textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes made with this update.

KEY MESSAGES

- Rain continues eastward this afternoon and evening before clearing for most early tonight. Dreary again Friday.

- Warmer temperatures for the weekend into next week, with mostly dry weather.

- Potential for thunderstorms returns Tue/Wed, a few of which could be strong to severe.

DISCUSSION

KEY MESSAGE 1...Rain continues eastward this afternoon and evening before clearing for most early tonight. Dreary again Friday.

Rain currently over central MA, RI, and eastern CT will slowly continue east and north this afternoon and evening ahead of an occluded front pushing through southern New England. Guidance indicates the moisture plume from the south helping fuel this rainfall has PWAT values between 1-1.25", with the higher values further to the east along the coast and over Cape Cod and the Islands. With regards to the chances for some embedded thunder later this evening, the chances are still low, but latest mesoanalysis does have some pockets of instability over eastern MA. So, occasional rumbles of thunder cannot be completely ruled out. Rainfall totals expected to range between 0.5" to 1.5"; higher totals are most likely in northern MA, with southern RI seeing the lower end of the scale. Elsewhere across the region, totals around 0.75-1.00" are more likely. Lows tonight will likely be in the mid to upper 40s.

Rain will taper off and become more of a drizzle tonight, likely sometime before midnight, as a surface low passes right over southern New England behind the front. This feature will also aid in the return of onshore flow. NE winds are expected to continue through Friday, limiting the chance for any significant improvements to cloud cover. The associated upper level low that's currently centered over Lake Ontario will move in overhead, and with it, cooler temperatures aloft through the column. 950 mb temperatures around 6-8C tomorrow afternoon combined with the persistent cloud cover will likely keep high temperatures in the 50s.

KEY MESSAGE 2...Warmer temperatures for the weekend into next week, with mostly dry weather.

A much improved forecast as we head into the weekend and mid level heights will finally be on the rise as a marginal ridging/zonal pattern moves in for the weekend. This W/SW flow advects a much warmer airmass overhead at 850 mb temps rise from 3C Friday to 12C over the weekend and then surging to near 18C by Tuesday/Wednesday. The result will be a stretch of warm weather this weekend, then highly anomalous warmth by Tuesday. High temperatures on Saturday will sit comfortably in the 70s, with upper 70s more likely Sunday and Monday, peaking on Tuesday with potential for widespread 80s. This, with dewpoints surging well into the 60s may make for a bit of a muggy day.

KEY MESSAGE 3...Potential for thunderstorms returns Tue/Wed, a few of which could be strong to severe.

As previously mentioned, dewpoints are expected to surge into the 60s on Tuesday and this together with temps in the 80s will contribute to >1000 J/kg of surface based CAPE with low level lapse rates of 8-9C/km. Lots of instability, but the missing piece is a good forcing mechanism as the cold front until later Wed or Wed night. That being said, there are signs of enough of a kink in the low level flow that there could be enough convergence to kick off some storms. Lack of bulk shear and poor ML lapse rates would limit vertical growth and how strong any storms could get but CSU and NSSL machine learning guidance both highlight Tuesday with a possibility of some severe storms. Stay tuned.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

Forecaster Confidence Levels...

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

00z TAF Update...

Tonight and Friday...Moderate confidence.

Showers were becoming more scattered in nature early this evening...but there still were some brief downpours. The heavier showers will depart over the next few hours...but pockets of light showers/drizzle and fog will become more of a concern overnight especially across eastern New England. These pockets of light showers/drizzle and fog will linger across eastern areas will linger into Friday morning and potentially into the afternoon across parts southeast New England.

Given the above...expect IFR-LIFR conditions to dominate into Friday morning towards the coast with gradual improvement during the day. Low end VFR-MVFR conditions will dominate across western MA/CT tonight into Friday. Light winds mainly from the N-NW tonight become N-NE 5-10 knots on Friday.

Friday Night...High confidence in trends with moderate confidence in timing.

Lingering low clouds depart Friday evening...perhaps persisting a bit longer towards the Cape and Islands. Otherwise...conditions improve to VFR but will have to watch for localized patchy ground fog developing late Friday night in the typically prone low-lying locations. Calm/light and variable winds.

KBOS...Moderate confidence in TAF.

KBDL...Moderate confidence in TAF.

Outlook /Saturday through Tuesday/...

Saturday through Sunday: VFR. Breezy.

Sunday Night through Monday Night: VFR.

Tuesday: VFR. Breezy.

MARINE

Forecaster Confidence Levels...

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

SE to E winds around 10-15 kt through the rest of today, but easterly swell increases wave heights to around 4-7 ft tonight and continue into Friday. Small Craft Advisories have been issued to account for the rising seas. Rain with embedded downpours continue through this afternoon and evening, with more intermittent showers, drizzle and fog for tonight into Friday.

Winds remain generally below 15 kt for Friday night. Seas will start to diminish Friday night as a coastal low well offshore continues pulling away, though Small Craft Advisories may need to continue through the overnight hours then.

Outlook /Saturday through Tuesday/...

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

Sunday through Tuesday: 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 2 AM Friday to 2 AM EDT Saturday for ANZ235-237-251. Small Craft Advisory from 11 PM this evening to 8 AM EDT Saturday for ANZ250-254>256.