Area forecast discussion...updated aviation National Weather Service St Louis MO 629 am CDT Tuesday may 21 2013 Short term...(through tonight) issued at 348 am CDT Tuesday may 21 2013 Focus through this period will be thunderstorms and rain chances. Surface analysis at 07z depicts the effective surface bndy across western Iowa into northwestern MO...then extending southwestward into eastern Kansas. Believe this is some sort of pre-frontal trough/dry line as it appears the actual surface fnt is still across eastern Nebraska into western Kansas. This trough/dry line should move eastward rather slowly today. A number of questions remain about today given the spread among model solutions. Expect ongoing precipitation to gradually move eastward out of the County Warning Area later this morning. Believe isod to scattered thunderstorms and rain will develop this afternoon along the trough/dry line. Setup today does not appear as favorable for severe weather today compared to yesterday. However...believe the GFS/NAM are underplaying the event today and tonight for the County Warning Area. Models forecast convection over arklatex region this afternoon/evening lifting northeastward tonight into the County Warning Area. This thunderstorms and rain will be driven by a vorticity maximum currently over northern nm/southern Colorado region. Models to some degree...except for the NAM...develop a surface wave along the surface trough tonight. This low should travel northeastward along the surface trough. The European model (ecmwf)/local WRF have a more northwestern solution and this seems reasonable as these models have a fairly good handle currently on the strength of this system. If this solution verifies...this low will provide enhanced shear as well as allow steeper lapse rates to advect into the area. Given forecasted hodographs and timing...believe thunderstorms and rain will be linear by the time they enter the County Warning Area. If this northern solution is correct...the day shift may need to consider a Flash Flood Watch for eastern portions of the County Warning Area. As for temperatures...trended at or above warmest MOS for today and cooler for tonight as the actual cold front finally moves through the area. Tilly Long term...(wednesday through monday) issued at 440 am CDT Tuesday may 21 2013 Focus starts to shift to temperatures as precipitation finally moves east of the area. With focus on today and tonight...only minor changes were made to the previous forecast as much of it still appears to be on track. Models are in remarkably good agreement through the period with respect to mass fields. Uncertainty remains for temperatures on Wed/thurs. Models suggest temperatures will struggle to reach 70s. However...given that it is may...if any sun manages to make it through the clouds...would be surprised if temperatures did not at least briefly reach upper 70s or into the lower 80s. With upper ridge building into the area on Sat and beyond...temperature forecast becomes more questionable with differing solutions at the surface. For now...made only minor changes...but believe a trend toward the GFS may be needed with a warmer and drier solution. Tilly && Aviation...(for the 12z tafs through 12z Wednesday morning) issued at 617 am CDT Tuesday may 21 2013 VFR conditions expected this morning as overnight convection has shifted south of the County Warning Area. Next upper level disturbance currently crossing the Southern Plains will lead to an increase in showers and thunderstorms ahead of a slow moving cold front late this afternoon and this evening. Rain chances to finally come to an end for terminals around sunrise Wednesday as the cold front moves east with winds shifting from the southwest to the west. Specifics for kstl... VFR conditions expected this morning with thinning cloud cover. Showers and thunderstorms expected to increase in coverage once again late this afternoon and evening...with cold frontal passage between 09z and 12z. Cvking && Lsx watches/warnings/advisories... MO...none. Illinois...none. && $$ Weather forecast office lsx