785  
FXUS65 KCYS 221100  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
500 AM MDT THU MAY 22 2025  
   
KEY MESSAGES
 
 
- WARMING TREND STARTS ON THURSDAY WITH WIDELY SCATTERED LATE  
EVENING AND OVERNIGHT THUNDERSTORMS POSSIBLE ACROSS THE EASTERN  
PLAINS.  
 
- ACTIVE PATTERN CONTINUES THROUGH THE END OF THE WEEK, WITH  
ANOTHER SEVERE WEATHER EVENT POSSIBLE FRIDAY AND AGAIN THIS  
WEEKEND.  
 
- RAIN AND STORM CHANCES CONTINUE THROUGH NEXT WEEK.  
 

 
   
SHORT TERM /THROUGH FRIDAY NIGHT/
 
 
ISSUED AT 204 PM MDT WED MAY 21 2025  
 
GUSTY NORTHWESTERLY WINDS CONTINUE ACROSS MUCH OF SOUTHEAST WYOMING  
AND WESTERN NEBRASKA WITH SCATTERED CLOUDS MOVING OVERHEAD. SOME  
AGITATED CUMULUS HAVE DEVELOPED ACROSS NORTHERN PORTIONS OF THE CWA  
THIS AFTERNOON AND ARE SLOWLY MOVING OFF TO THE SOUTHEAST TOWARDS  
THE NEBRASKA PANHANDLE. A FEW LIGHTNING STRIKES HAVE OCCURRED WITH  
THESE STORMS ACROSS CONVERSE AND NIOBRARA COUNTIES, THOUGH NOT  
STORMS ARE SEVERE AT THIS TIME. TEMPERATURES HAVE WARMED NICELY INTO  
THE MID-60S ACROSS THE PANHANDLE AND MID-50S TO LOW-60S ACROSS  
SOUTHEAST WYOMING. TEMPERATURES SHOULD CONTINUE TO INCREASE OVER THE  
NEXT HOUR OR TWO BEFORE CLOUD COVER OVERTAKES THE REGION AND  
TEMPERATURES BEGIN TO COOL. ANY LOCATIONS THAT EXPERIENCES A SHOWER  
OR THUNDERSTORM WILL BEGIN TO COOL MUCH SOONER THAN LOCATIONS THAT  
REMAIN DRY THIS AFTERNOON.  
 
NORTHWESTERLY FLOW ALOFT IS ONGOING THIS AFTERNOON ACROSS MUCH OF  
THE WESTERN CONUS AS A RIDGE ATTEMPTS TO AMPLIFY ALONG THE WEST  
COAST THIS AFTERNOON INTO THE OVERNIGHT HOURS. THE NORTHWESTERLY  
FLOW ALOFT COMBINED WITH THE FAIRLY MESSY RIDGE IN THE UPPER-LEVEL  
WILL ENABLE MULTIPLE DISTURBANCES AND ASSOCIATED VORTICITY MAXIMA TO  
PUSH THROUGH OVERHEAD PROVIDING SYNOPTIC LIFT TO MUCH OF THE CWA.  
ADDITIONALLY, THE UPPER-LEVEL JET WILL MOVE OVERHEAD IN A LOCATION  
CONDUCIVE FOR INCREASE SYNOPTIC LIFT WITH PORTIONS OF THE PANHANDLE  
BEING UNDER THE LEFT EXIT REGION AND FAVORABLE DYNAMICS IN THAT  
LOCATIONS. HOWEVER, GIVEN THE PROGRESSIVE NATURE OF THE DEVELOPING  
RIDGE OUT WEST, THE LEFT EXIT REGION WILL ONLY REMAIN OVER WESTERN  
NEBRASKA FOR A SMALL AMOUNT OF TIME THIS AFTERNOON, APPROXIMATELY  
NOW THROUGH ABOUT 03Z THIS EVENING. ANTICYCLONIC VORTICITY ADVECTION  
AT 500MB WILL MOVE IN AS THE JET PUSHES OFF TO THE NORTH AND EAST,  
LEADING TO SUBSIDENCE RETURNING, EFFECTIVELY DIMINISHING SHOWER AND  
STORMS CHANCES THIS EVENING. BROAD RIDGING WILL BE PRESENT AT 700MB  
WITH CONTINUATION OF THE NORTHWESTERLY FLOW AT THIS LEVEL. AS THIS  
RIDGE BUILDS AT 700MB, WARM AIR ADVECTION WILL BE PRESENT ACROSS  
SOUTHEAST WYOMING AND WESTERN NEBRASKA UNTIL AROUND 03Z. THIS WILL  
FURTHER FUEL SHOWER AND THUNDERSTORM CHANCES THIS AFTERNOON AS  
SYNOPTIC LIFT CONTINUES TO BE FAVORED IN THE LOW-LEVELS OF THE  
ATMOSPHERE. ADDITIONALLY, 700MB HEIGHT GRADIENTS ARE SLIGHTLY  
ELEVATED THIS AFTERNOON, LEADING TO AROUND A 40KT 700MB JET ACROSS  
THE SOUTHERN LARAMIE RANGE. HEIGHT GRADIENTS ARE EXPECTED TO RELAX  
BETWEEN 00 AND 03Z, LEADING TO DECREASING SURFACE WINDS LATER THIS  
EVENING INTO THE OVERNIGHT HOURS. A 700MB SHORTWAVE COMBINED WITH  
OVERALL SYNOPTIC LIFT WILL ENABLE STORMS TO CONTINUE TO DEVELOP  
ACROSS NORTHERN PORTIONS OF THE REGION, INCLUDING CONVERSE,  
NIOBRARA, SIOUX, AND DAWES COUNTY. WITH THE SOUTHEASTERLY STORM  
MOTION, THESE STORMS WILL EVENTUALLY MOVE INTO THE NEBRASKA  
PANHANDLE THROUGHOUT THE AFTERNOON AND EVENING.  
 
