144
FXUS65 KCYS 261122
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
522 AM MDT SUN APR 26 2026
KEY MESSAGES
- A MESSY PATTERN IS ANTICIPATED TODAY THROUGH MUCH OF THE
UPCOMING WEEK, ALLOWING FOR ONGOING PRECIPITATION CHANCES
ACROSS THE ENTIRE CWA. THE BEST CHANCE FOR PRECIPITATION WILL
BE SUNDAY, WITH WIDESPREAD SHOWERS AND THUNDER.
- A WINTER WEATHER ADVISORY HAS BEEN ISSUED FOR THE SIERRA MADRE
AND SNOWY RANGES FROM 6PM SATURDAY THROUGH 6AM MONDAY.
SHORT TERM /THROUGH MONDAY/
ISSUED AT 310 AM MDT SUN APR 26 2026
DENSE FOG IS BEING OBSERVED ALONG THE I-80 LARAMIE FOOTHILLS TO
CHEYENNE, VISIBILITIES ARE DOWN TO A QUARTER MILE. ANOTHER AREA OF
PATCHY FOG IS BEING OBSERVED ALONG I-20 NEAR SIDNEY. THIS ADVECTION
FOG IS LIKELY TO PERSIST INTO THE MORNING HOURS PER THE LATEST HRRR
GUIDANCE AND USING OBSERVATION PERSISTENCE FROM THE LAST TWO DAYS.
RADAR IS PICKING UP SCATTERED RAIN AND SNOW SHOWERS ALONG THE
RAWLINS, PINE RIDGE, AND CHADRON CORRIDOR. TEMPERATURES WILL TOP OUT
TODAY IN THE 50S FOR MOST PLACES, THE INTERIOR MOUNTAINS AND NORTH
OF THE NORTH PLATTE RIVER VALLEY WILL BE IN THE 40S. INSTABILITY IS
LACKING TO FORM THUNDERSTORMS THIS MORNING, HOWEVER AS THE UPPER
LEVEL DISTURBANCE PASSES OVER THIS AFTERNOON, THE CHANCES FOR STORMS
INCREASES. HI-RES MODELS ARE HIGHLIGHTING AN AREA OF 400-700 J/KG OF
SBCAPE FOR PORTIONS OF THE INTERMOUNTAIN RANGES. LIGHTNING DENSITY
PRODUCTS FROM THESE MODELS ARE LOW WHICH MAKES SENSE GIVEN THE
THERMODYNAMICS. ALSO, GIVEN THE LOW FREEZING LEVELS PAIRED WITH 40
KTS OF STORM EFFECTIVE WIND SHEAR, IT IS NOT OUT OF THE QUESTION
THAT SMALL HAIL OCCURS IN THE MOST VIGOROUS UPDRAFTS. OUTSIDE THE
STORM POTENTIAL WE ALSO HAVE A WINTER WEATHER ADVISORY OUT FOR THE
SIERRA MADRE AND SNOWY RANGES THROUGH SUNRISE MONDAY. THIS IS
PRIMARILY FOR THE PEAKS, BUT OUR OUTLOOK IS FOR 6-12 INCHES OF
SNOWFALL. THIS WILL MOST LIKELY BE SPREAD OUT OVER TWO BURST IN
SNOWFALL, ONE THROUGH TODAY AND AGAIN OVERNIGHT MONDAY. ALTHOUGH
SHOWER AND STORM ACTIVITY IS EXPECTED TO BE SCATTERED IN NATURE,
MOST LOCATIONS WILL LIKELY RECEIVE SOME FORM OF PRECIPITATION. QPF
RANGES BETWEEN 0.15" TO 0.5" OVER MUCH OF THE AREA. AS THE INITIAL
SHORTWAVE DEPARTS THE PRECIPITATION CHANCES FALL, BUT WITH NEAR OR
BELOW FREEZING TEMPERATURES, SHOWER ACTIVITY MAY CONVERT TO SNOW OR
MIX BY DAYBREAK. OUTSIDE THE MOUNTAINS MOST AREAS MAY ONLY RECEIVE A
TRACE TO A FEW HUNDREDTHS OF AN INCH. SOME PARTS OF NORTHERN
CONVERSE COUNTY MAY SEE AN INCH TO TWO INCHES OF SNOW. WINDS SHIFT
TO OUT OF THE NORTHWEST AND INCREASE MONDAY MORNING AS A SURFACE LOW
DEVELOPS AND MOVES EAST OF OUR LOCATION.
LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
ISSUED AT 310 AM MDT SUN APR 26 2026
THE UPPER-LEVEL TROUGH WILL SLOWLY DEEPEN AND CONTINUE ITS SLOW
EASTWARD PROGRESSION THROUGHOUT THE DAY MONDAY. A SUBTLE POSITIVE
TILT TO THE APPROACHING TROUGH WILL DEVELOP MONDAY EVENING, THOUGH
UPPER-LEVEL FLOW REMAINS LARGELY WEAK. A WEAK 500MB RIDGE WILL
UNDERCUT THE UPPER-LEVEL TROUGH, CONTINUING THE MESSY PATTERN THAT
HAS BEEN IN PLACE OVER THE PAST SEVERAL DAYS. 500MB VORTICITY
ADVECTION WILL PUSH INTO THE REGION BEHIND THE WEAK SHORTWAVE RIDGE
AND JUST AHEAD OF THE INCOMING UPPER-LEVEL TROUGH. THIS CYCLONIC
VORTICITY ADVECTION (CVA) WILL HELP THE TROUGH MOVE EASTWARD A TOUCH
QUICKLY, WHILE ALSO PROVIDING SYNOPTIC ASCENT ACROSS THE REGION. THE
MESSY 700MB FLOW WILL CONTINUE MONDAY WITH A BRIEF RIDGING
DEVELOPING BEFORE ADVECTING OFF TO THE EAST AND BEING ABSORBED INTO
THE LOWER-LEVEL FLOW BY MONDAY NIGHT. WARM AIR ADVECTION (WAA) IS
EXPECTED TO BE FAIRLY STRONG ACROSS THE COUNTY WARNING AREA (CWA) IN
THE AFTERNOON, FURTHER SUPPORTING SYNOPTIC ASCENT ACROSS THE REGION.
LOOKING AT THE SURFACE, NORTHERLY FLOW BEHIND A COLD FRONT ON SUNDAY
WILL KEEP THE REGION COOLER, IN THE 40S AND 50S EVERYWHERE, WITH
INCREASING CLOUDS THROUGHOUT THE DAY. BY MONDAY AFTERNOON, ANOTHER
SURFACE HIGH IS PROGGED TO DEVELOP OFF THE BLACK HILLS OF SOUTH
DAKOTA, LEADING TO SURFACE FLOWING TURNING FROM THE NORTH TO A MORE
EASTERLY TO SOUTHEASTERLY DIRECTION. PRECIPITABLE WATER VALUES (PWS)
WILL BE AVERAGE FOR THIS TIME OF YEAR PER THE NAEFS MEAN AND
CLIMATOLOGICAL PERCENTILE, SO SIGNIFICANT PRECIPITATION IS NOT
ANTICIPATED. HOWEVER, THE MOIST, EASTERLY UPSLOPE FLOW WILL ENABLE
CONTINUED SHOWER DEVELOPMENT ACROSS THE REGION EAST OF THE LARAMIE
RANGE. AS A RESULT, ANOTHER CLOUDY, COOL, AND WET DAY IS IN STORE
FOR MONDAY. TEMPERATURES ARE EXPECTED TO REMAIN WARM ENOUGH TO
PRIMARILY GET RAIN EAST OF THE LARAMIE RANGE, BUT A TRANSITION TO
SNOW IS POSSIBLE INTO THE OVERNIGHT HOURS AFTER THE SUN SETS.
ON TUESDAY, THE UPPER-LEVEL TROUGH THAT HAS BEEN PARKED ACROSS THE
INTERMOUNTAIN WEST WILL START TO LIFT NORTHEASTWARD INTO EASTERN
CANADA, WITH LARGELY ZONAL FLOW DEVELOPING IN ITS WAKE. A STRONG,
SUBTROPICAL UPPER-LEVE JET WILL PUSH NORTHWARD AND REMAIN JUST SOUTH
OF THE CWA, LEADING TO LARGELY BENIGN WEATHER FOR TUESDAY. BROAD,
NORTHWESTERLY FLOW IS ANTICIPATED AT 700MB, WITH WEAK WAA EXPECTED
THROUGHOUT THE MORNING AND AFTERNOON HOURS. WITH ADDED ASCENT TO THE
REGION FROM 700MB WAA, THE SKY WILL REMAIN MOSTLY CLOUDY,
PROHIBITING SURFACE TEMPERATURES FROM INCREASING TOO MUCH DURING THE
DAY. LARGELY NORTHWESTERLY FLOW IS EXPECTED AT THE SURFACE, WITH
ISOLATED TO SCATTERED SHOWERS EAST OF THE LARAMIE RANGE AND ISOLATED
TO SCATTERED SNOW SHOWERS WEST. TEMPERATURES WILL RISE INTO THE 50S
AND 60S EVERYWHERE. ACCUMULATION IS NOT ANTICIPATED TO BE
SIGNIFICANT, BUT ANOTHER DAY OF RAIN/SNOW WILL BE APPRECIATED ACROSS
THE REGION.
