Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 281434 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 934 AM EST SAT FEB 28 2015 .SYNOPSIS... HIGH PRESSURE WILL BUILD OVER THE REGION TODAY AND WILL SHIFT OFFSHORE SUNDAY. WEAK LOW PRESSURE CROSSES THE REGION SUNDAY NIGHT...PRODUCING SOME ACCUMULATING SNOW...BEFORE MOVING INTO THE CANADIAN MARITIMES ON MONDAY. HIGH PRESSURE CROSSES THE AREA MONDAY NIGHT AND TUESDAY. LOW PRESSURE WILL MOVE OUT OF THE GREAT LAKES TUESDAY NIGHT AND WILL TRACK NORTHEAST THROUGH THE ST LAWRENCE VALLEY ON WEDNESDAY...BRINGING A ROUND OF MIXED PRECIPITATION TO THE AREA. A COLD FRONT FOLLOWS WEDNESDAY NIGHT. HIGH PRESSURE BUILDS IN FOR THE END OF THE WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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UPDATE... HAVE UPDATED THE GRIDS BASED ON CURRENT TRENDS AND CONDITIONS. -7 DEGREES IN PORTLAND LAST NIGHT WAS VERY CLOSE TO THE ALL-TIME RECORD LOW OF -9. EXPECT TO FORECAST BELOW MODEL GUIDANCE AGAIN TONIGHT FOR THE MIN TEMPERATURES. SUNNY FOR THE REST OF TODAY...WITH LIGHT WINDS. FREEZING SPRAY ADVISORY WILL END SHORTLY. PREV DISC... HIGH PRESSURE WILL CONTINUE TO BUILD IN FROM THE WEST TODAY PROVIDING SUNNY SKIES AND SLIGHTLY WARMER TEMPS. HIGHS WILL RANGE FROM THE UPPER TEENS TO LOWER 20S NORTH AND MID TO UPPER 20S SOUTH.
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&& .SHORT TERM /SUNDAY/... HIGH PRESSURE WILL CREST OVER THE REGION TONIGHT. GOOD RADIATIONAL COOLING WILL AGAIN SEND TEMPS WELL BELOW NORMAL BUT NOT QUITE AS COLD AS FRIDAY NIGHT. COLDER MOUNTAIN VALLEYS WILL BOTTOM OUT BETWEEN 5 AND 15 BELOW. TEMPERATURES IN THE SOUTH WILL BE BETWEEN 5 ABOVE AND 5 BELOW. EXPECT SOME HIGH CLOUDS TO FILTER IN FROM THE WEST AFTER MIDNIGHT. CLOUDS WILL BE ON THE INCREASE SUNDAY AS HIGH PRESSURE SHIFTS EAST AND A COLD FRONT APPROACHES FROM THE WEST. HAVE GONE WITH LOW CHANCE POPS FOR SOUTHWEST ZONES FOR LATE IN THE DAY BUT EXPECT ANY SNOW SHOWERS TO BE LIGHT AND SPOTTY. HIGH TEMPS WILL CONTINUE BELOW NORMAL WITH READINGS RANGING THROUGH THE 20S TO NEAR 30. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... 500 MB PATTERN IN THE EXTENDED LOOKS TO REMAIN MOSTLY UNCHANGED THROUGH THE EXTENDED ALTHOUGH STARTING TO SEE SOME SEASONAL SHIFTING OF THE JET BACK TOWARD THE POLE. ALSO...SOME WEAKEN IN BOTH THE UPSTREAM AND DOWNSTREAM BLOCKS WILL ALLOW FOR SOME MORE COMPACT AND PROGRESSIVE WAVES TO DEVELOP WHICH SHOULD HELP TRANSPORT SOME WARMER INTO THE NERN CONUS...AT LEAST FOR SHORT PERIODS. FIRST ON THE AGENDA IS THE FAST MOVING WAVE THAT SWINGS SE OUT OF THE CANSDI9AN PRAIRIE AND THEN SHIFTS INTO NEW ENGLAND BEFORE SHOWING A BIT OF A NEGATIVE TILT. LOOKS LIKE THE ENERGY GET S INTO THE BASE OF THIS TROUGH TO LATE TO DEEPEN THE SFC LOW UNTIL IT IS TO OUR EAST...AND SO WE WILL SOME SNOW LATE