Severe Thunder Snow!?

[Andrew Pritchard]

The #%@% has hit the fan in central Illinois. I went out around 230 PM and got more than i bargained for. I measured sustained winds of 50-60 mph for about an hour, with higher gusts almost blowing my car off the road. Got some amazing video of the snow being blown horizontally at these speeds, along with video of a roof being ripped off of a big storage building...power lines downed, and other numerous things blowing across the road that shouldnt have been. Had a couple strikes of lightning as well during this! Snowfall totals only around 3 inches, here, but its the insane winds that were the story.

EDIT: I might also add, that there are stop signs bent at the base, flat against the ground.

 

[Thomas Loades]

Sounds like an event verging on a snow-downburst! (Or perhaps snow-derecho, for its longevity.)

 

[Joel Wright]

Yes this was quite a weird event. Apparently some kind of gravity wave propagated across the state and into NW IN. Valparaiso Indiana had a wind gust to 66mph with almost 6" of snow. A public weather statement from Lincoln IL had numurous reports of "non thunderstorm wind damage."

I'd like to see some kind of a event summary or case study on this interesting local event...

 

[Joe Nield]

I hate Illinois. You people get all the fun! :evil:

I'm sure many people on here remember the severe thunderstorm warnings issued by ILX back in January of 2003 for thundersnow.

Of course, I was in Long Beach at the time at the AMS conference. :roll:

 

[Saul Trabal]

I've seen severe thundersnow-in fact, I think that was one of my first threads here on this BBS.

This was during the Super Noreaster of 1996 (?). In my area, snow was the highest it had ever been-about 5 to 6 feet high. Visibility was near zero. The thundersnow squalls had almost continuous lightning-which if I'm correct, is virtually unheard of.

:shock:

 

[Scott A. Kampas]

Unlike the Feb 03 event, the wind doesn't seem to have been convectively induced or appreciably enhanced. There was significantly less lightning this time around and no snow rollers, but the heavy wet snow made for much more significant and widespread damage. ILX's LSR is quite impressive, pretty much every county in the CWA reported extensive trees and powerlines down. There was also structural damage with collapses and torn roofs. Not a fun day for travelers during the heaviest travel period of the year with the roads blocked by snow, ice, trees, powerlines, and extensive blackouts.

Scott

 

[Thomas Loades]

Why is lightning in a blizzard such an irregularity? Does the cold not work well with static electricity?

 

[David Draun]

The snowfall up here near Chicago was definitely convective in nature. Large heavy moisture laden snowflakes driven by very strong winds were definitely whiting out the area. Not too much lightning here, but there was occasional flickering more easily seen after dark. Many area forecasters had downplayed this event, but Tom Skilling mentioned local 5 inch amounts were possible, especially if thunderstorms occured. Wow, you can really rely on him sometimes. He nailed this one.

 

[Joe Nield]

Originally posted by Thomas Loades
Why is lightning in a blizzard such an irregularity? Does the cold not work well with static electricity?

Hope I have my details correct...

We all know convection requires instability. Since low levels are typically highly stable in the cold season, there must be a source of elevated instability to produce thundersnow.

Convective snow is fairly rare, as the static stability in snow profiles is typically fairly high compared to a typical convective profile. The convective process creates the charge separation that leads to lightning, so no convection, no lightning.

That said, situations with strong dynamic lifting can lead to thundersnow, by cooling the midlevels, thereby creating more elevated instability.

 

[Joe Zemek]

Denver, Land of Thundersnow

In my 10+years living there, I experienced the joy of thundersnow several times, almost always courtesy of a strong spring low with ample moisture.

My 2001 bustathon--er, chasecation ended with a thundersnow episode as I was returning my rental car to DIA on May 20. A compact but steep cold front (behind the low that made naders in OK that day) came barreling south along the Front Range (busting in KS the previous day I knew nothing about the DEN forecast) and a squall line shot up. A massive haboob sprouted in front of the line, and that cloud was throwing thousands of tumbleweeds hundred of feet up. Thunder was near-constant, and then the rain turned to snow in high winds. Denver only got a couple inches of actual snow, but there was some sig. wind damage b/c it was late enough in May that the trees were in full leaf.

 

[Marc Grant]

We got thundersnow here the beginning of the week. Local stations and SPC were predicting a quarter inch here in Kansas City with heavier snow to the east around Columbia, Missouri. We got between 6" and 8" here in Kansas CIty of very heavy, wet snow with power outages and tree damage.

 

[Glenn Rivers]

Thundersnow wind directions

I would like to know what direction the winds were from during the convectve snowstorm in IL and MO. When I looked at that storm it apeared to have a wind max well below 850 mb where E-NE winds were aligned oposite to the strong W-SW shear in the baroclinic zone N of the warm front and sfc low center. Was it this part of the storm that produced the wind damage?

 

[Andrew Pritchard]

Re: Thundersnow wind directions

Originally posted by Glenn Rivers
I would like to know what direction the winds were from during the convectve snowstorm in IL and MO. When I looked at that storm it apeared to have a wind max well below 850 mb where E-NE winds were aligned oposite to the strong W-SW shear in the baroclinic zone N of the warm front and sfc low center. Was it this part of the storm that produced the wind damage?

Winds that I witness varied...but were generally from the NE.

 

[Glenn Rivers]

Gravity waves in Nov 24 storm, Previous doc'd example

Joel Wright mentioned a gravity wave event in the Nov 24 Midwest storm.

If I can recall, there was a detailed study of gravity waves in a powerful Midwest storm that included numerous episodes of thundersnow on Dec 15,1987 (in the Monthly Weather Review). That storm was more wound up then the recent storm, had a well defined comma head, much lower surface pressure, and it's track was further N, with a direction more towards the NNE rather than the ENE-NE like the recent storm.

I believe that I read about 2 or 3 gravity waves in that storm, occuring in the prefrontal area N of the Warm front were surface obs were strong E winds, heavy snow, ice pellets and freezing rain. In this area of that storm strong warm advection was occuring at the 850 mb surface. I think that the gravity waves had an amplitude of >2 mb at the surface.

 

[Saul Trabal]

Seriously-how rare is it for thundersnow to have frequent lightning?

I've seen thundersnow a few times, However, the Super Storm of "96" generated thundersnow with frequent lightning. Then again, this storm was probably the type that only happens every 100-200 years.

I would categorize it as severe thundersnow. I've never seen thundersnow this powerful, ever.

:shock: