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

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FXUS64 KLIX 202038
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
338 PM CDT Sun Aug 20 2017

.SHORT TERM...

A strong upper level low pushing westward across the Gulf of
Mexico will be the main feature driving the weather forecast
through Tuesday. Through tomorrow, some increased mid-level
subsidence and drier air will keep a lid on most convective
potential. Expect to see a mainly clear and dry night in place
tonight. Temperatures will be very close to seasonal norms
overnight with lows cooling into the middle to upper 70s. Limited
mid-level moisture will persist into tomorrow morning, and have
limited POP of around 10 to 20 percent through the morning hours.
Cloud development should also remain fairly suppressed through the
morning hours. However, heading into the afternoon, some mid-level
moisture will begin to push in from the east as the upper level
trough axis passes through the CWA. As the trough axis continues
to push westward, the region will see deeper moisture and more
favorable forcing take hold in the mid-levels. As a result, expect
to see widely scattered showers and thunderstorms develop by the
late afternoon hours over much of the forecast area. Temperatures
will easily climb into the lower to middle 90s before this
convection begins to develop.

Tomorrow night will see the impacts of the deeper tropical
moisture advecting into the area along with increased forcing on
the eastern side of the trough axis. Expect to see scattered
convection persist through the overnight hours in the coastal
waters with most convective activity dissipating over inland areas
due to the loss of daytime heating and instability. However, the
surge of deep tropical moisture will result in much earlier
convective development on Tuesday. Expect to see scattered showers
and thunderstorms develop from late morning through the afternoon
hours. Temperatures should also be a couple of degrees cooler due
to the increase in cloud cover from the scattered thunderstorm
activity.

.LONG TERM...

Wednesday will see two features affecting the area. The tut low
progressing westward into the western Gulf will continue to pump
a plume of deep tropical moisture into the CWA resulting in
continued higher than average rain chances. At the same time, a
frontal boundary will begin to move into the Lower Mississippi
Valley from the northern Plains and Midwest. Expect to see higher
rain chances with these two features converging over the area, and
have POP values of 50 to 60 percent for Wednesday afternoon.
Temperatures should climb to near average readings around 90
degrees before the convection fully develops. As daytime heating
wanes Wednesday convection should turn isolated. However, do not
expect to see all of the convection dissipate since the frontal
boundary will continue to push toward the forecast area.

For the latter part of the week, from Thursday through Saturday,
a broad and fairly weak upper level ridge will take hold of the
forecast area. However, this ridge will not be strong enough to
dry out the atmosphere or cap off convective potential. At the
same time, the frontal boundary will turn stationary along the
northern Gulf coast by Thursday and remain parked over the region
through the upcoming weekend. Ample moisture pooling and forcing
along this frontal boundary will keep elevated rain chances in the
forecast each day. Have placed rain chances of 50 to 60 percent in
the forecast from late morning through the afternoon hours each
day. The convection should turn more isolated during the overnight
hours as temperatures fall into the 70s and instability values
decrease. Temperatures will generally be near or slightly below
normal during the day and near normal at night during the extended
forecast period. 32

&&

.AVIATION...

Convection has been extremely limited with relatively drier air over
the region. VFR conditions expected to persist though some light
radiational fog may attempt to develop by daybreak in some low lying
areas. Given soils able to dry somewhat today, fog formation may
more limited than this past morning. 24/RR

&&

.MARINE...

High pressure influences over the north gulf will maintain generally
light winds and low seas for much of the forecast period outside
occasional nocturnal convection associated with land breezes.
24/RR

&&

.DECISION SUPPORT...

DSS Code...Blue.
Deployed...None.
Activation...None.
Activities...Metwatch for NOHSEP.

DECISION SUPPORT SERVICES (DSS) CODE LEGEND
GREEN  = NO WEATHER IMPACTS THAT REQUIRE ACTION
BLUE   = LONG FUSED WATCH/WARNING/ADVISORY IN EFFECT OR HIGH
         VISIBILITY EVENT
YELLOW = HEIGHTENED IMPACTS WITH SHORT FUSED
         WATCH/WARNING/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 TONIGHT RISK SVR
         AND/OR DIRECT TROPICAL THREATS; EVENTS OF NATIONAL
         SIGNIFICANCE

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  74  92  73  92 /  10  30  10  30
BTR  75  93  76  91 /  10  30  10  40
ASD  76  92  76  92 /  10  20  20  40
MSY  78  91  78  90 /  10  20  20  50
GPT  77  90  77  91 /  10  20  20  30
PQL  76  91  76  91 /  10  20  20  30

&&

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

$$

32



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