Area Forecast Discussion
Issued by NWS Portland, ME

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637 FXUS61 KGYX 130738 AFDGYX Area Forecast Discussion National Weather Service Gray ME 338 AM EDT Mon May 13 2024 .SYNOPSIS...
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High pressure builds in and moves offshore today. A warm front stalls through central New England on Tuesday, then a slow moving cold front stalls on Wednesday. Low pressure passing south of New England spreads moisture and showers in from late Tuesday into Thursday. Conditions dry out late in the week as New England sees a period between systems, and then likely turns unsettled again by late next weekend.
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&& .NEAR TERM /TODAY/...
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Patchy fog may develop in areas where clouds clear out early this morning, but what does develop should quickly dissipate by 7 to 8 am. Otherwise, southerly flow returns today as a broad area of high pressure moves into the western Atlantic, centered just to the east of the Carolinas. Aloft, a 500mb ridge moves overhead, although just briefly, which will keep most of the area dry. We should start off with more sun today, but sufficient moisture around 850 mb and some low-level instability will bring partly sunny to mostly cloudy skies from late morning into the afternoon. Weak PVA aloft and an approaching warm front may bring a few showers into New Hampshire and the western Maine Mountains late in the afternoon or early evening, but again most will be dry with temperatures reaching the mid to upper 60s. Coastal areas will probably be a few degrees cooler with the seabreeze coming in off the chilly Gulf of Maine.
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&& .SHORT TERM /TONIGHT THROUGH TUESDAY/...
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Showers will continue to overspread the region from west to east through this evening and tonight as shortwave energy moves overhead. Highest coverage of showers is expected across central and northern areas with amounts ranging from 0.10" to 0.25" possible. Coverage of showers decreases with southward extent with a few hundredths to 0.10". Mostly cloudy skies will keep temperatures in the 40s to lower 50s. Most of these showers will shift east of the area Tuesday morning but may continue a little longer across northern and eastern areas near the warm front that looks to stall across western ME. Warm S/SW flow and more sunshine to the south and west of this boundary is expected to send temperatures well into the 70s across NH and SW Maine with 80 not out of the question in southern NH. Farther east, temperatures will be cooler with mostly 60s expected due to more cloud cover and more of a fetch of the Gulf of Maine. A cold front will approach the area in the afternoon from the west, aiding in additional shower development in the afternoon, especially northern and western areas. The previously mentioned warm temperatures and decent lapse rates aloft will result in a few hundred J/kg of MUCAPE per the 00Z HREF mean across NH and into the western ME mountains to support a few thunderstorms with perhaps small hail in addition to heavy downpours and lighting. CAMs are in pretty good agreement with bringing this convection farther to the south and east into early Tuesday evening.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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Overview... A cut off low gradually moves through the Ohio River Valley and south of New England Wednesday and Thursday. A short wave ridge passes through on Saturday, and then another system approaches New England by next Sunday. Details... A cold front sags southward late Tuesday night through Wednesday, with showers expanding along this front as a slow moving low tracks south of the area and sends moisture northward. Showers remain likely Tuesday evening into Tuesday night, and gradually increase as the front moves southward into coastal areas by Wednesday. The bulk of the moisture stays south of the region, but the slowing front serves to focus shower activity on Wednesday, and possibly into Thursday as well. The front stalls, likely through the middle of the forecast area from east to west. There will be wet periods during this timeframe into Thursday, but coverage looks to gradually lessen as the forcing weakens. Some showers still can`t be ruled out on Friday as the low tracks out to sea. A quick shortwave ridge likely passes through on Saturday, but the next system will be quick on it`s heals with moisture spreading in from the southwest. It`s still unclear whether this ridge will pass through during the day on Saturday, or if it moves through a bit more quickly and allows showers to move in by the afternoon hours. We`ll need to wait a little longer to iron out these details, but that looks like the set up at this point.
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&& .AVIATION /07Z MONDAY THROUGH FRIDAY/...
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Short Term...Patchy fog may develop in areas through 12Z this morning where clouds manage to clear out. Otherwise, VFR conditions today, but approaching low pressure will bring a round rain showers to the region from early this evening into Tuesday morning. MVFR to IFR cigs and MVFR vsbys are possible with this activity before a break and return to VFR conditions. Outside of showers, patchy fog is possible as well. Additional showers along with thunderstorms are then expected to develop Tuesday afternoon. Highest potential for impacts with these look to be generally along and north of a LEB-AUG line with IFR cigs/vsby possible. Marine fog may also impact PWM and RKD late Tuesday afternoon. Long Term...Ceilings lower at all terminals with showers Tuesday night, with MVFR conditions likely and periods of IFR possible. These conditions continue on Wednesday, and then gradually improve into the day on Thursday. VFR likely doesn`t return fully until Friday.
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&& .MARINE...
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Short Term...Broad high pressure moves into the western Atlantic today, centered just offshore of the Carolinas. This will bring a gradually increasing southerly flow through Tuesday, possibly bringing SCA conditions over the outer waters by late in the day Tuesday with wind gusts nearing 25 kt as low pressure and cold front approach the region. Shower chances will increase across the waters tonight into Tuesday. Long Term...The cold front continues to slowly approach the waters Tuesday night, and stalls near the coast or just inland from the coast by Wednesday. A slow moving low pressure system passes south of the waters Wednesday and Thursday. These two features bring freshening southerly flow, becoming easterly by Wednesday and Thursday, with SCA conditions possible during this time frame. This system slowly moves eastward on Friday, with waves likely lingering near 5ft on Friday.
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&& .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Combs SHORT TERM...Combs LONG TERM...Clair