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Severe Severe Wx Threat: March 28-31, 2017

Phillip l said:
How's it looking for Georgia? Not seeing much info on that.
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Rainy , the severe threat isn't impressive
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It seems that South al and west ga could have a shot at some strong storms developing ahead of this plume of moisture.
 
From past experience I would say the biggest threat will be alongthe track of the MCS and Mesolow along the coast. Don't be surprised to see some powerful supercells come ashore in that area of uninhibited cape and localized higher helicity.
 
Whatever model had the tstorms firing in the W SC area at about 11-12 noon, nailed it! It was right on time and placement was spot on! HRRR?
 
Even thought it's been cloudy most of the day these winds in Northwest MS are howling. Kinda wish I had a kite to fly, would be perfect weather for it.
 
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From SPC
A closed mid/upper-level low will continue a slow general eastward
progression from the lower MO Valley and Ozarks toward the lower OH
River Valley through tonight. A related surface low will continue to
develop east-northeastward from east-central MO into central IL,
while a warm front advances northward across eastern IL and much of
IN/OH. Overall buoyancy will remain modest today and cloud cover has
remained semi-prevalent into midday across the warm sector. However,
some cloud breaks are noted near/just east of the MS River with
mid/upper 50s and some lower 60s F surface dewpoints otherwise
expected to expand northward in tandem with the warm front.

As gradual air mass destabilization occurs, storms may first
intensify across far eastern MO into southern IL just ahead of the
surface low and in concert with the aforementioned cloud breaks at
late morning. Additional warm sector or near-warm-frontal-related
development should also occur this afternoon into IN/OH this
afternoon, while other storms should form near the cold front across
KY/TN. While buoyancy will not be robust in most areas, long/largely
unidirectional hodographs, albeit with some near-1km AGL hodograph
curvature, will support a mixed mode including supercells and fast
northeastward-moving bows. Severe hail and damaging winds will be
possible, with a least some tornado risk as well, particularly near
the warm front where low-level SRH will be maximized.

...Gulf Coast States/lower MS River Valley...
12Z Upper-air data and contemporary surface observations/visible
satellite imagery show that considerable convective overturning has
occurred across parts of the region via an overnight/early morning
MCS. Ahead of a slow-moving convective cluster across southeast MS
and coastal eastern LA at late morning, the main severe risk should
be confined to far southeast MS into southern AL/FL panhandle and
eventually southwest GA. For additional short-term details, see
Mesoscale Discussion 377.

Farther west, in the wake of the early-morning MCS, some additional
development may occur near the north/south-oriented cold front this
afternoon. However, persistent cloud cover, modest
moisture/buoyancy, and limited near-frontal convergence all imply
that any near-frontal severe risk later this afternoon/evening
should remain limited across the lower MS Valley vicinity.
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This event certainly just went in a completely strange direction than expected. I don't know what happened, and the HRRR keeps changing. Only thing I can say is that it is sunny, hazy, and quite warm here in North Georgia, and it seems that anything can happen.
 
The line developing Memphis and north is starting to get its act together in North MS as well. Starting to rain on I55 in Hernando, MS.
 
Watching radar to see if that coastal convection behavior... HRRR has it building and building and spreading across the SE AL/GA with lots of rain. I'm just eyeballing the radar but the past few frames almost seems to be sepreation the north convection from the southern storm and one would wonder if the moisture builds up or just rolls east and doesn't expended could have interesting results if such happens to perhaps allow some windows for convection to get built up in parts of AL/GA...I'm theorizing really just from what I'm looking at
 
Spc meso analysis page showing pretty decent amount of cape over Alabama pretty decent swath of 1500 through central Alabama doesn't look like much is stopping it
 
NWMSGuy said:
The line developing Memphis and north is starting to get its act together in North MS as well. Starting to rain on I55 in Hernando, MS.
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The problem is even if it gets going, winds through the column are veering unidirectional and the helicity isn't there. Low dps aren't helping.

OBs show the forming mesolow just off LA.
 
so heres the latest FFC discussion boy it's clear as mud!

.SHORT TERM /Tonight through Friday Night/...

Progressive pattern will continue through the short-term as an omega
block remains anchored over western Europe. Current water vapor loop
shows the center of a strong closed mid level low over southwest
Missouri...with several shortwaves rotating about cyclonic flow to
the south of this main low. This system is being pushed east by
potent...digging trough across the western US. Analysis of latest
sfc data reveals developing low pressure across eastern Missouri and
associated cold front draped south through lower Mississippi Valley
into the western Gulf. Warm front extends east and then southeast
across OH Valley and into Southern Appalachians...where it basically
marks the wedge front boundary from high pressure ridge extending
down Eastern US from Canada.

Radar mosaic beginning to finally light up to our west...while
activity continues to our east along and ahead of the wedge/warm
front. Large complex of thunderstorms across Gulf Coast has been
slow to move today...and is showing somewhat of a weakening trend.
Evolution of this activity into the evening hours introduces
forecast uncertainty...with many factors at play.

SPC mesoanalysis continues to portray dual jet dynamics across the
northern Gulf where right entrance region of polar jet
/associated with main closed low/ and left exit region of
subtropical jet /associated with southern shortwave/ are helping to
aid the Gulf Coast complex. As this system continues to push east
into our area...heights will continue to fall and broad scale ascent
will increase. Right now...indications are for the dual jet to
weaken as closed low moves northeast and southern wave moves east.
This would act to weaken the storm complex over the Gulf and not
completely shut off our moisture transport. However...there is the
potential for left exit region of subtropical jet to sustain the
complex into the FL panhandle and rob us some moisture.
However...as/if these processes occur...main closed low will take on
a negative tilt...which will enhance lift across a good majority of
Ga...regardless of Gulf evolution. So...all in all...evolution will
be a matter of which process is dominant.

With the above in mind...Storm development /supercellular in nature/
has already occurred across southern AL out ahead of the Gulf
complex. See no reason why these storms will not sustain themselves
through the daylight hours as adequate insolation has resulted in at
least 500-1000 J/kg MLCAPE. These storms will carry severe potential
should they move into western/SW Georgia later this afternoon given
increasing shear amidst unstable airmass. Think eventually discrete
activity will evolve into a cluster of thunderstorms /given veer-
back-veer wind profiles/ and move across majority of the area
overnight tonight into very early Friday. Regardless of discrete or
line activity....potential will exist for severe activity through
much of the overnight hours....just hard to say where exactly
largest threat will reside. All threats will be possible:
wind...hail...tornadoes. Will also monitor line of storms along the
cold front currently in western TN Valley...as this activity will
have strong lift to support it as it moves east tonight...though
aforementioned activity make have a negative effect on it.

Should see rapid clearing of precip Friday with perhaps some cu
lingering in the wake of the cold front. Surface high pressure will
be building in from the north Friday so expecting a pleasant
day...which will continue into the extended.
 
Arcc said:
The problem is even if it gets going, winds through the column are veering unidirectional and the helicity isn't there. Low dps aren't helping.

OBs show the forming mesolow just off LA.
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Yeah, right now that line is struggling to get going on the southern end in Mississippi. It's not really exploding or gaining much strength, at the moment.
 
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