529
FXUS65 KRIW 180901
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
201 AM MST TUE FEB 18 2025
KEY MESSAGES
- SNOW ACROSS THE WEST SLOWLY TAPERS OFF THIS AFTERNOON AND
TONIGHT.
- SNOW SPREADS SOUTHWARD EAST OF THE DIVIDE. LOCALLY HIGHER
AMOUNTS ARE POSSIBLE IN SNOWBANDS, BUT EXACT LOCATION OF THESE
IS UNCERTAIN.
- ANOTHER, WEAKER SYSTEM BRINGS A CHANCE OF LIGHT TO MODERATE
SNOW TO WESTERN WYOMING WEDNESDAY NIGHT INTO THURSDAY.
- DRIER AND WARMER FROM FRIDAY INTO THE WEEKEND.
DISCUSSION
ISSUED AT 157 AM MST TUE FEB 18 2025
IT LOOKS LIKE WE HAVE FINALLY TURNED THE CORNER ON THE ACTIVE
WEATHER. IT SEEMS LIKE THE ACTIVITY LEVEL ON THE WEATHER STOVE AS
TURNED UP TO HIGH FOR THE PAST SEVERAL DAYS. WE START LOWERING THAT
FOR TODAY, BACK TO MEDIUM HIGH FOR TODAY, MEDIUM FOR WEDNESDAY AND
THURSDAY, AND THEN BACK TO LOW FOR FRIDAY AND POSSIBLY THROUGH THE
WEEKEND. WITH THE CONTRASTS IN THE PATTERN, WE WILL AGAIN SPLIT THE
DISCUSSION INTO WEST AND EAST OF THE DIVIDE.
WEST OF THE DIVIDE...SNOW CONTINUES ACROSS THE WEST, ALTHOUGH
INTENSITY HAS LESSENED FOR MOST LOCATIONS, ESPECIALLY THE VALLEYS.
THE ADVISORIES EXPIRE HERE AT 5 AM, AND WE WILL LIKELY LET THEM
EXPIRE. THE CHANCE OF AN ADDITIONAL 2 INCHES IN THE VALLEYS IS AT
MOST 1 OUT OF 5. AS FOR THE MOUNTAINS, WE WILL LEAVE THOSE UP FOR
NOW AS THERE IS STILL AROUND A 3 OUT OF 5 CHANCE OF 6 INCHES OR MORE
OF SNOW ACROSS THE HIGHER ELEVATIONS OF THE TETONS AND SALT AND
WYOMING RANGES THROUGH THE LIFE OF THE WARNING. THE STEADIEST SHOULD
BE IN THE MORNING THROUGH, WITH GRADUALLY LESSER SNOWFALL RATES
THROUGH THE AFTERNOON BEFORE TAPERING TO ISOLATED SHOWERS AS THE JET
ENERGY MOVES AWAY. AS FOR FAR SOUTHERN AREAS, THE MAIN THREAT WILL
BE WIND ACROSS SOUTHERN LINCOLN AND SWEEETWATER COUNTIES WITH A
GREATER THAN 1 IN 2 CHANCE OF WIND GUSTS PAST 35 MPH. THESE WINDS
SHOULD LESSEN AFTER SUNSET THROUGH AS WE LOSE THE MIXING AND THE JET
ENERGY MOVES AWAY.
THE NEXT SYSTEM THEN APPROACHES THE AREA FOR WEDNESDAY NIGHT INTO
THURSDAY. THIS SYSTEM LOOKS MUCH WEAKER THAN THE PREVIOUS ONE AND
WILL BE FASTER MOVING. CURRENT SNOWFALL AMOUNTS, EVEN IN THE
MOUNTAINS, LOOK LIKE LOW LEVEL ADVISORIES AT BEST, EVEN HERE THERE
IS AT BEST A 1 OUT OF 6 CHANCE AT THE HIGHER ELEVATIONS. I AM A BIT
CONCERNED THOUGH ACROSS SWEETWATER COUNTY ON THURSDAY WHERE SOME JET
ENERGY PASSING TO THE SOUTH MAY ENHANCE SOME SNOW. THE BIGGEST
IMPACTS WOULD BE SOUTH OF INTERSTATE 80 BUT SOMETHING TO KEEP AN EYE
ON.
