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April 8-10 Severe threat


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The 18z 4km NAM is a bit quicker than the 12z.  I think from a chasing standpoint I'd prefer the faster 18z, as it would mean possibly not having to cross the Mississippi back into IL during the chase.  Of course the faster 18z wouldn't be very good news for the Chicago area.

 

Not really much to add to what everyone else has already mentioned today.  Still looks like a very nice event if the NAM's are correct.  Even the GFS would yield a significant severe event, just not as much tor potential.

 

Love the simulated sat shot forecasts off the 18z 4km NAM.

 

9au2ky.jpg
 
2v8pgrp.jpg
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Considering the track and deepening surface low, I'm really not sure why the GFS isn't backing the low level winds over IL/etc. I do recall that the old GFS had problems depicting the low level wind responses in cases like this, and if you do back them even south-southwesterly/southerly, low level shear goes up very fast given rapid veering to strong southwesterly flow at 850 mb.

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The 18z 4km NAM is a bit quicker than the 12z.  I think from a chasing standpoint I'd prefer the faster 18z, as it would mean possibly not having to cross the Mississippi back into IL during the chase.  Of course the faster 18z wouldn't be very good news for the Chicago area.

 

Not really much to add to what everyone else has already mentioned today.  Still looks like a very nice event if the NAM's are correct.  Even the GFS would yield a significant severe event, just not as much tor potential.

 

Love the simulated sat shot forecasts off the 18z 4km NAM.

 

9au2ky.jpg
 
2v8pgrp.jpg

 

Not good news for the Chicago area meaning less threat for severe or more dangerous weather?

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Considering the track and deepening surface low, I'm really not sure why the GFS isn't backing the low level winds over IL/etc. I do recall that the old GFS had problems depicting the low level wind responses in cases like this, and if you do back them even south-southwesterly/southerly, low level shear goes up very fast given rapid veering to strong southwesterly flow at 850 mb.

 

yeah it's interesting. I can name several cases where both were wrong in the amount of backing.

 

Take 5/19/13 in OK for example...the GFS was correct with backed sfc winds along the dryline while the NAM was too veered at the sfc. 

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When Gino brings things like these up, you pay attention.

It got my attention... actually, this whole thing had my attention with the posting of a Day 6 Outlook by the SPC.  Kind of feels odd outside right now, it's more November-ish, vs April, but we are expecting some serious storms (possibly) 48 hours from now. 

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Yeah there's a decent shot that the clock on Chicagoland's pretty stellar luck the last several years might be running low on batteries.

Was hoping you would chime in sooner or later since NW IN is home.  Situation does look quite volatile.   Hopefully storms will be winding down Thursday night when they get to the Indpls metro area but northern and central IL look very interesting.if models continue as they have been showing.

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0z NAM is a sig severe wx event in N. Illinois and S. Wisconsin on Thursday.

 

Not sure about those backing upper level winds over the area though, especially around 21z.

 

However, 4 km NAM is pretty friggin scary. Two bands of semi-discrete supercells.

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0z NAM is in and to me is a little more favorable for tornadoes then previous runs. By 21z sfc winds along I-39 are out of the due south and with what looks like a weaker/further north upper trof...the H5 flow and shear vectors become more favorable for isolated convection after initiation off the front. The 0z NAM goes not igniting storms at 21z to what looks like more isolated convection by 0z given the 3hr QPF tracks

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Pressure is gonna be on for this one, as we're going to have a local news station crew (WQAD) following us all day lol.  00z NAM would likely yield several tors over northern IL in the 21-01z time frame.  I'm not too worried about the slightly backed upper levels, since there's little if any drop off in velocity at that level.  Deepening surface low, significantly increasing vorticity advection, favorable shear vectors relative to the cold front, and ample cape should make for some nice sups for several hours Thu afternoon.  My only concern at this point is the potential leftover Plains convection/debris clouds from the previous day.

