May 7th-9th Severe Weather Episodes

[andyhb]

Even 19 May 2013 might be another example where storm coverage, at least, was underestimated down the dryline by CAMs the night prior. Perhaps someone else can recall in more detail.\

 

The NSSL WRF absolutely nailed this event the night prior, it had the two supercells (Edmond/Carney and Shawnee) in practically the exact locations they ended up verifying.

 

I wish I had a graphic of it, because it was almost creepy.

[KSWx]

The NSSL WRF absolutely nailed this event the night prior, it had the two supercells (Edmond/Carney and Shawnee) in practically the exact locations they ended up verifying.

 

I wish I had a graphic of it, because it was almost creepy.

 

Great write-up on the event which includes the graphics (comparison of radar and simulated reflectivity) you mentioned as well as a few other products:

 

https://ams.confex.com/ams/94Annual/webprogram/Handout/Paper234022/ATL_paper_AJC.pdf

[brettjrob]

The NSSL WRF absolutely nailed this event the night prior, it had the two supercells (Edmond/Carney and Shawnee) in practically the exact locations they ended up verifying.

 

I wish I had a graphic of it, because it was almost creepy.

 

Yeah, I do recall the NSSL WRF graphic that had one hour with a 10 mile wide swath that was entirely maxed out on the NSSL site's color table - the only time I've seen that. Couldn't recall how much of the other guidance supported sustained storms down to I-40, though. It's probably not a great example.

[Chicago Storm]

I'm not chasing Sunday or Monday, but as for Sunday I would likely start out in Woodward, OK.

Obviously the earlier best looking play in W. OK is more questionable now, this starting point would allow one to play S. KS or adjust further south if needed.

Obviously moisture and capping are the biggest concerns. Given forcing another concern of mine is coverage, as in there might be too much storm interference across the northern threat area near the KS/OK border on northward. Most guidance also has activity in the morning/day across portions of TX/OK/KS, but pushes it east of I-35 by afternoon. We'll have to see it that materializes, how long it lingers, and what affects it might have given initiation of the main event likely in the 18-20z range for the aforementioned northern threat area.

[jojo762]

Fairly large ENH area...

Day 2 

 

...THERE IS AN ENH RISK OF SVR TSTMS MONDAY AFTERNOON AND EVENING  
ACROSS PARTS OF NORTHEAST TEXAS...EASTERN OKLAHOMA...SOUTHEASTERN  
KANSAS...SOUTHWESTERN MISSOURI...WESTERN AND CENTRAL ARKANSAS AND  
NORTHWEST LOUISIANA...  
 
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SURROUNDING AREAS OF THE  
CENTRAL AND SOUTHERN PLAINS INTO MIDDLE MISSISSIPPI VALLEY...  
 
...THERE IS A MRGL RISK OF SVR TSTMS AS FAR NORTH AS THE MID  
MISSOURI VALLEY...AND AS FAR SOUTH AS THE TEXAS COASTAL PLAIN...  
   
..SUMMARY  
 
SEVERE STORMS ARE POSSIBLE MONDAY INTO MONDAY NIGHT ACROSS PARTS OF  
THE LOWER CENTRAL PLAINS INTO THE OZARK PLATEAU...AND PERHAPS  
SURROUNDING AREAS OF THE CENTRAL AND SOUTHERN PLAINS INTO THE MIDDLE  
AND LOWER MISSISSIPPI VALLEY.  
   
..SYNOPSIS  
 
A SIGNIFICANT MID-LEVEL CLOSED LOW EMERGING FROM THE INTERMOUNTAIN  
WEST STILL APPEARS LIKELY TO REACH THE NEBRASKA PANHANDLE VICINITY  
BY 12Z MONDAY. THIS FEATURE MAY THEN BEGIN TO PIVOT NORTHWARD  
TOWARD THE NORTHERN PLAINS...WHILE UNDERGOING CONSIDERABLE  
DEFORMATION /PARTICULARLY LATE MONDAY THROUGH MONDAY NIGHT/...AS A  
SIGNIFICANT UPSTREAM SHORT WAVE TROUGH CONTINUES TO DIG INTO THE  
NORTHERN ROCKIES. MODELS SUGGEST THAT THIS LATTER FEATURE WILL BE  
ACCOMPANIED BY AN EVOLVING LOW WHICH WILL BECOME THE MORE PROMINENT  
CIRCULATION BY 12Z TUESDAY.  
 
IN LOWER LEVELS...A BROAD DEEP AREA OF LOW PRESSURE MAY LINGER OVER  
THE CENTRAL PLAINS THROUGH MUCH OF THE DAY. BUT A WARM FRONT  
EXTENDING EAST OF THE LOW /ACROSS PARTS OF THE MID MISSOURI INTO  
MIDDLE MISSISSIPPI VALLEY/...AND A DRYLINE TRAILING TO THE SOUTH OF  
THE LOW /THROUGH THE CENTRAL AND SOUTHERN PLAINS/...MAY BECOME MORE  
DIFFUSE. CONTRIBUTING TO THIS...CONSIDERABLE CONVECTION MAY BE  
ONGOING AT THE OUTSET OF THE PERIOD ALONG THE WARM FRONT AND WITHIN  
THE WARM/MOIST SECTOR.  
 
CONSIDERABLE FURTHER MOISTENING OF THE WARM SECTOR BOUNDARY LAYER IS  
POSSIBLE ON CONTINUING RETURN FLOW FROM THE GULF OF MEXICO...AT  
LEAST AS FAR NORTH AS EASTERN OKLAHOMA/WESTERN ARKANSAS BY LATE  
AFTERNOON. BENEATH REMNANTS OF ELEVATED MIXED LAYER AIR...AND A  
GRADUALLY WARMING MID-LEVEL COLD POOL OVERSPREADING THE  
PLAINS...THIS PROBABLY WILL SUPPORT CAPE ON THE ORDER OF 1000-2000  
J/KG. STRONGEST INSTABILITY MAY BE MOSTLY FOCUSED ALONG THE DRYLINE  
FROM PARTS OF NORTHEAST TEXAS INTO SOUTHEAST KANSAS.  
HOWEVER...COINCIDING WITH LOWER/MID TROPOSPHERIC WARM  
ADVECTION...AND LARGE-SCALE ASCENT AHEAD OF AN IMPULSE PIVOTING  
AROUND THE SOUTHERN PERIPHERY OF THE DEFORMING CIRCULATION OVER THE  
NORTHERN PLAINS...GRADUAL DESTABILIZATION OF THE BOUNDARY LAYER  
NORTHEASTWARD INTO THE OZARK PLATEAU IS POSSIBLE MONDAY EVENING.  
   
..LOWER CENTRAL PLAINS INTO THE OZARK PLATEAU  
 
THERMODYNAMIC CONDITIONS...PARTICULARLY INITIALLY NEAR THE  
DRYLINE...ARE EXPECTED TO BE CONDUCIVE TO WIDELY SCATTERED TO  
SCATTERED SEVERE STORM DEVELOPMENT BY MONDAY AFTERNOON. THE MOST  
CONCENTRATED AND STRONGEST ACTIVITY IS STILL EXPECTED FROM PARTS OF  
NORTHEAST TEXAS AND EASTERN OKLAHOMA INTO PARTS OF SOUTHEAST  
KANSAS...AIDED BY 30-50 KT FLOW...VEERING FROM SOUTHERLY AT LOW  
LEVELS TO WEST SOUTHWESTERLY AT MID-LEVELS...BENEATH A STRONG  
HIGH-LEVEL JET. VERTICAL SHEAR WILL BE MORE THAN SUFFICIENT FOR A  
FEW SUPERCELLS...INCLUDING THE RISK FOR TORNADOES /A COUPLE PERHAPS  
STRONG/...IN ADDITION TO LARGE HAIL AND LOCALLY DAMAGING WIND GUSTS.  
THIS ACTIVITY IS EXPECTED TO DEVELOP EASTWARD...WITH DESTABILIZATION  
AND LARGE-SCALE ASCENT...INTO THE OZARK PLATEAU MONDAY EVENING. IT  
REMAINS UNCLEAR AT THIS TIME WHETHER STORMS WILL TEND TO REMAIN  
LARGELY DISCRETE IN NATURE...WITH CONTINUING TORNADIC POTENTIAL...OR  
WHETHER FORCING WILL SUPPORT THE UPSCALE GROWTH OF A MESOSCALE  
CONVECTIVE SYSTEM WITH DAMAGING WIND GUSTS BECOMING THE MORE  
PROMINENT SEVERE WEATHER THREAT...BEFORE DIMINISHING LATE MONDAY  
NIGHT.  
 
