Memorial Day weekend severe threats

[Indystorm]

1 hour ago, JoMo said:

10% hatched tornado. Yikes.

Stay vigilant and safe.  Hopefully there is nothing like a repeat in your immediate area.  But watch the boundary left behind those overnight storms to your southeast later in the day.

[Torchageddon]

 

[janetjanet998]

at 1145z there is a small convective system over NE KS moving due east .,,with an outflow boundary sagging south..

behind that over north central Kansas a weak line of elevated convection is ongoing and moving more SE...this may impact to the warm sector and could be the seeds for the big wind complex later....

will it weaken and let instability build up until late afternoon....or do we see an early start....time will tell

the 06z NAM nest has the north central convection becoming the main show but seems a little slow with the NE Kansas convection position

[janetjanet998]

An upgrade to high is possible

 

IDESPREAD SEVERE WIND GUSTS ARE FORECAST FROM THE OZARK REGION TO  
THE LOWER OHIO VALLEY TODAY.  ADDITIONALLY, VERY LARGE TO GIANT HAIL  
AND TORNADOES WILL BE POSSIBLE FROM THE RED RIVER VALLEY  
NORTHEASTWARD TO THE OZARK PLATEAU. DAMAGING WINDS, LARGE HAIL, AND  
A COUPLE TORNADOES WILL ALSO BE POSSIBLE ACROSS THE TENNESSEE  
VALLEY, MIDDLE OHIO VALLEY, AND PORTIONS OF THE MID-ATLANTIC.  
   
..SYNOPSIS  
  
THE UPPER-AIR PATTERN FEATURES A BROAD FETCH OF ZONAL TO  
WEST-SOUTHWESTERLY FLOW OVER MUCH OF THE CENTRAL/EASTERN U.S.,   
DOWNSTREAM FROM A POSITIVELY TILTED TROUGH.  THAT TROUGH -- NOW  
EVIDENT IN MOISTURE-CHANNEL IMAGERY FROM A LOW OVER NORTHERN MB  
ACROSS ND, WY, UT AND SOUTHERN NV -- SHOULD EXTEND FROM MN TO  
NORTHERN NM BY THE END OF THE PERIOD.   
  
AT THE SURFACE, 11Z ANALYSIS SHOWED A WAVY, GENERALLY  
QUASISTATIONARY FRONTAL ZONE FROM VA TO OH THEN WEST-SOUTHWESTWARD  
ACROSS SOUTHERN IL AND CENTRAL MO.  A COLD FRONT WAS EVIDENT FROM  
NORTHWESTERN IA ACROSS EASTERN/SOUTH-CENTRAL NE TO NORTHEASTERN NM.   
THE FRONT HAS BEEN DIFFUSED TEMPORARILY BEHIND AN OUTFLOW BOUNDARY  
RELATED TO ONGOING CONVECTION OVER NORTHEASTERN KS, BUT WILL CATCH  
UP TO THAT BOUNDARY AND THUS THE WARM SECTOR WITH TIME.  A WAVY  
DRYLINE WAS DRAWN FROM THE EASTERN TX PANHANDLE TO THE BIG BEND  
REGION.  THE DRYLINE WILL MOVE EASTWARD TODAY TO CENTRAL/SOUTHERN OK  
AND WEST-CENTRAL TX.  THE COLD FRONT WILL OVERTAKE THE DRYLINE AND  
THE OUTFLOW BOUNDARY FROM NORTHWEST-SOUTHEAST THROUGH THE OVERNIGHT  
HOURS, REACHING EASTERN MO AND NORTHEAST THROUGH SOUTHWEST TX BY  
12Z.    
   
