April 2-8, 2023 | Severe Storms

[BuckeyeGal]

5 hours ago, Iceresistance said:

This is eerily similar to March 31st...

That was my reaction, too. Not good.

[Hoosier]

I think you could argue for an eastward expansion of tomorrow's risk area, especially the enhanced area in northern IL, but it is still somewhat conditional on storms occurring.  Whatever does manage to occur in/around the moderate risk area is likely to be big trouble given the parameter space.

[ClicheVortex2014]

Bit of rotation in southern Georgia

[ElectricStorm]

Southern area upgraded to moderate for tomorrow.

Reading the discussion, looks like that's for an overnight threat. Not good, hopefully everyone has a way to get warnings 

Edited April 3, 2023 by ElectricStorm

[Hoosier]

Looks like the enhanced risk was expanded just about to Lake Michigan.

[ClicheVortex2014]

New discussion mentions the potential for strong and/or long-tracked tornadoes to continue into the nighttime hours. Interesting bit at the end.

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1255 PM CDT Mon Apr 03 2023

   Valid 041200Z - 051200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM EASTERN
   IOWA INTO NORTHWEST ILLINOIS...AND FROM SOUTHERN MISSOURI
   SOUTHWESTWARD TOWARD THE ARKLATEX....

   ...SUMMARY...
   A large area of severe potential will exist from Tuesday afternoon
   into Wednesday morning, from eastern portions of the Plains into the
   Missouri and mid/upper Mississippi Valleys. Strong tornadoes and
   particularly damaging winds are expected. Both afternoon and
   overnight potential will exist across various regions, including the
   risk of dangerous nighttime tornadoes.

   ...Synopsis...
   A large upper trough will move from the Rockies into the Plains on
   Tuesday, with an upper low tracking from WY to northern MN by
   Wednesday morning, deepening after 00Z. Meanwhile, upper ridging
   will occur over the eastern states. A strong 100 kt midlevel jet max
   will be positioned from NM into western KS during the day, with an
   intensifying jet core Tuesday night from KS into IA. Just ahead of
   the primary upper trough/jet, a leading speed max will strengthen
   from OK into KS and MO during the day, perhaps with a subtle lobe of
   cooling aloft.

   At the surface, low pressure will exist over eastern CO Tuesday
   morning, and will shift eastward across KS during the day,
   translating east/northeast along a cold front. This low will shift
   into IA by evening, and into WI by 12Z Wednesday. Ahead of the low,
   a prominent warm front will move rapidly north, beginning the day
   from northeast KS into central IL, and reaching near I-80 from IA
   into northern IL by 00Z. This boundary will continue north into
   southern WI and western Lower MI overnight, ahead of the surface
   low. Behind the low, a cold front will make an eastward push during
   the late evening and overnight across IA, northwest MO and eastern
   KS.

   South of the low, a dryline will stretch from eastern KS into
   central OK and north TX at 00Z, and may become stationary or even
   back westward over the southern Plains during the late evening and
   prior to the cold front arriving from the north.

   Given relatively high heights over the eastern CONUS preceding the
   upper trough, a very wide warm sector will develop from the surface
   low and dryline eastward well east of the MS River, with upper 60s F
   dewpoints common from eastern OK and AR southward. The combination
   of an expansive warm sector and strong shear, for long duration and
   in various forcing regimes, suggests that significant severe weather
   is likely. However, subtleties regarding timing with regard to the
   diurnal cycle, capping, and conflicting model output will make this
   prediction challenging, especially when weighing potential impacts
   to life and property.

   ...IA...northern MO...IL...southern WI - DAYTIME...
   The area near the warm front and later in late into the overnight
   hours ahead of the surface low will be a favored area for supercells
   and tornadoes. Storms are expected to form from northern MO into IA
   during the late afternoon, shifting northeastward with the warm.
   Low-level shear will be extremely favorable for tornadoes, as with
   over 300 m2/s2 SRH and MUCAPE perhaps up to 3000 J/kg. The steep
   lapse rates aloft will maximize updraft strength as well, resulting
   in strong tornadoes.  This threat may persist farther northeast into
   southern WI and northern IL into the night as the warm and unstable
   air with the warm front continues to move north with this strong
   system.

