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2021 Short/Medium Range Severe Thread


Hoosier
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Although there is no instability farther east, would not be surprised to see some isolated damaging gusts with that band of shallow showers.  Some of the background/synoptic gusts will be flirting with or exceeding 58 mph anyway, and it won't take much downward momentum with those showers to make that happen.

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Tomorrow's system is of the type that could create a substantial regional tornado outbreak if it were April with a wide open Gulf (thinking here of a certain date in 1965).

Quote
As strong southerly warm-sector winds advect a seasonably moist
   airmass northward, ahead of the fast-moving/vigorous storm system,
   rapid evolution of the atmosphere will occur both thermodynamically
   and kinematically across the central CONUS.


Of course, these days that's always when a winter pattern decides to finally set in. :rolleyes:

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41 minutes ago, CheeselandSkies said:

Tomorrow's system is of the type that could create a substantial regional tornado outbreak if it were April with a wide open Gulf (thinking here of a certain date in 1965).

Decent chance it will. Low-level shear is outrageous but deep-layer shear suggests storms will quickly line out. Could be a mix of sups and LEWPs that produce after dark tomorrow imo. There are many indicators for long-trackers should the Euro's forecast instability materialize. Any capping there would easily be overcome by the dynamics ahead of the rapidly deepening, neg tilt 500mb wave. Below is an area avg sounding from the NE ~quarter of IA at 00Z tmrw eve. 

1394747426_ScreenShot2021-12-14at12_43_20PM.thumb.png.3279741c0d2478feaec979437b3c4bdb.png

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Just now, purduewx80 said:

Decent chance it will. Low-level shear is outrageous but deep-layer shear suggests storms will quickly line out. Could be a mix of sups and LEWPs that produce after dark tomorrow imo. There are many indicators for long-trackers should the Euro's forecast instability materialize. Any capping there would easily be overcome by the dynamics ahead of the rapidly deepening, neg tilt 500mb wave. Below is an area avg sounding from the NE ~quarter of IA at 00Z tmrw eve. 

1394747426_ScreenShot2021-12-14at12_43_20PM.thumb.png.3279741c0d2478feaec979437b3c4bdb.png

Surprised you're so bullish given the lack of substantial instability. That said, at 75kt RM, any tornado that persists for more than 10 minutes will be a longer tracked tornado.

The army of long tracked EF0s is upon us.

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1 minute ago, hlcater said:

Surprised you're so bullish given the lack of substantial instability. That said, at 75kt RM, any tornado that persists for more than 10 minutes will be a longer tracked tornado.

The army of long tracked EF0s is upon us.

I was trying and apparently failed to say the caveat is definitely instability. The Gulf is wide open, and the Euro shows what is possible. The EPS has been showing increasing probs for a high end event, as well. I'm not saying there will be a lot of tornadoes, but some of the LEWPs embedded in the line should have no trouble producing. Widespread severe winds is the slam dunk here.

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2 minutes ago, purduewx80 said:

I was trying and apparently failed to say the caveat is definitely instability. The Gulf is wide open, and the Euro shows what is possible. The EPS has been showing increasing probs for a high end event, as well. I'm not saying there will be a lot of tornadoes, but some of the LEWPs embedded in the line should have no trouble producing. Widespread severe winds is the slam dunk here.

needs to be an enhanced risk for wind if you ask me. 

Right now, 5/30/0 probs seem reasonable. Could see this going to a 10 if we're looking at 1000 MLCAPE by tomorrow morning.

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GRR jumping all in on the wind event with this next one.  I recorded 64MPH with the last one.  Don't really want anything higher like they are saying.

We are issuing, with this forecast package, a High Wind Watch
from 7 pm Wednesday till 1 pm Thursday for all but the I-69 area.
The HREF ensemble mean wind gust forecast has 60 to 65 mph
forecast at 1 am Thursday from South Haven to north of the of
Traverse City. With the last event, on the 11th, it had a small
area of 50 to 55 mph south of Grand Haven. As it turned out, it
was low by 10 to 15 mph based on our observations. Given that and
that ECMWF has gusts to 60 from Holland north and the GFS has 60
mph all the way east to I-75 and 63 mph to 69 mph west of US-131,
it makes sense to have a High Wind Watch for all but the SE CWA
(I-69). The strongest winds will be from around 10 pm (ish) to 7
am (ish). The model forecasts have been very persistent with this
idea of very strong winds Thursday morning.

That is the key message from this forecast package, high winds
Thursday morning. As we have been writing about in all of our
recent AFDs, we have a rapidly deepening surface low that tracks
from eastern Colorado tomorrow morning to north of Lake Superior
by 7 am Thursday morning. The upper level wave goes negative tilt
tomorrow (which explains the rapid deepening). There is a
significant trop fold with this system too. The results of this
is the forecast wind fields significantly strong for this storm
than they were for the system we had on Saturday the 11th. At
Grand Rapids, the 925 mb wind is 10 knots higher than the previous
event. Over our northwest CWA the wind field is 20+ knots strong
at 925 mb and 850 mb and at least 10 to 20 knots stronger near the
surface. Remember we had gusts in the 60 to 65 mph range near the
coast with that storm, 50 to 60 mph inland. I would expect higher
gusts with this event than with that previous event.

 

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