884
FXUS65 KPUB 210614
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
1214 AM MDT Sat Sep 21 2024

.KEY MESSAGES...

- Rain showers spread from south to north across the area on
  Saturday, with scattered thunderstorms possible, especially
  south of Highway 50.

- Strong to potentially severe thunderstorms possible Saturday
  afternoon and evening for the San Luis Valley, southern
  mountains and portions of the Raton Mesa Region.

- Snow levels may drop down to 8000-9000 feet, but with heavy
  wet snow accumulations up to around 10 inches for the higher
  peaks above 10-11kft north of Hwy 50.

- Cold night time low temperatures are expected Sunday night
  into Monday morning, with a medium chance (40-50%) for low
  temperatures below 32 degrees especially across the San Luis
  Valley.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 341 PM MDT Fri Sep 20 2024

Currently, upper level low spinning over srn California at mid-
afternoon, while initial push of deeper moisture/instability
and weak short wave were producing a few showers/storms over the
far sern plains. Temps have popped up into the 70s/80s at many
locations, with deep mixing generating some pockets of breezy
s-sw winds, especially along I-25. For the remainder of the
afternoon into early evening, while most concentrated area of
lift and showers has shifted into KS, did keep kept low pops
along the NM and OK borders to account for potential storm
reformation, as low moisture lingers and CAMs hint at one more
wave of isolated convection possible. For late evening and
overnight, expect a lull in precip activity, as upper low is
still too far away to provide much vertical motion, and low
level moisture return is rather meager. Most models have backed
off precip chances overnight across the srn mts, and will remove
pops from all areas through 12z.

Saturday, upper low lifts across AZ toward the 4 Corners by
late afternoon, while surface cold front drops south over the
plains, ending up near the NM border by afternoon. Precip
development Sat morning appears to be rather slow, with
showers/light rain creeping northward from NM into srn zones
through the morning, reaching roughly the Arkansas River by
midday. By afternoon, upward motion begins to intensify, with
widespread showers/embedded thunderstorms across much of the
area by 00z. Limited surface instability will be the main
negative factor for strong/severe storm potential Sat, though
shear and dynamic lift will be very strong, and we could see at
least some stronger storms over the San Luis Valley and near the
NM border, where CAPE values reach perhaps 500 J/KG before
storm formation. Some light snow possible toward 00z over the
peaks of the central mountains, though colder air doesn`t arrive
until later, so any daytime accums will be fairly light.

For outdoor events Sat across the Pikes Peak and Pueblo region,
rain will likely hold off until afternoon, though cold frontal
passage early in the morning (7-9 am mdt) may produce some
rather strong (gusts 30-40 mph) north winds into midday.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 341 PM MDT Fri Sep 20 2024

No real big changes in thinking or even with the forecast at
the start of the period, as the anticipated large upper low
continues to push overhead and bring widespread showers and
thunderstorms to much of southern Colorado.

The severe risk across the San Luis Valley and far southern
I-25 corridor will continue to lower in the evening hours,
though forecast soundings indicating some instability lingering
into the evening in these locations. So, can`t completely rule
out an isolated strong to severe storm in these locations during
this time, but once again, the risk will further lower
especially as the greatest ascent shifts east northeast. Further
to the east, widespread showers with scattered thunderstorms
are appearing likely over the plains. The risk of storms will be
in place over most of the plains Saturday evening, however,
highest risk will be east of the I-25 corridor and especially
closer to the Colorado and Kansas border where the instability
axis will be shunted. This looks to be more elevated instability
and think the risk of severe storms will be low in the evening.
However, can`t rule out at least a stronger storm capable of
producing small hail, lightning, and brief heavy down pours.

Over the higher elevations, expect precip development to
continue though will continue to shift more northward in time.
If any of the precip hadn`t changed to snow by then this will
quickly change as the upper low pushes overhead and much colder
air moves in. Once again, no big change in thinking with snow
development from Saturday night into Sunday morning, with any
snow remaining on the higher elevations of the higher terrain
and at snow levels above 10 kft. With the arrival of the colder
air Saturday night into Early Sunday morning, could easily see
snow levels fall into the 8-9 kft range at least briefly. At
this time though, think there is a low chance (20- 30%) for snow
levels to drop to this range. If this were to occur, areas
impacted would be lower elevations of Teller, Lake, and Chaffee
counties. Will need to continue to monitor this potential,
especially as this precip wraps around the slowly lifting upper
low. Once again, no real big changes to snow totals with up to
around 10 inches of snow expected over the higher elevations of
the central mountains and Pikes peak by Sunday morning.
Additionally, no changes made to the current Winter Weather
Advisories in effect.

The upper low will continue to slowly lift to the northeast on
Sunday, with any lingering rain or snow diminishing and/or
shifting to the east/northeast. Clouds will persist though and
with a cooler air mass in place, cool and well below normal
temperatures are expected area wide on Sunday. This will
continue Sunday night into Monday morning, especially as clouds
clear and winds further diminish. Only made small changes to
Sunday nights low temps, with mid to upper 30s to low 40s
expected over the lower elevations. With some uncertainty to
some lingering cloud cover, did not go lower at this time. Do
think there is a medium chance (40-50%) for low temps to fall
below freezing across the San Luis Valley, and a low chance
(20-30%) for low temps to fall below freezing across the plains.

Additional trough swinging through early next week could bring
additional showers and thunderstorms to the region late Monday
into Tuesday. After this period, a drier period with more
seasonal temperatures are expected for the remainder of the
forecast period.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1207 AM MDT Sat Sep 21 2024

VFR conditions to continue to COS, PUB and ALS through through
at least 16Z, before showers and storms develop ahead of the a
upper level low moving across the Desert Southwest attm.

COS...Between 12Z-14Z, a cold front will move south across the
plains bringing gusty north winds to the terminal. Winds will go
around to upslope and expect lower cigs with showers of rain by
the afternoon time period. Some isold thunder cant be ruled out
later in the period.

PUB...After about 15 UTC, the cold front will push across the
terminal. Cigs will gradually lower as the day progresses with
showers by afternoon. ISOLD thunder could be possible later in
the afternoon.

ALS...VFR likely during the afternoon time period with winds
becoming northeast by afternoon. Sct showers with some isold
thunder possible.

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from noon today to noon MDT Sunday for
COZ058-060-082.

&&

$$

SHORT TERM...PETERSEN
LONG TERM...RODRIGUEZ
AVIATION...MW