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DanLarsen34

January 10-11 Severe Weather Threat

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Strange that there's no mention of this potentially significant severe set up in the Southeastern Forum. They're all worried about some flurries around the 15th or something.
If it doesn't involve snow in general, or a tornado in their backyard, they could care less. Has always been that way. That's why events even there usually end up here.

Sent from my SM-G973U using Tapatalk

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I think this is looking rather concerned across eastern TX into LA. That's a pretty significant EML advecting in from the Mexican Plateau characterized by mlvl lapse rates which may be in excess of 8.5-9 C/KM...typically I would be concerned about extremely strong capping, however, not with this forcing present. What this CAN, however, result in is a "less messy" warm sector with stronger heating than modeled...when you're talking about mlvl lapse rates that steep with sfc dews ~70...CAPE can become significant...1500-2000 J/KG of MLCAPE is very possible. bufkit soundings (IAH) also indicating > 500 J of 6km CAPE with > 45 m/s of shear...yikes.

Obviously shear orientation will result in a mixed storm mode, but we could be looking at a long-lived QLCS (I saw derecho mentioned and certainly can't disagree) with embedded tornadoes (perhaps a significant one) along with discrete supercells (especially Friday afternoon into early overnight) capable of tornadoes and a few intense tornadoes. There may also be some pretty large hail too...

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NAM and NAM nest slowed down some to match the Euro and Canadian better. Looks like a mixed mode of QLCS/Embedded sups/ and possibly a discrete mode as well. 

UH swath nam nest.png

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Regarding Saturday, the 12z NAM has SigTor values of 3-5 in southern Mississippi at 12z. Unlike many days in the summer, severe weather should be happening around 12z.

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The Slidell (LIX) office put out some stronger wording in their afternoon AFD. The potential certainly is there for a significant event for the region.

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1 hour ago, Calderon said:

The Slidell (LIX) office put out some stronger wording in their afternoon AFD. The potential certainly is there for a significant event for the region.

HUN has a pretty strongly worded AFD as well. 

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HGX's most recent AFD seems very reasonable for Friday.

Quote
LONG TERM [Friday Through Wednesday]...

On Friday, an amplified longwave trough will approach the south
central CONUS as an associated surface low and cold frontal
boundary pushes northeastward through the Arklatex and into the
Central Plains. The latest global model runs have come into
slightly better agreement with the timing and placement of the
trough, although the GFS still remains the slightly more
progressive solution compared to the ECMWF. Regardless, the
approach of this feature will result in the development of an
enhanced low level jet of 60+ kts over the eastern half of TX. As
a result, there will be an influx of Gulf moisture into the area
which should push PWAT values into the vicinity of 1.75 in ahead
of the approach of the surface cold front on Friday evening.

Mesoscale dynamics on Friday continue to look favorable for the
formation of severe storms. Most recent NAM guidance suggests
bulk shear values may reach 50 to 60 kts by late Friday afternoon,
and 0-1km Storm Relative Helicity values of 200 m2/s2 or higher
also appear possible across much of the region. Convective
development will be initially be limited by a fairly good capping
inversion, however this will erode with daytime heating and CINH
values are expected to be fairly limited by the early evening
hours. Given the aforementioned setup along with expected moderate
instability, the initial weather threat on Friday evening will be
the formation of discrete cells, some of which may become severe,
ahead of the advancing cold front. Strong winds, hail, and
isolated tornadoes are all possible threats with these storms. As
the surface cold front traverses the area, the convective mode
will transition to a linear pattern along the advancing boundary.
The front and associated storms will reach the northern and
western counties around 6 to 8 PM, the Houston metro area between
8 and 10 PM, and the coast between 10 PM and midnight. Stronger
storms within this line may continue to produce severe wind and
hail along with isolated tornadoes.

While we are still about two days out from the anticipated severe
weather and the exact timing and location of the greatest severe
threats will still be worked out over the coming several forecast
periods, now is a good time to ensure you have a plan in place to
protest yourself from severe weather threats. Make sure you have a
way to receive warnings (e.g. a NOAA Weather Radio, cell phone
alerts, local TV/radio media) and know your plan to take action
in the event that a warning is issued for your area.

Following Friday`s convective activity, a quieter rest of the weekend
looks to be in store as surface high pressure settles into the
area behind the departing front. Temperatures will fall back
towards seasonable values, and clear conditions are expected
through Sunday. By Monday, the surface high will slide eastward
and a tighter surface pressure gradient with onshore winds behind
it will bring Gulf moisture back into the region. This will
result in an increased chance of rain beginning on Monday
afternoon and persisting into mid-week.

Cady

 

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NAM is really showing something here...Could this be the first high risk of the year?

2020010900_NAMNST_052_30.19,-95.86_severe_ml.png

The NAM model are starting to show more discrete cells ahead of the cold front, not a whole lot but a decent bit.

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The Mobile Alabama area is really catching my attention right now. Good shear/ML cape combination around 18z Saturday (ECM) with large 3 KM cape. Critical angles are modest in the 40-50 degree range which would be a limiting factor. 

 

 

3cape mobile.png

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1 hour ago, It's Always Sunny said:

Dallas officially in the enhanced. Here we go...

