396
FXUS65 KCYS 091755
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1155 AM MDT THU APR 9 2026
KEY MESSAGES
- MULTIPLE, WEAKER COLD FRONT WILL PUSH THROUGH OVER THE NEXT
COUPLE OF DAYS, LEADING TO SLIGHTLY COOLER TEMPERATURES AND
INCREASING PRECIPITATION CHANCES HEADING INTO THE WEEKEND.
- THE FIRST STRONG THUNDERSTORMS COULD ARRIVE AS EARLY AS
SATURDAY AFTERNOON TO THE WESTERN NEBRASKA PANHANDLE.
SHORT TERM /THROUGH FRIDAY NIGHT/
ISSUED AT 129 AM MDT THU APR 9 2026
ZONAL FLOW RETURNS TO THE REGION FOR THURSDAY AS A BROAD, FLAT
TROUGH MOVES ACROSS CENTRAL CANADA. AN UPPER-LEVEL LOW JUST WEST OF
CALIFORNIA SLOWLY MOVES EASTWARD AND STALLS BRIEFLY TODAY AS A WEAK
RIDGE ATTEMPTS TO DEVELOP OUT AHEAD. MULTIPLE LOBES OF 500MB
VORTICITY WILL EJECT OUT AHEAD OF THE TROUGH, TRAVERSING THROUGH THE
UPPER-LEVEL RIDGE THIS EVENING. WEAK, SYNOPTIC LIFT WILL BE
ASSOCIATED WITH THIS CVA, MAINLY ALONG AND EAST OF THE LARAMIE
RANGE. 700MB FLOW REMAINS LARGELY LIGHT AND ZONAL THROUGH THE
MORNING HOURS BEFORE SHIFTING NORTHERLY THIS AFTERNOON AND EVENING
AS A WEAK COLD FRONT PUSHES THROUGH. WARM AIR ADVECTION WILL DEVELOP
THIS MORNING AND AFTERNOON, ALONG AND EAST OF THE LARAMIE RANGE,
LEADING TO WARMER TEMPERATURES AND SUPPORTING SYNOPTIC ASCENT. WITH
THE COLD FRONT PUSHING THROUGH AND MEETING WAA ACROSS MUCH OF THE
CWA, FOCUSED, MESOSCALE ASCENT IS EXPECTED THIS AFTERNOON ALONG THE
FRONT. PRECIPITATION IS MORE FAVORED TODAY DUE TO PERCEPTIBLE WATER
VALUES INCREASING INTO THE 90TH PERCENTILE, PER THE NAEFS
CLIMATOLOGICAL PERCENTILE, AND AMPLE LIFT ASSOCIATED WITH THE
APPROACHING FRONT. WHILE WIDESPREAD PRECIPITATION IS STILL NOT
EXPECTED, MORE LOCATIONS ARE FAVORED TO SEE AT LEAST A TRACE OF
PRECIPITATION THIS AFTERNOON AND EVENING. INSTABILITY WILL BE FAIRLY
MODEST THIS AFTERNOON, SO STRONG, ORGANIZED STORMS ARE NOT EXPECTED.
ADDITIONALLY, FORECAST RAP SOUNDINGS SUGGEST A STOUT, INVERTED-V
SIGNATURE, SO VERY GUSTY WINDS WILL BE POSSIBLE WITH ANY SHOWERS
THAT DEVELOP TODAY. TEMPERATURES WILL WARM INTO LOW-60S TO MID-70S
BEFORE THE COLD FRONT PUSHES THROUGH THE AFTERNOON. SOUTHERLY TO
SOUTHWESTERLY FLOW IS PROGGED TO RETURN LATE TONIGHT INTO THE EARLY
MORNING HOURS FRIDAY AS THE UPPER-LEVEL TROUGH SLOWLY APPROACHES THE
REGION.
SOUTHWESTERLY FLOW CONTINUES FRIDAY AFTERNOON AS THE UPPER-LEVEL
TROUGH PUSHES INTO THE WESTERN CONUS AND DIGS ACROSS CENTRAL AND
SOUTHERN CALIFORNIA. THE UPPER-LEVEL RIDGE OUT AHEAD OF THE
APPROACHING TROUGH WILL PUSH THROUGH THE CWA BY EARLY AFTERNOON,
LEADING TO SOUTHWESTERLY FLOW THROUGHOUT MUCH OF THE ATMOSPHERE. THE
FETCH OF SOUTHWESTERLY FLOW ORIGINATES OVER THE PACIFIC OCEAN, SO
AMPLE PACIFIC MOISTURE WILL MOVE INTO THE REGION THROUGHOUT THE DAY
TODAY AND INTO THE MORNING AND AFTERNOON HOURS SATURDAY. PW VALUES
ARE PROGGED TO INCREASE ABOVE THE 90TH PERCENTILE, PER THE NAEFS,
ESPECIALLY ACROSS WESTERN NEBRASKA ON FRIDAY. MULTIPLE LOBES OF
500MB VORTICITY WILL CONTINUE TO TRAVERSE ACROSS THE REGION AS THE
EJECT OUT AHEAD OF THE APPROACHING TROUGH. 700MB WARM AIR ADVECTION
INCREASES SIGNIFICANTLY FRIDAY MORNING INTO THE EARLY AFTERNOON
HOURS, WITH EVEN STRONGER WAA EXPECTED OVERNIGHT FRIDAY INTO THE DAY
SATURDAY. WITH A SURFACE HIGH OVER MINNESOTA AND LOWER PRESSURE WEST
OF THE ROCKY MOUNTAINS, A STRONG EAST/WEST SURFACE PRESSURE GRADIENT
WILL DEVELOP BY MIDDAY FRIDAY. AS A RESULT, MOIST, UPSLOPE FLOW IS
EXPECTED EAST OF THE LARAMIE RANGE, INCREASING PRECIPITATION
CHANCES, ESPECIALLY ALONG AND JUST EAST OF THE LARAMIE RANGE.
