757
FXUS64 KLUB 151920
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
220 PM CDT Sat Jun 15 2024

...New SHORT TERM, LONG TERM...

.SHORT TERM...
(This evening through Sunday)
Issued at 220 PM CDT Sat Jun 15 2024

Mid-level subsidence was noted over the entire forecast area this
afternoon on the heels of a shortwave trough shifting east of
Highway 83 in westerly flow. Despite this less than stellar theme
aloft, the low levels remain rather moist ahead of a surface trough
in eastern NM. West Texas mesonets have been sampling a corridor
of consistently breezier S-SE winds over the SW South Plains in
response to a mesolow near the Guadalupe Mountains. This locally
backed and breezier flow should aid with speed convergence and
eventually some storms late this afternoon and evening near the TX-
NM border provided convective temps in the mid 90s are realized.
Most recent HRRR runs have dialed back CI and overall coverage this
evening across our western zones, yet this is suspect in light of
ample heating, deeper mixing, modest CIN, and expanding cu field.
Unlike last evening, storms this evening will exhibit a better E-SE
push thanks to 30-35 knots of 0-6km shear. Inverted-V soundings with
around 1500 J/kg of MLCAPE and similar amounts of DCAPE favor severe
winds before activity declines overnight. Opted to keep NBM`s 20-30
PoPs largely intact on the Caprock as pros for CI outweigh the cons
at this time. Moist southerlies stay with us on Father`s Day, yet
chances for more storms trend toward zero under weak anticyclonic
flow and rising thicknesses.

&&

.LONG TERM...
(Sunday night through next Friday)
Issued at 220 PM CDT Sat Jun 15 2024

The mid/upper-level pattern will feature the amplification of a
large-scale, positively-tilted trough over the western U.S. as a
well-defined vorticity lobe rotates into the northern Great Basin
early Monday, effectively shunting the subtropical ridge over the
northeastern Pacific Basin southward. Farther east, a 596 dam,
mid/upper-level ridge will continue to wobble over the eastern
tranche of the U.S. as the belt of 250 mb flow between 90-100 kt
becomes increasingly meridional over the central and northern Rocky
Mountains, resulting in the CWA being positioned within the
inflection point of these features. A secondary, more-zonal 250 mb
jet streak is forecast to become coupled to the amplified flow over
the Great Basin, with the nose of the former 250 mb jet streak
emerging into western Texas and becoming increasingly difluent along
the apex of the flattening ridge over Mexico. At the surface, lee
cyclogenesis of a sub-990 mb low is expected to occur across eastern
Colorado in response to the geopotential height falls and related
DPVA, with a sharpened dryline extending southward along the TX/NM
state line by the afternoon hours Monday. The CWA will be enveloped
within the moist sector, where leeward pressure falls associated
with the deepening cyclone to the north generate an isallobaric
response that will cause winds to accelerate to 20+ mph with gusts
near the 30-35 mph range amidst intense heating. Temperatures are
forecast to reach the upper 90s across most of the CWA amidst a
plume of dewpoints potentially in excess of 60 degrees extending to
the west of the I-27/HWY-87 corridors.

A conditionally-unstable airmass is expected to develop as the
geopotential height falls and westerly, mid/upper-level flow
facilitate maintenance of the elevated mixed layer (EML) atop the
southerly low-level flow. The majority of the CWA will be capped,
especially in the Rolling Plains, and the dry and hot forecast has
been maintained across those locales as 700 mb flow remains veered
to the southwest. Intense, diabatic heating; confluent flow nearest
the dryline; and the advection of high theta-e air will act to
enhance localized areas of convergence along the dryline and erode
the strong MLCINH, which should allow parcels to maintain enough
residence time to overcome the deleterious effects of entrainment
and reach the LFC and result in the initiation of thunderstorms.
Low, mentionable PoPs (<15 percent) have been introduced for Monday
afternoon and evening across most locations west of the I-27/HWY-87
corridors. Coverage of storms should be widely-scattered at best,
with the thinking of cells remaining isolated given the potential
for multi-cellular splits early on in the convective stage and weak
forcing for ascent aloft. The magnitude of the storm-relative inflow
developing by the late-afternoon hours, in addition to the moist
boundary-layer (e.g., lower 100 mb mean mixing ratios near 14-15
g/kg), should also support updrafts wide enough to become sustained
for a few hours with supercell wind profiles present. The sizable
EML indicated on point and area-averaged soundings leads towards the
potential for rapid development; however, warm-cloud depths
approaching 13 kft AGL should temper the threat for large hail with
a focus towards damaging downdrafts and torrential rainfall. The
potential for severe-caliber convection will wane after dark as
diabatic stabilization occurs despite southerly winds remaining near
20 mph heading into the overnight hours.

Broadly cyclonic flow will continue to eclipse the CWA on Tuesday;
however, the primary cyclone associated with the mid/upper-level
troughing to the west is forecast to rotate into north-central
Canada, governing a poleward response to the ridging over the Gulf
of Mexico with a slight increase in geopotential heights occurring.
Hot and dry weather is expected area-wide on Tuesday as the airmass
will be strongly capped beneath the large EML aloft; however, the
presence of the EML remaining over the CWA will have implications
for the remainder of the forecast period. Thunderstorm chances are
forecast to improve across the entire CWA as southwesterly flow
aloft remains intact atop the reservoir of subtropical moisture
originating from the Gulf of Mexico. There are some differences
among the global NWP guidance on the position of the stalling front
to the north of the CWA on Wednesday as the aforementioned cyclone in
north-central Canada rotates into the Hudson Bay, but there exists a
consensus that the front will stall in the vicinity of the OK/TX PH;
and the thinking leans towards this scenario given the proximity of
the barotropic airmass spread across the region. NAEFS and ENS
guidance are indicating precipitable water (PWAT) content rising to
nearly two standard deviations above normal Wednesday night into
Thursday. Interpolation of the 20-21/00Z sounding climatology from
WFO MAF indicates that the forecast PWAT content will be near or
exceeding the 99th percentile across the CWA during this time. This
points towards the potential for heavy rain across portions of the
Caprock and Rolling Plains by the middle and end of next week;
however, specificity of where heavy rainfall occurs remains nebulous
owing to the limited predictability in the potential placement of
thunderstorms. The blended PoPs have been maintained, and it is
possible that PoPs may be increased in forthcoming cycles. Cooler
temperatures are also forecast by Wednesday onward as southeasterly
low-level flow remains intact beneath thickening cloud debris from
the daily rounds convection.

Sincavage

&&

.AVIATION...
(18Z TAFS)
Issued at 1210 PM CDT Sat Jun 15 2024

VFR with steady S-SE winds of 10-15 knots through tonight.
Confidence is growing that ISO-SCT TS develop W of LBB-PVW late
this afternoon and spread E through the evening. Inserted a VCTS
mention at these terminals before activity dwindles toward
midnight. Could see low CIGs develop at LBB around daybreak on
very moist S winds, but this threat looks too conditional for
mention in the TAF at this time.

&&

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

$$

SHORT TERM...93
LONG TERM....09
AVIATION...93