Area Forecast Discussion
Issued by NWS Corpus Christi, TX

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FXUS64 KCRP 181831
AFDCRP

Area Forecast Discussion
National Weather Service Corpus Christi TX
1231 PM CST Mon Dec 18 2017

.DISCUSSION...

Note Aviation Discussion corresponding to the 18z TAFs.

&&

.AVIATION...

Predomiante IFR/LIFR conditions expected during the TAF period.
Patchy/areas of light rain and isolated/scattered showers over
much of South Texas this afternoon. Isolated thunderstorms will
likley be confined over the coastal bend mainly near the
immediate coast, and offshore. This evening/tonight, expect sea
fog to develop over the bays/nearshore waters. Patchy light
rain/isolated showers are anticipated. The intensity and
coverage of precipitation expected to increase during the 12-18z
Tuesday period.

&&

.PREVIOUS DISCUSSION... /Issued 615 AM CST Mon Dec 18 2017/

DISCUSSION...

Update for 12Z aviation cycle.

AVIATION...

Today - Tonight...MVFR/IFR/LIFR. Poor flying conditions all
around. Low cigs, light rain, and fog will remain in place this
morning. Rain will taper off a bit across the western half of the
region during the afternoon hours. Winds back more onshore later
today keeping moisture streaming into the region and the poor
conditions in place. Warm front will lift through the region later
today with southeasterly winds behind it, though still relatively
weak. Do not think LLWS will be an issue but winds around 2000
feet do increase close to 30-35 knots later tonight. More rain is
expected to move in from the southwest late tonight. Areas of fog,
possibly dense closer to the coast, is expected as well. Medium
to high confidence.

PREVIOUS DISCUSSION... /Issued 433 AM CST Mon Dec 18 2017/

SHORT TERM (Today through Tuesday)...

Large upper level closed low pressure continues to spin just south
of the AZ/MX boarder sending lots of upper-level moisture into
our region. This feature will slowly move towards the north-
northeast as it starts to become an open wave. Ample surface lift,
especially along the coast this morning with coastal troughing,
and the positioning of the jet stream allow for continued chances
of showers and possibly isolated thunderstorms today and tonight.
Temperatures today will be warmer than yesterday owing to more of
an onshore flow developing, especially as the coastal trough moves
inland.

Expecting another round of showers and fog developing late tonight as
the aforementioned closed low moves farther east-northeast. Low-
level response with stronger east-southeast flow commences
allowing for elevated convection to potentially develop. Onshore
flow within the boundary layer also allows for better sea fog
development as dewpoints close to 70 degrees advect over low/mid-
60s shelf water temperatures. Do not really foresee the sea fog
diminishing much throughout the day Tuesday as the flow slowly
backs towards the south, though it may just shift out of the
Baffin Bay area and remain entrenched across the Corpus Christi
Bay and points farther north.

Cold front starts to slide towards the CWA by Tuesday afternoon
and a broken line of storms may develop just ahead of the boundary
tapping into the moisture rich warm sector across the region.
Highlighting areas across the Northern Coastal Bend back into the
Victoria Crossroads for possibly stronger storms, where the best
moisture profile and instability reside. Precipitation should
quickly end from west to east heading into Tuesday night.

LONG TERM (Tuesday night through Sunday)...

The upper level disturbance will be exiting the region Tuesday
night, with rain chances diminishing from west to east overnight.
Weak offshore flow will develop on Wednesday as this system moves
further east.  On Thursday onshore flow will return and strengthen
as a an upper level low digs into the Rockies and low pressure
deepens over the southern central plains.  Higher moisture will be
drawn back into the region, and an isolated shower may develop
across northeastern portions of the region Thursday.  The warming
trend will continue into the middle of the week, with high
temperatures on Thursday in the upper 70s to lower 80s across the
region.

Friday onward we continue to see discrepancies in forecast guidance.
The upper level low will open and move across the south, bringing a
cold front south into the region around Friday to Friday evening.
Consensus is generally trending closer to an earlier fropa, and have
kept the timing of the front moving through during the day on
Friday. Anticipate scattered showers to develop with sufficient
moisture across the region.  Saturday should be cooler, though still
keeping temperatures in the low 60s across most locations.  There is
further uncertainty between guidance, as the ECMWF wants to bring a
warm front back on Saturday evening while the GFS maintains a flow.
more northerly flow. For the time have trended a bit warmer on
Sunday. However, guidance does agree another deep longwave trough
will develop and an arctic airmass should sink south into the region
early next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi    62  78  57  76  58  /  40  30  10  10  10
Victoria          61  78  55  74  53  /  50  60  30  10  10
Laredo            59  72  52  75  58  /  60  30  10   0   0
Alice             62  79  55  78  57  /  50  40  10  10  10
Rockport          63  74  59  73  60  /  50  30  20  10  10
Cotulla           59  70  48  76  54  /  60  60  10   0   0
Kingsville        63  81  57  78  58  /  40  30  10  10  10
Navy Corpus       65  77  60  74  62  /  40  20  20  10  10

&&

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

&&

$$

WC/87...AVIATION



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