   ...Northeast TX into AR and into MO - OVERNIGHT...
   Confidence is increasing in the potential for rare and dangerous
   overnight tornadoes and damaging winds, and a Moderate Risk has been
   introduced for this region. The air mass will remain capped during
   the day, as boundary-layer moisture builds. Steep lapse rates will
   exist above the capping layer, which will not be particularly strong
   overnight due to robust moisture. As the cold front approaches from
   the west, the low-level jet will remain strong providing theta-e
   advection through the night. Nocturnal storms are forecast to erupt
   after 06Z, and perhaps closer to 08Z from southwest MO into western
   AR and into northeast TX. Hodographs will strongly favor tornadic
   supercells with effective SRH near 400 m2/s2. Further, steep lapse
   rates aloft and ample instability will favor strong tornadoes, and a
   long tracked tornado cannot be ruled out. This appears to be a rare
   case where the front may act more like a dryline during the
   overnight hours, with veering at 850 mb being more gradual. Capping
   is most likely to limit the eastward extent of the threat for
   southern areas near LA.

 

Quote

This appears to be a rare
   case where the front may act more like a dryline during the
   overnight hours, with veering at 850 mb being more gradual. Capping
   is most likely to limit the eastward extent of the threat for
   southern areas near LA.

 

[ClicheVortex2014]

Got a 8a-4p shift tomorrow but something tells me I'll be working longer than that. Won't be surprised if SPC upgrades our fire threat to extremely critical for tomorrow.

[ElectricStorm]

19 minutes ago, ClicheVortex2014 said:

Got a 8a-4p shift tomorrow but something tells me I'll be working longer than that. Won't be surprised if SPC upgrades our fire threat to extremely critical for tomorrow.

Yep

[snowlover2]

Rare day 3 update just issued to expand the slight risk west and south. Previous disco mentioned a couple of strong tornadoes possible. Wouldn't surprise me to see an enhanced area added when this becomes the day 2.

Quote

Day 3 Convective Outlook AMEND 1
   NWS Storm Prediction Center Norman OK
   0302 PM CDT Mon Apr 03 2023

   Valid 051200Z - 061200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS WEDNESDAY FROM THE
   GREAT LAKES REGION AND OHIO VALLEY SOUTHWESTWARD INTO THE LOWER
   MISSISSIPPI VALLEY...

   AMENDED FOR SLOWING UPPER TROUGH, WESTWARD EXPANSION OF SEVERE
   THREAT

   ...SUMMARY...
   Severe thunderstorms are possible over a large area from the Great
   Lakes region southwestward to the Lower Mississippi Valley
   Wednesday. This may include cells capable of producing tornadoes and
   extensive wind damage, primarily north of the Ohio River, with other
   severe storms expected into the lower Mississippi Valley.

   This amendment is primary due to the slowing upper trough, and the
   westward expansion of severe probabilities. Severe storms may be
   ongoing as far west as the St. Louis area at 12Z Wednesday, with
   favorable conditions remaining for tornadoes and damaging winds
   expending mainly northeastward. Farther south, lower 70s F dewpoints
   and heating ahead of a cold front is expected to support scattered
   storms during the day into the lower MS Valley, where mainly hail
   and damaging gusts will be possible. This westward demarcation of
   the severe threat will likely be adjusted further incoming updates.

   ...PREVIOUS DISCUSSION...

