460
FXUS65 KCYS 050414
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1014 PM MDT SUN MAY 4 2025
KEY MESSAGES
- PATTERN CHANGE TODAY AS AN OMEGA BLOCK TAKES HOLD ACROSS THE CENTRAL
CONUS. INCREASING PRECIPITATION CHANCES THROUGH THE WEEK.
- STRONG WINDS POSSIBLE ACROSS THE EASTERN PORTIONS OF THE
REGION TODAY AS A STRONG PRESSURE GRADIENT SETS UP.
- UNSETTLED WEATHER WITH SOAKING RAINS ON TUESDAY.
- DRYING CONDITIONS BY LATE-WEEK WITH TEMPERATURES RETURNING TO
ABOVE-NORMAL VALUES.
SHORT TERM /THROUGH MONDAY NIGHT/
ISSUED AT 201 PM MDT SUN MAY 4 2025
AFTERNOON SATELLITE AND RADAR SHOWS SCATTERED CONVECTION AND
SOME THUNDERSTORM ACTIVITY GOING UP ACROSS PORTIONS OF CARBON
AND ALBANY COUNTIES. ENVIRONMENTAL ANALYSIS SHOWS LIMITED
INSTABILITY WITH MUCAPE AROUND 500 J/KG OR LESS WHILE PWAT
VALUES OF 0.3-0.4IN ARE NOTED, SO MOST OF THIS ACTIVITY SHOULD
ONLY PRODUCE SPORADIC SHOWERS WITH LIMITED RAINFALL AS MOISTURE
REMAINS STUNTED ACROSS THE REGION, AND STRONGER MORE SEVERE
ACTIVITY UNLIKELY. MEANWHILE MODEST PRESSURE GRADIENTS HAVE
PROMOTED BREEZY WINDS TODAY WITH GUSTS IN THE 25-45 KNOT RANGE
FOR THE MOST PART, ALTHOUGH SOME FAVORABLE DOWNSLOPING DID
PRODUCE A FEW STRONGER GUSTS AT CHADRON JUST BEFORE THE
AFTERNOON. THESE BREEZY WINDS SHOULD DECLINE AS THE SUN SETS
OUTSIDE OF THE NORTHERN NE PANHANDLE WHERE A NOCTURNAL JET
SHOULD FUEL STRONGER GUSTS THROUGH THE EVENING AND OVERNIGHT BEFORE
WINDS FINALLY CALM BRIEFLY DURING THE EARLY MORNING HOURS ON
TUESDAY.
INTO MONDAY, THE UPPER LOW IN THE WESTERN US WILL CONTINUE TO
SHIFT EASTWARDS AND SIT OVER THE FOUR CORNERS REGION WITH THE
CENTER JUST SHIFTED JUST SOUTH MORE INTO THE DESERT SOUTHWEST.
THIS SHOULD STILL PROMOTE SCATTERED SHOWERS AND THUNDERSTORMS
FOR THE DAY ACROSS MOST OF THE REGION ALONGSIDE A COLD FRONT
THAT WILL BE DRAPED OVER THE NORTHWESTERN EDGE OF THE CWA
DURING THE MORNING AND WILL MOVE ACROSS THROUGH THE END OF THE
DAY. ANALYSIS SHOWS MODEST INSTABILITY ONCE AGAIN, GENERALLY
AROUND 500 J/KG ONCE AGAIN, BUT PWAT VALUES SHOULD AT LEAST RISE
A LITTLE FURTHER INTO THE 0.5-0.8IN RANGE, PROMOTING A BIT MORE
MOISTURE THAN TODAY'S ACTIVITY. AND WITH THE UPPER LEVEL SUPPORT
PRODUCING MORE LIFT, ACTIVITY WILL BE MORE WIDESPREAD AND NOT
LIMITED TO THE WESTERN PART OF THE CWA. HEAVIEST QPF CURRENTLY
LOOKS TO BE CENTERED ACROSS THE NORTHERN PORTIONS OF THE CWA IN
WYOMING WHERE STRONGER PWAT VALUES ALONGSIDE FRONTOGENIC FORCING
AND UPSLOPE SHOULD CONTRIBUTE TO AREAS OF STRONGER SHOWER AND
THUNDERSTORM ACTIVITY. AND ACROSS THE WHOLE CWA, A STRONGER
THUNDERSTORM WITH SOME MEAGER HAIL OR WINDS CANNOT BE COMPLETELY
RULED OUT FOR THE DAY, BUT WIDESPREAD STRONGER THUNDERSTORMS
ARE UNLIKELY. FINALLY, BREEZY CONDITIONS LIKELY ONCE AGAIN UNDER
THE ENHANCED PRESSURE GRADIENT AND A MODEST LOW-LEVEL JET,
PROMOTING WIDESPREAD GUSTS IN THE 25-40 KNOT RANGE YET AGAIN.
