549
FXUS64 KMOB 121032
AFDMOB

Area Forecast Discussion
National Weather Service Mobile AL
532 AM CDT Sun May 12 2024

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

.NEAR TERM...
(Now through Monday)
Issued at 532 AM CDT Sun May 12 2024

Break time is over as we head back into another active pattern to
start the week. Broad southwesterly flow will develop over the
area as a rather deep upper level low ejects out of the Desert
Southwest into the central Great Plains. A rather flat ridge will
be in place across the southern Gulf which will help pump moisture
northward slowly by Monday. At the surface, a warm front will
attempt to lift northward ahead of this system late tonight into
early Monday morning as moisture rapidly improves. PWATS will
climb to around 1.8 to 2.0 inches with PWATS south of the warm
front approaching 2.25 inches. With the ridge in place, expect
today to remain mostly dry; however, weak ascent over the warm
front may lead to some overrunning showers especially this morning
but rain overall should be light and isolated. Monday will be the
main event with multiple rounds of showers and storms. Heavy
rainfall appears to be the primary threat with also the potential
for strong to severe storms capable of all severe hazards. Storms
will likely continue into Monday night as the upper trough pivots
into the Mid-Mississippi valley.

Heavy Rainfall...Heavy rainfall appears to be the greatest threat;
however, there are confidence issues on where the heaviest rainfall
will fall. The overall setup supports somewhere in the general area
getting whacked with some heavy rainfall. You have the classic setup
with high PWATS, warm tropical rain processes, deep instability, a
low level jet perpendicular to the initiating boundary advecting
moisture towards the boundary with strong convergence and deep layer
flow/shear parallel to the boundary to support training. The main
question at play is where the heck this boundary will setup and
there appears to be two main scenarios possible.

Scenario 1. About half the guidance is trying to push the warm font
well inland Monday night with the heaviest rain axis occurring north
of our area. In this scenario, the worst rain likely falls north of
our area across central Alabama with our main rain maker coming
Monday night. However, confidence in this scenario does not seem as
high given historical difficulties that these types of systems have
trying to shove a warm front northward without igniting a mess of
storms. As a result this scenario seems the less likely solution
unfortunately but a forecaster can hope right?

Scenario 2. The rest of the guidance and high res guidance appears
to be slowly trending towards this solution. In this solution the
warm front gets hung up somewhere near the coast leading to
persistent training and overrunning of deep convection along and just
inland of the coast. The key player in this will be a MCS that
develops Sunday evening in Louisiana. If this system associated with
a lead shortwave arrives early and travels down the boundary, its
cold outflow will re-enforce the boundary allowing it to get
stuck somewhere in the southern half of the area. This would then
allow for steady southwesterly to southerly low level flow to pump
deep moisture over and unleash the Gulf of Mexico on the area.
Unfortunately, in setups where you tend to have this broad
southwesterly flow and attempt to move rather deep moist air
northward rather quickly it tends to fire off a lot more storms
than guidance thinks. The result is a better re-enforced boundary
and higher likelihood of the boundary getting hung up. As a result
the forecast leans towards the current model trends and this
scenario where the area receives 3 to 5 inches of rain with a
localized corridor of 6 plus inches across southeastern
Mississippi into coastal Alabama closest to the boundary. For this
a moderate risk of excessive rainfall has been issued and a flood
watch may be needed in forecast packages if confidence increases.
The one saving grace is we have not seen a ton of rain recently
and soil moisture is fairly dry. This will allow our sandy soils
to attempt to keep up with heavier rainfall. This may limit the
overall impact; however, we all know gulf coast rain rates can
dump and can quickly overpower the grounds ability to absorb
waters.

Severe... On top of heavy rainfall we could have a round of strong
to severe storms early Monday morning along that advancing warm front.
As previously discussed, a MCS will likely be traveling down the
warm front out of Louisiana and Mississippi. South of the warm front,
a rapidly destabilizing environment will support the potential of
deep surface based updrafts. On top of this, deep layer shear
values will be around 70 knots, with long curved hodographs along
the warm front. The main question will be what side of the front
will the storms ride. Typically storms like to stay on the
unstable side which would not be good. IF this cluster of storms
stays south of the warm front and the warm front can slide onshore
then a rather potent QLCS capable of damaging winds and tornadoes
will be possible. The big questions are 1. where does the warm
front setup and 2. does the storms stay south of the warm front
staying surface based. While the area is currently in a marginal
risk, an upgrade may be necessary if trends continue today across
southeastern Mississippi into coastal Alabama. BB/03

