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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