417
FXUS65 KBOU 121753
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1153 AM MDT Mon Oct 12 2026

.KEY MESSAGES...

- Unseasonably warm and mostly dry conditions will persist across
  the forecast area today before cooler temperatures arrive
  Tuesday.

- Isolated showers remain possible for the northern mountains
  through Monday, before precipitation chances increase and spread
  onto the plains from late Tuesday through Wednesday. Still some
  uncertainties on when things will start to dry out.

- A few inches of mountain snow becoming increasingly likely,
  mainly above 10,000 feet.

&&

.DISCUSSION /Through Sunday/...
Issued at 1122 PM MDT Sun Oct 11 2026

At the turn of 0Z this evening, satellite imagery shows the synoptic
pattern has evolved about as expected, with a deep longwave trough
situated across the West Coast and an upper-level closed low over
Washington and Oregon. Colorado remains downstream of the trough,
with southwesterly flow bringing gusty winds to some of our highest
peaks this afternoon and early evening (64 mph was observed at
Breckenridge Ski Resort). Unfortunately, moisture remnants of
Tropical Storm Rachel mostly stayed to our west and north, with only
a few showers and weak storms making their way into our mountains
today. A 60-70 kt 500 mb jet currently over western Colorado is
expected to shift eastward through the evening and overnight tonight
that will bring an uptick in winds across our highest elevations
tonight and Monday morning, with some breezy conditions also
expected along the Palmer Divide and and portions of the plains.
The strongest gusts (~55-65 mph) are expected to remain above
about 10,000 feet, but we may see a few downsloping gusts make
their way into the higher foothills. This will also allow for some
shower potential to persist mainly west of the Continental Divide
through the overnight hours.

Today (Monday) is still on track to be our last unseasonably warm
and mostly dry day before a significant cool down begins Tuesday.
700 mb temperatures are expected to cool by a few degrees over
Sunday that would bring a few degrees of cooling to the surface.
Temperatures are forecast to be in the upper 70s to low 80s across
the plains, 60s and 70s for the foothills, and 50s and 60s for
the mountain valleys. Precipitation chances will be limited to the
northern mountains and remain very light (a few hundredths, maybe
a few tenths for western Jackson County). A cold front is
expected to slide south into Colorado Monday evening that will be
the beginning of a period of much cooler temperatures and
increased precipitation.

The latest ensembles do show far more agreement this evening on how
the approaching trough will evolve through the middle of the week,
though a few slight differences do remain. By Tuesday morning, the
center of the closed low should be just about to the Great Basin and
moisture will start to increase over our mountain counties. The
lower elevations are expected to remain dry until sometime in the
late afternoon/evening, but we could see some rain showers and
snow showers (at our highest elevations) in the mountains
throughout the day. We will likely see snow levels change as we
approach midweek, with some slight differences remaining in timing
of the low, but at the surface, another cold front is expected
overnight Tuesday into Wednesday that will bring a second wave of
colder air to the forecast area as well as upslope flow. As of
now, the GFS is a touch faster with the low evolution that brings
700 mb temperatures down to around -2C to -3C by Wednesday
afternoon, whereas the ECMWF keeps them around 2-3C. This would
mean the difference between snow levels around 7,500` with the
lower temperatures vs. 9,000`+ for the warmer temperatures. Latest
omega fields put the greatest timing for synoptic lift to be
Wednesday (GFS in the morning/afternoon, ECMWF in the
afternoon/evening). Looking at precipitation chances, despite the
small discrepancies still remaining amongst guidance, there is
high confidence that the lower elevations will finally see some
much needed moisture with this passing system, as Wednesday is
expected to be a cool and damp day across the forecast area. As
for QPF totals, ensembles favor the eastern slopes of the Front
Range and the northern mountains, with the LREF Grand Ensemble
mean bringing .5" to .7" of rain to the I-25 Corridor by Wednesday
evening, and up to another .25" by Thursday evening. Snow looks
likely for the mountains and we could even see some light
accumulations reach the mountain valleys. At this time, forecasted snow
accumulations fall short of any Advisory levels (which could still
change), but we do expect to see some slick travel conditions
develop along our mountain passes on Wednesday, maybe into
Thursday. It seems the time has finally arrived to make sure
vehicles are ready for winter driving conditions for those who are
heading into the mountains. As for temperatures, the NBM is
notorious for struggling with pattern changes, so have started to
nudge temperatures downward to more align with MOS guidance. We
will have to monitor for potential Frost Advisory needs in the
upcoming forecast packages for later this week. After this system
moves through, trends indicate that warmer and drier conditions
should return for next weekend.

&&

.AVIATION /18Z TAFS through 18Z Tuesday/...
Issued at 1150 AM MDT Mon Oct 12 2026

VFR conditions through late tonight before low stratus becomes
likely early Tuesday. Winds will be south to southwest and gusty
this afternoon with some gusts as high as 20-25 kts at KDEN and
KAPA. KBJC has some southeast winds at this time, but will also
turn to the southwest later this afternoon with some lower wind
speeds than at the other two sites. The chance for southeast winds
to make it into KDEN over the next hour or so is low as seen on
the latest velocity trends.

Guidance, including BUFKIT soundings and MOS guidance, is in good
agreement about low stratus for the sites on Tuesday morning. A
pre-frontal push is slated to arrive around 5/6z turning winds to
the northwest before the front pushes through from north to south
around 10-12z and turns winds more to the north. Ceilings will
start to lower after 5z, but then drop to as low as 1000-2000 ft
AGL after 10z and lasting through at least 16z in general. As of
now, ceilings look lowest from ~13-16z Tuesday. Confidence is
highest at KDEN with a shorter window for the low stratus
currently expected at KAPA and slightly higher ceilings at KBJC.

Winds for tomorrow afternoon turn to the east for much of the
afternoon with speeds around 8-12 kts and ceilings slowly rising
through the afternoon. Near the end of this TAF period, ceilings
are again expected to lower ahead of the incoming storm system for
late Tuesday into at least Wednesday.

&&

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

&&

$$

DISCUSSION...9
AVIATION...MV

NWS BOU Office Area Forecast Discussion