FXUS64 KLIX 242214

Area Forecast Discussion
National Weather Service New Orleans LA
514 PM CDT Thu May 24 2018

.DISCUSSION...Convection had far greater coverage today Seabreeze
than the last few days finally. Seabreeze/Lakebreeze initiated
quickly and then most everything become dominated by outflow and
colliding boundaries. Due to the greater coverage highs were
definitely impacted with most places only in the 80s.

The ridge over the CONUS just east of the MS will continue to break
down as a trough works across the entire MS Valley. With that and
increasing moisture convection will have very little difficulty
developing again tomorrow. Much like today the seabreeze/lakebreeze
should initiate somewhat early and then convection will once again
be dictated by outflow and colliding boundaries. Overall expect most
of the area to at least see some rain or be fairly close to seeing
rain and while that may be the case at any given point not expecting
much more than scattered coverage.

Saturday could be a repeat of Friday with possibly even slightly
greater coverage of rain. Once again convection will be driven
diurnally as our tropical system we are watching may already be or
just starting to take shape in the southern Gulf.

Now as we look into Sunday and the first half of next week, some
good news, some bad news. First the bad news models have started
coming in-line and are indicating a better chance of seeing some
significant impacts across portions of the area. Good news the
models have started to come in-line and are increasing the
confidence of where impacts could be.

Over the last 12-24 hours the models have started to converge a
little and now indicate a track more towards the north-central LA
with 90L. They continue to slow the system as it gets trapped in a
very weak steering pattern Sunday through Tuesday. Forecast has it
basically just heading north slowly along a slight weakness over the
Lower Ms Valley and Tn Valley left over by the departing northern
stream trough. Latest thinking is that 90L will eventually become a
tropical cyclone this weekend and slowly approach the coast of
SELA/MS/AL sometime Monday.

One other concerning thing is now conditions could improve enough to
allow for slightly more strengthening then previously thought. Come
late Saturday and through Sunday night the shear will weaken and
models are indicating that there could be a favorable outflow
channel to the north of the system. In addition the water is fairly
warm across the central and north-central Gulf which is where this
system will track. Last drier air is not showing up as much in the
WV as yesterday and the system could be insulated from dry air. With
that we can not rule out a strong TS possibly even approaching a low
end hurricane approaching the coast. This would increase the impacts
from wind and tides but we still still feel that heavy/flooding rain
is the greatest concern especially over coastal MS.

As for the rain this is still tricky as we appear to be in the
gradient. Overall across SELA and southern/coastal MS we could see
rain range from just over an inch in the west to over 8 inches and
possibly a good bit more in the east. Even though confidence has
increased in the forecast we would like to not get too detailed at
this time on the where the cut off would be for heavy possibly flash
flooding rain and the typical daytime thunderstorms. That said we
feel the best location for heavy rain will be east of I-55 with a
focus likely over coastal MS where over 10 inches is not out of the
question. Widespread 4-8 is expected with some locations possibly
seeing more than double that when every thing is said and done (yes
more than 16 inches is possible if the system moves as slow as
expected and over coastal MS/SELA).

Obviously with a possible stronger storm the impact from winds and
tides/surge is higher especially near the coast of MS and SELA east
of the MS river. With the current forecast approaching the MS coast
and approaching slowly water will pile up along the coast of SELA
east of the MS River along with Lake P and across coastal MS. At
this time we are forecasting a slightly conservative (due to
uncertainty) 1-3 feet of surge in the Lake and 2-4 across coastal MS
and the the east facing coasts of SELA. Other issue to keep an eye
on surge wise would be inside Barataria Bay where strong persistent
winds out of the west could pile up water on the west side of
Plaquemines Parish. Winds would have the greatest impact right along
the coast and likely decrease pretty quickly inland and especially
to the northwest of the system.

Biggest concern with these impacts is track. Current track is not
the greatest news for our area. A slight jog to the west possibly
over SELA with a similar slow forward motion would increase pretty
much all of the impacts for a good portion of the CWA with flooding
rain a significant issue. A jog to the east staying towards AL will
lower most of the impact's for pretty much all of the CWA except
coastal MS. A track even further east (not out of the question since
we still dont even have a developed system yet) would pretty much
take all of the impacts out of our area.

We do want to point out that nothing has even developed yet and
models will struggle and swing significantly until there is
something developed. So continue to follow the forecast as this
evolves this holiday weekend.

If this system develops into a tropical cyclone (which we
think it eventually will) and attain tropical storms status it would
be named Alberto. Hurricane hunters are scheduled to investigate
tomorrow if there is something to investigate. in addition we will
begin 6 hourly balloon launches at 18z tomorrow. /CAB/


.MARINE...Winds are still on the lighter side and look to be
through Friday night and possibly into Saturday with our system
finally moving through the southern Gulf. Models have come into
agreement with a likely tropical cyclone moving into the north-
central Gulf late this weekend early next week. Winds will begin to
respond Sunday out of the northwest and there is a good chance that
Gale conditions could begin to develop then but at that time we are
anticipating a Tropical Depression if not Tropical Storm and with
that warnings will likely be in place. If the system goes further
east then we would likely have small craft advisories in place.
Conditions may not really improve until late Tuesday or more so
Wednesday as the system will be very slow to move. /CAB/


.AVIATION...Convection across the forecast area has really
diminished thanks to the outflow boundaries that moved through the
region. The one area with activity not too far away is MCB and
around PQL as well. Expect MVFR to VFR conditions to prevail
through the overnight hours. There could be some early morning
patchy fog that should quick dissipate after sunrise. Expect VFR
conditions and afternoon showers to prevail once again for
Wednesday. 13/MH



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; Marginal risk severe or excessive rain.
Yellow = Heightened impacts with short-fused watch, warning or
advisory issuances; radar support for Slight risk severe or
excessive rain.
Orange = High Impacts; Enhanced risk severe; nearby tropical events;
HazMat or other large episodes.
Red = Full engagement for Moderate to high risk of severe and/or
excessive rain, or direct tropical threats; Events of
National Significance.


MCB 69 85 68 86 / 50 50 30 60
BTR 72 88 71 88 / 40 60 30 60
ASD 71 89 71 86 / 30 60 40 70
MSY 74 88 74 87 / 20 70 30 60
GPT 73 87 73 85 / 30 60 50 70
PQL 70 86 70 85 / 30 60 50 70



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