Severe WX Severe Weather Threat June 19-22

[Kds86z]

Confidence is increasing in a higher end severe threat this weekend. Wording has gotten stronger on the new SPC day 3.

In addition, the Midwest could see severe weather Sunday and I expect that to be on the next extended.

SEVERE THUNDERSTORMS ARE POSSIBLE ACROSS PORTIONS OF THE CENTRAL
PLAINS VICINITY FROM SATURDAY AFTERNOON INTO SATURDAY EVENING. LARGE
TO VERY-LARGE HAIL, SEVERE WINDS (SOME 75+ MPH), AND TORNADOES ARE
POSSIBLE.

..CENTRAL PLAINS

MODEST SHORTWAVE RIDGING WITHIN THE PLAINS WILL BREAK DOWN AS A
SUBTLE SHORTWAVE APPROACHES THE CENTRAL ROCKIES DURING THE
AFTERNOON. GIVEN THE MODERATELY STRONG MID-LEVEL FLOW ACROSS THE
DIVIDE, A DEEPENING SURFACE LOW ALONG THE COLORADO/KANSAS BORDER
WILL AID MOISTURE RETURN INTO THE CENTRAL PLAINS SOUTH OF A STALLED
SURFACE BOUNDARY THAT WILL RETREAT NORTHWARD AS A WARM FRONT. WITH
MID/UPPER 50S F DEWPOINTS REACHING EASTERN COLORADO/WYOMING,
CONVECTION IS EXPECTED TO DEVELOP WITH THE TERRAIN OF SOUTHEAST
WYOMING AND PERHAPS ALONG THE SURFACE TROUGH AS WELL. STEEP
MID-LEVEL LAPSE RATES AND EFFECTIVE SHEAR NEAR 50 KT WILL SUPPORT
INITIAL SUPERCELL STRUCTURES. THESE STORMS WILL BE CAPABLE OF
LARGE/VERY-LARGE HAIL AND SEVERE WINDS, PARTICULARLY AS THEY
INTERACT WITH RICHER MOISTURE TO THE EAST. MOIST SOUTHEASTERLY
(BACKING TO NEAR EASTERLY ALONG THE SURFACE BOUNDARY) WILL ALSO
SUPPORT A THREAT FOR TORNADOES. THE TORNADO THREAT IS SOMEWHAT
UNCERTAIN GIVEN THE SOMEWHAT WEAK LOW-LEVEL FLOW. HOWEVER, SHOULD
STORMS REMAIN DISCRETE INTO THE EVENING, STRONG LOW-LEVEL
WINDS/LARGER HODOGRAPHS WOULD SUPPORT A GREATER TORNADO THREAT AND
POTENTIALLY A STRONGER TORNADO. WITH TIME, MODELS ARE IN GENERAL
AGREEMENT THAT SOME UPSCALE GROWTH WILL OCCUR. THIS APPEARS MOST
LIKELY TO OCCUR NEAR THE SURFACE BOUNDARY. AS THIS OCCURS, A MORE
ORGANIZED WIND THREAT WOULD DEVELOP AND WIND GUSTS OF 75+ MPH WOULD
BECOME MORE PROBABLE. AS CONFIDENCE IN THE CORRIDOR OF A POTENTIAL
MCS TRACK INCREASES, HIGHER PROBABILITIES WILL LIKELY BE NEEDED.

 

[CheeselandSkies]

Another one I can't chase. Working Sunday and then have plans in the afternoon (my wife and I are taking my parents to a dinner theatre show for Father's Day).

 

[TheSuckZone]

LOL

 

[slenker]

LOL

I'm tired boss.

 

[Brice W]

After everything that has happened this year I wouldnt sound the alarm bells until the day before. Theres only one thing different, this isn’t Illinois anymore. The plains might be in for a rude awakening from a long slumber.

LOL

View attachment 53745

 

[Kds86z]

@MichelleH can you pin? Thanks

 

[Kds86z]

 

[Kds86z]

 

[buckeye05]

This is so close to me I might have chase this one. A little nervous since this one looks a little more gnarly than the other setups I've chased recently but hey, sometimes you have to step outside of your comfort zone.

 

[Kds86z]

 

[Kds86z]

A LOWER PROBABILITY, BUT HIGHER POTENTIAL IMPACT SCENARIO COULD
DEVELOP ACROSS PARTS OF EASTERN MISSOURI INTO CENTRAL/SOUTHERN
ILLINOIS SUNDAY AFTERNOON IF A BETTER DEFINED, SURFACE LOW DEVELOPS
ALONG THE FRONT AND DEEPENS THROUGH THE DAY. THIS IS MOST NOTABLY
SHOWN BY THE NAM, BUT IS ALSO SHOWN TO A LESSER EXTENT BY THE ECMWF.
THIS COULD RESULT IN A LOCALIZED CORRIDOR OF GREATER TORNADO THREAT
ON SUNDAY DUE TO INCREASED LOW-LEVEL SHEAR. HOWEVER, THIS SCENARIO
WILL BE CONDITIONAL ON BOTH THE DEVELOPMENT OF THIS SURFACE LOW AND
THE LOCATION OF THE MORNING MCS. THEREFORE, GREATER PROBABILITIES
HAVE NOT BEEN ADDED, BUT THIS POTENTIAL SCENARIO WILL CONTINUE TO BE
MONITORED.

