Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/28/20

Area Forecast Discussion...UPDATED

National Weather Service Lubbock TX

 1018 PM CDT Tue Oct 27 2020

.UPDATE...
Mixture of freezing rain and sleet have been the dominate modes
within the band of heavier convective precipitation stretching
across the center of the FA. We could still see a little snow in
this general corridor before the precipitation shifts east, but
the wintry mix is eating into the potential snow totals across
the central South Plains, including in Lubbock. Hence, we have
reduced the forecast snow totals here, while maintaining 4 to 6
inches of snow across the far southwest Texas Panhandle and
northwest South Plains, where they will receive their best shot of
snow through the early morning hours. We did also expand the
thunder mention in the grids given the observed trends with the
activity this evening. The winter weather headlines remain
unchanged.

&&

.PREV DISCUSSION... /issued 643 PM CDT Tue Oct 27 2020/

AVIATION...
IFR conditions will persist for the majority of the upcoming TAF
period as a winter storm affects the region. Light freezing
drizzle will continue for much of the evening prior to the next
round of heavier precipitation later this evening into Wednesday
morning. Mostly freezing rain can be expected at KCDS while a
freezing rain/sleet/snow mix is expected at KLBB and KPVW. By
daybreak the majority of the heavier precipitation should be east
of all the terminals however light precipitation may linger
through mid to late morning as the upper level low moves through
the region. There is some potential for heavier wintry
precipitation to stick around for northern locations from roughly
CDS to near PVW late tomorrow morning into the afternoon however
confidence is not high on this scenario. Aircraft icing will
remain possible through this TAF period as cloud depths remain
around 8,000 feet. By tomorrow afternoon ceilings at the area
terminals may begin to gradually improve into the MVFR range. /WCI

PREV DISCUSSION... /issued 257 PM CDT Tue Oct 27 2020/

SHORT TERM...
The upper low was located over southwestern New Mexico and is slowly
moving towards the southeast. Water vapor imagery indicates that a
jet max may be rotating around the western periphery of this low.
This feature will be important to watch over the next 18 hours as it
may lead to a slightly farther south track to the upper level low
which the GFS has indicated with the latest run. A few brief sleet
and freezing rain showers continue to move towards the northeast
this afternoon as weak lift remains across the forecast area.
However, this lift should wane later this afternoon leading to a
lull in the showery winter precipitation. Even with the lull in
heavier precipitation light freezing drizzle will continue through
the evening.

The next area of large scale lift is across east central NM and this
will swing over the forecast area late this evening. As this feature
moves across the forecast area mid level cooling and moistening will
occur which will help erode the warm nose currently residing around
750-650mb. The 18z sounding from Amarillo indicates that this warm
nose has been eroded already while the Midland sounding has only
eroded slightly. This will allow for a sharp gradient in
precipitation type across the forecast area which will transition
eastward through the night. Still expecting mostly freezing rain for
locations off of the caprock with a mix of freezing rain, sleet, and
snow in the central South Plains with mostly snow in the extreme
southwestern Texas Panhandle. Lubbock continues to reside on the
gradient of where the heaviest icing will occur to the east and the
heaviest snowfall will occur to the northwest. Therefore, exact
amounts for the city of Lubbock can differ drastically depending on
how quickly the warm nose aloft is/is not eroded. Based on current
guidance a switch over to snow in Lubbock should occur around
midnight tonight with snow lingering through the morning on
Wednesday. Farther east across the Caprock this elevated warm nose
should never fully erode therefore a mix of freezing rain and
perhaps eventually some sleet should occur through the night. There
are some indications that elevated instability will be present with
this area of lift so also included a mention for a slight chance of
thunderstorms overnight. Any location that sees this convection
could see snow/ice totals rapidly increase.

Depending on the exact track of the upper level low an area of wrap
around moisture will move across the area on Wednesday. Some
guidance has this area moving as far south as a Lubbock to Guthrie
line, while most guidance keeps it across the southern Texas
Panhandle. As mentioned above, depending on if the jet energy can
force the upper level low a bit farther south than previous guidance
indicates, additional light to moderate wintry precipitation may
continue through late Wednesday morning. If the low tracks farther
north this activity should come to an end by daybreak Wednesday for
most locations within our forecast area except for the southern
Texas Panhandle. Most locations except for the southwest Texas
Panhandle should warm above freezing by Wednesday afternoon which
may help to improve road conditions across the region. /WCI

LONG TERM...
By 00Z Thursday, we may finally see which solution ended up handling
this system most effectively.  The GFS remains the more southerly
track though some 30-60 NM further north than we saw yesterday
whilst the NAM/ECM produces a wobble briefly into the SWRN Panhandle
before continuing eastward along the Red River Valley. Still, how
the system pans out for Wednesday night will depend on the track of
the low.  The low should exit the region on Thursday leaving us in a
period of NW flow aloft which will become zonal as a trough
translates across the northern half of the plains late Friday into
Saturday.  Flow will return to northwesterly in the wake of the
Friday system becoming increasingly southwesterly into the middle of
next week.

Ongoing precipitation should be tapering Wednesday evening (if any
is left at all). Temperatures across the Rolling Plains are
progged to be just above freezing during the afternoon though some
uncertainty exists as the cloud cover could limit diurnal heating.
Again, depending on the dynamical cooling associated with the
eventual track of the ejecting low, things could change. Would be
hard pressed, with the persistent overcast, and continued
northerly fetch to see temperatures rise too far above freezing.
As such, the precipitation phase and southerly extent for
Wednesday evening remains a bit unclear at this point. Given the
uncertainty, will continue with a rain/snow mix up across the
southern Panhandle and northern Rolling Plains. Once the
precipitation finishes late Wednesday, we`ll see a return to
mostly clear skies through next week. A dry front will help cool
things off for Sunday after peaking near 70 on Saturday. Generally
speaking, high temperatures will edge to slightly above average
for Saturday and beyond.

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
Ice Storm Warning until 1 PM CDT Wednesday for TXZ026-031-032-
037-038-043-044.

Winter Storm Warning until 1 PM CDT Wednesday for TXZ021>025-
027>030-033>036-039>042.

&&

$$

23/99