FXUS61 KBTV 230934
AFDBTV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
434 AM EST WED DEC 23 2009
.SYNOPSIS...
MOISTURE ROTATING AROUND AN UPPER LOW WILL BRING LIGHT SNOW TO THE
NORTH COUNTRY TODAY AND EARLY TONIGHT. 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 434 AM EST WEDNESDAY...AN UPPER LOW OVER NORTHERN NEW
ENGLAND WILL MOVE SOUTH TODAY AND BE SOUTH OF THE REGION EARLY
TONIGHT. MOISTURE FROM THE CANADIAN MARITIMES WILL CONTINUE TO
WRAP AROUND THIS CLOSED UPPER LOW AND WILL MOVE SOUTH INTO THE
REGION FROM QUEBEC TODAY. AS THIS LOW MOVES SOUTH TODAY AND TAKES
ITS COLD POOL OF AIR ALOFT WITH IT...THE 1000-500 MB THICKNESS
VALUES INCREASE THIS AFTERNOON...WHICH INDICATES SOME WARM
ADVECTION ALOFT. THIS IS SHOWN IN THE BUFKIT FORECAST SOUNDINGS AS
WELL. SO WILL SEE SOME WARM ADVECTION SNOWS TODAY. HAVE GONE WITH
A BLEND OF THE NAM AND GFS MOS POPS FOR TODAY...AND HAVE GONE
LIKELY POPS IN MOST LOCATIONS. MAINLY OVER THE ADIRONDACKS AND
GREEN MOUNTAINS...AND ALSO THE VERMONT SIDE OF THE CHAMPLAIN
VALLEY. LIKELY WILL SEE SOME MOISTURE OFF OF LAKE CHAMPLAIN TODAY
AS WINDS WILL BE FROM THE WEST AND NORTHWEST...SO THAT IS WHY WE
WENT WITH LIKELY POPS ON THE VERMONT SIDE OF LAKE CHAMPLAIN. GIVEN
THE COLD TEMPERATURES OVER THE REGION TODAY...HAVE GONE WITH A 20
TO 1 SNOW RATIO FOR DETERMINING SNOWFALL AMOUNTS FOR TODAY. GFS
MOS MAX TEMPERATURES LOOK A LITTLE TOO WARM TODAY...SO HAVE GONE A
DEGREE OR TWO BELOW THIS GUIDANCE.
&&
.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 /09Z WEDNESDAY THROUGH SUNDAY/...
THROUGH 06Z THURSDAY...WITH AN UPPER LOW MOVING OVER THE REGION
DURING THE FORECAST PERIOD...CONDITIONS WILL RANGE FROM VFR DOWN
TO IFR AT TIMES. THIS WILL BE DUE TO CEILINGS RANGING FROM
BKN015-050 AND VISIBILITY RANGING FROM P6SM DOWN TO 1SM AT TIMES
IN LIGHT TO MODERATE SNOWFALL...ESPECIALLY BEFORE 21Z THIS
AFTERNOON. WINDS WILL BE WNW 5-10KTS BECOMING LIGHT AND VARIABLE
BY 00Z THURSDAY.
OUTLOOK...06Z THURSDAY THROUGH SUNDAY...
06Z THURS THRU 12Z THUR...DEVELOPING VFR CONDITIONS BY 00Z THURS AT
ALL TAF SITES...MAYBE A BRIEF PERIOD OF MVFR CONDITIONS AT
SLK/BTV/MPV BTWN 00Z-04Z THURS.
12Z THUR THRU 12Z SAT...MAINLY VFR W/HIGH PRESSURE. SOME LIGHT PCPN
ENCROACHING FROM THE SW LATE IN THE PERIOD.
12Z SAT THRU 00Z SUN...VFR W/OCCNL MVFR/IFR IN SNOW AND/OR MIXED
PCPN AS OCCLUDED FRONT CROSSES AREA.
00Z SUNDAY THROUGH 00Z MONDAY...MAINLY VFR THOUGH WITH OCCNL MVFR IN
MTN SHSN...NAMELY AT THE KSLK TERMINAL.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...NONE.
NY...NONE.
&&
$$
SYNOPSIS...WGH
NEAR TERM...WGH
SHORT TERM...WGH
LONG TERM...JN
AVIATION...JN/TABER
