907
FXUS65 KBOU 031818
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1218 PM MDT Thu Sep 3 2026

.KEY MESSAGES...

- Warmer Thursday and Friday with mainly dry conditions.

- Return of better moisture by the weekend with an
  increasingchance for showers and thunderstorms.

- Still no significant pattern change on the horizon, with above
  normal temperatures continuing into next week.

&&

.DISCUSSION /Through Wednesday/...
Issued at 133 AM MDT Thu Sep 3 2026

Generally dry southwesterly flow aloft continues today. The main
players of the week - a strong closed 500mb low over the Pacific
Northwest, and a broad ridge centered across the
central/southeastern CONUS - won`t do much over the next 24-48
hours. For Colorado, that means most of the state will remain
relatively quiet over the next couple of days. Mid-level
temperatures near 14-17C today and tomorrow will likely lead to
high temperatures in the low 90s. The overall synoptic pattern
favors the development of a Denver cyclone today, and there may be
some minor temperature gradients across the metro depending on
where that sets up. While a couple of CAMs and REFS members
attempt to develop a shower or two near the convergence zone of
the cyclone this evening, that probability remains rather low
(~10%). Friday looks to be a similar story, though we should start
to see some gradual moisture advection into the region by the
afternoon and evening, leading to some scattered showers and
thunderstorms across the higher terrain... especially along/south
of I-70.

As we approach the weekend, the ridge is expected to build across
the Central Great Plains, while the upper trough remains nearly
stationary over western Washington/Oregon through at least Sunday.
That gives us a couple of days of fairly well aligned southerly or
south-southwesterly flow aloft, which should allow for a fairly
robust plume of moisture to stream into the region... perhaps even
advecting in some moisture from the now-Hurricane Marie. While the
increase in moisture should allow for widespread showers and
storms across the higher terrain, the absence of any meaningful
synoptic scale forcing will likely limit the amount of
precipitation across the plains, where thunderstorm chances would
be driven by a myriad of mesoscale influences.

Moisture is expected to hang around through Monday, but the ridge
is expected to expand a bit further west by sometime early next
week, shifting the flow aloft towards the west-southwest. Forecast
uncertainty quickly increases by mid-week. Across the 00z ensemble
suite, it`s close to a 50/50 split on maintaining a good moisture
feed into the state. However, there is a rather robust signal for
above normal temperatures to continue for the foreseeable future.
The last couple cycles of the ECMWF (along with the AIGEFS and
ECMWF AIFS ensemble) keep high temperatures in the 80s to low 90s
over the next several days, with no real hint of a substantial
pattern change anytime in the next 7-10 days.

&&

.AVIATION /18Z TAFS through 18Z Friday/...
Issued at 1217 PM MDT Thu Sep 3 2026

VFR conditions are expected through the TAF period. Winds are
becoming more light and variable, and will stay that way for the
next couple hours. By around 21Z, an easterly wind regime will
settle over the area, and winds should remain east/southeast for
much of the afternoon and evening, with some gustiness (15-20kt).
Once the sun goes down, we expect winds to start turning southerly,
reaching drainage by about 07Z. An easterly pattern is expected
again tomorrow morning and afternoon, with winds becoming
northeasterly around 18Z and southeasterly by 21Z.

Currently, CAMs suggest convection tomorrow starting around 22/23Z.
While convective conditions tomorrow look to be better than today,
confidence is still low (10-15%) on any precipitation. High-based
showers with the potential for gusty winds (20-30kt) would be the
main concern, so we`ve added in a Prob30 for 22-24Z. There`s some
uncertainty on the exact timing, but following current model
guidance, it looks like any convection tomorrow would be a late
evening event (23Z-02Z), so we expect to continue the Prob30 in the
00Z TAF.

&&

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

&&

$$

DISCUSSION...Hiris
AVIATION...AGS/MAI

NWS BOU Office Area Forecast Discussion