DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1251 PM CDT THU APR 28 2005 VALID 291200Z - 301200Z THERE IS A MDT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 15 W LIT 50 WSW ARG 15 NNW DYR 40 SW CKV 40 NNW MSL CBM 30 ENE JAN 45 NNE HEZ 30 WSW MLU 15 SW ELD 15 W LIT. THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 15 SSE BPT 25 SE CLL 25 NE CLL 15 S PRX 30 WNW PGO 45 E TUL 15 WSW JLN 20 SSE TBN IND DAY CMH UNI HTS 40 SW HSS 25 ENE CSG PFN. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 30 E PSX 35 ESE AUS 30 N DAL 45 WSW MKO 35 WNW TUL PNC 45 NE GAG DDC HLC HSI LNK OTM MLI CGX BEH AZO JXN DTW ERI BFD IPT ABE 35 SE NEL ...CONT... 50 E ECG RWI RDU 20 ESE CLT 20 E AGS 35 WNW CTY. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM SVE 35 NE RBL MHS MFR EUG SLE PDX YKM ALW SUN BYI 60 NNW ENV EKO LOL SVE. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 25 W RTN 40 SW COS 30 NNW COS LIC LAA DHT TCC LVS 25 W RTN. ...THERE IS A MDT RISK OF SVR TSTMS CENTRAL/ERN AR AND NRN LA EWD TO WRN TN AND CENTRAL/NRN MS... ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK FROM ERN TX/ERN OK TO THE OH/TN VALLEYS AND CENTRAL GULF COAST STATES... ...WIDESPREAD THREAT FOR SIGNIFICANT SEVERE STORMS EXPECTED FRIDAY AFTERNOON/NIGHT ACROSS PORTIONS OF THE LOWER/MID MS AND LOWER TN VALLEYS REGION... ...SYNOPSIS... SHORT WAVE TROUGHS...ONE CURRENTLY MOVING INTO CA/NV AND THE SECOND APPROACHING THE NRN ROCKIES ATTM...ARE EXPECTED TO PHASE FROM THE UPPER MS VALLEY TO LOWER TN VALLEY REGION BY FRIDAY NIGHT. A BROAD AND STRONG /70+ KT/ WSWLY MID LEVEL JET WILL ACCOMPANY THE SRN STREAM TROUGH AND IS EXPECTED TO NOSE INTO THE LOWER OH/LOWER TN VALLEYS BY 30/00Z. GIVEN THE BREADTH OF THIS MID-LEVEL JET...50+ KT WSWLY WINDS WILL EXTEND FROM SRN TX TO THE CENTRAL GULF COAST STATES DURING MUCH OF THE DAY 2 PERIOD. 12Z NAM IS SLOWER WITH THE MID LEVEL TROUGH AND FARTHER S WITH THE SURFACE LOW THAN ITS PREVIOUS RUNS...AND MORE IN AGREEMENT WITH THE GFS/ECMWF/CMC TIMING OF THIS STORM SYSTEM. A SURFACE LOW AS INDICATED BY THE 12Z NAM IS EXPECTED TO BE OVER NORTH CENTRAL TX AT 12Z FRIDAY...WITH THIS LOW DEEPENING AS IT TRACKS NEWD PER STRONG HEIGHT FALLS WITH THE PHASING MID LEVEL TROUGHS. THIS LOW SHOULD BE OVER CENTRAL AR BY 30/00Z AND INTO CENTRAL OH BY 12Z SATURDAY. A WARM FRONT IS EXPECTED TO EXTEND NEWD FROM THE SURFACE LOW INTO THE OH VALLEY...AND SHOULD REMAIN NEARLY STATIONARY. NAM SUGGESTS A DIFFERENTIAL HEATING BOUNDARY/ SECONDARY WARM FRONT WILL DEVELOP FRIDAY FROM