textproduct: Boston / Norton

WHAT HAS CHANGED

Chance for severe weather continues to be present for Thursday afternoon and evening. Damaging winds and an isolated tornado are possible.

KEY MESSAGES

- Gusty southerly winds with some showers and perhaps a few afternoon thunderstorms Thursday. Main threat for severe weather still looks to be to our west and south but is possible across SNE.

- Beautiful weather Fri into the weekend despite gusty west winds Fri-Sat. Highs mainly between 75 and 85 with low humidity.

- Potential for a much needed soaking rain to kick off the start of the next work week...But that is not set in stone.

DISCUSSION

KEY MESSAGE 1...Gusty southerly winds with some showers and perhaps a few afternoon thunderstorms Thursday. Main threat for severe weather still looks to be to our west and south but is possible across SNE.

After a mostly dry day Wednesday save for some isolated showers over western/central MA our next impactful bout of weather arrives overnight and Thursday. In the mid-levels a positively tilted trough digs into the eastern Great Lakes early Thursday moving then over New England later Thursday into Friday. This directs a plume of deep moisture and strong low to mid level winds overhead. A strong W/SW jet stretches from 850mb (50-60kts) to 500mb (80-95kts) contributing to some very strong wind shear values. 0-6km bulk shear values are on the order of 70-80kts with even more impressive low level shear values (0-1km SRH 300-400m2s2). The limiting factor for severe thunderstorm development will be (potentially) very marginal instability. The previously mentioned LLJ will act on an early morning warm front to bring a round of widespread showers and potentially some embedded thunderstorms after midnight through mid to late morning. These showers and associated lingering cloudcover will act to limit heating and destabilization for some time. Much will depend on if we get many breaks in the clouds in which highs initially expected in the 70s could jump up coincident with higher instability values. At the moment, thinking that the true warm sector/highest instability values, and greatest severe potential remains just to our south and west. However, it won't take much for such a borderline atmospheric setup to become much more volatile. Historically even low instability environments have been able to be overcome by particularly strong shear, so a Slight Risk (level 2 of 5) of severe weather remains in effect. The greatest threat would be from damaging winds, then tornado potential given the extreme low level shear values. For SNE, the most likely intersection of instability and strong shear (aka greatest severe threat) would be western MA and western CT during the mid afternoon to early evening. In sum, low confidence that severe weather materializes but high potential impact if it does. Timing is generally noon to 9pm (earlier west, later east).

Finally, regardless, Thursday will be gusty thanks to the strong LLJ overhead. Much will depend on amount of clearing and resultant diurnal heating as to how well the BL mixes, but BUFKIT soundings indicate potential for wind gusts of 25 to 35 mph, even up to 40 mph at times.

KEY MESSAGE 2...Beautiful weather Fri into the weekend despite gusty west winds Fri-Sat. Highs mainly between 75 and 85 with comfortable humidity.

A beautiful post-frontal airmass works into southern New England Fri and Sat. Low pressure tracking from Quebec into the Canadian Maritimes will result in gusty west winds of 25 to 35 mph Fri/Sat afternoons with perhaps even a few spots briefly gusting up to 40 mph. Winds should be a bit less on Sunday as the pressure gradient weakens.

Otherwise...beautiful weather expected Fri into the weekend with highs generally between 75 and 85 degrees and low humidity. Low temps will be pleasant too...mainly in the 50s to the lower 60s.

The weather will be dry for all intensive purposes. Some moisture starved northern stream energy may trigger a brief diurnally driven spot shower or two this weekend. But again it is pretty much a beautiful dry stretch of weather into the weekend.

KEY MESSAGE 3...Potential for a much needed soaking rain to kick off the start of the next work week...But that is not set in stone.

The potential continues for a much needed soaking rain to kick off the start of the next work week...But that will depend upon the track of low pressure. This still remains uncertain given these tracks are usually impacted by convective processes this time of year. Limited baroclinicity during the summer can also result in more difficulties...Not to mention we are still 5 days out in the future. Certainly the potential remains for a soaking rainfall and some of our guidance continues to indicate that potential...But whether or not that comes into fruition remains uncertain.

Drier and very pleasant summerlike weather should return Tue into Wed as high pressure builds in from the west. Temperatures look to be rather seasonable with comfortable humidity by the middle of next week.

AVIATION /00Z THURSDAY THROUGH MONDAY/

Forecaster Confidence Levels...

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

00z TAF Update...

Tonight...High Confidence.

Mainly VFR for most of tonight...But some scattered showers along with localized MVFR conditions will be possible across the interior after 08z/09z. S winds generally 10 knots or less.

Thursday...Moderate confidence.

A period of MVFR with even localized IFR conditions possible Thu morning with a round of showers. While a few showers possible anywhere Thu morning...the focus for them will likely be northwest of I-95 and especially across interior MA. The main threat for scattered showers and t-storms will be Thu afternoon/early evening ahead of the cold front. A few strong to severe thunderstorms are possible too...But that will depend on how much instability is generated ahead of the front.

A strong LLJ will result in southerly wind gusts of 25 to 35 knots developing by afternoon with a few gusts perhaps near 40 knots. Localized/brief stronger winds possible if any severe thunderstorms develop.

Thursday night...High confidence.

Any lingering SHRA/TSRA should depart the coast early-mid Thu evening with conditions quickly improving to VFR. Lower cigs/vsbys may linger until midnight or so for parts of the Cape and Islands. SW winds 7-15 knots shift to the W overnight.

KBOS Terminal...Moderate confidence in TAF. KBDL Terminal...Moderate confidence in TAF.

Outlook /Friday through Monday/...

Wednesday through Friday Night: VFR. Breezy.

Saturday: VFR. Windy with local gusts up to 30 kt.

Saturday Night: VFR. Breezy.

Sunday: VFR. Breezy. Slight chance SHRA.

MARINE

Forecaster Confidence Levels...

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

Through Thursday night: High confidence.

Gusty southwest winds expected Thursday. Much will depend on how warm we can get. Have high confidence in at least Small Craft Advisory conditions, with moderate confidence for gale force gusts across some of the eastern coastal waters. Gale Watches expanded to interior easter MA waters where proximity to land/better warming may help mix down marginal gale force winds.

Outlook /Thursday Night through Monday/...

Thursday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 8 ft. Slight chance of rain showers.

Juneteenth: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 7 ft.

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

Saturday Night: Winds less than 25 kt. Seas up to 5 ft.

Sunday: 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 11 AM to 7 PM EDT Thursday for ANZ230-236. Gale Watch from Thursday morning through Thursday evening for ANZ231-234-250-251-280. Small Craft Advisory from 11 AM Thursday to 1 AM EDT Friday for ANZ232-233. Small Craft Advisory from 11 AM Thursday to 8 PM EDT Friday for ANZ235-237-255-256. Small Craft Advisory from 2 PM Thursday to 8 PM EDT Friday for ANZ254.