785
FXUS65 KCYS 221100
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
500 AM MDT THU MAY 22 2025
KEY MESSAGES
- WARMING TREND STARTS ON THURSDAY WITH WIDELY SCATTERED LATE
EVENING AND OVERNIGHT THUNDERSTORMS POSSIBLE ACROSS THE EASTERN
PLAINS.
- ACTIVE PATTERN CONTINUES THROUGH THE END OF THE WEEK, WITH
ANOTHER SEVERE WEATHER EVENT POSSIBLE FRIDAY AND AGAIN THIS
WEEKEND.
- RAIN AND STORM CHANCES CONTINUE THROUGH NEXT WEEK.
SHORT TERM /THROUGH FRIDAY NIGHT/
ISSUED AT 204 PM MDT WED MAY 21 2025
GUSTY NORTHWESTERLY WINDS CONTINUE ACROSS MUCH OF SOUTHEAST WYOMING
AND WESTERN NEBRASKA WITH SCATTERED CLOUDS MOVING OVERHEAD. SOME
AGITATED CUMULUS HAVE DEVELOPED ACROSS NORTHERN PORTIONS OF THE CWA
THIS AFTERNOON AND ARE SLOWLY MOVING OFF TO THE SOUTHEAST TOWARDS
THE NEBRASKA PANHANDLE. A FEW LIGHTNING STRIKES HAVE OCCURRED WITH
THESE STORMS ACROSS CONVERSE AND NIOBRARA COUNTIES, THOUGH NOT
STORMS ARE SEVERE AT THIS TIME. TEMPERATURES HAVE WARMED NICELY INTO
THE MID-60S ACROSS THE PANHANDLE AND MID-50S TO LOW-60S ACROSS
SOUTHEAST WYOMING. TEMPERATURES SHOULD CONTINUE TO INCREASE OVER THE
NEXT HOUR OR TWO BEFORE CLOUD COVER OVERTAKES THE REGION AND
TEMPERATURES BEGIN TO COOL. ANY LOCATIONS THAT EXPERIENCES A SHOWER
OR THUNDERSTORM WILL BEGIN TO COOL MUCH SOONER THAN LOCATIONS THAT
REMAIN DRY THIS AFTERNOON.
NORTHWESTERLY FLOW ALOFT IS ONGOING THIS AFTERNOON ACROSS MUCH OF
THE WESTERN CONUS AS A RIDGE ATTEMPTS TO AMPLIFY ALONG THE WEST
COAST THIS AFTERNOON INTO THE OVERNIGHT HOURS. THE NORTHWESTERLY
FLOW ALOFT COMBINED WITH THE FAIRLY MESSY RIDGE IN THE UPPER-LEVEL
WILL ENABLE MULTIPLE DISTURBANCES AND ASSOCIATED VORTICITY MAXIMA TO
PUSH THROUGH OVERHEAD PROVIDING SYNOPTIC LIFT TO MUCH OF THE CWA.
ADDITIONALLY, THE UPPER-LEVEL JET WILL MOVE OVERHEAD IN A LOCATION
CONDUCIVE FOR INCREASE SYNOPTIC LIFT WITH PORTIONS OF THE PANHANDLE
BEING UNDER THE LEFT EXIT REGION AND FAVORABLE DYNAMICS IN THAT
LOCATIONS. HOWEVER, GIVEN THE PROGRESSIVE NATURE OF THE DEVELOPING
RIDGE OUT WEST, THE LEFT EXIT REGION WILL ONLY REMAIN OVER WESTERN
NEBRASKA FOR A SMALL AMOUNT OF TIME THIS AFTERNOON, APPROXIMATELY
NOW THROUGH ABOUT 03Z THIS EVENING. ANTICYCLONIC VORTICITY ADVECTION
AT 500MB WILL MOVE IN AS THE JET PUSHES OFF TO THE NORTH AND EAST,
LEADING TO SUBSIDENCE RETURNING, EFFECTIVELY DIMINISHING SHOWER AND
STORMS CHANCES THIS EVENING. BROAD RIDGING WILL BE PRESENT AT 700MB
WITH CONTINUATION OF THE NORTHWESTERLY FLOW AT THIS LEVEL. AS THIS
RIDGE BUILDS AT 700MB, WARM AIR ADVECTION WILL BE PRESENT ACROSS
