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000
FXUS61 KBTV 211733
AFDBTV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
133 PM EDT TUE MAY 21 2013

.SYNOPSIS...
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.

&&

.NEAR TERM /UNTIL 8 PM THIS EVENING/...
AS OF 132 PM EDT TUESDAY...NO SIGNIFICANT CHANGES MADE TO
FORECAST...GOING FORECAST IS IN GOOD SHAPE. DID LOWER TEMPS FOR
TODAY SLIGHTLY ACROSS OUR NORTHERN ZONES. PREVIOUS DISCUSSION
FOLLOWS.

LEADING SHORTWAVE TROUGH AND ASSOCIATED MESOSCALE CONVECTIVE
SYSTEM - WHICH BROUGHT 0.25 TO 0.50" RAINFALL TO MOST OF THE
REGION DURING THE PRE-DAWN HOURS - HAS NOW DEPARTED THE FORECAST
AREA INTO NRN NH. AS THE SHORTWAVE ALONG THE INTL BORDER BETWEEN
VT/QUEBEC SHIFTS EWD...SFC WINDS WILL TURN LIGHT NORTH TO NE
ACROSS NRN PART OF THE FORECAST AREA. IT CONTINUES TO APPEAR THAT
THE BEST CHANCE FOR DESTABILIZATION THIS AFTN WILL BE ACROSS SRN
HALF OF THE FORECAST AREA...AND S-CENTRAL VT IN PARTICULAR (TEMPS
REACH 75-78F ACROSS SRN VALLEYS THIS AFTN). IN THE
MEANTIME...LOOKING AT MOSTLY CLOUDY CONDITIONS THIS
MORNING...WITH SOME PARTIAL CLEARING THIS AFTN. HAVE ADJUSTED
POPS DOWNWARD IN THE WAKE OF THE MCS...WITH 30-50 POPS FOR RAIN
THIS AFTN/EARLY THIS EVENING. PREVIOUS DISCUSSION FOLLOWS...

PREVIOUS DISCUSSION: 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.

&&

.SHORT TERM /8 PM THIS EVENING THROUGH THURSDAY/...
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.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 425 AM EDT TUESDAY...TRENDS WL BE FOR DRIER AND COOLER WX
AS WE HEAD INTO THE MEMORIAL HOLIDAY WKND. BEST CHC FOR LINGERING
SHOWERS WL BE LATE THURS NIGHT INTO FRIDAY...AS FRNT IS SLOW TO
EXIT OUR CWA...AND SECONDARY S/W ENERGY DROPS ACRS OUR FA ON
FRIDAY. THIS ENERGY ALOFT...COMBINED WITH LEFTOVER 850 TO 500MB
RH WL PRODUCE SOME SCATTERED SHOWERS ON FRIDAY. HIGHEST CHC POPS
WL BE ACRS THE CENTRAL/NORTHERN MTNS OF VT. OTHERWISE...COOL
CANADIAN HIGH PRES BUILDS INTO OUR FA ON SATURDAY THRU MONDAY.
THIS WL PROVIDE REGION WITH MUCH LESS HUMIDITY...COOLER
TEMPS...AND BREEZY NORTHWEST WINDS OVER THE WEEKEND. GFS SHOWS A
BACKSIDE DEFORMATION ZNS DEVELOPING LATE FRIDAY NIGHT INTO
SATURDAY ACRS OUR CENTRAL/SOUTHERN ZNS. THIS WOULD PRODUCE SOME
LINGERING SHOWERS THRU EARLY SATURDAY MORNING...BUT GIVEN
UNCERTAINTY AND NARROW AXIS OF RH/LIFT WL KEEP SAT DRY ATTM.

SUNDAY...MID/UPPER LVL TROF WL BE LOCATED OVER EASTERN
CANADA...WHILE SFC HIGH PRES BUILDS INTO OUR CWA FROM THE CENTRAL
GREAT LAKES. THIS WL PRODUCE BREEZY NORTHWEST WINDS AT 10 TO 15
MPH...WITH GUSTS INTO THE 20S...ESPECIALLY ON BY SUNDAY AFTN.
TEMPS WL START IN THE MID 40S AND WARM INTO THE U50S MTNS TO
L/M60S CPV/SLV...WITH LOW RH VALUES. A GREAT DAY FOR OUTDOOR
ACTIVITIES. SOME PATCHY FROST IN THE COLDER/DEEPER MTN VALLEYS WL
BE POSSIBLE SUNDAY NIGHT/MONDAY MORNING...ESPECIALLY IF SFC HIGH
PRES BUILDS OVERHEAD...AS PROGGED BY THE ECMWF. BY MONDAY INTO
TUES...LLVL WAA DEVELOPS AND TEMPS RETURN TO NEAR NORMAL LEVELS.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
THROUGH 18Z WEDNESDAY...COMPLEX FCST AS LL MOISTURE CONTINUES
OVER MUCH OF THE AREA...WITH SOME BREAKS IN CLOUDS TO THE SOUTH
TRYING TO REACH NORTH. FRONTAL SYSTEM TO THE SOUTH ALSO HAS
INCREASING INSTABILITY ALONG IT...TRIGGERING SOME SHOWERS AND
THUNDERSTORMS WHICH SHOULD REMAIN SOUTH OF THE TAF SITES. MORE
CLOUDS MOVING IN FROM THE WEST. VRB CONDITIONS WILL PERSIST THIS
AFTN...MAINLY MVFR WITH PERIODS OF IFR CIGS. MPV AND RUT SEEING
THE MOST BREAKS IN CLOUDS AND VFR CONDITIONS...BUT MOISTURE AND
MVFR CIGS WILL REACH THESE SITES IN THE LATE AFTN TO EARLY
EVENING HRS.

MORE FOG/BR AND LOW CIGS WL BE POSSIBLE THIS EVENING ACRS TAF
SITES WITH LIGHT WINDS AND PLENTY OF LLVL MOISTURE.
ALSO...ANOTHER ROUND OF SHOWERS WITH EMBEDDED THUNDERSTORMS WL BE
POSSIBLE AFT 01Z TONIGHT...WITH MVFR TO IFR IN THE HEAVIER
SHOWERS. SHOWERS WILL TAPER OFF BY MID MORNING HOURS...WITH
GRADUALLY IMPROVING CONDITIONS.

OUTLOOK 18Z WEDNESDAY THROUGH SUNDAY...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/NEILES
SHORT TERM...BANACOS
LONG TERM...TABER
AVIATION...KGM/TABER