SPC AC 260551
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1251 AM CDT SUN JUL 26 2009
VALID 261200Z - 271200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM A PORTION OF THE MID
ATLANTIC INTO THE NERN STATES...
...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE LOWER MS
AND TN VALLEY...
...SYNOPSIS...
LARGE SCALE PATTERN WILL UNDERGO ONLY MINOR CHANGES SUNDAY WITH THE
PRIMARY FEATURE OF INTEREST BEING THE PERSISTENT UPPER LOW OVER THE
GREAT LAKES AND SERN CANADA. SERIES OF VORTICITY MAXIMA WILL ROTATE
THROUGH THIS FEATURE. CUTOFF LOW OVER THE PACIFIC NW WILL BEGIN TO
MOVE SEWD THROUGH THE NRN ROCKIES IN RESPONSE TO AN UPSTREAM IMPULSE
CRESTING UPPER RIDGE OVER WRN CANADA. NRN PORTION OF FRONT FROM THE
OH VALLEY SWWD INTO THE SRN PLAINS WILL MOVE EWD INTO THE NERN
STATES WHILE TRAILING PORTION STALLS OVER THE SRN PLAINS.
...MID ATLANTIC THROUGH NERN STATES...
MID 60S BOUNDARY LAYER DEWPOINTS WILL PERSIST IN PRE-FRONTAL WARM
SECTOR FROM MID ATLANTIC TO THE NERN STATES. POTENTIAL WILL EXIST
FOR AREAS OF CLOUDS AND ONGOING WEAK CONVECTION...ESPECIALLY OVER
THE MID ATLANTIC IN ASSOCIATION WITH VORT MAX NOW MOVING THROUGH KY
THAT WILL CROSS THE APPALACHIANS EARLY SUNDAY. PARTIAL CLEARING WILL
RESULT IN DESTABILIZATION BUT WITH MLCAPE LIMITED TO AOB 1500 J/KG
DUE TO WEAK MID LEVEL LAPSE RATES. BELT OF STRONGER SWLY MID-UPPER
FLOW ALONG PERIPHERY OF UPPER TROUGH WILL MAINTAIN 30-40 KT BULK
SHEAR. STORMS ARE EXPECTED TO REDEVELOP IN WEAKLY CAPPED PRE-FRONTAL
WARM SECTOR AND ORGANIZE INTO LINE SEGMENTS WITH POTENTIAL FOR
EMBEDDED SUPERCELL AND BOWING STRUCTURES. PRIMARY THREAT IS EXPECTED
TO BE ISOLATED DAMAGING WIND...BUT SOME HAIL MAY ALSO ACCOMPANY THE
STRONGER STORMS.
...LOWER MS AND TN VALLEY AREAS...
A COLD FRONT CURRENTLY STRETCHES FROM KY SWWD INTO NRN AR AND MAY
SETTLE SLOWLY SWD TODAY. A RESERVOIR OF STRONG INSTABILITY REMAINS
OVER A PORTION OF LOWER MS VALLEY WARM SECTOR WITH 2000-3000 J/KG
MLCAPE. AS THE BOUNDARY LAYER WARMS...STORMS MAY REDEVELOP ALONG AND
SOUTH OF THE FRONT DURING THE DAY. THIS REGION WILL REMAIN UNDER THE
INFLUENCE OF MODEST NWLY FLOW ALOFT WITH 20-30 KT BULK SHEAR
SUPPORTIVE OF MULTICELL CONVECTION. STORMS MAY ORGANIZE INTO LINE
SEGMENTS OR CLUSTERS AS THEY ADVANCE SEWD WITH A THREAT OF ISOLATED
DAMAGING WIND AND LARGE HAIL.
...CNTRL AND SRN HIGH PLAINS...
PLUME OF DEEPER MOISTURE AND IMPULSES ROTATING AROUND UPPER RIDGE
SHOULD ONCE AGAIN CONTRIBUTE TO STORMS DEVELOPING OVER THE HIGHER
TERRAIN OF CNTRL AND SRN ROCKIES. ACTIVITY WILL SUBSEQUENTLY MOVE
SEWD INTO THE HIGH PLAINS WHERE MODEST ELY POST FRONTAL COMPONENT
WILL MAINTAIN DEWPOINTS IN THE 50S. A FEW STORMS WILL HAVE THE
POTENTIAL TO PRODUCE ISOLATED DOWNBURSTS AND HAIL.
...NRN ROCKIES AREA...
STORMS WILL LIKELY REDEVELOP OVER THE NRN ROCKIES IN ASSOCIATION
WITH VORTICITY MAXIMA ROTATING THROUGH UPPER TROUGH AND WHERE NELY
UPSLOPE COMPONENT SHOULD MAINTAIN DEWPOINTS IN THE LOW 50S WITH
MLCAPE GENERALLY BELOW 1000 J/KG. THE STRONGER VERTICAL SHEAR
ASSOCIATED WITH SEWD ADVANCING UPPER LOW WILL REMAIN SW OF THE
GREATER INSTABILITY...BUT STEEP LOW LEVEL LAPSE RATES WILL SUPPORT A
THREAT OF ISOLATED DAMAGING WIND WITH THE STRONGER STORMS.
..DIAL/LEVIT.. 07/26/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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