHER. EVEN THE PROSPECT FOR LAKE-EFFECT LOOKS LOW AS FLOW WL BE RATHER WLY. SO DON/T EXPECT MUCH PCPN DURING THE PERIOD. && .SHORT TERM...TONIGHT AND WEDNESDAY. LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW HIGH PRESSURE STRETCHING FROM THE CENTRAL GREAT PLAINS...ACROSS THE GREAT LAKES...AND INTO QUEBEC THIS AFTERNOON. DESPITE THE SURFACE HIGH...LOW CLOUDS OVER WESTERN AND CENTRAL WISCONSIN ARE STUBBORNLY MOVING TO THE NORTHEAST. EARLIER FLURRY ACTIVITY OVER THE DOOR PENINSULA IS ALSO FINALLY STARTING TO MOVE TO THE EAST AS WELL. MEANWHILE...OVER THE LAKE WINNIPEG REGION...A DIVING SHORTWAVE IS SENDING A WARM FRONT TO THE SOUTHEAST. AS THE SURFACE HIGH DRIFTS TO THE SOUTH TONIGHT...CLOUDS AND TEMPS REMAIN THE MAIN FORECAST CONCERNS. TONIGHT...SURFACE HIGH PRESSURE WILL DRIFT TO THE SOUTH AS HEIGHT FALLS OCCUR OVER SOUTH-CENTRAL CANADA AND THE FAR NORTHERN PLAINS. LOW LEVEL SW WINDS WILL STRENGTHEN AND CONTINUE TO PUSH THE LOW STRATUS TO THE NE. BASED ON THE LATEST SATELLITE OBS...TEND TO THINK THE LOW STRATUS WILL STAY IN TACT OVER CENTRAL INTO EAST- CENTRAL WISCONSIN THROUGH MID-EVENING WHILE NORTH- CENTRAL WISCONSIN MAY ACTUALLY TURN PARTLY CLOUDY. UNLESS SOME HOLES DEVELOP LATER THIS AFTERNOON...WILL TREND THE FORECAST THIS DIRECTION. DRIER AIR IS THEN PROGGED TO PUSH THE STUBBORN STRATUS TO THE EAST LATE THIS EVENING AND OVERNIGHT. SOME HIGH CLOUDS MAY ARRIVE LATE AHEAD OF A SHEAR SHORTWAVE DIVING OVER SOUTH-CENTRAL CANADA. THE STRENGTHENING WIND FIELD AND CLOUD COVER WILL KEEP TEMPS WARMER THAN LAST NIGHT...AND WILL GO UPPER SINGLE DIGITS NORTH TO LOWER 20S SE. WEDNESDAY...THE SHEARED WAVE WILL SLIDE SOUTHEAST OVER LAKE SUPERIOR...AND PUSH A WEAKENING COLD FRONT ACROSS THE FORECAST AREA DURING THE MORNING. WILL SEE SOME SCT TO BKN MID CLOUDS WITH THE FRONT...BUT NO REAL THREAT OF SNOW SHOWERS EXCEPT OVER NORTHERN VILAS WHERE WNW WINDS MAY SEND A SCT SNOW SHOWERS ALONG THE U.P.-WISCONSIN BORDER. TEMPS A COUPLE DEGREES WARMER THAN TODAY OFF OF A WARMER START IN THE MORNING. .LONG TERM...WED NGT THROUGH NEXT TUE. TRENDED TEMPS DOWN A LITTLE BOTH THU AND FRI AS FCST AREA WL BE DOMINATED BY COLD AIR FLOWING SEWD FM CANADA. WLY FLOW SHOULD KEEP SIG LAKE-EFFECT NE OF THE AREA. THE CANADIAN GLOBAL MODEL BROUGHT SOME PCPN ACRS E-C WI ON THU NGT INTO FRI AS BAROCLINIC LEAF TYPE FEATURES SLIDES ACRS THE AREA. THE FEATURE WAS ALSO AT LEAST HINTED AT ON THE REST OF THE MODELS...BUT THEY WERE ALL WEAKER AND FARTHER S. SO CANADIAN SEEMS LIKE AN OUTLIER AND WL STICK WITH DRY FCST. && .AVIATION...LOW CLOUDS ARE HANGING TOUGH LATE THIS MORNING OVER WESTERN AND CENTRAL WISCONSIN...THOUGH THERE MAY BE A SLIGHT DIMINISHING TREND OF THE FLURRY ACTIVITY. LOW LEVEL WINDS WILL TURN TO THE SOUTHWEST THIS AFTERNOON...WHICH WILL TEND TO PUSH THE LOW CLOUDS TO THE EAST. AS A RESULT...HAVE MAINTAINED THE LOW END VFR BKN CONDITIONS OVER CENTRAL AND NORTH-CENTRAL TAF SITES THROUGH LATE THIS AFTERNOON AND EARLY THIS EVENING. SOME EROSION IS LIKELY THIS AFTERNOON...BUT QUITE DIFFICULT TO DETERMINE WHERE IT WILL OCCUR. LOW LEVEL DRY AIR WILL FINALLY SURGE INTO THE AREA THIS EVENING WHICH WILL CLEAR SKIES OUT. MID AND HIGH CLOUDS WILL ARRIVE LATE TONIGHT AHEAD OF THE UPPER LEVEL WAVE. THOUGH DO NOT SEE LOW CLOUDS REDEVELOPING...STRENGTHENING SW FLOW WILL LEAD TO LLWS DEVELOPING 09-15Z TOMORROW. MPC && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ MPC/SKOWRONSKI
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
146 PM CST TUE DEC 6 2011 UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE. .SHORT TERM...TODAY THROUGH WEDNESDAY. FORECAST CONCERNS THIS PERIOD...CLOUDS LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW HIGH PRESSURE STRETCHING FROM WESTERN LAKE SUPERIOR INTO WESTERN IA. LOWER CLOUD CLEARING OVER MUCH OF EASTERN WI AS DRIER AIR...SEEN ON GRB SOUNDING...WORKING IN. CLOUDS HANGING TOUGH OVER WESTERN PART OF STATE. SURFACE HIGH WILL CONTINUE TO SHIFT OVER STATE TODAY...EXITING TONIGHT WITH COLD FRONT ASSOCIATED WITH LOW MOVING THROUGH NORTHERN CANADA MOVING THROUGH STATE ON WED. QUESTION IS WHAT WILL HAPPEN WITH CLOUDS TODAY. AREA OF CONVERGENCE ASSOCIATED WITH WEAK SURFACE TROF OVER WESTERN WI TO WEAKEN THIS MORNING. SOME MODELS SHOW LOWER CLOUD MOVING BACK INTO EASTERN WI LATE TODAY AS LOW LEVEL WINDS SHIFT TO THE SOUTHWEST LATE. SOME SHOW CLOUD DISSIPATING THROUGH THE DAY AS SUPPORT WEAKENS. HAVE LEANED TOWARDS CANADIAN THAT SHOWS CURRENT CLEARING OVER EASTERN AND NORTH CENTRAL WI...THOUGH WILL STAY WITH PARTLY CLOUDY/PARTLY SUNNY WORDING GIVEN CIRRUS MOVING THROUGH AND SOME UNCERTAINTY. CLOUDS CONTINUE TO MOVE SOUTH OFF LAKE SUPERIOR/MICHIGAN IN THE FAR EAST. THUS CLEARING SLOWED A BIT FROM PREVIOUS FORECAST...THOUGH LITTLE CHANGE MADE IN TEMPERATURE FORECAST. .LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY. MODELS HAD AN UPPER TROUGH OVER MUCH OF THE CONUS EARLY IN THE PERIOD...WITH THE FLOW BECOMING ZONAL OVER THE UPPER GREAT LAKES BY EARLY NEXT WEEK. AN ARCTIC FRONT WILL BRING MUCH COLDER AIR INTO THE FORECAST AREA ON THURSDAY. HAVE A SLIGHT CHANCE OF SNOW SHOWERS IN VILAS COUNTY FOR THE END OF THE WORK WEEK. LAPSE RATES OVER LAKE SUPERIOR SHOULD BE STEEP...BUT WINDS APPEARED TO HAVE TOO MUCH OF A WESTERLY COMPONENT TO GO AS HIGH AS CHANCE POPS. NEAR OR ABOVE NORMAL TEMPERATURES CAN BE EXPECTED BY SUNDAY AS A SURFACE RIDGE PASSES EAST OF THE AREA AND SOUTHWEST WINDS BRING WARMER AIR INTO THE STATE. HAVE SOME SLIGHT CHANCE POPS LATE IN THE PERIOD WITH SHORT WAVE ENERGY AND A SURFACE LOW APPROACHING WISCONSIN. MAY NEED TO GO WITH HIGHER POPS IN THE AFTERNOON FORECAST PACKAGE OR TOMORROW MORNING IF CONDITIONS APPEAR MORE FAVORABLE FOR PRECIPITATION. && .AVIATION...LOW CLOUDS ARE HANGING TOUGH LATE THIS MORNING OVER WESTERN AND CENTRAL WISCONSIN...THOUGH THERE MAY BE A SLIGHT DIMINISHING TREND OF THE FLURRY ACTIVITY. LOW LEVEL WINDS WILL TURN TO THE SOUTHWEST THIS AFTERNOON...WHICH WILL TEND TO PUSH THE LOW CLOUDS TO THE EAST. AS A RESULT...HAVE MAINTAINED THE LOW END VFR BKN CONDITIONS OVER CENTRAL AND NORTH-CENTRAL TAF SITES THROUGH LATE THIS AFTERNOON AND EARLY THIS EVENING. SOME EROSION IS LIKELY THIS AFTERNOON...BUT QUITE DIFFICULT TO DETERMINE WHERE IT WILL OCCUR. LOW LEVEL DRY AIR WILL FINALLY SURGE INTO THE AREA THIS EVENING WHICH WILL CLEAR SKIES OUT. MID AND HIGH CLOUDS WILL ARRIVE LATE TONIGHT AHEAD OF THE UPPER LEVEL WAVE. THOUGH DO NOT SEE LOW CLOUDS REDEVELOPING...STRENGTHENING SW FLOW WILL LEAD TO LLWS DEVELOPING 09-15Z TOMORROW. MPC && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1151 AM CST TUE DEC 6 2011 .SHORT TERM...TODAY THROUGH THURSDAY NIGHT 332 AM CST TUE DEC 6 2011 MAIN FORECAST CONCERNS THIS PACKAGE...CLOUDS AND TEMPERATURES THRU THE PERIOD. DATA ANALYSIS AT 06Z HAD A RIDGE OF HIGH PRESSURE EXTENDING FROM NORTH OF LK SUPERIOR ACROSS MN TO NEB AND WESTERN KS. A LARGE AREA OF LOW PRESSURE WAS LOCATED OVER NORTH-CENTRAL CAN WITH FALLING PRESSURES IN THE NORTHERN PLAINS. STRATUS CLOUDS REMAINS TRAPPED ACROSS THE AREA...UNDER AN INVERSION BETWEEN 850-800MB AND EAST OF THE SFC RIDGE AXIS. WEST EDGE OF THE CLOUDS WAS NEAR A KDLH-KOTG LINE...MAKING VERY SLOW PROGRESS EAST/SOUTH. WEAK SFC-925MB TROUGH AND CONVERGENCE...ALONG WITH THE SLOWLY COOLING LOWER LEVELS CONTINUED TO SQUEEZE SOME FLURRIES/VERY LIGHT SNOW OUT OF THE COLUMN OVER MUCH OF WESTERN WI INTO EXTREME EASTERN MN. NO PROBLEMS NOTED WITH 06.00Z MODEL INITIALIZATIONS. SOLUTIONS QUITE SIMILAR FOR TODAY THRU THU NIGHT...AT LEAST WITH THE SHORTWAVES AND LARGER SCALE FEATURES. MODELS STILL STRUGGLING WITH THE LOWER LEVEL MOISTURE/RH FIELDS AND STRATUS CLOUDS ACROSS THE AREA. DPROG/DT OF 500MB HGTS AT 06.00Z SHOWED MODEL RUNS OF 04.00Z AND 05.00Z VERIFIED QUITE WELL ACROSS NOAM...FAVORING STRONGER OF EARLIER MODELS WITH THE NORTHERN PORTION OF THE TROUGH AND FASTER OF EARLIER MODELS WITH THE SOUTHWEST CONUS PORTION OF THE TROUGH. THRU TODAY/TONIGHT MODELS TREND TOWARD A TIGHTER/FASTER CONSENSUS WITH THE SOUTHERN PORTION OF THE TROUGH MOVING EAST INTO THE MID/LOWER MS VALLEY AND WEAKENING OF THE NORTHERN PORTION OF THE TROUGH AS IT MOVES EAST OF THE REGION. TREND CONTINUES FASTER WITH THE LOWER MS VALLEY TROUGH WED/WED NIGHT AS IT TO THE EAST COAST BY 12Z THU. BETTER CONSENSUS FOR BROAD TROUGHING/NORTHWEST FLOW TO DEVELOP OVER THE NORTH-CENTRAL CONUS/ GREAT LAKES REGION. THIS TROUGH DEEPENS OVER THE MID/UPPER MS VALLEY THU/THU NIGHT...BUT MINOR DIFFERENCES IN THE TIMING/STRENGTH DETAILS DEVELOP BY 12Z FRI. OVERALL BETTER RUN-TO-RUN CONSISTENCY FOR TODAY THRU THU NIGHT SHOWN BY ECMWF...ESPECIALLY WITH THE SOUTHERN STREAM ENERGY EARLY IN THE PERIOD. CHECK OF OBS VS. MODEL DATA AT 06Z SHOWED MODELS ALL QUITE GOOD WITH THE CENTRAL CONUS SFC MASS FIELDS...THOUGH AGAIN CONTINUED TO STRUGGLE WITH THE LOWER LEVEL RH AND STRATUS DECKS TRAPPED ACROSS THE REGION. ECMWF/ RUC LOOK TO BE DOING BEST WITH THE 925MB RH/STATUS CLOUDS OVER MN/ WI/IA WHILE ONLY MODEL SOME INDICATION OF THE FLURRIES WAS THE GFS. THUS NO CLEAR DETERMINISTIC MODEL FAVORITE. WITH MODELS TRENDING TOWARD A TIGHTER CONSENSUS MUCH OF THE PERIOD...FAVORED THE CONSENSUS. SHORT TERM FCST CONFIDENCE AVERAGE TO GOOD THIS CYCLE. IN THE SHORT TERM...LOW CLOUDS/CLEARING REMAIN PROBLEMATIC TODAY/ TONIGHT WITH TYPICAL POOR MODEL PERFORMANCE ON THIS AND THE TIME OF YEAR WHEN LOW CLOUDS LIKE TO HANG TOUGH. MODEL CONSENSUS KEEPS 70+ PERCENT 925MB RH OVER THE CENTRAL/EAST PARTS OF THE FCST AREA THRU THE DAY WITH ONLY SLOW EROSION/ADVECTION ON THE WESTERN SIDE. RAISED CLOUD COVER IN SKY GRIDS TO REFLECT A SLOWER/NON CLEARING TODAY. MOVED THE CLEARING INTO TONIGHT WITH INCREASING WEST SFC- 850MB FLOW NORTH OF THE LOW LEVEL RIDGE AXIS TO FINALLY ADVECT THE MOISTURE EAST AND OUT OF THE AREA. SFC-925MB TROUGH WEAKENS THRU THIS MORNING...BUT GIVEN SLOW MOVEMENT OF THE LOW LEVEL FEATURES... LINGERED SCT FLURRIES OVER THE NORTH HALF OF THE FCST AREA WHERE RADAR REFLECTIVITY/SFC OBS CONTINUED TO DETECT/REPORT FLURRIES AS OF 09Z. REST OF SHORT-TERM PERIOD GENERALLY COOL/QUIET. SHORTWAVE ENERGY PASSES NORTH OF THE FCST AREA WED/WED NIGHT WITH BULK OF FORCING/LIFT AND 850-500MB MOISTURE/SATURATION REMAINING NORTH OF THE FCST AREA. COLD/DRY AIRMASS SETTLES ACROSS THE AREA IN THE WAKE OF THIS SHORTWAVE TROUGH FOR THU/THU NIGHT. THIS AS MORE SHORTWAVE ENERGY DROPS SOUTHEAST ACROSS THE NORTHERN PLAINS FOR THU/THU NIGHT. BULK OF THE LOWER LEVEL THERMO-DYNAMIC FORCING AND INCREASE OF MOISTURE IN THE 925-700MB LAYER REMAINS SOUTH OF THE FCST AREA THU/THU NIGHT. ONLY LINGERED A SMALL -SN CHANCE ACROSS THE EXTREME SOUTH END OF THE FCST AREA THU NIGHT TO BLEND WITH NEIGHBORING GRIDS. SATURATION OF THE COLUMN OVER THE NORTH END OF THE FCST AREA THU/THU NIGHT...NORTH OF THE SHORTWAVE TRACK...AN ISSUE IN THE COLDER COLUMN THERE. MAY YET SEE SCT FLURRIES ALONG/NORTH OF HWY 29 THU/THU NIGHT BUT LEFT THIS DRY FOR NOW. GENERALLY CARRIED PARTLY CLOUDY TO MOSTLY CLEAR SKIES FOR WED THRU THU NIGHT. HIGH/LOW TEMPERATURES PROBLEMATIC WITH SNOW COVERING THE NORTHWEST HALF OF THE FCST AREA WHILE THE SOUTHEAST HALF IS SNOW-FREE. WITH MORE CLOUDS/OVERCAST TODAY...TRENDED HIGHS FOR MINIMAL DIURNAL SWING AND AT OR BELOW NUMERICAL GUIDANCE. WITH PARTLY CLOUDY SKIES TONIGHT BUT SOME SOUTHWEST GRADIENT WINDS...FAVORED A BLEND OF THE GUIDANCE LOWS. SOUTHWEST/WEST WINDS AHEAD OF THE NEXT COLD FRONT AND SOME SUNSHINE WED...TRENDED TOWARD WARMER OF GUIDANCE HIGHS... ESPECIALLY OVER THE SNOW-FREE SOUTHEAST HALF OF THE FCST AREA. APPEARS BOUNDARY LAYER WINDS WILL KEEP LOW LEVELS STIRRED WED NIGHT AND TRENDED TOWARD WARMER OF GUIDANCE LOWS. FAVORED A MODEL CONSENSUS OF HIGHS FOR THU...WHICH BLENDS WELL WITH NEIGHBORING GRIDS BUT MAY BE TOO WARM WITH MDT/STRONG LOW LEVEL COLD ADVECTION OVER THE REGION BY MID-DAY. FAVORED THE MODEL CONSENSUS FOR LOWS THU NIGHT...WHICH ALSO MAY BE TOO WARM IF WINDS ARE LIGHTER THAN EXPECTED ESPECIALLY OVER THE SNOW-COVERED PORTIONS OF THE FCST AREA. .LONG TERM...FRIDAY THROUGH MONDAY 332 AM CST TUE DEC 6 2011 LONG-TERM FCST CONFIDENCE AVERAGE. 06.00Z MEDIUM RANGE MODELS IN REASONABLE AGREEMENT WITH EACH OTHER AND THEIR PREVIOUS RUNS FRI THRU SUNDAY WITH THE LONGWAVE TROUGH BEING PROGRESSIVE AND HGTS RISING OVER THE UPPER MIDWEST FRIDAY INTO SUNDAY. COLD SFC HIGH PRESSURE DRIFTS OVER THE AREA FRI THEN MOVES SOUTH OF THE AREA FOR SAT/SUN. STRONG LOW LEVEL WARM ADVECTION SPREADS ACROSS THE AREA SAT INTO SAT NIGHT WITH 925MB TEMPS IN THE 0 TO +4C RANGE BY 12Z SUN. BELOW/MUCH BELOW NORMAL TEMPS FRI LOOK TO WARM TO ABOVE/MUCH ABOVE NORMAL BY SUN AS BULK OF THE WARM ADVECTION GOES INTO WARMING UNDER PARTLY CLOUDY/MOSTLY SUNNY SKIES. RAISED HIGHS A BIT OVER THE SOUTHEAST HALF OF THE FCST AREA SUN WITH THE LACK OF SNOW COVER. GFS/ECMWF SOLUTIONS DIVERGE FOR MON. ECMWF SLIDES A COLD FRONT AND WEAK LOW LEVEL COLD ADVECTION ACROSS THE AREA WHILE GFS TRACKS A LOW INTO NORTHWEST MN KEEPING THE AREA UNDER LOW LEVEL WARM ADVECTION. EITHER WAY...APPEARS SOME OF THE SNOW COVER WILL MELT SUN AND MON WILL SEE CONTINUED ABOVE NORMAL TEMPS. BIGGEST LONG-TERM QUESTION LOOKS TO BE WILL THERE BE ENOUGH LOWER LEVEL MOISTURE FOR A SMALL PRECIP CHANCE FOR PARTS OF THE AREA BY LATER MON. MODEL CONSENSUS DATA USED IN THE DAY 4-7 FCST GRIDS LOOKS TO HAVE ALL OF THIS WELL TRENDED FOR NOW. && .AVIATION...THROUGH 18Z WEDNESDAY 1151 AM CST TUE DEC 6 2011 BIGGEST CHALLENGE THIS TAF PERIOD ARE CEILINGS AND CLEARING TRENDS AT BOTH TAF SITES. CURRENTLY BAND OF MVFR CEILINGS STRETCHES FROM NORTHEAST IOWA...SOUTHEAST MINNESOTA...AND WESTERN WISCONSIN. INCLUDED A SHORT TEMPO GROUP AT KRST FOR SCATTERED FLURRIES AND SUB-MVFR CONDITIONS UNTIL MAIN RIDGE AXIS PUSHES THROUGH. EXPECTING CLEARING AND VFR CONDITIONS TO EDGE CLOSER TO KRST BY 02Z AND TO KLSE BY 05Z. WESTERN EDGE OF CLOUD COVER SEEMS TO BE MIXING BETTER THIS AFTERNOON...AND CLEARING TREND MAY BE FASTER IF THIS CONTINUES. VFR CONDITIONS WILL PERSIST OVERNIGHT AS WINDS SHIFT TO SOUTHWEST...AHEAD OF A COLD FRONT PROGGED TO MOVE THROUGH THE REGION. FRONTAL PASSAGE EXPECTED AT KRST AT 12Z WED AND AT KLSE AT 15Z. BROKEN MID TO HIGH LEVEL CLOUDS CURRENTLY OVER NORTH DAKOTA WILL MOVE IN THE WAKE OF FRONTAL PASSAGE AND WINDS AHEAD AND BEHIND THE FRONT WILL INCREASE TO 10-15 KT. && .ARX WATCHES/WARNINGS/ADVISORIES... 332 AM CST TUE DEC 6 2011 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM... RRS LONG TERM.... RRS AVIATION...ZT/MW
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
607 AM CST TUE DEC 6 2011 UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE .SHORT TERM...TODAY THROUGH WEDNESDAY. FORECAST CONCERNS THIS PERIOD...CLOUDS LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW HIGH PRESSURE STRETCHING FROM WESTERN LAKE SUPERIOR INTO WESTERN IA. LOWER CLOUD CLEARING OVER MUCH OF EASTERN WI AS DRIER AIR...SEEN ON GRB SOUNDING...WORKING IN. CLOUDS HANGING TOUGH OVER WESTERN PART OF STATE. SURFACE HIGH WILL CONTINUE TO SHIFT OVER STATE TODAY...EXITING TONIGHT WITH COLD FRONT ASSOCIATED WITH LOW MOVING THROUGH NORTHERN CANADA MOVING THROUGH STATE ON WED. QUESTION IS WHAT WILL HAPPEN WITH CLOUDS TODAY. AREA OF CONVERGENCE ASSOCIATED WITH WEAK SURFACE TROF OVER WESTERN WI TO WEAKEN THIS MORNING. SOME MODELS SHOW LOWER CLOUD MOVING BACK INTO EASTERN WI LATE TODAY AS LOW LEVEL WINDS SHIFT TO THE SOUTHWEST LATE. SOME SHOW CLOUD DISSIPATING THROUGH THE DAY AS SUPPORT WEAKENS. HAVE LEANED TOWARDS CANADIAN THAT SHOWS CURRENT CLEARING OVER EASTERN AND NORTH CENTRAL WI...THOUGH WILL STAY WITH PARTLY CLOUDY/PARTLY SUNNY WORDING GIVEN CIRRUS MOVING THROUGH AND SOME UNCERTAINTY. CLOUDS CONTINUE TO MOVE SOUTH OFF LAKE SUPERIOR/MICHIGAN IN THE FAR EAST. THUS CLEARING SLOWED A BIT FROM PREVIOUS FORECAST...THOUGH LITTLE CHANGE MADE IN TEMPERATURE FORECAST. .LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY. MODELS HAD AN UPPER TROUGH OVER MUCH OF THE CONUS EARLY IN THE PERIOD...WITH THE FLOW BECOMING ZONAL OVER THE UPPER GREAT LAKES BY EARLY NEXT WEEK. AN ARCTIC FRONT WILL BRING MUCH COLDER AIR INTO THE FORECAST AREA ON THURSDAY. HAVE A SLIGHT CHANCE OF SNOW SHOWERS IN VILAS COUNTY FOR THE END OF THE WORK WEEK. LAPSE RATES OVER LAKE SUPERIOR SHOULD BE STEEP...BUT WINDS APPEARED TO HAVE TOO MUCH OF A WESTERLY COMPONENT TO GO AS HIGH AS CHANCE POPS. NEAR OR ABOVE NORMAL TEMPERATURES CAN BE EXPECTED BY SUNDAY AS A SURFACE RIDGE PASSES EAST OF THE AREA AND SOUTHWEST WINDS BRING WARMER AIR INTO THE STATE. HAVE SOME SLIGHT CHANCE POPS LATE IN THE PERIOD WITH SHORT WAVE ENERGY AND A SURFACE LOW APPROACHING WISCONSIN. MAY NEED TO GO WITH HIGHER POPS IN THE AFTERNOON FORECAST PACKAGE OR TOMORROW MORNING IF CONDITIONS APPEAR MORE FAVORABLE FOR PRECIPITATION. && .AVIATION...DRIER AIR WORKING IN OVER EASTERN WI HAS CLEARED SKIES FOR MUCH OF EASTERN WI AND NORTH CENTRAL WI...NOW WORKING INTO CENTRAL WI. SUPPORT FOR FLURRIES/CLOUDS JUST WEST OF CWA/AUW TO DIMINISH THIS MORNING. THOUGHTS ARE CLOUDS WILL CONTINUE TO DIMINISH OVER WEST. INCREASING SOUTHWEST WINDS THIS EVENING...30 KTS AT 2K FT. THOUGH NOT STRONG ENOUGH DIFFERENCE FROM SURFACE FOR LLWS AT THIS TIME. TE && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
537 AM CST TUE DEC 6 2011 .SHORT TERM...TODAY THROUGH THURSDAY NIGHT 332 AM CST TUE DEC 6 2011 MAIN FORECAST CONCERNS THIS PACKAGE...CLOUDS AND TEMPERATURES THRU THE PERIOD. DATA ANALYSIS AT 06Z HAD A RIDGE OF HIGH PRESSURE EXTENDING FROM NORTH OF LK SUPERIOR ACROSS MN TO NEB AND WESTERN KS. A LARGE AREA OF LOW PRESSURE WAS LOCATED OVER NORTH-CENTRAL CAN WITH FALLING PRESSURES IN THE NORTHERN PLAINS. STRATUS CLOUDS REMAINS TRAPPED ACROSS THE AREA...UNDER AN INVERSION BETWEEN 850-800MB AND EAST OF THE SFC RIDGE AXIS. WEST EDGE OF THE CLOUDS WAS NEAR A KDLH-KOTG LINE...MAKING VERY SLOW PROGRESS EAST/SOUTH. WEAK SFC-925MB TROUGH AND CONVERGENCE...ALONG WITH THE SLOWLY COOLING LOWER LEVELS CONTINUED TO SQUEEZE SOME FLURRIES/VERY LIGHT SNOW OUT OF THE COLUMN OVER MUCH OF WESTERN WI INTO EXTREME EASTERN MN. NO PROBLEMS NOTED WITH 06.00Z MODEL INITIALIZATIONS. SOLUTIONS QUITE SIMILAR FOR TODAY THRU THU NIGHT...AT LEAST WITH THE SHORTWAVES AND LARGER SCALE FEATURES. MODELS STILL STRUGGLING WITH THE LOWER LEVEL MOISTURE/RH FIELDS AND STRATUS CLOUDS ACROSS THE AREA. DPROG/DT OF 500MB HGTS AT 06.00Z SHOWED MODEL RUNS OF 04.00Z AND 05.00Z VERIFIED QUITE WELL ACROSS NOAM...FAVORING STRONGER OF EARLIER MODELS WITH THE NORTHERN PORTION OF THE TROUGH AND FASTER OF EARLIER MODELS WITH THE SOUTHWEST CONUS PORTION OF THE TROUGH. THRU TODAY/TONIGHT MODELS TREND TOWARD A TIGHTER/FASTER CONSENSUS WITH THE SOUTHERN PORTION OF THE TROUGH MOVING EAST INTO THE MID/LOWER MS VALLEY AND WEAKENING OF THE NORTHERN PORTION OF THE TROUGH AS IT MOVES EAST OF THE REGION. TREND CONTINUES FASTER WITH THE LOWER MS VALLEY TROUGH WED/WED NIGHT AS IT TO THE EAST COAST BY 12Z THU. BETTER CONSENSUS FOR BROAD TROUGHING/NORTHWEST FLOW TO DEVELOP OVER THE NORTH-CENTRAL CONUS/ GREAT LAKES REGION. THIS TROUGH DEEPENS OVER THE MID/UPPER MS VALLEY THU/THU NIGHT...BUT MINOR DIFFERENCES IN THE TIMING/STRENGTH DETAILS DEVELOP BY 12Z FRI. OVERALL BETTER RUN-TO-RUN CONSISTENCY FOR TODAY THRU THU NIGHT SHOWN BY ECMWF...ESPECIALLY WITH THE SOUTHERN STREAM ENERGY EARLY IN THE PERIOD. CHECK OF OBS VS. MODEL DATA AT 06Z SHOWED MODELS ALL QUITE GOOD WITH THE CENTRAL CONUS SFC MASS FIELDS...THOUGH AGAIN CONTINUED TO STRUGGLE WITH THE LOWER LEVEL RH AND STRATUS DECKS TRAPPED ACROSS THE REGION. ECMWF/ RUC LOOK TO BE DOING BEST WITH THE 925MB RH/STATUS CLOUDS OVER MN/ WI/IA WHILE ONLY MODEL SOME INDICATION OF THE FLURRIES WAS THE GFS. THUS NO CLEAR DETERMINISTIC MODEL FAVORITE. WITH MODELS TRENDING TOWARD A TIGHTER CONSENSUS MUCH OF THE PERIOD...FAVORED THE CONSENSUS. SHORT TERM FCST CONFIDENCE AVERAGE TO GOOD THIS CYCLE. IN THE SHORT TERM...LOW CLOUDS/CLEARING REMAIN PROBLEMATIC TODAY/ TONIGHT WITH TYPICAL POOR MODEL PERFORMANCE ON THIS AND THE TIME OF YEAR WHEN LOW CLOUDS LIKE TO HANG TOUGH. MODEL CONSENSUS KEEPS 70+ PERCENT 925MB RH OVER THE CENTRAL/EAST PARTS OF THE FCST AREA THRU THE DAY WITH ONLY SLOW EROSION/ADVECTION ON THE WESTERN SIDE. RAISED CLOUD COVER IN SKY GRIDS TO REFLECT A SLOWER/NON CLEARING TODAY. MOVED THE CLEARING INTO TONIGHT WITH INCREASING WEST SFC- 850MB FLOW NORTH OF THE LOW LEVEL RIDGE AXIS TO FINALLY ADVECT THE MOISTURE EAST AND OUT OF THE AREA. SFC-925MB TROUGH WEAKENS THRU THIS MORNING...BUT GIVEN SLOW MOVEMENT OF THE LOW LEVEL FEATURES... LINGERED SCT FLURRIES OVER THE NORTH HALF OF THE FCST AREA WHERE RADAR REFLECTIVITY/SFC OBS CONTINUED TO DETECT/REPORT FLURRIES AS OF 09Z. REST OF SHORT-TERM PERIOD GENERALLY COOL/QUIET. SHORTWAVE ENERGY PASSES NORTH OF THE FCST AREA WED/WED NIGHT WITH BULK OF FORCING/LIFT AND 850-500MB MOISTURE/SATURATION REMAINING NORTH OF THE FCST AREA. COLD/DRY AIRMASS SETTLES ACROSS THE AREA IN THE WAKE OF THIS SHORTWAVE TROUGH FOR THU/THU NIGHT. THIS AS MORE SHORTWAVE ENERGY DROPS SOUTHEAST ACROSS THE NORTHERN PLAINS FOR THU/THU NIGHT. BULK OF THE LOWER LEVEL THERMO-DYNAMIC FORCING AND INCREASE OF MOISTURE IN THE 925-700MB LAYER REMAINS SOUTH OF THE FCST AREA THU/THU NIGHT. ONLY LINGERED A SMALL -SN CHANCE ACROSS THE EXTREME SOUTH END OF THE FCST AREA THU NIGHT TO BLEND WITH NEIGHBORING GRIDS. SATURATION OF THE COLUMN OVER THE NORTH END OF THE FCST AREA THU/THU NIGHT...NORTH OF THE SHORTWAVE TRACK...AN ISSUE IN THE COLDER COLUMN THERE. MAY YET SEE SCT FLURRIES ALONG/NORTH OF HWY 29 THU/THU NIGHT BUT LEFT THIS DRY FOR NOW. GENERALLY CARRIED PARTLY CLOUDY TO MOSTLY CLEAR SKIES FOR WED THRU THU NIGHT. HIGH/LOW TEMPERATURES PROBLEMATIC WITH SNOW COVERING THE NORTHWEST HALF OF THE FCST AREA WHILE THE SOUTHEAST HALF IS SNOW-FREE. WITH MORE CLOUDS/OVERCAST TODAY...TRENDED HIGHS FOR MINIMAL DIURNAL SWING AND AT OR BELOW NUMERICAL GUIDANCE. WITH PARTLY CLOUDY SKIES TONIGHT BUT SOME SOUTHWEST GRADIENT WINDS...FAVORED A BLEND OF THE GUIDANCE LOWS. SOUTHWEST/WEST WINDS AHEAD OF THE NEXT COLD FRONT AND SOME SUNSHINE WED...TRENDED TOWARD WARMER OF GUIDANCE HIGHS... ESPECIALLY OVER THE SNOW-FREE SOUTHEAST HALF OF THE FCST AREA. APPEARS BOUNDARY LAYER WINDS WILL KEEP LOW LEVELS STIRRED WED NIGHT AND TRENDED TOWARD WARMER OF GUIDANCE LOWS. FAVORED A MODEL CONSENSUS OF HIGHS FOR THU...WHICH BLENDS WELL WITH NEIGHBORING GRIDS BUT MAY BE TOO WARM WITH MDT/STRONG LOW LEVEL COLD ADVECTION OVER THE REGION BY MID-DAY. FAVORED THE MODEL CONSENSUS FOR LOWS THU NIGHT...WHICH ALSO MAY BE TOO WARM IF WINDS ARE LIGHTER THAN EXPECTED ESPECIALLY OVER THE SNOW-COVERED PORTIONS OF THE FCST AREA. .LONG TERM...FRIDAY THROUGH MONDAY 332 AM CST TUE DEC 6 2011 LONG-TERM FCST CONFIDENCE AVERAGE. 