textproduct: Gray - Portland

WHAT HAS CHANGED

Small Craft Advisories have been extended/issued for portions of the waters as well as a Gale Warning for the outer waters for gusty NW through tonight into Thursday morning.

KEY MESSAGES

1. High pressure builds in tonight and Thursday for mostly dry weather.

2. Low pressure crosses Friday through Friday night bringing beneficial rainfall.

3. Seasonably cold and blustery conditions arrive for the weekend, along with the chance for a few downed branches. Wintry conditions hazardous to hikers are expected through the higher terrain.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

High pressure centered over the Midwest will slide east tonight and become centered overhead during the day Thursday. Low pressure strengthening in the Canadian Maritimes will tighten the gradient over the area leading to breezy NW this evening into Thursday morning. As the high crests over the area Thursday, winds will relax and become light and variable Thursday afternoon. Skies will be partly to mostly sunny with highs ranging from the upper 40s north to near 60F south.

KEY MESSAGE 2 DESCRIPTION...

High pressure retreats to the east Thursday night with clouds increasing as the next low pressure system approaches from the Great Lakes. This low will continue to strengthen as it tracks towards the St Lawrence Valley Friday and into the Canadian Maritimes Saturday night. Precipitation will break out from west to east early Friday morning with widespread rainfall expected through out the day Friday. Thermal profiles may be cold enough for brief period of wintry mix at the highest elevations Friday morning. Latest forecast rainfall amounts will range from 0.5 inches south to 0.75 inches across the north with locally higher amounts in the mountains. Steady precipitation will transition to showers Friday night with cold air moving in allowing for a transition to snow showers in the mountains. As temperatures continue to cool into Saturday morning, snow will likely make it to the valley floors across the north.

KEY MESSAGE 3 DESCRIPTION...

The low pressure that passes through late this week deepens across the Canadian Maritimes by Saturday. As high pressure builds in from the west, a strong pressure gradient brings gusty conditions, as well as a seasonably cold airmass for mid October.

Wind gusts on Saturday will mainly be around 30-35 mph, with some gusts to around 40 mph. This will bring the chance for a few downed branches and isolated power outages as one of the first windier days of the season knocks off some weaker branches. Winds ease Saturday night, with lighter winds expected for Sunday.

Temperatures will be seasonably cold, especially for a day with a mix of sun and clouds. Highs mainly hold in the 30s across the north on Saturday, while the coastline struggles to reach 50 degrees. Scattered upslope snow showers are expected across the higher terrain. Rising modeled froude numbers indicate that some flurries and snow showers will make progress downwind of the mountains Saturday afternoon, only gradually drying up as they move southeastward. Lows will then be cold Saturday night, with widespread temperatures in the 20s, and below freezing temperatures expected all the way to the coastline.

Across the higher terrain, wintertime conditions are expected. Accumulating snowfall across the upslope terrain, temperatures in the teens, and wind chills well below zero are all expected. Wind gusts over 100 mph are expected on Mount Washington on Saturday. Any hikers or those above 2500ft should plan for wintertime conditions this weekend.

By Sunday, winds ease noticeably, and temperatures begin to rebound by a few degrees. Highs are expected to range from the low 40s across the north, to mid 50s along the coast by Sunday. This moderating trend continues into early next week, with high rebounding into the 60s in most areas for Monday and Tuesday. High pressure remains in control of the weather pattern for at least early to midweek next week, but models are indicating that low pressure likely begins to organize to our south during this timeframe, and will be worth monitoring through the forecast period.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

Through Thursday...Mainly VFR south of the mountains tonight with MVFR cigs likely along and north of the mountains including HIE. VFR is expected across the entire area Thursday, although some NW gusts 15-20 kts will be possible through the morning

Outlook...

Thursday night: Clouds thicken and lower with cigs approaching MVFR threshold Friday morning.

Friday-Friday night: Widespread IFR and rain are likely. Rain should taper off Friday night with improvement to MVFR or VFR. HIE may see lingering rain showers switch to snow showers with IFR or MVFR there.

Saturday: Rain and snow showers likely at HIE to bring MVFR/IFR. Elsewhere VFR, although it's possible a few showers make it downwind of the mountains. It also looks breezy with west to northwest winds of 30 kts possible.

Sunday-Monday: Mainly VFR.

MARINE

A cold front crossing the waters will freshen NW tonight with SCA conditions expected into Thursday morning. NW winds will gust to Gale force over the outer waters offshore the Mid Coast where a Gale Warning is in effect. High pressure builds in Thursday allowing for winds and seas to drop below SCA thresholds into Thursday night.

Low pressure approaches from the west early Friday and passes north of the waters Friday night. It will likely feature onshore SCA winds Friday, before turning NW Friday night through Saturday with gusts to Gale force possible. High pressure then builds in Sunday to Monday.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...Small Craft Advisory until 10 AM EDT Thursday for ANZ150-152. Small Craft Advisory from 3 AM to 10 AM EDT Thursday for ANZ151-154. Gale Warning from 3 AM to 10 AM EDT Thursday for ANZ180.