856
FXUS65 KCYS 031947
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
ISSUED BY NATIONAL WEATHER SERVICE RIVERTON WY
147 PM MDT THU SEP 3 2026
KEY MESSAGES
- RED FLAG WARNING IN EFFECT FOR CONVERSE AND NIOBRARA
COUNTIES.
- WARMING AND DRYING TREND EXPECTED THROUGH THE END OF THE WEEK.
- PRECIPITATION CHANCES RETURN FOR THE BEGINNING OF NEXT WEEK.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 139 PM MDT THU SEP 3 2026
TONIGHT…DRY SOUTHWEST FLOW ALOFT PREVAILS WITH A QUIET NIGHT ON TAP AND
COOL OVERNIGHT MINIMAL TO PRODUCE GOOD SLEEPING CONDITIONS FOR
OPENING UP WINDOWS.
FRIDAY…THE MAIN WEATHER STORY WILL BE THE HEAT, WITH SOUTHWEST WINDS
ALOFT AND SURFACE LOW PRESSURE AND A THERMAL RIDGE AXIS OVER OUR
COUNTIES. WITH 700 MB TEMPERATURES NEAR 15 CELSIUS AND DOWNSLOPE
WINDS AND LITTLE IF ANY CLOUD COVER, MAXIMUM TEMPERATURES WILL
SOAR INTO THE MID 80S TO NEAR 90 DEGREES WEST OF I-25, WITH
BLISTERING HEAT FURTHER EAST OF I-25, WITH MAXIMUM TEMPERATURES
IN THE 90S, TO NEAR 100 DEGREES OVER THE NEBRASKA PANHANDLE.
RECORD HIGH TEMPERATURES, YEAR AND FORECAST HIGH TEMPERATURES FOR
SEPTEMBER 4…
RAWLINS 95/1998…83
LARAMIE 89/2022…84
CHEYENNE 94/2022…90
CHADRON 104/1978…101
ALLIANCE 101/1998…96
SCOTTSBLUFF 102/1998…99
SIDNEY…100/1998…99
FRIDAY NIGHT…A WEAK SHORTWAVE TROUGH ALOFT MOVES TO OUR SOUTHERN
COUNTIES BY DAWN, SPAWNING ISOLATED TO SCATTERED SHOWERS NEAR
A CHEYENNE TO TORRINGTON LINE, OTHERWISE DRY AND COOL.
LONG TERM /FRIDAY THROUGH WEDNESDAY/
ISSUED AT 145 PM MDT THU SEP 3 2026
WEAK SOUTHWESTERLY UPPER-LEVEL FLOW IS ANTICIPATED FOR SATURDAY
WITH LAX PRESSURE GRADIENTS BETWEEN TROUGHING OVER THE PACIFIC
NORTHWEST AND A RIDGE TO THE SOUTHEAST. THE MAJORITY OF AREA
WILL BE CAPPED THROUGH THE EARLY AFTERNOON. A WEAK UPPER LEVEL
SHORTWAVE WOULD PROMOTE A FEW MORNING SHOWERS AND GENERAL
CLOUDINESS BEFORE MOVING THROUGH IN THE EARLY AFTERNOON. A FEW
SHOWERS AND THUNDERSTORMS MAY BE POSSIBLE IN THE MOUNTAINS AND ALONG I-25
EARLY ON WITH A FEW STORMS DEVELOPING IN THE NE PANHANDLE AREAS
LATER ON. A STORM OR TWO MAY BE MARGINALLY SEVERE, THOUGH
LIMITED BULK SHEAR (25-35 KT) AND CAPE (1000-1500 J/KG) WILL
KEEP MOST ACTIVITY ON THE WEAKER SIDE. PWAT VALUES ARE SLIGHTLY
ELEVATED COMPARED TO CLIMATE AVERAGE DUE TO SOME MONSOONAL FLOW,
SO, STORMS MAY BE BETTER ABLE TO PRODUCE BENEFICIAL RAIN WERE
THEY OCCUR. OUTSIDE OF STORMS AFTERNOON HIGH TEMPERATURES ARE
EXPECTED TO MAKE IT INTO THE 90S EAST OF I-25 AND 80S TO THE
WEST. MINIMUM RELATIVE HUMIDITY VALUES IN THE LOW 20S AND UPPER
TEENS COULD LEND ITSELF TO ELEVATED FIRE POTENTIAL THOUGH OVERNIGHT
RECOVERIES ARE GOOD.
