Synopsis...The aforementioned potent upper trough will begin its
march northeast across the Tennessee Valley Tuesday night and
lift northeast into Ohio by daybreak Monday morning. The
associated surface low developing over eastern Texas will lift
northeast across Louisiana and into northwestern Mississippi as
it continues to strengthen. An associated cold front will surge
quickly eastward across the northern Gulf Coast as a warm front
attempts to surge northward with the surface low. The progression
of the warm front will play a big role on the potential for severe
weather but more on that in the Severe section. Isolated to
scattered showers and thunderstorms will be possible with the
northward progressing warm front during the early evening hours
Tuesday night. However, the main show will arrive with the cold
front and prefrontal surface trough/convergence zone. A likely
line of strong to severe storms will have already developed
Tuesday afternoon along the surface trough/front and will be
barreling eastward likely reaching our southeastern Mississippi
counties before midnight. This line will be going nascar speeds as
it races across our area likely reaching I-65 around midnight and
departs the western Florida Panhandle sometime around or before
sunrise Wednesday. This line will bring the potential for strong
to severe storms with damaging wind gusts and tornadoes.
Severe...The severe threat is a rather tricky one as the ceiling
for this event could be quite high, but the floor could be quite
low. Really seeing three scenarios at this point that range from
rather significant to potentially not much at all and all three
are on the table at this point. With that said, the overall
environment is potent at least in the shear category. As the upper
trough strengthens a incredibly potent low level jet will develop
across the southeast with 850 mb winds in the 65 to 75 knot range
which is beyond bonkers. For reference, maybe only seen that once
in the last 4 years and with a nearly 100 to 110 knot 500 mb jet
moving overhead shear will not be an issue. The hodographs being
portrayed are almost comical with incredibly long-curved
hodographs with bulk shear in excess of 60 knots and 0-1km SRH 400
to 500 m2/s2. From a shear standpoint you really cannot get more
ripe for organized storms with high end damaging wind and stronger
tornado potential. The issue is the instability and it will be
lacking. Given our rather recent frontal passage and short return
flow period, rich Gulf moisture will be struggling to surge
northward at the last second. This will likely lead to marginal
instability maybe topping out at 1000 J/KG at best as mid-level
lapse rates attempt to steepen and better moisture surges in.
Along with the rather paltry instability, the upper forcing will
begin to move out of the area leading to less lift especially as
we move east of I-65 and approach the Florida Panhandle. This will
also complicate things as the combination of limited instability
and limited forcing usually does not mix well with insane shear
leading to storms struggling due to over-shearing. So there seems
to be three likely scenarios on the table.
1. The first is the line moving in from the west remains intact as
it progresses across the area as supercells form out ahead of the
line. This is probably worst case scenario likely leading to a
rather significant severe weather outbreak. This would be the
combination of slightly better lift and the higher end of
instability occurring. In this scenario a rather potent QLCS will
likely bring widespread damaging winds and several embedded
tornadoes for most of the area. Any supercells that would develop
ahead of the line would be capable of strong tornadoes given the
higher end environment. The main thing to watch the next 48 hours
will be the trend in instability. If model guidance trends upwards
then this scenario will be more likely. Right now confidence in
this is low probably around 20% chance of this happening.
2. The second scenario is the line approaches southeastern
Mississippi and then begins to slowly break apart as it moves
across our area. As the forcing lifts north, storms might become
more shear dominant leaving their cold pool in the dust as the
line breaks down into more semi-discrete cells. Given the shear
environment a couple of these cells would likely evolve into
supercells capable of tornadoes with a few strong tornadoes
possible. The question will be if there will be enough instability
to support the higher shear without the help of stronger forcing.
The best chance for that higher instability would be across the
Florida Panhandle so we would likely see a line of storms across
southeastern Mississippi capable of damaging winds and tornadoes
quickly turn into cells as it moves towards I-65 and the threat
move towards the northwestern Florida Panhandle with predominantly
a tornado threat. Confidence in this scenario is probably medium
around 50% but still a lot riding on it.
3. The final scenario would be the Forecasted Convective Amplification Deficiency. In this scenario the
instability just never really gets rich enough to support the
insane environment and the better lift lifts off to the north. In
this scenario the storms would be overpowered by the shear and
just fall apart leading to a broken line of showers across the
area. Sometimes the environment can be too hostile and with the
shear values in place this certainly could be possible. Imagine
the head of the storms moving so fast they detach from the legs
because the legs can`t keep up. Confidence in this is low around
30% but the floor is possible.
With all that said, the environment is there and very little
changes to the instability and lift could lead to significant
results. Given the incredibly high ceiling and still a solid
potential of some significant severe weather occurring across the
area the SPC has upgraded most of the area to an Enhanced risk
for severe weather.
High Winds....As the upper trough continue to strengthen and move
closer to the area, one of the more impressive low level jets I
have seen for this area will overspread. 65 to 75 knots at 850 mb
and well over 55 knots at 950 mb will provide a rather potent
reservoir of strong winds to mix down. As the aforementioned warm
sector moves north, these winds will be increasingly likely to mix
to the surface likely resulting in widespread areas of sustained
winds approaching 40 mph with local gusts in the 50 to 60 mph
range. Given recent rains and the potential for rain to be
occurring during this period, the potential for numerous trees to
come down across the area will be there. With trees comes
powerlines and power loss. Given the nocturnal nature of this
system and the higher potential for powerloss before the
approaching severe weather, it is critical that you have MULTIPLE
ways to receive warnings that will wake you up. Ensure that at
least two ways are battery powered and the batteries are charged
including phones and weather radios. A Wind advisory will be
needed and the potential for a high wind warning is certainly
there.
