212
FXUS65 KCYS 180116
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
616 PM MST WED DEC 17 2025
KEY MESSAGES
- WIDESPREAD STRONG TO LOCALLY DAMAGING WINDS WILL TURN
NORTHWEST THIS EVENING AND SPREAD OVER THE HIGH PLAINS
THROUGH THURSDAY MORNING.
- A COLD FRONT SWEEPING THROUGH THE AREA WILL BRING RAIN AND
SNOW SHOWERS AND POSSIBLE TRAVEL IMPACTS ALONG AND WEST OF THE
LARAMIE RANGE.
- ANOTHER SIGNIFICANT WIND EVENT IS EXPECTED THURSDAY NIGHT INTO
FRIDAY, POSSIBLY LINGERING INTO EARLY SATURDAY. WIND GUSTS UP
TO 90 MPH WILL BE POSSIBLE ONCE AGAIN ALONG PORTIONS OF THE
I-25 CORRIDOR WITH WIDESPREAD 60 TO 80 MPH GUSTS ELSEWHERE.
- ELEVATED TO NEAR CRITICAL FIRE WEATHER CONDITIONS WILL
CONTINUE THROUGH FRIDAY. GRASSLAND WILDFIRES WILL SPREAD
RAPIDLY IN DRY AND VERY WINDY CONDITIONS.
UPDATE
ISSUED AT 620 PM MST WED DEC 17 2025
A POCKET OF VERY DRY AIR IN THE MIDDLE TO UPPER ATMOSPHERE HAS
SLOTTED ITS WAY INTO THE UPPER LEVEL LOW. THIS AREA IS APPARENT
ON GOES WATER VAPOR IMAGERY COVERING MUCH OF SOUTHEAST WYOMING
AT THIS HOUR. THE ADDITION OF VERY DRY AIR AND SUBSIDENCE IS
HELPING TO SUPPORT EXTREME MOUNTAIN WAVE BREAKING ACTIVITY IN
THE LEE OF BOTH THE SNOWY AND SIERRA MADRE MOUNTAINS. AS THIS
REGION APPROACHES THE I-25 CORRIDOR, WE MAY SEE A RESURGENCE OF
WINDS OVER THE NEXT FEW HOURS. HOWEVER, THERE IS SOME
UNCERTAINTY REGARDING IF THIS MOUNTAIN WAVE POTENTIAL WILL
EXTEND TO THE LARAMIE RANGE TOO, SINCE RIDGE HEIGHT IS A FEW
THOUSAND FEET LOWER THAN BOTH RANGES TO THE WEST. WE WILL BE
WATCHING CLOSELY OVER THE NEXT FEW HOURS.
SHORT TERM /THROUGH FRIDAY/
ISSUED AT 430 PM MST WED DEC 17 2025
EXTREMELY STRONG WINDS CONTINUE ACROSS THE AREA THIS AFTERNOON. WE
OBSERVED SIGNIFICANT MOUNTAIN WAVE BREAKING ALONG THE I-25 CORRIDOR
EARLIER TODAY, CULMINATING IN MULTIPLE MEASURED WIND GUSTS IN EXCESS
OF 90 MPH ALONG THE INTERSTATE, AND A MAXIMUM OF 112 MPH IN THE
FOOTHILLS OF THE NORTHERN LARAMIE RANGE. GRADIENTS ARE PEAKING NOW
AND WILL LIKELY BEGIN TO DECLINE OVER THE NEXT FEW HOURS AS THE
STRONG SURFACE LOW ANALYZED AT 985-MB CURRENTLY IN WESTERN SOUTH
DAKOTA BEGINS TO RAPIDLY MOVE EASTWARD. THE COLD FRONT IS BEGINNING
TO ENCROACH ON OUR AREA, TRAILING TO THE SOUTHWEST OUT OF THE
AFOREMENTIONED SURFACE LOW. CONSIDERABLE INSTABILITY IS PRESENT
ALONG THIS BOUNDARY, SUCH THAT WE HAVE OBSERVED NUMEROUS LIGHTNING
STRIKES ALONG THE STRONG BAND OF FRONTOGENESIS MOVING INTO THE AREA.
