802 FXUS61 KCAR 051834 AFDCARArea Forecast Discussion National Weather Service Caribou ME 234 PM EDT Fri Sep 5 2025
.SYNOPSIS... A cold front crosses the region Saturday, stalls just offshore Saturday night and Sunday, then moves southeast as high pressure builds in Sunday night through Tuesday.
&&
.NEAR TERM /THROUGH SATURDAY NIGHT/... Light showers will continue across the forecast area today as a shortwave trough moves eastward. Although clouds are scattering out across the west behind the trough, southerly flow will keep pushing in low level moisture, and low clouds and fog will form again tonight, with fog most likely in the marine layer south of I-95.
On Saturday, the weather becomes more active with the approach of a cold front. A low level jet will increase ahead of the front, bringing increasingly gusty southerly winds through Saturday morning. Winds may gust up to 25 mph, particularly up the Penobscot river corridor, which will be aligned with the main wind direction. Rain will develop from the southwest Saturday afternoon, becoming a more dynamic system as it moves eastward. This is where the forecast becomes most challenging for tomorrow. CAMs are all indicating an enhanced area of precip along the front, but where exactly that band ends up is a little uncertain. There is high confidence that there will be a narrow corridor of QPF amounts greater than 1 inch. Right now that corridor seems to be located along the Central Highlands into southeast Aroostook County, but could shift either eastward or westward depending on the orientation of the low.
The other challenging feature with this system is the instability and how it will manifest along this front. CAPE values are actually somewhat low, and soundings are indicating a pretty good cap in the low levels, in particular where the marine layer has managed to sneak in. That being said, there is an incredible amount of shear, around 50 to 60 and in some places close to 70 knots of bulk shear with the strengthening low level jet. This would definitely be conducive for putting spin on anything that forms along the front. The question is whether storms will be able to maximize instability to overcome that cap and take advantage of the shear. SPC has extended the marginal risk for severe storms to just north of Bangor, showing a 5% risk for gusty winds. This definitely seems more likely than any hail, with high freezing levels and a challenging environment for mid-level growth.
Another concern is potential training with any thunderstorm development. This seems a little more likely with high PWATs and a storm development vector parallel with the main front. The one fortunate thing is that FFG is very high right now with the recent dry spell, so even with the factors aligned, we are not likely to get enough precip in any one area to cause flash flooding.
Thunderstorms will abate in the early evening on Saturday, but rain will continue through the night, progressing eastward ahead of the front. Storm total rain fall will be the heaviest in a swath from Greenville to Houlton, around 1.25".
&&
.SHORT TERM /SUNDAY THROUGH MONDAY/... Sunday...A weak upper level shortwave rides NE along the stalled front just offshore, potentially bringing another shot of rain mainly in the morning and mainly Downeast. Some uncertainty as to how far north the rain gets, and going with 60-80 percent PoPs Downeast, decreasing to 20 percent or less in the far N/NW. Probably another tenth to quarter inch of rain mainly Downeast. Cooler than Saturday with highs in the 60s.
Sunday Night...Decreasing clouds and dry. Tentatively left fog out of the forecast because there`s still somewhat of a pressure gradient over the area and only expect minor decoupling. Lows in the 40s to low 50s.
Monday...Upper trough axis moves through from west to east, but upper trough is fairly flat and we are at the southern end of the trough axis, so only expect enough instability/moisture for isolated showers mainly in the north. A bit cooler than average with highs in the low to mid 60s north and around 70 Downeast.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Monday night has a potential for frost, especially in the northern 2/3 of the area, as surface high pressure settles in. Went a bit cooler than guidance thanks to fairly high confidence in high pressure position with good decoupling. Also put in patchy valley fog. From Tuesday into Wednesday, high pressure moves SE of the area with a warming trend and temperatures returning back to around or a bit above average on Wednesday. Probably dry through Wednesday. Next cold front looks on track for Wednesday night or Thursday, but most models have minimal rain with this front as it doesn`t seem to tap into much if any moisture from the south, and going for just 10-30 PoPs. Cool air returns behind the front for Friday.
&&
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... NEAR TERM: IFR/occasional LIFR tonight as low clouds and fog form in the warm sector of the cold front. LLWS forming overnight as the atmosphere decouples and the LLJ strengthens. As the wind mixes down on Saturday, LLWS will weaken but surface winds will increase, up to 25 kts at BHB and BGR. Clouds will scatter out during the day, but by late afternoon on Saturday, cigs and vis will lower to IFR/LIFR in RA. Possible TS at BGR Saturday evening. Rain will continue overnight.
SHORT TERM: Sunday...VFR north, and MVFR or VFR Downeast with possible light rain and low ceilings in the morning, with any MVFR improving to VFR by 21z as the system exits to the east. Variable wind less than 10 kts.
Sunday night and Monday...VFR. W wind 5 kts Sunday night, increasing to 10 kts during the day Monday.
Monday night...VFR except IFR possible in patchy valley fog late at night. Light W wind becoming calm.
Tuesday...VFR. Light SW winds.
Wednesday...Mainly VFR, though MVFR/IFR possible near the coast early morning. S wind around 10 kts.
&&
.MARINE... NEAR TERM: Winds will increase to 25 kts beginning this evening. They will taper off overnight, but return on Saturday morning gusting as high as 30 kts. Seas will remain 3 to 5 feet through this period.
SHORT TERM: Conditions should remain below small craft levels Sunday to Wednesday. Seas could reach 4 ft during the day Monday, but chance of getting to 5 feet or greater (small craft advisory levels) is less than 20 percent.
&&
.CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Small Craft Advisory from 8 PM this evening to 11 PM EDT Saturday for ANZ050-051.
&&
$$
Near Term...LF Short Term...Foisy Long Term...Foisy Aviation...LF/Foisy Marine...LF/Foisy
NWS car Office Area Forecast Discussion