textproduct: Gray - Portland

SYNOPSIS

Low pressure will quickly pass over the region by this evening and overnight. This will bring widespread light snow accumulations to much of the forecast area before departing Monday. An active weather pattern will feature a few more chances of precipitation heading into the middle of next week.

NEAR TERM /THROUGH TODAY/

A fair day through mid to late afternoon. Dry conditions until then bring temps a little closer to seasonal norms in the upper 20s and mid 30s. A fast moving low pressure system approaches from the west later this afternoon and is expected to spread light snow from west to east across central and northern NH by early evening.

SHORT TERM /TONIGHT THROUGH MONDAY/

Weak low pressure is expected to move quickly across the forecast area tonight, likely across central/southern NH then off the Maine coast near PWM by 06z. Enough moisture and forcing for ascent in association with the system should be sufficient for a band of light snow to spread across the forecast area during the evening, especially north of the low track. Unless the low track changes, the highest accums should fall along the corridor of best mid level ascent which should be across the northern half of NH eastward into central ME. It is there where a stripe of 1-3" of snow falls with a few areas in the mountains possibly seeing as much as 4". Elsewhere, amounts should be 2" or less. Portions of southern NH into York County ME may not see much at all, most likely less than an inch.

There have been some signals in the guidance over the last couple of days that this system may deepen fast enough so that it throws back a band of enhanced snowfall to the coast. Some CAMs still show this potential, so we'll have to watch for some higher snowfall rates and amounts on the Midcoast Sunday evening.

Some slippery spots are likely for the Monday morning commute even though the bulk of the snow should have ended by then.

The system quickly departs Monday leaving us with cold and breezy weather, but dry.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/

Overview:

The 500 mb pattern across the CONUS will feature a persistent ridge over the West Coast and a low amplitude long wave trough over the eastern US. A series of embedded waves will bring chances for light precipitation starting Tuesday night through the end of the week. The second in the series looks to bring the best chance for widespread precipitation late Wednesday into Thursday morning. The ridge trough pattern shows signs of amplifying late next week through the weekend with temperatures dropping well below normal.

Impacts:

*Light snow will bring potential for slick roads Tuesday night and again late Wednesday into Thursday morning.

Details:

The long term period will start off cold with low temperatures Tuesday morning ranging from the single digits below zero north to single digits above zero near the coast. High pressure shifts south Tuesday while still providing mostly fair weather with highs Tuesday ranging from the teens north to upper 20s along the coast. The first in a series of short waves will bring chances for light snow Tuesday night that ends before the Wednesday morning commute. Moisture will be limited with snowfall generally a coating to 2 inches.

The next short wave will be quick to approach Wednesday with a surface low tracking west to east across northern New England. Subtle shifts in the track of this low will change how much above freezing air is able to work into the southern half of the forecast area while the mountain and north likely stay cold enough for all snow. The latest NBM has precipitation starting as snow before the rain/snow line pushes inland to the foothills Wednesday afternoon with the rain/snow line collapsing back to the coast Wednesday night. Overall QPF will be light on the order of 0.1 to 0.25 inches which could amount to a few inches of snow in the mountains and generally less than an inch south of the foothills due to changing to rain.

The trough over the eastern US will deepen late in the week while there is limited signal for additional widespread precipitation events. As the trough deepens colder air will gradually work into the region with below normal temperatures likely next weekend.

AVIATION /03Z SUNDAY THROUGH THURSDAY/

Short Term...Patchy Shallow ground fog may develop in spots very early this morning but should be dissipated by a cold front moving through prior to dawn. Other than some fog, expect ceilings to be VFR this morning into the afternoon hours today. MVFR/IFR ceilings then invade with quick moving low pressure this evening. This will also bring -SN to reduce vis to 1 to 2 miles overnight. Improvement is expected at or shortly after 10z Mon for much of the forecast area north of PSM/CON/LEB line.

Long Term...Mainly VFR Monday night through Tuesday. Light snow Tuesday night will bring at least the chances for MVFR with some improvement Wednesday morning. Another system crosses late Wednesday bringing light snow with snow changing to rain south of a line from KLEB to KAUG Wednesday afternoon. This will likely bring another period of at least MVFR Wednesday into Thursday morning.

MARINE

Short Term...Winds and seas remain below SCA criteria today into tonight. Quick moving low pres enters the Gulf of Maine early Monday morning, increasing winds to around 30 kts. Some gusts to gale may be attainable on the outer waters Monday morning, and a gale watch has been issued here. Have issued a small craft advisory for Casco and western Penobscot Bay along with the outer waters south of Portland.

Long Term...NW winds will be on a downward trend Monday night into Tuesday. A series of week systems cross northern New England Tuesday night into Thursday with winds likely bringing an extended period of SCA conditions.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Gale Watch from Monday morning through Monday afternoon for ANZ150-152. Small Craft Advisory from 4 AM to 11 PM EST Monday for ANZ151- 153. Small Craft Advisory from 1 AM Monday to 1 AM EST Tuesday for ANZ154.