787
FXUS65 KCYS 081159
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
559 AM MDT THU MAY 8 2025
KEY MESSAGES
- A WARMING TREND WILL BEGIN TODAY AND LAST THROUGH EARLY NEXT
WEEK WITH ISOLATED SHOWERS AND STORMS POSSIBLE MOST AFTERNOONS
- THE NEXT POTENTIAL STORM SYSTEM AROUND THE MIDDLE OF NEXT WEEK
WITH BRING COOLER TEMPERATURES, STRONGER WINDS, AND ANOTHER
CHANCE FOR SOME RAINFALL AND MOUNTAIN SNOW.
SHORT TERM /THROUGH FRIDAY NIGHT/
ISSUED AT 300 AM MDT THU MAY 8 2025
THE INFLUENCE OF THE SPRAWLING UPPER LEVEL LOW IS WANING TODAY AS
THE LOW CENTER SHIFTS EASTWARD ACROSS MISSOURI. DEEP EASTERLY FLOW
IS LINGERING WELL TO THE WEST OF THIS FEATURE THANKS TO A SECONDARY
UPPER LEVEL LOW STILL OVER CENTRAL COLORADO, BUT THIS IS EXPECTED
SHIFT EAST TODAY. RIDGING BUILDING IN JUST TO OUR WEST WILL LEAD TO
NORTHERLY FLOW ALOFT AND SOUTHERLY FLOW AT THE SURFACE BY MID
AFTERNOON. VERY DRY AIR WILL WORK IN TO THE MIDDLE ATMOSPHERE AROUND
500-MB AS THE DAY PROGRESSES, BUT LOW-LEVEL MOISTURE REMAINS FAIRLY
DECENT LINGERING BEHIND THE STORM SYSTEM FROM THE LAST FEW DAYS.
WHILE THERE IS NOT MUCH SYNOPTIC FORCING TODAY, CONVECTIVE
INSTABILITY AND MODEST CONVERGENCE RIGHT ALONG THE LARAMIE RANGE
SHOULD LEAD TO A FEW ISOLATED PM SHOWERS AND THUNDERSTORMS. THESE
ARE NOT EXPECTED TO BECOME PARTICULARLY STRONG WITH MARGINAL SURFACE
BASED CAPE AND VERY DRY AIR ALOFT, BUT SOME AREAS MAINLY BETWEEN
LARAMIE, CHEYENNE, AND WHEATLAND COULD SEE A BRIEF DOWNPOUR, SMALL
HAIL, AND/OR GUST WINDS. THIS ACTIVITY SHOULD WANE QUICKLY DURING
THE EARLY EVENING HOURS.
HEADING INTO FRIDAY, LOWER ATMOSPHERIC TEMPERATURES ARE EXPECTED TO
WARM A TOUGH ABOVE THURSDAY'S VALUES WHILE BOUNDARY LAYER MOISTURE
AND TEMPERATURES ALOFT REMAIN FAIRLY STEADY. THIS WILL RESULT IN
STEEPER LAPSE RATES AND INCREASED/MORE WIDESPREAD INSTABILITY FRIDAY
AFTERNOON. SYNOPTIC FORCING REMAINS WEAK THOUGH, AND CONVERGENCE
ALONG THE TERRAIN WILL BE LESS PREVALENT. AS A RESULT, PM SHOWERS
AND STORMS WILL BE POSSIBLE ACROSS A LARGER PORTION OF THE FORECAST
AREA (MOST OF SE WYOMING), BUT STILL SHOULD BE QUITE ISOLATED.
WARMER TEMPERATURES WILL MEAN DEEPER MIXED BOUNDARY LAYERS, SO
FRIDAY'S ACTIVITY MAY PRODUCE SOME GUSTIER WINDS.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
ISSUED AT 300 AM MDT THU MAY 8 2025
STRONG RIDGING ALOFT WILL DOMINATE THE FORECAST THROUGH EARLY NEXT
WEEK. THE RIDGE AXIS WILL MOVE OVERHEAD ON SATURDAY, PUSHING 500-MB
HEIGHTS TO NEAR THE CLIMATOLOGICAL 99TH PERCENTILE. VERY WARM AND
DRY AIR ALOFT WILL LEAD TO FEW, IF ANY, PM SHOWERS AND THUNDERSTORMS
ON SATURDAY. WHAT DOES FORM WILL PROBABLY BE MOSTLY VIRGA AND
CONFINED TO THE HIGHER TERRAIN. BY SUNDAY, THE RIDGE AXIS WILL SHIFT
TO OUR EAST AS A BROAD TROUGH BEGINS TO DIG INTO THE PACIFIC
NORTHWEST. WHILE 500-MB HEIGHTS WILL BEGIN TO DROP, SOUTHWEST FLOW
WILL KEEP LOW LEVEL WARM AIR ADVECTION GOING. THUS, EXPECT SUNDAY
AND MONDAY TO BE THE WARMEST DAYS OF THIS WARM SPELL. EXPECT
WIDESPREAD 80S EAST OF THE LARAMIE RANGE, WITH EVEN A SHOT AT 90F IN
THE TYPICAL WARM SPOTS SUCH AS TORRINGTON, SCOTTSBLUFF, AND CHADRON.
