267
FXUS64 KLUB 171732
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
1232 PM CDT Tue Sep 17 2024

...New AVIATION...

.SHORT TERM...
(Today and tonight)
Issued at 317 AM CDT Tue Sep 17 2024

As of 2AM CDT, the upper low can be seen spinning over Nevada on mid-
level satellite water vapor imagery, along with another upper low
spinning over the Carolinas with weak ridging between the two
systems. As the western low ejects northeastward today, several
waves of mid-level Pacific moisture will traverse the Rockies. An
initial wave of convection is ongoing across northeast New Mexico
early this morning and is expected to remain north of the forecast
area.

The best chances for precipitation today will be this afternoon
along surface troughing across eastern New Mexico. The line of
storms that develops this afternoon will push east-northeast into
West Texas early this evening. There remains some uncertainty with
how far south the line of storms will extend in coverage with the
best chances expected across the far southwest Texas Panhandle and
northern Rolling Plains. With the incoming trough axis and 30-40
knot jet aloft, large scale ascent will help to drive convection
coupled with the increased mid-level moisture. However, much of the
better forcing will clip our far western zones as the negatively
tilted trough axis swings into the central Rockies. Lee troughing
will strengthen across eastern Colorado with breezy southerly
surface winds and warm, above normal temperatures in the upper 80s
to lower 90s. The warmest temperatures will keep off the Caprock
where skies may stay a bit sunnier and winds will be slightly less
breezy. Afternoon instability parameters near the New Mexico and
Texas state line will feature MLCAPE values of less than 1000 J/kg
and most likely closer to 500 J/kg. With the approaching upper jet
and increased southwesterly flow aloft, 0-6 km bulk shear values
will be around 30 to 40 knots. Throw it all together and there is a
potential for a few strong to severe storms in the line as it pushes
east across the state line. The main threats will be damaging wind
gusts up to 60 mph, small hail and localized flooding with heavy
rainfall. PWATs will approach 1"-1.25", which is near the 90th
percentile for climatology and supports moderate to heavy rainfall.

As the evening progresses, the line of storms will continue to push
eastward across the forecast area. Once again, there remains
uncertainty in the how far south the line of storms will develop and
persist through the late evening hours tonight. Once again the best
chance for continued showers and storms will be across the far
southern Texas Panhandle and northern portions of the South and
Rolling Plains. As the sun sets this evening and surface
temperatures cool, storms will become elevated with MUCAPE around
1000 J/kg or less. The low level jet will ramp up late tonight to
around 20-30 knots with bulk shear values remaining around 30-40
knots. The threat for strong to severe storms will diminish as the
line pushes eastward tonight, but the environment will still be
capable of maintaining storms with gusty winds, small hail and brief
downpours.

Shower and thunderstorm activity should wane overnight tonight into
the early morning hours tomorrow. Temperatures will remain 5 to 10
degrees above normal in the 60s along the Caprock and lower 70s off
the Caprock. Childress Airport has the potential to tie or break the
record for warmest low on September 18th, which is currently at 72
degrees (set back in 2013).

&&

.LONG TERM...
(Wednesday through Monday)
Issued at 317 AM CDT Tue Sep 17 2024

Isolated-to-widely-scattered thunderstorms are forecast to affect
portions of the Caprock and Rolling Plains on Wednesday, with
additional storm chances remaining in the forecast heading into the
weekend. In the mid/upper-levels, a cyclonic gyre will have become
established across the western U.S., featuring a vertically-stacking
low associated with a negatively-tilted trough over the Yellowstone
River Valley; and another amplifying, positively-tilted trough
digging southward offshore the Klamath Mountains and Redwood Coast
of California. The Rex Block over the eastern U.S. should dissipate
by this point as a well-defined cyclone rotating over the Carolinas
becomes absorbed into the slow-moving, opening trough. This will
maintain the channel of broadly cyclonic flow over the CWA with the
left-exit region of the 250 mb jet streak gradually shifting
northward as the subtropical ridge centered over central Mexico
continues to amplify. Smaller-scale perturbations are expected to
translate through the belt of broadly cyclonic flow on Wednesday as
the CWA will be otherwise bereft of any significant vorticity
anomalies.

