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

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FXUS64 KLIX 061303
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
703 AM CST Tue Dec 6 2016

...SOUNDING DISCUSSION...

Winds from the west in the low and mid-levels behind the front
are bringing in much drier air with the precipitable water value
falling to 0.63 inches, which is a decrease of an inch from last
evening. There still remains a low stratus deck as noted by the
layer of saturation about 1500 feet above the ground. There are
also two temperature inversions present with the first from 2400
to 3100 feet and the second between 5200 to 6500 feet. A peak wind
speed of 120 knots was at 34000 feet.

12z balloon info: A routine flight ascending for 97 minutes to a
height of 20.9 miles above the ground bursting over Gulfcrest, AL
106 miles downrange from the office.

Ansorge

&&

.PREV DISCUSSION... /issued 351 AM CST Tue Dec 6 2016/

SHORT TERM...
Water vapor imagery shows upper level low moving rapidly
northeastward across northern Louisiana and Mississippi. Rainfall
has concluded with only post frontal boundary layer rolls seen on
radar. Looking at 11u-3.9u satellite, low level cloud deck is quite
expansive across the region. There area breaks along the southern
edge, which is coincident with the southern 1/3 of the CWA. Thinking
north of that area, cloudy skies will persist today, at least the
first half of the day. This will keep temps from warming much more
than about 5-8 degrees from the current temperatures. Going into
tonight, surface high pressure will advect colder air in which will
translate to lows in the mid 40s to lower 50s. Stuck close to MOS
guidance. Fairly benign weather expected on Wednesday with somewhat
zonal flow in place. Will see a slight bump in daytime highs as
winds slowly shift to south.

LONG TERM...
A broad long wave trough, enhanced by upper low near the Great
Lakes, will surge southward out of Canada into the central U.S.
Wednesday night. This will send a very strong cold front through the
region on Thursday. Models seem to jive pretty well on timing with
both bringing the frontal wind shift in to the CWA sometime around
sunrise, give or take a few hours. Airmass change should be fairly
close to the leading edge of these winds. There is some disparity
between models on how much rain will move across the forecast area.
With such limited moisture in place due to small window of southerly
winds to increase moisture, tend to prefer the output of the GFS.
This shows some showers moving in across northwestern forecast zones
with decreasing coverage as the cold front moves south. Since precip
will be post-frontal, lightning is quite unlikely. Total rainfall
amounts should be less than 0.1".

The following 2 days will be dominated by strong cold air advection
as 1030+mb surface high builds into the region. A drastic drop in
temperatures will ensue, with highs struggling upper 40s to mid 50s
Thursday and likely not even up to 50 on Friday. Nighttime lows are
looking to be in the mid/upper 20s along I-12 and north in LA and
all of coastal MS. South of there probably just above freezing to
upper 30s. Current forecast temps are close to previous, which maybe
a degree or 2 drop.

A warming trend will bring temperatures back to near normal over the
weekend as the upper trough axis exits the East Coast and surface
low shifts east. Models show a more northern stream upper level
trough will quickly track east across the country late this weekend
into early next week. Moisture returning to the area along with the
approach of another frontal boundary will lead to the next chance of
rain for the area.

Meffer

AVIATION...
Ceilings will rise from ovc010 to ovc030. Not expecting any large
breaks in cloud cover for any extended period of time today but
there could be a few times of short duration sct-bkn030 especially
for south shore terminals. Should see some sct020 conditions by
tonight. Winds will remain gusty this morning but should quickly
lower by noon.

MARINE...
Extended the small craft advisory out to noon even though winds
should quickly ease around that time. Should not have to bring up
any caution statements as winds back off rapidly around noon.
Winds will remain rather light through Wednesday. Another strong
cold front moves through Thursday and this could bring winds to the
upper threshold of advisory criteria with frequent gusts to gale
force. And cold air looks to spill over the northern gulf as well
for the end of the week. Winds will come back around to an onshore
flow as early as Saturnight and another cold front moving through by
the beginning of the new week.

DECISION SUPPORT...

DSS code: Blue.
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  61  46  65  45 /   0   0  10  30
BTR  64  48  68  47 /   0   0  10  30
ASD  66  47  67  50 /   0   0   0  20
MSY  64  52  67  52 /   0   0   0  10
GPT  67  51  67  51 /   0   0   0  10
PQL  68  46  65  47 /  10   0   0  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...Small Craft Advisory until noon CST today for GMZ530-532-534-536-
     538-550-552-555-557-570-572-575-577.

MS...None.
GM...Small Craft Advisory until noon CST today for GMZ532-534-536-538-
     550-552-555-557-570-572-575-577.

&&

$$


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