486
FXUS65 KCYS 290844
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
244 AM MDT WED APR 29 2026
KEY MESSAGES
- CHANCES FOR SCATTERED RAIN AND SNOW WILL CONTINUE THROUGH
THURSDAY NIGHT.
- WARMER AND DRIER CONDITIONS ARE EXPECTED TO RETURN FOR FRIDAY
INTO THE WEEKEND.
SHORT TERM /THROUGH THURSDAY NIGHT/
ISSUED AT 245 AM MDT WED APR 29 2026
OUR AREA IS IN BETWEEN UPPER LEVEL SHORTWAVE TROUGHS THIS MORNING,
LEAVING FAIRLY TRANQUIL CONDITIONS. A WEAK SURFACE HIGH OVER THE
CENTRAL PLAINS IS PRODUCING LIGHT SOUTHERLY WINDS OVER MOST OF OUR
HIGH PLAINS ZONES, WHICH IS KEEPING DEWPOINTS ELEVATED THIS MORNING.
WITH MAINLY CLEAR SKIES AND LIGHT WINDS, WE ARE SEEING SOME PATCHY
FOG AND LOW CLOUDS DEVELOPING. THE MAIN AREA OF THIS IS APPARENT ON
GOES SATELLITE IMAGERY, JUST ON THE CUSP OF SIDNEY AND ALLIANCE, AND
EXPANDING WESTWARD UP THE NORTH PLATTE RIVER VALLEY. OBSERVATIONS
ALSO INDICATE SOME VERY PATCHY RADIATION FOG DEVELOPING ELSEWHERE
OVER THE AREA, BUT THOSE LOCATIONS ARE NOT LARGE ENOUGH TO PRESENT
ON SATELLITE IMAGERY. AS THE SURFACE HIGH RETREATS FURTHER EAST, THE
WESTERLY COMPONENT OF THE SURFACE WIND WILL INCREASE SLIGHTLY, BUT
THIS SHOULD BE ENOUGH TO HOLD THE FOG FROM EXPANDING MUCH FURTHER TO
THE WEST (EXCEPT IN THE RIVER VALLEY). ANY REMAINING FOG SHOULD BURN
OFF FAIRLY QUICKLY AFTER SUNRISE TODAY AS NORTHWEST WINDS OVERSPREAD
THE AREA.
THE NEXT SUBTLE SHORTWAVE CURRENTLY VISIBLE ON SATELLITE IMAGERY
OVER CENTRAL UTAH WILL APPROACH THE AREA THIS AFTERNOON. THIS
FEATURE WILL HELP KICK OFF ANOTHER ROUND OF SCATTERED RAIN AND SNOW
SHOWERS LATE THIS MORNING OR EARLY IN THE AFTERNOON IN THE PLACE OF
MODEST CONVECTIVE INSTABILITY EXPECTED TO DEVELOP. FORECAST
SOUNDINGS SHOW A FAIRLY PRONOUNCED STABLE LATER RIGHT AROUND 500-MB
THIS AFTERNOON, WHICH WILL PUT A FAIRLY LOW HEIGHT LIMIT ON
DEVELOPING CONVECTION. THIS WILL IN TURN LIMIT THE POTENTIAL FOR
RAINFALL TODAY. THE HIGHEST CHANCE FOR SEEING MORE THAN A FEW
SPRINKLES IS ALONG OUR EASTERN ROW OF COUNTIES FROM CHADRON SOUTH
TOWARDS SIDNEY. WE WILL ALSO NEED TO WATCH THE VICINITY OF THE
LARAMIE RANGE AND THE HIGHER MOUNTAINS OF SOUTHEAST WYOMING WHERE
THE BOOST FROM OROGRAPHIC LIFT AND SOME LOW-LEVEL CONVERGENCE MAY
HELP ANCHOR SOME SHOWER ACTIVITY. IN THESE AREAS, PRECIPITATION
TYPE WILL PROBABLY BE SNOW.
