Special Weather Statement, NWS New Orleans, LA

Area Forecast Discussion
National Weather Service New Orleans LA
824 AM CDT WED AUG 10 2016

...SOUNDING DISCUSSION...

Record high atmospheric moisture persists with the precipitable
water at 2.49 inches and has remained above 2.4 inches the last
24 hours. With all the moisture and a low level inversion, some
areas of fog were able to form this morning. Winds throughout the
lower half of the atmosphere remain light and this environment
overall would support waterspouts. The convective temperature
remains in the upper 80s and with instability around 2000 J/kg,
thunderstorms will initiate around midday today over land areas and
coverage should be widespread across the area, especially near
coastal locations.

12z balloon info: A routine flight ascending 113 minutes and
bursting near the western shore of Lake Maurepas 46 miles
downrange from the office.

Ansorge

&&

.PREV DISCUSSION... /issued 411 AM CDT WED AUG 10 2016/

DISCUSSION...
Surface and mid level troughs located along the northeast Gulf
Coast region are embedded within broad upper level high pressure.
This will be the focus for numerous showers and thunderstorms
across the local forecast area. Radar currently shows quiet
conditions over SELA and south MS while it is much more active
south of LA and AL/FL panhandles in the open gulf waters. This
trend will likely persist through the early morning hours although
scattered storms will still be possible inland. Model consensus
for afternoon convection development today continues to be fairly
good as well as agreement with medium range models. There will
likely still be a coastal bias to spatial coverage and thus pops
have been adjusted accordingly.

Local upper air sounding precip water values continue to be at or
above record for this time of year. Model soundings suggest that
these current numbers will even go up Wed and Thu. As seen with a
few storms yesterday, one of the results of having deep tropical
moisture in place is that any storms of moderate intensity will
very efficient rain producers and could result in localized
flooding.

Moving into Thursday and Friday, models remain consistent in
indicating that the mid level low will move overhead. This will
continue to enhance convective development and likely keep the
nighttime more active than typical for this time of year. In
addition, the concern for more widespread heavy rainfall shifting
inland increases. Could be looking at 2-4" late Wednesday night
through Thursday and then similar amounts for the Thursday night
through Friday time frame. For now keeping the flood watch along
coastal parishes/counties but if models continue to indicate
further inland shift of precip, will likely need to include more
of the CWA in the watch.

An upper trough moving eastward across the midsection of the country
from Saturday through Monday will aide in keeping rain chances on
the higher side for the area. However, at this time it appears qpf
amounts will be on the downward trend.

MEFFER

AVIATION...

Will carry VCTS at all sites again during the afternoon hours. IFR
conditions will result if TS move over any particular site. As the
sfc low transits west, all terminals will be under the onshore flow
side of the low by Thursday morning. This will cause TSRA to become
a prevailing variable toward the end of the 12z taf pack.

MARINE...

Broad low over southern Alabama and the Florida panhandle is
competing with a strong high off the east coast causing a much
stronger pressure gradient to exist over the Florida coastal bend
than what we have locally. This gradient will slowly move west over
the remainder of the week and set up over the coastal waters mainly
east of the Mississippi River. This will cause a slow rise in wind
speeds starting today and lasting through the remainder of the work
week. A line of sfc convergence will remain over the coastal waters
today producing widespread sh/ts. Somewhat higher wind speeds will
be a result of this as well. SCC(Small Craft exercise Caution) will
be posted for the nearshore waters from Port Fourchon eastward
today. And (SCA)Small Craft Advisories will be posted for the outer
waters from the Mississippi River eastward. Winds are 20 to 25 knots
mainly in showers and thunderstorms but since this activity is so
widespread, advisories will be needed mainly for the areas most
affected. Marine flags may be expanded and extended over the next 24
hours to include more areas as sh/ts moves northward.

The line of sh/ts that are stalled over the north central gulf will
begin to move slowly northward tonight and Thursday as the sfc low
moves west bringing the onshore flow side of the low. This will
cause the numerous sh/ts to move from the offshore areas to the near
shore and coastal areas very slowly. Even though only caution
statements will be posted, these conditions will be dangerous for
small craft. The amount of rain falling within a short period could
overtake bilge capacity of small vessels rapidly, and wind speeds
are expected to range from 20 to 30kt in and near numerous sh/ts. As
this activity moves very slowly inland, conditions should begin to
improve by late Friday into Saturday.

DECISION SUPPORT...

DSS code: Blue.
Deployed: None.
Activation: None.
Activities: Flood Watch this evening through Friday morning.

