173
FXUS65 KRIW 220955
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
255 AM MST SAT FEB 22 2025
KEY MESSAGES
- MAINLY DRY WEATHER WITH TEMPERATURES SLIGHTLY COOLER THAN YESTERDAY
ARE EXPECTED TODAY.
- STRONG WINDS SUNDAY THROUGH MONDAY AFTERNOON ARE POSSIBLE,
ESPECIALLY ACROSS THE ABSAROKA MOUNTAINS AND THE CODY
FOOTHILLS. A HIGH WIND WATCH HAS BEEN ISSUED FOR THESE AREAS.
- SNOW CHANCES (80-95%) RETURN TO THE WESTERN MOUNTAINS SUNDAY THROUGH
TUESDAY WITH THE LOWER ELEVATIONS AND VALLEYS SEEING
PRIMARILY RAIN OR A RAIN/SNOW MIX.
- CONTINUING TO WATCH FOR THE POSSIBILITY OF ICE JAMMING AND
FLOODING SUNDAY THROUGH TUESDAY ACROSS THE BIGHORN BASIN AND
JOHNSON COUNTY. THIS IS DUE TO WARMING TEMPERATURES AND
CURRENT SNOWPACK IN THOSE AREAS.
DISCUSSION
ISSUED AT 254 AM MST SAT FEB 22 2025
CURRENT (09Z) WATER VAPOR IMAGERY SHOWS BROAD UPPER-LEVEL RIDGING
BUILDING INTO THE INTERMOUNTAIN WEST. A FETCH OF PACIFIC MOISTURE
ROUNDING THE PERIPHERY OF THE RIDGE IS ALLOWING FOR INCREASING UPPER-
LEVEL CLOUDS TO MAKE ITS WAY INTO WYOMING. CLOUD COVER TODAY WILL
LIMIT INSOLATION ACROSS THE AREA AND KEEP TEMPERATURES SLIGHTLY
COOLER COMPARED TO YESTERDAY. DESPITE THIS INCREASED MOISTURE,
HEIGHT RISES AND A LACK OF FORCING WILL KEEP MOST OF THE AREA DRY
TODAY. HOWEVER, I CANNOT RULE OUT LIGHT SNOW THIS AFTERNOON IN
HIGHER ELEVATIONS OF THE WESTERN MOUNTAINS. SNOW AMOUNTS WILL BE
MINIMAL WITH THE HIGHEST AMOUNTS BEING UP TO 0.5 INCH.
TONIGHT, THE RIDGE WILL CONTINUE TO EXPAND WITH MOSTLY ZONAL FLOW
RETURNING TO THE REGION. A 700MB WIND MAXIMUM SITUATED OVER MONTANA
WILL SHIFT SOUTH INTO NORTHERN WYOMING AND BRING WITH IT PACIFIC
MOISTURE BY SUNDAY AFTERNOON. THE DEEP ZONAL (WESTERLY) FLOW IS
FAVORABLE FOR SNOW CHANCES ACROSS THE WESTERN MOUNTAINS THROUGH MID-
WEEK. IN THE WESTERN MOUNTAINS, THERE IS A 70-80% CHANCE OF SNOW
AMOUNTS GREATER THAN 6 INCHES (MINIMUM AMOUNT FOR A WINTER WEATHER
ADVISORY) THROUGH EARLY TUESDAY MORNING. SNOW AMOUNTS GREATER THAN
10 INCHES DROPS CONSIDERABLY TO AROUND 30% THROUGH TUESDAY MORNING.
SNOW WILL BE CONFINED TO THE HIGHER ELEVATIONS AS TEMPERATURES
ACROSS THE WESTERN VALLEYS ARE FORECAST TO BE IN THE UPPER 30S TO
LOW 40S. THEREFORE, LIQUID PRECIPITATION CAN BE EXPECTED IN THE
WESTERN VALLEYS.
