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Area Forecast Discussion
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000
FXUS61 KBTV 221124
AFDBTV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
624 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 400 AM EST SATURDAY...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

&&

.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 /11Z 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 SATURDAY AFTERNOON... WINDS
GENERALLY OUT OF THE SOUTH WILL INCREASE THROUGHOUT THE DAY,
PEAKING BETWEEN 20 AND 30 KNOTS STARTING AROUND NOON 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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