LIX issues Area Forecast Discussion (AFD) at Feb 11, 8:48 PM CST ...New UPDATE...060
FXUS64 KLIX 120248
AFDLIX
Area Forecast Discussion
National Weather Service New Orleans LA
848 PM CST Tue Feb 11 2025
...New UPDATE...
.UPDATE...
Issued at 825 PM CST Tue Feb 11 2025
Frontal boundary based on radar, temperatures and winds, appears
to be near a Poplarville-Madisonville-Gonzales line at 8 PM CST.
Temperatures at that time ranged from the upper 50s across the far
northwest to lower and mid 70s ahead of the front. Areal coverage
of precipitation has diminished a fair amount over the past hour
or so.
Frontal boundary is becoming parallel to the upper flow, so it
shouldn't make a lot more eastward progress. But then...it wasn't
supposed to be as far east as it is at mid-evening. As shortwave
exits Mexico into Texas later tonight, front should begin to
retreat northward, and be north of the CWA by mid-morning at the
latest. That means for most of the area, temperatures may already
be close to their overnight lows, and could rise after midnight.
Did not make changes beyond sunrise Wednesday at this time, but
would note that thunderstorms could be approaching the northwest
corner of the CWA by sunrise or shortly after. The main threat of
severe weather would be later in the day, but even in the morning,
we'll need to monitor.
Will issue a ZFP update as well as the usual marine update in the
next 20-30 minutes.
&&
.SHORT TERM...
(This evening through Thursday night)
Issued at 219 PM CST Tue Feb 11 2025
A fast moving southern stream shortwave trough and attendant cold
front projected to pass through the area tomorrow into tomorrow
night will be the primary feature impacting the forecast through
the short term period. Another weaker shortwave passing through
the area currently will provide a period of shower activity to the
region through the overnight hours. The showers will be most
pronounced across southwest Mississippi with more isolated to
widely scattered activity further to the south. Fortunately, a
lack of decent instability has limited storm development with no
thunderstorm activity noted in the area this afternoon even as
temperatures warm into the lower 80s. Lows tonight will be mild as
southerly winds usher in a much warmer and more humid airmass, but
fog is not expected as wind speeds remain around 10 mph through
the night.
The next feature, as mentioned earlier, will begin to impact the
forecast area by the afternoon hours as strong deep layer forcing
interacts with a more unstable environment. This instability will
be supported by some mid-level cooling that will increase lapse
rates to around 6.0C/km tomorrow afternoon and evening. As these
lapse rates improve, mixed layer CAPE values will increase to
around 1000 J/KG, and this will be enough instability to support
some deeper updraft development. Additionally, the front moving
into the area will serve as a low level focusing mechanism for the
convection, and fully expect to see a convective line of
thunderstorms move in from the west by the late afternoon hours
across the western zones. Another area of convection is likely to
form out ahead of this line along a weak pre-frontal trough axis
draped across the I-12 corridor. This initial convection will tap
into a highly sheared environment as noted by 0-3km speed shear of
nearly 60 knots and some directional shear of around 200 m2/s2
tomorrow afternoon and evening. This period in the mid to late
afternoon and early evening hours could see a few severe storms
form, and the primary threat looks to be strong damaging wind
gusts. An isolated tornado may also form as any storms try to bow
out.
The main caveat with the initial convective activity is that
it is very likely going to lead to a region of increased low level
stability, and this will limit the severe potential heading into
the late evening and overnight hours. This is very evident in
model sounding analysis with the LCL and LFC rising above 850mb
and overall MLCAPE dropping below 500 J/KG. Additionally, the
greatest forcing and best shear will also be shifting out of the
area by 03z. However, there is a concern that the mean storm
motion will start to the match the orientation of the front
between 03z and 06z, and this will could lead to a period of
training thunderstorms producing heavy rainfall along the MS coast
and the southshore of Lake Pontchartrain. PWATS of near 1.5 inches
are also supportive of an increased late evening and early
overnight flood threat, and could support hourly rainfall rates of
1 to 2 inches per hour. After 06z, the threat will begin to shift
offshore as the parent trough axis pulls further away and the
front continues to move to the southeast.
Conditions will rapidly improve on Thursday as the front stalls
offshore with only some lingering coastal showers expected. Cooler
air will also be advecting into the region with temperatures
largely near average for this time of year. The flow aloft will
remain out of the southwest, so skies will be mostly cloudy as
moisture continues to stream into the upper levels.
