847
FXUS65 KCYS 152033
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
233 PM MDT WED OCT 15 2025
KEY MESSAGES
- A STORM SYSTEM WILL MOVE THROUGH THE AREA TODAY AND THURSDAY,
FIRST BRINGING SHOWERS AND THUNDERSTORMS, FOLLOWED BY
MOUNTAIN SNOW AND STRONG WINDS ACROSS THE WIND PRONE AREAS OF
SOUTHEAST WYOMING.
- A FEW OF THE THUNDERSTORMS THIS AFTERNOON MAY BECOME STRONG TO
MARGINALLY SEVERE, OF WHICH THEY MAY PRODUCE HAIL AND GUSTY
WINDS ALONG WITH HEAVY RAINFALL.
MESOSCALE
ISSUED AT 227 PM MDT WED OCT 15 2025
AFTERNOON GOES SATELLITE IMAGERY REVEALS A THICK BLANKET OF
PERSISTENT STRATUS CLOUD COVER OVER MUCH OF EAST-CENTRAL
WYOMING EAST OF THE LARAMIE RANGE, AS WELL AS THE NORTHERN AND
CENTRAL NEBRASKA PANHANDLE. THIS STRATUS CLOUD COVER IS A
VISIBLE SIGN OF ROBUST CIN/CAPPING WHICH REMAINS IN PLACE OVER
THIS REGION. FARTHER SOUTH ACROSS LARAMIE COUNTY WYOMING AS
WELL AS THE KIMBALL TO SIDNEY CORRIDOR IN THE SOUTHWEST NE
PANHANDLE...SURFACE HEATING AND MIXING HAS ERODED THE MORNING
FOG/CLOUD LAYER WITH AROUND 1000 J/KG OF SBCAPE PRESENT PER RAP
MESOANALYSIS FIELDS. TO THE WEST OF THE LARAMIE RANGE, DEWPOINT
DEPRESSIONS ARE MUCH HIGHER WITH SOME HIGH- BASED CONVECTIVE
CLOUD COVER DEVELOPING OVER THE SIERRA MADRE AND SNOWY RANGES.
AS WE MOVE THROUGH THE LATER AFTERNOON HOURS, A DEEP TROUGH WILL DIG
THROUGH THE GREAT BASIN AND FOUR CORNERS REGION. AHEAD OF THIS
SYSTEM...FAVORABLE DYNAMICS INCLUDING DIVERGENCE ALOFT, A POTENT MID-
LEVEL JET STREAK WITH 500MB WINDS IN THE 50-70KT RANGE, AND RAPIDLY
COOLING MID-LEVEL TEMPERATURES LEADING TO INCREASING LAPSE RATES
WILL ALL COMBINE TO PLACE A RATHER FAVORABLE PARAMETER SPACE FOR
STRONG THUNDERSTORMS OVER SOUTHEAST WYOMING AND WESTERN NEBRASKA.
THE LIMITING FACTOR IN THE THUNDERSTORM FORECAST TODAY WILL CONTINUE
TO BE INSTABILITY - OR RATHER A LACK THEREOF. WHILE CLOUDS HAVE
CLEARED ALONG THE I-80 CORRIDOR EAST OF THE LARAMIE RANGE AND
SURFACE DEWPOINTS ARE IN THE MID TO EVEN UPPER-50S, AIR TEMPERATURES
STILL NEED ABOUT 5-10 DEGREES OF WARMING TO SUPPORT ROBUST
CONVECTIVE INITIATION. GIVEN THE LARGE AMOUNT OF ML CIN STILL
IN PLACE, IT IS LIKELY THAT WE WILL HAVE TO RELY ON CONVECTIVE
INITIATION IN THE MOUNTAINS TO THE WEST, AS WELL AS
THUNDERSTORMS INITIATING ALONG A DEVELOPING DENVER CYCLONE
BOUNDARY IN NORTHEAST COLORADO. CAM GUIDANCE AND HREF ENSEMBLE
MEMBERS HAVE BEEN MORE CONSISTENT IN CI THIS AFTERNOON AND
EVENING IN THESE LOCATIONS, WITH STORMS MOVING NORTH OUT OF
COLORADO INTO SOUTHERN WYOMING AND SOUTHWEST NEBRASKA IN THE
23-01Z TIMEFRAME.
