Area Forecast Discussion
Issued by NWS Burlington, VT

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000
FXUS61 KBTV 010212
AFDBTV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
912 PM EST SAT FEB 28 2015

.SYNOPSIS...
DRY WEATHER CONTINUES TONIGHT WITH HIGH PRESSURE OVER THE AREA.
CLOUDS WILL BE ON THE INCREASE SUNDAY AS A WARM FRONT APPROACHES THE
REGION. THIS FEATURE WILL ALSO SPREAD SNOW ACROSS THE AREA LATE
SUNDAY AFTERNOON AND ESPECIALLY SUNDAY NIGHT. LIGHT SNOW ACCUMULATIONS
ARE EXPECTED BY MONDAY MORNING BEFORE THE SNOW TAPERS OFF THROUGHOUT
THE DAY.

&&

.NEAR TERM /UNTIL 7 AM SUNDAY MORNING/...
AS OF 911 PM EST SATURDAY...GOING FORECAST IN GOOD SHAPE...NO
SIGNIFICANT CHANGES MADE. HIGH PRESSURE OVER THE REGION WILL ALLOW
FOR CLEAR SKIES TO DOMINATE MUCH OF THE NIGHT. ANY EARLIER LAKE
EFFECT CLOUDS DOWNWIND OF LAKE ONTARIO HAVE SINCE DISSIPATED.
OTHERWISE...WILL SEE AN INCREASE IN HIGH CLOUDS TOWARDS MORNING AS
A SYSTEM APPROACHES FROM THE OHIO VALLEY. LOOKING AT LOWS
GENERALLY IN THE SINGLE DIGITS ABOVE AND BELOW ZERO...WITH SOME
-10 TO -15 DEGREE READINGS POSSIBLE IN THE COLDEST HOLLOWS OF THE
NORTHEAST KINGDOM.

&&

.SHORT TERM /7 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
AS OF 326 PM EST SATURDAY...FORECAST REMAINS ON TRACK FOR THE
SUNDAY-MONDAY TIME PERIOD WITH INCREASING CLOUDS AND SNOW LATER
SUNDAY AND SUNDAY NIGHT BEFORE TAPERING OFF TO SNOW SHOWERS ON
MONDAY. WARM FRONT...WARM AIR ADVECTION...AND EVENTUALLY THE UPPER
LEVEL TROUGH WILL ALL MOVE ACROSS THE NORTHEAST UNITED STATES AND
PROVIDE THE NECESSARY SUPPORT FOR THE SNOW. THESE FEATURES ARE
FAIRLY PROGRESSIVE AND NOT VERY STRONG...BUT ENOUGH TO PRODUCE
ACCUMULATING SNOWS ACROSS NORTHERN NEW YORK. LOOKING AT A
WIDESPREAD 1 TO 3 INCH SNOW ACROSS THE AREA WITH 2 TO 4 INCHES IN
THE MOUNTAINS AND PERHAPS SOME LOCALIZED AMOUNTS AROUND 5 INCHES
FOR THE SOUTHERN GREEN MOUNTAINS OF VERMONT. AGAIN MAIN TIME FOR
THIS SNOW WILL BE LATE IN THE DAY SUNDAY AND ESPECIALLY SUNDAY
NIGHT. SOUTHWEST FLOW ALOFT WILL BE A DOWNSLOPING FLOW AND PARTS
OF THE CHAMPLAIN VALLEY WILL LIKELY SEE THE LEAST AMOUNT OF SNOW
FROM THIS EVENT. THE UPPER TROUGH MOVES ACROSS THE REGION ON
MONDAY AND THE SNOW QUICKLY TAPERS TO SNOW SHOWERS WITH THE
MOUNTAINS HAVING THE BEST CHANCE FOR ADDITIONAL LIGHT SNOW
ACCUMULATIONS. THE SOUTHWEST FLOW ALOFT WILL LEAD TO WARMER
TEMPERATURES ON SUNDAY AND MONDAY WITH HIGHS IN THE 20S TO AROUND
30.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 343 PM EST SATURDAY...
TUESDAY... NEARLY ALL OF THE AVAILABLE GUIDANCE SHOWS THE HIGH
PRESSURE SLIDING OFFSHORE BY MONDAY AFTERNOON. THE WEST
NORTHWESTERLY WINDS THAT WILL KEEP TEMPS FROM WARMING MUCH ON
TUESDAY WILL GIVE WAY TO WARMER RETURN FLOW SOUTHERLY WINDS BY MID
AFTERNOON WHICH SHOULD ENABLE THE AREA TO WARM INTO THE MID 20`S
ACROSS THE FORECAST REGION BETWEEN NOON AND 7PM ON TUESDAY.  THE
WARMEST TIME OF THE DAY ON TUESDAY WILL ACTUALLY BE DURING THE
EVENING HOURS AS THE RETURN FLOW WILL PUSH WARMER AIR INTO THE
REGION THROUGH THE EVENING AHEAD OF AN ADVANCING SYSTEM. THE
TEMPERATURE TRENDS TUESDAY EVENING WILL ABSOLUTELY BE NON DIURNAL AS
OUR OVERNIGHT LOW WILL LIKELY OCCUR JUST AS PERIOD BEGINS AROUND 7-
8PM.

