River Flood Warning 23, NWS New Orleans, LA

AREA FORECAST DISCUSSION
National Weather Service New Orleans LA
342 AM CST Tue Mar 3 2020

.DISCUSSION...
The current upper level pattern shows a trough extending across the
upper Mississippi Valley and a close low near Baja California. The
shortwave that brought rain the the local area yesterday is quickly
racing east while the trough to the north digs south into the
midsection of the country. This will send a weakening cold front to
the area. Still looks like this boundary will be stalling right over
the CWA. That scenario will provide a focus for mostly shower
development with scattered storms. Some training may be possible but
thinking 1.5 PW isn't very high and thus rain rates not overly
intense. Storms will generally be elevated as model soundings show a
very pronouced warm nose at about 850mb. Therefore, marginal outlook
by SPC could be generous with small hail the main impact. Overnight
period could be conducive for fog development and may need a dense
fog advisory.

Likely the most impactful weather of the week will be coming late
Wednesay. The upper low currently off the CA coast will track across
Mexico tonight night and into/across central Texas Wed. Models show
a surface moving from Austin in the morning to right over Baton
Rouge just after dark. That will put the southern half of the CWA in
the warm sector. North of that thermal gradient will not see any
severe weather. Along and south of the warm front in the warm sector
is where the threat for severe weather is greatest. There's a Slight
Risk for severe weather and excessive rainfall over basically the
entire CWA. Best chances for severe are looking like along and south
of I-12 in LA and all coastal MS counties. Timing of the surface low
puts the window of severe threat beginning well into the afternoon
and carrying over into the evening hours from west to east across
the CWA. All modes of severe weather and heavy rainfall will be
possible. It will probably be "messy" event with embedded severe
storms rather than clear cut supercells.

The area should be quickly clearing out before sunrise Thursday as
the upper low races eastward. Skies my stay cloudy for much of the
day, but the rain should be done. Temps will be slightly cooler than
normal Thursday but quickly bounce back to and rise above climo
Friday into the weekend. Might even stay clear of rain through the
weekend.

MEFFER
&&

.AVIATION...
With the approach of a warm front late, low ceilings and reduced
visibility readings due to fog may occur during the afternoon and
persist possibly into the evening hours. There could be some LIFR
cigs as well late today and overnight. But most inland terminals
should stay above 1SM in vis while coastal sites could have vis
reductions to 1/2SM and possibly lower. There will also be a few
passing -SHRA today and tonight but may be too small of a chance to
show for now.

.MARINE...
Fog looks to remain an issue over most waters today. The dense fog
advisory over marine areas will be left in its current time frame to
make sure the fog production remains since dew pt values are very
close to water temps. Would normally like to see these dew pt temps
a little higher than water temps. Fog may be an issue once again
tonight as well. But as winds slowly rise to around 20kt over most
marine areas, fog will begin to get mixed out improving vis. This
may not be the case for the waters where a cold front stalls near
the coast. This could cause the lakes and Mississippi Sound to keep
fog in the fcast until a sfc low lifts NE.

A cold front will stall near the coast Wednesday morning and evolve
into a warm front as a sfc low moves into the area Wednesday night
into early Thursday. This will cause winds over the lakes and
Mississippi Sound to become easterly and weaker around 10kt. The
remaining marine areas will retain southerly winds of around 15kt
rising to 20-25kt by Wed night as the sfc low tracks NE over the
western portion of the coastal waters. This low will bring a cold
front through the northern gulf Thursday morning causing winds to
rapidly shift to W around 20kt then gradually become NW through the
day. Winds will then begin to shift to N and finally to E by the
weekend and ease back to around 10-15kt. As the sfc low lifts out of
the gulf Wed into Wed night it will help develop strong possibly
severe thunderstorms mainly over the lakes and sounds while the
remainder of the coastal waters should see only a some showers and
possibly a few thunderstorms but are not expected to be severe.

&&

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  77  61  68  56 /  60  70 100  90
BTR  80  65  72  57 /  50  60 100  90
ASD  79  62  73  57 /  50  60 100  90
MSY  78  66  77  60 /  40  50  80  80
GPT  75  62  69  59 /  50  60 100  90
PQL  76  62  72  59 /  40  60 100  90

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...Dense Fog Advisory until 10 AM CST this morning for GMZ530-532-
     534-536-538-550-552-555-557.

MS...None.
GM...Dense Fog Advisory until 10 AM CST this morning for GMZ532-534-
     536-538-550-552-555-557.

&&