..LOWER MISSOURI VALLEY, OZARKS TO OHIO VALLEY AND RED RIVER  
  
THE ONGOING CONVECTION OVER NORTHEASTERN KS WAS FORECAST BY MOST OF  
THE SYNOPTIC AND HIGH-RES PROGS INITIALIZING FROM 00-09Z TO WEAKEN  
AND SHRINK MUCH SOONER THAN EVIDENT IN CURRENT COVERAGE/INTENSITY.   
THIS CASTS SOME UNCERTAINTY ON THE NORTHERN AND WESTERN PARTS OF THE  
OUTLOOK AREA, IN TWO WAYS:  
1.  WHETHER THIS INITIAL CONVECTION AND RELATED ISALLOBARIC  
PERTURBATION WILL EVOLVE INTO OR DIRECTLY INFLUENCE THE  
EVENTUAL/EXPECTED MAJOR WIND-PRODUCING MCS AS IT ENCOUNTERS  
DIURNALLY DESTABILIZING AIR OVER EASTERN KS AND WESTERN MO, AND/OR  
2.  THE INFLUENCE OF THE TRAILING OUTFLOW BOUNDARY ON SUBSEQUENT  
THUNDERSTORM POTENTIAL OVER SOUTH-CENTRAL/SOUTHEASTERN KS.   
THUNDERSTORMS EITHER DEVELOPING ALONG THIS BOUNDARY, OR CROSSING IT  
FROM BEHIND, SHOULD GAIN ACCESS TO SURFACE-BASED INFLOW AND  
EXPAND/INTENSIFY RAPIDLY.    
  
IN EITHER EVENT, THE DOWNSHEAR AIR MASS WILL BE VERY FAVORABLE FOR  
UPSCALE ORGANIZATION OF A FORWARD-PROPAGATING, POTENTIALLY  
DERECHO-PRODUCING MCS.  SIGNIFICANT-SEVERE/HURRICANE-FORCE  
THUNDERSTORM GUSTS AND NUMEROUS DAMAGE REPORTS ARE POSSIBLE IN THE  
MODERATE-RISK AREA.  AN UPGRADE MAY BE WARRANTED LATER TODAY.  
HOWEVER, UNCERTAINTIES RELATED TO INFLUENCE OF THE ONGOING ACTIVITY  
AND TIMING OF GREATEST STORM ORGANIZATION PRECLUDE OFFERING ANY  
MORE-FOCUSED UNCONDITIONAL PROBABILITIES AT THIS TIME.  IN ADDITION  
TO WIND, LINE-EMBEDDED/TORNADIC CIRCULATIONS ARE POSSIBLE.  EMBEDDED  
SUPERCELLS MAY OCCUR, ESPECIALLY IN ANY FRONTAL BACKBUILDING THAT  
MAY OCCUR TOWARD NORTHEASTERN/CENTRAL OK LATE AFTERNOON AND EVENING.  
  
VERY STEEP MIDLEVEL LAPSE RATES WILL OVERLIE A RICHLY MOIST AND  
STRONGLY HEATED BOUNDARY LAYER CONTAINING UPPER 60S TO MID 70S F  
SURFACE DEW POINTS AND 15-18 G/KG MEAN MIXING RATIOS.  THIS YIELDS  
MLCAPE LOCALLY EXCEEDING 6000 J/KG IN FORECAST SOUNDINGS SOUTHEAST  
OF THE COLD FRONT AND OUTFLOWS, AND EAST OF THE DRYLINE, FROM THE  
WESTERN OZARKS ACROSS EASTERN OK TO THE RED RIVER, AMIDST  
EFFECTIVE-SHEAR MAGNITUDES OF 45-55 KT.  SUCH EXTREME INSTABILITY IS  
NEAR RECORD LEVELS, BASED ON HISTORIC SOUNDINGS.  THE CAPE-SHEAR  
PARAMETER SPACE APPEARS COMPARABLE TO A FAST-DEVELOPING,  
DRYLINE-INITIATED SUPERCELL/TORNADO EVENT ON 26 MAY 1997 IN EASTERN  
OK, BUT WITH THE ADDED RISK THIS TIME OF A DERECHO ON THE NORTHEAST  
SIDE.  SUCH EXTREME INSTABILITY WILL SUPPORT EXPLOSIVE GROWTH OF  
THUNDERSTORMS THAT DO BREAK THE CAP -- WHETHER THROUGH FORCED ASCENT  
ON A COLD POOL OR FRONT, OR IN ANY DISCRETE TO SEMI-DISCRETE CELLS  
THAT CAN MOVE OFF THE DRYLINE.  DRYLINE-STORM RISK IS CONDITIONAL  
AND MORE ISOLATED DUE TO THE STRONG EML AND RELATED CINH, BUT ALSO  
POTENTIALLY DANGEROUS WITH GIANT HAIL OF 3-5 INCHES IN DIAMETER AND  
SIGNIFICANT TORNADOES POSSIBLE.  BY LATE EVENING, A SWATH OF  
CONVECTION SHOULD EXTEND FROM THE OHIO VALLEY INTO SOUTHERN OK AND  
PERHAPS NORTH TX, WITH THE OVERALL SEVERE THREAT DIMINISHING  
OVERNIGHT.   

