903
FXUS65 KCYS 142057
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
257 PM MDT MON APR 14 2025
KEY MESSAGES
- WARMER AND DRIER WEATHER EXPECTED THROUGH MIDWEEK. THIS WILL
LEAD TO ELEVATED FIRE WEATHER CONCERNS.
- A PATTERN CHANGE IS EXPECTED AT THE END OF THE WEEK THAT WILL
BRING COOLER TEMPERATURES AND PRECIPITATION CHANCES.
SHORT TERM /THROUGH WEDNESDAY/
ISSUED AT 239 PM MDT MON APR 14 2025
SUNNY SKIES EXIST ACROSS MOST OF THE CWA THIS AFTERNOON. THE
EXCEPTION BEING THE NORTHERN WYOMING ZONES AND NORTHERN
NEBRASKA PANHANDLE. SCATTERED CLOUDS HAVE DEVELOPED IN THESE
AREAS THANKS TO AN UPPER-LEVEL SHORTWAVE TRACKING THROUGH SOUTH
DAKOTA THIS AFTERNOON. AS A RESULT, INCREASED POPS AROUND
CHADRON AND HARRISON TO INCLUDE SLIGHT CHANCE WORDING FOR
PRECIPITATION AS THERE ARE LIGHT RADAR RETURNS IN THE FAR
NORTHERN PANHANDLE. ANY ISOLATED SHOWER ACTIVITY WILL LIKELY BE
DONE BY THIS EVENING AS THE ATMOSPHERE BEGINS TO COOL AND
STABILIZE.
SHALLOW UPPER-LEVEL RIDGING WILL MOVE INTO THE ROCKIES ON TUESDAY,
ALLOWING 700 MB TEMPERATURES TO WARM UP. HIGH TEMPERATURES ON BOTH
TUESDAY AND WEDNESDAY WILL RETURN TO ABOVE AVERAGE WITH HIGHS IN THE
60S AND 70S. SUNNY SKIES ARE FORECAST FOR TUESDAY AS SUBSIDENCE
UNDER THE RIDGE KEEPS CONDITIONS DRY. UNFORTUNATELY, THIS WILL LEAD
TO ELEVATED FIRE WEATHER CONDITIONS ACROSS MUCH OF THE CWA. AN UPPER-
LEVEL DISTURBANCE ON WEDNESDAY WILL ERODE THE RIDGE AND BRING
INCREASED CLOUD COVER TO THE AREA WEDNESDAY AFTERNOON. BY LATE
AFTERNOON, HI-RES GUIDANCE DOES SHOW SOME LIGHT SHOWERS BEGINNING TO
MOVE INTO CARBON COUNTY DUE TO AN APPROACHING TROUGH. THIS TROUGH
WILL LEAD TO A PATTERN CHANGE LATER IN THE WEEK.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
ISSUED AT 239 PM MDT MON APR 14 2025
A MORE ACTIVE PATTERN IS EXPECTED TO RETURN TO THE AREA FOR THE END
OF THIS WEEK INTO EARLY NEXT WEEK. A BROAD, SLOW MOVING, AND
DISORGANIZED TROUGH WILL BE THE FIRST TO TRAVERSE THROUGH THE AREA
BETWEEN THURSDAY AND SUNDAY. THURSDAY LOOKS LIKE A TRANSITION DAY AS
STRONG VORT-MAX BEGINS TO DIG IN OVER THE SOUTHWEST CONUS BEFORE
CLOSING OFF. SOUTHWEST FLOW CONTINUES OVER THE AREA WITH ANOTHER
WEAKER VORT-MAX EJECTING OVER THE HIGH PLAINS. THIS WILL CARRY A
SURFACE LOW WITH IT, AND WRAP IN COOLER AIR BEHIND THE SURFACE
FRONT. MODELS ARE HANDLING THE TIMING OF THE FRONT DIFFERENTLY,
WHICH LEADS TO UNUSUALLY LARGE SPREAD BETWEEN SCENARIOS FOR
THURSDAY'S HIGHS. FOR EXAMPLE, THE NBM 25TH PERCENTILE HIGH FOR
CHEYENNE ON THURSDAY IS 52F, WHILE THE 75TH PERCENTILE IS 70F. THERE
IS HIGH CONFIDENCE THAT FRIDAY WILL BE SIGNIFICANTLY COOLER AS 700-
MB TEMPERATURES PLUMMET TO NEAR -10C, AROUND THE CLIMATOLOGICAL 10TH
PERCENTILE.
