Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 191821
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1221 PM CST Fri Jan 19 2018

.AVIATION...
Coastal troughing tucked in over the Coastal Bend region finally
on the move east. Expect band of showers over the 66R-HOU-GLS to
gradually break up and shift eastward. Short term issues with
reduced visibility in showers for HOU/SGR/LBX/GLS. As the trough
moves east expect CIGS to lower across the region this
afternoon/evening with IFR/LIFR conditions to blanket the region
by 06z. Some uncertainty as to whether VLIFR conditions will
develop inland after 09z. CXO northward probably has the greatest
chances of VLIFR. Slow improvement 14-17z to IFR/MVFR with a few
showers mainly after 15z. Winds increasing during the afternoon
Saturday and becoming more southerly and probably even gusty.

45

&&

.PREV DISCUSSION... /ISSUED 1003 AM CST Fri Jan 19 2018/

UPDATE...
The KHGX radar shows a band of showers stretching from Jackson
County southeast towards the Galveston Bay entrance this morning.
Expect this activity to persist and slowly translate east through
the day as an associated mid-level trough slides along the
northern Gulf coast. Morning soundings from Corpus Christi and
Lake Charles showed mid-level lapse rates between 6.7-7.2 C/km,
indicating enough instability is present for a few lightning
strikes. Have already observed a strike across Jackson County this
morning and have added a mention of isolated thunder within this
band through the rest of the day. Surface analysis shows a coastal
trough stretching from south of Galveston Bay to near Matagorda
Bay and southward. With deeper moisture over the northwest Gulf
promoting somewhat better surface-based instability (CAPE in
excess of 500 J/kg) and increased shear in the vicinity of this
coastal trough (effective bulk shear in excess of 30 knots),
cannot rule out a few strong thunderstorms across the offshore
waters this afternoon.

Minor updates were also made to temperatures and dewpoints based
on observational trends with highs in the 50s today as the coastal
trough/ what could be a developing warm front lifts inland. Some
locations may not see their high temperatures for today until
later this evening until this feature lifts inland.

Huffman

PREV DISCUSSION... /ISSUED 402 AM CST Fri Jan 19 2018/

DISCUSSION...
Early this morning an elongated 500mb trough stretched from the
Tennessee Valley across the Big Bend and into west cntl Mexico. A
well defined vort was noted just west of the area in scntl TX. At
the surface, a coastal trough has set up along the Texas coast.
Expecting an increase in precip coverage, especially south of I-10
and offshore this morning and afternoon as the upper trough &
vort advance eastward. A few thunderstorms are possible offshore.

Northeast winds across inland areas this morning will gradually
veer to the southeast late today into Saturday bringing areas of
fog/drizzle/-ra typically associated with an advancing warm front
off the Gulf. Nearshore water temperatures have cooled substantially
as of late (mid 40s bays, low 50s 20nm offshore) so would also
anticipate sea fog development as the warmer airmass moves
overhead.

The next trof now situated off the west coast will make its way
into the Plains late in the weekend. Its associated front should
push through se TX late Sunday night and off the coast by early
Monday morning. A band of shra/tstms will probably be associated
with the frontal passage, but overall instability is limited so
threat of strong/severe cells appears low. Sea fog will clear out
in its wake and dry, seasonable wx should then persist into mid
to late parts of next week. 47

MARINE...
Light/moderate east winds this morning will continue to slowly veer
to the southeast throughout this afternoon. Wind speeds will likely
be increasing as well today/tonight as an area of low pressure dev-
elops over the coastal waters of the lower TX coast. This system is
expected to slowly drift east/remaining offshore, but its proximity
should help to increase rain chances across the region. Between the
periods of unsettled weather, expect patchy sea fog to develop late
tonight as much warmer air is drawn across the cooler shelf waters.
This fog threat is likely to persist into Sun night...when the next
strong cold front is forecast to push off the coast. SCEC/SCA flags
are expected for Mon morning. 41

AVIATION...
Forecast expected to become messier as the day wears on as moisture
continues to move back into the area...along with lower CIGS/precip
from the SW. Based on the ongoing trends, will likely keep with the
MVFR CIGS for this afternoon/IFR CIGS for tonight...then timing the
bouts of showers with VCSH. With sea fog expected to be an issue at
GLS...will probably have to keep an eye on VIS there. 41

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      50  49  69  60  74 /  20  30  20  20  50
Houston (IAH)              54  53  71  60  74 /  40  30  30  20  30
Galveston (GLS)            55  55  64  58  68 /  60  50  30  20  20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION through late tonight for the
     following zones: Coastal waters from Freeport to the
     Matagorda Ship Channel out 20 NM...Coastal waters from High
     Island to Freeport out 20 NM.

     Small Craft Advisory until 6 AM CST Saturday for the following
     zones: Waters from Freeport to the Matagorda Ship Channel
     from 20 to 60 NM...Waters from High Island to Freeport from
     20 to 60 NM.

&&

$$

Discussion...14
Aviation/Marine...45


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