Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 030546 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 1246 AM EST TUE MAR 3 2015 .SYNOPSIS... A HIGH PRESSURE AREA WILL BUILD INTO THE REGION OVERNIGHT FROM THE GREAT LAKES WITH SKIES BECOMING CLEAR. THE HIGH PRESSURE AREA WILL BE SHORT LIVED AS A STORM SYSTEM MOVES IN FROM THE WEST TUESDAY NIGHT AND WEDNESDAY. WIDESPREAD SNOW WILL DEVELOP LATE TUESDAY AND END AS A LITTLE BIT OF MIX OR RAIN SHOWERS WEDNESDAY MORNING. IT WILL BE MILD WEDNESDAY, BUT COLDER AIR RETURNS WEDNESDAY NIGHT. HIGH PRESSURE WILL THEN REMAIN IN CONTROL UNTIL THE END OF THE WEEK. && .NEAR TERM /UNTIL 7 AM THIS MORNING/... AS OF 1217 AM EST TUESDAY...SKIES HAVE GENERALLY CLEARED OUT PER RECENT IR IMAGERY AND HAVE MADE SOME ADJUSTMENTS TO THE SKY GRIDS ACCORDINGLY. BOUNDARY LAYER STABILIZATION IS ALLOWING NW WINDS TO EASE...AND LIGHT AND VARIABLE WINDS NOTED AT 05Z FROM THE CHAMPLAIN VALLEY WWD...WITH A FEW SPOTS 5-10MPH WITH GUSTS 15-20 MPH IN THE CT RIVER VALLEY. SHOULD SEE THESE WINDS SUBSIDE AS WELL AS SURFACE RIDGE AXIS BUILDS EWD ACROSS NY INTO VT TOWARD DAYBREAK. RADIATIONAL COOLING CONDITIONS WILL BE QUITE GOOD OVER THE NEXT SEVERAL HOURS...SO LOWS ZERO TO -5F LOOK ON TRACK FOR THE NRN ADIRONDACKS AND FAR NERN VT...AND GENERALLY ZERO TO 8 ABOVE ELSEWHERE. POPS NIL. && .SHORT TERM /7 AM THIS MORNING THROUGH WEDNESDAY NIGHT/... AS OF 340 PM EST MONDAY...FAIRLY DECENT MODEL AGREEMENT, THOUGH SOME "DEVIL IN THE DETAILS" REGARDING THERMAL STRUCTURE ALOFT TUESDAY NIGHT WHICH DOES LEAD TO PRECIPITATION-TYPE ISSUES. LET`S JUST DISCUSS EACH 12-HOUR BLOCK OF TIME... TUESDAY: HIGH PRESSURE QUICKLY MOVES OFF TO THE EAST, SO WE START CLEAR BUT CLOUD OVER IN THE AFTERNOON. 925MB TEMPERATURES IN THE -12 TO -17C RANGE, WHICH WOULD SUPPORT HIGHS INTO THE MID 20S IN THE LOWER ELEVATIONS. FAIRLY ROBUST UPPER TROUGH AND ASSOCIATED SURFACE LOW WILL BE MOVING INTO THE GREAT LAKES REGION BY AFTERNOON. CONSIDERABLE WARM AIR ADVECTION, SO BY LATE AFTERNOON WE SHOULD SEE LIGHT SNOW BREAK OUT, ESPECIALLY FROM THE CHAMPLAIN VALLEY WESTWARD. TUESDAY NIGHT: VERY STRONG WARM AIR ADVECTION ONGOING. 850MB WINDS WILL INCREASE TO 45-55KTS OUT OF THE SOUTH/SOUTHWEST. THUS IT SHOULD GET FAIRLY BREEZY, IF NOT WINDY, IN THE CHAMPLAIN VALLEY. THINK WIND GUSTS TO 35 MPH ARE LIKELY. THE STRONG LOW/MID LEVEL JET WILL BRING WARMER AIR ALOFT, WHICH RESULTS IN A STRONG ISENTROPIC LIFT. SHOULD SEE A BURST OF MODERATE SNOW IN THE 8PM- 2AM TIMEFRAME PRETTY MUCH AREA WIDE. AFTER THAT TIME, TEMPERATURES IN THE 800-925MB LEVEL START TO SNEAK ABOVE 0C. THAT MEANS THE POTENTIAL FOR CHANGE OVER TO DIFFERENT PRECIP-TYPES. GOOD NEWS IS