Special Marine Warning 521, NWS New Orleans, LA

967 
FZUS74 KLIX 142213
MWSLIX

Marine Weather Statement
National Weather Service New Orleans LA
513 PM CDT Tue Sep 14 2021

GMZ532-142222-
/O.CAN.KLIX.MA.W.0521.000000T0000Z-210914T2230Z/
513 PM CDT Tue Sep 14 2021

...THE SPECIAL MARINE WARNING IS CANCELLED...

The affected areas were... 
Mississippi Sound...

The shower has weakened and no longer poses a significant threat to
boaters.

LAT...LON 3034 8891 3031 8896 3031 8904 3035 8908
      3036 8908 3039 8901 3039 8895
TIME...MOT...LOC 2211Z 151DEG 10KT 3044 8905 

$$

KLG

Area Forecast Discussion
National Weather Service New Orleans LA
403 PM CDT Tue Sep 14 2021

.SHORT TERM...Tropical Storm Nicholas is moving painfully slow to
the east and at times east-southeast today. Nicholas is not
anticipated to pick up any speed and this looks like it could lead
to a long night across portions of SELA and coastal MS. Rain has
been falling over the entire area all day but luckily it has been
more moderate rain with no extremely heavy bands yet. That said we
have seen widespread 2-3 inches of rain already with a few bands
of 3-4 isolated 5 inches and that one small area in EBR that is
now over 7 inches.

The forecast focus has not changed and remains on the potential for
flash flooding and possibly life threatening flash flooding. That
could be overnight tonight for a good chunk of SELA and then
possibly late Wednesday afternoon through Wednesday night for
coastal MS. That said confidence is low on any one location but high
that someone will get very heavy rain.

Tonight there is a lot of agreement that the next band of heavy rain
should begin to develop just off to our west and southwest around
22-00z and then slowly move east-northeast through the evening
and overnight hours. HRRR has been highlighting that potential for
a while and honestly it has preformed very well over the last 24
hours and currently is initialized well and already seeing
convection trying to get a little more invigorated from the TX/LA
border and southeast into the Gulf. This still isn't expected to
really develop till closer to 23-00z. Looking at WV one would be
hard pressed to think additional heavy rain will develop and move
into the area, that said there is still abundant moisture to tap
into while lift and forcing are both expected to increase
overnight. As Nicholas continues to slowly slide east along a semi
warm front along the coast a LL jet will try to get going across
the coast and into the Gulf. The nose of it will punch into south-
central and then southeastern LA overnight. The nose of that will
increase the LL convergence which will combine with
WAA/isentropic lift while occurring with ample moisture in place.
PWs will still range from near 2.2 to possibly 2.5". There will
still be divergence aloft and this all suggest efficient rain.
This will still be primarily a warm rain process so don't
anticipate extremely impressive towers or a lot of lightning. If
this band does get going as strong as it may then we will see
hourly rainfall rate of 2-3 inches per hour and possibly higher in
some areas with overnight totals of 5 inches and even greater in
isolated areas.

The heavy rain threat will slide east into coastal MS early tomorrow
with this band expected to continue to move east towards AL.
However, whatever is left of Nicholas will still be back in
southwest or south-central LA and very deep moisture will remain in
place. By tomorrow afternoon a line of additional storms could
develop from southwest to northeast from coastal SELA to coastal MS.
This will bring another round of moderate to heavy rain and after
everything finally starts to wind down some we could see widespread
5-10 inches of rain with locally higher amounts possibly even over
20 inches. 20 inches of rain would be a major problem but as long as
it doesn't fall mostly in one round the flash flooding may not be as
life-threatening. Most of this rain is anticipated to fall along and
south of the 10/12 corridors but if it occurs just north of the
interstates in SELA and across coastal MS river flooding will be a
concern. We still are under a Moderate Risk for excessive rainfall
tonight and through Wednesday night. There is a small chance we
could see a High risk depending on what occurs tonight.

Going into Thursday numerous to widespread showers and embedded
thunderstorms will continue to plague the region. Nicholas should be
dissipated by then but we will still be embedded in very deep
moisture and lower hghts aloft. The one positive is we should not
see any focused bands but heavy rain will still be possible and thus
flash flooding will still be a concern.

Coastal Flood Advisory was expanded to include the rest of the LA
coast outside of the tidal lakes and Hancock and Harrison county.
Still looking for 1-2 feet above astronomical. /CAB/

.LONG TERM...Again no major changes in the extended as the
focus is on the short term. Appending previous long term portion of
the discussion handling the forecast for Friday and into the
following work week. /CAB/

Previous Long Term...Still some uncertainty in the extended portion
of the forecast regarding the eventual disposition of Hurricane
Nicholas. Current NHC forecast (10 PM CDT Monday) has it dissipating
over south-central or southwest Louisiana Thursday. That being said,
at this time, don't see much in the way of drying forecast in the
column as a whole into and through the weekend. Convective
development will likely occur during the more usual diurnally
favored hours (afternoon over land) over the weekend. May see some
decrease in areal coverage by Monday or so.

Don't see much day to day change in temperatures until the expected
decrease in areal coverage around Monday or so, at which time temps
may creep upward a degree or two. /35/

&&

.AVIATION...18Z TAF DISCUSSION...Obviously main issue is rain, low
cigs, reduced vsbys, and even gusty winds. The low cigs will
continue through the night and with rain the vsbys will be reduced.
All terminals will be impacted and likely all will deal with
significant impacts for at least the next 12-18 hours. /CAB/

&&

.MARINE...Hazardous winds and seas will continue over the coastal
waters through tonight. winds of 15-20kts with frequent higher gusts
will continue but the bigger concern could be combined waves and
swells leading to total sea hghts of greater than 7' still.
Obviously higher winds and seas are expected with any thunderstorm
over the coastal waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  70  79  70  83 / 100  90  60  80
BTR  71  80  70  84 / 100  90  60  80
ASD  73  83  72  87 / 100  90  70  90
MSY  75  86  76  88 / 100  90  70  90
GPT  73  82  74  85 / 100  90  80  90
PQL  71  82  72  85 / 100 100  80  90

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Flash Flood Watch through Thursday morning for LAZ034>037-039-
     046>050-056>061-063>072-075>078.

     Coastal Flood Advisory until 7 AM CDT Thursday for LAZ064-
     066>070-076-078.

GM...Small Craft Advisory until 7 AM CDT Wednesday for GMZ550-552-555-
     557-570-572-575-577.

MS...Flash Flood Watch through Thursday morning for MSZ068>071-077-
     080>082.

     Coastal Flood Advisory until 7 AM CDT Thursday for MSZ080-081.

GM...Small Craft Advisory until 7 AM CDT Wednesday for GMZ552-555-557-
     570-572-575-577.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
115 PM CDT TUE SEP 14 2021

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

0112 PM     FLASH FLOOD      4 SW EAST NEW ORLEANS   30.02N 89.97W
09/14/2021                   ORLEANS            LA   EMERGENCY MNGR

            NOHSEP REPORTED MULTIPLE UNDERPASSES TO BE
            IMPASSABLE DUE TO HIGH WATER.

&&

MEFFER