Severe Weather Coordination Message #2 – Friday Afternoon & Evening 7/21/23 Severe Weather & Flood Potential

Hello to all…

..Isolated to scattered strong to severe thunderstorms are becoming more likely in Western, Central Massachusetts and Connecticut for Friday Afternoon and Evening between 2-9 PM. Strong to damaging winds, hail, heavy rainfall with urban and poor drainage flooding are the primary threats with an isolated tornado as a secondary threat. The Storm Prediction Center (SPC) has upgraded Western and Central Massachusetts and Connecticut to a slight risk for severe weather with a marginal risk through Rhode Island and the I-495 corridor of Eastern Massachusetts north of the Mass Pike..
..The Weather Prediction Center (WPC) has placed the same area in a marginal to slight risk of excessive rainfall..
..SKYWARN Self-Activation will monitor the severe weather and flood potential for Friday Afternoon and Evening..

An evolving severe weather scenario for today with increasing potential per model runs between last night and this morning. SPC has upgraded Western and Central Massachusetts to a Slight Risk for severe weather as noted in the headlines. The key factors for today include:

1.) Current radar shows showers and cloud cover over the Slight risk area with clearing behind this activity. This is associated with the warm front which is expected to slow down and hold near the Central Massachusetts to New Hampshire area. The amount of clearing for destabilization and instability will be critical for a more robust severe weather event in the Slight risk area.
2.) The overlap of instability with shear and forcing near the time of peak heating.
3.) The position of the warm front and how close it is to cold frontal thunderstorms will determine the level of rotation within the thunderstorms. Timing and whether two rounds of strong to severe thunderstorms may occur in the region is a bit lower confidence so the afternoon and early evening timeframe from 2-9 PM and perhaps slightly earlier in the afternoon will need to be watched.

SKYWARN Self-Activation will monitor the severe weather and flood potential for Friday Afternoon and Evening. This will be the last coordination message as we shift into operations mode unless time allows and a critical operational update is needed. 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:

NWS Boston/Norton Enhanced Hazardous Weather Outlook:

WPC Day-2 Excessive Rainfall Outlook & Discussion:

SPC Day-1 Convective Outlook:

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:
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