512
FXUS65 KCYS 190819
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
219 AM MDT TUE MAY 19 2026
KEY MESSAGES
- NEAR RECORD COLD MONDAY AND MONDAY NIGHT WILL LEAD TO
WIDESPREAD FREEZING TEMPERATURES, WHICH MAY DAMAGE SENSITIVE
VEGETATION AND OUTDOOR IRRIGATION SYSTEMS.
- SLOW WARMING TREND BY THE MID TO LATE WEEK WITH TEMPERATURES
NEAR NORMAL BY THURSDAY AND FRIDAY. NUMEROUS SHOWERS AND A
SLIGHT CHANCE OF THUNDERSTORMS EACH DAY, BUT MOSTLY THURSDAY
AND FRIDAY.
- ABOVE AVERAGE TEMPERATURES AND PLEASANT WEATHER EXPECTED FOR
THE WEEKEND.
SHORT TERM /THROUGH THURSDAY/
ISSUED AT 215 AM MDT TUE MAY 19 2026
RELATIVELY QUIET EARLY THIS MORNING AFTER AN EVENTFUL SUNDAY AND
MONDAY. ADDITIONAL STORM TOTAL SNOW AMOUNTS ARE TRICKLING IN AND
THERE ARE SOME IMPRESSIVE TOTALS ACROSS THE MOUNTAINS AND
ADJACENT VALLEYS. SEVERAL REPORTS OF 12 TO 18 INCHES FROM SOUTH
OF RAWLINS OVER TOWARDS ROCK RIVER. THE SNOWY RANGE LIVED UP TO
ITS NAME DURING THIS EVENT WITH A FEW SNOTEL SITES REPORTING
OVER 3 FEET OF SNOW AND NEARLY 3 INCHES OF SWE! ACCUMULATING
SNOW HAS ENDED ACROSS THE AREA WITH ONLY A FEW FLURRIES DETECTED
ON RADAR.
MAIN FORECAST CONCERN TODAY AND TONIGHT WILL BE THE VERY COLD
TEMPERATURES. CURRENT OBSERVATIONS ACROSS THE AREA SHOW
TEMPERATURES IN THE MIDDLE 20S TO LOW 30S. PORTIONS OF THE AREA
HAVE STRUGGLING WITH CLOUD COVER AND/OR GUSTY WINDS, BUT BOTH
ARE EXPECTED TO SUBSIDE OVER THE NEXT SEVERAL HOURS. KEPT LOW
TEMPERATURES AS IS WITH FREEZE WARNINGS IN EFFECT. THERE IS ALSO
THE POTENTIAL FOR FOG, BUT IT SHOULDN'T BE WIDESPREAD UNDER CAA.
ANOTHER ROUND OF FREEZING OR NEAR- FREEZING TEMPERATURES EXPECTED
TONIGHT, MAINLY WEST OF THE I-25 CORRIDOR. KEPT THE FREEZE
WATCH IN EFFECT TO SEE HOW THIS MORNING'S FREEZE WARNINGS DO
BEFORE UPGRADING. OTHERWISE, ANOTHER CHILLY DAY TUESDAY, BUT NOT
AS COLD AS YESTERDAY WITH HIGHS IN THE 40S TO MIDDLE 50S FOR
SOUTHEAST WYOMING, BUT NOT AS COLD ACROSS WESTERN NEBRASKA WITH
HIGHS 55 TO 60. MAY SEE A FEW LINGERING SNOW FLURRIES OR
SPRINKLES TODAY NEAR THE COLORADO BORDER AND IN THE MOUNTAINS.
SLIGHT WARMING TREND FOR WEDNESDAY AND THURSDAY, BUT NORTHWEST
FLOW ALOFT WILL CONTINUE...SO TEMPERATURES DURING THE AFTERNOON
WILL STRUGGLE TO REACH THE 50S WEST OF I-25, AND 60 FOR AREAS
EAST OF I-25. INSTABILITY WILL STILL BE PRESENT IN THIS PATTERN,
AND MODELS TEND TO UNDERESTIMATE DAYTIME CONVECTION. KEPT 20 TO
40 PERCENT POP FOR WEDNESDAY WITH SCATTERED RAIN SHOWERS AND
ISOLATED THUNDER EXPECTED, MAINLY WHERE IT'S WARMEST ALONG AND
WEST OF I-25. SOME SNOWPACK MAY REMAIN OVER CARBON AND ALBANY
COUNTIES...EVEN ON THURSDAY...WHICH WILL GREATLY DECREASE
POTENTIAL FOR CONVECTION. EVEN THURSDAY MORNING, LOW
TEMPERATURES IN THE UPPER 20S AND LOW 30S ARE EXPECTED OVER
THE HIGH VALLEYS OF CARBON AND ALBANY COUNTIES.
