FXUS61 KBTV 230001
AFDBTV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
701 PM EST TUE DEC 22 2009
.SYNOPSIS...
MOISTURE FROM THE CANADIAN MARITIMES WILL INTERACT WITH AN UPPER
LEVEL DISTURBANCE MOVING SOUTHEASTWARD ACROSS THE NORTH COUNTRY TO
BRING A PROLONGED PERIOD OF LIGHT SNOW TO NORTHERN VERMONT TONIGHT
THROUGH WEDNESDAY NIGHT. TEMPERATURES WILL REMAIN BELOW NORMAL
THROUGH WEDNESDAY...AND THEN MODERATE TO AROUND FREEZING FOR HIGHS
THURSDAY UNDER MAINLY SUNNY SKIES. THE NEXT CHANCE FOR PRECIPITATION
ARRIVES LATE FRIDAY NIGHT INTO SATURDAY.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
AS OF 701 PM EST TUESDAY...ALREADY SEEING FIRST SURGE OF WRAP
AROUND MOISTURE MOVING INTO NORTHERN VERMONT TONIGHT AND ALONG
WITH LOW LEVEL NORTH TO NORTHWEST FLOW...AREAL COVERAGE OF LIGHT
SNOW HAS INCREASED ACROSS THE CHAMPLAIN VALLEY. THE DEEPER
MOISTURE AND MORE FAVORABLE WARM AIR ADVECTION ARE STILL NORTH OF
THE BORDER AND WILL NOT IMPACT THE AREA UNTIL LATER TONIGHT. AS A
RESULT...HAVE UPDATED THE FORECAST TO MENTION CATEGORICAL SNOW
CHANCES OVER MUCH OF NORTHERN VERMONT...INCLUDING THE CHAMPLAIN
VALLEY. SHOULD SEE 1-3 OR 2-4 INCHES OF SNOW ACROSS NORTHERN
VERMONT BY MORNING. HAVE UPDATED THE FORECAST TO REFLECT THE
BETTER CHANCES FOR SNOW AND ACCUMULATIONS TONIGHT. REST OF
FORECAST REMAINS UNCHANGED AT THIS TIME.
PREVIOUS DISCUSSION...
AS OF 222 PM EST TUESDAY...AN INTERESTING WEATHER SCENARIO EXPECTED
TONIGHT AND WEDNESDAY. UPPER LOW OVER THE OTTAWA VALLEY/SERN
ONTARIO THIS AFTERNOON WILL CONTINUE TO SHIFT SLOWLY
SOUTHEASTWARD...AND WILL BE CENTERED EAST OF THE CT RIVER VALLEY
BY 12Z WEDNESDAY. THE UPPER LOW ITSELF IS NOT ASSOCIATED WITH MUCH
IN THE WAY OF PRECIPITATION. HOWEVER...INTERACTION OF ATLANTIC
MOISTURE AND ELY 700MB FLOW ACROSS NRN MAINE AND SRN QUEBEC WILL
EVENTUALLY WRAP AROUND THE UPPER LOW AND SWWD INTO THE NORTH
COUNTRY OVERNIGHT. DEFORMATION BAND AND ASSOCIATED 1-3SM LIGHT
SNOW OCCURRING AT 19Z ACROSS FAR N-CENTRAL/NERN VT WILL REMAIN
STATUS QUO UNTIL AROUND 04Z TONIGHT. THEREAFTER...DO EXPECT THE
CLEAR SKIES FROM BTV SWD TO BE REPLACED BY INCREASING CLOUDS WITH
WRAPAROUND FROM THE NORTH AND DEVELOPMENT OF LIGHT SNOW ACTIVITY
OVERNIGHT. BASED ON NAM AND GFS MODEL SOUNDINGS...ACTUALLY SHOULD
SEE LOW-LEVEL WAA FROM THE NORTH AND EAST AS CLOSED UPR LOW
PASSES. SOME SIMILARITIES TO THE MARCH 4 2006 CASE WHERE
OROGRAPHIC BLOCKING AND LOW INVERSION HEIGHT NEAR RIDGE TOP LEVEL
CAUSED SIGNIFICANT SNOWFALL ACROSS THE ERN CHAMPLAIN VALLEY AND
WRN SLOPES OF THE GREEN MTNS. MOISTURE AND DENDRITE GROWTH NOT
QUITE AS OPTIMAL LATE TONIGHT/WEDNESDAY AS THAT EVENT...BUT DO
EXPECT SOME OROGRAPHIC ENHANCEMENT BEGINNING AFTER MIDNIGHT
TONIGHT AND CONTINUING THROUGH MOST OF WEDNESDAY ACROSS THE
CENTRAL/NRN GREEN MTNS AND ADJACENT WRN SLOPES. POPS REFLECT
OROGRAPHIC NATURE OF SNOW TONIGHT...WITH 70-80 POPS NEAR THE NRN
GREENS AND ONLY AROUND 20 PERCENT IN THE VALLEYS OF WRN RUTLAND
COUNTY AND ERN WINDSOR COUNTY. SNOW RATIOS SHOULD BE
LARGE...ASSUMING 20:1 TO GET SNOWFALL AMTS OF 2-5" THROUGH 00Z THU
ACROSS THE CENTRAL/NRN GREENS AND LOCALLY TO 6" NEAR JAY PEAK. IN
THE CHAMPLAIN VALLEY...NOT MUCH ON THE NY SIDE BUT 1-3" POSSIBLE
FROM BTV EWD INTO THE FOOTHILLS. LIKEWISE...EXPECTING 1-3" IN THE
NRN ADIRONDACKS...FURTHER REMOVED FROM BETTER ADVECTION OF
ATLANTIC MOISTURE. BEST POTENTIAL - BUT STILL LIGHT SNOW -
ANTICIPATED FROM 06Z TONIGHT THROUGH 18Z THURSDAY. BECAUSE TOTAL
SNOWFALL AMOUNTS ARE STRETCHED OUT OVER A 24 HR PERIOD...RATES AND
AMTS BECOME TOO MARGINAL TO WARRANT A SNOW ADVISORY.
