346
FXUS65 KRIW 210447
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
947 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.
- A 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 60F 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 INCHES 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 CLOSED LOW CIRCULATIONS, THUS, ABOVE NORMAL
TEMPERATURES AND DRIER THAN NORMAL CONDITIONS LOOK TO CONTINUE
THROUGH THE END OF THE MONTH (40% CONFIDENCE).
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 945 PM MST FRI DEC 20 2024
VFR CONDITIONS WILL CONTINUE AT ALL TERMINALS THROUGH THE TAF
PERIOD. WINDS WILL REMAIN LIGHT FOR MOST TERMINALS AS WELL,
EXCEPT KCPR. WIND GUSTS WILL INCREASE 25 TO 30 KT AROUND 17Z AND
CONTINUE THROUGH THE REST OF THE PERIOD. OTHERWISE, MID TO HIGH
CLOUDS (SOME DUE TO LEE ENHANCEMENT OFF THE ABSAROKA AND WIND
RIVER MOUNTAINS) WILL CONTINUE TO STREAM OVER THE FORECAST AREA.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...HENSLEY
AVIATION...LAVOIE
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