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National Weather Service Forecast Discussion

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596
FXUS64 KHGX 200340
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1040 PM CDT Sun Apr 19 2026

...New DISCUSSION, MARINE...

.KEY MESSAGES...

- Light showers/virga expected throughout the day on Monday,
  especially along and west of I-45.

- Chances for thunderstorms return Tuesday into Wednesday with the
  potential for another round of locally heavy rainfall.

- Gradual warming trend throughout the work week with shower/storm
  chances increasing again going into the weekend.

&&

.DISCUSSION...
Issued at 1040 PM CDT Sun Apr 19 2026

With drier air filtering in throughout the day, some of us got to
enjoy peaks of sunshine and others did not. Areas around Matagorda
Bay were probably like "y`all got to see the sun?!" as PW values
remained near or above the 75th percentile (~1.36") leading to
persistent cloud cover. Even though there`s a bit of drier air at
the surface, there is enough saturation in the mid to upper levels
paired with an embedded shortwave leading to light rain/sprinkles.
Some of the rain is likely evaporating before reaching the surface
(virga), but obs down there have been reporting a trace to 0.01" of
rain here and there so some droplets are definitely reaching the
surface. Keep this in mind when we talk about Monday`s forecast!
While the northeasterly winds will be lighter tonight, cloud cover
will be on the rise overnight as moisture increases due to surface
high pressure kicking out to the east rather quickly. Typically, the
coldest night behind a cold front is the second night following
FROPA. This is one of those rare occasions where the first night
(Saturday night) was the coldest.

Monday may feature slightly cooler daytime high temperatures though
due to a mixture of the 850mb high remaining nearby (cooler
temperatures aloft), mostly cloudy skies, and scattered light
rainfall. High temperatures are expected to range from the upper 60s
to low 70s. As moisture continues to increase from southwest to
northeast, an embedded shortwave will push through and pair with a
strengthening LLJ overhead going into late Monday leading to
scattered light rain showers. This light rain could be a bit
widespread especially in the afternoon hours. Current model trends
shows this mainly being a west of I-45 issue in the morning, then
spreading eastward in the afternoon as lift becomes more favorable
with the LLJ strengthening along with moisture expansion. Now if you
look at model radar reflectivity, then look at a model sounding
you`ll note that there`s quite a bit of dry air at the surface.
Recall from the previous paragraph that we had a similar environment
on Sunday and received some light rain/sprinkles at the
surface...but the dry air layer is anticipated to be a bit deeper on
Monday (if you believe the HRRR it`s around ~3km). Light
rain/sprinkles can`t entirely be ruled out for Monday, especially
along and west of I-45. There certainly will be some evaporation
above the surface, but some raindrops will survive the trek to the
ground. Certainly not a rainout, but something to note! The more
convective rainfall returns on Tuesday/Wednesday.

The increase in moisture is mostly due to the development of a
coastal trough/low that develops on Monday along the South TX coast.
This pairs with yet another embedded shortwave trough and some added
instability. With PW values near or exceeding the 90th percentile
(~1.58"), there is some potential for locally heavy rainfall. As a
result, WPC has outlined most of Southeast TX in a marginal risk
(level 1 of 4) of excessive rainfall on Tuesday and Wednesday. Keep
in mind that this is taking into account the somewhat more saturated
soils from Saturday`s heavy rainfall, which would lead to quicker
transitions to runoff. Current QPF totals show a general widespread
1-2", but locally higher amounts will be possible. With PW values
near the 90th percentile, we can anticipate rainfall rates to be in
the 2-3+"/hr range again.

While there is slight downward trend in moisture availability on
Thursday, there will be enough in place to pair with more embedded
shortwaves for some isolated to scattered afternoon convection. What
I haven`t mentioned up till now is that ridging aloft will be in
place throughout most of the work week. Outside of the rain chances,
there will be a general warming trend throughout the week (after
Tuesday) with high temperatures returning back into the mid to
upper 80s towards the end of the work week. Our attention then
turns to an upper level low moving through the CONUS towards the
end of the work week and an approaching frontal boundary, which
brings our next chance of showers/storms going into next weekend.

Batiste

&&

.AVIATION...
(00Z TAF Issuance)
Issued at 623 PM CDT Sun Apr 19 2026

Predominately VFR overcast conditions across our terminals this
evening, with some MVFR ceilings possible to the southwest around
LBX. Light and variable winds overnight will gradually increase
through the morning to 8-12 kts out of the east. LBX will have
the best shot at seeing shower activity Monday as the highest rain
chances reside well west of the I-45 corridor.

McNeel

&&

.MARINE...
Issued at 1040 PM CDT Sun Apr 19 2026

Small Craft Advisories remain in effect for the Gulf waters through
late Sunday night, but small craft will need to exercise caution
through at least Monday night. Winds and seas are expected to
take a while to subside below the caution flag threshold. Wind
speeds remain elevated, but will gradually transition to easterly
overnight and southeasterly by Monday night. An extended fetch of
moderate southeasterly winds around midweek will likely lead to
another round of increased seas, especially in the offshore Gulf
waters. This may lead to another period of caution flags on
Wednesday into Thursday for the Gulf waters. Scattered light rain
is expected on Monday, but chances for storms return Tuesday into
Wednesday as an upper level disturbance pushes through. Water
levels are expected to remain near 3.0 feet above Mean Lower Low
Water during high tide cycles through at least midweek.

Batiste

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  55  69  58  68 /  10  30  70  80
Houston (IAH)  57  70  61  71 /  10  30  50  80
Galveston (GLS)  68  74  69  77 /  10  40  50  70

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Should Exercise Caution through late Monday night
     for GMZ330-335-350-355-370-375.

     Small Craft Advisory until 1 AM CDT Monday for GMZ350-355-370-
     375.

&&

$$

DISCUSSION...Batiste
AVIATION...Young
MARINE...Batiste

NWS HGX Office Area Forecast Discussion