SWODY2
SPC AC 271730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT SUN MAY 27 2007
VALID 281200Z - 291200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN AND
CNTRL PLAINS...
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF WEST TX AND FAR
SE NM...
..NRN AND CNTRL PLAINS...
A WELL-DEVELOPED UPPER-LEVEL TROUGH NEAR THE WEST COAST WILL MOVE
ACROSS THE PACIFIC NORTHWEST TONIGHT AND INTO THE NRN ROCKIES ON
MONDAY. AHEAD OF THE APPROACHING SYSTEM...LARGE-SCALE ASCENT WILL
INCREASE ACROSS THE NRN PLAINS MONDAY AS LIFT BECOMES ENHANCED DUE
TO A STRONG LOW-LEVEL JET. AT THE SFC...A COLD FRONT WILL MOVE SEWD
INTO THE DAKOTAS AS A LOW ORGANIZES IN CNTRL SD DURING THE DAY.
SCATTERED THUNDERSTORMS SHOULD INITIATE ALONG THE BOUNDARY BY LATE
AFTERNOON WITH MCS DEVELOPMENT LIKELY MONDAY EVENING. OTHER STORM
DEVELOPMENT SHOULD OCCUR SSWWD ALONG AN AXIS OF INSTABILITY IN WRN
NEB AND NERN CO DURING THE LATE AFTERNOON.
CONCERNING THE SEVERE THREAT...MODEL FORECASTS MOVE A 60-70 KT
MID-LEVEL JET OVER THE NRN ROCKIES EWD INTO THE HIGH PLAINS MONDAY.
THE EXIT REGION OF THIS JET WILL LIKELY SPREAD ACROSS THE DAKOTAS
MONDAY AFTERNOON ENHANCING LIFT AND INCREASING VERTICAL SHEAR ACROSS
THE REGION. FORECAST SOUNDINGS ALONG AND JUST SOUTHEAST OF THE
FRONT...SHOW MODERATE TO STRONG VERTICAL SHEAR WHICH WILL LIKELY
SUPPORT SCATTERED SEVERE STORMS. HOWEVER...THE TIMING OF INITIATION
STILL REMAINS QUESTIONABLE DUE TO A CAPPING INVERSION THAT WILL BE
IN PLACE. THE GFS SOLUTION SUGGESTS INITIATION WILL BE LATER AS THE
FORCING WITH THE UPPER-LEVEL TROUGH COMES OUT INTO THE PLAINS IN THE
EVENING. THE NAM AND NAMKF SOLUTIONS INITIATE STORMS SOONER. ONE
THING IS CERTAIN...THE ENVIRONMENT WILL BE FAVORABLE FOR SUPERCELLS
WITH LARGE HAIL ONCE INITIATION OCCURS. IN ADDITION...LOW-LEVEL
SHEAR PROFILES ON FORECAST SOUNDINGS ALSO APPEAR FAVORABLE FOR
TORNADOES. THE GREATEST TORNADO THREAT SHOULD EXIST NORTHEAST OF THE
SFC LOW ACROSS NCNTRL SD AND ERN ND AS THE LOW-LEVEL JET INTENSIFIES
DURING THE EARLY EVENING. ALSO...VERTICAL SHEAR PROFILES SHOULD BE
SUPPORTIVE OF AN ISOLATED SEVERE THREAT SSWWD INTO WRN NEB AND FAR
NE CO. THE MOST LIKELY AREA FOR MCS DEVELOPMENT WILL BE ALONG THE
FRONTAL BOUNDARY IN THE EVENING DUE TO THE STRENGTHENING LOW-LEVEL
JET. THIS WOULD ALLOW THE SEVERE THREAT TO CONTINUE FOR MUCH OF THE
EVENING ACROSS THE NRN PLAINS REGION. AN UPGRADE TO MODERATE RISK
MAY BECOME NECESSARY IN LATER OUTLOOKS ONCE THE TIMING OF THE
UPPER-SYSTEM AND THUNDERSTORM INITIATION BECOMES MORE APPARENT.
..WEST TX...
AN UPPER-LEVEL TROUGH IS FORECAST TO BE IN PLACE MONDAY IN NRN AND
CNTRL TX WITH NWLY FLOW ACROSS WEST TX. AT THE SFC...AN AXIS OF
INSTABILITY SHOULD EXIST TO THE EAST OF A SFC TROUGH LOCATED IN ERN
NM. SFC DEWPOINTS IN THE 60S F AND DESTABILIZATION SHOULD RESULT IN
MODERATE INSTABILITY ACROSS MUCH OF WEST TX BY MONDAY AFTERNOON.
THUNDERSTORMS SHOULD INITIATE ALONG THE WRN EDGE OF THE MOIST AXIS
AND MOVE EWD INTO INCREASING INSTABILITY.
FORECAST SOUNDINGS LATE MONDAY AFTERNOON ALONG THE INSTABILITY AXIS
SHOW MODERATE VERTICAL SHEAR EXISTING FROM AROUND MIDLAND TX
EXTENDING SWD TO THE BIG BEND REGION. THIS IS DUE TO DIRECTIONAL
TURNING FROM THE LOW TO MID-LEVELS WHICH SHOULD BE SUPPORTIVE OF
STORM ORGANIZATION. SUPERCELLS WITH LARGE HAIL WILL BE POSSIBLE DUE
TO THE STEEP MID-LEVEL LAPSE RATES AND WHERE INSTABILITY IS LOCALLY
MAXIMIZED LATE MONDAY AFTERNOON. THE THREAT MAY CONTINUE INTO THE
EVENING ESPECIALLY IF AN MCS ORGANIZES AND MOVES EWD ACROSS THE
REGION.
..OH VALLEY/CNTRL APPALACHIAN MTNS...
AT UPPER-LEVELS...A TROUGH WILL MOVE EWD ACROSS THE NERN U.S. AS A
RIDGE BECOMES MORE ESTABLISHED ACROSS THE OH VALLEY AND GREAT LAKES
REGION. AT THE SFC...A COLD FRONT SHOULD BE LOCATED FROM KY
EXTENDING EWD INTO VA MONDAY. SCATTERED THUNDERSTORMS SHOULD
INITIATE ALONG THE BOUNDARY AND IN THE HIGHER TERRAIN DURING THE
AFTERNOON. ALTHOUGH FORECAST SOUNDINGS SHOW WEAK VERTICAL SHEAR
PROFILES IN PLACE...POCKETS OF MODERATE INSTABILITY MAY DEVELOP
ALONG AND JUST SOUTH OF THE FRONT. THIS MAY RESULT IN A BRIEF WINDOW
FOR HAIL AND STRONG WIND GUSTS AS TEMPS MAX OUT IN THE LATE
AFTERNOON.
.BROYLES.. 05/27/2007
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