textproduct: Caribou

WHAT HAS CHANGED

- 8 AM: Updated Aviation Section for 12Z TAFs.

- Increased uncertainty in coverage of showers Monday night and showers and thunderstorms Tuesday.

KEY MESSAGES

1) Scattered showers and thunderstorms today, some could be strong to possibly severe. Stronger showers and storms may produce locally heavy rainfall, with the potential for localized flooding.

2) Scattered rain showers and thunderstorms Monday through Tuesday.

DISCUSSION

KEY MESSAGE 1... Scattered showers and thunderstorms today, some could be strong to possibly severe. Stronger showers and storms may also produce locally heavy rainfall, with the potential for localized flooding.

KEY MESSAGE 1 DESCRIPTION... A northern stream shortwave trough moves across southern Quebec today, with a surface cold front moving out ahead of it across Maine this afternoon and early this evening.

There should be sufficient sources of lift from the shortwave trough and the cold front to produce scattered to numerous showers and thunderstorms across the region, starting around midday along the western border with Quebec and ending around 6-7 pm along the eastern border with New Brunswick.

The strongest storms appear more likely along and north of a GNR-MLT line, where CAPE this afternoon should range from 1500-2500 J/kg, south of that line CAPE should range from 500-1500 J/kg and close to 0 near the immediate coast due to the marine layer. The bulk shear is more uniform, with values of 25-35 kt. There is also progged around 1000-1400 J/kg of Downdraft CAPE. The latter, coupled with the freezing level around 11-12K across the North and 12-14K further S, and with fairly uni- directional winds, yields the main threat being from strong to locally damaging winds. The storm mode should be bowing clusters, with a few discrete cells mainly ahead of those clusters. With Corfridi-vectors showing storm motion of 15-20KT, even with Precipitable Waters of 1.5-1.75", absent training, the flood threat is reduced from yesterday. The potential for locally heavy rainfall though remains.

KEY MESSAGE 2...Scattered rain showers and thunderstorms Monday through Tuesday.

KEY MESSAGE 2 DESCRIPTION... Rounds of shortwaves move to the north this week, bringing a chance for rain showers and some thunderstorms. Thunder possible in the north on Monday, area wide Monday night, and in the north on Tuesday. More showers are possible late week. Looking at potential for 500-1000 J/kg of surface CAPE, 30-40 kt of shear, but mid-level lapse rates are weak. A Cold front associated with a shortwave moving through Monday night seems to be weak as well. Overall, the environment does not look too impressive for strong thunderstorms, so could just be some brief isolated storms below severe criteria. PWATs generally in the 1.25-1.5 range, so locally heavy rainfall is not expected.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Today: Early IFR/LIFR at northern terminals will improve to VFR over the next couple of hours as rain showers move out, and IFR at coastal terminals will improve to VFR by mid morning as fog dissipates. Scattered rain showers this afternoon could lower cigs back towards MVFR/IFR once more. Isolated thunderstorm threat into the early evening hours.

Light and variable winds become SW at 5 to 10 kts this afternoon, except for a sea breeze develops at KBHB. Winds become light and variable again at all terminals early this evening.

Late tonight-Monday: VFR, with a low chance of MVFR in any passing shower or thunderstorm Monday afternoon. The best chance of a shower or storm is from KHUL on north. WNW-NW winds G15KT possible Monday afternoon.

Monday night-Tuesday: MVFR/IFR in showers late Monday night and Tuesday afternoon. Light winds Monday night/Tuesday morning, becoming W 5-10 kt with gusts 15-20 kt Tuesday afternoon. Patchy fog possible at KBHB/KBGR overnight.

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

Wednesday night-Thursday: MVFR/IFR possible in any showers. Winds W/SW at 5-10 kt.

MARINE

Winds should be 15 kt or less and seas 3 ft over the waters out to 60nm through Thursday.

Fog reducing visibilities to 1nm or less is likely over the waters through this morning. There is also the potential for some showers from Monday into Tuesday. There is a chance for thunderstorms over the waters on Thursday.

CAR WATCHES/WARNINGS/ADVISORIES

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