Area Forecast Discussion
Issued by NWS Portland, ME

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KGYX 251649 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 1249 PM EDT TUE AUG 25 2015 .SYNOPSIS... HUMID AND UNSETTLED CONDITIONS WILL CONTINUE THROUGH MID WEEK. A COLD FRONT WILL SLOWLY APPROACH FROM THE WEST TODAY...PROVIDING A ROUND OF SHOWERS AND THUNDERSTORMS. THE FRONT STALLS OVER THE AREA TONIGHT INTO WEDNESDAY AS WEAK LOW PRESSURE TRACKS NORTHEAST ALONG IT...WITH MORE SHOWERS AND THUNDERSTORMS EXPECTED. THE FRONT FINALLY EXITS THE REGION LATE WEDNESDAY. ANOTHER ROUND OF SHOWERS IS POSSIBLE ON THURSDAY MAINLY IN THE MOUNTAINS AS A SECOND COLD FRONT PUSHES THROUGH. DIRER AND RELATIVELY COOLER AIR WILL MOVE IN AT THE END OF THE WEEK AS HIGH PRESSURE BUILDS IN. AS THE HIGHS SETTLES SOUTH AND EAST OF US OVER THE WEEKEND...LOOK FOR MAINLY FAIR WEATHER AND A WARMING TREND. && .NEAR TERM /TODAY/...
-- Changed Discussion --
1245PM UPDATE... CONVECTIVE CLUSTER HAS FORMED MORE OF A LINE EXTENDING SOUTHWARD THROUGH CENTRAL NEW HAMPSHIRE AND INTO MASSACHUSETTS. EXPECT ACTIVITY TO CONTINUE TO GET GENERATED ALONG THIS LINE AND MOVE NORTHEASTWARD ALONG IT BEFORE FANNING OUT INTO A BROADER RAIN AREA OVER NORTHERN NEW HAMPSHIRE AND NORTHWEST MAINE. THIS LINE SHOULD MOVE SLOWLY TO THE EAST OVER THE NEXT FEW HOURS. ACTIVITY BEHIND THE LINE SHOULD BE SUPPRESSED AT LEAST FOR THE TIME BEING... THOUGH ADDITIONAL CONVECTION FORMING OVER VERMONT AND NEW YORK IS POSSIBLE WHICH COULD MOVE INTO THE AREA THIS EVENING. PRIMARY AREA OF SEVERE WEATHER CONCERN IS SOUTHERN NEW HAMPSHIRE EXTENDING INTO SOUTHWEST MAINE. HEAVY RAIN CONTINUES TO BE A THREAT AS STORMS TRAIN OVER THE SAME AREAS. 9AM UPDATE... HAVE UPDATED THE FORECAST TO ADJUST HOURLY PRECIPITATION CHANCES BASED ON LATEST RADAR TRENDS AND PROJECTED FORECAST. A CONGLOMERATION OF THUNDERSTORMS HAS MOVED NORTH AND SLIGHTLY EAST ACROSS WESTERN NEW HAMPSHIRE THIS MORNING AND SHOULD CONTINUE TO DO SO OVER THE NEXT FEW HOURS. FOG AND LOW LEVEL CLOUDS CONTINUE OVER COASTAL AREAS PARTICULARLY FROM PORTLAND EASTWARD. OTHERWISE NO CHANGES TO THE FORECAST FOR THE REST OF THE DAY. 7 AM UPDATE... A FEW TWEAKS TO THE CURRENT FORECAST TO ACCOUNT FOR LATEST RADAR TRENDS. A DISORGANIZED CLUSTER OF THUNDERSTORMS OVER WESTERN MASSACHUSETTS IS MOVING SLOWLY NE THIS MORNING. THIS AREA OF CONVECTION SHOULD AFFECT SW NEW HAMPSHIRE IN THE NEXT COUPLE OF HOURS BEFORE DISSIPATING. HAVE INCREASED POP TO LIKELY FOR THIS AREA. ORIGINAL DISCUSSION... THRU MORNING WE WILL SEE PLENTY OF FOG AND LOW CLOUDS. AND LIKE YESTERDAY...AS WE HEAT UP THESE CLOUDS WILL GRADUALLY LIFT AND SCATTER OUT. IT IS THESE BREAKS IN THE OVERCAST THAT WILL BE SO IMPORTANT TO THE AFTERNOON FORECAST. BOUNDARY LAYER IS CHARACTERIZED BY A WARM AND VERY MOIST AIR MASS ENTRENCHED ACROSS THE AREA. DESPITE POOR