Area Forecast Discussion National Weather Service Boston/Norton MA 320 AM EDT Mon Apr 20 2026 .WHAT HAS CHANGED... General forecast trends remain unchanged. KEY MESSAGES - Cool today with some scattered shower chances. Otherwise, dry and turning even colder overnight. - 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...Cool today with some scattered shower chances. Otherwise, dry and turning even colder overnight. An upper level trough settles overhead today, which will lead to colder air making its way into southern New England. 925 mb temperatures today struggle to get above 0C, supportive of highs only in the low 50s and upper 40s. Winds will be breezy and mostly NW with occasional gusts in the afternoon around 20-25 MPH. They will start to diminish as high pressure approaches from the west heading into tonight. Even with the aforementioned approaching high pressure, a weak low pressure passing through the region today will bring increased cloud cover and some scattered showers. Any showers that do pop up are expected more so in the afternoon hours today, and the highest chances are primarily centered around the northern MA border and the south coast. Eastern MA could see some as well, primarily in the later afternoon hours into the evening. With regards to any chances for thunder, chances are quite low. MUCAPE values in high res guidance are only around 200 J/kg along the south coast and generally north of MA through much of the afternoon, then shifting towards eastern MA towards 6 PM. HREF thunder probs are also below 10 percent. Some convective showers cannot be completely ruled out, but confidence in embedded thunder or lightning developing is low at this time. Outside these rain chances, conditions will be very dry as dew points are around 20 degrees lower than the expected air temperatures today. Tonight, it gets even colder as we have more of a radiational cooling setup. As the colder air builds in, any lingering showers may also mix with wet snowflakes, but chances for that remain very low. Skies clear and winds shift more N and go light overnight. The colder airmass remains affixed overhead, with 925 mb temperatures falling to around -5C overnight. In the interior, lows may dip into the low 20s, particularly in the higher elevations. Subfreezing temperatures are expected across southern New England, aside from more coastal areas. However, it will still get close to freezing in those areas, bottoming out in the mid 30s. Temperatures remain cool for Tuesday, though will steadily be improving as the upper level trough and associated cold airmass progress offshore. This improvement will be more noticeable Tuesday night as lows will generally be in the 30s across the region. High pressure builds in, maintaining dry conditions. 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 /07Z MONDAY THROUGH FRIDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 06z TAF Update: Through 12z...High Confidence. VFR. Diminishing wind gusts. W wind 5-10 kts. Today...Moderate confidence in showers. High confidence in overall trends. VFR, though ceilings will be closer to 040-060. Scattered showers possible, but exact location is still in flux. Cannot rule out wet snow flakes mixing in any lingering showers after sunset, particularly in the interior. WNW to NW wind at 10-15 kts, gusting occasionally to 20 kts for some terminals in the afternoon. 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 winds shift more SW towards the afternoon. KBOS Terminal... Moderate Confidence in TAF. Low probability for showers to develop at/near the terminal later this afternoon, but cannot be ruled out entirely. KBDL Terminal... High Confidence in TAF. Outlook /Tuesday Night through Friday/... Tuesday Night: Mainly VFR, with local MVFR possible. Slight chance SHRA. Wednesday: Mainly VFR, with local IFR possible. Slight chance SHRA. Wednesday Night through Friday: VFR. .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Through Tuesday...High Confidence. Winds remain mostly W over the southern waters and more S over the E/NE waters today, falling between 10-15 kts. Tonight, they become N between 10-20 kt. Winds slacken once again for Tuesday, falling to below 10 kt in the afternoon and gradually shifting more S to SW heading into Tuesday night. Seas through this period should remain between 2-3 ft with localized areas in the outer waters of 4 ft possible late tonight. Outlook /Tuesday Night through Friday/... Tuesday Night: Winds less than 25 kt. Wednesday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. Wednesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Thursday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. Thursday Night through Friday: Winds less than 25 kt. .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. DISCUSSION...Hrencecin AVIATION...Hrencecin MARINE...Hrencecin