textproduct: Boston / Norton

SYNOPSIS

High pressure builds into the region tonight bringing clearing skies light winds and cold conditions. A few passing showers or higher elevation flurries are possible Sunday as an upper level disturbance moves through then high pressure returns Monday. A frontal system will bring a period of rain late Tuesday into Tuesday night, then mild with a continued chance of showers Wednesday into Wednesday night ahead of an approaching cold front. Cooler and blustery conditions follow behind the front for Thanksgiving Day, then windy and cold weather for next Friday and Saturday.

NEAR TERM /THROUGH TONIGHT/

Key Messages:

* Chilly night under radiational cooling with temperatures in the 20s for most.

Light rain showers continue to push east through SNE today. Expecting showers to linger into the early afternoon across the South Coast, Cape and Islands; however, not expecting rainfall totals to exceed 0.25" A cold front will push through this afternoon/evening and help clear out the remaining cloud cover... unfortunately, most likely won't see much daylight before the sun sets.

High pressure builds in behind the cold front, and with winds dropping to less than 5 mph tonight, expecting quite a bit of radiational cooling to drop overnight temps into the mid 20s for most of SNE... mid 30s for Cape/Islands and low 20s for the higher elevations.

SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/

Key Messages:

* Scattered rain/snow showers Sunday afternoon

A low pressure system passes through the James Bay Sunday and brings a cold front through SNE. Will likely be enough lingering moisture through the mid-levels to support some light rain showers across the region. Given the higher elevations likely remaining near freezing levels, some snow may mix into the rain showers in far NW MA. Otherwise, afternoon high temperatures in the mid 40s for the remainder of southern New England.

LONG TERM /MONDAY THROUGH SATURDAY/

Key Messages:

* Dry and seasonably cool Monday, then milder with a period of rain late Tue into Tue night

* Mild with a chance of showers Wed and Wed night. Temps well above normal

* Blustery and turning cooler Thanksgiving day, then windy and cold Fri and Sat

Upper level trough axis will be east of New Eng by Mon and moving away with rising heights and ridging moving in from the west as surface high pres builds in. Sunshine and seasonable temps expected Mon then a fast moving shortwave will be moving NE from the Gt Lakes Tue with a warm front approaching from the SW. Modest low level jet will advect a decent moisture plume into SNE with PWATs up to 1 inch. This will bring a period of rain late Tue into Tue night with the steadier rainfall exiting by Wed as the low level jet moves to the east with dry slot moving in. However, with SW flow aloft persisting Wed ahead of a more amplified upper trough, moisture values will remain elevated and so the risk of showers will continue Wed although likely not a washout. Wed has the potential to be pretty mild as thermal ridge moves into the region ahead of the trough. 925 mb temps rise to 10-12C Wed and while this would normally support highs well into the 60s, cloud cover and shallow mixing will limit full heating potential. Still a mild day with highs well into the 50s and perhaps some lower 60s if we can get some sunshine.

Next in a series of shortwaves will be lifting to the north Wed night with the attendant cold front sweeping through the region late Wed night. This will likely be preceded by a period of showers Wed night, then clearing, blustery and turning cooler for Thanksgiving Day in the post frontal airmass as PWATs fall to 0.25" with falling 850 mb temps. Looking ahead to Friday and Saturday, windy and cold conditions anticipated as 850 mb temps fall to around -10C. Expected highs mid 30s to lower 40s. Upper trough moves through Fri so despite very dry airmass in place can't rule out a few passing flurries or snow showers Fri. Preliminary forecast sounding data from GFS suggests rather windy conditions Fri with potential for wind gusts approaching wind advisory criteria. NBM also showing 10- 40% probs of gusts exceeding 45 mph over the higher elevations which is a pretty strong signal at this time range. Less wind expected Saturday but still blustery and cold.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Forecaster Confidence Levels...

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

18z TAF Update:

Today: High confidence.

IFR-MVFR visby in rain/mist with mainly VFR-MVFR ceilings, improving to VFR thru 22z Sat from west to east. Light winds but will become WNW/NW under 10 kt.

Tonight: High confidence.

VFR; outside shot (< 30% prob) of sub-VFR patchy mist/fog in the western river valleys toward sunrise. NW winds under 10 kt early ease to light west.

Sunday: High confidence thru 18z, then confidence trends moderate to high.

VFR thru at least 18z, then ceilings turn more of a BKN/OVC VFR/MVFR range as weak low pressure moves in. Spotty/very light precip possible after 21z, mainly as -RA but snowflakes could mix in at ORH. Light W winds become SW and increase to 5-10 kt.

Sunday Night: Moderate confidence.

MVFR/VFR ceilings with light/spotty showers (snowflakes possible at ORH) early, but trending drier after 06z. Winds become NW around 10-13 kt thru overnight.

KBOS Terminal...High confidence in TAF. Ceilings are mostly VFR, reduced visbys (4-6 SM) in light rain/mist thru 16z, then improving to VFR as rain dissipates. Light S winds become WNW under 10 kt approx 16-18z Sat thru the period.

KBDL Terminal...High confidence in TAF.

VFR turning MVFR with light rain moving in after 10z.

Outlook /Monday through Thursday/...

Monday: VFR. Breezy.

Monday Night: VFR.

Tuesday: Mainly VFR, with local MVFR possible. Chance RA.

Tuesday Night: Mainly MVFR, with areas IFR possible. Breezy. RA.

Wednesday: Mainly VFR, with areas MVFR possible. Chance RA.

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

Thanksgiving Day: VFR. Breezy.

MARINE

Forecaster Confidence Levels...

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

Through Sunday night... High confidence.

Light winds and seas into Sunday as high pres builds over the waters. Winds shift to NW Sunday night with increasing gusts to 20-25 kt overnight and building seas.

Outlook /Monday through Thursday/...

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

Monday Night: Winds less than 25 kt.

Tuesday: Winds less than 25 kt. Chance of rain.

Tuesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas locally approaching 5 ft. Rain.

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

Wednesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. Chance of rain.

Thanksgiving Day: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of seas approaching 5 ft.

BOX WATCHES/WARNINGS/ADVISORIES

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