Area Forecast Discussion
Issued by NWS Burlington, VT

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000
FXUS61 KBTV 301501
AFDBTV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
1101 AM EDT THU JUL 30 2015

.SYNOPSIS...
WIDESPREAD SHOWERS AND THUNDERSTORMS ARE EXPECTED TODAY AS A COLD
FRONT MOVES ACROSS THE REGION. A FEW OF THESE THUNDERSTORMS HAVE
THE POTENTIAL TO BECOME STRONG TO SEVERE THIS AFTERNOON GUSTY
WINDS AND HEAVY DOWNPOURS. COOLER WEATHER RETURNS ON FRIDAY AS
THE COLD FRONT EXITS THE AREA.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 11 AM EDT THURSDAY...QUICK UPDATE TO ADJUST FOR HOURLY TEMP
TRENDS (A TAD COOLER BECAUSE OF CLOUD COVER), OTHERWISE FORECAST
IS IN GOOD SHAPE. THE QUESTION RIGHT NOW IS HOW MUCH WILL THE
SHOWERS MOVING ACROSS NY PUT THE DAMPER ON CONVECTIVE POTENTIAL
THIS AFTEROON. STILL CARRYING THE POTENTIAL FOR GUSTY WINDS AND
HEAVY RAIN DURING THE AFTERNOON, BUT THE QUESTION RIGHT NOW WILL
THE ATMOSPHERE DESTABILIZE SUFFICIENTLY BEFORE THE FRONT PUSHES
THROUGH MID TO LATE AFTERNOON. SEEING ONLY 500 J/KG MUCAPE RIGHT
FROM THE 12Z ALY AND BUF SOUNDINGS BUT GETTING UP TO 1500 J/KG
MU/SBCAPE FROM CWMW MODIFIED FOR SFC TEMPS IN THE LOWER TO MID
80S. STILL SEEING 70 DEGREE DEW POINTS PUSHING UP THE HUDSON
VALLEY AND OVER THE ST. LAWRENCE VALLEY AS FAR WEST AT CYOW, SO
IT`S POSSIBLE TO SEE THE NAM`S 1000+ J/KG CAPE JUST AHEAD OF THE
FRONT NEAR BTV AROUND 20-21Z AND ALONG WITH 30+ KT 0-6KM BULK
SHEAR WILL HAVE TO WATCH ANY STORMS THAT DO DEVELOP. ADDITIONALLY
CORFIDI VECTORS SMALL THIS AFTERNOON WITH LOW LEVEL JET PARALLEL
TO THE MEAN CLOUD LAYER, SO HEAVY RAINS STILL POSSIBLE IN A FEW
SPOTS DESPITE OVERALL PROGRESSIVE MOVEMENT OF THE SYSTEM.

