textproduct: Boston / Norton

WHAT HAS CHANGED

A Rip Current Statement has been issued for Cape Cod from 8 this evening through 7 am Monday.

KEY MESSAGES

- Fair weather for most areas except the Cape and Islands Sunday and Monday. A Rip Current Statement has been issued for Cape Cod tonight through early Monday.

- Temperatures on the lower end of seasonable as periodic chances for showers and thunderstorms return Mon-Wed (possibly into Thurs). Monitoring for increasing chances of localized heavy rainfall and potentially flash flooding.

DISCUSSION

KEY MESSAGE 1...Fair weather for most areas except the Cape and Islands Sunday and Monday. A Rip Current Statement has been issued for Cape Cod tonight into Sunday.

Another mostly clear day Sunday as weak high pressure maintains control. Height falls ahead of an approaching trough and a low pressure system passing well offshore brings moisture and clouds to the Cape and Islands Sunday afternoon. Model soundings indicate a shallow layer of moisture at the surface with dry air above. It is more likely that this layer will be too shallow to support any showers/drizzle. A worst case would be some patchy drizzle for the outer Cape/Islands. Aside from the clouds in some areas, it will be a mainly dry day with a northeasterly breeze for the eastern coastal areas. Temperatures likely range in the low to mid 80s for the interior and mid to upper 70s in the eastern and coastal areas.

A Rip Current Statement has been issued for the Cape as easterly winds and prolonged swells leads to a moderate to high chance for rip currents. While the highest risk exists along the Cape, an elevated chance of rip currents spans the south and east coastline with the greatest risk for the east-facing beaches along the Cape and Islands and portions of the east coast of MA.

Slightly warmer conditions across the interior on Monday with 925 mb temps warming to +20-23C translating to max temps in the mid and upper 80s. A deeper shortwave trough moves overhead, and with associated mid-level cooling should introduce increasing cloud cover by the afternoon. Guidance shows a 20-40% chance of showers across western portions of the CWA as forcing and instability build.

KEY MESSAGE 2...Temperatures on the lower end of seasonable as periodic chances for showers and thunderstorms return Mon-Wed (possibly into Thurs). Monitoring for increasing chances of localized heavy rainfall and potentially flash flooding.

Ensemble guidance has started to come into better consensus that a low pressure system will traverse through the Great Lakes Monday/Tuesday and into New England around Wednesday. This system will likely be accompanied by several embedded shortwaves and a mid- level trough, bringing chances for a few rounds of showers, and possibly thunderstorms, Monday through Wednesday... possibly lingering into Thursday. There continues to be a strong signal for PWATs 120-170 percent of normal to advect into the region by Tuesday, with deterministic guidance on the extreme high end of that range. Some guidance is also honing in on some potential for the low to slow on approach to New England as well as slower mid-level wind speeds, which would create an environment for training storms. Combined with the enhanced forcing of the low, the higher PWATs and potential for training, localized heavy rainfall and potentially flash flooding are becoming something to watch for. Unfortunately, there still remains a large amount of uncertainty in the guidance regarding where exactly the low could track, with some models indicating the low moving further south near NYC and some further north through northern MA. Depending on where exactly the low tracks, it's possible the threat ends up west/south of the region or confined to western portions of southern New England.

Otherwise, high temperatures are expected to remain on the lower end of seasonable, even dipping to slightly below normal at times given 850mb temperatures hovering around +12C to +14C through mid-week.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

Forecaster Confidence Levels...

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

00z TAF Update...

Tonight...Moderate confidence.

VFR for most. Very low chance of some marginal VFR/MVFR conditions across Cape and Island terminals. Best chance would be ACK after 05z. Otherwise, light and variable winds.

Sunday...High confidence overall (Moderate for cigs in far east).

VFR for most. Uncertainty in the potential for low clouds in eastern MA and how far west they extend will be the main challenge. Greatest risk for Cape and Nantucket with MVFR ceilings possible. E winds for the interior 5-10 kts. NE winds for east coast terminals 8-12 kts.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Monday through Thursday/...

Monday: VFR.

Monday Night: VFR. Slight chance SHRA.

Tuesday: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA, chance TSRA.

Tuesday Night: Mainly MVFR, with local IFR possible. Breezy. SHRA likely, chance TSRA.

Wednesday: Mainly VFR, with areas MVFR possible. Breezy. SHRA likely, chance TSRA.

Wednesday Night through Thursday: VFR. Breezy. Chance SHRA, slight chance TSRA.

MARINE

Forecaster Confidence Levels...

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

Through Tuesday...High confidence.

Light winds and seas 1-4 ft through Monday. Increasing winds and seas for Sunday; however, below SCA. NE winds 8-12 kts with gusts to 20 kts and seas 2-4 ft with 5 ft for the outermost southern waters. Seas increase to 4-6 ft later Tuesday afternoon with SCA conditions becoming More likely.

Increased risk for rip currents Sunday with the greatest risk for the east-facing beaches/coastline.

Outlook /Monday

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

Monday Night: Winds less than 25 kt.

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

Tuesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers, slight chance of thunderstorms.

Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Rain showers likely, slight chance of thunderstorms.

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

Thursday: Winds less than 25 kt. Rough seas up to 9 ft. Slight chance of rain showers.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...High Risk for Rip Currents through Monday morning for MAZ022. RI...None. MARINE...None.