226
FXUS65 KCYS 270452
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1050 PM MDT TUE AUG 26 2025
KEY MESSAGES
- COOL AND WET PATTERN EXPECTED THROUGH FRIDAY, WITH DAILY
CHANCES FOR PRECIPITATION AND HIGHS 5 TO 15 DEGREES BELOW
AVERAGE.
SHORT TERM /THROUGH WEDNESDAY NIGHT/
ISSUED AT 227 PM MDT TUE AUG 26 2025
CURRENT RADAR SHOWS STORMS DEVELOPING OVER THE HIGH TERRAIN EARLY
THIS AFTERNOON. HI-RES GUIDANCE SHOWS THESE STORMS PRIMARILY STAYING
WEST OF THE LARAMIE RANGE, BUT A FEW STORMS MAY BE ABLE TO SNEAK
INTO THE INTERSTATE 25 CORRIDOR THIS EVENING. WEAK INSTABILITY
SHOULD KEEP SEVERE STORMS AT BAY TODAY, BUT CANNOT RULE OUT A FEW
STORMS WITH GUSTY WINDS AND SMALL HAIL. WEAK SHOWERS WILL LINGER
INTO THE OVERNIGHT HOURS THANKS TO A STATIONARY DISTURBANCE OVER THE
PACIFIC NORTHWEST SENDING VORTICITY MAXES INTO THE CWA.
STORMS WILL GET AN EARLY START ON WEDNESDAY AS A WEAK RIDGE OVER
TEXAS AND THE DISTURBANCE OVER THE PACIFIC NORTHWEST FUNNEL MONSOON
MOISTURE INTO THE REGION FROM THE PACIFIC. SOUTHWEST FLOW WILL BRING
RICH MID-LEVEL MOISTURE TO THE CWA, WITH MODEL SOUNDINGS SHOWING
FAIRLY SATURATED MID TO UPPER-LEVEL PROFILES. PWATS WILL CLIMB ABOVE
THE 90TH PERCENTILE FOR MOST OF THE CWA, LEADING TO THE THREAT OF
HEAVY RAIN IN STORMS. LUCKILY, SOUNDINGS SHOW FAIRLY QUICK STORM
MOTIONS WHICH WILL HELP LIMIT FLOOD CHANCES. HOWEVER, THE CHANCE FOR
MULTIPLE ROUNDS OF STORMS OVER AN AREA COULD INCREASE FLOODING
CONCERNS. ONCE AGAIN, SEVERE CHANCES WILL BE SOMEWHAT LIMITED. MODEL
SOUNDINGS SHOW LESS THAN 1000 J/KG OF MUCAPE AND MINIMAL DCAPE.
HOWEVER, HI-RES GUIDANCE SHOWS A FEW STRONG STORMS DEVELOPING DURING
THE AFTERNOON WHICH COULD CONTAIN GUSTY WINDS AND SMALL HAIL. AS
PREVIOUSLY MENTIONED, SHOWERS AND STORMS COULD START DEVELOPING
EARLY WEDNESDAY MORNING AND CONTINUE THROUGHOUT MOST OF THE
DAY. STORMS WILL BE WIDELY SCATTERED ACROSS THE ENTIRE CWA, WITH
MOST CITIES HAVING A DECENT POTENTIAL AT SEEING SOME RAIN.
STORMS WILL CONTINUE THROUGH THE EVENING HOURS BEFORE GRADUALLY
TAPERING OFF WEDNESDAY NIGHT.
LONG TERM /THURSDAY THROUGH TUESDAY/
ISSUED AT 227 PM MDT TUE AUG 26 2025
UNSETTLED WEATHER WILL CONTINUE ON THURSDAY AS OUR PERSISTENT
MONSOONAL PATTERN REMAINS IN PLACE OVER THE CENTRAL ROCKIES. PWAT
NORMALIZED ANOMALIES WILL REMAIN IN THE 1-1.5 SIGMA RANGE PER
ENSEMBLE GUIDANCE OVER SOUTHEAST WYOMING AND WESTERN NEBRASKA.
FORECAST SOUNDINGS SHOW SUFFICIENTLY SATURATED PROFILES FOR HEAVY
DOWNPOURS IN ANY AFTERNOON THUNDERSTORMS THAT FORM. A SUBTLE
PERTURBATION ROUNDING THE TOP OF THE SUBTROPICAL RIDGE MAY HELP TO
ENHANCE ACTIVITY ON THURSDAY AFTERNOON COMPARED TO PRIOR DAYS IN
TERMS OF THUNDERSTORM COVERAGE. HOWEVER, POOR LAPSE RATES AND LOW
SHEAR VALUES WILL LIMIT THE THREATS IN ANY THUNDERSTORM ACTIVITY TO
HEAVY RAIN AND GUSTY WINDS BELOW 50 MPH.
