682 FXUS63 KDMX 070840 AFDDMX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 340 AM CDT TUE MAY 7 2013 .SHORT TERM.../TODAY /... ISSUED AT 337 AM CDT TUE MAY 7 2013 MAIN CONCERNS EARLY TODAY WILL BE SOME POTENTIAL YET FOR FOG THROUGH ABOUT SUNRISE. WESTERN RIVER VALLEYS CONTINUE TO SEE SLOWLY LOWERING VSBY AT THIS TIME...AND SUSPECT THAT PATCHY DENSE FOG MAY DEVELOP BETWEEN 4 TO 7 AM. THE REMAINDER OF THE AREA MAY SEE SOME GROUND FOG EARLY TODAY. AIRMASS HAS MODERATED SLOWLY WITH LESSENING INFLUENCE OF OLD LOW IN THE SOUTHEAST US EVEN WITH A TROUGH EXTENDING BACK TO THE NORTHWEST INTO IOWA. ITS LIKELY THAT BOUNDARY LAYER MOISTURE WILL BE RECYCLED AGAIN THIS AFTERNOON WITH PARTLY CLOUDY FAIR WX CU DEVELOPING DURING THE AFTERNOON HOURS. NOT LOOKING FOR ANY GREAT MIXING...BUT H850 TEMPS AGAIN SUPPORT A DEGREE OR TWO WARMER AFTERNOON HIGHS THAN MONDAY. AT H500...A WEAK VORT MAX OVER SOUTH DAKOTA AND NEBRASKA WILL SLOWLY DRIFT EAST. CURRENT RADAR AND SAT TRENDS SHOW LIGHT SHOWERS DEVELOPING IN CU FIELD THAT IS THICKENING TO THE WEST OF THE AREA. IN THE FAR WEST A SLIGHT CHANCE FOR LATE AFTERNOON SHOWERS OR A FEW THUNDERSTORMS WILL STILL BE POSSIBLE...BUT BETTER CHANCES REMAIN WEST OF THE AREA FOR TODAY. .LONG TERM.../TONIGHT THROUGH MONDAY/... ISSUED AT 337 AM CDT TUE MAY 7 2013 TONIGHT THE WEAK MEANDERING LOW OVER SOUTH DAKOTA WILL BEGIN TO SHIFT EAST AND DEEPEN INTO A SHORTWAVE TROUGH AS THE CLOSED LOW OVER THE S.W. UNITED STATES SHIFTS EAST. AS THIS OCCURS SHOWERS AND THUNDERSTORMS WILL DEVELOP MAINLY OVER THE WESTERN THIRD OF THE FORECAST AREA. IN ADDITION...FORCING INCREASES LATE TONIGHT INTO WEDNESDAY MORNING AS SOUNDINGS HINT AT A WEAK LOW LEVEL JET TAKING SHAPE. NOT LOOKING FOR MUCH IN THE WAY OF SEVERE STORMS AT THIS POINT BUT AN ISOLATED STORM COULD PRODUCE SOME LARGE HAIL OR STRONG WIND. DURING THE DAY ON WEDNESDAY THROUGH WEDNESDAY NIGHT THE LOW OVER SOUTH DAKOTA BECOMES AN OPEN WAVE THAT SHIFTS ACROSS IOWA. I EXPECT SHOWERS AND THUNDERSTORMS THROUGH THIS PERIOD AS WELL. STEEP LAPSE RATES AND A MODEST LOW LEVEL JET COULD ONCE AGAIN YIELD AN ISOLATED SEVERE STORM BUT LACK OF LARGE SCALE FORCING SHOULD KEEP THIS IN CHECK. HOWEVER THE NAM KEEPS THE QG FORCING ACROSS SOUTHERN/EASTERN IOWA LONGER ON WEDNESDAY AND I DID GO WITH A BLEND OF THE TWO MODELS IN THE GRIDS SO I DID KEEP PRECIP GOING LONGER IN THOSE AREAS. IN FACT MODEL QPF IS PRETTY IMPRESSIVE DURING THIS PERIOD SO THERE COULD BE SOME PERIODS OF MODERATE RAINFALL. NOT MUCH CHANGE FOR THE REMAINDER OF THE EXTENDED. STILL LOOKING AT A STRONG SHORT WAVE TO DROP DOWN ACROSS THE UPPER MIDWEST FRIDAY NIGHT THROUGH SATURDAY WHICH SHOULD BRING A QUICKER SHOT OF PRECIP FOLLOWED BY COLDER AIR FOR THE WEEKEND. THIS WILL BE FOLLOWED BY AN UPPER LEVEL RIDGE TO BUILD INTO THE REGION FROM THE WEST DURING THE EARLY PART OF NEXT WEEK. && .AVIATION...07/06Z ISSUED AT 1159 PM CDT MON MAY 6 2013 VFR CONDITIONS REMAIN IN PLACE AT ALL TAF SITES HOWEVER MVFR FOG IS BEGINNING TO FORM OVER WRN IA. ALTHOUGH THESE LOCATIONS WILL LIKELY SEE THE WORSE FOG CONDITIONS...FEEL AT LEAST MVFR FOG WILL ALSO DEVELOP EASTWARD INTO TAF SITES. POTENTIAL TO GO LOWER IS THERE...BUT HAVE NO CONFIDENCE IN ANY PARTICULAR LOCATION AT THE MOMENT. SCATTERED SHOWERS/TSTMS MAY AFFECT WRN IA BY LATE AFTERNOON AND EVENING...INCLUDING KFOD...BUT NOTHING MORE THAN VCSH WORDING FOR NOW UNTIL CONFIDENCE INCREASES. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...REV LONG TERM...FAB AVIATION...SMALL