281  
FXUS65 KRIW 181331  
AFDRIW  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE RIVERTON WY  
310 AM MDT SUN AUG 18 2019  
   
SHORT TERM
 
TODAY THROUGH MONDAY  
ISSUED AT 236 AM MDT SUN AUG 18 2019  
 
WEAK COLD FRONT THAT IS CURRENTLY ALONG THE CONTINENTAL DIVIDE  
WILL WASH OUR LASTER THIS MORNING, ALLOWING MUCH DRIER AIR TO  
SURGE BACK NORTHWARD ACROSS WYOMING. RED FLAG WARNINGS CONTINUE  
FOR ALL OF SOUTHWEST WYOMING WEST OF CASPER AND SOUTH OF THE OWL  
CREEK RANGE, WHILE THE SOUTHERN BIG HORN RANGE HAVE BEEN ADDED FOR  
TODAY. MONDAY EVEN DRIER AIR SURGES IN FROM THE SOUTHWEST,  
BRINGING HUMIDITY DOWN TO NEAR 10 PERCENT THROUGH THE AFTERNOON.  
WINDS WILL BE A BIT LOWER ON MONDAY, BUT SHOULD STILL BE BREEZY  
ENOUGH FROM THE WIND RIVER RANGE, THROUGH THE SOUTH PASS INTO  
NATRONA COUNTY FOR RED FLAG CONDITIONS TO CONTINUE.  
   
LONG TERM
 
MONDAY NIGHT THROUGH SUNDAY  
ISSUED AT 236 AM MDT SUN AUG 18 2019  
 
NOT TOO MUCH CHANGE IN THE FORECAST AS THE CONTINUING THEMES OF THE  
FORECAST WILL BE HOT AND MAINLY DRY. RIDGING WILL CONTINUE ACROSS  
THE AREA THROUGH THE PERIOD AND BRING ABOVE NORMAL TEMPERATURES. IF  
THERE IS SOME GOOD NEWS, IT IS THAT WITH A DECREASING PRESSURE  
GRADIENT ACROSS THE AREA, WINDS SHOULD DECREASE ACROSS THE AREA AND  
THIS SHOULD IMPROVE THE FIRE CONDITIONS SOMEWHAT. HOWEVER, WITH THE  
VERY DRY ATMOSPHERE IN PLACE, RELATIVE HUMIDITY WILL REMAIN IN THE  
TEENS FOR MANY LOCATIONS AND IN SOME AREAS FALL INTO THE SINGLE  
DIGITS AT TIMES.  
 
AS FOR TEMPERATURES, 90S WILL BE COMMONPLACE IN THE LOWER  
ELEVATIONS. REACHING 100 IS NOT EXPECTED THOUGH, GIVEN THE EVER  
SHORTENING DAYS AND LONGER NIGHT AS WE MOVE INTO LATE AUGUST.  
THE CHANCE OF PRECIPITATION LOOKS LIMITED AT BEST. THE NBM IS STILL  
A BIT HIGH ON POPS IN THE MOUNTAINS SO WE HAVE BLENDED IN SOME  
GFS/NAM/ECMWF TO GET THEM TO A MORE ACCEPTABLE LEVEL. THE POPS WILL  
STAY IN THE SLIGHT CATEGORY FOR TUESDAY AND WEDNESDAY. THE MODELS  
ARE ALSO HINTING A PATTERN FOR NEXT WEEKEND VERY SIMILAR TO THIS  
WEEKEND. THIS COULD MEAN A REPEAT OF DRY AND WINDY CONDITIONS AND A  
RETURN OF FIRE WEATHER CONCERNS.  
 

