286  
FXUS65 KRIW 210842  
AFDRIW  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE RIVERTON WY  
242 AM MDT THU OCT 21 2021  
   
SHORT TERM
 
(TODAY THROUGH FRIDAY)  
ISSUED AT 239 AM MDT THU OCT 21 2021  
 
AS OPPOSED TO THE LAST SEVERAL DAYS, A QUIET SHORT TERM FORECAST IS  
IN STORE. RIDGING HAS DEVELOPED ACROSS THE REGION, WHICH WILL KEEP  
MOST AREAS WARM AND DRY AS WE HEAD INTO THE WEEKEND. A QUICK-MOVING  
SHORTWAVE WILL CLIP NORTHWESTERN WY TODAY, WHICH COULD BRING SOME  
VERY ISOLATED SHOWERS ACROSS YELLOWSTONE PARK AND THE NORTHERN  
ABSAROKAS THIS MORNING. HIGH CLOUDS INCREASE OVERNIGHT AHEAD OF THIS  
SHORTWAVE AS WELL, WHICH MAY MODERATE THE RADIATIONAL COOLING  
OVERNIGHT. WITH THE RESIDUAL MOISTURE ACROSS THE LOWER WIND RIVER  
BASIN AND NATRONA COUNTY ALONG THE NORTH PLATTE RIVER, COULD SEE  
SOME PATCHY FOG THIS MORNING AGAIN. ADDED A LITTLE BIT OF PATCHY FOG  
IN THE GRIDS THROUGH 17Z TO COVER THIS POSSIBILITY. TEMPS WILL  
INCREASE INTO THE 60S ACROSS THE BIGHORN BASIN AND NORTHERN JOHNSON  
COUNTY AND LIKELY REMAIN IN THE 50S ELSEWHERE. BREEZY AGAIN ACROSS  
THE WIND CORRIDOR DURING THE AFTERNOON.  
 
TOMORROW WILL SEE MUCH OF THE SAME CONDITIONS AS THE RIDGE AXIS  
MOVES NEARLY DIRECTLY OVERHEAD BY THE AFTERNOON. THIS WILL RESULT IN  
EVEN WARMER TEMPS ACROSS THE REGION. MANY LOCATIONS WILL NEAR 60  
WITH MID 60S ACROSS THE BIGHORN BASIN AND JOHNSON COUNTY. LOW 60S  
ARE EVEN POSSIBLE ACROSS THE WESTERN VALLEYS. BREEZY WINDS WILL ONCE  
AGAIN OCCUR ACROSS THE WIND CORRIDOR. FRIDAY WILL ALSO BE DRY WITH  
PARTLY CLOUDY SKIES. HIGH CLOUDS WILL INCREASE AGAIN FRIDAY  
AFTERNOON AHEAD OF THE NEXT SYSTEM, WHICH WILL IMPACT THE REGION FOR  
THE WEEKEND, BUT MORE ON THIS IN THE EXTENDED FORECAST.  
   
LONG TERM
 
(FRIDAY NIGHT THROUGH WEDNESDAY)  
ISSUED AT 239 AM MDT THU OCT 21 2021  
 
AN ACTIVE PATTERN IS STILL EXPECTED INTO NEXT WEEK. SEVERAL WEATHER  
SYSTEMS WILL PASS THROUGH THE REGION WITH FREQUENT CHANGES TO  
WEATHER CONDITIONS ACROSS THE FORECAST AREA. A STRONG TO EVEN SEVERE  
WIND EVENT IS POSSIBLE MONDAY, ESPECIALLY ALONG THE WIND CORRIDOR  
FROM ROCK SPRINGS TO CASPER.  
 
SHORTWAVE TROUGH SWINGS NORTH LATE FRIDAY AND CLIPS NORTHWEST  
WYOMING. MID-LEVEL ENERGY ASSOCIATED WITH THIS TROUGH SHOULD STAY  
NORTH AND WEST OF THE AREA. SOME SNOW SHOWERS ARE POSSIBLE AT HIGH  
ELEVATIONS IN THE NORTHWEST PORTION OF THE FORECAST AREA. THE LARGER  
UPPER-LEVEL SYSTEM MOVES THROUGH SATURDAY WITH A BETTER CHANCE FOR  
PRECIPITATION ACROSS THE WEST. FOR LOWER ELEVATIONS ONSET OF  
PRECIPITATION SHOULD BE IN THE FORM OF RAIN. 700MB TEMPERATURES  
SATURDAY NIGHT DROP TO AROUND -6 C, SO A CHANGE OVER TO SNOW IS  
POSSIBLE. THEN A RAIN/SNOW MIX IS POSSIBLE SUNDAY MORNING, BUT  
PRECIPITATION SHOULD DECREASE INTO THE AFTERNOON AS A RIDGE  
DEVELOPS. IT'S POSSIBLE PRECIPITATION HOLDS ON IN THE WESTERN  
MOUNTAINS. THIS PRECIPITATION IS NOT EXPECTED TO MAKE IT EAST OF  
THE WIND RIVER AND ABSAROKA MOUNTAINS. SATURDAY WINDS WILL BE  
GUSTY FROM ROCK SPRINGS TO CASPER ALONG THE WIND CORRIDOR. SUNDAY  
NIGHT WINDS SHOULD DECREASE IN INTENSITY AS THE RIDGE MOVES  
OVERHEAD AND THE PRESSURE GRADIENT DECREASES.  
 
