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

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751
FXUS64 KLIX 080204
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
804 PM CST Wed Dec 7 2016

...SOUNDING DISCUSSION...
The sounding this evening still depicts the stratus clouds that
have been in place the past couple days with saturated conditions
in a layer from about 1300 to 3000 ft. This moisture is trapped
below a strong elevated inversion at 860 mb with a much drier
airmass above. The clouds will keep most of the area in the low
50s to upper 40s tonight. Winds are calm near the sfc and westerly
through the rest of the profile. Peak wind is 105 kts at 210 mb.

Krautmann

&&


.PREV DISCUSSION... /issued 344 PM CST Wed Dec 7 2016/

SHORT TERM...
Leading edge of shallow modified cool air is slowly infiltrating the area
with northerly component winds indicated at most locations already. The
deeper truly colder and drier air is still in northern Mississippi and
progressing steadily southward with a surge acceleration expected this
evening. Stronger but still shallow cold air advection is expected overnight
and wedging under a less stable airmass to produce a period of post-frontal
isentropic lift towards the morning. This is worthy of at least 20% mention
as the lift process will be countering downward momentum surfaces over time
to dry the lower column, though low cloudiness may be stubbon to flush out
until upper vorticity structure sweeps through the area later in the afternoon.
Temperatures Thusday night and Friday morning will be driven both by advection
and improving radiational conditions by morning to bring the more interior
areas into at least a light freeze. Low level winds may keep temperatures from
bottoming out fully Friday morning but these will abate during the day to
set up a better chance for moderate to borderline hard freeze for a short
duration Saturday morning for areas to the north of the tidal lakes and away
from marine influences. 24/RR

LONG TERM...
Models are still in agreement in showing a rather rapid moderation of the
air mass with return flow onsetting during the day Saturday. Moisture should
have time to recover for some rain chances along the next frontal passage
Sunday night into Monday morning. The zonal flow pattern aloft will essentially
shunt much of the colder air eastward with just fringe effect cooling for
early next week. Over-running flow pattern is being indicated for middle of
next week that may keep a generally wet stretch of days that can go a long
way in improving the drought conditions that have been affecting the area
of late. 24/RR

AVIATION...
IFR conditions currently impacting KMCB should persist through
around 21z before improving to MVFR conditions at 1500 to 2000 feet.
However, stratus build down tonight should allow for a return to
ceilings of 300 to 500 feet and alternate airport requirements after
08z. All of the other terminals will see continued MVFR ceilings of
1500 to 3000 feet today with a build down into IFR range of 500 to
1000 feet after 06z. At KHDC and KBTR further build down into LIFR
and alternate airport range could occur around 12z tomorrow.

Ceilings should gradually improve during the mid-morning hours into
MVFR range as a cold front moves through.  There maybe a few
showers, but the risk is too low to include in the forecast.
Ceilings should improve quickly after 18z tomorrow in the wake of
the cold front with VFR conditions expected to develop. Strong north
winds should also begin to develop with the strongest winds expected
at KMSY and KNEW. 32

MARINE...
No significant changes in thinking concerning the forecast this
afternoon.  A strong cold front is still expected to sweep through
the coastal waters tomorrow.  In the wake of the cold front, strong
offshore winds will develop.  Winds of 20 to 30 knots are expected
over the majority of the coastal waters, but the far western legs
mainly west of Grand Isle and Port Fourchon could see gale force
conditions of 30 to 40 knots.  These strong winds should persist
through Thursday night and slowly begin to ease on Friday as the
high becomes more centered over the region.  Very rough seas will
also develop in response to the winds with seas of up to 12 feet
possible in the outer waters.  Given these expected conditions, a
Gale Watch has been issued for the far western waters, and a Small
Craft Advisory has been issued for the remaining waters beginning
tomorrow morning.

The high will remain parked over the Southeastern states Saturday
and Sunday.  Winds will veer to the east and then southeast during
this period, and should remain fairly strong at 15 to 20 knots
Friday night and Saturday.  Seas will also remain choppy at 3 to 5
feet during this period.  By Sunday, the gradient should relax a bit
and winds should fall to between 10 and 15 knots over the coastal
waters.  Seas should also fall back into the 2 to 4 feet range by
Sunday.  A weaker cold front should pass through the waters on
Monday with wind shift to the northwest and increase in speed back
into exercise caution range expected. 32

DECISION SUPPORT...
DSS code: Blue.
Deployed: None.
Activation: None.
Activities: Gale Watch for western portions of gulf waters.

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  45  48  29  45 /  20  30   0   0
BTR  49  51  32  46 /  30  30  10   0
ASD  50  55  34  48 /  20  20  10   0
MSY  52  56  38  48 /  20  30  10   0
GPT  50  56  36  48 /  10  20  10  10
PQL  48  57  34  49 /  10  10  10  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...Small Craft Advisory from 9 AM Thursday to 9 PM CST Friday for
     GMZ536-538-552-555-557-572-575-577.

     Gale Watch from Thursday morning through Friday morning for
     GMZ550-570.

     Small Craft Advisory from 9 AM to 9 PM CST Friday for GMZ550-570.

     Small Craft Advisory from 9 AM Thursday to 9 AM CST Friday for
     GMZ530-532-534.

MS...None.
GM...Small Craft Advisory from 9 AM Thursday to 9 PM CST Friday for
     GMZ538-552-555-557-572-575-577.

     Gale Watch from Thursday morning through Friday morning for
     GMZ570.

     Small Craft Advisory from 9 AM to 9 PM CST Friday for GMZ570.

     Small Craft Advisory from 9 AM Thursday to 9 AM CST Friday for
     GMZ532-534.

&&

$$



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