569
FXUS64 KLUB 280556
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
1256 AM CDT Tue May 28 2024

...New AVIATION...

.SHORT TERM...
(This evening through Tuesday)
Issued at 242 PM CDT Mon May 27 2024

500 mb short wave ridging will drift eastward across the southern
High Plains during the short term period, but its strength will not
be sufficient to negatively affect thunderstorm potential. The more
interesting setup comes below 500 mb with the 700 mb ridge displaced
to the east over Oklahoma and North Texas with southwesterly flow
over the forecast area. Shifting to the surface and low levels,
a persistent lee trough across eastern New Mexico and a weak cold
front sagging southward through the Panhandle will continue to
promote an easterly low level component that will and subsequent
moisture advection. Dew point temperatures by 12Z Tuesday should
be above 50F New Mexico state line near 60F along I27 corridor and
perhaps pushing 70F eastern counties. Two periods for
thunderstorm development must be considered. The first is during
the early morning hours tomorrow when mid level moisture advection
and isentropic lift will likely initiate elevated convection in
the vicinity of the Red River but probably east of the forecast
area. Could see some of that development end up as far west as the
Childress area, but keeping a small slight chance mention there
looks adequate at this time. Focus then shifts to afternoon
convective initiation. There remain some variables that need to
be sorted to finalize specifics of the forecast, i.e.,
southwestward penetration (if any) of convective outflow into the
forecast area and how much that destabilizes the air mass behind
it and the eastward push to the dryline during the day Tuesday. In
general, there does not appear much forcing in the mid levels,
although there is some hint of a modest jet streak at 700 mb that
may be enough to mix the dryline more than 30-60 miles into the
forecast area from New Mexico, but given the richness of moisture
and the lack of dynamism to the pattern will pull thunderstorm
chances all the way back to the New Mexico state line. Progged
MLCAPE values of 2000-4000 J/kg and effective bulk shear values
in excess of 40 kts support the idea of supercellular structure
even before looking at hodographs (which then also support that
idea). SPC upgrade to enhanced risk mainly for very large hail and
destructive hail for roughly the southeastern quarter of the
forecast area looks on track with further refinements possible
once the mesoscale details mentioned above become clearer.

&&

.LONG TERM...
(Tuesday night through next Sunday)
Issued at 242 PM CDT Mon May 27 2024

Scattered-to-widespread, severe-caliber convection will be ongoing
across portions of the Caprock and into the Rolling Plains on
Wednesday evening. By this point, a mixed-mode of thunderstorms,
including supercells and congealing, multi-cellular clusters, are
expected to be the primary storm mode as strong theta perturbations
continue to accelerate upscale growth into an organized MCS. The
potential for significant gusts (i.e., >=75 mph) will accompany the
MCS as strengthening inflow-layer theta-e advection will be
surmounted by a reservoir of extreme instability with most-unstable
parcel trajectories yielding >4,000 J/kg of CAPE. It is possible
that meso-beta-scale convective vortices develop in proximity to the
strong rear-inflow jet(s), which would accentuate the potential for
wind-damage in addition to wind-driven hail events, after dark as
the MCS moves southeastward across portions of the Rolling Plains.
Flash flooding will occur from very heavy rain rates; however, the
potential for a prolonged flooding event is very low owing to the
anti-parallel Corfidi vectors relative to the MCS movement with a
downshear component in excess of 40 kt. The vorticity lobe aloft
should be convectively augmented in response to the MCS, with the
potential for a mesoscale high to develop and result in locally
strong wind gusts following steep pressure rises in the wake of the
MCS across portions of the South and Rolling Plains. This would, in
turn, cause an increase in forward-speed of the system as it is
currently forecast to exit the CWA near or after midnight CDT
(29/05Z) with the cold front quick to follow as it begins to stall
in the Permian Basin by Wednesday morning.

