588
FXUS65 KCYS 122356
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
556 PM MDT FRI SEP 12 2025
KEY MESSAGES
- DAILY CHANCES FOR AFTERNOON SHOWERS AND THUNDERSTORMS CONTINUE
THROUGH SATURDAY WITH GUSTY WINDS, DOWNPOURS, AND ISOLATED
HAIL POSSIBLE.
- A COLD FRONT WILL IMPACT THE AREA SATURDAY, BRINGING COOLER
TEMPERATURES THROUGH THE WEEKEND.
SHORT TERM /THROUGH SATURDAY/
ISSUED AT 230 PM MDT FRI SEP 12 2025
THE UPPER LEVEL LOW IS SLOWLY PUSHING INTO THE NORTHERN
INTERMOUNTAIN WEST. THIS WILL SEND A WAVE THROUGH OUR REGION TO
DEVELOP NUMEROUS TO WIDELY SCATTERED THUNDERSTORMS INF THE AFTERNOON
AND EVENING. THESE SHOWERS AND THUNDERSTORMS WILL OCCUR IN TWO
PHASES. THE FIRST PHASE WILL OCCUR FROM 1PM TO 6PM WHERE THE
STRONGER THUNDERSTORMS WILL DEVELOP. EVEN THOUGH THE FORECASTED CAPE
IS ONLY A COUPLE HUNDRED JOULES THE DOWNWARD CAPE OR DCAPE RANGES
FROM 400 TO 1000 JOULES ACROSS THE REGION WITH THE STRONGER DCAPE
BEING OVER THE EASTERN PORTION OF THE WYOMING AREA. THIS WILL LEAD
TO WINDS GUSTING BETWEEN 40 TO 60 MPH UNDERNEATH THESE SHOWERS.
AFTER 6PM OR 00Z OUR THUNDERSTORM POTENTIAL WILL TRANSITION TO
SHOWER POTENTIAL CREATING THE SECOND PHASE OR WAVE AS A COLD FRONT
PUSHES THROUGH. WITH THE SUN GOING DOWN THE PROGGED CAPE VALUES WILL
START TO DECREASE AND LITTLE IMPACTS ARE EXPECTED FROM OUR HIGH
BASED SHOWERS. THE SYNOPTIC SUPPORT FROM THE JET OVERHEAD SHOULD
SUSTAIN THE WEAK SHOWERS WELL INTO THE OVERNIGHT PERIOD. HOWEVER,
SATURDAY WILL BE ROUGHLY THE SAME SCENARIO AS TODAY. FOR SATURDAY,
SOME LEE CYCLOGENESIS IS CREATED FROM THE UPPER LEVEL TROUGH PUSHING
THROUGH ON FRIDAY. THIS WILL BE THE MAIN FORCING FOR EVENING
THUNDERSTORMS ON SATURDAY. THE SURFACE LOW WILL INCREASE THE FORCING
FOR SOME STRONGER THUNDERSTORMS. SOME OF THE HI-RES GUIDANCE SHOWS A
FEW POCKETS OF 1000 CAPE TOMORROW SO A FEW SEVERE THUNDERSTORMS MAY
BE POSSIBLE BUT OVERALL ANOTHER DAY OF GUSTY SHOWERS AND
THUNDERSTORMS WITH SMALL HAIL. THESE SHOWERS ARE EXPECTED TO GO INTO
THE OVERNIGHT PERIOD SATURDAY INTO SUNDAY AS THE SURFACE LOW EXITS
OUR REGION.
LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/
ISSUED AT 230 PM MDT FRI SEP 12 2025
AT THE START OF THE LONG TERM, AN UPPER LEVEL TROUGH SWEEPS ACROSS
THE CWA WITH ENERGY EMBEDDED, THIS WILL HELP KICK OFF INCREASED
CHANCES OF THUNDERSTORMS ALONG WITH HEAVY RAINFALL, INITIALIZING
FIRST ACROSS OUR WESTERN ZONES DURING THE MORNING HOURS. INSTABILITY
INDICES CURRENTLY LOOK RATHER MEAGER, SO ANY THUNDERSTORM ACTIVITY
SHOULD REMAIN SUB-SEVERE. STORMS WILL QUICKLY PUSH OFF TO THE EAST,
WITH THE GREATEST THUNDERSTORM THREAT ACROSS EASTERN WYOMING INTO
THE NEBRASKA PANHANDLE DURING THE AFTERNOON AND EVENING HOURS. A
TRANSITORY RIDGE BUILDS QUICKLY LATE SUNDAY ACROSS WESTERN PORTIONS
OF THE CWA, SLIDING EAST OVERNIGHT INTO EARLY MONDAY, DECREASING
ANY CHANCES OF PRECIPITATION AND STORM POTENTIAL. THIS IS SHORT
LIVED AS ANOTHER UPPER LEVEL TROUGH QUICKLY DIVES SOUTH INTO OUR CWA
ON THE BACKSIDE OF THE AFOREMENTIONED RIDGE. SO, BY LATE MONDAY,
EXPECT FLOW ALOFT TO BECOME SOUTHWESTERLY. THIS WILL INCREASE
MOISTURE ALONG WITH THE STORM THREAT FOR TUESDAY INTO WEDNESDAY. AS
WE ROUND OUT THE WORK WEEK, RIDGING ONCE AGAIN BUILDS BACK INTO THE
REGION, DRYING THINGS OUT AND LIMITING STORM POTENTIAL. SO, WHAT
ABOUT TEMPERATURES, WITH THE TRANSITORY RIDGE PUSHING THROUGH OUR
CWA ON MONDAY, EXPECT TEMPERATURES TO SOAR INTO THE LOWER TO
MID/UPPER 80S PRIMARILY EAST OF THE I-25 CORRIDOR AND INTO THE 70S
FOR OUR WESTERN COUNTIES. THESE WILL BE THE WARMEST TEMPERATURES FOR
THE LONG TERM PERIOD AS COOLER TEMPERATURES WILL RETURN TUESDAY AND
WEDNESDAY. AS WE ROUND OUT THE WORK WEEK, ANOTHER RIDGE BEGINS TO
PUSH INTO OUR CWA THAT WILL DECREASE THE STORM THREAT AND BRING
WARMER TEMPERATURES.
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 556 PM MDT FRI SEP 12 2025
HIGH BASED SHOWERS BETWEEN 8,000 TO 10,000FT MAY AFFECT KCDR AND
KSNY BETWEEN 02Z AND 04Z. SOME HI-RES GUIDANCE HAS OVERNIGHT
SHOWERS FOR THE WYOMING TERMINALS STARTING AROUND 04Z BUT IT IS
A LOW ENOUGH CONFIDENCE TO NOT PUT IT IN THE TAFS. TOMORROW
AFTERNOON SHOWERS AND THUNDERSTORMS ARE EXPECTED TO PUSH THROUGH
AGAIN AFTER 20Z.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...MM
LONG TERM...RZ
AVIATION...MM
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