737
FXUS65 KBOU 301755
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1155 AM MDT Sun Aug 30 2026

.KEY MESSAGES...

- Active monsoon pattern continues Sunday and Monday.

- Warm and dry pattern returns for most of the upcoming week.

&&

.DISCUSSION /Through Saturday/...
Issued at 1222 AM MDT Sun Aug 30 2026

There haven`t been too many significant changes in the large scale
pattern over the last 24 hours. A broad upper ridge remains
centered over the south central CONUS, with a trough noted over
the northern Rockies... leaving the area in broad southwesterly
flow aloft. This also puts us square in the middle of the
monsoonal moisture, and there`s been a good amount of
precipitation falling across northwestern Colorado, which has
spread as far east as Grand/Jackson county.

Overnight CAMs are actually in decent agreement in how today`s
convective potential plays out. Most guidance pushes a cluster of
showers and thunderstorms across Middle/North Park late this
morning into the early afternoon, which then advances east into
the Front Range and I-25 corridor by early/mid afternoon. The
convective environment is marginally favorable across most of the
lower elevations, with modest MLCAPE (~500 J/kg) but increased
deep layer shear. We can`t totally rule out a few strong to severe
wind gusts with any stronger showers/storms as convection
continues to push eastward through the afternoon and evening
hours.

Monday still looks to feature the best chance of precipitation
across most of our forecast area, as a more pronounced shortwave
races across the state during the afternoon/early overnight hours.
There`s timing differences across the various models, but
reasonably good agreement that a convective cluster will develop
across southwestern Colorado during the day, advancing into our
forecast area by the mid/late afternoon hours. Like the past few
days, meager surface/boundary layer moisture will limit
instability, but the stronger synoptic forcing should lead to more
widespread rainfall into Monday evening/Monday night.

By Tuesday, the center of the 500mb ridge should slide east into
the Ohio Valley, while a strong closed low spins off the coast of
British Columbia. Across the region, southwesterly flow aloft will
persist. Moisture will diminish through this timeframe, with
enough drying by Wednesday and Thursday that only a couple of
weak showers are in the forecast across the the high country.

The forecast pattern becomes a bit more complex as we approach
next weekend. The closed low near the Pacific Northwest coastline
will eventually drift onshore, and its approach towards our area
should lead to a more poleward component of the mid/upper level
winds. Further complicating the pattern is the potential tropical
cyclone development across the eastern Pacific, which could
contribute to additional tropical moisture advection into the
region by next weekend. There is a fairly large spread across the
overnight guidance and it`ll likely be a while until we have a
better handle on things, but the overall pattern would suggest
that we`ll see precipitation chances increase towards the end of
our forecast period.

&&

.AVIATION /18Z TAFS through 18Z Monday/...
Issued at 1145 AM MDT Sun Aug 30 2026

Radar as of 1745z shows a broken line of showers and
thunderstorms moving through Grand, Jackson, and western Larimer
counties. Based on the latest radar trends and CAMs, have kept a
TEMPO and VCSH starting at 20z (adjusted KBJC to start at 19z)
for the possibility of high-based showers and thunderstorms for
much of the afternoon. These could bring gusty outflow winds in
excess of 35 kts, rain, and briefly lowering ceilings. There is a
~30-40% chance that showers and thunderstorms linger through about
4z this evening. Behind the convection, winds should turn to
drainage rather quickly... as early as 4z.

Winds should turn clockwise to north-northeast to northeast by
early tomorrow afternoon. Tomorrow will be another day with a
TEMPO and VCSH starting at 20z for similar threats- gusty outflow winds
in excess of 35 kts, rain, and briefly lowering ceilings. Ceilings
could briefly drop to around 7000 feet AGL given more mid-level
moisture is expected to be present. A PRO30 or TEMPO will likely
be needed past 0z Tuesday in the next update.

&&

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

&&

$$

DISCUSSION...Hiris
AVIATION...MV