textproduct: Caribou

WHAT HAS CHANGED

- Aviation Section updated for issuance of the 12Z TAFs

- Confidence increasing in widespread convection tonight.

KEY MESSAGES

1) Surface smoke possible from this afternoon into tonight.

2) Scattered rain showers and thunderstorms today through Tuesday, with some locally heavy rainfall possible.

3) A round of widespread showers and thunderstorms expected Thursday throughout much of the day. A strong storm or two is possible.

DISCUSSION

KEY MESSAGE 1... Surface smoke possible from this afternoon into Tuesday.

KEY MESSAGE 1 DESCRIPTION... Satellite imagery indicated a plume of wildfire smoke from southern Quebec down into central New England. The HRRR and RAP smoke models continue to indicate that this could translate to surface smoke in our area from Monday afternoon into Tuesday. This could be noticeable with a slight reduction in the visibility.

KEY MESSAGE 2... Scattered rain showers and thunderstorms from this afternoon into Tuesday, with some locally heavy rainfall possible.

KEY MESSAGE 2 DESCRIPTION... A series of northern stream shortwaves cross the region this afternoon through Tuesday. At the surface a warm front approaches today, lifts through this evening, and followed immediately behind it by a cold front that crosses mainly overnight and early Tuesday morning. A trough of low pressure then pushes through later Tuesday.

The strongest of these shortwaves passes through tonight, this will bring the highest chance of showers across all of Eastern Maine, with chances this afternoon and Tuesday limited mainly across the North.

With CAPE this afternoon of only a few hundred J/kg, do not expect any strong storms. Tonight, showalter indices are forecast to be around 0 and no CAPE, expect mainly elevated convection, however with some lift ahead of the cold front, would not be surprised if there were a few surface based storms. Once again no strong storms expected.

On Tuesday do get CAPES up to 500-1000 J/kg across the North, with mainly southern portions of the area in the left front quadrant of a 100+ kt upper jet. This coupled with 30-35kt of bulk shear could produce some locally strong storms across the North, with possibly some strong gusty winds.

Precipitable waters of 1.25-1.5 inches across the north and 1.5-1.75 inches elsewhere ahead of the cold front could support some locally heavy rainfall from this afternoon into Tuesday morning.

KEY MESSAGE 3...A round of widespread showers and thunderstorms expected Thursday throughout much of the day. A strong storm or two is possible.

KEY MESSAGE 3 DESCRIPTION... A wave of upper level energy is expected to approach our area from the west Wednesday night and develop low pressure at the surface which will move into our area Thursday bringing a round of widespread showers and thunderstorms. Some areas could see a soaking rain based on where the strongest storms set up. Still uncertain right now as guidance is expressing some uncertainty in the position of the low pressure system but the North has the greatest chance with the likelihood of at least 0.5" of rain around 30%. Around 30-35 kts of deep-layer wind shear is expected with at least several hundred J/kg of instability, although some models show 1000-1500 J/kg. Certainly something to watch for rainfall potential and storm threat.

AVIATION /12Z MONDAY THROUGH FRIDAY/

High confidence in VFR through the TAF period. While an afternoon shower or thunderstorm is possible at northern terminals, confidence in its occurrence at any given terminal is too low to place in the TAFs at this time.

Winds at northern terminals become WSW at 5 to 10 kts by late morning. A sea breeze develops at KBGR/KBHB/coastal terminals around midday. Winds become light and variable throughout again this early this evening.

Late tonight: MVFR or lower possible in any convection, otherwise VFR.

Tuesday: VFR, except at northern terminals, where a brief period of MVFR is possible in any stronger convection. NW winds G15KT possible Tuesday afternoon.

Tuesday night-Wednesday: VFR. Winds W at 5-10 kt.

Wednesday night-Thursday: MVFR/IFR in showers and T-storms. Winds W/SW at 5-10 kt.

Thursday night-Friday: Lingering MVFR, especially at northern terminals in showers or isolated T-storms. NW winds 10 to 15 kts with gusts 20 to 25 kts.

MARINE

The waters out to 60nm should see sustained winds of 15 kt or less and seas of 3 ft or less through Tuesday. Showers and thunderstorms could impact the waters tonight.

Winds and seas below small craft advisory criteria on the coastal and intracoastal waters Tuesday night-Friday. Seas peak at 5 to 6 ft on the outer waters Friday. A chance of showers and thunderstorms over the waters Thursday into Thursday night.

CAR WATCHES/WARNINGS/ADVISORIES

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