textproduct: Caribou

WHAT HAS CHANGED

-Continued to lower dewpoints for today

-Made a general area of thunder on Tuesday. Confidence in some storm development on Tuesday increases.

-Added thunderstorm potential for Downeast areas Wednesday

-Added key message for frost/freeze potential early Friday morning and below average temperatures

-Removed key message for rain Sunday as chances have decreased and the overall impact is low if it occurs

KEY MESSAGES

1) Dry and breezy conditions today, potentially leading to some fire weather concerns.

2) Chance for thunderstorms and warm temperatures Tuesday and Wednesday afternoon. A few stronger storms are possible.

3) Below average temperatures are expected Thursday and Thursday Night. Near freezing temperatures are possible early Friday morning across the north, which may require actions to protect vulnerable plants.

DISCUSSION

KEY MESSAGE 1...Dry and breezy conditions today, potentially leading to some fire concerns.

KEY MESSAGE 1 DESCRIPTION... Period of high pressure today, as a warm front slowly begins to approach from the southwest. Front to the southwest brings in a few clouds, helping to keep daytime high temperatures around the mid-60s in northern and eastern Maine. Very dry mid-level moisture based on sounding analysis, with daytime minimum RHs expected to be upper 20s/low 30s in the northwest, and low 20s in northern and eastern Maine. Winds shift to the southwest, with some breezy conditions during the early evening, predominantly Downeast.

KEY MESSAGE 2...Chance for thunderstorms and warm temperatures Tuesday and Wednesday afternoon. A few stronger storms are possible.

KEY MESSAGE 2 DESCRIPTION... Ridging over the central Atlantic moves east Monday night, as a low pressure system and associated warm front moves into the region by Tuesday morning. A mid-level shortwave moves through during the afternoon into the evening. The region warms up as a warm front passes, raising daytime highs to roughly low-70s up north, low-80s in the Central Highlands, and mid-80s in the Bangor and Downeast region. Current uncertainty resides in the timing of the frontal system, as this will heavily impact daytime temperatures and precipitation timing.

Instability rises during the afternoon, bringing with it the chance for some thunderstorms across the Central Highlands, Bangor to Downeast region. On Tuesday, potential for roughly 1500 J/kg of CAPE, decent shear parameters, and PWATs roughly around 1.25 - 1.75 inches. The main threat with these storms seems to be severe wind gusts, as low-level lapse rates are close to 7 - 7.5C/km, and DCAPE is around 600-800 J/kg. There is also a chance for some hail to fall from some of these storms. Make sure to have access to ways for receiving warning alerts if a storm develops in your area. Thunderstorm potential will begin to dissipate by nighttime.

By Wednesday a strong cold front will approach the area, accompanied by much drier air at all levels behind it. Models differ significantly with the timing of the front, with the NAM and GFS on the faster and the CMC/ICON/ECMWF on the slower end. A faster solution would result in little to no convection as deeper moisture is forced over the ocean where conditions are extremely stable. Slower solutions would result in a narrow band of 500-1000 J/kg of MLCAPE across Bangor into Downeast Maine, which combined with stronger winds aloft providing 30-40 kts of 0-3km effective wind shear, could lead to an isolated thunderstorm capable of strong to damaging winds for coastal and Downeast areas. A majority of the time, slower solutions for frontal passages verify this time of year, so adjustments were made to expand PoPs and introduce thunder chances mainly Downeast and over the near coastal waters. The speed of the front will also impact temperatures, with slower solutions potentially allowing 80s to reach farther to the north. Max temperatures mainly in the 70s are forecast for northwestern with 80s most likely near and southeast of interstate 95. Dew points in the 60s early will make it feel a somewhat humid, but drier air and much lower dew points will quickly move in behind the front in the afternoon from northwest to southeast.

KEY MESSAGE 3...Below average temperatures are expected Thursday and Thursday Night. Near freezing temperatures are possible early Friday morning across the north, which may require actions to protect vulnerable plants.

KEY MESSAGE 3 DESCRIPTION... The frost/freeze program, marking the approximate beginning of the growing season, will expand north on Thursday to include most of the remainder of northern and eastern Maine aside from the far northwestern forecast zones. Strong cold air advection is expected on Thursday with 1000-500mb thicknesses decreasing below 540dam across much of northern Maine by Thursday evening. While winds will be lighter Thursday night, the center of the ridge of high pressure is expected to be well to the southwest across northern NY, VT, and western MA, helping to maintain a modest NW wind outside of sheltered valleys. A strong jet streak overhead will also maintain the risk for passing clouds. These factors make the actual degree of decoupling uncertain. Temperatures at or below freezing are most likely over the North Woods where the growing season does not start until June 1. Lows ranging from the mid 30s to lower 40s are favored elsewhere early Friday morning.

AVIATION /07Z MONDAY THROUGH FRIDAY/

Today...VFR. Winds shift from NW to W by later in the morning. Gusts up to 20 kts possible around KBGR.

Tonight...VFR/MVFR, with some rain showers at northern terminals. S winds at 5 - 10 mph. LLWS possible.

Tuesday...MVFR, potentially lower in terminals with severe thunderstorms. Best chance for thunderstorms is during the afternoon into evening. WSW winds G15-20KT possible Tuesday afternoon. LLWS possible.

Tuesday night: MVFR possible at northern terminals, IFR possible at KFVE. VFR elsewhere. SW winds 5 to 10 kts gusting to 20 kts.

Wednesday: MVFR early at northern terminals, otherwise VFR. Tempo MVFR/IFR is possible at BGR and Downeast terminals with a chance of a TSRA. Windy with WSW winds turning WNW at 15 to 20 kts with gusts to 30 to 35 kts.

Wednesday night to Thursday: VFR. NW winds 10 to 15 kts with gusts to 25 to 30 kts.

Thursday night: VFR. NW winds 5 to 10 kts.

Friday: VFR. NW winds 10 to 15 kts gusting to 20 to 30 kts.

MARINE

Winds stay below SCA Monday night, before creeping near marginal Small Craft criteria for the outer waters Tuesday. Chance for rain Monday night and Tuesday. S winds, becoming SW on Tuesday.

Marginal Small Craft Advisory seas around 4 to 6 feet are possible over the outer waters out to 25NM Tuesday night through Wednesday evening. Wave heights to around 5 to 7 feet are possible across the outermost waters from 25 to 60NM. Winds below advisory levels are expected through the forecast period, although some 25 kt gusts are possible across the outermost waters from 25 to 60NM offshore Tuesday night into Wednesday. An isolated thunderstorm is possible Wednesday afternoon, mainly closer to the coast. These thunderstorms may produce locally stronger wind gusts.

Sea surface temperatures remain very cold, but are beginning to moderate into the mid 40s.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...None.