839
FXUS65 KCYS 022355
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
555 PM MDT SAT MAY 2 2026
KEY MESSAGES
- WARMER AND DRIER WEATHER WILL CONTINUE THROUGH SUNDAY, LEADING
TO NEAR CRITICAL FIRE WEATHER CONDITIONS.
- THE POTENTIAL FOR COOL TEMPERATURES AND WIDESPREAD
PRECIPITATION CONTINUES TO INCREASE FOR MONDAY AFTERNOON
THROUGH WEDNESDAY MORNING. THUNDERSTORMS, BENEFICIAL RAINFALL,
AND ACCUMULATING SNOW ARE ALL POSSIBLE, BUT THE DETAILS ARE
STILL UNCERTAIN.
- DRIER, WARMER, AND WINDIER WEATHER RETURNS TO THE AREA FOR THE
SECOND HALF OF THE WORK WEEK.
SHORT TERM /THROUGH MONDAY/
ISSUED AT 350 PM MDT SAT MAY 2 2026
AN UPPER LEVEL RIDGE IS PASSING OVERHEAD THIS AFTERNOON AND
MOVING SOUTHEAST, ALLOWING FOR CLEAR SKIES APART FROM SOME
CIRRUS CLOUDS. DAYTIME HEATING WILL PROMOTE DEEP MIXING OF THE
NEAR SURFACE BOUNDARY LAYER AND WILL DROP RELATIVE HUMIDITY
VALUES INTO THE LOW TEENS AND SINGLE DIGITS FOR LOCATIONS EAST
OF THE LARAMIE RANGE. RECENT OBSERVATIONS FROM THE DOUGLAS TO
CHADRON CORRIDOR HAVE OBSERVED FREQUENT WIND GUSTS UP TO 25-30
MPH AND RH VALUES IN THE LOW TEENS. WITH THE OVER PERFORMING
WINDS AND HUMIDITY VALUES EXPECTED TO KEEP DECREASING THROUGH
THE AFTERNOON, WE HAVE ELECTED TO ISSUE A RED FLAG WARNING FOR
OUR NORTHERN CWA FIRE ZONES THROUGH 8 PM. ELSEWHERE, EAST OF THE
LARAMIE RANGE, INFREQUENT WIND GUSTS UP TO 25 MPH WILL PRECLUDE
CRITICAL FIRE WEATHER CONDITIONS. CONDITIONS STILL REMAIN
ELEVATED GIVEN THE VERY DRY HUMIDITY VALUES. A WEAK COLD FRONT
IS EXPECTED TO START MOVING INTO THE AREA THIS EVENING, BRINGING
WITH IT SLIGHTLY HIGHER RH VALUES AND A WIND SHIFT OUT OF THE
NORTH-NORTHEAST.
SUNDAY APPEARS TO BE SLIGHTLY COOLER WITH THE PASSAGE OF THE WEAK
FRONTAL BOUNDARY AND INCREASED CLOUDINESS FROM AN UPPER LEVEL
LOW MOVING OVER THE PACIFIC COAST. THE MORNING STARTS OFF COOL,
WITH MOST PLACES IN THE UPPER TO LOWER 30S. THE INCREASING MID
LEVEL MOISTURE CONTRIBUTED BY THE PACIFIC SYSTEM WILL HELP
SUPPORT A FEW SHOWERS AND THUNDERSTORMS IN THE AFTERNOON HOURS,
PARTICULARLY IN OUR NORTHERN CWA COUNTIES. THE RIGHT ENTRANCE
REGION OF A 500 MBAR JET STREAK ALONG WITH THE PASSAGE OF A WEAK
SHORTWAVE TROUGH WILL HELP PROVIDE LIFT FOR THESE STORMS.
MUCAPE VALUES RANGE FROM 500-700 IN MOST HIGH RESOLUTION
GUIDANCE. AN INVERTED-V SOUNDING WILL FAVOR HIGH BASED SHOWERS
AND STORMS. WITH THE PROPENSITY FOR DRY AIR ENTRAINMENT OF THE
DOWNDRAFT THESE SHOWERS AND STORMS WILL BE ON THE DRY SIDE.
