130
FXUS64 KLUB 181108
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
608 AM CDT Fri Oct 18 2024

...New AVIATION...

.SHORT TERM...
(Today and tonight)
Issued at 242 AM CDT Fri Oct 18 2024

07Z upper air analysis reveals an amplified, progressive pattern
traversing the Lower 48, where a positively-tilted, southern-stream,
shortwave trough continues to dig into the southern Great Basin and
eject towards the Four Corners region. The primary vorticity lobe
embedded within this shortwave trough was detected over VEF on
recent water-vapor imagery, and was rotating southeastward into
western AZ, while generating multiple baroclinic leafs that were
translating northeastward over the Upper Colorado River Basin. There
is also evidence of a closed, mid-level low beginning to form within
the base of this trough on water-vapor imagery. This closed low will
continue to expand in size over the next 24-hours as the polar jet
stream over southern Canada becomes zonally-oriented via influence
of an inverted trough upstream of North America, causing the
attendant shortwave trough to attain a neutral-tilt by tomorrow
morning, with the closed low meandering over the Mogollon Rim.

At the surface, the CWA was located within a broad, open moist
sector ahead of the amplifying trough to the west. Lee cyclogenesis
was ongoing across eastern Colorado this early-morning, where a
surface trough branches southward towards the Raton Mesa and along
the edge of the Mescalero Escarpment. This has left the CWA within a
field of backed/south-southeasterly flow, with the edge of the
Caprock Escarpment serving as a stark delineation in the magnitude
of theta-e advection; the warmer, more-moist tongue situated along
and west of the I-27 and HWY-87 corridors as per recent West Texas
Mesonet (WTM) data. The isallobaric response generated by the
amplified troughing regime over the western U.S. has maintained
blustery conditions, with winds gusting within the 20-30 mph range
beneath a low-level jet in excess of 50 kt/60 mph per real-time
LIDAR data out of LBB. Rapid boundary-layer moistening has since
occurred, with low stratus both forming and advecting poleward
across most of the CWA given the magnitude of the 850 mb moisture
transport vectors associated with the intense low-level jet.

Bands of elevated/non-surface-based showers were ongoing across far
southeastern NM with a couple of thunderstorms over the Big Bend
region, though flash density was low on the GLM data. These
convective bands were moving east-northeastward, but have
consistently shown signs of decay when approaching the TX/NM state
line. Therefore, in the immediate near-term, PoPs were lowered to
slight chance across the western zones with no lightning expected
through sunrise. The 18/00Z RAOB launched from WFO MAF last evening
sampled a tall, and very skinny, elevated mixed layer (EML), while
the EPZ RAOB had sampled a well-mixed boundary-layer and an ample
depth of mixed-layer theta-e advection that was advecting largely
poleward to southwesterly within the residual PBL. Coverage of the
WAA-induced showers are expected to be confined to areas along and
west of the I-27/HWY-87 corridors today, and significant adjustments
to the NBM PoPs were made with reductions into the 20-30 percent
range to account for this thinking.

Dense overcast will persist throughout the entire short-term period,
thus restricting the effects of diabatic heating. Temperatures will
struggle to rise out of the middle 60s across the South Plains, and
highs were lowered to align with the 00Z raw statistical guidance.
Further, the restriction of diabatic heating despite the presence of
strong, backed surface flow will directly result in most-unstable
parcel trajectories being the favored source for the initiation of
thunderstorms, which will also be inhibited via little-to-no CAPE
early-on in the day as geopotential height falls are slow to arrive.
Elevated, fast-moving, WAA-induced showers will steadily increase in
coverage as the afternoon progresses and the right-entrance region
to the 250 mb jet streak emerges over West Texas. Some lightning
will be possible, and those chances should be confined near the NM
state line through 00Z (7 PM CDT) this evening.

