Area Forecast Discussion
Issued by NWS Burlington, VT

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000
FXUS61 KBTV 290551
AFDBTV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
1251 AM EST SAT NOV 29 2014

.SYNOPSIS...
SURFACE HIGH PRESSURE ACROSS SOUTHERN CANADA WILL BUILD OVER THE
NORTH COUNTRY TONIGHT...RESULTING IN COLD TEMPERATURES AND
CLEARING SKIES. TEMPERATURES WILL DROP TO NEAR ZERO IN THE COLDER
MOUNTAINS VALLEYS TO UPPER TEENS IN THE CHAMPLAIN VALLEY. A WARM
FRONT WILL INCREASE THE CLOUDS ON SATURDAY WITH LIGHT SNOW
ARRIVING BY AFTERNOON. A DUSTING TO 2 INCHES OF SNOW ACCUMULATION
IS POSSIBLE WITH TEMPERATURES REBOUNDING TO ABOVE NORMAL LEVELS BY
SUNDAY.

&&

.NEAR TERM /UNTIL 7 AM THIS MORNING/...
AS OF 921 PM EST FRIDAY...FORECAST STILL IN GOOD SHAPE FOR
REMAINDER OF THE NIGHT WITH LINGERING NRN MTN SHSN/FLURRIES SLOWLY
COMING TO AND END LEAVING VARIABLY CLOUDY/PTLY CLOUDY SKIES ACROSS
THE AREA. SOME NATURAL VARIABILITY STARTING TO CROP UP IN HOURLY
T/TD OBSERVATIONS...BUT A QUICK LOOK AT FORECAST OVERNIGHT MINS
STILL APPEAR MOST REASONABLE OUT OF AVAILABLE GUIDANCE SO LEFT
THOSE VALUES UNCHANGED. PRIMARY ADJUSTMENT WAS TO DELAY ONSET OF
PCPN ACROSS THE AREA TOMORROW...KEEPING BULK OF LIGHT SNOWS/MIXED
PCPN OUT OF THE AREA UNTIL AFTER SUNSET. THIS IS IN BETTER
AGREEMENT WITH NEARLY ALL MODEL RH/OMEGA PROGS AND MOS OUTPUT.
STILL LOOKING AT A PERIOD OF LIGHT MIXED PCPN TOMORROW
EVENING/OVERNIGHT HOWEVER SO PLEASE REFER TO PRIMARY SHORT TERM
DISCUSSION BELOW DESCRIBING DYNAMICAL FORCING/REASONING ETC. HAVE
A GREAT NIGHT.

PRIOR NEAR TERM DISCUSSION FROM 628 PM EST FRIDAY...
FORECAST REMAINS MORE OR LESS ON TRACK AS OF EARLY EVENING.
ADJUSTED SKY COVER AND T/TD DATA TO MATCH CURRENT TRENDS. SNOW
SHOWERS/FLURRIES CONTINUE OVER THE NEXT FEW HOURS THEN WANE/END.
POTL BUST ON TEMPERATURES OVERNIGHT GIVEN FRESH SNOW COVER AND
CLEARING SKIES...BUT WARM THERMAL ADVECTION- DRIVEN MID CLOUDS
ARRIVE LATE SO TOUGH CALL. VALUES RANGING FROM 5-15 ABOVE WITH A
FEW UNLUCKY SPOTS AROUND ZERO STILL LOOK REASONABLE ATTM.

