Flash Flood Warning 5, NWS Lubbock, TX

Area Forecast Discussion
National Weather Service Lubbock TX
130 PM CDT Tue May 28 2024

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

.SHORT TERM...
(This evening through Wednesday)
Issued at 119 PM CDT Tue May 28 2024

17Z upper air analysis reveals a low-amplitude, shortwave trough
pivoting over the Desert Southwest and northern Mexico, with the
leading edge of the geopotential height falls nosing into central
New Mexico. This feature was translating through a larger-scale,
mid/upper-level ridge, which is currently centered over the Rocky
Mountains; and a dampened, mid-level jet streak near 35 kt was
rounding the base of this low-amplitude trough as it emerges into
western Texas. Mid-level, isentropic ascent is already present as
evident by the shallow field of altocumulus floccus advecting
eastward over the CWA. At the surface, a weak, lee cyclone was
analyzed near ROW, with the dryline extending to its south and a
quasi-stationary front branching eastward into the South Plains and
into the vicinity of LBB, before bending southeastward into the
southern Rolling Plains and northern Permian Basin. This stalled
front has become convectively-reinforced by a well-defined outflow
boundary generated by an MCS earlier this morning along the Upper
Red River Valley, and trends in visible satellite and West Texas
Mesonet (WTM) data indicate that the airmass in wake of this outflow
continues to recover. WSR-88D data also detects multiple waves with
this outflow boundary as it propagates westward, but it appears that
the waves are dissipating in amplitude as pressure tendencies have
risen 1 mb in the past hour as diabatic heating intensifies and the
forward-speed diminishes as it interacts with the front. The
differential heating associated with the passage of this outflow,
and the presence of the stalled front, has resulted in surface
temperatures breaching 90 degrees within the airmass across
locations along the HWY-385 corridor, while surface temperatures
remain in the middle-upper 70s across the Rolling Plains. WTM data
also indicates a corridor of mid-60 degree dewpoints advecting
northwestward along the theta-e gradient in the immediate vicinity
of the quasi-stationary front.

Explosive thunderstorm development is expected to occur this
afternoon near the triple point in the South Plains, where a tongue
of high theta-e air will continue to advect towards the surface low
(this is currently and has been evident on WTM data for the last
several hours). The 12Z RAOBs from WFO AMA and MAF observed MUCAPE
values between 1,500-3,000 J/kg amongst steep, mid-level lapse rates
between 8.8-9.4 deg C/km. Gradual, geopotential height falls, in
addition to intense, diabatic surface heating, should bolster both
mixed-layer CAPE values to >=2,500 J/kg across the Caprock this
afternoon amidst effective shear magnitudes approaching 50 kt as the
backed, southeasterly winds near 20-30 kt enhance the component of
low-level storm-relative inflow beneath the 250 mb jet streak at
around 50 kt. The convective reinforcement of the quasi-stationary
front juxtaposed to the belt of 20+ kt southeasterly flow will
result in an enhanced corridor of streamwise vorticity within the
inflow-layer, with storms rapidly becoming supercellular and
discrete propagation is expected as cells move near or along the
quasi-stationary front. LCLs will lower substantially as cells move
southeastward, and the ingestion of buoyant, high theta-e air; and
solenoidal flow along the stalled front is expected to result in an
initial threat for tornadoes, some of which could be rain-wrapped
and significant (i.e., capable of producing EF2+ damage), especially
along and west of the I-27 corridor. Supercells will also pose a
high threat for very large hail between 2-3 inches in diameter, and
potentially wide, bulbous downdrafts will augment the potential for
wind-damage with gusts to 80 mph possible.

The cold pools associated with potentially multiple supercells are
expected to result in upscale growth towards the evening across the
South Plains, with several swaths of 60-70 mph wind gusts and
isolated significant wind gusts between 75-85 mph possible as the
magnitude of downdrafts generate intense theta perturbations. A
forward-propagating MCS may materialize as the environment for MCS
maintenance remains unsupportive of back-building via anti-parallel
Corfidi vectors with a downshear component in excess of 40 kt. Flash
flooding will be possible from rain rates of 2+"/hr, but the fast
system motion will mitigate more-widespread flooding concerns. The
MCS/cluster of supercells is forecast to move southeastward this
evening and tonight as it progresses into the Rolling Plains, and
the potential exists for meso-beta-scale vortices to develop should
mesocyclones remain embedded within the MCS, which would maintain
the potential for significant (>=75 mph) wind gusts. The system is
forecast to clear the CWA near midnight CDT, with prevailing winds
remaining out of the east-southeast across the northern periphery of
the stalled front as it moves into the northern Permian Basin. Low
stratus will develop as the lower portions of the airmass reach
saturation as a backed, low-level jet remains positioned over the
CWA with temperatures falling into the upper 50s and lower 60s
tomorrow morning.

