Flash Flood Warning 12, NWS New Orleans, LA

759 
WGUS74 KLIX 171713
FFSLIX

Flash Flood Statement
National Weather Service New Orleans LA
1213 PM CDT FRI AUG 17 2018

LAC071-087-171722-
/O.CAN.KLIX.FF.W.0012.000000T0000Z-180817T1815Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
St. Bernard LA-Orleans LA-
1213 PM CDT FRI AUG 17 2018

...THE FLASH FLOOD WARNING FOR WEST CENTRAL ST. BERNARD AND
SOUTHWESTERN ORLEANS PARISHES IS CANCELLED...

The heavy rain has ended. Flood waters have receded. Flooding is no
longer expected to pose a threat. Please continue to heed any
remaining road closures.

LAT...LON 2992 9004 3004 9005 3003 9003 3005 9003
      3004 9002 3010 8991 3002 8988 2992 8988

$$

Area Forecast Discussion
National Weather Service New Orleans LA
953 AM CDT Fri Aug 17 2018

.SOUNDING DISCUSSION...
No problems with the flight this morning despite some pre-dawn
thunderstorms about 15 miles west of the station at launch. Very
moist sounding with a precipitable water of 2.23", up from 2.10"
past 12-24 hours. A pretty typical looking profile with moist
lapse rates just above a shallow surface inversion to an elevated
tropopause at 138 mb. Winds light SW 5-10 kt surface to 8500 ft,
then S 5kt to about 21kft, then NE 10-30 kt above through
tropopause. Balloon burst near Pass Manchac and I-55 corridor.

CHAP output on 360K lift from 906mb (most unstable lift for
forecast max temp 89F) shows a very precip efficient outcome.
Precipitation potential 5.90-7.99 inches, with a large percentage
of this already realized in the morning convection in St. Tammany
Parish. Gust potential 21 kt, which was already confirmed at KBTR
in the past hour.  24/RR

&&

.PREV DISCUSSION... /issued 354 AM CDT Fri Aug 17 2018/

SHORT TERM...
Seems to be a very normal summer cycle of sh/ts each day. In the
absence of any synoptic or dynamic system, buoyancy via heating is
the only lift producer. Therefore, development starts during the
early morning hours nearshore where the water temps=convective
temps. The air lifting over the gulf induces sinking air inland
causing stability over land. During the day, this same scenario
occurs from daytime heating inland. The large scale ascent inland
then induces sinking air over the waters causing stability to
increase in those areas. Then the evening comes and the
environment over land is worked over along with no more heating
causing stability to increase over land areas. This is the time
when both areas, marine and land, are relatively stable and sh/ts
decrease to almost zero until the sinking air over the marine
areas stop and the inversion can be destroyed from below which is
by late night into the early morning hours. And this whole cycle
starts again. This should be the case through much of the next
several days. This is ofcourse a crude explanation since there are
many other things taking place within this general scenario.

The extended shows a cold front moving into the deep south. This
is being advertised as an actual "cold" front by the end of next
week. But it is still August. It's not that this has never
occurred but it is rare to keep daytime highs in the mid to upper
80s this time of year along with dp temps in the mid 60s. But it
would be fantastic if it does occur.

AVIATION...

VFR conditions will predominate through the forecast period outside
of convective activity. Already seeing isolated activity over
coastal areas and scattered over coastal waters, so will need to
move mention of convection forward from previous forecast set. Will
probably use TEMPO again today, but forecast soundings aren't quite
as favorable for dounbursts today, compared to yesterday, and will
likely hold off on carrying a TEMPO VRB20G30KT in the 12z forecast
package. Convection likely to weaken or dissipate again in most
areas around 00z. 35

MARINE...

High pressure will remain centered east of the waters through early
next week. As a result, a prevailing onshore flow of 5 to 10 knots
is expected across most of the coastal waters through the period.
The only exception will be over the nearshore waters off the
Mississippi coast where a seabreeze is expected to develop each day.
This could induce some stronger onshore winds of 10 to 15 knots for
a few hours each afternoon across the Mississippi and Chandeleur
Sounds. Seas will range from 1 to 2 feet through the entire period
across all of the waters. Medium range models do depict at least a
brief period of northerly winds at midweek next week with a cold
frontal passage, but no strong winds indicated with this frontal
passage outside of convection. 35

DECISION SUPPORT...

