Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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953
FXUS64 KHGX 110414
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1014 PM CST Sat Dec 10 2016

.UPDATE...
Areawide overcast conditions this evening that will persist
through Sunday. An moderate onshore wind will continue to advect
in higher low level moisture...with stout 30 to 40 knot mid-level
southwesterlies overriding a relatively cool...moist near surface
layer. This isentropic upglide scenario will maintain mainly overcast
skies and increase the probabilities for southwest-moving-northeast
light rain showers. A near saturated column up to a near 800 mb
warm nose should support at least a moderate chance for periods of
very light rain. This warm air advection pattern will push daytime
temperatures up into the above normal upper 60s to lower 70s. Partially
cloudy skies with a weakened southerly wind may allow areas of fog
to develop during the overnight early Monday morning hours. 31

&&

.PREV DISCUSSION... /ISSUED 517 PM CST Sat Dec 10 2016/

AVIATION...
Can`t argue with trends already advertised in the 18z TAFs and
very little will be changed in the 00z package. Ceilings will
transition downward into MVFR territory later this evening, and
possibly down to IFR overnight near CLL. Very little improvement
expected during the day Sunday with 1000-2500ft decks persisting.
Southerly winds will become gusty during the late morning and
aftn hours. Look for some spotty -ra/dz as well during the aftn.
Timing/location is questionable so didn`t include mention in the
00z TAFs attm, but might need to in later issuances. 47

PREV DISCUSSION... /ISSUED 347 PM CST Sat Dec 10 2016/
After a chilly start this morning, not much in the way of
significant impacts from weather are expected for the next several
days, as a general warming trend is expected for the rest of the
weekend. A couple weak fronts should manage to push at least
partly into the area, but don`t look to do much beyond pause the
warming and bring a stretch of low rain chances to the area
through the week.

Tonight through Monday...
High pressure continues to slide across the Ohio Valley today. As
it slides off, easterly winds will become southeasterly and
further establish onshore flow. After a partial break in clouds
this morning, overcast skies have returned to the vast majority of
the area as Gulf moisture increases. There is a chance for some
showers tonight into Sunday as a very ill-defined midlevel
shortwave should move through the area, but soundings show a
pretty dry environment above the low-level saturation, so don`t
expect more than some weak warm-advection showers as we move into
a pre- frontal environment. Perhaps the more notable weather
feature will be the increase in temperatures, as low temps tonight
will likely be similar to our recent high temperatures thanks to
the influx of warmer, more moist air. High temperatures will also
be warmer, with places closer to the coast reaching into the mid
70s for Sunday and Monday. On Monday, a weak front should push at
least partly into the area. Guidance pretty unanimously brings
this front near the coast, though there isn`t a whole lot of upper
support for the front as upper flow remains disturbingly close to
zonal for such a surface solution. Given the relatively low impact
from such a weak front, have gone ahead and followed the guidance,
even if there is some doubt it will make it so far south. If that
doesn`t pan out, the difference will be little more than a
moderate wind shift and a few degrees of temperature.

Tuesday into next weekend...
As mentioned in the previous section, the first front will do
little more than slightly set back the warming trend. Though there
may be some question as to exactly where this will happen, the
front then looks to stall and slowly wash out of the next day or
so, stretching rain chances out into the middle of next week. By
that time, a reinforcing front looks to move through, which will
continue the potential for showers and maybe a rumble of thunder,
though some pretty fair midlevel warming looks to take place, and
the environment looks at least weakly capped. However, high
pressure in that front`s wake will at least make temperatures
notably cooler for a day or so. However, the progressive pattern
looks to continue, with the high moving on and onshore flow
returning to start a new warming trend into the late week. Beyond
then, look for yet another front to move through the area, but
good luck in trying to establish a solid timeframe on it. There is
considerable spread, not just between different models, but within
individual ensemble suites. For example, high temps in the 12Z GEFS
for Intercontinental at the end of next week range from 58 degrees
to 75 degrees. If meaningful, this would indicate a slight nudge
towards the warmer scenario preferred by the last shift. And,
given that a more meaningful front will require a more amplified
pattern, and this appears to be emerging in the operational
guidance, I am similarly inclined to slow things down a bit and
keep it warmer into Saturday. That said, I only nudged temps up a
bit from the previous shift`s compromise, and keep a bit of a
hedge towards a cooler scenario. In honor of today`s Army-Navy
game, a football metaphor: the forecast is essentially punting
now in hopes that the next run of models will give us better field
position on the next drive.  Luchs

MARINE...
Will continue the SCEC 20-60nm and transition over to an SCA tonight
with the expectation that winds will increase and seas will begin to
build.  As gradient tightens up this evening and throughout the
night with LLJ axis moving over SETX Sunday and Sunday night winds
may approach 20 knots in the far coastal waters. May see some sea
fog threat Monday after 06z for the Matagorda bay area and possibly
even into the Galveston Bay region by 12z. Confidence west is much
higher than near Galveston Bay. Weak cold front stalls inland late
Monday with a stronger cold front arriving Wednesday night. At least
a short period of SCA conditions in the wake of the front before it
returns back as a warm front early Friday. May have a great chance
of sea fog with the warm frontal passage. 45

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      50  70  57  69  54 /  20  30  20   0  10
Houston (IAH)              52  72  64  75  60 /  10  30  30  20  20
Galveston (GLS)            58  71  66  72  65 /  10  10  20  30  30

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...Small Craft Advisory until 6 AM CST Sunday for the following
     zones: Coastal waters from Freeport to the Matagorda Ship
     Channel out 20 NM...Coastal waters from High Island to
     Freeport out 20 NM...Waters from Freeport to the Matagorda
     Ship Channel from 20 to 60 NM...Waters from High Island to
     Freeport from 20 to 60 NM.

&&

$$

Discussion...31



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