Texas Winter 2019-2020

[Brent]

Hey everyone I live in Durant Oklahoma now, and I've really been paying attention to this trowel that is being forecast to appear somewhere in northern Texas and Oklahoma, and I noticed the 00z nam trended a bit further north, but its wobbling and the gfs trended south and west, what I am asking is do any of you think that I really could see some snow here on Saturday morning ? Or should I not be excited about this at all? I'm also aware the models are trending to a very dangerous severe weather outbreak as well so I will be paying close attention to that

It's possible but I'm guessing at best it'd probably be a dusting or so maybe we'll be surprised though

[Cerlin]

Hey everyone I live in Durant Oklahoma now, and I've really been paying attention to this trowel that is being forecast to appear somewhere in northern Texas and Oklahoma, and I noticed the 00z nam trended a bit further north, but its wobbling and the gfs trended south and west, what I am asking is do any of you think that I really could see some snow here on Saturday morning ? Or should I not be excited about this at all? I'm also aware the models are trending to a very dangerous severe weather outbreak as well so I will be paying close attention to that

You’re more likely to see snow than DFW is. I can’t say how likely that is (2% is greater than 1%, such as 80% is greater than 50%) but I wouldn’t rule it out. Especially if it continues to stall like the models are showing, in which case the “wrap around” will have more precipitation.

[bubba hotep]

GFS trend

[Jarodm12]

Thanks you all, finally something to be alittle excited about , of course because of the dynamic nature of this system we also first have to worry about damage to lives and property but perhaps on the other side a white blanket of prestine cold comfort ..

[TheProfessor]

I think that if there were any confidence of surface based discrete storms ahead of the squall line you'd see a Day 1 High risk go out. Otherwise I wouldn't be surprised if they went Moderate for day 2(but would also understand if they wanted to hold off.). I did see some VBV on the NAM profiles, but it was really only in the College Station area. Anyways, if this thing forms a few surface based storms out ahead of the main line it could end up being a devastating high end event.

[Cerlin]

GFS trend

https://i.ibb.co/LCc25LQ/gfs-asnow-scus-fh90-trend.gif

Lines up with what Euro has been showing for a few runs and the NAM, albeit not showing snow for DFW, is somewhat encouraging as well.

[Cerlin]

The EPS members aren’t...awful? About 40% of them have at least a dusting for DFW. None more than an inch. Eh.

[Brent]

Looks like the euro backed off on snow in the metro

[setxweathergal64]

I think that if there were any confidence of surface based discrete storms ahead of the squall line you'd see a Day 1 High risk go out. Otherwise I wouldn't be surprised if they went Moderate for day 2(but would also understand if they wanted to hold off.). I did see some VBV on the NAM profiles, but it was really only in the College Station area. Anyways, if this thing forms a few surface based storms out ahead of the main line it could end up being a devastating high end event.

I am in the Beaumont/Lumberton area. And I am high end freaking out with what I have been reading. What are you seeing trending as the biggest impact for this area? I am afraid I will definitely need xanax.

[wxman57]

I think that if there were any confidence of surface based discrete storms ahead of the squall line you'd see a Day 1 High risk go out. Otherwise I wouldn't be surprised if they went Moderate for day 2(but would also understand if they wanted to hold off.). I did see some VBV on the NAM profiles, but it was really only in the College Station area. Anyways, if this thing forms a few surface based storms out ahead of the main line it could end up being a devastating high end event.

I am in the Beaumont/Lumberton area. And I am high end freaking out with what I have been reading. What are you seeing trending as the biggest impact for this area? I am afraid I will definitely need xanax.

We will likely see a line of thunderstorms moving across southeast Texas Friday night. They'll reach your area in the early morning hours on Saturday. That's a good time of day for such squall lines to move through, as the heating of the day will be gone, and the line of storms will most likely weaken after midnight Friday. The line will move through very quickly. The worst will be over in 15-30 minutes or so. Might see some wind gusts 50-60 mph with golfball-sized hail. The more severe weather should pass to your north. I would expect some power outages all across SE TX tomorrow night. Lightning alone would cause outages. The strong winds that hit as the line approaches may take out some tree branches and trees, causing additional power outages.

Oh, one other thing. Sometimes these squall lines could be preceded by isolated thunderstorm cells that can produce tornadoes. It's these storms that may form out ahead of the squall line Friday evening that have the potential to be more severe. This type of event is not something that is rare in SE TX. We often see such severe weather in the fall and spring, ahead of each strong cold front.

[TheProfessor]

A lot of the eastern Metroplex folks are in the enhanced risk now. The thing to watch there would be how quickly storms form into a line.

[TheProfessor]

The 3KM NAM has been slowing this system down quite a bit and has shown some possible discrete cells out ahead of the line. However, there does appear to be some fairly significant VBV around 2-3 Km up, which would be low enough to disrupt any sustained supercell growth.

