Severe storms and possibly a few tornadoes possible today and tomorrow. Highest risk will be from OK to IL today, then shift a bit eastward Thursday.
Severe storm center just updated statement:
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Wed May 02 2018 Valid 021630Z - 031200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS NORTHWEST OK...SOUTHERN TO NORTHEAST KS...NORTHWEST MO... ...SUMMARY... Severe thunderstorms are expected across parts of the southern and central Plains into the middle Mississippi Valley this afternoon into tonight. Swaths of damaging winds, large to very large hail, and several tornadoes are anticipated, especially from western/central Oklahoma across southern to eastern KS and northern to central MO. ...Synopsis... A complex overall forecast with significant severe potential for all hazards evident across a large swath of the central/southern Great Plains this afternoon and evening. As such, have expanded Enhanced and Moderate risks with this update. ...KS/MO... The surface front is stalling from southwest KS to southern IA. A lead mid-upper speed max will eject northeast from NM/far west TX to central KS by this evening. This speed max will interact with the front and warm sector starting by early afternoon in southwest KS, where convective initiation is expected. Surface dewpoints in the mid to upper 60s, beneath mid-level lapse rates in excess of 8 C/km, will combine with daytime heating to support MLCAPE of 2500-3500 J/kg along and south of the stalled front. Effective bulk shear around 50 kt will be sufficient for supercells, though low-level shear/hodograph curvature will not be particularly large for most of the afternoon. The expectation is for initial supercells with very large hail to grow upscale into clusters and potentially bowing segments through the afternoon and evening while surging northeast along the front, with an increasing threat for widespread damaging winds by late afternoon, persisting into the evening across MO. The tornado threat is uncertain given the expected messy convective modes and relatively weak low-level shear through most of the afternoon. However, towards 00Z, increasing low-level shear in conjunction with the strongly unstable air mass may support semi-discrete tornadic supercells just ahead of/southeast of the emerging clusters/bows, where a couple strong tornadoes are possible. ...Western/central OK... A strongly unstable warm sector is expected into western OK this afternoon, with upper 60s surface dew points beneath very steep mid-level lapse rates. The dryline will mix east of the thicker high cloud band in west TX as surface temperatures warm into the mid 90s. Convergence along the dryline should strengthen beneath the mid-level speed max ejecting towards KS. This scenario should support discrete supercell development at least as far south as the Red River near the southwest OK/northwest TX border. MLCAPE of 3000-4000 J/kg and 50-60 kt effective shear will support at least very large hail. Forecast wind profiles will have some weakness near 700 mb this afternoon, though low-level shear will increase and become more favorable for tornadic supercells in the evening. The main uncertainty is whether discrete storm mode will persist into this time frame with most CAMs suggesting it will not. While this volatile setup has some potential to yield long-track supercells with a few strong tornadoes, will only expand but not upgrade probabilities with this outlook. ...West to central and north TX... Guidance appears to be trending faster with convection forming near the Permian Basin this evening along the retreating portion of the dryline. Very large hail will be the main initial threat with these storms given a highly favorable CAPE/shear combination. Upscale growth into clusters with both severe wind gusts and large hail will be possible tonight, with this activity eventually weakening overnight. ...Southern IA to northern/central IL... Clusters of strong to severe storms will probably develop this afternoon along the stalling to slow-moving cold front. While the overall intensity/coverage is not anticipated to be as large as farther southwest, all hazards appear possible with clusters/bows and a few embedded supercells. The late evening/overnight portion of the MO MCS may also affect parts of central IL with a wind threat as well.