000
FXUS64 KHGX 121146
AFDHGX
Area Forecast Discussion
National Weather Service Houston/Galveston TX
646 AM CDT Sat Sep 12 2020
.AVIATION [12Z TAF Issuance]...
VFR conditions have persisted overnight and should continue to do
so through the duration of the TAF period. Latest satellite
imagery shows clear skies across a majority of the area, while a
few showers and storms are lingering offshore. As a weak system
approaches from the east today, low-level moisture will be on the
rise and precipitation chances will increase as a result. Expect
scattered showers and storms to begin to impact the coastal and
metro terminals around 20Z and last until the loss of daytime
heating around 02-03Z. Have included VCTS wording in TAFs once
again given the expected scattered nature of storms.
&&
.PREV DISCUSSION... /ISSUED 409 AM CDT Sat Sep 12 2020/
DISCUSSION...
While the early half of our weekend continues yesterday`s fair
post-frontal weather, we will soon turn our focus to any potential
impacts from a low pressure area currently over the Gulf, as well
as Tropical Depression 19, currently over South Florida.
Though there is still considerable uncertainty given these
features` organization (or lack thereof), there is probably some
more confidence that direct impacts to our area will be limited to
marine areas, and for rip currents on Gulf-facing beaches.
Indirectly, however, we should still look for these two to bulk up
our moisture levels and fuel enhanced chances for showers and
thunderstorms, particularly closer to the coast.
Of course, given that there is still considerable uncertainty, we
must urge everyone to ensure their hurricane plans and kits are in
good shape, and to continue to monitor forecasts from our office
and the National Hurricane Center. Our area is still near the
"Cone of Uncertainty", and since tropical cyclones affect wide
swaths, we cannot guarantee a safe miss yet.
SHORT TERM [Through Monday Night]...
Rainfall chances will be on the rise this weekend as the first of
two systems that we are monitoring in the Gulf approaches SE Texas.
An initial surge of low-level moisture will come as an inverted
upper trough and associated weak surface low pushes into the Western
Gulf. While the system remains disorganized and its chances of
becoming a depression remain low (20 percent over the next 48h
per the latest NHC advisory), its approach will bring more
widespread precipitation coverage to the area through the
remainder of the weekend. The increase in near-surface moisture as
this feature approaches will be quite robust. While the 12Z suite
of deterministic runs has backed off slightly on surface PW
values, they nonetheless remain in agreement in showing numbers
reaching 2.25 to 2.5 inches by Sunday afternoon. Forecast
soundings continue to show convective temps in the 88-90F range
through Sunday evening, which should be easily reachable. Given
this, have maintained the increasing PoP trend for the morning
forecast package, with likely PoPs for the bulk of the CWA by
Sunday.
While precipitation will be increasing in coverage, expected
temperatures should remain near climatological norms with highs
today and Sunday expected to reach the low 90s in most locations.
Expect a slight uptick in lows and dew points as the offshore flow
that has allowed for some cooler and drier air to reach the area
develops a more easterly component. The majority of the CWA will see
heat indicies in the vicinity of 100 degrees through the weekend and
well into next week...keeping summer with us for the time being.
LONG TERM [Tuesday Through Saturday]...
Tuesday morning should dawn with the aforementioned lead trough
down near the Mexican coast in the extreme southwest Gulf/Bay of
Campeche, while TD 19 (likely a tropical storm by then) should be
near the north central Gulf coast, and very near if not already
making landfall there. By far, the operative words in that
sentence are the `should`s. While I`m definitely more confident in
this scenario today than I was 24 hours ago, it`s always important
to guard against nasty surprises this time of year.
Regardless, since I must make a deterministic forecast, let`s roll
with this scenario. What does that mean for Southeast Texas? Well,
I`ve had to trim back rain chances a little. We should still have
ample moisture for scattered to numerous showers and storms, but
these two features may be a little more discrete than previously
thought. The lead trough looks to stay far enough offshore that
its lingering effects into Tuesday will be a little smaller than I
had yesterday, and the more organized appearance of TD 19 should
keep its moisture envelope a little more compact, and give us some
more breathing room for late in the week (If this most recent Euro
run is correct, which immediately yanks the storm to the east
after landfall, we may get a LOT of breathing room). That said,
we`re still looking at precipitable water values around to above
two inches for nigh on the entire week, so I`m not going to be
taking a meat cleaver to the rain chances here, either.
All in all, yesterday I had described the major impact to our
sensible weather as strongly juicing up the typical pattern of
showers and storms. Now, I`d still expect some enhancement to it,
but it may be more modest than 24 hours ago.
MARINE...
As the weekend progresses, the offshore winds present over the past
several days will develop a more easterly component as a weak
surface low approaches the coastal waters. The NHC continues to
monitor this system for potential tropical development, though
chances for it to become a depression within the next two days
remain low (20 percent). Nonetheless, the approach of this system
will provide a surge of low-level moisture that will drive more
widespread precipitation development through the remainder of the
weekend. Brief gusty winds and heavy downpours will be possible
within individual storms associated with this feature. A second
and potentially more potent system, now Tropical Depression
Nineteen, will emerge into the eastern Gulf of Mexico later in the
weekend. This will bring with it an additional chance of
widespread precipitation and gusty winds as is pushes westward,
although uncertainty in the forecast remains high. Mariners should
continue to monitor the latest tropical weather information. The
most recent forecast information for each of these systems can be
accessed at
www.hurricanes.gov.
TROPICAL...
We continue to have several things to keep an eye on in the
tropical Atlantic basin, so here`s a roundup to keep everything
in order:
Gulf trough - This trough over the north central Gulf will pass by
our area in the short term, and still carries a low (20-30
percent) chance of development as it curves by us offshore. It is
expected to increase moisture to fuel daily showers and storms,
and is likely to increase seas and rip currents.
Tropical Depression 19 - Currently moving across South Florida,
this depression is forecast to emerge over the eastern Gulf and
gradually strengthen to at least a tropical storm as it heads
generally to the (west-)northwest. This storm should still be
monitored in the coming days, but it is more likely to take a
track to our east. We will also need to consider indirect impacts,
including continued increased swell/seas, strong rip currents on
Gulf-facing beaches, and enhanced shower/thunderstorm chances.
Tropical Storms Paulette and Rene - Neither storm over the open
Atlantic is anticipated to influence weather in Southeast Texas at
this time.
Invest 95L and a trailing African Easterly Wave - These waves,
near and west of the Cabo Verde islands, will need to be monitored
in the long term. These waves are closer to Africa than to even
the Lesser Antilles, and any predictions of their long term future
is mere speculation. There is no current indication that we have
any need to worry about either wave, but it would be foolish to
ignore them at this point, as well.
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 90 73 91 72 88 / 10 10 30 10 40
Houston (IAH) 93 76 93 76 92 / 20 40 70 20 50
Galveston (GLS) 92 81 92 81 89 / 40 50 70 50 60
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&
$$
DISCUSSION...Luchs
SHORT TERM...Cady
LONG TERM...Luchs
AVIATION...Cady
MARINE...Cady
TROPICAL...Luchs