ALSO...DRY/POWDERING NATURE OF THE SNOW TENDS TO MITIGATE TRAVEL
IMPACTS. WILL HIGHLIGHT IN THE HAZARDOUS WEATHER OUTLOOK FOR NOW
AND MENTION CENTRAL/NRN GREENS AND WEST SLOPES AS HIGHEST SNOWFALL
POTENTIAL.
LOWS TONIGHT WILL GENERALLY BE IN THE 0 TO 10F RANGE...AND REBOUND
INTO THE LOWER 20S FOR HIGHS TOMORROW.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
AS OF 222 PM EST TUESDAY...CLOSED 500MB LOW OVER ERN MA AT 00Z THURSDAY
SHIFTS SOUTHEAST OF NEW ENGLAND WITH MID-LEVEL HEIGHT RISES NOTED
OVER OUR FORECAST AREA DURING WEDNESDAY NIGHT. A HIGHLY AMPLIFIED
RIDGE AXIS AT THE SFC AND ALOFT BUILDS OVER THE NORTH COUNTRY
DURING THURSDAY AND THURSDAY NIGHT. LOOKING FOR MTN SNOW SHOWER
ACTIVITY ACROSS THE NRN ADIRONDACKS AND NRN VT TO GENERALLY COME
TO AN END DURING WEDNESDAY NIGHT. AN ADDITIONAL DUSTING TO AN INCH
IS POSSIBLE ACROSS NRN AREAS MAINLY BEFORE MIDNIGHT...WITH JUST A
FEW FLURRIES THEREAFTER AS MID-LEVEL SUBSIDENCE INCREASES IN
EARNEST. WITH CORE OF COLDEST MID-LEVEL TEMPERATURES SHIFTING EAST
OF NEW ENGLAND...THURSDAY MORNING LOWS SHOULDN/T BE QUITE AS COLD
WITH LOWS MAINLY IN THE TEENS.
SKIES SHOULD BECOME PARTLY TO MOSTLY SUNNY ON THURSDAY WITH THE
DEEP-LAYER RIDGE MOVING INTO PLACE. LOOKING AT 850MB TEMPS ALSO
MODERATING TO AROUND -2C BY AFTN...AND WITH SUNSHINE SHOULD SEE HIGH
TEMPS IN THE VALLEYS AROUND 32F ON THURSDAY. 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.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 222 PM EST TUESDAY...PRIMARY FOCUS DURING EXTENDED PORTIONS OF
FCST WILL BE BROAD SCALE LIFT AND ASSOC PCPN ASSOC W/OCCLUDED
FRONTAL BNDRY PUSHING NORTHEASTWARD ACROSS THE AREA SAT/SAT NIGHT.
PRIOR TO THIS HIGH PRESSURE WILL BE IN THE PROCESS OF SLOWLY
RETREATING EASTWARD DURING FRI/FRI NIGHT UNDER INCREASING
SOUTH/SOUTHEASTERLY FLOW. WILL KEEP THINGS MAINLY DRY HERE WITH
AMPLE SUN FRIDAY GIVING WAY TO INCREASING CLOUDS FRI NIGHT. WILL
MAINTAIN PRIOR FCSTS IDEA OF CHC POPS LATER FRIDAY NIGHT ACROSS
OUR SWRN ZONES AS FRONTAL BNDRY APPROACHES...BUT MOST AREAS SHOULD
REMAIN ESSENTIALLY DRY OVERNIGHT. MOS GUIDE MINS TOO COOL
HERE...TYPICAL IN NOCTURNAL RETURN FLOW REGIMES AND HAVE LEANED
CLOSER TO RAW GFS MODEL OUTPUT HERE.
