5/31/17 Severe Weather Update #2 (4 PM)

Good afternoon!

The forecast is mostly on track from this morning.

Scattered strong to severe storms are possible this afternoon and early evening, before a higher chance of storms that will be more clustered and more in number in the mid to late evening. Earlier modeling indicated the potential for a late evening squall line, but guidance now points to a broken line being more likely with a few clusters of storms that could be strong or severe. These storms will get their intensity to the west, in New York and western New England, where favorable storm formation conditions are in place.

Instability is marginal in some spots but is enough to maintain storms formed in an environment with decidedly more instability.

Surface based CAPE rates (in red) at the 3 PM hour and radar at 4:00 PM.

There is plenty of strong wind shear as well, which is more than plenty for organized severe weather. This helps result in the potential for damaging winds.

effective shear.PNG
Effective shear rate during the 3 PM hour.

Cold air aloft is contributing to steep lapse rates, which helps storm formation and survival, and aids the potential for large hail.

ll lapse.PNG
Steep low level lapse rates during the 3 PM hour. (Mid level lapse rates are about this steep as well.)


Low LCLs and backed surface winds contribute to the low chance of an isolated tornado, mainly in the western portions of our region and into eastern New York.

A special 2 PM Eastern (18Z) sounding at Albany, New York showing a low LCL and decisively backed winds.
18z hrrr
The 2 PM Eastern (18Z) HRRR shows slightly backed winds (at right) and a low LCL forecast for the evening at Orange, MA. Image via Bufkit (an NWS computer visualization program).

Finally, heavy rain and lightning are expected as well. The chance for storms should be over by 11 PM, but most likely will be prior to that. Storms should weaken as they get to the immediate coast and areas south of the Mass Pike.

Stay tuned to updates and warnings, and be ready to head to safety at a moment’s notice. If you can hear thunder, you are close enough to be struck by lightning.

Stay safe!

Published by Nathan Coram

Hello! I'm Nathan Coram, a 20 year old meteorology student and weather geek, and am in my junior year at UMass Lowell as a meteorology major. I am the current Vice President of the UML American Meteorological Society Local Student Chapter. Prior to at UML, I attended the Dracut school system for my K-12 years, having graduated from Dracut High in 2018. I first got into weather with the December 2008 ice storm, which knocked out my electricity for 4 days. I had no idea how it could be raining and becoming ice immediately, and how rain can knock out power. (Now I do - warm layer aloft, cold air at surface). But I didn't really get into it until the heat of July 2010 and specifically a few severe weather events during that month, followed by the year 2011, which featured several high profile weather events. Since then I have had a growing interest, and am hoping to make it into the meteorology field, preferably with NOAA/NWS. But for now, I'm blogging here on Dracut Weather (also on Twitter and Facebook), helping with the UML Weather Center social media, and tweeting about the weather on my own account as well. Thanks for visiting!

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