SPC AC 111947
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0247 PM CDT TUE MAY 11 2010
VALID 112000Z - 121200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM KS/OK/WRN N TX ENEWD INTO
THE LOWER OH VALLEY...
...KS/OK INTO WESTERN N TX...
FORECAST REMAINS GENERALLY ON TRACK ACROSS THE SRN PLAINS
REGION...AS WARM FRONTAL RETREAT CONTINUES ACROSS OK. A
HEATING/MOISTENING/DESTABILIZING ATMOSPHERE SPREADING NNWWD ACROSS
OK SHOULD SUPPORT AT LEAST ISOLATED STORM DEVELOPMENT THIS
AFTERNOON...AND HAVE SLIGHTLY INCREASED SEVERE WEATHER PROBABILITY
SWD OVER SWRN OK/WRN N TX IN RESPONSE TO SUBSTANTIAL ONGOING
DESTABILIZATION. A FURTHER INCREASE IN CONVECTION IS EXPECTED THIS
EVENING/OVERNIGHT...AS ASCENT ASSOCIATED WITH A SMALL SHORT-WAVE
TROUGH NOW EVIDENT ACROSS CENTRAL AND NERN NM/SERN CO SPREADS ACROSS
SWRN KS/THE TX AND OK PANHANDLES TOWARD WRN OK.
ALONG WITH A THERMODYNAMIC ENVIRONMENT QUITE SUPPORTIVE OF
LARGE/VIGOROUS STORMS...AN INCREASING SLY LOW-LEVEL JET THIS EVENING
BENEATH MODERATELY STRONG WSWLYS AT MID-LEVELS WILL PROVIDE SHEAR
SUPPORTIVE OF SUPERCELLS. THUS...POTENTIAL FOR VERY LARGE HAIL AND
LOCALLY-DAMAGING WINDS REMAINS EVIDENT...WITH A FEW TORNADOES ALSO
POSSIBLE -- PARTICULARLY OVER WRN AND N CENTRAL OK THIS AFTERNOON
AND EVENING.
WHILE MENTIONED AS A POSSIBILITY IN THE PRIOR FORECAST...INDICATIONS
THAT WARM SECTOR STORM COVERAGE SHOULD REMAIN SCATTERED TO ISOLATED
PRECLUDE AN UPGRADE TO MODERATE RISK...THOUGH THE POTENTIAL FOR
LOCALLY SIGNIFICANT SEVERE WEATHER REMAINS EVIDENT.
...LOWER MO/MID MS/LOWER OH VALLEYS...
COLD FRONT CONTINUES TO SAG SEWD ACROSS MO/IL ATTM...AS THE SURFACE
LOW MAKES SLOW EWD PROGRESS. AIRMASS AHEAD OF THE FRONT CONTINUES
TO DESTABILIZE...PARTICULARLY ACROSS SRN MO. HOWEVER...LITTLE CU
DEVELOPMENT IS EVIDENT LIKELY DUE THE LACK OF LARGE-SCALE ASCENT --
AS THIS REGION CONTINUES TO LIE WITHIN A REGION OF UPPER RIDGING.
AN ISOLATED STORM CANNOT BE RULED OUT THIS AFTERNOON...WHILE
ISOLATED OVERNIGHT DEVELOPMENT COULD ALSO OCCUR AS THE SHORT-WAVE
TROUGH NOW CROSSING TX APPROACHES THIS REGION. WITH
INSTABILITY/SHEAR COMBINATION SUPPORTIVE OF SEVERE POTENTIAL WITH
ANY STORM THAT CAN DEVELOP...WILL MAINTAIN SLIGHT RISK AS FAR ENEWD
AS THE LOWER OH VALLEY. HOWEVER...ATTM THE THREAT APPEARS
CONDITIONAL/LIMITED.
..GOSS.. 05/11/2010
.PREV DISCUSSION... /ISSUED 1120 AM CDT TUE MAY 11 2010/
...NORTHWEST OK/SOUTH CENTRAL KS...
MORNING WATER VAPOR IMAGERY SHOWS A DISTINCT SHORTWAVE TROUGH MOVING
ACROSS SOUTHERN AZ/NM. THIS FEATURE IS WELL HANDLED BY THE 12Z
NAM/GFS AND IS EXPECTED TO TRACK INTO THE TX PANHANDLE AND WESTERN
OK THIS EVENING. AS THE TROUGH APPROACHES...SOUTHERLY LOW LEVEL
WINDS ARE FORECAST TO STRENGTHEN RAPIDLY ACROSS TX/OK. THIS WILL
RESULT IN RAPID LOW LEVEL MOISTENING AND DESTABILIZATION OVER MUCH
OF NORTHERN OK/SOUTHERN KS AROUND OR AFTER DARK. FORECAST SOUNDINGS
IN NORTHWEST OK INDICATE AN EXTREMELY UNSTABLE ENVIRONMENT WITH VERY
STEEP MID LEVEL LAPSE RATES AND A WEAKENING CAP. ALSO...WIND
PROFILES STRENGTHEN DRAMATICALLY DURING THE EVENING WITH EFFECTIVE
SHEAR OF 40-50 KNOTS AND EFFECTIVE SRH VALUES OF 200-400 M2/S2.
THIS SUGGESTS THE RISK OF SUPERCELLS CAPABLE OF VERY LARGE HAIL AND
A FEW TORNADOES DURING THE EVENING OVER NORTHWEST OK...WITH SGFNT
HAIL THREAT SPREADING NORTHEASTWARD INTO CENTRAL KS BY LATE EVENING.
CONSIDERED AN UPGRADE TO MODERATE RISK FOR PORTIONS OF THIS
AREA...BUT HELD OFF DUE TO CONCERNS OF CONVECTIVE COVERAGE.
...REMAINDER OF OK...
A VERY MOIST AND STRONGLY UNSTABLE AIRMASS WILL BE PRESENT
THROUGHOUT OK THIS AFTERNOON AND EVENING...WITH VARIOUS MODEL
SOLUTIONS SUGGESTING CONVECTIVE INITIATION POSSIBLE ACROSS THE
STATE. WEAK FORCING SUGGESTS AREAL COVERAGE OF STORMS WILL BE
LIMITED. HOWEVER...THERMODYNAMICS AND WIND PROFILES ARGUE FOR A
RISK OF SUPERCELL STRUCTURES IN ANY STORMS THAT FORM TODAY.
...SOUTHERN MO/NORTHERN AR INTO LOWER OH VALLEY...
SURFACE BOUNDARY CURRENTLY EXTENDS FROM NORTHEAST OK INTO SOUTHERN
MO. DEWPOINTS ARE CLIMBING TO THE SOUTH OF THE BOUNDARY WITH MID
60S VALUES EXPECTED BY AFTERNOON AS FAR EAST AS WESTERN KY/SOUTHERN
IND. BROKEN CLOUD COVER WILL SOMEWHAT LIMIT THE DAYTIME
HEATING/DESTABILIZATION. HOWEVER...A RATHER WEAK CAP AND
CONVERGENCE ALONG THE BOUNDARY WILL LIKELY BE SUFFICIENT FOR
SCATTERED THUNDERSTORM DEVELOPMENT. VERTICAL SHEAR PROFILES IN THIS
AREA ARE STRONG ENOUGH TO SUPPORT A RISK OF ORGANIZED MULTICELL TO
SUPERCELL STORMS CAPABLE OF LARGE HAIL...DAMAGING WINDS...AND EVEN
AN ISOLATED TORNADO.
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
|
