textproduct: Gray - Portland

WHAT HAS CHANGED

715 Update...Forecast remains on track. Showers and isold thunder in northern ME and southern Quebec should mostly dry out before reaching our northern zones. Somerset County stands the best chance at receiving a little rain this evening.

KEY MESSAGES

1. Warm and mostly dry conditions will continue through Wednesday night.

2. Cool unsettled pattern Thursday through the weekend. Winter conditions possible above 4000 feet Saturday.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Locally high pressure will allow for dry and warm conditions this afternoon and evening. A cold front will move southward tonight, bringing shower chances over the northern of New Hampshire and northwestern Maine. The aforementioned cold front continues to move south Wednesday morning. This will allow for a mostly cloudy start to the day, but not expecting convective initiation of any kind as the front completely moves through before daybreak. An isolated shower can't be ruled out, but most places should stay dry. Behind the front, skies start to clear out and temperatures cool down. High temperatures tomorrow will be near 70F north of the mountains, with low to mid-80s elsewhere.

KEY MESSAGE 2 DESCRIPTION...

A familiar spring pattern develops around Thursday with multiple short waves or upper slows dropping south out of eastern Canada. The first wave crosses Thursday bringing a mix of sun and clouds with chances for showers. Highs on Thursday will be much cooler than Wednesday, ranging from the upper 50s north to upper 60s south. High pressure briefly builds in from the west Thursday night with lows in the 40s.

Global models and ensembles are in decent agreement that a compact upper low originating from the Arctic Circle will drop south across eastern Canada and will take aim at northern New England Friday afternoon. Friday will be mostly dry to start with increasing chances for showers Friday afternoon. The core of the cold air will hold off until the weekend with highs on Friday ranging from the upper 50s north to low 70s south. While models are in decent agreement that the compact upper low will cross over northern New England the are some timing differences with the GEFS faster to arrive and quicker to exit while the CMC/ECMWF ensembles are slower to arrive and slower to exit. Most solutions show the upper low spawning a surface low in Gulf of Maine bringing period of wet weather Saturday with showers possibly lingering into Sunday. The GEFS camp suggests that steady precipitation will end Saturday afternoon with the NBM tapering PoPs from 70 percent Saturday morning to around 50 percent Saturday evening. Within the upper low 850 mb temperatures will drop below freezing that will may allow for accumulating snow in the mountains Saturday above 4000 feet. Anyone making any hiking plans Friday night through Sunday should prepare for winter conditions, especially if traveling above 4000 feet. At lower elevations highs on Saturday will range from the 50s north to low 60s south. The surface low in the Gulf of Maine will also bring stiff east to northeast winds gusting up to 30 mph.

There will likely be some improvement sometime Sunday before yet another wave drops south out of Canada Monday. This will continue to keep chances of showers in the forecast through Monday.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

VFR will continue this afternoon, with mostly clear skies expected through the evening. Overnight, a brief period of low-level wind shear is expected from midnight until early morning. The LLWS is anticipated to be westerly (270-290) at 35-40kts. VFR will continue on Wednesday with a mid to high level cloud deck expected across the area through much of the morning. Skies will try to clear in the afternoon and VFR is likely through Wednesday night.

Outlook:

Thursday: Scattered showers and isolated thunder bring potential for periods of MVFR/IFR. Otherwise VFR outside of showers.

Thursday night-Friday: Mainly VFR. Chances for showers Friday afternoon bring potential for restrictions, particularly at HIE.

Saturday-Sunday: Periods of rain likely bring MVFR to IFR with ENE winds gusting 25 kts. Some improvement possible Saturday night into Sunday.

MARINE

Elevated seas and sub-SCA southerly winds are expected this afternoon, and will continue through early tomorrow morning. Seas of 3-6ft expected. Winds will slacken on Wednesday and generally become northerlies. Seas should range from 2-4ft on Wednesday.

Thursday-Monday...Winds and seas remain below SCA thresholds Thursday into Saturday morning. Low pressure develops in the Gulf of Maine Saturday with ENE winds shifting N bringing SCA conditions into Sunday morning. Winds drop below SCA thresholds Sunday.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until 5 AM EDT Wednesday for ANZ150-152.