Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 200853
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
353 AM CDT Fri Apr 20 2018

.NEAR TERM [Through Today]...

IR and night time microphysics RGB satellite imagery show high/mid
level clouds moving into SE Texas this morning. This has allowed
for temperatures to hover in the low/mid 50s for most areas, upper
50s for Houston south to the coast. Upper air analysis shows
subtropical jet stretching across northern Mexico into Texas which
is helping support mid/high level cloudiness. There should be some
divergence as the main jet streak approaches the area today which
could be strong enough to squeeze out a sprinkle or two this
morning into the early afternoon. The main problem is that the
boundary layer remains dry based on the 00Z DRT/CRP soundings as
well as HOU AMDAR soundings. This means any precipitation that
does form will likely evaporate before reaching the ground or
virga. Cloud cover still should limit some heating so maximum
temperatures in the low 70s look reasonable.

.SHORT TERM [Tonight Through Sunday]...

Tonight through Saturday return flow off the Gulf should set up
however moisture return looks slow and of poor quality. Dewpoints
gradually increase during the day Saturday going from the 50s to
mid 60s by the afternoon. During this time an upper level low now
positioned over the Desert SW/4 Corners Region should reach the
Southern Plains by 00Z Sunday. Strong W/NW oriented jet should
move over the region increasing large scale lift with a surface
low developing over north Texas. Decent LLJ should develop of
20-30kts in response to the lowering pressures but LLJ is expected
to veer during the day as the surface low moves east. The
elevated mixed layer will be present but certainly not as strong
as the last couple of thunderstorm episodes. Strong lift aloft
will limit capping however based on model soundings, boundary
layer moisture is weak which means there will still be some
convective inhibition to overcome. In the end, there should be
some forced lift resulting in convection with the meager 500-1000
J/kg of CAPE and that may be generous. SPC day 2 outlook has
marginal risk for the area and think that is on track. There could
be an isolated strong/severe storm to support a low end severe
threat. Deep layer shear increases to 50-60kts so there could be
some organized storms however the lack of instability will really
limit the capability of these storms to produce severe weather.
Bottom line the severe threat will be a function of boundary layer
moisture and instability which looks rather trashy to be blunt.
Cold front does push through early Sunday morning and still a
chance an isolated strong/severe storm could produce some hail,
but again thermodynamics profiles on model soundings really not
very supportive of severe deep convection other than wet bulb zero
heights will be lowering.

.LONG TERM [Sunday Night Through Friday]...

High pressure builds into the area late Sunday through Tuesday
allowing for near normal high temperatures and slightly below
normal low temperatures. GFS/ECMWF/CMC bring another front into
the area on Wednesday with a jet streak in the NW flow aloft which
could produce some showers or even an elevated thunderstorm.
Forecast will go with some 20 PoPs to cover this threat. Otherwise
temperatures will again be near normal ranges with somewhat lower
humidity for the latter part of April.

Overpeck

&&

.MARINE...

Northeasterly winds earlier this morning will gradually veer to
become easterly, then southeasterly through today and tonight. The
pressure gradient is expected to tighten back up, which will cause
winds to become breezy again. With astronomical tides already
relatively high, stiffer onshore flow will push water levels up even
more, and may reach high enough for  particularly vulnerable
locations like Highway 87 on Bolivar to potentially see some run up
issues.

A cold front will push offshore very late Saturday night or very
early Sunday morning, and cross the waters through the morning
hours. Winds will become northwesterly behind the front, and though
they don`t look to become excessively breezy, caution will still be
warranted at times on Sunday.

Luchs

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL)  71  55  74  56  72 /   0  20  60  50  10
Houston (IAH)          72  59  76  63  75 /   0  20  50  60  10
Galveston (GLS)        71  66  75  67  74 /   0  20  40  60  20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...None.
GM...None.

&&

$$

NEAR TERM...Overpeck
SHORT TERM...Overpeck
LONG TERM...Overpeck
AVIATION...Luchs
MARINE...Luchs
FIRE WEATHER...Luchs



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