022
FXUS65 KBOU 191131
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
431 AM MST Sun Jan 19 2025

.KEY MESSAGES...

- Bitter cold through Tuesday morning.

- For the plains, wind chills of -15F to -25F this morning and
  again late tonight through Tuesday morning.

- For the mountains and mountain valleys, the coldest conditions
  are expected Monday night and Tuesday morning with temperatures
  and wind chills falling to -35F to -45F.

- Another wave of light snow tonight and into Monday morning.

- Temperatures moderating somewhat through the rest of the week.

&&

.SHORT TERM /Through Tonight/...
Issued at 430 AM MST Sun Jan 19 2025

It`s been a chilly night across the area with most locations
falling below zero. Across the urban corridor temperatures have
dropped into the 5 above zero to 5 below zero range. At DIA, the
low so far has reached -11F. Most of the high country is running
-5F to -20F with the coldest valleys locations nearing -30F. The
high temperature forecast for today will be very challenging. The
day begins mostly sunny, but mid and high clouds move in mid to
late morning, with mostly cloudy skies for this afternoon. Airmass
will be warming, but how much will mix to the surface with cloud
cover and mainly weak winds. Like the previous shifts, will
undercut forecast model guidance with highs mainly in the teens
across northeast Colorado.

An upper level trough embedded in the north-northwest flow aloft
and cold front will bring the next shot of arctic air tonight. The
cold front pushes south through the area mid to late evening with
light snow developing behind it. Snowfall is expected to be light
and fluffy with up to 3 inches possible for the high country and
urban corridor. Where the orographic forcing is less, the plains
may see up to an inch of snow. This airmass will be a little
colder than the current one over us. Even with cloudy skies and a
little wind, temperatures are expected to fall below zero by 12Z
Monday morning.

&&

.LONG TERM /Monday through Saturday/...
Issued at 430 AM MST Sun Jan 19 2025

On Monday, an amplified upper level ridge of high pressure will be
centered just off the Pacific West Coast with a large and broad
upper level trough covering most of the Continental U.S. Colorado
will be under the influence of a moderate northerly flow aloft
with the Arctic airmass keeping its hold on our forecast area. The
day should start out with some light snow in the morning across
the Front Range Urban Corridor, mainly from the Boulder/Longmont
area south across Metro Denver into the Palmer Divide. The snow is
expected to diminish by late to mid morning as the upslope flow
decreases. Accumulations are expected to be light with amounts
less than an inch. The high country should also see some light
snow throughout the day with light accumulations as well. With the
Arctic airmass still in place and reinforced from the nigh
before, max temperatures will struggle to rise into the single
digits across most of the CWA with some below zero reading across
the higher mountains. In addition, there will be enough wind
across the plains to cause wind chill readings as low as -25F.

The overnight lows across the plains Monday night into Tuesday
morning are a little challenging as we see a balancing act between
radiational cooling due to clearing skies and warm air advection
from a downsloping flow. My best guess is that we will see the
coldest temperatures at DIA in the evening within a couple hours
after sunset with temperatures gradually warming up overnight as
the upslope flow and warm air advection kicks in. The mountains
will be even colder with temperatures ranging between -15F and -30F
with the potential for colder temperatures to -40F in favored
cold spots such as Antero Reservoir. These temperatures combined
with wind will result in wind chill values as low as -25F on the
plains Monday into Tuesday morning and as low as -45F in the high
country Monday night. Therefore, and Extreme Cold Warning remains
in effect for the plains through 9 am Tuesday morning and a
Extreme Cold Watch has been issued for the Mountains and Mountain
Valleys for the Monday evening through Tuesday morning period.

In addition, cross sections are showing a mountain wave setting up
on the lee of the Rockies with the Front Range Mountains and
foothills will seeing wind gusts between 45 and 60 mph from Monday
night through Friday.

The combination of warm air advection and the downsloping flow will
result in temperatures moderating into the 30s Tuesday through
Thursday on the plains with even milder temperatures in the mid
to upper 40s on Friday as we see some upper level ridging over
Colorado.

By next Saturday, models are hinting at a return to colder
unsettled weather as at another upper level trough and associated
cold front moves across the region.

&&

.AVIATION /06Z TAFS through 06Z Monday/...
Issued at 345 AM MST Sun Jan 19 2025

It will be mostly clear through 12-14Z. Patchy fog will remain
possible this morning to the north of Denver at KFNL and KGXY. Weak
southerly downslope winds are expected to prevent fog from forming
at KDEN and KAPA. Light winds to prevail Sunday while mid and high
clouds increase ahead of the next storm system. These light winds
turn northerly after 18Z. Gusty north winds to accompany the cold
front 04-06Z Monday. Clouds lower below 6000 feet a little after
00Z Monday. The clouds continue to lower with light snow forming
behind a cold front 04-06Z.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Extreme Cold Watch from Monday evening through Tuesday morning
for COZ030>034-037.

Cold Weather Advisory until 9 AM MST Tuesday for COZ038>051.

&&

$$

SHORT TERM...Meier
LONG TERM...JK
AVIATION...Meier