textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes with this forecast update.

KEY MESSAGES

1. Low strengthens as it tracks southeast across coastal Massachusetts this morning. This system will bring strong northeast winds across SW Maine and southern NH with moderate to heavy rainfall through mid morning.

2. Accumulating snowfall in the mountains along with wind chills in the teens to single digits bring winter conditions through this morning.

3. Frost is possible across the north Saturday night as a cool airmass settles in.

4. Unsettled pattern persists Sunday through Tuesday with a signal for a warming trend the second half of next week.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Latest water vapor imagery shows a potent upper low diving southeast across Vermont with a surface low starting to strengthen near the NH/MA. This low will track SE across Cape Cod around 8 AM this morning and continue to pull away from the area late this morning with winds and rain diminishing this afternoon.

Available 00Z guidance continues to show an axis of moderate to heavy rain north of the low track that will pivot near the NH/ME border around sunrise and then sink south through the morning. Overall QPF amounts have not changed all that much with 1-2 across much of western Maine and central through SE NH. Higher amounts remain likely in the mountains and areas near the pivot point which looks to be Carrol County through York and Cumberland Counties. A River Flood Warning remains in effect today for the Saco River at Conway as the river is forecast to cross minor flood stage. Otherwise the area should be able to handle the incoming rainfall and the risk for additional flood warnings/advisories is low. Rain will end north to south starting mid morning and will likely be offshore this afternoon with breaks of sun all the way to the coast by this evening.

A period of strong NE winds along SW Maine into southern NH remains likely through mid morning. There has been a slight down trend in peak gusts amongst 00Z hi res guidance and a slight shift south in the peak gusts. Have kept the Wind Advisories unchanged as 40 to 45 mph winds can still cause issues with trees being leafed out. The strongest winds will peak just after sunrise and will diminish through the morning while still remain breezy into the afternoon.

KEY MESSAGE 2 DESCRIPTION...

No significant changes noted in most recent model guidance with respect to snowfall in the higher terrain as well as the potential for brief bursts of snow down to lower elevations south of the White Mountains into the foothills of far western Maine. Wet bulb zero heights dropping as low as 500 feet could allow for some flakes to mix in across central NH and interior SW Maine while any accumulations still likely remain confined to 2000 feet or higher and more likely at or above 3000 feet. Snowfall amounts of 2-4 inches at 4000 feet remain possible with up to a foot on the highest peaks of the Presidentials. Strong winds in the mountains this morning will bring wind chills into the single digits in the mountains and near freezing at lower elevations. Wind chills likely remain in the teens across the high peaks of Presendentials so winter conditions likely persist through the day.

KEY MESSAGE 3 DESCRIPTION...

A cold air mass remains in place tonight with high pressure building in from the west. This will allow temperatures to drop into the low to mid 30s across the mountains and north and the potential for frost.

KEY MESSAGE 4 DESCRIPTION...

Active pattern continues Sunday as another short wave drops south out of Canada. Sunday will start off mostly dry with a mix of sun and clouds. The approaching short wave will allow clouds to blossom with convective showers and thunderstorms developing by the afternoon. Cold air aloft and freezing levels near 6000 feet may allow for some small hail or graupel with stronger cells. It will be warmer at the surface with highs Sunday ranging from the upper 50s north to upper 60s south.

The short wave will be slow to exit Monday with additional short waves upstream. This will bring continued chances for showers through Monday. The pattern remains locked in place into the middle of next week as the incoming short waves close off into an upper that meanders near the East Coast through Wednesday. There is a signal that ridging will possibly make an appearance the second half of next week for a warming trend.

AVIATION /01Z SATURDAY THROUGH WEDNESDAY/

Through 06z Sunday...Rainfall will become heavier into southern ME and NH with cigs deteriorating to MVFR/IFR. Northeasterly wind gusts of 30-40kt are likely at MHT/PSM/PWM into daybreak today with a period of LLWS at CON and MHT as the low circulation passes closest to these terminals. Conditions gradually improve to VFR from north to south through the day, with VFR becoming likely in the afternoon. VFR then likely prevails into Saturday night.

Outlook:

Sunday: VFR conditions expected in the morning before locally MVFR and IFR conditions become possible in afternoon showers that will last into the night. An isolated thunderstorm or two can't be ruled out, but coverage will remain low.

Monday: Patchy morning fog and a few lingering showers will give away to improving conditions as cloud decks scatter out and rise above 5K. Scattered showers may bring localized restrictions.

Tuesday - Wednesday: A few afternoon showers can't be ruled out bringing tempo MVFR ceilings, but overall improving aviation conditions.

Thursday - Friday: High pressure is favored with VFR conditions and no aviation impacts expected.

MARINE

Low pressure near the NH/MA border tracks southeast over Cape Cod this morning. A corridor of strong East- Northeast winds will increase early this morning and peak after sunrise and then will diminish into the afternoon. Storm Warnings and Gale Warnings remain in effect. While winds diminish this afternoon seas will remain elevated above 5 feet into tonight.

Unsettled pattern persists Sunday into the middle of next week with multiple troughs of low pressure crossing New England while winds and seas generally stay below SCA thresholds.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Wind Advisory from 5 AM to 11 AM EDT Saturday for MEZ018-023- 024. High Surf Advisory from 8 AM to 8 PM EDT Saturday for MEZ023- 024. NH...Wind Advisory from 5 AM to 11 AM EDT Saturday for NHZ010- 012>014. High Surf Advisory from 8 AM to 8 PM EDT Saturday for NHZ014. MARINE...Gale Warning from 2 AM to 2 PM EDT Saturday for ANZ150-152-153. Small Craft Advisory from 2 AM to 11 AM EDT Saturday for ANZ151. Storm Warning from 2 AM to 11 AM EDT Saturday for ANZ154-182- 184. Gale Warning from 2 AM to 8 PM EDT Saturday for ANZ180.