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2018 Short to Medium Range Severe Thread


tornadohunter

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New day 1 has an enhanced area for SE MO/S IL/SW IN/NW KY for wind and significant hail.

Quote

Day 1 Convective Outlook 
   NWS Storm Prediction Center Norman OK
   1253 AM CDT Thu May 31 2018

   Valid 311200Z - 011200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS
   SOUTHEAST MO...SOUTHERN IL...SOUTHERN IN...AND FAR WESTERN KY...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
   NORTHERN HIGH PLAINS...

   ...SUMMARY...
   Isolated to widely scattered severe thunderstorms remain possible
   Thursday from the Missouri Ozarks to the lower Ohio Valley and
   Tennessee Valleys as well as the northern High Plains and northern
   Rockies.

   ...Synopsis...
   Upper trough currently extending along the West Coast will gradually
   progress eastward throughout the day, likely extending from southern
   British Columbia through the Great Basin by 12Z Friday. Ridging will
   build across the Plains with the increasingly confluent flow ahead
   of the upper trough contributing to a gradual strengthening of the
   mid-level flow ahead of it. Farther east, the remnants of Alberto
   will continue northward into central Ontario, eventually becoming
   absorbed into the shortwave trough moving gradually across Ontario
   and upper Great Lakes.

   At the surface, low currently over eastern MT will become more
   defined throughout the day. Lee troughing will extend southward from
   this low to another low over southeast CO. Convective outflow from
   the ongoing MCS across northern OK/southern KS is expected to extend
   from southern IL across southern MO and into northeast OK.

   ...Ozark Plateau into the Mid-MS, Lower OH, and TN Valleys...
   Expectation is for the remnants/convectively induced vorticity from
   the ongoing MCS over northern OK/southern KS to move across central
   MO and into central IL from the early afternoon into the early
   evening. Outflow from this system will likely extend southwestward
   from southern IL across southern MO and into northeast OK. Both of
   these features (i.e. the vorticity maximum and outflow boundary)
   will act as stimuli for convection as the airmass destabilizes.
   Given the mesoscale nature of both of these features, some
   uncertainty exists regarding their actual location during the
   afternoon but consensus, both from the HREF members and NAM/GFS,
   places them near the areas described above.

   Airmass across the region will be quite moist with surface dewpoints
   in the upper 60s/low 70s and 100-mb mean mixing ratios near 15 to 16
   g per kg. Strong diurnal heating is also anticipated, with
   temperatures in the upper 80s during the afternoon.  Mid-level lapse
   rates aren't overly steep but the warm and very moist airmass still
   supports MLCAPE over 2500 J/kg. Additionally, some enhancement to
   the mid-level flow is possible as a result of the remnant MCS.
   Expectation is for initial discrete storms capable of very large
   hail to quickly transition into more linear/bowing segments favoring
   damaging wind gusts. Low-level flow isn't particularly favorable for
   tornadoes but the presence of the outflow boundary, strong low-level
   instability, and very moist airmass still supports a low-end tornado
   threat.

   Across the remainder of the region, favorable low-level moisture
   will result in afternoon destabilization and thunderstorm
   development amidst the broad low-level confluence. Isolated damaging
   wind gusts and hail will be possible with the more persistent
   updrafts and/or as a result of storm interactions.

 

 

day1otlk_1200.gif

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Watch just issued for SE IL and southern half of IN.

Quote

URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 136
   NWS Storm Prediction Center Norman OK
   1030 AM CDT Thu May 31 2018

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of
     Southeast Illinois
     Southern Indiana
     Northern Kentucky

   * Effective this Thursday morning and afternoon from 1030 AM
     until 500 PM CDT.

   * Primary threats include...
     Scattered large hail and isolated very large hail events to 2
       inches in diameter likely
     Scattered damaging wind gusts to 70 mph likely

   SUMMARY...A cluster of fast-moving thunderstorms over southern
   Illinois will track eastward across the watch area today, posing a
   risk of locally damaging wind gusts and hail.

   The severe thunderstorm watch area is approximately along and 60
   statute miles either side of a line from 45 miles west northwest of
   Evansville IN to 50 miles north northeast of Louisville KY. For a
   complete depiction of the watch see the associated watch outline
   update (WOUS64 KWNS WOU6).

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

   REMEMBER...A Severe Thunderstorm Watch means conditions are
   favorable for severe thunderstorms in and close to the watch area.
   Persons in these areas should be on the lookout for threatening
   weather conditions and listen for later statements and possible
   warnings. Severe thunderstorms can and occasionally do produce
   tornadoes.

   &&

   AVIATION...A few severe thunderstorms with hail surface and aloft to
   2 inches. Extreme turbulence and surface wind gusts to 60 knots. A
   few cumulonimbi with maximum tops to 500. Mean storm motion vector
   26035.

