682
FXUS65 KBOU 262052
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
252 PM MDT TUE AUG 26 2025
KEY MESSAGES
- SCATTERED TO NUMEROUS STORMS THROUGH THURSDAY WITH LOCALLY HEAVY
RAINFALL. SOME POTENTIAL FOR BURN AREA FLASH FLOODING AND
STREET/LOWLAND FLOODING WITH ANY OF THESE STORMS.
- GRADUAL DRYING TREND THROUGH THE WEEKEND, BUT STILL AT LEAST
SCATTERED STORMS EACH AFTERNOON AND EVENING.
- WARMER AND DRIER BY EARLY NEXT WEEK.
DISCUSSION /THROUGH TUESDAY/
ISSUED AT 251 PM MDT TUE AUG 26 2025
SCATTERED SHOWERS AND THUNDERSTORMS HAVE DEVELOPED PRETTY MUCH AS
EXPECTED, AND ARE NOW ATTEMPTING TO SPREAD/FORM EAST ONTO THE
I-25 CORRIDOR AND NEARBY ADJACENT PLAINS. WE'LL ALSO SEE
ADDITIONAL DEVELOPMENT IN THE MOUNTAINS THROUGH LATE AFTERNOON AS
AN EMBEDDED SHORTWAVE/LEFTOVER CONVECTIVE VORTEX IS NOTED LIFTING
NORTHEAST THROUGH WEST CENTRAL COLORADO. THIS FEATURE SHOULD
EVENTUALLY WEAKEN AND SHEAR, BUT KEEP A SECOND ROUND OF
SHOWERS/STORMS IN THE FORECAST INTO THIS EVENING. THE AIRMASS IS
QUITE MOIST, WITH PRECIPITABLE WATER (PW) VALUES NEAR 1.15" ALONG
THE I-25 CORRIDOR, AND 140-170% OF NORMAL FORECAST AREA-WIDE, SO
ANY OF THESE SHOWERS/STORMS WILL BE CAPABLE OF PRODUCING HEAVY
RAIN. SEE HYDROLOGY DISCUSSION SECTION BELOW FOR MORE DETAILS.
MOST STORMS WILL WEAKEN AND DISSIPATE AS THEY ATTEMPT TO MOVE EAST
INTO A MORE HOSTILE CONVECTIVE ENVIRONMENT ON THE EASTERN PLAINS.
FOR WEDNESDAY, WE'LL LIKELY START OFF WITH PATCHY FOG AND AREAS OF
STRATUS. THIS WILL OFFER UP FORECAST CHALLENGES AGAIN WITH REGARD
TO INSTABILITY, BUT AT THE SAME TIME ANOTHER SHORTWAVE IS EXPECTED
TO WORK ACROSS THE TOP OF THE RIDGE. THE CAP IS ADVERTISED TO BE
RELATIVELY WEAK, JUST LIKE TODAY, SO ANOTHER ROUND OF SCATTERED TO
NUMEROUS SHOWERS AND STORMS CAN BE EXPECTED. THE EC HAS THE
EMBEDDED JET STREAM FARTHER SOUTH, WHICH MEANS WE'D BE IN THE LEFT
EXIT REGION FOR THE HIGHEST COVERAGE. HOWEVER, THE GFS WAS A
LITTLE FARTHER NORTH WITH THE SPEED MAX AND INSTEAD OF HAVING
UPWARD FORCING COULD ACTUALLY BE WEAKLY SUBSIDENT AND SUGGEST
LOWER SHOWER/STORM COVERAGE. WE'LL LEAN MORE TOWARD THE EC
SOLUTION BUT THERE'S STILL NO GUARANTEE OF RAIN/STORMS AS WE'VE
SEEN THE LAST SEVERAL DAYS.
THURSDAY SHOULD BE ANOTHER ACTIVE WEATHER DAY WITH A PASSING
SHORTWAVE LIKELY ROUNDING THE TOP OF THE RIDGE, AND
PRECIPITABLE WATER VALUES STAYING HIGH.
FOR FRIDAY AND SATURDAY, WE'D EXPECT A GRADUAL DECREASE IN
CONVECTIVE COVERAGE AS THE FLOW ALOFT TILTS MORE WESTERLY AND
STARTS TO DRY. IT WAS INTERESTING THE SEE THE EC ENSEMBLES WERE
HOLDING PRECIPITABLE WATER IN LONGER IN CONTRAST TO THE GEFS.
WE'LL KEEP AT LEAST SCATTERED STORMS IN THE FORECAST.
