Marine Weather and Tide Forecast for Southwest Harbor, ME

NEAR TERM /THROUGH TODAY/
Midnight update...A line of showers and thunderstorms persists across the central part of the area. Adjusted pops to reflect this. Also, added isolated thunderstorms to the showers moving into the west. The severe thunderstorm watch has been allowed to expire.

Visible satellite imagery is showing clearing working into portions of the North Maine Woods and Central Maine Highlands allowing for some destabilization. Latest radar reflectivity is showing showers and isolated thunderstorms across Northwest Aroostook and Northern Somerset counties. More convection was tracking east from Quebec Province and will reach the western border later this afternoon/early evening. Main threats with any storms will be strong winds, hail, and heavy rain. The activity will weaken as it tracks eastward later this evening in the more stable air across eastern Maine. Still, locally heavy rainfall may continue to be a threat into tonight. It will remain mild and muggy overnight with lows generally in the 60s.
Some fog is expected, especially along the coast.

Surface low will track across far northern Maine Friday morning and then into the Canadian Maritimes Friday afternoon. An upper trough will also cross the region during Friday. Showers and an isolated thunderstorm are possible as this feature moves across.
Drier air will begin to move into the region later Friday afternoon as wind shift to Northwest. Afternoon highs will be in the low to mid 70s.

SHORT TERM /TONIGHT THROUGH SUNDAY/
Low pressure will track northeastward into the Canadian Maritimes by Friday evening. Any showers over the Crown of Maine will end by just after midnight Friday night. In the wake of the system, 850mb temperatures drop to 3-5C. Skies will be mostly clear south of Katahdin, and gradually clear to the north. However, northwest winds are expected to stay up through the night. Thus, not ideal conditions for radiational cooling. Low temperatures are expected to fall into the upper 40s in the North Woods, with 50s elsewhere. High pressure will dominate the weather on Saturday. This results in mostly sunny skies for much of the region. With downsloping northwesterly flow, the warmest temperatures will be in the Bangor region to the Downeast coast.
A few warmer spots could reach 80 degrees on Saturday.
Elsewhere, expect high temperatures in the 70s. Given dew point temperatures in the 40s to near 50 degrees, it will feel quite comfortable on Saturday.

Forecast confidence is below average for later Saturday night into Sunday morning. Model guidance shows a mesoscale convective system tracking out of Canada towards New England during that time.
However, there remains significant disagreement on the track of this MCS. The 12z ECMWF tracks the MCS over northern Maine, which would bring showers and thunderstorms to the area. The 12z GFS tracks the system into southern New England, keeping the area dry. The 12z CMC is something of a compromise solution, tracking over southern Maine.
Given these uncertainties, along with significant ensemble spread, decided to keep close to NBM guidance. Temperatures for Saturday night and Sunday will be close to seasonable levels.

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/
A large upper-level ridge of high pressure will build into the Mid-Atantic region early next week. This will result in warming temperatures across Northern and Eastern Maine for Monday and Tuesday. While the core of the heat is forecast to remain south of the area, 850mb temperatures are still likely to approach 20C by Tuesday. NBM temperature guidance is indicating that lower 90s are possible Tuesday in the Penobscot and Piscatquis valleys. In addition, dew point temperatures could approach 70 degrees in these areas. This will result in very uncomfortable conditions. A shortwave could bring a few showers or thunderstorms in the Crown of Maine later Monday. Models show a cold front moving through later Tuesday into Tuesday night, which would bring more widespread showers and thunderstorms. However, timing is still uncertain with the frontal passage. Currently expecting much cooler temperatures behind the front towards midweek.

AVIATION /04Z FRIDAY THROUGH TUESDAY/
NEAR TERM: MVFR conditions expected the remainder of the afternoon, with the exception of KBHB with IFR is expected in low clouds and fog.

IFR/LIFR expected tonight in low clouds/fog. Have included PROB30 this for the northern terminals, mainly 23z to 03z.

IFR/LIFR is expected Friday morning, then improving to VFR by afternoon. Scattered showers possible.

S wind 5 to 10 kt through Friday morning, then becoming NW by afternoon. Winds could be much gustier in the vicinity of any thunderstorms this evening.

SHORT TERM: Friday Night...Brief MVFR possible PQI northward in the evening with VCSH. Otherwise, VFR. W-NW winds 10-15 kts decreasing to 5-10 kts.

Saturday...VFR. NW winds 5-10 kts.

Saturday Night and Sunday...Mainly VFR. Periods of MVFR possible late Saturday night into early Sunday AM with VCSH and isolated TS.
Confidence is low at this time. Light and variable winds Saturday night. S winds 5-15 kts Sunday.

Sunday Night through Monday...Mainly VFR. S winds 5-10 kts.

Monday Night...VFR early. IFR or lower possible late with patchy fog. S winds 5-10 kts.

Tuesday...IFR or lower possible early AM with fog. Then mainly VFR/MVFR. VCTS in the PM. S winds 5-10 kts AM, becoming W in the PM.

MARINE
NEAR TERM: A Small Craft Advisory is in effect for the waters into Friday night with gusts up to 30 kt possible. Seas will build to around 6 to 7 feet for the outerwaters on Friday.
Visibility will be reduced to 1 NM or less in fog tonight into Friday.

SHORT TERM: Winds and seas will gradually diminish below Small Craft Advisory criteria Friday night. Conditions will then remain sub-SCA through the weekend and into early next week.

CAR WATCHES/WARNINGS/ADVISORIES
ME...None.
MARINE...Small Craft Advisory from 4 AM early this morning to 4 AM EDT Saturday for ANZ050-051.
Small Craft Advisory from 6 AM this morning to 11 PM EDT this evening for ANZ052.