Flooding in Texas, February 10, 2024

Area Forecast Discussion
National Weather Service Houston/Galveston TX
515 PM CST Sat Feb 10 2024

...New AVIATION...

.SHORT TERM...
(This evening through Sunday Night)
Issued at 302 PM CST Sat Feb 10 2024

Rain showers with a few rumbles of thunder got an early start this
morning and drifted northward along a shortwave embedded in the flow
aloft. These storms reached a "stopping" point once they converged
with a quasi-stationary frontal boundary located over the Brazos
Valley/Piney Woods. This resulted in a band of slow-moving moderate
to heavy rainfall that persisted over this area for a few hours and
resulted in street flooding in and around Bryan/College Station and
Madisonville. Even though these spots only saw between 1.5-2.5" of
rain, the saturated soils from the previous rainfall events led to
quick runoff which in turn led to the street flooding today. With
that increased runoff in mind, we'll have to monitor for river
responses as well especially along the Brazos (more on that in the
Hydrology section below). We definitely had/have the environment
favorable for heavy rain to develop for areas north of I-10 with
long-ish and skinny CAPE, mid/low RH greater than 80%, PW values
WELL above the 90th percentile (~1.33" vs 1.6"-1.8"), a warm cloud
layer greater than 12,000 ft, weak frontogenetic forcing along the
frontal boundary, parallel flow between upper levels and the frontal
boundary, and a weak but still viable LLJ around 30-40 knots. This
explains why there is a slight risk of excessive rainfall (level 2
out of 4) for this portion of Southeast TX for today.

The first round of rain will come to an end late tonight and there
will be a brief lull before the next round moves in on Sunday
morning...but before that we have some fog to tend with. Numerous
models depict the same story tonight with widespread fog developing,
especially near the coast where sea fog will develop shortly after
sunset. The persistent moisture and decreasing winds will allow for
patchy to areas of dense fog to spread inland and may end up
encompassing all of Southeast TX by early Sunday morning. So, those
that have plans to hit the roadways on Sunday morning should plan
some extra time to take the proper precautions for fog safety. As
this is going on, the upper level trough with an embedded upper low
moves through western TX and generates surface low pressure over
South TX on early Sunday morning. This pushes a warm front back
inland (thus adding to our fog potential) along with a subsequent
instability axis within the warm sector. There'll be a bit more
instability to work with on Sunday compared to today, but there'll
be a cap in place 800mb that gets stronger the further south you go.
Instability is also higher the further south you go, so that creates
an interesting scenario...if the cap were to be broken then we could
see some strong to severe storms. This appears more likely east of I-
45, which is where SPC has their slight risk of severe weather
(level 2 out of 5) for Sunday. Elsewhere, there is a marginal risk
(level 1 out of 5).

The cap will be the key to this event as some high-res guidance
depicts a decaying MCS moving through the Brazos Valley on Sunday
morning while some show just scattered showers. There is way more
confidence in drier air filtering behind the cold front as it pushes
through on Sunday morning/afternoon. PW values will go from near the
90th percentile in the morning to near the 10th percentile (~0.33")
in the afternoon...so it's quite the drop. The upper level low is a
slow mover though and doesn't push past us until Monday, so some
cloud cover will linger even behind the front on Sunday. As far as
temperatures go, expect highs in the upper 60s to mid 70s today and
approaching the upper 70s on Sunday with some pre-frontal heating.
Overnight temperatures will see the biggest difference as we go from
the upper 50s to low 60s tonight to the low to mid 40s on Sunday
night. It'll finally feel like it's February again rather an early
preview of Spring...

