238
FXUS65 KBOU 041803
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1203 PM MDT Fri Sep 4 2026

.KEY MESSAGES...

- Remaining warmer than normal through most of next week.

- Isolated to scattered showers expected into Saturday, with a few
  thunderstorms Saturday for the northeast plains.

- Higher coverage of showers/storms expected Sunday into Monday,
  although mostly on the weaker side. Daily shower potential will
  carry into most of next week as well.

&&

.DISCUSSION /Through Friday/...
Issued at 1153 AM MDT Fri Sep 4 2026

Low and behold, there are no big revelations with this afternoon`s
forecast package. As expected, we`re running a few degrees warmer
than yesterday and thus on track for a hot afternoon as highs
climb into the mid 90`s for the lower elevations. Once more,
aircraft-derived profiles show pronounced dry air in place,
ratified by the tongue of dry air aloft evident in water vapor
imagery. We should have a touch more mid-level moisture later
today relative to yesterday, enough for a few isolated high-based
showers mostly initiating off the higher terrain of the southern
Front Range mountains and Palmer Divide, but with a lack of
forcing these will generally fall apart as they transition into
the plains. In any case, some localized gusty outflows as high as
30-40 mph will be possible in their vicinity.

For Saturday, we eek out yet another slight increase in moisture
under southerly flow aloft, resulting in a modest rise in shower
coverage (still largely scattered for the mountains and urban
corridor). Enhanced easterly flow at the surface will support
some moisture advection into the eastern plains, pushing MLCAPE
values into the 750-1,250 J/Kg range by late afternoon, creating
potential for a stronger thunderstorm or two mainly for our
northeast plains. Bulk shear will be capped at around 25-30 kts
however, limiting the severe potential to more marginal
thresholds.

By Sunday and Monday, we do manage to advect more appreciable
subtropical moisture into the region, leading to greater coverage
of showers and storms. Synoptic forcing will remain limited
though, buffering the intensity of such activity. We never quite
lose the influence of the high pressure even with the increase in
moisture, so temperatures will remain warm with highs climbing
above 90F for a majority of the plains and urban corridor.

As we progress through the work week, the ridge looks to flatten
somewhat but its axis also shifts westward over or at least
closer to Colorado, thereby maintaining above-normal temperatures.
At this point, the vast majority of ensemble members (> 85%)
support the continuation of warm temperatures. If the high
pressure can remain relatively flat, we should still maintain
sufficient low and mid- level moisture as it wraps around the
ridge to allow for daily isolated to scattered showers and
thunderstorms across most of the region.

&&

.AVIATION /18Z TAFS through 18Z Saturday/...
Issued at 1153 AM MDT Fri Sep 4 2026

Light and variable winds will become east to southeast by 19Z.
Instability and moisture are limited today, but sufficient for
high-based showers. Main threat with this, is a brief microburst
or wind shift. Some models favor a west to northwest wind shift
associated with the convection after 00Z, while others do not.
It`s just as possible we see the bulk of convection south of
Denver and end up with a southerly wind shift, so opted to stick
with the southeast winds in the TAF. The threat for showers and
associated wind issues ends 02-03Z. On Saturday, instability and
moisture increase with the best chance for thunderstorms over the
northeast Colorado plains. There`s some uncertainty about how far
west the better instability will reach. Introduced a PROB30 for
thunderstorms beginning at 21Z. Main threat is expected to be
microbursts and gusty outflow winds leading to wind shifts.

&&

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

&&

$$

DISCUSSION...BRQ
AVIATION...BM

NWS BOU Office Area Forecast Discussion