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FXUS64 KLUB 251053

Area Forecast Discussion
National Weather Service Lubbock TX
553 AM CDT Tue Apr 25 2017

Main concern today will be windy conditions at all three sites. A
cold front will make its way through the region this evening with
subsequent lowering ceiling and increasing rain chances--
particularly at KPVW/KCDS. Use caution this afternoon around virga
showers (e.g. steer clear) as the airmass below the cloud base
is favorable for accelerating downbursts.


.PREV DISCUSSION... /issued 419 AM CDT Tue Apr 25 2017/

Quite an active short term this morning.  A shortwave trough was
analyzed this morning from the Great Basin thence southward into the
desert southwest. Accompanying this system is expansive mid and
upper level cloudiness extending out into the Pacific off the coast
of California and as far south as Central Sonora and Chihuahua.  The
trough axis is expected as it approaches West Texas making it
overhead by about 12Z Wed.  Previous runs had indicated that a small
closed circulation would form within the trough though this
morning`s data.  Only the GFS still hints at this and at that, for
only a few hours across NE NM.

For today, mid level winds will become increasingly southwesterly as
a 60-65 kt jet core moves across the area hinting that the best wind
dynamics will move NW to SE during the day.  H7 pressure gradients
would tend to suggest 30-35 kt sustained winds in the absence of
cloud cover.  However, as mentioned above, that`s not the case
today.  NWP appears to be struggling with respect to geospatial
coverage which is substantially greater than predicted.  Coverage is
not 100 pct though the southern fringe of cloudiness is a good 120
miles further south.  To compliment, as the winds become more
southwesterly, given the available moisture, an increase in mountain
wave activity would be expected.  This is starting to become evident
in the Manzano and Sacramento ranges.  In comparison with other
similar events, indications are that the winds should be quite
breezy, but largely remain just under advisory levels north of a
line from Morton to Tahoka with the caveat that if skies begin to
clear out, higher surface winds will result.  Southwest of this
line, will issue a wind advisory.

Conditions are very dry west of the dryline with dewpoint temps in
the teens.  However, some degree of top down moistening is expected.
 Still, the min RH values should drop into the lower to middle teens
this afternoon.  The lower RH values are progged in the southern
half of the region and would ordinarily trigger fire weather
concerns.  However, green-up is well underway, particularly in the
south, and thus we will handle today`s event with a rangeland fire
danger statement.

After 00Z Wed, things change as winds begin to veer with the
approach of a cold front. In fact speeds will increase, once again
across the South Plains and SW Panhandle, to the 25 mph range. Then,
with the approach of the trough axis, we`ll see some good mid-level
cooling.  While the boundary layer is expected to take a while to
moisten, there are indications of elevated instability which could
trigger some thunderstorms particularly across the northern half of
the area.  Early on, some of these may manifest themselves as virga
bombs with gusty winds reaching the surface.  Later in the evening,
soundings suggest some potential for heat bursts.  For days, a
number of models have suggested snow with the system though the
progged surface temp guidance is too warm. With sufficient
dynamical cooling, it may be possible, but the cooling would have
to be much more pronounced than suggested by NWP.

A positively tilted trough axis is on our doorstep late Tuesday night
and is east into Oklahoma by Wednesday night. Best chance for
precip as the trough axis moves across the Texas Panhandle will be
along our northern zones in the extreme southern Texas Panhandle
and northern Rolling Plains where dynamic forcing peaks mid
morning Wednesday and quickly shifts east-southeast.

Zonal flow aloft Thursday out ahead of the next deepening trough
will result in another windy day across the region as strong
surface westerlies spread eastward out of eastern New Mexico into
West Texas. Temperatures will be above normal Thursday with some
help from strong downsloping. Models seem to be struggling a
little with surface features in the wake of strong winds and
aforementioned approaching trough. The best gulf moisture return
will remain well to our east and southeast on Friday with
southwest surface winds producing modest warm advection at the
surface keeping highs well above normal on Friday before the first
of several cold fronts arrives after sunset Friday night. We`ll
see 15-20 degree drops on Friday for highs. Given lack of moisture
return and cool modified continental airmass behind the front, do
not expect any shower activity to be robust or widespread. GFS
indicates a more progressive and deeper closed low to effect us
for the remainder of the weekend which would pack best chances at
rain/rain showers in our northern zones again. We could see some
isolated thunderstorms embedded in any shower activity that
extends farther south into the Rolling Plains early Saturday in a
ribbon of baroclinic instability that quickly pushes east. The GFS
is mostly dry by early Sunday but with the slower evolution shown
by the ECMWF, similar baroclinic forcing could produce some
lingering showers and isolated thunderstorms early Sunday as well,
though confidence is low given anemic moisture profiles in lower
levels and surface. Behind the weekend system zonal flow sets up
again for the beginning of next week before the next trough
arrives by midweek.


Wind Advisory from 1 PM this afternoon to 7 PM CDT this evening
for TXZ033-034-039-040.



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