886
FXUS65 KRIW 290351
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
951 PM MDT FRI MAR 28 2025
KEY MESSAGES
- RAIN SHOWERS ARE EXPECTED (40-80%) ACROSS THE AREA THIS
AFTERNOON AND OVERNIGHT. JOHNSON AND NATRONA COUNTIES COULD
SEE PRECIPITATION AMOUNTS UP TO 0.30" TO 0.50" THROUGH MIDDAY
SATURDAY. AN EMBEDDED THUNDERSTORM CANNOT BE RULED OUT.
- WIDESPREAD PRECIPITATION IS FORECAST ACROSS THE AREA BY
SATURDAY AFTERNOON/EARLY EVENING WITH RAIN TRANSITIONING TO A
RAIN/SNOW MIX AND THEN SNOW OVERNIGHT SATURDAY INTO SUNDAY.
ALL SNOW IS EXPECTED IN THE MOUNTAINS.
- A WINTER WEATHER ADVISORY HAS BEEN ISSUED FOR THE EASTERN
SLOPES OF THE WIND RIVER MOUNTAINS, THE ABSAROKAS, AND THE
EASTERN BIGHORN SLOPES STARTING 4PM SATURDAY FOR SNOW AMOUNTS
BETWEEN 6-12 INCHES.
- A WETTER AND COOLER WEATHER PATTERN REMAINS IN PLACE THROUGH
THE FIRST HALF OF NEXT WEEK.
UPDATE
ISSUED AT 239 PM MDT FRI MAR 28 2025
SATELLITE WATER VAPOR IMAGERY SHOWS SOUTHWEST FLOW ACROSS THE
INTERMOUNTAIN WEST WITH AN EMBEDDED SHORTWAVE TROUGH MOVING INTO THE
REGION. THIS SHORTWAVE WILL PROVIDE SUPPORT ALOFT FOR SCATTERED RAIN
AND/OR SNOW SHOWERS ACROSS PORTIONS OF THE AREA BEGINNING THIS
AFTERNOON AND CONTINUING OVERNIGHT. THIS AFTERNOON, CHANCES (40-80%)
FOR SHOWERS EXIST ACROSS SWEETWATER COUNTY, PORTIONS OF THE
GREEN RIVER BASIN, AND EAST OF THE DIVIDE. THE FORECAST REMAINS
ON TRACK WITH PRECIPITATION FALLING LARGELY AS RAIN ACROSS MOST
OF THESE LOCATIONS THIS AFTERNOON AND EARLY EVENING WITH
TEMPERATURES 20-30 DEGREES ABOVE FREEZING. RAIN AMOUNTS ARE
STILL EXPECTED TO BE GREATEST (0.30-0.50 INCHES) ACROSS NATRONA
AND JOHNSON COUNTIES WITH MAXIMIZED LOW-LEVEL MOISTURE
CONVERGENCE AS A 700MB LOW DEVELOPS IN THAT AREA. A FEW
EMBEDDED THUNDERSTORMS CANNOT BE RULED OUT ACROSS NATRONA AND
JOHNSON COUNTIES WITH MID-LEVEL LAPSE RATES BETWEEN 8-8.5 C/KM.
THE BIGHORN MOUNTAINS CAN EXPECT A FEW INCHES OF SNOW OVERNIGHT
TONIGHT.
THE SHORTWAVE'S FORCING WILL BE EAST OF THE REGION BY SATURDAY
MORNING; HOWEVER, A FEW LINGERING LIGHT RAIN SHOWERS REMAIN POSSIBLE
(30-50%) ACROSS EASTERN NATRONA AND JOHNSON COUNTIES THROUGH MID-DAY
SATURDAY. THE NEXT CHANCES FOR WIDESPREAD RAIN AND SNOW IS SATURDAY
AFTERNOON AS ANOTHER SHORTWAVE AND A 700MB LOW TRAVERSES THE REGION.
THE 700MB LOW IS FORECAST TO TRACK FROM SOUTHERN WYOMING INTO
NORTHEAST WYOMING. THIS IS A FAVORABLE FLOW PATTERN FOR
SUFFICIENT UPSLOPE FOR THE EASTERN SLOPES OF THE WIND RIVER
MOUNTAINS, THE SOUTHERN PORTIONS OF THE ABSAROKAS, AND THE
EASTERN BIGHORNS. THERE IS AN 80% CHANCE OF AT LEAST 6 INCHES
OF SNOW IN THE AFOREMENTIONED LOCATIONS. THESE HIGHER
PROBABILITIES COMBINED WITH A FAVORABLE FLOW PATTERN, SUFFICIENT
MOISTURE (PWATS 0.25-0.35), AND BELOW FREEZING TEMPERATURES, A
WINTER WEATHER ADVISORY HAS BEEN ISSUED BEGINNING SATURDAY AT
4PM.