06.00Z MEDIUM RANGE MODELS IN REASONABLE AGREEMENT WITH EACH OTHER AND THEIR PREVIOUS RUNS FRI THRU SUNDAY WITH THE LONGWAVE TROUGH BEING PROGRESSIVE AND HGTS RISING OVER THE UPPER MIDWEST FRIDAY INTO SUNDAY. COLD SFC HIGH PRESSURE DRIFTS OVER THE AREA FRI THEN MOVES SOUTH OF THE AREA FOR SAT/SUN. STRONG LOW LEVEL WARM ADVECTION SPREADS ACROSS THE AREA SAT INTO SAT NIGHT WITH 925MB TEMPS IN THE 0 TO +4C RANGE BY 12Z SUN. BELOW/MUCH BELOW NORMAL TEMPS FRI LOOK TO WARM TO ABOVE/MUCH ABOVE NORMAL BY SUN AS BULK OF THE WARM ADVECTION GOES INTO WARMING UNDER PARTLY CLOUDY/MOSTLY SUNNY SKIES. RAISED HIGHS A BIT OVER THE SOUTHEAST HALF OF THE FCST AREA SUN WITH THE LACK OF SNOW COVER. GFS/ECMWF SOLUTIONS DIVERGE FOR MON. ECMWF SLIDES A COLD FRONT AND WEAK LOW LEVEL COLD ADVECTION ACROSS THE AREA WHILE GFS TRACKS A LOW INTO NORTHWEST MN KEEPING THE AREA UNDER LOW LEVEL WARM ADVECTION. EITHER WAY...APPEARS SOME OF THE SNOW COVER WILL MELT SUN AND MON WILL SEE CONTINUED ABOVE NORMAL TEMPS. BIGGEST LONG-TERM QUESTION LOOKS TO BE WILL THERE BE ENOUGH LOWER LEVEL MOISTURE FOR A SMALL PRECIP CHANCE FOR PARTS OF THE AREA BY LATER MON. MODEL CONSENSUS DATA USED IN THE DAY 4-7 FCST GRIDS LOOKS TO HAVE ALL OF THIS WELL TRENDED FOR NOW. && .AVIATION...TODAY AND TONIGHT 537 AM CST TUE DEC 6 2011 MAIN AVIATION CONCERN IS CEILINGS. A VARIETY OF CEILINGS CURRENTLY ENCOMPASS THE AREA...RANGING FROM IFR TO VFR. WITH A LIGHT WIND REGIME IN PLACE...IT IS EASILY POSSIBLE CEILINGS AT THE TAF SITES COULD VARY FOR A WHILE...RISING AND FALLING FROM TIME TO TIME. HOWEVER...AS THE DAY PROGRESSES...DAYTIME MIXING SHOULD PROMOTE A GRADUAL RISE IN CEILINGS. ANY CLEARING OF CLOUDS LOOKS TO WAIT UNTIL THIS EVENING...ASSOCIATED WITH A SURFACE HIGH PRESSURE RIDGE MOVING WEST TO EAST ACROSS THE TAF SITES. ONCE CLEAR...VFR CONDITIONS SHOULD THEN PERSIST THROUGH THE REST OF THE NIGHT. ANOTHER CONCERN IS WINDS LATE TONIGHT. IN THE WAKE OF THE RIDGE...SOUTHWEST WINDS ARE FORECAST TO INCREASE TO 10-15 KT AT BOTH TAF SITES. HOWEVER... 35-40 KT WINDS ARE PROGGED 1500-2000 FT ABOVE THE SURFACE. RIGHT NOW THERE IS NOT ENOUGH WIND TO INSERT LOW LEVEL WIND SHEAR...BUT IT IS SOMETHING TO MONITOR. && .ARX WATCHES/WARNINGS/ADVISORIES... 332 AM CST TUE DEC 6 2011 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM... RRS LONG TERM.... RRS AVIATION...AJ
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
405 AM CST TUE DEC 6 2011 .SHORT TERM...TODAY THROUGH WEDNESDAY. FORECAST CONCERNS THIS PERIOD...CLOUDS LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW HIGH PRESSURE STRETCHING FROM WESTERN LAKE SUPERIOR INTO WESTERN IA. LOWER CLOUD CLEARING OVER MUCH OF EASTERN WI AS DRIER AIR...SEEN ON GRB SOUNDING...WORKING IN. CLOUDS HANGING TOUGH OVER WESTERN PART OF STATE. SURFACE HIGH WILL CONTINUE TO SHIFT OVER STATE TODAY...EXITING TONIGHT WITH COLD FRONT ASSOCIATED WITH LOW MOVING THROUGH NORTHERN CANADA MOVING THROUGH STATE ON WED. QUESTION IS WHAT WILL HAPPEN WITH CLOUDS TODAY. AREA OF CONVERGENCE ASSOCIATED WITH WEAK SURFACE TROF OVER WESTERN WI TO WEAKEN THIS MORNING. SOME MODELS SHOW LOWER CLOUD MOVING BACK INTO EASTERN WI LATE TODAY AS LOW LEVEL WINDS SHIFT TO THE SOUTHWEST LATE. SOME SHOW CLOUD DISSIPATING THROUGH THE DAY AS SUPPORT WEAKENS. HAVE LEANED TOWARDS CANADIAN THAT SHOWS CURRENT CLEARING OVER EASTERN AND NORTH CENTRAL WI...THOUGH WILL STAY WITH PARTLY CLOUDY/PARTLY SUNNY WORDING GIVEN CIRRUS MOVING THROUGH AND SOME UNCERTAINTY. CLOUDS CONTINUE TO MOVE SOUTH OFF LAKE SUPERIOR/MICHIGAN IN THE FAR EAST. THUS CLEARING SLOWED A BIT FROM PREVIOUS FORECAST...THOUGH LITTLE CHANGE MADE IN TEMPERATURE FORECAST. .LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY. MODELS HAD AN UPPER TROUGH OVER MUCH OF THE CONUS EARLY IN THE PERIOD...WITH THE FLOW BECOMING ZONAL OVER THE UPPER GREAT LAKES BY EARLY NEXT WEEK. AN ARCTIC FRONT WILL BRING MUCH COLDER AIR INTO THE FORECAST AREA ON THURSDAY. HAVE A SLIGHT CHANCE OF SNOW SHOWERS IN VILAS COUNTY FOR THE END OF THE WORK WEEK. LAPSE RATES OVER LAKE SUPERIOR SHOULD BE STEEP...BUT WINDS APPEARED TO HAVE TOO MUCH OF A WESTERLY COMPONENT TO GO AS HIGH AS CHANCE POPS. NEAR OR ABOVE NORMAL TEMPERATURES CAN BE EXPECTED BY SUNDAY AS A SURFACE RIDGE PASSES EAST OF THE AREA AND SOUTHWEST WINDS BRING WARMER AIR INTO THE STATE. HAVE SOME SLIGHT CHANCE POPS LATE IN THE PERIOD WITH SHORT WAVE ENERGY AND A SURFACE LOW APPROACHING WISCONSIN. MAY NEED TO GO WITH HIGHER POPS IN THE AFTERNOON FORECAST PACKAGE OR TOMORROW MORNING IF CONDITIONS APPEAR MORE FAVORABLE FOR PRECIPITATION. && .AVIATION...A FEW FLURRIES OR SNOW SHOWERS CONTINUE OVER A CONVERGENT REGION OVER WEST CENTRAL WISCONSIN. OBSERVATIONS OVER CENTRAL WISCONSIN REPORTING 10 MILES WITH NO WEATHER PRESENT BUT ANTICIPATE FLURRY ACTIVITY OCCURRING WEST OF A LINE FROM RIB FALLS TO WISCONSIN RAPIDS INTO WAUSHARA COUNTY. RADARS ALSO SHOWING SOME RETURNS OVER THE LAKE MICHIGAN SHORELINE WITH NO GROUND TRUTH AND FINALLY SCATTERED SNOW SHOWERS WERE NOTED OVER VILAS. AS FAR AS CLOUDS...A SUCKER HOLE OPENED UP NORTHEAST WISCONSIN INCLUDING THE GRB VICINITY. BUT STILL EXPECT VFR CIGS TO DOMINATE OVERNIGHT INTO TUESDAY WITH SOME DECREASE IN CLOUDS LATER TUESDAY. TDH && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ TE/MG
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
332 AM CST TUE DEC 6 2011 .SHORT TERM...TODAY THROUGH THURSDAY NIGHT 332 AM CST TUE DEC 6 2011 MAIN FORECAST CONCERNS THIS PACKAGE...CLOUDS AND TEMPERATURES THRU THE PERIOD. DATA ANALYSIS AT 06Z HAD A RIDGE OF HIGH PRESSURE EXTENDING FROM NORTH OF LK SUPERIOR ACROSS MN TO NEB AND WESTERN KS. A LARGE AREA OF LOW PRESSURE WAS LOCATED OVER NORTH-CENTRAL CAN WITH FALLING PRESSURES IN THE NORTHERN PLAINS. STRATUS CLOUDS REMAINS TRAPPED ACROSS THE AREA...UNDER AN INVERSION BETWEEN 850-800MB AND EAST OF THE SFC RIDGE AXIS. WEST EDGE OF THE CLOUDS WAS NEAR A KDLH-KOTG LINE...MAKING VERY SLOW PROGRESS EAST/SOUTH. WEAK SFC-925MB TROUGH AND CONVERGENCE...ALONG WITH THE SLOWLY COOLING LOWER LEVELS CONTINUED TO SQUEEZE SOME FLURRIES/VERY LIGHT SNOW OUT OF THE COLUMN OVER MUCH OF WESTERN WI INTO EXTREME EASTERN MN. NO PROBLEMS NOTED WITH 06.00Z MODEL INITIALIZATIONS. SOLUTIONS QUITE SIMILAR FOR TODAY THRU THU NIGHT...AT LEAST WITH THE SHORTWAVES AND LARGER SCALE FEATURES. MODELS STILL STRUGGLING WITH THE LOWER LEVEL MOISTURE/RH FIELDS AND STRATUS CLOUDS ACROSS THE AREA. DPROG/DT OF 500MB HGTS AT 06.00Z SHOWED MODEL RUNS OF 04.00Z AND 05.00Z VERIFIED QUITE WELL ACROSS NOAM...FAVORING STRONGER OF EARLIER MODELS WITH THE NORTHERN PORTION OF THE TROUGH AND FASTER OF EARLIER MODELS WITH THE SOUTHWEST CONUS PORTION OF THE TROUGH. THRU TODAY/TONIGHT MODELS TREND TOWARD A TIGHTER/FASTER CONSENSUS WITH THE SOUTHERN PORTION OF THE TROUGH MOVING EAST INTO THE MID/LOWER MS VALLEY AND WEAKENING OF THE NORTHERN PORTION OF THE TROUGH AS IT MOVES EAST OF THE REGION. TREND CONTINUES FASTER WITH THE LOWER MS VALLEY TROUGH WED/WED NIGHT AS IT TO THE EAST COAST BY 12Z THU. BETTER CONSENSUS FOR BROAD TROUGHING/NORTHWEST FLOW TO DEVELOP OVER THE NORTH-CENTRAL CONUS/ GREAT LAKES REGION. THIS TROUGH DEEPENS OVER THE MID/UPPER MS VALLEY THU/THU NIGHT...BUT MINOR DIFFERENCES IN THE TIMING/STRENGTH DETAILS DEVELOP BY 12Z FRI. OVERALL BETTER RUN-TO-RUN CONSISTENCY FOR TODAY THRU THU NIGHT SHOWN BY ECMWF...ESPECIALLY WITH THE SOUTHERN STREAM ENERGY EARLY IN THE PERIOD. CHECK OF OBS VS. MODEL DATA AT 06Z SHOWED MODELS ALL QUITE GOOD WITH THE CENTRAL CONUS SFC MASS FIELDS...THOUGH AGAIN CONTINUED TO STRUGGLE WITH THE LOWER LEVEL RH AND STRATUS DECKS TRAPPED ACROSS THE REGION. ECMWF/ RUC LOOK TO BE DOING BEST WITH THE 925MB RH/STATUS CLOUDS OVER MN/ WI/IA WHILE ONLY MODEL SOME INDICATION OF THE FLURRIES WAS THE GFS. THUS NO CLEAR DETERMINISTIC MODEL FAVORITE. WITH MODELS TRENDING TOWARD A TIGHTER CONSENSUS MUCH OF THE PERIOD...FAVORED THE CONSENSUS. SHORT TERM FCST CONFIDENCE AVERAGE TO GOOD THIS CYCLE. IN THE SHORT TERM...LOW CLOUDS/CLEARING REMAIN PROBLEMATIC TODAY/ TONIGHT WITH TYPICAL POOR MODEL PERFORMANCE ON THIS AND THE TIME OF YEAR WHEN LOW CLOUDS LIKE TO HANG TOUGH. MODEL CONSENSUS KEEPS 70+ PERCENT 925MB RH OVER THE CENTRAL/EAST PARTS OF THE FCST AREA THRU THE DAY WITH ONLY SLOW EROSION/ADVECTION ON THE WESTERN SIDE. RAISED CLOUD COVER IN SKY GRIDS TO REFLECT A SLOWER/NON CLEARING TODAY. MOVED THE CLEARING INTO TONIGHT WITH INCREASING WEST SFC- 850MB FLOW NORTH OF THE LOW LEVEL RIDGE AXIS TO FINALLY ADVECT THE MOISTURE EAST AND OUT OF THE AREA. SFC-925MB TROUGH WEAKENS THRU THIS MORNING...BUT GIVEN SLOW MOVEMENT OF THE LOW LEVEL FEATURES... LINGERED SCT FLURRIES OVER THE NORTH HALF OF THE FCST AREA WHERE RADAR REFLECTIVITY/SFC OBS CONTINUED TO DETECT/REPORT FLURRIES AS OF 09Z. REST OF SHORT-TERM PERIOD GENERALLY COOL/QUIET. SHORTWAVE ENERGY PASSES NORTH OF THE FCST AREA WED/WED NIGHT WITH BULK OF FORCING/LIFT AND 850-500MB MOISTURE/SATURATION REMAINING NORTH OF THE FCST AREA. COLD/DRY AIRMASS SETTLES ACROSS THE AREA IN THE WAKE OF THIS SHORTWAVE TROUGH FOR THU/THU NIGHT. THIS AS MORE SHORTWAVE ENERGY DROPS SOUTHEAST ACROSS THE NORTHERN PLAINS FOR THU/THU NIGHT. BULK OF THE LOWER LEVEL THERMO-DYNAMIC FORCING AND INCREASE OF MOISTURE IN THE 925-700MB LAYER REMAINS SOUTH OF THE FCST AREA THU/THU NIGHT. ONLY LINGERED A SMALL -SN CHANCE ACROSS THE EXTREME SOUTH END OF THE FCST AREA THU NIGHT TO BLEND WITH NEIGHBORING GRIDS. SATURATION OF THE COLUMN OVER THE NORTH END OF THE FCST AREA THU/THU NIGHT...NORTH OF THE SHORTWAVE TRACK...AN ISSUE IN THE COLDER COLUMN THERE. MAY YET SEE SCT FLURRIES ALONG/NORTH OF HWY 29 THU/THU NIGHT BUT LEFT THIS DRY FOR NOW. GENERALLY CARRIED PARTLY CLOUDY TO MOSTLY CLEAR SKIES FOR WED THRU THU NIGHT. HIGH/LOW TEMPERATURES PROBLEMATIC WITH SNOW COVERING THE NORTHWEST HALF OF THE FCST AREA WHILE THE SOUTHEAST HALF IS SNOW-FREE. WITH MORE CLOUDS/OVERCAST TODAY...TRENDED HIGHS FOR MINIMAL DIURNAL SWING AND AT OR BELOW NUMERICAL GUIDANCE. WITH PARTLY CLOUDY SKIES TONIGHT BUT SOME SOUTHWEST GRADIENT WINDS...FAVORED A BLEND OF THE GUIDANCE LOWS. SOUTHWEST/WEST WINDS AHEAD OF THE NEXT COLD FRONT AND SOME SUNSHINE WED...TRENDED TOWARD WARMER OF GUIDANCE HIGHS... ESPECIALLY OVER THE SNOW-FREE SOUTHEAST HALF OF THE FCST AREA. APPEARS BOUNDARY LAYER WINDS WILL KEEP LOW LEVELS STIRRED WED NIGHT AND TRENDED TOWARD WARMER OF GUIDANCE LOWS. FAVORED A MODEL CONSENSUS OF HIGHS FOR THU...WHICH BLENDS WELL WITH NEIGHBORING GRIDS BUT MAY BE TOO WARM WITH MDT/STRONG LOW LEVEL COLD ADVECTION OVER THE REGION BY MID-DAY. FAVORED THE MODEL CONSENSUS FOR LOWS THU NIGHT...WHICH ALSO MAY BE TOO WARM IF WINDS ARE LIGHTER THAN EXPECTED ESPECIALLY OVER THE SNOW-COVERED PORTIONS OF THE FCST AREA. .LONG TERM...FRIDAY THROUGH MONDAY 332 AM CST TUE DEC 6 2011 LONG-TERM FCST CONFIDENCE AVERAGE. 06.00Z MEDIUM RANGE MODELS IN REASONABLE AGREEMENT WITH EACH OTHER AND THEIR PREVIOUS RUNS FRI THRU SUNDAY WITH THE LONGWAVE TROUGH BEING PROGRESSIVE AND HGTS RISING OVER THE UPPER MIDWEST FRIDAY INTO SUNDAY. COLD SFC HIGH PRESSURE DRIFTS OVER THE AREA FRI THEN MOVES SOUTH OF THE AREA FOR SAT/SUN. STRONG LOW LEVEL WARM ADVECTION SPREADS ACROSS THE AREA SAT INTO SAT NIGHT WITH 925MB TEMPS IN THE 0 TO +4C RANGE BY 12Z SUN. BELOW/MUCH BELOW NORMAL TEMPS FRI LOOK TO WARM TO ABOVE/MUCH ABOVE NORMAL BY SUN AS BULK OF THE WARM ADVECTION GOES INTO WARMING UNDER PARTLY CLOUDY/MOSTLY SUNNY SKIES. RAISED HIGHS A BIT OVER THE SOUTHEAST HALF OF THE FCST AREA SUN WITH THE LACK OF SNOW COVER. GFS/ECMWF SOLUTIONS DIVERGE FOR MON. ECMWF SLIDES A COLD FRONT AND WEAK LOW LEVEL COLD ADVECTION ACROSS THE AREA WHILE GFS TRACKS A LOW INTO NORTHWEST MN KEEPING THE AREA UNDER LOW LEVEL WARM ADVECTION. EITHER WAY...APPEARS SOME OF THE SNOW COVER WILL MELT SUN AND MON WILL SEE CONTINUED ABOVE NORMAL TEMPS. BIGGEST LONG-TERM QUESTION LOOKS TO BE WILL THERE BE ENOUGH LOWER LEVEL MOISTURE FOR A SMALL PRECIP CHANCE FOR PARTS OF THE AREA BY LATER MON. MODEL CONSENSUS DATA USED IN THE DAY 4-7 FCST GRIDS LOOKS TO HAVE ALL OF THIS WELL TRENDED FOR NOW. && .AVIATION...THROUGH 06Z WEDNESDAY 1045 PM CST MON DEC 5 2011 PERSISTENT LOW LEVEL SATURATION...PER RH FIELDS AND BUFKIT SOUNDINGS...SUGGEST THAT THE MVFR CIGS WILL HOLD INTO TUE AFTERNOON/EVENING. AN UPPER LEVEL SHORTWAVE TROUGH WILL HELP SWEEP THE LOW STRATUS TO THE EAST...AND MOST OF TUE NIGHT LOOKS SCT-SKC. BY WED MORNING CLOUDS ASSOCIATED WITH THE TROUGH WILL SLIDE IN...AND THERE COULD BE ANOTHER PERIOD OF MVFR CIGS IN THE AFTERNOON. A FEW FLURRIES WILL CONTINUE THROUGH THE OVERNIGHT HOURS...BUT DON/T SEE ANY REDUCTIONS TO VSBY. BELIEVE ANY THREAT FOR -FZDZ HAS ALSO ENDED. NORTHWEST WINDS WILL SWING TO THE SOUTHWEST BY LATE TUE AFTERNOON...AHEAD OF THAT SHORTWAVE...BUT SHIFT BACK TO THE NORTHWEST ON WED AS THE SYSTEM PASSES EAST. && .ARX WATCHES/WARNINGS/ADVISORIES... 332 AM CST TUE DEC 6 2011 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM... RRS LONG TERM.... RRS AVIATION..... RIECK
AREA FORECAST DISCUSSION
NWS GREEN BAY WI
1057 PM CST MON DEC 5 2011 UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE .SHORT TERM...TONIGHT AND TUESDAY. LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW THE STATE OF WISCONSIN LOCATED BETWEEN A COLD FRONT RUNNING UP THE EASTERN SIDE OF THE APPALACHIANS...AND A POLAR SURFACE HIGH STRETCHING ACROSS THE DAKOTAS EARLY THIS AFTERNOON. A WEAK SURFACE TROUGH REMAINS A NUISANCE WHICH HANGS BACK FROM JUST SOUTH OF MILWAUKEE TO EAU CLAIRE. RADAR RETURNS HAVE GRADUALLY ERODED OVER CENTRAL AND EAST-CENTRAL WISCONSIN OVER THE COURSE OF THE DAY...THOUGH BEEFIER RETURNS AND SURFACE OBS SHOW LIGHT SNOW SHOWERS OCCURRING OVER WESTERN WISCONSIN. SOME HOLES IN THE CLOUDS ARE TRYING TO DEVELOP OVER NORTHEAST WISCONSIN...AND PERHAPS INTO CENTRAL WISCONSIN AS WELL. AS THE SURFACE HIGH SHIFTS EAST TONIGHT...CLOUD TRENDS AND TEMPS ARE THE MAIN FORECAST CONCERNS. TONIGHT...HIGH PRESSURE OVER THE NORTHERN PLAINS WILL BUILD EAST OVER THE NORTHERN MISSISSIPPI VALLEY. HOWEVER...FLOW WILL CONTINUE TO BE OUT OF THE NORTH AND LIGHTLY ADVECTING CLOUDS OFF LAKE SUPERIOR. IN ADDITION...12Z GUIDANCE SUPPORTS LINGERING LOW LEVEL CONVERGENCE OVER CENTRAL WISCONSIN THAT WILL KEEP AN AREA OF ENHANCED RH IN PLACE. KEPT A FLURRY MENTION OVER THE FAR WESTERN CWA TO ACCOUNT FOR THIS. WITH PLENTY OF CLOUDS UPSTREAM...HAVE A HARD TIME GOING BELOW MOSTLY CLOUDY CONDITIONS. THERE WILL BE UNDOUBTEDLY SUCKER HOLES THAT WILL DEVELOP WITHIN THE STRATUS...MOSTLY LIKELY WITHIN THE DOWNSLOPING AREAS OF NORTHEAST WISCONSIN. WILL PLAY THE PROBABILITY THAT SCT CONDITIONS DEVELOP THERE...BUT LEAVE MOSTLY CLOUDY CONDITIONS ELSEWHERE...WITH SCT SNOW SHOWERS OVER THE SNOW BELT OF N-C WISCONSIN. LOWS IN THE LOWER TEENS NORTH TO MIDDLE 20S SOUTHEAST. TEMPS COULD BE MUCH COLDER OVER THE SNOW PACK OF N-C WISCONSIN IF HOLES IN THE CLOUDS DO DEVELOP THERE. TUESDAY...HIGH PRESSURE BUILDS INTO THE REGION TOMORROW. ANY SURFACE CONVERGENCE ALONG THE LINGERING TROUGH OVER CENTRAL WISCONSIN IS PROGGED TO DISSIPATE IN THE MORNING...BUT MODELS INDICATE THE REMNANTS OF THE ENHANCED RH MOVING EAST AS LIGHT SW FLOW DEVELOPS. ALSO SEE SIGNS OF STEEP LOW LEVEL LAPSE RATES WITH HEATING OF THE DAY THAT POINTS TOWARDS STRATO-CU DEVELOPING. WITH CLOUDS UNDER THE HIGH CURRENTLY...WILL SIDE MORE PESSIMISTICALLY WITH CLOUD COVER...WHICH WILL KEEP MOSTLY CLOUDY CONDITIONS OVER NORTH-CENTRAL WISCONSIN FOR THE MORNING...AND PARTLY CLOUDY CONDITIONS EVERYWHERE FOR THE AFTERNOON. HIGHS RANGING FROM THE LOWER 20S NORTH TO AROUND 30 DEGREES SOUTHEAST. .LONG TERM...TUESDAY NIGHT THROUGH NEXT MONDAY...THE MAIN FCST CONCERN IS THE ARRIVAL OF ARCTIC AIR LATER IN THE WEEK. SHORT-WAVE ENERGY CURRENTLY OVER THE GULF OF ALASKA WILL TOP THE WEST COAST RIDGE...THEN HELP TO CARVE A BROAD TROF OVER THE CENTRAL U.S. BY THURSDAY. A SURGE OF ARCTIC AIR IS EXPECTED TO ARRIVE IN WI ON THURSDAY...WITH H8 TEMPS PLUMMETING TO -16 TO -20 C BY FRIDAY. THIS WILL LEAD TO OUR COLDEST TEMPERATURES SO FAR THIS SEASON. THE COLDER WEATHER WILL NOT LAST LONG...AS SOUTHWEST WINDS DEVELOP IN THE WAKE OF THE RETREATING ARCTIC HIGH OVER THE WEEKEND. H8 TEMPS ARE EXPECTED TO SURGE TO 0 TO +4 C BY SATURDAY NIGHT/SUNDAY. A WEAK COLD FRONT IS EXPECTED TO MOVE THROUGH THE REGION ON WEDNESDAY...WITH A STRONGER ARCTIC FRONT ARRIVING ON THURSDAY. HAVE BEEN WATCHING FOR POSSIBLE SNOW DEVELOPMENT AS THE RRQ OF A STG UPPER JET INTERACTS WITH THE ARCTIC FRONT THURSDAY NIGHT INTO FRIDAY...BUT THE CONCENSUS OF THE MODELS...INCLUDING THE 12Z/MON ECMWF...IS THAT SNOW WILL DEVELOP TO OUR SOUTH AND EAST. WILL NOT CARRY ANY POPS AT THIS TIME...BUT SUBSEQUENT SHIFTS WILL STILL NEED TO KEEP AN EYE ON THIS. DESPITE THE PRESENCE OF A COLD AIR MASS FROM WEDNESDAY THROUGH FRIDAY NIGHT...WIND TRAJECTORIES WILL BE TOO WESTERLY FOR ANY APPRECIABLE LK-EFFECT SNOW. MODELS HAVE BACKED OFF SLIGHTLY ON THE MAGNITUDE OF THE COLD SNAP LATE IN THE WORK WEEK...WITH H8 TEMPS TRENDING A FEW DEGREES WARMER. EVEN SO...STILL EXPECT MAX TEMPS TO BE ABOUT 10 DEGREES BLO NORMAL ON FRIDAY. THE COLDER WEATHER WILL BE SHORT-LIVED... WITH ABOVE NORMAL TEMPERATURES QUICKLY RETURNING BY SUNDAY. A WEAK COLD FRONT MAY IMPACT THE REGION ON MONDAY...BUT SHOULD NOT HAVE ANY SIGNIFICANT IMPACT ON OUR WEATHER. && .AVIATION...A FEW FLURRIES OR SNOW SHOWERS CONTINUE OVER A CONVERGENT REGION OVER WEST CENTRAL WISCONSIN. OBSERVATIONS OVER CENTRAL WISCONSIN REPORTING 10 MILES WITH NO WEATHER PRESENT BUT ANTICIPATE FLURRY ACTIVITY OCCURRING WEST OF A LINE FROM RIB FALLS TO WISCONSIN RAPIDS INTO WAUSHARA COUNTY. RADARS ALSO SHOWING SOME RETURNS OVER THE LAKE MICHIGAN SHORELINE WITH NO GROUND TRUTH AND FINALLY SCATTERED SNOW SHOWERS WERE NOTED OVER VILAS. AS FAR AS CLOUDS...A SUCKER HOLE OPENED UP NORTHEAST WISCONSIN INCLUDING THE GRB VICINITY. BUT STILL EXPECT VFR CIGS TO DOMINATE OVERNIGHT INTO TUESDAY WITH SOME DECREASE IN CLOUDS LATER TUESDAY. TDH && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1045 PM CST MON DEC 5 2011 .SHORT TERM... 245 PM CST MON DEC 5 2011 BIGGEST FORECAST CONCERN IS ON CLOUDS AND TEMPERATURES...WITH LIGHT PRECIPITATION CHANCES THIS EVENING ALSO A CONCERN. 18Z WATER VAPOR IMAGERY SHOWS SHORTWAVE TROUGH OVER MINNESOTA...WHILE AT THE SURFACE A WEAK TROUGH WAS WORKING ITS WAY THROUGH THE FORECAST AREA...BUT WAS WEAKENING WITH TIME. THIS COMBINATION WAS PRODUCING WEAK LIFT THROUGH SATURATED LOWER LAYER AND THUS SURFACE REPORTS INDICATING MAINLY LIGHT SNOW AND FLURRIES...WITH SOME PATCHY FREEZING DRIZZLE. 05.12Z MODELS AGAIN IN GOOD AGREEMENT WITH THEIR MASS FIELDS. THERE IS SOME DIFFERENCES IN SPEED OF COLDER PLUNGE OF AIR ON THURSDAY...WITH THE NAM THE FASTEST. ONLY OTHER DIFFERENCE NOTED IS GFS A LITTLE FASTER IN PUSHING THE STRATUS OUT ON TUESDAY. FOR TONIGHT...SHORTWAVE IN MINNESOTA ROTATES INTO NORTHWEST WISCONSIN. MODEL SOUNDINGS INDICATE WEAK LIFT CONTINUES IN THE SATURATED LOWER LAYER DURING THE EVENING. 05.15Z RUC SOUNDINGS QUESTIONABLE WITH REGARDS TO ICE IN THE CLOUD LAYER...WHILE NAM SOUNDINGS SUGGEST MORE ICE. BASED ON REPORTS FROM THIS AFTERNOON MENTION FLURRIES AND PATCHY FREEZING DRIZZLE FOR THE EVENING HOURS. WITH THE CLOUDS DID GO ON THE WARMER SIDE OF THE GUIDANCE NUMBERS FOR LOWS TONIGHT. ON TUESDAY...GFS A LITTLE FASTER IN PUSHING THE STRATUS OUT OF THE AREA...WHILE THE NAM KEEPS 850MB-925MB MOISTURE OVER THE AREA THROUGHOUT THE DAY AND NOT CLEARING UNTIL EVENING. DID TAKE A COMPROMISE...WITH A CLEARING TREND FROM WEST TO EAST DURING THE AFTERNOON HOURS. TEMPERATURES WILL BE TRICKY WITH THE CLOUDS...BUT WITH THE MORE PESSIMISTIC OUTLOOK DID GO WITH THE COOLER OF THE GUIDANCE NUMBERS. DO EXPECT CLEAR SKIES...AT LEAST FOR A SHORT PERIOD OF TIME TUESDAY NIGHT. HOWEVER...ANOTHER SHORTWAVE BEGINS TO DROP SOUTHWARD OUT OF SOUTHERN CANADA LATE TUESDAY NIGHT...AND MODELS HINT AT AN INCREASE IN HIGH LEVEL CLOUDS. THESE CLOUDS THEN DROP ACROSS THE AREA ON WEDNESDAY AND WEDNESDAY NIGHT AHEAD OF THE ASSOCIATED COLD FRONT. TEMPERATURES LOOK TO BE A LITTLE MILDER AHEAD OF THE FRONT...BUT STILL BELOW NORMAL WITH HIGHS FROM THE MIDDLE 20S IN THE SNOW COVERED LOCATIONS...TO THE LOWER 30S IN THE NON SNOW COVERED AREAS. ON THURSDAY COLD AIR BEGINS TO SURGE INTO THE AREA BEHIND THE FRONT. AS MENTIONED BEFORE NAM QUICKER IN MOVING THIS COLD AIR INTO THE REGION AND AGAIN USED A MODEL CONSENSUS FOR HIGHS. 05.12 GFS AND ECMWF ALSO GENERATING SOME LIGHT PRECIPITATION ALONG THE LEADING EDGE OF THE COLD AIR ACROSS IOWA IN BAND OF WEAK FRONTOGENESIS. WITH THE BULK OF PUSH OF COLD AIR THURSDAY NIGHT...DID ADD SOME LOWER END SNOW PROBABILITIES ACROSS NORTHEAST IOWA AND SOUTHWEST WISCONSIN. .LONG TERM... 245 PM CST MON DEC 5 2011 A DRY NORTHWEST LOW PATTERN WILL CONTINUE FOR FRIDAY AND SATURDAY AND THIS WILL LEAD TO BELOW NORMAL TEMPERATURES. THE FLOW WILL BECOME MORE ZONAL ON SUNDAY AS A TROUGH BUILDS INTO THE WESTERN CONUS. AS THE TROUGH PROGRESSES INTO THE CENTRAL SECTIONS OF THE COUNTRY...THE FLOW WILL BECOME MORE SOUTHWESTERLY. DRY CONDITIONS WILL CONTINUE THROUGH MONDAY...BUT WITH A MORE SOUTHERLY WIND...TEMPERATURES WILL WARM SATURDAY AND SUNDAY...WITH HIGHS EXPECTED IN THE 30S BOTH SUNDAY AND MONDAY. && .AVIATION... 1045 PM CST MON DEC 5 2011 PERSISTENT LOW LEVEL SATURATION...PER RH FIELDS AND BUFKIT SOUNDINGS...SUGGEST THAT THE MVFR CIGS WILL HOLD INTO TUE AFTERNOON/EVENING. AN UPPER LEVEL SHORTWAVE TROUGH WILL HELP SWEEP THE LOW STRATUS TO THE EAST...AND MOST OF TUE NIGHT LOOKS SCT-SKC. BY WED MORNING CLOUDS ASSOCIATED WITH THE TROUGH WILL SLIDE IN...AND THERE COULD BE ANOTHER PERIOD OF MVFR CIGS IN THE AFTERNOON. A FEW FLURRIES WILL CONTINUE THROUGH THE OVERNIGHT HOURS...BUT DON/T SEE ANY REDUCTIONS TO VSBY. BELIEVE ANY THREAT FOR -FZDZ HAS ALSO ENDED. NORTHWEST WINDS WILL SWING TO THE SOUTHWEST BY LATE TUE AFTERNOON...AHEAD OF THAT SHORTWAVE...BUT SHIFT BACK TO THE NORTHWEST ON WED AS THE SYSTEM PASSES EAST. && .ARX WATCHES/WARNINGS/ADVISORIES... 245 PM CST MON DEC 5 2011 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM... RABERDING LONG TERM.... RABERDING AVIATION..... RIECK
