March 2nd Moderate Risk ArkLaTex

[Ed, snow and hurricane fan]

15 hours ago, cheese007 said:

Latest from FWD. They seem skeptical of storms forming ahead of the line and are talking about our old friend VBV limiting Tor potential. Bolding is mine

 

Concerning the severe weather threat(s): The primary threat early
in the event will be large hail due to steep lapse rates and
strong bulk shear and a more isolated convective/supercellular
mode. Once the convection congeals into a line the threat will
shift to primarily damaging winds with brief/embedded tornadoes.
It should be noted that the tornado threat appears less impressive
than prior model runs. One thing about the synoptic setup that is
not favorable for tornadoes is the flat/zonal 850mb pattern
across the southeastern US. A more favorable tornado setup would
feature ridging in this area. The implications are that this will
cause the 850mb cyclone to develop eastward very rapidly, and out
of phase with the main upper level trough and its forcing. As a
result the low level jet will shift east into the Lower
Mississippi Valley Thursday afternoon causing hodographs across
North and Central Texas to lose their cyclonic shape before the
forcing and boundary arrive. These more disorganized wind profiles
will feature veering winds, then backing winds, and then veering
winds again as height increases. While veer-back-veer profiles
still can support severe weather, and even tornadoes, they don`t
tend to support the strong or long-track tornadoes and can inhibit
low level mesocyclone intensification for very large hail
production. Still given the parameter space, we`ll need to
advertise all severe hazards with this event since a brief/weak
tornado is still a pretty big deal if it impacts your location
regardless if it`s delivered via supercell or QLCS.

 

3km and 12km NAM forecast soundings for DFW have a pronounced veer-back-veer mentioned above with an otherwise juicy sounding.  Should temper tomorrow's DFW tornado threat some.  SHV near midnight ahead of the QLCS looks more favorable for embedded tornadic supercells.  Maybe tomorrow's MOD get shaved a bit on the W side at the 11:30 update.

[Powerball]

Another thing I noticed is that the latest models runs have started to speed things up again.

Timing's going to be more of an issue for DFW than instability/dynamics. The later the timing, the better for a more widespread event as the line will have time to organize before exiting to the east.

[Iceresistance]

Looks like it's going to miss me to the south and east, it's going to be close though.

[Ed, snow and hurricane fan]

SWODY Day 1 enahnced, with 10% sig tornadoes and hail, in S Arkansas and a small bit of neighboring TN and MS

[Quincy]

3 minutes ago, Ed, snow and hurricane fan said:

SWODY Day 1 enahnced, with 10% sig tornadoes and hail, in S Arkansas and a small bit of neighboring TN and MS

Early convection quickly weakened and seems to be elevated. It is reinforcing the baroclinic zone. The cap should hold on until at least early to mid afternoon. Could see an intense supercell or two over southern Arkansas later. I wonder if today will end up having more discrete storms than tomorrow. It’s certainly possible. 

[Ed, snow and hurricane fan]

22 minutes ago, Quincy said:

Early convection quickly weakened and seems to be elevated. It is reinforcing the baroclinic zone. The cap should hold on until at least early to mid afternoon. Could see an intense supercell or two over southern Arkansas later. I wonder if today will end up having more discrete storms than tomorrow. It’s certainly possible. 

Latest HRRR interesting near TXK mid/late afternoon, 3 km NAM also seems interested in the general area, near the possible boundary reinforced by the weakening shower activity.

[cheese007]

49 minutes ago, Quincy said:

Early convection quickly weakened and seems to be elevated. It is reinforcing the baroclinic zone. The cap should hold on until at least early to mid afternoon. Could see an intense supercell or two over southern Arkansas later. I wonder if today will end up having more discrete storms than tomorrow. It’s certainly possible. 

Day-before-the-day seems to have been the play these last few years

[weatherextreme]

Looks like the 15% hatched tornado was moved a tad bit west and closer to DFW. 

[weatherextreme]

 

[weatherextreme]

Reed also mentioned that his you tube account was hacked 

[Ed, snow and hurricane fan]

I discovered Ryan Hall's YouTube last Spring.  He streams some chasers famous enough I've heard of them.

