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

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FXUS64 KLIX 102224

Area Forecast Discussion
National Weather Service New Orleans LA
424 PM CST Sat Dec 10 2016

.SHORT TERM (Tonight through Tuesday night)...

A very transitional pattern will take place as the southwest
portion of current arctic surface high pressure ridge over the
western to central Gulf coast region moves east into the western
Atlantic Ocean Sunday afternoon. The lingering very dry air this
afternoon will modify quickly this evening, however with near calm
winds and clear skies, temperatures are still expected to take a
big plunge and reach very close to the forecast lows (around the
colder MOS guidance numbers) by the late evening hours then level
off and probably rise a couple degrees towards sunrise.

A nearly zonal, but fast flow in the mid to upper levels will
dominate the pattern over the lower 48 states going into early
next week, with the main weather-making feature being a low
amplitude shortwave trough that will move across the plains and
Mississippi valley Sunday into Sunday night. Around the north Gulf
coast, a slow moving cold front will move through the Ark-La-Tex
and lower Mississippi valley region Sunday night into Monday, but
it looks like the front will likely remain just northwest of the
forecast area through Monday night before possibly sliding into
north and west portions Tuesday.

The main concern will be dense fog potential since water
temperatures have fallen into the mid to upper 50s over the colder
inland/near shore coastal waters, and forecast dewpoint
temperatures are expected to exceed these values Sunday afternoon
and beyond. SREF and MOS visibility guidance does a good job of
picking up on this, so with moderate to high confidence this
forecast package has introduced mention of areas of fog, and it is
likely later forecast packages will have to issue dense fog
advisories for late Sunday night into Monday morning, and again
possibly starting late afternoon to early evening coastal areas
Monday/Monday night and continuing into Tuesday morning.
Confidence in fog formation is lower on Tuesday however since it
is likely there will enough showers around to mix out fog except
over the colder near shore waters.

.LONG TERM (Wednesday through Saturday night)...

A cold front will get a push south and bring a brief shot of
cooler weather from late Wednesday into early Friday as a
mid/upper level shortwave trough amplifies as it moves east across
eastern portions of Canada and the U.S. This should also dry
things out Wednesday night into Thursday.

A potent storm system is expected to move onshore over the Pacific
coast late Thursday into Friday morning with the surface high
pressure area quickly moving east over the eastern states. This
will result in rapid return flow Friday into the early part of
next weekend. The next cold front continues to have timing
differences in the operational models similar to what was noted
in the early morning discussion with the ECMWF bringing the front
through about 24 hours faster than the GFS. As some of the
sheared shortwave energy moves out into the central states and
upper Mississippi valley, the faster approach of the cold front
late Saturday night would bring another chance of showers to
northwest portions of the forecast area. 22/TD



VFR conditions will prevail through the TAF period. Could start to
see some clouds around FL050 by early afternoon Sunday as low level
flow becomes onshore and moisture returns to the area. 35



With high pressure over northern Mississippi this afternoon, winds
continue to relax. Should be able to drop all headlines with
forecast issuance, but still have a couple elevated wind sensors on
oil rigs reporting 17 knots at 20Z. May need to make a last minute
change there. As the high continues to shift eastward, winds will
become east and then southeast over the next 24 hours. In the short
term, anticipate that winds will remain below 15 knots across most
or all of the coastal waters into midweek. Still some variance
between medium range models regarding any possible cold frontal
passages at midweek. For now will go with the consensus with no
significant cold air intrusions to produce advisory level winds.
Confidence in solution past about Tuesday or Wednesday is low. 35



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.

MCB  33  66  54  73 /   0   0  10  40
BTR  35  67  56  75 /   0   0  10  40
ASD  34  67  54  75 /   0   0  10  30
MSY  43  69  58  76 /   0   0  10  20
GPT  38  66  57  73 /   0   0  10  20
PQL  33  66  53  73 /   0  10  10  20



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