Area Forecast Discussion
Issued by NWS Lake Charles, LA

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691
FXUS64 KLCH 181202
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
602 AM CST Sat Nov 18 2017

.DISCUSSION...
For 12z TAF issuance.

&&

.AVIATION...
Not many changes to previous TAF thinking. Sfc obs show generally
partly cloudy skies/VFR conditions...the primary exception is KAEX
where MVFR ceilings are occurring within a larger area of lower
clouds over cntl/nrn LA. Forecast soundings indicate increasing
low-level moisture as we head through the morning and MVFR
ceilings are expected at all sites. Widely scattered showers are
progged to begin developing during the early afternoon per high-
res guidance...with the best shot at shower activity coming
along/just ahead of the expected cold front later this afternoon.
After FROPA, precip should come to an end while ceilings lift.
Main story through the entire period looks to be very elevated
winds, initially from the SW before veering to a nrly direction
behind the front.

25

&&

.PREV DISCUSSION... /issued 451 AM CST Sat Nov 18 2017/

SYNOPSIS...
Warmer surface temperatures on the back of increasing southerly
flow has only allowed temperatures to fall into the upper 60s to
lower 70s this morning. Lower pressure across north Texas and
central Oklahoma marked the leading edge of a strong cold front
traversing the Great Lakes to El Paso Texas. Radar activity was
quiet this morning with capping evident on the 00Z LCH sounding
last night near the 5-8K level. Satellite imagery showed low level
clouds advancing parallel to the cold front on a southwest to
northeast axis.

DISCUSSION...
Fog was absent this morning thanks to increasing southerly winds.
Higher dewpoint tongue of moisture was evident along the southeast
Texas coast and is expected to move into southwest Louisiana later
this morning into the afternoon.

Across the upper levels...a storm system continued to move into
the central plains carving out a deeper trough axis. This is
expected to continue today with an associated strong Canadian
cold front moving across the forecast area later this afternoon
and evening. A Wind Advisory is in effect this afternoon until
midnight as 20 to 30 mph winds develop behind the cold front.

The overall moisture profile has not changed to much as the PWAT
remain around 1.3 inches. However, decent low level convergence
and frontal lift should be enough to produce scattered showers
ahead of the front. Instability still looks rather weather weak
ahead of the front, with best upper level dynamics well off to the
northeast. Therefore, will keep the predominate weather as
showers.

A much cooler and drier air mass will then move in behind the
front for the remainder of the weekend. Surface ridge looks to
settle across the forecast area on Sunday night, and this will
likely provide rather chilly temperatures, with mid 30s for
Central Louisiana and the Lakes Area of Southeast Texas, with
upper 30s possible down to the usual cool spots of the I-10
corridor.

Surface ridge will move off to the east on Monday with some return
flow moisture and a moderation in temperatures.

Better agreement today in guidance for Tuesday through the
remainder of the Holiday week. The next Canadian cold front is
expected on Tuesday night. Operational ECMWF still looks to be on
the high end of the ensemble range when it comes to being too
robust on the return flow moisture and thus the pops for Tuesday
into early Wednesday. Therefore, will again go a little below
Superblend numbers for those days and closer to a ECMWF ensemble
mean/GFS compromise, which would bring low end chance pops for
Tuesday daytime, with a gradual decrease in pops Tuesday night
into Wednesday morning.

Guidance is also in better agreement with sweeping the front out
into the Gulf for Thanksgiving into next Friday, thus keeping
better moisture and any Gulf low development further to the south
and east of the forecast area. Therefore, a dry and rather cooler
Turkey day into Friday looks to be in the works.

MARINE...
Moderate southerly winds will continue ahead of a cold front
advancing across north Texas and central Oklahoma this morning.
Small Craft should exercise caution for the first half of today.
The strong cold front will sweep into the coastal waters early
this evening with good cold air advection moving over the
relatively warm Gulf waters. Frequent Gale force wind gusts up to
42 knots will trigger Gale Warnings for the nearshore and
offshore coastal waters from this evening through Sunday morning.
Winds will begin to decrease Sunday night as the high pressure
system behind the cold front settles across the coastal waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  81  41  62  35 /  30   0   0   0
LCH  81  47  64  39 /  40  10   0   0
LFT  82  47  63  39 /  40  20   0   0
BPT  82  46  65  42 /  30  10   0   0

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...Wind Advisory from noon today to midnight CST tonight for
     LAZ027>033-041>045-052>055-073-074.

TX...Wind Advisory from noon today to midnight CST tonight for TXZ180-
     201-215-216-259>262.

GM...Small Craft Advisory from 6 PM to 9 PM CST this evening for
     GMZ450-452-455-470-472-475.

     Small Craft Exercise Caution through this afternoon for GMZ450-
     470-472-475.

     Gale Warning from 9 PM this evening to 9 AM CST Sunday for
     GMZ450-452-455-470-472-475.

     Small Craft Advisory from 6 PM this evening to 9 AM CST Sunday
     for GMZ430-432-435.

     Small Craft Exercise Caution through this afternoon for GMZ452-
     455.

&&

$$



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