SWODY2
SPC AC 161727
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1227 PM CDT SUN SEP 16 2007
VALID 171200Z - 181200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE UPPER MS
VALLEY...NRN PLAINS AND CNTRL PLAINS...
..UPPER MS VALLEY/NRN AND CNTRL PLAINS...
AN UPPER-LEVEL TROUGH OVER THE WEST COAST WILL MOVE EWD ACROSS THE
INTERMOUNTAIN WEST TONIGHT INTO MONDAY. IN RESPONSE...A
WELL-DEVELOPED LOW-LEVEL JET IN THE CNTRL PLAINS WILL QUICKLY
TRANSPORT LOW-LEVEL MOISTURE NWD INTO THE NRN PLAINS AHEAD OF A COLD
FRONT MOVING SEWD ACROSS THE DAKOTAS MONDAY. LOW-LEVEL CONVERGENCE
IS FORECAST TO INCREASE IN THE WARM SECTOR DURING THE AFTERNOON
ALONG THE NWRN EDGE OF THE LOW-LEVEL JET. THIS COMBINED WITH SFC
HEATING SHOULD RESULT IN THE INITIATION OF SEVERAL THUNDERSTORM
CLUSTERS IN THE AFTERNOON FROM NRN MN EXTENDING SWWD ACROSS ERN SD
AND CNTRL NEB. LARGE-SCALE ASCENT AHEAD OF THE APPROACHING
UPPER-LEVEL TROUGH...LIFT FROM THE LOW-LEVEL JET AND MODERATE
INSTABILITY WILL LIKELY SUPPORT THE DEVELOPMENT OF SEVERAL MCS/S
ACROSS THE REGION BY MONDAY EVENING.
A 60 KT MID-LEVEL JET IS FORECAST TO EJECT NEWD ACROSS THE CNTRL AND
NRN PLAINS MONDAY WHICH WILL INCREASE VERTICAL SHEAR PROFILES ACROSS
THE REGION. FORECAST SOUNDINGS ALONG THE AXIS OF THE MID-LEVEL JET
SHOW 45 TO 50 KT OF 0-6 KM SHEAR MAINLY DUE TO SPEED SHEAR ABOVE 700
MB. THIS SHOULD BE SUFFICIENT FOR SUPERCELLS IN THE LATE AFTERNOON
ESPECIALLY WHERE INSTABILITY IS MAXIMIZED AND LOW-LEVEL WINDS ARE
LOCALLY BACKED. LARGE HAIL AND ISOLATED WIND DAMAGE WILL BE LIKELY
WITH SUPERCELLS. THE STRONG SPEED SHEAR SHOULD ALSO PROMOTE LINEAR
CONVECTIVE DEVELOPMENT WHICH SHOULD BECOME THE MORE DOMINANT MODE IN
THE EVENING AS THE LOW-LEVEL JET STRENGTHENS. MODEL FORECASTS ARE IN
RELATIVELY GOOD AGREEMENT DEVELOPING AN MCS ACROSS CNTRL AND SWRN
MN. THIS AREA SHOULD HAVE THE GREATEST POTENTIAL FOR WIND DAMAGE.
..CO/NRN NM...
AN UPPER-LEVEL TROUGH WILL MOVE INTO THE INTERMOUNTAIN WEST ON
MONDAY. JUST AHEAD OF THE UPPER-LEVEL TROUGH...LARGE-SCALE ASCENT
WILL LIKELY BE STRONG SPREADING EWD ACROSS CO AND NRN NM MONDAY
AFTERNOON. AS SFC TEMPS WARM...SCATTERED TO NUMEROUS THUNDERSTORMS
SHOULD INITIATE IN THE HIGHER TERRAIN AND IN THE NERN CO PLAINS.
FORECAST SOUNDINGS ACROSS THE REGION MONDAY AFTERNOON SHOW COLD
TEMPS ALOFT /500 MB TEMPS -10 TO -14C/ AND MODERATE TO STRONG
VERTICAL SHEAR WHICH MAY BE ENOUGH FOR A MARGINAL HAIL THREAT.
STRONG GUSTY WINDS MAY ALSO ACCOMPANY THE STRONGER CELLS ESPECIALLY
WHERE LOW-LEVEL LAPSE RATES ARE STEEPEST IN THE LATE AFTERNOON.
.BROYLES.. 09/16/2007
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