057  
FXUS65 KCYS 260014  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
614 PM MDT SAT OCT 25 2014  
   
UPDATE
 
 
ISSUED AT 545 PM MDT SAT OCT 25 2014  
 
LATEST WATER VAPOR LOOP WAS SHOWING THE UPPER LEVEL TROF MOVING  
INTO THE PACIFIC NORTHWEST WITH THE SURFACE FRONT EXTENDING FROM  
NORTHERN WYOMING INTO CENTRAL MONTANA. AHEAD OF THIS  
BOUNDARY...THE LOW LEVEL FLOW IS EXPECTED TO INCREASE AS THE NIGHT  
WEARS ON. IN FACT...LATEST AIRCRAFT DATA WAS SHOWING 40 TO 45KT  
SOUTHWEST WINDS ALREADY MOVING OUT OF UTAH. THIS APPEARS TO BE  
SETTING THE STAGE FOR HIGH WINDS 50 TO 60 MPH ACROSS ARLINGTON  
LATE TONIGHT AND POSSIBLY VEDAUWOO AND THE FOOTHILLS. AS A  
RESULT...WE ARE PLANNING ON ISSUING A HIGH WIND WARNING FOR AT  
LEAST THE ARLINGTON AREA AT THIS TIME WITH THE THREAT BEGINNING  
AROUND 08Z OR SO. NOT CONFIDENT ENOUGH ABOUT VEDAUWOO...DUE TO THE  
POTENTIAL FOR SOME CLOUD COVER FROM THE UPSLOPE FLOW WHICH MAY  
LIMIT MIXING. HOWEVER...WE WILL EVALUATE LATER THIS EVENING.  
 

 
   
SHORT TERM
 
(TONIGHT THROUGH MONDAY NIGHT)  
ISSUED AT 300 PM MDT SAT OCT 25 2014  
 
AFTERNOON WATER VAPOR IMAGERY LOOP SHOWED A HIGH AMPLITUDE RIDGE  
ENCOMPASSING MOST OF THE GREAT PLAINS AND FRONT RANGE. THE 20Z  
REGIONAL SURFACE ANALYSIS DEPICTED HIGH PRESSURE FROM THE DAKOTAS  
TO NEBRASKA. A WARM FRONT EXTENDED SOUTHEAST FROM A LOW NEAR SHERIDAN  
WYOMING THROUGH THE SOUTHWEST CORNER OF THE NEBRASKA PANHANDLE. SUNNY  
SKIES PREVAILED WITH ABOVE NORMAL TEMPERATURES...RANGING FROM THE  
MID 60S TO LOWER 80S. WINDS WERE LIGHT SOUTHEASTERLY ACROSS WESTERN  
NEBRASKA...WHILE GUSTY SOUTHWESTERLY WINDS WERE OBSERVED THROUGHOUT  
SOUTHEAST WYOMING.  
 
THE LATEST NUMERICAL MODEL GUIDANCE CONTINUES THE PROGRESSIVE LARGE  
SCALE PATTERN. THE GREAT PLAINS UPPER RIDGE SLIDES EAST THROUGH  
THE MIDWEST AND EASTERN CONUS THROUGH MONDAY. MEANWHILE...A EASTERN  
PACIFIC UPPER TROUGH MOVES THROUGH THE PACIFIC NORTHWEST AND NORTHERN  
ROCKIES SUNDAY...THEN DIGS SOUTH AND EAST ACROSS WYOMING AND THE  
NORTHERN GREAT PLAINS MONDAY. A STRONG PACIFIC COLD FRONT WILL PRECEDE  
THE TROUGH...PASSING THROUGH THE CWA SUNDAY. AHEAD OF THE FRONT...THE  
SURFACE PRESSURE GRADIENT TIGHTENS WITH 700MB WINDS PEAKING AROUND  
50 KT JUST BELOW THE INVERSION EARLY SUNDAY MORNING OVER CARBON  
AND ALBANY COUNTIES. THE CRAIG-CASPER GRADIENT PEAKS AROUND 50M DURING  
THIS TIME. SUSTAINED WESTERLY WINDS OF 35 TO 45 MPH WITH GUSTS TO  
AROUND 55 MPH WILL DEVELOP BETWEEN LARAMIE AND RAWLINS. THE GRADIENT  
AND WINDS DECREASE AFTER THE FRONTAL PASSAGE SUNDAY AFTERNOON. IT  
WILL BE ANOTHER UNSEASONABLY MILD AFTERNOON EAST OF THE LARAMIE  
RANGE SUNDAY...WITH COOLER TEMPERATURES SPREADING INTO THE WEST  
BEHIND THE COLD FRONT.  
 
PRECIPITATION-WIDE...SHOWERS DEVELOP SUNDAY MORNING AND AFTERNOON OVER  
THE SNOWY/SIERRA MADRE RANGES. THE PRECIPITATION PATTERN SPLITS  
SUNDAY NIGHT INTO TWO AREAS...ONE ACROSS FAR SOUTHERN/SOUTHEAST  
WYOMING AND SOUTHERN NEBRASKA PANHANDLE ASSOCIATED WITH A SURFACE  
LOW...AND THE OTHER ACROSS NORTHEAST AND EAST CENTRAL WYOMING.  
SNOW LEVELS WILL DROP TO AROUND 7000 FT BY MONDAY MORNING.  
PRECIPITATION AMOUNTS WILL GENERALLY BE ON THE LIGHT SIDE...WITH  
A FEW INCHES OF SNOW POSSIBLE OVER THE SNOWY/SIERRA MADRE RANGES.  
 
MONDAY WILL TURN OUT TO BE A COOL BREEZY DAY AS THE UPPER TROUGH  
PASSES OVERHEAD. LINGERING RAIN/SNOW SHOWERS ACROSS THE NORTH AND  
EAST PARTS OF THE CWA WILL END BY AFTERNOON WITH PARTIAL CLEARING.  
THE PRESSURE GRADIENT INCREASES MONDAY WITH GUSTY NORTHWEST WINDS.  
HIGH TEMPERATURES MONDAY WILL BE 20-25 DEGREES COOLER THAN  
SUNDAY...MORE TYPICAL OF LATE OCTOBER. UNDER MOSTLY CLEAR SKIES  
AND DIMINISHING WINDS...LOWS MONDAY NIGHT WILL PLUMMET INTO THE  
UPPER TEENS TO UPPER 20S.  
   
LONG TERM
 
(TUESDAY THROUGH SATURDAY)  
ISSUED AT 200 PM MDT SAT OCT 25 2014  
 
MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT THROUGH THE PERIOD. THE  
BEST CHANCE FOR ANY PCPN WOULD BE TUE OR WED BENEATH QUASI-ZONAL FLOW  
ALOFT AS A POSITIVE TILT SHORTWAVE MOVES OVER THE NORTHERN ROCKIES.  
GFS AND ECMWF BOTH SHOW THE BEST FORCING TO THE NORTH OF THE CWA  
THOUGH...SO HAVE MAINTAINED A DRY FORECAST FOR THIS TIME RANGE. IT  
WILL REMAIN COOL THROUGH TUE WITH GFS H7 TEMPERATURES STILL IN THE  
SINGLE DIGITS BELOW 0C. SUBSIDENCE AND WARMING TEMPERATURES ALOFT  
BENEATH AN AMPLIFYING UPPER RIDGE SHOULD YIELD A WARMING TREND WITH  
CONTINUED DRY CONDITIONS THROUGH THE END OF THE WORK WEEK. A WEAK  
SURFACE COOL FRONT IS LIKELY TO INTERRUPT THIS TREND THU. LATE IN  
THE PERIOD...THE MODELS AGREE ON A STRONG TROUGH DIGGING INTO THE  
GREAT BASIN. AT THIS TIME...IT APPEARS ANY ASSOCIATED PCPN SHOULD  
BE JUST BEYOND THE END OF THE EXTENDED FORECAST PERIOD.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)  
ISSUED AT 545 PM MDT SAT OCT 25 2014  
 
FRONTAL BOUNDARY IN WESTERN WYOMING IS PROGGED TO PUSH EAST  
THROUGH CENTRAL AND NORTHERN WYOMING OVERNIGHT AND THROUGH THE  
PANHANDLE IN THE MORNING. AHEAD OF THIS FRONT...IT WILL BE QUITE  
BREEZY IN RWL OVERNIGHT WITH SPEEDS GENERALLY HANGING AROUND 15 TO  
20KTS. HIGHER WIND SPEEDS WILL BEGIN MIXING DOWN DURING THE  
LATE MORNING INTO THE EARLY AFTERNOON ACROSS THE RWL...LAR AND CYS  
TAF SITES. SOME LOWER CLOUDS MAY DEVELOP OVER THE SUMMIT DURING  
LATE MORNING INTO THE AFTERNOON...BUT LAR AND CYS SHOULD SEE GOOD  
DOWNSLOPE FLOW WHICH WILL LIMIT THE POTENTIAL FOR CLOUD COVER AND  
ALLOW FOR GUSTY WEST WINDS AT SPEEDS OVER 25KTS.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 200 PM MDT SAT OCT 25 2014  
 
WARM...BREEZY AND DRY CONDITIONS WILL CONTINUE THIS AFTERNOON FOR  
AREAS ALONG AND JUST EAST OF THE LARAMIE RANGE. LOWEST HUMIDITIES  
WILL BOTTOM OUT BETWEEN 10 AND 15 PERCENT. FORTUNATELY...GUSTY WINDS  
WILL REMAIN WEST OF THE LARAMIE RANGE WHERE FUELS ARE NOT SUPPORTIVE  
OF RAPID FIRE GROWTH. STRONGER WINDS WILL DEVELOP SUNDAY AND MONDAY  
AS A COLD FRONT AND UPPER LEVEL TROUGH MOVE FROM WEST TO EAST. MUCH  
COOLER TEMPERATURES WILL INCREASE HUMIDITIES AND PROVIDE CHANCES FOR  
RAIN AND SNOW SHOWERS. SEASONABLY COOL AND DRY WEATHER WILL PREVAIL  
MID WEEK FOLLOWED BY A WARMING TREND FOR THE END OF THE WEEK.  
 

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

 
 

 
 
UPDATE...REC  
SHORT TERM...JAMSKI  
LONG TERM...HAMMER  
AVIATION...REC  
FIRE WEATHER...JAMSKI  
 
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