Area Forecast Discussion
Issued by NWS Portland, ME

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515 FXUS61 KGYX 282249 AFDGYX Area Forecast Discussion National Weather Service Gray ME 649 PM EDT Wed Jun 28 2017 .SYNOPSIS...
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A warm front will approach on Thursday and bring increasing chances of rain during the afternoon and especially the nighttime hours. Another low pressure system may affect the region on Saturday and possibly Sunday with more showers and thunderstorms.
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640 pm...Widely scattered showers and t-storms moving along what looks like weak sfc boundary extending from Coos county SE to Penobscot Bay. This will likely be the focus for any addl showers into early evening, as daytime heating fades. But even these should diminish mid-late evening. Otherwise skies stay clear through midnight or so, Did tweak mins upward a bit as clouds roll in from the west late, so low fall into the 50s. At 18z...several weak surface troughs were located across northern New England. These troughs combined with weak upper support and daytime heating were producing showers and scattered thunderstorms across the region. This activity will dissipate this evening with loss of heating and as upper trough slides offshore. For the balance of the night...skies will average partly cloudy as we see some warm air advection clouds move into the region from the west. Along the international border area there may even be a few showers towards morning. Lows tonight will range from the upper 40s to mid 50s.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... On Thursday...a warm front will lift north and east into the region. We`ll see thicker clouds along with an increasing chance of showers and a few thunderstorms as we head through the day. The heaviest and most persistent precipitation should be found over the northern half of New Hampshire eastward into Maine. Highs tomorrow will be mainly in the 70s. Showers and thunderstorm activity will taper from south to north as the warm front lifts northward across the area. Lows will range from the upper 50s to mid 60s. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... The first in a series of two surface low pressure systems will pass to our north, crossing over the Saint Lawrence River Valley on Friday. Ahead of this system, a warm front will enter and gradually cross New Hampshire and then Maine. A very warm and tropical airmass will accompany this system. Warm air advection will lead to H8 temperatures near +15C over southern areas, leading to heat index values between 90 and 95 degrees over extreme southwestern Maine and southern New Hampshire. Have highlighted this heat in the HWO and DSS slide. Surface dew points will climb through the 60s as precipitable water values climb to nearly 2 inches. Showers will be likely during the day with scattered thunderstorms. A few of these showers and storms will be strong as CAPE values increase to over 1000 J/Kg and boundaries will be in place during the day. Locally heavy rains are possible as well. The precipitation retreats northward to the mountains Friday night near the proximity of the warm front. It will be a warm, muggy night with patchy fog. On Saturday, temperatures climb to between 75 and 85 degrees, however it will fell warmer due to the increased dew point values. Temperatures over southern New Hampshire may reach 90 degrees during the afternoon. More showers with scattered thunderstorms will be on tap for Saturday as an upper level trough approaches from the west. Again, a few of these storms could be strong with gusty winds and areas of very heavy rain. A trough of low pressure will cross the region on Sunday with a few more showers and thunderstorms possible. However, this trough will shift the winds aloft to the west, gradually advecting in cooler and slightly drier air into the region. An upper level trough will allow for cold air advection to continue early next week. An upper level trough will situate itself north of the region, triggering a few diurnally driven showers and possibly a thunderstorm or two. However, this precipitation will be much less widespread in nature. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Short Term /through Thursday Night/...lcl MVFR psb through 23z in -shra/-tsra otw VFR with some patchy valley fog with lcl IFR conditions psb late tonight. Areas of MVFR Thu and Thu night in shra/tsra with lcl IFR psb vcnty mid coast Maine in fog and stratus. Long Term...Areas of IFR with local IFR conditions possible in overnight fog Saturday night and Sunday night as a moist, tropical airmass remains in place over the region. There will be scattered thunderstorms as well over the weekend, some of which may contain heavy rainfall. Scattered showers are possible next week, but it is a drier airmass in place and ceilings/visibilities will be improved. && .MARINE... Short Term /through Thursday Night/...winds and seas will remain below small craft through the day Thursday. Strengthening southerly flow behind a warm front Thursday Night will push winds and seas to near SCA threshold outside the bays. Long Term...Conditions will likely remain below SCA thresholds. However, will need to monitor for a brief period Saturday afternoon as the gradient wind may combine with a sea breeze for a brief period of gusty winds. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ SYNOPSIS...Schwibs NEAR TERM...Cempa/Schwibs SHORT TERM...Schwibs LONG TERM...Cannon AVIATION...Schwibs MARINE...Cannon/Schwibs is the U.S. government's official web portal to all federal, state and local government web resources and services.