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297
FXUS65 KPUB 192030
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
230 PM MDT Thu Sep 19 2024

.KEY MESSAGES...

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- Dry and generally quiet Today and Friday. Frost will be
  possible in the San Luis Valley Tonight.

- A few thunderstorms will be possible over the far southern
  plains Friday afternoon.

- Potent Fall system impacts the region through this weekend.

- Snow expected for higher elevations, especially central
  mountains and Pikes Peak.

- Low (~20%) confidence is severe weather across southern
  portions of the area.
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&&

.SHORT TERM /THROUGH FRIDAY/...
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Issued at 224 PM MDT Thu Sep 19 2024

Dry southwest flow will continue over our area today. Winds over the
plains this afternoon will shift to the SSE, becoming a bit breezy
at times. However, gusts will remain low enough to avoid any
critical fire weather conditons. Despite the dry surface conditions,
incoming mid-high clouds should help keep the area from getting much
warmer than the mid-highs 80s this afternoon.

Tonight, temperatures across the San Luis Valley will sink quickly
due to radiative cooling once again, hitting the low-30s. Frost will
be possible and could damage vulnerable vegetation.

For Friday, southwest flow aloft will increase over our region,
while southerly flow increases over our plains and the upper low
digs down into southern California. Some near-critical fire weather
conditions will be possible over parts of the plains during the
afternoon, but as more low-level moisture advects into the area
these conditions should stay marginal, so we should not require any
highlights. As moisture increases with southerly flow, isolated-
scattered showers and storms will be possible over our far southern
plains. Coverage will stay pretty low thanks to some lingering drier
air as well as a lack of overall forcing. As of now, models only
show 600 J/kg or less of CAPE out that way. High temperatures will
continue to be warm for one more day with highs climbing into the
low-90s over the eastern plains, and high-70s over the valleys.
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&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
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Issued at 224 PM MDT Thu Sep 19 2024

Friday Night: For the end of the week, active weather starts to make
a return as a strong Fall system approaches. Southwesterly flow will
start to increase ahead of a closed low, along with moisture as it
starts to advect northward. While most will remain dry Friday
evening and night, strengthening orographic forcing, along with
minor instability, will allow for showers, and even occasional
thundershowers, to develop along the mountains, though mostly along
the San Juan Mountains and southern Sangre de Cristo Mountains.
Beyond that, mostly light winds and mostly clear skies are
anticipated for the area, though clouds will start increase late in
the overnight hours. As for temperatures, a mild and cool night is
expected. Much of the region will cool to around seasonal lows for
late September, though downsloping winds across parts of the plains
may help to keep temperatures slightly above seasonal values.

Saturday - Sunday: For the weekend, active weather is expected to
increase for much of south central and southeastern Colorado. The
aforementioned closed low will pass over the region through
Saturday, and exit the area through Sunday. Ensemble model guidance
are in good agreement about this, and have come into better
agreement on timing as well, leading to now high (70-75%) confidence
in this pattern evolution. As this low passes over the region,
synoptic dynamics and orographic forcing will increase, along with
moisture as its pulled northward and wrapped around the low. For
Saturday, precipitation will increase from south to north starting
in the morning and become more widespread throughout the day, with
the greatest coverage along the mountains, where forcing will be
strongest. Then for Sunday, precipitation will start to lessen in
coverage throughout the day as the low treks eastward.
Wrap around precipitation on the backside of the low is expected to
persist though throughout most of the day and favor prominent
terrain features, such as the mountains and Palmer Divide, with the
greatest coverage of precipitation during the morning hours. With
that all said, while most precipitation will remain rain, elevations
generally around and above 10,000ft will experience snow. Given
the early season snow and at least minor impacts expected, a
Winter Weather Advisory has been issued for the Sawatch and
Mosquito Ranges, along with Pikes Peak, for mid day Saturday to
mid day Sunday. In addition, severe weather still remains a
concern across the southeastern plains during Saturday
afternoon, where the best combination of strong shear, moisture,
and instability will reside. With that said though, confidence
remains low (~20%) at this time in severe weather development,
given uncertainty in how much moisture and instability will
materialize. Otherwise, breezy conditions and cloudy skies are
anticipated, with clouds increasing throughout Saturday and then
decreasing through Sunday afternoon and evening. Looking at
temperatures, Fall makes a return to south central and
southeastern Colorado. Saturday, temperatures will hover around
and slightly below seasonal values given the system overhead and
a cold front draping across the area. For Sunday, temperatures
will sink to below seasonal values for late September for most
of the region given the post cold frontal airmass in place.

Monday - Wednesday: For the first half of next week, some active
weather will persist for south central and southeastern Colorado.
Northwest flow will prevail over the region behind the exiting low,
with an embedded shortwave pushing over the area around the Tuesday
timeframe. While overall forcing will lessen, orographics and an
uptick in forcing from the wave will allow for isolated to scattered
showers each day, especially Tuesday, with the greatest coverage of
precipitation remaining along the mountains, where forcing will be
greatest. Outside of that though, relatively light winds and periods
of scattered clouds are expected. Focusing on temperatures, Fall
sticks around. Much of the region will remain around and slightly
below seasonal values for late September.
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&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1124 AM MDT Thu Sep 19 2024

VFR conditions are expected at KALS, KCOS, and KPUB through 24
hours. Winds will generally be diurnally driven, though gusty south-
southeast winds between 20-25 knots are expected at all 3 TAF sites
this afternoon.

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
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Winter Weather Advisory from noon Saturday to noon MDT Sunday
for COZ058-060-082.
Frost Advisory from 3 AM to 8 AM MDT Friday for COZ069>071.
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&&

$$

SHORT TERM...GARBEROGLIO
LONG TERM...SIMCOE
AVIATION...GARBEROGLIO