textproduct: Caribou

WHAT HAS CHANGED

Increased fog tonight (Sunday night) and Monday night.

Increased chances for strong to possibly locally severe thunderstorms across the interior Tuesday afternoon.

Increased confidence in strong convection Friday afternoon/evening.

KEY MESSAGES

1) Areas of dense fog tonight (Sunday night), and possibly again Monday night. Fog will impact travel conditions.

2) Chance of showers persists late this (Sunday) afternoon through Monday afternoon, with possibly thunderstorms in Northern Maine Monday afternoon.

3) Chance of showers and thunderstorms north of Bangor Tuesday and mainly across northern Aroostook Wednesday.

4) Thunderstorms are possible Friday afternoon and evening, some of which may be locally strong with gusty winds and small hail.

DISCUSSION

KEY MESSAGE 1... Areas of dense fog tonight (Sunday night), and possibly again Monday night. Fog will impact travel conditions.

KEY MESSAGE 1 DESCRIPTION... Fog is the main concern. Dense fog was present Sunday morning especially near the coast. With the airmass getting even a bit moister, think that tonight will be a repeat performance, except areas further inland will have a better shot at getting the fog. The best chance of the dense fog is near the Downeast fog, but can't rule out significant fog further inland too. The fog should generally dissipate during the day Monday, but fog appears likely again Monday night. There may be a slightly later onset to the fog in the evening Monday compared to this (Sunday) evening, but still think the fog could be locally dense by later Monday night.

KEY MESSAGE 2... Chance of showers persists late this (Sunday) afternoon through Monday afternoon, with possibly thunderstorms in Northern Maine Monday afternoon.

KEY MESSAGE 2 DESCRIPTION... As of 2pm Sunday afternoon, lots of clouds and low-level moisture, but not much more than drizzle. There are some heavier showers/storms south of our area that will move north into especially eastern portions of our area and bring another shot of showers later this afternoon into the evening. Can't rule out an embedded storm and some heavier downpours, but nothing remotely strong for thunderstorms, and no flooding, with a few places getting another quarter inch of rain or a bit more. Probably some drying later tonight into Monday morning, but with a bit of clearing, expect enough instability to showers and storms to fire off by about midday. Scattered showers/storms are expected, with the best chance being inland away from the more stable marine layer. That said, even in the wetter north, only going with a 40-60 percent chance of showers/storms, best chance in the western North Woods. Monday won't be a rainout by any means. Can't rule out a couple of the storms being on the stronger side with gusty winds, but this is a pretty minimal threat, and there is some uncertainty how many storms can fire in the first place.

KEY MESSAGE 3... Chance of showers and thunderstorms north of Bangor Tuesday and mainly across northern Aroostook Wednesday.

KEY MESSAGE 3 DESCRIPTION... The axis of an upper level closed low that is gradually weakening as it passes to the north, then northeast Tuesday- Wednesday, should bring with it sufficient instability in the low-mid levels with its associated cold-pool aloft, that is should produce scattered to potentially numerous showers and isolated to scattered showers areawide on Tuesday.

By Tuesday afternoon, low to mid level lapse rates should be around 8-8.5C/km, with a few hundred J/kg of CAPE and around 35-45 kt of bulk shear. This should produce some strong to locally severe storms across the region north of Bangor. Wet bulb zero heights are around 7500-8500 ft away from the coast so the greatest risk would be small to possibly marginally severe hail.

On Wednesday,as the upper low weakens and retreats to the northeast, the threat will be limited to the North, with low level lapse rates around 7.5-8 C/km, around 500-1000 J/kg of CAPE and around 20-30 kt of shear. Once again strong to possibly locally severe storms are possible with mainly isolated storms across northern Aroostook. The wetbulb zero height is a little higher 8500-9000 J/kg, but still low enough to support hail. With the stronger CAPE, the main threat is both strong winds and small to marginally severe hail in the strongest convection across the North on Wednesday.

KEY MESSAGE 4... Thunderstorms are possible Friday afternoon and evening, some of which may be locally strong side with gusty winds and small hail.

KEY MESSAGE 4 DESCRIPTION... A cold front crosses the area Friday afternoon and evening on the leading edge of a full latitude trough pushing into the region, with the added support of a northern stream shortwave pushing through the trough around that time. With the potential for 500-1500 J/kg of CAPE and 25-35KT of bulk shear, there is a risk of some locally strong thunderstorms ahead of the front, with the main threat strong gusty winds.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Rest of Today...Mainly IFR with a intermittent MVFR possible. SE/W wind 5-10 kts. Can't rule out a storm after 21z, but not enough confidence to put in any TAFs.

Tonight...Conditions deteriorating to LIFR or lower at all terminals with low clouds and fog. Fairly high confidence in these low conditions. Light winds.

Monday...Conditions improving to VFR for most places by 18z, though MVFR/IFR could persist near the coast. Possibly an afternoon storm at northern terminals. S wind increasing to around 10 kts.

Monday Night...Conditions deteriorating to IFR or lower at all terminals. Not as high of confidence in the poor conditions as for tonight, but still at least 60 percent confidence in IFR prevailing. Light winds.

Tuesday: MVFR or lower possible in any stronger convection north of KBGR. Chance of MVFR or lower early Tuesday morning at all terminals in low ceilings and/or fog.

Tuesday night: VFR.

Wednesday: MVFR or lower possible in any stronger convection at KFVE/KCAR/KPQI, otherwise VFR.

Wednesday night-Thursday night: VFR. LLWS possible Thursday night.

Friday: VFR in the morning, then MVFR or lower possible in any showers or thunderstorms in the afternoon. LLWS possible. S winds G15-20KT possible.

MARINE

Fog over the waters through Monday night. S/SE winds 15 kts or less and seas 2-4 ft. A few storms possible over the waters late this afternoon into early this evening.

Sustained winds of 15 kt or less and seas of 4 ft or less are forecast on all waters out to 60NM from Tuesday through Friday.

There is a chance for dense fog on the waters Tuesday morning, reducing visibility to less than 1 nm. There is the chance for thunderstorms over the waters late on Friday.

CAR WATCHES/WARNINGS/ADVISORIES

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