MIDDAY CONVECTIVE SETUP.
By mid-morning, the Kansas-Missouri MCS had moved east leaving behind a mesoscale, rain-stablized airmass over Iowa and northern Missouri. Its southern edge was marked by a well-defined outflow boundary that extended across central Missouri into northeastern Kansas. There, it intersected the cold front. This boundary could be clearly seen on visible satellite imagery throughout the morning hours as a well-defined arc cloud line, and was also easy to follow throughout the entire day on the surface theta-e analysis (from PCGRIDDS). Thus, the early morning thunderstorm activity had produced an unexpected forecast factor for weather later in the day -- a boundary which was not resolved by any of the standard model runs. For example, the 6-hr forecast from the NGM (not shown) -- although finding clear indication of the quasi-stationary warm front in southern Iowa -- did not resolve the outflow feature.
Another sub-synoptic event of importance occurred when a short line of weak thunderstorms developed during the mid- to late- morning along a cloudy versus clear region in southwest Missouri. That activity quickly moved northeast into the stable rain-cooled region. The strongest of these storms was located where the new line intersected the outflow boundary. Though relatively short-lived, this activity served to keep a portion of the stable air mass cloud covered, and cool. The pocket of reinforced outflow may have played an important role in later convective development.