LONG TERM /TUESDAY THROUGH SUNDAY/
ISSUED AT 201 PM MDT SUN MAY 4 2025
AN UPPER-LEVEL LOW PRESSURE SYSTEM LOCATED OVER THE SOUTHERN
ROCKIES/SOUTHERN GREAT PLAINS WILL RESULT IN EASTERLY UPSLOPE FLOW
OVER SOUTHEAST WYOMING AND WESTERN NEBRASKA ON TUESDAY. FORECAST
GUIDANCE APPEARS TO HAVE COME INTO BETTER AGREEMENT IN TODAY'S 12Z
MODEL CYCLES INDICATING THE POTENTIAL FOR NOTABLE QPF OVER OUR
REGION OUT OF THIS SYSTEM, ESPECIALLY IN THE HIGHER TERRAIN OF
SOUTHEAST WYOMING. ENSEMBLE GUIDANCE GENERALLY SUPPORTS AT LEAST
0.5" OF RAIN IN THE CYS AREA NOW ON TUESDAY THROUGH TUESDAY NIGHT,
WITH UPWARDS OF 1" OF QPF LIKELY FOR THE LARAMIE RANGE AND SNOWY
RANGE THROUGH THIS TIMEFRAME. GIVEN COOLER TEMPERATURES ALOFT, SNOW
LEVELS WILL LIKELY DROP TO AROUND 8500' DURING THE EVENING HOURS
TUESDAY, RESULTING IN AT LEAST 6 INCHES OF SNOW IN THE SNOWY RANGE
ABOVE 9000' FROM THIS SYSTEM. A WINTER WEATHER ADVISORY MAY BE
NEEDED IN SUBSEQUENT FORECAST PACKAGES TO ADDRESS THIS LATE-SEASON
SNOW EVENT. RAIN MAY MIX WITH AND CHANGE TO SNOW IN THE HIGHEST
ELEVATIONS OF THE SOUTHERN LARAMIE RANGE AROUND THE I-80 SUMMIT AS
WELL, HOWEVER IMPACTS WILL BE QUITE LIMITED WITH WARM ROAD
TEMPERATURES EXPECTED.
EAST TO SOUTHEASTERLY UPSLOPE FLOW WILL CONTINUE ON WEDNESDAY HOWEVER
PRECIPITATION WILL BE MUCH MORE SCATTERED AS THE UPPER-LEVEL LOW
PRESSURE SYSTEM OVER THE SOUTHERN PLAINS BECOMES MORE VERTICALLY
STACKED AND DEAMPLIFIES. EXPECT LINGERING SHOWERS MOVING FROM EAST
TO WEST TO BRING AN ADDITIONAL 0.1 TO 0.2 INCHES OF RAIN FROM THE
LARAMIE RANGE EASTWARD THROUGHOUT THE DAY. HIGHER-RES GUIDANCE SUCH
AS THE NAM/RRFS INDICATE A BIT MORE POTENT SHOWER ACTIVITY WITH
MARGINAL INSTABILITY DEVELOPING BETWEEN BREAKS IN CLOUDS ON
WEDNESDAY AFTERNOON. ISOLATED LOCATIONS MAY SEE HIGHER AMOUNTS OF
RAINFALL THAN THE GENERAL TENTH TO TWO TENTHS AVERAGE ACROSS THE
AREA.
BY THURSDAY THIS SLOW-MOVING STORM SYSTEM WILL FINALLY DISSIPATE
WELL EAST IN THE SOUTHERN GREAT PLAINS. WEAK RIDGING WILL BEGIN TO
DEVELOP OVER THE SOUTHWESTERN CONUS LATER ON THURSDAY, LASTING
THROUGH FRIDAY AND EARLY NEXT WEEKEND. HOWEVER, SOUTHEAST WYOMING
AND WESTERN NEBRASKA WILL REMAIN ONLY ON THE EASTERN PERIPHERY OF
THIS RIDGE. ISOLATED TO SCATTERED AFTERNOON SHOWERS AND WEAK
THUNDERSTORMS ARE LIKELY EACH DAY, GENERALLY TIED TO THE HIGHER
TERRAIN AS SOME LINGERING MOISTURE IN THE MID-LEVELS TRAVERSES THE
RIDGE AND SPILLS OVER INTO THE HIGH PLAINS. WE ARE NOT EXPECTING
MUCH IN THE WAY OF ACCUMULATING RAIN OR SNOW FROM THESE DAILY SHOWER
EVENTS, HOWEVER LOCALIZED AREAS COULD PICK UP A TENTH OF AN INCH OR
SO PER GENERAL ENSEMBLE AVERAGES.
AFTER A COOL START TO THE WEEK WITH TEMPERATURES WELL-BELOW AVERAGE,
EXPECT REBOUNDING AFTERNOON HIGHS THROUGHOUT THE REMAINDER OF THE
WEEK. BY THURSDAY, MOST LOCATIONS WILL RETURN TO AROUND AVERAGE FOR
EARLY MAY, WITH TEMPS AROUND 5-10 DEGREES ABOVE AVERAGE BY FRIDAY
AND SATURDAY. FORECAST CONFIDENCE IS MODERATE TO HIGH THROUGHOUT THE
LONG-TERM PERIOD.
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...CG
LONG TERM...MAC
AVIATION...RUBIN
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