FXUS61 KBTV 271223
AFDBTV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
723 AM EST FRI NOV 27 2009
.SYNOPSIS...
A STRONG STORM WILL BRING RAIN...HIGH ELEVATION SNOW...AND WIND
TO THE NORTH COUNTRY THROUGH SATURDAY. LOW PRESSURE WILL INTENSIFY
RAPIDLY AS IT MOVES FROM CAPE COD INTO THE GULF OF MAINE TODAY
THEN INTO EASTERN CANADA SATURDAY. A WEAK RIDGE OF HIGH PRESSURE
WILL BRING A BREAK IN THE ACTION ON SUNDAY WITH FAIR WEATHER EXPECTED.
ANOTHER FRONTAL SYSTEM WILL BRING MORE SNOW AND RAING SUNDAY NIGHT
AND MONDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 425 AM EST FRIDAY...
WINTER WEATHER ADVISORY FOR 3-7" OF WET SNOW 18Z TODAY -16Z SAT
FOR ADIRONDACKS AND GREEN MTS EASTWARD...MAINLY ABOVE 1000 FT
WITH MOST ACCUMULATIONS COMING TONIGHT TAPERING OFF SATURDAY
MORNING.
RATHER TRICKY PTYPE PRECIP EVENT SHAPING UP AND WITH ALL THE
TRAVEL AND SHOPPING GOING ON TODAY THOUGHT A HIGHER ELEVATION ADVISORY
WAS PRUDENT.
INTIAL LOW LEVEL COLD AIR IS LACKING WITH NO POLAR AIRMASS AROUND
ANYWHERE SO ALL AREAS EXPECTED TO BEGIN AS RAIN.
KMWN AUTO ROAD VERTICAL PROFILE SHOWS FREEZING LEVEL BETWEEN 1600
FT (35 F) AND 2300 FT (31 F) EARLY THIS MORNING. ASSUMING FREEZING
LEVEL REMAINS AROUND 2000 FT... SNOW SHOULD BE ABLE TO MAKE IT
DOWN TO ABOUT 1000FT FT MSL WITH COOLING DUE TO MODERATE TO HEAVY
PRECIPITATION THIS AFTERNOON OR EARLY TONIGHT.
I EXPECT STRONG VERTICAL GRADIENT IN SNOWFALL WITH MOSTLY SNOW
ABOVE 2000 FT DOWN TO NIL BELOW 500 FT. WHERE TO DRAW THE LINE IS
TRICKY HOWEVER.
MODEL QPFS 1-2" WITH NAM A BIT ON THE HIGH SIDE WITH NEARLY 2.5"
IN THE GREEN MOUNTAINS. THINK THIS IS OVERDONE BUT 1-1.5" LIKELY
BASED ON GFS/SREF/HPC. PRECIPITABLE WATER 250% (1.60+") OF NORMAL
IS BEING INGESTED INTO THE STORM SYSTEM WHICH IS FORECAST TO BOMB
OUT TO BELOW 980MB NEAR PORTLAND MAINE THIS EVENING.
THINKING IS THAT SOME WET SNOW WILL MIX WITH RAIN THIS AFTERNOON
ABOVE 1000-1500 FT BUT WITH WARM GROUND AND TEMPS ABOVE FREEZING
DONT EXPECT MUCH ACCUMULATION...EXCEPT ABOVE 200O FT.
PRETTY MUCH WENT WITH A BLEND OF NAM/GFS TEMPS WHICH START OUT
AROUND 40 BUT FALL INTO THE 30S AFTER PRECIPITATION BEGINS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
AS OF 425 AM EST FRIDAY...
THE HEART OF THE STORM WILL BE GOING THIS EVENING WITH RAIN IN THE
CHAMPLAIN AND ST. LAWRENCE VALLEYS AND RAIN OR SNOW CHANGING TO
WET SNOW ELSEWHERE.
AFTER 00Z IS WHEN MOST OF OUR HIGHER ELEVATIONS OF 1000-2000 FT...WHERE
MOST PEOPLE LIVE...GET ABOUT 0.60-0.80" QPF AS SNOW.
SNOW LIQUID RATIOS PROBABLY 5 OR AT MOST 10:1 FOR WET SNOW
GENERALLY GIVE 3 TO 7 INCHES OF SNOW. CLOSER TO THE MOUNTAIN
SUMMITS COULD BE DOUBLE THAT AMOUNT WITH THE HIGHER RATIOS AND QPF
ESPECIALLY IN THE NRN GREEN MTS. A CHANGE IN RATIOS COULD YIELD
HIGHER OR LOWER AMOUNTS OF SNOW...SO STAY TUNED.
AS FAR AS WIND GOES....DON'T THINK WE WILL MIX ALL THE 50 KT 850MB WINDS
THAT WIND DOWN TO THE SURFACE HERE BUT WILL JUST MENTION GUSTY
WINDS T0 40 MPH.
