Monday, April 30, 2012

Discussion Concerning Multi-Day Severe Weather Threat (Tuesday-Wednesday)

This is a discussion concerning the multi-day severe weather potential for Tuesday and Wednesday. Further dates will not be included due to a lack of confidence.

Zonal flow of the jet stream aloft will carry several disturbances along its track. One of these disturbances will involve the lifting of a warm front north into the northern US, engulfing the Midwest and Plains in the warm sector of hot temperatures and humid air. As this happens, a cold front will eventually become present in the western portion of the Plains states before moving eastward.

Because this will be a zonal flow jet stream, indicating that the jet stream will be on the Canada/US border, that is where we will find the dynamics of shearing associated with this event. Bulk shearing will take place in Wisconsin, which is a reason for the slight risk included in the entire area of Wisconsin. However, slightly lower temperatures and associated dewpoints will act to level out the severe aspect. Nonetheless, the remains potential for some intense weather in that area.
Farther to the south, in north Illinois and the like, hotter temperatures and higher dewpoints will make for a hot, muggy day. Because dry air requires more heat to rise, expect convection to be fairly quick to get started. This may very well be hampered, however, especially without the aid of the jet stream, which will be displaced to the north. However, temperatures in the 70s-80s may be able to ignite some convection. If this happens, the main threats would include damaging wind and large hail. Tornadoes do not appear to be a concern south of Wisconsin, in north Illinois.

As mentioned previously, dry air requires more heat to rise. This normally would push down convection chances in Wisconsin, but the presence of the jet stream will cover that loss.

In the end, I find it more likely that the Wisconsin/Illinois border and north will get in on some of the strongest convection, while areas like North Illinois and possibly southern Iowa may be slotted out of this event. Time will tell.


ERN WX said...

I will try to put a few thoughts in.

ERN WX said...

... Thoughts... Still thinking a widespread severe outbreak looks possible. Tues. a moderate risk looks likely for parts of the SPC 30% zone. Hail, tornadoes and wind. Threat will virtually move further east every day. Just draw a straight line east and that will be the area affected by possible severe storms. More to come.

ERN WX said...

Day 3 (Wednesday), SPC indicates they may put higher risks in. Andrew, I know you are in that area, and I know you will be right on this whole situation. Stay safe!!! And keep up with the informative posts!!

Anonymous said...

so michigan looks to be largely out of threat wednesday, but should i be worried at all about thursday?

mike paulocsak said...

Ohio is getting HAMMERED right now! Alot of cloud to ground lightning.

Anonymous said...

Andrew, air that's more humid doesn't need higher temps to lift. Humid air is less dense and thus more unstable than dry air, so I don't see how it would be harder to lift humid air than dry air if the air temperature is the same.

Anonymous said...

Andrew, what is zonal flow?

Anonymous said...

April sure didn't want to end without a bang. S-central KS wasn't supposed to get hammered by supercells. Two touchdowns were reported in SW-KS and several in N-central OK. Medford OK has tornado damage. I was on my way home from Andover KS and the 60 kFT tornadic storms were far but close lightning. There were anvil crawlers and AG lightning. The AG lightning was lasting up to 7 seconds per strike at times! A AG struck very close in open field with few crawlers. It was blinding and amazing. I was on pure adrenaline. Anyone in the Day 2 areas WILL see that kind of anvil lightning with any high top cells. I also would expect a Mdt risk. If this is on you Andrew, take photos for us but do it with your ACES! Are you heading out ERN WX? May is inviting you to show what's in store or not. Stay safe everyone!

Andrew said...

ERN WX: Your thoughts are looking pretty good.

Anonymous: Yes. Thursday appears to have more risk in Michigan.

Anonymous #2: Sorry about that- Dry air needs hotter temperatures to lift. This discussion was pretty rushed yesterday.

Anonymous #3: It indicates the jet stream is moving from west to east on the Canada/US border.

ERN WX said...

My friend Anonymous from Kansas. I would certainly like to go out there this month. However, with my work schedule I can't get the 2 weeks off that I would want so I could do some storm chasing. As for my area, I might have some excitement this weekend, and storm chasing is on the list. I am seriously thinking about going into that area next March. I want to experience the cold side of a panhandle hook in that region and the side of severe t-storms all in 1 day!!! Plains blizzards are just so much different than they are along the East Coast. As long as there isn't any kind of problems, I have full intentions to go out to that area next year. A friend of mine has been begging me to go storm chasing in that area too. So, enjoy the weather, stay safe, and take care of yourself!!!!!!

Anonymous said...

ERN WX: I see the jet stream is going to be very high for weeks in the northeast with a big low. The problem I see is the dew points are not there. I remember going through harsh blizzards and nor'easters in NJ. Haven't experienced Plains winter storms yet except brutal <0 degree wind chills. Appalachian blizzards are extreme too but definately not worth chasing haha. I'm still waiting for my Skywarn number from Chance Hayes. I'll probably have to contact him again. I want my number before May has the chance to bring a final big event. I know summer will bring severe weather for you to watch and maybe chase. Take care!