Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 221150 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 650 AM EST SAT NOV 22 2014 .SYNOPSIS... SURFACE HIGH PRESSURE WILL SLIDE INTO THE ATLANTIC TODAY...SHIFTING WINDS OVER THE NORTH COUNTRY TO THE SOUTH TO SOUTHWEST. A DISTURBANCE IN THE FLOW ALOFT WILL BRING CLOUDS AND A LIGHT WINTRY MIX TO THE REGION THIS AFTERNOON INTO SUNDAY MORNING. A FEW RAIN SHOWERS LINGER MAINLY OVER THE HIGHER TERRAIN ON SUNDAY WITH TEMPERATURES WARMING INTO THE 40S. SUNDAY NIGHT INTO MONDAY WILL SEE A MORE SIGNIFICANT STORM SYSTEM BRING GUSTY WINDS AND MORE RAIN TO THE REGION. && .NEAR TERM /UNTIL 7 PM THIS EVENING/... AS OF 650 AM EST SATURDAY...OVERALL TEMPERATURES HAVE NOT FALLEN AS LOW AS PREVIOUSLY FORECAST THIS MORNING DUE TO INCREASED CLOUDS OVER MOST OF THE REGION. CLOUDS CONTINUE TO INCREASE FROM THE WEST AS SLIGHT UPPER LEVEL RIDGING THIS MORNING STARTS TO SLIDE EAST. PERIOD OF DRY WEATHER WILL BE ENDING THIS AFTERNOON AS SURFACE HIGH PRESSURE SLIDES SOUTH AND EAST INTO THE ATLANTIC TODAY. THIS WILL RESULT IN A RETURN OF SOUTHWEST FLOW WITH MODERATING TEMPERATURES AND AN INCREASE IN MOISTURE...WHICH WILL COINCIDE WITH A SHORTWAVE TROUGH AFFECTING THE NORTH COUNTRY. AS A RESULT, A LIGHT WINTRY MIX WILL SPREAD FROM SOUTHWEST TO NORTHEAST STARTING THIS AFTERNOON. THE SAINT LAWRENCE VALLEY AND ADIRONDACKS WILL BE THE FIRST AREAS TO SEE A MIX OF RAIN/SNOW/SLEET AND POCKETS OF FREEZING RAIN POSSIBLE IN THE LATE AFTERNOON/EVENING. MODEL GUIDANCE SHOWS STRONG 850MB JET AROUND 40-50 KTS WHICH WILL HELP HASTEN THE ARRIVAL OF WARM AIR. THIS WILL RESULT IN THE SAINT LAWRENCE VALLEY TRANSITIONING TO ALL RAIN BEFORE 00Z/SUNDAY...WHILE THE POTENTIAL FOR SLEET OR RAIN WILL BE MORE PREVALENT IN THE ADIRONDACKS AND INTO VERMONT. && .SHORT TERM /7 PM THIS EVENING THROUGH MONDAY/... AS OF 405 AM EST SATURDAY...INCREASING CHANCE FOR PRECIPITATION HEADING INTO TONIGHT WITH STRONG S/SW FLOW CONTINUING ACROSS THE NORTH COUNTRY. EXPECT MOST OF NRN NY TO TRANSITION TO RAIN SHORTLY AFTER 00Z..WITH EXCEPTION OF HIGHER ELEVATIONS TO CONTINUE TO SEE SLEEP AND POSSIBLE FREEZING RAIN. WHILE ACROSS THE CHAMPLAIN VALLEY, MOST OF THE NORTHEAST KINGDOM WILL SEE SLEET AND POSSIBLE FREEZING RAIN AS THE COMPLEX TERRAIN WILL HINDER SCOURING OUT THE COLDER AIR. MOST MODEL GUIDANCE SHOWS THAT BY 06Z/SUNDAY, WARMER AIR AND THEREFORE RAIN HAVE TAKEN OVER NRN NY, THE CHAMPLAIN VALLEY AND WILL INFILTRATING CENTRAL AND EASTERN VERMONT. AREAS THAT WILL SEE WINTRY MIX THE LONGEST WILL BE THE GREEN MOUNTAINS AND EASTWARD, WITH GREATEST POTENTIAL FOR FREEZING RAIN IN CENTRAL AND SOUTHERN VERMONT. COME 1Z SUNDAY MORNING, THE SHORTWAVE RESPONSIBLE FOR THIS PRECIPITATION WILL BE OVER EASTERN VERMONT...ALLOWING FOR A DRYING TREND FROM WEST TO EAST. ALL BUT EXTREME NORTHEAST VERMONT IS EXPECTED TO TRANSITION TO