108
FXUS65 KCYS 050918
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
318 AM MDT MON MAY 5 2025
KEY MESSAGES
- PATTERN CHANGE TODAY AS AN OMEGA BLOCK TAKES HOLD ACROSS THE CENTRAL
CONUS. INCREASING PRECIPITATION CHANCES THROUGH THE WEEK.
- BREEZY CONDITIONS RETURN TUESDAY INTO WEDNESDAY.
- DRYING CONDITIONS BY LATE-WEEK WITH TEMPERATURES RETURNING TO
ABOVE-NORMAL VALUES.
SHORT TERM /THROUGH TUESDAY NIGHT/
ISSUED AT 248 AM MDT MON MAY 5 2025
ANOTHER QUIET NIGHT ACROSS SOUTHEAST WYOMING AND WESTERN NEBRASKA
WITH ONLY SOME HIGH CLOUDS ALONG AND WEST OF THE LARAMIE RANGE. SOME
HIGH CLOUDS ARE STARTING TO MOVE OVER SIDNEY AND THE SOUTHERN
PANHANDLE, BUT OTHERWISE CLEAR SKIES. TEMPERATURES ARE QUITE MILD
TONIGHT WITH CURRENT TEMPERATURES AS OF 08Z IN THE 40S AND 50S.
CHADRON IS THE WARM SPOT TONIGHT WHERE DOWNSLOPING IS ONGOING WITH
WINDS GUSTING 30MPH AND ABOVE. GUSTY CONDITIONS WILL REMAIN ACROSS
THE REGION TODAY, BUT THE DOWNSLOPE COMPONENT SHOULD KEEP
TEMPERATURES QUITE MILD TONIGHT.
ACTIVE WEATHER CONTINUES TODAY THROUGH MID-WEEK AS THE UPPER-LEVEL
OMEGA BLOCK TAKES SHAPE ACROSS THE CENTRAL CONUS. CURRENT GOES-EAST
UPPER-LEVEL WATER VAPOR IMAGERY SHOWS THE CLOSED, STRONGER LOW
ACROSS THE EASTERN CONUS WITH THE WEAKER, WESTERN LOW OVER SOUTHERN
NEVADA AND CALIFORNIA AS OF 08Z TONIGHT. THIS ALIGNS QUITE WELL WITH
THE MODEL DEPICTION OF THE CURRENT CONDITIONS ACROSS THE CONUS. THE
WESTERN LOW WILL SLOWLY SLIDE EASTWARD TODAY, SETTING UP JUST SOUTH
OF THE FOUR CORNERS REGION BY 06Z TUESDAY. THE PLACEMENT OF THE
WESTERN LOW REMAINS A FAVORABLE ONE FOR PRECIPITATION ACROSS THE
CWA, BUT MODELS HAVE STARTED DECREASE IN TOTAL PRECIPITATION
AMOUNTS, TO BE EXPECTED AS MOST SYSTEMS THUS FAR HAVE DRASTICALLY
UNDER-PRODUCED AS FAR AS PRECIPITATION GOES. SOME PERSISTENCE
FORECASTING WAS USED WITH THIS MORNING'S UPDATE BY DECREASING QPF
VALUES ACROSS THE REGION, EVEN A BIT BELOW WHAT SOME MODELS WERE
SUGGESTING. AS DAYTIME HEATING WARMS TEMPERATURES INTO THE 60S AND
70S ONCE MORE, SOME DESTABILIZATION OF THE ATMOSPHERE IS EXPECTED
WITH MLCAPE VALUES AROUND 200 TO 500 JOULES OUT WEST AND MOSTLY
CAPPED EAST, WITH SOME POCKETS OF UN-CAPPED CAPE. FORECAST SOUNDINGS
SUGGEST DOWNDRAFT CAPE VALUES AROUND 500 TO 1000 JOULES, DEPENDING
ON WHERE SOUNDINGS ARE SELECTED. AS A RESULT, WITH THE MILD
INSTABILITY TODAY, GUSTY SHOWERS AND POTENTIALLY GUSTY THUNDERSTORMS
ARE EXPECTED ACROSS THE AREA. THE HRRR SUGGESTS NO UPDRAFT HELICITY
SWATHS, SO MOST STORMS THAT DEVELOP TODAY WILL LIKELY BE CLOSER TO
"GARDEN VARIETY" THUNDERSTORMS THAT COULD PRODUCE GUSTY WINDS IN
EXCESS OF 60MPH, BUT SUPERCELLS ARE NOT EXPECTED TODAY.
