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

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FXUS64 KLIX 250106
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
706 PM CST Tue Jan 24 2017

.SOUNDING DISCUSSION...

Routine flight terminated over Jackson County Mississippi between
Ocean Springs and Vancleave at a height of 106,000 feet, or 20
miles above the surface.

The airmass remained fairly dry with a precipitable water value of
0.58 inches. Inversions were based at 2400 and 8200 feet. The
freezing level was at 13,800 feet and the -20C level was at 23,500
feet.

Southeast winds at the surface became southwest by 2000 feet, and
westerly by 8000 feet, where they remained through 60,000 feet.
The peak wind was 98 knots at 290 mb or 32,100 feet. 35

&&

.PREV DISCUSSION... /issued 410 PM CST Tue Jan 24 2017/

SHORT TERM (Tonight through Thursday night)...

Day two of near-perfect, pleasant weather is ongoing this
afternoon as the large high pressure ridge maintains it`s grip on
the region. The change for Wednesday will be from a shortwave
trough that will move across the southwest states tonight and then
the southern plains on Wednesday before progressing east/northeast
across the mid/lower Mississippi valley Wednesday night. The
associated cold front will push through the forecast area late
Wednesday afternoon and Wednesday night, but one more unseasonably
warm January day on Wednesday is expected to join the unusually
long list of warm January days this year. Shear vorticity in the
mid levels and fairly strong upper level divergence, associated
with the right entrance region of a broad belt of strong upper
level winds moving across the northern Gulf coast states, will
create fairly strong synoptic scale lift. This lift should
overcome fairly meager/limited moisture and instability to produce
scattered showers and possibly a few thunderstorms, starting late
morning to midday in the northwest areas near southwest
Mississippi and adjacent east central/southeast Louisiana, then
spreading southeast through the afternoon and evening while ending
with the cold frontal passage. Rainfall amounts overall should be
light with some localized moderate amounts where any thunderstorms
occur.

Dry and cooler weather will return Thursday as high pressure
builds into the central Gulf coast region. Thursday night should
be the start of a string of colder nights with temperatures cold
enough for a brief light freeze or frost in colder inland areas.

LONG TERM (Friday through Tuesday night)...

A dry and cooler period is expected through the period. A mostly
zonal flow pattern aloft will prevail over the southern-most
states, however, an amplifying pattern in the northern to mid
latitudes will see a building ridge over the western states and
Canadian provinces with a deepening trough expected over the
eastern states over the weekend. Surface high pressure will build
in with cooler and drier air Thursday, then another reinforcement
of cooler air is expected as a strong shortwave trough swings
southeast through the Mississippi valley and southeast states
Sunday into early Monday. The GFS is stronger with this feature
and therefore is colder with temperatures while the ECMWF is
flatter and not as cool. Regardless, temperatures should remain a
bit below normal through the period. 22/TD

AVIATION...

VFR conditions will continue to prevail through around 10z. There
will be some increase in mid-level clouds during the evening hours
hours as a frontal system approaches from the northwest. Return flow
in advance of the front will also bring increased low level moisture
to the area. The increase in dewpoints into the middle 50s overnight
should support some radiation fog formation at KBTR...KMCB...and
KHDC between 10z and 14z. There will be an increase in boundary
layer flow, but it should remain light enough to support patchy
moderate fog with visibilities of 1 to 3 miles. Ceilings should also
decrease down to IFR range of around 500 to 1000 feet, and KMCB
could drop to LIFR range of 300 to 500 feet around 12z. After 14z,
increased boundary layer flow will mix out any fog, and should also
lift ceilings back to around 1000 to 1500 feet where fog occurred.
At the remaining terminals, the approach of the front will also
allow MVFR ceilings to develop by 18z tomorrow. Scattered showers
and possibly a few thunderstorms could also be developing by 18z
tomorrow in advance of the front. 32

MARINE...

South-Southwest flow of 10 to 15 knots should increase to 15 to 20
knots over the Gulf waters west of the Mississippi River tonight.
This has prompted the issuance of Exercise Caution flags.  Tomorrow,
this stronger onshore flow will overspread the remainder of the open
Gulf waters as a front approaches from the northwest and tightens
the pressure gradient over the region.  The front is expected to
pass through the area tomorrow evening and shift in winds to the
northwest is expected.  Wind speeds will also increase back into SCA
range of 20 to 25 knots for most of the waters excluding the tidal
lakes tomorrow night and then persist into Thursday. As the winds
increase seas will also increase from 1 to 3 feet up to 5 to 8 feet
by Thursday morning.  A persistent offshore flow of 15 to 20 knots
will then set up through the weekend over most of the waters. Over
the tidal lakes, the winds should decrease from 15 to 20 knots to 10
to 15 knots this weekend.  32

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  53  77  44  58 /   0  40  30   0
BTR  56  79  47  60 /   0  40  30   0
ASD  53  79  49  60 /   0  20  50   0
MSY  59  78  52  59 /   0  20  40   0
GPT  53  74  51  61 /   0  10  50   0
PQL  49  75  52  62 /   0  10  50   0

&&

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

$$



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