MEANWHILE, ANOTHER UPPER LEVEL SHORTWAVE WILL DIVE DOWN FROM THE
NORTH TONIGHT. THIS WILL BE ACCOMPANIED BY A DIFFUSE SURFACE COLD
FRONT SUPPORTING COLD AIR ADVECTION BEGINNING THIS AFTERNOON AND
SURFACE PRESSURE RISES FROM NORTH TO SOUTH. OVERNIGHT INTO THURSDAY
MORNING, THIS SURFACE HIGH WILL PUSH UP AGAINST THE HIGHER TERRAIN
OF SOUTHERN WYOMING AND STALL AS THE MESSY SHORTWAVE TROUGH INCHES
SOUTHWARD. MODELS SHOW SOME MODEST FRONTOGENESIS AND OVERRUNNING
DEVELOPING ALONG THE WY/CO BORDER DURING THIS PERIOD. A FEW MODELS
ALSO SHOW SOME SIMILAR FORCING DEVELOPING IN NORTHERN CARBON AND
ALBANY COUNTIES ALONG THE MORE SUBTLE TERRAIN BARRIER IN THAT AREA.
THIS SHOULD SUPPORT ANOTHER ROUND OF DEVELOPING SHOWER ACTIVITY.
OVERALL, THIS SYSTEM IS NOW EXPECTED TO TAKE A TRACK THAT IS
UNFAVORABLE FOR WIDESPREAD PRECIPITATION FOR OUR AREA. MOST OF THE
AREA WILL UNFORTUNATELY SEE LITTLE TO NO BENEFICIAL MOISTURE, BUT
THERE IS STILL A SLIVER OF HOPE FOR THE CHEYENNE TO ELK MOUNTAIN
CORRIDOR. CURRENT PROBABILITIES FOR 0.10" OR MORE OF LIQUID
PRECIPITATION ARE AROUND 30 TO 50% IN CHEYENNE, LARAMIE, AND
ELK MOUNTAIN. THIS INCREASES TO 50 TO 70% INCREASING IN
ELEVATION AROUND THE SNOWY RANGE (ESPECIALLY THE EAST SIDE) AND
THE SOUTHERN LARAMIE RANGE / I-80 SUMMIT. FURTHER NORTH,
PROBABILITIES FALL TO 10 TO 30% IN RAWLINS, WHEATLAND, KIMBALL,
AND SIDNEY, AND THEN DROP TO NEAR ZERO ALONG AND NORTH OF THE
NORTH PLATTE RIVER VALLEY. SNOW WILL BE THE DOMINANT
PRECIPITATION TYPE, BUT EXPECT TO SEE A RAIN/SNOW MIX BELOW
ABOUT 7000 FT IN ELEVATION. WE CURRENTLY HAVE APPROXIMATELY A 20
TO 30% CHANCE FOR REACHING ADVISORY CRITERIA SNOWFALL IN THE
SNOWY RANGE AND I-80 SUMMIT AREAS. THE TIMING IS A LITTLE
TRICKY, BUT EXPECT THIS TO PICK UP LATE TONIGHT OR EARLY
THURSDAY MORNING, AND CONTINUE THROUGH THE AFTERNOON BEFORE
TAPERING OFF THURSDAY EVENING. SOME ISOLATED THUNDER IS ALSO
LIKELY WITH THIS ACTIVITY.