Decision Support Services (DSS) Code Legend
Green  = No weather impacts that require action.
Blue   = Long-fused watch, warning, or advisory in effect or
         high visibility event.
Yellow = Heightened impacts with short-fused watch, warning
         or advisory issuances; radar support.
Orange = High Impacts; Slight to Moderate risk severe; nearby
         tropical events; HazMat or other large episodes.
Red    = Full engagement for Moderate risk of severe and/or
         direct tropical threats; Events of National Significance.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  90  76  87  75 /  70  60  80  70
BTR  91  76  87  76 /  60  60  80  60
ASD  90  76  86  76 /  80  80 100  70
MSY  90  78  83  77 /  80  80 100  60
GPT  89  78  84  77 /  80  80 100  70
PQL  89  76  86  76 /  80  60 100  70

&&

.LIX Watches/Warnings/Advisories...
LA...Flood Watch from 7 PM CDT this evening through Friday morning
     for LAZ040-059>070.

GM...Small Craft Advisory until 7 AM CDT Thursday for GMZ575-577.

MS...Flood Watch from 7 PM CDT this evening through Friday morning
     for MSZ080>082.

GM...Small Craft Advisory until 7 AM CDT Thursday for GMZ577.

&&

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE NEW ORLEANS LA
617 AM CDT WED AUG 10 2016

GMZ530-532-534-536-538-550-552-555-557-570-572-575-577-LAZ034>037-
039-040-046>050-056>072-MSZ068>071-077-080>082-102330-
LAKE PONTCHARTRAIN AND LAKE MAUREPAS-MISSISSIPPI SOUND-
LAKE BORGNE-CHANDELEUR SOUND-BRETON SOUND-
COASTAL WATERS FROM PORT FOURCHON LA TO LOWER ATCHAFALAYA RIVER
LA OUT 20 NM-
COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER
TO PORT FOURCHON LOUISIANA OUT 20 NM-
COASTAL WATERS FROM BOOTHVILLE LA TO SOUTHWEST PASS OF THE
MISSISSIPPI RIVER OUT 20 NM-
COASTAL WATERS FROM PASCAGOULA MISSISSIPPI TO STAKE ISLAND OUT
20 NM-
COASTAL WATERS FROM PORT FOURCHON LOUISIANA TO LOWER ATCHAFALAYA
RIVER LA FROM 20 TO 60 NM-
COASTAL WATERS FROM SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO
PORT FOURCHON LOUISIANA FROM 20 TO 60 NM-
COASTAL WATERS FROM STAKE ISLAND LA TO SOUTHWEST PASS OF THE
MISSISSIPPI RIVER FROM 20 TO 60 NM-
COASTAL WATERS FROM PASCAGOULA MISSISSIPPI TO STAKE ISLAND
LOUISIANA OUT 20 TO 60 NM-POINTE COUPEE-WEST FELICIANA-
EAST FELICIANA-ST. HELENA-WASHINGTON-ST. TAMMANY-IBERVILLE-
WEST BATON ROUGE-EAST BATON ROUGE-ASCENSION-LIVINGSTON-ASSUMPTION-
ST. JAMES-ST. JOHN THE BAPTIST-UPPER LAFOURCHE-ST. CHARLES-
UPPER JEFFERSON-ORLEANS-UPPER PLAQUEMINES-UPPER ST. BERNARD-
UPPER TERREBONNE-LOWER TERREBONNE-LOWER LAFOURCHE-LOWER JEFFERSON-
LOWER PLAQUEMINES-LOWER ST. BERNARD-NORTHERN TANGIPAHOA-
SOUTHERN TANGIPAHOA-WILKINSON-AMITE-PIKE-WALTHALL-PEARL RIVER-
HANCOCK-HARRISON-JACKSON-
617 AM CDT WED AUG 10 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST
LOUISIANA...SOUTH MISSISSIPPI AND THE ADJACENT COASTAL WATERS.

.DAY ONE...TODAY AND TONIGHT

A FLOOD WATCH HAS BEEN POSTED FOR COASTAL AREAS OF MISSISSIPPI
AND SOUTHEAST LOUISIANA STARTING THIS EVENING THROUGH FRIDAY
MORNING. HEAVY RAINFALL POTENTIAL WILL INCREASE FOR THE REMAINDER
OF THE WEEK. ACCUMULATIONS CLOSE TO 10 INCHES ARE POSSIBLE IN
LOCALIZED BANDS THROUGH SATURDAY. THE FLOOD WATCH WILL LIKELY BE
EXPANDED FARTHER INLAND OVER THE NEXT FEW DAYS AS CONDITIONS
WARRANT.

SCATTERED TO NUMEROUS THUNDERSTORMS ARE EXPECTED THROUGH TONIGHT WITH
A FEW STRONGER STORMS POSSIBLE AT TIMES. THE GREATEST RISK WILL BE
FREQUENT LIGHTNING STRIKES...WIND GUSTS 30 TO 40 MPH...AND LOCALLY
HEAVY RAINFALL THAT CAN RESULT IN LOCALIZED FLOODING OF LOW LYING
AND POORLY DRAINED AREAS. WATERSPOUTS AND TROPICAL FUNNELS WILL BE
POSSIBLE AS WELL.

