AFD - Boston

Near Term

THROUGH TONIGHT
An upper-level ridge and a surface high-pressure builds in from the south today, bringing a return to dry weather and sunny skies. 850mb temps warm from -5C to +2C, helping afternoon highs rise into the mid to upper 40s. Surface winds stay NW today, at 10-15mph, gusting 20-25mph in the afternoon..

Short Term

TUESDAY
Tonight: High-pressure centers just south of SNE tonight, allowing winds to go calm again overnight. Mid to high level clouds begin streaming in late overnight as a weak shortwave approaches from the Ohio River Valley. Still should see enough clear skies for radiational cooling to drop lows into the low to mid 20s once again.

Tomorrow: Increasing clouds as WAA increases ahead of the next shortwave to the west. Surface winds turn SSW at 10-15mph, gusting 20-25, once again in the afternoon. High temperatures only warm slightly compared to Monday, only topping out in the upper 40s to low 50s. Rain associated with the shortwave holds off until after sunset on Tuesday..

Long Term

TUESDAY NIGHT THROUGH SUNDAY

Key Messages:

* Rain Tuesday night into Wednesday as a warm front lifts across the region, turning mild with showers Wednesday afternoon. Drier for the end of the week into the weekend as high pressure builds in from the southwest, but cannot rule out festive flurries coming off the eastern Great Lakes.

* Colder Thursday into Saturday. Gusty west-northwest wind make temperatures feel more cold, especially Friday and Saturday. Then moderating temperature by the end of the weekend.

* Gale Force conditions are possible across all waters starting late Thursday through early Saturday.

Overview: Steadiest rainfall arrives Tuesday evening as a warm front lifts north, widespread rain ends Wednesday morning.

A mild day with hit-and-miss showers are expected as the region is placed under the warm sector. Following, robust shortwave/trough and frontal passage overnight into early Thursday morning. Cold front moves offshores on Thursday with the mid-level trough becoming cut off across the high latitudes Thursday through Friday. Tightening pressure gradient will bring gusty west-northwest winds as the magnitude of the 850mb jet increases between 35 and 50 knots late Thursday into early Saturday, ushering in a colder airmass. High pressure returns for the start of next weekend with diminishing winds.

Precipitation: Mentioned above, a warm front lifts across the region by Tuesday evening, steadiest rainfall overspreading the region from the southwest to northeast.

Rain may arrive as early as 4-6 PM for areas south/west of Hartford, CT. Southwest flow brings higher PWATs to southern New England, values between 1.0" and 1.3". Coupled with modest ascent, widespread rainfall expected well into the overnight hours, ending around daybreak Wednesday. Widespread rain will become showery, leading to hit-and-miss activity during the day as the region remains under the warm sector. The cold front moves through overnight and exits early Thanksgiving morning. Rainfall amounts are manageable, between 1/3" and 2/3", greatest at the south coast. As temperatures fall on Thanksgiving, upslope snow flurries are possible for high terrain of north/west Massachusetts. PWATs are considerably lower behind the front, though persistent west-northwest flow allows for lake effect snow showers coming off the eastern Great Lakes.

Do not expect any issues for southern New England, mainly periods of festive flurries. Otherwise, mainly dry weather this coming weekend as high pressure develops.

Temperatures: Spring-ish warmth for Wednesday as 925mb temperatures climb between +10C and +13C. Afternoon highs top off close to 60F across the coastal plain, while the rest of the region are between the upper and middle 50s. Cold front ushers in colder airmass with the 925mb temperatures lowering to 0C on Thanksgiving, and then down to -5C for Friday and Saturday! On Thanksgiving day, afternoon highs are in the upper 40s near the coast and upper 30s in the higher terrain. West-northwest gusts have it feel as if it were in the 30s for much of the region. As expected, Friday and Saturday are much cooler, afternoon highs in the lower 40s to upper 30s across the coastal plain and near freezing in the higher terrain.

But, it will feel as if it were below freezing for much of the region during the afternoon because of those gusty west-northwest winds. Temperatures begin to moderate by the end of the weekend.

Winds: Thursday through early Saturday southern New England is in between two pressure systems; high pressure to the southwest and a low pressure system to the northeast. Resulting in a strengthening pressure gradient. 850mb winds ramp up late Thursday, with the core of the strongest wind aloft, 35 to 50 knots, Friday/Saturday. BUFKIT soundings have the mixed layer fairly deep due to the CAA, making it possible to access those winds aloft and transport to the surface. Gusts of 30 to 40 mph possible, DESI probabilites of gusts 30 mph or higher are 70-90 percent.

Gale Force gusts are possible for all the waters, with high probabilites between 60-80 percent..

Aviation

Forecaster Confidence Levels...

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

12z TAF Update:

Today: High confidence.

VFR. WNW winds at 5-10 knots, gusting up to 20 knots in the afternoon.

Tonight: High confidence.

VFR. Calm to light SW wins.

Tomorrow: High Confidence

VFR. Increasing SW winds at 5-10 knots, gusting up to 20 knots. Rain enters from west to east, between 21z and 00z.

KBOS Terminal...High confidence in TAF.

VFR. WNW winds at 5-10 knots gusting 20 knots.

KBDL Terminal...High confidence in TAF.

VFR. Winds aloft remain around 35 knots with calm surface winds will bring wind shear concerns through about 14z. Winds tomorrow increase to 5-10 knots and could gust 15-20 knots.

Outlook /Tuesday Night through Friday/...

Tuesday Night: Mainly IFR, with local MVFR possible. Breezy. RA, patchy BR.

Wednesday: Mainly IFR, with areas VFR possible. Breezy. Chance RA, patchy BR.

Wednesday Night: Mainly VFR, with local IFR possible. Breezy. Chance RA.

Thanksgiving Day: VFR. Windy with local gusts up to 30 kt.

Thursday Night through Friday: VFR. Windy with gusts up to 35 kt.

Marine

Forecaster Confidence Levels...

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

Today through Tuesday... High confidence.

* Small Craft Advisory for all southern waters through early Monday afternoon, then sub-criteria conditions through early Thursday.

* Potential for westerly Gale Force conditions Thursday afternoon through early Saturday across all waters.

A exiting low pressure system over the Bay of Fundy moves east into the North Atlantic while high pressure builds across the waters of southern New England. Residual gusty northwest wind and rough seas across the southern waters subside by early afternoon, until then a Small Craft Advisory remains in effect until 1 PM today for gusts up to 25-30 knots and seas 3-5 feet. Wind shifts to the southwest on Tuesday with gusts less than 20 knots across all waters and seas between 2 and 4 feet.

Outlook /Tuesday Night through Friday/...

Tuesday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Rain, patchy fog. Visibility 1 to 3 nm.

Wednesday: Winds less than 25 kt. Areas of seas approaching 5 ft. Rain, patchy fog. Visibility 1 to 3 nm.

Wednesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Chance of rain. Local visibility 1 to 3 nm.

Thanksgiving Day: Strong winds with gusts up to 35 kt. Areas of rough seas.

Thursday Night: Strong winds with gusts up to 40 kt. Rough seas up to 13 ft.

Friday: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 13 ft. Slight chance of rain.