Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 121139

Area Forecast Discussion
National Weather Service Houston/Galveston TX
639 AM CDT Mon Apr 12 2021

.AVIATION [12Z TAF Issuance]...

Areas of radiation fog and IFR cigs are present to the west of the
I-10 corridor this morning, with LBX/SGR reporting reduced
visibilities over the past few hours. Fog should begin to lift
after sunrise upon daytime heating. Elsewhere, conditions remain
generally clear. Persistent onshore flow will result in increasing
cloud cover throughout the day today ahead of the approach of a
surface cold front overnight. Cigs should drop to MVFR levels
after 00Z, with scattered showers beginning to develop ahead of
the advancing boundary by the early hours of tomorrow morning.
With coverage expected to be fairly isolated in nature, have
maintained VCSH wording in the current TAF package.



.PREV DISCUSSION... /ISSUED 422 AM CDT Mon Apr 12 2021/

SHORT TERM [Today Through Tuesday]...

South to southeasterly winds, though fairly light, will continue
to steadily supply SE TX with moisture as we begin the week. The
synoptic pattern remains relatively unchanged, with broad surface
high pressure remaining in place over the southeastern Gulf, lower
pressures over the Four Corners region, and a fairly zonal pattern
aloft. Total PWs should reach 1.25in or higher across the
majority of the area by this afternoon given the aforementioned
persistent moisture transport, with the most ample tongue of
moisture in the vicinity of Matagorda Bay. With little in the way
of surface instability, capping at around 900mb, and a lack of a
synoptic trigger mechanism, Monday should be mostly rain-free.
Expect slightly unseasonably warm conditions to remain the story
with daytime highs reaching the low to mid 80s. Lows will only
drop to around 65-70 as increasing cloud cover and WAA will
inhibit nocturnal cooling.

By late Monday, a weak surface cold front will enter the southern
Plains and advance towards SE TX by early Tuesday. Scattered
showers and storms will begin to develop ahead of the approaching
boundary by early Tuesday, increasing in coverage as the boundary
reaches the Houston metro area by Tuesday afternoon. Highs on
Tuesday will be dependent on the exact progression of the surface
boundary. The northern third of the area will struggle to reach
the upper 70s given the expected CAA behind the advancing
boundary, while the metro area and coast should remain in the low
to mid 80s.


LONG TERM [Tuesday Night Through Monday]...

Global models continue to show the frontal boundary stalling out
along the coast on Tuesday night, and slowly advancing towards the
coast throughout the day on Wednesday. Meanwhile, with the 500mb/300mb
pattern remaining generally zonal, a series of weak disturbances
embedded within the mean flow along with the presence of the front
will provide the area with periods of scattered showers and
storms through the end of the week. While moisture will be
abundant (total PWs of 1.5 to 1.75 in), model soundings indicate
marginal instability and thus do not anticipate widespread
coverage of any developing storms nor particularly strong
intensity. Through the end of the week, most locations look to
receive around an inch of new rainfall.

A slight cooldown in temperatures is expected during the latter
half of the week as weak northeasterly winds remain persistent
over most of SE TX. Area-wide high temperatures should be confined
to the upper 70s on Thursday, and the upper 60s to mid 70s on
Friday. Given the persistent cloud cover, however, radiative
cooling will not be particularly efficient and overnight lows will
remain in the upper 50s to mid 60s.

A second, stronger surface cold front is expected to traverse the
area on Friday afternoon/evening with more widespread showers and
storms expected to accompany its passage. This will pave the way
for a cooler and drier weekend as moderate offshore winds develop
in the wake of the departing boundary on Saturday, with highs
through Monday not expected to eclipse the mid 70s and overnight
lows dipping into the upper 40s/lower 50s.




Winds and seas continue to diminish across the coastal waters,
and the caution flags have been allowed to expire for the offshore
waters as a result. The onshore wind pattern will likely persist
through mid-week, though wind speeds do not look to exceed caution
thresholds during this time. A weak cold frontal boundary will
approach the area on Tuesday, but is expected to stall near the
coast before slowly pushing offshore on Wednesday. Scattered to
isolated showers and storms will accompany the advancing front,
with weak offshore winds briefly developing in its wake on
Wednesday night and Thursday. A second, stronger cold front will
approach the coast on late Friday/early Saturday.



College Station (CLL)      86  64  77  64  75 /  10  30  30  50  30
Houston (IAH)              85  69  83  70  78 /  10  30  40  40  40
Galveston (GLS)            79  71  80  72  78 /   0  20  30  30  40




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