ENVIRONMENTAL WINDS WILL SLOWLY DECREASE THROUGHOUT THE DAY AS THE
SURFACE PRESSURE GRADIENTS ACROSS THE CWA DECREASES. HOWEVER, A
FAIRLY WEAK SURFACE LOW WILL ATTEMPT TO DEVELOP ACROSS SOUTHWESTERN
SOUTH DAKOTA, LEADING TO BREEZY CONDITIONS THROUGHOUT MUCH OF THE
DAY ALONG WITH THE INCREASING PRECIPITATION CHANCES. WITH THE
POSITION OF THIS SURFACE LOW SO FAR TO THE SOUTHWEST, THE STRONGEST
WINDS WILL LIKE BE IN WESTERN CARBON COUNTY TO AREAS WEST OF CARBON
COUNTY INTO RIVERTON'S CWA.
THE SURFACE LOW THAT DEVELOPS TODAY WILL LEAD TO A COLD FRONT
PUSHING THROUGH THE REGION LATE TONIGHT INTO EARLY TOMORROW MORNING.
THIS FRONT WILL FURTHER ACT TO INCREASE PRECIPITATION CHANCES, WHILE
ALSO DROPPING DAYTIME HIGHS ON TUESDAY INTO THE 40S IN WYOMING AND
LOW-60S IN NEBRASKA. TUESDAY DOES LOOK TO BE THE MORE DYNAMICALLY
ACTIVE DAY FOR THE REGION, AS THE UPPER-LEVEL WESTERN LOW OF THE
OMEGA BLOCK BEGINS TO LIFT TO THE EAST-NORTHEAST ACROSS NORTHERN NEW
MEXICO INTO SOUTHERN COLORADO AND WESTERN KANSAS/OKLAHOMA. WITH THIS
PLACEMENT OF THE LOW, EASTERLY FLOW WILL DEVELOP THROUGHOUT THE
ATMOSPHERE, LEADING TO A CLOUDY AND WET DAY FOR THE CWA. THE WESTERN
LOW AT 700MB WILL MEANDER IN A SIMILAR DIRECTION AS A HIGH DEVELOP
OVER NORTH AND SOUTH DAKOTA. WITH THE ANTICYCLONIC FLOW NORTH OF THE
REGION AND CYCLONIC FLOW SOUTH OF THE REGION, EASTERLY WINDS WILL BE
ENHANCED BETWEEN THE TWO FEATURES, LEADING TO STRONG EASTERLY FLOW
AT 700MB AND NEAR THE SURFACE. STRONG WINDS ARE ONCE AGAIN EXPECTED
THROUGHOUT THE DAY TUESDAY AS A STRONG SURFACE PRESSURE GRADIENT
SETS UP ACROSS THE REGION AND REVERSE CRAIG TO CASPER HEIGHT
GRADIENTS APPROACH 100M. EXPECTING STRONG, EASTERLY FLOW AT THE
SURFACE WITH WINDS POTENTIALLY GUSTING UPWARDS OF 35MPH. STRONG,
EASTERLY FLOW IS NOT AS COMMON HERE AS STRONG WESTERLY FLOW,
THEREFORE, SOME MORE SENSITIVE OUTDOOR FOLIAGE MAY STRUGGLE DURING
THE DAY TUESDAY TO STAY UPRIGHT. HOWEVER, WITH THE MOIST
SOUTHEASTERLY FLOW IN PLACE FOR A FEW DAYS LEADING UP TO TUESDAY,
AMPLE MOISTURE WILL BE AVAILABLE ACROSS EASTERN WYOMING AND WESTERN
NEBRASKA. WITH THE MOIST, UPSLOPE FLOW PRESENT THROUGHOUT MUCH OF
THE ATMOSPHERE, EXPECT A VERY CLOUDY, FOGGY, MISTY, AND RAINY DAY
TUESDAY. SOME MODELS HAVE RAIN DEVELOPING AND BECOMING TRAPPED ALONG
THE EASTERN SLOPE OF THE LARAMIE RANGE, WHICH COULD LEAD TO
SIGNIFICANT RAINFALL FOR THIS REGION. HOWEVER, AS WITH THE OTHER
TRENDS, DECIDED TO DECREASE TOTAL ACCUMULATED PRECIPITATION USING
SLIGHT PERSISTENCE FORECASTING. DID NOT DECREASE TOTALS AS
SIGNIFICANTLY AS MONDAY, BUT DECREASE THEM SEVERAL HUNDREDTHS. MOST
