textproduct: Boston / Norton

WHAT HAS CHANGED

Rain chances are increasing for the Sunday/Monday period.

KEY MESSAGES

- Mostly dry weather prevails this week with continued seasonable temperatures after a very chilly start this morning.

- The holiday weekend favors dry weather for the first half, but chances are increasing that remnants of a tropical system bring rain to the region Sunday/Monday.

DISCUSSION

KEY MESSAGE 1...Mostly dry weather prevails this week with continued seasonable temperatures after a very chilly start this morning.

Very chilly temperatures out there as of 3AM with 32F in Orange, 35F in Taunton, and 35F in Willimantic to name a few. This is the result of high pressure overhead promoting efficient radiational cooling with calm winds and clear skies. The exception is along the coast and in urban centers where, for instance, Boston and Providence are 49F and 45F respectively. It will be a quick warm-up today as winds back out of the SW advecting in warm air and moisture ahead of a weak trough that swings through on Thursday. This trough will do a few things. First, it will make for warmer temperatures. This goes for afternoon highs thanks to a warmer airmass (925mb temps 5C warmer than yesterday) as well as overnight lows (modest LLJ keeping the boundary layer from decoupling). Resulting highs will reach into the mid 60s today and the low 70s on Thursday before a trailing cold front brings cooler weather Friday into the weekend. The second impact of this trough will be increasing moisture going into Thursday which will lead to higher dewpoints (humidity) and increased cloudcover ahead of the cold front. Marginal moisture, though, will mean showers are isolated at best.

KEY MESSAGE 2...The holiday weekend favors dry weather for the first half, but chances are increasing that remnants of a tropical system bring rain to the region Sunday/Monday.

High pressure solidly in control on Saturday will bring a beautiful, seasonably cool day with plenty of sun. Attention then turns to the latter half of the holiday weekend. Unfortunately the probability of unsettled weather around Sunday/Monday has increased. We are monitoring Tropical Depression Nine in the Gulf which will eventually make its way north up the Mississippi Valley, potentially interacting with a northern stream trough and being swept over the northeast bringing wet weather sometime Sunday or Monday. Confidence has increased in this outcome as probabilities of at least 0.01" of rain have increased in both the EPS and GEFS ensembles. Certainly nothing is set in stone at this point, but it is worth keeping an eye on how the forecast evolves over the next several days if you have outdoor plans.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Forecaster Confidence Levels...

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

12z TAF Update...High confidence.

VFR conditions through Thursday. Calm winds tonight then shift to the SW Wed into Wed night with some 20-25 knot gusts expected Wed afternoon. Gusty SW winds continue Thursday. Slight chance SHRA.

KBOS Terminal...High confidence in TAF

KBDL Terminal...High confidence in TAF.

Outlook /Thursday Night through Sunday/...

Thursday Night: VFR.

Friday: VFR. Breezy.

Friday Night through Saturday Night: VFR.

Sunday: VFR. Breezy.

MARINE

Forecaster Confidence Levels...

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

Tonight through Thursday night...High confidence.

Winds shift to the SW Wed into Wed night. Some SW wind gusts of 20-25 knots expected Wed afternoon and night. Some potential to approach small craft advisory level winds but things are too marginal to issue a headline at this point.

Outlook /Thursday Night through Sunday/...

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

Friday through Saturday Night: Winds less than 25 kt.

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

BOX WATCHES/WARNINGS/ADVISORIES

CT...Frost Advisory until 9 AM EDT this morning for CTZ002>004. MA...Frost Advisory until 9 AM EDT this morning for MAZ004>006-009- 011>013-017-018-020-021-026. Freeze Warning until 9 AM EDT this morning for MAZ002-003-008- 010. RI...Frost Advisory until 9 AM EDT this morning for RIZ001-003-006. MARINE...None.