LIX issues Area Forecast Discussion (AFD) at Feb 7, 1:16 PM CST ...New AVIATION...263
FXUS64 KLIX 071916
AFDLIX
Area Forecast Discussion
National Weather Service New Orleans LA
116 PM CST Fri Feb 7 2025
...New AVIATION...
.SHORT TERM...
(Today through Saturday)
Issued at 346 AM CST Fri Feb 7 2025
Fog this morning will likely be more dense than it has been so far
this week. A low level strat deck has moved in just under the bottom
of the sub inversion at 1004mb. This layer under the inversion is
about 400ft thick. The 1004mb sub inversion has a strong wet bulb
drying as well. ThetaE numbers are very good. Winds are veering off
the sfc and winds just off the sfc are transporting air from the SW
which is high dew pt high RH air from the gulf. Since the winds at
the sfc are basically calm, the transport is occurring above the sfc
and has to cool via radiative processes. SST are about the same temp
as the dew pt temp of the incoming air within this 400ft layer,
therefore the sfc can support but not produce. But, when we look
upward in the sounding profile we can see very well where this
cooling is coming from. Basically, this pattern is part advective
and part radiation. The advective part has been explained. The
radiative part is from two levels. The first is the sub inversion at
1004mb where the heat from the 300ft deck can escape efficiently.
This causes the low level cloud deck to cool and lower as time moves
forward. Earlier there was a 7kft deck that can still be seen with
sat imagery moving over the SE portion of the area. This deck is
responsible for the lower 300ft deck not being able to make it to
the sfc and so vis is higher under this 7kft deck. The reason for
this is the 7kft deck slows the radiative heat exchange from below
to a crawl. Even though the sub inversion above the 7kft deck has
a huge wet bulb drop of 9C through a deep layer, the radiative
heat has to pass through this upper deck first which slows this
process to a crawl. But when this 7kft deck moves away, the
cooling through this layer is so efficient and quick that vis
rapidly falls to 1/4 mile or less as the lower 300ft deck hits the
sfc. This sounding profile is also a strong super fog sounding
indicated by these two strong sub inversions with strong wet bulb
falls. This is very typical of a build down fog regime. It acts
like a conveyor, whereas the moisture and heat is brought in on SW
winds above the sfc beneath the lowest sub inversion. The heat is
then lost upward through the inversions, the strat deck cools and
sinks and as the droplets are accumulating on everything taking
moisture out of the air, it is replenished by this conveyor
process. The reason we call this a super fog process is that any
additional particulate matter, such as smoke from fires, will add
to the condensation process much faster producing an extreme
amount of droplets causing vis to go rapidly to zero where these
additional aerosols are located. This is compounded by a stalling
front, which is also a good fog producer, over southern Arkansas
to central Miss this morning. This front will move back north
tonight while another front starts to move toward the area Sat.
This front will begin to slow late Sat into Sat night. This does
not help with the fog problem and successive nights of dense fog
is likely through the weekend.
&&
.LONG TERM...
(Saturday night through Thursday)
Issued at 346 AM CST Fri Feb 7 2025
There is very little upper level support for the cold front moving
in for Sun as the H3 jet begins to parallel the sfc boundary. This
means the front will creep into the northern most portion of the
area and meander around at best. Basically we should just see a few
light showers and fog around. The front will stall over the northern
most part of the area Sun night into Monday. A digging trough will
give some forcing to this boundary as it draws it slowly northward
Mon night into early Tue. Another front will move in as the upper
support begins to lift out causing this thermal boundary to move
back over the same area and maybe even deeper into our area by Wed.
This time there could be some storms with it as the support begins
to lift out. As the pattern becomes more progressive, this front
will stall then get brought north and again another frontal system
moves in to possibly clear all this mess out toward the end of next
week.
&&
.AVIATION...
(18Z TAFS)
Issued at 1244 PM CST Fri Feb 7 2025
Greatest concern with TAFs will be fog and low clouds again
tonight. Both are expected to quickly develop and move back inland
this evening and by midnight or shortly after most terminals will
be back in IFR or even LIFR status from either cigs or vsbys and
likely both. Marine fog and low clouds will develop fastest among
terminals that are on the immediate coast like NEW and GPT with
impacts possibly as early as 2/3Z. Fog will quickly move into
those sites and then 1/4sm vis or lower may plague those two
locations for 10-12 hours. OVC and BKN cigs will also be around
800-1k ft early this evening and then continue falling through the
night. MSY will quickly follow behind these two and then the rest
of the area will see conditions deteriorate. Conditions much like
this morning will be slow to improve with the most inland
terminals improving the fastest and NEW and GPT seeing impacts
last the longest. /CAB/
&&
.MARINE...
Issued at 346 AM CST Fri Feb 7 2025
Light southerly winds will remain into the first half of next week
and should also remain 15kt or less. Fog is expected to be an issue
for some coastal waters mainly in the nearshore waters and
especially the Miss River nightly. Most if not all of the Miss River
will have dense fog through mid morning today. The dense fog
advisory will remain for all protected and nearshore waters through
10 am today. There is the possibility that some marine areas hold
this fog for a large portion of the day. Marine roadways will be
impacted as well.
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 61 81 62 79 / 0 0 0 10
BTR 65 84 65 83 / 0 0 0 10
ASD 63 81 62 80 / 0 10 0 10
MSY 64 80 63 79 / 0 10 0 10
GPT 60 72 60 75 / 10 20 10 10
PQL 62 78 60 79 / 0 10 10 10
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...Dense Fog Advisory until 2 PM CST this afternoon for GMZ532-534-
536-538-555-557.
MS...None.
GM...Dense Fog Advisory until 2 PM CST this afternoon for GMZ534-536-
538-555-557.
&&
$$
SHORT TERM...TE
LONG TERM....TE
AVIATION...CAB
MARINE...TE
Source:
LIX issues Area Forecast Discussion (AFD) at Feb 7, 1:16 PM CST ...New AVIATION...---------------
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