SUNDAY AND MAINLY SUNDAY NIGHT. QPF LOOKS TO COME IN THE AROUND 0.20-0.25" FAIRLY EVENLY ACROSS THE CWA...AND THIS SHOULD GENERALLY TRANSLATE TO 2-4" OF SNOW GIVEN SNOWFALL RATIOS OF ROUGHLY 10-15 TO 1. HIGHEST AMTS LOOK TO BE IN THE SRN THIRD OF NH...WITH LOWEST AMTS IN INTERIOR CENTRAL ME. SNOW SHOULD WIND DOWN IN MOST PLACES BY 12Z...WITH WEST WINDS PICKING UP BY MIDDAY AND TEMPS RISING INTO THE LOW-MID 30S NEAR THE COAST AND IN SRN NH...AND IN THE MID- UPPER 30S IN THE NORTH. COLD AIR FILTERS IN MON NIGHT WITH LOWS DROPPING BACK DOWN BETWEEN -5 AND +10 F. TUE WILL BE A LITTLE COLDER AS LIGHT FLOW BECOMES MORE ONSHORE AND CLOUDS ROLL IN FROM THE NEXT APPROACHING FROM THE SW. THIS NEXT SYSTEM WILL FEATURE A 500MB CLOSED LOW WELL TO OUR NW AND A FEW WEAK WAVES ROTATING AROUND IT AND GRADUALLY FLATTENING OUT THE RIDGE UNTIL THE KICKER WAVE COME THRU ON THU. THIS WILL KEEP THINGS UNSETTLED FROM TUE NIGHT INTO THE THU...ALTHOUGH THE HIGHEST CONFIDENCE IN PRECIP OCCURRING FOR NOW TUE NIGHT INTO WED MORNING. IT WILL START OUT AS SNOW...BUT IT WILL BE ACCOMPANIED BY DECENT SW FLOW ALOFT...AND MAIN CHUNK OF HIGH SHIFTS OFF TO THE EAST AND DOES NOT ENTRENCH ITSELF TO THE NE. THIS SHOULD ALLOW THE WARN AIR TO MOVE IN FAIRLY CLOSE TO THE SFC. THE QUESTION IS HOW LONG DOES THE COLD AIR DAM AT THE SFC HOLD ON...GIVEN THE DEEP SNOWPACK. MODELS ARE PROBABLY OVERDOING THE WARM TO SOME DEGREE. HAVE INCLUDED FZRA IN THE MIX ON WED. STILL SYSTEM IS FAIRLY PROGRESSIVE AND QPFS GENERALLY LOOK TO BE IN THE HALF INCH BALLPARK...SO NOT A BIG EVENT FOR NOW. MODELS DO WANT TO STALL THE FRONT JUST TO OR S WED NIGHT INTO THU...AND THEN DEVELOP A WAVE ALONG THE FRONT. FOR NOW MODELS GENERALLY AGREE THAT MOST OF ANY PRECIP STAYS TO OUR S...BUT HAVE KEPT THE CHC POPS IN THE FORECAST TO COVER THIS POSSIBILITY. COLDER HIGH PRESSURE THEN BUILDS IN FOR FRI. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/... SHORT TERM...VFR TODAY THROUGH TONIGHT. AREAS OF MVFR CIGS DEVELOPING LATE SUNDAY. LONG TERM...WILL LKLY SEE IFR CIGS/VIS IN SN FOR A GOOD CHUNK OF SUN NIGHT AT ALL TERMINALS...BUT SHOULD SEE RAPID IMPROVEMENT OT VFR FORM SW TO NE DURING MON MORNING /EXCEPT KHIE WHICH WILL SEE OCCNL MVFR-IFR IN SHSN THRU MON AFTERNOON. VFR HOLDS MON NIGHT AND TUE BEFORE ANOTHER SYSTEM MOVES IN TUE AND WILL PRODUCE FLIGHT RESTRICTIONS LATE TUE NIGHT INTO WED. && .MARINE... SHORT TERM...FREEZING SPRAY ADVISORY THROUGH LATE MORNING. LONG TERM...EXPECT TO NEED AN SCA MONDAY AFT INTO MON NIGHT IN W FLOW. MAY NEED GALES FOR A PERIOD LATE MON AND MON EVENING...BEFORE WINDS DIMINISH LATE MON NIGHT. SCA MAY BE NEEDED AGAIN IN SW FLOW LATE TUE NIGH AND WED. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...FREEZING SPRAY ADVISORY UNTIL NOON EST TODAY FOR ANZ150>152. && $$

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