SOUTHEAST WYOMING AND WESTERN NEBRASKA UNTIL AROUND 03Z. THIS WILL
FURTHER FUEL SHOWER AND THUNDERSTORM CHANCES THIS AFTERNOON AS
SYNOPTIC LIFT CONTINUES TO BE FAVORED IN THE LOW-LEVELS OF THE
ATMOSPHERE. ADDITIONALLY, 700MB HEIGHT GRADIENTS ARE SLIGHTLY
ELEVATED THIS AFTERNOON, LEADING TO AROUND A 40KT 700MB JET ACROSS
THE SOUTHERN LARAMIE RANGE. HEIGHT GRADIENTS ARE EXPECTED TO RELAX
BETWEEN 00 AND 03Z, LEADING TO DECREASING SURFACE WINDS LATER THIS
EVENING INTO THE OVERNIGHT HOURS. A 700MB SHORTWAVE COMBINED WITH
OVERALL SYNOPTIC LIFT WILL ENABLE STORMS TO CONTINUE TO DEVELOP
ACROSS NORTHERN PORTIONS OF THE REGION, INCLUDING CONVERSE,
NIOBRARA, SIOUX, AND DAWES COUNTY. WITH THE SOUTHEASTERLY STORM
MOTION, THESE STORMS WILL EVENTUALLY MOVE INTO THE NEBRASKA
PANHANDLE THROUGHOUT THE AFTERNOON AND EVENING.
WITH AMPLE SYNOPTIC LIFT PRESENT ACROSS THE REGION AND THE
ADDITIONAL FORCING FOR ASCENT WITH THE 700MB SHORTWAVE, SHOWERS AND
STORMS ARE ALREADY FORMING ACROSS NORTHERN LOCATIONS. TAKING A LOOK
AT RAP FORECAST SOUNDING, STRONG LOW-LEVEL LAPSE RATES WILL BE
PRESENT ACROSS MUCH OF THE PANHANDLE, WITH SBCAPE VALUES INCREASING
AROUND THE 500 J MARK NOW THROUGH THIS EVENING. RAP SOUNDINGS SHOW
THE CLASSIC INVERTED-V SOUNDING SHAPE, INDICATING AN INCREASING
RISK FOR STRONG, DAMAGING WINDS GUSTS ACROSS THE PANHANDLE WITH AND
SHOWER AND STORM THAT MOVES ACROSS THIS REGION. CURRENT SPC
MESOANALYSIS DATA SUGGESTS THAT THE MAXIMUM SBCAPE VALUES ARE
ONGOING NOW AND EXPECTED TO CONTINUE FOR THE NEVER SEVERAL HOURS
BEFORE THE SBCAPE BOUNDARY SLOWLY MOVES OFF TO THE NORTHEAST INTO
SOUTH DAKOTA. DCAPE VALUES HAVE RISEN TO AROUND 600 TO 700 J, AND
ARE EXPECTED TO CONTINUE RISING OVER THE NEXT FEW HOURS. SHEAR IS
FAIRLY WEAK, ONLY AROUND 35 KTS, SO THE HAIL THREAT IS FAIRLY LOW AT
THIS TIME, HOWEVER DRY MID- AND LOW-LEVELS MAY FAVOR THE DEVELOPMENT
OF SOME SMALL HAIL WITH ANY OF THE THUNDERSTORMS THIS AFTERNOON. SPC
HAS PLACED PORTIONS OF THE NEBRASKA PANHANDLE UNDER A MARGINAL RISK
(LEVEL 1 OF 5) FOR DAMAGING WINDS, AS EXPECTED WITH INVERTED-V
SOUNDINGS AND STEEP LOW-LEVEL LAPSE RATES. HOWEVER, SOME SMALL HAIL
CANNOT BE COMPLETELY RULED OUT, AS WELL AS THE POTENTIAL FOR SOME
DRY THUNDERSTORMS, OR STORMS WITH RAIN THAT IS NOT REACHING THE
GROUND, BUT STILL HAVE LIGHTNING ASSOCIATED WITH THEM, DUE TO THE
DRY LOW-LEVELS. THE MAIN RISK SHOULD COME TO AN END BETWEEN 00 AND
03Z AT THE UPPER-LEVEL SUPPORT WEAKENS AND THE ATMOSPHERE BECOMES
MORE STABLE INTO THE LATE AFTERNOON AND EVENING HOURS.