LOCATIONS CURRENTLY FORECAST TO HAVE BETWEEN 0.3 AND 0.6IN OF
PRECIPITATION ACCUMULATION MONDAY THROUGH WEDNESDAY MORNING.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
ISSUED AT 248 AM MDT MON MAY 5 2025
THE OMEGA BLOCK THAT WAS IN PLACE DURING THE BEGINNING OF THE WORK
WEEK WILL BEGIN TO BREAK DOWN ON WEDNESDAY. MOST OF THE HEAVIEST
PRECIPITATION WILL BE DONE BY THIS POINT, BUT LINGERING SHOWERS CAN
BE EXPECTED THROUGHOUT THE DAY WEDNESDAY. CONTINUED EASTERLY FLOW
WILL ALLOW SHOWERS TO PERSIST MAINLY EAST OF THE LARAMIE RANGE,
ALTHOUGH HIGH TERRAIN SHOWERS CANNOT BE RULED OUT EITHER. MODEL
SOUNDINGS SHOW A RATHER LACKLUSTER ENVIRONMENT WITH COOLER
TEMPERATURES, A FEW HUNDRED J/KG OF MUCAPE AND UNIMPRESSIVE LAPSE
RATES. SEVERE STORMS WILL NOT BE LIKELY, BUT A FEW LOCATIONS COULD
HEAR A RUMBLE OF THUNDER OR SEE SMALL HAIL AND GUSTY WINDS.
ADDITIONAL QPF AMOUNTS ON WEDNESDAY WILL BE RELATIVELY LOW ACROSS
MOST OF THE AREA, WITH THE INTERSTATE 80 CORRIDOR BETWEEN CHEYENNE
AND SIDNEY THE MOST LIKELY AREA TO SEE OVER 0.1 INCHES. SHOWER
ACTIVITY WILL DIMINISH OVERNIGHT WEDNESDAY.
CONDITIONS LOOK TO DRY OUT AND WARM UP FOR THE END OF THE WEEK AS AN
UPPER-LEVEL RIDGE BUILDS OVER THE ROCKIES. TEMPERATURES WARM UP TO
ABOVE AVERAGE WITH HIGHS IN THE 60S AND 70S THURSDAY AND FRIDAY,
WITH 80 DEGREE TEMPERATURES POTENTIALLY MAKING A RETURN ON SATURDAY.
MOST LOCATIONS WILL ALSO SEE MOSTLY SUNNY SKIES AS SUBSIDENCE UNDER
THE RIDGE KEEPS CLOUDS AT BAY. HOWEVER, LONG RANGE MODELS DO SUGGEST
PRECIPITATION MAKING A RETURN TO THE AREA LATER IN THE WEEKEND.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 1007 PM MDT SUN MAY 4 2025
SOUTHERLY FLOW ALOFT WILL CONTINUE WITH A WEATHER DISTURBANCE
HELPING TO INCREASE CHANCES FOR SHOWERS AND THUNDERSTORMS ON
MONDAY.
WYOMING TAFS...SCATTERED CLOUDS FROM 10000 TO 15000 WILL PREVAIL
UNTIL 12Z, THEN CEILINGS WILL RANGE FROM 4000 TO 10000 FEET
UNTIL 18Z, THEN CEILINGS WILL RANGE FROM 3500 TO 5000 FEET WITH
SHOWERS REDUCING VISIBILITIES TO 3 MILES UNTIL 01Z, THEN
CEILINGS WILL RANGE FROM 2500 TO 3500 FEET. WINDS WILL GUST TO
35 KNOTS AT LARAMIE AND CHEYENNE, AND TO 25 KNOTS AT RAWLINS
FROM 15Z TO 01Z.
NEBRASKA TAFS...CLEAR SKIES WILL OCCUR UNTIL 15Z, THEN CEILINGS
WILL RANGE FROM 5000 TO 10000 FEET AFTER 15Z, WITH PERIODS OF
SHOWERS AT SCOTTSBLUFF AND SIDNEY FROM 20Z TO 01Z, REDUCING
VISIBILITIES TO 4 MILES. WINDS WILL GUST TO 30 KNOTS AT
SCOTTSBLUFF, SIDNEY AND ALLIANCE UNTIL 01Z, AND WILL GUST TO
25 KNOTS AT CHADRON.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...AM
LONG TERM...SF
AVIATION...RUBIN
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