789  
FXUS65 KCYS 232019  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
219 PM MDT SUN JUL 23 2017  
   
SHORT TERM
 
(THIS EVENING THROUGH TUESDAY)  
ISSUED AT 217 PM MDT SUN JUL 23 2017  
 
PRETTY QUIET AND HOT WEATHER PATTERN WILL BE IN PLACE THROUGH MONDAY  
WITH STRONG RIDGING ALOFT AND LIMITED MONSOONAL MOISTURE. VISIBLE  
IMAGERY SHOWS SCATTERED CUMULUS ACROSS SOUTHEAST WY WITH THE BEST  
VERTICAL DEVELOP ALONG THE SOUTHERN LARAMIE RANGE NEAR THE COLORADO  
BORDER. WHILE MUCH OF THE CWA WILL REMAIN STORM FREE THROUGH THE  
EVENING, THE HRRR HAS BEEN CONSISTENT AT SHOWING ISOLATED CONVECTION  
DEVELOPING BY LATE AFTN OVER THE LARAMIE RANGE, SPREADING EASTWARD  
INTO ADJACENT PLAINS. WILL MAINTAIN POPS AROUND 20 PERCENT THROUGH  
THE EARLY EVENING. WITH DEEP BOUNDARY LAYERS AND HIGH T/TD SPREADS,  
THINKING THAT GUSTY OUTFLOW AND DOWNDRAFTS WILL BE THE MAIN THREAT.  
 
THE PATTERN WILL BE SIMILAR FOR MONDAY WITH RIDGING/SUBSIDENCE ALOFT  
KEEPING TSTM CHANCES RATHER LIMITED. IT WILL BE THE WARMEST DAY IN  
THE SHORT TERM WITH HIGHS RISING INTO THE 90S TO LOW 100S ACROSS THE  
PLAINS. A SFC TROUGH WILL STRETCH FROM AROUND LARAMIE TO CHADRON  
DURING THE AFTN. NOT EXPECTING MUCH CONVECTIVE INITIATION ALONG THE  
TROUGH EXCEPT IN AREAS NEAR THE SOUTHERN LARAMIE RANGE. THE MODELS  
CONTINUE TO SHOW MIDLVL FLOW BECOMING MORE SOUTHWESTERLY BY TUESDAY,  
WHICH WILL TRANSPORT SUBTROPICAL MOISTURE INTO THE CWA, ESPECIALLY  
ACROSS SOUTHEAST WY. THE GFS HAS PW VALUES RISING TO AROUND 1 INCH  
OVER AREAS TO THE WEST OF THE LARAMIE RANGE BY TUESDAY AFTN. WITH A  
WEAK SHORTWAVE TROUGH MOVING INTO NORTHWEST COLORADO, THERE WILL BE  
A MUCH BETTER CHANCE OF STORMS, PARTICULARLY OVER THE WESTERN MTNS  
(SIERRA MADRE/SNOWY RANGE). HEAVY RAIN WILL DEFINITELY BE A  
POSSIBILITY WITH DEEP MONSOONAL MOISTURE IN PLACE. WENT AHEAD AND  
INCREASED POPS OVER AREAS TO THE WEST OF THE LARAMIE RANGE BY  
TUESDAY AFTN.  
   
LONG TERM
 
(TUESDAY NIGHT THROUGH SATURDAY)  
ISSUED AT 217 PM MDT SUN JUL 23 2017  
 
ENERGETIC WEST-SOUTHWEST FLOW ALOFT WILL KEEP AN ACTIVE PATTERN  
IN PLACE TUESDAY NIGHT THROUGH THURSDAY. MONSOONAL MOISTURE WILL  
RIDE OVERHEAD WITHIN THIS FLOW PATTERN, SO EXPECT TO SEE A GOOD  
CHANCE FOR SHOWERS AND THUNDERSTORMS THROUGH THIS TIME. A FRONT  
RIDING SOUTH ACROSS THE FORECAST AREA TUESDAY NIGHT WILL KEEP  
SHOWERS/STORMS ONGOING THROUGH THE NIGHT, WITH UPSLOPE STRATUS A  
GOOD POSSIBILITY IN THE POST FRONTAL ENVIRONMENT WEDNESDAY  
MORNING. THE BEST COVERAGE FOR CONVECTION WEDNESDAY AFTERNOON WILL  
BE ALONG AND WEST OF I-25. RETURN MOISTURE IN LLVL SOUTHEASTERLY  
UPSLOPE FLOW LOOKS TO COMBINE WITH MODERATE VALUES OF BULK SHEAR  
ON THURSDAY TO SET THE STAGE FOR A BROADER COVERAGE OF ACTIVITY  
ACROSS THE AREA, WITH PERHAPS A STRONGER STORM OR TWO. A RIDGE  
WILL BUILD TO OUR WEST ON FRIDAY, WITH A SHORTWAVE MOVING ACROSS  
WYOMING IN WEST-NORTHWEST FLOW. THIS WAVE WILL DRAG ANOTHER FRONT  
SOUTH ACROSS THE AREA WITH CONVECTION LIKELY TO BE CONFINED ALONG  
THE FRONT AND WITHIN THE HIGHER TERRAIN. SATURDAY WILL BE DRIER  
OVERALL WITH WARM TEMPS AND SUBSIDENCE ALOFT.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)  
ISSUED AT 1141 AM MDT SUN JUL 23 2017  
 
VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. MODELS ARE STILL  
SOMEWHAT INCONSISTENT WITH AFTERNOON THUNDERSTORM POTENTIAL, BUT  
IT SEEMS THAT THERE IS A BETTER CHANCE FOR KCYS AND KLAR FOR THIS  
AFTERNOON AND EVENING. THUS, ADDED IN VCTS FOR THESE LOCATIONS.  
WIND GUSTS OF 20 TO 25 KTS ARE STILL POSSIBLE LATER THIS AFTERNOON  
AT MOST LOCATIONS AS WELL. WINDS WILL DIMINISH OVERNIGHT, THEN  
WILL RAMP UP LATER MONDAY MORNING ESPECIALLY ACROSS THE PLAINS.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 217 PM MDT SUN JUL 23 2017  
 
MINIMAL FIRE WEATHER CONCERNS THROUGH THE MIDDLE OF NEXT WEEK. WITH  
A WARM AND DRY AIRMASS IN PLACE, MINIMUM HUMIDITY VALUES WILL DROP  
TO 13-20 PERCENT OVER PORTIONS OF SOUTHEAST WYOMING THIS AFTERNOON  
AND MONDAY AFTERNOON. WE ARE NOT EXPECTING ANY CRITICAL FIRE  
WEATHER CONDITIONS HOWEVER, AS WINDS WILL BE RELATIVELY LIGHT. AN  
INCREASE IN MONSOONAL MOISTURE ON TUESDAY AND WEDNESDAY WILL BRING  
HIGHER RELATIVE HUMIDITY VALUES AND A BETTER CHANCE OF WETTING  
RAINS.  
 

 
   
CYS WATCHES/WARNINGS/ADVISORIES
 
 
WY...NONE.  
NE...NONE.  

 
 

 
 
SHORT TERM...ZF  
LONG TERM...RJM  
AVIATION...RJM  
FIRE WEATHER...ZF  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab WY Page
The Nexlab NE Page Main Text Page