291  
FXUS63 KUNR 150739  
AFDUNR  
 
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY  
NATIONAL WEATHER SERVICE RAPID CITY SD  
139 AM MDT SUN SEP 15 2019  
   
DISCUSSION
 
(TODAY THROUGH SATURDAY)  
ISSUED AT 133 AM MDT SUN SEP 15 2019  
 
THE LATEST SURFACE ANALYSIS HAS A LEE TROUGH/WEAK WARM FRONT OVER  
EASTERN WY. WATER VAPOR IMAGES AND THE RAP ANALYSIS SHOWED A  
DIRTY, LOW-AMPLITUDE RIDGE OVER THE NORTHERN ROCKIES. SOME HIGH  
CLOUDS WERE SWEEPING ACROSS THE CWA.  
 
TODAY THROUGH MONDAY NIGHT, UPPER RIDGE BUILDS OVER THE MO RIVER  
VALLEY IN RESPONSE TO DEEPENING UPPER TROUGH OVER THE WEST COAST.  
STRONG THERMAL RIDGE BUILDS OVER THE CWA BRINGING HIGH TEMPERATURES  
AROUND 10F ABOVE AVERAGE. THE HRRR-SMOKE SUGGESTS SMOKE WILL MOVE  
OVER PARTS OF THE CWA TODAY FROM WESTERN CONUS WILDFIRES. A WEAK  
SHORT-WAVE TROUGH WITH LIMITED FORCING AND MOISTURE MOVES THROUGH  
TONIGHT WITH SOME CLOUDS. ANOTHER SLIGHTLY STRONGER SHORT-WAVE  
TROUGH MOVES THROUGH MONDAY NIGHT, WITH LOW-LEVEL JET/850-700MB  
THETA-E ADVECTION EXPECTED. SOME STORMS MAY FORM JUST EAST OF THE  
CWA.  
 
TUESDAY WILL BE A TRANSITION DAY AS A STRONGER SHORT-WAVE TROUGH  
EJECTS NORTHEAST FROM THE WEST COAST UPPER LOW. MOISTURE WILL BE  
LIMITED AHEAD OF THE WAVE, BUT SYNOPTIC FORCING, FRONTOGENESIS, AND  
MIDLEVEL MOISTURE SHOULD BE SUFFICIENT FOR SCATTERED TSRA TUESDAY  
AFTERNOON AND EVENING. THE MAIN THREAT APPEARS TO BE GUSTY WINDS  
GIVEN UNIDIRECTIONAL HODOGRAPHS, A LINEAR STORM MODE, AND A DRY  
BOUNDARY LAYER. A STRONG COLD FRONT THEN MOVES THROUGH WITH GUSTY  
WEST/NORTHWEST WINDS TUESDAY EVENING LINGERING INTO WEDNESDAY  
MORNING.  
 
WEDNESDAY THROUGH SATURDAY, SOUTHWEST FLOW ALOFT TRANSITIONS TO A  
LARGE UPPER TROUGH MOVING THROUGH THE NORTHERN PLAINS LATER FRIDAY  
INTO SATURDAY. A COOLING TREND IS EXPECTED, ESPECIALLY FRIDAY AND  
SATURDAY, ALONG WITH INCREASED PRECIPITATION CHANCES AT THE END OF  
THE WEEK.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)  
ISSUED AT 1025 PM MDT SAT SEP 14 2019  
 
VFR CONDITIONS CAN BE EXPECTED THROUGH SUNDAY EVENING.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 133 AM MDT SUN SEP 15 2019  
 
RELATIVE HUMIDITIES WILL DROP INTO THE TEENS OVER NORTHEASTERN  
WY/FAR SOUTHWESTERN SD THIS AFTERNOON. FORECAST SOUNDINGS SHOW  
DEEP MIXING WITH POTENTIAL GUSTS OF 20-25 MPH, JUST SHORT OF RED  
FLAG CRITERIA.  
 

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

 
 

 
 
DISCUSSION...BUNKERS  
AVIATION...7  
FIRE WEATHER...BUNKERS  
 
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