 

Significant northward expansion of the hatched area as well. Also big ENH with sig severe hatched for day 3 encompassing most of MS and AL

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This continues to look scarier and scarier...especially when you consider the best ingredients lining up at night. NAM showing a rather large area too of 1500+ MLCAPE...quite alarming given the other parameters in place. Forcing and s/w support not lacking either 

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Major veer-backing above 850mb in a lot of those soundings. Wind profiles get somewhat more favorable Saturday over MS/AL compared to Friday over TX/LA, but this wind profile is probably about the best I've found and even it is fairly unidirectional. I would look for a QLCS capable of widespread damaging winds and a few embedded tornadoes, some possibly strong. However, I'm not sold on the potential for sustained free warm sector supercells capable of long-track, EF3+, widely visible tornadoes. Not to say this couldn't still overachieve in that regard a la 12/16.

ecmwf_full_2020010900_066_33.25--88.5.png

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Mean wind isn’t on the hodograph (In that sounding) so storms should naturally turn right. The VBV doesn’t necessarily inhibit tornado genesis unless it’s below 750mb. I have noticed that on a lot of violent tornado days there is a bit (not a ton) of VBV at just above 700mb.  

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7 minutes ago, JasonOH said:

Mean wind isn’t on the hodograph (In that sounding) so storms should naturally turn right. The VBV doesn’t necessarily inhibit tornado genesis unless it’s below 750mb. I have noticed that on a lot of violent tornado days there is a bit (not a ton) of VBV at just above 700mb.  

I'm sure too the overall environment would certainly play a factor too? For example, there is going to be extremely favorable ingredients in the lowest 3 and especially 1 km's...plenty of directional shear, pretty low LCL's, and more than sufficient instability...should see plenty of sfc vorticity juxtaposed with ample 3km CAPE 

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Still thinking southern Alabama is most at risk for a strong tornado on Saturday. 3km CAPE is very high (near 200 j/kg) in some areas. 

deep south supercells nam3k.JPG

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This is in SE TX right around when the NAM peaks the STP. Most striking thing is seeing MLCAPE values just under 2000 J/KG. Also it's pretty backed in the lowest km. 

2020010912_NAM_042_29.86,-95.55_severe_m

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1 hour ago, cheese007 said:

Not looking forward to my drive from Fort Worth to Dallas around 2 - 3 PM tomorrow

I'll be driving from the west side of Fort Worth to northern Tarrant County around that same time (just before that) as well.  Today's 12z NAM3k and HRRR runs both suggest storm initiation around 2pm or so for DFW.  If the 12z NAM3k verifies things wouldn't be too bad in Tarrant County, but that 12z HRRR run spells trouble with semi-discrete activity.

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1 hour ago, CheeselandSkies said:

Major veer-backing above 850mb in a lot of those soundings. Wind profiles get somewhat more favorable Saturday over MS/AL compared to Friday over TX/LA, but this wind profile is probably about the best I've found and even it is fairly unidirectional. I would look for a QLCS capable of widespread damaging winds and a few embedded tornadoes, some possibly strong. However, I'm not sold on the potential for sustained free warm sector supercells capable of long-track, EF3+, widely visible tornadoes. Not to say this couldn't still overachieve in that regard a la 12/16.

 

This strikes me as a warm-season plains chaser mindset, when this is a cool season Gulf Coast / Dixie Alley setup.  "Widely visible tornadoes" isn't really relevant when storms are moving at warp speed and LCLs are scraping the ground.   

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3 minutes ago, Drz1111 said:

This strikes me as a warm-season plains chaser mindset, when this is a cool season Gulf Coast / Dixie Alley setup.  "Widely visible tornadoes" isn't really relevant when storms are moving at warp speed and LCLs are scraping the ground.   

Can also throw in the fact that the greatest tornado potential also extends into the overnight hours 

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53 minutes ago, BrandonC_TX said:

I'll be driving from the west side of Fort Worth to northern Tarrant County around that same time (just before that) as well.  Today's 12z NAM3k and HRRR runs both suggest storm initiation around 2pm or so for DFW.  If the 12z NAM3k verifies things wouldn't be too bad in Tarrant County, but that 12z HRRR run spells trouble with semi-discrete activity.

I'll be driving from about the dead center of Tarrant to far north Dallas. In a convertible of all things

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1 minute ago, JasonOH said:

45% Sig Wind driven Moderate for tomorrow. 

54C9619E-3C1B-4302-A5DE-7CF27A4235BE.gif

Day 2 Severe Weather Outlook is only the fourth (4) time SPC has issued a Day 2 Moderate Risk in January, & first since 2013.

 

From Patrick Marsh ^

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14 minutes ago, Bob's Burgers said:

Day 2 Severe Weather Outlook is only the fourth (4) time SPC has issued a Day 2 Moderate Risk in January, & first since 2013.

 

From Patrick Marsh ^

Wouldn't they have done it for the January day in 2017 that became a high risk on Day 1?

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1 minute ago, CheeselandSkies said:

Wouldn't they have done it for the January day in 2017 that became a high risk on Day 1?

I looked it up and the Moderate was a Day 1 0600 UTC upgrade. Here is the outlook created on 1730 UTC Jan 21

jan 2017.JPG

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I'm just wondering if there isn't going to be more warm sector activity out ahead of this line than is being advertised at the moment. The area I'm most interested in is eastern TX and LA as the LLJ ramps up in the overnight hours. Like @CheeselandSkies I'm certainly not sold on that, but I'm not going to eliminate that possibility just yet either.

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