textproduct: Boston / Norton

WHAT HAS CHANGED

After a couple of unseasonably mild days around midweek, temperatures then tumble into the 30s to lower 40s on northeast winds late in the week. Wintry precipitation possible in interior Southern New England Thurs or Fri but uncertain on the timing.

KEY MESSAGES

- Mainly dry weather with a warming trend through Monday.

- Unseasonably mild with breezy southwest winds for midweek, with highs in the 60s and possibly into the 70s with enough breaks in cloud cover. Best chance for showers, possibly a rumble or two of thunder Wed afternoon and evening as cold front lurches slowly offshore overnight.

- Much colder and more unsettled late week, with highs in the 30s/lower 40s on NE winds. Rain and possibly wintry precip potential either Thurs or Fri but timing is uncertain.

DISCUSSION

KEY MESSAGE 1...Mainly dry weather with a warming trend through Monday.

Upper trough and cold pool moves through this afternoon then offshore this evening. There may be a few snow showers spilling into NW MA through this afternoon with its passage, otherwise dry weather tonight and lasting into Monday with dry NW flow aloft in place. High pressure will be the dominant feature as it builds south of New Eng tonight, before moving offshore Sunday into Monday. There will be periods of mid-high cloud cover at times as the polar jet will set up across New Eng, but overall partly to mostly sunny skies during the day. With return SW flow developing Sunday, a moderating trend will begin with temps reaching 45-50F. Decent pressure gradient develops so it will be breezy with soundings showing a well mixed boundary layer supportive of 20-30 mph gusts at times. Further warming expected on Monday as 925 mb temps reach 8-10C Mon which supports highs into the low-mid 60s.

KEY MESSAGE 2...Unseasonably mild and turning breezy for midweek, with highs in the 60s and possibly into the 70s with enough breaks in cloud cover. Best chance for showers, possibly a rumble or two of thunder Wed afternoon and evening as cold front lurches slowly offshore overnight.

A frontal system moving through the Upper Midwest and Gt Lakes region will draw an unseasonably mild airmass into the Northeast states Tue and Wed on SWly low-level winds of 40-50 kt at 925 mb. This supports a spell of mild temperatures centered around midweek; biggest potential fly in the ointment is there should be at least some cloud cover around, which opens the door for questions on how much diurnal insolation we can realize. Even still, with 925 mb temps on the order of +14 to +16C and 850 mb temps in the +10 to +12C range, even some cloud cover should offer highs at least in the 60s, with a conditional shot at 70s if we can generate any persistent breaks in cloudiness. Tue night also looks quite mild with lows only falling into the 50s, so could be a night to open up the windows. SW winds would see to favor milder temperatures making it all the way to the coast without a risk for seabreezes, and that's especially the case for Wed ahead of a cold front, with pretty strong SWly winds aloft supporting SW wind gusts into the 25- 35 mph range.

There could be some hit-or-miss light rains Tue as the warmer air aloft starts to come in, but the better chance for showers is along the frontal system's cold front which moves in Wed afternoon and into Wed evening. Low chance for a rumble or two of thunder during the daytime hrs Wed too given weak instability. Front then moves more slowly moving offshore overnight to early Thurs. Will have to watch how slowly this front pushes offshore as recent ECMWF guidance showing a possible secondary low forming along the slowing frontal zone into early Thurs, which would mean lingering rain into the early morning hours Thurs along the southern roughly third of Southern New England.

KEY MESSAGE 3...Much colder and more unsettled late week with highs in the 30s/lower 40s on NE winds. Rain and possibly wintry precip potential either Thurs or Fri but timing is uncertain.

Much cooler and more unsettled weather for late in the week. The cold front from midweek should have made it far enough offshore Thurs to allow for a shallow cold airmass to advect southeast associated with a 1040+ mb high pressure cell over northeast ME. 925 mb temps drop from around +14-16C from Wed afternoon and then tumble down to a chilly 0 to -2C by Thurs, some 24 hours later on increasing NE winds. Partly to mostly cloudy skies both Thurs and Fri will only keep highs in the mid 30s to mid 40s at best. So we'll go from opening up your windows to closing them and possibly needing to turn the heat on late in the week; typical late-March weather in New England.

The bigger issue here though is the arrival of the next frontal system. GFS/GEFS is more progressive/earliest arrival being closer to Thurs, while the ECMWF/EPS is closer to Friday. That'll be important because the potential exists for some wintry precip at onset in at least interior Southern New England pending surface temps. So some potential for wintry precip again as we close out the month of March, but at this day-6/day-7 timeframe it's unclear if it ends up being Thurs or Fri.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

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

00Z TAF Update...

Tonight through Sunday night...High Confidence

Diminishing wind overnight becoming SW by daybreak then gusts to 25 kt developing in the afternoon. S-SW wind 5-15 kt Sun night.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Monday through Thursday/...

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

Monday Night: Mainly VFR, with areas MVFR possible. Breezy. Slight chance RA.

Tuesday: Mainly VFR, with areas MVFR possible. Windy with local gusts up to 30 kt. Slight chance SHRA.

Tuesday Night: Mainly VFR, with areas MVFR possible. Windy with gusts up to 35 kt. Slight chance SHRA.

Wednesday: Mainly MVFR, with areas VFR possible. Windy with gusts up to 35 kt. Chance SHRA.

Wednesday Night: MVFR/IFR conditions possible. Breezy. Chance RA.

Thursday: MVFR. Breezy. Chance RA.

MARINE

Forecaster Confidence Levels...

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

NW winds below SCA thresholds tonight, then becoming SW Sunday with gusts to 25 kt developing in the afternoon/evening. SCA issued for most of the waters.

Outlook /Monday through Thursday/...

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

Monday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Slight chance of rain.

Tuesday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Slight chance of rain showers.

Tuesday Night: Strong winds with gusts up to 40 kt. Rough seas up to 14 ft. Slight chance of rain showers.

Wednesday: Strong winds with gusts up to 35 kt. Rough seas up to 13 ft. Chance of rain showers.

Wednesday Night: Winds less than 25 kt. Areas of rough seas. Rain.

Thursday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Chance of rain.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from noon to 8 PM EDT Sunday for ANZ230>237-251. Small Craft Advisory from noon Sunday to 2 AM EDT Monday for ANZ250-254.