481
FXUS65 KCYS 071027
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
427 AM MDT WED MAY 7 2025
KEY MESSAGES
- FOG PERSISTS THIS MORNING AROUND THE HIGHER ELEVATIONS OF I-80
AND IN LARAMIE COUNTY.
- CHANCES FOR SHOWERS AND ISOLATED THUNDERSTORMS CONTINUE TODAY
AS A SLOW SPRING STORM SYSTEM DEPARTS.
- A WARMING TREND WILL BEGIN THURSDAY AND LAST THROUGH EARLY
NEXT WEEK WITH AN ISOLATED CHANCE FOR AFTERNOON SHOWERS AND
STORMS EACH DAY.
SHORT TERM /THROUGH THURSDAY NIGHT/
ISSUED AT 420 AM MDT WED MAY 7 2025
CURRENT GOES SATELLITE IMAGERY SHOWS A DEEP MOISTURE PLUME DIRECTED
NEARLY DUE WESTWARD ACROSS THE AREA, SANDWICHED BETWEEN THE
DISORGANIZED UPPER LEVEL LOW OVER THE TEXAS PANHANDLE, AND A WEAK
UPPER LEVEL HIGH OVER THE DAKOTAS. EASTERLY UPSLOPE FLOW EXTENDS
THROUGH NEARLY THE ENTIRE TROPOSPHERE WITH MODEST ISENTROPIC UPGLIDE
ALONG ITS TRAJECTORY. THIS HAS PRODUCED FAIRLY WIDESPREAD SHOWERS
AND A FEW EMBEDDED THUNDERSTORMS THROUGH THE NIGHT, BUT DRY AIR IS
BEGINNING TO WORK IN FROM THE EAST IN THE MIDDLE TROPOSPHERE. RADAR
SHOWS THE MAIN REGION OF RAINFALL RUNNING UP INTO THE TERRAIN
BARRIER AT THIS HOUR, WITH MORE LIMITED SHOWER ACTIVITY DEVELOPING
BEHIND. THIS WILL CONTINUE THROUGH THE MORNING, BUT OVERALL COVERAGE
WILL BE MUCH LESS THAN WHAT WE SAW DURING THE EVENING AND OVERNIGHT
HOURS AS A RESULT OF MODEST NEGATIVE THETA-E ADVECTION. THE LACK OF
LARGE-SCALE LIFT TODAY (OUTSIDE OF OROGRAPHICS) SHOULD ALLOW FOR A
BIT MORE PARTIAL CLEARING OF THE CLOUD DECK. AFTER A SHORT BREAK IN
THE EARLY AFTERNOON, ANOTHER ROUND OF SHOWERS AND ISOLATED
THUNDERSTORMS MAY TRY TO TAP INTO SOME SHALLOW INSTABILITY. A WARM
LAYER AROUND 400-MB WILL KEEP STORMS FROM GETTING TOO TALL. SHOWERS
AND STORMS THAT DEVELOP WILL TAKE ON A VERY UNUSUAL ENE TO WSW STORM
MOTION VECTOR.
AFTER MIDNIGHT, THE WIND PROFILE WILL DIVERT AWAY FROM EASTERLY
UPSLOPE AS THE CLOSED LOW SLOWLY TRACKS FURTHER TO THE EAST. EXPECT
PLENTIFUL SUNSHINE ON THURSDAY AS RIDGING EXPANDS OVER THE AREA. A
FEW ISOLATED SHOWERS AND/OR STORMS MAY DEVELOP, MAINLY OVER THE
HIGHER TERRAIN BUT DRIER AIR AND WARM TEMPERATURES ALOFT WILL LIMIT
THE STRENGTH AND COVERAGE OF ANY DEVELOPING CONVECTION.
LONG TERM /FRIDAY THROUGH TUESDAY/
ISSUED AT 420 AM MDT WED MAY 7 2025
STRONG RIDGING IS EXPECTED TO DOMINATE MOST OF THE LONG TERM
FORECAST PERIOD. ON FRIDAY, WE WILL HAVE A STRENGTHENING RIDGE OVER
THE DESERT SOUTHWEST. HOWEVER, A SLOW MOVING VORT-MAX ABANDONED OVER
EASTERN WYOMING WILL MEANDER THROUGH THE AREA, AND MAY BE ENOUGH TO
KEEP SOME UNSETTLED WEATHER IN THE PICTURE. WARMING IN THE LOWER
ATMOSPHERE WHILE THE UPPER ATMOSPHERE STAYS FAIRLY STEADY IN
TEMPERATURE WILL LEAD TO STEEPER LAPSE RATES COMPARED TO
THURSDAY. THE MODEST SYNOPTIC BOOST FROM THE ORPHANED VORT-MAX
SHOULD HELP INCREASE PM SHOWER/STORM COVERAGE SLIGHTLY. MORE
WIDESPREAD POPS ARE PRESENT FRIDAY AFTERNOON, BUT MOST AREAS ARE
UNDER 30%. THE RIDGE AXIS WILL SHIFT OVERHEAD ON SATURDAY, WHEN
500-MB HEIGHTS SHOULD REACH THEIR PEAK. VERY DRY AIR IN THE
MID-LEVELS WILL LIKELY PREVENT MUCH MORE THAN A FEW SHALLOW
VIRGA SHOWERS ON SATURDAY. SOUTHWEST FLOW ALOFT WILL INCREASE
SUNDAY INTO EARLY NEXT WEEK AS THE RIDGE SHIFTS TO OUR EAST.
700-MB TEMPERATURES WILL CREST MONDAY OR TUESDAY (DEPENDING ON
THE TIMING OF THE NEXT TROUGH DIVING IN THE PACIFIC NORTHWEST),
AT OVER CLIMATOLOGICAL 90TH PERCENTILE. EXPECT TO SEE WIDESPREAD
80S BELOW 5000 FEET IN ELEVATION, AND EVEN A RUN AT 90F FOR
SOME OF THE TYPICAL HOTTER SPOTS. ISOLATED SHOWERS AND
THUNDERSTORMS WILL REMAIN POSSIBLE EACH AFTERNOON SUNDAY INTO
EARLY NEXT WEEK, BUT WIDESPREAD PRECIPITATION IS UNLIKELY.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1145 PM MDT TUE MAY 6 2025
A SOGGY STORM SYSTEM IS CONTINUING TO PRODUCE DIFFICULT
AVIATION CONDITIONS TONIGHT. IFR IS MOST LIKELY AT WYOMING
TERMINALS WITH LOW CLOUDS PUSHING UP AGAINST THE MOUNTAINS.
PERSISTENT LIFR IS EXPECTED TO CONTINUE INTO WEDNESDAY MORNING
AT KCYS. IN NEBRASKA, ON AND OFF SHOWERS AND A FEW THUNDERSTORMS
WILL PRODUCE BRIEF MVFR TO IFR CONDITIONS UNTIL THEY BEGIN TO
DECREASE IN COVERAGE AFTER ABOUT 10Z. EXPECT SOME PARTIAL
LIFTING/CLEARING LATE MORNING INTO THE EARLY AFTERNOON BEFORE
ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS DEVELOPS MID
AFTERNOON, MAINLY IMPACTING KAIA, KBFF, AND KSNY.
CYS WATCHES/WARNINGS/ADVISORIES
WY...WINTER WEATHER ADVISORY UNTIL 6 AM MDT EARLY THIS MORNING FOR
WYZ114.
DENSE FOG ADVISORY UNTIL 9 AM MDT THIS MORNING FOR WYZ116>118.
NE...NONE.
SHORT TERM...MN
LONG TERM...MN
AVIATION...MN
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