820  
FXUS65 KCYS 220545  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
1045 PM MST SUN JAN 21 2018  
   
UPDATE
 
 
ISSUED AT 609 PM MST SUN JAN 21 2018  
 
UPDATED FORECAST TO EXPIRE/CANCEL THE WINTER STORM WARNING ALONG  
AND EAST OF I-25 INTO THE CENTRAL AND NORTHERN NEBRASKA PANHANDLE.  
OBSERVATIONS ACROSS THESE AREAS HAVE SHOWN A STEADY IMPROVEMENT IN  
VISIBILITIES. BLOWING AND DRIFTING SNOW WITH PERIODS OF LIGHT SNOW  
ARE EXPECTED INTO LATE THIS EVENING, BUT ADDITIONAL SNOW  
ACCUMULATIONS WILL BE MINIMAL. WIND GUSTS SHOULD BE MAINLY BELOW  
40 MPH IN THESE AREAS AS WELL, SO BLOWING SNOW IMPACTS SHOULD NOT  
BE THAT MUCH OF A THREAT, ALTHOUGH DRIFTING SNOW WILL LIKELY BE  
THE MAIN IMPACT THROUGH TONIGHT. FURTHER EAST, WILL KEEP THE  
WINTER STORM WARNING GOING FOR THE SOUTHERN NE PANHANDLE, WITH 1  
MILE VISIBILITIES AND HAZARDOUS TRAVEL CONDITIONS IN THOSE AREAS.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH MONDAY NIGHT)  
ISSUED AT 237 PM MST SUN JAN 21 2018  
 
MODERATE TO HEAVY SNOW CONTINUES ACROSS THE NEBRASKA PANHANDLE  
THIS AFTERNOON. HEAVIEST SEEMS TO BE STAYING SOUTH ACROSS EASTERN  
COLORADO AND EXTREME SOUTHEASTERN NEBRASKA/NORTHWEST KANSAS. HAVE  
BEEN PARING DOWN WARNINGS FROM WEST TO EAST THROUGH THE DAY TODAY,  
BUT STILL EXPECTING IMPACTS EAST ACROSS THE WYOMING PLAINS AND  
NEBRASKA PANHANDLE THROUGH REMAINDER OF THE AFTERNOON. WARNINGS  
REMAIN IN PLACE FOR THESE AREAS.  
 
WINDS ARE GOING TO BE AN ISSUE THIS EVENING INTO MONDAY. SNOWPACK  
IS COMPRISED OF VERY FINE SNOW AND IS VERY LIGHT WEIGHT AND NON  
COMPACTING. BY THIS EVENING, GFS SHOWING 850MB WINDS OUT IN THE  
PANHANDLE SHIFTING TO THE NORTHWEST AND INCREASING TO 30-35KTS.  
COULD SEE IMPACTS FROM BLOWING SNOW THIS EVENING ALONG AND EAST OF  
THE LARAMIE RANGE. EVENING SHIFT MAY WANT TO CONSIDER A BLOWING  
SNOW ADVISORY AFTER CURRENT WARNINGS EXPIRE.  
 
A BIGGER ISSUE FOR THE SOUTH LARAMIE RANGE AND ARLINGTON TONIGHT  
THROUGH MONDAY. CRAIG TO CASPER 850/700MB GRADIENTS INCREASING TO  
AROUND 50MTRS AFTER 09Z TONIGHT. QUALITY OF THE SNOW COULD CREATE  
VERY SERIOUS PROBLEMS FOR TRAVEL ON INTERSTATE 80 OVER THE SUMMIT  
AND OUT BY ARLINGTON. CONSIDERED A GROUND BLIZZARD WARNING BUT  
DECIDED ON ISSUING NEW WINTER STORM WARNINGS FOR ZONES 110 AND 116  
(ARLINGTON/I-80 SUMMIT) EVENING/OVERNIGHT SHIFTS MAY WANT TO  
UPGRADE ONCE THE NEW FORECAST RUN COMES IN LATER.  
 
ANOTHER WEAK SHORTWAVE MONDAY EVENING MAY BRING ANOTHER SHOT OF  
SNOW OUT IN THE SNOWY/SIERRA MADRE RANGES. DUE TO QUICK MOVEMENT  
OF THIS FEATURE, DO NOT EXPECT A LOT OF ACCUMULATION.  
   
LONG TERM
 
(TUESDAY THROUGH SATURDAY)  
ISSUED AT 443 AM MST SUN JAN 21 2018  
 
WE NOTE A MODEST WARMUP WEDNESDAY INTO THURSDAY, THEN OUR NEXT  
CHANCE AT SNOW LOOKS TO BE SHAPING UP FOR FRIDAY AS AN OPEN UPPER  
WAVE MOVES ACROSS THE CENTRAL ROCKIES. THIS NEXT SYSTEM DOES NOT  
LOOK TO BE AS STRONG AS THE COLORADO LOW WE ARE DEALING WITH  
TODAY.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH MONDAY EVENING)  
 
MOST TERMINALS ACROSS SE WYOMING HAVE IMPROVED TO VFR LATE THIS  
EVENING AS THE STORM SYSTEM, WHICH BROUGHT HEAVY SNOW TO PORTIONS OF  
THE AREA, CONTINUES TO MOVE EAST ACROSS THE CENTRAL GREAT PLAINS.  
MVFR VIS AND CIGS WILL CONTINUE AT KSNY THROUGH MIDNIGHT DUE TO SOME  
BLOWING SNOW AND FALLING SNOW. THESE CONDITIONS MAY LINGER THROUGH  
EARLY MONDAY MORNING BEFORE SUNRISE. OTHERWISE, WILL HAVE TO MONITOR  
THE POTENTIAL OF BLOWING SNOW FROM KRWL EASTWARD TO KLAR AND EVEN  
KCYS THROUGH EARLY MONDAY MORNING AS THE LLVL PRESSURE GRADIENT  
INCREASES.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 237 PM MST SUN JAN 21 2018  
 
MINIMAL FIRE WEATHER CONCERNS EXPECTED NEXT FEW DAYS AS WIDESPREAD  
SNOW IN PLACE FROM TODAYS SNOW STORM WILL REMAIN. COLD TEMPERATURES  
TO KEEP HUMIDITY HIGH AND WELL ABOVE CRITICAL LEVELS. ANOTHER COLD  
FRONT AND STORM SYSTEM WILL SWEEP ACROSS THE REGION BY THE END OF  
THE WEEK, BRINGING THE NEXT CHANCE OF SNOW TO THE AREA.  
 

 
   
CYS WATCHES/WARNINGS/ADVISORIES
 
 
WY...WINTER STORM WARNING FROM 11 PM THIS EVENING TO 2 PM MST MONDAY  
FOR WYZ110-116.  
 
NE...NONE.  
 

 
 

 
 
UPDATE...TJT  
SHORT TERM...GCC  
LONG TERM...JG  
AVIATION...TJT  
FIRE WEATHER...GCC  
 
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