&&

.SHORT TERM /7 AM THIS MORNING THROUGH SUNDAY NIGHT/...
AS OF 340 PM EST FRIDAY..A LARGE SWING IN TEMPS ARE EXPECTED FROM
A COLD MORNING ON SATURDAY TO MUCH ABOVE NORMAL VALUES BY
SUNDAY...ALONG WITH A PERIOD OF LIGHT ACCUMULATING SNOWFALL. THE
COMBINATION OF STRONG LLVL WAA/FGEN FORCING FROM 850 TO
700MB...GOOD RIBBON OF RH >80%...AND SOME 5H ENERGY WL PRODUCE A
BAND OF SNOW ACRS OUR CWA ON SAT AFTN INTO SAT EVENING. SNOW
ACCUMULATIONS WL RANGE FROM A DUSTING TO 2 INCHES WITH QPF <
0.10". USING THE RH FIELDS AND COMPOSITE REFLECTIVITY PROGGS
PLACES THE SNOW BAND ACRS THE SOUTHERN SLV/WESTERN DACKS BTWN 18Z-
21Z SAT...INTO THE NORTHERN DACKS AND CPV AROUND 00Z SUNDAY...AND
IMPACTING CENTRAL/NORTHERN VT BTWN 00Z-06Z SUNDAY. SOUNDINGS SHOW
GOOD RH/OMEGA AND FAVORABLE SNOW GROWTH ALL INTERSECTING EACH
OTHER...SUPPORTING BIG FLAKE SIZE. EXPECTING ONLY A 1 TO 3 HOUR
WINDOW OF PRECIP LATE SAT AFT INTO SAT NIGHT ASSOCIATED WITH THIS
WARM FRNT FEATURE. PROGGED 85H TEMPS REMAIN BTWN -8C AND -10C ON
SAT...BUT WARM TO NEAR 0C BY 12Z SUNDAY. THIS LLVL WAA COMBINED
WITH INCREASED SOUTHWEST WINDS WL RESULT IN TEMPS WARMING
OVERNIGHT SAT INTO SUNDAY...WITH COLDEST READINGS IN THE DEEPER
VALLEYS OF CENTRAL/EASTERN VT...WHERE THE COLD AIR REMAINS
TRAPPED. WL MENTION HIGHS MAINLY IN THE 20S TO L30S ON
SATURDAY...WITH LOWS RANGING FROM THE UPPER TEENS NEK/EASTERN VT
TO NEAR 30F CPV/SLV...WITH TEMPS WARMING TWD 12Z SUNDAY. WINDS WL
INCREASE SHARPLY AFT 00Z SUNDAY...ESPECIALLY MTN SUMMITS
ASSOCIATED WITH 925MB TO 850MB JET OF 40 TO 50 KNOTS...HELPING TO
ADVECT THE WARMER AIR INTO OUR CWA.

FOR SUNDAY...THICKNESS AND LLVL TEMPS INCREASE QUICKLY UNDER BOARD
SW FLW...WHILE BEST 850 TO 500MB RH IS NORTHEAST OF OUR CWA BY 12Z.
HOWEVER...SOUNDINGS SHOW PLENTY OF MOISTURE BTWN SFC AND 850MB ON
SUNDAY...ALONG WITH WEAK UVVS FIELDS...SO THINKING AREAS OF DRIZZLE
WL BE LIKELY...WITH SOME FREEZING DRIZZLE POSSIBLE BTWN 1800 FEET
AND 2500 FT THRU 18Z SUNDAY...BEFORE ENTIRE THERMAL PROFILE WARMS
ABOVE 0C. ALSO...HIGH RESOLUTION MODEL DATA SHOWS POTENTIAL FOR COLD
AIR TO GET TRAPPED IN THE DEEPER VALLEYS OF VT ON SUNDAY
MORNING...RESULTING IN AREAS OF LIGHT FREEZING DRIZZLE. ICE
ACCUMULATION WL BE MINOR...WITH NO SIGNIFICANT IMPACTS ANTICIPATED
ATTM. TEMPS BY SUNDAY AFTN WL WARM INTO THE 40S SLV/CPV WITH
MID/UPPER LVL NEK/MTNS. A VERY WARM NIGHT EXPECTED ON SUNDAY
NIGHT...WITH TEMPS HOLDING STEADY IN MOST LOCATIONS WITH BREEZY
SOUTHWEST WINDS....AHEAD OF SHARP SFC BOUNDARY. THIS BOUNDARY WL
INCREASE THE CHCS FOR MAINLY RAIN SHOWERS AFT 06Z...ALONG WITH
FALLING TEMPS ACRS NORTHERN NY TWD 12Z MONDAY. PRECIP AMOUNTS WL BE
LIGHT ASSOCIATED WITH SFC COLD FRNT THRU 12Z MONDAY.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 340 PM EST FRIDAY...LOOKS LIKE A WEEK OF FAST-CHANGING
WEATHER. 12Z GUIDANCE SUITE IN DECENT AGREEMENT UP TO WEDNESDAY,
THEN THE GFS AND ECMWF GO THEIR OWN WAY. HAVE STUCK WITH A BLEND
FOR MONDAY-WEDNESDAY, AND LEANED A BIT MORE TOWARD THE ECMWF AFTER
THAT. RAMBLING THOUGHTS FOR EACH DAY ARE BELOW:

