2012-05-24 FCST: OK/KS/MO/IA/IL/MN/WI/MI

[Jason Persoff]

I'm not seeing any chatter on tomorrow, and in particular, not in the locations that the GFS suggest to me. While the SWODY2 highlights a See Text over KS, my eye is much more focused farther south into OK.

The right entrance region of a potent H5 jet streak will move over OK by 00z. A dry punch appears to form over the TX PH into W OK during that time frame. The cap is potent as you move south with temperatures exceeding 10-15 degrees over much of OK. With the dry punch serving as a focusing mechanism, storms that do form should be able to be sustained courtesy of the upper levels. Unfortunately, CAPE will be in short supply, but rotational and speed shear are both in place.

Lacking the accustom familiarity of the COD site for finer scale details, I'm left hoping that sfc obs and SAT in am will help distinguish a defined spot. OFBs from tonight will likely serve to locally enhance convection.

Preliminary target will be nonspecifically in NW OK possibly into SW KS.

 

[Dan Robinson]

Boom or bust day in all of the potential target areas. Wisconsin boasts the best hodographs, but suffers from the least amount of CAPE. Kansas and Oklahoma suffer from the nearly unbreakable cap. I like the compromise between cap, instability, low-level wind profiles and upper support in eastern Iowa down through northern/central Missouri. There's a good chance storms will struggle with capping issues and a narrow instability axis, but if storms can mature they will do so in a favorable kinematic environment for supercells. My preliminary target is Keokuk, Iowa by mid-afternoon, but I will be watching for storms that can get going farther south as they will be moving slower and have a wider instability axis to traverse. The Mississippi River will likely be a huge factor in chase logistics, as crossings are few.

 

[CGardner]

As it stands now, I'm with Dan on the compromise area. I'm in the Quad, and the winds are screaming out of the SE. Checking the SREF, I calculated that the hodographs look best in NE IA and S Wis, and the SRH, shear also look good in those areas too later on. If the convection can stay north of those areas and here, then the CAPE will build. As with moisture, still questionable, but the strengthening high pressure system off the Mississippi coast and the deepening low trough will help direct winds and Gulf moisture up this way. As with the time, mmm, yeah I'm probably going to head up to Dubuque and Prarie Du Chien here in a couple of hours. Overall, I think it will be a decent day, just have to check how much moisture has advected up this way.

 

[Jesse Risley]

On the northern end of the synoptic system, it appears that a pretty stalwart mid-level jet core will take aim on the western Great Lakes region later today as the trough continues gyrating across the southern Prairie Provinces of Canada (SK and MB). A potent H5 jet core of 80+ kts should approach the Superior Upland region after 20z, with a mature 992 mb surface low orienting itself proximal to far western Lake Superior by 00z. A stationary frontal boundary that presently lies from just east of MSP to near OAX appears to be the focal point for some ongoing morning convection as it is co-located with some forcing for ascent at 500 mb.

As already noted, the one proverbial fly in the ointment for this region today (E MN/W WI/W UP MI) may be the rather torpid moisture profiles, yielding a narrower instability axis across the region, though lapse rates are not progged to be abysmal. However, SFC-500 mb bulk shear values of 70-80kts will enter the region late this afternoon as the best upper-level dynamics nose into the region, coupled with a fairly strong surface low and H85 winds at 50+ kts, which is not to be ignored.

Given the strong forcing and mostly unidirectional shear profiles being depicted on the vast lot of forecast Skew-t/Log-P diagrams for late afternoon and early evening, as the strong forcing molests any residual EML across the region, damaging winds will likely be the main threat via more linear-based storm modes. It appears as if T/Td depressions are progged to slightly decrease with height (i.e., slightly higher RH aloft versus drier RH in the lowest levels) on some of the aforementioned sounding forecasts, fomenting negatively bouyant air parcels aloft.

Nevertheless, the strong shear profiles and backed winds relative to the surface forcing and INVO of the surface cyclogenesis are not to be ignored, as this suggests that, given at least marginally favorable instability profiles, there MAY at least be a somehwhat heightened risk for tornadoes (perhaps one or two of which could be strong) as ample horizontal (streamwise) vorticity will likely exist in the PBL with favorable 0-1 km shear profiles. I'd expect this threat to be exacerbated if storm modes remain more discrete for an extended length of time, though there is some dubiety about that given the strong frontal forcing - of note is the strength of surface winds and the rather magnanimous H85 (progged) shear profiles.

Further south, instability does look to be better across MO, later extending in WC and NC IL, and the models seem to be picking up on a pre-frontal trough axis initially igniting convection INVO the Mississippi River by later afternoon, with the main forcing generating a broken line of linear-based storms across E IA and N MO by 00z. Initially, storm initiation along the pre-frontal wind shift may be something to watch with greater scrutiny, as the instability will be generous across the region, though lack of better helical flow relative to storm motion suggests that, again, damaging winds are probably the cardinal threat across MO/IL and probably far S WI.