RAIN AT THIS POINT. ANY SNOW/SLEET ACCUMULATION WILL LIMITED TO A DUSTING UP TO 2 INCHES. AS FOR ICE ACCRETION, GREATEST POTENTIAL FOR ACCRETION WILL BE BETWEEN 06Z AND 12Z SUNDAY ACROSS CENTRAL AND EASTERN VERMONT. ONLY EXPECTING MOST AREAS THAT DO RECEIVE FREEZING RAIN TO SEE A TRACE, WITH MELTING OCCURRING SUNDAY MORNING. THERE WILL BE SOME LINGERING LIGHT PRECIPITATION SUNDAY MORNING...MAINLY IN THE FORM OF LIGHT RAIN. WITH PASSAGE OF SHORTWAVE...SOME UPPER LEVEL RIDGING DEVELOPS OVER THE REGION. SO ALTHOUGH CLOUDS WILL REMAIN...IT SHOULD BE MOSTLY DRY FOR THE AFTERNOON AND EVENING HOURS. TEMPERATURES WILL BE MILDER WITH HIGHS IN THE 40S. LATE SUNDAY NIGHT, A WARM FRONT WILL APPROACH FROM THE SOUTHWEST, INCREASING POPS FROM SOUTHWEST TO NORTHEAST AFTER MIDNIGHT. TEMPERATURES WILL BE WARM IN THE MID TO UPPER 30S, KEEPING PRECIPITATION IN THE FORM OF RAIN. AS PART OF A CLOSED SURFACE LOW PRESSURE SYSTEM, WINDS WILL BECOME STRONG AND GUSTY OUT OF THE SOUTH WITH MORE MOISTURE AVAILABLE THAN TONIGHTS DISTURBANCE. EXPECT 0.25- 0.50 INCH OF RAINFALL BY MONDAY EVENING. EVEN THOUGH CLOUDS WILL BE ABUNDANT ON MONDAY, SO WILL WARM AIR ADVECTION WITH HIGHS IN THE 50S. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... AS OF 315 AM EST SATURDAY...CHANGES TO THE EXTENDED FORECAST OVER PREVIOUS VERSION AS ECMWF HINTS AT POTENTIAL FOR COASTAL LOW AND SNOW CHANCES LATE WEDNESDAY AND WEDNESDAY NIGHT. NO MODEL CONSENSUS HOWEVER WITH GFS KEEPING LOW FURTHER EAST WITH DRY FORECAST. THE EXTENDED PERIOD IS DOMINATED BY A 500 MB TROUGH OVER THE EASTERN TWO THIRDS OF NORTH AMERICA, WITH INDIVIDUAL SHORTWAVE TROUGHS MOVING THROUGH THE MEAN TROUGH. STARTING AT BEGINNING OF EXTENDED PERIOD 00-12Z TUESDAY THE REGION IS IN THE WARM SECTOR OF THE SURFACE LOW WITH MAIN PRECIP AREA MOVED EAST. LINGERING RAIN SHOWERS ENDING WEST TO EAST DURING THIS PERIOD. BLENDED SUPERBLEND POPS THIS PERIOD WITH 3 HOURLY NAM12 POPS TO ADD PRECIP TIMING ALONG A WEAK SURFACE WAVE MOVING THROUGH THAT WILL PROVIDE A FOCUS FOR THE SHOWERS AND START A COOLING TREND IN TEMPS. COULD BE SOME SNOW MIXED IN OVER HIGHER TERRAIN TOWARDS MORNING. COLD AIR ADVECTION PATTERN ON TUESDAY WITH WINDS TURNING MORE SOUTHWESTERLY AND SURFACE FRONT MOVING TO THE ATLANTIC COAST. NOTICEABLY COOLER THAN PREVIOUS DAY, WITH TEMPERATURES TRENDING TO NORMAL. WILL CONTINUE SLIGHT CHANCE POPS OVER NORTHERN MOUNTAINS WITH POTENTIAL FOR UPSLOPE SNOW SHOWERS...AND CHC POPS SOUTHWEST ST. LAWRENCE COUNTY JUST ON EDGE OF WEAK LAKE EFFECT SNOW BAND. NOW FOR THE CHANGE IN THE FORECAST. NEXT SHORTWAVE TROUGH MOVES OUT OF SOUTHERN STREAM AND FOCUSES MORE PRECIP ALONG THE FRONT, WHICH IS FORECAST TO BECOME DRAPED ALONG THE EASTERN US COAST LATE WEDNESDAY INTO WEDNESDAY NIGHT. MODEL TRENDS UP TO NOW HAVE BEEN FOR AN OPEN WAVE IN 500 MB FLOW WITH PRECIP CONCENTRATED ALONG THE COASTAL