SPC AC 230556
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1256 AM CDT TUE JUN 23 2009
VALID 231200Z - 241200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTION OF THE N CENTRAL
U.S. INCLUDING THE UPPER MS AND MID MO VALLEYS...
...SYNOPSIS...
LITTLE CHANGE IS FORECAST ALOFT ON THE LARGE SCALE...AS A TROUGH/LOW
REMAINS OFF THE W COAST...A SECOND TROUGH/LOW LINGERS NEAR THE E
COAST...AND AN EXPANSIVE RIDGE AGAIN PREVAILS OVER THE CENTRAL
CONUS.
A SHORT-WAVE TROUGH MOVING ENEWD ACROSS MT/ND AND THE CANADIAN
PRAIRIE INTO WRN ONTARIO WITH TIME WILL HELP DRIVE A COLD FRONT SEWD
ACROSS THE N CENTRAL CONUS...WITH THIS BOUNDARY PROVIDING A FOCUS
FOR STORM DEVELOPMENT AND SOME SEVERE POTENTIAL THIS PERIOD.
...UPPER MS VALLEY SWWD ACROSS THE MID MO VALLEY INTO SERN WY/NERN
CO...
A CLUSTER OF STORMS MAY BE ONGOING AT THE START OF THE PERIOD INVOF
N CENTRAL AND NERN NEB/S CENTRAL AND SERN SD...WHICH SHOULD WEAKEN
THROUGH THE MORNING. PRESENCE OF LARGE-SCALE SUBSIDENCE ON NRN
FRINGE OF THE MID-LEVEL RIDGE SHOULD SUPPRESS NEW STORM DEVELOPMENT
AS THE AIRMASS DESTABILIZES AHEAD OF THE APPROACHING COLD FRONT INTO
THE AFTERNOON. BY MID TO LATE AFTERNOON HOWEVER...HEATING/MIXING
COMBINED WITH LOW-LEVEL CONVERGENCE INVOF THE FRONT -- AND NEAR
REMNANT CONVECTIVE CARCASS INVOF IA LEFT OVER FROM EARLIER STORM
CLUSTER -- SHOULD RESULT IN SCATTERED STORM DEVELOPMENT FROM NRN MN
SWWD INTO NRN NEB. STORMS SHOULD ALSO DEVELOP OVER NERN CO/SERN
WY...JUST N OF THE SURFACE FRONT WHERE ELY/NELY LOW-LEVEL UPSLOPE
FLOW AIDES STORM INITIATION.
WHILE NOT PARTICULARLY STRONG...VEERING FLOW WITH HEIGHT ACROSS THIS
AREA SHOULD YIELD SHEAR SUFFICIENT FOR ORGANIZED/ROTATING STORMS.
THUS -- EXPECT LARGE HAIL AND DAMAGING WINDS WITH THE STRONGER
CELLS. ATTM...WILL MAINTAIN ONLY 15% SEVERE PROBABILITY...AS
PRESENCE OF LARGE-SCALE RIDGING ALOFT SHOULD ACT TO LIMIT OVERALL
STORM COVERAGE/INTENSITY.
CONVECTION MAY LINGER INTO THE EVENING AS LOW-LEVEL FLOW INCREASES A
BIT FROM THE SW ACROSS WRN IA AND VICINITY...TURNING MORE SEWD AS IT
NEARS THE ERN FRINGE OF THE MID-LEVEL RIDGE. WEAKER SHEAR AND
DIURNAL STABILIZATION SHOULD HOWEVER YIELD A DIMINISHING SEVERE
THREAT OVERNIGHT.
...THE SOUTHEAST...
ANOTHER DAY OF SCATTERED SHOWERS AND THUNDERSTORMS IS
ANTICIPATED...AS SMALL SHORT-WAVE FEATURES CONTINUE MOVING SWD/SSEWD
ACROSS THE REGION ON THE ERN FRINGE OF THE CENTRAL U.S. RIDGE --
THROUGH A MOIST/UNSTABLE AFTERNOON AIRMASS. WHILE OVERALL SEVERE
POTENTIAL SHOULD REMAIN FAIRLY LOW...LOCALLY-STRONGER/SEVERE STORMS
WILL BE POSSIBLE -- PARTICULARLY WHERE CLUSTERS OF CELLS CAN
ORGANIZE AND MOVE SWD AS SMALL W-E LINE SEGMENTS. ACTIVITY SHOULD
DIURNALLY DIMINISH DURING THE EVENING.
..GOSS/SMITH.. 06/23/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
|
