textproduct: Boston / Norton

WHAT HAS CHANGED

No changes to the forecast for this update cycle.

KEY MESSAGES

- Warm and humid weather will continue through Friday, with a low risk of showers and thunderstorms.

- Dry and seasonable weather with low humidity levels this weekend into Monday, but turns hot and humid by midweek.

DISCUSSION

KEY MESSAGE 1...Warm and humid weather will continue through Friday, with a low risk of showers and thunderstorms.

Regional radar shows showers and thunderstorms across eastern PA to Long Island, with a few showers in southern New England. The region is situated between a frontal boundary across the eastern Great Lakes to northern New England and deep moisture across the Mid-Atlantic region. Drier air has limited coverage of showers and thunderstorms across the forecast area. The best chance of additional showers and thunderstorms is west of I-95 through the evening hours.

The frontal boundary will slowly sag into the region Friday while moisture increases across the region. Cloud cover and patchy fog are expected to increase in coverage tonight. As the boundary lies across the forecast area, a weak shortwave trough will approach the area Friday. The chance for showers and thunderstorms will increase through peak heating hours, however the risk remains low. Any fog and low clouds will erode early in the morning with low clouds persisting the longest along the southern coast. There will be a low risk of showers Friday night.

KEY MESSAGE 2...Dry and seasonable weather with low humidity levels this weekend into Monday, but turns hot and humid by midweek.

After Friday evening's cold frontal passage into the southern waters, high pressure from Canada builds southward with cyclonic flow aloft. This will bring a cooldown toward more seasonable summer temperatures in the mid 70s to low to mid 80s, with low humidity levels and dry weather Saturday through Monday. Other than some cooler seabreezes near the eastern coast, it's otherwise shaping up to be a great weekend.

By Tuesday and especially Wednesday, temperatures become quite hot as 850 mb temps soar again into the +18 to +22C range. These values are similar (somewhat cooler by comparison) to our last extended spell of high heat/humidity. The potential could exist for temperatures in the 90s with high humidity levels perhaps necessitating a period of heat headlines for midweek. The risk for thunderstorms looks limited, with a better chance on Wednesday as NW flow aloft increases and a plume of elevated mid-level lapse rates builds in favoring stronger instability.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

Forecaster Confidence Levels...

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

00z TAF Update:

Through 12z Friday: Moderate confidence.

Generally VFR, but a couple things to watch. One is widely SCT TSRA near Berkshire County, which are slowly moving east. Main risk for TS tonight looks to be at BDL but chances are pretty low and messaged with PROB30 thru 02z. Meanwhile, starting to see IFR- LIFR stratus along the south coast; potential for MVFR- IFR ceilings as far north as PVD to OWD by 06z, but confidence is lower if it slips into BOS/BED. SW winds around 7-12 kt, with gusts to 25 kt eastern and southeast MA, though gusts subside to sustained SW winds 5-10 kt overnight.

Friday: Moderate confidence.

Main issue for the TAFs Fri is the timing of the cold front southward. Current indications are for winds turning NWly under 10 kt for BDL-ORH-BED-BOS between 13-15z with BKN/OVC VFR ceilings; winds turning NE under 10 kt at BOS early afternoon. Thinking area more favored to see SCT SHRA/TS is from HFD to PVD south and east after 17z, after overnight stratus disperses. A slower passage would put more TAFs at risk for SHRA/TS.

Friday Night: High confidence.

Lingering SHRA/TS moves offshore early Fri night to VFR conditions. Outside chance at river valley fog if skies can clear out. Winds become light northerly overnight.

KBOS Terminal...Moderate confidence. Thinking stratus near south coast should stay far enough south of the airport. Windshift to NW under 10 kt by 13-15z Fri, then turning NE under 10 kt with BKN VFR ceilings. Slower frontal timing will affect timing of windshifts Fri.

KBDL Terminal...Moderate to high confidence. PROB30 for TSRA thru 02z Fri, otherwise, VFR should prevail with a windshift to NW around 13-15z Fri.

Outlook /Saturday through Tuesday/...

Saturday: VFR. Slight chance SHRA.

Saturday Night through Monday Night: VFR.

Tuesday: VFR. Breezy.

MARINE

Forecaster Confidence Levels...

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

Through Friday Night...High confidence.

Mostly tranquil boating conditions this evening. A weak front approaches the waters from the NW Friday, but is not likely to pass the southern coastal waters until late Friday night at the earliest. A risk for scattered showers or thunderstorms tonight across the southern waters. Some risk for more afternoon and evening showers and thunderstorms Friday.

Outlook /Saturday through Tuesday/...

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

Saturday Night: Winds less than 25 kt.

Sunday through Monday Night: Winds less than 25 kt. Seas locally approaching 5 ft.

Tuesday: Low risk for Small Craft Advisory winds with areas of gusts up to 30 kt. Areas of seas approaching 5 ft.

BOX WATCHES/WARNINGS/ADVISORIES

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