Area Forecast Discussion
Issued by NWS Corpus Christi, TX

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FXUS64 KCRP 180506 AAD
AFDCRP

Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
1106 PM CST Tue Jan 17 2017

.DISCUSSION...

See Aviation Discussion for 06Z TAFS.

&&

.AVIATION...

Good area of showers and isolated storms will impact KVCT for the
next hour or so, which are occurring due to the impacts of the
upper level support. Expect this upper support to diminish by 12Z
if not earlier, with frontal forcing being the main issue for the
eastern terminals 12Z and beyond. Winds are expected to weaken
south of the frontal boundary the next few hours, with winds
remaining northerly at KLRD. Convergence will be sufficient for
TEMPO showers (thunder at KVCT) for eastern terminals through at
least a part of the morning, before winds gradually become more to
the northwest and drier air comes in to limit rain chances. When
the winds shift, should see an improvment in CIGS and VSBYS during
the daytime. However, eastern terminals likely will see no better
than MVFR through the afternoon. After sunset, should not see any
significant rainfall until after terminal forecast ends with the
main issue whether CIGS will be VFR or MVFR and if fog will come
back. For now, am going with VFR conditions at KALI KCRP and KLRD
but keeping MVFR/IFR at KVCT. Also, will hold off on return of
fog as if any occurs it will have to be radiation fog which with
enough high cover around do not think it as likely.

&&

.PREVIOUS DISCUSSION... /Issued 836 PM CST Tue Jan 17 2017/

DISCUSSION...

Made a few changes on the forecast for the first and second
periods based on radar trends, RUC/GFSLAMP model output and HRRR
model trends. In a nutshell, looks like the boundary is sinking a
bit south but will go only a bit more. Most of the convection has
been out west and adjusted rain chances up there (and lowered
them southeast this evening), then kept pretty much the same POPs
after 06Z but did bring the rain over the eastern areas a bit
later (broke up weather grid). Lots of weather in the grids
between 09Z and 15Z including rain with isolated thunder, patchy
and areas of fog. Based on model temperature output, adjusted
min/max grid accordingly using Min/Max tools (adjusting min temp
down a degree and the max temp grid up a degree). Midshift can
handle the changes for Wednesday as-needed. Always a tough
temperature forecast with a stalled front in the area. Product
updates have been issued. Any changes to the marine grids were to
the weather and subtle changes to the afternoon winds on
Wednesday.

PREVIOUS DISCUSSION... /Issued 629 PM CST Tue Jan 17 2017/

DISCUSSION...

See MARINE and AVIATION discussion for update on marine and 00Z
TAFS, respectively.

MARINE...

Fog is starting to develop over the bays and nearshore waters as
seen by web cams. For now, will handle it with MWS as RUC13
soundings indicate some of the heavier fog/VSBYS may improve a
bit overnight. Will monitor conditions but did mention that if fog
becomes more dense than a Dense Fog Advisory will be
needed/issued. MWS and CWF have been issued/updated.

AVIATION...

Most of the convection has been showery with not much thunder and
think this trend will continue for KVCT, KALI and KCRP. However,
there will be a better chance for thunder at KLRD starting around
04Z and continuing until around 09Z (have VCTS/TEMPO TSRA) as jet
streak moves across the region. Farther east, I believe the
forcing will mainly be frontal with not as much large scale lift
so will continue with showers, with most of the showers overnight
and before 15Z. Tricky one is KVCT where they could be close
enough to the larger scale lift to warrant some thunder (so did
include a TEMPO toward 12Z). Rain chances will diminish much at
KLRD after 15Z, with clearing late with drier NW winds coming in
(have going VFR by 20Z). Farther east, more chances for showers in
the morning, with the showers shifting more to the coast during
the afternoon as the winds gradually shift more westerly. This
will help CIGS to improve but only MVFR during the afternoon.
Before 12Z will have LIFR conditions mainly due to cigs but could
also have some VSBYs 2SM or less. Lots of things to consider, but
overall this is the scenario so see the individual terminal
forecasts for more precise station information.

