679
FXUS65 KCYS 022340
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
ISSUED BY NATIONAL WEATHER SERVICE RIVERTON WY
540 PM MDT WED SEP 2 2026
KEY MESSAGES
- RED FLAG WARNING IN EFFECT FOR CONVERSE AND NIOBRARA
COUNTIES.
- WARMING AND DRYING TREND EXPECTED THROUGH THE END OF THE WEEK.
- PRECIPITATION CHANCES RETURN FOR THE BEGINNING OF NEXT WEEK.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 201 PM MDT WED SEP 2 2026
A FEW THUNDERSTORMS ARE ALREADY POPPING UP ON RADAR EARLY THIS
AFTERNOON AS A STRONG SHORTWAVE SWINGS THROUGH THE MAIN TROUGH
OVER THE PACIFIC NORTHWEST, SENDING SOME WEAK VORTICITY MAXES
INTO WYOMING. MESOANALYSIS SHOWS VERY LITTLE MLCAPE PRESENT
THROUGH THE AFTERNOON WITH WEAK SHEAR SO SHOWERS AND STORMS WILL
BE SHORT-LIVED. THE SURFACE REMAINS DRY, WITH OBSERVATIONS
SHOWING DEWPOINTS IN THE 30S AND 40S. MODEL SOUNDINGS SHOW STEEP
INVERTED-V PROFILES, LEADING TO DCAPE VALUES WELL OVER 1000
J/KG. SO WHILE SEVERE STORMS ARE NOT ANTICIPATED THIS AFTERNOON
AND EVENING, A FEW ROGUE GUSTS OVER 60 MPH WILL BE POSSIBLE.
HI- RES GUIDANCE SHOWS STORMS CONTINUING THROUGH THE EVENING
WITH A FEW LINGERING SHOWERS POSSIBLE AFTER MIDNIGHT. OUTSIDE OF
STORMS, SOME BACKGROUND WINDINESS CAN BE EXPECTED ACROSS
SOUTHEAST WYOMING THIS AFTERNOON. A WEAK 250 MB JET CURRENTLY
SITS OVER THE CWA, SO GUSTS OVER 45 MPH CAN BE EXPECTED,
ESPECIALLY WEST OF THE LARAMIE RANGE.
WITH THE SHORTWAVE MOVING INTO CANADA, THE CWA WILL REMAIN
SANDWICHED BETWEEN A STAGNANT TROUGH OVER THE PACIFIC NORTHWEST
AND A BROAD RIDGE OVER THE EASTERN HALF OF THE COUNTRY. THE
RESULTANT WEATHER ON THURSDAY WILL BE QUIET, WITH WARM
TEMPERATURES EXPECTED EAST OF THE LARAMIE RANGE AND SEASONABLE
TEMPERATURES WEST OF THE RANGE. HIGH TEMPERATURES EAST OF THE
LARAMIE RANGE WILL BE A FEW DEGREES WARMER COMPARED TO WEDNESDAY
AS WARMER 700 MB AIR MOVES INTO THE CWA. HIGHS WILL REACH THE
MID 80S TO MID 90S WHICH IS ABOUT 5 TO 10 DEGREES ABOVE AVERAGE
FOR THE START OF SEPTEMBER. HIGHS WEST OF THE LARAMIE RANGE WILL
BE IN THE 70S, WHICH IS MORE SEASONABLE FOR THIS TIME OF YEAR.
THE FORECAST AREA WILL BE MORE IN THE INFLUENCE OF THE RIDGE ON
THURSDAY, SO MOSTLY SUNNY SKIES ARE EXPECTED WITH LITTLE TO NO
CHANCE OF PRECIPITATION. BREEZY CONDITIONS WILL CONTINUE FOR
AREAS WEST OF THE LARAMIE RANGE UNDER SOUTHWEST FLOW. NEAR
IDENTICAL CONDITIONS ARE EXPECTED ON FRIDAY. TEMPERATURES WILL
BE A FEW DEGREES WARMER THAN THURSDAY AS THE RIDGE AXIS ACTUALLY
RETROGRADES BACK WESTWARD TOWARD THE CENTER OF THE COUNTRY.
SUNNY SKIES WILL STILL PREVAIL THROUGH THE DAY FRIDAY WITH
CONTINUED BREEZINESS OUT WEST.
LONG TERM /THURSDAY THROUGH WEDNESDAY/
ISSUED AT 201 PM MDT WED SEP 2 2026
SATURDAY...SOUTHWEST FLOW ALOFT PREVAILS. LOOKS LIKE WITH A
MINOR STREAM OF THE MONSOONAL MOISTURE TAP, WE ANTICIPATE
ISOLATED TO WIDELY SCATTERED SHOWERS AND THUNDERSTORMS IN THE
AFTERNOON AND EVENING.
SUNDAY...THE PRECIPITABLE WATER VALUES INCREASE SOMEWHAT AS
MONSOONAL MOISTURE INCREASES. WITH THAT SAID, EXPECT SCATTERED
AFTERNOON SHOWERS AND THUNDERSTORMS TO FORM OVER AND NEAR OUR
SNOWY RANGE AND LARAMIE RANGE IN THE AFTERNOON DUE TO OROGRAPHIC
EFFECTS AND DIFFERENTIAL HEATING, WITH MOST OF THE CONVECTION
PROPAGATING OVER THE NEBRASKA PANHANDLE IN THE EVENING.
MONDAY...SOMEWHAT DRIER AIR ALOFT MOVES OVERHEAD UNDER
SOUTHWEST FLOW ALOFT, WHICH SHOULD CORRESPOND TO AN AREAL
DECREASE IN AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS.
TUESDAY AND WEDNESDAY...AGAIN, SOMEWHAT DRIER AIR INFILTRATES
OUR WESTERN COUNTIES USING PRECIPITABLE WATER VALUES, WITH A BIT
BETTER MOISTURE FURTHER EAST, THUS ISOLATED TO SCATTERED
SHOWERS AND THUNDERSTORMS EXPECTED MAINLY OVER THE MOUNTAINS AND
EASTWARD.
AVIATION /00Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 539 PM MDT WED SEP 2 2026
SHOWERS THIS EVENING LINGER OVER KCYS, KCDR, AND KBFF BEFORE
MOVING OUT LATER THIS EVENING. THESE SHOWERS ARE PRODUCING SOME
RAIN AND GUSTY WINDS. GUSTY WINDS ARE TO BE EXPECTED OVER THIS
TAF PERIOD, ESPECIALLY OVER THE WYOMING TERMINALS. VFR
CONDITIONS ARE EXPECTED TO PREVAIL THROUGHOUT THE TAF PERIOD.
CYS WATCHES/WARNINGS/ADVISORIES
WY...RED FLAG WARNING FROM NOON TO 7 PM MDT THURSDAY FOR WYZ417-418.
NE...NONE.
SHORT TERM...WFOCYS
LONG TERM...WFOCYS
AVIATION...WFOCYS
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