774
FXUS65 KBOU 122051
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
251 PM MDT Sat Sep 12 2026

.KEY MESSAGES...

- Slightly cooler today, then unseasonably warm along the Front
  Range and I-25 Corridor Sunday.

- High-based showers with gusty winds possible Sunday afternoon.

- Unsettled pattern next week, with cooler weather arriving by
  Tuesday. Locally heavy rain becoming increasingly likely.


&&

.DISCUSSION /Through Saturday/...
Issued at 244 PM MDT Sat Sep 12 2026

It is a bit milder than previously forecast today, with
temperatures still in the 70s for much of the low elevations and
only a few 80s over the Palmer Divide. The cooler temperatures
have been in part due to the cold front that pushed through early
this morning, as well as a streak of high clouds that has moved in
from NW to SE Colorado. Cumulus cloud cover is increasing over
the mountains with a few showers and thunderstorms already moving
through the Front Range. Although moisture transport is not
particularly enhanced this afternoon, precipitable water (PW)
values remain slightly above normal over the state. The better
chance for rain this afternoon will reside over the high terrain,
although we do not expect rainfall to amount more than a trace.
For the Denver metro and I-25 corridor, current soundings show a
very capped profile, which comes at no surprise given the cool
temperatures in place. However, any high-based showers or storms
that are able to move off of the foothills and over the plains
will be able to produce gusty winds up to 40 mph in its vicinity.


Upper level ridging over Colorado returns for just a day tomorrow,
making Sunday the warmest day of the week. Afternoon temperatures
will climb into the upper 80s and lower 90s over the Denver area and
I-25 corridor. Portions of the northeast Colorado plains, such as
Phillips and Sedgwick counties, may struggle to warm up due to
lingering morning stratus keeping cooler and moister air locked near
the surface. A few factors will play into tomorrow`s afternoon and
evening shower potential. First, southwest flow aloft will begin to
advect monsoonal moisture into the region, with PW values increasing
to >150% of normal by late afternoon. This uptick in moisture will
begin over western Colorado and gradually move east over the Front
Range and plains. Model soundings over the Denver metro show good
agreement in DCAPE values soaring into the 1200-1700 J/kg range and
a well-defined inverted-V sounding. Despite the dry low levels, high-
based showers and microbursts will be able to produce wind gusts up
to 50 mph, even with little to no precipitation at the surface. A
lee cyclone east of Denver could provide additional forcing and a
push of higher dewpoints in the early evening hours. A second
round of showers and storms will be possible over the mountains
Sunday night into the early morning hours of Monday.

The active weather pattern will continue Monday through Thursday as
monsoonal moisture transport intensifies and shower coverage becomes
more numerous, particularly over the high terrain. Cooler
temperatures are also in store this week, with afternoon highs only
reaching the mid 70s to low 80s at low elevations, and 50s-60s for
the mountains. At this time, Tuesday looks to be the best chance for
locally heavy rainfall for both the mountains and low elevations.
However, Wednesday and Thursday could also be quite unsettled and
wet days if a shortwave tracks through northern Colorado, as some
model guidance has suggested. Ensemble trends do appear bring
quieter and dry weather for the weekend.


&&

.AVIATION /18Z TAFS through 18Z Sunday/...
Issued at 1134 AM MDT Sat Sep 12 2026

Winds are beginning to settle into an easterly component across
the TAF sites early this afternoon. Expect wind speeds to see a
slight strengthening through the afternoon, but keep the easterly
component outside of any outflows or microbursts. Mid-level
moisture is expected to increase with showers and thunderstorms
already present across the higher elevations. This will increase
potential for afternoon/evening virga showers if things can hold
together coming off the higher terrain. A PROB30 has been
introduced to now include KDEN to account for this potential from
22Z to 1Z this afternoon. Microbursts/gusty outflows around 30kts
will be possible with any passing showers. Expecting winds to
turn to the southeast then settle into drainage at KDEN/KAPA, with
KBJC remaining light and variable through the overnight hours.

Slightly higher confidence in afternoon showers and maybe a weak
storm to pass across the TAF sites on Sunday. DCAPE looks slightly
more impressive and instability will be marginal for lightning
potential, but a PROB30 has been introduced at KDEN at 21Z, with
potential for a TEMPO to be considered for the evening hours in
the next TAF package. Gusts between 30-40kts will be possible with
any passing showers/storms Sunday afternoon/evening.

&&

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

&&

$$

DISCUSSION...AA
AVIATION...9

NWS BOU Office Area Forecast Discussion