textproduct: Gray - Portland

SYNOPSIS

A cold front crosses tonight into Thursday, bringing blustery conditions for Thanksgiving through the holiday weekend. Another cold front approaches later in the day on Sunday. Some mixed wintry precipitation is possible Sunday night across portions of the interior as the next wave of low pressure arrives.

NEAR TERM /UNTIL 6 AM THURSDAY MORNING/

630 PM Update...Warm front remains nearly stationary across southern NH at this time with Nashua near 60F and Concord in the upper 40s. North of the front scattered showers remain along with fog, especially from Portland on north and east. Not much is going to change until a cold front/occlusion sweeps across the CWA around and a few hours after midnight. Thereafter, the fog will lift and the scattered showers should move out.

Previously...

A lingering cold air dam keeps much of Maine and central New Hampshire socked in with low clouds and fog into this evening. Far southern New Hampshire and the Maine coast breaks into some warmer air by late afternoon with temps in the 50s.

The cold front associated with a broad low pressure system in the Great Lakes pushes through during the overnight hours tonight. This brings one more round of more organized shower activity through the overnight hours, with the highest coverage across northern locations. Precip may also end as a few snowflakes along the Canadian border late tonight. The front moves east of the area by daybreak tomorrow, with drier air moving in behind the front.

SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/

Drier air steadily moves in during the daytime tomorrow on a freshening westerly breeze. More sunshine returns downwind of the mountains with temps mainly holding in the 40s. Across the mountains and foothills, upslope conditions brings more cloud cover with highs in the 30s. After a mainly dry period through the morning hours, upslope snow showers increase during the afternoon hours as moisture from the Great Lakes begins to arrive on westerly flow.

Temps drop into the 20s across the area Thursday night as the colder airmass begins to settle in. The parent low in the Great Lakes moves through Quebec during the overnight. With multiple troughs pivoting around this low, upslope snow showers continue through the overnight hours across the higher terrain, and likely increase in coverage towards daybreak on Friday.

LONG TERM /FRIDAY THROUGH WEDNESDAY/

Key Messages: * Low pressure tracking north of the forecast area Friday will support snow in the mountains and occasional passing snow showers for the interior and foothills through the afternoon. Combined with breezy conditions, some of these may cause brief lowered visibility. * Pattern remains active with two additional chances of precipitation before midweek next week.

Details: Stacked low pressure over Quebec will slowly move east into the Canadian Maritimes Friday and Friday night. This leaves the forecast area in broad cyclonic flow through the day Friday. There will be weak embedded shortwaves within this circulation, and they will aid in developing some snow showers through Friday afternoon.

What moisture is in the low levels may be further accentuated by moisture from the Great Lakes, leading to periods of light snow through the day for those NW of the foothills and ridges. Given the brisk flow, do expect some of these to carry into the interior as snow showers. However, moisture depth overall is a concern, and any added downslope drying will further weaken precip downstream. Did increase PoPs above NBM suggestion into the Kennebec Valley and eastern foothills given low level instability, added lift from aforementioned shortwaves, and enough moisture to at least support a flurry or sprinkle now and then Fri afternoon.

Upper trough will tend to become more rounded, less sharp Friday as it tracks out of the Great Lakes. This tends to slow the arrival of LLJ into New England until later Friday. With deep mixing, can't rule out some surface gusts to 40 mph to go along with some of the snow showers in the afternoon. As mentioned, timing of the strongest winds aloft may arrive later in the day, towards the evening. So then adds the complicating question of how does the transport of these gusts to the surface fair once daytime heating is waning. At this time, expect the bulk of gusts to fall between 20 and 30 mph, with gusts to Gale force over the coastal waters.

Upslope snow showers may continue in some capacity into early Saturday before drying with building ridge. This keeps Saturday dry but cool ahead of the next weather system late Sunday through Monday morning. This system looks to take a similar track into Quebec, but moving quickly. Deepening into the Maritimes, there should be a period of moderate precipitation across the forecast area as convergence at the surface and divergence aloft suggests decent lift. Cool temperatures ahead of this system provide the chance for snow in the mountains. Phase and speed of the low limits the chance of a coastal low developing. This would aid in maintaining cooler temps across the interior, but at this time looks warm to support mostly rain for the coast and interior.

The associated cold front will lift through by noontime Monday, with another break of dry weather Tuesday before the next system nears the region midweek overnight into Wednesday.

AVIATION /00Z THURSDAY THROUGH MONDAY/

Short Term...IFR to LIFR lingers across most terminals into this evening until the passage of a cold front after midnight. MVFR breaks are most likely at MHT, CON, and PSM this afternoon. The front brings clearing, with most terminals returning to MVFR and VFR late tonight toward daybreak on Thursday. VFR prevails at most terminals through tomorrow night, but HIE and LEB likely return with MVFR ceilings with upslope winds by late tomorrow afternoon, persisting through tomorrow night.

Long Term...MVFR ceilings linger around the mountains Friday through Saturday, elsewhere VFR. It will be gusty Friday with LLT amid deep mixing. SHSN most common in the mountains, but may spill into the foothills towards AUG/IZG/LEW. SW gusts 20 to 35 kts possible into early evening, shifting W overnight. Breezy Saturday as well but not as strong, dry. Clouds thicken and lower again Sunday as next system approaches late Sunday into Monday morning. Would expect MVFR ceilings with some IFR at times. SN may be dominant precip type for HIE and mtn region, with RA elsewhere.

MARINE

Short Term...A cold front clears the waters late tonight and Thursday morning. Increasing westerly winds bring SCA conditions by daybreak Thursday, which continue through Thursday night. Near gale conditions are possible by daybreak on Friday.

Long Term...Gale conditions still likely Friday, especially on the outer coastal waters. These will tend to subside for Saturday and Saturday night, before increasing again towards Gale Sunday afternoon. Outer waters may only be below SCA criteria for Saturday night. Second period of Gales wanes into Monday.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory from 4 AM Thursday to 7 AM EST Friday for ANZ150-152>154. Gale Watch from Friday morning through Saturday morning for ANZ150-152-154.