Severe WX April 22-24th, 2020 Severe Weather Threat

[Bevo]

The DFW Metro forecast continues looking more frightening the closer we get to it. I would not be surprised to see the SPC go moderate risk tomorrow, potentially going PDS Tornado Watch.
There still appear to be uncertainties with what will happen in the morning/early afternoon but the atmosphere will be VERY volatile. Some models have been showing a cap in place, but some also show the cap breaking, especially in the late afternoon. I think based on what recent runs have been showing the window of greatest concern for the tornado threat will be around 3-7PM for the DFW metro.

 

[Brice]

For tomorrow's severe threat or Thursday's?

 

[Bevo]

And this is tomorrow?

Yes. Here’s a potential model around 4 PM I saw floating around via Twitter.

 

[Brice]

Yes. Here’s a potential model around 4 PM I saw floating around via Twitter.
[/QUOTE

East Texas could take a beating with those cells.

 

[Brice]

The DFW Metro forecast continues looking more frightening the closer we get to it. I would not be surprised to see the SPC go moderate risk tomorrow, potentially going PDS Tornado Watch.
There still appear to be uncertainties with what will happen in the morning/early afternoon but the atmosphere will be VERY volatile. Some models have been showing a cap in place, but some also show the cap breaking, especially in the late afternoon. I think based on what recent runs have been showing the window of greatest concern for the tornado threat will be around 3-7PM for the DFW metro.

I'm also assuming the cape will break around 2:00-2:30 CDT?

 

[Equus]

It might turn out tomorrow is the big show IF the cap can break at an opportune time. Definitely intrigued as that seems to have uptrended.

 

[Brice]

If it breaks early then by 3PM i would expect them to go MDT in my opinion.

 

[Bevo]

This is probably the scariest weather day I’ve seen in 28 years of living here i don’t know what the mesoscale looked like during the Garland 2015 EF4 though.
The discussion among the local forecasters has been on the strength of the cap. Some are saying it’s pretty weak. The latest full run of the HRRR has pretty much all of Dallas county in a sigtor of 7 around 3/4 PM...yikes almighty.

 

[Brice]

This is probably the scariest weather day I’ve seen in 28 years of living here i don’t know what the mesoscale looked like during the Garland 2015 EF4 though.
The discussion among the local forecasters has been on the strength of the cap. Some are saying it’s pretty weak. The latest full run of the HRRR has pretty much all of Dallas county in a sigtor of 7 around 3/4 PM...yikes almighty.

That's very scary and concerning.

 

[Brice]

If the cap is weak then storms will blow like a bomb very early.

 

[Bevo]

If the cap is weak then storms will blow like a bomb very early.

There are models that don’t show any storm development at all, or very little. We will have to wait until the next SPC update, probably even the one after that, in order to get a better handle on the trends. Tomorrow will very much be a “wait and see” kind of day. The consolation is that once the dry line moves through, everything will fizzle out and the threat will be over. This is also not an overnight event so it will be easy to look at the sky and see if there are clouds or if something ugly is coming.

 

[Matt Grantham]

Fortunately, I have the ability to tell which one currently stands to be more accurate and it is not BMX with that forecast.

Please enlighten us at BMX.

 

[Brice]

Please enlighten us at BMX.

Y'all might be busy on Thursday.

 

[Brice]

There are models that don’t show any storm development at all, or very little. We will have to wait until the next SPC update, probably even the one after that, in order to get a better handle on the trends. Tomorrow will very much be a “wait and see” kind of day. The consolation is that once the dry line moves through, everything will fizzle out and the threat will be over. This is also not an overnight event so it will be easy to look at the sky and see if there are clouds or if something ugly is coming.

If there's no overnight threat that could be setting the table to be more active on Wednesday. Though I thought models were showing messy convection in Texas and Louisiana in the morning.

 

[Brice]

includes
the potential for fairly strong capping associated with elevated
mixed-layer air, which may initially suppress convective
development, particularly along a sharpening dryline to the south of
the surface cyclone. This may also impact areas east of the
dryline, across much of eastern Texas, but considerable model output
appears to suggest that large-scale forcing for ascent, likely aided
by lower/mid tropospheric warm advection, may support increasing
convective development by midday across this region, before
spreading toward the lower Mississippi Valley. This activity could
be accompanied by some risk for severe hail, but probably would also
reinforce stable boundary layer conditions.

