992
FXUS64 KHGX 091121
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
621 AM CDT Thu May 9 2024

...New AVIATION...

.SYNOPSIS...
Issued at 340 AM CDT Thu May 9 2024

Early season heat takes center stage for one more afternoon, then
we look warily northwest to see what...if anything...comes our way
tonight bearing any threat for severe storms. Temperatures will
tone down going into the end of the week after a weak cold front,
turning the focus of the forecast to rainfall potential Sunday
into Monday. A few key takeaways:
- Look for peak heat index values to again rise to around or over
  100 degrees away from the Gulf this afternoon thanks to humid
  conditions and high temperatures around 90 degrees. This first
  multi-day stretch of above-average heat is a good chance to
  stretch out those heat safety muscles, as summer is rapidly
  arriving.
- Meanwhile, over North and Central Texas, we expect storms to get
  going late in the afternoon, and make their way eastward. In
  general, the highest threat is to the north, with a less
  favorable environment southward. A threat level 3 of 5 (Enhanced
  Risk) exists northward of a line roughly from College Station to
  Livingston. A threat level 2 of 5 (Slight Risk) exists southward
  of there to roughly I-10. A threat level 1 of 5 (Marginal Risk)
  is in place for much of the area south of I-10. The primary
  threat in the afternoon will be large hail, potentially even
  significant hail larger than 2 inches in diameter. The primary
  threat will shift more towards damaging wind gusts in the
  evening. An isolated tornado is a lesser concern, but cannot be
  ruled out.
- We`re also still watching the potential for locally heavy
  rainfall on Sunday and Monday from another round of showers and
  thunderstorms. WPC indicates a Marginal to Slight risk of
  excessive rain each day (threat levels 1 and 2 of 4). Continue
  to monitor the forecasts heading into the weekend for the latest
  analysis.

&&

.SHORT TERM...
(Today through Friday Night)
Issued at 340 AM CDT Thu May 9 2024

Oh, it`s starting to feel a lot like summer...everywhere you
sweat... We`ve been talking about this for several days now, so I
don`t want to risk beating this point too frequently, but early
season heat continues to be a sneaky threat for heat exhaustion
and heat stroke, as the numbers are lower than we see in the teeth
of summer, but our bodies aren`t quite acclimated to it yet. The
same situation is there today, thanks to highs again around 90
degrees with a peak heat index around or just over the century
mark (except on the Gulf, things look a bit cooler there). Hang in
there, today will be last day with widespread above average heat,
and things will continue to moderate just a bit into next week.
But if you love it hot, don`t worry - there`s a lot more where
this came from.

Of course, with temperatures this high and ample moisture in
place, evidenced by widespread dewpoints in the middle 70s, we`ve
got a deep pool of thunderstorm fuel in place, but like yesterday,
we`ll largely be in search of a mechanism for initiation. That
mechanism exists off to the northwest of our area along a dryline,
and eventually, an incoming "cold" front. Eventually, storms that
fire away from our area, may become a concern as they push
eastward off the initiating boundary. mean HREF SBCAPE values
exceed 4000 J/Kg in our northwest closest to the initiation
region. The max values start to get a little stupid, exceeding
5000 J/Kg. Should any storms manage to push their way in from the
west/northwest, that instability combined with shear in excess of
30 knots should sustain any storms that come into the area. The
big question again is...do any storms get in here at all?
Convective initiation should again focus well to the north of the
area, where there`s much better forcing. Still, late this
afternoon into the overnight hours does look to feature a small
shortwave trough passing aloft, which could be enough to get some
isolated storms going.

Given the big amounts of instability at play, the initial
threat...mostly out of our area, but perhaps sneaking into the
northwest if they move in early enough, will be large hail,
potentially greater than 2 inches in diameter. Eventually, as the
sun sets, and we lose that pool of extreme instability, we`ll
likely see any development there is grow upscale along/ahead of
the incoming front for the overnight hours. The threat should then
transition from hail to large swaths of damaging straight line
wind gusts, though a brief tornado can`t be totally ruled out
either.

One important note with today`s setup - because our primary
question is convective initiation, many of us, even in the
enhanced risk area, may well see nothing at all. Can`t have severe
storms if there aren`t any storms to begin with! But also, with
our north on the edge of the pool of extreme instability, if we
get a couple storms to pop up, we can expect them to cook.

Any storms that do make their way through the area should be
moving on to the east and out of our portion of Southeast Texas
not too long after midnight. Behind them, a weak "cold" front
looks to push its way through the area to the Gulf by Friday
morning. It will help tamp down temperatures modestly, but do not
get too excited here. Cold air advection behind the front will be
limited, and while the post-frontal airmass will also be modestly
drier, our main achievement will be to see dewpoints drop out of
the 70s. Indeed, this time of year, while we can expect to see
some slight cooling well inland, the day after a cold front on the
coastal plain is often just as...or even a bit hotter than the day
before, thanks to seeing more sun and the more efficient heating
of drier air. I was pleasantly surprised to see the NBM actually
catch onto that for once, and mostly rolled with its temperatures
rather than trying to Frankenstein together an inland and a
coastal high temperature forecast. Finally, we should see whatever
modest relief we`re going to see behind this front settle deeper
into the area Friday night. Except within a county of so of the
Gulf, we can expect low temps Friday night to make it below 70
degrees.

