769
FXUS65 KBOU 150521
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1021 PM MST Tue Jan 14 2025

.KEY MESSAGES...

- Dry Wednesday and Thursday with warmer temperatures. Big change
  arrives Friday.

- Bitter cold temperatures this weekend, with low temperatures
  below zero Saturday night and Sunday night. Staying very cold
  through at least Monday. Wind chill values as low as -30 F
  possible across portions of the I-25 corridor and eastern
  plains.


- Accumulating snow potential is high (>80%) for Friday night into
  Saturday. Heaviest totals likely in/near the foothills and I-25
  Corridor with several inches likely (>60%). A chance (30-40%)
  that light snow lingers into Monday.

&&

.UPDATE...
Issued at 748 PM MST Tue Jan 14 2025

Isolated flurries in the mountains will taper off over the next
couple of hours. Aside from minor and highly targeted edits in
our high valleys to lower overnight temperatures slightly, no
meaningful changes were made to the forecast this evening.

&&

.SHORT TERM /Through Wednesday/...
Issued at 222 PM MST Tue Jan 14 2025

Lingering flurries in the mountains will end this evening as
drier/more subsident air builds in behind today`s weak passing
trough. That also means clearing skies, light winds, and strong
radiational cooling overnight. We cooled off some of the colder
valleys, with a couple high mountain valleys expected to reach -15
to -25F again. Mostly single digits to lower teens expected on
the plains, but a little warmer near the foothills with a light
downslope component.

Nearly full sunshine should return on Wednesday with the upper
level ridge building across the area. We`ll also see warm
advection, but generally northerly flow and not too much downslope
component. We`ll also have sharp inversions to start the day, so
modest warming expected. That said, we did bump up temps a bit
from the previous forecast as we expect nearly full sunshine and
rather strong warm advection just off the deck.

&&

.LONG TERM /Wednesday night through Tuesday/...
Issued at 222 PM MST Tue Jan 14 2025

Upper level high pressure over the Rocky Mountain Region will bring
dry and mild weather to North Central and Northeastern Colorado for
the start of the forecast period. The large upper level ridge of
high pressure over the Western U.S. will start breaking down on
Thursday with a more zonal flow setting up over Colorado. Some
downsloping flow associated with this pattern should result in
warmer temperatures on Thursday with high temperatures on the plains
climbing into the upper 40s to mid 50s.

On Friday, we should see a big change in the weather as a broad
upper level trough of low pressure deepens over the Central/Northern
Rockies and Great Plains States and an associated Arctic cold front
moves into Colorado from the north. Latest models are showing
Friday`s temperatures climbing into the lower to mid 40s by noon and
then sharply dropping during the afternoon behind the passage of the
cold front. Model soundings are showing the moisture lagging behind
the front by a few hours with the column (surface to 600MB) becoming
saturated after 00Z Saturday. With this scenario, would expect some
snow showers to develop across the Front Range Foothills and
adjacent plains by late afternoon with snow increasing during the
evening hours. Upslope flow, Frontogenic lift, Isentropic Upglide
and a favorable Dendritic growth profile associated with the Arctic
front combined with QG lift from a 90KT+ upper jet should result in
accumulating snow from the Front Range Mountains eastward across the
Front Range Urban Corridor/Palmer Divide and adjacent plains Friday
night into Saturday afternoon.

Snow is expected to end by Saturday evening as moisture and lift
decrease. However, with the Arctic airmass around can`t rule out a
few lingering light snow showers and flurries.

Many of the models are suggesting a secondary surge of Arctic air
along with another round of light snow moving into the forecast area
Sunday night into Monday morning. Due to run to run inconsistencies
and model differences there is some uncertainty in this, but the
models are trending toward this solution.

As for the temperatures, much below normal readings are expected
from Saturday through Tuesday morning. Due to model differences
and run to run fluctuations, there is uncertainty when we will see
the coldest temperatures across the forecast area. At this time,
Sunday and Monday look to be the coldest days of the week with
high temperatures only climbing into the single digits most areas
with temperatures plunging below zero Sunday, Monday and Tuesday
mornings. In addition, periods of bitterly cold wind chills
between -15 and -35 Degrees will be possible across portions of
the Front Range Urban Corridor and Plains with even colder readings
in the higher mountains. As a result, cold/extreme cold headlines
may be needed.

Warmer and drier conditions are expected on Tuesday due to some
downsloping flow and upper level ridging.

&&

.AVIATION /06Z TAFS through 06Z Thursday/...
Issued at 1017 PM MST Tue Jan 14 2025

Stubborn deck of 9000 ft ceilings refuses to scatter out.
Satellite shows this cloud deck may linger for a few more hours
thru at least 07z. Once this cloud deck scatters out VFR
conditions will follow through Wed aftn.  Winds have gone light
drainage and will continue overnight but should become more SW
by 12z. For Wed, hi res data has varying directions thru the day.
Have opted to continue with a SW component, however, they could
switch to a more northerly direction for a few hours in the aftn.

&&

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

&&

$$

UPDATE...Rodriguez
SHORT TERM...Barjenbruch
LONG TERM...JK
AVIATION...RPK