Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 182023

Area Forecast Discussion
National Weather Service Houston/Galveston TX
323 PM CDT Wed Jul 18 2018

Upper level high pressure near the 4 corners will maintain a firm
grip over SE TX through early net week. The ridge will expand
eastward and become centered over the panhandle by early Saturday
with heights building to 595 dm over the region. 850 temps warm
considerably through early next week and 100 degree heat is
expected over much of the area. The only uncertainty regarding the
forecast is the amount of dry air that will mix to the surface
and the inland extent of the sea breeze. Have held off on a Heat
Advisory for today as the sea breeze is struggling to move inland
and dew points are mixing out. On Thursday and Friday, have used
the raw NAM12 dew points which shows significant mixing over the
NW zones. A Heat Advisory may be required in the afternoon for the
coastal zones as the sea breeze moves inland.

Hot temperatures are expected over the weekend with 100 degrees or
higher expected most areas except along the coast. Again, the
level of mixing/dry air will determine heat index values. At this
time, it appears that max heat index values will rise to between
108 and 112 degrees on Sat/Sun. This will require a Heat Advisory.
The upper ridge will retreat a bit westward on Monday and Tuesday
but the strength of the ridge will preclude any mention of rain
through Tuesday. 850 mb temps are warmest on Monday and think
Monday will be the hottest day of this unseasonably warm period.
The upper high moves further west on Tuesday into Wednesday as an
upper low over the northern Gulf coast moves west. The lower
heights would suggest slightly cooler temperatures and an increase
in rain chances. Some differences between the warmer/drier ECMWF
and the cooler and wetter GFS. The ECMWF rebuilds the upper ridge
into Texas toward the end of the week. The Canadian model also
keeps the ridging in place so have leaned toward the warmer/drier
ECMWF for the long term portion of the forecast. 43


Surface high pressure settled into the northwestern Gulf has
weakened any discernible larger scale onshore pressure gradient.
This has allowed for a general weak southwesterly breeze. The
diurnal thermal gradient will swing coastal winds around to the
south and slightly strengthen them late in the day. The overall
relatively weaker southwesterly fetch will keep average sea heights
at or under 3 feet throughout the week. High pressure at all levels
will also inhibit any shower or thunderstorm development. 31


College Station (CLL)      76 101  77 102  77 /  10  10  10   0   0
Houston (IAH)              78  99  79 100  78 /  10  10  10  10   0
Galveston (GLS)            82  92  82  92  82 /  10  10  10  10   0




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