WEDNESDAY THROUGH THE END OF THE LONG TERM PERIOD WILL BE LARGELY
DOMINATED BY A DEVELOP UPPER-LEVEL TROUGH THAT WILL BE SLOW TO
INITIATE AND BECOME MESSY FAIRLY QUICKLY. AN UPPER-LEVEL RIDGE JUST
OFF THE WESTERN COAST OF THE CONUS WILL SLOWLY MOVE ON SHORE AND
AMPLIFY WEDNESDAY AND THURSDAY, BUT POOR 500MB VORTICITY ADVECTION
WILL CAUSE THIS RIDGE TO ESSENTIALLY COLLAPSE AND LEAD TO A CUT OFF
LOW DEVELOPING BY FRIDAY MORNING BEFORE BEING ABSORBED INTO A
LARGER SCALE TROUGH BY FRIDAY AFTERNOON. BY SATURDAY AFTERNOON, THIS
LOW WILL HAVE BEEN ABSORBED INTO THE FLOW AS WEAKER RIDGE DEVELOPS
OVER THE INTERMOUNTAIN WEST. 700MB FLOW REMAINS WEAK WITH LIMITED
FEATURE OF NOTE THROUGH THE WEEKEND. WITH THE MESSY UPPER-LEVEL
PATTER WITH MINIMAL SUPPORT FOR SYNOPTIC ASCENT, CONDITIONS ARE
ANTICIPATED TO START DRYING OUT WEDNESDAY THROUGH THE END OF THE
WEEK WITH FIRE WEATHER CONCERNS STARTING TO SNEAK BACK INTO THE
REGION BY THE WEEKEND. AFTER A COOL DAY ON THURSDAY AS THE CUTOFF
LOW TURNING INTO AN UPPER-LEVEL SHORTWAVE IMPACTS THE REGION AND
DECREASES TEMPERATURES, A STRONG WARMING TREND WILL RETURN WITH
HIGHS BACK INTO THE 60S AND 70S FOR THE WEEKEND.
AVIATION /12Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 518 AM MDT SUN APR 26 2026
A CHALLENGING FORECAST THIS MORNING ACROSS MUCH OF THE REGION.
CLOUD DECKS HAVE DROPPED WELL BELOW LIFR AND INTO THE VLIFR
CONDITIONS AT KCYS, KLAR, AND KSNY. FOG HAS BEEN ROLLING ACROSS
MANY TERMINALS, OSCILLATING THE VISIBILITY FROM AROUND 1/2 MILE
TO 3 MILES ACROSS MANY TERMINALS. THIS OSCILLATION WILL CONTINUE
THROUGH THE MORNING HOURS, WITH BRIEF PERIODS OF IMPROVED
VISIBILITY, BUT VERY LOW CEILINGS WILL REMAIN. CEILINGS WILL
START TO LIFT IN THE AFTERNOON HOURS BEFORE ISOLATED TO
SCATTERED SHOWERS AND STORMS DEVELOP FROM SOUTHWEST TO
NORTHEAST. ANY SHOWER OR STORM THAT DEVELOPS WILL BE CAPABLE OF
PRODUCING GUSTY AND ERRATIC WINDS. BEST CHANCE OF STORMS WILL BE
AT THE KCYS, KLAR, AND KSNY WHERE PROB30 GROUPS HAVE BEEN ADDED
TO THE TAFS. CEILINGS BEGIN TO DROP ONCE MORE THIS EVENING INTO
THE OVERNIGHT HOURS WITH VISIBILITIES FOLLOWING SOON AFTER.
CYS WATCHES/WARNINGS/ADVISORIES
WY...WINTER WEATHER ADVISORY UNTIL NOON MDT TODAY FOR WYZ112-114.
DENSE FOG ADVISORY UNTIL NOON MDT TODAY FOR WYZ116-117.
NE...NONE.
SHORT TERM...RV
LONG TERM...AM
AVIATION...AM
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