LAPSE RATES ALOFT...EVEN MARGINAL HEATING OF THIS LOW LEVEL AIR MASS WILL SUPPORT DESTABILIZATION. THIS HEATING IS MOST LIKELY TO OCCUR IN POCKETS...AS ONGOING CONVECTION FROM THIS MORNING SPREADS EXTRA CLOUD COVER INTO THE AREA...AND WHILE MORNING FOG SLOWLY LIFTS. AT THIS HOUR CONVECTION ALLOWING MODELS STRONGLY FAVOR BEST AIR MASS RECOVERY TO OCCUR OVER SOUTHERN NH. AS THE DAY WEARS ON...A MODEST CYCLONICALLY CURVED H5 JET WILL WORK TOWARDS NEW ENGLAND. SHEAR WILL CONSEQUENTLY INCREASE THRU THE DAY...AND PROVIDE MORE THAN ENOUGH TURNING IN THE ATMOSPHERE FOR STORM ORGANIZATION. AS UPPER LOW IS ONLY SLOWLY INCHING EAST...THERE WILL BE A BIT OF A LACK OF FORCING OVERALL...SO STORM COVERAGE SHOULD NOT BE WIDESPREAD. PRIMARY THREAT WILL BE GUSTY WINDS...BOTH VIA WET MICROBURSTS OR AS DEEP SW UNIDIRECTIONAL WINDS ALOFT INCREASE LATER IN THE AFTERNOON. GIVEN TENDENCY FOR CONVECTION ALLOWING MODELS TO LEAN TOWARDS SOMEWHAT DISCRETE STORM STRUCTURES LARGE HAIL CANNOT BE RULED OUT...IN ADDITION TO AN ISOLATED TORNADO. THE LATTER IS MITIGATED MAINLY BY THE WEAKER FLOW IN THE LOWEST 3 KM OF THE ATMOSPHERE. THAT BEING SAID...A WARM FRONTAL FEATURE WILL BE DRAPED ACROSS NH DURING THE AFTERNOON...SO NEAR AND JUST N OF THIS BOUNDARY WILL BE A LOCALLY HIGHER TORNADO THREAT. IN ADDITION TO THOSE STORM THREATS...DEEP SW FLOW WILL TEND TOWARDS TRAINING OF INDIVIDUAL CELLS. THIS WILL COMPOUND AN ALREADY MOIST ENVIRONMENT FAVORABLE FOR HEAVY RAINFALL...SO FLASH FLOODING WILL BE JUST AS LIKELY THIS AFTERNOON.
-- End Changed Discussion --
&& .SHORT TERM /TONIGHT AND WEDNESDAY/... COLD FRONT WILL VERY SLOWLY PROGRESS ACROSS THE AREA OVERNIGHT...SO THE THREAT FOR SHOWERS WILL LINGER ACROSS EASTERN ZONES WELL INTO THE NIGHT. AGAIN GIVEN THE DEEP SW FLOW...THE TENDENCY FOR TRAINING WILL CONTINUE AS WELL...AND HEAVY RAINFALL IS A POSSIBILITY. ONSHORE FLOW WILL CONTINUE...ESPECIALLY ACROSS MAINE...AND ALLOW FOG/STRATUS TO REDEVELOP TONIGHT AHEAD OF THE FRONT. THE EXTENT OF LOW CLOUDS WILL DEPEND ON HOW FAR EAST THE FRONT CAN ADVANCE...BUT GENERAL MODEL CONSENSUS IS THAT EASTERN ZONES REMAIN DOWNSTREAM OF THE BOUNDARY UNTIL WEDNESDAY. AGAIN WILL KEEP HIGHEST POP IN THE EASTERN ZONES TO ACCOUNT FOR SLOW FRONTAL MOVEMENT. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... HIGH IMPACT WEATHER: NONE. OVERALL 500MB PATTERN TREND IS TO TREND AWAY FROM MORE AMPLIFIED BLOCKY PATTERN AT THE START OF THE FORECAST PERIOD...TO LARGE SCALE RIDGING BUILDING OVER THE EASTERN 2/3 OF THE UNITED STATES AND TROUGHING NEAR THE WEST COAST BY EARLY NEXT WEEK. INITIALLY A LARGE CLOSED LOW SOUTH OF JAMES BAY WILL LIFT NE THURSDAY AND FRIDAY...WITH ZONAL FLOW TAKING OVER THIS WEEKEND. FINALLY THAT RIDGE STARTS TO BUILD IN EARLY NEXT WEEK. 850MB TEMPERATURES WILL INCREASE FROM 8-10C AT THE END OF WEEK TO 12-15C MONDAY AND TUESDAY. SENSIBLE WEATHER