07/18/07 NOW: MT/WY/SD/NE/MN/IA/MO/WI/IL/MI/IN/OH/KY

[MatthewCarman]

MOD risk for severe storms from NE/SD east through IA into IL and IN. Looks like a hail event that will turn into a damaging wind event. Several people are saying this has the potential for a derecho later on. Severe storms ongoing in se SD and a watch is expected soon for all of northern IA. Another watch could be issued in WI soon. The potential for tornadoes appears low but SPC does have a 2% chance for part of SD/NE and nw IA.

Things are getting active. Who is chasing? Thoughts?

 

[Derrick Herndon]

I really wanted to go out today given the forecast the next 1-2 weeks but I am having a hard time getting excited about this setup. RUC forecasts are indicating quite a bit of the dry air just above the sfc indicated in this am's soundings will advect northeast into the southern portion of the MDT risk area. The lack of good surface convergence is also a limiting factor. Sitting in OMA at the moment.

 

[Andrew Pritchard]

MOD risk for severe storms from NE/SD east through IA into IL and IN. Looks like a hail event that will turn into a damaging wind event. Several people are saying this has the potential for a derecho later on. Severe storms ongoing in se SD and a watch is expected soon for all of northern IA. Another watch could be issued in WI soon. The potential for tornadoes appears low but SPC does have a 2% chance for part of SD/NE and nw IA.

Things are getting active. Who is chasing? Thoughts?

Haha, we do all have access to and are aware of what the SPC is saying... so not to be rude, but that should generally be left out of a NOW thread.

Complex forecast indeed for today, which has talked me out of leaving this area. Extreme instability is already building into most of Iowa where the cap is still stout, but slowly eroding at this moment. Air mass is very worked over further to the east into northern Illinois at this time, so I don't think we'll see much severe development in this area for a good part of the day, though some isolated storms are possible along the boundary left by morning convection.

My guess is severe storms should hold off for a while longer, but then increase in coverage across Iowa, generally near Interstate 80 and then progess/develop eastward into northern Illinois. The cap will likely remain for a little while longer, but of course with such instability, and the low level jet cranking in and increasing surface convergence we should be looking at a decent coverage of severe weather by sunset or shortly after.

 

[Andrew Pritchard]

Looks like we might see that disorganized area of convection might start congealing into a bow echo soon over central Iowa. Have to watch that area as it rides the boundary into eastern Iowa. Might start seeing some wind reports in the next hour or so.

 

[Joel Wright]

The large cluster of storms in northwest IA is continuing to organize as it moves into an even more unstable airmass to its southeast. As the cold pool gets deeper I think we can expect this to become a rather significant wind machine as it moves/propagates across IA.

The cells to the north along the synoptic boundary in central WI look pretty interesting too. I don't think the tornadic threat is quite so high up there, but if they stay discrete for any length of time a few of them could produce.

 

[MatthewCarman]

Severe storms continue to move through central and north central IA. A storm near Grundy Center now capable of producing a tornado. Looks like I could get 50+-60+ MPH winds winds within the hour or so. Will let you guys know if I get anything severe.

 

[MatthewCarman]

I saw some very slight rotation after the leading edge of clouds moves through with a area of onominus clouds. Also winds gusted over 50 MPH on the leading edge of storms.

 

[Chad Cowan]

The newly SVR warned storm in Mchenry Co in nc IL is exhibiting some pretty strong rotation. It had a TVS marker briefly and has been trying to take a right turn relative to the line and break away. The environment isn't primed for tornadic activity, but it may spin one up.

 

[MatthewCarman]

Possible tornado now near Iowa City as indicated by radar. Remember that Iowa city was hit in May of 2006 by a strong tornado. Another tornado may be north of this one near Cedar Rapids as indicated by radar. Funnel clouds reported in Linn County IA. Also destructive 70+ MPH winds may acompany these tornadoes.

 

[James Hammett]

Several funnel cloud reports east and south of Cedar Rapids, IA. Live TV coverage here:

http://www.kwwl.com/

 

[Dustin Wilcox]

Storms have finally rapidly developed near the SD/NE boarder near Yankton, these should continue to intensify as they work South, would expect a watch very shortly. Parameters remain very stout across the area and I would expect that these storms should remain severe well through the night, it is going to be interesting to watch their evolution and see the interactions that will occurr with the numerous number of boundaries in the area.

 

[Mike Hollingshead]

Severe warned one east of Lake Andes had a very sweet backsheared anvil with mammatus before being obscured by low clouds. I was headed for it, but am stopped with the one at Spencer NE, which is taking on supercell structure visually. Base lowering now. I think it has hope so long as the thing west of it doesn't get going too.

 

[David Draun]

Northern Cook County, IL getting slammed with heavy rain and wind approaching severe levels. I just heard a small tree limb snap outside the window. SVR just expired for the area. GRLevel3 showing several meso markers on the leading edge of the storms, gustnadoes or outflow cirdulations perhaps? The lightning is nearly constant!

No convective deflector operating tonight!

I broke it.

 

[Dustin Wilcox]

Storm moving into Knox CO NE certainly looks interesting at this point, appears to have taken on Supercell characteristics for at least the time being, radar is representing a pretty stout updraft will tops to 57K ft. Mikes storm near Spencer according to radar also appears to be SLOWLY trying to intensify as it appears it may be fighting off convection to the West.

 

[Scott Lincoln]

GRLevel3 showing several meso markers on the leading edge of the storms, gustnadoes or outflow cirdulations perhaps?

No.... the algorithm for meso and tvs detection that puts the icons into GR3 will show all kinds of shear markers along the leading edge of strong storms like this. The sharp wind shift and wind speed gradient is responsible for triggering the mesos in that program. The newer algorithm used in GR2Analyst is much stricter in displaying mesos and TVSs, and you wont see nearly as many along simple convergence boundaries. NEXRAD also cannot resolve gustnadoes, as they are formed at the surface along the outflow. The only place where you should really worry about any mesos being associated with real circulation would be at the apex of any bows that form.