textproduct: Boston / Norton

SYNOPSIS

Arctic airmass moves in this morning and for much of the day today with wind chill values dropping to between 0 to 10 below. Cold weather continues tonight into Tuesday but with much lighter winds. Dry weather continues on Wednesday but with significantly milder temperatures. Unseasonably mild temperatures Thursday into early Friday will be accompanied by a period of heavy rain and potentially a brief period of strong southerly wind gusts. Sharply colder air works back into the region later Friday into early Saturday with a second round of strong northwest wind gusts. This cold will not last long with milder temperatures returning by the end of next weekend.

NEAR TERM /UNTIL 6 PM THIS EVENING/

Key Messages...

* Bitterly cold wind chills between 0 and 10 below zero this morning

* Gusty WNW winds through this afternoon with highs mainly in the 20s

Very cold temps early this morning coupled with the blustery winds were resulting in bitterly cold wind chills between 0 and 10 below zero. Sunshine to start the day with some scattered clouds during the afternoon. Steep pressure gradient and decent mixing brings down some gusty winds from a 40-50kt low level jet. Expecting gusts between 25 and 35 mph around the region especially across the higher terrain. Coldest day of the season so far ahead with 850s struggling to rise much above -15C. Highs should be held in the 20s across the region. Stiff winds keep wind chill temperatures firmly in the upper single digits and lower teens during the afternoon.

SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/

Key Messages...

* Diminishing winds and cold tonight

* Final day of near or below freezing temperatures before a warm up for the rest of the week

Tonight...

Mostly cloudy skies expected overnight but not much in the way of precipitation. There is a low chance for a stray snow shower from the Great Lakes to make it into the Berkshires later tonight as a weak mid level disturbance passes well to the north. Should see gusty winds quickly wind down after sunset as model soundings show the boundary layer decoupling. Another cold night ahead with thinning cloud cover bringing increasingly favorable conditions for radiational cooling. Should see lows in the upper single digits in the terrain and upper teens along the coastal plain.

Tuesday...

Final day near freezing temps for the rest of the week for most of us except near the coast where temps will climb near 40. Temperatures aloft warm quite a bit from around -10C Tuesday morning to perhaps as high as +3C by 00z. Surface high pressure positioned to the south will support mainly dry conditions and light southwesterly winds.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/

Key Messages...

* Dry, breezy & significantly milder Wed with highs well into the 40s to perhaps near 50 in a few spots

* Unseasonably mild late Thu into Fri morning with showers and potentially a period of heavy rain/briefly strong wind gusts

* Brief shot of much colder air later Fri/Fri night with high confidence in a period of strong northwest wind gusts

* A few brief rain/snow showers possible Sat night into Sun, otherwise turning milder again with highs Sun in the 40s to near 50

Details...

Tuesday night and Wednesday...

High pressure off the mid-Altantic coast moves further east out into the Atlantic Tue night into Wed. The result will be a southwest flow of milder air working into southern New England. Lows Tue night will be in the upper teens and 20s...but temps should begin to rise near the south coast as southwest winds pickup. A mixture of clouds and sunshine Wed with gusty SW winds and 850T rising above 0C will result in a significantly milder afternoon. High temps Wed should reach well into the 40s...perhaps even flirting with 50 in a few spots.

Thursday into Friday...

Given that the pattern has flipped to a -PNA...a strong upper level disturbance will race across the U.S./Canadian border. This will spawn a strong surface low pressure system that will track well to our north across Quebec late Thu into early Fri. The magnitude of this surface low pressure system will result in a strong southerly LLJ ahead of the approaching cold front. The ensemble situational awareness table indicates this LLJ 2-3 standard deviations above normal with Pwats of 1+ inches. The combination brings a round of showers with potentially brief heavy rainfall sometime in the late Thu to early Fri time frame. Temperatures will likely rise into the 50s and perhaps even approach 60 out ahead of the cold front Thu night into early Fri. The GFS/EC/CMC all indicate a southerly LLJ of nearly 80 knots. The global guidance often underestimates the magnitude of the LLJ...but we are way outside the window of any high resolution guidance. Nonetheless...that is a pretty strong signal from the global guidance. So we will have to watch for a brief period of strong southerly wind gusts if we are able to mix out the inversion. Always difficult to determine...and sometimes strongest winds remain just off the deck but we will need to watch this in the coming days.

Behind this cold front...there is a brief shot of much colder air that will surge into the region late Fri/Fri night. The pressure rise/fall couplet and a sharp drop in temperatures will result in a period of strong WNW wind gusts behind the front. We are much more confident in this second round of strong wind gusts because the atmosphere will be so well mixed.

Next Weekend...

Brief shot of colder weather follows on Saturday...with dry weather and high temperatures mainly in the 30s to near 40. Given that we are now in zonal flow aloft...this return to chilly temperatures will be short-lived. Shortwave trough departs and a warm front may bring a few brief rain/snow showers to the region late Sat night and/or Sun. Otherwise...breezy and milder Sun with highs well into the 40s.

AVIATION /08Z MONDAY THROUGH FRIDAY/

Forecaster Confidence Levels...

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

06Z Update

Today...High Confidence

Mainly VFR with NW gusts up to 30 knots. A few fair-weather clouds early, but should be VFR. VFR CIGS developing during the afternoon.

Tonight...High Confidence.

VFR CIGS. Lighter W winds.

Tuesday... High Confidence

VFR. Light SW winds.

KBOS Terminal...High confidence in TAF

KBDL Terminal...High confidence in TAF.

Outlook /Tuesday Night through Friday/...

Tuesday Night: VFR. Breezy.

Wednesday: VFR. Windy with local gusts up to 30 kt.

Wednesday Night through Thursday: VFR. Breezy.

Thursday Night: MVFR/IFR conditions possible. Strong winds with gusts up to 45 kt. SHRA.

Friday: Mainly VFR, with local IFR possible. Strong winds with gusts up to 45 kt. SHRA.

MARINE

Forecaster Confidence Levels...

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

Today Through Tuesday Night...High confidence.

Northwest Gales continue through 20z this afternoon with wind gusts between 25 and 35 kt. Areas of light to moderate freezing spray will finally dissipate by afternoon. Elsewhere, small craft advisory conditions expected in Narragansett Bay and Boston Harbor. Gales subside to small craft advisory by late afternoon/early evening and further diminish tonight.

Outlook /Tuesday Night through Friday/...

Tuesday Night: Moderate risk for Small Craft Advisory winds with areas of gusts up to 30 kt. Seas locally approaching 5 ft.

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

Wednesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas.

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

Thursday Night: Moderate risk for gale force winds with gusts up to 45 kt. Areas of rough seas. Rain showers.

Friday: gale force winds with gusts up to 45 kt. Rough seas up to 16 ft. Rain showers.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 3 PM EST this afternoon for ANZ230- 236. Gale Warning until 1 PM EST this afternoon for ANZ231>235-237- 250-251-254>256. Freezing Spray Advisory until 10 AM EST this morning for ANZ232>234.