Marine Weather and Tide Forecast for West Yarmouth, MA

NEAR TERM /THROUGH TONIGHT/
Key Messages...

* Mostly dry with scattered rain/snow showers possible this afternoon and evening.

Clouds overspread southern New England with vigor this afternoon ahead of an advancing cold front. This front was still back in central NY and PA, and should move past our region by midnight or so. While accompanied by a modest mid level shortwave, there is not a lot of humidity to work with, especially within the dendritic snow growth region. Upstream observations did show some snow across NY state, with some visibilities as low as 1 statute mile.

Latest runs of the HRRR and RAP were more aggressive in bringing some rain or snow showers to MA late this afternoon and evening, but am leery due to the large surface dew point depressions. Did introduce a chance for measurable precipitation, but no more than 30%. Will continue to monitor the progress of showers later today, and will adjust as needed.

Clouds a likely here to stay for a while, which will help prevent strong radiational cooling. Expecting low temperatures to be near normal for mid January.

SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/
Key Messages...

* Turning colder and blustery.

Colder air makes more of a push across southern New England during this time period. Low pressure over the Maritimes and a high pressure over the Plains will maintain a persistent W to NW flow. This will begin the trend for below normal temperatures.
Becoming much drier, so little chance for precipitation. Ocean- effect showers are possible across the outermost coastal waters.

LONG TERM /WEDNESDAY THROUGH SUNDAY/
Key Messages:

* Dry with below normal temps Wed-Thurs.

* Temps then modify to slightly above normal levels by Fri into the weekend, but likely to be accompanied by cloud cover.

* Next chance of widespread precip not until the weekend?

Details:

Dry weather with a period of below normal temperatures are expected for Wed and Thurs with the colder air being reinforced by the eventual passage of northern-stream shortwave trough energy coming out of the Canadian Prairies in central Canada. This airmass does not look to be as cold and also not nearly as windy as last week's shot of cold air; however, we are expecting highs in the mid 20s to near freezing with lows in the single digits to the mid teens.
Temperatures then modify by Fri into the weekend as southerly flow increases with near to above normal temperatures (highs mid 30s to low 40s), although it may also be accompanied by a good amt of cloud cover.

Overall this portion of the forecast is generally a dry one. Our next chance for significant precip may not arrive until the weekend, as a deep 500 mb trough establishes itself across much of the central/east-central CONUS per consensus in ensemble means. There continue to be some ensemble members which bring weak/sheared-out 500 mb vort energy from the southern Plains states into the mid-Atlc and Northeast but this is not well agreed upon. Will continue to advertise Chance PoP for timing-dependent snow-to-rain showers Sat and Sun and then adjust pending trends in the guidance.

AVIATION /20Z MONDAY THROUGH FRIDAY/
Forecast Confidence Levels:

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

Through Tonight: High confidence.

VFR cigs. Passage of a cold front between 00-06z from W to E will bring a windshift from WSW/SW 5 kt or less to W/NW and increasing to 8-12 kt, with gusts 20-25 kt. Low risk for a

Tuesday and Tuesday Night: High confidence.

VFR. Gusty W winds continue 10-15 kts gusting 20-25 kts.

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Wednesday through Friday/...

Tuesday Night through Wednesday Night: VFR. Breezy.

Thursday through Friday: VFR.

MARINE
Forecaster Confidence Levels:

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

High confidence.

Through Tuesday Night...

A cold front moves across the waters overnight, which will bring a windshift to WNW with speeds increasing to around 20-25 kt toward early Tue morning. Small Craft Advisories remain in effect for the outer waters during this time.

Outlook /Wednesday through Friday/...

Tuesday Night: Strong winds with gusts up to 30 kt. Areas of rough seas.

Wednesday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Chance of freezing spray.

Wednesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft.

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

Thursday Night through Friday: Winds less than 25 kt. Areas of seas approaching 5 ft.

BOX WATCHES/WARNINGS/ADVISORIES
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 6 PM Tuesday to 7 AM EST Wednesday for ANZ235-237.
Small Craft Advisory from 1 AM Tuesday to 7 AM EST Wednesday for ANZ250.
Small Craft Advisory until 7 AM EST Wednesday for ANZ254>256.