Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 241123 AAA AFDGYX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GRAY ME 723 AM EDT MON AUG 24 2015 .SYNOPSIS... HUMID AND UNSETTLED CONDITIONS CONTINUE THROUGH THE FIRST PART OF THE WEEK AS A SERIES OF WEAKENING COLD FRONTS MOVE INTO THE REGION. BY TUESDAY AND WEDNESDAY WE WILL SEE HUMIDITIES START TO DROP OFF AND THE THREAT OF SHOWERS WILL BE LIMITED TO NORTHERN AREAS. NOTICEABLY COOLER AND DRIER AIR MOVES IN FOR THE END OF THE WEEK INTO SATURDAY. && .NEAR TERM /THROUGH TONIGHT/...
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UPDATE...MOSTLY MINOR CHANGES TO THE CURRENT FORECAST BASED ON LATEST OBSERVATIONAL TRENDS. THIS INCLUDED BLENDING IN THE LAST SEVERAL RUNS OF THE HRRR POP GRIDS TO EXPAND THE AREA UNDER THREAT FOR AN ISOLATED SHOWER EARLY TODAY. PREVIOUS DISCUSSION...MARINE FOG/STRATUS LAYER WELL ENTRENCHED ACROSS INLAND ZONES THIS MORNING. EXPECT THIS TO HANG TOUGH INTO THE MORNING...WITH NO REAL IMPETUS TO REMOVE IT BESIDES HEATING OF THE BOUNDARY LAYER. THE CLOUDS SHOULD AT LEAST PARTIALLY SCATTER OUT BY AFTERNOON. THESE POCKETS OF HEATING WILL ALLOW FOR SOME ISOLATED SHOWERS TO FORM...VERY MUCH THE HIT AND MISS VARIETY GIVEN THE LACK OF CONCENTRATED FORCING.
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&& .SHORT TERM /TUESDAY/... PERSISTENCE LOOKS LIKE THE BEST BET FOR TONIGHT...WITH FOG/STRATUS REFORMING ACROSS INLAND ZONES S OF THE MTNS. HAVE ADDED AREAS OF FOG FOR NOW...THOUGH PATCHY DRIZZLE IS POSSIBLE AGAIN AS WELL ESPECIALLY NEAR THE COAST. TUE IS A TRICKY FORECAST...AS UPPER LOW PRES MOVES EWD AND PUSHES A COLD FRONT SLOWLY TOWARDS THE AREA. THERE SHOULD BE EXTENSIVE CLOUD COVER ACROSS THE FORECAST AREA TUE...THOUGH BREAKS IN THE OVERCAST ARE EXPECTED. THESE POCKETS OF HEATING COUPLED WITH DEWPOINTS WELL INTO THE 60S...WILL LEAD TO REGIONS OF CAPE APPROACHING 1000 J/KG. MID LEVEL LAPSE RATES ARE POOR...SO THIS CAPE WILL BE MORE OF THE LONG...SKINNY VARIETY ASSOCIATED WITH HEAVY RNFL SOUNDINGS THAN WIDESPREAD SEVERE WX. THAT BEING SAID...MODEST H5 JET AND RIGHT ENTRANCE REGION WILL APPROACH NEW ENGLAND IN THE AFTERNOON. WITH LIGHT SELY FLOW IN THE BOUNDARY LAYER...THIS WILL SUPPORT AMPLE SHEAR ACROSS THE REGION. THESE HIGH SHEAR/LOW CAPE ENVIRONMENTS ARE NOTORIOUSLY HARD TO FORECAST IN THIS PART OF THE COUNTRY...AND AT LEAST MARGINALLY SEVERE STORMS ARE A POSSIBILITY TUE AFTERNOON. SPC SREF PRODUCTS ARE BEGINNING TO KEY ON AT LEAST PART OF THE AREA SEEING A HIGHER POTENTIAL FOR SEVERE WX...AND NCAR ENSEMBLE GUIDANCE IS SUPPORTIVE OF A WARM FRONTAL FEATURE LINGERING OVER THE FORECAST AREA...MOST LIKELY SRN NH. WITH LCLS NEAR 1000 M IN THAT VICINITY...THE INGREDIENTS ARE ALL IN PLACE SUCH THAT AN ISOLATED TORNADO CANNOT BE RULED OUT. HOWEVER CONFIDENCE IN THAT EXACT SCENARIO IS LOW...SO FOR NOW GUSTY WINDS WILL BE ADDED TO THE GRIDS WHERE CAPE IS FORECAST TO EXCEED 1500 J/KG...ACROSS SRN NH AND THE CT RIVER VALLEY. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... HIGH IMPACT WEATHER: THUNDERSTORMS MAY PRODUCE STRONG GUSTY WINDS AND VERY HEAVY DOWNPOURS TUESDAY EVENING. 