323
FXUS64 KLIX 171718 AAC
AFDLIX

Area Forecast Discussion...UPDATED
National Weather Service New Orleans LA
1218 PM CDT Sat Aug 17 2024

...NEW AVIATION...

.UPDATE...
Issued at 1017 AM CDT Sat Aug 17 2024

Just after 10am and temperatures already soaring into the 90s
across the CWFA this morning. Needless to say there will not be
any changes to the ongoing heat headlines this afternoon/evening.
Otherwise, POPs this morning will remain on the lower side across
the CWFA. Over the last hour or so a couple of very isolated
narrow/weak updrafts have developed for a few out there. This
should remain very limited as upper levels are a bit on the warm
side and instability will be lackluster...at least initially.
Convection odds increase later this evening and closer to midnight
CAMs are suggesting convection to occur over southern MS, MS Gulf
Coast, and Florida Parishes. Respectively made the change to add
at least lower end POPs. Instability again will be there with 2500
J/KG of SBCAPE to work with and DCAPE in excess of 1000 J/KG
suggest that a wind potential will certainly be there in updrafts
that are a bit wider and more robust. Outside of the adjustment in
POPs this evening no other forecast changes with this midpoint.
(Frye)

&&

.SHORT TERM...
(Today through Sunday)
Issued at 358 AM CDT Sat Aug 17 2024

Typical Summer night across the region. Convection that fired
yesterday afternoon persisted into the evening a little before
tapering off with mostly clear skies but still mild and rather
humid conditions. Temperatures by 7z were generally in the upper
70s to lower 80s and we should continue to see a slow fall till
sunrise.

Two biggest questions through the weekend remain how hot and
oppressive do we get followed by how much and especially when can
convection fire. The large mid lvl ridge that has dominated the area
continues to slide west and will amplify over the Rockies. This is
in response to a deep Pac low digging south off the west coast and
the L/W trough digging over the eastern CONUS. This eventually
places us under northerly and northwesterly flow which will have
some rather strong implications on convection and more so timing.
The ridge will still have a rather strong influence over the area
today as it is still building to the west. Finally by mid/late
afternoon today it should be centered over northern NM which we will
finally move under northwest flow but it will be very weak today.
Nothing else though will be much different from what occurred
yesterday. PWs will still be hovering just abv 2" and with
temperatures expected to quickly rise into the 90s once again
instability will not be in question. DCAPE may not be as high today
as it has been in previous days but it will likely be abv 1000 j/kg
for much of the area. Given the slowly developing and very weak
northerly/northwesterly flow today given is likely going to be
initially driven by the sea/lake breeze and the boundary collisions.
As for timing, high pressure at the sfc which is expected to
dominate the region through the weekend, will not greatly help
things to kick off. The very weak synoptic wind field would also
suggest sea/lake breeze and other boundaries (outflow/differential
heating) as the driving factor today. LL winds will be light as well
and with h85 winds chaotic or even out of the north, not expecting
the seabreeze to get going quickly either. Fcst sndgs suggest the
convective temp will be around 93-95 and with that storms will
likely hold off on initiation till mid afternoon say 19/20z.

That does bring into question of the current Heat Adv and whether
some areas need to be upgraded to an Excessive Heat Warning. First
thought was we probably needed to upgrade a few locations mainly
around the title lakes, immediate coast of MS, and possibly up the
MS and Pearl River valleys but digging in a little more and things
look far more borderline. Main issues is looking at what occurred
yesterday. With no glaring changes in conditions or setup why should
things be much different. Almost all of our official obs remained
just below Warning criteria and with that decided to hold off on any
upgrade at this time. That isn`t to say we won`t hit Excessive Heat
anywhere today and it is probably a good but that we will reach that
in a few areas. Either way it is still going to be rather miserable
and if you are outside during the late morning to mid afternoon
hours, drink plenty of water and have a way to cool off.

