3/11/06 FCST: Great Lakes to Western Gulf Coast

[Skip Talbot]

I've been watching this setup for the past few days, and the models continue to indicate strong warm air advection via a low moving through MN. Temperatures forecast to breach 70 with dewpoints approaching 65 acorss central IL into IN. SPC mentioned the cap being an issue, especially on the GFS. However, the nam indicates a relatively little cinh over the main instability axis. Cape is actually forecast to exceed 2000 JKg in eastern IL by 21z with speed shear over 50 knots. Directional shear looks adequate with a nice veering from the surface to 850mb, and 1km SRH values over 150 on the IN border. Saturday could turn out to be a nice chase setup, and a good first run for us midwest chasers.

 

[Tim Gonyo]

I'm really liking Saturday around the Champaign/Urbana area... going to wait on later model runs in order to fine tune that decision. If Saturday looks good, anyone in the midwest want to chase together? I'm near Milwaukee, WI. Let me know.

 

[Alex Lamers]

Well I have to say I'm a little perplexed. The NAM and GFS give SE WI about -4 to -6 best LI values with a considerable band of moisture convergence passing through peak heating but don't generate ANY convection! They do however generate some convection south of us in NE IL. Now I am considering a chase at the moment but the sprawling Chicago Metro area has me concerned. NAM goes highs 65-70 in far SE WI with dewpoints approaching 60 F...its just so frustrating that they don't have any precipitation.

That being said a few models do show some precip showing up in SE WI. Best shot for us looks to actually be Friday Night with best LI's on the order of -2 to -4 and some warm advection precip spreading across. Liking the possibility of elevated hailers here.

If I could see a reasonable chase target outside of Chicago metro I might consider heading out.

Thoughts on N IL/S WI?

 

[Tony Lyza]

The 0000z NAM concerns me. It predicts 500-1000 J/kg MLCAPE all the way up to my area :shock:, with localized areas of 3000+ J/kg MLCAPE:
http://www.rap.ucar.edu/weather/model/eta4...hr_sfc_cape.gif

Even though it does not depict much, if any, CINH, it does not depict any development...
http://www.rap.ucar.edu/weather/model/eta4...hr_sfc_prcp.gif

The LI's are depicted to be -4 to -6 over a very expansive area:
http://www.rap.ucar.edu/weather/model/eta4...hr_sfc_pwat.gif

There should be good backing of the winds at 700mb and 850mb across IL/IN:
http://www.rap.ucar.edu/weather/model/eta4...8hr_700_wnd.gif
http://www.rap.ucar.edu/weather/model/eta4...8hr_850_wnd.gif

There will be a strong system at the 500mb level (up to about 110kt):
http://www.rap.ucar.edu/weather/model/eta4...8hr_500_wnd.gif

A very intense jet stream disturbance of up to 150kt will be entering the area:
http://www.rap.ucar.edu/weather/model/eta4...8hr_250_wnd.gif

This may seem like a bit of wishcasting, but I really think that Saturday could get quite rough across many of the areas hit hard today (3/9), only a bit farther north. I think any tornado threat should be maximized over a good portion of Illinois and Indiana due to the good backing of the 850mb and 700mb winds. Now, we wait and see...[/url]

BTW Alex, if I were planning a chase based on this model run, I would go to north central or east central Illinois or western Indiana. Just stay away from Chicago and stay out of the Illinois River Valley (try to cross on really major routes ala I-39). Then again, I wouldn't plan anything for final until tomorrow night.

 

[Skip Talbot]

Well, I spent some time on the 0z run. There look like two areas of potential initation. One is the cold front draping southwest through MO, off the surface low in Iowa/MN. That cold front is going to push through into IL later in the evening. If that is the only show in town, I think our chase chances are shot. With the extreme amount of shear, a nasty squall is inevitable and it will be booking.

The second area, and the one that I'm rooting for is the sector behind the warm front extending east southeast across central IL. There is a big hole in the CINH over the instability axis at 18z over central IL, and thus I think this would be a good starting point. However, vertical velocities are silent in the vicinity, only popping up on the cold front later that evening. The 2000+ cape bullseye is still stuck on Champaign at 21z. With the speed shear around 60 knots, we'll need a source of lift (the warm front?) and we are set.

Right now I'm eyeballing an area from Peoria to Lincoln around noon, and I'll move east with the instability until the storms fire, which should be in the early afternoon. I think its important to stay on the nose of that jet. If the warm sector doesn't pan out though I think the day is going to bust with a nighttime squall. I hope SPC is right about scattered to isolated storms developing across IL in the afternoon.

 

[J West]

WI is out of play at this point, unless something drastic happens in the next 24 hrs. That's ok by me, since chasing around here with trees and traffic is nerve-racking at best.

IMHO, the I-39 cooridor from the Rockford metro area south will be in play and I think Skip is on track with Central IL. If past history means anything, I think you guys could camp out in the Lincoln NWS parking lot and let the storms come to you then move east with them. It appears that region of IL is it's own little convective hotspot.

I'll be in DuPage county all day, but if something pops to the SW of there I might head down and play it. Any storms that form will be hauling butt so without an ISP escort, I'm guessing we will have to pick and choose carefully. I'd think that Tony will either get some discrete cells forming around 1400 local time, or he'll get stuck with the convective trash that formed into a squall line around sundown.

