281  
FXUS63 KFSD 242342 AAA  
AFDFSD  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE SIOUX FALLS SD  
642 PM CDT THU JUN 24 2021  
   
SHORT TERM
 
(THIS EVENING THROUGH FRIDAY)  
ISSUED AT 335 PM CDT THU JUN 24 2021  
 
THE FOCUS OF THE SHORT-TERM FORECAST IS THE POTENTIAL FOR  
CONVECTION TONIGHT AND FRIDAY. THE SURFACE FRONT HAS NOW SETTLED  
OVER FAR SOUTHERN NEBRASKA AND INTO SOUTHERN IOWA. THE 850 MB  
FRONT EXTENDS FROM THE NEBRASKA AND SOUTH DAKOTA BORDER INTO  
NORTHWESTERN IOWA. AS THE JET STREAK COMES INTO THE PLAINS LATER  
THIS AFTERNOON, STORMS ARE EXPECTED TO DEVELOP NEAR THE SURFACE  
BOUNDARY. THIS SHOULD REMAIN THE FOCUS OF CONVECTION MUCH OF THE  
NIGHT. TOWARD SUNRISE ON FRIDAY, ANOTHER JET STREAK WILL MOVE  
INTO CENTRAL NEBRASKA WITH THE EXIT REGION APPROACHING THE SIOUX  
CITY AREA. LAPSE RATES ARE LESS THAN 7 C/KM AND EVEN ELEVATED  
INSTABILITY IS LIMITED BUT INTERACTION WITH THE 850 MB FRONT  
RESULT IN ISOLATED SHOWERS OR THUNDERSTORMS ON FRIDAY MORNING. AS  
THE JET STREAK CONTINUES TO TRACK NORTHEAST THROUGH THE DAY, THERE  
WILL BE A CONTINUED CHANCE FOR STORMS FROM CENTRAL SD EASTWARD  
ALONG THE NEBRASKA AND SOUTH DAKOTA BORDER INTO NORTHWESTERN IOWA.  
INSTABILITY REMAINS VERY LIMITED SO ANY STORMS WILL NOT BECOME  
SEVERE WITH VERY LIMITED COVERAGE THROUGH FRIDAY AFTERNOON.  
RAINFALL WILL GENERALLY BE LESS THAN A TENTH OF AN INCH ALTHOUGH  
ISOLATED AMOUNTS OVER A QUARTER OF AN INCH WILL BE POSSIBLE IF  
STRONGER UPDRAFTS CAN DEVELOP.  
 
ELSEWHERE SKIES WILL BE PARTLY TO MOSTLY CLOUDY. WITH DRIER AIR  
FILTERING SOUTH THROUGH THE EVENING ON NORTHEASTERLY WINDS, LOWS  
OVERNIGHT WILL DROP INTO THE UPPER 50S NORTH OF I90 WITH MID 60S  
ALONG HWY 20 WHERE CLOUDS AND DEEPER MOISTURE ARE EXPECTED. AT  
LEAST SOME SUN THROUGH MUCH OF FRIDAY, TEMPERATURES DURING THE DAY  
WILL GENERALLY BE IN THE 80S, EXCEPT IN SOUTH CENTRAL SOUTH DAKOTA  
WHERE CLOUDS AND A FEW SHOWERS BY AFTERNOON WILL KEEP HIGHS IN THE  
MID TO UPPER 70S.  
   
LONG TERM
 
(FRIDAY NIGHT THROUGH THURSDAY)  
ISSUED AT 335 PM CDT THU JUN 24 2021  
 
THE NEXT CHANCE OF RAIN WILL COME ON FRIDAY NIGHT THROUGH THE  
WEEKEND. THE BEST MOISTURE AND INSTABILITY WILL REMAIN CONFINED  
ACROSS KANSAS AND MISSOURI. HOWEVER, THE 850 MB FRONT WILL REMAIN  
ACROSS NORTHWESTERN IOWA ON FRIDAY NIGHT. A COMBINATION OF LARGE  
SCALE ASCENT WITH THE JET STREAK AND FRONTOGENETICAL LIFT ALONG  
THE FRONT IS EXPECTED TO DEVELOP SCATTERED SHOWERS AND  
THUNDERSTORMS OVERNIGHT. THE BEST CHANCE WILL BE ACROSS  
NORTHWESTERN IOWA SOUTHEAST OF A LINE FROM SPENCER TO SIOUX CITY.  
IF ANY SIGNIFICANT RAINFALL WILL OCCUR, IT LOOKS TO BE AT THIS  
TIME IN PORTIONS OF NORTHWESTERN IOWA. NORTH OF THE BOUNDARY, DRY  
AIR WILL CONTINUE TO BE ADVECTED SOUTHWESTWARD AND THIS WILL  
REALLY LIMIT ANY CHANCE FOR RAIN OVER MOST OF SOUTHEASTERN SOUTH  
DAKOTA AND SOUTHWESTERN MINNESOTA. A TROUGH WILL REMAIN OVER THE  
AREA THIS WEEKEND. SHORT WAVES WILL ROTATE AROUND THE LONG WAVE  
TROUGH SATURDAY AND SUNDAY. AS MENTIONED ABOVE, THE DEEP MOISTURE  
WILL BE CONFINED WELL SOUTH OF THE AREA. BUT WITH RELATIVELY COLD  
AIR ALOFT, THE COMBINATION OF SURFACE HEATING DURING THE DAY AND  
LARGE SCALE ASCENT MAY PRODUCE SCATTERED SHOWERS AND THUNDERSTORMS  
DURING THE AFTERNOON AND EVENING. THERE IS NO GUARANTEE THAT ANY  
LOCATION WILL SEE RAIN AND RAINFALL AMOUNTS THIS WEEKEND LOOK TO  
BE LIGHT AS WELL. WITH THE UPPER TROUGH IN PLACE AND LOTS OF  
CLOUDS, TEMPERATURES WILL BE BELOW NORMAL IN THE MID TO UPPER 70S.  
 
