SWODY2
SPC AC 191725
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1225 PM CDT WED MAY 19 2010
VALID 201200Z - 211200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN TX/OK EWD ACROSS
AR/LA/MS AND INTO WRN AL/TN...
...SYNOPSIS...
AN UPPER LEVEL TROUGH FROM NEB/KS SWD INTO CENTRAL TX AT DAYBREAK IS
FORECAST TO EJECT SLIGHTLY NEGATIVELY-TILTED ACROSS THE LOWER/MS
VALLEY...AS A STRONG UPPER TROUGH DEEPENS AND MOVES EWD ACROSS THE
WRN STATES. MODELS ONLY SUGGEST A WEAK SURFACE TROUGH WILL BE
ASSOCIATED WITH UPPER TROUGH...WITH A MINOR SURFACE LOW LOCATED IN
WRN MO AND TRAILING SURFACE FRONT/TROUGH EXTENDING SWWD INTO NRN TX.
ALSO...WHILE THE SYNOPTIC WARM FRONT MAY BE IN MO...MORNING
CONVECTION IS LIKELY TO MAINTAIN A SUBTLE WARM FRONT FROM THE
ARKLATEX REGION SEWD INTO SRN AL DURING THE DAY THU.
...ERN TX/OK EWD ACROSS AR/LA/MS AND INTO WRN TN/AL...
SEVERE EVOLUTION ON THU WILL BE COMPLICATED BY WIDESPREAD CONVECTION
THAT IS EXPECTED TO BE ONGOING AT 12Z FROM MO/AR SWWD INTO SERN
OK/NRN TX. ALTHOUGH THE UPDRAFTS MAY BE SLIGHTLY DECOUPLED FROM
BOUNDARY LAYER...SHEAR AND INSTABILITY WILL BE FAVORABLE FOR THESE
STORMS TO BE SEVERE ACROSS AR...WRN TN...SERN OK AND NRN TX DURING
THE MORNING. PRIMARY THREAT SHOULD BE WIND DAMAGE AS CONGEALED
DOWNDRAFTS SHOULD HAVE CONSOLIDATED STORMS INTO ONE OR MORE MCS/S.
HOWEVER...WIND PROFILES/MODERATE INSTABILITY MAY ALSO SUPPORT AN
ISOLATED TORNADO AND SEVERE HAIL THREAT.
NAM/GFS SHOW DIFFERENT EVOLUTION OF CONVECTIVE PCPN ON THU. NAM HAS
BEEN CONSISTENT IN MORNING STORMS BEING MAINTAINED AND INTENSIFYING
AS A FORWARD PROPAGATING QLCS FROM THE ARKLATEX ESEWD ALONG BOUNDARY
INTO MS DURING THE AFTERNOON. THIS SOLUTION APPEARS MOST REASONABLE
GIVEN THE STRONG FORCING SPREADING EWD IN ASSOCIATION WITH THE UPPER
TROUGH. THE STRONG INSTABILITY AND FORECAST LINE MOTION AT 40-50 KT
WOULD BE VERY SUPPORTIVE OF DAMAGING WINDS...SOME WHICH COULD BE
SIGNIFICANT. ADDITIONALLY... THE LOW/DEEP LAYER SHEAR WOULD SUPPORT
TORNADOES WITHIN EMBEDDED BOWS. IF THIS SCENARIO APPEARS
LIKELY...PORTIONS OF AREA MAY BE UPGRADED TO A MODERATE RISK ON
UPCOMING DAY 1 OUTLOOKS.
FURTHER WEST ACROSS ERN OK AND NRN TX...AFTER MORNING CONVECTION
SHIFTS EAST OF THE AREA...PARTY CLOUDY SKIES SHOULD ALLOW
TEMPERATURES TO WARM INTO THE UPPER 70S AND 80S. THESE READINGS PLUS
THE MOIST BOUNDARY LAYER...EAST OF SURFACE TROUGH...WILL RESULT IN
MLCAPE VALUES FROM 2000-3000 J/KG. WEAK CONVERGENCE AND POSSIBLE
SUBSIDENCE BEHIND MCS OVER THE LOWER MS VALLEY MAY LIMIT STORM
COVERAGE. HOWEVER...MID LEVEL SPEED MAX COMBINED WITH STRONG
INSTABILITY AND 40-50 KT DEEP LAYER SHEAR WOULD SUPPORT AT LEAST
ISOLATED INTENSE SUPERCELLS BY LATE AFTERNOON. WHILE THE DEGREE OF
SHEAR AND VERY MOIST BOUNDARY LAYER MIGHT SUPPORT A TORNADO OR
TWO...RELATIVELY WEAK WINDS FROM THE SURFACE-700 MB SUGGEST THAT
VERY LARGE HAIL AND WIND DAMAGE WOULD BE THE PRIMARY THREATS WITH
THESE STORMS.
..IMY.. 05/19/2010
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