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

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FXUS64 KLIX 050602

Area Forecast Discussion
National Weather Service New Orleans LA
1202 AM CST Mon Dec 5 2016

The anticipated lull in rain coverage has occurred as an upper
level impulse exits the region. Another in a series of impulses in
advance of the main upper level shortwave trough will likely cause
increased isentropic lift and renewed rain coverage and possibly
isolated thunderstorms later on tonight or early Monday morning.
Lowered the rain chances slightly, but not to the degree of
current low coverage on radar. The anticipated severe thunderstorm
and heavy rainfall potential for Monday afternoon and evening
still looks about the same given initial analysis of 00z model
data. Will have more details on the full early morning forecast
discussion and the soon to be released SPC Day One Convective
Outlook. 22/TD


The LIFR CIGS early this evening scattered out leaving VFR
conditions in place for many airports in recent hours. It is
anticipated that IFR/LIFR will once again become widespread
overnight into Monday until the warm front lifts north allowing
for warmer temperatures and somewhat higher CIGS. The current lull
in rain will likely end as another round of rain develops late
tonight and early Monday. SHRA/TSRA may produce heavier rainfall
and possibly strong wind gusts Monday afternoon and evening, and
later TAF issuances will better time these threats. 22/TD


.PREV DISCUSSION... /issued 614 PM CST Sun Dec 4 2016/

Area radars indicated widespread rain with an occasional isolated
thunderstorm across the forecast area. Went ahead and raised the
rain chance to 100 percent tonight in most areas, although there
may be a break for a portion of the night. More persistent
moderate to heavy rainfall in some areas could result in heavy
ponding of water resulting in minor street flooding, however more
significant flooding is not expected. With the exception of some
hourly temperature and dewpoint/relative humidity updates tonight,
the rest of the forecast looked on track. 22/TD

Although some recent lower stratus decks scattered out over some
airports over the last hour leaving VFR conditions, it is still
anticipated that IFR to mostly LIFR conditions and rainy/misty
conditions will prevail the next 24 hours. 22/TD

PREV DISCUSSION... /issued 407 PM CST Sun Dec 4 2016/

Between surface low systems at this time as a weak low moved
through this morning and now awaiting genesis of next low pressure
system in response to upper level dynamics moving out of western
Mexico. An active weather period is expected monday with the low
deepening upon approach from the west gulf into central Louisiana,
placing much of the CWA in the warm sector of sorts, though stable
marine layer influences may maintain mostly elevated convection
above a stable inversion layer for quite some time. The convection
may flush out to a surface base closer to the coast where marine
supercells may be capable of producing tornadic waterspouts that
threaten near coastal areas Monday afternoon and early evening.
Otherwise, primary threat modes would be damaging wind gusts that
can penetrate to the surface along with some hail in cold pool
from elevated convective processes. Timing of best opportunity
still appears to be between 3 pm and 9 pm from west to east.
Meanwhile, heavy rain threat still seems plausible given
orientation of deep tropical fetch from the Pacific at jet level
and increased jet support and omega from approaching system. At
this time, areal average rainfall between 2 and 4 inches should be
the norm over Acadiana and the Atchafalaya Basin area, with lesser
totals likely farther east through midnight Monday night.
Tuesday should be a relatively lull period between fronts with
temperatures recovering a bit under partly cloudy and drier skies.

Winter temperatures are expected to arrive with a couple of
frontal passages in relatively rapid progression Wednesday and
Thursday. Some light to moderate freeze conditions may result for
Friday morning and Saturday morning in the interior sections away
from maritime influences. Models still indicate some pre-frontal
convection along the immediate frontal zone Wednesday, but the
subsequent surge should be dry passage Thursday. High pressure
moderates rather quickly over the weekend with return flow and
moisture return by late Saturday into Sunday. 24/RR

Most terminals currently reporting IFR to LIFR ceilings, with the
exception of KGPT and KNEW, and KNEW was a recent improvement.
Terminals are mainly already in the cooler air to the north of a
boundary along the Louisiana coast. Expect that terminals will have
MVFR conditions at best, and more likely IFR to LIFR overnight and
Monday morning. The threat of thunder is non-zero overnight, but
probabilities not high enough to mention in the terminals until late
morning on Monday. 35

Winds and seas are expected to begin responding to cyclogenesis in
the west gulf later tonight as the strong upper cut-off low
ejects from the Baja California area. There may be a brief lull in
winds tuesday before a surge of modified arctic air pushes off the
coast Wednesday, then becoming re-enforced by a fresh canadian
high pressure area thursday. This will bring high end small craft
advisory conditions with frequent gale force gusts along with high
seas for much of the day thursday and thursday night before
settling friday. 24/RR

DSS code: Blue.
Deployed: None.
Activation: None.
Activities: Monitoring convective and heavy rainfall trends through
            Monday night.

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.
Yellow = Heightened impacts with short-fused watch, warning or
         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 risk of severe and/or
         direct tropical threats; Events of National Significance.


MCB  51  66  52  64 / 100  90  70  10
BTR  54  67  53  66 / 100  90  60  10
ASD  55  69  54  67 / 100  80  70  10
MSY  60  69  57  66 / 100  80  70  10
GPT  58  68  57  67 / 100  80  70  10
PQL  57  66  57  68 / 100  80  70  10



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