861  
FXUS63 KFSD 270854  
AFDFSD  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SIOUX FALLS SD  
354 AM CDT SAT MAY 27 2017  
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 354 AM CDT SAT MAY 27 2017  
 
MID LEVEL TROUGH CONTINUES TO DIG ACROSS CENTRAL NORTH DAKOTA INTO  
SOUTHEAST WYOMING EARLY THIS MORNING. THIS FEATURE WILL TRACK  
EASTWARD THROUGH THE REGION TODAY AND TONIGHT, BEFORE EXITING INTO  
THE UPPER MISSISSIPPI VALLEY LATE TONIGHT. FRONTOGENETIC FORCING  
DEVELOPING IN SOUTH CENTRAL SD INTO NORTH CENTRAL NEBRASKA IS  
PRODUCING A BAND OF LIGHT TO MODERATE RAIN SHOWERS, EXTENDING SOUTH  
TO A COMPLEX OF THUNDERSTORMS IN KANSAS. DRY AIR REMAINS AN OBSTACLE  
HEADING NORTH OF THE MISSOURI RIVER, WITH HIGH CLOUD BASES AND DRY  
LOW LEVELS PREVENTING MUCH OF THE ACTIVITY FROM REACHING THE SURFACE  
NEAR AND NORTH OF I-90. MODELS TRACK THE BAND OF SHOWERS EASTWARD  
THROUGH THE REGION, THROUGH LATE MORNING, WITH MORE SPOTTY LIGHT  
SHOWERS ACTIVITY POSSIBLE BEHIND THE MAIN BAND THIS AFTERNOON. WILL  
LEAVE THE HIGHEST CHANCES FOR MEASURABLE RAIN NEAR OUR SOUTHERN  
BORDER/MISSOURI VALLEY AND INTO NORTHWEST IOWA WITH THE INITIAL BAND  
OF RAIN THIS MORNING. ELEVATED INSTABILITY IS PRETTY MEAGER AND  
LARGELY LIMITED TO NEAR THE MISSOURI VALLEY, SO WILL LEAVE ONLY  
ISOLATED MENTION IN OUR FAR SOUTH. TEMPERATURES WILL BE TRICKY GIVEN  
CLOUD COVER CONCERNS. LOOKS LIKE WE COULD GET ENOUGH CLEARING OR  
SCATTERING OF CLOUDS IN THE AFTERNOON TO WARM INTO THE UPPER 60S TO  
LOWER 70S.  
 
TONIGHT, CLOUDS WILL DECREASE OVERALL BEHIND THE DEPARTING WAVE.  
WILL NEED TO WATCH THE POTENTIAL FOR A SECONDARY SHORTWAVE TO TRACK  
THROUGH THE NORTHERN PLAINS IN THE EVENING AND EARLY MORNING HOURS.  
AT THIS POINT IT LOOKS LIKE THE BETTER SUPPORT FOR PRECIPITATION WILL  
REMAIN NORTH OF THE FORECAST AREA, SO WILL LEAVE THE FORECAST DRY.  
LOWS WILL BE IN THE UPPER 40S TO LOWER 50S.  
   
LONG TERM
 
(SUNDAY THROUGH FRIDAY)  
ISSUED AT 354 AM CDT SAT MAY 27 2017  
 
ON SUNDAY, THE AREA WILL GENERALLY BE BETWEEN THE EXITING WAVE FROM  
SATURDAY NIGHT, AND NEXT UPSTREAM LOBE, WITH THE DAY FILLED WITH  
LARGER-SCALE SUBSIDENCE FORCING. WILL BE DIFFICULT FOR MOST OF THE  
DAY TO FIND MORE THAN A FEW DIURNAL CLOUDS, WITH PERHAPS ENOUGH  
DESTABILIZATION TO OVERCOME THE FORCING BY VERY LATE DAY AROUND KMML  
AREA. IT WILL BE A BREEZY AND SEASONABLY WARM DAY OVERALL, LIKELY  
EVEN CONSIDERED WINDY IN MANY SPOTS AS MIXING BECOME FAIRLY  
SIGNIFICANT WITH 25 TO 30 KNOTS ATOP THE MIXED LAYER. BY EVENING,  
THE UPSTREAM JET STREAK WILL SWING SOUTHEAST INTO EASTERN SD AND  
COULD SEE A COUPLE OF ROGUE SHOWERS AND ISOLATED THUNDERSTORMS PUSH  
INTO AREAS NORTH OF I-90 DURING THE EVENING HOURS BEFORE LOSS TO THE  
DIURNAL CYCLE.  
 
