Marine Weather and Tide Forecast for South Yarmouth, MA

KEY MESSAGES

- Mainly dry with seasonable temperatures through the weekend.

- Unsettled weather for early to mid-week next week with periodic chances for scattered showers and thunderstorms.

DISCUSSION
KEY MESSAGE 1...Mainly dry with seasonable temperatures through the weekend.

A few showers and embedded weak storms are possible over our coastal waters early this morning as the cold front pushes offshore. By sunrise, the front should be fully through pushing out any remaining showers. Weak mid-level troughing will persist with drier and cooler conditions in the post-frontal airmass.
925 mb temperatures drop a few degrees from yesterday yielding cooler high temperatures in the upper 70s to near 80 for southern New England today. The airmass will be noticeable drier as well bringing more comfortable humidity levels as surface high pressure builds in from the west. This will also keep winds on the lighter side with light NW winds and local sea breezes for the coastal areas.

Surface high pressure builds further over the region Friday continuing through the weekend with flow aloft becoming more zonal. Weak subsident flow will keep conditions dry. Winds remain light under surface high pressure with winds becoming easterly for the weekend. 925mb temperatures range 16-21C supporting highs in the low to mid 80s in most spots, perhaps a tad cooler in the immediate coastal areas where sea breezes/onshore flow will be prevalent. Surface high pressure pushes offshore through the day Sunday as a mid-level trough approaches from the west. The drier airmass should stay in place during the day suppressing most shower development.

KEY MESSAGE 2...Unsettled weather for early to mid-week next week with periodic chances for scattered showers and thunderstorms.

The pattern becomes more unsettled early next week with a mid-level trough positioned across the northeast and a series of disturbances moving through the flow. Overall there is a good signal for increasing moisture with PWATs slightly above normal which will support increased chances for periodic scattered showers and thunderstorms early next week through mid-week. Temperatures lean toward seasonable values in the low 80s.

AVIATION /12Z THURSDAY THROUGH MONDAY/
Forecaster Confidence Levels...

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

12Z Update...

Today...High confidence.

VFR. Winds WNW to NW for most terminals 5-10 kts. Sea breezes likely for the coastal areas developing 18-20Z as NW winds weaken. If Winds may become more variable later in the afternoon and evening for the interior terminals. Sea breezes shift toward S/SSE 21-00Z becoming S/SSW after 00Z.

Tonight...High confidence.

VFR. Light to calm winds overnight out of the SW.

KBOS Terminal...High confidence in TAF.

Higher confidence in a sea breeze developing after 18z this afternoon. Otherwise, VFR with NW winds shifting to the E after 18z.

KBDL Terminal...High confidence in TAF.

Outlook /Friday through Monday/...

Friday through Sunday Night: VFR.

Monday: VFR. Slight 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 Thursday Night

Winds shift to the NW early this morning as a cold front moves through. Scattered showers and perhaps an isolated weak storms are possible early this morning over the coastal waters as the front slowly shifts eastward. Majority of the showers should exit the outer coastal waters by 12Z this AM. Winds have fallen below SCA criteria; however, lingering 5-6 ft seas will keep SCAs going through the afternoon for the far southern inner waters and through tonight for the southern outer waters.

High Surf Advisory remains in effect for exposed southern coastlines through this evening. Prolonged period of higher seas and SW flow have increased the risk for rip currents. The higher risk continues today and decreases Friday. Seas recede to 4 ft Thursday night with light winds over the waters.

Outlook /Friday through Monday/...

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

Friday Night: Winds less than 25 kt.

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

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

Sunday: Winds less than 25 kt.

Sunday Night: Winds less than 25 kt. Slight chance of rain showers.

Monday: Winds less than 25 kt.

BOX WATCHES/WARNINGS/ADVISORIES
CT...None.
MA...High Surf Advisory until 8 PM EDT this evening for MAZ020>024.
RI...High Surf Advisory until 8 PM EDT this evening for RIZ006>008.
MARINE...Small Craft Advisory until 2 PM EDT this afternoon for ANZ235- 237.
Small Craft Advisory until 11 PM EDT this evening for ANZ254>256.