[csnavywx]

Explosive....

 

Note the hail analogs and matching sig. hail parameter. Not a lot of capping either, just a diurnal inversion.

 

[Memphis Weather]

Can't be too often you get a SPC outlook discussing potential of a derecho *and* 5-inch diameter hail....

[bjc0303]

9 minutes ago, csnavywx said:

Explosive....

 

Note the hail analogs and matching sig. hail parameter. Not a lot of capping either, just a diurnal inversion.

 

Capping is likely to spread into SGF as the stronger/steeper/warmer EML temps are advected eastward.

[janetjanet998]

The atmosphere can do amazing things in these sets ups..

 

I remember about 8 years ago a wild derecho over S IL with 110  MPH wind gust and an EYE...and in the northern eye wall Tornadoes 

and damaging wake low winds on its NW side

[brettjrob]

Should be a crazy day with widespread significant severe, but the MCS-driven crashing front, packed-isobar scenario looks to be unfolding, which should put a fairly low ceiling on any widespread supercell tornado potential. Still a serious situation for the general public -- as mentioned above, this kind of environment often does "crazy" things with any storm mode or mixture thereof.

[janetjanet998]

13z HRRR seems to develop storms along the true WF over central MO and also a little further south(maybe an old outflow boundary)..also maybe discrete for a couple of hours

[csnavywx]

46 minutes ago, bjc0303 said:

Capping is likely to spread into SGF as the stronger/steeper/warmer EML temps are advected eastward.

Short range guidance shows some capping moving in (as does the visible sat with the telltale washboard appearance to the southwest), though convT could easily be reached. Bit of orographic lift could fire off a few cells over the Ozarks ahead of the main line.

[bjc0303]

29 minutes ago, brettjrob said:

Should be a crazy day with widespread significant severe, but the MCS-driven crashing front, packed-isobar scenario looks to be unfolding, which should put a fairly low ceiling on any widespread supercell tornado potential. Still a serious situation for the general public -- as mentioned above, this kind of environment often does "crazy" things with any storm mode or mixture thereof.

Yeah, not liking the prospects of widespread supercell activity, however... Storms will organize fast, could go from Tcu to tornado in progress in very quick time. Might be a day where you just have to be there as early as possible, might get a tornado, then you're going to have to reposition as your storm gets enveloped by precip/upscale growth occurs. You may have to hop on every storm that goes up, and hope it produces, move on, etc.

[Santa Clause]

Yea, tornado potential does not have me buying in or interested. If derechos are your thing, then big day ahead.

[bjc0303]

8 minutes ago, Wmsptwx said:

Yea, tornado potential does not have me buying in or interested. If derechos are your thing, then big day ahead.

There very well could be (probably will be) several tornadoes from both the linear systems and the initial discrete supercells, even some strong ones possibly. To write that off would be absurd.

But things are going to evolve quickly.

[Indystorm]

We may still get unwanted surprises this afternoon and evening.  It is scary to scan parameters on the SPC meso page even this early in the day and anticipate what might come later.  9.5 mid level lapse rate.  Possible record CAPE values?  An historic derecho with at least some supercell tors thrown in for good measure.  Don't underestimate low level helicity and boundaries.

[bjc0303]

1 minute ago, Indystorm said:

We may still get unwanted surprises this afternoon and evening.  It is scary to scan parameters on the SPC meso page even this early in the day and anticipate what might come later.  9.5 mid level lapse rate.  Possible record CAPE values?  An historic derecho with at least some supercell tors thrown in for good measure.  Don't underestimate low level helicity.

How can something be historic before it even happens?

