Area Forecast Discussion
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FXUS64 KLUB 282317

Area Forecast Discussion
National Weather Service Lubbock TX
617 PM CDT WED SEP 28 2016

Great flying weather through the TAF cycle with light easterly
winds and only some passing mid-high clouds. VFR will prevail.


.PREV DISCUSSION... /issued 312 PM CDT WED SEP 28 2016/

The initial wind shift to the northeast associated with a weak front
is currently passing through our north and northeast counties. The
front will get a stronger push going this evening once the boundary
layer starts to cool and decouple. Easterly winds will continue most
of the day Thursday as the surface ridge noses into the region and
brings a noticeably cooler airmass into the area. Moisture advection
however appears to be fairly minimal aside from a temporary surge
behind the front. The temporarily higher dewpoints should bring more
mild night-time temperatures for most locations but the risk of fog
still appears to be very low. Highs on Thursday should only reach
into the lower to middle 70s, or about 10 to 15 degrees cooler than
today. Also, there will be a gradual increase in high level cloud
cover from the southwest, as upper-level moisture from weakening
tropical cyclone Roslyn gets directed toward West Texas by an upper
low over southern California.

Stationary ridging aloft will deamplify on Friday and nearly flatten
by the weekend all ahead of pattern change to deep cyclonic SW
flow early next week. Cool surface pressure ridge in place
Thursday night will yield to steady pressure falls and surface
troughing throughout the day on Friday. Although initially paltry,
return flow moisture should gain momentum this weekend as
trajectories improve from the Gulf. Concurrently, depression of
the upper ridge on Saturday should allow some influx of
subtropical moisture aloft, possibly enhanced by the remains of
TD Roslyn presently SW of Baja. This may breed top-down saturation
and light precip in our western zones on Saturday, but initial
inspection appears too marginal for measurable precip chances.
However, this theme should change particularly by Tuesday once
height falls ensue in advance of a digging longwave trough progged
to span the length of the Rockies.

Although a modest dryline looks to unfold on Monday, convective
prospects look to be squashed by warming mid-level temps and
veered/SW surface flow hampering low level convergence. PoPs
were inserted over the eastern half of the CWA by Tue as mid-
level cooling and background ascent improve with the approach of
the upper trough axis. Low level moisture looks to peak on Tue
complete with a sharper dryline in the vicinity. Fall climatology
tends to favor a more westward dryline position in these setups,
but will not draw into this too much given this is such a distant
system. On that note, how solidified the trough remains beyond Tue
is unclear among raw and ensemble output with the GFS favoring
additional lobes of vorticity rotating across the region versus a
more progressive ECMWF solution. Regardless, very breezy (20-30
mph) gradient winds seem suitable for Mon and Tue west of the
dryline in this pattern, with some window for even higher winds if
the trough assumes a sharper structure per the ECMWF and some
GEFS members.


.LUB Watches/Warnings/Advisories...


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