BROAD UPPER-LEVEL RIDING IS EXPECTED TO CONTINUE THURSDAY ONWARDS AS
THE WEST COAST RIDGE SLOWLY MOVES INTO THE INTERMOUNTAIN WEST. WITH
THE BROAD RIDING IN PLACE, THE OVERALL SUBSIDENCE ASSOCIATED WITH
RIDGES WILL BE A BIT WEAKER AS THE RIDGE ITSELF IS BROAD AND FAIRLY
WEEK. AS A RESULT, 500MB VORTICITY MAXIMA WILL CONTINUE TO EJECT OUT
ACROSS SOUTHEAST WYOMING AND WESTERN NEBRASKA LEADING TO CONTINUED
PRECIPITATION CHANCES ACROSS THE REGION AS SYNOPTIC LIFT FROM THE
VORTICITY LOBES IS STRONGER THAN THE WEAK SUBSIDENCE FROM THE MESSY
RIDGE ALOFT. ADDITIONALLY, A 700MB LOW WILL ATTEMPT TO DEVELOP
ACROSS MONTANA, LEADING TO ADDITIONAL LIFT ACROSS THE REGION AND A
STRENGTHENING 700MB HEIGHT GRADIENT ONCE AGAIN. AS A RESULT, GUSTY
WINDS ARE EXPECTED AT THE SURFACE ONCE AGAIN THURSDAY. CAPE VALUES
LOOK TO LOW TO NON-EXISTENT ACROSS MUCH OF THE CWA, EXCEPT FOR A
SMALL SWATCH ACROSS THE SOUTHERN LARAMIE RANGE. THEREFORE, ANY
SHOWERS AND STORMS THAT DEVELOP ON THURSDAY WILL LIKELY FORM OVER
THE LARAMIE RANGE DUE TO OROGRAPHIC LIFT IN THIS REGION AND
PROPAGATE OFF THE MOUNTAINS. THESE STORMS SHOULD BE ABLE TO SUSTAIN
THEMSELVES A BIT INTO THE LOW-ELEVATIONS WITH THE ADDITIONAL FORCING
FROM THE DEVELOPING 700MB LOW AND WARM AIR ADVECTION AT 700MB AS
WARMER AIR GETS DRAWN INTO THE 700MB LOW. FORECAST SOUNDINGS FROM
THE RAP ONCE AGAIN SUGGEST AN INVERTED-V PROFILE ACROSS THE SOUTHERN
LARAMIE RANGE, WITH INVERTED-V SOUNDINGS DOWNWIND OF THE MOUNTAINS
INTO THE LOWER-ELEVATIONS. ADDITIONALLY, RAP SOUNDINGS SUGGEST AROUND
40KTS OF SHEAR, LEADING TO A LOW-CAPE HIGH-SHEAR ENVIRONMENT SETTING
UP FOR THURSDAY. STORMS THAT COME OFF THE LARAMIE RANGE MAY STRUGGLE
TO SUSTAIN THEMSELVES AND MAY COLLAPSE SHORTLY AFTER MOVING OFF THE
RANGE. THEREFORE, GUSTY SHOWERS AND STORMS ARE POSSIBLE ONCE AGAIN
TOMORROW ALONG AND JUST EAST OF THE SOUTH LARAMIE RANGE.
