textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes to the forecast.

KEY MESSAGES

- Periods of heavy rain and a few embedded t-storms today into Tuesday across parts of CT, RI, and SE MA. Rain continues to overspread the region through tonight, but will be lighter towards the NH border.

- Mainly dry mid-week as higher temperatures and humidity return. Shower and thunderstorm chances return Friday, possibly lingering into Saturday.

DISCUSSION

KEY MESSAGE 1...Periods of heavy rain and a few embedded t-storms today into Tuesday across parts of CT, RI, and SE MA. Rain continues to overspread the region through tonight, but will be lighter towards the NH border.

Rain to the south of the region is slowly moving northward towards southern New England, picking up a bit towards the south coast of CT. Drier air remains settled over much of Massachusetts north of the RI and CT borders, limiting the spread of rain there. High pressure over northern New England nosing down into the region is also a key factor here. Rain is not expected to really pick up until this evening into tonight for parts of CT, SE MA, and RI when the low to the south of Long Island is expected to continue pushing north. Up towards northern MA, rain may not start until around midnight.

With the approaching low, a boundary will also push northward that will clash with high pressure, a PWAT plume with values up to (and even exceeding) 2.0", and a LLJ with winds around 30 kt at 925 mb. This would be a main driver for widespread heavy rainfall along the boundary, which guidance has still struggled to find a more concrete solution to. Rainfall totals between 1-3" are still expected over much of southern New England, with lighter totals expected closer to the NH border. Locally higher totals between 4-6" remain a possibility over parts of CT, RI, and SE MA. Even with the spread in guidance regarding where these totals may be, a number of models still key in on those areas as having the highest risk for these totals. For these reasons, a Flood Watch remains in effect through tomorrow afternoon for our counties in northern CT into RI and SE MA to the Cape.

Rainy conditions are expected to continue through much of Tuesday -- mainly in eastern MA and RI -- as the low pressure continues northeastward and its associated shortwave moves east from the Great Lakes. The low passes the region Tuesday night with the upper level shortwave moving over Maine, and high pressure to the north continues spreading southward over southern New England as it departs. Showers may persist into Tuesday night, but these are not expected to be nearly as impactful as today & tonight's rainfall.

KEY MESSAGE 2...Mainly dry mid-week as higher temperatures and humidity return. Shower and thunderstorm chances return Friday, possibly lingering into Saturday.

A mid-level ridge and subsequent surface low will start to build over the mid-Atlantic and New England regions Wednesday, bringing a spell of mainly dry weather through most of Thursday. 925mb temperatures rising to near 20C and plenty of sunshine will allow for surface temperatures to begin to creep up above seasonable norms... likely near 90 across most of southern New England Wednesday and Thursday. Another shortwave trough and cold front pushing through sometime Thursday may bring chances for showers and thunderstorms Friday. Depending on the timing of the FROPA, showers could linger into Friday.

AVIATION /19Z MONDAY THROUGH SATURDAY/

Forecaster Confidence Levels...

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

18Z TAF Update...

No major changes in trends.

Through Tuesday...Moderate confidence.

VFR conditions early this morning will gradually deteriorate to MVFR levels today into tonight from southwest to northeast with brief bouts of IFR conditions possible too. This will be associated with periods of rain, which may fall heavy at times across parts of CT/RI/SE MA. An embedded t-storm or two is possible in this same area as well. The process of lower cigs/vsbys and steady rain will be slowest to arrive across northeast MA where it may take until this evening or even later for MVFR conditions to develop. Periods of rain will continue into Tue especially across eastern MA/RI. MVFR with localized IFR conditions will also continue into Tue. E winds 6-12 knots today gradually becoming NE at 8-16 knots by Tue. Some gusts to 20-25 kt are possible tonight into Tue, primarily over the Cape and Islands. Gusts also a possibility for eastern MA Tue morning into the afternoon.

Tuesday Night...Moderate confidence.

Rain clears out of the region Tuesday night, though onshore winds may keep conditions generally MVFR with areas of IFR across southern New England. Lower cigs more likely over eastern MA and RI.

KBOS Terminal...Moderate confidence in TAF. Higher confidence in overall trends, but exact timing is less certain.

KBDL Terminal...Moderate confidence in TAF.

Outlook /Wednesday through Saturday/...

Wednesday: VFR. Breezy.

Wednesday Night: VFR.

Thursday through Thursday Night: VFR. Breezy.

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

Friday Night: VFR. Slight chance SHRA.

Saturday: VFR. Slight chance SHRA, slight chance TSRA.

MARINE

Forecaster Confidence Levels...

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

Through Tuesday Night...High confidence.

Weak high pressure over eastern Canada will continue combining with low pressure tracking south of the waters. Resultant E wind gusts of 20-30 kt that will track northward tonight into Tuesday will prevail over the waters. Winds will also end up shifting more NE tonight into Tuesday. These will likely continue through Tuesday night as well. Small Craft Advisories were extended for the northeastern outer waters through Tuesday night as a result. Seas to 5 ft build over the southern waters tonight, then shift to the eastern waters Tuesday into Tuesday night. Pockets of 6 ft seas are possible closer to the northern ocean water zones.

Outlook /Wednesday through Saturday/...

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

Wednesday Night through Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft.

Thursday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers, slight chance of thunderstorms.

Friday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers, slight chance of thunderstorms.

Friday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers.

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

BOX WATCHES/WARNINGS/ADVISORIES

CT...Flood Watch through Tuesday afternoon for CTZ002>004. MA...Flood Watch through Tuesday afternoon for MAZ017>022. RI...Flood Watch through Tuesday afternoon for RIZ001>008. MARINE...Small Craft Advisory from 2 AM to 8 PM EDT Tuesday for ANZ231>234-251. Small Craft Advisory until 8 PM EDT Tuesday for ANZ235-237-256. Small Craft Advisory from 2 AM Tuesday to 8 AM EDT Wednesday for ANZ250-254. Small Craft Advisory until 8 AM EDT Wednesday for ANZ255.