Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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908
FXUS64 KHGX 182159
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
359 PM CST Wed Jan 18 2017

.SHORT TERM (Tonight through Thursday Night)...
A broken line of showers and thunderstorms extends from near Moss
Hill southwest to Freeport and out into the Gulf of Mexico. This
line will continue to push east into southwestern Louisiana over
the next few hours, clearing the forecast area between 7 and 9 PM
CST this evening. Some modest training within this line has
resulted in rain totals approaching 1-1.5 inches in parts of
southwest Harris County this afternoon, but with the main line
shifting east... the heavy rain threat will shift east with it.
May see at least a lingering heavy rain threat in southern
Liberty, Chambers, and Galveston counties as this line exits
through the remainder of the evening as a 20-25 knot low level jet
ahead of this line on the Lake Charles VAD Wind Profiler feeds
additional moisture across these counties.

Drier conditions will briefly settle in across the region this
evening before another disturbance approaches the region after
midnight tonight. Afternoon water vapor analysis shows an upper
low stretching from northwest New Mexico to western Kansas and as
this trough swings into the Central Plains tonight and Thursday,
an associated trough axis will drag across Texas.

Increasing divergence ahead of this axis will overspread the
region after midnight tonight, resulting in another round of
scattered to numerous showers developing southwest of the region
and spreading northeast during the early morning hours on
Thursday. While rainfall totals during this time are forecast to
be (much) lighter than what was observed this morning (0.5-1 inch
along and south of Highway 59), will need to keep an eye on any
remnant boundaries left over from today`s rain that may serve as a
focus for higher rainfall amounts. Starting to see a signal for
this possibility in the 18Z NAM and latest runs of the RAP
guidance. As of now, the most likely culprit for any kind of
enhanced rainfall would be the front that our current showers are
pushing east along (especially if it does not move as far east as
model guidance indicates)... which would affect areas east and
southeast of the Houston metro.

With the main trough axis clearing the region midday Thursday,
drier conditions will overspread the region from west to east with
clearing skies and highs in the upper 60s to low 70s during the
afternoon. Partly cloudy skies and lows in the mid 50s to low 60s
are forecast on Thursday night.

Huffman

&&

.LONG TERM (Friday through Wednesday)...
Unsettled weather will quickly return on Friday as an upper trough
just off the West Coast swings into the Southern Plains. Warm air
advection showers will spread inland during the morning with
increasing lift and instability from heating resulting in
scattered shower and thunderstorm development by Friday afternoon. A
130 knot upper level jet moving across the region during this time ahead
of this trough as well as increased upper level forcing, combined
with mid- level lapse rates approaching 7 C/km and 0-6 km bulk
shear values 50-55 knots, may result in a threat for a few strong
to severe thunderstorms. Will need to keep an eye on how later
guidance evolves with timing (as this is a bit faster than what
00Z guidance was indicating).

Height falls associated with a secondary disturbance dropping
farther south across Texas on Saturday will induce a surface
cyclone over the Southern Plains, with scattered showers and
thunderstorms on Saturday and temperatures in the low to mid 70s being
quickly replaced by Sunday as drier and cooler conditions become
established behind a Pacific front sweeping across the region.
Wind Advisories will likely be needed in the wake of this front
with strong northwest winds 20-30 MPH possible for much of the day
Sunday. Recent rainfall should mitigate against more widespread
fire weather concerns, but will need to keep an eye on how dry the
air is behind this front for possible fire weather issues.

Otherwise, shortwave ridging builds in across the region at the
beginning of the upcoming week with dry conditions persisting
through Tuesday before another cold front reaches the region on
Wednesday.

Huffman

&&

.MARINE...
Light to moderate onshore winds will become west to northwest
tonight through tomorrow morning as a weak front moves off the
coast. The onshore flow returns Thursday night, then look for
mainly south to southwest winds to persist through Saturday. Also
expecting periods of fog (some possibly dense). A strong cold
front moves through the area Saturday night with very strong west
to northwest winds and very rough seas developing in its wake.
Gale Watch/Warning will likely be needed, and Storm Watch/ Warning
will be possible. A Low Water Advisory will probably be needed for
Galveston Bay too due to lowering water levels. 42

&&

.FIRE...
Look for a strong front to move through the area Saturday night
with windy and dry conditions developing in its wake through
Sunday night and Monday morning. Fire weather watches and/or red
flag warnings might be needed on Sunday due to the strong winds,
but at this time it looks like relative humidities will not get
low enough. 42

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      52  72  55  75  58 /  30  10  10  20  30
Houston (IAH)              57  70  58  77  61 /  60  60  10  10  50
Galveston (GLS)            62  68  63  71  64 /  60  70  10  20  50

&&

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

$$

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



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