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Significant Severe Events: June 14th-19th


andyhb

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SEVERE WEATHER STATEMENT

NATIONAL WEATHER SERVICE OMAHA/VALLEY NEBRASKA
1033 AM CDT MON JUN 16 2014
 
NEC109-155-161615-
/O.CON.KOAX.SV.W.0178.000000T0000Z-140616T1615Z/
SAUNDERS NE-LANCASTER NE-
1033 AM CDT MON JUN 16 2014
 
...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1115 AM CDT
FOR CENTRAL SAUNDERS AND NORTH CENTRAL LANCASTER COUNTIES...
 
AT 1033 AM CDT...A SEVERE THUNDERSTORM WAS LOCATED 8 MILES SOUTHEAST
OF VALPARAISO...OR 13 MILES NORTH OF LINCOLN...MOVING NORTHEAST AT 
30 MPH. THIS STORM HAS PRODUCED HAIL 3 INCH HAIL IN RAYMOND...WHICH 
IS LARGER THAN BASEBALL SIZE. 
 
THIS IS A VERY DANGEROUS STORM.
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Important point, and a true point.  If you looks at sfc observations behind this current convection, there's very little, if any, effect from any sort of residual cold pool.  Until an organized cold pool develops, this convection in and of itself bears very little consequence to what's going to happen later.

Radar trends indicate that one-hourly precipitation in association with the multicellular cluster is decreasing, albeit slowly. I would agree that the dryline looks best just to be on the safe side, but I think that the threat farther NE looks increasingly like a "go" as rainfall continues to decrease. I expect some strong surface heating early this afternoon in parts of nern NE. Anyone who disagrees may feel free to correct me.

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VALID 161630Z - 171200Z

 

...NRN/CNTRL PLAINS INTO UPPER MIDWEST TODAY THROUGH TONIGHT...

12Z OBSERVED SOUNDINGS FROM LBF...DDC...AND TOP SHOWED A VERY MOIST
BOUNDARY LAYER WITH LOWEST-100-MB MEAN-MIXING RATIOS OF 14-15 G PER
KG SURMOUNTED BY 700-500-MB LAPSE RATES OF 8-9 C/KM. DIFFERENTIAL
ADVECTIONS ASSOCIATED WITH A NEWD-MIGRATING 40-50 KT LLJ AND
STRENGTHENING SWLY FLOW IN THE 700-500-MB LAYER WILL RESULT IN THE
DEVELOPMENT OF A SIMILAR THERMODYNAMIC STRATIFICATION INTO THE MID
MO VALLEY TODAY WITH AFTERNOON MLCAPE VALUES OF 3000-4000+ J/KG TO
THE S OF THE WARM FRONT.

SEVERE TSTMS HAVE DEVELOPED THIS MORNING FROM THE VICINITY OF THE
WARM FRONT OVER ERN SD SWD INTO THE WARM SECTOR OVER ERN NEB WITH
THIS ACTIVITY LIKELY BEING FORCED BY WAA ALONG THE LLJ AND FORCING
FOR ASCENT ATTENDANT TO THE ABOVE-MENTIONED SHORT-WAVE TROUGH MOVING
INTO THE NRN AND CNTRL PLAINS. GIVEN THE CONTINUED INFLUX OF THE
MODERATE TO STRONGLY UNSTABLE AIR MASS FROM THE S/SW...EXPECT A
SUBSET OF THESE STORMS TO EVOLVE INTO A FORWARD PROPAGATING MCS
/WITH EMBEDDED SUPERCELL AND BOWING STRUCTURES/ WITH THE RISK FOR
VERY LARGE HAIL...TORNADOES...AND POTENTIALLY WIDESPREAD DAMAGING
WINDS AFFECTING PORTIONS OF SRN MN AND IA THROUGH THIS
AFTERNOON...AND EVENTUALLY INTO PARTS OF WI AND NRN IL THIS EVENING
INTO TONIGHT.


OTHER MORE ISOLATED STORMS ARE EXPECTED TO DEVELOP THIS AFTERNOON
FROM WRN SD TO N-CNTRL KS AS LOW-LEVEL CONVERGENCE IS ENHANCED BY
THE DEEPENING SURFACE LOW OVER SWRN NEB. THE CO-LOCATION OF MODERATE
TO STRONG INSTABILITY WITH VERTICALLY VEERING WIND PROFILES WITH
35-50 KT OF EFFECTIVE BULK SHEAR WILL BE QUITE FAVORABLE FOR
SUPERCELLS CAPABLE OF VERY LARGE HAIL...AND TORNADOES...A COUPLE OF
WHICH COULD BE SIGNIFICANT. THE GREATEST TORNADO RISK MAY
MATERIALIZE WITH ANY MATURE SUPERCELLS THAT CAN FAVORABLY INTERACT
WITH THE OUTFLOW BOUNDARY GENERATED BY THE EARLY-DAY STORMS OVER ERN
PARTS OF SD/NEB.

 

SPC 1630Z D1 outlook keeps MDT Risk with 10% TOR, 45% wind, and 45% hail. The dryline looks to be the best bet for a significant tornado or two. Personally, I would have gone with 15% TOR as the cold pool doesn't look to be a significant player in the wake of the multicellular cluster in nern NE.

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Some of us are betting on this stuff....

 

J/k, it doesn't really matter.

Interesting the HRRR keeps popping stuff in the western risk zone and killing it like an hour or three later. Wonder why. 

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Interesting the HRRR keeps popping stuff in the western risk zone and killing it like an hour or three later. Wonder why. 

Over north central Nebraska? That stuff looks to be behind the dry line and there probably isn't enough buoyancy and lift to keep it going compared to the stuff that looks to fire on the dry line and east of it.

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Interesting the HRRR keeps popping stuff in the western risk zone and killing it like an hour or three later. Wonder why. 

HRRR also appears to rapidly diminish instability/ CAPE after initiation of those storms... That'd be my best guess as to why those storms collapse after about 1-2 hours. Don't appear to be behind the DL imo.

 

EDIT: At least diminish the instability where the storms are located, but not so much to the NE and E and Sfc-based CIN also ramps up A LOT.

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HRRR also appears to rapidly diminish instability/ CAPE after initiation of those storms... That'd be my best guess as to why those storms collapse after about 1-2 hours. Don't appear to be behind the DL imo.

 

If he is talking about north central Nebraska then it is behind the dryline...

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HRRR initiates in east-central Nebraska... 

EDIT: I believe he was talking about what it develops in EC NE not NC NE.

 

The 15z HRRR did not have a good handle at all with the convection currently ongoing moving into western IA.

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HRRR initiates in east-central Nebraska... 

EDIT: I believe he was talking about what it develops in EC NE not NC NE.

15z had like one or two behind the dry line but most of the activity in NE doesn't last long on that run. 

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15z had like one or two behind the dry line but most of the activity in NE doesn't last long on that run. 

 

Yeah I am not buying the stuff on the dryline falling apart like it shows and even at face value there is a 6 hour window where the dryline stuff maintains itself nicely, it isn't until after 03z that it is choked off by SBCIN.

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That storm NE of Omaha is looking good, beginning to develop an appendage on reflectivity.

Plus the environment these storms will be in for a few hours hours is going to be pretty favorable. At least if the SRH and SHR keeps shifting further east along with the current storms.

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In the longer term I'd watch the cells coming north out of KS near Superior.  Effective sig tor up to 10, CAPE near 5000, rich moisture and strong helicity are signs that we may have a very active afternoon and evening.

 

There's nothing on the satellite... those returns near Superior are probably associated with chaff or ACCAS.

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