FXUS61 KBTV 231944
AFDBTV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
244 PM EST WED DEC 23 2009
.SYNOPSIS...
A SLOW-MOVING UPPER LEVEL DISTURBANCE CENTERED OVER VERMONT THIS
AFTERNOON WILL BRING ADDITIONAL PERIODS OF LIGHT SNOW THIS EVENING
BEFORE GRADUALLY ENDING. AN ADDITIONAL INCH OR SO OF SNOW
ACCUMULATION IS POSSIBLE ACROSS THE ADIRONDACKS AS WELL AS
NORTHWESTERN AND NORTH-CENTRAL VERMONT. THE UPPER DISTURBANCE WILL
SHIFT SOUTHEAST OF THE AREA YIELDING DRIER AND MILDER CONDITIONS
FOR CHRISTMAS EVE DAY AND CHRISTMAS DAY...WITH VALLEY HIGHS IN THE
LOW TO MID 30S. THE NEXT WEATHER SYSTEM APPROACHES LATE FRIDAY
NIGHT AND SATURDAY WITH A WINTRY MIX AND GUSTY WINDS EXPECTED.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 239 PM EST WEDNESDAY...INTERESTING WX PATTERN CONTINUES WITH
THE NORTH COUNTRY AFFECTED BY ATLANTIC MOISTURE PLUME EXTENDING
FROM SOUTHEAST OF THE CANADIAN MARITIMES WWD INTO OUR REGION.
THERE IS ALSO A SLOW MOVING UPPER LOW OVER VT THIS
AFTERNOON...WITH ASSOCIATED CYCLONIC FLOW AIDING IN THE WESTWARD
TRANSPORT OF MOISTURE FROM THE CANADIAN MARITIMES.
MID-LEVEL VORT AXIS OVER VT HAS SETTLED ONLY VERY SLOWLY SWD DURING
THE PAST SEVERAL HRS. THERE IS AN AXIS OF DRIER AIR WHICH HAS
WRAPPED IN ACROSS NRN VT...WITH PRIMARY MOIST CONVEYOR BELT A BIT
FURTHER NORTH - EXTENDING FROM THE CROWN OF MAINE WWD ACROSS SRN
QUEBEC INTO THE ST. LAWRENCE VALLEY. WE EXPECT A LULL IN THE LIGHT
SNOW ACTIVITY THRU 22Z...HOWEVER...PROBABLY ONE MORE BURST OF SNOW
ACROSS THE NRN ADIRONDACKS AND NWRN/N-CENTRAL VT BETWEEN 22-04Z AS
WRAPAROUND MOIST AXIS SHIFTS ACROSS OUR REGION. SNOW ACCUMULATIONS
FROM A DUSTING TO 2 INCHES ARE POSSIBLE 22-04Z ACROSS THE NRN
ADIRONDACKS...CENTRAL/NRN CHAMPLAIN VLY...AND THE GREEN MOUNTAINS
BEFORE ENDING. PRECIPITATION SHADOWING ACROSS THE VALLEYS OF
RUTLAND/WINDSOR COUNTIES SHOULD YIELD LITTLE OR NO ACCUMULATION.
LOOKING AT MODEL SOUNDINGS...AS WAA CONTINUES FROM THE NORTH AND
NORTHEAST...VERTICAL TEMPERATURE PROFILES BECOME MORE FAVORABLE FOR
A BRIEF PERIOD OF FREEZING DRIZZLE AS PRECIP ENDS AROUND MIDNIGHT OR
SHORTLY THEREAFTER. HAVE INCLUDED THIS POSSIBILITY IN THE
GRIDS...BUT AMTS WILL BE EXTREMELY LIGHT AND TRAVEL CONDITIONS
SHOULDN/T CHANGE APPRECIABLY. OVERALL...EXPECT SOME MINOR TRAVEL
DELAYS AS A FUNCTION OF SOME SNOW COVERED ROADS AND PERIODS OF
LOWER VISIBILITY IN SNOW THRU MIDNIGHT.
SKIES REMAIN MOSTLY CLOUDY TO CLOUDY LATE THIS AFTN THROUGH TONIGHT.
