687 FXUS63 KMPX 101137 AFDMPX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 637 AM CDT SUN MAR 10 2013 .DISCUSSION... ...MAIN CONCERN DURING THE FORECAST PERIOD IS TODAY THROUGH TONIGHT... FRONTAL BOUNDARY IS ON THE FAR EASTERN EDGE OF THE FA AT THIS TIME AND WILL CONTINUE MOVING AWAY FROM THE AREA TODAY. A SURFACE LOW PRESSURE SYSTEM OVER NORTHWESTERN MO THIS MORNING WILL MOVE SLOWLY EAST NORTHEAST...BEFORE TAKING A MORE NORTHEASTERLY TURN AS THE 500H LOW COMES TO A CRAWL OVER NORTHEASTERN KANSAS. AS THE SURFACE LOW TURNS MORE NORTHEAST DURING THE DAY...IT WILL BEGIN SPREADING PRECIPITATION INTO THE FA. P TYPE CONCERNS EXIST OVER PARTS OF WEST CENTRAL WISCONSIN...WHERE A RAIN/SNOW MIX IS PROBABLE FOR MUCH OF THE DAYTIME HOURS. FORECAST SOUNDINGS DO SHOW A PRONOUNCED WARM LAYER OVER EAU CLAIRE AT 800H THROUGH THE AFTERNOON...BEFORE THE PROFILE COOLS SUFFICIENTLY TO PRODUCE MAINLY SNOW AFTER 00Z. FORECAST SOUNDINGS ELSEWHERE SHOW ENOUGH COOL AIR PLACE TO SUPPORT SNOW THIS AFTERNOON. THE BRUNT OF THE HEAVY SNOW WILL FALL JUST TO OUR SOUTHEAST...BUT WE WILL BE PARTIALLY SIDE SWIPED BY THE HEAVIEST SNOW BAND. MODELS HAVE COME IN TO BETTER AGREEMENT CONCERNING THE PLACEMENT OF THE HEAVIEST SNOWFALL. GFS AND ECMWF HAVE ULTIMATELY SHIFTED THE PRECIPITATION SLIGHTLY WEST/WITH THE ECMWF BEING FARTHER WEST/...BUT THE GFS WANTS TO PUT DOWN NEAR AN INCH OF PRECIPITATION ALONG THE IOWA BORDER. THE ECMWF IS CLOSER TO HALF AN INCH...WHICH IS MUCH MORE REASONABLE. THE SREF IS REMARKABLY CLOSE TO THE GFS IN THE PLACEMENT OF ACCUMULATING SNOWFALL...BUT WITH MUCH LOWER AMOUNTS. THE NAM HAS BECOME AN OUTLIER AT THIS POINT...AND KEEPS MOST OF THE PRECIPITATION TO THE SOUTH AND EAST OF THE FA. IF THE NAM SOLUTION PANS OUT...VERY LITTLE ACCUMULATING SNOWFALL WILL BE SEEN. FORTUNATELY...THE RAP...MPXWRF...AND FIM ALL LOOK MORE LIKE THE GFS/ECMWF/SREF SOLUTIONS IN REGARDS TO THE PLACEMENT OF THE SNOWFALL. THE HEAVIEST PRECIPITATION WILL OCCUR THIS EVENING THROUGH THE OVERNIGHT HOURS...WITH THE FAR SOUTH AND EASTERN COUNTIES SEEING GENERALLY 3 TO 6 INCHES OF SNOWFALL BY TOMORROW MORNING. DECIDED TO UPGRADE FREEBORN AND EAU CLAIRE COUNTIES TO A WINTER STORM WARNING...WITH A STRIP OF COUNT INES UNDER A WINTER WEATHER ADVISORY FROM SOUTH CENTRAL MN THROUGH PARTS OF WEST CENTRAL WISCONSIN. MONDAY AND BEYOND... A CLIPPER SYSTEM IS EXPECTED TO QUICKLY MOVE SOUTHEAST ACROSS CANADA ON MONDAY...AND SPREAD SOME LIGHT SNOW INTO THE FA MONDAY NIGHT INTO TUESDAY. THE WAVE WILL CATCH UP TO AND MERGE WITH THE MORE POWERFUL SYSTEM THAT WILL BE THE CAUSE OF TODAY'S