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

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FXUS64 KLIX 200455
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
1155 PM CDT Mon Oct 19 2020

.UPDATE...
Updated for the 06Z aviation discussion.

&&

.AVIATION...
LIFR conditions are possible for some area airports during the
early morning hours Tuesday into the late morning, especially
BTR, MCB, and HDC. These conditions will mainly be a result of
radiation fog, which will cause low ceilings and visibilties in
the area. Some area airports could have lower ceilings from fog as
well, especially just above the surface, like KHUM and KASD. MSW

&&

.PREV DISCUSSION... /issued 341 PM CDT Mon Oct 19 2020/

SYNOPSIS...

Surface high pressure over much of the eastern half of the country
with the axis extending from Nova Scotia to southeast Louisiana. A
wavy frontal system extends from near Toronto to western Arkansas,
west Texas and then northward along the lee side of the Rockies.

Locally, it took longer than expected for fog to burn off this
morning, but there is clearly onshore flow occurring, and even one
or two showers on the sea breeze boundary over Jackson and
Harrison Counties on the Mississippi coast. Also, there are a few
showers over the Gulf of Mexico south of Southwest Pass that
appear to be associated with a weak easterly wave which the models
aren`t picking up on very well.

Temperatures at the 3 pm hour are generally in the lower and
middle 80s with dew points upper 60s and lower 70s.

SHORT TERM...

Tropical Storm Epsilon south of Bermuda has really bottled up any
eastward progression of the upper level pattern across the mid-
latitudes.

The weak wave producing showers over the Gulf becomes rather
diffuse over the next 24 hours or so. The wave behind it,
approaching Florida this afternoon, makes it as far west as the
eastern Gulf of Mexico before a southern stream shortwave picks it
up and lifts it northward into Georgia by Thursday. That shortwave
will move across the local area Thursday into Friday. There`s
sufficient moisture getting lifted northward off the Gulf for
scattered to numerous showers and a few storms during the
afternoon hours Thursday and Friday. Not going to be a major rain
maker, but a few areas east of Interstate 55 are starting to get a
little dry. Only about 2.5 inches of rain since the start of
September, so some rain will be helpful.

The other forecast concern in the short term will be the potential
reoccurrence of fog during the overnight hours. Probably more of a
threat tonight than tomorrow night, especially over the north half
of the area. While fog is mentioned in the grids, will hold off on
a pre-emptive advisory until we can pin down the extent a little
better. Some potential that low clouds occur and not fog.

Well above normal temperatures to continue, especially through
Wednesday. Trending toward the warmer side of guidance on highs
through Wednesday, which is about 8-10 degrees above normal.
Overnight lows are a similar magnitude above normal, but those
numbers are pretty close to each other. Better chances for
clouds/precip on Thursday may hold highs closer to 80 than the mid
and upper 80s of the next 2 days.

LONG TERM...

Could be some lingering showers Friday night and Saturday across
mainly eastern locations as the southern stream shortwave exits
the area. Sunday looks to be relatively dry across the area.
Temperatures will remain much above normal, but not quite as warm
as the next couple of days.

By Monday, differences start to creep into the forecast. The
ECMWF is a bit quicker bringing a cold front toward the area as a
deep trough digs through the Plains States into the middle
Mississippi River Valley. Probably won`t have much impact on
Monday`s weather, but it certainly will beyond that. Temperatures
by mid-week next week (Wednesday and/or Thursday) could be 20
degrees (or more) cooler than Monday if the GFS verifies. The
ECMWF is a little slower on the cold air, but still with a rather
healthy drop. Could also be a decent rain event ahead of the front
Tuesday night into Wednesday, considering the dryness mentioned
above.

AVIATION...

This morning`s fog took a little longer to dissipate than
expected, with the fog area a little farther east than
anticipated by about 30 miles. Clouds have scattered out this
afternoon with VFR conditions. Do anticipate redevelopment of low
clouds and/or fog after 08z Tuesday. Likely to have IFR or lower
conditions at most terminals beyond that point through about 15z
Tuesday before transitioning to VFR by afternoon.

MARINE...

High pressure over the southeast U.S. will generally remain in
place through Wednesday. A weak easterly wave is likely to move
into the northeast Gulf the next couple days before getting lifted
northward into Georgia by a southern stream shortwave. The
resultant pressure gradient will generally maintain moderate
easterly winds across the north gulf through most of the week with
periods of 15 to 20 knots and elevated sea heights at times
through Thursday. Will go with Exercise Caution headlines for most
of the 20-60 nm legs tonight, and will probably need them at times
for the next several days/nights.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  83  64  83  64 /   0   0   0   0
BTR  85  66  86  65 /   0   0   0   0
ASD  85  64  85  64 /   0   0   0   0
MSY  84  69  83  70 /   0   0   0   0
GPT  82  66  82  67 /   0   0   0   0
PQL  85  63  86  65 /   0   0   0   0

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Dense Fog Advisory until 10 AM CDT Tuesday for LAZ034>037-039-
     040-046>050-056>058-071-072.

GM...None.
MS...Dense Fog Advisory until 10 AM CDT Tuesday for MSZ068>071-077.

GM...None.
&&

$$



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