National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBTV 210803
AFDBTV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
403 AM EDT TUE MAY 21 2013

.SYNOPSIS...
-- Changed Discussion --
AN ACTIVE PERIOD OF WEATHER IS EXPECTED ACROSS THE NORTH COUNTRY
THROUGH THURSDAY. AN AREA OF LOW PRESSURE ACROSS SOUTHEASTERN
ONTARIO WILL TRACK EASTWARD ALONG A STATIONARY FRONT PROVIDING A
FOCUS FOR SHOWERS AND A FEW EMBEDDED THUNDERSTORMS THIS MORNING.
THIS ACTIVITY WILL GENERALLY PUSH EAST OF THE CONNECTICUT VALLEY
BY MID MORNING. THE FRONT SETTLES SOUTHWARD THIS AFTERNOON...WITH
ADDITIONAL THUNDERSTORMS GENERALLY FOCUSED ACROSS SOUTH-CENTRAL
VERMONT. THE BOUNDARY WILL SHIFT BACK NORTH AS A WARM FRONT
TUESDAY NIGHT INTO WEDNESDAY. THE ASSOCIATED WARM AND MOIST AIR
MASS FOR WEDNESDAY AND THURSDAY WILL BRING ADDITIONAL ROUNDS OF
THUNDERSTORMS BOTH WEDNESDAY AND THURSDAY AFTERNOON. WHILE IT
WON/T BE RAINING CONTINUOUSLY...BRIEF HEAVY DOWNPOURS WILL BRING
OVER AN INCH OF RAIN TO MOST SECTIONS OF THE NORTH COUNTRY OVER
THE NEXT 48 TO 72 HOURS. TEMPERATURES WILL GENERALLY BE ABOVE
NORMAL OVER THE NEXT SEVERAL DAYS. A COOLER AND DRIER AIR MASS IS
EXPECTED TO RETURN FOR THE UPCOMING HOLIDAY WEEKEND.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 8 PM THIS EVENING/...
-- Changed Discussion --
AS OF 358 AM EDT TUESDAY...30-40 KT SWLY LOW-LEVEL JET PER KTYX VAD
WIND PROFILE AT 0730Z CONTINUES TO PROVIDE SOURCE OF ELEVATED
INSTABILITY TO ONGOING LINE OF SHOWERS AND EMBEDDED TSTMS ACROSS
THE NRN ADIRONDACKS. MODERATELY STRONG 850MB WAA WILL BUILD EWD
ACROSS THE CHAMPLAIN VALLEY AND INTO CENTRAL/S-CENTRAL VT OVER THE
NEXT 2-4 HOURS ALONG/NORTH OF E-W ORIENTED QUASI-STATIONARY BNDRY.
THIS WILL ALLOW SHOWERS AND EMBEDDED CONVECTIVE ACTIVITY TO
CONTINUE EASTWARD WITH BRIEF HEAVY DOWNPOURS AND A FEW RUMBLES OF
THUNDER FROM THE CHAMPLAIN VALLEY EWD THRU MID MORNING. ONCE THIS
INITIAL AREA OF ACTIVITY PASSES...THE REMAINDER OF THE DAY (LATE
MORNING/AFTN) WILL SEE JUST A CHANCE OF ADDITIONAL SHOWERS/TSTMS
WITH WEAK 700-500MB SHORTWAVE RIDGING IN PLACE. IT APPEARS BEST
INSTABILITY WILL BE ACROSS FAR SRN CWA...AND THIS IS WHERE 40-50
POPS AND CHANCE OF TSTMS IS MENTIONED. 30 POP WITH JUST A SLIGHT
CHANCE OF TSTMS ACROSS NWRN VT/NRN NY FOR THE AFTN HRS. GOOD
NORTH-SOUTH GRADIENT IN TEMPS THIS AFTN. PARTIAL SUNSHINE WILL
ALLOW TEMPS TO REACH THE MID 70S ACROSS RUTLAND/WINDSOR COUNTIES
BUT SEVERAL DEGREES COOLER ACROSS NRN HALF OF THE AREA. WINDS
GENERALLY LIGHT AND VARIABLE...AND SHOULD TREND LIGHT NORTH ACROSS
NRN VT AND NELY AROUND 10 KTS IN THE ST. LAWRENCE VALLEY THIS AFTN
IN THE WAKE OF THIS MORNING/S SHOWERS AND TSTMS. FRONTAL
ZONE/NORTH WINDS WILL LIKEWISE LIMIT INSTABILITY ACROSS NRN
SECTIONS THIS AFTN...ANOTHER REASON IT APPEARS BEST CHANCE FOR
TSTM REDEVELOPMENT THIS AFTN WILL BE ACROSS S-CENTRAL VT.
-- End Changed Discussion --

&&

.SHORT TERM /8 PM THIS EVENING THROUGH THURSDAY/...
-- Changed Discussion --
AS OF 358 AM EDT TUESDAY...ADDITIONAL ROUNDS OF SHOWERS AND
POSSIBLE TSTM ACTIVITY WILL BRING A TOTAL OF 1-1.25" OF RAINFALL
TO THE REGION BY THURSDAY EVENING.

