textproduct: Boston / Norton

SYNOPSIS

Gusty winds expected Friday with scattered light snow showers possible for western MA and pockets of flurries for the interior. Still colder for Saturday but not as windy compared to Friday. Low pressure passes to our north and west Sunday afternoon and night bringing a period of rain with it. Cooling down again for Monday as a cold front passes through. Monitoring possible storminess around Tuesday and/or into Wednesday which could bring wintry weather or rain to Southern New England.

NEAR TERM /UNTIL 6 AM FRIDAY MORNING/

As we near sunset, the boundary layer will begin to decouple resulting in diminishing gusts this evening. No concerns for impacts tonight. Dry conditions with SW winds around 8-15 mph. Temperatures drop into the mid to upper 20s for the interior and low 30s closer to the coast.

SHORT TERM /6 AM FRIDAY MORNING AND FRIDAY NIGHT/

Key Messages:

* Gusty westerly winds with gusts 25-35 mph. Wind chills 20s to low 30s.

* Few scattered snow showers/flurries possible for western/central MA.

Details...

A deep upper level trough shifts further east across the region on Friday bringing in a core of colder temperatures into southern New England. A 40-45 kt LLJ will be positioned across the region. Cold air advection and a tightened pressure gradient will help mix down the higher winds aloft to the surface. Model soundings show ample mixing in the boundary layer, though there is some question in how deep it mixes which will dictate the magnitude of gusts. A good portions of solutions show gusts ranging from 30-40 mph. Although there are some solutions that show deeper mixing (closer to 850mb or even above) which would result in potential for higher gusts up to 40 mph or even some isolated 45 mph for the spots in the higher terrain. Overall expect a gusty day with gusts 30-40 mph, with lower end potential for gusts up to 45 mph for the highest spots of the Worcester Hills or Berkshires. Cooler temperatures aloft will support a cooler day overall with highs upper 30s to low 40s and mid- upper 30s for the high elevation spots. However, with the additional of the gusty winds, it will make temperatures feel more like 20s for the higher elevations and low 30s elsewhere. Make sure you bundle/layer up if going outdoors.

As the trough pushes eastward, winds shift more westerly are the surface with steering winds closer to WNW with indications of additional moisture moving in from the west. High-resolution guidance continues to show the potential for lake-effect streamers to extend far enough east to make it to the Berkshires in the afternoon. We'll have to see how well these hold together, especially as we get to the east slope of the Berkshires it will need to overcome some downslope component. This could mean some scattered snow showers for western MA or potentially approaching central MA. Any trace-light accumulation limited to localized high terrain of the Berkshires most likely. Can't rule out very localized flurries elsewhere tomorrow, mainly for western MA where there is better moisture. Overall, tomorrow may be a day for some festive flakes, no major impacts are expected.

Gusty winds gradually decrease overnight into early Saturday AM. Despite elevated winds overnight, it will be chilly with low temperatures dropping into the low-mid 20s for the higher terrain and mid 20 to low 30s elsewhere.

LONG TERM /SATURDAY THROUGH THURSDAY/

Key Messages:

* Still cooler but not as windy for Saturday.

* Low pressure brings rain later Sunday into Sunday night; drying out Monday to go along with cooler temperatures.

* An interior-SNE wintry weather and coastal-plain rain or wet snow- to-rain event remains on the table sometime Tue/Wed; adverse impact possible but confidence in the details is still low.

Details:

High pressure continues to build into Southern New England on Saturday, which will continue to favor drier weather to go along with modifying, albeit still below normal temps. Saturday also looks to feature winds more on the blustery side than gusty (e.g. as compared to Friday), as gradient continues to slacken and weaker windspeeds at the top of the modeled PBL. Early lows Sat night before we start to increase cloud cover and warm advection takes place pre-dawn Sunday.

