Flash Flood Warning 68, NWS New Orleans, LA

Area Forecast Discussion...UPDATED
National Weather Service New Orleans LA
630 AM CDT Sat Sep 3 2022

...New AVIATION...

.SHORT TERM...
(This evening through Sunday night)
Issued at 349 AM CDT Sat Sep 3 2022

Some light patchy fog has developed across the fog favored
portions of the northern CWFA this AM. This should dissipate
rapidly after sunrise. Otherwise, modest nocturnal convection has
developed across the open Gulf waters south of Terrebonne early this
morning. This activity has developed along the moisture gradient.
Aloft, the region remains between a developing upper level
weakness over the lower Missouri River Basin and a weak H5 ridge
over the Florida Peninsula. The winds through the column should
become more unidirectional today, which should finally erode the
mid and upper level dry layer that has protected most of us from
shower and T'storm activity over the last few days. From the 00z
RAOB locally, precipitable waters have jumped up just a bit
(although still below climo) to around 1.70". Going into the
afternoon, PWATs should continue to rebound closer to 2.2" or so,
which when coupled with the active southwesterly flow and diurnal
cycle should provide enough evidence for a higher POP day today.
With the pattern some hydro concerns could arise, especially if
storms cluster from SW to NE within the mean flow.

Going into Sunday and into the new workweek, not much in the upper
level or surface pattern changes. The active SWerly flow will
continue with no real change in the dominant synoptic features in
play. The primary challenge will likely be timing of weak mid
level impulses within the SWerly flow. The max rain potential
would likely occur if timing of the impulse(s) coincide with the
diurnal cycle. However, even residual weak surface boundaries
(i.e. outflow) could help generate "off hour" convection, if you
will. Regardless, there are plenty of signals for higher-end
CLIMO POPs through the period. As for temperatures, timing of
convection will play a large role in afternoon temperature
forecasts. True, the increase in rain/clouds will keep
temperatures lower, but only if there isn't a late initiation. The
thought is late morning to early afternoon, which would cap
heating at or below 90F for most of us, but a slight delay could
mean the difference in MaxTs remaining in the 80s vs 90s.
(Frye-28)

&&

.LONG TERM...
(Tuesday through Friday night)
Issued at 349 AM CDT Sat Sep 3 2022

Not a whole lot of change in thinking for the long term forecast.
Next week each day will be pretty much a rinse and repeat of
numerous showers and thunderstorms throughout the day, mainly during
the normal diurnal cycle from the late morning through the early
evening. Convection will be mainly focused along sea and lake breeze
boundaries. PoPs are expected to be on the order of 70-80% each
afternoon through the long term period. Deep tropical moisture will
continuously flow in next week with persistent southerly flow at the
surface and southwesterly flow aloft. This paired with PWs on the
order of 2.0-2.2 and the already saturated soil, we may see some
flash flooding issues next week. This would be mostly for urban
areas and any areas that see training of storms or multiple rounds
of storms in a short period of time. Rain rates could be on the
order of 3-4 inches per hour in the stronger storms that develop. On
a better note, higher chances of rain leads to lower temperatures.
High temperatures look to be limited to the low to mid 80s later in
the period. HL

&&

.AVIATION...
(12Z TAFS)
Issued at 629 AM CDT Sat Sep 3 2022

Fog for MCB should dissipate shortly after sunrise. Otherwise,
convection increases today. At this juncture, wasn't confident to
indicate anything lower than VFR/MVFR, but short fused IFR TEMPOs
may be required later this morning or into the afternoon hours.
For now, continued VCs for thunder with showers prevailing for
most locations this afternoon and kept some mention of showers
(VCs) overnight for most terminals near the coast. MCB again may
experience patchy fog overnight. Mainly light and variable winds
outside of thunderstorms.

&&

.MARINE...
Issued at 349 AM CDT Sat Sep 3 2022

Generally favorable marine conditions are forecast through the
weekend and into early next week. Light to moderate southerly or
westerly winds are anticipated with seas generally at or below 3
ft over the open Gulf waters. Otherwise, the main concern would be
increasing convection over the next few days. The strongest
showers and T'storms may produce locally higher winds and seas as
well as frequent cloud-to-water lightning and brief heavy
rainfall. (Frye-28)

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  87  71  84  69 /  80  40  80  20
BTR  88  73  86  73 /  90  40  80  30
ASD  90  73  89  73 /  80  40  80  30
MSY  88  76  87  76 /  90  50  80  30
GPT  89  74  88  74 /  70  40  80  40
PQL  89  73  89  73 /  70  40  80  40

&&

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

SHORT TERM...Frye-28
LONG TERM....HL
AVIATION...Frye-28
MARINE...Frye-28