..KERR.. 05/08/2016  

[KSWx]

Lol, someone at the SPC is mixing the outlooks all up at the moment.

[jojo762]

Downgraded to just ENH... 

Day 1

 

...THERE IS AN ENH RISK OF SVR TSTMS ACROSS MUCH OF CENTRAL KS INTO  

NWRN OK...  
 
...THERE IS A SLGT RISK OF SVR TSTMS FROM NEBRASKA SWD INTO W CNTRL  
TX AND EWD INTO THE MID MO VALLEY...  
 
...THERE IS A MRGL RISK OF SVR TSTMS FROM THE CNTRL PLAINS TO THE  
RIO GRANDE VALLEY...  
   
..SUMMARY  
 
SEVERE THUNDERSTORMS ARE LIKELY ACROSS MUCH OF THE CENTRAL AND  
SOUTHERN PLAINS SUNDAY AFTERNOON AND EVENING. VERY LARGE HAIL AND A  
FEW TORNADOES ARE ANTICIPATED WITH THE PRIMARY THREAT AREA FROM  
CENTRAL KANSAS INTO NORTHWESTERN OKLAHOMA BEGINNING LATE AFTERNOON.  
   
..SYNOPSIS  
 
AN UPPER LOW WILL SHIFT SLOWLY EWD ACROSS THE CNTRL ROCKIES WITH  
EXPANDING AREA OF STRONG SWLY CYCLONIC FLOW ALOFT FROM NRN MEXICO  
INTO THE CNTRL/SRN PLAINS. PRECEDING THE MAIN JET MAX WILL BE A  
LEADING DISTURBANCE MOVING RAPIDLY TOWARD THE I-35 CORRIDOR IN KS/OK  
BY MIDDAY WHICH MAY RESULT IN EARLY ELEVATED THUNDERSTORMS. THIS  
WILL ALSO TEMPORARILY VEER 850 MB WINDS BEFORE THEY RESPOND TO THE  
DEEPENING LOW AND BACK AGAIN BY LATE AFTERNOON.  
 
AT THE SURFACE...LOW PRESSURE IS FORECAST TO DEEPEN OVER SWRN KS  
WITH A DRYLINE ARCING SEWD TO NEAR THE TX PANHANDLE/OK BORDER AT  
00Z...AND CONTINUING SWD INTO NWRN TX WHERE IT WILL STALL AND  
ACTUALLY RETREAT DURING THE EVENING. STRONG HEATING WILL OCCUR  
BEHIND THE DRYLINE...WITH UPPER 50S TO LOWER 60S F DEWPOINTS  
DEVELOPING TO THE E WHICH WILL RESULT IN A ZONE OF MODERATE  
INSTABILITY. WIND PROFILES WILL FAVOR SUPERCELLS ALONG AND E OF THE  
DRYLINE...BUT CAPPING WILL BE A CONCERN TOWARD I-35 FROM CNTRL OK  
INTO TX DUE TO A RELATIVELY COOL BOUNDARY-LAYER.  
 
