Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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390
FXUS64 KHGX 241822
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1222 PM CST Sat Feb 24 2018

.AVIATION...
VFR conditions are expected to prevail through the afternoon at
the inland Southeast Texas terminals. Cannot rule out a few brief
drops to MVFR as ceilings continue to lift, but daytime heating
will limit this window to only the first few hours of the 18Z TAF.
Along the coast, MVFR sea fog appears to be lifting (aided by
increasing southerly winds) and should these winds remain elevated
through the afternoon VFR may need to be prevailed at Galveston
as well. The KHGX VAD wind profiler shows 30-35 knot winds within
4kft AGL and observations have already shown some of these winds
being transported to the surface. Expect 15-20 knot winds to
continue through the afternoon with gusts approaching 25-30 knots
through sunset at the inland terminals. SHRA with a few embedded
TSRA have also been able to develop early this afternoon as an
impulse evident on SPC Mesoanalysis lifts across North Texas and
CLL, UTS, and possibly CXO may be skirted by this activity before
it diminishes with loss of forcing.

Winds will decrease somewhat as a prefrontal trough and associated
cold front reach the terminals. The initial approach of both of
these features looks to result in a west to southwest wind shift
after 00Z with a thin band of showers and a few thunderstorms
developing along this line. Latest high resolution guidance shows
somewhat questionable convergence along this line, which has
developed south of DFW/DAL as of this writing, leading to low
confidence on terminal impacts as it arrives. TEMPO groups may be
needed with the 21Z amendment for CLL and UTS based on radar
trends. Expect the front to push to near the coast sometime around
10-12Z. Upglide behind the front may allow for SHRA to linger
behind the front as far north as IAH Sunday morning before another
impulse lifting out of Mexico arrives and allows activity to
spread farther north towards CLL and UTS. Enough forcing may be
present with this impulse to tap into some elevated instability
across the region (MUCAPEs around 500 j/kg and mid-level lapse
rates around 7 C/km) to result in embedded TSRA development by
late morning Sunday. IFR and MVFR conditions are expected to
prevail as this rain develops along the coast and spreads inland.

Huffman

&&

.PREV DISCUSSION... /ISSUED 1132 AM CST Sat Feb 24 2018/

UPDATE...
A Wind Advisory has been issued for Colorado, Austin, Waller, Fort
Bend, and Brazoria counties and southwestward. The Wind Advisory
is in effect until 4 PM this afternoon. Observations have shown
sustain winds speeds near 25 mph, with frequent wind gusts above
30 mph. Daytime heating will result in the mixing of these
stronger winds aloft down to the surface. Hazardous travel
conditions will be possible, especially along elevated roadways
and bridges. We will continue to monitor observations for
potential expansion in area of the Wind Advisory, as well as
monitor trends in observations if conditions look likely to
continue into the early evening hours.

Hathaway

PREV DISCUSSION... /ISSUED 1025 AM CST Sat Feb 24 2018/

UPDATE...
Starting off your weekend with a muggy Saturday morning, as
southerly winds are helping to keep dew points in the mid 60s to low
70s. Mostly cloudy skies will hold tight throughout the day today,
and expecting high temperatures to reach into the upper 70s. Have
lowered our high temperatures today a tad, to account for this cloud
cover.

Low level winds will increase in speed this morning, helping to mix
out the patchy fog along the nearshore waters and both Matagorda
and Galveston Bays. Additionally, breezy conditions will be felt
across southeast Texas today as these low level winds mix down to
the surface. Low level winds speeds will decrease tonight,
allowing for the development of patchy fog to return to the
forecast shortly after sunset. The SREF and HRRR are both
indicating the potential for patchy fog returning to the coastal
waters between 00-06Z Sunday.

Upper level water vapor imagery continues to show a long strand of
disturbances, embedded in southwesterly flow aloft helping to act
as a forcing mechanism this morning. Radar imagery is pick up on
some scattered showers producing light rain in the far northern
reaches of our forecast area around College Station. Short term
guidance such as the HRRR and Texas Tech WRF are keeping most of
the shower and isolated thunderstorm activity north of a line
from Washington to Trinity county. This region will likely see
the best chance for precipitation as we move into the afternoon
hours as an area of low pressure shifts northeast of Texas. Still
cannot completely rule out a few isolated strong cells in this
region, as low level instability increases this afternoon, with
surface to 3 km lapse rates approaching 6-6.5 deg C/km. Moisture
will also be on tap with precipitable water values ranging between
1.6-1.8 inches. Gusty winds will likely be the main threat
possible beneath some of the stronger storms this afternoon.

Hathaway

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      77  54  67  48  73 /  70  20  60  20   0
Houston (IAH)              79  61  67  53  74 /  40  60  80  30  10
Galveston (GLS)            77  65  70  61  69 /  20  80  60  50  10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Wind Advisory until 4 PM CST this afternoon for the following
     zones: Austin...Brazoria...Colorado...Fort Bend...Jackson...
     Matagorda...Waller...Wharton.

GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 6 PM CST this evening
     for the following zones: Coastal waters from Freeport to
     the Matagorda Ship Channel out 20 NM...Coastal waters from
     High Island to Freeport out 20 NM...Waters from Freeport to
     the Matagorda Ship Channel from 20 to 60 NM...Waters from
     High Island to Freeport from 20 to 60 NM.

&&

$$

Discussion...08
Aviation/Marine...14



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