MONDAY: SHARP COLD FRONT WILL QUICKLY PUSH EAST OF THE FORECAST
AREA BY LATE MORNING (IF NOT A BIT EARLIER). ASSUMING WE`VE GOT
THE TIMING OF THE FRONTAL PASSAGE CORRECT, HIGH TEMPERATURES WILL
OCCUR BETWEEN 6AM-10AM, AND THEN FALL. SO EVEN THOUGH THE FORECAST
WORDS MAY SAY "HIGH OF 40", THE REALITY IS THAT MOST OF THE DAY
WILL BE IN THE 20S! COULD BE A BRIEF PERIOD OF GUSTY WINDS WITH
THE FRONTAL PASSAGE AND JUST BEHIND IT AS STRONG COLD AIR
ADVECTION COMMENCES. NOT A LOT OF MOISTURE WITH THE FRONT, BUT
SHOULD BE A FEW SHOWERS AROUND. INITIALLY RAIN SHOWERS, BUT WILL
TURN QUICKLY TO SNOW SHOWERS -- AND BY EARLY AFTERNOON BE FOCUSEDMORE
ACROSS THE HIGHER TERRAIN. PERHAPS A DUSTING IN LOWER ELEVATIONS
AND AN INCH OR SO IN THE HIGHER TERRAIN. VERY PROGRESSIVE/FAST
FLOW PATTERN. HIGH PRESSURE QUICKLY BUILDS IN OVERNIGHT AND SHOULD
RESULT IN CLEAR SKIES. THE HIGH PRESSURE DOES HAVE IT`S SOURCE IN
FAR NORTHWEST CANADA AND WILL BE ASSOCIATED WITH 925MB
TEMPERATURES OF -12 TO -18C. THIS MEANS TEMPERATURES GENERALLY IN
THE 0F TO +15F RANGE HERE AT GROUND LEVEL. BY THE WAY, THE
PRESSURE IN THE CENTER OF THAT HIGH WILL BE ABOUT 1044MB (30.82").

TUESDAY: STRONG HIGH PRESSURE BEGINS TO PUSH TO OUR EAST, BUT
KEEPS ITS INFLUENCE OVER US FOR MOST OF THE DAY. WITH 925MB
TEMPERATURES STILL IN THE -12 TO -15C RANGE, HIGHS EVERYWHERE WILL
BE SUB-FREEZING. PERHAPS JUST MID 20S FOR THE "WARMER" VALLEYS.
THIS IS ABOUT 10-12 DEGREES BELOW NORMAL. SOUTHWEST RETURN FLOW
BEGINS TUESDAY NIGHT AS THE HIGH MOVES EAST. IN GENERAL, WE`LL
PROBABLY SEE A QUICK FALL OF TEMPERATURES EARLY IN THE EVENING AND
THEN STEADY/SLOW RISE LATER AT NIGHT. TIMING OF THE RETURN FLOW
THIS FAR OUT IS QUITE DIFFICULT, SO JUST WENT WITH MODEL BLEND FOR
LOWS. SO GENERALLY 10-20F, COLDEST IN THE NORTHEAST KINGDOM.
RATHER HIGH POTENTIAL FOR TEMPERATURE BUSTS IN THIS FORECAST.

WEDNESDAY: LOW PRESSURE MOVES QUICKLY ACROSS THE GREAT LAKES WITH
A STRONG LOW LEVEL SOUTHERLY JET OF 40-50KT DEVELOPING. THIS
STRONG JET WILL BRING MUCH WARMER AIR ALOFT -- AND THUS MAKE FOR
ISSUES WITH PRECIPITATION TYPE. LIKED THE ECMWF DEPICTION OF THE
TEMPERATURES ALOFT (925MB TEMPERATURES +1 TO +3C BY 18Z), AND
THUS EXPECT INITIAL BOUT OF LIGHT SNOW TO TURN INTO A BRIEF
PERIOD OF LIGHT SLEET BEFORE TURNING INTO A BOUT OF LIGHT RAIN.
CAN`T RULE OUT SOME ISOLATED LIGHT FREEZING RAIN IN PARTS OF
EASTERN VERMONT WHERE COLD AIR REMAINS STUCK IN VARIOUS NOOKS AND
CREVICES. SURFACE PRESSURE PATTERN SHOWN BY BOTH THE ECMWF AND GFS
INDICATE THE LIKELIHOOD OF COLD AIR DAMMING DOWN ALONG THE NEW
ENGLAND COAST. ALL OF THIS TRANSITION SHOULD HAPPEN IN 6-8 HOURS
TIME. HIGHS SHOULD RANGE FROM THE MID 30S TO LOWER 40S IN THE
VALLEYS. COULD BE A LITTLE BREEZY IN THE CHAMPLAIN & ST LAWRENCE
VALLEYS WITH THE STRONG LOW LEVEL JET, BUT PRECIPITATION SHOULD
STABILIZE THE BOUNDARY LAYER AND KEEP THE STRONGEST OF THE WINDS
FROM FULLY MIXING TO THE SURFACE. THOUGH THIS WILL BE A MIX OF
WINTRY PRECIPITATION EVENT, IT DOES LOOK LIKE OVERALL
PRECIPITATION AMOUNTS WILL BE LESS THAN 1/3", SO NOT ANTICIPATING
ANYTHING MAJOR. THE "WARM UP" WILL BE SHORT LIVED. THE FAST MOVING
LOW WILL PASS BY TO OUR NORTH WEDNESDAY EVENING, DRAGGING A COLD
FRONT THROUGH. THUS TEMPERATURES FALL BACK BELOW FREEZING. ANY
REMAINING PRECIPITATION WILL END AS SNOW.

