Dec 19, 2004
Lenexa, KS
Well, strong cold front will likely kick off thunderstorms throughout the plains states on Monday. But, where is the main question. Broad range of possibilities still, from central NE through Iowa and into Wisconsin. Current NAM run has the best potential in Wisconsin, but that will be to far for myself. I will be opting Iowa/Nebraska...

NAM runs seemed to be the odd model by the talk of forecasters... But, it has became in tune to the GFS as well over this mornings run. Both indicate the front to be from Lincoln, NE through Fort Dodge, IA and up to the UP of Michigan. Both models are indicating that a large portion of the precip. will be post-frontal along the edge of a large instability axis. This should be a good thing, beings highest shear values as well as SRH/EHI values are just behind the front. Overall precip patterns are largely unique with the models. NAM indicated a line of storms through WI and into northeast IA, another line then in NE and western IA. GFS indicates several seperate potential MCS's from WI, another in northeast Iowa and one along the MO River.

Overall large portion of the plains may see severe weather possible... UP of Michigan/WI/MN/IA/NE all potential chase areas, but the best choice still remains unknown.
This mornings NAM is in and it looks like I may have a good area of storms over central Iowa. Which would be on the western edge of the 25% probability that SPC has issued on their day 2. I believe that I will play out some area around the MO River to central Iowa area... Very rough area that hopefully can be narrowed down come tomorrow morning.

Flow looks decent in the area, although upper level flow could be better. Some directional shear looks to be present... Divergence at 300 has a nice bullseye over northcentral Iowa along the front, 700 temps should be no problem as they range from 9 to 11 C. Instabiltity should be strong with cape values nearing 5000 j/kg. Helicty is primarily behind the front, altough some seems to overlap the front across northereastern Iowa. Td's will be in the mid 70s along with great LI's. LCL heights drop rapidly along the front, with values going well below 500 meters... This helps me tend to believe there will be at least an isolated tornadic risk given some shear. This is backed up by EHI's in the 2-3 range across north central Iowa as well...

GFS run is the favored run though... Waiting for it to come in, but the NAM/GFS have been fairly similar lately.
After looking over the latest data...it looks like the best severe potential will set up shop near the IA/MN border. Shear values and CAPE look pretty favorable for supercells during the afternoon. My bet on any tornadic potential will be over Northern IA where CAPE 4000-5000 J/KG and shear values 50-55 kts should be prevalent. Otherwise this thing looks to be a big damaging wind/hail event after it gets itself going.
The blob of convection on the MN/IA border should push the effective warm front further south into IA. The 06z NAM is running with this. The canopy of crud cloud shield should further limit prospects north of the IA border. All the parameters still look to be in place, albeit further south. West-central IA might be a good place to be during the afternoon... say the Denison area. I suspect SPC will trim back tor threat for MN and enhance it for IA.
Yeah, I see what you mean-that MCS will likely put a damper on things along the IA/MN Border. Looks like the attention now shifts to Central and Western IA depending on where the warm front ends up later. Any outflow boundaries left behind should hopefully help things a long a bit.
12z NAM painting some interesting potential from east-central NE up into north-central IA with a substantial EHI max. If storms can take advantage of the well-backed low-level flow along/north of this boundary things could get interesting later today over this area. At any rate, the set-up seems to have more potential than I earlier thought. I will be closely monitoring the northward progression of the surface wind shift that at 15z appears to lie from southeast NE into southwest IA.
Severe thunderstorm watch box up over N. IL. Looks like some of the outflow boundaries could be the focus for new development as the MCV in Iowa moves in. Right now as of 1600Z, there is one cell over the Quad Cities area and that's about it.