Edit: VBV is even more significant on the 12z HRRR, it's definitely something to watch that could really limit this event.

[cheezyWXguy]

The 3KM NAM has been slowing this system down quite a bit and has shown some possible discrete cells out ahead of the line. However, there does appear to be some fairly significant VBV around 2-3 Km up, which would be low enough to disrupt any sustained supercell growth.

Edit: VBV is even more significant on the 12z HRRR, it's definitely something to watch that could really limit this event.

What is causing the VBV to become more prominent? Is it the drier air at around 750mb?

[ThunderSleetDreams]

I like the way we are progressing once we get past January 17-19th. I'd like to keep that PNA around neutral.

[TheProfessor]

The 3KM NAM has been slowing this system down quite a bit and has shown some possible discrete cells out ahead of the line. However, there does appear to be some fairly significant VBV around 2-3 Km up, which would be low enough to disrupt any sustained supercell growth.

Edit: VBV is even more significant on the 12z HRRR, it's definitely something to watch that could really limit this event.

What is causing the VBV to become more prominent? Is it the drier air at around 750mb?

It's really the evolution of the storm on the models and the winds veering with height first then backing, On a hodograph you'll usually see it move back in the opposite direction of what was drawn. Sometimes it might cross over itself creating a loop. You actually want to have dry air around the 700 to 750mb height, it's how you get the loaded gun sounding.

[orangeblood]

GEFS Members starting to get awfully noisy for frozen precip next Friday Jan. 17th into the following week across parts of Texas!

[cheezyWXguy]

The 3KM NAM has been slowing this system down quite a bit and has shown some possible discrete cells out ahead of the line. However, there does appear to be some fairly significant VBV around 2-3 Km up, which would be low enough to disrupt any sustained supercell growth.

Edit: VBV is even more significant on the 12z HRRR, it's definitely something to watch that could really limit this event.

What is causing the VBV to become more prominent? Is it the drier air at around 750mb?

It's really the evolution of the storm on the models and the winds veering with height first then backing, On a hodograph you'll usually see it move back in the opposite direction of what was drawn. Sometimes it might cross over itself creating a loop. You actually want to have dry air around the 700 to 750mb height, it's how you get the loaded gun sounding.

Thanks for explaining the dry air, that makes sense. As for the VBV, I get what it looks like on a hodograph, but what actually causes VBV to be present in certain situations? Is it like, an issue with vertical stacking of the system or something?

[TheProfessor]

What is causing the VBV to become more prominent? Is it the drier air at around 750mb?

It's really the evolution of the storm on the models and the winds veering with height first then backing, On a hodograph you'll usually see it move back in the opposite direction of what was drawn. Sometimes it might cross over itself creating a loop. You actually want to have dry air around the 700 to 750mb height, it's how you get the loaded gun sounding.

Thanks for explaining the dry air, that makes sense. As for the VBV, I get what it looks like on a hodograph, but what actually causes VBV to be present in certain situations? Is it like, an issue with vertical stacking of the system or something?

As far as what causes VBV it likely does have to with how the system is stacked, though I can't really tell you with certainty. There's only one study on veer back veer as far as I know and it was really to test whether or not it really disrupts tornado formation. One thing the study found is that veer back veer that's above the lower kilometers likely won't have a huge impact on Supercell growth The study also suggests that forecasters mostly focus on other more important parameters like SRH lol. Anyways you don't want your mid-latitude cyclones to be vertically stacked. Unlike hurricanes, a strengthening Low will be tilted with height and as it becomes stacked it starts to weaken and occlude.

[TheProfessor]

What Reed Timmer said in a recent Facebook post is interesting and could play a part in tomorrow's storms.
"Here is a wedge TORNADO forming at close-range near Dierks, Arkansas on April 13, 2018, I could be targeting a similar area in SW AR tomorrow night. Hodographs in 4-13-18 environment also had long 0-1 km shear vectors and some veer-back-veer above. Typically a massive low-level shear vector can more than compensate for liimting factors from subtle veer-back-veer pattern aloft or even shallow critical angles on the hodograph."

(He had a video of a wedge posted below that comment)

[1900hurricane]

That is about how I understand it too. A slower system in a blockier regime often features a more unidirectional wind field, a symptom of a more stacked system (less overall veering of winds with height). There's basically always some irregularity in the wind field in actuality, i.e. it's never a perfect and constant veering with height, but with a more unidirectional wind field, any irregularity gets magnified.

I'm not sure if this is the same resource TheProfessor is referring to, but here's a recorded presentation from AMS on backing aloft in a supercell environment.

How Much does “Backing Aloft” Actually Impact a Supercell?