FXUS61 KBTV 231734
AFDBTV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
1234 PM EST WED DEC 23 2009
.SYNOPSIS...
MOISTURE ROTATING AROUND AN UPPER LOW WILL BRING PERIODS OF SNOW
TO THE NORTH COUNTRY TODAY AND EARLY TONIGHT. HIGHEST SNOWFALL
ACCUMULATIONS WILL BE ACROSS NORTHWESTERN VERMONT INTO THE CENTRAL
AND NORTHERN GREEN MOUNTAINS. A RIDGE OF HIGH PRESSURE WILL BUILD
SOUTH FROM CANADA ON THURSDAY AND WILL REMAIN OVER THE REGION
THROUGH CHRISTMAS DAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 924 AM EST WEDNESDAY...SLOW-MOVING UPPER LOW IS CENTERED
ACROSS N-CENTRAL VT AT 14Z WITH CONVEYOR OF MOISTURE EXTENDING
FROM THE CANADIAN MARITIMES AROUND THE NORTH SIDE OF THE UPPER LOW
INTO THE NORTH COUNTRY. CONVEYOR OF MOISTURE IS ALSO ASSOCIATED
WITH A WARM ADVECTION REGIME COMING IN FROM THE NORTH.
KCXX AT 1420Z SHOWS WAVES OF VARIABLE REFLECTIVITY MOVING FROM
NORTH TO SOUTH...ASSOCIATED WITH VARIABLE INTENSITY SNOWFALL.
MODEL SOUNDINGS REMAIN FAVORABLE FOR GOOD DENDRITE SNOW GROWTH
WITH DEEP SATURATED LAYER ON GFS SOUNDING THRU -12 TO -18C LAYER
THRU ABOUT 21Z BEFORE WARMING OUT OF OPTIMAL SNOW GROWTH ZONE.
PERIODS OF SNOW WILL CONTINUE...ESPECIALLY ACROSS THE CHAMPLAIN
VALLEY INTO THE WESTERN SLOPES OF THE GREEN MTNS WITH FAVORABLE
UPSLOPE REGIME IN PLACE. FORESEE AN ADDITIONAL 2 TO 3 TO PERHAPS 4
INCHES IN SPOTS FOR NWRN VT INTO THE CENTRAL AND NRN GREENS.
AN ADDITIONAL 1 TO 3 INCHES IS EXPECTED ACROSS THE NORTHERN
ADIRONDACKS AND AREAS OF CENTRAL/NRN VT EAST OF THE GREEN MTNS.
LESSER AMTS ARE EXPECTED IN THE SOUTHERN VALLEY OF RUTLAND AND
WINDSOR COUNTY...WITH GENERALLY A DUSTING TO 2 INCHES EXPECTED
THERE. LONG DURATION EVENT...BUT THERE ARE SLICK SPOTS AND AREAS
OF REDUCED VISIBILITY. HAVE EMPHASIZED THIS IN RECENTLY ISSUED
SPECIAL WEATHER STATEMENT.
HIGHS TODAY WILL GENERALLY BE IN THE UPPER TEENS TO NEAR
20F...EXCEPT LOW TEENS IN THE NRN ADIRONDACKS AND FAR NERN VT.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
AS OF 434 AM EST WEDNESDAY...4 KM WRK MODEL SHOWING SOME UPSLOPE
SNOW WILL PERSIST ACROSS THE WESTERN SLOPES OF THE GREEN MOUNTAINS
AND THE ADIRONDACKS...SO HAVE GONE WITH LIKELY POPS OVER THE
WESTERN SLOPES OF THE GREEN MOUNTAINS. LOOKS LIKE MIN TEMPERATURES
WILL OCCUR EARLY WEDNESDAY NIGHT...AS MOS GUIDANCE SHOWING THESE
TEMPERATURES WILL SLOWLY INCREASE OVERNIGHT. A RIDGE OF HIGH
PRESSURE WILL BUILD SOUTH FROM CANADA ON THURSDAY AND WILL REMAIN
THROUGH CHRISTMAS DAY...WITH FAIR AND DRY WEATHER EXPECTED. GFS
MOS MAX TEMPERATURES LOOK A BIT TOO WARM...SO HAVE GONE ABOUT 2
DEGREES LOWER THAN THIS GUIDANCE.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 400 AM EST WEDNESDAY...MAIN WEATHER FEATURE IN THE EXTENDED
WILL BE A BROAD...SLOW MOVING LOW PRESSURE SYSTEM AND ITS
ASSOCIATED FRONTAL BOUNDARY...THAT SETS UP OVER THE CENTRAL PLAINS