   ...Synopsis...
   Within the more amplified branch of split flow emanating from the
   mid-latitude Pacific, the center of a broad and deep, occluding
   cyclone is forecast to migrate across and northeast of the Lake
   Superior vicinity before beginning to weaken Wednesday through
   Wednesday night.  As this occurs, it appears that mid-level ridging
   centered along an axis across the Yucatan Peninsula into western
   Atlantic will remain a prominent influence across much of the
   Southeast, while short wave ridging also overspreads the Northeast
   and Canadian Maritimes.

   Models indicate that a narrow corridor of increasing low-level
   moisture, ahead of the cold front trailing the cyclone, will
   overspread much of the Ohio Valley and lower Great Lakes region. 
   The trailing flank of the cold front probably will stall across the
   lower Mississippi Valley into northwestern Gulf coastal plain,
   beneath the northwestern periphery of the mid-level ridging.

   ...Lower Great Lakes into lower Mississippi Valley vicinity...
   Most model output generally indicates that the core of stronger
   southerly low-level flow, initially including 50+ kt around 850 from
   the Mid South through lower Michigan, will rapidly shift across the
   lower Great Lakes region and weaken some by mid afternoon,  However,
   southwesterly mean flow on the order of 40-70 kt may linger as far
   southwest as the lower Ohio Valley through much of the day.  This
   will contribute to an environment at least conditionally support of
   organized severe thunderstorm development.  With sufficient
   destabilization, this may include an evolving squall line with
   embedded and perhaps preceding discrete supercells.

   Destabilization remains a bit uncertain, based on the latest model
   output, with perhaps considerable warm sector cloud cover inhibiting
   insolation.  Based on ensemble output, the 03/00Z NAM might be a bit
   of an outlier indicating sizable mixed-layer CAPE developing across
   southern lower Michigan and adjacent portions of Indiana/Ohio by
   early Wednesday afternoon, perhaps beneath a remnant plume of
   modestly steep mid-level lapse rates.  If it becomes more apparent
   in subsequent model output that this environment will materialize,
   severe probabilities will probably need to be increased, with the
   risk including at least a bit more appreciable potential for a
   couple of strong tornadoes.

   South of the Ohio Valley, through lower Mississippi Valley, severe
   weather potential appears more limited as low-level flow weakens
   along the stalling frontal zone.

   ..Jewell.. 04/03/2023

 

[ClicheVortex2014]

Rare mid-day day 3 outlook update. They expanded the slight risk west because the system is trending slower. 

Edit: I got beat

Edited April 3, 2023 by ClicheVortex2014

[BuckeyeGal]

6 minutes ago, snowlover2 said:

Rare day 3 update just issued to expand the slight risk west and south. Previous disco mentioned a couple of strong tornadoes possible. Wouldn't surprise me to see an enhanced area added when this becomes the day 2.

 

What does the circle of dashed lines indicate?

[snowlover2]

Just now, BuckeyeGal said:

What does the circle of dashed lines indicate?

Threat of significant severe.

[Hoosier]

Surprised they actually did a special outlook, but the westward expansion would've been inevitable given the model trends.  

[StormfanaticInd]

That warm front has some impressive parameters for tomorrow on the hrrr

Edited April 3, 2023 by StormfanaticInd

[Crowbar]

1 hour ago, snowlover2 said:

Rare day 3 update just issued to expand the slight risk west and south. Previous disco mentioned a couple of strong tornadoes possible. Wouldn't surprise me to see an enhanced area added when this becomes the day 2.

 

Ouch - looks like I may end up coming home early to work or just stay home all together.  Don't need my car to get hailed on or blown away. 

[StormfanaticInd]

Highly anomalous instability with this system coupled with very strong shear 🤔🤔

[StormfanaticInd]

1 hour ago, snowlover2 said:

Rare day 3 update just issued to expand the slight risk west and south. Previous disco mentioned a couple of strong tornadoes possible. Wouldn't surprise me to see an enhanced area added when this becomes the day 2.

