SWODY1
SPC AC 031254
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0754 AM CDT THU SEP 03 2009
VALID 031300Z - 041200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
LITTLE CHANGE IN THE LARGE SCALE PATTERN EXPECTED OVER THE LWR 48
THROUGH FRI AS THE MAIN BELT OF THE WLYS REMAINS CONFINED TO THE
PACIFIC NW AND CANADA. IN THE STATES...GRT BASIN RDG WILL BE
TEMPORARILY SUPPRESSED BY SHORTWAVE TROUGH NOW IN WA. THE IMPULSE
SHOULD CONTINUE NE INTO ERN AB EARLY FRI AS DOWNSTREAM UPR LOW NOW
IN ERN NEB SETTLES SLOWLY S INTO KS. FARTHER E...A VORT MAX NOW
OVER WRN TN SHOULD TRACK SLOWLY E/ENE WITHIN THE BROADER SCALE
TROUGH PERSISTING OVER THE EAST.
AT LWR LVLS...WEAK FRONT MARKING SW EDGE OF GRT LKS/OH VLY SFC RDG
WILL REMAIN NEARLY STNRY FROM ERN CO/SW KS SSE INTO THE RED RVR VLY
REGION OF OK/TX. FARTHER N...A FRONTAL SEGMENT TIED TO ERN NEB UPR
LOW WILL MOVE SLOWLY S FROM WRN/CNTRL NEB INTO NW KS. STILL FARTHER
N/NW...A MORE PROGRESSIVE FRONTAL SYSTEM WILL CROSS THE NRN
RCKYS/NRN HI PLNS IN ASSOCIATION WITH WA/AB UPR IMPULSE. IN THE
EAST...INVERTED TROUGH ACCOMPANYING THE W TN UPR VORT SHOULD
GRADUALLY WEAKEN...WHILE OLD STNRY FRONT PERSISTS FROM OFF THE NC
CST SW ACROSS CNTRL FL INTO THE CNTRL GULF OF MEXICO.
...SRN OK INTO N CNTRL/NE TX...
ON-GOING WAA STORMS IN ERN OK/WRN AR SHOULD WEAKEN LATER THIS
MORNING AS LLJ WEAKENS. ADDITIONAL STORMS MAY FORM THIS AFTN ALONG
AND NE OF STALLED SFC FRONT NEAR THE RED RVR AS HEATING AND WEAK
CONVERGENCE MINIMIZE CINH. ERN EXTENSION OF EML PLUME AND SFC
DEWPOINTS IN THE LOW 60S F SHOULD YIELD 1500-2000 J/KG SBCAPE.
BOUNDARY LAYER WILL BE DRIER AND MORE DEEPLY-MIXED WITH SW EXTENT
FROM FRONT...SUPPORTING A THREAT FOR STG STORM OUTFLOW...BUT ALSO
REDUCED CAPE. LOW LVL FLOW WILL BE WEAK THROUGHOUT THE REGION.
NEVERTHELESS...VEERING WIND PROFILES AND RELATIVELY STG UPR LVL FLOW
/50-60 KTS AT 250 MB/ MAY SUPPORT STORM LONGEVITY/
ORGANIZATION...AND POSE A THREAT FOR ISOLD SVR HAIL AND WIND THROUGH
EARLY TONIGHT.
...CNTRL PLNS/CNTRL HI PLNS INTO OK/TX PANHANDLES/NE NM...
WIDELY SCTD AFTN/EVE TSTMS EXPECTED INVOF FRONT AND PREFRONTAL
TROUGH FROM S CNTRL NEB SWWD INTO PARTS OF KS AND SE CO/NE NM.
ACTIVITY WILL BE AIDED BY WEAK BUT DIURNALLY-ENHANCED UPSLOPE FLOW
IN CO/NM. SFC DEW POINTS MID 50S TO LOW 60S WILL BE PRESENT OVER
THE LWR PLNS....WITH LWR VALUES FARTHER W. THIS MOISTURE...
COMBINED WITH SFC HEATING...WILL HELP BOOST AFTN SBCAPE TO 1500-2000
J/KG IN WRN/NRN KS AND SRN NEB. BELT OF 30 KT NW MID LVL FLOW ON SW
FLANK OF NEB UPR LOW WILL YIELD 35-40 KT DEEP NWLY SHEAR IN WRN/NRN
KS. THIS SHOULD SUPPORT SUSTAINED STORMS AND POSSIBLE WEAK
SUPERCELLS WITH ISOLD SVR HAIL/WIND.
THE STORMS MAY EVOLVE INTO ONE OR TWO SMALL CLUSTERS THAT PERSIST
SSE INTO THE OK/TX PANHANDLES...PORTIONS WRN OK...AND/OR NW TX LATER
TONIGHT. THESE CLUSTERS MAY POSE A THREAT FOR ISOLD SVR HAIL/WIND
AS THEY MOVE MORE OR LESS PARALLEL TO FRONTAL ZONE/INSTABILITY
GRADIENT. RELATIVELY WEAK DEEP SHEAR/ABSENCE OF A WELL-DEFINED LLJ
AND DIURNAL COOLING SHOULD LIMIT OVERALL SVR POTENTIAL.
..CORFIDI/SMITH.. 09/03/2009
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