textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes.

KEY MESSAGES

- Gradual clearing today with a low chance of showers in parts of the interior. Drier into Wednesday.

- Generally becoming unsettled once again towards the second half of the week into the start of next week.

DISCUSSION

KEY MESSAGE 1...Gradual clearing today with a low chance of showers in parts of the interior. Drier into Wednesday.

Low pressure continues to pull off to the east and northeast today, which will allow for slow clearing, developing from west to east. Onshore flow persists as this low pulls further away from the region, which will likely keep temperatures near the coasts slightly cooler in the 70s. The rest of southern New England may reach the low 80s, as that's where clouds should scatter out sooner. With the clearer conditions inland, it will also be less humid as winds shift more northwest. A spot shower or two cannot be entirely ruled out across much of central MA into RI, CT this afternoon. Tonight should be calm with patchy fog possible and lows in the 60s.

Zonal flow persists aloft into Wednesday as an upper level low tracks well to our north across the Hudson Bay. Some guidance does indicate some shortwave energy moving within the flow across the region later Wed into Thu which could lead to a spot shower or two, however the more favorable parameters remain to our north and west.

KEY MESSAGE 2...Generally becoming unsettled once again towards the second half of the week into the start of next week.

A stronger shortwave within the flow aloft makes its way east heading into Thursday, bringing with it more favorable dynamics and moisture for showers. Discrepancies still remain regarding the wave's track across the ensemble and deterministic guidance, with the GEFS continuing to show higher probabilities for 24 hour rainfall of 0.1"+ extending into CT, SE MA, and RI while the ECMWF and Canadian ensembles continue to favor a more southern track. NAEFS guidance, notably, keeps the more anomalous moisture off to our south and east, though PWAT values reaching to around 1.5" are not out of the question.

Under the post-frontal airmass Friday with high pressure overhead, conditions will be drier overall. Temperatures will likely be in the low 80s and down to the mid 70s, particularly along the coasts where onshore winds will keep it slightly cooler. Conditions become unsettled once more, though, as we keep an eye on a deepening trough digging into the Great Lakes region towards the weekend period. Shortwaves moving along the boundary that may stall just off the east coast could bring chances for showers. Thunderstorms could be a possibility depending on if these waves could take advantage of daytime heat. More details will become apparent as we approach this timeframe.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Forecaster Confidence Levels...

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

12z TAF Update...

Today and tonight...Moderate confidence in trends with low confidence in timing especially near the coast.

Low end MVFR-IFR with localized LIFR conditions early this morning should gradually improve today. Gradual improvement should occur from west to east through the afternoon with most locations eventually improving to VFR. However...timing remains uncertain especially on the coast. In fact...given onshore flow we can not rule out low clouds/fog bank flirting with coastal sections through the afternoon and never fully departing.

Regardless...low clouds and fog patches should return sometime tonight in some locations from east to west given the cooling boundary layer and dewpoints remaining into the 60s. Timing and westward extend of the low cloud/fog bank remains uncertain though...but areas near the coastal plain will likely be impacted. Low end MVFR-IFR conditions expected to redevelop along with the potential for some LIFR conditions too.

Winds will generally be light to calm through tonight...generally 10 knots or less but with onshore flow along the coast.

Wednesday...High confidence.

Drier westerly flow of air should allow for low clouds/fog patches that do develop overnight to burn off much quicker then today. Most locations should be VFR by mid-late Wed morning. WSW winds of 5-10 knots

KBOS Terminal...Low confidence in TAF.

We are leaning to the the LIFR conditions early this morning gradually improving and eventually reaching MVFR-VFR levels by mid-afternoon. However...that is not a guarantee given onshore flow and dewpoints in the 60s. It is possible that low clouds and a fog bank flirt with the terminal through the afternoon.

KBDL Terminal...Moderate confidence in TAF.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: VFR.

Thursday: VFR. Slight chance SHRA, slight chance TSRA.

Thursday Night through Friday Night: VFR. Slight chance SHRA.

Saturday: VFR. Chance SHRA.

MARINE

Forecaster Confidence Levels...

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

Through Wednesday Night...Moderate confidence.

Low pressure continues to shift farther off to the east. Seas diminish more to 2-4 ft across the coastal and nearshore waters. Ocean waters off to the east may take longer to drop off as they may get to around 5-6 ft heading into tonight. By Wednesday, seas fall to 2-3 ft across all waters. Winds through this period remain generally under 15 kt outside of occasional gusts in the afternoons. More N winds shift W, then S tonight, then more SW by Wednesday night.

A higher rip current risk is expected for east-facing beaches where a Rip Current Statement is in effect from 8 AM this morning through 8 PM tonight.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Winds less than 25 kt.

Thursday: Winds less than 25 kt. Slight chance of rain showers.

Thursday Night: Winds less than 25 kt. Chance of rain showers, slight chance of thunderstorms.

Friday through Saturday: Winds less than 25 kt. Chance of rain showers.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...High Risk for Rip Currents through this evening for MAZ007-015-016- 019-022-024. RI...None. MARINE...None.