802
FXUS65 KRIW 220438
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
938 PM MST WED JAN 21 2026
KEY MESSAGES
- MORE SEASONABLE TEMPERATURES HAVE SETTLED ACROSS THE REGION
AND WILL PERSIST THROUGH FRIDAY.
- A COLD FRONT WILL BRING CHANCES FOR LIGHT SNOW SHOWERS
FRIDAY, MAINLY EAST OF THE DIVIDE WITH A QUICK INCH OR TWO
POSSIBLE IN SOME LOCATIONS.
- SOME OF THE COLDEST TEMPERATURES OF THE SEASON LOOK
INCREASINGLY POSSIBLE FOR THE WEEKEND WITH LOW TEMPERATURES
NEARING OR EVEN DROPPING BELOW ZERO.
UPDATE
ISSUED AT 1204 PM MST WED JAN 21 2026
A FEW THINGS TO EMPHASIZE REGARDING THE UPCOMING FORECAST AND
PREVIOUS DISCUSSION. THE MAIN FOCUS WILL BE LATE THIS WEEK INTO
THE WEEKEND WITH A FRONTAL PASSAGE THAT WILL USHER IN SOME OF
THE COLDEST TEMPERATURES OF THE SEASON. FIRSTLY, MODELS HAVE
CONTINUED TO SHOW GREATER CHANCES FOR SNOWFALL IN ASSOCIATION
WITH THE FRONTAL PASSAGE FRIDAY. THE BEST CHANCES LOOK TO BE
ACROSS PORTIONS OF THE BIGHORN BASIN ALONG WITH JOHNSON AND
NATRONA COUNTIES. THE TIMING FOR THESE SHOWERS WOULD BE
THROUGHOUT THE DAY FRIDAY STARTING FRIDAY MORNING THROUGH THE
EVENING. OVERALL, SNOW AMOUNTS LOOK MINIMAL BUT THERE IS A
SOLID 30-60% CHANCE FOR A QUICK INCH OR TWO OF SNOW ACCUMULATION
IN THE AFOREMENTIONED AREAS.
THE OTHER ELEMENT TO EMPHASIZE WILL BE THE PUSH OF VERY COLD
AIR THAT SETTLES IN ACROSS THE REGION THROUGH THE WEEKEND. THERE
IS THE POSSIBILITY FOR EVEN COLDER TEMPERATURES THIS WEEKEND
THAN WHAT IS CURRENTLY FORECAST. HOWEVER, A FEW THINGS WILL
NEED TO OCCUR FOR COLDER TEMPERATURES TO DEVELOP. THE FIRST WILL
BE CLEARING OF SKIES FRIDAY NIGHT INTO THE MORNING HOURS ON
SATURDAY. THE OTHER BEING HOW MUCH SNOW ACCUMULATION HAPPENS ON
FRIDAY, WHICH WOULD LIMIT ANY RADIATIONAL WARMING FROM THE
GROUND. RECENT FORECAST MODEL RUNS HAVE TRENDED TOWARDS
WIDESPREAD COLDER TEMPERATURES FOR MUCH OF THE STATE. THE BEST
CHANCES FOR SOME VERY COLD TEMPERATURES LOOK TO BE ACROSS
PORTIONS OF JOHNSON AND NATRONA COUNTIES, WHERE LIGHT SNOW
ACCUMULATION MAY OCCUR FRIDAY ALONG WITH CLEARING SKIES
OVERNIGHT INTO SATURDAY MORNING. PROBABILISTIC GUIDANCE IS
HIGHLIGHTING THIS AREA AND IS SHOWING A 30-50% CHANCE FOR LOWS
NEARING OR EVEN BELOW -10 FOR SATURDAY MORNING. HIGH
TEMPERATURES WOULD ALSO BE IMPACTED WITH MUCH COLDER VALUES
POSSIBLE FOR SATURDAY AND SUNDAY. HOWEVER, THERE ARE STILL SOME
THINGS THAT WILL NEED TO BE IRONED OUT OVER THE NEXT FEW DAYS.
