[Alert]LIX issues Area Forecast Discussion (AFD) at Jan 7, 5:37 AM CST ...New SHORT TERM, LONG TERM, AVIATION, MARINE...

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LIX issues Area Forecast Discussion (AFD) at Jan 7, 5:37 AM CST ...New SHORT TERM, LONG TERM, AVIATION, MARINE...

387 
FXUS64 KLIX 071137
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
537 AM CST Tue Jan 7 2025

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

.SHORT TERM...
(Today through Wednesday Night)
Issued at 417 AM CST Tue Jan 7 2025

Quite the chilly 24 hrs it has been and well it will continue to
be quite chilly for at least another 48 with below normal
temperatures through the forecast. The main fcst problem in the 
next 36-48 hours is temperatures and where additional headlines
for wind chills and min temps will be needed.

Currently temps are ranging from the upper 20s to mid 30s however
some of the more typical cold spots have stalled as a thick layer
of stratus has drifted in from the east and is hanging across
portions of southern MS and just across the border into LA. After
sunrise this cloud deck should begin to slowly erode along the
edges and much of the region should see a fairly sunny day today
before thicker cirrus starts to filter in form the southwest
tonight. You can easily see these clouds coming out of the Pacific
and over Mexico on satellite but as we move into more zonal like 
flow later today and tonight the bulk of these thicker clouds may
hang just south of the area providing a more favorable rational
cooling night tonight. With a very dry airmass in store and chilly
afternoon highs as a starting point the stage is set for another 
cold night with actual lows likely colder tomorrow. We still won't
be in the greatest radiational cooling set up as those high 
clouds could impact and LL winds will still be a little on the 
high side. That could promote a little mixing causing the boundary
layer to not cool quite as fast. If those high clouds sneak in 
then that will also have some small impact on the temps. However 
it still looks like widespread freezing temps and even with winds
of 5-8 mph there is a good shot of getting wind chills values at 
or just below 20 across southwest MS and below 25 down to I-12 and
across I-10 over coastal MS. South of that temps should have 
little problems falling to near or just below freezing. Not 
everyone will get below freezing across the south but a majority 
of the area will. With those temps and wind chills the current 
Cold Weather Adv and Freeze Watch look good and remain in place. 

Wednesday the pattern begins to amplify as a strong disturbance
already working south across the west coast deepens and digs into
the Baja. This low will close off and continue to dig up halfway
through the Baja by late Wednesday. Some weak s/w ridging over TX
and into the southern Plains should push the jet off to our
northwest and with that the cirrus likely lifts north with
generally clearing skies during the evening hours. This could set
the stage for possibly the coldest night of about half of the CWA
as radiational cooling conditions may be the best we will see
over this stretch. High pressure at the sfc will have built in
sufficiently and is starting to slide east this generally allows
for a better cold air drainage setup. Combine that with light
winds and likely clearing skies initially and we could cool off
very quick. This night has the potential to be very cold for the
northeastern half of the CWA with widespread lower to mid 20s
possible. With that additional Cold Weather Adv and Freeze 
Watch/Warnings will likely be needed for some areas Wednesday 
night. That said, this is highly dependent on two things. The baja
low and how fast/slow it wants to begin lifting out and the
associated sfc low that is expected to develop with it. Models
have trended slower and this could lead to conditions remaining
more favorable for a much colder thursday morning than previously
advertised and that could also come into play with the forecast
for Thursday now. /CAB/

&&

.LONG TERM...
(Thursday through Monday) 
Issued at 417 AM CST Tue Jan 7 2025

This forecast for Thursday through Friday night continues to
become problematic but interesting. Models continue to come into
better agreement with timing and location of features but they are
also coming into better agreement with a very impactful forecast
across the south with winter weather likely to wreak havoc on
portions of the ARKLATEX and ARKLAMISS however the winter weather
is not the only concern. Locally heavy rain could become quite 
the concern for the portions of the Gulf coast. 

It is beginning to look more and more likely that a sfc low will
begin to take shape along the lower and central TX coast Thursday
and slowly work NNE-NE Thursday evening before turning more to the
ENE-E early Friday. This southern and slower shift in some of the
models makes sense given the L/W trough digging more and moving 
slower. As additional energy keeps riding south down the back side
of the L/W trough it will continue to try and anchor the base of
the trough back to the southwest with a very positive titled
trough axis laying out from the Great Lakes back to the Baja. The
slow progression of this L/W trough and increasing southwest flow
aloft will have a strengthening mid lvl jet across TX and through
the Lower MS Valley Thursday night and through Friday with mdls
now advertising 110 kts across LA and MS Friday evening. This
increasing energy will help with the development of the sfc low
but with the very positive tilt to the trough and associated mid
lvl energy we will see the LL winds respond with a h85 jet around
45-50 kts developing Thursday night and Friday across southeast LA
and moving east through coastal MS. This is providing rather
extreme LL WAA and strong LL convergence across our entire CWA
with the nose of the jet moving east across the northern half of
the CWA just off to the north and northeast of the sfc low. The
sfc low will take a more ENE to east turn following the strong 
WAA along coastal LA. Very strong upper lvl jet energy will race 
out across the southern Plains and through the Mid MS Valley and 
into the TN Valley towards the Tobacco Rd area Thursday night and
then stretch across all of the Lower MS Valley through Mid 
Atlantic States as well as strengthen. This is going to provide 
ample divergence aloft over top the strong LL jet. With this 
dynamic of a system and the very strong kinematic field and setup 
moisture is going to surge into the area quickly Thursday night 
and through Friday with some of the models now trying to indicate 
PWS greater than 1.75". This would be close if not a record 
depending on the day. It is well abv anything we have measured on 
Jan 10th but we have 1 measurement on the 11th at 1.86" in 2020 
and 00z on the 12th at 1.97" in 2013...otherwise every other 
measurement from the 10th and 11th is below 1.67. So yeah that is 
a lot of moisture to work with along with a lot of favorable jet 
dynamics and lift. The only thing that is lacking is instability.
I would not anticipate any sfc based instability inland given the
track of the sfc low but even elevated instability appears to be 
lacking. However given the time of the year the very cold air 
currently in place and the deep L/W trough with a very shallow 
positive slope it makes sense that we will likely be dealing 
moderate to heavy showers. Now that is not to say there may not 
be a rumble or two of thunder and given the highly dynamic set up,
slantwise convection could help to provide some elevated 
instability leading to a few embedded thunderstorms.