PREVIOUS DISCUSSION...FORECAST REMAINS ON TRACK FOR THE
POTENTIAL FOR STRONG TO SEVERE STORMS TODAY AS A COLD FRONT SHIFTS
THROUGH THE REGION. CURRENT RADAR AND SURFACE ANALYSIS SHOW THE
BOUNDARY CURRENTLY OVER THE WESTERN TIP OF LAKE ERIE WHILE
CONVECTION IS FIRING UP ON THE EASTERN SHORE. DOESN`T MATTER WHICH
MODEL YOU PICK, THEY ALL SHOW JUST ABOUT THE SAME TIMING FOR
CONVECTION SHIFTING INTO THE BTV CWA TODAY. CURRENT ARRIVAL/EXIT
TIMING LOOKS TO BE 13-17Z IN THE SAINT LAWRENCE VALLEY AND
NORTHERN ADIRONDACKS, 16-20Z IN THE CHAMPLAIN VALLEY, AND 17-21Z
ACROSS CENTRAL AND EASTERN VERMONT. WITH THIS TIMING IN MIND, THE
GREATEST THREAT FOR ANY SEVERE STORMS WILL BE FROM THE CHAMPLAIN
VALLEY AND POINTS EASTWARD WHERE THE BEST SURFACE HEATING WILL
TAKE PLACE. STILL LOOKING AT ROUGHLY 1000-2000 J/KG OF CAPE
DEVELOPING BY MID-DAY FROM THE CHAMPLAIN EASTWARD, WITH 0-6KM
SHEAR OF ABOUT 30-40 KNOTS WHICH SHOULD BE ENOUGH TO DEVELOP A
NARROW BAND OF ORGANIZED THUNDERSTORMS. WIND SHEAR IS MOSTLY UNI-
DIRECTIONAL FROM THE SOUTHWEST AND PARALLEL TO THE FRONT, SO THE
PRIMARY SEVERE THREAT WILL BE DAMAGING WINDS FROM BOWING SEGMENTS
WITH A FAIRLY MINIMAL HAIL THREAT DUE TO HIGH FREEZING LEVELS.
SECONDARY THREAT WILL BE THE POTENTIAL FOR HEAVY DOWNPOURS WITH
PWATS PUSHING CLOSE TO 2", BUT STORMS SHOULD BE MOVING QUICK
ENOUGH TO MITIGATE ANY FLASH FLOOD CONCERNS. HIGHS TODAY WILL
RANGE THROUGH THE 80S TO NEAR 90 IN SOME PLACES. BASED ON
CONVECTIVE TIMING, HIGH TEMPS ARE EXPECTED TO BE REACHED AROUND
MID-DAY ACROSS VERMONT, AND LATE AFTERNOON ACROSS NORTHERN NEW
YORK.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
AS OF 410 AM EDT THURSDAY...AS THE AFOREMENTIONED SURFACE FRONT
CLEARS THE REGION TO OUR EAST CONVECTION WILL QUICKLY DIE OFF THIS
EVENING WITH CLEARING SKIES EXPECTED AFTER 00Z. SOUTHWEST FLOW
CONTINUES ALOFT AS A LARGE-SCALE CLOSED LOW TAKES RESIDENCE OVER
JAMES BAY RESULTING IN A SLOW ARRIVAL OF THE COOLER POST-FRONTAL
AIR. OVERNIGHT LOWS WILL REMAIN ABOVE NORMAL BUT COOLER THAN THE
PREVIOUS 2 NIGHTS WITH TEMPS FALLING INTO THE 60S FOR MOST, EXCEPT
SOME 50S IN THE ADIRONDACKS.

