Area Forecast Discussion
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FXUS64 KLUB 230520

Area Forecast Discussion
National Weather Service Lubbock TX
1220 AM CDT Thu Mar 23 2017

A 40-50 knot southerly LLJ has developed and it could lead to
periods of LLWS when the surface winds drop off. This appears
most likely at KCDS where a LLWS mention was included.
Additionally, we could still see MVFR to IFR cigs affect the
terminals early Thursday morning, but this remains uncertain and
have only hinted at the possibility in the TAFS. The southerly
winds will really increase during the day Thursday peaking at
25-30+ knots during the afternoon. An AWW may eventually be needed
at KLBB. These strong winds will loft a bit of dust, though
unless winds are stronger than currently expected visibilities
will likely remain VFR. Finally, scattered convection will likely
develop Thursday evening, with KLBB and KPVW having a decent shot
of experiencing a storm between 00-03Z.


.PREV DISCUSSION... /issued 344 PM CDT Wed Mar 22 2017/

.Threat of severe thunderstorms still on track late Thursday...

Pesky low stratus which kept much of the srn Panhandle cool and
cloudy for most of the day has finally cleared out as of 3 pm,
leaving mostly sunny skies across the forecast area. Upsloping E-SE
winds were advecting moisture westward with 40-50 degree dewpoints
area-wide, and mid to upper 50 dewpoints not far off to our south
and east, poised to race back tonight.

A deep upper-level trough currently along the Pacific coast will
move across the Great Basin and desert southwest tonight, and into
the 4-corners region during the day Thursday. As it does, it will
induce a strong srly low-level jet over West Texas overnight, and
this will help bring those higher dewpoints into the area early
Thursday. It is still a little uncertain what the extent will be, if
any, of low stratus development after midnight. Best indications are
that we could see some patches focused across the western South
Plains into the far southern Texas Panhandle. Lows tonight will be
on the mild side due to the srly breezes and moisture - mainly in
the 50s.

As cyclogenesis occurs on Thursday across eastern Colo. into eastern
NM, southerly winds will continue to pick up through the day, likely
becoming sustained near 30 to 40 mph across much of the area in the
afternoon. A wind advisory will likely be needed and some blowing
dust across the Caprock is likely as well.

The surface trough/dryline is expect to tighten up in the vicinity
of the state line Thursday afternoon, perhaps bending a bit east
into the southwest Texas Panhandle on it`s northern extent.

Forecast sounding to the east of the dryline suggest that EML
capping will hold through most of the afternoon, but as strong
height falls overspread the dryline after 21 UTC or so, it appears
that the cap can be breached along the dryline corridor. Most of the
available model guidance is in good agreement showing scattered
convective development in the vicinity of the dryline around 21 to
23 UTC. Storms that develop should be able to exploit an environment
of moderate instability (about 1000 J/kg of CAPE) and very strong
shear to quickly become strong to severe. The elongated,
relatively straight-line hodographs suggest that splitting
supercells are a possible mode early with the primary threats of
large hail and damaging wind gusts. However, there may be a short
window for a tornado threat centered around 00 UTC where LCLs
lower slightly and low-level winds back. However, as the Pacific-
type front merges and overtakes the dryline, storms are expected
to transition fairly quickly into a more linear mode by early

Upper trough initially centered near the Four Corners Thursday
evening is progged to close off and deepen considerably overnight,
before trekking across the OK Panhandle on Friday and becoming
vertically stacked while filling. Deep ascent will become maximized
Thu evening as strong height falls and a Pacific front impinge on
moist southerly winds - likely increasing to wind advisory values
before sunset when the greatest pressure couplet unfolds. As cited
in the short term, storm modes should become progressively
clustered through the evening as linear forcing amplifies along
the front, before convection quickly exits off the Caprock before
midnight and leaves our eastern zones before daybreak Friday.

Friday is looking even windier than Thursday as strong northerly
LLJ unfolds on the backside of the cyclone across the eastern
Panhandles. Models show anywhere from 40 to 60 knots at 850mb from
the western Panhandle extending SE into our northern two rows of
counties, so a high wind watch will likely be issued if this theme
persists. Soundings show some mid-level moisture within a stout
cold pocket which could breed showers and further enhance this
deep momentum transfer.

In the wake of the filling cyclone, a far lesser trough is
expected to track east over the northern Panhandle on Sunday. This
wave has little opportunity for moisture recovery locally, so
sensible weather will be relegated to a dry cold front from the
north which could impact moisture return for the next, and more
vigorous cyclone shaping up to our west by early next week. Models
seem quite eager to restore Gulf moisture to West TX by early next
week with this system, and unfortunately model spread has
increased with the 12Z model cycles regarding the evolution of
this trough. A blended approach between the faster ECM and CMC
and the slower GFS offers the most value at the moment until
model continuity improves.




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