726
FXUS65 KCYS 111731
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1131 AM MDT SUN OCT 11 2026
KEY MESSAGES
- ABOVE AVERAGE TEMPERATURES AND CHANCES FOR GUSTY SHOWERS AND
SOME ISOLATED STORMS THROUGH SUNDAY.
- A PATTERN CHANGE WILL BRING A GRADUAL COOL DOWN AND INCREASED
CHANCES FOR PRECIPITATION THIS WEEK. MODERATE TO HEAVY
RAINFALL POSSIBLE TUESDAY NIGHT THROUGH WEDNESDAY NIGHT WITH
SOME MOUNTAIN SNOW EXPECTED.
SHORT TERM /THROUGH MONDAY NIGHT/
ISSUED AT 225 AM MDT SUN OCT 11 2026
CURRENT OBSERVATIONS ACROSS THE REGION SHOW MOSTLY CLOUDY TO
CLOUDY SKIES AND PERIODS OF LIGHT RAIN ALONG AND WEST OF THE
I-25 CORRIDOR EARLY THIS MORNING. RAINFALL HASN'T AMOUNTED TO
TOO MUCH THUS FAR, EVEN WITH A FEW THUNDER SHOWERS LAST EVENING.
THIS ACTIVITY IS ON THE FAR EASTERN PERIPHERY OF THE POTENT
PACIFIC STORM SYSTEM DIGGING SOUTH ACROSS CALIFORNIA AND OREGON
EARLY THIS MORNING. THIS PACIFIC STORM WILL ALLOW THE REMNANTS
OF TROPICAL STORM RACHAEL TO LIFT NORTHWARD OVER UTAH AND
WYOMING TODAY BRINGING SOME MUCH NEEDED RAINFALL TO THOSE AREAS.
ALTHOUGH WE'RE EXPECTING AN INCREASE IN RAINFALL (AND POSSIBLE
THUNDER) TODAY, THE MAIN FORCING WILL LIKELY REMAIN JUST WEST OF
THE FORECAST AREA WHERE FLOODING MAY BECOME A PROBLEM IN UTAH
AND EASTERN IDAHO. THIS SYSTEM WILL ALSO BRING THE FIRST
WIDESPREAD SNOWFALL TO THE NORTHERN ROCKY MOUNTAINS TODAY AND
MONDAY.
EXPECT SIMILAR CONDITIONS AT THE START OF TODAY COMPARED TO
SATURDAY, WITH SHOWERS AND THUNDERSTORMS GRADUALLY INCREASING IN
COVERAGE FROM WEST TO EAST ACROSS SOUTHEAST WYOMING...MAINLY
THIS EVENING AND TONIGHT. A LITTLE COOLER THIS AFTERNOON, MAINLY
DUE TO THE INCREASE IN CLOUD COVER AND 700MB TEMPERATURES
LOWERING A DEGREE OR TWO BEHIND A MIDLEVEL COOL FRONT. PWATS ARE
FORECAST TO INCREASE BETWEEN 0.75 TO 1.25 INCHES ACROSS THE
AREA, EASILY ABOVE THE 95TH PERCENTILE FOR THIS TIME OF THE YEAR
AS THE REMNANT TROPICAL SYSTEM LIFTS NORTH. ALSO, MODELS HAVE
TRENDED MUCH HIGHER WITH WINDS OVER CARBON AND ALBANY COUNTIES
TONIGHT WITH THE GFS AND NAM NOW SHOWING 700MB WINDS BETWEEN 50
TO 60 KNOTS. BELIEVE THIS IS THE MIDLEVEL REFLECTION OF THE
REMNANT (SUB)TROPICAL STORM QUICKLY LIFTING NORTH ACROSS CENTRAL
WYOMING TONIGHT. THIS MAKES SENSE GIVEN THE PWAT VALUES WILL
INCREASE TONIGHT ABOVE THE 99TH PERCENTILE AND CLOSE TO 00Z TO
12Z MAXES AHEAD OF THE SUBTROPICAL LOW, BASED ON NAEFS
CLIMATOLOGY FOR MID OCTOBER. ISSUED A HIGH WIND WATCH FOR MOST
OF CARBON COUNTY AND FAR WESTERN ALBANY COUNTY, INCLUDING THE
ARLINGTON/ELK MOUNTAIN WIND PRONE AREA, LATE THIS AFTERNOON
