textproduct: Caribou

WHAT HAS CHANGED

- Slow moving showers and storms on Sunday could lead to localized significant rainfall.

KEY MESSAGES

1) Showers this weekend along with a slight chance of afternoon thunderstorms. Slow moving showers 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 remain uncertain.

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

DISCUSSION

KEY MESSAGE 1...Showers this weekend along with a slight chance of afternoon thunderstorms. Slow moving showers on Sunday could lead to localized significant rainfall.

KEY MESSAGE 1 DESCRIPTION... A broad upper level trough continues to sit over the state this weekend, persisting an unsettled pattern with scattered rain showers every day. The greatest chance for rain showers will be across the north, closer to the center of the source of broad instability, though showers down through Bangor and the Interior Downeast region are possible as well. Weak CAPE with the instability from this synoptic pattern could support isolated afternoon thunderstorms each afternoon through this weekend.

On Sunday, tall skinny CAPE profiles are found on forecast soundings. This is accompanied with 1.1 to 1.2 inch PWATs. Though these PWATs do not exceed the 90th percentile from either KCAR or KGYX sounding climatology, they are indicative of healthy moisture availability. Given light and variable steering winds Sunday afternoon, showers which develop will be slow to exit the area which they develop, which could lead to localized significant rainfall. Showers and storms will be scattered in nature, so there could be sharp gradients between areas which receive no rain at all next to areas which receive at least half an inch of rainfall from a single storm.

Temperatures will be cool, especially across the north where persistent cloud cover will limit surface heating, and temperatures are expected to remain below average through the weekend. For Bangor and the Downeast region, increased breaks in the cloud cover will allow temperatures into the 70s.

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

KEY MESSAGE 2 DESCRIPTION... A shortwave moves into the region out of southern New England Monday evening. Models continue to differ on the track of the low. The GFS has a slow track off the coast with the majority of the precip offshore, though some moderate to heavy rain into Washington county as the low exits the area. The ECMWF has a quick moving low along the coast and producing a significant rainfall across the Coastal and Interior Downeast regions. The CMC has a broad open wave which tracks furthest north, across the center of our forecast area. The model trends operational and ensembles have been all over the place, with differing trends in strength, timing, and track. This system will need to continue to be monitored but with the long wave trof expect chances of rain to remain elevated and below to near normal temperatures.

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

KEY MESSAGE 3 DESCRIPTION... Global ensembles continue the positive Pacific North American Pattern across the CONUS. This will result in large ridging over the Western US with long wave troffing in the east impacting the Northeast. This will keep the pattern progressive but allow for multiple shortwaves to produce frontal systems and precipitation chances. Temperatures will generally lift into the 70s each day, though a couple of days could see highs into the lower 80s. The persistent upper level trough will keep the chances of showers and thunderstorms possible. It should not be a complete washout but will need to monitor the trends to see when synoptic/mesoscale features impact the region. Significant model differences in timing/strengths of systems exist for mid to late week. This continues with the theme from CPC of near to below normal temps and above normal precipitation.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

Early this morning...Mostly VFR conditions south of KHUL. Scattered rain showers from KHUL north could lead to periods of MVFR cigs for northern terminals. W to NW winds 5 to 10 kts.

Today...VFR/trending towards VFR across all terminals as any lingering MVFR cigs scatter out. -SHRA through this morning, becoming more isolated in the afternoon. Winds shifting NW to NNW at 10 to 15 kts with gusts 20 to 30 kts in the afternoon.

Tonight...VFR across all terminals. BCFG possible, especially around terminals which saw daytime rain. Winds becoming light and variable.

Sunday...Generally VFR across all terminals, with brief periods of MVFR cigs possible in rain showers. Slight chance for thunderstorms in the afternoon. Winds light and variable.

Monday - Monday night...MVFR/IFR in heavier showers, with a chance of thunderstorms. S winds 5 to 10 kts, becoming NE 5 to 10 kts overnight. Uncertainty in track of low pressure system, which could shift precip more offshore and shift forecasted wind direction.

Tuesday... MVFR/IFR in heavier showers, with a chance of thunderstorms. Improving to VFR late afternoon. NE winds 5 to 10 kts gusting to 20 kts, shifting to NW 5 to 10 kts.

Wednesday...Mainly VFR. Possible MVFR northern terms in the afternoon with showers and chance of thunderstorms. NW winds 5 to 10 kts.

MARINE

Seas 4 to 6 ft continue for a few more hours across the coastal waters from 25 NM to 60 NM out before seas continue to decrease. Across all marine zones, decreasing winds and seas today through Monday. Winds and seas will begin to increase once more Monday night as a low pressure system crosses the waters. Exact track is uncertain, but increasing confidence the track will bring stronger winds to the Gulf of Maine, with gusts approaching small craft advisory criteria out to 25 NM. Current forecast is for conditions to remain sub gale, but will be closely monitored as should the low intensify more quickly and track along the coast, gales could become more likely.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...Small Craft Advisory until 2 PM EDT this afternoon for ANZ050- 051.