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