374
FXUS64 KSJT 221901
AFDSJT

Area Forecast Discussion
National Weather Service San Angelo TX
201 PM CDT Sun Sep 22 2024

...New LONG TERM...

.SHORT TERM...
(Today and tonight)
Issued at 342 AM CDT Sun Sep 22 2024

...Thunderstorms expected this afternoon through tonight...

Currently, an upper level low is located over CO, with southwest
flow over west central Texas. This low is expected to open into a
wave while slowly moving east into the central and southern plains
by Monday morning. This will maintain southwesterly flow over our
area. At the surface, a cold front is expected to move south into
our CWA by this afternoon, making its way through the rest of the
area by late tonight. Scattered to widespread thunderstorms are
expected to develop along and ahead of the cold front this
afternoon, and continue through most of the overnight hours.

With temperatures warming well into the 80s to lower 90s this
afternoon, combined with plentiful low level moisture
(precipitable water values near 2 inches), low levels will
destabilize ahead of the front. Mixed layer CAPE values are
forecast to be in the 500 to 1500 J/kg range during peak heating
hours. Deep layer shear values of 40 to 50 knots over the area,
combined with the instability will allow some of the storms to
become strong, with a few storms possibly severe. The main concern
with the storms will be wind gusts over 60 mph, but hail up to
the size of quarters will also be possible. After sunset,
instability will wane, and although storms may continue, the
concern for severe weather will diminish. The other concern will
be heavy rain and localized flooding with precipitable water
values near 2 inches.

Storms are expected to develop first over the Big Country along
the front, then spread southward over the rest of the area during
the afternoon and overnight hours as the front moves south.
Overall coverage should diminish late tonight, but isolated to
scattered activity will still be possible after midnight, mainly
south of Interstate 20.

&&

.LONG TERM...
(Monday night through next Sunday)
Issued at 159 PM CDT Sun Sep 22 2024

...Cool and wet pattern through Wednesday with drier and warmer
conditions expected by the end of the work week...

Overnight Monday into Tuesday, the upper level shortwave
trough associated with the primary cold front will exit off to our
northeast, leaving our area in brief zonal flow. Some HREF
members are picking up on convection forming across our central
counties as an embedded shortwave impulse tracks across the area.
Have capped PoPs during this timeframe in the chance category as
certainty with this development is limited but still possible as
the earlier cold front is not expected to scour out any moisture
(as shown by forecasted PWats in the 1.4+ inches range). The
better chances for showers and storms look to come later in the
day on Tuesday into early Wednesday. An upper low is expected to
drop south out of the Northern Great Plains and into the Central
Plains/Mid Mississippi Valley. This will send another upper level
trough axis through the region. An attendant cold front is also
expected to swing south through the area during this Tuesday/early
Wednesday timeframe. The NAM and many of the European ensemble
members seem set on a potentially wet frontal passage with the GFS
ensemble members painting a much drier picture. Will keep with
the blended solution for now, showing chance PoPs mainly through
12Z Wednesday. Any convective activity looks to wane through the
day on Wednesday as the front continues to push well south and
east of our area. With the rain chances and continued high amounts
of moisture across the area, temperatures will remain fairly
consistent Tuesday and Wednesday with highs in the upper 70s to
mid 80s and lows in the upper 50s to mid 60s.

Models seem to be in good agreement that much drier air will begin
to filter in at the surface behind the cold front Wednesday, leading
to a dry pattern for the end of the work week and weekend. Surface
flow will generally stay out of the north through this timeframe,
limiting moisture return. The aforementioned upper low is expected
to become cut-off from the main flow during this timeframe and will
stay in the general vicinity of the Southern Plains. How the track
of the potential tropical system across the gulf impacts this
remains to be seen but consensus for now is that we will stay to the
west of the low in an area of weak subsidence. High temperatures for
the late week/weekend timeframe will be on a steady upward trend as
the 850 mb thermal ridge begins to slowly work its way back into the
area. Daytime highs will approach 90 degrees again by the weekend.
Overnight lows are expected to be on the cool side in the mid 50s to
low 60s.

&&

.AVIATION...
(18Z TAFS)
Issued at 1256 PM CDT Sun Sep 22 2024

Ceilings have lifted to VFR across the terminals early this
afternoon. Still expecting a cold front to move south across
the terminals late this afternoon and evening, with FROPA at KABI
around 22Z, KSJT around 00Z and the far southern terminals by mid
to late evening. Showers and thunderstorms are expected to
develop along and behind the front, and will include TEMPO groups
for TS this forecast cycle. Precipitation is expected to end
across the far southern terminals by mid to late morning tomorrow.
Also, ceilings are expected to lower to IFR overnight, and
persist through at least the mid morning hours.

&&

.PRELIMINARY POINT TEMPS/POPS...
Abilene     61  75  62  85 /  80  30  40  40
San Angelo  63  77  64  86 /  70  40  30  30
Junction    67  83  66  88 /  40  30  10  30
Brownwood   64  78  64  85 /  60  40  30  40
Sweetwater  60  75  63  85 /  70  30  30  40
Ozona       64  78  65  86 /  70  40  20  20
Brady       65  78  65  85 /  50  40  30  30

&&

.SJT WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...20
LONG TERM....50
AVIATION...24