590
FXUS65 KRIW 210439
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
939 PM MST TUE JAN 20 2026
KEY MESSAGES
- MOSTLY CLEAR SKIES OVERNIGHT, WITH CHILLY DAYBREAK
TEMPERATURES IN THE SINGLE DIGITS FOR BASINS EAST OF THE
DIVIDE, AND NEGATIVE SINGLE DIGITS FOR WESTERN VALLEYS.
- TEMPERATURES GRADUALLY COOL FOR THE REMAINDER OF THE WORK WEEK.
- FRIDAY AND SATURDAY LOOK TO BE THE COLDEST DAYS OVER THE NEXT
WEEK.
- MAINLY DRY AND MILD CONDITIONS RETURN FOR THE START OF NEXT
WEEK.
UPDATE
ISSUED AT 1230 PM MST TUE JAN 20 2026
NOT MUCH TO ADD IN REGARDS TO THE PREVIOUS DISCUSSION. THE FRONT
HAS BEGUN TO MOVE ACROSS THE STATE BRINGING WITH IT SCATTERED
SNOW SHOWERS. THESE SHOWERS ARE CURRENTLY MOVING THROUGH THE
BIGHORN BASIN AND PORTIONS OF JOHNSON COUNTY. SHOWERS WILL
CONTINUE TO SPREAD SOUTH BUT COVERAGE LOOKS TO GRADUALLY
DISSIPATE THE FARTHER SOUTH THEY GO. INCREASING WINDS ALONG WITH
BRIEF PERIODS OF MODERATE SNOWFALL MAY LEAD TO SOME DIFFICULT
TRAVEL CONDITIONS ESPECIALLY ACROSS JOHNSON COUNTY AND THE
BIGHORN BASIN THIS AFTERNOON AND EVENING. THE ONLY OTHER
NOTEWORTHY UPDATE REGARDING THE FORECAST IS THE POTENTIAL FOR
SOME OF THE COLDEST TEMPERATURES OF THE SEASON FOR THE UPCOMING
WEEKEND. MODELS HAVE STARTED TO SHOW THE POSSIBILITY FOR SOME
RATHER COLD AIR MAKING ITS WAY INTO THE STATE IN ASSOCIATION
WITH THE FRONTAL PASSAGE FRIDAY. 700 MB TEMPERATURES CURRENTLY
RANGE FROM -15 TO -20C ACROSS CENTRAL WY INTO THE NORTHEASTERN
CORNER OF THE STATE. THIS WOULD TRANSLATE TO LOWS POSSIBLY IN
THE SINGLE DIGITS TO MAYBE BELOW ZERO IN SOME LOCATIONS
ESPECIALLY WHERE SNOW COVER EXISTS SUCH AS WESTERN VALLEYS.
PROBABILISTIC GUIDANCE CURRENTLY SHOWS MANY LOCATIONS EAST OF
THE DIVIDE HAVING A 40-70% CHANCE OF SEEING LOWS BELOW 5 DEGREES
OVER THE WEEKEND. COLDER LOWS BELOW ZERO LOOK MORE LIKELY
(50-80%) WEST OF THE DIVIDE WHERE SNOW COVER EXISTS.
TEMPERATURES LOOKS TO REBOUND BY THE START OF NEXT WEEK AS HIGH
PRESSURE ONCE AGAIN TRIES TO REASSERT ITSELF ACROSS THE WESTERN
CONUS.
DISCUSSION
ISSUED AT 228 AM MST TUE JAN 20 2026
THERE ARE CERTAIN MILESTONES I WATCH THROUGH THE FIRST PART OF
THE YEAR. NOT BEING A WINTER LOVER, THESE ARE MARKERS I USE TO
SEE WHEN WINTER WILL END (ALTHOUGH I WOULD TAKE THIS ONE
EVERY TIME). TODAY IS THAT WE ARE A MONTH PAST THE SOLSTICE.
HOWEVER, WE STILL HAVE A LONG WAY TO GO, AND TODAY WILL BE A
REMINDER OF THAT IN PORTIONS OF THE AREA.
THE FIRST WILL TODAY, AS A COLD FRONT DROPS SOUTHWARD ACROSS THE
AREA. THE AIR BEHIND IT IS NOT ALL THAT COLD THOUGH. IT ALSO HAS
LITTLE MOISTURE TO WORK WITH. HOWEVER, THERE WILL BE IMPACTS,
ESPECIALLY TO ONE PORTION OF THE AREA. AND THIS IS JOHNSON
COUNTY. IT WILL NOT BE A LONG IMPACT THOUGH, THE ONLY LASTING
AROUND 6 HOURS, GENERALLY FROM AROUND 10 AM TO 4 PM. FIRST THE
SNOWY PART. THIS LOOKS TO BE THE LEAST IMPACTFUL, ALMOST ALL OF
THE LOWER ELEVATION LOCATIONS HAVE LESS THAN A 1 IN 5 CHANCE OF
AN INCH OR MORE OF SNOW, WITH ONLY A SMALL PORTION OF THE
BIGHORNS HAVING AT LEAST A 1 IN 2 CHANCE OF 2 INCHES OR MORE.