Batiste

&&

.LONG TERM...
(Monday through next Friday)
Issued at 302 PM CST Sat Feb 10 2024

Surface high pressure will move in from the west during the day
Monday. Winds are expected to decrease as the pressure gradient
relaxes in the afternoon. CAA will keep temperatures on the cooler
side, with highs in the 50s, inland lows in the 30s, and coastal
lows in the 40s Monday into Monday night.
High pressure will pass over SE Texas Tuesday, and E/SE winds will
develop by Tuesday evening as it continues off to the east. As
expected, onshore flow will trigger a warming trend with highs in
the 60s to lower 70s around the middle of the week.

Rain chances will return to SE Texas on Thursday as PWATs respond to
the onshore flow and increase to around 1-1.5". This will occur
ahead of an upper level trough that approaches from the Baja,
California area. At this time it looks like rain chances may
continue into Friday as PWAT values continue to trend upward and a
coastal low develops in the NW Gulf. With this being later in the
period, location/timing of this next system is likely to change, but
in any case, more rain is in the forecast.

Adams

&&

.AVIATION...
(00Z TAF Issuance)
Issued at 506 PM CST Sat Feb 10 2024

While there is currently a mixture of VFR to MVFR conditions
across the area with CIGs between 1500 and 4000ft, we can expect
deteriorating conditions after sunset with increasing coverage of
showers and isolated thunderstorms, lowering CIGs, and patchy fog.
Another round of thunderstorms will move through CLL and UTS
between 2 and 4z this evening, then we can expect just scattered
SH across much of the area overnight until a cold front arrives
tomorrow. CIGs will lower to 300-700ft with patchy, but dense at
times, fog developing after sunset and continuing until the FROPA
tomorrow morning. This FROPA should pass through CLL around
13-14z, IAH around 15-17z, and then through GLS around 18-21z.
Showers will accompany the frontal passage with TS expected at the
northern terminals (CLL, UTS, and possibly CXO). While the FROPA
will bring in better, drier conditions, MVFR CIGs will likely
linger for a few hours post-front with VFR conditions arriving in
the late afternoon or evening hours.

Fowler

&&

.MARINE...
Issued at 302 PM CST Sat Feb 10 2024

Light to moderate winds and cold shelf/bay waters will allow for sea
fog to develop across the bays/nearshore waters through Sunday
evening, especially during the overnight hours. This sea fog could
become locally dense at times, bringing visibility down to 1 nm or
less. A Marine Dense Fog Advisory is in effect from 6PM this evening
through 9 AM Sunday. The chance of showers and storms will continue
through Sunday, courtesy of a slow/stalled cold front. This cold
front should push offshore Sunday night, with dry and breezy
conditions developing in the front's wake. These moderate to strong
northerly winds will likely warrant Small Craft Advisories through
Monday. Winds should relax Monday night with onshore flow returning
Tuesday evening. Light winds and low seas persist afterwards through
mid next week.

Adams

&&

.HYDROLOGY...
Issued at 302 PM CST Sat Feb 10 2024

Saturated soils from the previous rainfall events combined with
1-3" of rainfall occuring in areas that received the bulk of the
previous rain has led to increased runoff and street flooding.
We've received multiple reports of street flooding occuring in
College Station and Madisonville. With rainfall continuing across
portions of the Brazos Valley and the Piney Woods and an
additional round of rainfall expected on Sunday morning, we'll
have to monitor area rivers/streams/bayous for responses
especially along the Brazos and Trinity Rivers. Another round of
localized street flooding cannot be ruled out with the next round
of storms on Sunday morning, but it's worth noting that it'll move
quicker than today's showers/storms.

You can monitor current and forecast conditions at this weblink:
water.weather.gov/ahps2/forecasts.php?wfo=HGX

Batiste

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)	  58  69  42  57 /  50  80   0   0
Houston (IAH)			  64  76  44  59 /  40  70   0   0
Galveston (GLS)			  62  71  46  59 /  20  40   0   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Dense Fog Advisory until 9 AM CST Sunday for GMZ330-335-350-355-
     370-375.

&&

SHORT TERM...Batiste
LONG TERM....Adams
AVIATION...Fowler
MARINE...Adams