MONDAY AND TUESDAY WILL BE THE MOST IMPACTFUL PERIOD FOR WEATHER  
CONDITIONS ACROSS THE AREA. A DEEP TROUGH MOVES IN FROM THE WEST  
WITH STRONG WARM AIR ADVECTION AHEAD OF IT. MONDAY AFTERNOON A VERY  
TIGHT PRESSURE GRADIENT IS SITUATED ACROSS THE AREA. OVER THE  
SOUTHEAST 700MB WINDS MAX OUT ANYWHERE FROM 55-65 KNOTS. CURRENTLY  
SURFACE GUSTS ARE EXPECTED TO BE IN THE 50-60 MPH RANGE ACROSS THE  
SOUTHEAST WIND CORRIDOR. WINDS WILL ALSO BE STRONG IN THE MOUNTAIN  
PASSES THROUGHOUT THE FORECAST AREA. THESE VALUES COULD INCREASE IN  
THE COMING DAYS AS WE GET A BETTER HANDLE ON THE SYSTEM. THIS SYSTEM  
IS NOT EXPECTED TO BE A BIG PRECIPITATION MAKER. IT LOOKS TO BE TOO  
PROGRESSIVE WITH A SINGLE BAND OF PRECIPITATION EAST OF THE DIVIDE  
POSSIBLE ALONG THE COLD FRONT TUESDAY, OTHERWISE THE MOUNTAINS  
SHOULD SEE THE BULK OF THE RAIN AND SNOW. TUESDAY NIGHT NORTHWEST  
WINDS BEHIND A COLD FRONT SHOULD BE GUSTY ACROSS THE AREA.  
 
AS THE BACKSIDE JET MOVES IN ON WEDNESDAY THERE SHOULD STILL BE  
ENOUGH MOISTURE IN THE WESTERN MOUNTAINS FOR PRECIPITATION TO  
CONTINUE THERE WITH NORTHWEST FLOW. WEST WINDS CONTINUE ON WEDNESDAY  
AND COULD BE GUSTY, BUT NO AREAS WILL SEE EVEN CLOSE TO THE VALUES  
EXPECTED ON MONDAY. BEYOND WEDNESDAY A BROAD RIDGE SHOULD BEGIN TO  
BUILD ACROSS THE REGION, WHICH SHOULD QUIET THINGS DOWN FOR A BIT.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)  
ISSUED AT 239 AM MDT THU OCT 21 2021  
 
WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS TERMINALS  
 
ALL TERMINALS TO BE VFR THROUGH THE FORECAST PERIOD. MID AND HIGH  
CLOUD COVER INCREASES PERSISTS THROUGH THURSDAY MORNING. A FEW SNOW  
SHOWERS AND OBSCURED MOUNTAIN TOPS POSSIBLE UNTIL 15Z/THURSDAY  
BEFORE THE WAVE CLEARS THE REGION AROUND MIDDAY THURSDAY. SURFACE  
WIND SPEEDS TO BE GENERALLY 10 KTS OR LESS THROUGH 12Z/FRIDAY. A  
MAINLY CLEAR SKY IS EXPECTED AFTER 21Z THURSDAY.  
 
EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL TERMINALS  
 
VFR TO PREVAIL AT ALL TERMINALS THROUGH THE PERIOD. MID AND HIGH  
CLOUD COVER CONTINUES THROUGH TOMORROW AROUND 18Z THURSDAY. KCPR  
SOUTHWEST SURFACE WIND WILL INCREASE AGAIN AROUND MIDDAY THURSDAY  
AND CONTINUE THROUGH THE AFTERNOON BEFORE DECREASING AGAIN SHORTLY  
AFTER SUNSET. ALL OTHER TERMINALS TO SEE WIND LESS THAN 10 KTS.  
 
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZDV AND ZLC FOR  
THE LATEST INFORMATION ON ICING AND TURBULENCE FORECASTS.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 239 AM MDT THU OCT 21 2021  
 
TODAY AND TOMORROW WILL SEE MAINLY JUST HIGH CLOUDS AND DRY  
CONDITIONS. A FEW ISOLATED SHOWERS ARE POSSIBLE ACROSS THE FAR  
NORTHWEST THIS MORNING, BUT NO ACCUMULATION IS EXPECTED, AS ANY  
SHOWER WOULD BE BRIEF AND VERY LIGHT. BREEZY SW WINDS WILL OCCUR  
ACROSS THE USUAL AREAS DURING THE AFTERNOONS. TEMPERATURES WILL BE  
SEASONAL TO JUST ABOVE NORMAL OVER THE NEXT FEW DAYS. A SYSTEM WILL  
MOVE INTO WESTERN WY THIS WEEKEND, WHICH COULD BRING A FEW INCHES OF  
SNOW TO THE WESTERN MOUNTAINS, WITH A BIT OF RAIN FOR THE VALLEYS. A  
MORE POTENT TROUGH WILL MOVE INTO THE REGION FOR THE EARLY PART OF  
THE WEEK, WHICH WILL BRING VERY GUSTY SW WINDS TO THE WIND CORRIDOR.  
GUSTS OVER 60 MPH ARE POSSIBLE ACROSS PARTS OF ZONES 280 AND 289  
MONDAY AFTERNOON DUE TO A VERY STRONG JET AHEAD OF THE TROUGH.  
PRECIPITATION WILL BE MINIMAL EAST OF THE DIVIDE WITH BOTH SYSTEMS,  
BUT WEST OF THE DIVIDE WILL LIKELY SEE SOME RAIN AND SNOW SHOWERS  
BEGINNING SATURDAY AFTERNOON THROUGH THE EARLY PART OF NEXT WEEK.  
 

 
   
RIW WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
SHORT TERM...HENSLEY  
LONG TERM...ROWE  
AVIATION...AR/HATTINGS  
FIRE WEATHER...HENSLEY  
 
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