636  
FXUS65 KCYS 222326  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
426 PM MST SUN JAN 22 2017  
   
SHORT TERM
 
(THIS EVENING THROUGH MONDAY NIGHT)  
ISSUED AT 320 PM MST SUN JAN 22 2017  
 
QUIET WEATHER THIS AFTERNOON WILL BEGIN TO CHANGE TONIGHT AS A  
PACIFIC STORM SYSTEM...CURRENTLY OFF THE OREGON  
COASTLINE...REDEVELOPS OVER WYOMING AND THE EASTERN PLAINS LATE  
TONIGHT. MODELS ARE IN MUCH BETTER AGREEMENT WITH THE POSITION AND  
MOVEMENT OF THE LOW PRESSURE SYSTEM WITH ONLY SOME SLIGHTLY  
DIFFERENCES IN TIMING AND HOW FAR SOUTH THE LOW DEVELOPS. MODELS  
ARE TRENDING MORE PROGRESSIVE WITH NO PARTICULAR SOLUTION SHOWING  
THE SYSTEM DIGGING SOUTHWARD AND SLOWING DOWN. THERE ARE SOME  
DIFFERENCES WITH THE ENSEMBLE RUNS WITH A NOTICEABLE HIGH STANDARD  
DEVIATION TO THE EAST...LIKELY SUGGESTING THE SYSTEM MAY MOVE EVEN  
FASTER THAN PREVIOUSLY THOUGHT. STARTED INCREASING POP THIS  
EVENING FOR CARBON AND PORTIONS OF ALBANY COUNTIES. DO NOT EXPECT  
THE STEADIER SNOWFALL TO ARRIVE UNTIL EARLY MONDAY MORNING ACROSS  
THE VALLEYS. WENT WITH A WINTER WEATHER ADVISORY FOR THE  
MOUNTAINS. CURRENT THINKING IS PERIODS OF SNOW WITH 3 HOUR LULLS  
IN BETWEEN INDIVIDUAL SHORTWAVES ARE EXPECTED WHICH MAY LIMITED  
OVERALL ACCUMULATION AND IMPACTS AS THE STORMS ENERGY TRANSLATES  
EASTWARD. WILL HAVE TO KEEP AN EYE ON THE VALLEYS OF CARBON COUNTY  
AND THE FOOTHILLS OF THE SNOWY RANGE FOR POTENTIAL TRAVEL IMPACTS  
TONIGHT THROUGH MONDAY NIGHT. AS OF RIGHT NOW...IT APPEARS  
ACCUMULATING SNOWFALL WILL COME IN BURSTS WITH LONG STRETCHES OF  
NO SNOW AT ALL.  
 
FURTHER EAST...THE COLD FRONT WILL PROVIDE ENOUGH LLVL LIFT FOR  
SNOW SHOWER ACTIVITY ON MONDAY AND MONDAY EVENING. THIS IS WHERE  
TIMING DIFFERENCES ARE KEY AS THE ECMWF SHOWS A QUICK INCH OR TWO  
OF SNOW ALONG THE I80 CORRIDOR MONDAY EVENING WHILE THE OTHER  
MODELS SHOW MAINLY DRY CONDITIONS WITH A BRIEF BAND OF RAIN/SNOW  
MOVING THROUGH DURING THE AFTERNOON. THE STORM WILL BEGIN TO  
INTENSIFY ON TUESDAY ACROSS SOUTH DAKOTA AND NEBRASKA WITH  
MODERATE TO POTENTIALLY HEAVY SNOW POSSIBLE. CONFIDENCE IS  
INCREASING FOR 4+ INCHES OF SNOWFALL ACROSS THE NORTHERN  
PANHANDLE OF NEBRASKA LATE MONDAY NIGHT WITH WINDS OVER 20 KNOTS.  
ISSUED A WINTER STORM WARNING FOR THE CHADRON AREA AND NORTHERN  
SIOUX COUNTY BEGINNING LATE MONDAY NIGHT AFTER MIDNIGHT. BELIEVE  
THIS AREA HAS THE BEST CHANCE TO SEE WINTER STORM CONDITIONS WITH  
STRONG WINDS AND THE POTENTIAL FOR BLOWING SNOW IN ADDITION TO  
MODERATE TO HEAVY SNOW AT TIMES. HOWEVER...THERE IS SOME CONCERN  
WITH THE WIND DIRECTION AND SNOW SHADOWING FROM THE BLACK HILLS  
WHICH MAY LIMIT SNOW ACCUMULATIONS. UPPER LEVEL DYNAMIC ARE NOT  
FAVORABLE AS WELL WITH THE JET STREAM PUSHING SOUTHEAST AT THIS  
TIME. FURTHER SOUTH...EXPECT WINDS OFF THE PINE RIDGE TO PROVIDE  
ENOUGH DOWNSLOPE TO LIMIT STEADY SNOWFALL...ALTHOUGH AN ADVISORY  
IS POSSIBLE. EVERYWHERE ELSE...GENERALLY EXPECT 1 TO 3 INCHES OF  
SNOW WITH LESS THAN AN INCH ACROSS THE SOUTHERN NE PANHANDLE.  
   
