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Severe WX Severe Weather Threat 3/14-3/16

Clancy said:
While, like Fred mentioned, NAM has some serious thermodynamic problems, that hodograph is just absolutely disgusting.
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Just to make sure my earlier comments were correctly understood, it was likely underdoing warm sector temperatures on Friday afternoon on the 00z run, not overdoing anything. If anything, the NAM is probably waking up and catching onto reality... which it usually doesn't do until about 48-60 hrs out, if even then.
 
keithGA said:
From the NAM in Central MS.

View attachment 35146
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well i have to admit ignoring any downtrends , derecho mess, and the whole updraft/downdraft balance quality and not having the SRH 1km at 420+, i would honestly be thinking this could have a chance now of being a superoutbreak, everything else seems perfect at this point.

i think a devastating outbreak is the most likely thing to happen at this point (using the OIS definition)
1741780335863.png
 
joshoctober16 said:
well i have to admit ignoring any downtrends , derecho mess, and the whole updraft/downdraft balance quality and not having the SRH 1km at 420+, i would honestly be thinking this could have a chance now of being a superoutbreak, everything else seems perfect at this point.

i think a devastating outbreak is the most likely thing to happen at this point (using the OIS definition)
View attachment 35148
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I’ve got a terrible feeling about this.
 
FFC with a good breakdown of the threat for North Georgia. TLDR: Early Saturday threat needs to be watched, discrete daytime activity is in question but would be dangerous if it develops, and a broken QLCS will move in overnight with abundant tornado potential. Additionally, flooding could be a significant issue.
Forecast:

Some lingering rain and thunderstorms may still be around on early
Thursday night when the long term forecast picks up as a quick
hitting upper level wave progresses across the area. Can`t rule out
something being strong, but with loss of daytime heating and not
much in the way of dynamics to support the system, chances of seeing
a strong to severe thunderstorm will have greatly diminished.
Anything ongoing should quickly begin to collapse.

Moving forward, the main focus remains the severe threat over the
weekend. Models remain consistent with the setup - a sharp wave will
dig into the west CONUS Thursday night and then eject into the Great
Plains on Friday. Lee cyclogenesis will occur driving surface low
and upper level system towards midwest/Great Lakes that becomes
increasingly vertically stacked and stalls. Cold front will be
driven into Arklatex region with copious moisture advection
occurring in the south from the Gulf. Models show the possibility
of some elevated rain/convection that could occur on Friday night
into Saturday morning (the Euro suite being a bit more aggressive
with this than the GEFS). This will need to be monitored,
especially given we are getting in range of higher resolution
guidance, as if any of this is able to tap into the boundary layer
the shear profiles in place will be a bit worrisome (hence the
Marginal Risk for Friday over NW GA). Following this, a secondary
wave pushes into larger trough over the CONUS and brings the
entire system to the east, with height falls overriding the moist
boundary layer in the southeast. Copious lift ensues alongside a
significant mass response. Low level jet of 60+ kts overspreads
north and central Georgia overnight Saturday into Sunday ahead of
a cold front as system progresses to the east. Severe weather
looks likely ahead of this, with all modes still possible
(tornadoes, wind, hail).

Questions remain on what if any convection could get going in the
warm sector ahead of the front given models continue to show a lack
of instability after sunset and relatively poor lapse rates before
that. However, shear profiles are impressive during the day into the
night, and if something can get going ahead of this could certainly
have the opportunity to have supercellular characteristics. This is
likely what would drive any hail threat. Going into the overnight,
the cold front pushing into the area will likely have an ongoing
linear system with embedded QLCS elements. While the thermodynamics
remain very marginal, ensembles still show decent probabilities of
seeing over 500 J/kg of CAPE which will be more than enough given
shear profiles. Hodographs continue to look quite elongated with
very impressive 0-1 km SRH of greater than 350-400 m2/s2 and 0-3 km
SRH approaching or exceeding 500 in some cases. Needless to say, if
something is capable of ingesting some streamwise vorticity, it will
have a hefty amount of it to work with to help with overcoming the
thermodynamic limitations. Tornadoes and damaging winds will likely
be in play as this line to broken line of storms marches across
north and central Georgia. SPC continues to maintain a risk area
equivalent to an Enhanced Risk (Level 3 of 5) for much of western
and northern Georgia, with equivalent Slight Risk (Level 2 of 5)
across the rest of the CWA.