FOR FRIDAY AND SATURDAY THE CLOSED LOW OVER JAMES BAY REMAINS THE
DOMINANT WEATHER MAKER ACROSS THE NORTH COUNTRY WITH SEVERAL PIECES
OF SHORTWAVE ENERGY MOVING THROUGH THE GENERALLY WEST/SOUTHWEST FLOW
ALOFT. FIRST PIECE OF WEAK ENERGY SHIFTS THROUGH FRIDAY WITH A FEW
ISOLATED SHOWERS POSSIBLE ACROSS THE NORTHERN TIER OF THE CWA, BUT
MORE SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE POSSIBLE
SATURDAY AS A STRONGER SHORTWAVE SHIFTS EAST FROM THE GREAT LAKES.
HIGHS BOTH DAYS WILL BE VERY SEASONAL IN THE UPPER 70S TO MID 80S,
WITH FRIDAY NIGHT LOWS IN THE MID 50S TO LOW 60S.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 312 AM EDT THURSDAY...THIS MORNING`S GLOBAL OPERATIONAL
RUNS AND SUPPORTING ENSEMBLE MEMBERS REMAIN IN OVERALL GOOD
AGREEMENT ON THE LARGE-SCALE SYNOPTIC FEATURES FROM SUNDAY ONWARD.
THIS WILL FEATURE A SLOWLY EVOLVING AND BROAD UPPER TROUGH ACROSS
THE NORTHERN GREAT LAKES AND CANADIAN PRAIRIES EASTWARD INTO THE
NORTHEASTERN TIER OF THE COUNTRY INTO EAST-CENTRAL CANADA.
NORTHERN NEW YORK AND NEW ENGLAND WILL GENERALLY LIE ON THE
SOUTHERN PERIPHERY OF THIS FEATURE WITH A RATHER ACTIVE WEATHER
PATTERN TAKING SHAPE AS FAST FLOW ALOFT BRINGS SEVERAL SHORTWAVES
AND CHANCES OF SHOWERS/STORMS TO THE REGION. NO WIDESPREAD SEVERE
WEATHER IS EXPECTED, BUT CONFIDENCE ON TIMING AND STRENGTH OF
INDIVIDUAL SHORTWAVE FEATURES IS MODEST AT BEST, TYPICAL UNDER
SUCH SCENARIOS. IN GENERAL THE BEST THREAT OF PRECIPITATION WILL
OCCUR DURING THE AFTERNOON AND EARLY EVENING HOURS WHEN WEAK TO
MODEST INSTABILITY WILL EXIST. WITH LOW TO MID LEVEL FLOW
REMAINING WEST TO SOUTHWESTERLY, NEAR SEASONAL TEMPERATURES AND
TOLERABLE HUMIDITY LEVELS ARE EXPECTED WITH A SLIGHT COOLDOWN BY
THE MIDDLE OF NEXT WEEK AS UPPER TROUGH MAKES ITS FURTHEST INROADS
SOUTH.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
THROUGH 12Z FRIDAY...MAINLY VFR. FRONTAL BOUNDARY PUSHES THROUGH
THE AREA WITH SHOWERS/STORMS POSSIBLE FROM WEST TO EAST IN THE
13-21Z TIME FRAME. A FEW STORMS MAY TREND STRONG TO LOCALLY SEVERE
WITH TURBULENCE/GUSTY WINDS FROM KPBG/KBTV AND POINTS EAST. BRIEF
IFR VISIBILITY/MVFR CIGS POSSIBLE WITH THIS ACTIVITY. SHOWERS/STORMS
TO CLEAR EASTERN TERMINALS BY 21Z. WINDS SOUTHERLY FROM 6-12 KTS
AND OCCASIONALLY GUSTY THROUGH 00Z, TRENDING LIGHT AFTERWARD. SOME
POSSIBILITY OF PATCHY IFR IN BR/FG AFTER06Z FRIDAY BUT LOW
CONFIDENCE AT THIS TIME.

OUTLOOK 12Z FRIDAY THROUGH MONDAY...
12Z FRI - 12Z SAT: MAINLY VFR. CHANCE MVFR/IFR FOG MAINLY AT
MPV/SLK 06/12Z SAT.

12Z SAT ONWARD: MAINLY VFR, THOUGH DAILY CHANCES OF SHRA/TSRA WITH
BRIEF MVFR/IFR POSSIBLE IN HEAVIER CONVECTIVE DOWNPOURS.

&&

.MARINE...
AS OF 410 AM EDT THURSDAY...BOATERS SHOULD EXERCISE CAUTION IF
PLANNING ON RECREATING ON LAKE CHAMPLAIN TODAY AS A COLD FRONT
SHIFTING THROUGH THE REGION WILL PRODUCE A LINE OF POTENTIALLY
STRONG THUNDERSTORMS. WE CURRENTLY EXPECT STORMS TO IMPACT THE
LAKE CHAMPLAIN BASIN BETWEEN NOON AND 4 PM WHERE THE GREATEST
THREAT WILL BE STRONG TO LOCALLY DAMAGING WINDS IN EXCESS OF 50
MPH. WINDS OF THIS MAGNITUDE CAN EASILY OVERTURN VESSELS SO BE
PREPARED TO SEEK SAFE HARBOR SHOULD SEVERE THUNDERSTORMS DEVELOP.
MONITOR NOAA WEATHER RADIO FOR UPDATES THROUGH THE MORNING.

&&

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

&&

$$
SYNOPSIS...LAHIFF/SISSON
NEAR TERM...LAHIFF/SISSON
SHORT TERM...LAHIFF
LONG TERM...JMG
AVIATION...JMG
MARINE...LAHIFF



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