WITH AMPLE SYNOPTIC LIFT PRESENT ACROSS THE REGION AND THE  
ADDITIONAL FORCING FOR ASCENT WITH THE 700MB SHORTWAVE, SHOWERS AND  
STORMS ARE ALREADY FORMING ACROSS NORTHERN LOCATIONS. TAKING A LOOK  
AT RAP FORECAST SOUNDING, STRONG LOW-LEVEL LAPSE RATES WILL BE  
PRESENT ACROSS MUCH OF THE PANHANDLE, WITH SBCAPE VALUES INCREASING  
AROUND THE 500 J MARK NOW THROUGH THIS EVENING. RAP SOUNDINGS SHOW  
THE CLASSIC INVERTED-V SOUNDING SHAPE, INDICATING AN INCREASING  
RISK FOR STRONG, DAMAGING WINDS GUSTS ACROSS THE PANHANDLE WITH AND  
SHOWER AND STORM THAT MOVES ACROSS THIS REGION. CURRENT SPC  
MESOANALYSIS DATA SUGGESTS THAT THE MAXIMUM SBCAPE VALUES ARE  
ONGOING NOW AND EXPECTED TO CONTINUE FOR THE NEVER SEVERAL HOURS  
BEFORE THE SBCAPE BOUNDARY SLOWLY MOVES OFF TO THE NORTHEAST INTO  
SOUTH DAKOTA. DCAPE VALUES HAVE RISEN TO AROUND 600 TO 700 J, AND  
ARE EXPECTED TO CONTINUE RISING OVER THE NEXT FEW HOURS. SHEAR IS  
FAIRLY WEAK, ONLY AROUND 35 KTS, SO THE HAIL THREAT IS FAIRLY LOW AT  
THIS TIME, HOWEVER DRY MID- AND LOW-LEVELS MAY FAVOR THE DEVELOPMENT  
OF SOME SMALL HAIL WITH ANY OF THE THUNDERSTORMS THIS AFTERNOON. SPC  
HAS PLACED PORTIONS OF THE NEBRASKA PANHANDLE UNDER A MARGINAL RISK  
(LEVEL 1 OF 5) FOR DAMAGING WINDS, AS EXPECTED WITH INVERTED-V  
SOUNDINGS AND STEEP LOW-LEVEL LAPSE RATES. HOWEVER, SOME SMALL HAIL  
CANNOT BE COMPLETELY RULED OUT, AS WELL AS THE POTENTIAL FOR SOME  
DRY THUNDERSTORMS, OR STORMS WITH RAIN THAT IS NOT REACHING THE  
GROUND, BUT STILL HAVE LIGHTNING ASSOCIATED WITH THEM, DUE TO THE  
DRY LOW-LEVELS. THE MAIN RISK SHOULD COME TO AN END BETWEEN 00 AND  
03Z AT THE UPPER-LEVEL SUPPORT WEAKENS AND THE ATMOSPHERE BECOMES  
MORE STABLE INTO THE LATE AFTERNOON AND EVENING HOURS.  
 
