Area Forecast Discussion
Issued by NWS Pueblo, CO

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FXUS65 KPUB 131112
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
512 AM MDT Wed Mar 13 2024

.KEY MESSAGES...

- Mountain snows will increase in intensity through tonight.
  Showers and a few thunderstorms will spread into the plains
  this afternoon and expand eastward through tonight with snow
  levels dropping to around 4500 feet towards morning.

- Heavy wet snow continues for the mountains, valleys and
  adjacent plains through Friday with 1-2 feet of snow expected
  for the southeast mountains and Pikes Peak Region. Widespread
  travel impacts likely.

- Still some uncertainties with snow levels which could increase
  snow amounts if a quicker and more persistent rain to snow
  switch over occurs on Thursday for southern El Paso, eastern
  Fremont and Pueblo counties.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 351 AM MDT Wed Mar 13 2024

Today...

The latest high res guidance suggests that QPF will continue to
increase throughout the day and really begin to ramp up between 21Z
and 00Z (3 to 6 PM). There is also going to be a fair amount on
instability moving over the area (especially for this time of year)
as the initial wave transitions overhead, with CAPE values getting
close to 1000 J/kg over the Pikes Peak Region by around 21Z (3 PM).
In addition, steeper lapse rates of up to around 9 C/km concentrated
over a vast area of SE Colorado will also help to initiate
thunderstorms off of the mountains this afternoon, and then these
will be moving over the adjacent valleys and plains. Heavier bursts
of snow, with thunder, will be possible over the higher elevations,
and some of these that move out into the San Luis Valley and over
the plains could produce small hail and/or graupel/snow pellets.
This could also bring down snow levels temporarily over the higher
elevations of the plains and within the San Luis Valley with the
heavier convective showers and thunderstorms. There could also be
snow squalls possible with this kind of instability in place. Snow
will generally increase in intensity across the higher terrain, with
the heaviest amounts shifting throughout the day from the southwest
mountains to the central and southeast mountains. With the
convective element of these showers, very heavy amounts of snow
could cause rapid accumulations of snow in a short duration for the
higher elevations, and anyone hiking should prepare for that.
Showers and storms will continue to expand eastward across all of
the plains into the early evening hours.

Northwesterly winds will come northeasterly by later in the morning
across the plains, which will continue to advect in colder
temperatures and help to lower snow levels going into the later
evening hours. High temperatures up until that time will max out in
the upper 50s to lower 60s for most locations across the plains,
with even a few mid 60s for the far southeastern plains. Across the
higher terrain, it will be relatively cooler with extensive cloud
cover and increasing snow moving over, and only top out in the 20s
and 30s for most of the higher elevations, although it will be
warmer in the San Luis Valley and upper Arkansas River Valley due to
the downsloping winds, and will likely make it into the low 50s for
some locations.

Tonight...

As the shortwave continues to progress eastward, there will be a
good amount of upper level diffluence moving over and the 700-500 mb
column will become more saturated given a well-defined moisture belt
evident in the deterministic models. 700 mb winds will also be
shifting to a more easterly direction and help to advect in more
moisture within the TROWAL (trough of warm air aloft) as the
associated surface low ejects out over the southern portion of
Kansas. Surface winds also being primarily out of the NE direction
will provide upsloping across the I-25 corridor. The combination of
all of these parameters will result in there being high amounts of
QPF for the southeastern mountains and plains, especially up against
to east-facing slopes of the mountain/plains interface. Depending on
the freezing level (which continues to be a challenge in determining
where this will establish itself after the colder air has
infiltrated the plains) could bring about very heavy amounts of
snow. With recent warmer temperatures, the other challenge will be
how quickly that snow will begin to accumulate on road surfaces.
However, with higher amounts of precip expected over the Palmer
Divide area, the I-25 corridor will likely experience travel impacts
going into the later hours of the night as roads become more slick
and slushy. It will also be a "wetter" snow. Temperatures will
continue to fall into the low 30s for most of the plains, and likely
it will remain rain for elevations less than 5000 feet, although
with heavier showers, this could also be temporarily reduced with
rapid accumulating snow possible for areas such as Pueblo.
Otherwise, most of the impacts will be felt with locations above
6000 feet in elevation. This snow or rain/snow mix will continue
across most of the I-25 corridor with more tricky travel issues for
the morning commute.   -Stewey

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 351 AM MDT Wed Mar 13 2024

Key Messages:

- Heavy wet snow expected for the mountains, valleys and adjacent
plains through Friday with the heaviest snowfall amounts this season
expected for the southeast mountains and Pikes Peak Region where 1
to 2 feet with locally higher amounts will fall.

- Still some uncertainties with snow levels which could increase
snow amounts if a quicker and more persistent rain to snow switch
over occurs on Thursday for southern El Paso, eastern Fremont and
Pueblo counties.

