484
FXUS65 KCYS 271729
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1129 AM MDT WED AUG 27 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 THURSDAY NIGHT/
ISSUED AT 159 AM MDT WED AUG 27 2025
ANOTHER NIGHT SOCKED IN THE LOW STRATUS AND FOG FOR MUCH OF THE CWA
AS EXCESS MOISTURE REMAINS IN PLACE. A FEW LIGHT SHOWERS ARE
DRIFTING ACROSS THE WESTERN ZONES AS OF 0730Z TONIGHT. THESE SHOWERS
ARE NOT STRONG AND TEND TO FALL APART SHORTLY AFTER DEVELOPING.
HOWEVER, THE LOCATIONS SEEING THESE SHOWERS ARE SOME OF THE MORE
MOISTURE-STARVED AREAS WHERE ANY AMOUNT OF PRECIPITATION IS
INCREDIBLY BENEFICIAL. TEMPERATURES REMAIN MILD TONIGHT WITH THE
CLOUDS INSULATING THE SURFACE LAYER, WITH TEMPERATURES CURRENTLY IN
THE MID-50S TO MID-60S ACROSS THE ENTIRE CWA. WINDS ARE MOSTLY CALM
ACROSS SOUTHEAST WYOMING, BUT SOME STRONGER WINDS AND GUSTS ARE
PRESENT ACROSS WESTERN NEBRASKA. LOW CLOUDS OVER CHEYENNE
SPECIFICALLY HAVE BEEN OSCILLATING TONIGHT, WITH HEAVIER CLOUD COVER
FADING THEN COMING BACK IN FORCE. SIMILARLY, FOG HAS DRIFTED INTO
THE CHEYENNE AREA BEFORE DISSIPATING ONCE MORE. THIS OSCILLATION IS
EXPECTED FOR MOST OF THE NIGHT TONIGHT.
NORTHWESTERLY FLOW HAS FINALLY TRANSITIONED TO MORE WESTERLY AND
EVEN SOUTHWESTERLY IN THE UPPER-LEVELS OF THE ATMOSPHERE THIS
MORNING AS A RIDGE SLOWLY MOVES EASTWARD AND BUILDS. A MONSOONAL
MOISTURE PUSH BEGAN TONIGHT AND WILL CONTINUE THROUGH THE DAY,
KEEPING MUCH OF THE REGION RATHER WET AND HUMID ONCE AGAIN TODAY. A
700MB LOW IS PROGGED TO DEVELOP LATER THIS MORNING ACROSS IDAHO,
LEADING TO STRONG FORCING ACROSS THE REGION TODAY. COUPLED WITH A
WEAK 500MB SHORTWAVE, THIS FORCING WILL INCREASE PRECIPITATION
CHANCES THIS AFTERNOON. PRECIPITATION WILL SPREAD WEST TO EAST LATER
THIS MORNING AND THROUGH THE AFTERNOON HOURS, AS WESTERLY STEERING
FLOW ADVECTS SHOWERS AND STORMS EASTWARD. MULTIPLE ROUNDS OF SHOWERS
AND STORMS ARE POSSIBLE TODAY AS SEVERAL 500MB VORTICITY MAXIMA
EJECT ACROSS THE REGION PROVIDING SYNOPTIC SUPPORT FOR ADDITION LIFT
AND SHOWER/STORM DEVELOPMENT. WHILE SHOWERS AND STORMS WILL BE
MOVING AT A DECENT SPEED (AKA, NOT STATIONARY), MULTIPLE ROUNDS OF
THE SAME LOCATIONS ARE INCREASING FLOODING THREATS TODAY. THE
WEATHER PREDICTION CENTER HAS INCLUDED MUCH OF SOUTHEAST WYOMING IN
A MARGINAL RISK FOR EXCESSIVE RAINFALL THIS AFTERNOON, WITH A SMALL
SUBSECTION WITHIN THE SLIGHT RISK FOR EXCESSIVE RAINFALL. LUCKILY,
SEVERE PARAMETERS ARE WEAK THIS AFTERNOON, WITH MINIMAL CAPE AND
SHEAR ACROSS THE REGION, SO SEVERE WEATHER IS NOT EXPECTED. INSTEAD,
MULTIPLE ROUNDS OF PRECIPITATION ARE LIKELY, WITH THE I-80 CORRIDOR
POTENTIALLY SEEING INCREASED FLOODING THREATS FROM TRAINING STORMS.