...MUCH OF CNTRL KS INTO NWRN OK AND VICINITY LATE AFTERNOON INTO  
EARLY EVENING...  
THE EXPECTED QUALITY OF LOW-LEVEL MOISTURE...EFFECTS OF AN EARLY  
DISTURBANCE ALOFT AND PRECIPITATION...CAPPING AND LACK OF CONSISTENT  
MODEL QPF PROGS CURRENTLY PRECLUDE A MODERATE RISK. HOWEVER...AT  
LEAST ISOLATED SIGNIFICANT SEVERE STORMS APPEAR LIKELY DURING A  
SHORT TIME WINDOW FROM LATE AFTERNOON INTO EARLY EVENING FROM CNTRL  
KS INTO NWRN OK.  
 
SURFACE OBSERVATIONS AND LATEST OBSERVED SOUNDINGS ACROSS THE SRN  
PLAINS INDICATE MAINLY 50S F DEWPOINTS AS FAR S AS CNTRL TX...WITH A  
CORRIDOR OF MID 60S F DEWPOINTS ACROSS DEEP S TX AND IMMEDIATELY  
OFFSHORE. ALSO NOTED ON THE 00Z/8TH SOUNDINGS WAS A STRONG CAPPING  
INVERSION. WHILE STRONG SLY FLOW WILL OCCUR ACROSS THE REGION  
THROUGHOUT THE DAY...MODELS SUCH AS THE NAM APPEAR TO BE  
OVER-FORECASTING THE BOUNDARY-LAYER MOISTURE MAGNITUDE GIVEN CURRENT  
OBSERVATIONS. MORE LIKELY...ANY MID 60S F DEWPOINTS THAT DO DEVELOP  
WILL BE SHALLOW/SKIN LAYER...WITH A MEAN MIXED-LAYER DEWPOINT CLOSER  
TO PERHAPS 60-62. THE GFS SOUNDINGS APPEAR TO BE CLOSER TO REALITY  
IN THAT REGARD.  
 
HEATING MAY ALSO BE LIMITED DUE TO THE EARLY WAVE PASSAGE WITH A N-S  
ORIENTED ZONE OF ELEVATED RAIN AND THUNDERSTORMS FORECAST BY SEVERAL  
MODELS...FOCUSED OVER CNTRL/ERN KS INTO NRN OK. SOME MARGINAL HAIL  
CANNOT BE RULED OUT WITH THIS ACTIVITY GIVEN COOL TEMPERATURES  
ALOFT.  
 
BY LATE AFTERNOON...CONVERGENCE SHOULD INCREASE ALONG THE DRYLINE  
FROM WRN KS INTO WRN OK. STRONG HEATING WILL CLEARLY RESULT IN DEEP  
MIXING...AND A NARROW ZONE OF MODERATELY UNSTABLE AND UNCAPPED AIR  
IS EXPECTED TO SUPPORT SCATTERED SUPERCELL DEVELOPMENT. STRONGLY  
VEERING WINDS WITH HEIGHT AND INCREASING SPEED SHEAR IN THE MID TO  
UPPER LEVELS WILL FAVOR VERY LARGE HAIL. STORM MODE ALSO SUGGESTS A  
FEW TORNADOES WILL BE POSSIBLE...WITH STRENGTH PERHAPS DEPENDENT ON  
BOUNDARY LAYER MOISTURE QUALITY. AT ANY RATE...THESE CELLS SHOULD  
PROGRESS INTO THE EARLY EVENING HOURS BUT A CAPPING INVERSION MAY  
LIMIT THEIR EWD EXTENT TO JUST W OF I-35/N OF I-40 IN OK...AND  
LITTLE IF ANY ACTIVITY FARTHER S INTO NWRN TX. STORMS ARE EXPECTED  
TO BE MOST NUMEROUS ACROSS KS NEAR THE LOW...AND WHERE TEMPERATURES  
WILL BE COOLER ALOFT. OTHER HAILSTORMS ARE LIKELY INTO NEBRASKA IN A  
ZONE OF WARM ADVECTION NEAR WARM FRONT. A FEW CLUSTERS OF STORMS  
COULD PERSIST INTO ERN KS AND WRN MO...WITH A HAIL AND WIND THREAT.  
   