FRONTAL ZONE THEN PUSHES UP AND ACROSS THE REGION SAT/SAT NIGHT WITH
WIDESPREAD ALBEIT FAIRLY LIGHT PCPN. PCPN LIKELY TO BEGIN AS A
PERIOD OF SNOW...THOUGH WITH SUCH STRONG SOUTH/SERLY WIND FIELDS
ALOFT (50-70 KT) HARD TO SEE THAT THIS WILL BE ANYTHING BUT BRIEF AS
MILDER AIR RUSHES IN ALOFT. THUS WILL ADVERTISE PCPN CHARACTER
TRANSITIONING TO A MIX AND/OR LIGHT RAIN BY LATER IN THE DAY ON
SATURDAY INTO SATURDAY NIGHT BEFORE COLDER AIR PUSHES IN FROM THE
WEST TOWARD SUNDAY MORNING. TEMPS TO HOLD RELATIVELY MILD THROUGH
THE OVERNIGHT HOURS...THEN AS ALLUDED TO ABOVE BEGIN TO FALL LATE.
COULD ALSO SEE A FEW GUSTS IN THE 35-45 MPH RANGE ALONG FAVORED GAP
WIND LOCNS ALONG WRN GREEN MTN SLOPES DURING THIS PERIOD...BUT A
QUICK LOOK AT SOUNDING PROFILES SUPPORT A MAINLY STABLE LOWER PBL
W/THIS EVENT.
THEREAFTER...SFC FRONT PUSHES WELL EAST OF THE AREA DURING SUNDAY AS
FLOW TURNS WESTERLY UNDER FAIRLY STRONG COLD AIR ADVECTION. TEMPS
LIKELY TO ONLY RISE A TAD FROM PRIOR NIGHTS MINS WITH HIGHS LIKELY
OCCURRING DURING THE MORNING HOURS. SOME LAKE AND/OR OROGRAPHICALLY
ENHANCED SHSN HERE AND ONWARD INTO MONDAY BUT DEEPER MOISTURE REALLY
ABSENT THUS LOOKING AT ONLY MINOR ACCUM...WITH LITTLE IF ANYTHING IN
BROADER VALLEY LOCALES. TEMPS TREND BACK TO NEAR OR SLIGHTLY BELOW
SEASONAL NORMS. BY MONDAY NIGHT RESIDUAL MOISTURE AND SECONDARY SFC
TROUGH ASSOC W/OLD PARENT OCCLUDED SYSTEM PUSHES INTO THE REGION
WITH LINGERING THREAT OF SHSN ACROSS THE NORTH. BEHIND THIS BNDRY
COLDER AIR LIKELY ON TAP BY NEXT TUESDAY THOUGH WITH A TREND TOWARD
FAIR/DRY CONDS.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
THROUGH 00Z THURSDAY...COMPLICATED AND COMPLEX WX SETUP ACRS OUR
TAF SITES WITH LOW FCSTER CONFIDENCE THRU THE NEXT 12 TO 18 HRS.
FCST CHALLENGE WL BE AREAL COVERAGE/INTENSITY OF -SW ACRS TAF
SITES...ALONG WITH ASSOCIATED CIGS/VIS. CRNT RADAR SHOWS
DEVELOPING -SW ACRS THE CPV ATTM...IMPACTING BTV WITH VIS AT 2SM
IN -SW. MEANWHILE...TRENDS CONT TO INCREASE IN AREAL
COVERAGE/INTENSITY UPSTREAM ACRS SOUTHERN CANADA AND WOULD EXPECT
MORE -SW WITH VIS BTWN 1-3SM AND CIGS AROUND OVC020 AT BTV. AS
MID/UPPER LVL CLOSED CYCLONIC CIRCULATION MOVES EAST OF TAF SITES
BY 06Z TONIGHT...AND MID LVL WAA DEVELOPS...WOULD NOT BE SURPRISED
A PERIOD OF 1/2SM IN MODERATE SNOW DEVELOPS ACRS THE CPV BTWN 08Z-
14Z WEDS. THIS WL BE ENHANCED BY LLVL CONVERGENCE FROM THE VALLEY
AND LAKE CHAMPLAIN MOISTURE. FOR MPV/SLK...EXPECT PERIODS OF -SW
TO DEVELOP BTWN 02-06Z TONIGHT AND CONT INTO WEDS WITH MVFR TO IFR
CONDITIONS POSSIBLE. MAINLY VFR CONDITIONS WL PREVAIL AT MSS/RUT
THRU 00Z THURS. CIGS/VIS SHOULD IMPROVE AFT 18Z THURS ACRS ALL TAF
SITES...AS MOISTURE DECREASES AND WINDS BECMG SOUTHERLY.
OUTLOOK...00Z THURSDAY THROUGH SUNDAY...
00Z 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...EVENSON
NEAR TERM...EVENSON
SHORT TERM...BANACOS
LONG TERM...JMG
AVIATION...TABER
