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Displaying AFOS PIL: AFDLUB Received: 2018-10-11 21:02 UTC

FXUS64 KLUB 112102

Area Forecast Discussion
National Weather Service Lubbock TX
402 PM CDT Thu Oct 11 2018

Low clouds have hung around for much of the day across all but 
the Rolling Plains. This has held highs in the mid 50s across most
of the South Plains with mid 60s across the Rolling Plains. Low
clouds have also killed off any chances for thunderstorms along
the TX/NM state line but we could still see occasional showers and
drizzle heading into tonight into tomorrow morning. There will be
a short lull in precipitation Friday afternoon before rain chances
start to increase late Friday with the approach of the remnants of
Sergio. Models continue to have slightly different tracks with the
GFS taking the heaviest precipitation north; the ECMWF NAM and CMC
all carry the heaviest precipitation south. However, the trend
from the 00Z runs of tracks converging close to the forecast area
does continue so we should see the bulk of the moisture and lift
move near the area providing another round of good precipitation
chances and locally heavy rainfall. The bulk of the precipitation
will shift east of the forecast area by Saturday night which then
turns attention to the first part of next week, which is also
where the "fun" begins in the forecast process.

A strong cold front will dive south through the weekend arriving
into the northern part of the forecast area by late Sunday
morning. A quick check of the source region for this front
indicates the air will come from the Northwest Territories and
Nunavut region where temperatures were generally in the low 20s. 
Although this isn't too terribly cold, both the GFS and ECMWF keep
a continued meridional flow through the first part of next week 
which will allow a continued flow of cold air into the region. As 
the front pushes through the area, lift along and behind the front
along with a weak shortwave should help to increase rain chances 
although much of the deep moisture will have shifted east of the 
area by that time. Cloud cover and the strong north wind will make
it feel rather chilly on Sunday. By far the biggest concern will 
be whether we will see a first freeze for parts of the area Monday
morning with the trend in all the operational runs and ensembles 
continuing to drop temperatures 3-5 degrees each run. Extremely 
high standard deviations in the ensemble runs show that there 
continues to be a lot of uncertainty on how cold we will be Monday
morning but the northwestern South Plains generally north and 
west of a Tulia to Morton line may see temperatures in the 29-32 
degree range by Monday morning. Precipitation chances will also 
linger into Monday morning so there will be a potential for a mix 
of snow and rain across this area and possibly some snowfall up 
around Rhea, Bovina, and Friona but we do not expect any 
accumulations at this time.

Clouds will remain over the area through the day Monday which is
one reason highs will struggle to make it out of the low 40s
across the area. This will also set up the potential for a more
widespread freeze and potential hard freeze Tuesday morning.
Confidence is very low on how things will unfold for Tuesday
morning because both models show we keep southwesterly flow above
a dry boundary layer. This typically pulls in moisture from the
Pacific resulting in mid to high level clouds that would blanket
the area and keep radiational cooling from occurring. The flip 
side is that even with the cloud cover, both the ECMWF and GFS 
show that 850 hPa temps will be at or below freezing indicating a 
pretty cold airmass over the area. Finally, the ECMWF shows the 
surface ridge setting in over the region Tuesday morning with dry 
advection all day; two of the three things needed for excellent 
radiational cooling and colder temperatures. Operational model 
blends were coming in colder than what the published forecast has 
but even going towards the warmer guidance values would have the 
freezing line as far south and east as Childress to Tahoka. This 
is a pretty big change from previous runs and we will need to 
watch closely heading through the weekend to see how the models 
handle this airmass which historically has been poorly with the 
first "major" cold front of the season.

Beyond Tuesday, a gradual warmup is expected but with highs still
10-15 degrees below normal through Friday. This is likely due to
continued southwesterly flow over the region due to a persistent
western U.S. trough keeping mid-level moisture and associated
cloud cover over the region. We will also see rain chances return
by Wednesday as a series of shortwaves move over the region
providing weak lift and moisture for rain. Too early to pinpoint
what days will be favored and much of the focus for this forecast
was for precipitation this weekend and cold weather early next