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000
FXUS61 KBTV 181657
AFDBTV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
1257 PM EDT SAT MAY 18 2013

.SYNOPSIS...
A LARGE AREA OF HIGH PRESSURE WILL CONTINUE TO BUILD DOWN FROM
EASTERN CANADA AND PERSIST OVER NORTHERN NEW ENGLAND THROUGH MUCH OF
THE WEEKEND. LOOK FOR MORE DRY WEATHER WITH JUST A SLIGHT CHANCE OF
SHOWERS SUNDAY AFTERNOON. A GRADUAL WARMING TREND IS ALSO EXPECTED
FOR THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 1257 PM EDT SATURDAY...500 MB HEIGHTS CONTINUE TO SLOWLY
RISE FROM WEST TO EAST WITH THE AREA UNDER MOSTLY SUNNY SKIES.
TEMPERATURES HAVE WARMED INTO THE MID/UPPER 60S WITH A FEW LOWER
70S IN THE SAINT LAWRENCE VALLEY. STILL A FEW MORE HOURS LEFT OF
SUNSHINE SO HAVE ADJUSTED MAXES UP A COUPLE DEGREES FURTHER TO THE
UPPER 60S TO THE MID 70S. ALSO CHANGED THE WORDING TO SLIGHT
CHANCE TO COVER THE SHOWER ACTIVITY ACROSS THE NORTHEAST KINGDOM.
REGIONAL RADAR SHOWS SOME ISOLATED TO WIDELY SCATTERED SHOWERS
BREAKING OUT ACROSS THE WHITE MOUNTAINS OF NORTHERN NEW HAMPSHIRE
AND INTO NORTHWESTERN MAINE. OVERALL COVERAGE OF SHOWERS WILL BE
FEW AND FAR BETWEEN WITH THE BUILDING HEIGHTS BUT CAN`T RULE OUT A
SHOWER IN THE NORTHEAST KINGDOM GIVEN THE WEAK SHORTWAVE TROUGH
DIVING SOUTHEASTWARD GRAZING THE BORDER OF NORTHEAST VT/NH LATE IN
THE DAY. DEWPOINTS WERE ALSO TWEAKED DOWNWARD THROUGH THE
AFTERNOON TO BETTER MATCH CURRENT OBSERVATIONS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/...
AS OF 351 AM EDT SATURDAY...A FAIRLY QUIET NIGHT IS EXPECTED AS
THE AFOREMENTIONED AREA OF HIGH PRESSURE CONTINUES TO SLOWLY SLIDE
SOUTHEASTWARD OFF THE NEW ENGLAND COAST. UPPER TROUGH OVER THE
GULF OF MAINE ALSO SHIFTS EASTWARD A BIT ALLOWING MID LEVEL
HEIGHTS TO SLOWLY RISE ACROSS THE BTV CWA...AND THUS EXPECTING A
GENERALLY CLEAR TO PARTLY CLOUDY NIGHT WITH LOWS RUNNING AT OR
SLIGHTLY ABOVE NORMAL IN THE 40S TO LOCALLY NEAR 50 IN THE
CHAMPLAIN VALLEY. SOUTHERLY RETURN FLOW INCREASES GOING INTO
SUNDAY ALONG WITH AN INCREASE IN LOW/MID LEVEL MOISTURE. MID LEVEL
HEIGHTS CONTINUE TO SLOWLY RISE BUT FLOW ALOFT REMAINS OUT OF THE
NORTHWEST. THIS COMBINED WITH SOME WEAK SURFACE INSTABILITY IN THE
AFTERNOON COULD SPARK A FEW ISOLATED SHOWERS...THOUGH MAINLY
ACROSS THE HIGHER TERRAIN AND PROBABLY NOT REALLY AMOUNTING TO
MUCH. HIGHS CONTINUE TO RUN ABOVE NORMAL AS 925MB TEMPS RISE INTO
THE LOWER TEENS SUPPORTING HIGHS SIMILAR TO SATURDAY...MAYBE A
DEGREE OR TWO WARMER. ANY ISOLATED SHOWERS DISSIPATE SUNDAY NIGHT
WITH THE LOSS OF DAYTIME HEATING...AND EXPECT A FAIRLY MILD NIGHT
WITH PARTLY TO MOSTLY CLOUDY SKIES AND MODEST SOUTHERLY FLOW
KEEPING TEMPS FROM FALLING OUT OF THE 50S FOR MOST LOCATIONS.
CHAMPLAIN VALLEY MIGHT NOT EVEN BREAK 60. FOR MONDAY...UPPER
TROUGH OFF THE GULF OF MAINE FINALLY SHIFTS FAR ENOUGH EAST TO
ALLOW UPPER RIDGING TO BUILD INTO PORTIONS OF THE NORTHEAST. SIMILAR
TO SUNDAY...FLOW ALOFT REMAINS OUT OF THE NORTHWEST THOUGH...AND
WITH INCREASING MOIST SOUTHERLY FLOW AT THE SURFACE WE COULD AGAIN
SEE SOME ISOLATED SHOWERS ACROSS THE AREA. WARMING TREND ALSO
CONTINUES FOR MONDAY WITH HIGHS GOING A FEW MORE DEGREES HIGHER
THAN THE PREVIOUS DAYS INTO THE MID TO UPPER 70S TO LOCALLY NEAR
80 IN THE ST. LAWRENCE VALLEY.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 322 AM EDT SATURDAY...OVERALL A MORE ACTIVE PATTERN
ANTICIPATED FOR DAYS 4 THROUGH 7. RELATIVELY GOOD CONSISTENCY
BETWEEN 00Z ECMWF AND 00Z GFS THROUGH THE PERIOD. THAT SAID...SYNOPTIC
PATTERN INVOLVES A SLOW SWD MOVING FRONTAL ZONE TUE-WED FOLLOWED
BY THE APPROACH OF A CLOSED UPR LOW THU-FRI THAT SUGGESTS TIMING
ERRORS ARE POSSIBLE IN EXPECTED WX CONDITIONS.

