2011-05-10 FCST: IL/MO/IA/MN

[Jim Parsons]

GFS is showing some pretty huge CAPE along the IL, MO border. The CAP seems to be a little weak but might be enough to hold off initiation until later in the afternoon. Directional shear seems to be better middle afternoon than later in the day.

 

[Dean Baron]

Still pretty far out but the GFS has been pretty consistent in keeping shear to a minimum. The placement of he low has been all over the place so it's hard to really say much at this point. We'll see how it pans out over the next couple of days.
MODS: Can we add IA to the title?

 

[Skip Talbot]

I have no confidence in the solutions the GFS is plotting for this day, which changed significantly just last night. Prior to that the models had a cold front pushing through the Midwest on Tuesday. I'm also worried about moisture return given that the GFS is +10 on the dewpoints compared to the NAM out to 84 hours in many places. You'd think by Tuesday we could get some moisture return up into the Midwest, however.

At face value I see an undersheared setup, no good lift from upper level dynamics, and little focus at the surface initiation other than the warm front. Ample moisture and enhanced directional shear on the warm front for slow moving sups with very large hail, however. That's almost pure speculation at this point though as I'm still uncertain as to what we're working with on the 8th in terms of capping and lift, let alone on the 10th.

 

[Dan Rupnow]

May want to add MN to this thread, as this date is now in range of the NAM, and certainly looks interesting for the southern half of MN. 12Z NAM showing a surface low over SW MN at 00Z with an attendant WF extending east across S MN into SW WI, as well as a dryline extending to the south into W IA. Forecast highs around 85F, along with copius boundary layer moisture in the form of >70F surface dews yield impressive CAPE values of at least 4,000 J/Kg. NAM also erodes a nice hole in the cap over SC MN as H7 temps cool into the afternoon. Possible fly in the ointment could be that the best upper lvl dynamics still lag a bit to the west, but that could change in later model runs. Attm, am thinking the triple point area would provide the best source of lift for storm initiation, however, we are still a few days out so things can and will change.

 

[Jim Parsons]

Southern MN is showing some much better shear than down south around the IL, MO, IA borders....NAM is showing some nice CAPE & EHI and a slightly better moisture return than the GFS is showing. Still a few days out, things can change....

 

[Skip Talbot]

much better shear than down south around the IL, MO, IA borders

The solutions plotted by the NAM and GFS for Tuesday have shifted such that I wouldn't even consider the MO/IL/IA corner to be in play anymore. Neither model is plotting any significant source of lift as the trough is well to the midwest, its hundreds of miles from any front, and I don't see any early/overnight convection laying down outflow boundaries in the area either. The area looks like it will be largely capped as well.

The 12z NAM paints such a pretty picture over southern MN that I don't think I'd even consider chasing the southern plains dryline that I think most people were eying for Tuesday. With a warm front/dryline triple point, extreme instability in the warm sector, and great directional shear on the warm front, any storm that fires off the forecast dryline bulge in southern MN and interacts with that warm front could be a tornado machine. The 12z GFS isn't too far off with its solution, keeping the surface features not as tightly defined as the NAM, but still a very impressive setup across southern MN maybe into northern IA.

 

[Jim Parsons]

Thanks for the input Skip...I gave up on the IL, IA, MO play as soon as I checked out the new model runs today and the MN, IA play is looking very nice. Another plus with the northern target is that the storm motion is looking fairly decent...No chasing after storms that are moving 50+kts.

 

[Andy Wade]

Clearly MN is the place to be Tuesday--unless you're in finals week at OU! (Oh, and gas prices, but that's another thread...) The Day 2 slight risk and the Mon. 00Z GFS run are making me think about a short trip to SW OK, maybe the Lawton area. GFS hints the cap might break in places along the dryline near or just N of the I-44 corridor. Forecast hodos in the evening are fairly good-sized with a weird figure-8 shape at mid to upper levels--enough shear for supercells (40-50 kt) but probably not a real tornado threat (even though SPC suggests isolated tornadoes). LCLs along/E of the dryline are < 1000 m. NAM, on the other hand, wants to mix the dryline east beyond I-35 by evening.

