199  
FXUS63 KUNR 091104  
AFDUNR  
 
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY  
NATIONAL WEATHER SERVICE RAPID CITY SD  
504 AM MDT SUN AUG 9 2020  
   
DISCUSSION
 
(TODAY THROUGH SATURDAY)  
ISSUED AT 240 AM MDT SUN AUG 9 2020  
 
CURRENT SURFACE ANALYSIS SHOWS ONE FRONTAL BOUNDARY JUST SOUTH  
AND EAST OF THE REGION, WITH A COLD FRONT OVER MT ALSO APPROACHING  
THE AREA. UPPER LEVEL ANALYSIS SHOWS LOW PRESSURE OVER CENTRAL  
CANADA SHIFTING SLOWLY NORTHEASTWARD, WITH NEAR ZONAL FLOW ACROSS  
THE NORTHERN PLAINS. SHORTWAVE ENERGY THAT BROUGHT STORMS  
YESTERDAY AFTERNOON AND EVENING IS MOVING ACROSS EASTERN PORTIONS  
OF THE NORTHERN PLAINS. A FEW SHOWERS AND STORMS LINGER OVER PARTS  
OF SOUTHWEST INTO SOUTH CENTRAL SD EARLY THIS MORNING. SKIES ARE  
CLEARING ELSEWHERE TO THE NORTH AND WEST WITH TEMPS MOSTLY IN THE  
60S AND LOWER 70S. WINDS ARE VARIABLE ACROSS THE AREA BETWEEN THE  
TWO FRONTAL BOUNDARIES.  
 
COLD FRONT TO THE NORTHWEST WILL PUSH THROUGH THE AREA TODAY,  
BRINGING BREEZY NORTHWESTERLY WINDS TO MOST AREAS BEHIND IT. HIGHS  
WILL RANGE FROM THE MID TO UPPER 70S OVER PORTIONS OF NORTHEAST WY  
AND THE HIGHER BLACK HILLS TO THE LOW TO MID 90S OVER FAR SOUTHERN  
SD. THE FRONT LOOKS TO BE DRY AS IT CROSSES MOST OF THE AREA.  
HOWEVER, AS THE FRONT REACHES CENTRAL SD IN THE AFTERNOON, STORMS  
ARE EXPECTED TO DEVELOP ALONG AND AHEAD OF IT. A STORM OR TWO COULD  
CLIP FAR SOUTH CENTRAL SD DURING THE LATE AFTERNOON AND EARLY  
EVENING. THE BETTER INSTABILITY FOR STRONGER STORMS WILL BE SOUTH  
AND EAST OF THE AREA BY THIS TIME, BUT SHEAR LOOKS TO BE SUFFICIENT  
FOR A POSSIBLE SEVERE STORM LATE IN THE DAY OVER THE TRIPP COUNTY  
AREA. A POST FRONTAL SHORTWAVE WILL MOVE ACROSS THE AREA LATER  
SUNDAY NIGHT, WITH A CHANCE FOR SHOWERS AND A FEW THUNDERSHOWERS  
OVER A GOOD PORTION OF THE FORECAST AREA, BUT ESPECIALLY FROM THE  
BLACK HILLS TO SOUTH CENTRAL SD.  
 
MONDAY LOOKS TO BE A PLEASANT DAY WITH SKIES BECOMING MOSTLY SUNNY  
AND HIGHS IN THE MID 70S TO MID 80S. A WEAK DISTURBANCE, COMBINED  
WITH DEVELOPING LOW LEVEL JET AND THETA-E ADVECTION OVER THE AREA,  
WILL LIKELY BRING AT LEAST ISOLATED SHOWERS AND STORMS MONDAY NIGHT  
INTO EARLY TUESDAY.  
 
BUILDING RIDGE OVER THE PLAINS MIDWEEK WILL BRING HOTTER CONDITIONS  
BACK TO THE REGION. HIGHS WILL BE IN THE UPPER 80S AND 90S ACROSS  
MUCH OF THE PLAINS WEDNESDAY AND THURSDAY. WEAK DISTURBANCES MOVING  
THROUGH THE RIDGE MAY BRING A FEW STORMS AT TIMES, ESPECIALLY LATE  
DAY INTO THE EVENING, BUT MANY AREAS COULD STAY DRY. ANOTHER UPPER  
LEVEL SYSTEM IS PROGGED TO TRACK ACROSS SOUTHERN CANADA LATE WEEK,  
EVENTUALLY DRAGGING A COLD FRONT ACROSS THE NORTHERN PLAINS, LIKELY  
FRIDAY AND FRIDAY NIGHT. NEAR AVERAGE TEMPERATURES SHOULD RETURN FOR  
THE WEEKEND.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)  
ISSUED AT 502 AM MDT SUN AUG 9 2020  
 
PATCHY FOG ACROSS PORTIONS OF NORTHWEST SOUTH DAKOTA WILL BRING  
SOME LOCAL IFR CONDITIONS. FOG WILL DISSIPATE EARLY THIS MORNING  
AS A COLD FRONT MOVES THROUGH. GUSTY NORTHWEST WINDS WILL SPREAD  
ACROSS THE PLAINS OF WESTERN SOUTH DAKOTA BEHIND THE FRONT...WITH  
GUSTS TO AROUND 35 MPH. WINDS WILL DIMINISH LATE THIS  
AFTERNOON/EARLY EVENING.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 240 AM MDT SUN AUG 9 2020  
 
A COLD FRONT WILL PASS THROUGH NORTHEAST WYOMING AND NORTHWEST  
SOUTH DAKOTA THIS MORNING AND THE REST OF THE AREA DURING THE  
MIDDAY AND AFTERNOON HOURS. BREEZY CONDITIONS WILL DEVELOP ACROSS  
MUCH OF THE AREA, ESPECIALLY THE NORTHWEST AND WEST CENTRAL SD  
PLAINS. MINIMUM RELATIVE HUMIDITIES WILL DROP TO AROUND 20 PERCENT  
ACROSS FIRE ZONES 317, 322, AND INTO 326.  
 
NEAR TO BELOW AVERAGE TEMPERATURES WILL PREVAIL FOR MONDAY INTO  
TUESDAY, BEFORE HOT AND DRIER CONDITIONS RETURN FOR MID TO LATE  
WEEK. RELATIVE HUMIDITIES WILL LIKELY DROP TO NEAR OR BELOW 15  
PERCENT FROM NORTHEAST WYOMING INTO PARTS OF SOUTHWEST SOUTH DAKOTA  
WEDNESDAY THROUGH FRIDAY. WINDS AT THIS TIME LOOK TO BE BELOW RED  
FLAG CRITERIA, AT LEAST ON WEDNESDAY AND THURSDAY.  
 

 
   
UNR WATCHES/WARNINGS/ADVISORIES
 
 
SD...NONE.  
WY...NONE.  

 
 

 
 
DISCUSSION...26  
AVIATION...7  
FIRE WEATHER...26  
 
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