LONG TERM
 
(TUESDAY THROUGH SUNDAY)  
ISSUED AT 208 PM MST SUN JAN 22 2017  
 
CYCLONIC FLOW ALOFT CONTINUES OVERHEAD AND WITH A MOIST  
ATMOSPHERE, MOST LOCATIONS WILL CONTINUE TO SEE LIGHT SNOW, THOUGH  
COVERAGE SHOULD DECREASE IN THE AFTERNOON AS THE BEST LIFT DECREASES  
OVER OUR COUNTIES. CONTINUED COLD WITH CLOUD COVER AND FALLING SNOW.  
 
WEDNESDAY...TEMPERATURES ABOUT THE SAME AS TUESDAY WITH LITTLE  
CHANGE IN THICKNESSES OR 700 MB TEMPERATURES ALONG WITH PLENTY OF  
CLOUD COVER. ASIDE FROM SOME OROGRAPHIC SNOW SHOWERS OVER OUR SNOWY  
AND SIERRA MADRE RANGES IN MOIST NORTHWEST FLOW ALOFT, IT WILL BE  
DRY.  
 
THURSDAY...COOL, CYCLONIC FLOW ALOFT CONTINUES KEEPING THE COLD AIR  
REINFORCED OVER OUR COUNTIES AND HIGH TEMPERATURES LOOK TO BE  
SIMILAR TO THOSE OF WEDNESDAY.  
 
FRIDAY...SLOW WARMING TREND CONTINUES, LIMITED BY THE NORTHERLY  
FLOW ALOFT.  
 
SATURDAY...TEMPERATURES ABOUT 5 DEGREES WARMER THAN FRIDAY, ALTHOUGH  
WARMING TREND AGAIN LIMITED BY THE NORTHERLY FLOW ALOFT. CONTINUED  
DRY WITH LIMITED LOW AND MID LEVEL MOISTURE.  
 
SUNDAY...FLOW ALOFT BACKS TO NORTHWEST AND BASED ON THICKNESSES AND  
700 MB TEMPERATURES, WE WILL SEE A SLOW WARMING TREND CONTINUING,  
THOUGH IT WILL BE BREEZY TO WINDY BASED ON PROJECTED LOW AND MID  
LEVEL GRADIENTS.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)  
ISSUED AT 423 PM MST SUN JAN 22 2017  
 
WYOMING TAFS...VFR PREVAILS, EXCEPT AT RAWLINS WHERE MVFR  
DEVELOPS FROM 04Z TO 09Z, THEN IFR AFTER 09Z.  
 
NEBRASKA TAFS...VFR PREVAILS, WITH NEAR MVFR CONDITIONS FROM  
12Z TO 20Z.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 208 PM MST SUN JAN 22 2017  
 
NO FIRE WEATHER CONCERNS THROUGH THE WEEK WITH TEMPERATURES NEAR OR  
BELOW NORMAL WITH HIGH RELATIVE HUMIDITIES. ANOTHER ROUND OF SNOW  
IS EXPECTED MONDAY AND TUESDAY AS STORM SYSTEM MOVES ACROSS THE  
AREA.  
 

 
   
CYS WATCHES/WARNINGS/ADVISORIES
 
 
WY...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 6 PM MST  
TUESDAY FOR WYZ112-114.  
 
NE...WINTER STORM WATCH FROM LATE MONDAY NIGHT THROUGH TUESDAY  
EVENING FOR NEZ002-095.  
 

 
 

 
 
SHORT TERM...TJT  
LONG TERM...RUBIN  
AVIATION...RUBIN  
FIRE WEATHER...TJT  
 
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