SPC AC 041720
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1220 PM CDT SAT JUL 04 2009
VALID 051200Z - 061200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CAROLINAS
AND TN VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL HIGH
PLAINS...
...CAROLINAS/TN VALLEY/LOWER MS VALLEY...
NORTHWEST FLOW WILL BE IN PLACE ACROSS THE MS VALLEY SUNDAY AS A
SUBTLE BUT BROAD UPPER-LEVEL TROUGH MOVES EWD ACROSS THE ATLANTIC
SEABOARD. AT THE SFC...A LOW IS FORECAST TO MOVE EWD INTO THE
CAROLINAS WITH A COLD FRONT EXTENDING WWD ACROSS THE SRN APPALACHIAN
MTNS INTO THE LOWER MS VALLEY. IT APPEARS LIKELY THAT A PERSISTENT
CLUSTER OF THUNDERSTORMS FROM OVERNIGHT ACTIVITY WILL BE ONGOING
ALONG THE COLD FRONT SUNDAY MORNING MOVING SSEWD INTO THE TN VALLEY
BY EARLY AFTERNOON. MODEL FORECASTS SOUTH OF THIS CLUSTER OF
THUNDERSTORMS ACROSS THE WARM SECTOR DEVELOP POCKETS OF MODERATE
INSTABILITY SUNDAY WITH SCATTERED SFC-BASED STORMS INITIATING BY
AFTERNOON. FORECAST SOUNDINGS SUNDAY AFTERNOON ALONG THE FRONTAL
BOUNDARY AND ACROSS THE WARM SECTOR SHOW PRIMARILY UNIDIRECTIONAL
WIND PROFILES WITH ABOUT 30 KT OF VERTICAL SHEAR. THIS SHOULD BE
SUPPORTIVE OF ISOLATED SEVERE LINE-SEGMENTS CAPABLE OF PRODUCING
WIND DAMAGE ESPECIALLY AS LOW-LEVEL LAPSE RATES STEEPEN IN THE
AFTERNOON. HAIL WILL ALSO BE POSSIBLE ESPECIALLY WHERE INSTABILITY
BECOMES MAXIMIZED. A LOCALLY GREATER SEVERE THREAT MAY EXIST ACROSS
PARTS OF THE SRN APPALACHIANS AND CAROLINAS WHERE MODEL ENSEMBLES
FORECAST GREATER STORM COVERAGE AND STRONGER LOW-LEVEL FLOW. A FEW
SEVERE STORMS WILL ALSO BE POSSIBLE WSWWD INTO THE LOWER MS VALLEY
WHERE MODERATE INSTABILITY IS FORECAST. HOWEVER...THE SEVERE
POTENTIAL SHOULD BECOME INCREASINGLY MARGINAL WITH WWD EXTENT DUE TO
WEAKER VERTICAL SHEAR AND LESSENING LARGE-SCALE ASCENT.
...CNTRL HIGH PLAINS/SRN PLAINS...
AN UPPER-LEVEL RIDGE WILL BE IN PLACE ACROSS THE ROCKIES SUNDAY WITH
A LEE TROUGH LOCATED ALONG THE FRONT RANGE SWD INTO NE NM. SCATTERED
THUNDERSTORMS WILL DEVELOP IN THE HIGHER TERRAIN EARLY SUNDAY
AFTERNOON SPREADING SLOWLY ESEWD INTO THE CNTRL HIGH PLAINS.
FORECAST SOUNDINGS IN ERN CO AND NE NM AT 21Z SHOW MLCAPE VALUES IN
THE 1500 TO 2000 J/KG RANGE ALONG WITH 40 KT OF VERTICAL SHEAR
PRIMARILY DUE TO STRONGER WINDS ALOFT. THIS ALONG WITH STEEP
MID-LEVEL LAPSE RATES SHOULD SUPPORT ISOLATED SEVERE STORMS WITH
HAIL POTENTIAL. WIND DAMAGE WILL ALSO BE POSSIBLE AS THE STORMS
MATURE LATE SUNDAY AFTERNOON. ERN COLORADO MAY HAVE THE BEST
POTENTIAL FOR SEVERE WHERE THE MODELS SUGGEST VERTICAL SHEAR MAY BE
REGIONALLY MAXIMIZED AND LARGE-SCALE ASCENT SHOULD BE ADEQUATE DUE
TO A SUBTLE DISTURBANCE MOVING ESEWD OVER THE ERN PART OF THE
UPPER-LEVEL RIDGE. FURTHER SOUTHEAST ACROSS PARTS OF CNTRL AND NORTH
TX...A FEW MARGINALLY SEVERE STORMS MAY OCCUR SUNDAY AFTERNOON
MAINLY NEAR A FRONTAL BOUNDARY WHERE MODEL FORECASTS SHOW
SUBSTANTIAL DIRECTIONAL SHEAR AND POCKETS OF MODERATE INSTABILITY.
...PACIFIC NORTHWEST...
A SFC TROUGH IS FORECAST TO BE IN PLACE SUNDAY EAST OF A PACIFIC
COLD FRONT LOCATED IN ORE AND WA. MODERATE INSTABILITY IS FORECAST
ALONG THE SFC TROUGH SUNDAY AFTERNOON WHERE SCATTERED THUNDERSTORMS
WILL LIKELY DEVELOP IN THE HIGHER TERRAIN. AS STORMS INCREASE IN
COVERAGE LATE SUNDAY AFTERNOON...A MARGINAL SEVERE THREAT MAY EXIST
ON THE WRN SIDE OF THE UPPER-LEVEL RIDGE WHERE FORECAST SOUNDINGS
SHOW VERY STEEP LOW-LEVEL LAPSE RATES AND ABOUT 30-35 KT OF VERTICAL
SHEAR.
..BROYLES.. 07/04/2009
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
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