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

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FXUS64 KLIX 271341
AFDLIX

AREA FORECAST DISCUSSION
National Weather Service New Orleans LA
841 AM CDT Sat May 27 2017

.SOUNDING DISCUSSION...
This morning`s flight shows moisture slowly creeping in through
the upper layers of the atmosphere. The temp profile between 925mb
and 850mb showed an unrealistic lapse rate and therefore was
deleted. The rest appears normal for an upper 80 degree day.
Convection will be suppressed today by the combination of lack of
moisture and strong inversion at 800mb.

MEFFER
&&

.PREV DISCUSSION... /issued 337 AM CDT Sat May 27 2017/

SHORT TERM...
Cold front well to the north of the area is moving slowly
southward and should be in the vicinity of Texarkana to NE
Arkansas by this evening. A few very strong explosive areas of
severe thunderstorms are expected to develop just north of that
line and move slowly south this afternoon. Outflows from these
storms should move southward through a less dense environment this
evening and reach the Natchez area just after dark. The first of
many sea breezes should also be in this general vicinity after
dark as well. An area of showers and possibly a few thunderstorms
could form along a line from Alexandria to Natchez this evening.
A strong inversion should hold for our area through Sunday
morning keeping chances of sh/ts at low levels. After noon
Sunday, that inversion weakens but is not destroyed. This will
make any thunderstorms capable of breaking this cap and developing
late Sunday afternoon and evening have a better chance of
becoming severe. The frontal boundary and sea breeze will also
clash along the Alexandria to Natchez line, but this time, the
sh/ts will begin to make a slow march southward into the northern
portion of the area which may also help chances of producing a
severe thunderstorm or two. Upper jet influences should also be
capable of developing another area of sh/ts along the coastal
areas from Corpus to near New Orleans during this same time frame.

The front stalls Sunday evening over the area and becomes very
diffuse at the sfc. The 850mb reflection remains and this boundary
along with daily sea breeze collisions will maintain a daily
barrage of sh/ts. Some or these could be strong during peak
heating the remainder of the week. But the best time frame for
receiving a strong or severe thunderstorm looks to be Sunday
afternoon through Monday. SPC has the entire area under marginal
risk for Sunday and Sunday night. Marginal to slight risk looks to
be a good bet starting noon Sunday through Monday.

There is no focused deep moisture fetch to any one area along the
stalled boundary but instead is spread over a large area. Without
this concentration of deep moisture, flooding issues are not
expected through the end of the work week for our area. Although,
if any certain location falls under two or three of these
thunderstorms, there can always be the potential to see some
minor flooding.

LONG TERM...
We should begin to see a deeper tropical moist fetch from the
southern gulf into the Texas coastal bend starting Thursday. This
is not uncommon this time of year and Houston as well as other
surrounding areas have been known to take on extensive flooding
issues from some of these scenarios over past years. Models are in
disagreement of which way to resolve the tropical wave issue by
next weekend. The GFS would like to keep a steady flow into the
Houston area but spread this fetch eastward into our area by the
weekend. The EURO stills wants to develop a weak system over the
NW gulf. The synoptic field can be better resolved from these
global suites and so the deep moist fetch from the southern gulf
through the Texas coast into the center of the country has a
little more credence than these models trying to develop a
mesoscale disturbance.

In short, higher chances of rain look to be in the fcast again by
next weekend and this will be shown in the extended. But as for
the mesoscale development, there needs to be a strongly concerted
and successive effort by both model suites, if not more models,
agreeing on this scenario before it can be set as a part of the
fcast, especially in the extended.

AVIATION...

MVFR ceilings will linger overall of the terminals through around 15
to 16z this morning.  The ceilings should improve into VFR range
after 16z, and remain so through at least 00z.  By 06z, another
round of MVFR ceilings should be in place at most of the terminals.

MARINE...

A fairly benign weather pattern for the coastal waters through the
period as a broad area of high pressure remains centered over the
eastern Gulf of Mexico and Florida through the middle of next week.
A general onshore wind of around 10 knots and seas of around 2 to 3
feet can be expected in the open waters.  Closer to the coast in the
sounds and tidal lakes, waves of 1 to 2 feet and lighter winds of 5
to 10 knots are expected through tomorrow.  On Monday and Tuesday, a
weak front will stall near these waters resulting in variable winds
of 5 knots or less.  Thunderstorm activity will also be possible
during this time, and these storms could produce locally stronger
winds for brief periods of time.  By Wednesday, the front should be
dissipated and general onshore flow of 5 to 10 knots should be
reinstated.  32

DECISION SUPPORT...
DSS CODE...Blue.
DEPLOYED...None.
ACTIVATION...None.
ACTIVITIES...Monitoring flooding along the Mississippi and
             Pearl Rivers.

DECISION SUPPORT SERVICES (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 SEVERE; NEARBY
         TROPICAL EVENTS; HAZMAT OR OTHER LARGE EPISODES
RED    = FULL ENGAGEMENT FOR MODERATE TONIGHT RISK SVR
         AND/OR DIRECT TROPICAL THREATS; EVENTS OF NATIONAL
         SIGNIFICANCE

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  89  73  89  70 /  10  10  20  40
BTR  91  74  90  71 /  10  10  20  40
ASD  88  74  89  72 /  10  10  10  30
MSY  89  75  89  75 /  10  10  10  30
GPT  87  75  87  75 /  10  10  10  30
PQL  87  73  87  74 /  10  10  10  30

&&

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

$$



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