660
FXUS64 KHGX 310543
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1243 AM CDT Sun Aug 31 2025

...New DISCUSSION, MARINE...

.KEY MESSAGES...
Issued at 1243 AM CDT Sun Aug 31 2025

- An environment supportive of localized heavy rain continues
  through the weekend. A slight risk of excessive rain (threat
  level 2 of 4) is in place Sunday, with most of the area seeing a
  marginal risk for excessive rain (threat level 1 of 4) on Labor
  Day.

- After the holiday, expect rain chances to decrease as drier air
  filters into the region. Potential for showers and storms may
  start to work back in late in the week.

- High temperatures should remain relatively near seasonal
  averages; a bit cooler where it rains, a bit warmer where it
  does not. At night, lows should gradually slide through the 70s
  towards the upper 60s inland as the drier air filters in.

&&

.DISCUSSION...
Issued at 1243 AM CDT Sun Aug 31 2025

If you were a fan of Saturday`s weather around the area, I got
some real good news for you about the rest of the holiday weekend,
because it`s going to largely be a lot more of the same for the
next couple of days. And it`s certainly got its perks, as some
folks up around the Pineywoods and east of the Houston metro
had temperatures stay in the lower half of the 80s. Of course, the
price of that was plenty of showers and storms, which isn`t
necessarily ideal for a holiday weekend. Given our,
uh...reputation...with holidays though, getting away with a single
flood advisory for some heavy street ponding for some inside the
Beltway isn`t that bad.

Sunday...looks like more of the same. We will continue to have
some of the ingredients for heavy rain - a stalled boundary with
precipitable water around the 90th percentile, and an upper ridge
that has retreated enough that multiple shortwave troughs will be
making their way through the pattern in the northwest flow
overhead. Soundings indicate a skinny CAPE profile, with
sufficient instability for stronger storms in a moisture-laden
atmosphere.

But...not all of the holes in the swiss cheese model of
disasters appear to be lining up, which should mitigate a more
widespread heavy rain threat, and keep concerns limited to
where/if locally heavy rain falls over a vulnerable spot (low-
lying, poor drainage, etc). For instance, Corfidi vectors aren`t
terribly alarming - they aren`t really favorably large, but also
aren`t indicative of very slow movement and/or backbuilding. We`d
instead need other mesoscale features to keep storms from moving,
similar to what we saw over the Houston core earlier in the day.
Additionally, the low-level moisture transport is somewhat
shallow. 925 mb moisture transport vectors are pretty solidly
onshore and working at pumping moisture into Southeast Texas, but
there`s virtually no moisture transport at 850 mb, instead looking
more steady state.

Ultimately, there`s certainly some concern for localized flooding
issues emerging, and there is a slight risk for excessive rain
(threat level 2 of 4) across the area tomorrow as we have a second
day with scattered to numerous storms expected to pop up across
the area. HREF probabilities for 1 inch per hour rain rates do
appear as a speckling of low signal across the area, but perhaps
more west of the Brazos and right on the coast than other places.
Again, an indication that there`s some support for big rainers
there, but no strong signal for any given spot. There was some
consideration given to issuing a flood watch, but without the
confidence for impacts to a specific area, we`re opting to hold
off...for now. Should a better alignment of concerning factors
begin to emerge, we could always opt to issue one on a shorter
fuse.

Monday...more or less run it back. The stalled front does look
like it should drift a little farther south, and that will shift
low level flow more northeasterly, at least farther inland. This
will start to filter in some drier air, but we should still be in
a fairly moist environment with continued vort maxes traversing
the northwest flow aloft. With a bit of the edge taken off, WPC
stepped things back to a marginal risk for excessive rain (threat
level 1 of 4) for all but our northernmost reaches, which will be
most likely to see the tap turn off as moisture levels start to
back down.

The rest of the week...doesn`t seem to have quite as much to say
about it. Rain potential will back down into the middle of the
week, with the initial front pushing off into the Gulf, and a
reinforcing front solidly establishing the lack of rain potential
arriving late on Tuesday (or early Wednesday?). I don`t think
Tuesday is entirely dry, and perhaps not even following days, but
whatever rain there is should be pretty scarce. Of course, we can
also anticipate daytime temperatures to go up with that as well.
While cloudy, stormy Sunday/Monday see highs mostly in the 80s or
around 90 at most, we`ll see highs drift back up into the 90s for
once the drier air moves in. BUT! the drier air will help the
humidity situation be less oppressive, and allow for a bit more
cooling at night thanks to the lower temperature floor the
decreased dewpoints set! By Wednesday night, I`m forecasting lows
in the 60s for all but those right on the Gulf or in the Houston
urban heat island. This likely does not mean cool nights for me,
but I`m happy for y`all that get them.

Now, for the last few nights, you`ve caught me on here trying to
be cautiously optimistic about a late week front.
And...honestly...a lot of the things that I`ve been pinning my
hope on are still there. Anomalously high U winds at 500 mb with
anomalously low V winds, 850 temps at or below the 10th percentile
pushing as deep as the Red River Valley and parts of North Texas
late in the week... I`m not asking for much here, just some days
with highs closer to 80 than 90! And yet...the NBM remains
stubbornly warm into the weekend, with widespread highs around 90.
Even worse, cooler Euro Ensemble 850 temps have pulled back
farther north, closer to what NAEFS has been showing. It`s got a
forecaster wondering if he`s been wishcasting. And...maybe I am. I
do note that LREF`s primary cluster does show a stronger upper
trough than the grand mean, and even though it doesn`t appear to
have noticeably cooler surface temps anymore, I`d rather a
stronger upper trough supporting an incoming front than a weaker
one (please do not look at any of the other clusters, which are
at best slower and at worst stronger than the grand ensemble
mean). So, after all that, I continue to stick near the
deterministic NBM numbers, with a slight hedge to the cooler side.
I continue to think that the error of the NBM`s forecast will
continue to be towards the side of lower temps, but there is not
yet enough evidence out there to push me to decisively push the
forecast that way, and that error ultimately may not be very
large, even if it occurs.


&&

.AVIATION...
(00Z TAF Issuance)
Issued at 631 PM CDT Sat Aug 30 2025

SHRA/TSRA activity is expected to diminish this evening, with
areas of MVFR and potentially IFR developing overnight. SHRA may
develop again late tonight (after 09Z), mostly in our southern
and coastal zones. By mid morning Sunday, the chance of shra/tsra
increases from north to south. For now, chance of seeing at least
rain is high enough to warrant VCSH mention in most of the TAFs,
while TSRA is limited to a PROB30. That being said, we may have to
upgrade the TSRAs to TEMPO groups when confidence increases
regarding TSRA coverage and timing. Winds will generally be light
and variable. But higher winds are likely in the vicinity of TSRA.

&&

.MARINE...
Issued at 1243 AM CDT Sun Aug 31 2025

A stalled frontal boundary will continue to bring scattered
showers and thunderstorms to the region through the holiday
weekend. Some of the stronger storms will be capable of producing
locally heavy rainfall. Winds outside of storms will generally be
light and variable. However, locally stronger winds in the
vicinity of thunderstorms should be expected. Additionally, the
environment will continue to be supportive of isolated
waterspouts, and we may see more on top of those observed during
the day on Saturday. While rain chances should dwindle inland,
daily isolated to scattered showers and storms may persist over
the Gulf.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  75  83  72  87 /  40  80  40  50
Houston (IAH)  77  85  75  89 /  30  60  30  50
Galveston (GLS)  80  87  79  87 /  30  50  50  70

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

DISCUSSION...Luchs
AVIATION...Self
MARINE...Luchs