Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 242329
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
629 PM CDT SUN JUL 24 2016

.AVIATION...
Still seeing some SHRA/TSRA around inland TAF sites, so will carry VCTS
through 01Z or 02Z. After that, loss of daytime heating should make
for a quiet night with mainly light and variable winds. Looks like an
active day tomorrow with better SHRA/TSRA coverage that will be slow
to move. For now, mainly went with VCSH in the morning and PROB30 TSRA
in the afternoon (future TAFs will probably be able to get a better
handle on when to go with TEMPO groups to replace the PROB30). Activity
might not end up decreasing in coverage and intensity until around the
mid evening hours (sometime around 25/02Z-25/03Z). After a quiet Monday
night, anticipate seeing another active day on Tuesday.  42
&&

.PREV DISCUSSION... /ISSUED /

DISCUSSION...
The key issue in the forecast will focus on an incoming trough
that will bring the most serious rainfall potential in some time
to the area. However, while confidence is high in the first half
of the week - particularly Monday - bringing higher rain chances,
there is continuing uncertainty about fine details. There
continues to be divergent model guidance for the rebuilding of the
ridge in the wake of the trough`s passage, which has implications
for both lingering rainfall potential and high temperatures deeper
into the week.

Today into Monday...
Despite the appearance of less capping, showers and storms have
struggled again to get going this afternoon. While more development
has occurred than yesterday, convection has continued to be more
widely scattered than perhaps first anticipated. There should
be some further increase in coverage into the early evening, but
loss of heating will cause convection to wrap up. The WRF-ARW
has backed off late evening precip in the area, which seems
reasonable based on observational trends today, and have not
bumped PoPs up north. Focus then turns to the approach of both a
vort max from the Mississippi Valley and a TUTT low that`s working
its way across the Gulf from the east. Ultimately, took a bit of a
middle road in bringing up clouds and precip chances through the
morning, but focused on putting likely PoPs more in the afternoon.
For the most part, temperatures are cooler than previous days, but
still brought the westernmost counties up into the middle 90s on
the thought that clouds/rain will be late enough to get a bit more
heating in. Still, faster timing could make this a bad move.

Monday night through Wednesday...
As the inverted trough works its way deeper into Texas, there
becomes a divergence in the guidance as to how long upper weakness
in the height field continues. The GFS builds things back a little
more quickly, and while Tuesday carries relatively high rain
chances, things quickly get back to resembling the diurnal
seabreeze pattern. The Euro, on the other hand, keeps the ridge
from building back quite so quickly, and stays more wet. The GFS
appears to handle the transition more awkwardly, so the forecast
hedges towards the Euro. However, a deep reading of the PoP grids
does show slightly lower chances well inland from the seabreeze
zone in deference to a scenario with a stronger ridge.
Temperatures are cooler than normal, but still in the vicinity of
90 degrees.

Thursday into the weekend...
Model divergence continues to spread in the extended, keeping
confidence on many details low. The GFS continues to be towards
the drier edge of the guidance envelope, and even cuts off
seabreeze convection by early next week. The Euro, on the other
hand, swings the other way, keeping more widespread rain in the
forecast straight into next week. For what its worth, this is at
least a step forward from yesterday, in which the GFS and Euro
took turns flipping places with each other from run to run. While
a fan of how the Euro handles to exit of the inverted trough
earlier, am wondering if it is falling a bit towards its old trap
of not being quite progressive enough in the long term. Thus, the
forecast takes a bit of a middle road here - splattering some
amount of PoPs through the period, but focusing more on the
seabreeze zone. This may not be the most realistic of scenarios,
but am aiming to be more probabilistic rather than deterministic
here, as this allows for an easy pivot either way as confidence
in the preferred scenario becomes higher. Have trended
temperatures upwards, but the degree to which we warm will again
be dependent on rain coverage.
25

MARINE...
Light wind regime in place across the area. Deep moisture
spreading into the area will lead to an increase in showers and a
few thunderstorms tonight especially toward morning. May see a few
short-lived waterspouts Monday and Tuesday morning. Light
landbreeze possible again around Galveston Bay. Onshore flow will
dominate the wind field across the area through Thursday with
winds varying from southwesterly to southeasterly being mainly
diurnally driven. Rain chances taper down Wednesday. 45

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      78  95  76  92  75 /  20  50  30  60  30
Houston (IAH)              78  93  77  90  76 /  20  60  30  60  30
Galveston (GLS)            82  89  80  87  81 /  20  50  40  60  30

&&

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

$$

Discussion...33
Aviation/Marine...42



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