A low-amplitude, shortwave ridge is forecast to shift over the CWA
on Wednesday as a high-level, split-flow pattern remains intact
across the Lower 48 where a pseudo-Omega Block develops along the
Medicine Line/49th parallel. This progressive wave train will
modulate the amplitude and position of the 594 dam ridge centered
over central Mexico, resulting in quasi-zonal flow to persist over
West Texas during this time. At the surface, the quasi-stationary
front should be located in the Permian Basin and bend northwestward
into New Mexico where it should be dammed along the lee of the Rocky
Mountains. Post-frontal, east-northeasterly flow will be ongoing
beneath a thick, low-level stratus deck which will inhibit diabatic
heating. Mild temperatures are expected, and PoPs were lowered
substantially area-wide for Wednesday afternoon as the post-frontal
airmass will also be convectively overturned. The lack of surface
and low-level convergence, restricted diabatic heating, and the
passage of the shortwave ridge overhead and attenuated mid-level
flow should dampen the development of convection on Wednesday
afternoon. Further lowering of PoPs may be required in forthcoming
prognostications as confidence increases in the timing of the dry
period.

By Wednesday evening, the quasi-stationary front draped across the
Permian Basin should undergo warm-frontogenesis ahead of the
approach of a low-amplitude, shortwave trough pivoting over the Four
Corners region. Gradual cooling of the mid-levels and forced ascent
along the passage of the warm front may generate an overnight round
of showers and thunderstorms as the 700 mb trough arrives, and the
already-moist boundary-layer will result in low stratus expanding
westward towards the TX/NM state line as the low-level jet
strengthens to around 30 kt. As the shortwave trough emerges over
the southern Rocky Mountains, the associated cross-barrier flow will
generate a lee cyclone at around 998 mb in eastern New Mexico, with
a sharpening dryline extending southward near the TX/NM state line.
Guidance continues to indicate the potential for a well-defined
thermal axis to develop ahead of the dryline/moist axis, both of
which would serve as a foci for explosive thunderstorm development
on Thursday, especially near the triple point; however, the exact
positions of these mesoscale boundaries remains unclear. Therefore,
the blended PoPs have been maintained with the best chances for
severe-caliber convection occurring with eastward extent from the
TX/NM state line.

Significant-severe thunderstorms will be possible on Thursday
afternoon and evening, with point and area-averaged forecast
soundings indicating mixed-layer CAPE between 2,500-3,500 J/kg and
most-unstable parcels yielding over 4,000 J/kg; and these estimates
appear to be accurate given the lack of a synoptic-scale front aloft
eroding the EML entirely. The combination of the strong-extreme
instability, in addition to the cross-boundary shear vectors and
effective shear magnitudes near 40 kt, indicates an environment
favorable for supercells and the potential for tornadoes. Upscale
growth into a larger-scale complex is possible as relatively
straight hodographs aloft would favor storm-splitting and
destructive interference, and with the poleward advection of
precipitable water (PWAT) content exceeding the 99th percentile
(e.g., forecast PWAT values between 1.40-1.60"), the potential for
flash flooding will exist once again on Thursday night across
portions of the South Plains and into the Rolling Plains. Sounding
climatology from WFO AMA and MAF for Thursday evening (31/00Z)
indicate PWAT values of 1.28" and 1.45" for the 99th percentile,
respectively. Timing of the convective episode(s) on Thursday will
continue to be refined in the coming days.

Quasi-zonal flow is forecast to persist by the end of the week and
into next weekend as the Omega Block across southern Canada meanders
eastward, which will maintain cross-boundary shear vectors in the
presence of the dryline in the vicinity of West Texas. The blended
PoPs were accepted with the potential for strong-to-severe-caliber
convection to last through the end of the period for portions of the
CWA.

Sincavage

&&

.AVIATION...
(06Z TAFS)
Issued at 1242 AM CDT Tue May 28 2024

Lower ceilings are developing around CDS this morning however they
should remain VFR until sunrise. Then there is a 10%-30% chance of
ceilings lowering into the MVFR range however this is highly
dependent on thunderstorm outflow across North Texas and western
Oklahoma. A dryline situated across the South Plains will lead to
thunderstorm development across the area this afternoon and
evening however with uncertainties regarding morning convection
the timing and location of the afternoon convection remains
uncertain. All terminals will have the potential to see
thunderstorm activity today though with gusty and erratic winds,
large hail, and visibility reductions due to heavy rainfall.
Easterly winds may also become gusty this afternoon and evening.

&&

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

$$

SHORT TERM...07
LONG TERM....09
AVIATION...58