000 FXUS63 KFSD 051522 AFDFSD AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 1000 AM CDT FRI SEP 5 2008 .DISCUSSION... SHRA ASSCD WITH MID LVL WAVE MOVG EWD OVER SRN CWA SOUTH OF I90 REST OF DAY AS PER FCST. BEEFED UP POPS SOME MORE. CLOUDS AND PRECIP WILL PUT DAMPER ON TEMPS IN SRN CWA...EVEN THOUGH AIR MASS COOLER TO THE NORTH...SO TEMPS PRETTY UNIFORM IN CWA. BEST CHC MIXING AND WARMEST TEMPS IN WRN CWA LATER IN AFTN AS CLOUDS CLEAR OUT BEHIND WAVE. EXCPT TO FINE TUNE TIMING AND POPS...NO BIG CHGS TO PREV FCST. RYRHOLM && .AVIATION... MAINLY VFR THROUGH THE TAF FORECAST PERIOD. MARGINAL MVFR CEILINGS WILL BE POSSIBLE TOWARDS THE HON AREA THIS AFTN...HOWEVER THICKER STRATO CU WILL BE FOUND FARTHER NORTH INTO NE SD. SHRA MAINLY NEAR MISSOURI RIVER ATTM WILL MOVE EWD OVER NWRN IA THIS AFTN. CEILINGS WITH THE SHOWER ACTIVITY ARE EXPECTED TO REMAIN IN THE 4 TO 8 KFT RANGE...AND EXPECT FOR ISOLATED HEAVIER SHOWERS...VSBYS WILL REMAIN ABOVE 6 MILES. && .PREV DISCUSSION... LONG WAVE TROFFING CONTS TO DOMINATE THIS AREAS WX THRU THE ENTIRE WEEKEND...WHICH WL BRING OFF AND ON CHCS FOR SHRA AND SEASONABLY COOL TEMPS. CONSIDERING THE AMOUNT OF S/W ENERGY PERIODICALLY MOVG THRU THE UPPER TROF...THE NAM AND GFS ARE PRETTY SIMILAR WITH ONLY MINOR TIMING DIFFERENCES AND SUBTLE SPATIAL DIFFERENCES...ESP ON SAT AND SAT NIGHT. ATTM...UNR AND LBF 88D RADARS SHOW PLENTY OF ECHOES MOVG EWD. THIS ACTIVITY IS ASSOCIATED WITH A DECENT S/W CURRENTLY MOVG INTO SERN WY AND CENTRAL/ERN CO. THE NAM AND GFS ARE VERY SIMILAR IN TIMING THE S/W ACROSS THE CENTRAL PLAINS...IN ADDITION TO BRINGING A FAIR AMOUNT OF MID AND UPPER QG FORCING NWD TO ABOUT I 90. THEREFORE KEPT THE CURRENT FCST GOING OF BRINGING SMALL POPS AS FAR N AS I 90... STEADILY INCREASING THEM HEADING SWD. DECIDED TO RAISE POPS IN THE LIKELY CATEGORY ACROSS OUR FAR SOUTH CLOSER TO THE MAIN WAVE...BUT PCPN AMOUNTS WL STILL BE LIGHT IN OUR FA. AM STILL BANKING THAT THE UPPER LOW TO OUR NORTH WL STAY TOO FAR NORTH TO GIVE AREAS FM HURON TO MARSHALL MN A CHC FOR RAIN. NONETHELESS...CLOUD COVER WL INCREASE ACROSS OUR NORTH ANYWAY. DUE TO THE ABUNDANT CLOUDS EVERYWHERE... TRENDED TOWARD THE COOLER GUIDANCES WHICH WERE THE FWC AND MET. TONIGHT...LOWS ARE TRICKY DUE TO WHAT IS LIKELY TO BE VARIABLE CLOUD COVER. OUR S/W TODAY EXITS QUICKLY THIS EVENING AND WL LIKELY CLEAR OUT THE CLOUD COVER BEHIND IT FOR A WHILE. HOWEVER THE NEXT S/W THEN DIVES DOWN THE NW FLOW ALOFT INCREASING THE CLOUDS ACROSS OUR WEST LATE TONIGHT. THEREFORE HAD A TENDENCY TO GO AOA MOST GUIDANCE LOWS IN OUR FAR WEST...WITH MUCH COOLER READINGS IN OUR FAR EAST WHERE SKY COVER MAY BE MOSTLY CLEAR LONGER. THEN SAT AND SAT NIGHT CONDITIONS LOOK INCREASINGLY SHOWERY. SATURDAYS