Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 271253 AAB AFDGYX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GRAY ME 753 AM EST TUE JAN 27 2015 .SYNOPSIS... STRONG LOW PRESSURE WILL MOVE NORTHEASTWARD TO JUST SOUTH OF NANTUCKET MASSACHUSETTS TODAY. THE LOW WILL LINGER AROUND THROUGH WEDNESDAY BRINGING A SIGNIFICANT SNOWFALL TO OUR REGION. ANOTHER STORM SYSTEM WILL LIKELY BRING A GENERAL SNOWFALL TO THE AREA ON FRIDAY. && .NEAR TERM /THROUGH TONIGHT/...
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UPDATE...HAVE ADJUSTED POP TO FOCUS CATEGORICAL ALONG INTENSE SNWFL BAND. BUMPED TOTALS UP BENEATH THE BAND AS IT WILL BE NEARLY STATIONARY FOR THE NEXT SEVERAL HOURS. MEASURING WILL BE NEARLY IMPOSSIBLE...BUT TOP 10 SNWFL APPEARS WITHIN REACH UNDER THIS DEFORMATION BAND. TRAVEL IS GOING TO BE NEAR IF NOT IMPOSSIBLE GIVEN THE COMBINATION OF SNWFL RATES AND WIND GUSTS PRODUCING WHITEOUT CONDITIONS. INTENSE MESOSCALE DEFORMATION BAND HAS ROTATED FULLY ONSHORE NOW. SNWFL RATES OF 2 TO 4 INCHES PER HOUR ARE OCCURRING BENEATH THIS BAND. HAVE UPDATED SNWFL AMOUNTS IN THE PREVIOUS AND NEXT 6 HOUR PERIODS TO GET A MORE ACCURATE UP TO DATE TOTAL ACCUMULATION GRID TO THIS HOUR. AGAIN MORE FOCUS IS ON THE COAST AND IMMEDIATE INTERIOR FOR HIGHER SNWFL AMOUNTS...WHILE TRIMMING THE NRN EDGE BACK. SN IS ONLY NOW BEGINNING TO FALL IN THE MTNS...SO AT BEST COULD ONLY HAVE AN INCH OR TWO ACCUMULATION THRU 12Z FOR THESE AREAS. PREVIOUS DISCUSSION...AS MENTIONED IN THE PREVIOUS UPDATE...00Z MODEL GUIDANCE HAS LATCHED ONTO THE IDEA OF SLIGHTLY WEAKER S/WV FEATURE PHASING WITH THE INITIAL STORM SYSTEM THAT EXITED THE EAST COAST YESTERDAY. THIS HAS ALLOWED THE SYSTEM TO SLIP FURTHER E...RATHER THAN A STRONGER CAPTURE AND TUG BACK TO THE W. GFS...CMC- REGIONAL...ECMWF...AND NAM ALL HAVE SIMILAR IDEAS REGARDING EVOLUTION FOR THE REST OF TODAY. SNOWFALL... AT THIS HOUR A VERY INTENSE BAND OF SNWFL IS MORE OR LESS PARALLELING THE COAST...AND SLOWLY INCHING NWWD. MODELED QPF HAS BEEN KEYING ON THE COAST OR JUST INLAND FOR SEVERAL RUNS NOW. TOSSING QPF ASIDE AND LOOKING ALOFT...NAM...GFS...AND ECMWF FEATURE STRONG FRONTOGENESIS AT H7. WITHIN THIS BAND OF FRONTOGENESIS THERE IS ALSO A DEFORMATION MAXIMUM. THE STRONGEST BANDS OF SNWFL ARE FAVORED JUST ON THE COOL SIDE OF