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

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FXUS64 KLIX 281749
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
1249 PM CDT Sat May 28 2022

.AVIATION (18Z TAFs valid through 00z Sunday)...
VFR expected through Sunday with high pressure in control. While
some of the model guidance shows light radiational fog developing
toward sunrise at the typical fog-prone terminals like KMCB, it`s
unlikely given how dry the airmass is. Only cloud cover will be
few-sct CU during peak heating this afternoon and tomorrow with
bases 3-5 kft AGL. Light and variable winds are expected
throughout the period. -JRK

&&

.PREV DISCUSSION... /issued 1000 AM CDT Sat May 28 2022/

..MORNING UPDATE...
The forecast was in good shape, so only minor tweaks to the
forecast was needed and mainly in our coastal waters where the
residual surface trough resides. Isolated showers and
thunderstorms was added the forecast from about 20 miles off the
Terrebonne-Lafourche-Plaquemines Parish coastline, southward.
Sunny skies will prevail on land except for a few CU developing
late in the day in coastal areas of SE LA and MS. Just like
yesterday, it won`t feel particularly hot or humid (especially
considering we`re only 4 days away from the start of
meteorological summer) with temperatures peaking in the mid to
upper 80s and dewpoints in the 50s. -JRK

PREV DISCUSSION... /issued 321 AM CDT Sat May 28 2022/

SYNOPSIS...

The upper low that brought the mid-week weather has moved eastward
to western Pennsylvania, with a trough axis into the eastern Gulf
of Mexico. Upper ridging extended from west Texas to the western
Great Lakes. The old frontal boundary is definitely offshore of
southeast Louisiana, with a narrow band of showers noted over the
coastal waters. This boundary divides an airmass with dew points
in the 50s and lower 60s to the north, from air with dew points in
the lower 70s to the south.

SHORT TERM (through Monday night)...

As the upper low continues to move off the New England coast over
the weekend, a weak trough will remain over the northeast Gulf of
Mexico. The upper ridge will move eastward to the Carolinas by
Monday. The northeast Gulf trough will continue to weaken as it
drifts westward over the next few days, and be centered in our
eastern coastal waters by Monday.

Current precipitable water values are around 0.8 inches and
unlikely to change much over the next 24 hours. Even as we get
into Sunday and Monday afternoons, those levels don`t increase to
much more than an inch. Per GFS forecast soundings, mid level RH
values don`t get to much more than 30-40 percent Sunday and Monday
afternoons. While the proximity of the upper trough is a bit
concerning, the moisture profile makes it difficult to create a
case for much more than extremely isolated (<10% coverage)
convection on land until perhaps very late Monday night in the
extreme southeast portion of our CWA. A bit better chance over the
coastal waters, but even then, very isolated.

Spread in temperature guidance through Monday is minimal for most
locations, would trend toward upper end on highs and lower end on
lows where differences exist. 35

LONG TERM (Tuesday and beyond)...

Subsidence and strong mid-level capping associated with a broad
mid to upper level ridge axis parked over the Lower Mississippi
Valley will begin to weaken slightly on Tuesday as the ridge axis
shifts west and a broad closed upper low retrogrades west from the
eastern seaboard. At the same time, persistent southeasterly flow
off the Gulf of Mexico will usher in an increasingly moist and
unstable airmass. Precipitable water values will gradually rise
from around 1.25 inches Tuesday morning to around 1.75 inches by
Wednesday afternoon. This increase in available moisture will be
directly related to the mid-levels gradually moistening up in
response to the decreasing subsidence aloft. The amount of
instability as noted by SBCAPE in excess of 1500 J/KG will be
sufficient to overcome the weak capping inversion in place both
Tuesday and Wednesday as temperatures climb into the upper 80s and
lower 90s. Convection will be highly diurnal with most activity
peaking in the mid to late afternoon hours before gradually
dissipating in the early evening hours, and the primary threat
from any deeper convective cells will be gusty winds in excess of
30 mph. The convective activity will be fairly isolated each day
and will typically fire up along weak mesoscale boundaries. PoP of
20 to 30 percent reflects this risk each day.

On Thursday and Friday, the area will be firmly planted between the
ridge over the Southern Plains and the upper level low over the
Southeast.  As a result, a deep layer northerly flow pattern will be
in place in the mid and upper levels.  In the low levels, onshore
flow will continue to pump a warm and unstable airmass into the area
on Thursday.  Precipitable water values will remain high at around
l.75 inches, and SBCAPE should peak around 1500 to 2000 J/KG each
afternoon.  The other concern on Thursday is a high amount of
downdraft CAPE with values around 1000 J/KG possible as some drier
air does continue to reside between 850 and 700mb.  If any deeper
convective cells develop, the potential for some strong to
potentially severe wind gusts will exist Thursday afternoon into
early Thursday evening.  A weak frontal boundary may slip through
the area Thursday night into Friday morning as a northern stream
trough passes well north of the region, but confidence on this
occurring is low.  In any event, a northerly flow regime will remain
in place in the mid and upper levels, and the forecast currently
calls for additional scattered convective development as reflected
by PoP values of 30 to 40 percent Friday afternoon as highs climb
back into the upper 80s and lower 90s.  PG

MARINE...

A comparatively quiet period for marine interests, especially over
the next 36 hours. As surface high pressure moves to the east,
wind flow will regain an onshore component from the southeast by
late Sunday. Winds may near 15 knots at times, mainly over the
western open waters, late Sunday onward, but don`t see
indications of winds above that thru the forecast period. 35

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  61  91  66  90 /   0   0   0  10
BTR  63  91  67  90 /   0   0   0  10
ASD  64  90  69  90 /   0   0   0  10
MSY  70  90  73  90 /   0   0   0  10
GPT  68  88  72  87 /   0   0  10  10
PQL  65  87  70  87 /   0  10  10  10

&&

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

$$


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