Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/30/19

Area Forecast Discussion

National Weather Service Lubbock TX

 904 PM CDT Tue Oct 29 2019


.UPDATE...
Area temps have continue fall across the region with freezing
conditions as far south as Tahoka and Post. Given the trends, have
decreased overnight lows several degrees though I would not be too
surprised for lows to dip a few more degrees beyond values
indicated in this package. The pre-existing forecast already
undercut model guidance but it is clear that even lower values are
indicated tonight. Given the onset of freezing drizzle reported
at KLBB, light precip at KCDS and an increase in RADAR echoes
across the area, have extended the Winter Weather Advisory
southward by one row of counties and issued a Special Wx Stmt for
the Rolling Plains for near-freezing temperatures. The impacts
will depend heavily on how much moisture can be squeezed out of a
relatively shallow moist layer and how efficient that the
isentropic ascent thickens this layer. Given how airmasses of
similar type have behaved in the past, the misting should persist
through the night and we could see some bands of modest
precipitation form. Still, it does not take much ice to make quite
the mess.



&&

.PREV DISCUSSION... /issued 645 PM CDT Tue Oct 29 2019/

AVIATION...
Winter hazards abound in West Texas this evening. Ceilings are
hovering close to IFR/VFR thresholds and the expectation is that
KPVW and KLBB should go IFR shortly after sunset. Widespread light
freezing drizzle should affect all three terminals. Timing onset
is nebulous though the risk should increase after 02Z. Multiple
PIREPs of icing have been received in a very shallow freezing
layer just above the surface though AMDAR soundings indicate >0C
temps from near 6kft up to 13kft. FZDZ may lead to reduced braking
action on RWY surfaces overnight into tomorrow morning.

PREV DISCUSSION... /issued 302 PM CDT Tue Oct 29 2019/

DISCUSSION...
Minor impacts from winter weather, mainly freezing rain and
freezing drizzle, expected overnight tonight into Wednesday
morning for areas north and west of roughly a Morton, Lubbock,
Crosbyton, Matador, to Childress line.

Cold air continues to slowly filter in across the region this
afternoon on easterly surface winds. Cloud cover has been locked
in place even as it tries to erode from the west which has also
helped to keep temperatures from warming much through the day on
the West Texas Mesonet and NWS observation sites. Expect a
gradual fall in temperatures tonight and also another day of
remaining steady through mid-day as a reinforcing front pushes
into the region Wednesday morning. Model sounding forecasts from
the high spatio-temporal resolution models show that profiles
across the forecast area will see a layer drop below freezing from
the surface to around 3kft across the Caprock with warm air on
top of this layer. Also start to see strong isentropic lift
developing across the region through the overnight hours. Synoptic
lift will also increase ahead of the main trough moving out
across the Rockies late Wednesday. Moisture will be trapped in the
layer with the strongest isentropic lift and combined with the
dynamic lifting ahead of the main trough should be enough to get
precipitation to develop. Trend with the models through the
morning into the afternoon has been towards colder temperatures
and a stronger signal for a freezing rain/drizzle event with
perhaps some sleet or brief snow across the far northwestern South
Plains.

Main impact will likely be a light glaze of frozen rain on
elevated surfaces, bridges, and overpasses starting around
midnight and lasting through Wednesday morning mainly across the
northern two-thirds of the Caprock and northern quarter to third
of the Rolling Plains. Biggest uncertainty will revolve around the
intensity of the precipitation; all of the models show very light
rates/amounts so accumulations are expected to be light but there
could be a few pockets of slightly heavier amounts along the edge
of the Caprock where easterly surface flow ahead of the next front
Wednesday Morning may help provide some localized enhancement.
Have opted to go with a Winter Weather Advisory for areas generally
north and west of a Morton, Lubbock, Crosbyton, Matador, to
Childress line for light accumulations of ice. May see some snow
or sleet mix in briefly across the far northwestern South Plains
where temperature profiles drop low enough to support those
precipitation types. As the trough swings out into the Central
Plains, should see rapid clearing from west to east late in the
day so that we may have a brief window for temperatures to climb
above forecast highs, especially across the western South Plains
where it may clear early enough to warm temps up a bit. The
downside is that clear skies, light wind, dry air, and the
potential for the center of the surface ridge to be over the area
so that morning lows on Thursday morning could drop into the mid-
teens for the Caprock with near 20 for the Rolling Plains. If, and
this is a big if; there could be spots on the Caprock that see
perfect conditions for temperatures to drop into the upper single
digits to near 10 degrees. Will have to evaluate through the next
24 hours to see how things evolve with frozen precipitation at the
surface and atmospheric conditions for radiational cooling.

Rest of the forecast for Thursday afternoon through the end of
this cycle is relatively quiet with generally progressive flow
aloft. Weak cold front will arrive Friday to keep temperatures in
check and rest of the forecast will remain dry.

Jordan

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
Freeze Watch from Wednesday evening through Thursday morning for
TXZ037-038-043-044.

Winter Weather Advisory until 1 PM CDT Wednesday for TXZ021>037-
039>042.

&&

$$

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