textproduct: Boston / Norton

WHAT HAS CHANGED

Wind gust forecast has increased slightly for Wednesday and Small Craft Advisories have been issued for nearshore waters.

KEY MESSAGES

- Unsettled pattern mid to late week brining wind and rain.

- Unseasonable warmth expected this weekend into early next week.

DISCUSSION

KEY MESSAGE 1...Unsettled pattern mid to late week brining wind and rain.

High pressure shifts offshore tonight as a low pressure system approaches from the Great Lakes. Aloft, a trough approaches and slows down as it closes off over the northeast. This aids development of a wave of low pressure over the area, which will likely have some interaction with a passing offshore low.

In terms of weather, this pattern will result in windy conditions with some showers on Wednesday and then more widespread wet conditions Thursday into Friday. Given the complex interactions, confidence is on the lower side overall through this time period.

Gusts were adjusted above the NBM for Wednesday given expected mixing and LLJ. Even if the lesser mixed NAM is correct, gusts could still peak at 30 to 35 mph. There is some uncertainty with mixing in a southerly flow, but confidence was high enough to bump up forecast.

A good soaking rain over a 24+ hour period is possible Thursday into Friday, especially for eastern areas. Given the complex interaction there is still a large amount of spread in the guidance. This can be seen with the latest NBM 10th percentile QPF showing roughly 0.25- 0.50 inches while the 90th percentile shows over 2 inches. At this time there are no flooding concerns.

KEY MESSAGE 2...Unseasonable warmth expected this weekend into early next week.

Upper trough exits and heights rise into the weekend and early next week, supporting above-normal temperatures with highs in the 70s and 80s. Confidence is lower regarding timing and coverage of any precipitation due to potential embedded shortwaves, but overall trends favor mainly dry conditions with only low- probability scattered showers or thunderstorms Saturday into Sunday. By Monday, an anomalous ridge builds over the Northeast, supporting continued dry and warm conditions into early next week.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

Forecaster Confidence Levels...

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

00Z TAF Update:

Tonight...High confidence.

VFR. Wind becoming light to calm interior and SW 5-10 kt neat the coast.

Wednesday...High confidence. VFR cigs. Brief -SHRA with MVFR possible across interior terminals during the morning. Increasing S winds with gusts to 25 kt developing. Conditions trend to MVFR-IFR west to east after midnight Wednesday night with showers overspreading the region.

KBOS...High confidence.

KBDL...High confidence.

Outlook /Wednesday Night through Sunday/...

Wednesday Night: Mainly VFR, with local IFR possible. Breezy. Chance SHRA, patchy BR.

Thursday: Mainly MVFR, with local IFR possible. Breezy. SHRA, slight chance TSRA, patchy BR.

Thursday Night: Mainly MVFR, with areas IFR possible. SHRA, slight chance TSRA, patchy BR.

Friday: MVFR/IFR conditions possible. Chance SHRA.

Friday Night: Mainly VFR, with local MVFR possible.

Saturday and Sunday: VFR. Breezy.

MARINE

Forecaster Confidence Levels...

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

Today through Wednesday...High confidence.

Winds and waves increase in a southerly flow on Wednesday. Small Craft Advisories have been issued on all waters. There is higher confidence in wind gusts right along the coast, where gusts could peak around 30 kt. Gusts will be closer to 20-25 kt for open waters.

Outlook /Wednesday Night through Sunday/...

Wednesday Night: Small Craft Advisories in effect into early Wednesday night.

Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft. Rain showers, patchy fog.

Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Rain showers, slight chance of thunderstorms, patchy fog.

Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers.

Friday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers.

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

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

Sunday: Winds less than 25 kt. Seas under 5 ft.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...None.