Skip to main content.

National Weather Service Forecast Discussion

Related quick links> 5 Day Forecast, Local Advisories, Drought Monitor, UV Forecast, Air Quality Forecast 
411
FXUS64 KHGX 201124
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
624 AM CDT Mon Apr 20 2026

...New AVIATION...

.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...
(12Z TAF Issuance)
Issued at 614 AM CDT Mon Apr 20 2026

VFR conditions are expected through the next 12-18 hours. Cigs
will gradually lower through the day as moisture increases, but so
categorical degradations are expected. Chances for SHRA will
increase from SW to NE this afternoon into tonight. TSRA probs are
low enough to keep mention out of the TAFs this cycle, but will
continue to be monitored for tonight heading into Tuesday. Winds
will generally remain out of the east around 6-12 kt, except GLS
where gusts of 20-25 kt remain possible.

Young

&&

.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)  69  58  68  62 /  30  70  80  40
Houston (IAH)  70  61  71  65 /  30  50  80  50
Galveston (GLS)  74  69  77  71 /  40  50  70  70

&&

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

&&

$$

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

NWS HGX Office Area Forecast Discussion