Flash Flood Warning 65, NWS New Orleans, LA

Area Forecast Discussion
National Weather Service New Orleans LA
553 AM CDT Fri Aug 26 2022

...MORNING UPDATE...
Due to internal coordination involving antecedant conditions and
lower FFG numbers, we will post a flood watch by 6am for those
areas with the highest saturation.

&&

.PREV DISCUSSION... /issued 404 AM CDT Fri Aug 26 2022/

SHORT TERM (Today through Sunday)... Trying to find the old stalled
inverted trough and sfc low is difficult this morning, but there is
some evidence that it is located along the coast and just offshore.
PW values are still expected to be 2+" and convective temps are
still near the SST numbers simply telling us this is still a very
tropical air mass. But with the even weaker sfc low and attendant
boundary near or just offshore today, the focus for heavy rainfall
should be at the coast or just offshore. This will be the reason for
not posting a flood watch. So, long story longer, this does not mean
there will be no heavy rain producing storms around, there just
should not be as many as there have been inland. But with any heavy
rainfall, the potential that an isolated location could see flooding
is still possible as grounds are absolutely soaked. Saturation
numbers are very high at 50% for almost all the northern half of the
area and some values at and around 80% for coastal Miss counties.
The only areas on the lower side are south of the tidal lakes coming
in from 20-40% saturation. There are some mild changes coming though
even if temporary. The first thing will be some subsident "drier"
air moving over the area Saturday into early Sunday. This can be
seen in WV imagery along the 24N-25N latitude line over the gulf.
With the inland progression of this subsident area, we have lowered
precip numbers back to around 70% which is pulling away from the NBM
guidance to the dry side and this may be generous for a few areas.
This subsident area is being cause by the interaction of two systems
at the moment. The upper low moving into centeral Mexico and the
upper trough over our area. The upper low will continue westward
while a very weak easterly wave moves west into the southern gulf
with upper diffluence and some SW shearing. This wave is not very
discernible in WV, but pressure fields show a gentle inverted
troughing feature there extending all the way into Florida.
Currently this wave is moving into the Yucatan this morning. Once
this enters the gulf, it should become more evident. As this
moisture gets funneled northward over the western gulf in the coming
days, it will push this subsident area over us by Saturday and early
Sunday. This doesn't shut down the precip but will drop it back a
good bit temporarily. The moisture from this wave will get drawn
northward and by late Sunday into the first of next week and we will
see our area back in this old routine. The dry air will cause some
of the thunderstorms to have some good outflows though.

LONG TERM (Monday and Beyond)...

We will be in a mostly zonal flow pattern aloft to start off the
week, with no obvious dominant upper level pattern. At the surface
we will be in a fairly consistent easterly to southeasterly flow
which will bring plenty of moisture into the area. PWs are looking
to be around climate norms (2.0") or higher through the extended
period. Although there won't be a focus for convection, outside of
lake/sea breeze or outflow boundaries, PoPs will still be on the
order of 60-75% each day due to the lack of any ridging in the upper
levels. Temperatures will be in the mid 80s to low 90s each day,
depending on where showers and thunderstorms set up.

HL

AVIATION...(12z)
IFR and LIFR conditions again found at the normal spots like around
MCB with cigs and vis restrictions. BTR will keep their low cigs as
well until after sunrise today. Again, all terminals will have a
very high prob of getting IFR and LIFR with SHRA/TSRA. Vis and low
cigs are expected again tonight mainly for inland sites. Otherwise,
VFR conditions will be seen.

MARINE... Thunderstorms will continue to form over the nearshore
waters over the next several days mainly during the late night into
mid morning hours. Winds and seas will remain in a light southerly
flow of 5 to 10 knots and seas of 2 feet or less. The main concern
from any thunderstorms will be brief periods of gusty winds, heavy
rainfall, and the potential for a few waterspouts. Waterspout
activity will lower for Saturday and Sunday but will be back with us
by Monday and well into the work week.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  83  69  85  70 /  90  30  70  20
BTR  85  73  89  74 /  90  30  70  20
ASD  87  73  88  74 /  90  40  70  20
MSY  85  76  88  76 /  80  40  70  20
GPT  86  74  87  75 /  80  50  70  20
PQL  87  73  87  73 /  80  50  70  20

&&

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

Special Weather Statement
National Weather Service New Orleans LA
526 AM CDT Fri Aug 26 2022

LAZ059-060-087>090-261100-
Central Plaquemines LA-St. Charles LA-Lower Jefferson LA-
Upper Plaquemines LA-Upper Jefferson LA-Upper Lafourche LA-
526 AM CDT Fri Aug 26 2022

...A strong thunderstorm will impact portions of southeastern St.
Charles, east central Lafourche, northwestern Jefferson and
northwestern Plaquemines Parishes through 600 AM CDT...

At 526 AM CDT, Doppler radar was tracking a strong thunderstorm near
Barataria, or 14 miles northeast of Larose, moving north at 15 mph.

HAZARD...Winds in excess of 30 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Belle Chasse, Marrero, Avondale, Timberlane, Harvey, Westwego, Jean
Lafitte, Woodmere, Lafitte, Estelle and Barataria.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 2959 9013 2964 9028 2991 9025 2986 8998
TIME...MOT...LOC 1026Z 201DEG 14KT 2969 9019

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...30 MPH

HL

Special Weather Statement
National Weather Service New Orleans LA
651 AM CDT Fri Aug 26 2022

LAZ069-261215-
Lower Plaquemines LA-
651 AM CDT Fri Aug 26 2022

...A strong thunderstorm will impact portions of central Plaquemines
Parish through 715 AM CDT...

At 650 AM CDT, Doppler radar was tracking a strong thunderstorm
capable of producing a waterspout near Buras, or 19 miles southeast
of Port Sulphur, moving northeast at 15 mph.

HAZARD...Waterspouts and winds in excess of 30 mph.

SOURCE...Radar indicated.

IMPACT...Waterspouts can easily overturn boats and create locally
         hazardous waters. Gusty winds could knock down tree limbs
         and blow around unsecured objects.

Locations impacted include...
Buras, Boothville-venice, Boothville, Buras-triumph, Empire and
Boothville Asos.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Conditions are favorable for the development of weak, brief funnel
clouds. This type of funnel cloud is harmless, but on rare occasions
they can briefly touch down, producing wind gusts over 50 mph. If a
funnel cloud is spotted move indoors and report your sighting to the
National Weather Service.

&&

LAT...LON 2937 8958 2940 8955 2939 8953 2942 8953
      2938 8952 2940 8947 2938 8942 2939 8941
      2939 8937 2938 8933 2938 8939 2933 8937
      2936 8937 2933 8935 2935 8930 2933 8926
      2924 8950
TIME...MOT...LOC 1150Z 230DEG 12KT 2932 8948

WATERSPOUT...POSSIBLE
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...30 MPH

HL