FOR TONIGHT...700MB SHORTWAVE RIDGE FLATTENS/SHIFTS EAST OF THE
AREA OVERNIGHT. IT APPEARS ANOTHER WEAK WAVE LOW WILL DEVELOP
ALONG THE FRONTAL ZONE ACROSS THE NRN GREAT LAKES ALLOWING FOR
ANOTHER SURGE OF S-SW FLOW AT 850MB ACROSS FRONTAL ZONE. OVERALL
EVOLUTION SUGGESTS INCREASE IN ISENTROPIC ASCENT WITH INCREASING
CHANCES FOR SHOWERS AND A FEW ELEVATED TSTMS...ESPECIALLY AFTER
MIDNIGHT. HAVE INDICATED MOSTLY CLOUDY TO CLOUDY CONDITIONS....AND
THE SOUTH WINDS AND CLOUDS WILL KEEP TEMPS ON THE MILD
SIDE...GENERALLY UPR 50S TO AROUND 60. MAINTAINED SLIGHT CHANCE OF
TSTM MENTION IN THE FORECAST GRIDS.

NORTH COUNTRY GENERALLY IN THE WARM SECTOR ON WEDNESDAY AS FRONTAL
ZONE RETREATS BACK NORTH OF THE INTL BORDER. DIFFICULT TO SEE MUCH
IN THE WAY OF LOW-LEVEL CONVERGENCE...AND MID-LEVEL FLOW HAS SLIGHT
ANTICYCLONIC CURVATURE. PBL DEWPOINTS DO INCREASE INTO THE LOW
60S...AND WITH PARTIAL SUN CONDITIONS SHOULD RESULT IN SBCAPE VALUES
AROUND 1000 J/KG. AGAIN...MARGINAL/WEAK FORCING IN PLAY SO WHILE
POTENTIAL FOR ORGANIZED STORMS IS LOW...ISOLD TO SCT -TSRA IS
POSSIBLE...LIKELY PEAKING WITH DAYTIME HEATING MAX IN THE MID-LATE
AFTN HOURS. A FEW STRONGER STORMS MAY PRODUCE SMALL HAIL WITH
LOCALLY HEAVY DOWNPOURS. VALLEY HIGHS ON WEDNESDAY WILL REACH THE
UPR 70S TO AROUND 80.

POSITIVE TILT UPR TROUGH AND COLD FRONTAL ZONE APPROACHES SLOWLY
LATE WEDNESDAY NIGHT INTO THURSDAY. THIS SHOULD GENERATE A MORE
WIDESPREAD THREAT OF SHOWERS AND TSTMS BY THURSDAY AFTN. DEEP-
LAYER SWLY FLOW IN ADVANCE OF THE FRONTAL BNDRY WILL ENSURE
MOISTURE/SOME INSTABILITY ON THURSDAY...THOUGH MID-LEVEL LAPSE
RATES WILL BE RELATIVELY POOR AROUND 6 C/KM. WITH PEAK
HEATING...MAY BE SUFFICIENT FOR A SEVERE STORM OR TWO WITH GUSTY
WINDS AND MARGINALLY SVR HAIL DURING THURSDAY AFTN...ESPECIALLY
CENTRAL/S-CENTRAL VT BASED ON CURRENT INDICATIONS. HIGHS THURSDAY
WILL RANGE FROM THE MID-UPR 70S ACROSS VT TO THE UPR 60S TO NEAR
70F IN THE NRN ADIRONDACKS.
-- End Changed Discussion --

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 425 PM EDT MONDAY...

A COLD FRONT WITH SHOWERS AND THUNDERSTORMS ON THURSDAY WILL USHER
IN COOLER AND MAINLY DRY WEATHER FOR THE UPCOMING MEMORIAL DAY
WEEKEND.

CONFIDENCE FAIRLY HIGH IN THE LARGE-SCALE FEATURES AS UPPER TROF
PASSES SLOWLY ACROSS THE REGION. SOME UNCERTAINTY IN HOW THE TROF
EVOLVES AND HOW FAST IT MOVES OUT TOWARD THE END OF THE PERIOD.

