Special Weather Statement, NWS Houston/Galveston, TX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
347 PM CDT Fri Apr 9 2021

.SHORT TERM [Through Saturday Night]

The main weather concern is the potential for strong to severe
thunderstorms this afternoon and tonight; however, the main
limiting factor continues to be a strong cap. This limiting
factor continues to keep our confidence levels low to moderate for
any convection initiation across the region.

Southerly flow continues to increase this afternoon with gusts
from 20 to 30 mph across most of the region. This pattern will
continue to draw higher sfc dew points, ahead of an approaching
surface low and associated sfc boundary. The low is currently
moving across northwest TX/southwest OK while a dryline is
bisecting TX from north to south, just west of the Brazos Valley.
Early this afternoon, a broad region of thunderstorms began to
develop across the ARLATEX region, with a few showers/lightning
strikes developing over Houston county. This activity is aided by
decent southerly LLJ and steep lapse rates. Will continue to
monitor the evolution of these storms and the potential for some
clearing across southeast TX over the next few hours as any break
in clouds may help spark any convection activity. The environment
still looks conducive for strong to severe thunderstorms. 18Z
soundings still suggest MUCAPE 2,500-3,500 J/kg this afternoon and
evening with effective shear (EBWD) around 30-40 kts under very
steep low to mid- level lapse rates. However, with cloud cover and
850:700 mb temperatures in the 12-16 C range any potential
convective updraft will have to overcome the strong capping
inversion. If storms develop this afternoon and evening, discrete
storms will be the primary storm mode through this evening as
0-6km shear remains quasi- normal to the boundary. The greatest
threat will be along and north of I-10 with large hail and
damaging winds as the main risks. An isolated tornado cannot be
ruled out given strong favorable conditions. As we progress into
the evening hours, the main focus for showers and thunderstorms
will be along the convergence zone as the cool front moves
southeast into the region. The front will move across our
northwestern counties around midnight, then moving southeast into
the coast by daybreak. Will continue to monitor the passage of
this front, as strong to severe storms will be possible along the
boundary. The main areas of concern will be across our northwest
and northern counties with damaging winds as the primary severe
weather risk. The severe weather threat gradually diminishes as
the front moves into the Houston metro area and into the coastal
zones by early Saturday morning.

Another concern early Saturday morning will be the potential for
fog, some locally dense, ahead of the front. The greatest risks
look possible along the coast as soundings suggest a well-
saturated low- mid layer under a persistent southerly flow.

North to northeast winds are expected on Saturday; however,
afternoon temperatures will once again climb into the mid 70s to
low 80s. Surface ridging anchored over northeast TX will result in
relatively dry conditions and light northeast to east winds
through the end of the short-term period.

05

.LONG TERM [Sunday Through Friday]...

E/SE winds are expected to be in place across SE TX by Sun with low-
level moisture holding off its return until Mon. These increased PWs
(from 1.3 to 1.8 inches) are forecast to persist as a large east-to-
west swath across the northern Gulf/and adjacent states for most of
next week. The moisture is expected to help fuel the development of
scattered SHRAs (and isolated TSRAs) each day given the nearly cons-
tant approach/passage of weak upper level disturbances (embedded in
the generally zonal flow aloft), as well as weak surface convergence
along/near the various frontal boundaries lingering over the region.
Timing of said disturbances should be one of the main problems with
this pattern and the upcoming forecast and just kept with the broad
brushing of mostly 20-30% POPs each day next week. And with regards
to temperatures (even with the persistent rain chances/clouds), the
overall trend(s) should lean more toward the warmer side of normals
next week. There will likely be a day or two here and there that'll
be cooler per the various frontal boundaries (for northern counties
in particular), did keep with mostly lower to mid 80s for highs and
mid to upper 60s for lows through Mon-Weds. Perhaps slightly cooler
Thur/Fri. 41

&&

.AVIATION [18Z TAF Issuance]...

