Severe Weather Coordination Message #2 – Sunday Evening 9/12/21-Monday Morning 9/13/21 Severe Weather Potential

Hello to all…

..Isolated to Scattered Strong to Severe Thunderstorms are possible across Western Massachusetts and Western Connecticut Sunday Evening into early Monday Morning. There could be two rounds one during roughly between 4-8 PM Sunday Evening though this is more conditional and less likely than a second potentially more potent round between 10 PM Sunday Evening-6 AM EDT Monday Morning. Strong to damaging winds, hail, frequent lightning, and heavy downpours leading to urban and poor drainage flooding are the main threats..
..The Storm Prediction Center (SPC) has continued Western and Central Massachusetts and Connecticut in a marginal risk for severe weather Sunday Night into Monday Morning and the Weather Prediction Center (WPC) has placed the same area in a marginal risk for excessive rainfall in the same areas..
..SKYWARN Self-Activation will monitor the severe weather potential potential for Sunday Night into Monday Morning..

A front will move across Southern New England Sunday Night into Monday Morning. Typically, this unfavorable timing would not support severe thunderstorm development but due to strong shear, dynamics and lift from the front, there is the potential for isolated to scattered strong to severe thunderstorms. The headlines depict the current thinking. Key factors include:

1.) The instability levels and whether those levels are sufficient combined with strong wind shear and jet dynamics for severe weather potential.
2.) Whether severe thunderstorms in Central and Eastern New York presuming they develop as expected starting out in Michigan and Western New York will maintain their intensity as they move into Southern New England.
3.) The earlier Sunday Evening threat is more conditional as there would be sufficient shear and instability but a lack of strong trigger in the atmosphere means that no thunderstorms form during the first half of Sunday Evening but if something were to form, it could go severe rapidly. Models differ on whether a few rapidly developing strong to severe thunderstorms occur or if there is no activity. Later at night, there will be the trigger and wind shear but instability will be in question with a lack of heating but an “elevated mixed layer” may allow for better instability offsetting lack of heating creating better severe weather potential overnight than normal for the region.

SKYWARN Self-Activation will monitor the severe weather potential potential for Sunday Night into Monday Morning. This will be the last coordination message as we shift into operations mode. Below is the NWS Boston/Norton Area Forecast Discussion, Enhanced Hazardous Weather Outlook, WPC Excessive Rainfall Outlook and SPC Day-1 Convective Outlook:

NWS Boston/Norton Area Forecast Discussion:

NWS Boston/Norton Enhanced Hazardous Weather Outlook:

WPC Excessive Rainfall Outlook:

SPC Day-1 Convective Outlook:

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:
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