710
FXUS65 KCYS 100825
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
225 AM MDT SAT OCT 10 2026
KEY MESSAGES
- ABOVE AVERAGE TEMPERATURES DRY CONDITIONS FOR MOST OF
SATURDAY. SHOWERS & THUNDERSTORMS POSSIBLE THIS EVENING FOR
MAINLY SOUTHEAST WYOMING.
- A PATTERN CHANGE WILL BRING A GRADUAL COOL DOWN AND INCREASED
CHANCES FOR PRECIPITATION SUNDAY THROUGH MUCH OF NEXT WEEK.
SHORT TERM /THROUGH SUNDAY NIGHT/
ISSUED AT 215 AM MDT SAT OCT 10 2026
A FEW MORE WARM DAYS STILL ON TRACK THIS WEEKEND WITH MODELS IN
PRETTY GOOD AGREEMENT THROUGH SUNDAY NIGHT, SHOWING A SLOW AND
GRADUAL COOL-DOWN AS WE HEAD INTO LATE SUNDAY AND EARLY MONDAY
MORNING WHERE TEMPERATURES WILL LIKELY LOWER BACK DOWN CLOSER TO
AVERAGE FOR THIS TIME OF THE YEAR. ALL MODELS ARE IN BETTER
AGREEMENT (COMPARED TO A FEW DAYS AGO) AND SHOW THE STRONG
PACIFIC STORM SYSTEM DIGGING SOUTH ACROSS THE PAC NW AND THE
SIERRA NEVADA RANGE THIS WEEKEND, POSSIBLY BRINGING BENEFICIAL
RAINFALL TO THE GREAT BASIN. IN OUR NECK OF THE WOODS, CENTRAL
WYOMING WILL BE THE FRINGE OF THIS ACTIVITY WITH MAINLY DRY AND
WARM CONDITIONS ALONG AND EAST OF THE INTERSTATE 25 CORRIDOR.
FOR THIS MORNING, INTERVALS OF MIDLEVEL CLOUDS PUSHING OVER THE
AREA BASED ON THE CURRENT IR SATELLITE LOOP. SOME RETURNS
BETWEEN 10K TO 15K FEET SHOWN ON KCYS RADAR, BUT BASED ON
OBSERVATIONS ACROSS THE AREA, IT IS LIKELY STILL TOO DRY FOR
ANY RAINFALL TO REACH THE SURFACE. EXPECT THIS TO BE THE CASE
FOR MOST OF THE DAY WITH LOW TO MIDLEVEL MOISTURE ADVECTION
GRADUALLY INCREASING THROUGH THE AFTERNOON. NOT MUCH FORCING
(EARLY) TODAY WITH MODELS SHOWING A SUBTLE VORT MAX LIFTING
NORTHEAST ACROSS WYOMING LATER TODAY INTO LATE THIS EVENING. A
UPPER LEVEL JET COUPLET ALSO LIFTS NORTHEAST COLOCATED WITH THE
VORT MAX. THIS WILL LIKELY BE ENOUGH TO GENERATE NUMEROUS
SHOWERS AND A FEW THUNDERSTORMS ACROSS MAINLY CARBON AND ALBANY
COUNTIES THIS EVENING AND INTO TONIGHT. CAN'T RULE OUT SOME OF
THIS ACTIVITY MOVING INTO, AND EAST OF, THE I-25 CORRIDOR...BUT
CONFIDENCE IS LIMITED WITH LOW LEVEL MOISTURE ADVECTION TAKING
QUITE A BIT OF TIME. CONVECTIVE PARAMETERS ARE MARGINAL WITH 100
TO 400 J/KG OF CAPE AND LAPSE RATES AROUND 5 TO 7 C/KM. SHOULD
BE ENOUGH FORCING TO GENERATE SOME MODERATE RAIN SHOWERS. A FEW
THUNDERSTORMS ARE POSSIBLE AS WELL, SO ADDED SOME PROB THUNDER
OF 15% TO 20% (SLIGHT CHANCE). HIGH RES GUIDANCE IS STILL
SHOWING SOME MORE ORGANIZED BANDS OF THUNDERSTORMS TONIGHT,
LIKELY DUE TO THE POSITION OF THE JET AND THE VORT MAX PUSHING
EAST. ADDED THE POTENTIAL FOR STRONG GUSTY WINDS TO THE
FORECAST...MAINLY FOR CARBON AND ALBANY COUNTIES. REMAINING
RELATIVELY WARM FOR THIS TIME OF THE YEAR, WITH AFTERNOON HIGHS
AROUND 70 WEST OF I-25 AND MID 70S TO MID 80S ACROSS THE EASTERN
PLAINS.
