Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 291636 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 1236 PM EDT WED JUL 29 2015 .SYNOPSIS... WARMER THAN NORMAL TEMPERATURES AND HUMID CONDITIONS WILL CONTINUE ACROSS MAINE AND NEW HAMPSHIRE THROUGH THURSDAY. A COLD FRONT MOVING INTO THE REGION WILL BRING THE THREAT FOR STRONG TO SEVERE THUNDERSTORMS TO THE REGION THURSDAY AFTERNOON AND EVENING. BEHIND THIS FRONT...SOMEWHAT DRIER AIR WILL FILTER INTO THE REGION FOR FRIDAY. THIS WEEKEND...A SERIES OF WEAK DISTURBANCES MAY BRING A FEW SHOWERS AND THUNDERSTORMS PRIMARILY TO THE MOUNTAINS...WITH TEMPERATURES NEAR OR SLIGHTLY ABOVE SEASONAL NORMALS. && .NEAR TERM /UNTIL 8 PM THIS EVENING/... 1235 PM...MINOR ESTF UPDATE TO INGEST THE CURRENT MESONET VALUES INTO 1ST PERIOD GRIDS. PREV DISC... 940 AM...MINOR ESTF UPDATE TO REFLECT CURRENT MESONET IN 1ST PERIOD GRIDS. I ALSO ADJUSTED MAXIMUM TEMPERATURES UP A DEGREE OR TWO IN SOME AREAS BASED ON THE 12Z KGYX RAOB. THE WEAK SURFACE BOUNDARY REMAINS ORIENTED FROM NORTHWEST TO SOUTHEAST AND IS SITUATED FROM NORTHERN NEW HAMPSHIRE THROUGH CENTRAL MAINE. THAT SHOULD PROVIDE A FOCUS FOR WIDELY SCATTERED CONVECTION. REWORKING THE 12Z KGYX RAOB YIELDS CAPES NEAR 1500 J/KG WITH POTENTIAL FOR GUSTY WINDS IN ANY CELLS THAT DO DEVELOP. PREV DISC... .UPDATE... EARLY MORNING SHOWERS HAVE DRIED UP AND HAVE LOWERED POPS FOR THE NEXT COUPLE OF HOURS. SOME PATCHY FOG STILL AROUND WITH MORE CLOUDS MOVING IN FROM THE NORTH. && .SHORT TERM /8 PM THIS EVENING THROUGH 6 PM THURSDAY/... CONVECTION DIES DOWN AFTER SUNSET AND TEMPERATURES COOL OFF SOMEWHAT BUT NOT AS MUCH AS PREVIOUS NIGHTS AS WARM AIR ADVECTION ARRIVES AHEAD OF DECENT SHORT WAVE TROUGHING. ONCE AGAIN THURSDAY WILL BE QUITE WARM AND ONLY A COUPLE DEGREES COOLER THAN WEDNESDAY DUE TO INCREASED MOISTURE. THE SET UP FOR THURSDAY`S THUNDERSTORMS LOOKS MORE POTENT WITH BETTER KINEMATICS AND OVERALL FORCING THAN TODAY. THE STRONGEST STORMS WILL BE AHEAD OF THE COLD FRONT. WE COULD HAVE EARLY INITIATION AND STORM MODE WILL BE SUPERCELLULAR. BESIDES HAIL... DAMAGING WINDS...AND FLASH FLOODING... EHI VALUES AND OTHER SPC INDICES ARE HIGH FOR ROTATION AND SUSTAINED SUPERCELLS IN PARTS OF MAINE... INDICATING PLENTY OF SHEAR FOR ROTATION. THIS IS CONCERNING AND WOULD NOT BE SURPRISED IF WE HAD A TORNADO SOMEWHERE IN FRANKLIN OR SOMERSET COUNTIES. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... HIGH IMPACT WEATHER POTENTIAL: ISOLATED SEVERE THUNDERSTORM POTENTIAL BEGINNING SATURDAY AND CONTINUING INTO EARLY NEXT WEEK. THE GREATEST THUNDERSTORM COVERAGE FOR THE FRIDAY-SUNDAY PERIOD APPEARS TO BE ON SATURDAY AFTERNOON. PATTERN SUMMARY: EARLY MORNING WATER VAPOR IMAGERY SHOWS IMPRESSIVE SHORTWAVE ENERGY MOVING EAST ALONG THE US/CANADIAN BOARDER WEST OF THE GREAT LAKES. THERE IS GOOD DETERMINISTIC/ENSEMBLE GUIDANCE AGREEMENT THAT THIS FEATURE WILL CONTINUE TO MOVE EAST AND REINVIGORATE LONGWAVE TROUGHING NEAR HUDSON BAY. THIS PATTERN IS NOT ALL THAT ABNORMAL FOR THIS TIME OF YEAR AND WHILE 500 HPA HEIGHTS WILL BE A TAD BELOW NORMAL...T8S WILL REMAIN NEAR NORMAL. GIVEN OUR LOCATION ON THE SOUTHERN PERIPHERY OF THIS DEVELOPING LONGWAVE TROUGHING...WE WILL HAVE ACCESS TO ROBUST WINDS