GUSTY WINDS AND LIGHTNING ARE POSSIBLE. AN ISOLATED STORM OR TWO
MAY DEVELOP FURTHER SOUTH FROM LARAMIE COUNTY EAST TO CHEYENNE
CO., HOWEVER GIVEN THE EVEN DRIER CONDITIONS, ANY MEASURABLE
RAINFALL IS UNLIKELY. RELATIVE HUMIDITY VALUES ARE EXPECTED TO
BE LOW AGAIN SUNDAY WITH WIDESPREAD MINIMUMS IN THE LOW 20S DOWN
TO 15%. WINDS APPEAR TO BE LIGHT AND VARIABLE, SO NO CRITICAL
FIRE CONDITIONS ARE ANTICIPATED, THOUGH CONDITIONS REMAIN
ELEVATED.
MONDAY THE PACIFIC SYSTEM STARTS TO MAKE ITS WAY EAST INTO THE
SOUTHWEST AND TURN NORTHEASTWARD. THE POSITIVELY TILTED TROUGH
BECOMES ELONGATED AS IT BEGINS TO MERGE WITH THE TROUGH OVER
CANADA WITH THE AXIS OF THE TROUGH CENTERED OVERHEAD. A
VORTICITY MAXIMUM ON THE WESTERN PERIPHERY OF THE NORTH TROUGH
WILL PROVIDE THE MAJORITY OF LIFT AND MOSITURE FOR A PERIOD OF
UNSETTLED WEATHER STARTING MONDAY AFTERNOON. AT THE SURFACE A
STRONG COLD FRONT WILL BE MOVING SOUTH OUT OF CANADA. ALONG AND
BEHIND THIS FRONT WILL BE THE FOCUS OF WIDESPREAD SHOWERS AND
THUNDERSTORMS. POPS ARE AROUND 40-70% FOR A GOOD AMOUNT OF THE
AREA IN THE AFTERNOON, WITH GREATER COVERAGES IN OUR WESTERN
AREAS. AHEAD OF THE COLD FRONT, AND WEST OF THE LARAMIE RANGE,
STEEP 0-3 KM LAPSE RATES AND MARGINAL EBWD MAY SUPPORT A FEW
STRONG STORMS CAPABLE OF SMALL HAIL AND GUSTY WINDS.
LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
ISSUED AT 350 PM MDT SAT MAY 2 2026
TEMPERATURES WILL CONTINUE
TO DROP THROUGH THIS PERIOD AHEAD OF ANOTHER VORT-MAX DROPPING DOWN
FROM THE NORTH WHICH SHOULD ARRIVE TUESDAY AFTERNOON OR EVENING.
MODELS ARE NOW IN FAIRLY GOOD AGREEMENT SHOWING THE CLOSED LOW OVER
THE SOUTHWEST GETTING ABSORBED BY THE PARENT TROUGH TUESDAY NIGHT
INTO WEDNESDAY MORNING. IN TERMS OF OUR OUTCOME ON THE GROUND, WE
SHOULD SEE SNOW LEVELS STARTING OFF AROUND 9 TO 10 KFT MONDAY
AFTERNOON, BUT THIS WILL RAPIDLY DROP OVERNIGHT AND THROUGH THE DAY
TUESDAY. THE LATEST LREF HAS 700-MB TEMPERATURES DOWN TO -4C OVER
CHEYENNE BY DAYBREAK TUESDAY, WITH HIGH CONFIDENCE IN VALUES BETWEEN
-5 AND -8C DURING MOST OF THE DAYTIME HOURS TUESDAY AND INTO
WEDNESDAY MORNING. THIS WOULD BE COLD ENOUGH TO RAIN CHANGING TO OR
MIXING WITH SNOW FOR THE ENTIRE AREA. THERE IS STILL A BIT OF
UNCERTAINTY IN THE TIMING. IF MOST OF THE SNOW FALLS DURING THE DAY,
THE SNOW ACCUMULATION EXPECTATIONS WILL BE CONSIDERABLY LESS DUE TO
THE VERY STRONG EARLY MAY SUN, WHEREAS SNOWFALL AT NIGHT WOULD BE
MUCH MORE LIKELY TO ACCUMULATE. AS A RESULT, WE WON'T GET INTO TOO
