April 10th - April 13th(?) Severe Weather, Moderate risk in place for Iowa today

[Iceresistance]

Local met from KFOR

 

[Quincy]

I don’t think it’s a slam dunk that there’s initiation up and down the dryline on Tuesday, but I think there’s a strong possibility that the cap is at least locally breached. Any sustained storms that can form will have the potential to produce very large hail and tornadoes.

I can envision a scenario where most areas see nothing, but one or two intense supercells form.

The Euro has been very consistent with convective initiation. The NAM doesn’t convect, but point forecast soundings only show minimal capping. It wouldn’t take much modification at all to break the cap and produce a few intense storms, per NAM progs. 

[DanLarsen34]

50 minutes ago, Quincy said:

I don’t think it’s a slam dunk that there’s initiation up and down the dryline on Tuesday, but I think there’s a strong possibility that the cap is at least locally breached. Any sustained storms that can form will have the potential to produce very large hail and tornadoes.

I can envision a scenario where most areas see nothing, but one or two intense supercells form.

The Euro has been very consistent with convective initiation. The NAM doesn’t convect, but point forecast soundings only show minimal capping. It wouldn’t take much modification at all to break the cap and produce a few intense storms, per NAM progs. 

Not comparing these two setups when I say this, but I believe we had a similar issue in modeling in the the build-up to 4-14-2012 where some models were initiating no convection align the dry line despite minimal capping. 

[jojo762]

51 minutes ago, DanLarsen34 said:

Not comparing these two setups when I say this, but I believe we had a similar issue in modeling in the the build-up to 4-14-2012 where some models were initiating no convection align the dry line despite minimal capping. 

Yes, the NAM wasn't convecting the night/days leading up to that event... HOWEVER, it was extremely obvious that we were going to get storms that day given the dynamics at play, etc. I feel as though Tuesday is much less obvious -- however, the NAM is absolutely out to lunch showing zero CI along the dryline, esp in Oklahoma. Some of this morning's 12z NAM soundings in KS had a lot of CINh, which obviously worries me... But when all is said and done I think we get a fairly sizable outbreak of severe storms on Tuesday. Tornado threat is tricky despite pretty looking colors on the parameter maps, because we will likely have at least some residual CINh -- meaning storms could potentially struggle to maintain surface-based status. 

I'm pretty bullish overall on Tuesday. It *will* be a day we all remember for a while -- but for what reason? Epic cap bust or substantial tornado outbreak are both on the table.

[Radtechwxman]

What does everyone think of Wed? Really comes down to timing here in IL. Nam seems to be very fast like gfs and pretty much kills severe threat here because of early timing. Hoping euro is right on timing. This latest run looks a lot more messy as well. Wish I could chase Tues. Hoping for something local Wed here but not feeling optimistic about my chances. 

[Powerball]

3 minutes ago, StormChaser4Life said:

What does everyone think of Wed? Really comes down to timing here in IL. Nam seems to be very fast like gfs and pretty much kills severe threat here because of early timing. Hoping euro is right on timing. This latest run looks a lot more messy as well. Wish I could chase Tues. Hoping for something local Wed here but not feeling optimistic about my chances. 

Northward extent is in question, but in general, it seems that will be the big day right now.

[Radtechwxman]

8 minutes ago, Powerball said:

Northward extent is in question, but in general, it seems that will be the big day right now.

Yeah I'm definitely skeptical of instability north of I72 and even I70. Could be a HSLC setup which would favor a qlcs. 

[Ed, snow and hurricane fan]

SETX imbyism, 12Z GFS has S winds at 850 mb, RH above 50%.  Houston area usually stays capped between the warm, dry 850-700 mb flow off the Mexican plateau and morning overcast from humid air across cold shelf waters, but the cap looks breakable around here Tuesday afternoon/evening.  18Z GFS also shows almost no cap.  NAM has a cap, but not the forged steel cap usually seen down here.

Still looks more favorable for severe farther North, but this looks at this point more favorable than two weeks ago with the AUS/CLL area tornadoes.

 

 

 

 

[RCNYILWX]

What does everyone think of Wed? Really comes down to timing here in IL. Nam seems to be very fast like gfs and pretty much kills severe threat here because of early timing. Hoping euro is right on timing. This latest run looks a lot more messy as well. Wish I could chase Tues. Hoping for something local Wed here but not feeling optimistic about my chances. 