Some clearing will be possible around KCLL by mid-afternoon; but
continued with MVFR to low-end VFR conditions across most
terminals this afternoon and evening. A few showers and storms
look possible north of KUTS; however, with strong cap in place,
storms look to remain further north of our terminals. Gusty
southerly winds from 20-25 kts are expected through early evening.
A cold front will move across the region after midnight. MVFR to
IFR conditions due to low visibility and a few showers will be
possible ahead and along the boundary. KLBX and KGLS could see low
visibility through the end of the TAF period.

05

&&

.MARINE...

The tightened gradient ahead of the next cold front will help keep
SCEC conditions in place over the offshore waters through the rest
of the afternoon and early evening. For the overnight hours, there
is still a chance of some patchy sea fog over the bays/intracoast-
al waterways as the onshore flow remains in place. But we should be
seeing improved conditions by sunrise with the passage of the cold
front into our marine waters. Isolated showers/thunderstorms could
accompany this line as it moves southward into the Gulf. Otherwise,
look for generally moderate N winds to develop by Sat afternoon...
then decreasing to a light NE flow for Sat night. Mostly light E/SE
winds starting on Sun are forecast to prevail through much of next
week. However, there are also indications of increasingly unsettl-
ed weather next week as a series of weak upper level disturbances/
deepening moisture help produce scattered showers/isolated thunder
storms each day. 41

&&

.FIRE WEATHER...

The oft-neglected side of cold fronts shoving dry lines much
further eastward than mixing alone allows shows up in our forecast
for this weekend. Yes, we will get a taste of some unseasonably
dry air. Right now, relative humidity is forecast to fall below 30
percent, and to around 25 percent in isolated spots both Saturday
and Sunday. At the same time, we'll be expecting moderate to
occasionally gusty northeast winds. The strongest winds should be
Saturday morning before humidity gets particularly low. On Sunday,
winds should be lighter still, and begin to veer more easterly to
southeasterly as the day goes on. With winds becoming more
onshore, humidity will be higher as the work week begins.

This misalignment of the strongest winds and lowest humidity make
it pretty likely that we will not realize any critical fire
weather conditions this weekend. But, we are starting to reach
that time of year when air this dry is becoming less common, and
when paired with moderate winds, this weekend could be more
conducive for fire growth than typical for early April - for
better or for worse. This would be particularly true in
contiguous, grassy fuel beds, which will be most responsive to the
low humidity.

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL)  58  78  51  85  60 /  20   0   0   0   0
Houston (IAH)          65  81  56  84  63 /  30  10   0   0   0
Galveston (GLS)        69  79  65  81  68 /  20  10   0   0   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...None.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 10 PM CDT this evening
     for the following zones: Waters from Freeport to Matagorda
     Ship Channel TX from 20 to 60 NM...Waters from High Island
     to Freeport TX from 20 to 60 NM.

&&

SHORT TERM...05
LONG TERM...41
AVIATION...05
MARINE...41
FIRE WEATHER...Luchs

Special Weather Statement
National Weather Service Houston/Galveston TX
544 PM CDT Fri Apr 9 2021

TXZ163-092315-
Houston TX-
544 PM CDT Fri Apr 9 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN HOUSTON COUNTY UNTIL
615 PM CDT...

At 541 PM CDT, Doppler radar was tracking strong thunderstorms
between Crockett and Weches, moving northeast at 40 mph.
Intensification is possible, and a severe thunderstorm warning
might be needed.

Half inch hail and wind gusts up to 50 mph will be possible with this
storm.

Locations impacted include...
Kennard and Weches.

A Severe Thunderstorm Watch remains in effect until 1100 PM CDT for
southeastern Texas.

LAT...LON 3157 9525 3158 9517 3156 9514 3155 9515
      3154 9514 3152 9510 3150 9509 3149 9511
      3147 9510 3146 9507 3147 9506 3144 9504
      3144 9501 3142 9500 3141 9498 3140 9498
      3139 9496 3126 9539 3148 9538 3159 9527
TIME...MOT...LOC 2241Z 239DEG 49KT 3147 9517