FRONT TO THE EAST OF THE FORECAST AREA AND A DRY THANKSGIVING. ECMWF INTRODUCES SOME UNCERTAINTY HOWEVER AS IT SHARPENS UP THE LONGWAVE500 MB TROUGH AND HAS A MORE WESTERLY TRACK FOR THE SHORTWAVE TROUGH. THIS SPINS UP A COASTAL LOW AND MOVES IT ACROSS CAPE COD AROUND 06Z TUES WHILE GFS KEEPS IT EAST OF THE BENCHMARK AND DRY FORECAST FOR US. SOME GFS ENSEMBLE MEMBERS ALSO DEVELOP A SHARPER 500 MB TROUGH. GIVEN THE UNCERTAINTY, AND SIGNIFICANCE OF TRAVEL DAY BEFORE THANKSGIVING, IT IS PRUDENT TO GO WITH A CHANCE FOR SNOW LATE WEDNESDAY AND WEDNESDAY NIGHT. GOOD COORDINATION WITH NEIGHBORING OFFICES ON THIS AND WE MATCH UP WELL. REGARDLESS OF EXACT TRACK OF SHORTWAVE TROUGH AND SURFACE LOW...GFS AND ECMWF AGAIN IN AGREEMENT IN PASSAGE OF COLD FRONT BY FRIDAY WITH TEMPERATURES TRENDING DOWNWARD THE END OF THE PERIOD. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... THROUGH 12Z SUNDAY...MAINLY VFR FOR MOST OF THE TAF PERIOD, THEN CONDITIONS DETERIORATE IN THE LAST HALF TO MVFR CIGS AND SOME MIXED PRECIP. EXCEPTION EARLY ON AT KSLK/KMSS WHERE MVFR CIGS PRESENT IN LOW LEVEL MOISTURE. EXPECTING THESE LOWER CLOUDS TO DISSIPATE AND MID LEVEL CLOUDS TO TAKE OVER FOR REST OF THE DAY. SOUTHERLY FLOW HAS DEVELOPED ACROSS THE REGION AND SOUTHERLY WINDS TO INCREASE TODAY AS STRONGER BOUNDARY LAYER WINDS MIX DOWN. GUSTS TO 25KTS WILL BE COMMON, AND AIRCRAFT WILL ENCOUNTER SOUTHWEST WINDS OVER 40KTS ABOVE 2000 FT AGL. BATCH OF WARM FRONTAL PRECIP TO MOVE IN LATE IN THE PERIOD BUT COVERAGE WILL BE SPOTTY EARLY ON SO STUCK WITH VCSH AS PREVIOUS FORECAST. ADDED -RA AFT 00Z KSLK/MSS WHERE TEMPERATURES WARM ABOVE FREEZING AND LIKELY POPS IN FORECAST. WITH SOUTHERLY FLOW PRECIP WILL BE SCARCE IN CHAMPLAIN VALLEY SO KBTV/KPBG VCSH ALL THE WAY THROUGH. COLDER TEMPS HOLD ON LONGER KRUT/KMPV AS PRECIP CHANCES RAMP UP, SO THOSE AREAS GOT A PERIOD OF -RAPL MIX. OUTLOOK 06Z SUNDAY THROUGH WEDNESDAY... 12Z - 00Z MONDAY...MIX OF VFR AND MVFR WITH PRECIPITATION MAINLY IN THE EAST COMING TO AN END, -RAPL CHANGING TO -RA AS WARMER TEMPERATURES. 00Z MONDAY - 12Z TUESDAY...BRIEF PERIOD OF VFR THROUGH 06Z MONDAY BEFORE TRENDING TO MVFR AND POSSIBLE IFR IN MIXED PRECIPITATION AS A WARM FRONT LIFTS THROUGH THE REGION. 12Z TUESDAY - 00Z THURSDAY...GENERALLY VFR WITH MVFR/IFR LAKE EFFECT POSSIBLE AT KSLK. && .MARINE... A LAKE WIND ADVISORY IS IN EFFECT FOR TODAY... WINDS GENERALLY OUT OF THE SOUTH WILL INCREASE THROUGHOUT THE DAY, PEAKING BETWEEN 20 AND 30 KNOTS TODAY AND LASTING INTO THIS EVENING. WAVE HEIGHTS WILL BUILD TO 2 TO 4 FEET, RESULTING IN ROUGH CONDITIONS ESPECIALLY IN SOUTHWARD FACING BAYS AND INLETS. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...NONE. NY...NONE. && $$ SYNOPSIS...KGM NEAR TERM...KGM SHORT TERM...KGM LONG TERM...HANSON AVIATION...HANSON MARINE...KGM

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