762  
FXUS65 KCYS 241731  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
1130 AM MDT SUN JUN 24 2018  
   
SHORT TERM
 
(TODAY THROUGH TUESDAY)  
ISSUED AT 223 AM MDT SUN JUN 24 2018  
 
RADAR SHOWED A BAND OF SHOWERS EXTENDING FROM NORTHERN COLORADO  
THROUGH SOUTHEASTERN WYOMING AND INTO THE WESTERN NEBRASKA  
PANHANDLE. TO THE NORTH AND WEST, REGIONAL MOSAICS SHOWED A CLEAR  
SPIN TO THE PRECIP WITH THE CENTER OF AN AREA OF LOW PRESSURE  
LOCATED NEAR CASPER. THIS SHOWER ACTIVITY WAS ASSOCIATED A  
SHORTWAVE TROUGH MOVING IN FROM THE WESTERN CONUS. 500 MB HEIGHT  
FIELDS SHOWED THE MAJORITY OF THE TROUGH STILL TO THE WEST OVER  
IDAHO AND MONTANA. THIS SYSTEM WILL DIVE TO THE EAST SOUTHEAST  
THROUGH THE MORNING HOURS FIRING OFF ADDITIONAL SHOWERS AND STORMS  
AS LIFT OVERSPREADS A MOIST LOW LEVEL AIRMASS.  
 
THE FLOOD WATCH FOR CONVERSE AND NIOBRARA COUNTIES IN WYOMING  
CONTINUES UNTIL MIDNIGHT TONIGHT AS MORE SHOWER AND STORM ACTIVITY  
IS EXPECTED TO BRING HEAVY RAINFALL. LATEST AUTOMATED GAUGES AND  
RADAR ESTIMATES SHOW A WELL DEFINED BAND OF HEAVIER QPE NEAR 0.5  
INCHES ALONG THE SOUTHERN PARTS OF THE WATCH AREA RADAR AND CAMS  
CONTINUE TO SUGGEST THAT SEVERAL MORE ROUNDS OF SHOWERS AND  
THUNDERSTORMS THAT WILL MOVE OVER THE WATCH AREA TODAY. THIS  
ADDITIONAL PRECIP MAY CAUSE SOME FLOODING GIVEN THE SATURATED  
GROUND.  
 
SHOWERS AND STORMS WILL BEGIN TO DISSIPATE AND MOVE TO THE EAST  
LATER THIS EVENING THROUGH EARLY MONDAY BRINGING A TEMPORARY END  
TO THE WET AND ACTIVE WEATHER. WITH DRYING DOWNSLOPE WINDS,  
TEMPERATURES WILL BE NEAR NORMAL BUT WILL BEGIN AN UPWARD TREND  
INTO THE MIDDLE OF THE WEEK.  
 
