Area Forecast Discussion
Issued by NWS Corpus Christi, TX

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FXUS64 KCRP 162353 AAA
AFDCRP

Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
553 PM CST Tue Jan 16 2018

.DISCUSSION...Will allow Winter Weather Advisory to expire for
areas along Highway 281 at 00Z. Satellite imagery shows some
enhancement to clouds moving up from Deep South Texas. There has
been intermittent freezing drizzle reported over the Coastal Bend.
Will keep Coastal Bend in the advisory until 9 PM. Wind Chill
Advisory expires for the western Brush Country at 6 PM also as
wind speeds diminish there. See Aviation section for 00Z TAFs.

&&

.AVIATION...A band of freezing rain and sleet will continue to
move across the Victoria Crossroads in region of better isentropic
lift for the next 2-3 hours. This could lead to brief MVFR
ceilings and vsbys. For the Coastal Bend, MVFR ceilings are
lingering in this area. Freezing drizzle will be possible early
this evening with MVFR vsbys expected. Later this evening, the
ceilings will lift to VFR levels for all of South Texas. May even
see some clearing in the VCT area early Wednesday morning. Winds
will be gusty this evening along the coast with north winds
weakening overnight.

&&

.PREVIOUS DISCUSSION... /Issued 430 PM CST Tue Jan 16 2018/

SHORT TERM (Tonight through Wednesday)...

Back edge of precip continues to shift east across S TX this
afternoon. Drier air in the sfc-H9 layer continues to build
southeast into the region resulting in diminishing precip chances.
This drying trend will continue this evening as isentropic
downglide strengthens. Therefore, I have canceled the Winter
Weather Advisory for the Brush Country...and the remaining areas
of the Winter Weather Advisory will likely be able to be canceled
early.

Once the wintry precip shifts east of the area, the primary
weather hazards then become freezing temps and wind chills. Strong
north winds continue this afternoon across primarily the eastern
half of the region. Wind speeds should continue to slowly weaken
tonight as arctic high pressure builds into the area...which when
combined with cold temps will result in a continuation of cold
wind chills. As such, the Wind Chill Advisory continues for the
eastern 2/3 of S TX through tonight/Wed morning and for the
western Brush Country through late afternoon (as wind speeds
should weaken further across the W Brush Country). If wind speeds
decrease even further overnight...then additional areas of the
Wind Chill Adv may be able to be canceled.

Forecast min temps are a bit problematic for tonight. Temps may
actually rise a couple of degrees late this afternoon and early
evening as some drier air filters into the region.
Overnight...widespread cloudiness should result in temps holding
nearly steady until late in the night. At that time, some
thinning of the overcast should occur which should then allow for
a little better thermal cooling...which should allow temps to
approach the currently forecast min temps. If cloud cover remains
rather thick, then min temps may end up being higher than
forecast.

Wednesday will be cold across the entire CWA. Persistent cloud
cover will keep modified arctic air trapped near the sfc which
should keep nearly the entire area in the 30s for the entire day.
Many areas may remain below freezing through much of the morning.
Some sunshine will be possible by late in the day across the
Victoria area...but even then temps should remain below 40
degrees. One noticeable difference in Wednesday`s weather will be
the weaker wind speeds.

LONG TERM (Wednesday night through Tuesday)...

Main forecast issue in the shorter term of this package is whether
precipitation will return Wednesday night, and whether that
precipitation will be wintry in nature. Looking at the upper air
pattern and the model soundings, feel that rainfall (if any) will be
limited to the extreme southern areas and that will mainly be after
midnight. With temperatures in some areas falling near freezing, we
could see some VERY LIGHT precip amounts toward morning and into
Thursday morning over southern inland areas. However, model
soundings kind of show some good dry layers overnight and Thursday
in those freezing areas, so confidence in this happening is not high
(unfortunately ECMWF was not available and GFS was coming in
spotty). In short, feel that the better chances for rainfall will be
Thursday afternoon and Thursday night when the upper trough gets
closer to the region and the isentropic pattern looks much more
favorable (due to coastal trough). By then we should see
temperatures above freezing and any rainfall will be liquid. Do have
near or below freezing temperatures Wednesday night away from the
coast, and another Freeze Warning may be needed by Wednesday
afternoon for some areas Wednesday night/Thursday morning. Will need
to see better dynamics and/or isentropic pattern to develop earlier
for any wintry precip early Thursday morning. For temperatures,
generally went with a blend of the NAM12 and HiRes models for
Wednesday night, with cooler guidance Thursday for highs.

