textproduct: Caribou

WHAT HAS CHANGED

- The forecast timing of the cold front on Wednesday has sped up slightly, making it a more nocturnal/early morning passage, reducing the potential for thunderstorms Wednesday.

- Strong to severe storms continue to be possible this afternoon and evening, with no significant changes to this.

KEY MESSAGES

1) Strong to severe storms with gusty wind gusts are possible this afternoon and evening as temperatures warm through the mid week. Please stay weather aware as showers and storms move through the next couple of days.

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...Strong to severe storms with gusty wind gusts are possible this afternoon and evening as temperatures warm through the mid week. Please stay weather aware as showers and storms move through the next couple of days.

KEY MESSAGE 1 DESCRIPTION...Surface low pressure is crossing northern Maine into Canada this afternoon, and observed temperatures range in the 50s and 60s along the coast, on the mountains, and across northern Aroostook County, with 70s and 80s elsewhere. Seeing some surface based CAPE across southern and central areas, but much of the region remains capped. Models have surface CAPE values peaking around 700- 900 J/kg this afternoon, highest in Penobscot and Hancock counties. The NAM3 is extra bullish with SBCAPE as high as 1800-2000 J/kg, but this seems overdone as we see plenty of clouds from this morning's rain showers hanging around.

Effective bulk wind difference shear is being modeled around 40-45 knots and Pwats are expected to be around 1.75-2.00" in southern Penobscot, Hancock, and Washington counties, with Pwats farther north much lower 1.30-1.50". Low level lapse rates 8.0-8.5 C/km will be a contributor in how strong any developing storms get, and anticipated DCAPE values continue to run around 500-700 J/kg. All of this together indicates some potential for gusty to severe winds in any thunderstorms that occur this afternoon south of Aroostook County. Some hail is not out of the question, but not a major threat. All that being said, the clouds will likely limit sunshine, surface heating, and instability. Forcing also looks less than ideal, though a warm front and a weak upper shortwave could be triggers for cells to pop up here and there.

As a stronger cold front approaches early Wednesday, there is another chance for some showers, though its timing looks early enough in the morning to keep surface instability very low, but there could still be a rumble of thunder from elevated instability. Lows tonight will fall into the mid 50s to mid 60s. As cold air aloft arrives, however, even showers could produce slightly gusty winds 25-35 mph Wednesday afternoon. Highs Wednesday should reach into the mid 70s and 80s, with warmest temps in eastern areas that have more time to warm up ahead of the front.

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, resulting in highs only in the 50s and lower 60s, warmest along the coast. Thursday night, a modest low level jet looks to develop overhead, likely keeping unsheltered spots from decoupling, and clouds should be on the increase throughout the night as well. Drier air with dew points in the 20s and lower 30s may also prevent frost formation. Even without frost, some damage to plants is possible in these conditions with temperatures falling into the lower and mid 30s in northern areas as high pressure noses in from the Great Lakes.

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. Lows Friday night and Saturday morning are forecast in the 30s to mid 40s, but may end up being lower in ideal radiational cooling conditions. Dew points will also be higher in the upper 20s to mid 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. Our next chance of precipitation will be early next week.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

This afternoon: Strong to severe storms with gusty wind gusts are possible this afternoon. All sites except KFVE are VFR, but most sites should see ceilings lowering towards MVFR as showers arrive this afternoon. Winds west-southeast at KFVE, more northeasterly at KCAR and KPQI, while winds are out of the southwest at KBGR. Wind gusts 15-25 knots possible. Best chance for thunderstorms is during the afternoon into evening. Moving through, thunderstorms could produce additional gusty winds, lightning, and small hail.

Tonight: Ceilings lowering to MVFR and IFR levels for most sites with winds light and variable, terrain or geographically driven. On and off showers are possible throughout the night. LLWS beginning 04Z-09Z Wednesday and continuing into Wednesday morning daylight hours.

Wednesday: Ceilings increase again to MVFR or VFR levels with shower chances continuing. Winds increasing out of the southwest with gusts 25-35 knots.

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

Thursday night: VFR. WNW winds 5-10 kts.

Friday: VFR. NW winds NW winds 10-15 kts with gusts to 25 kts.

Friday night to Saturday: VFR with light and variable winds, increasing to around 5-10 kts during the day.

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.

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 passing rain this afternoon, and chance for rain 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 until 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.