DSS code: Green.
Deployed: None.
Activation: None.
Activities: None.

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; Marginal risk severe or excessive rain.
Yellow = Heightened impacts with short-fused watch, warning or
         advisory issuances; radar support for slight risk severe
         or excessive rain.
Orange = High Impacts; Enhanced risk severe; nearby tropical events;
         HazMat or other large episodes.
Red =    Full engagement for Moderate to high risk of severe and/or
         excessive rainfall, or direct tropical threats; Events of
         National Significance.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  93  73  92  73 /  50  20  70  20
BTR  93  74  92  75 /  50  20  60  20
ASD  91  76  92  76 /  50  20  60  30
MSY  90  77  92  78 /  50  20  60  30
GPT  90  78  91  77 /  50  30  60  30
PQL  90  76  91  77 /  60  30  60  40

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...None.
GM...None.
&&

Hazardous Weather Outlook
National Weather Service New Orleans LA
331 AM CDT Fri Aug 17 2018

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>082-172045-
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-
331 AM CDT Fri Aug 17 2018

This Hazardous Weather Outlook is for portions of Southeast
Louisiana...South Mississippi and the adjacent coastal waters.

.DAY ONE...Today and Tonight

Scattered thunderstorms are expected today into the evening
hours. One or two storms could be strong with gusty winds,
frequent lightning and locally heavy rain. Waterspouts will be
possible over the coastal waters.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Scattered to numerous thunderstorms are expected each day during
the period, with storms diminishing in number by Wednesday or
Thursday. A few storms could become strong each day, producing
gusty winds, frequent lightning and brief heavy rainfall.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated at this time.

Special Weather Statement
National Weather Service New Orleans LA
608 AM CDT FRI AUG 17 2018

LAZ040-171145-
St. Tammany-
608 AM CDT FRI AUG 17 2018

...A STRONG THUNDERSTORM WILL AFFECT WEST CENTRAL ST. TAMMANY
PARISH...

At 608 AM CDT, a strong thunderstorm was located near Covington,
moving north at 5 mph.

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

Locations impacted include...
Covington and Abita Springs.

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 3038 9003 3040 9015 3054 9014 3051 8994
TIME...MOT...LOC 1108Z 187DEG 6KT 3044 9008

Special Weather Statement
National Weather Service New Orleans LA
846 AM CDT FRI AUG 17 2018

LAZ047-048-171415-
West Baton Rouge-East Baton Rouge-
846 AM CDT FRI AUG 17 2018

...CLUSTERS OF STRONG THUNDERSTORMS WILL AFFECT SOUTHEASTERN WEST
BATON ROUGE AND WESTERN EAST BATON ROUGE PARISHES...

At 839 AM CDT, clusters of showers and thunderstorms will track
north across West and East Baton Rouge parishes during this morning
commute. Motorists will encounter periods of heavy rainfall that
will likely reduce visibilities on Interstate 10 around and west of
Baton Rouge.

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

Locations impacted include...
Baton Rouge, Zachary, Baker, Port Allen, Brusly, Westminster,
Merrydale, Brownfields, Greenwell Spring, Gardere and Baton Rouge
Airport.

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

LAT...LON 3066 9128 3058 9099 3057 9099 3036 9111
      3041 9131
TIME...MOT...LOC 1339Z 196DEG 8KT 3046 9119

Special Weather Statement
National Weather Service New Orleans LA
1044 AM CDT FRI AUG 17 2018

LAZ061>064-171630-
Orleans LA-Upper St. Bernard LA-Upper Plaquemines LA-
Upper Jefferson LA-
1044 AM CDT FRI AUG 17 2018

...SPECIAL WEATHER STATEMENT...

At 1044 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near New Orleans to Terrytown. These storms
were nearly stationary and producing heavy rainfall.

Winds in excess of 30 mph will be possible with these storms.

Locations impacted include...
New Orleans, Timberlane, Belle Chasse, Harvey, Chalmette, Gretna,
Terrytown, Arabi and Lakefront Airport.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 2985 9006 3003 9008 3004 9004 3003 9003
      3004 9003 3004 8999 2984 8995
TIME...MOT...LOC 1544Z 284DEG 0KT 3002 9003 2991 9000