047
FXUS65 KCYS 171958
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
158 PM MDT MON AUG 17 2026
KEY MESSAGES
- THERE IS A MARGINAL RISK (LEVEL 1 OF 5) OF SEVERE WEATHER FOR
THE NEBRASKA PANHANDLE TODAY.
- THERE IS ANOTHER MARGINAL RISK (LEVEL 1 OF 5) FOR TUESDAY
AFTERNOON COVERING THE MAJORITY OF THE FORECAST AREA.
- SEASONABLE TEMPERATURES AND CHANCES FOR SCATTERED PM SHOWERS AND
THUNDERSTORMS CONTINUE THROUGH WEDNESDAY.
- WARMER AND DRIER WEATHER WILL RETURN TO THE AREA THURSDAY AND
FRIDAY.
SHORT TERM /THROUGH TUESDAY NIGHT/
ISSUED AT 155 PM MDT MON AUG 17 2026
AS THE UPPER-LEVEL RIDGE ATTEMPTS TO STRENGTHEN THROUGHOUT THE DAY,
A LOW PRESSURE SYSTEM WILL BE MOVING ACROSS THE CANADIAN
PROVIDENCES. THE TROUGH CREATED BY THE SYSTEM WILL BE MOVING THE
INTERMOUNTAIN WEST MONDAY AND TUESDAY. FOR TODAY OUR WESTERLY FLOW
WILL CONTINUE TO DRY OUT THE LOWER LEVELS ALONG AND EAST OF THE I-25
CORRIDOR SEVERELY LIMITING TODAYS SHOWER POTENTIAL FOR SOUTHEAST
WYOMING. THE NEBRASKA PANHANDLE WILL BE SLIGHTLY CAPPED THROUGH THE
MORNING ALLOWING FOR ENHANCED MOISTURE RETENTION COMPARED TO
WYOMING. AS THE DRYLINE PUSHES EASTWARD, IT WILL LEAD TO FORCING FOR
WESTERN NEBRASKA. WITH RESIDUAL MOISTURE AND SUPPORT FROM 500MB
VORTICITY MAXIMA, SHOWERS AND STORMS ARE ANTICIPATED TO DEVELOP THIS
AFTERNOON. MLCAPE VALUES INCREASE THIS AFTERNOON TO AROUND 1000 TO
1500 J/KG IN WESTERN NEBRASKA. FORECAST SOUNDINGS FROM THE RAP
SUGGEST STOUT INVERTED-V SIGNATURES WEST OF THE DRYLINE ACROSS
SOUTHEAST WYOMING, WITH MORE FAVORABLE SEVERE SOUNDINGS IN WESTERN
NEBRASKA, THOUGH STILL WILL SUBSTANTIAL DCAPE VALUES. THE STORM
PREDICTION CENTER (SPC) HAS COVERED MUCH OF THE NEBRASKA PANHANDLE
IN A MARGINAL RISK (LEVEL 1 OF 5) MOSTLY FOR SEVERE WIND AND THE
POSSIBILITY OF HAIL GREATER THAN 1 INCH. MULTIPLE LOBES OF 500MB
VORTICITY CONTINUE TO TREK ACROSS THE REGION TUESDAY AFTERNOON INTO
THE OVERNIGHT HOURS, DUE TO INCREASED VORTICITY FROM THE PROXIMITY
OF THE UPPER-LEVEL TROUGH. THE SLIGHTLY COMPRESSED HEIGHT GRADIENT
WILL LEAD TO MORE SHEAR ACROSS THE REGION, WITH STRONG 700MB WARM
AIR ADVECTION ALLOWING INCREASED FORCING. THE TERRAIN-INDUCED
DRYLINE WILL RETREAT WESTWARD TUESDAY AFTERNOON, ALLOWING STRONGER
MOISTURE ADVECTION ALONG AND EAST OF THE LARAMIE RANGE, SETTING UP
ANOTHER DAY WITH INCREASED PRECIPITATION CHANCES. WITH STRONGER
FORCING, INCREASED MOISTURE, AND INCREASED SHEAR IN THE REGION,
STORMS WILL HAVE A BETTER CHANCE OF BECOMING SEVERE ON TUESDAY, WITH
LARGE HAIL AND DAMAGING WINDS POSSIBLE ONCE MORE. SPC HAS EXPANDED
THE MARGINAL RISK (LEVEL 1 OUT OF 5) TO INCLUDE MAJORITY OF THE
FORECAST AREA.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
ISSUED AT 155 PM MDT MON AUG 17 2026
GLOBAL MODEL GUIDANCE HAS TRENDED FASTER IN AMPLIFYING THE UPPER
LEVEL RIDGE OVER THE WESTERN CONUS AND TRANSITIONING OUR AREA TO A
NORTHWEST FLOW PATTERN. AS A RESULT OF THIS TREND, THE SHORTWAVE
TROUGH RIDING ON THE BACK EDGE OF THE ZONAL FLOW PATTERN HAS
ACCELERATED FROM A WEDNESDAY PM ARRIVAL TO A WEDNESDAY AM ARRIVAL.
