Flash Flood Warning 53, NWS New Orleans, LA

Area Forecast Discussion
National Weather Service New Orleans LA
1130 AM CDT Mon Aug 8 2022

...UPDATE...Sent out a quick update to the grids earlier to adjust
PoPs up a little, especially along the coast and speed things up
some. As anticipated storms were able to get going a little
faster than yesterday given the shift to a more southeast flow
form the sfc to h85. That along with a weakening ridge aloft and
PWs still abv 2" is providing little resistance to getting storms
to develop. The increasing low level moisture is also making it a
little more favorable for waterspouts out there and we have had a
few reports already over Lafourche parish and near Ocean Springs,
MS. /CAB/

&&

.AVIATION...18z TAF Package...Convection will once again be the
biggest impact to the area but even outside of storms there are
some minor impacts still over most of the area. SCT to BKN skies
around 1500-3k ft is impacting much of the area leading to
multiple terminals dropping into MVFR status. Convection will
likely impact most of the region through the day and into the
early evening hours but will slack off after sunset. Then once
again the biggest issue could be pockets of low cigs and reduced
vsbys causing a few terminals to fall into MVFR and possibly even
IFR status. /CAB/

&&

.PREV DISCUSSION... /issued 631 AM CDT Mon Aug 8 2022/

AVIATION (12Z TAF DISCUSSION)...Overall, VFR conditions will be
the prevailing condition at the terminals. However, scattered
convection will develop today after 15z, and this could briefly
impact the terminals at times through the afternoon hours. If a
storm looks to impact a terminal, generally an hour or less of
reduced visibilities, gusty winds, and lightning can be expected.
The convection should largely dissipate by 00z. There may also be
a very brief period of fog and stratus development around 12z
tomorrow morning at MCB due to the formation of a weak surface
based temperature inversion. PG

PREV DISCUSSION... /issued 302 AM CDT Mon Aug 8 2022/

SHORT TERM (Today through Wednesday)...Little change in thinking
from the previous forecast concerning the overall trend of
gradually increasing moisture, lift, and rain chances through
Wednesday. The overall upper level pattern will see an inverted
trough axis gradually shift from the eastern Gulf into the central
Gulf through the first half of the week. As this trough moves
closer to the central Gulf coast, precipitable water values will
increase from near climatological norms of around 2 inches today
to around 2.25 inches by Wednesday. Sounding analysis indicates
that more efficient warm rain processes will also become more
likely within any convection that develops by Wednesday. Thus, a
gradual increase in hourly rainfall rates from 1 to 2 inches per
hour today to 2 to 4 inches per hour on Wednesday is expected.
This will lead to an increased threat of some localized street
flooding issues in low lying and poorly drained areas by
Wednesday. Additionally, an astronomically higher tide range is in
place this week, and this will lead to minor coastal flooding
issues on south and east facing shores. This minor coastal
flooding could exacerbate street flooding issues in low lying
coastal areas as the heavier rainfall be slower to drain. The
primary area of concern will be in Hancock County this week, but
some issues may also occur outside of the levee system in Saint
Bernard Parish by Wednesday. High temperatures will be near
average today, and should start to trend slightly cooler than
average by Wednesday due to expected increase in convective
development.

LONG TERM (Thursday through Sunday)...A pattern change is still
expected to occur during the latter portion of the week as an
inverted trough axis pushes into the western Gulf and a strong
longwave trough axis deepens over the eastern third of the CONUS.
Both of these features will be working in tandem on Thursday as a
plume of deep tropical moisture is drawn northward toward an
approaching frontal boundary. As precipitable water values rise
above the 90th percentile for early August, model soundings
indicate the potential for highly efficient rainfall processes to
be in place throughout the day and even into the overnight hours
on Thursday night. Rainfall rates could approach 3 to 5 inches per
hour in a few locations, and threat of more substantial localized
flooding will exist in our more flood prone locations.
Additionally, an anomalously high tide cycle will also continue
with minor coastal flooding expected on south and east facing
shores. This could exacerbate local drainage issues in a few
spots, primarily in Hancock County. The extensive cloud cover and
rainfall in the area should keep highs well below average in the
mid 80s.

From Friday through Sunday, the influence of the inverted trough
will wane as the system pushes into Texas. Instead, a deep layer
northerly flow pattern will take over across the central Gulf
coast. Drier air in the mid and upper levels will feed into the
area, and precipitable water values should decrease at least back
to more normal levels for this time of year, and possibly even
below normal by Saturday and Sunday if a weak frontal boundary is
able to push far enough offshore. Largely stuck with NBM PoP
values over the upcoming weekend. These values are close to
climatology at 40 to 50 percent each day. The main concern during
this time frame will be the potential for strong wind gusts to
accompany some of the deeper convective cells as drier mid-level
air is entrained into the updraft cores. Temperatures should also
recover a bit with highs closer to average in the upper 80s and
lower 90s each day. The other issue will continued minor coastal
flooding concerns in more flood prone spots of Hancock County and
Lower Saint Bernard Parish as astronomically higher tides persist.
Fortunately, the threat of flooding from Friday through Sunday
will be substantially reduced as rainfall rates fall back to the
more typical 1 to 2 inches per hour range.

AVIATION...Overall, VFR conditions will be the prevailing
condition at the terminals. However, scattered convection will
develop today after 15z, and this could briefly impact the
terminals at times through the afternoon hours. If a storm looks
to impact a terminal, generally an hour or less of reduced
visibilities, gusty winds, and lightning can be expected. The
convection should largely dissipate by 00z.

MARINE...A persistent southeast flow of 10 to 15 knots and seas
of 1 to 3 feet is expected through tomorrow. By mid-week, a weak
low pressure system in the central Gulf could push winds up to
around 15 knots in the offshore waters, and seas could briefly
increase to 4 feet on Wednesday and Thursday. This low will track
into Texas by Friday, and winds are expected to drop back to 10
knots or less. Wind direction should also turn more southwesterly
as a weak frontal boundary stalls near the coast. Seas will
correspond by falling back below 3 feet. The other concern will be
the typical pop up thunderstorm activity seen during the Summer
months that could produce short-lived strong wind gusts and
waterspouts.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  93  71  89  71 /  40  20  60  20
BTR  92  74  90  73 /  40  20  60  20
ASD  91  73  88  74 /  70  20  60  20
MSY  90  77  88  77 /  60  20  60  20
GPT  88  75  87  76 /  80  20  60  20
PQL  89  74  89  74 /  80  20  60  20

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...Coastal Flood Advisory until noon CDT today for MSZ080.

GM...None.
&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
949 AM CDT MON AUG 8 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0925 AM     WATER SPOUT      7 E CUT OFF             29.51N 90.21W
08/08/2022                   LAFOURCHE          LA   BROADCAST MEDIA

            MEDIA RELAYED A PICTURE OF A WATERSPOUT ON
            SOCIAL MEDIA NEAR CUT OFF.

&&

JZ

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1102 AM CDT MON AUG 8 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1055 AM     WATER SPOUT      5 SW GULF PARK ESTATES  30.33N 88.81W
08/08/2022                   GMZ532             MS   EMERGENCY MNGR

            EM AND MEDIA REPORTED A WATERSPOUT OFF THE
            COAST OF OCEAN SPRINGS.

&&

JZ