523
FXUS64 KLUB 201133
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
633 AM CDT Mon May 20 2024

...New AVIATION...

.SHORT TERM...
(Today and tonight)
Issued at 227 AM CDT Mon May 20 2024

Quiet weather but hot temperatures are expected today across the
forecast area. Zonal mid to upper level flow today will begin to
back to southwest this evening as trough over the north Rockies and
Great Basin moves to the east. At the surface, a weak pressure
trough will linger across the Panhandle and South Plains today with
a weak pressure gradient across the forecast area as a tighter
gradient and stronger surface winds will be focused to our east from
North Texas into Oklahoma. This flow will result in a veered surface
flow with southwest to west winds developing area wide which will in
turn shift rich surface moisture in place off the Caprock early this
morning eastward with dry air spreading across the area throughout
the day. As for temperatures, progged 1000-500 mb thickness
increases suggest warmer temperatures than yesterday, but a weaker
downslope component could offset this. The exception could be off
the Caprock where drier air could allow for those warmer
temperatures to be realized. The bulk of guidance seems a bit too
cool relative to what the setup appears to be and have thus tried to
trend the MaxT grid toward the higher end of guidance while the
blend looks for fine for tonight`s lows.

&&

.LONG TERM...
(Tuesday through Sunday)
Issued at 227 AM CDT Mon May 20 2024

The mid/upper-level pattern on Tuesday will feature a synoptic-scale
trough encompassing the western two-thirds of the U.S., where
multiple smaller-scale troughs and vorticity lobes will pivot about
a gyre embedded within the waveguide as a response from an anomalous
ridge in the northeastern Pacific Ocean. The leading shortwave
trough is forecast to eject into the north-central Great Plains on
Tuesday afternoon, while the core of a 250 mb jet streak translates
over the CWA. A cirrus shield congruent with this jet streak should
eclipse at least the southern half of the CWA on Tuesday, though
this should have limited effect on boundary-layer mixing. The
backing to the mid-level flow in the wake of the aforementioned
shortwave trough (e.g., 700-500 mb flow near 50 kt) will result in a
small warm nose/subsidence layer above 700 mb, and when combined
with the slightly negative geopotential height falls, temperatures
will peak in the upper 80s to middle 90s from northwest-to-southeast
across the CWA, respectively, on Tuesday. Mid-level flow will weaken
heading into the afternoon hours as the CWA becomes far removed from
the ejecting shortwave trough, and only breezy, west-southwesterly
winds are expected to develop in concert with peak heating.

Broad, southwesterly flow will persist over the region heading into
Wednesday as the high-level, split-flow pattern remains intact.
Elongation of the 250 mb, subtropical jet streak is forecast to
evolve as the anomalous ridging over the northeastern Pacific Ocean
begins to collapse; and this will shift the cirrus shield east of
the CWA on Wednesday. At the surface, a cold front originating from
the vertically-stacking cyclones over the Corn Belt will have surged
southward across the central Great Plains and is forecast to arrive
in the extreme southern TX PH prior to sunrise on Wednesday. The
front should reach the southern South and Rolling Plains by the late
morning hours; however, presence of an increasingly barotropic
airmass to the south should slow the fast, forward-speed of the
front with the front forecast to stall either in the aforementioned
locales or in the northern Permian Basin. The blended prognosis on
the frontal position was acceptable and has been maintained with
this forecast package, though additional adjustments to the front as
it becomes quasi-stationary may be necessary in forthcoming cycles.
Cooler, though still warm, temperatures will follow the front with
highs ranging from the lower-to-upper 80s from the extreme southern
TX PH into the southern South and Rolling Plains are also forecast
for Wednesday afternoon.

Advection of an elevated mixed layer (EML) from the prior day as a
function of the mid-level cooling associated with the geopotential
height falls will continue atop the pre- and post-frontal airmass on
Wednesday. Forecast soundings indicate most-unstable parcels
potentially yielding >=2,500 J/kg CAPE within a belt of strong,
southwesterly, deep-layer flow; and lapse rates throughout the EML
near 7.5 deg C/km. Low chances for convection will depend on the
position of the quasi-stationary front, and are currently confined
to the southeastern Rolling Plains. Thunderstorms that initiate
along, or in the post-frontal airmass (i.e., non-surface-based),
will have a mean storm motion vector to the east at nearly 40 kt and
prospects for supercells remain east of the CWA at this time. The
severe weather threat for the small area of PoPs on Wednesday is,
therefore, low; and NBM PoPs were trimmed as thinking is leaning
towards the southeastern zones being bereft of convection during the
afternoon and evening hours Wednesday. Meanwhile, a well-defined
shortwave trough on the southern tranche of the cyclonic gyre
embedded within the larger-scale troughing is forecast to dig into
the northern Rocky Mountains heading into Thursday morning.

The mass response ahead of the amplifying trough to the west will
result in lee cyclogenesis across eastern New Mexico, along with the
quasi-stationary front transitioning into a warm front and moving
northward across the CWA during the overnight hours Wednesday into
Thursday morning. The dryline, previously eroded from the passage of
the front but still intact within the pre-frontal airmass in
southwestern Texas, will also mix northward, perhaps along or east
of the edge of the Mescalero Escarpment. Rapid boundary-layer
moistening is forecast to occur on Thursday morning, with dewpoints
potentially reaching 60 degrees along the I-27/HWY-87 corridors. Low
PoPs have been maintained, with the "silent" 10-percent PoP contour
drawn back to the I-27 corridor as elevated, WAA thunderstorms may
be ongoing during this time as another 700 mb trough arrives ahead
of the leading mid-level perturbation. Global NWP guidance is in
excellent agreement with the position of the shortwave trough as it
ejects into the northern Great Plains, with high confidence in the
dryline mixing into the Rolling Plains on Thursday. The glancing
influence of the negatively-tilting shortwave trough over the
northern Great Plains amidst the return flow, hot temperatures, and
strong to potentially extreme instability in the moist sector favors
severe thunderstorms. The orientation of the deep-layer flow would
favor splitting supercells, though it is too early for specificity
on storm characteristics with chances for storms ending Thursday
night. Dry, hot, and breezy weather is then forecast through the end
of the period as the CWA remains within the inflection point of the
subtropical ridge over Mexico and the progressive flow over the
northern U.S.

Sincavage

&&

.AVIATION...
(12Z TAFS)
Issued at 632 AM CDT Mon May 20 2024

VFR conditions to continue through the TAF period.

&&

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

$$

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