ISOLATED TO SCATTERED SHOWERS ARE EXPECTED THROUGHOUT THE AFTERNOON
AND EVENING ON FRIDAY. SIGNIFICANT PRECIPITATION TOTALS ARE NOT
ANTICIPATED AT THIS TIME, BUT ANOTHER 0.03 TO 0.10 INCHES OF RAIN IS
POSSIBLE, WITH HIGHER AMOUNTS POSSIBLE UNDER ANY HEAVIER SHOWERS
THAT DEVELOP. TEMPERATURES WILL ONLY INCREASE INTO THE MID-50S TO
MID-60S, WITH THE COOLEST TEMPERATURES EAST OF THE LARAMIE RANGE
WHERE THE COOLER, UPSLOPE FLOW WILL BE ONGOING AS WELL AS INCREASING
CLOUD COVERAGE.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
ISSUED AT 129 AM MDT THU APR 9 2026
NO MAJOR CHANGES TO THE LONGER TERM FORECAST. PLEASE SEE PREVIOUS
DISCUSSION FOR MORE DETAILS.
UNSETTLED WEATHER WILL CONTINUE INTO THE EARLY PART OF NEXT WEEK
ACROSS THE REGION. BY THIS WEEKEND, THE WEATHER PATTERN ON THE
SYNOPTIC SCALE WILL FEATURE A BROAD, STRENGTHENING UPPER LEVEL RIDGE
OVER THE CENTRAL AND EASTERN CONUS, WITH TROUGHING OVER THE WEST
COAST. A SERIES OF UPPER LEVEL SHORTWAVES MOVING THROUGH THE
SOUTHWEST FLOW ALOFT ACROSS THE ROCKIES WILL KEEP PRECIPITATION
CHANCES AND THE POTENTIAL FOR STRONGER WINDS IN THE FORECAST.
FIRST, SATURDAY IS CONTINUING TO BE A DAY TO WATCH FOR THE POTENTIAL
FOR A FEW STRONG THUNDERSTORMS. THE RIDGE AXIS WILL PEAK OVERHEAD ON
SATURDAY BEFORE STARTING TO SHIFT EASTWARD LATER IN THE PERIOD. 700-
MB TEMPERATURES PEAK AROUND +6 TO +8C. LOOK FOR SATURDAY TO BE THE
WARMEST DAY OF THE PERIOD AS A RESULT, WITH WIDESPREAD UPPER 60S TO
70S EXPECTED. A FEW LOW 80S COULD SHOW UP IN THE LOWEST ELEVATIONS
TOO. AT THE SURFACE, WE WILL OPEN UP SATURDAY WITH SOUTH TO
SOUTHEAST FLOW OVER THE HIGH PLAINS AROUND THE PERIPHERY OF A VERY
LARGE SURFACE HIGH PRESSURE SYSTEM POSITIONED WELL TO THE EAST. GULF
MOISTURE ADVECTION LOOKS TO BE EXCELLENT FOR THIS TIME OF YEAR, WITH
DEWPOINTS EXPECTED TO REACH INTO THE LOW 40S FOR ALL ALONG AND EAST
OF I-25. MORNING LOW CLOUDS AND/OR FOG LOOK LIKE A GOOD BET, BUT FOG
WAS NOT ADDED TO THE FORECAST YET SINCE WE ARE STILL A FEW DAYS OUT.
FORECAST SOUNDINGS SHOW A FAIRLY POTENT SUBSIDENT DRY LAYER ON TOP
OF THE SHALLOW SURFACE MOISTURE, WHICH WILL PLAY A ROLE IN THE
POTENTIAL FOR AFTERNOON CONVECTION. BROAD SOUTHWEST FLOW ALOFT WILL
SUPPORT LEE CYCLOGENESIS ACROSS CENTRAL WYOMING DURING THE DAY ON
SATURDAY. AS THIS ADVANCES EASTWARD, WE SHOULD SEE THE DRYLINE WHICH
WILL BE POSITIONED ALONG THE LARAMIE RANGE MOVE EASTWARD THROUGH THE
DAY. HOW FAR THE MOISTURE RETREATS TO THE EAST WILL BE THE MAIN
UNCERTAINTY CONCERNING THUNDERSTORM POTENTIAL. AN APPROACHING VORT-
MAX WILL ENHANCE SYNOPTIC LIFT DURING THE AFTERNOON AND EVENING
HOURS, WHICH SHOULD KICK OFF SOME SCATTERED PM SHOWERS AND ISOLATED
THUNDERSTORMS. THE RIGHT BALANCE BETWEEN THE CAPPING INVERSION
WEAKENING, AND THE BOUNDARY LAYER NOT DRYING OUT TOO MUCH WILL NEED
TO BE STRUCK IN ORDER TO GET MORE ORGANIZED THUNDERSTORM POTENTIAL.