..W CNTRL INTO NWRN TX OVERNIGHT  
 
HEIGHT FALLS/COOLING ALOFT WILL OCCUR OVERNIGHT AS A SECONDARY  
SHORTWAVE TROUGH DEVELOPS OVER SWRN TX. THIS WILL DRIVE A COLD FRONT  
EWD WHICH WILL INTERACT WITH AN UNSTABLE AIR MASS AIDED BY A STRONG  
SLY LOW-LEVEL JET. A MIXED STORM MODE APPEARS LIKELY WITH BOTH HAIL  
AND WIND POSSIBLE AS STORMS EVOLVE TOWARD W CNTRL AND NWRN TX.  
 
..JEWELL/ROBINSON.. 05/08/2016  

[rolltide_130]

Lol, someone at the SPC is mixing the outlooks all up at the moment.

 

It's the servers. These things are horrific at updating when there's high traffic on the SPC site (I.E before potential severe outbreaks)

[Chinook]

Note: you can find SPC products at http://kamala.cod.edu/spc

 

the 06z update usually updates just after 06z, even if there is a little delay on the SPC web pate

[jojo762]

Honestly a bit surprised there is not a MDT risk still for very large hail somewhere in SW/SC KS

[nwohweather]

00z RAOB at AMA shows some pretty insane lapse rates. 10.0C/KM 0-3KM Lapse Rate, whereas the SPC mesoanalysis page currently shows AMA at ~7.0C/KM... Same goes for 700-500mb layer being off by a bit... These lapse rates will be completely untouched-- due to the absence of overnight/morning convection and be allowed to advect into the warm sector tomorrow, should help instability quite a bit, among other things... Should also make for some prolific hail producers.

God 10° C/KM is a completely unstable atmosphere as you gotta remember the dry lapse rate is 10° as well. Don't see that often

[andyhb]

The rare 06z downgrade. Good to see a proactive approach as opposed to last Tuesday's.

[rolltide_130]

Looks like they went 10% hatched on the TOR. Those things have busted left and right lately. Looks like isolated 60's DP's have made it to about central TX. Couple spots of upper 60's along the coast. I'm fairly doubtful those advect northward enough though. 

[KSWx]

Note: you can find SPC products at http://kamala.cod.edu/spc

 

the 06z update usually updates just after 06z, even if there is a little delay on the SPC web pate

 

 

Good call, I rarely stay up this late and don't usually catch them when they first come out, thanks.

[rolltide_130]

Honestly a bit surprised there is not a MDT risk still for very large hail somewhere in SW/SC KS

 

Ehhh I'm not really. Looks like capping could be a legit concern even with the lapse rates in place. I kinda thought Broyles was being overzealous putting out the D2 MDT and well, it got downgraded on the initial D1. Seems like they're being a bit more conservative after 4/26 which frankly is a better call. No sense in trying to put out a higher-end outlook if there's uncertainties on the table. 

[jojo762]

Ehhh I'm not really. Looks like capping could be a legit concern even with the lapse rates in place. I kinda thought Broyles was being overzealous putting out the D2 MDT and well, it got downgraded on the initial D1. Seems like they're being a bit more conservative after 4/26 which frankly is a better call. No sense in trying to put out a higher-end outlook if there's uncertainties on the table. 

In Kansas... Capping will not be nearly as much of a concern as it will in OK. 

[andyhb]

In Kansas... Capping will not be nearly as much of a concern as it will in OK. 

 

Yes but the parameters otherwise aren't as impressive there as in OK. I thought they might have kept it in for hail given the steep mid level lapse rates, but the tornado potential is looking quite questionable at this point.

[jojo762]

Yes but the parameters otherwise aren't as impressive there as in OK. I thought they might have kept it in for hail given the steep mid level lapse rates, but the tornado potential is looking quite questionable at this point.

Yeah.... I said for hail. Tornado potential is quite a bit more conditional than very large hail is in Kansas.

[nwohweather]

Ehhh I'm not really. Looks like capping could be a legit concern even with the lapse rates in place. I kinda thought Broyles was being overzealous putting out the D2 MDT and well, it got downgraded on the initial D1. Seems like they're being a bit more conservative after 4/26 which frankly is a better call. No sense in trying to put out a higher-end outlook if there's uncertainties on the table.

