textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes.

KEY MESSAGES

- Cooler and dry weather through Saturday. Turning overcast with even cooler temps (60s) for Saturday, with rain developing later Saturday evening.

- Cool with widespread rain Sunday.

- Warming trend next week. Scattered showers lingering Monday with another chance of showers Wed.

DISCUSSION

KEY MESSAGE 1...Cooler and dry weather through Saturday. Turning overcast with even cooler temps (60s) for Saturday, with rain developing later Saturday evening.

The surface high pressure over the Great Lakes expands over New England on Friday and Saturday with subsidence keeping things dry and sunny to start. Friday will feature sunny skies, cool onshore breezes, and high temperatures in the mid 60s to low 70s. The exception will be along the immediate coast where those seabreezes keep temps in the upper 50s to low 60s. This cooler airmass with 850mb temps in the 2-3C range doesn't change much over the course of the next 48 hours, but Saturday will be cooler if mainly due to increased cloudcover as moisture streams overhead ahead of our next wet weather system. The dry air in the low/mid levels and stubborn high pressure will keep the rain at bay for much of the region on Saturday, so while it will be cool and cloudy, many of those with outdoor plans should be able to keep them. The most likely to stay dry will be areas RI north and east, with a better chance for afternoon or evening rain further west in CT and MA.

KEY MESSAGE 2...Cool with widespread rain Sunday.

Widespread warm frontal precipitation overspreads the region Saturday evening/night and continues all day Sunday as an area of low pressure traverses the region. It brings with it ample moisture (PWATs approaching 1.75", in the 99th percentile of climatology) and forcing with 35-50 kt LLJ which will also serve to make it gusty, especially over the waters. Before all is said and done, most locations are likely to pick up a half inch to an inch of rain by Sunday night. Sunday will also be the coldest day of the forecast, with rainy, cloudy conditions leading to highs in the 50s.

KEY MESSAGE 3...Warming trend next week. Scattered showers lingering Monday with another chance of showers Wed.

The Memorial Day forecast is by no means settled, but it looks more favorable than Sunday at the very least. Some of the guidance including the ECMWF are a bit drier with the low exiting and drier conditions for Monday, while the GFS continues to be the wettest solution with the follow-up shortwave more robust leading to another wet day. Leaning on ensemble guidance for now, though the EPS and GEFS are also in different camps with a 10-20% and 40-50% chance of AOA 0.10" of rain Monday respectively. What is more certain is that Monday will be the start of a warm-up with zonal flow at 500 mb and a surge of 850 mb temps closer to 12-13C. This will mean highs back in the 70s and low 80s by Tuesday. Our next shortwave arrives around midweek but details are unclear at this point.

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...

Friday...High confidence.

VFR. NE winds 8-15 kt, with gusts to 20 kt Cape/Islands diminishing in the afternoon. Sea-breezes developing on the eastern MA coast.

Friday Night...High confidence.

VFR. Increasing mid and high-level clouds. NE winds less than 5 kt.

Saturday...High confidence.

VFR. SE winds 5 to 10 kts. CIGs lowering from west to east through the afternoon and evening ahead of -SHRA.

KBOS...High confidence in TAF.

KBDL...High confidence in TAF.

Outlook /Saturday through Tuesday/...

Saturday Night: VFR. Breezy. SHRA likely.

Sunday: Mainly VFR, with local IFR possible. Breezy. SHRA.

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

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

Monday Night: Mainly VFR, with local MVFR possible. Slight chance SHRA.

Tuesday: VFR.

MARINE

Forecaster Confidence Levels...

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

Winds and seas to remain below small craft advisory criteria through at least midday Sat. NE to E winds through Fri night around 10-15 kt, with E/ESE winds at similar speeds for the southern waters, and seas 4 ft or less all waters.

Into Sat of the holiday weekend, ESE winds around 15-20 kt with fringe small craft advisory winds/seas over the southern waters especially later in the day. Rain will also develop around late Sat/Sat night over the southern waters. Increasing, more solid-SCA E/SE winds 25-30 kt and seas 5-9 ft (higher southern waters over the open-ocean) then develop for Sunday for your holiday boating plans, to go along with steady rain which could reduce visibility.

Outlook /Saturday through Tuesday/...

Saturday: Winds less than 25 kt.

Saturday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Seas locally approaching 5 ft. Chance of rain showers.

Sunday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Rain showers.

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

Memorial Day: Winds less than 25 kt. Areas of rough seas. 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. Seas locally approaching 5 ft.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...None.