Area Forecast Discussion
Issued by NWS

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285
FXUS64 KLUB 121737
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
1137 AM CST Tue Dec 12 2017

.AVIATION...
Great flying weather will persist with clear skies and relatively
light winds. A FROPA will bring a northerly wind shift to the
terminals late Wednesday morning, which will be included in future
TAFs.

&&

.PREV DISCUSSION... /issued 259 AM CST Tue Dec 12 2017/

DISCUSSION...
Blocking ridge along the West Coast is still shown to break down
beginning Friday ahead of a parade of Pacific troughs - the first of
which should stir up our downslope winds and wildfire concerns on
Saturday. Until then, pleasant breezes will be the norm under dry
northwest flow and one more meager cold front due for arrival by
Wednesday afternoon. The broad trough responsible for this front may
still acquire a bit more cyclonic curvature and upper divergence by
Thursday (per several runs of the ECMWF), but to what degree this
results in mid-level ascent and saturation well downstream of the
Sangre de Cristos is not clear. Opted to insert a bit more clouds on
Thursday as this trough axis approaches, but pattern recognition
skills would suggest if anything falls in the western Panhandle and
western South Plains that it should remain virga given such a short
duration of ascent on top of sizable sub-cloud moisture deficits.

Following a modest reinforcement of cool air Thursday night behind
the upper trough, lee troughing will gain strength on Friday before
peaking in intensity on Saturday under deep westerly flow. This will
all occur in response to the ridge-toppling trough which is forecast
to cross our domain Sat night and early Sunday. Friday shows some
opportunity for elevated to briefly critical wildfire conditions
mainly on the Caprock, before expanding over a larger area on
Saturday under a more definitive wildfire regime. Current ensemble
data stack a 30-40 knot 850mb jet and robust thermal ridge from
eastern NM into western OK by Saturday afternoon, all ahead of a
Canadian front. Superblend is still not doing this pattern much
justice for the time being (due in large part to its blend of older
model runs that suppress valuable signals among newer NWP runs), so
we have raised Saturday`s high temps and winds to be more in sync
with the pattern. This is supported well by MOS from the GFS and
ECMWF, along with NationalBlend data. Following FROPA Saturday
night, the base of a digging trough should cross the region and
possibly wring out enough residual Pacific moisture for some
flurries. However, similar to reasons cited for Thursday`s trough
we will keep precip mention out for the time being, especially
knowing how often models underestimate low level drying in these
regimes.

Early next week shows a very quiet and mild pattern under zonal
flow, until ensembles and raw models favor a return to a strongly
positive PNA regime with prospects for sharply colder air as we
head into Christmas Weekend.

&&

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

$$

99/99/23



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