[stormdragonwx]

2 hours ago, Ed, snow and hurricane fan said:

SWODY Day 1 enahnced, with 10% sig tornadoes and hail, in S Arkansas and a small bit of neighboring TN and MS

I suspected as much. The day before the day could be interesting.

[Calderon]

Also monitoring a potential sleeper hail threat near SAT and AUS areas towards the midnight timeframe. 

[weatherextreme]

 

[Normandy]

The system that will cause tomorrows event just crashed ashore here in Southern California.  Micro sized Hail and strong winds (even continuing on the backside of the low).  I’d watch out tmr. 

[weatherextreme]

From Little Rock NWS

 

Thursday...

Will opt to recycle the discussion for Thursday from the mid-shift
as nothing the dayshift did could really improve upon their work.
Main talking points for Thursday will still be the uncertainty
regarding the northward extent of the wrm frnt, which could greatly
limit the extent of severe weather potential Thursday night...

Despite the exit of upper shortwave troughing Wed night, lingering
instability and ongoing WAA aloft will support at least some
convective potential overnight into Thurs morning, some of which may
be severe. This will also be a crucial trend to monitor thru
today/tonight as this area of convection may alter the warm sector,
potentially reconfiguring the greatest severe threat area later in
the day.

Additionally, guidance remains persistent in its depiction of
showers with embedded thunder lingering over portions of central/Nrn
AR during the morning and afternoon. Deep moisture, including very
moist low-levels, suggests the development of a strong Swrd moving
cold pool is unlikely, although even modestly rain-cooled air will
have the potential to push the warm front Swrd. As mentioned above,
model variability remains regarding this particular evolution with
lingering questions about the northward extent of the best BL air
and warm sector.

A Swrd trend is noted based on consecutive model runs, but to what
degree this will occur remains unclear. Locations along/south of the
boundary will see instability on the order of 2000 to 2500
SBCAPE/MLCAPE as well as strong moisture convergence along the
boundary. As of this writing, this boundary appears most likely to
set up from near Mena to Hot Springs to Stuttgart to near Holly
Springs, MS, but again, this will likely change in future cycles. A
more Srn shift would push us towards a best case scenario for AR,
but a more Nrn shift will push us towards a more worst case scenario
with more of AR in the volatile warm sector.

Further complicating the Thurs severe threat are progged phasing
issues between the warm sector and more robust forcing for ascent.
The incoming upper trough/cyclone will assume a negative tilt as it
approaches AR, but only neutral to weak height falls are expected
thru much of the day. After 03/00Z, more impressive height falls
begin to overspread the warm sector, thus supporting an increase in
more intense convection. This will occur in tandem with a rapid
increase in tropospheric flow as a 160 to 180 kt upper jet impinges
on the area and a very intense 70 to 80 kt LLJ develops by evening.

Storm modes and timing also remain nebulous, partly due to the lack
of more robust synoptic forcing during the day and the yet-to-be-
determined ability for moisture convergence along the boundary, or
free convection within the somewhat capped warm sector, to generate
storms. BRN values exceeding 10 indicate enough shear/instability
balance for organized modes once initiation occurs with multiple
modes likely, including strong supercells and clusters/segments.
Upscale growth along an Ewrd-racing cold front Thurs night will
support an intense squall line during the overnight hours.

Enough shear/curvature/instability will exist such that all severe
hazards will be possible anytime Thurs, but the developing LLJ
during the evening will significantly enlarge hodographs with SRH
values jumping to between 400 to 600+ m^2/s^2 within the warm
sector, and especially near the boundary. This presents a concerning
scenario regarding tornado potential with the parameter space more
than adequate for several strong/violent tornadoes along/S of the
boundary.

