Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Apr 18 2023 17:31:24 ACUS02 KWNS 181731 SWODY2 SPC AC 181729 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1229 PM CDT Tue Apr 18 2023 Valid 191200Z - 201200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF WESTERN OKLAHOMA AND INTO CENTRAL KANSAS AND INTO CENTRAL IOWA... ....SUMMARY... Severe thunderstorms with the potential for giant hail, a risk for a couple of tornadoes, and severe gusts will be possible late Wednesday afternoon into Wednesday night across parts of the central states. ....Central Great Plains into the mid-upper MS Valley... A stationary mid-level low over western ND and associated larger-scale trough over the Interior West, will result in a belt of strengthening southwesterly mid- to high-level flow across the central-southern Great Plains into parts of the Corn Belt. A surface low initially over ND will occlude and weaken while another surface low develops over the KS during the day. A frontal zone will extend from the northern low southward to near the IA/NE border and to the low over KS. A dryline will extend southward from central KS through western OK and west-central TX. Southerly low-level flow will advect moisture northward from the TX/OK into KS and eastern NE with surface dewpoints forecast to reach the upper 50s to near 60 deg F over western IA to the lower-mid 60s over central KS/western OK. Strong diurnal heating is forecast over the Great Plains in the warm sector ahead of a 70-kt 500-mb speed max forecast to move into KS during the overnight. Of particular note, a low-level thermal ridge is forecast to extend from the TX Panhandle northeastward into central KS abutting the dryline near the I-135 corridor. It is on the northeast periphery of the steep 0-3-km lapse rates and beneath the left exit region of the upper jet that convective initiation is most probable during the late afternoon/early evening. Forecast soundings show a moderate to very unstable boundary layer (MLCAPE ranging from 2000 J/kg near the IA/NE border to 3000 J/kg near the dryline). As the cap weakens by mid-late afternoon, widely spaced CI attempts will likely become evident. It seems plausible isolated storms will eventually develop near/northeast of the triple point with the potential for rapid supercell development. Forecast hodographs enlarge in the lowest 2-km AGL layer during the 22z-01z period, and in addition to risk for very large hail, a tornado threat may also develop. Storm coverage is expected to increase during the evening as the LLJ intensifies and into the overnight and perhaps preferentially develop along the front while growing upscale and moving east into the lower MO Valley late. A lingering hail/wind risk will probably accompany this activity. Farther south along the dryline over south-central KS to near the Red River, the leading edge of strong, westerly 80-90 kt 200-mb flow will overspread the warm sector by late afternoon, thereby elongating the hodograph. Very strong heating may lead to local erosion of the cap with one or a few updrafts becoming sustained and quickly evolving to a discrete supercell mode. A conditionally very favorable environment over OK for a giant-hail risk (diameters 3+ inches) may develop with any supercell. As this activity matures during the early evening, increasing CINH with east extent and with the onset of diurnal cooling will combine to limit the tornado risk before CINH eventually overwhelms lingering updrafts and coincides to a dissipation of the storm activity by mid evening. ....TX dryline... Model guidance currently indicates a paucity of convective potential along the dryline over parts of northwest TX southward to the Edwards Plateau. A conditionally very unstable boundary layer and deep-layer shear will support supercell potential. Any storm that manages to develop will likely pose a large-hail threat for at least an hour or two before this risk diminishes by mid evening. ...Smith.. 04/18/2023 $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .