213  
FXUS65 KCYS 282237  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
337 PM MST SAT FEB 28 2015  
   
SHORT TERM
 
(THIS EVENING THROUGH MONDAY NIGHT)  
ISSUED AT 340 PM MST SAT FEB 28 2015  
 
A FEW SNOW FLURRIES WILL LINGER ALONG THE EASTERN FRINGES OF THE  
SOUTHERN LARAMIE RANGE THROUGH THIS AFTERNOON. THE MAIN CHANCES  
FOR ACCUMULATING SNOW WILL OCCUR THIS EVENING AND INTO THE  
OVERNIGHT AS SUBTLE SHORTWAVE FEATURES MOVE INTO SOUTHEAST WYOMING  
FROM COLORADO...AND ELEVATED WARM ADVECTION DEVELOPS. THE BEST  
CHANCES FOR SNOW ACCUMULATIONS OUTSIDE OF THE MOUNTAINS WILL BE  
ALONG AND NEAR THE COLORADO BORDER BUT EVEN THERE ANY  
ACCUMULATIONS WILL BE MINIMAL AND GENERALLY LESS THAN ONE INCH.  
KEPT SLIGHT CHANCES GOING INTO EAST CENTRAL WYOMING AND THE  
NORTHERN NEBRASKA PANHANDLE...BUT IT IS LOOKING LESS LIKELY THAT  
ANY SNOW WILL OCCUR IN THOSE AREAS TONIGHT OR TOMORROW WITH THE  
BEST UPPER LEVEL FORCING WELL TO THE SOUTH.  
 
WILL HAVE TO KEEP AN EYE ON HOW THE UPPER LEVELS EVOLVE EARLY NEXT  
WEEK. MODELS SHOWING A CUT OFF LOW EJECTING NORTHEASTWARD OUT OF  
CALIFORNIA AS A KICKER DROPS SOUTH OFF THE PACIFIC NORTHWEST  
COAST. ECMWF INITIALLY KEEPS MUCH OF THE ENERGY OVER SOUTHCENTRAL  
WYOMING MONDAY INTO MONDAY NIGHT AND THEN QUICKLY PUSHES THINGS  
EASTWARD. THE GFS BRINGS THE MAIN ENERGY OVER FAR SOUTHEAST  
WYOMING AND PRODUCES HIGHER AMOUNTS OF PRECIPITATION THERE. NOT  
CONFIDENT IN EITHER SOLUTION AND SOMEWHAT SURPRISED HOW MUCH  
PRECIPITATION THE MODELS ARE PRODUCING GIVEN THE PLACEMENT OF THE  
UPPER LEVEL JET.  
 
DEPENDING ON THE NEXT ROUND OF MODEL RUNS...MAY NEED WINTER WEATHER  
HEADLINES FOR SOUTHCENTRAL WYOMING MONDAY THROUGH MONDAY NIGHT.  
LIGHT SNOW COULD START FALLING IN THAT AREA LATE SUNDAY NIGHT BUT  
AT THIS TIME IT APPEARS A MAJORITY OF THE SNOW WILL FALL AFTER 12Z  
MONDAY THROUGH MONDAY NIGHT ACROSS THIS AREA.  
   
LONG TERM
 
(TUESDAY THROUGH SATURDAY)  
ISSUED AT 315 PM MST SAT FEB 28 2015  
 
MAIN FORECAST CONCERN IN THE MEDIUM RANGE WILL BE THE CONTINUING  
WINTER WEATHER EVENT ON TUESDAY. MODELS ARE IN PRETTY GOOD  
AGREEMENT WITH THIS STORM SYSTEM...SHOWING A SECONDARY SHORTWAVE  
ALOFT DIGGING SOUTHWARD...WHICH WILL BE ASSOCIATED WITH THE  
ARCTIC AIRMASS MOVING INTO WYOMING EARLY TUESDAY MORNING. HIGH  
TEMPERATURES ON TUESDAY WILL LIKELY BE SIMILAR TO THE LOW  
TEMPERATURES MONDAY NIGHT...AND GENERALLY IN THE TEENS TO LOW 20S.  
TEMPERATURES WILL LOWER INTO THE SINGLE DIGITS AND LOW TEENS  
THROUGH THE AFTERNOON AS THE 1035MB ARCTIC HIGH AT THE SURFACE  
MOVES INTO THE AREA. KEPT A 60 PCT TO 80 PCT CHANCE OF SNOW FOR  
MOST OF SOUTHEAST WYOMING INTO TUESDAY EVENING FOR AN ADDITIONAL 1  
TO 3 INCHES OF SNOW ACCUMULATION. LOW TEMPERATURES TUESDAY NIGHT  
WILL BE TRICKY AND WILL GREATLY DEPEND ON THE EXTENT OF SURFACE  
SNOW COVER...DEPTH...AND IF SKIES CLEAR OUT OR NOT. CONSIDERING HOW  
PROGRESSIVE THE SYSTEM IS AS INDICATED BY MODELS...BELIEVE MOST OF  
THE FORECAST AREA AND ESPECIALLY NORTH OF I80...WILL HAVE CLEARING  
SKIES OVERNIGHT. LOW TEMPERATURES MAY APPROACH -15 TO -20 IN THE  
MORE SHELTERED VALLEYS ACROSS SOUTHEAST WYOMING WITH THE CENTER OF  
THE ARCTIC HIGH JUST EAST OF THE LARAMIE RANGE.  
ELSEWHERE...TEMPERATURES BETWEEN -5 TO -10 APPEAR LIKELY AT THIS  
TIME IF BROKEN TO OVERCAST CONDITIONS CONTINUE THROUGH MOST OF THE  
NIGHT.  
 
WEDNESDAY THROUGH THE END OF THE WEEK...SOME FLURRIES ARE POSSIBLE  
AS THE STORM SYSTEM EXITS THE REGION TO OUR SOUTH. WEDNESDAY WILL  
BE THE COLDEST DAY OF THE WEEK WITH HIGHS STRUGGLING TO REACH THE  
LOW TO MID TEENS. KEPT HIGHS A FEW DEGREES ABOVE MOS...BUT GAMBLING  
THAT THE WESTERLY WINDS AND MARCH SUNSHINE WILL RESULT IN  
TEMPERATURES A FEW DEGREES HIGHER THAN GUIDANCE.  
OTHERWISE...TEMPERATURES MAY BE STUCK IN THE SINGLE DIGITS THROUGH  
THE AFTERNOON. EITHER WAY...A WARMING TREND IS EXPECTED FOR THE  
REMAINDER OF THE WEEK AS THE STRONG EASTERN PACIFIC RIDGE EXPANDS  
EASTWARD A BIT INTO THE CENTRAL AND SOUTHERN ROCKY MOUNTAINS. DUE  
TO POTENTIAL SNOW COVER...DID KEEP TEMPERATURES LOWER THAN MOS  
THROUGH THE WEEK...WITH TEMPERATURES ABOVE GUIDANCE BY NEXT  
WEEKEND AS MOST OF THE SNOW SHOULD MELT BY THAT TIME. EXPECT HIGHS  
TO RETURN TO THE 40S TO AROUND 50 BY FRIDAY AND SATURDAY  
AFTERNOON.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH SUNDAY EVENING)  
ISSUED AT 231 PM MST SAT FEB 28 2015  
 
MVFR CIGS WILL CONTINUE FOR PORTIONS OF SOUTHEAST WYOMING AND  
WESTERN NEBRASKA LATE THIS AFTERNOON AND INTO THIS EVENING DUE TO  
LLVL UPSLOPE FLOW. ISOLATE SNOW FLURRIES WILL GENERALLY STAY NEAR  
KCYS INTO THIS EVENING...UNTIL LIGHT SNOW DEVELOPS FROM SOUTH TO  
NORTH ALONG THE I80 CORRIDOR BY 04Z LATE THIS EVENING. IFR  
CONDITIONS AND LIGHT SNOW ARE EXPECTED NEAR KLAR...KCYS...AND  
POSSIBLY KSNY AFTER 03Z. THE NORTHWARD EXTENT OF THIS SNOW SHOULD  
REMAIN SOUTH OF A LINE FROM KRWL TO KAIA. THIS SNOW SHOULD  
DIMINISH IN INTENSITY BY SUNDAY MORNING WITH A RETURN TO MVFR OR  
HIGHER CONDITIONS BY THE AFTERNOON.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 240 AM MST SAT FEB 28 2015  
 
C0LDER THAN NORMAL TEMPERATURES...AMPLE SURFACE MOISTURE FROM  
SNOWFALL...AND HIGH RELATIVE HUMIDITIES WILL PRECLUDE FIRE WEATHER  
CONCERNS THROUGH NEXT WEEK.  
 

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

 
 

 
 
SHORT TERM...SML  
LONG TERM...TJT  
AVIATION...TJT  
FIRE WEATHER...MAJ  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab WY Page
The Nexlab NE Page Main Text Page