FRIDAY NIGHT. HIGH PRESSURE BLOCKING PATTERN OVER THE EAST COAST
STALLS THE APPROACH OF THIS SYSTEM. SOUTH WINDS AHEAD OF THE FRNT
WILL ALLOW FOR WAA TO WORK INTO THE REGION ON SATURDAY. 850 TEMPS
COULD REACH INTO THE +1C(NORTH) TO +5C(SOUTH) RANGE. THIS IS GOING
TO SET UP A POTENTIAL MIXED PRECIP SITUATION FOR MUCH OF THE CWA
SAT INTO SUN. WILL CONTINUE FORECAST TREND OF -SW AT THE
ONSET...MIXING WITH/CHANGING TO -RW IN SPOTS AS WARMER AIR GETS
SFC TEMPS ABV FREEZING...THEN BACK TO -SW ON BACKSIDE OF SYSTEM AS
COLDER AIR RETURNS ON WNW FLOW. POTENTIAL FOR EVEN SOME
SLEET/FREEZING RAIN TO WORK INTO COLDER SPOTS OF E VT/DACKS. WILL
LEAVE OFF FOR NOW AND LET LATER SHIFTS GET UPDATED DATA ON TRACK
OF SFC LOW. FURTHER STALLING COULD NEGATE SOME CD AIR AT THE SFC
IN SPOTS DUE TO PROLONGED EXPOSURE TO WARM AIR SURGE W/ SFC HIGHS
REACHING INTO THE 30S IN MOST SPOTS. AXIS OF QPF WILL SLOW TRUDGE
THRU THE CWA LATE SATURDAY INTO SUNDAY AFTNOON. HAVE ADJUSTED POPS
TO SHOW MVMNT OF FRNT THRU THE CWA. W/ SFC LOW HANGING BACK SO FAR
OVER THE CENTRAL PLAINS...SOME DRIER AIR WILL WORK INTO THE MIX
AND HELP TO SHUT DOWN -SW. SUNDAY NIGHT INTO MONDAY AFTERNOON
SURFACE LOW CONTINUES TO SLOWLY MOVE EAST OVER SOUTHERN
ONTARIO...W/ MDLS PUTTING CWA UNDER WEST FLOW THAT WILL CONTINUE
-SW...MAINLY OVER HIR TRRN. BY MIDDAY MONDAY...A SECONDARY
FRNT/TROUGH SETS UP ALONG SOUTHERN CANADIAN BORDER AND PIVOTS THRU
THE NORTHEAST BEHIND UPPER TROUGH...WHICH EXITS OFFSHORE. MOST
PRECIP HERE WILL BE FROM UPSLOPE/OROGRAPHIC EFFECTS DUE TO LACK OF
QPF. SOME LK EFFECT POSSIBLE BFR WINDS SHIFT TO THE NNW BEHIND
FRNT.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
THROUGH 18Z THURSDAY...MOIST MARITIME FLOW WRAPPING SOUTHWARD ACROSS
THE AREA OVER THE NEXT 24 HOURS SHOULD ENSURE OCCNL LIGHT SNOW AND
MVFRCIGS/VSBYS AT NORTHERN TERMINALS THROUGH 06Z THURSDAY. SOME
PATCHY FZDZ ALSO POSSIBLE DURING THE 04-09Z TIME FRAME. DEVELOPMENT
OF SHARP LOW LEVEL INVERSION WILL LIKELY ALLOW WIDESPREAD MVFR TO
OCCNL IFR CIGS TO CONTINUE AFTER 12Z THURSDAY...THOUGH WITH ANY
LINGERING LIGHT PCPN ENDING. WINDS TO GENERALLY BE LESS THAN 10
KNOTS FROM THE WEST TO NORTHWEST TODAY...TRENDING NORTHWEST TO NORTH
AFTER 00Z.
OUTLOOK...18Z THURSDAY THROUGH MONDAY...
18Z THUR THRU 12Z SAT...MAINLY VFR W/HIGH PRESSURE. SOME LIGHT PCPN
ENCROACHING FROM THE SW LATE IN THE PERIOD.
12Z SAT THRU 12Z SUN...VFR W/OCCNL MVFR/IFR IN SNOW AND/OR MIXED
PCPN AS OCCLUDED FRONT CROSSES AREA.
12Z SUNDAY THRU 00Z MONDAY...MAINLY VFR THOUGH WITH OCCNL MVFR IN
MTN SHSN...NAMELY AT THE KSLK TERMINAL.
00Z MONDAY THRU 00Z TUE...VFR W/OCCNL MVFR/IFR IN SHSN AS UPPER LOW
AND STRONG COLD FRONT AFFECT THE REGION.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...NONE.
NY...NONE.
&&
$$
SYNOPSIS...WGH
NEAR TERM...BANACOS
SHORT TERM...WGH
LONG TERM...JN
AVIATION...JMG
