553
FXUS64 KHGX 050433
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1133 PM CDT Sat May 4 2024

...New AVIATION...

.SHORT TERM...
(This evening through Sunday Night)
Issued at 401 PM CDT Sat May 4 2024

Key Messages:

Flood Watch in effect through Sunday evening for portions of SE
Texas

Widespread 1-3" with isolated higher amounts of 4-8" possible
tonight through Sunday night (highest amounts generally along and
north of I-10)

Showers continuing to move through Polk County this afternoon. With
a warm, moist, and unstable environment isolated activity could
continue north of I-10 through the afternoon.

Our attention turns to tonight through the Sunday night period. SE
Texas remains under a warm, moist, and unstable airmass. The current
environment will set the stage for the next heavy rainfall event. A
shortwave trough will bring another thunderstorm complex that will
move across Central Texas later tonight. The MCS is projected to
arrive at our western border (Brazos Valley/Piney Woods) after
midnight. Showers and thunderstorms will increase in coverage and
spread SE Sunday as another MCS makes its way through the area.
Soundings reveal a deep saturated layer, PWs near 1.75-2", and a
deep warm cloud layer. This, in addition to a developing LLJ will
contribute to high precipitation efficiency, and heavier rainfall.
Precipitation totals will average 1-3" with smaller areas receiving
higher amounts of 4-8" (generally along and north of I-10).

Unfortunately, much of this area has already been impacted by heavy
rain in the last 7 days, so it will not take much to trigger flash
flooding once again. For this reason, WPC has kept the Brazos
Valley, Piney Woods, and down to the far NW portion of Harris County
in a Slight Risk for Excessive Rainfall while much of the rest of
the area (with the exception of the immediate coast) remains in a
Marginal Risk for today into tonight.

For Sunday the majority of the area will be in a Slight Risk for
Excessive Rainfall as rounds of showers and storms continue to move
through. There is a bullseye for the Moderate Risk area that is
focused over portions of Houston County, much of the Brazos Valley,
down to the I-10 corridor and east into Liberty County. With many
locations within these areas having experienced the most impacts
from recent rainfall, any rainfall over these areas would contribute
to or worsen existing flooding.

In addition to the flood threat, SPC has placed much of the area in
a Marginal Risk and a sliver of the Brazos Valley in a Slight Risk
for severe weather tonight. For tomorrow, the SW CWA is in a Slight
Risk and the rest of the area in a Marginal Risk. There is
sufficient instability with this stronger shortwave, so a few storms
could become strong to severe and produce large hail and damaging
winds.

As this event unfolds, please make sure to have multiple ways to
receive warnings, avoid driving across flooded roads, and do not
drive around barricades. Remember, "Turn Around Don`t Drown!"

Adams

&&

.LONG TERM...
(Monday through next Friday)
Issued at 401 PM CDT Sat May 4 2024

The heavy rain threat finally comes to an end on Monday allowing for
rivers to have an extended period to drain. Widespread rain chances
don`t return till the end of the work week, but with southwesterly
flow aloft dominating throughout much of the week we`ll move into a
period of above normal temperatures. Subtle ridging briefly builds
in on Monday allowing for temperatures to increase into the upper
80s...and the temperature climb doesn`t stop there. An upper level
low will persist in the Northern Plains into midweek, which kicks
the ridge axis eastward...but helps to induce southwesterly flow
aloft. 850mb temperatures subsequently surge into the 99th to MAX
percentile (NAEFS/GEFS), so expect temperatures from Tuesday into
the end of the work week to be in the upper 80s to low 90s.

The hottest temperatures are expected on Wednesday and Thursday with
widespread highs in the low to mid 90s. With grounds already
saturated though, this may lead to higher amounts of humidity so
we`ll have to monitor heat index values. Wednesday and Thursday are
again the days to monitor as heat index values look to range from 98-
105F. Given the early onset of this heat (our bodies aren`t
acclimated to the heat just yet) in addition to lingering effects
from the previous rainfall in some areas (power outages & clean-up
efforts), there is at least some chatter around here about the
potential for a Heat Advisory.