Set up still looks favorable for a heavy wet snow in and near the
mountains across southern CO into Friday.  Deformation band
precipitation shield will set up across the area Thursday with
impressive isentropic upglide, and 20-30 kts of northeast to
easterly upslope flow focusing on the southeast mountains, as the
upper low drops southward into the Desert Southwest ejecting energy
across southern CO within a prolonged diffluent upper flow pattern.
Still looks like the southeast mountains will fair the best with 1
to 2 feet of snow likely based on NBM probabilities greater than 60%-
100% range for greater than 12", and 60%-80% range for greater than
24". There an impressive 50-70% of members with over 30 inches of
snow across the Wets with slightly lower probabilities across
northern Teller county. Current suite of Warnings still looks on
target and no changes were made.

Snow levels drop more quickly in the latest model runs which raises
concerns for heavier snow accumulations in some of the bordering
zones such as southern El Paso, Pueblo and eastern Fremont counties.
Nice band of heavier precipitation sets up across Pueblo, Crowley
and Otero counties Thursday where isentropic upglide appears to
maximize. Some high res models show a precipitation minima across
southern El Paso county given the northerly flow off the Palmer
Divide, which gives pause for an upgrade to a warning in spite of an
earlier switch over. Pueblo county also has quite a range in snow
totals given a greater likelihood for some melt off on Thursday as
temperatures bump up above freezing during the afternoon.  Areas in
all 3 counties are showing up to 12 inches possible nearer the
mountains and south slopes of Monument Ridge. Will hold the course
for now and let later shifts see how things develop in later runs,
but even after extensive QPF edits this morning, still getting more
solid advisory numbers across the majority of these zones. Suspect
QPF in the models could be running a little hot as well away from
the terrain.  Either way, areas bordering the warning zones will
likely have strong gradients and heavier snow near the higher
terrain. There will be some blowing snow with north winds gusting up
to 35 mph across the Palmer Divide and El Paso County. However,
given the heavy wet nature to the snow, this may limit blowing and
drifting some.  Either way, travel will be treacherous.

QPF has increased across the southeast plains with the overnight
runs, but warmer temperatures should keep mostly rain, with brief
rounds of rain/snow mixes during the overnight and early morning
hours through Friday. Little to no accumulation expected.

A period of snow spreads into the San Luis Valley, with 2 rounds
possible. One comes in Thursday morning, then another comes in on
Friday. With a pause in between have upgraded the watch to a Winter
Weather Advisory given the chance for some melting between rounds of
snow. The upper low wobbles around across western AZ, southern CA
Thursday night through Friday.  This will keep snow going across
much of the area Thursday night though precipitation rates decrease
some. Another round of rain/snow spreads northward Friday morning as
energy ejects northward from the upper low across southern CO.
Suspect heavier precipitation will be more confined to the better
upper level difluence across the southwest mountains and San Luis
Valley.

Precipitation decreases late Friday, but the pattern remains active
and unsettled as the closed low meanders across the southwest U.S.
spreading rounds of snow showers across the mountains each day into
early next week.  Moisture becomes more limited with time, so
generally episodic light to moderate snow can be expected across the
higher terrain each day. Temperatures will gradually warm through
the period. -KT

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 351 AM MDT Wed Mar 13 2024

VFR conditions are expected to prevail for all TAF sites for most of
the first half of the forecast period, but then continue to
deteriorate thereafter to IFR and possible LIFR conditions due to
reduced VIS and lowering CIGs with the onset of SHSN for KALS, and
SHRA or SHRASN for KCOS and KPUB. SHRA/SHRASN will transition to SN
after 06Z at KCOS but more than likely remain as RA for KPUB through
the rest of the forecast period. Winds will be synoptically driven
at all terminals, primarily out of the S to SSW at KALS, and
initially out of the NNW at KCOS and KPUB, with a shift to a more
NE`ly direction at KCOS and E to ESE direction at KPUB by later in
the day, then return to a more N-NNE direction at both locations
towards the end of the forecast period. -Stewey

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 6 AM MDT Thursday for COZ058-060-
061.
Winter Weather Advisory until 6 AM MDT Thursday for COZ059-
062>064-066-068.
Winter Storm Warning from 6 AM Thursday to 6 PM MDT Friday for
COZ064>068.
Winter Weather Advisory from 6 AM Thursday to noon MDT Friday
for COZ069>071.
Winter Storm Warning from 6 PM this evening to 6 PM MDT Friday
for COZ072>075-079-080-087-088.
Winter Storm Warning until 6 AM MDT Friday for COZ076-081-082.
Winter Storm Warning from 6 PM this evening to 6 AM MDT Friday
for COZ077-078-084.
Winter Weather Advisory from midnight tonight to noon MDT
Friday for COZ083-085-086.

&&

$$

SHORT TERM...STEWARD
LONG TERM...TORGERSON
AVIATION...HODANISH/STEWARD


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