Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 160517
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1117 PM CST Wed Nov 15 2017

.AVIATION...
Mid-level clouds continue to hang tough over many sites, though
continued signs of erosion are occurring. Though this deck has
held off the development of fog so far, VLIFR conditions have
already developed at LBX, and IAH on the fringe of the deck now
has MVFR visibility. Thus, keep similar trends with the
expectation that these mid-level clouds will continue to erode in
the overnight hours, but delay some in bringing them in. Given the
trends at IAH and LBX, suspect that lower visibilities will ensue
even before the mid-level deck has fully gone away.

GOES-16 nighttime microphysics imagery also shows lower clouds
developing over Liberty County. Though not over any TAF sites yet,
do expect weak isentropic lift to continue to build these clouds
through the night as well, which would result in MVFR ceilings in
addition to visibilites.

Both ceilings and visibility should improve by late morning or
early afternoon, with VFR returning. Every expectation that we`ll
see similar results tomorrow night as well, but this lies beyond
the scope of the current forecast for all but IAH - here, begin to
hint at more of the same in a similar pre-frontal environment.

Luchs

&&

.PREV DISCUSSION... /ISSUED 838 PM CST Wed Nov 15 2017/

NEAR TERM [Through Tonight]...
GOES 16 IR/Fog channels picking up on low/mid level cloud deck
with surface obs showing ceilings around 6000-7000ft. This cloud
cover shows signs of eroding basically along and southeast of the
US 59/I-69 corridor through Houston. Expectation is for the
clouds to continue to erode and then fog to form overnight. Still
the fog forecast hinges on cloud cover eroding. That said
temperatures are in the low 70s to upper 60s and surface dewpoints
are higher in the mid/upper 60s so it may not take as much
cooling to achieve saturation and fog. Adjusted the forecast to
delay the on set of patchy/areas of fog across the area. Also
adjusted the min temperature forecast up a couple of degrees since
there will not be much cooling and dewpoints are higher.

Cold front is still slated for Saturday, but despite some
moisture return, rain chances really do not look that high.
Instability looks meager at best, and capping, well capping is
strong just by looking at 850mb southwesterly winds and
temperatures around 17-19C. For now just adjusted PoPs down to 20
percent and mention showers at this point, but consider yourself
lucky if you get any rain with the front. Max temperatures on
Saturday may also be a bit higher than currently in the forecast
so look for future forecasts to adjust those numbers. High temps
will also be subject to timing of the cold front which is far from
a slam dunk forecast as well.

Overpeck

PREV DISCUSSION /Issued 534 PM CST Wed Nov 15 2017/...

AVIATION.../00Z TAF/
Large midlevel cloud deck continues to blanket most of Southeast
Texas, leaving LBX on the fringe and GLS the lone site completely
in the clear. Winds have been more easterly than the expected
southeasterly and very light to calm, perhaps because of a subtle
surface trough. Do expect bases to lower overnight and eventually
drop to MVFR late. This poses the question on fog potential with
low clouds in place. Think there is enough low level moisture and
light winds, combined with the clouds today keeping temperatures a
little more in check, that fog may still emerge. That said, of
the sites under the deck, only take CXO to IFR visibility and hold
the rest at MVFR. Do go much more aggressive with fog at LBX
under more clear skies.

Tomorrow, delay improvement to VFR more than guidance, but think
that by mid-afternoon ceilings should be above the MVFR threshold
across the area. Perhaps am optimistic in going SCT with those
afternoon clouds, and a repeat of today is not out of the
question.

Luchs

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      65  79  65  82  66 /  10  20  10  20  10
Houston (IAH)              64  79  64  81  68 /  10  20  10  10  10
Galveston (GLS)            69  76  69  77  70 /  10  10  10  10  10

&&

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

$$

Discussion...39
Aviation/Marine...25



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