BROAD UPPER-LEVEL RIDING IS EXPECTED TO CONTINUE THURSDAY ONWARDS AS  
THE WEST COAST RIDGE SLOWLY MOVES INTO THE INTERMOUNTAIN WEST. WITH  
THE BROAD RIDING IN PLACE, THE OVERALL SUBSIDENCE ASSOCIATED WITH  
RIDGES WILL BE A BIT WEAKER AS THE RIDGE ITSELF IS BROAD AND FAIRLY  
WEEK. AS A RESULT, 500MB VORTICITY MAXIMA WILL CONTINUE TO EJECT OUT  
ACROSS SOUTHEAST WYOMING AND WESTERN NEBRASKA LEADING TO CONTINUED  
PRECIPITATION CHANCES ACROSS THE REGION AS SYNOPTIC LIFT FROM THE  
VORTICITY LOBES IS STRONGER THAN THE WEAK SUBSIDENCE FROM THE MESSY  
RIDGE ALOFT. ADDITIONALLY, A 700MB LOW WILL ATTEMPT TO DEVELOP  
ACROSS MONTANA, LEADING TO ADDITIONAL LIFT ACROSS THE REGION AND A  
STRENGTHENING 700MB HEIGHT GRADIENT ONCE AGAIN. AS A RESULT, GUSTY  
WINDS ARE EXPECTED AT THE SURFACE ONCE AGAIN THURSDAY. CAPE VALUES  
LOOK TO LOW TO NON-EXISTENT ACROSS MUCH OF THE CWA, EXCEPT FOR A  
SMALL SWATCH ACROSS THE SOUTHERN LARAMIE RANGE. THEREFORE, ANY  
SHOWERS AND STORMS THAT DEVELOP ON THURSDAY WILL LIKELY FORM OVER  
THE LARAMIE RANGE DUE TO OROGRAPHIC LIFT IN THIS REGION AND  
PROPAGATE OFF THE MOUNTAINS. THESE STORMS SHOULD BE ABLE TO SUSTAIN  
THEMSELVES A BIT INTO THE LOW-ELEVATIONS WITH THE ADDITIONAL FORCING  
FROM THE DEVELOPING 700MB LOW AND WARM AIR ADVECTION AT 700MB AS  
WARMER AIR GETS DRAWN INTO THE 700MB LOW. FORECAST SOUNDINGS FROM  
THE RAP ONCE AGAIN SUGGEST AN INVERTED-V PROFILE ACROSS THE SOUTHERN  
LARAMIE RANGE, WITH INVERTED-V SOUNDINGS DOWNWIND OF THE MOUNTAINS  
INTO THE LOWER-ELEVATIONS. ADDITIONALLY, RAP SOUNDINGS SUGGEST AROUND  
40KTS OF SHEAR, LEADING TO A LOW-CAPE HIGH-SHEAR ENVIRONMENT SETTING  
UP FOR THURSDAY. STORMS THAT COME OFF THE LARAMIE RANGE MAY STRUGGLE  
TO SUSTAIN THEMSELVES AND MAY COLLAPSE SHORTLY AFTER MOVING OFF THE  
RANGE. THEREFORE, GUSTY SHOWERS AND STORMS ARE POSSIBLE ONCE AGAIN  
TOMORROW ALONG AND JUST EAST OF THE SOUTH LARAMIE RANGE.  
 
BROAD, UPPER-LEVEL RIDGING CONTINUES INTO THE DAY FRIDAY, LEADING TO  
WEAK SUBSIDENCE ACROSS THE REGION AND WARMING TEMPERATURES. AN  
INCOMING TROUGH OFF THE WEST COAST WILL BE THE NEXT BIG WEATHER  
MAKER FOR THE REGION (SEE LONG TERM DISCUSSION). WITH THE BROAD  
RIDGE ONCE AGAIN FRIDAY, MULTIPLE 500MB VORTICITY LOBES WILL LIKELY  
MOVE OVERHEAD, LEADING TO THE POTENTIAL FOR SHOWERS AND STORMS IN  
THE AFTERNOON HOURS. FORECAST SOUNDING FROM THE NAM SUGGEST A  
SIMILAR SET UP, WITH INVERTED-V SOUNDING PRESENT ONCE MORE,  
ESPECIALLY ACROSS THE NEBRASKA PANHANDLE. NAM SBCAPE VALUES ARE  
QUITE HIGH AROUND 1000 J, BUT THIS IS STILL A FEW DAYS OUT AND THE  
NAM TENDS TO HAVE A MOISTURE BIAS THAT COULD ARTIFICIALLY INCREASE  
SBCAPE VALUES. FRIDAY IS ALSO STILL A FEW DAYS AWAY AND WITH THE  
POTENTIAL SEVERE EVENT TODAY, MORE ATTENTION WILL BE GIVEN TO THE  
FRIDAY FORECAST ONCE TODAY'S THREAT IS OVER WITH, LIKELY WITH  
TONIGHT'S FORECAST UPDATE.  
 

