183
FXUS65 KCYS 220951
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
251 AM MST SUN DEC 22 2024
KEY MESSAGES
- A HIGH WIND WARNING IS IN EFFECT FOR THE WIND PRONE AREAS OF
SOUTHEAST WYOMING BEGINNING LATE SATURDAY EVENING AND
CONTINUING THROUGH SUNDAY AFTERNOON.
- MOUNTAIN SNOW LIKELY, BEGINNING SUNDAY AFTERNOON AND
CONTINUING THROUGH MONDAY.
- ACTIVE WEEK AHEAD WITH SEVERAL SYSTEMS PUSHING ACROSS THE
REGION. SOME SNOW POSSIBLE FOR CHRISTMAS DAY.
SHORT TERM /THROUGH MONDAY NIGHT/
ISSUED AT 250 AM MST SUN DEC 22 2024
CURRENT IR SATELLITE LOOP SHOWS MID TO HIGH CLOUDS INCREASING
OVER SOUTHEAST WYOMING AND INTO WESTERN NEBRASKA EARLY THIS
MORNING. THESE CLOUDS ARE ASSOCIATED WITH A PACIFIC UPPER LEVEL
TROUGH QUICKLY MOVES EAST OVER MONTANA. THIS TROUGH IS INITIALIZING
EVEN WEAKER THAN IT WAS YESTERDAY AND FURTHER NORTH COMPARED TO
THE LAST 24 TO 48 HOURS. THEREFORE, PEAK WIND SPEEDS ACROSS THE
WIND PRONE AREAS SHOULD NOT BE AS HIGH AS PREVIOUSLY EXPECTED.
KEPT THE HIGH WIND WARNINGS GOING FOR TODAY WITH BORDEAUX
GUSTING TO 57 MPH AT 200 AM. WINDS HAVE BEEN SLOW TO INCREASE,
BUT SHOULD CONTINUE TO TREND HIGHER THROUGH THE MORNING HOURS.
NUDGED WIND SPEEDS DOWN A LITTLE BASED ON RECENT MODEL TRENDS,
BUT STILL EXPECT SOME WIND PRONE LOCATIONS TO SEE PEAK GUSTS
AROUND 65 MPH TODAY. GUIDANCE NO LONGER SHOWS THE SUB-WIND PRONE
AREAS REACHING CRITERIA TODAY. HOWEVER, IT WILL STILL BE WINDY
LATE THIS MORNING THROUGH THIS AFTERNOON.
WEAK COOL FRONT WILL SWING THROUGH THE FORECAST AREA THIS
AFTERNOON AND INTO THIS EVENING. IT WILL STILL BE WELL ABOVE
AVERAGE FOR THIS TIME OF THE YEAR WITH HIGHS IN THE MID 50S TO
LOW 60S, WHICH SHOULD BE A FEW DEGREES COOLER THAN YESTERDAY.
OTHERWISE, EXPECT SOME MOUNTAIN SNOWFALL TO DEVELOP LATE THIS
AFTERNOON, BUT MAINLY TONIGHT, AS THE COOL FRONT STALLS ACROSS
THE MOUNTAINS AND THE NEXT PACIFIC WAVE BEGINS TO PUSH ONSHORE
ACROSS OREGON AND WASHINGTON STATE. THIS TROUGH IS FORECAST TO
DIG SOUTH INTO WYOMING AS WE HEAD INTO MONDAY WITH STEADY
SNOWFALL EXPECTED FOR THE MOUNTAINS. PERIODS OF SNOW ARE
FORECAST FOR THE VALLEYS, INCLUDING SARATOGA, RAWLINS, AND
ELK MOUNTAIN...AND PERHAPS LARAMIE. HOWEVER, LITTLE IF ANY SNOW
ACCUMULATION EXPECTED FOR THE HIGH VALLEYS WITH THIS EVENT DUE
TO THE LACK OF DYNAMIC FORCING, WEAK LIFT, AND LITTLE UPPER
LEVEL SUPPORT. EXPECT ISOLATED OR SCATTERED BRIEF FLURRIES
POSSIBLE. FOR THE MOUNTAINS, SNOWFALL TOTALS HAVE CONTINUED TO
TREND HIGHER WITH THE HIGHER PEAKS OF THE SNOWY RANGE AND SIERRA
MADRE RANGE BETWEEN 6 TO 8 INCHES AT THIS TIME THROUGH MONDAY
EVENING, MAINLY DUE TO DECENT UPSLOPE SOUTHWEST WINDS. IF THIS
TREND CONTINUES OVER THE NEXT 24 HOURS, MAY NEED A LAST MINUTE
WINTER WEATHER ADVISORY FOR MODERATE SNOW ACCUMULATIONS ABOVE
9000 FEET. SINCE THIS SNOWFALL DOESN'T APPEAR TO BE STEADY UNTIL
MONDAY MORNING, DECIDED TO HOLD OFF ON ANY ADVISORIES FOR THE
MOUNTAINS AT THIS TIME.