BROAD, UPPER-LEVEL RIDGING CONTINUES INTO THE DAY FRIDAY, LEADING TO
WEAK SUBSIDENCE ACROSS THE REGION AND WARMING TEMPERATURES. AN
INCOMING TROUGH OFF THE WEST COAST WILL BE THE NEXT BIG WEATHER
MAKER FOR THE REGION (SEE LONG TERM DISCUSSION). WITH THE BROAD
RIDGE ONCE AGAIN FRIDAY, MULTIPLE 500MB VORTICITY LOBES WILL LIKELY
MOVE OVERHEAD, LEADING TO THE POTENTIAL FOR SHOWERS AND STORMS IN
THE AFTERNOON HOURS. FORECAST SOUNDING FROM THE NAM SUGGEST A
SIMILAR SET UP, WITH INVERTED-V SOUNDING PRESENT ONCE MORE,
ESPECIALLY ACROSS THE NEBRASKA PANHANDLE. NAM SBCAPE VALUES ARE
QUITE HIGH AROUND 1000 J, BUT THIS IS STILL A FEW DAYS OUT AND THE
NAM TENDS TO HAVE A MOISTURE BIAS THAT COULD ARTIFICIALLY INCREASE
SBCAPE VALUES. FRIDAY IS ALSO STILL A FEW DAYS AWAY AND WITH THE
POTENTIAL SEVERE EVENT TODAY, MORE ATTENTION WILL BE GIVEN TO THE
FRIDAY FORECAST ONCE TODAY'S THREAT IS OVER WITH, LIKELY WITH
TONIGHT'S FORECAST UPDATE.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
ISSUED AT 204 PM MDT WED MAY 21 2025
A SLOW MOVING TROUGH WILL PUSH THROUGH THE
INTERMOUNTAIN WEST THIS WEEKEND CREATING SOME PRECIPITATION CHANCES
ACROSS THE FORECAST AREA. SATURDAY, A 700MB LOW WILL PUSH INTO THE
INTERMOUNTAIN WEST FROM THE MORNING AND THROUGH THE AFTERNOON. THIS
LOW WILL PROVIDE ENOUGH SYNOPTIC SUPPORT FOR WIDESPREAD RAINFALL AND
HAVE A FEW VORTICITY MAXIMA'S DEVELOP TO CREATE POCKETS OF ENHANCED
RAINFALL IN A FEW AREAS. FOR THE MESOSCALE FORCING, A COLD FRONT
DEVELOPS AND MOVES ACROSS THE AREA IN THE AFTERNOON AND EVENING
CREATING A LINE OF HEAVY RAIN AS IT MOVES THROUGH. HOWEVER, THE
CONVECTIVE THUNDERSTORM ACTIVITY LOOKS TO BE LIMITED DUE TO THE
OVERCAST CLOUDY CONDITIONS LIMITING THE CAPE POTENTIAL FOR SATURDAY.
THE GLOBAL MODELS STILL WANT TO THROW A BLANKET OF 1200 CAPE FOR THE
AFTERNOON BUT THAT MAY BE A LITTLE OVERDONE GIVEN THE CLOUDY
CONDITIONS. SUNDAY, THE MID LEVEL LOW WILL SLOWLY START TO PUSH OUT
OF OUR FORECAST AREA CONTINUING THE PRECIPITATION CHANCES THROUGH
SUNDAY EVENING WITH SOME RESIDUAL SYNOPTIC SUPPORT FROM THE
DEPARTING LOW.
NEXT WEEK, MODELS ARE STILL A LITTLE DIVERGENT ON HOW AMPLIFIED THIS
TRANSIENT RIDGE THAT SETS UP IS. BUT THE AREA LOOKS TO START TO DRY
OUT MONDAY INTO TUESDAY TO GIVE US A BRIEF BREAK OF PRECIPITATION
BEFORE ANOTHER SYSTEM MOVES THROUGH THE AREA MID TO LATE NEXT WEEK.
AVIATION /12Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 500 AM MDT THU MAY 22 2025
WEAKENING STORM SYSTEM ACROSS THE NORTHERN PLAINS WILL ACCELERATE
EASTWARD TONIGHT. UPPER LEVEL RIDGING WILL BUILD OVER WYOMING FOR
THURSDAY WITH ANOTHER ROUND OF THUNDERSTORMS POSSIBLE LATE THURSDAY
EVENING AND OVERNIGHT AS A POTENT UPPER LEVEL DISTURBANCE MOVES
NORTHEAST OVER THE AREA.
HAZARDS/WEATHER TRENDS: VFR CONDITIONS EXPECTED OVER THE NEXT 18
HOURS WITH CLEAR SKIES AND LIGHT/VARIABLE WINDS EXPECTED THROUGH 15Z
THURSDAY. WINDS ARE FORECAST TO SHIFT INTO THE SOUTH OR SOUTHEAST
FOR MOST TERMINALS BY 18Z THURSDAY. ANOTHER ROUND OF THUNDERSTORMS
ARE POSSIBLE FOR KLAR, KBFF, KAIA, KCDR, AND KCYS AFTER 00Z FRIDAY.
THESE THUNDERSTORMS MAY LINGER PAST 06Z FRIDAY FOR KCDR AND KAIA AND
MAY CONTAIN HAIL AND LOCALLY GUSTY WINDS. THIS IS A CONDITIONAL RISK
WITH PROBABILITIES BETWEEN 20% TO 40%. THESE THUNDERSTORMS SHOULD
MOVE EAST OF KCDR AND KAIA BY 08Z FRIDAY.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...AM
LONG TERM...MM
AVIATION...TJT
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