FXUS64 KHGX 192012

Area Forecast Discussion
National Weather Service Houston/Galveston TX
312 PM CDT Thu Jul 19 2018

At 200 PM, a weak area of low pressure was noted over southern
Kansas with an area of high pressure over the west central Gulf
with a light south-southwest flow over the region. Satellite
derived PW fields show a swath of 2.0 to 2.1 inches hugging the
coast. Daytime heating and the sea breeze could generate an
isolated shower early this evening near the coast but think
subsidence from an expanding upper ridge will keep things quiet.
Speaking of the upper ridge, it is located over central New Mexico
and extends east into western LA. 850 mb temperatures have warmed
and are now 22 C at both LCH and CRP. There are still several
hours of heating to go and temperatures still have the potential
to reach 100 degrees over the W-NW parts of the region and maybe
into the Houston area.

Both the NAM and the ECMWF show significant warming at 850 mb on
Friday and beyond while the GFS doesn't show nearly as much
warming. With a building 597 dM ridge building over the state, it
seems reasonable to expect some warming at 850 mb so will lean
toward the NAM and ECMWF for temperatures through the weekend.
Triple digit heat should return to most of SE TX on Friday and
peak over the weekend with the warmest temperatures of the year
possible on Sunday and Monday. There is considerable dry air in
the soundings so there should be some mixing of drier air to the
surface. The extent of the mixing will be critical in determining
afternoon heat index values. Have again leaned toward the drier
raw NAM12 dew points and blended it with Hi-Res ARW/NMM dew
points. Even leaning toward the the drier guidance still produces
heat index values between 105-110 degrees tomorrow and as high as
112 degrees on Saturday. A Heat Advisory may be required on Friday
but will not issue the Advisory at this time. Would prefer to
wait and see what the maximum heat index values/temperatures are
today and evaluate again with the 00z data.

The GFS remains aggressive with bringing an upper level low into
the area toward the middle of next week. Both the ECMWF and the
GFS bring a weak front into the region on Tuesday but the GFS is
producing precipitation on the boundary while the EC keeps things
dry. The upper ridge begins to retreat at this time and the
northerly upper flow supports bringing the front south. However,
the ridge is close enough to impart subsidence so will again lean
toward the drier guidance. Heights begin to fall during the second
half of next week and slightly cooler surface temperatures are
expected. PW values will increase to between 1.80 and 2.00 inches
so the combination of lower heights, daytime heating and
increasing moisture should allow for some scattered showers and
thunderstorms next Thursday and Friday.


Generally expecting moderate south to southwest winds in a
10 to 15 knot range, smooth to slightly choppy bays waters
and 2 to 4 foot seas for the next several days. Area winds
and seas have a chance on getting a little higher, & small
craft advisories might occasionally be needed. 42


College Station (CLL) 77 101 77 103 77 / 10 0 0 10 0
Houston (IAH) 78 100 79 101 78 / 10 10 0 10 0
Galveston (GLS) 82 92 83 92 82 / 10 10 0 10 0



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