Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 152333 AFDGYX Area Forecast Discussion National Weather Service Gray ME 633 PM EST Wed Nov 15 2017 .SYNOPSIS... High pressure will retreat offshore tonight. Low pressure will advance into New England late tonight...with a secondary low developing over southern New England on Thursday. This system will track through the Gulf of Maine late Thursday and Thursday night. Coastal rain and some accumulating interior snows are expected. Cold high pressure builds in again for Friday before the next storm system arrives this weekend with another mixed bag of precipitation. High pressure then returns for early next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 630 pm Update: Input latest mesonet data. Mostly clear skies and light winds at this time allowed temps to fall rather quickly into the upper 20s to lower 30s. Made some minor adjustments to temps for the evening. Also, some lower clouds have spread southwest into the midcoast area so needed some adjustment to sky cover in those areas. No other changes were made at this time. Previous Discussion: At 19z...a 1026 millibar high was draped across eastern New England. GOES visible imagery showed some low clouds over southern and western New Hampshire otherwise skies were clear across the forecast area. The leading edge of an extensive cloud deck was over the eastern Great Lakes and upstate New York and advancing steadily eastward. For tonight...clouds spread east into the forecast area in advance of the next storm system with developing onshore flow bringing some marine stratus into coastal sections by late tonight. light warm air advection precipitation should reach western New Hampshire and the international border area towards dawn with the column cooling enough at onset for some wet snow or a rain snow mix. Expect the remainder of the forecast area to remain dry overnight. Lows will range from the mid 20s to lower 30s. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... On Thursday...the shortwave impulse over the eastern Great Lakes will race into New England as it goes negative tilt. In response...the surface low over Quebec and trailing frontal system through the mid Atlantic will see a secondary low rapidly develop over eastern New England. By evening...this secondary low will become the dominant low as it parallels the downeast coast. Warmer air will initially be pushed north into the area with any morning rain/sleet/snow changing to rain with the exception of the mountains and international border where a rain/sleet/snow mix continues. By evening...the column will begin to cool from west to east as the secondary low becomes dominant...with rain and rain/snow mix transitioning to snow in many locations before ending. The models continue to show a stubborn low level warm layer into Thursday night that should limit snowfall potential...especially along the coastal plain. The mountains...mainly above 2000 ft should see a several inches of accumulation. The jackpot should be the white mountains and other high terrain where a good 4 to 7 inches is likely. The remaining uncertainty of this forecast is precipitation type...which ultimately depends on how fast the secondary low becomes dominant and cools the atmospheric column late tomorrow and tomorrow night. Northwest winds will increase behind the departing coastal low in the predawn hours of Friday at 15 to 25 MPH with gusts to 35 MPH. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Friday morning begins with a system exiting the region to our north and east. Good cold air advection behind the system will produce gusty winds throughout the day on Friday. High pressure will dominate Friday night and most of Saturday before our next system begins to approach from the west late Saturday through Sunday. Southerly flow ahead of the system will allow for some relatively mild temperatures Saturday. The system moves through mainly during the overnight hours Saturday night and into Sunday. Temperatures should remain warm enough for most areas to see rain. However, locations in the mountains could be cold enough to see at least a mix and the higher elevations will likely see all snow with a couple of inches of accumulation. The system exits quickly on Sunday with high pressure building over the region through the remainder of the forecast period. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Short Term /through Thursday Night/...VFR. Late tonight into Thursday morning, precipitation is expected to overspread the region from west to east resulting in MVFR conditions turning to IFR for the bulk of Thursday. IFR conditions are then expected to linger into Thursday night before gradually improving to MVFR. NW winds will gust up to 30 kt in the predawn hours on Friday. Long Term...VFR on Saturday will deteriorate to LIFR/IFR Saturday night in rain and fog, and possibly snow over higher elevations. VFR conditions return Sunday for the remainder of the long term. && .MARINE... Short Term /Through Thursday night/...The gale watch has been converted to a Gale warning for all waters for late Thursday Night and Friday. Long Term...Strong cold air advection on Friday will result in winds strong enough to meet Gale Warning criteria. Another system moves through Saturday night and gusty winds are once again expected for Sunday. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Gale Warning from 1 AM to 8 PM EST Friday for ANZ150>154. && $$ NEAR TERM...Marine

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