textproduct: Boston / Norton

WHAT HAS CHANGED

Cancelled the flood watch for CT and lowered rainfall totals across Connecticut and Central Massachusetts to 1 to 2 inches. Otherwise, no significant changes to the forecast

KEY MESSAGES

- Periods of rain, heavy at times continues through much of the day today. Chance for thunderstorms and isolated flooding, mainly across the Cape and Islands.

- Mainly dry with a warming trend through midweek followed by an increased chance for scattered showers and thunderstorms later in the week.

DISCUSSION

KEY MESSAGE 1...Periods of rain, heavy at times continues through much of the day today. Chance for thunderstorms and isolated flooding, mainly across the Cape and Islands.

Theme of the last 12 hours has been to reduce the scope and intensity of the flooding threat for much of the area. That being said, we cannot fully rule out at least isolated instances of flooding through this afternoon, especially across RI and much of Eastern MA. Current radar shows areas of tropical rain rates offshore in the higher PWAT airmass. Further north, it's a mostly stratiform cool-season type rainfall regime with cloud tops <15kft and KDP values <1.0 db. As a result, rain totals have, so far, underperformed across much of Southern New England. Environment becomes increasingly favorable for heavy rain into the early morning hours as a 925 mb LLJ increases to 30kts around weak low pressure and advects higher K-values northward. BUFKIT soundings across Rhode Island and SE MA show warm cloud depths approaching 13kft and PWAT values increasing to 2.00" in the predawn hours. Thus, thinking the highest chance for flooding will be in these areas. Looking like a mostly beneficial rainfall event elsewhere with much of the CWA experiencing D1-D2 drought conditions. 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 2-4" are possible parts of RI, and SE MA. Even with the reduction in QPF among guidance, a chance for training showers and thunderstorms means the flood watch will remain in effect across CT, RI, and SE MA.

Rainy conditions continue through much of the day today mainly in eastern MA and RI as the low pressure continues northeastward and its associated shortwave moves east from the Great Lakes. The bulk of the heavy rain is expected to remain offshore The low passes offshore overnight 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 overnight across eastern MA and the Islands, but these are not expected to be nearly as impactful as this morning's rainfall.

KEY MESSAGE 2...Mainly dry with a warming trend through midweek followed by an increased chance for scattered showers and thunderstorms later in the week.

Ridging builds across the eastern CONUS Wednesday and Thursday allowing for a warming and drying trend. Closer to the surface, 925mb temperatures rise to near 20C, allowing 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. Guidance currently shows FROPA sometime later Thursday and well after peak heating. Future forecasts will monitor the threat for convection as we get closer to the late week period.

AVIATION /06Z TUESDAY THROUGH SATURDAY/

Forecaster Confidence Levels...

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

06Z TAF Update...

Adjusted onset time of -SHRA and MVFR/IFR ceilings forward a couple of hours.

Today...Moderate confidence.

Any lingering VFR conditions N of ORH deteriorate to MVFR/IFR. Some periods of rain could be heavy at times across parts of RI/SE MA. An embedded t-storm or two is possible in this same area as well. Periods of rain will continue today especially across eastern MA/RI. MVFR with localized IFR conditions will also continue through much of the day. Winds today from the NE at 8-16. Some gusts to 20-25 kt primarily over the Cape and Islands.

Tonight...Moderate confidence.

Rain clears out of the region tonight, 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. Possible lingering -SHRA and or -DZ thru 05z for the Cape and Islands.

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: VFR. Breezy.

Thursday Night: VFR. Breezy. Slight chance SHRA, slight chance TSRA.

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

Friday Night: VFR. Slight chance SHRA.

Saturday: VFR.

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 low pressure passes well S of the waters and slides up against high pressure over northern New England. Resultant NE wind gusts of 20-30 kt through much of the day today. These will likely continue through the overnight as well. Small Craft Advisories were extended for the northeastern outer waters through tonight 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 through Wednesday Night: Winds less than 25 kt. Seas up to 5 ft.

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

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

Friday: Winds less than 25 kt. Seas locally 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...None. MA...Flood Watch through this afternoon for MAZ017>022. RI...Flood Watch through this afternoon for RIZ001>008. MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ231>235-237-251-256. Small Craft Advisory until 8 AM EDT Wednesday for ANZ250-254- 255.