SWODY2
SPC AC 200618
DAY 2 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0118 AM CDT SUN APR 20 2008
VALID 211200Z - 221200Z
...NO SVR TSTM AREAS FORECAST...
CORRECTED FOR GENERAL THUNDER OUTLOOK LINE
...SYNOPSIS...
UPPER JET MAX WILL EJECT NWD ALONG THE ERN PERIPHERY OF WRN U.S.
UPPER THROUGH THE DAKOTAS EARLY MONDAY...WHILE ANOTHER SHORTWAVE
TROUGH EJECTS NEWD INTO THE CNTRL PLAINS MONDAY EVENING...REACHING
THE UPPER MS VALLEY LATE MONDAY NIGHT. IN WAKE OF THE LEAD IMPULSE A
COLD FRONT WILL MOVE EWD AND SWD INTO THE UPPER MS VALLEY AND
THROUGH THE CNTRL PLAINS. BY MONDAY EVENING THE FRONT IS FORECAST TO
EXTEND FROM MN SWWD THROUGH SWRN KS...REACHING WRN WI SWWD INTO NWRN
OK BY THE END OF THIS PERIOD. DRYLINE WILL LIKELY MIX EWD INTO CNTRL
OK AND CNTRL TX BEFORE RETREATING OVERNIGHT.
...CNTRL PLAINS THROUGH MIDDLE AND UPPER MS VALLEY REGION...
PARTIALLY MODIFIED CP AIR WITH BOUNDARY LAYER DEWPOINTS IN THE LOW
TO MID 60S WILL ADVECT THROUGH PRE-FRONTAL WARM SECTOR AS FAR NORTH
AS KS WITH DEWPOINTS IN THE 50S LIKELY FARTHER NORTH INTO THE UPPER
MS VALLEY. PLUME OF STEEP MID LEVEL LAPSE RATES WILL EXIST IN WARM
SECTOR ABOVE RETURNING MOIST AXIS. WHILE THIS WILL CONTRIBUTE TO
DESTABILIZATION...IT SHOULD SERVE TO EFFECTIVELY CAP MUCH OF THE
WARM SECTOR TO SURFACE BASED STORMS. MODERATE MLCAPE WILL BE
POSSIBLE ACROSS KS WHERE LOW CLOUDS MIX OUT...BUT WITH INSTABILITY
MORE MARGINAL WITH NWD EXTENT INTO THE UPPER MS VALLEY WHERE
MOISTURE WILL BE MORE LIMITED. A FEW ELEVATED STORMS WILL BE
POSSIBLE WITHIN WEAK WARM ADVECTION REGIME AHEAD OF THE FRONT OVER
THE UPPER MS VALLEY EARLY MONDAY. SOME HAIL MAY BE POSSIBLE WITH
THIS ACTIVITY. STRONGER STORMS MAY REDEVELOP DURING THE EVENING FROM
PARTS OF CNTRL KS SPREADING NEWD THROUGH ERN NEB AND IA AS FORCING
ASSOCIATED WITH EJECTING SHORTWAVE TROUGH ENHANCES LIFT...PRIMARILY
IN POST FRONTAL ZONE. MUCH OF THIS ACTIVITY WILL BE ELEVATED...BUT
EFFECTIVE SHEAR INCREASING TO AROUND 40 KT AND STEEP MID LEVEL LAPSE
RATES WILL SUPPORT A THREAT FOR LARGE HAIL. STORMS DEVELOPING CLOSER
TO THE SURFACE FRONT MAY ALSO BE CAPABLE OF PRODUCING STRONG WIND
GUSTS. A SLIGHT RISK MAY NEED TO BE REINTRODUCED ACROSS PARTS OF
THIS AREA ONCE HIGHER CONFIDENCE IS ESTABLISHED.
...OK AND TX...
RICHER LOW LEVEL MOISTURE WITH DEWPOINTS IN THE LOW TO MID 60S WILL
RETURN NWD BENEATH STEEP MID LEVEL LAPSE RATES. HOWEVER...THE MOIST
BOUNDARY LAYER WILL LIKELY REMAIN SHALLOW GIVEN FORECAST SWLY 850 MB
TRAJECTORIES. SWLY FLOW ALOFT WILL LIKELY MAINTAIN A WARM EML OVER
THE MOIST AXIS WITH A CAP EXPECTED DURING THE DAY. GIVEN THE DEEPER
ASCENT ASSOCIATED WITH EJECTING SHORTWAVE TROUGH EXPECTED TO REMAIN
NORTH OF THIS REGION AND POTENTIAL FOR A STRONG CAP...THUNDERSTORM
INITIATION ALONG THE DRYLINE IS EXPECTED TO REMAIN LIMITED.
THERMODYNAMIC AND KINEMATIC ENVIRONMENT WOULD SUPPORT SUPERCELLS IF
A STORM OR TWO MANAGED TO DEVELOP...THEREFORE HAVE INCLUDED
CONDITIONAL 5% SEVERE PROBABILITIES IN THIS REGION.
...MO AND AR...
WARM ADVECTION ASSOCIATED WITH THE MODEST SWLY LOW LEVEL JET MAY
CONTRIBUTE TO A FEW STORMS DEVELOPING IN THIS REGION OVERNIGHT. THE
THERMODYNAMIC ENVIRONMENT MAY SUPPORT A THREAT FOR HAIL WITH THE
STRONGER STORMS.
...ERN NC...
COLD AIR ALOFT WITH -20 AT 500 MB NEAR UPPER LOW CENTER MAY SUPPORT
A THREAT FOR MARGINALLY SEVERE HAIL WITH STORMS DEVELOPING DURING
THE AFTERNOON.
..DIAL.. 04/20/2008
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