Area Forecast Discussion
Issued by NWS Lake Charles, LA

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FXUS64 KLCH 251149
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
649 AM CDT THU AUG 25 2016

.DISCUSSION...
25/12Z TAF Issuance.

&&

.AVIATION...
Sctd SHRA/TSRA are already developing along the coast, but
activity so far remains well away from srn TAF sites although ltg
associated with storms east of Cameron has been vsbl at KLCH.
Otherwise, VFR conditions are noted with SCT/BKN cirrus over the
area. Some patchy fog was occasionally reducing vsbys at KAEX to
MVFR but expect this to lift after 13Z. Sctd to nmrs SHRA/TSRA
expected to develop during the morning and continue through the
aftn as an ely wave interacts with ample moisture acrs the region.
MVFR/IFR cigs and vsbys as well as gusty winds will be possible
during periods of convection, with VFR prevailing otherwise.
Expect convection to diminish during the evening as the impulse
aloft moves further west and daytime heating wanes.

24

&&

.PREV DISCUSSION... /issued 429 AM CDT THU AUG 25 2016/

SYNOPSIS...
Good confidence remains in the forecast through the weekend. Still
a lot of uncertainty in the forecast for next week. However, the
confidence is not quite as low as yesterday at this time, as
extended global guidance at 25/00Z is a little bit more consistent
and clustered together.

Latest upper air analysis shows that the center of the mid/upper
level ridge as move to the northeast some and is over northern
Mississippi/Northern Alabama area. Water vapor imagery shows
moisture increasing over the forecast area as an easterly wave is
moving westward around the ridge. This is confirmed by the latest
24/07Z GPS-MET data, with PWAT between 2.0 and 2.2 inches across
the immediate area, with values around 2.25 to 2.3 just off to the
east. Radar also is showing a few nocturnal showers and
thunderstorms developing along the coast and offshore, another
indication in the increase in moisture as last night at this time
the radar was quiet.

Some patchy fog remains an issue in a few spots with visibilities
below 2 miles at times. Fog will remain patchy in nature before
lifting shortly after sunrise.

In the broader picture, Satellite shows a tropical disturbance
(Invest 99L) still disorganized over the Atlantic with a broad
low northwest of Puerto Rico and northeast of the Dominican
Republic moving to the west-northwest.

Rua

DISCUSSION...
The upper level ridge will continue to move off to the northeast
today into the weekend before becoming anchored over the Mid-
Atlantic region.

This will allow a series of easterly waves/upper level
disturbances to move around the ridge into the forecast area. The
first will move across later today and linger over western
portions for Friday, with another scheduled for Saturday into
Sunday.

Therefore, moisture values will be high today with PWAT values
around 2.25 inches and Mean RH over 75 percent. Expect a good
coverage of scattered showers and thunderstorms by afternoon with
daytime heating. Overall average rainfall amounts today will be
between 1/4 and 1/2 inch. However, due to the high moisture
content in the atmosphere, a few locally torrential downpours can
be expected that may bring a quick 1 to 2 inches of rainfall.

Most of the activity will diminish with the loss of daytime
heating...with re-development during the overnight over the
coastal waters moving onshore before daybreak...mainly over
western portions of the forecast area, as some drier air may move
ahead of the next wave and into eastern portions of the forecast
area.

With a series of waves and high moisture continuing into the
weekend, a decent chance for scattered showers and thunderstorms
will continue, mainly during the afternoon hours.

Uncertainties still arrive in the forecast for next week, as a
lot will depend on what becomes of Tropical Invest 99L and where
it goes. As is usual in this stage, before system gets a well
defined low center, and becomes better organized, guidance could
have large errors, with possible large swings in positioning and
strength from run to run.

At-least the latest global models have started to show a more
consistent feature moving into south Florida on Sunday, then
either northwest through the Florida Peninsula or up the west
coast of Florida holding on to a consistent solution from run to
run with location and strength. If this trend continues, more
emphasis for impacts from this system will be for the Florida
Peninsula and the extreme northeast Gulf of Mexico. This is due to
the upper level ridge being centered slightly further to the north
and weaker in nature.

At this point, superblend still looks reasonable for the forecast
area, meaning climo type pops and temps.

Rua

MARINE...
A more prevailing light easterly flow can be expected to develop
today, with some increase in wind speeds to moderate levels by
Friday into the weekend, as the coastal waters will be on the
periphery of a surface ridge located northeast of the region.
Showers and thunderstorms will be increasing today...with a good
coverage of convection continuing off and on into the weekend...as
a series of upper level disturbances move across the region. Winds
and seas will be locally higher near the storms.

Rua

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  93  74  93  73 /  60  20  40  20
LCH  92  75  91  75 /  50  40  40  20
LFT  92  75  92  75 /  60  20  30  20
BPT  92  76  90  76 /  50  40  50  30

&&

.LCH Watches/Warnings/Advisories...
LA...None.
TX...None.
GM...None.
&&

$$

PUBLIC/MARINE...07
AVIATION...24


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