433
FXUS65 KCYS 111728
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1128 AM MDT FRI SEP 11 2026
KEY MESSAGES
- ANOTHER CRITICAL FIRE WEATHER DAY ON FRIDAY ALONGSIDE GUSTY,
DRY SHOWERS AND/OR DRY THUNDERSTORMS POSSIBLE.
- QUICK COOL DOWN ON SATURDAY WITH TEMPERATURES WARMING AGAIN ON
SUNDAY FOLLOWED BY AN EARLY WEEK COOLING PERIOD MONDAY AND
TUESDAY.
- INCREASING MOISTURE SHOULD LEAD TO PRECIPITATION CHANCES OVER
THE WEEKEND FOLLOWED BY DAILY SHOWER AND THUNDERSTORM CHANCES
NEXT WEEK.
SHORT TERM /THROUGH SUNDAY NIGHT/
ISSUED AT 230 AM MDT FRI SEP 11 2026
FORECAST WILL EBB AND FLOW OVER THE NEXT SEVERAL DAYS AS WE SEE
TEMPERATURES OSCILLATE UP AND DOWN AND MOISTURE CHANCES INCREASE
THROUGH THE WEEKEND. ALOFT, WE'LL SEE MORE ZONAL FLOW RETURN
TODAY WITH AN INCREASING LOW-LEVEL JET AND MID LEVEL MOISTURE
RETURNING, WITH A QUICK SHORTWAVE DISTURBANCE MOVING ACROSS THE
FORECAST AREA. ON SATURDAY, THIS PATTERN SHOULD CONTINUE, BUT A
TRANSIENT RIDGE WILL OVERTAKE MOVING INTO EARLY SUNDAY, BUT BY
THE AFTERNOON AND EVENING A PACIFIC LOW SWINGING INLAND WILL
START TO ENCROACH THE FORECAST AREA BY LATE IN THE PERIOD INTO
EARLY MONDAY. AT THE SURFACE, TROUGHING AND A COLD FRONT WILL
PASS ACROSS OUR AREA TODAY, WITH THIS FRONT LIFTING BACK UP AS A
WARM FRONT SATURDAY EVENING, AND THEN DROPPING BACK DOWN ACROSS
THE FORECAST AREA SUNDAY INTO MONDAY.
FOR TODAY, THIS PATTERN WILL PRODUCE NOTABLY WARM DAYTIME
TEMPERATURES EAST OF THE LARAMIE RANGE, WITH HIGHS BETWEEN THE
80'S TO 90'S (MEANWHILE A MUCH COOLER DAY EXPECTED TO THE WEST
WITH HIGHS IN THE 70'S). WHILE MID LEVEL MOISTURE DOES BEGIN TO
MOVE INTO THE AREA, LOW LEVEL MOISTURE WILL REMAIN LACKING, WITH
CRITICALLY LOW RELATIVE HUMIDITY VALUES EXPECTED YET AGAIN
ALONGSIDE GUSTY WINDS. BECAUSE OF THIS, A RED FLAG WARNING IS
ONCE AGAIN IN EFFECT ACROSS THE REGION, BUT THIS TIME PRIMARILY
FOR OUR EASTERN ZONES INCLUDING CHEYENNE AND SURROUNDING FIRE
ZONES ALONGSIDE THE NEBRASKA PANHANDLE. FURTHER WEST, WHILE
WINDS WILL BE PRETTY GUSTY AND SITTING JUST UNDER HIGH WIND
WARNING CRITERIA, RH VALUES ARE EXPECTED TO BE A BIT HIGHER
ALONGSIDE THE COOLER AFTERNOON TEMPERATURES, AT LEAST ENOUGH SO
TO KEEP THIS AREA JUST OUTSIDE OF CRITICAL CRITERIA (THOUGH
ELEVATED FIRE WEATHER CONDITIONS ARE STILL ANTICIPATED).
FINALLY, WE SHOULD SEE THE RETURN OF CLOUDS ALONGSIDE THE
POTENTIAL FOR SOME SHOWERS OR STORMS, BUT WITH INVERTED V
PROFILES FROM THE DRY LOW LEVELS, ANTICIPATING MOST OF THIS
ACTIVITY TO STRUGGLE TO REACH THE SURFACE, WITH GUSTY VIRGA OR
DRY THUNDERSTORMS THE MOST LIKELY ACTIVITY FOR THE DAY.
