231 
FXUS65 KBOU 211128
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
528 AM MDT Mon Sep 21 2026

.KEY MESSAGES...

- Cooler conditions continue Monday, with more limited shower and
  thunderstorm coverage.

- Gradual warming returns Tuesday, with generally isolated
  precipitation chances each day.

&&

.DISCUSSION /Through Sunday/...
Issued at 1215 AM MDT Mon Sep 21 2026

Current radar imagery shows a few strong thunderstorms lingering 
over Elbert and Lincoln counties as well as a couple of weak showers 
over the northern Colorado plains. Any storm that is able to 
strengthen over the next hour or two will be able to produce large 
hail and torrential rainfall. However, we believe the severe 
thunderstorm threat to be nearing its end for the night as 
mesoanalysis shows an overworked atmosphere and decreasing CAPE. 
Areas of patchy fog will likely develop due to the low level 
moisture left over from today's convection and small dewpoint 
depressions. 

Monday afternoon looks to be fairly quiet as a weak ridge builds 
over Colorado and subsidence gives way to mostly sunny skies. 
Temperatures will remain slightly cooler than normal, with afternoon 
highs mainly in the low 70s at low elevations, and 50s-60s for the 
mountains. Model guidance suggests a weak shortwave grazing 
southeast Colorado Monday night as well as an increase in wind 
speeds at the 700mb level. Given the slightly above normal moisture 
already in the environment, few sprinkles over the plains cannot be 
ruled out late Monday night into Tuesday morning. 

The upper level ridge tracks east and flow aloft turns southwesterly 
on Tuesday. At least a few isolated showers seem possible over the 
high terrain due to the slight uptick in monsoonal moisture, with
the plains remaining dry. One point of uncertainty for Tuesday is
that model guidance suggests breezy southerly winds over eastern 
Colorado/western Kansas which could lead to a richer atmosphere 
for storm development, although instability should remain fairly 
limited. 

A disturbance will track north from New Mexico onto Colorado on 
Wednesday, which will bring a better chance for showers and 
storms over the eastern Colorado plains in the late afternoon and 
evening. The mountains will see an increase in shower activity 
Wednesday afternoon as well, but it remains unclear whether any 
showers from the foothills would survive and make their way onto 
the Denver metro or if low level moisture will be transported west
enough. Moisture will generally remain above normal through the 
entire forecast period, and models have been consistent in 
bringing precipitable water values that are at least 150% of 
normal to the region Wednesday through Friday. However, given the 
cooler temperatures expected to be in place, lifting mechanisms 
will be needed for meaningful rainfall to come to fruition.

&&

.AVIATION /12Z TAFS through 12Z Tuesday/...
Issued at 523 AM MDT Mon Sep 21 2026

Low to mid-level stratus, with variable bases between 020 and 060
and localized CIGS, are present across the Denver metro early this
morning and will linger over or in the vicinity of the terminals
through mid-morning (~15Z, +/- 1 hr). Latest observations from
KAPA also indicate a patchy near-surface deck a few hundred feet
above the ground, though don't believe this is widespread. With
high clouds beginning to fill into the Front Range, it will be
become harder to monitor this low-level stratus. Needless to say,
cloud cover/CIG forecast is low confidence for the morning period.
Confidence in prevailing VFR conditions at the terminals rises 
past 15-16Z.

Once past this morning period, VFR conditions should prevail for
the remainder of the TAF period at all terminals. No convective
activity is expected today. As for winds, current light drainage
wind will shift to prevailing east flow near midday, gradually
veering towards southerly drainage again this evening.

&&

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

&&

$$

DISCUSSION...AA
AVIATION...BRQ