866
FXUS65 KBOU 162138
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
238 PM MST Sun Nov 16 2025

.KEY MESSAGES...

- Fast moving storm system will bring snow to the mountains this
  evening through most of Monday. Travel impacts tonight and
  tomorrow, highest impacts for Rabbit Ears Pass.

- Strong, gusty winds develop across the Front Range
  Mountains/Foothills late Tonight and Monday.

- Still watching potential for a stronger early season storm next
  week, but considerable uncertainty. It will be cooler through
  the week ahead.

&&

.DISCUSSION /Through Sunday/...
Issued at 238 PM MST Sun Nov 16 2025

The closed upper low moving into western Utah will push northeast
tonight and move across southern Wyoming Monday morning. Moderate
QG lift on the front end of this system will bring what should be
an organized area of precipitation across our mountains starting
mid evening. We see that as the best opportunity for snow
accumulation and travel impacts in the mountains of the I-70
Corridor/Summit County. The main moisture band then continues to
lift northeast with some drying and tapering off of the snow
showers late tonight. However, orographics strengthen from a more
favorable westerly component in the wake of the upper low, and it
still appears moisture profiles will be favorable for additional
accumulations in most of the mountains north of the I-70 Corridor
through at least mid afternoon Monday. We`ll maintain the Winter
Weather Advisory for the mountains from Rabbit Ears Pass northward
where latest guidance supports 4-10" snowfall with locally higher
amounts. We still think most of the northern Front Range will see
3-6". Meanwhile, the I-70 mountain corridor and Summit County
most likely sees 0.5 to 3" amounts due to poor orographic
contribution when the best moisture comes across this evening,
and then residing south of the main mid level moisture plume on
Monday when the better orographics finally arrive.

With regard to winds, the potent upper level trough moving to our
north and east and strengthening gradients/flow aloft will mean
strong, gusty winds developing along the Front Range. There are
still indications we see a mean state critical layer develop by
09Z tonight, and cross sections show cross mountain component
strengthening to 30-35 kts. Typically, if these scenarios unfold
we can double that magnitude, so peak gusts could reach 75 mph in
local spots 09Z-12Z. Otherwise, we`ll have to rely on the brute
force and modest stability at mountain top to generate high winds.
For now, the stable layer appears limited by mountain snowfall and
an elevated stable layer through most of Monday, so the chances
of High Wind Warning criteria being met are likely confined to
localized areas in the Boulder County foothills. We`ll message
that accordingly and not issue a High Wind Warning at this time
since more widespread high winds are not anticipated. We`ll
continue to monitor as the night progresses of course, but latest
models were also trending slightly weaker.

Tuesday will feature drier and calmer conditions as an upper level
ridge bumps up across the forecast area. Temperatures will remain
cooler than what we`ve recently experienced to be sure, but still
a few degrees above normal.

We`re pretty certain Wednesday will still be a relatively dry and
mild day, still caught under some ridging as the next storm system
slides slowly across the SoCal region. That`s where the fun
begins.

A considerable amount of uncertainty exists with how this upper
low is treated, and any interaction with the northern piece of
energy that comes out of the parent trough and ejects eastward
across the U.S./Canadian border. A bundle of solutions exist;
some showing an open trough kicking slightly faster across the
forecast area, some ejecting the low to the E/SE into Texas, a few
still incorporating the northern stream energy into the SoCal
low, and still a few others (the potentially important ones)
kicking the upper low E/NE across northern New Mexico into the OK
Panhandle. The latter solution would favor a more significant
precipitation event, but even some of those would be too far south
to bring significant precipitation into the Front Range. IF, and
that`s a relatively big IF, the stronger slightly northern track
could verify then we would see more impactful weather. The latest
ensemble data shows about 25-35% of the ECMWF and AI members push
out this solution with heavier precipitation and measurable snow
back to Denver, while about 50% have lighter precipitation and
minimal if any snow, while the other 15-25% are relatively dry.
GEFS numbers have significantly lower potential.

Whatever the case, there is a LOT of uncertainty at this point
so we need to stay away from picking/choosing any one particular
run or even cluster of models (which are fairly evenly split at
this time). While it will be difficult to phase the energy
together at any given point, this storm system still bears
watching. Given this unique and relatively unstable synoptic
setup, we may not know much more for a couple days yet - stay
tuned for the latest.

There is still some weak trailing troughing possible into Saturday,
but overall drier and slightly warmer (near normal) weather
should return at some point next weekend.

&&

.AVIATION /18Z TAFS through 18Z Monday/...
Issued at 1041 AM MST Sun Nov 16 2025

Main concern is the winds over the next 30 hours. To start, light
and VRB winds are on course to transition to diurnal easterlies
given sufficient sunshine and weak gradient. Those winds will then
turn E-SE-S through 04Z. After 04Z, high based showers
(sprinkles/virga) will approach which means a period of gusty
outflow winds from the SSW will be likely (60% chance), so added a
TEMPO G30kts to account for that, with a low probability (20%
chance) of 35-40 kts per latest HRRR.

After that disturbance moves across, we`ll see a mountain wave
develop as west/southwest flow strengthens. Thus, some occasional
West gust to 25 kts will be possible as far east as KDEN 08Z-15Z.
Upper level trough passes by/before 15Z so that`s when stronger
subsidence arrives. That should be enough to bring some of the
strong/gusty winds near the foothills eastward onto the adjacent
plains including KDEN and KAPA. We may approach crosswind
thresholds, especially if a more westerly component wind occurs,
but currently forecast 280 degrees with G25-30 kts starting 16Z
and continuing through about 21Z. After 21Z, we should see a
decrease of W/NW winds, and even a 30-40% chance of some variable
winds working into KDEN and KAPA.

KBJC, on the other hand, will be much more vulnerable to the
strong, gusty winds downsloping off the foothills. We`ve bumped up
the TEMPO winds overnight to account for potential of initial
mountain wave, but then higher confidence of stronger and more
persistent winds developing by 14Z-15Z Monday with gusts to 35-45
kts likely.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 8 PM this evening to 5 PM MST
Monday for COZ031.

&&

$$

DISCUSSION...20
AVIATION...20

NWS BOU Office Area Forecast Discussion