580
FXUS65 KCYS 120846
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
246 AM MDT MON OCT 12 2026
KEY MESSAGES
- ABOVE AVERAGE TEMPERATURES WITH SCATTERED SHOWERS AND ISOLATED
THUNDERSTORM TO START OF THE WEEK. SOME SHOWERS AND THUNDER
SHOWERS MAY CONTAIN GUSTY WINDS.
- MUCH COOLER FOR THE REST OF THE WEEK WITH MODERATE TO HEAVY
RAINFALL POSSIBLE ACROSS MOST OF SOUTHEAST WYOMING AND WESTERN
NEBRASKA LATE TUESDAY THROUGH EARLY THURSDAY MORNING.
- FIRST HEAVY MOUNTAIN SNOW LIKELY TUESDAY AND WEDNESDAY AS THE
PACIFIC STORM SYSTEM SLOWLY MOVE ACROSS THE AREA. SIGNIFICANT
ACCUMULATIONS POSSIBLE ABOVE 8500 FEET.
- FIRST WIDESPREAD FREEZE LOOKING MORE LIKELY LATE WEDNESDAY
NIGHT AND/OR THURSDAY NIGHT INTO FRIDAY MORNING, ENDING THE
GROWING SEASON.
SHORT TERM /THROUGH LATE TUESDAY/
ISSUED AT 250 AM MDT MON OCT 12 2026
HIGH WIND WARNING REMAINS IN EFFECT FOR MOST OF (LOWER) CARBON
COUNTY, INCLUDING THE ELK MOUNTAIN/ARLINGTON WIND PRONE AREA
EXTENDING EASTWARD INTO FAR WESTERN ALBANY COUNTY EARLY THIS
MORNING. WINDS HAVE BEEN GUSTING BETWEEN 65 TO 73 MPH
CONSISTENTLY AS THE REMNANTS OF THE TROPICAL SYSTEM, WHICH
IMPACTED ARIZONA AND SOUTHERN CALIF THIS PAST WEEKEND, EJECTS
NORTHEAST ACROSS WESTERN WYOMING. WARNING WILL REMAIN VALID
UNTIL 600 AM, AND WILL THEN HAVE TO REEVALUATE IF WE NEED TO
EXTEND THE HW WARNING THROUGH SUNRISE. THIS WIND EVENT IS NOT
LIKE OUR OTHER TYPICAL WIND EVENTS AND HAS BEEN TRICKY TO PIN
DOWN DUE TO DIFFERENT FORCING MECHANISMS. OTHERWISE, ADDED FOG
TO THE FORECAST FOR THE NORTHERN AND CENTRAL NEBRASKA PANHANDLE
WITH CHADRON AND ALLIANCE REPORTING FOG OVER THE LAST FEW HOURS,
EXPECT THESE CONDITIONS TO LINGER THROUGH SUNRISE BEFORE FOG
LIFTS LATER THIS MORNING.
MODELS HAVE TRENDED A LITTLE MORE DRY TODAY THAN PREVIOUSLY
EXPECTED, SO LOWERED POP BELOW 30 PERCENT FOR MOST OF THE
MORNING AND EARLY AFTERNOON FOR CARBON AND ALBANY COUNTIES. KEPT
POP BELOW 10 PERCENT FURTHER EAST AS MODELS CONTINUE TO SHOW A
SUBTLE SHORTWAVE RIDGE LIFTING NORTHEAST ACROSS THE FRONT RANGE
AND ROCKY MOUNTAIN REGION THROUGH THE AFTERNOON HOURS. SHOULD BE
ONE MORE RELATIVELY PLEASANT DAY ACROSS THE REGION BEFORE
INCREASING CLOUDINESS ACROSS THE MOUNTAINS AND EASTERN PLAINS
LATE THIS AFTERNOON AND TONIGHT. RELATIVELY MILD ENTERING MID
OCTOBER WITH HIGHS IN THE 60S NORTH OF I-80, AND GENERALLY IN
THE LOW TO UPPER 70S FROM LARAMIE EASTWARD TO ALLIANCE NEBRASKA
AND SIDNEY NEBRASKA. HOWEVER, THIS BREAK WILL BE SHORT-LIVED AS
ALL MODELS INDICATE THE PACIFIC STORM SYSTEM WILL BECOME CLOSED
OFF FROM THE MEAN FLOW ALOFT...AND GRADUALLY TRACKING EASTWARD
ACROSS THE GREAT BASIN AND UTAH BY LATE MONDAY NIGHT AND EARLY
TUESDAY MORNING. EXPECT ANOTHER INCREASE IN SHOWERS AND
THUNDERSTORMS LATE THIS AFTERNOON THROUGH TONIGHT, AND AGAIN
TUESDAY AFTERNOON. CONVECTIVE PARAMETERS ARE MARGINAL, SO EXPECT
MAINLY RAIN SHOWERS (HEAVY AT TIMES) AND EMBEDDED THUNDER.
