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

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247
FXUS64 KLIX 280910
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
410 AM CDT Fri Apr 28 2017

.SHORT TERM...
No appreciable differences in thinking. Waking up this morning
will catch one with a different feel once outdoors. Dew pt temps
have been rapidly rising into the lower to mid 70s and this will
make for a very muggy difference compared to yesterday. Some of
this moisture will be able to lift via isentopic forcing and
boundary layer frictional convergence. It may be enough to cause a
few areas of light rain or dizzle mainly during the morning but a
passing light shower will remain possible through the day. Winds
will also start to respond to a tightening pressure gradient
today. Breezy conditions with wind speeds on the order of 15 mph
with gusts to 20 mph will be observed over most areas today. Wind
speeds will rise further to 20-25mph by Saturday morning and
possibly sustained at around 25 mph Sunday. Gusts should be strong
enough to get to 30-35mph for both Saturday and Sunday.

The large bulk of severe weather associated with this system will
be to our north and northwest. But there will remain a high
potential for widespread strong thunderstorms with several of
these becoming severe. Strong damaging wind speeds look to be the
most efficient varaiable at the moment. This is due to the
addition of momentum transfer from thunderstorm activity to the
sfc where there will already be winds around 25mph. Any
thunderstorm will not have to produce more than a 25mph wind to
cause some fairly strong cumulative wind speeds. Other modes of
severe weather will not be left out though. The last but just as
important thing will be rainfall amounts. Total amounts during the
entire event look to be 2 to 4 inches with isolated higher amounts through
Sunday night. Goes without saying that if the majority of this
amount falls within a short period flooding would be possible.

Tides will begin to be on the rise today through the weekend
reaching their peak Sunday. Levels are expected to be 1-2 feet
above normal Saturday and 2 feet above normal Sunday. This would
bring up the possibility of coastal flooding for those areas most
vulnerable. The highest potential of coastal flooding will be
during high tide times which will be from late morning through
early afternoon each day through the weekend.

.LONG TERM...
Dry air will move in behind this front once it moves through the
area Sunday night. A meridional dew pt gradient will set up over
the area Monday through Tuesday. Tuesday night should find this
gradient(warm front) being lifted northeast ahead of the next
cold front. This feature could be strongly forced depending on how
deep the polar jet digs over the gulf south, which would lead to a
good bit of thunderstorm activity once again. This could run in
two different directions at this time. One would be a clean
frontal passage with the jet digging only deep enough to cause the
sfc low to remain progressive. This is the view from the GFS. The
other, which actually may have a little more credence to it, would
dig the polar jet soutward well into south Texas before becoming
progressive. This would take more time and help a sfc low form
near the gulf coast or just inland by Thursday. During the time
the jet takes to become progressive, a cold front will become
quasi-stationary either at the coast or just offshore. This will
allow many small disturbances to use the baroclinic frontal
interface to transport moisture northeast along the boundary and
develop areas of thunderstorms for a few days. This could set up a
wet pattern for a few days toward the end of next week.

This may be getting far out in advance but the large scale pattern
is suggesting the expansive upper high normally over the desert
southwest will get displaced by a west coast trough forcing the
stacked high eastward. This would bring some of the warmest temps
of the year to the area by next weekend. So, long story short,
temps in the 90s look to be just around the corner.

&&

.AVIATION...

Moisture return associated with a warm front has yielded low cigs
across the forecast area this morning. Expect MVFR to some IFR
conditions to be at a few terminals this morning. Conditions will
improve a little bit as the morning goes on but expect mainly MVFR
conditions to prevail through the morning hours. Winds will be
elevated through the weekend. Winds will be out of the south
today...breezy conditions will prevail 10 to 20 knots at all
terminals are possible. 13/MH

&&

.MARINE...

The pressure gradient over the Gulf will be increased over the
coastal waters through the weekend in response to a deepening low
pressure system over the Plains. Southerly winds of around 20 knots
are expected today.  Small Craft Advisories are posted for the
entire coastal waters through Sunday morning as the waters will be
hazardous all weekend...granted there will be a portion of Saturday
where the criteria may not be met...that will quickly change. There
is also an outside chance that the Small Craft Advisory may have to
be upgraded to a Gale Warning. This will have to be watched as this
system evolves. Gulf waters due to these winds and seas of up to 7
feet. The tightening pressure gradient will result in strong onshore
winds of 25 to 30 knots impacting the coastal waters from Saturday
afternoon through Sunday evening. Very rough seas of up to 12 feet
could also impact the open Gulf waters during this period. Over the
sounds and lakes waves of up to 6 feet will be possible.

Winds will shift to the northwest late Sunday night and Monday in
the wake of the low pressure system and cold front. Winds should
remain elevated at around 20 knots through morning hours on Monday
and seas will remain rough. Conditions will begin to improve Monday
night and Tuesday as high pressure settles directly over the waters.
Winds will veer back to the east by Tuesday and decrease to between
10 and 15 knots. Seas should also fall back to 2 to 4 feet by
Tuesday morning. 13/32

&&

.DECISION SUPPORT...
DSS CODE...Blue.
DEPLOYED...None.
ACTIVATION...None.
ACTIVITIES...Monitoring severe potential for Sunday.

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.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  85  72  87  72 /  20  10  30  30
BTR  87  74  86  74 /  20  10  30  30
ASD  84  73  85  74 /  20  10  30  20
MSY  85  74  84  74 /  20  10  20  20
GPT  81  75  83  75 /  20  10  30  20
PQL  82  72  84  73 /  20  10  30  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...Small Craft Advisory until 7 AM CDT Sunday for GMZ536-538-550-
     552-555-557-570-572-575-577.

     Small Craft Advisory from 4 PM this afternoon to 7 AM CDT Sunday
     for GMZ530-532-534.

MS...None.
GM...Small Craft Advisory until 7 AM CDT Sunday for GMZ538-550-552-
     555-557-570-572-575-577.

     Small Craft Advisory from 4 PM this afternoon to 7 AM CDT Sunday
     for GMZ532-534.

&&

$$



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