381 FXUS63 KARX 052341 AFDARX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 541 PM CST SAT JAN 5 2013 .SHORT TERM...THROUGH MONDAY NIGHT 201 PM CST SAT JAN 5 2013 MAIN FORECAST CONCERN IS WITH THE PRECIPITATION CHANCES TONIGHT. SURFACE ANALYSIS EARLY THIS AFTERNOON SHOWS AN AREA OF LOW PRESSURE OVER NORTHEAST MINNESOTA NEAR KDLH WITH A COLD FRONT EXTENDING SOUTHWEST INTO KANSAS. WATER VAPOR SATELLITE SHOWING THREE SYSTEMS THAT WILL IMPACT THE REGION TONIGHT. UPPER LEVEL LOW AND SHORT WAVE TROUGH MOVING ACROSS NORTHERN MISSOURI WILL CONTINUE TO MOVE OFF TO THE EAST/NORTHEAST TONIGHT TOWARD LAKE ERIE. AS IT DOES...A SHORT WAVE TROUGH OVER SOUTH DAKOTA WILL MOVE SOUTHEAST ACROSS IOWA INTO THE OHIO RIVER VALLEY. THIS WAVE WILL RAPIDLY PUSH THE SURFACE LOW AND COLD FRONT ACROSS THE REGION THROUGH THE REMAINDER OF THE AFTERNOON AND THIS EVENING. THE THIRD SHORT WAVE TROUGH IS MOVING INTO NORTH DAKOTA FROM MANITOBA AND IS EXPECTED TO MOVE RIGHT TOWARD THE AREA THROUGH THE NIGHT. THE FIRST SYSTEM IS EXPECTED TO PASS BY FAR ENOUGH TO THE SOUTH TO NOT HAVE AN IMPACT ON THE AREA. HOWEVER...THE SECOND SHORT WAVE TROUGH AND SURFACE SYSTEM MAY HAVE ENOUGH GOING TO POSSIBLY PRODUCE SOME LIGHT FREEZING DRIZZLE ALONG AND AHEAD OF THE COLD FRONT. THE 05.12Z NAM SHOWS SOME WEAK OMEGA...ON THE ORDER OF ABOUT 1 UBAR/S...IN THE 0-2 KM LAYER WHERE SOME WARM AIR ADVECTION WILL BE OCCURRING IN THE SOUTHWEST FLOW AHEAD OF THE COLD FRONT. THE NAM AND 05.16Z RAP BUFKIT SOUNDINGS SHOW THE LOW LEVELS SATURATING UP TO BETWEEN 2 AND 3 KM BEFORE THE FRONT COMES THROUGH. HOWEVER...SOMEWHAT CONCERNED THAT THE BEST LIFT MAY BE NEAR THE TOP OR JUST ABOVE THE SATURATED LAYER AND THUS MAY NOT BE ABLE TO PRODUCE A WHOLE LOT OF DRIZZLE. STILL ENOUGH OF A CONCERN TO KEEP THE LOW CHANCES FOR THE FREEZING DRIZZLE AND NO CHANGES ARE PLANNED TO THE CURRENT FORECAST. THE THIRD SHORT WAVE TROUGH IS PRODUCING SOME REPORTS OF LIGHT SNOW ACROSS NORTH DAKOTA AND SOUTHERN MANITOBA WITH MVFR VISIBILITIES. HOWEVER...THESE REPORTS ARE VERY SPORADIC WITH NOT MUCH AREAL COVERAGE. THE FORECAST SOUNDINGS DO NOT SHOW THIS WAVE PRODUCING MUCH OMEGA TONIGHT AS IT APPROACHES BUT IT SHOULD PRODUCE UP TO 12 PVU/S OF VORTICITY ADVECTION IN THE 500-300 MB LAYER. SOMEWHAT CONCERNED THAT THE MODELS MAY BE UNDERDONE WITH THE AMOUNT OF LIFT THIS WAVE WILL PRODUCE AND THAT IT COULD END UP PRODUCING A PERIOD OF VERY LIGHT SNOW BUT WILL MAINTAIN THE FLURRIES AS THERE IS SOME QUESTION AS TO WHETHER THE MID LEVELS WILL SATURATE ENOUGH TO ALLOW FOR ANYTHING MORE THAN FLURRIES. AFTER THIS WAVE MOVES BY...QUIET AND WARMER WEATHER WILL SET UP OVER THE REGION. THE SURFACE HIGH THAT WILL BE OVER THE REGION SUNDAY WILL MOVE OFF TO THE EAST SUNDAY NIGHT AS A SYSTEM ROLLS ACROSS SOUTHERN CANADA. THE PRECIPITATION FROM THIS SYSTEM WILL STAY WELL TO THE NORTH BUT IT WILL HELP DRAW WARMER AIR IN WITH HIGHS MONDAY EXPECTED TO TOP OUT IN THE LOWER 30S ACROSS THE ENTIRE AREA. .LONG TERM...TUESDAY THROUGH SATURDAY 201 PM CST SAT JAN 5 2013 MEDIUM RANGE MODELS HAVE STARTED TO COME INTO BETTER AGREEMENT WITH THE SYSTEM