Area Forecast Discussion
Issued by NWS Portland, ME

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158 FXUS61 KGYX 281653 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1153 AM EST Tue Feb 28 2017 .SYNOPSIS... Warm weather continues today and intensifies on Wednesday as a warm front lifts through the region. Temperatures will be near record warm levels before a cold front moves across the area Wednesday night. Showers and thunderstorms will be possible as the front moves through. Colder air rushes in behind the front Thursday morning and lasts through the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Update... Have updated the grids for solid cloud cover early this afternoon over southern portions of NH and southwest ME. Otherwise, partly to mostly sunny conditions furthern to the north. The warming trend may trigger additional ice jams later today or Wednesday. Lowered forecast highs over southern areas today due to the persistent cloud cover. Prev Disc... 555 AM Update... Have updated to show a low chance of showers across southern NH where some drizzle has developed in warm air advection regime. Cloud cover, winds, temperatures on track. Previous discussion... Continued warmth today with readings in the 40s and 50s areawide. A shortwave and associated frontal fracture approaches today from the SW with increasing cloud cover from the south expanding north during the day. This will keep temperatures a bit lower than otherwise. Light QPF still being advertised by the models this evening and overnight as the moisture increases and the warm front lifts north. P-type should be mainly rain with any light accumulations confined to the mountains. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/... We should stay above freezing tonight with warm overnight lows as the warm front moves north and we remain in the warm sector. This system will deepen quickly into a ~987 mb low center Thursday afternoon centered near Lake Ontario. Lapse rates from 700-500 mb increase to 6-7 C/km and convection will increase in coverage and intensity. There are a couple concerns with this system for Wednesday. Although CAPE will be relatively low, shear will be extremely high with 0-1 km approaching 50-60 kts and lapse rates. Depending on the cloud cover/any breaks allowing for heating, any storms that do develop will rotate and there will be a real concern for damaging winds/tornadoes. Basin averaged QPF isn`t extremely high but anomalies and return intervals for the PW values are pinging this as an extreme event. There will be the possibility for heavy rainers, especially along the front with a deep and warm boundary layer, and this will contribute to downward momentum transfer of strong winds. In fact, several other factors are anomalously significant as well including MSLP and 850/925 mb temperatures. Needless to say another very warm day with 850 mb temperatures once again 2 to 3 standard deviations above normal. We will be very close to breaking the record at Concord (65 degrees in 1972) while Portland will likely be a few degrees short (59). PoPs diminish Wednesday night as the low quickly ejects north. Expecting a cloudy, foggy night with some residual showers across the Canadian border. Lows will drop into the lower 30s north to 40s south. && .LONG TERM /THURSDAY THROUGH MONDAY/... Cold air will be pouring in on westerly winds Thursday morning. The cold advection will promote good mixing of the lower levels of the atmosphere, especially downwind of the mountains. It should be a windy day, though just how windy is a little bit uncertain. The GFS is stronger with the winds aloft and would suggests winds could gust closer to wind advisory levels. At the moment we will go with 35 to 40 mph gusts, but a few gusts higher would not be out of the question. Temperatures may end up falling through the day as cold advection continues. Below normal temperatures are expected Friday and Saturday, with the cold reaching its peak intensity on Saturday. Might even approach wind chill advisory criteria in the north on Saturday. Highs on Saturday will be about 10 degrees below normal. Expect gradually moderating temperatures Sunday and Monday. The next significant chance of precipitation will be Monday night as the next trough moves into the area from the west. Precipitation type seems to favor snow at this point though the warm advection would raise suspicions for more of a mix of precipitation types possible. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... Short Term...VFR clouds will gradually decrease throughout the day today and tonight to MVFR conditions with possibly lower as moisture pools along a northward moving warm front. -SHRA will increase in coverage with the chance for -FZRA, IP, or -SN away for HIE and possibly AUG. Amounts will be very light if the threat does develop. Expecting some fog developing with increasing moisture tonight. In addition there will be a chance of -TSRA Wednesday afternoon mainly in the MHT/CON/LEB corridor and perhaps including PWM and HIE later on. Long Term...MVFR conditions linger in the mountains on Thursday while the rest of the area goes VFR to clear. Westerly winds will gust to 30 KT on Thursday, with a few stray gusts higher than that. Should see a fairly prolonged period of VFR conditions through the weekend. && .MARINE... Short Term...Currently winds and seas have diminished and have allowed the SCA to expire. Have issued a gale watch beginning Wednesday evening and into Thursday evening as a strong front affects the waters. Long Term...Westerly winds behind the cold front will likely reach gale force on Thursday. These winds diminish below gale force through the evening hours. Continued offshore cold advection flow will continue through Saturday with winds likely staying above 25 KT through most of this time period. It is possible that winds could again reach gale force on Saturday as the pressure gradient tightens a bit. && .HYDROLOGY... There are currently no problems noted on the rivers as ice movement from a few days ago has largely stopped. But continued warm weather especially on Wednesday could get things flowing again and will raise the possibility for more ice jam related flooding. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Gale Watch from Wednesday evening through Thursday evening for ANZ150>154. && $$ JC

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