855
FXUS65 KCYS 101115
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
515 AM MDT THU SEP 10 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 1219 AM MDT THU SEP 10 2026
TRANSIENT RIDGING TODAY CONTINUES TO PRODUCE SOME OF THE DRIEST
CONDITIONS WE'VE SEEN, WITH SURFACE PRESSURE GRADIENTS IN THE
WESTERN HALF OF OUR CWA PROMOTING CRITICAL FIRE WEATHER
CONDITIONS FROM GUSTY WINDS. LOOKING AT LATEST HIGH RESOLUTION
OUTPUT, SEEING ENOUGH CONCERN OF MORE WIDESPREAD 20-40 MPH WIND
GUSTS TO EXPAND THE RED FLAG WARNINGS ACROSS THE REGION,
INCLUDING MORE OF THE MOUNTAINS THROUGH THE LARAMIE SUMMIT AREA
AND INTO PLATTE AND GOSHEN COUNTIES. IN FACT, WOULD NOT BE
SURPRISING TO SEE RED FLAG CONDITIONS POSSIBLY EXPANDING INTO
LARAMIE COUNTY, BUT FOR NOW HAVE LEFT THE CHEYENNE ZONE OUT, BUT
WILL PASS ALONG CONCERNS TO THE INCOMING DAY SHIFT. OUTSIDE OF
THIS CRITICAL FIRE WEATHER ENVIRONMENT, SENSIBLE WEATHER
CONCERNS ARE NIL DURING AN OTHERWISE BENIGN WEATHER DAY, WITH
HIGHS AROUND 5 TO 8 DEGREES ABOVE NORMAL.
FRIDAY WE'LL SEE INCREASING ZONAL FLOW WITH MONSOONAL MOISTURE
BEGINNING TO RETURN, THOUGH WE'LL STILL REMAIN NOTABLY DRY
OVERALL. AT THE SURFACE, A COLD FRONT SHOULD DROP DOWN FROM THE
NORTH AND FULLY PASS ACROSS OUR REGION BY SATURDAY MORNING.
WHILE THE INCREASED MOISTURE MAY BRING A CHANCE AT PRECIPITATION
RETURNING, INVERTED V PROFILES REMAIN PREVALENT ACROSS THE
FORECAST AREA, MEANING WE SHOULD CONTINUE TO PRIMARILY SEE GUSTY
VIRGA SHOWERS AND PERHAPS SOME DRY LIGHTNING. GUSTIER WINDS
SHOULD SHIFT FURTHER EAST, AND WITH RH VALUES REMAINING IN THE
TEENS ACROSS FAR EASTERN WYOMING AND THE NEBRASKA PANHANDLE,
IT'S VERY LIKELY WE'LL NEED TO CONTINUE RED FLAG WARNINGS AND
EXTEND THEM TO THE EAST FOR THE DAY. OTHERWISE, TEMPERATURES
LARGELY SIMILAR TO THURSDAY, STILL REMAINING SEVERAL DEGREES
ABOVE NORMAL BEFORE THE COLD FRONT DROPS US BACK DOWN OVER THE
WEEKEND.
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 /12Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 512 AM MDT THU SEP 10 2026
VFR CONDITIONS EXPECTED OVER THE NEXT 24 HOURS. WINDS BECOMING
BREEZY FROM THE W TO SW FOR WYOMING TERMINALS THIS AFTERNOON,
WEAKENING DURING THE EVENING AND OVERNIGHT. MEANWHILE, NEBRASKA
TERMINALS SHOULD THEN SEE GUSTY WINDS BEGINNING DURING THE
EVENING HOURS AND INTO THE OVERNIGHT, FROM THE SW TO S. EXPECT
SKC WITH A CLOUD DECK MOVING IN DURING THE AFTERNOON AND EVENING
HOURS AT MID TO MOSTLY HIGH LEVELS AT FEW TO SCT.
CYS WATCHES/WARNINGS/ADVISORIES
WY...RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING FOR WYZ419>429-
432.
NE...NONE.
SHORT TERM...CG
LONG TERM...RV
AVIATION...CG
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