ON SATURDAY HIGHS SHOULD DROP DOWN INTO THE 70'S TO 80'S, WITH
LOCATIONS WEST OF THE LARAMIE RANGE ACTUALLY A LITTLE WARMER
OVERALL AS IT REMAINS JUST OUTSIDE OF THE COLD FRONT WHICH
SHOULD BE HUNG UP ON THE HIGH TERRAIN. WHILE SURFACE PROFILES
WILL BE SLIGHTLY MORE MOIST, WE SHOULD CONTINUE TO STRUGGLE TO
PRODUCE MORE NOTEWORTHY PRECIPITATION, WITH ONLY SLIGHT CHANCES
OF ANOTHER BATCH OF SHOWERS AND STORMS. BUT THEN INTO SUNDAY AS
MORE MOISTURE ARRIVES WE SHOULD FINALLY HAVE THE RETURN OF
NOTEWORTHY PRECIPITATION ON THE DAY. PWAT VALUES SHOULD CLIMB IN
EXCESS OF 175-200% OF NORMAL, ROUGHLY EQUIVALENT TO 1-1.3
INCHES. WHILE INSTABILITY WILL BE LOW TO MODERATE OVERALL, SHEAR
SHOULD ACTUALLY BE PRETTY FAIR TO GOOD FOR THE DAY, WITH BULK
SHEAR VALUES OF 50-60 KNOTS POSSIBLE. SO NOT ONLY SHOULD WE SEE
STORMS WITH DECENT RAINFALL POTENTIAL, SEVERE STORMS CANNOT BE
RULED OUT AS WELL WITH GUSTY WINDS AND LARGE HAIL POSSIBLE,
PRIMARILY ALONG THE EASTERN WYOMING BORDER THROUGH THE NEBRASKA
PANHANDLE. FINALLY, 850 MB CRAIG TO CASPER PRESSURE GRADIENTS
FOR THE DAY EXCEEDING 50M WILL BE CLOSE TO GIVING US OUR FIRST
HIGH WIND EVENT OF THE FALL, BUT EXPECTING OUR BREEZIEST
LOCATIONS TO REMAIN JUST UNDER CRITERIA, LIKELY AROUND 50-55
MPH. IN HOUSE RANDOM FOREST MODEL GUIDANCE AGREES WITH THE ABOVE
WIND OUTCOME, WITH RAWLINS THE CLOSEST TO NEARING HIGH WIND
WARNING CRITERIA AT 40%. THAT BEING SAID, WITH HOW WYOMING IS,
DON'T BE SURPRISED IF WE DO GET A SITE OR TWO NEARING OR
REACHING 60 MPH GUSTS.
LONG TERM /MONDAY THROUGH THURSDAY/
ISSUED AT 235 PM MDT THU SEP 10 2026
ON SUNDAY AN UPPER LEVEL SYSTEM MAKES ITS WAY INTO THE PNW. GUIDANCE
IS SHOWING THE POTENTIAL FOR STORMS WITH THIS RETURN FLOW AHEAD OF
THE UPPER LEVEL SYSTEM'S PASSAGE. THE MAIN RISK AREA FOR THESE
STORMS IS EAST OF I-25. SUNDAY NIGHT INTO MONDAY MORNING SHOWS A
COLD FRONT PASSING OVER THE CWA. AFTER THIS FRONT MOVES OUT, A RIDGE
STARTS TO BUILD, BRINGING COOLER TEMPERATURES AND DRYER AIR. SOME
STORM AND SHOWER ACTIVITY IS POSSIBLE TUESDAY EVENING WITH RETURN
FLOW. A SHORTWAVE PASSES THROUGH ON THURSDAY EVENING, ALLOWING THE
RIDGE TO CONTINUE TO BUILD. 700MB TEMPERATURES ARE IN THE 10-15C
RANGE IN THIS LONG TERM PERIOD. TEMPERATURES START TO COOL OFF AND
FEEL MORE LIKE FALL AS THE WEEK PROGRESSES.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 1128 AM MDT FRI SEP 11 2026
THIS AFTERNOON, WINDS WILL BE OUT OF THE W TO NW AND BECOME BREEZY
OVER THE WY TERMINALS, WEAKENING IN THE EVENING AND OVERNIGHT.
DAYTIME WINDS ARE EXPECTED TO BE BETWEEN 20-40 KNOTS. WINDS OVER THE
NE TERMINALS ARE ALSO EXPECTED TO BE BETWEEN 20-40 KNOTS, STAYING
GUSTY THROUGH TOMORROW AFTERNOON. SKY CONDITIONS ARE EXPECTED TO BE
MAINLY FEW TO SCT WITH HIGH LEVEL CLOUD DECKS. THERE IS A CHANCE FOR
SOME SHOWERS OR STORMS, BUT THE PROBABILITIES REMAIN TOO LOW TO
INCLUDE IN THE TAFS. OTHERWISE, VFR CONDITIONS ARE EXPECTED FOR THIS
TAF PERIOD.
CYS WATCHES/WARNINGS/ADVISORIES
WY...RED FLAG WARNING UNTIL 7 PM MDT THIS EVENING FOR WYZ429>433.
NE...RED FLAG WARNING UNTIL 7 PM MDT THIS EVENING FOR NEZ434>437.
SHORT TERM...CG
LONG TERM...ML
AVIATION...ML
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