Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 291746 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 1246 PM EST THU JAN 29 2015 .SYNOPSIS... A WEAK CLIPPER LIKE SYSTEM WILL PRODUCE A WIDESPREAD LIGHT SNOW THIS EVENING INTO FRIDAY...FOLLOWED BY UPSLOPE SNOW SHOWERS AND BITTERLY COLD TEMPERATURES FRIDAY NIGHT. HIGH PRESSURE WILL BUILD IN FOR THE WEEKEND WITH TEMPERATURES MUCH BELOW NORMAL. TEMPERATURES OF 10 TO 15 DEGREES BELOW NORMAL WILL PERSIST INTO THE MIDDLE OF NEXT WEEK. && .NEAR TERM /UNTIL 4 PM THIS AFTERNOON/... AS OF 1211 PM EST THURSDAY...CLOUDS ON THE INCREASE FROM WEST TO EAST ACROSS FORECAST AREA AS HIGH PRESSURE MOVES EAST OF THE REGION AND SHORTWAVE AND ASSOCIATED CLIPPER SYSTEM APPROACH FROM THE GREAT LAKES. RADAR SHOWING SOME PRECIPITATION ALOFT ENTERING SAINT LAWRENCE COUNTY...BUT WITH VERY DRY AIR STILL IN PLACE IN THE LOW LEVELS...BELIEVE IT WON`T BE UNTIL LATE IN THE DAY WHEN SOME LIGHT SNOW DEVELOPS IN WESTERN PORTION OF FORECAST AREA. TEMPS RESPONDING TO THE MORNING SUN AND DEVELOPMENT OF RETURN SOUTHERLY FLOW...SO GOING FORECASTED HIGHS IN THE MID 20S TO NEAR 30 STILL LOOKS OKAY. ONLY CHANGES TO FORECAST WITH LATEST UPDATE WERE SOME ADJUSTMENTS TO HOURLY TEMPS EARLY THIS AFTERNOON TO ACCOUNT FOR LATEST OBS AND TRENDS. && .SHORT TERM /4 PM THIS AFTERNOON THROUGH SATURDAY/... AS OF 629 AM EST THURSDAY...SNOW WILL SPREAD INTO THE ST LAWRENCE VALLEY...AFFECTING THE AFTERNOON/EVENING COMMUTE. A STRONG SOUTH- SOUTHWESTERLY LOW LEVEL JET WILL BRING GUSTY WINDS, RESULTING IN BLOWING SNOW AND REDUCED VISIBILITIES. THIS JET WILL ALSO CAUSE SHADOWING AFFECTS IN THE CHAMPLAIN VALLEY AND NORTHEASTERN SLOPES. AS PWATS REACH AROUND HALF AN INCH TONIGHT, THIS WILL COINCIDE WITH THETA-E RIDGE, SO EXPECT HEAVIEST SNOWFALL TO OCCUR MAINLY BETWEEN 06Z-15Z FRIDAY. THE CENTER OF THE CLIPPER TRAVERSES NEAR THE INTERNATIONAL BORDER EARLY FRIDAY MORNING THEN REDEVELOPS OFF THE SOUTHERN NEW ENGLAND COAST IN THE AFTERNOON AS THE ASSOCIATED MID LEVEL TROUGH BEGINS TO NEGATIVELY TILT. THIS TILTING WILL RESULT IN THE SURFACE LOW SLOWING ITS PROGRESSION AND KEEPING CENTRAL AND EASTERN VERMONT IN SNOW/SNOW SHOWERS INTO FRIDAY AFTERNOON/EVENING. BEHIND THE SURFACE LOW, SOUTHERLY WINDS OVER THE NORTH COUNTRY WILL SHIFT NORTHEAST. THIS COMBINED WITH LINGERING MOISTURE WILL PRODUCE UPSLOPE SNOW SHOWERS WITH FROUDE NUMBERS SHOWING BLOCKED FLOW. WHEN ALL IS SAID AND DONE, EXPECT 3-6 INCHES OF SNOWFALL FOR THE ST LAWRENCE VALLEY, STRETCHING ACROSS THE NORTHERN TIER OF OUR ZONES INTO THE CENTRAL CHAMPLAIN VALLEY, NORTHWESTERN, NORTH CENTRAL AND NORTHEASTERN VERMONT. DUE TO SHADOWING, ESSEX COUNTY NY AND THE SOUTHERN CHAMPLAIN VALLEY AND SOUTH CENTRAL VT LOOK TO RECEIVE 2-4 INCHES. LOCALLY HIGHER AMOUNTS ARE POSSIBLE, ESPECIALLY IN THE IN THE WESTERN ST LAWRENCE VALLEY, AS MODELS DEPICT BEST MOISTURE AND DEFORMATION TO OCCUR IN THIS AREA. THE NW FLOW WILL USHER IN COLDER AIR WITH NON DIURNAL TREND EXPECTED FRIDAY. DRIER AIR WILL ALSO BE FILTERING IN, ALLOWING SKIES TO CLEAR. AS THE SURFACE LOW BECOMES A COASTAL LOW, THE SURFACE PRESSURE GRADIENT WILL INCREASE LATE FRIDAY INTO FRIDAY NIGHT WITH HIGH PRESSURE BUILDING TO OUR WEST. THESE FEATURES WILL RESULT IN VERY COLD TEMPERATURES FRIDAY NIGHT INTO SATURDAY. 