Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 211740
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1240 PM CDT Wed Sep 21 2016

.AVIATION...
Dry air over the eastern half of the CWA should keep clouds at bay
for the rest of the afternoon. Short term guidance suggests that
showers may clip the coast south of Freeport but area TAF sites
will likely remain dry. Moisture levels creep back up tonight as a
weak boundary over the GULF becomes diffuse and onshore winds
redevelop in response to lowering pressures out west. The RAP
brings in a slug of moisture prior to sunrise and develops showers
along a developing coastal trough. The RAP looks overdone but
all models show some weak speed and directional convergence along
the coast. Daytime heating and ample moisture should allow for
scattered showers on Thursday afternoon and added a VCSH at KIAH
between 19-00z Thursday. 43

&&

.PREV DISCUSSION... /ISSUED /

UPDATE...
A very pleasant start to the day per a relatively drier resident
air mass. One lone shower off the SW Brazoria coastline formed
along what looks like a remnant land breeze boundary. LCH sounding
depicting 1.24 inch pwat column moisture and this is being advected
into southeastern Texas upon easterly steering flow. This drier
air, in tandem with the subsidence provided by the 593 dam upper
ridge centered over the Red River Valley, has created mostly sunny
skies; forecast afternoon temperature trends warming into the low
to mid 90s. Afternoon mix down of mid-level air will lower interior
surface dew points into the 60s, possibly as low as the lower 60s
across the far northern counties; this will translate to today`s
relative humidities lowering into the mid 30 to lower 40/50 percentiles.
East flow veers onshore by early tomorrow morning and lower level
moisture will begin its climb, reaching recent near 2 inch pwats
over the weekend. Drier air aloft with an overnight decoupled wind
field/near surface inversion, will create an environment
conducive to early morning (inland rural) patchy fog development.
31

PREV DISCUSSION...

DISCUSSION...

The passage of the weak cool front has brought drier and slightly
cooler air to SE TX overnight/this morning. However with the lower
dew points (along with clear skies/calm winds) we will also see
some patchy fog across the area through the mid morning hours. Of
note over the nearshore waters, a couple of showers did manage to
develop (moving to the SW). Despite the cooler (than it has been)
start to the day, high temps this afternoon are still expected to
be slightly above normal. However heat indicies should remain be-
low critical levels given the drier air mixing into the region.

Rain chances still progged to return to the region later tonight/
early tomorrow morning via the south as deeper moisture begins to
move in from the Gulf. With the surface high moving off to the NE
and pressure falling over the Rockies, onshore winds will develop
late tonight and slowly strengthen through Sat (as a storm system
develops and moves into western Central Plains). No major changes
with the chance POPs already in the grids for this time.

While in much better agreement with each other with this run...we
are still seeing a lot of discrepancies with extended models from
previous runs. The consensus remains with a highly amplified slow
moving upper low/trof developing out west Sun before it begins to
slowly translate east with an associated cold front. (!!!) Storms
along/ahead of this boundary will keep POPs elevated Mon/Mon nite.
Confidence levels on this panning out: muted optimism. 41

MARINE...
Northeasterly flow in place this morning with 1-2 foot seas.
Isolated showers a good bet through the morning hours with what
appears to be a boundary from GLS southeastward. Winds should be on
the increase Thursday through Saturday and might even flirt with
SCEC well offshore Friday evening and Saturday evening. Seas should
build to 3 to 5 feet with a long SE fetch.  A little more confidence
that first potent cold front expected to move offshore
Monday...still unsettled on rain chances and timing but overall
pattern looks conducive to pushing the front into the Gulf. Offshore
winds (moderate) prevail Tue-Wed. 45

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      96  72  94  75  91 /   0   0  10  10  30
Houston (IAH)              95  73  92  75  89 /   0  10  20  10  30
Galveston (GLS)            90  81  89  81  87 /  10  10  20  20  40

&&

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

$$

Discussion...31
Aviation/Marine...43



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