textproduct: Boston / Norton

WHAT HAS CHANGED

Gale Warnings posted for the eastern coastal waters as well as the MA bays and sounds.

KEY MESSAGES

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

- Dry weather Friday and Saturday with gusty west winds. Highs mainly between 75 and 85 with comfortable 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 today. Main threat for severe weather still looks to be to our west and south, but is possible across our region.

Showers were overspreading our region early this morning ahead of an approaching warm front. The timing of this warm front will be critical to our weather today. Besides providing a focus for thunderstorms, if our region can get into the warm sector of a low pressure earlier in the day, the potential for some strong to severe thunderstorms will go up.

Projected wind shear values are impressive, with values not usually seen across southern New England. Effective bulk shear of 40-60 kt and 0-1 km storm relative helicity values of 200-400 m2/s2 raise the threat of strong straightline wind damage and perhaps a tornado. The primary limiting factor will be how much instability can be generated.

Showers earlier this morning should also mean lingering clouds for a time. This is where the timing of getting into the warm sector of a low pressure over southeast Canada becomes important. Most-unstable CAPE values between 500-1,000 J/kg are expected. Those are more typical for our region, and don't really suggest the risk for widespread severe weather. There have been numerous cases where strong shear can compensate for weaker instability.

Putting this all together, a level 2 of 5 risk for severe thunderstorms remains in place across our region today. The most likely intersection of instability and strong shear remains across 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).

KEY MESSAGE 2...Dry weather Friday and Saturday with gusty west winds. Highs mainly between 75 and 85 with comfortable humidity.

Drier and less humid weather anticipated for Friday into Saturday. However, it should still be gusty into Saturday before gusts diminish some for Sunday. Sunday could be dry for most as well, but there is a risk for some showers from mid afternoon into the evening hours.

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. That will depend upon the track of low pressure, which is not well defined just yet. Even the timing remains uncertain.

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

AVIATION /06Z THURSDAY THROUGH MONDAY/

Forecaster Confidence Levels...

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

Today...Moderate confidence.

A period of MVFR with even localized IFR conditions possible this morning with a round of SHRA, which could be anywhere across our region. The focus for them will likely be northwest of I-95 and especially across interior MA. The main threat for scattered SHRA and TSRA will be this afternoon and early evening ahead of the cold front. A few strong to severe TSRA are possible.

A strong LLJ will result in southerly wind gusts of 25 to 35 kt by afternoon with a few gusts perhaps near 40 kt. Localized/brief stronger winds possible if any severe TSRA develop. LLWS expected towards the Cape and islands.

Tonight...High confidence.

Any lingering SHRA/TSRA should depart the coast by 02Z with conditions quickly improving to VFR thereafter. 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.

Friday...High Confidence.

VFR. gusty W winds up to 30 kt.

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

Outlook /Friday Night through Monday/...

Friday Night through Saturday Night: VFR. Breezy.

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

Sunday Night: VFR. Chance SHRA.

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

MARINE

Forecaster Confidence Levels...

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

Through Friday: High confidence.

Gusty southwest winds expected today. Converted the Gale Watches to Warnings with the expectation of frequent gusts to 35-40 kt. The RI coastal waters are a more complicated forecast. The potential for the same strong winds are there, however the boundary layer mixing might not be as efficient. Continued Small Craft Advisories there, but will need to monitor conditions closely. Rough seas and gusty winds likely linger across the outer southern coastal waters into Saturday, but not confident enough yet to extend the existing advisories.

Outlook /Friday Night through Monday/...

Friday Night through Saturday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas.

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

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

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

Monday: Winds less than 25 kt. Areas of rough seas. Chance of rain showers, slight chance of thunderstorms.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Gale Warning from 1 PM this afternoon to 7 PM EDT this evening for ANZ230. Gale Warning from 11 AM this morning to 10 PM EDT this evening for ANZ231>234-250-280. Small Craft Advisory from 11 AM this morning to 8 PM EDT Friday for ANZ235-237-255-256. Small Craft Advisory from 11 AM this morning to 7 PM EDT this evening for ANZ236. Gale Warning from 11 AM this morning to 7 PM EDT this evening for ANZ251. Small Craft Advisory from 1 PM this afternoon to 8 PM EDT Friday for ANZ254.