Area forecast discussion National Weather Service La Crosse WI 1214 PM CDT Friday may 24 2013 Short term...(today and tonight) issued at 230 am CDT Friday may 24 2013 850 mb moisture transport/jet will kick off/enhance showers/isolated storms over Minnesota/northern Iowa tonight...along and north of a surface warm front. Corfidi vectors would take the complex southeast. Models at odds with each other on where the more likely precipitation will lie...generating the main mass of precipitation in slightly different locations. This lowers forecast confidence in where to place the higher precipitation chances. Trends seem to favor the southwest 1/2 of the forecast area though...and will side with that. Long term...(saturday through thursday) issued at 230 am CDT Friday may 24 2013 An upper level ridge holds across the upper Mississippi River valley into the early part of the new work week...slowly shifting east for the following weekend. Trough holds west of the ridge...spitting out pieces of upper level energy from time to time. While not an overtly strong...blocking type pattern...its not moving very fast at all...with little in the way of 250-300 mb jets to move it along. And despite having the ridge over the region for the next few days...this does not mean its going to be dry. NAM/GFS/ECMWF all have a warm front hanging across the Central Plains/middle Mississippi River valley through the weekend...finally getting a push northward through the forecast area on Tuesday. 850 mb moisture transport is fairly persistent into and through the boundary into the middle of next week. This transport will be a main focus for shower/storm development...and where this noses into will house the better initiation regions. Models focus their quantitative precipitation forecast on the moisture transport - vicinity of the warm front...and can/T fault this placement. Any mesoscale convective vortex from overnight convection will be another consideration...although ferreting out where these may move is more problematic farther out in the forecast period. With the push northward on Tuesday of the warm front...warmer/seasonable air should return...along with instability and thus better chances for thunderstorms if convection can develop. Overall...rain will be on the radar nearly every day through the weekend and into the middle part of next week. That does not mean everyday will be a wash out though...or that everyone will see rain everyday. Rain chances will be higher to the southwest through the weekend...gradually moving northward for the start of the new work week. && Aviation...(for the 18z tafs through 18z Saturday afternoon) issued at 1214 PM CDT Friday may 24 2013 Focus of the forecast is on the potential for showers late tonight into Saturday morning. Short wave trough in the Lee of The Rockies over Wyoming is expected to top the mean ridge and slide across the region late tonight and Saturday morning. An axis of moisture transport is expected to develop this afternoon ahead of this wave then Bend to the northeast and be focused into the area late tonight. However...this will be weakening through the night and will not be very strong by the time it becomes focused on the local area. The forcing from the wave and the weak moisture transport should be enough to generate some showers. Expect these will move into both taf sites between 09z and 12z. The showers should be light enough to not produce any visibility restriction but could produce some MVFR ceilings as the rain saturates the low levels of the column enough to allow the ceilings to lower. The 24.09z sref shows the better probabilities of this occurring are west of the Mississippi River so have included this at krst. The isentropic upglide on the 300k surface begins to weaken after 15z Saturday but does continue for the remainder of the morning and should be enough to keep some showers or sprinkles going through the end of the forecast period. && Arx watches/warnings/advisories... WI...none. Minnesota...none. Iowa...none. && $$ Short term.....Rieck long term......rieck aviation...04