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2017 Short/Medium Range Severe Thread


Hoosier

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This is more LR as far as analogs are concerned, but the February-based experimental analogs from Tropical Tidbits (looking at Z500, MSLP and SST) hint at an increase in severe potential towards the latter part of March and through April. Every single year here had a significant severe weather outbreak over some portion of the country in late March or April. April 2011 needs no introduction, 4/2/1982, 4/27-28/2014, 3/27 + 4/25-27/1994 and 3/28/2007 along with the two high risk busts that could've been much bigger in April.

http://o.aolcdn.com/hss/storage/fss/3b7826ba22e7781e64eabbab3ce57a8/analogs_monthly_z500.png

This would also tend to line up with some of the subseasonal trends being seen in AAM/GWO and the MJO (along with the current substantially positive TNI). See Victor Gensini's and Anthony Masiello's (HM) tweets for more info on the former.

The CFS chiclet chart has also been rather consistently signalling an uptick as well, especially into April, although part of that is more climatological.

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18z gfs shows a shortwave ahead of a surface on the 24th. 12z EURO indicates potential as well. The CFS chicklets have been showing potential for a while now. Both the euro and GFS have dew points of mid 50s around the i70 corridor. Figure it's worth keeping an eye on.  

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Rogue severe thunderstorm developed out of nowhere west of Springfield--SPI now under a warning until 7AM.  Sharp lightning and torrential rain here now.

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Lincoln IL
612 AM CDT FRI MAR 17 2017

The National Weather Service in Lincoln has issued a

* Severe Thunderstorm Warning for...
  Northwestern Christian County in central Illinois...
  Central Sangamon County in central Illinois...

* Until 700 AM CDT

* At 611 AM CDT, a severe thunderstorm was located near New Berlin,
  or 10 miles west of Springfield, moving east at 45 mph.

  HAZARD...60 mph wind gusts and half dollar size hail.

  SOURCE...Radar indicated.

  IMPACT...Hail damage to vehicles is expected. Expect wind damage
           to roofs, siding, and trees.

* Locations impacted include...
  Springfield, Taylorville, Chatham, Rochester, Kincaid, New Berlin,
  Edinburg, Bulpitt, Jerome, Southern View, Leland Grove, Grandview,
  Berry, Curran, Berlin, Sangchris Lake State Park, Sharpsburg, Roby
  and Farmingdale.

 

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Marginal D3 risk for SE IA/N MO/WC IL Sunday:

http://www.spc.noaa.gov/products/outlook/day3otlk.html

...Lower Missouri Valley/Mid Mississippi Valley...
   An upper-level ridge is forecast to move across the Great Lakes
   region and mid Mississippi Valley on Monday as a low-amplitude
   shortwave trough moves across the central Plains. As this feature
   approaches the lower to mid Missouri Valley, a 40 to 50 knot
   low-level jet is forecast to strengthen during the afternoon and
   evening. Moisture advection along with steep lapse rates associated
   with an elevated mixed layer should result in an axis of instability
   from KS extending northeastward into southern IA. Both the NAM and
   GFS develop convective precipitation on the nose of the low-level
   jet across southern IA, northern MO and into western IL late Sunday
   evening into the overnight period. NAM forecast soundings in this
   vicinity at 06Z/Monday show a boundary layer inversion but have
   substantial CAPE above 850 mb. This combined with the steep lapse
   rates and some speed shear in the mid levels may be enough for a
   marginal hail threat. The threat would be most likely during the
   last 6 to 9 hours of the period.

   ..Broyles.. 03/17/2017

 

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Very impressive elevated cape showing up on many of the models for tomorrow night over parts of Iowa/Missouri/Illinois.  Wide area of >2000J/kg showing up on the NAM products, with a few areas even exceeding 3000J/kg.  That's pretty impressive for mid-March.  Looks like it will get put to use too, as a decent little short-wave should ignite several clusters of storms around and after midnight.  I expect SPC will need to upgrade to slight, and honestly maybe even enhanced may be needed if some of these soundings end up being correct.  Several reports of golf ball hail or larger won't surprise me.  Nice LLJ feeding into these things as well.  Wind and tor threat should be about zero, as these things will be feeding on parcels well above the BL.  

Check out this cherry picked sounding for central Iowa at 10pm.  Over 4000J/kg lol.  Heck of a warm nose moving in there right off the surface.

ix5udw.jpg

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On 3/12/2017 at 9:58 PM, andyhb said:

This is more LR as far as analogs are concerned, but the February-based experimental analogs from Tropical Tidbits (looking at Z500, MSLP and SST) hint at an increase in severe potential towards the latter part of March and through April. Every single year here had a significant severe weather outbreak over some portion of the country in late March or April. April 2011 needs no introduction, 4/2/1982, 4/27-28/2014, 3/27 + 4/25-27/1994 and 3/28/2007 along with the two high risk busts that could've been much bigger in April.

http://o.aolcdn.com/hss/storage/fss/3b7826ba22e7781e64eabbab3ce57a8/analogs_monthly_z500.png

This would also tend to line up with some of the subseasonal trends being seen in AAM/GWO and the MJO (along with the current substantially positive TNI). See Victor Gensini's and Anthony Masiello's (HM) tweets for more info on the former.

The CFS chiclet chart has also been rather consistently signalling an uptick as well, especially into April, although part of that is more climatological.

Early April honestly looks like it's going to have serious potential. GEFS and EPS look like an extended period of SW flow aloft although looks more like a plains thing.

