663
FXUS65 KBOU 300151 CCA
AFDBOU

Area Forecast Discussion...CORRECTED
National Weather Service Denver/Boulder CO
751 PM MDT Sat Aug 29 2026

.KEY MESSAGES...

- Showers and thunderstorms capable of producing gusty winds
  remain possible through this evening.

- Active monsoon pattern continues Sunday and Monday.

- Warm and dry pattern returns for most of next week.

&&

.DISCUSSION /Through Saturday/...
Issued at 1216 PM MDT Sat Aug 29 2026

This morning`s upper air maps show little change from this time
yesterday outside of a slight eastward progression of the upper-
level ridge, turning flow aloft slightly more westerly today.
Temperatures stayed mild overnight, with the majority of the urban
corridor starting today out in the mid to upper 60s. This should
make for another hot day across the forecast area, as temperatures
are expected to warm into the low to mid 90s before we see scattered
showers and storms develop this afternoon. A mountain wave cloud is
observed across the northern urban corridor this morning that may
slow surface heating beneath it, but slightly cooling 700 mb
temperatures this afternoon associated with a mid-level front,
will aid in increased instability and help kick off showers and
storms by this afternoon. CAMs continue to show slightly better
storm coverage today, with a round of more diurnal convection
expected this afternoon ahead of a more linear cluster this
evening. Today`s CAMs also show a more predominant surface front
or outflow moving from northwest to southeast across the forecast
area with this evening`s showers/storms, bringing a swath of
strong to severe winds across the urban corridor (50-60 mph) as it
passes, with speeds gradually diminishing as they move across the
plains. Showers may linger through late tonight before things
stabilize.

On Sunday, an upper-level low is expected to move across the
Northern Rockies, shifting the center of the upper-level ridge east
over Oklahoma/Arkansas. This will allow for mid-level monsoonal
moisture to continue to flow into Colorado. PWATs are expected to
average around 130% of normal, and afternoon showers and storms
are expected once again. MLCAPE looks to slightly increase over
today, and this morning`s CAMs show some strong to severe winds
possible along a line of storms across the plains. 0-6 km bulk
shear will range from 25-35 kts that will support potential for a
few more organized storms. Afternoon highs are expected to be a
few degrees cooler behind today`s front, with portions of the
urban corridor staying under 90F for a change.

One more active day is expected on Monday as PWAT values are
expected to increase a tad more (150-170% of normal). Despite the
increased moisture, southwesterly flow aloft will increase and
keep afternoon showers and storms moving swiftly, helping to limit
flooding concerns, though there may be some localized heavy
rainfall along the Front Range Mountains, where moisture is
expected to be greatest. Some uncertainties remain with regards
to the proximity of a 500 mb jet max throughout the day, that may
determine the best location for storm development. Additionally,
timing of an expected shortwave could enhance synoptic forcings if
it moves through in the afternoon. The latest GFS would support
at least some slight benefits with it showing it passing over
Colorado in the late afternoon/early evening. However, the ECMWF
shows a delayed arrival, with it passing through closer to Tuesday
morning. Will have to continue to monitor these subtle
differences, but expect greater coverage of storms to be in the
area of the right entrance of the speed max. Temperatures are
forecast to be near normal, with low to mid 80s expected across
the plains, and low to mid 70s for the mountain valleys.

A gradual warming and drying trend is expected from Tuesday
onward with southwesterly flow aloft persisting as the upper-
level ridge remains centered over the eastern CONUS. There will
still be enough moisture in place for some isolated to scattered
afternoon showers/storms each afternoon.

&&

.AVIATION /00Z TAFS through 00Z Monday/...
Issued at 550 PM MDT Sat Aug 29 2026

As of 2345z, KFTG shows showers and an outflow boundary with
gusty winds are grazing the southern side of KDEN. Winds should
mostly have a southerly component behind this activity. A broken
line of showers is also moving through Larimer County and far
western Weld County at this time. There is a low (~20%) chance of
lightning with these storms. This is still on track to reach the 3
sites between about 2z and 4z this evening, bringing gusty north
winds in excess of 35 kts and the chance of showers.

Winds are expected to turn to drainage tonight after the showers
subside. By tomorrow morning, winds will start to turn clockwise
to NNW for the afternoon. We now have a TEMPO and VCSH starting
at 20z tomorrow for the possibility of high-based showers and
thunderstorms for much of the afternoon, bringing gusty winds in
excess of 35 kts, rain, and briefly lowering ceilings. There is a
20% chance that showers and thunderstorms linger past 0z tomorrow
evening, but there is not enough confidence yet to include this in
the TAF. Regardless, behind the convection, winds should turn to
drainage.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...9
AVIATION...MV

NWS BOU Office Area Forecast Discussion