Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 280641 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 241 AM EDT FRI AUG 28 2015 .SYNOPSIS...
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HIGH PRESSURE CENTERED OVER THE NORTHEASTERN UNITED STATES WILL BRING SEASONABLY MILD WEATHER THROUGH SATURDAY. A SERIES OF WEAK COLD FRONTS WILL MOVE THROUGH THE REGION SUNDAY AND MONDAY WITH A SLIGHT CHANCE OF A SHOWER OVER THE MOUNTAINS. HIGH PRESSURE SOUTH OF THE REGION NEXT WEEK WILL PROVIDE FOR INCREASING HEAT AND HUMIDITY...WITH LITTLE CHANCE FOR PRECIPITATION THROUGH MIDWEEK.
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&& .NEAR TERM /THROUGH TODAY/...
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HIGH PRESSURE CENTERED OVER WESTERN PENNSYLVANIA THIS MORNING WILL PROVIDE A MOSTLY SUNNY DAY ACROSS THE REGION TODAY WITH COMFORTABLE HUMIDITIES AND LIGHT NW WINDS. ACROSS THE MOUNTAINS...PARTLY CLOUDY SKIES CAN BE EXPECTED. ANY VALLEY FOG SHOULD BURN OFF QUICKLY THIS MORNING WITH TEMPERATURES CLIMBING TO THE 70S TO LOWER 80S ACROSS THE REGION THIS AFTERNOON. COASTAL AREAS WILL SEE A SEA BREEZE DEVELOP DURING THE AFTERNOON.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM SATURDAY/...
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CLEAR SKIES COMBINED WITH DRY AIR AND LIGHT WINDS WILL LEAD TO ANOTHER PLEASANT NIGHT TONIGHT WITH TEMPERATURES DROPPING INTO THE 40S IN THE MOUNTAINS AND 50S ELSEWHERE. WITH THE COOL TEMPERATURES...FOG WILL AGAIN DEVELOP IN THE COLDER VALLEYS. THE RIDGE OF HIGH PRESSURE WILL BEGIN TO MOVE OFF THE COAST SATURDAY. THIS WILL ALLOW HUMIDITIES TO START TO INCREASE A BIT LATE IN THE DAY...ESPECIALLY ACROSS WESTERN NH. AFTERNOON SEA BREEZES ARE EXPECTED AGAIN ALONG THE COAST.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
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HIGH IMPACT WEATHER POTENTIAL: NIL. PATTERN SUMMARY: EARLY MORNING WATER VAPOR IMAGERY INDICATES A GENERAL WEST NORTHWEST FLOW ACROSS MUCH OF NOAM BETWEEN SPRAWLING RIDGE OVER THE SOUTHWESTERN STATES AND SEMI-PERMANENT TROUGH NEAR HUDSON BAY. THIS TROUGH AXIS REMAINS CENTERED NEAR OUR LATITUDE...THE RESULT BEING A SIGNIFICANTLY DRIER AND SOMEWHAT COOLER AIRMASS THAN WAS OVERHEAD EARLIER IN THE WEEK. LOOKING AHEAD...PRIMARY CONTROLLING FEATURES FOR THE LONG TERM FORECAST PERIOD WILL BE STRENGTHENING/BROADENING LONGWAVE TROUGH ALONG THE WESTERN COAST OF NOAM...WITH SUBSEQUENT BUILDING OF HEIGHTS ACROSS THE EASTERN TWO THIRDS OF NOAM WEST OF ONGOING BLOCKING /-NAO/ ACROSS THE NORTHERN ATLANTIC. PATTERN RECOGNITION WOULD SUGGEST THAT THE GREATEST CHANCE FOR ANY SENSIBLE