EARLY WEEK CONDITIONS WILL BE COURTESY OF THE INFLUENCE FROM CLOSED  
LOW OVER THE WESTERN GREAT LAKES ALONG WITH VARIOUS IMPULSES ON THE  
MERRY-GO-ROUND THROUGH THE NORTHERN PLAINS. WHILE SIGNIFICANT  
WEATHER WILL BE ABSENT, A COUPLE OF ITEMS DESERVE MENTION. FIRST,  
TEMPERATURES WILL BECOME COOLER THAN NORMAL ONCE AGAIN TO START THE  
WEEK, AND HAVE HEDGED TEMPS A BIT LOWER THAN CLIMATOLOGICALLY  
IMPACTED GUIDANCE. NORTHWEST WINDS WILL ALSO LIKELY BE A BIT  
STRONGER EACH DAY AS DEEP MIXING IS FAVORED. WITH COOL TEMPS ALOFT,  
LIKELY TO GET A FEW CYCLONIC CORE SHOWERS ON MONDAY AFTERNOON MAINLY  
IN/NEAR SOUTHWEST MN, BUT AGAIN APPEARS TIMING OF LARGER SCALE WAVES  
IS A BIT OFF TO GET AN OPTIMAL COUPLING OF FORCING. IN FACT,  
POTENTIAL WITH THE DYNAMICS ALONG WITH A SUBTLE WAVE MONDAY NIGHT  
THAT SHOWERS LINGER SOMEWHAT INTO THE EVENING HOURS COMPARED TO  
CURRENT FORECAST. LESS DEPTH TO ANY ML INSTABILITY EXPECTED TUESDAY  
AFTERNOON AND EARLY EVENING, SO MORE ON WAY OF DIURNAL CLOUDS BUT A  
LESSER CHANCE FOR SHOWERS.  
 
TROUGHING RELAXES ACROSS THE REGION A BIT FOR WEDNESDAY WITH SURFACE  
RIDGE AXIS DRIFTING EASTWARD ACROSS THE AREA. DRY AND A BIT MILDER  
IN ORDER. ALL MODELS INDICATE A CONTINUED PROGRESSION OF UPPER RIDGE  
EASTWARD THROUGH THE NORTHERN PLAINS WILL BEGIN TO ALLOW RETURN FLOW  
BY LATER WEDNESDAY NIGHT, AND ENCROACHMENT OF SOME LOWER- TO MID-  
LEVEL MOISTURE ALONG WITH GRADUAL ARRIVAL A BETTER ELEVATED MIXED-  
LAYER. FOR NOW, MAIN LOWER-LEVEL SYNOPTIC BOUNDARY LOOKS TO REMAIN  
WELL SOUTH OF THE AREA, WITH AN OCCASIONAL INCURSION OF ELEVATED  
PRECIP THREAT MAINLY THROUGH THE MISSOURI RIVER VALLEY, ESPECIALLY  
AROUND LATER THURSDAY OR EARLY FRIDAY. CERTAINLY WILL BE WORKING  
TOWARD/ABOVE NORMAL BY END OF THE FORECAST PERIOD.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)  
ISSUED AT 1038 PM CDT FRI MAY 26 2017  
 
VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. ISOLATED TO  
SCATTERED SHOWERS WILL DEVELOP LATE TONIGHT AND PUSH ACROSS THE  
AREA ON SATURDAY, THOUGH IMPACTS WILL BE MINIMAL.  
 

 
   
FSD WATCHES/WARNINGS/ADVISORIES
 
 
SD...NONE.  
MN...NONE.  
IA...NONE.  
NE...NONE.  

 
 

 
 
SHORT TERM...  
LONG TERM...CHAPMAN  
AVIATION...JM  
 
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