AREA FORECAST DISCUSSION
NWS ALBANY NY
1245 AM EST THU DEC 8 2011 .SYNOPSIS... A STORM SYSTEM WILL LIFT NORTHEAST FROM THE DELMARVA REGION THIS EVENING...TO THE EAST END OF LONG ISLAND AROUND MIDNIGHT...AND THEN INTO THE GULF OF MAINE THURSDAY MORNING. THIS STORM TRACK WILL RESULT IN RAIN CHANGING TO SNOW THIS EVENING ACROSS MUCH OF THE REGION WITH SIGNIFICANT SNOWFALL ACCUMULATIONS OVERNIGHT IN MANY AREAS. THE HEAVIEST SNOW IS EXPECTED TO FALL ACROSS THE NORTHERN TACONICS...EASTERN CATSKILLS...BERKSHIRES AND SOUTHERN GREEN MOUNTAINS. HEAVY RAIN WILL CONTINUE TO FALL OVERNIGHT ACROSS THE MID HUDSON VALLEY AND LITCHFIELD HILLS. && .NEAR TERM /THROUGH THURSDAY/... AS OF 930PM RADAR FSI CROSS SECTIONS AND SPOTTER REPORTS HAVE RAIN CHANGING TO SNOW AROUND THE GREATER CAPITAL DISTRICT. THIS IS RUNNING AN HOUR OR TWO BEHIND GRIDS AND MADE MINOR CHANGES. THIS PROCESS WILL RAPIDLY CHANGE RAIN OVER TO SNOW IN NEXT 1-2 HOURS. 00UTC NAM IN LINE WITH PVS QPF AND THINKING. NO DEPARTURES THERE. ONCE PCPN CHANGES OVER BURST OF SNOW FOR SEVERAL HOURS IN MASSIVE TILTED FRONTOGENESIS AS MESOSCALE BAND HAS SET UP FM SW VT TO CATSKILLS (CSTAR) WHILE PCPN MAY BE CHANGING OVER 1-2 HOURS LATER...DONT THINK IT WILL SIGNIFICANTLY ALTER CURRENT THINKING ON AMOUNTS OR HEADLINES GIVEN CHARACTER AND FORCING OF THE SNOW OVERNIGHT. ALL 3 HOUR PRESSURE MAX FALLS ARE NOW OFFSHORE NJ/DELMARVA. RAPID DEEPENING WILL OCCUR NEXT FEW HOURS AS 500HPA SHORT WAVE INTERACT WITH STRONG BAROCLINIC ZONE ALONG COAST. AS OF 7PM...NOT MAKING ANY CHANGES ATTM. AWAITING CHANGE OVER TO SNOW. ON ALB 00UTC ALB SOUNDING +4C WARM NOSE REMAINS AT 3500 MSL. FSI CROSS SECTIONS CAPPI INDICATE BRIGHT BAND LOWERING TO GROUND IN MONTGOMERY/SCHOHARIE COUNTIES...BUT ONLY ONE REPORT OF SNOW IN WEST SCHOHARIE COUNTY AN HOUR AGO. BANDLETS (CSTAR III) HAVE SET UP ACROSS RGN WITH SOME ALONG BRIGHT BAND AXISES AND OTHERS IN RN TO +RN AREAS. 18UTC NAM/GFS SHOW ALL THE RIGHT FEATURES FOR FORMATION OF A MAJOR BAND OVER FCA. 20UVM IN MAX DENDRITIC GROWN ZONE BY 03UTC...STRONG TILTED FRONTOGENESIS AND EPV. SO THE STAGE IS SET...JUST AWAITING THE ARRIVAL OF THE COLDER AIR OR ITS DYNAMIC CREATION. SFC PRES FALLS HAVE SHIFTED TO NJ-DELMARVA COAST BUT 3HR VALUES REMAIN REMAIN ON ORDER OF 4-6MB. WX WATCH CONTINUES. WINTER STORM WARNINGS ARE IN EFFECT FOR TONIGHT FOR THE EASTERN CATSKILLS...NORTHERN TACONICS...BERKSHIRES AND SOUTHERN GREEN MOUNTAINS AND WINTER WEATHER ADVISORIES IN EFFECT FOR THE SOUTHEAST ADIRONDACKS...LAKE GEORGE SARATOGA REGION...EASTERN MOHAWK VALLEY...SACANDAGA REGION...GREATER CAPITAL DISTRICT AND CENTRAL TACONICS. A FLOOD WATCH IS IN EFFECT THROUGH THURSDAY MORNING FOR THE MID HUDSON VALLEY...SOUTHERN TACONICS AND LITCHFIELD HILLS. SNOWFALL ACCUMULATIONS ARE GENERALLY EXPECTED TO BE 3 TO 8 INCHES IN THE ADVISORY AREA AND 5 TO 12 INCHES IN THE WARNING AREA EXCEPT ACROSS THE CENTRAL AND SOUTHEAST CATSKILLS...NORTHERN BERKSHIRES AND HIGHER TERRAIN OF THE SOUTHERN GREEN MOUNTAINS WHERE 8 TO 16 INCHES OF SNOW IS EXPECTED. TOTAL RAINFALL AMOUNTS IN THE FLOOD WATCH AREA ARE EXPECTED TO BE IN THE 1.75 TO 2.25 INCH RANGE. AS OF 530 PM EST...CLOUD TOPS CONTINUE TO COOL ACROSS THE FA WITH 21Z KALB SOUNDING INDICATING A WARM TONGUE OF 4C AT AROUND 875 MB WITH THE FREEZING LEVEL AT AROUND 775 MB OR 6.6 KFT. HAVE RECEIVED A REPORT OF 1 INCH OF SNOW THUS FAR IN CHARLOTTEVILLE IN SCHOHARIE COUNTY WITH HEAVY WET SNOW AND A TEMP OF 36 DEGREES AT AN ELEVATION OF AROUND 1500 FEET. EXPECT A RAPID CHANGEOVER TO SNOW THIS EVENING ACROSS MUCH OF THE FA MAINLY BETWEEN 00Z AND 03Z WITH VERY HEAVY SNOW EXPECTED TO FALL DURING MUCH OF THE NIGHT BEFORE TAPERING OFF LATE. THE ONLY AREAS WHICH ARE NOT EXPECTED TO RECEIVE MUCH SNOW ARE FAR NORTHWEST PORTIONS OF THE FA INCLUDING THE WESTERN ADIRONDACKS AND WESTERN MOHAWK VALLEY WHERE VERY LITTLE QPF EXPECTED...NORTHERN FRINGE OF PCPN SHIELD AND FAR SOUTHEAST PORTION OF FA WHICH WILL REMAIN TOO WARM FOR MUCH IN THE WAY OF SNOW MAINLY FROM THE MID HUDSON VALLEY EAST TO THE LITCHFIELD HILLS WHERE A FLOOD WATCH IS IN EFFECT. MANY FAVORABLE FACTORS FOR HEAVY SNOW ARE IN PLACE ACROSS MUCH OF THE FA WITH THE MOST SIGNIFICANT FACTORS BEING IMPRESSIVE FRONTOGENESIS H8-H7 EXTENDING FROM THE CATSKILLS NORTHEAST TO SOUTHERN VERMONT AT 00Z AND THEN SHIFTING TO AN ORIENTATION FROM JUST EAST OF THE CAPITAL DISTRICT THROUGH THROUGH THE NORTHERN BERKSHIRES INTO SOUTHERN VERMONT AT 06Z. AS THE EVENING WEARS ON THE SNOW GROWTH REGION BECOMES INCREASINGLY MORE FAVORABLE WITH THE -12 TO -18 C TEMP SLICING THROUGH A REGION OF +20 UBAR/SEC. IN ADDITION IMPRESSIVE EPV EXISTS IN LOWER LEVELS ESPECIALLY BTWN 00Z AND 06Z. THE LATEST HRRR COL MAX REFLECTIVITY ALSO INDICATES IMPRESSIVE BANDED PCPN ESPECIALLY ACROSS THE HIGHER TERRAIN IN THE WARNING AREA BETWEEN 03Z AND 06Z WITH THE BACK EDGE OF THE PCPN SHIELD EXITING THE FA FROM WEST TO EAST BETWEEN 08Z AND 10Z. EXPECT LOW TEMPS TONIGHT TO RANGE FROM THE MID 20S NORTHWEST TO MID 30S FAR SOUTHEAST. ON THURSDAY EXPECT IMPROVING CONDITIONS WITH HIGH PRESSURE MOVING IN AND MAINLY DRY CONDITIONS WITH HIGHS RANGING FROM THE UPPER 20S TO LOWER 30S NORTHWEST TO LOWER 40S FAR SOUTHEAST. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... THU NT...BACKING LOW LEVEL WINDS SHOULD ALLOW ANY LINGERING SNOW BANDS/SNOW SHOWERS TO SHIFT NORTHWARD INTO THE WESTERN ADIRONDACKS...WITH ADDITIONAL ACCUMS POSSIBLE BEFORE INVERSION HEIGHTS LOWER AND DIMINISH INTENSITY OF ANY SNOWBANDS. ELSEWHERE...INITIALLY CLEAR TO PARTLY CLOUDY SKIES SHOULD BECOME MOSTLY CLOUDY LATER AT NIGHT AS MID LEVEL ISENTROPIC LIFT INCREASES AHEAD OF NEXT APPROACHING SHORTWAVE. EXPECT MINS TO FALL INTO THE TEENS AND 20S...WARMEST ACROSS VALLEY REGIONS. FRI-SAT...UPPER LEVEL TROUGH WILL APPROACH FROM THE W...AND PASS ACROSS FRI NT. A SFC COLD FRONT ASSOCIATED WITH THIS FEATURE WILL CROSS THE REGION LATE FRI OR FRI EVE...PRECEDED AND ACCOMPANIED BY SNOW SHOWERS. THEN...BEHIND THE FRONT...BANDS OF SNOW SHOWERS AND POSSIBLE SNOW SQUALLS WILL BE POSSIBLE...INITIALLY FAVORING PORTIONS OF THE WESTERN MOHAWK VALLEY/SCHOHARIE VALLEY...THEN GRADUALLY SHIFTING NORTHWARD INTO THE WESTERN ADIRONDACKS BY SAT. THERE IS SOME POTENTIAL FOR LOCALLY HEAVY SNOWFALL AMTS WITHIN SOME OF THESE BANDS...AND WILL MENTION THIS POSSIBILITY IN THE HWO...WITH GREATEST THREAT ACROSS THE WESTERN ADIRONDACKS. EXPECT FRI MAXES TO REACH THE 30S IN MOST AREAS...EXCEPT AROUND OR INTO THE LOWER 40S WITHIN THE VALLEYS...WITH 20S ACROSS HIGHER ELEVATIONS. COLDER AIR BEHIND THE FRONT WILL MOVE IN FOR FRI NT AND SAT...WITH FRI NT MINS IN THE TEENS AND LOWER 20S...AND SAT MAXES MAINLY IN THE 30S WITHIN VALLEYS...AND 20S ACROSS HIGHER ELEVATIONS. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... THIS PERIOD WILL BE FAIRLY QUIET AS HIGH PRESSURE BUILDS INTO THE MID ATLANTIC REGION SATURDAY NIGHT AND DOMINATES OUR WEATHER INTO THE EARLY PART OF THE COMING WEEK. A CHANCE OF SOME LAKE ENHANCED SNOW SHOWERS SATURDAY NIGHT...THEN DRY UNTIL TUESDAY NIGHT WHEN A WEAK BOUNDARY BRINGS ABOUT SOME SNOW AND RAIN SHOWERS WEST OF THE HUDSON VALLEY WEDNESDAY. THE PERIOD STARTS OFF CHILLY...LOWS FROM AROUND 10 TO 20 ABOVE ON SUNDAY MORNING...WITH HIGHS SUNDAY ONLY IN THE UPPER 20S TO THE MID 30S. TEMPERATURES WILL GRADUALLY MODERATE WITH HIGHS RISING TO THE UPPER 30S AND LOWER 40S BY TUESDAY AFTERNOON. FOR THE MOST PART...USED HPC GUIDANCE TO POPULATE THE GRIDS. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... AS OF 0530Z...PCPN HAS CHANGED OVER TO SNOW AT THE KGFL/KALB/KPOU TAF SITES. EXPECT THE SNOW AND MAINLY IFR CONDITIONS TO CONTINUE UNTIL AROUND 08Z TO 09Z...WITH A RAPID IMPROVEMENT TO VFR CONDITIONS AFTER 09Z. VFR CONDITIONS THEREAFTER UNTIL THE END OF THE TAF PERIOD AT 06Z FRIDAY. NORTHERLY WINDS AT 5 TO 15 KTS WITH SOME GUSTS TO 20 KTS POSSIBLE AT THE TAF SITES (PRIMARILY KALB/KPOU)...THEN BECOMING NORTHWEST AFTER THE SNOW ENDS AND INCREASING TO 10 TO 15 KTS BY MID MORNING WITH GUSTS OF 20 TO 25 KTS. BY LATE IN THE AFTERNOON THE WINDS WILL SUBSIDE TO 10 KTS OR LESS AN DSHIFT TO THE SOUTHWEST...THEN LIGHT SOUTH OR SOUTHWEST WINDS AFTER 00Z FRIDAY. OUTLOOK... LATE THU NT-SAT...MAINLY VFR...SLIGHT CHC -SHSN. BREEZY. SUN-MON...VFR...NO SIG WX. && .HYDROLOGY... A SIGNIFICANT MIXED PRECIPITATION EVENT WAS OCCURRING ACROSS THE REGION WITH STORM TOTAL LIQUID AMOUNTS FROM LESS THAN A QUARTER INCH IN NORTHERN HERKIMER COUNTY TO A LITTLE OVER TWO INCHES IN THE LOWER HUDSON VALLEY OF NEW YORK AND THE LITCHFIELD HILLS OF CONNECTICUT. OVER COOLER REGIONS SUCH AS THE HIGHER ELEVATIONS OF THE CATSKILLS...BERKSHIRES...AND GREEN MOUNTAINS OF SOUTHERN VERMONT A SUBSTANTIAL AMOUNT OF THIS PRECIPITATION IS FORECAST TO COME AS SNOW. ACROSS OUR SOUTHERNMOST COUNTIES...EASTERN ULSTER DUTCHESS...AND LITCHFIELD...MOST OF THE PRECIPITATION WILL COME AS RAIN AND LOCALLY HEAVY AMOUNTS MAY AMOUNT TO ENOUGH TO RESULT IN SOME MINOR FLOODING OF ROADS AND PARKING AREAS AND CAUSE RISES OF SEVERAL FEET ON RIVERS AND STREAMS. FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...FLOOD WATCH UNTIL 9 AM EST THURSDAY FOR CTZ001-013. NY...WINTER STORM WARNING UNTIL 6 AM EST THURSDAY FOR NYZ047-051- 054-058-063. WINTER WEATHER ADVISORY UNTIL 6 AM EST THURSDAY FOR NYZ039>043- 048>050-052-053-059>061-082>084. FLOOD WATCH UNTIL 9 AM EST THURSDAY FOR NYZ064>066. MA...WINTER STORM WARNING UNTIL 6 AM EST THURSDAY FOR MAZ001-025. VT...WINTER STORM WARNING UNTIL 6 AM EST THURSDAY FOR VTZ013-014. WINTER WEATHER ADVISORY UNTIL 6 AM EST THURSDAY FOR VTZ015. && $$ SYNOPSIS...11 NEAR TERM...11/SNYDER SHORT TERM...KL LONG TERM...RCK AVIATION...GJM HYDROLOGY...RCK
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
304 AM CST THU DEC 8 2011 .DISCUSSION... 856 PM CST SMALL UPDATES HAVE BEEN MADE FOR THE REMAINDER OF TONIGHTS FORECAST...WITH ATTENTION TURNING TO THURSDAY NIGHTS SNOW POTENTIAL. VARIABLE CLOUD COVERAGE BY OVERNIGHT IS MAKING IT CHALLENGING ON THE TEMPERATURE FORECAST. WITH AN INITIAL COLD FRONT CONTINUING TO LOSE DEFINITION AS IT DRAPES INTO NORTHERN IL...LOW CLOUDS HAVE DIMINISHED IN COVERAGE. SATELLITE TRENDS AND RUC SOUNDINGS ACROSS NORTHEAST IL INDICATE TEMPORARY SCATTERED CLOUDS ARE LIKELY TO CONTINUE TO PROPAGATE SOUTHEAST. CLOUDS ALONG THE MID-LEVEL BAROCLINIC ZONE SEEN AT 700 MB ON THIS EVENINGS UPPER AIR ANALYSIS WILL ALSO CONTINUE TO SLOWLY FILTER INTO THE AREA THROUGH THU MORNING. SO WILL CONTINUE TO ADJUST SKY TRENDS...BUT ALL IN ALL VARIABLE TO PARTLY CLOUDY WORDING IS PROBABLY THE BEST BET. EVEN THOUGH THE HOURLY TREND WILL DEPEND HEAVILY ON HOW ANY CLOUDS UNDULATE IN COVERAGE...LOW TEMPERATURES STILL LOOK ON TRACK. SCATTERED MID-TEENS ARE FORECAST TOWARDS ROCKFORD AND STERLING...WITH LOWER TO MID 20S TOWARDS THE LAKE AND INTO NORTHWEST IN. A LOOK AT THE LATEST GUIDANCE...08.00 NAM AND 07.21 SREF...AS WELL AS UPSTREAM TRENDS ARE STARTING TO SUPPORT THE LIKELY SCENARIO THAT A MINOR ACCUMULATING SNOW EVENT WILL BE SEEN IN THE FORECAST AREA...ESPECIALLY THE SOUTHEAST QUARTER TO THIRD. THE UPPER AIR ANALYSES THIS EVENING DEPICTED THE STRONG UPPER JET /OVER 120 KTS AT UNR/ HEADING TOWARDS THE AREA WHICH WILL PROVIDE MORE CONCENTRATED UPPER SUPPORT DURING TUE AFTERNOON AND NIGHT. SATURATION AND QG FORCING WITH THE WAVE WILL NOT ARRIVE INTO PARTS OF OUR AREA UNTIL THE NIGHT...LIKELY BY 03Z. THE NEW NAM OUTPUT INDICATES MIXING RATIOS NEAR 2 G/KG ON THE FAVORED SURFACES WHERE LIFT IS OCCURRING INTO THE FAR SOUTHEAST...AND THAT IS NEARLY COINCIDENT WITH THE DENDRITIC GROWTH AREA. WHILE TOP-DOWN METHODS ON THE NAM SOUNDINGS WARM SOME ON THE WAY DOWN...RATIOS STILL LOOK TO BE ON THE HIGHER SIDE AS INDICATED BY EVEN THE PRIOR NAM RUNS. THE SREF GUIDANCE HAS BECOME MORE FOCUSED ON ITS SNOW PROBABILITIES...INDICATING A RIBBON ACROSS THE SOUTHEAST /GIBSON CITY TO RENSSELAER/ WHERE OVER ONE INCH OF SNOW IS FORECAST BY THE MEAN OF THE MEMBERS. EVEN THE PRIOR RUNS OF THESE MODELS AND THE GFS...EC...AND NMM WRF...INDICATE THE FAR SOUTHERN TIER OF COUNTIES TO SEE SNOW...AND COULD ENVISION BASED ON RATIOS AND RECENTLY COOLED GROUND TEMPERATURES THAT ONE TO TWO INCH ACCUMULATIONS ARE POSSIBLE. MINOR ACCUMULATIONS OF A COUPLE TENTHS AS FAR NORTH AS CHICAGO CANNOT BE RULED OUT DEPENDING ON IF THE ATMOSPHERE CAN SATURATE...AND LIGHT AMOUNTS ARE FORECAST THAT FAR NORTH BY THE 18.00 NAM. WILL RE-ISSUE AN SPS TO HIGHLIGHT FOR NOW AND BRIEF THE OVERNIGHT SHIFT. MTF && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 06Z... * ISOLATED THREAT FOR -SN THURSDAY EVENING SHEA //DISCUSSION...UPDATED 06Z... LIGHT WESTERLY WINDS WILL CONTINUE OVERNIGHT AS AN APPROACHING NORTHERN HIGH PLAINS SYSTEM AND ANOTHER COLD FRONT DROPS SOUTHEAST ACROSS WISCONSIN DURING THE DAY TODAY. THIS SYSTEM IS EXPECTED TO PRODUCE SOME LIGHT SNOWFALL BUT THE ZONE OF BEST FORCING AT THIS POINT LOOKS TO BE ALONG A NORTHERN MISSOURI...CENTRAL IL...NORTHEAST INDINANA AXIS SO THREAT OF ANY PRECIPITATION AT THE LOCAL TERMINALS QUITE SMALL. SHEA //ORD AND MDW CONFIDENCE...UPDATED 06Z... * HIGH CONFIDENCE IN ALL ELEMENTS SHEA //OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z... FRIDAY...VFR. SATURDAY...VFR. SUNDAY...VFR. MONDAY...VFR INTO EVENING...SLGT CHC -SN PRODUCING MVFR CIGS AND/OR VSBYS OVERNIGHT. TUESDAY...MVFR CIGS POSSIBLE. TRS && .MARINE... 305 AM CST A PROLONGED PERIOD OF GENERALLY WEST WINDS IS SETTING UP FOLLOWING THE PASSAGE OF A COLD FRONT. ANOTHER SURGE OF COLD AIR ASSOCIATED WITH A SECONDARY COLD FRONT WILL PUSH ACROSS THE LAKE LATER TODAY...KEEPING WESTERLY WINDS IN THE 25 TO 30 KT INTO SATURDAY. AN UPPER LEVEL TROUGH CROSSING THE GREAT LAKES REGION FRIDAY AND FRIDAY NIGHT WILL BRING VERY COLD AIR ALOFT OVER LAKE MICHIGAN. COMBINED WITH RELATIVELY WARMER LAKE SURFACE WATER...A VERY UNSTABLE ENVIRONMENT WILL SET UP OVER THE LAKE...BRINGING A CHANCE FOR WATERSPOUTS. BY SATURDAY...WINDS WILL SHIFT SOUTHWESTERLY AS HIGH PRESSURE BUILDS ACROSS THE OHIO VALLEY WHILE A WEAK LOW PRESSURE SYSTEM TRACKS ACROSS THE UPPER GREAT LAKES. THE HIGH WILL BE FAR ENOUGH TO THE SOUTH THAT WINDS WILL REMAIN AROUND 30 KT THROUGH THE WEEKEND. KREIN && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE BURNS HARBOR TO MICHIGAN CITY IN UNTIL 10 AM SATURDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
205 AM CST THU DEC 8 2011 .DISCUSSION... 856 PM CST SMALL UPDATES HAVE BEEN MADE FOR THE REMAINDER OF TONIGHTS FORECAST...WITH ATTENTION TURNING TO THURSDAY NIGHTS SNOW POTENTIAL. VARIABLE CLOUD COVERAGE BY OVERNIGHT IS MAKING IT CHALLENGING ON THE TEMPERATURE FORECAST. WITH AN INITIAL COLD FRONT CONTINUING TO LOSE DEFINITION AS IT DRAPES INTO NORTHERN IL...LOW CLOUDS HAVE DIMINISHED IN COVERAGE. SATELLITE TRENDS AND RUC SOUNDINGS ACROSS NORTHEAST IL INDICATE TEMPORARY SCATTERED CLOUDS ARE LIKELY TO CONTINUE TO PROPAGATE SOUTHEAST. CLOUDS ALONG THE MID-LEVEL BAROCLINIC ZONE SEEN AT 700 MB ON THIS EVENINGS UPPER AIR ANALYSIS WILL ALSO CONTINUE TO SLOWLY FILTER INTO THE AREA THROUGH THU MORNING. SO WILL CONTINUE TO ADJUST SKY TRENDS...BUT ALL IN ALL VARIABLE TO PARTLY CLOUDY WORDING IS PROBABLY THE BEST BET. EVEN THOUGH THE HOURLY TREND WILL DEPEND HEAVILY ON HOW ANY CLOUDS UNDULATE IN COVERAGE...LOW TEMPERATURES STILL LOOK ON TRACK. SCATTERED MID-TEENS ARE FORECAST TOWARDS ROCKFORD AND STERLING...WITH LOWER TO MID 20S TOWARDS THE LAKE AND INTO NORTHWEST IN. A LOOK AT THE LATEST GUIDANCE...08.00 NAM AND 07.21 SREF...AS WELL AS UPSTREAM TRENDS ARE STARTING TO SUPPORT THE LIKELY SCENARIO THAT A MINOR ACCUMULATING SNOW EVENT WILL BE SEEN IN THE FORECAST AREA...ESPECIALLY THE SOUTHEAST QUARTER TO THIRD. THE UPPER AIR ANALYSES THIS EVENING DEPICTED THE STRONG UPPER JET /OVER 120 KTS AT UNR/ HEADING TOWARDS THE AREA WHICH WILL PROVIDE MORE CONCENTRATED UPPER SUPPORT DURING TUE AFTERNOON AND NIGHT. SATURATION AND QG FORCING WITH THE WAVE WILL NOT ARRIVE INTO PARTS OF OUR AREA UNTIL THE NIGHT...LIKELY BY 03Z. THE NEW NAM OUTPUT INDICATES MIXING RATIOS NEAR 2 G/KG ON THE FAVORED SURFACES WHERE LIFT IS OCCURRING INTO THE FAR SOUTHEAST...AND THAT IS NEARLY COINCIDENT WITH THE DENDRITIC GROWTH AREA. WHILE TOP-DOWN METHODS ON THE NAM SOUNDINGS WARM SOME ON THE WAY DOWN...RATIOS STILL LOOK TO BE ON THE HIGHER SIDE AS INDICATED BY EVEN THE PRIOR NAM RUNS. THE SREF GUIDANCE HAS BECOME MORE FOCUSED ON ITS SNOW PROBABILITIES...INDICATING A RIBBON ACROSS THE SOUTHEAST /GIBSON CITY TO RENSSELAER/ WHERE OVER ONE INCH OF SNOW IS FORECAST BY THE MEAN OF THE MEMBERS. EVEN THE PRIOR RUNS OF THESE MODELS AND THE GFS...EC...AND NMM WRF...INDICATE THE FAR SOUTHERN TIER OF COUNTIES TO SEE SNOW...AND COULD ENVISION BASED ON RATIOS AND RECENTLY COOLED GROUND TEMPERATURES THAT ONE TO TWO INCH ACCUMULATIONS ARE POSSIBLE. MINOR ACCUMULATIONS OF A COUPLE TENTHS AS FAR NORTH AS CHICAGO CANNOT BE RULED OUT DEPENDING ON IF THE ATMOSPHERE CAN SATURATE...AND LIGHT AMOUNTS ARE FORECAST THAT FAR NORTH BY THE 18.00 NAM. WILL RE-ISSUE AN SPS TO HIGHLIGHT FOR NOW AND BRIEF THE OVERNIGHT SHIFT. MTF && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 06Z... * ISOLATED THREAT FOR -SN THURSDAY EVENING SHEA //DISCUSSION...UPDATED 06Z... LIGHT WESTERLY WINDS WILL CONTINUE OVERNIGHT AS AN APPROACHING NORTHERN HIGH PLAINS SYSTEM AND ANOTHER COLD FRONT DROPS SOUTHEAST ACROSS WISCONSIN DURING THE DAY TODAY. THIS SYSTEM IS EXPECTED TO PRODUCE SOME LIGHT SNOWFALL BUT THE ZONE OF BEST FORCING AT THIS POINT LOOKS TO BE ALONG A NORTHERN MISSOURI...CENTRAL IL...NORTHEAST INDINANA AXIS SO THREAT OF ANY PRECIPITATION AT THE LOCAL TERMINALS QUITE SMALL. SHEA //ORD AND MDW CONFIDENCE...UPDATED 06Z... * HIGH CONFIDENCE IN ALL ELEMENTS SHEA //OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z... FRIDAY...VFR. SATURDAY...VFR. SUNDAY...VFR. MONDAY...VFR INTO EVENING...SLGT CHC -SN PRODUCING MVFR CIGS AND/OR VSBYS OVERNIGHT. TUESDAY...MVFR CIGS POSSIBLE. TRS && .MARINE... 