Marine Weather and Tide Forecast for Falmouth, ME

NEAR TERM /THROUGH SATURDAY/
745 PM Update... Weakening thunderstorms are continuing to slowly push eastward at this hour across north-central NH and interior western ME. Storm strength has been on a noticeable decline with the loss of daytime heating and therefore the threat for gusty winds/hail has ended but locally heavy rainfall remains possible. Along the Mid- Coast, fog is moving onshore with KRKD already down to 1/4SM. Will monitor trends to determine if a dense fog advisory will be needed. Made some adjustments to PoPs, temperatures, and sky cover but the overall forecast thinking remains on track.

Previously...
Radar imagery currently shows numerous pulse thunderstorms across the interior. These storms are producing heavy downpours, and may have the potential to produce some gusty winds and small hail as well. Storms are slow moving and there is some training, so localized flash flooding may occur with some heavier storms. Coastal areas should stay mostly dry this evening, as the sea breeze should keep more stable air over the coast.

After the frontal passage late tonight, marine fog builds back into the coastal plain. Scattered showers and developing fog overnight should allow for mild low temperatures tonight, with lows in the 50s and 60s.

SHORT TERM /SATURDAY NIGHT THROUGH 6 PM SATURDAY/
Key Points:

-Rounds of storms tomorrow may bring damaging winds and localized flash flooding to New Hampshire and western ME. The damaging wind threat looks to be across southwestern New Hampshire, while the flooding threat tomorrow is highest from the foothills and points north.

-The SPC has issued a Slight Risk for Severe Weather in Southwest NH

-The WPC has issued a Slight Risk for a 15% chance of excessive rainfall from the foothills and points north.

Details:

Visibility restrictions will be possible through most of the day tomorrow as very light onshore winds continue to advect fog into much of western Maine. Fog will keep high temperatures across Maine lower, and keep the environment more stable. Over western and southern NH, there should be thinner clouds with more breaks in them. This will allow for warmer high temperatures and allow for the environment to destabilize, becoming more conducive for severe weather.

The environment tomorrow afternoon features 1000-1500J/kg of CAPE, some wind shear and 100m^2/s^2 of low-level helicity. These parameters suggest that damaging winds and hail are possible with thunderstorms across southwestern NH. In addition, multiple rounds of showers and storms across the north tomorrow may produce some localized flash flooding as well.

The strongest storms move across western NH in the mid-afternoon, with another round of storms possible later on in the evening. Fog over Maine will allow for the marine layer to advect all the way to the mountains, with most storms weakening as they enter these areas of fog.

LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/
The surface low will exit into Downeast Maine Sunday morning while the 500 mb crosses overhead through the day. There could be fog and low stratus lingering in the morning, especially over eastern areas, but otherwise the upper low will bring another day of high shower coverage during the day and into Sunday night, especially inland and toward the mountains with activity more scattered farther south and closer to the coast. I don't think there's enough instability to include thunderstorms in the forecast at this point as models are mostly showing on the order of a couple hundred J/kg of CAPE.

The upper low shifts east of the area early next week to around Nova Scotia, but broad troughing across the NE and enough residual moisture will still be sufficient enough for isolated to scattered showers to develop (lower coverage than Sunday), mainly during the daytime hours. Temperatures will be in the mid 50s to lower 60s for the most part on Monday and then a touch cooler on Tuesday.

Another slow-moving, upper low then enters the picture for the second half of next week with models in good agreement a 500-mb low closing off near the Great Lakes that will slowly head toward New England. Shower chances will ramp back up as a result with cloudier conditions and temperatures staying on the cooler side.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/
Short Term...

Thunderstorms and fog will keep restrictions mostly down this evening, likely continuing through Saturday and Saturday night as fog and multiple rounds of showers and storms move across NH and ME.

Long Term...LIFR to IFR fog and/or stratus may stick around 12-15Z Sunday, mainly in the RKD-AUG corridor...otherwise showers will again be likely during the day Sunday into Sunday and could produce IFR to MVFR conditions. For Monday and Tuesday.. MVFR ceilings possible during the first part of Monday, but coverage of showers will be lower and mostly during the daytime hours these days. Chances for showers and and flight restrictions then increase toward the middle of next week.

MARINE
Short Term...

2-4ft seas expected this evening through Sunday morning. This afternoon, winds will be southerly at 6-11kts. Winds strengthen to 8- 13kts Saturday morning ahead of a frontal boundary. The frontal boundary crosses the waters tomorrow night, with winds shifting to westerlies at 6-11kts by Sunday morning.

Long Term...Winds become westerly Sunday and then northwesterly Monday into Tuesday as surface low pressure moves east of the waters. Gusts to 20-25 kt may occur from time to time during this period, but in general things look to remain under SCA levels through Wednesday.
Winds become east to northeast toward the second half of next week with developing low pressure to the south. It's uncertain what track the low will take, but SCA conditions are possible toward late week.

HYDROLOGY
Torrential downpours with rain rates as high as 1-3" per hour from slow-moving showers and storms will pose a risk of flash flooding through this evening, mainly from the mountains northward. Multiple rounds of showers and storms are again possible during the day Saturday and could pose another threat of flash flooding. The threat is highest from the foothills and points north on Saturday where WPC has highlighted a Slight Risk of Excessive Rainfall.

GYX WATCHES/WARNINGS/ADVISORIES
ME...None.
NH...None.
MARINE...None.