THROUGH TONIGHT. GUSTS BETWEEN 55 MPH TO 65 MPH ARE POSSIBLE
WITH SUSTAINED WINDS AROUND 30 TO 35 MPH. MODELS ALSO INDICATE
SOME STRONG LEE-SIDE SUBSIDENCE NEAR THE SIERRA MADRE AND SNOWY
RANGE, SO WILL HAVE TO KEEP AN EYE ON THIS. CONVECTIVE WINDS
WILL ALSO BE A CONCERN ALONG WITH VERY WINDY ENVIRONMENTAL
WINDS DURING THE LATE AFTERNOON AND EVENING HOURS. CONTINUED TO
INCREASE POP TONIGHT UP TO 70 PERCENT FROM CARBON COUNTY
NORTHEAST TO CONVERSE AND NIOBRARA COUNTY...WITH VALUES
GRADUALLY TAPERING DOWN EAST OF I-25. MULTIPLE BANDS OF SHOWERS
AND EMBEDDED THUNDER ARE EXPECTED...MAINLY BETWEEN 3 PM TODAY
AND MIDNIGHT TONIGHT. REMNANT SHOWERS ARE POSSIBLE EARLY MONDAY
MORNING, BUT SHOULD REMAIN IN THE MOUNTAINS AND NEARBY VALLEYS
ACROSS CARBON COUNTY.
FOR MONDAY, PLEASANT MOST OF THE DAY WITH MILD TEMPERATURES IN
THE MID 60S TO MID 70S ACROSS MOST OF THE REGION...PERHAPS
AROUND 80 FOR THE CENTRAL TO SOUTHERN NEBRASKA PANHANDLE. MODELS
SHOW A VERY SUBTLE SHORTWAVE RIDGE AXIS BUILDING INTO THE FRONT
RANGE BEHIND THE SUBTROPICAL REMNANT LOW...WHICH IS FORECAST TO
LIFT INTO THE DAKOTAS AND SOUTHERN CANADA. THIS BREAK WILL BE
SHORT-LIVED AS ALL MODELS INDICATE THE PACIFIC STORM SYSTEM
CLOSING OFF FROM THE MEAN FLOW AND EVENTUALLY TRACKING EASTWARD
ACROSS THE GREAT BASIN AND UTAH BY LATE MONDAY NIGHT. EXPECT
ANOTHER INCREASE IN SHOWERS AND THUNDERSTORMS. CONVECTIVE
PARAMETERS ARE MARGINAL, SO EXPECT MAINLY RAIN SHOWERS (HEAVY AT
TIMES) AND EMBEDDED THUNDER. COOLER AIR CONTINUES TO MOVE INTO
THE REGION MONDAY NIGHT WITH LOW TEMPERATURES FINALLY BEGINNING
TO FEEL MORE LIKE FALL (MID 30S TO LOW 40S).
LONG TERM /TUESDAY THROUGH SATURDAY/
ISSUED AT 119 AM MDT SUN OCT 11 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 /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1131 AM MDT SUN OCT 11 2026
WIND WILL BE THE PRIMARY AVIATION WEATHER CONCERN THROUGH THE
FORECAST PERIOD AS RAIN SHOWERS MOVE THROUGH THIS AFTERNOON AND
EVENING, FOLLOWED BY A STRONG LOWER JET. GUSTY ERRATIC WINDS ARE
ANTICIPATED IN/NEAR ANY SHOWER FOR THE WY TERMINALS (MAINLY RWL
AND LAR), WITH SPEEDS POSSIBLY APPROACHING 50 KTS. LOW LEVEL
WIND SHEAR IS THEN LIKELY OVERNIGHT FOR MOST TERMINALS.
MEANWHILE, AN AREA OF STRATUS MONDAY MORNING COULD BRING MVFR
CEILINGS FROM RWL TO CDR.
CYS WATCHES/WARNINGS/ADVISORIES
WY...HIGH WIND WARNING FROM 3 PM THIS AFTERNOON TO 6 AM MDT MONDAY
FOR WYZ104-109>111.
NE...NONE.
SHORT TERM...TJT
LONG TERM...RV
AVIATION...DS
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