005
FXUS64 KLUB 231729
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
1129 AM CST Mon Dec 23 2024

...New AVIATION...

.KEY MESSAGES...

 - Fog will continue to affect portions of the Caprock and most
   of the Rolling Plains through late-morning.

 - Drizzle is forecast to affect the Rolling Plains tomorrow
   morning.

 - Chance of showers Thursday morning generally east of I-27. Warmer
   and dry thereafter.

&&

.SHORT TERM...
(Today and tonight)
Issued at 317 AM CST Mon Dec 23 2024

07Z upper air analysis reveals a low-amplitude trough at 300 mb
pivoting over south-central Texas, while mid-level flow becomes
quasi-zonal across the Lower 48. Farther west, subtle shortwave
perturbations ejecting ahead of amplified, negatively-tilted trough
pivoting towards the Pacific Northwest have generated a well-defined
PV streamer evident on water-vapor imagery over the northern Sonoran
Desert and into the Upper Colorado River Basin. This has generated
multiple bands of cirrus that continue to advect eastward towards
the CWA, while the evolving PV streamer imparts slightly-negative
geopotential height falls over nosing towards the Four Corners
region. Return flow has since become established ahead of this
incoming PV streamer, as the cross-barrier flow and geopotential
height falls have resulted in the formation of a low-level jet
stream originating out of the TX Big Bend via the increase in
leeward pressure falls. A narrow corridor of low-level stratus has,
and will continue, to advect and/or form across the Caprock and
Rolling Plains through sunrise as theta-e advection strengthens
from the development of the southern-stream shortwave troughing.

At the surface, a lee cyclone was located between AMA and BGD, with
a dryline extending south-southwestward from AMA towards LLN-HOB on
recent West Texas Mesonet (WTM) and METAR data. Weak frontogenesis
was underway, with a cold front branching westward from the surface
low towards TCC per recent WTM data. Southwesterly winds remain
elevated via the response of the leeward pressure falls associated
with the geopotential height falls; and the weak, isallobaric
response from the nearby surface low. Surface winds were increased
accordingly through 15Z to best match the current observations, as
gusts between 20-25 mph have been observed so far this morning. Fog
has also been maintained in the official forecast through 15Z as
well, as LBB, PVW, and VUF have reported visibility as low as three
miles. However, locally dense fog will remain possible across some
locales in the southern South and Rolling Plains through sunrise.

Meso-alpha-scale frontogenesis will continue throughout the rest of
the morning, with both the cold front and surface low progressing
southward throughout the short-term period. Fog should dissipate by
the late-morning hours as the approaching surface cold front advects
drier air into and east of the I-27 corridor, and as the nose of
warm theta-e advection shifts eastward. CAA in wake of this front
will be weak, and temperatures are still expected to range from the
middle 50s to upper 60s today, with the coolest temperatures in the
far southern TX PH. Scattered-to-broken, low-level clouds will
linger in the Rolling Plains this afternoon while mixing out
entirely on the Caprock as westerly flow persists in the pre-frontal
airmass across the South Plains. The cirrus shield will continue to
thicken today as significant amplification of the mid/upper-level
flow occurs today, with the nose of a 300 mb jet streak on the
downstream tranche of the amplifying ridge nosing into West Texas by
this evening. The base of the mid-level trough should pass overhead
after dark, which will cause the surface low and cold front to
continue moving south and east of the CWA after sunset.

The airmass will saturate thereafter across the Rolling Plains, with
the depth of the low-level stratus deck becoming deep enough to
produce light drizzle. Therefore, light drizzle has been introduced
into the official forecast through sunrise Tuesday for the Rolling
Plains. Northerly, post-frontal winds should remain elevated (e.g.,
near 10 mph), which will counteract the potential for fog as the
winds combined with the thickening stratus deck keep relative
humidity closer to 90-percent at the surface. Clouds will clear with
westward extent across the Caprock Escarpment, with the sky becoming
clear near the NM state line as confluent flow associated with the
exit-region of the highly amplified jet streak emerges into the CWA
following the further development of the shortwave trough over the
southern Great Plains. Low temperatures were cooled to align with
the recent MOS guidance, with lows ranging from around 30 degrees
near the NM state line to the middle 40s in the Rolling Plains.

Sincavage

&&

.LONG TERM...
(Tuesday through Sunday)
Issued at 317 AM CST Mon Dec 23 2024

A relatively active weather pattern is in store this week. A cold
front and resultant light northerly winds will bring high
temperatures closer to normal in the mid-to-upper 50s Tuesday. Winds
will turn southerly Christmas Day, but this will have little effect
on temperatures which will be similar to that of the previous day.
Unfortunately no white Christmas this year. A strong upper low will
approach from the west through Christmas Day evening. Although areas
to the east towards the Metroplex look to see the most active
weather from this system, surface winds will develop a slight
easterly component and moisture advection east of I-27 looks
favorable enough to merit a chance of showers which could be
increased in subsequent forecasts if current model trends hold.
Although the T word has not been used around here in some time, the
forcing parameters ahead of the aforementioned low are impressive
enough in combination with a ~30-40 kt LLJ that some elevated
convection/isolated thunderstorms cannot be ruled out for the late-
evening time period. Confidence remains on the lower end and
conditions are much more favorable for potential severe weather
farther east through Thursday, so keep that in mind if traveling
to/from that way. Nonetheless any storms in our area should be
generally confined to the southern/eastern Rolling Plains and severe
weather is not expected. A parade of upper troughs will move through
thereafter into the weekend, however dry westerly surface winds
eliminated any precipitation chances and allow for a gradual warmup
of temperatures, possibly to near 70 towards the New Year.

&&

.AVIATION...
(18Z TAFS)
Issued at 1120 AM CST Mon Dec 23 2024

Stratus has cleared much of the forecast area but will linger a
bit longer at KCDS. There should be a period of VFR conditions at
all three terminals before stratus builds southward behind a cold
front that will move past the terminals later this
afternoon/evening. Stratus is most likely at KCDS and least
favorable at KLBB where chances at this point are near 50/50. MVFR
ceilings at first will lower to IFR at KCDS.

&&

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

$$

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