Area Forecast Discussion
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FXUS64 KLUB 212036

Area Forecast Discussion
National Weather Service Lubbock TX
336 PM CDT Tue Mar 21 2017

At 3 pm, a cold front was slowly advancing south-southwest across
the forecast area. Cooler air filling in from the north was
resulting in a decent gradient in temperatures across the area,
running from the low 90s in the south and southeast to the middle
70s across the north. The high so far at Lubbock has been 92 - one
degree short of the record. With the winds having turned to the
north, we may not get the extra two degrees needed to break our high
temperature record for a third straight day.

Aside from the heat, modest moisture residing and pooling along the
front from the central South Plains into the southeast Rolling
Plains, and lift from the cold front and a minor shortwave, may be
just enough to produce an isolated t-storm or two during the next
few hours. We have adding an isolated mention of thunder to account
for this. Tonight, increasing isentropic ascent over the cool, and
modestly moist upslope flow in the wake of the front should produce
some low stratus. Unfortunately, the extent of these low clouds is
uncertain, and if and how long they linger into Wednesday may have
an impact in temperatures. The most likely scenario is that the
clouds will linger through late morning or midday across much of the
far southeast Texas Panhandle and northern Rolling Plains.
Temperatures in those areas may struggle to make it out of the 60s
if clouds are slow to clear off, while across the remainder of the
area we are expecting highs in the 70s to low 80s. At least we
shouldn`t be breaking any high temperature records Wednesday.

The core changes with this forecast involved shoving PoPs further
west on Thursday afternoon, and introducing blowing dust both
Thursday and Friday when advisory level winds appear a good bet.
Otherwise, a welcome pattern change remains on the horizon beginning
Thursday and continuing through early next week in response to an
active split flow regime presiding over the western US. The end
result will be a string of southern stream troughs and upper
cyclones impacting the local area complete with a return to more
seasonable temps.

The first of these waves will turn quite potent by Thu night as it
lifts across the CO Plateau and undergoes its greatest deepening.
Ahead of this upper trough, low level moisture advection will
dominate the whole of the CWA on Thursday as stout pressure falls
bullseye in NM, effectively anchoring the dryline just west of the
TX-NM state line. The southerly gradient winds will only ramp up
throughout the afternoon and could easily hit advisory levels on the
Caprock - a rare, but not impossible occurrence in these parts.
Erosion of shallow stratus by midday will garner enough heating and
deeper mixing along the dryline, but afternoon PoPs were pushed
farther west as this dryline and more importantly the key background
ascent simply arrive too late in the day. Forcing with these
very dynamic troughs is often narrow in width and confined to
the strongest height falls and/or Pacific cold fronts, so precip is
likely to blossom in coverage Thu night as the ascent races east.
Despite meager CAPEs, history has shown that strong ascent can
compensate for CAPE and produce robust updrafts and severe episodes.
Expectation is for linear multicells to race NE overnight ahead of
aggressive dry slotting, with PoPs ending on the Caprock by midnight.

Gradual filling of the upper cyclone across the northern TX
Panhandle on Friday will do little to prevent strong westerly
gradient winds from overspreading most of the CWA. Boosted these
winds toward the windier CONSMOS, which could easily hit high wind
criteria at times. Fortunately, temps behind the Pacific front will
be cool enough to keep RH values from getting too low for critical
fire concerns. However, this cooling is so robust aloft under a
-20C cold pocket that convective showers remain possible, especially
in our N-NW zones nearest the wraparound moisture of the upper low.
Thereafter, a much weaker trough passes over the Panhandles on Sun,
but offers little time for low level moisture recovery, so PoPs
remain dry. This could change by early/mid next week as a third
trough gears up close to the region with more time for moisture
return and perhaps rainfall.




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