S/W MOVES EWD WITH THE NAM QUICKER AND FURTHER SOUTH THEN THE GFS. THAT FAR OUT...DECIDED TO HANG MY HAT MORE ON THE GFS AND ALMOST PULLED OUR POPS IN OUR FAR EAST IN SW MN DOWN TOWARD STORM LAKE IA. HOWEVER...EVEN THE SLOWER GFS SHOWS SOME UPPER QG FORCING IN OUR EAST SAT AFTERNOON. SO ULTIMATELY DECIDED TO KEEP OUR LOW POPS GOING. BUT THE CHCS LOOK FOR RAIN LOOK PRETTY GOOD BY AFTERNOON IN OUR FAR WEST NEAR THE MO RIVER PER THE GFS. WHETHER IT RAINS OR NOT...CLOUD COVER LOOKS TO BECOME ABUNDANT AS IT WORKS ITS WAY EWD. SO ONCE AGAIN TRENDED MOST OF OUR MAX TEMPS BLO GUIDANCE READINGS. THIS WL HAVE TO WATCHED AS IF THE CLOUD COVER PANS OUT...EVEN THESE HIGHS MAY BE TOO WARM. SAT NIGHT...BOTH THE NAM AND GFS ARE PRETTY SIMILAR IN BRINGING A STRONG S/W THRU THIS AREA WITH JET ENERGY AND PLENTY OF MID AND UPPER LEVEL PV WITH IT. AGAIN...FOLLOWED THE MORE NLY TRACK PER THE GFS FOR THE HIGHEST POPS. BUT IF FUTURE RUNS CONT TO SHOW THIS STRONG WAVE...THE CHCS FOR EVERYONE GETTING SOME RAIN IN THIS FA ARE PRETTY GOOD. THIS WAVE WAS ACTUALLY SHOWN MORE FOR SUNDAY MORNING ON YESTERDAYS RUNS...SO TIMING IS STILL UNCERTAIN FOR HIGHEST POPS. FOR LOWS...WENT CLOSER TO THE WARMER MAV READINGS DUE TO CLOUD COVER ONCE AGAIN. IF THE CURRENT SOLNS PAN OUT...SUNDAY WL BE THE LAST DAY WHERE WE KEEP THE LONG WAVE TROFFING OVR THIS AREA AND COLD TEMPS ALOFT. WITH THE CHILLY TEMPS ALOFT...KEPT SOME SMALL POPS GOING...WITH THE HIGHEST POPS IN OUR NORTHEAST IN THE MORNING WITH THE DEPARTING SAT NIGHT S/W. GIVEN H85 TEMPS...SUNDAY STILL LOOKS CHILLY AND NOTICED THAT THE MET AND MAV HAVE BEGUN A PROCESS OF COOLING MAX TEMPS OFF WHICH WE ALREADY STARTED PREVIOUSLY. THE NAM EXPLODES A BUNCH OF PCPN IN OUR WRN FA SUNDAY NIGHT IN ASSOCIATION WITH A VERY STRONG WAVE...THE LAST WAVE...MOVG THRU THE UPPER MEAN TROF. IN ADDITION...THE NAM SOLUTION HAS A STRONG JET STREAK IN NRN MN AND THE UPPER LAKES WHICH PLACES THIS AREA FIRMLY IN THE RR QUAD. THE GFS IS MUCH FURTHER SOUTH WITH THE JET STREAK...NEAR I 90. GIVEN THE TRENDS OF THE NAM BEING INCONSISTENT THAT FAR OUT...WENT WITH THE GFS SO FAR WITH OUR SMALL POPS IN OUR EAST AND SOUTH... FOLLOWING THE POSITIVE TILTED UPPER TROF THAT THE GFS ADVERTISES. NO REAL CHANGES MADE TO EARLY NEXT WEEK...AS THE MODELS STILL SHOW THE BIG UPPER TROF DEPARTING EWD ON MONDAY. HOWEVER ONE TRICKY ITEM THAT WILL NEED TO BE LOOKED AT BY THE DAYSHIFT...IS THAT THE ECMWF SHOWS A QUICK MOVG WAVE MOVG EWD AFFECTING OUR SRN FA ON MONDAY. THE GFS WAS FURTHER S WITH THE ENERGY AND DID NOT AFFECT THIS AREA. THE ECWMF LOOKS TO BE FURTHER NORTH THAN THE GFS LIKE THE NAM WAS AT 84 HRS 12Z MON. MJF/LIEBL && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE IA...NONE. NE...NONE. && $$