DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 211731
SWODY2
SPC AC 211729

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 PM CDT SAT MAR 21 2009

VALID 221200Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SRN SD...CNTRL
NEB AND WRN NEB...

...GREAT PLAINS...
A WELL-DEVELOPED UPPER-LEVEL TROUGH WILL MOVE QUICKLY EWD ACROSS THE
INTERMOUNTAIN WEST SUNDAY AS A POWERFUL 100 TO 110 KT MID-LEVEL JET
ROUNDS THE BASE OF THE TROUGH ACROSS THE SWRN STATES. AHEAD OF THIS
SYSTEM...A LEAD SHORTWAVE TROUGH IS FORECAST TO MOVE OVER THE GREAT
PLAINS SUNDAY AFTERNOON AND EVENING. AS THIS FEATURE MOVES INTO THE
CNTRL AND NRN PLAINS LATE SUNDAY AFTERNOON...SCATTERED THUNDERSTORMS
SHOULD DEVELOP ALONG THE AXIS OF A 40 TO 50 KT LOW-LEVEL JET FROM
ERN SD SWD INTO CNTRL KS. HOWEVER...MODEL FORECASTS DISAGREE ON HOW
FAR WEST THE CONVECTION WILL INITIATE. THIS ACTIVITY COULD INITIALLY
BE SFC-BASED BUT SHOULD QUICKLY BECOME ELEVATED AS A CAPPING
INVERSION BECOMES ESTABLISHED ACROSS THE PLAINS SUNDAY NIGHT.
FORECAST SOUNDINGS FROM THE GFS IN ECNTRL NEB NEAR THE CONVECTIVE
LINE AT 22Z SHOW RELATIVELY WEAK VERTICAL SHEAR PROFILES. THIS
COMBINED WITH THE WEAK INSTABILITY COULD KEEP ANY SEVERE THREAT
MARGINAL. IF THE NAM SOLUTION VERIFIES WITH A LINE FURTHER
WEST...SLIGHTLY STRONGER VERTICAL SHEAR AND STEEPER MID-LEVEL LAPSE
RATES WOULD BE SUFFICIENT FOR HAIL AND/OR MARGINALLY SEVERE WIND
GUSTS. THIS THREAT COULD EXTEND AS FAR SSWWD AS THE TX PANHANDLE.

AS THE UPPER-LEVEL TROUGH AND DEVELOPING UPPER-LEVEL LOW BEGIN TO
EJECT NEWD ACROSS THE CNTRL ROCKIES SUNDAY EVENING INTO THE
OVERNIGHT PERIOD...MODEL FORECASTS DEVELOP SCATTERED THUNDERSTORMS
ON THE NOSE OF A PLUME OF STEEP MID-LEVEL LAPSE RATES FROM WCNTRL
NEB NEWD INTO SRN SD. THIS ACTIVITY WOULD SPREAD NEWD ACROSS THE
REGION DURING THE LATE EVENING AND OVERNIGHT PERIOD. FORECAST
SOUNDINGS AT 03Z TO 06Z IN WCNTRL NEB SHOW VERY STEEP MID-LEVEL
LAPSE RATES...MODERATE VERTICAL SHEAR AND COLD AIR ALOFT /500 MB
TEMPS AROUND -18C. ALTHOUGH THE ACTIVITY SHOULD REMAIN
ELEVATED...THE THERMODYNAMIC AND SHEAR ENVIRONMENT WOULD BE
FAVORABLE FOR ISOLATED SUPERCELLS WITH LARGE HAIL.

..BROYLES.. 03/21/2009

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