189
FXUS65 KBOU 130005
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
605 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 /00Z TAFS through 00Z Monday/...
Issued at 537 PM MDT Sat Sep 12 2026

This afternoon`s showers and storms have struggled to hold
together as they move off the higher terrain. While there was a
brief shower observed at KBJC a short time ago, any mention of
showers and gusty winds has been removed from the TAF for the rest
of the evening. A surface cyclone has made for a tricky wind
forecast this afternoon. Enhanced southwesterly winds are
currently in place at KAPA while KDEN has managed to keep an
easterly component for the past few hours. There is high
uncertainty in the wind forecast for the next few hours as the
center of the cyclone is now moving northeast towards KDEN.
Based on tracking tools, was originally thinking winds across the
KDEN airfield turn to the south by roughly 0015Z, but latest radar
scans show it`s washing out as it moves north across Arapahoe
County. This may keep winds more easterly at KDEN before
a more southeasterly turn by around 3Z, and turning south and
settling into drainage for the overnight hours. A broader
circulation still remains in place that seems to be keeping KAPA
winds from the SW, while KBJC is holding onto N to NE winds. There
is higher confidence in the forecast after 3Z

For tomorrow, slightly higher confidence remains in afternoon
showers and maybe a weak storm to pass across the TAF sites.
DCAPE looks slightly more impressive (~1500J/kg) and instability
will be marginal for lightning potential, but a PROB30 has been
introduced at all TAF sites starting at 21Z/22Z, with a TEMPO now
in place for the evening hours (through 3Z). Gusts between
30-40kts will be possible with any passing showers/storms
afternoon/evening.


&&

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

&&

$$

DISCUSSION...AA
AVIATION...9

NWS BOU Office Area Forecast Discussion