000
FXUS61 KBTV 211139
AFDBTV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
739 AM 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 720 AM EDT TUESDAY...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 /12Z TUESDAY THROUGH SATURDAY/...
THROUGH 12Z WEDNESDAY...WIDELY VARYING CONDITIONS CONT ACRS OUR
TAF SITES THIS MORNING WITH VFR AT RUT/BTV...MVFR AT
MPV/SLK/MSS...AND IFR AT PBG. EXPECT CIGS/VIS TO IMPROVE BTWN
14-15Z AT PBG. RADAR SHOWS CLUSTER OF SHOWERS...WHICH MAY IMPACT
RUTLAND TAF SITE BTWN 13-16Z THIS MORNING WITH MVFR POSSIBLE. WINDS
BEHIND LINE OF SHOWERS WITH SHIFT TO A NORTHERLY DIRECTION 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. ALSO...ANOTHER ROUND OF SHOWERS WITH EMBEDDED
THUNDERSTORMS WL BE POSSIBLE AFT 02Z TONIGHT...WITH MVFR TO IFR IN
THE HEAVIER SHOWERS.
OUTLOOK 12Z 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...TABER
AVIATION...TABER
