textproduct: Gray - Portland

WHAT HAS CHANGED

No major changes were needed for this forecast package.

KEY MESSAGES

1. Showers remain possible in the mountains through Friday, with more widespread showers possible Saturday. Generally drier weather Sunday into early next week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

An upper low will continue to drift east southeast, from central Quebec today, to far northern Maine tonight/Friday, and eventually over to Nova Scotia by Saturday.

This pattern will lead to plenty of cloud cover/mist/drizzle for the rest of this afternoon and into tonight. We could see a few breaks in the clouds over New Hampshire later this afternoon which could lead to some isolated/scattered showers and a rumble of thunder or two. RAP soundings suggest we could see 500 to 1000 J/kg of MUCAPE over southern New Hampshire with 30 to 35 knots of effective shear. Thus, if a storm can become established here, it could become strong with some gusty winds and/or small hail. Still this activity will only be hit or miss (and likely more miss than hit) with the best chances along and north of the mountains.

We will likely see widespread patchy fog develop over much of the forecast area tonight, especially in the valleys and where some of the heavier rain fell. More isolated showers are then possible Friday afternoon over the mountains as a few strands of vorticity wrap around the upper low to the northeast. Highs on Friday should be a little bit warmer than today with fewer clouds outside of the mountains. Values will mainly range from the lower 70s north, to the lower 80s south.

The chance for showers continues Saturday as an embedded wave within the broad cyclonic flow aloft pivots through northern New England. Associated moisture ahead of a vort max with daytime heating should be enough to set off widespread showers in the afternoon to evening. The more mild temperatures should keep instability and the warm cloud depth marginal, therefore think warm rain processes won't be favorable for heavy rain rates. That said, a passing shower could provide a good downpour as well as the possibility these congeal into broader periods of rain across the interior.

Resulting NW flow brings a drier and breezy airmass Sunday before the low completely departs. This mostly dry weather looks to remain in place through Wednesday, with just a few showers possible in the mountains daily. Temperatures warm a couple degrees with highs in the upper 70s to around 80 through early week.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

MVFR or lower ceilings are expected to continue through much of the day with some brief improvements this afternoon. Periodic fog and mist will also be possible through the rest of today, especially in the valleys and along the coast. A few isolated showers will be possible this afternoon with a stray rumble of thunder or two across southern New Hampshire. More fog then brings vsbys down on the coastal plain tonight and in the valleys before improving early Friday. Enhanced LLWS is not anticipated through the period.

Friday-Friday night: Improving conditions, with MVFR still possible in brief afternoon showers. Valley fog is possible at LEB and HIE at night.

Outlook...

Saturday: MVFR cigs could linger from LEB to HIE along the US/CAN border. SHRA develop across much of the interior, continuing into the evening.

Saturday night: SHRA decrease, but there is a chance MVFR cigs remain over a portion of the area.

Sunday: VFR, drier with breezy NW winds. No sig wx.

Sunday night: VFR with decreasing clouds, overnight valley fog possible.

Monday and Monday Night: VFR, not as breezy. No sig wx.

Tuesday: VFR, no sig wx.

MARINE

A period of near SCA conditions will be possible today as a weak wave of low pressure passes north of the waters but winds and waves will be on the downtrend through the afternoon. A cold front then crosses the waters tonight, with improving conditions to follow. Areas of fog will be possible over the waters tonight into Friday morning. Northerly flow brings fair conditions through the rest of the day on Friday.

Low pressure will be near Nova Scotia come Saturday, with breezy NNW winds. Some gusts near 30 kts possible on the outer waters, continuing overnight. Winds slacken Sunday into early next week as areas of high pressure near New England and the Northeast.

GYX WATCHES/WARNINGS/ADVISORIES

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