DRIER AIR AND MORE SUBSIDENCE IN THE WAKE OF THIS FEATURE HAS
MODIFIED THE FORECAST FOR WEDNESDAY SOMEWHAT BY PUSHING THE MOISTURE
OUT FASTER. WHAT LOOKED LIKE A POTENTIALLY POTENT SEVERE WEATHER
SETUP YESTERDAY HAS NOW BEEN NUDGED FURTHER TO THE SOUTHEAST, SUCH
THAT STORM CHANCES ARE REDUCED FOR THE MAJORITY OF THE AREA. THERE
IS STILL THE POTENTIAL FOR A FEW ISOLATED STRONG TO SEVERE STORMS IN
THE EASTERN AND SOUTHEASTERN PORTIONS OF THE FORECAST AREA, BUT LOOK
FOR A DRIER DAY THAN PREVIOUSLY ANTICIPATED ALONG AND WEST OF A
CHEYENNE TO HARRISON LINE.
THIS ALSO ACCELERATES THE ONSET OF THE NEXT ROUND OF HOT
TEMPERATURES AS RIDGING BUILDS IN TO OUR WEST. EXPECT HIGHS TO CLIMB
A FEW DEGREES ABOVE AVERAGE ON WEDNESDAY, THEN 5 TO 10 DEGREES ABOVE
FOR THURSDAY THROUGH SATURDAY. WE PROBABLY WON'T BE TOTALLY DRY ON
THURSDAY AND FRIDAY, BUT EXPECT PM CONVECTION TO BE MUCH MORE
LIMITED AND LIKELY CONFINED TO AREAS IN OR NEAR THE HIGHER TERRAIN
OF SOUTHERN WYOMING. ATTENTION WILL SHIFT BACK TO FIRE WEATHER
DURING THIS PERIOD AS WELL. WESTERLY WINDS MOVING INTO THE AREA
BEHIND WEDNESDAY'S SHORTWAVE TROUGH WILL LEAD TO AT LEAST ELEVATED,
IF NOT CRITICAL, FIRE WEATHER CONDITIONS ALONG AND WEST OF THE
LARAMIE RANGE. THE WINDS APPEAR A LITTLE LIGHTER FOR THURSDAY AND
FRIDAY, BUT MODEL GUIDANCE HAS BEEN CONSISTENTLY TOO LOW ON WINDS IN
CARBON AND ALBANY COUNTIES LATELY.
THE UPPER LEVEL RIDGE WILL VERY GRADUALLY SHIFT EASTWARD OVER THE
COURSE OF THE WEEK, SLIDING EAST OF THE FOUR CORNERS BY THE WEEKEND.
THIS WILL ALLOW A FRESH TAP OF MONSOON MOISTURE TO BE PULLED
NORTHWARD INTO THE GREAT BASIN AND FOUR CORNERS STATES, EVENTUALLY
WORKING ITS WAY OVER THE TOP OF THE RIDGE AND INTO OUR AREA. AS A
RESULT, LOOK FOR INCREASED COVERAGE OF PM SHOWER AND THUNDERSTORM
ACTIVITY FOR THE WEEKEND WITH TEMPERATURES REMAINING ABOUT 5 TO 10
DEGREES ABOVE SEASONAL AVERAGES.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 1210 PM MDT MON AUG 17 2026
A FEW ISOLATED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ONCE
AGAIN THIS AFTERNOON AND EVENING, BUT OVERALL COVERAGE WILL BE
LOWER THAN THE LAST SEVERAL DAYS. THE MAIN CONCERN TODAY WILL BE
GUSTY OUTFLOW WINDS, THOUGH A BRIEF VIS DROP IN HEAVY RAINFALL
REMAINS POSSIBLE. PROB30 GROUPS ARE INTRODUCED FOR MOST
TERMINALS AS CONFIDENCE REMAINS LOW IN TIMING AND EXACT LOCATION
OF THIS ACTIVITY.
OVERNIGHT WINDS WILL BE ALL OVER THE PLACE AS LARGE-SCALE FLOW
REMAINS WEEK, BUT OUTFLOW BOUNDARIES FROM DISTANT SHOWERS AND
THUNDERSTORMS MAY TRAVEL FAR AWAY FROM THEIR SOURCE AND REACH
OUR AREA. THERE IS LOW CONFIDENCE IN THE DIRECTION, AND
SEVERAL SITES MAY GO VARIABLE. A FEW STRONGER GUSTS ARE POSSIBLE
DEPENDING ON THE AFOREMENTIONED OUTFLOWS, BUT CONFIDENCE WAS
TOO LOW TO ADD TO THE TAF.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...MM
LONG TERM...MN
AVIATION...MN
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