808
FXUS65 KCYS 121956
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
156 PM MDT SAT SEP 12 2026
KEY MESSAGES
- COOLER TEMPERATURES ON SATURDAY ALONGSIDE SOME ISOLATED SHOWER
OR STORM CHANCES BUT REMAINING WEAK OVERALL.
- TEMPERATURES WARM ON SUNDAY AND MONDAY WITH INCREASING
PRECIPITATION CHANCES, THOUGH MONDAY MAY SEE THE RETURN OF
CRITICAL FIRE WEATHER CONDITIONS.
- MUCH COOLER ON TUESDAY WITH TEMPERATURES A FEW DEGREES WARMER
THROUGH THE END OF NEXT WEEK AND DAILY CHANCES OF SHOWERS AND
THUNDERSTORMS.
SHORT TERM /THROUGH MONDAY/
ISSUED AT 156 PM MDT SAT SEP 12 2026
A FEW AFTERNOON AND EVENING SHOWERS ARE FOLLOWING THE AXIS OF
INSTABILITY ALONG THE SOUTHERN HALF OF THE FORECAST AREA AS A WEAK
SHORTWAVE PUSHES THROUGH THE AREA. A FEW BRIEF SHOWERS ARE POSSIBLE
WITH SOME OF THE STRONGER STORMS BUT NOTHING SEVERE OR HEAVY RAIN IS
EXPECTED. THESE SHOWERS ARE EXPECTED TO LAST THROUGH THE EVENING
WITH SHOWERS POSSIBLE ABOUT AS FAR NORTH AS SCOTTSBLUFF, NE. WIND
GUSTS ARE EXPECTED TO LAST OVERNIGHT EAST OF THE I-25 CORRIDOR AS
THE UPPER LEVEL LOW PUSHES INTO THE INTERMOUNTAIN WEST FROM PACIFIC
NORTHWEST NEAR MONTANA. SCATTERED THUNDERSTORMS BE POSSIBLE TOMORROW
AS ANOTHER SHORTWAVE PASSES THROUGH OUR NECK OF THE WOODS. SOME
STRONG TO POSSIBLY SEVERE THUNDERSTORMS COULD DEVELOP IN THE LATE
AFTERNOON AS A SURFACE LOW MOVES NORTHEAST THROUGH OUR FORECAST
AREA. CAPE VALUES LOOK TO BE BETWEEN 500 TO 1,000 JOULES WITH COUPLE
POTENTIAL POCKETS OF 2,000 JOULES AS DEPICTED BY THE RAP BETWEEN 3
TO 7PM. THE SYNOPTIC FORCING OF THE SURFACE LOW SHOULD SUSTAIN THE
SHOWERS AND THUNDERSTORMS THROUGH THE EVENING. HOWEVER, IN THE
MORNING WE HAVE A SUBSTANTIAL CAP TO ERODE AWAY IN THE MORNING AND
AFTERNOON BEFORE ANY STRONG TO SEVERE THUNDERSTORMS COULD DEVELOP.
IT WILL BE A LITTLE TOUGH TOO SINCE THE FORECASTED CONVECTIVE
TEMPERATURE FOR TOMORROW IS IN THE MID 80'S AND THE FORECASTED HIGH
TEMPERATURE ARE EITHER AT OR BELOW THE CONVECTIVE TEMPERATURES.
BECAUSE OF THIS SETUP WITH THE STRONG MORNING CAPPING SPC HAS US IN
A GENERAL THUNDER RISK FOR SUNDAY FAVORING THE LOW LEVEL COOL
TEMPERATURES AND STRONG CAPPING LIMITING ANY POTENTIAL SEVERE
THUNDERSTORMS.
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
ISSUED AT 156 PM MDT SAT SEP 12 2026
ACTIVE WEATHER IS EXPECTED FOR MUCH OF THE UPCOMING WEEK WITH
MULTIPLE UPPER-LEVEL DISTURBANCES PUSHING THROUGH THE REGION. MONDAY
FEATURES THE STRONGEST DISTURBANCE EXPECTED FOR THE WEEK AS A STOUT
UPPER-LEVEL TROUGH DIGS ACROSS MONTANA WITH A 100KT JET ALONG THE
SOUTHEASTERN PORTION. THE JET WILL MOVE EASTWARD WITH THE UPPER-
LEVEL LOW, PLACING THE CWA WITHIN THE RIGHT ENTRANCE REGION OF THE
UPPER-LEVEL JET FOR MUCH OF THE DAY MONDAY. ENHANCED, DYNAMICALLY-
DRIVEN ASCENT WILL PROVIDE MUCH NEEDED FORCING FOR SHOWERS AND
THUNDERSTORMS MONDAY MORNING AND AFTERNOON. MULTIPLE 500MB VORTICITY
MAXIMA WILL EJECT ACROSS THE AREA AS THE UPPER-LEVEL LOW MOVES
EASTWARD, FAVORING ADDITION FORCING ACROSS MUCH OF THE REGION. THE
700MB LOW IS EXPECTED TO BE DISPLACED TO THE NORTH ACROSS THE
SOUTHERN SASKATCHEWAN PROVINCE. WHILE THIS LOW WILL BE DISPLACED TO
THE NORTH, IT LOOKS TO BE QUITE STRONG, WITH AN ASSOCIATED JET
AROUND 50 TO 60KTS OVER THE NORTHERN PLAINS. FOR SOUTHEAST WYOMING
AND WESTERN NEBRASKA, THE LOW WILL LEAD TO STRONG, WESTERLY FLOW
ACROSS THE CWA AROUND 40 TO 45KTS MONDAY MORNING. IF YOU HAVE LIVED
IN THIS AREA FOR A WHILE NOW, YOU MAY KNOW WHERE THIS IS HEADING...
