SPC AC 111250
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0750 AM CDT TUE AUG 11 2009
VALID 111300Z - 121200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE SRN PLNS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE TN VLY/SRN
APPALACHIANS...
...SYNOPSIS...
SLIGHT AMPLIFICATION WILL OCCUR THIS PERIOD AS SERN U.S. RDG
RETROGRESSES TO THE SRN/CNTRL RCKYS AND TROUGH NOW EXTENDING FROM
THE CNTRL PLNS TO UPR GRT LKS AMPLIFIES SE INTO THE OH AND TN VLYS.
THE TROUGH...CONSISTING OF A MAIN VORT CENTER OVER NRN IA AND A
SERIES OF WEAKER DISTURBANCES IN WNW FLOW OVER THE CNTRL RCKYS/PLNS
...SHOULD REACH THE WRN SLOPES OF THE APPALACHIANS BY 12Z WED.
FEATURES WILL REMAIN DIFFUSE AT THE SFC. A WEAK COLD FRONT WILL
SETTLE SLOWLY S/SE ACROSS THE SRN PLNS...THE OZARKS...THE OH/TN
VLYS...AND THE MID ATLANTIC STATES...AUGMENTED BY CONVECTIVE OUTFLOW
FROM THE SRN PLNS TO MS DELTA. THE FAR WRN PART OF THE BOUNDARY
WILL MOVE SLOWLY WSW OVER THE SRN HIGH PLNS.
...SRN HI PLNS...
COMPOSITE OUTFLOW BOUNDARY FROM OVERNIGHT TSTMS HAS BECOME ORIENTED
FROM NE NM AND THE TX PANHANDLE ESE ACROSS N TX INTO NRN LA.
CONVERGENCE INVOF THIS FEATURE...AND INFLUENCE OF PASSING
DISTURBANCES IN NWLY MID LVL FLOW...SHOULD FOSTER CONTINUED
REGENERATION OF EXISTING STORMS. ADDITIONAL DEVELOPMENT SHOULD
OCCUR ALONG MUCH THE SAME AXIS LATER TODAY AS SFC HEATING BOOSTS
SBCAPE TO AOA 2000 J/KG BENEATH ERN EXTENSION OF EML.
REGION S AND W OF OUTFLOW BOUNDARY WILL BECOME ESPECIALLY WARM IN NE
NM/NW TX...WITH INCREASING BOUNDARY LAYER MOISTURE WITH ESE
EXTENT. WEAK/DIURNALLY-ENHANCED LOW LVL SELY FLOW SURMOUNTED BY 25
KT NWLY MID LVL FLOW WILL RESULT IN 30+ KT DEEP UNIDIRECTIONAL NWLY
SHEAR. THIS SETUP SHOULD SUPPORT ORGANIZED/SUSTAINED
TSTMS...INCLUDING A FEW SUPERCELLS WITH LARGE HAIL AND STRONG WINDS.
THE STORMS SHOULD EVOLVE INTO SMALL SE-MOVING CLUSTERS THIS EVE
THROUGH TONIGHT. ADDITIONAL ACTIVITY MAY CONTINUE TO FORM UPSTREAM
ACROSS THE OK/TX PANHANDLE REGION AND NE NM THROUGH EARLY
WED...RESULTING IN REPEAT EPISODES OF STORMS IN SOME AREAS.
...MID SOUTH/TN VLY/SRN APPALACHIANS...
WEAK COMPOSITE OUTFLOW BOUNDARY EXTENDING ROUGHLY NEWD FROM CNTRL MS
INTO ERN TN/KY SHOULD FOCUS AFTN/EVE STORMS AS HEATING BOOSTS WARM
SECTOR SBCAPE TO 1500-3000 J/KG. DESPITE MODEST DEEP WLY SHEAR /0-6
KM VALUES AOB 30 KTS/...THE DEGREE OF INSTABILITY AND PERSISTENT
HEIGHT FALLS ASSOCIATED WITH AMPLIFYING UPR TROUGH SUGGEST
LIKELIHOOD FOR SUSTAINED STORM CLUSTERS WITH DMGG WIND AND
MARGINALLY SVR HAIL.
...UPR OH VLY/LWR GRT LKS TO CNTRL NEW ENGLAND...
A SECONDARY W/E FRONT NOW OVER SRN LWR MI/SRN ONTARIO SHOULD MOVE
S/SE TODAY BENEATH AMPLIFYING UPR TROUGH. ALTHOUGH CONVERGENCE WILL
BE WEAK...THE BOUNDARY MAY BE THE FOCUS FOR SCTD AFTN STORMS FROM
NRN PORTIONS OF IND...OH..AND PA INTO NY/CNTRL NEW ENGLAND AS SBCAPE
INCREASES TO AOA 1500 J/KG AND DPVA STRENGTHENS. 30+ KT MID LVL WLY
FLOW MAY SUPPORT UPSCALE ORGANIZATION INTO A FEW SMALL
CLUSTERS....AND SEASONABLY STRONG /80 KT/ HI LVL FLOW WILL ENHANCE
STORM VENTING/UPR DIVERGENCE. SVR THREAT SHOULD...HOWEVER...BE
LIMITED BY MODEST SFC HEATING/WEAK MID LVL LAPSE RATES...AND BY
WEAK/DISORGANIZED LOW LVL WIND FIELD.
...MID ATLANTIC CST TO CNTRL/ERN CAROLINAS...
DEEP WLY FLOW WILL MAINTAIN LEE TROUGH E OF THE CNTRL/SRN
APPALACHIANS. THAT FEATURE...AND POSSIBLY DIFFUSE COLD FRONT IN
PA/NJ...MAY FOCUS SCTD STRONG TO MARGINALLY SVR AFTN/EVE STORMS.
AIR MASS WILL BE MODERATELY UNSTABLE AND SOME STORMS MAY YIELD GUSTY
WINDS. BUT MODEST DEEP SHEAR AND WEAK MID LVL LAPSE RATES WILL
LIMIT SVR POTENTIAL.
..CORFIDI/BOTHWELL.. 08/11/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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