The ejecting cyclone late Thurs will cause the warm sector to
quickly surge Nwrd immediately ahead of a NEwrd moving sfc cyclone,
progged to move across NWrn AR during the overnight. This may offer
some window for pre-squall-line convection over central/Ern AR
before widespread damaging winds and embedded tornadic circulations
within the squall line sweep W to E across the Srn half of the area
Thurs night. Convection will end by dawn with lingering wrap around
moisture supporting rainfall across Nrn AR during the day Fri,
although this will be much more benign with the severe threat ending
by 03/12Z.

Bottom line: an outbreak of severe weather is still likely
Thurs/Thurs night, but the highest threat will reside along and S of
the warm front, the placement of which remains unclear and may
continue to present high uncertainty thru the event.

Flooding will also be likely thru Fri morning as moisture parameters
remain very high thanks to continued strong moisture advection.
Training storms are likely along/north of the front. This area was
recently inundated with several inches of rain with NASA SPoRT-LIS
data showing a swath of soil moisture values near the 95th
percentile stretching from near DEQ to near MEM. Given moisture
parameters and the potential for a few to several inches or more of
QPF, flash flooding will be likely, some of which could be
significant. The White River Basin has several points still in flood
as of this morning with worsening hydrologic conditions expected
within that basin and new flooding possible in other basins. There
is some lingering uncertainty with the QPF footprint with the latest
guidance hinting at a NWwrd shift in max amounts, so further
adjustments one way or another are possible.

[Iceresistance]

@Ed, snow and hurricane fanStorms firing in Arkansas for today, there is a Moderate risk in place tomorrow. (Change the title to include "Moderate risk Wednesday"?)

[nwohweather]

50 minutes ago, weatherextreme said:

From Little Rock NWS

 

Thursday...

Will opt to recycle the discussion for Thursday from the mid-shift
as nothing the dayshift did could really improve upon their work.
Main talking points for Thursday will still be the uncertainty
regarding the northward extent of the wrm frnt, which could greatly
limit the extent of severe weather potential Thursday night...

Despite the exit of upper shortwave troughing Wed night, lingering
instability and ongoing WAA aloft will support at least some
convective potential overnight into Thurs morning, some of which may
be severe. This will also be a crucial trend to monitor thru
today/tonight as this area of convection may alter the warm sector,
potentially reconfiguring the greatest severe threat area later in
the day.

Additionally, guidance remains persistent in its depiction of
showers with embedded thunder lingering over portions of central/Nrn
AR during the morning and afternoon. Deep moisture, including very
moist low-levels, suggests the development of a strong Swrd moving
cold pool is unlikely, although even modestly rain-cooled air will
have the potential to push the warm front Swrd. As mentioned above,
model variability remains regarding this particular evolution with
lingering questions about the northward extent of the best BL air
and warm sector.

A Swrd trend is noted based on consecutive model runs, but to what
degree this will occur remains unclear. Locations along/south of the
boundary will see instability on the order of 2000 to 2500
SBCAPE/MLCAPE as well as strong moisture convergence along the
boundary. As of this writing, this boundary appears most likely to
set up from near Mena to Hot Springs to Stuttgart to near Holly
Springs, MS, but again, this will likely change in future cycles. A
more Srn shift would push us towards a best case scenario for AR,
but a more Nrn shift will push us towards a more worst case scenario
with more of AR in the volatile warm sector.

Further complicating the Thurs severe threat are progged phasing
issues between the warm sector and more robust forcing for ascent.
The incoming upper trough/cyclone will assume a negative tilt as it
approaches AR, but only neutral to weak height falls are expected
thru much of the day. After 03/00Z, more impressive height falls
begin to overspread the warm sector, thus supporting an increase in
more intense convection. This will occur in tandem with a rapid
increase in tropospheric flow as a 160 to 180 kt upper jet impinges
on the area and a very intense 70 to 80 kt LLJ develops by evening.

Storm modes and timing also remain nebulous, partly due to the lack
of more robust synoptic forcing during the day and the yet-to-be-
determined ability for moisture convergence along the boundary, or
free convection within the somewhat capped warm sector, to generate
storms. BRN values exceeding 10 indicate enough shear/instability
balance for organized modes once initiation occurs with multiple
modes likely, including strong supercells and clusters/segments.
Upscale growth along an Ewrd-racing cold front Thurs night will
support an intense squall line during the overnight hours.