THIS IS POSSIBLE, BUT FAR FROM A GUARANTEE. WITH GOOD VERTICAL WIND
SHEAR IN PLACE, A FEW STRONG THUNDERSTORMS WILL BE POSSIBLE, BUT
UNCERTAINTY IS CONSIDERABLE AT THIS LEAD TIME.
SUNDAY WILL BE A FEW DEGREES COOLER THAN SATURDAY BEHIND THE INITIAL
SHORTWAVE TROUGH ALOFT. THERE WILL STILL BE A CHANCE FOR PM SHOWERS
AND THUNDERSTORMS, BUT COVERAGE AND INTENSITY LOOKS TO BE MORE
LIMITED. THERE WILL ALSO BE A SHORT WINDOW FOR HIGH WINDS IN THE
WIND PRONE AREAS SATURDAY NIGHT INTO SUNDAY MORNING AS WE SEE A
BRIEF SURGE IN 700-MB HEIGHT GRADIENTS AND WINDS BEHIND THE
DEPARTING VORT-MAX. LOW-LEVEL MOISTURE WILL BE REDUCED SIGNIFICANTLY
FOR SUNDAY, SUCH THAT ELEVATED TO NEAR CRITICAL FIRE WEATHER
CONCERNS MAY RETURN TO THE PICTURE TOO. PRECIPITATION CHANCES WILL
INCREASE AGAIN MONDAY INTO WEDNESDAY NEXT WEEK AS THE BROAD UPPER
LEVEL LOW OVER THE WEST COAST FINALLY MOVES INLAND. WHILE THERE IS
GOOD AGREEMENT ON THE OVERALL SYNOPTIC EVOLUTION, THE DEVIL IS IN
THE DETAILS. THE EXACT TRACK AND STRENGTH OF THE UPPER LEVEL LOW
COMBINED WITH THE POTENTIAL FOR INTERFERENCE FROM OTHER SHORTWAVE
TROUGHS EITHER EJECTING AHEAD OF THE MAIN SYSTEM OR RIDING TO THE
NORTH WILL DETERMINE PRECIPITATION AMOUNTS. UNFORTUNATELY FOR OUR
DROUGHT STRICKEN AREA, THE PROBABILITY FOR SIGNIFICANT, WIDESPREAD
RAINFALL OR SNOWFALL CONTINUES TO DECREASE. WHILE THE DETERMINISTIC
ECMWF CONTINUES TO SHOW A PROMISING TRACK WITH PLENTIFUL
PRECIPITATION, IT APPEARS TO BE AN OUTLIER AMONGST ITS OWN ENSEMBLE
SYSTEM. CLUSTER ANALYSIS SUGGESTS THAT THE PROBABILITY OF A SYSTEM
CAPABLE OF MEANINGFULLY IMPROVING THE DROUGHT (0.5" OR MORE OVER A
LARGE AREA) IS ONLY AROUND 10 TO 20% PER THE LREF. DEPENDING ON THE
EXACT TRACK OF THE UPPER LEVEL LOW, THERE WILL ALSO BE A POTENTIAL
FOR HIGH WINDS IN THE WIND PRONE AREAS DURING THIS PERIOD.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 1146 AM MDT THU APR 9 2026
THE WIND DIRECTION WILL CONTINUE TO ROTATE ALL THROUGH THE
COMPASS OVER THE TAF PERIOD, ESPECIALLY OVER THE PLAINS. A
BACKDOOR COLD FRONT PUSHING IN FROM THE NORTHEAST WILL TURN
WINDS NORTH TO NORTHEAST OVER THE PLAINS OVER THE COURSE OF THE
AFTERNOON. IN ADDITION, WIDELY SCATTERED SHOWERS WILL DEVELOP
ALONG THE I-80 CORRIDOR. THESE WILL BRING THE POTENTIAL FOR
GUSTY AND ERRATIC WINDS AND A FEW RUMBLES OF THUNDER, BUT THE
PROBABILITY OF A DECREASE IN FLIGHT CATEGORY IS LOW.
WINDS WILL THEN GRADUALLY WEAKEN AND TURN EAST, AND
THEN SOUTHEAST THROUGH THE EVENING AND OVERNIGHT HOURS. MOISTURE
ADVECTION FRIDAY MORNING WILL INCREASE THE CHANCE FOR CIG
REDUCTIONS. CYS HAS AN 80% CHANCE OF MVFR AND 50% OF IFR CIGS.
PROBABILITIES ARE AROUND 30 TO 50% FOR MVFR AT SNY, AIA, AND
BFF.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...AM
LONG TERM...MN/AM
AVIATION...MN
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