FURTHER DRYING IS MORE CONFIDENT TO OCCUR SUNDAY THROUGH EARLY
NEXT WEEK. THIS OCCURS AS NORTHWEST FLOW DEVELOPS IN RESPONSE TO
A HIGH AMPLITUDE RIDGE BUILDING OVER THE GREAT BASIN AND NORTHERN
ROCKIES. THE FLOW WILL STILL BE SUBJECT TO WEAK SHORTWAVES AND
BACKDOOR COOL FRONTS SLOWING ANY WARMING TREND INTO NEXT WEEK.
TEMPERATURES WILL REMAIN BELOW NORMAL THROUGH THE ENTIRE PERIOD,
BUT SLOWLY WARM INTO THE LOWER 80S IN THE LOWER ELEVATIONS.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1152 AM MDT TUE AUG 26 2025
LATEST ACARS SOUNDINGS SHOW A WEAKER CAP COMPARED TO YESTERDAY,
AND SUNSHINE AFTER THIS MORNING'S STRATUS IS AIDING
DESTABILIZATION. WE SHOULD GET AT LEAST WEAKENING CONVECTION TO
ROLL OFF THE FRONT RANGE FOOTHILLS THIS AFTERNOON AND EARLY
EVENING, BUT A GREATER THAN 50% CHANCE OF THUNDER AS THE AIRMASS
IS SLIGHTLY MORE UNSTABLE. WE'LL HAVE TEMPO TSRA IN THE TAFS FOR
THAT REASON, MOST LIKELY CENTERED ON 21Z-01Z (ON THE LATTER PART
OF THIS PERIOD FOR KDEN). VISIBILITY RESTRICTION TO <1SM IS
POSSIBLE IN THE CORES, CONSIDERING THE HIGH PRECIPITABLE WATER AND
EXPECTED RAIN RATES. IT'S STILL NOT CERTAIN THAT WE'LL SEE TS VS
SH, SINCE THERE WAS A BATCH OF CLOUDS ASSOCIATED WITH MORNING
CONVECTION THAT COULD INTERFERE WITH STORM DEVELOPMENT.
WHILE SHOWERS SHOULD END BY 02Z-03Z AND DRAINAGE WINDS KICK IN
THROUGH ABOUT 10-11Z, MODELS ARE IN REASONABLE AGREEMENT WITH A
WEAK DENVER CYCLONE OR WEAK SURGE FROM THE NORTH BEFORE DAYBREAK
WEDNESDAY. IN THEORY, THIS COULD EASILY BRING A COMBINATION OF
RADIATION/ADVECTION FOG INTO KDEN AND SURROUNDING LOCATIONS
12Z-15Z. IF FOG/LOW STRATUS DEVELOPS, IT SHOULD GRADUALLY LIFT
15Z-18Z WITH DAYTIME HEATING AND MIXING AGAIN. THUNDERSTORM
CHANCES WILL RETURN WEDNESDAY AFTER 21Z.
HYDROLOGY
ISSUED AT 251 PM MDT TUE AUG 26 2025
PRECIPITABLE WATER VALUES WILL REMAIN HIGH NEAR 1.15-1.25" AND
140-170% OF NORMAL THROUGH THURSDAY. THE PEAK IS LIKELY TO OCCUR
WEDNESDAY. WARM CLOUD DEPTHS WILL BE NEAR 5,000-6,000 FEET DEEP,
LEADING TO MORE EFFICIENT RAIN PROCESSES. STORM MOTIONS WILL
LIKELY BE SLOWEST TODAY PER OVERALL WIND PROFILES, WITH SPEEDS OF
10-18 MPH THROUGH THIS EVENING, BUT INCREASING SLIGHTLY TO 15-22
MPH WEDNESDAY AND THURSDAY. STRONGER STORMS WILL BE CAPABLE OF
PRODUCING 1-2" OF RAIN IN 30-45 MINUTES, WHICH MEANS BURN SCARS
WOULD BE THE MOST SUSCEPTIBLE TO FLASH FLOODING, BUT ALSO SOME
FLOODING CONCERNS TO URBAN/LOWLAND AREAS SHOULD STRONGER STORMS
OCCUR DOWN INTO THE I-25 CORRIDOR AND ADJACENT PLAINS.
THERE IS SOME THREAT OF STRONGER STORMS WEDNESDAY AND THURSDAY
GIVEN AN UPTICK IN INSTABILITY. HOWEVER, AT THIS TIME IT APPEARS
THE SLIGHTLY FASTER STORM MOTIONS MAY OFFSET THE HIGHER INTENSITY.
STILL SOMETHING TO KEEP AN EYE ON, HOWEVER, AS THE STRONGER
STORMS WILL BE CAPABLE OF PRODUCING THE HIGHER END RAIN RATES
MENTIONED ABOVE.
BOU WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...BARJENBRUCH
AVIATION...BARJENBRUCH
HYDROLOGY...BARJENBRUCH
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