textproduct: Gray - Portland

WHAT HAS CHANGED

Gale Watches have been converted to Warnings Friday night through Saturday.

Snow levels have trended lower Friday night into Saturday morning with winter conditions possible above 2500 feet.

KEY MESSAGES

1. Cold rainfall and high elevation snow late Friday into Saturday morning with NE winds gusting to 35 mph along the coastal plain. Hikers should prepare for winter conditions above 2500 feet.

2. An extended period of cool and unsettled conditions looks increasingly likely for much of next week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Forecast remains on track for an upper low to dive south over western New England Friday night with a surface low quickly moving through the Gulf of Maine Saturday morning. The faster timing trend continues to hold with precipitation starting late Friday and ending NW to SE Saturday morning with improving conditions Saturday afternoon. There has been a slight westward shift in axis of heaviest QPF while pool of cold air aloft will still move over the entire area.

Friday will start off with a mix of sun and clouds with clouds increasing the second half of the day. Precipitation chances increase NW to SE Friday afternoon with highs ranging from the 50s north to 60s south before precipitation starts. Rain will become widespread Friday night with rain changing to snow at the higher peaks as T8s drop as low as -4C. Latest BUFKIT profiles show wet bulb zero heights dropping below 2000 feet in the heavier precipitation with snow levels from the latest NBM dropping as low as 2500 feet. Low temperatures Friday night will range from the mid 30s north to low 40s south with elevations AOA 2500 dropping below freezing. Winter conditions are likely in the mountains with several inches of snow possible at the higher peaks of the Presidentials by Saturday morning. Northeast winds will also ramp up Friday night bringing windchills below freezing at lower elevations across the north and into the single digits across the highest peaks.

Total QPF remains largely unchanged from previous forecast while the axis of heaviest precipitation has shifted slightly west. This brings an area of 1-2 inches across far western Maine into the White Mountains with amounts decreasing towards central Maine and southwest NH. Precipitation will start to end Saturday morning as both the upper low and surface low scoot southeast away from the Gulf of Maine. Before the system exits there will be a period of northeast winds gusting 30-35 mph along the coastal plain with higher gusts along the immediate coast early Saturday morning. Latest available NWP guidance start to show height rises Saturday afternoon that may allow for clearing skies with northeast winds diminishing.

KEY MESSAGE 2 DESCRIPTION...

Cool conditions settle in for Saturday night behind the departing system , with frost possible across the northern valleys as lows fall into the 30s. At this point winds look to ease Saturday evening across the north, so cloud cover looks to be the determining factor on how low temps can go.

From Sunday through at least midweek, a deep trough looks likely to settle in across the Northeast with multiple shortwaves diving southward through the trough almost daily. These bring the chance for showers each day, with breaks of sunshine also likely from time to time between systems.

The next shortwave looks likely for Sunday afternoon and Sunday night. After a relatively bright start to the day on Sunday allows for temps to warm into the 60s, pop up showers become likely for the afternoon hours as the shortwave moves in. This system looks slow to depart, with showers likely continuing across at least part of the forecast area for Sunday night and Monday.

After this system, skill drops off significantly in trying to time each following shortwave. It remains possible that some of them miss to the west as the dive southward, or don't organize into a surface low until they're south of New England. So it's important to know that the week is not a continuous washout, but periodically unsettled as multiple shortwaves bring additional intervals of shower chances.

At this point there looks to be at least two more shortwaves between Tuesday and Thursday. These systems looks compact enough so that they don't affect all of northern New England at the same time. So where they bring showers at what times remains uncertain. Where sunshine appears outside of these system likely brings temperatures that quickly warm into the 60s and low 70s. Cloudier and rainier locations likely see temps fall and remain in the 50s.

We'll try to take these shortwaves two at a time at this point, but the overall message is that an extended unsettled pattern looks to be setting up through at least midweek next week.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

Through Saturday...Mainly VFR tonight through Friday morning. Clouds thicken and lower with increasing chances for rain from NW to SE Friday afternoon. IFR to LIFR is likely Friday night into Saturday morning in low cigs and rain. NE winds will gust to 25 to 30 kts south of the mountains late Friday night into Saturday morning with higher gusts possible for coastal terminals. Conditions improve NW to SE Saturday morning with a trend towards VFR Saturday afternoon.

Outlook...

Saturday night: VFR likely prevails.

Sunday-Monday: VFR gives way to showers and at least periods of MVFR conditions.

Monday night-Wednesday: Periods of MVFR with showers are likely.

MARINE

Winds and seas remain below SCA thresholds through Friday. Low pressure dropping southeast through the Gulf of Maine Friday night and Saturday will bring a period of northeast Gales with seas quickly building to 7-10 feet. This system exits southeast Saturday afternoon with north winds relaxing while seas remain elevated into Saturday night.

An unsettled pattern brings multiple small low pressure systems through the waters Sunday through midweek. These lows bring changing conditions and shifting winds as they pass and deepen offshore. The best chance for at least periods of SCA conditions look to be late Sunday through Monday, and then late Tuesday through Wednesday.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Gale Warning from 2 AM to 2 PM EDT Saturday for ANZ150-152>154. Gale Warning from 2 AM to 8 PM EDT Saturday for ANZ180-182-184.