QPF shouldn`t be left out of the discussion either, especially
given WPC maintains a Slight Risk of flash flooding over NW GA.
One potential "failure mode" for significant impacts in northern
Georgia may be a more steady stream of rain from the deep lift
into the system that results in even less favorable thermodynamics
at the surface that makes surface based convection difficult to
achieve. The trade-off will be a lot of rainfall in this scenario.
Experimental NBM 5.0 shows probabilities of rainfall greater than
3" over 48 hours to be about 60%. This likely wouldn`t create huge
impacts, but could lead to minor flooding. Probabilities drop off
quite a bit for over 5", going down to about 10%, which means that
5" is pretty representative of the probable worst case scenario
(90th percentile) over the two days (with the majority likely
falling on Saturday). This could lead to flash flooding and
impacts to local creeks and streams, which should be monitored.
Otherwise, forecast rainfall amounts are currently 1-3" across the
CWA.

On Sunday, this line of storms will likely be continuing to the east
as the entire system continues to shift. Shear from the upper level
won`t be quite as strong with eastward extent, but the system will
still have plenty to work with. Some reintensification of the line
may be possible during the afternoon with day time heating, but some
questions as to whether or not it will have already exiting east
central Georgia by that time. SPC equivalent Slight Risk area is in
line with this thinking on Sunday. Tornadoes and strong damaging
winds remain the primary threats as the system pushes to the east.
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joshoctober16 said:
well i have to admit ignoring any downtrends , derecho mess, and the whole updraft/downdraft balance quality and not having the SRH 1km at 420+, i would honestly be thinking this could have a chance now of being a superoutbreak, everything else seems perfect at this point.

i think a devastating outbreak is the most likely thing to happen at this point (using the OIS definition)
View attachment 35148
Click to expand...

If the models still looks this dire tomorrow evening, I'll probably agree with you.
 
Getting into some fairly rare territory with the parameters in play at this point. The temporal extent of the threat is also pretty wild, with strong tornado potential for like 36+ hours; the SPC explicitly has N AL/N MS with a conditonal (weak forcing) strong supercell tornado risk Friday overnight now, ahead of even the morning QLCS that precedes the main show, so it's gonna be a long couple days of weather watching
 
Equus said:
Getting into some fairly rare territory with the parameters in play at this point. The temporal extent of the threat is also pretty wild, with strong tornado potential for like 36+ hours; the SPC explicitly has N AL/N MS with a conditonal (weak forcing) strong supercell tornado risk Friday overnight now, ahead of even the morning QLCS that precedes the main show, so it's gonna be a long couple days of weather watching
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Was really hoping N. AL would avoid an overnight threat, so I could rest up for Saturday, but that doesn't look likely at this point.
 
Equus said:
Getting into some fairly rare territory with the parameters in play at this point. The temporal extent of the threat is also pretty wild, with strong tornado potential for like 36+ hours; the SPC explicitly has N AL/N MS with a conditonal (weak forcing) strong supercell tornado risk Friday overnight now, ahead of even the morning QLCS that precedes the main show, so it's gonna be a long couple days of weather watching
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Yeah, the amount of hours this event has is something I find really impressive, and I'm struggling to come up with many good comparisons.
 
From HUN's discussion


Some limiting factors in the severe weather could
be the actual sfc low pressure track with a further south and east
track limiting some of the severe potential, but at the same time
increasing the heavy rain threat. However, with the latest few
ensemble runs, this solution appears less likely.
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