 

[Karen Politte]

I think that, after almost going out and chasing the last system across OK but deciding against it at the last minute......I'd lean more towards sticking someplace with the best shot at some decent, deep moisture.

ATTM, this looks like AR, with the GFS advertising 65+ Tds by 0Z Sun. With that, it is not unreasonable to expect CAPE values exceeding 2000 somewhere. Paint that over a 50+kt deep layer shear value somewhere, and you've already got my ears pricked up. SPC also seem to agree, with another early-March-looking, horrendous 30% hatched area for severe probability blanketing the Arklatex and the whole of AR.

Maybe a lucky chase over the Bootheel/northeastern AR will be in order? Starting point Jonesboro, AR? Not bad chase country I understand.

That's my pigeon-hole-cast. Maybe more later. Good luck to anybody who gets the machettes out and chases.

K.

>>[insert witticism about the forecast date being my birthday here/]<<

:wink:

 

[Matthew Havin]

Resonding to Karen:

NE Arkansas is not a bad place to chase. A historical tornado maxima lies NE of Little Rock to the bootheel of Missouri and east of Batesville-Greers Ferry Lake. Roads are flat, outside of Crowley's Ridge, and extremely flat when east of the ridge in the Delta Valley farmlands. For spotting, a mixture of trees and fields covering up to a few hundred acres where you can find a good peek at storms. Avoid anything south of I-40. Jonesboro has a wi-fi hotspot at the Super 8 in town.

 

[Skip Talbot]

Yes, the thread title should be reflected to change the new target areas running from AR to TX.

As for IL, the 12z run still looks quite promising with 3000 JKg plotted west of Springfield at 21z and a 100 knot midlevel jet edging in. Right now I'm eyeballing an area from Springfield to St. Louis, right along the best instability and where the jet will catch up with it that afternoon. CINH looks weak so I'll be out there early.

 

[Jim Bishop]

I was skeptical at first but now that the GFS breaks out convection along the dryline in East Texas I do believe this is going to be a chase opportunity. Simon and I may just end up packing up our Stormgasm booth early at the TESSA convention. But the cap is going to be strong, but hopefully the dryline and large scale ascent associated with a curved upper jet streak will be enough to break it. We shall see.

 

[Scott Olson]

Perhaps im being to biased to not wanting to drive 600 miles to IL or MO, but as of right now im planning a chase to eastern Iowa. GFS/NAM show the low in MN as rather weak but GEM Ensemble/RUC/UKMET show potiental for a much stronger low pressure system (SD/MN). Both NAM & NMM-WRF show show a 999mb low in C IA around 21z with another low in MN. Both also show convection breaking out around 21z about 60 miles E of Des Moines. NAM shows 300 j/kg 0-3km CAPE, which im highly skeptical of.

Also, 30-35kts 0-3km shear vector (not much shear above 3km) but not a very favorable orientation of deep shear vector (near parallel to cold front. The idea is the storm moving NE would move to the WF (near TP) and then ride along the boundary providing plenty of 0-1km SRH for tornadic possibility. Honestly, a long shot and central/south IL looks much better. If I actually followed through with this, storm motion which starts releatively reasonable 25-30kts gets a little fast 40kts. Im real skeptical of 60 degree dewpoints pushing into E IA tommorow. If distance wasn't a factor I would be in S IL or SE MO.

-Scott Olson

 

[Scott Lincoln]

Definitely a window of favorable parameters in eastern Iowa, not so much for tornadoes, but severe in general. I was surprised to see my BUFKIT lit up with numbers!

Problem is that window ends right around early afternoon. Something to watch, but its kinda a long shot.

 

[Gabe Garfield]

Based on the 12Z Eta, there are two places that I believe hold real promise for tornadic supercells tomorrow. First, the warm front could be a significant player if instability can develop along and slightly north of the front. Places that will be primed in this first area include the MN/IA/WI border region southeast to C/N IL to S/C IN. Tremendous shear will exist (as usual) on the north side of this boundary. Should storms form and be relatively discrete, I would expect at least a few tornadoes.

The second area to be considered will be N AR into S MO. High octane moisture is in place along the Gulf Coast and should advect nicely into this region by 00z tomorrow (according to the Eta). As a result of this and cooling aloft, significant CAPE should develop tomorrow. Though shear is certainly lesser than areas northward, sufficient shear should be in place for supercells. What intrigues me now is the spotty lack of CIN (according to the Eta) along the border region of AR/MO. This suggests to me that several supercells should be able to form in this region. With the high degree of CAPE and the increasing magnitude of the ll shear toward dark, a few strong tornadoes appear possible.

Gabe

 

[Tony Cook]

Simon and I may just end up packing up our Stormgasm booth early at the TESSA convention.

Anyone else planning on going to TESSA, and now having thoughts about chasing instead? I am torn right now.

TonyC

 

[Matthew Havin]

For those thinking of SE MO, NE AR, and S IL, study up on your topo maps, bridge crossing and forest areas. In Missouri, don't even think of crossing west of Highway 67 no matter what the models have (and that is still too hilly). Don't forget where you are in SE MO as well, since there are only a few bridges across the Miss into S IL. Southern Illinois is a boatload of forests, and Arkansas has its good spots as I mentioned earlier. Good luck for those chasing tomorrow, I think just east of STL metro and to the south and east will be prime tomorrow during the late afternoon and early evening.