MUCH DETAIL ON THE POTENTIAL SNOWFALL AMOUNTS. THE CURRENT MOST
LIKELY SCENARIO WOULD MEAN ACCUMULATING SNOW ABOVE ABOUT 5500 FT IN
ELEVATION. THE 12Z LREF CLUSTERS HAVE TRENDED THE HIGHEST
PROBABILITIES FOR PRECIPITATION FURTHER SOUTH ONTO THE COLORADO SIDE
OF THE BORDER. CHEYENNE NOW HAS A 60-70 PERCENT CHANCE FOR GREATER
THAN 0.5 INCHES OF PRECIPITATION AND SCOTTSBLUFF HAS A 20 TO 30
PERCENT CHANCE. THE CURRENT FORECAST HAS STILL BEEN TRENDED TOWARDS
THE 25TH PERCENTILE AS THEIR IS STILL VARIABILITY IN THE STORM TRACK
AND PREVIOUS STORMS FIZZLED OUT AND NOT BEING ABLE TO OVERCOME OUR
STOUT DRY LAYER NEAR THE SURFACE. A FEW RAIN AND SNOW SHOWERS MAY
LINGER INTO WEDNESDAY WITH TEMPERATURES REMAINING 10 TO 15F BELOW
SEASONAL AVERAGES. RIDGING WILL BUILD BACK INTO THE WESTERN CONUS
FOR THE END OF THE UPCOMING WORK WEEK. WE MAY SEE A PERIOD OF WINDY
CONDITIONS WEDNESDAY NIGHT THROUGH THURSDAY AS THIS TRANSITION
OCCURS. CURRENT PROBABILITIES FOR HIGH WINDS IN THE WIND PRONE AREAS
ARE AROUND 20 TO 40%. WARM AIR ADVECTION WILL RETURN QUICKLY DURING
THIS PERIOD AS WELL. WE SHOULD SEE TEMPERATURES CLIMB BACK TO NEAR
SEASONAL AVERAGES ON THURSDAY, AND THEN ABOVE AVERAGE BY FRIDAY.
AVIATION /00Z TAFS THROUGH 00Z MONDAY/
ISSUED AT 541 PM MDT SAT MAY 2 2026
CLEAR TO PARTLY CLOUDY SKIES SHOULD ALLOW VFR CONDITIONS AT ALL
TERMINALS THROUGH THE EVENING, WITH SOME LOWERING IN CEILINGS
POSSIBLE AS MOISTURE STARTS STREAMING IN FROM THE SYSTEMS TO OUR
NORTHWEST. A WEAK COLD FRONT WILL DROP SOUTH OVER MOST TERMINALS
EXCEPT KRWL OVERNIGHT. A WIND SHIFT FROM THE NORTH-NORTHEAST IS
ANTICIPATED WITH THIS FRONT WITH SLIGHTLY LOWER CEILINGS TO
AROUND 10 KFT. A VERY SHALLOW INVERSION IS POSSIBLE WITH THIS
FRONT, HOWEVER WINDS ALOFT ARE NOT PARTICULARLY STRONG. SUNDAY
AFTERNOON SOME THUNDERSTORMS ARE POSSIBLE FOR KBFF, KCDR, AND
KAIA. THESE STORMS ARE SCATTERED IN NATURE. IF ONE APPROACHES
THE VICINITY OF A TERMINAL ONE CAN EXPECT LIGHTNING AND GUSTY
VARIABLE WINDS. SOME HIGH RESOLUTION MODELS ARE SUGGESTING
GUSTS ABOVE 40 KNOTS ARE POSSIBLE ON THE ADVANCING SIDE OF THESE
STORMS HIGHLIGHTING A DRY MICROBURST POTENTIAL.
CYS WATCHES/WARNINGS/ADVISORIES
WY...RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING FOR WYZ417-418.
NE...RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING FOR NEZ434-435.
SHORT TERM...RV
LONG TERM...MN/MM
AVIATION...RV
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