179
FXUS65 KCYS 161857
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
ISSUED BY NATIONAL WEATHER SERVICE RAPID CITY SD
1257 PM MDT WED JUL 16 2025
KEY MESSAGES
- SCATTERED STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED
WEDNESDAY AFTERNOON AND EVENING IN SOUTHEAST WYOMING AND
SOUTHWEST NEBRASKA. LARGE HAIL IS THE PRIMARY THREAT, BUT ALL
SEVERE WEATHER HAZARDS ARE POSSIBLE.
- WARMER TEMPERATURES AND ISOLATED TO SCATTERED LATE DAY
SHOWERS AND THUNDERSTORMS WILL OCCUR FOR THURSDAY THROUGH
EARLY NEXT WEEK.
SHORT TERM /THROUGH THURSDAY/
ISSUED AT 1248 PM MDT WED JUL 16 2025
CURRENT SATELLITE IMAGERY SHOWS LOW STRATUS COVERING AREAS EAST OF
THE LARAMIE RANGE. SATELLITE ALSO SHOWS SOME GRADUAL CLEARING
WITHIN THE STRATUS, WHICH WILL LIKELY LEAD TO DESTABILIZATION
LATER THIS AFTERNOON. LOW STRATUS FROM WEAK SOUTHERLY AND
EASTERLY FLOW WILL PROVIDE AMPLE MOISTURE FOR STORMS. A SHARP
DRYLINE ALONG THE LARAMIE RANGE, AS WELL AS A WEAK DISTURBANCE
ALOFT WILL PROVIDE THE NEEDED LIFT FOR STORMS TO INITIATE LATER
TODAY. HI-RES GUIDANCE STILL SHOWS AN ACTIVE AFTERNOON AND
EVENING, MAINLY ACROSS SOUTHEAST WYOMING WHERE STORMS HAVE THE
GREATEST POTENTIAL TO BE SEVERE. GFS SOUNDINGS SHOW A STRONGLY
CAPPED NEBRASKA PANHANDLE THROUGH THE AFTERNOON, WHICH WILL HELP
LIMIT BOTH STORM DEVELOPMENT AND STRONG STORMS. BY MID-
AFTERNOON, THE CAPPING INVERSION ALONG THE INTERSTATE 25
CORRIDOR WILL BE ERODED. THIS IS LIKELY AROUND THE TIME WHEN
STRONGER STORMS WILL START TO DEVELOP. MODEL SOUNDINGS ALONG
THE INTERSTATE 25 CORRIDOR DO SHOW AN ENVIRONMENT FAVORABLE FOR
SEVERE WEATHER. MUCAPE VALUES ARE AROUND 1400 J/KG WITH
EFFECTIVE SHEAR VALUES AROUND 40 KTS. THIS LENDS ITSELF TO A
SEVERE HAIL THREAT, AS WELL AS THE MORE DISCRETE CELLS MODELS
ARE SHOWING. DCAPE VALUES ARE AROUND 1000 J/KG WEST OF THE
LARAMIE RANGE WHERE IT IS DRIER AND SUNNIER. THESE AREAS COULD
SEE SOME SEVERE WIND GUSTS WITH STORMS. CANNOT RULE OUT AN
ISOLATED TORNADO THIS AFTERNOON WITH ELEVATED SFC-3KM SRH AND
EFFECTIVE SHEAR VALUES. HEAVY RAIN IS ALSO EXPECTED IN STORMS
WITH PWATS ABOVE THE 90TH PERCENTILE FOR CLIMATOLOGY. LUCKILY,
STORMS APPEAR TO BE QUICK MOVING THIS AFTERNOON, HOWEVER,
MULTIPLE ROUNDS OF STORMS AS SUGGESTED BY SOME MODELS COULD LEAD
TO LOCALIZED FLASH FLOODING. STRONGEST STORMS SHOULD END BY
ABOUT 8 PM WITH SOME LINGERING SHOWERS AND STORMS POSSIBLE
THROUGH MIDNIGHT.
