ZCZC SPCSWOMCD ALL ACUS11 KWNS 122245 SPC MCD 122245 IAZ000-MNZ000-SDZ000-130045- Mesoscale Discussion 0460 NWS Storm Prediction Center Norman OK 0545 PM CDT Tue Apr 12 2022 Areas affected...Parts of southeastern South Dakota...northwestern through central Iowa...and far southern Minnesota Concerning...Tornado Watch 111...113... Valid 122245Z - 130045Z The severe weather threat for Tornado Watch 111, 113 continues. SUMMARY...Sustained strong supercells appear increasingly likely through early evening. Some probably will pose a risk for producing tornadoes, particularly around the Storm Lake and Fort Dodge IA areas by 7-9 PM CDT, where a strong tornado or two is possible. Additional, a severe thunderstorm watch will probably be issued soon to the north of the current watch, where severe hail may become an increasing concern this evening. DISCUSSION...Thunderstorms are now initiating along the warm frontal zone, north through east of a deep surface cyclone slowly migrating east-northeast of the Sioux City area. This is being supported by lift driven by low-level warm advection, and perhaps a subtle mid-level perturbation forecast to migrate north-northeastward across the mid Missouri Valley around Sioux City through early evening. The strongest thunderstorms probably will tend to evolve along the front to the east-southeast of the warm front/dryline intersection, now generally east of the Missouri River, where a narrow tongue of modest boundary-layer moistening wrapping toward the surface low center may be contributing to mixed-layer CAPE as high as 3000 J/kg to the southwest of Fort Dodge. Into the the 00-02Z time frame, southerly 850 mb flow across the narrow warm sector, into and across the warm frontal zone is forecast to strengthen to 50-60+ kt, contributing to very large, clockwise curved low-level hodographs. As this occurs, the warm frontal zone is expected to become the focus for intensifying supercells, including the evolution of strong low-level mesocyclones, potentially capable of producing tornadoes. The warm front is rather sharp, and the air to the north of the front rather cool and stable. However, the front is slowly advancing northward, and model forecast soundings indicate low-level thermodynamic profiles will destabilize across much of northwestern through north central Iowa into early evening. It appears possible that this will become sufficient for tornado development, with highest probabilities for sustained/longer track tornadic supercell development around the Storm Lake/Fort Dodge Iowa vicinities. As storms progress north of the warm frontal zone, into the colder air, stronger cells could continue to pose a risk for severe hail while the tornado threat diminishes. ..Kerr.. 04/12/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...DMX...FSD... LAT...LON 43069668 43609604 42869318 41819404 42209459 42649566 43069668 NNNN