SURFACE TEMPERATURES SHOULD ACTUALLY SLOWLY RISE AS THERMAL LOW
ALOFT DEPARTS TO THE SOUTHEAST. THIS IS CAPTURED IN THE MOS
GUIDANCE...WITH TEMPS REACHING THE LOW 20S IN THE CHAMPLAIN VALLEY
BY 12Z THURSDAY...AND UPR TEENS ELSEWHERE. WINDS WILL GENERALLY BE
NW AT 5-10 MPH.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 239 PM EST WEDNESDAY...SKIES WILL BE MOSTLY CLOUDY TO START THE
DAY THURSDAY WITH LOW-LEVEL INVERSION AND MOISTURE IN PLACE...BUT
ANTICIPATE INCREASING SUNNY BREAKS BY THE AFTN. MID-LEVEL HEIGHTS
BEGIN TO RISE IN EARNEST AFTER 18Z AS RIDGE AXIS SFC AND ALOFT
BEGINS TO SHIFT EWD INTO THE NORTH COUNTRY. LOOKING AT 850MB TEMPS
MODERATING TO -1C TO -2C BY AFTN...AND WITH PARTIAL SUNSHINE
SHOULD SEE HIGH TEMPS IN THE VALLEYS AROUND 32 TO 35F ON THURSDAY.
THE LAST TIME KBTV WAS ABOVE FREEZING WAS DECEMBER 15TH...SO THIS
WILL BE A WELCOME BREAK FOLLOWING 8 CONSECUTIVE DAYS BELOW NORMAL.
SHOULD BE A NICE WINTER DAY WITH LIGHT WIND CONDITIONS.
TEMPERATURES SHOULD FALL BACK INTO THE TEENS THURSDAY NIGHT UNDER
MOSTLY CLEAR SKIES AND LIGHT AND VARIABLE WINDS. A FEW UPPER
SINGLE DIGIT LOWS ARE POSSIBLE ACROSS FAR NERN VT.
WEATHER REMAINS NICE ON CHRISTMAS DAY WITH SURFACE RIDGE AXIS
SHIFTING EWD ACROSS NEW ENGLAND AND RELATIVELY DRY DEEP-LAYER
CONDITIONS. DO NOT ANTICIPATE ANY PRECIPITATION. WINDS WILL AGAIN BE
LIGHT WITH MOSTLY SUNNY SKIES THROUGH AT LEAST EARLY TO MID
AFTERNOON...WITH INCREASING CLOUDS LATE - MAINLY ACROSS NRN NY. HIGH
TEMPERATURES WILL BE IN THE MID 30S IN MOST LOCATIONS.
WEATHER BECOMES MORE INTERESTING AGAIN DURING FRIDAY NIGHT AS
OCCLUDED FRONTAL BOUNDARY APPROACHES FROM THE SOUTHWEST. SHOULD
START TO SEE SOME GUSTY SOUTHEASTERLY WINDS 20-30 MPH BY DAYBREAK
ACROSS THE HIGHER TERRAIN AND ALONG THE WESTERN SLOPES OF THE GREEN
MTNS AS PRESSURE GRADIENT INCREASES. FOLLOWED SREF POPS BRINGING
INCREASING POPS ACROSS THE REGION OVERNIGHT...FROM SW-NE. THERMAL
PROFILES SUPPORT ONLY A BRIEF PERIOD OF SNOW AT THE ONSET...THEN A
MIX OF SLEET AND POSSIBLE FREEZING RAIN DEVELOPING ACROSS ST.
