Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 190841
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
341 AM CDT Wed Jul 19 2017

.DISCUSSION...
Hot days ahead as the ridge of death builds over the Southern
Plains. For at least the next couple of days, and perhaps longer,
many will have the potential for max heat indices in the 105-108
range, and flirtation with the heat advisory threshold. So, whether
or not a heat advisory is issued, be aware that it will be hot, and
a bit hotter than is typical for mid to late July in Southeast
Texas. So, while awareness of hazardous heat and heat illness is a
staple of our summer here, it will be worthwhile to be even a little
more sensitive than usual for the next several days.

Beyond the hot weather, look for continued isolated to scattered
showers and thunderstorms in the coming days, but as Tuesday has
already begun to show, as the upper ridge begins to flex its
muscle over the Southern Plains, most of our convective action
will be restricted to near the coast right along the seabreeze
boundary, with lesser potential farther north.

.NEAR TERM [Through Today]...

Two big focus points today - how much will see rain, and how hot
will it get? Tuesday was likely a pretty good template for roughly
how today will go, in that the best coverage for showers and
storms will be near and south of I-10. More isolated coverage, and
likely even less coverage than before, should be expected farther
north, but can`t guarantee that it will be completely dry for
all. Suspect that where convection is more active, we`ll still
see some potential for isolated heavy rains and localized flooding
issues as precipitable water near the coasts are still progged to
be around two inches, though the juiciest air is now more likely
to be offshore as the ridge builds. Farther north, precipitable
water values more in the 1.5 to 1.67 inch range is more likely,
and should mitigate heavy rain concerns as cells are also likely
to be shorter lived.

Now, as far as temps - College Station was able to reach up to 97
degrees on Tuesday. Houston was a bit cooler than expected, likely
thanks to some help from high debris clouds from the day`s
convection. Up CLL`s way, nudge up a degree or so, and if we get
good, full sun all day, 100 probably isn`t out of the question.
More coastward, the forecast probably leans a bit towards the
worst case - debris clouds are probably going to help someone stay
a few degrees cooler than I have forecast, but without a real firm
idea of just how that`s going to play out, chose to err a bit more
towards the warm side. Also have a suspicion that the models are
overmixing slightly this afternoon (as they are often wont to do
this time of year), and have slightly nudged the dewpoints up.
This yields max heat indices between 100 and 108. Fortunately,
temps and dewpoints will create a bit of a sliding scale - if
temps are a bit higher, it`s likely because of greater mixing and
lower dewpoints (and vice versa). So, though we are flirting with
the heat advisory threshold, will hold off today as I suspect it
may be tough to manage widespread heat indices over 108.

.SHORT TERM [Tonight Through Friday]...

The short term is really more of the same summer weather that
Houston and the surrounding area is so famous for. Hot, muggy, and
daily isolated to scattered convection. Yesterday and today are
probably a good expectation for Thursday and Friday as well.
Midlevel ridging should continue to build over Kansas/Oklahoma,
and slowly slide east towards the Midsouth by Friday evening. In
response to this, we may see some modest heights rises, but our
500mb heights don`t look to push much above 594 dm. Indeed, GFS
and Euro both continue to show some lingering vorticity, so I`m
keeping PoPs higher than I might otherwise do.

Ultimately, impact on sensible weather is probably less than the
words I`m giving it. Best rain chances will continue to be near
and south of I-10, and College Station may get a couple more
chances to hit the century mark. We`ll probably be continuing
daily deliberations as max heat indices flirt with the advisory
criterion. But without a real big height rise, my first
inclination is that the end result will be very much like today`s
forecast. (Let`s see if I`m still saying that tomorrow...)

.LONG TERM [Friday Night Through Wednesday]...

As we head into the weekend, the upper high`s center drifts
eastward and washes out some, leaving a relatively flat upper
height/wind pattern. Meanwhile, remnant vorticity from an exiting
upper trough in the polar jet will work its way back from the
off the Georgia coast to along the northern Gulf coastline. The
vort max looks to approach the Upper Texas coast this weekend.
This should start to boost PoPs back up slightly, at least near
and east of the I-45 corridor, particularly as this also looks to
be prepared with a moisture surge and precipitable water values
back up over 2 inches. Here, this vort max approaches the keeper
of the ridge of death. The questions of its name and quest may be
easy enough, but there seems to be pretty strong confidence in the
models that the third question must be along the lines of "What is
the derivation of the vorticity equation from first principles?"
as this feature gets sheared apart early next week. The result
should be some drier days to begin the new week. Beyond that,
the models begin to diverge on specifics, but the general idea
will likely be some kind of small variation on the typical summer
theme.

&&

.AVIATION [06Z TAF Issuance]...

VFR conditions are expected to prevail through the taf period. A few
spots of very patchy fog may develop right around sunrise this
morning across areas that received rain today, but confidence is too
low to include in any tafs at this time. Showers and storms will
likely develop across the southern half of the area (KIAH and
southward) tomorrow, with less coverage expected than on Tuesday.
11

&&

.MARINE...

Light to moderate south to southeast winds will continue for the
remainder of the week (higher winds and seas are possible in/around
any shower and thunderstorm activity). Mainly moderate south winds
(possibly approaching caution levels) and slightly higher seas are
anticipated over the weekend in response to a tightening pressure
gradient. 42

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL)  97  76  98  76  98 /  10  20  10  10  10
Houston (IAH)          95  77  95  77  94 /  20  20  20  10  30
Galveston (GLS)        89  81  90  82  89 /  20  20  20  10  30

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...None.
GM...None.

&&

$$

NEAR TERM...Luchs
SHORT TERM...Luchs
LONG TERM...Luchs
AVIATION...42
MARINE...42



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