157 PM CST A COLD FRONT MOVING ACROSS LAKE SUPERIOR AND WISCONSIN THIS AFTERNOON WILL MOVE ACROSS LAKE MICHIGAN LATER THIS AFTERNOON AND EVENING. THIS WILL HELP KEEP THE WINDS AROUND 25 TO 30 KT TONIGHT AS THE WINDS BECOME NORTHWESTERLY. A PROLONGED PERIOD OF BRISK WEST TO NORTHWESTERLY WINDS IS EXPECTED INTO SATURDAY AS HIGH PRESSURE MOVING FROM THE PLAINS EASTWARD ACROSS THE MID MISSISSIPPI VALLEY...WILL CONTINUE TO PRODUCE A DECENT PRESSURE GRADIENT ACROSS THE GREAT LAKES. LATER SATURDAY THE WINDS LOOK TO SWITCH OUT OF THE SOUTHWEST AND INCREASE TO AROUND 30 KT AGAIN AS THE SURFACE HIGH SHIFTS ACROSS THE OHIO VALLEY AND ANOTHER AREA OF LOW PRESSURE MOVES ACROSS THE PRAIRIE PROVIDENCES OF CANADA. IT APPEARS THAT THESE SOUTHWESTERLY WINDS WILL CONTINUE INTO EARLY NEXT WEEK AS THE SURFACE HIGH CONTINUES TO DOMINATE ACROSS EASTERN CONUS. THERE COULD EVEN BE A PERIOD OF LOW END GALE FORCE WINDS DURING THIS PERIOD. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO BURNS HARBOR UNTIL 10 PM THURSDAY. SMALL CRAFT ADVISORY...NEARSHORE BURNS HARBOR TO MICHIGAN CITY IN UNTIL 10 AM SATURDAY. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1227 AM CST THU DEC 8 2011 .DISCUSSION... 856 PM CST SMALL UPDATES HAVE BEEN MADE FOR THE REMAINDER OF TONIGHTS FORECAST...WITH ATTENTION TURNING TO THURSDAY NIGHTS SNOW POTENTIAL. VARIABLE CLOUD COVERAGE BY OVERNIGHT IS MAKING IT CHALLENGING ON THE TEMPERATURE FORECAST. WITH AN INITIAL COLD FRONT CONTINUING TO LOSE DEFINITION AS IT DRAPES INTO NORTHERN IL...LOW CLOUDS HAVE DIMINISHED IN COVERAGE. SATELLITE TRENDS AND RUC SOUNDINGS ACROSS NORTHEAST IL INDICATE TEMPORARY SCATTERED CLOUDS ARE LIKELY TO CONTINUE TO PROPAGATE SOUTHEAST. CLOUDS ALONG THE MID-LEVEL BAROCLINIC ZONE SEEN AT 700 MB ON THIS EVENINGS UPPER AIR ANALYSIS WILL ALSO CONTINUE TO SLOWLY FILTER INTO THE AREA THROUGH THU MORNING. SO WILL CONTINUE TO ADJUST SKY TRENDS...BUT ALL IN ALL VARIABLE TO PARTLY CLOUDY WORDING IS PROBABLY THE BEST BET. EVEN THOUGH THE HOURLY TREND WILL DEPEND HEAVILY ON HOW ANY CLOUDS UNDULATE IN COVERAGE...LOW TEMPERATURES STILL LOOK ON TRACK. SCATTERED MID-TEENS ARE FORECAST TOWARDS ROCKFORD AND STERLING...WITH LOWER TO MID 20S TOWARDS THE LAKE AND INTO NORTHWEST IN. A LOOK AT THE LATEST GUIDANCE...08.00 NAM AND 07.21 SREF...AS WELL AS UPSTREAM TRENDS ARE STARTING TO SUPPORT THE LIKELY SCENARIO THAT A MINOR ACCUMULATING SNOW EVENT WILL BE SEEN IN THE FORECAST AREA...ESPECIALLY THE SOUTHEAST QUARTER TO THIRD. THE UPPER AIR ANALYSES THIS EVENING DEPICTED THE STRONG UPPER JET /OVER 120 KTS AT UNR/ HEADING TOWARDS THE AREA WHICH WILL PROVIDE MORE CONCENTRATED UPPER SUPPORT DURING TUE AFTERNOON AND NIGHT. SATURATION AND QG FORCING WITH THE WAVE WILL NOT ARRIVE INTO PARTS OF OUR AREA UNTIL THE NIGHT...LIKELY BY 03Z. THE NEW NAM OUTPUT INDICATES MIXING RATIOS NEAR 2 G/KG ON THE FAVORED SURFACES WHERE LIFT IS OCCURRING INTO THE FAR SOUTHEAST...AND THAT IS NEARLY COINCIDENT WITH THE DENDRITIC GROWTH AREA. WHILE TOP-DOWN METHODS ON THE NAM SOUNDINGS WARM SOME ON THE WAY DOWN...RATIOS STILL LOOK TO BE ON THE HIGHER SIDE AS INDICATED BY EVEN THE PRIOR NAM RUNS. THE SREF GUIDANCE HAS BECOME MORE FOCUSED ON ITS SNOW PROBABILITIES...INDICATING A RIBBON ACROSS THE SOUTHEAST /GIBSON CITY TO RENSSELAER/ WHERE OVER ONE INCH OF SNOW IS FORECAST BY THE MEAN OF THE MEMBERS. EVEN THE PRIOR RUNS OF THESE MODELS AND THE GFS...EC...AND NMM WRF...INDICATE THE FAR SOUTHERN TIER OF COUNTIES TO SEE SNOW...AND COULD ENVISION BASED ON RATIOS AND RECENTLY COOLED GROUND TEMPERATURES THAT ONE TO TWO INCH ACCUMULATIONS ARE POSSIBLE. MINOR ACCUMULATIONS OF A COUPLE TENTHS AS FAR NORTH AS CHICAGO CANNOT BE RULED OUT DEPENDING ON IF THE ATMOSPHERE CAN SATURATE...AND LIGHT AMOUNTS ARE FORECAST THAT FAR NORTH BY THE 18.00 NAM. WILL RE-ISSUE AN SPS TO HIGHLIGHT FOR NOW AND BRIEF THE OVERNIGHT SHIFT. MTF && .AVIATION... //ORD AND MDW CONCERNS...UPDATED 06Z... * ISOLATED THREAT FOR -SN THURSDAY EVENING SHEA //DISCUSSION...UPDATED 06Z... LIGHT WESTERLY WINDS WILL CONTINUE OVERNIGHT AS AN APPROACHING NORTHERN HIGH PLAINS SYSTEM AND ANOTHER COLD FRONT DROPS SOUTHEAST ACROSS WISCONSIN DURING THE DAY TODAY. THIS SYSTEM IS EXPECTED TO PRODUCE SOME LIGHT SNOWFALL BUT THE ZONE OF BEST FORCING AT THIS POINT LOOKS TO BE ALONG A NORTHERN MISSOURI...CENTRAL IL...NORTHEAST INDINANA AXIS SO THREAT OF ANY PRECIPITATION AT THE LOCAL TERMINALS QUITE SMALL. SHEA //ORD AND MDW CONFIDENCE...UPDATED 06Z... * HIGH CONFIDENCE IN ALL ELEMENTS SHEA //OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z... * FRIDAY...VFR. SATURDAY...VFR. SUNDAY...VFR. MONDAY...VFR INTO EVENING...SLGT CHC -SN PRODUCING MVFR CIGS AND/OR VSBYS OVERNIGHT. TUESDAY...MVFR CIGS POSSIBLE. * TRS && .MARINE... 157 PM CST A COLD FRONT MOVING ACROSS LAKE SUPERIOR AND WISCONSIN THIS AFTERNOON WILL MOVE ACROSS LAKE MICHIGAN LATER THIS AFTERNOON AND EVENING. THIS WILL HELP KEEP THE WINDS AROUND 25 TO 30 KT TONIGHT AS THE WINDS BECOME NORTHWESTERLY. A PROLONGED PERIOD OF BRISK WEST TO NORTHWESTERLY WINDS IS EXPECTED INTO SATURDAY AS HIGH PRESSURE MOVING FROM THE PLAINS EASTWARD ACROSS THE MID MISSISSIPPI VALLEY...WILL CONTINUE TO PRODUCE A DECENT PRESSURE GRADIENT ACROSS THE GREAT LAKES. LATER SATURDAY THE WINDS LOOK TO SWITCH OUT OF THE SOUTHWEST AND INCREASE TO AROUND 30 KT AGAIN AS THE SURFACE HIGH SHIFTS ACROSS THE OHIO VALLEY AND ANOTHER AREA OF LOW PRESSURE MOVES ACROSS THE PRAIRIE PROVIDENCES OF CANADA. IT APPEARS THAT THESE SOUTHWESTERLY WINDS WILL CONTINUE INTO EARLY NEXT WEEK AS THE SURFACE HIGH CONTINUES TO DOMINATE ACROSS EASTERN CONUS. THERE COULD EVEN BE A PERIOD OF LOW END GALE FORCE WINDS DURING THIS PERIOD. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO BURNS HARBOR UNTIL 10 PM THURSDAY. SMALL CRAFT ADVISORY...NEARSHORE BURNS HARBOR TO MICHIGAN CITY IN UNTIL 10 AM SATURDAY. && $$
AREA FORECAST DISCUSSION
NWS TOPEKA KS
347 AM CST THU DEC 8 2011 .DISCUSSION... TODAY AND TONIGHT...AN UPPER LEVEL TROUGH OVER THE NORTHERN HIGH PLAINS WILL DIG SOUTHEAST TODAY ACROSS THE CENTRAL PLAINS. THE STRONGER MID-LEVEL FRONTOGENETICAL FORCING AHEAD OF THE H5 TROUGH WILL SHIFT SOUTHEAST ACROSS SD INTO EASTERN NE...IA AND NORTHERN MO. A BAND OF WEAKER MID-LEVEL FRONTOGENETICAL FORCING WILL EXTEND SOUTHWEST INTO NORTHEAST KS THIS AFTERNOON AND INTO THE EVENING HOURS BEFORE SHIFTING EAST. THE GFS MODEL FORECAST THE THE STRONGEST ASCENT AND ENOUGH MOISTURE FOR 1 TO 2 INCHES OF SNOWFALL ACROSS THE NORTHERN COUNTIES OF THE CWA. THE NAM AND ECMWF ARE NOT AS AMPLIFIED AND ONLY SHOW ABOUT HALF OF AN INCH TO ONE INCH OF SNOW ACROSS THE NORTHEAST COUNTIES OF THE CWA. THERE MAY ONLY BE TRACE AMOUNTS OF SNOWFALL ACROSS THE SOUTHERN COUNTIES OF THE CWA LATE THIS AFTERNOON AND THIS EVENING. ONCE THE H5 TROUGH AXIS SHIFTS SOUTHEAST OF THE PLAINS TONIGHT...THE SNOW SHOULD END FROM NORTHWEST TO SOUTHEAST ACROSS THE CWA DURING THE LATE EVENING HOURS. A SECOND H5 TROUGH WILL DIG SOUTHWARD ACROSS THE EASTERN PLAINS THEN MOVE SOUTHEAST ACROSS IA INTO NORTHERN MO DURING THE EARLY MORNING HOURS OF FRIDAY. ATTM...THE STRONGER FORCING WILL REMAIN NORTH AND NORTHEAST OF THE CWA...THUS ANY LIGHT SNOW SHOULD MOVE SOUTHEAST FROM EASTERN NE...SOUTHEAST ACROSS IA INTO NORTHERN MO THROUGH THE MORNING HOURS OF FRIDAY. HIGHS TODAY WILL RANGE FROM THE LOWER TO MID 30S ACROSS THE NORTHERN COUNTIES WHERE CLOUD COVER WILL INCREASE DURING THE MID MORNING HOURS TO THE THE UPPER 30S TO AROUND 40S ACROSS EAST CENTRAL KS. FRIDAY...A SURFACE RIDGE OF HIGH PRESSURE WILL BUILD SOUTHWARD ACROSS EASTERN KS. LOW-LEVEL CAA WILL KEEP HIGHS IN THE LOWER TO MID 30S...EVEN THOUGH SKIES WILL CLEAR DURING THE AFTERNOON HOURS. SATURDAY THROUGH MONDAY...THE FLOW ALOFT WILL BECOME ZONAL. SOUTHWEST TO SOUTHERLY SURFACE WINDS WILL ALLOW HIGH TEMPERATURES TO WARM INTO THE LOWER 40S ON SATURDAY WITH MID TO UPPER 40S SUNDAY AND MONDAY. MONDAY NIGHT AND TUESDAY...AN UPPER LEVEL TROUGH WILL DIG SOUTHWARD ACROSS THE WESTERN CONUS INTO THE DESERT SOUTHWEST. A WEAK H5 TROUGH WILL MOVE EAST ACROSS THE NORTHERN PLAINS AND WILL CAUSE A WEAK COLD FRONT TO PUSH SOUTHEAST ACROSS THE CWA. THE LOW-LEVELS OF THE ATMOSPHERE LOOK TOO DRY FOR MEASURABLE PRECIPITATION TO DEVELOP ALONG OR BEHIND THE FRONT. HIGHS ON TUESDAY WILL COOL SLIGHTLY INTO THE UPPER 30S TO LOWER 40S. TUESDAY NIGHT AND WEDNESDAY...THE GFS AND ECMWF MODEL SOLUTIONS DIFFER IN THE MOVEMENT OF THE UPPER LOW THAT EJECTS OUT EITHER EAST OR NORTHEAST INTO THE SOUTHERN AND CENTRAL PLAINS. THE GFS SHOWS THE UPPER LOW MOVING DUE EAST ACROSS WEST TX INTO SOUTHERN OK. THE ECMWF...SHOWS MORE OF AN OPEN WAVE LIFTING TO THE NORTHEAST ACROSS KS AND NE. IF THE GFS WERE TO VERIFY THE CWA WOULD REMAIN DRY BUT COLDER. IF THE ECMWF WERE TO VERIFY THE RAIN AND PERHAPS A FEW ISOLATED THUNDERSTORMS WILL DEVELOP AS DEEPER MOISTURE AND WARMER AIR ADVECT NORTHWARD ACROSS THE STATE TUESDAY NIGHT INTO WEDNESDAY. ATTM...I WILL KEEP AT LEAST A CHANCE FOR RAIN ACROSS THE CWA ON WEDNESDAY WITH HIGHS IN THE MID TO UPPER 40S...MAY BE EVEN LOWER TO MID 50S IF THE ECMWF SOLUTION VERIFIES. GARGAN && .AVIATION... THE LATEST RUC AND NAM FORECAST SOUNDINGS DO NOT COOL SFC TEMPS OFF AS MUCH AS EARLIER RUNS. BECAUSE OF THIS THEY ARE LESS AGGRESSIVE IN SATURATING THE BOUNDARY LAYER. SINCE CONDITIONS ARE GOOD FOR RADIATIONAL COOLING AND THE POTENTIAL FOR SOME GROUND FOG EXISTS... WILL KEEP A MENTION FOR TOP AND MHK WHERE THE KS RIVER COULD PROVIDE ADDITIONAL BOUNDARY LAYER MOISTURE. MODELS CONTINUE TO SHOW A WEAK SHORTWAVE MOVING ACROSS THIS AFTERNOON AND EVENING. FORCING FOR PRECIP IS NOT OVERWHELMING. HOWEVER IT LOOKS LIKE THERE COULD BE A 3 TO 4 HOUR WINDOW FOR SOME LIGHT SNOW...ESPECIALLY ACROSS NORTHEAST KS. WITH GOOD CONSENSUS IN MODEL QPF...HAVE SOME CONFIDENCE IN LIGHT SNOW DEVELOPING WITH INTENSITY BEING FAIRLY LIGHT AND LITTLE ACCUMULATION. THEREFORE ONLY TAKE THE TAFS TO MVFR IN SPITE OF THE MET MOS SHOWING IFR CONDITIONS. WOLTERS && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
303 AM CST THU DEC 8 2011 .DISCUSSION... DAYS 1-2... THE MAIN FORECAST FOCUS WILL BE ON THE CHANCE FOR LIGHT PRECIP EARLY IN THE PERIOD. WV IMAGERY AND 00Z UPPER AIR ANALYSIS INDICATES AN UPPER LEVEL SHORTWAVE DIPPING SOUTHEAST OUT OF CANADA INTO THE NORTHERN ROCKIES. A POOL OF H7 MOISTURE IS ACCOMPANYING THE SHORTWAVE EXTENDING FROM EASTERN MONTANA EAST AND SOUTHEAST INTO THE NORTHERN PLAINS. A COLD FRONT IS PUSHING SOUTH ACROSS SOUTH DAKOTA NEARING NORTHERN NEBRASKA. SHORT RANGE MODELS INDICATE THE UPPER LEVEL SHORTWAVE SWINGING SOUTHEAST OUT OF THE NORTHERN ROCKIES INTO THE NORTHERN PLAINS TODAY. IT WILL HELP USHER A COLD FRONT SOUTH INTO WESTERN KANSAS BY THIS AFTERNOON BRINGING WITH IT MUCH COOLER AIR INTO THE REGION. VERY LITTLE IN THE WAY OF PRECIP IS EXPECTED WITH A LACK OF MOISTURE IN THE LOWER LEVELS. HOWEVER, AREAS OF LIGHT FREEZING DRIZZLE OR SNOW CANNOT BE COMPLETELY RULED OUT THIS AFTERNOON ACROSS NORTHERN PORTIONS OF THE CWA AS TEMPERATURES COOL DOWN QUITE A BIT NEARLY SATURATING THE LOWER LEVELS. FLURRIES ARE POSSIBLE THIS EVENING WITH MODEL SOUNDINGS SHOWING BELOW FREEZING TEMPERATURES AT ALL LEVELS. OTHERWISE, FAIRLY DRY CONDITIONS ARE EXPECTED INTO THE WEEKEND AS UPPER LEVEL RIDGING BUILDS INTO THE INTERMOUNTAIN WEST FRIDAY. TEMPERATURES WILL BE BELOW NORMAL TODAY AS COLDER AIR BEGINS TO FILTER SOUTH INTO WESTERN KANSAS BY EARLY THIS AFTERNOON BEHIND A COLD FRONT MOVING ACROSS THE AREA. ALL MODELS SHOW H85 TEMPERATURES DROPPING TO NEAR TO JUST BELOW 0C ACROSS MUCH OF THE CWA BY MID DAY. EXPECT HIGHS ONLY UP INTO THE 30S(F) BY THIS AFTERNOON WITH A FEW LOWER 40S(F) POSSIBLE IN OUR SOUTHEAST, ESPECIALLY WITH INCREASING CLOUDS. TEMPERATURES WILL REMAIN FAIRLY COLD FRIDAY AS SURFACE HIGH PRESSURE DRIFTS EAST ACROSS THE CENTRAL PLAINS KEEPING THE SAME GENERAL AIR MASS IN PLACE ACROSS WESTERN KANSAS. SHOULD SEE FAIRLY SIMILAR HIGHS ON FRIDAY EVEN WITH FEWER CLOUDS EXPECTED. DAYS 3-7... SPLIT UPPER LEVEL FLOW CONTINUES INTO THE WEEKEND OVER THE PLAINS. A STRONG UPPER LEVEL SHORTWAVE TROUGH DIGS INTO THE PACIFIC NORTHWEST ON SUNDAY. BY MONDAY THE NEW ECMWF HAS A CUTOFF UPPER LOW JUST WEST OF THE SOUTHERN CALIFORNIA COASTLINE AND THE GFS IS FASTER WITH A MORE OPEN UPPER LOW OVER SOUTHERN CALIFORNIA. ON TUESDAY A NORTHERN BRANCH WAVE MOVES ACROSS THE UPPER MIDWEST WITH THE GFS CONTINUES TO PUSH A CLOSED UPPER LOW INTO NEW MEXICO WHILE THE SLOWER ECMWF AND GEM HAVE A TROUGH MORE WEST INTO SOUTHERN CALIFORNIA. FOR WEDNESDAY THE GFS CONTINUES A FASTER AND MORE SOUTHERN TRACK INTO NORTHEASTERN TEXAS WHILE THE ECMWF HAS A NEGATIVELY TILTED OPEN SHORTWAVE TROUGH LIFTING NORTHEASTWARD INTO NEBRASKA. THE NEW CANADIAN HAS THE UPPER LOW ON SATURDAY EVENING JUST INTO SOUTHWEST KANSAS AND IS MORE NEUTRALLY TILTED. WHAT THIS MEANS ANY SENSIBLE WEATHER WILL HOLD OFF UNTIL THE UPPER LEVEL LOW LIFTS OUT INTO THE PLAINS ON WEDNESDAY. LOTS OF MODEL DIFFERENCES WILL MAKE THIS FORECAST INTO THE MIDDLE OF NEXT WEEK A VERY LOW CONFIDENCE FORECAST WITH THE TRACK OF THE UPPER LOW. THE ECMWF AND GFS HAVE RAIN AND THE CANADIAN HAS RAIN OR SNOW. FOR NOW WILL HOLD ONTO CONSENSUS MODEL THAT HAS MOSTLY RAIN AND WARMER TEMPS. IN GENERAL A LEE LOW WILL BRING WARMER SOUTH TO SOUTHWEST SURFACE WINDS INTO THE WEEKEND WITH HIGHS INTO THE 40S. CANADIAN HIGH PRESSURE MOVES INTO THE PLAINS ON MONDAY AND TUESDAY WITH SLIGHTLY COOLER HIGH TEMPERATURES. THEN FOR WEDNESDAY THE ECMWF HAS THE UPPER LOW MUCH MORE NORTH AND BRINGS IN HIGHER DEWPOINTS AND QPF TO WESTERN KANSAS. FOR NOW WILL CONTINUE WITH CONSENSUS POPS AND TEMPS WHICH FAVOR HIGHEST POPS SOUTH AND EAST FA AND HIGHS IN THE 50S. OVERNIGHT LOWS LOOK TO BE IN THE 20S WEST AND NORTHWEST FA TO THE 30S IN THE SOUTH AND SOUTHEAST. && .AVIATION... FOR THE 06Z TAF ISSUANCE... THIS EVENING`S KDDC UPPER AIR SOUNDING CONTINUES TO SHOW DEEP DRY LOWER AND MIDDLE TROPOSPHERIC LAYERS WITH DEEP NORTHWEST FLOW ALOFT. THE LATEST RAPID REFRESH RUC MODEL IS DELAYING THE DEVELOPMENT OF MVFR STRATUS CONSIDERABLY LATER INTO THE LATE AFTERNOON ACROSS NORTHWEST KANSAS. CONSIDERING THE CURRENT LACK OF LOW CLOUD DEVELOPMENT ACROSS THE NORTHERN HIGH PLAINS REGION, WE CAN`T FIND A GOOD REASON TO DISCOUNT THIS MODEL SHIFT AND HAVE DELAYED MVFR CEILINGS BY ABOUT 8 HOURS IN THE TAF TIME FRAME. && .PRELIMINARY POINT TEMPS/POPS... DDC 37 17 37 17 / 10 10 0 0 GCK 33 15 33 15 / 10 10 0 0 EHA 35 17 32 20 / 10 10 0 0 LBL 37 18 37 18 / 10 10 0 0 HYS 32 15 30 15 / 40 20 0 0 P28 42 20 38 18 / 10 10 0 0 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ FN32/06/06
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
1148 PM CST WED DEC 7 2011 .UPDATE... && .PREV DISCUSSION... /ISSUED 546 PM CST WED DEC 7 2011/ UPDATE... AVIATION /FOR THE 06Z TAF ISSUANCE/ THIS EVENING`S KDDC UPPER AIR SOUNDING CONTINUES TO SHOW DEEP DRY LOWER AND MIDDLE TROPOSPHERIC LAYERS WITH DEEP NORTHWEST FLOW ALOFT. THE LATEST RAPID REFRESH RUC MODEL IS DELAYING THE DEVELOPMENT OF MVFR STRATUS CONSIDERABLY LATER INTO THE LATE AFTERNOON ACROSS NORTHWEST KANSAS. CONSIDERING THE CURRENT LACK OF LOW CLOUD DEVELOPMENT ACROSS THE NORTHERN HIGH PLAINS REGION, WE CAN`T FIND A GOOD REASON TO DISCOUNT THIS MODEL SHIFT AND HAVE DELAYED MVFR CEILINGS BY ABOUT 8 HOURS IN THE TAF TIMEFRAME. PREV DISCUSSION... /ISSUED 341 PM CST WED DEC 7 2011/ SYNOPSIS... ON THE SYNOPTIC SCALE TODAY...AN UPPER LOW WAS CENTERED OVER THE SOUTHERN APPALACHIANS WITH WIDESPREAD PRECIPITATION OVER MUCH OF THE MID ATLANTIC AND INTERIOR NORTHEAST CONUS. SHORTWAVE RIDGING WAS INFLUENCING SENSIBLE WEATHER OVER THE CENTRAL CONUS WITH DOWNSLOPE WARMING OCCURRING OVER THE CENTRAL PLAINS. AFTERNOON TEMPERATURES ROSE TO THE MID AND UPPER 40S OVER SOUTHWEST KANSAS IN THE DOWNSLOPE NORTHWEST WINDS. ANOTHER SHORTWAVE TROUGH WAS LOCATED OVER THE ALBERTA ROCKIES AND CONTINUED TO MOVE SOUTHEAST AROUND THE SOUTHEAST SIDE OF A LARGE LONGWAVE CYCLONE THAT WAS CENTERED OVER WESTERN HUDSON BAY. -UMSCHEID DISCUSSION... DAYS 1-2... THE SHORTWAVE TROUGH OVER SOUTHERN ALBERTA WILL REACH WYOMING BY 12Z THURSDAY...AND A BAND OF MID LEVEL FRONTOGENESIS AND ENHANCED RH WILL DEVELOP AHEAD OF THE DISTURBANCE OVER WESTERN NEBRASKA. THIS WILL SHIFT SOUTHEAST THROUGH THE DAY THURSDAY ACROSS SOUTHERN NEBRASKA/NORTHERN KANSAS. IN THE LOWER TROPOSPHERE (900 TO 800MB)...LOW LEVEL RH WILL INCREASE TO THE POINT THAT LOW STRATUS WILL FORM BY LATE MORNING BEHIND THE DEVELOPING SURFACE COLD FRONT. A FETCH OF NORTHEAST WINDS IN THIS LAYER WILL DEVELOP WHICH WILL HAVE UPSLOPE COMPONENT FROM SOUTHEAST NEBRASKA/NORTHEAST KANSAS TO SOUTHWEST KANSAS. A WEAK CYCLONIC CIRCULATION WILL DEVELOP OVER NORTHWEST OKLAHOMA AROUND 850MB...WHICH WILL YIELD SOME WEAK FRONTOGENESIS ACROSS THE SOUTHERN DDC FA BY LATE IN THE DAY/EARLY EVENING THURSDAY. THE SATURATION OF THE 900-800MB LAYER WILL STILL BE PRETTY FAR NORTH OF THE BEST FRONTOGENESIS IN THIS LAYER...SO THIS DISCONNECT BETWEEN THE SATURATION AND LIFT WILL LIMIT WIDESPREAD DRIZZLE FORMATION. NEVERTHELESS...THE UPSLOPE ALONE ON THE NORTHEAST WINDS MAY BE ENOUGH TO GENERATE AT LEAST PATCHY FREEZING DRIZZLE. THE DEPTH OF THE SATURATED LAYER DURING THE DAY AND EARLY EVENING TOMORROW IS EXPECTED EXTEND UP TO ABOUT 800 OR 750MB...WHERE TEMPERATURES WILL BE -4 OR -5C...SO THE PRECIPITATION TYPE SHOULD BE FREEZING DRIZZLE INSTEAD OF SNOW FLURRIES. A DEEPER MOIST LAYER IS EXPECTED FARTHER NORTH LATE IN THE DAY (SAY NORTH OF HIGHWAY 4)...AND THE PROBABILITY OF SNOW FLURRIES IS GREATER...SO WILL CARRY FREEZING DRIZZLE OR SNOW FLURRIES UP THERE LATE IN THE DAY/EARLY EVENING. THE EVENT...SHOULD IT EVEN UNFOLD...WILL END BY LATE EVENING/MIDNIGHT TIME FRAME AS THE SHORTWAVE TROUGH RESPONSIBLE QUICKLY EXITS THE CENTRAL PLAINS. THE REMAINDER OF THE FORECAST WILL BE DRY THROUGH FRIDAY AS SUBSIDENCE PREVAILS AND SKIES CLEAR. VERY COLD AIR IS NOT EXPECTED AFTER THIS WAVE MOVES BY AS MID LEVEL DOWNSLOPE WILL DEVELOP ONCE AGAIN IN THE 850-700MB LAYER...WHICH WILL SUPPORT SURFACE HIGHS IN THE UPPER 30S TO LOWER 40S. -UMSCHEID DAYS 3-7... THE EXTENDED PERIOD BEGINS 00Z SATURDAY. HAVE STUCK WITH THE INITIALIZED CR ALLBLEND GRIDS AS THIS WAS THE CONSENSUS ESTABLISHED WITH SURROUNDING WFOS. THERE IS A BIT OF UNCERTAINTY NEXT WEDNESDAY REGARDING POPS. THIS IS VERY FAR IN THE EXTENDED PERIOD AND IS A LOW CONFIDENCE FORECAST AS THERE ARE SIGNIFICANT DIFFERENCES BETWEEN THE 12Z GFS AND 12Z ECMWF IN ADDITION BETWEEN THE 00Z ECMWF AND 12Z ECMWF. SATURDAY/SUNDAY: KANSAS WILL BE IN SPLIT FLOW NEXT WEEKEND. INCREASING WESTERLY FLOW IN ASSOCIATION WITH THE SOUTHERN BRANCH JET WILL RESULT IN SURFACE LEE TROUGHING ACROSS EASTERN COLORADO. 850 HPA TEMPERATURES ARE FORECAST IN THE 2 TO 3 DEG C RANGE WHICH SUPPORT TEMPERATURES IN THE 40S DEG F ACROSS THE REGION...WHICH IS NEAR CLIMATOLOGY. THE FORECAST WILL REMAIN DRY WITH BREEZY SOUTHERLY TO SOUTHWESTERLY WINDS. LOWS WILL BE NEAR NORMAL TOO...PARTICULARLY SUNDAY WITH 20S DEG F PREVAILING FOR SW KANSAS. MONDAY: AN UPPER LEVEL SHORTWAVE TROUGH IN ASSOCIATION WITH THE NORTHERN BRANCH JET WILL USHER IN A COLD FRONT MONDAY. THIS FRONT DOESN`T LOOK VERY STRONG AND IS EXPECTED TO BE DRY. TEMPERATURES WILL COOL DOWN ABOUT 5 OR SO DEGREES MONDAY. ANOTHER IMPACT FROM THE FRONT WILL BE INCREASING CLOUD COVER, MAINLY IN THE FORM OF MID TO HIGH LEVEL CLOUDS. TUESDAY: WE WILL BE IN BETWEEN WEATHER SYSTEMS. THE SOUTHERN BRANCH JET WILL INTENSIFY RESULTING IN THE FORMATION OF A WEAK LEE SURFACE TROUGH AND SLIGHT WARMER TEMPERATURES (WARM AIR ADVECTION PATTERN). WE COULD SEE SOME HIGH LEVEL CLOUDS CONTINUING TUESDAY AS WELL AS MID TO UPPER LEVEL FLOW INCREASES FROM THE SOUTHWEST IN ASSOCIATION WITH THE APPROACHING SHORTWAVE TROUGH/JET. -SUGDEN WEDNESDAY: THERE ARE LARGE DIFFERENCES BETWEEN THE GFS AND ECMWF AT THIS POINT. THEY BOTH SHOW AN UPPER LEVEL SYSTEM MOVING ACROSS THE REGION WITH RETURN FLOW SETTING UP AND HIGHER DEWPOINTS ADVECTING IN FROM THE GULF OF MEXICO (30S TO 40S DEG F). AS MENTIONED ABOVE, LEFT POPS ALONE FOR THIS PERIOD DUE TO THE TIMING DIFFERENCES. THE 12Z ECMWF IS ALSO DRIER THAN THE 00Z ECMWF WHICH FURTHER COMPLICATES THE WEATHER SCENE IN ABOUT A WEEK FROM NOW. -SUGDEN && .PRELIMINARY POINT TEMPS/POPS... DDC 16 37 18 39 / 0 10 10 0 GCK 14 32 17 36 / 0 10 10 0 EHA 15 34 18 35 / 0 10 10 0 LBL 16 39 19 39 / 0 10 10 0 HYS 14 31 15 33 / 10 10 10 0 P28 18 43 21 41 / 0 10 10 0 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ FN99/99
AREA FORECAST DISCUSSION
NWS TOPEKA KS