LOCATIONS EAST OF THE DIVIDE SUNDAY THROUGH MONDAY AFTERNOON CAN
EXPECT MAINLY DRY WEATHER WITH WIND. THE WESTERLY 700MB WIND
MAXIMUM, A TIGHT PRESSURE GRADIENT, AND A SHARP 700MB TEMPERATURE
GRADIENT ACROSS NORTHERN WYOMING WILL ALLOW FOR HIGH WIND POTENTIAL
SUNDAY THROUGH MONDAY AFTERNOON ACROSS THE ABSAROKA MOUNTAINS AND
THE CODY FOOTHILLS. A HIGH WIND WATCH HAS BEEN ISSUED FOR THESE
AREAS FOR WEST WINDS 30 TO 40 MPH AND GUSTS UP TO 70 MPH. THE WATCH
IS IN EFFECT FROM EARLY SUNDAY MORNING THROUGH MONDAY AFTERNOON.
STRONG WINDS CANNOT BE RULED OUT FOR SOUTH PASS, OVER MOUNTAINS, AND
THE WIND CORRIDOR DURING THROUGH TUESDAY. HOWEVER, CONFIDENCE IS
MUCH LOWER IN REACHING HIGH WIND CRITERIA DUE TO NOT AS FAVORABLE
FLOW.
CONFIDENCE IS HIGH IN WARMER TEMPERATURES EAST OF THE DIVIDE WITH
HIGHS IN THE 50S FOR LOWER ELEVATIONS SUNDAY THROUGH TUESDAY. THIS
BRINGS CONTINUED CONCERN FOR ICE JAMMING AND FLOODING FOR AREAS
ACROSS THE NORTHERN BIGHORN BASIN AND JOHNSON COUNTY.
THERE IS CONSENSUS AMONGST GUIDANCE IN A SHORTWAVE DROPPING THROUGH
WYOMING TUESDAY INTO WEDNESDAY. WITH THE AVAILABLE PACIFIC MOISTURE,
THIS BRINGS THE NEXT CHANCE FOR PRECIPITATION (BOTH FROZEN AND
LIQUID) TO WESTERN AND NORTHERN WYOMING. HIGH ELEVATIONS CAN
ANTICIPATE SNOW AND THE BIGHORN BASIN WILL SEE RAIN CHANCES WITH
THIS SYSTEM. ENSEMBLE GUIDANCE IS IN AGREEMENT IN RIDGING BUILDS
BACK INTO THE REGION WEDNESDAY THROUGH THE END OF THE WORK WEEK.
THIS RIDGE WILL CUT OFF AVAILABLE MOISTURE FOR THE INTERMOUNTAIN
WEST AND KEEP PRECIPITATION CHANCES VERY LOW (LESS THAN 10%
CHANCE).
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 949 PM MST FRI FEB 21 2025
VFR CONDITIONS PREVAIL ACROSS ALL TERMINALS THROUGH MUCH OF THE TAF
PERIOD. MID TO HIGH LEVEL CIRRUS WILL BEGIN TO FILL SKIES OVER ALL
TERMINALS THROUGH THE OVERNIGHT INTO SATURDAY MORNING. A SCT/BKN200
CLOUD DECK WILL LINGER ACROSS THE REGION THROUGH MUCH OF THE
AFTERNOON ON SATURDAY. WINDS INCREASE AT KCPR, KCOD, AND KRKS DURING
THE EARLY AFTERNOON ON SATURDAY. WESTERLY WINDS OF 20 TO 30 KNOTS
WITH GUSTS OF 35 TO 40 KNOTS WILL BE POSSIBLE AT THESE TERMINALS
WITH SLIGHTLY WEAKER WINDS FOR KRKS. KRIW WILL NEED TO BE MONITORED
AS HI-RES MODELS ARE SHOWING A NORTHWESTERLY DRAINAGE WIND DEVELOP
DURING THE EVENING. THIS DRAINAGE WIND MAY BE QUITE GUSTY AT TIMES
WITH WINDS OF 15 TO 25 KNOTS WITH PERIODIC GUSTS NEAR 30 KNOTS.
WINDS GRADUALLY DECREASE BY THE LATE EVENING WITH KCOD POSSIBLY
SEEING GUSTY WINDS LINGER THROUGH THE END OF THE 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
HIGH WIND WATCH FROM LATE TONIGHT THROUGH MONDAY AFTERNOON FOR
WYZ002-003.
DISCUSSION...GERHARDT
AVIATION...DZIEWALTOWSKI
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