335
FXUS65 KCYS 221152
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
552 AM MDT FRI AUG 22 2025
KEY MESSAGES
- A MARGINAL RISK (1 OF 5) OF SEVERE WEATHER & HEAVY RAINFALL IS
EXPECTED TODAY ACROSS A MAJORITY OF THE CWA, WITH STRONG
WINDS AND LARGE HAIL POSSIBLE.
- COOL AND WET PATTERN EXPECTED FOR THE ENTIRETY OF THE FORECAST
PERIOD, WITH DAILY CHANCES FOR PRECIPITATION AND HIGHS 5 TO 15
DEGREES BELOW AVERAGE.
SHORT TERM /THROUGH SATURDAY NIGHT/
ISSUED AT 250 AM MDT FRI AUG 22 2025
WITH THE COLD FRONT NOW ACROSS THE REGION ALONGSIDE A DEEP UPPER
LOW EXPECTED TO SET UP AND CONTROL THE EASTERN US THROUGH AT
LEAST TUESDAY OR WEDNESDAY OF NEXT WEEK COMBINED WITH HIGH
PRESSURE RIDGING TO THE SOUTH TO SOUTHWEST, A NORTHWESTERLY FLOW
PATTERN WILL ESTABLISH ITSELF ALLOWING MONSOONAL MOISTURE TO
RIDE AROUND THE PERIPHERY OF THE RIDGE WHILE COOLER CANADIAN AIR
CONTINUES TO STREAM IN FROM THE NORTHWESTERLY FLOW, CAUSING
BELOW AVERAGE TEMPERATURES AND DAILY PRECIPITATION CHANCES
THROUGH THE NEXT SEVEN DAYS. FOR TODAY, MODEST INSTABILITY AND
SHEAR ALONGSIDE STEEP LAPSE RATES SHOULD ALLOW FOR FRESH DAYTIME
CONVECTION TO FORM AND CONTINUE THROUGH THE EVENING, WITH
MULTIPLE ROUNDS OF STRONGER TO MARGINALLY SEVERE STORMS
POSSIBLE. ONE OF THE PRIMARY CAVEATS THOUGH WILL BE CLOUD COVER,
AS MODELS DO EXPECT AT LEAST SCATTERED TO BROKEN CLOUDS THROUGH
THE DAY WHICH COULD INHIBIT SOME DAYTIME HEATING. STILL, WITHOUT
SIGNIFICANTLY OVERCAST SKIES, WE SHOULD SEE ENOUGH HEATING TO
PRODUCE THIS ACTIVITY, WITH HAIL AND WINDS THE PRIMARY HAZARDS.
ALSO WITH MULTIPLE PERIODS OF STORMS COMBINED WITH THE POTENTIAL
FOR LOCALLY HEAVY DOWNPOURS, A MARGINAL RISK OF FLOODING IS
EXPECTED, AND ALTHOUGH SEVERE CHANCES MAY LESSEN AFTER TODAY,
THE MARGINAL FLOODING RISK SHOULD EXTEND INTO NEXT WEEK.
FOR SATURDAY, OUR PRECIPITATION CHANCES MAY DWINDLE AS SOME OF
THE CAMS ARE NOT EXPECTING MUCH NEW DEVELOPMENT, POSSIBLY A
COMBINATION OF MID-LEVEL MOISTURE WANING BRIEFLY AND REMAINING
CLOUD COVER INHIBITING DAYTIME HEATING, BUT NOT ALL HIGH
RESOLUTION GUIDANCE IS IN AGREEMENT YET AND SOME STILL FIRE OFF
FRESH CONVECTION. WITHOUT STRONGER SUPPORT THOUGH, THIS
ACTIVITY SHOULD BE GARDEN VARIETY RAIN AND STORMS, WITH SEVERE
ACTIVITY UNLIKELY. FINALLY TODAY SHOULD BE THE WARMEST DAY
OVERALL OF THE NEXT WEEK, WITH WIDESPREAD HIGHS IN THE MID 70'S
TO MID 80'S.
LONG TERM /SUNDAY THROUGH THURSDAY/
ISSUED AT 250 AM MDT FRI AUG 22 2025
CONDITIONS WILL REMAIN LARGELY THE SAME THROUGH THE LONG TERM
FORECAST PERIOD AS TROUGHING TO THE EAST AND RIDGING TO THE
SOUTH TO SOUTHWEST CONTINUES TO FUEL A NORTHWESTERLY FLOW
PATTERN, BRINGING MOISTURE AND COOLER TEMPERATURES ACROSS THE
REGION. THIS SHOULD STAY THE COURSE UNTIL THE MIDDLE OF NEXT
WEEK WHEN THE TROUGH WILL BE CONTINUING EASTWARDS AND ITS
INFLUENCE WANING WHICH WILL ALLOW THE RIDGE TO BRIEFLY TRY AND
REBUILD, BUT ENSEMBLE CLUSTERS ARE IN AGREEMENT THAT THE RIDGE
SHOULD FLATTEN AS IT BEGINS MOVING BACK OVER, WHICH WILL TEMPER
THE WARMTH THAT WE MIGHT SEE. FOR SUNDAY THE COOLING TREND
CONTINUES, WITH TEMPERATURES IN THE 70'S OUTSIDE OF A FEW
LOCATIONS IN OUR NORTHERN ZONES THAT MAY PEAK IN THE 80'S.
