Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA

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000
FXUS64 KLIX 251120
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
620 AM CDT Sat Jun 25 2022

.AVIATION (12Z TAF DISCUSSION)...

VFR conditions are expected for all area terminals through mid to
later portions of the morning hours. Scattered TSRA is expected
to develop early to mid afternoon areawide with greater coverage
potential expected across eastern terminals. A few storms may be
locally strong today with the main threats being strong downdraft
winds/possible microbursts and periodic reductions in flight
categories from reduced VIS in heavy rain. Have approximately
timed best coverage potential for TAF sites with VCTS due to
variability in coverage, with most areas becoming dry around
00-02Z with some lingering storms possible across coastal/southern
SE LA around or shortly after sunset, but will see VFR conditions
prevail overnight. KLG

&&

.PREV DISCUSSION... /issued 430 AM CDT Sat Jun 25 2022/

SHORT TERM (Today through Monday Night)...

Plenty to discuss in the short term as we begin to see a
transition in the overall weather pattern from extreme heat, to
greater rain chances this weekend into early next week. Starting
off with early this morning, no surprise the same large-scale
ridge remains anchored over the central/southern US, as we reside
generally on the southeastern periphery of the ridge center over
the Arklatex. Meanwhile off to our east, a plume of deeper
tropospheric moisture over the Florida Peninsula and associated
weak mid-level trough will continue to build west within
increasing easterly mid-level flow over the northern Gulf. The
reflection of greater total moisture will yield an increase in
afternoon convective coverage east across the Gulf coast, with
some modest influence into our area today as well. HREF members
depict a pretty confident scenario today given this steady
environmental transition, with deeper convective initiation
possibly beginning across eastern areas today late morning/early
afternoon, increasing in coverage towards the west throughout the
afternoon. Due to the potential for deeper convection, especially
across eastern areas, it is possible some could become deep
enough to produce SW surging outflow boundaries helping to
propagate pulse-storm clusters southwest through the day. Not
entirely confident on the extent of deeper (>2.0 to 2.20" PW) air
making it into our area just yet enough to produce more
widespread, potentially cold- pool driven convective complexes
versus the environment more favorable for it out east, however,
will need to watch if deeper convection does organize (potentially
into a SW surging MCS) over the AL/FL coast and attempts to drive
into our eastern areas later this evening. Adjustments were made
to PoPs today to keep the higher bias going applied to the
forecast from the afternoon forecast package yesterday increasing
to the 30-40% range, as well as slightly later into the evening in
case convection does attempt to become cold-pool driven and
propagates later to around or slightly after sunset into
southern/coastal SE LA areas.

Additionally, taking a closer look at HRRR soundings for later
this afternoon and comparing to observed soundings yesterday
afternoon shows very little thermodynamic changes other than the
uptick in tropospheric moisture as mentioned before. We will see
another wet microburst potential in any locally stronger storms
today given Theta-E Index maintaining noticeably high in the
35-39C range which is supportive of water-loading in elevated
cores, combined with a deep PBL mixed-layer and around 1000-1200
J/kg DCAPE. Also with a bit more noticeable mid-level flow, should
any cluster of storms attempt at becoming slightly more organized
(possibly messy linear segments) along southwest surging outflow
boundaries, this could also lead to a slight increase in the risk
for strong, possibly localized severe downburst winds but will
continue to highlight the threat being more isolated for now.

As for the heat today, we will remain enough within the influence
of the ridge to keep conditions hot yet again. However, will
maintain an advisory for all areas today due to lower confidence
climbing towards excessive heat conditions (and related impacts),
but will still advertise the heat to be dangerous today with heat
indicies in the 108-112 degree range late morning/early afternoon
prior to deepening mixing and scattered showers/storms increasing
in coverage.

We dry out tonight, then going into the day on Sunday we finally
feel the greater influence of increased moisture over our area
(anomalously high precipitable water even for this time of the
year in the 2.2-2.4"+ range, all well above the max moving
average according to sounding climatology). Mean storm flow will
continue out of the northeast on Sunday, with convection likely
ongoing across marine areas all throughout the morning,
transitioning inland throughout the day. This will help to back
temperatures down more during the day, with max heat indicies just
barely near advisory criteria for now. Not overly confident on an
advisory on Sunday yet largely due to the greater increase in
convective potential and cloud cover, but will take a closer look
with the afternoon package. Can`t rule out locally strong storms
once again with strong downdraft winds the main threats, however
given the greater tropospheric moisture, intense rainfall rates
will also be a noticeable threat leading to localized flash
flooding. But, should refrain from becoming a significant threat
at this time given somewhat progressive storm motion towards the
WSW/SW.

As been advertised for several days now, we will see a front
slowly sag south into the southern MS valley region Sunday,
closing in to our local area on Monday. No real major changes to
the environment on Monday with widespread showers/storms likely
yet again throughout the morning for coastal/marine areas to
inland during the afternoon/evening hours. Given the continuation
of anomalously high PW and light mean storm motion, localized
flash flooding will remain a threat as well as a few strong storms
producing gusty downdraft winds. KLG

LONG TERM (Tuesday through Saturday)...

Going into Tuesday/mid-week, the NHC has highlighted a 20% chance
of tropical development generally across portions of the
northwestern Gulf. Some indications of slow, steady development
has been hinted at in model guidance trends (ECMWF Ens prob TD
~10% for now, as well as GFS runs hinting at a subtle, weak
surface low developing). Tracing where weak surface cyclogenesis
occurs is a bit difficult as it could be dependent on where deep
coastal marine convection is maintained (within the same deeper
moisture plume drifting east responsible for our increase in
rain/storm chances). The GFS does spin up a quick surface low
mainly across the NW gulf/coastal SE TX which, given the placement
of the front could aid in surface weak surface low genesis in
this location plus somewhat favorable anti-cyclonic upper-level
flow and light to almost weak 200-850mb wind shear. Something to
monitor for now but overall through mid-week, the main story will
continue to be widespread shower/storms persisting but will
continue to keep the excessive heat down enough to not be a major
concern.

Not going to dive much into late week/next weekend quite yet but
am not seeing much of a drastic change in the overall weather
pattern with persistent mainly afternoon shower/storm coverage
each day which again will continue to keep heat concerns down. KLG

MARINE...

Mostly calm conditions are forecast today as high pressure remains
in control of the region. Some isolated to scattered marine storms
will be possible this morning, and again more near coastal
locations later this afternoon with a few locally strong or
severe. Main threats will be waterspouts, gusty winds to >34kts
and locally enhanced wave/seas. Shower and storm coverage
increases Sunday through the rest of the upcoming week with the
same threats for strong to locally severe storms persisting. But
conditions will be mainly calm outside of any thunderstorm
activity. KLG

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  99  74  96  73 /  30  20  50  20
BTR  99  76  96  74 /  40  30  40  30
ASD  99  77  94  74 /  40  30  60  40
MSY  97  80  93  78 /  40  30  50  40
GPT  98  78  91  76 /  40  40  70  40
PQL  97  76  90  74 /  40  50  70  40

&&

.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-
     080>082.

GM...None.
&&

$$


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