THE SURFACE LOW WITH THIS SYSTEM WILL DIVE SOUTHEASTWARD FROM THE
BLACK HILLS TOWARDS CENTRAL NEBRASKA, WITH A STRONG, TRAILING COLD
FRONT. THIS LOW PROGRESSION IS FAVORABLE FOR STRONG, WEST TO EAST
SURFACE PRESSURE GRADIENTS TO DEVELOP ACROSS WESTERN PORTIONS OF THE
AREA AND ACROSS THE LARAMIE RANGE. THE SURFACE PRESSURE GRADIENT
ACROSS THE LARAMIE RANGE PEAKS AROUND 2 TO 3MB MONDAY MORNING. GFS
OMEGA FIELD SUGGEST MODEST TO STRONG DOWNWARD MOTION ALONG THE
LARAMIE RANGE AND JUST EAST. WITH ALL THESE FACTORS CONSIDERED,
MONDAY MORNING WILL LIKELY SEE VERY STRONG WINDS ACROSS MUCH OF THE
REGION, THOUGH A HIGH WIND WARNING IS CURRENTLY NOT ANTICIPATED, BUT
THIS MAY CHANGE AS THIS EVENT MOVES INTO THE SHORT TERM. IN-HOUSE
RANDOM FOREST MODEL GUIDANCE IS GIVING AROUND A 30 TO 40% CHANCE FOR
HIGH WINDS AT ARLINGTON, RAWLINS, BORDEAUX, COLEMAN, AND NORTHERN
CARBON COUNTY. THEREFORE, HIGH WIND CRITERIA WINDS CANNOT BE
COMPLETELY RULED OUT AT THIS TIME AND THIS SETUP WILL NEED TO BE
MONITORED CLOSELY AS MONDAY MORNING APPROACHES.
IN ADDITION TO THE POTENTIAL FOR STRONG TO NEAR-HIGH WIND CRITERIA
WINDS, THIS SYSTEM WILL BRING A STRONG COLD FRONT TO THE REGION,
DROPPING TEMPERATURES FROM THE LOW-70S TO UPPER-80S ON MONDAY INTO
THE UPPER-60S TO MID-70S ON TUESDAY. MOST LOCATIONS EAST OF THE
LARAMIE RANGE WILL BE AROUND 10 TO 12 DEGREES COOLER ON TUESDAY.
ADDITIONALLY, ISOLATED TO SCATTERED SHOWERS WILL BE POSSIBLE MONDAY
WITH THE FRONT MOVING THROUGH, RESULTING IN LOW-LEVEL FORCING FOR
ASCENT. DEWPOINTS IN THE 50S AND 60S EAST OF THE LARAMIE RANGE ON
MONDAY WILL FAVOR PRECIPITATION DEVELOPMENT WITH THE FRONT, BEFORE
DEWPOINTS TANK INTO THE 30S AND 40S BEHIND THE FRONT. WITH THE
FRONTAL PASSAGE TIMING, PRECIPITATION WILL BE LARGELY CONFINED TO
THE I-80S CORRIDOR ACROSS THE REGION. THE LONG RANGE MODELS
CURRENTLY SUGGEST THAT SOME CAPE MAY BE PRESENT ACROSS THE REGION
MONDAY MORNING AND AFTERNOON, SO AN ISOLATED STORM OR TWO CANNOT BE
RULED OUT ESPECIALLY ACROSS THE SOUTHERN PANHANDLE.
AFTER THE COLD FRONT MONDAY, TEMPERATURES WILL REMAIN QUITE NICE
THROUGH THE REMAINDER OF THE WEEK, LIKELY STAYING IN THE 60S AND 70S
WITH A COUPLE OF LOW-80S POSSIBLE WEDNESDAY. DAILY PRECIPITATION
CHANCES ARE EXPECTED AS THE UPPER-LEVEL FLOW REMAINS MORE DYNAMIC
THAN IT HAS BEEN IN THE PAST SEVERAL WEEKS.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 1151 AM MDT SAT SEP 12 2026
SOME SHOWERS POSSIBLY WEAK THUNDERSTORMS WILL BE SKIRTING
THROUGH KLAR AND KCYS THIS AFTERNOON. MOSTLY VIRGA ANTICIPATED
BUT THERE MAY BE A BRIEF SHOWER OR TWO THIS AFTERNOON. BY THE
EVENING THESE SHOWERS ARE EXPECTED TO MAKE IT TO KSNY AND
POSSIBLY AS FAR NORTH AS KBFF. WINDS LOOK TYPICAL FALL SEASON
THROUGH THE DAY WITH SOME BRIEF STRONG GUSTS POSSIBLE
UNDERNEATH THESE SHOWERS/ WEAK THUNDERSTORMS. WIND GUSTS MAY
LAST THROUGH THE NIGHT FOR KCYS AND THE NEBRASKA TERMINALS AS AN
UPPER LEVEL LOW STARTS TO PUSH INTO THE INTERMOUNTAIN WEST
TIGHTENING OUR PRESSURE GRADIENT.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...MM
LONG TERM...AM
AVIATION...MM
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