Marine Weather and Tide Forecast for Southwest Harbor, ME

NEAR TERM /THROUGH TUESDAY/
642 PM Update: Light snow has begun to spread across the forecast area this evening ahead of the incoming clipper system.
Snowfall intensities remain very light for the time being, but may increase towards more moderate snowfall overnight tonight.
The previous forecast remains on track with only minor adjustments made based on current observations and trends.

Previous Discussion: The weak warm front with the low pressure system over the Great Lakes will swing through the region tonight. For this evening, the pre frontal instability that produced flurries will move out of the area and the next round of light snow will move into the SW. The weak warm front will lift through the region tonight.
As it does, mid level energy over Quebec will merge with the weakening low, to become a new surface low pressure center over the waters. This energy will stay over the region for the night and into Tuesday causing light snow.

By Tuesday morning, light snow will continue mainly across the north. High res models show bands of snow across the south, so decided to include chance snow in the south. Snow accumulations will be around 1-2 inches in the north and around 0.5 inches in the south. Temps in the 20s across the region.

SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/
The intensifying low exits east of Nova Scotia Tuesday night along with the supporting upper low, with troffing extending back across the forecast area. Early light snow will taper to snow showers across northern areas Tuesday night with little additional snow accumulation. Across Downeast areas, expect mostly cloudy skies along with a slight chance of light snow early then partly cloudy late. The Maritimes system moves slowly east Wednesday, with high pressure building toward the region late. Expect mostly cloudy skies along with a slight chance of snow showers across the north and mountains Wednesday, with partly sunny skies Downeast. The pressure gradient between the exiting Maritimes system and building high pressure will support gusty northwest winds Wednesday. High pressure builds toward the region Wednesday night with partly cloudy skies north, partly cloudy/mostly clear Downeast. High pressure crosses the region Thursday. Across northern areas, expect partly sunny skies early with clouds then increasing. Expect partly cloudy skies Downeast. Expect near normal level temperatures Wednesday, with slightly below normal level temperatures Thursday.

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
High pressure begins to move east Thursday night with mostly cloudy skies north, mostly/partly cloudy Downeast. A weak cold/occluded front is possible early Friday. Low pressure tracking across the Great Lakes toward Quebec province then draws a warm front toward the region late. Expect mostly cloudy skies north, partly/mostly cloudy Downeast Friday. Uncertainty increases Saturday regarding the track of low pressure crossing Quebec province.
Indications are that a warm front should cross the region Saturday. However, the frontal timing will be dependent on the eventual track of the low. Warmer air will be drawn north across the region in the wake of the warm front. Generally expect precipitation in the form of snow across northern areas. A snow/rain mix, or even a total transition to rain, could occur across Downeast areas dependent on the extent of warmer air which is drawn north. The extent of warming will also be dependent on the eventual track of the low. The low should then begin to draw a cold front across the region Saturday night, though again timing differences persist. Uncertainty persists Sunday regarding how rapidly the front moves east which could keep a slight chance of snow showers across the forecast area.
The location of the front Monday remains uncertain. Indications are that low pressure could develop somewhere along the front during Monday. Though where low formation occurs, along with the track/intensity of any low, remains uncertain. Potential impacts across the forecast area will be dependent on the eventual track and intensity of any low. Near normal, to slightly below normal, level temperatures are expected Friday/Sunday, with above normal level temperatures Saturday.
Temperatures Monday will be dependent on the eventual track of possible low pressure.

AVIATION /23Z MONDAY THROUGH SATURDAY/
NEAR TERM: Aroostook Terminals...Low end VFR to MVFR tonight with low cigs and occasional marginal MVFR vis due to light snow. MVFR conditions will continue through Tuesday due to low cigs and light snow. Light and variable winds.

Downeast Terminals...VFR conditions will continue through tonight with VFR/MVFR from around midnight into Tuesday morning due to reduced vis and lower cigs in light to moderate snow.
VFR conditions return through the day Tuesday. Light and variable winds.

SHORT TERM: Tuesday night.. MVFR, occasional IFR, north with light snow tapering to snow showers. VFR, occasional MVFR, Downeast with a slight chance of light snow early. West/northwest winds 10 to 15 knots.

Wednesday...VFR, occasional MVFR, north with a chance of snow showers. VFR Downeast. Northwest winds 10 to 20 knots with gusts up to around 25 knots.

Wednesday night through Thursday...VFR. Northwest winds 10 to 15 knots, becoming west/northwest 5 to 10 knots Wednesday night.
Variable winds 5 to 10 knots Thursday.

Thursday night through Friday...VFR/MVFR. Variable winds 5 to 10 knots Thursday night. South/southwest winds 5 to 10 knots Friday.

Friday night...VFR/MVFR, occasional IFR, north with a chance of snow. VFR/MVFR Downeast. Southwest/south winds around 10 knots.

Saturday.. MVFR/IFR. A chance of snow north. A chance of snow/rain Downeast. South/southwest winds 10 to 15 knots.

MARINE
NEAR TERM: Winds and seas will remain below SCA levels tonight and Tuesday.

SHORT TERM: A Small Craft Advisory has been issued for all the waters from Tuesday evening into Wednesday evening, which will likely need extending through Wednesday night. Conditions are expected to be below small craft advisory levels Thursday. A slight chance of snow early Tuesday night. Light freezing spray Wednesday night into Thursday morning.

CAR WATCHES/WARNINGS/ADVISORIES
ME...None.
MARINE...Small Craft Advisory from 11 PM Tuesday to 7 PM EST Wednesday for ANZ050>052.