textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes were made to the forecast during this update.

KEY MESSAGES

- Cold front brings the wettest period of this week Wednesday afternoon into Thursday with scattered showers, a few embedded thunderstorms, and a return of cooler conditions.

- Dry, seasonable and a little breezy for the latter part of the workweek.

- Weekend looks unsettled with a couple periods of showers, one on Saturday and the other towards Sunday evening

DISCUSSION

KEY MESSAGE 1...Cold front brings the wettest period of this week Wednesday afternoon into Thursday with scattered showers, a few embedded thunderstorms, and a return of cooler conditions.

Dry weather prevails for most into Wednesday morning. There is a slight risk for a stray shower or thunderstorm to reach northwest MA later this evening. This risk is anticipated to diminish quickly after sunset.

Wind gusts were also starting to increase in speed, albeit a little later than we were originally thinking. Still expecting a potent low level jet to be overhead through tonight. While gust speeds will diminish after sunset, winds likely remain gusty right into Wednesday morning.

A slow-moving cold front moves across southern New England from late Wednesday afternoon as it approaches western New England, into early Thursday morning when it should move offshore. This will likely be the wettest period for this week. That said, still looking at the possibility for 0.5-1.0 inch of rainfall, which would be helpful given our recent dry conditions. Feeling a bit more confident in drier conditions into Thursday afternoon. Not overly concerned about the risk for thunderstorms. The most likely locations would be across the coastal waters south of New England.

Temperatures are going to be noticeably cooler, in the upper 60s to lower 70s Wednesday.

KEY MESSAGE 2...Dry, seasonable and a little breezy for the latter part of the workweek.

Frontal system from Wed/Wed night will continue to lurch offshore by early on Thurs. Cool, dry advection regime on WNW winds then takes hold for Thurs and into Fri, with lower dewpoints (falling thru the 30s), partly to mostly sunny skies and temps falling to more seasonable early-May levels in the mid to upper 60s. Of the two days, Fri looks to be the most breezy with gusts to 25 mph. But all in all, nice stretch of weather to close out the workweek.

KEY MESSAGE 3...Weekend looks unsettled with a couple periods of showers, one on Saturday and the other towards Sunday evening.

Although the daytime hours Sun might not be too bad, on the whole the weekend is an unsettled one with a couple opportunities for rain. One comes in with a progressive 500 mb shortwave trough and weak sfc low that moves ENE from the OH Valley into the Northeast, bringing a good chance at wetting rainfall. Rain chances then decrease into the latter half of the evening into at least the first part of Sun. The second system looks to be more of a rain-maker than this first one does, due to potential phasing between a southern- stream 500 mb vort maxima rippling through the Gulf Coast states with northern stream broader troughing north of the Gt Lakes region. The timing and details regarding this frontal system are still hazy but the timing looks to be more centered at absolute earliest late Sun afternoon, but more probable Sun night into Mon. Left NBM temps unchanged for Sun in the lower to mid 70s Sun, but we'll have to see if we can shake free of cloud cover from the Sat system as those could be a couple degrees too warm if cloud cover sticks around during the daytime hrs Sun.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

Forecaster Confidence Levels...

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

00z TAF Update:

Tonight: High confidence.

VFR through at least 08z Wed. Some risk for MVFR stratus to develop from IJD-PVD-SE MA airports after 08z Wed. SW winds 12-15 kt with gusts to 25 kt, with low level wind shear more probable overnight when gusts ease some.

Wednesday and Wednesday Night: Moderate confidence.

Otherwise, Low-end VFR to MVFR conditions dominate Wednesday. Numerous showers will overspread the region from west to east, mainly during the afternoon hours. Showers move offshore Wednesday night. IFR conditions improve from west to east after midnight.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Thursday through Sunday/...

Thursday: VFR. Slight chance SHRA.

Thursday Night: VFR.

Friday: VFR. Breezy.

Friday Night: VFR.

Saturday: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA.

Saturday Night: VFR. Slight chance SHRA.

Sunday: VFR. Breezy.

MARINE

Forecaster Confidence Levels...

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

Through Wednesday Night...High confidence.

Gale-force gusts nearshore this evening should diminish after sunset. Small Craft Advisories will need to replace the Gale Warnings later this evening. Small Craft Advisory conditions persist into late Wednesday, then gradually improve Wednesday night.

Showers expected to develop across the coastal waters Wednesday afternoon, then gradually taper off late Wednesday night into Thursday morning from west to east.

Outlook /Thursday through Sunday/...

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

Thursday Night through Friday Night: Winds less than 25 kt. Seas up to 5 ft.

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

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

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 8 PM EDT Wednesday for ANZ230>237- 251. Small Craft Advisory until 4 AM EDT Thursday for ANZ250. Small Craft Advisory until 8 AM EDT Thursday for ANZ254>256.