357
FXUS64 KMOB 121211
AFDMOB

Area Forecast Discussion
National Weather Service Mobile AL
610 AM CST Wed Feb 12 2025

...New AVIATION...

.AVIATION...
(12Z TAFS)
Issued at 610 AM CST Wed Feb 12 2025

IFR to VLIFR ceilings will slowly become MVFR ceilings today with
widespread showers and thunderstorms likely occurring through
most of the day. The best chance for impactful thunderstorms will
be mainly north of I-10, especially along the highway 84. Some
storms could be severe this afternoon with damaging winds and
potentially a tornado or two. Ceilings will drop to IFR tonight as
a line of strong to severe thunderstorms moves in from the west
along an approaching cold front. Low level wind shear will be
present at around 40 knots at 2kft out of the southwest. Storms
will progress from west to east mainly after midnight resulting in
in reduced visibility`s, gusty winds and IFR to VLIFR ceilings.
BB-8

&&

.PREV DISCUSSION... /issued 449 AM CST Wed Feb 12 2025/

..New NEAR TERM, SHORT TERM, LONG TERM, MARINE...

NEAR TERM...
(Now through Thursday night)
Issued at 449 AM CST Wed Feb 12 2025

Two rounds of strong to severe storms are expected today along
with the potential for localized heavy rainfall.
A HIGH risk of rip currents and a HIGH Surf Advisory will also
begin Wednesday and persist through the week. For information on
each hazard, please reference the appropriate section of the
discussion.

Synopsis...A rather broad longwave upper trough with two embedded
shortwaves will move into the eastern US today through Thursday.
The two embedded shortwaves will be the focus for our two
possible rounds of strong to severe storms this afternoon and
evening. The first shortwave is already starting to slowly
overspread the deep south as increased showers have begun to
overspread areas to our west. The second shortwave will quickly
follow on it heels late this afternoon and into the overnight
hours before lifting out of the area by Thursday morning. At the
surface, a surface boundary from yesterdays system has sagged as
far south as Mobile county this morning. This boundary will
quickly begin to lift northward this morning in response to the
approaching shortwave. South of the boundary, rich Gulf moisture
will surge northward on the back of a strengthening low level
jet. Based on current guidance we expect this boundary to lay out
west to east mainly around the highway 84 corridor. Where this
front ends up will play a big role on the potential for more
significant severe potential. Nonetheless, the first round of
strong to severe storms should begin by early afternoon along this
boundary zone. By late afternoon into the evening, the first
shortwave will lift out as the final shortwave enters from stage
left. This will be the final push during the overnight hours. More
widespread thunderstorms will develop along the rapidly
approaching cold front, a pre- frontal trough and the warmfront
itself. Depending on the location of the warmfront/modified
outflow boundary from the afternoon round, storms south of the
boundary would pose a severe risk throughout the night.

By Thursday morning, the longwave upper trough will push through
as the shortwave trough lifts out to the northeast. This will
allow for the cold front to clear the area ending all rain
chances. Cooler temperatures will arrive in the fronts wake as dry
conditions prevail on Thursday. BB-8

Severe storms...After yesterdays Gulf coast "surprise" the last
thing any of us want to talk about is another round of severe
weather yet here we are talking about two with the potential for
significant severe. The forecast has certainly trended more
concerning since last night; however, there still remains a lot
of moving parts that could limit the severe potential this
afternoon and evening.We are looking at two separate waves of
strong to severe convection to occur Wednesday afternoon and
overnight Wednesday.

The first will be mainly across that same highway 84
corridor during the mid/late morning into the mid/late afternoon
hours. This will likely be along that stalled warm frontal zone
that will likely end up around the highway 84 corridor by midday
today. The tricky part about this will be the difference between
surface based storms capable of damaging winds and tornadoes and
elevated storms capable of hail. With how tight the gradient
across the boundary will be, these two areas could only be
separated by a few miles. North of this boundary elevated storms
will likely be ongoing with the potential for some small hail
given marginal mid-level lapse rates, weak storm relative inflow
and strong deep layer flow. I would not be shocked to see a couple
hail reports Wednesday mainly north of highway 84. One
thing to note is that general storm mode will likely be
north/northeasterly which will promote storms crossing the
boundary quickly. This may limit the severe potential as storms
may struggle to organize before crossing and becoming elevated. If
this were to happen then the afternoon severe treat could be
limited. However, CAMs continue to generally becoming more robust
on the development of adequate instability near and south of the
Highway 84 corridor, with ample shear in place as the shortwave
begins to move across the region. Robust low level instability and
sfc- based CAPE will be present, with 3km CAPE values in the 100
to 150j/kg range and sfc-based instability on the order of 1,000
to 1,500j/kg. This combined with 50 to 60 knots of deep layer
shear and large, curved hodographs yielding 1km and 3km SRH values
on the order of 200-250 m2/s2 and 300 to 350 m2/s2 will promote a
severe weather threat with potential hazards including damaging
wind gusts and tornadoes. IF, a storm can become more established
prior to reaching the boundary zone, the kinematics and
thermodynamic environment would likely also support the potential
for a significant tornado or two (EF-2+). The afternoon certainly
has a high ceiling if storms can stay on the unstable side of the
boundary and take full advantage of the environment in place. As
mentioned, the fine line between seeing nothing and seeing
significant severe storms this afternoon along the highway 84
corridor is incredibly small and it will not take much for things
to escilate significantly.

