Special Weather Statement, NWS New Orleans, LA

Area Forecast Discussion
National Weather Service New Orleans LA
356 AM CDT Tue Mar 23 2021

.SHORT TERM (Today through Wednesday Night)...Winds ahead of a cold
front moving toward the area today will produce winds around 20-
25mph for a good portion of areas south of Lake Pontchartrain and a
wind advisory will be in place for only these areas for several
hours today. A cold front will move into Louisiana before
stalling late today as jet level winds with split flow help lift
an abundance of moisture along and ahead of the front. This
disturbance will eject eastward very slowly as horizontal focing
becomes very weak. The disturbance will move over a very deep
moist environment with PW values reaches number above record
values for this time of year from 1.6-1.9" today through Thursday.
This will keep the Flash Flood Watch in place with no changes.
The split jet flow will then become re-established back west over
a new front that will be moving through Texas Wed night which will
bring the next round of strong to possibly severe thunderstorms
with heavy rain. Grounds should be quite saturated with the first
round of heavy rain today through tonight and successive bouts of
the wet stuff could cause more issues in places that don't have
issues with the first wave. The other problem, although to a
lesser degree will be strong and severe thunderstorms. Each day
through Thursday will hold the potential for an isolated strong or
severe TS. All modes will be possible but the main attributes
should be heavy rainfall, wind and hail.

.LONG TERM (Thursday through Sunday)...
By Thursday, a fast-moving upper shortwave will be racing
northeastward from Texas into the Ohio valley. This shortwave will
push a weak cold front into the local area. The forcing along and
ahead of the front should keep rain chances high into Thursday
afternoon. The good news is that the axis of heaviest rainfall looks
like it will have shifted northward away from the local area by
Thursday as the best forcing will be closer to the surface low,
which is forecast to pass to the northwest of the local area. With
the heavy rain on Tuesday and Wednesday, think it's still prudent to
maintain the Flash Flood Watch through Thursday evening at this time
since nearly all rain will likely be runoff at that point, so any
kind of efficient showers/storms could be problematic.

Also continues to look like a few severe storms will be possible on
Thursday. The air mass ahead of the cold front also looks to be
plenty unstable with upwards of 1000 J/kg surface-based CAPE across
much of the area. Shear parameters are similarly favorable for
severe weather with surface to 1km storm relative helicity in excess
of 300 m2/s2. One question mark for convection ahead of the front
will be how much daytime heating can contribute to destabilization
given the forecast cloud cover, though upper dynamics may be able to
overcome this limitation either way. What looks a little more
certain is the development of a QLCS along/just ahead of the
boundary. By the time the boundary moves into the local area,
vertical wind profiles are more unidirectional, and the threat
appears to be mostly due to straight-line wind gust potential.

The front should push through late Thursday, providing us a brief
reprieve from the active weather on Friday. Am generally only
carrying a slight chance of showers for areas generally along/east
of the I-59 corridor for Friday. But as mentioned, the reprieve will
only be brief. The weekend will see a return of scattered showers
and storms. By Saturday, Thursday's cold front lifts back northward
as a warm front and on Sunday another cold front will push into the
area, possibly bringing a quick shot of cooler weather to the Gulf
south for the start of the next work week.

&&

.AVIATION...
Conditions will begin deteriorating after sunrise Today. Widespread
showers and thunderstorms with heavy rainfall are expected
along/ahead of a slow-moving cold front. Have tried to time the
period of strongest t-storms with a tempo group at each terminal,
but generally expect MVFR to IFR conditions to affect all terminals
through most of the day and through tonight. South to Southeast
winds will also be gusty at times.

&&

.MARINE...
A cold front could stall over the northern gulf Thursday night into
Friday before lifting back to the north. Winds will remain southerly
around 20kt ahead of the front wiht a few hours of easing wind
speeds from time to time but will keep the small craft advisory
through these periods since winds will rise back to these levels
after each lull. Once the front stalls, winds may shift over the
western sections of the coastal waters to a light westerly direction
Friday but will quickly become southerly again after the warm front
lifts out. These conditions should last through the weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  68  61  75  66 / 100  60  80  80
BTR  71  63  78  68 / 100  50  80  70
ASD  71  63  75  67 / 100  90  80  70
MSY  73  65  77  69 / 100  90  80  60
GPT  70  64  72  67 / 100  90  80  70
PQL  71  61  73  64 / 100  90  80  60

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Flash Flood Watch from 8 AM CDT this morning through Thursday
     evening for LAZ034>037-039-040-046>050-056>072.

     Wind Advisory from 8 AM this morning to 3 PM CDT this afternoon
     for LAZ058>070.

GM...Small Craft Advisory until 1 AM CDT Friday for GMZ530-532-534-
     536-538-550-552-555-557-570-572-575-577.

     Flash Flood Watch from 8 AM CDT this morning through Thursday
     evening for GMZ530.

MS...Flash Flood Watch from 8 AM CDT this morning through Thursday
     evening for MSZ068>071-077-080>082.

GM...Small Craft Advisory until 1 AM CDT Friday for GMZ532-534-536-
     538-550-552-555-557-570-572-575-577.

&&

Special Weather Statement
National Weather Service New Orleans LA
900 AM CDT Tue Mar 23 2021

LAZ036-037-MSZ069-231430-
St. Helena-East Feliciana-Amite-
900 AM CDT Tue Mar 23 2021

...A STRONG THUNDERSTORM WILL AFFECT NORTHERN ST. HELENA...
NORTHEASTERN EAST FELICIANA PARISHES IN SOUTHEASTERN LOUISIANA AND
SOUTHEASTERN AMITE COUNTIES...

