textproduct: Boston / Norton

WHAT HAS CHANGED

No major changes for the first part of the forecast. Increased chance for snowfall on Sunday with minor accumulations possible. Still looking at a period of much colder temperatures Monday into Tuesday.

KEY MESSAGES

- Cool tonight and seasonable tomorrow. then warmer Saturday.

- Cold front likely brings a period of accumulating snow Sunday afternoon. Front will be followed by significantly colder air with temperatures falling to 10-15 degrees below average early next week.

- Unsettled and warmer weather remains possible next week, but uncertainty remains high.

DISCUSSION

Key Message 1...Cool tonight and seasonable tomorrow, then warmer Saturday.

We remain under a weak troughing pattern through the rest of this week, which will keep southern New England in more seasonable conditions. Lows tonight will be cool, falling into the teens and even the single digits up in parts of the interior with radiational cooling expected as high pressure moves in. Some localized radiational fog is a possibility, but generally, most won't see it tonight as it will be quite dry. A weak low pressure will pass well offshore, but a low chance for some snow showers over Nantucket still exists.

High pressure remains in place for Friday, leading to lighter winds that shift more S to SW as the high progresses east. High temperatures remain seasonable in the upper 30s to low 40s and sunny skies. With the light S flow, warmer, more moist air will filter in; 925 mb temperatures climb to around 2C-5C Friday evening into Saturday. Lows Friday night will only dip into the 20s with some spots in the low 30s near the coast. More areas could end up seeing some fog Friday night into Saturday morning as dewpoint depressions approach 0F as well. High temperatures Saturday could approach the 50s with this trend continuing and an upper level ridge settled aloft.

Key Message 2...Cold front likely brings a period of accumulating snow Sunday afternoon. Front will be followed by significantly colder air with temperatures falling to 10-15 degrees below average early next week.

Model guidance continues to trend stronger with a shortwave passing to the NW of the CWA Sunday. A bit of a wetter appearance to the PWAT fields with the most recent guidance increasing to between 0.5 and 0.6 inches. High temperatures ahead of the front increase to the mid 30s along the coastal plain and closer to freezing in the interior. These marginal surface temps paired with the late February sun angle likely mean that snow will have a difficult time sticking to roadways on the coastal plain. Slippery conditions become more likely further inland. A very cold airmass settles in behind the front Sunday night with 850mb temps falling to between -12 and -15C! Low temperatures on Sunday and Monday morning will be in or near the single digits, with Mondays highs in the low to mid 20s. Winds will be rather calm during this arctic outbreak, keeping the wind chill index from dropping below zero.

Key Message 3...Unsettled and warmer weather remains possible next week, but uncertainty remains high.

Temperatures are expected to warm back to more seasonal levels Tuesday through the rest of next week, with highs in the upper 30s to low 40s. Guidance continues to advertise some kind of overrunning event as warm air aloft overspreads lingering low level cold air over the Northeast Wednesday. While confidence remains quite low at this time, these types of events tend to bring mixed precipitation and icing. A strengthening southeast ridge should keep the theme of warmer temperatures going through much of next week.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

Forecaster Confidence Levels...

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

00z TAF Update...

Tonight...High Confidence

VFR with brief periods of MVFR possible in any localized radiational fog that develops in the CT Valley and parts of the coastal plain. Mostly dry overall, but misty conditions can't be ruled out entirely. Not expected to last very long between 06z-09z. Light NW to calm winds.

Tomorrow...High Confidence.

VFR. Light SW winds under 10 knots.

Tomorrow Night...Moderate Confidence.

VFR with areas of MVFR possible in BR over the CT Valley, RI, and into NE MA. Light SW winds, becoming calm in some locations.

KBOS Terminal...High confidence

KBDL Terminal...High confidence

Low chance for radiational BR tonight after midnight.

Outlook /Saturday through Tuesday/...

Saturday: VFR. Breezy.

Saturday Night: VFR.

Sunday: Mainly VFR, with local IFR possible. Breezy. Chance SN.

Sunday Night: VFR. Breezy.

Monday: VFR. Slight chance SN.

Monday Night: VFR.

Tuesday: VFR. Slight chance SN.

MARINE

Forecaster Confidence Levels...

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

Through Friday Night...High confidence.

Winds remain less than 20 kt through tonight aside from occasional gusts across the outer waters. S to SW winds remain mostly between 5-10 kt into tomorrow night with the exception of the outer northernmost waters where winds to 20 kt are possible. Seas 5-6 feet linger across the southern outer waters through Friday so SCA headlines will remain.

Outlook /Saturday through Tuesday/...

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

Saturday Night: Winds less than 25 kt.

Sunday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of snow.

Sunday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of freezing spray.

Monday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of snow.

Monday Night: Winds less than 25 kt. Slight chance of snow.

Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ235- 237. Small Craft Advisory until 1 AM EST Saturday for ANZ254>256.