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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBTV 220254
AFDBTV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
1054 PM EDT TUE MAY 21 2013

.SYNOPSIS...
AN ACTIVE PERIOD OF WEATHER IS EXPECTED ACROSS THE NORTH COUNTRY
THROUGH THURSDAY. A FRONT SETTLES SOUTHWARD THIS AFTERNOON...WITH
ADDITIONAL THUNDERSTORMS GENERALLY FOCUSED ACROSS SOUTH-CENTRAL
VERMONT. THE BOUNDARY WILL SHIFT BACK NORTH AS A WARM FRONT
TONIGHT INTO WEDNESDAY. THE ASSOCIATED WARM AND MOIST AIR
MASS FOR WEDNESDAY AND THURSDAY WILL BRING ADDITIONAL ROUNDS OF
THUNDERSTORMS BOTH WEDNESDAY AND THURSDAY AFTERNOON. 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 AM WEDNESDAY MORNING/...
-- Changed Discussion --
AS OF 1049 PM EDT TUESDAY...LINE OF STRONG THUNDERSTORMS WEAKENING
AS IT EXITS FORECAST AREA TO THE EAST. STILL A LOT OF CONVECTION
SOUTH OF BTV CWA AT THIS TIME ASSOCIATED WITH WARM FRONT. THIS
BOUNDARY WILL BE LIFTING NORTH OVERNIGHT...SO HAVE KEPT HIGH POPS
FOR OCCASIONAL SHOWERS WITH THE CHANCE OF THUNDERSTORMS. ADJUSTED
HOURLY TEMPS FOR NEXT FEW HOURS BASED ON LATEST OBS AND
TRENDS...BUT OVERNIGHT MINS STILL OKAY.

PREVIOUS DISCUSSION...
LINE OF THUNDERSTORMS WITH HISTORY OF SEVERE MOVING RAPIDLY ACROSS
CHAMPLAIN VALLEY AT THIS TIME. STRONG STRONG TO SEVERE DESPITE
LACK OF SURFACE BASED INSTABILITY. THIS LINE WILL MOVE ACROSS
VERMONT THIS EVENING A BREAK IN SHOWERS/THUNDERSTORMS WILL THEN
FOLLOW FOLLOWED BY MORE WIDESPREAD SHOWERS WITH CHANCE OF THUNDER
OVERNIGHT AS WARM FRONT LIFTS NORTH ACROSS THE REGION. SOME
ADJUSTMENTS MADE TO EARLY THIS EVENING TO REFLECT LATEST
TRENDS...BUT OVERNIGHT PORTION OF FORECAST ON TRACK.

EARLIER DISCUSSION...
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.
-- End Changed Discussion --

&&

.SHORT TERM /8 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
AS OF 415 PM EDT TUESDAY...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 TILTED 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.

COLD FRONT WILL FINALLY CROSS THE FORECAST AREA THURSDAY
NIGHT...THOUGH UPPER LEVEL TROF AND LOW WILL TRAIL BEHIND. SLOW
MOVING FLOW CONTINUES AS SURFACE LOW SLOWLY CREEPS EASTWARD AWAY
FROM THE REGION. CHANCE FOR SHOWERS FINALLY DECREASES AT THE END
OF THE PERIOD THURSDAY NIGHT.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 225 PM EDT TUESDAY...DEPARTING LOW PRESSURE SYSTEM WILL
HAVE POSITIVELY TILTED UPPER LEVEL TROUGH MOVE OVER THE NORTH
COUNTRY ON FRIDAY...KEEPING CHC OF SHOWERS OVER MUCH OF THE AREA.
LATE FRIDAY IN TO FRIDAY NIGHT...TROUGH LOOKS TO TILT NEUTRAL TO
NEGATIVE AS THE SFC LOW PUSHES OFF THE NEW ENGLAND COAST. SFC LOW
TRAVERSES NEWD NEAR NEWFOUNDLAND...KEEPING BACK/WRN EDGE OF
PRECIP NEAR VT...THEREFORE HAVE KEPT SLGT CHC POPS OVER VT FRIDAY
NIGHT THROUGH FIRST HALF OF SATURDAY. AS HIGH PRESSURE BUILDS
OVER SW HUDSONS BAY...EXTENDING SWD OVER THE CENTRAL GREAT
LAKES...A SHORTWAVE ROTATING ABOUT THE UPPER LEVEL LOW OVER NEW
ENGLAND WILL BE FAIRLY DRY BUT BRING CLOUDS FOR THE REST OF
SATURDAY INTO SATURDAY NIGHT. ON SUNDAY...SOME TROUGHINESS
REMAINING OVER ERN ZONES...WITH CLOUDS OVER MOST OF VT. THE SFC
HIGH PRESSURE AND SOME UPPER LEVEL RIDGING WILL TAKE HOLD OF THE
REGION FOR THE REST OF THE PERIOD.

BELOW NORMAL MAX TEMPS WILL GRADUALLY TREND WARMER THROUGHOUT THE
PERIOD WITH MIN TEMPS GENERALLY IN THE 40S.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
THROUGH 00Z THURSDAY...COMPLEX FORECAST AS LOW LEVEL MOISTURE
CONTINUES OVER MUCH OF THE AREA ALONG WITH CHANCE OF SHOWERS AND
SOME THUNDERSTORMS THROUGH THE PERIOD. WARM FRONT SOUTH OF
FORECAST AREA THIS EVENING WILL LIFT NORTH ACROSS THE FORECAST
AREA OVER THE NEXT 24 HOURS. CIGS LOWERING TO MVFR TONIGHT WITH
IFR POSSIBLE...ESPECIALLY SLK/MPV/MSS. VSBYS LOWERING TO IFR IN
SHOWERS AND SCATTERED THUNDERSTORMS. LINE OF STRONG TO SEVERE
THUNDERSTORMS THIS EVENING...WITH MORE WIDESPREAD SHOWERS AND
EMBEDDED THUNDER OVERNIGHT. THUNDERSTORMS WEDNESDAY AFTERNOON MAY
ALSO BE ACCOMPANIED BY GUSTY WINDS.

OUTLOOK 00Z THURSDAY THROUGH SUNDAY...OCCASIONAL SHOWERS WITH
EMBEDDED THUNDERSTORMS WILL CONTINUE WEDNESDAY NIGHT INTO
THURSDAY. VFR WITH PERIODS OF MVFR/IFR IN HEAVIER SHOWERS.
SHOWERS AND MVFR CONDITIONS STILL POSSIBLE FRIDAY BEFORE SURFACE
HIGH PRESSURE BUILDS IN OVER THE WEEKEND WITH MAINLY VFR
CONDITIONS.

&&

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

&&

$$
SYNOPSIS...BANACOS/NEILES
NEAR TERM...RJS/NEILES
SHORT TERM...BANACOS/NEILES
LONG TERM...KGM
AVIATION...RJS/KGM