766
FXUS65 KBOU 261138
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
538 AM MDT TUE AUG 26 2025
KEY MESSAGES
- CONTINUED ACTIVE PATTERN THROUGH THE NEXT SEVERAL DAYS, WITH
BELOW NORMAL TEMPERATURES LIKELY.
- THE MAJORITY OF DAYS WILL HAVE WIDESPREAD COVERAGE OF SHOWERS
AND STORMS ACROSS THE HIGHER TERRAIN AND SCATTERED COVERAGE
ACROSS THE LOWER ELEVATIONS.
- LOCALLY HEAVY RAINFALL POSSIBLE, INCLUDING SOME POTENTIAL FOR
BURN AREA FLASH FLOODING WITH ANY STORMS OVER THE NEXT FEW DAYS.
UPDATE
ISSUED AT 342 AM MDT TUE AUG 26 2025
IT'S BEEN ANOTHER OVERNIGHT PERIOD FEATURING AN UNCERTAIN
STRATUS/FOG FORECAST ACROSS THE PLAINS. THERE'S QUITE A BIT OF LOW
CLOUD COVER AND MIST, WITH A FEW SPOTS WHERE LOWER VISIBILITIES
HAVE BEEN A LITTLE MORE CONSISTENT. THE PAST SEVERAL RUNS OF THE
HRRR BRING IN SOME DENSER FOG INTO THE NORTHERN METRO AND NORTH
TOWARDS GREELEY NEAR SUNRISE, BEFORE BURNING OFF THE LOW CLOUD
COVER BY THE LATE MORNING HOURS. DID ADD FOG INTO THE GRIDS IN
RESPONSE.
MEANWHILE, GUIDANCE LARGELY AGREES ON HOW CONVECTION WILL EVOLVE
ACROSS THE HIGH COUNTRY TODAY, WITH A BAND OF ORGANIZED
SHOWERS/STORMS GRADUALLY LIFTING OFF TO THE EAST/NORTHEAST DURING
THE AFTERNOON HOURS. THE ONE REMAINING QUESTION IS HOW MUCH OF
THAT RAIN SURVIVES THE JOURNEY THROUGH THE FOOTHILLS INTO THE I-25
CORRIDOR. ULTIMATELY THIS WILL LIKELY DEPEND ON HOW MUCH
MOISTURE/INSTABILITY PERSISTS OVER THE DENVER METRO DURING THE
EARLY AFTERNOON HOURS. I WOULD FAVOR THE PARK COUNTY INTO THE
SOUTHERN FOOTHILLS/PALMER DIVIDE FOR THE HEAVIEST RAINFALL
POTENTIAL... WITH DECREASING CHANCES HEADING NORTH OF DENVER.
TOMORROW MAY FEATURE BETTER ORGANIZED STORMS ACROSS THE PLAINS,
THOUGH THERE WILL LIKELY BE LESS STORM COVERAGE IN GENERAL.
GUIDANCE GENERALLY FAVORS THE NORTHEASTERN HALF OF OUR CWA AND
POPS WERE SHIFTED THAT DIRECTION.
DISCUSSION /THROUGH MONDAY/
ISSUED AT 226 PM MDT MON AUG 25 2025
A WAVE OF SHOWERS AND STORMS IS MOVING ACROSS THE FOOTHILLS AND
ONTO THE I-25 CORRIDOR THIS AFTERNOON. WITH AMPLE MOISTURE FOR
COLORADO STANDARDS AND LONG, SKINNY CAPE PROFILES, THE SHOWERS
AND STORMS ARE PRODUCING EFFICIENT RAINFALL. WITH SLOW MOVING
STORMS, THIS MAY PROVIDE A FLASH FLOODING THREAT ESPECIALLY OVER
THE BURN AREAS. HOWEVER, SINCE IT WAS CLOUDY ALMOST THE ENTIRE DAY
AND LOW LEVEL TEMPERATURES DID NOT WARM UP VERY MUCH, THE
INSTABILITY IS QUITE LIMITED. MIXED-LAYER CAPE IS AROUND 500 J/KG
FOR MUCH OF THE AREA AND NO SEVERE STORMS ARE EXPECTED. IN
ADDITION, THE LACK OF VERY INTENSE UPDRAFTS/STORMS IS LIMITING THE
FLASH FLOODING THREAT AS WELL. OVERALL, THERE IS OPTIMISM THAT
THERE WILL BE GREAT COVERAGE OF SHOWERS AND STORMS WITHOUT THE
FLOODING RAINFALL.
TUESDAY WILL BEGIN IN A SIMILAR WAY TO TODAY. THERE WILL BE PATCHY
FOG ACROSS THE SOUTH PLATTER RIVER VALLEY AND SOME FOG COULD
DEVELOP OVER THE DENVER METRO. A SHORTWAVE TROUGH WILL ARRIVE MUCH
LATER IN THE AFTERNOON THAN MONDAY WHICH MEANS SHOWERS AND STORMS
WILL BE SLOWER TO DEVELOP. THE HIGHER TERRAIN WILL SEE STORMS
BEGIN IN THE EARLY AFTERNOON WITH 70-80 PERCENT COVERAGE. ACROSS
THE I-25 CORRIDOR AND EASTERN PLAINS, CONDITIONS WILL BE SOMEWHAT
STABLE. WHILE MODELS LIKE THE HRRR PRODUCE STRONG STORMS, THERE IS
SKEPTICISM DUE TO THE STABILITY AND A SOLUTION MORE LIKE THE NAM
NEST IS FAVORED. THAT IS, SHOWERS AND STORMS WEAKENING
SUBSTANTIALLY AS THEY HEAD OVER LOWER ELEVATIONS.
WEDNESDAY AND THURSDAY APPEAR TO BE WET WITH MORE INTENSE STORMS
THAN MONDAY AND TUESDAY. EACH DAY WILL HAVE A SHORTWAVE TROUGH
THAT WILL BE PROVIDING FORCING AS WELL AS DEEPENING A SURFACE LOW
PRESSURE SYSTEM OVER SOUTHEAST COLORADO. THIS WILL INCREASE THE
EASTERLY, UPSLOPE FLOW AND WILL KEEP THE HIGH MOISTURE VALUES IN
PLACE. IT REMAINS TO BE SEEN IF TEMPERATURES WILL ACTUALLY WARM UP
AS THE MODELS SUGGEST BUT IF TEMPERATURE DO REACH THE 80S ACROSS
THE PLAINS EACH DAY, THERE COULD BE STRONG TO SEVERE STORMS. WHAT
IS MORE LIKELY IS THESE STORMS WILL PRODUCE HEAVY RAINFALL WHICH
COULD LEAD TO FLASH FLOODING. POPS ARE GENERALLY IN THE 60-80%
RANGE FOR EACH DAY.
THERE WILL BE A SLIGHT DECREASE IN PRECIPITABLE WATER ON FRIDAY
AND SATURDAY WHICH WILL LEAD TO LESS COVERAGE OF STORMS.
SCATTERED SHOWERS AND STORMS ARE STILL EXPECTED WITH A FLASH FLOOD
THREAT.
THE WET PATTERN MAY END ON SUNDAY OR MONDAY AS DRIER AIR MOVES IN
WITH SUBSIDENT FLOW. A RIDGE ALOFT APPEARS IT MAY DEVELOP INTO
EARLY NEXT WEEK WITH WARMER AND DRIER WEATHER.
AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 535 AM MDT TUE AUG 26 2025
MAIN AREA OF STRATUS/FG RESIDES NORTH OF BJC/DEN AT THE TIME OF
THIS UPDATE. GUIDANCE STILL TRIES TO ADVECT THIS INTO THE AREA
OVER THE NEXT COUPLE HOURS, WITH SOME BRIEF REDUCTIONS TO IFR/LIFR
CONDITIONS POSSIBLE THROUGH ABOUT 15Z OR SO. SHOULD SEE ANY
STRATUS LIFT OUT OF THE TERMINALS BY LATE MORNING. IT STILL LOOKS
LIKE WE'LL HAVE A PERIOD OF SCATTERED SHRA/TSRA THIS AFTERNOON AND
EVENING, THOUGH THIS HAS TRENDED A TOUCH SLOWER. MAIN IMPACTS
WOULD LIKELY BE CENTERED AROUND THE 00Z TIMEFRAME WITH LOWER
CIGS/VISBY AS THE MAIN IMPACTS.
DRAINAGE WINDS SHOULD ESTABLISH LATER THIS EVENING, WITH A RETURN
TO VFR CONDITIONS. ANOTHER WEAK DENVER CYCLONE MAY DEVELOP BY
WEDNESDAY MORNING, BUT AT THIS POINT THERE ISN'T MUCH OF A SIGNAL
FOR STRATUS OR FOG.
HYDROLOGY
ISSUED AT 226 PM MDT MON AUG 25 2025
PRECIPITABLE WATER VALUES WILL BE WELL ABOVE NORMAL TODAY AND
TUESDAY. STORMS THAT DEVELOP WILL BE SLOW MOVING AND WILL HAVE
EFFICIENT RAINFALL PROCESSES. THIS WILL LEAD TO A THREAT OF FLASH
FLOODING ESPECIALLY OVER THE BURN AREAS. HOWEVER, THERE WILL BE
LIMITED INSTABILITY EACH DAY SO THERE IS HOPE THAT STORMS WILL NOT
BE INTENSE ENOUGH TO PRODUCE MUCH FLOODING.
SIMILAR MOISTURE AND RAINFALL PROCESSES ARE EXPECTED WEDNESDAY AND
THURSDAY. HOWEVER, THERE WILL BE BETTER FORCING AND HIGHER
INSTABILITY VALUES EACH DAY. THEREFORE, THE THREAT OF FLASH
FLOODING WILL INCREASE AND A FLOOD WATCH FOR FLASH FLOODING MAY BE
NEEDED.
BOU WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...HIRIS
DISCUSSION...DANIELSON
AVIATION...HIRIS
HYDROLOGY...DANIELSON
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