textproduct: Boston / Norton

WHAT HAS CHANGED

Increased the probability of showers for the Cape and Islands Saturday night into Sunday.

KEY MESSAGES

- Mostly clear, breezy, and cooler today and tonight.

- Scattered showers Saturday with a better chance for rainfall Saturday night into Sunday

- A dry and mild start to the week gives way to unsettled conditions mid to late week.

DISCUSSION

KEY MESSAGE 1... Mostly clear, breezy, and cooler today and tonight.

Mostly sunny day ahead behind departing low pressure with scattered CU developing as New England finds itself on the periphery of an upper level low with relatively cold temps aloft. Seasonable temps expected with highs low-mid 60s, except cooler higher terrain.

Dry weather continues for the first half of the overnight. Clouds lower and thicken with scattered showers possible after midnight as a weak shortwave approaches from the west. Best chance for shower activity will be across the interior.

KEY MESSAGE 2...Scattered showers Saturday with a better chance for rainfall Saturday night into Sunday

00z guidance has continued to trend toward a more amplified, further west track with the coastal low for this weekend. In fact, the NBM 50th percentile QPF Saturday night into Sunday has increased to 0.5- 0.75" for much of SE Massachusetts. These changes likely stem from a trend towards a significantly deeper longwave trough Saturday night and Sunday. Further shifts in the orientation and amplitude of this flow could force an even further west track with a risk for rain and showers further inland.

Consensus of the low track is still well SE of the 40N/70W benchmark at the closest approach of a low pressure trending towards Sunday morning. As previously mentioned, the trend has been for increased rainfall chances across the Cape and islands, as well as portions of the coastal plains of MA and RI. Not looking at much rainfall when all is done by Sunday afternoon. Expecting amounts 0.10 inch or less north and west of I-495, with perhaps 0.50-0.75 inch across the Cape and islands.

KEY MESSAGE 3...A dry and mild start to the week gives way to unsettled conditions mid to late week.

Deep trough moves east of the region Monday with increasing heights around an amplifying ridge across the Mid Atlantic. It will remain mainly dry and breezy Monday ahead of an approaching cold front. POPs increase to between 20 and 30 percent Tuesday with the greatest risk for showers Wednesday night into Thursday. Mid week weather will be largely dependent on a low pressure that moves through the Great Lakes and pushes a couple of fronts across our region. Will also be quite a bit warmer early next week with highs rising into the middle and upper 70s Tuesday and Wednesday.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

Forecaster Confidence Levels...

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

06z TAF Update...High confidence in trends. Moderate confidence in timing.

Patches of MVFR across eastern MA thru the next several hours with isolated areas of low elevation fog. Otherwise, VFR develops today and tonight. Chance for scattered showers late tonight across the interior. Winds 5-10 kt this morning increasing to 10-15 kt this afternoon, then becoming light overnight.

KBOS Terminal...Moderate confidence in TAF. Main uncertainty is the when conditions fully improve to VFR

KBDL Terminal...Moderate confidence in TAF.

Outlook /Saturday Night through Tuesday/...

Saturday Night: Mainly VFR, with areas MVFR possible. Chance RA.

Sunday: Mainly VFR, with local MVFR possible. Breezy. Chance RA.

Sunday Night: VFR.

Monday through Monday Night: VFR. Breezy.

Tuesday: VFR. Windy with gusts up to 30 kt. Slight chance SHRA.

MARINE

Forecaster Confidence Levels...

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

Light NW winds this morning increasing to between 10 and 15 kt with gusts up to 25 kt this afternoon and evening. Winds shift to the SW later this afternoon into the overnight Seas 4-6 ft over outer waters will subside late tonight into Saturday. SCA for seas will continue until this time. Watching for seas to increase Sunday afternoon behind a coastal storm.

Outlook /Saturday Night through Tuesday/...

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

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

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

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

Monday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Seas up to 5 ft.

Tuesday: Low risk for gale force winds with gusts up to 35 kt. Areas of rough seas.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ250. Small Craft Advisory until 2 AM EDT Saturday for ANZ254>256.