CENTRAL AR EWD ALONG THE SRN TN BORDER. ...OZARKS TO ARKLATEX AND EWD ACROSS TN VALLEY/CENTRAL GULF COAST STATES... THUNDERSTORMS...POTENTIALLY SEVERE...ARE EXPECTED TO BE ONGOING AT THE START OF THE PERIOD ACROSS ERN OK INTO PORTIONS OF SRN MO/SWRN AR AS A RESULT OF WAA ALONG THE NOSE OF A 50 KT SWLY LLJ. THIS ACTIVITY IS EXPECTED TO SPREAD NEWD INTO THE LOWER OH VALLEY REGION ALONG THE NRN WARM FRONT. THESE THUNDERSTORMS WILL BE SUPPORTED BY DEEP LAYER ASCENT/WAA AS THE LLJ TRANSLATES EWD TO THE LOWER MS VALLEY AND WITHIN THE EXIT REGION OF THE MID LEVEL JET. ALTHOUGH MODELS SUGGEST THE MAIN AXIS OF THE MID LEVEL JET WILL BE FROM NRN TX TO THE OH VALLEY...A SRN STREAM JET APPEARS TO MOVE EWD ACROSS THE LOWER MS VALLEY PROVIDING SUFFICIENT DIFFLUENT FLOW ALOFT. THE SRN PERIPHERY OF THIS THUNDERSTORM ACTIVITY IS EXPECTED TO DEFINE THE DIFFERENTIAL HEATING BOUNDARY FOR THE FORMATION OF THE SECOND WARM FRONT. THIS BOUNDARY ALONG WITH A COLD FRONT AND DRY LINE TRAILING SSWWD FROM THE SURFACE LOW OVER CENTRAL AR BY 30/00Z WILL BE THE PRIMARY FOCI FOR SEVERE STORMS BY LATE FRIDAY AFTERNOON. THE SLOWER TIMING OF THE MID LEVEL TROUGH WILL ALLOW MORE MOISTURE TO RETURN NWD WITHIN THE WARM SECTOR ALONG A STRENGTHENING SLY LLJ. THIS MOISTURE COMBINED WITH STEEP LAPSE RATES AND SURFACE HEATING WILL RESULT IN A VERY UNSTABLE AIR MASS /MLCAPE 2500+ J/KG/ ACROSS THE MODERATE RISK AREA. STRONG DEEP LAYER SHEAR /50-60 KT/ WILL BE FAVORABLY ORIENTED FOR SUPERCELLS WITH THE POTENTIAL FOR SIGNIFICANT TORNADOES AND HAIL...ESPECIALLY WITHIN THE MODERATE RISK AREA ALONG AND EAST OF THE SURFACE LOW TRACK. THIS LATE AFTERNOON/EARLY EVENING SEVERE ACTIVITY IS EXPECTED TO CONGEAL INTO A SQUALL LINE AND MOVE ESEWD ACROSS THE TN VALLEY AND CENTRAL GULF COAST STATES WITH DAMAGING WINDS BECOMING THE PRIMARY THREAT FRIDAY NIGHT. ...OH VALLEY REGION... 12Z NAM SUGGESTS SOME BREAKS IN THE CLOUDS ARE POSSIBLE ACROSS THE LOWER OH VALLEY INTO SRN IND/WRN KY PROMOTING AREAS OF MODERATE INSTABILITY BY EARLY FRIDAY AFTERNOON. DEEP LAYER SHEAR WOULD BE SUFFICIENT FOR SUPERCELLS WITH THUNDERSTORM ACTIVITY IN THIS AREA. ...ERN TX... ALTHOUGH MUCH OF ERN TX WILL BE LOCATED SOUTH OF THE MID LEVEL JET AND THUS WILL HAVE RELATIVELY WARM MID LEVEL TEMPERATURES...STRONG SURFACE HEATING MAY BE STRONG ENOUGH TO OVERCOME THE CAP BY MID-LATE FRIDAY AFTERNOON. IF STORMS CAN DEVELOP...DEEP LAYER SHEAR AND MODERATE INSTABILITY WILL SUPPORT SUPERCELLS WITH SIGNIFICANT HAIL LIKELY GIVEN STEEP LAPSE RATES. ..PETERS.. 04/28/2005