Area Forecast Discussion
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FXUS64 KLUB 172316
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
616 PM CDT Sun Mar 17 2024

...New AVIATION...

.SHORT TERM...
(This evening through Monday)
Issued at 222 PM CDT Sun Mar 17 2024

The western CONUS rex block and the mid/upper low trapped under it
remain in place with the low continuing to sit over Arizona.
However, a shift to the west of this feature toward southern
California and a significant mid/upper trough swinging southeastward
over the upper Midwest and western Great Lakes to the Ohio Valley
during the next 24 hours will result in upper level ridging becoming
centered over the southern High Plains while a modest cold front
backdooring into the forecast area courtesy of the midwest upper
trough will bring drier low to mid level air over the area. Shower
chances now look to be confined to western zones near the New Mexico
state line this evening before exiting the forecast completely
overnight through Monday. The northeast to southwest clearing trend
will persist this evening as well and will allow for a wider diurnal
range in temperatures tonight and Monday. Highs Monday will be
limited some by modest upslope flow and cool air mass behind the
backdoor cold front, but plenty of mid-March insolation should help
push temperatures into the 60s for most to all of the forecast
area.

&&

.LONG TERM...
(Monday night through next Saturday)
Issued at 222 PM CDT Sun Mar 17 2024

The Rex Block located over the western U.S. will begin to collapse
early Tuesday as the upstream tranche of a large-scale trough
encompassing the eastern seaboard begins to broaden, and as a train
of PV streamers propagating towards the Pacific Northwest perturb
the once-stable blocking pattern. The cut-off, mid-level low
meandering over the Desert Southwest will gradually rotate eastward
on Tuesday as the collapse occurs while a well-defined anticyclone
at the surface and mid-levels remains anchored over southeastern
Texas. The resultant surface pattern will feature a strengthening in
southwesterly flow as an isallobaric response is generated from lee
cyclogenesis to the north of the CWA beneath an ejecting vorticity
lobe that should become increasingly stretched within the confluent
flow aloft. High temperatures were raised from the blended guidance
as there are indications of mixing heights ascending to near 700 mb
in the Rolling Plains as the lowering of terrain enhances the
effects of compressional warming despite the likelihood of mid-level
cloud debris advecting northeastward over the entire CWA as the
steering flow aligns to the southwest ahead of the cut-off low.

Breezy, southwesterly winds are forecast to remain intact during the
overnight into Wednesday morning as cyclogenesis continues across
the west-central Great Plains, which will keep low temperatures in
check amidst humid conditions as the surface reaches saturation. The
Rex Block will have completely collapsed by Wednesday morning, with
the cut-off low transitioning into an open wave; however, there are
some indications that a small, closed (not cut-off) circulation is
maintained as the southern-stream trough ejects eastward over the
southern Rocky Mountains. (All cut-off lows are closed, but not all
closed lows are cut-off.) Isallohypsic tendencies will not be
particularly impressive with this ejecting shortwave trough;
however, the geopotential height falls and attendant geostrophic
deformation should have a large enough response to transition the
diffuse surface trough dammed up against the edge of the Mescalero
Escarpment into a dryline on Wednesday morning. Eastward propagation
of the dryline should be slow throughout the day due to the dampened
state of large-scale forcing for ascent, with the dryline crossing
the TX/NM state line by the late morning hours.

Elevated, WAA-induced convection may be ongoing during the early
morning hours Wednesday across portions of the South Plains as the
base of the shortwave trough pivots over south-central New Mexico.
The primary form of convection will be showers; however, a slight
chance mention of thunderstorms was added into the official forecast
as the elevated mixed layer (EML) advects eastward in response to
the gradual cooling of the mid-levels. While the surface will be
stable, LFCs will be rooted above the nocturnal inversion (i.e.,
elevated), with indications of theta-e becoming constant with height
at and above the LCL. Presence of an ACCAS field would allow parcels
to reach the LFC, and with only minimal CAPE (e.g., most-unstable
trajectories yielding <=200 J/kg) needed for updrafts to generate
lightning. Severe thunderstorms are not expected on Wednesday
morning, though instances of small hail will be possible with the
deeper cores. It remains nebulous if and where a dryline bulge
occurs due to the uncertainty of this ejecting trough remains open
or if vorticity lobe(s) can be maintained within the small
waveguide. The presence of such a feature would result in a
wavy/bulging dryline; however, additional computations of NWP will
be needed to resolve this scenario.

Widespread cloud debris is also forecast to delay the erosion of
surface-based convective inhibition, though high temperatures will
still be a few degrees warmer than Tuesday. Furthermore, a washed
out/diffuse dryline orientation is expected irrespective of any
bulging as this ejecting wave remains compact and low-amplitude,
with most guidance indicating weakly confluent flow in the dry and
moist sectors throughout peak heating. It appears that the best
potential for surface-based (albeit high-based) thunderstorms will
be across the Rolling Plains by the afternoon and evening hours as
the depth of the EML improves, leaning towards the possibility of
strong convective gusts with thunderstorms given the eventual
evolution of an Inverted-V boundary-layer in the Rolling Plains (the
precursor of this PBL profile can be seen in forecast soundings the
day prior). Storm-splits would be favored due to relative straight
hodographs, with loosely-organized clusters a possibility as storms
propagate eastward on Wednesday night with precipitation ending by
Thursday morning. A weak cold front will move through the CWA
following the departure of the southern-stream shortwave trough on
Thursday morning, and high temperatures on Thursday will be similar
to the prior day as CAA will remain weak post-FROPA. Breezy, dry,
and warm conditions are forecast heading into next weekend as the
upper air pattern becomes zonal and surface troughing becomes
established across the region.

Sincavage

&&

.AVIATION...
(00Z TAFS)
Issued at 608 PM CDT Sun Mar 17 2024

Skies will gradually clear through the evening. While brief MVFR
CIGs cannot be ruled out (particularly for KPVW and KLBB) for the
next few hours, VFR conditions are expected to persist through the
TAF period. Light winds will continue.

&&

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

$$

SHORT TERM...07
LONG TERM....09
AVIATION...19


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