SPC AC 191724
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1224 PM CDT SAT SEP 19 2009
VALID 201200Z - 211200Z
...NO SVR TSTM AREAS FORECAST...
...CNTRL PLAINS/MID-MO VALLEY...
A RELATIVELY HIGH-AMPLITUDE UPPER-LEVEL TROUGH WILL MOVE EWD AROSS
THE NRN ROCKIES SUNDAY EMBEDDED IN A MUCH LARGER AND BROAD
UPPER-LEVEL TROUGH OVER THE PLAINS STATES AND MS VALLEY. AT THE
SFC...A WELL-DEFINED NORTH TO SOUTH COLD FRONT WILL MOVE EWD INTO
THE HIGH PLAINS. AHEAD OF THE FRONT...LOW-LEVEL MOISTURE WILL
INCREASE NWD ACROSS THE CNTRL PLAINS UNDERNEATH A STRONG CAPPING
INVERSION. ISOLATED THUNDERSTORMS APPEAR MOST LIKLEY TO DEVELOP
ALONG THE FRONTAL BOUNDARY IN THE HIGHER TERRAIN OF NERN CO AND SW
WY SUNDAY AFTERNOON GRADUALLY MOVING EWD INTO THE HIGH PLAINS AND
EXPANDING IN COVERAGE FROM NORTH TO SOUTH FROM SRN SD ACROSS WRN NEB
INTO NW KS BY MID TO LATE SUNDAY EVENING.
FORECAST SOUNDINGS ACROSS THE REGION AT 00Z SHOW STRONG DIRECTIONAL
VEERING BELOW 700 MB BUT LITTLE SPEED SHEAR RESULTING IN 0-6 KM
SHEAR VALUES PEAKING AT ABOUT 25 KT. THE SHEAR SHOULD BE WEAK ENOUGH
TO KEEP ANY SEVERE THREAT MARGINAL. HOWEVER...A FEW OF THE STRONGER
CELLS MAY HAVE A POTENTIAL FOR HAIL DUE TO STEEP MID-LEVEL LAPSE
RATES EXCEEDING 8.0 C/KM ASSOCIATED WITH AN EML ADVECTING EWD OUT OF
CO AND WY. IN SPITE OF THE INCREASE IN THUNDERSTORM ACTIVITY DURING
THE EVENING...FORECAST SOUNDINGS MAINTAIN A STRONG CAPPING INVERSION
SUGGESTING THE ELEVATED CONVECTION WILL HAVE TROUBLE PRODUCING
STRONG WIND GUSTS.
...OH AND TN VALLEYS...
A BROAD UPPER-LEVEL TROUGH WILL BE IN PLACE ACROSS MUCH OF THE CNTRL
AND ERN STATES. A SLIGHTLY MORE AMPLIFIED AND NEGATIVLEY TILTED
SECTION OF THE TROUGH IS FORECAST FROM THE MID-MS VALLEY SEWD ACROSS
THE GULF COAST STATES. SCATTERED THUNDERSTORMS SHOULD BE ONGOING
SUNDAY MORNING ALONG AND AHEAD OF THE AXIS OF THE UPPER-LEVEL TROUGH
WITH STORM COVERAGE INCREASING DURING THE AFTERNOON DUE TO
DESTABILIZATION. ALTHOUGH...VERTICAL SHEAR PROFILES ACROSS THE
REGION APPEAR ON THE LOW-SIDE FOR SEVERE STORMS...BOUNDARY LAYER
FLOW ASSOCAIATED WITH A LOW-LEVEL JET FROM NE MS NWD INTO IND AND OH
MAY BE ENOUGH FOR A FEW STRONG WIND GUSTS WITH THE MORE PERSISTENT
LINE-SEGMENTS.
..BROYLES.. 09/19/2009
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
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