Severe Threat Aug. 6th

[pen_artist]

Thought I would go ahead and get a thread started for what is looking to be a more consistent signal for an subform wide severe weather event this coming weekend. 

 

 

Day 4-5 discussion: 

A rather potent mid/upper shortwave trough for this time of year
   will develop eastward from the Mid/Upper MS Valley to the
   Northeast/Mid-Atlantic vicinity Sunday and Monday. At the surface, a
   deepening low will move across IA and WI/MI on Sunday, before
   lifting east/northeast across Ontario and Quebec on Monday. A
   trailing cold front will sweep across the Midwest and likely be
   approaching the I-95 corridor by Tuesday morning. Enhanced midlevel
   southwesterly flow associated with upper trough atop a very
   moist/unstable boundary layer will set the stage for a multi-day
   severe weather episode ahead of the eastward-advancing cold front. 

   All severe hazards appear possible on Sunday from portions of
   eastern IA through southern WI/MI into much of IL/IN, northern KY,
   and western OH, as a linear convective system moves east across the
   region. Tornado potential likely will be focused closer to the
   surface low track, and along a warm front extending from the low
   east/southeast across parts of southern WI/MI into northern IL/IN. 

   The system will continue east on Monday, impacting portions of the
   upper OH Valley/Lower Great Lakes/central Appalachians vicinity. The
   surface low will be shifting further northeast into Canada.
   Nevertheless, large-scale ascent associated with the upper trough,
   and moderate vertical shear atop very moist and unstable boundary
   layer will continue to support severe convection ahead of the
   eastward advancing cold front. Damaging winds will likely be the
   greatest concern on Monday.

[A-L-E-K]

ready 2 tor

[CheeselandSkies]

18Z GFS might be the start of the cave, finally has the low along the MS River at 00Z Monday. Environment still doesn't look super impressive, though* (at least not over nearly as widespread an area as the Day 4 highlight). Seems like the trough comes out a bit positively tilted with most of the flow hanging on the back side. Meanwhile, 12Z NAM had the sfc low center over northern WI at 00Z Monday; 18Z has it over the IA/MO/IL confluence, but at about the same longitude. Lots yet to be sorted out.

*No doubt due in large part to the massive amount of convection the model breaks out.

[SolidIcewx]

57 minutes ago, CheeselandSkies said:

18Z GFS might be the start of the cave, finally has the low along the MS River at 00Z Monday. Environment still doesn't look super impressive, though* (at least not over nearly as widespread an area as the Day 4 highlight). Seems like the trough comes out a bit positively tilted with most of the flow hanging on the back side. Meanwhile, 12Z NAM had the sfc low center over northern WI at 00Z Monday; 18Z has it over the IA/MO/IL confluence, but at about the same longitude. Lots yet to be sorted out.

*No doubt due in large part to the massive amount of convection the model breaks out.

Probably will be way off even into the final hours leading up to the event 

[Chinook]

1 hour ago, SolidIcewx said:

Probably will be way off even into the final hours leading up to the event 

The severe weather events in the recent 1-2 weeks have had a lot of storm reports, so don't give up on it just yet.

[SolidIcewx]

9 minutes ago, Chinook said:

The severe weather events in the recent 1-2 weeks have had a lot of storm reports, so don't give up on it just yet.

Ohh I was referring to models usually being all over the place until the final 6 hours or so before it starts. I have high hopes for a fun drive to Columbus 

[CheeselandSkies]

...and 0Z NAM now flipped to progressive solution with warm sector into central/even southern IN by 00Z Monday. Sayonara.

[sbnwx85]

I usually save this for winter but it's never too early to break it out.

[Chinook]

2 hours ago, sbnwx85 said:

I usually save this for winter but it's never too early to break it out.

My thinking is usually global models have a better handle on upper level winds, which is a huge part of forecasting.

[CheeselandSkies]

Good write-up from LOT:

 

Quote

.LONG TERM...
Issued at 334 AM CDT Fri Aug 4 2023

Saturday night through Thursday...

Several upstream convective episodes stand between now and the
potential for severe thunderstorms into the region Sunday
afternoon. Successive MCVs, starting with ongoing convection over
Kansas, will advect at least some energy into a weakening ridge
across Iowa and northern Missouri through tonight. The residual
wave will drift toward the CWA by late Saturday afternoon, with
the potential for slow-moving convection to affect much of
northern Illinois Saturday evening into the overnight hours as
mid-level lapse rates begin to steepen above gradual low-level
moistening. A strong mid-level trough will then shift across the
forecast area on Sunday. Anomalously strong dynamics for early
August, highlighted by a surface low strengthening to sub-1000hPa
over Lake Michigan Sunday night, will support a conditional severe
thunderstorm threat Sunday afternoon.

A few failure modes exist for severe weather potential into our
forecast area, with most of these modes favoring higher severe
storm potential to remain south and east of much of the CWA.
Timing of the main trough digging into Wisconsin and northern
Illinois remains the biggest question in severe potential this far
northwest. Next, upstream MCVs or convective enhancement through
Saturday night may muddle the set-up by introducing convective
contamination and widespread cloud cover into Sunday morning. This
would jeopardize airmass recovery Sunday afternoon. Finally,
steeper mid-level rates and the associated low-level EML capping
may outrun the best forcing, which would favor higher coverage of
more modest convection instead of lower coverage of severe
convection.

