470
FXUS65 KCYS 021122
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
ISSUED BY NATIONAL WEATHER SERVICE RIVERTON WY
522 AM MDT WED SEP 2 2026
KEY MESSAGES
- WARMING AND DRYING TREND EXPECTED THROUGH THE END OF THE WEEK.
SHORT TERM /THROUGH THURSDAY/
ISSUED AT 441 AM MDT WED SEP 2 2026
TODAY, THE UPPER-LEVEL RIDGE CONTINUES TO BUILD OVER THE
CENTRAL US WITH THE BACK SIDE OF THE RIDGE PUSHING INTO THE
INTERMOUNTAIN WEST AS THE RIDGE BROADENS OUT. ANOTHER WEAK
SHORTWAVE LOOKS TO MOVE THROUGH THE INTERMOUNTAIN WEST
DEVELOPING SOME CHANCES FOR WEAK SHOWERS THIS AFTERNOON AND
EVENING. MODEL GUIDANCE SHOWS A FEW VORT-MAXES TO ACCOMPANY THIS
WAVE BUT OVERALL, THE SYNOPTIC SUPPORT IS PRETTY WEAK. MLCAPE
AND SURFACE-BASED CAPE VALUES ARE BOTH ONLY A COUPLE HUNDRED
JOULES DESPITE SOME MOISTURE BEING ADVECTED IN WHILE IN
SOUTHWEST FLOW. THE AREAS WITH THE HIGHEST CHANCES ARE GOING TO
BE THE MOUNTAINOUS AND MOUNTAIN ADJACENT REGIONS OF ALBANY,
CARBON, AND LARAMIE COUNTIES IN SOUTHEAST WYOMING. BULK SHEAR
ALSO STARTS OUT FAIRLY WEAK AROUND 20 TO 30KTS AND INCREASES AS
THE EVENING PROGRESSES. HOWEVER, ONCE THE SUN GOES DOWN WE LOSE
ALMOST ALL INSTABILITY ACROSS THE FORECAST AREA AS BULK SHEAR
BECOMES IN AN ACCEPTABLE RANGE OF 35 TO 45 KNOTS ALOFT. SO
THERE IS A CHANCE THAT AS THE SUN GOES DOWN THESE SHOWERS
BECOME PULSE-Y SHORT LIVED THUNDERSTORMS WHERE THE GREATEST
THREAT WILL BECOME LIGHTNING AND GUSTY WINDS UNDERNEATH THE
STORMS. PAST 6PM UNCERTAINTY INCREASES FOR THE SHOWERS/STORMS
BEING STRONG ENOUGH TO PRODUCE RAIN BEFORE DISSIPATING SHORTLY
AFTER SUNSET. WINDS WILL BE SLIGHTLY GUSTY BETWEEN 30 AND 40 MPH
FOR AREAS WEST OF I-25 TODAY AND THURSDAY AFTERNOON AS THE
WAVES TIGHTEN THE GRADIENT AS THEY MOVE THROUGH THE
INTERMOUNTAIN WEST. THERE ARE LESS CHANCES FOR SHOWERS THURSDAY
AFTERNOON AS RH VALUES DROP BETWEEN 12 AND 20 PERCENT FOR
ELEVATED TO BORDERLINE RED FLAG CONDITIONS. HOWEVER, THE
STRONGEST WINDS DONT LINE UP WITH THE AREAS OF LOWEST RH. SO,
CONFIDENCE IN REACHING RED FLAG CRITERIA IS LOW BUT THE AREAS
WITH THE STRONGEST WINDS ONLY LOOK TO DROP INTO THE 20 AND 30
PERCENT RANGE (ALBANY, CARBON, AND LARAMIE COUNTY). SO, NO FIRE
WEATHER PRODUCTS WERE ISSUED DURING THIS TIME.
LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/
ISSUED AT 155 PM MDT TUE SEP 1 2026
FRIDAY...ALTHOUGH A BIT OF PSEUDO MONSOONAL MOISTURE AT MID
LEVELS WILL BE OVER OUR FORECAST AREA, THE DEEPER MOISTURE ON
SOUTHWEST FLOW ALOFT WILL REMAIN OVER COLORADO AND NEW MEXICO,
THUS CONTINUED DRY FOR US. 700 MB TEMPERATURES SUGGEST SUMMER
LIKE HEAT WILL CONTINUE FOR WARM WEATHER LOVERS.
