SWODY1
SPC AC 211608
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1108 AM CDT TUE OCT 21 2008
VALID 211630Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE CENTRAL
AND SRN HIGH PLAINS...
...CENTRAL/SRN HIGH PLAINS INTO OK...
STRONG UPPER LOW AND ASSOCIATED SHORTWAVE TROUGH WILL CONTINUE
DIGGING SEWD INTO THE CENTRAL HIGH PLAINS...WHILE SEASONABLY STRONG
SURFACE COLD FRONT NOW MOVING OUT OF THE NRN HIGH PLAINS SURGES
ESEWD INTO THE CENTRAL HIGH PLAINS THIS AFTERNOON. PERSISTENT
SURFACE HIGH PRESSURE OVER THE DEEP SOUTH CONTINUES TO LIMIT LOW
LEVEL MOISTURE RETURN AHEAD OF THIS SYSTEM...ALTHOUGH LOWER-MID 50S
F SURFACE DEW POINTS AND PW/S AROUND 1 INCH REMAIN IN PLACE OVER THE
SRN PLAINS. STRENGTHENING SLY LLJ AHEAD OF DEEPENING SYSTEM MOVING
ACROSS THE NRN/CENTRAL ROCKIES WILL ALLOW THIS MOISTURE TO SPREAD
NWWD INTO THE CENTRAL HIGH PLAINS THROUGH THE DAY...WHERE STRONG
SURFACE HEATING WILL PROVIDE STEEP LOW TO MID LEVEL LAPSE RATES.
COMBINATION OF STRENGTHENING LARGE SCALE ASCENT AND MARGINAL
INSTABILITY AHEAD OF FAST MOVING SURFACE COLD FRONT SHOULD SUPPORT
INCREASE IN ROBUST MOIST CONVECTION ALONG AND JUST BEHIND THE FRONT
DURING THE MID TO LATE AFTERNOON OVER PORTIONS OF ERN CO/SWRN NEB.
FORECAST SOUNDINGS SUGGEST MLCAPE WILL STRUGGLE TO REACH 500-750
J/KG OVER THIS REGION...THOUGH VERY STRONG SHEAR PROFILES WILL
REMAIN QUITE FAVORABLE FOR STORM-SCALE ORGANIZATION. EXPECT
ISOLATED LARGE HAIL AND DAMAGING WINDS TO ACCOMPANY STRONGER STORMS
AS ACTIVITY QUICKLY EVOLVES INTO A LINEAR MCS OR BROKEN
LINES...LIKELY BEING UNDERCUT AND FORCED QUICKLY SEWD THROUGH THE
EVENING BY STRONG COLD FRONT. SEVERE THREAT WILL LIKELY CONTINUE
INTO THE MID TO LATE EVENING AS ACTIVITY MOVES THROUGH AREA OF
GREATER INSTABILITY OVER WRN KS...BUT EXPECT COOLING BOUNDARY LAYER
AND GRADUALLY STRENGTHENING CAP WILL BEGIN INHIBITING EFFECTIVE
PARCELS FROM ROOTING INTO THE SURFACE AND DAMAGING WIND THREAT
SHOULD ABATE OVERNIGHT. REGARDLESS... THUNDERSTORMS WILL LIKELY
CONTINUE AND POSSIBLY INCREASE JUST BEHIND THE FRONT ACROSS WRN
OK/CENTRAL KS WITH COMBINATION OF STRONG GRADIENT/POST-FRONTAL
SURFACE WINDS AND WEAK MUCAPE SUPPORTING AT LEAST ISOLATED/MARGINAL
SEVERE THREAT INTO WEDNESDAY MORNING AND WILL MAINTAIN LOW SEVERE
PROBABILITIES INTO THIS REGION.
...NERN OK INTO S-CENTRAL/SERN KS THIS AFTERNOON...
SUBTLE SOUTHERN STREAM IMPULSE CONTINUES TO EJECT ENEWD AND SHEAR
APART OVER THE SRN HIGH PLAINS AND SRN KS THIS MORNING. THIS SYSTEM
MAY SUPPORT RENEWED THUNDERSTORM DEVELOPMENT DURING THE AFTERNOON AS
MODEST HEATING OCCURS ALONG EVOLVING SURFACE WARM FRONT NOW LIFTING
NWD FROM E-CENTRAL INTO NWRN OK LATE THIS MORNING. SLY LOW LEVEL
FLOW IN RESPONSE TO THIS SYSTEM WILL MAINTAIN VERY FAVORABLE LOW
LEVEL SHEAR INTO SERN KS THIS AFTERNOON...ALTHOUGH FORECAST
SOUNDINGS INDICATE ACTIVITY MAY REMAIN SLIGHTLY ELEVATED ALONG/NORTH
OF DEVELOPING WARM FRONT. SHOULD ANY CELL ROOT INTO THE BOUNDARY
LAYER...ACTIVITY COULD ORGANIZE/DEVELOP LOW LEVEL ROTATION GIVEN
DEGREE OF SHEAR. WEAK INSTABILITY AND SLIGHTLY ELEVATED NATURE MAY
LIMIT OVERALL SEVERE THREAT...BUT THREAT IS NOT NEGLIGIBLE AND WILL
MAINTAIN LOW PROBABILITIES.
..EVANS/SMITH.. 10/21/2008
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