Area Forecast Discussion
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FXUS64 KLUB 122347

Area Forecast Discussion
National Weather Service Lubbock TX
647 PM CDT Sat Aug 12 2017

VFR conditions have recently developed at KCDS leaving all three
TAF sites currently VFR. This should change though later tonight
into Sunday morning as relatively cool and very moist air combine
with weak upslope flow to bring a prolonged period of stratus
and/or fog with all terminals likely dropping to IFR and/or LIFR.
Eventually the ceilings should lift and scatter with VFR
returning to the terminals Sunday afternoon. The exact timing of
the category changes is somewhat uncertain so amendments are
likely. Additionally, widely scattered convection currently over
the southwest Texas Panhandle and western South Plains could
potentially affect KPVW and/or KLBB later this evening, though it
will most likely diminish before doing so. However, convective
redevelopment will be possible late this evening into early Sunday
as a southerly LLJ cranks up to our south impinging on the area,
so any of the terminals could potentially be affected by this
activity. That said, confidence in coverage/location/timing of any
late night showers/storms is too low to warrant including a
mention in the TAFs at this point. Additional storms may be in the
area Sunday afternoon, though chances appear better Sunday


.PREV DISCUSSION... /issued 337 PM CDT Sat Aug 12 2017/

Mid-level trough and an associated MCV were making steady progress
across our Rolling Plains` counties this afternoon ahead of a distinct
layer of subsidence. One final vestige of mostly moderate rain
accompanied this MCV and is on track to exit east of Highway 83
before 5 PM. Otherwise, conditions in the wake of this impulse
are largely stable despite a very moist boundary layer and
improving insolation. However, high res water vapor imagery does
reveal a small cyclonic curl over southeast NM which could easily
spur some precip later this afternoon and evening as it
overspreads the South Plains. For this reason, opted to extend
isolated storm mention through the night area wide.

Potential for fog overnight does have legitimacy given such moist
low levels from recent widespread rains and light upslope winds.
Such a scenario occurred with ease last week Wed following similar
soaking rains that led to descending stratus, but how widespread
and dense the fog becomes is not in good agreement among the fine
res models, so will just address this with patchy fog for now.

Barring some lingering showers off the Caprock early Sunday and a
few afternoon storms near the NM state line, much of the day
looks to be uneventful as transient upper ridging overspreads the
area. This story should hold until Sunday evening when the next
trough in westerly flow arrives from the Colorado Plateau. The
general model consensus is for organized storm clusters to wander
ESE overnight within 1500-2500 J/kg of MLCAPE and 30-40 knots of
0-6km bulk shear. This could easily support some supercells early
in the convective mode, mainly N-NW of our CWA where initiation
is preferred, before outflow consolidation breeds more linear
modes. Some severe episodes do appear possible late Sunday.

Beginning Monday, a large scale pattern change kicks into gear as
the subtropical high relocates over the Deep South. This results
in mean troughing over the western CONUS through the week and
weak cyclonic SW flow locally. Although this transition will tug a
mostly diffuse/tattered layer of monsoonal moisture across West
TX, this moisture will have to contend with some mid-level warming
and drying given deeper SW flow. Alone, this doesn`t bode well
for widespread rain chances, but rather isolated to scattered
storms given a pattern more representative of late Spring than
late Summer. This theme is most evident from Tue-Fri as SW flow
supports a sloshing dryline in our vicinity. Area soundings show
convective temps may have a hard time being met most days, but any
perturbations in the SW flow aloft could easily augment ascent.
As such, PoPs next week remain in the 20-30 percent range for now
with seasonal temps.




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