 

[Jim Parsons]

The southern MN, northern IA area is still looking pretty nice for tomorrow....The 18z & 0z GFS is showing a nice dryline bulge pushing up into MN. MLCAPE is showing almost 5000 and a CAP(according to the GFS) that looks like it should break sometime late afternoon. My concern is that the NAM seems to be showing some weakening in the shear in the later part of the day as well as a poss unbreakable CAP....Any thoughts????

 

[Jeff Duda]

Although the 12Z NAM this morning has looked better for the area than it had in previous runs, it still looks like you're going to have a real tough time getting sufficient deep-layer shear for supercells. Not to mention, the target has shifted northeast such that it is now over the Mississippi River valley, not great for chasing terrain.

 

[Justin Turcotte]

Better shear with lower instability in eastern ND/northwest MN. Very unstable with less shear along with stronger cap in southern MN. There could be a happy middle between the two but I'll take the better sheared environment closer to the low in eastern ND/northwest MN given that's where I'm at and will be working the day shift. Even here there is not much turning with height above H85. A storm is going to need to really hug the boundary to provide chaseworthy material. GFS and GEM look quite similar with warm front lifting through MN and dryline-warm front occlusion of sorts in northeast ND. Both models offer decent moisture convergence along the front. The NAM is suppressed to the south and discounted (for now). Main concern is potential for a lot of low cloud ahead of the warm front but I have lived in the area enough to know all it takes is a couple hours of solar to get things popping. I've seen far superior set-ups in eastern ND but this is the first one of the year.

 

[Jim Parsons]

The more I look at the models, the more I am concerned over the lack of shear and the capping in s/e MN. The high CAPE and moisture(and that I have the day off) wants to lure me into what would turn out to be nothing more than a big rain producing MCS...I'll wait and see what changes with the next model runs.

 

[Skip Talbot]

NAM has been consistently plotting a big hole in the cap for the past several runs as evident by the LSI's:
http://68.226.77.253/models/eta/central/CENTRAL_ETA212_ATMOS_LSI_36HR.gif

The lack of upper level support, lift, and shear does have me a little nervous. Still 30+ knots of effective shear in areas should be enough to support some supercells:
http://68.226.77.253/models/eta/central/CENTRAL_ETA212_ATMOS_ESHR_36HR.gif

Perhaps if we get some deviant motions along that warm front, the storms will be moving against the mean flow and making their own shear. What has me most worried is just getting initiation though. The precip plots are quiet on the NAM and 4km WRF. I'll probably be trying to play the far western fringes of the instability/moisture tongue trying to get as close to that upper level energy over SD/ND as I can. The terrain is going to be better further west too as right now that warm front is being plotted up in bear and lake country.

 

[Bob Conzemius]

Just looked at the 00Z NAM for central Minnesota Valid 0000 UTC/11 May, and the big CAPE is looking rather interesting. Honestly, I'm really unsure about initiation because forcing weakens with time, but models seem to be onto something in central MN moving into northeastern Minnesota or northwestern Wisconsin. Whether this is something that is initially surface-based and manages to tap into the low-level shear along the warm front or simply develops as an elevated mess after dark I do not know, but there is a consistent convective precipitation among the models in that area. It's hard to ignore such huge CAPE when it's within three hours of home (and therefore not a huge risk/investment). I may head south-southwest around noon tomorrow (toward AXN) if it looks like the NAM/WRF forecast is verifying.

-Bob

 

[Kelly Sugden]

Today could be a sleeper day across Kansas. I'm liking what the HRRR/RUC is showing. Something to watch. Cap is large but a slight impulse over western Texas might initiate some storms.