   
LONG TERM
 
(TUESDAY NIGHT THROUGH SATURDAY)  
ISSUED AT 325 AM MDT SUN JUN 24 2018  
 
MODELS ARE IN MUCH BETTER AGREEMENT THROUGH NEXT WEEK COMPARED TO  
24 HOURS AGO. ALL MODELS SHOW A NEARLY ZONAL PATTERN INTO  
WEDNESDAY AS THE MAIN JET LIFT NORTH OF THE REGION OVER MONTANA  
AND THE DAKOTAS. EXPECT MAINLY DRY CONDITIONS THROUGH THURSDAY AS  
THE UPPER LEVEL FLOW BACKS MORE INTO THE SOUTHWEST OVER TIME AHEAD  
OF THE NEXT PACIFIC UPPER LEVEL TROUGH. DO NOT SEE MUCH IN THE WAY  
OF PRECIPITATION DURING THIS TIME, ALTHOUGH A FEW ISOLATED  
THUNDERSTORMS ARE POSSIBLE LATE WEDNESDAY AFTERNOON/EVENING AS A  
WEAK FRONT/CONVERGENCE BOUNDARY SETS UP NEAR THE LARAMIE RANGE.  
THE PRIMARY DIFFERENCE COMPARED TO YESTERDAY IS ON THURSDAY, AS  
MODELS ARE MUCH DRIER COMPARED TO LAST NIGHTS 00Z RUN. KEPT ANY  
MENTION OF SHOWERS AND THUNDERSTORMS FAR TO THE NORTH OF I-80, AS  
DRY SOUTHWEST FLOW IS EXPECTED FOR MOST OF SOUTHEAST WYOMING AND  
THE SOUTHERN NE PANHANDLE. MODELS REMAIN IN GOOD AGREEMENT ON  
FRIDAY AND SATURDAY AS A PACIFIC COLD FRONT MOVES THROUGH THE AREA  
AND STALLS NEAR THE COLORADO BORDER. HOWEVER, THIS SOLUTION IS  
DIFFERENT COMPARED TO MOST 00Z MODEL RUNS FROM YESTERDAY, WHICH  
SHOWED VERY DRY AIR OVER THE AREA. THE ECMWF SEEMS TO BE THE MOST  
CONSISTENT, SO INCREASED POP BETWEEN 20 TO 45 PERCENT MAINLY NORTH  
OF I-80 FROM FAR EASTERN WYOMING TO WESTERN NEBRASKA. MODELS ALSO  
SHOW THE POSSIBILITY OF MCS DEVELOPMENT ACROSS WESTERN NEBRASKA  
LATE FRIDAY AS THE LLVL JET STRENGTHENS AHEAD OF A WEAK SHORTWAVE.  
CONTINUED THE TREND OF RELATIVELY HIGH POP THROUGH SATURDAY WITH  
ALL MODELS SHOWING UNSETTLED WEATHER AND COOLER TEMPERATURES  
RETURNING TO THE REGION. OVERALL, TEMPERATURES SHOULD BE WELL  
ABOVE NORMAL FOR THIS TIME OF THE YEAR THROUGH THE FORECAST  
PERIOD. THURSDAY MAY BE THE WARMEST DAY OF THE YEAR, SO FAR, WITH  
700MB TEMPERATURES PUSHING 20C TO 23C DEGREES DURING THE  
AFTERNOON. THIS MAY RESULT IN HIGHS WELL INTO THE 90S IN MOST  
AREAS WITH EVEN 100-105 OVER THE LOWER ELEVATIONS NEAR THE  
COLORADO BORDER.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z MONDAY MORNING)  
ISSUED AT 1130 AM MDT SUN JUN 24 2018  
 
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ASSOCIATED WITH A UPPER  
LOW PRESSURE SYSTEM WILL DEVELOP AND GRADUALLY SHIFT WEST TO EAST  
THIS AFTERNOON AND EARLY EVENING. CONFIDENCE NOT HIGH ENOUGH FOR  
TEMPO PERIODS OF CONVECTION, BUT WILL MAINTAIN VCSH/VCTS IN TAFS.  
THE EXCEPTION WILL BE RAWLINS WHERE SLIGHTLY DRIER MORE STABLE AIR  
WILL PRECLUDE SHOWER DEVELOPMENT. THERE WILL BE BRIEF MVFR VIS/CIG  
IN VICINITY OF THE HEAVIER CONVECTION.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 223 AM MDT SUN JUN 24 2018  
 
AN AREA OF LOW PRESSURE AND ASSOCIATED COLD FRONT WILL BRING  
NUMEROUS SHOWERS AND THUNDERSTORMS THROUGH EARLY MONDAY. WETTING  
RAIN AND HIGHER RELATIVE HUMIDITY WILL KEEP FIRE DANGER LOW  
THROUGH MID WEEK. THINGS WILL BEGIN TO WARM UP AND DRY OUT  
NEXT WEEK AS RIDGING TAKES HOLD.  
 

 
   
CYS WATCHES/WARNINGS/ADVISORIES
 
 
WY...FLOOD WATCH THROUGH THIS EVENING FOR WYZ101>103.  
 
NE...NONE.  

 
 

 
 
SHORT TERM...ADL  
LONG TERM...TJT  
AVIATION...MAJ  
FIRE WEATHER...ADL  
 
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