117
FXUS64 KLUB 161128
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
628 AM CDT Mon Sep 16 2024

...New AVIATION...

.SHORT TERM...
(Today and tonight)
Issued at 311 AM CDT Mon Sep 16 2024

As of 1AM CDT, mid-level satellite water vapor imagery and upper air
RAP analysis has the low across northern Cali before it is expected
to dive south into central Cali by this afternoon and then swing
eastward tonight over Nevada. Meanwhile, a broader low across the
southeast will remain stationary with a ridge sprawled over the Mid-
Atlantic/New England states blocking any forward progression. Weak
ridging will be in place over the Southern Great Plains today;
however, weak west-southwesterly flow will begin to meander into
West Texas with the incoming trough axis. Increased mid-level
Pacific moisture is present this morning across the Desert Southwest
with convection already developing. Storms are expected to continue
across western New Mexico and into Colorado today, with this
convection to remain west of the forecast area. Height falls this
afternoon with weak lee troughing across eastern Colorado will give
way to breezy southerly winds, especially along the Caprock.
Additionally, a weak stationary front will be draped along a line
from roughly Vigo Park to Jayton (nearly along the Caprock
Escarpment). Isolated 10 PoPs were added for the potential of a
storm or two developing. Dewpoints will be in the lower 60s east of
this boundary coupled with hot temperatures in the lower 90s. Lift
along the stationary boundary may help to initiate convection with
instability parameters supportive of an isolated storm or two,
similar to yesterday afternoon. Though unlikely, a strong storm
cannot be ruled out with MLCAPE values of less than 1000 J/kg and
bulk shear of 20-30 knots. Any storms that develops will be short-
lived with chances coming to an end after sunset as there remains
little to no forcing aloft with the weak ridging. Winds will
diminish tonight after midnight, with above normal low temperatures
mostly in the 60s and a few lower 70s across the Rolling Plains by
early tomorrow morning.

&&

.LONG TERM...
(Tuesday through Sunday)
Issued at 311 AM CDT Mon Sep 16 2024

The potential for thunderstorms remains intact for the upcoming week
and into next weekend as a progressive, northern-stream pattern
results in the formation of a cyclonic gyre over the western U.S. as
the synoptic-scale blocking across the eastern seaboard is slow to
erode. At the beginning of the period, the mid/upper-levels will
feature a southern-stream, neutrally-tilting trough with a 250 mb
jet streak approaching 100 kt rounding its base as it pivots over
the southern Great Basin. This trough is forecast to have a closed,
mid- and high-level low embedded within as it ejects northeastward
towards the central Rocky Mountains and becomes negatively-tilted by
Tuesday afternoon. The 250 mb jet streak will emerge over the
southern Rocky Mountains and nose into West Texas by the evening
hours, resulting in a significant increase in upper-level divergence
coupled with strongly difluent flow. Geopotential height falls will
be only slightly negative as the vertically-stacking cyclone
associated with the negatively-tilting trough is displaced nearly
800 tangential miles to the north-northwest of the CWA (e.g., over
the State of Wyoming) while the northern apex of the subtropical
ridge remains positioned over the Permian Basin.

At the surface, the CWA will be enveloped within a broad, open moist
sector as the synoptic cold front moves across the southern Rocky
Mountains and begins to stall as it enters the High Plains during
the afternoon hours Tuesday. Southerly winds will become breezy as a
result of the strong, leeward pressure falls associated with the
stacking cyclone well to the north of the CWA, as winds will become
coupled to the strengthening low-level jet stream throughout the
course of the day. Winds were raised a couple of kt from the blended
initialization due to indications of the lee cyclone deepening to
near 992 mb on Tuesday afternoon. The highest wind speeds will occur
across the Caprock with gusts to 30 mph expected in the afternoon as
vertical mixing heights peak in depth, and winds should also back to
the southeast towards the evening hours while continuing to advect a
plume of lower 60 degree dewpoints across most of the CWA.

Despite the weak, geopotential height falls, southwesterly flow in
the mid-levels that gradually veers with height will maintain the
elevated mixed layer (EML) atop Inverted-V boundary-layer profiles.
The EML is forecast to be characterized by MLCAPE values >500 J/kg
with most-unstable parcels yielding nearly 1,000 J/kg by the late-
afternoon hours, particularly across the western and northwestern
zones where geopotential height tendencies begin to increase and
cooling in the mid-levels is greatest. Large-scale forcing for
ascent will moderate with southward extent from the core of the
negatively-tilting trough; however, numerous thunderstorms are
forecast to unzip along the north-south-oriented cold front as it
enters the Pecos River Valle by late Tuesday afternoon. PoPs were
raised into the likely category (i.e., 60-percent) for Tuesday
evening across the western South Plains and the far southwestern
Texas Panhandle given the expectation for storms to linearize along
and ahead of the cold front.

The well-mixed boundary-layer will garner the potential for strong
wind gusts in excess of 50 mph across the western zones before
convection becomes more-tempered in intensity following the loss of
diurnal heating and as the surface cold front lingers west of the
New Mexico state line. Convective coverage is forecast to become
more-scattered with eastward extent towards the I-27 and HWY-87
corridors, with low chances lingering throughout the nighttime hours
as the once-high-based storms become rooted above the decoupling
boundary-layer (i.e., transitioning into elevated convection). Low
PoPs were, therefore, expanded from the NBM across portions of the
Caprock and Rolling Plains through sunrise Wednesday, with the best
potential across the far southern TX PH as upper-level divergence
intensifies with northward extent.

There is excellent agreement among the global NWP guidance for a
synoptic-scale gyre to evolve by mid-week across the western half of
the U.S., resulting in some deamplification of the flow over the
CWA. The Rex Block should begin to collapse by this point as a
barotropic low (currently Potential Tropical Cyclone Eight) begins
its post-tropical transition within the dampened field of synoptic
flow across the eastern seaboard, maintaining a blocking pattern at
the very least. The position of these large-scale features should
keep the stalling front near the TX/NM state line on Wednesday and
allow the subtropical ridge over central Mexico to shift northward.
Low PoPs were introduced across the Rolling Plains on Wednesday
evening as the EML, albeit tall and skinny, remains intact amidst
persistent, although weakening, moist ascent within the mid-level
theta surfaces. Convective coverage is forecast to be isolated at
this time, though a brief period of widely-scattered storms will be
possible across the Rolling Plains on Wednesday evening.

Increasing geopotential heights as the subtropical ridge sloshes
northward on Thursday will nix any thunderstorm potential; however,
additional chances for thunderstorms remain in the forecast from
Friday and through this weekend as a positively-tilted trough within
the southwestern tranche of the cyclonic gyre digs into the Great
Basin. Blended PoPs were maintained through the end of the period
given considerable agreement among the global NWP guidance suites
for a more-progressive troughing pattern to develop following the
erosion of the gyre to the west of the region.

Sincavage

&&

.AVIATION...
(12Z TAFS)
Issued at 602 AM CDT Mon Sep 16 2024

VFR conditions are expected through the period at all three TAF
sites. There is a low potential for an isolated shower or storm
near PVW/CDS this afternoon and evening, thus no mention was
included in this TAF issuance. Otherwise light and variable winds
will become predominantly south-southeasterly through the day and
increase to around 10 to 15 knots. Winds will taper late tonight,
but remain south-southeasterly through the end of the period.

&&

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

$$

SHORT TERM...11
LONG TERM....09
AVIATION...11