March 26-28 Severe Threat

[King James]

Cold and foggy, wf doesn't stand a chance here

Skilling agrees with you. West and south of city for any tornadoes

[andyhb]

Liking the IA triple point right now given the dry slot pushing in. Should see large hodographs juxtaposed with sufficient low level buoyancy for tornado potential there. The junk further south and lack of warm frontal progression really has me questioning the current moderate risk area.

[Indystorm]

Champaign  68/66    Effingham  73/68      how far north that WF progresses today is the key....as is the strength of the deepening surface low.

[hawkeye_wx]

Some locations in southeast Iowa are approaching 70º as well.  It's still 48º here.

[Jackstraw]

 SEL7

   URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 67
   NWS Storm Prediction Center Norman OK
   140 PM EDT Sat Mar 28 2020

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     much of Indiana
     much of Ohio
     western Pennsylvania
     the northern West Virginia Panhandle

   * Effective this Saturday afternoon and evening from 140 PM until
     800 PM EDT.

   * Primary threats include...
     Scattered large hail events to 1.5 inches in diameter possible
     Isolated damaging wind gusts to 65 mph possible
     A tornado or two possible

[WeatherMonger]

T'storm watch for IN/OH/W PA

 

[Chicago Storm]

SPC holding on to that outlook is not going to fair well at all.

[Jackstraw]

8 minutes ago, Indystorm said:

Champaign  68/66    Effingham  73/68      how far north that WF progresses today is the key....as is the strength of the deepening surface low.

Agree.  Also storms are firing along a prominent OFB from this mornings convection.along I-70 in IN.  I'm still concerned about some unusually large hail for central IN.  I hate hail lol.

Edit:  That WF is also meandering.  Temps dropped 12 degrees in the last 90 min with no precip.

[Chicago Storm]

8 minutes ago, andyhb said:

Liking the IA triple point right now given the dry slot pushing in. Should see large hodographs juxtaposed with sufficient low level buoyancy for tornado potential there. The junk further south and lack of warm frontal progression really has me questioning the current moderate risk area.

Generally agree. IA into far NE MO and far W IL is the only area that is really interesting.

However, even there you have to question the full quality of final recovery.

[Quincy]

Just now, Chicago Storm said:

Generally agree. IA into far NE MO and far W IL is the only area that is really interesting.

However, even there you have to question the full quality of final recovery.

Better lapse rates aloft will help to some degree, but time will tell soon. High res guidance shows surface temps spiking up over the next 1-2 hours, so we’ll find out soon if that verifies. 

[jojo762]

5 minutes ago, Chicago Storm said:

SPC holding on to that outlook is not going to fair well at all.

Did the same thing 5/18/17 with a high risk, turned out to be a mostly bad outlook... Different set of circumstances that day though..

EDIT: Also looks like we have CI along the PCF north of SGF.

[janetjanet998]

mini discrete cells developing north of SGF MO....and other CU building from that in an arc into SW IA

main show may be starting

[andyhb]

6 minutes ago, Chicago Storm said:

Generally agree. IA into far NE MO and far W IL is the only area that is really interesting.

However, even there you have to question the full quality of final recovery.

I mean model soundings up there are yielding moderate buoyancy even with 67/63 type T/Td pairs, which I think is achievable with the dry slot. Cold air aloft helping a lot.

[Quincy]

2 minutes ago, andyhb said:

I mean model soundings up there are yielding moderate buoyancy even with 67/63 type T/Td pairs, which I think is achievable with the dry slot. Cold air aloft helping a lot.

Which is what we’re just about seeing now:

[AlbiaHawk]

 Sunny 70 degrees and 64 RH in Mount Pleasant, Iowa. Watching and waiting. 

[andyhb]

Obs > CAMs especially on a day like this.

[featherwx]

if I’m in Chicago would it be worth driving a couple hours W/SW at this point to catch the action later? seems like the good stuff might stay even further away than that at this point...

[Indystorm]

27 minutes ago, Jackstraw said:

Agree.  Also storms are firing along a prominent OFB from this mornings convection.along I-70 in IN.  I'm still concerned about some unusually large hail for central IN.  I hate hail lol.

Edit:  That WF is also meandering.  Temps dropped 12 degrees in the last 90 min with no precip.

Wind has turned north here as well now.  And you may have a couple svr cells with quarter hail headed your way.

[Jackstraw]

Tor watch incoming for MO and southern IL

 

[Indystorm]

Based on that recently issued SPC meso discussion it looks like St. Louis metro area could be in line for some long tracked tornadoes later on today.

[jojo762]

Looks like we have CI in NE MO. Just had some radar returns pop in Macon County.

[jojo762]

 Mesoscale Discussion 0251
   NWS Storm Prediction Center Norman OK
   0133 PM CDT Sat Mar 28 2020

   Areas affected...Parts of central/northeast Missouri into southeast
   Iowa and portions of west central Illinois

   Concerning...Severe potential...Tornado Watch likely 

   Valid 281833Z - 282030Z

   Probability of Watch Issuance...80 percent

   SUMMARY...The initiation of scattered supercells appears
   increasingly probable during the next few hours.  Tornadic
   potential, including the risk for strong tornadoes, seems likely to
   increase by 4-6 PM CDT.

