SPC AC 212014
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0314 PM CDT THU AUG 21 2003
   
   VALID 212000Z - 221200Z
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 20 NW
   ROC FKL 45 NNW EVV 20 WSW DYR 25 E LFT LCH 45 NE HOU 20 WSW UMN 25
   NW PNC 25 SW RSL MHK MLI 35 WSW MBL 50 NW PLN 25 N ANJ
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 45 SSE DRT 40 WNW AUS
   10 NNW ACT 20 W DUA 25 NNW FSI 25 NW PVW 40 NNW HOB 15 SSE ELP
   ...CONT... 10 NW SFO MFR 40 N RDM 15 WSW BTM 55 N BIL 15 NNW GDV 60
   S Y22 45 SW RAP 35 S BFF 15 WSW MCK 40 WSW LNK 40 NW LWD 10 ENE LNR
   10 NNE OSH 15 NE MQT ...CONT... 40 SSE AUG 15 WSW BML 15 NNW HGR 25
   W RIC 25 N HSE
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM CENTRAL GREAT LAKES TO
   PORTIONS KS...AND OZARKS TO SABINE RIVER REGION...
   
   ...SYNOPSIS...
   PROGRESSIVE NRN STREAM PATTERN WILL CONTINUE FROM PACIFIC NW TO NEW
   ENGLAND.  MOST CRITICAL MID-UPPER LEVEL FEATURE IS STRONG SHORTWAVE
   TROUGH -- EVIDENT ATM ON MOISTURE CHANNEL IMAGERY FROM NWRN ONT AND
   LS SWD ACROSS PORTIONS UPPER MI AND WI.  THIS TROUGH SHOULD MOVE EWD
   ACROSS REMAINDER UPPER AND LOWER MI THROUGH PERIOD.  ASSOCIATED SFC
   COLD FRONT -- ANALYZED FROM ERN/CENTRAL UPPER MI SWWD ACROSS WI TO
   NWRN KS -- SHOULD DECELERATE OVER CENTRAL PLAINS AS IT MOVES RAPIDLY
   EWD OVER MI AND SRN ONT.  PREFRONTAL SFC TROUGH AND WIND SHIFT LINE
   -- NOW CROSSING CENTRAL/SRN LM AND NRN LOWER MI -- WILL PROVIDE
   ANOTHER FOCUS FOR CONVECTIVE POTENTIAL.  MID-UPPER LEVEL SHORTWAVE
   TROUGH NOW INDICATED OVER SWRN UT/SWRN NV AREA SHOULD CONTINUE
   LIFTING NWD ACROSS ERN NV/WRN UT THROUGH REMAINDER AFTERNOON.
   
   ...GREAT LAKES STATES TO CENTRAL PLAINS...
   REF WW 878 AND ASSOCIATED MESOSCALE DISCUSSIONS FOR NEAR-TERM FCST 
   GUIDANCE.  PRIMARY FOCI FOR SEVERE POTENTIAL FOR REMAINDER PERIOD
   WILL BE COLD FRONT AND PREFRONTAL TROUGH.  LATTER IS SUPPORTING LINE
   OF STRONG/SEVERE TSTMS NOW OVER NWRN LOWER MI...WHICH MAY
   BACKBUILD/DEVELOP SWD TO INCLUDE MORE OF LOWER PENINSULA.  DISCRETE
   SUPERCELLS MAY OCCUR WITHIN BAND TSTMS ALSO INCREASING OVER PORTIONS
   CENTRAL/ERN UPPER PENINSULA SHOULD INCREASE IN
   COVERAGE/INTENSITY...MOVE EWD AND AFFECT PORTIONS NRN LM
   AND LOWER MI WITH DAMAGING WIND AND LARGE HAIL POSSIBLE.  ADDITIONAL
   DEVELOPMENT POSSIBLE ALONG/AHEAD OF FRONT OVER PORTIONS
   IL/INDIANA/OH THIS AFTERNOON...PRODUCING POTENTIALLY DAMAGING
   WIND...WITH MLCAPE GENERALLY IN 2000-2500 J/KG.  LOW-MIDLEVEL FLOW
   MAGNITUDES AND VERTICAL SHEAR DECREASE SUBSTANTIALLY WITH SWWD
   EXTENT ALONG FRONT AND TOWARD MIDLEVEL RIDGE. 
   HOWEVER...MODERATE-STRONG INSTABILITY WILL CONTRIBUTE TO AT LEAST
   BRIEF SEVERE THREAT WITH CELLS DEVELOPING ALONG FRONT OR IN ADJACENT
   PORTIONS WARM SECTOR...AS FAR WWD AS CENTRAL/ERN KS WHERE LOW LEVEL
   CONVERGENCE AND CU/TCU ARE INDICATED ATTM.
   
