textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes to the forecast with this update. 00z aviation update.

KEY MESSAGES

- Showers and an isolated thunderstorm will move through the area this afternoon into early Thursday.

- A cool down to near seasonable temperatures with unsettled conditions this weekend through early next week.

DISCUSSION

KEY MESSAGE 1...Showers and an isolated thunderstorm will move through the area this afternoon into early Thursday.

Increasing clouds and increasing shower chances this afternoon from west to east as a cold front approaches the area from the west. Latest KBOX reflectivity showing the first batch of light to moderate rainfall quickly moving east across central MA/CT. Latest CAMs/short term guidance show this batch quickly moving east and out of the area by early evening. Current SPC mesoanalysis not showing much in the way of instability, so current thinking is that any embedded thunder will be quite localized with this activity. Guidance is also trending toward a second batch of post frontal precipitation after 00Z this evening, mainly for southern portions of the CWA. Total rainfall amounts of just a few tenths for most, with higher amounts in any thunderstorms. Best chances for the amounts, and attendant embedded thunder, are across the Berkshires and points north and west.

Cloud cover and precip will limit high temperatures today, relative to the past few days, in the mid and upper 60s.

KEY MESSAGE 2...A cool down to near seasonable temperatures with unsettled conditions this weekend through early next week.

Drying behind the front Thursday into Friday with high building to the south. Temperatures will be in the 60s (cooler in the mountains, warmer at the coast) Thursday, with chilly lows on Friday morning in the upper 30s and low 40s, under good radiational cooling conditions away from from the coast.

Conditions then look unsettled for the weekend. The next opportunity for rain arrives sometime early Saturday as a mid- level trough and weak surface low pressure system passes through the northeast. Raw type of day with highs in the lower 60s; probabilities of rain of half an of an inch or more is around 20- 30% per NBM. Mother's Day for now is trending dryer for the area, with low to mid 70s under partly to mostly cloud skies. Thereafter a series of shortwaves traverse the region, with uncertainty on the sensible weather. Rain chances increase Sunday night into Monday with rain likely by Monday afternoon. NBM probabilities of more than 0.5" are between 30-50%, but only 10-20% for more than in inch.

AVIATION /00Z THURSDAY THROUGH MONDAY/

Forecaster Confidence Levels...

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

00z TAF Update:

Tonight...Moderate confidence.

MVFR and IFR expected through tonight with showers continuing to move offshore overnight. MVFR/IFR conditions improve from west to east heading into Thursday morning. Winds remain gusty through just before midnight tonight over the Cape terminals, with ACK remaining gusty through 09z tonight. Elsewhere, breezy conditions will continue to diminish tonight.

Thursday...High confidence.

VFR across the region by the morning hours. Wind WNW 8-12 kt.

Thursday Night...High confidence.

VFR. Winds fall to around 5 kt at WNW, becoming more W heading into the early morning hours Friday.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Friday through Monday/...

Friday: VFR. Breezy.

Friday Night: VFR.

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

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

Sunday: Mainly VFR, with areas MVFR possible. Breezy. Slight chance SHRA.

Monday: VFR with MVFR or lower possible in showers.

MARINE

Forecaster Confidence Levels...

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

Through Thursday...High confidence.

Small Craft Advisory conditions will continue into this afternoon, then gradually improve tonight. Seas remain elevated on the southern waters into early Thursday afternoon.

Outlook /Friday through Monday/...

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

Friday Night: Winds less than 25 kt. Seas locally approaching 5 ft.

Saturday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers.

Saturday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers.

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

Monday: Winds less than 25 kt. Seas less than 5 ft.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ230- 236. Small Craft Advisory until midnight EDT tonight for ANZ231>235- 237-251. Small Craft Advisory until 4 AM EDT Thursday for ANZ250. Small Craft Advisory until 8 AM EDT Thursday for ANZ254. Small Craft Advisory until 2 PM EDT Thursday for ANZ255-256.