IN THE EXTENDED PERIOD (MON - THU), THE BIG NEWS IS THE  
DEVELOPMENT OF AN EXTREMELY STABLE UPPER AIR PATTERN OVER NORTH  
AMERICA. BOTH THE ECMWF AND GFS/CANADIAN (NAEFS) ENSEMBLES SHOW  
THE DEVELOPMENT OF A STRONG RIDGE ALONG THE WEST COAST OF NORTH  
AMERICA. THE ENSEMBLE MEAN HEIGHTS AT 200 AND 500 MB ARE EXPECTED  
TO BE NEAR OR ABOVE RECORD VALUES THROUGH ALL OF NEXT WEEK. AT THE  
SAME TIME, A VERY STRONG RIDGE IS PROJECTED TO SET UP OFF THE  
EAST COAST OF NORTH AMERICA THIS WEEKEND. WHILE NOT AS  
CLIMATOLOGICALLY ANOMALOUS AS THE WEST COAST RIDGE, HEIGHTS ARE  
WELL ABOVE NORMAL OFF NEW ENGLAND AT LEAST THROUGH THE MIDDLE OF  
NEXT WEEK - PERHAPS LONGER IF THE ECMWF ENSEMBLE IS CORRECT. WHAT  
THIS MEANS LOCALLY IS THAT A PERSISTENT TROUGH IS EXPECTED TO SIT  
OVER THE NORTHERN PLAINS AND GREAT LAKES WELL INTO NEXT WEEK. HOW  
LONG AND HOW FAR WEST THE TROUGH IS LOCATED IS DEPENDENT ON THE  
STRENGTH OF THE EAST COAST RIDGE. THE GENERAL CONSENSUS IS THE  
TROUGH AXIS WILL BE CENTERED OVER MN OR EASTERN DAKOTAS EARLY NEXT  
WEEK AND THEN SLOWLY SHIFT EAST TOWARD THE GREAT LAKES AS THE  
EAST COAST RIDGE BREAKS DOWN BY MID TO LATE NEXT WEEK. AS THE  
TROUGH SHIFTS TO THE EAST, HEAT WILL BEGIN TO RETURN TO THE AREA  
LATE NEXT WEEK. AS FOR PRECIPITATION, THE BEST CHANCE FOR RAIN  
WILL BE EAST OF THE TROUGH AXIS FROM IOWA INTO THE GREAT LAKES.  
WHILE INDIVIDUAL SHORT WAVES MOVING SOUTHWARD ON THE BACKSIDE OF  
THE TROUGH COULD BRING CHANCES FOR RAIN EARLY NEXT WEEK, THE  
TIMING AND LOCATION OF THESE SHORT WAVES IS VERY UNCERTAIN. THAT  
MEANS THAT BEYOND THIS WEEKEND, THE CHANCE OF A SIGNIFICANT  
RAINFALL APPEARS LOW.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)  
ISSUED AT 642 PM CDT THU JUN 24 2021  
 
VFR CONDITIONS WILL PREVAIL THROUGH THE MAJORITY OF THE PERIOD. SCATTERED  
SHOWERS WILL EXIT NORTHWEST IOWA EARLY THIS EVENING. OTHERWISE  
ANVIL CIRRUS WILL SPREAD THROUGH THE REGION TONIGHT AS STORMS  
CONTINUE IN EASTERN NE AND WESTERN SD. WINDS REMAIN LIGHT  
OVERNIGHT, MAINTAINING AN EASTERLY COMPONENT WELL INTO FRIDAY.  
ANOTHER ROUND OF SCATTERED SHOWERS AND STORM IS POSSIBLE FRIDAY  
AFTERNOON ALONG AND SOUTHEAST OF THE SUX TO SPW CORRIDOR, BUT  
CONFIDENCE IS TOO LOW TO INCLUDE IN THE TAF AT THIS TIME.  
 

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

 
 

 
 
SHORT TERM...SCHUMACHER  
LONG TERM...SCHUMACHER  
AVIATION...BP  
 
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