Chances for elevated showers and storms will increase heading into
tonight as the mid- and high-level closed lows rotate into the Four
Corners region, and as the trough begins to attain its neutral-tilt.
The 18/00Z EPZ RAOB last evening also observed a semi-circle
hodograph, which reflects the magnitude of the WAA response ahead of
the troughing (storm-relative helicity is proportional to thermal
advection), and this particular observation bolsters confidence in
the forecast evolution of the hodograph profiles tonight across the
South Plains. The backing of the mid- and high-level flow as the
base of the trough settles over the southern Rocky Mountains will
advect the modest EML sampled on upstream RAOBs over the South
Plains tonight, with MUCAPE profiles near 750 J/kg to perhaps as
high as 1,000 J/kg; the latter values closer to the NM state line.
Better chances for thunderstorms exist after sunset tonight across
the South Plains, and the formation of small, weak, mid-level
mesocyclones combined with wet-bulb zero heights as low as 7,000 ft
AGL should foster the potential for a couple of sub-severe hail
events with the more-organized clusters of convection heading into
early Saturday morning across portions of the South Plains.

Sincavage

&&

.LONG TERM...
(Saturday through Thursday)
Issued at 242 AM CDT Fri Oct 18 2024

A bowling ball cutoff low will be spinning over Arizona Saturday and
Sunday before it slowly meanders northeastward heading into early
next week. With the placement of the upper low, much of the best
moisture and ascent aloft will be along and west of the Texas and
New Mexico state line. South-southeasterly surface flow will persist
through the weekend along the western periphery of the surface ridge
over the Tennessee Valley. Continued GoM moisture will help to give
way to dewpoints in the upper 50s to lower 60s. Streams of moist
isentropic lift will allude to persistent cloud cover and light to
moderate shower activity Saturday and Sunday moving from south-to-
north. Saturday afternoon will feature the potential for a narrow
corridor of instability across eastern New Mexico and into far West
Texas. MUCAPE values are generally around 500-1000 J/kg, while
effective shear values are around 40 knots and supportive of a
strong to severe thunderstorm. The main threats with any storms will
be damaging winds, large hail and heavy rainfall with PWATs near 1",
which is above the 90th percentile of climatology. Therefore,
localized flooding may be possible with some of the stronger
updrafts. As storms move east-northeast, the threat for severe
weather will quickly diminish with a lack of forcing and flow aloft
farther away from the upper low.

Precipitation chances continue through the morning and afternoon
hours Sunday with continued low-level moisture and a tongue of theta-
e across the South Plains and far southwest Texas Panhandle. As the
low swings to the northeast late Sunday evening and into the
overnight hours, any precipitation chances will also shift east
across the forecast area. The best chances will remain across the
far southern Texas Panhandle and north into Amarillo`s area as the
upper right entrance region of the jet moves over West Texas and
provides dynamical lift for enhanced shower and thunderstorm
activity. PWATs will remain around 1" with once again a heavy
rainfall and localized flooding concern, especially Sunday evening.
Precipitation chances will come to an end Monday from west to east
as the Pacific front associated with the upper low brings in dryer
air. Persistent cloud cover over much of the forecast area Saturday,
Sunday and into Monday will give way to near normal temperatures,
but with a gradual warming trend. The warmest temperatures daily
will be off the Caprock where clouds may break and bring some
sunshine. Tuesday and onward will feature zonal flow ahead of
another ridge with warm, above normal temperatures and dry
conditions returning to the forecast area.

&&

.AVIATION...
(12Z TAFS)
Issued at 608 AM CDT Fri Oct 18 2024

Poor flying conditions will continue for the next 24 hours at
KCDS, KLBB, and KPVW. MVFR CIGs will persist throughout the scope
of the TAF period at KLBB and KPVW, along with strong, southerly
winds with gusts near 30 kt expected. Bands of showers continue to
move northward near the TX/NM state line, but should stay west of
the terminals. Coverage of -SHRA/-TSRA this afternoon will be too
limited to warrant a mention of a prevailing or PROB30 group.
However, chances for -TSRA will increase from the west later
tonight, potentially affecting KLBB and KPVW early tomorrow
morning. Timing will be refined in forthcoming TAF cycles.

Sincavage

&&

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

$$

SHORT TERM...09
LONG TERM....11
AVIATION...09