Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 261126 AAA AFDGYX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GRAY ME 626 AM EST MON JAN 26 2015 .SYNOPSIS... LOW PRESSURE WILL BEGIN TO DEVELOP OFF THE MID ATLANTIC COAST TODAY THEN RAPIDLY INTENSIFY AS IT MOVES NORTHEASTWARD TO JUST SOUTH OF NANTUCKET MASSACHUSETTS ON TUESDAY. THE LOW WILL LINGER AROUND THROUGH WEDNESDAY BRINGING A SIGNIFICANT SNOWFALL TO OUR REGION. THERE IS ALSO THE POTENTIAL FOR ANOTHER STORM LATE WEEK OR EARLY IN THE WEEKEND BUT CONFIDENCE IS LOW AT THIS TIME. && .NEAR TERM /TODAY/... UPDATE...HAVE ADJUSTED TEMPS BASED ON LATEST OBSERVATIONAL TRENDS. LOWERED MINS A FEW DEGREES FOR MOST AREAS...AS CIRRUS SHIELD HASN/T SIGNIFICANT IMPACTED RADIATIONAL COOLING POTENTIAL. PREVIOUS DISCUSSION...GENERALLY QUIET WX FOR MOST OF TODAY. IT WILL BE COLD WITH HIGH PRES OVERHEAD...AND WINDS GRADUALLY INCREASING FROM THE NE THRU THE DAY. LATE IN THE DAY SOME SN IS POSSIBLE ACROSS SRN NH AS LOW PRES BEGINS TO GET ORGANIZED S OF NEW ENGLAND. && .SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... A DANGEROUS AND POTENTIALLY CRIPPLING COASTAL STORM IS SET TO AFFECT THE REGION BEGINNING LATE TODAY THRU TUE NIGHT. LOW PRES WILL MOVE THRU THE CAROLINAS TODAY...AND EXIT THE EAST COAST. HERE IT WILL RAPIDLY DEVELOP OVER THE RELATIVELY WARM WATERS OF THE ATLANTIC. LOW PRES WILL DROP SOME 20 MB IN 24 HOURS...AND TAKE A POSITION S OF NEW ENGLAND AND STALL OR SLOWLY DRIFT TOWARDS KACK. HEADLINES REMAIN MOSTLY THE SAME...WITH THE EXCEPTION BEING ERN HILLSBOROUGH BEING ADDED TO THE BLIZZARD WARNINGS. A DEPARTING JET STREAK IN EXCESS OF 150 KTS N OF THE CANADIAN MARITIMES WILL COMBINE WITH A SLY JET STREAK OFF THE EAST COAST IN EXCESS OF 130 KTS TO PROVIDE A STAGE FOR RELATIVELY EXPLOSIVE DEVELOPMENT OF LOW PRES. GFS CROSS SECTIONS THRU FORECAST AREA FROM ROUGHLY KPWM TO KHIE SHOW INTENSE FRONTOGENESIS WITHIN A LAYER NEAR H7. THE UPPER LEVEL DYNAMICS ARE SUCH THAT AGEOSTROPHIC FORCING WILL PROVIDE STRONG LIT THRU THE DENDRITIC GROWTH ZONE. SNWFL WILL BE IDEAL AND FAIRLY EFFICIENT GIVEN THE WINDS FORECAST ALOFT. GFS HAS THIS AXIS ALIGNED NEARLY ON TOP OF THE COASTLINE. GIVEN THE FEATURES AVAILABLE ONE CAN INFER THAT THE ECMWF IS SHIFTED SLIGHTLY NW OF THE GFS AXIS. ALTERNATIVELY...FINDING THE AREA WITHIN THE MODELED FRONTOGENESIS AT H8 ON THE COOL SIDE OF THE DEFORMATION MAXIMUM SUPPORTS THIS ASSESSMENT OF THE ECMWF BEING SLIGHTLY FARTHER NW WITH IDEAL SNWFL. HOWEVER...THERE ARE SOME CONCERNS LEFT REGARDING THIS STORM AND THE OVERALL POTENTIAL FOR HIGH SNWFL AMOUNTS. MODELED QPF IS STRUGGLING TO ECLIPSE 2 INCHES FOR MOST AREAS OUTSIDE OF EXTREME SRN NH. THIS WOULD MAKE IT HARD FOR MANY AREAS TO SEE 2 FEET OF SNWFL. IN ADDITION...OCCLUSION WILL ACT TO SHUT DOWN WAA PROCESSES AND CUT OFF THE INTENSE LIFT NECESSARY FOR SNWFL RATES IN EXCESS OF 2 INCHES PER HOUR. THESE TYPES OF RATES WILL BE NEEDED TO SEE WIDESPREAD 20 INCH TOTALS. FINALLY...A STRONG COASTAL FNT WILL DEVELOP. THIS WILL NOT MARK THE BOUNDARY BETWEEN SNWFL AND RA...BUT NEAR FREEZING AIR AND AIR IN THE TEENS AND SINGLE DIGITS. INTENSE LOW LEVEL LIFT NEAR THIS BOUNDARY MAY ENHANCE SNWFL IMMEDIATELY ON THE COLD SIDE...BUT FARTHER NW COULD SEE A BIT OF SUBSIDENCE AND LOWERED TOTALS. FOR THESE REASON I TENDED TO KEEP SNWFL TOTALS SIMILAR TO THE PREVIOUS SHIFT...WITHOUT DRAMATIC INCREASES. THOUGH ISOLATED AMOUNTS IN EXCESS OF 2 FEET ARE POSSIBLE...ESPECIALLY COASTAL SRN NH AND THE MONADNOCKS...WHERE STRONG ELY UPSLOPE WILL ENHANCE AMOUNTS. THE GREATEST PERIOD OF CONCERN IS LOOK TO BE ROUGHLY 12Z TO 21Z