402
FXUS64 KLUB 210756
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
256 AM CDT Tue May 21 2024

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

.SHORT TERM...
(Today and tonight)
Issued at 256 AM CDT Tue May 21 2024

An upper level short wave trough will lift northeastward across the
central High Plains this morning which will in turn drag a Pacific
cold front eastward across the forecast area. A decrease in high
temperatures of about 5-8 degrees relative to yesterday and in line
with MOS and NBM looks fine. West winds behind the front will become
breezy and gusty, diminishing and backing with sunset this evening.
Overnight conditions will generally remain mild, although a Canadian
cold front will bring cooler temperatures as it enters the northern
zones late tonight as another short wave trough moves across the
central High Plains.

&&

.LONG TERM...
(Wednesday through Monday)
Issued at 256 AM CDT Tue May 21 2024

The CWA will be beneath a belt of broadly cyclonic flow associated
with a synoptic-scale trough spreading across the central and
western U.S., where a distinct gyre featuring numerous shorter-wave
perturbations and vorticity lobes will be rotating about the gyre
situated over the northern U.S. and into southern Canada. The
leading, negatively-tilted shortwave trough will be pivoting over
the Boundary Waters region as the surface-to-mid-level lows become
vertically-stacked. At the surface, the corresponding cold front
generated by this occluding system is expected to reach the extreme
southern TX PH at the start of the period (12Z Wednesday). The
forward-speed of the front will slow down as the front moves beneath
the northern periphery of a barotropic airmass as a mid/upper-level
anticyclone near 594 dam meanders over central Mexico, and the front
is forecast to become quasi-stationary across the northern Permian
Basin and branch northeastward into the Upper Red River Valley.
Blustery, northerly winds will accompany the frontal passage due to
the spike in pressure tendencies at around 6 mb/3 hr; however,
pressure tendencies will be quick to stabilize as the surface
anticyclone in its wake remains weak (near 1012 mb) and the front
begins to stall. The post-frontal airmass will also be heavily
modified by convective episodes to the north of the CWA days prior,
with dewpoints recovering into the lower 50s along the I-27/HWY-87
corridors by late morning.

The geopotential height falls associated with the glancing influence
of the negatively-tilted trough will have advected a sizable
elevated mixed layer (EML) overhead by this time, as southwesterly
flow persists above the shallow, post-frontal airmass. Baroclinity
of the front may also be enhanced by convective outflow, which would
raise the potential for non-surface-based (elevated) thunderstorms
to form across the southern and southeastern Rolling Plains along
the cold front as it begins to stall. With LFCs rooted above the
stable, post-frontal airmass, convective movement will be governed
by advection with a mean storm motion vector to the east-northeast
near 40 kt. Long, relatively straight hodographs would support
splitting cells with the potential for storms to become strong or
even severe; however, the uncertainty with the latter revolves
around how long cells remain within the southeastern Rolling Plains
after initiation. Low PoPs have been maintained across the eastern
and southeastern Rolling Plains, with the best chances for a large
hail event occurring in the southeastern zones where the EML will be
characterized by MUCAPE values in excess of 3,000 J/kg amidst the
amplified, deep-layer flow as a 250 mb jet streak near 140 kt
translates over the region. Elsewhere, blustery, northeasterly winds
will taper off by the early afternoon with pleasant conditions as
temperatures range between the upper 70s to upper 80s from the
extreme southern Texas Panhandle into the southern South and Rolling
Plains, respectively. Temperatures were lowered a few degrees from
the blended initialization with a 50 percent weighting towards MOS.

High-level, split-flow will remain intact heading into Wednesday
night as the elongated 250 mb jet streak over the CWA branches from
the Pacific to Atlantic coasts, while several series of mid-level
perturbations rotate about the broader, synoptic-scale troughing and
over the CWA. The 1012 mb surface high will begin to rotate into
southern Oklahoma on Wednesday night as the quasi-stationary front
begins to transition into a warm front and lifts northward across
the CWA heading into early Thursday morning. Rapid boundary-layer
moistening will immediately follow the passage of this warm front,
with dewpoints rising into the upper 50s and lower 60s across the
Caprock, and into the middle 60s in the Rolling Plains, as the
backed, nocturnal wind maximum strengthens to near 30-35 kt during
the morning hours Thursday. Elevated thunderstorms will be possible
for locations near and east of the I-27/HWY-87 corridors as the warm
front lifts northward across the CWA beneath the sizable EML for
most-unstable parcels. The magnitude of the warm-frontogenesis
should be enough to force parcels to the LFC, with cells that
develop racing to the northeast at nearly 50 kt as storm motion is
once again governed by advection ahead of a 700 mb trough. Low PoPs
(15 percent) were, therefore, introduced for areas near and east of
the I-27/HWY-87 corridors, and for all of the Rolling Plains, given
the thinking above. The potential for elevated thunderstorms will
wane after sunrise as the low-level jet veers and the warm front
accelerates far to the northeast of the CWA.

Broadly cyclonic flow will remain intact on Thursday; however, the
orientation of the deep-layer flow is forecast to attain a westerly
component by the latter half of the day as a basal shortwave trough
with a well-defined vorticity lobe becomes neutrally-tilted over the
northwestern Great Plains. The position and geometry of this feature
will cause the dryline to mix eastward into the Rolling Plains on
Thursday as a lee cyclone deepens to near 994 mb along the CO/KS
state line. Global NWP and now-in-range mesoscale guidance is in
agreement with the dryline mixing off of the Caprock; however, the
outlier is the in-range mesoscale guidance with keeping the dryline
anchored near the edge of the Caprock Escarpment given its position
of the shortwave trough being more-west than other guidance. The
thinking continues to trend towards the dryline mixing farther east
than the mesoscale outlier owing to the magnitude of the mass
response, depth of mixing and intensity of dry-bulbing behind the
dryline, and the position and magnitude of the east-west-oriented
250 mb jet streak. Thunderstorms, some severe, remain in the
forecast across the Rolling Plains on Thursday afternoon. However,
the residence time of convection in the eastern zones may be short
as cells develop and move east of the 100th meridian quickly with
right-moving storm motion vectors near 30 kt, and chances will end
after sunset. Quasi-zonal flow is forecast to evolve by Friday and
into the weekend as the gyre embedded within the persistent and
broad, synoptic-scale troughing shifts northward into west-central
Canada. Other than a front moving in Friday morning, hot, dry, and
breezy weather remains in the forecast for this weekend and into
early next week.

Sincavage

&&

.AVIATION...
(06Z TAFS)
Issued at 1221 AM CDT Tue May 21 2024

VFR conditions to continue through the TAF period. A Pacific cold
front will sweep eastward across the area Wednesday morning with
breezy and gusty west winds at the terminals until sunset when
winds will diminish and back to south.

&&

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

$$

SHORT TERM...07
LONG TERM....09
AVIATION...07