THAT AS TYPICAL WITH WARM AIR ADVECTION PRECIPITATION EVENTS, MOST OF THE PRECIPITATION IS OVER WITH PRIOR TO THE MIXING. MODELS ALSO TYPICALLY SHOW US GETTING MORE PRECIPITATION THAN REALITY DURING THESE WARM AIR ADVECTION SYSTEMS, SO I ENDED UP TAKING A MODEL BLEND AND THEN CUTTING BACK A LITTLE. THINK IN GENERAL 0.2 TO 0.3" OF "LIQUID", HOWEVER THE STRONG WINDS WILL RESULT IN SIGNIFICANT SHADOWING/DRYING IN THE CHAMPLAIN VALLEY, SO ONLY ABOUT 0.1" OR SO THERE. TRICKY PART IS TRYING TO ESTIMATE THE SNOW-LIQUID RATIO. BEST GUESS IS WE WILL BE SOMEWHERE IN THE 10-13:1 RANGE. THIS GIVES A GENERAL 2-4" OF SNOW, PRIOR TO ANY MIXING HAPPENING. FOR THE MIXING POTENTIAL, NOTED THE NAM, WHICH IS USUALLY A COLDER MODEL, WAS WARMEST AND BROUGHT THE MIX ALL THE WAY UP TO NORTHERN VT. GFS WAS COLDEST AND KEPT EVERYTHING TO THE SOUTH OF VERMONT. THE EURO AND THE LOCAL 12KM WRF WERE IN-BETWEEN. ENDED UP USING THE 12KM WRF FOR A LITTLE FINER RESOLUTION. BOTTOM LINE, ANY MIX SHOULD BE CONFINED TO SOUTH-CENTRAL VERMONT AND THE ST LAWRENCE VALLEY. AT THIS POINT WILL NOT ISSUE ANY WINTER WEATHER ADVISORIES. WE`LL SEE IF LATER MODEL RUNS HAVE A DIFFERENT TREND. A LITTLE NORTHWARD JOG IN THE MODELS WOULD MEAN A MUCH WETTER (AND LIKELY WARMER) SITUATION. WEDNESDAY: LIGHT PRECIPITATION IN THE MORNING SHOULD TAPER OFF AND END AS LIGHT RAIN SHOWERS FOR MOST EVERYONE. YEP, STILL LOOKING FOR A WONDERFULLY WARM DAY -- WELL, IF YOU CAN CALL 40S WARM. STUCK WITH A GUIDANCE MIX THAT HAS BURLINGTON REACHING THE LOWER 40S, BUT NOTED THAT SOME GUIDANCE INDICATED MID TO EVEN UPPER 40S. IT WILL ALL DEPEND ON HOW SOON THE COLDER AIR STARTS TO MAKE IT`S WAY IN. GIVEN WINDS TURNING WESTERLY DURING THE DAY (EG: DOWNSLOPING), AND A DRY SLOT LIKELY GIVING SOME BREAKS IN THE CLOUDS, I`D GIVE UPPER 40S ABOUT A 40% CHANCE OF HAPPENING. MAYBE THAT IS JUST ME WISH-CASTING ;) WEDNESDAY NIGHT: THE WARMTH IS SHORT LIVED. WINDS TURN NORTHWEST AND COLD-AIR ADVECTION CONTINUES. SHOULD DROP INTO THE TEENS ACROSS VERMONT, WITH LOWS CLOSER TO ZERO OUT IN THE ST LAWRENCE VALLEY. STILL SOME WIND AND SOME CLOUDS ABOUT AND PERHAPS A MOUNTAIN FLURRY. STUCK TO A GUIDANCE BLEND FOR TEMPERATURES. && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 315 PM EST MONDAY... GIVEN THE LACK OF ACTIVE WEATHER EXPECTED IN THE EXTENDED I`LL FORGO DAILY DESCRIPTIONS IN FAVOR OF A BROAD GENERAL IDEA OF THE PATTERN FROM THURSDAY ONWARD. A BROAD NORTHERN UPPER LEVEL TROUGH WILL COMBINE WITH A BROAD DOME OF HIGH PRESSURE TO SUPPRESS ANY SYNOPTIC FORCING OF PRECIP WITH THE LONE EXCEPTION BEING A WEAK SHORTWAVE DISTURBANCE ON SATURDAY. THAT WILL BRING A CHANCE OF SNOW SHOWERS ESPECIALLY IN THE