1118 PM CST WED DEC 7 2011 ...AVIATION UPDATE... .DISCUSSION... SEE PREV DISCUSSION. && .AVIATION... THE LATEST RUC AND NAM FORECAST SOUNDINGS DO NOT COOL SFC TEMPS OFF AS MUCH AS EARLIER RUNS. BECAUSE OF THIS THEY ARE LESS AGGRESSIVE IN SATURATING THE BOUNDARY LAYER. SINCE CONDITIONS ARE GOOD FOR RADIATIONAL COOLING AND THE POTENTIAL FOR SOME GROUND FOG EXISTS... WILL KEEP A MENTION FOR TOP AND MHK WHERE THE KS RIVER COULD PROVIDE ADDITIONAL BOUNDARY LAYER MOISTURE. MODELS CONTINUE TO SHOW A WEAK SHORTWAVE MOVING ACROSS THIS AFTERNOON AND EVENING. FORCING FOR PRECIP IS NOT OVERWHELMING. HOWEVER IT LOOKS LIKE THERE COULD BE A 3 TO 4 HOUR WINDOW FOR SOME LIGHT SNOW...ESPECIALLY ACROSS NORTHEAST KS. WITH GOOD CONSENSUS IN MODEL QPF...HAVE SOME CONFIDENCE IN LIGHT SNOW DEVELOPING WITH INTENSITY BEING FAIRLY LIGHT AND LITTLE ACCUMULATION. THEREFORE ONLY TAKE THE TAFS TO MVFR IN SPITE OF THE MET MOS SHOWING IFR CONDITIONS. WOLTERS && .PREV DISCUSSION... /248 PM CST WED DEC 7 2011/ WEAK MID-LEVEL DISTURBANCE COMBINED WITH MID-LEVEL ISENTROPIC LIFT HAS LED TO AN AC DECK ACROSS EASTERN NEBRASKA...FAR NORTHEAST KS AND AREAS EAST THIS AFTERNOON. THIS SHOULD MOVE OFF TONIGHT WITH SOME CLEARING EXPECTED. WEAK PRESSURE GRADIENT TONIGHT COMBINING WITH MOSTLY CLEAR SKIES COULD LEAD TO SOME LIGHT FOG IN PLACES NEAR SUNRISE. WOULD NOT EXPECT IT TO BE DENSE OR WIDESPREAD AND HAVE NOT MENTIONED IT IN THE GRIDS/FORECAST. ON THURSDAY...A LITTLE MORE DEFINED UPPER TROUGH SWINGS SOUTHEASTWARD OUT OF NEBRASKA WITH ASSOCIATED MID AND UPPER LEVEL FORCING. ATMOSPHERE QUITE STABLE AND MOISTURE LACKING...SO WHILE SATURATION WILL OCCUR AND SNOW WILL RESULT...DO NOT EXPECT ANY SIGNIFICANT ACCUMULATION. AFTERNOON CHANCES SHOULD REMAIN NORTH OF I70. GDP THURSDAY NIGHT THROUGH SATURDAY...WEAK FRONTOGENESIS CONTINUES THROUGH AT LEAST THE EARLY EVENING HOURS ON THURSDAY AS THE TROF NEARS. LOW TO MID LEVELS SHOULD BE SATURATED ENOUGH FOR LIGHT SNOW TO SWING EAST THROUGH MAINLY NORTHERN AND CENTRAL LOCATIONS. MAY SEE THE SNOW LAST LONG ENOUGH FOR VERY LOW ACCUMULATIONS TO RESULT...WITH THIS FAST-MOVING SYSTEM EXITING BY DAWN. NAM AND GFS ARE QUITE SIMILAR WITH ANOTHER AREA OF LIGHT SNOW DEVELOPING IN CENTRAL NEBRASKA LATE IN THE NIGHT...APPARENTLY TIED TO ANOTHER AREA OF WEAK FRONTOGENESIS AROUND 850MB AS THE UPPER TROF PASSES. WITH QUESTIONS ON THE POSITIONING OF THIS FEATURE AND THE LIKELY LIMITED IMPACT OF THIS SHALLOW AND TRANSIENT FORCING...WILL NOT MENTION ANY PRECIP/FLURRIES AT THIS POINT. SKIES SHOULD SLOWLY CLEAR FRIDAY AND MAY SET THE STAGE FOR A RATHER COOL FRIDAY NIGHT IF SNOWPACK AND WEAK WIND FIELDS CAN ALIGN A BIT BETTER THAN EXPECTED CURRENTLY. WARM AIR ADVECTION ENSUES BY LATE IN THE NIGHT FOR A MUCH WARMER SATURDAY ON SOUTHWEST WINDS. KP SATURDAY NIGHT THROUGH WEDNESDAY...ON SUNDAY WEAK WARM AIR ADVECTION WILL CONTINUE ACROSS THE CENTRAL U.S. WITH WEAK UPPER LEVEL RIDGING IN PLACE. SOUTHERLY FLOW WILL CONTINUE ACROSS THE REGION WITH HIGH PRESSURE OVER THE OHIO RIVER VALLEY AND LEE CYCLOGENESIS TAKING PLACE. WITH PLENTY OF INSOLATION TEMPERATURES WILL WARM INTO THE LOW AND MID 40S ON SUNDAY. LATE MONDAY INTO TUESDAY MORNING A TROUGH WILL MOVE ACROSS THE NORTHERN PLAINS. THIS TROUGH WILL PUSH A WEAK COLD FRONT THROUGH THE CWA LATE MONDAY INTO TUESDAY MORNING. COLD AIR ADVECTION WILL BE SHORT-LIVED WITH BOTH THE GFS AND ECMWF INDICATING AN UPPER LEVEL TROUGH THAT WILL EJECT OUT OF THE DESERT SOUTHWEST INTO THE CENTRAL PLAINS LATE TUESDAY INTO WEDNESDAY. MODELS INDICATE THAT MOISTURE RETURN AND LIFT AHEAD OF THIS SYSTEM WILL BE SUFFICIENT FOR PRECIPITATION ACROSS THE CWA LATE TUESDAY NIGHT AND CONTINUING INTO THE DAY ON WEDNESDAY. AT THIS TIME...THE DOMINANT PRECIPITATION TYPE SHOULD BE RAIN WITH TEMPERATURES WARMING OVERNIGHT TUESDAY WITH 850 MB TEMPERATURES APPROACHING 6-10 DEGREES CELSIUS TUESDAY NIGHT. A WARM FRONT IS EXPECTED TO RACE NORTH OF THE CWA DURING THE DAY ON WEDNESDAY WITH HIGHS PUSHING INTO THE UPPER 40S AND LOWER 50S ACROSS THE CWA. MEA && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$
AREA FORECAST DISCUSSION
NWS LOUISVILLE KY
1211 AM EST THU DEC 08 2011 ...Updated Aviation Discussion... ...Forecast Update... Did a minor update to account for current temperature and sky trends. The remaining forecast is on track. Updated products have been issued. Dry air continues to migrate into the forecast area. Current T/Td spreads of generally 6-9 degrees yields relative humidity values in the 70 to low 80 percent range. Latest guidance, particularly LAMP data, handle the current conditions well and keep a 4-5 degree spread through the morning hours. With this T/Td spread and westerly wind speeds in the 3-5 mph range overnight, believe it will be difficult for fog formation. Additionally, the gusty northwest winds this afternoon across much of the forecast area actually aided in drying the surface a bit. At this time, the only potential location for fog formation would be confined to the water surfaces of rivers and lakes in the form of steam fog (also known as evaporation fog), as this cold airmass works over slightly warmer river/lake waters. Once again, this would be localized to very near the water surface, if fog were to form. && .Short Term (Tonight and Thursday)... First off, snow band was not as impressive as the HRRR earlier today made it out to be. County officials in our Lake Cumberland region have all indicated very little snow stuck. Webcams from that area also look mostly just wet and not white. Had some pictures with snow from the LEX-area webcams in a brief band that went through their in the last couple of hours, but likewise nothing has accumulated. Surface temperatures are just too warm, in the mid 30s along with the still wet grounds from the rain earlier in the week. Sunshine is poking out some in cloud cover west of a KLEX to Scottsville line. With any heating though, additional low clouds are developing. These clouds may yet produce some scattered very light flurries across central KY, but temperatures will not be cool enough where these clouds are to promote lots of snow. With the cloud cover, temperatures are holding to around 40 degrees at most. Skies should clear out overnight as deep dry air moves into the region. High pressure will move in south of the region, so expect a general westerly wind through the night. Expect temperatures to fall into the 20s areawide overnight under these clear skies. Sheltered locations may see the low 20s. High pressure will be centered over the Appalachians during the day Thursday. Thus expect a southwesterly flow. Clear skies should allow us to reach the low/mid 40s areawide, roughly 5 degrees below normal. .Long term (Thursday night - Wednesday)... A digging shortwave will dive from the northern plains into the lower Great Lakes on Friday. Moisture return ahead of this system will be limited and therefore continued to only mention flurries in the forecast early Friday morning across southern Indiana, gradually working eastward across north central Kentucky and the Bluegrass through the day. Temperatures ahead of the front will likely warm enough for just sprinkles in the late morning and afternoon. In the morning and the evening, moisture to about 700 mb should yield some potential for ice crystals as temps at this level will be around -10 C. No impacts from these flurries are anticipated. Otherwise, cold frontal boundary moves through Friday afternoon and evening with a cold airmass lurking for the weekend. Lows Friday night are expected to drop into the lower 20 in most spots, with a few upper teens possible across southern Indiana and perhaps the Bluegrass. High temperatures on Saturday will struggle, only making it to the low and mid 30s. Saturday night will bring more temperatures right around the 20 degree mark. Sunday into the middle of next week, mid level flow will gradually transition from a progressive zonal flow then try to head back toward the classic La Nina pattern we have been seeing which would yield southwest flow aloft with a ridge to our southeast and a developing trough over the western CONUS. Will keep forecast through Wednesday dry, although some signs point to another potent system tracking into the region possibly Thursday or Friday. Although this is pretty far out, confidence in the recent pattern supported by teleconnections could lead to another substantial precipitation event across the Ohio Valley. Stay tuned. Highs through the first half of next week will gradually moderate toward the mid 40s, with upper 40s and low 50s ahead of the next system possible on Wednesday. Lows each night will be in the 20s, warming to the low 30s by Wednesday morning. && .Aviation (06Z TAF Issuance)... Latest satellite imagery reveals clear skies at the terminals this evening. VFR conditions are expected through the TAF period as high pressure builds in from the west. Dry air continues to push into the region and T/Td spreads are still forecast to be large enough to limit fog formation overnight. In fact, a look at all of the available 08/00Z guidance shows very little if any fog development overnight as the surface winds stay up around 2-4 knots. Winds should slacken late tonight and then resume after sunrise out of the southwest as high pressure moves into the Appalachian mountains. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...NONE. KY...NONE. $$ Update...........MJP Short Term.......RJS Long Term........BJS Aviation.........MJ
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1234 AM EST THU DEC 8 2011 UPDATED AVIATION DISCUSSION FOR 06Z TAFS .SYNOPSIS /ISSUED AT 354 PM/... WV IMAGERY AND RUC ANALYSIS INDICATED CYCLONIC MID/UPPER LEVEL FLOW AROUND A VORTEX OVER HUDSON BAY BRINGING NRN STREAM WNW FLOW FROM SRN CANADA INTO THE UPPER GREAT LAKES. AN UPSTREAM SHORTWAVE TROUGH WAS MOVING THROUGH SRN MANITOBA WITH ANOTHER TRAILING SHRTWV OVER NRN SASK. AT THE SFC...WINDS WERE VEERING W TO WNW BEHIND A TROUGH/FRONT THAT MOVED THROUGH THIS MORNING. A TRAILING ARCTIC FRONT NEAR LAKE WINNIPEG WAS DROPPING TOWARD THE AREA WITH MUCH COLDER AIR BEHIND IT WITH TEMPERATURES FROM -5 TO 5F OVER NORTHERN MANITOBA/SASK. VIS LOOP INDICATED CLEARING SKIES OVER THE WEST HALF OF THE CWA AS DRIER AIR MOVES INTO THE REGION. EVEN WITH 850 MB TEMPS AROUND -11C...SKIES HAD CLEARED OVER MUCH OF WRN LAKE SUPERIOR. && .SHORT TERM...TONIGHT AND THURSDAY CLOUDS AND SCT LIGHT LAKE EFFECT SNOW SHOWERS ARE EXPECTED TO REDEVELOP OVER WRN LAKE SUPERIOR INTO WRN UPPER MI THIS EVENING AS GREATER LOW LEVEL MOISTURE MOVES TOWARD THE AREA...PER VIS LOOP. PASSAGE OF THE SASK SHRTWV AND ARCTIC FRONT THU MORNING WITH INCREASING 850-700 MB MOISTURE AND INVERSION HEIGHTS CLIMBING AROUND 8K FT WILL PROVIDE A SIGNIFICANT BOOST TO THE LAKE EFFECT SNOW. SNOW GROWTH ALSO LOOKS FAVORABLE AS THE DGZ WILL BE RIGHT IN THE BEST OMEGA/UPWARD MOTION. GIVEN MODEL QPF AND SNOW/WATER RATIOS APPROACHING 30/1 WOULD NOT BE SURPRISED TO SEE PERIODS OF MODERATE TO HEAVY SNOWFALL. THE MOST PERSISTENT LOW LEVEL CONV AND CHANCE FOR GREATEST ACCUMULATION IS EXPECTED FROM FAR NE ONTONAGON COUNTY INTO CENTRAL HOUGHTON COUNTY...FROM GREENLAND TO TWIN LAKES. INCREASINGLY CONVERGENT WRLY FLOW. INCREASING WINDS GUSTING TO NEAR 30 MPH AT TIMES ON THURSDAY WILL ALSO SHARPLY REDUCE VSBYS IN BLOWING SNOW AS WELL AND CAUSE DRIFTING SNOW ACROSS THE ROADS. SO...WITH THE LIKELIHOOD OF AN EXTENDED PERIOD OF LES...HEAVY SNOW AT TIMES...A LAKE EFFECT SNOW WARNING WAS ISSUED. CONFIDENCE IN ACCUMULATIONS BY LATE THURSDAY IS LIMITED BY UNCERTAINTY ON WHERE THE HEAVIER BANDS WILL DEVELOP AND HOW LONG THEY WILL PERSIST. SNOWFALL GENERALLY FROM 3 TO 7 INCHES IS LIKELY WITH SOME HIGHER LCL AMOUNTS. LOCATIONS NEAR LAKE SUPERIOR EAST OF MUNISING...FROM GRAND MARAIS TO TWO HEART MAY ALSO SEE A PERIOD OF HEAVIER LES IF THE EXPECTED DOMINANT BAND SAGS SOUTHWARD WITH SLIGHTLY VEERING WINDS THU. UNCERTAINTY REMAINS WHETHER THE HEAVIER SNOW WILL REMAIN OFFSHORE OR MOVE INLAND...SO NO HEADLINES WERE ISSUED AT THIS TIME. .LONG TERM /THURSDAY NIGHT THROUGH NEXT WEDNESDAY/... SIGNIFICANT LAKE EFFECT SNOW IS THE MAIN CONCERN FOR THE INITIAL PORTION OF THE LONG TERM. LARGE SCALE TROUGH WITH COLDEST AIR OF SEASON THUS FAR TO PUSH INTO THE AREA SETTLES OVER MUCH OF THE EASTERN CONUS TO END THE WEEK. NOT MUCH IN THE WAY OF LARGER SCALE SHORTWAVES THAT WILL BRING WIDESPREAD SNOW TO THE AREA...BUT SIGNIFICANT LK EFFECT FOR WEST FLOW AREAS IS LIKELY AS H85 TEMPS TUMBLE TO AROUND -18C BY FRIDAY. MODEL SOUNDINGS INDICATE LAKE INDUCED CAPES AOA 600J/KG WHILE LAKE EQUIBRIUM LEVELS ARE OVR 10 KFT AGL. HIGHER OVERWATER INSTABILITY IS SUPPLEMENTED BY STRONG LOW-LEVEL (SFC-H95) CONVERGENCE. MODELS ARE ACTUALLY IN VERY GOOD AGREEMENT WITH OVERALL SCENARIO THOUGH SUBTLE SHIFTS IN BLYR WINDS MAKE ALL THE DIFFERENCE AS TO THE LOCATIONS THAT END UP WITH THE HIGHEST SNOW AMOUNTS. BY LATE THURSDAY AND INTO THURSDAY NIGHT...SHEAR WITHIN THE SFC-H8 LAYER IS QUITE LOW...LEADING TO BETTER CHANCE THAT DOMINANT BANDS CAN ORGANIZE. WINDS BECOMING WESTERLY AT 925MB WITH WSW OR SW SFC WINDS OVR UPR MI (ENHANCED BY NIGHTTIME LAND BREEZES) WOULD FAVOR STRONGEST CONVERGENCE/HEAVIER SNOW BANDS OVR WESTERN UPR MI FM ONTONAGON THROUGH TWIN LAKES/PAINESDALE. WARNING WILL CONTINUE FOR THOSE AREAS THROUGH LATE FRIDAY FOR THIS PROLONGED HEAVY LAKE EFFECT SNOW EVENT. STORM TOTALS OVER A FOOT SEEM PRETTY LIKELY IF THE PRIMARY SNOW BAND STAYS STATIONARY FOR REASONABLE AMOUNT OF TIME. HIGHER TERRAIN AREAS OF REST OF HOUGHTON COUNTY WILL ALSO SEE OFF-AND-ON HEAVIER SNOW SHOWERS. ALSO EXPECT SOME HEAVIER SNOW TO OCCUR OVR SOUTHERN PORTIONS OF HOUGHTON COUNTY...MAINLY NORTH OF M-38. ADVY WILL COVER THIS POSSIBILITY. EXPECT VERY LITTLE IF ANY SNOW TOWARD KENTON/SIDNAW ALONG M-28. KEWEENAW COUNTY IS MORE OF A QUESTION MARK AS THE MORE WNW BLYR WINDS THERE ARE NOT AS FAVORABLE. STILL THOUGH...DEGREE OF INSTABILITY AND SUFFICIENT MOISTURE PRESENT COULD LEAD TO LOCALIZED HEAVY AMOUNTS OVR HIGHER TERRAIN THERE AS WELL. AN ADVISORY WILL HANDLE THIS FOR NOW...THOUGH LATER UPGRADE COULD BE NEEDED. EXPECT QUIET WEATHER FOR REST OF THE CWA THURSDAY NIGHT INTO FRIDAY. TEMPS WILL BE ON THE CHILLY SIDE THOUGH WITH NIGHTTIME LOWS THURSDAY NIGHT TOWARD THE ZERO MARK OVR INTERIOR SW UPR MI AND HIGHS ON FRIDAY MAINLY STAYING IN THE TEENS. BY LATE FRIDAY...WEAKER TROUGH FCST TO SLIDE THROUGH THE AREA MAY VEER WINDS TO MORE NW LEADING TO INCREASED CHANCES OF LAKE EFFECT SNOW SHOWERS INTO FAR EASTERN SECTION OF CWA...MAINLY EAST OF MUNISING AND WELL NORTH OF NEWBERRY. LAKE EFFECT SNOW PARAMETER DEVELOPED BY NWS GAYLORD WHICH INCORPORATES 1000-850MB SHEAR/850-700MB RH/H85 TEMPS INDICATES FAVORABLE SETUP FOR HEAVY SNOW RATES IN THOSE EASTERN AREAS FRIDAY AFTN/FRIDAY EVENING. SNOWFALL RATES UP TO 2 INCHES PER HOUR COULD OCCUR IN THOSE AREAS AND HEADLINES MAY BE NEEDED AT SOME POINT. HOWEVER...WILL LEAVE THOSE DECISIONS TO LATER SHIFTS AS EXPECT VERY LITTLE SNOWFALL IN THOSE AREAS THROUGH FRIDAY MORNING. TROUGH AND COLDER AIR SFC-H85 SLOWLY HEAD INTO LOWER GREAT LAKES FRIDAY NIGHT INTO SATURDAY. WARM AIR ADVECTION STARTS UP BY SATURDAY LEADING TO A PUSH OF ISENTROPIC ASCENT 285-290K (750-650MB) ACROSS MUCH OF THE CWA. UVM IN THE LAYER FAIRLY STRONG...BUT TROUBLE IS THERE IS DRY AIR LINGERING BLO H85 THRU THE DAY. COULD BE SOME FLURRIES OR LIGHT SNOW SHOWERS...BUT BETTER SATURATION WILL KEEP THE GREATER CHANCE OF ACCUMULATING SNOWS MORE INTO ONTARIO. GUSTY SW WINDS WILL ADD CHILL TO THE AIR DESPITE SFC TEMPS REBOUNDING INTO LOWER TO MIDDLE 20S. FOR THE EXTENDED...TROUGH THAT WAS OVER THE AREA FOR MUCH OF THIS WEEK IS FCST TO EASE INTO EASTERN CANADA LEADING TO MORE OF A ZONAL FLOW PATTERN/WARMING TREND BY EARLY NEXT WEEK. WEAK SHORTWAVE/WARM FRONT SLIDES ACROSS UPR LAKES MONDAY BUT MOISTURE IS MINIMAL SO DO NOT EXPECT A WHOLE LOT OF PRECIPITIATON. BETTER CHANCE OF PRECIPITATION WOULD BE FARTHER NORTH CLOSER TO H85-H7 FRONTOGENESIS AND RIGHT ENTRANCE REGION OF UPR JET OVR ONTARIO. ANOTHER TROUGH FORMING OVR SCNTRL CANADA IS FCST TO MOVE ACROSS THE UPR GREAT LAKES LATE TUESDAY INTO WEDNESDAY. DIFFERENCES BEGIN TO APPEAR WITH REGARD TO DEPTH OF TROUGH BY WEDNESDAY. LAST TWO RUNS OF GFS CLOSED THE TROUGH OFF OVR UPR MISSISSIPPI RIVER VALLEY/UPR LAKES. MEANWHILE... RECENT RUNS OF THE ECMWF AND PREVIOUS RUNS OF GFS INDICATED MORE OF A PROGRESSIVE SYSTEM...WITH DEEPER SYSTEM FORMING OVR CNTRL PLAINS MID-LATE NEXT WEEK. ENSEMBLES FM GFS/ECMWF/CANADIAN SHED LITTLE LIGHT ON THE SUBJECT WITH MIXED SIGNALS IN TERMS OF STRENGTH AND MOVEMENT OF THE TROUGHS. DOES SEEM THAT AT LEAST ECMWF WOULD SUPPORT BETTER CHANCE OF ORGANIZED PRECIPITATION IN THE MIDWEEK TIME FRAME. WILL NOT PUT TOO MUCH EMPHASIS ON THIS YET THOUGH AS SUPPORT FOR THAT IDEA REMAINS LIMITED SUPPORT LOOKING AT OTHER AVILABLE GUIDANCE AND ENSEMBLES. && .AVIATION /FOR THE 06Z TAF ISSUANCE/... PASSAGE OF THE FIRST IN A SERIES OF LO PRES TROFS WL BRING IFR CONDITIONS TO THE EXPOSED CMX LOCATION THAT WL EXPERIENCE MORE SGNFT LK MOISTENING DESTABILIZATION EARLY THIS MRNG. ALTHOUGH THERE MAY BE SOME -SHSN AT IWD AND SAW...ANY REDUCED CIG/VSBY WL BE MORE LIMITED WITH LESS LK MODIFICATION AND/OR DOWNSLOPE WIND COMPONENT. EXPECT A PERIOD OF IMPROVEMENT TOWARD SUNRISE AS A TRAILING SFC HI PRES RDG/AXIS OF DRIER AIR FOLLOWING THE TROF SHIFTS OVHD. BUT THE LULL WL BE ONLY TEMPORARY WITH A SECOND LO PRES TROF FOLLOWING THRU AT MID MRNG. THIS DEEPER TROF WL BE FOLLOWED BY STRONGER W WINDS THAT WL CAUSE GUSTS AS HI AS 30 KT OVER THE EXPOSED KEWEENAW/CMX. THE COMBINATION OF FALLING LK EFFECT SN AND BLSN WHIPPED UP BY THESE STRONG WINDS WL LIKELY LEAD TO LIFR CONDITIONS AT THAT SITE. THE DRY NATURE OF THE ARCTIC AIRMASSES WL LIMIT DETERIORATION AT IWD AND ESPECIALLY SAW...WHERE THE PREVAILING WLY WIND COMPONENT WL DOWNSLOPE/DRY AND RESULT IN PREDOMINANT VFR CONDITIONS. && .MARINE /FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE/... WINDS MAINLY OUT OF A WESTERLY DIRECTION OVER 20KTS WILL PREVAIL THROUGH MUCH OF THE PERIOD. THE WINDS/WAVES ALONG WITH PLENTY OF COLD AIR WILL RESULT IN THE POTENTIAL FOR FREEZING SPRAY TONIGHT INTO FRIDAY. WESTERLY GALES ARE EXPECTED TO RETURN AROUND SUNRISE THURSDAY BEHIND AN ARCTIC FRONT OVER THE WEST HALF...BEFORE EXTENDING THROUGH CENTRAL AND EASTERN LS THROUGH EARLY THURSDAY EVENING. EXPECT STRONG HIGH PRESSURE ACROSS SW CANADA TO WEAKEN ACROSS THE PLAINS STATES FRIDAY...WHILE EXTENDING A RIDGE ACROSS LS BY FRIDAY NIGHT. LOW PRESSURE OVER MANITOBA SATURDAY MORNING WILL SLIDE ACROSS ONTARIO SATURDAY AFTERNOON AND EVENING...WHILE DRAGGING A TROUGH OVER LS. A PERIOD OF SW GALES IS POSSIBLE SATURDAY AHEAD OF THE LOW. ANOTHER LOW PRESSURE SYSTEM...OVER THE DAKOTAS SUNDAY MORNING...WILL LIKELY FILTER ACROSS LAKE SUPERIOR SUNDAY NIGHT. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... LAKE EFFECT SNOW WARNING UNTIL 7 PM EST FRIDAY FOR MIZ002-003. LAKE EFFECT SNOW ADVISORY UNTIL 7 PM EST FRIDAY FOR MIZ001-084. LAKE SUPERIOR... GALE WARNING FROM 7 AM THIS MORNING TO 1 AM EST FRIDAY FOR LSZ263>267. LAKE MICHIGAN... NONE. && $$ SYNOPSIS...JLB SHORT TERM...JLB LONG TERM...JLA AVIATION...KC MARINE...JLB
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
355 AM EST THU DEC 8 2011 .SYNOPSIS... HIGH PRESSURE THURSDAY. COLD FRONT FRIDAY NIGHT. HIGH PRESSURE FOR THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... CLEARING ACROSS THE LOWLANDS HAS RESULTED IN STRONG RADIATIONAL COOLING. STILL EXPECTING TEMPS TO CRASH THROUGH EARLY MORNING HOURS. CLEARING HAS STALLED A BIT IN THE MOUNTAINS WHERE EKN AND BKW STILL REPORTING BKN CLOUD COVER. EXPECTING THESE SITES TO CLEAR OUT COMPLETELY BY 10Z. CURRENT IR SATELLITE IMAGERY SHOWS SHALLOW CLOUD DECK KNOCKING ON THE DOORSTEPS OF OUR SE OHIO COUNTIES. LATEST RUN OF THE RUC HAS THIS FEATURE DIAGNOSED WELL WITH COINCIDING 850MB MOISTURE MOVING ACROSS OUR NORTHERN TIER COUNTIES AND SLOSHING UP AGAINST THE HIGH TERRAIN OF THE NE MNT COUNTIES. RESULTANT RUC SOUNDINGS DISPLAYED IN BUFKIT TRYING TO DEVELOP LOW STRATUS AGAINST THE MOUNTAINS AROUND 12Z. NOT COMPLETELY SOLD ON THIS AS RUC 850MB MOISTURE SHOULD ERODE FURTHER DOWNSTREAM OF THE SOUTHERN GREAT LAKES. ALSO...WARMING TREND IN 850MB TEMPS SHOULD HELP TO DRY THE COLUMN FURTHER. ALL TOLD...WILL NOT INCLUDE STRATUS DEVELOPMENT IN THIS PACKAGE...BUT WILL CONTINUE TO MONITOR FORTHCOMING GUIDANCE AND TRENDS. A CHANGE OF PACE TODAY...RELATIVE TO THE LAST FEW DAYS. SUNNY SKIES WITH COLDER TEMPERATURES ARE EXPECTED AS CWA IS NOW UNDER THE CONTROL OF A SURFACE HIGH. && .SHORT TERM /FRIDAY THROUGH SUNDAY/... NEXT SYSTEM TO DEAL WITH WILL BE A MOISTURE STARVED COLD FRONT EXPECTED TO ENTER THE SOUTHEAST OHIO ZONES AFTER 18Z FRIDAY. SREF PROBABILITIES OF ACCUMULATING PRECIPITATION ARE ON THE LOW SIDE...BELOW 50 PERCENT...AND WILL HAVE A TOUGH TIME SATURATING ABOVE ABOUT 750MB. THAT BEING SAID...SNOW SHOWERS ARE POSSIBLE UPON PASSAGE...LIKELY NOT ACCUMULATING OR GIVING TRACE ACCUMULATIONS. OF MORE SIGNIFICANCE IS THE AIRMASS BEHIND THE COLD FRONT. 500MB HEIGHTS DROP IN THE POST FRONTAL TROUGH...AND 850MB TEMPERATURES ALSO DECREASE INTO THE MINUS TEENS COME SATURDAY. THERMAL TROUGH AT THIS LEVEL WILL PERSIST OVER THE NORTHEAST MOUNTAINS...AND WITH A CLEARING SKY...SATURDAY NIGHT TEMPERATURES LOOK VERY COLD. STRONG HIGH PRESSURE SETTLES IN OVER THE REMAINDER OF THE WEEKEND IN A LARGELY DRY PATTERN THROUGH EARLY NEXT WEEK. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... A BREAK FROM ANY RAIN OR SNOW WILL OCCUR DURING THE FIRST SEVERAL DAYS OF THIS PERIOD. A POCKET OF COLD AIR WILL BE IN PLACE THANKS TO SURFACE HIGH PRESSURE. AS THE SURFACE HIGH PRESSURE SLIDES NORTHEAST...POCKET OF COLDEST TEMPERATURES WILL ALSO FOLLOW. SUNDAY THROUGH TUESDAY WILL FEATURE MOSTLY SUNNY SKIES DURING THE DAY AND CLEAR AND COLD AT NIGHT. THE NEXT SYSTEM WILL APPROACH THE AREA DURING THE MID WEEK. WILL CONTINUE TO MONITOR THE SYSTEM AS IT DEVELOPS. GENERALLY FOLLOWED HPC GUIDANCE WITH ONLY A FEW MODIFICATION. && .AVIATION /09Z THURSDAY THROUGH MONDAY/... CONDITIONS CONTINUE TO IMPROVE EARLY THIS MORNING FROM W TO E. MVFR IN MOUNTAINS AS CLOUD COVER AND -SN LINGER A FEW HOURS LONGER. CLEAR SKY WEST FROM CRW-CKB LINE RESULTING IN VFR...EXPECTING THIS TREND TO CONTINUE PUSHING EAST BETWEEN 06Z TO 12Z. CEILING UNLIMITED AND VSBY UNRESTRICTED 12Z TO 18Z. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z FRIDAY... FORECAST CONFIDENCE: HIGH. ALTERNATE SCENARIOS: THERE IS A CHANCE THAT SOME STRATUS MAY REFORM IN WEST VIRGINIA AT 1 TO 2 THSD FT ON EITHER SIDE OF DAWN/12Z THURSDAY. BUT WITH WIND AND LOWERING DEW POINTS...DID NOT GO WITH THAT SCENARIO IN THE 00Z TAF FORECASTS. 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 THU 12/08/11 UTC 1HRLY 08 09 10 11 12 13 14 15 16 17 18 19 EST 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14 CRW CONSISTENCY H H H H H H H H H H H H HTS CONSISTENCY H H H H H H H H H H H H BKW CONSISTENCY M M M M H H H H H H H H EKN CONSISTENCY M M H M M H H H H H H H PKB CONSISTENCY H H H H H H H H H H H H CKB CONSISTENCY H H H H H H M M H H H H AFTER 06Z FRIDAY... NO WIDESPREAD IFR EXPECTED. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...26/TAX NEAR TERM...TAX SHORT TERM...26 LONG TERM...JB AVIATION...TAX
