SWODY1
SPC AC 121609
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1109 AM CDT FRI OCT 12 2007
VALID 121630Z - 131200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
A STRONG UPPER TROUGH WILL DIG SEWD INTO THE GREAT BASIN/DESERT SW
THROUGH TONIGHT. AHEAD OF THIS SYSTEM...UPPER RIDGING WILL PREVAIL
ACROSS THE CENTRAL CONUS. MEANWHILE AN UPPER LOW OVER THE GREAT
LAKES WILL REMAIN NEARLY STATIONARY. AT THE SFC...A LEE TROUGH OVER
THE CENTRAL/SRN HIGH PLAINS MAY PROVIDE THE FOCUS FOR ISOLATED TSTMS
THIS AFTERNOON. A FEW OF THESE TSTMS COULD POSE A SVR HAIL THREAT.
ADDITIONAL TSTMS ARE EXPECTED TO DEVELOP LATER TONIGHT OVER THE
CENTRAL PLAINS IN RESPONSE TO A STRENGTHENING LOW LEVEL JET AND
INCREASING LARGE SCALE FORCING AHEAD OF THE SWRN CONUS UPPER TROUGH.
..SRN HIGH PLAINS...
A LEE TROUGH EXTENDING ALONG THE KS/CO AND NM/TX BORDER THIS MORNING
WILL REMAIN NEARLY STATIONARY THROUGH THE AFTERNOON IN RESPONSE TO
AN APPROACHING SEASONABLY STRONG UPPER TROUGH THAT IS MOVING INTO
THE GREAT BASIN/SOUTHWEST. MODERATE INSTABILITY /MLCAPE FROM
1000-1500 J/KG/ SUPPORTED BY STEEP MID LEVEL LAPSE RATES /7-7.5 DEG
C/KM/ AND SFC DEWPTS IN THE 55-60 DEG F RANGE WILL EXIST OVER THE
AREA THIS AFTERNOON. VERTICAL SHEAR WILL INCREASE WITH TIME...AS MID
LEVEL FLOW INCREASES TO AROUND 30 KTS AHEAD OF GREAT BASIN UPPER
TROUGH. HOWEVER...LARGE SCALE FORCING WILL REMAIN WEAK DURING PEAK
HEATING PERIOD...AS THE UPPER RIDGE REMAINS CENTERED OVER THE HIGH
PLAINS REGION. SUFFICIENT CONVERGENCE ALONG THE LEE TROUGH MAY
SUPPORT ISOLATED TSTM DEVELOPMENT AND AFOREMENTIONED
SHEAR/INSTABILITY WOULD FAVOR A SVR HAIL THREAT WITH ANY TSTM THAT
DEVELOPS. HOWEVER...LOW SVR HAIL PROBABILITIES WILL CONTINUE...GIVEN
THE LARGE SCALE PATTERN AND UNCERTAINTY IN THE COVERAGE OF THE SVR
THREAT.
..CENTRAL PLAINS...
NOCTURNAL CONVECTION OVER KS/NWRN OK IS EXPECTED TO GRADUALLY WANE
THIS AFTERNOON AS LOW LEVEL JET/INFLOW WEAKENS. ADDITIONAL TSTMS ARE
EXPECTED TO DEVELOP THIS EVENING/OVERNIGHT ACROSS NERN CO...NRN
KS/SRN NEB AND EVENTUALLY INTO NWRN MO/SWRN IA AS THE LOW LEVEL JET
STRENGTHENS. 1000-2000 J/KG OF MUCAPE AND 35 KTS OF CLOUD LAYER
SHEAR MAY BE SUFFICIENT TO SUPPORT ISOLATED SVR HAIL WITH THE
STRONGEST TSTMS.
.CROSBIE/HALES.. 10/12/2007
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