   ...WRN GULF COAST TO ARKLATEX REGION...
   REF SPC WW 879.  SCATTERED TSTMS SHOULD CONTINUE THROUGH EARLY
   EVENING WITH POTENTIAL FOR BRIEF/ISOLATED SEVERE GUSTS...IN
   ENVIRONMENT OF DEEP NELY FLOW...SFC DEW POINTS LOW-MID 70S F...AND
   MLCAPES 3000-4000 J/KG OUTSIDE OUTFLOW POOLS.  STRONGEST ACTIVITY
   MAY OCCUR ALONG BOUNDARY INTERSECTIONS WHERE LIFT IS LOCALLY
   MAXIMIZED...WITH SOME ORGANIZED MULTICELLS AND POSSIBLY MCS
   SUBSEQUENTLY DEVELOPING.  REF SPC MESOSCALE DISCUSSION 2210 FOR
   NOWCAST DETAILS.  THREAT SHOULD DIMINISH CONSIDERABLY AFTER ABOUT 2Z
   WHEN DIABATIC COOLING AND COMBINED OUTFLOW COVERAGE REDUCES
   SFC-BASED CONVECTIVE INSTABILITY.  ALTHOUGH LACK OF SIGNIFICANT
   VERTICAL SHEAR SHOULD KEEP MAGNITUDE OF SEVERE WIND/HAIL
   MARGINAL...ENOUGH CLUSTERING/CONCENTRATION OF EVENTS IS POSSIBLE TO
   WARRANT CATEGORICAL OUTLOOK.
   
   ...GREAT BASIN AREA...
   WIDELY SCATTERED TSTMS ARE EXPECTED REMAINDER AFTERNOON OVER 
   WIDESPREAD AREA FROM NRN AZ ACROSS MUCH OF NV AND SRN/WRN UT. 
   NARROW BELT OF ENHANCED MIDLEVEL FLOW AROUND W SIDE OF ANTICYCLONE
   WAS NOT WELL SAMPLED BY 12Z RAOBS BUT IS EVIDENT IN MOISTURE CHANNEL
   IMAGERY AND VWP DATA.  RESULTANT ENHANCEMENTS TO LOW-MIDLEVEL SHEAR
   SHOULD AID ORGANIZATION ENOUGH FOR ISOLATED HAIL AND STRONG-SEVERE
   GUSTS IN DEEPEST AND MOST PERSISTENT CONVECTION.  SPC MESOSCALE
   DISCUSSION 2211 CONTAINS NOWCAST DETAILS.  BULK OF CONVECTIVE THREAT
   WILL BE BEFORE APPROXIMATELY 2Z...THEN GENERAL STABILIZATION
   EXPECTED FROM BOTH CLOUD/PRECIP COVERAGE AND LOSS OF INSOLATION.
   
   ..EDWARDS.. 08/21/2003
   
   ...NOTICE...
   FOR USERS DECODING THE POINTS PARAGRAPH HEREIN...LATITUDE AND
   LONGITUDE POINTS FOR THE CATEGORICAL AND PROBABILISTIC OUTLOOK
   GRAPHICS ALSO ARE LOCATED IN A SEPARATE PRODUCT UNDER THE WMO
   HEADINGS WUUS01 PTSDY1...WUUS02 PTSDY2...AND WUUS03 PTSDY3.  THE
   INCLUSION OF POINTS IN THIS PRODUCT WILL EVENTUALLY BE DISCONTINUED.
   
   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED FOR 0100Z