THE MAIN IMPACT LOOKS TO BE THE WIND. THIS WILL BE ESPECIALLY
SO IN THE FAVORED NORTHWEST FLOW / COLD ADVECTION LOCATIONS.
AND THIS INCLUDES, OBVIOUSLY, JOHNSON COUNTY. PROBABILISTIC
GUIDANCE GIVES AT LEAST A 2 OUT OF 3 CHANCE OF WIND GUSTS PAST
50 MPH THERE, AS WELL AS IN SOME OF THE WINDIER LOCATIONS WEST
OF CODY AND HIGHWAY 120. WE DID GIVE THOUGHT TO A HIGH WIND
WARNING. HOWEVER, THE 700 MILLIBAR WINDS ONLY TOP OUT AT AROUND
45 KNOTS. IN ADDITION, THIS WOULD BE A BRIEF TIME, MAINLY POST
FRONTAL BETWEEN AROUND 12 AND 3 PM. WE WILL ISSUE A SPECIAL
WEATHER STATEMENT TO COVER FOR THIS ALONG WITH REDUCED
VISIBILITY FROM POSSIBLE BLOWING AND DRIFTING SNOW WITH THE
FRONTAL PASSAGE. ALL SNOW SHOULD END SHORTLY AFTER SUNSET, WITH
A CLEARING SKY AND CHILLY TEMPERATURES OVERNIGHT.
ANOTHER COLD FRONT WILL THEN APPROACH AND MOVE THROUGH THE AREA
ON WEDNESDAY. THIS ONE HAS EVEN LESS MOISTURE TO WORK WITH AND
WOULD ONLY PRODUCE SOME SNOW SHOWERS OVER THE WESTERN BIGHORNS.
THE MAIN CONCERN WILL AGAIN BE STRONG WIND. MOST MOS GUIDANCE
KEEPS WIND BELOW HIGH WIND CRITERIA, BUT IT WILL BE BLUSTERY IN
THE SAME LOCATIONS MUCH OF WEDNESDAY, WITH AROUND A 1 IN 2
CHANCE OF WIND GUSTS PAST 45 MPH IN SIMILAR AREAS AS THIS
AFTERNOON. THIS SYSTEM WILL ALSO USHER IN A COLDER AIR MASS,
ALTHOUGH THE CORE OF THE COLD AIR WILL REMAIN EAST OF THE
FORECAST AREA. THE COLDEST AREAS WILL BE JOHNSON AND NATRONA
COUNTIES, WHERE HIGHS ON THURSDAY COULD BE 20 DEGREES COLDER
THAN TODAY, ALTHOUGH THERE IS A SPREAD IN THE MODEL GUIDANCE. A
THIRD FRONT THEN MOVES THROUGH ON FRIDAY, THIS ONE AGAIN DRY
ALTHOUGH IT WILL BRING ANOTHER SHOT OF COOLER AIR. HOWEVER,
TEMPERATURES SHOULD ONLY AVERAGE 5 TO 10 DEGREES BELOW NORMAL,
NOTHING OUT OF THE ORDINARY. SOME GUIDANCE DOES SHOW A BIT OF
MOISTURE OVERRUNNING THE COLD DOME FRIDAY NIGHT AND SATURDAY,
POSSIBLY BRINGING SOME LIGHT SNOW TO SOUTHERN WYOMING, BUT THIS
IS FAR FROM CERTAIN. THEN STARTING LATER THIS WEEKEND AND INTO
EARLY NEXT WEEK, RIDGING LOOKS TO BUILD ACROSS THE AREA AND
BRING A RETURN TO NEAR TO ABOVE NORMAL TEMPERATURES.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 939 PM MST TUE JAN 20 2026
VFR CONDITIONS WITH MOSTLY CLEAR SKIES ARE FORECAST OVER THE
NEXT 24 HOURS. GIVEN THE STRONG NORTHWESTERLY FLOW ALOFT, THE
PATTERN DOESN'T LOOK SUPPORTIVE OF FOG TONIGHT, BUT FROST IS
LIKELY (80% CHANCE) GIVEN VERY CLEAR SKIES AND STRONG
RADIATIONAL COOLING OF SURFACES OVERNIGHT.
SCATTERED HIGH CIRRUS CLOUDS MOVE INTO THE REGION DURING THE
DAY WEDNESDAY, BUT NO CLOUDS UNDER 12K FEET AGL ARE EXPECTED FOR
TAF SITES. WINDS WILL BE MUCH LIGHTER ON WEDNESDAY, WITH A FEW
LOCATIONS SEEING AFTERNOON GUSTS IN THE 20 KT RANGE. NO
PRECIPITATION IS FORECAST UNTIL FRIDAY.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...DZIEWALTOWSKI
DISCUSSION...HATTINGS
AVIATION...VANDENBOOGART
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