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NWS SIOUX FALLS SD
1058 PM CST WED DEC 7 2011 .DISCUSSION.../ISSUED AT 758 PM CST/ WENT AHEAD AND INCREASE LOWS ABOUT 5 TO 8 DEGREES IN MOST SPOTS AS CLOUD COVER NOW SEEMS TO BE LOCKED IN FOR THE NIGHT...ESPECIALLY WITH THE APPROACH OF THE UPPER LEVEL WAVE IN THE NORTHERN ROCKIES. SO...BASICALLY LOOKING AT TEMPERATURES RANGING FROM AROUND THE MID TEENS TO LOWER 20S. DID ADD SOME FLURRIES AND A SLIGHT CHANCE FOR LIGHT SNOW IN THE FAR SOUTHERN CWA FRO 9-12Z AS THE RUC AND HRRR CONTINUE TO INDICATE THAT SOME SNOWFALL MAY GET SQUEEZED OUT OF THE MID LEVEL DECK MOVING SOUTHWARD. THIS DOES NOT SEEM COMPLETELY OUT OF THE QUESTION SINCE THE THERMAL PROFILE BECOMES MORE DENDRITIC IN THE STRONGER FORCING AT THIS TIME AND OUR LOWEST LEVELS ARE NOT COMPLETELY DRY SO COULD SEE SOME FLAKES WITH THE BETTER CHANCES NEAR THE MISSOURI RIVER FROM ABOUT 9Z THROUGH 15Z. /08 && .AVIATION.../FOR THE 06Z TAF ISSUANCE/ GENERAL VFR CONDITIONS EXPECTED THROUGH 06Z FRI. VERY SMALL THREAT FOR MARGINAL MVFR STRATUS LATE TONIGHT AND EARLY MORNING BEHIND COLD FRONT...BUT BELOW MENTIONABLE THRESHOLD...AT WHICH TIME A FEW FLURRIES AT BEST FOR KSUX AREA...WHICH SHOULD NOT BREACH INTO MVFR VISIBILITIES. /CHAPMAN && .PREV DISCUSSION.../ISSUED AT 252 PM CST/ FRONTAL BOUNDARY CONTINUES TO DROP SOUTHWARD ACROSS THE REGION THIS AFTERNOON...AND WILL EXIT THE AREA BY THIS EVENING. MAIN CHALLENGE TONIGHT WILL BE IN TEMPERATURES...WITH STRONG COLD AIR ADVECTION BEHIND THE FRONT...MUTED BY CLOUD COVER EXPECTED TO BE OVER MUCH OF THE AREA DURING THE OVERNIGHT HOURS. WITH BREAKS IN THE CLOUDS...WILL SEE TEMPERATURES FLUCTUATE DEPENDING ON THE CLOUD COVER...THOUGH WILL SEE A GENERAL DOWNWARD TREND THROUGH THE NIGHT WITH LOWS JUST UNDER 10 THROUGH THE HURON TO BROOKINGS CORRIDOR...TO THE MID TEENS ALONG THE MISSOURI RIVER CORRIDOR WHERE CLOUDS WILL BE MORE DOMINANT. MODELS CONTINUING SLIGHT SOUTHWARD TREND WITH PRECIP CHANCES ON THURSDAY...AS NORTHERN STREAM WAVE DROPS SOUTHEAST INTO THE NORTHERN PLAINS. 700MB FRONTOGENESIS STILL HUGS THE MISSOURI RIVER VALLEY... HOWEVER MOST MODELS SHOWING A DRY LAYER IN THE ATMOSPHERE NORTH OF THE RIVER THAT WILL LIMIT NORTHWARD EXTENT OF ACCUMULATING PRECIP. HAVE SCALED POPS BACK TO JUST OUR FAR SOUTHERN AREAS...GENERALLY SOUTH OF LAKE ANDES/KYKN/KSLB LINE...WITH JUST A FEW TENTHS OF SNOW AT BEST IN THESE AREAS. 850MB BAROCLINIC ZONE LINGERS FROM NORTH CENTRAL NEBRASKA INTO SOUTHWEST SOUTH DAKOTA INTO THE EVENING AS THE MAIN WAVE DROPS THROUGH THE DAKOTAS....AND THIS COULD KEEP SOME LIGHT SNOW OR FLURRIES GOING JUST TO OUR SOUTHWEST INTO THURSDAY EVENING. WILL KEEP IT DRY IN OUR AREA...THOUGH SOME MID CLOUDS WILL LIKELY HANG AROUND IN THE WESTERN PORTIONS OF THE MISSOURI RIVER VALLEY THROUGH 06Z BEFORE DRIER MID LEVEL AIR PUSHES SOUTH WITH THE WAVE. FOCUS FOR THE REMAINDER OF THE WEEK AND INTO THE WEEKEND WILL BE ON TEMPERATURES...WITH POTENTIAL FOR SOME DECENT RADIATIONAL NIGHTTIME COOLING. SURFACE RIDGE AXIS SHIFTS INTO NEBRASKA SO WILL LIKELY NOT SEE WINDS GO COMPLETELY CALM EXCEPT IN MORE SHELTERED AREAS. HOWEVER EVEN WITH RELATIVELY LIGHT WEST-SOUTHWEST WINDS EXPECTED OVER THE SNOWPACK AREAS...SHOULD SEE QUICK EVENING DROPS IN TEMPERATURES ACROSS OUR SOUTHEAST THURSDAY AND FRIDAY NIGHTS...WITH NON-DIURNAL RISE IN TEMPERATURES EXPECTED LATER FRIDAY NIGHT AS WINDS/CLOUDS INCREASE AHEAD OF WARM FRONT. DAYTIME TEMPERATURES SHOULD SEE GRADUAL DECREASE IN EFFECT OF SNOWPACK ON READINGS...THOUGH COULD STILL HOLD HIGHS BACK A FEW DEGREES ON FRIDAY WITH FULL SUNSHINE AND LIMITED MIXING. LONGER RANGE STILL LOOKS RELATIVELY DRY THROUGH TUESDAY...WITH MODELS SHOWING DECENT AGREEMENT DIGGING YET ANOTHER WAVE INTO THE SOUTHWEST CONUS WHILE SEPARATE NORTHERN STREAM TROUGH SLIDES EAST ACROSS THE CANADIAN BORDER. WEAK WAVE SEEN EJECTING OUT OF SOUTHWEST SYSTEM INTO THE MIDDLE MISSOURI VALLEY ON MONDAY. FORECAST SOUNDINGS QUITE SPARSE ON MOISTURE ABOVE 850MB...BUT SIMILAR IN SHOWING STRONG NORTHWARD PUSH OF LOW LEVEL MOISTURE/STRATUS AHEAD OF COLD FRONT IN THE LATE NIGHT/MORNING HOURS. MOISTURE PROFILES FROM ALL MODELS ARE REMINISCENT OF DRIZZLE SOUNDINGS...WITH LACK OF MOISTURE IN CRITICAL ICE-BEARING LAYER ALOFT...BUT TOUGH TO PINPOINT THREAT OF POTENTIAL FREEZING PRECIP AT DAY 4-5 RANGE SO WILL JUST GO WITH MENTION OF LIGHT RAIN/SNOW WITH SLIGHT CHANCE POPS IN OUR FAR SOUTHEAST DURING THE DAY MONDAY. GREATER DIFFERENCES IN THE MODELS ARISE BY THE MIDDLE OF NEXT WEEK IN HANDLING OF NORTHERN STREAM TROUGH AS IT MOVES ACROSS THE GREAT LAKES AND EASTERN CANADA...AS WELL AS SOUTHWEST CONUS CUTOFF. GFS STRONGER/SLOWER WITH NORTHERN STREAM TROUGH WHILE ALSO MAINTAINING STRONGER SOUTHWEST SYSTEM...WITH ANOTHER RELATIVELY WEAK WAVE LIFTING NORTHEAST THROUGH THE PLAINS MIDWEEK. ECMWF ON THE OTHER HAND IS SLIGHTLY WEAKER/FASTER WITH THE NORTHERN STREAM TROUGH... ALLOWING STRONGER CHUNK OF ENERGY TO LIFT NORTHEAST INTO THE PLAINS ON WEDNESDAY. EITHER SCENARIO GIVES AT LEAST SOUTHERN PARTS OF OUR AREA A CHANCE OF PRECIP LATE IN THE FORECAST PERIOD. MAIN DIFFERENCE IS STRONGER ECMWF SPREADS THE PRECIP MUCH FARTHER NORTHEAST THAN THE GFS. IN EITHER CASE...SEEMS SOME CHANCE POPS ARE WARRANTED FOR THE DAY 7 TIMEFRAME AT THIS TIME. AFOREMENTIONED DIFFERENCES ALSO RESULT IN DRASTICALLY DIFFERENT LOW LEVEL TEMPERATURE PROFILES...WITH ECMWF PULLING WARMER AIR MUCH FARTHER NORTH THAN GFS WHERE NORTHERN STREAM REMAINS DOMINANT. WITH RIDE WITH BLEND OF THE TWO SOLUTIONS AND KEEP PRECIP TYPE AS ALL SNOW FOR NOW...BUT WARMER ECMWF COULD BRING A THREAT OF LIQUID PRECIP INTO THE MIX AND WILL KEEP A CLOSE EYE ON TRENDS FOR THIS OVER THE NEXT FEW DAYS. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. NE...NONE. IA...NONE. && $$
AREA FORECAST DISCUSSION
NWS DENVER CO
826 AM MST THU DEC 8 2011 .UPDATE...CURRENT WEATHER CAMS SHOW SNOW HAS BECOME MORE WIDESPREAD IN THE MOUNTAINS EARLY THIS MORNING. ALREADY ONE HALF TO ONE INCH OF SNOW AS FAR SOUTH AS COPPER MOUNTAIN. RADAR AND SATELLITE TRENDS ALONG WITH SHORT RANGE MODEL GUIDANCE OF RUC AND HRRR SHOWING THIS SNOW WILL CONTINUE THROUGH THE REST OF THE MORNING AND THEN DECREASE. THE SAME CAN BE SAID OVER THE NORTHEAST CORNER OF THE STATE WHERE BAND OF SNOW WILL DROP SLOWLY SOUTH/SOUTHEAST ACROSS THAT AREA. THE CHANCE OF SNOW WILL DECREASE RATHER RAPIDLY TO THE SOUTH AND WEST TOWARD DENVER WHERE LOW LEVEL AIR IS SIGNIFICANTLY DRIER AND LARGE SCALE SUBSIDENCE WILL TAKE HOLD EARLIER IN THE AFTERNOON. && .AVIATION...GOING FORECAST ON TRACK WITH ONLY A CHANCE OF LOWER MVFR CEILINGS DEVELOPING WITH THE WEAK FRONTAL PUSH. THIS WEAK FRONT IS STILL EXPECTED TO REACH THE FRONT RANGE AIRPORTS AROUND 18Z WITH ONLY A SLIGHT WIND SHIFT FROM AN EASTERLY DIRECTION. && .PREV DISCUSSION... /ISSUED 310 AM MST THU DEC 8 2011/ LONG TERM...THERE WILL BE A DECREASING NORTHWEST FLOW ALOFT ON FRIDAY WITH A DRYING AND SLOW WARMING TREND ACROSS COLORADO. THIS TREND WILL CONTINUE THROUGH THE WEEKEND AS THE GREAT BASIN RIDGE OF HIGH PRESSURE SHIFTS OVER COLORADO AND WEAKENS A BIT. TEMPERATURES WILL WARM TO AROUND SEASONABLE NORMALS WITH PLENTY OF SUNSHINE AND DRY CONDITIONS. BY EARLY NEXT WEEK...SPLIT FLOW PATTERN DEVELOPS OVER MUCH OF THE WEST WITH CLOSED LOW DEVELOPING ACROSS SOUTHERN CALIFORNIA ON MONDAY WHILE WEAKER NORTHERN BRANCH STRETCHES A WEAK TROF ACROSS THE NORTHERN PLAINS STATES AND BRUSHES NORTHERN COLORADO WITH A WEAK FRONT AND COOLER TEMPERATURES. THIS PATTERN EVOLUTION SHOWS QUITE A BIT OF UNCERTAINTY AS THE EUROPEAN/GEM SOLUTIONS ARE DEEPER WITH THE LOW YET EJECTS IT FURTHER NORTH INTO COLORADO ON WEDNESDAY WHILE THE GFS SOLUTION HAS THE LOW ACROSS NEW MEXICO AND TEXAS. THE EUROPEAN TRAJECTORY WOULD FAVOR A CHANCE OF SNOW AND COOLER TEMPS WHERE VERY LITTLE EFFECT WOULD BE FELT FROM THE FURTHER SOUTH GFS SOLUTIONS. GFS ENSEMBLE MEMBERS NOT MUCH HELP AS SOLUTIONS ARE ALL OVER THE BOARD. THIS ALL MEANS VERY LITTLE CHANGES TO THE OUT DAYS IN THE LONG TERM FORECAST. WILL KEEP A SLIGHT CHANCE OF SNOW OVER THE ENTIRE CWA FOR LATE TUESDAY AND WEDNESDAY. $$ AVIATION...A CDFNT WILL MOVE ACROSS NERN CO LATER THIS MORNING AND AFTN HOWEVER BOTH THE NAM AND HRRR KEEP THE MAIN PUSH OVER THE PLAINS AND KIND OF BACK DOOR THE FNT INTO THE FNT RANGE BY EARLY TO MID AFTN WITH VERY WK UPSLOPE. OVERALL IT LOOKS LIKE POTENTIAL FOR LOW CEILINGS AND SOME FOG WILL REMAIN LOW THRU 18Z HOWEVER THEY COULD EVENTUALLY BACK IN FM THE NE AND E BY MID TO LATE AFTN ALTHOUGH NEITHER THE LATEST NAM OR HRRR EVER SHOW THEM AFFECTING THE AIRPORT. FOR NOW WILL GO WITH A TEMPO GROUP AS CONFIDENCE IS NOT VERY HIGH. MEANWHILE THERE IS A 10% CHANCE OF A FEW SNOW FLURRIES THIS AFTN AS A WK TROUGH MOVES ACROSS. WINDS EARLY THIS MORNING WILL BE LIGHT WLY AND THEN BECOME LIGHT SLY BY 15Z. BY EARLY AFTN AS THE FNT BACKDOORS IN THE WINDS WILL BECOME LIGHT ESE BASED ON THE LATEST HRRR. FOR THIS EVENING COULD STILL SEE SOME POTENTIAL FOR LOW CLOUDS AND FOG ALTHOUGH NAM KEEPS BEST CHC TO THE NORTH AND EAST OF AIRPORT. AFTER 06Z THE LOW LEVEL WINDS BECOME MORE WSW WHICH SHOULD KEEP THE LOW CLOUDS EAST OF THE AIRPORT. && .BOU WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...BARJENBRUCH LONG TERM....ENTREKIN AVIATION...BARJENBRUCH
AREA FORECAST DISCUSSION
NWS DENVER CO
310 AM MST THU DEC 8 2011 SHORT TERM...A WK UPPER LEVEL TROUGH WILL MOVE SE ACROSS THE AREA TODAY WITH SOME VERY WK MID LVL QG ASCENT. CROSS-SECTIONS SHOW ENOUGH MOISTURE WILL BE AVAILABLE FOR A CHC OF SOME LIGHT SNOW IN THE MTNS MAINLY OVER ZNS 31 AND 33. EAST OF THE MTNS A CDFNT WILL MOVE ACROSS NERN CO LATER THIS MORNING THRU THE AFTN HOURS HOWEVER UPSLOPE FLOW WILL BE WK. MEANWHILE THE FAR NERN PLAINS WILL ALSO BE AFFECTED BY A WK UPPER LEVEL JET WHICH COULD LEAD TO A CHC OF LIGHT SNOW THRU THE AFTN HOURS MAINLY FM STERLING EASTWARD. ELSEWHERE ACROSS THE PLAINS THERE WILL ONLY BE A SLIGHT CHC OF -SHSN. SOUNDINGS SHOW AIRMASS WILL BE COLD ENOUGH FOR PCPN TO FALL AS SNOW SO WILL NOT MENTION ANY FREEZING DRIZZLE ACROSS NERN CO. HIGHS THIS AFTN WILL GENERALLY BE IN THE 25 TO 30 DEGREE RANGE ACROSS NERN CO BEHIND THE CDFNT AS COLD SFC HIGH PRESSURE BUILDS INTO THE RGN. FOR TONIGHT WILL HAVE A DRY FCST AS THE WK UPPER LEVEL TROUGH MOVES AWAY FM THE AREA. SOME FOG COULD DVLP OVER THE PLAINS THIS EVENING AND LINGER OVERNIGHT. .LONG TERM...THERE WILL BE A DECREASING NORTHWEST FLOW ALOFT ON FRIDAY WITH A DRYING AND SLOW WARMING TREND ACROSS COLORADO. THIS TREND WILL CONTINUE THROUGH THE WEEKEND AS THE GREAT BASIN RIDGE OF HIGH PRESSURE SHIFTS OVER COLORADO AND WEAKENS A BIT. TEMPERATURES WILL WARM TO AROUND SEASONABLE NORMALS WITH PLENTY OF SUNSHINE AND DRY CONDITIONS. BY EARLY NEXT WEEK...SPLIT FLOW PATTERN DEVELOPS OVER MUCH OF THE WEST WITH CLOSED LOW DEVELOPING ACROSS SOUTHERN CALIFORNIA ON MONDAY WHILE WEAKER NORTHERN BRANCH STRETCHES A WEAK TROF ACROSS THE NORTHERN PLAINS STATES AND BRUSHES NORTHERN COLORADO WITH A WEAK FRONT AND COOLER TEMPERATURES. THIS PATTERN EVOLUTION SHOWS QUITE A BIT OF UNCERTAINTY AS THE EUROPEAN/GEM SOLUTIONS ARE DEEPER WITH THE LOW YET EJECTS IT FURTHER NORTH INTO COLORADO ON WEDNESDAY WHILE THE GFS SOLUTION HAS THE LOW ACROSS NEW MEXICO AND TEXAS. THE EUROPEAN TRAJECTORY WOULD FAVOR A CHANCE OF SNOW AND COOLER TEMPS WHERE VERY LITTLE EFFECT WOULD BE FELT FROM THE FURTHER SOUTH GFS SOLUTIONS. GFS ENSEMBLE MEMBERS NOT MUCH HELP AS SOLUTIONS ARE ALL OVER THE BOARD. THIS ALL MEANS VERY LITTLE CHANGES TO THE OUT DAYS IN THE LONG TERM FORECAST. WILL KEEP A SLIGHT CHANCE OF SNOW OVER THE ENTIRE CWA FOR LATE TUESDAY AND WEDNESDAY. $$ AVIATION...A CDFNT WILL MOVE ACROSS NERN CO LATER THIS MORNING AND AFTN HOWEVER BOTH THE NAM AND HRRR KEEP THE MAIN PUSH OVER THE PLAINS AND KIND OF BACK DOOR THE FNT INTO THE FNT RANGE BY EARLY TO MID AFTN WITH VERY WK UPSLOPE. OVERALL IT LOOKS LIKE POTENTIAL FOR LOW CEILINGS AND SOME FOG WILL REMAIN LOW THRU 18Z HOWEVER THEY COULD EVENTUALLY BACK IN FM THE NE AND E BY MID TO LATE AFTN ALTHOUGH NEITHER THE LATEST NAM OR HRRR EVER SHOW THEM AFFECTING THE AIRPORT. FOR NOW WILL GO WITH A TEMPO GROUP AS CONFIDENCE IS NOT VERY HIGH. MEANWHILE THERE IS A 10% CHANCE OF A FEW SNOW FLURRIES THIS AFTN AS A WK TROUGH MOVES ACROSS. WINDS EARLY THIS MORNING WILL BE LIGHT WLY AND THEN BECOME LIGHT SLY BY 15Z. BY EARLY AFTN AS THE FNT BACKDOORS IN THE WINDS WILL BECOME LIGHT ESE BASED ON THE LATEST HRRR. FOR THIS EVENING COULD STILL SEE SOME POTENTIAL FOR LOW CLOUDS AND FOG ALTHOUGH NAM KEEPS BEST CHC TO THE NORTH AND EAST OF AIRPORT. AFTER 06Z THE LOW LEVEL WINDS BECOME MORE WSW WHICH SHOULD KEEP THE LOW CLOUDS EAST OF THE AIRPORT. && .BOU WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...RPK LONG TERM....SWE AVIATION...RPK
AREA FORECAST DISCUSSION
NWS JACKSONVILLE FL
952 AM EST THU DEC 8 2011 .UPDATE...WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW BROAD MID- UPPER TROUGHING ACROSS THE SRN CONUS WITH UPPER LEVEL DISTURBANCE MOVING ACROSS THE OK/TX/AR AREA. SHOULD SEE ASSOCD HIGH CLOUDS MOVE ACROSS OUR AREA IN THE AFTERNOON AND TONIGHT. SFC HIGH IS SITUATED ACROSS THE LOWER MS VALLEY TO ERN TN WITH TYPICAL INVERTED TROUGHING NOTED ALONG OUR COAST. LLVL FLOW IS NLY BUT JUST ABOVE THE SFC HAS TURNED NE. BROKEN-OVERCAST STRATOCU CLOUDS AROUND 2-3 KFT HAVE ADVANCED WELL INLAND NOW TO DUVAL COUNTY SW TO MARION COUNTY. THESE CLOUDS ASSOCD WITH COLDER AIRMASS MOVING OVER WARM ATLC WATERS/WEAK ISENTROPIC LIFT AND LLVL CONVERGENCE. HAVE ADJUSTED SKY CONDS UP TO MOSTLY CLOUDY AND TWEAKED TEMPS DOWN OVER THE SE ZONES. A FEW SPRINKLES POSSIBLE LATER IN THE AFTN NEAR THE COAST S OF DUVAL BUT THINK WILL LEAVE OUT FOR NOW DUE TO SHALLOW NATURE OF THIS MOISTURE. && .AVIATION...MVFR CIGS AROUND FL020-030 EXPECTED FOR JAX/CRG/VQQ AND GNV FOR DURATION OF THE DAY AS STRATOCU MOVES INLAND. PROBABLY LOOKING AT MVFR DEVELOPING AT SSI AROUND THE 16Z-18Z TIME FRAME SO AMENDMENTS TO FOLLOW. OUTLOOK FOR TONIGHT CALLS FOR MVFR CIGS WITH THE BEST CHANCES COASTAL COUNTY TAFS. && .MARINE...NLY WINDS AT 15-20 KT AT 41012 WITH SEAS OF 5 FT. THIS IS SLIGHTLY BELOW CURRENT WINDS SO WILL ADJUST WINDS A BIT DOWNWARD REST OF TODAY BUT ADVISORY FOR OFFSHORE LOOKS GOOD...AND WINDS ANTICIPATED TO BE AROUND THE 15-20KT RANGE NEARSHORE. RIP CURRENTS: MODERATE RISK AS WINDS SHIFTING TO NE AND LOW E SWELLS. && .PRELIMINARY POINT TEMPS/POPS... AMG 59 35 63 42 / 0 0 10 10 SSI 58 47 64 49 / 0 10 10 20 JAX 60 44 67 47 / 0 10 10 10 SGJ 60 51 68 54 / 10 20 10 20 GNV 61 42 68 48 / 0 10 10 10 OCF 63 46 71 51 / 0 10 10 10 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...NONE. GA...NONE. AM...SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR ALTAMAHA SOUND GA TO FERNANDINA BEACH FL 20 NM TO 60 NM OFFSHORE- FERNANDINA BEACH TO ST AUGUSTINE FL 20 NM TO 60 NM OFFSHORE- ST AUGUSTINE TO FLAGLER BEACH FL 20 NM TO 60 NM OFFSHORE. && $$ SHASHY/WALKER
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
640 AM EST THU DEC 8 2011 UPDATED AVIATION DISCUSSION FOR 12Z TAFS .SYNOPSIS /ISSUED AT 545 AM/... WV IMAGERY AND RUC ANALYSIS INDICATED CYCLONIC MID/UPPER LEVEL FLOW AROUND A VORTEX OVER HUDSON BAY BRINGING NRN STREAM WNW FLOW FROM SRN CANADA INTO THE UPPER GREAT LAKES. A SHORTWAVE MOVING THROUGH THE UPPER GREAT LAKES EARLY THIS MORNING ALONG WITH ITS ASSOC SFC TROUGH IS HELPING TO FOCUS AN INTENSE LAKE ENHANCED SNOW BAND OVER SOUTH CENTRAL LAKE SUPERIOR AND THE ERN UPR MI SHORELINE IN THE PAST HR AS NOTED ON RADAR IMAGERY. A STRONG 140 KT UPR JET MAX DIVING DOWN THROUGH ALBERTA WILL HELP AMPLIFY MID-UPR LVL TROF OVER THE UPPER GREAT LAKES LATE TONIGHT AND FRIDAY AS WELL AS POSSIBLY BRING SOME ENHANCEMENT TO LES BANDS OVER LAKE SUPERIOR. ABUNDANT DRY AIR UPSTREAM OVER THE NRN PLAINS AS NOTED ON SATELLITE IMAGERY AND SFC OBS HAS THUS FAR INHIBITED ORGANIZATION OF LES BANDS OVER WRN LAKE SUPERIOR DESPITE ADVECTION OF -15C 850 TEMPS INTO AREA. && .DISCUSSION... MAIN CONCERN IS LES POTENTIAL AND ONGOING HEADLINES OVER WRN UPR MI INTO FRIDAY. CONCERN TODAY WILL BE ABUNDANT DRY AIR UPSTREAM...WHICH IS DEPICTED FAIRLY WELL BY GFS BUFR SNDGS...AND HOW MUCH THIS DRY AIR WILL NEGATIVELY AFFECT ORGANIZATION OF LES BANDS AND THUS POTENTIAL FOR HEAVY SNOW ACCUMULATION AT LEAST TODAY. ALL 00Z MODELS INCLUDING LOCAL MESOSCALE MODELS ARE LESS BULLISH ON LAKE EFFECT QPF THAN PREV RUNS AND AGAIN THIS IS LIKELY DUE TO DRIER AIR UPSTREAM OF THE LAKE AND LACK OF SYNOPTIC SCALE FORCING. EVEN THOUGH SNOW GROWTH REMAINS GENERALLY FAVORABLE WITH 25-30/1 SNOW WATER RATIOS EXPECTED...GENERALLY DECIDED TO TRIM BACK LES ACCUMS TO 2 TO LOCALLY 5 INCHES OVER WARNING AND ADVISORY AREAS OF NRN ONTONAGON...HOUGHTON AND KEWEENAW COUNTIES TODAY DUE TO IMPACTING DRY AIR. GUSTY WEST WINDS TO 30 MPH WILL LIKELY CAUSE CONSIDERABLE BLOWING SNOW AND REDUCED VSBYS IN ANY MODERATE LES BANDS THAT FORM OVER HEADLINE REGIONS. LOCATIONS NEAR LAKE SUPERIOR EAST OF MUNISING...FROM GRAND MARAIS TO TWO HEART MAY ALSO SEE A PERIOD OF BRIEF HEAVY SNOW EARLY THIS MORNING WITH BAND MOVING ACROSS ERN LAKE SUPERIOR ATTM. AS MENTIONED BEFORE PLENTY OF UNCERTAINTY EXISTS WITH EVOLUTION OF LES BANDS TODAY AND WHETHER ANY HEAVIER WILL MOVE INLAND OR OFFSHORE...SO NO HEADLINES WERE ISSUED FOR ERN COUNTIES AT THIS TIME. LARGE SCALE TROUGH WITH COLDEST AIR OF SEASON THUS FAR TO PUSH INTO THE AREA TONIGHT INTO FRIDAY. MODELS NOT DEPICTING MUCH IN THE WAY OF ANY SIGNIFICANT SHORTWAVES THAT WOULD AID IN ENHANCEMENT TO LES BANDS. HOWEVER...COMBINATION OF POSSIBLE WEAK ENHANCEMENT WITH ARRIVAL OF TROUGH...H85 TEMPS LOWERING TO AROUND -18C BY 12Z FRIDAY AND INCREASING LOW-LVL CONVERGENCE FROM NIGHTTIME LAND BREEZES...MAY BE JUST ENOUGH TO ORGANIZE FORMATION OF DOMINANT BAND OVER SRN LAKE SUPERIOR AS DEPICTED BY 00Z MODELS. INTERESTINGLY ENOUGH...MODEL AVG QPF NOT AS HEAVY AS PREV RUNS FOR TONIGHT INTO FRIDAY MORNING...AND THIS IS AGAIN LIKELY TO DUE TO AFFECTS OF VERY DRY AIR UPSTREAM. STILL WOULD EXPECT TOTAL SNOW ACCUMS TO EXCEED A FOOT AT FAVORED HIGHER TERRIAN LOCATIONS THROUGH ENTIRE EVENT. WRN INTERIOR LOCATIONS MAY DIP CLOSE TO ZERO TONIGHT WHILE HIGHS ON FRIDAY WILL STAY MAINLY IN THE LOWER TEENS. BY LATE FRIDAY...WEAKER TROUGH FCST TO SLIDE THROUGH THE AREA MAY VEER WINDS SLIGHTLY MORE NW LEADING TO INCREASED CHANCES OF DOMINANT LES BAND MOVING INTO FAR EASTERN SECTION OF CWA...MAINLY EAST OF MUNISING AND WELL NORTH OF NEWBERRY. SOME MODERATE TO POSSIBLE HEAVY SNOWFALL COULD WARRANT A HEADLINE AT SOME POINT FOR THESE COUNTIES. TROUGH AND COLDER AIR SFC-H85 SLOWLY HEAD INTO LOWER GREAT LAKES FRIDAY NIGHT INTO SATURDAY. WARM AIR ADVECTION STARTS UP BY SATURDAY LEADING TO A PUSH OF ISENTROPIC ASCENT 285-290K (750-650MB) ACROSS MUCH OF THE CWA...BUT LIMITED MOISTURE SHOULD KEEP CWA DRY. LES BANDS WILL PUSH OFFSHORE BY LATE FRI NIGHT INTO EARLY SATURDAY AS GUSTY SW WINDS LOWERS WIND CHILL VALUES IN THE MORNING DESPITE SFC TEMPS REBOUNDING INTO LOWER TO MIDDLE 20S SAT AFTERNOON. MODELS STILL IN AGREEMENT WITH SHORTWAVE AND PASSAGE OF FRONTAL BOUNDARY BRINGING ANOTHER CHC OF SNOW..POSSIBLY MIXED WITH RAIN EAST HALF ON MONDAY WITH SOME LINGERING LIGHT SNOW POSSIBLE MON NIGHT INTO TUE. && .AVIATION /FOR THE 12Z TAF ISSUANCE/... A CONTINUED WESTERLY FLOW OF COLD AIR ACROSS THE WARM WATERS OF LAKE SUPERIOR...AND INCREASED LIFT FROM THE TERRAIN ENHANCEMENT OF THE KEWEENAW PENINSULA WILL AID IN KEEPING LAKE EFFECT SNOW SHOWERS IN PLACE AT CMX. LIFR CEILINGS AND VIS WILL REMAIN POSSIBLE...PARTICULARLY WITH BLSN THANKS TO GUSTY WINDS OVER 30KTS. FARTHER TO THE SOUTH...A LESS FAVORABLE WIND DIRECTION AT IWD WILL MAINLY RESULT IN A FEW FLAKES OF SNOW...AND HIGH END MVFR CEILINGS AND VIS. SOME SNOW SHOWERS HAVE BEEN ABLE TO SLIDE TO SAW...BUT HAVE REMAINED LIGHT AND SHELTERED SO FAR...WITH HIGH END MVFR POSSIBLE IN THE HEAVIER BANDS THERE AS WELL AS MUCH OF THE SNOW REMAINS OFFSHORE. && .MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/... THE UPPER GREAT LAKES WILL REMAIN BETWEEN STRONG A LOW ACROSS HUDSON BAY...AND STRONG HIGH PRESSURE OVER W CANADA AND THE NORTHERN PLAINS THROUGH TONIGHT...WITH WESTERLY GALES TO 35KTS CONTINUING INTO THE EVENING HOURS. EXPECT THE HIGH TO SLIDE TO THE CENTRAL PLAINS OVERNIGHT...BEFORE SHIFTING TO THE OHIO VALLEY AND MID ATLANTIC THIS WEEKEND. THE RESULT WILL BE A RIDGE SLIDING OVER THE UPPER GREAT LAKES FRIDAY AND FRIDAY NIGHT...WEAKENING OVER THE WEEKEND. LOW PRESSURE ACROSS SOUTH CENTRAL CANADA SUNDAY MORNING SHOULD SLOWLY PUSH ACROSS LS AND MANITOBA MONDAY AFTERNOON THROUGH TUESDAY. OUT AHEAD OF THIS LOW...STRONG SW WINDS AND POSSIBLY GALES TO 35KTS WILL BE POSSIBLE SATURDAY. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... LAKE EFFECT SNOW WARNING UNTIL 7 PM EST FRIDAY FOR MIZ002-003. LAKE EFFECT SNOW ADVISORY UNTIL 7 PM EST FRIDAY FOR MIZ001-084. LAKE SUPERIOR... GALE WARNING UNTIL 1 AM EST FRIDAY FOR LSZ263>267. GALE WARNING UNTIL 7 PM EST /6 PM CST/ THIS EVENING FOR LSZ241>244. LAKE MICHIGAN... NONE. && $$ SYNOPSIS...VOSS DISCUSSION...VOSS AVIATION...KF MARINE...KF
