Area Forecast Discussion
Issued by NWS Portland, ME

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287 FXUS61 KGYX 171050 AFDGYX Area Forecast Discussion National Weather Service Gray ME 650 AM EDT Mon Jul 17 2017 .SYNOPSIS... Bermuda high pressure over the western Atlantic will reinforce a warm and humid air mass over New England through much of the week. A weak upper level disturbance will slowly track across northern New England today and Tuesday, triggering showers and thunderstorms mainly in the afternoons. Humid conditions continue with increasing heat Wednesday and Thursday. A cold front will trigger showers and thunderstorms on Thursday before it crosses New England Thursday night. Expect less humid conditions behind the cold front through the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Update... Have updated the grids based on current surface observations and satellite data. Fog continues across much of the region. There is patchy dense fog which triggered the issuance of two Special Weather Statements. Otherwise, visibilities have not been consistently low in many areas, increasing and decreasing at times. In any case, the fog will begin to lift over the next hour or so. Convection over northern New York will shift east. There still remains a threat of a few storms producing strong gusty winds, hail and locally heavy downpours. Will continue to monitor. Minor adjustments made for temperatures, current cloud cover and dew points. Pops modified to slow down the increasing morning chances for showers in the mountains. Prev Disc... Dense fog in many locations will lift this morning. This may slow down portions of the early morning commute. Will monitor how widespread the fog becomes. A dense fog advisory may be required for portions of the forecast area this morning. An upper level trough will approach from the west today. This will increase low and mid level lapse rates over the region, destabilizing the atmosphere. CAPE values increase rapidly today in the absence of much of a cap, mainly away from the coastline. Scattered showers and thunderstorms will erupt. A few of the storms may contain gusty winds and small hail. Precipitable water values will be on the increase again, and a few of the storms may contain locally very heavy downpours. Most areas will top out between 75 and 85 degrees for highs. It will be cooler along the Midcoast as the fog lurks near the coast much of the day.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Any ongoing strong convection should weaken after sunset this evening. Scattered showers and thunderstorms will persist however. The least likely region to receive a thunderstorm will once again be the coast, in a region of relatively stable air. Fog will form again, especially along and near the coastline where visibilities could drop to a quarter mile in some areas. The upper level trough will gradually exit the region on Tuesday. However, there will still be scattered showers and a few thunderstorms. Once again the convection will mainly be away from the coastline. 70s for daytime highs will be widespread in Maine with lower 80s over portions of New Hampshire. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Decaying upper trough moves east Tuesday night, with any lingering showers dissipating during the evening hours. Any weak surface frontal boundary associated with the passage of this trough will be imperceptible in the temperature, dewpoint, or wind fields as the warm, humid air remains in the area, intensifying a bit as the week goes on. The best day of the workweek looks to be Wednesday, as weak subsidence in the wake of the trough suppresses afternoon convection and temperatures warm into the 80s areawide. Another trough approaches from the west on Thursday, with the heat and humidity reaching its peak ahead of it. Based on model forecast 850MB temperatures, parts of the area could see 90 degrees on Thursday. This heat and humidity will fuel showers and thunderstorms Thursday afternoon, aided by lift ahead of the approaching trough. This trough heads off to the east Thursday night, with a cold front bringing a slight change in air mass for Friday. Cooler and less humid conditions are expected on Friday, though there will again be a chance of afternoon showers mainly in the north and east beneath a lingering upper trough. Continental high pressure crosses the area on Saturday, providing a good amount of sunshine along with less humid though still seasonably warm conditions. The next trough approaching the area may begin to affect the region as early as Sunday with another chance of rain. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... Short Term...Early morning IFR/LIFR ceilings and visibilities in fog improving to VFR conditions through the morning. There will be a few showers and thunderstorms this afternoon, mainly over New Hampshire reducing conditions briefly to IFR. LIFR conditions tonight in developing dense fog, slowly improving on Tuesday. Long Term...Expect VFR conditions and light winds Wednesday and Thursday with a sea breeze near the coast. Showers and thunderstorms are likely Thursday afternoon, especially away from the immediate coast. These will diminish Thursday night, with another round of showers possible in the north on Friday. && .MARINE... Short Term...Winds and seas expected to remain below SCA thresholds with generally a light gradient over the coastal waters. Long Term...A light southerly flow continues through Thursday. A cold front will cross the Gulf of Maine early Friday but winds will again be fairly light behind it. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Cannon SHORT TERM...Cannon LONG TERM...Kimble

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