SWODY2
SPC AC 211720
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1220 PM CDT MON APR 21 2008
VALID 221200Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF NWRN/CENTRAL
TX INTO WRN LA...
...SYNOPSIS...
BROAD MID LEVEL TROUGH WILL DEEPEN OVER THE WEST COAST LATE IN THE
FORECAST PERIOD...WITH DOWNSTREAM RIDGE BUILDING ALOFT FROM TX INTO
THE OH RIVER VALLEY. MEANWHILE...PERSISTENT UPPER LOW OVER NC WILL
BEGIN SHIFTING SEWD OFF THE CAROLINA COAST TUESDAY AFTERNOON. A
MINOR SHORTWAVE TROUGH MOVING OVER THE SRN HIGH PLAINS MONDAY
AFTERNOON/NIGHT IS FORECAST TO DAMPEN-OUT AS IT SHIFTS SEWD ACROSS
THE MID SOUTH/LOWER MS RIVER VALLEY TUESDAY AFTERNOON. SURFACE COLD
FRONT WELL-DEFINED OVER THE SRN HIGH PLAINS INTO ERN KS EARLY MONDAY
AFTERNOON WILL CONTINUE SEWD THROUGH THE DAY 1 PERIOD...BUT IS
FORECAST TO STALL AND LOSE DEFINITION TUESDAY AS LOW LEVEL MASS
FIELDS RESPOND TO STRONGER SYSTEM MOVING ACROSS THE WRN U.S. LATE IN
THE PERIOD.
...MID MS RIVER VALLEY INTO THE LOWER MS RIVER VALLEY/ERN TX...
CLUSTERS OF STRONG...ISOLATED SEVERE THUNDERSTORMS MAY BE ONGOING
OVER PORTIONS OF MO/AR/ERN OK AT THE BEGINNING OF THE PERIOD NEAR
SURFACE COLD FRONT. THIS ACTIVITY IS EXPECTED TO BE SLIGHTLY
ELEVATED...ALTHOUGH SUFFICIENT MID LEVEL COLD AIR/LAPSE RATES SHOULD
SUPPORT AT LEAST A THREAT OF HAIL WITH THE STRONGER CORES. THIS
ACTIVITY SHOULD WEAKEN THROUGH THE MORNING ON THE NRN END.
HOWEVER...STORMS SHOULD INTENSIFY/DEVELOP INTO MUCH OF LA/ERN TX
THROUGH THE DAY AS WEAK MID LEVEL IMPULSE DIGS SEWD OVER THE REGION.
MID LEVEL WINDS ARE FORECAST TO REMAIN MODEST...THOUGH SHEAR
PARAMETERS WILL BE BOOSTED BY NWLY FLOW ALOFT OVERSPREADING SSELY
SURFACE WINDS WITH 25-35 KT EFFECTIVE SHEAR FORECAST BY MOST MODEL
SOUNDINGS. IN ADDITION...-12C TO -14C H5 TEMPS WILL EXIST ATOP VERY
RICH LOW LEVEL MOISTURE /UPPER 60S-LOWER 70S SURFACE DEW POINTS/ AND
SUPPORT MODERATE INSTABILITY WHERE HEATING CAN BE MAXIMIZED. EXPECT
STORMS WILL INCREASE INTO MULTICELL CLUSTERS WITH THREATS OF LARGE
HAIL AND ISOLATED DAMAGING WINDS WITH THESE WEAKLY-ORGANIZED STORMS.
SEVERE THREAT IS EXPECTED TO DIMINISH DURING THE EARLY EVENING.
...CENTRAL/NWRN TX...
MIXING OVER THE HIGH PLAINS IS EXPECTED TO PUSH DRY LINE EWD INTO
NWRN TX TUESDAY AFTERNOON...WHERE TRIPLE POINT MAY SETUP WNW OF ABI
ALONG STALLED SURFACE COLD FRONT. SWLY FLOW ALOFT WILL REMAIN
MODEST DURING THE LATE AFTERNOON...BUT STILL SUPPORTIVE OF 35-45 KT
DEEP LAYER SHEAR ATOP ELY SURFACE FLOW. MODELS SEEM CONSISTENT IN
WEAKENING/BREAKING CAP AMONGST STRONG INSTABILITY /MLCAPE AOA 2000 J
PER KG/ AND EXPECT A FEW ROBUST STORMS TO DEVELOP OVER THIS REGION
LATE IN THE DAY. ALTHOUGH LOW LEVEL WINDS/SHEAR WILL REMAIN QUITE
WEAK...VERY STEEP LAPSE RATES WITH H5 TEMPS FROM -12C TO -14C AND
SUFFICIENT DEEP LAYER SHEAR FOR SUPERCELLS WILL ENHANCE THE
POTENTIAL FOR LARGE HAIL/DAMAGING WINDS. WITH INCREASING SLY LLJ
OVER WRN TX AFTER DARK...A FEW ELEVATED STORMS WITH POTENTIAL FOR
HAIL MAY ALSO INCREASE FARTHER W-NW LATE IN THE PERIOD.
..EVANS.. 04/21/2008
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