WHILE INSTABILITY PROFILES LEAVE MUCH TO BE DESIRED, THE KINEMATIC
PROFILE DOES SUPPORT MULTICELL TO SUPERCELL THUNDERSTORM MODE WITH
ANY CONVECTION THAT CAN MAINTAIN ITSELF IN THE CHEYENNE CWA EAST OF
THE LARAMIE RANGE THIS EVENING. LONG, CURVING HODOGRAPHS ARE PRESENT
BY 0Z AS THE SOUTHEASTERLY LOW-LEVEL JET INTENSIFIES UNDERNEATH
STRONG SOUTHWESTERLY FLOW ALOFT. EFFECTIVE BULK SHEAR OVER 60 KNOTS
AND 0-3KM SRH IN THE 150-300 RANGE AS SEEN ON BOTH THE NAM NEST AND
RECENT HRRR RUNS ALSO SUPPORT ROTATING UPDRAFTS WITH THREATS FOR
HAIL OVER 1" IN DIAMETER AND GUSTY OUTFLOW WINDS. IF SURFACE
TEMPERATURES WERE A FEW DEGREES WARMER, A TORNADO THREAT WOULD ALSO
BE PRESENT. ULTIMATELY HOWEVER, THE MOST LIKELY SCENARIO THIS
AFTERNOON AND EVENING WILL BE FOR SURFACE-BASED THUNDERSTORMS TO
QUICKLY BECOME ELEVATED AND LOSE THEIR PUNCH NORTH OF THE I-80
CORRIDOR GIVEN CAPPING REMAINING IN PLACE. AS STRONGER FORCING MOVES
IN ALOFT AFTER 0Z, ANOTHER ROUND OF STRONGER SHOWERS AND
THUNDERSTORMS WILL LIKELY FORM OVER THE LARAMIE RANGE AND MOVE
THROUGH EAST-CENTRAL WYOMING. THESE STORMS, LIKELY ELEVATED ON TOP
OF THE STABLE BOUNDARY LAYER, COULD ALSO BRING A WIND AND HAIL
THREAT FROM WHEATLAND THROUGH TORRINGTON AND CHADRON THROUGH
AROUND 6Z TONIGHT.
SHORT TERM /THROUGH THURSDAY NIGHT/
ISSUED AT 345 AM MDT WED OCT 15 2025
FORECAST REMAINS ON TRACK TODAY AND TONIGHT WITH MODELS
CONTINUING TO INDICATE 99TH+ PERCENTILE PWATS ACROSS MOST OF THE
EASTERN HIGH PLAINS. THIS IS EVIDENT WITH THE WIDESPREAD DENSE
FOG EARLY THIS MORNING WITH VISIBILITY DOWN TO ONE EIGHTH OF A
MILE AT TIMES ALONG AND EAST OF THE I-25 CORRIDOR. EXPANDED THE
DENSE FOG ADVISORY FURTHER WEST TO INCLUDE MOST OF THE
INTERSTATE 25 CORRIDOR UP TO CONVERSE COUNTY. CURRENT SURFACE
OBSERVATIONS SHOW DEWPOINTS ABOVE 55 DEGREES ACROSS WESTERN
NEBRASKA, WHICH IS GOING TO SET UP A POTENTIALLY ACTIVE PERIOD
OF WEATHER THE NEXT 24 TO 36 HOURS.
FOG IS FORECAST TO SLOWLY LIFT BY NOON TODAY AS A WARM FRONT
SLOWLY LIFT NORTHEAST ACROSS THE FORECAST AREA. IR SATELLITE
LOOP SHOWS THE STRONG UPPER LEVEL LOW PRESSURE CENTER STARTING
TO TRACK EASTWARD ACROSS THE GREAT BASIN REGION EARLY THIS
MORNING. THIS FEATURE, ALONG WITH THE STATIONARY FRONT, WILL BE
RESPONSIBLE FOR LATE SEASON THUNDERSTORM ACTIVITY OVER THE NEXT
24 TO 30 HOURS. THUNDERSTORMS HAVE ALREADY BEEN OBSERVED LATE
LAST NIGHT ACROSS CARBON AND CONVERSE COUNTIES WELL AHEAD OF THE
UPPER LEVEL LOW. THERE REMAINS A CONDITIONAL RISK FOR STRONG TO
SEVERE THUNDERSTORMS FOR AREAS JUST EAST OF THE LARAMIE RANGE
EASTWARDS ACROSS ALL OF WESTERN NEBRASKA. HOWEVER, MUCH OF THE
THUNDERSTORM ACTIVITY ISN'T EXPECTED TO FORM UNTIL THE EVENING
HOURS AND ESPECIALLY OVERNIGHT DUE TO THE REMAINING STRATUS DECK
AND ARRIVAL OF DYNAMIC FORCING...WITH MODEL SOUNDINGS SHOWING
CONDITIONAL INSTABILITY AND INCREASING LAPSE RATES TONIGHT AS
THE COLD POOL ALOFT MOVES OVER THE AREA. THIS IS GOING TO LEAD
TO A TRICKY FORECAST AFTER NOON TODAY FOR THIS TIME OF THE YEAR.
