Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
723
FXUS64 KLIX 241437
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
937 AM CDT Mon Jul 24 2017

.UPDATE...
Will be updating the zone package to issue a Flash Flood Watch for
a large portion of the forecast area through Tuesday afternoon.
A weak and subtle near surface ripple is indicated in surface
analysis with very rich moisture. Storms are showing back building
and training characteristics on both a land breeze convergence
zone along the immediate MS coast and another convergence zone
near the LA/MS state line. Rainfall rates around 2 inches per hour
or more will be common, with accumulations under the training in
the 5 to 7 inch range over the next 24 to 36 hours.

&&

.SOUNDING DISCUSSION...
Very moist sounding with a precipitable water of 2.30 inches,
which is almost 2 standard deviations above normal for this date.
Ran CHAP to assess potentials, using 360K lift from the LCL of
877mb. This yielded non-severe Ricks Index of 69, gust potential
18kt, no hail, no tor though waterspouts will be probable.
Rainfall potential is 4.92 to 6.88 inches, which appears
plausible to attain in the current situation and will be the basis
for the Flash Flood Watch, mentioning accumulations in the 5 to 7
inch range over the next 24-36 hours. 24/RR

&&

.DECISION SUPPORT...
DSS code: Yellow
Deployed: None.
Activation: None.
Activities: Flash Flood Watch

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.

&&

.PREV DISCUSSION... /issued 323 AM CDT Mon Jul 24 2017/

SHORT TERM...
All indications of the high over the gulf edging northward and settling
into the extreme coastal areas this morning. All sh/ts will
continue to move from west to east in the relatively deep flow
between this high and the trough that is developing very close to
the northeast corner of the area. Winds will remain slightly
elevated due to these two competing systems and sh/ts will also
begin to show a strong formation gradient from drier at the
Louisiana coast west of Plaquemines Parish inland where it will be
much wetter. The high will wobble northward into southwest
Louisiana but the more moist conditions associated with the sfc
troughiness will remain anchored over the eastern portion of the
area until the end of the week. As the weekend approaches, a cold
front should be pushing south over Tennessee into Mississippi
Friday which will be close enough to enhance suppression here.
This will all but shut down all sh/ts activity Friday. The cold
front will move through the area Saturday evening or Sunday
morning with what looks like a good bit of sh/ts activity which
could be strong or even severe especially associated with a
strong cold front this time of year. As the jet energy supporting
the cold front moves over the Pacific, the lack of RAOB sites will
cause models to be back and forth with the temporal and spacial
placement of this front until the energy causing this scenario
dumps into the Pacific coast and we again get a proper sampling of
this jet feature. Deep dry air behind the front will be a welcome
change, but these type of conditons do not last long this time of
year.

AVIATION...
Ceilings developing this morning from BKN015 northeast to OVC090
southwest. This will continue with sh/ts causing ceilings to lower
to around OVC020 as they move over terminals today. Most activity
should remain along and north of a lime from BTR to MSY. A few
showers may develop overnight once again but chances of any
particular site observing rain will be small enough to keep out of
prevailing groups.

MARINE...
High pressure becoming well established and should stall today
over the north central gulf while a weak trough develops near the
area today. This is now causing a slightly tighter gradient and
higher winds around 15kt out of the southwest and west as the high
settles up against a developing trough near the coast. Showers
and thunderstorms will remain more prevalent during the early
morning hours and of course winds and seas will be higher near
storms. But most of this activity will now become focused east of
the Miss River. Much less sh/ts activity is expected west of the
river seaward from the coast.

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.
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  85  74  89  73 /  70  30  50  10
BTR  88  75  91  74 /  70  20  20  10
ASD  88  77  91  77 /  70  30  40  20
MSY  89  77  92  77 /  70  20  20  10
GPT  87  77  90  77 /  70  30  50  30
PQL  87  76  89  76 /  70  40  60  30

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Flash Flood Watch through Tuesday evening for LAZ034>037-039-040-
     046>050-056>065-071-072.

GM...None.
MS...Flash Flood Watch through Tuesday evening for MSZ068>071-077-
     080>082.

GM...None.
&&

$$

24/RR



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.