textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes to the forecast into this afternoon.

KEY MESSAGES

- Dry start to the day today with scattered showers and isolated thunderstorms developing in the afternoon. Near- seasonable temperatures.

- First half of next week dominated by cooler temperatures and off- and-on showers.

- Confidence decreases in forecast for late-week. More likely leaning dry and warm. Still monitoring in potential for a coastal system to bring showers late Thursday and Friday.

DISCUSSION

KEY MESSAGE 1...Dry start to the day today with scattered showers and isolated thunderstorms developing in the afternoon. Near- seasonable temperatures.

Brief period with weak high pressure in place will bring a dry start to the day today with a mix of sun and clouds. Temperatures aloft warm a few degrees from yesterday allowing temperatures to recover back to more seasonable values in the upper 60s and low 70s. Clouds increase in the afternoon as the next shortwave approaches. This shortwave trough will drop southward bringing a slight uptick in moisture to support scattered showers developing in the afternoon. The morning sunshine and warmer temperatures should also help build marginal instability to support a few brief downpours or an isolate weak storm.

Showers continue early tonight gradually decreasing in coverage through the overnight period as the remainder of the system shifts across the region.

KEY MESSAGE 2...Unsettled conditions for the first half of the week with periods of isolated to scattered showers.

Another push of cold air gets ushered into the region Monday behind the Sunday night's system. This will bring cool day with cooler than normal highs in the upper 50s and 60s. Expect warmer temperatures in the CT Valley in the mid to upper 60s while onshore flow keeps the east coastal areas on the cooler side struggling to get into the low 60s. A weak trailing piece of shortwave energy drops south during the day Monday. Not much moisture to work with, but there is a low chance (< 30%) to support isolated/pop-up showers in the afternoon.

Tuesday, the core of lower 500mb heights shifts east although souther New England still remains under a trough aloft. With the slight moderation in heights, temperatures aloft follow by warming a few degrees from Monday. This should support a more seasonable day with high temperatures in the low to mid 70s with local sea breezes. Coastal areas may end up a bit cooler in the upper 60s where the sea breeze sets up. There are indications across model guidance for another weak piece of shortwave energy shifting southward across the region resulting in another shot for some pop-up showers in the afternoon.

KEY MESSAGE 3...Confidence decreases in forecast for late-week. More likely leaning dry and warm. Still monitoring in potential for a coastal system to bring showers late Thursday and Friday.

Uncertainty grows in the forecast as we head into late-week. Ensemble guidance shows a general consensus with an amplified upper level trough nudging east into the region. A chunk of solutions indicate that a closed low develops at the base of the upper trough near the Carolinas then tracking in a north/east Thursday into Friday. Ensemble means are currently favoring this closed low to track well offshore of the region resulting in dry conditions. However, there have been individual solutions across deterministic and ensemble guidance that indicate a closer pass to the 40N/70W benchmark which may bring showers to the eastern portions of the region. If it does end up dry, there is a signal for a strong ridge aloft to bring an anomalously warm airmass into the region. This may support summer-like temperatures in the low to mid 80s, perhaps nearing 90s in the Valleys.

AVIATION /08Z SUNDAY THROUGH THURSDAY/

Forecaster Confidence Levels...

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

Through 12Z...High confidence.

VFR. Winds NW/NNW for most terminals. Lingering gusts 20-25 kts for HYA/ACK through 12Z.

Sunday...Moderate (shower chances/timing and sea breeze)

VFR. Generally a light westerly component winds. Potential for SE seabreeze to develop late morning into the afternoon, though lower confidence. There is an increasing chance for scattered showers developing mid to late afternoon. Confidence still not quite high enough in the coverage of showers to include as TEMPO, so messaged showers as PROB30s for now. Timing is moderate-high confidence. Low chance for a weak isolated thunderstorm. Brief MVFR possible in any heavier showers.

Sunday Night...High Confidence.

VFR for most of the night. Light W/WNW winds. Any remaining showers diminish by 04Z. Can't rule out a stray shower overnight. Potential for MVFR ceilings to push in after 10Z for the east coast/Cape terminals along with a shift to more NE flow.

KBOS...High confidence in trends. Moderate confidence in timing.

KBDL...High confidence in trends. Moderate confidence in timing.

Outlook /Monday through Thursday/...

Monday: Mainly VFR, with local MVFR possible. Slight chance SHRA.

Monday Night: VFR.

Tuesday: VFR. Slight chance SHRA.

Tuesday Night through Thursday: VFR.

MARINE

Forecaster Confidence Levels...

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

Today and Tonight...High Confidence.

NW winds continue to decrease across the water early this morning, less than 25 kts by 12Z. SCAs remain in place for outer coastal waters for 5-6 ft seas. Cape Cod Bay/Nantucket sound and Mass Bay falls below 5 ft this morning followed by the norther outer coastal waters by this evening. Seas stay around 5 ft through late tonight for the southern outer coastal waters.

Outlook /Monday through Thursday/...

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

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

Tuesday through Tuesday Night: Winds less than 25 kt.

Wednesday through Wednesday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers.

Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 11 AM EDT this morning for ANZ231- 232-251. Small Craft Advisory until 8 PM EDT this evening for ANZ250. Small Craft Advisory until 11 PM EDT this evening for ANZ254>256.