At 900 AM CDT, a strong thunderstorm was located near Clinton, moving
northeast at 40 mph.

Winds in excess of 30 mph are possible with this storm.

Locations impacted include...
Clinton, Wilson, Norwood, Felps, Darlington, Gillsberg and
Easleyville.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 3076 9106 3094 9117 3118 9070 3093 9057
TIME...MOT...LOC 1400Z 245DEG 35KT 3090 9105

MSW

Special Weather Statement
National Weather Service New Orleans LA
911 AM CDT Tue Mar 23 2021

LAZ034-046-047-231445-
Iberville-Pointe Coupee-West Baton Rouge-
911 AM CDT Tue Mar 23 2021

...A STRONG THUNDERSTORM WILL AFFECT WEST CENTRAL WEST BATON ROUGE...
SOUTHERN POINTE COUPEE AND NORTHWESTERN IBERVILLE PARISHES...

At 911 AM CDT, a strong thunderstorm was located over Krotz Springs,
moving east at 30 mph.

Winds in excess of 30 mph are possible with this storm.

Locations impacted include...
New Roads, Livonia, Maringouin, Fordoche, Rosedale, Grosse Tete,
Erwinville and Lottie.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 3071 9141 3043 9131 3040 9163 3044 9164
      3050 9171 3050 9175 3051 9175 3051 9173
      3052 9173 3056 9176 3059 9176
TIME...MOT...LOC 1411Z 255DEG 25KT 3049 9175

MSW

Special Weather Statement
National Weather Service New Orleans LA
929 AM CDT Tue Mar 23 2021

LAZ036-037-071-MSZ069-070-231500-
St. Helena-Northern Tangipahoa-East Feliciana-Pike-Amite-
929 AM CDT Tue Mar 23 2021

...A STRONG THUNDERSTORM WILL AFFECT NORTHERN ST. HELENA...
NORTHEASTERN EAST FELICIANA AND NORTHWESTERN TANGIPAHOA PARISHES...
SOUTHWESTERN PIKE AND SOUTHEASTERN AMITE COUNTIES...

At 928 AM CDT, a strong thunderstorm was located near Felps, or 11
miles northeast of Clinton, moving east at 45 mph.

Winds in excess of 40 mph are possible with this storm.

Locations impacted include...
Kentwood, Felps, Darlington, Gillsberg and Easleyville.

LAT...LON 3083 9089 3101 9098 3115 9061 3092 9044
TIME...MOT...LOC 1428Z 247DEG 39KT 3095 9085

MSW

Special Weather Statement
National Weather Service New Orleans LA
957 AM CDT Tue Mar 23 2021

LAZ037-039-071-MSZ069>071-231530-
Washington-St. Helena-Northern Tangipahoa-Pike-Walthall-Amite-
957 AM CDT Tue Mar 23 2021

...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN ST. HELENA...
NORTHWESTERN TANGIPAHOA AND NORTHWESTERN WASHINGTON PARISHES...
SOUTHWESTERN WALTHALL...SOUTHERN PIKE AND SOUTHEASTERN AMITE
COUNTIES...

At 957 AM CDT, a strong thunderstorm was located near Osyka, or 14
miles south of Mccomb, moving east at 35 mph.

Winds in excess of 40 mph are possible with this storm.

Locations impacted include...
Magnolia, Kentwood, Osyka and Mount Herman.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 3092 9058 3110 9063 3120 9021 3093 9016
TIME...MOT...LOC 1457Z 261DEG 29KT 3103 9052

MSW

Special Weather Statement
National Weather Service New Orleans LA
1031 AM CDT Tue Mar 23 2021

MSZ070-071-231600-
Pike-Walthall-
1031 AM CDT Tue Mar 23 2021

...A STRONG THUNDERSTORM WILL AFFECT WALTHALL AND EAST CENTRAL PIKE
COUNTIES...

At 1031 AM CDT, a strong thunderstorm was located near Tylertown, or
12 miles west of Kokomo, moving east at 30 mph.

Winds in excess of 30 mph are possible with this storm.

Locations impacted include...
Tylertown and Salem.

LAT...LON 3118 9003 3117 9000 3113 9000 3113 8994
      3112 8994 3111 8993 3105 9026 3125 9034
      3133 9004
TIME...MOT...LOC 1531Z 254DEG 28KT 3116 9021

MSW

Special Weather Statement
National Weather Service New Orleans LA
1122 AM CDT Tue Mar 23 2021

LAZ046-049-056-057-231645-
Iberville-Ascension-Assumption-St. James-
1122 AM CDT Tue Mar 23 2021

...A STRONG THUNDERSTORM WILL AFFECT SOUTHWESTERN ASCENSION...WESTERN
ST. JAMES...SOUTHEASTERN IBERVILLE AND NORTHERN ASSUMPTION
PARISHES...

At 1122 AM CDT, a strong thunderstorm was located near Pierre Part,
or 10 miles north of Belle River, moving east at 35 mph.

Winds in excess of 40 mph are possible with this storm.

Locations impacted include...
Donaldsonville, Napoleonville, Paincourtville, Belle Rose and
Supreme.

LAT...LON 3013 9125 3011 9087 2987 9091 2985 9092
      2994 9125 3000 9126 3000 9123 3004 9122
      3003 9124 3004 9126
TIME...MOT...LOC 1622Z 275DEG 30KT 3003 9118

MSW