Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 251926
AFDGYX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
326 PM EDT FRI JUL 25 2014

.SYNOPSIS...
HIGH PRESSURE OVER THE REGION TONIGHT MOVES INTO THE WESTERN
ATLANTIC ON SATURDAY. AN UPPER LEVEL TROUGH OF LOW PRESSURE MOVES
INTO THE AREA ON SUNDAY AND BRINGS SHOWERS AND ISOLATED
THUNDERSTORMS THROUGH MONDAY OR TUESDAY. HIGH PRESSURE BUILDS IN
AGAIN FOR THE END OF THE WEEK.

&&

.NEAR TERM /TONIGHT/...
AFTERNOON CUMULUS AND ANY ISOLATED SHOWERS SHOULD DISSIPATE THIS
EVENING... LEAVING A MOSTLY CLEAR SKY AND CALM WINDS. THIS WILL
ALLOW GOOD RADIATIONAL COOLING CONDITIONS WITH TEMPERATURES
FALLING INTO THE 50S (40S NORTH) WHICH IS NOT QUITE AS COOL AS
LAST NIGHT DUE TO A LITTLE MORE MOISTURE IN THE AIR. VALLEY
LOCATIONS WILL LIKELY SEE FOG AGAIN... WITH DENSE FOG POSSIBLE
IN THE CONNECTICUT RIVER VALLEY.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
SOUTHWEST FLOW ACROSS THE AREA ON SATURDAY BRINGS WARMER
TEMPERATURES AND HIGHER HUMIDITY. MAY SEE SOME SCATTERED SHOWERS
AND AN ISOLATED THUNDERSTORM IN THE MOUNTAINS IN THE AFTERNOON
RESULTING FROM THE DIURNALLY DRIVEN INSTABILITY. THIS MAY BE AIDED
BY A WEAK SHORTWAVE TROUGH PASSING NEAR THE CANADIAN BORDER.
OVERALL INSTABILITY LEVELS ARE FAIRLY LOW... SO THUNDER CHANCES
ARE FAIRLY LOW.

BROAD UPPER TROUGH BEGINS TO MOVE INTO THE AREA SATURDAY NIGHT.
THE FIRST IN A SERIES OF MORE DISTINCT SHORTWAVE TROUGHS WITHIN
THE BROADER TROUGH WILL MOVE ACROSS NEW ENGLAND SATURDAY NIGHT...
WITH SHOWERS SPREADING WEST TO EAST ACROSS THE REGION BEGINNING
LATE IN THE EVENING. COULD SEE AN ISOLATED THUNDERSTORM AS
TEMPERATURES COOL ALOFT. LOWS WILL BE WARMER... IN THE UPPER 50S
AND LOW 60S DUE TO CLOUDS AND MORE MOISTURE.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
A PERIOD OF UNSETTLED WX WILL LAST THRU THE ENTIRE LONG TERM FCST
PERIOD ...ESPECIALLY FOR THE FIRST TWO DAYS.

THE UPPER LVL PATTERN SHOWS A CUTOFF LOW OVER ERN CANADA WELL TO OUR
N ON SUNDAY. A STRONG SHORT WAVE TROF DRIVES SE THRU THE NRN TIER OF
STATES AS IT ROTATES AROUND ON THE S SIDE OF THE LARGER CUTOFF LOW.
THIS KICKS OUT A WEAKER SHORT WAVE TROF INTO THE NE U.S. WHICH
BRINGS US OUR FIRST ROUND OF UNSETTLED WX WITH SHRA/TSTM ACTIVITY.

ANOTHER WEAK SHORT WAVE TROF SPINS OUT DIRECTLY AHEAD OF THE
APPROACHING STRONG SHORT WAVE TROF FOR SUNDAY NGT. NEXT THE STRONG
SHORT WAVE TROF  WEAKENS AS IT SHEARS OUT TO THE NE, CROSSING THE NE
U.S. ON MONDAY. THIS TROF IS NOW MOVING TO THE E SIDE OF THE LARGER
CUTOFF LOW THAT IS NOW EXPANDING TO INCLUDE ERN CANADA INTO MUCH OF
THE ERN U.S. WHILE THIS UPPER LVL PATTERN IS EVOLVING THE SFC SHOWS
DISORGANIZED AREA OF LOW PRESSURE ACROSS MUCH OF THE GREAT LAKES
REGION WITH A WARM FNT EXTENDING TO THE E AND APPROACHING THE FCST
AREA FROM THE S.

