Area Forecast Discussion
Issued by NWS Burlington, VT

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000
FXUS61 KBTV 270951
AFDBTV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
551 AM EDT SUN JUL 27 2014

.SYNOPSIS...
ACTIVE PERIOD OF WEATHER IS EXPECTED ACROSS THE NORTH COUNTRY
TODAY INTO MONDAY. INITIAL AREA OF SHOWERS AND THUNDERSTORMS WILL
MOVE ACROSS THE REGION THROUGH THE MORNING HOURS...WITH RE-
DEVELOPMENT OF THUNDERSTORMS...SOME STRONG...DURING THE AFTERNOON.
A POTENT MID-SUMMER LOW WILL TRACK ACROSS THE NORTH COUNTRY ON
MONDAY WITH A WETTING RAINFALL TO THE REGION WITH POTENTIAL FOR
THUNDERSTORMS ACROSS EASTERN VERMONT. GRADUALLY IMPROVING
CONDITIONS TUESDAY INTO MIDWEEK...WITH HIGH TEMPERATURES BEING A
FEW DEGREES BELOW NORMAL THROUGH MIDWEEK.

&&

.NEAR TERM /UNTIL 7 PM THIS EVENING/...
AS OF 437 AM EDT SUNDAY...ONGOING LINE OF HEAVIER SHOWERS AND
THUNDERSTORMS NOW ENTERING THE ST. LAWRENCE VALLEY EARLY THIS
MORNING. THIS ACTIVITY TIED TO AN INITIAL SHORTWAVE MOVING INTO
EASTERN VERMONT PER WV IMAGERY AND WEAK INSTABILITY ALOFT
(SHOWALTERS -1 TO -2). LIGHTER SHOWERS ACROSS WESTERN HALF OF
VERMONT. EXPECT THE SOLID LINE OF HEAVIER SHOWERS/THUNDERSTORMS TO
MOVE ACROSS THE GREENS AND INTO EASTERN VERMONT THROUGH THE
MORNING/EARLY AFTN HOURS. I`VE SHOWN RELATIVELY HIGH POP (LIKELY
TO LOW CATEGORICAL) TO COVER THIS ONGOING ACTIVITY THROUGH THE
MORNING.

FOCUS FOR THE AFTN THEN SHIFTS TOWARDS POTENTIAL FOR RE-DEVELOPING
CONVECTION AND ITS AREAL COVERAGE. FEEL THAT SOME CLEARING IN THE
WAKE OF MORNING SHOWERS WILL ALLOW FOR SOME DESTABILIZATION. I
DON`T THINK THE DEGREE OF INSTABILITY WILL BE QUITE AS HIGH AS WHAT
THE 4-KM NAM OR WRF BTV-4 IS SHOWING (NEAR 2000 J/KG CAPE)...BUT
VALUES AROUND HALF THAT SEEM REASONABLE WITH BREAKS IN THE CLOUDS
AND MID-LEVEL LAPSE RATES OF AROUND 6C/KM. WIND FIELDS ALSO
STRENGTHEN TO PRODUCE 0-6 KM BULK SHEAR MAGNITUDES OF 30-35 KTS.
HOWEVER BY AFTN THE NORTH COUNTRY WILL BE IN BETWEEN THE DEPARTING
SHORTWAVE AND A MUCH MORE POTENT SHORTWAVE TROUGH DIVING SOUTHWARD
TOWARD THE CENTRAL APPALACHIANS...IN MID-LEVEL SUBSIDENT/WEAK HEIGHT
RISE REGIME. THAT SHOULD HELP TO SUPPRESS OR KEEP A MORE ISOLATED TO
WIDELY SCATTERED COVERAGE TO ANY STORMS THAT CAN DEVELOP LATER THIS
AFTERNOON. I THOUGHT ABOUT INTRODUCING ENHANCED WORDING FOR GUSTY
WINDS AND SMALL HAIL BUT OVERALL LIMITED AREAL COVERAGE SUGGESTED
AGAINST DOING SO. IT`S ALSO DIFFICULT TO PINPOINT A FAVORED AREA
FOR STRONGER STORMS TODAY...BUT WOULD THINK EASTERN VERMONT WOULD
HAVE A TOUGHER TIME CLEARING AND LOWER INSTABILITY THERE. I WILL
MENTION POTENTIAL FOR STRONGER STORMS IN THE HWO HOWEVER. OVERALL
QPF TODAY GENERALLY A QUARTER TO AS MUCH AS A HALF-INCH (LOCALLY
HIGHER IN THUNDERSTORM DOWNPOURS).

