Area Forecast Discussion
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990
FXUS64 KLUB 172341 AAA
AFDLUB

Area Forecast Discussion...UPDATED
National Weather Service Lubbock TX
641 PM CDT Tue Apr 17 2018

.AVIATION...
VFR conditions will continue through the next 24 hours although
there will still be some blowing dust at KLBB and KPVW through 03
UTC. Wind speeds will decrease a bit after sunset from the
southwest but a cold front will move across the area after
midnight local time which will bring the wind around to the north
to northwest and could also remain gusty at times. Wind speeds
will then remain sustained in the 10 to 20 knot range through
Wednesday afternoon.

Jordan

&&

.PREV DISCUSSION... /issued 403 PM CDT Tue Apr 17 2018/

DISCUSSION...
For the remainder of this evening: Windy southwesterly winds of 25
to 35 mph are expected to persist through early Wednesday
morning. A Pacific front is progged to rapidly move into and
through the region late this evening bringing winds around to the
NW. Speeds are expected to remain up in the 20-30 mph range.
Observational data across NRN NM/SRN CO are not showing much
evidence of the Pacific front taking shape and as such there is
some uncertainty of timing and intensity of the winds behind the
system. Sometimes, these Pacific fronts can kick up a great deal
of dust as they come through. Whether or not this occurs tonight
remains to be seen. A cold front should then work its way through
the CWFA before sunrise. Some diminishing of speeds looks to be
likely behind the cold front though the more significant decrease
will be expected during the day tomorrow.

This said, it`s time for a transition in West Texas Weather.
Today`s wind and dust is expected to be replaced by thunderstorms
later this week. A large amplitude, negatively tilted trough is
transitioning to our northwest with ridging following, in turn for
Wednesday. As the ridge moves into our part of the country, the
next upper low will move onshore the NORCAL coast and push toward
the Four Corners area. All model solutions have slowed the
progress of this system (which was originally anticipated to be
about a day earlier). The low now makes Four Corners around mid
day on Friday which is a bit of a sweet spot for West Texas
springtime severe weather. Furthermore, after that, the track of
the low is much further south than previously indicated (some days
ago) with the low tracking across the TX Panhandle. The ECM
continues to exhibit the slowest movement of the system and this
trend certainly seems to have merit. Northwest flow aloft builds
in for the latter weekend with ridging affecting the southern
CONUS through the remainder of the forecast. An upper level
shortwave does transition up near the Canadian border on Tuesday
but it`s influences appear to be relatively minor at this time.

Turning to the sensible weather, winds have continued to ramp
upwards as expected.  The main energy with the triggering trough is
placed across southern Colorado.  Quite notable is the Dust RGB
plume coming off of the Great Sand Dunes NP near KALS.  We are still
expecting lower end advisory speeds this afternoon with breeziness
continuing into the evening hours.  A cold front will sweep through
later this evening bringing winds around to the northwest; they will
still remain breezy behind the front through Wednesday morning.   By
Wednesday afternoon, high pressure will settle into the region
bringing about much lighter wind speeds through return flow will
return by sunset.  The best moisture advection of Gulf moisture is
expected to our west across Central NM with tstms firing during the
late afternoon across the Sacramentos and Pecos Valley.  A stray
storm could move into our western zones but that looks like a very
weak bet at this point.  Friday will be a different story for us. We
may see some streamer showers during the morning hours out west with
more vigorous convection anticipated during the afternoon.  Given
progged wind fields, we may see a squall line further north with
perhaps a bit more of a discrete mode activity further south.  With
a system of this intensity, a couple of rounds of convection appears
possible through the day and well into the overnight hours perhaps
transitioning to rain as the low passes overhead and a cold front on
Saturday morning.  Generally speaking, guidance tends to hold onto
precip longer than it should and thus will go ahead and show things
drying out by Saturday afternoon based more on local experience
rather than a firm model indication.  The airmass behind the front
will not be particularly cold but we can expect northerly surface
flow to persist into Sunday afternoon especially out east.  Gulf
moisture then builds back into the area late Monday and Tuesday
ahead of the next system.

Looking more at the storm potential for Friday, bulk shear values of
50-70 kts.  Instability appears to be rather limited (surprising low
given the pattern) with MUCAPE struggling to make it over 500J/kg
during the afternoon.  However, with dynamical cooling aloft, MUCAPE
appears to climb to near 1k J/kg when the main push comes through.
The CAPE to shear ratio would tend to be a limiting factor for many
storms to become established though some low topped supercells are
certainly within reason given the shear profiles.  Certainly, a wind
threat will exist along with a marginal hail threat.  We will have
to be careful regarding the potential for tornadoes Friday afternoon
given the low level shear. Put another way, it doesn`t look so
much as an instability driven event as does it look to be a
dynamically driven event. This is typical for our early season
storms. If the upper low tracks as expected, we will be placed in
the left entrance (favorable) region of lift Friday evening as
the jet core passes to our south. Good Q-vector convergence is
noted across our part of WTX.

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until midnight CDT tonight for TXZ021>044.

Wind Advisory until 10 PM CDT this evening for TXZ021>042.

&&

$$

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