THURSDAY/FRIDAY: AS MENTIONED ABOVE, LIKED THE ECMWF SOLUTION OVER
THE GFS. IN THIS SCENARIO, ANOTHER FAIRLY STRONG (BUT ONLY 1035MB
THIS TIME) HIGH QUICKLY BUILDS IN AND PUSHES THE COLD FRONT WELL
TO THE SOUTH. LEADS TO A DRY THURSDAY, AND MOST OF FRIDAY. HOWEVER
WITH THE HIGH PUSHING EAST DURING THE DAY FRIDAY, OUR FLOW AGAIN
TURNS SOUTHERLY AND STARTS BRINGING UP THE MOISTURE FROM THE FRONT
TO THE SOUTH BY THE AFTERNOON. FOR THAT REASON, I DID PUT IN SOME
LOW POPS (20-30%) AND PAINTED IN MOSTLY CLOUDY SKIES. TO CONTRAST,
THE GFS NEVER PUSHES THAT WEDNESDAY COLD FRONT TOO FAR AWAY. THE
HIGH IT BRINGS IN FOR THURSDAY IS TO OUR NORTH, WITH SOUTHWEST
FLOW ALOFT OVERRUNNING THE FRONT RESULTING IN CLOUDS AND LIGHT
PRECIPITATION (IN THE FORM OF A WINTER MIX) THURSDAY AND FRIDAY.
LOOKING AT THE VARIOUS 12Z GFS ENSEMBLE MEMBERS, THERE WAS NOT ANY
CONSISTENCY WITH THE OPERATIONAL RUN, SO WHAT THAT ALL MEANS IS
LOW CONFIDENCE IN THE FORECAST TO END THE WEEK.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
THROUGH 12Z SUNDAY...VARIABLY CLOUDY SKIES ARE EXPECTED THROUGH
THE TAF PERIOD...BUT CEILINGS WILL PREDOMINANTLY BE VFR THROUGH
01Z SUNDAY. TRENDING OVERCAST THIS EVENING WITH SCATTERED SNOW
SHOWERS BEGINNING AFTER 01Z SUNDAY. MAJORITY OF THE ACTIVITY WILL
BE LIGHT. CARRIED 5-6SM -SHSN FOR ALL TAF SITES AT THIS POINT.
HIGH PRESSURE IN PLACE PROVIDING LIGHT AND VARIABLE WINDS TO
START THE PERIOD. SURFACE HIGH DRIFTS EAST OF NEW ENGLAND THIS
EVENING AND OVERNIGHT WITH INCREASING SOUTHERLY GRADIENT WINDS
EXPECTED DURING THE OVERNIGHT PERIOD. LOCALIZED CHANNELING IN THE
CHAMPLAIN VALLEY WILL BRING SOUTH WINDS AROUND 15-18 KTS WITH
GUSTS 25-30 KTS AT BTV AFTER 03Z SUNDAY.

OUTLOOK 12Z SUNDAY THROUGH WEDNESDAY...GENERALLY VFR DURING SUNDAY
AND EARLY SUNDAY NIGHT. A COLD FRONT SHIFTING EWD ACROSS THE AREA
06-12Z MONDAY COULD BRING MVFR SCATTERED RAIN SHOWERS...PERHAPS
ENDING AS LIGHT SNOW SHOWERS OR FLURRIES MONDAY MORNING (BEST
CHANCE OF ANY SNOW SHOWERS WILL BE AT SLK/MPV MONDAY MORNING).
HIGH PRESSURE RETURNS BRINGING GENERALLY VFR WEATHER CONDITIONS
18Z MONDAY THROUGH 06Z WEDNESDAY. NEXT WARM FRONTAL BOUNDARY
BRINGS A CHANCE OF RAIN OR SNOW SHOWERS 06Z WED THROUGH 00Z
THURSDAY...WITH INTERVALS OF MVFR CONDITIONS POSSIBLE. THE
MAJORITY OF THIS ACTIVITY IS EXPECTED TO BE LIGHT.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...NONE.
NY...NONE.

&&

$$
SYNOPSIS...TABER
NEAR TERM...JMG
SHORT TERM...TABER
LONG TERM...NASH
AVIATION...BANACOS


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