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
624 AM EST THU DEC 8 2011 .SYNOPSIS /ISSUED AT 545 AM/... WV IMAGERY AND RUC ANALYSIS INDICATED CYCLONIC MID/UPPER LEVEL FLOW AROUND A VORTEX OVER HUDSON BAY BRINGING NRN STREAM WNW FLOW FROM SRN CANADA INTO THE UPPER GREAT LAKES. A SHORTWAVE MOVING THROUGH THE UPPER GREAT LAKES EARLY THIS MORNING ALONG WITH ITS ASSOC SFC TROUGH IS HELPING TO FOCUS AN INTENSE LAKE ENHANCED SNOW BAND OVER SOUTH CENTRAL LAKE SUPERIOR AND THE ERN UPR MI SHORELINE IN THE PAST HR AS NOTED ON RADAR IMAGERY. A STRONG 140 KT UPR JET MAX DIVING DOWN THROUGH ALBERTA WILL HELP AMPLIFY MID-UPR LVL TROF OVER THE UPPER GREAT LAKES LATE TONIGHT AND FRIDAY AS WELL AS POSSIBLY BRING SOME ENHANCEMENT TO LES BANDS OVER LAKE SUPERIOR. ABUNDANT DRY AIR UPSTREAM OVER THE NRN PLAINS AS NOTED ON SATELLITE IMAGERY AND SFC OBS HAS THUS FAR INHIBITED ORGANIZATION OF LES BANDS OVER WRN LAKE SUPERIOR DESPITE ADVECTION OF -15C 850 TEMPS INTO AREA. && .DISCUSSION... MAIN CONCERN IS LES POTENTIAL AND ONGOING HEADLINES OVER WRN UPR MI INTO FRIDAY. CONCERN TODAY WILL BE ABUNDANT DRY AIR UPSTREAM...WHICH IS DEPICTED FAIRLY WELL BY GFS BUFR SNDGS...AND HOW MUCH THIS DRY AIR WILL NEGATIVELY AFFECT ORGANIZATION OF LES BANDS AND THUS POTENTIAL FOR HEAVY SNOW ACCUMULATION AT LEAST TODAY. ALL 00Z MODELS INCLUDING LOCAL MESOSCALE MODELS ARE LESS BULLISH ON LAKE EFFECT QPF THAN PREV RUNS AND AGAIN THIS IS LIKELY DUE TO DRIER AIR UPSTREAM OF THE LAKE AND LACK OF SYNOPTIC SCALE FORCING. EVEN THOUGH SNOW GROWTH REMAINS GENERALLY FAVORABLE WITH 25-30/1 SNOW WATER RATIOS EXPECTED...GENERALLY DECIDED TO TRIM BACK LES ACCUMS TO 2 TO LOCALLY 5 INCHES OVER WARNING AND ADVISORY AREAS OF NRN ONTONAGON...HOUGHTON AND KEWEENAW COUNTIES TODAY DUE TO IMPACTING DRY AIR. GUSTY WEST WINDS TO 30 MPH WILL LIKELY CAUSE CONSIDERABLE BLOWING SNOW AND REDUCED VSBYS IN ANY MODERATE LES BANDS THAT FORM OVER HEADLINE REGIONS. LOCATIONS NEAR LAKE SUPERIOR EAST OF MUNISING...FROM GRAND MARAIS TO TWO HEART MAY ALSO SEE A PERIOD OF BRIEF HEAVY SNOW EARLY THIS MORNING WITH BAND MOVING ACROSS ERN LAKE SUPERIOR ATTM. AS MENTIONED BEFORE PLENTY OF UNCERTAINTY EXISTS WITH EVOLUTION OF LES BANDS TODAY AND WHETHER ANY HEAVIER WILL MOVE INLAND OR OFFSHORE...SO NO HEADLINES WERE ISSUED FOR ERN COUNTIES AT THIS TIME. LARGE SCALE TROUGH WITH COLDEST AIR OF SEASON THUS FAR TO PUSH INTO THE AREA TONIGHT INTO FRIDAY. MODELS NOT DEPICTING MUCH IN THE WAY OF ANY SIGNIFICANT SHORTWAVES THAT WOULD AID IN ENHANCEMENT TO LES BANDS. HOWEVER...COMBINATION OF POSSIBLE WEAK ENHANCEMENT WITH ARRIVAL OF TROUGH...H85 TEMPS LOWERING TO AROUND -18C BY 12Z FRIDAY AND INCREASING LOW-LVL CONVERGENCE FROM NIGHTTIME LAND BREEZES...MAY BE JUST ENOUGH TO ORGANIZE FORMATION OF DOMINANT BAND OVER SRN LAKE SUPERIOR AS DEPICTED BY 00Z MODELS. INTERESTINGLY ENOUGH...MODEL AVG QPF NOT AS HEAVY AS PREV RUNS FOR TONIGHT INTO FRIDAY MORNING...AND THIS IS AGAIN LIKELY TO DUE TO AFFECTS OF VERY DRY AIR UPSTREAM. STILL WOULD EXPECT TOTAL SNOW ACCUMS TO EXCEED A FOOT AT FAVORED HIGHER TERRIAN LOCATIONS THROUGH ENTIRE EVENT. WRN INTERIOR LOCATIONS MAY DIP CLOSE TO ZERO TONIGHT WHILE HIGHS ON FRIDAY WILL STAY MAINLY IN THE LOWER TEENS. BY LATE FRIDAY...WEAKER TROUGH FCST TO SLIDE THROUGH THE AREA MAY VEER WINDS SLIGHTLY MORE NW LEADING TO INCREASED CHANCES OF DOMINANT LES BAND MOVING INTO FAR EASTERN SECTION OF CWA...MAINLY EAST OF MUNISING AND WELL NORTH OF NEWBERRY. SOME MODERATE TO POSSIBLE HEAVY SNOWFALL COULD WARRANT A HEADLINE AT SOME POINT FOR THESE COUNTIES. TROUGH AND COLDER AIR SFC-H85 SLOWLY HEAD INTO LOWER GREAT LAKES FRIDAY NIGHT INTO SATURDAY. WARM AIR ADVECTION STARTS UP BY SATURDAY LEADING TO A PUSH OF ISENTROPIC ASCENT 285-290K (750-650MB) ACROSS MUCH OF THE CWA...BUT LIMITED MOISTURE SHOULD KEEP CWA DRY. LES BANDS WILL PUSH OFFSHORE BY LATE FRI NIGHT INTO EARLY SATURDAY AS GUSTY SW WINDS LOWERS WIND CHILL VALUES IN THE MORNING DESPITE SFC TEMPS REBOUNDING INTO LOWER TO MIDDLE 20S SAT AFTERNOON. MODELS STILL IN AGREEMENT WITH SHORTWAVE AND PASSAGE OF FRONTAL BOUNDARY BRINGING ANOTHER CHC OF SNOW..POSSIBLY MIXED WITH RAIN EAST HALF ON MONDAY WITH SOME LINGERING LIGHT SNOW POSSIBLE MON NIGHT INTO TUE. && .AVIATION /FOR THE 06Z TAF ISSUANCE/... PASSAGE OF THE FIRST IN A SERIES OF LO PRES TROF WL BRING IFR CONDITIONS TO THE EXPOSED CMX LOCATION THAT WL EXPERIENCE MORE SGNFT LK MOISTENING DESTABILIZATION EARLY THIS MRNG. ALTHOUGH THERE MAY BE SOME -SHSN AT IWD AND SAW...ANY REDUCED CIG/VSBY WL BE MORE LIMITED WITH LESS LK MODIFICATION AND/OR DOWNSLOPE WIND COMPONENT. EXPECT A PERIOD OF IMPROVEMENT TOWARD SUNRISE AS A TRAILING SFC HI PRES RDG/AXIS OF DRIER AIR FOLLOWING THE TROF SHIFTS OVHD. BUT THE LULL WL BE ONLY TEMPORARY WITH A SECOND LO PRES TROF FOLLOWING THRU AT MID MRNG. THIS DEEPER TROF WL BE FOLLOWED BY STRONGER W WINDS THAT WL CAUSE GUSTS AS HI AS 30 KT OVER THE EXPOSED KEWEENAW/CMX. THE COMBINATION OF FALLING LK EFFECT SN AND BLSN WHIPPED UP BY THESE STRONG WINDS WL LIKELY LEAD TO LIFR CONDITIONS AT THAT SITE. THE DRY NATURE OF THE ARCTIC AIRMASSES WL LIMIT DETERIORATION AT IWD AND ESPECIALLY SAW...WHERE THE PREVAILING WLY WIND COMPONENT WL DOWNSLOPE/DRY AND RESULT IN PREDOMINANT VFR CONDITIONS. && .MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/... THE UPPER GREAT LAKES WILL REMAIN BETWEEN STRONG A LOW ACROSS HUDSON BAY...AND STRONG HIGH PRESSURE OVER W CANADA AND THE NORTHERN PLAINS THROUGH TONIGHT...WITH WESTERLY GALES TO 35KTS CONTINUING INTO THE EVENING HOURS. EXPECT THE HIGH TO SLIDE TO THE CENTRAL PLAINS OVERNIGHT...BEFORE SHIFTING TO THE OHIO VALLEY AND MID ATLANTIC THIS WEEKEND. THE RESULT WILL BE A RIDGE SLIDING OVER THE UPPER GREAT LAKES FRIDAY AND FRIDAY NIGHT...WEAKENING OVER THE WEEKEND. LOW PRESSURE ACROSS SOUTH CENTRAL CANADA SUNDAY MORNING SHOULD SLOWLY PUSH ACROSS LS AND MANITOBA MONDAY AFTERNOON THROUGH TUESDAY. OUT AHEAD OF THIS LOW...STRONG SW WINDS AND POSSIBLY GALES TO 35KTS WILL BE POSSIBLE SATURDAY. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... LAKE EFFECT SNOW WARNING UNTIL 7 PM EST FRIDAY FOR MIZ002-003. LAKE EFFECT SNOW ADVISORY UNTIL 7 PM EST FRIDAY FOR MIZ001-084. LAKE SUPERIOR... GALE WARNING UNTIL 1 AM EST FRIDAY FOR LSZ263>267. GALE WARNING UNTIL 7 PM EST /6 PM CST/ THIS EVENING FOR LSZ241>244. LAKE MICHIGAN... NONE. && $$ SYNOPSIS...VOSS DISCUSSION...VOSS AVIATION...KF MARINE...KF
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
545 AM EST THU DEC 8 2011 .SYNOPSIS... HIGH PRESSURE THURSDAY. COLD FRONT FRIDAY NIGHT. HIGH PRESSURE FOR THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... 600AM UPDATE... FORECAST REMAINS LARGELY ON TRACK. UPDATE INSERTED FOR CLOUD DECK CONTINUING TO LINGER IN THE NORTHERN MOUNTAINS EARLY THIS MORNING. PREVIOUS DISCUSSION... CLEARING ACROSS THE LOWLANDS HAS RESULTED IN STRONG RADIATIONAL COOLING. STILL EXPECTING TEMPS TO CRASH THROUGH EARLY MORNING HOURS. CLEARING HAS STALLED A BIT IN THE MOUNTAINS WHERE EKN AND BKW STILL REPORTING BKN CLOUD COVER. EXPECTING THESE SITES TO CLEAR OUT COMPLETELY BY 10Z. CURRENT IR SATELLITE IMAGERY SHOWS SHALLOW CLOUD DECK KNOCKING ON THE DOORSTEPS OF OUR SE OHIO COUNTIES. LATEST RUN OF THE RUC HAS THIS FEATURE DIAGNOSED WELL WITH COINCIDING 850MB MOISTURE MOVING ACROSS OUR NORTHERN TIER COUNTIES AND SLOSHING UP AGAINST THE HIGH TERRAIN OF THE NE MNT COUNTIES. RESULTANT RUC SOUNDINGS DISPLAYED IN BUFKIT TRYING TO DEVELOP LOW STRATUS AGAINST THE MOUNTAINS AROUND 12Z. NOT COMPLETELY SOLD ON THIS AS RUC 850MB MOISTURE SHOULD ERODE FURTHER DOWNSTREAM OF THE SOUTHERN GREAT LAKES. ALSO...WARMING TREND IN 850MB TEMPS SHOULD HELP TO DRY THE COLUMN FURTHER. ALL TOLD...WILL NOT INCLUDE STRATUS DEVELOPMENT IN THIS PACKAGE...BUT WILL CONTINUE TO MONITOR FORTHCOMING GUIDANCE AND TRENDS. A CHANGE OF PACE TODAY...RELATIVE TO THE LAST FEW DAYS. SUNNY SKIES WITH COLDER TEMPERATURES ARE EXPECTED AS CWA IS NOW UNDER THE CONTROL OF A SURFACE HIGH. && .SHORT TERM /FRIDAY THROUGH SUNDAY/... NEXT SYSTEM TO DEAL WITH WILL BE A MOISTURE STARVED COLD FRONT EXPECTED TO ENTER THE SOUTHEAST OHIO ZONES AFTER 18Z FRIDAY. SREF PROBABILITIES OF ACCUMULATING PRECIPITATION ARE ON THE LOW SIDE...BELOW 50 PERCENT...AND WILL HAVE A TOUGH TIME SATURATING ABOVE ABOUT 750MB. THAT BEING SAID...SNOW SHOWERS ARE POSSIBLE UPON PASSAGE...LIKELY NOT ACCUMULATING OR GIVING TRACE ACCUMULATIONS. OF MORE SIGNIFICANCE IS THE AIRMASS BEHIND THE COLD FRONT. 500MB HEIGHTS DROP IN THE POST FRONTAL TROUGH...AND 850MB TEMPERATURES ALSO DECREASE INTO THE MINUS TEENS COME SATURDAY. THERMAL TROUGH AT THIS LEVEL WILL PERSIST OVER THE NORTHEAST MOUNTAINS...AND WITH A CLEARING SKY...SATURDAY NIGHT TEMPERATURES LOOK VERY COLD. STRONG HIGH PRESSURE SETTLES IN OVER THE REMAINDER OF THE WEEKEND IN A LARGELY DRY PATTERN THROUGH EARLY NEXT WEEK. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... A BREAK FROM ANY RAIN OR SNOW WILL OCCUR DURING THE FIRST SEVERAL DAYS OF THIS PERIOD. A POCKET OF COLD AIR WILL BE IN PLACE THANKS TO SURFACE HIGH PRESSURE. AS THE SURFACE HIGH PRESSURE SLIDES NORTHEAST...POCKET OF COLDEST TEMPERATURES WILL ALSO FOLLOW. SUNDAY THROUGH TUESDAY WILL FEATURE MOSTLY SUNNY SKIES DURING THE DAY AND CLEAR AND COLD AT NIGHT. THE NEXT SYSTEM WILL APPROACH THE AREA DURING THE MID WEEK. WILL CONTINUE TO MONITOR THE SYSTEM AS IT DEVELOPS. GENERALLY FOLLOWED HPC GUIDANCE WITH ONLY A FEW MODIFICATION. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... MVFR CONDITIONS LINGERING IN CKB AND EKN FOR CIGS WITH RESIDUAL CLOUD DECK THAT IS RELUCTANT TO ERODE. CLEAR SKY OVER THE LOWLANDS RESULTING IN VFR...EXPECTING ALL SITES VFR AFTER 14Z. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z FRIDAY... FORECAST CONFIDENCE: HIGH. ALTERNATE SCENARIOS: CLOUD DECK OVER CKB AND EKN COULD BECOME MORE PERSISTENT...LASTING BEYOND 14Z. 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. UTC 1HRLY 11 12 13 14 15 16 17 18 19 20 21 22 EST 1HRLY 06 07 08 09 10 11 12 13 14 15 16 17 CRW CONSISTENCY H H H H H H H H H H H H HTS CONSISTENCY H H H H H H H H H H H H BKW CONSISTENCY H H H H H H H H H H H H EKN CONSISTENCY M M M M M M H H H H H H PKB CONSISTENCY H M M H H H H H H H H H CKB CONSISTENCY M M M M M M H H H H H H AFTER 12Z FRIDAY... NO WIDESPREAD IFR EXPECTED. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...26/TAX NEAR TERM...TAX SHORT TERM...26 LONG TERM...JB AVIATION...TAX
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1231 PM EST THU DEC 8 2011 UPDATED AVIATION DISCUSSION FOR 18Z TAFS .SYNOPSIS /ISSUED AT 545 AM/... WV IMAGERY AND RUC ANALYSIS INDICATED CYCLONIC MID/UPPER LEVEL FLOW AROUND A VORTEX OVER HUDSON BAY BRINGING NRN STREAM WNW FLOW FROM SRN CANADA INTO THE UPPER GREAT LAKES. A SHORTWAVE MOVING THROUGH THE UPPER GREAT LAKES EARLY THIS MORNING ALONG WITH ITS ASSOC SFC TROUGH IS HELPING TO FOCUS AN INTENSE LAKE ENHANCED SNOW BAND OVER SOUTH CENTRAL LAKE SUPERIOR AND THE ERN UPR MI SHORELINE IN THE PAST HR AS NOTED ON RADAR IMAGERY. A STRONG 140 KT UPR JET MAX DIVING DOWN THROUGH ALBERTA WILL HELP AMPLIFY MID-UPR LVL TROF OVER THE UPPER GREAT LAKES LATE TONIGHT AND FRIDAY AS WELL AS POSSIBLY BRING SOME ENHANCEMENT TO LES BANDS OVER LAKE SUPERIOR. ABUNDANT DRY AIR UPSTREAM OVER THE NRN PLAINS AS NOTED ON SATELLITE IMAGERY AND SFC OBS HAS THUS FAR INHIBITED ORGANIZATION OF LES BANDS OVER WRN LAKE SUPERIOR DESPITE ADVECTION OF -15C 850 TEMPS INTO AREA. && .DISCUSSION... MAIN CONCERN IS LES POTENTIAL AND ONGOING HEADLINES OVER WRN UPR MI INTO FRIDAY. CONCERN TODAY WILL BE ABUNDANT DRY AIR UPSTREAM...WHICH IS DEPICTED FAIRLY WELL BY GFS BUFR SNDGS...AND HOW MUCH THIS DRY AIR WILL NEGATIVELY AFFECT ORGANIZATION OF LES BANDS AND THUS POTENTIAL FOR HEAVY SNOW ACCUMULATION AT LEAST TODAY. ALL 00Z MODELS INCLUDING LOCAL MESOSCALE MODELS ARE LESS BULLISH ON LAKE EFFECT QPF THAN PREV RUNS AND AGAIN THIS IS LIKELY DUE TO DRIER AIR UPSTREAM OF THE LAKE AND LACK OF SYNOPTIC SCALE FORCING. EVEN THOUGH SNOW GROWTH REMAINS GENERALLY FAVORABLE WITH 25-30/1 SNOW WATER RATIOS EXPECTED...GENERALLY DECIDED TO TRIM BACK LES ACCUMS TO 2 TO LOCALLY 5 INCHES OVER WARNING AND ADVISORY AREAS OF NRN ONTONAGON...HOUGHTON AND KEWEENAW COUNTIES TODAY DUE TO IMPACTING DRY AIR. GUSTY WEST WINDS TO 30 MPH WILL LIKELY CAUSE CONSIDERABLE BLOWING SNOW AND REDUCED VSBYS IN ANY MODERATE LES BANDS THAT FORM OVER HEADLINE REGIONS. LOCATIONS NEAR LAKE SUPERIOR EAST OF MUNISING...FROM GRAND MARAIS TO TWO HEART MAY ALSO SEE A PERIOD OF BRIEF HEAVY SNOW EARLY THIS MORNING WITH BAND MOVING ACROSS ERN LAKE SUPERIOR ATTM. AS MENTIONED BEFORE PLENTY OF UNCERTAINTY EXISTS WITH EVOLUTION OF LES BANDS TODAY AND WHETHER ANY HEAVIER WILL MOVE INLAND OR OFFSHORE...SO NO HEADLINES WERE ISSUED FOR ERN COUNTIES AT THIS TIME. LARGE SCALE TROUGH WITH COLDEST AIR OF SEASON THUS FAR TO PUSH INTO THE AREA TONIGHT INTO FRIDAY. MODELS NOT DEPICTING MUCH IN THE WAY OF ANY SIGNIFICANT SHORTWAVES THAT WOULD AID IN ENHANCEMENT TO LES BANDS. HOWEVER...COMBINATION OF POSSIBLE WEAK ENHANCEMENT WITH ARRIVAL OF TROUGH...H85 TEMPS LOWERING TO AROUND -18C BY 12Z FRIDAY AND INCREASING LOW-LVL CONVERGENCE FROM NIGHTTIME LAND BREEZES...MAY BE JUST ENOUGH TO ORGANIZE FORMATION OF DOMINANT BAND OVER SRN LAKE SUPERIOR AS DEPICTED BY 00Z MODELS. INTERESTINGLY ENOUGH...MODEL AVG QPF NOT AS HEAVY AS PREV RUNS FOR TONIGHT INTO FRIDAY MORNING...AND THIS IS AGAIN LIKELY TO DUE TO AFFECTS OF VERY DRY AIR UPSTREAM. STILL WOULD EXPECT TOTAL SNOW ACCUMS TO EXCEED A FOOT AT FAVORED HIGHER TERRIAN LOCATIONS THROUGH ENTIRE EVENT. WRN INTERIOR LOCATIONS MAY DIP CLOSE TO ZERO TONIGHT WHILE HIGHS ON FRIDAY WILL STAY MAINLY IN THE LOWER TEENS. BY LATE FRIDAY...WEAKER TROUGH FCST TO SLIDE THROUGH THE AREA MAY VEER WINDS SLIGHTLY MORE NW LEADING TO INCREASED CHANCES OF DOMINANT LES BAND MOVING INTO FAR EASTERN SECTION OF CWA...MAINLY EAST OF MUNISING AND WELL NORTH OF NEWBERRY. SOME MODERATE TO POSSIBLE HEAVY SNOWFALL COULD WARRANT A HEADLINE AT SOME POINT FOR THESE COUNTIES. TROUGH AND COLDER AIR SFC-H85 SLOWLY HEAD INTO LOWER GREAT LAKES FRIDAY NIGHT INTO SATURDAY. WARM AIR ADVECTION STARTS UP BY SATURDAY LEADING TO A PUSH OF ISENTROPIC ASCENT 285-290K (750-650MB) ACROSS MUCH OF THE CWA...BUT LIMITED MOISTURE SHOULD KEEP CWA DRY. LES BANDS WILL PUSH OFFSHORE BY LATE FRI NIGHT INTO EARLY SATURDAY AS GUSTY SW WINDS LOWERS WIND CHILL VALUES IN THE MORNING DESPITE SFC TEMPS REBOUNDING INTO LOWER TO MIDDLE 20S SAT AFTERNOON. MODELS STILL IN AGREEMENT WITH SHORTWAVE AND PASSAGE OF FRONTAL BOUNDARY BRINGING ANOTHER CHC OF SNOW..POSSIBLY MIXED WITH RAIN EAST HALF ON MONDAY WITH SOME LINGERING LIGHT SNOW POSSIBLE MON NIGHT INTO TUE. && .AVIATION /FOR THE 18Z TAF ISSUANCE/... A CONTINUED WESTERLY FLOW OF COLD AIR ACROSS THE WARM WATERS OF LAKE SUPERIOR...AND INCREASED LIFT FROM THE TERRAIN ENHANCEMENT OF THE KEWEENAW PENINSULA WILL AID IN KEEPING LAKE EFFECT SNOW SHOWERS IN PLACE AT CMX. LIFR TO VLIFR VIS WILL REMAIN POSSIBLE...PARTICULARLY WITH BLSN THANKS TO GUSTY WINDS OVER 30KTS. FARTHER TO THE SOUTH...A LESS FAVORABLE WIND DIRECTION AT IWD WILL MAINLY RESULT IN A FEW FLAKES OF SNOW...AND HIGH END MVFR CEILINGS AND VIS. SOME SNOW SHOWERS MAY BE ABLE TO SLIDE TO SAW LATER TODAY AND TONIGHT...BUT WILL REMAIN LIGHT...WITH HIGH END MVFR POSSIBLE IN THE HEAVIER BANDS THERE. KEPT ANY SNOW OUT OF THE TAF AT SAW AS MUCH OF THE SNOW WILL REMAIN OFFSHORE. && .MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/... THE UPPER GREAT LAKES WILL REMAIN BETWEEN STRONG A LOW ACROSS HUDSON BAY...AND STRONG HIGH PRESSURE OVER W CANADA AND THE NORTHERN PLAINS THROUGH TONIGHT...WITH WESTERLY GALES TO 35KTS CONTINUING INTO THE EVENING HOURS. EXPECT THE HIGH TO SLIDE TO THE CENTRAL PLAINS OVERNIGHT...BEFORE SHIFTING TO THE OHIO VALLEY AND MID ATLANTIC THIS WEEKEND. THE RESULT WILL BE A RIDGE SLIDING OVER THE UPPER GREAT LAKES FRIDAY AND FRIDAY NIGHT...WEAKENING OVER THE WEEKEND. LOW PRESSURE ACROSS SOUTH CENTRAL CANADA SUNDAY MORNING SHOULD SLOWLY PUSH ACROSS LS AND MANITOBA MONDAY AFTERNOON THROUGH TUESDAY. OUT AHEAD OF THIS LOW...STRONG SW WINDS AND POSSIBLY GALES TO 35KTS WILL BE POSSIBLE SATURDAY. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... LAKE EFFECT SNOW WARNING UNTIL 7 PM EST FRIDAY FOR MIZ002-003. LAKE EFFECT SNOW ADVISORY UNTIL 7 PM EST FRIDAY FOR MIZ001-084. LAKE SUPERIOR... GALE WARNING UNTIL 1 AM EST FRIDAY FOR LSZ263>267. GALE WARNING UNTIL 7 PM EST /6 PM CST/ THIS EVENING FOR LSZ241>244. LAKE MICHIGAN... NONE. && $$ SYNOPSIS...VOSS DISCUSSION...VOSS AVIATION...TITUS MARINE...KF
AREA FORECAST DISCUSSION
NWS GLASGOW MT
249 PM MST THU DEC 8 2011 .SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SATURDAY... WATER VAPOR IMAGERY AND 500 MB HEIGHT FIELD SHOWING THE VERY STRONG AND CLOSED UPPER LOW CENTER OVER HUDSON BAY AND ITS ASSOCIATED LARGE SCALE UPPER TROUGH SPREADING OVER A LARGE PORTION OF THE NORTH AMERICAN CONTINENT. JUST RECENTLY THIS AFTERNOON THE BASE OF THE STRONGER PORTION OF THE LARGE TROUGH HAS TAKEN ON A STRANGE SQUARISH SHAPE. VERY SLIGHT LARGE SCALE TROUGHING IS ALSO PRESENT IN THE SOUTHERN STREAM ACROSS THE SOUTHERN U.S. STATES. AN UPPER LEVEL RIDGE AND ITS ASSOCIATED AREA OF HIGH PRESSURE IS GAINING STRENGTH JUST OF THE PACIFIC NORTHWEST COAST. LOCALLY...CLOUDS QUICKLY FORMED OVER THE CWA TODAY RIGHT ALONG THE SURFACE RIDGE AXIS WITH CLEARER SKIES OFF TO THE NORTHEAST AND CLOUDY SKIES CENTRAL AND SOUTHWEST. ENOUGH ASCENT IS PRESENT TO SET OFF SOME VERY LIGHT VIRGA AND MAYBE SOME FLURRIES AS IS EVIDENCED BY THE LIGHT RADAR REFLECTIVITIES TODAY. THE HRRR MODEL HAS BEEN VERY ACCURATE IN DEPICTING THIS ACTIVITY WHEREAS THE OTHER OPERATIONAL MODEL SOLUTIONS DID NOT BOTHER MUCH WITH IT. TRIED TO FOLLOW THE TREND OF THIS HRRR MODEL FOR THE VERY NEAR SHORT TERM THROUGH TONIGHT AS FLURRIES SHIFT SOUTHWEST AND DIMINISH SOUTHWARD. ALSO...TONIGHT...WIND CHILL VALUES WILL APPROACH 20 BELOW ZERO AGAIN ESPECIALLY OVER OUR FAR NORTHEAST ZONES. BUT WITH WINDS FORECASTED BELOW 10 MPH...FELT IT WAS SUFFICIENT TO ONLY MENTION IT IN THE HWO. BEGINNING FRIDAY...THE ARCTIC AIR MASS AND HUDSON BAY LOW QUICKLY GIVE WAY TO THE APPROACHING HIGH PRESSURE AND WARMER TEMPERATURES FROM THE WEST. HIGHS SHOULD REBOUND EASILY INTO THE MID 20S CENTRAL AND WELL ABOVE FREEZING OVER OUR SOUTHWESTERN ZONES. ANOTHER PERIOD OF CLOUDINESS WILL SWEEP OVER NORTHEAST MONTANA ON FRIDAY BUT I EXPECT ANY PRECIPITATION TO REMAIN WELL NORTH OF THE INTERNATIONAL BOARDER. TRIED TO SHOW THE TREND WITH SOME SILENT POPS AND SKY COVER. SATURDAY...THE UPPER RIDGE FLATTENS SOMEWHAT BUT STILL MANAGES TO MAKE SIGNIFICANT INROADS INTO OUR AREA...BRINGING TEMPERATURES ABOVE FREEZING TO ALL OF NORTHEAST MONTANA EXCEPT THE FAR NORTHEAST LITTLE CORNER. MOSTLY CLEAR SKIES AND NO PRECIPITATION TO START THE WEEKEND. BMICKELSON .LONG TERM...SATURDAY NIGHT THROUGH THURSDAY... MADE SOME INCREASES WITH POPS FOR SUNDAY NIGHT AND ESPECIALLY MONDAY. A SYSTEM LOOKS STRONGER WITH SOME OF THE MODELS AND CONSISTENT ON THE ECMWF. ALSO RAISED POPS SLIGHTLY NEAR THE END OF THE PERIOD CLOSER TO CLIMATOLOGY WITH AN UPPER TROUGH IN THE WESTERN STATES. REST OF FORECAST LOOKED GOOD. JAMBA PREVIOUS DISCUSSION... THE EXTENDED PERIOD FEATURES A SERIES OF SHORTWAVE TROUGHS AND RIDGES IN A PROGRESSIVE PATTERN. LIMITED MOISTURE WITH EACH OF THE WEATHER SYSTEMS WILL LIMIT PRECIP CHANCES. TEMPERATURES WILL BE WITHIN 10 DEGREES OF NORMAL DURING THE WHOLE PERIOD. AN UPPER RIDGE MOVES TO THE EAST SATURDAY NIGHT AND SUNDAY WITH AN UPPER TROUGH MOVING THROUGH EASTERN MONTANA ON MONDAY. THIS WILL BRING A DRY COLD FRONT ACROSS THE AREA ON SUNDAY. LOOK FOR SOMEWHAT COLDER AIR SUNDAY NIGHT AND MONDAY. SHORTWAVE RIDGE FOLLOWS ON TUESDAY. ECMWF CURRENTLY WARMER THAN THE GFS WITH THE TEMPERATURES. WILL FORECAST ON THE COLDER SIDE OF THE POSSIBILITIES FOR NOW GIVEN THAT LIGHT WINDS SHOULD LEAD TO POOR MIXING WITH LOW LEVEL INVERSIONS TRAPPING COLD AIR AT THE SURFACE. ANOTHER SHORTWAVE TROUGH MOVES THROUGH THE AREA WEDNESDAY AND THURSDAY WITH ANOTHER DRY COLD FRONT AND SOMEWHAT COLDER AIR. FORRESTER && .AVIATION... CLOUDS AND ANY FLURRIES WILL EXIT TO THE SOUTHEAST THIS EVENING. A WARM FRONT THEN MOVES EAST ACROSS THE AREA FRIDAY BUT LITTLE OR NO FLURRIES ARE EXPECTED. WINDS ARE TO REMAIN LIGHT THROUGH THE PERIOD. MVFR CONDITIONS ARE POSSIBLE WITH THE FLURRIES...BUT VFR IS GENERALLY EXPECTED. JAMBA && .GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ WEATHER.GOV/GLASGOW