WE SHOULD THEN ENTER A QUIETER PERIOD OF WEATHER AS RIDGING BUILDS
OVER THE AREA FROM FRIDAY THROUGH AT LEAST MOST OF SUNDAY. ANOTHER
SYSTEM MAY APPROACH THE AREA SUNDAY BUT EXPERIENCE HAS TOLD ME THAT
THE MODELS ARE USUALLY TOO FAST WITH PACIFIC SYSTEMS SO MAY GUT
TELLS ME THIS WOULD BE MORE OF A MONDAY SYSTEM.
EAST OF THE DIVIDE...THINGS GET MORE COMPLICATED OVER HERE. SNOW HAS
FINALLY BEGUN IN EARNEST ACROSS THE NORTHERN BIG HORN BASIN AS THE
ARCTIC BOUNDARY CONTINUES TO SLOWLY OOZE SOUTHWARD. AS EXPECTED, IT
LOOKS LIKE THE EASTERN BIGHORN BASIN WILL SEE THE HIGHEST SNOW. THE
PROBLEM HERE IS THAT THIS WILL BE MAINLY DRIVEN BY JET DYNAMICS, AND
THIS MEANS ONE OF MY FAVORITE THINGS (NOTE MY EXCESSIVE NEW ENGLAND
/ GEN X SARCASM), CONVECTIVE SNOW BANDS. THOSE WONDERFUL THINGS THAT
WE CAN'T PINPOINT AND CAN MEAN THE DIFFERENCE OF SEVERAL INCHES OF
SNOW OVER ONLY A FEW MILES. THE BEST CHANCE OF THEM WOULD BE IN THE
BIGHORN BASIN SO WE WILL LEAVE THE ADVISORIES ALONE HERE, WE ALSO
ISSUED AN ADVISORY FOR NORTHERN JOHNSON COUNTY WHERE RADAR SHOWS
SNOW CONTINUING TO FEED INTO THE AREA. EVEN IN THE BIG HORN BASIN,
MOST AREAS WOULD SEE 3 INCHES OF ADDITIONAL SNOW AT THE MOST, EXCEPT
IN THE BANDING. AND THIS LEADS US TO FREMONT AND NATRONA COUNTIES.
HERE THERE IS AT MOST A 1 IN 6 CHANCE OF 2 INCHES OF SNOW OR MORE
ACCORDING TO THE ENSEMBLE SUITE. A SMALL AREA MAY GET SEVERAL INCHES
THOUGH. THE CHANCE IS LESS THERE THOUGH AND SHOULD NOT BE AS
WIDESPREAD. SO, SINCE WE FEEL IT WOULD COVER A SMALL AREA, WE WILL
NOT EXTEND WINTER WEATHER ADVISORIES HERE. ANYTHING HERE WOULD BE A
LATER IN THE AFTERNOON OR EVENING EVENT, SO THE DAY CREW CAN
TAKE ANOTHER LOOK. ALL SHOWERS SHOULD END AFTER MIDNIGHT.
THE NEXT CONCERN IS FOR TEMPERATURES. IT WILL BE QUITE CHILLY WITH
THE ARCTIC AIR SEEPING SOUTHWARD. AREAS ACROSS THE NORTHERN BIGHORN
BASIN MAY BE APPROACHING COLD WEATHER ADVISORY TERRITORY. THIS IS
NOT CERTAIN. FIRST, THERE WILL NOT BE MUCH WIND, SO APPARENT
TEMPERATURES WILL NOT DIFFER A LOT. AND, IF IT STAYS CLOUDY THROUGH
MUCH OF THE NIGHT THIS WOULD HOLD TEMPERATURES UP. PLUS, WE ALREADY
HAVE WINTER WEATHER ADVISORIES IN EFFECT. SO, WE WILL HOLD OFF ON
ANY COLD ADVISORIES UNTIL THE SNOW ENDS. FURTHER SOUTH, CLOUD COVER
WILL STICK AROUND LONG ENOUGH TO HOLD TEMPERATURES UP SOMEWHAT.