LAWRENCE/FRANKLIN COUNTIES IN NRN NY BY 12Z SATURDAY. DETAILS ARE
STILL PENDING...BUT THOSE WITH TRAVEL PLANS DURING THE PRE-DAWN
HOURS SATURDAY - ESPECIALLY ACROSS NRN NY - SHOULD CHECK FOR UPDATED
FORECASTS DUE TO POSSIBLE WINTRY TRAVEL CONDITIONS. POPS ARE ONLY IN
THE 25-40 PERCENT RANGE ACROSS VERMONT BETWEEN 06-12Z SATURDAY. LOW
TEMPERATURES FRIDAY NIGHT WILL VARY WIDELY FROM EAST TO WEST...WITH
LOWS IN THE MID TEENS ACROSS THE NORTHEAST KINGDOM AND RANGING UP TO
THE MID 20S FROM THE CHAMPLAIN VALLEY WESTWARD.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 239 PM EST WEDNESDAY...COMPLEX WX THEN AFFECTS AREA SATURDAY
INTO SATURDAY NIGHT AS WARM/OCCLUDED FRONTAL BNDRY PUSHES SLOWLY
NORTHEASTWARD ACROSS THE AREA. WITH FAVORABLE WIND FIELDS AND
DECENT DYNAMICAL SUPPORT HAVE OPTED TO RAISE POPS INTO THE
CATEGORICAL RANGE HERE...WHICH SEEMS REASONABLE GIVEN SUCH GOOD
MODEL CONSISTENCY OVER TIME. LATEST LOOK AT TEMP PROFILES FROM THE
NEAR SFC LYR TO 850 MB SHOWING PRONOUNCED WARMING ON THE HEELS OF
ROBUST 50-70 KT SERLY FLOW AT MID LVLS AND BASED ON THESE TYPES OF
SETUPS HISTORICALLY...SEE NO REASON TO DISCOUNT ATTM. THUS EXPECT
MOST PCPN SHOULD FALL IN MIXED FORM ACROSS ERN VT/NRN SLV DURING
THE PERIOD...WITH LITTLE IN THE WAY OF SNOW ACCUM AND A TRANSITION
TO RAIN ACROSS THE DACKS/SRN SLV/CHVLY THROUGH THE DAY ON
SATURDAY. PCPN AMOUNTS LIKELY TO MIMIC PATTERN IN MODERATE TO
STRONG SERLY FLOW EVENTS...WITH HIGHEST TOTALS ALONG THE ERN
SLOPES OF THE SRN GREENS AND ACROSS THE SLV...WITH LESSER AMNTS
ELSEWHERE DUE TO SHADOWING EFFECTS. THAT SAID...SOME LIGHT ICING
CONCERNS CERTAINLY POSSBL HERE...ESP IN ERN VT AND MORE
SPECIFICALLY IN NRN SLV WHERE LL PRESSURE-DRIVEN CHANNELING
EFFECTS WILL LIKELY KEEP COLDER NERLY FLOW LOCKED IN. HAVE
ATTEMPTED TO TREND TEMP PROFILES CLOSER TO RAW AND/OR BIAS
CORRECTED MODEL NUMBERS...SHOWING A NON-DIURNAL TREND AS MAX TEMPS
OCCUR LATE IN THE DAY ON SATURDAY...THEN HOLD NEARLY STEADY
OVERNIGHT...ESP EAST.
BY SUNDAY SFC COLD FRONT CROSSES THE AREA AS MID LVL TEMPS DROP
SHARPLY UNDER STRONG COLD AIR ADVECTION. HIGHS SHOULD OCCUR
RELATIVELY EARLY IN THE DAY BEFORE HOLDING STEADY OR SLOWLY FALLING
THROUGH TIME. HAVE MAINTAINED AT LEAST A CHC FOR SHSN HERE...BUT
OVERALL TREND WILL BE TOWARD DRIER CONDS THROUGH TIME. THEN MAINLY
CLOUDY AND SEASONABLY COOL SUNDAY NIGHT UNDER NEUTRAL ADVECTION
ALONG WITH A FEW SHSN...ESP NRN MTNS.
THEREAFTER...MEDIUM RANGE SOLNS COMING INTO BROAD AGREEMENT SHOWING
SHARP UPPER TROUGH AND ATTENDANT ARCTIC FRONTAL BNDRY TO DIG RAPIDLY
SOUTHWARD INTO THE NORTHEAST LATER MONDAY INTO MONDAY NIGHT. THIS
FEATURE WILL LIKELY BE ACCOMPANIED BY A BROAD INCREASE IN SHSN
AND/OR POSSBL SQUALLS...ESP DURING TROUGH/FRONTAL PASSG. PRIMARY WX
HIGHLIGHT THOUGH WILL BE A RETURN TO MUCH COLDER TEMPS BY LATER
MONDAY NIGHT INTO TUESDAY AS VALUES FALL TO SOME 15-20 DEG BELOW
NORMAL ON GUSTY NWRLY WINDS. THEN MAINLY DRY AND SEASONABLY COLD BY
NEXT WEDNESDAY AS SFC HIGH PRESSURE BUILDS EASTWARD.
&&
.AVIATION /20Z 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
MVFR CIGS/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...BANACOS
NEAR TERM...BANACOS
SHORT TERM...BANACOS
LONG TERM...JMG
AVIATION...JMG
