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Severe Severe Threat 4-13/14

SPC Disco
Lower CO River Valley mid-level speed max is forecast to eject
through the base of western US trough during the day1 period before
translating into MO by 14/18z. This feature will induce a surface
low that should track near/along the I-70 corridor from KS into
central IL by peak heating Saturday. An attendant warm front will
advance into the OH Valley early in the period; however, the
strongest diurnal heating/steep low-level lapse rate environment are
expected to be confined to portions of IL/IN immediately ahead of
the surface low. Strong/severe convection is expected to develop
ahead of the cold front by early afternoon across IL then spread
into western IN by late afternoon.

A secondary mid-level speed max should dig south-southeast into
Mexico which should encourage height falls across the lower MS
Valley region during the day. It's not entirely clear whether a
secondary, weaker surface low will evolve along the advancing cold
front across LA/MS but it appears a wave should evolve which will
encourage low-level convergence. Latest model guidance suggest a
pronounced southerly LLJ will translate east across the Mid South
and vertical shear profiles will be more than sufficient for
organized long-lived updrafts. If boundary-layer heating is as
pronounced as the NAM suggests over eastern MS/western AL a corridor
of 2000+ J/kg SBCAPE could evolve ahead of the front. Large-scale
forcing suggests considerable amount of frontal convection but
isolated supercells could also develop ahead of the boundary. If
discrete storms evolve the tornado threat would be greater than with
the frontal squall line.
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Well then
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Sent from my SM-G955U using Tapatalk
 
...East TX/OK to the Lower Mississippi Valley...
Have upgraded to a tornado-driven Moderate risk centered on the
Ark-La-Tex to central AR with the potential for several tornadoes to
occur within this region late today through tonight.

Middle 60s surface dew points are prevalent from central OK to the
Ark-La-Tex and should be diurnally maintained ahead of the dryline
across eastern OK and most of AR. A swath of 50+ kt 850-mb
southerlies will persist, yielding increasing boundary-layer
moisture through this evening beneath an elevated mixed-layer. This
should result in a broad plume of MLCAPE from 1500-2500 J/kg.
Mid-level height falls in conjunction with confluent low-level flow
should result in scattered storms developing in the mid-late
afternoon from the Ark-La-Tex through central AR. More isolated,
initially discrete storms should also develop along the dryline in
east TX/OK. Enlarged low-level hodographs, which should further
increase in size this evening, will support all hazards. While
convective mode will likely transition to predominately clusters
during the evening, the potential for a several hour window of
numerous supercells traversing the Ark-La-Tex to central AR region
yields increased confidence in the possibility of several tornadoes,
some of which should be strong.

During the overnight, a secondary strengthening of the low-level jet
towards the Lower Mississippi Valley will likely yield upscale
growth into one or more larger QLCSs that accelerate eastward. Such
an evolution will favor a potentially widespread damaging
wind/embedded tornado threat continuing east into early Saturday.
Overall intensity should be tempered to some degree by convection
outpacing surface-based instability, especially with northeast
extent.
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Here’s why they upgraded.
 
Stormlover said:
Very odd that BHM continues to have their own graphics for enhanced, slight, etc that is very different from the SPC. This causes confusion for the public.
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Agreed it's not a minor difference either. SPC has enhanced risk into the Tennessee Valley. Meanwhile BMX keeps the enhanced risk below I-20. We may never get agreement between news stations and the weather service but sure we can at least get the different departments within the weather service to provide a clear concise message.
 
Nice discussion from Tallahassee NWS on possibilities further east and south of the main threat we're all looking at right now ...

.SHORT TERM [Tonight Through Sunday]...

In the upper levels a cut-off low will be over the Midwest this
weekend. A ridge will be over the Northeast. At the surface a low
will move over the Midwest dragging a cold front through the
Southeast. The greatest chance for rain and thunderstorms will be
Saturday night and Sunday. Some severe storms are likely. SPC has
the region in a slight risk for severe storms. Storms will be moving
through SE Alabama and the FL Panhandle late Saturday night and
early Sunday. The threat will shift eastward on Sunday. The main
hazard will be damaging winds but isolated tornadoes are also
possible.

Instability will be low Saturday night but these storms will develop
well to the west and may hold together and move through as a squall
line late Saturday night and into Sunday morning. Instability will
be higher farther east in SC Georgia and the FL Big Bend on Sunday
afternoon. Storms will likely either redevelop or strengthen by
Sunday afternoon. Deep layer shear will be high around 50 knots.
 
Last edited:
Snowflowxxl said:
Odds it goes moderate tomorrow?
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Until we get to development time, I wouldn't rule it out nor would I expect a major outbreak. Usually one factor can change the game. Regardless, I think this has a big linear storm potential and more of a supercell risk than previous systems since there is more areas at risk.
 
ww0039_radar_big.gif

URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 39
NWS Storm Prediction Center Norman OK
115 PM CDT Fri Apr 13 2018

The NWS Storm Prediction Center has issued a

* Tornado Watch for portions of
Northwest Arkansas
Southeast Kansas
Southwest Missouri
Eastern Oklahoma
North central Texas

* Effective this Friday afternoon and evening from 115 PM until
1000 PM CDT.

* Primary threats include...
A few tornadoes and a couple intense tornadoes possible
Scattered large hail and isolated very large hail events to 2.5
inches in diameter likely
Scattered damaging wind gusts to 70 mph possible

SUMMARY...Storms developing along and ahead of the dryline are
expected to intensify and evolve into supercells capable of very
large hail, damaging wind and a few tornadoes.

The tornado watch area is approximately along and 70 statute miles
east and west of a line from 55 miles east northeast of Chanute KS
to 20 miles east southeast of Waco TX. For a complete depiction of
the watch see the associated watch outline update (WOUS64 KWNS
WOU9).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Tornado Watch means conditions are favorable for
tornadoes and severe thunderstorms in and close to the watch
area. Persons in these areas should be on the lookout for
threatening weather conditions and listen for later statements
and possible warnings.

&&

AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 2.5 inches. Extreme turbulence and surface wind
gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean
storm motion vector 24035.
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Darklordsuperstorm said:
Agreed it's not a minor difference either. SPC has enhanced risk into the Tennessee Valley. Meanwhile BMX keeps the enhanced risk below I-20. We may never get agreement between news stations and the weather service but sure we can at least get the different departments within the weather service to provide a clear concise message.
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I saw that yesterday and was confused myself...seems weird as the Huntsville NWS showed the same as the SPC map... but today at least BMX pretty much matches what the SPC has....weird. Their explanation on facebook was they essentially saw things differently and created their own outlook.
 
and
Darklordsuperstorm said:
Agreed it's not a minor difference either. SPC has enhanced risk into the Tennessee Valley. Meanwhile BMX keeps the enhanced risk below I-20. We may never get agreement between news stations and the weather service but sure we can at least get the different departments within the weather service to provide a clear concise message.
Click to expand...
they finally went along with the SPC, there was no reason to be confusing people before
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