FXUS61 KBTV 271911
AFDBTV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
211 PM 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 RAIN SUNDAY NIGHT
AND MONDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 1105 AM EST FRIDAY...990 MB SFC LOW LOCATED JUST SE OF CAPE
COD LATE THIS MORNING WILL CONTINUE TO DEEPEN RAPIDLY THIS PM AS
IT LIFTS NORTH TOWARDS GULF OF MAINE. RAIN OVERSPREADING FORECAST
AREA THIS MORNING. EXPECT COVERAGE TO CONTINUE TO INCREASE THIS
PM...AND INTENSITY OF PCPN WILL INCREASE AS WELL...ESPECIALLY OVER
ERN VT. SOME WET SNOW MAY MIX IN AT TIMES OVER HIR TRRN AS COLDER
AIR WORKS IN ALOFT. WITH THE CLOUD COVER AND PCPN...TEMPS WON'T BE
CHANGING MUCH FROM CURRENT READINGS. FOG WAS RATHER DENSE IN SPOTS
EARLIER THIS MORNING...BUT VSBYS HAVE IMPROVED OVER PAST HOUR.
GOING FCST HAS EVERYTHING PRETTY WELL COVERED...SO NO UPDATE
NEEDED ATTM. WINTER WX ADVISORIES FOR ADRNDKS AND MUCH OF VT
OUTSIDE OF CHMPLN VLY REMAIN IN EFFECT.
PREVIOUS DISCUSSION...
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.
INITIAL 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 NIGHT/...
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 /MONDAY THROUGH THURSDAY/...
AS OF 210 PM EST FRIDAY...SHOWERS WILL CONTINUE ON MONDAY AS LOW
PRESSURE SYSTEM TRACKS NORTHEAST ALONG THE SAINT LAWRENCE
VALLEY...AND SHOULD BE ENDING BY LATE AFTERNOON. SOME WRAP AROUND
SNOW SHOWERS IN THE HIGHER TERRAIN IS EXPECTED MONDAY NIGHT.
UPPER LEVEL TROF WILL CROSS THE REGION MONDAY NIGHT. THEN AN
UPPER LEVEL RIDGE AND SURFACE HIGH PRESSURE WILL BUILD OVER THE
EASTERN CONUS FOR TUESDAY AND TUESDAY NIGHT. A LOW PRESSURE
SYSTEM WILL PASS TO OUR NORTH ON WEDNESDAY...AND UPPER LEVEL TROF
WITH EMBEDDED SHORT WAVE WILL CROSS THE NORTH COUNTRY BRINGING
ANOTHER CHANCE FOR SHOWERS...ESPECIALLY ACROSS OUR NORTHERN
ZONES. ANOTHER LOW PRESSURE SYSTEM MAY FORM OFF THE CAROLINA
COAST ON THURSDAY...TRACKING NORTHEAST ALONG THE EAST COATS.
STILL LOTS OF UNCERTAINTY IN THE FORECAST BEYOND DAY 5.
&&
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
THROUGH 18Z SATURDAY...A LOW PRESSURE AREA OFF THE COAST OF MAINE
WILL CONTINUE TO MOVE NORTHEASTWARD THIS AFTERNOON AND EVENING.
CEILINGS HAVE LOWERED TO MVFR/IFR. COLDER AIR ALOFT HAS WORKED
INTO THE REGION AND RAIN HAS CHANGED TO SNOW ACROSS THE HIGHEST
ELEVATIONS. RAIN SHOULD CHANGE OVER TO SNOW AT SLK AND MPV
TONIGHT...WITH RUT A LITTLE LATER DURING THE OVERNIGHT. VALLEY
TERMINALS SHOULD HAVE ALL RAIN THROUGH THE END OF THE EVENT.
SURFACE WIND GUSTS AT OR ABOVE 20 KNOTS WILL DEVELOP THIS EVENING
ACROSS THE REGION...AND CONTINUE THROUGH 18Z SATURDAY.
OUTLOOK 18Z SATURDAY THROUGH WEDNESDAY...SATURDAY...GUSTY
NORTHWEST WINDS. SUNDAY...MAINLY VFR...AS A WEAK RIDGE OF HIGH
PRESSURE BUILDS INTO THE REGION. SUNDAY NIGHT...MVFR/IFR
CONDITIONS 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. WEDNESDAY...MVFR IN LIGHT
SNOW SHOWERS ACROSS THE NORTHERN AREAS.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...WINTER WEATHER ADVISORY UNTIL 11 AM EST SATURDAY FOR VTZ003-
004-006>008-010-012-016>019.
NY...WINTER WEATHER ADVISORY UNTIL 11 AM EST SATURDAY FOR
NYZ029>031-034.
&&
$$
SYNOPSIS...SISSON
NEAR TERM...RJS/SISSON
SHORT TERM...SISSON
LONG TERM...NEILES
AVIATION...NEILES
