Area Forecast Discussion
Issued by NWS Pueblo, CO

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
000
FXUS65 KPUB 121104
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
504 AM MDT Tue Mar 12 2024

.KEY MESSAGES...

- Snow will be increasing and expanding eastward across the
  higher terrain tonight.

- Heavy snow likely for the southeast and southwest mountains
  and adjacent higher terrain above 5500 feet Wednesday into
  Friday.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 348 AM MDT Tue Mar 12 2024

Today...

Upper level flow is nearly zonal currently over the region, with
only a weak perturbation transitioning overhead this morning, which
could allow for a few more isolated snow showers to be possible over
the highest peaks of the central mountains. Other than that, dry
conditions can be expected for today across the CWA. Winds at the
surface will be out of the west to southwest across the higher
elevations and northwest for most locations across the plains. The
afternoon will yield some stronger wind gusts out of the southwest
for the San Luis Valley, although RH values are not expected to get
down to the 15 percent threshold. There will also be some stronger
and gusty winds for the far southeastern plains, although these are
not expected to get above the threshold to warrant critical fire
weather conditions as well. Even though the winds are not quite
there, given that there are still very dry conditions in place with
RH values forecast to be in the low teens for much of the plains, it
is still advised to exercise caution when engaging in any activity
that could cause a spark, as critically primed fuels are in
abundance over much of the plains and susceptible to quick fire
ignition. Mostly clear skies can be expected this morning, with
increasing mid to high level clouds by later today as a major
shortwave trough upstream approaches the region. The downsloping
winds will also help to warm the plains into the upper 60s to low
70s, which is still around 10 degrees above the seasonal average for
this time of year. The higher elevations will have temperatures max
out in the 30s and 40s for most areas, with 50s for the upper
Arkansas River Valley and San Luis Valley.

Tonight...

The major shortwave upstream over the northwestern states will
deepen and propagate eastward, allowing for mid to upper level flow
out of the southwest to advect in moisture and provide increasing
snow showers across the ContDvd initially, and then expanding
eastward across the rest of the higher terrain through the night.
The highest QPF with the high resolution models, given the
southwesterly flow, looks to be over the eastern San Juan Mountains,
and especially on the southwestern facing slopes. Some of the
guidance also suggests that a few showers could be moving over into
the adjacent plains, with the more likely area being over the Palmer
Divide. Because there will still be relatively warmer temperatures
in place, any of these should be in the form of rain, and because
the lower levels are dry, much of this will likely evaporate before
it reaches the surface (virga). The mostly cloudy to overcast skies,
along with a weak meso-low pressure center over the plains, will
keep temperatures modified and warmer than average. Lows will only
get down into the upper 30s to low 40s across the plains, and
generally in the teens to 20s for high country, with even some low
30s within the mid to upper Arkansas River Valley.   -Stewey

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 348 AM MDT Tue Mar 12 2024

Active pattern continues in the long term forecast as the upper
low drops southward along the UT/NV line then wobbles around
across the Desert Southwest through Friday before filling and
shifting southwestward as an upper jet drops southward out of
Canada through the northern/central plains over the weekend.

Main impact weather for southern CO still looks to be Wednesday
through Friday as southern CO comes under diffluent flow aloft
and a cold front drops southward across the plains Wednesday and
Wednesday night. Snow will spread into the western mountains on
Wednesday then begin to fill in across the southeast mountains
and adjacent plains as the front drops southward and some
convective instability develops in the afternoon. Snow levels
initially start out around 7000 feet, but will drop to around
5000 feet or a little lower during the overnight hours as colder
air spreads in from the north. A leading wave will rotate around
the east side of the upper low Wednesday night which will
provide some upper forcing Wednesday night through Thurs AM when
the heavier precipitation falls in and near the SE mountains.
Fairly sustained NE upslope flow keeps precipitation going
through Thursday as the upper low drops southward into southern
CA/SW AZ region. Although the brunt of the upper forcing shifts
to the southwest, the upper level difluence aloft continues into
Friday for southern areas and deepening northeast to easterly
flow will spread the focus for the heaviest precipitation
westward into the San Luis Valley and southwest mountains
Thursday night into Friday before precipitation tails down from
north to south in the later periods.

