360
FXUS65 KPUB 180532
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
1132 PM MDT Tue Sep 17 2024

.KEY MESSAGES...

- Strong to severe storms possible rest of this afternoon and early
  evening across the plains.

- Patchy frost/light freeze possible for central San Luis Valley
  tonight.

- Dry and breezy on Thursday. Spotty near-critical fire weather
  conditions are expected across the area.

- Cooler and wetter conditions this weekend across the area.
  Best chance of showers and storms will be on Saturday.

&&

.UPDATE...
Issued at 656 PM MDT Tue Sep 17 2024

Update to allow Severe Thunderstorm Watch to expire as
scheduled over the remainder of the southern and eastern
plains. Strong storms are likely to continue until 8PM across
portions of eastern Las Animas, Bent, Prowers, and Baca
counties, but storms are expected to remain sub-severe through
the remainder of the evening.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 308 PM MDT Tue Sep 17 2024

Currently

At 2 pm, A line of broken storms extended from just west of COS S-
sw`d into the southern Sangres. Other additional showers and storms
were noted over the CONTDVD region. Over the plains the atmosphere
was destabilizing and winds aloft were increasing. SPC has already
issued a watch for the region and lasts until early evening.

Rest of today into early evening...

Storms will continue to progress steadily northeastward. Given the
shear, storms will likely move across the region as a broken line.
Dewpts were noted in the U40s to lower 50s, and CAPE values were
around 500-1000 Js, with the better instability generally east of a
line from KLIC to KTAD. Strong forcing was pushing out in advance of
a negatively tilted closed low pushing east-northeast out of Nevada.

Main severe threat continues to be strong winds, as HRRR guidance
continues to show strong gusts with storms, and the environment is
favorable for strong gusts given the well mixed lower atmosphere and
DCAPE values greater than 1000 Js over the far eastern plains.

Overall, activity should move out of the region by early to mid
evening.

Later tonight through tomorrow...

Much drier air will advect in behind this system and dry weather is
expected tonight into tomorrow all areas. Only weather concern will
be the San Luis valley where temps will be in the 32-34 range and
pockets of frost are likely over the central valley floor.

Temps tomorrow will be above normal over the plains, with mid 80 to
around 90F plains and L70s valleys.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Issued at 308 PM MDT Tue Sep 17 2024

Thursday...

Dry and warm conditions will persist across the area on Thursday as
we sit in between two upper lows. Breezy southwest flow will have
temperatures remain mostly steady, with highs in the mid-high 80s
over the plains while the high valleys remain in the 70s. With the
dry airmass remaining in place, Rh values will hover around 15-20
percent through most of the afternoon, while surface winds sit
around 10-15 mph. Unless we get more mixing than the models are
expecting, which is possible but not likely, critical fire weather
conditions will be marginal. Otherwise, the day will be relatively
quiet.


Friday Onwards...

Models have reached better agreement on the track of the next
incoming low as we approach this weekend. Friday will largely be a
transition day, with high temperatures about 5 degrees higher than
Thursday, along with slightly increased moisture from the incoming
system.

As we move into Saturday, models have continued trending south with
the evolution of the upper level pattern, now sending a closed low
directly over Colorado. As it moves in, a cold front will push south
across the area late Friday night into early Saturday. Along the
front, localized convergence and a good amount of monsoon moisture
could net us a healthy amount of precipitation. The exact amounts,
as well as what kind of precipitation (convective vs more
stratiform) we may see will largely be dependent on frontal timing
and instability. As of now, the GFS only shows a few hundred J/kg of
CAPE over the plains, and the system is moving relatively quickly,
so amounts may not be all that high. However, there is still time
for these details to become better resolved in the data.

There is still a bit of uncertainty amongst the model guidance with
regards to the speed of the low as well. The GFS has consistently
been one of the faster models, and the Canadian has been largely
tagging along the last few runs. However, the EC is currently
looking slow compared to the other deterministic guidance by several
hours. Additionally, any shift to the N-S extent of the track will
have a big impact on precip amounts. High temperatures will drop
around 10 degrees as well, in mainly in the 70s to low-80s out east.

For Sunday, post-frontal air will cool us off even more, with highs
in the 60s-70s across the CWA. Some isolated-scattered POPS remain,
but at this point models begin to diverge again on the departure of
the low. Most of the better forcing and moisture will be off to our
north and east, though if the low intensifies faster we may get some
more potent wraparound precipitation into the Palmer Divide. Still
plenty of time for those details to be resolved. Models are much
less clear beyond that, though the cooler pattern may possibly
extend into early next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1132 PM MDT Tue Sep 17 2024

VFR conditions are expected at all three TAF sites, KCOS, KPUB, and
KALS, for the next 24 hours. winds will be light and diurnally driven.
Very little if any clouds are expected.

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...EHR
SHORT TERM...HODANISH
LONG TERM...GARBEROGLIO
AVIATION...KT