RSS FeedsIssued by NWS Sioux Falls, SD
000 FXUS63 KFSD 250305 AFDFSD AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 905 PM CST TUE NOV 24 2009 .DISCUSSION... NARROW RIDGE EXTDG NE TO SW OVER CNTRL CWA MOVG SEWD WITH LOW CLOUDS RELUCTANT TO LEAVE FAR ERN CWA...AND MID AND HIGH CLOUD BAND RAPIDLY APPROACHING FM THE NW IN CWA. THIS BAND HAD SCT SPRKLS WITH IT AND MAY HAVE TO BE PUT IN GRIDS...BUT APPEARS TO BE FALLING APART ATTM. FORTUNATELY TEMPS RISING WELL ABV FRZG ALONG WITH BRF NWLY WIND GSTS WITHIN THE BAND...AND WILL TRY ALSO TO PUT IN UPDATED GRIDS. MAIN COOLING FM ALOFT AND CHC -SHSN SHOULD DVLPG SEWD ACROSS MAINLY NRN CWA AFT MIDN WITH MAIN SHORT WAVE DIGGING SEWD. WILL CONSIDER UPDATING ZFP FOR SPKLS...OTRW MAIN CHANGES WILL BE IN GRIDS. /RSR && .AVIATION... SOLID LOW CLOUDS WITH MVFR VSBY AND MVFR/IFR CIGS CONTINUE TO HANG TOUGH E OF A KMML TO KSUX LINE AT MID EVENING. THIS AREA SHUD CONTINUE TO PULL SLOWLY EWRD THRU THE LATE EVENING. ANOTHER FEATURE WHICH WL DEGRADE AVIATION CONDITIONS IS A STRONG SYSTEM DIGGING SOUTHEASTWARD ACRS ND AT 03Z. THIS WL PUSH A NOTABLE COLD FRONT THROUGH THE AREA OVERNIGHT...MARKED BY SHARPLY INCREASING NW SFC WINDS...AND SHUD BE ASSOCIATED WITH SOME LOWER CLOUDS AGAIN ALONG WITH THREAT FOR A BRIEF PERIOD OF SNOWFALL. THERE WILL BE AN INITIAL PUSH OF MID LVL MOISTURE THIS EVENING WHICH COULD BRING A BRIEF SPRINKLE AND VFR CIGS. THE LOWER CLOUDS ARE ASSOCIATED WITH THE STRONGER UPPER LEVEL WAVE...WHICH WL DROP SE INTO MN THE LAST HALF OF THE NIGHT INTO EARLY WED MORNING. A NARROW BAND OF SCATTERED SNOW SHOWERS ARE POSSIBLE BEHIND THE FRONTAL BNDRY...WHICH WOULD LKLY BE ACCOMPANIED BY MVFR CIGS/VSBYS AND WIND GUSTS TO 25-35 KTS. WINDS WL REMAIN A GUSTY 25 TO 35 KTS THRU MUCH OF DAY WITH EVEN MODEST MIXING DUE TO COLD TEMPERATURES ALFT ON WED...AND WITH MOISTURE PRESENT FROM RECENT RAINFALL...WILL LIKELY GET DEVELOPMENT OF DIURNALLY DRIVEN SC BY 16-17Z DURING THE DAY ON WEDNESDAY. /CHAPMAN && .PREV DISCUSSION... LOW PRESSURE CENTERED ACROSS CENTRAL IOWA LATE THIS AFTERNOON WILL SHIFT EAST INTO NORTHERN ILLINOIS AND THE WESTERN GREAT LAKES REGION BY WEDNESDAY MORNING. LOW CLOUDS AND LIGHT RAIN ACROSS NORTHWEST IOWA WILL GRADUALLY SHIFT TO THE EAST. DEBATED AS TO WHETHER OR NOT TO THROW A LOW POP IN ACROSS NORTHWEST IOWA THROUGH EARLY EVENING...OR TO JUST COVER WITH MENTION OF DRIZZLE. BACK TO THE NORTHWEST...COLD FRONT PLOWING THROUGH NORTHEAST MONTANA THIS AFTERNOON SWINGING INTO THE WESTERN DAKOTAS TONIGHT. LOW LEVEL LAPSE RATES BECOME FAIRLY STEEP IMMEDIATE BEHIND THE FRONT...AND DESPITE THE OVERALL LACK OF MOISTURE...HAVE UPPED MENTION OF FLURRIES TO CHANCE POPS ACROSS NORTHERN HALF OF CWA...WITH ONLY A 20 PERCENT CHANCE SOUTH OF INTERSTATE 90. BELIEVE WHATEVER FALLS MAY BE A