textproduct: Gray - Portland

WHAT HAS CHANGED

Little has changed since the last update of the latest forecast package. Gales hoisted for Casco Bay and Penobscot Bay.

KEY MESSAGES

1. Winds peak early this morning, gusting 30 to 40 MPH at times. However, they will gradually diminish late morning through the afternoon hours.

2. There are several chances for wintry precipitation next week, beginning with a minor system Tuesday night into Wednesday. The potential for a more impactful system exists late week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... Forecast soundings continue to show the potential for widespread 30 to 40 mph gusts into this morning. However, winds are expected to diminish as the day progresses allowing for apparent temperatures to rise well into the 20s this afternoon.

Otherwise, after a mainly sunny morning (except the mountains where some upslope snow flurries and snow showers may still be ongoing) clouds will increase again this afternoon as WAA ensues in advance of a low pressure system quickly moving eastward across the northern Great Lakes. Little in the way of precipitation is expected with this feature other than some light snow showers in the far northern mountains.

Warm air advection continues on Tuesday with with highs around 40s at lower elevations downwind of the mountains.

KEY MESSAGE 2 DESCRIPTION... The ridge slides east Tuesday night with a broad trough starting to slide in from the west. Low pressure approaches at the surface with an attendant frontal boundary starting to break out light precipitation across the area. Temperatures should be low enough for this to start as snow in the northern half of the CWA, but they will be more marginal for the southern half which is likely see it start as rain. The front crosses the area Wednesday keeping precipitation going. Continued southwesterly flow drives temperatures into the low to mid 40s for much of the area, so rain is expected to be dominant for most of the day. After midnight, cold air begins sinking back into the area transitioning precipitation to snow from north to south through the overnight period. Ensembles have increased slightly for the Wednesday period, now 0.10-0.25" in 24 hours which is light, and its expected to be mostly rain, so any snow may only amount to a coating to maybe an inch from the foothills north, with any accumulation less likely for points south.

Uncertainty remains in how things evolve after that. Models suggest development of a coastal low off the Delmarva Thursday that slowly works its way eastward. With the trough axis also continuing eastward we could see light snow continue into Thursday as the low pressure pulls in colder air. Ensemble support remains low for anything significant out of this with mean QPF spread currently 0.10-0.25" between models. Snow ratios tend to be higher in these situations, so this would be the better chance for a widespread light accumulation through Thursday night. Otherwise, the support is for the higher axis of moisture to stay well offshore. Some light showers could linger into Friday morning as low pressure departs, then a brief shortwave ridge looks to make for a dry Friday night and Saturday. The better signal for a more impactful system looks to come late in the weekend, with cluster analysis showing more than half of ensemble solutions having significant QPF. However, this is at the tail end of the forecast period and low pressure origin and track are going to play a huge role in the outcome. For now just worth a mention and some chance PoPs.

AVIATION /12Z MONDAY THROUGH FRIDAY/

Upslope snow showers and MVFR CIGs continue this morning. Gradually as winds shift to more southwesterly this afternoon those CIGs will scatter out and the threat of snow showers comes to an end. Otherwise VFR conditions remain. Westerly winds will be most gusty this morning, with surface gusts up to 30 kt. By this afternoon winds will diminish to a steady breeze around 7 to 10 kt. VFR tonight and Tuesday.

Outlook:

Tuesday night: IFR possible in snow showers at LEB and HIE. MVFR possible in rain showers elsewhere.

Wednesday: LEB and HIE gradually improve to MVFR as snow tapers off. VFR to possibly MVFR prevails at all other terminals.

Wednesday night IFR possible in snow showers at LEB and HIE. MVFR restrictions more likely at other terminals in light rain early but could lower to IFR if rain transitions to snow.

Thursday and Friday: More widespread precipitation (mostly snow) and IFR flight restrictions possible.

MARINE

Gales will diminish this afternoon but remain at SCA levels tonight before diminishing Tuesday.

SCA conditions return Tuesday night as low pressure crosses through the Gulf of Maine. Wind gusts ease Wednesday afternoon, but seas don't follow suit until Wednesday night. Sub-SCA conditions prevail until Thursday night when the weather pattern becomes quite active and several low pressure systems look to make there way through potentially keeping SCA conditions around through the weekend.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Gale Warning until 1 PM EST this afternoon for ANZ150-152-154. Gale Warning until 9 AM EST this morning for ANZ151-153.