textproduct: Caribou

WHAT HAS CHANGED

-Extreme Heat Watch converted to Heat Advisory for southern Piscataquis, southern Penobscot and Hancock Counties

- Reduced thunderstorm chances through tonight and Thursday due to high model uncertainty

KEY MESSAGES

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

2) Thunderstorms remain possible this evening through Saturday. A conditional threat for severe storms exists.

DISCUSSION

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

KEY MESSAGE 1 DESCRIPTION... The warmest days overall will be Thursday and Friday though. The low- level winds switch to a more westerly direction on Thursday, which will limit the marine influence and bring hot temperatures everywhere. Highs likely to be around 90 and into the mid 90s and dewpoints in the mid 60s to mid 70s. Dewpoints mix out into the low- mid 60s over the far north behind weak sfc trof. 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. Extreme Heat Watch has been converted to a Heat Advisory and will run through the day on Friday for heat indices approaching 105 degrees.

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 should be a few degrees cooler in the north, reaching the upper 80s but temperatures will remain stuck in the 90s over the Downeast and Bangor regions. Heat indices will be around 100 degrees which justifies a Heat Advisory for areas south of the Katahdin region.

Temperatures and humidity will be much lower Saturday and on a decreasing trend each day through Monday as a cooler, drier airmass works its way into the region behind a cold front departing early in the morning. Even still, heat indices will reach the upper 80s and possibly low 90s over the Bangor and Downeast regions which, while below advisory criteria, still warrants concerns over heat risk during the holiday weekend.

KEY MESSAGE 2...Thunderstorms remain possible this evening through Saturday. A conditional threat for severe storms exists.

KEY MESSAGE 2 DESCRIPTION... Guidance continues to suggest a low chance for thunderstorms overnight tonight. Earlier runs had suggested a strong complex of storms moving through but recent runs have since backed off. Ample instability exists, even into the overnight hours, but questions still remain as to if storms can even develop given the strong capping. However, with CAPE between 2000-3000 J/kg and 0-6km shear of 25-30kts, cannot rule out a severe storm producing damaging winds.

Another round of storms is possible Thursday with a similar setup to today. A conditional threat for some severe storm clusters exists given high instability up to 2000 J/kg and 25-35 kts of 0-6km shear. Guidance again shows the possibility storm clusters from Canada could move in overnight but are divided on how strong they would be or even if they would reach our area.

Storms are possible late Friday as well, but the focus for Friday appears to favor the far north as a distinct surface cold front approaching from the north. Confidence is a bit higher given the stronger forcing.

Heading into Saturday the 4th, there could be a few storms depending on where the departing cold front is which is still uncertain. The coverage of showers/storms for Saturday looks isolated at best, and it's also likely most places will stay dry. Looking fairly quiet into Sunday.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

Through 00z this evening...VFR. SW winds 5-10kts with ocnl gusts to 15kts.

Tonight...VFR Aroostook terminals through 06z, then possibly dropping to MVFR cigs after 06z. Conditions improve to VFR after sunrise. BGR dropping to MVFR vsbys in BCFG between 07-11z with BHB down to IFR from 07-12z. SW winds generally 5kts or less. LLWS possible at FVE this evening.

Thursday... Mainly VFR. W winds 5-10kts.

Thursday night...Mainly VFR. W winds 5-10kts. LLWS possible Thursday night.

Friday-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 Friday, becoming NW Saturday.

Sunday...Mainly VFR with light N winds around 5KT.

Monday...Mainly VFR, except for a chance of MVFR in an isolated afternoon shower or thunderstorm. Light and variable winds.

MARINE

Wind gusts aob 25kts through Friday morning. Seas will range from 4- 6ft between 25-60NM tonight through Thursday morning, diminishing after that through Friday morning. Visibilities will be reduced in fog tonight and again Thursday night. Winds and seas remain below SCA criteria Friday through Monday.

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. Heat Advisory from 11 AM Thursday to 7 PM EDT Friday for MEZ015-016-029-031. Air Quality Alert until 11 PM EDT this evening for MEZ029. MARINE...None.