Area Forecast Discussion
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FXUS64 KLUB 231819

Area Forecast Discussion
National Weather Service Lubbock TX
119 PM CDT MON MAY 23 2016

MVFR cloud layer at KCDS should gradually lift this afternoon.
KLBB and KPVW should remain in VFR remainder of the day with more
veered surface winds and storm initiation most likely just to the
east. Opted to not mention thunder specially this time for KCDS
as not confident enough that storms will generate near enough. But
will add if they approach, of course. Low clouds around MVFR
levels should steer back into KLBB and KCDS later tonight.


The atmosphere is primed for another severe thunderstorm event
later today, with a juiced lower level atmosphere of mid to upper
60s and even lower 70s dewpoints contributing to convective energy
levels on the order of 5000 joules per kilogram. The subtropical
jet has shifted slightly south while a wave lifting into western
Colorado on a branch of the polar jet places our area squarely
between with potential once again for strong upper level
difluence. A trailing wave over southern Arizona appears destined
for the southern high plains, arriving mid to late evening, or
mostly after the peak heating has ended. We also have a well
defined outflow boundary from last evenings storms lying from near
Caprock Canyons State Park to Matador, and possibly a weaker
boundary from Southland to Justiceburg. The RAP appears to be
picking up on both these boundaries, while the TTU WRF has latched
onto the stronger northern boundary, in particular, where it has
placed the bulk of activity later today. Flow today appears
slightly faster, which argues a bit for less flood threat, though
rich moisture of an inch and a half precipitable water counters
to some extent. Any slow right moving supercell will have flood
threat by this evening.

Anyway, the particulars once again will come into where storms
initiate and then mature. We favor a few cells initiating along
the dry line from near Tahoka to just east of Lubbock then towards
SILVERTON, then maturing perhaps within those favored regions
mentioned above. We have adjusted thunder chances slightly higher
near those two boundaries. We are holding off on a flash flood
watch for now, would like to see more agreement within the short
range solutions, but this remains possible. Expecting a severe-
type watch to be issued, very possibly a tornado watch, by mid or
late this afternoon favoring the eastern half of our area.


.PREV DISCUSSION... /issued 635 AM CDT MON MAY 23 2016/

MVFR to IFR ceilings have overspread the terminals again this
morning, but they will gradually lift and scatter to VFR levels by
late morning. The next concern is for deep moist convection by
mid-late afternoon. Any of the terminals could experience a late
afternoon/evening storm, but the best chances reside at KCDS
where a PROB30 group was included. Another round of low clouds
will then be possible early Tuesday morning as moisture returns
back westward.

PREV DISCUSSION... /issued 412 AM CDT MON MAY 23 2016/

We will see another opportunity for significant severe weather
across some of the same locations that experienced it Sunday
afternoon and evening.

Early this morning a large MCS, the spawn of convection that
initiated in the eastern Texas Panhandle, was tracking through south-
central Oklahoma and parts of North Texas. Conditions were much
quieter in the wake of MCS over the South Plains region with
impressive low-level moisture (dewpoints in the mid-upper 60s) and
areas of stratus streaming back northward across the FA. Aloft, one
vortex within the broad western trough was spinning slowly eastward
into southwest Saskatchewan while additional energy was digging
toward California. This pattern will be slow to evolve today leaving
West Texas under continued moderate southwesterly flow aloft. We
could see one weak ripple within the southwest flow approach later
this afternoon, but the primary driver of the next round of
convection will be tied to strong daytime heating/mixing that will
erode the CIN by mid-late afternoon. There is good agreement that
the dryline will mix to at least the I-27/US-87 corridor, and
perhaps the eastern edge of the Caprock, by late this afternoon
where it will be the focus for scattered storm development.
Very strong instability (SBCAPE of 3000-5000 J/kg) and 0-6 km shear
around 40 knots will promote explosive storm development, with
supercell and multicell storm modes likely. Very large hail will be
the greatest threat early on, but the increasing LLJ and dropping
LCLs will support an increasing tornado threat too during the
evening hours. Additionally, relatively slow storm motions and the
abundant moisture (and strong moisture flux) will favor localized
very heavy rains too, though exactly where this heavy rain will fall
is uncertain. We did consider issuing a flash flood watch for
portions of our northeast zones, where some spots saw 5 to 8+ inches
last night, but given a fair amount of uncertainty with regards to
the location and coverage of the heavier rain later today, we
decided to hold off at this point and will let the next shift

The convection may again organize into an MCS late tonight and there
are even indications of additional storm development locally late
tonight, perhaps tied to a little additional upper support, but
confidence in this is low. However, we have maintained low PoPs late
tonight with this in mind after carrying high chance PoPs over
roughly the eastern half of the CWA this afternoon and evening.

Aside from the severe thunderstorm prospects, it will be another hot
day, with highs climbing into the low to mid-90s west of the dryline
this afternoon, while upper 80s to low 90s will be common further

The chance of strong and severe thunderstorms will continue Tuesday
afternoon and evening. The dryline is expected to mix to near the
edge of the Caprock by mid to late afternoon. Strong heating
across the area will boost temps into the 90s and yield MLCAPEs
of 2500-3500 J/kg to the east of the dryline, and perhaps higher
in the eastern Rolling Plains. There does not appear to be much in
the way of synoptic-scale ascent spreading over the dryline in the
afternoon per model progs, but forecast soundings do show CINH
diminishing to near zero by 4 to 5 pm. Very large hail once again
looks to be the biggest threat from any storms, although again
there may be a window of a tornado threat in the early evening due
to backing and strengthening low-level winds.

Deep-layer flow appears to veer westerly enough on Wednesday to
shunt the deeper moist axis and thunder chances to our east.
However, the dryline should begin to retreat Wednesday night as the
flow begins to respond to a more pronounced upper low/trough digging
into the desert southwest. Recent trends have continued to show a
somewhat slower and deeper track for this system and thus our
confidence is improving that moisture will move back west to
support t-storm chances at least for the Rolling Plains by Thursday
afternoon. In fact, the GFS suggests we may see some elevated
activity Thursday morning farther to the west, but we have kept
the morning PoPs below mention for now. Also of note is that the
CIPS analog guidance is beginning to indicate some severe weather
potential across the region on Thursday, so something to watch.
Mid-level drying and weak shortwave ridging then follows on
Friday which should keep convection at bay. For Memorial Day
weekend, it still looks like the forecast area will come under the
influence of a large upper-level trough to our west, which should
allow Gulf moisture to become established across the area and
support a chance of thunderstorms much of the weekend - although
the details are still uncertain.


.LUB Watches/Warnings/Advisories...


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