THIS WILL PROGRESS EASTWARD VERY QUICKLY, WITH THE BEST FORCING
DEPARTING THE AREA BY AROUND 7PM. WE WILL BE MONITORING THE
POTENTIAL FOR SNOW SQUALLS IN CARBON AND ALBANY COUNTY OVER THE NEXT
1-2 HOURS AS THIS FEATURE MOVES THROUGH THE AREA.
BEHIND THE FRONT THIS EVENING, WE WILL GET A BREAK FROM THE
EXCESSIVELY STRONG WINDS (75+ MPH), BUT EXPECT WINDS TO REMAIN
STRONG AND GUSTY OVER MOST OF THE AREA, BUT TURNING MORE NORTHWEST
ESPECIALLY OVER THE HIGH PLAINS. WIDESPREAD GUSTS OF 50 TO 65 MPH
WITH ISOLATED GUSTS TO 75 MPH WILL CONTINUE IN THE NORTHWEST FLOW
OVERNIGHT AND INTO THURSDAY MORNING AS TEMPERATURES DROP. SINGLE
DIGIT WIND CHILLS WILL BE WIDESPREAD BY DAYBREAK THURSDAY! HIGH WIND
WARNINGS WERE EXTENDED UNTIL 11AM FOR ALL AREAS ALONG AND EAST OF I-
25, WHILE THOSE TO THE WEST SHOULD BE ABLE TO DROP OFF AT MIDNIGHT
(EXCEPT THE WIND PRONE AREAS). THIS PHASE OF THE EVENT IS ASSOCIATED
WITH A STING JET WRAPPING AROUND THE BACKSIDE OF THE DEPARTING UPPER
LEVEL LOW. THE BEST FORCING WILL DEPART MID MORNING, AND WE SHOULD
SEE WINDS GRADUALLY DECREASING THROUGHOUT THE DAY.
THERE WILL BE LITTLE REST FOR THE WIND WEARY IN OUR AREA, AS ANOTHER
EVENT IS INCREASINGLY LIKELY TO FOLLOW RIGHT ON THE HEELS OF THIS
EVENT. THE UPPER LEVEL RIDGE WILL AMPLIFY AND EXPAND EASTWARD
THURSDAY NIGHT INTO FRIDAY WHILE ANOTHER UPPER LEVEL LOW RACES INTO
THE PACIFIC NORTHWEST. THIS WILL SUPPORT ANOTHER ROUND OF DEEP LEE
CYCLOGENESIS OVER NORTHERN MONTANA OR SOUTHERN ALBERTA. A SURFACE
TROUGH WILL TRAIL SOUTHWARD ALONG THE FRONT RANGE OF THE ROCKIES,
CAUSING THE MSLP GRADIENT TO CLIMB ONCE AGAIN AS EARLY AS SUNSET
THURSDAY. WINDS WILL RETURN FIRST TO THE WIND PRONE AREAS, THEN
SPREAD INTO ADJACENT AREAS OF CARBON/ALBANY COUNTIES DURING THE
EVENING, AND FINALLY INTO THE I-25 CORRIDOR AFTER MIDNIGHT. AT FIRST
GLANCE, FRIDAY'S EVENT LOOKS TO HAVE QUITE A BIT IN COMMON WITH
TODAY'S WIND EVENT. LOW LEVEL HEIGHT AND MSLP GRADIENTS CLIMB BACK
UP TO IMPRESSIVE HEIGHTS, MAXIMIZING FRIDAY MORNING. 700-MB WINDS
ARE EVEN STRONGER THAN TODAY'S EVENT, WITH LREF MEAN 700-MB WINDS
EXCEEDING 70 KNOTS OVER THE ENTIRE I-25 CORRIDOR FOR MOST OF FRIDAY
MORNING. WHILE THERE IS VARIABILITY IN TIMING, MOST MODELS SHOW A
REGION OF 85+ KNOT 700-MB WINDS OVER THE LARAMIE RANGE AT SOME POINT
DURING THIS EVENT. IN ADDITION, MODELS SHOW A FAIRLY POTENT
INVERSION DEVELOPING BETWEEN 600 AND 650-MB. THIS IS SLIGHTLY HIGHER
