Area Forecast Discussion
Issued by NWS Corpus Christi, TX

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FXUS64 KCRP 211052
AFDCRP

Area Forecast Discussion
National Weather Service Corpus Christi TX
552 AM CDT Wed Apr 21 2021

.AVIATION...

VFR conditions will prevail today, though occasional MVFR
ceilings are possible across the Coastal Plains this morning.
Breezy conditions are expected through the day today, diminishing and
shifting to the east then southeast this afternoon. Cloud cover
will begin to increase late in the TAF period, with MVFR ceilings
expected to develop from south to north beginning 06Z.

&&

.PREV DISCUSSION... /Issued 430 AM CDT Wed Apr 21 2021/

SHORT TERM (Today through Thursday)...

Cool temperatures will continue today, with highs in the 70s across
South Texas. Breezy north-northeast flow is expected through this
morning, with winds beginning to weaken and shift to the east-
southeast later this afternoon. Moisture and warm air will return
with the onshore flow, so a few isolated showers may be possible
across the Rio Grande Plains as a weak surface trough moves over the
area. A weak mid-level shortwave will move over South Texas Thursday
which, combined with the increasing low level moisture, a warm front
over Central Texas, and some isentropic lift, should provide enough
support for some isolated to scattered showers. Showers will begin
across the west Thursday morning, then spread east by Thursday
afternoon/evening.

LONG TERM (Thursday Night through Tuesday)...

Not much change from the previous forecast. The focus of the
forecast continues to be on the severe weather potential for Friday.
A deep mid to upper level trough will shift eastward into the state
from New Mexico during the day Friday. As this progression occurs, a
strong disturbance at the surface will pull a warm front northward
through South Texas, and will place the area in the warm sector
ahead of an incoming Pacific front. This will create an environment
favorable for thunderstorms, with strong to severe thunderstorms
possible for portions of South Texas.

Favorable factors for strong to severe thunderstorms remain evident
in the latest model guidance. GFS soundings show most of South Texas
in a largely unstable environment with CAPE values around 2200 J/kg,
minimal CIN, steep mid-level lapse rates (7-8 C/km), DCAPE around
1200 J/kg, and effective shear over 50 knots. Plenty of moisture is
available to fuel storms as PWAT values continue to come in at
around 1.8" Friday. Strong isentropic lifting, a weak cap, and some
mid-level vorticity will help with convective initiation ahead of
the Pacific front.

Medium confidence on the potential for severe weather Friday, as the
timing and cap development/strength continue to be key factors.
Latest model guidance suggests a window of opportunity for strong to
severe thunderstorms Friday afternoon. A strong cap is expected to
develop during the evening hours on Friday, so if the progression of
the synoptic pattern is slowed, severe weather potential would
decrease as the cap strengthens.

Nonetheless, scattered to numerous thunderstorms will be possible
over South Texas Friday, especially north and east of San Patricio
County. SPC has the Victoria Crossroads in a slight risk for severe
weather Friday, and a marginal risk for the northern Coastal Bend
into the northern Coastal Plains. Primary threats will be wind and
hail.

Rain chances will decrease Friday night as the disturbance continues
its eastward progression. Much drier air is expected in South Texas
in the wake of the Pacific front Saturday. Temperatures through the
long-term period are expected to be in the mid to upper 80s along
the coast and the 90s to around 100 in and west of Brush Country.
Models hint at another cold front approaching the area at the end of
the extended period bringing our next chance for precipitation.

MARINE...

Moderate to strong northeast winds will continue through the morning
in response to the passage of a cold front. A Small Craft Advisory
will remain in effect for the Bays and Waterways through early this
morning, and across the Coastal Waters through mid- morning. Winds
will weaken and shift to moderate onshore flow this afternoon and
evening and persist through Thursday. Small Craft Advisory
conditions will be possible over the nearshore and offshore waters
Thursday night through early Saturday morning before winds weaken
and seas subside below 7 feet. A Pacific front will pass through
Saturday morning, causing weak to moderate winds to shift out of the
northwest through the day. Winds will then turn northeasterly
Saturday night through Sunday morning, becoming easterly by Sunday
night. Isolated to scattered showers are possible Thursday through
early Thursday night, with isolated thunderstorms are possible
overnight Thursday night. Greatest coverage is expected Friday and
over the nearshore waters with scattered showers and thunderstorms
possible, decreasing to isolated Friday night.

&&

.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi    70  62  75  70  86  /   0  20  30  30  40
Victoria          71  53  73  68  80  /   0  10  30  40  80
Laredo            77  62  80  72  96  /  10  30  40  20   0
Alice             75  60  77  70  92  /   0  20  40  30  30
Rockport          71  64  77  72  83  /   0  10  30  30  50
Cotulla           77  59  78  70  94  /   0  30  40  30  20
Kingsville        72  61  76  70  91  /   0  20  30  30  20
Navy Corpus       68  65  74  73  81  /   0  10  30  30  40

&&

.CRP WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory until 11 AM CDT this morning 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 8 AM CDT this morning For the
     following zones: Bays and Waterways from Baffin Bay to Port
     Aransas...Bays and Waterways from Port Aransas to Port
     O`Connor.

&&

$$

LS/77...AVIATION


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