THE DEFORMATION MAXIMUM...WITHIN THE STRONGEST FRONTOGENESIS. AS OF THE 06-09Z PERIOD THIS IS VERIFYING NICELY. BY 12Z MODELS SUGGEST THIS SIGNAL PIVOTS INLAND MORE...AND BECOMES NEARLY STATIONARY THRU 18Z. DURING THIS TIME BUFKIT SOUNDINGS FOR COASTAL LOCATIONS BRIEFLY ATTEMPT TO NEAR MOIST ABSOLUTELY UNSTABLE ABOVE H7. WOULD NOT BE SURPRISED TO SEE REPORTS OF THUNDER SN...BUT AT THE VERY LEAST CONVECTIVE ELEMENTS WILL HELP TO INCREASE SNWFL RATES TO 2-4 INCHES PER HOUR AT TIMES. HAVE ADJUSTED THE HIGHEST SNWFL AMOUNTS TOWARDS THE COAST SOME. THE OTHER FACTOR TO CONSIDER WITH SNWFL AMOUNTS IS VERY DRY AIR IN PLACE AND JUST N OF THE FORECAST AREA. NLY WINDS WILL ADVECT THIS AIR SWD...ERODING THE NRN EDGE OF SNWFL AS WE/VE SEEN FOR MUCH OF THE NIGHT. THAT IN COMBINATION WITH THE EWD MODEL SHIFT WILL YIELD A MUCH SHARPER SNWFL GRADIENT THAN ORIGINALLY FORECAST. FOR NOW ONLY SIGHTLY LOWERED AMOUNTS IN THE N...BUT SUBSEQUENT UPDATES MAY NEED MORE AGGRESSIVE LOWERING OF TOTALS. WINDS... 27.00Z ECWMF CONTINUED WITH THE IDEA OF ROTATING A POTENT LOW LEVEL JET NWD ACROSS THE FORECAST AREA TODAY. AT 900 MB IT INCREASED FROM ITS PREVIOUS FORECAST TO 80 KTS. GIVEN THE DEEP COLD AIR IN PLACE...MIXING HEIGHTS ARE QUITE HIGH FOR A NOREASTER EVEN WITH A LARGE INVERSION IN PLACE. EVEN A FRACTION OF THIS LOW LEVEL JET MIXING DOWN...ESPECIALLY DURING THE HEAVIEST SNWFL...YIELDS THE POTENTIAL FOR GUSTS ABOVE 50 KTS NEAR THE COAST. GIVEN THAT WINDS ARE ALREADY GUSTING ABOVE 30 KTS...THIS SEEMS ENTIRELY REASONABLE. INCREASED WIND FORECAST SLIGHTLY FROM PREVIOUS PACKAGE. WIND POTENTIAL DECREASES FAIRLY QUICKLY THE FURTHER INLAND ONE GOES...BUT GUSTS AROUND 25 TO 30 KTS WILL BE POSSIBLE. BASED ON BUFKIT SOUNDINGS...BEST WIND POTENTIAL WILL OCCUR FROM THIS MORNING THRU EARLY AFTERNOON. TEMPS... COLD HIGH PRES TO THE N AND NLY WINDS WILL ENSURE THAT TEMPS REMAIN FAIRLY STATIC THRU THE DAY. EXPECT THAT MUCH OF THE EVENT WILL SEE SNWFL IN THE TEENS AND SINGLE DIGITS. STRONG SYSTEM TO OUR S AND THOSE NLY WINDS WILL ALSO KEEP COASTAL FRONT OFF SHORE...AND ANY ADDITIONAL QPF ENHANCEMENT OFF SHORE TOO. COLD TEMPS AND STRONG WINDS WILL ALSO COMBINE TO PRODUCE BITTERLY COLD WIND CHILLS. IF STRANDED OUT IN THE STORM...THESE CONDITIONS COULD PRODUCE A POTENTIALLY LIFE THREATENING SITUATION.