HYDRO COULD BE A CONCERN ALSO WITH SOME HEADWATER GUIDANCE AROUND
2" IN 12HR WHICH IS AN OUTSIDE POSSIBILITY BUT WILL HOLD OFF ON
ANY KIND OF HYDRO HEADLINES THAT SINCE A GOOD FRACTION OF WHAT
FALLS IN THE HEADWATERS WILL BE SLUSHY SNOW.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 315 AM EST FRIDAY...A LOW PRESSURE AREA FROM THE GREAT
LAKES WILL MOVE NORTHEAST UP THE SAINT LAWRENCE VALLEY LATE SUNDAY
AND MONDAY. THIS LOW WILL BRING A COLD FRONT THROUGH THE REGION ON
MONDAY. WILL BRING IN SOME SNOW TO THE REGION SUNDAY NIGHT...AND
THEN SOME RAIN AND SNOW SHOWERS ON MONDAY. A WARM FRONT
APPROACHING THE REGION WILL BRING A CHANCE OF SNOW SHOWERS TO THE
REGION ON TUESDAY. THE FORECAST AREA WILL BE BETWEEN A COLD FRONT
OVER CANADA AND A DEVELOPING LOW PRESSURE AREA OVER THE CAROLINAS
ON WEDNESDAY...SO WILL GO WITH MAINLY CLOUDY SKIES FOR WEDNESDAY.
A LOW PRESSURE AREA MOVING NORTHEAST UP THE ATLANTIC COAST
WEDNESDAY NIGHT WILL BE SOUTH OF CAPE COD EARLY THURSDAY. HAVE
GONE WITH SLIGHT CHANCE POPS FOR SOUTH CENTRAL VERMONT FOR LATE
WEDNESDAY NIGHT AND THURSDAY... WITH THE REMAINDER OF THE FORECAST
AREA REMAINING MOSTLY DRY.
&&
.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
THROUGH 12Z SATURDAY...A LOW PRESSURE AREA OFF THE MID ATLANTIC
COAST THIS MORNING WILL DEEPEN AND MOVE NORTHWARD TODAY...
REACHING THE GULF OF MAINE BY 00Z SATURDAY. CEILINGS WILL LOWER TO
MVFR/IFR TODAY...WITH RAIN MOVING INTO THE REGION BETWEEN 14Z-16Z
FRIDAY. THE HIGHER TERRAIN OF THE ADIRONDACKS AND THE GREEN
MOUNTAINS WILL BE OBSCURED IN CLOUDS AND REMAIN SO THROUGH 12Z
SATURDAY. COLDER AIR ALOFT WILL WORK INTO THE REGION LATER THIS
AFTERNOON...WITH RAIN CHANGING TO SNOW OVER THE HIGHER ELEVATIONS
OF THE ADIRONDACKS AND GREEN MOUNTAINS. MODELS DIFFER AS TO WHAT
TIME THIS WILL OCCUR...AS ONE MODEL SUGGESTS A CHANGE TO SNOW BY
EARLY AFTERNOON AT SLK AND MPV...WHILE ANOTHER MODEL SUGGESTS THIS
WILL OCCUR LATE THIS AFTERNOON AND EARLY THIS EVENING. HAVE
SOMEWHAT LOW CONFIDENCE IN THE TAFS FOR MPV AND SLK AS TO WHAT
TIME THIS CHANGE TO SNOW WILL OCCUR...BUT COULD POTENTIALLY OCCUR
EARLIER THAN WHAT IS INDICATED IN THE CURRENT TAF FORECASTS FOR
MPV AND SLK. EXPECTING MAINLY ALL RAIN IN THE CHAMPLAIN AND SAINT
LAWRENCE VALLEYS. EXPECTING SURFACE WIND GUSTS AT OR ABOVE 20
KNOTS TO DEVELOP THIS EVENING ACROSS THE REGION...AND CONTINUE THROUGH
12Z SATURDAY.
OUTLOOK 12Z SATURDAY THROUGH TUESDAY...IFR/MVFR IN SNOW SHOWERS
ON SATURDAY MAINLY OVER THE HIGHER TERRAIN. GUSTY NORTHWEST
WINDS.
SUNDAY...MAINLY VFR ON SUNDAY...AS A WEAK RIDGE OF HIGH PRESSURE
BUILDS INTO THE REGION.
SUNDAY NIGHT...EXPECTING MVFR/IFRCONDITIONS IN LIGHT SNOW TO
DEVELOP ACROSS THE REGION.
MONDAY...MVFR/IFR IN RAIN AND SNOW SHOWERS...AS A COLD FRONT
MOVES INTO THE REGION.
TUESDAY...MVFR/IFR IN LIGHT SNOW POSSIBLE AS A WARM FRONT
APPROACHES THE REGION.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 11 AM EST
SATURDAY FOR VTZ003-004-006>008-010-012-016>019.
NY...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 11 AM EST
SATURDAY FOR NYZ029>031-034.
&&
$$
SYNOPSIS...SISSON
NEAR TERM...SISSON
SHORT TERM...SISSON
LONG TERM...WGH
AVIATION...WGH