ON THURSDAY THE COLD FRONT WILL MOVE SLOWLY SOUTHEAST THROUGH THE
AREA. INSTABILITY EXPECTED TO BE MARGINAL WITH CAPE VALUES AROUND
500 J/KG OR SO AND WILL DEPEND UPON CLOUD COVER. WITH LESS CLOUD
COVER VALUES COULD CLIMB NEAR 1000 J/KG ESPECIALLY SOUTH AND EAST
OF BTV. IF THE INSTABILITY MATERIALIZES AND 0-6KM BULK SHEAR
VALUES OF 30-40 KTS WILL HAVE TO WATCH FOR A FEW STRONGER STORMS.
HIGHS SHOULD BE IN THE 70S WITH 850 TEMPS AROUND +12C.

THURSDAY NIGHT WILL FEATURE A TRANSITION TO MUCH COOLER TEMPS WITH
850 TEMPS FALLING TO NEAR 0C BY 12Z FRIDAY. COULD BE SOME
LINGERING SHOWERS OVER NIGHT.

A COOL NW FLOW ON FRIDAY AND SATURDAY WITH 850 TEMPS AROUND 0 WILL
KEEP HIGH TEMPERATURES IN THE UPPER 50S TO MID 60S WITH PLENTY OF
CUMULUS CLOUDS AND EVEN A CHANCE OF A SHOWER DURING THE AFTERNOON
OR EVENING HOURS ESPECIALLY IN THE MOUNTAINS. LOW TEMPERATURES
WILL BE MAINLY 35 TO 45.

SUNDAY AND MONDAY SHOULD BE DRY AS HIGH PRESSURE MOVES INTO THE
NORTHEAST AND TEMPERATURE WILL BEGIN TO RETURN TO NORMAL WITH
HIGHS IN THE UPPER 60S TO LOW 70S AND LOWS IN THE 40S.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
THROUGH 06Z WEDNESDAY..DIFFICULT TAFS WITH CRNT OBS RANGING FROM
LIFR AT MPV IN FOG TO VFR CONDITIONS AT BTV/RUT/MSS. EXPECT FOG TO
CONTINUE THRU 07Z...BEFORE LIFTING AS MID LVL CLOUDS INCREASE AT
MPV. OTHERWISE...CRNT RADAR SHOWS A LINE OF SHOWERS WITH EMBEDDED
STORMS ACRS WESTERN SLV...THIS PRECIP WL IMPACT SLK BY
07Z...PBG/BTV/RUT BTWN 08Z-10Z...AND THRU OUR TAF SITES BY 12Z
THIS MORNING. EXPECT BRIEF GUSTY WINDS TO 25 KNTS...HEAVY RAIN
WITH MVFR CIGS/VIS LIKELY WITH A CHC OF IFR VIS/CIGS IN THE
HEAVIEST SHOWERS. RAP13 SOUNDINGS SHOW LOTS OF LLVL RH
REDEVELOPING AFT 09Z...FROM WEST TO EAST ACRS OUR CWA. HAVE
INCLUDED A PERIOD OF IFR CIGS AT MPV/SLK/MSS...WITH MVFR
CONDITIONS AT PBG/BTV. WINDS BEHIND LINE OF SHOWERS WITH SHIFT TO
A NORTHERLY DIRECTION THIS MORNING...WHICH WL HELP TO ENHANCE LLVL
CIGS AT MSS/BTV. MVFR/IFR CIGS WL CONT THRU 14Z...BEFORE SLOWLY
LIFTING TO MVFR/VFR CONDITIONS BY 15Z. BEST INSTABILITY/SFC
HEATING FOR ADDITIONS SHOWERS/STORMS THIS AFTN WL BE AT
SLK/RUT/MPV. MORE FOG/BR AND LOW CIGS WL BE POSSIBLE TUESDAY
EVENING ACRS OUR TAF SITES WITH LIGHT WINDS AND PLENTY OF LLVL
MOISTURE.

OUTLOOK 06Z WEDNESDAY THROUGH SATURDAY...
OCCASIONAL SHOWERS WITH EMBEDDED THUNDERSTORMS WL CONT FOR WEDS
INTO THURS...BEFORE SFC HIGH PRES AND CLRING DEVELOPS BY THE
WEEKEND. VFR WITH PERIODS OF MVFR CONDITIONS IN THE HEAVIER
SHOWERS/STORMS WL BE POSSIBLE. IN ADDITION...AREAS OF FOG/BR WITH
LIFR CONDITIONS WL BE POSSIBLE AT SLK/MPV.

&&

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

&&

$$
SYNOPSIS...BANACOS
NEAR TERM...BANACOS
SHORT TERM...BANACOS
LONG TERM...SISSON
AVIATION...TABER