textproduct: Boston / Norton

WHAT HAS CHANGED

Extended the Small Craft Advisory for the outer waters through 8pm Friday.

KEY MESSAGES

- Steady rain continues through much of the day giving way to a clearing trend from west to east this afternoon.

- Cooler and mainly dry this weekend with a coastal storm passing well offshore.

- Warmer albeit unsettled conditions return next week.

DISCUSSION

KEY MESSAGE 1... Steady rain continues through much of the day giving way to a clearing trend from west to east this afternoon.

Broad lift from approaching low pressure brings a shield of rain to southern New England through much of the day today. Main area of low pressure tracks through the St. Lawrence Valley. Weak secondary low tracking from mid Atlantic will help enhance showers mainly across eastern Mass and the Islands this afternoon into the early evening. High-res guidance still shows some elevated instability developing by the afternoon as the dry slot works its way overhead. Best chance for any isolated thunder will be on the edge of the dry slot focused near Cape Cod and Islands, but moreso offshore. Solid rainfall event on the order of around 0.5" for most, but still much needed given recent rainfall departures.

KEY MESSAGE 2...Cooler and mainly dry this weekend with a coastal storm passing well offshore.

Amplified pattern over the weekend should feature a building ridge of high pressure over central Canada which traps a closed 532 decimeter upper low over southern Ontario. There are still slight differences among global guidance in the exact location and strength of the ridge over Canada. The ECMWF shows a more southern solution and thus a bit more in the way of shower activity later Saturday afternoon. On the whole, southern New England should be far enough removed from coldest air aloft to keep us mostly dry, especially given W/NW flow, but pattern certainly favors diurnal clouds and perhaps a few afternoon sprinkles over weekend.

Guidance continues to show a fairly weak low that may bring a few showers or perhaps a period of light rain to the southern coast and the Cape/Islands Saturday night into Sunday morning. Recent trends still paint a weak unamplified picture with the majority of the EPS and GEFS ensembles showing a further offshore track.

KEY MESSAGE 3... Warmer albeit unsettled conditions return next week.

Pattern relaxes a bit early next week as closed low lifts farther north, but we remain under broad cyclonic flow aloft. Eventually longer range guidance shows closed low setting up near upper Great Lakes, putting us in SW flow aloft. This could end up bringing more moisture and warmer air into region by Tuesday/Wednesday as weak front approaches resulting in scattered showers. Ensemble guidance shows 850 mb temp anomalies climbing to +10F above climo Tuesday and Wednesday of next week.

AVIATION /06Z THURSDAY THROUGH MONDAY/

Forecaster Confidence Levels...

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

06z TAF Update: Moderate confidence due to timing of flight categories.

Widespread -SHRA thru 14z with IFR ceilings/visibilities. Showers come to an end around midday today with gradual improvement to MVFR ceilings, and possibly VFR later in day with the exception of Cape Cod and Islands.

Quick improvements to VFR from W to E tonight with slower improvements for the Cape and Islands.

KBOS Terminal...Moderate confidence. Reduced confidence in the end time of IFR/LIFR this afternoon.

KBDL Terminal...High confidence in TAF.

Outlook /Friday Night through Monday/...

Friday Night: VFR.

Saturday through Saturday Night: VFR. Chance RA.

Sunday: VFR. Breezy. Slight chance RA.

Sunday Night: VFR.

Monday: VFR. Breezy.

MARINE

Forecaster Confidence Levels...

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

High confidence through the end of the week.

Pressure gradient between slow-moving low pressure SE of the 40/70 benchmark and high pressure over the Canadian Maritimes keeps E/NE winds in play through the end of the week.

Main issue will be the long fetch of NE winds resulting in rough seas of 5 to 8 feet on outer waters through Thu where SCA remains posted. Areas of fog will persist through tonight along with showers.

Outlook /Friday Night through Monday/...

Friday Night: Winds less than 25 kt. Seas up to 5 ft.

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

Saturday Night through Sunday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain.

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

Monday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Seas up to 5 ft.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 8 AM EDT Friday for ANZ250. Small Craft Advisory until 8 PM EDT Friday for ANZ254>256.