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

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FXUS64 KLIX 160901
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
401 AM CDT Fri Oct 16 2020

.SHORT TERM (Today through Saturday Night)...

The day has come! The arrival of the well advertised and much
needed cold front is here. Early morning observations along with
GOES-16 Night Microphysics imagery shows the front pushing quickly
across half of our CWA (as I type this), with low clouds right
along and behind the front ranging from 500 to 1500ft AGL.
Temperatures are somewhat slow to respond, with about a 10 degree
drop in around 75 miles difference from along the front to well
behind it meaning this is not a real powerful front, but enough to
make a difference looking ahead. Short-range guidance early this
morning is in good agreement over the potential for what appears
to be two individual areas of light rain chances. One - Generally
along and just behind the front as it races south across coastal
SE LA (southshore on south) and coastal MS this morning. Model
soundings show just enough slightly elevated instability above a
prominent frontal inversion right behind the front, coupled with
just enough negative omega to help develop a few isolated showers
in this area, likely continuing south across marine zones later
this morning. Two - A few isolated stratiform showers may be
possible north of I-10/12 across the Florida Parishes and SW MS
this morning caused from another slither of elevated instability
in the 850-750MB layer as the thermal profile resembles largely
most adiabatic above the deepening frontal inversion below. Both
areas of showers wont last long and will likely dissipate by late
morning, with lingering clouds likely through the early/mid
afternoon hours due to elevated low-level moisture residing behind
the front. However, CAM`s and blends agree that most of this
should dissipate by atleast later this afternoon, but this could
be too late for many areas to warm up much. Decided to pull
afternoon highs a tad down below what the blends suggest, but
still am at the top end of the model suite suggestions. Meaning,
don`t be surprised some areas afternoon highs could bust below
what is current in forecast, especially if the clouds struggle to
dissipate later today. Otherwise, we are headed towards a chilly
night tonight and early Saturday. Regardless of persistent
easterly winds thanks to a nearby area of high pressure stretched
across the Appalachians, we should still dip down into the
mid/upper 40`s to lower 50`s (mid 50`s southshore and coastal SE
LA) even without maximized radiative cooling processes at work.
Few drainage spots across the Northshore and coastal MS could end
up in the lower to mid 40`s, but that may be a stretch.

Saturday is shaping up to be a picture perfect day with ample
sunshine and highs in the 70`s - a true taste of fall. I didn`t
mention this yesterday morning but I continue to drag Td`s down
from 12Z Sat onward towards peak afternoon mixing as the blends
typically struggle here. I wouldn`t be surprised these
adjustments might not be enough, with the potential for some Td`s
in the mid to upper 30`s along/north of I-10/12 which will lead
to MinRH`s dipping well into the mid to upper 20`s in this area.
Bumped lows a few degrees down again Saturday night/Sunday
morning, but winds steadily begin to clock more out of the ESE to
eventual SE which will help pull Gulf moisture back north yet
again. KLG

.LONG TERM (Sunday through Thursday)...

Moisture steadily begins to return thanks to the aforementioned
area of high pressure pulling east across the Mid-Atlantic. This
will help draw afternoon highs back up to the 80`s with dewpoints
(during peak mixing) in the 60`s. Cant rule out some low clouds,
but mainly a nice day again. Late hour CAM`s hint at a few coastal
showers early Sunday primarily due to low-level to surface
moisture advection, but nothing worthy of mentioning in the
forecast just yet. Staring off Monday of next week, the
atmospheric upper-air pattern steadily deamplifies after the
departure of the east coast trough/associated front and becomes
quasi-zonal. This helps for ridging to build from northern Mexico,
east across the Gulf and into the west Atlantic. Some subtle
breaks in heights between both upper-high centers near the Baja,
and another elongated high just off the east coast of Florida
could support the return of some isolated showers in the afternoon
hours, but primarily speaking such anomalously high heights
around here, this will bring the warm weather right back to the
area. GFS guidance shows this breakdown between both upper-level
high height centers with some relatively progressive SW to NE flow
aloft combined with subtle troughing/PVA near the area which may
need to be watched for increasing rain chances Monday and
especially into Tuesday, but may be met with another cold front
late next week/into the following weekend. Meanwhile, long range
guidance continues in very good support over the idea that a
hurricane develops in the west-central Caribbean next weekend,
with a potential second system to its north. Main idea here is
that we transition into a much more progressive/deeper upper-air
pattern which will gracefully shoo these systems away from the
mainland US. Besides, climatology favors this type of track given
this time of the year. The next two names look to be Epsilon and
Zeta and will still need to be watched. If we make it to Zeta,
that would tie the most active season on record matching 2005. By
the time model guidance suggest Zeta to develop, this would place
2020`s season two months earlier than 2005 which has been the
general pace all season. But overall, look for several more
chances of cooler weather looking ahead to late October. KLG

.AVIATION...

.UPDATED 0454Z...

Cold front positioned from KMCB-KHZR at 05Z should clear KBTR
between 06-07Z, then through remainder of terminals between
10-11Z. Some MVFR ceilings on cold air advection post-frontal to
linger into the early morning hours, then clearing from north-to-
south by mid to late morning for VFR CAVOK conditions remainder of
valid TAF period. Gusty winds 20-27kt during daytime heating to
settle a bit after sunset. 24/RR

.MARINE...

A cold front is expected to race across all coastal marine zones
early this morning. Winds sustained at fresh breeze is expected,
with stronger gusts 25-30 knots possible at times, especially
across outer 20-60nm zones later today. Small Craft Advisories
that were placed yesterday has been timed more specific with the
timing of the front, pulling back nearshore zones including the
tidal lakes/sounds to begin at 12Z this morning, followed by outer
zones starting at 15Z. All zones remain in effect through 12Z
Saturday, but have pulled 20-60nm zones through 15Z SUN as winds
steadily diminish followed by a transition from northeast to
easterly winds. Waves and seas will respond following the frontal
passage but swell with time, peak wave heights of 2 to 4 feet
expected in the tidal lakes and sounds, to 3 to 7 feet increasing
through later today for offshore SE LA/S MS zones. Gusty winds
continue at times through late weekend and into early next week as
winds shift more from the east, but increased fetch will keep
wave heights slightly elevated through the time frame with no
additional hazards expected at this time. KLG


&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  68  47  74  58 /  20   0   0   0
BTR  68  48  75  59 /  10   0   0   0
ASD  70  47  75  59 /   0   0   0   0
MSY  70  57  75  66 /  10   0   0   0
GPT  71  50  74  62 /  10   0   0   0
PQL  73  45  76  59 /  20   0   0   0

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...Small Craft Advisory from 7 AM this morning to 10 AM CDT
     Saturday for GMZ550-552-555.

     Small Craft Advisory from 7 AM this morning to 7 AM CDT Saturday
     for GMZ530-532-534-536-538-557.

     Small Craft Advisory from 10 AM this morning to 10 AM CDT
     Saturday for GMZ570-572-575-577.

MS...None.
GM...Small Craft Advisory from 7 AM this morning to 10 AM CDT
     Saturday for GMZ552-555.

     Small Craft Advisory from 7 AM this morning to 7 AM CDT Saturday
     for GMZ532-534-536-538-557.

     Small Craft Advisory from 10 AM this morning to 10 AM CDT
     Saturday for GMZ572-575-577.

&&

$$


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