LONG TERM /TUESDAY THROUGH SATURDAY/
ISSUED AT 203 AM MST SUN DEC 22 2024
TUESDAY...AS A RIDGE ALOFT MOVES OVERHEAD, A DRIER AND COOLER DAY IS
ON TAP IN THE WAKE OF THE SHORTWAVE TROUGH ALOFT AND WITH 700 MB
TEMPERATURES NEAR -1 CELSIUS.
CHRISTMAS...A TRANSITORY RIDGE ALOFT MOVES OVERHEAD EARLY IN THE
DAY, IN ADVANCE OF THE NEXT PROGRESSIVE SHORTWAVE TROUGH ALOFT
MOVING OVER COLORADO. THE TRAJECTORY OF THIS TROUGH SUGGESTS THAT
MOST OF THE SNOW ASSOCIATED WITH THE SYSTEM WILL REMAIN TO OUR SOUTH
ACROSS COLORADO, THOUGH WE WILL STILL SEE CHANCES FOR SNOW OVER AND
NEAR THE MOUNTAINS ALONG AND WEST OF I-25 IN THE MORNING, AND WEST
OF A DOUGLAS TO SIDNEY LINE IN THE AFTERNOON. 700 MB TEMPERATURES
NEAR -5 CELSIUS WILL YIELD MAXIMUM TEMPERATURES IN THE 40S.
THURSDAY...A PRIMARILY DRY DAY IS EXPECTED WITH A SHORTWAVE RIDGE
MOVING OVERHEAD, ALTHOUGH THERE WILL BE A CHANCE OF AFTERNOON
OROGRAPHIC SNOW SHOWERS FOR THE SIERRA MADRE RANGE IN ADVANCE OF THE
NEXT SHORTWAVE TROUGH ALOFT.
FRIDAY...ANOTHER SHORTWAVE TROUGH ALOFT MOVES OVERHEAD, SPREADING
OROGRAPHIC SNOW SHOWERS OVER OUR SNOWY AND SIERRA MADRE RANGES,
THOUGH WITH MINIMAL PRECIPITATION ELSEWHERE AS THE SYSTEM IS
MOISTURE LACKING. 700 MB TEMPERATURES NEAR -6 CELSIUS WILL YIELD
MAXIMUM TEMPERATURES IN THE MID TO UPPER 30S WEST OF I-25, WITH
LOWER TO MID 40S EAST OF I-25.
SATURDAY...FAST MOVING NORTHWEST FLOW ALOFT DEVELOPS IN THE WAKE OF
THE SHORTWAVE TROUGH ALOFT PASSAGE, PRODUCING A BREEZY TO WINDY DAY,
WITH SLIGHTLY WARMER TEMPERATURES DUE TO LESS CLOUD COVER COMPARED
TO FRIDAY.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 1019 PM MST SAT DEC 21 2024
THE MAIN AVIATION CONCERNS TONIGHT INTO SUNDAY AM ARE DUE TO
WIND GUSTS AND LLWS. EXPECT LLWS TO DEVELOP OVER THE NEXT FEW
HOURS AT ALL TERMINALS, WITH OCCASIONAL GUSTS MAKING IT TO THE
SURFACE AT WYOMING TERMINALS. GUSTY W TO NW WINDS CAN BE
EXPECTED SUNDAY MID MORNING THROUGH MID AFTERNOON BEFORE
WEAKENING FOR THE LATE AFTERNOON. A WEAK STORM SYSTEM MAY BRING
LOWERING CIGS AND POSSIBLY A FEW SNOW SHOWERS TO THE VICINITY OF
KRWL SUNDAY LATE AFTERNOON AND EVENING, BUT CONFIDENCE IS TOO
LOW TO ADD TO THE TAF AT THIS TIME.
CYS WATCHES/WARNINGS/ADVISORIES
WY...HIGH WIND WARNING UNTIL 5 PM MST THIS AFTERNOON FOR WYZ106-116-
117.
HIGH WIND WARNING UNTIL 8 PM MST THIS EVENING FOR WYZ110.
NE...NONE.
SHORT TERM...TJT
LONG TERM...RUBIN
AVIATION...MN
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