WEATHER WOULD HAVE TO COME EARLIER IN THE PERIOD...WHEN THE BAND OF STRONGEST WESTERLIES ALOFT IS NEARBY...AND BEFORE IT IS SHUNTED NORTH BY DEVELOPING RIDGING. BEYOND THIS...THE PRIMARY WEATHER STORY SHOULD BE INCREASING WARMTH AS ANOMALOUS HEAT BUILDS ACROSS CENTRAL NOAM EARLY IN THE WEEK...SPILLING EAST AS THE WEEK PROGRESSES. GUIDANCE TRENDS/CONFIDENCE: LONGWAVE PATTERN AGREEMENT IS RATHER STRONG THROUGH THE LONG TERM FORECAST PERIOD...HAVING IMPROVED OVER THE PAST FEW DAYS. PRIMARY DIFFERENCES ARE FOCUSED AROUND THE EVOLUTION OF ERIKA AS IT MOVES NORTHWESTWARD TOWARDS THE SOUTHEASTERN UNITED STATES. REGARDLESS OF THESE DIFFERENCES...THE VAST MAJORITY OF DETERMINISTIC/ENSEMBLE MEMBERS KEEP ANY IMPACTS FROM ERIKA /RAIN OR OTHERWISE/ WELL SOUTH OF THE REGION....WHICH FITS WELL WITH DOMINANT EASTERN NOAM RIDGING...WHICH YIELDS LITTLE IN THE WAY OF A PATH NORTHWARD FOR SUCH A SYSTEM. THE DETAILS... BEST SIGNAL FOR PRECIPITATION POTENTIAL COMES RIGHT OFF THE BAT AS A WEAK COOL FRONT SETTLES THROUGH THE REGION SATURDAY NIGHT/SUNDAY SUNDAY IN TANDEM WITH A POORLY DEFINED SHORTWAVE AT H5...BUT A MODEST JET STREAK AT H2. MOISTURE RETURN AHEAD OF THIS BOUNDARY IS NOT IMPRESSIVE. AS MENTIONED IN PREVIOUS DISCUSSIONS...TIMING OF THIS FRONTAL BOUNDARY MAY GIVE THE BEST CLUE AS TO WHETHER IT CAN PRODUCE PRECIPITATION ACROSS THE AREA...BUT THIS REALLY DOES NOT LOOK LIKE A WIDESPREAD RAIN PRODUCER. 30-50 PERCENT OF SREF MEMBERS PRODUCE PRECIPITATION...AND THE SREF IS TYPICALLY A BIT BULLISH...SO SEE LITTLE REASON TO STRAY MUCH ABOVE 20-30 PERCENT POPS FOR NORTHERN AREAS...WITH DOWNSLOPING SOUTH OF THIS LIKELY PRECLUDING ANYTHING BUT SOME INCREASED CLOUDINESS REACHING COASTAL AREAS. MONDAY: NORTHWEST FLOW ALOFT WILL TRY TO MAKE ONE LAST STAND ON MONDAY AS IMPRESSIVE SHORTWAVE ATTEMPTS TO CARVE ITSELF OUT OVER THE CANADIAN MARITIMES. THE GFS IS MUCH MORE AGGRESSIVE WITH THIS FEATURE THAN THE GGEM/ECMWF...AND IS ON THE STRONGER SIDE OF THE GEFS ENVELOPE. THE ECMWF SOLUTION LOOKS LIKE A REASONABLE COMPROMISE IN THIS CASE...DRIVING A WEAK COOL FRONT THROUGH THE REGION DURING THE DAY MONDAY. THE UPPER WAVE IS MORE IMPRESSIVE THAN THE DAY PREVIOUS...BUT MOISTURE IS AGAIN NOT TERRIBLY IMPRESSIVE...AND THE DYNAMIC FORCING REALLY GIVES ONLY A GLANCING BLOW...SO WILL STICK WITH 20-30 POPS FOR THIS PERIOD. DEEP-LAYER RIDGING LOOKS TO BE IN FIRM CONTROL OF WEATHER ACROSS THE REGION FOR TUESDAY AND WEDNESDAY WITH LITTLE SENSIBLE WEATHER TO SPEAK OF. WITH SURFACE HIGH PRESSURE CENTERED SOUTH/SOUTHWEST OF THE REGION WILL ALLOW A MODEST RETURN OF LLEVEL MOISTURE...WITH INCREASING HUMIDITY TO GO ALONG WITH WARMING