Area Forecast Discussion
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817
FXUS64 KLUB 031123
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
523 AM CST Sat Dec 3 2016

.AVIATION...
IFR conditions expected to persist at LBB and CDS with LIFR at
PVW, though the other two TAF sites may briefly drop at times to
LIFR as well. As mixing occurs after sunrise, cigs expected to
slowly lift towards the higher end of IFR by mid morning. Do not
expect conditions to improve much past that.

&&

.PREV DISCUSSION... /issued 443 AM CST Sat Dec 3 2016/

SHORT TERM...
IR Satellite showed a still strengthening upper level low over
northwestern Mexico this morning with copious moisture rotating
around this feature into West Texas. Southeasterly winds at H850
were helping to keep a persistent warm nose aloft and temperatures
at the surface aoa freezing with a nearly saturated airmass are all
combining to make widespread freezing precipitation difficult to
form. H850 height falls will be minimal over the next 24 hours, so
cooling from that aspect will be unlikely. Model soundings keep
showing a turning of winds at 850 mb to the northeast, but this
backing component has yet to show. In fact, there has been a slight
trend to a more east/southeasterly wind at 850. Though aiding in the
isentropic upglide of this system, it is doing no good at ridding us
of the nettlesome warm nose.

The upper level low looks to take an even further southerly jog than
previous model runs, now moving down the western coast of Mexico
over the next 24 hours. There will still be enough moisture and
energy from the system to create yet another dreary, soggy day,
however the question remains who still has the chance at wintry
precipitation. As the models have had an extremely difficult time,
as usual, resolving the warm nose component, a tricky forecast has
presented itself again this morning. Most of the area, including the
Rolling Plains and central South Plains will stay in an all liquid
phase of precipitation today with the entire column staying well
above freezing. For portions of the western South Plains and the
southwestern TX Panhandle, it gets a bit more complicated. Bright
banding has been evident on radar this morning along the TX/NM
border between Lea and Yoakum counties and just beyond that, a snow
signature has been evident at times across portions of Lea county.
However, with the radar scanning at approximately 6000 ft at that
point, it is unlikely anything frozen has made it to the surface
thus far. It is encouraging to see these signatures, though, as it
shows the processes to form frozen hydrometeors are ongoing aloft,
so areas, especially across the northwest where temperatures are
closer to falling to freezing, still have a chance at seeing some
accumulating winter precipitation. Though a few places across the
western South Plains may be lucky enough to see a few flakes mixed
in with the rain this morning, the likelihood and coverage is too
low to warrant mention in the official forecast. Likewise, with the
continued southeasterly winds aloft, have pulled the frozen precip
line slightly further northwest.

LONG TERM...
It`s cool this morning and it will get colder next week. Upper low
should be situated across Sinaloa by Sunday morning and the track
appears to be a bit further south as compared to last night`s data.
The GFS and ECM seem to be in good agreement though some modest
speed differences are indicated.  Today`s track takes the low across
Ciudad Acuna thence into the ArkLaTex by early Tuesday morning.  To
our north, cold air has begun its move from northern Nunavut aided
by a series of polar lows.  A number of trough axes will rotate
around the southern periphery of the lower heights with the first
passing to our north mid to late Monday with another, more
pronounced, trough approaching Wednesday morning.  The front
expected from the synoptic setup is looking to make it all the way
to Belize if not further south.  The airmass is cold, but not
bitterly so and the Texas Valley doesn`t look to freeze with this
system.  Thereafter, NW flow followed by ridging looks to make its
way into West Texas.  Model spread is fairly narrow to our west
through up toward the NERN CONUS, it`s a different story.

Precipitation should be largely done by 12Z Sunday though
northeasterly winds and clouds will keep things on the chilly side.
A surface high settles in for Sunday night. As the low comes
across southern Texas on Monday, our southeastern zones, in
particular,have a modest risk of seeing some precipitation. Then,
on Tuesday the first of the cold fronts enters the picture
Tuesday morning though return flow will quickly become
established as sfc troughing strengthens out west. The more
significant front arrives during the day on Wednesday which
perhaps a bit slower than indicated yesterday. However, given the
strength of the system, would not be surprised to see things speed
up over the next couple of runs. After a cold Thursday,
temperatures should start to recover into Friday.

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon CST today for TXZ021-022-027-
028.

&&

$$

99/99/74



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