HIGHER TERRAIN OF THE ADIRONDACKS AND GREENS. CONCERNING TEMPERATURES... WE WILL SEE A GENERAL WARMING PATTERN WITH THURSDAY AND FRIDAY BEING THE COLDEST TWO DAYS WITH HIGHS IN THE LOW TO MID 20S WARMING TO MORE SEASONABLE TEMPS AROUND FREEZING TO THE MID 30S OVER THE WEEKEND. OVERNIGHT LOWS WILL BE QUITE CHILLY ON THURSDAY AND FRIDAY NIGHT AS MOSTLY CLEAR SKIES WILL ALLOW FOR GOOD RADIATIONAL COOLING BRING LOWS IN THE LOW SINGLE DIGITS ABOVE AND BELOW ZERO. INTO THE WEEKEND WITH THE WARMING TREND CONTINUING OVERNIGHT LOWS SHOULD WARM INTO THE MID TEENS TO NEAR 20 INSIDE THE CHAMPLAIN VALLEY. WINDS DURING THE PERIOD WILL BE GENERALLY LIGHT TO MODERATE WEST TO SOUTHWESTERLY UNDER THE UPPER LEVEL TROUGH AXIS WITH MOSTLY CLEAR SKIES EXCEPT FOR A SHORT PERIOD OF INCREASING CLOUDS NEAR THE INTERNATIONAL BORDER EARLY SATURDAY MORNING. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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THROUGH 06Z WEDNESDAY...VFR CONDITIONS WILL PERSIST INTO THE MID- DAY HOURS TUESDAY WITH LIGHT WINDS THIS MORNING TURNING SOUTHERLY AND INCREASE TUESDAY AFTERNOON...WITH 15-30 KNOT GUSTS LIKELY...ESPECIALLY BTV/PBG/SLK. MID/HIGH DECK OF CLOUDS ALSO INCREASES BETWEEN 12-18Z...FOLLOWED BY A MVFR LOW CLOUDS MOVING IN WITH A PERIOD OF SNOW INTO NORTHERN NY AND MSS/SLK AFTER 20Z. THIS SNOW AND MVFR CONDITIONS WILL MOVE INTO THE CHAMPLAIN VALLEY...AFFECTING KPBG/KBTV AND KRUT STARTING AROUND 22Z THEN INTO CENTRAL VT AND KMPV AROUND 23Z. PERIODS OF IFR/LIFR EXPECTED IN HEAVIER SHOWERS 21Z-05Z AT KSLK/KMSS AND 00Z-04Z AT KPBG/KBTV/KRUT AND KMPV. STRONG LOW LEVEL JET WILL MOVE OVER THE AREA AROUND 00Z BETWEEN 2-4KFT. THIS MAY PRODUCE SOME LOW LEVEL WIND SHEAR WHILE SNOW SHOWERS CREATE STABILITY AND MINIMIZE WIND GUSTS. BUT ANY BREAKS IN SHOWERS, ESPECIALLY IN THE CHAMPLAIN VALLEY AFTER 04Z, WILL LEAD TO WIND GUSTS OF 20-30KTS AS MIXING OCCURS. OUTLOOK 06Z WEDNESDAY THROUGH SATURDAY... 06Z WEDNESDAY THROUGH 18Z WEDNESDAY... MVFR/IFR IN PERIODS OF LIGHT SNOW LIFTING TO VFR WEDNESDAY AFTERNOON AS PRECIPITATION MIXES WITH RAIN SHOWERS AND DISSIPATES. 18Z WEDNESDAY THROUGH 00Z FRIDAY...MAINLY VFR ALTHOUGH SOME PERIODS OF MVFR/IFR ARE POSSIBLE IN LIGHT SNOW SHOWERS AS SYSTEM SLIDES TO THE SOUTH. 00Z FRIDAY THROUGH 12Z SATURDAY...VFR UNDER RIDGE OF HIGH PRESSURE. 12Z SATURDAY ONWARD...MVFR/IFR POSSIBLE IN SNOW SHOWERS WITH FRONTAL SYSTEM.
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&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...NONE. NY...NONE. && $$ SYNOPSIS...NASH NEAR TERM...BANACOS SHORT TERM...NASH LONG TERM...DEAL AVIATION...KGM

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