Low pressure over Michigan early Sunday tracks NW to N of Southern New England on Sunday; offering a period of steadier light rains to break out Sunday afternoon and into the night as PWAT values rise to around 0.6 to 0.8 inches. Temps Sunday in the middle 40s to be warm enough in all areas for a plain rain but Sunday in general looks pretty raw. So a cloudy and rainy Sunday awaits us with total rains 0.25-0.4"; significant rainfall is not expected in a rather progressive mid-level flow pattern. Cold front then moves offshore early on Mon, which will bring another period of blustery NW winds and drier weather; to go along with another reinforcing shot of cold temps (ECMWF showing 925 mb temps around -3 to -6C). Early-day highs Mon before colder air oozes in Mon afternoon allowing for falling temps into Mon aftn/evening.

We continue to monitor developments regarding low pressure which develops as a trough digs in southern Rockies/Desert SW and moves ENE through the southern/south-central tier of states to near/south of Southern New England or nearby waters Tue or Wed. The exact track, when precipitation begins and the temperature structure are all still uncertain at this time; which will all drive what falls, for how long it falls, how much of what falls accumulates as well as what impacts we could see (if any). Initial early look at a predominantly wintry event for the interior and either a mainly plain rain or gloppy/sloppy wet snow-to-rain scenario for the RI/MA coastal plain still seems a reasonable first guess. The above-stated uncertainties are too great to get into rain or snow accumulations as of yet, but if the above p-type scenario holds, accumulations based on positive snow-depth-change methodologies probably would perform reasonably well. The past 24-hours worth of GEFS/EPS mean low centers and ensemble member lows have shown a track tendency further north and west, over or inside of the 40N/70W benchmark. On that basis, there are increasingly fewer ensemble member outcomes that are entirely shutouts. There's still quite a bit we don't know as of yet but the potential exists for some wintry weather with some impacts around Tue or Wed, better chances north and west of I-95. Stay tuned!

AVIATION /20Z THURSDAY THROUGH TUESDAY/

Forecaster Confidence Levels...

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

18Z update...

Today/Thanksgiving...High Confidence.

VFR. SCT-BKN clouds 4000-9000 ft this afternoon. W winds 10-15 kts with gusts 20-30 kts. Gusts decreasing after 21z as we lose sunlight.

Tonight...High Confidence.

VFR. SW winds 8-12 kts.

Friday...High Confidence.

VFR. Gusty winds develop 14-16z as the boundary layer mixes out. W winds 15-25 kts with gusts 25-30 kts. Can't rule out an isolated gusts up to 35 kts, mainly for the the higher terrain and Cape/Islands. Periods of SCT-BKN decks 5000-10,000 ft. Can't rule out an isolated flurry for western terminals.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Saturday through Tuesday/...

Saturday: VFR. Breezy.

Saturday Night: VFR.

Sunday: MVFR/IFR conditions possible. Breezy. RA likely.

Sunday Night: Mainly VFR, with local MVFR possible. Breezy. RA likely.

Monday: VFR. Breezy.

Monday Night: VFR.

Tuesday: Mainly VFR, with areas IFR possible. Breezy. Chance SN, chance RA.

MARINE

Forecaster Confidence Levels...

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

Today through Friday Night... High confidence.

* Gale Warning for Friday through early Saturday across all waters.

Small craft conditions continue over the waters tonight. Higher winds expected on Friday. Winds expected to increased after 15z. West winds 25-35 kts with gusts at 40 kts. Greatest probability of hitting Gale criteria more consistently will be the southern waters Friday late morning and afternoon. Winds and seas slowly decrease overnight Friday into early Saturday. Gale Warning will be in effect for all marine zones starting 12z Friday, through 12Z Saturday.

Outlook /Saturday through Tuesday/...

Saturday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas.

Saturday Night: Winds less than 25 kt.

Sunday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Seas locally approaching 5 ft. Chance of rain.

Sunday Night: Moderate risk for Small Craft Advisory winds with local gusts up to 30 kt. Rough seas up to 10 ft. Rain likely.

Monday: Winds less than 25 kt. Local rough seas. Slight chance of rain.

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

Tuesday: Winds less than 25 kt. Chance of rain. Local visibility 1 to 3 nm.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 6 AM EST Friday for ANZ230>237-250- 251-254>256. Gale Warning from 6 AM to 7 PM EST Friday for ANZ230-236. Gale Warning from 6 AM Friday to 7 AM EST Saturday for ANZ231>235-237-250-251-254>256.