Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 081729

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1229 PM CDT Thu Jun 8 2023

...New AVIATION...

(Today through Friday Night)
Issued at 358 AM CDT Thu Jun 8 2023

A rather complex atmospheric setup has been bestowed upon southeast
Texas today. Mid/upper subtropical ridge will build further north
over Texas. However, there will only be a modest increase in
mid/upper level pressure heights. In addition, NW flow aloft will be
increasing as the aforementioned increased ridging tightens the
mid/upper level pressure gradient resulting in about 20-30 knots of
0-6KM bulk shear. Instability will also be plentiful in part thanks
to the heat and humidity that will greet you when you step outside
today. Widespread afternoon highs in the low-90s with dew points
around 70F are expected. This will translate to heat index values in
the upper-90s for many locations. Going back to the instability,
HREF MUCAPE ensemble means are showing widespread values of 2000-
2500 J/kg with forecast soundings showing potential for CAPE
exceeding 3000 J/kg. We also will have to contend with the prospect
of low-level mesoscale boundaries thanks to the sea breeze as well
as potential outflow boundaries from overnight MCS`s in central and
southern Texas. All these aforementioned factors are leading to an
increasing chance of thunderstorms, especially this afternoon. PoPs
for most of the CWA have been increased to the 40-50 percent range.
Given the high instability and sufficient shear, a few strong to
severe thunderstorms will be possible. The Storm Prediction Center
currently has most of our region in a Level 1 out of 5 risk for
severe thunderstorms. It is not out of the question that they could
upgrade the risk to a 2 out of 5 for portions of the CWA. The
primary concern will be damaging winds gusts. Worth mentioning that
this complex setup results in some heightened uncertainty. This can
be seen via the wide ranging solutions of the current CAMs. Most of
the CAMs are indicating convective development over our CWA. It`s
the exact location of these thunderstorms that one will see the most
disagreement in the convection model guidance.

Ridging will build even more on Friday resulting in lower PoPs and
higher temps. Still, some weak shortwave action embedded in the
synoptic flow could spark off a few isolated thunderstorms. But the
bigger story will be the temperatures. Friday`s highs are expected
to average in the mid-90s. Couldn`t rule out a few locations
reaching the upper-90s. Upper-80s to low-90s are expected near the
beaches. Once the humidity is factored into the equation, many of
you will have heat index values reaching the low-100s. Tis the
season to drink plenty of water! If you do not need to be outside,
stay indoors during the hottest hours of the day. Remember to LOOK
before you LOCK. Also, if you think it is hot outside then so do
your pets!


(Saturday through Wednesday)
Issued at 358 AM CDT Thu Jun 8 2023

I have precisely one (1) day with PoPs that rise into at least the
slight chance category, and that is right on the front end on
Saturday. Ridging will be coming to command the region, but not
before we squeeze one more day with isolated to scattered showers
and storms out. With the beefy, subtropical ridge building in from
the southwest, it`s surely no surprise that the best rain chances
will be to the northeast, generally beyond Lake Livingston and
towards the Pineywoods, were PoPs peak out at 30-40 percent.
Things dip down to around 20 percent near the I-45 corridor, and
dwindle to 5 percent or less pretty quickly once you head
southwest of the Colorado River. The last lingering storms should
wrap up in the early evening, mainly north of Houston.

Okay, with that first day out of the way, let`s focus on the real
star of the long term forecast, the heat. Our big ensemble systems
remain highly confident in unseasonably hot temps, using 850 mb
temperatures as a proxy signal. Both the NAEFS and EPS ensemble
mean 850 temps begin to exceed the 90th percentile as early as
Saturday afternoon, and just crank up into the new week. 97th
percentile temps show up on Sunday, and 99th percentile temps
arrive Monday. By mid-week, 850 temps exceeding the 99th
percentile are widespread, and the hot spots begin to max out the
climo. The Euro ensemble mean goes so far as to suggest record
850 temps area-wide later next week, with the only saving grace
being that this occurs overnight Wednesday into Thursday.

