409
FXUS65 KRIW 041925
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
125 PM MDT MON MAY 4 2026
KEY MESSAGES
- THE FIRST OF A SERIES OF COLD FRONTS HAS MADE IT TO THE
CONTINENTAL DIVIDE TODAY, WHICH WILL KEEP IT COOLER THIS
AFTERNOON. SCATTERED RAIN SHOWERS AND THUNDERSTORMS WILL
DEVELOP THIS AFTERNOON, WITH MORE WIDESPREAD PRECIPITATION
TONIGHT.
- WEATHER SYSTEM BRINGS WIDESPREAD RAIN AND SNOW TONIGHT THROUGH
TUESDAY EVENING, MAINLY FOR CENTRAL AND SOUTHERN PORTIONS OF
THE AREA.
- WINTER WEATHER ADVISORIES HAVE BEEN ISSUED FOR THE EASTERN
SLOPES OF THE WIND RIVER MOUNTAINS AND BIGHORN MOUNTAINS,
MAINLY FOR SOUTH PASS AND POWDER RIVER PASS.
- FREEZE WATCHES REMAIN IN EFFECT FOR TUESDAY NIGHT INTO
WEDNESDAY MORNING, WITH WIDESPREAD TEMPERATURES BETWEEN 20
AND 30 DEGREES.
UPDATE
ISSUED AT 121 PM MDT MON MAY 4 2026
SCATTERED RAIN SHOWERS AND THUNDERSTORMS WILL DEVELOP AND MOVE
THROUGH THE AREA THIS AFTERNOON TRANSITIONING TO MORE OF A
WIDESPREAD RAIN OR SNOW FROM CENTRAL TO SOUTHERN PORTIONS OF THE
AREA. THUNDERSTORMS SHOULD BE WEAK TODAY, SO ONLY SOME SMALL HAIL,
GUSTY WIND, AND HEAVY RAIN WILL BE THREATS. THE PRECIPITATION
FORECAST FOR TONIGHT THROUGH TUESDAY NIGHT REMAINS DIFFICULT DUE TO
MANY COMPETING FACTORS. THERE IS BETTER CONSENSUS ON THE TIMING OF
THE SECOND COLD FRONT MAKING IT TO THE CONTINENTAL DIVIDE BY SUNRISE
TUESDAY AND PUSHING SOUTHWEST THROUGH SWEETWATER AND LINCOLN
COUNTY BEFORE NOON. THIS SECONDARY COLD FRONT WILL BRING MUCH
COOLER AIR ALOFT AND RESULT IN A CHANGEOVER TO ALL SNOW ONCE IT
PASSES THROUGH. THERE MAY BE A MIX OF RAIN AND SNOW TUESDAY
AFTERNOON FOR LOWER ELEVATIONS DUE TO SOME DAYTIME SURFACE
HEATING, BUT DROPPED HIGH TEMPERATURES FOR TUESDAY, BECAUSE
THICK CLOUD COVER COMBINED WITH FALLING SNOW WILL REALLY
MITIGATE MOST OF THE DAYTIME HEATING. INCREASED PRECIPITATION
AMOUNTS FOR THE WIND RIVER BASIN AS WELL AS NATRONA COUNTY WHERE
FAVORABLE JET DYNAMICS COMBINED WITH UPSLOPE FLOW WILL LIKELY
(60-70%) LEAD TO MORE PRECIPITATION THAN MODEL GUIDANCE IS
DEPICTING. SNOW AMOUNTS ARE ONLY A TRACE TO 4 INCHES FOR LOWER
ELEVATIONS DUE TO A GOOD PORTION OF THE PRECIPITATION FALLING
DURING THE DAY ON TUESDAY. THE MAY SUN ANGLE COMBINED WITH
TEMPERATURES IN THE MID TO UPPER 30S WILL GREATLY LIMIT SNOWFALL
ACCUMULATIONS DURING THE DAY ON TUESDAY. LOCATIONS WITH THE
HIGHEST IMPACTS FROM SNOW TONIGHT THROUGH TUESDAY EVENING WILL
BE POWDER RIVER PASS, SOUTH PASS, BEAVER RIM AND JEFFREY CITY,
LANDER, AND ALONG US 20/26 FROM MONETA TO NATRONA.
THE FREEZE WATCHES REMAIN IN EFFECT FOR TUESDAY NIGHT INTO WEDNESDAY
MORNING, WITH WIDESPREAD LOW TEMPERATURES FROM 20 F TO 30 F ACROSS
LOWER ELEVATIONS. A WARMUP WILL OCCUR THURSDAY AND FRIDAY, WITH
SLIGHTLY COOLER TEMPERATURES AND MORE PRECIPITATION CHANCES THIS
WEEKEND. NEXT WEEK LOOKS MUCH WARMER AND COULD PUT AN END TO ANY
POTENTIAL FOR WINTER WEATHER THIS SEASON FOR LOWER ELEVATIONS.
DISCUSSION
ISSUED AT 200 AM MDT MON MAY 4 2026
IR CURRENTLY DEPICTS A CLOSED LOW TO THE SOUTHWEST NEAR
CALIFORNIA AS WV SHOWS THE PFJ DIPPING FURTHER SOUTH OUT OF
CANADA AND MONTANA INTO NORTHEASTERN PORTIONS OF THE STATE.