THE PRECIPITATION OUTCOME IS MORE UNCERTAIN. THE SYNOPTIC SET UP FOR
THIS SYSTEM IS VERY DISORGANIZED, SO WHILE THERE IS POTENTIAL FOR
MUCH OF THE AREA TO SEE APPRECIABLE PRECIPITATION, THERE ARE ALSO
SEVERAL FAILURE MODES. THE OVERALL MOST LIKELY SCENARIO ON THE
SYNOPTIC SCALE INCLUDES THE FIRST STRONG LOW CLOSING OFF BY FRIDAY
OVER THE GREAT BASIN, AND THEN SLOWLY DRIFTING EASTWARD AS THE
PARENT TROUGH LIFTS AWAY TO THE NORTHEAST. ONCE THE NEXT TROUGH
STARTS TO DROP INTO THE PACIFIC NORTHWEST OVER THE WEEKEND, THE
CLOSED LOW WOULD THEN GET PICKED UP AND EJECTED TO THE NORTHEAST.
ENSEMBLE MEMBERS CAN BE SPLIT INTO 3 CLUSTERS. THE LARGEST CLUSTER,
MAKING UP JUST UNDER 50% OF MEMBERS, DEPICTS A FASTER MOVING UPPER
LEVEL LOW THAT STAYS FURTHER NORTHEAST AND DOES NOT SEPARATE AS FAR
FROM THE PARENT TROUGH. THIS SCENARIO IS GENERALLY THE WETTEST FOR
THE AREA, WITH MOST OF THE PRECIP FALLING IN SOUTHEAST WYOMING. A
SECOND SCENARIO WITH ABOUT 25% OF MEMBERS HAS A SLOWER MOVING AND
MORE SEPARATED UPPER LEVEL LOW, BUT THIS STAYS A LITTLE FURTHER
NORTH. OVERALL PRECIPITATION AMOUNTS ARE CLOSE TO THE FIRST
SCENARIO, BUT IT TAKES A BIT LONGER TO GET THERE AND KEEPS
TEMPERATURES MUCH COLDER INTO THE WEEKEND. THE LAST SCENARIO IS THE
DRIEST, AND SPLITS THE TROUGH VERY CLEARLY AND DROPS THE CLOSED LOW
WELL TO THE SOUTHWEST. THIS KEEPS OUR AREA MUCH DRIER AND NOT AS
COOL. OVERALL, SOME PRECIPITATION LOOKS LIKE A GOOD BET MORE MOST OF
THE AREA, BUT IT REMAINS TO BE SEEN IF THIS WILL BE ABLE TO MAKE A
DENT IN THE DROUGHT. REGARDING PRECIPITATION TYPE, THIS WILL BE A
PRETTY COLD SYSTEM FOR THIS TIME OF YEAR. SNOW LEVELS MAY BE AS LOW
AS 4000 FT, MEANING THAT THE MAJORITY OF THE AREA WILL SWITCH TO
SNOW QUICKLY SOMETIME THURSDAY NIGHT BEHIND THE SURFACE FRONT. ONCE
THE SYSTEM EJECTS TO THE EAST ON SUNDAY, EXPECT TEMPERATURES TO WARM
BACK TO NEAR AVERAGE FOR THIS TIME OF YEAR, BUT ADDITIONAL SHORTWAVE
TROUGHS IN THE PIPELINE WILL KEEP LOW-END POPS IN THE FORECAST
THROUGH MONDAY.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 1133 AM MDT MON APR 14 2025
VFR CONDITIONS EXPECTED FOR THE FORECAST PERIOD. GUSTY NORTHWEST
WINDS WILL CONTINUE OVER THE HIGH PLAINS THROUGH AROUND SUNSET,
WITH WIDESPREAD GUSTS OF 30 TO 35 KNOTS ANTICIPATED AT NEBRASKA
TERMINALS. WINDS WILL SHIFT TO NORTH TO NORTHEAST THIS EVENING,
AND MAY BECOME VARIABLE FOR A FEW HOURS BEFORE SETTLING ON
MOSTLY SOUTH AFTER MIDNIGHT.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...SF
LONG TERM...MN
AVIATION...MN
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