Area Forecast Discussion
Issued by NWS Corpus Christi, TX

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FXUS64 KCRP 190447 AAC
AFDCRP

Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
1047 PM CST Sun Feb 18 2018

.DISCUSSION...

See .AVIATION discussion for 06Z TAFS.

&&

.AVIATION...

CIGS over the eastern terminals will be IFR/MVFR at times
initially, then become MVFR (or close to at KVCT) toward sunrise
as low level jet get cranking. CIGS are then expected to improve
by early afternoon to VFR with increasing winds. With 40 to 45
knot jet toward morning, will have wind shear in the terminals
(borderline at KCRP) as winds decrease to less than 12 knots most
locations (mainly speed shear). Winds will only slowly diminish
again Monday evening and am expecting that overall the CIGS may
become MVFR late in the period. However, TAFS are already long due
to strong winds initially then no gusts then improving CIGS then
increasing winds then diminishing winds then lowering CIGS just
make too long of a forecast to have more than 1 period after
20/00Z. Ergo, will go with a overall forecast for now and less
later shifts add periods if or as needed.

&&

.PREVIOUS DISCUSSION... /Issued 858 PM CST Sun Feb 18 2018/

DISCUSSION...

Just a few subtle adjustments to the previous package to align the
current forecast with the observations and trends. Will likely
remain on the warm side tonight as winds keep a well mixed layer
in the area. Fog should not be an issue inland. Product updates
out.

MARINE...

Still a potential for some sea fog tonight, but am expecting
visibilities to be above 1 mile as winds will keep things well
mixed. However, will continue to monitor, as shelf waters in some
places are still in the lower/mid 60s with dew points in the upper
60s. Will refresh MWSCRP.

PREVIOUS DISCUSSION... /Issued 534 PM CST Sun Feb 18 2018/

DISCUSSION...

See .AVIATION discussion for the 00Z TAFs.

AVIATION...

Evening sounding going up right now is showing wind 16016KT at
1000 feet and 16040KT at 2000 feet. Thus, with these winds the fog
issues tonight will be minimal, and am expecting the CIGS to be
higher and take a bit longer to develop (more mixing). Thus, am
going with MVFR CIGS at most terminals (TEMPO MVFR at KLRD and
TEMPO IFR at the other terminals when the winds diminish). With
that kind of low level jet already will have wind shear in KALI
and KVCT (it is already in there) but will hold off at KCRP and
KLRD as winds will stay up (may have to include these two later if
either the winds come down enough to warrant it. Winds appear to
be even stronger on Monday, especially in the afternoon once the
low clouds mix out and the higher boundary layer winds mix down.
Am expecting VFR all terminals by 19Z.

PREVIOUS DISCUSSION... /Issued 306 PM CST Sun Feb 18 2018/

SHORT TERM (Tonight through Monday Night)...

The weak front that had stalled across the CWA yesterday has lifted
north and has about washed out. An upper level low pressure
system digging southeast out of the Pac NW will lead to the
associated sfc low to move southeast across the central plains.
This, in turn, will strengthen the low level jet across S TX
tonight to around 40-45kt. This will result in increasing low
level moisture through the short term. Clouds rather than fog are
expected tonight, except across the bays and nearshore waters
where SST are cooler. However, SST are beginning to warm and with
a stronger wind field, should hinder the sea fog from becoming
widespread dense. Sea fog is forecasted for Mon night as well,
however confidence is decreasing that sea fog will occur Mon
night due to stronger winds and warming SSTs.

Precip is not expected tonight as the low level moisture will be
limited, along with a strong capping inversion. As the moisture
deepens Mon, isol showers will become possible along the northern
waters and northeastern CWA due to low level convergence then across
the western and northern portions of the CWA through the afternoon
due to increasing instability and a weak embedded upper level short
wave. Mon night a stronger short wave is progged to move northeast
across S TX leading to better chances of showers and thunderstorms
across the north and western CWA. Across the southern Coastal
Bend, models prog the moisture to be limited, thus kept pops at
only 10 percent with chc pops across the far northwestern CWA.

Temperatures will remain above normal with highs on Mon in the upper
80s across the Brush Country.

MARINE...

Onshore winds will strengthen tonight to mod levels with brief mod
to strong winds across the offshore waters. Winds may approach
advisory levels across the offshore waters late tonight and again
Mon night, but should generally remain at caution levels. During
the day Monday, a mod onshore flow will prevail with the southern
bays possibly reaching advisory levels briefly in the afternoon.

LONG TERM (Tuesday through Sunday)...

The extended part of the forecast will feature several chances of
showers and thunderstorms across South Texas.

On Tuesday, a deep upper level trough across the western CONUS will
slowly trudge to the east. Out of ahead of this system, low level
southeasterly flow will continue to bring warm and moist air into
South Texas. PW values will climb as high as 1.5 to 1.7 inches by
Tuesday afternoon. Chances for showers and thunderstorms will begin
to increase Tuesday as embedded impulses in southwest flow rotate
around base of trough and move northeast across the area. Timing of
these individual impulses is difficult to pinpoint at this time, but
best chances of showers and storms will be across the northern parts
of the area on Tuesday.

Cold front will be pushing southward across the state Tuesday night
into Wednesday. For South Texas, the boundary should be moving
through during the afternoon to early evening hours. Chances for
showers and storms will increase further as the boundary progresses
through the area. Pops on Wednesday will range from around 50
percent out west to 80 percent across the Victoria Crossroads. Rain
chances will shift to the east Wednesday night as the boundary nears
the coast.

Rain chances will continue into Thursday as overrunning pattern sets
up, with showers and storms possible again on Friday as boundary
retreats to the north. Kept pops in the 30 to 40 percent range for
these days.

Another upper level trough will move out of the western states next
weekend. Potential also exists that another front may move through
the region next weekend, but models exhibit some timing differences
at this time. Superblend pops were toned down a bit for Saturday and
next Sunday and only have 20 to 30 pops at this time.

Regarding temperatures, warmest day of the extended will be Tuesday
with well above normal temperatures. Highs on Wednesday should be
able to climb into the mid 70s to low 80s prior to fropa. Much
cooler conditions are expected on Thursday behind the front with
highs only in the 60s. A moderating trend will begin Friday and
continue to Saturday as boundary retreats and southerly flow
returns.

&&

.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi    66  80  67  80  67  /  10  10  10  30  40
Victoria          64  78  67  78  66  /  10  20  20  50  60
Laredo            67  88  70  87  67  /  10  10  20  30  40
Alice             66  85  68  84  67  /  10  10  20  30  40
Rockport          64  73  66  76  66  /  10  20  10  40  50
Cotulla           65  87  67  85  65  /  10  20  30  50  50
Kingsville        68  84  69  83  68  /  10  10  10  30  40
Navy Corpus       65  74  66  77  66  /  10  10  10  30  40

&&

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

&&

$$

GW/86...AVIATION



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