Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 150801 AFDGYX Area Forecast Discussion National Weather Service Gray ME 301 AM EST Wed Nov 15 2017 .SYNOPSIS... High pressure builds in from the north today and continues the cool weather. Low pressure is expected to develop over southern New England early Thursday and move into 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 builds in early next week. && .NEAR TERM /THROUGH TODAY/... Surface high pressure will be centered over NH and ME today. However, moisture trapped beneath a subsidence inversion has allowed for a stubborn deck of clouds early this morning. As drying continues, the clouds are expected to thin out with mostly sunny skies expected for most locations by mid morning. However, it may take til around midday for this to happen in some areas, especially in southern NH. Otherwise, light winds are expected with highs mainly in the 40s. && .SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/... A rapidly advancing short wave trough will approach from the west tonight. As a result clouds are expected to increase from west to east, especially after midnight. Moisture and forcing for ascent will further increase toward dawn a likely result in light precipitation developing across western zones. At this time, it looks to be a light mixed bag with some snow, sleet, and a few pockets of freezing rain possible in the CT river valley. Will have to watch this for possible minor travel inconveniences for the Thursday morning commute. Precipitation will continue to overspread the area early Thursday morning. As southerly winds increase, most areas will see rain but the mountains should hang on to enough cold air to allow for a mix for much of the day. Accumulating snow is likely there, especially at higher elevations. Things get interesting Thursday afternoon. As has been advertised in deterministic models and ensembles for the last few days, secondary low pressure still looks to develop to our south and move into the Gulf of Maine by later Thursday afternoon. The main question has been will this low develop fast enough and close enough to the coast to allow for a period of heavy precipitation Thursday afternoon and evening. At this time, the consensus of deterministic and ensemble solutions is yes. However, there remains some spread - with a few late bloomer solutions still on the table which would keep heaviest precip offshore. At this time will continue to take a consensus approach which brings a period of moderate to possibly heavy precipitation to mainly coastal and central zones Thursday afternoon and evening due to rapidly developing frontogenetical forcing. The main issue then becomes precipitation type. As the forcing for ascent increases, cold air should be drawn in and/or manufactured. This should result in any mixture of precipitation changing to snow in the mountains. The big question mark is the area roughly from interior Cumberland County ME northeastward to the KLEW- KAUG corridor on north/northeastward into the foothills where the column below 850 mb will be well above freezing to start. As long as strong frontogenetical forcing occurs, the column should cool enough to at least end the precipitation as some snow. This will have to be watched closely, but for now will forecast an inch or two along the I-95 corridor north of Gray, with several inches in the mountains. Mesoscale details will become clearer over the next 24 hours - but until then it is hard to know how forcing will exactly unfold Thurs afternoon and evening. Stay tuned. && .LONG TERM /FRIDAY THROUGH TUESDAY/... A fairly high amplitude and progressive pattern develops over the next week driving several systems through northern New England. Friday will see the upper level low departing to the northeast leaving the region under northwesterly flow. Have increased PoP as well as QPF and snow for far northern New Hampshire as the flow direction strongly favors snow showers hanging on throughout the day up there. Elsewhere to the south and east expect skies to become clear. Friday night look for brief ridging to build into the region with clear skies ahead of the next system. Looking ahead to the weekend the overall forecast confidence decreases. An upper level trough will swing east through the CONUS with the attendant surface low tracking up the St. Lawrence valley and pushing a warm front and then cold front through Northern New England. While a storm is likely, the timing as well as precipitation type is still uncertain. Timing continues to push back with precipitation arriving later in the day on Saturday. This is most likely the result of the blocking pattern currently present in the northern hemispheric flow which will need to break down in order for this storm to progress into our region. The trend towards a later start time may ultimately result in precipitation not starting until much later in the afternoon. The second portion of the uncertainty in this system is the precipitation type. Along the warm front, some overrunning aloft may push enough warm air over the surface cold from Friday night for light icing. As the timing of the precipitation becomes later however, the window of time below freezing for freezing rain also decreases. With quite light qpf amounts and high uncertainty have opted not to include mention of Freezing rain at this time but this will need to be monitored. With the low occluding to our northwest the time in the warm sector will be brief as a cold front sweeps across the region early Sunday morning. This will rapidly change over the northern portion of the area to snow as the precipitation comes to an end. Similar to the forecast for Friday morning have left upslope snow shower in the mountains lingering into Monday. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... Short Term...VFR conditions are expected today and through much of tonight. Later tonight into Thursday morning, precipitation is expected overspread the region from west to east resulting in MVFR conditions turning to IFR for the bulk of Thursday. IFR conditions are then expected for Thursday night. Long Term... MVFR showers will linger in the mountains on Friday while elsewhere VFR continues. Another storm system will approach the region for the weekend. On Saturday the warm front lifts northward with MVFR ceilings moving in. Expect periods of IFR in snow through the north overnight Saturday into Sunday morning before conditions return to VFR area wide by Sunday afternoon. && .MARINE... Short Term...Have issued a gale watch for all waters starting Thursday night as low pressure passes through the Gulf of Maine. W/NW winds gusting to gale force are expected in the wake of the system into Friday. Long Term...Gales will subside on Friday evening as the low departs the region. A warm front will cross the area on Saturday bringing scattered showers. Another cold front will cross the waters on Sunday and winds behind the front will once again gust to near Gale by Sunday afternoon. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Gale Watch from late Thursday night through Friday evening for ANZ150>154. && $$ NEAR TERM...Ekster SHORT TERM...Ekster LONG TERM...Curtis

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