Severe Weather Coordination Message #1 – Tuesday Evening 7/20/21 & Wednesday PM/Evening 7/21/21 Severe Weather & Flash Flood Potential
Hello to all…
..Isolated to Scattered Strong to Severe Thunderstorms are possible tonight between 6 PM-12 AM Tuesday Evening across Western Massachusetts with more widespread potential for Isolated to Scattered Strong to Severe Thunderstorms Wednesday Afternoon and Evening across much of Southern New England. The Storm Prediction Center (SPC) has placed Western Massachusetts in a marginal risk for severe weather for Tuesday Evening and much of Southern New England in a marginal risk for severe weather Wednesday. Strong to damaging winds, hail, frequent lightning and urban and poor drainage flooding to flash flooding are the main threats..
..SKYWARN Self-Activation will monitor the severe weather and flood potential for Tuesday Evening and again Wednesday Afternoon and Evening..
We are continuing to compile reports, pictures and videos from the last few days of severe weather and flash flooding. If time allows, a post severe weather and flash flood coordination message around the weather events this past weekend and potentially a summary of all the various events going back to the week off July 4th will be compiled and posted by the end of this week. It has been a very active month of July for areas from the Boston to Providence corridor north and west in the NWS Boston/Norton coverage area.
Two more rounds of severe weather potential for the region starting this Tuesday Evening with the potential for isolated to scattered strong to severe thunderstorms across Western Massachusetts from the Berkshires through Franklin, Hampden, Hampshire and Worcester Counties. The Key factors on the Tuesday severe weather potential is as follows:
1.) The overlap of strongest instability and shear is not in sync with one another but if more instability lingers overnight or shear can compensate for lowering instability, strong to severe thunderstorms would become more likely for Tuesday Evening.
2.) The timing of the impulse and front approaching Southern New England and how that affects coverage of strong to severe thunderstorms in this area.
3.) Western Massachusetts has been extremely wet throughout the last few days and weeks so even non-severe thunderstorms that contain heavy downpours could result in greater flooding impacts than normal in this area.
As we get into Wednesday, the coverage of isolated to scattered strong to severe thunderstorms will be wider across Southern New England as a cold front brings an end to the heat and humidity and will finally allow for a longer period of drier weather for at least Thursday and Friday in Southern New England. The headlines depict the current thinking and key factors include:
1.) Any lingering cloud cover from strong to severe thunderstorms Tuesday Night into early Wednesday.
2.) Timing of the cold front through the region Wednesday and whether it is timed with peak heating and instability.
3.) Level of sufficiently strong wind shear in the atmosphere
4.) Similar to Tuesday’s potential, much of interior Southern New England from roughly a Boston to Providence line has been very wet so even non-severe thunderstorms that contain heavy downpours could result in greater flooding impacts than normal in these areas.
SKYWARN Self-Activation will monitor the severe weather and flood potential for Tuesday Evening and again Wednesday Afternoon and Evening. This will be the only coordination message for Tuesday’s severe weather potential. Given operations may be needed for severe weather and flood potential Tuesday Evening, the next coordination message on Wednesday’s severe weather potential will likely by 11 AM Wednesday Morning unless time allows for an update sooner and there is a significant change to Wednesday’s severe weather potential. Below is the NWS Boston/Norton Area Forecast Discussion, Enhanced Hazardous Weather Outlook and SPC Day-1 and Day-2 Convective Outlooks:
NWS Boston/Norton Area Forecast Discussion:
NWS Boston/Norton Enhanced Hazardous Weather Outlook:
SPC Day-1 Convective Outlook:
SPC Day-2 Convective Outlook:
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: firstname.lastname@example.org
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