textproduct: Boston / Norton

WHAT HAS CHANGED

High Risk of rip currents through this evening for the south-facing beaches of Marth'a Vineyard and Nantucket. A marginal Small Craft Advisory issued for Buzzards Bay and Vineyard Sound for Tuesday afternoon.

KEY MESSAGES

- Mainly dry and seasonable conditions, outside of a stray shower this afternoon and Tuesday afternoon.

- Main risk for a round of scattered showers and a few thunderstorms will be sometime late Thu/Thu night into Fri with summerlike humidity. Mainly dry & seasonable weather favored for the weekend.

DISCUSSION

KEY MESSAGE 1...Mainly dry and seasonable conditions, outside of a stray shower this afternoon and Tuesday afternoon.

The synoptic setup for the next several days is as follows. A mid- level low, which is easily seen on GOES water vapor imagery across northern New York, will move into northern New England before drifting east into the Canadian Maritimes by Wednesday. Locally, Wednesday brings a subtle shortwave ridge. In general, expect benign conditions through the first half of Thursday as surface high pressure expands into the Northeast from the Midwest. However, a stray pop-up shower or thunderstorm remains possible this afternoon and Tuesday afternoon due to cyclonic flow, which will promote diurnal cu development amid steep low-level lapse rates (greater than 8C/km) along a trough. No severe weather is expected, as mid- level lapse rates remain poor (less than 6C/km). Areas with the best chance of experiencing a brief shower or storm (less than a 25 PoP) through this afternoon are west of KIJD, KORH, and KFIT, associated with the passage of a weak surface trough. Thereafter, cannot discredit a shower farther east along the Boston-to-Providence corridor. Similar conditions are expected again Tuesday. Wednesday into Thursday, the mid-level shortwave ridge moves through, providing another dry day Wednesday. However, the ridge shifts east by Thursday ahead of an approaching trough, which has the potential to bring numerous showers late Thursday into Friday. More on that in Key Message 2.

As for temperatures, expect a seasonable week, with afternoon highs in the lower 80s and higher-terrain communities in the northern Worcester Hills and eastern Berkshires remaining in the middle to upper 70s. Nightly lows will be a touch cooler as clear skies and light winds allow for radiational cooling, with temperatures slipping back into the 50s while urban areas remain near 60 degrees. This setup may allow for another night of low stratus or fog. Confidence in how widespread it becomes remains low; however, it does not appear this round of fog will be as prevalent as last night.

KEY MESSAGE 2...Main risk for a round of scattered showers and a few thunderstorms will be sometime late Thu/Thu night into Fri with summerlike humidity. Mainly dry & seasonable weather favored for the weekend.

The next shortwave trough approaches from the west by late in the work week. Ahead of this approaching shortwave...summerlike humidity will return Thu into Fri. Timing quite uncertain this far out in the forecast...But appears there will be the potential for a round of scattered showers and a few thunderstorms sometime in the late Thu/Thu night into Fri time frame. CSU machine learning probs do indicate some low probs for severe weather/heavy rainfall potential...But that is really just climo for an approaching shortwave this time of year. So not much more we can say at this point. Current guidance does indicate that drier/seasonable weather is favored to return for the upcoming weekend.

AVIATION /18Z MONDAY THROUGH SATURDAY/

Forecaster Confidence Levels...

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

18z TAF Update:

Through 12z...Moderate to high confidence.

VFR. SW to WSW wind gusts of 20 to 25 kt through 23-00z, diminishing thereafter. A stray shower or thunderstorm remains possible this afternoon, primarily west of KIJD, KORH, and KFIT through 00z. Thereafter, cannot discredit a shower farther east toward the KBOS to KPVD corridor. Overnight, light to calm winds and clear skies may allow for areas of fog. Confidence in how widespread fog becomes remains low, though it does not appear this round will be as prevalent as last night.

Tuesday...High confidence in trends, lower confidence in shower coverage.

VFR. WSW to W winds 8 to 12 kt, with gusts up to 18 kt. A stray shower or thunderstorm is possible during the afternoon, though confidence in areal coverage remains low.

Tuesday Night...

VFR and dry. W to WNW winds less than 5 kt.

KBOS Terminal...High confidence.

Wind gusts through 23-00z, then SSW to SW winds overnight at 5 to 8 kt. Winds shift to WSW to W Tuesday, with speeds of 10 to 12 kt and gusts up to 18 kt.

KBDL Terminal...High confidence.

Outlook /Wednesday through Saturday/...

Wednesday through Wednesday Night: VFR.

Thursday: VFR. Breezy. Chance SHRA, chance TSRA.

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

Friday: VFR. Chance SHRA, slight chance TSRA.

Friday Night through Saturday: VFR.

MARINE

Forecaster Confidence Levels...

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

Through Tuesday Night...High confidence.

Fairly quiet boating conditions through the first half of this week as high pressure develops across the Midwest before expanding toward the waters off the coast of southern New England. Gusty southwest flow develops Tuesday, with gusts around 20 kt. However, Vineyard Sound and Buzzards Bay are oriented roughly parallel to the wind, allowing for a localized enhancement from funneling. Have opted to issue a marginal Small Craft Advisory for gusts up to 25 kt Tuesday afternoon. Conditions improve overnight into early Wednesday morning as winds shift to the northwest.

Swell periods of 11-12 seconds are expected off the coasts of Martha's Vineyard and Nantucket, which will lead to a higher risk of rip currents along south-facing beaches there, warranting expansion of the Rip Current Statement over the Vineyard. A moderate risk for rip currents extends along SE MA and RI beaches due to swells as well.

Outlook /Wednesday through Saturday/...

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

Wednesday Night through Thursday: Winds less than 25 kt.

Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, slight chance of thunderstorms.

Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers.

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

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

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...High Risk for Rip Currents until 6 PM EDT this evening for MAZ023- 024. RI...None. MARINE...Small Craft Advisory from 11 AM to 8 PM EDT Tuesday for ANZ233- 234.