WEDNESDAY...THE MODELS HAVE COME INTO SLIGHTLY BETTER CONSENSUS
TODAY BUT STILL OFFER SLIGHTLY DIFFERENT SOLUTIONS THERMALLY. THE
BROAD SENSE OF THE FORECAST REMAINS THAT A DEVELOPING UPPER LEVEL
TROUGH NORTH OF THE GREAT LAKES WILL SPAWN A SURFACE LOW PRESSURE
SYSTEM OVER THE GREAT LAKES. THAT SURFACE SYSTEM WILL FEED OFF BOTH
A NORTHERLY STREAM OF ENERGY AND A SOUTHERLY STREAM OF MOISTURE FROM
THE DEPARTING HIGH PRESSURE SYSTEM AND TRACK UP THE SAINT LAWRENCE
VALLEY. THE NET RESULT WILL BE A WIDESPREAD PRECIPITATION EVENT
WEDNESDAY EARLY MORNING INTO THE EARLY AFTERNOON. PTYPE REMAINS THE
BIGGEST FORECAST CHALLENGE FOR THIS EVENT AS ITS CURRENTLY TOO FAR
IN THE FUTURE TO HAVE MUCH CERTAINTY IN HOW FAR NORTH THE MODELS
BRING THE WARM AIR BEFORE THE COLD FRONT REACHES THE AREA. THE GFS
DEVELOPS A STRONGER LOW PRESSURE SYSTEM THAN THE ECMWF WHICH IS MORE
OF AN EMBEDDED SHORT WAVE CONNECTED TO AN UPSTREAM LOW PRESSURE
SYSTEM.

GIVEN THE TWO SCENARIOS AT THIS POINT I OPTED FOR A BLEND OF THE
TWO SOLUTIONS REGARDING POPS AND SURFACE TEMPS. THE GFS IS NO
LONGER SHOWING A SIGNIFICANT SURFACE BOMB DEVELOPING WHICH LEADS
TO ENHANCED CONFIDENCE IN THIS RUN VERSUS YESTERDAYS 12Z RUN. FOR
THERMAL PROFILES I OPTED TO CONTINUE TO USE THE GFS BECAUSE OF THE
EXTRA VERTICAL LEVELS AVAILABLE FOR A TOP DOWN PTYPE APPROACH.
THIS LEAD TO THE ONSET OF THE PRECIP BEGINNING AS LIGHT SNOW
SHOWERS THEN TRANSITIONING BY MIDNIGHT OVER NORTHERN NEW YORK TO A
WINTRY MIX. THAT WILL CONTINUE TO TRANSITIONS FROM THE SOUTHWEST
TO NORTHEAST SHIFTING MORE TOWARDS RAIN AND FREEZING RAIN BY MID
MORNING ON WEDNESDAY. THE CONCERN RIGHT NOW IS HOW TO DEAL WITH
THE RAIN THAT FALLS AND MEETS ROADS WHERE GROUND TEMPS WILL STILL
POTENTIALLY BE AT OR BELOW 32F. EITHER WAY THE NEXT RESULT OF RAIN
OR FREEZING RAIN WOULD BE ICING ON THE ROAD SURFACES AND THE
CURRENT SNOW PACK. AS THE LOW PUSHES THROUGH THE REGION THERE WILL
BE MODERATELY STRONG WINDS ESPECIALLY ALOFT GUSTING TO 40-50KTS
ABOVE 2000 FT. CURRENTLY THE ECMWF RUNS A SOUTHWESTERLY JET AT
850MB APPROACHING 60KTS INTO THE SAINT LAWRENCE VALLEY AND 850MB
WINDS BETWEEN 45-55KTS INTO THE CHAMPLAIN VALLEY AND WESTERN SLOPE
OF THE GREENS. GIVEN THE SOUTHWESTERLY COMPONENT OF THE WINDS
ALOFT AT 850 AND 700MB EXPECT THAT WOULD RESULT IN SHADOWING OF
THE CHAMPLAIN VALLEY SO TOTAL QPF WOULD BE LOWERED IN THE
CHAMPLAIN VALLEY AND IN THE NORTHEAST KINGDOM. THE GFS DOES A
DECENT JOB OF SHOWING THAT AS OF THE 12Z RUN.

MAX TEMPS ON THURSDAY AHEAD OF THE RESULTANT COLD FRONT THAT WILL
PASS IN THE MID AFTERNOON HAVE A REAL GOOD SHOT AT WARMING INTO THE
MID TO LOW 40S UNDER STRONG SOUTHWESTERLY FLOW.  THE LATER THE FRONT
COMES THROUGH THE BETTER SHOT AT NEAR 50 DEGREES FOR SOUTHERN
VERMONT NEAR RUTLAND.  I OPTED TO GO SLIGHTLY ABOVE GUIDANCE ON
WEDNESDAY FOR MAX TEMPS BUT WAS A BIT RESERVED IN HOW FAR ABOVE
GUIDANCE BECAUSE THE CURRENT EXISTING SNOW PACK SHOULD MODERATE HOW
MUCH LOW LEVEL WARMING IS POSSIBLE.

