000 FXUS63 KFSD 270313 AFDFSD AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 913 PM CST MON JAN 26 2009 .DISCUSSION... WEAK UPPER WAVES STILL APPARENT IN WATER VAPOR IMAGERY MOVING EAST-NORTHEAST ACROSS THE REGION. HOWEVER...DRY AIR APPEARS TO BE STRONGER FORCE THIS EVENING AS LINGERING AREAS OF FLURRIES AND LIGHT SNOW OVER THE NORTHERN PLAINS HAVE BEEN SLOWLY DIMINISHING. WILL KEEP FLURRIES GOING ACROSS THE SOUTHERN HALF OF THE FA FOR THE BALANCE OF THE EVENING...THEN TRIM BACK TO JUST THE SOUTHEAST CORNER AS TRAILING WAVE SLIDES UP THROUGH NEBRASKA. BEST CHANCES OF LIGHT SNOW ACCUMULATIONS LOOK TO REMAIN SOUTH OF OUR AREA LATE TONIGHT INTO TUESDAY MORNING...SO TRIMMED BACK ALREADY LOW CHANCE POPS TO JUST A SLIGHT CHANCE IN THE FAR SOUTH/SOUTHEAST...WITH FLURRIES ELSEWHERE SOUTHEAST OF VERMILLION SD-SPIRIT LAKE IA LINE. TEMPS HAVE BEEN IN PRETTY GOOD SHAPE OVER OUR FA...THOUGH BRIEF CLEARING IN LOCATIONS OUTSIDE OUR BORDERS INDICATE QUICK DROP POSSIBLE WITH ANY HOLES IN THE CLOUDS. NO SIGNIFICANT ADJUSTMENTS TO TEMPS ANYWHERE BUT DID LOWER A FEW DEGREES HERE AND THERE GIVEN CONTINUED DRYING AND POTENTIAL FOR SOME POCKETS OF CLEARING LATE TONIGHT. UPDATED GRIDS/PFM/ZFP HAVE BEEN SENT. && .AVIATION... CONTINUING TO SEE A FEW AREAS OF LIGHT SNOW/FLURRIES THIS EVENING ACROSS THE REGION AS A SERIES OF DISTURBANCES PUSH EASTWARD. ANTICIPATE THAT MAINLY VFR CONDITIONS WILL PREVAIL THROUGH SOUTHEASTERN SOUTH DAKOTA THROUGH 12Z TUESDAY WITH DRY LOW LEVEL AIR IN PLACE ACROSS THAT AREA. FARTHER TO THE SOUTH...SLIGHTLY DEEPER LOW LEVEL MOISTURE WILL ALLOW FOR MVFR CIGS AT KSUX THROUGH MUCH OF THE NIGHT. MAY SEE ADDITIONAL LIGHT SNOW DEVELOP THROUGH EASTERN NEBRASKA AND WESTERN IOWA LATER TONIGHT...BUT THINK THAT MOST OF THIS ACTIVITY WILL REMAIN SOUTH OF KSUX AS DRYING TAKES PLACE IN THE MID LEVELS. HOWEVER...CANNOT RULE OUT A BRIEF PERIOD OF LIGHT SNOW NEAR THAT TAF SITE AFTER 10Z....DROPPING VISIBILITIES INTO THE MVFR CATEGORY. && .PREV DISCUSSION... PERIODIC SHOTS OF LIGHT SNOW WILL CONTINUE ACROSS THE FORECAST AREA AS ADDITIONAL WEAK WAVES ROUND THE BASE OF THE UPPER LEVEL TROUGH ACROSS THE WESTERN PLAINS. AS OF 20Z...SHORTWAVE VISIBLE ON WATER VAPOR ACROSS NORTHWEST NEBRASKA. THIS IS CREATING SOME LIGHT SNOW ACROSS NORTH CENTRAL NEBRASKA INTO SOUTH CENTRAL NEBRASKA. AS WAVE CONTINUES TO LIFT TO THE NORTHEAST...EXPECT SNOW TO SPREAD INTO WESTERN PORTIONS OF FORECAST AREA BUT SHOULD WEAKEN WITH TIME AS WAVE RUNS INTO DRIER AIR AS IT LIFTS TO THE NORTHEAST. SECOND WAVE ACROSS EASTERN COLORADO EXPECTED TO LIFT TO THE NORTHEAST CREATING AN ADDITIONAL THREAT OF LIGHT SNOW ACROSS SOUTHERN CWA. AROUND LOWEST 12K FEET OF ATMOSPHERE LOCATED WITHIN THE ICE GROWTH LAYER...SO GIVEN WEAK LIFT SHOULD BE ABLE TO