As for the strong to severe aspect we are probably looking a very
similar setup to yesterday although we may not see quite as much of
that mid lvl drier air which is leading to the slightly lower DCAPE
values. As for Sunday though that may have a much better chance of
strong to severe storms.

So why does Sunday look like it may have a better chance of strong
to severe storms. On Sunday our ridge will be firmly entrenched over
the continental divide with our L/W trough digging through the
southeastern CONUS. Northwest flow will be in place and there is
strong agreement from most of the model solutions that the mid lvl
flow could be rather impressive for this time of the year. H5 winds
will increase to 20kts and there are some indications that it could
be up to 25kts. Mid lvl northerly/northwesterly of 15 kts is good
enough to add a punch to Summer thunderstorms but 20-25kts
definitely makes it more interesting. Also as has been mentioned
numerous times northerly/northwesterly flow leads to convection
developing late in the day. What does this mean then, we will have
no issues warming up and becoming quite unstable and all guidance is
indicating MLCAPE values around 3K j/kg. Lastly we will see a surge
of mid lvl dry air moving in as well and this will enhance the risk
for damaging winds. Ok all that makes it sound like a rather decent
chance of seeing severe storms but and yes there is usually always a
but, are we too far west. There is a chance and maybe a decent
chance that the convection that develops which will likely become an
strong to severe MCS could move right on the periphery of our CWA
across southeastern MS and into coastal AL and coastal MS. The
potential is there for severe weather Sunday but it may only occur
across the northeastern 3rd of the CWA. /CAB/

&&

.LONG TERM...
(Sunday night through Friday)
Issued at 358 AM CDT Sat Aug 17 2024

As we head into the next work week its the old saying, as much as
some things change they stay the same. We will see a push of
drier air and slightly lower rain chances but we will look to be
hot. No adjustments made from the NBM as it appears to be a good
blend of the medium range guidance.

With the ridge still in place to our west and the L/W trough
remaining over the east coast through Wednesday we will remain under
northerly flow. This does try to send a week front through the area
overnight Sunday or early Monday. Pressure and wind field would
suggest probably overnight but LL moisture suggest Monday morning.
The drier air will be a welcome touch but LL temps will not drop and
afternoon highs will continue to climb into the mid to upper 90s.
Even morning lows don`t really cool much until mid to late in the
week as we start to see the pattern shift with the ridge beginning
to build back to the northeast.

As for rain potential, Monday has the highest chance through much
of the week as we will still have enough moisture in place to get
some afternoon convection but it would likely be the southern half
of the CWA. Drier air continues to work into the area driving the
moisture south and that likely keep much of the area rain free
Tuesday through Thursday. /CAB/

&&

.AVIATION...
(18Z TAFS)
Issued at 1216 PM CDT Sat Aug 17 2024

VFR conditions are largely expected through the cycle. Cannot rule
out some evening convection this evening generally before 06z and
the best potential being for terminals along and north of I10.
Outside of convection, MCB may have limited VIS around sunrise,
especially if rain occurs. Otherwise, light and variable winds
expected. (Frye)

&&

.MARINE...
Issued at 358 AM CDT Sat Aug 17 2024

High pressure remains in place through the weekend and even with
a weak front pushing towards the coast Monday conditions will
remain rather benign outside of any thunderstorm. Daily isolated
to scattered rain chances remain mainly during the early morning
timeframe each day. Expect slightly elevated northerly winds with
the front before slacking off when the following surface high
settles over later in the week.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  75  99  74  93 /  20  10  30  30
BTR  80 101  80  96 /  20  10  20  40
ASD  77 100  79  96 /  20  10  30  40
MSY  80  98  80  96 /  10  10  20  40
GPT  78  97  79  96 /  30  10  30  30
PQL  77 101  78  99 /  30  20  40  30

&&

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

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

GM...None.
&&

$$

UPDATE...RDF
SHORT TERM...CAB
LONG TERM....CAB
AVIATION...RDF
MARINE...CAB