379
FXUS65 KCYS 030923 AAD
AFDCYS
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHEYENNE WY
323 AM MDT SAT MAY 3 2025
KEY MESSAGES
- A PLEASANT SATURDAY EXPECTED ACROSS THE REGION AHEAD OF A
COOLER, MORE UNSETTLED PATTERN FOR SUNDAY ONWARDS.
- INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS MONDAY
THROUGH WEDNESDAY WITH SOME SNOW FOR OUR MOUNTAINOUS REGIONS.
SHORT TERM /THROUGH SUNDAY NIGHT/
ISSUED AT 208 AM MDT SAT MAY 3 2025
CLEAR SKIES AND CALM WINDS OVERNIGHT TONIGHT WITH ONLY A FEW HIGH
CLOUDS DRIFTING JUST SOUTHEAST OF CHEYENNE COUNTY. TEMPERATURES ARE
REMAINING FAIRLY MILD, DESPITE THE CLEAR SKIES OVERHEAD. MOST
LOCATIONS ARE IN THE 40S, WITH ONLY A FEW SITES IN THE LOW- TO MID-
30S. CLEAR SKIES CONTINUE THROUGH THE DAY.
TEMPERATURES ON SATURDAY WILL WARM NICELY INTO THE UPPER-60S TO MID-
70S ACROSS THE REGION UNDER AND UPPER-LEVEL RIDGE BUILDING OVER THE
INTERMOUNTAIN WEST. SUBSIDENCE FROM THIS RIDGE WILL LEAD TO CLEAR
SKIES, LIGHT WINDS, AND NO PRECIPITATION CHANCES ACROSS THE REGION.
DURING THE DAY, THE OMEGA BLOCK WILL CONTINUE TO BUILT AND
STRENGTHEN ACROSS THE CENTRAL CONUS, PROPAGATING JUST FAR ENOUGH
EAST TO PUT THE CWA UNDER A FAVORABLE REGIME FOR PRECIPITATION
STARTING SUNDAY ONWARDS. PRECIPITATION CHANCES DO NOT START RAMPING
UP UNTIL SUNDAY AFTERNOON ONWARDS, DUE TO THE INFLUENCE OF THE UPPER-
LEVEL RIDGE ACROSS THE REGION.
ON SUNDAY, THE UPPER-LEVEL OMEGA BLOCK WILL MOVE JUST FAR ENOUGH
EAST TO PUT THE CWA DOWNSTREAM OF THE WESTERN UPPER-LEVEL LOW. AS A
RESULT, SOUTHERLY TO SOUTHEASTERLY WINDS THROUGHOUT THE ATMOSPHERE
WILL CONTINUOUSLY ADVECT IN ADDITIONAL MOISTURE FROM MOISTURE-RICH
REGIONS OF THE SOUTHERN CONUS. SEVERAL 500MB VORTICITY MAXIMA WILL
EJECT OUT AHEAD OF THE WESTERN LOW, LEADING TO THE DEVELOPMENT OF
SHOWERS AND POTENTIALLY EVEN SOME THUNDERSTORMS SUNDAY AFTERNOON AS
DAYTIME TEMPERATURES WARM INTO THE 60S AND 70S ONCE MORE. THE
EASTERN LOW OF THE OMEGA BLOCK AT 700MB WILL WOBBLE WESTWARD
THROUGHOUT THE DAY SUNDAY, LEADING TO INCREASED HEIGHT GRADIENTS
BETWEEN THE TWO LOWS AND THE RIDGE SANDWICHED BETWEEN. AS A RESULT,
A 700MB JET, AROUND 40 TO 45KTS, DEVELOPS ACROSS EASTERN PORTIONS OF
THE CWA. SURFACE WINDS WILL RAMP UP DUE TO THE TIGHTENING HEIGHT
GRADIENT AT 700MB LEADING TO A VERY WINDY DAY ON SUNDAY FOR
LOCATIONS THAT USUALLY REMAIN OUT OF HIGH WIND DURING THE WINTER.
PRIMARY CONCERN FOR THESE STRONG, SOUTHERLY WINDS WILL BE LOCATIONS
JUST DOWNSTREAM OF THE PINE RIDGE ACROSS THE NORTHERN PANHANDLE.
SOME DECENT DOWNWARD OMEGA VALUES EXIST ACROSS THE PINE RIDGE IN THE
NORTHERN PANHANDLE SUNDAY EVENING INTO EARLY MONDAY MORNING.
