Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 240436

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1136 PM CDT SAT JUL 23 2016

Only slight changes made to TAFS with 06Z update. Did add a window
for vicinity shower...VCSH...for IAH...HOU and LBX in addition to
the window for GLS which was already in place. Radar composites
show a few showers over the Gulf off the Louisiana coast and not
out of the question a few of those could stream in toward the
Texas coast toward daybreak and Sunday morning for GLS and LBX.
High res rapid refresh hints at that occurring. For HOU and IAH
threat for isolated convection will be again mid afternoon as sea
breeze lifts north. Coverage will again be minimal Sunday
afternoon and most areas will remain dry. Much better chances of
showers and thunderstorms on Monday...but that is beyond the
forecast period for these TAFS. 18



Quick glance at the afternoon climate shows that Houston IAH did
top out at 100 degrees for a high temperature. This will be the
first time in 2016 that IAH reached the 100 degree mark. Average
first day for reaching 100 degrees for a high temperature is July
17 so just a few days later than that. The average last day for
reaching 100 degrees for a high temperature is Aug 13 so looks
like climatological speaking there are a few more days where we
have the potential to reach 100 degrees. That said, there have
been several times Houston IAH reached 100 degrees for a high
temperature in September like 109 in the year 2000 which is the
all time record high.

Looking at the forecast, everything looks on track with the
latest data and observation trends. Upper level trough will work
into the area starting tomorrow and impact the area mainly Monday
and Tuesday. This should support the best chances of rain for the
area and keep max temps more the the 90s.



Another day today like the past few with generally VFR conditions
and dry other than isolated convection along sea breeze in the
afternoon. This afternoons showers and few storms over SE Texas
have already dissipated for the most part. Expect tomorrow to be
similar to today except for perhaps more development to the east.
Monday looks to be more active with more widespread
convection...but that falls outside TAF will go out
again with VFR conditions and no mention of precip other than a
VCSH around daybreak for GLS which was retained from previous
issuance. Cant rule out a few streamer showers at that time off
the Gulf. 18


By mid-afternoon, scattered to numerous cumulus clouds have
developed across the area per visible imagery. However, it was
noted outside the office earlier today that there had been little
vertical development in the early cu growth thanks to a lingering
subsident cap from the retreating ridge. While there has been
improvement since then, the radar has stayed pretty quiet - the
only returns have been along the seabreeze, mainly in Chambers
County, with Harris County`s first cell popping into existence.
Despite sufficient moisture and a retreating ridge, a weak vort
max evident in water vapor imagery has not made its way into the
area as quickly as expected this afternoon, which likely has made
the difference in the amount of convection.

Tonight through Sunday...
The midlevel ridge should continue to retreat, while a vort max
drifts westward out of the Mid-South, while the surface pattern
remains relatively similar. Sunday should be similar to today
then, albeit a touch cooler and with an expectation for better
convective development.

Monday through Wednesday...
The vort max/inverted trough should be moving through the area
Monday, and by afternoon flow should set up a surge of moisture
into the area, giving us a deep moisture pool and a much more
favorable environment for rain and storms. At the same time,
steering winds look pretty light, so locally heavy rainfall could
be a possibility. The inverted trough will slowly move past the
area through the midweek, which should drag out an increased
potential for rainfall for Tuesday and Wednesday, though Monday is
likely to show the most potential. With the lower midlevel heights
along with likely increased cloudiness and rain, daytime
temperatures should be cooler the first half of the week, but also
means cooler low temperatures may not manifest.

Beyond Wednesday...
Upper ridging will try to build back in late in the week, but
guidance continues to show a weakness, or maybe even a col in the
flow over our area continuing. So, while temperatures should nudge
upward and convection trend downward, it still seems prudent to
keep some potential for precipitation into the weekend.

Southerly flow on tap tonight with a typical increase during the
late afternoon through midnight then relaxing toward morning with
another landbreeze. Showers should be scattered across the Upper
Texas Coastal Waters Sunday morning as deeper moisture expands
westward. Coverage should linger through Monday morning as inverted
upper trough migrates into SETX. Seas of 1-2 fee with winds 5-13
knots should prevail throughout the period.


College Station (CLL)      78  98  77  95  76 /  10  20  10  50  20
Houston (IAH)              78  96  79  93  78 /  10  40  10  60  20
Galveston (GLS)            82  91  81  89  81 /  20  30  30  50  20




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