With all that said, the latest guidance suite favors a corridor
of severe weather potential somewhere across Illinois and Indiana
where these factors all align. High MLCAPE values from a moist and
unstable August air mass with modest deep-layer shear and a
favorable low-level kinematic field will support all severe
weather hazards with initial supercells. This includes a locally
higher tornado risk closer to the surface low into the CWA
conditional on larger-scale differences in timing noted above.

 

[A-L-E-K]

[SolidIcewx]

3 minutes ago, A-L-E-K said:

Better break out the flood jeans

[CheeselandSkies]

Yeah looks like massive amounts of rain wrecks the instability.

[frostfern]

It trended south. 

[hawkeye_wx]

The 12z Euro has gone slower and south with the strong wave.

[CheeselandSkies]

Yesterday Day 4 outlook was talking about warm front with primary threat over southern WI. Last 2 NAM runs have like zero EHI north of about I-64 in IL. 
Ironically, after the GFS was the most progressive solution by far the last couple days, the 18Z actually retrogrades the low center a bit from 21Z Sunday to 00Z Monday. Even so, the warm sector environment isn't very impressive up north along the triple point/WF, mucked up by widespread ongoing convection at 00Z Monday.

Moreover, it seems this system has trended sort of disjointed, with the SFC low still forecast in a favorable position for a S WI/N IL tornado threat, but the main 500mb jet now forecast much further south, with the speed max/left exit region being over SW IN/KY.

This is why they shouldn't bother getting too cute with these outlooks in July/August.

[SolidIcewx]

2 hours ago, CheeselandSkies said:

Yesterday Day 4 outlook was talking about warm front with primary threat over southern WI. Last 2 NAM runs have like zero EHI north of about I-64 in IL. 
Ironically, after the GFS was the most progressive solution by far the last couple days, the 18Z actually retrogrades the low center a bit from 21Z Sunday to 00Z Monday. Even so, the warm sector environment isn't very impressive up north along the triple point/WF, mucked up by widespread ongoing convection at 00Z Monday.

Moreover, it seems this system has trended sort of disjointed, with the SFC low still forecast in a favorable position for a S WI/N IL tornado threat, but the main 500mb jet now forecast much further south, with the speed max/left exit region being over SW IN/KY.

This is why they shouldn't bother getting too cute with these outlooks in July/August.

Give it 24 and watch it flip back north lmao. It’s entertaining to say the least

[Chicago Storm]

In terms of this sub-forum, I'd actually be more interested in the severe threat with the MCV across portions of IL/IN on Saturday...more-so that the severe threat with the main storm system on Sunday across the Western portion of the sub-forum.

Likely we'll see a solid corridor with flood potential across portions of MO/IL/IN, tonight through Saturday as well.

[frostfern]

4 hours ago, CheeselandSkies said:

Yesterday Day 4 outlook was talking about warm front with primary threat over southern WI. Last 2 NAM runs have like zero EHI north of about I-64 in IL. 
Ironically, after the GFS was the most progressive solution by far the last couple days, the 18Z actually retrogrades the low center a bit from 21Z Sunday to 00Z Monday. Even so, the warm sector environment isn't very impressive up north along the triple point/WF, mucked up by widespread ongoing convection at 00Z Monday.

Moreover, it seems this system has trended sort of disjointed, with the SFC low still forecast in a favorable position for a S WI/N IL tornado threat, but the main 500mb jet now forecast much further south, with the speed max/left exit region being over SW IN/KY.

This is why they shouldn't bother getting too cute with these outlooks in July/August.

Frustrating how the models are more consistent long range than short range.  The early ECMWF consistency didn’t really make a lot of sense though.   I’d expect that kind of pattern with a developing low to jump around each run.  I just hope the season lingers like it did 2018 and 2019.  Those years were full of storms, and well north of I-80 warm sectors, right up to and even into October.

[hardypalmguy]

Yeah looks like massive amounts of rain wrecks the instability.

Dude I need to chase.

[Lightning]

This lead wave currently in northern MO  being stronger is significantly impacting Aug 6th and 7th event.  Models are all over the place.  The 0z RGEM has me mostly dry 

[HillsdaleMIWeather]

lol

[cyclone77]

5 hours ago, HillsdaleMIWeather said:

lol

That'll need adjusting northwestward into eastern IA and northwestern IL in later outlooks.

[Powerball]

4 minutes ago, cyclone77 said:

That'll need adjusting northwestward into eastern IA and northwestern IL in later outlooks.

But for now, they're Bunting...

[SolidIcewx]

That’s a hell of a shift looking like I’ll get dunked on in Columbus 

[Chinook]

New outlook. wow, slight risk in Kentucky. so exciting. Maybe Illinois will get a few storms.

[cyclone77]

lol at no tor probs in Iowa.

[Powerball]

I see a bunch of new names on the Outlooks issued today.

I'm guessing these are new grad hires or interns...

[Chinook]

two tornado warnings near Lafayette IN

[Columbus]

Hoping for some fun in Cbus tomorrow. (First time poster, long time lurker!)