863
FXUS64 KLIX 292359
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
659 PM CDT Sat Jun 29 2024

...New AVIATION...

.SHORT TERM...
(This evening through Sunday night)
Issued at 341 PM CDT Sat Jun 29 2024

Main concern in the short term continues to be heat and humidity.
While afternoon highs are only a couple degrees warmer than normal
for this time of year, a very humid airmass is in place, with
dewpoints in the mid to upper 70s. These high dewpoints have a
twofold effect on the heat across the area - 1) it limits
overnight cooling and 2) it results in high heat index values
during the afternoon.

Have upgraded the excessive heat watch to an excessive heat
warning for areas generally along/south of the I-10/12 corridor
but away from the immediate coast of SE LA, and also along the
Atchafalaya River up through Wilkinson County. In these areas,
higher dewpoints will combine with afternoon temperatures to
result in heat index values of 110-115. While not everywhere in
the warning will reach warning criteria (heat index of 113 or
higher), there is enough threat that it seems warranted,
especially since the overnight lows across most of the warning
area will struggle to drop below 80 degrees.

Those most vulnerable to heat effects will be the elderly, very
young, and also those who are ill. The overnight lows will be
especially impactful for those who lack access to adequate air
conditioning since the warm temperatures will limit their ability
to cool their bodies even overnight.

With ample moisture in place, expect afternoon showers and storms
to develop again tomorrow. However, onset will again be delayed
until generally mid to late afternoon due to weak subsidence
aloft associated with the high pressure centered to our north. Any
showers/storms that develop will have plenty of moisture to work
with, so while area average rainfall will be low, a few places
could see half an inch or more in a relatively short period.

&&

.LONG TERM...
(Monday through Friday night)
Issued at 341 PM CDT Sat Jun 29 2024

The northern stream upper level trough moves through the Great Lakes
Sunday evening and continue eastward into the Atlantic Ocean Monday.
The base of this trough doesn`t reach much farther south than the
Appalachian Mountains as it shifts offshore. This track is why a
weak backdoor front comes into the CWA from the northeast just ahead
of the trailing ridge. That upper ridge, in the wake of this trough,
will be sliding east across the entire Mississippi Valley Monday
afternoon into Tuesday. Global models have been extremely consistent
from run to run for a few days now showing a 596dm high will be
centered near the Akrlatex region Monday afternoon. Excluding rain
potential, increasing 500mb heights will bring already above normal
weekend temps up even more. Guidance spread through the forecast
period is fairly minimal and as of 12z runs, Monday has the
potential to be the warmest with highs mid/upper 90s to 100 degrees
which is nearly 10 degrees above normal. Convective coverage will
probably be the bigger deciding factor on max temps and heat
impacts. That previously mentioned weak backdoor front looks to
stall near the Gulf Coast, which combined with forecast temps, would
support scattered to numerous showers and storms. If convective
initiation is early enough, heat indicies will get knocked down
quickly. However, if not too early, widespread upper 70 to 80 degree
dewpoints with hot temps may bring heat indicies well into Heat
Advisory range and possibly many areas with Excessive Heat
Warning temps. Tuesday will virtually mirror Monday as the upper
ridge just slides slightly eastward. Still looking at the same
heat/convection timing challenges in the late morning and
afternoon hours. As the rest of the week progresses, repeated
northern stream troughs/shortwaves will steadily flatten out the
ridge aloft and eventually cause it to retrograde to the west. As
the subsidence slowly fades from this upper level pattern change,
should eventually see some less extreme temps and more widespread
daily convection.

&&

.AVIATION...
(00Z TAFS)
Issued at 655 PM CDT Sat Jun 29 2024

Currently none of the convection across the area is impacting any
terminals this evening. Expect that convection to dissipate
shortly after the sun goes down. VFR conditions will prevail
tonight and into tomorrow. Similar to today, convection is
expected to initiate around 18-19z tomorrow when the convective
temperature is reached. Pinpointing where this will occur is a
challenge, thus only VCTS was mentioned. Expect that activity to
continue until the sun goes down.

&&

.MARINE...
Issued at 341 PM CDT Sat Jun 29 2024

Daily thunderstorms will continue to be the primary concern across
marine areas. Otherwise, conditions will remain fairly benign with
gradient winds no higher than 10-15 knots and waves/seas mostly 3
ft or less.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  75  93  76  94 /  20  60  20  60
BTR  80  98  79  98 /  20  50  20  70
ASD  81  95  80  96 /  20  50  20  70
MSY  81  95  83  95 /  10  60  20  80
GPT  80  95  80  95 /  20  60  30  60
PQL  80  97  79  99 /  20  60  40  60

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Heat Advisory until 7 PM CDT this evening for LAZ034>037-039-
     046>048-056>060-064-065-071-076>090.

     Excessive Heat Warning from 10 AM to 7 PM CDT Sunday for LAZ034-
     035-046>048-056>060-064-065-076>090.

     Heat Advisory from 10 AM to 7 PM CDT Sunday for LAZ036-037-039-
     066>071.

GM...None.
MS...Heat Advisory until 7 PM CDT this evening for MSZ068>071-077-
     083>088.

     Excessive Heat Warning from 10 AM to 7 PM CDT Sunday for MSZ068-
     083>088.

     Heat Advisory from 10 AM to 7 PM CDT Sunday for MSZ069>071-077.

GM...None.
&&

$$

SHORT TERM...DM
LONG TERM....ME
AVIATION...JZ
MARINE...DM