500 MB PATTERN FEATURES MULTIPLE OMEGA BLOCKING STRETCHED FROM EUROPE WWD TO ERN PACIFIC...WHICH MEDIUM TO LONG RANGE MODELS EVENTUALLY BREAK DOWN AS TROUGH DRIVES EQUATORWARD OFF THE POLE ACROSS ALASKA. MAIN FEATURE WILL BE THE 500MB CLOSED LOW OVER THE GREAT LAKES REGION...WHICH SLOWLY BREAKS DOWN AND LIFTS POLEWARD AS IT MOVES EAST DURING THE MIDWEEK BEFORE EVENTUALLY FLATTENING AND ALLOWING RIDGING TO BUILD IN FOR THE THE END OF THE WEEK AND THE WEEKEND. SENSIBLE WEATHER WILL START UNSETTLED AS FRONTAL BOUNDARY APPROACHES WITH WARM HUMID AIR IN PLACE AHEAD OF IT. SOME SEVERE THREAT INTO TUE EVENING...BUT OF MORE CONCERN FOR TUE NIGHT WILL BE POTENTIAL HEAVY RAINS IN TSRA AND TRAINING AHEAD OF THE FRONT. AS A WEAK SFC WAVE MOVES ALONG IT. SHRA SHOULD WIND DOWN BY WED MORNING...WITH SOME CLEARING POSSIBLE AND SOMEWHAT COOLER AND DRIER AIR FOR LATE WED AND WED NIGHT. AS THE 500MB LOW LIFTS NWD...WILL SEE ANOTHER WAVE ROTATE AROUND IT ON THURSDAY...AND THIS WILL DRIVE ANOTHER FRONT THRU THE REGION...AND COLD SET OFF A ANOTHER ROUND SHOWERS...AND MAYBE A FEW TSRA...ALTHOUGH THIS MAY BE LIMITED TO THE NRN ZONES. MORE NOTICEABLY COOLER AND DRIER AIR MOVE IN FOR FRI INTO SAT AS HIGH PRES BUILDS IN. ANOTHER WEAK WAVE IN THE 500MB FLOW APPROACHES SUNDAY...BUT FLOW SHIFTS SW AND WARMER AIR RETURNS WITH A THREAT FOR SHRA LATE SUNDAY OR EARLY NEXT WEEK. TEMPERATURES WILL BEGIN TO DROP OFF IN STEPS...FIRST ON WED WITH HIGHS IN THE 70S TO LOW 80S...AND THEN ANOTHER STEP DOWN FOR THU- SAT WITH HIGHS MOSTLY IN THE 70S TO AROUND 80 AND OVERNIGHT LOWS IN THE 50S...WHICH WILL BE RIGHT AROUND NORMAL. AFTER THIS 850 TEMPS LOOK TO RISE ABOVE NORMAL TOWARD THE END OF THE WEEKEND AND INTO EARLY NEXT...WHICH WILL MEAN WARMER TEMPS...CLIMBING INTO THE80S MANY SPOTS FOR SUN AND MON. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... SHORT TERM...AREAS OF IFR AND LIFR WILL PERSIST SOUTH OF THE MTNS THRU MID MORNING IN MARINE FOG/STRATUS LAYER. DAYTIME HEATING WILL ALLOW THIS LAYER TO LIFT/SCATTER OUT WITH TIME...THOUGH AREAS OF MVFR ARE STILL EXPECTED THIS AFTERNOON. WIDELY SCATTERED SHRA ARE POSSIBLE THIS AFTERNOON...WITH ISOLATED TSRA. NOT CONFIDENT ENOUGH TO PLACE IN TAFS AT THIS TIME. MARINE FOG/STRATUS RETURNS TONIGHT...WITH AREAS OF IFR AND LIFR MAINLY FOR COASTAL AND SRN NH TERMINALS. BY MID MORNING REMAINING STRATUS WILL LIFT/SCATTER OUT AGAIN...WITH AREAS OF MVFR CLOUDS IN THE AFTERNOON. SHRA/TSRA WILL BE A LITTLE MORE WIDESPREAD...ESPECIALLY ACROSS NH...WITH MVFR OR LOWER POSSIBLE IN HEAVIER CONVECTION. LONG TERM...TUE NIGHT WILL REMAIN UNSETTLED WITH SHRA/SHRA AND ANOTHER ROUND OF FOG...ESPECIALLY OUTSIDE THE MOUNTAINS. BY WED SHOULD SEE PREVAILING VFR THRU THE END OF THE WEEK...WITH VLY FOG EXPECTED EVERY NIGHT. && .MARINE... SHORT TERM...WINDS AND SEAS REMAIN BELOW SCA THRESHOLDS THRU TUE. WARM AND MOIST AIR MASS REMAINS IN PLACE OVER THE WATERS THRU TUE AS WELL. THIS WILL LEAD TO AREAS OF FOG...ESPECIALLY AT NIGHT. LONG TERM...ANY HIGHER SWELL OF AROUND 40-5 FT WILL BE SUBSIDING TUE NIGHT AND BOTH SEAS/WINDS WILL REMAIN COMFORTABLY BLO SCA LVLS THRU THE END OF THE WEEK. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$ NEAR TERM...LEGRO SHORT TERM...LEGRO LONG TERM...CEMPA AVIATION...CEMPA MARINE...CEMPA/LEGRO

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