925MB TEMPS WILL FALL INTO THE NEGATIVE UPPER TEENS TO AROUND -20C FRIDAY NIGHT, WHICH WILL BE REFLECTED AT THE SURFACE IN TERMS OF SATURDAY MORNING LOWS RANGING FROM -2F TO -17F. THIS COLD AIR WILL COINCIDE WITH NORTHWEST WINDS OF 10-20 MPH, PRODUCING WIND CHILL VALUES OF -20 TO -35. IF MODELS CONTINUE THIS TREND, WIND CHILL HEADLINES MAY NEED TO BE ISSUED. SATURDAY WILL NOT WARM UP MUCH WITH NEW SNOW HELPING TO REFLECT INSOLATION. MAX TEMPERATURES WILL RANGE FROM NEAR ZERO TO 12F. INCREASING SUNSHINE WILL HELP, BUT WINDS WILL BE SLOW TO SUBSIDE. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... AS OF 341 AM EST THURSDAY...MODELS SHOWING AN ARCTIC COLD FRONT TO MOVE THROUGH THE REGION SATURDAY NIGHT...SO HAVE GONE WITH SLIGHT CHANCE POPS FOR SNOW SHOWERS...ALTHOUGH MOISTURE APPEARS TO BE LIMITED WITH THIS FEATURE. A RIDGE OF HIGH PRESSURE WILL SLIDE EAST FROM THE GREAT LAKES ON SUNDAY AND WILL REMAIN THROUGH SUNDAY NIGHT. ECMWF AND GFS MODELS DEVELOP A LOW OFF THE MID ATLANTIC COAST EARLY MONDAY AND TAKE IT SOUTH OF THE BENCHMARK (40N 70W) BY 18Z MONDAY...WITH THE ECMWF FURTHER SOUTH THAN THE GFS MODEL. THE CANADIAN GLOBAL MODEL IS SLOWER THEN THE GFS AND ECMWF AND TAKES A LOW JUST NORTH OF THE BENCHMARK (40N 70W) AFTER 00Z TUESDAY. THE CANADIAN GLOBAL LOOKS TO BE THE OUTLIER AND WAS NOT USED. HAVE LEANED TOWARD THE COMPROMISE GFS SOLUTION FOR MONDAY. THE GFS HINTS THAT THE NORTHERN EDGE OF ANY SNOW ON MONDAY WOULD JUST BARELY MAKE IT INTO SOUTH CENTRAL VERMONT ON MONDAY...SO HAVE JUST GONE WITH SLIGHT CHANCE POPS FOR SNOW SHOWERS IN RUTLAND AND WINDSOR COUNTIES ON MONDAY...WITH THE REMAINDER OF THE REGION REMAINING DRY. IF ECMWF MODEL IS RIGHT...THAN THE ENTIRE FORECAST AREA WOULD REMAIN DRY MONDAY AND MONDAY NIGHT. ANOTHER COLD FRONT WILL APPROACH THE REGION TUESDAY NIGHT AND WEDNESDAY...SO HAVE GONE WITH SLIGHT TO LOW CHANCE POPS FOR SNOW SHOWERS TUESDAY NIGHT AND WEDNESDAY. TEMPERATURES WILL BE WELL BELOW NORMAL FOR EARLY FEBRUARY. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... THROUGH 18Z FRIDAY...VFR AREA WIDE, BUT THAT WILL BE CHANGING OVER THE NEXT 4-8 HOURS AS LIGHT SNOW SPREADS FROM WEST TO EAST. MAY TAKE A COUPLE OF HOURS BEFORE CEILINGS AND VISIBILITIES FALL INTO THE IFR CATEGORY WHEN THE SNOW STARTS. GUSTY SURFACE SOUTHERLY WINDS (AT LEAST 25KTS) IN THE CHAMPLAIN VALLEY WILL ACT TO KEEP CONDITIONS A LITTLE BETTER (EG: MVFR VISIBILITY & VFR CEILINGS) FOR MUCH OF THE NIGHT. BORDERLINE ON LOW-LEVEL WIND SHEAR BETWEEN 00-06Z SO DIDN`T INCLUDE IT, BUT WILL NOTE THAT WINDS AT 2000FT WILL BE IN THE 30-40KT RANGE DURING THAT TIME -- WITH A BURST OF EVEN STRONGER WINDS AT 4000FT. A COLD FRONT WILL PUSH THROUGH DURING THE 12Z-18Z TIMEFRAME, AND START TO GUST TO 20KT IN PLACES BY 18Z. COULD BE A BIT OF BLOWING SNOW, ESPECIALLY IN MASSENA WHERE THE WINDS WILL BE THE STRONGEST. EXPECT IN THE CHAMPLAIN VALLEY (EG: BTV) THAT THE LOWEST CEILINGS AND VISIBILITIES WILL LIKELY OCCUR AFTER THE FRONT PASSES THROUGH AND WINDS CHANGE TO NORTHWEST. OUTLOOK 18Z FRIDAY THROUGH TUESDAY... 18Z FRIDAY-12Z SATURDAY...SLOW IMPROVEMENT FROM IFR TO MVFR AS SNOW SLOWLY ENDS. GUSTY NORTHWEST WINDS WILL RESULT IN AREAS OF BLOWING SNOW. 12Z SATURDAY-12Z MONDAY...VFR. 12Z MONDAY-00Z WEDNESDAY...PROBABLY VFR. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 1 AM EST SATURDAY FOR VTZ001>008-010-016>018. NY...WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 7 PM EST FRIDAY FOR NYZ026>031-087. && $$ SYNOPSIS...KGM NEAR TERM...RJS SHORT TERM...KGM LONG TERM...WGH AVIATION...NASH

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