SQUEEZE OUT A TENTH OR TWO OF SNOW. UNCERTAIN AS TO WHETHER SNOW WILL ACTUALLY RESULT IN MEASURABLE ACCUMULATIONS...SO HAVE STUCK FAIRLY CLOSE TO GUIDANCE POPS WITH MAIN FOCUS ACROSS NORTHWEST IOWA. WITH WEAK FLOW ACROSS THE FORECAST AREA...HAVE COOLER LOWS TO THE NORTH WHERE DRIER AIR WILL REMAIN. LIGHT SNOW CHANCES WILL CONTINUE IN MAINLY THE SOUTHEAST THIRD OF THE CWA ON TUESDAY MORNING. A FINAL SHOT OF UPPER LEVEL SUPPORT WITH A SMALL AREA OF MID LEVEL FORCING SHOULD BE ENOUGH TO SUPPORT FLURRIES AND MAYBE A COUPLE OF TENTHS OF ACCUMULATION. BY AFTERNOON...EXPECT CLOUDS TO SCOUR OUT FROM WEST TO EAST AS THE COLD HIGH PRESSURE WORKS SOUTHEAST. SOUTHERLY WINDS WILL RETURN ON TUESDAY AS WELL...BUT ANY REAL WARMING WILL BE CONFINED TO AREA MAINLY WEST OF THE JAMES. HIGH WILL RANGE FROM THE MID TEENS IN SW MN TO THE MID 20S IN SC SD. BY TUESDAY NIGHT...SOUTHERLY FLOW WILL STRENGTHEN AHEAD OF A TROUGH OF LOW PRESSURE. EXPECT SOMEWHAT OF A NONDIURNAL TEMPERATURE TREND AND WILL STICK WITH THIS IDEA FROM PREVIOUS FORECASTS. ALSO EXPECT THE DEW POINT TO RISE LATE TUESDAY NIGHT THROUGH WEDNESDAY AS WINDS TURN WEST AND NORTHWEST BEHIND THE TROUGH. LOWS WILL MAINLY BE IN THE SINGLE DIGITS WITH WARMER READINGS EXPECTED OVER THE WEST THIRD OF THE CWA BY SUNRISE WED MORNING. UPPER LEVEL SUPPORT SKIMS THE AREA ON WEDNESDAY MORNING AND WILL CONTINUE SMALL POPS IN MAINLY SOUTHWEST MN. A BREEZY DAY IS ON TAP AS THIS WAVE PASSES WITH MORE MILD TEMPERATURES. HIGHS WILL RANGE FROM THE MID 20S IN SW MN TO THE MID 30S IN SC SD. LATE WEDNESDAY NIGHT INTO THURSDAY MORNING WILL SEE ANOTHER SHOT OF UPPER LEVEL SUPPORT SEEN NICELY ON THE 1.5 PRESSURE LEVEL. PROBABLY A LITTLE BETTER CHANCE FOR SOME LOW END MEASURABLE SNOWFALL AMOUNTS. AS THIS WAVE PASSES A COLD FRONT WILL SNEAK SOUTH AND AFFECT MAINLY THE EASTERN HALF OF THE CWA. HIGHS ON THURSDAY WILL RANGE FROM AROUND 15 IN SW MN TO NEAR 30 IN SC SD. IN THE LATTER PERIODS(FRI/MON)...STILL LOOKING LIKE SPLIT FLOW WITH OUR CWA ON THE SOUTHERN FRINGES OF THE NORTHERN STREAM ACTIVITY. WE DO HAVE A COUPLE OF PIECES OF ENERGY PASS BY...ONE SATURDAY NIGHT WITH A SECOND REINFORCING SHOT OF JET ENERGY ON SUNDAY NIGHT. NEITHER STRONG ENOUGH OR POSITIONED PROPERLY TO WARRANT ANY MENTION OF PRECIPITATION AT THIS TIME. SO...WITH THE BETTER UPPER LEVEL FORCING TO THE NORTH AND NO SOUTHERN STREAM ENERGY...WILL CONTINUE A DRY FORECAST. AS FOR TEMPERATURES...WILL CONTINUE TO WAVER ABOUT PLUS OR MINUS 10 DEGREES OF CLIMATOLOGY THROUGH THE PERIOD...BUT LIKELY THAT WE WILL HAVE MORE DAYS ABOVE THAN BELOW. SATURDAY COULD PROVE TO BE VERY MILD WITH A SLIGHTLY SLOWER FRONT AND WENT WARMEST ON THIS DAY. && .FSD WATCHES/WARNINGS/ADVISORIES... IA...NONE. MN...NONE. NE...NONE. SD...NONE. && $$ JH/JM