DISCUSSION
ISSUED AT 208 AM MDT FRI MAR 28 2025
RAIN SHOWERS MOVED OVER YELLOWSTONE NP EARLY THIS MORNING, WITH THE
EXPECTED COLD FRONT LAGGING A COUPLE OF HOURS BEHIND. RAIN TO
RAIN/SNOW SHOWERS WILL OCCUR OVER FAR WESTERN PORTIONS FROM THE
INCOMING BAND OF PRECIPITATION FROM ID THROUGH 12Z. WINDS WILL TURN
WEST-NORTHWEST IN THE WAKE OF THE FRONT AS IT PROGRESSES EASTWARD
THIS MORNING, WITH GUSTS OF 35 TO 45 MPH OCCURRING BETWEEN 08Z AND
13Z. THESE WINDS WILL BE DECREASING TOWARD THE END OF THIS TIMEFRAME
AND THE COLD FRONT EXITING THE CWA BY 15Z.
TEMPERATURES WILL BE 10 TO 15 DEGREES COOLER TODAY, AS A RESULT OF
THE FRONT, WITH HIGHS RETURNING TO THE 50S AND 60S. WINDS WILL NOT
BE AS STRONG AS YESTERDAY EITHER. A SHORTWAVE TROUGH FROM AN UPPER
LOW SITTING OFF THE PACNW COAST WILL APPROACH THE REGION TODAY,
BRINGING THE CHANCE FOR WIDELY SCATTERED SHOWERS BACK TO THE CWA.
THE BEST CHANCES (30-50%) LOOK TO BE OVER FAR NORTHWESTERN PORTIONS
AND THE WIND CORRIDOR. THERE COULD BE ENOUGH INSTABILITY WITH THE
SHOWERS OVER YELLOWSTONE AND THE JACKSON VALLEY FOR A THUNDERSTORM
TO OCCUR. THE SHOWERS OVER THE WIND CORRIDOR WILL SPREAD INTO
JOHNSON COUNTY THROUGH THE EVENING, WITH A 40-70% CHANCE FOR SHOWERS
TO OCCUR IN THIS AREA (JOHNSON/NATRONA COUNTIES) AS WELL AS FAR
EASTERN SWEETWATER COUNTY FROM 04Z-09Z. THIS WILL BE DUE TO A
MIDLEVEL LOW THAT WILL MOVE OVER EASTERN SWEETWATER COUNTY TO
SOUTHERN NATRONA COUNTY DURING THIS TIME. PRECIPITATION WILL BECOME
CONFINED TO JOHNSON/NATRONA COUNTIES AFTER 09Z, WITH PRECIPITATION
AMOUNTS OF 0.3" TO 0.5" POSSIBLE THROUGH 18Z. THIS WILL BE DUE TO
FAVORABLE, PERSISTENT UPSLOPE FLOW AS THE MIDLEVEL LOW STALLS. SNOW
LEVELS LOOK TO DROP TO 7000FT TONIGHT, WHICH WILL LEAD TO A FEW
INCHES OF SNOW OVER THE BIGHORNS FROM THIS EVENT TONIGHT.
PRECIPITATION CHANCES WILL CONTINUE TO BE WIDESPREAD ACROSS THE CWA
SATURDAY, AS THE UPPER LOW MOVES ONSHORE AND OVER THE PACNW,
WEAKENING AND FILLING AS IT PROGRESSES EASTWARD. THE BEST CHANCES
WILL OCCUR BY LATE AFTERNOON WITH CHANCES FOR ISOLATED THUNDERSTORMS
BEING MORE WIDESPREAD AS WELL. THIS WILL BE DUE TO STEEP LOW LEVEL
LAPSE RATES. ALSO, THERE COULD BE RAIN AND/OR SNOW SHOWERS OCCURRING
SATURDAY AFTERNOON SO TECHNICALLY THERE COULD BE THUNDER SNOW. THE
MOST LIKELY LOCATION OF THIS OCCURRING WOULD BE OVER SOUTHERN
FREMONT COUNTY, FROM SOUTH PASS/RED CANYON TO JEFFREY CITY. APART
FROM THE REDUCTION IN VISIBILITY, THE MAIN IMPACT FROM ANY SNOW
SHOWER WILL BE SNOW AND WILL BE CONFINED TO GRASSY AREAS.
