textproduct: Boston / Norton

WHAT HAS CHANGED

While no significant changes were made to the forecast, continue to refine summery temperatures and timing of precipitation for this coming weekend.

KEY MESSAGES

- Quiet and dry stretch of weather through Saturday, with unseasonably warm temperatures.

- Showery activity becomes more likely late Saturday into Sunday with a frontal passage.

- Drier and cooler conditions early next week.

DISCUSSION

KEY MESSAGE 1...Quiet and dry stretch of weather through Saturday, with unseasonably warm temperatures.

Confidence remains high in dry and unseasonably warm weather through the daylight hours Saturday as surface high pressure shifts from the Great Lakes toward the southeastern CONUS while mid-level ridging settles across the Northeast. Temperatures aloft continue to warm, with 850 mb temperatures rising to around +13C to +15C today and Friday, then +15C to +18C Saturday. Highs today should top out in the 80s for most, with the greatest potential for 90 degree temperatures across the Connecticut River and Merrimack Valleys where downsloping and deeper mixing are maximized. Friday and Saturday are expected to be the warmest days, with highs in the upper 80s to lower 90s becoming more widespread away from the immediate coast, where onshore flow should still provide some moderation. NBM probabilities continue to indicate a 70 to 80 percent chance of exceeding 90 degrees across the Connecticut River and Merrimack Valleys Friday afternoon, while much of the coastal plain away from the shoreline has a 50 to 60 percent chance. One caveat Saturday will be increasing cloud cover and a low risk for a late-day shower, mainly northwest of the I-91 corridor.

KEY MESSAGE 2...Showery activity becomes more likely late Saturday into Sunday with a frontal passage.

Confidence continues to increase that most, if not all, of the daylight hours Saturday remain dry, though a brief afternoon shower cannot be ruled out northwest of the I-91 corridor as a front approaches from northern New England. Given summerlike warmth and modest humidity (dewpoints near 60F), a limited risk for an isolated thunderstorm with locally heavy downpours exists Saturday afternoon, though confidence remains low and any activity should remain isolated.

By Sunday, a more defined mid-level trough and associated shortwave energy become established over southern New England, supporting a better signal for scattered showers as weak surface low pressure develops along a weakening frontal boundary. Temperatures trend notably cooler, generally 10 to 15 degrees lower than Saturday, though exact values will depend on frontal timing. Eastern areas may cool more quickly with northeasterly flow off the Gulf of Maine, while interior locations such as Springfield and Hartford could remain relatively warmer.

KEY MESSAGE 3...Drier and cooler conditions early next week.

Conditions trend drier Monday into Tuesday as the weekend system gradually shifts east of New England. Some uncertainty remains regarding how quickly lingering troughing departs, which will influence temperatures and cloud cover early next week. For now, expect cooler conditions Monday with a gradual warming and drying trend by Tuesday.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

Forecaster Confidence Levels...

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

18z TAF Update...

Through Friday...High confidence.

VFR conditions continue through Friday. Seabreezes this afternoon should kick back out within the next hour or two. Otherwise, SW winds sustained just over 10 kt through the rest of this afternoon and 20-25 kt gusts towards the south coast and Cape. Similar story for Friday as seabreezes move in early afternoon/late morning and kick back out towards sunset in the midst of persistent SW winds in SE MA and coastal areas. W winds expected Friday across much of the region.

For tonight, winds drop off below 5 kt for most. Some patchy fog cannot be ruled out, particularly in SE MA.

KBOS...High confidence in TAF.

KBDL...High confidence in TAF.

Outlook /Friday Night through Tuesday/...

Friday Night: VFR.

Saturday: VFR. Breezy. Slight chance SHRA, slight chance TSRA.

Saturday Night: VFR. Breezy. Chance SHRA, slight chance TSRA.

Sunday: Mainly VFR, with areas MVFR possible. Breezy. SHRA likely, chance TSRA.

Sunday Night: Mainly VFR, with local IFR possible. Breezy. Chance SHRA, patchy BR.

Monday: Mainly VFR, with local MVFR possible. Breezy. Slight chance SHRA.

MARINE

Forecaster Confidence Levels...

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

Today through Friday...High confidence.

Winds and seas remain below SCA criteria through Friday. SW winds increase to around 15-20 kt today, with occasional marginal SCA- level gusts near 25 kt across the Cape and Islands waters, including Buzzards Bay, Vineyard Sound, and Nantucket Sound, where stronger SW flow is favored through sunset. A similar setup may develop again Friday, though confidence is too low at this time to warrant an additional Small Craft Advisory. Seas remain 3 ft or less on all waters.

Outlook /Friday Night through Tuesday/...

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

Saturday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft.

Saturday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers, slight chance of thunderstorms, patchy fog.

Sunday: Winds less than 25 kt. Local rough seas. Rain showers likely, slight chance of thunderstorms, patchy fog.

Sunday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers, patchy fog.

Monday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Seas up to 5 ft. Slight chance of rain showers.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 9 PM EDT this evening for ANZ232>234.