NWS Forecast Discussion
For Fremont, NH
000 FXUS61 KGYX 230252 AFDGYX Area Forecast Discussion National Weather Service Gray ME 952 PM EST Wed Jan 22 2020 .SYNOPSIS... High pressure brings fair weather and a warming trend to the region through Thursday. A cold front will sink gradually south into the area late Thursday through Friday accompanied by a few clouds. A coastal storm may bring accumulating snow to much of the region over the weekend into early next week, but rain and mixed precipitation are also possible depending on system track. && .NEAR TERM /OVERNIGHT/... 10PM UPDATE... Have updated the forecast primarily to adjust overnight lows based on latest observations and trends. Some higher level clouds have drifted through the region, but they are more sparse for now. They may thicken up especially in the north with time overnight, but in general we`ve seen some decent cooling. Overnight lows tonight should be warmer than the past few nights, though, as low level dewpoints have climbed. 630 PM UPDATE... Clouds are moving into the region as ridging aloft shifts to the SE. Some ribbons of vorticity are allowing high clouds into NH and northwestern Maine. These will eventually shift farther east-southeast, allowing for another cold and mostly clear night. Light southerly flow at the surface and the aforementioned clouds will keep it from getting nearly as cold as last night. Overnight lows were adjusted closer to the HRRR and HREF, and range from the upper single digits to the mid teens. ORIGINAL DISCUSSION... At 19z a 1035 millibar high was centered over the DELMARVA. With the exception of some patchy low and mid clouds...GOES imagery showed mainly clear skies across the area. Sunshine and moderating 850 millibar temperatures have allowed the mercury to rebound to near or slightly above normal for the date...with readings in the upper 20s and lower 30s. For tonight...a few high clouds will spill over the top of the ridge otherwise a mainly clear and cold night with lows ranging from the single numbers to mid teens. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... On Thursday...the high remains centered to our south. The ridge will allow for more sunshine on Thursday and mild temperatures as winds continue out of the southwest, both at the surface and aloft. With nearly full sunshine, temperatures will reach the lower 40s over southern areas. Mostly sunny skies...moderating 850 millibar temperatures...and light southwest flow will allow temperatures to warm into the mid 30s to lower 40s...or a good ten degrees above average for the date. Thursday night...an east-west oriented cold front will begin to sag slowly southward into the area as high pressure builds east into Quebec province. We`ll see some clouds spread into northern and eastern sections overnight with the front. Just how fast the clouds arrive will determine when we put a lid on radiational cooling. I`ve gone below machine guidance in many areas especially south and west where the bulk of the night should be mostly clear. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... By Friday morning, a ridge of high pressure centered over central Quebec will extend eastward across the Canadian Maritimes, and will continue to bring fair conditions to New England through early Saturday. This ridge will be anomalously warm for this time of the year, with origins from the Pacific Ocean, rather than northern Canada. This means that temperatures will be above normal into the weekend, and that there will not be a major source of cold air nearby or in place as a storm system approaches for late Saturday through Monday. The storm system is currently located over the Pacific northwest US. It is expected to emerge over the central Plains and strengthen until it becomes an occluded area of low pressure over the Ohio River valley by late Friday. The low will slowly move eastward and will likely cross through southern or central New England on Sunday. There has been a notable shift in the GFS, ECMWF, Canadian, and their respective ensemble suites to a more northern and warmer track of the low pressure over the last few model runs. This shift in model output coincides with the actual system coming ashore across the Northwest US and entering the RAOB network. This means that the latest models runs have a better sampling of the system itself than the previous runs did, so it`s difficult to say whether the shift of the models to a warmer solution is due to better sampling, or the beginning of a trend toward an even warmer solution. Regardless, with the better sampling, recent model trends, and only marginally cold enough air across the region, there is sufficient reason to believe that this system will feature a considerable deal of mixing with rain, and a full blown changeover is quite possible across the coastal plain. The mountains stand the best chance of remaining all snow through the event. The storm is expected to move quite slowly, with the low pressure center not expected to depart the Gulf of Maine until Monday afternoon. With a slow track nearby, precipitation will likely linger right through the day on Monday, but it will not be continuous from late Saturday through Monday. Precipitation is likely to be more showery and periodic across central and southern zones by Sunday afternoon, with the mountains standing the best chance of experiencing more continuous precipitation with bands of snow rotating in on the backside of the low into Monday. Tides will also have to be watched closely during the Sunday midday high tides. The astronomical high tide is 10ft in Portland on Sunday. The slow progression and timing of the storm could bring enough storm surge and large waves to cause some minor coastal flooding concerns on Sunday. After the system, high pressure will build across New England through midweek next week, with temperatures returning to near normal. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... Short Term...Light winds expected tonight and Thursday as high pressure moves through the region. Only some high level cloudiness so expect VFR conditions all areas. Long Term... VFR conditions will continue into early Saturday as high pressure persists across the region. A storm system is expected to bring snow, likely mixing with rain across the coastal plain, which will reduce visibilities and ceilings at times late Saturday through Monday. Gusty winds will also accompany the system, with east winds progressively shifting to the northwest from Sunday through Monday. && .MARINE... Short Term...Light winds expected over the next few days as high pressure moves across the region. Long Term... High pressure will persist through early Saturday. An area of low pressure will slowly cross the waters Saturday Night through Monday, likely bringing a period of easterly gales Sunday morning. The system will then slowly exit the Gulf of Maine on Monday morning, with freshening northerly winds on the backside. High pressure will build in behind the system across the waters early next week. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM UPDATE...Kimble SHORT TERM...Schwibs LONG TERM...Clair