QUIETER WEATHER SHOULD THEN MOVE IN FOR MUCH OF THE REST OF THE
PERIOD. ONE SMALL FLY IN THE OINTMENT WOULD BE SOME LIGHT SNOW IN
THE WIND RIVER BASIN IF ENOUGH MOISTURE CAN CROSS THE DIVIDE FROM
THE WEDNESDAY NIGHT/ THURSDAY SYSTEM IN THE WEST. AMOUNTS SHOULD BE
VERY LIGHT THOUGH, ALMOST CERTAINLY LESS THAN AN INCH. RIDGING
SHOULD THEN BRING DRY WEATHER THROUGH THE WEEKEND AS RIDGING BUILDS
OVER THE AREA. TEMPERATURES WILL GRADUALLY WARM AS WELL. HOW FAST
DEPENDS ON SNOW COVER THOUGH, WITH THE WARMEST IN AREAS WITH LESS
SNOW COVER. IT WORTH NOTING THAT WE WILL BE TWO MONTHS PAST THE
SOLSTICE, AND THE SUN ANGLE IS THE SAME AS MID OCTOBER. SO, THIS
COULD ENHANCE THE MELTING OF THE SNOW, ESPECIALLY OVER THE WEEKEND
WHEN TEMPERATURES WILL BE THE WARMEST.
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 950 PM MST MON FEB 17 2025
SNOW BANDS CONTINUE TO MOVE THROUGH THE AREA OVER THE NEXT 24 HOURS
AND WILL BECOME VERY PREVALENT TUESDAY AFTERNOON. THE HEAVIEST SNOW
BANDS TUESDAY AFTERNOON WILL BE CAPABLE OF PRODUCING LIFR CONDITIONS
DUE TO REDUCED VIS FROM SNOW AND LOW CIGS. MOST TERMINALS WILL HAVE
MVFR/IFR CONDITIONS AS THE SNOW BANDS MOVE THROUGH. FOR THE EXACT
TIMING PLEASE REFER TO THE TAFS AS TIMING WILL BE DIFFERENT FOR
EACH TERMINAL ACROSS THE AREA. SOME SNOW LINGERS ACROSS PORTIONS OF
THE BIGHORN BASIN, WIND RIVER BASIN, AND INTO NATRONA COUNTY TUESDAY
EVENING, OTHERWISE SNOW ENDS TUESDAY EVENING, WITH IMPROVING
CONDITIONS. FOG HAS DEVELOPED AT KPNA AND COULD HANG AROUND
THROUGH TUESDAY MORNING.
WIND WILL BE GUSTY WEST OF THE CONTINENTAL DIVIDE AS A COLD FRONT
ATTEMPTS TO MAKE IT ACROSS THE CONTINENTAL DIVIDE TUESDAY
AFTERNOON/EVENING. BEHIND THE FRONT WIND WILL BE FROM THE NORTHEAST.
THERE WILL BE GUSTS OF 20-25 KNOTS AT KBPI/KPNA AND 25-35 KNOTS AT
KRKS FROM THE WEST/NORTHWEST TUESDAY AFTERNOON. FREQUENT MOUNTAIN
OBSCURATION CONTINUES 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
WINTER STORM WARNING UNTIL 11 PM MST THIS EVENING FOR WYZ001-
002-012-024.
WINTER WEATHER ADVISORY FROM 5 AM EARLY THIS MORNING TO 5 PM
MST THIS AFTERNOON FOR WYZ003-005-006.
WINTER WEATHER ADVISORY UNTIL 5 PM MST THIS AFTERNOON FOR
WYZ004-008-010-014.
WINTER WEATHER ADVISORY UNTIL 5 AM MST EARLY THIS MORNING FOR
WYZ013-023-025.
DISCUSSION...HATTINGS
AVIATION...ROWE
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