Enough shear/curvature/instability will exist such that all severe
hazards will be possible anytime Thurs, but the developing LLJ
during the evening will significantly enlarge hodographs with SRH
values jumping to between 400 to 600+ m^2/s^2 within the warm
sector, and especially near the boundary. This presents a concerning
scenario regarding tornado potential with the parameter space more
than adequate for several strong/violent tornadoes along/S of the
boundary.

The ejecting cyclone late Thurs will cause the warm sector to
quickly surge Nwrd immediately ahead of a NEwrd moving sfc cyclone,
progged to move across NWrn AR during the overnight. This may offer
some window for pre-squall-line convection over central/Ern AR
before widespread damaging winds and embedded tornadic circulations
within the squall line sweep W to E across the Srn half of the area
Thurs night. Convection will end by dawn with lingering wrap around
moisture supporting rainfall across Nrn AR during the day Fri,
although this will be much more benign with the severe threat ending
by 03/12Z.

Bottom line: an outbreak of severe weather is still likely
Thurs/Thurs night, but the highest threat will reside along and S of
the warm front, the placement of which remains unclear and may
continue to present high uncertainty thru the event.

Flooding will also be likely thru Fri morning as moisture parameters
remain very high thanks to continued strong moisture advection.
Training storms are likely along/north of the front. This area was
recently inundated with several inches of rain with NASA SPoRT-LIS
data showing a swath of soil moisture values near the 95th
percentile stretching from near DEQ to near MEM. Given moisture
parameters and the potential for a few to several inches or more of
QPF, flash flooding will be likely, some of which could be
significant. The White River Basin has several points still in flood
as of this morning with worsening hydrologic conditions expected
within that basin and new flooding possible in other basins. There
is some lingering uncertainty with the QPF footprint with the latest
guidance hinting at a NWwrd shift in max amounts, so further
adjustments one way or another are possible.

Once the warm front placement becomes clearer, I think we see a High risk tomorrow. With that kind of helicity in place there is serious risk for violent tornadoes and with a low LCL you could see some solid long trackers

[stormdragonwx]

My target area looks to be verifying. I would have picked this spot if I chased down there today.

[Wmsptwx]

Sooo no Huntsville tornado talk

[KoalaBeer]

11 minutes ago, Wmsptwx said:

Sooo no Huntsville tornado talk

CC drop west of Hackelburg as well. 
 

 

[Wmsptwx]

8 minutes ago, KoalaBeer said:

CC drop west of Hackelburg as well. 
 

 

Looks like best storm of the evening! Huntsville had rotation weaken, thankfully.

[Chargers09]

warning for softball hail immediately to the sw of SA

[Ed, snow and hurricane fan]

37 minutes ago, Chargers09 said:

warning for softball hail immediately to the sw of SA

 

[Normandy]

Another thing of note that was strange with this system in so cal…..very cold.  Caused snow in lower mountain elevation and the micro hail I previously mentioned.  I imagine that cold element will have some factor in the severe tomorrow but would love a mets thoughts

[nwohweather]

Another thing of note that was strange with this system in so cal…..very cold.  Caused snow in lower mountain elevation and the micro hail I previously mentioned.  I imagine that cold element will have some factor in the severe tomorrow but would love a mets thoughts

Definitely some steep lapse rates in play

[Powerball]

12z Hi-Res models definitely looking more volatile for DFW late this afternoon, showing more of a favorable setup for tornadic storms. I'm sure it's in part because of the warm front getting hung up further SE.

I wouldn't be surprised if the moderate risk area gets expanded NW a bit.

[Quincy]

Wonder if this may affect the tornado potential a bit around the DFW area:

 

[Wmsptwx]

High end tornado days are so hard to get, all the little details have to be just right.

[Quincy]

1 minute ago, Wmsptwx said:

High end tornado days are so hard to get, all the little details have to be just right.

True. Then there are times when all of the ingredients are off the charts and nothing happens. Severe weather is so complex.