171
FXUS65 KBOU 260523
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1123 PM MDT Fri Sep 25 2026

.KEY MESSAGES...

- Drier and warmer this weekend, with highs reaching into the 80s
  across the plains.

- Decreasing chances (now 10%-40%) for mountain snow above
  11,000ft late Monday into Tuesday.

- Potential for heavy rain Tuesday into Thursday, but confidence
  in amounts and locations remains low.

&&

.DISCUSSION /Through Friday/...
Issued at 1110 PM MDT Fri Sep 25 2026

While most of today`s activity has died down, we still have a few
showers making their way across the eastern plains, and we expect
them to continue weakening as they move east. As skies clear up and
winds become light behind these showers, we could see some patchy
fog develop in the northeastern counties for a few hours tonight.

Tomorrow and Sunday should both be much quieter weather days, thanks
to subsidence from an upper-level ridge building over the area
tonight into tomorrow. Zonal flow aloft from the ridge with some
downsloping will bring some breezier conditions to the mountains and
foothills in the early morning, with wind gusts of about 20-30 kts
across the area and gusts up to 40 kts possible for the higher
elevations. Dewpoints should drop into the 20s and 30s as the ridge
moves into our CWA, and our high temperatures are expected to be in
the mid 60s-70s for the mountains and low- to mid-80s for the
plains. With both subsidence from the ridge and drier conditions at
the surface, this weekend should stay dry and mostly sunny, though
Sunday afternoon and evening could see a few showers over the
mountains.

Models are trending slightly slower with the upper level trough/low
next week. This has a few impacts on our potential weather for the
Monday through Thursday time period: One, the slower trough will
push our better rain chances to later in the week, lowering our
precip chances (and therefore snow chances) for the Monday and
Tuesday time frame. Two, the slower track could allow for the
remnants of Hurricane Polo to merge with the trough prior to it
moving towards our area, which would give us better moisture and
rain chances for late Tuesday through Wednesday. However, models
are also trending a bit further south with the low, which will
keep the best rain chances to the south/southeast of our forecast
area. It also looks like the change in the positioning/timing of
the upper low has impacted the strength of the cold front late
Monday into Tuesday. The surface troughing and front are much
weaker in the recent runs compared to those over the past few
days. The weaker front and warmer temperatures will impact our
snow chances Monday night/Tuesday morning in the higher terrain.
Snow chances and amounts for this time period continue to
decrease, with chances for at least a dusting of snow lowering
into the 10% to 40% range for our higher mountain elevations
(generally above 12,000ft now).

For late Tuesday through Thursday, models have been pretty
consistent with a swath of heavy rain developing, as moisture
streams into the area and the upper low progresses from the SW
U.S. into the central/south central U.S. However, the placement of
this swath varies from run to run. Similar to everything else, it
will depend on the evolution of the upper level system and
surface low. Unfortunately for us, we look to be on the northern
periphery of the higher rain totals, which means that there could
be a pretty tight rainfall gradient somewhere over our forecast
area (or potentially even just to the south of our area, missing
us), where some people see multiple inches and others just a bit
further north see tenths at most. The placement of this strong
gradient will likely be the most difficult thing for us forecast,
and one of the most impactful parts of the forecast. The speed of
the upper level low will determine when the rain chances end for
us, with some members holding onto to rain chances through early
Friday, while others have us drying out Thursday.

&&

.AVIATION /06Z TAFS through 06Z Sunday/...
Issued at 1121 PM MDT Fri Sep 25 2026

VFR conditions expected through the TAF period. Slightly elevated
drainage winds are in place and will last through the night at
KDEN and KAPA. KBJC will likely see more of a downslope wind (W to
NW) for much of the overnight. There is a low chance (~15%) that
KBJC gusts to about 15-20 kts overnight if these stronger winds
can make it off the higher terrain.

Winds eventually turn to east/southeast by the afternoon and then
remain rather light at all three sites. Drainage should settle in
once again on Saturday night. Only a few to sct mid- and high-
level clouds are expected through the period.


&&

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

&&

$$

DISCUSSION...AP/AGS
AVIATION...MV

NWS BOU Office Area Forecast Discussion