Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 151058
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
558 AM CDT Tue May 15 2018

.AVIATION...
Areas of fog will affect KSGR and KLBX this morning but current
thinking is that only some very shallow ground fog will affect
the Houston terminals and should not limit visibility. Initial
heating this morning could briefly produce a sct/bkn025 deck
between 15-17z. Drier air aloft will mix down this afternoon and
not seeing much in the way of cloud cover. Cirrus returns tonight
as convective debris from NC TX drifts to the SE. Differential
heating should be strong enough to generate another sea breeze
today and will affect KIAH between 21-22z. 43

&&

.PREV DISCUSSION... /ISSUED 401 AM CDT Tue May 15 2018/

DISCUSSION...
Early morning water vapor imagery and 00Z RAOB analysis show
upper ridging nosing into Texas from Mexico. Regional radar mosaic
shows the state is mostly dry this morning, save for a
thunderstorm complex translating eastward along the Red River.
Closer to home, patchy fog was gradually spreading in areas
outside of the Houston metro where passing cirrus has done little
to impede radiational cooling. Some of the fog that develops this
morning will be locally dense, but expect all fog that develops to
lift around or shortly after 9 AM as insolation increases.

More heat is expected today with temperatures again approaching
record high values this afternoon in the low to mid 90s. While a
dry airmass (precipitable water values only 1.1-1.2 inches)
precludes mention of any rain during the morning hours, small
disturbances rotating around the periphery of the upper ridge
today look to trigger rounds of showers and thunderstorms across
portions of Oklahoma and North Texas. Several higher resolution
models, including a few of the SPC HREF members, HRRR, and TTU-
WRF, indicate that enough of a cold pool may be able to develop
with some of this activity that weakening shower or thunderstorm
activity may be able to propagate into the Brazos Valley by this
evening. A very dry subcloud layer and downdraft CAPE values in
excess of 1000 J/kg appear supportive of an environment capable of
that, but due to the aforementioned concerns with available
moisture have only added silent 10 PoPs to the forecast for the
Brazos Valley this afternoon and evening. For tonight, expect
another round of radiation fog developing west and southwest of
the Houston metro as lows fall into the mid 60s to low 70s.

Surface high pressure sliding into the northwest Gulf during the
day Wednesday will veer surface winds to the west and southwest
across the region, warming up high temperatures a degree or two
more than today into the mid 90s. Wednesday may again be another
day with record high temperatures. Shortwave ridging amplifies
over Texas Wednesday night through Friday as a compact closed low
moves into the Four Corners region from the Pacific with upper
troughing over the northeast Gulf. Mid-level (500 MB) heights in
the 582-585 decameter range combined with west to southwest
surface winds will promote afternoon temperatures into the low to
mid 90s across most of Southeast Texas during this time, again
approaching record values at many locations. Increased subsidence
from the presence of this ridging will keep the late week period
dry for Southeast Texas.

Despite the persistence of the upper ridge heading into the
weekend and beginning of next week, temperatures are expected to
moderate a few degrees into the upper 80s to lower 90s as the
surface high over the northwest Gulf slides east and allows for
south to southeast surface winds to resume. It won`t feel too much
cooler though, as onshore winds maintain elevated near surface
moisture and keep heat index values in the mid 90s. May see enough
moisture return for a few isolated showers or possibly a
thunderstorm to develop along a potential sea breeze on Sunday and
Monday, but generally dry weather is expected to continue into
the upcoming week.

Huffman

MARINE...
High pressure over the eastern Gulf and lower pressures over West
Texas will maintain onshore winds through the week. The gradient
will remain very weak and a weak land breeze could develop late
and early morning before differential brings winds back to the
S-SE. Winds will begin to increase on Friday as low pressure
develops over the Texas panhandle and deepens as it moves across
the southern plains. A moderate onshore flow will prevail through
the weekend. Tide levels are expected to increase toward Friday
with tide levels approaching 3 feet. 43

CLIMATE...
Near to record high temperatures will be possible across
Southeast Texas over the next few days. A listing of these record
high temperatures for the Southeast Texas climate sites are
included below. Because of how early in the season this heat is
occurring, residents may be more prone to heat illness and are
encouraged to take proper precautions if spending extended time
outdoors this week.

..MAY 15...
LOCATION         RECORD HIGH     YEAR
Houston IAH           92         2003
Houston HOU           94         1978
College Station       95         1925
Galveston             89         1875

..MAY 16...
LOCATION         RECORD HIGH     YEAR
Houston IAH           93         2003
Houston HOU           93         1933
College Station       95         2003
Galveston             90         1875

..MAY 17...
LOCATION         RECORD HIGH     YEAR
Houston IAH           95         1894
Houston HOU           94         1998
College Station       96         1925
Galveston             87         2017

Huffman

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      92  67  92  68  93 /  10  10   0   0  10
Houston (IAH)              94  70  94  71  94 /  10   0   0   0  10
Galveston (GLS)            84  74  88  75  89 /   0   0   0   0  10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Dense Fog Advisory until 9 AM CDT this morning for the following
     zones: Austin...Coastal Brazoria...Coastal Jackson...
     Coastal Matagorda...Colorado...Fort Bend...Inland
     Brazoria...Inland Jackson...Inland Matagorda...Waller...
     Wharton.

GM...NONE.
&&

$$

Discussion...14
Aviation/Marine...43



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