368
FXUS65 KCYS 182104
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
304 PM MDT MON MAY 18 2026
KEY MESSAGES
- ACCUMULATING SNOW THROUGH MONDAY AFTERNOON WITH WINTER STORM
WARNINGS FOR MANY OF OUR HIGH ELEVATION AND MOUNTAIN ZONES AND
WINTER WEATHER ADVISORIES FOR NEARBY ZONES.
- 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. CHANCE OF SHOWERS AND A
SLIGHT CHANCE OF THUNDERSTORMS EACH DAY THROUGH FRIDAY
EVENING.
SHORT TERM /THROUGH WEDNESDAY NIGHT/
ISSUED AT 302 PM MDT MON MAY 18 2026
ON THE BACKSIDE OF THE STRONG SYSTEM MOVING UP INTO NEBRASKA WE
SHOULD SEE SNOW AND PRECIPITATION BEGINNING TO SUBSIDE INTO THE
EVENING HOURS. STRONG PRESSURE GRADIENTS DID PRODUCE SIGNIFICANT
WIND GUSTS AND, COMBINED WITH THE HEAVY WET SNOW, NEAR TO
BLIZZARD CONDITIONS WERE NOTED THIS MORNING, PARTICULARLY IN
CARBON COUNTY, SHUTTING DOWN I-80 AND LEAVING SEVERAL PEOPLE
WITHOUT POWER ACROSS THE AREA. MOVING INTO THIS EVENING AND
OVERNIGHT, WE'LL SEE CONCERNS SHIFT TO COLD TEMPERATURES AS THE
COLD AIRMASS IN PLACE COMBINED WITH SNOWPACK OR CLEARING SKIES
HELPS TO PRODUCE NEAR TO POSSIBLY RECORD LOW TEMPERATURES. THE
ENTIRE FORECAST AREA IS UNDER A FREEZE WARNING DUE TO THIS
EXPECTED COLD, WITH TEMPERATURES IN THE TEENS TO MID 20'S ALL
THE WAY THROUGH THE NEBRASKA PANHANDLE. COLD SENSITIVE PLANTS,
CROPS, AND EQUIPMENT WILL BE IMPACTED NOTABLY BY THIS FREEZE.
AFTER THIS, LOOK FOR A SLOW WARMING TREND THROUGH WEDNESDAY
AS OUR PATTERN ADVECTS WARMER TEMPERATURES FROM THE SOUTHWEST AS
WE STAY GENERALLY UNDER WEAK TROUGHING ALOFT WITH SOUTHWESTERLY
TO WESTERLY FLOW AT 500MB PRIOR TO THE NEXT QUICK HITTING SYSTEM
AT THE END OF THE WEEK. BOTH TUESDAY AND WEDNESDAY WILL FEATURE
SMALL EMBEDDED SHORTWAVES WHICH COULD PRODUCE SOME SCATTERED
SHOWERS OR POSSIBLY EVEN A WEAK THUNDERSTORM, BUT OVERALL
ACTIVITY LOOKS TO REMAIN MINIMAL AND FAIRLY INCONSEQUENTIAL. AS
TEMPERATURES STEADILY RISE THE REGION WILL SLOWLY WARM, BUT
DON'T EXPECT A QUICK SHOT OF WARMTH. HIGHS TUESDAY REACH INTO
THE 40'S TO 50'S OUTSIDE OF CARBON COUNTY WHERE THE LINGERING
SNOWPACK WILL LIKELY KEEP THE AREA COOL IN THE 30'S FOR THE DAY.
TUESDAY NIGHT INTO WEDNESDAY LOWS WILL ONCE AGAIN DESCEND INTO
THE 30'S EAST OF THE LARAMIE RANGE, WHILE TO THE WEST WE'LL SEE
ANOTHER HARD FREEZE IN THE TEENS TO 20'S (ALSO INCLUDING
CONVERSE COUNTY TO THE NORTH). A FREEZE WATCH HAS BEEN ISSUED
FOR TOMORROW NIGHT, WITH AN UPGRADE TO WARNING LIKELY. MOVING
INTO WEDNESDAY HIGHS CONTINUE TO RECOVER INTO THE 40'S TO 60'S,
WITH LOWS BACK INTO THE 30'S TO 40'S WITH SUB-FREEZE
TEMPERATURES ONCE AGAIN WEST OF THE LARAMIE RANGE.