ON FRIDAY, A PUSH OF DRIER AIR FROM THE WEST WILL MAKE ITS WAY
THROUGH SOUTHEAST WYOMING AND WESTERN NEBRASKA ALONG THE
NORTHERN PERIPHERY OF THE MONSOONAL RIDGE. FORECAST SOUNDINGS
INDICATE A MUCH DRIER PROFILE IN THE MID-LEVELS AND THUS
THUNDERSTORM CHANCES WILL BE QUITE A BIT LOWER. THE ONE
EXCEPTION TO THIS FORECAST IS THE ECMWF ENSEMBLE MEAN WHICH DOES
FAVOR SLIGHTLY HIGHER PRECIPITATION CHANCES THAN THE REST OF
THE NAEFS MEMBERS.
BY SATURDAY THROUGH EARLY NEXT WEEK, DEEPER RIDGING WILL BEGIN TO
BUILD IN OVER THE GREAT BASIN AND FOUR CORNERS REGION. SUBTROPICAL
MOISTURE BECOMES MORE SUPPRESSED, WITH PWAT VALUES RETURNING TO
BELOW-AVERAGE OVER OUR REGION AND DEEPER MOISTURE BECOMING
SUPPRESSED WELL TO THE SOUTH INTO SOUTHERN COLORADO AND NEW MEXICO.
DRIER, LIGHT NORTHWEST FLOW WILL FAVOR SLIGHTLY WARMER TEMPERATURES
STARTING SATURDAY AND LASTING THROUGH EARLY NEXT WEEK, WITH LOW POPS
FORECAST.
GIVEN THE DRIER AIR IN PLACE WITH GENERALLY LIGHT SURFACE FLOW, AS
WELL AS OUR INCREASINGLY LONGER NIGHTS AS WE MOVE TOWARD THE END OF
SUMMER , CHILLY MORNINGS CAN BE EXPECTED THROUGH THE WEEKEND WITH
WIDESPREAD LOW TO MID 40S ACROSS THE HIGHER ELEVATION TOWNS OF
SOUTHEAST WYOMING. FOR ANY OUTDOOR ENTHUSIASTS CAMPING IN THE HIGHER
ELEVATIONS OF THE SNOWY RANGE AND SIERRA MADRE RANGE OVER LABOR DAY
WEEKEND...DO NOT BE SURPRISED IF YOU SEE A BIT OF FROST ON YOUR
TENTS DURING THE EARLY MORNING HOURS AS SUMMER COMES TO A CLOSE!
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1050 PM MDT TUE AUG 26 2025
ACTIVE WEATHER OVER THE NEXT 24 TO 30 HOURS ACROSS SOUTHEAST WYOMING
AND WESTERN NEBRASKA AS A POTENT DISTURBANCE ALOFT, AND AMPLE
MONSOON MOISTURE, MOVES EAST ACROSS THE AREA ON WEDNESDAY.
HAZARDS/WEATHER TRENDS: BANDS OF RAIN SHOWERS AND LOW CIGS/FOG ARE
THE PRIMARY CONCERNS LATE TONIGHT AND EARLY WEDNESDAY MORNING. HIGH
RES GUIDANCE CONTINUES TO SHOW THE POTENTIAL FOR LIFR CIGS AND FOG
FOR KCYS AND KSNY, AND TO A LESSER EXTENT...KBFF AND KAIA. INCLUDED
PREVAILING IFR FOR KCYS AND KSNY WITH SREF/HREF PROBABILITIES >40%.
BANDS OF LIGHT RAINFALL CONTINUE TO PUSH EAST ACROSS KRWL AND KLAR
TONIGHT, SO CAN'T RULE OUT SOME MVFR CIGS WITH THIS ACTIVITY.
AFTER 15Z WEDNESDAY, ATTENTION THEN SHIFTS TO THE POTENTIAL FOR
HEAVY SHOWERS AND THUNDERSTORMS AS THE DISTURBANCE MOVES ACROSS THE
AREA. KCYS HAS THE BEST CHANCE TO SEE MULTIPLE PERIODS OF HEAVY
RAINFALL BASED ON LATEST MODEL GUIDANCE. LESSER CHANCES ELSEWHERE,
SO KEPT THE PROB30 GROUPS FOR ALL OTHER TERMINALS. WESTERN NEBRASKA
TERMINALS MAY STRUGGLE TO GET MUCH PRECIPITATION OUT OF THIS DUE TO
THE LACK OF INSTABILITY.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...SF
LONG TERM...MAC
AVIATION...TJT
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