000
FXUS64 KLCH 171754
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
1254 PM CDT Thu Aug 17 2017

.UPDATE...
Updated for 18Z TAF issuance.

&&

.AVIATION...
VFR this afternoon across taf sites. VCTS cannot be
ruled out at AEX and vcsh at LCH. A little gust of wind
with early mixing. Winds should settle back down between 18Z and
19Z. Could see a bit of wind gust around AEX with storms in the
area along with some lightning strikes. Convection should begin to
wane with loss of daytime heating this evening. Brief spots of MVFR
fog cannot be ruled out at AEX between 09-12Z Friday morning,
confidence is low though so did not include it for now.

&&

.PREV DISCUSSION... /issued 1010 AM CDT Thu Aug 17 2017/

UPDATE...
The upper air sounding from KLCH this morning did show some
slightly drier air in the mid levels helping to drop the
precipitable water values below 2 inches and mid range relative
humidity below 50 percent. Therefore, there should be less in the
way of convection today, although there will still be a few
showers or storms from the daytime heating as convective
temperature of 89F will be met.

The main story this afternoon looks to be the heat away from any
cooling showers. The dew points have been in the upper 70s to
lower 80s so far this morning, and as of 17/15Z the heat index at
KLCH was 106F, with a number of sites already seeing heat index
values between 101F and 105F. Short term guidance and trends would
put reliable dew point readings staying in the 76F to 79F range
through the afternoon producing a quite muggy air mass. Therefore,
the heat index is likely to reach 108F or possibly higher at a
number of locations. Thus, will keep the heat advisory going for
today.

On-going forecast looks good and no changes at this time.

Rua

PREV DISCUSSION... /issued 649 AM CDT Thu Aug 17 2017/

DISCUSSION...
For 12z TAF issuance.

AVIATION...
No significant changes to previous TAF thinking. VFR to prevail
through the period. High pressure building aloft will limit
convective coverage today with the best chance for showers/storms
being across the ern sites during max heating.

25

PREV DISCUSSION... /issued 351 AM CDT Thu Aug 17 2017/

DISCUSSION...A surface ridge remains stretched from the Atlantic
into the northern gulf coast this morning. This is keeping the hot
and moist flow off the gulf in place. Aloft the region is under a
weakness between two ridges to the east and west, however a
slightly drier air mass has moved in aloft.

Today a decrease in rain chances is expected as the slightly drier
air mass and ridging builds in aloft, however with ridge not
firmly in control, isolated to scattered storms are still
expected. Unfortunately, with a decrease in rain chances comes an
increase in temperatures. Highs today will generally be in the mid
90s away from the coast. These temperatures combined with the very
moist dewpoints in the upper 70s will create apparent temps in the
105 to 110 range. Criteria for a heat adv is 108, so the advisory
is in effect through 7 PM.

Friday guidance indicates a slight decrease in dewpoints as mixing
knocks off a degree or two. This may hold a portion or all of the
area just below heat adv criteria, but just barely with forecast
apparent temps still ranging from 103-108.

This weekend moisture will increase aloft with PWATs climbing
north of 2". This will increase rain chances and cloud cover into
next week. This will also decrease high temperatures a degree or
two.

MARINE...The sub-tropical ridge will remain to the east of the
region through the period. This will keep a light to modest
onshore flow in place.

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  94  75  94  75 /  30  10  40  20
LCH  93  78  94  78 /  20  10  20  10
LFT  94  77  94  77 /  20  10  30  20
BPT  94  77  94  77 /  20  10  20  10

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...Heat Advisory until 7 PM CDT this evening for LAZ027>033-041>045-
     052>055-073-074.

TX...Heat Advisory until 7 PM CDT this evening for TXZ180-201-215-216-
     259>262.

GM...None.
&&

$$


AVIATION...06