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nrgjeff

Saturday May 27, 2017 Mid-South Mauler

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High CAPE moderate shear severe weather outbreak is becoming likely on Saturday from the southern Plains to the Ohio Valley, including our own Mid-South. While the southern Plains may get rocked, my focus will be in/near our subforum region and the Mid-South.

Friday IL/IN may go in Illinois and Indiana as the Thursday night Plains MCS ejects up that way and leaves an outflow boundary warm front hybrid. Friday heights will be rising slightly, and the next short-wave may be back in Missouri, but IL/IN will have high CAPE on a boundary. Still I would at least watch Friday. Atmosphere sometimes give hints of over/under the day before. 

Saturday could be a severe weather outbreak all the way from Oklahoma to Ohio, including all points in between and slightly south. Sunday morning the Saturday reports chart may look like something from an April outbreak. This time we trade in strong wind shear for high CAPE. Speed shear will be plenty for supercells though. Low level shear will be quite impressive on the synoptic warm front and any outflow boundaries from Friday night rain in Hosier Alley. 

Mid-South: On Saturday morning I expect a warm front and/or outflow boundaries to be draped near the Ohio River. Low pressure should track out of Missouri into the region. Smaller meso-lows are possible along the Ohio River Valley boundary as it lifts north. Locally higher storm-relative-helicity will be found east of any lows and really all along the boundary. Low level jet, which has frustrated Plains chasers, will be pumping right into the Mid-South. Mid-upper level winds will be WSW, none of this VBV prone SSW stuff. Though speed shear is not exceptionally high, turning with height and CAPE will both be robust. Stout upper level wave will come out by 00Z 5/28 and spark severe thunderstorms ahead of itself Saturday afternoon. 

SPC has Enhanced Risk Day 3. Pretty easy to read between the lines that a Moderate Risk is coming, perhaps as early as Day 2. MDT would probably centered from eastern OK into the Ozarks, but may extend into our Mid-South. At any rate Saturday severe storms are likely and may include tornadoes.

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Severe weather outbreak is still on-deck Saturday from Oklahoma, through Kansas and Missouri, into southern Illinois and Western Kentucky. Mid-South I am mainly referring to Western Kentucky and adjacent areas. Eastern Tennessee Valley will have its chance of thunderstorms this weekend, but Saturday big severe should be Mid-South and west.

Scenario 1: Some CAMs forecast MCSs to develop Saturday morning/midday around the Missouri Bootheel and also back toward KCMO. Warm front will be lifting north through the Mid-South. If the KCMO MCC accelerates it could become a serial derecho into eastern Missouri, Illinois and Western Kentucky. Might be some leading edge spin-ups or isolated cells ahead. Still the main threat would obviously be widespread straight line winds.

Scenario 2: Narrow path exists to warm front tornadoes. If the Bootheel MCS stabilizes Missouri early, the following KCMO MCC might slow down and weaken. Such a scenario would allow intense heating on the warm front, with afternoon supercells on the warm front from Missouri through Illinois and possibly West Kentucky. Either way CAPE is forecast quite high. LLJ is veered off but it can be less of a show stopper in the Mississippi Valley.

The other path to a few tornadoes involves the MCC locally enhancing the LLJ ahead of itself. Really narrow road with MCC chasing down anything.

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Son graduates Saturday then we are headed to the Land between the Lakes on the Tn side,rented a huge 14 br house for kin folk and all as my son wanted to go fishing.Crap of a time for severe weather.:(

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5 hours ago, jaxjagman said:

Son graduates Saturday then we are headed to the Land between the Lakes on the Tn side,rented a huge 14 br house for kin folk and all as my son wanted to go fishing.Crap of a time for severe weather.:(

You ever swing through E TN, we can put you on some trout on the South Holston.

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URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 280
   NWS Storm Prediction Center Norman OK
   515 PM CDT Sat May 27 2017

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     Southern Illinois
     Southwest Indiana
     Western and south-central Kentucky
     Far southeast Missouri
     Western and middle Tennessee

   * Effective this Saturday afternoon from 515 PM until Midnight
     CDT.

   ...THIS IS A PARTICULARLY DANGEROUS SITUATION...

   * Primary threats include...
     Widespread damaging winds expected with scattered significant
       gusts to 80 mph likely
     Scattered large hail and isolated very large hail events to 2
       inches in diameter possible
     A few tornadoes possible

   SUMMARY...A very fast-moving line of convection will continue to
   pose a risk for widespread wind damage as it races
   east-southeastward through the evening hours. A few tornadoes and
   hail will also be possible with the fast-moving squall line and/or
   other line-preceding storms.

   The severe thunderstorm watch area is approximately along and 70
   statute miles north and south of a line from 30 miles west northwest
   of Cape Girardeau MO to 55 miles east southeast of Bowling Green KY.
   For a complete depiction of the watch see the associated watch
   outline update (WOUS64 KWNS WOU0).

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Saw the Cumberland Plateau tornado warnings while we were sniffing the dirt in the Missouri Bootheel. Note the Bootheel through eastern Arkansas (the Delta) is as flat as eastern North Dakota or the western Texas Panhandle, and flatter than much of Kansas, Nebraska or Oklahoma. 

Bootheel.thumb.jpg.bc8573819113b28911f4f6507477b142.jpg

Marston MO Hwy EE or Elm St. Nightmare on Elm Street? Leading severe warned cell being swallowed up by rapidly advancing derecho. Believe straight line winds kicked up the dust which later became a massive wall hundreds of feet high, but not particularly photogenic. Possibly it started as a gustnado here, but will book it as straight line winds. Eventually lots of leaves, twigs and other very small debris was hurled across I-55 behind us as we moved south and ended the chase.

Lack of tornadoes was expected by that morning. It had become obvious that the LLJ was going to flake out. Examples of veered off (5/10/08 and 5/6/03) were no longer valid. They had veered LLJ. Saturday had no LLJ. However we figured take a shot at high CAPE, knowing it would probably be straight line winds. Derecho checklist was met. Still good to meet up and get out there.

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Quote
Public Information Statement
National Weather Service Morristown TN
739 PM EDT Sun May 28 2017 /639 PM CDT Sun May 28 2017/

...PUBLIC INFORMATION STATEMENT...

National Weather Service storm survey team investigated storm
damage in Morgan, Roane, Loudon, Knox and Blount counties. These
storms did exhibit some weak rotation aloft on radar at times as
the line of storms passed through these counties, but no tornado
paths were found by the survey team. The majority of the damage
consisted of downed trees with damage to structures due to trees
falling on the structures. Winds within the damage areas were
estimated at 70-80 mph.

The overall event that marched through the area was a Derecho,
with widespread thunderstorm wind damage. Within the Derecho, a
bow echo surged forward in these counties where the strongest
winds were indicated.

My house lost power for 24 hours but thankfully we had no damage to speak of.  Others in my neighborhood were still without power as of yesterday afternoon.  I've seen many large trees down around the area.

 

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