SUNDAY IS MUCH THE SAME AS MONDAY. THE TROUGH OVER THE PACIFIC NW
WILL INCH CLOSER TO OUR AREA ALLOWING FOR SLIGHTLY BETTER FORCING
AND ADVECTION OF MONSOON. THEREFORE, THE ODDS OF STORMS INCREASE.
THE FORECASTED POPS ARE ABOUT 40-60% AREA WIDE, WHILE MODEL ENSEMBLES
ARE A LITTLE MORE GIVING WITH 50-75% CHANCES OF RAIN. PW VALUES
OF AN INCH TO 1.5 OVER SOUTHEAST WYOMING AND THE NEBRASKA
PANHANDLE MAY LEAD TO A SNEAKY FLOODING POTENTIAL. CORFIDI
VECTORS ARE IN THE 15 TO 20 KNOT RANGE WITH BUNKERS RIGHT MOTION
BEING NEARLY STATIONARY. THESE PARAMETERS ARE SENSITIVE TO DETAILS
THAT ARE HARD TO RESOLVE AT THIS RANGE, BUT THE CHANCE OF SLOW
MOVING AND HEAVY RAINFALL PRODUCING STORMS IS POSSIBLE.
THE TREND OF SHOWERS AND THUNDERSTORMS CONTINUE THROUGH MONDAY
AND TUESDAY AS THE STUBBORN TROUGH TO THE NORTHWEST FINALLY
EJECTS INTO THE CENTRAL PLAINS. WHILE MOISTURE WILL REMAIN
HIGH, A LOBE OF DRIER AIR ASSOCIATED WITH A RIDGE TO THE EAST
MAY BE PULLED IN AHEAD OF THE TROUGH WHICH WOULD REDUCE RAIN
POTENTIAL. HOWEVER, SINCE THE TROUGH IS EJECTING IT IS POSSIBLE
THAT CYCLOGENESIS OCCURS NEARBY INCREASING THE SEVERE WEATHER
POTENTIAL. SOME MACHINE LEARNING MODELS ARE HIGHLIGHTING AN
UPTICK IN THAT POTENTIAL FOR THE NEBRASKA PANHANDLE AREA.
THE DETAILS OF HOW THIS UNFOLDS WILL BE IRONED OUT AS WE GET
CLOSER.
THE REMAINDER OF THE LONG TERM IS IN A DRYING TREND. THE
RIDGE NOSES IN. THIS WOULD NOT COMPLETELY SHUT DOWN STORM
ACTIVITY.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 1142 AM MDT THU SEP 3 2026
VFR CONDITIONS EXPECTED THROUGHOUT THE FORECAST PERIOD. A FEW TO SCATTERED
CUMULUS AND CIRRUS CLOUDS THIS AFTERNOON. WINDS OUT OF THE WEST TO
SOUTHWEST FOR MOST TERMINALS UNDER THE INFLUENCE OF AN UPPER LEVEL RIDGE.
WINDS RELAX TONIGHT TO BECOME VARIABLE AFTER 01/02Z. A WEAK SHORTWAVE TROUGH
WILL PASS THROUGH FRIDAY MORNING TO CREATE SOME CLOUD COVERAGE. MOST OF
THIS COVERAGE PASSES BY AROUND THE END OF THE FORECAST PERIOD.
CYS WATCHES/WARNINGS/ADVISORIES
WY...RED FLAG WARNING UNTIL 7 PM MDT THIS EVENING FOR WYZ417-418.
NE...NONE.
SHORT TERM...WFOCYS
LONG TERM...WFOCYS
AVIATION...WFOCYS
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