972
FXUS65 KPUB 152034
AFDPUB

Area Forecast Discussion
National Weather Service Pueblo CO
234 PM MDT Sun Sep 15 2024

.KEY MESSAGES...

- Showers and thunderstorms will be possible into the evening, with
an isolated severe threat across far southeastern Colorado.

- The chance for showers and thunderstorms will increase on
  Monday for the San Juans and San Luis Valley.

- Strong to severe storms possible Tuesday afternoon, mostly
  across the eastern plains.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 232 PM MDT Sun Sep 15 2024

The latest mid-level analysis indicates that a trough axis is
centered along the Pacific NW coast with the local area in a moist,
southwesterly flow ahead of this feature. East of the area, weak
ridging is in place over the central and southern Plains. The latest
relative humidity time-height cross section for Pueblo indicates a
dry layer from the surface up to around 500mb. A RAP sounding for
KPUB shows this well with an inverted V signature from 525mb down to
the surface. The latest satellite imagery and radar show convection
developing from the San Luis Valley eastward to SE Plains with
partly cloudy skies across much of the area.

This evening and tonight, the trough and its associated closed low
will slide southward into northern California and the mid-level
ridge keeps its strong hold across the southern and central Plains.
This will leave the local area in a southwesterly flow between the
two features. Instability will be relatively weak for thunderstorms
this evening (in the 500-1000 J/kg), but enough to provide
instability for the possibility of isolated thunderstorms. A strong
to severe wind threat cannot be ruled out given the inverted V
signature indicated by RAP model soundings. Showers and storms will
mostly diminish overnight everywhere except the San Juan Mountains.
For the San Juans, deeper moisture will advect into the area from
the southwest, allowing for the chance (30-50%) of showers and
thunderstorms to continue overnight and trend upward to be more
likely (60% probability) near dawn on Monday. The snow level will
drop to around 13,500 ft, so not out of the question some of our
highest peaks will see some snow mixing in late Sunday night into
Monday morning.

On Monday, mid-level moisture will stream into the area from the
southwest, increasing cloud coverage and showers and thunderstorm
chances with fuel from day-time heating. Instability, for the
majority, appears weak (<500 J/kg SBCAPE) and shear is marginal (25-
30kts 0-6km bulk shear). Thus, showers and thunderstorms should be
most likely over the San Luis Valley and San Juan Mountains with the
best access to monsoonal moisture, with lesser chances eastward to a
nearly dry forecast for the extreme southeastern Colorado.

For temperatures, the forecast is closest to the National Blend of
Models. Lows tonight will range from the lower 60s in SE Colorado to
the lower to mid 50s along the I-25 corridor to the mid 40s in the
San Luis Valley to the 30s in the highest terrain. On Monday, areas
across the Plains of far southeastern Colorado will see the warmest
temperatures closer to the ridge with some locations warming into
the lower 90s. Temperatures will be progressively cooler westward,
in the 80s along the I-25 corridor, in the upper 60s to lower 70s in
the San Luis Valley to the 40s and 50s across higher terrain.  /04-
Woodrum/

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 232 PM MDT Sun Sep 15 2024

Monday Night: Monday evening and night will bring some active
weather to portions of south central and southeastern Colorado. An
amorphous wave will be exiting the region, with moist southwest flow
persisting behind the wave. While broader forcing will lessen,
orographic forcing will continue given the rising southwest flow.
With broader forcing decreasing, most showers and storms across the
region are expected dissipate during the evening hours and much of
the area will remain dry. The exception to this will be along the
mountains, particularly the San Juan Mountains, where orographic
forcing will persist given the increasing southwest flow and
increasing moisture. While only mostly showers are expected,
occasional rumbles of thunder and thundershowers are possible given
minor instability remaining overnight. Otherwise, mild temperatures,
relatively light winds, and partly cloudy skies are anticipated.
Looking at temperatures, much of the region will remain mild and
above seasonal values overnight given downsloping winds and cloud
cover.

