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

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FXUS64 KLIX 290459

Area Forecast Discussion
National Weather Service New Orleans LA
1159 PM CDT Tue Mar 28 2017

Transition from mostly VFR to mostly MVFR with some spotty TEMPO
IFR, mainly due to CIGS, will occur overnight into early Wednesday
morning before improvement back to VFR late Wednesday morning.
Lower conditions are expected to return Wednesday evening as lower
level clouds develop. 22/TD


.PREV DISCUSSION... /issued 414 PM CDT Tue Mar 28 2017/

DISCUSSION...Due to being backed up today and down much of the
afternoon this discussion will be a little abbreviated and will
mainly focus on the system Thursday. As expected today was rather
quiet and warm. Maybe one or two showers over Jackson county MS
but that was about it.

Tonight through Wed evening we will be dominated by a ridge sliding
to the east. This will keep things quiet and warm. Biggest weather
impact could be some fog tomorrow morning however winds look like
they should remain strong enough just off the deck to promote
stratus and not much in the way of fog.

Early Thu morning and possibly into the evng hrs could be quite
active. There could actually be 2 rounds although the first round if
it does reach the region will likely be right at the end of its
cycle. The main activity looks to take place late Thu morning and
through the day.

We are still anticipating a deep system to work across the Plains
and into the Mid MS Valley Thu. Not much has changed in the
thinking. A lot of ingredients appear to be coming together but
there is still one or two significant issues that could keep things
from materializing. There will still be a split jet over or near the
region with a very impressive diffluent pattern. If we are not
contaminated from the previous days/nights activity that tries to
move in there will be more than sufficient instability to work with
and the mid lvl lapse rates continue to look extremely steep right
around 7-8 C/km. No shortage of forcing with the possibility of a
lead s/w or even the main trough going neutral to negative close to
the region.

The biggest question is still placement of the best divergence
aloft. If it is over the region and we destabilize like many of the
mdls have been showing then we could see rapid to explosive
thunderstorm development during the late morning through the
afternoon and possibly into the evng hrs. Large hail could be a
significant concern with damaging winds and tornadoes also possible.
If the placement of the divergence is over the coastal waters we
would likely see some sort of MCS develop along the coast or even
just off of it in the Gulf. This would effectively cut the area off
and keep things far quieter. the other issue is left over
convection/debris from expected severe weather from Wed and Wed night
off to our west that tries to push in. If it makes a greater push
east as it dies it will not allow the region to destabilize as
fast/much however given the dynamics in place we will still likely
see severe weather just not at the level of what we could see if the
upper jets line up.

We are currently in a SLIGHT risk over the entire area but if the
mdls get into better agreement with a few features we could easily
see a portion of the area upgraded.

Activity should quickly diminish Thu night as a cold front swings
through and then we will be quiet Fri and Sat. Models really begin
to diverge Sunday and more so as we head into next week. That said
the pattern is very active and at some point b/t late Sun and
through Tue we will likely see quite a bit of showers and
thunderstorms activity with all modes of severe weather possible
including heavy rain. So once we get through Thu all eyes will
move to this system. /CAB/

AVIATION...VFR conditions will persist through 06z for most of the
terminals. Some MVFR ceilings may develop around 03z at KGPT.  After
06z, the development of another low level inversion will once again
allow ceilings to drop to between 300 and 800 feet at all of the
terminals.  As ceilings drop, visibilities will fall to between 3
and 5 miles at most locations. However, KHDC and KMCB could see
visibilities fall to around 1 mile.  Not expecting as much reduced
visibilities as the last few nights due to a bit more boundary layer
mixing through the night.  Conditions will begin to improve from
LIFR/IFR to MVFR after 15z as daytime heating mixes out the
inversion. 32

MARINE...The pressure gradient over the Gulf will begin to increase
tonight in advance of an approaching low pressure system.  Have
raised exercise caution flags for the western waters as winds
increase to 15 to 20 knots later tonight.  These exercise caution
conditions should overspread the remaining Gulf waters by Wednesday
night and then persist through Thursday night.  Seas should increase
to between 4 and 6 feet during this period.  Conditions could
increase into small craft advisory range for brief period of time.
In the wake of the low, winds will turn more westerly and also
decrease to around 10 knots on Friday as high pressure moves across
the Gulf South.  The high will shift to the east of the region by
Saturday allowing winds to veer back to the southeast and increase
to 10 to 15 knots.  As another low approaches from the west Saturday
night and Sunday, onshore flow should increase back into exercise
caution range of 15 to 20 knots. 32

DSS CODE...Blue.
ACTIVITIES...Monitoring Severe Weather Potential on Thursday

Decision Support Service (DSS) Code Legend:
GREEN  = No weather impacts that require action
BLUE   = Long fused Watch/Warning/Advisory in effect or high
         visibility event
YELLOW = Heightened impacts with short fused
         Watch/Warning/Advisory issuances; Radar support
ORANGE = High Impacts - Slight to Moderate risk of severe weather;
         Nearby tropical events, HAZMAT or other large episodes
RED    = Full engagement for moderate risk of severe weather; Direct
         tropical threats; events of national significance.


MCB  65  85  66  81 /  10  10  20  70
BTR  65  87  67  79 /  10  10  40  80
ASD  66  84  66  80 /  10   0  10  70
MSY  69  85  69  80 /  10  10  10  70
GPT  68  81  66  79 /  10  10  10  70
PQL  64  82  65  80 /  10   0  10  60



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