Flash Flood Warning 10, NWS New Orleans, LA

Area Forecast Discussion
National Weather Service New Orleans LA
1257 PM CDT Tue Mar 22 2022

... MESOSCALE UPDATE...
There have been some interesting trends developing in the most
recent HRRR models and the satellite features. Mainly of note is
the continued presence of a surface low further south than
anticipated yesterday and this feature is still evident in the
models and the surface winds and observations. The LL 850 jet is
now squarely over our area encompassing all of SE LA, S MS, and
some of coastal MS. The combination of these features indicate the
increasing favorability for tornadogenesis.

The most recent runs of the 16Z HRRR and other CAMs are indicating
the increased potential over the next couple of hours of discrete
cells out ahead of the line of storms. Mainly the models are
indicating this concern is highest for areas along and north of
the I-10/I-12 corridor, including S MS, Baton Rouge metro, and the
northshore areas of Lake Pontchartrain. These cells would have the
ability to produce tornadoes and the environment is increasingly
conducive for strong tornadoes to develop as well.

The 18Z sounding launched at KLIX shows that we are no longer
capped, so any storms that form out ahead would be able to pop and
really strengthen quickly. And our surface winds are still
southeasterly, which will aid directional shear.

An interesting satellite feature that has been noticed as well is
the presence of some dry air intrusion just ahead of the front.
This dry air could clear out our area ahead of the line and allow
for cells to start popping up along a boundary. Obviously, too
much dry air however could hinder development.

But in general, we are entering an increasingly favorable
environment for discrete cells and tornadogenesis ahead of the
line of storms over the next hour or two, based on satellite and
radar trends, short-term models, and observations. MSW

&&

.PREV DISCUSSION... /issued 433 AM CDT Tue Mar 22 2022/

SHORT TERM (Today through Thursday)...Some prefrontal activity
does get going this morning but low instability, lack of any
forcing either via buoancy or boundary in the area, these showers
and maybe a thunderstorm should not be the main interest today,
although will be watched. Looking at the main event(thunderstorms
along front with QLCS evolution), some slight but important
changes to guidance this morning shows the upper level split flow
moving out of SE TX/SW LA into central LA then into SW Miss to
central Miss. This makes sense as the synoptic ridge is stubborn
to move east and therefore the upper diverent flow provided
between the subtrop jet and polar jet is forced nothward over the
NW side or this ridge. Moving beneath the upper jet level, all
other parameters seem to follow this pattern as well. Low
level(850) near 70kt jet nose also moves over this same region.
Then looking at instability to provide any focus or forcing to any
cells that develop ahead of the main line is lacking but there is
opportunity if cloud cover can be eroded and enough heating can
be achieved. Advected CAPE values are not bad around 1500-2000J.
3CAPE values are north of 100J. LCL/LFC are coupled and will
fluctuate from 1200-200ft through the day. Low level dynamics are
very strong, 0-3 helicity values ranging from 400 to near 700. But
these numbers are just as robust north and NW of the area co-
located with the best mid- upper dynamics. Every model(s) show
this very same scenario from ensemble members to deterministic to
probabalistic runs. We should see the line begin moving into the
area around noon or shortly after and should be out of the area by
midnight or shortly after. The main forcing will be provided by
the front itself. With the main support moving near and then north
of the area, there is a good chance that some cells along the
line will produce strong damaging winds and tornadoes and as far
as probabilities for either, this is how they are arranged via the
NMB probs of getting damaging winds(16%), tornado(14%) and
hail(11%). These numbers are higher when looking at neural
networks for the same variable but still show a slight shift
north for the highest probs. So all modes will be possible but
the environment is not as supportive of hail as much as it is for
wind and tornadoes. The question again will be how many storms
will produce and with the previous mention of stronger variables
NW and north of the area, would not be surprised to see the
highest risk areas shifted north a bit but still covering a
large portion of the area. These changes would be minor and
regardless of where these levels are located, it is important to
have some way of getting warnings for your location. The next
thing will be the flash flood watch and there is no doubt that
this will be kept as is. PW numbers are still coming in at
1.8-2.0" with a very efficient rainfall process and a somwhat
slowing of the line as it moves through. This should be enough to
see some widespread 1-2" totals with swaths of 3" and isolated 5".
Rainfall rates should be impressive as well with up to 5"/hr
possible. Basically, we will message this as 1-3" with isolated
totals up to 5". Once the line moves to the east, strong stability
settles over the area bringing a dry fcast for the remainder of
Wed thru Thu.

