421
FXUS65 KBOU 310928
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
328 AM MDT SAT MAY 31 2025
.KEY MESSAGES.
- SCATTERED AFTERNOON SHOWERS AND THUNDERSTORMS CONTINUE THROUGH
SUNDAY (MAINLY OVER THE HIGHER TERRAIN).
- WARMER WEATHER MAKES A RETURN THROUGH THE WEEKEND, WITH HIGHS
BACK INTO THE LOW 80S FOR MOST OF THE PLAINS.
- WETTER PATTERN RETURNS EARLY NEXT WEEK (MON-WED), ALONG WITH A
RETURN TO BELOW NORMAL TEMPERATURES. SNOWMELT PLUS RAINFALL WILL
LEAD TO HIGH FLOWS ON MOUNTAIN STREAMS.
UPDATE
ISSUED AT 256 AM MDT SAT MAY 31 2025
NO SIGNIFICANT UPDATES TONIGHT, WITH MOST OF THE PREVIOUS
DISCUSSION BELOW STILL VALID. TODAY SHOULD SEE NEAR NORMAL
TEMPERATURES WITH JUST A FEW SHOWERS AND THUNDERSTORMS ACROSS THE
HIGHER ELEVATIONS, WHILE THE PLAINS STAY PARTLY CLOUDY. SUNDAY
STILL LOOKS TO BE THE WARMEST DAY OF THE WEEK, WITH DETERMINISTIC
AND MOS GUIDANCE SUGGESTING MID/UPPER 80S HIGHS ACROSS THE LOWER
ELEVATIONS.
FOR EARLY NEXT WEEK, MODELS CONTINUE TO GRADUALLY CONVERGE ON A
PRETTY WET SOLUTION ACROSS MOST OF OUR CWA. ENSEMBLE MEAN QPF IS
CLOSE TO 1-1.5" ACROSS MOST OF THE FRONT RANGE AND DENVER METRO,
WITH A HANDFUL OF ENSEMBLE MEMBERS SUGGESTING AS MUCH AS 2-4" OF
RAIN IN PLACES. THERE IS ALSO RELATIVELY HIGHER CONFIDENCE THAN
NORMAL IN A >0.5" RAINFALL EVENT ACROSS DENVER, WITH ECMWF 10TH
PERCENTILE QPF NEAR 0.75-1.25" THROUGH TUESDAY NIGHT. WITH SUCH A
STRONG SIGNAL FOR RAIN... IT'S NOT A SURPRISE THAT NBM POPS/QPF
ARE BULLISH IN THAT PERIOD, AND I DIDN'T SEE A NEED TO STRAY FROM
THAT TONIGHT.
DISCUSSION /THROUGH FRIDAY/
ISSUED AT 244 PM MDT FRI MAY 30 2025
SHOWERS AND THUNDERSTORMS WILL MOVE SOUTHEAST OFF THE MOUNTAINS
ONTO THE ADJACENT PLAINS OVER THE NEXT SEVERAL HOURS. IT APPEARS
CAPES IN THE I-25 CORRIDOR ARE 400-1000 J/KG, BUT THIS INITIAL
BATCH OF SHOWERS WILL CREATE A CLOUDIER AND COOLER ENVIRONMENT
THAT WILL LIMIT THE INTENSITY OF LATER SHOWERS. GUSTY WINDS SHOULD
BE THE MAIN THREAT. THIS ACTIVITY SHOULD WANE IN THE EARLY EVENING
HOURS, THOUGH THE ACCOMPANYING CLOUDS WILL LINGER FOR A WHILE.
LATE TONIGHT, THE NEXT FRONTAL SURGE WILL COME THROUGH ON THE EDGE
OF A NORTHERN PLAINS SHORTWAVE. THE MODELS HAVE BEEN HINTING AT A
STRATUS DECK FOR A FEW HOURS IN THE MORNING, THEN CLEARING SKIES
FOLLOWED BY A BIT LESS MOUNTAIN CONVECTION TOMORROW. SUNDAY WE'LL
BE UNDER A RIDGE WITH A PRETTY DRY ENVIRONMENT, BUT STILL WARM
ENOUGH FOR A FEW MOUNTAIN STORMS.
THERE'S REASONABLE AGREEMENT NOW ON THE STRUCTURE AND TIMING OF
THE MONDAY/TUESDAY TROUGH AND FOLLOWING SHORTWAVE. THERE ARE STILL
SOME UNCERTAINTIES ON TIMING AND THE AMOUNT OF PRECIPITATION THAT
WILL BE GENERATED. A COLD FRONT SHOULD DROP ACROSS COLORADO LATE
IN THE DAY MONDAY, MOVING INTO A FAIRLY DRY ENVIRONMENT. MOST OF
THE PRECIPITATION WILL BE BEHIND THE FRONT AND TROUGH IN THE AREA
OF SYNOPTIC LIFT MONDAY NIGHT, INTO TUESDAY MORNING ON THE PLAINS.
