508  
FXUS65 KCYS 022355  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
555 PM MDT WED SEP 2 2015  
   
UPDATE
 
 
ISSUED AT 554 PM MDT WED SEP 2 2015  
 
WENT AHEAD AND CANCELLED THE RED FLAG WARNINGS EARLY AS LOW LEVEL  
HUMIDITIES ARE ON THE INCREASE AND WINDS HAVE BEEN DECREASING OVER  
THE PAST COUPLE HOURS. UPDATES HAVE BEEN SENT.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH FRIDAY)  
ISSUED AT 151 PM MDT WED SEP 2 2015  
 
A FEW SHOWERS OR THUNDERSTORMS WILL BE POSSIBLE THROUGH EARLY  
EVENING MAINLY ALONG AND WEST OF THE THE LARAMIE RANGE BUT THE  
OVERALL CHANCE FOR PRECIPITATION IS LOW ACROSS THE FORECAST AREA.  
THAT WILL CHANGE TOMORROW AS A LATE SEASON PUSH OF MONSOON MOISTURE  
MOVES ACROSS THE REGION. CHANCES FOR THUNDERSTORMS WILL INCREASE  
WITH THE MAIN THREAT FOR PRECIPITATION LATE AFTERNOON AND EVENING  
IN ASSOCIATION WITH SHORTWAVE ENERGY. MODELS DO VARY A BIT IN THE  
TIMING AND LOCATION OF THE SHORTWAVE SO TOUGH TO PINPOINT THE  
HIGHEST POTENTIAL BUT CONFIDENT MUCH OF THE FORECAST AREA WILL  
RECEIVE SOME MEASURABLE RAIN. DO NOT SEE A SEVERE THUNDERSTORM  
THREAT BASED ON MODEL PROGGED SOUNDINGS BUT THE SOUNDINGS ARE  
TROPICAL IN NATURE SUCH THAT HEAVY RAIN IS LIKELY WITH A FEW  
THUNDERSTORMS. FORTUNATELY IT LOOKS LIKE STORM WILL MOVE FAST ENOUGH  
SUCH THAT THE FLASH FLOOD THREAT WILL BE ON THE LOW SIDE...ALBEIT  
HIGHER THAT CLIMATOLOGY.  
 
SHORTWAVE ENERGY WILL SHIFT NORTHEAST OF THE FORECAST AREA THURSDAY  
NIGHT WITH SHOWERS AND THUNDERSTORMS ENDING AFTER MIDNIGHT. LATE  
THURSDAY NIGHT THROUGH FRIDAY MORNING SHOULD BE DRY ACROSS THE  
AREA BUT CONTINUED MOIST SOUTHWEST FLOW ALOFT WILL BRING ANOTHER  
CHANCE FOR AFTERNOON AND EVENING THUNDERSTORMS WITH THE MAIN  
CHANCES OVER SOUTHEAST WYOMING. DO NOT SEE ANY THREAT FOR SEVERE  
THUNDERSTORMS BUT AGAIN A FEW HEAVY RAINERS WILL BE POSSIBLE.  
   
LONG TERM
 
(FRIDAY NIGHT THROUGH WEDNESDAY)  
ISSUED AT 1251 PM MDT WED SEP 2 2015  
 
LATEST MEDIUM RANGE MODEL GUIDANCE IS IN GOOD AGREEMENT THIS WEEKEND  
PROGGING THE NORTHWEST CONUS UPPER LOW TO LIFT NORTHEAST AND WEAKEN  
THROUGH IDAHO AND MONTANA ON SUNDAY. MOIST SOUTHWEST FLOW ALOFT AND  
ACCOMPANYING SHORTWAVE WILL PRODUCE WIDELY SCATTERED SHOWERS AND  
TSTORMS FRIDAY NIGHT AND SATURDAY...FOLLOWED BY DRIER AND WINDIER  
CONDITIONS SATURDAY NIGHT AND SUNDAY. A TIGHT PRESSURE GRADIENT  
PRECEDING A PACIFIC FRONT WILL PRODUCE THE GUSTY WESTERLY WINDS. THE  
FRONT WILL PASS THROUGH SUNDAY AFTERNOON WITH COOLER...MORE SEASONAL  
TEMPERATURES FOR THE UPCOMING WEEK. THERE ARE SOME MODEL DIFFERENCES  
BY THE MIDDLE OF NEXT WEEK WITH THE GFS DIGGING A UPPER TROUGH AND  
SURFACE FRONT SOUTH INTO THE INTERMOUNTAIN WEST. THE PREFERRED ECMWF  
AND ENSEMBLES MAINTAIN A DRY ZONAL FLOW ALOFT.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)  
ISSUED AT 442 PM MDT WED SEP 2 2015  
 
VFR CONDITIONS THIS EVENING WITH WINDS EASING NEAR SUNSET. GOING  
TO SEE AN INCREASE IN MONSOONAL MOISTURE THURSDAY THAT WILL BRING  
INCREASED CHANCES FOR SHOWERS AND THUNDERSTORMS FOR AREAS WEST OF  
THE LARAMIE RANGE. TIMING LOOKS TO BE AFTER 20Z-21Z FOR KRWL AND  
KLAR. MAYBE A LITTLE LATER FOR AIRPORTS EAST OF THE LARAMIE RANGE.  
WILL TRY TO NAIL DOWN TIMING A LITTLE BETTER ON UPCOMING TAF  
ISSUANCES.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 230 PM MDT WED SEP 2 2015  
 
THE THREAT OF CRITICAL FIRE CONDITIONS WILL DECREASE TOMORROW WITH  
ONLY MINIMAL CONCERNS THE REST OF THIS WEEK AND WEEKEND. SUBTROPICAL  
MONSOON MOISTURE WILL MOVE INTO THE AREA TOMORROW WITH SCATTERED  
SHOWERS AND THUNDERSTORMS DEVELOPING IN THE AFTERNOON AND EVENING.  
MUCH OF SOUTHEAST WYOMING AND POTENTIALLY THE NEBRASKA PANHANDLE  
WILL BE AFFECTED BY SHOWERS AND THUNDERSTORMS. A FEW STORMS ARE  
EXPECTED TO PRODUCE HEAVY RAIN. THE ONLY POTENTIAL FIRE WEATHER  
CONCERN THURSDAY IS INTO EAST CENTRAL WYOMING WHERE HUMIDITY  
VALUES MAY DIP TO AROUND 15 PERCENT BEFORE THE MONSOON MOISTURE  
ARRIVES. FORTUNATELY WINDS SHOULD BE ON THE LIGHT SIDES IN THE 5  
TO 10 MPH RANGE WITH ONLY A FEW GUSTS OF 15 TO 20 MPH INTO WESTERN  
CONVERSE COUNTY.  
 
CHANCES FOR SHOWERS AND THUNDERSTORMS WILL CONTINUE RIGHT THROUGH  
THE WEEKEND AS MOISTURE SOUTHWEST FLOW ALOFT REMAINS IN PLACE. THE  
MODELS DO SHOW A STRONGER WEATHER SYSTEM MOVING ACROSS THE NORTHERN  
ROCKIES SUNDAY WHICH SHOULD BRING STRONGER WINDS AND COOLER AIR TO  
THE AREA.  
 

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

 
 

 
 
UPDATE...GCC  
SHORT TERM...SML  
LONG TERM...MAJ  
AVIATION...GCC  
FIRE WEATHER...SML  
 
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