DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 090541
SWODY1
SPC AC 090539

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1239 AM CDT THU SEP 09 2010

VALID 091200Z - 101200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE NRN HIGH PLAINS...

...SYNOPSIS...
PV-ANOMALY AT THE BASE OF THE WRN STATES TROUGH WILL TRANSLATE ENE
AND REACH THE NRN HIGH PLAINS THURSDAY NIGHT. DOWNSTREAM LEE
TROUGH/LOW WILL STRENGTHEN DURING THE AFTERNOON ACROSS ERN PARTS OF
MT AND WY WITH SUBSEQUENT MOVEMENT INTO THE WRN DAKOTAS AND NEB
PANHANDLE THURSDAY EVENING.

...NRN HIGH PLAINS...
MID-LEVEL HEIGHT FALLS ON THE ORDER OF 30-60 METERS/12 HR ASSOCIATED
WITH THE ADVANCING UPPER TROUGH WILL INDUCE INCREASING SSELY LLVL
FLOW OVER THE HIGH PLAINS ON THURSDAY. THIS WILL TRANSPORT UPR
50S/MID 60S SURFACE DEW POINTS NWWD INTO ERN MT AND TO THE E OF THE
LEE TROUGH OVER NEB AND THE DAKOTAS. MID-LEVEL LAPSE RATES OF 7.5-8
DEG C PER KM ATOP THIS RETURNING MOISTURE WILL CONTRIBUTE TO MLCAPES
OF 1000-2000 J/KG BY AFTERNOON.

BAND OF ASCENT AHEAD OF THE PRIMARY PV-ANOMALY WILL BE IMPETUS FOR
HIGH-BASED CONVECTIVE INITIATION BY MID-AFTERNOON NEAR THE WY/NEB/SD
BORDER AS HEATING/MOISTENING WEAKENS INHIBITION. STORMS WILL GROW
STRONGER BY EARLY EVENING AS THEY ENCOUNTER COMPARATIVELY MORE
ROBUST INSTABILITY OVER SWRN ND...WRN SD AND THE NEB PANHANDLE.
OTHER STORMS WILL FORM FARTHER NW DURING THE EARLY EVENING OVER ERN
MT AND ROTATE ENE INTO WRN ND IN ASSOCIATION WITH THE PRIMARY UPPER
IMPULSE.

INITIAL STORMS WILL LIKELY EVOLVE INTO SUPERCELLS OWING TO 40-45 KTS
OF EFFECTIVE SHEAR AND MAGNITUDE OF MID-LEVEL LAPSE RATES. LARGE
HAIL...UP TO GOLFBALL SIZE...WILL BE THE PRIMARY THREAT AND STORMS
WILL TEND TO REMAIN DISCRETE THE LONGEST FROM WRN SD SWD INTO THE
NEB PANHANDLE. EVENTUALLY LOOSELY ORGANIZED LINE SEGMENTS WILL
BECOME THE PRIMARY MODE AS STORMS CONTINUE EWD ONTO THE LOWER
PLAINS. THE SEVERE THREAT SHOULD GRADUALLY WANE OVERNIGHT AS
ACTIVITY BECOMES MORE ELEVATED AND FARTHER REMOVED FROM THE
INSTABILITY.

..RACY/SMITH.. 09/09/2010

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