819
FXUS65 KRIW 181100
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
400 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 WAS
TURNED UP TO HIGH FOR THE PAST SEVERAL DAYS. WE START LOWERING
THAT FOR TODAY, DOWN 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 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
SNOW SHOULD BE IN THE MORNING THOUGH, 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
THOUGH 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
MY 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 BIGHORN 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 HERE ALONE. WE ALSO
ISSUED AN ADVISORY FOR NORTHERN JOHNSON COUNTY WHERE RADAR
SHOWS SNOW CONTINUING TO FEED INTO THE AREA. EVEN IN THE
BIGHORN BASIN, MOST AREAS WOULD SEE 3 INCHES OF ADDITIONAL SNOW
AT THE MOST, EXCEPT IN THE AREAS WHERE A LOCALIZED BAND OCCURS.
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, BUT
THE CHANCE IS LESS AND SHOULD NOT BE AS WIDESPREAD COMPARED TO
THE BANDS EXPECTED IN THE BIGHORN BASIN. SO, SINCE WE FEEL IT
WOULD COVER A SMALL AREA, WE WILL NOT EXTEND WINTER WEATHER
ADVISORIES IN THE WIND RIVER BASIN. 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 HOWEVER. 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. TEMPERATURES
WILL GRADUALLY WARM AS WELL. HOW FAST DEPENDS ON SNOW COVER
THOUGH, WITH THE WARMEST TEMPERATURES OCCURRING IN AREAS WITH
LESS SNOW COVER. IT IS 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 /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 350 AM MST TUE FEB 18 2025
WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS TERMINALS.
VLIFR/LIFR CONDITIONS CONTINUE AT KBPI/KPNA AS FOG DEVELOPED
ONCE AGAIN EARLIER MONDAY NIGHT. THESE CONDITIONS ARE NOT
EXPECTED TO IMPROVE UNTIL 18Z. WINDS WILL BE INCREASING AROUND
THIS TIME AS WELL, MIXING THE FOG OUT. SNOW WILL CONTINUE AT
KJAC THROUGH MUCH OF THE PERIOD, WITH SNOW BANDS POSSIBLE AT
KBPI/KPNA AND KRKS IN THE AFTERNOON. IFR/MVFR CONDITIONS ARE
EXPECTED WITH THE SNOW. WIND GUSTS OF 25 TO 30 KT WILL BE COMMON
ACROSS MUCH OF THE AREA THROUGH THE AFTERNOON AS WELL. SNOW IS
EXPECTED TO END AT KJAC BY 06Z, WITH MARGINAL MVFR CONDITIONS
LINGERING THROUGH THE REST OF THE NIGHT.
EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL TERMINALS.
SNOW BANDS CONTINUE TO MOVE THROUGH THE AREA AND WILL BECOME
VERY PREVALENT THIS AFTERNOON. THE HEAVIEST SNOW BANDS 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 AROUND 06Z, WITH IMPROVING
CONDITIONS. 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 UNTIL 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...LAVOIE/ROWE
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