Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 131552 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1152 AM EDT Tue Mar 13 2018 .SYNOPSIS... A nor`easter will intensify and move up the coast today bringing widespread heavy snowfall to New Hampshire and Maine. Along the coast blowing snow and wind gusts to 35 mph are expected to bring near blizzard conditions. Snow will continue into tonight before coming to an end for most of the region Wednesday morning. An upper level low will remain in the region through the start of the weekend with upslope snow showers continuing in the mountains. && .NEAR TERM /UNTIL 7 PM THIS EVENING/...
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1150 AM...NWS Doppler Radar mosaic shows several bands of moderate to heavy snowfall pivoting westward across the region around intense ocean storm currently situated east of the 40N/70W benchmark. Snowfall rates will range from around an inch per hour outside the bands and between one to three inches per hour in the higher reflectivity bands. For this ESTF update...I made minor adjustments to 6 hour snowfall grid to reflect the heavier band vicinity of the Connecticut Valley and to ingest the 15z mesonet into near term grids. Prev Disc... 910 13z a 970 millibar low was rapidly deepening south of the 40N/70W benchmark with three hour pressure falls on the order of 8 millibars. NWS Doppler Radar mosaic shows bands of heavy snow approaching the coast that will pivot onshore during the next 1 to 3 hours. For this ESTF update...I made minor adjustments to near term grids to reflect the latest mesonet as well as radar trends. Prev disc... Challenging forecast this morning. Surface low now rapidly deepening east of the delmarva peninsula. 3 hourly pressure falls have been averaging in the 6-8mb range for the past several hours as the system consolidates, deepens and moves to the north northeast. Numerical guidance in good agreement as to the track, with some minor variations in track of course, but the spread has much decreased. Some variations in QPF are still pretty notable with the NAM being by far the wettest, and the GFS on the dry side. QPF based on a consensus without the NAM. Regardless of the finer points of the exact magnitude the message cannot be lost that this is a significant snowfall for the whole region, especially in a band from southeast New Hampshire right up through central Maine. Mesoscale models show strong frontogenetic forcing in two bands one affecting western areas and the other, main mesoscale snow band rotating into coastal sections this afternoon, and later pivoting over central and mid-coast maine. At this point greatest snowfall totals look to occur in mid-coast Maine. Also of note are the thermal/stability profiles in the boundary layer allowing the cold conveyor of the system to mix down to the surface. Mixing heights around 2kft as the low level northeasterly jet increases should bring a fairly long (6 hours give or take) period of frequent gusts of 40-50 mph to coastal Maine and New Hampshire. HRRR/RAP/NAM3KM profiles for PWM/PSM/RKD all consistently showing these winds making it to the surface during the afternoon and early part of the evening. Some hints that these conditions could reach interior portions of central and southwest maine but low confidence in that outcome at this point. These strong winds are also coincident with the period of best dendritic snow growth across the region, and very strong deep layer lift. With the winds, and the very heavy snow being coincident in time, blizzard conditions are now expected, and a blizzard warning has been issued for coastal Maine and New Hampshire. Winds begin to drop off and heaviest snow lifts to the northeast beginning this evening.
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&& .SHORT TERM /7 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... Storm will continue to lift into the Maritimes Wednesday bringing the steady synoptic snow to and end. Steep lapse rates and upslope snow will cause lighter snow to continue into Wednesday in the mountains and foothills with additional lighter accumulations. Accumulating snow is less likely in coastal areas during the day on Wednesday. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... For the end of the week an upper level trough remains over the region bringing continued northwesterly flow and upslope snow showers. That trough will gradually break down and move east as the strong high pressure south of Greenland finally begins to decay. As we move into the weekend the closed low moves east and a brief upper level ridge tries to build in. Thursday and Friday will be fairly similar with temperatures climbing above freezing along the coast and near freezing in the mountains during the day with lows in the mid 20s at night. Persistent mountain snow showers will bring some light accumulations. Saturday and Sunday weak high pressure builds into the region as skies become partly sunny. By the start of next week another trough looks to set up along the east part of CONUS putting the storm track back up the east coast by the middle of next week. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/... Short Term...IFR/LIFR conditions developing and continuing into the evening. All terminals beginning to improve beginning late this evening in southern New Hampshire and improving to the northeast early Wednesday. Long Term...MVFR snow showers will be the rule through the northern mountains through most of the period as an upper level low parks over the maritimes and keep upslope showers going through the weekend. Elsewhere VFR conditions are expected. && .MARINE... Short Term...Already blowing gales along the coast with storm conditions developing by mid day. Winds begin to slack as best gradient lifts to the northeast tonight. Long Term...Persistent NW flow will keep small craft conditions around through the end of the week on the outer waters. Over the weekend winds and seas will subside as weak high pressure moves through the area. && .TIDES/COASTAL FLOODING... A nor`easter will intensify and move up the coast today. As it does persistent onshore flow will result in a storm surge of around 2ft. Storm force northeasterly winds will result in near shore waves of up to 15ft. While astronomical tides are fairly modest the combination of surge and wave action may lead to some beach erosion and exacerbate erosion of previous storms. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...Winter Storm Warning until 8 AM EDT Wednesday for MEZ012- 018>020. Winter Storm Warning until 2 PM EDT Wednesday for MEZ007>009- 013-014-021-022. Blizzard Warning until 2 AM EDT Wednesday for MEZ023>028. Coastal Flood Advisory until midnight EDT tonight for MEZ023. NH...Winter Storm Warning until 8 AM EDT Wednesday for NHZ003>013- 015. Winter Storm Warning until 2 PM EDT Wednesday for NHZ001-002. Blizzard Warning until 2 AM EDT Wednesday for NHZ014. Coastal Flood Advisory until midnight EDT tonight for NHZ014. MARINE...Gale Warning until 2 AM EDT Wednesday for ANZ151-153. Storm Warning until 8 PM EDT this evening for ANZ150-152-154. && $$ ES is the U.S. government's official web portal to all federal, state and local government web resources and services.