Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

FXUS64 KHGX 101717

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1217 PM CDT Sat Jun 10 2023

...New AVIATION...

(18Z TAF Issuance)
Issued at 1203 PM CDT Sat Jun 10 2023

VFR conditions are mainly anticipated this afternoon. That said,
we are planning to add a VCTS to the 18z TAFs for the metro
airports with the past several HRRR runs being fairly consistent
showing a cell or two potting up in that general vicinity in the
21-23z timeframe. Otherwise, attention shifts to the north this
heading into the evening and overnight hours where guidance is
still depicting a complex of tstms developing and moving se across
the region bringing the potential for some strong-severe storms in
between 1-7z, north-to-south. Fcst confidence is highest across
our northern terminals (CLL, UTS, CXO) and progressively less so
further south to the coast as we get a touch more stable after
sunset. But for all intents and purposes, aviation interests
across all of the region should remain alert as these things can
move faster than models predict. Strong winds will be the primary
hazard with hail secondary.

After the rain clears out, MVFR ceilings could develop across the
Brazos Valley late tonight, and possibly for a few hours elsewhere
in the early to mid morning hours as we get some heating. VFR
conditions emerge across all of the area by late morning with sw-
ssw winds 10-20kt. 47


(Today through Sunday Night)
Issued at 226 AM CDT Sat Jun 10 2023

Our well-advertised early summer week of heat is indeed on the
way...but first, one last day with potential for showers, storms,
and yes, even severe thunderstorms, particularly north of the
Houston metro. On top of that, expect another day with temperatures
in the lower to middle 90s, except perhaps right on the Gulf, which
is likely to fall just slightly short of the 90 degree mark. All in
all, this is roughly around or a little above average for early to
mid June. And so, while warm, today still signifies a little more of
us being in transition to the heat to come.

Turning our attention to rain chances for today, I`m looking at
three different mechanisms. The first is related to storms currently
ongoing, making their way out of the Hill Country. These storms will
weaken as they make their way across the I-35 corridor, but some
remnants may manage to survive to our far northwestern corner,
including spots like Caldwell and Bryan/College Station in the 5-8am
window. There`s not much to say here other than these storms may not
make it at all, but if they do, could be a bit of a nature`s alarm
clock up there with a handful of lightning strikes.

More meaningfully, we begin to look up to Northwest Oklahoma and
their ongoing complex of storms. These storms explicitly are
unlikely to impact our area. However, their outflow could provide
the focus for an early round of showers and thunderstorms, primarily
impacting the northeastern corner of our area from mid-day into the
early evening. This rough area would be around and northeast of Lake
Livingston, including Houston, Trinity, Polk, and San Jacinto
counties. These storms will have the bonus of being able to tap into
the peak instability of the day, and HREF min SBCAPE up there this
afternoon is still above 2000 J/Kg, easily enough to support
stronger storms.

What does seem to be a bit lacking, however, is deep shear. Progged
shear is still in the 20-25 knot range, which is enough to support
some modest storm organization, but is definitely the limiting
factor here. Some stronger storms are definitely possible, but CAM
guidance does not seem to be hitting them too aggressively. Still,
with a lot of instability, we are capable of seeing storms with
strong, gusty winds and some small hail. This window isn`t one to be
slept on, but isn`t necessarily our biggest worry for the day either.

Finally, we come to the third feature I`ve got an eye on for storms,
and at this point seems to be the greatest hazard for severe weather
both in intensity and extent. Like the other two groups, we look
outside the area for the genesis of this group of storms. Expect
strong to severe storms to initiate off the dryline in North Texas
early this afternoon and make their way east to east-southeast into
the early evening hours. As they approach Southeast Texas, these
initially discrete storms should begin to congeal into a quasi-
linear convective system. There`s certainly some fuzziness as to
when exactly that will happen, but somewhere in a 5-8 pm window
seems most likely. If this transition is later and we see more
discrete storm cells move in from the northwest, folks around
Crockett, Madisonville, B/CS, and Caldwell could see a threat for
all modes of severe weather, including damaging winds, large hail
(perhaps even in excess of 2" in diameter), and even a very slim
chance of a tornado.

While that scenario is possible, and a threat to be aware of, what`s
more likely is that the storms are in the process of transitioning
or are fully transitioned to a complex of storms.
This line of storms will then march across Southeast Texas towards
the Gulf through the evening, reaching the coast around midnight.
This transition, along with the typical loss of surface connection
after sundown, should functionally eliminate the tornado threat.
Hail threat should also diminish significantly with this transition
as well. Large hail is still a possibility given some modest height
falls aloft as a vort max looks to roll overhead at this time, but
the significant hail threat should go away completely. What is most
likely to stick around is the threat of straight-line, damaging wind
gusts. This severe setup is a fairly common one here for wind
damage, with the internal dynamics of the thunderstorm complex
helping maintain severe storms well after the sun has gone down and
the usual end time for our typical "summertime popup" storms.

