textproduct: Caribou

WHAT HAS CHANGED

-Issued Heat Advisory for today for Central Penobscot County for heat indices in the upper 90s.

KEY MESSAGES

1) Very warm to hot temperatures and high humidity Wednesday through Friday will lead to hazardous heat, with little reprieve each night.

2) Thunderstorms remain possible this evening through Saturday. Storms could be on the stronger side.

DISCUSSION

KEY MESSAGE 1...Very warm to hot temperatures and high humidity Wednesday through Friday will lead to hazardous heat, with little reprieve each night.

KEY MESSAGE 1 DESCRIPTION... A bit warmer today, and noticeably more humid as well. The warmest days overall will be Thursday and Friday though. That said, today will be warm enough to be warrant a heat advisory from Bangor to Dover-Foxcroft, where highs approaching 90 with oppressive dewpoints in the low to mid 70s will lead to heat indices 95-100F. Very warm elsewhere today, but probably shy of advisory criteria. With an onshore breeze, the Downeast coast will be the most comfortable with highs generally in the 70s.

The low-level winds switch to a more westerly direction on Thursday, which will limit the marine influence and bring hot temperatures everywhere. We are looking at highs from the upper 80s to mid 90s and dewpoints in the mid 60s to mid 70s. Heat indices will be 90-105F, lowest in the north and warmest from Dover-Foxcroft south to the general Bangor region and to Bar Harbor. We are leaving the extreme heat watch in effect and not converting to warning yet, as just not enough confidence in 105F (warning criteria) heat indices.

Extremely mild Thursday night, with lows in the upper 60s to mid 70s. Those without air conditioning will really be feeling impacts at this point.

Friday looks a touch cooler in the north with slightly drier air (though it will still be hot). Meanwhile, Downeast and the coast will be just as hot as the slightly cooler/drier airmass moving in from the north will not be there quite yet. Generally mid 90s for highs Bangor, Downeast, and the coast, with heat indices around 100F.

For the holiday weekend and into early next week, temperatures will be a touch more tolerable, with mainly 80s for highs and 55 to 65 for lows. So still warmer than normal, but not as bad as Wednesday to Friday.

Also of note today is an air quality alert for coastal Hancock for ground level ozone, with the alert highlighting air quality that is unhealthy for sensitive groups. In addition to the ground-level ozone, skies remain rather smoky over the area, with air quality in the moderate category due to the smoke/particulate matter. Skies will remain somewhat smoky the next few days, with a plethora of fires/smoke sources upwind of us from Quebec to the Alberta and south through the Rockies of the Western US.

KEY MESSAGE 2...Thunderstorms remain possible Wednesday through Saturday. Storms could be on the stronger side.

KEY MESSAGE 2 DESCRIPTION... The region remains between a strong upper level high anchored over the Mid Atlantic states and an upper level low over Quebec Wednesday-Friday. Guidance suggests that thunderstorm chances for Wednesday afternoon are diminishing, though some models try to bring a complex of thunderstorms Wednesday afternoon/evening. Plenty of instability exists on Wednesday but with capping inversion aloft and little forcing, thinking that anything that develops should be isolated. With CAPE between 2000-3000 J/kg and 0-6km shear of 25-35kts, cannot rule out a severe storm producing damaging winds.

Another round of storms is possible Thursday late afternoon and evening with a similar pattern to Wednesday, though again guidance is all over the place with the location or even the existence of a complex of storms. Could be strong to severe storms, or could be nothing. Our confidence is really low.

Storms are possible late Friday as well, but the focus for Friday appears to favor the far north as there is a more distinct surface cold front approaching from the north.

Heading into Saturday the 4th, there could be a few storms, but the existence of any storms depends on the progress of a weak cold front through the area. The coverage of showers/storms for Saturday looks isolated to scattered at best, and it's also possible most places will stay dry. Looking fairly quiet into Sunday.

AVIATION /13Z WEDNESDAY THROUGH SUNDAY/

Today...After early MVFR at Downeast terminals, all sites will be VFR today. There remains a very small chance of a thunderstorm but have not included in TAFs. SW winds 5-10kts.

Tonight...Mainly VFR. MVFR/IFR possible at BGR and BHB late. LLWS possible at FVE. WSW winds 5-10kts.

Thursday-Saturday: Mainly VFR, except for a chance of MVFR or lower in any fog late at night/early in the morning and a brief chance for MVFR in any thunderstorms. WSW-W winds G15-20KT possible during the day Thursday to Saturday. LLWS possible Thursday night.

Sunday...Mainly VFR with light winds.

MARINE

Southwest winds increase to around 25kts from 25-60NM tonight with seas also increasing over this area to 5ft. Intracoastal and waters out to 25NM will remain below small craft levels through the period. Some showers are possible in the afternoons/evenings. Humid airmass will keep visibilities reduced in fog Wednesday night, though conditions appear to improve Thursday into Friday.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Heat Advisory from 11 AM to 8 PM EDT Thursday for MEZ005-006. Heat Advisory until 8 PM EDT this evening for MEZ011-015-016- 031. Heat Advisory from 11 AM Thursday to 8 PM EDT Friday for MEZ011-017-030-032. Extreme Heat Watch from Thursday morning through Thursday evening for MEZ015-016-029-031. Air Quality Alert until 11 PM EDT this evening for MEZ029. MARINE...None.