165  
FXUS65 KCYS 241806  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
1206 PM MDT THU APR 24 2014  
   
SHORT TERM
 
(TODAY THROUGH SATURDAY)  
ISSUED AT 338 AM MDT THU APR 24 2014  
 
FAIRLY TRANQUIL WEATHER PATTERN THROUGH MUCH OF THE SHORT TERM.  
SHORTWAVE IS CURRENTLY MOVING THROUGH EASTERN MONTANA WITH THE  
TROUGH AXIS JUST TO THE EAST OF THE CWA. MID AND HIGH LEVEL CLOUDS  
ARE CLEARING OUT NICELY IN THE SUBSIDENCE BEHIND THE SHORTWAVE.  
WINDS THIS AFTN WILL BE WEAKER THAN YESTERDAY AS THE FLOW ALOFT IS  
NOT AS STRONG. 1 KM AGL WINDS ARE GENERALLY 30-35 KTS OVER  
SOUTHEAST WY WITH 20-25 KTS OVER THE WESTERN NEBRASKA PANHANDLE.  
WITH THE DEEP MIXING THAT IS PROGGED...AFTN MIN RH VALUES WILL  
DROP TO 15-20 PERCENT OVER MUCH OF THE PLAINS. UPGRADED THE FIRE  
WEATHER WATCH TO A RED FLAG WARNING FOR FWZ 312 AND 313 (THE  
SOUTHERN NEBRASKA PANHANDLE) AS RH VALUES WILL BE AROUND 15  
PERCENT WITH WEST WIND GUSTS TO 25-30 MPH. WIND WILL DROP OFF  
NICELY TONIGHT AS A SHORTWAVE RIDGE MOVES OVERHEAD ALONG WITH A  
LOSS OF LLVL MIXING.  
 
FLOW ALOFT BECOMES MORE SOUTHWESTERLY ON FRI AS A LARGE SCALE  
TROUGH APPROACHES THE WEST COAST. SFC WINDS WILL TURN TO THE SOUTH  
AND SOUTHEAST LATE IN THE DAY. ABOUT 5 DEGREES OF WARMING IS  
EXPECTED AS 700MB TEMPS WARM TO AROUND 7C BY THE AFTN. WILL LIKELY  
BE GREATER COVERAGE OF AFTN CUMULUS AS LI VALUES FALL TO AROUND  
0C...HOWEVER SHOWER DEVELOPMENT WILL BE LIMITED. FLOW ALOFT BACKS  
TO THE SOUTH ON SAT AS DEEP UPPER TROUGH PUSHES INTO UTAH. ANOTHER  
WARM DAY WITH TEMPS ABOVE NORMAL. CLOUD COVER WILL BE ON THE  
INCREASE BY THE AFTN AS LARGE SCALE LIFT BEGINS TO SPREAD OVER THE  
REGION. INCLUDED A SLIGHT CHANCE OF TSTMS OVER THE CWA DURING THE  
AFTN WITH THE INCREASING UPPER LEVEL DIVERGENCE AND WEAK  
INSTABILITY. COLD FRONT DOES NOT MOVE OVER THE CWA UNTIL LATE SAT  
EVENING AND INTO SAT NIGHT.  
   
LONG TERM
 
(SATURDAY NIGHT THROUGH WEDNESDAY)  
ISSUED AT 338 AM MDT THU APR 24 2014  
 
SATURDAY NIGHT...TIGHTLY WRAPPED UPPER TROUGH PROGGED TO MOVE FROM  
THE FOUR CORNERS TO EAST CENTRAL OR SOUTHEAST COLORADO BY  
DAWN...WITH SURFACE LOW PRESSURE STRENGTHENING OVER WESTERN  
NEBRASKA. ALTHOUGH LOW LEVEL WINDS WILL REMAIN DOWNSLOPE  
NORTHWESTERLY OVER OUR COUNTIES...IT APPEARS THAT STRONG UPWARD  
VERTICAL MOTION WILL BE ABLE TO COMPENSATE FOR LOW LEVEL DOWNSLOPE...  
PRODUCING SCATTERED TO NUMEROUS SHOWERS...WITH GREATEST AREAL  
COVERAGE OVER OUR WESTERN COUNTIES. TEMPERATURES APPEAR COLD ENOUGH  
FOR A TRANSITION TO SNOW OVER MOST LOWER ELEVATIONS EXCEPT WESTERN  
NEBRASKA. ENOUGH DYNAMICAL LIFT FOR ISOLATED EVENING THUNDERSTORMS.  
 
