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

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FXUS64 KLIX 241820
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
120 PM CDT Thu Jun 24 2021

.UPDATE...

Scattered showers and thunderstorms developed fairly early again
today, but thus far there has not been any flooding issues. Will
likely see some locally higher rainfall amounts and some flooding
where slower moving bands/clusters at times where convergent or
slow moving wind/seabreeze boundaries set up. Away from the rain
areas, several locations have seen temperatures rise to near 90
with very muggy conditions helping push the heat index readings up
to around 105. Only minor forecast updates were made to today and
tonight`s forecast.

&&

.AVIATION...

VFR conditions are expected to prevail through early tonight with
the exception being mostly brief lower conditions in isolated to
scattered SHRA/TSRA through late afternoon. Some lower conditions
with low CIGS and some patchy fog could repeat again late tonight
into early Friday, but at this point the only location that has
highest confidence to include in forecast is KMCB. Scattered
SHRA/TSRA is expected to develop again on Friday.

&&

22/TD

.PREV DISCUSSION... /issued 325 AM CDT Thu Jun 24 2021/

SYNOPSIS...

Frontal boundary that was located over the area 24 hours ago
appears to have shifted to the north of the area. Dew points are
pretty uniformly in the mid 70s this morning, with temperatures
ranging from the mid 70s to lower 80s at 3 AM CDT. Aloft, ridging
has shifted eastward a bit, and is now centered over Texas with an
extension into the northwest Gulf of Mexico. A few patches of fog
noted in observations over the last couple of hours, but doesn`t
seem to be persistent at this time.

SHORT TERM (through Saturday)...

The upper ridging over Texas doesn`t look to move much for the
next 48 hours or so. At this time, it doesn`t appear that the
ridge is going to be strong enough to inhibit convective
development totally. Afternoon precipitable water values remain
near 2 inches, which should allow scattered to numerous showers
and storms to develop. If convection allowing models are any
indication, it may take longer for thunderstorms to develop than
it has in recent days. Activity should be primarily in the
afternoon hours and along convergence boundaries, such as lake and
sea breeze boundaries. Low level wind fields are rather weak (5
mph or less mean wind at MSY, for example), and anything that
does develop isn`t going to move much, and probably rain itself
out. Areal coverage looks to drop off somewhat on Friday, and a
little more on Saturday. An inverted trough/easterly wave
approaches from the northeast Gulf of Mexico on Saturday night,
but any significant precipitation impact is likely to hold off
until Sunday.

Temperature guidance in the short term is surprisingly well
clustered. That being said, high and low temperatures the last few
days have generally run above the operational guidance. NBM
numbers are a little higher than the operational guidance, and
this looks reasonable over the next couple of days. If any
adjustments are necessary, it`d be to bump things up a degree or
two. 35

LONG TERM (Sunday and beyond)...

An inverted trough axis will continue to impact the area on
Sunday. A pool of deep tropical moisture and enhanced forcing on
the eastern side of this trough axis will support continued shower
and thunderstorm development throughout the day on Sunday and
into Sunday night. Precipitable water values will be elevated in
the range of 2 to 2.5 inches, so a risk of high rain rates and
localized flooding will exist Sunday into Monday. Given the ample
lift and high moisture content in place, high POP values of 60 to
80 percent are forecast. Temperatures should also be a bit cooler
than average due to the expected extensive cloud cover in place.

The inverted trough axis will continue to pull to the west into the
state of Texas on Monday, and increasing mid to upper level ridging
will start to build over the area from the east.  In the low levels,
the ridge axis will remain centered over western Atlantic, and this
will keep a prevailing deep layer onshore flow in place through the
middle of the week.  Overall, this synoptic pattern is very typical
of the Summer months, and a largely Summer like pattern of diurnally
induced convection is expected each day.  Precipitable water values
will remain somewhat elevated at around 2 inches on Monday, and
overall convective coverage will higher on this day.  Have maintained
high POP for the afternoon hours at between 60 and 80 percent with
the highest rain chances across the western third of the CWA where
precipitable water values will be highest.  By Tuesday and
Wednesday, the influence of the ridge will be greater and
precipitable water values will be closer to 1.75 inches.  POP values
are forecast to be slightly lower in the 40 to 60 percent chance
range with POP maximizing in the afternoon hours.  A diurnal minimum
with only isolated convective coverage is expected in the late
evening and overnight hours each day.  Temperatures should also warm
to more normal readings with highs near 90. PG

AVIATION (12z TAF Package)...

A stratus deck has been rather patchy over the last few hours, and
could build down into FG/BR around sunrise, similar to what
happened 24 hours ago. A period of IFR and LIFR ceilings is
possible at all of the terminals until about 14z. After 14z,
increased boundary layer mixing will allow for a return to
prevailing MVFR ceilings between 1500 and 2500 feet. Shower and
thunderstorm development should also increase in coverage by 18z,
and will likely hold onto prevailing SHRA and VCTS wording to
reflect the convective risk this afternoon. The convection should
dissipate after 00z as daytime heating wanes with prevailing VFR
conditions forecast through 06z Friday, with the potential for
another round of lower ceilings toward 12z Friday. PG/35

MARINE...

Main marine concern over the next few days will continue to be
the threat of thunderstorms. Prevailing winds will mostly top out
in the 10 to 15 knots range through the weekend, so am not really
anticipating any wind-related headlines over the coastal waters
through the weekend, although it might be borderline on Saturday
afternoon/evening. 35

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  91  73  89  72 /  50  30  50   0
BTR  92  74  91  74 /  60  20  60   0
ASD  91  74  89  74 /  50  20  50  10
MSY  91  77  90  78 /  50  20  60  10
GPT  89  75  86  76 /  50  20  50  10
PQL  88  73  86  73 /  60  20  50  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...None.
GM...None.
&&

$$


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