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&& .SHORT TERM /WEDNESDAY/... LOW PRES OCCLUDES AND UPPER LOW DRIFTS ACROSS THE AREA THRU WED. THIS WILL CONTINUE -SN FOR MUCH OF THE PERIOD...THOUGH INTENSITY WILL BE FAR LESS THAN THAT EXPERIENCED TODAY. AN ADDITIONAL COUPLE OF INCHES OF ACCUMULATIONS IS POSSIBLE. TEMPS WILL BE ON THE COOL SIDE WITH GUSTY WLY WINDS. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... 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 - FRIDAY NIGHT...SUNDAY NIGHT-MONDAY...THE MOST LIKELY TIME FRAMES FOR OUR FORECAST AREA AT MOMENT. WE BEGIN THE PERIOD ON A QUIET NOTE UNDER RIDGING SURFACE AND ALOFT THURSDAY. THE NEXT SYSTEM ARRIVES BY FRIDAY MORNING WITH A GENERAL SNOWFALL ENDING FRIDAY NIGHT. BEHIND THIS SYSTEM...WEAK RIDGING FOLLOWS FOR SATURDAY INTO SUNDAY. MORE UNCERTAINTY WITH THE NEXT SYSTEM FOR SUNDAY NIGHT - MONDAY AS THE BULK OF THE PRECIPITATION SHIELD MAY REMAIN OFFSHORE. && .AVIATION /13Z TUESDAY THROUGH SATURDAY/... SHORT TERM...WIDESPREAD IFR AND LIFR IS DEVELOPING FROM SRN NH TO COASTAL ME AT THIS HOUR. THIS TREND WILL CONTINUE AS HEAVY SNWFL BAND SLOWLY ROTATES NEWD. THIS WILL CONTINUE THRU EARLY AFTERNOON. KLEB AND KHIE WILL BE SLOWER TO SEE IFR CONDITIONS...POSSIBLY HOLDING OFF UNTIL MID MORNING OR LATER. COASTAL TERMINALS WILL SEE NNELY WIND GUSTS NEAR 45 KTS AT TIMES. SNWFL WINDS DOWN BY TUE EVENING...THOUGH PCPN LINGERS INTO WED. COULD SEE SCATTERED IFR CONDITIONS WILL LINGERING SHSN. LONG TERM... FRI...MVFR IN SNOW WITH LCL IFR CONDS PSSBL. NW SFC WIND GUSTING TO 25 KT. && .MARINE... SHORT TERM...STORM WARNINGS REMAIN IN EFFECT FOR ALL WATERS...EXCEPT FOR OUTER WATERS S OF CAPE ELIZABETH. HERE A PERIOD OF 65 KT GUSTS APPEARS LIKELY...SO HAVE ISSUED A HURRICANE FORCE WIND WARNING. ALSO MODERATE FREEZING SPRAY IS ALREADY OCCURRING ON THE WATER BASED ON BUOY OBSERVATIONS. HAVE ISSUED A FREEZING SPRAY ADVISORY THRU WED MORNING AS A RESULT. LONG TERM... THU NIGHT - SAT...GALE FORCE WINDS ARE POSSIBLE. && .TIDES/COASTAL FLOODING... LARGE...BATTERING WAVES ARE BUILDING THIS MORNING RIGHT AROUND HIGH TIDE. THIS IN COMBINATION WITH A TWO FOOT STORM SURGE WILL ALLOW PORTLAND AND HAMPTON TO REACH THEIR FLOOD STAGE. WINDS WILL SWITCH TO THE NORTH THIS AFTERNOON JUST PRIOR TO HIGH TIDE...WHICH MAY REDUCE THE STORM SURGE. USED THE NORTH ATLANTIC REGIONAL TEAM WAVE RUNUP MATRICES TO FORECAST AND WARN FOR THE TWO HIGH TIDES TODAY. THE OUTPUT SHOWS WAVE ACTION WILL ALLOW FOR LOCALLY SIGNIFICANT EROSION AS WELL AS OVERWASH AT FORTUNES ROCKS...JENNIS...CAMP ELLIS AND FERRY BEACHES IN MAINE AND NEW HAMPSHIRE. NERACOOS SPLASH-OVER NOMOGRAMS ALSO SHOWING SIGNIFICANT ISSUES AT THE TIME OF HIGH TIDE FOR THE BEACHES SOUTH OF PORTLAND. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...WINTER STORM WARNING UNTIL 4 AM EST WEDNESDAY FOR MEZ007>009- 012>014. BLIZZARD WARNING UNTIL 4 AM EST WEDNESDAY FOR MEZ018>028. COASTAL FLOOD ADVISORY UNTIL 6 PM EST THIS EVENING FOR MEZ025>028. COASTAL FLOOD WARNING UNTIL 6 PM EST THIS EVENING FOR MEZ023- 024. NH...WINTER STORM WARNING UNTIL 4 AM EST WEDNESDAY FOR NHZ002>009- 011-015. BLIZZARD WARNING UNTIL 4 AM EST WEDNESDAY FOR NHZ010-012>014. WINTER WEATHER ADVISORY UNTIL 4 AM EST WEDNESDAY FOR NHZ001. COASTAL FLOOD WARNING UNTIL 6 PM EST THIS EVENING FOR NHZ014. MARINE...STORM WARNING UNTIL 7 AM EST WEDNESDAY FOR ANZ150>153. FREEZING SPRAY ADVISORY UNTIL 7 AM EST WEDNESDAY FOR ANZ150>154. HURRICANE FORCE WIND WARNING UNTIL 3 PM EST THIS AFTERNOON FOR ANZ154. && $$ NEAR TERM...LEGRO

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