SO THIS OCCURRING IS DEFINITELY NOT SET IN STONE, BUT IT BEARS
MONITORING OVER THE NEXT FEW DAYS.
DISCUSSION
ISSUED AT 158 AM MST WED JAN 21 2026
IT HAS BEEN A VERY MILD WINTER ACROSS MOST OF THE AREA SO FAR THIS
YEAR. IT HAS TURNED MORE SEASONABLE LATELY, BUT WE HAVE BEEN LACKING
SOME REALLY COLD TEMPERATURES. MANY LOCATIONS CONTINUE TO AVERAGE
MORE THAN 10 DEGREES ABOVE NORMAL THROUGH METEOROLOGICAL WINTER
(DECEMBER THROUGH FEBRUARY). AND LOCALLY, HERE AT THE HUMBLE
RIVERTON WEATHER ABODE AND IN NEARBY LANDER, I WAS LOOKING AT BELOW
ZERO LOWS, OR THE LACK OF THIS YEAR. AT THE AIRPORT, WE HAVE NOT
DONE IT ONCE SO FAR THIS WINTER. THIS CURRENTLY THE SECOND LATEST
(2000 WAS JANUARY 29TH) AND LANDER, WHICH HAS RECORDS THAT DATE BACK
TO 1891, IT IS THE THIRD LATEST (FEBRUARY 25 IN 1934 IS THE LATEST).
WE MAY FINALLY HAVE A CHANCE TO REACH THAT MARK, BUT IN A FEW DAYS.
TODAY LOOKS TO BE A SEASONABLE AND MAINLY DRY DAY. WE CAN'T
COMPLETELY RULE OUT A STRAY SNOW SHOWER OVER THE BIGHORNS, BUT THE
CHANCE IS SO LOW (LESS THAN 1 OUT OF 10) WE HAVE LEFT IT OUT OF THE
FORECAST. THIS WILL BE COURTESY OF ANOTHER COLD FRONT DROPPING
SOUTHWARD THROUGH THE AREA, AND HAS EVEN LESS MOISTURE THAN THE
ONE YESTERDAY. THE MAIN IMPACT WILL BE MORE GUSTY WIND, MAINLY
OVER JOHNSON COUNTY, AS IS USUAL WITH COLD ADVECTION / NORTHWEST
FLOW SITUATIONS. I HAVE A SMALL CONCERN FOR A FEW HIGH WIND
GUSTS, AS THE NBM ENSEMBLE GUIDANCE HAS A 1 IN 2 CHANCE OF WIND
GUSTS OF 50 MPH AND THERE IS SOME RIGHT FRONT JET DYNAMICS FOR
A BIT OF DOWNWARD FORCING. THE STRONGEST WIND WOULD ONLY LAST
AROUND 6 HOURS. THIS IS A BIT SIMILAR TO YESTERDAY EXCEPT NO
SNOW, WHEN THE HIGH WIND GUSTS WERE ISOLATED. SO, NO WIND
HIGHLIGHTS ALTHOUGH WE MAY ISSUE A SPECIAL WEATHER STATEMENT.
GUSTY BREEZES MAY BE FOUND ELSEWHERE BUT NO HIGH WIND.
THURSDAY LOOKS TO BE A DAY OF NEAR TO BELOW NORMAL TEMPERATURES,
WITH BREEZES THAT WILL MAKE IT THE COOLEST DAY IN A WHILE. IT LOOKS
MAINLY DRY DURING THE DAY, BUT THE QUESTION IS WHAT WILL HAPPEN WHEN
THE THIRD COLD FRONT THIS WEEK APPROACHES AND MOVES THROUGH THE
AREA. THIS ONE HAS ARCTIC AIR BEHIND IT AND AS A RESULT LITTLE
MOISTURE. HOWEVER, IT DOES HAVE SOME RIGHT REAR QUADRANT ENERGY THAT
MAY ENHANCE UPWARD MOTION SOMEWHAT. THE PROBLEM IS THERE IS LITTLE
MOISTURE TO LIFT. THERE IS A MODEL SPREAD WITH THE DETERMINISTIC
MODELS, WITH THE ECMWF THE WETTEST, BUT EVEN IT ONLY GIVES
BARELY OVER A TENTH OF AN INCH OF QPF. AS FOR PROBABILISTIC
GUIDANCE, THE BEST CHANCE OF OVER AN INCH OF SNOW IS AROUND
CASPER, WHERE SOME ANAFRONTAL NORTHERLY FLOW MAY BRING A BRIEF
PERIOD OF UPSLOPE, BUT EVEN HERE IT IS ONLY AROUND 1 OUT OF 3
THROUGH FRIDAY NIGHT. SNOW SHOWERS COULD FALL IN AREAS SIMILAR
TO TUESDAY. THE SNOW WILL NOT BE THE MAIN CONCERN THOUGH.
