273
FXUS65 KCYS 151136
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
536 AM MDT TUE APR 15 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, INCLUDING
SHOWERS, STORMS, AND THE RETURN OF WIDESPREAD SNOW.
SHORT TERM /THROUGH WEDNESDAY/
ISSUED AT 203 AM MDT TUE APR 15 2025
UPPER LEVEL RIDGING WILL KEEP CONTROL OF THE REGION FOR AT LEAST
TODAY, WITH TEMPERATURES EXPECTED TO WARM BACK INTO THE 60'S AND
70'S TODAY AND POSSIBLY SOME 80'S BY TOMORROW. UNFORTUNATELY
WITH DRY CONDITIONS AT THE SURFACE, WE CAN ALSO EXPECT THIS TO
BRING ELEVATED FIRE WEATHER CONCERNS ACROSS THE REGION AS
MINIMUM RH VALUES DROP INTO THE TEENS AND EVEN SOME SINGLE
DIGITS TODAY. THANKFULLY WHERE RH VALUES LOOK TO BE LOWEST IN
EASTERN WYOMING, WIND GUSTS SHOULD ONLY BE PEAKING AROUND 15-20
MPH, AND FUELS SEEM TO STILL BE MOIST ENOUGH THAT THEY SHOULDN'T
BE CONDUCIVE OF RED FLAG CONDITIONS. MEANWHILE INTO THE
NEBRASKA PANHANDLE, RH VALUES WILL BE SLIGHTLY HIGHER, STILL
TEENS THOUGH, AND WINDS MAY BE SLIGHTLY HIGHER NEARING THE
CRITICAL THRESHOLD OF 25 MPH, BUT THIS SHOULD BE A BRIEF MEETING
AND SHOULDN'T BE SUSTAINED LONG ENOUGH TO WARRANT A RED FLAG
WARNING HERE EITHER.
ON WEDNESDAY OUR CLEAR SKIES WILL GIVE WAY TO CLOUDS AND THE
BEGINNING OF RAIN MOVING IN OVERNIGHT AS THE RIDGE FLATTENS AND
THEN DEEP UPPER LEVEL TROUGHING OVERSPREADS THE REGION. AT THE
SURFACE, A COLD FRONT SHOULD ENTER NORTHERN WYOMING BY WEDNESDAY
EVENING, AND WILL MOVE INTO SOUTHEASTERN WYOMING OVERNIGHT INTO
THURSDAY MORNING. A WIDESPREAD CHANCE OF SHOWERS WILL OCCUR
DURING THE LATER EVENING INTO THE OVERNIGHT HOURS, WITH A MORE
WIDESPREAD LIKELY CHANCE OF RAIN MOVING INTO THE LONG TERM ON
THURSDAY. STILL THIS SHOULD BE DELAYED JUST ENOUGH THAT WE
SHOULD SEE ONE FINAL DAY OF SPRING WARMTH BEFORE A MORE WINTER
STYLE PATTERN EMERGES INTO THE BEGINNING OF THE LONG TERM.
LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/
ISSUED AT 203 AM MDT TUE APR 15 2025
NO MAJOR CHANCES TO THE LONG TERM FORECAST WITH THIS FORECAST
UPDATE. SYNOPTIC FLOW REMAINS FAVORABLE FOR A POTENTIALLY IMPACTFUL
LATE SEASON SYSTEM PROGGED TO MOVE THROUGH THE REGION THURSDAY
THROUGH SUNDAY. TOTAL SNOW ACCUMULATION CONTINUES TO SLOWLY COME
DOWN AS LONG RANGE MODELS CONTINUE TO BETTER RESOLVE THIS SYSTEM.
HOWEVER, STORM TOTALS JUST UNDER ADVISORY CRITERIA ARE CURRENTLY
FORECAST FOR THIS PERIOD, THOUGH MUCH OF THE EARLY ROUNDS OF SNOW
WILL LIKELY MELT AND SINK INTO THE GROUND. THIS SYSTEM CONTINUES TO
FAVOR BENEFICIAL MOISTURE, BUT IS NOT EXPECTED TO BE A DROUGHT
BUSTER BY ANY MEANS. FOR MORE INFORMATION, SEE PREVIOUS DISCUSSION
ADDED BELOW...
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 /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 531 AM MDT TUE APR 15 2025
THE UPPER LEVEL RIDGE IS EXPECTED TO GET SUPPRESSED SOMEWHAT
TODAY WHICH WILL TEND TO WARM UP THINGS TODAY COMPARED TO
YESTERDAY. THIS WILL ALSO ALLOW FOR DOWNSLOPING WEST WINDS TO
AFFECT KLAR/KCYS TAF SITES TODAY. OTHERWISE, LIGHT WINDS ARE
EXPECTED ALONG WITH VFR CONDITIONS.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...CG
LONG TERM...AM
AVIATION...REC
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