Sincavage

&&

.LONG TERM...
(Wednesday night through next Monday)
Issued at 119 PM CDT Tue May 28 2024

Barring some remnant elevated convection Wednesday morning, the
remainder of the day is looking very stable under widespread low
clouds and moist easterly flow that backs all the way into NM.
Some thinning to this stratus is likely through the afternoon, yet
limited windows for strong heating should keep a hefty cap intact
and close the door to additional storms. Feel the global models
are overblown with QPF off the Caprock through the afternoon given
such muted forcing in continued semi-zonal flow, so NBM's PoPs
were trimmed lower and kept more in line with the drier CAMs. This
story changes by Thursday as a shortwave trough turns our flow
aloft more cyclonic and a modest upper jet streak noses over the
South Plains. This improved flow is forecast to nudge a weak
surface low and dryline out of NM before stalling from the western
TX PH through the western South Plains by peak heating. Models
still differ on various factors to these boundaries - the greatest
of which may involve an outflow-enhanced cold front diving south
from the TX PH through the day which would throw a monkey wrench
into storm chances and even high temps. Provided low clouds ahead
of the dryline can erode, the lid should be breakable by late
afternoon especially as the shortwave trough draws closer. Severe
storms are certainly on the table with all modes possible yet
again.

Storm chances trend lower by Friday in the wake of the shortwave
trough, although this is not reflected well by the NBM which depicts
likely PoPs at times which has poor support from the latest models.
Opted to undercut NBM's PoPs for Friday mainly given the overarching
theme of subsidence which should overturn by Saturday as the next
shortwave trough arrives in westerly flow. Models and ensembles are
in surprisingly good agreement with Saturday's precip chances and an
overall weak cap, so this may be our final hurrah for rain chances
before a tall dome of high pressure sets its sights on West Texas
early next week complete with a return to hotter temps.

&&

.AVIATION...
(18Z TAFS)
Issued at 1217 PM CDT Tue May 28 2024

Severe thunderstorms are expected to affect KCDS, KLBB, and KPVW,
this afternoon and evening. Surface wind gusts near 50 kt and very
large hail in excess of two inches in diameter surface-to-aloft
will accompany the severe storms. TEMPO groups were assigned to
all terminals but adjustments to timing may be required. Storm
chances will end from northwest-to-southeast tonight with the
prevailing wind remaining out of the southeast and east. MVFR CIGs
will develop tomorrow morning at all terminals and last through
the end of the TAF period.

Sincavage

&&

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

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

Hazardous Weather Outlook...UPDATED
National Weather Service Lubbock TX
1106 AM CDT Tue May 28 2024

TXZ021>044-291615-
Parmer-Castro-Swisher-Briscoe-Hall-Childress-Bailey-Lamb-Hale-Floyd-
Motley-Cottle-Cochran-Hockley-Lubbock-Crosby-Dickens-King-Yoakum-
Terry-Lynn-Garza-Kent-Stonewall-
1106 AM CDT Tue May 28 2024

This Hazardous Weather Outlook is for the South Plains, Rolling
Plains, and the far Southern Texas Panhandle.

.DAY ONE...This afternoon and tonight.

Severe thunderstorms will develop this afternoon and persist through
the evening hours. The primary hazards will include very large hail
to the size of baseballs, damaging wind gusts up to 80 mph, and a few
tornadoes, especially along the Interstate 27 corridor. Flash
flooding will also accompany storms this afternoon and evening.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Severe thunderstorm chances are forecast to increase on Thursday.
All hazards will be possible, including: damaging winds, very large
hail, although unlikely a tornado or two cannot be ruled out.

The potential for severe weather remains in the forecast heading
into the weekend.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed.

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