076  
FXUS65 KCYS 232016  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
216 PM MDT MON APR 23 2018  
   
SHORT TERM
 
(THIS EVENING THROUGH WEDNESDAY NIGHT)  
ISSUED AT 330 PM MDT MON APR 23 2018  
 
TONIGHT...LOOKS AND FEELS LIKE SPRING OUTSIDE. SURFACE LOW PRESSURE  
CONTINUES TO DEVELOP ACROSS OUR WESTERN COUNTIES WITH DECENT  
PRESSURE RISES OVER NORTHERN WYOMING AND DECENT PRESSURE FALLS OVER  
SOUTHEAST WYOMING AND WESTERN NEBRASKA. AS A VIGOROUS SHORTWAVE  
TROUGH ALOFT AND ITS ASSOCIATED STRONG COLD FRONT PASS OUR COUNTIES  
THE REST OF TODAY, EXPECT INCREASING COVERAGE OF SHOWERS AND  
ISOLATED THUNDERSTORMS, SOME OF WHICH MAY PRODUCE SMALL HAIL AND  
WIND GUSTS UP TO 50 MPH BASED ON SHEAR AND INSTABILITY EXPECTATIONS.  
SHOWERS AND THUNDERSTORMS WILL BE MOST NUMEROUS OVER WESTERN  
NEBRASKA THIS EVENING NEAR THE COLD FRONT WITH SCATTERED SHOWERS  
AFTER MIDNIGHT, MAINLY OVER WESTERN NEBRASKA.  
 
TUESDAY...BLUSTERY AND COLD DAY AS THE SHORTWAVE TROUGH ALOFT MOVES  
SLOWLY ACROSS WESTERN NEBRASKA WITH COLD AIR ADVECTION AT LOW LEVELS  
ACROSS OUR COUNTIES. LOW AND MID LEVEL GRADIENTS SUGGEST A WINDY DAY  
AT MOST LOCATIONS.  
 
TUESDAY NIGHT...DRYING OUT PERIOD AS THE SHORTWAVE TROUGH ALOFT  
MOVES TO NORTHWEST KANSAS WITH DECREASING CLOUD COVER. HARD FREEZE  
EXPECTED WITH COLD AIRMASS, CLEARING SKIES AND LIGHT WINDS.  
 
WEDNESDAY...MUCH WARMER WITH A TRANSITORY SHORTWAVE RIDGE ALOFT OVER  
OUR COUNTIES AND PLENTY OF SUNSHINE. WITH 700 MB TEMPERATURES RISING  
NEAR 4 CELSIUS, EXPECT MAXIMUM TEMPERATURES IN THE 60S AT LOWER  
ELEVATIONS.  
 
WEDNESDAY NIGHT...ANOTHER COLD FRONTAL PASSAGE, MOSTLY DRY, AS A  
SHORTWAVE TROUGH SWINGS SOUTHEASTWARD ACROSS THE DAKOTAS. OROGRAPHIC  
TYPE SHOWERS EXPECTED AFTER MIDNIGHT OVER THE NORTHERN LARAMIE RANGE  
AND NEARBY PORTIONS OF CONVERSE COUNTY, OTHERWISE DRY. NOT QUITE AS  
COLD AS THE AIRMASS RECOVERS AND MIXING LIMITS COOLING.  
   
LONG TERM
 
(THURSDAY THROUGH MONDAY)  
ISSUED AT 330 PM MDT MON APR 23 2018  
 
WEAK COLD FRONT THURSDAY MOVES THROUGH THE AREA DURING THE DAY FOR  
SOME LIGHT RAINSHOWERS. AFTER THIS FRONT MOVES THROUGH LOOKING AT  
RISING 500MB HEIGHTS AND WARMER TEMPERATURES. BY SATURDAY, 700MB  
TEMPERATURES UP TO +8C. MEX GUIDANCE FOR SATURDAY SHOWING 78 FOR A  
HIGH AT CHEYENNE AND 80 FOR SIDNEY. DID GO ABOVE GUIDANCE ON  
FORECAST TEMPERATURES.  
 
ANOTHER SHORTWAVE POSSIBLE FOR SUNDAY INTO MONDAY NEXT WEEK. GFS  
FURTHER NORTH OVER THE ECMWF. THAT FAR OUT, CONFIDENCE IS LOW ON  
POPS AND THE FORECAST TRACK IS SURE TO CHANGE BETWEEN NOW AND  
THEN.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)  
ISSUED AT 1012 AM MDT MON APR 23 2018  
 
INTRODUCED THUNDERSTORMS INTO THE 18Z TAFS THIS AFTERNOON. LATEST  
HRRR GUIDANCE SHOWING EARLIER THAN EXPECTED DEVELOPMENT THIS  
AFTERNOON, SO MOVED UP TIMING AS WELL. POSSIBILITY OF SEEING KCYS  
GOING IFR AS WINDS TURN NORTHEASTERLY SHORTLY AFTER 00Z. WILL  
CONTINUE TO MONITOR UNFOLDING EVENTS.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 230 PM MDT MON APR 23 2018  
 
COLD FRONT MOVING THROUGH SOUTHEAST WYOMING THIS AFTERNOON WILL  
BRING WIDESPREAD WETTING RAINS AND MOUNTAIN SNOW TO THE AREA.  
COLDER TEMPERATURES TUESDAY BEFORE HIGH PRESSURE BUILDS  
IN. WARMER TEMPERATURES SHOULD END OUT THE WEEK. WITH RECENT  
RAINFALL AND UPCOMING WARM TEMPERATURES, WOULD EXPECT A RAPID  
ACCELERATION OF GREENUP ACROSS BOTH SOUTHEAST WYOMING AND  
NEBRASKA PANHANDLE FIRE WEATHER ZONES. FIRE WEATHER WILL NOT BE A  
CONCERN THIS WEEK.  
 

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

 
 

 
 
SHORT TERM...RUBIN  
LONG TERM...GCC  
AVIATION...GCC  
FIRE WEATHER...GCC  
 
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