   ...Hart

 

ww0136_radar.gif

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IWX issued a head-scratching 3 t-storm warnings for my county in a half an hours' time for some pulse storms earlier this afternoon. So of course, I had to deploy spotters just so they could report no hail and no winds reported over 20 mph. :huh:

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Thought I was going to get split by the bow echo moving south of me and scattered severe moving just north of me but an OFB moving NE from the north part of the bow echo moved in and a storm exploded just west of me. Wasn't severe but had 30-40mph winds and torrential rain.

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...and yet another t-storm warning for my county today with no severe weather, just a nice summer's night thunderstorm. At least my spotters weren't playing whack-a-mole like we did with the pulse storms this afternoon.

I'm thinking 4 warned storms in a 7 hour period with no severe has to be some kind of record.

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On 5/31/2018 at 10:14 PM, IWXwx said:

...and yet another t-storm warning for my county today with no severe weather, just a nice summer's night thunderstorm. At least my spotters weren't playing whack-a-mole like we did with the pulse storms this afternoon.

I'm thinking 4 warned storms in a 7 hour period with no severe has to be some kind of record.

Yeah, definitely a bizarre weather day. Received zero actual severe reports, as in measurements, but TONS of gorgeous photos. I mean, if the bulletins were reworded as Sexy Cloud Warnings or something, then I'd say their accuracy would be 110%!

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Maybe I'm thinking too much into this, but I'm extremely interested if there's a relationship between the behavior of 2010s severe wx as a whole, and the late 1980s, and you could probably even include the early 30s and late 40s as well. All of these periods where characterized by low tornado counts, and many of these years were also fighting drought conditions in at least some part of the plains/midwest. Seems to be a distinct spacial correlation between these periods, almost like a 20-30 year oscillation. But correlation isn't causation. I wish someone smart would do a research paper into this, I think there might be something there.

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18 hours ago, hlcater said:

Maybe I'm thinking too much into this, but I'm extremely interested if there's a relationship between the behavior of 2010s severe wx as a whole, and the late 1980s, and you could probably even include the early 30s and late 40s as well. All of these periods where characterized by low tornado counts, and many of these years were also fighting drought conditions in at least some part of the plains/midwest. Seems to be a distinct spacial correlation between these periods, almost like a 20-30 year oscillation. But correlation isn't causation. I wish someone smart would do a research paper into this, I think there might be something there.

That is interesting, and worth noting although the detailed tornado record doesn't really go back far enough to draw any definitive conclusions.

However, the late '80s dry period didn't come right on the heels of a Super Outbreak, which had been ~10 years prior. Will also be interesting to see if the downswing is followed by a significant upswing as happened in the '90s. Pretty much every year in the first half of that decade except 1994 had impressive tornado activity throughout multiple regions and throughout different times of the spring, and in the fall as well (November 1992). Frankly I think we were lucky to get through that period without a mass-fatality event like occurred twice in 2011, with the impressive numbers of intense, long-track tornadoes in various outbreaks from 1992-93.

Back on topic, today's potential in the Dakotas seems to have diminished. GFS continues to tease the possibility of some active days next week, but also the possibility that it could be another dud (speaking here for MBY and areas within daily local chase range - southern WI, IA east of I-35 and IL north of I-80, possibly SE MN along the I-90 corridor).

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There's a bunch of big stuff from just west of Cedar Rapids over to central Iowa.  It is expected to dive south and miss CR.  It has been one of those years in which all the big stuff avoids my yard.  However, my garden could certainly do without the 70 mph wind and golfball size hail being reported.

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3 minutes ago, hawkeye_wx said:

There's a bunch of big stuff from just west of Cedar Rapids over to central Iowa.  It is expected to dive south and miss CR.  It has been one of those years in which all the big stuff avoids my yard.  However, my garden could certainly do without the 70 mph wind and golfball size hail being reported.

Yeah it's been a very slow year.  Think we've been in a slight risk once, and it was walked back to a marginal the day of.  

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32 minutes ago, Hoosier said:

Looks like LAF is getting nailed.  The airport gusted to 52 mph on the most recent ob... which is impressive as it seemed like it often came in on the lower end when I was there.

Might get hammered here before long if those storms NW of me hold together.

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Looks like the next several days are going to be quite conducive to MCSs across the sub. Some people don't like MCSs, but I for one will never turn them down. (unless its at 9 AM washing out severe weather, thats always fun.) Maybe a shot at something early on in the day Saturday and especially Sunday out here. However, because it's 2018, any formidable speed shear just doesn't exist, so neither day looks like anything more than a mesoscale day.

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