SWODY1
SPC AC 221957
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0257 PM CDT WED JUN 22 2011
VALID 222000Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE GREAT
LAKES/MID-ATLANTIC STATES TO THE TN/LOWER MS RIVER VALLEYS...
...EASTERN THIRD OF THE CONUS...
FEW CHANGES...SEE PRIOR DISCUSSION BELOW AND SUBSEQUENT MESOSCALE
DISCUSSIONS/WATCHES. SEVERAL CORRIDORS OF WIND DAMAGE /AND PERHAPS
SOME SEVERE HAIL/ ARE EXPECTED TO BE THE PRIMARY CONCERNS.
...PORTIONS OF EASTERN ORE/SOUTHEAST WA INTO ID...
INTRODUCED LOW SEVERE HAIL/WIND PROBABILITIES FOR THIS AFTERNOON AND
EVENING FOR PORTIONS OF THE REGION. COINCIDENT WITH THE LEADING EDGE
OF HEIGHT FALLS AHEAD OF AN UPPER TROUGH NEARING THE BC/PACIFIC
NORTHWEST COAST...A RELATIVELY WARM/MOIST AND STRONGLY SHEARED
ENVIRONMENT MAY SUPPORT SOME SUSTAINED TSTMS CAPABLE OF MARGINALLY
SEVERE HAIL AND/OR WIND.
..GUYER.. 06/22/2011
.PREV DISCUSSION... /ISSUED 1119 AM CDT WED JUN 22 2011/
...SYNOPSIS...
LARGE...VERTICALLY STACKED LOW CONTINUES ITS RELATIVELY SLOW
MOVEMENT ENEWD ACROSS SRN WI TODAY TO OVER NRN LM TONIGHT. BAND OF
STRONGER WINDS ARE ROTATING EWD AROUND THE UPPER LOW ACROSS OH/TN
VALLEYS INTO THE NERN STATES AS DOWNSTREAM RIDGE SHIFTS OFFSHORE.
COLD FRONT FROM SRN LM THRU LWR OH VALLEY PUSHES EWD ACROSS OH RIVER
VALLEY THIS AFTERNOON TRAILING BACK TO SRN OK WHERE IT HAS STALLED.
E OF COLD FRONT AIR MASS REMAINS VERY MOIST TO THE ATLANTIC COAST
WITH THE NEW ENGLAND AREA THE EXCEPTION REMAINING COOLER AND MORE
STABLE.
WHILE THERE IS POTENTIAL MDT INSTABILITY OVER A LARGE AREA ERN
STATES...CLOUD COVER AND LACK OF STEEP MID LEVEL LAPSE RATES WILL
MODULATE THE AMOUNT OF SEVERE POTENTIAL THIS AFTERNOON. FROM TN
VALLEY NWD MORE THAN SUFFICIENT FLOW TO SUPPORT ORGANIZED
THUNDERSTORMS AND DEVELOPMENT OF COLD POOLS...THE DIFFICULTY IS
IDENTIFYING AREAS OF GREATEST POTENTIAL GIVEN SUBTLE SURFACE
FEATURES OTHER THAN THE COLD FRONT.
...LWR GREAT LAKES SWD THRU OH/TN VALLEYS...
STORMS SHOULD GRADUALLY FORM THIS AFTERNOON ALONG AND JUST AHEAD OF
THE COLD FRONT WITH MAINLY A DAMAGING WIND AND MARGINAL HAIL THREAT.
AMPLE MOISTURE EXISTS TO THE E OF THE FRONT WITH PRECIPITABLE WATER
OF 1.25 TO 1.50 INCHES. ALTHOUGH CIN IS NOW MINIMAL...OVERALL LAPSE
RATES PROFILES ARE WEAK. THEREFORE...EXPECT A SLOW INCREASE IN
CONVECTION AS DESTABILIZATION CONTINUES WITH HEATING.
DEEP LAYER FLOW FIELDS ARE MORE THAN SUFFICIENT FOR ORGANIZED STORMS
WITH 30 KT JUST OFF THE SURFACE INCREASING TO OVER 50 KT IN THE MID
LEVELS. INITIAL ACTIVITY MAY EVENTUALLY ORGANIZE COLD POOLS AND MOVE
NEWD WITH DAMAGING WIND POTENTIAL INCREASING.
...MID ATLANTIC STATES...
INITIAL AREA OF LIKELY CONCERN FOR SEVERE STORM DEVELOPMENT IS THE
LEE TROUGH FROM PA TO VA WHERE CONVERGENCE WILL FOCUS INITIATION
WITHIN A VERY MOIST POTENTIALLY MDTLY UNSTABLE AIR MASS. MID LEVEL
STRONGER FLOW WILL BE INCREASING EWD ACROSS THIS AREA DURING THE
AFTERNOON...SUPPORTING DEVELOPMENT OF COLD POOLS AND A DAMAGING WIND
THREAT.
FURTHER S INTO CAROLINAS HAVE INCREASED THE SEVERE THREAT FOR LATER
THIS AFTERNOON/EVENING AS COLD POOLS SHOULD EVOLVE FROM THE STORMS
FURTHER W AND THEN MOVE INTO EXPECTED STRONG INSTABILITY OVER
CAROLINAS WITH STEEP LOW LEVEL LAPSE RATES FROM THE STRONG DAYTIME
HEATING. AGAIN OVERALL SHEAR PROFILES OF 25KT OR SO SUFFICIENT TO
MAINTAIN FORWARD PROPAGATING COLD POOLS THRU THE EVENING GIVEN THE
PRESENCE OF MLCAPES AOA 1500 J/KG AND DCAPES IN EXCESS OF 1000 J/KG.
...GULF STATES...
VERY MOIST AIR MASS WITH PWATS TO NEAR 2 INCH REMAINS IN PLACE
ACROSS MS/AL AND SPREADING EWD INTO NRN GA. WITH ONLY MODEST SHEAR
AND RELATIVELY WEAK MID LEVEL LAPSE RATES...SEVERE THUNDERSTORM
DEVELOPMENT WILL FAVOR THOSE AREAS THAT CAN HEAT SUFFICIENTLY THIS
AFTERNOON TO PUSH UP THE CAPE AND DCAPE AND REMOVE EXISTING CINH.
STORMS WILL DEVELOP UPSCALE INTO FORWARD PROPAGATING LINE
SEGMENT/CLUSTERS WITH AN INCREASED WIND DAMAGE THREAT.
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