021  
FXUS65 KCYS 261659  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
1059 AM MDT SAT JUL 26 2014  
   
SHORT TERM
 
(TODAY THROUGH MONDAY)  
ISSUED AT 235 AM MDT SAT JUL 26 2014  
 
TODAY...BY THIS AFTERNOON...NAM SHOWS A LOW LEVEL CONVERGENCE  
BOUNDARY SETTING UP FROM NEAR RAWLINS TO CHEYENNE. LOOKS LIKE ENOUGH  
CONVERGENCE ALONG THE BOUNDARY TO SPARK ISOLATED AFTERNOON  
THUNDERSTORMS FROM RAWLINS TO CHEYENNE...WITH GREATEST AREAL  
COVERAGE OVER THE SOUTHERN LARAMIE RANGE.  
 
TONIGHT...STORMS WILL DECREASE QUICKLY THIS EVENING WITH LOSS OF  
DAYTIME HEATING AND AS COOLER AIR BUILDS SOUTHWARD.  
 
SUNDAY...COMBINATION OF RIDGING ALOFT STRENGTHENING ALONG WITH THE  
LOW LEVELS BECOMING MORE STABLE...WILL PRODUCE A DRY DAY ASIDE FROM  
PERHAPS AN ISOLATED AFTERNOON THUNDERSTORM OVER OUR SOUTHERN  
MOUNTAINS. COOLER DAY WITH THICKNESS FALLS AND UPSLOPE EAST WINDS.  
 
SUNDAY NIGHT...ANOTHER COOL AND DRY OVERNIGHT PERIOD WITH LIGHT  
SOUTHEAST WINDS.  
 
MONDAY...CONTINUED RELATIVELY COOL FOR LATE JULY PER THICKNESS  
TRENDS. LOOKS LIKE ENOUGH LOW AND MID LEVEL MOISTURE RETURN TO  
PRODUCE ISOLATED LATE DAY THUNDERSTORMS ALONG AND WEST OF INTERSTATE  
25...DRY ELSEWHERE.  
   
LONG TERM
 
(TUESDAY THROUGH FRIDAY)  
ISSUED AT 235 AM MDT SAT JUL 26 2014  
 
MEDIUM RANGE MODEL GUIDANCE IS IN GOOD AGREEMENT WITH A LARGE SCALE  
UPPER RIDGE ENCOMPASSING MUCH OF THE WESTERN US THROUGH THE EXTENDED  
PERIOD. THIS FEATURE WILL DRIFT SLOWLY EASTWARD WITH TIME...BUT THE  
MAIN RIDGE AXIS SHOULD STAY WEST OF THE CWA THROUGH FRI. THIS KEEPS  
ACTIVE NORTHWEST FLOW ALOFT INTACT OVER THE CENTRAL ROCKIES THROUGH  
MOST OF THE NEXT WEEK...CONTRIBUTING TO FREQUENT CONVECTIVE CHANCES  
AND SEASONABLE TEMPERATURES. BEST CHANCE FOR WIDESPREAD PCPN APPEARS  
TO BE FROM TUE AFTN THROUGH WED WHEN BOTH THE GFS AND ECMWF BRING A  
SUBSTANTIAL WAVE OF 700-300 MILLIBAR MOISTURE ALONG THE EDGE OF THE  
RIDGE. THIS OCCURS ALONG WITH THE PASSAGE OF A LLVL COLD FRONT WHICH  
ENHANCES MOIST LLVL UPSLOPE OVER THE PLAINS. CANNOT RULE OUT MORE OF  
A PROLONGED/WIDESPREAD PCPN EVENT HERE WITH MANY LOCATIONS SEEING A  
DECENT AMOUNT OF RAINFALL. MIDLVL SUBSIDENCE STARTS TO SPREAD INTO  
THE AREA LATE IN THE WEEK. HOWEVER...LLVL UPSLOPE PERSISTS AND THE  
MODELS DO HANG ON TO AVAILABLE MID AND HIGH LEVEL MOISTURE. OPTED TO  
GO WITH ISOLATED POPS ON THU/FRI AFTN AND EVE. OVERALL TEMPERATURES  
THIS PERIOD SHOULD BE RIGHT AROUND SEASONABLE NORMS. MAIN CHALLENGE  
WILL BE HIGHS WED WITH THE ENHANCED LIKELIHOOD OF PLENTY OF CLOUDS  
AND POSSIBLE PCPN. TRENDED A FEW DEGREES BELOW CONSENSUS MOS FOR THE  
HIGH PLAINS GIVEN HIGH CONFIDENCE IN PERSISTENT LLVL UPSLOPE PLAYING  
A ROLE HERE.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z SUNDAY MORNING)  
ISSUED AT 1057 AM MDT SAT JUL 26 2014  
 
THUNDERSTORMS TODAY WILL BE CONFINED TO EXTREME SOUTHEAST WYOMING  
NEAR THE COLORADO BORDER. CONTINUED THE VCTS WORDING IN THE 18Z  
TAFS FOR KCYS AND KLAR THIS AFTERNOON. CHANCES ARE MOST LOCATIONS  
WILL STAY DRY TODAY. WITH WARM TEMPERATURES...WE WILL SEE GUSTY  
WINDS ONCE AGAIN THIS AFTERNOON THROUGH EARLY EVENING. VFR AT ALL  
LOCATIONS.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 235 AM MDT SAT JUL 26 2014  
 
HUMIDITIES WILL RANGE FROM 10 TO 15 PERCENT THIS AFTERNOON FROM  
RAWLINS TO DOUGLAS...THOUGH FORTUNATELY WITH MINIMAL WINDS.  
HUMIDITIES WILL INCREASE SUNDAY AND MONDAY LESSENING THE FIRE  
WEATHER CONCERNS.  
 

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

 
 

 
 
SHORT TERM...RUBIN  
LONG TERM...HAMMER  
AVIATION...CLAYCOMB  
FIRE WEATHER...RUBIN  
 
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