textproduct: Caribou

WHAT HAS CHANGED

-Decreased thunder chances on Tuesday to slight chance.

-Dropped daytime temperatures early next week.

KEY MESSAGES

1) Slow moving showers and thunderstorms on Sunday could lead to localized significant rainfall.

2) A low pressure system passes through the region Monday night into Tuesday, while track and timing remains uncertain.

3) Prolonged troughing in the Northeast will lead to multiple rounds of showers and storms this week.

DISCUSSION

KEY MESSAGE 1...Slow moving showers and thunderstorms on Sunday could lead to localized significant rainfall.

KEY MESSAGE 1 DESCRIPTION... An unsettled pattern continues tomorrow with a better chance for showers and thunderstorms in the afternoon. Better instability will be confined to wrn areas with CAPES from 500-800 J/kg. Although PW values will be right around, if not slightly better than normal, locally heavy rainfall will be possible with any storms that can develop. This is because Corfidi Vectors are very light, pretty much less than 5kts most places in the afternoon. Flow is very weak up through the tropopause with significant rainfall possible in one area and not in the one next to it. One-hour FFG values are around 1 inch/hour across the north and 1.25-1.50 inches in central areas.

KEY MESSAGE 2...A low pressure system passes through the region Monday night into Tuesday, while track and timing remains uncertain.

KEY MESSAGE 2 DESCRIPTION... Shortwave moves through region Monday afternoon into Tuesday evening. With this system, moisture quickly increases throughout Maine, and rain showers, with an isolated thunderstorm, are possible. Models seem to favor the general path of the low pressure staying south of Maine, but there is uncertainty in the timing and exact track. Models that seem to have a more southern low pressure system, bring less precipitation to the Downeast region, while models favoring a farther north low pressure system, bring more precipitation to the Downeast region. Global models seem to be trending northeast with the low, bringing more rain to the coastline. Stuck with the NBM for this update, since it shows the general trend well between models. The best chance for precipitation is going to be interior and coastal Downeast, with gradually lighter showers expanding farther inland. How far inland the precipitation reaches, is going to depend on the track. Looking at between 1 to 1.5 inches of rain possible Downeast.

Minimal instability could lead to some isolated thunderstorms in the Central Highlands and northern regions. Southerly flow should keep Downeast stable enough to avoid convection. Around 500 J/kg of CAPE, and some decent low-level lapse rates could get some thunder rumbles over the region in the afternoon. Decreased thunder chances however, since shear and helicity look weak, and some CIN is present. Will have to continue to monitor to see how trends progress.

KEY MESSAGE 3...Prolonged troughing in the Northeast will lead to multiple rounds of showers and storms this week.

KEY MESSAGE 3 DESCRIPTION... Positive PNA pattern over the Atlantic parks a high pressure system over the west, resulting in prolonged troughing over the region, with multiple rounds of rain showers moving through. Cool temperatures generally in the 70s. Overnight lows generally in the 50s. Prolonged trough results in multiple rounds of showers, with chances for thunderstorms each afternoon.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Mainly VFR at all terminals tonight, though a very brief MVFR cig may be present over the next hour or two this afternoon. After 00z low cigs should begin to improve to VFR. FVE, CAR and PQI may see light showers between 00 and 04z tonight but no restrictions are expected. NW winds 5-10kts tonight.

Sunday...Mainly VFR with showers and tstms developing in the afternoon. Confidence is low with -tsra impacting any one terminals and will need to wait until next set of TAFs. Light winds expected.

Sunday night...VFR and showers early with MVFR/IFR possible late. Cannot rule out fog developing in areas that received rainfall on Sunday. Calm winds.

Monday - Monday night...MVFR/IFR in rain showers at all terminals, and with a chance of thunderstorms at KFVE/KCAR/KPQI/KHUL. S winds at 5 to 10 kts, becoming E at 5 to 10 kts overnight. Uncertainty in track of low pressure system, which could shift precip more offshore and shift forecasted wind direction.

Tuesday - Tuesday night... MVFR/IFR in rain showers at all terminals, and with a chance of thunderstorms at KFVE/KCAR/KPQI/KHUL. Improving to VFR late afternoon. E/SE winds at 5 to 10 kts, gusting to 20 kts, shifting to NW 5 to 10 kts.

Wednesday - Wednesday night...Mainly VFR. Possible MVFR at KFVE/KCAR/KPQI/KHUL in the afternoon with showers and chance of thunderstorms. NW winds at 5 to 10 kts. Become light and variable overnight.

Thursday...Possible MVFR at KFVE/KCAR/KPQI/KHUL, in the afternoon with showers and chance of thunderstorms. S/SE winds at 5 - 10 kts.

MARINE

Seas around 4ft will continue this afternoon before dropping Sunday morning and continuing between 1-2 feet into Monday morning. All waters will see winds below 20kts throughout the near term period. Patchy fog will reduce visibilities over the waters on Sunday night.

Below SCA conditions Monday. Seas creep up to 5 ft on Tuesday into Wednesday. Rain and patchy fog Monday night into Tuesday. Chance for thunderstorms Tuesday. S winds on Monday, shift to the NW on Tuesday night.

CAR WATCHES/WARNINGS/ADVISORIES

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