Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 171204

Area Forecast Discussion
National Weather Service Houston/Galveston TX
604 AM CST Tue Jan 17 2017

Surface analysis at 11Z has cold front ever so slowly from
KELA/KTME to north of KIAH. TAF for IAH has wind shift closer to
16Z based on mesoscale models but obs showing this may need to be
moved up closer to 14-15Z. TAFs will keep mainly MVFR/IFR ceilings
going through much of the next 24 hrs. Ceilings may be more MVFR
during the afternoon but IFR will be possible going into the
overnight period again. Also IFR may be more possible behind the
front for KCLL/KUTS/KCXO. Shower activity will also affect
ceilings so expect there to be some fluctuations in conditions.

Models hit tomorrow morning harder with convection and overall
pattern suggests more widespread convection. TAFs will go with
mention of thunderstorms in the morning and then perhaps tapering
off depending upon upper level support and any stabilization of
the boundary layer. Needless to say but cold front combined with
convection both surface based and elevated may for challenging
TAFs for the next 24 to 48 hours.



UPDATE...issued dense fog advisory for Galveston Bay and adjacent
waters. Potential for visibility to drop below 1 nautical mile
through the morning hours.


.PREV DISCUSSION... /ISSUED 415 AM CST Tue Jan 17 2017/

Chances for rain and thunderstorms will continue over Southeast
Texas through Thursday. The main driver for the rain chances will
be an upper level low pressure trough which this morning extended
from the western Great Lakes region southwest to Baja California.
A nearly stationary front will meander over the forecast area to
help provide a low level focus.

The first item of concern is the increasing chances for showers
and isolated thunderstorms today. The next item of concern is the
impact of widespread rain and thunderstorms on Wednesday and
Wednesday night.

The models looked to be in fairly good agreement with an upper low
forming over AZ/NM early this morning with the system then pushing
into the Plains over the next couple of days. Water vapor showed
a decent moisture tap from the Pacific developing today. Although
some training may bring localized decent rainfall amounts focused
to where the frontal boundary will be located, the showers should
be moving fairly quickly and not be as widespread as tomorrow. On
Wednesday, the NAEFS model showed PWs reaching to the 99th
percentile as the area comes under the influence of the right-rear
quadrant of the upper jet. Given these factors, think that
widespread rain and thunderstorms look better on Wednesday and
Wednesday night.

The GFS and ECMWF are in remarkably good agreement for the end of
the week going into early next week. As the upper level system
moves northeastward on Thursday, the rainfall threat will move
east and off the coast probably during Thursday afternoon. An
upper level shortwave ridge will then bring drier conditions on
Friday before another broader upper trough moving from the Pacific
Northwest into the Plains sends a series of shortwave troughs
overhead Friday night through Sunday. This upper level system
will become better organized as it moves into the Mississippi
valley and finally drag the cold front off of the coast on Sunday.
Drier and slightly cooler conditions will follow the front on
Monday with a warming trend beginning by Tuesday.


Seas of 5 to 6 feet offshore this morning should gradually decrease
today with a cold front slowly pushing to the coast allowing for
lower winds. A very moist airmass remains south of the front with
dewpoints in the upper 60s to low 70s. Patchy sea fog has developed
but visibility remains around 2 to 3 miles. Possible that visibility
could drop below 1 mile this morning so we will monitor for a
possible dense fog advisory. The threat for sea fog may continue the
next few days due to the high moisture but winds may be the
determining factor. Winds may become a bit more easterly if the cold
front pushes closer to the coast today and tomorrow. Threat for sea
fog may end on Thursday as winds become westerly and offshore.

In the extended forecast, the next strong cold front to push off the
coast will be Saturday night into Sunday for the weekend. Small
craft advisory conditions look likely at this time, and may possibly
have gale force wind gusts with very rough seas.



College Station (CLL)      58  52  59  52  71 /  60  80  80  50  20
Houston (IAH)              73  63  71  59  72 /  70  80  80  70  50
Galveston (GLS)            68  64  68  62  67 /  50  70  70  70  70


GM...Dense Fog Advisory until 11 AM CST this morning for the
     following zones: Coastal waters from High Island to
     Freeport out 20 NM...Galveston Bay.



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