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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

                            
000
FXUS64 KHGX 192340
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
640 PM CDT Mon Aug 19 2019

.AVIATION...
Scattered showers and thunderstorms will end within the next hou
or so with skies clearing and VFR conditions expected for most
of the night. PW values recharge by morning and reach 2.00 inches
by 12z and peak around 18z between 2.10 and 2.20 inches.
Convective temperatures are between 90-92 degrees so another
active day is expected with shra/tsra redeveloping near the coast
by morning and spreading inland with heating. Added a Prob30 for
KIAH for the afternoon. Leaned toward a blend of the ARW/GFS and
TT WRF for precip chances on Tuesday. 43

&&

.PREV DISCUSSION... /ISSUED 315 PM CDT Mon Aug 19 2019/ 

DISCUSSION...

Today appears to be coming in just a touch cooler than yesterday,
and that is the beginning of a slow draw down in heat that will
persist through the week. Don't get too excited, though - we'll
only be making our way to normal summertime heat from our more
dangerous heat last week. As conditions become more typical, we're
also seeing the return of daily scattered showers and storms,
mainly in the vicinity of the coast. Guidance continues to sour 
on the disturbance slated to scrape up the western Gulf this 
weekend, and while it still looks like it should bring more
widespread rain chances, confidence is slowly growing that heavy
rains will not be in the cards.

NEAR TERM [Through Tonight]...

Radar shows that a lot of our morning and early afternoon
convection has waned or moved off to the east, and there is less
activity out there now than earlier in the day. However, satellite
indicates a few more areas where cumulus clouds are beginning to
pile up, so we're almost certainly not quite done yet for the
afternoon. Of course, as we settle into the typical diurnal
routine, look for any showers or storms to wrap themselves up
pretty quickly as the sun goes down early this evening.

SHORT TERM [Tuesday Through Thursday Night]...

The strong midlevel ridging that had been centered over Texas
is not really weakening any, but it is drifting slowly westward.
As it does so, will be looking for small, but sustained drops in
high temperatures each day this week. Shower and storm activity
should manage to be similar today for the next couple of days, but
the best forcing aloft to support vertical growth of updrafts will
be offshore, so we may see convection over land suppressed
slightly. With the mesoscale driving so much already, any
difference may be only barely perceptible. 

LONG TERM [Friday Through Monday]...

By Friday, the midlevel vort max we've been referring to for a few
days now should be making its way into the northwestern Gulf as it
comes up the western Gulf coast. Both the Euro and particularly
the GFS find a way to be even less enamored of this feature as it
moves into our region, and at this point there isn't even a
surface trough underneath the midlevel disturbance. 

What we do still see, though, is a decidedly higher precipitable 
water content make its way over Southeast Texas, so at least we 
should see the increased moisture make for more widespread rain 
chances, rather than seeing convective activity pinned to the 
seabreeze zone. More widespread rains, however, will not
necessarily translate to heavier rain for us. A lot will depend on
specifics I will not pretend we can reliably forecast at this
range, but in general, as long as the strong model consensus for
the track of the midlevel vort max holds, it will be safely
offshore, and on the backside, we'll be looking for offshore flow
in the 700-500 mb layer. As a result, progged rainfall totals are
not terribly impressive inland, and max out around an inch or two
at the coast, even. 

As noted in past days, we are still at range and plenty of 
details could change to give us a different setup. But at this 
point, the trend continues to be our friend - we're still looking 
at better, more widespread rain, but nothing excessive expected. 
Knocking on wood that it stays that way.

AVIATION [18Z TAF Issuance]...

Scattered SHRA/TSRA has developed south of I-10 this afternoon, 
and is expected to continue to push northward over the next
several hours. Metro terminals can expect to see intermittent
precipitation through approximately 22Z this afternoon. Aside 
from the possibility of any temporarily reduced visibilities from 
convection this afternoon, conditions should remain within VFR 
thresholds at all sites through the duration of the TAF period. 
Winds through the rest of the day remain out of the S/SE at around
10 knots. As high pressure builds into the region tonight and 
into tomorrow, winds should become lighter and variable. Current 
high-resolution model guidance suggests that showers and storms 
will again develop over the coastal waters tomorrow morning, 
although confidence in the extent to which this activity will push
inland is not high at this time.

Cady

MARINE...

Moderate onshore flow begins to taper off slightly tonight as high 
pressure begins to build into the region. Winds remain out of the
south to southeast winds at 10 to 15 knots, diminishing to 5 to 
10 knots overnight. Scattered showers and thunderstorms are 
possible tomorrow, which could result in some higher gusts during 
the afternoon. Winds begin to diminish to around 5 to 10 knots 
late Monday as high pressure builds into the region, producing 
lower seas through the end of the week.

Strong rip currents will be possible along Gulf-facing beaches 
overnight and into tomorrow morning. A Rip Current Statement remains 
in effect through 10AM CDT Tuesday morning. If traveling to the 
beach, always remember to exercise caution while swimming and only 
enter the water in areas where lifeguards are on duty.

Cady

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      77  99  76  98  76 /   0  20   0  10   0 
Houston (IAH)              79  95  78  95  78 /  10  40   0  20  10 
Galveston (GLS)            83  90  83  90  83 /  40  60  10  30  20 

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk through Tuesday morning for the following 
     zones: Brazoria Islands...Galveston Island and Bolivar 
     Peninsula...Matagorda Islands.

GM...NONE.
&&

$$

Discussion...47
Aviation/Marine...43