Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 231742
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1242 PM CDT Tue May 23 2017

.AVIATION...
Still anticipating SHRA/TSRA to develop along and ahead of a cold front
and move generally from the NW to the SE across parts of SE TX this
afternoon through this evening. Look for associated lower ceilings
and visibilities with these storms. Skies will gradually clear out
behind the storms with VFR conditions expected for the overnight hours
and on into the day tomorrow. N to NW winds this afternoon could get
gusty in/around possibly strong/severe storms.  42
&&

.PREV DISCUSSION... /ISSUED 1038 AM CDT Tue May 23 2017/

UPDATE...
Main changes made to the ongoing forecast include updating rain
chances, clearing sky cover west of Interstate 45 based on
satellite trends, and increasing temperatures for this afternoon.

Surface analysis as of 8 AM CDT showed a cold front stretching
from west of the D/FW Metroplex southwest towards the Davis
Mountains in West Texas. Dry and mostly sunny to partly cloudy
conditions are expected to persist across most of the forecast
area this morning ahead of the cold front, but the northern
counties may see a light shower or possibly a thunderstorm as
diminishing morning convection reaches the Piney Woods from North
Texas. Attention this afternoon will then turn to the approach of
the cold front from the northwest as diurnal heating ahead of the
front contributes to enough destabilization (2000-2500 J/kg of
SBCAPE) ahead of the front to promote scattered thunderstorms
along and ahead of the front. With the left front region of a
100-120 knot upper level jet moving across the region and
effective bulk shear values exceeding 35 knots during this time,
organized thunderstorms (possibly supercells) will be capable of
becoming strong to severe. Morning soundings from Lake Charles and
Corpus Christi showed mid-level lapse rates ranging from 7.7-8.2
C/km and these steep rates will enhance updraft acceleration as
well as enhance the potential for damaging winds. Drier air in the
mid-levels (wet bulb zero heights 10.8-11.6kft on morning
soundings) will also enhance evaporational cooling, allowing for
low enough freezing levels to promote large hail development. In
addition to thunderstorms capable of large hail and damaging
winds, brief heavy downpours will also be possible but fast storm
motions out of the northwest at 20-25 knots should mitigate
against any widespread flooding concerns.

Best chances for severe weather appears to be west of Interstate
45 at this time, but the severe weather threat will exist across
the entire region before the front clears the coast. May see a
few showers initiate ahead of the front along a prefrontal
trough/wind shift by early afternoon, with the front (and
associated thunderstorms) reaching the northern forecast area by 4
PM, the Houston metro by 8 PM, and moving off the coast by
midnight.

Will have to keep a close eye on temperatures today as they are
already higher than guidance and have concerns that the clearing
skies that are occurring now may result in higher temperatures
than currently forecast west of Interstate 45 (which would also
increase the severe weather threat as it results in even more
instability). High temperatures are currently forecast to rise
into the low to mid 80s.

Huffman

PREV DISCUSSION... /ISSUED 517 AM CDT Tue May 23 2017/

DISCUSSION...
Per trends overnight, it looks like the cap is holding over SE TX
as the strong convection moving in from the west falls apart when
entering the area. Surface analyses showing that the main frontal
moved offshore last night with weak/steady CAA in its wake so far
this morning. However, we are not quite out of the woods just yet.
The approach/passage of the strong shortwave timed with peak heat-
ing and the stronger front will be enough to break the cap by the
late afternoon/early evening hours. Also of note...are progs of a
strongly divergent upper jet structure at this same time. SPC has
SE TX in Marginal for today with the main threats being hail/wind.

The passage of the cold front tonight will usher in drier/quieter
period of weather for the area through the rest of the week. Cool-
er temps/dewpoints overnight through most of Weds should begin to
modify Thurs with the return of onshore winds/low-level moisture.
The next best chances for rain are expected to return to the area
late Sat as another front moves into and then stall just north of
the region. Models are then drawing a series of disturbances from
the west (via the zonal upper flow) to interact with the boundary.
41

MARINE...
Showers and thunderstorms will be possible this afternoon through
tonight ahead of an approaching cold front which should push off the
coast late tonight/early Wednesday morning. Moderate northerly winds
and building seas are expected in the wake of this front, and
caution or advisory flags may be required. Onshore winds are set to
return to the area overnight Wednesday night before strengthening
with a tightening gradient the rest of the week and into the
weekend. 11

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      81  57  83  63  89 /  50  30  10   0   0
Houston (IAH)              84  59  84  63  89 /  30  60  10   0   0
Galveston (GLS)            82  64  81  72  85 /  20  50  10   0   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

Discussion...14
Aviation/Marine...42


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