 
   
AVIATION
 
FOR THE 12Z TAFS THROUGH 12Z MONDAY  
ISSUED AT 730 AM MDT SUN AUG 18 2019  
 
LOWER CLOUD DECK VARYING AROUND KCPR WILL DISSIPATE BETWEEN 14Z AND  
15Z/SUN AS SURFACE FLOW SWITCHES TO THE SOUTHWEST AND ADVECTS DRIER  
AIR ACROSS KCPR. OTHERWISE, ALL TERMINALS WILL BE VFR THROUGH  
12Z/MON. IMPACTS WILL CENTER ON GUSTY WESTERLY SURFACE WIND 20-30KTS  
AT KRKS, AND TO A SLIGHTLY LESSER EXTENT AT KBPI AND KPNA. KJAC,  
KLND, AND KRIW SHOULD ALL SEE AFTERNOON WINDS OF 12-22KTS. WINDS  
WILL DIMINISH QUICKLY BETWEEN 01Z-02Z/MON AS DAYTIME MIXING  
DECREASES WITH THE SETTING SUN.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 236 AM MDT SUN AUG 18 2019  
 
...RED FLAG WARNINGS CONTINUE OVER MUCH OF CENTRAL AND SOUTHWEST  
WYOMING THROUGH MONDAY EVENING...  
 
CRITICAL FIRE WEATHER CONDITIONS STILL EXPECTED TODAY ACROSS MUCH  
OF CENTRAL AND SOUTHWEST WYOMING. THE COLD FRONT YESTERDAY WILL  
DISSIPATE LATER THIS MORNING, ALLOWING DRIER AIR TO PUSH BACK TO  
THE NORTHEAST. CONFIDENCE REMAINS HIGH FOR HUMIDITY FALLING TO 10  
TO 15 PERCENT AND WINDS 15 TO 20 MPH, WITH FREQUENT GUSTS  
APPROACHING 30 MPH. WITH THE DRIER AIR RETURNING NORTHEASTWARD,  
THE SOUTHERN BIG HORN RANGE WILL ALSO BEGIN TO SEE CRITICAL  
CONDITIONS THIS AFTERNOON, SO THE WARNINGS HAVE BEEN EXTENDED  
NORTHWARD INTO ZONE 285.  
 
MONDAY LOOKS TO BE ANOTHER CRITICAL DAY ACROSS WYOMING, BUT  
CONFIDENCE IS A BIT LOWER DUE TO ADJUSTMENTS IN THE FORECAST. THE  
HUMIDITY VALUES WILL CRASH AGAIN DURING THE AFTERNOON AS A DRIER  
AIRMASS SHIFTS IN FROM THE SOUTHWEST, POSSIBLY DROPPING BELOW 10  
PERCENT SOUTH AND WEST OF THE DIVIDE. THE WIND FIELD WILL BE  
LIGHTER DURING THE DAY, ESPECIALLY FOR THE WIND RIVER BASIN AND  
SOUTHERN SWEETWATER COUNTY. WINDS STILL LOOK TO RACE ACROSS THE  
WIND RIVER RANGE, ACROSS SOUTH PASS, AND INTO NATRONA COUNTY, SO  
THOSE AREAS WILL CONTINUE WITH WARNINGS ON MONDAY. ANOTHER WIND  
SURGE MAY RACE IN FRO THE SOUTHWEST ROUGHLY FROM KEMMERER TO SOUTH  
PASS, SO THE WARNINGS WILL BE CONTINUED FOR SUBLETTE, LINCOLN, AND  
SWEETWATER COUNTIES, WITH THE FOCUS BEING THROUGH SOUTHERN  
SUBLETTE COUNTY.  
 
ELEVATED FIRE WEATHER CONDITIONS EXPECTED ON TUESDAY FOR MOST  
AREAS. WINDS ARE FORECAST TO BE LOWER FOR MOST AREAS, SO FULL RED  
FLAG WARNINGS ARE LESS LIKELY AT THIS POINT.  
 

 
   
RIW WATCHES/WARNINGS/ADVISORIES
 
 
RED FLAG WARNING UNTIL 9 PM MDT MONDAY FOR WYZ277>280-288-289-  
300-416.  
 
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR WYZ283-414.  
 
RED FLAG WARNING FROM NOON TODAY TO 9 PM MDT THIS EVENING FOR  
WYZ285.  
 

 
 

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