That's for the Southern Plains tomorrow,

 

[Bevo]

If there's no overnight threat that could be setting the table to be more active on Wednesday. Though I thought models were showing messy convection in Texas and Louisiana in the morning.

Messy and less discrete, mainly favoring a large hail threat and wind. There could be some isolated tornadoes with that wave but it is not expected to be like the second wave that could happen in the afternoon. That one will be much more volatile because there could be some daytime heating involved during peak hours and that is about when the dry line will begin to move through the metro. NAM has been showing clouds pretty much all day which would be the ideal at this point...

 

[Brice]

Most of East Texas will be in around High 70s to Low 80s so if we do see clouds or not, we will have a exceptional amount of instability.

 

[Brice]

I will see all of you around 9:00 AM goodnight everyone, Bevo nice, fun, and, active talk!

 

[Bevo]

I will see all of you around 9:00 AM goodnight everyone, Bevo nice, fun, and, active talk!

Stay safe if you live in the area too! I might stay up to see the next SPC Day 1 update out of curiosity. Also because I can’t sleep!

 

[Bevo]

SPC Day 1 update:

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1245 AM CDT Wed Apr 22 2020

Valid 221200Z - 231200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
THE SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY...

...SUMMARY...
Severe thunderstorms are expected to develop in the southern Plains
east of I-35 today, spreading eastward into the Arklatex and Lower
Mississippi Valley this evening into tonight. Very large hail will
be possible in the southern Plains with wind-damage and a tornado
threat likely from the southern Plains eastward into the Lower
Mississippi Valley.

...Southern Plains/Arklatex/Lower Mississippi Valley...
A positively tilted upper-level trough will move eastward across the
southern and central Plains today. Ahead of the trough, a corridor
of low-level moisture and instability will be in place at the start
of the period from the western Texas Hill Country northward into
western Oklahoma. At the start of the period, scattered
thunderstorms should be ongoing along the northern edge of moderate
instability in northwest Oklahoma extending eastward into the
stronger low-level flow over northeastern Oklahoma. The storms are
expected to move eastward this morning as the instability corridor
to the south becomes more unstable with time. At the surface, a low
will develop in central Oklahoma this morning. Further south along
and to the east of a surface trough and dryline, boundary-layer
heating will trigger cell initiation in an uncapped airmass. This
convection will increase in intensity just east of the I-35 corridor
late this morning. Forecast soundings across south-central Oklahoma
and east-central Texas by midday show moderate instability, strong
deep-layer shear and steep mid-level lapse rates. This will support
supercell development with large hail by late morning. Hailstones of
greater than 2 inches in diameter will be possible with the more
intense supercells along the most unstable portions of the surface
trough.

The tornado threat may begin in central Oklahoma near the surface
low and develop southward into east-central Texas with the
developing storms. The tornado threat is expected to become
maximized with an eastward-moving complex of storms into the
Arklatex during the afternoon. 0-3 km storm-relative helicities in
the 400 to 500 m2/s2 range could support a strong tornado with any
supercell that becomes dominant. This complex of storms should also
have a wind-damage threat. This threat should increase as the storms
move into the Arklatex this afternoon, coincident with downdraft
maturation. An enhanced-wind damage threat could extend as far east
as the Mississippi River this evening. Although the severe threat
should become more isolated during the overnight period, a
wind-damage and tornado threat could continue as far east as the
central Gulf Coast states.

..Broyles/Lyons.. 04/22/2020

Most noticeable changes:
-Large expansion of the ENH risk area into ArkLaTex and even a portion of Mississippi (East TX through ArkLaTex/Miss this will be an overnight threat!)
-Expansion and narrowing of the sig severe hail threat basically down I-35 from Norman/OKC to almost Austin
-Corridor of hatched 10% sigtor shifted eastward out of DFW metro (but with the crazy parameters in play, continue to be alert)
-rabbit-shaped outlook