&&

.LONG TERM...
(Saturday through Wednesday)
Issued at 340 AM CDT Thu May 9 2024

Surface high pressure slides east through the Southern Plains on
Saturday, allowing onshore flow to gradually return during the day.
Remnants of the frontal boundary will gradually lift north as a warm
front Saturday night, suppling additional moisture and bringing PWs
of 1.5-2.0 inches. Lifting from the boundary will be further
supplemented by weak impulses aloft from a cutoff low over the
Desert Southwest. This should produce scattered showers and storms,
beginning over out west/southwestern counties early Sunday and
spreading to the remainder of SE Texas later that morning. Around
this point, the closed low/trough will be near the TX/OK Panhandle,
providing additional lift as stronger impulses pass over the area.
Combining this forcing with the lifting warm sector should allow for
more widespread showers/thunderstorms to develop during the
afternoon/evening. Forecast soundings also suggest high
precipitation efficiency in this environment, favoring the potential
for locally heavy rainfall. WPC has portions of SE Texas under a
Slight (level 2/4) to Marginal (level 1/4) Risk of excessive
rainfall for Mother`s Day on Sunday.

Shower/storm activity should briefly decreases during the overnight
hours as the main forcing axis from the upper level trough slides
eastward towards the Mississippi River Valley. Global models
indicate another shortwave trough passing overhead on Monday,
bringing an additional round of thunderstorms. Forecast soundings
seem to suggest sufficient shear & instability available for
stronger storms to develop during this period. Additionally, these
storms will still be capable of producing locally heavy rainfall,
and thus WPC has maintained a Slight (level 2/4) to Marginal (level
1/4) Risk of Excessive rainfall over portions of SE Texas on Monday.
Forecasted rainfall totals from Sunday through Monday night will be
around 1-3" with the highest amounts expected generally north of the
I-10 corridor.

Rain chances diminish into early Tuesday morning as PWs drop under
1.0" in the wake of the shortwave & upper trough. This will bring
calmer, more benign weather for Tuesday with highs in the 80s to
lower 90s. However, moisture begins to return Tuesday night, with
rain chances returning on Wednesday and continuing late into the
week.

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 621 AM CDT Thu May 9 2024

Frustration potential with this forecast is high to say the least.
MVFR at best around the area early this morning, with pockets of
IFR or LIFR. This is likely to be a bit variable but remaining in
this range to start, gradually improving to a hazy VFR for the
afternoon. Big uncertainty in possible storms this evening. May
see severe storms...or may see nothing, and probably nothing in
between. Went conservative and sketched out VCTS at sites where,
if storms do occur, are most likely to be in the neighborhood.
Certainly not enough confidence for even a TEMPO at this point.
Once storms clear, weak front will move through. Eventually will
turn winds more north/northeasterly, but will likely get a stretch
of light/VRB winds first. Incoming airmass likely not enough of a
change to prevent return to MVFR conditions overnight.

&&

.MARINE...
Issued at 340 AM CDT Thu May 9 2024

Light to moderate onshore flow is expected today ahead of a frontal
boundary. This persistent fetch will bring seas of 3-6 feet in the
Gulf and elevated tide levels along the coast. High flows from
rivers, creeks and streams will lead to above normal water levels in
the bays and intercoastal water way this week, which may make
navigation difficult at times. A cold front will push offshore
during the early morning hours of Friday. Moderate offshore winds
behind the front may warrant caution flags into the weekend. Onshore
flow returns Saturday night/Sunday as a warm front moves onshore.
Periods of showers and thunderstorms will be possible from Sunday
through early next week.

&&

.HYDROLOGY...
Issued at 426 PM CDT Wed May 8 2024
Updated 340 AM CDT Thu May 9 2024

A slightly higher chance for thunderstorms exists again today,
but is still not expected to be widespread enough to result in
any additional areal flooding. Although there have been decreases
in the water levels along the rivers, some will remain swollen
for days (possibly weeks). Do NOT go around barricades and stay
out of the floodwaters. Do NOT return to homes until officials
deem that it is safe.

River flooding continues for parts of Southeast Texas, particularly
along portions of the Trinity river. The following river points are
at Moderate or Major flood stage as of Wednesday afternoon:

- Trinity River (Liberty): Major Flood Stage
- Trinity River (Goodrich): Moderate Flood Stage
- Trinity River (Moss Bluff): Major Flood Stage
- Trinity River (Riverside): Moderate 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.

Also of note is that the downstream runoff from the previous
rainfall will cause continued rises along the Brazos River through
the end of the week.

24/Luchs

&&

.CLIMATE...
Issued at 340 AM CDT Thu May 9 2024

Hobby Airport keeps the record high minimum train rolling,
breaking the daily record again yesterday. The low of 78 degrees
eclipsed the previous record of 77, set all the way back in 2022.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  89  69  83  64 /  20  30  10  10
Houston (IAH)  90  72  88  68 /  10  10  10  10
Galveston (GLS)  82  75  84  72 /  10  10  10   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

SHORT TERM...Luchs
LONG TERM....03
AVIATION...Luchs
MARINE...03