PRECIPITATION WILL CONTINUE THROUGH SATURDAY NIGHT WITH SNOW
OCCURRING FOR MOST AREAS BY 06Z SUNDAY. THE MAIN LOW WILL TAKE A
SIMILAR TRACK AS TONIGHT, MOVING ACROSS SWEETWATER COUNTY TOWARD
SOUTHERN NATRONA COUNTY BETWEEN 00Z AND 06Z SUNDAY. ANY SNOW
ACCUMULATION IN THE LOWER ELEVATIONS WILL OCCUR OVERNIGHT, WITH THE
BETTER ACCUMULATIONS STAYING IN GRASSY AREAS. CONFIDENCE FOR HIGHER
SNOWFALL TOTALS (8 TO 12 INCHES) ARE IN THE BIGHORNS AND THE
SOUTHERN END OF THE ABSAROKAS, WHILE THE TIMING FOR GOOD UPSLOPE
FLOW OVER THE EAST SLOPES OF THE WIND RIVER MOUNTAINS IS SUSPECT AT
THIS TIME. THERE COULD BE A VERY SHALLOW LAYER (SFC-750MB)
COMPONENT, WITH BACKING WINDS TO THE NORTHWEST AT 700MB. OTHERWISE,
SNOWFALL AMOUNTS IN THE MOUNTAINS WILL RANGE BETWEEN 3 TO 6 INCHES.
PRECIPITATION WILL END FROM THE SOUTHWEST TO THE NORTHEAST THROUGH
THE DAY SUNDAY AS THE LOW EXITS EASTWARD. A TRANSITORY RIDGE WILL BE
IN PLACE BY SUNDAY NIGHT, AS ANOTHER UPPER LOW MAKES ITS WAY TO THE
PACNW. THIS WILL KEEP PACIFIC MOISTURE STREAMING OVER THE REGION AND
COULD RESULT IN ISOLATED RAIN SHOWERS OVER WESTERN AND SOUTHERN
PORTIONS AND SNOW IN THE WESTERN MOUNTAINS. THIS WOULD LIKELY
CONTINUE AND BECOME MORE WIDESPREAD INTO TUESDAY.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 951 PM MDT FRI MAR 28 2025
A BROAD LOW PRESSURE SYSTEM WILL BRING SCATTERED SHOWERS TO MUCH OF
THE AREA OVER THE NEXT 24 HOURS. SHOWERS SHUOULD ONLY BE
ISOLATED THROUGH AROUND 18Z FOR MOST TAF SITES THROUGH. THE
EXCEPTION WILL BE AROUND KCPR WHERE SHOWERS SHOULD LINGER
THROUGH THE NIGHT AND NORTHEAST WINDS BEHIND AN ASSOCIATED COLD
FRONT AT KCPR WILL KEEP IFR CIGS IN THE AREA, EVEN AFTER
PRECIPITATION ENDS, AND IFR CONDITIONS WILL CONTINUE THROUGH THE
END OF THE PERIOD. OTHERWISE, CIGS REMAIN AROUND FL100 THROUGH
THE PERIOD FOR ALL TERMINALS. SKIES DO START TO CLEAR A BIT
SATURDAY AFTERNOON, BUT ANOTHER ROUND OF PRECIPITATION WILL
BEGIN TO MOVE IN FROM THE SOUTHWEST STARTING AT AROUND 23Z
SATURDAY, AND SPREADING FROM WEST TO EAST.
WINDS REMAIN LIGHT FOR MOST TERMINALS THROUGH THE PERIOD. FOR KCPR,
KWRL, KRIW, AND KLND WINDS WILL BECOME NORTHEASTERLY BEHIND THE COLD
FRONT OVERNIGHT.
PLEASE SEE THE AVIATION WEATHER CENTER AND/OR CWSU ZDV AND ZLC FOR
THE LATEST INFORMATION ON SMOKE, ICING, AND TURBULENCE
FORECASTS.
RIW WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY FROM 4 PM SATURDAY TO NOON MDT SUNDAY
FOR WYZ002-015.
WINTER WEATHER ADVISORY FROM 4 PM SATURDAY TO 6 PM MDT SUNDAY
FOR WYZ009.
UPDATE...GERHARDT
DISCUSSION...LAVOIE
AVIATION...HATTINGS
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