Special Weather Statement, NWS Houston/Galveston, TX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
318 PM CDT Tue Aug 3 2021

.DISCUSSION...

A stalled, weak front is providing the focus for the development
of showers and thunderstorms today - enhanced nearer to the front
(and the coast), and more sparse well inland. With the remains of
this front not really expected to move much in the short term,
we'll expect this to continue, along with slightly cooler
temperatures to go with it.

High pressure, and onshore flow will slowly re-establish
themselves over the area at the end of the week, which will bring
the coverage of afternoon showers and storms back to more typical
summertime levels, and with warmer conditions as well. High
temperatures above 90 become more likely on Saturday, and
exceedingly likely from Sunday into early next week, indicating
that typical August conditions will be back in full force.

.SHORT TERM [Through Wednesday Night]...

As of 2PM, a weak cold front was extending along a line from
Victoria to Hobby Airport to Beaumont with a pre-frontal boundary
extending just offshore. Aloft, a weak shortwave trough was moving
over the western Gulf of Mexico, bringing the chances for showers
and storms over the waters. While convective activity will be
decreasing over the few hours, latest PWAT analysis shows an
increase in values (around 2.0 inches)across most of the CWA. Deep
low-level moisture, daytime heating and increasing low-level lapse
rates (~6.5 C/km) will allow for showers and thunderstorms through
early this evening. Deep moisture axis resides south of I-10; thus,
these locations will have better precipitation chances. As typical
in weak low-level cold advection setup and enhanced low level lapse
rates, a few funnel clouds will be possible into early this evening
over the coastal counties.

As the frontal boundary moves well offshore later tonight,
precipitation chances diminish far inland as a ridge of high
pressure builds in. In fact, per water vapor imagery, a drier
airmass is beginning to filter in from the north-northwest at mid-
levels. This will result in lower PWs tonight and Wednesday, mainly
north of I-10. However, precipitation chances will still be possible
south of I-10 on Wednesday given the combination of PWATs around 2.0
inches, daytime heating and bay/seabreeze interaction. Highs will
generally be in the low 90s. These values are near to slightly below
normal for early August standard.

.LONG TERM [Thursday Through Tuesday]...

By Thursday morning, we'll start to see Atlantic ridging try to
build back westward across the Gulf. We'll probably still be
underneath a relative weakness in any ridging aloft, which should
allow for a greater than typical amount of afternoon showers and
thunderstorms, and hold temperatures down closer to 90 degrees.

As we head into the weekend, the ridge should begin to gradually
assert itself more with each passing day. Unsurprisingly, that
means a slow downward trend in coverage of afternoon convection,
and a gradual climb of afternoon highs back towards the mid-90s.
Even by Sunday afternoon, though, 500 mb heights only look to be
about 592 dm, so I'd still expect at least a climatologically
typical amount of showers and storms. For those who stay dry,
though, highs in the mid-90s and onshore flow pumping in some more
humid Gulf air will allow heat index values to drift back up
towards 105 at their peak.

Conditions look to stay pretty static from Sunday through the
early part of next week, and so the forecast remains pretty close
to persistence for the back portion of the forecast period right
now. For example, the middle quartile in the NBM distribution
for high temps at IAH only changes from 92-97 degrees on Sunday to
93-98 degrees on Tuesday. The GFS does hint at slightly stronger
ridging, with a 596 dm high nearby. That would probably heat us up
a little more and likely provide enough subsidence to clamp down
on afternoon convection as well. But for now, all indications are
this is probably on the warmer end of possible scenarios.

&&

.AVIATION [18Z TAF Issuance]...

A weak frontal boundary is currently along and south of a line
from KVCT to KHOU to KBMT. Isolated showers will continue across
all sites, with thunderstorms possible late this afternoon/early
evening. The best chance for -TSRA looks to be for terminals south
of KIAH through 00Z Wednesday. Gusty/erratic winds and low visby
are expected with any strong storms. Showers and thunderstorms
return offshore late tonight, possibly impacting KLBX and KGLS
around daybreak. Light northerly winds will transition to the
northeast and east tonight and Wednesday. MVFR ceilings will
persist over the inland terminals through mid-afternoon, then VFR
conditions are expected at all sites.

&&

.MARINE...

A stalled frontal boundary near the coast will fuel showers and
thunderstorms late into the week. Seas will remain 1 to 2 feet,
except in and near thunderstorms where seas will be more agitated.
Once high pressure reasserts itself over Texas by the weekend,
moderate onshore flow will resume. Expect seas to build to 2 to 3
feet, with a more typical daily pattern of showers and
thunderstorms.

At the coasts, tide levels pretty close to astronomical
predications can be expected for the time being. As onshore flow
becomes stronger late in the week, they may begin to slowly drift
more above those normals. The resumption of onshore flow will also
begin to introduce some higher rip current risk as well.

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL)  74  92  73  91  74 /   0  20  10  40  20
Houston (IAH)          76  93  75  93  76 /  20  30  20  50  20
Galveston (GLS)        80  89  80  90  81 /  40  30  30  50  40

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...None.
GM...None.

&&

DISCUSSION...Luchs
SHORT TERM...05
LONG TERM...Luchs
AVIATION...05
MARINE...Luchs

Special Weather Statement
National Weather Service Houston/Galveston TX
538 PM CDT Tue Aug 3 2021

TXZ237-238-338-032315-
Inland Brazoria TX-Inland Galveston TX-Coastal Galveston TX-
538 PM CDT Tue Aug 3 2021

...A strong thunderstorm will impact portions of west central
Galveston and east central Brazoria Counties through 615 PM CDT...

At 537 PM CDT, Doppler radar was tracking a strong thunderstorm over
Santa Fe, moving south at 10 mph.

HAZARD...Winds in excess of 30 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Southern League City, Texas City, Dickinson, La Marque, Santa Fe and
Hitchcock.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 2948 9512 2946 9502 2929 9501 2934 9525
TIME...MOT...LOC 2237Z 013DEG 6KT 2941 9510

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...30 MPH