So with all of the said, the concern is increasing that locally 
heavy rain is likely going to impact portions of southeast LA and 
southern MS. There is a Marginal Risk for Excessive Rainfall 
across pretty much the entire CWA but this is likely just the 
beginning to stepping up the risk as it wouldn't be a shock to see
some portions of the area under a Slight Risk later today or more
likely tomorrow night. Without getting to detailed in locations 
because small adjustments will make large differences in impacts 
it does looks like a rather heavy band of rain will develop to 
the north and northeast of the sfc low Thursday night and through 
a good chunk of Friday. That band at this time could set up from 
southwest LA across the FL parishes and southwest MS and then 
slowly slide east over that time. Widespread rainfall of 1-3 
inches are currently forecast across the entire CWA but if this 
develops like we are beginning to think that band could easily be 
more like 3-5 with isolated higher amounts from Thursday through 
Friday night. Now 3-5 inches of rain over 24-to 36 hrs is not 
outrageous for our area however given the very cold temperatures 
we will have been dealing with in the preceding 72 hours the 
ground will not absorb that rain and we could easily see rain 
quickly runoff leading to some local flooding concerns. 

As for winter weather concerns. With the later arrival of rain it
should allow the area to warm up enough Thursday that all rain
could be liquid. But and there is a but, the LL will still be very
dry and if cloud cover holds off all night Wednesday night
allowing the area to just bottom out for Thursday morning. Then 
if the clouds quickly try to move in around sunrise that would 
really hurt the daytime heating and any initial showers could 
still lead to some light wintry mix, most likely freezing 
drizzle/rain. That would be very short lived and as we have 
mentioned the impacts would be more wow and conversational and not
hazardous. The slow increase in moisture and virga light rain 
will not lead to strong evaporative cooling and will moisten up 
the Lower levels of the atmosphere more so than provide much if 
any cooling. We still need to watch closely as any more southward 
shifts or faster approach of the heavy rain could lead to stronger
evaporative cooling especially northwest areas. /CAB/

&&

.AVIATION...
(06Z TAFS)
Issued at 1143 PM CST Mon Jan 6 2025

In general, winds have been dying down as the boundary layer
decouples tonight. The two sites that will stick with the elevated
winds are MSY and NEW as the north wind off the frictionless Lake
keeps it from decoupling like the rest of the area. Otherwise, dry
air will keep VFR conditions around throughout the entire forecast
period. /JZ/

&&

.MARINE...
Issued at 417 AM CST Tue Jan 7 2025

Still a little breezy on the waters this morning and with that SCY
and SCS headlines have been extended till noon. After that winds
should relax enough as high pressure builds in. This should
provide more optimal marine conditions through Wednesday evening.
Heading into Thursday winds and seas will begin to ramp back up
and become hazardous through the rest of the week. A Gulf low is 
forecast to develop and move into the region and bring multiple 
impacts to the area. /CAB/

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  44  24  45  23 /   0   0   0   0 
BTR  49  28  50  29 /   0   0   0   0 
ASD  49  25  51  25 /   0   0   0   0 
MSY  48  35  49  34 /   0   0   0   0 
GPT  48  29  50  27 /   0   0   0   0 
PQL  51  26  53  24 /   0   0   0   0 

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Cold Weather Advisory until 9 AM CST this morning for LAZ034>037-
     039-046>048-056>060-064>071-076>090.

     Cold Weather Advisory from midnight tonight to 9 AM CST 
     Wednesday for LAZ034>037-039-046>048-071-076-079>084.

     Freeze Watch from late tonight through Wednesday morning for 
     LAZ056>060-064>067-077-078-085>090.

GM...Small Craft Advisory until 8 AM CST this morning for GMZ530-532-
     534.

     Small Craft Advisory until noon CST today for GMZ536-538-550-552-
     555-557-570-572-575-577.

MS...Cold Weather Advisory until 9 AM CST this morning for MSZ068>071-
     077-083>088.

     Cold Weather Advisory from midnight tonight to 9 AM CST 
     Wednesday for MSZ068>071-077-083>088.

GM...Small Craft Advisory until 8 AM CST this morning for GMZ532-534.

     Small Craft Advisory until noon CST today for GMZ538-550-552-555-
     557-570-572-575-577.

&&

$$

SHORT TERM...CAB
LONG TERM....CAB
AVIATION...JZ
MARINE...CAB

Source: LIX issues Area Forecast Discussion (AFD) at Jan 7, 5:37 AM CST ...New SHORT TERM, LONG TERM, AVIATION, MARINE...

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