textproduct: Gray - Portland

WHAT HAS CHANGED

Snowfall amounts have slightly increased for a weak system crossing Saturday with the latest snowfall forecast calling for widespread 1-2 inches with locally higher amounts.

KEY MESSAGES

1. A cold airmass will usher into the area this morning on breezy winds making for a cold morning with wind chills near zero degrees and colder in the mountains. This cold airmass will set the stage for light accumulating snow through the day Saturday leading to slick travel

2. We continue to closely monitor trends for Sunday night into Monday as a signal for a coastal storm still exists, but higher than normal uncertainty remains between model solutions. Otherwise, below normal temperatures through much of next week along with an active weather pattern will continue to provide chances for snow.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... A short wave trough axis crosses the area this morning with WNW winds ramping up around day break. These winds will gust 25-30 mph through the morning and when combined with colder air moving into the region wind chills will range from 10 degrees below zero across the north and around zero degrees across southern NH and coastal Maine.

The next weak system will approach from the Great Lakes tonight spreading light snow across the region with the first wave arriving before day break Saturday. The low center will track NW of the area Saturday afternoon with a warm front pressing through southern New England. The latest available CAM guidance shows modest Fgen forcing around 700 mb that could lead to a period of moderate snow across south-central NH and interior SW Maine Saturday afternoon. Warm air advection will bring the potential for temperatures near the coast and southeast NH to warm into the mid 30s that may limit accumulations. Overall accumulations are forecast to be a widespread 1-2 inches from the coast to the mountains with this snowfall occurring across SE NH and coast Maine Saturday morning before the potential changeover. Across the higher terrain of the Monadnock through central NH into the foothills of Maine there is potential for higher amounts approaching 3 inches. Precipitation will come to and end Saturday evening.

KEY MESSAGE 2 DESCRIPTION... Will need to continue to monitor a potential coastal low late Sunday into Monday, which may bring some accumulating snowfall to at least portions of the region. While global ensemble suites continue to favor a more offshore track, keeping the majority of precipitation too far east, the AI ECMWF and GFS show a rather strong signal for at least some snow accumulations, especially across southern areas. One thing to watch is the timing and placement of a cold front, which will help to serve as a steering mechanism for this system. Temperature profiles support this to be a snow event and given the potential for some impacts to the Monday morning commute, it bears watching. The WPC Probabilistic Winter Storm Severity Index shows around a 20-30% chance for at least minor impacts.

Below normal temperatures return for next week as our weather pattern remains on the active side. Models suggest that clippers from the Great Lakes Region continue to traverse the area along with several upper level waves traversing the broad trough. There isn't a signal for anything impactful at the moment, and midweek looks mostly dry as high pressure noses into the region, but some chances for snow showers are in the forecast late week.

AVIATION /03Z FRIDAY THROUGH TUESDAY/

Upslope clouds and -SHSN will continue to bring at least MVFR at KHIE through the first half of tonight. Some MVFR cigs are holding at KRKD, but is expected to exit by 08Z as winds shift westerly. Elsewhere VFR is expected with VFR for all TAF sites by early Friday morning as W winds increase, with some gusts to 20 kt before dawn. Expect gusts to increase further Friday morning after sunrise, 20 to 25 kt.

Outlook:

Friday night: VFR becoming MVFR/IFR cigs as clouds thicken/lower. Light SN possible late.

Saturday: Light snow is likely for all TAF sites through Saturday morning bringing the potential for IFR. During the afternoon, PSM, PWM, and RKD improve to MVFR if rain or a rain/snow mix remains the dominant precipitation type.

Saturday Night: Gradual improvement from IFR to MVFR overnight as precipitation wraps up and ceilings begin to lift.

Sunday: Ceilings may lift to VFR for a time on Sunday, but would quickly return to MVFR as another system moves into the region.

Sunday Night: MVFR for most terminals with IFR visibility restrictions possible in snow for coastal TAF sites.

Monday: Potential for MVFR or worse restrictions in possible SN. Forecast confidence is low. Conditions should improve by late day.

Monday Night: VFR prevails at all terminals.

Tuesday: VFR prevails at all terminals.

MARINE

Low pressure exits to the northeast with westerly winds increasing through day break. These westerly winds will bring Gales over the outer waters and SCA conditions in the Bays. Winds drop below SCA thresholds tonight while seas will remain around 5 feet into Saturday. A warm front pushes into the waters Saturday with SW winds approaching 20-25 kts.

There won't be much of a reprieve from SCA conditions as seas stay around 5 ft through the day Sunday. Winds then ramp up with frequent gusts 25kt+ by Monday afternoon. Gale force westerly winds possible Monday night-Tuesday as a coastal low approaches or crosses over the waters. SCA conditions will likely linger through mid-week.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Gale Warning from 3 AM to 4 PM EST Friday for ANZ150-152-154. Small Craft Advisory until 4 PM EST Friday for ANZ151-153.