The upper trough will begin to move away from South Texas late
Thursday night, and the coastal trough will weaken by Friday. As a
result, on Friday most of the rain chances will be limited to the
eastern portions of South Texas (and if the upper trough is faster
more like the coastal areas and offshore). Upper ridge begins to
build Friday night and Saturday before another storm system moves
toward the Southern Plains on Sunday. Looks like most of South Texas
will be dry-slotted for this event, with maybe just a small chance
over the SE coastal areas and better chances near Victoria and
offshore on Sunday as the expected mid level cap develops. Drier air
moves in Sunday night, with no rainfall expected Monday and Tuesday.
There is a hint of maybe enough moisture return Tuesday night for
some showers, but for now kept things dry. For the Friday through
Tuesday time frame, generally accepted the Superblend guidance
(except for the changes made to the weather and POP grids).

&&

.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi    27  37  33  46  42  /  20   0  20  30  50
Victoria          22  37  27  45  39  /  10   0  10  10  30
Laredo            28  36  32  43  37  /  10   0  10  10  20
Alice             27  36  32  44  39  /  10   0  20  30  40
Rockport          27  38  35  47  44  /  20   0  10  20  40
Cotulla           27  36  30  44  36  /  10   0  10  10  20
Kingsville        27  37  32  45  41  /  20   0  20  30  50
Navy Corpus       31  37  37  48  46  /  30   0  20  30  50

&&

.CRP WATCHES/WARNINGS/ADVISORIES...
TX...Winter Weather Advisory until 6 PM CST this evening For the
     following zones: Jim Wells...Live Oak.

     Freeze Warning until noon CST Wednesday For the following zones:
     Aransas...Bee...Calhoun...Duval...Goliad...Jim Wells...
     Kleberg...La Salle...Live Oak...McMullen...Nueces...
     Refugio...San Patricio...Victoria...Webb.

     Wind Chill Advisory until 10 AM CST Wednesday For the following
     zones: Aransas...Bee...Calhoun...Duval...Goliad...Jim
     Wells...Kleberg...Live Oak...McMullen...Nueces...Refugio...
     San Patricio...Victoria.

     Winter Weather Advisory until 9 PM CST this evening For the
     following zones: Aransas...Bee...Calhoun...Goliad...
     Kleberg...Nueces...Refugio...San Patricio...Victoria.

     Wind Chill Advisory until 6 PM CST this evening For the
     following zones: La Salle...Webb.

GM...Small Craft Advisory from 10 PM this evening to 2 PM CST
     Wednesday For the following zones: Waters from Baffin Bay
     to Port Aransas from 20 to 60 NM...Waters from Port Aransas
     to Matagorda Ship Channel from 20 to 60 NM.

     Gale Warning until 10 PM CST this evening For the following
     zones: Coastal waters from Baffin Bay to Port Aransas out
     20 NM...Coastal waters from Port Aransas to Matagorda Ship
     Channel out 20 NM...Waters from Baffin Bay to Port Aransas
     from 20 to 60 NM...Waters from Port Aransas to Matagorda
     Ship Channel from 20 to 60 NM.

     Small Craft Advisory until midnight CST tonight For the
     following zones: Bays and Waterways from Baffin Bay to Port
     Aransas...Bays and Waterways from Port Aransas to Port
     O`Connor.

     Small Craft Advisory from 10 PM this evening to 9 AM CST
     Wednesday For the following zones: Coastal waters from
     Baffin Bay to Port Aransas out 20 NM...Coastal waters from
     Port Aransas to Matagorda Ship Channel out 20 NM.

&&

$$

TMT/89...AVIATION


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