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FXUS61 KGYX 022110 AFDGYX

Area Forecast Discussion National Weather Service Gray ME 410 PM EST Sat Dec 2 2023

SYNOPSIS
Low pressure approaches from the Ohio Valley late tonight and Sunday bringing increasing chances for snow across the north and rain south of the mountains. Low pressure forming near southern New England will bring the potential for significant snowfall across the foothills and points northward while there is uncertainty in the rain/snow line across the south. There remains potential for impacts into the Monday morning commute due to wintry conditions. The system exits Monday afternoon with snow showers lingering into Monday night. A drying trend follows into mid week.

NEAR TERM /UNTIL 6 AM SUNDAY MORNING/
A fairly calm night tonight with some patchy fog across the mountains and interior. Winds should become more directional from the northeast after midnight, and this will be critical for bringing cool air in ahead of precipitation Sunday afternoon.

SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/
A winter storm will impact the region Sunday into Monday morning.

Low pressure passing up the eastern Great Lakes will combine with return flow to bring moisture through the column into New England. While QPF trends have lightened from yesterday, some localized areas could see enhancement, namely the mountains and potential areas of central Maine where banding could enhance snow rates. Overrunning moisture may contribute to seeder/feeder mechanisms allowing a bit earlier start time than prev forecast.

All snow is expected across the mountains and foothills where snow will begin shortly after noontime Sunday. Here, a Winter Storm Watch has been issued where snow amounts may total above 6 or 8 inches of snow. Notable snow rates may not enter the region until mid afternoon Sunday as the low tracks through the eastern Great Lakes. Further enhancement of rates is forecast into the overnight and early Monday morning hour. HRRR rates show this most likely across portions of central ME; Franklin/Somerset Co. These rates may approach 1" per hour during the early Monday morning timeframe as low pressure deepens and starts to transfer to the Gulf of Maine. Snow consistency may be wet, allowing for weighing on tree branches were snow accumulation continues. Combined with this, winds across the ridges may gust up to 35 mph at times from the east.

For portions of central and western NH, valleys are expected to warm enough to keep snow ratios low. This will affect accumulation in the lowland, with higher elevations seeing more accumulation. Thus travel here will be slick or treacherous at times depending on elevation. Despite this, overall confidence is below Warning level snows will impact the lower elevations, and a Winter Weather Adv was instilled here. Extension of the Advisory may be needed if snow prolongs into Monday.

The most uncertainty currently lies with a region over interior Maine towards the ME capitol region. While model consensus continues to bring warm surface temps here, cold air damming ahead of the advancing low should lock in temperatures close to freezing in this region. The NAM has been the most continuous with this, but HRRR also resembles this pattern which enhances confidence. Combined with increasing precipitation rates into the overnight period, what falls may well be mostly snow in this region. It has been noted that sometimes the HRRR can overdo the NE cold advection in a dam situation, so did edit values a bit warmer than HRRR brings. Regardless of outcome, Monday morning's commute would line up well with when a heavier band of precipitation may be tracking through the region, leading to snow being the likely precip type at the time. Thus preparations for slick travel the morning of should be taken.

Mostly rain is expected along the immediate coast and outside of higher terrain of southern NH. However, with cold air aloft, can't rule out snow mixing in for a decent portion of the event, particularly towards the Midcoast of Maine. The problem for snow accumulation comes with much lower ratios which will inhibit good dendrite resilience at surface conditions.

Precip rates as well as accumulation potential will begin to dwindle across southern and central NH and southern ME through the early Mon morning hours. This comes as the DGZ begins to dry and the result may be drizzle or just some flakes for the morning commutes in southern NH.

LONG TERM /MONDAY THROUGH FRIDAY/
Monday will feature a departing low pressure system, with the steady snow ending during the morning hours in the mountains and foothills. However, the low levels will remain moist as the mid levels dry out, so we suspect there will be a decent amount of drizzle around Monday, especially on the coastal plain.

The column moistens up again late Monday and Monday evening as the main main short wave trough moves overhead. Enough forcing for ascent looks to be present to allow for a period of snow showers, with some accumulations possible especially in the mountains and foothills.

The system departs later Monday night and Tuesday with drier conditions expected. Another short wave trough, likely moisture starved, looks to move through later Tuesday night Wednesday with the potential for a few more snow showers.

The next chance of widespread but mainly light precipitation looks to be Friday or Saturday.

AVIATION /20Z SATURDAY THROUGH THURSDAY/
Short Term...LIFR, IFR, and MVFR are expected through Sunday night. MVFR ceilings this evening will trend IFR tonight, remaining down through the day Sunday and Sun night. RA will onset during the late morning for terminals such as MHT, PSM, CON. Further to the north, this will fall as RA/SN such as LEB PWM, and RKD. Further yet, all SN will be possible for points from HIE to AUG. SN would hinder vis down to a mile or less at times through Sunday night. Heavier snow bands will be possible from IZG to GNR late Sun night, with vis potentially down to one half mile.

Long Term...Low cigs and periods of rain and snow likely bring IFR conditions Monday into Monday night. Coastal and southern terminals likely see mainly rain while the snow falls in the interior. Conditions likely improve to mainly VFR Tuesday into Wednesday.

MARINE
Short Term...While low pressure will be passing through the waters over the next 36 hours, little more than SCA conditions are expected. These will primarily take place during the Sunday afternoon through Monday morning timeframe. NE winds will gust to 30 kt at times, with just a few hours of 25 kt possible for bays/harbors.

Long Term...Winds and seas generally stay below SCA thresholds Monday afternoon into Midweek but a few bouts of 25 kt gusts and a few 5 footers can't be ruled out during the period.

GYX WATCHES/WARNINGS/ADVISORIES
ME...Winter Storm Watch from Sunday afternoon through Monday morning for MEZ007>009-012>014-033.
Winter Storm Watch from Sunday evening through Monday morning for MEZ020>022.
NH...Winter Storm Watch from Sunday afternoon through Monday morning for NHZ001-002-004.
Winter Weather Advisory from 1 PM Sunday to 10 AM EST Monday for NHZ003-005-006.
MARINE...Small Craft Advisory from 1 PM Sunday to 1 PM EST Monday for ANZ150-152-154.

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