LONG TERM /FRIDAY THROUGH TUESDAY/
ISSUED AT 245 AM MDT WED APR 29 2026
THE UNSETTLED WEATHER PATTERN WILL PAUSE FRIDAY MORNING AS THE MESSY
SHORTWAVES / UPPER LEVEL LOW GETS PUSHED SOUTH INTO NEW MEXICO. A
DISORGANIZED RIDGE WILL TRY TO EXPAND INTO THE NORTHERN ROCKIES OVER
THE TOP OF THIS SYSTEM. WHILE THE PATTERN WILL REMAIN MESSY, MODELS
ARE IN FAIRLY GOOD AGREEMENT THAT WE WILL SEE WARMER AND DRIER
WEATHER RETURN TO THE AREA TO BEGIN THE MONTH OF MAY. 700-MB
TEMPERATURES WILL CLIMB TO AROUND -2 TO 0C ON FRIDAY, THEN +2 TO +4C
FOR SATURDAY, AND SUNDAY. EXPECT HIGH TEMPERATURES NEAR AVERAGE ON
FRIDAY, THEN CLIMBING ABOVE AVERAGE FOR SATURDAY AND SUNDAY, BY
ABOUT 10F. DRIER AIR WILL ALSO WORK BACK INTO THE AREA WITH
PRECIPITABLE WATER VALUES APPROACHING THE CLIMATOLOGICAL 10TH
PERCENTILE. THIS WILL PUSH HUMIDITY BACK DOWN TO NEAR OR BELOW
CRITICAL THRESHOLDS AND INCREASE FIRE WEATHER CONCERNS. HOWEVER, THE
BRIGHT SIDE IS THAT THE HIGHLY DISORGANIZED UPPER LEVEL WIND FIELD
SHOULD KEEP WINDS FAIRLY LIGHT ACROSS THE AREA, KEEPING RED FLAG
CONCERNS AT BAY AT LEAST FOR FRIDAY AND SATURDAY. WINDS ARE EXPECTED
TO TICK UPWARDS SUNDAY, BUT MID TO UPPER LEVEL MOISTURE WILL BEGIN
TO RECOVER AS WELL. EXPECT A FEW HIGH-BASED PM SHOWERS TO RETURN TO
THE FORECAST SUNDAY.
LOOKING AHEAD INTO THE EARLY PART OF NEXT WEEK, WE SHOULD START TO
EAST BACK INTO A MORE UNSETTLED WEATHER PATTERN. THE PRIMARY PLAYER
ON THE SYNOPTIC SCALE WILL BE A LARGE, SPRAWLING UPPER LEVEL CLOSED
LOW SLOWLY MEANDERING INLAND FROM THE WEST COAST. MEANWHILE,
THE PERSISTENT UPPER LEVEL LOW OVER THE HUDSON BAY WILL CONTINUE
TO SPIN OVER THE AREA, SENDING OCCASIONAL WEAK SHORTWAVE
TROUGHS DROPPING DOWN FROM THE NORTH. THE CURRENT MOST LIKELY
OUTCOME IS FOR CONTINUED MILD TEMPERATURES ON MONDAY AND TUESDAY
WITH DAILY CHANCES FOR PM SHOWERS AND THUNDERSTORMS. BY THE
VERY END OF THE FORECAST PERIOD TOWARDS NEXT WEDNESDAY, THE
PRIMARY CLOSED LOW MAY BE ARRIVING NEAR OUR AREA, WHICH WILL
INCREASE THE CHANCES FOR A COOL DOWN AND WIDESPREAD STRATIFORM
PRECIPITATION. CONFIDENCE REMAINS VERY LOW IN ANY DETAILS
CONCERNING PRECIPITATION AMOUNTS OR TIMING.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1145 PM MDT TUE APR 28 2026
THE MAIN CONCERN TONIGHT WILL BE FOG AT KSNY AND KAIA WHICH CAN BE
SEEN ON GOES NIGHTTIME MICROPHYSICS IMAGERY AS CLEAR SKIES COMBINED
WITH WEAK UPSLOPE FLOW IS IN PLACE. OGALLALA IS CURRENTLY REPORTING
FOG AS WELL, SO DECIDED TO ADD THESE INTO THE TAFS UNTIL 12Z BEFORE
THE LOW-LEVEL MOISTURE BEGINS TO MIX OUT AND WINDS TURN MORE
WESTERLY. CAN EXPECT LIFR CONDITIONS IN THESE CONDITIONS, ALTHOUGH
CONFIDENCE REGARDING EXACT TIMING AND LONGEVITY IS MODERATE (40-50%
CHANCE).
FOR THE REMAINING TERMINALS, A COMBINATION OF VFR AND MVFR
CONDITIONS WILL PREVAIL AS CIGS LOWER BELOW 3 KFT IN THE VICINITY OF
ANY SHOWERS TOMORROW AFTERNOON. SHOWER COVERAGE IS EXPECTED TO
INCREASE AFTER 18Z BEFORE WINDING DOWN SHORTLY AFTER SUNSET. EXPECT
5-10 KNOT SW FLOW TO VEER TO MORE WESTERLY DURING THE DAY, BEFORE
TURNING TO NORTHERLY THROUGH THE REMAINDER OF THE TAF PERIOD.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...MN
LONG TERM...MN
AVIATION...NB
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