textproduct: Gray - Portland

WHAT HAS CHANGED

Increased chances for showers farther south toward the Maine coast this afternoon based on trends, but no changes needed to the forecast otherwise.

KEY MESSAGES

1. Scattered showers and isolated storms are possible into early this evening and will be followed by another chance for showers Saturday and Saturday night.

2. Drier conditions arrive Sunday through Tuesday morning. A return to more damp conditions is possible mid to late week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

An upper low centered just to our north will slowly move eastward tonight and become nearly stationary in the vicinity of Nova Scotia through Saturday. Cyclonic flow and shortwaves stemming from this low will bring scattered showers and isolated storms during the first part of this weekend, mainly during the daytime hours. The better chances today will be around the mountains and western ME and then a few may linger in the mountains through tonight. Not expecting as much in the way of fog overnight into early Saturday as winds may stay up just enough, but I do have patchy fog in the forecast along the Connecticut, Pemi, and Saco River valleys where winds do look light enough.

On Saturday, clouds will increase in the morning and afternoon with the better chances for showers across the mountains and NH this time around as a backdoor front moves through the area. Temperatures come down a few degrees with most in the low-mid 70s, but some locations that stay cloudier could remain in the 60s. It will also be somewhat breezy, especially across western ME, where gusts will be out of the north around 20 mph at times.

Another wave drops south into northern New England Saturday night, which could bring a few more showers to NH and the mountains. Due to this chance, valley fog has been left out of the forecast for Saturday night.

KEY MESSAGE 2 DESCRIPTION...

High pressure will arrive from the west come Sunday morning. Predominantly northwest winds linger for the day, remaining breezy due to the tight pressure gradient just east. Despite the decreasing clouds, temperatures will be similar to Saturday, in the low to mid 70s.

Overnight, the high may never make it directly overhead. This keeps some gradient wind over the northern and eastern CWA. While skies clear, this could keep the night from being more efficient for cooling. Spots that do stand to drop a few extra degrees would be to the south and west. This could let lows in the mid 40s trickle into parts of southern NH.

High pressure over the Great Lakes Monday will provide another pleasant day with dry weather. Temps tick a few degrees warmer as the source region is from the west, the same for Tuesday. However, a weak cold front will be moving through northern New England. There could be a few showers that accompany passage, but not enough to help with ongoing dry conditions.

Guidance continues to depict a larger system moving into the region in the mid to late week timeframe. While ensembles depict a likely probability of greater than 500 kg/m/s of IVT, it is progressive and quickly translates the forecast area. This seems to mirror a lot of our systems this summer, and may be just enough to deliver a wetting rain, too little to make a larger dent in rainfall deficits.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Through 18z Saturday...Primarily VFR into this evening, although isolated showers or storms could bring brief MVFR to IFR restrictions. For tonight, valley fog is again likely to bring IFR to LIFR restrictions at LEB and HIE. Elswhere, a period of MVFR to IFR ceilings is possible from late tonight into Saturday morning, but conditions should return to VFR by early Saturday afternoon.

Rest of Saturday: Mainly VFR, but scattered showers could bring TEMPO MVFR, mainly for the NH terminals.

Saturday night: A few showers may linger with MVFR cigs over NH, and then more valley fog is possible late at HIE and LEB. Otherwise, VFR.

Sunday: VFR with decreasing clouds, breezy NW winds.

Sunday Night: VFR. Some valley fog possible late for LEB/HIE.

Monday and Tuesday: VFR with no sig wx. Wind shift possible with passing cold front.

Wednesday: Chance of SHRA advancing from the west through the day. This could bring MVFR cigs.

MARINE

Through Saturday night...Low pressure slowly moves east toward Nova Scotia tonight with winds turning northerly. The low remains centered just east of Nova Scotia through Saturday night, keeping winds out of the north. Gusts may occasionally approach SCA levels Saturday and Saturday night over portions of the waters, but confidence is not there to issue an SCA yet.

Winds remain primarily offshore through the period. This will result in lowering wave heights nearshore, but wind wave does build on the outer waters. A cold front will approach the waters Tuesday evening.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...None.