476
FXUS65 KCYS 150537
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1035 PM MST SUN DEC 14 2025
KEY MESSAGES
- ARCTIC COLD FRONT WILL LINGER ACROSS THE EASTERN PLAINS
SUNDAY WITH COLD TEMPERATURES AND SOME PATCHY FREEZING FOG
ACROSS WESTERN NEBRASKA.
- WARMING TREND EXPECTED LATER TODAY THROUGH EARLY NEXT WEEK WITH
STRONG WINDS RETURNING TO SOUTHEAST WYOMING TUESDAY THROUGH
THURSDAY.
- NEXT CHANCE FOR PRECIPITATION ON WEDNESDAY WITH PERIODS OF SNOW
AND RAIN POSSIBLE.
SHORT TERM /THROUGH MONDAY NIGHT/
ISSUED AT 1258 PM MST SUN DEC 14 2025
MILD AND GENERALLY TRANQUIL WEATHER WILL CONTINUE OVER SOUTHEAST
WYOMING AND WESTERN NEBRASKA THROUGHOUT THE SHORT-TERM PERIOD. A
SPRAWLING RIDGE OF HIGH PRESSURE CONTINUES TO DOMINATE THE
SYNOPTIC WEATHER PATTERN OVER THE SOUTHWESTERN CONUS, DIRECTING
THE JET STREAM AND RELATED STORM TRACK FAR INTO THE PACIFIC
NORTHWEST AND CANADIAN MARITIME. AS HEIGHTS HAVE CONTINUED TO
BUILD OVER THE PAST DAY OR SO, TIGHTER GRADIENTS HAVE ALSO
RETREATED TO THE NORTH, RESULTING IN FAR LOWER WIND SPEEDS OVER
THE WYOMING HIGH COUNTRY. LIGHT WESTERLY FLOW TODAY AROUND THE
TOP OF THE RIDGE WILL RESULT IN ANOTHER DAY OF RECORD-HIGH
TEMPERATURES, WITH CHEYENNE ALREADY BREAKING THEIR HIGH
TEMPERATURE AS OF 1PM THIS AFTERNOON. HIGH CIRRUS CLOUDS WILL
DRIFT EASTWARD THIS EVENING WITH A MOSTLY CLEAR OVERNIGHT
EXPECTED.
SHORT-TERM ENSEMBLE GUIDANCE REMAINS IN EXCELLENT AGREEMENT
SHOWING A GRADUAL BREAKDOWN IN RIDGING OVER THE REGION ON MONDAY
THROUGH TUESDAY. AS THIS OCCURS, HEIGHT GRADIENTS WILL INCREASE
ALONG WITH A MODEST INCREASE IN WESTERLY FLOW ALONG THE TOP OF
THE RIDGE AXIS. THESE TWO ELEMENTS WILL COMBINE TO INCREASE
SURFACE WIND SPEEDS ACROSS THE TYPICAL WIND-PRONE CORRIDORS OF
SOUTHEAST WYOMING ON MONDAY AND INTO TUESDAY. IN-HOUSE GUIDANCE
DOES SHOW THE POTENTIAL FOR HIGH-WIND CRITERIA EXCEEDANCE IN THE
SNOWY RANGE FOOTHILLS BY MONDAY NIGHT, HOWEVER RECENT RUNS HAVE
SOMEWHAT DELAYED THE START OF THIS HIGH WIND EVENT. THEREFORE,
WE WILL OPT TO HOLD OFF ON ANY WATCH PRODUCTS AT THIS TIME.
DESPITE SLIGHTLY LOWER HEIGHTS, FASTER WESTERLY FLOW WILL
INCREASE DOWNSLOPING EFFECTS AND AFTERNOON HIGH TEMPERATURES
WILL CONTINUE TO RUN NEAR RECORD HIGH VALUES EARLY THIS WEEK.
OVERALL FORECAST CONFIDENCE IS VERY HIGH WITH REGARD TO THE
TEMPERATURE FORECAST AND MODERATE WITH THE WIND SPEED FORECAST
GIVEN SOME UNCERTAINTY IN HIGH-WIND RAMP-UP TIMING.
LONG TERM /TUESDAY THROUGH SUNDAY/
ISSUED AT 1258 PM MST SUN DEC 14 2025
WITH A GENERALLY LOW AMPLITUDE UPPER AIR PATTERN THROUGH THE NEXT
WEEK THERE IS GOOD SYNOPTIC AGREEMENT UPON HOW THE PATTERN UNFOLDS.