FORECAST SOUNDINGS FROM THE NAM, RAP, AND GFS ALSO SUGGEST INVERTED-
V SOUNDINGS WITH STEEP MID- AND LOW-LEVEL LAPSE RATES. THIS SUGGESTS
THAT STRONG WINDS ALOFT ARE FAVORED TO MIX DOWN TO THE SURFACE WITH
THE STEEP LAPSE RATES PRESENT. CHADRON COULD SEE SOME FAIRLY STRONG
GUSTS POTENTIALLY APPROACHING HIGH WIND CRITERIA GUSTS DUE TO BOTH
ENVIRONMENTAL WINDS AND SUBTLE DOWNSLOPING FROM THE PINE RIDGE.
DECIDED NOT TO ISSUE HIGH WIND HEADLINES FOR THIS REGION AS FORECAST
GUSTS REMAIN BELOW CRITERIA AND THE CONFIDENCE IS NOT THERE FOR HIGH
WINDS AT CHADRON, BUT IT IS DEFINITELY A POSSIBILITY. WILL LET DAY
CREW TAKE ANOTHER LOOK AT THE WINDS TO DETERMINE IF ANY HEADLINES
ARE NECESSARY.
LONG TERM /MONDAY THROUGH FRIDAY/
ISSUED AT 208 AM MDT SAT MAY 3 2025
AN ACTIVE PATTERN IS EXPECTED FOR THE LONG TERM AS A WEAK OMEGA
BLOCK PATTERN SETS UP OVER CONUS MONDAY THROUGH WEDNESDAY. UPPER-
LEVEL LOWS LOCATED ROUGHLY OVER THE FOUR CORNERS REGION AND MIDWEST
WILL STAGNATE OVER THESE AREAS FOR A FEW DAYS WITH A RIDGE STUCK
BETWEEN THEM. PLACEMENT OF THE FURTHER WEST LOW WILL ALLOW
SUFFICIENT MOISTURE TRANSPORT FROM THE GULF. IN FACT, NAEFS
CLIMATOLOGY SHOWS IVT VALUES IN THE 90TH PERCENTILE AND ABOVE FOR
PORTIONS OF THE CWA ON MONDAY. BECAUSE THE LOW OVER THE FOUR CORNERS
IS EXPECTED TO SIT OVER THE SAME SPOT FOR A FEW DAYS, CONTINUED
MOISTURE FROM THE GULF WILL LEAD TO A PROLONGED PERIOD OF WET
WEATHER FOR THE BEGINNING OF THE WORK WEEK. PRECIPITATION CHANCES
ARE EXPECTED MONDAY THROUGH WEDNESDAY WITH WIDESPREAD SCATTERED
SHOWERS LIKELY DURING THIS TIME. SEVERE WEATHER SEEMS UNLIKELY AT
THIS TIME AS COOLER, BELOW AVERAGE TEMPERATURES ARE EXPECTED WITH
THIS LOW, LEADING TO ONLY A FEW HUNDRED J/KG OF CAPE EACH DAY AND
RATHER UNIMPRESSIVE LAPSE RATES. STILL CANNOT RULE OUT GUSTY WINDS
AND HAIL IN THESE STORMS, HOWEVER, IT SEEMS LIKE POTENTIAL RAINFALL
AMOUNTS WILL BE THE MORE IMPRESSIVE FACTOR OVER THESE FEW DAYS.
ENSEMBLE MEANS FROM BOTH THE GFS AND ECMWF ARE RATHER CONSISTENT,
SHOWING ANYWHERE FROM 0.4 TO 0.75 INCHES OF RAINFALL OVER THE THREE
DAY PERIOD. THESE ENSEMBLES ARE ACTUALLY HIGHER AROUND THE CHEYENNE
AREA, SHOWING ABOUT AN INCH OF QPF, WHICH WOULD HELP WITH THE BELOW
AVERAGE PRECIPITATION AMOUNTS THIS YEAR.
CONDITIONS LOOK TO DRY OUT AND WARM UP FOR THE END OF NEXT WEEK AS
THE OMEGA BLOCK BREAKS DOWN AND AN UPPER-LEVEL RIDGE BUILDS OVER THE
ROCKIES. TEMPERATURES MAKE A RETURN TO ABOVE AVERAGE WITH HIGHS IN
THE 60S AND 70S ON BOTH THURSDAY AND FRIDAY. MOST LOCATIONS WILL
ALSO SEE MOSTLY SUNNY SKIES AS SUBSIDENCE UNDER THE RIDGE KEEPS
CLOUDS AND PRECIPITATION AT BAY.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 1004 PM MDT FRI MAY 2 2025
A RIDGE ALOFT WILL PREVAIL THROUGH THE PERIOD. CLEAR SKIES WILL
CONTINUE. WINDS WILL GUST TO 20 KNOTS AT RAWLINS FROM 16Z TO
00Z.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...AM
LONG TERM...SF
AVIATION...RUBIN
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