Jarrod Cook
Looks like my backyard for this one, the overnight convection I think will indeed hamper things up here a bit. Although right now we are beginning to rise back up... I should be within an hour or so of any main target for today. Haven't had time to really check anything beings I was out with those storms last night until around 4 am. Right now I was thinking around the Carrol area, or possibly around Ida Grove... We'll see how it plays out in the early afternoon.
Clarion, IA (KCAV) has a pretty good skew-t. It appears the CAP is in place. I'd expect initiation at about 3-4 pm at or west of Clarion. It seems like today things are back building from the east.
Looks like things are already trying to get going in far nw IA se of Sioux Falls aways. Hmmm.
With stuff firing over NW IA, target area will shift a little south and east (armchair chasing, hehe) to clear air just to the south of that newly formed line of garbage. Problem will be upper level support although the low level shear is fairly impressive for this time of the year. If convection can hold off a little longer (good moisture convergence occuring however), I would suspect a sup or two, probably some weak tornadoes.
Line across northwestern Iowa is nothing except some good rain... Hardlly any thunder with it even. Just complicates things up even more, as well as the new stuff northeast of SUX. Best area looks to be on a line from SUX to Storm Lake. cap looks like it is already weakening, so I don't see the storms holding off to much longer. Probably middle afternoon instead of the late afternoon/evening that SPC was stating. I may take off here in an hour or so towards Storm Lake and set up there. Hard to say with all of this crap all around.
MD 1863 just issued talking about isolated tornados being possible over north central Iowa. For some reason, the link is screwed up. You have to squint your eyes and read the small graphic overview that contains all the MD's.

I wish I could go out, but I think I'd be too late if I left now.

EDIT: Finally the link is working, I had to hit refresh on it a couple times. They say the heating is there and CAPE is increasing. Is anyone else on this? I believe their little arrow points to Emmetsburg area. Not for sure though.
I'm sitting in Le Mars, IA where I found WIFI... letting a grungy cell go to my east. 82/77 here... winds are light but are backed to SE from here northward. Neligh profiler shows 500mb wind has increased to 35kts, pointing in this direction. Would help if sfc temps could warm a little under this stubborn mid cloud. May drift north after a bit.
Edward, Yes that lil' arrow seems to point into Palo Alto co, the emmetsburg area. Sigtor on the SPC page puts a bullseye of 2 across northwest Iowa. That will likely be increasing as the mid level winds increase along this afternoon. Looks like I may not have to go to far, I think I'll stay around here for a while instead of heading down towards Storm Lake.
That's probably not the best choice. If something forms, it will likely form along a line from Storm Lake to north of Waterloo at this point.
You wont want to attack these storms from the north, so best shot is to look for WIFI to your south.
First tornado warning is out of Wisconsin?!?! Hrm, I didn't see that one coming. Apparently there's a rotating wall cloud that has been reported with it. I keep hoping for that WW to come out. Just as they said on that area forecast discussion out of NWS DMX, it looks like things are coming together and intensifying...sort of.
Looks like a small discrete cell trying to go up in NC IA, its struggling though, probably with the mid-level junk, but the parameters its sitting in are very favorable for sup and tors. I know Darin Brunin and Dick McGowan are out chasing in the area, trying to get ahold of them at the moment.
First tornado warning is out of Wisconsin?!?! Hrm, I didn't see that one coming. Apparently there's a rotating wall cloud that has been reported with it.

I was on that cell in Walworth County....ragged structure, briefly had a slooooowly rotating wall cloud for about a minute, but dissapated rapidly as the storm fell apart as it moved east across the county (closer to Lake Michigan)

I was on the second cell thru the county again around 1700, and it was even worse looking.
Funny report out of WV...

0625 PM TSTM WND DMG TORNADO 38.33N 81.86W


SPC has it listed as a tornado.



EDIT: Ick, the format didn't stick, basically its a report of wind damage in the town of "tornado, west virginia"
pretty good storms moving through the nw burbs of chicago, i guess there has been damage to the American airlines hangar at ohare (63mph wind)
Very interesting on the ARX radar... If you loop it, you can see the radar echos "pulse down" as the squall line roars overhead. I wonder if the heavy precipitation distrupted the beam?

Interesting - you're right. I thought the line was weakening, but now it looks like it did before. Good observation. I'm sure you're right about the beam. I'm guessing the heavy precip near the antenna attenuated the signals somewhat.

Jarrod Cook