A LITTLE COOLER ON SUNDAY, MAINLY DUE TO INCREASING CLOUD COVER,
BUT 700MB TEMPERATURES DO LOWER A DEGREE OR TWO COMPARED TO
SATURDAY. PACIFIC STORM SYSTEM WILL STILL BE LOCATED ROUGHLY
OVER THE SAME AREA AS LATE SATURDAY WITH THE SYSTEM DIGGING
INTO SOUTHERN CALIFORNIA. SLIGHTLY BETTER CONVECTIVE PARAMETERS
AND FORCING OVER MOST OF SOUTHEAST WYOMING ON SUNDAY WITH MORE
FAVORABLE LAPSE RATES AND LOW TO MID LEVEL MOISTURE WITH
DEWPOINTS INCREASING INTO THE MID TO UPPER 40S. INCREASED POP
ACROSS MOST OF SOUTHEAST WYOMING AND THE FAR WESTERN NEBRASKA
PANHANDLE SUNDAY AFTERNOON AND SUNDAY EVENING FOR AT LEAST
SCATTERED TO NUMEROUS RAIN SHOWERS AND ISOLATED THUNDER. MAY BE
SOME HEAVY RAINFALL WITH SOME OF THIS ACTIVITY AS IT RAPIDLY
LIFTS NORTHEAST. CAN'T RULE OUT SOME HIGH ELEVATION SNOW, BUT
SNOWLEVELS WILL LIKELY BE BETWEEN 11,000 TO 12,000 FEET AT THE
START OF THIS EVENT. SOME COOLER AIR WILL MOVE INTO WYOMING
SUNDAY NIGHT, WITH OVERNIGHT LOW TEMPERATURES CLOSER TO THE LOW
TO MID 40S BY EARLY MONDAY MORNING.
LONG TERM /MONDAY THROUGH FRIDAY/
ISSUED AT 220 AM MDT SAT OCT 10 2026
MONDAY SEES THE MAJORITY OF THE UPPER LEVEL SUPPORT AND MOISTURE
LIFT NORTH OF THE AREA. DRY, SINKING AIR ON THE BACKSIDE OF THE
SYSTEM MOVES IN WHICH DAMPENS RAIN POTENTLY. THE BEST SIGNAL FOR
RAIN REMAINS TO THE WEST IN CARBON COUNTY. WINDS STAY GUSTY BEHIND
THE SYSTEM. GLOBAL MODEL ENSEMBLES HAVE BETWEEN 50 AND 60 PERCENT OF
MEMBERS WITH WIND GUSTS ABOVE CLIMATE AVERAGE FOR THIS TIME OF YEAR.
OUR IN-HOUSE HIGH WIND ML MODEL IS GIVING ELEVATED WIND GUSTS AROUND
40-50 MPH FOR THE ARLINGTON AND RAWLINS WIND PRONE AREAS. SOME SPOTS
ALONG I-25 COULD GET SOME OF THESE GUSTS. NOTHING QUITE REACHING
HIGH WIND CRITERIA AT THIS TIME, THOUGH TRENDS ARE SLIGHTLY
INCREASING.
OVERNIGHT MONDAY THE TROUGH OVER THE WEST COAST MOVES EASTWARD.
AHEAD OF THE SYSTEM THE SUBTROPICAL JET INTENSIFIES WITH THE
TIGHTENING OF 250 MBAR PRESSURE GRADIENTS BETWEEN THE TROUGH AND AN
UPPER LEVEL RIDGE OVER TX AND NORTHERN MEXICO. BEING ON THE LEFT
EXIT REGION OF THE JET COULD INCREASE SYNOPTIC LIFT. PWATS ARE IN
THE 90 TO 99 PERCENTILE, WHICH IS ABOUT HALF AN INCH. FORECAST
SOUNDINGS HAVE MOST OF THIS MOISTURE RESIDING BELOW 500 MBAR, SO
SHALLOW SHOWERS ARE ANTICIPATED WITH LOW RAINFALL RATES MAINLY IN
OUR WESTERN AREAS.
WE SEE A WEAK RETURN FLOW AT THE SURFACE TUESDAY IN RESPONSE TO THE
PACIFIC SYSTEM MOVING EAST AND SURFACE LEE CYCLOGENESIS STARTING. A
LULL IN RAIN IS POSSIBLE GIVEN BEING REMOVED FROM THE FAVORABLE
SYNOPTIC LIFTING PROVIDED BY THE JET AND SUBTLE RIDGING NOSING IN.