TEMPERATURES /SEE BELOW/. THERE IS SOME WEAK AGREEMENT IN THE GUIDANCE THAT AS WE REACH THE END OF THIS FORECAST PERIOD ON THURSDAY...THE SHARPENING RIDGE TO THE WEST OF THE REGION MAY ALLOW FOR ENERGY TO DROP INTO NORTHERN NEW ENGLAND /RIDGE ROLLERS/ RATHER THAN REMAINING WELL NORTH OF THE AREA. CLEARLY THERE ISN/T ANY SKILL TIMING THIS 7 DAYS OUT...BUT PATTERN RECOGNITION WOULD SUGGEST THAT POPS NEAR CLIMO LEVELS /SLIGHT CHANCE/ ARE LIKELY WARRANTED TO END THE PERIOD. TEMPERATURES: A WARMER THAN NORMAL FORECAST PERIOD IS IN STORE...WITH T8S SPENDING MUCH OF THE WEEK IN THE MID TEENS. THIS SUPPORTS HIGHS WELL INTO THE 80S OUTSIDE OF THE MOUNTAINS AND IMMEDIATE MAINE COAST. TEMPS ALOFT APPEAR TO REACH THEIR WARMEST LEVELS TOWARD THE END OF THIS FORECAST PERIOD WITH T8S +1-2 SIGMA...LIKELY ALLOWING THE WARMEST SPOTS TO REACH 90 AT LEAST ONCE DURING THE WEEK. WARMEST DAY IN THE FORECAST IS CURRENTLY WEDNESDAY...AS SOMEWHAT HIGHER PRECIPITATION CHANCES ON THURSDAY TEMPERS CONFIDENCE IN READINGS CONTINUING THIS WARM THROUGH THE END OF THE WEEK. HUMIDITY WILL NOT BE OPPRESSIVE...BUT WILL BE INCREASINGLY NOTICEABLE DURING THE WEEK WITH NO SIGNIFICANT COOLING FORESEEN AT LEAST THROUGH NEXT WEEKEND.
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&& .AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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SHORT TERM...MAINLY VFR CONDITIONS EXPECTED TODAY AND SATURDAY WITH SOME IFR CONDITIONS EXPECTED IN VALLEY FOG EARLY THIS MORNING AND AGAIN TONIGHT INTO SATURDAY MORNING. LONG TERM...NO ORGANIZED AREA OF RESTRICTIONS IS EXPECTED THROUGH THE LONG TERM FORECAST PERIOD...WITH THE GREATEST THREAT FOR ANY SHRA ACTIVITY COMING ON SUNDAY AND MONDAY /COVERAGE LOOKS NO GREATER THAN WIDELY SCATTERED/. OUTSIDE OF THIS...LIGHT WINDS AND GRADUALLY INCREASING BOUNDARY LAYER MOISTURE SUGGEST THAT VALLEY FOG AT HIE/LEB WILL BE POSSIBLE EACH MORNING.
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&& .MARINE...
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SHORT TERM...WINDS AND SEAS EXPECTED TO REMAIN BELOW SCA CRITERIA TODAY THROUGH SATURDAY. LONG TERM...A PERIOD OF GENERALLY LIGHT WINDS IS EXPECTED THROUGH THE LONG TERM FORECAST PERIOD WITH HIGH PRESSURE ANCHORED ALONG THE EAST COAST...WITH BOTH WINDS/WAVES REMAINING BELOW SCA LEVELS THROUGH THE PERIOD.
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&& .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$ SYNOPSIS...ARNOTT NEAR TERM...JENSENIUS SHORT TERM...JENSENIUS LONG TERM...ARNOTT AVIATION...ARNOTT/JENSENIUS MARINE...ARNOTT/JENSENIUS

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