Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 312048
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
348 PM CDT Wed Aug 31 2016

.DISCUSSION...
Isolated to scattered showers and thunderstorms continue to drift
southwest across the region this afternoon, with greatest coverage
of this activity focusing around the Matagorda Bay area. SPC
Mesoanalysis shows negligible effective bulk shear across the
region, which is limiting overall storm organization/longevity.
However, CIRA layer precipitable water estimates still show 2-2.1
inch precipitable water air pooled over the southwestern counties
and storms will be capable of brief heavy rain and a strong wind
gust or two as updrafts become water-loaded and collapse. Without
any real upper level support for storms today, expect all activity
to dissipate with loss of daytime heating with dry conditions
overnight and lows in the mid 70s to low 80s.

Afternoon water vapor imagery shows a shortwave trough over
Kansas/Nebraska, another upper trough swinging across the Great
Lakes, and an expansive plume of moisture associated with now
Tropical Storm Hermine over the southeastern Gulf of Mexico. Upper
ridging over the Southern Plains this afternoon will continue to
slide towards Southwest Texas on Thursday, but forecast
precipitable water values are expected to remain elevated in the
1.8-2.0 inch range. While increased subsidence from upper ridging
will help limit overall shower and thunderstorm development,
expect another day with mainly daytime isolated showers and
thunderstorms capable of brief heavy rainfall and highs in the low
to mid 90s.

Earlier this afternoon Tropical Depression 9 was upgraded to
Tropical Storm Hermine. This system is expected to remain well
east of Southeast Texas, with the shortwave trough swinging across
the Great Lakes this afternoon expected to influence the steering
flow for Hermine drawing it northeast to the Florida Big Bend late
Thursday night/early Friday morning. Northeasterly flow across the
western Gulf in response to Hermine combined with above normal
astronomical tides will result in elevated tides through the end
of the week, however, as Hermine moves farther away from the
region.

The shortwave trough over Kansas/Nebraska will rotate around the
upper ridge, reaching Texas on Friday and sending a weak cold
front into the region. With north/northeasterly surface flow in
place as a result of Hermine, not expecting too much of a
noticeable wind shift with this front but a moisture discontinuity
associated with this front may provide enough of a focusing
mechanism for isolated to scattered thunderstorms to develop
across western/southwestern portions of the region on Friday as
the cold front backdoors into and stalls across the region.

Broad, flat ridging is expected across the southern CONUS through
the weekend with the remnant frontal boundary serving as a
focusing mechanism for isolated to scattered shower and
thunderstorm development again on Saturday. Expect temperatures
only a few degrees cooler as a result of the front, with highs in
the upper 80s to low 90s. Return flow develops on Sunday as a lee
trough develops across the High Plains and expect this returning
moisture to aid in increased shower and thunderstorm coverage on
Monday. Upper ridging intensifies and recenters over the Gulf
Coast states at the beginning of next week as a longwave trough
moves onto the West Coast, with low, diurnally driven rain chances
expected into the middle of next week.

Huffman

&&

.MARINE...
Hoisted a Small Craft Advisory for our southern 20-60 nm
waters through midnight tonight for elevated seas mainly
due to swells associated with Tropical Storm Hermine. Do
expect these higher seas to gradually come down over the
next couple of days as Hermine moves further away then
eventually inland across the Florida Gulf Coast, but we
might need to extend our flags beyond midnight if the
seas do not come down as anticipated.  42

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      76  95  75  91  72 /  10  20  20  30  10
Houston (IAH)              77  96  77  93  74 /  10  20  10  30  10
Galveston (GLS)            81  92  81  89  79 /  10  20  10  30  20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until midnight CDT tonight
     FOR THE FOLLOWING ZONES: Waters from High Island to
     Freeport from 20 to 60 NM.

     Small Craft Advisory until midnight CDT tonight FOR THE
     FOLLOWING ZONES: Waters from Freeport to the Matagorda Ship
     Channel from 20 to 60 NM.

&&

$$

Discussion...14
Aviation/Marine...42



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