Toss the GFS. I'd be really surprised if it's not doing the same over-deepening and earlier closing off of short-wave troughs that it exhibited leading up to the February winter storms. The much quicker and thus earlier occlusion process has been resulting in the much faster frontal timing and a much lower ceiling threat on Wednesday. The 18z run did show some baby steps toward the consensus later frontal timing on Wednesday, with the front not coming through Chicago until 00z now.

Problem with the NAM at this range as well is that the wave is not coming ashore until tomorrow morning and thus off its domain currently. The gap is filled in with an interpolation from GFS domain. So it shouldn't be too surprising that the NAM also has a faster frontal timing than the foreign guidance.

It's times like this (barring an unexpected GFS "win") when the GFS and many GEFS members being bad is that it unnecessarily adds uncertainty to a forecast on big picture items that wouldn't be there if we weren't using the GFS.

Edit: Regarding chaseability locally on Wednesday, there's the morning/mid day southern wave that may cause destabilization issues depending on how quick it is to get out. On the other hand, just for reference, April 9, 2015 also had extensive earlier convection.

There's definitely questions on storm mode even with the later frontal timing. The magnitude of forcing, less than ideal shear vector orientation to the cold front, and the rapid fwd propagation of the front may spell fairly quick transition to QLCS east of the MS River.

[Radtechwxman]

1 hour ago, RCNYILWX said:

Toss the GFS. I'd be really surprised if it's not doing the same over-deepening and earlier closing off of short-wave troughs that it exhibited leading up to the February winter storms. The much quicker and thus earlier occlusion process has been resulting in the much faster frontal timing and a much lower ceiling threat on Wednesday. The 18z run did show some baby steps toward the consensus later frontal timing on Wednesday, with the front not coming through Chicago until 00z now.

Problem with the NAM at this range as well is that the wave is not coming ashore until tomorrow morning and thus off its domain currently. The gap is filled in with an interpolation from GFS domain. So it shouldn't be too surprising that the NAM also has a faster frontal timing than the foreign guidance.

It's times like this (barring an unexpected GFS "win") when the GFS and many GEFS members being bad is that it unnecessarily adds uncertainty to a forecast on big picture items that wouldn't be there if we weren't using the GFS.

Edit: Regarding chaseability locally on Wednesday, there's the morning/mid day southern wave that may cause destabilization issues depending on how quick it is to get out. On the other hand, just for reference, April 9, 2015 also had extensive earlier convection.

There's definitely questions on storm mode even with the later frontal timing. The magnitude of forcing, less than ideal shear vector orientation to the cold front, and the rapid fwd propagation of the front may spell fairly quick transition to QLCS east of the MS River.

 

I'm pretty much expecting qlcs at this point because overall shear vectors seem largely parallel to front and wind fields aloft are more southerly as the trough really goes neg tilt. Why I like low amplitude waves better than full latitude troughs when it comes to neg tilt esp because I feel you tend to get more meridional flow over warm sector with full latitude troughs. Also instability looks rather limited up this way but shear is ample. HSLC and strong forcing on cf racing east to me screams qlcs. 

[DanLarsen34]

 

[jojo762]

The 00z HRRR was (predictably?) rough for KS/OK. Big time throwback to the 4/9/11 Mapleton, IA tornado though with a lone-ranger INVOF the triple point.

HRRR soundings I pulled from KS all exhibited fairly minimal CINh, so I'm honestly curious what exactly we're missing as far as the model not initiating... 

EDIT: Besides the fact that the wave is probably just a *touch* too far west...

[Iceresistance]

3 minutes ago, jojo762 said:

The 00z HRRR was (predictably?) rough for KS/OK. Big time throwback to the 4/9/11 Mapleton, IA tornado though with a lone-ranger INVOF the triple point.

HRRR soundings I pulled from KS all exhibited fairly minimal CINh, so I'm honestly curious what exactly we're missing as far as the model not initiating... 

EDIT: Besides the fact that the wave is probably just a *touch* too far west...

Did initiate in Southern Oklahoma & Northern Texas

[stormdragonwx]

The next few days (Tues/Weds in particular) will indeed be interesting. Something like 5/20/2013 or 5/20/2019? it could swing either way.