BY MIDDAY TUESDAY THE DEEP LIFT IS GONE, BUT THERE COULD STILL BE
SOME SHALLOW OVERRUNNING OF THE COOL AIR ON THE PLAINS AND SOME
LIFT FROM CONTINUING LOW LEVEL UPSLOPE ON THE EAST SIDE OF THE
MOUNTAINS. MEANWHILE, THE MOUNTAINS WILL BE A A COOL MOIST AND
SLIGHTLY UNSTABLE AIRMASS FOR CONTINUING SHOWERS. A SECONDARY
TROUGH MOVING THROUGH A SIMILAR AIRMASS WILL KEEP SHOWERS GOING ON
WEDNESDAY, THOUGH THEY SHOULD BE LIGHTER AND MAYBE NOT AS
WIDESPREAD.
SOME MODEL RUNS HAVE UP TO 2 INCHES OF RAIN IN THE MONDAY
AFTERNOON THROUGH WEDNESDAY AFTERNOON PERIOD, WITH UP TO 3 INCHES
ON THE EAST SLOPES OF THE FRONT RANGE. ENSEMBLE MEANS ARE ABOUT
HALF OF THAT. THE MAIN PERIOD OF PRECIPITATION SHOULD BE MONDAY
NIGHT, WITH STEADY BUT LIGHTER RAIN CONTINUING ON THE EAST SIDE OF
THE MOUNTAINS TUESDAY. IN ADDITION, THERE WON'T BE MUCH SNOW AS
THERE'S ONLY A LITTLE COOLING ALOFT AND SNOW LEVELS WILL LIKELY
STAY AROUND OR ABOVE 10,000 FEET. OVERALL, WE THINK THE THREAT OF
LARGE SCALE FLOODING IS LOW, BUT THE COMBINATION OF SNOWMELT FROM
WARM TEMPERATURES SUNDAY AND MONDAY FOLLOWED BY THE RAIN WILL
CREATE HIGH STREAM FLOWS IN THE MOUNTAINS, ESPECIALLY TUESDAY INTO
WEDNESDAY. WE'VE ISSUED A FLOOD WATCH FOR THE UPPER COLORADO RIVER
AROUND GRAND LAKE AND IN ROCKY MOUNTAIN NATIONAL PARK, WHICH
APPEARS TO BE THE MOST SUSCEPTIBLE AREA FOR MINOR FLOODING. IF WE
WIND UP WITH HIGHER END RAIN AMOUNTS, WE MAY SEE SIMILAR ISSUES OF
MINOR FLOODING IN VULNERABLE AREAS ACROSS THE HIGH COUNTRY. ODDS
OF ANY PROBLEMS AT LOWER ELEVATIONS LOOK LOW, ALTHOUGH THE RIVERS
THAT HAVE SNOWMELT IN THEM WILL WIND UP WITH SIGNIFICANT RISES.
LATER NEXT WEEK, THERE'S A WARMING TREND BUT PROBABLY STILL ENOUGH
MOISTURE AROUND FOR TYPICAL THUNDERSTORMS. THE SEVERE THREAT
THROUGH ALL OF THIS IS PROBABLY RATHER LOW DUE TO A FAIRLY DRY
ENVIRONMENT FOLLOWED BY A MORE STABLE ONE. AS WE WARM LATE NEXT
WEEK THE CHANCES MAY INCREASE.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 1150 PM MDT FRI MAY 30 2025
VFR CONDITIONS ARE FORECAST THROUGH THE TAF PERIOD. WEAK DRAINAGE
WINDS HAVE ATTEMPTED TO DEVELOP THIS EVENING, BUT WILL LIKELY
REMAIN LIGHT AND SOMEWHAT VARIABLE THROUGH MOST OF THE OVERNIGHT
HOURS. A WEAK PUSH OF MOISTURE COULD LEAD TO SOME SCT/BKN CLOUDS
AROUND 030-050 BY AROUND 12Z, BUT THIS STILL LOOKS FAIRLY MARGINAL
WITH LOW CHANCES OF MVFR CONDITIONS.
ANY STRATUS SHOULD BURN OFF FAIRLY QUICKLY SATURDAY MORNING, WITH
WINDS SHIFTING TO THE NORTH, THEN NORTHEAST DURING THE DAY. SPEEDS
SHOULD REMAIN AT OR BELOW 10KT.
BOU WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...HIRIS
DISCUSSION...GIMMESTAD
AVIATION...HIRIS
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