THURSDAY... THE SURFACE LOW WILL PUSH OUT OF THE AREA GIVING WAY TO
ANOTHER BUILDING SURFACE RIDGE BELOW A WEAK UPPER LEVEL TROUGH.  THE
 RESULT OF THAT COMBINATION WILL BRING COLD TEMPS ONCE AGAIN AS WE
WILL STRUGGLE TO WARM BEHIND THE COLD FRONT INTO THE MID 20S IN THE
VALLEYS AND UPPER TEENS ACROSS THE HIGHER TERRAIN OF THE ADIRONDACKS
AND GREEN MOUNTAINS. ANY LINGERING UPPER LEVEL ENERGY WILL SQUEEZE
OUT A FEW OROGRAPHIC SNOW SHOWERS SO I DIDN`T REMOVE ALL THE POPS
UNTIL LATE THURSDAY EVENING. AS THE RIDGE BUILDS IN THE CLOUDS WILL
DECREASE AND THE MODERATE WINDS WILL SLOWLY WEAKEN BECOMING LIGHT
AND WESTERLY TOWARDS INTO THE EVENING. OVERNIGHT THE DECREASING
CLOUD COVER AND WEAKENING WINDS SHOULD ALLOW THE NOCTURNAL WINDS
OVER SOUTHERN VERMONT TO DECOUPLE ALLOWING FOR GOOD RADIATIONAL
COOLING IN VERMONT WITH DECENT COOLING EXPECTED FURTHER NORTH.
OVERNIGHT LOWS WILL BE IN THE LOW SINGLE DIGITS ACROSS THE AREA WITH
TEMPS JUST BELOW ZERO IN THE TYPICAL COOL SPOTS OVER THE NORTHEAST
KINGDOM AND ACROSS SARANAC LAKE.

FRIDAY...UNDER STRONG HIGH PRESSURE THE WEATHER WILL BE DRY AND
TEMPS WILL ONLY WARM TO THE UPPER TEENS TO LOW 20S. NOT MUCH ELSE TO
DISCUSS.  OVERNIGHT LOWS WILL BE IN THE LOW TEENS IN THE VALLEYS
WITH SINGLE DIGITS ABOVE ZERO EXPECT ELSEWHERE.

SATURDAY...AT DAY 7 ONE CAN ONLY PUT SO MUCH STOCK IN THE MODELS AND
SO I JUST WENT WITH THE ECMWF WHICH DOESN`T CURRENTLY PROJECT A
STRONG LOW LEVEL TROUGH ADVANCING THROUGH THE REGION. BASED ON THE
CURRENT GUIDANCE EXPECTED THE BROAD AREA OF HIGH PRESSURE TO STILL
BE OVER THE REGION RESULTING IN TEMPS IN THE MID 30S UNDER SOUTHERLY
TO SOUTHWESTERLY WINDS.

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
THROUGH 00Z MONDAY...VFR EXPECTED THROUGH MUCH OF THE
PERIOD INTO SUNDAY...WITH MVFR/IFR DEVELOPING IN LIGHT SNOW SUNDAY
AFTERNOON AND EVENING. CLEAR SKIES AND GENERALLY LIGHT AND LOCALLY
VARIABLE WINDS WILL PREVAIL THROUGH MUCH OF THE NIGHT...WITH AN
INCREASE IN VFR MID/HIGH CLOUDS SUNDAY MORNING. WILL SEE CEILINGS
LOWERING AND AREAS OF LIGHT SNOW DEVELOPING BETWEEN 17Z-19Z ON
SUNDAY AND CONTINUING THROUGH THE REMAINDER OF THE DAY. GREATEST
IMPACTS AT RUT/MSS/SLK/MPV WITH LEAST AT PBG/BTV WITH DOWNSLOPING
SOUTHWESTERLY FLOW. SURFACE WINDS ON SUNDAY STRENGTHEN OUT OF THE
SOUTH TO 5-15 KNOTS...WITH GUSTS UP TO 20 KNOTS AT BTV.

OUTLOOK 00Z MONDAY THROUGH THURSDAY...

00Z MONDAY-00Z TUESDAY...VARIETY OF FLIGHT CATEGORIES IN PERIODS
OF SNOW SHOWERS WITH WEAK LOW PRESSURE SYSTEM. GREATEST CHANCES OF
IFR OR LOWER AT MPV/SLK.

00Z TUESDAY-18Z TUESDAY...VFR CONDITIONS UNDER HIGH PRESSURE.

18Z TUESDAY ONWARD...INCREASING CHANCE FOR MVFR/IFR IN MIXED
PRECIPITATION AS LOW PRESSURE SYSTEM APPROACHES FROM THE
SOUTHWEST.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...NONE.
NY...NONE.

&&

$$
SYNOPSIS...EVENSON
NEAR TERM...EVENSON/MUCCILLI
SHORT TERM...EVENSON
LONG TERM...DEAL
AVIATION...DEAL/MUCCILLI


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