ALOFT WITH THE CORE OF THE JET ALOFT NEARBY...WITH NUMEROUS WEAK SHORTWAVES IN THE BROADLY CYCLONIC FLOW ALOFT MOVING ACROSS NEW ENGLAND. OVERALL...THIS PORTENDS TEMPERATURES NEAR OR SLIGHTLY ABOVE SEASONAL NORMS THROUGH THE FORECAST PERIOD...WITH OCCASIONAL BOUTS OF ISOLATED/SCATTERED SHOWERS/STORMS ASSOCIATED WITH THE AFOREMENTIONED MID LEVEL SHORTWAVES IN THE BROADLY CYCLONIC FLOW ALOFT. CERTAINLY NO WASHOUTS EXPECTED GIVEN THIS PATTERN...BUT WITH DECENT WINDS ALOFT IN PLAY...CAN/T RULE OUT A FEW ISOLATED SEVERE STORMS DURING THIS PERIOD. DETAILS: DRIER AIR WORKS INTO THE REGION BEHIND DEPARTING COLD FRONT THURSDAY NIGHT...THUS ANY SHOWER/THUNDERSTORM ACTIVITY TO START THE PERIOD WILL SHIFT SOUTH AND EAST OF THE REGION WITH DRIER AIR ARRIVING FROM THE NORTH AND WEST. THIS DRIER REGIME SHOULD ALLOW MOST LOCATIONS TO REMAIN DRY FOR THE DAY FRIDAY...WITH PERHAPS ONE OR TWO SHOWERS OVER THE MOUNTAINS GIVEN CLOSER PROXIMITY TO THE COLD POOL AT H5. SOMEWHAT MORE ROBUST SHORTWAVE ENERGY ARRIVES ON SATURDAY...WITH AN INCREASED CHANCE FOR SHOWERS AND THUNDERSTORMS...AGAIN GREATEST IN THE MOUNTAINS...BUT SPREADING SOUTH AND EAST SOMEWHAT WITH THE IMPROVED FORCING. BEHIND THIS SHORTWAVE...THERE IS MODEST AGREEMENT ON QUIETER CONDITIONS FOR THE DAY SUNDAY IN A BROADLY SUBSIDENT REGIME WITH SOMEWHAT DRIER AIR OVERHEAD. THUS...MUCH LIKE FRIDAY...WILL RESTRICT ANY LOW POPS TO THE MOUNTAINS. MORE OF THE SAME AS WE REACH MONDAY-TUESDAY OF NEXT WEEK...WITH DECREASING AGREEMENT ON SHORTWAVE TIMING AMONG DETERMINISTIC AND ENSEMBLE GUIDANCE MEMBERS. THE RESULT...UNFORTUNATELY...IS THAT ISOLATED/CHANCE POPS WILL BE WARRANTED THROUGH THE END OF THE FORECAST...PARTICULARLY EACH AFTERNOON...ESPECIALLY FURTHER NORTH AND WEST /BOTH DUE TO TERRAIN ENHANCEMENT AND PROXIMITY TO MID-UPPER LEVEL FORCING/. TEMPERATURES: TEMPERATURES LOOK TO BEGIN THE PERIOD ABOVE SEASONAL NORMS FRIDAY...WITH SOME DOWNSLOPE ASSISTANCE UNDER WESTERLY WINDS. FOR THE REMAINDER OF THE PERIOD...TEMPERATURES LOOK TO BE CLOSE TO...OR JUST A BIT ABOVE SEASONAL NORMS...WITH T8S NEARLY STEADY IN THE LOW TO MID TEENS. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... SHORT TERM /THROUGH 00Z FRI/...AREAS OF MVFR OVERNIGHT IN STRATUS AND FOG WITH LCL IFR PSBL BTWN 09 AND 12Z TODAY IN PLACES WHICH RECEIVED RAINFALL EARLIER. VFR PREVAILING TODAY WITH LCL MVFR PSBL AFT 18Z IN WIDELY SCT SHRA AND TSRA VCNTY OF KAUG AND KRKD. AREAS MVFR AFT 00Z THU IN STRATUS AND FOG WITH LCL IFR PSBL BTWN 08 AND 12Z THU. LONG TERM...SHOWER AND THUNDERSTORM ACTIVITY THURSDAY AFTERNOON MAY LINGER THROUGH THE EVENING...WITH CONTINUED ISOLATED-SCATTERED MVFR-IFR RESTRICTIONS GIVING WAY VFR CONDITIONS THROUGH FRIDAY. ADDITIONAL ISOLATED-SCATTERED SHOWER AND THUNDERSTORM ACTIVITY POSSIBLE SATURDAY /MOST LIKELY TO IMPACT LEB/HIE/ WITH VFR CONDITIONS DOMINATING ELSEWHERE...AND FOR ALL LOCATIONS ON SUNDAY. && .MARINE... SHORT TERM...WAVES AND WIND GUSTS WILL APPROACH SCA CONDITIONS IN THE FAR OUTER WATERS LATE THURSDAY NIGHT. LONG TERM...MARGINAL SCA WINDS/WAVES THURSDAY EVENING WILL SUBSIDE AND REMAIN BELOW SCA LEVELS THROUGH THE WEEKEND. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$ ES

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