SNOWFALL. SNOWFALL AMOUNTS FROM THE CLIPPER WILL GENERALLY BE UNDER AN INCH. ADDITIONAL CHANCES FOR LIGHT SNOW STILL ARE LIKELY NEAR THE END OF THE WEEK AS A PACIFIC NORTHWEST UPPER TROUGH APPROACHES THE AREA. EXPECT CLOUDY CONDITIONS TO CONTINUE FOR MOST OF THE FORECAST PERIOD...ALONG WITH TEMPERATURES SLIGHTLY BELOW NORMAL. && .AVIATION.../12Z TAF ISSUANCE/ MAIN FORECAST CONCERN IS WHETHER STORM SYSTEM TO OUR SOUTH BEGINS TO SPREAD -SN FURTHER NORTH THAN EXPECTED. THIS WOULD CAUSE A LONGER DURATION OF MVFR CIGS...WITH OCCASIONAL IFR/MVFR VSBYS IN SNOW. MVFR/IFR CIGS ARE WIDESPREAD ACROSS MPX FA WITH -SN/IP AS CLOSE AS MKT/FBL/AEL. SINCE 1030Z...A BAND OF LIGHT PRECIPITATION HAS EXPANDED NORTHWARD ACROSS SC/EC MN WHICH MAY CLIP MSP/RNH BY 15Z. WILL CONTINUE THE SAME SCENARIO WITH THE BULK OF THE PRECIPITATION STAYING SOUTH OF MSP/RNH...BUT AFFECTING EAU BY 15Z WITH IFR CIGS/VBSYS IN SN. AXN/RWF/STC WILL CONTINUE TO BE OUT OF THE PRECIPITATION AREA...BUT REMAIN MVFR/IFR FLIGHT STATUS THRU THE FORECAST PERIOD AS MOISTURE AND CYCLONIC FLOW AROUND THE STORM SYSTEM TO OUR S/SE CONTINUES. WINDS SPDS WILL BE GUSTY WITH SUSTAINED WINDS ARND 14-16 KTS...WITH GUSTS OF 20-24 KTS LIKELY. A MORE NNE FLOW IS EXPECTED FOR RNH/MSP/EAU AS THE SFC LOW MOVES FROM EASTERN KANSAS...NE TOWARD SE WI. KMSP... MAIN FORECAST CONCERN IS WHETHER -SN AND LOWER VSBYS AFFECT THE AIRPORT TERMINAL LATER TODAY...AND TONIGHT AS THE STORM SYSTEM TO OUR SOUTH...HOLDS CLOSE TO THE AREA. MVFR CIGS WILL CONTINUE THRU THE TAF PERIOD...WITH SOME CIGS AOA 1.7K BY LATE MORNING/AFTN. HOWEVER...WITH DEEP MOISTURE REMAINING OVER THE TERMINAL SITE...EXPECT CIGS TO HOLD IN THE MVFR RANGE...OR POSSIBLY LOWER TO 1.5K OVERNIGHT. IN ADDITION...MAY NEED TO LOWER VSBYS IF -SN IS CLOSER THAN EXPECTED AFT 00Z/11. WINDS WILL REMAIN FROM THE N/NNE TODAY WITH GUSTS OF 20 TO 24 KTS THRU 00Z. A MORE N/NNW IS EXPECTED OVERNIGHT WITH DECREASING SPDS. /OUTLOOK FOR KMSP/ MONDAY...MVFR CIGS POSSIBLE. NW WIND 10 TO 20 KT. MONDAY NIGHT/TUESDAY...MVFR CIGS/VSBYS POSSIBLE WITH -SN. NW AROUND 10 KTS. TUESDAY NIGHT...MVFR CIGS POSSIBLE EARLY. NW WIND 10 TO 20 KT. WEDNESDAY AND WEDNESDAY NIGHT...VFR. NW WIND 5 TO 15 KT BACKING SOUTH. ..JLT.. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 7 AM CDT MONDAY FOR FARIBAULT-GOODHUE-STEELE-WASECA. WINTER STORM WARNING FROM 1 PM THIS AFTERNOON TO 7 AM CDT MONDAY FOR FREEBORN. WI...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 10 AM CDT MONDAY FOR CHIPPEWA-DUNN-PEPIN-RUSK. WINTER STORM WARNING FROM 7 PM THIS EVENING TO 10 AM CDT MONDAY FOR EAU CLAIRE. && $$ SPD/JLT