WILL START WITH SHOWERS AND THUNDERSTORMS SHIFTING EAST AND OUT OF THE FORECAST AREA WEDNESDAY EVENING...WITH A SLIGHT DROP IN RH/TEMPERATURES WEDNESDAY NIGHT. ANOTHER WAVE WILL ROTATE AROUND THE LOW ALOFT ON THURSDAY AND PUSH ANOTHER COLD FRONT THRU. THIS COULD SET OFF A SCATTERED SHOWERS AND EVEN A THUNDERSTORM...WHICH WILL PROBABLY BE LIMITED TO THE NORTHERN ZONES CLOSER TO THE BEST DYNAMICS...WHILE THE COAST SHOULD STAY DRY IN DOWNSLOPE. BEYOND THAT LOOK FOR MAINLY DRY AND GENERALLY FAIR WEATHER FRIDAY THROUGH MONDAY...ALTHOUGH A WEAK 500MB WAVE PASSING NORTH OF THE FORECAST AREA COULD PRODUCE A FEW SHOWERS IN THE MOUNTAINS SATURDAY NIGHT OR SUNDAY. TEMPERATURES WILL START NEAR NORMAL THURSDAY AND FRIDAY...AT LEAST FOR MAXES. OVERNIGHT LOWS MAY CONTINUE TO RUN SLIGHTLY ABOVE NORMAL WEDNESDAY NIGHT INTO THURSDAY NIGHT BEFORE THE DRIEST AIR MOVES IN FRIDAY...WITH HIGHS IN THE 70S TO AROUND 80...AND LOWS IN THE 50S TO AROUND 60. THE COOLEST NIGHT WILL PROBABLY BE FRIDAY NIGHT INTO SATURDAY MORNING WITH LOWS DROPPING INTO THE 50S EVERYWHERE...AND MAYBE A FEW UPPER 40S IN THE MOUNTAIN VALLEYS. TEMPERATURES WILL GRADUALLY WARM OVER THE WEEKEND AS WARMER AIR MOVES IN ALOFT ON THE ZONAL FLOW...WITH HIGHS REACHING INTO THE 80S IN MOST SPOTS BY MONDAY. && .AVIATION /13Z TUESDAY THROUGH SATURDAY/... SHORT TERM...AREAS OF LIFR IN FOG AND DRIZZLE WILL PERSIST THRU MORNING ACROSS EXTREME COASTAL NH AND MUCH OF WESTERN MAINE. EXPECT VERY GRADUAL IMPROVEMENT TODAY...BUT WITH COLD FRONT EDGING CLOSER THERE WILL BE MORE AREAS OF MVFR THAN YESTERDAY AFTERNOON. SHOWERS AND THUNDERSTORMS WILL ALSO CONTINUE TO FORM ALONG THE FRONT AND BECOME MORE WIDESPREAD WITH DAYTIME HEATING. SHOWERS ARE LOOKING MORE LIKELY AT NH TERMINALS THAN WESTERN MAINE AT THIS TIME...THOUGH EVENTUALLY RAINFALL WILL WORK THRU BOTH STATES. TIMING AND LOCATION OF THUNDERSTORMS REMAINS SOMEWHAT UNCERTAIN AT THIS HOUR...SO WILL START WITH A PROB30 FOR NOW. FOG/STRATUS WILL MOVE BACK INTO THE COAST AFTER 00Z TONIGHT...ESPECIALLY ACROSS WESTERN MAINE. LONG TERM...SOME AREAS OF FOG AND LOW CLOUDS WILL BE POSSIBLE WEDNESDAY NIGHT...BUT PROBABLY NOT AS PREVALENT NOR AS IMPACTFUL AS THE LAST FEW NIGHTS. AFTER THAT...THURSDAY THRU SATURDAY WILL FEATURE MAINLY VFR...WITH THE EXCEPTION OF VALLEY FOG EACH NIGHT. && .MARINE... SHORT TERM...WINDS AND SEAS EXPECTED TO REMAIN BELOW SCA THRESHOLDS THRU WEDNESDAY. WIDESPREAD FOG AND LOW CLOUDS WILL PERSIST THRU MORNING TODAY...SCATTERING OUT THIS AFTERNOON. IT SHOULD RETURN AGAIN TONIGHT...MAINLY CONFINED TO COASTAL MAINE WATERS. LONG TERM...MAY SEE SOME LINGERING LIGHT FOG WEDNESDAY NIGHT...BUT OTHERWISE SEAS/WINDS WILL BE COMFORTABLY BELOW SCA LEVELS THURSDAY THRU SATURDAY. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$ NEAR TERM UPDATE...KIMBLE

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.