The evening into overnight hours Wednesday night will be the
trickiest part of the forecast. A more substantial shortwave will
move across the area and the cold front will begin approaching from
the west. Afternoon convection will likely dictate the exact
positioning of the surface warm front/stalled boundary, which will
be one of the foci for more robust storm development early on where
semi-discrete supercells could materialize. Likewise, the
presence of a pre-frontal trough may also help instigate more
isolated thunderstorm development nearer the I-65 corridor,
however this may be removed far enough from better forcing for
ascent to help mitigate a more robust severe weather potential
there. Guidance does vary quite a bit on the exact evolution of
these features as they hinge on the evolution of the afternoon
convection. The further north the initiating boundary is, the
better the forcing that will be present for the development of
convection. Most the guidance is generally in agreement on the
eastward progression of the cold front; however, vectors become
parallel to the initiating boundary and any convection along the
front may struggle to remain surface based and repeatedly become
undercut. Our main focus will likely turn towards the
aforementioned pre-frontal trough and positioning of the warm
front/stalled boundary for any more robust severe potential.
Overall environment will remain sufficient for organized severe
weather with around 1,000j/kg of surface based instability
maintaining itself into the overnight hours and large, curved
hodographs maintaining similar shear and SRH values as the prior
shortwave had to work with. Given this, the expectation would be
for a continued threat of damaging winds and tornadoes in any of
the more robust convection. Models seem to agree on forcing
lifting out during the mid to late overnight hours with a decaying
line of showers and storms prior to daybreak east of the I-65
corridor. Overall, it appears the greatest threat for severe
weather will remain in the vicinity of the Highway 84 corridor,
with a diminishing threat with southward and eastward extent as
better forcing remains over interior counties. BB-8 MM/25

Heavy rainfall...Heavy rainfall appears to be a hazard that has
slowly become more concerning over the last 12 hours or so. I will
start with this overall setup does not necessarily support a
widespread heavy rainfall threat, especially given our rather dry
antecedent conditions. The problem is that recent guidance has
supported the potential of training convective storms over the same
areas for several hours in a row. With PWATS around 1.5 to 1.75
inches and deep instability, warm rain processes will be able to
produce rather efficient rainfall rates. These rates coupled with
storms training over one another along the aforementioned
boundary zones can quickly pile up the rainfall if things don`t
move. Most of the area will likely get a nice 1 to 3 inches of
rain with 2 to 4 inches across our northern tier of counties. Our
concern is in the higher ceiling totals that could occur. Some
guidance this morning has highlighted some areas that could see
up to 6 to 8 inches. The issue is that where that occurs will be
very localized and where that happens (if it happens) is
impossible to pin down until its almost happening. Given the
localized nature of that potential and the overall dry conditions,
we have elected to not go with a Flood Watch for flash flooding.
However, some flash flooding could occur this afternoon and into
the evening as heavier rain rates overwhealm dry conditions. BB-8

Other Hazards...On top of the severe storms and flooding, we have
the usual suspects to contend with along our coastal areas. Given
a stout southerly wind, surf heights will build to around 4 to 6
feet leading to dangerous surf conditions and a High Risk of rip
currents. Also gusty winds will be possible this afternoon as the
low level jet strengthens leading to wind gusts around 30 mph this
afternoon. While this is below advisory criteria, it is enough to
make driving across areas bridges a littler hairy.