SMALL CRAFT ADVISORIES HAVE BEEN POSTED FOR THE OUTER COASTAL
WATERS FROM THE MISSISSIPPI RIVER EAST. WINDS OF 20 TO 25 KNOTS
WILL BE FOUND MOSTLY IN AND NEAR WIDESPREAD SHOWERS AND
THUNDERSTORMS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY
THE FLOOD WATCH WILL CONTINUE THROUGH FRIDAY MORNING. SOME OF THE
HEAVIEST RAINFALL IS EXPECTED THROUGHOUT THE EARLY MORNING AND
DAYLIGHT HOURS THURSDAY. TOTAL ACCUMULATIONS CLOSE TO 10 INCHES
ARE POSSIBLE IN LOCALIZED BANDS THROUGH SATURDAY. THE FLOOD WATCH
WILL LIKELY BE EXPANDED FARTHER INLAND OVER THE NEXT FEW DAYS AS
CONDITIONS WARRANT.

SCATTERED TO NUMEROUS THUNDERSTORMS ARE EXPECTED THROUGH THE
ENTIRE PERIOD WITH A FEW STRONGER STORMS POSSIBLE AT TIMES. THE
GREATEST RISK WILL BE FREQUENT LIGHTNING STRIKES...WIND GUSTS 30
TO 40 MPH...AND WIDESPREAD LOCALLY HEAVY RAINFALL THAT CAN RESULT
IN LOCALIZED FLOODING OF LOW LYING AND POORLY DRAINED AREAS.
WATERSPOUTS AND TROPICAL FUNNELS WILL BE POSSIBLE EACH DAY.

SMALL CRAFT ADVISORIES MAY BE EXPANDED AND EXTENDED INTO THURSDAY
IF WINDS CONTINUE AT 20 TO 25 KNOTS AND SPREAD OVER MORE OF THE
COASTAL WATERS. THESE CONDITIONS ARE EXPECTED TO REMAIN MAINLY
FROM PORT FOURCHON EASTWARD.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED AS EARLY AS THURSDAY MORNING FLASH
FLOODING POTENTIAL.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
828 AM CDT WED AUG 10 2016

LAZ069-101415-
LOWER PLAQUEMINES-
828 AM CDT WED AUG 10 2016

...A STRONG THUNDERSTORM WILL AFFECT SOUTHEASTERN PLAQUEMINES
PARISH...

AT 828 AM CDT...A STRONG THUNDERSTORM WAS LOCATED NEAR BURAS...OR 21
MILES SOUTHEAST OF PORT SULPHUR...MOVING SOUTHEAST AT 10 MPH.

WINDS IN EXCESS OF 30 MPH ARE POSSIBLE WITH THIS STORM.

LOCATIONS IMPACTED INCLUDE...
BOOTHVILLE...VENICE...BURAS-TRIUMPH...BURAS...BOOTHVILLE-VENICE AND
BOOTHVILLE ASOS.

TORRENTIAL RAINFALL IS ALSO OCCURRING WITH THIS STORM...AND MAY CAUSE
LOCALIZED FLOODING. DO NOT DRIVE YOUR VEHICLE THROUGH FLOODED
ROADWAYS.

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 2924 8949 2925 8946 2930 8964 2940 8952
      2939 8952 2939 8942 2938 8933 2937 8939
      2936 8940 2931 8921 2924 8924 2928 8919
      2917 8915 2915 8925 2916 8915 2910 8912
      2913 8918 2901 8934
TIME...MOT...LOC 1328Z 300DEG 8KT 2926 8948

ANSORGE

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
909 AM CDT WED AUG 10 2016

LAZ069-101500-
LOWER PLAQUEMINES-
909 AM CDT WED AUG 10 2016

...A STRONG THUNDERSTORM WILL AFFECT SOUTH CENTRAL PLAQUEMINES
PARISH...

AT 909 AM CDT...A STRONG THUNDERSTORM WAS LOCATED NEAR VENICE...OR 27
MILES SOUTHEAST OF PORT SULPHUR...MOVING SOUTHEAST AT 5 MPH.

WINDS IN EXCESS OF 30 MPH ARE POSSIBLE WITH THIS STORM.

THIS STORM WILL REMAIN OVER MAINLY RURAL AREAS OF SOUTH CENTRAL LOWER
PLAQUEMINES PARISH.

TORRENTIAL RAINFALL IS ALSO OCCURRING WITH THIS STORM...AND MAY CAUSE
LOCALIZED FLOODING. DO NOT DRIVE YOUR VEHICLE THROUGH FLOODED
ROADWAYS.

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 2904 8932 2908 8937 2903 8933 2907 8937
      2901 8935 2914 8940 2924 8949 2925 8946
      2927 8964 2933 8953 2927 8935 2916 8925
      2907 8930 2915 8927 2912 8931 2921 8933
      2915 8939 2908 8931
TIME...MOT...LOC 1409Z 309DEG 7KT 2919 8941

ANSORGE