(yes there's a reason why I chose those two similar dates)

[Ed, snow and hurricane fan]

Unforecast thunderstorm in Houston now, lights blinked, lost internet for a few minutes, my laptop has a battery, no problems, my Promethean board shut down and scanned its drive for errors starting back up but is good.

 

I assume the only a few balloon sites in Mexico missing this, and a too subtle for satellite disturbance.  At diurnal minimum temp.

[DanLarsen34]

 

[radarman]

Some early, poorly modeled, elevated cells moving through DFW with non-severe hail.  But definitely supercell structure.  Pretty classic conditional risk later on today as the instability builds with no obvious trigger but a favorable wind field.  Could be some picturesque conditions.

[Ed, snow and hurricane fan]

12Z NAM and FV3 are pretty unimpressive with the dryline today.  Ditto 14Z HRRR

 

Arkansas looks interesting, maybe.

[Ed, snow and hurricane fan]

Anyone know who'll be doing 18Z balloons?

[Iceresistance]

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

Anyone know who'll be doing 18Z balloons?

Maybe Arkansas & SE Oklahoma

[OceanStWx]

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

Anyone know who'll be doing 18Z balloons?

Looks like at least FWD and LZK.

[Powerball]

1 hour ago, radarman said:

Some early, poorly modeled, elevated cells moving through DFW with non-severe hail.  But definitely supercell structure.  Pretty classic conditional risk later on today as the instability builds with no obvious trigger but a favorable wind field.  Could be some picturesque conditions.

An interesting (albeit messy) setup indeed.

What's intriguing to me is that those early storms suggests the cap along the dry line might not be all that strong as convective temps are hit this afternoon. The early convection might have also help with laying out some outflow boundaries as a trigger later today.

Another thing to note is the area currently under the enhanced risk is socked in low clouds, while pretty decent heating has commenced down here in the Metroplex.

[radarman]

11 minutes ago, Powerball said:

An interesting (albeit messy) setup indeed.

What's intriguing to me is that those early storms suggests the cap along the dry line might not be all that strong as convective temps are hit this afternoon. The early convection might have also help with laying out some outflow boundaries as a trigger later today.

Another thing to note is the area currently under the enhanced risk is socked in low clouds, while pretty decent heating has commenced down here in the Metroplex.

Those cells must have originated above the EML, it was pretty darn stout at 12z.  I think that could be why the mesos didn't resolve that activity, with no obvious forcing and a capped environment.  Anyway, not sure about the cap implications later on, but I do think your point about possible boundaries could be good one if they don't mix out beforehand.  If something surface based managed to pop it would have the atmosphere totally to itself and look out... but even if it's just another elevated cell or two it could still produce severe hail. 

[SmokeEater]

Hatched added to the 10% in AR.

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[KSWx]

Downgrade to 5% tor for most of the forecast area on the Day 2 update with the 10% hatched over Iowa; Triple point seems to be the play.

 

 

[radarman]

1 hour ago, Powerball said:

An interesting (albeit messy) setup indeed.

What's intriguing to me is that those early storms suggests the cap along the dry line might not be all that strong as convective temps are hit this afternoon. The early convection might have also help with laying out some outflow boundaries as a trigger later today.

Another thing to note is the area currently under the enhanced risk is socked in low clouds, while pretty decent heating has commenced down here in the Metroplex.

you may have been correct there... FWD saying the cap has substantially weakened based on aircraft data

[Powerball]

HRRR does have an Inverted-V sounding for later this afternoon over DFW.

Will have to watch for downburst winds if/when anything develops.

[Powerball]

1 minute ago, radarman said:

you may have been correct there... FWD saying the cap has substantially weakened based on aircraft data

Will have to keep an eye on the CU field moving SE out of Denton County up to the Red River. That's where I would expect something, if anything, to pop up.

[Powerball]

Models have consistently shown a weak MCV tracking across East Central TX and Western LA during peak heating tomorrow, which (if legit) should help to trigger fairly extensive activity down there.

That said, it might it up leaving somewhat of a "lull" in the coverage of activity to the north of it and to the south of the areas closer to the main trough in KS / IA / NE / MO.

[SmokeEater]

Little Rock may have issues later...

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