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0z NAM is in and to me is a little more favorable for tornadoes then previous runs. By 21z sfc winds along I-39 are out of the due south and with what looks like a weaker/further north upper trof...the H5 flow and shear vectors become more favorable for isolated convection after initiation off the front. The 0z NAM goes not igniting storms at 21z to what looks like more isolated convection by 0z given the 3hr QPF tracks

Had the exact same thoughts basically, can see what appears to be 2 separate discrete tracks over northern IL on the 12km, one right across Chicagoland. Extremely impressive sig tor and supercell composite values for this area on that run. The surface low position being a hair farther south keeps the warm front in closer proximity.
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I wouldn't sleep on tomorrow along the warm front in NE MO/W IL/SE IA. Parameters are looking pretty damn good there.

Just mentioned that in the other thread.

 

That area actually looks much better than Kansas, if there's enough forcing to overcome capping and early activity isn't an issue.

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Just mentioned that in the other thread.

 

That area actually looks much better than Kansas, if there's enough forcing to overcome capping and early activity isn't an issue.

Yeah my worry would be too much early convection, however if things don't go nuts, that area could be prime real estate.

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Here is a little something to excite the Indiana and Michigan posters as you wake up this morning. Discreet convection still ongoing at 03Z on the 06Z 4km NAM.

nam4km_ref_uv10m_ncus_15.png

Well, that's interesting!

These last couple of NAM runs have been pretty intense for Nrn IL. Only things I see that could impede this so far is the upper levels not fulfilling or left over convection not allowing as much heating/destabilization, both of which have been addressed so far. Now time to hurray up and wait for awhile.

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SVR a couple of counties to the south of here for half dollar size hail.

 

BULLETIN - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
727 AM EDT WED APR 8 2015

THE NATIONAL WEATHER SERVICE IN INDIANAPOLIS HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
SOUTHERN MONTGOMERY COUNTY IN WEST CENTRAL INDIANA...
PARKE COUNTY IN WEST CENTRAL INDIANA...
NORTHERN PUTNAM COUNTY IN WEST CENTRAL INDIANA...
EAST CENTRAL VERMILLION COUNTY IN WEST CENTRAL INDIANA...

* UNTIL 815 AM EDT

* AT 724 AM EDT...A SEVERE THUNDERSTORM WAS LOCATED 7 MILES NORTH OF
CLINTON...AND MOVING EAST AT 35 MPH.

HAZARD...HALF DOLLAR SIZE HAIL.

SOURCE...RADAR INDICATED.

IMPACT...DAMAGE TO VEHICLES IS EXPECTED.

* LOCATIONS IMPACTED INCLUDE...
ROCKVILLE...GREENCASTLE...MECCA...BLOOMINGDALE...TURKEY RUN STATE
PARK...MARSHALL...JUDSON...WAVELAND...CECIL HARDEN LAKE...
RUSSELLVILLE...BAINBRIDGE...CARPENTERSVILLE...GROVELAND...FILLMORE
AND ROACHDALE.

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Hearing some reports of small hail on the west side. Not much here, good bit of thunder and lightning though.

 

Consider the source.  :whistle:  :lol:

 

0754 AM HAIL LAFAYETTE 40.41N 86.87W

04/08/2015 M0.50 INCH TIPPECANOE IN BROADCAST MEDIA

0.25 TO 0.50 HAIL.

 

A solid garden variety thunderstorm here. Just had a big crack of thunder. Welcome back t&l, it's been awhile. :)

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Consider the source.  :whistle:  :lol:

 

0754 AM HAIL LAFAYETTE 40.41N 86.87W

04/08/2015 M0.50 INCH TIPPECANOE IN BROADCAST MEDIA

0.25 TO 0.50 HAIL.

 

Just a solid garden variety thunderstorm here. Just had a big crack of thunder. Welcome back t&l, it's been awhile. :)

Haha, I was hearing the same thing from a friend. But yeah, good to hear the rumbles :)

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Just had a svr t storm go through the Indy metro.  Reports of over 2 inches of rain an hour as well.  Power flickered.  Most of the largest hail reports came from the south side of the metro although I saw a one inch hail report from Meridian Hills on the north side.  No hail IMBY.

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LOT and the posters i respect all sound bullish but this one sure smells like a warm front bust for NE Illinois, especially Chicago proper on north towards Geos. But what do i know and we'll find out soon enough, everything looks dope if things can come together.

 

I'd agree with this.  i see things gradually shifting east and weakening in our northern neck of the woods.

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