Severe Weather Coordination Message #2 – Friday 5/15/20 Severe Weather Potential

Hello to all…

..Severe Weather Risk has shifted a bit further north and west with Western and Northern Massachusetts into Southern New Hampshire, clipping parts of Northwest Connecticut as the key risk area but all areas should monitor similar to the previous coordination message particularly interior Southern New England..
..Scattered to Numerous Strong to Severe Thunderstorms are likely Friday particularly across Western and Central Massachusetts and Northern Connecticut but also possible in interior Northern Rhode Island through interior Northeast Massachusetts along and north and west of the Boston to Providence. Strong to damaging winds, hail, frequent lightning and heavy downpours resulting in urban and poor drainage flooding are the primary threats with the secondary threat for an isolated tornado particularly in Western New England..
..The Storm Prediction Center (SPC) has shifted the enhanced risk area to focus on Western and Central Massachusetts as far east as North-Central Middlesex County Massachusetts clipping a portion of Northwest Connecticut. A slight risk of severe weather exists for the rest of Northern Connecticut, Rhode Island and interior Eastern Massachusetts up to the Boston to Providence corridor. East coastal and south coastal Massachusetts and Rhode Island remain in a marginal risk for severe weather..
..SKYWARN Self-Activation with Amateur Radio call-up nets are likely after 3 PM ET Friday Afternoon. The timeframe for severe weather is between 3-10 PM Friday Afternoon and Evening..

At 1110 AM, the warm front has shifted through Southern New England with clearing evident on visible satellite imagery across interior Southern New England across, Connecticut, Western, Central and Northeast Massachusetts from the Boston to Providence corridor north and west. Clearing is also starting in southeastern areas as well. Based on the timing of the cold front being a bit later, the focus for more widespread strong to severe thunderstorms is across Western and Northern Massachusetts and Southern New Hampshire clipping Northwest Connecticut. Radar does show an area of showers over Southern Ontario Canada and lighter showers in South-Central New York where which may be an area that allow severe thunderstorms to develop in the earlier peak heating timeframe of 3-7 PM and will bear watching. The headlines depict the current thinking. Key factors include:

1.) Clearing allows for the expected heating and destabilization as modeled. This is progressing as expected.
2.) The position of the warm front verifies allowing most of Southern New England to be in the warm sector. This has progressed as expected.
3.) The position of and timing of the cold front is a bit later than previously forecasted which is why the enhanced risk for severe weather has shifted into Northwest Connecticut, Western and Central Massachusetts through North-Central Middlesex County Massachusetts and Southern New Hampshire. The key item is whether the warm/cold frontal positions will allow for the triggering mechanism to be close enough for severe thunderstorms to develop ahead of the main line increasing the severe weather risk. The squall line of severe thunderstorms will arrive towards sunset where instability will be dropping but jet dynamics and forcing could allow the severe thunderstorms along the line or activity ahead of the line to maintain itself for 2-3 hours after sunset with the focus again in Northwest Connecticut, Western and Central Massachusetts through North-Central Middlesex County Mass and Southern New Hampshire. If the timing is later or jet dynamics do not compensate to maintain the squall line of activity or any activity ahead of the squall line, the severe weather potential would be more muted and/or isolated to scattered in nature. Regardless, the potential will have to be monitored closely.

SKYWARN Self-Activation with Amateur Radio call-up nets are likely after 3 PM ET Friday Afternoon. This will be the last coordination message as we shift into operations mode. Below is the NWS Boston/Norton Special Weather Statement on Severe Weather Potential, Hazardous Weather Outlook, Enhanced Hazardous Weather Outlook and SPC Day-1 Convective Outlook:

NWS Boston/Norton Special Weather Statement:
https://kamala.cod.edu/ma/latest.wwus81.KBOX.html

NWS Boston/Norton Hazardous Weather Outlook:
https://kamala.cod.edu/ma/latest.flus41.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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