403
FXUS65 KCYS 092334
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
534 PM MDT WED SEP 9 2026
KEY MESSAGES
- DRY CONDITIONS EXPECTED THROUGH FRIDAY ALONGSIDE CRITICAL
FIRE WEATHER CONDITIONS.
- MOISTURE AND COOLER TEMPERATURES RETURN FOR THE WEEKEND, WITH
ANOTHER SHOT OF COOLER AIR TO START NEXT WEEK.
SHORT TERM /THROUGH FRIDAY NIGHT/
ISSUED AT 145 PM MDT WED SEP 9 2026
WEATHER IN THE SHORT TERM IS RATHER BENIGN AS THE FORECAST AREA SITS
IN QUASI-ZONAL FLOW THROUGH AT LEAST FRIDAY. ALTHOUGH BENIGN,
CONDITIONS WILL BE CONDUCIVE FOR FIRE WEATHER. ZONAL FLOW ALOFT WILL
LEAD TO WINDY CONDITIONS AT THE SURFACE AS A DECENT MSLP GRADIENT
SETS UP OVER THE WESTERN HALF OF THE CWA. EVEN 850 MB CAG TO CPR
HEIGHT GRADIENTS SHOW A SLIGHT RESPONSE, PEAKING INTO THE 40 METER
RANGE ON BOTH THURSDAY AND FRIDAY. WINDS ALOFT DURING THE DAY WILL
ONLY RANGE FROM 30 TO 35 KTS, SO WHILE NOT HIGH WINDS, 30 TO 40 MPH
GUSTS AT THE SURFACE WILL BE FAVORABLE FOR RAPID FIRE SPREAD.
WESTERLY FLOW WILL USHER A VERY DRY AIRMASS INTO THE AREA WEDNESDAY
AFTERNOON. THIS AIRMASS WILL STICK AROUND THROUGH THURSDAY NIGHT,
LEADING TO LOW RELATIVE HUMIDITY. OVERNIGHT HUMIDITY RECOVERIES BOTH
WEDNESDAY AND THURSDAY NIGHT WILL BE POOR, AS BREEZY CONDITIONS KEEP
THE SURFACE DRY. THURSDAY WILL BE THE DRIEST DAY WITH RELATIVE
HUMIDITY FALLING INTO THE SINGLE DIGITS FOR MOST OF THE FORECAST
AREA. HIGH TEMPERATURES WILL ALSO WARM ABOUT 5 TO 10 DEGREES
COMPARED TO WEDNESDAY. RED FLAG WARNINGS ARE ALREADY IN PLACE THIS
AFTERNOON THROUGH THURSDAY EVENING, MAINLY FOR CARBON COUNTY AND THE
CENTRAL TO NORTHERN LARAMIE RANGE. THE FIRE WEATHER THREAT SHIFTS
EASTWARD ON FRIDAY INTO NEBRASKA AS A WEAK DISTURBANCE ALOFT RAISES
MID-LEVEL RELATIVE HUMIDITY OVER THE WESTERN ZONES.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
ISSUED AT 145 PM MDT WED SEP 9 2026
A COLD FRONT SHOULD HAVE MADE ITS WAY THROUGH THE AREA OVERNIGHT
FRIDAY. THE TIMING IS IN FAIRLY GOOD AGREEMENT BETWEEN GLOBAL MODELS
WITH A FIVE DEGREE DROP IN THE MORNING MINIMUM TEMPERATURES COMPARED
TO FRIDAY. THIS WILL TRANSLATE INTO A PLEASANT AFTERNOON WITH HIGHS
IN THE UPPER 70S TO LOW 80S. THE NORTHERLY WINDS BEHIND THE FRONT
SWAP TO SOUTHEASTERLY IN THE AFTERNOON WITH THE RETURN FLOW. ALOFT
IT IS POSSIBLE THAT A SHORTWAVE TROUGH IS PASSING THROUGH THE AREA.
THIS SHORTWAVE WOULD PROVIDE A LITTLE MORE LIFT AND MOISTURE TO
PERHAPS KICK OFF SCATTERED SHOWERS AND THUNDERSTORMS WITH IVT IN THE
90TH PERCENTILE.
SUNDAY WE SHOULD START TO FEEL THE EFFECTS OF A NEW UPPER LEVEL
SYSTEM MOVING INTO THE PACIFIC NORTHWEST. STRONGER RETURN FLOW AHEAD
OF THIS SYSTEM'S PASSAGE WOULD INCREASE STORM POTENTIAL. SOME
MACHINE LEARNING MODELS ARE DEPICTING A RISK AREA ON AND EAST OF I-
25. ENSEMBLE MODELS HAVE 75 PERCENT OF MEMBERS HAVING CAPE AND SHEAR
VALUES ABOVE CLIMATOLOGICAL AVERAGE AND ABOUT 30-50 PERCENT HAVING
VALUES ABOVE THE 90TH PERCENTILE OF CLIMATE. IN OTHER WORDS THE
SIGNAL FOR SEVERE WEATHER IS STARTING TO SHOW IN GUIDANCE. A COLD
FRONT ASSOCIATED WITH THE PACIFIC SYSTEM PASSES THROUGH SOMETIME
SUNDAY NIGHT INTO MONDAY MORNING.
POST FRONT TEMPERATURES COOL AND A DRYING TREND STARTS AS A RIDGE
BUILDS UP AGAIN. RETURN FLOW POSSIBLE ON TUESDAY WHICH COULD ALLOW
MORE DIURNAL SHOWER AND STORM ACTIVITY. THE SIGNAL FOR ANOTHER
SYSTEM AT THIS RANGE IS MURKY. IF NO OTHER SYSTEM TURNS UP IN
ENSEMBLES EXPECT THE RIDGING PATTERN TO PERSIST IN THE LONG
TERM.
AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 517 PM MDT WED SEP 9 2026
THE CIRRUS SHIELD THAT HAS BEEN MOVING OVER THE AREA THIS
AFTERNOON WILL DEPART THIS EVENING LEAVING SKIES CLEAR. WINDS
ARE GENERALLY GUSTY OVER KRWL AND KLAR, BUT ARE EXPECTED TO
CALM IN THE NEXT FEW HOURS WITH THE LOSS OF DAYTIME HEATING. THE
SAME OCCURS AT ALL OTHER TERMINALS WITH CALM AND SOMETIMES
VARIABLE WINDS. THERE IS A LOW CONFIDENCE SIGNAL OF PATCHY FOG
OR LOW CLOUD CEILINGS IN SOME HIGH RESOLUTION MODELS FOR THE
NEBRASKA PANHANDLE TERMINALS. THE GREATEST SIGNAL BEING FOR
KSNY. HOWEVER, TRENDS HAVE BEEN TOWARDS LOWER RELATIVE HUMIDITY
VALUES AT THE SURFACE, SO TAFS CURRENTLY DO NOT INCLUDE FOG IN
THE FORECAST. TOMORROW MORNING, ABOUT 15Z, WINDS PICK UP AGAIN
OUT OF THE WEST WITH GUSTS TO 25-30 KNOT POSSIBLE AT KRWL, KLAR,
AND KCYS.
CYS WATCHES/WARNINGS/ADVISORIES
WY...RED FLAG WARNING UNTIL 8 PM MDT THURSDAY FOR WYZ419>422-425-
427.
NE...NONE.
SHORT TERM...SF
LONG TERM...RV
AVIATION...ML/RV
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