FOR SUNDAY, A WEAK SHORTWAVE EJECTING OUT OF THE WEST COAST TROUGH
MAY LEAD TO SLIGHTLY MORE WIDESPREAD SHOWERS AND THUNDERSTORMS, BUT
THIS WILL PROBABLY BE MAINLY VIRGA WITH DEWPOINT DEPRESSIONS PUSHING
50F AND LIMITED MOISTURE ALOFT. LOW LEVEL WINDS ARE ALSO EXPECTED TO
CREEP UP AGAIN. SUNDAY AND MONDAY COULD BE QUITE WINDY IN CARBON
COUNTY WITH STRONG SOUTHWEST FLOW, WHILE BREEZY SOUTHERLIES DOMINATE
THE HIGH PLAINS.
THE POWERFUL RIDGE IS EXPECTED TO BREAK DOWN AROUND THE MIDDLE OF
NEXT WEEK AS THE BROAD TROUGH BEGINS TO MIGRATE INLAND. THE FIRST
SHORTWAVE EJECTING OUT WILL BE AROUND LATE TUESDAY INTO WEDNESDAY,
BUT MODEL CONSENSUS CURRENTLY HAS THE UPPER LEVEL LOW CENTER
TRAVERSING ACROSS WYOMING. THIS IS GENERALLY TOO FAR NORTH FOR
WIDESPREAD PRECIPITATION IN OUR AREA. ENSEMBLE MEANS LOOK FAIRLY
DECENT FOR WIDESPREAD RAINFALL, BUT A CLOSER LOOK REVEALS THAT THIS
IS DUE TO A SMALL MINORITY (ABOUT 10% OF MEMBERS) TRACKING THE UPPER
LEVEL LOW JUST SOUTH OF THE AREA AND THUS DELIVERING IMPRESSIVE
RAINFALL TOTALS. IN THIS CASE, THE MEDIAN IS A MUCH BETTER
APPROXIMATION OF THE MOST LIKELY SCENARIO, WHICH CURRENTLY SHOWS
FAIRLY LITTLE PRECIPITATION OUTSIDE OF THE MOUNTAINS AND US-20
CORRIDOR. A TRACK JUST NORTH OF THE AREA WILL ALSO LEAD TO STRONGER
WINDS ALONG THE I-80 CORRIDOR, AND THUS THERE IS THE POTENTIAL TO
FOR ANOTHER LATE SEASON HIGH WIND WARNING IN THIS AREA. ABOUT 25% OF
ENSEMBLE MEMBERS SHOW 700-MB WIND SPEEDS HIGH ENOUGH FOR A FAIRLY
WIDESPREAD HIGH WIND EVENT ON WEDNESDAY.
AVIATION /12Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 526 AM MDT THU MAY 8 2025
SHALLOW, ISOLATED FOG MAY LEAD TO BRIEF VIS DROPS FOR THE NEXT
1-2 HOURS AT KSNY AND KAIA. CONDITIONS WILL TREND VFR AFTER WITH
MAINLY CLEAR SKIES. A FEW ISOLATED SHOWERS/STORMS ARE EXPECTED
TO DEVELOP BETWEEN KLAR AND KCYS MID AFTERNOON, AND MAY BRING A
BRIEF DROP TO MVFR CIGS/VIS ALONG WITH GUSTY AND ERRATIC WINDS.
THIS ACTIVITY SHOULD WIND DOWN EARLY EVENING AND GIVE WAY TO
MAINLY CLEAR SKIES OVERNIGHT.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...MN
LONG TERM...MN
AVIATION...MN
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