LONG TERM /THURSDAY THROUGH MONDAY/
ISSUED AT 302 PM MDT MON MAY 18 2026
HEADING TOWARDS THE END OF THE WORK WEEK, A SHORTWAVE TROUGH WILL
PUSH THROUGH SOUTHEASTERN WYOMING AND WESTERN NEBRASKA ON THURSDAY
PROVIDING A SOURCE OF LARGE-SCALE FORCING FOR ASCENT. ENSEMBLE
GUIDANCE HAS PWAT AROUND THE 75TH PERCENTILE RELATIVE TO CLIMATOLOGY
IN ADDITION TO MEDIAN SBCAPE AROUND 300 J/KG, SO SHOWERS AND
THUNDERSTORMS ARE A GOOD BET LATER IN THE AFTERNOON AND EVENING.
EFFECTIVE BULK SHEAR IS PROGGED TO RANGE FROM 25-30 KNOTS, SO
WIDESPREAD SEVERE THUNDERSTORMS ARE NOT EXPECTED, ALTHOUGH CAN'T
RULE OUT A FEW STORMS PRODUCING MARGINALLY SEVERE GUSTY WINDS AND
HAIL. GIVEN THE INCREASED CLOUD COVER LATER IN THE DAY, HIGH
TEMPERATURES ARE EXPECTED TO BE 5-10 DEGREES BELOW CLIMATOLOGY IN
THE 60S EAST OF THE LARAMIE RANGE, AND 50S WEST. 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 /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 1146 AM MDT MON MAY 18 2026
IFR TO LIFR IN PLACE FOR THE WYOMING TERMINALS AS VISIBILITIES
REMAIN UNDER 3 MILES AND CIGS REMAIN AT OR BELOW 2 KFT. FOR THE
NEBRASKA TERMINALS, MVFR TO IFR REMAIN ESPECIALLY IN THE VICINITY OF
ANY HEAVIER SHOWERS. EXPECT CIGS TO GRADUALLY INCREASE AFTER 06Z AS
THIS WINTER STORM WRAPS UP WITH THE EXCEPTION OF KLAR AND KRWL WHERE
LOW CLOUDS ARE EXPECTED TO REMAIN IN PLACE THROUGH 12Z IN ADDITION
TO BLOWING SNOW AT KRWL. 15-20 KNOT NE WINDS WILL REMAIN IN PLACE
THROUGH 00Z, GUSTING TO 25-30 KNOTS BEFORE BACKING TO NW AFTER 06Z.
AS SURFACE HIGH PRESSURE SETTLES INTO THE REGION BEHIND THE ONGOING
SYSTEM, WINDS WILL DECREASE TO AROUND 10 KNOTS.
CYS WATCHES/WARNINGS/ADVISORIES
WY...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 10 AM MDT TUESDAY FOR
WYZ113.
FREEZE WARNING FROM 8 PM THIS EVENING TO 10 AM MDT TUESDAY FOR
WYZ101-102-106>108-115>119.
WINTER WEATHER ADVISORY UNTIL 6 PM MDT THIS EVENING FOR WYZ101-
105-106-110-111-115-117.
FREEZE WATCH FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY MORNING
FOR WYZ101-115.
WINTER STORM WARNING UNTIL 6 PM MDT THIS EVENING FOR WYZ103-
104-109-112-114-116.
FREEZE WARNING UNTIL NOON MDT TUESDAY FOR WYZ104-105-109>111.
FREEZE WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY MORNING
FOR WYZ104-105-109>111-113-116.
NE...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 10 AM MDT TUESDAY FOR
NEZ002-003-020-021-054-055.
FREEZE WARNING FROM 8 PM THIS EVENING TO 10 AM MDT TUESDAY FOR
NEZ019-095-096.
SHORT TERM...CG
LONG TERM...NB
AVIATION...NB
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