A big thing to consider here is the interplay between the complex`s
cold pool and the environmental shear. Whereas the afternoon storms
discussed earlier will have lots of instability to play with but
limited by shear, the evening/nighttime storms will have less
instability (but still sufficient, assuming the storm complex
continues to force parcels high enough to tap into that instability)
but notably more shear. HREF mean shear is progged to be 30-40
knots, oriented almost perfectly normal to the expected complex of
storms. With a strong enough cold pool, these two factors will help
sustain severe storms with damaging winds deep into our area,
perhaps as far as I-10. All the way to the coast is not off the

The limiting factor with this batch of storms will be near the
surface. Once the sun is down, we`ll start to get a rapidly
stabilizing layer near the surface. So, even if we have an elevated
complex of storms producing severe winds, they may not be able to
drill their way all the way to the ground through that surface
inversion. At least, not in a widespread manner. The result may be
something along the lines of more widespread damaging winds in
storms as the storms enter our area, with pockets of surfacing
damaging winds becoming more isolated farther southeast and deeper
into the evening. Eventually, the severe winds become cut off from
the ground entirely, the cold pool/shear balance is upset, and the
storms weaken as they approach the Gulf Coast. For longtime watchers
of the weather around here, this should sound pretty familiar, and
is a big part of why we so frequently have severe threats that are
highest in the northern part of the area, and gradually diminish
towards the coast. Expect that again tonight.

Once that`s out of the way, likely around midnight, but perhaps as
late as 3 or 4 am, things should clear out and we`ll make our way
into the torchy portion of the forecast. Highs on Sunday should make
their first jump from just a little above average to noticeably
above average, with inland highs more in the middle 90s, and even
some upper 90s emerging in the hot spots. This is just the start,
however, and I`ll turn it over to the long term to discuss the heat
in more detail.


(Monday through Friday)
Issued at 226 AM CDT Sat Jun 10 2023

The long range continues to appear toasty due to a strong
mid/upper ridge, centered over Mexico, that will dominate the
weather through the next week. The ridge bulges northward over
Texas on Monday into Tuesday, sending 500MB pressure heights over
590 dam. West to southwest flow aloft will result in strong WAA in
the mid-levels with 850mb temps upwards of 5 degrees celsius
above normal on Monday and Tuesday. Shortwaves will traverse west
to east along the northern periphery of the ridge, remaining far
enough north to keep PoPs out of the CWA. Onshore flow is
expected to increase by Tuesday due to an increasing pressure
gradient between a subtropical surface ridge well to our east and
falling surface pressures over western and northern Texas.
Afternoon highs are expected to average in the mid/upper-90s
across the CWA with lows generally in the mid/upper-70s.

Temperatures are likely to become even toastier during the second
half of the week. There are some mixed signals regarding how high
those temperatures go. However, keep in mind that those mixed
signals are basically a debate between weather or not afternoon
high temperatures hover near 100F or manage to rise well above the
century mark in some areas. In other words, it`s going to be hot
regardless. By Wednesday and Thursday, a more aggressive
shortwave riding along the northern periphery of the high is
expected to pass north of the CWA. The mid/upper ridge may erode
slightly during this time. In addition, some weak PVA may be
introduced over southeast TX which could suffice for more
afternoon clouds. The continuation of the aforementioned
increasing onshore flow will also have a tendency to enhance the
Gulf`s influence on our temps and humidity (more humid but perhaps
keeping temps a tad lower). All these factors would suggest
afternoon highs more in the upper-90s. However, there are other
factors that support hotter temperatures. Increased mid-level WAA
due to strong SW flow aloft could send 850mb temps up to around
10 degrees celsius above normal. Global ensembles also indicate
low PWAT anomalies which could greatly limit afternoon cloud cover
despite the PVA induced lift from the shortwave on Wednesday and
Thursday. For now, we are going with afternoon temperatures in the
upper-90s to low-100s over most of the FA during the second half
of the week. Given the expected heat and humidity, the chance is
increasing that we will be issuing heat advisories and potentially
excessive heat warnings by the middle of the upcoming week.

For those planning outdoor activities, please be advised that the
risk of dangerous heat continues to increase for this upcoming
week. Heat safety precautions will be a must. Stay hydrated. LOOK
before you LOCK. If you can, stay indoors during the hottest hours
of the day. If it`s too hot for you, then it is probably too hot
for your pets as well.



Issued at 226 AM CDT Sat Jun 10 2023

Other than the risk for a few thunderstorms late today into
tonight, the forecast is mostly dry through the next week.
Gradually increasing onshore flow is expected this weekend through
the middle of the week. Caution flags are possible as early as
Sunday. Best chance of caution level winds will be Monday night
through Wednesday night. Cannot rule out periods of advisory
level winds. This increased onshore flow will also enhance the rip
current risk. Seas are expected to gradually increase over the
next several days, peaking in the 4 to 6 foot range offshore by
Wednesday. Winds and seas may decrease somewhat going into
Thursday and Friday. However, no significant change in the pattern
is expected through week`s end.


College Station (CLL)  95  71  97  73 /  30  60   0   0
Houston (IAH)  95  73  97  74 /  30  50   0   0
Galveston (GLS)  87  77  88  79 /  10  20   0   0




$$ is the U.S. government's official web portal to all federal, state and local government web resources and services.