SUNDAY...STRONG UPPER TROUGH SLOWLY PIVOTS OVER NORTHEAST COLORADO  
AND WESTERN NEBRASKA...PRODUCING PLENTY OF UPWARD VERTICAL MOTION  
AND SCATTERED TO NUMEROUS SHOWERS OVER OUR COUNTIES...MOST NUMEROUS  
OVER THE OROGRAPHICALLY FAVORED MOUNTAINS. WILL BE INTERESTING TO  
SEE OF TEMPERATURES WILL BE COLD ENOUGH FOR SNOW...THOUGH FOR NOW...  
PROGGED THICKNESSES SUGGEST MOSTLY RAIN EAST OF INTERSTATE 25.  
BLUSTERY AND RAW DAY WITH BRISK NORTH WINDS AND COLD TEMPERATURES.  
 
MONDAY...UPPER TROUGH PROGGED TO SLOWLY DRIFT EAST...THOUGH STILL  
PRODUCING AT LEAST SCATTERED SHOWERS OVER OUR COUNTIES IN THE  
WRAPAROUND PRECIPITATION BAND. CONTINUED COOL AND WINDY PER PROGGED  
GRADIENTS AND THICKNESSES.  
 
TUESDAY...ANOTHER WINDY AND UNSETTLED DAY AS THE UPPER TROUGH SLOWLY  
PROGRESSES EASTWARD...THOUGH WITH ANOTHER VORTICITY TAIL LIKELY  
AFFECTING OUR EASTERN COUNTIES IN THE AFTERNOON IN THE WRAPAROUND  
PRECIPITATION BAND.  
 
WEDNESDAY...MOST PRECIPITATION SHOULD COME TO AN END AS THE UPPER  
TROUGH PROGRESSES FURTHER EAST...AND BELIEVE THE ECMWF IS OVERDONE  
WITH RESPECT TO QPF...AND PREFER THE DRIER GFS QPF VERSION.  
CONTINUED COOL AND WINDY PER PROGGED GRADIENTS AND THICKNESSES.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z FRIDAY MORNING)  
ISSUED AT 1206 PM MDT THU APR 24 2014  
 
GUSTY WESTERLY WINDS WILL CONTINUE TO IMPACT THE FORECAST AREA  
TODAY WITH GUSTS OF 25 TO 35 KTS EXPECTED ACROSS SOUTHEAST  
WYOMING...AND 20 TO 30 KTS IN NEBRASKA. THE STRONGEST WINDS WILL  
OCCUR ALONG AND WEST OF THE LARAMIE RANGE. WINDS WILL EASE AFTER  
SUNSET...AND WILL VEER TO THE SOUTH-SOUTHWEST AND INCREASE FRIDAY  
MORNING. VFR CONDITIONS WILL PREVAIL...WITH A HIGH CLOUD DECK  
MOVING OVERHEAD FROM THE WEST.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 338 AM MDT THU APR 24 2014  
 
TEMPERATURES WILL WARM INTO THE 60S THIS AFTERNOON OVER THE  
WESTERN NEBRASKA PANHANDLE. WITH A DRY AIRMASS IN PLACE...MINIMUM  
AFTERNOON HUMIDITY VALUES WILL DROP TO AROUND 15 PERCENT. IN  
ADDITION...WEST WINDS WILL BE BREEZY IN THE AFTERNOON WITH GUSTS TO  
25-30 MPH. A RED FLAG WARNING IS IN EFFECT FOR THE SOUTHERN  
PANHANDLE THIS AFTERNOON. WARM TEMPERATURES WILL CONTINUE THROUGH  
SATURDAY WITH HUMIDITY VALUES DROPPING INTO THE 15-20 PERCENT  
RANGE. WINDS WILL BE WEAKER ON FRIDAY AND SATURDAY...SO ONLY AN  
ELEVATED FIRE WEATHER THREAT IS FORECASTED AT THIS TIME.  
 

 
   
CYS WATCHES/WARNINGS/ADVISORIES
 
 
WY...NONE.  
NE...RED FLAG WARNING UNTIL 7 PM MDT THIS EVENING FOR NEZ312-313.  
 

 
 

 
 
SHORT TERM...FINCH  
LONG TERM...RUBIN  
AVIATION...RJM  
FIRE WEATHER...FINCH  
 
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