Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 290455
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1155 PM CDT Sun May 28 2017

.AVIATION...
SHRA/TSRA continue moving through Southeast Texas late this evening.
06Z TAFs have a mix of SHRA and TSRA, especially at the southern sites,
for the overnight hours. Expect to see activity decrease in coverage
from N to S overnight, but any boundaries lingering in the area could
lead to additional development during the day tomorrow. For this reason,
leaving VCSH and VCTS in the TAFS for much of the day tomorrow and
on into tomorrow evening.  42
&&

.PREV DISCUSSION... /ISSUED 1044 PM CDT Sun May 28 2017/

UPDATE...
Currently showers and thunderstorms are draped across generally a
line from Colorado County over to Polk/Liberty Co line. The cold
front itself appears to still be hung up over FWDs area, with
the showers and storms pushing southeast through our area along an
outflow boundary. Pretty much all of the upcoming forecast depends
heavily on where these two boundaries end up heading into
tomorrow. For now, the severe threat seems to be diminishing and
transitioning into more of a heavy rainfall event. We`ve already
had many reports of road closures up in Crockett due to high
water, and the KSHV radar has estimated around 4 to 7 inches of
rain up in Houston County over the course of the evening, starting
around 4-5 PM. Luckily it seems that the current line of storms
has slightly picked up in speed, and as long as it keeps moving
the flooding threat should be limited to nuisance flooding.
However, additional problems may occur if storms develop further
north and move across some of the already harder hit areas.

Heading into overnight tonight/tomorrow... forecast depends on
where the two aforementioned boundaries end up. Short term
guidance is suggesting the outflow boundary from the current line
of storms may end up somewhere near/along the coast with the cold
front itself somewhere near the HWY 59 corridor. Current activity
should generally diminish overnight well inland with the loss of
daytime heating/forcing. Showers and storms will likely flare up
again tomorrow after sunrise as a disturbance currently near
Laredo pushes eastward towards our area. This will likely cause a
blossoming of showers/thunderstorms across much of SE Texas, with
a general focus near the coastal areas where the remnant outflow
will likely be. Right now, the activity tomorrow looks to be more
of a heavy rainfall threat than anything with forecast PWs in the
2.2-2.4 inch range. 11

PREV DISCUSSION... /ISSUED 624 PM CDT Sun May 28 2017/

AVIATION...
Area should see increasing SHRA/TSRA coverage this evening as activity
builds in from the N and NW along and ahead of a cold front. 00Z TAFs
are messy with lots of VCSH and VCTS. After this evening, there are
lots of timing uncertainties concerning not only the possible SHRA/TSRA
but also wind directions and ceilings as we move into the overnight
hours and on into the day tomorrow. Generally going with MVFR ceilings
overnight becoming VFR tomorrow afternoon with MVFR/IFR levels quite
possible in and around the SHRA/TSRA.  42

PREV DISCUSSION... /ISSUED 346 PM CDT Sun May 28 2017/

DISCUSSION...
Line of storms likely about to fire along a frontal boundary
draped across ncntl Texas. As previously talked about, the atmos
is very unstable in advance w/ high CAPES and low LI`s. Anticipate
some severe storms to emerge as they make their way into se Tx
this evening. Severe Thunderstorm Watch is in effect generally
northwest of a Columbus-Livingston line until 10 pm. Dependent on
strength/movement trends, we may end up needing to add the metro
area to the watch as well. Aircraft soundings around there still
indicate some capping at 700mb, but has eroded some since this
morning. Almost all hazards are are the table with hail/winds the
primary threat, followed by localized heavy rain amounts & rates,
and finally a low (but non-zero) chance of a tornado.

This storm complex will send a boundary southward, and this will
determine the overall threat and/or locations for future hazardous
wx as another shortwave makes its way in from the sw late tonight
and Monday. Ongoing thinking continues to point to the southern
1/3 of the region being the more favored spot, but if a boundary
ends up well off the coast later tonight, pops and qpf amounts
will need to be adjusted downward Monday. Unfortunately, but not
unexpectedly, there isn`t a good model consensus.

Coastal troffiness is expected into midweek. Deeper moisture and convergence
along the trof (along with some passing upper impulses) will probably
trigger overnight and morning precip closer to the coast followed
by inland expansion with daytime heating. Looks like the trof
could wash out and we`d lose a surface focusing mechanism later in
the week, but atmos still looks plenty moist for higher end &
diurnally driven pops through the remainder of the work week.

There will probably be some locations we`ll need to keep an eye on
as we go thru the week as rainfall adds up. As ground gets more
saturated it won`t be able to absorb as much water, and higher
rain rates themselves could become more of a problem in regards to
flash flooding as this occurs. 47

MARINE...
Southeasterly winds have picked back up from earlier this morning.
These may reach into caution criteria later tonight. Otherwise,
showers and thunderstorms could become focused along the coast
south of Freeport overnight tonight and then up the coast during the
day on Monday. Models continued to struggle as to the timing and
location of thunderstorm development. Winds should become more
easterly on Monday before returning to the southeast Monday night.
Southeasterly winds are then expected for the remainder of the week
with the strongest winds during the night and early morning
periods.  40

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      69  80  68  85  69 /  80  50  30  40  30
Houston (IAH)              74  80  69  85  71 /  70  70  50  50  30
Galveston (GLS)            77  82  74  83  76 /  60  80  60  50  40

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk until midnight CDT tonight for the
     following zones: Brazoria...Chambers...Galveston...
     Matagorda.

GM...NONE.
&&

$$

Discussion...11
Aviation/Marine...42


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