At the surface, lee cyclogenesis will be ongoing across eastern
Colorado with a 998-1000 mb low forecast to develop by the afternoon
hours Wednesday. This cyclone will be embedded along the stalling
Pacific cold front that branches southward from the occluding
cyclone in the northwestern Great Plains, with a secondary surface
low forecast to develop across southeastern New Mexico. The dryline
will branch southward from this secondary low while the stalled
front bends farther to the southwest into southern New Mexico.
Leeward pressure falls will also begin to slacken compared to the
prior day, though the breezy, southerly fetch will remain intact
with winds between 10-20 mph amidst the plume of lower-middle 60
degree dewpoints advecting across the moist sector. A narrow
corridor of strong theta-e advection is forecast to become
established by the early-afternoon hours across the Caprock, and to
the east of the dryline and cold front intersection, with an
expectation for a well-mixed boundary-layer to evolve with PBL
heights ascending to near 700 mb coupled with Inverted-V profiles.
Full insolation and deep mixing will cause temperatures to breach 90
degrees area-wide, though the southerly fetch will mitigate further
effects of adiabatic compression, so temperatures were tweaked
slightly to align with the 00Z MOS guidance.

The elevated mixed layer will remain intact as flow throughout the
steering layer remains oriented out of the southwest, with
individual and area-averaged forecast soundings continuing to
indicate MLCAPE values between 750-1,000 J/kg and most-unstable
parcel trajectories yielding <1,500 J/kg of CAPE. The arrival of a
ribbon of high-altitude cirrus advecting overhead from the southwest
will serve as a source of large-scale lift atop an increase in low-
level confluence. Surface convergence will maximize in proximity to
the diffuse dryline, with isolated-to-widely-scattered storms
forecast to develop during the afternoon and evening hours across
portions of the Caprock and Rolling Plains. Low PoPs were once again
added across a large portion of the CWA on Wednesday compared to the
dry NBM, but were capped 20-percent for now. Initial cells will
split given the nearly linear orientation of hodographs throughout
the mean cloud-layer, but the dampened, mid-level flow and high LCLs
will favor the merging of cold pools as the evening progresses. It
is possible that a slow-moving, loosely-organized line of storms
develops, before succumbing to the effects of nocturnal cooling and
decoupling of the boundary-layer. Warm and muggy conditions will
follow heading into Thursday morning area-wide as the dryline
remains stalled near the TX/NM state line.

The negatively-tilted trough will cross north of the 49th parallel
heading into Thursday and become absorbed into a northern-stream
trough over far northwestern Canada, allowing the positively-tilted
trough digging into the western U.S. coast to pivot inland over the
Sierra Nevada Mountains. Geopotential height tendencies will become
positive as the subtropical ridge over central Mexico continues to
amplify and shift farther north, resulting in hot and dry weather
area-wide on Thursday. The synoptic-scale gyre is forecast to erode
by the end of the week following the absorption of the stacked low
and further amplification of the subtropical ridge, with global NWP
remaining in agreement of the southern-stream trough attaining a
neutral-tilt late Friday into Saturday. High-level divergence will
be most significant to the west of the CWA on Friday as a 250 mb jet
streak near 100-kt rounds the base of the neutrally-tilting trough,
with scattered storms forecast to remain most west of the TX/NM
state line; however, a few storms may clip the western zones late
Friday night.

Storm chances are forecast to expand eastward across most of the
Caprock and Rolling Plains heading into Saturday as the trough
ejects over the central Rocky Mountains while potentially becoming
negatively-tilted. However, there remains discrepancies among the
guidance with respect to the amplitude and timing of the trough
ejection. PoPs remain low (e.g., isolated-to-widely-scattered) for
Saturday, and further adjustments will be required in forthcoming
forecast cycles until guidance begins to converge on the evolution
of the latter uncertainty. A dry and warm forecast continues to be
advertised thereafter and through the end of the period as the
mid/upper-level pattern should begin to deamplify.

Sincavage

&&

.AVIATION...
(18Z TAFS)
Issued at 1224 PM CDT Tue Sep 17 2024

Thunderstorms are expected west of KLBB and KPVW this evening with
a small chance of reaching the terminals late this evening.
However, chances are low of this activity reaching KLBB with
slightly higher chances of reaching KPVW. Otherwise, VFR is
anticipated at all TAF sites.

&&

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

$$

SHORT TERM...11
LONG TERM....09
AVIATION...01