727
FXUS64 KLUB 211055
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
555 AM CDT Sat Sep 21 2024

...New AVIATION...

.SHORT TERM...
(Today and tonight)
Issued at 350 AM CDT Sat Sep 21 2024

Water vapor imagery currently shows the FA beneath the upper level
ridge, with the center of the high pressure parked near the central
Texas region. To our east, the upper level trough is currently
positioned over southern desert southwest where it is expected to
track into the Four Corners region by this afternoon. As the trough
tracks closer to the FA the associated 50 to 60 knot jet streak will
clip portions of the West Texas region.

One more day of above normal hot temperatures is in store for the
region as an incoming cold front shows us a slight glimpse of
fall temperatures. A surface low to our north is expected to
strengthen and begin tightening the pressure gradient across the
region. This will lead to breezy southerly conditions this
afternoon around 10 to 20 mph with gusts up to 30 mph. Given the
breezy southerly flow and similar thickness values most of the
region can expect similar temperatures as previous days in the 90s
to lower 100s. However, some areas across the far southwestern
Texas Panhandle and northern South Plains may see highs top out
in the upper 80s as model guidance hints at FROPA entering our NW
zones by early this afternoon. Therefore, if the front arrives
before peak heating hours we could see a slight temperature
gradient across the FA this afternoon.

Meanwhile, southerly to southeasterly flow from the surface to H7
will continue to influence increased moisture being pumped into the
FA from the Gulf of Mexico. Additionally, ample pacific moisture
wrapping along the western side of the upper level ridge will track
through most of the FA over the next 24 hours. As the upper level
low begins to barrel closer to the region, we can expect increased
chances for thunderstorms beginning as early as mid-morning into
early afternoon depending on when convective Ts are met. An H7 theta-
e ridge encompassing most of the South Plains and far central and
southwestern Texas Panhandle is expected to develop this afternoon
east of the dryline and ahead of the incoming front. This
highlighted area, relatively west of the I-27 corridor will be
primed with decent mid-level LR, MLCAPE up to 2000 J/kg, and
effective bulk shear around 55 knots. All of which support strong to
severe thunderstorms capable of producing damaging wind gusts and
large hail. All hazards will be at play this afternoon with a
tornado or two possible given 0-3km shear around 20 knots and
veering winds with height although 0-1km shear remains unimpressive
and relatively less than 5 knots. Regardless, the area to see an
increased risk for tornadoes looks to be near the frontal boundary;
which is expected to stall around the far southwestern TX Panhandle
this afternoon. Storm motions are expected to be pretty fast,
however given forecasted PWATs around 1.5" we could see localized
flash flooding develop with stronger storm that develop.
Thunderstorms are expected to continue into the overnight hours as
they track from west to east into the Rolling Plains. Overnight lows
are expected to be much cooler than previous nights for most as the
front begins its surge southward with lows ranging from the upper
50s in our northwest counties to low 70s across our southeastern
counties. As the front pushes southward we will see an additional
round of thunderstorms track into the FA. For more information
regarding precipitation chances heading into Sunday morning check
out the long term discussion below.

&&

.LONG TERM...
(Sunday through Friday)
Issued at 350 AM CDT Sat Sep 21 2024

Just in time for the first day of fall, a cold front Sunday morning
will usher in below normal temperatures, breezy north winds and
more importantly a decent shot at rain for those areas that miss
out today and tonight. The surface map by daybreak Sunday should
feature a cold front across our Panhandle counties accompanied by
scattered to numerous showers and thunderstorms, mainly along and
east of a low-level moist axis progged to bisect the forecast area
from SW-NE. Other than frontal convergence, background ascent in
the form of upper divergence and height falls looks pretty muted
well south of an upper low lifting from CO into NE. Along with a
faster FROPA, the highest PoPs will likely shift into the southern
Rolling Plains by early afternoon as aggressive low-level drying
and subsidence overspread the remainder of the CWA during this
time. If convection can grow upscale Sunday afternoon in the
southern Rolling Plains, then a greater heavy rain threat would be
in the cards given anamolously high PWATs approaching two inches.
NBM`s post-frontal PoPs from Sunday afternoon through the
overnight were dialed lower to account for the overwhelmingly
drier 00Z guidance which best fits this faster FROPA theme. Temps
by early Monday morning over much of the Caprock now look to fall
well into the 40s under clearing skies and diminishing N winds.

Other than a few straggler showers in our far southeastern zones
early Monday morning, mostly clear skies and dry conditions prevail
as surface high pressure moves across the CWA underneath weakly
cyclonic westerly flow. This flow aloft turns sharply cyclonic on
Tuesday as a vigorous trough dives south from the CO Plateau before
pinching off an upper low somewhere over West TX by Wednesday. Long
range models are showing less spread with this low`s position by
Wednesday as the ECMWF has trended closer to the GFS solution. Moist
isentropic flow should ramp up late Monday night through Tuesday in
advance of this trough/low resulting in a broad field of showers and
some storms. Am not buying the unusually mild GFS/MEX temps in this
otherwise cloudy and cool pattern for Tuesday, so have stuck to the
NBM`s temps which are supported well by the ECM MOS. Heavy rain
remains some concern in this pattern given the long residence time
of saturated ascent with PWATs of 0.3 to 0.5" above normal, although
unlike the convectively-driven heavy rains such as today and Sunday,
Tuesday looks to be more of a prolonged/beneficial soaking rain.
Rain chances gradually taper thereafter as ensembles build a modest
rex block over the Great Plains with the upper low poised anywhere
from the TX Panhandle to the Chihuahuan Desert. Oddly, the 00z GEFS
is closer to the ECM and EPS regarding the upper low hanging closer
to our neck of the woods on Thursday than the deterministic GFS, but
this is too distant to justify making any changes to the mostly dry
NBM. High temps slowly moderate by late week following a welcome
fall cooldown.

&&

.AVIATION...
(12Z TAFS)
Issued at 551 AM CDT Sat Sep 21 2024

Southeasterly winds will begin to pick up by mid-morning where
they are expected to become breezy around 15 to 20 knots with
gusts up to 30 knots. Thunderstorms are expected to develop this
afternoon where they will track east into all TAF sites late this
afternoon and evening which may threaten VFR conditions. Exact
timing in storms remains a bit uncertain but regardless, gusty and
erratic winds and locally heavy rainfall may be associated with
stronger storms.


&&

.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...12
LONG TERM....93
AVIATION...12