Area Forecast Discussion
Issued by NWS Portland, ME

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733 FXUS61 KGYX 171645 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1145 AM EST Fri Nov 17 2017 .SYNOPSIS... Northwesterly flow in the wake of a departing low pressure system will bring some gusty winds today. High pressure will build in overnight before sliding offshore on Saturday. A warm front will lift northward on Saturday night with a mix of rain showers south and rain/snow in the north. A cold front will cross the region on Sunday bringing gusty winds and accumulating snow to the mountains. High pressure builds in for the start of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1145 AM...Minor ESTF update to reflect current low cloud coverage as well as the latest mesonet in near term grids. Prev Disc... 900 AM...For this ESTF update I adjusted cloud cover to reflect low cloud trends on GOES imagery and to ingest the current mesonet into near term grids. Morning KGYX raob supports gusty northwest winds today with a few gusts to near 40 mph possible with daytime mixing and momentum transport. Prev disc... 7am update... Just some minor updates to the cloud clover and pops. Snow showers continue along the spine of the mountains. Prev...Low pressure over New Brunswick brings a strong pressure gradient and northwesterly flow to the region this morning. Winds are gusting to 20 - 25kts across the region currently and expected to increase to 25 - 30kts through the morning hours. Forecast soundings show a well mixed lower layer and a few gusts to 40kt are possible. After noon the low will move off to the northeast allowing the winds to subside through the evening. The northwesterly flow is also generating upslope showers and clouds. Expect far northern New Hampshire to pick up a dusting of snow this morning with clouds lingering through the day. Downwind of the mountains downslope drying and clearing has already eroded the low clouds in most places and skies will become sunny for most of the day.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Overnight a brief ridge of high pressure builds in ahead of the next system. With calming winds, especially towards the high center north and west of the region have gone on the lower end for temperatures overnight with the north dropping to around 10F. Saturday will see the high pressure pass through as southerly flow and increased cloud cover moves in ahead of the next system. The warm front will begin to push northwards with temperatures climbing above freezing throughout the area and as warm as 50F on the Massachusetts border. Precipitation will just begin to approach the region from the west late Saturday afternoon. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Focus of the extended is on the strong low pressure forecast to NEwd thru the St. Lawrence Valley this weekend. S/wv trof tracking across the central CONUS is forecast to amplify and become negatively tilted as it crosses the Northeast. Strong low pressure will develop ahead of the s/wv and drive a cold front thru the forecast area. 17.00z NAM remains an outlier...by developing low pressure and tracking it thru Srn New England. This is a much colder scenario...and has little support except from a small handful of 17.00z GEFS and EPS members. That being said...12z raob network should begin to sample the s/wv in question across the West Coast...and this should provide some higher confidence in model forecasts. In the meantime I will lean towards the GEFS and EPS solutions...with strong consensus track thru the St. Lawrence. That will initially bring precip to the area along the warm front. Some of this may fall with the column cold enough for snow...especially at elevation. Gradually a non-diurnal temp trend will warm the boundary layer up for mostly rain. With strong forcing for ascent and PWAT values pushing 1 inch...250 percent of normal...a sharp line of heavy rainfall is possible along the cold front. Winds will be gusty ahead of the line...but I am expecting enough of an inversion to keep the bulk of that aloft. Post-front however mixing depths increase sharply and CAA will help mix down stronger winds aloft. Forecast soundings show the potential for fairly widespread 40 kt gusts in the Wly flow behind the front. Those gusty winds look to continue right into Mon...though gradually diminishing over time. Some wind headlines look likely for Sun...possibly into Sun night. The pattern behind this system looks generally zonal. This will bring fast moving s/wv trofs and mainly upslope snow showers. Temps will remain near to below normal. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... Short Term... Low ceilings have eroded this morning as downslope winds result in drying conditions through the coastal plain. VFR with wind gusts to 25 - 30 kts expected today, with MVFR in SHSN in the mountains early this am. Winds will diminish late today with high pressure building in and VFR holding through Saturday. Long Term...Conditions...if not already IFR...will deteriorate quickly Sat night. RA will overspread the region...with some SN across the far interior. Some LLWS is probable...especially Sat night across the Srn half of the forecast area. Cold front comes thru Sun afternoon...with winds shifting Wly and precip becoming more showery. Conditions will quickly improve to VFR S of the mtns...with lingering MVFR at HIE in upslope flow. Surface wind gusts 35 to 40 kts possible at all terminals Sun. Gusty winds will continue into Sun night and Mon. Generally VFR S of the mtns...with Wly flow continuing upslope clouds at HIE. && .MARINE... Short Term...Northwesterly flow and cold air advection in the wake of the departing storm will see winds increase through the morning with gusts to gale force and a gale warning remains in effect for today. Winds will decrease as high pressure moves into the area overnight. Saturday will see a warming trend as southerly flow ahead of the next system moves into the area. Long Term...Sly flow increases thru Sat night...though forecast soundings suggest wind gusts may stay just below gale force. Gale force winds are most likely when CAA begins and wind direction shifts to Wly. Outside of the bays winds may even gust to near storm force for a time Sun into Sun evening. Winds will stay gusty thru Sun night. With offshore flow seas will build to 10 to 15 ft outside of the bays. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Gale Warning until 8 PM EST this evening for ANZ150>154. && $$ ES

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