textproduct: Caribou

WHAT HAS CHANGED

- Cancelled the Gale Warning. - Issued a Small Craft Advisory for ANZ051 til 8 AM Friday. - Updated the aviation discussion.

KEY MESSAGES

1) Widespread moderate to heavy rain into tonight, with localized flooding possible. Gusty winds are also expected, especially within any strong showers and storms.

2) Showers Friday into the weekend along with a slight chance of afternoon thunderstorms Sunday.

DISCUSSION

KEY MESSAGE 1...Widespread moderate to heavy rain into tonight, with localized flooding possible. Gusty winds are also expected, especially within any strong showers and storms.

KEY MESSAGE 1 DESCRIPTION... A compact strong low pressure system in Southern Quebec is kicking off rain across much of the area this afternoon. Elevated instability and higher PWATs are working into GYX CWA heading for portions of CAR CWA this afternoon. The key message remains on track for the potential of excessive rainfall. The greatest concern for isolated localized flash flooding will be across the Central Highlands.

The moisture for this system will be well supported, with model agreement that PWATs will approach 1.1 to 1.2 inches in the north and 1.3 to 1.4 inches Downeast through most of the event. For the northern half of the CWA, 1.2 inches is around the 90th percentile for KCAR PWAT climatology, which is 1.25 inches. For Downeast, 1.4 is around the 90th percentile for KGYX PWAT climatology, which is 1.44 inches. Exceedance of the climatological 90th percentile for PWATs is one factor to consider for the potential for efficient, heavy rainfall, and for this ingredient the forecast is considered marginal.

Long, skinny CAPE profiles are another ingredient that would favor flooding rain potential. That said, across the Downeast region, the marine layer presents a deep low level inversion that inhibits CAPE development, and there is little instability at all to work with. (There is, however, no shortage of shear, with 0-6 km bulk shear approaching 60 kts)

The 50 kt LLJ will likely mix some momentum to the surface within moderate to heavy rainfall, leading to gusty winds which could occasionally reach 30 to 35 mph in strength, especially across higher terrain.

KEY MESSAGE 2...Showers Friday into the weekend along with a slight chance of afternoon thunderstorms Sunday.

KEY MESSAGE 2 DESCRIPTION... An upper level low will slowly cross the region Friday into the weekend while a series of disturbances move around the low. Cold air aloft will help increase diurnal instability. Unsettled conditions with a chance of showers will occur Friday through the weekend, with a slight chance of afternoon thunderstorms on Sunday. The better shower/thunderstorm chances should occur across northern areas. Another system approaches Monday night.

AVIATION /02Z FRIDAY THROUGH TUESDAY/

Overnight...Across northern areas MVFR/IFR, occasional LIFR, with showers. Across Downeast areas, IFR/LIFR through early morning then VFR/MVFR with showers ending. South/southeast winds 10 to 15 knots with gusts up to around 20 knots, becoming southwest. Southwesterly low level wind shear.

Friday...Across northern areas, MVFR/IFR early then VFR/MVFR. Showers. Across Downeast areas, occasional MVFR possible early. Otherwise, VFR. Southwest winds 10 to 15 knots with gusts up to 20 to 25 knots.

Friday night...VFR/MVFR. Showers likely north. Southwest/west winds 10 to 15 knots.

Saturday...VFR/MVFR with a chance of showers. West/southwest winds 10 to 15 knots with gusts up to around 20 knots, becoming west/northwest.

Saturday night...VFR/MVFR. A slight chance of showers, mostly north. Some patchy fog is possible. Northwest winds 10 to 15 knots, becoming north/northwest 5 to 10 knots.

Sunday...VFR/MVFR with a chance of showers. Slight chance of an afternoon thunderstorm. West/northwest winds 5 to 10 knots, becoming variable.

Sunday night...VFR. Winds light and variable.

Monday...MVFR/IFR in heavier showers, with a chance of thunderstorms. South winds 5-10 knots, becoming northeast 5-10 knots.

MARINE

Have cancelled all Gale Warnings. A Small Craft Advisory is in effect for the coastal and intra-coastal waters through 8 AM Friday. Scattered/numerous showers through early morning. Winds relax to 25kt or less on the Coastal Waters Friday AM and Friday Eve on the outer waters. Seas remain in SCA criteria on Friday on the Coastal Waters with winds/waves below SCA on Intra- Coastal Waters on Friday. 4-5ft seas on Coastal Waters on Saturday and winds/seas below SCA on Sun-Mon.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...Small Craft Advisory until 8 AM EDT Friday for ANZ050>052.