Severe Weather Coordination Message #2 – Thursday Evening 7/29/21-Early Friday Morning 7/30/21 Severe Weather & Flood Potential

Hello to all..

..Isolated to Scattered Strong to Severe Thunderstorms still possible anytime late Thursday Afternoon into early Friday Morning along and south of the Mass Pike. Strong to damaging winds, hail, frequent lightning and heavy rainfall leading to urban and poor drainage flooding are the primary threats but even an isolated weak tornado is a secondary threat. The Storm Prediction Center (SPC) has continued the region along and south of the Mass Pike in Massachusetts, Rhode Island and Connecticut in a marginal risk for severe weather..
..The Weather Prediction Center also has the entire region in a slight risk for excessive rainfall for the possibility of training thunderstorms in some localized areas where there has been prior heavy rainfall..
..SKYWARN Self-Activation will monitor the severe weather potential anytime late Thursday Afternoon into early Friday Morning with the highest potential late Thursday Night into early Friday Morning..

A warm front is in the vicinity of Southern New England late Thursday Afternoon into early Friday Morning before a cold front sweeps through the area. This will set the stage for isolated to scattered strong to severe thunderstorm potential along and south of the Mass Pike. The headlines depict the current thinking. Key factors include:

1.) Instability levels will likely be muted but wind shear and helicity or turning in the atmosphere would be sufficient for strong to severe thunderstorm development and could compensate for limited instability. The helicity level and other factors mean an isolated weak tornado is possible.
2.) How far north the warm sector moves into Southern New England and whether it encompasses the southern part of Southern New England, much of or all of Southern New England or if it stays shunted south of Southern New England. Current models and conditions show the marginal risk area will remain along and south of the Mass Pike in Southern New England.
3.) There is the possibility of excessive rainfall and flooding issues if thunderstorms train over a localized area particularly in areas that have had prior heavy rainfall and this will bear monitoring.

SKYWARN Self-Activation will monitor the severe weather potential anytime late Thursday Afternoon into early Friday Morning with the highest potential late Thursday Night into early Friday Morning. This is the last coordination message as we shift into operations mode. Below is the NWS Boston/Norton Area Forecast Discussion, Enhanced Hazardous Weather Outlook, SPC Day-1 Convective Outlook and WPC Excessive Rainfall Outlook:

NWS Boston/Norton Area Forecast Discussion:
https://kamala.cod.edu/ma/latest.fxus61.KBOX.html

NWS Boston/Norton Enhanced Hazardous Weather Outlook:
https://www.weather.gov/box/ehwo

SPC Day-1 Convective Outlook:
https://www.spc.noaa.gov/products/outlook/day1otlk.html

WPC Excessive Rainfall Outlook:
https://www.wpc.ncep.noaa.gov/#page=ero

Respectfully Submitted,

Robert Macedo (KD1CY)
ARES SKYWARN Coordinator
Eastern Massachusetts ARES Section Emergency Coordinator
Home Phone #: (508) 994-1875 (After 6 PM)
Home/Data #: (508) 997-4503 (After 6 PM)
Work Phone #: 508-346-2929 (8 AM-5 PM)
Email Address: rmacedo@rcn.com
http://ares.ema.arrl.org
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