Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 271344 AFDGYX Area Forecast Discussion National Weather Service Gray ME 844 AM EST Mon Feb 27 2017 .SYNOPSIS... Low pressure will pass north of the region today allowing somewhat warmer temperatures to stream in from the south and west. A weak cold front pushes south but will weaken and stall over the region before moving north Wednesday as a warm front. Much warmer temperatures arrive behind this warm front on Wednesday, but they will not last long. A cold front moves through Wednesday night with much colder air arriving behind it and lasting through the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 843am Update...Quick update this morning to account for current temperature trends. Forecast package remains largely intact except for a few very minor tweaks. 650 AM Update... Only minor changes to the forecast early this morning. Sun and a dry airmass in place will allow for quick warming today. Previous discussion... Water vapor imagery shows broad zonal flow over the region with a few clouds affecting the Connecticut River Valley and northern zones as a frontal system approaches the international border. Light rain and snow showers will develop today mainly over just the northern third of the region. QPF amounts will be light but there could be some light accumulations. Westerly winds will help boost temperatures into the mid to upper 50s south with mid to upper 40s for the foothills. Across the mountains cloud cover will keep readings near 40. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... We will have some lingering cloud cover across the north tonight with the boundary stalling in the area. This could keep the odd shower in the region overnight but forcing for ascent will be weak and without daytime heating not expecting much to come of it. Again we are looking at very warm weather for Tuesday. Showers will begin over southern NH and coastal Maine in the late afternoon as a warm front lifts north. Any measurable precipitation amounts will arrive after sunset. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... We will see quite the topsy-turvy temperature trend this week as our region will be within an active zone of the Westerlies caught in between impressive warmth to the south and building cold to the north. The temperatures will reach its peak on hump day before taking a tumble Thursday into the weekend. Temperature differences across this time period could be 50 degrees or more. It all begins with a warm front lifting north across the area Tuesday night into Wednesday morning. Ahead of this front expect some cold air damming in an east-southeast pressure gradient. Although this will be a briefly dammed flow, temperatures in the cold sector ahead of the warm front are not all that cold. So even in the cold air dammed areas, temperatures may be near or just above freezing. Warm advection precipitation will begin Tuesday night and spread north as the warm front lifts across the area. It is possible that some areas of northern New Hampshire and interior western Maine could see a brief period of freezing rain if temperatures can drop to around the freezing point before the warm front lifts through overnight. If this does occur any icing will be very light and temporary as temperatures quickly warm well above freezing by Wednesday morning behind the warm front. Very warm air venting from the southern portion of the continent will stream north into the area behind the warm front on Wednesday. We will again see 850 MB temperatures near +10C which, if mixed fully to the surface, would translate to temperatures in the 70s. There is some uncertainty as to whether any of our area will see full mixing as there may be a fair amount of cloud cover. Low level winds will have more of an onshore component to them across Maine which should temper the warmth there a bit. But it does appear likely that we will see a break in the precipitation and possibly a few breaks in the cloud cover as well on Wednesday as the warm front lifts well to the north and the cold front presses eastward through the Great Lakes. Some of the models (ex. GFS) paint QPF across the entire Northeast for a full 24 hours as subtle features advance through the southwesterly flow, but this may be a bit unrealistic. A solution more similar to the NAM seems more likely with precipitation focused along and ahead of the warm front Wednesday morning and then along and ahead of the cold front Wednesday evening. In between there will be a period of southwesterly flow which will promote better mixing especially over southeastern New Hampshire. This is where the best chance exists to see 70 degrees. It is worth noting that Concord still had 10 inches of snow on the ground as of yesterday morning, but this snow depth will have very little effect on temperatures during this period especially considering the majority of this warmth is achieved through advection/mixing of the warm air venting out of the southern half of the country. The record high temperature on Wednesday, March 1 in Concord is 65 degrees and this will be in jeopardy. A cold front will swing east out of the Great Lakes and into New England Wednesday night. Expect a chance of showers as this moves through, and considering how deep we will be in the warm sector it is possible that there could be a few thunderstorms as the front moves through. Temperatures will come crashing down behind the front, falling through the 40s by Thursday morning. High temperatures on Thursday may occur in the morning hours as cold advection will be strong all day. This cold advection will allow for efficient mixing of stronger winds aloft down toward the surface with gusts to 35 mph possible. Cold air should last into the weekend, with most of the area seeing at least two full days below freezing. A weak impulse will move around the back side of the upper trough through southern New England on Friday. Models disagree on the placement of this feature, but there is an outside chance it could provide a quick shot of snowfall as it moves by. The coldest day will be Saturday before a warm up begins again on Sunday. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... Short Term...Expect VFR conditions throughout the period. Gusty westerly flow will allow winds to gust to around 20-25 kts at all terminals before diminishing tonight. Long Term...IFR conditions will be possible Tuesday night as a warm front moves through bringing light rain and low clouds. Should see mostly VFR conditions during the day Wednesday before showers and a possible thunderstorm move through Wednesday evening ahead of a cold front. Winds behind the front on Thursday could gust to 30KT. && .MARINE... Short Term...SCA has been expanded to go ahead and include the bays as opposed to later since seas are increasing this morning. Winds diminish tonight but seas remain high so will leave the end time this evening so it can be converted to a Small Craft for Hazardous Seas if desired. Long Term...Southwesterly flow behind a warm front on Wednesday could reach advisory levels. A cold front crossing the waters Wednesday night into Thursday morning will bring cold advection and gale force northwest winds on Thursday. && .HYDROLOGY... The flood watch has been cancelled as almost all rivers have crested and the flooding potential has diminished. Warmer temperatures today may start ice moving again so we will continue to monitor it closely. More warm temperatures this week could cause another round of snow melt allowing any remnant ice on the rivers to start moving again. This will increase the chance of flooding especially on Wednesday into early Thursday. Colder weather arriving late in the week should cut off the snow melt and allow river levels to recede again. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ150>154. && $$ Pohl

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