DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1157 AM CDT THU APR 29 2004 VALID 301200Z - 011200Z THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 35 E DRT 25 ENE BGS 15 WSW GAG EMP 25 SW IRK 35 NNE PIA 15 N DNV 25 NNW EVV 25 E PAH UOX 20 WNW HEZ 15 SE POE 20 W BPT 40 NNW PSX 35 NNW NIR 25 NW COT 35 E DRT. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 50 WNW DRT 20 NNE MAF 40 NE ROW 25 E GNT 45 NNE CEZ 35 SSW 4FC 35 N LAA 40 W BIE 30 NNE OMA 30 S LSE 20 SSW MTW 110 E OSC ...CONT... 10 NNE BOS 30 NNE ROA 10 NNE CLT 25 SE SAV. ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER OH VALLEY INTO THE SRN PLAINS AND LOWER MS VALLEY... ...SYNOPSIS... AMPLIFIED LARGE-SCALE PATTERN WILL PERSIST OVER THE CONUS ON THE DAY 2 PERIOD WITH RIDGING ALONG THE W COAST AND TROUGHING FROM THE N-CNTRL STATES INTO THE SRN ROCKIES/SRN HIGH PLAINS. MORE SPECIFICALLY...DEEPENING OF NRN STREAM TROUGH FROM CNTRL CANADA INTO THE UPPER MIDWEST WILL OCCUR WITH A CONCURRENT WEAKENING AND EVOLUTION OF UPPER LOW OVER 4-CORNERS REGION INTO A POSITIVELY TILTED TROUGH. SUBSEQUENT EWD PROGRESSION WILL BRING THIS TROUGH INTO THE SRN PLAINS DURING THE LATTER HALF OF THE FORECAST PERIOD. IN THE LOW-LEVELS...THERE IS SOME UNCERTAINTY AS TO THE INITIAL LOCATION OF SURFACE COLD FRONT WITH THE EMC ENSEMBLE MEAN SUGGESTING A SLIGHT SRN ADJUSTMENT TO 29/12Z OPERATIONAL ETA/GFS SOLUTIONS. THIS ENSEMBLE SOLUTION PLACES FRONTAL BOUNDARY FROM NERN IL SWWD THROUGH CNTRL OK INTO SERN NM BY LATE AFTERNOON WITH ATTENDANT DRYLINE SWD THROUGH S-CNTRL OK INTO W-CNTRL OR CNTRL TX. THESE BOUNDARIES WILL BE THE FOCUS FOR SEVERE TSTM DEVELOPMENT THROUGH THE FORECAST PERIOD. ...LOWER OH VALLEY SWD INTO THE SRN PLAINS/LOWER MS VALLEY... NWD ADVECTION OF RICH LOW-LEVEL MOISTURE CURRENTLY ACROSS SRN TX WILL CONTINUE THROUGH THE DAY 1 AND INTO THE DAY 2 PERIOD AHEAD OF COLD FRONT WITH MID 60S DEWPOINTS EXPECTED N OF THE RED RIVER BY FRIDAY AFTERNOON. WHEN COUPLED WITH STEEP MID-LEVEL LAPSE RATES OF 7.5 TO 8.5 C/KM...EXPECT A STRONGLY UNSTABLE WARM SECTOR WITH MLCAPES OF 2000-3000 J/KG FROM CNTRL OK SWD INTO CNTRL/SRN TX. ALTHOUGH BOUNDARY-LAYER MOISTURE WILL BE SLIGHTLY LOWER...POCKETS OF MODERATE INSTABILITY WILL ALSO LIKELY DEVELOP NEWD AHEAD OF COLD FRONT INTO THE LOWER OH VALLEY DURING THE AFTERNOON HOURS. ELEVATED STRONG TO POTENTIALLY SEVERE TSTMS MAY BE ONGOING INITIALLY OVER PORTIONS OF KS...OK AND POSSIBLY WRN MO/NWRN AR ALONG LLJ AXIS. DIURNAL WEAKENING OF LLJ SHOULD LEAD TO GRADUAL DEMISE/ DISORGANIZATION OF THIS DEVELOPMENT THROUGH THE MORNING HOURS. SUSTAINED ISENTROPIC ASCENT INTO RIGHT ENTRANCE REGION OF UPPER JET STREAK OVER THE GREAT LAKES SHOULD CONTRIBUTE TO VIGOROUS SURFACE-BASED DEVELOPMENT BY AFTERNOON ALONG FRONT FROM PORTIONS OF CNTRL IL SWWD ACROSS CNTRL MO AND INTO OK. ADDITIONAL DEVELOPMENT WILL ALSO BE POSSIBLE AT THIS TIME SWD ALONG DRYLINE INTO W-CNTRL OR CNTRL TX. PARALLEL ALIGNMENT OF MID AND UPPER-LEVEL FLOW TO SURFACE FRONT SUGGESTS THAT STORMS SHOULD QUICKLY EVOLVE INTO A EWD/SEWD MOVING LINE WITH DAMAGING WINDS AND LARGE HAIL BEING THE PRIMARY SEVERE WEATHER THREATS. ALONG DRYLINE...MORE NORMAL ORIENTATION OF DEEP-LAYER SHEAR VECTOR TO BOUNDARY SUGGESTS MORE DISCRETE STORMS /SUPERCELLS/ WITH LARGE HAIL AND POSSIBLY A TORNADO OR TWO. GIVEN THE DEGREE OF WARM SECTOR INSTABILITY ACROSS OK INTO TX...A FEW SIGNIFICANT SEVERE WEATHER EVENTS WILL BE POSSIBLE. EXPECT EVOLUTION INTO QUASI-LINEAR MCS TOMORROW NIGHT OVER THE SRN PLAINS WITH A CONTINUED WIND/HAIL THREAT INTO WRN PORTIONS OF LOWER MS VALLEY. ..MEAD.. 04/29/2004