Area Forecast Discussion
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FXUS64 KLUB 190847

Area Forecast Discussion
National Weather Service Lubbock TX
347 AM CDT WED OCT 19 2016

An upper level short wave trough moving across the northern Rockies
this morning will drive a cold front south through the central high
plains into the Panhandle and South Plains later today as the upper
trough moves onto the northern plains. The front initially surges
southward on the higher terrain of northeastern New Mexico, the
western Texas Panhandle, and the western South Plains, although
cooler air will lag the initial wind shift by several hours. Even
through the cooler air will lag, will see enough cool advection with
initial wind shift to result in about a 15 degree gradient from
northwest to southeast in high temperatures this afternoon.
Objective guidance has increased several degrees, and given the
expected surface pattern think this is the direction to go with the
high temperature forecast. MOS numbers may be just a touch high and
will undercut them slightly.

With sunset this evening will see the front surge southward through
the remainder of the South Plains as well as the Rolling Plains. In
the pre-frontal environment this afternoon enough low level moisture
advection will occur into the southern Rolling Plains to generate a
decent amount of CAPE. The 00z NAM progs around 2500 J/kg MLCAPE
early this evening with 0-6 km bulk shear around 25 kts, supported
in part by WSW winds in the mid to upper levels south of the
aforementioned upper trough. The cap is progged to be fairly weak,
enough so that the frontal intrusion may be enough to fire some
isolated to scattered thunderstorms in the far southeast corner of
the forecast area.

Lastly, have increased overnight lows just a bit. Again, objective
guidance trended that direction. It has been difficult to get cooler
than MOS recently in the first night after a frontal passage, and
wind speeds are likely to remain at or above 10 mph through most, if
not all, of the night which will favor warmer temperatures. Will
increase temperatures by a magnitude similar to the increase in MOS
from 12 hours earlier. This will be just under guidance, so there
may be some room to increase again later today, if necessary.

Tonight`s upper trough and cold front will have exited the region
by daybreak Thursday, though steady NE winds of 15-20 mph show no
sign of relenting until mid-to-late afternoon ahead of a surface
high. This high remains ill-timed for an optimum freeze in our
climatologically favored NW zones as it is still progged to shift off
the Caprock by midnight ahead of increased mixing on SW breezes.
Still...temps will probably fall off aggressively early Thu night on
until light winds rebound. Off the Caprock, locations such as Spur
and Aspermont can be quite the dark horse with low temps in these
patterns, so have undercut MOS there to capture some of this

Lee troughing to our west from Friday through Tuesday will ensure
dry and breezy S-SW gradient winds each afternoon. Thicknesses
recover nicely this weekend as an upper anticyclone translates
east across central TX before being replaced by steady height
falls and increasing mid-upper moisture in SW flow. Depth of the
low level moisture recovery by early next week still appears a bit
overdone on the GFS, whereas the GEFS mean and ECMWF paint a
more reasonable scenario. If anything, we may see a greater
contribution of moisture via top-down saturation if we can source
subtropical moisture from a few waves minoring out downstream
of the Occidentals. At the very least, we increased cloud cover as
early as Saturday hinting at cirrus spilling in behind the upper
ridge, but enough moistening of the column and more importantly lift
look too difficult to come by until perhaps Tuesday night when
GEFS ensembles and operational models key on increased cyclonic
flow tied to a broader trough centered in the Pacific NW. Opted to
keep precip chances absent Tue night as such a subtle feature so
many days out is likely to undergo further model evolutions in the
coming days.


.LUB Watches/Warnings/Advisories...


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