HIGHS SHOULD TOP OUT IN THE 70S TO A SPOT 80 TODAY...GENERALLY
COOLEST ACROSS THE HIGH TERRAIN AND IN EASTERN VERMONT WHERE
SHOWERS/STORMS WILL TAKE LONGER TO CLEAR (I.E. LESS TIME FOR AFTN
BREAKS IN CLOUDS).

&&

.SHORT TERM /7 PM THIS EVENING THROUGH TUESDAY/...
AS OF 437 AM EDT SUNDAY...ACTIVE PERIOD OF WEATHER THEN CONTINUES
LATER SUNDAY NIGHT AND ESPECIALLY ON MONDAY. MORE GRADUAL
IMPROVEMENT FOR TUESDAY BUT STILL GENERALLY UNSETTLED WITH THE
NORTH COUNTRY UNDER A WELL-ADVERTISED 500 MB TROUGH.

TONIGHT: STILL CAN`T RULE OUT AN ISOLATED STRONGER STORM EARLY
EVENING BUT ALREADY LIMITED INSTABILITY WILL BECOME EVEN MORE SO BY
DARK. THE STRONG...POSITIVELY TILTED SHORTWAVE TROUGH ASSUMES A
NEGATIVE TILT BY 12Z MONDAY AND INDUCES SFC LOW DEVELOPMENT NEAR
CENTRAL PA LATER TONIGHT. THERE`S SOME QUESTION MARKS AS TO THIS
LOW`S EXACT TRACK ESPECIALLY IN LIGHT OF POTENTIAL MASS FIELD
CHANGES GIVEN A POTENTIAL SEVERE WEATHER EVENT IN THE MID-ATLANTIC
/APPALACHIANS TODAY. THERE APPEARS TO BE BETTER AGREEMENT ON A MORE
INTERIOR TRACK (LOW ROUGHLY CENTERED OVER THE HUDSON VALLEY REGION
BY 12Z MONDAY) - AND THERE ARE GOOD SIGNALS IN HIGH RES MODELS OF A
BAND OF MODERATE RAIN ON THE NORTHWEST PERIPHERY OF SFC LOW`S
TRACK. THAT BAND OF MODERATE RAIN LOOKS TO OVERSPREAD SOUTHERN
VERMONT INTO THE ADIRONDACKS THROUGH 12Z MONDAY. INITIALLY KEPT
POPS AROUND CHANCE CATEGORY BUT BEGIN TO TREND UPWARD AFTER
MIDNIGHT TO LIKELY/LOW CATEGORICAL BY THE PRE-DAWN HOURS. LOWS
UNLIKELY TO FALL MUCH UNDER OVERCAST SKIES...UPPER 50S TO MID 60S
GENERALLY A DEGREE OR TWO WARMER THAN MAV OR MET MOS GUIDANCE.

MONDAY & MONDAY NIGHT: SFC LOW THEN TRACKS UP THE CHAMPLAIN
VALLEY/GREEN MOUNTAINS THROUGH 00Z TUESDAY...500 MB TROUGH ALSO
PIVOTS NORTHWARD BUT APPEARS TO CLOSE OFF BY MONDAY EVENING. WITH
THAT EXPECTED LOW TRACK...IT LEAVES CENTRAL/EASTERN VERMONT IN THE
WARM SECTOR. FAVORABLE WIND SHEAR PARAMETERS FOR STRONG
THUNDERSTORMS IF GREATER INSTABILITY CAN BE REALIZED (GENERALLY IS
HIGHEST IN THE 00Z GFS) IN THIS CORRIDOR. NORTHWEST OF THE LOW
TRACK...MORE STRATIFORM MODERATE RAIN WILL PIVOT NORTH-NORTHEASTWARD
ACROSS NORTHERN NY AND THE NORTHERN CHAMPLAIN VALLEY. I`VE INDICATED
CHANCE THUNDER FOR CENTRAL AND EASTERN VERMONT IN PROGGED WARM
SECTOR...BUT HAVE OTHERWISE KEPT THUNDER OUT ELSEWHERE WHERE IT`S
LIKELY TO BE MORE RAIN-COOLED/STABLE. CATEGORICAL POPS OFFERED
MONDAY WITH GRADUAL TAPER TO HIGH CHANCE/LIKELY THROUGH MONDAY
EVENING. TEMPS ARE TRICKY/DEPENDENT ON LOW TRACK...BUT LIKELY TO BE
BELOW NORMAL AND CLOSER TO NORMAL IF WARM SECTOR CAN GET
ESTABLISHED. HIGHS IN NORTHERN NY MAY STRUGGLE TO REACH 70 DEGREES
IN A CLOUDY/RAINY DAY...AND CLOSER TO THE MID/UPPER 70S IN CENTRAL
AND EASTERN VERMONT. QPF MONDAY RANGES FROM LESS THAN A HALF-INCH
FOR THE SAINT LAWRENCE VALLEY... .75-1" FOR MUCH OF VERMONT TO JUST
A TICK OVER AN INCH FOR THE ADIRONDACKS. NOT ANTICIPATING ANY HYDRO
ISSUES FROM THIS AMOUNT OF RAIN GIVEN HOW DRY IT HAS BEEN.

