Area Forecast Discussion
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FXUS64 KLUB 250049
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
749 PM CDT Tue Apr 24 2018

.UPDATE...
A couple things, first strong north winds behind the cold front
are developing another column of counties west of the currently
advised column. We added the column from Castro County southward
through Lamb, Hockley, and Terry Counties. Second, convective
activity continues to develop westward along the frontal boundary.
Short term solutions struggling a bit with this activity. RMcQueen

&&

.PREV DISCUSSION... /issued 653 PM CDT Tue Apr 24 2018/

AVIATION...
Nearby strong to severe thunderstorm just east-southeast of KLBB
at the start of this TAF. Solutions agree that activity will pull
gradually east of KLBB but we retained a VCTS at KLBB for a few
more hours. Cumulus field near KCDS and KPVW doesn`t appear
bubbling much and solutions keep convection away for much of the
evening anyway, so removed VCTS for the evening at these sites.
Cold front also moving southward and we timed arrival close to the
latest HRRR trends - a little quicker than the previous set - and
also upped wind speeds. Low cloud deck and increasing showers
coverage later tonight also timed a little more closely to HRRR
trends though this will likely need adjustment by if not earlier
than the next TAF issuance. Mostly MVFR seems favored but deck may
drop near 1000 feet briefly later tonight at both KLBB and KPVW.
So, forecast will try to remain fluid to this quickly changing
environment and we will adjust to the confident trends we see
during the evening. RMcQueen

PREV DISCUSSION... /issued 328 PM CDT Tue Apr 24 2018/

DISCUSSION...
Dynamic weather remains on tap through the night with the
potential for a low end severe event early this evening, gusty
post-frontal winds, and a more widespread precipitation
overnight. The forecast area remains just downstream from a low
amplitude upper level ridge that is centered over New Mexico while
further north from the Great Salt Lake to South Dakota lies an
upper level trough with a closed low at its eastern end near the
South Dakota/Nebraska line. During the next 24 hours or so the
upper ridge will squeezed westward by the upper trough toward a
higher amplitude ridge that will form over the Great Basin toward
southern California. The upper trough/low will rotate to the
south-southeast across the central Plains on Wednesday exiting
toward the lower Mississippi Valley tomorrow evening while
upstream another trough takes shape over the Dakotas.

In the very near term the focus remains on thunderstorm potential
with the possibility of some isolated severe. Surface analysis and
radar imagery clearly showing a low near Brownfield with north
winds to the west and northwest of Lubbock, hot and dry southwest
winds to the southwest of the low and more backed and humid flow
to the east and northeast of the low. The expected convective
temperature of 88F seems to be working out well with elevated
radar echoes developing with cumulus congestus southwest of
Lubbock. CAM`s have been consistent with developing this
convection into thunderstorms as they move into better low level
moisture vicinity Tahoka to Post then progressing it in a general
eastward direction with potential for a northeasterly directed
storm split and potential for supercell development southern
Rolling Plains as indicated by progged Supercell Composite values
in excess of 4 from SPC analysis pages. Isolated strong wind gusts
remain possible particularly early in with the high-based echoes,
transitioning to more of a hail threat as storms hit better
moisture. However, of note is that for now surface moisture is
under-performing relative to the model progs by a few degrees
Fahrenheit. This will have some ramifications on CAPE, but mixed
level values should still exceed 1000 J/kg in this area of
concern.

About the time the thunder winds down (02-04Z) a strong cold
front that is located across the northern Texas Panhandle mid-
afternoon will push quickly through the forecast area with 20-30
mph expected. There is a good chance of slightly higher wind
speeds along the NM state line correlated with strongest progged
post-frontal pressure rises. Will issue a Wind Advisory for most
of the night there.

The third issue of the night is additional precipitation
potential. The upper trough/low to our north will move southward
bringing its own mid level moisture with. Model progs support
robust isentropic lift over the frontal surface in advance of the
upper trough. This will lead to increasing showers across the
forecast area, still favoring the eastern half of the forecast
area, but also the possibility of extending toward eastern New
Mexico. Of interest is the amount of elevated instability progged
to develop after 06z with some indications of CAPE in excess of
1000 J/kg supporting the idea of additional thunder late tonight.
Isentropic lift and mid level moisture will move quickly eastward
after sunrise Wednesday with precip ending from NW to SE followed
by clearing in a similar direction later in the morning.

Beyond Wednesday things do not look nearly as dynamic. The next
upper trough mentioned above will drive a cold front into the
region Thursday afternoon or evening, but the window for any
meaningful low level moisture return looks negligible and have
pulled precip mention. Heading into the weekend the upper trough
across the eastern CONUS is replaced by ridging with increased
cyclonic flow across the western CONUS, the Pacific NW initially,
building southward Monday. This pattern will bring the potential
for diurnally-driven dryline type convection possibly as early as
Saturday but with a bit better confidence Saturday through
Tuesday.

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 5 AM CDT Wednesday for TXZ021-022-027-028-
033-034-039-040.

&&

$$

05/99


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