Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 271141

Area Forecast Discussion
National Weather Service Houston/Galveston TX
641 AM CDT MON JUN 27 2016

Expect similar scenario as yesterday with isolated to scattered
convection developing from daytime heating and moist flow off the
Gulf. With weak mean flow...sea breeze could help focus storms
this afternoon. Already have a few showers SW zones streaming in
off the Gulf. Could see some afternoon thunderstorms as well once
air mass destabilizes further. coverage in models suggests
isolated to scattered...model soundings show around 1500J
CAPE...which may be overdone but would be enough to support
thunder. Better chance of showers and thunderstorms tomorrow as
cold drop drops south through the back door. Reilly



Upper air analysis from 00z soundings and current water vapor
imagery shows a weak upper low over west Texas and upper level
ridge over the Arklatex. Both features should weaken today as
upper level ridge over the 4 corners and southern Rockies becomes
more established. Based on 00z CRP/LCH soundings, precipitable
water values across the area are around 1.8 inches. Based on model
soundings, convective temps should be around 90F today so it may
take a bit more heating to support convection. Boundary layer flow
looks to turn more to the NE and allow for higher moisture to
develop along a frontal boundary. This may allow for better rain
chances N and E of Houston this afternoon. Overall think scattered
showers will be possible with isolated thunderstorms. CAPE looks
to reach moderate level by afternoon with 1500-2500 J/kg across
the area. Model soundings do show an inverted V from 850mb and
below. Some of the stronger storms could produce downburst winds
in additions to brief heavy rainfall.

By Tuesday an upper level trough should deepen over the Great
Lakes with the ridge stretching from the Great Basin to southern
Rockies. Frontal boundary will push south and southwest towards
the area and increase moisture ahead of it. Precipitable water
values reach 2-2.2 inches with CAPE of more than 2500 J/kg. This
environment is more conducive for heavy rainfall and isolated
severe threat with hail/downburst winds. Storm motions will also
be quite slow so heavy rainfall will be a concern and could see
some stronger storms producing higher rain rates 1-2 inches an
hour. With the pulse nature of convection, storms may only exist
for an hour or two. Mesoscale outflow boundary interaction will
determine where new storms may develop and if updrafts can be
maintained for extended periods of time.

Wednesday the frontal boundary should have pushed to near the
coast with possible wind shift well into the Gulf. Dewpoints may
lower some Wednesday into Wednesday night behind the boundary or
for areas mainly north of I-10. The drier air may limit
thunderstorm chances to along the coast and offshore in the Gulf
Wednesday into Thursday. GFS is trending towards a drier forecast
with lower rain chances headed into the weekend since moisture
levels decrease. ECMWF is not so robust with a frontal push like
the GFS but it has not been as aggressive with rain chances as the
GFS had been. The ECMWF like the GFS has most of the precipitation
off the Gulf coast Wednesday into Thursday.

Friday through Independence day weekend the GFS has become a bit
more aligned with the ECMWF in that the upper level ridge expands
over Texas by Sunday/Monday. This will support lower rain chances
for the weekend and higher day time max temps. The ridge should
persist over much of Texas for much of next week. It looks like if
SE Texas does not get any rainfall through the next 3 or 4 days
then it might be awhile until another rain event.


Winds will be light and variable over the waters through Tuesday
given high pressure and weak pressure gradient over the area. A
weak cold front will approach the waters Tuesday and stall out
near or off the coast Tuesday evening...bringing increasing
thunderstorm chances with locally higher winds and seas possible
in and near thunderstorms. GFS most progressive with this
front...actually pushing it across the waters while other models
stall it out closer to the coast. An onshore flow will eventually
redevelop on Thursday but will not begin to strengthen until
Saturday as low pressure over W TX begins to deepen. Reilly


College Station (CLL)      95  76  92  75  94 /  20  10  50  20  20
Houston (IAH)              94  77  93  75  93 /  30  20  60  40  30
Galveston (GLS)            89  80  88  78  88 /  20  20  50  50  50



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