textproduct: Gray - Portland

WHAT HAS CHANGED

No significant changes to forecast thinking early this Wednesday morning.

KEY MESSAGES

1. A brief warm up and a few showers are possible on Thursday ahead of a frontal passage that will bring seasonable temperatures back to end the work week.

2. An area of low pressure may bring increased rain chances early next week following a dry and mild weekend.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... After a cold morning temperatures will moderate today, as 850 temperatures climb to +6 to +9 C ahead of a trough. With plenty of sun south of the mountains temperatures should be able to fully mix into the low to mid 60s. Clouds move in early over the mountains so expect temperatures there to top out in the 50s for the most part. These warmer 850 temperatures are going to make for a comparatively warmer night with temperatures only falling into the 40s area wide. A few showers are possible tonight mainly over the mountains as the front approaches the area.

The 07/00Z CAMs suggest the more organized band of showers at the New Hampshire boarder in the early hours of Thursday morning, moving into western Maine around day break. There is decent agreement amongst the CAMs that these produce a general tenth to a quarter of an inch for most of the area, with southern New Hampshire being the most likely to miss out or only get a few hundredths. There is also some suggestion that a few locations may see greater than a quarter of an inch if they get under a more robust shower. Dry air quickly fills in behind the front so shower activity looks to become greatly reduced by the afternoon hours with areas south of the mountains breaking out into full sun. Temperatures here should be able to climb into the upper 60s and low 70s. In the north where it will stay a bit cloudier and cooler air will work in first, temperatures likely only top out in the low to mid-60s. Continued troughing aloft and northwest flow will also provide the forcing to sustain showers in the mountains through Friday night. Temperatures Thursday night will only be slightly cooler than tonight.

Troughing slowly exits the area on Friday, but areas south of the mountains should remain dry and mostly sunny. 850 mb temperatures drop back down to -1 to +3 C, which would suggest highs in the low to mid-60s. In the mountains where clouds and showers linger, expect to top out in the 50s. As high pressure begins to build into the region Friday night, we could see an opportunity for radiational cooling once again pushing lows into the 30s for most of the area.

KEY MESSAGE 2 DESCRIPTION...

High pressure will allow for a dry and relatively mild weekend with daytime highs on Saturday into the lower to middle 60s south of the mountains before potentially reaching the lower 70s on Sunday as flow becomes southwesterly. Forecast uncertainty then increases towards early next week as an approaching frontal boundary and area of low pressure approaches from the south and west. There is generally moderate confidence that rain will occur sometime between the Sunday night to Monday night timeframe, but potential rainfall amounts are of much lower confidence. For now, the areas most likely to receive beneficial rainfall for the ongoing drought conditions look to be southern and coastal communities but a lot can change given we are still several days out. After a mild start to the week, cooler temperatures are likely to arrive by late week.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

Through 06Z Thursday... Some patchy valley fog is possible at LEB and HIE this morning. Otherwise, VFR prevails through today at most TAF sites, with MVFR ceilings possible at HIE and other mountain terminals ahead of a frontal passage tonight. Southerly wind gusts 15-20 kt are possible during the day. Showers are possible tonight in the mountains as well.

Outlook: Thursday: MVFR possible with showers through the morning. Conditions quickly improve to VFR south of the mountains for the afternoon, whereas MVFR may linger in the mountains.

Friday: VFR conditions expected outside of the mountains, MVFR may linger in the mountains

Saturday-Sunday: VFR conditions likely with WSW flow prevailing.

MARINE

Generally southerly winds will prevail through tonight, until a frontal passage turns them more westerly on Thursday. This frontal passage may also briefly bring wind gusts near 25 kt and wave heights near 5 ft, but otherwise sub- SCA conditions are expected through Friday as high pressure will then begin building over the waters.

Outlook: Southwesterly winds may gust up to around 30 kts late Sunday into Sunday night with seas building to 4-7 ft, highest outside of the bays.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Freeze Warning until 8 AM EDT this morning for MEZ019-020. Frost Advisory until 8 AM EDT this morning for MEZ021>028. NH...Frost Advisory until 8 AM EDT this morning for NHZ010-012-013. MARINE...Small Craft Advisory from 6 PM this evening to 8 PM EDT Thursday for ANZ150>152-154. Small Craft Advisory from 6 PM this evening to 2 PM EDT Thursday for ANZ153.