WITH MLCAPE NEAR 1000 J/KG AND MUCAPE CLOSER TO 1500 J/KG LATE
THIS EVENING, WORDED FORECAST FOR STRONG TO SEVERE THUNDERSTORMS.
THE MOST FAVORABLE LOCATIONS ARE NORTHEAST OF A LINE FROM
CASPER WYOMING TO BRIDGEPORT NEBRASKA WHERE FORCING SHOULD BE
THE STRONGEST NORTH OF THE DEVELOPING SURFACE LOW. HOWEVER,
LOCATIONS ALONG THE I-80 CORRIDOR HAVE A DECENT CHANCE AT SEEING
SOME ACTIVITY AS WELL, ESPECIALLY IF THE FORECAST LOCATION OF
THE SURFACE LOW IS JUST A LITTLE OFF. HIGH RES CAMS HAVE BEEN
CONSISTENT, SO INCREASED POP AND PROB THUNDER ACROSS THE MOST
FAVORABLE AREAS. MULTIPLE LINES OF CONVECTION ARE EXPECTED
THROUGH MIDNIGHT TONIGHT WITH SOME ACTIVITY LINGERING INTO EARLY
THURSDAY MORNING. STRONG GUSTY WINDS, HAIL, AND BRIEF VERY
HEAVY RAINFALL ARE THE MOST LIKELY THREATS WITH THESE STORMS.
VARIABLES THAT MAY BUST THIS FORECAST INCLUDE MID TO UPPER LEVEL
CLOUDS MOVING INTO THE AREA EARLY, A STUBBORN STRATUS DECK
AND/OR FOG LINGERING THROUGH THE AFTERNOON, AND THE UPPER LEVEL
LOW SLOWING DOWN TODAY. PRETTY CONFIDENT THAT MID TO UPPER LEVEL
CLOUDINESS MAY NOT BE MUCH OF A PROBLEM GIVEN CURRENT TRENDS ON
IR SATELLITE EARLY THIS MORNING.
FOR THURSDAY, ALL MODELS SHOW THE UPPER LEVEL LOW LIFTING
NORTHEAST FROM THE SALT LAKE CITY AREA TO CENTRAL AND NORTHEAST
WYOMING BY THURSDAY AFTERNOON. THIS POSITION IS A LITTLE FURTHER
SOUTH AND EAST COMPARED TO 24 HOURS AGO. EXPECT ANOTHER ROUND
OF PRECIPITATION THURSDAY WITH STRONG JET ENERGY OUT AHEAD OF
THE TROUGH AXIS. ANY THUNDERSTORM ACTIVITY LOOKS TO BE IN THE
MORNING, WITH RAIN SHOWER ACTIVITY ALONG THE SURFACE COLD FRONT,
WHICH COULD STALL ACROSS THE EASTERN PLAINS IN THE AFTERNOON
AND EVENING. HIGH TEMPERATURES WILL RETURN TO SLIGHTLY BELOW
AVERAGE ON THURSDAY FOR MOST AREAS WITH HIGHS IN THE MID 40S TO
UPPER 50S ACROSS SOUTHEAST WYOMING, AND LOW TO MID 60S ACROSS
WESTERN NEBRASKA. GIVEN THE STORM TRACK, WINDS ARE ALSO
EXPECTED TO INCREASE WITH WINDY CONDITIONS LOOKING MORE LIKELY
ACROSS SOUTHEAST WYOMING THURSDAY AFTERNOON AND EVENING.
