Area Forecast Discussion
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000
FXUS64 KLUB 190905
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
405 AM CDT Sat May 19 2018

.DISCUSSION...
We expect a better chance for thunder this afternoon and early
evening than previously expected, and a severe threats at that,
though situation remains conditional. Last evenings thunderstorm
outflow and overnight dry-line retreat have pushed low level
moisture back to near I-27 north of Lubbock, and to around the
Brownfield Highway, to the south. Fairly compact upper low was
over northeast Colorado heading northeast into southern Nebraska
and a bit weaker later today with decreasing influence our area. A
low amplitude wave was along the west coast, while mid to upper
flow remained backed out of the southwest, across the southern
high plains. Water Vapor satellite indicated some tendency for
backing and a bit of moistening especially from the southwestern
South Plains into southeast New Mexico, though still was fairly
dry. A mid and upper level jet around 40-50 knots was crossing the
South Plains before daybreak, and will pull into Oklahoma during
the daytime, putting much of the South Plains region in the right
jet entrance region, favorable for lift, by late morning and
afternoon. Also, a surface frontal boundary continued to sag
southward very near the extreme southwestern Panhandle already,
and should hang up somewhere over our northern zones later this
morning. Low level flow looks likely to remain generally southerly
or southeasterly most areas but near our southwest border by this
afternoon.

Several solutions including the HRRR, RAP, and HREF have been
trending toward eruption along the dryline by midday from near
Brownfield and Lubbock then northeast into the southeast Panhandle
or northern Rolling Plains, with activity perhaps lining out and
then pressing into the central and southern Rolling Plains later
this afternoon. Other solutions, such as the TTU WRF and GFS,
remained skeptical. Fairly high values of potential maximum
convective energy look like will hold over the southeast 40% or so
of our area - as much as 3000 to 4000 Joules per Kilogram - which
gives potential for substantial hail and wind threat, especially
given bulk shear speeds around 35 knots. So, there will be a
threat for organized convective modes developing. High-based
storms expected on the Caprock, where inhibition looks fairly
small given expected heating, and should storms spread outflows
to the east, will stand a chance to break stronger cap over the
Rolling Plains. The Storm Prediction Center, meanwhile, has
substantially upgraded to "slight risk" for the eastern half of
our area, with an "enhanced risk" covering our northeast. We have
increased thunder mention to solid chance from the eastern South
Plains into the Rolling Plains and southeast Panhandle, and added
the severe thunderstorm tag to the gridded forecast.

Still unclear how far west storms will develop tonight along the
re-advancing cold front with solutions still at odds, but all
solutions develop thunderstorms as the front moves further south,
and especially across the southern and eastern parts of our area
as the night progresses where the higher CAPE levels are expected
to be. Could be an active night, with strong to severe storms
along and just behind the front. Front will end up south of our
area on Sunday with much cooler air spreading in, and at least
briefly tapering shower/thunder chances during the day especially
for northern zones, if not southern zones as well, though we are
holding onto "chance" mention with this forecast.

By Sunday night and Monday, upper flow will further back from the
southwest as the next upper low digs into the southwest. This will
pull deeper moisture back across our western zones in particular,
and supports return to solid shower or thunder chances, especially
if a weak subtropical impulse gets pulled up towards the area out
of northern Mexico late Monday into early Tuesday as solutions
are currently suggesting. This impulse may be in tandem with the
upper low lifting northward into the Great Basin Tuesday, and the
northern Rockies Wednesday. Overall this scenario looks like will
lead to better upper level difluent flow over our area, supporting
sold chances of thunder through Tuesday and Wednesday, with
highest chances still favoring western zones as upper ridge
building may begin suppressing chances over the Rolling Plains by
Wednesday. This upper ridge looks like will retrograde overhead
Wednesday night but by Thursday into Friday will place us in
northwest flow aloft. Currently uncertain if this ridge will be
sharp enough to totally shut down thunder chances - we will hold
onto some very low mention favoring generally western and northern
counties by the end of the week.

Interesting, and hopeful pattern for rain chances. After initial
severe risk today and tonight, severe chances will return to some
extent off and on during the week; seasonal reasons for severe
are reason to keep mention in the Hazardous Weather Outlook.
RMcQueen

&&

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

$$

05/99



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