Severe Weather Coordination Message #2 – Saturday Afternoon & Evening 6/19/21 Severe Weather Potential

Hello to all…

..Isolated to Scattered Strong to Severe Thunderstorms are possible mid-to-late Saturday Afternoon and Evening across areas of Southern New England along and south of the Mass Pike though areas north of the Mass Pike should continue to monitor with a timeframe of after 3-4 PM til 12 AM Saturday with strong to damaging winds, hail, frequent lightning and heavy rainfall with urban and poor drainage flooding as the main threats.
..The Storm Prediction Center (SPC) has focused the marginal risk for severe weather for Saturday to areas along and south of the Mass Pike with the latest update but areas north of the Mass Pike should continue to monitor..
..SKYWARN Self-Activation will monitor the severe weather potential for Saturday late Afternoon and Evening..

An impulse in the atmosphere will move into Southern New England mid to late Saturday Afternoon into Saturday Evening with the potential for isolated to scattered strong to severe thunderstorms. The headlines depict the current thinking. Key factors include:

1.) Amount of available instability since the impulse will move through past peak heating.
2.) Wind shear profiles are favorable which may compensate for lower instability if current timing in the late afternoon/early evening holds.
3.) If timing of the impulse is earlier than currently expected allowing better overlap of higher instability with strong wind shear and the impulse acting as a trigger in the atmosphere.
4.) Amount of available moisture in the atmosphere and the moisture return as we get toward later afternoon and evening. Areas of north of the Mass Pike have drier dewpoints but areas along and south of the Mass Pike has higher dewpoints and moisture available which is why the marginal risk for severe weather is focused on that area.

SKYWARN Self-Activation will monitor the severe weather potential for Saturday Afternoon and Evening. 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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