SWODY1
SPC AC 210058
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0758 PM CDT SAT AUG 20 2011
VALID 210100Z - 211200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SRN MO AND NRN
AR...
...SYNOPSIS...
A BROAD CYCLONIC FLOW REGIME/STRONGER FLOW ALOFT WILL CONTINUE TO
EVOLVE SWD INTO THE GREAT LAKES...WITH AMPLIFICATION SEWD TO THE OH
VALLEY THIS FORECAST PERIOD. MEANWHILE...A MID MS VALLEY/OZARKS
SHORTWAVE TROUGH AND ATTENDANT BAND OF 40-50 KT WLY MIDLEVEL WINDS
WILL ADVANCE ESEWD INTO THE OH/TN VALLEYS TONIGHT. AT THE
SURFACE...A COLD FRONT ATTENDANT TO THE LARGE SCALE TROUGH EXTENDED
FROM SWRN ONTARIO TO NRN IND...ERN IL THROUGH SWRN MO...AND WSWWD
THROUGH CENTRAL OK TO THE TX PANHANDLE LATE THIS AFTERNOON. BY 12Z
SUNDAY...THIS BOUNDARY SHOULD EXTEND FROM THE LOWER GREAT LAKES
THROUGH ERN OH...KY TO NRN AR AND WWD INTO OK.
...SRN MO/AR TO LOWER TN VALLEY/PARTS OF MID SOUTH...
ONGOING CLUSTER OF STRONG TO SEVERE STORMS HAS EVOLVED OVER FAR SRN
MO INTO NWRN AR INVOF OF THE NRN EXTENT OF A WWD MOVING CONVECTIVE
OUTFLOW BOUNDARY AND ITS INTERSECTION WITH A SSEWD ADVANCING COLD
FRONT TOWARD NRN AR AND ERN OK. IN THE SHORT TERM...STRONGEST
INSTABILITY RESIDES ALONG THE SRN-WRN FLANKS OF THE CLUSTER/MCS WITH
20 KT OF SSWLY LOW LEVEL FLOW INTO THIS SYSTEM SUPPORTING ADDITIONAL
DEVELOPMENT IN THE SHORT TERM /THROUGH 02Z/. FOR ADDITIONAL
DETAILS...REFER TO SPC MESOSCALE DISCUSSION #2029. AFTER
02Z...MODELS SUGGEST A WLY LLJ...THOUGH MODEST IN SPEED /20-30 KT/
ACROSS NRN AR...AND THE ESEWD TRACK OF THE MID MS VALLEY/OZARKS
TROUGH SUGGEST SOME POTENTIAL FOR STRONGER...SOME SEVERE STORMS TO
SPREAD E TOWARD SERN MO/NERN AR. FOR THESE REASONS...THE SLIGHT
RISK AREA HAS BEEN EXPANDED EWD WITH THIS OUTLOOK ISSUANCE.
...ERN IL/IND/WRN OH...
MIDLEVEL ASCENT ATTENDANT TO THE APPROACH OF THE MID MS VALLEY
SHORTWAVE TROUGH SHOULD PROVE SUFFICIENT IN SUPPORTING A FEW
ADDITIONAL MORE ROBUST UPDRAFTS/STRONGER STORMS ACROSS ERN IL TO
WRN/SRN IND THROUGH THE EVENING/EARLY OVERNIGHT PERIOD. SHORT TERM
MODELS SUGGEST A CONVECTIVE POTENTIAL WILL OCCUR THIS FORECAST
PERIOD INTO THE LOWER OH VALLEY. HOWEVER...WEAK LOW LEVEL
CONVERGENCE AND WEAK LOW LEVEL WAA INDICATE THAT THE LIKELIHOOD FOR
STRONGER STORM DEVELOPMENT AND WEAKENING DEEP LAYER SHEAR WILL
PRECLUDE AN ORGANIZED SEVERE THREAT.
..PETERS.. 08/21/2011
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