 

[WeathermanLeprechaun]

@mods, any chance you could pin this thread?


That 00z HRRR seemed like pretty classic bait, bunch of UH tracks but the environment wasn't greatly like you would've thought with several supercells, with strong tornadoes. I do expect a few tornadoes from this setup though, maybe after 00z when the PBL begins to decouple and the LLJ kicks in.

As for Sunday, I'm not stuck on the NAM solution regarding that stronger surface low as it's done that before where it suggests a more robust low and it's more of a one off what if type run. The morning MCS will also leave questions on how storms develop. With the weaker surface low, low level shear doesn't suggest any notable tornado threat with Sunday but trends can happen. We will see. We will not know how this day goes until the morning convection moves thru.

 

[Kds86z]

Latest day 1:

..SUMMARY

SEVERE THUNDERSTORMS ARE LIKELY ACROSS PORTIONS OF THE CENTRAL
PLAINS VICINITY FROM SATURDAY AFTERNOON INTO SATURDAY EVENING. LARGE
TO VERY-LARGE HAIL, SEVERE WINDS (SOME 75+ MPH), AND TORNADOES ARE
POSSIBLE.

..CENTRAL PLAINS

WITH THE APPROACH OF THE MODEST SHORTWAVE TROUGH, A LEE CYCLONE WILL
DEEPEN THROUGH THE AFTERNOON NEAR THE COLORADO/KANSAS BORDER. MID
60S F DEWPOINTS ARE POSSIBLE IN PARTS OF THE CENTRAL HIGH PLAINS
WITH UPPER 60S F DEWPOINTS MORE PROBABLE INTO CENTRAL/EASTERN
KANSAS. CONVECTION IS EXPECTED TO DEVELOP WITHIN THE HIGHER TERRAIN
OF SOUTHEAST WYOMING/SOUTHWEST SOUTH DAKOTA AND WITHIN THE LEE
TROUGH/CYCLONE BY MID/LATE AFTERNOON. EARLIER THUNDERSTORM
DEVELOPMENT DOES APPEAR POSSIBLE WITHIN WEAK WARM ADVECTION NEAR THE
NORTHWARD LIFTING SURFACE BOUNDARY IN CENTRAL/EASTERN NEBRASKA.
40-50 KT OF EFFECTIVE SHEAR AND STEEP MID-LEVEL LAPSE RATES WILL
PROMOTE INITIAL SUPERCELLS CAPABLE OF LARGE/VERY-LARGE HAIL, SEVERE
WINDS, AND TORNADOES. THE DEGREE OF TORNADO RISK IS SOMEWHAT
UNCERTAIN AS THERE COULD BE A RELATIVELY QUICK TRANSITION TO LINEAR
MODES. DISCRETE STORMS THAT CAN PERSIST INTO THE EVENING WOULD
ENCOUNTER GREATER LOW-LEVEL SHEAR AS THE LOW-LEVEL JET STRENGTHENS.
A STRONG TORNADO WOULD BE POSSIBLE ESPECIALLY NEAR THE SURFACE
BOUNDARY WHERE SURFACE WINDS WILL REMAIN BACKED. QLCS CIRCULATIONS
WILL REMAIN POSSIBLE WITHIN LINEAR MODES AS WELL. AS LINEAR/BOWING
SEGMENTS DEVELOP DURING THE EVENING, THE RISK FOR SEVERE WIND GUSTS
(SOME 75+ MPH) WILL INCREASE. THE SOUTHERN EXTENT AND EASTERN EXTENT
OF THE MOST INTENSE ACTIVITY IS A BIT UNCERTAIN, BUT SOME RISK WILL
REMAIN EVEN INTO THE OVERNIGHT ON ACCOUNT OF THE VERY MOIST AIRMASS
AND LIMITED MLCIN.

 

[Kds86z]

 

[buckeye05]

Chasing wise, I’m not really a fan of how the models are trending sloppier combined with the SPC comment about a possible quick transition to linear mode. The only silver lining is the HRRR’s insistence on a lone supercell that fires along I-80 in west Nebraska. There could be massive chaser convergence though if that’s how it plays out.

 

[Kds86z]

 

[Kds86z]

 

[Kds86z]

 

[WeathermanLeprechaun]

Chasing wise, I’m not really a fan of how the models are trending sloppier combined with the SPC comment about a possible quick transition to linear mode. The only silver lining is the HRRR’s insistence on a lone supercell that fires along I-80 in west Nebraska. There could be massive chaser convergence though if that’s how it plays out.

If I was you, i wouldn't chase what appears to be a setup that will favor grungier, HP supercells with massive chaser convergence. There's always better (AND PHOTOGENIC) days to come that you should probably save for.

 

[WeathermanLeprechaun]

Regarding Sunday, the morning MCS will have implications on placement of risk area and the greatest svr area that more eastward. Or the MCS decays into the main svr event as we seen two days ago in IL/IN/OH. I am watching NE OK though for a conditional significant svr supercell or two. A few tornadoes, maybe even deviant given slack mid level winds but strong LLJ emerging, and large hail.