THE MAIN CONCERN WILL BE THE COLD TEMPERATURES, THE COLDEST OF THE
YEAR FOR MANY LOCATIONS. MODELS HAVE TRENDED COLDER THAN YESTERDAY.
AND ALTHOUGH THE CORE OF THE COLD AIR WILL REMAIN WELL EAST OF
WYOMING, SOME AREAS WILL SEE 700 MILLIBAR TEMPERATURES AS LOW AS
MINUS 20C. THIS IS THE BEST CHANCE FOR AREAS LIKE RIVERTON AND
LANDER TO FINALLY FALL TO BELOW ZERO. PROBABILISTIC GUIDANCE
GIVES AT LEAST A 1 IN 2 CHANCE OF LOWS BELOW ZERO ACROSS MOST
AREAS EAST OF THE DIVIDE. THE ONE CONCERN I HAVE IS THAT THE
COLD ADVECTION MAY HAVE TO OVERCOME CLOUD COVER. HOWEVER, FRIDAY
NIGHT LOOKS TO BE THE COLDEST NIGHT IN A WHILE FOR MANY
LOCATIONS.
SATURDAY LOOKS DRIER AND A BIT WARMER BEFORE ANOTHER COLD FRONT
MOVES THROUGH SATURDAY NIGHT AND SUNDAY WITH A REINFORCING SHOT OF
COLDER AIR. THIS IS SIMILAR TO THE LAST FEW, WITH MORE WIND
IMPACTS THAN SNOW AS IT IS, SAY IT WITH ME, MOISTURE STARVED.
FOLLOWING THAT, FLOW TURNS MORE ZONAL AGAIN AND WILL BRING A
RETURN TO NEAR TO SOMEWHAT ABOVE NORMAL TEMPERATURES BY EARLY
NEXT WEEK.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 930 PM MST WED JAN 21 2026
FEW-SCT FL200-300 THROUGH 18Z. CLOUDS WILL INCREASE TO BKN
THROUGH THE AFTERNOON, BECOMING OVC AFTER 00Z OVER KRIW/KLND,
KCPR AND JOHNSON COUNTY. THIS WILL ALSO LEAD TO MOUNTAIN
OBSCURATIONS OVER THE BIGHORNS AND CASPER MOUNTAINS AS CEILINGS
DROP TO FL070. THIS TREND OF BKN-OVC SKIES WILL SPREAD ACROSS
THE REST OF THE AREA EAST OF THE DIVIDE (KCOD/KWRL) AS A
COLD/ARCTIC FRONT DROPS SOUTHWARD. MOUNTAIN OBSCURATIONS WILL
ALSO INCREASE OVER THE NORTHWESTERN MOUNTAINS TOWARD 06Z FRIDAY.
CHANCES FOR LIGHT SNOW WILL ALSO INCREASE AFTER 06Z FRIDAY
BEHIND THE COLD/ARCTIC FRONT. OTHERWISE, WINDS WILL BE LIGHT
(11KT OR LESS) THROUGH THE TAF PERIOD.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZDV AND ZLC FOR
THE LATEST INFORMATION ON ICING AND TURBULENCE FORECASTS.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...DZIEWALTOWSKI
DISCUSSION...HATTINGS
AVIATION...LAVOIE
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