textproduct: Caribou

WHAT HAS CHANGED

- Increased shower/thunderstorm chances a bit for Wednesday afternoon in Northern Maine. - Added patchy valley fog for tonight.

KEY MESSAGES

1) Wednesday afternoon, scattered showers and isolated thunderstorms in Northern Maine. Late this (Tuesday) afternoon and early this evening, a smaller chance of showers and storms over only far Northern Maine.

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...Wednesday afternoon, scattered showers and isolated thunderstorms in Northern Maine. Late this (Tuesday) afternoon and early this evening, a smaller chance of showers and storms over only far Northern Maine.

KEY MESSAGE 1 DESCRIPTION... Threat of showers/storms today and tomorrow. The better chance is tomorrow, but first, for today, there are some showers west of Quebec City with a very weak system. Can't rule out a few showers and perhaps a storm making it into far Northern Maine late this afternoon or early this evening, with the best chance over the St John Valley. The vast majority of places will stay dry. Nothing strong expected.

The shower/storm threat for Wednesday looks a bit greater. Surface-based instability increases, with CAPE values possibly over 1000 J/kg in Northern Maine. Shear however is quite weak. So while there will be scattered showers and isolated storms in Northern Maine (mainly north of Lincoln and Dover-Foxcroft, as more stable air south of there should keep it too stable), we don't anticipate anything severe. Can't rule out a bit of small hail and gusty winds from the most potent cells.

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. Newest model runs show a trend of a model intense low developing to the W of the state. This intensification has greatly increased the QPF amounts, especially across the north.

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... Per the previous discussion: 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 /18Z TUESDAY THROUGH SUNDAY/

Rest of This Afternoon...VFR. W/NW wind around 10 kts, subsiding toward 0z.

Tonight...VFR, though can't rule out localized brief fog. Not confident enough in any fog to put into TAFs. Light winds.

Wednesday...VFR. Possible afternoon showers/storms at Aroostook terminals, but not enough confidence to put into TAFs. S wind 5-10 kts.

Wednesday Night...VFR Aroostook terminals, but IFR likely developing BGR/BHB after 6z. Light S winds.

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-Sunday: MVFR/IFR in rain showers, especially at northern terminals. WNW 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. Marine fog likely developing 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.