Marine Weather and Tide Forecast for York Harbor, ME

NEAR TERM /UNTIL 6 PM THIS EVENING/
Update...Minor changes to reflect latest observational trends.

Previous discussion...Low pressure is beginning to take shape as the upper forcing crosses the Mid Atlantic and precip shield consolidates south of New England. That will steadily expand northeastward today...but with lingering influence of departing high pressure that may be a slow march across the forecast area.
It may take until mid afternoon to reach parts of western ME.

Deep onshore flow and plenty of clouds and precip/evaporational cooling it will be a struggle for temps to climb much. Topping out around 50 may be a stretch. The record cold high temp for the day is a bit of a warm one surrounded by cooler days...with PWM 50 in 2011 and CON 51 in 1939. These records are very much in play today...and not the kind of record we are looking to set.

SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/
Storm will reach peak intensity tonight. The strongest winds will be skirting the coastline at this time. Northeast gusts will generally be between 30 and 40 kt...but with full leaf out it may not take much for limbs to come down and power outages to result. The wind advisory remains in effect for all coastal zones.

This is also the period when the strongest dynamic cooling will be occurring under strong lift. In addition precip melting thru the column will also help to cool things into the 30s at elevation. Forecast temp profiles are near isothermal around freezing above about 1500 feet. So I anticipate some accumulation above that level. I have my eye mostly on the Monadnock region...where some power infrastructure exists in that elevation range. A 2 to 3 inch snowfall after leaf out could be enough to take down some limbs.

The storm will begin to occlude into Fri morning and precip intensity will start to diminish as dry slot pushes into the area
Snow in the mtns may begin to mix
but overall it will be a pretty wintry day in the high peaks. Elsewhere it will likely stay in the 40s. By the end of the day precip will be tapering to showers.

LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
Long term Update...01z NBM has been blended in and doesn't result in much in the way of changes in the long term. While dry period will be had early to mid week it will still remain relatively unsettled.

Overview...

Low pressure slowly moves east of New England on Saturday, with the upper level low lagging behind and not fully exiting until Monday. A moderating trend returns early to midweek next week as ridging builds eastward across New England. At the same time, a cut off upper level low likely deepens across the Great Lakes, and may approach New England by late next week.

Details...

The slow moving low pressure center will drift through the Gulf of Maine Friday night and into the Canadian Maritimes on Saturday. The upper level low follows in it's tracks, keeping bands of light rain and showers moving through northern New England on Saturday. The most widespread coverage of rain will be across the higher terrain and northern areas on Saturday. Scattered shower activity is more likely across the rest of the forecast area, with an uptick in coverage across western areas during the afternoon hours as the upper level low increases the shower activity.

The upper level low center moves into the Canadian Maritimes on Sunday, with a lingering trough across New England behind it. This makes for a brighter and warmer day overall, but some pop up shower activity is likely across the higher terrain during the afternoon with the cold air aloft. Outside of the mountains, temperatures begin to rebound, likely reaching into the low to mid 60s. With more clouds and some showers, northern areas and the higher terrain likely remain in the low to mid 50s.

By Monday, ridging begins to build in from the west, with high pressure also building in from the west at the surface. This continues the moderating trend, with highs warming into the 60s to low 70s with increased sunshine. The coverage of 70s expands on Tuesday across the area. The high pressure center moves offshore by midweek, providing the set up for a steadier sea breeze. At the same time, a deepening cut off low across the Great Lakes likely begins to approach and continue moving closer toward the end of the week.
This brings an increasing chance for showers and cooler temps toward the end of the week, but will be highly dependent on the track of the cut off low. Should the low end up further south, ridging would remain in place and warmer temperatures continue, so we'll continue to monitor the progress of this feature over the next several days.

AVIATION /12Z THURSDAY THROUGH MONDAY/
Short Term...Widespread MVFR conditions this morning as onshore winds continue to carry moisture inland. CIGs will lower thru the day as rain also moves in from southwest to northeast. Areas of IFR will begin to develop late this afternoon and early this evening and expand northeast thru the night. Near the coast northeast gusts up to 35 or 40 kt are possible overnight. This will also be when some of the heaviest precip occurs...and VIS may fall to IFR at times. Some gradual improvement in conditions is expected Fri...especially across southwest zones.

Long Term...Lingering IFR to MVFR conditions generally improve toward more MVFR ceilings on Saturday, with IFR most likely at HIE.
Gradual improvement back to VFR is likely on Sunday, with MVFR ceilings most likely at HIE. VFR prevails during at least the daytime Monday through Wednesday, with nighttime valley fog possible each night.

MARINE
Short Term
As low pressure deepens today
winds and seas will increase thru the overnight. Strong gales are expected for all waters...and seas outside of the bays will build in excess of 12 feet. Once the storm reaches peak intensity and begins to slowly drift away...winds and seas will begin to diminish Friday afternoon.

Long Term...Seas gradually drop below 5ft on Saturday as low pressure slowly moves away through the Canadian Maritimes. High pressure then gradually builds across the waters early to mid week next week, bringing fair conditions.

TIDES/COASTAL FLOODING
As winds and seas increase today they will begin to drive a growing storm surge thru tonight. Guidance is forecasting a surge somewhere between 1 and 2 ft...peaking around or after midnight. The good news is that this is going to occur closer to low tide than high tide. However water levels approaching action stage and large near-shore waves could lead to splash over at the more vulnerable coastal locations.

GYX WATCHES/WARNINGS/ADVISORIES
ME...Wind Advisory from 2 PM this afternoon to 7 AM EDT Friday for MEZ023>028.
NH...Wind Advisory from 2 PM this afternoon to 7 AM EDT Friday for NHZ014.
MARINE...Gale Warning from 2 PM this afternoon to noon EDT Friday for ANZ150>154.