textproduct: Caribou

WHAT HAS CHANGED

-Issued a Frost Advisory for tonight for northern zones where the frost/freeze program is now active.

-Small chance for at least areas of frost across the North Saturday night.

-Increasing confidence in widespread soaking rainfall from Sunday night into Memorial Day.

KEY MESSAGES

1) Widespread frost is expected across the North tonight and likely across the north Friday night. This may lead to damage to sensitive vegetation. There is also a low end chance for at least areas of frost across the North Saturday night.

2) Widespread soaking rain likely From Sunday night into Memorial Day. This could help aid in mitigating on going drought conditions across portions of the region.

DISCUSSION

KEY MESSAGE 1... Widespread frost is expected across the North tonight and likely across the north Friday night. This may lead to damage to sensitive vegetation. There is also a low end chance for at least areas of frost across the North Saturday night.

KEY MESSAGE 1 DESCRIPTION... The frost/freeze program has expanded north today to include all areas except far northwestern Maine. Strong cold air advection will continue today with high temperatures in the 50s across northern Maine and 60s for Bangor and points south of Baxter State Park. 1000-500mb thicknesses will fall to at or below 540dam over much of the forecast area by this evening. High pressure will be centered to the west of the area over northern NY/VT/NH, so a modest breeze will prevent decoupling for many locations. However, some of the colder valleys may decouple and fall to near freezing. The NBM 10th percentile was blended in to lower low temperatures slightly tonight, resulting in temperatures between below 36 degrees along and north of Baxter State Park. A Frost Advisory has been issued for portions of this area where the frost/freeze program has started. To the south from southern Piscataquis County into Central Penobscot and Northern Washington Counties, some areas may reach below 36 degrees as well, but coverage of these temperatures was not sufficient for an advisory for these zones based on the current forecast. Note that some zones under the frost advisory may not see frost due to very dry dew points in the lower 20s, but nonetheless some damage to sensitive plants is still possible in these locations. Slightly warmer temperatures are expected Friday as highs ranging from around 60 in the far north to the upper 60s for Bangor and Downeast Maine.

Deep layered ridging builds into the area Friday night through Saturday night. The model trend has been for a slower progression of the ridge to the east, and as a result, less cloud cover over the region Saturday night, due to the next system being farther west than previously forecast by 12z Sunday.

The resulting subsidence under the ridge will provide for minimal if any cloud cover Friday night, and quite possibly on Saturday night as well. While winds will be light Friday night they should be near calm for most of Saturday night with the surface high overhead, until light onshore return flow sets up late. Friday night should in general by as cool, if not a degree or so cooler than tonight. So there is a high likelihood for needing frost advisories over the same area as tonight. There is also a low end chance that on Friday night a frost advisory might be needed for the next row of zones to the south and that a freeze watch/warning could be needed for Northeast Aroostook.

For Saturday night, if the trend in slower progression of the deep layered ridge axis and surface high to the east holds, then lows could end up at least a category lower than currently forecast. This will allow for confidence to increase beyond the current low end chance for frost across at least portions of the North.

KEY MESSAGE 2... Widespread soaking rain likely From Sunday night into Memorial Day. This could help aid in mitigating on going drought conditions across portions of the region.

KEY MESSAGE 2 DESCRIPTION... A northern stream trough approaches from the west Sunday night, then crosses Maine on Memorial Day. This should result in a weak coastal low developing south of Long Island/Cape Cod Sunday night, then pass near/just to the south of the mouth of the Gulf of Maine Monday.

This likely will be bring a widespread soaking rain to the region from Sunday night into Memorial Day, with the potential for a widespread 1/4 to 1/2 inch of rainfall area wide. As a result expect Monday to be cooler than Sunday, with highs from the mid 50s to around 60.

AVIATION /06Z THURSDAY THROUGH MONDAY/

VFR through Friday. NW winds 10-15 kts gusting to 20-25 kts today, becoming light tonight, and increasing to 10-15 kts with gusts to 20-30 kts Friday.

Friday-Sunday...VFR. NW winds G15-20KT possible Friday.

Sunday night-Monday...MVFR or lower likely developing from SW to NE Sunday night, then IFR or lower possible Monday. LLWS possible Monday, with the best chance at southern terminals.

MARINE

Winds and seas will remain below advisory criteria through Friday. Sea surface temperatures remain in the mid 40s.

A fairly relaxed pressure gradient over the waters Friday night-Monday should limit winds over the coastal waters to 15 kt or less and seas to 4 ft or less. Over the outer waters Friday-Monday winds should be 20 kt or less and seas at or below 5 ft.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Frost Advisory from midnight tonight to 7 AM EDT Friday for MEZ002-005-006-010. MARINE...None.