FRONTAL BOUNDARY SAGGING SWD FROM SERN ONTARIO/SRN QUEBEC IN
CONFLUENT ZONAL FLOW REGIME ALOFT HAS THE POTENTIAL TO BRING AN
UNSETTLED PERIOD OF WEATHER WITH ABUNDANT SHOWERS AND POSSIBLE TSTMS
TUESDAY INTO TUESDAY NIGHT. SOME QUESTION AS TO HOW FAR SOUTH THE
FRONTAL ZONE SAGS ON WEDNESDAY; WITH BUILDING HEIGHTS ALOFT IT IS
POSSIBLE THAT WEDNESDAY COULD BE DRIER (ESPECIALLY ACROSS THE NRN
HALF OF THE CWA)...BUT GFS/ECMWF HAVE FRONTAL PLACEMENT AND TEMPORAL
DIFFERENCES THAT ARE DIFFICULT TO RECONCILE AT THIS POINT. HAVE
CONTINUED CHANCE POPS FOR SHOWERS BUT LEFT MENTION OF TSTMS OUT OF
THE FCST FOR WEDNESDAY WITH LESS MOIST CONDITIONS NORTH OF THE
FRONT. UPSTREAM CLOSED UPR LOW/VORT MAX EVENTUALLY SHIFTS EWD FROM
THE GREAT LAKES WITH ESTABLISHMENT OF MOIST SWLY FLOW IN ADVANCE OF
THIS FEATURE BRINGING POTENTIAL INSTABILITY AND ADDITIONAL CHANCES
FOR SHOWERS AND TSTMS FOR THURSDAY AFTN. CHANCES FOR SHOWERS
CONTINUE THURSDAY NIGHT INTO FRIDAY GIVEN ANTICIPATED SLOW-MOVING
NATURE OF UPR LOW. TEMPERATURES THROUGH THE PERIOD ARE GENERALLY
EXPECTED SEVERAL DEGREES ABOVE NORMAL...WITH ABUNDANT CLOUDS KEEPING
OVERNIGHT LOWS ON THE MILD SIDE. GENERALLY LOOKING AT HIGHS IN THE
LOW TO MID 70S AND LOWS IN THE 50S...POSSIBLY LOW 60S IN THE
CHAMPLAIN VALLEY ON MONDAY NIGHT.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
THROUGH 12Z SUNDAY...VFR AT THE TAF SITES. SURFACE HIGH PRESSURE IN
CONTROL ACROSS THE NORTH COUNTRY WILL BRING CLEAR SKIES THIS
MORNING AND SCATTERED FAIR WX CUMULUS CLOUDS WITH DAYTIME HEATING
THIS AFTERNOON. ANY EARLY AM VALLEY FOG WILL DISSIPATE BY
13Z...AND HAS ALREADY DONE SO AT MPV/MSS WHERE THERE WAS BRIEF FOG
DURING THE PRE-DAWN HRS. GENERALLY LIGHT WIND CONDITIONS
CONTROLLED BY LOCAL TOPOGRAPHIC EFFECTS.

OUTLOOK 12Z SUNDAY THROUGH WEDNESDAY...HIGH PRESSURE SLIDES EWD INTO THE
GULF OF MAINE ON SUNDAY WITH SOUTH WINDS 10-15 KTS DEVELOPING AT THE
TAF SITES. THERE IS A SLIGHT CHANCE OF RAIN SHOWERS...MAINLY ACROSS
THE HIGHER ELEVATIONS WITH BEST CHANCE OF BRIEF MVFR CONDITIONS AT
SLK/MPV. OTHERWISE...SHOULD BE GENERALLY VFR SUNDAY INTO SUNDAY
NIGHT. A FRONTAL BOUNDARY SAGGING SWD FROM ONTARIO/QUEBEC EVENTUALLY
BRINGS THE THREAT FOR SHOWERS AND POSSIBLE TSTMS. SOME TIMING
UNCERTAINTIES AT THIS POINT...BUT BEST CHANCES FOR RAINFALL APPEAR
TO BE TUESDAY/WEDNESDAY. ANTICIPATE PERIODS OF MVFR AND PERHAPS
BRIEF IFR CONDITIONS.

&&

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

&&

$$
SYNOPSIS...LAHIFF
NEAR TERM...LAHIFF/LOCONTO
SHORT TERM...LAHIFF
LONG TERM...BANACOS
AVIATION...BANACOS