textproduct: Boston / Norton

WHAT HAS CHANGED

Sunday looking like the wettest day of the holiday weekend with drier days on either side.

KEY MESSAGES

- Seasonable temps with scattered showers Thursday morning, lingering longest over CT, RI and SE MA. Dry and mild weather continues Friday.

- Cooler temperatures through Memorial Day Weekend. Unsettled weather returns for the weekend, but not a washout every day. Sunday is the wettest of the three days.

DISCUSSION

KEY MESSAGE 1...Seasonable temps with scattered showers Thursday morning, lingering longest over CT, RI and SE MA. Dry and mild weather continues Friday.

As the low pressure moves off into the North Atlantic, Thursday will be a transition between two starkly different airmasses. The post frontal airmass has arrived with cooler NW flow in place across SNE. High pressure over the Great Lakes will be slow to advance eastward over the next 24 hours as will the drier air it brings with it. We remain on the northern periphery of deeper moisture to our south. With zonal flow in the mid levels and a weak shortwave this morning we'll see a resurgence of light showers, lingering longest over CT, RI, and southeast MA through noon. By afternoon drier air sinks further south and skies will clear making way for a good radiational cooling night under high pressure so have leaned on MOS guidance for low temps. Expect plenty of sun Friday under strong subsidence, with highs in the upper 60s to low 70s (normal for late May).

KEY MESSAGE 2...Cooler temperatures through Memorial Day Weekend. Unsettled weather returns for the weekend, but not a washout every day. Sunday is the wettest of the three days.

Guidance is slowly coming into better agreement on the weather for the upcoming holiday weekend. While we continue to forecast a cooler than normal weekend with wet weather, the full three day weekend shouldn't be a washout. As it stands now, surface high pressure will be fighting to keep low pressure from the OH valley and its associated wet weather at bay as long as possible; this means the earlier in the day on Saturday the better chance we stay dry, it could even hold out for a fully dry Saturday, especially toward northeast/north central MA. Eventually the shortwave and wet weather move over SNE Saturday night/Sunday and this looks to be the most likely "washout" day before the low moves east of MA by Monday with drier air funneling in and making for a more pleasant day than Sunday. Sunday will also be breezy as a 25-35kt LLJ moves overhead. Temperatures bottom out on Sunday with highs in the upper 50s, warming into the upper 60s and 70s by Monday.

AVIATION /06Z THURSDAY THROUGH MONDAY/

Forecaster Confidence Levels...

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

06Z TAF Update...

Through 12Z...Moderate confidence.

VFR. N winds 5-10 kts. -SHRA possible.

Thursday...High confidence.

VFR. Scattered showers redeveloping near the south coast Thu morning with brief MVFR possible. N wind 5-10 kt with sea- breezes developing by midday.

Thursday night...High confidence.

VFR. Light wind.

Friday...High confidence.

VFR. NE winds 5-10 kts.

KBOS...High confidence in TAF.

KBDL...High confidence in TAF.

Outlook /Friday Night through Monday/...

Friday Night: VFR.

Saturday: VFR. Chance SHRA.

Saturday Night through Sunday: VFR. Breezy. SHRA likely.

Sunday Night: VFR. Chance SHRA.

Memorial Day: Mainly VFR, with local MVFR possible. Chance SHRA.

MARINE

Forecaster Confidence Levels...

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

Winds NW 10-15 kts with sea-breezes developing over nearshore waters in the afternoon. Light winds Thu night becoming N-NE overnight into Friday.

Outlook /Friday Night through Monday/...

Friday Night: Winds less than 25 kt.

Saturday: Winds less than 25 kt. Chance of rain showers.

Saturday Night through Sunday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Rain showers likely.

Sunday Night: Winds less than 25 kt. Seas up to 5 ft. Rain showers likely.

Memorial Day: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers.

CLIMATE

Record Highs for Wed May 20...

BOS 91/1996 BDL 99/1996 PVD 95/1996 ORH 91/1903

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 2 AM EDT early this morning for ANZ254>256.