Area Forecast Discussion
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926
FXUS64 KLUB 161737
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
1137 AM CST Fri Feb 16 2018

.AVIATION...
The main aviation concern is the possible development of low
ceilings across the area overnight. The latest guidance is less
supportive of this so we have trended the ceilings up into VFR
range, although the potential remains for category reductions.
Otherwise, scattered rain showers may cause periodic reductions
in surface vsby, especially overnight, but these are expected to
be light. Breezy northeast winds will diminish through the
afternoon and eventually shift through south to west by Saturday
morning.

&&

.PREV DISCUSSION... /issued 515 AM CST Fri Feb 16 2018/

AVIATION...
Following VFR with light rain at times this morning, ceilings
should collapse to MVFR and eventually IFR at times tonight at
all terminals. This trend will accompany a larger swath of steady
rain expected to clear the terminals before daybreak Saturday.
Temps should remain above freezing through the period with snow
levels holding over 9000 feet MSL.

PREV DISCUSSION... /issued 409 AM CST Fri Feb 16 2018/

DISCUSSION...
The cold front continues to rapidly push south across the forecast
area this morning and will clear our counties within the next
hour. Strong north wind will continue through the morning before
gradually slowing down through the afternoon and quickly shifting
back to the south by sunset. Highs are going to be tricky thanks
to the combination of cloud cover and cold advection through the
morning but we should be about 35 degrees colder than yesterday
across the area. The second thing we are seeing is increasing
returns on radar as a stream of Pacific moisture moves over the
forecast area from the southwest. A very dry boundary layer with
dewpoint depressions on the order of 20 degrees F is evaporating
much of the precipitation before it reaches the ground but I would
not be surprised if a few locations see a few drops on the ground.
So far, none of the West Texas Mesonet locations that have been
under the stronger radar returns have reported measurable
precipitation but a webcam in Levelland does show the streets are
wet from the band moving over the city at the time of this AFD.

Although some areas could pick up a trace to a couple hundredths
of an inch this morning, the better chances continue to appear to
be after sunset through midnight across the Caprock. Chances will
then spread east to the Rolling Plains shortly after midnight
before tapering off quickly before sunrise. Where the heaviest
amounts of rainfall will be continues to be tricky as all models
still show a relatively narrow band of precipitation developing
underneath the right entrance region of a strong jet stream that
sags across the area this afternoon. Lift associated in this
region of the jet combined with the passage of the base of a weak
trough will combine to produce the precipitation. All models show
at least a quarter of an inch of rain could fall in some
locations with a few models approaching half an inch which is
probably a bit optimistic based on the amount of moisture and
short time frame precipitation would fall. As for the location of
the heaviest part of the band, high-resolution models have
shifted a bit further north to between Lubbock and Clovis while
the coarser global models keep the heaviest precipitation from
Lubbock to Childress. Last thing to look at was any model
ensembles including the TTU-WRF ensemble data which all favor the
Lubbock/Clovis banding. Timing for the heaviest rainfall would be
near the TX/NM state line by sunset increasing through the evening
into the central South Plains, then shifting east through
midnight into the Rolling Plains shortly after, and coming to an
end before sunrise Saturday across the eastern Rolling Plains.

After this round of precipitation, we will remain under generally
zonal to weak southwesterly flow through much of next week. Models
show that low-level moisture will return as early as Sunday night
with the development of a dryline feature by sunrise Monday.
Surface dewpoints could approach 60 degrees east of the dryline by
Monday morning with near 40 across the South Plains. There could
be a few showers Sunday night under a low-level jet that develops
across the Rolling Plains but these will likely be very light.
Drier air will rapidly mix east through the day however on Monday
pushing the dryline into Central and North Texas allowing some
downslope warming on Monday afternoon. Tuesday remains uncertain
as the GFS brings a backdoor cold front across the forecast area
through the afternoon while the ECMWF holds the front up across
Kansas/Colorado until Tuesday night. There could be some showers
along the front as it pushes through any remaining moisture behind
the dryline but coverage looks to be too low to include any
mentionable PoPs at this time. The front will definitely be
through the area for Wednesday which will drop highs back into the
upper 40s to near 50. Return flow will then become reestablished
Thursday night which could mean a return of some rain chances
just beyond the end of this forecast. The increasing moisture will
likely result in low clouds and temps in the low 60s to end out
this forecast.

Jordan

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

33



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