Flash Flood/Severe Weather Coordination Message #1 – Sunday 9/13/26 Flash Flood/Isolated Severe Thunderstorm Potential

Hello to all…

..Flash Flooding possible in portions of South-Central and Southeast Massachusetts from roughly the Mass Pike South through Rhode Island and Eastern Connecticut Sunday Morning through early Sunday Evening. A secondary risk for an isolated severe thunderstorm with strong to damaging winds, frequent lightning and even an isolated weak tornado possible..
..A Flood Watch is now in effect for Windham County Connecticut, Rhode Island, Southern Worcester, Norfolk, Suffolk, Bristol, Plymouth, Barnstable, Dukes and Nantucket Counties of Massachusetts from late tonight through Sunday Afternoon for a localized band of 2-4″ of rain embedded in a more widespread area of 0.50″-2.00″ rainfall. This excessive rainfall could cause flash flooding particularly if it falls in an urbanized/poor drainage area..
..SKYWARN Self-Activation with Amateur Radio Call-Up Nets possible if a warning is issued. Pictures and videos of wind damage, hail, flooding etc. can be sent as a reply to this email, via our Facebook/X/Bluesky feeds or the email address pics@nsradio.org with credit given to the spotter unless otherwise indicated..

The headlines depict the current thinking on flood potential and a low risk of an isolated severe thunderstorm with damaging wind or perhaps a weak tornado. Key factors include:

1.) Axis of heavy rainfall could be anywhere in the flood watch area and there have been deviations north and south of this heavier rain axis on the various high resolution models. Exact placement wont be known until a few hours before the event occurs as the rain moves in the area and the bands setup.
2.) Given a mesocale low will be over the area, these sometimes have the potential for an isolated severe thunderstorm and even a weak tornado over the area. Instability will be limited but ocean temperatures being near peak levels will mitigate the stabilizing influence of the marine layer. This is a secondary and low risk for the region but will be monitored.

SKYWARN Self-Activation with Amateur Radio Call-Up Nets possible if a warning is issued. Pictures and videos of wind damage, hail, flooding etc. can be sent as a reply to this email, via our Facebook/X/Bluesky feeds or the email address pics@nsradio.org with credit given to the spotter unless otherwise indicated. This will likely be the only coordination message as we shift into operations mode Sunday Morning. Below is the NWS Boston/Norton Area Forecast Discussion, Flood Watch Statement and Enhanced Hazardous Weather Outlook:

NWS Boston/Norton Area Forecast Discussion:
https://forecast.weather.gov/product.php?site=NWS&issuedby=BOX&product=AFD&format=CI&version=1&glossary=1&highlight=off

NWS Boston/Norton Flood Watch Statement:
https://forecast.weather.gov/product.php?site=NWS&issuedby=BOX&product=FFA&format=CI&version=1&highlight=off&glossary=0

NWS Boston/Norton Enhanced Hazardous Weather Outlook:
https://www.weather.gov/erh/ghwo?wfo=box

Respectfully Submitted,

Robert Macedo (KD1CY)
ARES SKYWARN Coordinator
Eastern Massachusetts ARES Section Emergency Coordinator
Home Phone #: (508) 994-1875
Home/Data #: (508) 997-4503
Email Address: rmacedo@rcn.com
https://ares.ema.arrl.org
https://www.wx1box.org
Like us on Facebook – https://www.facebook.com/wx1box
Follow us on Twitter – https://twitter.com/wx1box
Subscribe on YouTube – https://www.youtube.com/@wx1box-nwsboston-amateur-radio