251
FXUS65 KBOU 161741
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1041 AM MST Sun Nov 16 2025

.KEY MESSAGES...

- One more day with well above normal temperatures today, before a
  cooling trend through the rest of the week.

- Storm system expected to bring snow to the mountains this
  evening through most of Monday. Travel impacts possible tonight
  and tomorrow, mainly over Rabbit Ears Pass.

- Potential for strong gusty winds across the Front Range
  mountains/foothills Monday.

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

&&

.UPDATE...
Issued at 231 AM MST Sun Nov 16 2025

A few updates of note tonight... mainly for tonight/Monday. The
main upper trough axis over southern California this morning is
expected to eject into northwestern Colorado by early Monday
morning, before drifting east-northeastward into western Nebraska
by Monday evening. That track should promote two distinct period
of snowfall across the mountains - an initial organized band of
snow this evening associated with the main QG ascent ahead of the
shortwave, followed by a period of orographically-driven snowfall
as moisture wraps around the low in the west-northwesterly flow.
Most of the overnight guidance has increased QPF by quite a bit
across the Park Range, and the combination of 3-10" of snow along
with blowing snow potential is enough to add in a relatively short
Winter Weather Advisory there.

Overnight guidance was also a little more bullish with the wind
potential across the Front Range Monday behind the departing upper
low. There were a couple of rather extreme solutions offered by
the 00z CAMs (namely the 00z HRRR/WRF-ARW) that developed a rather
strong (albeit brief) mountain wave with cross sections noting a
pronounced wind shear layer from roughly 550-400mb. These two
model runs appear to be outliers and our forecast is closer to the
rest of the multi-model mean from tonight... which would still
support gusts of 55-65 mph. While a High Wind Watch was briefly
considered, I`d want to see far more consistency from the rest of
today`s guidance before issuing any headline.

Finally... the potential storm system for the latter half of this
upcoming week continues to cause headaches. Models generally
struggle with cutoff lows in the medium range period, and given
how many moving pieces there are to the synoptic pattern during
this period, it seems like it would be exceptionally difficult to
"thread the needle" and find a storm track that would produce
sufficient moisture/upslope and cold air to give any of our lower
elevations a real taste of winter.

&&

.DISCUSSION /Through Saturday/...
Issued at 245 PM MST Sat Nov 15 2025

One more warm day is on tap for Sunday before the weather pattern
changes to a cooler and more unsettled regime.

Our current upper level ridge will shift east Sunday as the upper
low off SoCal opens up and lifts northeast into the Great Basin.
This will keep the mild airmass in place for one more day, and
there should be more sunshine as upper level moisture and
cloudiness decreases by early Sunday morning. Southerly gradients
increase over the eastern plains for breezy conditions there.

The upper trough ejects northeast from Utah into southern Wyoming
Sunday night. The best QG lift and moisture combination is staying
a bit farther north than advertised yesterday, so the chances of
showers on the adjacent plains has decreased in all but the
northern border area. Most of the mountains should still see a
round of snow starting Sunday evening, but the best backlash and
leftover moisture with stronger westerly orographics for Monday
morning appears to have shifted to near the Wyoming border area so
the higher storm totals (4 to locally 8+") will be confined to the
Park Range. Amounts of generally 2-5" expected for the northern
Front Range Mountains and RMNP, while Summit County and I-70
Mountain Corridor will be mostly shadowed during the best lift
Sunday evening - so look for 0.5-3" amounts there. Overall,
generally minor travel impacts expected Sunday night into early
Monday morning for the alpine areas above 9,000 feet, but enough
for slick and hazardous travel conditions due to temps falling
into the 20s Sunday night and allowing freeze-up.

Cooler air infiltrates the region Monday behind the upper level
trough/cold front, which will then stick around through Tuesday
despite dry conditions and upper ridging. It will also be windy
over the northern mountains and northeastern plains Monday in this
system`s wake. Potential gusts to 50-60 mph and some blowing snow
over the higher peaks Monday, while the northeast plains could
see gusts to 35-40 mph depending on how low level gradients
respond.

The main question that lies ahead is the track and intensity of
the next storm system that could impact the area anywhere from
late Wednesday into Friday. Operational models including the GFS
and ECMWF were trending more toward a solution of kicking the
next upper level low from southern California east/northeast
across the Southern/Central Rockies and into the adjacent High
Plains by Thursday or Thursday night, a rather favorable track for
significant precipitation. Ensembles were trending this way as
well, but at a much slower pace and a considerable amount of
those had differing tracks or much weaker solutions. Meanwhile, a
look at AI output over the last two runs showed much higher
probabilities (~80%) for measurable precipitation for the forecast
area including Denver and northeast plains Thursday to Friday,
with 35-50% having measurable snowfall for Denver. Operational
ensembles meanwhile, had about 10-20% lower odds but the trends
were higher over the last 12-24 hours. Considering the latest
trends, we have increased PoPs from previous forecasts.

This storm system bears watching given potential for a negatively
tilted system, which would spell incorporation of gulf moisture,
slower movement, deeper upslope, and significant precipitation. It
should also be noted that temperatures could end up on the
marginal side for snow. Finally, it needs to be stated that the
trough could get kicked out much faster and weaker than the latest
operational runs. There is a LOT of uncertainty at this point and
stay away from picking/choosing any one particular run. However,
given the potential noted above, this storm system and the latest
trends will be monitored closely over the next couple days.

&&

.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.

&&

$$

UPDATE...Hiris
DISCUSSION...20
AVIATION...20