Area Forecast Discussion
Issued by NWS Portland, ME

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000 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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