Severe WX Multi-day Severe Weather Threat 3/12-3/14/2019

[MattPetrulli]

HRRR/NAM look very interesting, especially for the southern threat area.

 

[Darklordsuperstorm]

What's nam showing?

 

[NWMSGuy]

Any thoughts on that storm heading toward Panola County, Ms?

 

[Weatherphreak]

Nam and HRRR both show worrisome supercell look for North Central Alabama. HRRR has everything coming through before dark. NAM is a little slower with storms coming through after dark for Huntsville. Nam is more of a line of supercells where the HRRR has a more discrete look. It’ll be interesting to see which verifies closer to reality.

 

[StormStalker]

The wind is howling out there tonight.

 

[Fred]

Tomorrow might be interesting if the instability is there as per HRRR and NAM.

 

[Xenesthis]

Well game on

 

[Equus]

Thaaaat's a bit of a higher risk than I was expecting, heh. Lots of last minute threat changs this year.

 

[Daryl]

 

[CheeselandSkies]

New tornado watch out for parts of AR/TN/MS. Wasn't expecting things to be cranking this early.

 

[Richardjacks]

Notice how the HRRR SigTor seems to match up with reflectivity...illustrating this is a very conditional threat. If storms do get going, there will be a tornado threat.

 

[CheeselandSkies]

Goodness, some of the HRRR sim ref plots almost resemble a Super Outbreak (or at the very least, Veterans Day 2002) scenario with broken lines of kidney-bean shaped cells with long UH tracks stretching from Alabama to Michigan. Of course, if such a scenario was considered likely today, there would be a high risk in place. I don't envy SPC this year, with just about every event having the conditional potential for something very ugly to happen, but only if everything falls into place just so as occurred at Beauregard on 3/3.

*One thing I would keep an eye on for you Alabamians, the HRRR has been pretty consistent with a strong UH track somewhere near Cullman Co. or just north. Time to go watch the Weather Xtreme Video...

 

[NorthGaWeather]

13z outlook snippet

Thunderstorms should redevelop or intensify in advance of the cold
front this afternoon as large-scale ascent within the left exit
region of a 100-kt jet streak approaches the OH/TN Valley region.
Farther south, forcing becomes a bit more nebulous however a more
favorable thermodynamic environment with lower CINH will be in
place. Most CAM guidance maintains discrete or semi discrete storms
initially, with a transition to a more linear structure across
northern portions of the risk area with time due to stronger
large-scale forcing. Primary storm modes for storms that can persist
within the strong shear environment will be supercells and bowing
segments, with a risk for damaging winds, tornadoes, and large hail.

Should a corridor of stronger heating/greater instability develop,
confidence would increase regarding introduction of a significant
tornado risk area given the very favorable background environment.
This may be needed in later outlooks as the effects of ongoing
precipitation is assessed.

https://www.spc.noaa.gov/products/outlook/day1otlk.html

 

[Kory]

This is a case where instability will not be a problem for us. Best dynamics will be lifting away from Dixie but there appears to be an overlap for best dynamics and instability later this afternoon. By this evening, the low level dynamics are weakening and pulling northward.

 

[Bama Ravens]

It seems like every threat I’m in the marginal risk and then end up in the slight or enhanced right before time for the event. Frustrating.

 

[Bama Ravens]

Something of note: BMX said in their morning AFD that the HRRR is the most aggressive of the CAMs, but it has run “too hot” in previous events.

 

[Weatherphreak]

Something of note: BMX said in their morning AFD that the HRRR is the most aggressive of the CAMs, but it has run “too hot” in previous events.

Definitely think the HRRR is worse case scenario. NAM isn’t as robust but still would cause some trouble.

 

[Xenesthis]

It looks to me that TN has the best dynamics and heating. I will be curious to see how the next few hours evolve. I figure if we can get in the mid 70’s we will have issues.

 

[MattPetrulli]

It looks to me that TN has the best dynamics and heating. I will be curious to see how the next few hours evolve. I figure if we can get in the mid 70’s we will have issues.

I also like the southern target area more, but we'll see how it plays out

 

[Jacob]

Definitely think the HRRR is worse case scenario. NAM isn’t as robust but still would cause some trouble.

Compared to the NAM, the HRRR is a good 4-5° warmer on temperatures and 2-3° warmer on dewpoints across much of central/northern AL this afternoon. We should have a pretty good idea by noon or so which one is closer to reality.