textproduct: Caribou

WHAT HAS CHANGED

- Tuesday: New models data has shown a significant decrease in shower and thunderstorms chances for Tuesday afternoon. Upper air model soundings indicate very dry air at the surface and up to around 750mb. Instability is still present on Tuesday, so cannot rule out isolated showers. However, still uncertain if any showers will reach the ground.

KEY MESSAGES

1) Cool temperatures will continue through the weekend, with areas of frost developing over much of the area tonight. Precautions should be taken to protect sensitive vegetation.

2) Thunderstorms possible in the afternoon Sunday and Monday.

3) Much warmer Wednesday through Friday, with finally two dry days in a row Wednesday and Thursday.

DISCUSSION

KEY MESSAGE 1...Cool temperatures will continue through the weekend, with areas of frost developing over much of the area tonight. Precautions should be taken to protect sensitive vegetation.

KEY MESSAGE 1 DESCRIPTION... As an upper level trough persists over the area, maintaining the cool air mass in place. Skies continue to clear through the late afternoon and early evening hours, with decreasing winds becoming calm overnight. This will generate ideal radiational cooling conditions that will allow for a strong surface inversion to form and temperatures to quickly drop overnight.

Temperatures tonight could fall into the low to mid 30s throughout the forecast area, with typical colder valleys potentially falling to around 30 or even below 30 into the North Woods. A freeze warning is in place for northeast Aroostook county as many of the colder valleys could drop below freezing overnight. Sub-freezing temperatures are also briefly possible into northern Penobscot and southern Aroostook counties, especially in sheltered river valleys.

The frost advisory currently extends through southern Piscataquis county and central Penobscot county, though if skies clear out more quickly in the Bangor and Downeast regions, patchy frost could develop into these regions as well.

A frost threat could return Sunday night as well, but will be much more limited in areal extent, possibly just across the north should cloud cover remain limited in this area.

KEY MESSAGE 2...Thunderstorms possible in the afternoon Sunday and Monday.

KEY MESSAGE 2 DESCRIPTION... Sunday: Steep lapse rates may support thunderstorm development Sunday afternoon, though with limited CAPE and a low track that is west of the forecast area, the threat is limited to the Central Highlands for a few hours Sunday afternoon.

Monday: As the secondary trof rotates around the low, vort max energy will move over the region. Thunderstorms will be possible Monday afternoon. The main threat Monday is over Northern Maine (mainly north of Millinocket) where there is a chance of showers and 15 percent chance of thunderstorms. Strong/severe storms are not expected.

KEY MESSAGE 3...Much warmer Wednesday through Friday, with finally two dry days in a row Wednesday and Thursday.

KEY MESSAGE 3 DESCRIPTION... Per the previous discussion: High pressure builds in Wednesday and Thursday, with means finally some dry days for the vast majority of the area. Temperatures also rebound to around 70 on Wednesday and then potentially around 80 Thursday/Friday. We are fairly confident in above average temperatures Thursday/Friday, but just how much above average is the question. Highs of 75-85 seem like a reasonable expectation. Shower/storm chances could begin to return Friday, though plenty of uncertainty that far out.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Tonight - Sunday...VFR conditions across all terminals. Winds light and variable.

Sunday night...VFR across northern terminals, with trends to MVFR and IFR possible at GNR into BGR and BHB as rain showers move through. Winds light and variable.

Monday-Tuesday...Mainly VFR, with MVFR possible at times due to afternoon showers and storms possible Monday/Tuesday. Light and variable winds, then N wind 5-10 kts on Tue.

Wednesday-Thursday...Mainly VFR. Light and variable winds, then WSW winds 5-10 kts Thu.

MARINE

Conditions remain sub advisory tonight through through Sunday night, with offshore winds becoming light and seas only around 2 to 3 ft.

Quiet conditions on the waters Monday through Thursday with seas generally 3 ft or less and winds below small craft criteria.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Freeze Warning from 10 PM this evening to 7 AM EDT Sunday for MEZ002. Frost Advisory from 10 PM this evening to 7 AM EDT Sunday for MEZ005-006-010-011-031. MARINE...Gale Warning until 8 PM EDT this evening for ANZ080-081.