LONG TERM /FRIDAY THROUGH TUESDAY/
ISSUED AT 222 AM MDT WED OCT 15 2025
HEADING INTO THURSDAY NIGHT, THE NEXT ROUND OF HIGH WINDS WILL
ARRIVE. THE COLD FRONT WILL CAUSE MSLP GRADIENTS TO TIGHTEN WEST OF
THE LARAMIE RANGE, WHICH WILL IN TURN CAUSE 700 MB WINDS TO INCREASE
UP TO 60 KTS OVER THE USUAL SOUTHEAST WYOMING WIND PRONES. STRONG
SUBSIDENCE WILL EASILY PUSH THESE WINDS DOWN TO THE SURFACE. 60+ MPH
WINDS WILL BE POSSIBLE AT ARLINGTON, BORDEAUX AND THE SOUTH LARAMIE
RANGE LATE THURSDAY NIGHT INTO FRIDAY MORNING. WINDS WILL GRADUALLY
DECREASE THROUGHOUT THE DAY FRIDAY AS THE TROUGH PUSHES AWAY.
FOR THE WEEKEND, MODELS ARE STRUGGLING WITH THE SHORTWAVE ENERGY
DIGGING SOUTHEAST OUT OF WESTERN CANADA. ALL MODELS SHOW A
STRONG COLD FRONT, WITH THE POTENTIAL OF SOME LOWER ELEVATION
RAIN/SNOW MIX SATURDAY MORNING. HOWEVER, MODELS ARE OUT OF PHASE
WITH THIS TROUGH AXIS WITH THE GFS THE MOST PROGRESSIVE...SHOWING
IT CLIPPING THE AREA BUT MAINLY MOVING ACROSS THE DAKOTAS. THE
CANADIAN AND ECMWF SHOW THE TROUGH DIGGING FURTHER SOUTH WITH
POSSIBLE SNOW DOWN TO NEAR 6000 FEET AS 700MB TEMPERATURES LOWER
TO -4C TO -8C. ENSEMBLE SPREADS AMPLIFY THIS DISAGREEMENT WITH
LOW CONFIDENCE WITH POP AND TEMPERATURE FORECASTS. SIMILAR
PATTERN UNFOLDS FOR EARLY NEXT WEEK WITH LARGE TEMPERATURE AND
POP SPREADS AS ANOTHER PROGRESSIVE SHORTWAVE MOVES EAST ACROSS
THE AREA. DECENT MODEL AGREEMENT WITH THE ECMWF AND CANADIAN,
BUT THE GFS SHOWS A RIDGE AXIS DOMINATING THE WEATHER PATTERN ON
MONDAY. LOWERED MAX AND MIN TEMPERATURES SATURDAY THROUGH
MONDAY, AND KEPT 15 TO 30 PERCENT POP FOR NOW.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1148 AM MDT WED OCT 15 2025
DENSE FOG AND LOW STRATUS ARE BEGINNING TO MIX OUT FROM SOUTH TO
NORTH ACROSS THE REGION THIS MORNING. THAT BEING SAID, LINGERING
LOW CLOUDS AND SOME POSSIBLE LOCALIZED FOG MAY STILL BE POSSIBLE
THROUGH THE EARLY AFTERNOON, PARTICULARLY FOR OUR NEBRASKA
PANHANDLE SITES. LATER THIS AFTERNOON INTO THE EVENING,
THUNDERSTORMS ARE EXPECTED ACROSS THE REGION, AND COULD EVEN
BRING LOCALLY STRONG TO SEVERE VARIABLE WIND GUSTS. LOWERED
CLOUD DECKS AND LINGERING RAIN OR MIST MAY THEN RETURN OVERNIGHT
INTO TOMORROW MORNING, THOUGH ANY LOWERED VISIBILITIES ARE NOT
EXPECTED TO BE NEARLY AS SIGNIFICANT AS THIS MORNING'S ACTIVITY.
FINALLY, WINDS WILL BE BREEZY THIS AFTERNOON, WITH GUSTS 20-30
KNOTS POSSIBLE, RELAXING LATER THIS EVENING AND PICKING BACK UP
FROM A MORE WESTERLY DIRECTION TOMORROW MORNING INTO THE
AFTERNOON.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
MESOSCALE...MAC
SHORT TERM...TJT
LONG TERM...TJT/SF
AVIATION...CG
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