Area Forecast Discussion
Issued by NWS Lake Charles, LA

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235
FXUS64 KLCH 270233
AFDLCH

Area Forecast Discussion
National Weather Service Lake Charles LA
933 PM CDT TUE JUL 26 2016

.UPDATE...
Upper air analysis from 27/00Z shows the upper level low/inverted
trof over the region and bisecting the forecast area. This is
confirmed by watching the motion of convection on local radars,
with activity north of the Highway 190 corridor moving in a
westerly or southwesterly direction...and activity south of the
I-10 corridor and over the coastal waters moving in an easterly or
northeast direction. The upper air sounding from Lake Charles at
27/00Z still shows very moist air mass in place with Precipitable
Water value over 2.10 inches and mid level and low level RH over
75 percent.

Normally in these situations with a moist/tropical like air mass
and upper level trof, nocturnal activity will contract and develop
closer to center of the inflow. This seems to be what latest radar
trends are, as northern activity is diminishing, and activity near
the coast on the increase or very least, holding together. Latest
short term guidance also favors this scenario.

Therefore, will make minor adjustments to the grids, with higher
pops south of the I-10 corridor for the remainder of the night.
Some brief gusty winds and downpours may accompany the convection
through the night.

Rua

&&

.PREV DISCUSSION... /issued 648 PM CDT TUE JUL 26 2016/

DISCUSSION...
For the 07/27 0000 UTC TAF package.

AVIATION...
Convection has lifted north of the coastal terminals, with showers
and thunderstorms currently ongoing over Central LA. Latest
guidance suggests this activity will wane this evening with the
loss of diurnal instability, with new development taking place
over the Gulf waters or near the coast after 06Z. Inserted a brief
TEMPO for KAEX based on current observations and radar trends, but
otherwise prevailed VFR for the evening and overnight hours. Do
not currently anticipate a repeat of the low CIGS and/or VSBYS
that developed last night, as rains today were not nearly as
widespread as they were on Monday, but will monitor obs/guidance
trends through the evening. For convection tomorrow, inserted VCTS
at 15Z for all terminals given current temporal/spatial
uncertainty, but this may be nudged back a bit earlier at the
coastal sites as guidance trends are starting to suggest.

13

PREV DISCUSSION... /issued 353 PM CDT TUE JUL 26 2016/

SYNOPSIS...
Regional radar mosaic shows widespread convection acrs the nwrn
Gulf Coast, although most of the activity is occurring either side
of the LCH CWA. That said, some sctd small showers and isltd tstms
have been trying to develop along a seabreeze boundary near the
coast along with a few small showers and storms inland acrs the
lakes region of se TX and cntl LA. Some more potent convection is
poised to cross the Atchafalaya River into portions of Acadiana
over the next hour or so.

Precip water per the 12Z KLCH sounding not quite as robust as the
last couple of days, coming in at 2.2 inches, but still well abv
normal. However, water vapor imagery indicates some slightly drier
air aloft over the area, and this, combined with abundant cloud
cover and a prevailing NE to E wind, has kept convection
generally in check this aftn.

24

DISCUSSION...
Few changes to the fcst the next few days as the broad trough aloft
remains over the nwrn Gulf. The sfc/low lvl trough will slide slowly
north through Wed, with ridging building west behind it allowing
low lvl s/sw flow to resume. By Thursday, the upr trough will
stall, become elongated and merge with a shortwave digging se over
the MS valley. This will leave a weakness aloft between the
subtropical ridge off the SE CONUS and a ridge over the Desert SW.

The combination of the weakness aloft and ample tropical moisture
over the area will result in abv normal chcs for showers and
storms each day through the weekend. Precip water values are fcst
to remain abv 2 inches and storms will be capable of very heavy
rainfall and high rain rates. Daily convective coverage will
gradually trend down by late in the weekend into early next week
as the weak trough meanders over the lower MS Valley.

With an unsettled weather pattern in place, temperatures should
stay mostly near or below normal for aftn highs through the week.
However, a few locations could reach the middle 90s where
showers/clouds fail to materialize. By the weekend and into early
next week, aftn highs are expected to trend back toward normal/abv
normal temps with heat index values likewise climbing into the
100-105 range.

24

MARINE...
A lt to modt onshore flow will continue through the period as high
pres becomes re-established acrs FL into the nrn Gulf.
Sctd to nmrs showers and tstms are expected mainly fm overnight into
late morning as a disturbance aloft moves slowly west the next few
days.

24

&&

.PRELIMINARY POINT TEMPS/POPS...
AEX  74  89  74  90 /  40  70  30  50
LCH  77  89  77  91 /  30  50  30  40
LFT  77  90  76  92 /  40  50  30  40
BPT  77  92  77  93 /  30  60  20  40

&&

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

$$

PUBLIC...07



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