Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Mar 13 2024 12:57:35 ACUS01 KWNS 131257 SWODY1 SPC AC 131256 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0756 AM CDT Wed Mar 13 2024 Valid 131300Z - 141200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF NORTHEASTERN KANSAS AND NORTHWESTERN MISSOURI... ....SUMMARY... Large to very large hail, severe thunderstorm gusts and a few tornadoes are expected this afternoon into evening across parts of the central Plains and lower Missouri Valley. Isolated severe storms may occur late this afternoon across parts of the southern Plains. ....Synopsis... The mid/upper-level synoptic pattern will amplify through the period and into day 2, as a shortwave trough now over the interior Northwest digs mostly southward and strengthens. The main vorticity max, then over the Great Basin, and the associated/developing closed 500-mb circulation, will make their closest approach to the outlook area during the afternoon into early evening. Meanwhile, smaller perturbations -- evident in moisture-channel imagery over southwestern and eastern CO -- will move northeastward toward positions over northern NE and western KS by 00Z. This will occur in a regime of broadly difluent flow aloft, leftward of the 500-300-mb jet maxima. By 12Z, the 500-mb low that will anchor a multi-day, cutoff Southwestern cyclone should be located near LAS. A series of vorticity lobes/maxima will extend from the southeastern quadrant of the cyclone, over AZ, northeastward across the central Plains to near southern Lake Michigan. At the surface, 11Z analysis showed weak lows near MCI and between SPD-LBL, connected by a quasistationary frontal zone that arched across southeastern KS and northwestern OK. The western low should deepen and migrate eastward then northeastward across western/ central KS into this evening, prompting the boundary to move northward across central/eastern KS and central/northern MO as a warm front. A dryline -- initially analyzed from a frontal intersection over northern OK to west-central TX then southward into Coahuila -- should mix eastward today. The dryline should arch from central to southeastern KS, northeastern to south-central OK, and north-central TX into the Edwards Plateau by late afternoon, before retreating westward. ....Central Plains/Lower MO Valley... Isolated to scattered thunderstorms are expected to develop this afternoon, in an arc extending from near the western KS low eastward to east-northeastward over northern KS, then east-southeastward across central/eastern MO and perhaps south-central IL. Supercells with all severe hazards are possible, including at least a few tornadoes and significant (2+ inch) hail. The greatest concentration of severe threat appears to be in northeastern KS and northwestern MO, in and near the "enhanced" area. Activity should develop preferentially along/near the frontal zone and shift northward to northeastward only a little faster than the boundary, thereby remaining in a narrow sector of favorable buoyancy, low-level shear and boundary-layer vorticity for some time before moving into cooler air and weakening. Nearby parts of the dryline also might form a storm or two. In the frontal corridor near I-70 in northern KS to northwestern MO, modified model soundings depict strong veering of flow with height (contributing to locally favorable hodographs and SRH), steep midlevel lapse rates, and adequate low-level moisture, with dewpoints commonly reaching the low/mid 50s F. MLCAPE should range from around 500-1000 J/kg over a very narrow, northward-moving sliver of west-central/ north-central KS to a broader area of 1500-2500 J/kg developing to between MHK-COU, then weaker (but still sufficient for strong-severe storms) eastward into IL. Deep shear should be favorable in I-70 corridor as well, though it will be maximized farther south ahead of the dryline where initiation is more uncertain. Many models (including most HREF members) have been depicting earliest convection initiation near or after 00Z, which seems somewhat late given: 1. Their known biases (e.g., excess RAP/HRRR mixing/drying, too-cool NAM surface conditions, poor resolution of very narrow warm sectors, etc.), 2. The overall pattern and history of similar scenarios, with sufficient frontal convergence/lift for convection typically earlier in the afternoon and closer to the low, and 3. Expected diurnal destabilization (from both warm advection and surface heating) around the dryline, frontal zone and leading edge of the dry slot aloft. Notably, experimental MPAS members are sooner to initiate and farther south, more in line with conceptual models. During late afternoon and early evening, a window of tornado opportunity may be maximized with discrete cells in LLJ-enlarged hodographs, before the near-surface layer nocturnally stabilizes too much. Coverage is expected to increase for a few hours after 00Z, maximizing hail/wind threat density, though at least isolated severe potential may persist into the following morning over eastern parts of the outlook area. ....Southern Plains... Isolated thunderstorm(s) may form late this afternoon along a roughly 300-nm long segment of the dryline over portions of south-central/southeastern KS, into east-central OK and adjoining parts of north TX. While development and maintenance of any cells forming in this regime is in question due to EML-related capping, any sustained storms can become supercells with all hazards possible -- including very large hail. Except for the strong CINH, the parameter space will be favorable, with stronger surface heating, greater low-level moisture (dewpoints mid 50s to low 60s F) and faster mid/upper winds (contributing to 50-60 kt effective-shear magnitudes) than farther north. However, uncertainty is too great to focus larger unconditional probabilities on any particular part of this corridor. ...Edwards/Dean.. 03/13/2024 $$ = = = 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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .