940
FXUS65 KBOU 101109
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
509 AM MDT WED SEP 10 2025
KEY MESSAGES
- CONTINUED ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THE
NEXT FEW DAYS. BETTER CHANCES FOR RAINFALL BY FRIDAY.
- WARM WEATHER CONTINUES ALL WEEK, WITH 90F POSSIBLE TODAY AND
THURSDAY. SLIGHTLY COOLER TEMPERATURES THIS WEEKEND INTO NEXT
WEEK.
DISCUSSION /THROUGH TUESDAY/
ISSUED AT 222 PM MDT TUE SEP 9 2025
A WEAK UPPER LEVEL RIDGE AXIS CONTINUES TO DRIFT EASTWARD TODAY. A
WEAK MID-LEVEL TROUGH, COMBINED WITH MODEST INSTABILITY ACROSS THE
REGION, HAS ALLOWED FOR WIDELY SCATTERED CONVECTION TO DEVELOP
ACROSS OUR FORECAST AREA OVER THE LAST COUPLE OF HOURS... AND THIS
SHOULD CONTINUE THROUGH AT LEAST THE EARLY EVENING. CHANCES FOR
MEANINGFUL RAINFALL WILL BE FAIRLY LOW TODAY, BUT WE COULD SEE A
COUPLE STRONGER STORMS FURTHER EAST (ALONG/EAST OF AN AKRON TO
LIMON LINE) WHERE THERE'S A LITTLE MORE INSTABILITY AND DEEP LAYER
SHEAR. SHORT TERM GUIDANCE ISN'T PARTICULARLY BULLISH WITH THE
THREAT AND WITH THE BETTER SEVERE ENVIRONMENT FURTHER EAST, I
SUSPECT WE'LL GET A COUPLE STRONG STORMS WITH A BRIEF HAIL/WIND
THREAT BEFORE THEY DRIFT OUT OF THE CWA.
THE FORECAST PATTERN THE REST OF THE WEEK STILL LOOKS FAIRLY
STRAIGHTFORWARD, AS DEEP TROUGH OVER THE MOUNTAIN WEST DEVELOPS
AND STALLS OUT. GUIDANCE SHOWS NEAR TO ABOVE NORMAL MOISTURE
ACROSS THE REGION, BUT WITH DAILY CHANCES FOR SHOWERS/STORMS. THE
BETTER CHANCES WILL BE OVER THE FAR WESTERN EDGES OF THE CWA, WITH
LOWER CHANCES ALONG AND EAST OF THE I-25 CORRIDOR. WITH THE
INCREASED SOUTHWESTERLY/DOWNSLOPE FLOW, WE'LL ALSO SEE
TEMPERATURES WARM SLIGHTLY... WITH SOME GUIDANCE HINTING AT 90F
HIGHS BOTH TOMORROW AND THURSDAY OVER MOST OF THE METRO/PLAINS.
IT'S BEEN QUITE SOME TIME SINCE WE'VE SEEN A 90F HIGH IN DENVER
(AUGUST 21ST), BUT 90S IN EARLY/MID SEPTEMBER ISN'T PARTICULARLY
RARE.
THE UPPER TROUGH SHOULD EVENTUALLY EJECT INTO THE NORTHERN
ROCKIES/GREAT PLAINS BY FRIDAY OR SATURDAY. WITH THE INCREASE IN
PVA/QG ASCENT, THERE WOULD BE BETTER SUPPORT FOR CONVECTION ACROSS
THE LOWER ELEVATIONS, THOUGH MOST GUIDANCE IS STILL FAIRLY DRY
OVERALL. POPS WILL AT LEAST GO UP 10-20% COMPARED TO
WEDNESDAY/THURSDAY, BUT AT THIS POINT THE TROUGH PASSAGE WON'T BE
TOO IMPRESSIVE. ON THE OTHER HAND, THE SHIFT TO A COOLER ZONAL
FLOW SHOULD GET TEMPERATURES CLOSER TO NORMAL (UPPER 70S TO LOW
80S).
FORECAST CERTAINTY DECREASES QUITE A BIT BEYOND THE TROUGH
PASSAGE, WITH SIGNIFICANT DIFFERENCES IN THE UPPER LEVEL PATTERN
BY MONDAY/TUESDAY OF NEXT WEEK. THE NBM/MULTI-MODEL MEAN APPEARS
GOOD ENOUGH IN THIS PERIOD AND FEW CHANGES WERE MADE BEYOND THE
WEEKEND.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 509 AM MDT WED SEP 10 2025
THE MAIN AVIATION CONCERN WILL SURROUND THE POTENTIAL FOR ANOTHER
ROUND OF GUSTY AND VARIABLE SHOWER/STORM OUTFLOWS THIS AFTERNOON.
OTHERWISE VFR CONDITIONS WILL PERSIST AS ANY FOG/LOW STRATUS WOULD
STAY WELL SOUTH AND SOUTHEAST OF THE DENVER AREA TAF SITES.
THE AIRMASS IS EXPECTED TO HAVE A LITTLE MORE CAP THAN YESTERDAY
IN A WEAKLY SUBSIDENT ENVIRONMENT, WHICH MEANS COVERAGE SHOULD BE
A LITTLE MORE LIMITED THAN YESTERDAY. HOWEVER, WE STILL EXPECT
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS TO DEVELOP IN THE
AREA 20Z-22Z WITH STRONG DIURNAL HEATING, AND THEN PUSH EAST OF
THE TAF SITES BY 02Z. SUFFICIENT DCAPE WILL BE PRESENT FOR ANOTHER
CHANCE (~40-50%) OF GUSTY OUTFLOW WINDS TO ~35 KTS. WE'LL HAVE A
PROB30 FOR THIS CHANCE, ALTHOUGH WE'LL ONCE AGAIN HAVE POTENTIAL
FOR TEMPO VRB WINDS 21Z-02Z IF CONFIDENCE OR COVERAGE OF STORMS
INCREASES. OTHERWISE, WE'LL SEE A FAIRLY NORMAL DIURNAL
PROGRESSION OF WINDS, WITH THE EXCEPTION OF THE INTERRUPTION BY
ANY SHOWER OUTFLOWS 21Z-03Z. AFTER THOSE SHOWERS/STORMS MOVE AWAY,
THE INITIAL SOUTHERLY DRAINAGE WINDS COULD BE ENHANCED WITH GUSTS
~20 KTS THROUGH 06Z, BEFORE RELAXING AGAIN OVERNIGHT.
BOU WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...HIRIS
AVIATION...BARJENBRUCH
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