AREA FORECAST DISCUSSION...UPDATED
NWS GLASGOW MT
940 AM MST THU DEC 8 2011 .SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH SATURDAY... UPDATED THE FORECAST TODAY TO TRY TO GET AHEAD OF SOME POSSIBLE FLURRIES INDICATED BY THE HRRR MODEL FOR THIS AFTERNOON AND EVENING. SINCE THAT MODEL WAS THE ONLY CORRECT MODEL FOR YESTERDAYS SNOWFALL...TRYING TO LEAN A LITTLE MORE IN THAT DIRECTION. OTHER MODELS INDICATING AN INCREASE IN CLOUDINESS AS WELL...SO I BUMPED UP POPS A BIT AND PUT IN SOME FLURRIES FOR THE IMMEDIATE SHORT TERM. BMICKELSON PREVIOUS SHORT TERM DISCUSSION...MASSIVE HUDSON BAY LOW PRESSURE SYSTEM RESULTING IN A STRONG NW FLOW ALOFT WITH STEADY COLD ADVECTION FOR NE MT. THIS MORNINGS LOWS RUNNING 20F COLDER THAN YESTERDAY...AND HIGHS WILL BE AROUND 15F COLDER THAN YESTERDAY...AS THE COLD AIR ADVECTION ENDS THIS AFTERNOON. THIS ASSOCIATED WITH A POLAR SURFACE HIGH FROM NW CANADA THAT CALVED OFF MOVING SE ACROSS THE ROCKIES YESTERDAY...ONE CENTER NOW OVER SE AB/NC MT. THIS CENTER WILL BE OVER E MT THIS AFTERNOON AND EVENING. SATELLITE PICTURES SHOW A BAND OF MID-LEVEL OVERCAST ALIGNED ALONG THE STRONG NW JET IN A SLIGHTLY CYCLONIC FLOW. THIS COVERS ROUGHLY SW THIRD OF OUR CWA...NOT MOVING MUCH...BUT IT IS SHALLOW AND SHOULD GRADUALLY BREAK UP AS THE DAY GOES ON. REST OF FORECAST AREA IS CLEAR. CLOSED UPPER HIGH ALONG PACIFIC COAST MOVES ACROSS THE INLAND WEST AND WEAKENS FRI/SAT. THIS BRINGS MUCH WARMER AIR ALOFT TO OUR AREA FRIDAY. SURFACE PRESSURE GRADIENTS ARE WEAK AND FORECAST SOUNDINGS SHOW SURFACE-BASED INVERSION REMAINING ALL DAY. ALTHOUGH NOT GREAT...THERE WILL ALSO BE A SIGNIFICANT SNOW COVER EFFECT AND MOST OF THE CWA HAS AN INCH OR TWO ON GROUND. THE OTHER NEGATIVE FOR FRIDAY IS THERE WILL BE MOSTLY CLOUDY SKIES HOLDING THE COLDER AIR IN MORE. THIS IS WARM ADVECTION MID/HIGH CLOUDS...AND WE WILL BE ON THE COLD SIDE OF THE RIDGE TOO. MOS LOOKS REASONABLE...BUT WILL GO ON THE COLD SIDE FOR THE LOWER MILK/LOWER MISSOURI RIVER VALLEYS. FURTHER WARMING ALOFT FOR SAT...THICKNESSES WELL INTO THE 540S DM. 850 MB TEMPS CLIMB TO AS HIGH AS 7C. WEAK PRESSURE PATTERN SIMILAR TO FRI THOUGH. HOWEVER SAT SHOULD HAVE FULL SUNSHINE EFFECT AND THE RIDGE WILL WEAKEN TO A MODERATE WESTERLY FLOW FAVORING SIGNIFICANT SHALLOWING OUT AND MODIFICATION OF THE COLDER AIR. STILL THE LOWER MILK/LOWER MISSOURI RIVER VALLEYS WILL LAG BEHIND IN THE WARMER TEMPS. SIMONSEN .LONG TERM...SATURDAY NIGHT THROUGH THURSDAY... THE EXTENDED PERIOD FEATURES A SERIES OF SHORTWAVE TROUGHS AND RIDGES IN A PROGRESSIVE PATTERN. LIMITED MOISTURE WITH EACH OF THE WEATHER SYSTEMS WILL LIMIT PRECIP CHANCES. TEMPERATURES WILL BE WITHIN 10 DEGREES OF NORMAL DURING THE WHOLE PERIOD. AN UPPER RIDGE MOVES TO THE EAST SATURDAY NIGHT AND SUNDAY WITH AN UPPER TROUGH MOVING THROUGH EASTERN MONTANA ON MONDAY. THIS WILL BRING A DRY COLD FRONT ACROSS THE AREA ON SUNDAY. LOOK FOR SOMEWHAT COLDER AIR SUNDAY NIGHT AND MONDAY. SHORTWAVE RIDGE FOLLOWS ON TUESDAY. ECMWF CURRENTLY WARMER THAN THE GFS WITH THE TEMPERATURES. WILL FORECAST ON THE COLDER SIDE OF THE POSSIBILITIES FOR NOW GIVEN THAT LIGHT WINDS SHOULD LEAD TO POOR MIXING WITH LOW LEVEL INVERSIONS TRAPPING COLD AIR AT THE SURFACE. ANOTHER SHORTWAVE TROUGH MOVES THROUGH THE AREA WEDNESDAY AND THURSDAY WITH ANOTHER DRY COLD FRONT AND SOMEWHAT COLDER AIR. FORRESTER && .AVIATION... CLOUDS ARE EXPECTED TO INCREASE OVER THE TAF SITES TODAY. FLURRIES CAN BE EXPECTED IN THE AREA THIS AFTERNOON IF NOT LOW VFR CLOUDINESS. VISIBILITIES COULD BRIEFLY DROP INTO MVFR CATEGORY. ANOTHER BAND OF CLOUDINESS WILL MOVE ACROSS THE AREA FRIDAY...AND BRIEF FLURRIES ARE AGAIN POSSIBLE. JAMBA && .GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ WEATHER.GOV/GLASGOW
AREA FORECAST DISCUSSION...CORRECTED HYDROLOGY
NWS NORTH PLATTE NE
348 PM CST THU DEC 8 2011 .DISCUSSION... BANDED FOLDS OF THETA E AND EPV CONTINUE TO PRODUCE LIGHT TO MODERATE SNOW. THE RUC SUGGESTS THIS SNOW SHOULD MOVE OUT OF THE FCST AREA BY 02-03 UTC THIS EVENING. ANOTHER WEAK WAVE ACROSS ERN MT THIS AFTN SHOULD SLICE THROUGH NCNTL NEB MAINLY AFTER 06Z TONIGHT THROUGH 15Z FRIDAY. THE NAM...GFS AND GEM SUPPORT THIS SOLN. WE CONTINUE THE PATCHY FREEZING DRIZZLE ACROSS PARTS OF SCNTL AND SWRN NEB THIS EVENING. AN ARCTIC FRONT CURRENTLY NEAR KTIF WILL MOVE SOUTH AND WASHOUT PERHAPS DRYING THE MIDLEVEL ALLOWING FOR LOW LEVEL SATURATION AND FREEZING DRIZZLE. BEHIND THE SECOND DISTURBANCE TONIGHT ANOTHER ARCTIC HIGH WILL BUILD INTO THE UPPER MISSOURI BASIN AND BE CENTERED OVER WRN SD/ND FRIDAY MORNING. THIS IS A BIG BREAK FOR THE FCST AREA AS LOWS OF -20F OCCURRED BENEATH ACROSS WRN CANADA THURSDAY MORNING. THIS HIGH IS FCST TO DRIFT THROUGH THE FCST AREA FRIDAY PRODUCING CLEAR SKIES AND COLD WEATHER WITH HIGHS ONLY IN THE 20S. BY FRIDAY EVENING...LOW PRESSURE WILL BE TRACKING CNTL CANADA PRODUCING AS WARM WESTERLY H850MB FLOW WITH H850 TEMPS RISING TO NEAR 0C BY SATURDAY MORNING. THUS LOWS SHOULD OCCUR AT OR BEFORE MIDNIGHT MOST AREAS AND THEN WARM. FOR SATURDAY...WEST AND SOUTHWEST WINDS CONTINUE WITH HIGHS IN THE 40S. WINDS TAKE A MORE SOUTHERLY TACK SUNDAY AHEAD OF A COLD FRONT PROGGED TO MOVE THROUGH SUNDAY NIGHT AND MONDAY. STILL HIGHS SUNDAY SHOULD RISE INTO THE 40S. A COLD FRONT MOVING THROUGH MONDAY IS EXPECTED TO TAKE THE EDGE OFF HIGHS. 30S APPEAR TO BE THE OPERATIVE MODE. THE GEM...GFS AND ECM ARE IN GOOD AGREEMENT ON A SIGNIFICANT SHORT WAVE TRACKING THROUGH THE CNTL PLAINS WEDNESDAY. TEMPS MIGHT BE WARM ENOUGH FOR RAIN AS H10-5 THICKNESSES HOVER NEAR 546DAM AND H850MB TEMPS -3 TO 0C. A CHANCE OF RAIN AND SNOW IS SHOWN EAST WITH SLIGHT CHANCE OF SNOW WEST. THE GFS AND GEM SHOW EVAPORATIVE COOLING WHILE THE ECM DOES NOT. THIS SYSTEM SHOULD EXIT WEDNESDAY NIGHT WITH ANOTHER STRONG COLD FRONT DROPPING TOWARD THE FCST AREA. && .AVIATION... OR 18Z TAFS...SMALLER SCALE FRONTOGENETIC BAND SLIDING ACROSS THE SANDHILLS INTO LATE AFTERNOON LOWERING CREATING VSBYS TO 3/4 TO 1/2SM AT TIMES THOUGH LATE AFTERNOON. THIS AREA OF HEAVIER SNOWFALL LIES BETWEEN THE KLBF AND KVTN TAF SITES...BUT MAY APPROACH THE KLBF TAF SITE BY 22Z. LATEST NAM AND HRRR SUGGEST THIS WILL SLIDE NORTH AND EAST OF KLBF HOWEVER AND AS SUCH HAVE NOT LOWERED VSBY AT KLBF DUE TO THIS FEATURE. THIS TIGHTER...SMALLER SCALE BAND LIKELY A RESULT OF LINGERING BUT WEAK FRONTOGENESIS IN A REGION OF NEGATIVE EPV IN THE 700-600MB LAYER. WOULD EXPECT THIS BAND TO DISSIPATE IN THE NEXT 2 TO 3 HRS AS WEAK INSTABILITY STABILIZES BUT WILL MONITOR. LARGER SCALE DRIER AIR IS WORKING IN ACROSS THE WESTERN PORTION OF THE STATE AND RADAR ECHOES ARE DECREASING SOME FROM WEST TO EAST AND WILL EXPECT THAT TREND TO CONTINUE THROUGH EVENING. FOR TONIGHT...SECONDARY SHORT WAVE SHOULD BE ENOUGH TO GENERATE FLURRIES TO -SN ACROSS THE NORTHERN PORTION OF THE STATE...THOUGH A MORE SHALLOW AREA OF LIFT CLOSER TO THE SURFACE AND FAVORABLE CROSS-OVER TEMPS SHOULD LEAD TO AT LEAST BR BUT POSSIBLY FZFG OVERNIGHT FURTHER SOUTH AND NEAR THE KLBF SITE. WILL BE REFINING THIS PORTION OF THE FORECAST IN THE NEXT FEW HOURS SINCE CONFIDENCE IN THIS SCENARIO IS LOW AT THE MOMENT. A GENERAL CLEARING TREND IS EXPECTED BY LATE MORNING FRIDAY. && .HYDROLOGY... A FLOOD WARNING FOR ICE JAMMING HAS BEEN ISSUED ON THE NORTH PLATTE RIVER AT LEWELLEN. THE FLOOD WARNING WILL CONTINUE UNTIL FURTHER NOTICE. WEATHER CONDITIONS FEATURING WARM TEMPS DURING THE DAYTIME AND SINGLE DIGITS AT NIGHT THIS WEEKEND COULD CAUSE THE JAMMING TO PERSIST. && $$ SHORT TERM/LONG TERM...CDC AVIATION...JWS
AREA FORECAST DISCUSSION...UPDATED
NWS NORTH PLATTE NE
312 PM CST THU DEC 8 2011 .DISCUSSION... BANDED FOLDS OF THETA E AND EPV CONTINUE TO PRODUCE LIGHT TO MODERATE SNOW. THE RUC SUGGESTS THIS SNOW SHOULD MOVE OUT OF THE FCST AREA BY 02-03 UTC THIS EVENING. ANOTHER WEAK WAVE ACROSS ERN MT THIS AFTN SHOULD SLICE THROUGH NCNTL NEB MAINLY AFTER 06Z TONIGHT THROUGH 15Z FRIDAY. THE NAM...GFS AND GEM SUPPORT THIS SOLN. WE CONTINUE THE PATCHY FREEZING DRIZZLE ACROSS PARTS OF SCNTL AND SWRN NEB THIS EVENING. AN ARCTIC FRONT CURRENTLY NEAR KTIF WILL MOVE SOUTH AND WASHOUT PERHAPS DRYING THE MIDLEVEL ALLOWING FOR LOW LEVEL SATURATION AND FREEZING DRIZZLE. BEHIND THE SECOND DISTURBANCE TONIGHT ANOTHER ARCTIC HIGH WILL BUILD INTO THE UPPER MISSOURI BASIN AND BE CENTERED OVER WRN SD/ND FRIDAY MORNING. THIS IS A BIG BREAK FOR THE FCST AREA AS LOWS OF -20F OCCURRED BENEATH ACROSS WRN CANADA THURSDAY MORNING. THIS HIGH IS FCST TO DRIFT THROUGH THE FCST AREA FRIDAY PRODUCING CLEAR SKIES AND COLD WEATHER WITH HIGHS ONLY IN THE 20S. BY FRIDAY EVENING...LOW PRESSURE WILL BE TRACKING CNTL CANADA PRODUCING AS WARM WESTERLY H850MB FLOW WITH H850 TEMPS RISING TO NEAR 0C BY SATURDAY MORNING. THUS LOWS SHOULD OCCUR AT OR BEFORE MIDNIGHT MOST AREAS AND THEN WARM. FOR SATURDAY...WEST AND SOUTHWEST WINDS CONTINUE WITH HIGHS IN THE 40S. WINDS TAKE A MORE SOUTHERLY TACK SUNDAY AHEAD OF A COLD FRONT PROGGED TO MOVE THROUGH SUNDAY NIGHT AND MONDAY. STILL HIGHS SUNDAY SHOULD RISE INTO THE 40S. A COLD FRONT MOVING THROUGH MONDAY IS EXPECTED TO TAKE THE EDGE OFF HIGHS. 30S APPEAR TO BE THE OPERATIVE MODE. THE GEM...GFS AND ECM ARE IN GOOD AGREEMENT ON A SIGNIFICANT SHORT WAVE TRACKING THROUGH THE CNTL PLAINS WEDNESDAY. TEMPS MIGHT BE WARM ENOUGH FOR RAIN AS H10-5 THICKNESSES HOVER NEAR 546DAM AND H850MB TEMPS -3 TO 0C. A CHANCE OF RAIN AND SNOW IS SHOWN EAST WITH SLIGHT CHANCE OF SNOW WEST. THE GFS AND GEM SHOW EVAPORATIVE COOLING WHILE THE ECM DOES NOT. THIS SYSTEM SHOULD EXIT WEDNESDAY NIGHT WITH ANOTHER STRONG COLD FRONT DROPPING TOWARD THE FCST AREA. && .AVIATION... OR 18Z TAFS...SMALLER SCALE FRONTOGENETIC BAND SLIDING ACROSS THE SANDHILLS INTO LATE AFTERNOON LOWERING CREATING VSBYS TO 3/4 TO 1/2SM AT TIMES THOUGH LATE AFTERNOON. THIS AREA OF HEAVIER SNOWFALL LIES BETWEEN THE KLBF AND KVTN TAF SITES...BUT MAY APPROACH THE KLBF TAF SITE BY 22Z. LATEST NAM AND HRRR SUGGEST THIS WILL SLIDE NORTH AND EAST OF KLBF HOWEVER AND AS SUCH HAVE NOT LOWERED VSBY AT KLBF DUE TO THIS FEATURE. THIS TIGHTER...SMALLER SCALE BAND LIKELY A RESULT OF LINGERING BUT WEAK FRONTOGENESIS IN A REGION OF NEGATIVE EPV IN THE 700-600MB LAYER. WOULD EXPECT THIS BAND TO DISSIPATE IN THE NEXT 2 TO 3 HRS AS WEAK INSTABILITY STABILIZES BUT WILL MONITOR. LARGER SCALE DRIER AIR IS WORKING IN ACROSS THE WESTERN PORTION OF THE STATE AND RADAR ECHOES ARE DECREASING SOME FROM WEST TO EAST AND WILL EXPECT THAT TREND TO CONTINUE THROUGH EVENING. FOR TONIGHT...SECONDARY SHORT WAVE SHOULD BE ENOUGH TO GENERATE FLURRIES TO -SN ACROSS THE NORTHERN PORTION OF THE STATE...THOUGH A MORE SHALLOW AREA OF LIFT CLOSER TO THE SURFACE AND FAVORABLE CROSS-OVER TEMPS SHOULD LEAD TO AT LEAST BR BUT POSSIBLY FZFG OVERNIGHT FURTHER SOUTH AND NEAR THE KLBF SITE. WILL BE REFINING THIS PORTION OF THE FORECAST IN THE NEXT FEW HOURS SINCE CONFIDENCE IN THIS SCENARIO IS LOW AT THE MOMENT. A GENERAL CLEARING TREND IS EXPECTED BY LATE MORNING FRIDAY. && .HYDROLOGY... ICE JAMMING HAS DEVELOPED ON THE NORTH PLATTE RIVER BETWEEN LEWELLEN AND NORTH PLATTE. A FLOOD ADVISORY WILL CONTINUE UNTIL FURTHER NOTICE. WEATHER CONDITIONS FEATURING WARM TEMPS DURING THE DAYTIME AND SINGLE DIGITS AT NIGHT THIS WEEKEND COULD CAUSE THE JAMMING TO PERSIST. && $$ SHORT TERM/LONG TERM...CDC AVIATION...JWS
AREA FORECAST DISCUSSION
NWS NORTH PLATTE NE
244 PM CST THU DEC 8 2011 .DISCUSSION... BANDED FOLDS OF THETA E AND EPV CONTINUE TO PRODUCE LIGHT TO MODERATE SNOW. THE RUC SUGGESTS THIS SNOW SHOULD MOVE OUT OF THE FCST AREA BY 02-03 UTC THIS EVENING. ANOTHER WEAK WAVE ACROSS ERN MT THIS AFTN SHOULD SLICE THROUGH NCNTL NEB MAINLY AFTER 06Z TONIGHT THROUGH 15Z FRIDAY. THE NAM...GFS AND GEM SUPPORT THIS SOLN. WE CONTINUE THE PATCHY FREEZING DRIZZLE ACROSS PARTS OF SCNTL AND SWRN NEB THIS EVENING. AN ARCTIC FRONT CURRENTLY NEAR KTIF WILL MOVE SOUTH AND WASHOUT PERHAPS DRYING THE MIDLEVEL ALLOWING FOR LOW LEVEL SATURATION AND FREEZING DRIZZLE. BEHIND THE SECOND DISTURBANCE TONIGHT ANOTHER ARCTIC HIGH WILL BUILD INTO THE UPPER MISSOURI BASIN AND BE CENTERED OVER WRN SD/ND FRIDAY MORNING. THIS IS A BIG BREAK FOR THE FCST AREA AS LOWS OF -20F OCCURRED BENEATH ACROSS WRN CANADA THURSDAY MORNING. THIS HIGH IS FCST TO DRIFT THROUGH THE FCST AREA FRIDAY PRODUCING CLEAR SKIES AND COLD WEATHER WITH HIGHS ONLY IN THE 20S. BY FRIDAY EVENING...LOW PRESSURE WILL BE TRACKING CNTL CANADA PRODUCING AS WARM WESTERLY H850MB FLOW WITH H850 TEMPS RISING TO NEAR 0C BY SATURDAY MORNING. THUS LOWS SHOULD OCCUR AT OR BEFORE MIDNIGHT MOST AREAS AND THEN WARM. FOR SATURDAY...WEST AND SOUTHWEST WINDS CONTINUE WITH HIGHS IN THE 40S. WINDS TAKE A MORE SOUTHERLY TACK SUNDAY AHEAD OF A COLD FRONT PROGGED TO MOVE THROUGH SUNDAY NIGHT AND MONDAY. STILL HIGHS SUNDAY SHOULD RISE INTO THE 40S. A COLD FRONT MOVING THROUGH MONDAY IS EXPECTED TO TAKE THE EDGE OFF HIGHS. 30S APPEAR TO BE THE OPERATIVE MODE. THE GEM...GFS AND ECM ARE IN GOOD AGREEMENT ON A SIGNIFICANT SHORT WAVE TRACKING THROUGH THE CNTL PLAINS WEDNESDAY. TEMPS MIGHT BE WARM ENOUGH FOR RAIN AS H10-5 THICKNESSES HOVER NEAR 546DAM AND H850MB TEMPS -3 TO 0C. A CHANCE OF RAIN AND SNOW IS SHOWN EAST WITH SLIGHT CHANCE OF SNOW WEST. THE GFS AND GEM SHOW EVAPORATIVE COOLING WHILE THE ECM DOES NOT. THIS SYSTEM SHOULD EXIT WEDNESDAY NIGHT WITH ANOTHER STRONG COLD FRONT DROPPING TOWARD THE FCST AREA. && .AVIATION... OR 18Z TAFS...SMALLER SCALE FRONTOGENETIC BAND SLIDING ACROSS THE SANDHILLS INTO LATE AFTERNOON LOWERING CREATING VSBYS TO 3/4 TO 1/2SM AT TIMES THOUGH LATE AFTERNOON. THIS AREA OF HEAVIER SNOWFALL LIES BETWEEN THE KLBF AND KVTN TAF SITES...BUT MAY APPROACH THE KLBF TAF SITE BY 22Z. LATEST NAM AND HRRR SUGGEST THIS WILL SLIDE NORTH AND EAST OF KLBF HOWEVER AND AS SUCH HAVE NOT LOWERED VSBY AT KLBF DUE TO THIS FEATURE. THIS TIGHTER...SMALLER SCALE BAND LIKELY A RESULT OF LINGERING BUT WEAK FRONTOGENESIS IN A REGION OF NEGATIVE EPV IN THE 700-600MB LAYER. WOULD EXPECT THIS BAND TO DISSIPATE IN THE NEXT 2 TO 3 HRS AS WEAK INSTABILITY STABILIZES BUT WILL MONITOR. LARGER SCALE DRIER AIR IS WORKING IN ACROSS THE WESTERN PORTION OF THE STATE AND RADAR ECHOES ARE DECREASING SOME FROM WEST TO EAST AND WILL EXPECT THAT TREND TO CONTINUE THROUGH EVENING. FOR TONIGHT...SECONDARY SHORT WAVE SHOULD BE ENOUGH TO GENERATE FLURRIES TO -SN ACROSS THE NORTHERN PORTION OF THE STATE...THOUGH A MORE SHALLOW AREA OF LIFT CLOSER TO THE SURFACE AND FAVORABLE CROSS-OVER TEMPS SHOULD LEAD TO AT LEAST BR BUT POSSIBLY FZFG OVERNIGHT FURTHER SOUTH AND NEAR THE KLBF SITE. WILL BE REFINING THIS PORTION OF THE FORECAST IN THE NEXT FEW HOURS SINCE CONFIDENCE IN THIS SCENARIO IS LOW AT THE MOMENT. A GENERAL CLEARING TREND IS EXPECTED BY LATE MORNING FRIDAY. && $$ SHORT TERM/LONG TERM...CDC AVIATION...JWS
AREA FORECAST DISCUSSION
NWS LUBBOCK TX
149 PM CST THU DEC 8 2011 .UPDATE... UPDATED FOR WARMER TEMPERATURES AGAIN THIS AFTERNOON...CLOSE TO LATEST RUC SOLUTION WHICH SEEMS TO BE STRUGGLING LESS WITH THE THINNING SNOW COVERAGE THAN EITHER THE WRF/NAM OR GFS. FRONT STILL EXPECTED TO DROP SOUTHWARD THIS EVENING. RMCQUEEN && .AVIATION... PRE-FRONTAL VFR CONDITIONS WITH DOWNSLOPE BREEZES. COLD FRONT WILL EDGE SOUTHWARD THIS EVENING...CLOSE TO PREVIOUS TIMING. WE ARE LEANING MORE TOWARDS AREAS OF SURFACE SATURATION DEVELOPING LATER TONIGHT...POSSIBLE FOG...WHILE THE GFS STILL FAVORS LIFTING THIS INTO A LOW STRATUS DECK NEAR OR SHORTLY AFTER SUNRISE FRIDAY. WE WILL RETAIN TEMPO GROUPS FOR NEAR-IFR STRATUS LAYER STARTING BEFORE DAYBREAK FRIDAY. RMCQUEEN && .PREV DISCUSSION... /ISSUED 555 AM CST THU DEC 8 2011/ AVIATION... VFR CONDITIONS WILL PERSIST AT BOTH KLBB AND KCDS THROUGH AT LEAST 09/00Z. CONFIDENCE THEN DECREASES AS MODELS SHOW A MOISTENING LOW LEVEL ATMOSPHERE IN THE WAKE OF A COLD FRONT. CURRENT INDICATIONS SUGGEST THAT IFR CIG RESTRICTIONS COULD OCCUR DURING THE 06-12Z TIME-FRAME. FOG MAY BE AN OUTSIDE POSSIBILITY...BUT CONFIDENCE IN THIS IS LOW GIVEN CONTINUED NORTH/NORTHWESTERLY WINDS WHICH MAY HELP LIMIT SURFACE FOG POTENTIAL. PREV DISCUSSION... /ISSUED 406 AM CST THU DEC 8 2011/ SHORT TERM... TODAY/S FORECAST IS COMPLICATED BY AN ANTICIPATED FRONTAL PASSAGE. THE CURRENTLY DIFFUSE FRONTAL BOUNDARY OVER THE CENTRAL PLAINS WILL MAKE AN ACCELERATED PUSH SOUTHWARD TODAY IN THE WAKE OF A SHARPENING SHORTWAVE TROUGH OVER THE NORTHERN PLAINS/UPPER MIDWEST. MODELS SHOW THIS FRONT ENTERING THE EXTREME SOUTHWESTERN PANHANDLE BY LATE AFTERNOON...THEN CLEARING THE FORECAST AREA BY 06-09Z. TIMING OF THE FRONT AND PROSPECTS FOR AT LEAST SOME MID/HIGH CLOUDS ASSOCIATED WITH A SUBTLE SHORTWAVE TROUGH SEEN IN VAPOR IMAGERY OVER NEW MEXICO WILL MAKE FOR PROBLEMATIC AFTERNOON TEMPERATURE FORECASTS. AS WAS THE CASE YESTERDAY...MOS VALUES APPEAR LOW GIVEN PROGGED LOW LEVEL THERMAL PROFILES AND THICKNESSES. THUS HAVE EDGED FORECAST TEMPERATURE MAXIMA UP 5+ DEGREES RELATIVE TO GUIDANCE. FORECAST PROFILES SHOW CONSIDERABLE POST FRONTAL MOISTENING OF THE LOWER TROPOSPHERE BY LATE EVENING/OVERNIGHT. GIVEN PERSISTENT NORTH/NORTHWESTERLY DOWNSLOPE WINDS NEAR 10 KT WILL FAVOR AN INCREASING STRATUS DECK VERSUS FOG ATTM. LONG TERM... NEAR ZONAL FLOW ALOFT WILL ENSUE LATE THURSDAY THROUGH FRIDAY...AS AN UA DISTURBANCE ACROSS THE CENTRAL/HIGH PLAINS DIVES A COLD FRONT ACROSS THE SOUTHERN PLAINS TODAY. ALTHOUGH UPPER LEVEL ATMOSPHERIC LEVELS APPEAR RATHER DRY /PWATS BELOW 0.40 INCHES/...POST FRONTAL LOW LEVEL MOISTENING IS EXHIBITED FRIDAY MORNING...WITH HINTS OF POTENTIAL FOG. HOWEVER..NORTHERLY WIND SPEEDS AOA 10 KTS MAY AID TO MITIGATE THE PRODUCTION OF FOG AND WILL NOT ADD A MENTION WITH THIS FORECAST PACKAGE ATTM. THUS CURRENT THINKING IS THAT COOL TEMPS /30S AND 40S / AND INCREASING LOW LEVEL CLOUDINESS WILL BE THE RULE. SFC RIDGE WILL TRANSLATE NE OF THE REGION ON SATURDAY...AND PROMOTE SFC WINDS TO VEER TO A MORE SOUTH TO SOUTHEASTERLY/UPSLOPE WIND COMPONENT...WHICH MAY ENSUE THROUGH MONDAY MORNING. TEMPS WILL WARM INTO THE 40S AND 50S ON SUNDAY AND MONDAY AS SHORTWAVE RIDGING PASSES OVERHEAD...AND SLIGHTLY BREEZY SOUTHERLY SFC WINDS OCCURS DURING THE AFTERNOON HOURS. FURTHERMORE....BOTH THE GFS AND ECMWF HINT AT THE NORTHWARD TRANSPORT OF LOW LEVEL MOISTURE AND LIGHT QPF VALUES ESPECIALLY ACROSS ERN ZONES THROUGH THE AFOREMENTIONED PERIOD. CONCURRENTLY...THE EVOLUTION OF FLOW ALOFT FROM NEAR ZONAL TO SW FLOW WILL TAKE PLACE...AS A PACIFIC UA LOW COMMENCE TO MOVE ESE ACROSS CALIFORNIA. THEREAFTER...MODELS STILL STRUGGLE WITH HOW THIS UA DISTURBANCE WILL EVOLVE. IF FOLLOWING THE GFS /WHICH HAS SHOWN INCONSISTENCY FROM RUN TO RUN THE LAST FEW DAYS/ QUICKLY PROPAGATES THE PACIFIC UA DISTURBANCE ACROSS THE DESERT SW ON TUESDAY AND ACROSS THE CWA ON WEDNESDAY. A BREEZY NORTHWESTERLY PACIFIC FRONT WILL MOVE ACROSS THE REGION WEDNESDAY WITH A DECLINE IN PRECIP FROM WEST TO EAST. THE SYSTEM WILL BE EAST OF THE CWA BY THURSDAY. PRECIP TYPE APPEARS TO BE ALL LIQUID AS 850 MB TEMPS REMAIN ABOVE 0 DEGREES CELSIUS. HOWEVER THE GFS COULD BE OVER DOING THE WARMTH ALOFT AND WITHIN THE BL. THE ECMWF SOLUTION ON THE OTHER-HAND IS A BIT STRONGER WITH THE UA LOW AS IT SLOWLY TRANSLATES IT TO ACROSS THE DESERT SW WEDNESDAY MORNING...BEFORE EJECTING NE TO ACROSS THE CENTRAL PLAINS WEDNESDAY NIGHT. BREEZY WESTERLY WINDS WILL ENSUE AS THE SYSTEM BRUSHES THE CWA. AN ALL LIQUID PRECIP TYPE IS ALSO SHOWN BY THE ECMWF. WILL TEND TO LEAN TOWARDS THE ECMWF AS IT HAS BEEN MOST CONSISTENT. HOWEVER...HAVE DECIDED TO MAINTAIN SILENT POPS /ALTHOUGH BUMPED POPS TO 10 PERCENT TUESDAY NIGHT-WEDNESDAY/ ATTM AS THE ANALYSIS OF FUTURE MODEL RUNS FOR CONSISTENCY IS HIGHLY DESIRED. && .PRELIMINARY POINT TEMPS/POPS... FRIONA 15 33 20 40 22 / 0 10 0 0 0 TULIA 20 36 22 42 23 / 10 10 0 0 0 PLAINVIEW 21 37 23 43 25 / 0 10 0 0 0 LEVELLAND 19 38 24 43 25 / 0 10 0 0 0 LUBBOCK 21 39 24 44 26 / 0 10 0 0 10 DENVER CITY 21 39 24 43 27 / 0 10 0 0 10 BROWNFIELD 21 39 25 44 27 / 0 10 0 0 10 CHILDRESS 25 38 27 47 28 / 10 10 0 0 0 SPUR 24 38 25 46 27 / 0 10 0 0 10 ASPERMONT 26 41 28 48 30 / 0 10 0 0 10 && .LUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 05/99/05