TUE. HERE THE BEST COMBINATION OF SNWFL AND WINDS LOOKS MOST LIKELY. THE ECMWF HAS A 65+ KT LOW LEVEL JET AT 900 MB LIFTING NWD ACROSS THE AREA. DEEP COLD AIR IN PLACE WILL ALLOW SOME OF THIS TO MIX DOWN FAIRLY EASILY. GIVEN THE EXPECTED SNWFL AROUND THAT TIME...AND POTENTIALLY 45-50 KT GUSTS MIXING DOWN...BLIZZARD WARNINGS LOOK GOOD. ELSEWHERE COULD SEE BRIEF NEAR-BLIZZARD CONDITIONS BUT THERE WAS NOT ENOUGH CONFIDENCE TO EXPAND...OUTSIDE OF ERN HILLSBOROUGH. WHERE THE COMBINATION OF 1 INCH OR MORE PER HOUR RATES AND 50 KT GUSTS OCCURS...TRAVEL WILL BE IMPOSSIBLE AND LIFE THREATENING. THE NEXT 12 HOURS WILL BE CRITICAL AS MODELS BEGIN TO HONE IN ON THE MESOSCALE DETAILS. SOME SURPRISES ARE STILL LIKELY WITH THIS STORM...AS THE VERY DYNAMIC EVENTS CAN CAUSE NWP TO STRUGGLE AT TIMES. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... THE MODELS ARE IN GENERAL AGREEMENT ON THE LONG WAVE PATTERN THROUGH EARLY NEXT WEEK. HOWEVER...SIGNIFICANT DIFFERENCES EXIST WITH TIMING AND STRENGTH OF INDIVIDUAL SHORTWAVES LEADING TO DECREASED CONFIDENCE IN SENSIBLE WEATHER. THE OVERALL THEME IS WESTERN RIDGE AND EASTERN TROUGH FOR THE CONUS...WITH AN EXTENDED PERIOD OF BELOW NORMAL TEMPERATURES AND A CHANCE FOR SYNOPTIC SNOWS ROUGHLY EVERY TWO DAYS...WITH FRIDAY...SUNDAY...AND NEXT TUESDAY FOR OUR FORECAST AREA. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... SHORT TERM...HIGH CONFIDENCE IN IFR AND LOWER CONDITIONS BEGINNING IN SRN NH THIS EVENING...AND ACROSS NRN NH AND WRN ME EARLY TUE. SNWFL RATES OF 2 INCHES OR MORE PER HOUR ARE POSSIBLE DURING THE DAY TUE. STRONG NELY WIND GUSTS ARE EXPECTED FOR COASTAL TERMINALS...REACHING UP TO 50 MPH AT TIMES. CONDITIONS GRADUALLY IMPROVE LATE TUE NIGHT INTO WED. SNWFL WILL CONTINUE INTO WED...WITH SCT IFR CONDITIONS POSSIBLE. LONG TERM... WED...AREAS OF MVFR IN SNOW SHOWERS. NW WIND GUSTING TO 25 KT. FRI...AREAS OF MVFR IN SNOW WITH LCL IFR CONDS PSSBL. && .MARINE... SHORT TERM...WINDS AND SEAS WILL TURN NELY AND GRADUALLY BUILD TODAY. TONIGHT INTO TUE WINDS AND SEAS INCREASE DRAMATICALLY. STORM FORCE WIND GUSTS ARE LIKELY ON ALL WATERS...WITH SEAS BUILDING TO 25-30 FT ON THE OUTER WATERS. CANNOT RULE OUT A FEW GUSTS IN EXCESS OF HURRICANE FORCE TUE...ESPECIALLY ON THE HIGHER PLATFORMS OF MISM1 AND IOSN3. LONG TERM... WED...GALE FORCE WINDS ARE LIKELY. FRI...GALE FORCE WINDS ARE POSSIBLE. && .TIDES/COASTAL FLOODING... TIDES ARE RELATIVELY LOW IN THE ASTRONOMICAL CYCLE HOWEVER PROLONGED NORTHEASTERLY FLOW WILL BUILD SEAS OF 25 TO 30 FEET OFFSHORE. THIS MAY BE ENOUGH TO PRODUCE MINOR FLOODING AROUND THE TIMES OF HIGH TIDE. BEACH EROSION AND SPLASHOVER ARE LIKELY. AT PORTLAND HIGH TIDE IS 10.0 FT AT 420AM TUESDAY...9.1FT AT 453PM TUESDAY...AND 9.8FT AT 523AM WEDNESDAY. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...WINTER STORM WARNING FROM 10 PM THIS EVENING TO 4 AM EST WEDNESDAY FOR MEZ007>009-012>014. BLIZZARD WARNING FROM 10 PM THIS EVENING TO 4 AM EST WEDNESDAY FOR MEZ018>028. COASTAL FLOOD WATCH FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT FOR MEZ023>028. NH...WINTER STORM WARNING FROM 10 PM THIS EVENING TO 4 AM EST WEDNESDAY FOR NHZ002>009-011-015. BLIZZARD WARNING FROM 10 PM THIS EVENING TO 4 AM EST WEDNESDAY FOR NHZ010-012>014. WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 4 AM EST WEDNESDAY FOR NHZ001. COASTAL FLOOD WATCH FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT FOR NHZ014. MARINE...STORM WARNING FROM 1 AM TUESDAY TO 7 AM EST WEDNESDAY FOR ANZ150>154. && $$ NEAR TERM...LEGRO

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