Area forecast discussion National Weather Service Omaha/valley NE 617 PM CDT Sat may 25 2013 Aviation... 00z tafs for koma...klnk and kofk. Forecast in regards to thunderstorms and rain is not clear. Models have differing solutions with coverage and development. Felt chances were low enough to leave thunderstorms and rain out of forecast prior to 09z. But will keep a close eye on that and amend as needed. Activity over the High Plains will try to track east later tonight. Overall expect ceilings to lower overnight into the MVFR category and possibly to IFR. IFR conditions would be most likely 09z-14z. Like today...ceilings should tend to improve toward VFR by late morning or early afternoon. Miller && Previous discussion... /issued 311 PM CDT Sat may 25 2013/ Discussion... Although timing of highest concentration of any convection is the main challenge for any given period well into next week...pattern looks to remain active with precipitation chances good if not likely most areas most evenings/overnight periods. At 19z surface boundary extended from just north of fnb to just SW of olu/bvn with residual cool outflow from morning convection reinforcing front. Convergence near boundary had increased cumulus field west-central zones and latest rap mesoscale analysis placed axis of 2000-3000 j/kg ml cape across that area with little/no cin. So there remains some possibility of convection developing near/north of this boundary early this evening...especially as any subsidence effects of departing mesoscale convective vortex from earlier convection gets farther removed. Later this evening/overnight High Plains convection will probably make a run toward/into forecast area...possibly consolidating more across northern zones aided by rr entrance region of weak upper jet segment. However...can/T rule out activity farther S as well since boundary may not move much tonight. Low level jet does strengthen some into front overnight...but strongest/more convergent area not necessarily focused across the forecast area...so confidence on widespread heavy rainfall not very good. That said...small area of northern Iowa zones did pick up 1-2+ inches of rain last night and that area appears to have the highest chance of significant rains tonight as moisture remains plentiful with precipitable waters around 1.5 inches. Thus issued a small Flash Flood Watch NE of Omaha to match up with dmx where heavier rain was more widespread. Decreased probability of precipitation diurnally on Sunday like today although it was noted that for several runs now NAM had developed a small mesoscale convective system and dropped it southeast across forecast area during the afternoon. Forecast was not based on that scenario. Also models hinting at more low level moisture with low clouds possibly lingering into the afternoon. Thus increased sky cover. If clouds hold all day convective development could be altered as well as high temperatures. Otherwise...likely probability of precipitation many areas again were mentioned Sun night. Monday possibly a very similar scenario...although finer details probably impacted by previous periods convection both days. Some indication by models that a front...possibly aided by overnight convection...will push S into northern zones on Tuesday as a stronger wave ejects across Canadian prairie. Cooling at 850 mb minimal for that area...but NE winds and possible low clouds could keep maximum temperatures cooler and this could need attention in later forecasts. Otherwise...this boundary and upper trough beginning to approach area will keep area active Tuesday/Tuesday night. Wednesday could possibly be more of a lull with warmer temperatures before stronger energy punches across Central Plains Wednesday night/Thursday increasing coverage/chances again. Although severe potential will exist into Tuesday...this stronger trough could bring a heightened risk of severe weather to area late next week. Chermok && Oax watches/warnings/advisories... NE...none. Iowa...Flash Flood Watch from midnight CDT tonight through Sunday morning for iaz043-055-056. && $$