Now, this is all very interesting, but other than perhaps
reinforcing the high confidence in some hot days ahead, it doesn`t
reveal a whole lot of new information we weren`t looking at the
past couple of nights. Where the uncertainty comes in, as it so
often does, is how this hot 850 mb temperature translates to
surface temperatures, where we`re living. And, unfortunately, I
don`t necessarily have a lot to report there. The EPS Extreme
Forecast Index is really suggesting higher confidence in extreme
heat well to our west, but remains coy in our area. The EFI for
max temps through next Wednesday flit above 0.5 in isolated spots,
but there`s not really a strong signal here. Ensemble cluster
analysis of max temps suggests that there is not a lot of
variation from the multi-model mean in the most prominent
scenarios. If anything, there may be a little bust potential for
things to come in a bit cooler than progged, but the difference
here is still small and probably too much of a stretch to do
anything but plant some anxiety about my forecast.

All in all, this idea of having unseasonably hot temperatures but
with a signal for extreme heat relatively lacking, I`m comfortable
mostly running with a blend of the deterministic NBM and the NBM
median for temps, to give me a slight hedge towards heat.
Widespread inland highs in the middle to upper 90s are here as
early as Sunday, and especially Tuesday through Thursday. As we
push into the back half of the week, upper 90s become the norm
inland, while highs reaching 100 degrees begin to emerge. Of
course, onshore flow helps keep things slightly cooler at the
coast, but even there, look for highs around and above 90 degrees.

Taking a look at the NBM distribution, 90 degree highs are
basically certain except right on the Gulf the whole period. This
is not really a surprise, as this time of year, a 90 degree high
is right around average, give or take a degree or two. Stepping it
up to triple digits, and we see some more nuance. The probability
of reaching 100 degrees starts to sneak in from the west as early
as even Saturday - those that have the least chance for rain could
see their odds of hitting the century mark up as high as 8-12
percent. The first isolated spots of 50 percent probability show
up Monday, mainly around the Brazos Valley in our climatological
hot spot west of the Houston metro.

Things get more interesting later in the week, as the
probabilities for hitting 100 continue to increase. The absolute
numbers seem to top out around 75 percent in the second half of
the week, but the area of 50 percent or higher probability grows
to cover nearly all of the area from I-10 northward. With a large
swath of our forecast area seeing a 50-75 percent chance of
reaching 100 degrees at their specific point, I`ve got to think we
are basically certain to see someone, somewhere in the area make
the mark later next week. To get otherwise would require a whole
lot of coin flips going in one particular way.


(18Z TAF Issuance)
Issued at 1224 PM CDT Thu Jun 8 2023

Starting to see thunderstorms develop between UTS and CLL. The
atmosphere will be very unstable this afternoon, so expecting
at least SCT TSRA in a couple of hours, some strong and/or severe
TSRA are possible, especially near CLL. Will have a TEMPO to TSRA
this aft for inland TAF sites. Convection will propagate to the
SE and last until early eve.



Issued at 358 AM CDT Thu Jun 8 2023

Generally light, westerly to southwesterly winds are expected today,
shifting to southerly and strengthening to become more moderate to
late Friday into the weekend. To go along with that, seas will be
pretty flat to begin with and gradually make their way up to a 2
to 4 foot range. Moderate to gusty south winds should prevail in
the first half of next week, and look to increase enough that we
will have to evaluate the need for caution flags and perhaps even
a brief small craft advisory at times next week.

Rain chances dwindle this weekend, with scattered shower and
storm coverage today decreasing each day into the weekend. From
then on, dry weather prevails deep into next week.


College Station (CLL)  92  69  95  73 /  30  20  10  10
Houston (IAH)  92  72  95  72 /  30  20  20   0
Galveston (GLS)  88  77  90  79 /  20  20  10   0




LONG TERM....Luchs
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