BEYOND THE MONDAY NIGHT CLIPPER TO THE NORTH ALONG THE INTERNATIONAL
BORDER WILL BE A STRONGER WAVE COME WEDNESDAY THAT DIVES A BIT
FURTHER SOUTH INTO THE NORTHERN TIER US STATES WITH SUBTLE TIMING
AND STRENGTH DIFFERENCES AMONG GLOBAL ENSEMBLES. THE GEFS AND EURO
ENSEMBLES SHOW GOOD AGREEMENT ON TRACK AND TIMING OF THE WAVE BUT
DISAGREE SLIGHTLY ON THE AMPLITUDE. WHEREAS THE GEFS AND CANADIAN
ENSEMBLES AGREE BETTER ON THE AMPLITUDE OF THE WAVE AS IT PASSES TO
OUR NORTH BUT SHOW SUBTLE TIMING DIFFERENCES WITH THE GEFS BEING
SLIGHTLY SLOWER IN ITS PROGRESSION. NOW WHAT DO THESE DIFFERENCES
MEAN IN TERMS OF IMPACTS FOR THE FORECAST AREA? PROBABLY JUST
DIFFERENCES IN WHEN THE WIND SHUTS OFF AFTER IT BEGINS.
ENSEMBLE MEMBERS SHOW DECENT AGREEMENT WITH REGARDS TO THE STRENGTH
OF 700MB FLOW TUESDAY MORNING THROUGH WEDNESDAY MORNING AHEAD OF THE
WAVE AS THE 25TH TO 75TH RANGE IS ROUGHLY 40-50KTS MEANING THIS
EARLY WEEK PERIOD LIKELY STAYS CONFINED TO THE WIND PRONES FOR HIGH
WINDS WITH IN-HOUSE GUIDANCE SUPPORTING THIS. LOOKING AT WED AM
THROUGH THUR AM WE SEE 700MB FLOW TICKS UP OVER 60KTS WITH SOME
MEMBERS SHOWING AS HIGH AS 70KTS OR MORE (LOW CONFIDENCE ON THAT).
THIS WILL LIKELY BRING MORE WIDESPREAD HIGH WINDS TO THE REGION WITH
AVAILABLE GUIDANCE SHOWING THIS TO BE A MORE WIDESPREAD EVENT LIKELY
BLEEDING OUTSIDE THE WIND PRONES AND INTO THE ADJACENT HIGH PLAINS.
THIS WEDNESDAY EVENT LOOKS TO BE A QUICK HITTER AND NOT LONG LASTING
THANKFULLY (<24 HOURS). THE PRESSURE GRADIENT THEN LOOKS TO REVERSE
FOR THURSDAY (ONCE WINDS DIE DOWN ON WHICH TIMING IS STILL LOW
CONFIDENCE) SHUTTING OFF THE WIND MACHINE FOR A SHORT TIME BEFORE
ANOTHER SURGE IN WINDS ALOFT BRINGS FLOW EQUAL TO IF NOT SLIGHTLY
STRONGER THAN THE WEDNESDAY EVENT. THIS WOULD BEGIN LATE THURSDAY
LASTING WELL INTO FRIDAY AND POSSIBLY EARLY SATURDAY. FLOW THEN
LOOKS TO TURN MORE ZONAL WITH LESSER CHANCES FOR SHORTWAVE ACTIVITY
TO BRING IMPACTFUL WINDS THE REGION.
ALONG WITH THE WINDS SHOULD COME SOME LIGHT SHOTS OF MOISTURE
WED/THUR AND AGAIN NEXT WEEKEND. THIS WOULD BE MOST IMPACTFUL FOR
THE HIGH TERRAIN (ABOVE 8000FT) WHERE A FEW INCHES OF SNOW WOULD BE
EXPECTED THOUGH CAN'T RULE OUT A FEW HUNDREDTHS OF RAIN OR A DUSTING
OF SNOW IN THE LOW ELEVATIONS. LOOKING AT TEMPS QUICKLY WE ARE QUITE
A BIT ABOVE AVERAGE (37-42F ALONG EAST OF I25) WITH HIGHS LIKELY TO
REACH WELL INTO THE 50S FOR AREAS BELOW 7000FT WEDNESDAY AND THEN
FRIDAY THROUGH THE WEEKEND. THURSDAY WILL BE SLIGHTLY COOLER IN THE
40S BEHIND A COLD FRONT. LOW TO MID 60S EVEN APPEAR PROBABLE
WEDNESDAY AND FRIDAY WITH HIGH TEMPERATURE RECORDS VERY MUCH IN
DANGER FOR MOST LOCATIONS ON FRIDAY.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 1035 PM MST SUN DEC 14 2025
QUIET CONDITIONS WITH RELATIVELY LIGHT WINDS AND CLEAR SKIES
CONTINUE THROUGH MONDAY, BEFORE WINDS INCREASE OVER THE SOUTHEAST
WYOMING TERMINALS MONDAY NIGHT.
HAZARDS/WEATHER TRENDS: VFR CONDITIONS EXPECTED WITH LIGHT AND
VARIABLE WINDS OVERNIGHT THROUGH SUNRISE MONDAY.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...MAC
LONG TERM...WFOCYS
AVIATION...TJT
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