NEAR TERM /THROUGH MONDAY/
10pm Update...
Only very minor change to lower temperatures in a few spots that are already near forecast lows, specifically southern Washington County and portions of the North Woods. Some cirrus spilling into Northern Maine from the north. Cirrus isn't too thick and it shouldn't impact temperatures too much. Airmass is much warmer in general, and lows tonight will be a good amount warmer than last night. There is a fair amount of smoke in the atmosphere, but it is mostly well above the surface and not impacting air quality much.

Previous Discussion...
The center of a 590dam high at 500mb will drift over Southern New England tonight as a 1028mb surface high drifts over Georges Bank in the Gulf of Maine. Expecting winds to go calm tonight, nearly clear skies again except some high clouds across the north and dry conditions means decoupling expected. Steep inversion will allow for river valley fog once again, perhaps some low stratus along the shoreline. Temperatures fall back into the low to mid 50s. Warmer 850mb temps of +19C to +20C spill over the north side of this high. Modeled soundings are showing 12z 850mb temps at CAR around +18C. The daily record for soundings tomorrow is 15.4C so likely beating that record. High pressure barely moves tomorrow with mainly sunny skies expected with perhaps some occasional cirrus. Modeled soundings showing decent mixing tomorrow up to 800mb with 15-20kt winds so expecting those W-SW winds tomorrow at times gusty. 850mb temps warming into the +19C to +21C range will make for a very warm September day. High temperatures top out in the low to mid 80s across much of the area which may approach a few daily records.
The core of the warmest temps will be St. John Valley to Baxter to Bangor including Caribou, Houlton and the Route 9 corridor to Washington County. Upper 70s to low 80s along the Downeast coast with slight wind off the water and around 80F in the North Woods. This is anywhere from 10-15 degrees above normal for September 16th. One thing to note, minimum RHs will drop into the 45-50% range tomorrow afternoon. Persistent long term dry conditions combined with warm temperatures, breezy winds and relatively lower RHs values will need to watch for maybe some fire wx concerns.

SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/
A ridge of high pressure remains positioned over northern New England through the middle of the week. Heading into the day on Tuesday, an occluded front will begin to sag southwards towards the St. John Valley. With a 1024 mb high sitting across the Gulf of Maine, however, the weakening front will not be able to overcome this blocking pattern, and should wash out north of the forecast area through the middle of the week. The proximity of this feature could lead to an increase in cloud cover though. At the same time, a cut-off low will approach from along the Mid- Atlantic coast, but once again the ridge of high pressure is likely to be too strong for the low to push into our forecast area. Instead, an increase in cloud cover is likely across the Downeast region on Wednesday with this low approach.

With return flow wrapping around the backside of the high pressure through the middle of the week, warm temperatures will remain in the area, with highs in the low to mid 80s both Tuesday and Wednesday. At night, surface decoupling and mostly clear skies will allow for temperatures to drop into the mid to upper 50s.

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
A backdoor front may retreat through the area from the northeast late Thursday through the day on Friday. This front is fueled by Canadian Maritime moisture, which could bring isolated to scattered rain showers into the forecast area as the boundary passes through. The change in airmass will allow for temperatures to fall back into a more seasonal range by this weekend. Behind the backdoor front, high pressure returns to the area, with dry conditions persisting through the upcoming weekend.

AVIATION /02Z MONDAY THROUGH FRIDAY/
NEAR TERM: VFR. Between 09-12z BCFG may cause FEW001 cigs. Added LLWS to FVE, CAR, and PQI for winds to 25 kt around 1,000 ft above ground from about 7-13z. Winds at the surface, however, will only be S/SW 5 kts or less tonight thanks to a strong inversion. Tomorrow VFR. W-SW winds 5-15kt a few afternoon gusts up to 20kt.

SHORT TERM: Mon night - Tues night...VFR. Patchy valley fog each morning.
SW winds 5 to 10 kts gusting to 20 kts Tues afternoon, shifting W Tues night.

Wed - Wed night...VFR. Winds light and variable.

Thurs - Fri...Mainly VFR. Possible MVFR showers for northern terminals. NE winds around 5 kts each afternoon, becoming light overnight.

MARINE
NEAR TERM: Winds/seas below SCA conditions through tomorrow evening. SW winds expected and may gust up to 20kt tomorrow over the outer Coastal Waters. Seas 1-2ft tonight and 2-3ft tomorrow.
Sea surface water temperatures are generally 54-58F from the Downeast coast out 25nm and east to the Hague Line with coldest water temperatures in Passamaquoddy Bay and near the Bay of Fundy.

SHORT TERM: Winds and seas remain below small craft levels through the middle of the week. Seas from 1-3 feet through Thursday before increasing Friday into Saturday to around 5 feet.

CLIMATE
Near record high temperatures possible this week. Although some of the records look to be well out of reach there are a few records that could potentially be tied or broken. Here are the record highs and forecast highs for Monday through Wednesday September 16th-18th.

9/16: Caribou: 88F, 1939 (forecast high 84F)
Bangor: 97F, 1939 (forecast high 84F)
Millinocket: 93F, 1939 (forecast high 84F)
Houlton: 82F, 2017 (forecast high 84F)

9/17: Caribou: 88F, 2018 (forecast high 85F)
Bangor: 88F, 1991 (forecast high 85F)
Millinocket: 90F, 1939 (forecast high 85F)
Houlton: 85F, 2018 (forecast high 84F)

9/18: Caribou: 86F, 1942 (forecast high 81F)
Bangor: 87F, 1992 (forecast high 82F)
Millinocket: 87F, 1991 (forecast high 82F)
Houlton: 82F, 2015 (forecast high 82F)

CAR WATCHES/WARNINGS/ADVISORIES
ME...None.
MARINE...None.