The southwesterly flow aloft means we remain in good positioning for
shortwaves to pass through and generate some showers/storms. These
aren`t anticipated to be widespread though. The first rain chance
comes on Wednesday, but as of right now it appears that most of the
convection will dissipate before it reaches Southeast TX from the
north thanks to a subsidence inversion layer aloft. We`ll see if the
LLJ can help overcome that cap, but it doesn`t look too likely at
the moment (never say never though). Our best chance of rain is at
the end of the work week as a weak frontal boundary approaches. Rain
chances first appear across the Brazos Valley/Piney Woods on
Thursday afternoon, then the rest of Southeast Texas Friday and into
the weekend.

Batiste

&&

.AVIATION...
(06Z TAF Issuance)
Issued at 1133 PM CDT Sat May 4 2024

Starting to become active in the CLL-UTS areas with several strong
TSRA, and this increasing SHRA/TSRA trend can be expected overnight
across the area along with lowering ceilings to mainly MVFR and possible
IFR when in/near any storms. Locally heavy rain is possible too. Will
carry lingering SHRA/TSRA in the TAFs for the morning and afternoon
hours (roughly 12Z-24Z) along with some lifting ceilings. Confidence
remains on the high side for the first 6 to 12 hours of the TAFS and
on the low side for the last 12 to 18 hours of the TAF. Heading into
tomorrow evening/night, will carry MVFR ceilings/visibilities for now.

42

&&

.MARINE...
Issued at 401 PM CDT Sat May 4 2024

Moderate to occasionally strong onshore winds and elevated seas will
prevail through the weekend and into next week. Winds and seas will
reach Small Craft Should Exercise Caution levels at times. Shower
and thunderstorm chances continue over the weekend, but a more organized
line of thunderstorms is expected to approach the coast early Sunday
morning, potentially bringing gusty winds. Drier conditions return to
the area during the upcoming week.

42

&&

.HYDROLOGY...
Issued at 401 PM CDT Sat May 4 2024

The Flood Watch has been extended to 7pm CDT Sunday evening and
expanded to now include Austin/Colorado Counties. Additional heavy
rainfall is expected in areas that have already received excessive
amounts of rain over the past few days. At this time, we are
anticipating an average of an additional 1-3" of rain with smaller
areas of 4-8" possible within the watch area. With soils already
saturated, this will likely lead to quick runoff and rapid responses
along area rivers/creeks/bayous.

Moderate to major river flooding continues for parts of Southeast
Texas, particularly along portions of the Trinity, San Jacinto, and
Navasota rivers. The following river points are either at or
forecast to go into Major flood stage:

- Trinity River (Riverside): Major Flood Stage
- Trinity River (Liberty): Major Flood Stage
- Trinity River (Goodrich): Major Flood Stage
- Trinity River (Moss Bluff): Moderate forecast to go to Major
- West Fork San Jacinto (Conroe): Major Flood Stage
- West Fork San Jacinto (Humble): Major Flood Stage
- San Jacinto (Sheldon): Major Flood Stage
- East Fork San Jacinto (New Caney): Major Flood Stage
- Navasota River (Normangee): Major Flood Stage Remember to heed
  any instructions from your local officials and to never travel
  through flooded areas or roadways. TURN AROUND, DON`T DROWN.
  Please monitor updated forecasts via the NWS AHPS website and/or
  the new NWS NWPS webpage (https://water.noaa.gov/) as the river
  flood threat continues.

Batiste

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  69  81  70  86 /  70  70  10   0
Houston (IAH)  72  82  72  87 /  50  60  20  10
Galveston (GLS)  73  80  73  82 /  30  60  20   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flood Watch through Sunday evening for TXZ163-164-176>179-
     195>200-210>214-300-313.

GM...Small Craft Should Exercise Caution through Sunday evening for
     GMZ370-375.

&&

$$