Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 221736 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 1236 PM EST SAT NOV 22 2014 .SYNOPSIS...
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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.
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&& .NEAR TERM /UNTIL 7 PM THIS EVENING/...
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AS OF 1016 AM EST SATURDAY...SWLY FLOW CONTINUES TO INCREASE BETWEEN SURFACE HIGH PRESSURE CENTERED ACROSS THE MID-ATLANTIC REGION...AND LOW PRESSURE OVER JAMES BAY. MAIN UPDATE THIS MORNING WAS TO INCREASE SWLY WINDS IN THE WIDER VALLEYS (CHAMPLAIN AND ST. LAWRENCE)...INCLUDING GUSTS 30-35 MPH THROUGH MID-LATE THIS AFTERNOON. THE LAKE WIND ADVISORY ALSO CONTINUES FOR LAKE CHAMPLAIN FOR SOUTH-SOUTHWEST WINDS 20-30 KTS. THE INCREASING SWLY FLOW WILL ALSO MARK THE ONSET OF A MODERATING TEMPERATURE TREND...WHICH WILL CONTINUE THROUGH MONDAY. DESPITE THE ABUNDANT MID TO UPPER LEVEL CLOUDS...TEMPERATURES WILL MODERATE INTO THE MID TO UPPER 30S THIS AFTERNOON FROM THE WEST SLOPES OF THE GREENS/CHAMPLAIN VALLEY AND POINTS WEST. COLD DENSE AIR WILL BE SLOWER TO SCOUR OUT EAST OF THE GREEN MOUNTAIN SPINE...SO LOOKING AT HIGHS IN THE LOW-MID 30S ACROSS CENTRAL/EASTERN VT. OVERALL...TEMPERATURES WILL BE 5-10F WARMER THIS AFTERNOON IN COMPARISON TO OBSERVED CONDITIONS YESTERDAY. SHORTWAVE TROUGH OVER NERN OH/SWRN NY WILL MAKE RAPID NEWD TRANSLATION...ALONG WITH ASSOCIATED 50-55 KT 900-850MB LOW-LEVEL JET. BASED ON NAM12/BTV-4/BTV-12KM WRF...LOOKING AT SOME LIGHT PRECIPITATION ASSOCIATED WITH THIS FEATURE MOVING INTO THE ST. LAWRENCE VALLEY AND ADIRONDACKS AROUND 21Z (4PM). GRIDS ALREADY HAVE PRECIPITATION TYPE WELL-COVERED...WITH A MIX OF RAIN AND SOME ICE PELLETS FOR THE ST. LAWRENCE VALLEY...AND SNOW/IP ACROSS THE HIGHER ELEVATIONS OF THE ADIRONDACKS. QUICK/SHORT-DURATION EVENT YIELDS LESS THAN 0.10" QPF FOR MOST LOCATIONS...SO ANY FROZEN PRECIPITATION LESS THAN 1". NOT LOOKING FOR ANY SIGNIFICANT TRAVEL ISSUES...ESPECIALLY WITH SFC TEMPS WARMING ABOVE FREEZING IN MOST SPOTS. COULD BE A SLICK SPOT OR TWO LATE THIS AFTERNOON (ESPECIALLY AT ELEVATION)...WHICH IS WELL COVERED IN HAZARDOUS WEATHER OUTLOOK. PRIMARY CHANGE WAS TO INCREASE WIND SPEEDS/GUSTS WITH THIS UPDATE.
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&& .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/...
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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.
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&& .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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THROUGH 18Z SUNDAY...MAINLY VFR THRU 06Z, THEN CONDITIONS DETERIORATE TO MVFR CIGS AND SOME MIXED PRECIP. SOUTHERLY WINDS CONTINUE TODAY AS STRONGER BOUNDARY LAYER WINDS MIX DOWN. GUSTS TO 25 KTS OCCURRING ESPECIALLY AT BTV AND PBG, AND AIRCRAFT WILL ENCOUNTER SOUTHWEST WINDS OVER 40KTS ABOVE 2000 FT AGL. BATCH OF WARM FRONTAL PRECIP TO MOVE IN OVERNIGHT BUT COVERAGE WILL BE SPOTTY EARLY ON SO STUCK WITH VCSH AS PREVIOUS FORECAST. HAVE PREVAILING -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. PRECIP SHOULD BE MOVING OUT OF THE AREA BY ABOUT 12Z AT ALL SITES...WITH CONDITIONS IMPROVING TO VFR AGAIN. OUTLOOK 18Z SUNDAY THROUGH THURSDAY... THRU 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. 00Z THURSDAY ONWARD...COASTAL SYSTEM TO POSSIBLY IMPACT THE REGION...THOUGH LOTS OF UNCERTAINTY AT THIS TIME.
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&& .MARINE...
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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.
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&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...NONE. NY...NONE. && $$ SYNOPSIS...KGM NEAR TERM...BANACOS SHORT TERM...KGM LONG TERM...HANSON AVIATION...NEILES/HANSON MARINE...KGM

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