SPC AC 291251
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0751 AM CDT WED APR 29 2009
VALID 291300Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE SRN AND CNTRL
PLNS...
...SYNOPSIS...
BROAD BAND OF LOW AMPLITUDE CYCLONIC FLOW WILL PERSIST ACROSS THE
PLNS...S AND E OF ELONGATING UPR LOW OVER THE PACIFIC NW/NRN RCKYS.
THE LOW SHOULD REDEVELOP E INTO THE NRN PLNS TONIGHT/EARLY THU AS
STRONG SPEED MAX NOW ENTERING THE NRN GRT BASIN CONTINUES ENE INTO
WY AND THE DAKOTAS. FARTHER S...A SPEED MAX IN THE WEAKER SRN
STREAM...NOW OVER NW MEXICO/SRN AZ...SHOULD REACH WRN/CNTRL TX BY
EVE...AND LA/AR EARLY THU.
AT THE SFC...EXPECT DIFFUSE WARM FRONT TO CONTINUE REDEVELOPING NWD
ACROSS THE SRN/CNTRL PLNS...WHILE A SEPARATE WARM FRONT EVOLVES MUCH
FARTHER N ACROSS THE NRN PLNS/UPR MS VLY IN ASSOCIATION WITH LEE
CYCLONE IN WRN SD. OVER THE SRN PLNS...A REMNANT FRONTAL
SEGMENT/OUTFLOW BOUNDARY LIKELY WILL PERSIST FOR AT LEAST PART OF
THE DAY INVOF THE RED RVR AND NW TX.
...SRN PLNS...
LOOSELY-ORGANIZED MCS NOW OVER NW TX/SW OK SHOULD CONTINUE GENERALLY
E THROUGH THE MORNING...WITH NEW CELL DEVELOPMENT MOST LIKELY ON ITS
SRN AND SERN FLANKS. RELATIVE WEAKNESS IN THE 700-500 MB FLOW
LIKELY WILL LIMIT STRENGTH/LONGEVITY OF INDIVIDUAL STORMS. BUT
GIVEN QUALITY OF MOIST INFLOW /PW AROUND 1.40 INCHES/ AND LOW LVL
SHEAR ASSOCIATED WITH 40+ KT LLJ...POTENTIAL WILL REMAIN FOR
EMBEDDED LEWPS/SMALL BOWS WITH WET MICROBURSTS AND MARGINALLY SVR
HAIL.
SW OF THE MCS...STRONG SFC HEATING SHOULD OCCUR THIS AFTN ALONG AND
S OF TRAILING OUTFLOW BOUNDARY/LINGERING WARM FRONTAL SEGMENT OVER
NW AND W CNTRL TX. COMBINATION OF HEATING WITH RICH BOUNDARY LAYER
MOISTURE AND STEEP MID LVL LAPSE RATES SHOULD BOOST SBCAPE TO AOA
2500 J/KG. MAX SFC TEMPERATURES SHOULD OCCUR JUST ABOUT THE TIME
THAT LEADING EDGE OF PREVIOUSLY-MENTIONED SRN STREAM SPEED MAX
OVERSPREADS THE REGION. WITH 500 MB WSWLY FLOW INCREASING TO AOA 40
KTS...SETUP SHOULD PROVE FAVORABLE FOR DEVELOPMENT OF DISCRETE
SUPERCELLS. THESE COULD PRODUCE A FEW TORNADOES...IN ADDITION TO
VERY LARGE HAIL AND LOCALLY DMGG WINDS THROUGH EARLY TONIGHT.
...CNTRL PLNS...
SFC-BASED INSTABILITY WILL ALSO INCREASE OVER THE CNTRL PLNS TODAY
AS HEATING OCCURS ALONG AXIS OF LOW LVL MOISTURE RETURN WITH LLJ.
THE GREATEST DESTABILIZATION SHOULD OCCUR ALONG WRN EDGE OF THE LLJ
IN WRN KS...WHERE HEATING WILL BE MAXIMIZED BENEATH EML. FARTHER
N...DESTABILIZATION MAY MAXIMIZE ALONG DEVELOPING COLD FRONT/TROUGH
IN WRN/CNTRL NEB AND S CNTRL SD. FORCING FOR ASCENT SHOULD REMAIN
WEAK AS REGION WILL LIE S OF GRT BASIN SPEED MAX AND N OF JET STREAK
AFFECTING THE SRN PLNS. BUT LOW LVL CONVERGENCE ALONG LEE
TROUGH/DRY LINE IN KS...ALONG COLD FRONT IN NEB...AND NEAR TRIPLE
POINT IN SD...SHOULD SUPPORT SCTD AFTN/EVE STORMS. SOME OF THESE
COULD BECOME WEAK SUPERCELLS OR AT LEAST SUFFICIENTLY SUSTAINED TO
YIELD LARGE HAIL/LOCALLY DMGG WIND AND PERHAPS A TORNADO.
FARTHER E...STRONG TSTMS WILL ALSO BE POSSIBLE ALONG WARM FRONT
SEGMENT OVER THE LWR MO VLY...WHERE MOISTURE WILL INCREASE ALONG LLJ
ON ERN FRINGE OF EML. RELATIVELY WEAK LARGE SCALE FORCING FOR
ASCENT AND LIMITED SFC HEATING SHOULD LIMIT ASSOCIATED SVR THREAT.
...AR/TN VLY...
SFC HEATING INVOF DIFFUSE WARM FRONT AND/OR ON ERN FRINGE OF CLOUD
SHIELD ASSOCIATED WITH OK/TX MCS SHOULD YIELD A FAVORABLE
THERMODYNAMIC ENVIRONMENT FOR AFTN STORMS OVER PARTS OF AR AND THE
TN VLY GIVEN A NWD SURGE OF MOISTURE ON ERN SIDE OF SRN PLNS LLJ.
HOWEVER...REGION WILL BE WELL REMOVED FROM STRONGER FLOW ALOFT...
AND MID LVL LAPSE RATES WILL REMAIN WEAK. THUS...OVERALL SVR THREAT
SHOULD BE LOW.
..CORFIDI/SMITH.. 04/29/2009
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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