Tuesday: Tuesday brings an uptick in active weather for much of
south central and southeastern Colorado. A closed low to the
northwest of the region will quickly eject to the northeast
throughout the day. While the core of this feature will remain to
the northwest and north of the area, strong synoptic and orographic
forcing is still expected as the southern fringes of the low passes
over. Along with that, a moisture plume will advect northward ahead
of the primary larger wave. With the surge in forcing and moisture,
there is high to very high (70-90%) confidence in scattered showers
and storms throughout the day. Showers and storms will initially
blossom along the Continental Divide area during the morning hours,
and then push eastward, following the strongest forcing throughout
the day. A few strong, to possibly severe, thunderstorms are
possible, especially across the eastern plains, during the afternoon
hours when moisture, instability, and shear will be maximized. The
most likely hazard with any stronger storms will be strong outflow
winds given DCAPE values around 1000-1200 J/kg, but also due to
mature thunderstorm downdrafts mixing stronger winds aloft to the
surface. With that all said, as the low/wave continues to rapidly
eject to the northeast and exit the region, forcing will quickly
lessen, and any showers or storms present across the area are
anticipated to dissipate during the evening hours. Otherwise during
the day, warm temperatures, windy conditions, and partly cloudy
skies are expected. As for temperatures, areas generally along and
east of the I-25 corridor will hover around and slightly above
seasonal values given less clouds, while areas generally west of
there will hover around and slightly below seasonal values given
early daytime cloud cover.

Wednesday - Thursday: For part of the midweek period, a period of
quieter weather is anticipated. Southwest flow will reestablish over
south central and southeastern Colorado, though drier air will be in
place behind the Tuesday storm system. So while orographic forcing
will continue, the drier air will limit precipitation development,
and given that, dry conditions are expected for much of the region.
The exception to this may be a highly isolated shower or two along
the mountains, though mostly on Thursday. The greatest concern for
Wednesday and Thursday will be returning critical fire weather
conditions. Given the drier conditions and breezy winds persisting,
critical fire weather conditions may materialize for portions of the
lower elevations, though confidence is low (20-30%) in timing and
areas of greatest concern at this time. Outside of that though, warm
temperatures continue, with breezy winds, and scattered afternoon
clouds. Focusing on temperatures, the warmth does continue. Most of
the region will remain above seasonal values for mid September.

Friday - Saturday: For the end of the week and start of the weekend,
active weather makes a return to south central and southeastern
Colorado. Synoptically the broad trough that brought the Tuesday
system will finally push eastward, bringing another wave during this
timeframe. Ensemble model guidance are in relatively good agreement
about this, leading to at least medium to high (50-70%) confidence
in this pattern evolution. With the uptick in forcing, and despite
moisture remaining limited, showers and thunderstorms are expected
to increase in coverage, especially along the mountains where
forcing will be greatest. Besides that though, cooler temperatures,
relatively lighter winds, and periods of cloudy skies are
anticipated. Looking at temperatures, yep a cool down is expected.
Friday will hover around seasonal temperatures, with temperatures
dropping below seasonal values Saturday as the system pushes
overhead and shoves a cold front southward during this period.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1139 AM MDT Sun Sep 15 2024

VFR conditions will mostly prevail across the terminals
throughout the TAF period as the lower levels remain dry. Some
high-based showers and thunderstorms will develop this
afternoon nearby the terminals, however confidence is not high
enough in coverage/restrictions to mention as a TEMPO group.
Thus, prevailing VCSH is mentioned starting at 19Z at Alamosa
and at 21Z at Pueblo and Colorado Springs. Showers and storms
will diminish by around 02Z as VFR conditions continue overnight
into early on Monday. Winds will mostly be southerly through the
period at 10-15 kts with gusts to 20-25 kts through 01Z and
then decreasing to less than 10 kts overnight.

&&

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

&&

$$

SHORT TERM...WOODRUM
LONG TERM...SIMCOE
AVIATION...WOODRUM