TUESDAY: UPPER TROUGH EXITS WITH STILL SOME LINGERING SHOWERS
PARTICULARLY ACROSS HIGHER TERRAIN. NORTHWEST FLOW...MDT COLD
ADVECTION (850 TEMPS DURING TUESDAY PLUNGE TO +6 TO +8C) AND PARTLY
CLOUDY SKIES PRODUCES BELOW NORMAL HIGHS IN THE 60S TO THE LOWER 70S.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 421 AM EDT SUNDAY...

A SLOW WARMING TREND TO NEAR NORMAL TEMPERATURES IS EXPECTED BY THE
END OF THE WEEK WITH THE HIGHEST CHANCE OF SHOWERS AND THUNDERSTORMS
ON THURSDAY.

MODELS IN GOOD AGREEMENT THAT A DEEP LARGE SCALE TROUGH WILL
REMAIN OVER THE EASTERN US CENTERED NEAR 80 DEG W WITH A RIDGE OVER
THE INTER-MOUNTAIN WEST THROUGHOUT THE PERIOD...THOUGH WEAKENING
WITH RISING HEIGHTS.

THOUGH A SHOWER CAN`T BE COMPLETELY RULED OUT ANY AFTERNOON DURING THIS
PERIOD WITH THE UPPER TROUGH JUST OFF TO THE WEST...THE BEST
CHANCE FOR SEEING SHOWERS AND THUNDERSTORMS WILL BE THURSDAY
AFTERNOON AS A SHORT WAVE WITH COLD AIR ALOFT SWINGS ACROSS THE
AREA WITH SOME INSTABILITY AND SOME QG FORCING.

THE UPPER TROUGH WEAKENS BUT REMAINS IN PLACE FRIDAY INTO THE
WEEKEND BUT RETROGRADES A FEW DEGREES WESTWARD IN RESPONSE TO A
BUILDING ATLANTIC RIDGE ALOFT, RISING HEIGHTS OVER THE EAST COAST
WITH A BERMUDA HIGH STRENGTHENING AT THE SURFACE...WHICH IS FAIRLY
TYPICAL FOR LATE SUMMER. SOME SMALL CHANCE OF SHOWERS AND
THUNDERSTORMS WILL CONTINUE EACH DAY AS AREA REMAINS LOCKED INTO THE
EASTERN SIDE OF THE UPPER TROF.

SLIGHTLY BELOW NORMAL MAX TEMPS ARE EXPECTED WEDNESDAY WITH PARTLY
SUNNY SKIES. HIGHS TEMPS MAINLY IN THE 70S WITH 850 TEMPS ONLY
AROUND 8-10C.

850 MB TEMPS WARM A COUPLE DEGREES EACH DAY SO THAT BY THURSDAY
THROUGH SATURDAY SHOULD BE 12-14C. WITH PARTIAL SUN UNDER DIURNAL
CUMULUS CLOUDS EXPECT HIGHS MODERATING TO NEAR NORMAL -
UPPER 70S LOWER 80S.