MOVING INTO MONDAY, HIGHS DROP DOWN INTO THE 60'S TO 70'S,
CONTINUING THROUGH TUESDAY WITH TEMPERATURES THEN RISING BACK UP
A FEW DEGREES BACK INTO THE 70'S TO LOW TO MID 80'S FOR THE
MIDDLE TO BACK HALF OF NEXT WEEK. OUR NORTHERN TO NORTHEASTERN
ZONES WILL BE THE WARMEST, AND THESE ARE THE LOCATIONS ALSO
EXPECTED TO STRUGGLE TO RECEIVE PRECIPITATION THROUGH THE NEXT
WEEK WITH THE BEST MOISTURE AND SUPPORT FOR RAINFALL LIMITED TO
OUR SOUTHERN AND CENTRAL ZONES. ON THE NOTE OF MOISTURE, 7-DAY
QPF TOTALS FROM THE NBM SHOW 1-2 INCHES FOR OUR CENTRAL AND
SOUTHERN COUNTIES, HIGHEST IN LARAMIE COUNTY WHERE THE BEST
CHANCES OF DAILY PRECIPITATION IS EXPECTED. BOTH THE ECMWF AND
GFS ENSEMBLES ARE IN GOOD AGREEMENT ON WHERE THE BEST MOISTURE
WILL BE AND FAIRLY LOCKED IN OVERALL ON HOW QPF SHOULD EVOLVE
FOR OUR REGION, WITH A 40-90% PROBABILITY OF 7-DAY QPF TOTALS OF
1+ INCH FOR OUR SOUTHERN COUNTIES, WITH PROBABILITIES DWINDLING
AS YOU MOVE NORTHWARD FROM THERE. THAT GIVES AT LEAST MODERATE
OVERALL CONFIDENCE IN THE NBM'S QPF TOTALS, WHICH WILL LIKELY BE
ENHANCED LOCALLY BY HEAVIER DOWNPOURS FROM ISOLATED STORMS. HOT
AND DRY APPEARS GONE FOR NOW UNDER THIS PATTERN.
AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 546 AM MDT FRI AUG 22 2025
VERY MESSY FORECAST TODAY AS WE ARE EXPECTING BOUTS OF SHOWERS
AND THUNDERSTORMS ACROSS THE REGION WITH HIGH RESOLUTION MODEL
GUIDANCE IN POOR AGREEMENT ON WHEN AND WHERE ACTIVITY WILL
OCCUR. FOR ALMOST ALL SITES, HAVE ADDED PROB30 GROUPS FOR
THUNDERSTORMS WITH THE POTENTIAL FOR A STRONGER TO NEAR SEVERE
STORM AT ALL SITES EXCEPT FOR KCDR WHICH SHOULD REMAIN OUTSIDE
OF THE STRONGER ACTIVITY. CLOUD DECKS EXPECTED TO GENERALLY MID
TO LOW, AT AROUND 5-10K FEET, WITH THE EXCEPTION OF TWO SITES:
KCDR CURRENTLY ALREADY HAS LOWER DECKS IMPACTING, BUT THESE
SHOULD CLEAR UP AS THE SUN RISES, AND KCYS IS EXPECTED TO SEE
UPSLOPE FLOW WHICH WILL LIKELY CAUSE LOWER DECKS AND POSSIBLY
SOME FOG WITH THE ABUNDANT MOISTURE WE'RE EXPERIENCING TOMORROW
MORNING. PREVAILING WINDS BREEZY FROM AN EASTERLY TO
NORTHEASTERLY DIRECTION PRIMARILY, WITH MORNING AND AFTERNOON
GUSTS 20-30 KNOTS, WITH ERRATIC AND POSSIBLY STRONGER GUSTS NEAR
OR UNDER ANY PRECIPITATION. ALL OF THIS WILL RESULT IN A
MIXTURE OF PERIODS OF VFR CONDITIONS WITH MVFR OR LOWER POSSIBLE
WITH ANY STORMS, AND KCYS POSSIBLY REACHING IFR OR LOWER WITH
FOG TOMORROW MORNING.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...CG
LONG TERM...CG
AVIATION...CG
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page