210
FXUS65 KBOU 121121
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
521 AM MDT FRI SEP 12 2025
KEY MESSAGES
- SCATTERED SHOWERS AND THUNDERSTORMS EXPECTED THROUGH SATURDAY.
- COOLING TEMPERATURES THROUGH THE WEEKEND.
- UNSETTLED, UNCERTAIN PATTERN FOR MOST OF NEXT WEEK.
DISCUSSION /THROUGH THURSDAY/
ISSUED AT 204 PM MDT THU SEP 11 2025
EARLY AFTERNOON CONVECTION HAS BEEN A BIT MORE WIDESPREAD THAN
ORIGINALLY THOUGHT ACROSS THE I-25 CORRIDOR. INITIAL CONVECTIVE
CELLS THAT INITIATED NEAR THE BASE OF THE FOOTHILLS IN A SHALLOW
UPSLOPE FLOW REGIME HAVE DRIFTED EAST OVER THE LAST COUPLE OF
HOURS, THOUGH RADAR INDICATIONS ARE THAT THESE HAVE BECOME LESS
ORGANIZED AND OUTFLOW DOMINANT. WE'LL LIKELY CONTINUE TO SEE BRIEF
PULSES UP ALONG THE SURFACE CONVERGENCE BETWEEN THE OUTFLOW AND
CONTINUED EAST/NORTHEAST FLOW, BUT WIDESPREAD RAIN CHANCES ARE
STILL FAIRLY LOW FOR ANY GIVEN POINT ACROSS THE REST OF THE URBAN
CORRIDOR. FURTHER NORTHEAST, BETTER MOISTURE PREVAILS (SFC TDS IN
THE 50S) AND SPC MESOANALYSIS SUGGESTS ANYWHERE FROM 1000-2000
J/KG OF MLCAPE ALONG WITH 30-40KT EFFECTIVE BULK SHEAR. HOWEVER,
IT'S STILL FAIRLY CAPPED THERE AND GUIDANCE GENERALLY KEEPS THINGS
QUIET OUT THERE. WE COULD ALSO SEE A STRONG STORM OR TWO OVER THE
HIGHER ELEVATIONS, BUT MODEST INSTABILITY WILL LIMIT THE SEVERE
POTENTIAL.
SOUTH-SOUTHWESTERLY FLOW ALOFT SHOULD CONTINUE INTO TOMORROW AS A
TROUGH AXIS SLOWLY ADVANCES EAST TOWARDS COLORADO BY FRIDAY
MORNING. GUIDANCE DEVELOPS A PRETTY GOOD PLUME OF SHOWERS AND
EMBEDDED THUNDERSTORMS BY FRIDAY MORNING FROM SOUTHWEST COLORADO
INTO OUR I-70 MOUNTAIN CORRIDOR, WHICH SLOWLY PUSHES
NORTH/NORTHEASTWARD THROUGH THE DAY. THE EXPANSIVE CLOUD COVER,
ALONG WITH COOLER MID-LEVEL TEMPERATURES FROM THE APPROACHING
TROUGH, SHOULD KEEP TEMPERATURES SEVERAL DEGREES COOLER THAN TODAY
(UPPER 70S TO LOW 80S). WE'LL SEE HOW MUCH OF THAT MOISTURE CAN
MAKE IT INTO THE LOWER ELEVATIONS... BUT THE BETTER CHANCES FOR
PRECIPITATION WILL BE ACROSS THE SOUTHWESTERN/WESTERN PORTIONS OF
THE CWA.
THE TROUGH AXIS IS EXPECTED TO SHARPEN AND BECOME NEGATIVELY
TILTED BY SATURDAY NIGHT OR SUNDAY MORNING AS THE PRIMARY
SHORTWAVE EJECTS INTO COLORADO. THE INCREASING QG ASCENT AND
MOISTURE SHOULD LEAD TO BETTER COVERAGE OF SHOWERS AND STORMS
ACROSS THE LOWER ELEVATIONS. WHILE THERE ARE STILL SOME TIMING
DIFFERENCES TO RESOLVE, THE MAJORITY OF DETERMINISTIC/ENSEMBLE
GUIDANCE FAVORS SATURDAY AFTERNOON INTO SATURDAY NIGHT FOR THE
DENVER AREA, WITH CHANCES FOR RAIN LINGERING ACROSS THE NORTHEAST
CORNER SUNDAY.
AS WE GET INTO NEXT WEEK, MODELS HAVE TRENDED TOWARDS A
COOLER/MORE UNSETTLED PATTERN AS A CLOSED 500MB LOW DROPS FROM THE
PACIFIC NORTHWEST TOWARDS WYOMING, PLACING OUR REGION IN A COOLER,
MORE ZONAL FLOW ACROSS THE FORECAST AREA. WHILE THERE MAY BE A
BRIEF WARMUP MONDAY OR TUESDAY, TEMPERATURES SHOULD CONTINUE TO BE
NEAR NORMAL. AFTER A DRYING TREND SUNDAY THROUGH TUESDAY... A
GRADUAL INCREASE IN MOISTURE IS ANTICIPATED BY MID-WEEK NEXT WEEK.
AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 514 AM MDT FRI SEP 12 2025
VFR CONDITIONS WILL PREVAIL FOR ALL TERMINALS THROUGH THE TAF
PERIOD. FOR THIS MORNING, S/SW FLOW WILL REMAIN IN PLACE, WITH
OCCASIONAL GUSTS 15-20 KTS MIXING IN AT TIMES FROM WEAK, HIGH-
BASED -SHRA. THESE WILL BE ISOLATED DURING THE MORNING, AND MAINLY
CONFINED TO THE S AND SW OF THE DENVER METRO.
WIND DIRECTION WILL SHIFT TO THE W/NE 17-19Z, WITH -SHRA/-TSRA
POTENTIAL INCREASING AFTER 20Z. THE MOST FAVORABLE WINDOW FOR
-TSRA IMPACTS AND BKN-OVC CIGS ~060-070 WILL BE 22Z-02Z, BUT
SHOWERS MAY LINGER THROUGH THE EVENING.
GUSTY OUTFLOW WINDS IN THE VICINITY OF ANY CONVECTION WILL BE THE
PRIMARY CONCERN, WITH MODERATE TO HIGH CONFIDENCE IN PEAK GUST
POTENTIAL NEAR 35 KTS. EXPECT A RETURN TO SOUTHERLY DRAINAGE FLOW
OVERNIGHT.
BOU WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...HIRIS
AVIATION...RODRIGUEZ
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