Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jan 16 2023 19:45:26 ACUS01 KWNS 161945 SWODY1 SPC AC 161943 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0143 PM CST Mon Jan 16 2023 Valid 162000Z - 171200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN IA INTO NORTHWEST IL AND OVER THE SOUTHERN GREAT BASIN... ....SUMMARY... A brief tornado or two and marginally severe hail will be possible in a portion of eastern Iowa to northwest Illinois through sunset. Marginally severe hail and wind will also be possible over the southern Great Basin into early evening. ....20z Update... Only minor changes to the 10 percent general thunder line in the Midwest have been made with the 20z Update. A low potential for a low-topped supercell will continue across east-central IA into northwest IL the next 2-3 hours. Current convection is occurring ahead of the axis of modest surface-based instability. However, additional cells may develop within narrow wedge of instability with time. The risk will rapidly diminish beyond 23-00z as boundary-layer cooling ensues. Additional isolated strong storms may produce sporadic hail and strong gusts across parts of the southern Great Basin into this evening. ...Leitman.. 01/16/2023 ..PREV DISCUSSION... /ISSUED 1026 AM CST Mon Jan 16 2023/ ....Eastern IA and northwest IL... Favorable wind profiles for low-topped supercells will be present in the southeast quadrant of a 994-mb surface cyclone tracking from southwest to northeast IA. Surface temperatures have warmed into the mid 50s to low 60s in a confined corridor centered on LWD-CDJ before broadening across central MO, with relatively ample insolation beneath the mid-level dry slot. The 12Z NAM and most HREF members appear much too cool within the thermal axis compared to 16Z observations. The RAP/HRRR-based guidance appear closer to reality but may be a bit too moist given an even narrower corridor of low 50s surface dew points from southwest to north-central MO. But further mixing and poleward moisture advection may be just enough, given the mid-level cold pocket of -22 to -24 C at 500 mb, to support meager MLCAPE approaching 500 J/kg towards mid-afternoon. While it is plausible that convection may fail to adequately intensify this afternoon, observational trends along with HRRR/RRFS guidance suggest the threat for a couple brief tornadoes and marginally severe hail is large enough to warrant low severe probabilities. Convection will subside quickly after sunset as it outpaces the narrow plume of weak surface-based instability. ....Southern Great Basin... A shortwave impulse centered over central CA will move east into the southern Great Basin through this evening. Ascent ahead of this wave appears favorably timed with the diurnal heating cycle to support at least isolated thunderstorm development this afternoon. However, abundant cloud coverage suggests surface warming will be limited. Nevertheless, the presence of surface dew points in the 40s should still yield meager buoyancy with MLCAPE of 250-500 J/kg. Combined with effective shear near 40 kts, the setup could support a couple updrafts with weak mid-level rotation. Marginally severe hail and wind appear to be the primary threats. $$ = = = 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) .