Snowfall amounts are still a challenge as much will depend on
the strength of the leading wave ejecting across CO, and snow
levels as this is still a relatively warm system for much of the
plains. To further complicate matters, snowfall will likely melt
off some during the day light hours for the lower elevations.
So in spite of some healthy QPF values ranging from roughly 1/2
inch to around an inch across the San Luis Valley and the I-25
corridor counties, wavering snow levels and above freezing
temperatures during the day light hours may reduce storm
impacts below 6000 feet. NBM shows a strong signal (80-100% of
model members) for 6" or more of snow for most of Fremont
county, the Wet Mountains, and the Palmer Divide and the
southern I-25 corridor counties. Have expanded Winter Storm
Watches to include these areas. Probabilities of 12" or more of
snow is in the 80%+ range across northern El Paso and Teller
county, the Wets and Sangres and western and central portions of
Huerfano county as well as the southwest mountains, which lends
confidence to expanding existing Watches to include these new
areas.

Mountains will fair best with Pikes Peak, the Wet mountains and
Sangre De Cristo mountains looking to see the heaviest
accumulations of a foot to close to 2 feet for the favored
northeast facing slopes. The eastern San Juans will also see
good orographics and upper difluence with up to 2 feet of snow
possible.

Some areas to monitor will be southern El Paso county, eastern
Fremont county around Canon City, southern Pueblo county and the
San Luis Valley, where intense snowfall rates during the colder
portions of the storm could lead to travel impacts. Suspect
these areas may need winter weather advisories as the event gets
closer, but as snow amounts are still prone to change, will
hold off issuing these for now.

Meanwhile, the southeast plains of Kiowa, Bent, Prowers and Baca
Counties are not likely to fair as well from this storm with
predominantly rain with some brief rain/snow mix Thu and Fri
mornings. However precipitation amounts are more likely to stay
in the 0.10 to 0.25 range.

As the storm fills over the southwest, we will see continued
unsettled weather with isolated to scattered showers through the
weekend over and near the mountains. A reinforcing cold front
will drop through the plains, but it appears the colder air
will stay off to the east. Saturday will likely stay below
normal for temperatures but warm back to near normal for Sunday.
Temperatures rebound early next week, though there is
considerable uncertainty as to how the cut off low across the
southwest U.S. ejects eastward to our south, which could have
minor affects on temperatures due to cloud cover. Main
precipitation chances should stay confined closer to the upper
low which will likely remain to our south.  -KT


&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 348 AM MDT Tue Mar 12 2024

VFR conditions are expected to prevail for all TAF sites (KALS,
KCOS, and KPUB) throughout the forecast period. Winds will be light
(less than 10 kts) and mainly influenced by diurnal affects at both
KCOS and KPUB. At KALS, they will also be mostly influenced by
diurnal affects as well, although with a low pressure system
advancing towards the region, the tightening of the surface pressure
gradient will help to increase afternoon winds out of the southwest,
which could gust up to around 25 kts. There will also be increasing
mid to upper level decks, and lowering for KALS with some VCSH or
-SHRASN/-SHSN possibly on station towards the end of the forecast
period. While confidence is low of any precip occurrence at KALS
being heavy enough to restrict VIS, it could temporarily reduce CIGs
and VIS down to MVFR or possibly IFR criteria periodically after 05Z.
-Stewey

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from 6 PM this evening to 6 AM MDT
Thursday for COZ058-060-061.
Winter Weather Advisory from 6 PM this evening to 6 AM MDT
Thursday for COZ059-062>064-066-068.
Winter Storm Watch from Thursday morning through Friday
afternoon for COZ064>068.
Winter Storm Watch from Wednesday evening through Friday
afternoon for COZ072>075-079-080-087-088.
Winter Storm Watch from Wednesday morning through late
Thursday night for COZ076-081-082.
Winter Storm Watch from Wednesday evening through late
Thursday night for COZ077-078-084.

&&

$$

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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.