Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Mar 22 2023 13:05:51 ACUS01 KWNS 221254 SWODY1 SPC AC 221252 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0752 AM CDT Wed Mar 22 2023 Valid 221300Z - 231200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM CENTRAL/NORTHERN MISSOURI AND SOUTHERN IOWA EASTWARD TO NORTHERN INDIANA... ....SUMMARY... Isolated strong to severe thunderstorms -- capable of large hail -- are possible from central/northern Missouri and southern Iowa eastward to northern Indiana. ....Synopsis... A broad fetch of zonal (in the East) to southwesterly (over the Rockies) flow is in place ahead of a synoptic trough over the West Coast. That trough contains a low located near SFO, which is expected to devolve to a minor, open-wave vorticity lobe as the broader-scale trough shifts eastward. By 12Z tomorrow, the 500-mb trough should reach parts of UT/CO, southwestward across AZ, northern Baja, and Pacific waters to the southwest. Downstream, a compact northern-stream shortwave trough will eject from its present location over eastern MN/western WI, across Lake Superior to northern ON. This will occur as an upstream perturbation -- evident in moisture-channel imagery from southeastern SK across south- central MT -- moves eastward over northern MN through 00Z, then crosses Lake Superior tonight. At the surface, 11Z analysis showed a primary low over northern MN, associated with the leading northern-stream shortwave trough. A cold front was drawn from there across southwestern IA to near FRI, becoming wavy/quasistationary across south-central/southwestern KS to a weak low between TAD-LHX. The northern low should move to near Thunder Bay, ON, by 00Z, with cold front across eastern WI, northwestern IL, and western MO, becoming quasistationary to warm across central KS, and warm to another low in northeastern CO near ITR. A dryline -- initially drawn intersecting the front in the P28/PTT area across western OK to the MAF area and Big Bend -- will become better-defined today and move slightly eastward, as return flow increases moisture to its east. However, lift along the dryline and nearby frontal segment should be too weak to yield surface-based convection today with a strong cap -- as sampled by 12Z regional RAOBs. Instead, the bulk of convective concern will be downshear in a zone of elevated instability. ....MO/IA/IL/IN... A very conditional, isolated risk of strong/severe thunderstorms may develop in the next few hours, within the existing plume of low- level warm advection and moisture transport across parts of northern MO to western IL. Near-term forecast soundings suggest enough increase in theta-e near 850 mb -- beneath favorable midlevel lapse rates -- to yield around 1000-1500 J/kg MUCAPE, amidst about 35-40 kt effective-shear magnitudes. As the ongoing LLJ weakens through late morning into midday, so should any already low severe potential. A second round of strong-severe convection -- likely better- organized and larger due to greater moisture, shear and lift -- should sweep eastward across the outlook area tonight, offering isolated severe hail. Though much of the area will be located ahead of the surface cold front, the boundary layer will be stable, still under primary influence of relatively low-theta-e trajectories that followed the prior cold frontal passage. Elevated warm advection and moisture transport/advection above that, however, will occur in and near a 50-60-kt southwesterly, nocturnal LLJ. This again will steepen low/middle-level lapse rates, but with deeper/greater buoyancy rooted lower (around 850-900 mb), and MUCAPE around 1000- 1500 J/kg. Stronger upper-level winds and deep shear are expected as well, with effective-shear magnitudes 55-65 kt. Supercells and organized multicellular clusters are possible. Given the potential for clustering of convection and the shallowness of the stable boundary layer (especially over western/southern parts of the outlook area), a few strong gusts are possible as well. However, the severe-wind threat appears too conditional for categorical-level wind probabilities at this time. ...Edwards/Dean.. 03/22/2023 $$ = = = 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) .