 

 

[Santa Clause]

2 minutes ago, bjc0303 said:

There very well could be (probably will be) several tornadoes from both the linear systems and the initial discrete supercells, even some strong ones possibly. To write that off would be absurd.

But things are going to evolve quickly.

I should be clearer, today has extremely dangerous potential and certainly the threat for that type of Tornado exists, but for chasers and those who enjoy a good discrete supercell, today looks less promising.

[Indystorm]

1 hour ago, bjc0303 said:

How can something be historic before it even happens?

 

 

I perhaps should have said "possible historic derecho."  It's all about surveying current parameters and anticipating what might possibly evolve later compared with parameters for past events.

[JoMo]

What's causing all the clouds and attempted shower/storm over the OK/KS border in NE OK?

[janetjanet998]

3 minutes ago, JoMo said:

What's causing all the clouds and attempted shower/storm over the OK/KS border in NE OK?

was just about to post about that...and MO too

14z HRRR(at least the 1st few frames) picking up on it

perhaps lift from the MVC more NW?

may prevent CAPE from reaching full potential later over parts of MO?

 

[bjc0303]

Isentropic ascent along the outflow boundary evident in N OK would be responsible for that, perhaps weak ascent from perturbations aloft contributing.

[Weatherdemon]

5 minutes ago, JoMo said:

What's causing all the clouds and attempted shower/storm over the OK/KS border in NE OK?

Looks like there are a several boundaries laid down causing most except the cell on the OK/KS border but it's laying down a boundary too.

edit: he's right about the N boundary.

[janetjanet998]

ESOSCALE DISCUSSION 0862  
NWS STORM PREDICTION CENTER NORMAN OK  
0959 AM CDT SAT MAY 27 2017  
  
AREAS AFFECTED...SOUTHERN/EASTERN KANSAS INTO THE MISSOURI  
OZARKS/LOWER MISSOURI VALLEY  
  
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE   
  
VALID 271459Z - 271700Z  
  
PROBABILITY OF WATCH ISSUANCE...40 PERCENT  
  
SUMMARY...AT LEAST ONE, IF NOT SEVERAL, SEVERE WEATHER WATCHES ARE  
LIKELY TODAY ACROSS THE AREA.  AT THE PRESENT TIME, THIS SEEMS MOST  
PROBABLE LATER THIS AFTERNOON, RATHER THAN EARLY.  
  
DISCUSSION...THUNDERSTORM ACTIVITY CONTINUES TO DEVELOP ACROSS AND  
NORTHEAST OF PORTIONS OF THE MIDDLE/LOWER MISSOURI VALLEY, IN  
ASSOCIATION WITH AN INITIAL WEAK IMPULSE WITHIN THE MID-LATITUDE  
WESTERLIES, WHICH IS EXPECTED TO PROGRESS TOWARD THE UPPER MIDWEST  
THROUGH MID TO LATE AFTERNOON.  IT APPEARS THAT THIS ARCING BAND  
WILL PROGRESS THROUGH A NARROW CORRIDOR OF RELATIVELY MOIST AIR  
AHEAD OF IT, BEFORE APPRECIABLE HEATING AND DESTABILIZATION CAN TAKE  
PLACE.  AND NORTHEAST OF THE DES MOINES IA/KIRKSVILLE MO AREAS, NEAR  
SURFACE INFLOW IS LIKELY TO BECOME DRIER AND MORE STABLE, WHICH  
APPEARS TO LIMIT SEVERE WEATHER POTENTIAL.  
  