WITH TIME THE SFC LOW BECOMES BETTER ORGANIZED WITH A TRAILING COLD
FNT MOVING THRU THE FCST AREA ON MONDAY. THE FNT BECOMES STALLED
OVER THE ERN SEABOARD DUE TO THE UPPER LVL CUTOFF LOW PROVIDING A
BROAD SW FLOW ALOFT OVER THE ERN U.S. WHICH NEARLY PARALLELS THE NOW
STALLING FNT. WEAK LOW PRESSURE ALSO FORMS ALONG THIS FNT AND TRACKS
N NE ALONG THE BOUNDARY ON TUESDAY.

ON WEDNESDAY THE CUTOFF LOW IS LIFTING TO THE N BUT MAINTAINS A
WEAKER SHORT WAVE TROF EXTENDING S THRU THE ERN SEABOARD. THIS KEEPS
A SW FLOW ALOFT BUT ALSO PUSHES THE FNT OFFSHORE AND BRINGS A DRY
SLOT NE ALONG THE ERN U.S. THOUGH THIS SUGGESTS DRY WX THE CYCLONIC
FLOW ALOFT AND NEARBY FNT WILL KEEP A SLGT CHC OF SHRA ACTIVITY
AROUND.

THIS PATTERN CONTINUES THURSDAY AND FRIDAY AS A SERIES OF WEAK UPPER
LVL IMPULSES ROTATE AROUND THE MAIN CUTOFF LOW PROVIDING THE IMPETUS
FOR A SLGT CHC SHRA/POSSIBLE TSTM ACTIVITY AS THE SFC FNT OFF SHORE
WIGGLES BACK AND FORTH AS WEAK SFC LOWS TRACK ALONG IT DUE TO THE
PASSAGE OF THE UPPER LVL IMPULSES.

USED A BLEND OF VARIOUS MODELS...HPC GUIDANCE...PREVIOUS FCST FOR
PERSISTENCE AND CLIMATOLOGY FOR THE LONG TERM FCST.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
SHORT TERM...WILL SEE VALLEY FOG AGAIN TONIGHT AT LEBANON AND
WHITEFIELD. DEW POINTS ARE A BIT HIGHER THAN YESTERDAY SO
CONFIDENCE IN FOG IS A BIT HIGHER AS WELL. CONCORD HAD A BRIEF
PERIOD OF SCATTERED LOW CLOUDS THIS MORNING... AND SUSPECT THAT IS
A HINT THAT FOG MAY OCCUR TONIGHT GIVEN GREATER MOISTURE AND
SIMILAR RADIATIONAL COOLING CONDITIONS. OTHERWISE EXPECT VFR
CONDITIONS THROUGH SATURDAY EVENING. SHOWERS MOVE ACROSS THE
REGION SATURDAY NIGHT WITH MVFR/IFR CONDITIONS POSSIBLE AT TIMES.

LONG TERM /SUNDAY THROUGH WEDNESDAY/...AN EXTENDED PERIOD OF
UNSETTLE WX WITH SHRA/TSTMS AND MVFR/IFR CONDITIONS POSSIBLE...
ESPECIALLY SUNDAY THRU MONDAY AND LESS LIKELY TUESDAY THRU
WEDNESDAY.

&&

.MARINE...
SHORT TERM...SOUTHWEST FLOW STRENGTHENS OVER THE WATERS AS THE
CENTER OF HIGH PRESSURE MOVES OFFSHORE AND A TROUGH OF LOW
PRESSURE APPROACHES FROM THE WEST. CURRENTLY EXPECT WINDS TO STAY
BELOW ADVISORY LEVELS. ALTHOUGH GUIDANCE CONTINUES TO FORECAST 5
TO 6 FT WAVES... THIS SEEMS A BIT TOO HIGH GIVEN THE SOUTHWEST
WINDS HAVE A SHORTER FETCH AND WINDS ARE NOT THAT STRONG. GREATEST
CHANCE OF 5 FT WAVES WILL BE IN THE CENTRAL GULF OF MAINE WATERS
EAST OF PORTLAND.

LONG TERM /SUNDAY THROUGH WEDNESDAY/...S SW FLOW AHEAD OF AN
APPROACHING COLD FNT MAY CREATE SCA WIND GUSTS OVER THE OPEN
WATERS SUNDAY INTO MONDAY. THE CONTINUED ONSHORE FLOW WILL LIKELY
PUSH SEAS TO SCA LEVELS SUNDAY THRU MONDAY NGT. THE FNT STALLS
NEAR OR JUST E OF THE WATERS TUESDAY THRU WEDNESDAY KEEPING WINDS
AND SEAS BELOW SCA LEVELS.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...NONE.
NH...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...CAPRIOLA
NEAR TERM...KIMBLE
SHORT TERM...KIMBLE
LONG TERM...CAPRIOLA
AVIATION...CAPRIOLA/KIMBLE
MARINE...CAPRIOLA/KIMBLE





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