PREVIOUS DISCUSSION... /Issued 344 PM CST Tue Jan 17 2017/

SHORT TERM (Tonight through Wednesday night)...

Chances for showers and thunderstorms will continue through the
short term. A cold front currently extends from Victoria back
westward and west southwestward to south of Cotulla. Isolated
convection (mainly showers) this afternoon will move northward
across the area this afternoon.

The frontal boundary will remain stalled across the area this
evening into Wednesday. This will set the stage for additional
showers and thunderstorms across South Texas. Despite limited
instability, shear will be sufficient enough for strong
thunderstorms. A few storms could become severe though with
strong winds and a brief spin-up may be possible with a storm that
interacts with the boundary. Elevated convection north of the
boundary from the northern Brush Country into the Victoria
Crossroads could pose a marginally severe threat. SPC maintains a
marginal risk of severe storms over the area late this evening
into tonight. Also, a threat for moderate to heavy rain at times
will as deep moisture (PWs 1.5 to 1.6) will pool along and north
of boundary.

Latest guidance brings the front closer the Middle Texas Coast on
Wednesday. This will favor chances for showers and storms
continuing across the eastern and northeastern parts of the area
on Wednesday. Slight drier air will move into the Rio Grande
Plains which will diminish rain chances somewhat across the west
tomorrow. High temperatures will be tricky with the front draped
across the area. Temps should generally range from the mid/upper
60s across the Rio Grande Plains, northern Brush Country, and
Victoria Crossroads to lower and mid 70s across the Coastal Bend.

One last round of convection will be possible Wednesday night
into early Thursday morning as main upper trough axis approaches
from the west.

LONG TERM (Thursday through Tuesday)...

Convection Thursday should be confined to the morning hours and
primarily across the coastal counties and offshore. Parent trough
axis is prog to shift east across the CWA around midday with
significantly drier airmass throughout the entire atmospheric column
developing in the afternoon. Result should be clearing skies from
west to east through the day. Moisture quickly tries to build back
northward on Friday in the sfc-H8 layer with an increase in cloud
cover expected during the day across mainly the eastern half of S
TX. Another mid/upper level trough is prog to approach the region
Friday afternoon and if enough moisture can advect north through the
day...then an isolated shower or thunderstorm may occur in the
afternoon. For now...will carry only 20 POPs across the coastal
areas and offshore where best moisture depth is prog to occur. Wind
profile from the surface through H2 is prog to become more WSW by
Saturday and result in warm adiabatic flow through the day. Max
temps Saturday may be the warmest of the extended forecast with most
inland locations warming well into the 80s /isolated upper 80s
possible/.

Strong cyclogenesis is prog to occur Saturday night across the TX
Panhandle with a 991mb low hooking and kicking ENE over N TX...and
sending a Pacific cold front across the region. Storm system is prog
to become stacked over N TX through the day Sunday with potential
existing for a strong wind event across South Texas. Strong mixing
of adiabatic processes...with H85 wind speeds prog to be around
50kts nearly areawide...could result in widespread strong sfc winds
during the day Sunday. Guidance`s placement of synoptic features
strongly correlates to some of the stronger non convective wind
events across South Texas. If current forecast pans out...wind
advisories and/or high wind warnings may be required Sunday...along
with red flag fire weather conditions.

System kicks east early next week with mid/upper level ridging
building into the region along with continued dry conditions and
another significant warming trend.

&&

.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi    66  69  57  75  59  /  60  60  50  30   0
Victoria          60  65  56  73  56  /  90  80  50  20   0
Laredo            56  63  55  78  57  /  70  30  30  10   0
Alice             63  67  56  77  56  /  70  50  50  10   0
Rockport          66  68  57  72  61  /  60  70  60  30   0
Cotulla           55  61  51  78  53  /  70  40  30  10   0
Kingsville        65  68  58  77  58  /  60  50  50  20   0
Navy Corpus       66  68  58  72  62  /  60  60  60  30   0

&&

.CRP WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.

&&

$$

GW/86...AVIATION


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