Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 221446 AFDGYX Area Forecast Discussion National Weather Service Gray ME 946 AM EST Sun Jan 22 2017 .SYNOPSIS...
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A cold front will stall to our south through tonight as high pressure builds by to our north over eastern Canada. A storm system tracking up the coast will bring wintry precipitation to the area Monday and Tuesday. A cold upper trough will remain over the area through the latter part of the week with a return to colder temperatures. Scattered snow showers in the mountains and foothills can be expected through the latter part of the week.
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945 AM...The backdoor front has now dropped to our south and we find ourselves in light northeast flow with 1031 millibar high situated just east of Hudson Bay. GOES imagery shows widespread clouds across the region with clearing confined to areas north of the Saint Lawrence river. Despite the lack of sunshine`ll be another unseasonably mild day across the forecast area. For this ESTF update...I ingested the current mesonet into near term grids and adjusted pops to reflect current radar trends. Otherwise...only minor adjustments were needed. Prev disc... Update... Have updated the grids based on current conditions. A weak front will be situated over southern New Hampshire today. In this proximity, pockets of drizzle or very light rain may develop from time to time. This weak feature is being picked up by latest set of mesoscale models. Fortunately, surface temperatures remain above freezing over much of New Hampshire. Nevertheless, similar to yesterday, this area will need to be monitored closely for pockets of -FZDZ. Patchy fog will continue through the morning hours as well. Prev Disc... High pressure will rebuild into the region from Canada as a backdoor cold front crosses northern New England. The boundary will stall near southern New Hampshire. Once again, patchy drizzle may break out today with the most likely location being near and along this boundary. Surface temperatures continue to be very mild for this time of the year with most areas climbing to above freezing as the drizzle forms over southern portions of the region. Nevertheless, this area will need to be monitored closely as there remains the possibility of pockets of freezing drizzle to break out. By afternoon, temperatures will be near 40 degrees in southern locations, despite modest cold air advection.
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&& .SHORT TERM /5 PM THIS AFTERNOON THROUGH 6 PM MONDAY/... Similar conditions will persist tonight with the possibility of drizzle with freezing drizzle potentially breaking out as the night goes on. Not entirely sure this will be in the form of flurries arriving off the ocean or drizzle/freezing drizzle as dynamics slowly increase. By Monday, the coastal front will be nearly fully developed as warm air advection increases in the soundings. The wet bulbing effect will allow for snow to break out across the interior with a mixture of rain and snow along the shoreline. Blended models together, however we leaned more towards the cooler Euro. Surface temperatures are expected to be cooler with readings in the mid 20s in the north to the mid 30s in the south as cold air damming continues. This sets the stage for a complex forecast in the long range. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... A vertically stacked low pressure system will lift northeast from the southeastern US up the eastern seaboard reaching the Gulf of Maine by Monday night and Tuesday. A generous amount of qpf will be associated with the system as per models and its source region would suggest. Ahead of this system a Canadian ridge of high pressure will be centered to the north of northern New England suppling cold air drainage from the north in the low levels. This all will make for a very complex forecast. PTYPE will be a major forecast challenge as boundary layer temps along southern and coastal areas should quickly warm above critical levels change any snow or mix over to rain rather quickly before any accumulations. Further inland will be more of a problem where cold air damming will be occurring and deep enough, along with UVV helping in mixing down some additional cold air, plus some evapo cooling, all for a time allowing for the precipitation to remain snow through part of Monday night allowing the potential of some significant snow accumulations to occur. A matter of a 2 deg Celsius swing could make for significant changes in the forecast. It appears several warm layers will work well inland by later Monday night due to the very strong ESE 50-65kt low/mid level jet changing most areas over to a prolonged period of sleet or even some freezing rain. Used a blend of the models for overall forecast but weighed heavily on the EURO/NAM blend especially for PTYPE using the BTV top-down approach. Winds along the immediate coast may get gusty for a time late Monday night as the warm low level east winds mix down to the surface. Have opted to hold off on any winter storm watches at this time due to a high degree of uncertainty on PTYPE. All models agree on system exiting into the maritimes Tue night gradually bringing an end to the mixed precipitation. Wednesday a weak dirty ridge of high pressure moves over the area allowing some scattered snow showers in the mountains otherwise partly sunny conditions elsewhere with mild temps. By Thursday a broad colder upper trof moves into the Northeast allowing for scattered snow showers mainly in the mountains. This broad colder cyclonic flow will continue Friday and into the weekend with colder temps and scattered snow showers mainly in the mountains. Stayed with superblend for the latter part of the week and into the weekend. && .AVIATION /15Z SUNDAY THROUGH THURSDAY/... Short Term...Generally MVFR conditions will persist with patchy fog and low clouds. Conditions deteriorating to IFR and LIFR with the development of steady precipitation over southern areas late in the day Monday. Long Term...IFR to LIFR conditions Monday night through much of Tuesday in precipitation. Conditions slowly improve Tuesday night. VFR conditions expected Wednesday. Thursday scattered MVFR conditions in snow showers in the mountains, VFR elsewhere. && .MARINE... Short Term...Winds will be on the increase Monday afternoon, gusting into the Gale force category, before reaching storm force over the outer waters towards evening. Wave will be rapidly building as well in response to the increasing wind fields. Long Term...Storm Warnings have been issued for Monday night into Tuesday over the outer waters. Gale Warnings have been issued in the bays beginning Monday afternoon into Tuesday. Ahead of the approaching coastal low a very strong pressure gradient will develop due to the high to the north allowing low level wind gusts to exceed 50 kts over the outer waters at times. Also increased seas forecast for the outer waters to near 20 ft which was above guidance. && .TIDES/COASTAL FLOODING... Despite being in the low portion of our astronomical tide cycle, large building waves may produce some erosion and splash- over near the times of high tide Monday night and Tuesday. Preliminary storm surge values appear to be around 1.5 to 2 feet with a persistent...strong easterly wind developing. A coastal flood advisory may be needed from the impact of the wave action. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Gale Warning from 3 PM Monday to 11 AM EST Tuesday for ANZ151- 153. Storm Warning from 6 PM Monday to 11 AM EST Tuesday for ANZ150- 152-154. && $$ ES is the U.S. government's official web portal to all federal, state and local government web resources and services.