Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 280439
AFDGYX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
1239 AM EDT MON JUL 28 2014

.SYNOPSIS...
LOW PRESSURE TRACKS INTO SOUTHERN NEW ENGLAND LATE TONIGHT... THEN
MOVES NORTHEAST THROUGH NEW HAMPSHIRE AND MAINE ON MONDAY...
BRINGING SHOWERS AND THUNDERSTORMS WITH IT. A STATIONARY FRONT
REMAINS ALONG OR JUST OFF THE COAST TUESDAY THROUGH SUNDAY WITH
WEAK AREAS OF LOW PRESSURE MOVING NORTH ALONG THE BOUNDARY.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
1235 AM UPDATE...A SMALL AREA OF SHWRS AND PSBLY AN EMBDD TSTM
ACRS ECENTRAL NH WEAKENING BUT SLOWLY DRIFTING E. MADE SOME ADJ
FOR POPS TO COVER THIS AREA FOR THE NEXT FEW HRS...OTRW LOWERED
POPS ELSWHR OVER ERN AND OVER THE WATERS. HRRR SHOWS NEXT ROUND OF
SHWRS/TSTMS TO ROATE NEWD ARND 11Z AND THEN NEWD IN SRN/WRN ME BY
14Z. HRRR HAS BEEN PERFORMING WELL SO THIS TIMING IS ACCEPTED.
MADE SOME SIG ADJ TO POPS TO REFLECT THIS THINKING. ALSO PUT IN
WORDING FOR HVY DOWNPOURS AND GSTY WINDS WITH SOME OF THE STORMS
AS INDICES INICATE SOME STG TSTM ACTVTY SHOULD MOVE THRU THE FA
TODAY.

PREV FCST:
PREVIOUSLY...FIRST STRONG SHORTWAVE IS EXITING THE FORECAST AREA
THIS AFTERNOON... WITH RAIN AND EMBEDDED THUNDERSTORMS MOVING INTO
EASTERN MAINE. BEHIND IT... SOME SUNSHINE HAS ALLOWED THE
ATMOSPHERE TO DESTABILIZE A BIT MORE. A VORT MAX IS ALSO MOVING
THROUGH NORTHERN NEW ENGLAND... HELPING TO TRIGGER SOME SCATTERED
SHOWERS AND THUNDERSTORMS AS IT MOVES EAST. WILL LIKELY SEE SOME
OF THIS ACTIVITY REACH NEW HAMPSHIRE THIS AFTERNOON AND EVENING.
WIND SHEAR SHOULD BE SUFFICIENT FOR SUPERCELLS... WITH LOW LEVEL
DIRECTIONAL SHEAR ENOUGH TO SUPPORT CYCLONICALLY ROTATING
UPDRAFTS. INSTABILITY IS THE BIGGEST QUESTION MARK IN THIS
EVENING/TONIGHT FORECAST. HOWEVER... IT IS WORTH NOTING THAT MANY
NORTHERN NEW ENGLAND TORNADOES OCCUR IN WEAKLY UNSTABLE AND HIGHLY
SHEARED ENVIRONMENTS... SO WILL HAVE TO BE ESPECIALLY VIGILANT FOR
ROTATING STORMS THIS EVENING. COVERAGE OF STORMS IS EXPECTED TO BE
SCATTERED... SO POP IS ONLY IN THE CHANCE RANGE THROUGH THE
EVENING. WILL LIKELY SEE A BREAK IN THE RAIN TONIGHT BEFORE MORE
RAIN MOVES NORTH INTO THE AREA BY MORNING.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 AM TUESDAY/...
LOW PRESSURE SYSTEM STRENGTHENS AS IT TRACKS THROUGH SOUTHERN NEW
ENGLAND TOMORROW AND TURNS NORTH THROUGH NEW HAMPSHIRE AND WESTERN
MAINE. THIS WILL BE SIMILAR TO A WINTER TIME SYSTEM... WITH A WARM
FRONT DEVELOPING OFFSHORE AND PRECIPITATION WRAPPING INTO AND
AROUND THE LOW. CONFIDENT IN AREA-WIDE COVERAGE OF RAIN
TOMORROW... SO WENT WITH VERY HIGH POP NEAR 100 PERCENT... WITH
THE HOURLY TREND SHOWING A PROGRESSION OF RAIN FROM SOUTH TO
NORTH. THERE MAY BE ENOUGH INSTABILITY TO LEAD TO A FEW
THUNDERSTORMS WITHIN THE BROADER AREA OF RAIN AS WELL. STILL SEE A
STRONGLY SHEARED ENVIRONMENT... SO WOULD NOT BE OUT OF THE
QUESTION TO GET SOME ROTATING UPDRAFTS.