SHORT LIVED BUT INTENSE SNOW BURST. EVEN IF TEMPERATURES ARE IN THE LOWER 30S AT AND JUST ABOVE THE SURFACE...BELIEVE PRECIPITATION WILL FALL ENTIRELY AS SNOW. STRONG NORTHWEST WINDS WILL FOLLOW BEHIND THE FRONT...WITH 925 HPA WINDS OF 30-35 KNOTS. /BT A FAIRLY COLD AND DYNAMIC SYSTEM WILL MOVE THROUGH ON WEDNESDAY WITH A BAND OF SNOW LIKELY OVER THE EASTERN PART OF THE CWA. AMOUNTS SHOULD NOT BE MUCH...BUT NOT OUT OF THE QUESTION TO SQUEEZE AN INCH OR SO OUT OF WHAT IS AVAILABLE. FAIRLY STRONG MID LEVEL FORCING ON THE NOSE OF THE INCOMING UPPER LEVEL FORCING EARLY...GIVES WAY TO A MORE CONVECTIVE SCENARIO IN THE AFTERNOON. THE OTHER CONCERN WILL BE WIND. BUFKIT FROM BOTH THE NAM AND GFS SUGGEST SOMETHING CLOSE TO 40 KNOTS IN THE MIXED LAYER...SO NOT OUT OF THE QUESTION TO REACH WIND ADVISORY CRITERIA. WILL NOT ISSUE AN ADVISORY AT THIS TIME...BUT NORTHWEST WINDS OF 20 TO 30 MPH WITH GUSTS AROUND 35 MPH VERY LIKELY. BY WEDNESDAY NIGHT...WILL KEEP A SMALL CHANCE FOR LIGHT SNOW IN THE FAR EAST AS SYSTEM EXITS...OTHERWISE EXPECT CLEARING FROM THE WEST AND SLOWLY DIMINISHING WINDS. WILL AIM FOR LOWS IN THE TEENS IN THE FAR WEST AND MID 20S IN THE FAR EAST. THURSDAY WILL BE COOL BUT DRY AS A RIDGE OF HIGH PRESSURE WORKS ACROSS THE CWA. COULD SEE SOME LOWER TO MID LEVEL CLOUDS DEVELOP ON WARM ADVECTION AS RIDGE OF HIGH PRESSURE SHIFTS EAST. HIGHS NEAR NORMAL FROM THE MID 30S IN THE EAST TO THE MID 40S WEST. A GRADUALLY INCREASING WIND ON THURSDAY NIGHT MAY SEE LOWS BOTTOM OUT IN THE WEST AROUND MIDNIGHT THEN SLOWLY RISE TOWARDS SUNRISE. LOWS SHOULD MAINLY BE IN THE 20S. WARM AIR WILL WORK NORTHWARD ON FRIDAY AND HAVE SIDED CLOSER TO THE GFS/EC SOLUTIONS. DO NOT AGREE WITH THE NAM DROPPING A WEAK BOUNDARY SOUTH...SO WILL STICK WITH A SOUTHEAST WIND AND TEMPERATURES FROM THE MID 40S IN SW MN TO THE MID 50S ALONG THE MO RIVER VALLEY. IN THE LATTER PERIODS(SAT/TUE)...MODELS IN FAIRLY GOOD AGREEMENT ON SWINGING THROUGH A LARGE SCALE UPPER LEVEL TROUGH ON SATURDAY. SPLIT FLOW LOOKS HIGHLY PROBABLE DURING THIS PERIOD AS A STRONG SOUTHERN STREAM JET STREAK SPREADS ACROSS THE FAR SOUTHERN U.S. AND ANOTHER STRONG NORTHERN STREAM JET STREAK WORKS INTO WESTERN CANADA. WHILE PRECIPITATION NOT IMPOSSIBLE...THE BETTER CHANCES SHOULD BE WELL OFF TO THE NORTH AND SOUTH OF THE AREA. WILL CONTINUE THE CHANCE FOR A LITTLE LIGHT SNOW ON SUNDAY AS A WEAK WAVE MOVES THROUGH THE AREA. OTHERWISE...WILL STICK WITH AT OR BELOW NORMAL TEMPERATURES THROUGH THE PERIOD BUT WILL NEED TO WATCH FOR SOME POTENTIALLY WARMER CONDITIONS BY TUESDAY AS LOW PRESSURE COULD REALLY GET CRANKING OVER THE SOUTHEAST U.S. AND A NORTHERN STREAM WAVE MOVES THROUGH SOUTHERN CANADA SETTING UP A SOUTH TO SOUTHWEST FLOW. /08 && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. $$
