Area Forecast Discussion
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FXUS64 KLUB 232023

Area Forecast Discussion
National Weather Service Lubbock TX
323 PM CDT FRI SEP 23 2016

Increasing shower and thunderstorm chances highlight the coming 24
hours, with a few strong to marginal severe storms and locally
heavy rain possible by Saturday afternoon/evening.

We have seen another day of breezy southerly winds supply above
average temperatures with dewpoint levels edging up slightly from
yesterday. Where the best moisture is in place off the Caprock we
have seen a decent cumulus field develop, and we can`t rule out a
rogue shower/storm within this moderately unstable and weakly capped
air through early this evening. However minimal forcing and a weak
speed bump in the vertical temperature profile call into question
whether any deep convection can become rooted. For now we continue
to maintain PoPs of 10-15% with no explicit storm mention, though we
will watch this closely through the early evening.

Attention then turns to a well-developed upper level low spinning
over Utah early this afternoon. This low will translate
northeastward emerging over the northern High Plains on Saturday
while troughing persists and amplifies across the southern Rockies
as strong jet energy digs southward on the west side of the lifting
low. As this occurs, weak height falls will spread from west to east
across the region tonight into Saturday. The tail end of a Pacific
front/surface trough associated with the northern low will also
advance eastward across the TX/NM line late tonight before stalling
out somewhere across the South Plains Saturday afternoon. The
approaching surface trough and a glancing shot of the large scale
forcing should support isolated to widely scattered storm
development which will spread from west to east late tonight into
Saturday morning. Depending on how the morning activity evolves and
how much diabatic heating can be realized (amidst increasing
moisture and cloud cover ahead of the surface trough) storm
redevelopment will be possible, with the greatest chances across
roughly the eastern half of the FA. Increasing mid-level flow and
the potential for moderate instability could support a few strong to
marginally severe storms. Additionally, PWATs rising over 1.5
inches will provide a locally heavy rain threat.

Lows tonight should be a couple degrees warmer than last night due
to the increased moisture and southerly breezes, except over the
northwest zones where drier air and lighter winds toward morning
should secure another start in the 50s. The increased moisture and
cloud cover along with declining heights will knock highs Saturday
down a bit from today, closer to late September averages.

A period of quite cool and damp, if not down right wet, conditions
is still on track. This scenario will come courtesy of a cold
front and a closed low to our west and southwest. Precipitation
Saturday night will come as the closed low takes shape across New
Mexico with an almost southerly flow overhead tapping into deep
moisture currenly in place across the Mexican interior. Sunday
morning hours will see the cold front enter the forecast area,
sweeping pretty quickly through the area, passing into the Permian
Basin and Big Country by the end of the day. Meanwhile, mid level
lift is enhanced Sunday into Sunday night as mid level cyclogenesis
takes shape in the vicinity of the Big Bend east of the parent mid
and upper level low/trough. Rain chances will linger into Monday
as mid level flow that will be easterly in response to the
cyclogenesis becomes southerly as the resulting low near the Big
Bend dissipates with the parent low beginning to retrograde
westward toward Sonora. The response ends up being moist
isentropic lift over much of the region into Monday night.

Of note through this period. At this time, we think the best heavy
rain potential will come Saturday night into Sunday and focus
across the Rolling Plains where dynamic/moisture interaction will
be greatest. The amount of post-frontal precipitation will depend
in large part on how much sub-cloud dry air filters in behind the
front and on the magnitude of lift well behind the surface front
Sunday night and Monday. Current thinking favors good rain chances
that 48 hour period but with fairly small QPF amounts relatively
speaking. Finally, this amount of cloud cover and rainfall should
favor pretty narrow diurnal ranges in tempertures both Sunday and
Monday. For now have run with the model blend, which narrowed the
range from the previous forecast, but it will be of note that any
prolonged period of daytime preciptiation Sunday and Monday would
increase the likelihood of even narrower ranges (e.g., see MAVMOS
lows and highs for Monday).

Precipitation chances should begin to wind down Tuesday as upper
level ridging begins to build over Texas. The ejection of what
will be left of the Sonoran upper low across the plains states
Wednesday could bring a quick shot at convection on Wednesday.
Otherwise, Tuesday through Friday looks dry with temperatures
returning to more seasonal levels.


.LUB Watches/Warnings/Advisories...


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