Marine Weather and Tide Forecast for West Yarmouth, MA

KEY MESSAGES

- Scattered showers and perhaps isolated t-storms this afternoon. Focus across eastern New England where activity may linger into part of the evening. Dry/cooler weather follows tonight into Mon night.

- Summerlike temperatures expected Tuesday through the weekend, with a multi-day stretch of 90+ degree temperatures in some locations possible.

DISCUSSION
KEY MESSAGE 1...Scattered showers and perhaps isolated t-storms this afternoon. Focus across eastern New England where activity may linger into part of the evening. Dry/cooler weather follows tonight into Mon night.

A dynamic shortwave/cold pool aloft will drop south into the region this afternoon. Although the low level moisture will be lacking...the dynamics/cold pool aloft will result in several hundred J/KG of Cape developing which potentially may approach 1000 J/Kg near the south coast. This will trigger scattered this afternoon with potentially isolated t-storms. Perhaps some gusty winds/small hail would be possible if a t-storm is able to develop given cold pool aloft and modest T/Td spreads. Activity will focus across eastern New England...where it may linger into part of this evening.

Otherwise...drier/cooler air will continue to work into the region tonight on northerly flow behind the cold front. Low temps tonight will be in the 50s...But some of our typically prone low-lying locations will briefly decouple and allow for lows in the middle to upper 40s.

Large high pressure builds across the region Mon into Mon night.
This will result in sunny skies on Mon with highs in the upper 70s to near 80...But cooler upper 60s to lower 70s on parts of the very immediate coast with onshore flow. Mainly clear skies with light/calm winds Mon night will result in a good night of radiational cooling. Low temps Mon night will be in the 40s across the outlying locations to generally lower to middle 50s elsewhere.
However...the Urban Heat Island of Boston will only drop to around 60 as southwest flow begins to warm advect.

KEY MESSAGE 2...Summerlike temperatures expected Tuesday through the weekend, with a multi-day stretch of 90+ degree temperatures in some locations possible.

We are still anticipating a steady warming trend to our temperatures starting Tuesday, as an amplified upper level ridge moves in and then begins to flatten around late week into the weekend. By Wednesday, 850 mb temps are in the mid to upper teens C range to go along with an uptick in humidity levels. We could be looking at a few consecutive days of 90+ degree temperatures with heat indices possibly warranting heat headlines. The bigger uncertainty on the temperature forecast is the potential for thunderstorms, which is still a little uncertain, but the chances for storms increases as we move into late in the week into the weekend as the ridge axis flattens and allows for increasing midlevel winds to interact with the northern/western periphery of the building heat.

AVIATION /18Z SUNDAY THROUGH FRIDAY/
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

18z TAF Update...High confidence.

VFR conditions dominate through Monday night
However
scattered showers will develop this afternoon with perhaps an isolated t-storm or two which may linger into part of the evening across eastern New England. This activity may result in briefly lower cigs/vsbys. In addition...a brief period mainly MVFR cigs roughly in the 22z to 06z may sweep across the region from north to south with the greatest risk across eastern MA/Cape and Islands. Outside of those two items...VFR conditions right through Monday night.

As for winds...NW wind gusts of 20-25 knots this afternoon shift to the N tonight. Brief N wind gusts of 20-25 knots with the strongest near the coast before they gradually diminish or even decouple in the typically prone spots overnight. Light NE winds Mon becoming SW Mon night.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Tuesday through Friday/...

Tuesday through Tuesday Night: VFR. Breezy.

Wednesday: VFR. Breezy. Slight chance SHRA.

Wednesday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA, slight chance TSRA.

Thursday: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA, slight chance TSRA.

Thursday Night: VFR.

Friday: VFR. Chance SHRA, slight chance TSRA.

MARINE
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Tonight through Monday night...High confidence.

Shortwave/cold front crosses the region by early-mid evening. This will bring a surge of N wind gusts of 25 knots especially across our eastern waters. Small craft headlines have been posted for most of our waters. High pressure building into the region Mon will result in winds/seas dropping below small craft headlines from north to south...but it may take until late afternoon/early evening across our southeast most outer-waters.

Lastly...will need to watch for a few showers and isolated t-storm developing nearshore later today into early this evening...
particularly near the south coast. Gusty winds/small hail and lightning possible with any t-storm.

Outlook /Tuesday through Friday/...

Tuesday: Winds less than 25 kt.

Tuesday Night: Winds less than 25 kt. Seas locally approaching 5 ft.

Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft.

Wednesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Rain showers likely, slight chance of thunderstorms.

Thursday: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers.

Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers.

Friday: Winds less than 25 kt.

BOX WATCHES/WARNINGS/ADVISORIES
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 7 PM this evening to 10 AM EDT Monday for ANZ231>235-237-250-251.
Small Craft Advisory until 4 PM EDT Monday for ANZ254>256.