 
   
LONG TERM /SATURDAY THROUGH WEDNESDAY/
 
 
ISSUED AT 204 PM MDT WED MAY 21 2025  
 
A SLOW MOVING TROUGH WILL PUSH THROUGH THE  
INTERMOUNTAIN WEST THIS WEEKEND CREATING SOME PRECIPITATION CHANCES  
ACROSS THE FORECAST AREA. SATURDAY, A 700MB LOW WILL PUSH INTO THE  
INTERMOUNTAIN WEST FROM THE MORNING AND THROUGH THE AFTERNOON. THIS  
LOW WILL PROVIDE ENOUGH SYNOPTIC SUPPORT FOR WIDESPREAD RAINFALL AND  
HAVE A FEW VORTICITY MAXIMA'S DEVELOP TO CREATE POCKETS OF ENHANCED  
RAINFALL IN A FEW AREAS. FOR THE MESOSCALE FORCING, A COLD FRONT  
DEVELOPS AND MOVES ACROSS THE AREA IN THE AFTERNOON AND EVENING  
CREATING A LINE OF HEAVY RAIN AS IT MOVES THROUGH. HOWEVER, THE  
CONVECTIVE THUNDERSTORM ACTIVITY LOOKS TO BE LIMITED DUE TO THE  
OVERCAST CLOUDY CONDITIONS LIMITING THE CAPE POTENTIAL FOR SATURDAY.  
THE GLOBAL MODELS STILL WANT TO THROW A BLANKET OF 1200 CAPE FOR THE  
AFTERNOON BUT THAT MAY BE A LITTLE OVERDONE GIVEN THE CLOUDY  
CONDITIONS. SUNDAY, THE MID LEVEL LOW WILL SLOWLY START TO PUSH OUT  
OF OUR FORECAST AREA CONTINUING THE PRECIPITATION CHANCES THROUGH  
SUNDAY EVENING WITH SOME RESIDUAL SYNOPTIC SUPPORT FROM THE  
DEPARTING LOW.  
 
NEXT WEEK, MODELS ARE STILL A LITTLE DIVERGENT ON HOW AMPLIFIED THIS  
TRANSIENT RIDGE THAT SETS UP IS. BUT THE AREA LOOKS TO START TO DRY  
OUT MONDAY INTO TUESDAY TO GIVE US A BRIEF BREAK OF PRECIPITATION  
BEFORE ANOTHER SYSTEM MOVES THROUGH THE AREA MID TO LATE NEXT WEEK.  
 

 
   
AVIATION /12Z TAFS THROUGH 12Z FRIDAY/
 
 
ISSUED AT 500 AM MDT THU MAY 22 2025  
 
WEAKENING STORM SYSTEM ACROSS THE NORTHERN PLAINS WILL ACCELERATE  
EASTWARD TONIGHT. UPPER LEVEL RIDGING WILL BUILD OVER WYOMING FOR  
THURSDAY WITH ANOTHER ROUND OF THUNDERSTORMS POSSIBLE LATE THURSDAY  
EVENING AND OVERNIGHT AS A POTENT UPPER LEVEL DISTURBANCE MOVES  
NORTHEAST OVER THE AREA.  
 
HAZARDS/WEATHER TRENDS: VFR CONDITIONS EXPECTED OVER THE NEXT 18  
HOURS WITH CLEAR SKIES AND LIGHT/VARIABLE WINDS EXPECTED THROUGH 15Z  
THURSDAY. WINDS ARE FORECAST TO SHIFT INTO THE SOUTH OR SOUTHEAST  
FOR MOST TERMINALS BY 18Z THURSDAY. ANOTHER ROUND OF THUNDERSTORMS  
ARE POSSIBLE FOR KLAR, KBFF, KAIA, KCDR, AND KCYS AFTER 00Z FRIDAY.  
THESE THUNDERSTORMS MAY LINGER PAST 06Z FRIDAY FOR KCDR AND KAIA AND  
MAY CONTAIN HAIL AND LOCALLY GUSTY WINDS. THIS IS A CONDITIONAL RISK  
WITH PROBABILITIES BETWEEN 20% TO 40%. THESE THUNDERSTORMS SHOULD  
MOVE EAST OF KCDR AND KAIA BY 08Z FRIDAY.  
 

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

 
 

 
 
SHORT TERM...AM  
LONG TERM...MM  
AVIATION...TJT  
 
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