Issued by NWS Sioux Falls, SD
000 FXUS63 KFSD 241041 AFDFSD AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 440 AM CST TUE NOV 24 2009 .DISCUSSION... REMAINING BAND OF RAINFALL REMAINS ATTM JUST BEHIND THE SFC INVERTED TROF. THIS BAND OF RAIN WL VERY LIKELY CONT TO DRY UP AS OVERALL DRIER AIR ADVECTS IN FM THE W. HOWEVER...THE MAIN UPPER WAVE IS NOTED ON WV IMAGERY IN THE KANSAS CITY AREA. THIS UPPER LOW HAS DEVELOPED MORE RAINFALL IN SERN NEB AND WRN IA...THE NRN EXTENT OF WHICH IS SCOOTING NWD TOWARD OUR ERN FA. THEREFORE HIGH POPS ARE STILL WARRANTED IN OUR EXTREME E THIS MORNING ALONG THE H85 CONVERGENT AXIS...THEN TAPERING OFF THIS AFTERNOON. FOR TEMPS... DECENT DIURNAL REBOUND IS IN STORE FOR OUR WRN FA AS THEY MIX TO ABOUT H9. CONVERSELY IN OUR EXTREME EAST...EXPECTING TEMPS TO NOT HARDLY BUDGE. TONIGHT AND WED...NEXT SYSTEM OF CONTINENTAL POLAR AIR MOVES RAPIDLY SEWD FM CANADA. MODELS ARE STILL SHOWING A SURGE OF STRATOCU COMING DOWN WITH THIS WAVE LATE TONIGHT. SINCE DRY AIR EXISTS OVER IT IN THE MID LEVELS...OPTED TO JUST MENTIONE FLURRIES AFTER MIDNIGHT... EXCEPT IN NW IA WHERE CONDS MAY REMAIN TOTALLY DRY. THEN ON WED... RH TIME SECTIONS FM BOTH THE NAM AND GFS SHOW SOME DEEPENING OF THE MOISTURE THRU THE NE HALF OF THE FSD FA...COUPLED WITH ASCENT. THEREFORE STILL CONCERNED ABOUT SNOW SHOWERS IN OUR NE HALF...WITH SOME HALF WAY DECENT ACTIVITY WHICH MAY FALL IN SW MN. COUPLED WITH WINDY CONDS...WED WL NOT BE A PLEASANT DAY AND IF -SHSN DOES BEGIN TO MEASURE A BIT IN SW MN...BLSN IS A POSSIBILITY. SOMETHING TO CONSIDER IF TRAVELING IN SW MN ON WED. WL KEEP MONITORING THAT SITUATION. CONCERNING TEMPS...THE GUIDANCE VALUES STILL SEEM TOO WARM FOR WED GIVEN THE H925-H9 TEMPS. THEY WOULD BE REACHED IF SKY COVER WAS PARTLY CLOUDY TO SUNNY. BUT IF WE ARE BANKING ON MOSTLY CLOUDY CONDS...THEN GOING BLO GUIDANCE VALUES SEEM PRUDENT. JUST NOT EXPECTING A BIG REBOUND OF WED MORNING LOWS IF OUR FA IS INDEED MOSTLY CLOUDY. THE SYSTEM RAPIDLY EJECTS EWD WED NIGHT...LEAVING A QUIET WX PATTERN FOR THE REST OF THE WEEK AS UPPER RIDGING TAKES OVER. THUR NIGHT A LOT OF WAA RETURNS. BOTH THE NAM AND GFS PAINT SOME MID LEVEL MOISTURE MOVG FM W TO E ACROSS THIS FA BUT COUPLED WITH VERY DRY LOW LEVELS. THEREFORE LEFT THUR NIGHT DRY...BUT INCREASED THE CLOUD COVER. ALSO WENT A BIT NON DIURNAL FOR MIN TEMPS THUR NIGHT WITH SOME WARMING AFTER MIDNIGHT. /MJF && .AVIATION... RAIN CONTINUES TO FALL NEAR THE INVERTED SFC TROUGH EXTENDING ACROSS IA AND N INTO MN EARLY THIS MORNING. THE MAIN BAND OF RAIN EXTENDS FROM AROUND MML THROUGH FSD TO AROUND VERMILLION. AS HIGH PRESSURE BUILDS INTO ERN SD AND SFC TROUGH SLIDES EAST...RAIN WILL SHIFT INTO CNTRL MN AND CNTRL IA FOR LATER THIS MORNING...THEN TAPERING OFF THROUGH THE AFTERNOON. LOW CIGS WILL BE THE MAIN AVIATION CONCERN TODAY. 3 TO 5 HUNDRED FT CEILINGS WILL BE FOUND ALONG AND JUST WEST OF THE SFC TROUGH AXIS. CIGS WILL IMPROVE TO VFR FROM W TO E THROUGH THE DAY AS DRY AIR PUNCHES IN FM THE W. WHILE ONE TROUGH EXITS THE AREA THIS AFTERNOON AND EVENING...THE NEXT SYSTEM APPROACHES. AN UPPER LEVEL AREA OF LOW PRESSURE WILL DIVE OUT OF CANADA...RAPIDLY MOVING ACROSS THE AREA LATE TONIGHT AND WED. MOISTURE IS LIMITED WITH THIS SYSTEM...BUT TEMPERATURES ARE COLD ENOUGH TO PRODUCE SNOW SHOWERS. EXPECTING A BRIEF PERIOD OF REDUCED VSBYS WITH FALLING SNOW LATE TONIGHT FOR SE SD...BUT COULD SEE A MORE PERSISTANT PERIOD OF SNOW INTO SW MN WED. 20 TO 30 KT SFC WINDS WILL OCCUR FOLLOWING THE PASSAGE OF THE UPPER LEVEL LOW AND ASSOCIATED COLD FRONT. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. $$
