Severe Weather Coordination Message #2 – Tuesday Late Afternoon and Evening 7/27/21 Severe Weather Potential

Hello to all…

..Isolated to Scattered Strong to Severe Thunderstorms likely across much of Southern New England late Tuesday Afternoon and Evening anytime between 5 PM-12 AM Tuesday. 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 upgraded Massachusetts from Norfolk County north and west, Northern Connecticut and Northern Rhode Island near the Massachusetts state line to a Slight risk for severe weather with all other areas of Southern New England in a marginal risk for severe weather for Tuesday..
..SKYWARN Self-Activation will monitor the severe weather potential for late Tuesday Afternoon and Evening across the region..

Another round of isolated to scattered strong to severe thunderstorms are likely across much of Southern New England Tuesday as a cold front will bring an end to a short round of heat and summer temperatures in the region. The headlines depict the current thinking which is an upgrade from yesterday evening. Key factors include:

1.) The timing of the cold front as it moves into Southern New England and whether it’s passage is close enough to the higher level of instability parameters to trigger strong to severe thunderstorm development. That is currently expected based on the present model trends.
2.) Wind shear will be strongest in Northern New England but sufficiently wind shear values will be present particularly in the slight risk area that if it overlaps with higher levels of instability or can offset instability as it drops towards sunset would allow for strong to severe thunderstorm development. This is now depicted in several of the high resolution convective models.
3.) Some instability parameters along with higher levels of wind shear could persist passed peak heating to allow for continued strong to severe thunderstorm development well into the evening and allow for severe weather potential in the southern portions of Southern New England provided those favorable parameters occur as forecasted and current model trends support this idea for at least a few isolated to scattered strong to severe thunderstorms for this area.

SKYWARN Self-Activation will monitor the severe weather potential for late Tuesday Afternoon and Evening across the region. 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 and SPC Day-1 Convective 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

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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