CURRENT MODEL TRENDS CONTINUE THE SOUTHWARD PROGRESSION OF THE
JET WITH A JET MAX OF 120KTS PUSHING INTO THE NEXT SHORTWAVE
EXPANDING ACROSS MUCH OF THE CWA FOR MONDAY. THIS WILL DROP A
COLD FRONT THROUGH THE AREA IN THE MORNING HOURS THAT WILL SEE
COOLER TEMPERATURES FROM SUNDAY AROUND 10 TO 15 DEGREES FOR
AFTERNOON HIGHS. OTHERWISE, SCATTERED RAIN SHOWERS EXPECTED WITH
THE FRONT THAT WILL EXPAND INTO THE EVENING AND OVERNIGHT HOURS
AS THE SHORTWAVE PROGRESSIVELY MOVES ACROSS THE CWA. MINIMAL
IMPACTS EXPECTED WITH ANY SNOW ACCUMULATIONS CONSTRAINED TO
HIGHER ELEVATIONS EVEN ABOVE MOUNTAIN PASSES.
TUESDAY WILL SEE A MORE WIDESPREAD MOUNTAIN SNOW/VALLEY RAIN
EFFECT AS THE AFOREMENTIONED LOW TO THE SOUTHWEST WILL EMBED
INTO THE POSITIVELY TILTED TROUGH EXTENDING FROM THE DAKOTAS.
MORE AMPLE DIVERGENCE ALOFT EXPECTED, ESPECIALLY ACROSS THE
SOUTHERN HALF OF THE CWA WHERE QPF AMOUNTS COULD PUSH OVER A
QUARTER INCH (60-70%) IN SOME SPOTS ALONG THE I-80 CORRIDOR OF
SWEETWATER COUNTY AND POINTS SOUTH TO THE COLORADO BORDER.
OTHERWISE, SNOWFALL RATES FOR THE HIGHER ELEVATIONS WILL BE
GREATEST DURING THE AFTERNOON AND INTO THE EVENING HOURS.
MINIMAL IMPACTS EXPECTED TO MOUNTAIN PASSES (SOUTH PASS THE ONLY
ONE TO PUSH ADVISORY LEVEL AMOUNTS). HOWEVER, WITH THE WARM
TEMPERATURES AHEAD OF THIS SYSTEM AND MORE OF A LONGER DURATION
TIME FRAME, ANY ISSUANCES WERE HELD OFF AT THIS TIME FOR TUESDAY
AND TUESDAY NIGHT. HOWEVER, A REINFORCEMENT OF COOLER AIR
EXPECTED INTO WEDNESDAY MORNING SEEING A WIDESPREAD BELOW
FREEZING EVENT FOR BASINS EAST OF THE DIVIDE. AS SUCH, FREEZE
WATCHES CONTINUE WITH THIS BEING THE COLDEST MORNING OF THE WEEK
AHEAD.
ADDITIONAL PRECIPITATION CHANCES WITH MINIMAL IMPACTS EXPECTED
THURSDAY AND THURSDAY NIGHT AS THE MAIN TROUGH EXITS TO THE
EAST. THIS WILL GIVE WAY TO UPPER LEVEL RIDGING TO BUILD BACK IN
FRIDAY AND INTO THE WEEKEND WITH DRY CONDITIONS AND A WARMING
TREND EXPECTED. NORTHWEST FLOW ALOFT EXTENDS THROUGH INTO EARLY
NEXT WEEK WITH A MINOR SHORTWAVE PUSHING TO THE NORTHEAST
SATURDAY AFTERNOON THAT MIGHT SEE SOME SPORADIC SHOWERS FOR THE
BIGHORNS AND NORTHEASTERN COUNTIES, BUT MUCH OF THE ACTIVITY
WILL REMAIN NORTHEAST.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 1114 AM MDT MON MAY 4 2026
A COMPLEX WEATHER PATTERN THROUGH THE NEXT 24 HOURS (AND BEYOND).
TODAY, AFTERNOON HEATING COMBINED WITH AN APPROACHING FRONT WILL
HELP TO CREATE SHOWERS AND THUNDERSTORMS ACROSS THE AREA, GENERALLY
THROUGH ABOUT 02Z. LOCATIONS GENERALLY HAVE A 15 TO 40 PERCENT
CHANCE OF SEEING A SHOWER OR STORM, WITH THE MAIN HAZARD BEING GUSTY
OUTFLOW WINDS UP TO 40 KNOTS. CHANCES DON'T COMPLETELY END THIS
EVENING, HOWEVER, AS THE FRONT BEGINS TO MOVE THROUGH. PRECIPITATION
MODE SHOULD CHANCE FROM A SHOWERY COVERAGE TO MORE WIDESPREAD
PRECIPITATION, AND WILL CHANGE FROM RAIN TO SNOW OR RAIN/SNOW MIX
OVERNIGHT FOR MOST LOCATIONS. BETWEEN THE HOURS OF 00Z AND 12Z IS
CHALLENGING DUE TO THE COMPLEX TRANSITION OF AFTERNOON SHOWERS
ENDING, WIDESPREAD PRECIPITATION STARTING, THE FRONT MOVING THROUGH,
AND WHEN/IF A TRANSITION FROM RAIN TO ANY SNOW OCCURS. FOR MOST
LOCATIONS, PRECIPITATION CONTINUES THROUGH THE END OF THE PERIOD
ONCE IT BEGINS THIS EVENING OR OVERNIGHT. KCOD, KJAC, AND KWRL WOULD
BE THE LEAST FAVORED FOR THIS CONTINUOUS PRECIPITATION.
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
FREEZE WATCH FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY MORNING
FOR WYZ003>006-010-011-017-018-020.
WINTER WEATHER ADVISORY FROM 1 AM TUESDAY TO 1 AM MDT
WEDNESDAY FOR WYZ009-015.
UPDATE...ROWE
DISCUSSION...LOWE
AVIATION...WITTMANN
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