111  
FXUS65 KRIW 271954  
AFDRIW  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE RIVERTON WY  
1254 PM MST THU FEB 27 2020  
   
SHORT TERM
 
THIS EVENING THROUGH SATURDAY  
ISSUED AT 1253 PM MST THU FEB 27 2020  
 
HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE WEST AND BRING DRY  
AND SETTLED WEATHER THROUGH SATURDAY. THERE COULD BE SOME VERY  
ISOLATED SNOW SHOWERS IN THE NORTHWEST MOUNTAINS THIS AFTERNOON BUT  
THEY WILL BRING LITTLE ACCUMULATION AND NOT IMPACTFUL. THE BIGGEST  
CHALLENGES FOR THIS PERIOD WILL BE TEMPERATURE TRENDS AND WINDS AS  
THE NEXT SYSTEM APPROACHES ON SATURDAY. VALLEY/BASIN INVERSIONS HAVE  
BEEN HANGING TOUGH IN THE WEST AND SO AREAS LIKE AFTON AND BIG PINEY  
HAVE BEEN SLOW TO WARM IN THE MORNING. THIS WILL LIKELY TRANSLATE TO  
A LOWER HIGH TEMP UNTIL THE NEXT SYSTEM IS ABLE TO SCOUR OUT THE  
INVERSIONS. AS THE UPPER LEVEL TROUGH MOVES FROM CANADA INTO THE  
INTERMOUNTAIN WEST EXPECT BREEZY CONDITIONS ON FRIDAY AND STRONG WINDS  
SATURDAY AFTERNOON IN THE WIND CORRIDOR FROM THE GREEN MOUNTAINS  
THROUGH NATRONA COUNTY AND IN THE ABSAROKA MOUNTAINS.  
 
THE NEXT WEATHER SYSTEM IN THE FORM OF A PACIFIC SYSTEM WILL BEGIN  
TO APPROACH THE AREA ON SATURDAY. MODELS HAVE CONTINUED TO SLOW THE  
PROGRESS OF THE SYSTEM AND IT NOW LOOKS LIKE ONLY THE FAR NORTHWEST  
AREAS, YELLOWSTONE NP AND NORTHERN TETON MOUNTAINS, WILL SEE ANY  
ACTIVITY SATURDAY EVENING. WE HAVE ADJUSTED POPS TO REFLECT THIS.  
   
LONG TERM
 
SATURDAY NIGHT THROUGH THURSDAY  
ISSUED AT 1253 PM MST THU FEB 27 2020  
 
SATURDAY NIGHT HAS ALL OF THE MODELS SHOWING A TROUGH ACROSS THE  
WESTERN U.S. INTO SOUTH-CENTRAL CANADA. MAIN UPPER LOWS ASSOCIATED  
WITH THIS TROUGH ARE AROUND NORTHEASTERN OREGON AND ANOTHER IN  
CENTRAL MANITOBA. WITH THE MAIN UPPER LOWS ROUGHLY ACROSS SOUTH-  
CENTRAL MANITOBA AND N. CALIFORNIA. THE TROUGH WILL SPLIT/STRETCH  
OUT SUNDAY WITH THE TROUGH AXIS PULLING ACROSS THE AREA SUNDAY NIGHT.  
 
SEVERAL WEATHER ELEMENTS COMING TOGETHER SUNDAY FOR THE POTENTIAL OF  
SIGNIFICANT SNOW MAINLY OVER CENTRAL AND SOUTHERN AREAS. MODELS ARE  
HINTING A JET COUPLET BETWEEN THE POLAR AND SUBTROPICAL JET STREAM  
AT 300MB, STRONG FRONTOGENESIS IN THE LOWER LEVELS PULLING SOUTH  
SUNDAY, ISENTROPIC LIFT MAINLY OVER THE SOUTH, AND A DECENT  
DENDRITIC GROWTH ZONE FOR A PERIOD OF TIME. THE MODELS HAVE COME  
MUCH MORE IN LINE WITH THE SPLITTING OF THIS TROUGH, SO WE ARE  
KEEPING THE HIGHER POPS AND SNOW AMOUNTS FROM THE PREVIOUS SHIFT.  
STILL EXPECTING SOME HIGHLIGHTS OVER CENTRAL/SOUTHERN AREAS, LEANING  
TOWARD ADVISORY AMOUNTS FOR NOW. THE SNOW WILL COME TO AN END FROM  
NORTH TO SOUTH LATE SUNDAY NIGHT INTO EARLY MONDAY MORNING.  
 
BEHIND THE FRONT, DRY CONDITIONS ARE EXPECTED, BUT WILL BE SHORT-  
LIVED AS A NEW STORM SYSTEM WILL MOVE INTO THE FORECAST AREA. THIS  
STORM, CURRENTLY IN THE GULF OF ALASKA, WILL RAPIDLY DRIVE SOUTHEAST  
INTO THE PACIFIC NORTHWEST MONDAY NIGHT AND INTO THE ROCKIES EARLY  
TUESDAY. SNOW WILL HIT NORTHWESTERN WYOMING LATE MONDAY AND SPREAD  
EAST OF THE DIVIDE THROUGH TUESDAY INTO TUESDAY NIGHT. THERE IS THE  
POTENTIAL FOR SIGNIFICANT SNOW OVER THE NORTHWEST BASED ON CURRENT  
DATA, HOWEVER CENTRAL AND EASTERN AREAS WILL NOT SEE MUCH. ALSO  
WINDY CONDITIONS ARE POSSIBLE WEDNESDAY FOR AREAS THAT FAVOR STRONG  
NORTHWEST WINDS.  
 
NORTHWEST FLOW IN THE WAKE OF THE TROUGH WEDNESDAY COULD RESULT IN A  
RETURN TO SOME SNOW SHOWERS FALLING MAINLY OVER THE NORTHWEST.  
THURSDAY WILL SEE DRIER CONDITIONS ACROSS THE REGION.  
 

 
   
AVIATION
 
FOR THE 18Z TAFS THROUGH 18Z FRIDAY  
ISSUED AT 1030 AM MST THU FEB 27 2020  
 
EXPECT VFR CONDITIONS ACROSS THE AREA THROUGH THE TAF PERIOD WITH  
VARIABLE MID TO HIGH LEVEL CLOUDS.  
 
A GUSTY WEST TO SOUTHWEST WIND WILL CONTINUE AT KCPR THROUGH MUCH OF  
THE TAF PERIOD. WINDS WILL SUBSIDE BELOW 15 KTS AT KCPR AFTER 00Z  
FRIDAY, PICKING UP AGAIN AFTER 15Z FRIDAY. KRKS WILL SEE AN INCREASE  
IN SPEED AFTER 21Z TODAY AND THEN DIMINISHING AFTER AROUND 04Z  
FRIDAY.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 1253 PM MST THU FEB 27 2020  
 
EXPECT MOSTLY DRY CONDITIONS AND WARMING TEMPERATURES THROUGH  
SATURDAY AS HIGH PRESSURE MOVES OVER THE AREA. A GUSTY WIND WILL  
OCCUR IN THE FAVORED AREAS FROM ROCK SPRINGS THROUGH CASPER AND IN  
THE ABSAROKAS. RELATIVE HUMIDITY WILL REMAIN ABOVE CRITICAL LEVELS  
FOR THE NEXT SEVERAL DAYS. MIXING AND SMOKE DISPERSAL WILL BE  
GENERALLY POOR TONIGHT AND FRIDAY. THE NEXT WEATHER SYSTEM ARRIVES  
SATURDAY NIGHT INTO SUNDAY WITH SOME WIDESPREAD SNOW.  
 

 
   
RIW WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
SHORT TERM...HULME  
LONG TERM...SWANSON  
AVIATION...SWANSON  
FIRE WEATHER...HULME  
 
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