THAN THE INVERSION HEIGHT IN TODAY'S SETUP, AND A LITTLE BIT ABOVE
MOUNTAIN TOP HEIGHT FOR THE LARAMIE RANGE. THIS REDUCES CONFIDENCE
IN REACHING THE 90+ MPH GUSTS AGAIN, BUT THE EVEN STRONGER FLOW
ALOFT SUGGESTS THAT OVERALL FRIDAY'S EVENT MAY BE OF SIMILAR
MAGNITUDE TO TODAY'S. THAT BEING SAID, A WIDESPREAD HIGH WIND EVENT
IS A NEAR GUARANTEE ONCE AGAIN, WITH WIND GUSTS OF 75+ MPH EXPECTED
IN THE WIND PRONE AREAS. THE PRIMARY UNCERTAINTIES REMAINING ARE
WHETHER WE WILL BE ABLE TO REALIZE THE POTENTIAL FOR 90 TO 100 MPH
WINDS IN THE I-25 CORRIDOR ONCE AGAIN, AND HOW FAR EAST OF I-25 THE
STRONG WINDS WILL SPREAD DURING THE DAY ON FRIDAY. FOR NOW, ANOTHER
HIGH WIND WATCH HAS BEEN ISSUED FOR MOST OF SOUTHEAST WYOMING ALONG
AND WEST OF I-25.
IN ADDITION TO THE CONTINUED STRONG WINDS, FIRE WEATHER WILL BE A
CONCERN THROUGH AT LEAST FRIDAY. EVEN THOUGH TEMPERATURES ARE
EXPECTED TO DROP TONIGHT, MUCH DRIER AIR WILL MOVE IN WITH IT,
LEADING TO LOWER RH TOMORROW COMPARED TO TODAY. AS TEMPERATURES WARM
FRIDAY, RH WILL DROP FURTHER, WITH CURRENT EXPECTATIONS FOR RH
BETWEEN 15 AND 20% OVER MUCH OF THE HIGH PLAINS MIDDAY FRIDAY.
COMBINED WITH EXTREMELY STRONG WINDS ESPECIALLY IN SOUTHEAST
WYOMING AND PARCHED, DORMANT GRASSES, EXPECT TO FIND SIGNIFICANT
CONTROL ISSUES FOR ANY GRASSLAND WILDFIRES THAT ARE SPARKED
OVER THE NEXT FEW DAYS.
LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
ISSUED AT 430 PM MST WED DEC 17 2025
A BROAD RIDGE WILL BE THE DOMINATE PATTERN FOR THE
LONG TERM. FRIDAY NIGHT INTO SATURDAY, AN ALBERTA CLIPPER WILL MOVE
ACROSS THE US/CANADA BORDER COMPRESSING THE PRESSURE GRADIENT
AGAINST OUR BROAD RIDGE. THIS IN TURN WILL SUSTAIN OUR 700MB JET
INTO THE 60 TO 70KTS RANGE. CONCURRENTLY THE GLOBAL MODEL OMEGA
FIELDS ARE STILL SHOWING MAXED OUT DOWNWARD OMEGAS INDICATIVE OF
ANOTHER HIGH WIND EVENT CONTINUING THROUGH THE OVERNIGHT PERIOD. OUR
IN HOUSE ALGORITHM ALSO AGREES AS IT GIVES A 75 TO 80 PERCENT PROB
OF ACHIEVING A HIGH WIND CRITERIA. THE HIGH WIND FORECAST GETS A
LITTLE TRICKY THROUGH THE WEEKEND AS THERE IS A LITTLE BIT OF TIMING
DISAGREEMENT WITH THE ARRIVAL OF THE NEXT WAVE BETWEEN THE GLOBAL
MODELS. TO ADD TO THE UNCERTAINTY, THE ENSEMBLE CLUSTER ANALYSIS
DEPICTED ABOUT EQUAL CHANCES FOR THE GFS SOLUTION OF A MORE
PROGRESSIVE SYSTEM LIMITING THE LULL IN HIGH WINDS SATURDAY INTO
SUNDAY, AND THE EURO DELAYED SOLUTION THAT HAS THE WAVE ARRIVING
ABOUT LATE SUNDAY NIGHT INTO MONDAY MORNING. BEHIND THIS WAVE THE