SATURDAY...LOW AND MID LEVEL MOISTURE INCREASES SOMEWHAT VIA
PRECIPITABLE WATER CONTENT, AND THE DEEPER MOISTURE WILL CREATE
WIDELY SCATTERED SHOWERS AND A FEW THUNDERSTORMS FROM THE
LARAMIE VALLEY TO NEAR DOUGLAS AND NEARBY LOCATIONS IN THE
AFTERNOON AND EVENING HOURS. DRY ELSEWHERE. THE DECENT 700 MB
TEMPERATURES WILL AID IN KEEPING SIMILAR TEMPERATURES TO FRIDAY.
SUNDAY...BENEFICIAL RAINS LOOK QUITE PROMISING AS THERE WILL BE
AN INCREASE IN PRECIPITABLE WATER VALUES VIA A BETTER MONSOONAL
MOISTURE TAP. THE COMBINATION OF PASSING SHORTWAVE TROUGHS
ALOFT AND LOW LEVEL MECHANICAL LIFT AND OROGRAPHIC EFFECTS WILL
HELP PRODUCE SCATTERED AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS, MOST NUMEROUS OVER AND NEAR THE MOUNTAINS.
MONDAY...WITH ADEQUATE LOW AND MID LEVEL MOISTURE AVAILABILITY
COMBINED WITH UPSLOPE LIFT AND PASSING SHORTWAVE TROUGHS ALOFT,
EXPECT SCATTERED AFTERNOON SHOWERS AND THUNDERSTORMS MAINLY OVER
AND WEST OF INTERSTATE 25, WITH THE SHOWERS AND THUNDERSTORMS
PROPAGATING AND DEVELOPING MAINLY EAST OF I-25 IN THE EVENING.
STILL SOME UNCERTAINTY WITH REGARD TO MAXIMUM TEMPERATURES, AS
AN EARLY SEPTEMBER COLD FRONT MAY PASS ACROSS OUR COUNTIES
BRINGING IN A REFRESHING RESPITE FROM THE HEAT. WITH STILL SO
MUCH UNCERTAINTY, WILL LEAVE THE WARMER TEMPERATURES AS IS TO
BLEND IN WITH OUR NEIGHBORING OFFICES, BUT THIS DAY WILL LIKELY
BE COOLER THAN CURRENTLY FORECASTED.
TUESDAY...AN AUTUMNAL LIKE PATTERN GREETS US SYNOPTICALLY FOR
SEPTEMBER WITH A RATHER SIGNIFICANT SHORTWAVE TROUGH ALOFT
TRAVELING EASTWARD ACROSS MONTANA. STILL ENOUGH ATMOSPHERIC
MOISTURE TO PRODUCE SCATTERED SHOWERS AND THUNDERSTORMS SOUTH OF
A RAWLINS TO SCOTTSBLUFF LINE. AGAIN, TEMPERATURES MAY BE COOLER
THAN CURRENTLY FORECASTED WITH LATER MODEL RUNS AND TRENDS.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 521 AM MDT WED SEP 2 2026
A SHORTWAVE WILL PUSH THROUGH THIS AFTERNOON AND EVENING FOR
POSSIBLE SHOWER CHANCES. THE HIGHEST CHANCES FOR SHOWERS IS
BETWEEN 21Z AND 00Z FOR KCYS AND KLAR. HOWEVER, THERE IS ALMOST
NO ENERGY FOR SHOWERS TO SUSTAIN THEMSELVES MEANING ITS HARD TO
TELL HOW MUCH RAIN WILL FALL IF ANY FALLS OVER THE TERMINALS.
VCSH WAS USED BECAUSE THERE WAS NO CONSENSUS BETWEEN HI-RES
MODELS FOR TIMING AND INTENSITY. THE 12Z MODEL RUNS SHOULD
PROVIDE ENOUGH CONFIDENCE TO UPGRADE TO PROB30 IN THE TAFS.
THESE SHOWERS LOOK TO BE SOMEWHERE BETWEEN 10,000FT AND 15,000FT
SO VFR CONDITIONS ARE EXPECTED THROUGHOUT THE TAF PERIOD.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...WFOCYS
LONG TERM...WFOCYS
AVIATION...WFOCYS
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