QUIETER WEATHER IS EXPECTED FOR THURSDAY. SOUTHERLY FLOW AND
RESIDUAL MOISTURE FROM STORMS WILL LIKELY LEAD TO ANOTHER
ROUND OF LOW STRATUS DURING THE MORNING HOURS. HOWEVER, ZONAL
FLOW ALOFT WILL HELP DRY OUT THE MID-LEVELS AND CLEAR CLOUDS OUT
BY THE AFTERNOON. STORMS WILL STILL BE POSSIBLE DURING THE
AFTERNOON HOURS FROM A WEAK DISTURBANCE ALOFT, HOWEVER, COVERAGE
AND INTENSITY OF STORMS WILL BE MUCH LOWER THAN TODAY.
LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/
ISSUED AT 344 AM MDT WED JUL 16 2025
A ZONAL FLOW PATTERN WILL TAKE OVER ALOFT ON THURSDAY AND
DOMINATE MUCH OF THE NORTHERN HALF OF THE CONUS INTO THE
WEEKEND. DRIER WESTERLY FLOW ALOFT WILL REDUCE THE RISK FOR
STORMS ON THURSDAY, BUT ISOLATED THUNDERSTORMS WILL STILL BE
POSSIBLE, MAINLY ALONG THE I-80 CORRIDOR. MONSOON MOISTURE WILL
BE PULLED INTO THE FLOW ON FRIDAY, CAUSING PERCEPTIBLE WATER
AND MID-LEVEL MOISTURE IN GENERAL TO RECOVER. WHILE MID TO UPPER
LEVEL MOISTURE SHOULD IMPROVE FOR FRIDAY, THE DRYLINE IS
EXPECTED TO BE POSITIONED FURTHER EAST, RESULTING IN FAIRLY
STEADY PRECIPITABLE WATER THURSDAY INTO FRIDAY. EXPECT TO SEE
SOME HIGH-BASED SHOWERS AND THUNDERSTORMS WITH GUSTY WINDS
POSSIBLE ON FRIDAY ALONG WITH WARM TO HOT TEMPERATURES.
ENSEMBLES INDICATE THAT THE DRYLINE WILL MOVE BACK TO THE WEST
ON SATURDAY WHILE DECENT MID TO UPPER LEVEL MONSOON MOISTURE
REMAINS IN PLACE. EXPECT THIS TO THEN BRING THE HIGHEST CHANCE
FOR MORE WIDESPREAD SHOWER AND THUNDERSTORM COVERAGE OF THE LONG
TERM PERIOD. FOR SUNDAY THROUGH TUESDAY OR SO, EXPECT DECENT
MONSOON MOISTURE TO REMAIN IN PLACE ALOFT, BUT WE MAY LOSE THE
BOUNDARY LAYER MOISTURE FOR SEVERAL DAYS, LEADING TO MORE
ISOLATED PM THUNDERSTORM ACTIVITY EACH OF THOSE DAYS.
ADDITIONALLY, AN UPPER LEVEL TROUGH DIGGING INTO THE NORTHWEST
WILL AMPLIFY THE DOWNSTREAM RIDGE OVER THE CENTRAL PLAINS,
LEADING TO ANOTHER WARM TREND TO CARRY THROUGH THE MIDDLE PART
OF NEXT WEEK.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1050 AM MDT WED JUL 16 2025
LOW STRATUS CONTINUES FOR AREAS EAST OF THE LARAMIE RANGE LATE
THIS MORNING. LOW CIGS WILL LIKELY BURN OFF EARLY THIS
AFTERNOON, ALLOWING DESTABILIZATION FOR STORMS TO FORM. THE MAIN
AVIATION CONCERN THIS AFTERNOON WILL BE STRONG TO SEVERE STORMS
WITH HEAVY RAIN. MODERATE TO HEAVY RAIN WILL LIKELY LEAD TO
VISIBILITY DROPS IN ANY STORMS PASSING OVER A TERMINAL. MVFR TO
IFR VISIBILITY WILL BE POSSIBLE IN HEAVY RAIN. STRONG, GUSTY
WINDS AND LARGE HAIL WILL ALSO BE POSSIBLE IN STORMS THIS
AFTERNOON AND EVENING. MORE LOW STRATUS WILL BUILD IN LATE
TONIGHT AND CONTINUE THROUGH THURSDAY MORNING.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...SF
LONG TERM...
AVIATION...SF
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