Mixing ratio… a clue to short term development

It's a summer day at 4:00 pm. Zones are due and a front is over the northwest part of your state. Upper dynamics are very weak. Although clouds are associated with the front, surface, radar, or satellite data does not indicate formation of convective rainfall. Morning RAOBs were stable, even with some lift caused by the front. You decide to leave thunderstorms out of the forecast. However, the zones have to be updated one hour later as the convective rainfall develops along the front. Sound familiar? By using the meso-analysis programs, especially the SMR (Surface Mixing Ratio) chart combined with the instability chart and surface convergence one can often not only determine where (from moisture convergence) but in the short range (one to four hours) when (from the surface mixing ratio chart combined with surface heating) showers will occur.