Fwd: Severe threat Wednesday

---------- Forwarded message ----------
From: Philip C. Ordway <pcordway@gmail.com>
Date: Tue, Jun 21, 2016 at 9:02 AM
Subject: Re: Severe threat Wednesday
To: "go@blogger.com" <go@blogger.com>

Things are really coming together for a severe weather outbreak tomorrow (Wednesday) in the Chicago area. Peak daytime heating will meet a very moist, unstable air mass. A SW low-level jet will add fuel right as a trough approaches from the west. This is a classic set up that, under similar circumstances in the past, has produced numerous supercell thunderstorms. The analogs point to some of the more destructive "derecho" events (large, well organized masses of thunderstorms with destructive straight-line winds). 

At this point I think there is a strong likelihood (70% for me vs. 45% in the current NWS forecast) that locations in the Chicago area will see severe storms tomorrow. Large-scale high winds and/or tornadoes are the primary threats, with the attendant power outages and tree/structural damage likely in their wake. The threat for strong (EF3 or greater) tornadoes is somewhat low, but several weaker (and still deadly/destructive) tornadoes are more likely. With >2" of evaporated moisture certain locations could see some flooding problems too. The main threat will be widespread destructive winds of 60-80+ mph. 

We will likely be confirmed or upgraded in the SPC convective outlook later today. By tonight or tomorrow morning we should also get a slightly better sense of timing and favored locations. From here it looks like late-afternoon into the evening are most favored for severe storms, and there will likely be some lesser thunderstorms earlier in the day on Wednesday (in the morning toward lunch) as the warm front passes. But as with all severe thunderstorm events it is nearly impossible to get precise with timing and location inside of a few hours and many thousand square miles. 

Here is a sample of of the data/forecasts as they stand:

WIDESPREAD DAMAGING WINDS...A FEW TORNADOES AND LARGE HAIL ARE     EXPECTED ACROSS NORTHERN ILLINOIS...SOUTHERN WISCONSIN...NORTHERN     INDIANA AND SOUTHWEST LOWER MICHIGAN DURING THE LATE AFTERNOON AND     EVENING ON WEDNESDAY. 

We are closely monitoring the potential for numerous to widepsread severe thunderstorms, as well as torrential rainfall and flooding on Wednesday. The combination of an unseasonably strong storm system and a warm and humid air mass could yield significant severe weather somewhere over the region. All severe hazards are possible. Small scale details not yet known will affect the locations and magnitude of impacts. At this point the potential for more widespread storms is during the later afternoon and evening. The bottom line is, pay very close attention to the latest forecast updates and practice your severe weather safety plans to be ready if severe weather strikes your area on Wednesday.

Daniel Shaw ‏@DanielShawAU   hou

I'm extremely concerned about the upcoming forecast and upgraded risk in heavily populated areas tomorrow.

On Mon, Jun 20, 2016 at 9:39 PM, Philip C. Ordway <pcordway@gmail.com> wrote:

Happy Solstice!

It is still early but there is an emerging threat for severe weather on Wednesday that bears watching. Details will be coming tomorrow and Wednesday as warranted -- anyone with travel or outdoor plans should keep an eye on things.