&&

.AVIATION /10Z SUNDAY THROUGH THURSDAY/...
THROUGH 06Z MONDAY..TRENDING MVFR EARLY THIS MORNING WITH SHOWERS
ALREADY OVER THE REGION AND WITH THUNDERSTORMS MOVING INTO THE
REGION FROM ONTARIO ASSOCIATED WITH A WEAK WARM FRONT.

CHANCE OF SHOWERS ARE NEAR 80 PERCENT THROUGH ABOUT 15Z TODAY THEN DECREASE.

CHANCES OF THUNDER ARE INCREASING ESPECIALLY FROM SLK TO BTV AND
RUT TO MPV MOVING WEST TO EAST 09-13Z BUT WILL HANDLE WITH
AMENDMENTS AS IT REMAINS TO BE SEEN EXACTLY WHERE THE
THUNDERSTORMS TRACK AND IF THEY HOLD TOGETHER.

VISIBILITIES EXPECTED TO REMAIN MAINLY VFR...EXCEPT SOME BRIEF
REDUCTIONS TO MVFR/IFR POSSIBLE IN ANY HEAVIER SHOWERS OR ISOLATED
THUNDERSTORMS.

CEILINGS WILL GRADUALLY LOWER AND PERIODS OF MVFR ARE LIKELY ON
BACK SIDE OF RAIN SHOWERS...LASTING UNTIL LATE MORNING WHEN SHOWER
THREAT DECREASES. CEILINGS LIFT BACK TO VFR BY SUNDAY AFTERNOON.

SCATTERED SHOWER AND ISOLATED THUNDERSTORM DEVELOPMENT POSSIBLE
AGAIN SUNDAY AFTERNOON/EVENING AHEAD OF A SLOW SOUTHWARD MOVING
COLD FRONT IN CANADA. WILL SHOW WITH VCSH/VCTS FOR NOW AS PROBABILITIES
DROP TO 20-30 PERCENT.

SHOWER AND THUNDER CHANCES DROP THIS EVENING UNDER VFR CONDITIONS.
COULD BE SOME FG/BR CHANCES LATER TONIGHT IF CLEARING SKIES AND
LIGHT WINDS PREVAIL AS FRONTAL SYSTEM STALLS TO OUR NORTH.

LIGHT SOUTH WINDS TONIGHT TURN SOUTH/SOUTHWEST ON SUNDAY FROM 5 TO
10 KNOTS. SOME GUSTS TO 20 KNOTS POSSIBLE.

OUTLOOK 06Z MONDAY THROUGH THURSDAY...

06Z MON - 12Z TUE...PERIODS OF MVFR IN RAIN SHOWERS AND ISOLATED
THUNDERSTORMS. LOCAL IFR POSSIBLE.

12Z TUE - 12Z THU...TRENDING VFR. POSSIBLE IFR/LOWER VISIBILITY IN
OVERNIGHT FOG/MIST MPV AND SLK.

12Z THU ONWARD...MAINLY VFR ALTHOUGH BRIEF PERIODS OF MVFR
POSSIBLE IN SCATTERED SHOWERS...MAINLY SLK/MSS.

&&

.MARINE...
AS OF 550 AM EDT SUNDAY...A LAKE THUNDERSTORM ADVISORY IS NOW IN
EFFECT FOR LAKE CHAMPLAIN. A LINE OF THUNDERSTORMS HAS DEVELOPED
OVERNIGHT AND NOW EXTENDS FROM ST. LAWRENCE COUNTY TO THE EASTERN
SHORE OF LAKE ONTARIO. WHILE THERE IS NO IMMEDIATE THREAT OF
LIGHTNING ON LAKE CHAMPLAIN...EXPECT THESE STORMS TO APPROACH LAKE
CHAMPLAIN BY MID-MORNING. BOATERS AND OTHERS NEAR THE LAKE SHOULD
BE PREPARED TO SEEK SAFE HARBOR AS THESE STORMS MOVE
THROUGH...WITH OCCASIONAL TO FREQUENT LIGHTNING...HEAVY DOWNPOURS
PRODUCING BRIEFLY LOWERED VISIBILITY...AND ROUGH SEAS.

ADDITIONAL THUNDERSTORMS MAY DEVELOP AGAIN LATER THIS AFTERNOON.

&&

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

&&

$$
SYNOPSIS...LOCONTO
NEAR TERM...LOCONTO
SHORT TERM...LOCONTO
LONG TERM...SISSON
AVIATION...SISSON
MARINE...LOCONTO












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