Area Forecast Discussion Issued by NWS
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000
FXUS64 KLUB 290750
AFDLUB
Area Forecast Discussion
National Weather Service Lubbock TX
250 AM CDT Fri Mar 29 2024
...New SHORT TERM, LONG TERM, FIRE WEATHER...
.SHORT TERM...
-- Changed Discussion --
(Today and tonight)
Issued at 250 AM CDT Fri Mar 29 2024
06Z upper air analysis reveals a broad, positively-tilted trough
branching across the far northeastern Pacific Ocean and into the
Intermountain West, with a weakening surface and mid-level cyclone
rotating offshore of the Olympic Peninsula. Another well-defined
cyclone was located due west of the 130th meridian and along the
40th parallel, and will continue to rotate southeastward towards
northern California throughout the period as a 250 mb jet streak
near 150 kt digs southward on the western flank of the surface and
mid-level circulations. The broadly cyclonic flow extending eastward
of these features contains numerous smaller-scale perturbations that
were translating east-northeastward as the exit-regions of jet
streaks analyzed by the 29/00Z upper air maps near 100 kt and 50 kt
at 250 mb and 500 mb, respectively, nose into West Texas. Presence
of these jet streaks have and will continue to advect a plume of mid-
and high-level moisture originating from the northeastern Pacific
Ocean, particularly along the southern-stream belt of deamplified
flow. The cross-barrier component to the broadly cyclonic flow will
also maintain renewed genesis of orographically-induced cirrus
banding, with an expectation for thickening overcast to occur
throughout the remainder of the morning and into the afternoon
across the entire forecast area.
At the surface, a diffuse trough was delineated generally along the
100th meridian as per recent METAR and West Texas Mesonet (WTM)
data, where flow remains weakly confluent along its axis while
remaining veered across the Caprock Escarpment. The nearest lee
cyclone was analyzed in far southwestern Nebraska, though there
appear to be indications of a weaker, secondary surface low forming
across east-central New Mexico. LIDAR data out of LBB has also
detected rapid intensification of the low-level jet (LLJ), with a
speed near 50-55 mph at an altitude of around 700 ft AGL. After
sunrise, the boundary-layer will begin to couple with dispersion of
the intense flow associated with the LLJ occurring as it translates
to the surface. This will result in breezy winds developing by the
late morning hours while flow also veers southwestward behind the
quasi-stationary surface trough as the lee cyclone to the north
gradually rotates eastward.
The surface trough should transition into a dryline today beneath
the glancing influence of the amplifying trough to the west, and the
net response from the geostrophic deformation aloft should cause the
dryline to become much more sharp than yesterday (e.g., a dewpoint
gradient of around 20 degrees over 30 miles across the Rolling
Plains). Advection of the cirrus shield overhead will maintain some
degree of subsidence in the mid-levels, which should be enough to
prevent even warmer temperatures from coming to fruition. The
dryline will retreat westward after sunset, while secondary
cyclogenesis occurs later tonight across the TX PH, causing the
dryline to arc nearly eastward across the extreme southeastern TX PH
before bending southward in the southwestern South Plains. This will
result in a temperature gradient of nearly 15 degrees heading into
Saturday morning, ranging from the lower 40s to middle 50s from
northwest-to-southeast, respectively, across the CWA beneath a
clearing sky as high-level flow veers westward.
Sincavage-- End Changed Discussion --
&&
.LONG TERM...
-- Changed Discussion --
(Saturday through Thursday)
Issued at 250 AM CDT Fri Mar 29 2024
The last weekend of March is shaping up mild and breezy despite an
influx of high clouds in deep SW flow. This moisture is courtesy of
a healthy subtropical jet preceding an upper low forecast to shift
from SOCAL on Saturday to the Colorado Plateau by Monday. Meanwhile
in the low levels, a dryline should be bisecting the CWA from SW-NE
on Saturday morning all the while a backdoor cold front makes a run
for our nern zones on the heels of a weak low departing into OK.
These fronts can loiter much longer than models depict, so am a bit
skeptical of NBM`s quick rebound to southerly winds and very mild
temps in the Childress area by Saturday afternoon. Even with less
wind than today, the dryline should easily mix off the Caprock by
the afternoon, then retreat Saturday night before stronger SW winds
from lee cyclogenesis in CO shove this east on Sunday. In contrast
to the MAV`s much warmer highs this weekend, NBM`s temps seem legit
given mostly cloudy skies on tap.
Global models are in good agreement with strong height falls
impacting the region on Monday as the upper low kicks across the
Colorado Plateau. The remnants of the mid-level low over SOCAL
are progged to drift east and over the Desert Southwest during
this time and result in a broad, positively-tilted trough axis
occupying the central and swrn CONUS by Tuesday morning. Upshot of
this is that precip chances could start as early as Monday
morning across our eastern zones as height falls and a Pacific
cold front impinge on the retreating dryline. However, models are
mixed on how fast the main upper low lifts out and consequently
how much, if any, additional precip is on hand for the rest of our
CWA. NBM`s PoPs through Tue morning look okay for now given the
wealth of model spread and run-to-run variability, although its
post-dryline winds were bumped up on Monday afternoon given the
overall windier pattern. The next cold front dives south Monday
night and could boost precip chances pending any residual moisture
under the broad upper trough, though this may need to be culled in
later forecasts if the trough trends more progressive and drier.
Temps tumble to below normal territory for Tuesday ahead of
milder values by Wednesday.-- End Changed Discussion --
&&
.AVIATION...
(06Z TAFS)
Issued at 1217 AM CDT Fri Mar 29 2024
VFR prevails for the TAF period. LLWS will continue throughout the
overnight hours and dissipate shortly after sunrise. LIDAR data
out of LBB sampled a low-level jet near 40 kt at 700 ft AGL, and
those shear magnitudes are expected to persist at KLBB and KPVW
throughout the night. Shear magnitudes will be similar at KCDS
based off of recent VWP data from the KFDR Doppler RADAR with
heights at around 1 kft AGL. Winds will become breezy with gusts
up to 30 kt possible tomorrow afternoon as LLWS dissipates and
translates to the ground.
Sincavage
&&
.FIRE WEATHER...
-- Changed Discussion --
Issued at 250 AM CDT Fri Mar 29 2024
Critical fire weather conditions will be possible across areas
within the current Red Flag Warning this afternoon. The combination
of breezy, southwesterly winds; very warm temperatures, and minimum
RH values in the lower teens should result in RFTIs around 3 to
locally 4. However, ERC percentiles are not impressive and are
hovering near the 50th percentile. This, combined with above normal
fuel moisture and a thickening overcast, will preclude concerns for
critical fire weather across the rest of the Caprock Escarpment.
Winds will also shift slightly to the south-southwest ahead of the
dryline in the Rolling Plains this afternoon. The Red Flag Warning
will be maintained, and a Fire Danger Statement will be issued in
place of the current Fire Weather Watch less the counties along the
edge of the Caprock Escarpment. Winds will diminish rapidly after
sunset tonight while becoming west, with RH recovery between 40-50
percent behind the dryline and 90 percent in the southeastern
Rolling Plains.
Fire weather concerns taper on Saturday until stronger southwest
winds resume on Sunday, mainly near the TX/NM border. Critical
fire potential could expand over much of the Caprock on Monday,
although some rain chances by this time along with cooler
temperatures could temper this threat at times.-- End Changed Discussion --
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
Red Flag Warning from noon today to 8 PM CDT this evening for
TXZ021-027-033-039.-- End Changed Discussion --
&&
$$
SHORT TERM...09
LONG TERM....93
AVIATION...09