Today’s Severe Weather Potential
Risk for Scattered Strong to Severe Thunderstorms this Afternoon/Early Evening Mainly Across Connecticut, Rhode Island, and Southeast Massachusetts
Heat
Today will be the final day of hot temperatures (near or a little above 90 degrees away from the south coast) before a return to more seasonable temperatures Thursday into the weekend behind a cold front.
Thunderstorms
The very warm temperatures will cause the atmosphere to once again become unstable this afternoon into early evening. The area of greatest risk for strong to severe thunderstorms, however, will be across Connecticut, Rhode Island, and southeast Massachusetts. The warm temperatures under abundant sunshine will provide steep low level lapse rates (very warm near the surface and significantly cooler aloft). For thunderstorms to develop, there also has to be moisture. Although not super moist, there appears to be sufficient moisture for thunderstorm development with dew points in the mid 60s. The approaching cold front will initiate low level moisture convergence and provide a mechanism for broader uplift, which will help trigger the convection (i.e., thunderstorm development). Another ingredient for severe thunderstorms is the magnitude of vertical wind shear. In this case, the vertical wind shear is marginally strong enough to support a few organized thunderstorms (or clusters of thunderstorms) capable of producing localized strong wind gusts.
The approaching cold front is moving a little faster than originally projected by most models earlier in the week. What may have been a prefrontal trough well ahead of the cold front in an air mass characterized by both low level and mid-level instability helped trigger clusters of strong to severe thunderstorms yesterday across portions of northern MA as far south as the Mass Pike region. This was more like the extent of activity expected further north and northwest across VT and upstate NY based on earlier model projections. Credit is due for the National Weather Service’s Storm Prediction Center that adjusted the marginal severe thunderstorm risk further south and east yesterday in advance of the thunderstorms.
The faster cold front in turn places the greatest risk of strong to severe thunderstorms across CT, RI, and southeast MA this afternoon and evening where the best overlap of instability and frontal induced uplift is expected. Although this is the region with the greatest instability, mid-level lapse rates appear weaker than what was observed yesterday. There is at the time of this writing a subtle hint of low-level convergence focused south of the Mass Pike.
The main threat posed by thunderstorms later today will be localized damaging wind gusts in addition to lightning, a threat with any thunderstorm. Recall that the criteria for severe thunderstorms include damaging wind gusts and/or large hail. However, dangerous lightning is associated with all thunderstorms, and slow moving or repetitive thunderstorm cells can produce localized flooding from heavy downpours. Today’s concern is primarily the risk of highly localized damaging wind gusts across the southern third of southern New England.
Memorial Day Weekend
The holiday weekend will likely feature seasonable temperatures or possibly a little cooler than average temperatures. Although no severe weather is expected, there could be a risk of one or two bouts of showers. There is little consistency from model to model or from any one model from run to run. Interestingly, the Boston Weather Forecast Office noted that the AI based models appear dryer than the legacy dynamic models (with most of the shower activity centered just south of New England). Unfortunately, the bottom line is that it’s still too soon to have much confidence in the duration and areal extent of any shower activity this weekend.
Next Message
The next message will likely be the regularly scheduled weekly significant weather outlook on Monday, May 25, unless much greater clarity can be gleaned for the holiday weekend. No hazardous weather is expected over the Memorial Day holiday weekend, and folks with outdoor plans should monitor the latest forecasts from the local National Weather Service (for most of southern New England, go to: weather.gov/box).
About this Blog and Disclaimer
The National Weather Service monitors the weather 24/7 and updates forecasts, watches, and warnings as necessary. For most of southern New England, refer to your local Weather Forecast Office for the latest forecast/warning information at weather.gov/box. For information from other Weather Forecast Offices, go to weather.gov and click on the location of interest on the map.
The frequency of this blog will depend upon the nature of the weather threat and availability of the author. Thus, for the latest information on weather forecasts and warnings, refer to the National Weather Service, which monitors and forecasts the weather 24/7.
Blue Hill Observatory and Science Center (BHOSC)
The BHOSC maintains a continuous daily observation record that dates from February 1, 1885 without interruption and provides educational information on weather and climate to area students and the community at large. Your support of BHOSC is much appreciated and enables this nonprofit organization to maintain the long-term climate record at the Blue Hill Observatory (longest continuous record in North America) and provide valuable educational resources on weather and climate via outreach to schools, site visits/tours, webinars, and conferences. For more information on the Blue Hill Observatory and Science Center, explore bluehill.org.
Message issued May 20, 2026 by:
Bob Thompson
Retired National Weather Service Meteorologist
Blue Hill Observatory and Science Center Board member
