Boston, MA 02113 Weather

What Has Changed

The offshore coastal storm has been classified as Subtropical Storm Josephine, though expected impacts across southern New England remain largely unchanged. Brief storm-force gusts are possible across the outer southeastern waters today, but confidence remains too low to upgrade Gale Warnings. Small Craft Advisories will likely be needed as Gale Warnings expire from west to east tonight into Friday.

Key Messages

- Subtropical Storm Josephine brings showers to far southeastern Massachusetts, along with dangerous marine conditions and gusty winds.

- Fairly cool on Friday with a very low chance of an early morning shower over the eastern waters. Otherwise, moderating temperatures and dry conditions are expected for the weekend into early next week.

Discussion

KEY MESSAGE 1...Subtropical Storm Josephine brings showers to far southeastern Massachusetts, along with dangerous marine conditions and gusty winds.

The coastal storm we've been monitoring this week acquired subtropical characteristics Wednesday afternoon and was classified as Subtropical Storm Josephine by the National Hurricane Center (NHC). The storm remains roughly 250 to 300 miles south-southeast of Nantucket over the warm waters of the Gulf Stream. So, what does this mean for southern New England? Simply put, the change in classification does not alter our expected impacts. As discussed last night, our forecast and messaging remain largely unchanged. In fact, the NHC anticipates Josephine will transition to a post- tropical cyclone later today.

Dangerous to life-threatening marine conditions remain the primary concern, particularly across the ocean waters southeast of Nantucket. Gale Warnings remain in effect across the coastal waters. There is potential for a brief period of storm-force gusts of 50 kt or greater across the outer southeastern waters this morning into early afternoon. However, confidence in the coverage and duration of these stronger gusts remains too low to warrant an upgrade to Storm Warnings at this time.

On land, north to northeast wind gusts of 20 to 30 mph are expected across the interior, with 35 to 45 mph along the coastal plain, strongest across Cape Cod and the Islands. Beach erosion also remains possible along east-facing shorelines due to persistent northeast winds and large waves.

As of early this morning, KBOX radar returns show a shield of precipitation pivoting westward toward Cape Cod and the Islands. However, much of this precipitation is struggling to reach the ground due to dry air near the surface associated with high pressure to our north. Most of southern New England will remain dry, although a few light showers could extend as far west as southeastern Massachusetts, generally east of a New Bedford to Plymouth line. The greatest chances for measurable rainfall remain from Nantucket to Chatham through the first half of today.

Farther west, sunshine will allow temperatures to reach the middle 60s, while persistent cloud cover across eastern portions of the region will keep highs in the upper 50s to lower 60s. Northeast winds gradually diminish from west to east this afternoon as Josephine tracks northeast into the North Atlantic, aided by an approaching northern-stream shortwave and associated trough.

Aviation

Forecaster Confidence Levels...

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

12Z TAF Update:

Today...High confidence in trends.

VFR conditions prevail at most terminals with the exception of the Cape/Islands terminals this morning with MVFR ceilings. Few remaining showers clip the outer Cape and ACK this AM, but should end by 14/15Z. Ceilings improve to VFR between 16Z and 19Z for Cape/Islands. NE winds of 15 to 25 kt along the eastern and southeastern coast, with gusts of 25 to 40 kt. Strongest gusts expected at ACK, with lower gusts along the coastal plain. Farther inland, N winds of 10 to 14 kt with gusts of 20 to 25 kts.

Tonight...High confidence.