IN THE WAKE OF THIS LEAD ACTIVITY, AN AREA OF ENHANCED LOWER/MID  
TROPOSPHERIC WARM ADVECTION IS ALSO MAINTAINING CONVECTIVE  
DEVELOPMENT ACROSS PARTS OF EAST CENTRAL AND NORTHEAST KANSAS, ON  
THE NORTHERN PERIPHERY OF A PLUME OF VERY WARM, ELEVATED MIXED LAYER  
AIR.  THIS FORCING IS EXPECTED TO CONTINUE TO DEVELOP SOUTHEASTWARD,  
NEAR AND TO THE WEST THROUGH SOUTH OF KANSAS CITY INTO THE 18-21Z  
TIME.   IN THE PRESENCE OF STEEP MID-LEVEL LAPSE RATES, RELATIVELY  
STRONG SHEAR, AND SIZABLE CAPE EVEN FOR ELEVATED MOIST PARCELS, THE  
RISK FOR AT LEAST SEVERE HAIL MAY NOT BE NEGLIGIBLE, AND COULD  
POSSIBLY INCREASE A BIT THROUGH EARLY AFTERNOON.  HOWEVER, RAPID  
SUBSTANTIVE INTENSIFICATION SEEMS LIKELY TO AWAIT WEAKENING OF  
INHIBITION FOR MOIST BOUNDARY LAYER PARCELS, AND THIS SEEMS MOST  
PROBABLE SOUTHEAST OF THE KANSAS CITY METRO INTO THE MISSOURI OZARKS  
LATER THIS AFTERNOON.  
  
SOME RECENT NEW CONVECTIVE DEVELOPMENT IS ONGOING ACROSS PARTS OF  
THE MISSOURI OZARKS, NEAR THE INTERSECTION OF AN OUTFLOW BOUNDARY  
LEFT BY PRIOR CONVECTION, AND AN APPARENT SOUTHEASTWARD ADVANCING  
GRAVITY WAVE.  SIMILAR TO CONVECTION TO THE NORTHWEST, THIS ACTIVITY  
MAY PERSIST AND CONTINUE TO SLOWLY INCREASE WHILE DEVELOPING  
SOUTHEASTWARD ALONG THE RETREATING OUTFLOW BOUNDARY ACROSS SOUTHERN  
MISSOURI.  BUT SIGNIFICANT RAPID INCREASE ACCOMPANIED BY MORE  
PROMINENT SEVERE WEATHER POTENTIAL WILL PROBABLY REQUIRE  
CONSIDERABLE FURTHER DOWNSTREAM BOUNDARY LAYER HEATING AND  
DESTABILIZATION.  

[OUGrad05]

Any thoughts as to why the models are generally keeping NE OK dry until near dark?  In some cases after dark?  Warm sector basically stays quiet until 7pm on one model and nearer 9 on a couple others....yet these same models in many cases depict little or no CINH.  Other factors seem to point to CI around 4pm.  I don't get it, what am I (or the models) missing?

[Quincy]

17 minutes ago, OUGrad05 said:

Any thoughts as to why the models are generally keeping NE OK dry until near dark?  In some cases after dark?  Warm sector basically stays quiet until 7pm on one model and nearer 9 on a couple others....yet these same models in many cases depict little or no CINH.  Other factors seem to point to CI around 4pm.  I don't get it, what am I (or the models) missing?

Minimal large scale forcing? 09z HRRR suggests 12hr 500mb height rises of 10-20m between 09-21z. There's also a southeastward-surging boundary moving through late this morning.

[OUGrad05]

3 minutes ago, Quincy said:

Minimal large scale forcing? 09z HRRR suggests 12hr 500mb height rises of 10-20m between 09-21z. There's also a southeastward-surging boundary moving through late this morning.

Yeah, I'm not sure what to make of that gravity wave or whatever moving through.  

[tornadoguy11]

What's the website that updates the SPC faster then the actual SPC page?


Sent from my iPhone using Tapatalk

[Quincy]

1 minute ago, OUGrad05 said:

Yeah, I'm not sure what to make of that gravity wave or whatever moving through.  

I know it's just a small area, but I'm currently in Vinita with -RA and low overcast ceilings. Ugly, but that may work to keep LCLs down in the area. 

[OUGrad05]

3 minutes ago, Quincy said:

I know it's just a small area, but I'm currently in Vinita with -RA and low overcast ceilings. Ugly, but that may work to keep LCLs down in the area. 

I'm home in Owasso, its sunny again here, you'll get clearing soon I suspect.

[Quincy]

1 minute ago, OUGrad05 said:

I'm home in Owasso, its sunny again here, you'll get clearing soon I suspect.

I'm not concerned, especially based on satellite trends. Heading up to Joplin to assess and keep a wide area in play for this afternoon.