Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 270851
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
351 AM CDT Thu Apr 27 2017

.DISCUSSION...
Dry conditions are expected across the region today in the wake of
yesterday`s cold front, which has pushed off the Upper Texas coast
and stretches across the northwest Gulf from Harlingen to New
Orleans early this morning. After a cool start inland with
morning temperatures in the mid 40s to mid 50s, surface high
pressure sliding east of the region and onshore flow resuming will
allow afternoon temperatures to rebound into the upper 70s to mid
80s. This southerly flow will promote moisture return tonight,
resulting in increasing cloud cover and overnight lows about 10-15
degrees warmer than this morning in the low 60s to low 70s.

Southerly flow will strengthen during the day Friday to 10-15 MPH
as height falls in advance of an upper disturbance near the Four
Corners results in the development of a surface low over West
Texas. This flow combined with insolation will result in another
day where 90+ degree temperatures are within reach, with a few
records possibly approached along the coast. Forecast soundings
show the atmosphere remaining capped during the day Friday and
expect dry weather to continue as a result, but with moisture
being trapped under this inversion cloud cover may prevent a few
locations from getting as warm as currently forecast. Persistent
warm air advection and associated moisture return will allow for
isolated showers to develop inland late Friday night/early
Saturday morning, with overnight lows only falling into the mid to
upper 70s. This may tie or break record high minimums at several
locations across Southeast Texas.

As the upper low near the Four Corners reaches the Southern Plains
on Saturday and sends a stationary front over Oklahoma south as a
cold front, southerly winds will increase further as the pressure
gradient tightens. Winds along the coast on Saturday may
strengthen enough to warrant a Wind Advisory. Isolated to
scattered showers will remain possible across the inland areas
throughout the morning Saturday, with a weakening cap during the
afternoon hours even allowing for the development of a few
thunderstorms. Persistent cloud cover will not offer much of a
diurnal range, with highs in the low to mid 80s.

Model guidance has been fairly consistent with the timing of the
cold front this weekend, bringing it into the Brazos Valley
Saturday night, sweeping it across most of Southeast Texas through
the early morning hours, and clearing the region mid to late
morning Sunday. As mid-level flow becomes more southwesterly with
the passage of the upper low, the cap may restrengthen a bit
across Southeast Texas. Given the increasing divergence also
associated with this low, this may only limit intensity or delay
onset of initial thunderstorm activity with lift from the upper
low and convergence along the front still resulting in the
development of widespread showers and thunderstorms along the cold
front. With mean winds in the cloud bearing layer (850-300 MB)
oriented parallel to the cold front, expect thunderstorms to grow
upscale into a line/complex that marches progressively across the
region with the front.

Veering wind profiles ahead of the front will continue
to promote the potential for organized thunderstorm development,
including the potential for strong to severe thunderstorms as 0-6
km bulk shear values exceed 35 knots. Increasing mid-level lapse
rates ahead of the front (8-8.5 C/km) will result in thunderstorms
capable of producing damaging winds and large hail, but will also
need to monitor any cells that may develop ahead of the
thunderstorm line as well as the leading edge for a transient
tornado threat as an increasing low level jet results in 0-1 km
bulk shear values exceeding 30 knots. Locally heavy rain will also
remain possible as atmospheric moisture content exceeds the 90th
percentile for this time of year, but expect the overall speed of
the frontal system to mitigate against widespread flooding
concerns.

Rain chances will quickly end from west to east behind the front
by Sunday afternoon, with cooler and drier conditions ending the
weekend as highs only reach the upper 60s to mid 70s. Quasizonal
flow becoming established in the wake of this weekend`s system
will allow for dry weather and a gradual warming trend on Monday
and Tuesday. Rain chances return to the forecast by the middle of
next week as another cold front approaches the region.

Huffman

&&

.MARINE...
Strong NNE winds early this morning will diminish quickly as high
pressure settles over TX. Onshore winds will resume later today
as high pressure moves off to the east. A Small Craft Advisory
will likely be required Friday night through Saturday night as SSE
winds strengthen in response to deep low pressure over south
Texas. The low will move NE and drag a cold front across SE TX
early Sunday morning. An abrupt wind shift to the NNW is expected
in the wake of the front and another SCA will be required on
Sunday. A light to occasionally moderate onshore flow will develop
Monday and continue into Tuesday as high pressure drifts east and
away from the state.

Will need to keep an eye on elevated water levels and risk of rip
currents going into the weekend. Tide levels could potentially
exceed 3.5 feet near high tide early Saturday morning. A Coastal
Flood Watch or Advisory may be required late Friday night into
early Saturday. 43

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      82  67  91  75  86 /   0  10  10  20  40
Houston (IAH)              84  68  90  77  84 /   0  10  10  20  40
Galveston (GLS)            78  73  83  77  81 /   0  10  10  20  20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...Small Craft Advisory until 4 AM CDT early this morning for the
     following zones: Coastal waters from Freeport to the
     Matagorda Ship Channel out 20 NM...Coastal waters from High
     Island to Freeport out 20 NM...Galveston Bay...Matagorda
     Bay...Waters from Freeport to the Matagorda Ship Channel
     from 20 to 60 NM...Waters from High Island to Freeport from
     20 to 60 NM.

     SMALL CRAFT SHOULD EXERCISE CAUTION until 7 AM CDT this morning
     for the following zones: Coastal waters from Freeport to
     the Matagorda Ship Channel out 20 NM...Coastal waters from
     High Island to Freeport out 20 NM...Galveston Bay...
     Matagorda Bay.

     SMALL CRAFT SHOULD EXERCISE CAUTION until 10 AM CDT this morning
     for the following zones: Waters from Freeport to the
     Matagorda Ship Channel from 20 to 60 NM...Waters from High
     Island to Freeport from 20 to 60 NM.

&&

$$

Discussion...14
Aviation/Marine...43



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