textproduct: Caribou

WHAT HAS CHANGED

- Increased the chance for rain showers and thunderstorms each afternoon through mid week based on weak low level instability and plentiful surface heating.

- Below normal temperatures and showery conditions expected this weekend along with a few thunderstorms

KEY MESSAGES

1) Showers and isolated thunderstorms possible each afternoon today and Wednesday.

2) Localized flooding is possible Thursday through Thursday night.

3) Below normal temperatures and showery conditions likely this weekend along with a few thunderstorms.

DISCUSSION

KEY MESSAGE 1...Showers and isolated thunderstorms possible each afternoon today and Wednesday.

KEY MESSAGE 1 DESCRIPTION... The low to mid levels begin to dry out through the day on Tuesday as high pressure moves into the area. However, steep low to mid level lapse rates will accompany this drying process, and with what moisture does linger through the day today, diurnally- driven convection is possible through this afternoon, with a few isolated showers prior to stability returning to the region later tonight. The most likely area for showers to develop this afternoon will be across northern Aroostook county.

Again on Wednesday, lingering low level moisture, though slight, could be enough to support isolated shower and thunderstorm development during peak heating Wednesday afternoon. For Wednesday, the most likely area of development will be in the North Woods through the Central Highlands, and showers could then spread eastward into Wednesday evening. Low level lapse rates may approach 8 C/km and CAPE could exceed 500 J/kg Wednesday afternoon, which are ingredients that could support isolated thunderstorm development, especially with orographic lift over the Central Highlands.

KEY MESSAGE 2...Localized flooding is possible Thursday through Thursday night.

KEY MESSAGE 2 DESCRIPTION... A large and seasonably strong low pressure system is expected to progress NE across the Great lakes and into Canada on Thursday. Rain is generally expected to spread across the region from west to east throughout the day on Thursday, eventually tapering off overnight as drier air works its way in. Guidance continues to show a low-level jet passing through the area Thursday evening which will act to bring ample low-level moisture into the area, contributing to rainfall up to 1 inch in some places. Ensembles show PWAT values at the 85th percentiles, hinting at a significant rainfall event. As a result, some localized flooding, especially where any thunderstorms may develop, is possible. Any storms should be relatively weak, however. Questions still remain as to how much moisture will advect into the region and how much the low retrogrades, which could result in rain bands slowing down and dumping more precipitation.

KEY MESSAGE 3...Below normal temperatures and showery conditions likely this weekend along with a few thunderstorms.

KEY MESSAGE 3 DESCRIPTION... Upper-level low pressure sticks around through much of the weekend which should contribute to cooler temperatures, running around 5 degrees below normal. In addition, cold air aloft and lift from shortwave energy should contribute to scattered showers and possibly a few thunderstorms. Generally less confident on the thunderstorm threat due to weak instability and heating.

AVIATION /04Z TUESDAY THROUGH SATURDAY/

Early morning/prior to 12z: The remnants of a collapsing cold front across northern terminals created an outflow boundary which has scattered out low ceilings and helped limit fog at northern terminals. That said, patchy fog may remain in the area and a slight chance (5 percent) remains that fog could impact visibility once more at these terminals prior to 12z. For BGR and BHB, VFR conditions continue. Washington county terminals will likely remain LIFR in fog through the early morning hours before they clear out as well.

Today: VFR conditions continue across all terminals. NW winds 5 to 10 kts this afternoon with occasional gusts to 20 kts. Isolated -SHRA possible through the late afternoon at northern terminals.

Tonight: VFR for all terminals. Patchy fog may briefly develop near northern terminals but limits to visibility are unlikely. Winds light and variable.

Wednesday: VFR across all terminals. S to SW winds 5 to 10 kts with gusts to 20 kts. Isolated showers at northern terminals with a slight chance for thunderstorms in the area.

Wednesday night: VFR. Light S wind.

Thursday-Thursday night: IFR/LIFR in locally heavy rain. S-SE winds 10-15 kts with gusts up to 25 kts possible. LLWS possible at southern terminals.

Friday: Improvement to MVFR at southern terminals early Friday morning, then gradual improvement throughout the day. Locally heavy rainfall possible early. WSW winds 10-15 kts with gusts up to 25 kts.

Saturday: MVFR/IFR in rain showers, especially at northern terminals. W winds 5-10 kts.

MARINE

Winds, including gusts, should be 20 kt or less and seas 4 ft or less on all waters out to 60NM through Wednesday night.

Winds and seas will increase Thursday through Thursday night. Winds for intracoastal and coastal waters could reach gusts up to 25-30 kts. Gusts 30-35 kts in the waters out to 60nm. Seas Thursday night should increase to 5-8 ft, then gradually decrease on Friday to 4-6 ft Friday afternoon. Expected a period of 7-8 sec for Thursday night-Friday with a S fetch. Seas below SCA criteria on the coastal and intracoastal waters Friday night through Saturday.

CAR WATCHES/WARNINGS/ADVISORIES

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