690
FXUS65 KRIW 201945
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1245 PM MST FRI DEC 20 2024
KEY MESSAGES
- UNSEASONABLY WARM WEATHER CONTINUES THROUGH EARLY NEXT WEEK.
- A SERIES OF SHORTWAVES WILL BRING SNOW TO THE WESTERN
MOUNTAINS BEGINNING SATURDAY NIGHT, BUT LITTLE TO NO SNOW
EAST OF THE DIVIDE.
- WHITE CHRISTMAS LOOKING VERY UNLIKELY FOR MOST LOCATIONS.
DISCUSSION
ISSUED AT 1243 PM MST FRI DEC 20 2024
HIGH PRESSURE WILL CONTINUE TO BUILD OVER THE NEXT SEVERAL DAYS, AND
THUS THE UNSEASONABLY WARM AND DRY WEATHER WILL ALSO CONTINUE.
WARMEST TEMPERATURES WILL OCCUR TOMORROW (SATURDAY) WITH HIGHS
APPROACHING 60 FOR PORTIONS OF JOHNSON COUNTY AND NEAR CASPER. THESE
AREAS, ALONG WITH PORTIONS OF THE BIGHORN BASIN COULD SEE RECORD
HIGH TEMPERATURES TIED OR BROKEN (70% CHANCE). TEMPERATURES WILL BE
IN THE UPPER 40S AND LOW 50S ELSEWHERE EAST OF THE DIVIDE AND MID TO
UPPER 30S ACROSS LOWER ELEVATIONS WEST OF THE DIVIDE. NOTABLY, HIGH
ELEVATION LOCATIONS, AS HIGH AS 10,000FT, COULD SEE TEMPERATURES
NEAR TO EVEN ABOVE FREEZING (60% CHANCE OF >32F ABOVE 10,000FT).
SATURDAY NIGHT INTO SUNDAY WILL SEE THE FIRST OF SEVERAL SHORTWAVES
MOVE THROUGH, AND ATTEMPT TO BREAK DOWN THE RIDGE. THE FIRST
SHORTWAVE WILL BE WEAK AND MOSTLY DRY. GENERALLY 1 TO 3 INCHES OF
SNOW ACROSS THE TETONS SATURDAY NIGHT THROUGH THE DAY SUNDAY, WITH
LITTLE TO NO ACCUMULATION ACROSS OTHER MOUNTAINS AND VALLEYS. THERE
ALSO COULD BE IMPACTS EAST OF THE DIVIDE, BUT DUE TO WIND, NOT SNOW.
WINDS WILL INCREASE WITH A TIGHTENING GRADIENT AND JET SUPPORT
SATURDAY NIGHT INTO SUNDAY. GREATEST CHANCES FOR POTENTIAL HIGH WIND
WOULD BE OUTER DRIVE (SOUTH SIDE OF CASPER) (70% CHANCE) AND SOUTH
PASS/RED CANYON (70% CHANCE) ALONG WITH THE ABSAROKAS AND CODY
FOOTHILLS (40% CHANCE).
SUNDAY NIGHT INTO MONDAY WILL SEE A MORE ELONGATED SHORTWAVE WITH A
BIT MORE PACIFIC MOISTURE WITH IT. THIS SHORTWAVE COULD RESULT IN 4
TO 6 INCHES ACROSS THE TETONS, WITH LOCALLY HIGHER AMOUNTS IN
FAVORED PEAKS, WITH 2 TO 4 ACROSS OTHER WESTERN RANGES AND AROUND 1
INCH IN THE WESTERN VALLEYS. THIS SHORTWAVE DOES NOT LOOK TO HAVE
MUCH JET SUPPORT AND THE GRADIENT WILL BE MUCH WEAKER, SO WIND
IMPACTS ARE NOT EXPECTED WITH THIS SHORTWAVE.
BECAUSE OF THE PROGRESSIVE NATURE OF THESE SHORTWAVES, EAST OF THE
DIVIDE LOCATIONS WILL SEE NO SNOW FROM EITHER OF THESE SHORTWAVES.
THE EXCEPTION WOULD BE THE HIGHEST PEAKS OF THE BIGHORNS, AND EVEN
THEN, LESS THAN 0.5 INCHES OF SNOW SHOULD BE EXPECTED TOTAL FROM
EITHER SHORTWAVE.
THE NEXT SHORTWAVE LOOKS TO BE CHRISTMAS DAY (WEDNESDAY), BUT MODELS
CONTINUE TO LACK CONFIDENCE IN EXACT TRACK AND INTENSITY OF THAT
WAVE. OVERALL, ANY IMPACTS ARE LOOKING LIMITED TO THE WESTERN
MOUNTAINS GIVEN LATEST TRENDS. THIS MEANS, FOR THE MAJORITY OF US, A
WHITE CHRISTMAS IS LOOKING TO BE A NO-SHOW THIS YEAR. THE PATTERN
LOOKS TO CONTINUE TO BE PROGRESSIVE WITH BROAD TROUGHINESS BEYOND
MID-WEEK, BUT MODELS ARE STRUGGLING TO RESOLVE ANY DEFINITIVE
FEATURES OR CLOSE LOW CIRCULATIONS, THUS, ABOVE NORMAL TEMPERATURES
AND DRIER THAN NORMAL CONDITIONS LOOK TO CONTINUE THROUGH THE END OF
THE MONTH (40% CONFIDENCE).
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 1046 AM MST FRI DEC 20 2024
VFR CONDITIONS ARE EXPECTED AT TERMINAL THROUGH THE PERIOD AS
RIDGING PERSISTS ACROSS THE REGION. KCPR WILL SEE A GUSTY WIND
THROUGH THE DAYLIGHT HOURS TODAY BEFORE DECREASING. OTHERWISE,
ANY CEILINGS WILL REMAIN HIGH.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...HENSLEY
AVIATION...MYERS
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