&&
.LONG TERM...
(Friday through Monday night)
Issued at 219 PM CST Tue Feb 11 2025
Another weak shortwave trough will slip through the area on
Friday, but continued northeast flow in the low levels will keep
things fairly stable. The end result will be more of an
overrunning rainfall event with scattered showers throughout the
day. Temperatures will remain near average with readings warming
into the mid 60s during the afternoon hours. As this trough ejects
to the east, a surface high will also shift to the east and allow
for a more southerly flow regime to develop during the overnight
hours. A surge of warmth and moisture will sweep in and push
overnight lows into the 50s and lower 60s, but winds will be
strong enough to keep advection from forming.
Saturday will be warm and breezy in advance of a deepening
longwave trough axis, but overall conditions should be dry through
at least the early afternoon hours. Temperatures will be very warm
with highs easily climbing into the low to mid 80s over inland
areas and the upper 70s along the coast. These values will be near
or above record levels. A strengthening low level jet through
the day and ample boundary layer mixing will support very breezy
conditions on Wednesday with southerly winds of 20 to 25 mph and
gusts to 35 mph in the cards.
The main show will take place Saturday night as the longwave
trough begins to eject out of the southern Plains and takes on a
more negative tilt. Very favorable shear and ample instability as
noted by MLCAPE of 1500 J/KG should support a round of strong to
severe thunderstorms in advance of the front during the overnight
hours. All convective modes and threats appear to be possible at
this point, and this will be further refined as we get closer to
the weekend. Fortunately, this will be fast moving threat, so the
heavy rainfall concerns on Saturday night are more limited.
The front and parent trough will quickly pull east early Sunday
and strong subsidence will take hold. Skies will rapidly clear
through the morning hours, but a much colder airmass will be
advecting into the area. Temperatures will be below average on
Sunday and Monday as a 925mb thermal trough axis transits through
the region. Highs will only warm into the 50s on Sunday before
rebounding back to more average values on Monday, and overnight
lows will dip into the 30s Sunday night. A light freeze has a high
potential of occurring over the northern half of the forecast
area.
&&
.AVIATION...
(00Z TAFS)
Issued at 543 PM CST Tue Feb 11 2025
Cold front at forecast issuance time was near a K0R0 (Columbia,
MS) to KBTR to KLFT line, with winds shifting from SW to NW and a
significant temperature drop. While terminals were VFR at
issuance, except MVFR at KMCB, expect conditions to deteriorate
this evening, with most at MVFR to IFR by 06z. Scattered SHRA
expected overnight, with any significant threat of TSRA not
increasing until about midday Wednesday. Don't have high confidence
in timing of a 2 hour window for TSRA at any particular terminal
at this time. Will not be able to totally eliminate TSRA threat
until beyond 06z Thursday, and maybe not that soon.
&&
.MARINE...
Issued at 219 PM CST Tue Feb 11 2025
Rough conditions will be the rule through the weekend as a series
of fast moving storm systems impacts the region, and small craft
advisories are now in effect for the open Gulf waters starting
tonight. Winds will range between 15 and 25 knots with higher
gusts and seas of 5 to 8 feet are expected in the offshore waters
through the period with waves of 3 to 5 feet in the sounds and
lakes.
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 58 82 49 61 / 90 80 80 10
BTR 59 83 54 64 / 70 80 70 10
ASD 66 83 57 68 / 60 80 100 20
MSY 67 82 59 67 / 50 70 90 20
GPT 64 76 58 70 / 60 70 100 30
PQL 67 79 59 71 / 50 70 100 40
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...Small Craft Advisory from midnight tonight to 6 AM CST Thursday
for GMZ550-552-570-572.
Small Craft Advisory from 6 AM Wednesday to 6 AM CST Thursday
for GMZ555-557-575-577.
MS...None.
GM...Small Craft Advisory from midnight tonight to 6 AM CST Thursday
for GMZ552-570-572.
Small Craft Advisory from 6 AM Wednesday to 6 AM CST Thursday
for GMZ557-575-577.
&&
$$
SHORT TERM...PG
LONG TERM....PG
AVIATION/UPDATE...RW
MARINE...PG
Source:
LIX issues Area Forecast Discussion (AFD) at Feb 11, 8:48 PM CST ...New UPDATE...---------------
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