LATER ON THURSDAY, MODELS SHOW A POTENT CLIPPER SYSTEM OUT OF
ALBERTA CANADA DIGGING SOUTH INTO WYOMING AND SLOWING DOWN. WILL
HAVE TO MONITOR THIS SYSTEM FOR ADDITIONAL MOUNTAIN SNOWFALL,
BUT EXPECT MOST OF THE LOWER ELEVATIONS TO STAY AS RAINFALL.
GOOD FORCING WITH THIS CLIPPER WITH ANOTHER SHOT OF COOLER AIR.
DAYTIME INSTABILITY WILL AID IN SHOWER AND THUNDERSTORM
DEVELOPMENT WITH CAPE VALUES BETWEEN 400 TO 800 J/KG. COULD SEE
SOME DECENT RAINFALL AMOUNTS INTO FRIDAY. INCREASED POP ABOVE 60
PERCENT FOR MOST OF THE AREA WITH THE LIKELIHOOD OF MULTIPLE
ROUNDS OF SHOWERS MOVING THROUGH THE REGION.
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
ISSUED AT 303 PM MDT MON MAY 18 2026
A SECONDARY VORTICITY MAXIMUM WILL PROPAGATE ACROSS OUR REGION
ON FRIDAY, COMBINED WITH PWAT NEAR THE 60TH PERCENTILE,
RESULTING IN ANOTHER CHANCE FOR A FEW SHOWERS AND THUNDERSTORMS
WITH LITTLE CHANGE IN HIGH TEMPERATURES FROM THE PREVIOUS DAY
GIVEN THE CLOUD COVER.
INTO THE WEEKEND, 500 MB HEIGHTS RISE AS WEAK LONGWAVE RIDGING
ESTABLISHES ITSELF ACROSS THE ROCKY MOUNTAIN WEST, RESULTING IN A
WARMING TREND AND MOSTLY DRY CONDITIONS. HIGH TEMPERATURES ARE
EXPECTED TO BE NEAR CLIMATOLOGY (AVERAGE HIGH IN CHEYENNE ON MAY 23
IS 67 DEGREES), WITH 60S WEST OF THE I-25 CORRIDOR AND 70S FURTHER
EAST. THE WARM UP WILL CONTINUE SUNDAY INTO MONDAY AS THE RIDGE AXIS
SHIFTS OVER WYOMING, RESULTING IN ABOVE-AVERAGE TEMPERATURES AND
LITTLE TO NO CHANCES OF PRECIPITATION.
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 1122 PM MDT MON MAY 18 2026
RAIN/SNOW ACTIVITY WILL BE COMING TO AN END ACROSS ALL THE TERMINALS
OVER THE NEXT HOUR OR SO. WITH THE ADDED MOISTURE WE'VE SEEN ACROSS
SOUTHEAST WYOMING COUPLED WITH WINDS BECOMING LIGHT AND VARIABLE,
BR AND/OR FG MAY DEVELOP AND IMPACT KRWL, KLAR, AND KCYS WITH VIS
1SM OR LESS AND CIGS DOWN TO 500 FEET, POSSIBLY LOWER AT TIMES.
AFTER ABOUT 15Z, CIGS AND VIS WILL IMPROVE FOR THE AFOREMENTIONED
TERMINALS. FOR THE NEBRASKA PANHANDLE SITES, CIGS WILL LIFT
OVERNIGHT WITH WINDS GENERALLY STAYING VARIABLE TO AROUND 6
KNOTS.
CYS WATCHES/WARNINGS/ADVISORIES
WY...FREEZE WARNING UNTIL 10 AM MDT THIS MORNING FOR WYZ101-102-
106>108-113-115>119.
FREEZE WATCH FROM LATE TONIGHT THROUGH WEDNESDAY MORNING FOR
WYZ101-115.
FREEZE WARNING UNTIL NOON MDT TODAY FOR WYZ104-105-109>111.
FREEZE WATCH FROM THIS EVENING THROUGH WEDNESDAY MORNING FOR
WYZ104-105-109>111-113-116.
NE...FREEZE WARNING UNTIL 10 AM MDT THIS MORNING FOR NEZ002-003-
019>021-054-055-095-096.
SHORT TERM...TJT
LONG TERM...NB
AVIATION...RZ
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