NWS Forecast Discussion
For Fremont, NH
000 FXUS61 KGYX 061618 AAB AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 1118 AM EST Fri Dec 6 2019 .SYNOPSIS... A weak area of low pressure will cross the region this afternoon. Much colder air will sweep across the forecast area tonight and Saturday. Warmer temperatures and some rain are expected early next week before a cold front brings in another dose of Arctic cold during the second half of the next work week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1115 AM Update... Dry air is still eroding the leading edge of the precipitation shield, which is making its way across southern NH and into SW Maine. We should start seeing snow reach the ground shortly in southern and central NH, but it may take a little bit longer in ME. Still expecting minor accumulations as most guidance deepens the low only once its offshore. So we could see some accumulations over the islands and Downeast along the Maine coast. 930 AM Update... GOES satellite and radar imagery are showing snow moving across NY State and into Vermont this morning. Have only changed weather and QPF/snow amounts lightly as near term CAM models are still indicating 1-3" across southern NH through tonight, with less coverage north and east. Short of an advisory, we will likely issue an SPS for slick commutes this afternoon. Still we have a little way to go with top-down saturation with dew points only in the lower teens in NH and ME. Update...Have updated the forecast based on current observations and latest radar imagery. Have upped snowfall amounts slightly over southern portions of the forecast area. Latest mesoscale model trends have increased the QPF for southern New Hampshire and extreme southwest Maine overnight. Otherwise, just minor changes to the latest forecast package. Prev Disc...Scattered upslope snow showers will gradually end over the mountains this morning. A clipper type system will then cross the region this afternoon. Have leaned closely towards the higher pops of the latest HRRR as snow will likely develop over southern New Hampshire during the late morning hours before pushing east. With the track of this system, expect an inch or two snow accumulation across southern New Hampshire and into portions of York County in Maine. Some of the higher elevations over southern New Hampshire may pick up a little more in the way of precipitation. Further to the north, there may be a only a coating of snow. Winds will become light this afternoon in advance of this weak system with highs in the 20s to lower 30s in most areas. && .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/... Light snow continues for a short period along and near the coastline as the low slowly intensifies as it exits into and through the Gulf of Maine. Much colder air will follow this system on northwesterly breezes tonight with upslope snow showers continuing in the mountains. By Saturday, the core of the cold air will be over the region. There will be good mixing with temperatures in the -14C to -18C range, yielding highs only in the teens and 20s across the region. Saturday night will likely be the coldest night over the next few days as high pressure crests over the region. There is the potential for good radiational cooling in some areas with a fresh snowfall and clear skies. Question will be the gradient and whether or not winds can go calm during the night as a ridge of high pressure remains to our west during much of the night. Nevertheless, expect readings in the single numbers in many areas. Sunday will remain fair and dry as high pressure begins to exit off the coastline. A gradual warm up will begin as well which sets us up for the long range portion of the forecast. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... The high pressure ridge will crest across New England on Sunday and continue eastward into the Central Atlantic and strengthen on Monday and Tuesday. A shortwave will dive southeast through the High Plains over the weekend and will lead to the development of low pressure across the Great Lakes on Monday. The low will strengthen as it rides east-northeastward through the eastern Great Lakes and down the Saint Lawrence River Valley through late Tuesday. Moisture will ride north on the western periphery of the ridge, and the strengthening low pressure center will lead to the development of widespread precipitation across the northeast. Some spotty precipitation is possible by the late morning hours Monday, but the bulk of the precipitation looks to arrive late in the afternoon and evening Monday. The steadiest precipitation from this round looks most likely to wind down by Tuesday Morning, but showers may linger through the afternoon on Tuesday. The progression of the frontal boundary has been the subject of some disagreement between the models late Tuesday and into Wednesday. The GFS has been progressively slower with the frontal passage over the past several runs, and the latest ECMWF has lurched to a slower fropa solution. This has implications for precipitation, with another round of moisture riding north along this front late Tuesday and into early Wednesday. This would lead to another period of predominantly rainfall, with very little if any break from the first round. An extended period of warm air advection will initiate on Sunday, occuring above the surface earlier on Sunday. Temperatures will be slow to rise above freezing near the surface across interior sections through Monday morning, but the threat for any light freezing rain at the onset of the precipitation appears to be diminishing with the arrival of the precipitation not being until later on the day Monday. Additionally, with the extended period of WAA lasting into Tuesday, warming above freezing appears inevitable at this point across the entire CWA, with temperatures warming into the 50s across the coastal plain. Once the frontal boundary passes, CAA will take hold on Wednesday as an Arctic high pressure center builds across the region Thursday and Friday. Long range deterministic models and ensembles support below normal temperatures late in the week, perhaps aided by a secondary cold front. Unsettled weather is likely to persist after cold FROPA under mean troughing, most likely relegated to the upslopes. && .AVIATION /16Z FRIDAY THROUGH TUESDAY/... Short Term...VFR conditions in the north with MVFR and areas of LIFR conditions in snow over southern sections today. Conditions improve tonight outside the mountains on brisk northwesterly breezes. VFR conditions will then dominate through Sunday. Long Term...Ceilings lower and rain overspreads the area Monday with likely degradation to MVFR CIGS, IFR CIGs/VSBY in pockets of heavier rainfall. Southerly surface winds generally