textproduct: Caribou

WHAT HAS CHANGED

- Added a Small Craft Advisory for outer-waters tonight into Wednesday

- Added frost/freeze potential Friday night into Saturday morning into the key message and lowered low temperatures

KEY MESSAGES

1) Chance for thunderstorms and warm temperatures this afternoon and Wednesday afternoon.

2) Below average temperatures are expected Thursday through Saturday night. Near freezing temperatures are possible early Friday and Saturday mornings across the north, which may require actions to protect vulnerable plants.

DISCUSSION

KEY MESSAGE 1...Chance for thunderstorms and warm temperatures this afternoon and Wednesday afternoon.

KEY MESSAGE 1 DESCRIPTION...Low pressure system, mid-level shortwave, and associated warm front moves through the region this morning. Region warms ahead of warm frontal passage, raising the daytime highs to roughly upper 60s in the north, and low 80s in the Central Highlands, and mid-80s in the Bangor and Downeast region. Maine stays within the warm sector of this frontal system until cold front passes Wednesday night. As a result, daytime highs on Wednesday are near the upper-70s in the north, mid-80s in the Central Highlands and Bangor regions.

Instability rises during the afternoon on Tuesday, bringing with it the chance for some thunderstorms across the Central Highlands, and Bangor to Downeast regions. Based on sounding analysis, there is generally 1,000 2,000 J/kg of CAPE, decent shear parameters, and PWATs roughly around 1.25-2.0 inches. The main threat with these storms seems to be severe wind gusts, as low-level lapse rates are decently steep and DCAPE values around 600-800 J/kg. There is room for some hail development in some of these stronger storms. Thunderstorm chances decrease as the sun sets. Primarily random single cell storms that pop-up, so hard to pin-point an exact location of storm development. Generally, anticipating anywhere in the I-95 corridor and south has the best chances of seeing a severe thunderstorm, gusty winds, and small hail. Tornado threat is non-zero, based on favorable instability (helicity and LCL heights), but gusty winds and small hail are the primary threats.

As cold front approaches Wednesday, there is another chance for some thunderstorms. Soundings show 1000-1500 J/kg of CAPE, 500-600 J/kg of DCAPE, and decent lapse rates. Most favorable parameters for any thunderstorms, are confined to the Downeast and eastern Maine region, during the afternoon into evening period. Regardless of storm development, however, is that there is expected to be some gusty winds during the day (gusts 30mph are possible during the afternoon).

KEY MESSAGE 2...Below average temperatures are expected Thursday through Saturday night. Near freezing temperatures are possible early Friday and Saturday mornings across the north, which may require actions to protect vulnerable plants.

KEY MESSAGE 2 DESCRIPTION... The frost/freeze program will expand across much of the rest of northern and eastern Maine on Thursday except across the North Woods and Saint John Valley, where it begins on June 1. Strong cold air advection is expected Thursday behind a cold front, with 1000-500mb thicknesses dropping below 540dam for much of the northern half of the forecast area by Thursday night. With a strong jet streak overhead and moderate surface pressure gradient, decoupling is less likely except across the most sheltered valley locations. Some cloud cover is also possible late. Drier air with dew points in the mid 20s may also prevent frost formation. Even without frost, some damage to plants is possible in these conditions as 2 meter temperatures fall into the mid 30s north of Baxter State Park.

By Friday night the surface ridge of high pressure extends over the area from central Quebec. This will lead to lighter winds and a better chance of decoupling over more areas, especially the lower elevations of northern Maine. Low temperatures into early Saturday morning may be a few to several degrees lower than blended guidance as a result. Dew points will also be higher in the upper 20s and lower 30s, leading to more frost formation potential across northern zones. Below average temperatures will continue for Saturday and Saturday night, but a moderation is expected as high pressure moves over and eventually east of the area.

MARINE

Small Craft Advisory for outer waters in effect for tonight into Wednesday, with seas around 5ft and some wind gusts to 25kts possible. Chance for some marine fog this morning. Chance for passing rain today, and chance for rain and thunderstorms on Wednesday. SW winds today into Wednesday.

Winds and seas are likely to remain below SCA criteria Wednesday night through early next week.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Air Quality Alert from 10 AM this morning to 10 PM EDT this evening for MEZ029-030. MARINE...Small Craft Advisory from 8 PM this evening to 8 PM EDT Wednesday for ANZ050-051.