MOST SHOWER ACTIVITY, IF WE SEE IT DURING THE DAY, WOULD STILL BE
KEPT TO CARBON COUNTY. BY THE EVENING AND OVERNIGHT THE ADVANCING
SYSTEM SHOULD BE CLOSE ENOUGH TO START KICKING OFF SHOWERS. THE
RETURN FLOW COULD MOISTEN THE SURFACE LAYER ENOUGH THAT WE SEE SOME
AREAS OF FOG DEVELOP IN THE CENTRAL AND EASTERN PARTS OF OUR AREA
TOWARDS MORNING.
BY WEDNESDAY AND THURSDAY WE HIT A FORECAST HORIZON WITH THE
PROGRESSION OF THIS TROUGH. THE GENERAL TREND HAS BEEN TOWARDS A
SLOWER SYSTEM, THOUGH MODELS LIKE THE GFS ARE A LITTLE MORE
PROGRESSIVE AND AMPLIFIED, SHOWING A MORE NEGATIVE TILT TO THE
TROUGH SHAPE. PERHAPS THIS INCREASES LIFT AND INSTABILITY TO PRODUCE
THUNDERSTORMS OVER THE NEBRASKA PANHANDLE WEDNESDAY. BUT IF YOU GO
WITH THE EURO SOLUTION THE TROUGH IS NOT AS AMPLIFIED. THE EURO AND
CANADIAN MODEL SOLUTIONS ARE FOR THE SYSTEM TO THEN RETROGRADE BACK
WEST AND NOT MOVE MUCH THROUGH THE REMAINDER OF THE FORECAST PERIOD.
ADDITIONALLY, SOME MAJOR DISAGREEMENT IN THE 00Z RUNS OF GLOBAL
MODELS ON A CLIPPER LIKE SYSTEM SWINGING SOUTHEAST OUT OF CANADA.
GFS, AND EVEN THE EURO AIFS, DO RESOLVE THE CLIPPER AND EJECTS THE
TROUGH NORTHEAST. THIS HAS MAJOR IMPLICATIONS TO THE LONG RANGE
FORECAST. IF THE CLIPPER SOLUTION IS CORRECT COLDER AIR CAN BE
ANTICIPATED WITH THE POTENTIAL OF SOME LOCATIONS SEEING FREEZING
OVERNIGHT TEMPERATURES. BUT IF THIS IS NOT CORRECT, CONTINUED MILD
TEMPERATURES ARE LIKELY. THE FEATURES THAT CAUSE THIS UNCERTAINTY
APPEARS TO BE THE STRENGTH OF THE RIDGE TO THE NORTH IN CANADA AND IF
IT ALLOWS A TROUGH EJECTION TO OCCUR NEAR ALASKA AROUND OCTOBER
14TH. SO, WATCHING THE PROGRESSION OF THESE FEATURES AROUND THAT
TIMEFRAME IN THOSE LOCATIONS SHOULD HELP RESOLVE WHAT OUR LONG TERM
FORECAST.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 1138 PM MDT FRI OCT 9 2026
THERE IS ENOUGH OF A SIGNAL OF LLWS FOR KCYS IN RECENT MODEL
GUIDANCE THROUGH 16Z TO INCLUDE IT IN THE 06Z TAFS. WINDS ARE
LIGHT AND VARIABLE AT MOST TERMINALS EXCEPT KRWL WHERE NEARBY
STATION OBSERVATIONS ARE MEASURING WINDS OUT OF THE SOUTHWEST AT 20
KNOTS. VFR CONDITIONS ARE EXPECTED THROUGH THE AFTERNOON HOURS
BEFORE SHOWER ACTIVITY INCREASES. A FEW EMBEDDED THUNDERSTORMS
MAY OCCUR. COVERAGE IS SCATTERED WITH THE GREATEST CHANCE FOR
RAIN OVER KRWL. THERE IS A POSSIBILITY OF VISIBILITY DROPPING
DURING MODERATE RAINFALL TO MVFR UNDER THE HEAVIEST ACTIVITY,
ALONG WITH GUSTY WINDS TO 40 KNOTS. THESE CONDITIONS MAY BE
INCLUDED IN FUTURE TAFS AS CERTAINTY INCREASES.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...TJT
LONG TERM...RV
AVIATION...RV
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