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Area Forecast Discussion (AFD)

Issued by Houston/Galveston, TX (HGX)

                            
000
FXUS64 KHGX 182053
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
353 PM CDT Sun Aug 18 2019

.DISCUSSION...

Our extended heat wave is trying to cling to our area again today,
but as we head deeper into the week, we should slowly drift back
towards more seasonable heat. This is, of course, still quite hot.
Along with temperatures, the summertime daily rain pattern will
reign with nocturnal showers and storms over the Gulf pushing 
inland with the sea breeze. A slug of tropical moisture is
expected to arrive for the weekend, which would generate more
widespread showers and storms. At this time, it continues to
appear that the heaviest rainfall will be offshore, but it
deserves watching in the coming days to ensure that expectation
does not change.


.NEAR TERM [Through Tonight]...

Radar shows that rain showers from earlier in the day have largely
ended or moved out of the area, and temperature measurements
across the area have spiked in their wake. Combined with plenty of
humidity, the heat index has risen into triple digits across the
entire area, and reaching as high as 110 around Galveston Bay and
in other localized spots.

The main concern for the rest of the afternoon will be
temperature/heat index maximums and potential for rain. Satellite
imagery indicates that there may not be much potential for much
more in the way of rain except in the far east. There may be a
boundary that a late cell could spark off of up around
Bryan/College Station, but suspect we're lacking enough surface 
convergence on that boundary for anything to get going.

Meanwhile, Galveston is one degree shy of a record high even
without the offshore flow required for extreme heat on the island.
We're running out of time to warm up more, so I'm disinclined to
say there will be a record, but it's certainly possible.

.SHORT TERM [Monday Through Tuesday Night]...

Continued good agreement for the area of high moisture air lurking
over the Gulf on GOES TPW imagery to make its way to Southeast
Texas tomorrow. As such, I keep high chance PoPs in place along
the seabreeze, and even this may end up being a bit conservative.
We should see slightly lower temperatures as well with some more
cloud cover, at least near the coast. Farther inland, a run for
the upper 90s and even a 100 degree spot or two is still probable.


.LONG TERM [Wednesday Through Sunday]...

Summer summer summertime, time to sit back and watch what could be
best called as "typical Houston August" commands the bulk of the
week. With upper ridging sliding off to the west and allowing for
a bit of weakness over our area, temperatures and heat indices
should slowly back down from "absurdly hot" to "normal hot". This
is still pretty hot, and you should still expect a triple digit
peak heat index...just closer to 100 than 110. Along with that,
routine scattered shower and thunderstorm development, focused
primarily near the seabreeze, can also be expected.

Look for change to come this weekend as a tropical upper low,
potentially with a surface trough reflection at the surface makes
its way up the west coast of the Gulf from the Bay of Campeche.
Model guidance continues to have pretty strong agreement against
any tropical cyclogenesis, but we'll have to keep a close eye on
it in case anything changes. What this feature will have,
regardless of any development, is a strong slug of tropical
moisture. This should help fuel more widespread showers and storms
in Southeast Texas this weekend. We'll also have to look at heavy
rain potential - for now, model guidance agreement remains strong
that the heaviest rain will be well offshore, and as long as the
upper vort max takes the path that is progged, that is a good
expectation. It will be something to watch just to be safe, but as
of now there's no evidence that it will cause serious problems for
our area.

&&

.AVIATION [18Z TAF Issuance]...

Mainly VFR conditions through the duration of the TAF period are 
expected. Radar imagery currently shows some diurnally driven 
showers and thunderstorms developing south of I-10 and tracking 
northeastward towards the metro terminals. Scattered SHRA/TSRA 
should continue through around 00Z this afternoon around IAH, HOU, 
SGR, and CXO. Winds remain generally out of the S/SW at 10 to 15 
knots through the remainder of the afternoon, tapering off to around 
5 kts at inland sites overnight. Some higher gusts are possible with 
any developing thunderstorms. Expecting VFR cigs and visibilities at 
all terminals through the duration of the period. The possibility 
for a brief hour or two of MVFR cigs at northern sites tomorrow morning 
remains as in  previous days, but confidence not high enough to include 
in TAFs at this time.

Cady

&&

.MARINE...

A moderate onshore flow pattern continues tonight through Monday 
night, with south to southeast winds around 15 knots and seas around 
4 feet expected over the coastal waters. 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 
tonight through tomorrow afternoon. If traveling to the beach, 
remember to exercise caution if entering the water and only swim in 
areas with lifeguards on duty.

Cady

&&

.CLIMATE...

Hot and breezy today across the area with a warm start. Galveston 
looks to be setting a new record high minimum for the 18th of 
August.  86-87 degrees so far and the previous record holder was 84 
degrees in 2017. The record high was 96 degrees in 2011 and it has 
reached 95.
                     Aug 18th     18th        Aug 19th     19th
                     Record High  Record High Record High  Record High
                     Minimum/Year Year        Minimum/Year Year

Galveston GLS........84/2017      96/2011     84/2005      96/1995
Hobby HOU............81/2011      102/2011    80/2017      103/2011 
Bush IAH.............83/2010      108/1909    80/2018      107/1909
College Station CLL..81/1982      106/1945    79/2010      105/2011

So it probably goes without saying but we have been hot and remain hot
as would be expected in August. On top of that we need rain with nearly 
all of our counties averaging 575 on the KBDI or greater.

45

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL)  78  99  79 100  76 /   0  20   0  20   0 
Houston (IAH)          80  96  81  97  78 /  10  50  10  40   0 
Galveston (GLS)        85  91  86  91  83 /  20  40  30  40  20 

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...High Rip Current Risk through Monday morning for the following 
     zones: Brazoria Islands...Galveston Island and Bolivar 
     Peninsula...Matagorda Islands.

     Heat Advisory until 7 PM CDT this evening for the following 
     zones: Chambers...Coastal Galveston...Galveston Island and 
     Bolivar Peninsula...Inland Galveston.

GM...None.

&&

$$

NEAR TERM...Luchs
SHORT TERM...Luchs
LONG TERM...Luchs
AVIATION...Cady
MARINE...Cady 
CLIMATE...45