textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes to overall forecast thinking this afternoon...with rainfall totals 0.5-2.0 inches from northwest to southeast.

KEY MESSAGES

1.Beneficial rainfall expands inland tonight with locally heavy rainfall along the coast with more showery conditions expected this weekend.

2. Cooler temperatures arrive later this weekend and remain through next week areawide. There will be multiple chances for light precipitation, including light snow or snow showers for the higher peaks of the White Mountains.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Band of shower/thunderstorm activity continues just south and east of a stalled frontal boundary along the coast of ME through southern New England. As impressive upstream closed low moves towards this boundary tonight...it will help back the low/mid level flow and push precipitation increasingly inland while at the same time low pressure will develop along the front reaching a position within the Gulf of Maine by Saturday evening. Primary forecast concerns through Saturday night revolve around precipitation amounts...and then cooling temperatures by late Saturday/Saturday night as the upper low arrives from the west potentially changing the PTYPE to snow over the higher mountain peaks late Saturday night.

QPF: Pretty sharp gradient from NW to SE given the frontal location. Have followed pretty close to REFS mean for totals through the period...with 0.5-0.75" in the mountains...around an inch in the foothills...and then 1.5-2" along the coastal plain. While some poor drainage ponding is possible, especially given fallen leaves...no widespread flooding is expected.

Thunder: Elevated instability has spawned a few lightning strikes north of the frontal boundary today across SE NH and far SW ME. This will likely continue through tonight with little overall motion to the frontal surface and modest mid level lapse rates ongoing. This should end by daybreak Saturday as the warm sector pulls further offshore.

PTYPE: Very warm to start the period with no PTYPE concerns. As the upper low arrives Saturday night...thicknesses fall and we should see temperatures support a changeover to snow above 4kft by daybreak Sunday with some further cooling after that. Thus...the highest peaks will see some accumulation before the low pulls away from the region.

KEY MESSAGE 2 DESCRIPTION... Sunday is expected to start out mostly cloudy with lingering light rain, but low pressure will exit to the east and northeast later in the day, with northwest winds in its wake pulling some drier air. So we should see some peaks of sunshine in the afternoon, although the mountains and areas to the northwest will likely remain mostly cloudy with a chance of upslope showers, perhaps mixing with snow in the highest elevations. High temperatures will be in the 50s for most, except cooler in the 40s in the mountains.

Going into the first half of next week a more typical November pattern will be in place with longwave troughing across eastern Canada and into the Northeastern US. Shortwaves crossing through New England will bring multiple chances for light precipitation... but primarily in the mountains with upslope flow in place. With colder air aloft, expect some of this to be snow as we go up in elevation, and some light accumulations will be possible on the highest peaks. Elsewhere, periods of mostly cloudy skies are possible during the days with broad cyclonic flow in place, and precipitation chances are lower, but not zero, especially if Froude numbers are high enough. Highs will generally in the 50s except 40s across the north.

For the second half of the week, upslope mountain precip may continue in the mountains as troughing remains favored. Latest ensemble also favors temperatures further trending cooler with highs perhaps limited to the 40s areawide.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Summary: Deteriorating conditions this evening as a wave of low pressure brings rain across most of the region. Some improvement will occur on Saturday though showery conditions with some restrictions are expected through the weekend.

Restrictions: Rain expands in coverage through this evening with conditions deteriorating to LIFR/IFR except LEB/HIE where restrictions will hold off until overnight as most of the rain passes south of these locations. Some minor improvement is expected Saturday morning though MVFR/IFR restrictions remain likely through the day with showers...with conditions likely deteriorating again Saturday night. More substantial improvement is expected by the daytime on Sunday.

Winds: Light/variable winds continue through this evening will gradually turn northerly /northeasterly along the coast/ 5-10kts overnight and remain northerly around 10kts for the day Saturday before diminishing to 5-10kts Saturday night.

LLWS: LLWS is not expected through Saturday night.

Thunder: Isolated thunderstorms possible all sites except LEB/HIE through tonight.

Outlook: An active pattern will bring low pressure across the region Monday and again Tuesday night with showers...esp in the mountains with MVFR restrictions likely at HIE and possibly LEB with other sites likely remaining mostly VFR with a few isolated restrictions as these low pressure areas move through.

MARINE

This evening through Saturday night: Winds remain light as a frontal surface resides close to the Maine coast as of this afternoon. Low pressure will develop along this front on Saturday...moving into the Gulf of Maine Saturday night. Northwest winds strengthen Saturday night...nearing SCA thresholds as we reach daybreak Sunday.

Sunday-Friday...Low pressure lifts northward into the Maritimes Sunday into Monday and then remain in the vicinity of the Maritimes through at least the middle of next week. This will bring a general west to northwest over the waters, and periods of SCA conditions will be possible Sunday into early next week as multiple weak fronts cross. A weaker pressure gradient show allow winds and seas to remain below SCA levels for the second half of next week.

GYX WATCHES/WARNINGS/ADVISORIES

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