textproduct: Boston / Norton

WHAT HAS CHANGED

Splashover to minor coastal flooding possible around the midnight high tide cycle for eastern coastal Massachusetts. Also, the gusts associated with the cold front will bring marginal small craft conditions to the southern waters. Otherwise, forecast hasn't deviated from the previous discussion.

KEY MESSAGES

- Nuisance coastal flooding, mainly splashover is possible tonight around the midnight high tide cycle for east coast of Massachusetts; including the island of Nantucket.

- Steady rain arrives Sunday with the passage of a cold front and a period of breezy northwest winds. Turning much colder Sunday night.

- Generally dry but cooler Monday morning. Increasing clouds andspotty rain showers possible Monday afternoon with a weak area of low pressure.

- Return to seasonable temperatures through Wednesday before another cold front sweeps through.

DISCUSSION

KEY MESSAGE 1...Nuisance coastal flooding, mainly splashover is possible tonight around the midnight high tide cycle for east coast of Massachusetts; including the island of Nantucket.

Guidance this morning continues to point towards very minor coastal flooding for eastern Massachusetts and Nantucket during the overnight high tide cycle (around midnight). Combination of onshore flow and the astronomical tides could lend to splashover to minor coastal flooding for most vulnerable low-lying locations. And as a result, have opt'd to issue a Coastal Flood Statement. Please avoid any prone area and never drive through standing water.

KEY MESSAGE 2...Steady rain arrives Sunday with the passage of a cold front and a period of breezy northwest winds. Turning much colder Sunday night.

Rest of Saturday and tonight should remain dry, however, a bank of stratus off the coast will move onshore tonight. Low clouds and few areas of drizzle (mainly across eastern SNE) through Sunday morning, in addition to areas of locally dense fog across eastern MA. As for the rest of Sunday, expecting a raw and chilly day. In fact, high temperatures in the low to mid-50s occur during the late morning, as a strong cold front will move through and send temperatures falling shortly there after. This cold front brings widespread rain and a few rumbles of thunder with limited instability. Rainfall rates are moderate to heavy with PWATs 1.2" to 1.4" - rainfall amounts are in the neighborhood of 0.25" to 0.50" with lower totals along and east of I-95. Though, any convective showers have potential for heavier rainfall - cannot discredit the HREF which shows potential for localized values above an inch. And with much colder air advecting into SNE, snow showers remain possible for the highest terrain of western MA. Don't expect any impacts, but a light coating on elevated surfaces remains possible. Associated with the cold front is a brisk NW wind, gusts 20-30 MPH late morning and early afternoon will lead to overall raw and chilly feeling. Clearing Sunday night and easing winds, temperatures fall into the low to mid-30s, while the higher terrain of northern Worcester County and NW MA dip into the upper 20s.

KEY MESSAGE 3...Generally dry but cooler Monday morning. Increasing clouds and spotty rain showers possible Monday afternoon with a weak area of low pressure.

A colder airmass moves over southern New England Monday in the wake of the cold front from Sunday. 925mb temperatures drop to below 0C and 850mb temperatures drop to near -10C, leading to cooler surface temperatures across the region... coastal regions might reach into the low 50s, but most areas will likely remain in the upper 40s for highs. Breezy westerly winds veering northwesterly early to mid morning with some gusts possible in the higher elevations. Winds will start to diminish as high pressure approaches from the west, and lows Monday night likely fall into the 20s for southern New England, with the exception being the Cape/Islands and immediate coastal regions.

As we get into range for high-resolution guidance, confidence is slowly ticking up in a weak area of low pressure spinning up ahead of an approaching high pressure system that leads to increasing cloudiness and spotty rain showers across southern New England Monday afternoon. Exactly where these showers might develop remains uncertain due to the wide range in both ensemble and deterministic model guidance. Otherwise, incoming high pressure should keep the region dry for much of the start of the week before it exits heading into Wednesday.

KEY MESSAGE 4... Return to seasonable temperatures through Wednesday before another cold front sweeps through.

High temperatures climb Tuesday and Wednesday before another cold front moves through New England later Wednesday, bringing chances for more rain showers. Winds return to southwesterlies, supporting more seasonable highs in the upper 50s/low 60s. Ensembles indicate a ridge building in towards the end of the week then a large low pressure system moving through the Great Lakes over the weekend. This would bring dry conditions through late week then a return for rain chances through the weekend.

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.

IFR/LIFR CIGS with visibility rapidly deteriorating to IFR/LIFR as fog moves in, especially across the Cape and Islands. NE winds veer around to SE/S 5-10 knots.

Sunday: Moderate Confidence.

IFR/LIFR through the early morning hours with areas of mist or drizzle. Locally dense fog possible across Cape Cod and Islands through mid-morning. Cold front brings widespread RA from west to east, 12z-15z, SW winds around 10 knots, becoming W/NW and increasing to 10-15 knots with gusts 20-25 knots post-frontal passage.

Sunday Night: High Confidence.

VFR. Diminishing wind gusts. W wind 5-10 knots.

KBOS Terminal... Moderate Confidence in TAF.

IFR visby quickly deteriorates to LIFR this evening. Pockets of DZ overnight into early Sunday morning. RA arrives 14z-16z, LLWS ahead of the cold front too. Wind shifts to the W/NW by 18z-20z with gusts 20-25 knots. Becoming VFR late in the day Sunday.

KBDL Terminal... Moderate Confidence in TAF.

Outlook /Monday through Thursday/...

Monday: VFR. Breezy. Slight chance SHRA.

Monday Night through Tuesday: VFR.

Tuesday Night through Wednesday: VFR. Breezy. Slight chance SHRA.

Wednesday Night through Thursday: VFR.

MARINE

Forecaster Confidence Levels...

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

Tonight through Sunday Night: High Confidence.

Overnight there are areas of low clouds and fog, SE to S wind less than 25 knots and seas 2-4 feet. Strong cold front Sunday brings SCA conditions, seas 3-5 feet, and W-NW gust up to 25 knots for southern and eastern outer and waters south of mainland RI Sunday into early Monday morning. Winds shift NW and ease following this frontal passage late Sunday night.

Outlook /Monday through Thursday/...

Monday through Monday Night: Winds less than 25 kt. Slight chance of rain showers.

Tuesday: Winds less than 25 kt.

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

Wednesday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers.

Wednesday Night through Thursday: Winds less than 25 kt.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 11 AM to 6 PM EDT Sunday for ANZ235- 237. Small Craft Advisory from 11 AM to 11 PM EDT Sunday for ANZ254>256.