Arapahoe Basin

000
FXUS65 KBOU 211810
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1210 PM MDT Wed Oct 21 2026

.KEY MESSAGES...

- Warm and dry conditions continue across the lower elevations for
  the next few days, with scattered light rain and snow showers
  across the higher elevations.

- Cooler, unsettled weather potentially returns this weekend
  across the forecast area, including the Front Range/I-25
  corridor.

- At least a brief warm-up likely sometime early or mid-week next
  week.

&&

.DISCUSSION /Through Tuesday/...
Issued at 1142 PM MDT Tue Oct 20 2026

The next couple of days will be dominated by broad south-
southwesterly flow aloft, as a strong trough to the west slowly 
drifts off to the northeast, while a ridge slowly builds just to 
the east of our forecast area. Embedded in the flow is some 
extremely impressive moisture. Forecast PW and 500/700mb specific 
humidity increases significantly over the next 24 hours or so, 
with most of these values reaching standardized anomalies of 4-6 
sigma... well outside climatology for this time of year. Of 
course, the flow aloft is rather unfavorable for significant 
orographic precipitation here. We should still manage scattered 
rain and snow showers both Wednesday and Thursday, but the more 
impressive rainfall totals will be confined to southwest Colorado.
The pattern will also favor above normal temperatures across the 
region, with snow levels sitting around 12-14kft, and highs in the
70s across most of the plains.

The mid-level flow strengthens a bit on Friday as a shortwave 
rotates around the parent trough axis from southeastern Utah into 
western Wyoming. 700-500mb flow approaches 30-40kt Friday 
afternoon with a generally dry/subsident airmass... which should 
allow for a few gusts of 30-40 mph across the eastern plains. A 
fairly strong lee cyclone over northern Colorado would likely 
limit wind gusts along and north of I-76, meaning that the 
northwest Denver metro could see a fairly calm day while the 
southeast metro ends up rather breezy. These details are hard to 
pinpoint but should become more clear over the next couple days 
where CAMs will be available. Across the mountains, there could be
a few showers during the day but most of the moisture exits the 
area pretty quickly. 

While the main trough ejects out of the region on Friday, 
guidance is insistent that at least one piece of this trough will 
be left over the desert southwest. There's still considerable 
spread across both the physics and AI-based forecast guidance in 
this period, though it appears we are starting to see a gradual 
convergence towards a single solution, where the leftover piece of
the trough drifts northward and closes off sometime on Saturday. 
That closed low then lifts northeastward and eventually interacts 
with a relatively confluent northern jetstream... leading to the 
upper low shearing out Sunday into Monday. The 700mb low, though 
weaker throughout the period, follows a similar track, with the 
flow briefly aligned to advect some deeper moisture into eastern 
Colorado Saturday night through Sunday.
Current winds are light and variable over the Denver area with a 
shift to the ESE expected in the next hour or two. Southeasterly 
winds should pick up (~12KT) at around 21Z at KDEN and KAPA, with 
much weaker speeds at KBJC. Southerly winds will begin to develop 
over much of the CO plains and Denver metro in the evening, with a 
light (<06KT) northwest wind at KBJC.

Mid level clouds will increase this evening as Pacific moisture 
arrives to area. A stray sprinkle cannot me ruled out over the 
Denver metro in the very early morning hours, but we expect 
shower/storm chances to increase (20-30% chance) Wednesday 
afternoon. While the exact timing and coverage of storms making it 
to the Denver area remains uncertain at this time, model guidance 
suggests at least isolated showers (likely able to produce a bit of 
lightning) in the vicinity of the airports starting at around 20Z-
22Z, and perhaps continuing into the evening hours. 
We'll see quite the change from Friday to Saturday across most of
the lower elevations, as a cold front pushes into the region. 
While temperatures on Friday may hit 80F, most of the lower 
elevations will struggle to reach 60F on Saturday. Similar or even
cooler temperatures are expected by Sunday with cooling mid-level
temperatures and increased cloud cover. The GFS remains on the 
warmer side of guidance this evening, with the ECMWF and the AI 
GEFS/ECMWF ensemble are ~10-15F cooler. Either way, highs will 
return to near or slightly below normal values, along with 
increasing cloud cover and precipitation chances by Saturday 
night. Given the large spread across current guidance it's 
difficult to say too much more than that. Current trends continue 
to push more significant moisture into the region for Sunday, 
though our new PoP forecast isn't too much higher than previous 
forecast cycles. There is at least some reason for optimism if 
you're hoping for meaningful precipitation.

Beyond this weekend, most guidance does (at least briefly) 
suggest that temperatures will warm back into the 60s across the 
plains, with generally dry conditions. However, it's difficult to 
read too much into this given the uncertainty with the the 
northern jetstream beyond roughly days 4-5. The multi-model mean 
would be warm and dry through the end of the forecast period, with
a more active forecast pattern closer to the end of the month.

&&

.AVIATION /18Z TAFS through 18Z Thursday/...
Issued at 1208 PM MDT Wed Oct 21 2026

Current winds are light and variable over the Denver area with a 
shift to the ESE expected in the next hour or so. Southeasterly 
winds should pick up (~12KT) at around 21Z at KDEN and KAPA, with 
much weaker speeds at KBJC. Southerly winds will begin to develop 
over much of the CO plains and Denver metro in the evening, with a
light (<06KT) northwest wind at KBJC.

Mid level clouds will increase this evening as Pacific moisture 
arrives to area. A stray sprinkle cannot me ruled out over the 
Denver metro in the very early morning hours, but we expect 
shower/storm chances to increase (20-30% chance) Wednesday 
afternoon. While the exact timing and coverage of storms making it 
to the Denver area remains uncertain at this time, model guidance 
suggests at least isolated showers (likely able to produce a bit of 
lightning) in the vicinity of the airports starting at around 20Z-
22Z, and perhaps continuing into the evening hours. 

&&

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

&&

$$

DISCUSSION...Hiris
AVIATION...AA