textproduct: Gray - Portland

SYNOPSIS

Upslope snow will persist across the mountains and far north through Tuesday with gusty westerly winds. High pressure will build across New England by the middle of the week, allowing for calmer winds and mainly dry conditions. The next widespread precipitation chance then comes Friday into Saturday.

NEAR TERM /TODAY/

Vertically stacked low pressure is located across Downeast ME and Nova Scotia early on this Monday morning with cyclonic flow prevailing across New England under northwesterly flow. This is allowing for continued upslope snow across the mountains as well as towards the Canadian Border. As expected, this snow is beginning to become more confined to these areas and this will continue to be the trend through this morning. It will otherwise be a breezy and cold morning with low temperatures falling to near or below freezing in most locations and windchill values around 10 degrees colder. There is some potential for a few icy spots this morning where residual moisture freezes, especially across untreated surfaces.

Low pressure will remain across the Maritimes today with northwesterly flow persisting across the region. Forecast soundings show around 40 kts at the top of a well mixed layer this morning through this afternoon, which will allow for gusts between 35-40 mph at times. Some locally stronger wind gusts are possible across the downslope regions as Froude numbers remain high. It will otherwise be a mainly cloudy day with upslope snow continuing across the north and mountains. High temperatures will range from the lower 30s across the north with lower 40s south and along the coast.

SHORT TERM /TONIGHT THROUGH TUESDAY/

Monday night will be cold with low temperatures falling into the 20s areawide but windchills will be into the single digits and teens from north to south. Northwesterly winds will weaken a little but gusts up to around 25 mph will remain possible. Upslope snow will continue across the mountains and far north with several inches of accumulation likely.

The upper level pattern will begin to flatten on Tuesday as high pressure builds to our west over the Ohio River Valley. A brighter day is likely with partly to mostly sunny skies south of the mountains and somewhat lighter westerly winds at around 15-25 mph. Despite the added sunshine, daytime highs will remain below avg with readings mainly into the 30s across the interior with low 40s in southern NH and along the coast.

LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/

Update...No notable changes were made to the extended forecast. High pressure and zonal flow are likely Wednesday and Thursday, with a low moving through the area on Friday and Saturday. A lot of uncertainty remains on the details of this weekend's system but wintry precipitation can not be ruled out. Troughing moves in behind the aforementioned system, with cooler temperatures possible for early next week.

Previously... We start out the long term under northwest flow aloft, leading to some lingering upslope snow showers through the day on Tuesday across the mountains. Westerly winds will also remain breezy through the day on Tuesday, diminishing late. The flow then starts to deamplify a bit Tuesday night into Wednesday as modest ridging approaches. Most of the showery activity in the mountains should diminish late Tuesday into Wednesday but a shower or two will be possible across the north country on Wednesday.

A low amplitude ridge axis crosses the region Wednesday night with a quick moving (mainly dry) shortwave on it's heels Thursday. Most of the forcing from this weak wave should remain south of our forecast area but a glancing blow could lead to some low precipitation chances across southern New Hampshire with little to no impact. The flow then becomes nearly zonal until Friday afternoon when we transition back into southwest flow aloft in advance of the next longwave trough. Widespread medium to high precipitation chances then spread across the forecast area Friday afternoon through at least Saturday morning, but considerable uncertainty remains about how long precipitation may linger with significant differences noted among the global deterministic models. Perusing the latest cluster analysis, at this point it seems like a more progressive open wave scenario is clearly favored rather than a stronger/closed low solution. If these trends keep up, then liquid precipitation totals are likely to mainly fall in that 0.25 to 0.50 inch range with only light snow totals in the higher elevations.

Regarding temperatures, we should very gradually warm through the week. That being said, we start off with highs below normal (mid to upper 20s north, to the low to mid 40s south) on Tuesday, and move towards highs only around normal (upper 30s to mid 40s north, to the upper 40s to lower 50s south) by Friday/Saturday. It should be noted that NBM temperature spreads remain high Friday and Saturday, likely a symptom of the pattern uncertainty discussed above.

AVIATION /04Z MONDAY THROUGH FRIDAY/

Short Term...VFR conditions will persist through the period except at KHIE where MVFR CIGs and -SN will remain possible with upslope flow. NW winds will prevail with gusts up to 30 kts. No LLWS is anticipated.

Long Term...VFR is likely through most of this week. A return of widespread precipitation chances could lead to some restrictions late in the week and into the weekend.

MARINE

Short Term...W-NW gales are expected through tonight with gusts up to 40 kts and seas of 4-7 ft outside of the bays. Across the bays, gusts up to 30 kts and seas of 1-4 ft are expected.

Long Term...Conditions go below SCA thresholds by Wednesday morning, with northwest flow weakening. Winds become lighter and more variable through the end of the week, with both winds and seas expected to stay below SCA thresholds through the second half of this week.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Gale Warning until midnight EST Monday night for ANZ150-152- 154. Small Craft Advisory until midnight EST Monday night for ANZ151-153.