textproduct: Caribou

WHAT HAS CHANGED

- Updated aviation discussion for 12z TAFs.

- Added isolated thunderstorms to the eastern St. John Valley with a weak 500mb shortwave.

- Lowered high temps by 1-2 degrees along the Downeast coast as the increasing seabreeze develops this afternoon.

- Added patchy to areas of dense fog tonight over the Coastal Waters into Downeast Maine coast.

KEY MESSAGES

1) Very warm and increasingly humid conditions will persist through late week, with the highest temperatures focused inland.

2) Shower chances return this evening and persist into the weekend.

DISCUSSION

KEY MESSAGE 1...Very warm and increasingly humid conditions will persist through late week, with the highest temperatures focused inland.

KEY MESSAGE 1 DESCRIPTION... The overall 500mb ridging remains over the area with very warm 850mb temperatures into late week. The ridge becomes contaminated allowing for the return of clouds and showers but the airmass remains very warm. Although not record breaking it will be uncomfortable for some with minor to moderate heat risk mainly impacting the most vulnerable groups. Today expecting highs well into the 80s with upper 80s from the Bangor Region into Southern Aroostook County. A increasing seabreeze today will cool the Downeast coast in the late morning into afternoon and the seabreeze boundary will push to Bangor by late afternoon. The seabreeze will be some nice relief to those needing to be outdoors. Dew points remain in the upper 50s to near 60F so once again its a dry day and not humid.

Thursday the focus of the hot temperatures shifts north into Northern Maine where highs will top out in the upper 80s to around 90F. Expecting mid to upper 70s Downeast thanks to a wind off the Gulf of Maine and Bay of Fundy with low 80s around Bangor to Topsfield. A touch of the muggies on Thursday with dew points climbing into the low to mid 60s so it will feel humid. Friday once again will be into the mid to upper 80s especially across Northern Maine and the Central Highlands. 70s Downeast with low 80s in the Bangor Region to St. Croix region. Dew points will again be in the 60-65F range so slightly humid conditions. Both Thursday and Friday will feature minor to moderate heat risk away inland mainly impact the most vulnerable groups.

KEY MESSAGE 2...Shower chances return this evening and persist into the weekend.

KEY MESSAGE 2 DESCRIPTION... This afternoon a weak 500mb shortwave will cross the Gaspe Peninsula and create some showers and perhaps a thunderstorm over the Notre Dame Mountains just north of the St. John Valley. A few of these showers may skim the area into the St. John Valley especially the eastern half from Frenchville eastward. Latest RRFS, HRRR, NAM 3km, FV3 and Canadian RDPS all suggesting this with perhaps 100-200j/kg of SBCAPE. The probabilities are low but not zero so went with 15-20 percent POPs and isolated thunder this afternoon till sunset. Otherwise this evening shower chances return for southern portions of the CWA from the Central Highlands south to coastal Downeast this evening. We aren't expecting anything too significant, with just a chance of showers. With the airmass beginning to moisten with increasing onshore flow, we should see a marine layer with areas of fog setting up starting Wednesday night for Downeast up to around Lincoln area.

Shortwave moves over the region Thursday, bringing some moisture and instability into the region. Decent low-level lapse rates, but southeast flow provides a marine layer over eastern Maine, stabilizing the surface. There is some mid-level instability, but mid-level lapse rates are very poor. Without strong forcing, not expecting too much in terms of storm development. Could be a few thunderstorms in the west, such as northern Somerset and western Piscataquis, since the marine layer will be confined to the windward side of the Longfellow Mountains.

Weak ridging takes over on Friday with some increasing instability in the afternoon. Expect some afternoon showers with possible thunderstorms. By Friday night, the cold front boundary will move from W to E. There is low to moderate confidence in thunderstorm development during the night due to frontal lifting, some elevated CAPE, and steep low level lapse rate. The lose of diurnal heating might decrease the chances of thunderstorms, but cannot rule it out. Saturday could see a higher possibility for afternoon thunderstorms.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Today...VFR with VRB winds. BHB and BGR a S-SSW wind develops this afternoon as a seabreeze. Generally 5-10kt with a few gusts to 15kt.

Tonight...VFR with BKN cigs at FVE, CAR, PQI and HUL. MVFR becoming IFR for BGR and BHB. -SHRA and BR/FG developing. LIFR vsby is possible.

Thursday...Any IFR/LIFR recovering to MVFR/VFR by afternoon for BHB/BGR with VFR at FVE, CAR, PQI and HUL. Light and variable winds expected.

Thursday Night...VFR at northern terminals. MVFR or lower possible early in the morning and late at night at southern terminals. Light and variable winds.

Friday...Mainly VFR, except for a brief period of MVFR is possible with any showers at FVE/CAR/PQI. SSE winds 5-10 kts.

Friday Night-Saturday...MVFR/IFR in rain showers. Slight chance for thunder at northern terminals. SE-S winds 5-10 kts shifting SW-W during the day.

Saturday Night-Sunday...VFR, becoming MVFR/IFR Sunday. SW-W winds 5-15 kts.

MARINE

A light to moderate pressure gradient will limit winds to 15 kt or less and seas to 3 ft or less over the coastal waters through Saturday. Winds tick up 15-20kt on Sunday. Over the outer waters (25-60nm) expecting winds generally less than 20 kt and seas to 5 ft or less through Sunday. Over the outer waters wind gusts may reach 25kt Sunday night. Fog is possible starting tonight into Thursday afternoon. Another round of fog possible Thursday night/early Friday morning. There is the potential for some showers over the waters tonight into Thursday then another round Friday night into Saturday night.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...None.