Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 292019
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
319 PM CDT SUN MAY 29 2016

.DISCUSSION...
Visible satellite imagery this afternoon shows cloud cover
thinning across SE Texas with some cumulus/stratocumulus
development. Temperatures have reached mid/upper 80s once again
early this afternoon. There may be enough cloud cover to limit the
extent of heating today. An isolated shower or storm may still
form if bay/sea breeze can develop. Ridging aloft and cap may just
be enough to keep convection from forming. ACARS soundings show
weak capping around 800-700mb but has dry air over the moist
boundary layer. This has allowed for precipitable water values
around 1.4 to 1.5 inches across the area. Deep convection will
have a tough time forming just due to day time heating and without
any low level forcing. The same type of conditions are expected
Monday. Forecast will keep thunderstorm chances in the 10-20
percent range this afternoon through tomorrow.

Tuesday will be more of a transition day from more of a dry
pattern back to a wet pattern. Will SE Texas catch a break for
a while from heavy rainfall and flooding? It is not looking good.
Tuesday rain chances range from 20-30 percent with precipitable
water increasing above 1.5 inches and the upper level ridge
breaking down further. Best chances will be over the Brazos Valley
on Tuesday if the cap can weaken. GFS/NAM soundings seem to
suggest a weak cap but with lack of a low level boundary it may be
difficult for storms to develop. More likely scenario will be if
storms forming in west central Texas can move into the area. Even
that is a stretch for Tuesday/Wednesday.

Wednesday into Wednesday night an upper level trough over the S
Rockies moves towards the Big Bend of Texas. This helps increase
the jet over Texas and certainly provides a more favorable
environment for thunderstorm activity. Instability will be
greatest over the area Wednesday into Thursday with CAPE 2000-3000
J/kg. Deep layer shear will be increasing but remaining around 30
knots. Precipitable water increases to around 1.7 to 2.0 inches
Wednesday and more widespread 1.8-2.0 inches of precipitable water
over the area Thursday into Friday. Upper level trough slowly
moves east through the end of the week. GFS/ECMWF/Canadian all
have a broad upper level low over Texas Thursday/Friday which will
be slow moving. Given high moisture expected, upper level low and
for good measure a weak surface trough boundary in the area
Friday, there will be the potential for more heavy rainfall. Any
severe weather looks to be more on Wednesday into Thursday and
most likely a marginal threat since shear will support
multicellular convection. Hail and downburst winds will be the
main threats in addition to the heavy rainfall threat. At this
point it is still hard to pinpoint how much rain will fall over
the area but possibly another 1 to 2 inches for the Wednesday to
Friday time frame. Any additional rainfall will prolong river
flooding. River levels will likely not go up with additional
rainfall except for fast responding basins like Harris County
bayous. Rivers will just take longer to recede with additional
rainfall. Upper level trough axis will remain over SE Texas
through Mississippi River valley so likely hold onto thunderstorm
chances through the weekend.

Overpeck

&&

.MARINE...
A fairly quiet forecast for the upper TX coastal waters these next
few days as high pressure holds over the region. Light/moderate on-
shore winds will prevail with sea and tides remaining low. Changes
possible starting mid week on into the end of the week with as the
next storm system begins to move into the state. A slight increase
with wind speeds possible Weds/Thur with the approach of disturban-
ces from the west which will help to tighten the pressure gradient
over the near/offshore waters. Increased storm coverage could also
make for elevated winds/seas in/near these storms. Extended models
still hinting at the possibility of a cold front by the end of the
week...but have been a little less enthusiastic about it with this
latest run. Will be interesting to see how later runs resolve this
(but thinking FROPA less likely given the time of year). 41

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      71  86  71  84  71 /  10  20  20  40  40
Houston (IAH)              70  86  72  86  72 /  10  20  10  30  30
Galveston (GLS)            76  83  77  85  78 /  10  10  10  20  20

&&

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

$$

Discussion...39
Aviation/Marine...41



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