FXUS61 KBOX 201742 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 142 PM EDT Mon Apr 20 2026 .WHAT HAS CHANGED... General forecast trends remain unchanged. && .KEY MESSAGES... - Chilly temperatures tonight will be followed by a period of dry/quiet weather ahead of our next chance for showers Tuesday night into Wednesday - Seasonable temperatures return Wednesday and through the rest of the week. - Some uncertainty remains for the latter half of the week regarding the chance for more unsettled conditions. && .DISCUSSION... KEY MESSAGE 1...Chilly temperatures tonight will be followed by a period of dry/quiet weather ahead of our next chance for showers Tuesday night into Wednesday. Short-wave energy moving over southern New England this afternoon ejects southeast overnight bringing an end to any afternoon showers. Northwest flow follows with moderate low-level CAA that will bring 925 hPa temps down to -5C. Additionally, with light winds and clear skies, we can expect a chilly night with well below normal temperatures in the upper 20s to low 30s for much of southern New England. Locations across the interior Northwest may even observe temperatures in the high teens. A mid-level ridge builds in from the west tomorrow afternoon which will bring 925 hPa temps up closer to 0C. This will support a second consecutive afternoon with high temperatures peaking in the low 50s. Overall a dry and sunny Tueday dominated by surface high pressure. As surface high pressure shifts east tomorrow night into Wednesday, return flow and warm advection from the south may support a few isolated to scattered showers across southern New England. KEY MESSAGE 2...Seasonable temperatures return Wednesday and through the rest of the week Some showers are a possibility once again heading into Wednesday as a weak boundary approaches, but more seasonable temperatures make a return as the trough from early this week exits. 925 mb temperatures recover to around 5C, supporting more seasonable highs in the low to mid 50s. NW flow makes a return heading into Thursday in the wake of that weak boundary, and high pressure builds back in then as upper level ridging approaches, keeping southern New England dry. Highs for Thursday and Friday should also remain seasonable barring any drastic changes in upcoming forecasts. KEY MESSAGE 3...Some uncertainty remains for the latter half of the week regarding the chance for more unsettled conditions There are still some discrepancies regarding the placement of the western edge of the upper level trough that becomes centered over the Canadian Maritimes, which may affect how far east warmer temperatures aloft make it for the second half of the week. These would, in turn, affect highs later this week and into the weekend. This also impacts when and where we could see some more unsettled conditions make a return during that same time period. The ridge progressing east approaches southern New England Friday, but depending on that upper level low and how far west it lingers, we may see some showers and cooler conditions. Aside from that, another frontal system arriving Saturday may provide our next chance for some rain. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 18Z TAF Update: Through 00Z...High Confidence VFR with -SHRA through 20-21Z. West/northwest winds from 5 to 10 knots. Tonight...High confidence. VFR. Skies becoming clear, NW wind becomes NNW to N 5-10 kts and lighter heading into Tue AM. Tuesday...High confidence. VFR. Light NNE east winds to start 5-10kts, becoming light SW for interior terminals in afternoon. It may stay more light easterly for the east coast terminals (BOS, Cape/Islands). KBOS Terminal...High Confidence in TAF. Sea-breeze tomorrow between 15-16Z. KBDL Terminal... High Confidence in TAF. Outlook /Wednesday through Saturday/... Wednesday: Mainly VFR, with local IFR possible. Slight chance SHRA. Wednesday Night: Mainly VFR, with local MVFR possible. Thursday: VFR. Breezy. Thursday Night through Friday: VFR. Friday Night through Saturday: VFR. Slight chance SHRA. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Tonight through Tomorrow Night High pressure moves over the coastal waters tonight through tomorrow bringing relatively calm conditions to the coastal waters. Generally expect seas with significant wave heights 3 feet or less and modest wind speeds around 10 knots with some gusts to 15 knots possible. Winds will be out of the north tonight and tomorrow before a shift to southerly flow tomorrow night. Outlook /Wednesday through Saturday/... 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. Thursday Night through Friday Night: Winds less than 25 kt. Saturday: Winds less than 25 kt. Slight chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ DISCUSSION...RM AVIATION...RM MARINE...RM