Area Forecast Discussion
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FXUS64 KLUB 280841

Area Forecast Discussion
National Weather Service Lubbock TX
341 AM CDT SUN AUG 28 2016

Convection was slowly waning early this morning but is expected to
pick up again this afternoon and tonight. An upper low currently
spinning over northern Arizona will slowly move east-southeast today
to western New Mexico by tonight. This will place the upper level
jet streak just to our west but will likely play a role in
convective chances tonight. Upper level divergence will move
overhead from the west by this evening. Until then, a lead short
wave trough seen on water vapor over New Mexico early this morning
may produce enough lift for another round of afternoon convection. A
southeasterly low level jet will increase this evening supplementing
lift from the upper trough/upper level jet.

Southeasterly low level flow through the day will result in an
increase in low level theta-e values. Precipitable water will
further increase today as well with values on the order of 150-200
percent of normal. It may depend on the model of choice, but mixed
layer instabilities will be between 500 and 1500 J/kg with this
increase in low level moisture. Because of the low level jet
increase this evening, there will be no shortage of elevated
instability during the overnight hours. Given the best low level and
upper level lift entering this evening, precipitation chances will
be maximized after 00Z and will favor areas on the caprock. Similar
to convection early this morning, propagation will be to the
southeast into the low level jet. With the low level jet feeding
into the southwest flow aloft there will be a potential for training
convection although it is not the ideal setup.

Deep subtropical moisture will continue pumping into the southern
Rockies and adjacent high plains well into next week as an upper
trough edges slowly east into the southern Rockies and high
pressure stays to our east. Low pressure along the Texas coast
will meander into south Texas providing a supply of low to mid
level moisture into our area as well. Jet energy just northwest of
our area will gradually become more of a factor for western and
northern areas through mid week as the upper low edges into
western New Mexico, favoring increasing chances these days. In
addition, both GFS and WRF/NAM indicate potential for drawing one
or more impulses northward from Mexico, especially around Tuesday
and early Wednesday. With slow filling of the upper low to our
west, we might expect gradual veering of mid and upper flow, but
that is only as valid as the current vision of things to come
which solutions already have markedly trended towards a much more
influential southwest trough the past 4 nights. Precipitable Water
values will remain in the 1.5 inch range through late Wednesday
before tapering, so we have changed character of precipitation
from light to moderate intensity. Along with higher rain chances
through at least mid-week will come lower projected high
temperatures. August will end with a period of below normal
temperatures covering most of the final 3 weeks of the month.

Following ejection of what might be a final series of 300
millibar troughs late Wednesday or early Thursday, upper
heights should rebound along with much more veered mid and upper
flow. The deep airmass should dry, but it will take more time to
dry in the lower levels. A lingering low chance of thunder Friday
will be conditional on height rises on one hand, and how much the
extra surface warmth will be able to generate surface instability
on the other. Drier veered flow should continue early next
weekend as a weakening low pressure trough edges into the west
although impossible at this point to eliminate potential for
isolated thunder. The forecast for next Saturday will show dry,
however, along with additional warming into next weekend. RMcQueen


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