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24 minutes ago, cyclone77 said:

Very impressive elevated cape showing up on many of the models for tomorrow night over parts of Iowa/Missouri/Illinois.  Wide area of >2000J/kg showing up on the NAM products, with a few areas even exceeding 3000J/kg.  That's pretty impressive for mid-March.  Looks like it will get put to use too, as a decent little short-wave should ignite several clusters of storms around and after midnight.  I expect SPC will need to upgrade to slight, and honestly maybe even enhanced may be needed if some of these soundings end up being correct.  Several reports of golf ball hail or larger won't surprise me.  Nice LLJ feeding into these things as well.  Wind and tor threat should be about zero, as these things will be feeding on parcels well above the BL.  

Check out this cherry picked sounding for central Iowa at 10pm.  Over 4000J/kg lol.  Heck of a warm nose moving in there right off the surface.

ix5udw.jpg

Eh, impressive indeed but... not a lot of bulk shear or ESRH so storm organization/rotation (key for large hail) looks unlikely. 

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1 hour ago, bjc0303 said:

Eh, impressive indeed but... not a lot of bulk shear or ESRH so storm organization/rotation (key for large hail) looks unlikely. 

There's a lot of CAPE in the hail growth zone... I don't think it will be super difficult getting large hail reports even if there are some organization issues.  

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The sounding above shows how much elevated cape the models are putting out in a few areas.  This one is a little more typical of the environment, and has better bulk shear.  Should be more than sufficient for some very large hail reports IMO.  This one is a little north of Muscatine @6z.

70kr5y.jpg

 

By the way the 18z 4k NAM has a few areas of 4500J/kg+ over central Iowa now.  

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1 hour ago, Jim Martin said:

At the Triple Point of W Central Illinois, Southeast Iowa, and Northeast Missouri late tonight.

nam_2017031912_018_40.6--91.43.png

Looking solid.  LLJ pointing right into that area later tonight.  Nice theta-e surging into this area as well.  Most of the guidance is kicking things off around or shortly after midnight.  Going to be fun to watch, and worth staying up for.  

EDIT:  The EL is way up at 13km, so with the overshooting tops we could see storms punching up to near 50kft.

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3 hours ago, cyclone77 said:

Agreed.  Was surprised as well, but they're the experts lol.  I guess we'll see how she shakes out later tonight.

Well honestly, you've probably been paying more attention to it than me, but the NAM CAPE values at least are pretty decent above the stable boundary layer.  

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1 minute ago, Hoosier said:

Well honestly, you've probably been paying more attention to it than me, but the NAM CAPE values at least are pretty decent above the stable boundary layer.  

 

Yeah they've been pretty respectable.  Even the normally conservative EC has been forecasting 2000J/kg for the last several runs over parts of the risk area.  Storm speeds are relatively slow tonight, so could see several reports of hail covering the ground along with the large hail reports.

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Looking at some of the forecast sounding output values has been a bit leading.  One of the ones I like to look at are shear values from the LCL to the EL.  Well, in tonight's case it's a bit misleading, as the winds near the LCL are fairly brisk(LLJ), so the bulk shear between there and the EL looks pretty meh.  However, if you go up a ways there's a range of weaker flow in the 3-5km range, generally around 20kts.  From 5-12km shear increases dramatically, and leads to bulk shear values over 40kts which is more than sufficient.  Also some "fat" cape in that range.  Another misleading shear value is the surface to 8km value.  It's sort of meaningless since we won't be drawing from anything below 1km tonight.  

 

Nice plume of mid LR out in the plains and western MW.  Always nice to see.

ka5hkg.jpg

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16 minutes ago, cyclone77 said:

Looking at some of the forecast sounding output values has been a bit leading.  One of the ones I like to look at are shear values from the LCL to the EL.  Well, in tonight's case it's a bit misleading, as the winds near the LCL are fairly brisk(LLJ), so the bulk shear between there and the EL looks pretty meh.  However, if you go up a ways there's a range of weaker flow in the 3-5km range, generally around 20kts.  From 5-12km shear increases dramatically, and leads to bulk shear values over 40kts which is more than sufficient.  Also some "fat" cape in that range.  Another misleading shear value is the surface to 8km value.  It's sort of meaningless since we won't be drawing from anything below 1km tonight.  

 

Nice plume of mid LR out in the plains and western MW.  Always nice to see.

ka5hkg.jpg

This is exactly what EBWD and ESRH are used for :)

 

EBWD is respectable but... still looks like storms will have a rough time staying organized. 

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Several severe warnings so far, with a few 1" hail reports.  Golf ball size hail reported in Galesburg earlier.  LLJ is going to continue to feed these, so we should see the dominant storms to continue the large hail threat through daybreak.  Won't be surprised to see 2"+ hail at some point tonight.

Quite the light show right now here.  Storms are still a good 15 miles west of here, but the western/northwestern sky is lighting up quite frequently.

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39 minutes ago, cyclone77 said:

Several severe warnings so far, with a few 1" hail reports.  Golf ball size hail reported in Galesburg earlier.  LLJ is going to continue to feed these, so we should see the dominant storms to continue the large hail threat through daybreak.  Won't be surprised to see 2"+ hail at some point tonight.

Quite the light show right now here.  Storms are still a good 15 miles west of here, but the western/northwestern sky is lighting up quite frequently.

For sure. Just woke up nearly falling off the bed lol here in du page.

Constant deep rippage thunder and bangs rattling windows/walls. Sounded like a constant barrage was barreling in.

Had some nice CtGs around. Missed the hail.

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9 minutes ago, Castaway said:

For sure. Just woke up nearly falling off the bed lol here in du page.

Constant deep rippage thunder and bangs rattling windows/walls. Sounded like a constant barrage was barreling in.

Had some nice CtGs around. Missed the hail.

Sweet.  Just had a short barrage of peas here.  Lightning continues to be very frequent.  Almost continuous.  Surprising lack of CGs overall though.  It's been 95% intracloud, however there's been a few close hitting CGs that shook the house.   

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