National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS64 KHGX 192324
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
624 PM CDT Fri Apr 19 2024

...New AVIATION...

.SHORT TERM...
(This evening through Saturday Night)
Issued at 233 PM CDT Fri Apr 19 2024

A LL boundary is currently draped across the region, extending
west to east from Colorado County to Liberty County. Scattered
shower activity has developed along the boundary this afternoon.
The boundary and its associated rain showers should drift
northward as the afternoon progresses into the evening. Also
monitoring some northward progressing showers offshore. Generally
speaking, any rainfall activity is expected to be isolated to
widely scattered. Couldn`t rule out an isolated thunderstorm.
Temperatures are mostly in the low 80s under mostly cloudy skies
with humid conditions. Temps may warm a couple more degrees
before sunset yields to another cloudy muggy night in the low 70s.
Areas north of the boundary are expected to fall into the 60s.

While we enjoy this humid afternoon with a rain shower here and
there, a broad mid/upper trough with a leading mid/level
southwesterly jet streak is pushing eastward across SW CONUS. By
tomorrow, and especially tomorrow night, this feature will provide
various synoptic mid/upper forcings that will support widespread
showers and thunderstorms. The UL flow at 300-250mb will become
increasingly diffluent while mid/upper west-southwesterly shear
gradually increases in the 700-500mb layer. This shear orientation
will be roughly parallel to the aforementioned boundary, which
will be stalled near our northern counties as we begin our
Saturday. Eventually, building sfc high pressure from the north
will push the boundary southward. Deep LL convergence (sfc-850mb)
associated with the boundary is apparent in the guidance. Global
and HREF ensemble means indicate a high chance of widespread
1.70-1.90" PWAT values with some potential of exceeding 2.00".

So what do the these parameters mean for our Saturday? Though the
primary shower/thunderstorm concern is for Saturday evening/night,
a series of vort maxes embedded in the flow aloft could foment
scattered shower and thunderstorm activity as early as Saturday
afternoon, especially north of I-10. HREF members also suggest we
shouldn`t rule out isolated to widely scattered showers in the
morning. PWs, UL diffulence, mid/upper shear, and PVA all begin to
approach their peak late afternoon and into the evening hours on
Saturday. This is when heavier showers/storms are more likely to
be supported, especially near the boundary. Now here is where
things get tricky. Where will this boundary be? How fast it will
push southward? Will it stall? There is high confidence that the
mid/upper levels will support plentiful ascent for widespread
showers/thunderstorms. There is high confidence in favorable
conditions for heavy rainfall. But there is less confidence in the
exact position of the LL boundary when these other parameters
line up. This has significant implications on where the heaviest
rainfall occurs. The best chance of heavy rainfall (where locally
several inches of rainfall could occur over a short period of
time) continues to be north of I-10. Widespread totals north of
I-10 are still forecast to be in the 1-3 inch range. But locally
much heavier totals are likely in locations that receive the
heaviest showers and thunderstorms late Saturday afternoon into
the overnight. The Weather Prediction Center has issued a slight
(level 2 of 4) risk of excessive rainfall north of I-10. Farther
south, the risk is marginal (level 1 of 4).

Self

&&

.LONG TERM...
(Sunday through next Thursday)
Issued at 233 PM CDT Fri Apr 19 2024

Rain should be coming to an end Sunday morning as this system pushes
out of here and the front makes further southward progress off the
coast. Cooler, drier air will be filtering in, though clouds might
hang around for a good part of the day before scattering out Sunday
night.

Surface high pressure will begin moving off to the east Monday,
though we`ll still probably see some recycled drier air backdoor
into parts the region at times. It probably won`t be until midweek
when we see more noticeable dewpoint modifications and warming
overnight lows.

A prevailing onshore flow will be the rule during the second half of
the workweek into the weekend. Slight chances of mainly diurnally
driven shra and/or tstms are a possibility, though some subtle mid-
upper ridging will be a limiting factor. 47

&&

.AVIATION...
(00Z TAF Issuance)
Issued at 618 PM CDT Fri Apr 19 2024

Primarily VFR conditions right now with the exception of LBX with
MVFR CIGs and GLS with IFR CIGs. Isolated SHRA continuing along
the sea breeze this evening, expected to end near sunset with loss
of daytime heating. CIGs and some VSBY drops expected tonight
with widespread MVFR expected. Chance of overnight IFR also
increasing and will likely be updated in next TAF cycle. Any sites
at IFR should improve to MVFR by mid to late morning Saturday.

&&

.MARINE...
Issued at 233 PM CDT Fri Apr 19 2024

Onshore flow will persist into Saturday. Periods of haze and fog can
be anticipated but it is not expected to become dense. The next cold
front and associated showers and thunderstorms will push off the
coast late Saturday night followed by moderate north and northeast
winds and building seas in its wake. Small Craft Advisories will
likely be required. As high pressure begin moving east of the region
on Monday, onshore winds will resume. As the pressure gradient
tightens Wed-Fri, look for a fetch of moderate southeast winds to
set up across the Gulf during the second half of the week. 47

&&

.HYDROLOGY...
Issued at 333 PM CDT Fri Apr 19 2024

Conditions are favorable for some locally heavy rain Saturday evening
an overnight. Though there is some uncertainty exactly where it will
fall, latest guidance tends to favor locations north of I-10.
Several inches of rain in a short time period will runoff and could
pose a flash flood threat. Residents north of I-10 should be on the
lookout for rises on area creeks, streams and rivers. Contingency
forecasts highlight the potential for minor river flooding.
Additional impacts are possible for smaller tributaries. Lastly,
area reservoirs are full, so any runoff will need to be released.
Pay attention to updated forecasts. 47/KLG

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  67  75  53  63 /  20  80  90   0
Houston (IAH)  71  81  58  66 /  20  60  80  20
Galveston (GLS)  71  77  61  70 /  10  20  80  30

&&

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

$$

SHORT TERM...Self
LONG TERM....47
AVIATION...Adams
MARINE...47