700MB JET LOOKS TO BE AROUND 55 TO 60KTS WHICH WOULD BE ENOUGH TO
ACHIEVE HIGH CRITERIA. SO DEPENDING ON THE TIMING OF THIS WAVE WE
COULD SEE A LULL IN HIGH WINDS SATURDAY AFTERNOON THROUGH SUNDAY
MORNING. THE GLOBAL OMEGA FIELDS HAVE SOME DOWNWARD MOTION BUT THE
700MB JET ISN'T PORTRAYED AS HAVING SUSTAINED WINDS OF 55KTS OR
HIGHER DURING THAT TIME. BUT TO ADD SOME CONFIDENCE IN THE LULL IN
HIGH WINDS. OUR IN-HOUSE ALGORITHM SHOWS HIGHER CONFIDENCE WITH 40
TO 60 PERCENT PROBS OF ELEVATED WINDS AS OPPOSED TO WINDS THAT MEET
THE HIGH WIND CRITERIA. AFTER THE OPEN WAVE MOVES THROUGH THE WINDS
ON THE BACKSIDE LOOK CURRENTLY MORE ELEVATED WITH THE 700MB JET
BEING BETWEEN 40-55KTS. SO THE WINDS LOOK TO REMAIN GUSTY THROUGH
THE START OF THE WORK WEEK AT THE VERY LEAST. TEMPERATURES ON THE
OTHER HAND LOOK TO REMAIN IN THE HIGH 50'S TO LOW 60'S THROUGHOUT
THE LONG TERM AS THIS RIDGE IS FORECASTED TO REMAIN ANCHORED OVER
THE WEST HALF OF THE UNITED STATES. OVERNIGHT TEMPERATURES WILL DROP
INTO THE HIGH TWENTIES SATURDAY NIGHT MAKING IT THE COLDEST NIGHT AS
THE REST OF THE FORECASTED TEMPERATURES LOOK TO BE IN THE 30'S
POSSIBLY 40'S THROUGH CHRISTMAS DAY.
AVIATION /00Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 458 PM MST WED DEC 17 2025
MVFR TO VFR CONDITIONS THROUGH THE TAF PERIOD FOR THE WYOMING
TERMINALS AND VFR CONDITIONS ARE EXPECTED FOR THE NEBRASKA
TERMINALS. WINDS ARE EXPECTED TO REMAIN STRONG AND GUSTY THROUGH
THE TAF PERIOD FOR THE WYOMING TERMINALS, HOWEVER AFTER 20Z THE
WINDS WILL START WINDING DOWN FOR THE NEBRASKA TERMINALS FOR A
BRIEF LULL. THE RAIN SHOULD START TO DISSIPATE AS IT MOVES
EASTERLY PAST KCYS. KCYS MAY SEE SOME BRIEF SHOWERS BUT
SHOULDN'T BE ANYTHING MEASURABLE IF IT DOES REACH THE GROUND.
CYS WATCHES/WARNINGS/ADVISORIES
WY...HIGH WIND WARNING UNTIL 11 AM MST THURSDAY FOR WYZ102-106>108-
110-116>119.
HIGH WIND WARNING UNTIL MIDNIGHT MST TONIGHT FOR WYZ101-
103>105-109-113-115.
HIGH WIND WATCH FROM THURSDAY EVENING THROUGH LATE FRIDAY
NIGHT FOR WYZ101-107-118.
HIGH WIND WATCH FROM THURSDAY EVENING THROUGH LATE FRIDAY
NIGHT FOR WYZ103-105-106-109-113-115-117.
HIGH WIND WATCH FROM THURSDAY AFTERNOON THROUGH SATURDAY
MORNING FOR WYZ104-110-116.
NE...HIGH WIND WARNING UNTIL 11 AM MST THURSDAY FOR NEZ002-003-
019>021-054-055-095-096.
UPDATE...MN
SHORT TERM...MN
LONG TERM...MM
AVIATION...MM
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