IMO it's more so the actual actions in the moment as opposed to the outlooks. The real mess up was that awful PDS watch a few weeks ago

[weatherextreme]

Honestly a bit surprised there is not a MDT risk still for very large hail somewhere in SW/SC KS

 

 

After reading over the wordings It doesn't seem like they completely closed the books on a potential moderate for later outlooks.

[rolltide_130]

Yeah.... I said for hail.

 

They went 30% so it's not exactly low-end. Even 4/26 maxed out at 45% and the thermodynamic environment was significantly more impressive. Frankly seems like a good outlook to me until the moisture comes more into clarity. 

[bjc3395]

God 10° C/KM is a completely unstable atmosphere as you gotta remember the dry lapse rate is 10° as well. Don't see that often

Simultaneously, this is why capping looks to be such an issue tomorrow.

[Chinook]

God 10° C/KM is a completely unstable atmosphere as you gotta remember the dry lapse rate is 10° as well. Don't see that often

That's just the strong deep mixing you see over the Rockies, Arizona deserts, Great Basin desert, and the Plains west of the dryline.

[thewxmann]

Simultaneously, this is why capping looks to be such an issue tomorrow.

 

Actually capping is an issue despite those lapse rates. The EML does not appear to be particularly hot. It's just that the surface temperatures are going to be particularly cool. (Low-mid 70's temperatures in May in OK with a lee cyclone developing is a bit of a debby-downer.)

[nwohweather]

That's just the strong deep mixing you see over the Rockies, Arizona deserts, Great Basin desert, and the Plains west of the dryline.

It's just a shock to the system for someone who has lived in the Great Lakes their whole lives lol. Hell were lucky to approach 8 normally

[thewxmann]

BTW, Day 2 for Monday is an ENH with potential of strong tornadoes mentioned.

[Chinook]

Rocks, dry sand, and dry ground at higher elevations absorb the sunshine better, because there is less atmosphere in the way. It happens even better if there isn't much moisture in the atmosphere, or if there aren't any clouds. Then the atmosphere responds by mixing. You can get 95F at Denver, but you wouldn't get 95F at 5280 ft above sea level in Ohio. (That would be an 850mb temp of 35C) The whole western region mixes adiabatically to support warm temps at 4000-5000 ft, at certain times.

[nwohweather]

Rocks, dry sand, and dry ground at higher elevations absorb the sunshine better, because there is less atmosphere in the way. It happens even better if there isn't much moisture in the atmosphere, or if there aren't any clouds. Then the atmosphere responds by mixing. You can get 95F at Denver, but you wouldn't get 95F at 5280 ft above sea level in Ohio. (That would be an 850mb temp of 35C) The whole western region mixes adiabatically to support warm temps at 4000-5000 ft, at certain times.

Makes sense. Back in early March during a nice heatwave on our vacation in the Smokies we climbed up to 5-6000 feet and there was zero air. Granted it was dry, but 80/45 is still more humid than what it is out that way. It was actually very strange to feel almost no mixing, the wind was entirely zero at that elevation

[JasonOH]

At this point, i think 65 degree dews can make it to the Kansas border, but that isn't assured. The HRRRX, which has been on fire with dew points, gives me some confidence here. Right now, it looks like we are going to on I40 west and take the northwest passage to around Sieling or a bit further east. From there we will make the decision based on Obs weather to go north or stay and wait for the cap to break. I think there should be one storm in NW Oklahoma, and nothing further south. I think that that NW OK far southern Kansas will have the best overlap of shear, instability, and the cap actually breaking.

[jojo762]

Just an update on the current moisture situation... at least some moistening will continue to occur likely resulting in SFC DPs in the 63 to 66 range... Biggest question will be the depth of the low-level moisture. 

 

12Z OUN RAOB shows somewhat quality depth of the low-level moisture, despite the meager 58 DP (but that has/will go up.) Also, soundings from around the area...OUN/FWD/DDC... reveal that an impressive EML advected overnight into the plains.