SPC AC 290548
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1248 AM CDT WED JUN 29 2011
VALID 301200Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN PLAINS
AND UPPER MS VALLEY...
...NRN PLAINS/UPPER MS VALLEY...
AN UPPER-LEVEL TROUGH IS FORECAST TO APPROACH THE NRN PLAINS
THURSDAY AS A MID-LEVEL JET STRENGTHENS AND MOVES INTO THE REGION
FROM THE SOUTHWEST. THIS WILL TAKE PLACE ACROSS A BROAD WARM SECTOR
ACROSS THE NRN PLAINS AND UPPER MS VALLEY. ALTHOUGH THE MODELS SHOW
A STRONGLY TO EXTREMELY UNSTABLE AIRMASS BY THURSDAY AFTERNOON...A
CAPPING INVERSION WILL LIKELY PREVENT CONVECTIVE INITIATION ACROSS
MOST OF THE REGION UNTIL THE EVENING WHEN LARGE-SCALE ASCENT WILL
INCREASE FROM THE WEST. HOWEVER...THE EXACT TIMING OF CONVECTIVE
INITIATION REMAINS HIGHLY UNCERTAIN DUE TO THE DRASTIC DIFFERENCES
IN THE NAM AND GFS SOLUTIONS. THE GFS SOLUTION WHICH IS CLOSER TO
THE ECMWF SOLUTION...IS MUCH FASTER WITH THE NEWD MOVEMENT OF THE
UPPER-LEVEL TROUGH WHICH COULD RESULT IN RAPID CONVECTIVE
DEVELOPMENT ACROSS NRN SD NEWD ACROSS CNTRL AND ERN ND AFTER 00Z
FRIDAY.
FORECAST SOUNDINGS IN NRN SD AND ERN ND AT 03Z SHOW MLCAPE VALUES IN
THE 3500 TO 5000 J/KG RANGE WITH SOME EVEN HIGHER AND 0-6 KM SHEAR
VALUES OF 45 TO 50 KT. THIS IS AN IMPRESSIVE ENVIRONMENT AND
SUPERCELL DEVELOPMENT APPEARS PROBABLE UPON INITIATION ESPECIALLY
ACROSS ERN ND. HAVE ADDED A 30 PERCENT SEVERE PROBABILITY AND
SIG-HATCHED AREA IN ERN ND AND FAR NW MN WHERE VERY LARGE HAIL COULD
OCCUR. THE ENHANCED SEVERE THREAT AREA IS LOCATED WHERE THE MODELS
MAXIMIZE THE COMBINATION OF INSTABILITY AND DEEP LAYER SHEAR AND ARE
THE MOST IN AGREEMENT CONCERNING STORM INITIATION. SOME TORNADOES
WILL ALSO BE POSSIBLE ESPECIALLY IF THE FASTER GFS SOLUTION VERIFIES
IN WHICH CONVECTION DEVELOPS SOONER AND THE LOW-LEVEL JET MOVES INTO
THE REGION EARLIER. IF A FAST MOVING CLUSTER OF STORMS OR A SMALL
MCS CAN ORGANIZE...THEN A WIND DAMAGE THREAT COULD ALSO EXIST.
FURTHER TO THE EAST IN THE UPPER MS VALLEY...THUNDERSTORM INITIATION
WILL ALSO BE POSSIBLE THURSDAY AFTERNOON ALONG A NORTH TO SOUTH
GRADIENT OF MODERATE TO STRONG INSTABILITY. THE MOST LIKELY LOCATION
FOR STORM INITIATION WOULD BE EAST OF AN UPPER-LEVEL RIDGE AXIS
ACROSS WI...UPPER MI AND NERN IL WHERE THE COMBINATION OF
INSTABILITY AND DEEP LAYER SHEAR WOULD SUPPORT A THREAT FOR HAIL AND
STRONG WIND GUSTS. THE CONVECTIVE THREAT IS EXPECTED TO REMAIN
ISOLATED DUE TO WARM TEMPS ALOFT AND A LACK OF LARGE-SCALE ASCENT.
..BROYLES.. 06/29/2011
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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