Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 211216 AFDGYX Area Forecast Discussion National Weather Service Gray ME 716 AM EST Sun Jan 21 2018 .SYNOPSIS... A weak cold front will drop south across northern New England today and stall over southern New England tonight. Low pressure moving through the Great Lakes will spread some light snow across the region late Monday into Monday night, with the stalled front lifting northward as a warm front. Low pressure tracks east along this front on Tuesday with snow changing to sleet and freezing rain before temperatures warm. As the low moves east it will pull a cold front through the region Tuesday night with colder weather arriving for the next few days. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Update... Have updated the grids based on current conditions. Temperatures have begun the morning very mild with readings above freezing in most locations, even northern areas. Have adjusted afternoon highs upwards based on this trend. Much of the cloud cover in central Maine has dissipated with plenty of low clouds situated over New Hampshire. Have adjusted the forecast accordingly for this morning based on most recent satellite imagery. Otherwise, no significant changes to the forecast. Prev Disc... Clouds will continue to streak across the forecast area in the proximity of a weak, stalled out front. High clouds will persist in the south with low cloudiness over central and northern areas. Early morning fog in the Keene area is expected to dissipate after sunrise. Expect 30s in northern areas today, with lower to mid 40s in the south allowing for more melting. The gradient will relax towards the afternoon hours. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... Clouds will increase and thicken tonight as a warm air advection pattern develops after midnight and the front begins to move north. This warm front will likely stall near the Massachusetts and New Hampshire state lines tonight and Monday. This will allow a nose of colder, drier air to filter into the region as high pressure remains entrenched over southeast Canada. Wet bulbing effect will likely allow the precipitation type to begin as all snow even over southern areas. However, significant warming aloft will occur by late Monday allowing for some rain and snow mix over far southern New Hampshire as the precipitation will remain light. This mix will occur as boundary layer temperatures warm into the 30s late in the day as a broad area of low pressure heads towards the Great Lakes. A wave of low pressure will likely form along the Maine coast however as we head into the long term portion of the forecast. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Surface warm front tries to lift northward Monday night, but cold air damming at the surface will likely hold tough and force this warm front aloft. Light snow ahead of the warm front moves across the area with generally 1 to 3 inches expected. Temperatures aloft warm above freezing after the warm front passes, though any precipitation behind the warm front will likely be in the form of light drizzle or freezing drizzle. Next round of precipitation arrives on Tuesday as the complex low pressure system arrives from the west. Steadier precipitation picks up again, this time with a highly inverted low level temperature profile supporting widespread freezing rain to the north of the surface warm/coastal front. Models still are having a tough time resolving this low level cold wedge of air, though the CMC and NAM have done the best job showing the cold surface temperatures hanging on through midday Tuesday in interior western Maine. Have based the temperature and wind forecast off of a blend of these two models with some manual adjustments. Although we do expect much of the area to see some freezing rain, the impact will likely be less than normal considering the coating of snow expected beforehand. South of the warm/coastal front temperatures will warm into the 40s to low 50s ending the freezing rain threat. Cannot rule out a rumble of thunder considering moist adiabatic mid level temperature profile. Cold/Occluded front pushes through the area Tuesday afternoon and evening, ending the steadier precipitation. With winds shifting to the west behind the front, any remaining cold air damming will break allowing the dammed areas to warm up a bit before colder temperatures arrive by Wednesday morning. Some lingering snow showers are possible through the day Wednesday as the upper low moves by. Colder temperatures expected Thursday and Friday, though not all that cold by mid winter standards or even this winter standards. Surface high pressure shifts across the area Friday night allowing a southerly flow to bring a warm up for next weekend. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... Short Term...VFR conditions today with areas of MVFR ceilings in the mountains. Areas of MVFR ceilings develop later tonight into Monday as onshore flow sets up. Long Term...Expect IFR conditions with light snow moving across the area Monday night. Snow changes to sleet and freezing rain on Tuesday across interior portions, while southern, western, and coastal sections will warm above freezing earlier in the day Tuesday. Expect low level wind sheer in the cold air dammed areas of interior western Maine and eastern New Hampshire. Cold front moves through Tuesday evening bringing the steadier precipitation to an end and a gradual improvement to VFR by Wednesday. Lower ceilings may linger in the mountains right through the day Wednesday into Wednesday night before dispersing. && .MARINE... Short Term...Gradient continues to relax. Have dropped SCAs for the early morning hours. A few gusts near 25 kt are possible well off the Midcoast region early, but these will be diminishing as well. Long Term...Warm front lifts north across the Gulf of Maine Monday into Monday night. Low pressure moving east along the front will allow southerly winds to increase to gale force ahead of it. There is a low probability that some storm force gusts could occur. The low will drag a cold front across the Gulf of Maine late Tuesday, with winds behind the front possibly reaching gale force again on Wednesday. && .HYDROLOGY... Many rivers remain frozen and/or affected by ice jams. With additional liquid precipitation expected over much of the area on Tuesday, it is possible that there could be more ice movement and some minor flooding into Wednesday. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ Kimble/Cannon

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