BB-8

LONG TERM...
(Friday through Tuesday)
Issued at 449 AM CST Wed Feb 12 2025

Upper-level troughing over the western US at the start of the
period will quickly move across the southern US through Sunday
before exiting into the western Atlantic by Monday. Out ahead of
it, a persistent southwesterly flow pattern aloft will continue
through Sunday morning before becoming more zonal after it passes
overhead. At the surface, a frontal boundary, which passed through
the area during the near term, will lift back to the north as a
warm front Friday night. After passing, ample moisture advects
into the area from the Gulf, with ensembles painting high
probabilities of PWATs greater than 1.3 inches (these values are
more than 2 standard deviations above climatological norms for
this time of year) and dewpoints greater than 65 degrees across
the area for Saturday. As the upper trough approaches the area, a
strong cold front is expected to approach and sweep through the
local area sometime late Saturday into Sunday morning. Behind it,
a cooler, drier airmass filters in for the remainder of the
extended period.

We continue to monitor the potential for severe weather sometime
Saturday night as the cold front moves through the area. Guidance
continues to suggest broad diffluence aloft and strong deep layer
shear across the Deep South as the upper trough takes on a more
neutral tilt and ejects northeastward. Factoring in a potent LLJ (on
the order of 50 to 60 knots), modeled hodographs are curved and
rather large, supportive of streamwise vorticity ingestion from the
surface all the way through the mid-levels. Instability also looks
favorable, with ensembles suggesting that CAPE values will likely
exceed 500 J/kg and select deterministic runs suggesting around 1000
J/kg. Assuming the typical cool season low-end bias that global
models tend to have with instability, I feel that once we get into
the range of the CAMs, these values will likely increase further
given the strong WAA regime in place and long recovery time. Putting
these together suggests that the environment will be supportive of
storm organization and robust, rotating updrafts.. primed for an all-
hazards severe weather event. One question that is still left
unanswered is storm mode. Ridging/subsidence may hold long enough to
limit discrete cell development out ahead of the cold front,
suggesting that the cold front may act as the primary focus for
storm development. This would lead to the primary mode being a
potent and quick-moving QLCS. However, it should be stressed that if
ridging is a bit weaker and there are other low-level boundaries in
place (ie pre-frontal troughs, confluence zones, etc), the
environment would be supportive of discrete supercells, possibly
resulting in a higher-end event. CAMs should hopefully resolve this
once the event gets into their time range, so we will continue to
monitor trends closely over the coming days. As far as risk area,
CIPS Analogs and CSU-MLP probabilities continue to show a strong
severe signal across the entirety of the Deep South, extending
across our local area. The latest Day 4 outlook from SPC has a newly-
added 30% risk area extending from Louisiana to central Alabama.
This area does clip our northwestern-most zones. The remainder of
the area is under a 15% risk area. Further refinements of the risk
area can be expected over the coming days, and once we get CAM
guidance, timing and impacts can be discussed in greater detail. /96

MARINE...
Issued at 449 AM CST Wed Feb 12 2025

Patchy dense marine fog has formed across Mobile and
Pensacola bays this morning. Onshore flow continues to strengthen
this morning, lingering through late Wednesday night. Moderate to
occasionally strong offshore flow follows in the wake of a cold
frontal passage Thursday. Moderate, to at times strong onshore
flow returns ahead of the next system this weekend, with moderate
to strong offshore flow returning Sunday following the passage of
a strong cold front. A Small Craft Advisory goes into effect this
morning through Wednesday night, with additional Small Craft
Advisories likely needed throughout the late week into the weekend
timeframe. BB-8

&&

.PRELIMINARY POINT TEMPS/POPS...
Mobile      79  56  68  42  65  57  76  56 /  80  90  20   0  20  20  20  90
Pensacola   76  62  71  47  65  60  74  62 /  50  90  50   0  20  20  10  90
Destin      75  63  71  50  66  61  72  64 /  40  90  60  10  20  10  10  80
Evergreen   80  56  67  39  67  52  77  57 /  80  90  20   0  10  20  20  90
Waynesboro  79  48  62  36  65  52  78  51 /  90  90   0   0  10  30  30 100
Camden      78  50  62  37  66  52  76  53 /  90  90  10   0  10  30  20  90
Crestview   79  61  72  43  68  54  76  61 /  60  90  50   0  20  10  10  80

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...High Rip Current Risk through late Thursday night for ALZ265-266.

     High Surf Advisory from noon today to noon CST Thursday for
     ALZ265-266.

FL...High Rip Current Risk through late Thursday night for FLZ202-204-
     206.

     High Surf Advisory from noon today to noon CST Thursday for
     FLZ202-204-206.

MS...None.
GM...Dense Fog Advisory until 9 AM CST this morning for GMZ630>632-
     634.

     Small Craft Advisory until midnight CST tonight for GMZ670-675.

&&

$$

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