041 
FXUS65 KBOU 130541
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1141 PM MDT Sat Sep 12 2026

.KEY MESSAGES...

- 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 /06Z TAFS through 06Z Monday/...
Issued at 1141 PM MDT Sat Sep 12 2026

Winds have established a fairly normal drainage pattern (SSW-SW),
and should dominate through 14Z...although a brief light westerly
shift is possible (30% chance) during the overnight. Winds on 
Sunday will turn more SE-E 16Z-20Z per expected pressure gradient 
patterns, and gradually increase in speeds to 8-14 kts. 

The main concern will shift to potential gusty outflow winds from
high based convection. We do see great enough confidence to
maintain the TEMPO VRB G35kts, as DCAPE grows to 1500 J/kg and
we'll likely reach full mixing to the LCL given the rather hot
temperature forecast and sufficient sunshine. Sunday appears to 
be a slightly later convective day, with any threat (PROB30) 
holding off til 22Z-23Z, and then greatest threat (TEMPO) 00Z-03Z.
Given magnitude of DCAPE, there's a slight (20%) chance of G45 
kts impacting the airports. 

Winds will settle down by/shortly after 03Z Monday and return to 
fairly normal diurnal wind patterns. 

&&

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

&&

$$

DISCUSSION...AA
AVIATION...20