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May 21-22 Midwest & Great Lakes Severe Threat


SEMIweather

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There is obviously still time for models to back off, but that time is becoming short. These kinds of increases in parameters in the hours leading up to an event generally lead to productive outbreaks of severe weather.

SREF_prob_combined_sigtor__f012.gif

09z run valid at 21z

SREF_prob_combined_sigtor__f018.gif

Versus 03z run valid at 21z

Unfortunately, if this threat verifies, I can see many getting caught off-guard. It hasn't helped that LSX has been extremely conservative on the prospects of severe. A day or two ago they stated that it would be a stretch to see more than a very isolated severe threat, and hadn't even mentioned tornadoes until this morning's AFD.

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There is obviously still time for models to back off, but that time is becoming short. These kinds of increases in parameters in the hours leading up to an event generally lead to productive outbreaks of severe weather.

Yeah more often than not, when it jumps up this dramatically right before the event it has yielded very well.

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Yeah more often than not, when it jumps up this dramatically right before the event it has yielded very well.

This kind of trend is a lot more eye catching because we're not the day before the event. This is a forecast valid 12 hours in the future.

It is worth noting that while this is a jump from a moderate value to a high value, even small increases to marginal values this late in the game can be significant as models can be latching onto a favorable signal.

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This kind of trend is a lot more eye catching because we're not the day before the event. This is a forecast valid 12 hours in the future.

It is worth noting that while this is a jump from a moderate value to a high value, even small increases to marginal values this late in the game can be significant as models can be latching onto a favorable signal.

Yeah, I think the last time we had a day of jump upward like this was June 5th last year, and that day yielded significantly. Of course I am not saying this day will but just as a point of previous reference.

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This kind of trend is a lot more eye catching because we're not the day before the event. This is a forecast valid 12 hours in the future.

It is worth noting that while this is a jump from a moderate value to a high value, even small increases to marginal values this late in the game can be significant as models can be latching onto a favorable signal.

I'm thinking further south right now...kind of looks like a big more chances of storm interactions the further north you go and closer to the forcing. I'm hoping for something big and isolated which the latest HRRR is hinting at in central IL south of I-80.

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looking at 12z RUC, 12Z NAM just off the press and most importantly current conditions..

This is going to be a huge day..

while the 12z NAM is a little tamer, 12z RUC has 65 kt 700mb wind max punching into N IL at 21z....this often leads to very strong winds this time of year which is why SPC 45% wind probs here...that should be hatched later

this may end up being a "high end" moderate day of central IL into WI..just look at all the spin out there around the low which will enhance the tornado threat

also with the threat over a wide area all the way down into texas...if it wasn't for the insane April..this may be one of the top three events of the year

giving the storm coverage over a decent population,at this time I think a 65+ prelim tornado report day is possible and a total severe report day of 800+ (12z to 12z)

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I'm thinking further south right now...kind of looks like a big more chances of storm interactions the further north you go and closer to the forcing. I'm hoping for something big and isolated which the latest HRRR is hinting at in central IL south of I-80.

I'm in agreement that things become more isolated the farther down the line you head. And the SREF is bringing a secondary area of higher probabilities into central Illinois at 00z.

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Really? It looks like a deformation-type setup to me versus a severe weather setup.

NAM/Ukie/GGEM further north, and trending N with each run. Its more or less something to monitor, depends on the strength of that Upper Low over Canada. If it's strong then we are missed to the south if it isn't as strong or transient then we could sneak a risk out for the Southern half of the state.

Of course the better potential will be further south as of now.

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NAM/Ukie/GGEM further north, and trending N with each run. Its more or less something to monitor, depends on the strength of that Upper Low over Canada. If it's strong then we are missed to the south if it isn't as strong or transient then we could sneak a risk out for the Southern half of the state.

I guess we'll see.

I would prefer if we had more amplification of the ridge with the actual front settling to the south, but I guess the chance for a severe weather event isn't zero.

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you can see CU building in perhaps a convergence zone well ahead of the front over western MO into IA..the moisture return is over central IL in that cloud arc heading north..here 10 degree jumps in dewpoints occur as it moves north

this may pop rather soon...new RUC hints at that

post-142-0-30441400-1306076132.gif

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