EXPECTED TO IMPACT THE GREAT LAKES FOR THE LATTER HALF OF THE WEEK. THE 05.00Z ECMWF HAS REMAINED CONSISTENT WITH ITS PREVIOUS RUNS ON THE TRACK OF THE SYSTEM WHILE THE 05.12Z GFS HAS SHIFTED CONSIDERABLY TOWARD THE ECMWF SOLUTION. THE MODELS ARE NOW VERY SIMILAR IN TIMING BUT THE GFS STILL DOES NOT BRING THE SYSTEM AS FAR NORTH AS THE ECMWF. BY 11.00Z /FRIDAY EVENING/ THE ECMWF PLACES THE UPPER LEVEL LOW NEAR THE WISCONSIN-ILLINOIS BORDER BETWEEN KDBQ AND KRST WHILE THE GFS IS FARTHER SOUTH NEAR KSTL. THE AGREEMENT THAT WAS IN PLACE HAS BEEN THROWN OUT THE WINDOW BY THE 05.12Z ECMWF HAS IT HAS COME IN SLOWER AND FARTHER SOUTH AND IS NOT SIMILAR WITH ITS TRACK TO THE GFS. WITH THE DISPARITY BETWEEN THE MODELS...THE ONLY CHANGE MADE TO THE MODEL CONSENSUS GRIDS WAS TO WEDNESDAY NIGHT. WITH THE ECMWF NOW BEING SLOWER...IT SUGGESTS THE PRECIPITATION WILL NOT MOVE IN UNTIL THURSDAY...SO WILL NOW GO WITH A DRY WEDNESDAY NIGHT. THE PRECIPITATION FROM THIS SYSTEM SHOULD START TO MOVE OUT THURSDAY NIGHT OR FRIDAY BUT WILL QUICKLY BE FOLLOWED BY THE NEXT SYSTEM. THE MODELS MAINTAIN A SOUTHWEST FLOW ALOFT BEHIND THIS SYSTEM AND QUICKLY EJECT OUT ANOTHER SYSTEM FROM THE SOUTHERN ROCKIES. THE ECMWF IS QUICKER AND FARTHER NORTH THAN THE GFS IN THE UPPER LEVELS...BUT THE SURFACE TRACKS LOOK TO BE SIMILAR GOING FROM NEAR KMCI TOWARD KMKE EITHER SATURDAY OR SATURDAY NIGHT. THE ECMWF SUGGESTS THE FIRST SYSTEM WILL BRING ENOUGH WARM AIR NORTH TO PRODUCE PRIMARILY RAIN OR A RAIN/SNOW MIX. HOWEVER...THE BAROCLINIC ZONE LEFT BEHIND MAY BE JUST TO THE SOUTHEAST GIVING THE SECOND SYSTEM ENOUGH COLD AIR TO WORK WITH TO PRODUCE MAINLY SNOW. && .AVIATION...TONIGHT AND SUNDAY 541 PM CST SAT JAN 5 2013 THE FOCUS INTO TOMORROW IS WITH THE PERIODIC LOW CEILINGS THAT WILL OCCUR INTO TOMORROW MORNING. THE FIRST SYSTEM IS CURRENTLY MOVING THROUGH NORTHERN ILLINOIS AND HAS BROUGHT SOME 2-3KFT BKN TO OVC CEILINGS UP ACROSS NORTHEAST IOWA...FAR SOUTHEAST MINNESOTA AND SOUTHWEST WISCONSIN. HIGH LEVEL CLOUDS ARE CURRENTLY OBSCURING THE VIEW OF THE LOW LEVEL CLOUDS ON SATELLITE...BUT SOME OBSERVATIONS IN SOUTHEAST MINNESOTA HAVE BEEN SHOWING THAT THAT WESTERN EDGE OF THE DECK IS SLOWLY MOVING EAST. DECIDED TO PLAY IT PESSIMISTIC WITH KEEPING THE MVFR CEILINGS IN AT LSE THROUGH THE NIGHT...BUT THERE COULD BE A BRIEF PERIOD WHERE IT JUMPS UP TO VFR THIS EVENING. OTHERWISE...A COLD FRONT WILL MOVE THROUGH LATER THIS EVENING WITH WINDS COMING AROUND TO THE NORTHWEST AND ANOTHER BAND OF MVFR TO IFR CEILINGS EXPECTED TO LAST THROUGH THE OVERNIGHT HOURS. SATELLITE SHOWS THAT THESE CEILINGS ARE FAIRLY SCATTERED TO BROKEN AT THIS POINT...BUT FORECAST GUIDANCE IS SHOWING A RAPID MOISTENING OF THE LOW LEVELS THIS EVENING. SO...WILL MAINTAIN THE FORECAST...BUT CONFIDENCE IS NOT AS HIGH THAT THESE LOW CEILINGS WILL BE AS PREVALENT AS ADVERTISED. CONDITIONS WILL IMPROVE TOMORROW MORNING AS DRIER AIR MOVES IN ON THE BACK SIDE OF THIS SYSTEM. && .ARX WATCHES/WARNINGS/ADVISORIES... 201 PM CST SAT JAN 5 2013 WI...NONE. MN...NONE. IA...NONE. && $$ SHORT TERM...04 LONG TERM...04 AVIATION...HALBACH