 

Wednesday is trending in the wrong direction. 🌪️

[StormfanaticInd]

LOT

Severe weather potential Tuesday PM is very conditional. This
morning`s soundings across the central and southern plains
showed an impressive EML. This strong EML will advect into our
region Tuesday with very warm temps at the base of this EML likely
to result in a strong capping inversion. Amplifying ridge over
the eastern U.S. will result in strongly rising heights Tuesday
over the area, which generally speaking results in subsidence.
Beneath the strong cap and within the warm sector, an unseasonably
warm and moist air mass will advect northward, resulting in classic
"loaded gun" forecast soundings.

The million dollar question is will there be a strong enough
trigger to break through the cap, resulting in explosive severe
thunderstorm development. GFS and ECMWF continue to break out
convection over eastern IA/NE MO/NW IL tomorrow afternoon. It
appears they keying in on a subtle shortwave (and 500 mb speed
max) associated with the sub-tropical jet stream over northern old
Mexico. Given the expected magnitude of the cap, certainly
reasons to doubt CI will take place, but the strong and consistent
signal in guidance certainly can`t be ignored. The forecasted
explosively unstable and strongly sheared environment makes the
prospects of CI particularly concerning. Conditions would be quite
favorable for severe thunderstorms with large to very large hail.
Some tornado threat would exist, mainly near the warm front where
LCLs will be lower and winds more backed. Progged storm motion of
right moving supercells suggests storms may have a hard time
latching onto the warm front, instead crossing the strong warm
front. A hail threat would still exists with these storms moving
north of the warm front.

If these storms develop (which is far from a certainty), they
would likely move out of the area by mid to late evening as
shortwave and warm front both lift north. Most of the area will
transition to windy, warm, and humid (for this time of year)
conditions Tuesday night with temps holding well into the 60s all
night with dewpoints mostly in the lower 60s. It is this air mass,
which should remain modestly unstable, that should still be in
place Wednesday morning.

Growing increasingly concerned that there will be a severe threat
Wednesday morning, at an unusual time of day. While instability
will not be particularly strong (MLCAPE likely less than 1000
j/kg), extreme shear profiles and strong synoptic ascent with the
approaching front and upper trough would support a threat of
severe thunderstorms. Primary threat would probably be damaging
winds with a secondary threat being tornadoes. Strong synoptic
winds could approach advisory criteria in the wake of the
morning/midday cold frontal passage.

[StormfanaticInd]

1 hour ago, snowlover2 said:

Threat of significant severe.

Significant severe weather possible if not likely. Most likely will be upgraded tomorrow 

[StormfanaticInd]

 

[StormfanaticInd]

Could be some elevated storms tonight with some hail given the elevated cape

 

[Neoncyclone]

Gonna have to watch and see how much dry air gets dragged into the warm-sector in the morning, there's a very high ceiling for this event but the failure modes are also more evident.

[ElectricStorm]

Seems like this will be a fine line between significant tornado event or a cap bust for the northern area tomorrow. I don't think the overall storm coverage in that area will be like it was Friday, but I also don't really see a total cap bust. Anything that does form will be a major tornado threat, even if it's just a few storms. 

I'm pretty worried about the southern area, especially since it will be overnight. It's not very often you see an intense tornado threat during the night but that seems to be the case here. 

Overall I'm not really seeing a high risk upgrade yet for either area but I could see a possible upgrade later on if it looks like storm coverage will be greater than currently modeled. Either way this will likely be another big-time event, hopefully everyone is prepared. 

Edited April 4, 2023 by ElectricStorm

[Hoosier]

Not that anybody is doing this, but if you're in Chicago metro, don't sleep on Wednesday just because it's a morning threat.  Environment is pretty supportive of severe wx including poss tornadoes by mid-late morning.

[StormfanaticInd]

On 4/2/2023 at 2:39 PM, StormfanaticInd said:

 

This might end up being a good call given what I'm seeing on the hrrr and some other models. The environment would be extremely supportive of any storm that can manage to break the cap. Very conditional threat with a high ceiling and also big bust potential imo