PRECIPITATION WILL COME IN BANDS INITIALLY (THROUGH EARLY
TUESDAY), WITH A MORE SOLID COVERAGE BY THE MIDDLE OF THE WEEK
AS THE PACIFIC STORM SYSTEM MOVES INTO THE ROCKY MOUNTAIN
REGION. COOLING TREND WILL BE MORE NOTICEABLE ON TUESDAY WITH
HIGHS STRUGGLING TO REACH THE UPPER 50S AND LOW 60S ACROSS THE
WHOLE AREA AS 700MB LOWER BELOW +5C. LOW TEMPERATURES EARLY
TUESDAY WILL LIKELY BE IN THE 30S TO LOW 40S ACROSS THE AREA.
NOT EXPECTING A FREEZE QUITE YET, BUT THAT'S A DEFINITE
POSSIBILITY AS WE HEAD INTO WEDNESDAY AND THURSDAY (PLEASE SEE
LONG TERM DISCUSSION FOR MORE INFO).
LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/
ISSUED AT 111 AM MDT MON OCT 12 2026
OUR WARM STREAK COMES TO A CLOSE TUESDAY WITH COOLER TEMPERATURES
EXPECTED. THE UPPER LEVEL SHORTWAVE PASSING NORTH OF OUR AREA AHEAD
OF THE STALLED UPPER LEVEL LOW WILL HELP PUSH A COLD FRONT SOUTH.
THE COOLER AIR IS RATHER SHALLOW AND WILL HAVE A HARD TIME PUSHING
PAST THE LARAMIE RANGES. LOCATIONS ALONG AND EAST OF I-25 SHOULD SEE
ABOUT A 10 TO 15 DEGREE DROP IN AFTERNOON TEMPERATURES COMPARED TO
MONDAY, WHILE FURTHER WEST A MODEST 5 DEGREE DROP IS EXPECTED. THE
TRENDS FROM YESTERDAY ARE TOWARDS A MORE SUBSTANTIAL COLD FRONT THAT
STALLS FURTHER SOUTH, THUS PUSHING THE AXIS OF BEST THETA-E
ADVECTION SOUTHWARD INTO COLORADO. THIS WILL BE THE FAVORED CORRIDOR
FOR HEAVIER CONVECTIVE RAINFALL WHEN THE UPPER LEVEL SYSTEM
APPROACHES. SCATTERED SHOWERS PASS THROUGH THE AREA THROUGH THE DAY
POST FRONT DUE TO ISENTROPIC LIFT AHEAD OF THE UPPER LEVEL LOW. NOT
MUCH RAINFALL FROM THESE SHOWERS, BUT A DREARY AND CLOUDY DAY CAN BE
EXPECTED.
OVERNIGHT, BETTER FORCING BEGINS TO MOVE IN WITH THE UPPER LEVEL
SYSTEMS ARRIVAL. THE BEST OPPORTUNITY FOR BENEFICIAL RAINFALL OCCURS
TUESDAY NIGHT THROUGH WEDNESDAY. GRAND ENSEMBLES HAVE THE BEST
CHANCES OF RAINFALL IN THE WESTERN AND SOUTHERN PORTION OF THE AREA
WHERE THE MEAN PRECIPITATION TOTALS ARE BETWEEN HALF AN INCH AND AN
INCH. IF WE MANAGE TO PULL OFF SOME MUCAPE ON OUR SIDE OF THE
SYSTEM, A FEW THUNDERSTORMS OR CONVECTIVELY ENHANCED SHOWERS MAY
MATERIALIZE TO GIVE LOCALLY HIGHER AMOUNTS. THE SNOW LEVEL SHOULD
ALSO BE LOW ENOUGH ON THE WESTERN HALF OF THE SYSTEM TO ALLOW
ELEVATIONS AT OR ABOVE ABOUT 8500 FEET TO SEE PRECIPITATION CROSS
OVER TO SNOW. THIS WOULD LET THE PEAKS OF THE SIERRA MADRE AND SNOWY
RANGES SEE SNOWFALL. IT IS A LITTLE SOON TO TALK ABOUT POSSIBLE
RANGES OF SNOWFALL AT THE PEAKS GIVEN THE WIDE ENVELOPE OF AMOUNTS
IN ENSEMBLES CURRENTLY.
