Area Forecast Discussion
Issued by NWS

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FXUS64 KLUB 150009 AAA

Area Forecast Discussion...UPDATED
National Weather Service Lubbock TX
609 PM CST Sat Jan 14 2017

We expect low ceilings and visibilities to remain near or below
airport minimums through Sunday morning. -DZ with Occasional -RW
at KLBB while KCDS and KPWV will be cold enough for -FZDZ and
-FZRA showers. A line/cluster of TSRA should move across the area
Sunday morning through early afternoon.


Sub-freezing temps have retreated north about a county in the
Rolling Plains, but are hanging tough in the northern South Plains
- West Texas Mesonet obs show all of Hale County is below
freezing. In fact, Hale and Swisher Counties probably have the
highest chance of seeing ice impacts as precipitaion should be
heaviest there - with much lighter amounts expected farther east.
We are going to extend the freezing rain advisory into Hale County
and through the night. Finally, we will hoist a dense fog advisory
to cover the remainder of the forecast area overnight. We expect
low visibilities to expand this evening and persist until the
convective activity approaches Sunday morning.


.PREV DISCUSSION... /issued 343 PM CST Sat Jan 14 2017/

Much to the dismay of NWP guidance, marginally freezing temps
remained entrenched this afternoon generally along and east of a
Tulia-Plainview-Post line and are already undergoing a slow
westward advance. Calls to spotters and the observed icing to
various mesonet rain gauges confirm a glaze of ice on elevated
surfaces and grass, but roads have faired perfectly fine and
should remain so for the remainder of the night given earlier
pre-treatment. However, a few webcams as far west as Lubbock and
even Whiteface recently iced over. With this theme in mind, we
may need to extend and expand the freezing rain advisory before 6
PM for marginal icing of unpaved surfaces.

The only major change in this forecast was to lower temps tonight
to account for the observed trends mentioned above and to insert
widespread fog through Sun morning. PoPs tonight look to focus
mostly across eastern NM and bleed over into our western zones
along a retreating, north-to-south oriented baroclinic zone that
is evident on 850 mb RAOB charts. Under such moist meridional
flow, this boundary has proven very efficient in concentrating
cell training and some heavy rainfall. With this westward
displacement of precip from the freezing temps, we may be able to
let the freezing rain advisory expire at 6 PM. Also, a larger lull
in precip could be in the making tonight as subsidence may very
well gain ground over much of the CWA in response to the
strongest ascent well to our west with the upper cyclone. Still,
low level jet mechanics should encourage improved isentropic
ascent at times.

As the upper cyclone lifts northeast to near Carlsbad by 3 PM
Sunday, very impressive height falls will begin overspreading the
region complete with a Pacific front racing eastward. Such linear
and sharp forcing complete with elevated CAPE around 500 J/kg
fits the bill for a fast-moving squall line by midday as shown by
several convective models. Hail and heavy rain should be the
highlights with this line of storms before rapid drying of the
column aloft ensues from SW-NE late in the day. With the low
tracking a little more east Sun night, possibility for deformation
zone snow to graze our N-NW counties looks a bit better, but have
kept amounts under one inch as thermal profiles vary considerably
between the colder NAM and ECMWF versus the milder GFS.

MLK Day will set the tone for a mostly quiet and seasonable first
half to the work week under broad/elongating upper troughing.
There is a small opportunity for some of this reloading of trough
energy to re-saturate the prior dry slot and garner light showers
in the western Panhandle Mon night, but otherwise the next real
forecast challenge will be how warm and potentially windy we trend
by late week with a series of energetic Pacific troughs passing
largely to our north. Opted to keep winds closer to MOS with high
temps straying very little from the mild Superblend.


Dense Fog Advisory until 9 AM CST Sunday for TXZ021-022-027-028-

Freezing Rain Advisory until 9 AM CST Sunday for TXZ023>026-



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