499 FXUS61 KGYX 110142 AFDGYX Area Forecast Discussion National Weather Service Gray ME 942 PM EDT Thu Apr 10 2025 .SYNOPSIS... A cutoff low will stall south of New England Friday through the weekend, bringing an extended period of cool and unsettled weather conditions beginning late tonight. The system then moves away by Monday with a return to drier and warmer conditions early next week as high pressure returns. A cold front approaches from the west Tuesday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 915pm Update...Overnight, a shield of precipitation associated with a trough will move SW to NE across the forecast area. Precipitation will start as a mix of rain and snow. As precipitation rates increase evaporative cooling will allow for snow to become the dominat precipitation type. Blended in some of the most recent hi- res guidance which nudged temperatures down 1-2 degrees going into the morning commute and increased PoPs. This resulted in minor snowfall accumulations, less than 1 inch into the lower Merrimack Valley and the Seacoast. The timing of snowfall will likely lead to some slick travel during the mornin commute across southern New Hampshire. Rain and snow tapers off tomorrow morning, as high pressure works in from the east. 545pm Update...Previous forecast remains on track. Made some small tweaks to temperatures and cloud cover to better reflect current observations and satellite imagery. Previously... High pressure continues to drift into the Canadian Maritimes tonight. At the same time, clouds have been on the increase ahead of our next storm system, and will continue to thicken into the evening. A broad trough spawns a surface low near the Carolinas through tomorrow. The first wave of moisture associated with this trough and developing system moves in overnight tonight. With dry air in place, temperatures will mainly settle into the low to mid 30s by the time the precip arrives. A band of precip is likely to reach into southern and western New Hampshire shortly after midnight tonight. As precip intensity increases, rain likely transitions to snow. Accumulations are mostly going to be confined to the higher terrain, especially across southwest New Hampshire where a couple inches are possible. However, as the snow intensity increases, some brief light accumulations and slick spots can`t be ruled out by daybreak tomorrow all the way into Manchester and the Seacoast. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... The precip continues to dissipate as it moves northward tomorrow morning. Central Maine and the MidCoast are the most likely to remain drier as the forcing weakens under the influence of high pressure to the northeast. Snow is likely to fall where precip intensity is sufficient, but a switch to rain is likely in the lighter areas during the morning. After this batch dissipates, the day will mostly remain cloudy and cool with highs generally in the low 40s. A northeasterly flow will keep a steady supply of cool air fresh, while only areas that see a few more peaks of sun are likely to reaching into the mid or upper 40s into central Maine. Much of tomorrow night looks dry, but the next round of precip will move northward toward the area through the overnight as the low drifts northward. Similar to first batch, precip type will rely on precip intensity, with snow confined to the moderate precip areas. Exactly where these areas are remains in question, as much of the moisture pivots toward the northwest across southern New England as the forcing weakens. There remains substantial disagreement amongst the high res guidance even from this short of distance out on how much of this moisture reaches in by daybreak on Saturday morning. The best chance will once again be across southern New Hampshire, but it remains entirely possible that the moisture holds off until the daytime on Saturday. We`ll continue to watch this closely as the next few model runs come to try to get a better handle on this feature. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Overview: Coastal low pressure will progressively track north Saturday, bringing snow accumulations ahead of a swap to rain. Another area of low pressure passes off the coast that may continue precipitation chances for coastal areas Sunday. Monday appears dry with brief high pressure, before another low across central Quebec brings a cold front through Tuesday. The region will continue to experience effects of this broad upper low through to Wednesday. Details: For Saturday, a cooler trend has been in play with a low track that is more east along the coast. This seems to be a steady consensus in guidance. On the contrary, timing consistency is still to be desired. Two camps seem to play with precip onset into southern NH and then the remainder of the forecast area. The quicker guidance includes the GFS, NAMnest and to some extent the ECMWF. Slower guidance includes the Canadian, NAM, and HRRR. Sat morning QPF spread among the NBM is as much as three tenths of an inch in southern NH. So there is plenty to refine around onset time. This timing will affect ptype and possible accumulation of wet snow. A earlier start time would have greater time in cooler temps to produce snow, while a later arrival could bring more rain/snow mix and affect accumulation rate on the ground and elevated surfaces. Once timing is resolved, greater confidence will arrive in possible impacts, if any. The quicker GFS does carry enough frontogenesis to produce a transitory snow band across coastal and interior areas of southern/central NH into southern ME. Increased rates could overcome warm surfaces in this band bringing accumulation. Given the weakening trend of the low as it tracks north, have opted to go with a slower arrival time for much of the area, but do entertain some wet snow accumulation in southern NH and the western NH mountains. If low strength can maintain longer, then should look for possible impacts associated with banding into the lower elevations and coast. Timing and spatial differences continue into Sunday as a low further off the coast follows northward. Deterioration of the initial low south of New England will expand the influence of cyclonic flow, resulting in a period of greater moisture content off the coast. How far inland this influences either precipitation or just cloud cover differs. Kept a chance of rain in the forecast for the coast and parts of the interior through Sunday given this uncertainty. Will need to keep an eye on if dry continental air is more readily advected south across the forecast area to keep this moisture off the coast. Greater consensus is given Monday into Monday evening as high pressure quickly passes through the area. This could be the bright(er) spot of the forthcoming week before a cold front arrives and the region experiences unsettled weather under an upper low through mid to late week. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... Short Term...VFR conditions lower to IFR late tonight across southern terminals with light snow and some rain arriving. RKD and AUG mostly remain with VFR conditions through tomorrow night. Elsewhere, ceilings lower in the precip tonight, and then gradually improve to MVFR to VFR conditions tomorrow afternoon. These MVFR to VFR conditions continue through most of Friday night, with IFR conditions possible toward daybreak Saturday at MHT and PSM with the next round or rain and snow. Long Term...RA/SN will be moving into the area from south to north Saturday morning. Ceilings will generally be MVFR, but pockets of IFR are possible at this time. SN will change to RA in the afternoon, but remain snow over the mountains. Precipitation shrinks to the coast Sunday, with MVFR ceilings continuing and possible IFR near or just off shore. Conditions trend to VFR Monday under high pressure. && .MARINE... Short Term...High pressure remains centered across the Canadian Maritimes, while a slow moving area of low pressure remains south of New England. Increasing northeasterly flow develops through Friday night, with SCA conditions possible by Friday night. Long Term...Weakening low pressure will drift north Saturday, bringing NE flow and building wave heights. This should be enough to bring SCA conditions, but winds remain below criteria. Wave heights may remain 5 to 6 ft until Monday when high pressure moves overhead. A cold front will approach the waters Tuesday morning. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Clair/Palmer/Schroeter SHORT TERM...Clair LONG TERM...Cornwell