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

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FXUS64 KLIX 250904
AFDLIX

AREA FORECAST DISCUSSION
National Weather Service New Orleans LA
404 AM CDT Tue Apr 25 2017

.Short Term...
Quiet weather expected today as trough moves off the east coast and
upper ridge builds over the Central Gulf Coast. Strong subsidence
underneath high pressure will suppress most cloud cover development
outside of occasional cirrus clouds. Temperatures will begin to
moderate today as 500mb heights increase. A roughly 5 degree
increase is likely which puts highs around 80 to 85. Most of the
blended guidance was too cold, so stuck with MAV/MEX numbers.
Enhanced southerly flow today will bring moisture back into the
area. This will take dewpoints into the lower 60s tonight which will
limit cooling. Thus, lows should be quite a bit warmer tonight than
this morning.

.Long Term...
The biggest impact periods of the extended forecast come in
Wednesday night and in the latter half of the weekend. Starting with
the first, a broad upper level trough exists just west of the
Rockies over the Pacific Northwest. This trough will continue
eastward today and begin to dig south and sharpen on Wednesday as it
tracks into the Central Plains. Models are in good agreement that
the trough will then lift northeast towards the Great Lakes
Wednesday night. A frontal boundary associated with the upper trough
will be the focus for shower and thunderstorm activity that moves
through the CWA. Convection should be on the western doorstep of the
forecast area Thursday at 00z and exiting eastern areas around
sunrise Thursday. The typical pop coverage in similar weather
patterns is more storms along the LA/MS border and minimal along the
LA coast(example: the last system that just moved through). The
threat for severe weather will be in a similar with the best probs
north of I-12 and minimal threat on the coast. Model soundings show
this as well with a mid level warm nose that doesn`t erode and much
weaker winds in the column at points further south than north. ML
CAPE values over 2000j/kg, LI`s -6 to -8 combined with shear over
40 knots will be sufficient for severe thunderstorms in those
northern areas.

The second impactful event is looking be more potent than the first.
The main upper trough will be closing a low and rotating negative as
it digs well into Texas and the lower Mississippi Valley Saturday
into Sunday. A wide swath of showers and embedded strong/severe
thunderstorms will march across the state. Surface winds look to be
strong, surging gulf moisture inland which should bring dewpoints
into the lower/mid 70s. CAPE values will once likely be over 2000
j/kg. That type of moisture and instability combined with a 50+kt
mid level jet may set the stage for maybe a few significantly strong
cells. All modes of severe weather possible although tornadoes and
wind seem to be the more likely threats. Timing is the biggest ?? a
attm as models are 6-12 hours faster than 24 hrs ago. Will likely
see flucuations until the event occurs.

MEFFER
&&

.AVIATION...
Clear skies into the morning hours with a few terminals having some
vis restrictions. A ceiling at BKN030-040 looks to develop by late
morning and early afternoon today. Would like to see this begin to
initialize before 12z taf issuance. If the ceiling does not begin to
develop before issuance, will opt to keep this level prevailing SCT.
prevail through tomorrow afternoon resulting in VFR conditions at
all of the terminals. Winds will begin to shift to due south and
remain through this taf cycle.

&&

.MARINE...
Onshore wind will become established today then gradually increase
to 10 to 15 knots by the evening hours. Winds should further
increase Wednesday as a strong low pressure system moves into the
Plains states increasing the pressure gradient over the Gulf. Expect
to see a period of exercise caution and possibly small craft
advisory conditions from tonight through Thursday morning.  The
front should stall over the north central gulf very close to the
coast. This should cause an onshore flow to remain over most of the
coastal waters with the exception of mainly the protected waters
which will shift to a northwest direction and quickly ease Thursday.
this quick stalling and subsequent rapid movement back to the north
will be in response to another stronger cold front that is expected
to affect the marine areas Saturday through Monday morning.
Southerly winds ahead of this front will be capable of producing
high end advisory conditions and a potential to even cause low end
gales either sustained or in gusts starting Saturday night. Once the
front passes Sunday evening, northerly winds just as strong are
expected but should have a shorter duration as winds begin to
subside Monday.

&&

.DECISION SUPPORT...
DSS CODE...Green.
DEPLOYED...None.
ACTIVATION...None.
ACTIVITIES...None.

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  83  61  84  61 /   0   0  10  70
BTR  84  65  85  60 /   0   0  10  70
ASD  81  62  82  64 /   0   0   0  60
MSY  81  64  85  65 /   0   0  10  60
GPT  80  65  79  71 /   0   0  10  60
PQL  80  60  80  67 /   0   0  10  50

&&

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

$$


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