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

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FXUS64 KLIX 281113 AAA

Area Forecast Discussion...UPDATED
National Weather Service New Orleans LA
513 AM CST Tue Nov 28 2023


(Today through Thursday)
Issued at 300 AM CST Tue Nov 28 2023

Some echoes have been showing up overnight on KMOB across the far
northwestern tier. A quick look at the mid and upper levels
explains why this is as an H5 shear/vort axis resides over the
region. This is helping produce the virga on radar and the high
cirrus deck over the area. So, taking a look at the latest RAOB
one will see why POPs are as close to zero percent as they could
be with echoes on the radar. The boundary layer and most of the
column is bone dry and a simple vort axis will not provide enough
lift to modify rain probs. That said, the upper level cloud deck
is keeping our region from radiating as effectively with
temperatures not dropping off as much as they would
just a degree or two warmer than initially thought.

At the surface today, high pressure will begin to migrate into the
region from the west, which should break the surface pressure
gradient down a good bit leading to mostly calm conditions.
Overnight tonight with calm winds and clear skies, temperatures
will drop into the 30s for most locations north of the lake
including the MS Gulf Coast. Temperatures will also be the coolest
along the drainage basins over the Pascagoula and Pearl Basins.
Temps as low at the upper 20s cannot be ruled out. For this went
ahead with the period 2 freeze warning generally along and north
of the I10/12 corridor. Coastal Jackson and Hancock Co., were
included again because the drainage areas affecting the coastal
zones respectively.

Wednesday will start out cold, but this will begin the transition
to warmer weather as the surface high exits stage east allowing
for a developing onshore/return flow to take shape. This return
flow will start to bring in much warmer and more moist air into
the region from the central Gulf. The upper level pattern will
quickly evolve from a cool and dry northwest flow to a very active
southwest flow on the northwest periphery of an H5 ridge over the
western Caribbean. This regime change comes with slightly higher
heights, which along with the return flow developing will allow
temperatures to warm overnight Wednesday and and especially during
the day on Thursday. Attention shifts quickly upstream on
Thursday with a strong shortwave trough ejecting from the Four
Corners region and into the high plains. As the feature takes on a
negative tilt, confluence in the mid levels ahead, and H3 jet
dynamics ramp up over the Red River, widespread showers and
thunderstorm activity is anticipated to develop across the Sabine
River Basin and quickly spread into our region PM on Thursday.
Again, low severe probs cannot be ruled out here, but as stated in
the last few discussions, best ascent will be north and west of
our CWFA. (Frye)


(Thursday night through Monday)
Issued at 300 AM CST Tue Nov 28 2023

The mid level impulse that will help in part generate the
widespread shower and thunderstorm activity in the short term will
move northeastward quickly and begin to weaken over the Great
Lakes region. Back home, we will start the long term same as we
ended the short term with active southwesterly flow. As the
parent trough moves northeast, the surface front will stall as it
becomes parallel to the mean upper level flow. By Friday
afternoon a break in the rainfall is anticipated, however, eyes
shift quickly upstream again over the western Gulf of Mexico.
Another wet pattern looks probable in the globals by late Friday
and into Saturday. Depending on where the front stalls will likely
indicate the heaviest rainfall amounts. There will be some
convection along and south of the front with elevated thunder
possible with heavy rainfall rates along and north/west of the
surface front.

Beyond this second impulse, things do become a bit more fuzzy in
terms of timing of additional shortwaves within the southwest
flow. The front will remain locked in place at least into the
start of the new workweek. Any vort or weak trough within the
flow will help generate additional showers and storms through
early Sunday morning. Right now, Globals are showing anywhere
between 3 to 5 inches of rainfall across the region. Exact values
are a bit lower confidence and of course exactly where, but given
the orientation of the surface front it is a bit more confident
that a good soaking rainfall is in the cards for the first weekend
of December.

One slight change this round is the globals are a bit more
progressive with moving the front downstream as a stronger upper
level short wave begins to slide eastward and eventually leading
to a more zonal or progressive flow aloft on Sunday. This will
finally take the front east of the region allow for clouds to
break and cold air advection, albeit weak to develop. Confidence
this scenario within the D6-8 timeframe is low so we will continue
some lower-end POPs for continuity, but if these trends continue
we will likely need to clear any precip mention beyond 18z on
Sunday. (Frye)


(12Z TAFS)
Issued at 507 AM CST Tue Nov 28 2023

VFR conditions through the cycle. The high cirrus will begin to
decrease through the morning. Northerly winds will also decrease
generally below 10kts. However, winds off the lake will remain
elevated for NEW before gradually decreasing with time. (Frye)


Issued at 300 AM CST Tue Nov 28 2023

High pressure will begin to move into the region later today,
which will help decrease winds and seas over the local waters.
Cautionary headlines continue through the morning, but again
improvement is anticipated shortly. Later today and Wednesday look
favorable, however, at the very least a moderate onshore flow
begins to develop as the high exits to our east by early Thursday.
Rain and storms also increase after noon on Thursday as the low
level flow continues to increase ahead of the next system. At
least cautionary headlines will be needed late this week and into
the weekend. (Frye)


MCB  59  31  60  41 /   0   0   0   0
BTR  62  34  64  48 /   0   0   0  10
ASD  61  33  62  44 /   0   0   0   0
MSY  59  46  62  51 /   0   0   0   0
GPT  60  37  60  46 /   0   0   0   0
PQL  62  31  63  40 /   0   0   0   0


LA...Freeze Warning from 1 AM to 7 AM CST Wednesday for LAZ034>037-

MS...Freeze Warning from 1 AM to 7 AM CST Wednesday for MSZ068>071-



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