Long Term (Thursday night and beyond)...

Upper troughing will be exiting the area Thursday night, with any
precipitation well to the east of the area. Upper ridging will
remain primarily over the Rockies through the weekend. At the
surface, high pressure over the Plains States Friday morning will
gradually work eastward and be centered off the east coast of
Florida by Monday. The current storm system will have brought dry
air to the area by Thursday with dew points in the 40s well into the
Gulf of Mexico. With no significant onshore winds until at least
Monday, if that soon, the threat of precipitation will be very low
through at least Tuesday.

With dry air in place, morning lows this weekend will be on the cool
side, roughly 5-8F below normal for several mornings. Highs likely
to be pretty close to normal through the weekend, then as onshore
flow returns on Monday, it should lead to high temperatures moving
into the 80s for midweek next week. 35

AVIATION...
Gusty southeast winds with sustained 20+ knots and gusts exceeding
30 knots. While SHRA could occur at any time, will limit TSRA for
now, to a 2 hour window with main band of convection. Localized IFR
and potential for gusts exceeding 40 knots with main band of
convection. Improvement will occur several hours behind main
convection.

MARINE...Small Craft Advisory will remain as posted. Winds will
continue to increase through the day today then shift to W and
remain elevated on the back side of the front swinging through early
Wednesday, and will slowly ease going into Wednesday
afternoon/night. Some extension of the advisory may be possible if
waves/seas remain elevated. Surface winds remain breezy through late-
week, but nothing significant in regards to impacts even going into
early parts of next weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  77  48  66  41 /  90  70   0   0
BTR  79  48  67  43 / 100  30   0   0
ASD  81  53  69  44 /  70  90   0   0
MSY  80  53  67  49 /  70 100   0   0
GPT  75  56  69  46 /  50  80   0  10
PQL  76  58  69  45 /  50  90   0  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Wind Advisory until 9 PM CDT this evening for LAZ034>037-039-
     046>050-056>061-063>072-075>078.

     Coastal Flood Advisory until 7 PM CDT this evening for
     LAZ066>070-075-076.

     Flood Watch through late tonight for LAZ034>037-039-046>050-071-
     072-075-076.

GM...Small Craft Advisory until noon CDT Wednesday for GMZ530-532-534-
     536-538-550-552-555-557-570-572-575-577.

MS...Wind Advisory until 9 PM CDT this evening for MSZ068>071-077-
     080>082.

     Coastal Flood Advisory until 7 PM CDT this evening for
     MSZ080>082.

     Flood Watch through late tonight for MSZ068>071-077-080.

GM...Small Craft Advisory until noon CDT Wednesday for GMZ532-534-536-
     538-550-552-555-557-570-572-575-577.

&&

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

Special Weather Statement
National Weather Service New Orleans LA
301 PM CDT Tue Mar 22 2022

MSZ069-070-222030-
Pike MS-Amite MS-
301 PM CDT Tue Mar 22 2022

...A strong thunderstorm will impact portions of northwestern Pike
and northeastern Amite Counties through 330 PM CDT...

At 301 PM CDT, Doppler radar was tracking a strong thunderstorm near
Mccomb, moving northeast at 60 mph.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Mccomb and Summit.

This includes Interstate 55 in Mississippi between mile markers 15
and 24.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

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

A Tornado Watch remains in effect until 700 PM CDT for southern
Mississippi.

&&

LAT...LON 3120 9050 3120 9066 3126 9071 3135 9061
      3135 9030
TIME...MOT...LOC 2001Z 224DEG 53KT 3126 9058

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

KLG