textproduct: Boston / Norton

WHAT HAS CHANGED

Small Craft Advisories extended and expanded into the eastern outer waters on late Sunday through Monday.

KEY MESSAGES

- Rain arrives late Saturday leading to a soggy and cool Sunday with much needed rainfall. Cool daytime highs Sunday will rise Sunday night.

- Wet to start Memorial Day, drying out through the day followed by summer-like warmth for the middle of next week before trending more seasonable with a few showers to end the week.

DISCUSSION

KEY MESSAGE 1...Rain arrives late Saturday leading to a soggy and cool Sunday with much needed rainfall. Cool daytime highs Sunday will rise Sunday night.

High pressure centered to our north and east will direct cool, easterly onshore flow into southern New England today. This trajectory with thickening and lowering clouds ahead of a warm front will lead to a cool day, topping out in the mid 60s. Fortunately, model soundings indicate a good amount of dry air in the low/mid levels and this, together with stubborn high pressure will keep the rain at bay for much of the region on Saturday. The most likely to stay dry all day will be areas RI north and east, with a better chance for afternoon or evening rain further west in CT and MA.

By mid to late afternoon widespread, isentropically forced rainfall overspreads western CT/MA slowly expanding north and east. This is the start of a prolonged period of wet weather that continues through at least Sunday night. Forcing comes from low/mid level convergence and a potent 30-50 kts LLJ acting on an anomolously moist airmass (PWATs approaching 1.75"). Expecting rainfall totals of 0.5-1" for most of the region, with 1-2" more likely along the south coast of RI and MA before all is said and done. Small Craft Advisories are in place on Sunday where better mixing over the water will lead to wind gusts 25 to 35 mph while over land, gusts of 20 to 30 mph are more likely.

KEY MESSAGE 2...Wet to start Memorial Day, drying out through the day followed by summer-like warmth for the middle of next week before trending more seasonable with a few showers to end the week.

The mid level trough axis crosses SNE on Memorial Day ushering in a period of drier, zonal flow to later be followed by much more amplified flow late week. What it means for the Memorial Day is a transition between a very wet low passage on Sunday/Sunday night and dry high pressure on Tuesday. While confidence is only moderate at this point, ensemble and deterministic guidance would suggest an improving forecast through the day; read: best chance of lingering showers early in the morning, with decreasing POPs as the day progresses. This together with significantly warmer temperatures in the low 70s will make Monday more palatable than Sunday for many, even if clouds will be slow to clear.

Models then agree on a warmer and drier period through mid week as 850 mb temps rise to the 12-13C range meaning we'll be back into the 80s Tuesday, flirting with the upper 80s by Wednesday. For the back half of the week, the previously mentioned return to amplified flow introduces more rain chances and cooler periods.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

Forecaster Confidence Levels...

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

06z TAF Update:

Overall high confidence.

VFR conditions expected through Saturday. Calm winds early this morning become 5-10 kts out of the SE after 12-14Z. Rain reaches BDL by 21-23Z. This rain then expands eastward through 06z. Cigs eventually lower to MVFR by 06Z Sunday in western CT and by 15Z Sun in eastern MA/RI. SHRA then continues all day Sunday, ending Monday morning.

KBOS...High confidence in TAF.

KBDL...High confidence in TAF.

Outlook /Sunday Night through Wednesday/...

Sunday Night: MVFR/IFR conditions possible. Breezy. Chance SHRA, isolated TSRA.

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

Monday Night: VFR. Slight chance SHRA.

Tuesday: Mainly VFR, with local IFR possible.

Tuesday Night: VFR.

Wednesday: VFR. Breezy. 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.

Saturday winds will be out of the E/SE 5-10 kts except 10-15 kts on the southern waters. A frontal system will bring enhanced southeast winds, building seas, and steady rain for the waters this evening through Sunday. Over the southern waters, SE winds increase to 25-30 kt by tonight, continuing through Sunday.

Seas 1-4 ft on Saturday build to 6 to 10 ft through Sunday. SCAs are in effect for Sunday into Sunday night. Rain, some heavy at times Sunday, could reduce visibility as well.

Outlook /Sunday Night through Wednesday/...

Sunday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Rain showers, slight chance of thunderstorms.

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

Monday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers.

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

Tuesday Night: Winds less than 25 kt.

Wednesday: Winds less than 25 kt. Slight chance of rain showers.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 5 AM Sunday to 2 AM EDT Monday for ANZ231. Small Craft Advisory from 2 AM Sunday to 5 AM EDT Monday for ANZ232>235-237. Small Craft Advisory from 8 PM this evening to 5 AM EDT Monday for ANZ254>256.