Area Forecast Discussion
Issued by NWS Lake Charles, LA

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FXUS64 KLCH 192344
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
544 PM CST Thu Jan 19 2017

.DISCUSSION...
20/00Z TAF Issuance.

&&

.AVIATION...
Convection has moved east as the upper trof moves through the
area. This activity is being followed by a SCT/BKN midlevel cloud
deck with a lower stratocu deck further west producing BKN/OVC
MVFR cigs. A brief period of VFR can be expected early this
evening, with cigs developing and lowering as the stratocu spreads
east. Southerly winds will lighten this evening, and combined
with abundant leftover moisture, allow for the development of IFR
cigs/vsby reductions in fog through early tomorrow morning.
Conditions will improve by 15-16Z with VFR expected to prevail
during the day as winds become southwesterly 5-10 kt.

24

&&

.PREV DISCUSSION... /issued 357 PM CST Thu Jan 19 2017/

SYNOPSIS...
Weak surface boundary has moved across the forecast area and is
becoming increasingly diffuse and should wash out soon. Upper
level trough from the Central Plains down into East Texas is
pivoting off to the northeast and this is bringing a dry slot into
the forecast area according to latest water vapor imagery, which
is bringing an end to the shower activity from west to east.

Rua

DISCUSSION...
Upper level trough will continue to move off to the northeast with
a drier and more stable air mass moving into the forecast area
tonight, which will end shower activity. With a stable boundary
layer and light winds, along with wet grounds, can expect at-least
patchy fog for the overnight into early Friday morning.

Progressive pattern will mean the drier and stable conditions will
be short lived.

Next upper level system will form by late Friday over the Central
Plains and move off to the northeast on Saturday, replaced by a
more robust mid-latitude cyclone that will move from the lee of
the Rockies into the Lower Mississippi Valley from Saturday Night
into Sunday.

Initial upper level system will allow for a quick return of
moisture and warm air advection a top the stable boundary layer by
late Friday, with lift and low level convergence interacting with
the return flow moisture for widespread showers and a few elevated
type thunderstorms to develop.

Increasing wind dynamics, with low level jet 30 to 35 knots over
Southeast Texas and Southwest Louisiana, with 35 to 40 knots over
South Central Louisiana developing Friday Night, with mid level
jet streak of 60 knot plus winds moving across during that time
period. This will increase wind sheer throughout the atmospheric
profile with bulk shear between 60 and 65 knots. Elevated
instability also looks decent according to progged values of CAPE
and Showalter Index. 85H- 50H lapse rates at favorable
6.5-7.5c/km levels, with a relatively cool mid levels with 50H
temperatures around (-15C), all indicate that the stronger storms
will be capable of producing hail, that could be on the severe
side. A marginal risk of severe weather is already outlined in the
day 2 for all of the forecast area, with a slight risk for the
eastern portions during that time frame for mainly hail, as
thunderstorms in the forecast area should remain elevated, with a
better chance for surface based further to the east and northeast
of the forecast area.

A brief break between disturbances during the daytime on Saturday
will mean just scattered activity at best, mainly from daytime
heating.

The storm system moving through on late Saturday Night into Sunday
will push a cold front across the forecast area with a chance of
showers and thunderstorms, ending early in the day. Main story
with this feature will be the strong gradient winds from the west
and northwest on Sunday into Sunday Night, with wind advisory a
strong possibility.

Cooler and drier weather for the first part of the week, with the
next cold front scheduled on early Wednesday to bring a much
cooler air mass.

Rua

MARINE...
A weak surface boundary moving across the coastal waters this
late afternoon into evening hours will wash-out therefore, any
westerly or offshore winds will quickly become modest onshore by
morning.

A developing low pressure system in the Central Plains will
increase the onshore flow for late Friday...Friday Night and into
Saturday, with also a return of showers and a few thunderstorms.

A second, and deeper low pressure system will move across the
Southern Plains into the Lower Mississippi Valley on Saturday
Night into Sunday. This low will push a cold front across the
coastal waters early Sunday. A big pressure gradient behind the
front will allow for very strong and gusty west to northwest winds
developing during the day on Sunday and continuing through Sunday
Night into early Monday. Sustained winds, especially over the
outer waters, will be around 35 knots and Gale Force, with gusts
over 45 knots to near 50 knots are probable. This will build seas
in the outer waters to 10 to 14 feet.

Winds and seas will gradually subside on Monday into Monday night
as the low moves off to the northeast.

Rua

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  54  76  58  73 /  10  10  70  40
LCH  59  76  62  75 /  10  10  70  30
LFT  59  78  66  78 /  10  10  70  40
BPT  59  77  62  77 /  10  10  70  30

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...None.
TX...None.
GM...None.
&&

$$


AVIATION...24



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