Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 181750

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1150 AM CST Wed Jan 18 2017

After a brief lull through the mid to late morning hours, the
next round of rainfall expected for the region is beginning to
move into the areas west of the Brazos River late this morning.
Associated with a mid-level shortwave trough, this activity will
continue to translate across Southeast Texas through the remainder
of the afternoon hours... with the bulk of rain clearing the
Houston Metro around 4-5 PM and the remainder of Southeast Texas
7-8 PM this evening. Surface analysis showed a stationary frontal
boundary draped roughly along the Highway 59 corridor. Enhanced
convergence along this feature combined with instability from
heating obtained through breaks in the clouds as well as much
above normal atmospheric moisture (precipitable water values
around 1.6 inches per SPC Mesoanalysis) will result in at least a
locally heavy rain threat continuing generally for counties along
and south of Interstate 10 through the remainder of the afternoon.
Overall, widespread rain totals up to an inch will be possible...
but stronger cells will be capable of isolated 1 to 3 inch amounts
that will exaggerate ongoing flooding. Parts of the Houston metro
saw 4 to 6 inches of rain this morning and have been slow to drain
today, which prompted the issuance of an Areal Flood Warning for
ongoing flooding issues. While heavy rain and flooding will be the
primary hazard from showers and thunderstorms this afternoon, any
storm that develops along and south of the stationary frontal
boundary will pose a low-end severe weather threat with 1000-1500
J/KG of SBCAPE and effective bulk shear values on the order of 30
knots in place creating a threat for organized multicellular
convection as the shortwave trough lifts across the region. Mid-
level lapse rates are weak limiting an overall hail threat, but
water loading of updrafts will help create a gusty windy threat.
Will also need to monitor cells that move along the frontal
boundary for a brief tornado threat with enough low level shear
present along this feature to produce some rotation.

Subsidence in the wake of the passing shortwave will offer a
brief respite in rain chances this evening, before a trough axis
with an upper low centered over the Texas/Oklahoma Panhandles late
this morning swings across the region early Thursday morning. Lift
associated with this trough axis will result in light rain
spreading along the coast from the southwest. The bulk of the rain
early Thursday morning looks to focus along the frontal boundary,
which should be pushed into the Gulf with the approach/passage of
the upper low`s trough axis. As of now, this would result in
totals being highest along the Upper Texas coast and south of the
Houston metro (totals up to 1 inch)... but trends in the progress
of this boundary will need to continue to be monitored during the
overnight period. May see period of fog (some dense) developing
south of this frontal boundary as moisture continues to pool ahead
of it Thursday morning before the front moves off the coast with
the trough axis by Thursday afternoon.



SHRA/TSRA and associated mainly MVFR/IFR ceilings and visibilities
will be moving generally to the E and NE across the area through
around 18/21Z. Activity should decrease in coverage from west to
east as the afternoon progresses, but there could still be some
lingering SHRA maybe around the HOU and GLS areas through around
19/00Z. Expect most sites to see a break in the rains this evening
before the next round of SHRA/TSRA develop and move through the area
during the overnight hours (look for lowering ceilings and
visibilities (MVFR/IFR) before the storms arrive). After tomorrow
morning`s mess of storms/low ceilings/fog, look for improving
improving conditions area wide as the day progresses.  42


College Station (CLL)      56  53  72  55  77 /  90  30  20   0  10
Houston (IAH)              71  60  73  58  78 /  70  70  70  10  10
Galveston (GLS)            74  64  69  63  73 /  50  70  70  10  20




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