   DISCUSSION...Rapid deepening of the surface cyclone now centered
   over southeastern Nebraska is ongoing, with an axis of 2-4 mb
   2-hourly surface pressure falls now pivoting northeastward, to the
   northeast of the lower Missouri Valley.  To the southeast of cyclone
   center, a dryline continues to sharpen across southwestern Iowa and
   western Missouri, and may maintain identity into late afternoon,
   advancing northeastward just ahead of a surging cold front.

   Strengthening and backing (to southerly) 850 mb flow ahead of these
   boundaries is forecast to contribute to enlarging clockwise curved
   low-level hodographs by late afternoon, beneath a very strong
   (90-110 kt) 500 mb jet.  As this occurs, the environment appears
   likely to become increasingly conducive to tornadic supercells given
   sufficient boundary-layer destabilization.

   Mid/high-level cloudiness and precipitation, to the south of the
   warm front near the Missouri/Iowa border, continues to slow boundary
   layer destabilization in the warm sector.  However, a tongue of mid
   60s+ surface dew points appears to be in the process of advecting
   north of the Missouri Ozarks, ahead of the dryline, in response to
   the strong surface pressure falls.

   As a vigorous upstream mid-level trough and embedded closed low
   accelerate northeast of the central Plains, broadly anticyclonic
   mid-level flow will increasingly transition to cyclonic across the
   region through 21-23Z.  The leading edge of stronger difluence aloft
   may already be aiding convective development near the dryline and
   warm front, southeast of Shenandoah IA.  A further increase in
   discrete storm development appears possible within the next couple
   of hours, along/ahead of the dryline to the south.  Further
   development, intensification and northeastward advection of storms
   now spreading across the Missouri Ozarks also appears possible
   within the warm sector.

   Regardless, storms interacting with the warm front probably will
   pose a risk for tornadoes, while strong deep-layer wind fields and
   shear within the destabilizing open warm sector will contribute to
   fast storm motions and potential for long-lived/long track
   supercells with increasing potential to produce strong tornadoes
   across northeast Missouri into southeast Iowa and adjacent west
   central Illinois by 21-23Z.

   ..Kerr/Goss.. 03/28/2020

[AlbiaHawk]

PDS coming or strongly worded Tor Watch??

 

[Chinook]

As an interesting note, we'll have some storms develop near or at areas of 90 kt of effective shear. I don't think I've seen that. Most of the time, you can only get up to about 70 kt of shear in areas of surface instability.

[Indystorm]

4 minutes ago, AlbiaHawk said:

PDS coming or strongly worded Tor Watch??

 

I'd guess a strongly worded tor watch.  PDS watches I think are automatic with high risk, and I don't know if high risk will be issued in the latest update.  But I think you can have PDS watches without a high risk.  Hopefully a met can enlighten us.

[xjcsa]

4 minutes ago, Indystorm said:

I'd guess a strongly worded tor watch.  PDS watches I think are automatic with high risk, and I don't know if high risk will be issued in the latest update.  But I think you can have PDS watches without a high risk.  Hopefully a met can enlighten us.

PDS watches depend on the evaluation of the risk at the time of watch issuance, not on the outlook risk level.

[CryHavoc]

7 minutes ago, Indystorm said:

I'd guess a strongly worded tor watch.  PDS watches I think are automatic with high risk, and I don't know if high risk will be issued in the latest update.  But I think you can have PDS watches without a high risk.  Hopefully a met can enlighten us.

PDS watches are very common/frequent with MDT risk days as well, especially with elevated tornado probabilities.

[Indystorm]

PDS Tornado Watch
PDS tornado watches are issued when there is a higher than normal risk of multiple strong to violent tornadoes – especially those that are predicted to be long-track in nature, with path lengths of more than 20 miles – in the watch area (usually amounting to damage consistent with EF4 or EF5 tornadoes at maximum), in addition to including significant wind and hail damage. This enhanced wording in a Tornado Watch is meant to alert the public of the potential for very life-threatening severe weather. While there are no set criteria for a PDS watch to be issued, they are usually issued when the potential exists for a major tornado outbreak. These types of tornado watches represent about 90% of PDS watches issued by the Storm Prediction Center. PDS Tornado Watches are often issued on high risk days for severe weather.        From SPC

[Jackstraw]

Cell split in SE IA, looking froggy

[snowlover2]

24 minutes ago, Indystorm said:

I'd guess a strongly worded tor watch.  PDS watches I think are automatic with high risk, and I don't know if high risk will be issued in the latest update.  But I think you can have PDS watches without a high risk.  Hopefully a met can enlighten us.

And even if you don't have a PDS watch you can still get violent tornadoes. Only need to go back to the memorial day tornado outbreak as evidence of that.