textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes.

KEY MESSAGES

- Another day of large temperature swings. Backdoor front retreats north early this morning then drops back south this afternoon.

- Colder day Thursday then a milder but unsettled pattern prevails over the weekend.

DISCUSSION

KEY MESSAGE 1...Another day of large temperature swings. Backdoor front retreats north early this morning then drops back south this afternoon.

Backdoor front has stalled its progress southward and was located roughly from Orange, MA to Providence, RI and the immediate south coast of MA. E/NE winds in cool sector have brought in low clouds and patchy fog and much cooler temperatures in upper 30s and 40s, while to the west southerly winds prevail along with temperatures in 60s. Severe storms that moved through central and eastern NY have slowly weakened as they encountered a less favorable airmass over southern New England, though the leading edge of the activity did show some decent signals for wind damage over western MA which prompted earlier warnings and resulted in sporadic wind damage.

After an initial band of showers passes through the region early this morning, the front will gradually retreat northward as low pressure tracking across northern New England induces more of a S/SW flow. This will bring a warmup across most of region by sunrise despite cloud cover and scattered showers, and we may see some breaks of sunshine later this morning into early afternoon when highs for the day will occur. However, next short wave and high pressure to our north will force backdoor front back southward again this afternoon, this time all the way through southern New England, and offshore later in day. We're not expecting as abrupt of a temperature drop that we experienced yesterday, but it will still be noticeable.

Although we may see some scattered showers this afternoon, most of showers will be focused closer to front across CT, RI, and southeast MA where models show better low level wind and moisture convergence. There is even some marginal instability there but most likely not enough to support thunder.

KEY MESSAGE 2...Colder day Thursday then a milder but unsettled pattern prevails over weekend.

Backdoor front will remain suppressed to our south Thursday as strong high pressure heads to Nova Scotia and maintains E/NE winds across region. Certainly looks like a cool and damp day for all, but there are some prospects for drying out in afternoon as weak wave of low pressure passes offshore. Temperatures should actually hold in 30s most of the day which could even result in a little sleet mixing in at times north of I-90 (but nothing impactful).

Once the high moves farther out to sea, our front once again lifts to north in response to next low pressure system tracking through the upper Great Lakes. Temperatures will once again warm into 60s if not 70s away from ocean influence thanks to increasing S/SW flow. Pattern remains unsettled through weekend as we become sandwiched between Great Lakes trough and subtropical ridge off East Coast, leading to moist and relatively warm broad SW flow aloft. This pattern also favors showers from time to time, especially later Saturday into Sunday.

We should see a return to drier and more seasonable temperatures early next week as stronger upper trough moves through Sunday and finally kicks front out to sea.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

Forecaster Confidence Levels...

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

06Z TAF Update...Moderate confidence.

Backdoor front stalled near a line from ORE-PVD. MVFR/IFR ceilings with NE winds in its wake will improve overnight once front lifts back to north. VFR to west of front with S winds.

LLWS expected overnight, especially near coast, with 020 winds 230-240/50-60kt.

A few passing showers are possible today with S/SW winds, then backdoor front once again drops S during afternoon and evening, this time through more of southern New England, with wind shift to N/NE and lowering ceilings to MVFR/IFR. Also expecting a period of showers, mainly focused near South Coast, later in day and into tonight. Slow improvement Thursday.

KBOS Terminal...Moderate confidence in TAF. Lower confidence on whether or not IFR cigs return this afternoon and it's possible OVC008 follows wind shift to N/NE.

KBDL Terminal...Moderate confidence in TAF. Lower confidence on timing of MVFR ceilings and it's possible OVC012 follows wind shift to N/NE.

Outlook /Thursday Night through Sunday/...

Thursday Night: MVFR/IFR conditions possible. Breezy. Chance SHRA, chance FZRA.

Friday: Mainly VFR, with local IFR possible. Breezy.

Friday Night: VFR. Breezy.

Saturday: VFR. Chance SHRA.

Saturday Night: Mainly VFR, with local IFR possible. Breezy. Chance SHRA.

Sunday: MVFR/IFR conditions possible. Windy with areas of gusts up to 30 kt. SHRA likely.

MARINE

Forecaster Confidence Levels...

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

High confidence through the weekend.

SCAs remain posted mainly on south coastal waters for increasing SW winds today as backdoor front retreats northward early this morning, then settles over south coastal waters tonight and Thu with wind shift to NE but diminishing winds and seas.

Next potential round of SCA winds and seas should arrive Fri night and Sat as SW winds increase ahead of low pressure tracking through upper Great Lakes.

Outlook /Thursday Night through Sunday/...

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

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

Friday Night: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas.

Saturday through Saturday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers.

Sunday: Strong winds with gusts up to 35 kt. Areas of rough seas. Chance of rain showers.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 7 PM EDT this evening for ANZ232>234. Small Craft Advisory until 6 PM EDT Thursday for ANZ235-237- 254>256. Small Craft Advisory until 2 PM EDT this afternoon for ANZ236. Small Craft Advisory from 2 AM to 6 PM EDT Thursday for ANZ250.