SWODY1
SPC AC 220534
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1234 AM CDT MON SEP 22 2008
VALID 221200Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN PLAINS
AND CNTRL HIGH PLAINS...
...NRN PLAINS AND CNTRL HIGH PLAINS...
AN UPPER-LEVEL TROUGH OVER THE INTERMOUNTAIN WEST IS FORECAST TO
MOVE QUICKLY NEWD ACROSS THE ROCKIES TODAY WITH THE LEADING EDGE OF
ASCENT REACHING THE NRN PLAINS THIS AFTERNOON. AT THE SFC...A
WELL-DEFINED COLD FRONT WILL ORGANIZE AND MOVE EWD INTO THE CNTRL
DAKOTAS. AHEAD OF THE FRONT...A 40 TO 50 KT LOW-LEVEL JET WILL
RESULT IN SUBSTANTIAL MOISTURE ADVECTION IN THE PLAINS WITH SFC
DEWPOINTS LIKELY REACHING THE LOWER 60S F INTO PARTS OF THE DAKOTAS
BY LATE AFTERNOON. THIS SHOULD RESULT IN AN AXIS OF MODERATE
INSTABILITY FROM ERN ND SSWWD INTO NW NEB WITH MLCAPE VALUES LIKELY
REACHING THE 1000 TO 2000 J/KG RANGE. ALTHOUGH THE MODELS SHOW A
CAPPING INVERSION THROUGH EARLY AFTERNOON...THE CAP IS FORECAST TO
WEAKEN BY LATE AFTERNOON ALLOWING FOR SCATTERED STORM INITIATION
ALONG AND AHEAD OF THE BOUNDARY. MODEL FORECASTS ARE IN GENERAL
AGREEMENT RAPIDLY INCREASING CONVECTIVE COVERAGE THIS EVENING WITH
AN MCS DEVELOPING IN THE CNTRL DAKOTAS. DUE TO THE AMOUNT OF ASCENT
ASSOCIATED WITH THE EJECTING UPPER-LEVEL TROUGH...A LARGE CLUSTER OF
STORMS SHOULD PERSIST THROUGH LATE TONIGHT INTO ERN ND AND NW MN.
CONCERNING THE WIND SHEAR ENVIRONMENT...A 50 TO 60 KT MID-LEVEL JET
IS FORECAST TO EJECT NEWD ACROSS THE REGION THIS AFTERNOON. THE JET
MAX WILL STRENGTHEN VERTICAL SHEAR PROFILES ALONG THE WRN EDGE OF
THE INSTABILITY AXIS WITH FORECAST SOUNDINGS SHOWING 0-6 KM SHEAR
GENERALLY REACHING THE 45 TO 55 KT RANGE. THIS SHOULD SUPPORT
SUPERCELL DEVELOPMENT ESPECIALLY WITH STORMS THAT REMAIN DISCRETE
ALONG THE FRONT OR EWD INTO THE WARM SECTOR. THE THREAT FOR LARGE
HAIL MAY BE GREATEST IN WCNTRL SD AND NW NEB WHERE TEMPS ALOFT WILL
BE COOL AND THE INSTABILITY/VERTICAL SHEAR COMBINATION IS FORECAST
TO BE MAXIMIZED. AN ISOLATED ROTATING STORM MAY ALSO OCCUR IN ERN WY
WHERE VERTICAL SHEAR WILL BE STRONG AND MID-LEVEL LAPSE RATES WILL
BE QUITE STEEP. AS THE LOW-LEVEL JET STRENGTHENS EARLY THIS EVENING
ACROSS THE PLAINS...DISCRETE ROTATING STORMS IN THE CNTRL DAKOTAS
SHOULD BE CAPABLE OF PRODUCING LARGE HAIL AND PERHAPS A TORNADO. THE
AMOUNT OF LARGE-SCALE ASCENT AND NORTH TO SOUTH ORIENTATION OF THE
BOUNDARY MAY ALSO ENCOURAGE THE DEVELOPMENT OF A SQUALL-LINE. IF
THIS OCCURS...HAIL AND WIND DAMAGE WOULD BE THE PRIMARY THREATS BY
THE EARLY TO MID-EVENING ALONG THE FRONTAL BOUNDARY. THE SEVERE
THREAT SHOULD BECOME INCREASINGLY MARGINAL DURING THE OVERNIGHT
PERIOD AS STORMS BECOME ELEVATED IN NATURE.
..BROYLES/SMITH.. 09/22/2008
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.
No comments:
Post a Comment