&&

.SHORT TERM...
(Monday night through Tuesday night)
Issued at 532 AM CDT Sun May 12 2024

Wet sums up much of the short term. Will start this period with
upper trof axis aligned from IA, southwest to TX. East of the
trof axis, high level southwest flow will be on the increase
Monday night from the TN/Lower MS River Valley southwest to across
LA and east TX. Within this zone, deep layer ascent is focused
and intersecting a plume of Gulf moisture spreading northward off
the Gulf and atop a warm front which is forecast to lift northeast
across the local area. PoP`s increase markedly Monday night as
deep layer ascent approaches and maximizes where anomalously high
PWAT ranges 2 to 2.25" over the local area. These values lie well
above 2 standard deviations above the climatological means and in
fact, if verifies, would be near the max in the climate data set
for May 14th. There is increased concern for back-building
convection within an area of low level thickness divergence,
moisture convergence and healthy night-time instability with 0-1km
MuCAPE ranging 1000-2000 J/KG on average in the evolving warm
sector Monday night. This signals a potential risk of locally
heavy rain leading to localized flooding in areas that cannot
drain off short duration heavy rainfall quickly enough. In
consideration for this, a small, targeted moderate risk of
excessive rain was outlooked from southern MS to coastal
southwest AL. Question is how fast the upper support swings
through Monday night and Tuesday morning which will be the driving
factor for eventual duration and storm totals. Forecasters will
also be monitoring for the potential of strong to perhaps a few
severe storms early in the short-term. The risk though remains
marginal but as stated above, an upgrade is possible if kinematics
line up and confidence of occurrence increases.

Tuesday morning, the axis of organized showers/storms and higher
PoPs shifts eastward to along and east of I-65 before upper
support moves out during the afternoon and PoPs lower. Latest
gridded storm total rainfall forecast ending Tuesday evening
ranges 3 to 5 inches. Locally higher amounts off this range is
possible.

Tuesday night, may be some residual showers and storms mainly out
over the Gulf waters but drier deep layer air is forecast to be
spreading in from west to east following the passage of a cold
front.

High temperatures in the lower to mid 80s Tuesday will be near
seasonal. Lows in the mid 60s interior to lower 70s coast Monday
night will be well above normal. A tad "cooler" Tuesday night in
the lower 60s northwest of I-65.

The Rip Risk is expected to rise to High by Tuesday and remain
there through most of the rest of the week. /10


&&

.LONG TERM...
(Wednesday through Saturday)
Issued at 532 AM CDT Sun May 12 2024

Another round of unsettled weather is expected going into the
medium range. To open up the long term, Wednesday looks to be
rain-free. Then, another trough at high levels eases eastward
across the Lower MS River Valley by the end of the work week. This
feature brings a return chance of showers/storms Thursday through
Saturday with the higher probabilities in this period being
Friday.

Highs in the mid to upper 80s. Lows Wednesday night are expected
to range from around 60 well inland to near 70 close to the coast,
with mid 60s along and north of Highway 84 to lower half of the
70s along the coast expected for Thursday and Friday nights. /10

&&

.MARINE...
Issued at 532 AM CDT Sun May 12 2024

Winds will slowly become onshore this afternoon and
increase in advance of our next system early this week. Rain and
storms return to the marine waters Monday and Tuesday as winds and
seas steadily increase. Seas should remain elevated through the week
as another system moves through by the end of the week. BB/03

&&

.PRELIMINARY POINT TEMPS/POPS...
Mobile      82  68  82  68  85  67  87  66 /  20  60  90 100  70  10   0   0
Pensacola   82  72  80  72  83  71  86  69 /  20  40  90  80  80  20  10   0
Destin      82  72  80  74  82  73  85  70 /  20  20  80  80 100  20  10   0
Evergreen   82  62  79  67  85  64  86  61 /  10  40  90  90  80  10   0   0
Waynesboro  79  62  78  65  85  61  86  60 /  20  60 100  80  50   0   0   0
Camden      79  62  75  65  84  62  83  59 /  10  50  90 100  70  10   0   0
Crestview   84  62  81  68  84  66  88  62 /  20  30  80  80 100  10  10   0

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...None.
&&

$$

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