textproduct: Boston / Norton

WHAT HAS CHANGED

Updated Aviation section, otherwise no significant changes.

KEY MESSAGES

- Sunny & cool today with highs in the upper 40s to the lower 50s except near 40 along parts of the immediate eastern MA coast. Cold tonight with clear skies/light winds & lows mainly in the 20s.

- Dry with moderating temps Thu/Fri. Highs in the 50s/near 60 Thu & well into the 60s on Fri.

- Pleasant April weather this weekend with highs mainly in the upper 50s to the lower 60s. Generally dry this weekend outside a few brief showers possible Fri night/early Sat morning.

- Temperatures uncertain on Mon depending on speed of a warm front, but by Tue it will be unseasonably warm with many locations potentially reaching 80+. Dry weather dominates Mon and Tue outside a few brief showers possible.

DISCUSSION

KEY MESSAGE 1...Sunny & cool today with highs in the upper 40s to the lower 50s except near 40 along parts of the immediate eastern MA coast. Cold tonight with clear skies/light winds & lows mainly in the 20s.

A large 1035+ mb high pressure system will be centered across the region today. This will result in sunny skies...light winds and cool temperatures. The strong April sunshine will allow highs to reach the upper 40s to the lower 50s. However...a weak pressure gradient will allow sea breezes to develop along portions of the immediate coast by afternoon. This will result in afternoon temperatures mainly in the upper 30s and lower 40s along the eastern MA coast.

High pressure will remain in control of our weather tonight as it slowly moves east of the region. Light/calm winds, clear skies and a dry airmass for April standards will allow for ideal radiational cooling tonight. Temps will drop quickly after sunset...Low temps by daybreak Thu will be mainly in the 20s but some upper teens are possible in the normally coldest outlying locations. The urban heat island of Boston will be the mild spot with overnight lows in the lower 30s.

KEY MESSAGE 2...Dry with moderating temps Thu/Fri. Highs in the 50s to near 60 Thu & well into the 60s Fri.

The upper trough over the Northeast shifts east of the region Thu into Fri. The ensembles are in very good agreement in westerly flow aloft and above normal height fields. The result will be moderating temps Thu and Fri with continued dry weather. Highs on Thu will be mainly in the 50s to perhaps near 60 in a few spots. By Fri highs will be well into the 60s across much of the region.

KEY MESSAGE 3...Pleasant April weather this weekend with highs mainly in the upper 50s to the lower 60s. Generally dry this weekend outside a few brief showers possible Fri night/early Sat morning.

A weak cold front crosses the region Fri night into early Sat morning. Forcing and deep layer moisture is rather limited...but a few brief showers will be possible. Otherwise...a 1035 mb high pressure system will build in from the west for the weekend. This will result in very pleasant April weather for the rest of the weekend. Highs will mainly be in the upper 50s to the lower 60s with cooler conditions at times along parts of the immediate coast with sea breezes.

KEY MESSAGE 4...Temperatures uncertain on Mon depending on the timing of a warm front, but by Tue it will be unseasonably warm with many locations potentially reaching 80+. Dry weather dominates Mon and Tue outside a few brief showers possible.

High pressure shifts east of the region early next week. The long range ensembles indicate upper level ridging over the Gulf nosing northward into New England with well above normal height fields. High temps on Mon are uncertain depending on the timing of a warm frontal passage. The GFS is quickest with highs well into the 70s...while the CMC/ECMWF are slower indicating highs in the 50s to the lower 60s. However...by Tue the guidance is in very good agreement in the potential for many locations to see high temps of 80+ with southwest flow. Still a lot can change in this time range...but certainly the potential for summerlike warmth by next Tue afternoon.

A few showers will be possible with the warm front on Mon and perhaps by later Tue/Tue night with shortwave energy approaching from the west. But overall...much of this time may feature dry weather.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

Forecaster Confidence Levels...

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

18z TAF Update:

Rest of the Afternoon through Thursday: High confidence.

VFR through this period. Winds this afternoon N/NE around 5-10 kt, a bit stronger 10-15 kt Cape and Islands, with seabreezes along the eastern MA coast. Winds tonight trend light SE, calm at times. Winds for Thursday trend SE to S around 5-10 kt, on the higher end of that range with occasional gusts to 20-22 kt for interior Southern New England airports.

Thursday Night: High confidence overall, though moderate along the south coast, Cape and Islands.

Mainly VFR; though with returning shallow moisture off the water, the potential exists for patchy MVFR-IFR visby fog after 01z Friday for PVD and the Cape airports. It is possible it may end up being still too dry for much development. South/southwest winds 5-10 kt inland, though light southerly/southeasterly over the south coast.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Thursday Night through Monday/...

Thursday Night through Friday: VFR. Breezy.

Friday Night: VFR. Breezy. Chance SHRA.

Saturday: VFR. Breezy.

Saturday Night through Sunday: VFR.

MARINE

Forecaster Confidence Levels...

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

Through Thursday Night: High confidence.

Winds and significant wave heights remain below small craft advisory thresholds through Thursday night. NE/E winds 15-20 kt today ease tonight and become SE around 10 kt or less (and could turn calm for a while overnight). SE to S winds increase again Thurs to around 10-15 kt, though some gusts could approach SCA criterion over the waters east of Gloucester. Wave heights under 4 ft all waters. Possible risk for marine fog Thursday night, especially in the southern waters and adjacent to Cape Cod.

Outlook /Thursday Night through Monday/...

Thursday Night: Winds less than 25 kt.

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

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

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

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

BOX WATCHES/WARNINGS/ADVISORIES

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