Area Forecast Discussion
Issued by NWS Houston/Galveston, TX
FXUS64 KHGX 211221
Area Forecast Discussion
National Weather Service Houston/Galveston TX
721 AM CDT Sun Aug 21 2016
For the 12Z TAFs, the main aviation concerns center around
SHRA/TSRA near the terminals today and patchy fog development
early Monday morning.
Morning surface analysis showed a cold front draped from near KSHV
to KUVA, with regional radars showing SHRA/TSRA ongoing along this
frontal boundary. Also noted was a small surface low centered in
between K3T5 and KVCT, with a north-south outflow boundary
oriented along a KCFD-KELA line. These small scale features were
also serving as focusing mechanisms for TSRA/SHRA activity.
Scattered to numerous SHRA/TSRA are expected to continue across
Southeast Texas through early evening with upper level divergence
and tropical moisture in place across the region, but terminal
impacts and their timing will likely be driven by the evolution
of smaller scale features today and frequent amendments are
likely. SHRA/TSRA will be capable of producing IFR and MVFR
ceilings and visibilities, as well as gusty and erratic winds.
Expect a lull in activity this evening with loss of heating and
the departure of upper level support, with streamer showers
possible near Galveston early Monday morning. Have gone ahead and
included a VCSH mention in for the extended Houston-IAH TAF late
Monday morning, with diurnally driven showers and thunderstorms
Otherwise, recent rainfall and light winds overnight may produce
patchy fog near outside of the Houston terminals/Galveston early
Monday morning. Light south to east winds are expected through the
TAF period with VFR conditions outside of SHRA/TSRA.
.PREV DISCUSSION... /ISSUED /
Axis of deep moisture (PW 2.2"+) over the northwestern counties
this morning extending to the SW toward Gonzales and Cotulla and
Zapata (PW 2.4-2.6"). Moderate to light rains falling over the
Flash Flood Watch area this morning and should continue for at
least a few more hours. MCV near Gonzales has gone nearly
stationary and this should help to focus rainfall over the coastal
counties and into the Columbus area this morning. Have raised POPS
over the southwest areas this morning. Storms that develop in the
watch area should be slow moving and capable of heavy rain today
and so have extended the FFA through 7 pm...primarily for the wet
ground and the possibility of more storms there today.
Yegua/Davidson creeks responding to the heavy rains Saturday night
with bankfull to near flood stage. Further south today and over
the Metro area expect to see storms continue to develop over the
SW counties this morning then expand north and northeast by early
this afternoon. Brief heavy rains will be possible areawide but
with the slowing storm motions in the FFA area - runoff problems
should be focused there. All this rain and associated cloud cover
will likely lead to a relatively cool day in the west with a
little warmer over the east...still near normal to slightly below.
As the stalled front weakens further and then retreats northwest
late this morning the heaviest rainfall will likely be focused
well to the southwest of the region with significant flooding
issues...travel into that area may be very hazardous.
Rain chances taper down Monday as drier air intrudes into SETX
with the richer moisture over the northeastern counties with
higher rain chances over the central and eastern areas. Temperatures
climbing into the mid 90s Tuesday and continuing through Wednesday
and possibly Thursday with diurnal seabreeze pattern storms. Moisture
back on the increase Thursday through Saturday and should see a
more east to southeast low level flow with the upper flow becoming
more southeast and increasing.
Showers and thunderstorms are expected to increase across the
coastal waters this morning as deeper moisture over South Texas
early this morning spreads across the western Gulf, with storms
possibly lingering into the late afternoon hours. Periods of rain
are expected through midweek across the waters as surges of
additional moisture reach the Upper Texas Coast. Light to
occasionally moderate onshore flow is also expected to persist
through midweek, with slightly stronger winds during the overnight
hours. A more easterly flow is expected by late week as a broad
surface high over the southeast US spreads into the northern Gulf.
Otherwise, expect seas generally in the 2-4 ft range with tide
levels within 1 foot of normal.
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 86 73 89 75 93 / 80 40 40 20 20
Houston (IAH) 88 74 91 76 92 / 70 20 50 10 40
Galveston (GLS) 89 82 89 82 89 / 50 20 40 20 20
TX...Flash Flood Watch through this evening FOR THE FOLLOWING ZONES: