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

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FXUS64 KLIX 271103
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
503 AM CST Sun Nov 27 2022

...New SHORT TERM, LONG TERM, AVIATION, MARINE...

.SHORT TERM...
(Today through Monday)
Issued at 453 AM CST Sun Nov 27 2022

After everything moved through it got very quiet and
all impacts ceased even before 6z. Showers and thunderstorms were
widespread yesterday with 1-2 inches across much of the area and
even a few strong to severe storms. We did have one confirmed
tornado, an EF1 over Paradis.

Next 48 hours is going to be uneventful with fairly nice weather.
Clouds may finally return Monday night but until then we will
likely see mostly clear skies. As yesterdays system continues to
pull away we will remain under weak southwest flow. No CAA will be
taking place and the only real change will just be continued dry air
moving over the region in the mid and upper levels which can easily
be seen on WV. H925 temps will remain steady today and tomorrow
hovering around 13-14c and this should translate to upper 60s to mid
70s across the region the next 2 days but come Tuesday there is a
chance we could be warmer and much warmer.

Heading into Monday night and Tuesday we will see changes commence
but this will take some time as even by 00z Tue we appear to still
be rather dry with moisture still contained well into the Gulf and
really little if any tap into the Pacific. The subtropical jet
doesn`t appear to ramp up till overnight or even early morning hours
Tuesday while high pressure at the sfc finally slides far enough
east to allow for return flow to set up late Monday night. The
return flow will become strengthened by a developing sfc low along
the lee side of the Rockies around the CO/KS border. This is all in
response to our next system dropping down the Pacific coast Monday
and Monday night. This will finally allow moisture to increase with
clouds returning overnight but impacts are not anticipated until
Tuesday and Tuesday night when showers and thunderstorms slowly
return and even the small chance of a few strong to severe storms
however, that risk is low with the greatest potential likely
remaining north and possibly well north of the CWA. /CAB/


&&

.LONG TERM...
(Monday night through Saturday)
Issued at 453 AM CST Sun Nov 27 2022

Main forecast issue in the entire package is the Tuesday through
Wednesday morning time frame. After that we will be fairly quiet
again into next weekend. Models seem to be in overall decent
agreement with the mid week system but the uncertainty in how this
all plays out is quite high. Right now I would say confidence is
low in the forecast but I guess the best description right now
would be Low Probability: High Impact. With broad model agreement
along with uncertainty, made no deviations from the NBM.

So lets just get down to it for the Tuesday and Tuesday night
system. We are already in southwest flow even as our system is
digging across the Continental Divide and trying to get into the 4
Corners late tomorrow and early Tuesday. By midday Tuesday the
mid lvl jet core will be at and starting to round the base of the
trough. This will end the digging of the system and it will move
more east. At the same time a southern stream mid lvl jet core
will begin to merge with it over southern Plains/Red River Valley
and into the northern portions of the Lower MS Valley. This will
enhance the mid level winds in that area. However due to this,
the trough axis will remain well northwest and north of the region
and from Tuesday afternoon through Wednesday morning there will
basically be no appreciable change in the mid lvls over our area.
H5 hghts and temps will generally remain steady; 579-582dm and
-10 to -11C respectively. At the sfc the developing sfc low along
the Lee of the Rockies mentioned earlier will lift to the
northeast across the Mid MS Valley by late afternoon and then
quickly to the NNE into the Upper Great Lakes before 6z! That is
moving quite fast and far to our north and then by Wednesday
morning the sfc low will slow down as it moves into southern
Ontario with the trailing cold front just starting to enter the
CWA around sunrise. Much like the mid lvl hghts, the sfc pressure
remains relatively steady as well, 1010-1014mb. At a quick glance
this is not generally our typical severe weather setup for the
northern central Gulf coast. That said there are a number of
parameters and ingredients that suggest if we can get a few potent
storms to develop the potential is there for some decent impacts.

First the thermodynamics are actually not lacking. Even though mid-
lvl temps don`t cool the LL temps do increase a touch and this
will lead to mid lvl lapse rates around 6.5 C/km. This will be
more of a nocturnal event for our area so the MLCAPE values will
be more representative and these could approach 1200 J/kg but
because this is overnight the 0-3km CAPE will not be very high but
could still reach 70 J/kg. The low level lapse rate is not too
impressive either and may approach 6 C/km. Showalters will be
around -3 to -4 C. This all suggest more than enough instability
available and its not just elevated.

The kinematic field is a little bit of a question mark though. There
are pros and cons with respect to severe weather. Winds will
increase and could be quite strong at multiple levels but the
position of the cores relative to our area may not be overly
favorable. First the LL jet get going overnight with h85 winds
increasing to 35-45kts maybe even approaching 50kt in southwest MS
but the core (which could be around 65-70kt) will be well off to
our north. This puts our area on the back end of the LL jet and
therefore leads to more LL diffluence. Looking at the jet setup,
this will run through TX, the upper portions of the Lower MS
Valley, and into the OH Valley. The stronger winds could be more
over the Red River Valley and into Arkansas and that could help
provide some slightly better diffluence aloft. Looking at the mid
levels, winds will gradually increase through the night from
around 35-40kt in the afternoon to just under 60kt around sunrise
over southwest MS. However the core which will be much stronger
(possibly 100-110kt) but it will be WELL north going from OK
towards the MO Bootheel. This leads to a lack of any real punch
into our area and just slowly increasing broad lift and that
strongest could be after 6z which looks like will be behind many
other peak parameters.

This wind field will lead to strong and favorable shear values but
again there could be some timing issues as the best SRH will be
around 00-06/09Z and the strongest mid lvl winds/support/forcing
looks to be around 6-12/15z. Winds will veer with hght through much
of the evening but the peak in turning will occur from 3-6/9Z. 0-1km
and 0-3km SRH respectively should range from 250-300 and 300-400
around 3 and 6Z across southwest MS and then slowly drop before LL
winds finally become more unidirectional after 9z. 0-6km bulk shear
is favorable and more than adequate ranging from 45-50kt all night
and this would help the potential for organized storms.

So looking at many of the parameters and indices there are numerous
things that point to the potential for high impact storms,
especially over southwest MS. SPC has included areas along and
northwest of a line from Tylertown, Ms to Denham Springs to New
Iberia in a Slight Risk with the rest of the region in a Marginal
Risk. Overall this doesn`t appear bad but do feel the Slight Risk is
a little larger than anticipated of our area. Too many features
point to the severe potential struggling for most of our area. First
and is just the synoptic setup which historically isn`t favorable.
The CIPS really only highlights one severe weather event and that
was the 1995 Veterans Day event which focused across north LA,
central MS, and across AR but there was one report of a tornado near
McComb. Other than that nothing else is showing up. We will be in
the unfavorable location with respect to the LL jet. The strong mid
lvl forcing will be well north with only gradual broad lift
occurring over the region and possibly the strongest forcing
occurring once we begin to lose the better shear values. So with
that overall at this time not overly impressed with the set up for
our area but this system is only just now coming into the upper air
network over the PAC northwest so we could see some slightly larger
changes in the next few model runs. Also will not ignore this system
by any means as we mentioned earlier even though the probability of
of something occurring appears low the potential for high impacts is
there.

So look for rain to begin to return Tuesday with embedded
thunderstorms and then greater potential for thunderstorms overnight
with the best chance for severe storms during the overnight hours
possibly as early as 3z but more likely after 6z. Remember it only
takes one storm and we saw that yesterday with the tornado over
Paradis

After sunrise things will quickly dry out and quiet down again.
through the remainder of the week we will see a ridge build over the
Gulf and into the southern Plains and Lower MS Valley Friday and
into the weekend. This will continue to keep the region dry and
likely start to warm things up some. /CAB/

&&

.AVIATION...
(12Z TAFS)
Issued at 453 AM CST Sun Nov 27 2022

TAFs will be quiet through this forecast. All terminals will remain
in VFR status with no impacts expected and likely not to return till
at the earliest overnight monday but more likely on tuesday. /CAB/

&&

.MARINE...
Issued at 453 AM CST Sun Nov 27 2022

Cold front has moved all the way into the northeastern and
central Gulf. With drier and slightly cooler air sliding in this is
continuing to keep winds elevated across the coastal waters but
these should begin to wane some this afternoon. High pressure
although weak will build across the area today and that should
finally get winds to fall below adv criteria later today with light
winds through tomorrow. By Monday night winds will already begin
to increase. High pressure will then be centered over the
Appalachians and a sfc low will begin developing over the CO/KS
border. This will cause winds to quickly return to onshore and
increase with headlines possible Tuesday. /CAB/

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  69  46  70  52 /   0   0   0   0
BTR  72  49  73  56 /   0   0   0   0
ASD  72  51  73  55 /   0   0   0   0
MSY  73  57  72  61 /   0   0   0   0
GPT  70  54  71  58 /   0   0   0   0
PQL  69  52  70  54 /   0   0   0   0

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...Small Craft Advisory until 1 PM CST this afternoon for GMZ530-
     532-534-536-538-550-552-555-557-570-572-575-577.

MS...None.
GM...Small Craft Advisory until 1 PM CST this afternoon for GMZ532-
     534-536-538-550-552-555-557-570-572-575-577.

&&

$$


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