621
FXUS64 KHGX 192327
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
627 PM CDT Fri Jul 19 2024

...New AVIATION...

.SHORT TERM...
(This evening through Saturday Night)
Issued at 315 PM CDT Fri Jul 19 2024

With a surface boundary remaining across the area tonight through Saturday
night, rain chances will remain in the forecast with the greatest concentration
possibly setting up closer to the coast...generally near/around I-10
southward (including off the coast) where the highest precipitable water
values are expected to reside. Storms still look like they will be mostly
hit-and-miss, but those spots that do receive any slow moving activity
could get a quick 1 to 2 inches. With the area remaining in between
ridging aloft to our west and northwest and ridging aloft to our east,
we could experience some hard to time weak impulses/shortwaves that
could possibly enhance our rain chances, but this general scenario looks
to be more of a possibility heading on in to Sunday and beyond (see
the Long Term section below).

For temperatures, have generally stuck with lows in the low to mid 70s
inland and in the upper 70s to around 80 right along the coast, and
have similarly stuck with Saturday`s highs in an upper 80s to low 90s
range.

42

&&

.LONG TERM...
(Sunday through next Thursday)
Issued at 315 PM CDT Fri Jul 19 2024

By Sunday, we`ll be fully engulfed in a wetter than normal period
that will extend well into next week. We start things out on Sunday
with an upper level trough continuing to extend down into the
Mississippi River valley, which will stay stagnant over this area as
it becomes stuck between two upper level ridges on opposite sides of
the CONUS. Throughout the week, we`ll add a couple of more
ingredients that makes the environment increasingly favorable for
heavy rainfall to occur. First things first, there will be no shortage
of moisture availability as PW values climb up to 1.9"-2.1" by late
Sunday and remains generally above 2.0" throughout the week and even
climbing as high as 2.4-2.5" at times. For perspective, the 90th
percentile for this time of year is ~2.16". With plenty of lift
around from numerous rounds of shortwaves providing PVA along with
lingering boundaries from previous rounds of storms, we`re expecting
multiple rounds of widespread heavy rainfall throughout the week.
With steady onshore flow from the Gulf of Mexico, we`ll have enough
instability in place for thunderstorms to develop as well...which
does play a role in the heavy rain forecast given extended warm
cloud layers for the development of bigger droplets in deeper
convection.

By Tuesday afternoon, we`ll see a jet streak (albeit a weak-ish one)
extend into northeast Texas. This places us in a region of upper
level divergence and that prevails for at least a few days. On top
of that, we`ll also have speed divergence aloft. Both of these upper
level features act to move mass away from the area, which leads to
decreased surface pressure. I think we all know what that would
favor...rain! On Thursday, we add in a weak LLJ (20-25 knots) that
may be enough for some convective enhancement. High rainfall rates
(2-3+"/hr) will be possible in any of the stronger storms and could
potentially lead to localized minor flooding in vulnerable areas
(low-lying areas and areas with poor drainage). Areas that receive
higher rainfall totals earlier in the week will be more susceptible
to flooding potential with additional heavy rain quickly turning
into runoff.

With ALL of that in mind, let`s point out that WPC has outlined
portions of Southeast Texas in a marginal risk of excessive rainfall
(level 1 out of 4) on Sunday and Tuesday next week. For Monday,
there is a marginal to slight risk (level 2 out of 4) with greater
potential for flood impacts around the Brazos Valley. We`ll likely
see "at least" a marginal risk for excessive rainfall continue
throughout the work week as multiple rounds of heavy rain are
expected. For rainfall totals, we`re looking at widespread amounts
of 3-5" between Monday and Thursday with isolated higher totals
possible. We`ll be monitoring our area rivers/creeks/bayous
throughout the week as well and will provide additional
updates/forecasts on any potential river flooding as the event
unfolds.

On the plus side, this extended period of rainy weather will
coincide with a period of below normal temperatures! We`ll go from
high temperatures in the low 90s on Sunday to high temperatures in
the mid to upper 80s (and possibly lower depending on the timing and
duration of rainfall on any particular day) through the end of the
work week. The last time we had multiple days below 90F in the City
of Houston was back in mid May. To put things into perspective of
where we could be...this time last year our high temperatures (not
just heat index values) were near or exceeding 100F. The third week
of July is also on average when we usually see our first 100F
temperatures. So, the rainfall will be our saving grace from
experiencing our typical scorching temperatures (as long as it`s not
too much rain falling at one time). This extended period of rainfall
is excellent news for daytime nap fans like myself...but it`s also
unfortunately good news for mosquitoes as well...

Batiste

&&

.AVIATION...
(00Z TAF Issuance)
Issued at 621 PM CDT Fri Jul 19 2024

Seeing a few SHRA popping up near HOU, these are in the vicinity
of the quasistationary front/bay breeze. Think we will see these
continue for a couple more hours. Tomorrow, the front will likely
begin to lift north during the afternoon and be a focus for
scattered SHRA/TSRA.

Wood

&&

.MARINE...
Issued at 315 PM CDT Fri Jul 19 2024

Winds will be briefly offshore through the early afternoon today
with a weak frontal boundary pushing off of the coast. Winds return
back to onshore by this evening where they will prevail along with 1-
3 foot seas into next week. The main story will be daily chances for
showers and storms into next week. Some of these storms may be
capable of producing locally higher winds and seas at times.

Batiste

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  72  94  74  94 /   0  10   0  20
Houston (IAH)  76  92  76  92 /  20  40  20  80
Galveston (GLS)  79  89  80  90 /  50  50  30  80

&&

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

$$

SHORT TERM...42
LONG TERM....Batiste
AVIATION...Wood
MARINE...Batiste