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fxus64 klch 220941 
afdlch

Area forecast discussion
National Weather Service Lake Charles la
441 am CDT Tue Aug 22 2017

Discussion...
fairly complicated forecast in the works for the coming week.

Short term...
scattered to numerous showers and thunderstorms are expected to
develop this afternoon in response to what is left of the TUTT
wave moving into the western Gulf. With the area now on the east
side of the system, the higher moisture should result in more
showers and thunderstorms than we have seen over the last couple
of days. However, being as these storms will still be primarily
diurnally driven, the are expected to weaken and dissipate around
sunset.

By Wednesday, the TUTT washes out/is absorbed by the remnants of
Harvey which will be emerging off the West Coast of the Yucatan
Peninsula. More on that in a moment. Meanwhile, a digging upper
trough and associated cold front is expected to stall across
northern Louisiana/southern Arkansas during the day Wednesday
which will provide an extra shot of moisture and lift across the
region for another round of scattered to numerous convection. With
something resembling forcing near the area, it wouldn't be
surprising to see some of these storms lingering through the night
Wednesday into Thursday morning.

Long term...
Thursday, a northwestward waddling and reintensifying Harvey will
be traversing the central Gulf of Mexico and here's where things
get really tricky. Model guidance diverges significantly with
regards to the evolution of Harvey beyond Thursday. The 00z GFS
brings a more intense Harvey (possibly a hurricane) into The Big
Bend region of Texas somewhere around Matagorda Bay by midday
Friday. Meanwhile, a slower Euro brings a slightly weaker system
to the coast right along the Texas/Mexico border before very
slowly having it drift inland north of Brownsville before
completely stalling it across south central Texas through the
entire weekend. Now, here's why this is important to US. Both
models eventually turn a weakening tropical system northeast
into an upper trough along the East Coast...and across southeast
Texas and southwest Louisiana. The big question (which will
remain unanswered for the time being) is when. The faster...and I
use that term relatively...GFS brings rain bands into southeast
Texas and into southeast Louisiana as early as Friday with the
remnants sitting over the region until Monday before pushing off
to the northeast. The slower Euro keeps the storm sitting over
south central Texas before meandering it back into the Gulf and up
the coast pushing rain bands across our area beginning Sunday all
the way through early Wednesday.

So which is it going to be? Given the very inconsistent run to
run nature of the guidance over the past 24 hours, I can't answer
that. The official forecast reflects this uncertainty by including
elevated pops from Saturday through Wednesday with the
understanding that the system will not be over the area for that
full five day period. That said, the trend appears to be for a
fairly slow, erratic and decaying tropical system to move through
the area over the weekend into early next week. That means the
potential for very high rainfall totals and and significant flash
flooding early next week. After collaboration with surrounding
wfos and wpc, the official forecast reflects this trend with
considerably higher quantitative precipitation forecast values, but these values were tempered
from their maximum potential due to uncertainty. Once the
evolution of Harvey becomes more certain, the entire forecast will
become better refined.

Jones



&&

Marine...
light southeast winds and low seas will continue through
Wednesday as surface high pressure ridges west across the Gulf
states. Scattered showers and thunderstorms are expected each
afternoon. The high is forecast to breakdown late Wednesday as
the region is squeezed between an approaching cold front to the
north and what is likely to be a regenerating Harvey over the
southern Gulf of Mexico. Elevated winds and seas are possible
through the weekend over the Gulf waters pending the eventual
track and strength of this system, which at this time is forecast
to move ashore near the Texas and Mexico border late Friday before
moving up the Texas coast through the weekend into early next
week.

&&

Preliminary point temps/pops...
aex 92 73 91 73 / 50 20 50 30
lch 91 77 91 77 / 50 20 40 30
lft 92 77 92 77 / 50 20 40 30
bpt 91 75 92 76 / 50 20 40 30

&&

Lch watches/warnings/advisories...
la...none.
Texas...none.
GM...none.
&&

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