AFTER WEDNESDAY WE STILL HAVE UNCERTAINTY IN THE EVOLUTION OF THE
FORECAST. AS MENTIONED IN THE PREVIOUS FEW DISCUSSIONS THE
UNCERTAINTY LIES IN IF THE UPPER LEVEL SYSTEM IS PICKED UP BY A
SOUTHEASTWARD ADVANCING CLIPPER OUT OF CANADA. THE CONSENSUS
STARTING TO RESOLVE IN DIFFERENT MODELS AND ENSEMBLES ARE TOWARDS
THE SOLUTION THAT THE TROUGH EJECTION THAT BECOMES THE CLIPPER
OCCURS NEAR ALASKA AND MOVES SOUTHEAST. STILL, THERE ARE A FEW
MODELS SUCH AS THE ECMWF THAT KEEP THE RIDGE TO THE NORTH STRONG
ENOUGH TO BLOCK THE CLIPPER AND INSTEAD THE UPPER LEVEL SYSTEM
STALLS AND LINGERS OVER OUR AREA WHILE DECAYING THROUGH THE FORECAST
PERIOD. THIS WOULD KEEP TEMPERATURES MORE MILD AND GIVE BETTER
CHANCES OF RAINFALL, BUT DOES APPEAR TO BE THE OUTLIER SOLUTION IN
MORE RECENT MODEL CYCLES. IF WE COMMIT TO THE GFS, AND A MAJORITY OF
ENSEMBLE SOLUTIONS AT THIS POINT, OF THE SYSTEM BEING PICKED UP BY
THE CLIPPER THEN WE CAN EXPECT A COLD END TO THE FORECAST. AS THE
UPPER LEVEL SYSTEM DEPARTS THE COLD AIR BEHIND IT WILL BE FORCED
SOUTHEAST BY A STRONG RIDGE. GUSTY WINDS MAY ACCOMPANY THE COLD AIR
OVER THE PLAINS REGIONS. FRIDAY MORNING LOOKS PARTICULARLY CHILLY
WITH PERHAPS THE FIRST WIDESPREAD FREEZE OF THE SEASON FOR A GOOD
PORTION OF THE AREA. CURRENTLY THE LIKELIHOOD OF FREEZING
TEMPERATURES FROM THE GRAND ENSEMBLE FOR AREAS ALONG AND EAST OF I-
25 ARE 20-40%, WHILE WEST HAVE A 50-80% CHANCE. IT IS IMPORTANT TO
MENTION THAT A GOOD NUMBER OF THE GEFS ENSEMBLE MEMBERS ARE MORE
AGGRESSIVE WITH THE PROGRESSION OF THE TROUGH THAT PROMOTES THESE
COLD TEMPERATURES AND ARE SKEWING THE OUTCOME OF THE GRAND ENSEMBLE
TOWARDS THE COLDER SOLUTIONS. IF WE GET A SOLUTION SOMEWHERE IN THE
MIDDLE WE COULD HAVE A PORTION OF THE UPPER LEVEL TROUGH ELONGATE
AND STRETCH SOUTHWEST WHILE THE MAJORITY GETS SWEPT UP. A SMALL
CHANCE THIS SOLUTION ALLOWS SOME UPSLOPE FLOW WITH THE REMAINING
MOISTURE TO CREATE SNOW SHOWERS. SNOW LEVELS WITH BE FAIRLY LOW AT
AROUND 6-5000 FEET. SATURDAY MORNING LOOKS ALSO CHILLY AS THE
WESTERN EDGE OF THE COLD AIR MASS LINGERS OVER THE PANHANDLE. AFTER
THE COLD SPELL WE WARM UP IN THE RETURN FLOW POST FRONT SATURDAY AND
SUNDAY AFTERNOONS.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 1106 PM MDT SUN OCT 11 2026
WINDS HAVE DECREASED AT MOST TERMINALS TONIGHT, OTHER THAN KLAR
AND KRWL. WINDS WILL REMAIN LIGHT AND VARIABLE FOR THE TERMINALS
WITH WINDS INCREASING INTO THE AFTERNOON HOURS. KLAR AND KRWL
WILL REMAIN GUSTY THROUGHOUT THE NIGHT AND FOR MUCH OF THE DAY
TOMORROW. LOW CLOUDS STARTED TO MOVE INTO KCDR TONIGHT WITH LOW
CEILINGS EXPECTED TO CONTINUE FOR THE NEXT SEVERAL HOURS. KAIA
MAY ALSO SEE DECREASING CEILINGS AFTER 11Z WHEN UPPER-LEVEL
CLOUDS CLEAR OUT. IFR CEILINGS WILL BE POSSIBLE. ALL CEILINGS
IMPROVE AFTER 15Z IN THE MORNING.
CYS WATCHES/WARNINGS/ADVISORIES
WY...HIGH WIND WARNING UNTIL 6 AM MDT EARLY THIS MORNING FOR WYZ104-
109>111.
NE...NONE.
SHORT TERM...TJT
LONG TERM...RV
AVIATION...AM
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