HIGH TEMPERATURES REACH THE 70S... ONCE RAIN MOVES OFF TO THE
NORTH AND SOME CLEARING BEGINS. MAY SEE SOME UPSLOPE SHOWERS IN
THE MOUNTAINS BEHIND THE LOW MONDAY AFTERNOON AND EVENING... BUT
THE GENERAL TREND ACROSS THE AREA WILL BE FOR DRYING CONDITIONS.

&&

.LONG TERM /TUESDAY THROUGH MONDAY/...
A PERIOD OF UNSETTLED WEATHER WILL LAST THRU MOST OF THE ENTIRE LONG
TERM FORECAST PERIOD.

THE UPPER LEVEL PATTERN SHOWS A CUTOFF LOW CENTERED AROUND THE GREAT
LAKES REGION. THIS SYSTEM DRIFTS AROUND SOUTHERN CANADA AND THE
NORTHERN U.S. THRU FRIDAY NIGHT BEFORE IT EVOLVES INTO AN OPEN
WAVE OVER THE WEEKEND. OVERALL THIS PATTERN KEEPS A SW FLOW ALOFT
OVER THE EASTERN U.S. AS A RESULT A FRONTAL BOUNDARY REMAINS
NEARLY STATIONARY ALONG OR JUST OFF THE EAST COAST. WEAK LOW
PRESSURE SYSTEMS WILL MOVE NE ALONG THE BOUNDARY AT TIMES THRU THE
LONG TERM FORECAST PERIOD. THE MODELS INDICATE THE DEEP LAYER FROM
SURFACE TO 500 MB IS RELATIVELY DRY AS A DRY SLOT WRAPS TO THE N
NE ACROSS THE EAST COAST. HOWEVER, THE UPPER LEVEL TROUGH...UPPER
LEVEL SW FLOW AND SURFACE BOUNDARY SUPPORT THE THREAT OF
CONVECTION...MAINLY DURING THE DAY TIME INTO EARLY EVENING HOURS.
THE CHANCE OF PRECIPITATION THOUGH WILL BE NO MORE THAN A SLIGHT
CHANCE OR CHANCE.

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

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
SHORT TERM...MOSTLY VFR CONDITIONS THIS EVENING... BUT COULD SEE
SOME FOG DEVELOPING AGAIN EAST OF PORTLAND AFFECTING PRIMARILY
AUGUSTA AND ROCKLAND. THIS WILL BE AIDED BY WET GROUND... HIGH DEW
POINTS... AND A PERSISTENT SSE ONSHORE FLOW. THERE IS AN OUTSIDE
CHANCE OF A THUNDERSTORM THIS AFTERNOON/EVENING PRIMARILY OVER NEW
HAMPSHIRE. EXPECT LOWERING CEILINGS AND RAIN TO MOVE IN BY
MORNING... SPREADING FROM SOUTH TO NORTH ACROSS THE REGION ON
MONDAY.

LONG TERM /TUESDAY THROUGH FRIDAY/...A PERIOD OF UNSETTLED WEATHER
WITH A THREAT OF SHOWERS/THUNDERSTORMS WHICH COULD PRODUCE MVFR OR
POSSIBLY IFR CONDITIONS DURING THE LONG TERM FORECAST PERIOD FROM
TUESDAY THRU FRIDAY. THE CONVECTION WILL BE MOSTLY CONFINED DURING
THE DAYTIME INTO EARLY EVENING HOURS.

&&

.MARINE...
SHORT TERM...SOUTHERLY FLOW INCREASES TO 20 OR 25 KT BY MONDAY
MORNING... WITH WAVE HEIGHTS GRADUALLY BUILDING AS WELL. MODEL
GUIDANCE CONTINUES TO OVERDO THE WAVE HEIGHTS BY A SIGNIFICANT
MARGIN. HAVE UNDERCUT THIS GUIDANCE SUBSTANTIALLY... BUT STILL
COULD SEE 7 FT WAVES IN THE EASTERN WATERS.

LONG TERM /TUESDAY THROUGH FRIDAY/...RESIDUAL ROUGH SEAS ON
TUESDAY MAY STILL BE AT SCA LEVELS OVER THE OPEN WATERS. OTHERWISE
A NEARLY STATIONARY FRONT STALLED ALONG OR JUST OFF THE EAST COAST
WILL DOMINATE THE WEATHER PATTERN THRU THE LONG TERM FORECAST
PERIOD KEEPING THE FLOW RELATIVELY WEAK RESULTING IN WINDS AND
SEAS STAYING BELOW SCA LEVELS.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...NONE.
NH...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 6 AM EDT
     TUESDAY FOR ANZ150>154.

&&

$$






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