Jump to content
  • Member Statistics

    17,163
    Total Members
    7,904
    Most Online
    Michael Butler
    Newest Member
    Michael Butler
    Joined

April 12th-14th Severe Threat


Geoboy645
 Share

Recommended Posts

Models have been pretty consistently showing at least a medium level severe threat on our region on the 12th and 13th. The 12th has triple point potential out in Iowa and the 13th could be a very large part of the forum. The 13th already has most of illinois under a 15 or 30 percent on the day 4-8 outlook. This could be a very active few days of severe weather. 

Link to comment
Share on other sites

2 hours ago, Chicago Storm said:


That’s not even close to being an issue in this case.

Agreed.  The best severe wx could be south of I-80, but the reasoning being used is not correct.  The warm front won't get hung up in IL in this situation.

Link to comment
Share on other sites

7 minutes ago, Hoosier said:

Agreed.  The best severe wx could be south of I-80, but the reasoning being used is not correct.  The warm front won't get hung up in IL in this situation.

If I were in Green Bay/C WI, then I'd be concerned about WF positioning.

  • Like 1
Link to comment
Share on other sites

The synoptic warm front will be way north, but Tuesday evening/night convection will have neutralized the steeper lapse rates until more can advect in from the SW.  Iowa into Illinois won't have a problem but that's too far to drive.  Its so hard to get good instability into S Mich/ or N Indiana this time of year.  I guess weak tornadoes can still happen with a skinny CAPE when the dynamics are really amped, but not as fun as something like 4/7/20.  That was a weird NW flow situation though.  I don't know how the old school outbreaks in the 50s and 70s happened.  Somehow there wasn't convection the previous day in the plains to eat up the instability?

  • Like 1
Link to comment
Share on other sites

2 hours ago, frostfern said:

The synoptic warm front will be way north, but Tuesday evening/night convection will have neutralized the steeper lapse rates until more can advect in from the SW.  Iowa into Illinois won't have a problem but that's too far to drive.  Its so hard to get good instability into S Mich/ or N Indiana this time of year.  I guess weak tornadoes can still happen with a skinny CAPE when the dynamics are really amped, but not as fun as something like 4/7/20.  That was a weird NW flow situation though.  I don't know how the old school outbreaks in the 50s and 70s happened.  Somehow there wasn't convection the previous day in the plains to eat up the instability?

One of the reasons Palm Sunday 1965 is so fascinating to me. Basically the only example in somewhat recent history of a true regional outbreak that affected IA, IL, WI, IN and MI with sig :twister:. And coming early in the season as it did, at a time when the lakes are usually a negating factor for instability in at least part of the region.

Link to comment
Share on other sites

40 minutes ago, CheeselandSkies said:

One of the reasons Palm Sunday 1965 is so fascinating to me. Basically the only example in somewhat recent history of a true regional outbreak that affected IA, IL, WI, IN and MI with sig :twister:. And coming early in the season as it did, at a time when the lakes are usually a negating factor for instability in at least part of the region.

The lakes aren't as big of a factor when you have a strong low level jet and with a backed surface wind there can even be some enhancement from the lake breeze.  Though they don't tend to produce a :twister: directly over the lake, supercells can usually cross it just fine.  I think the really big outbreaks had an exceptionally strong westerly dry push off the Rockies.  The dryline moved all the way east to the MS river.  There was a similar type of event in November of 2013, but of course the heating was less due to the November sun angle.  If that kind of synoptic event happened in April with the longer days there could very well have been very large destructive tornadoes into Michigan.  As it was there were still a few QLCS-type tornadoes into Michigan with waning instability after dark.

  • Like 2
Link to comment
Share on other sites

47 minutes ago, frostfern said:

The lakes aren't as big of a factor when you have a strong low level jet and with a backed surface wind there can even be some enhancement from the lake breeze.  Though they don't tend to produce a :twister: directly over the lake, supercells can usually cross it just fine.  I think the really big outbreaks had an exceptionally strong westerly dry push off the Rockies.  The dryline moved all the way east to the MS river.  There was a similar type of event in November of 2013, but of course the heating was less due to the November sun angle.  If that kind of synoptic event happened in April with the longer days there could very well have been very large destructive tornadoes into Michigan.  As it was there were still a few QLCS-type tornadoes into Michigan with waning instability after dark.

A number of the more notorious tornado outbreaks in the region have had this... like a dryline or at least hybrid dryline feature.  Palm Sunday had it.  Another one that had, and one of the more extreme examples of it, was 4/3/1956.  I remember seeing a midday surface map with dews in the 60s in places like Milwaukee and Chicago and dews in the 20s around Rockford and Madison, and they were still out ahead of the synoptic cold front.

  • Thanks 1
Link to comment
Share on other sites

Iowa's setup tomorrow looks primed. Moisture is currently overperforming HRRR progs, zero morning convection concerns, vectors off the boundary are 90 degrees, massive hodographs with large 0-3km curvature will support supercells, 2500-3000 MLCAPE will ensure updrafts are robust... There really isn't anything that's missing.

I was previously not super confident moisture would reach the triple point with sufficient quality, but obs tonight are suggesting that will not be an issue. Therefore, the only thing that remains that could disrupt or otherwise attenuate the setup is if the core of the lift is either slow and doesnt overspread the warm sector before dark or delivers a glancing blow such that storms that do initiate are too far NW and are elevated. Would probably be introducing a 15H at 06z for NW IA.

  • Thanks 1
Link to comment
Share on other sites

It looks like the kind of situation where coverage peaks after dark, but there’s enough instability it won’t even matter.  It will just prolong the tornado threat into the late evening.  Might get some really long tracked tornadic supercells.

Link to comment
Share on other sites

I'm kinda unsure on the supercell potential in Iowa. NWS seems to be banking on 3KM NAM's solution of instant QLCS, with any window for discrete activity being back in Nebraska. I can't get that far in time after work today. HRRR meanwhile looks epic, with long-tracked discrete cells with a robust UH streaks in an extremely volatile environment; and it has been basically consistent with it since this evening came in range.

Link to comment
Share on other sites

18 hours ago, frostfern said:

It looks like the kind of situation where coverage peaks after dark, but there’s enough instability it won’t even matter.  It will just prolong the tornado threat into the late evening.  Might get some really long tracked tornadic supercells.

Hello December yikes!

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...