FORECAST SOUNDINGS FOR THE REGION FURTHER SUPPORT MINIMAL TO NO
SEVERE WEATHER THREAT, BUT AN INCREASED HEAVY RAIN THREAT AS
MOISTURE EXTENDS THROUGH MUCH OF THE ATMOSPHERE AND PRECIPITABLE
WATER VALUES ARE IN THE MAXED OUT FOR PORTIONS OF THE REGION WITH
THE REMAINING AREA IN THE 95TH TO 99TH PERCENTILE FOR THIS TIME OF
YEAR, PER THE NAEFS MEAN.
A SIMILAR SETUP IS EXPECTED FOR THURSDAY AS PRIMARILY WESTERLY FLOW
DOMINATES THE UPPER-ATMOSPHERE. THE UPPER-LEVEL RIDGE ACROSS THE
SOUTHERN CONUS WILL PUSH NORTHWARD THURSDAY, TURNING FLOW MORE DUE
WESTERLY. MULTIPLE 500MB VORTICITY MAXIMA WILL EJECT ACROSS THE
REGION, PROVIDING SYNOPTIC SUPPORT FOR LIFT IN THE LATE MORNING AND
AFTERNOON HOURS ONCE AGAIN. WHILE WESTERLY UPPER-LEVEL FLOW IS
USUALLY NOT CONDUCIVE TO MUCH PRECIPITATION CHANCE, THE EXCESS
MOISTURE THAT HAS BEEN SITTING ACROSS THE REGION WILL KEEP MOST
AREAS MORE MOIST THAN USUAL, AIDING IN PRECIPITATION CHANCES DESPITE
THE LESS FAVORABLE UPPER-LEVEL FLOW. ADDITIONALLY, AT 700MB A
DIFFUSE SHORTWAVE WILL PUSH THROUGH THE REGION, PROVIDING ADDITIONAL
SUPPORT FOR PRECIPITATION DEVELOPMENT. THURSDAY DOES APPEAR A LITTLE
LESS FAVORABLE FOR WIDESPREAD PRECIPITATION, BUT ONLY IN THAT THE
FORCING IS NOT AS DEFINED AS WHAT IS EXPECTED FOR WEDNESDAY.
HOWEVER, MULTIPLE ROUNDS OF SHOWERS AND STORMS WILL ONCE AGAIN BE
POSSIBLE THURSDAY AFTERNOON AS THE 500MB DISTURBANCES PUSH THROUGH
THE FLOW AND THE DIFFUSE 700MB SHORTWAVE ALSO PUSHES THROUGH.
PRECIPITABLE WATER VALUES ARE ONCE AGAIN ABOVE THE 90TH PERCENTILE
FOR SEVERAL LOCATIONS, SO EXCESSIVE RAINFALL IS ONCE AGAIN A THREAT.
THE WEATHER PREDICTION CENTER HAS ALSO HIGHLIGHTED MUCH OF THE
REGION IN A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR THURSDAY.
OVERALL, ANOTHER COOL AND WET DAY EXPECTED ACROSS SOUTHEAST WYOMING
AND WESTERN NEBRASKA.
LONG TERM /FRIDAY 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 /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1129 AM MDT WED AUG 27 2025
SCATTERED TO WIDESPREAD SHOWERS ARE EXPECTED ACROSS THE WYOMING
TERMINALS. DUE TO THE WEAK NATURE OF THE SHOWERS ITS A LITTLE
UNCERTAIN AS TO WHETHER THE SHOWERS WILL MOVE INTO THE NEBRASKA
PANHANDLE. THE CEILINGS WILL FLUCTUATE BETWEEN SCATTERED,
BROKEN, AND OVERCAST THROUGHOUT THE DAY. THIS MAKES FORECASTED
VFR TO MVFR CONDITIONS DIFFICULT BUT ASSUME THE CLOUD MAY TURN
OVERCAST AT THE REPORTED ALTITUDE LATER IN THE DAY ESPECIALLY
FOR OUR WYOMING TERMINALS.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...AM
LONG TERM...MAC
AVIATION...MM
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