SPC AC 051256
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0756 AM CDT SAT JUL 05 2008
VALID 051300Z - 061200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE NRN PLNS...
...SYNOPSIS...
POSITIVE TILT IMPULSE NOW CROSSING THE NRN RCKYS WILL CONTINUE E
INTO WRN ONTARIO BY THE END OF THE PERIOD AS FLATTENED RIDGE
PERSISTS FROM THE SRN GRT BASIN TO THE CNTRL HI PLNS. FARTHER
E...SATELLITE SHOWS A WEAK TROUGH EVOLVING OVER THE LWR OH VLY ATTM.
THIS FEATURE SHOULD EDGE SLOWLY E TOWARD WRN FLANK OF DOMINANT WRN
ATLANTIC RIDGE.
AT LWR LEVELS...EXPECT COLD FRONT NOW OVER ERN MT TO REACH ERN
ND/CNTRL SD THIS EVENING...AND N CNTRL MN/CNTRL SD BY 12Z SUNDAY.
AHEAD OF THE FRONT...LEE TROUGH SHOULD PERSIST FROM S CNTRL SD S/SW
INTO WRN NEB/NE CO. FARTHER SE...DIFFUSE FRONT EXPECTED TO REMAIN
MORE OR LESS STATIONARY FROM THE MID ATLANTIC CST SW ACROSS THE TN
VLY INTO THE OZARKS.
...NRN PLNS...
INCREASING SLY FLOW AND DOWNWARD MIXING AHEAD OF ASSOCIATED COLD
FRONT SHOULD ALLOW MID 60S SFC DEWPOINTS TO SPREAD N INTO THE
CNTRL/ERN DAKS TODAY...BENEATH STRONG EML CAP. ELEVATED
CONVECTION/CLOUDS ABOVE CAP MAY PERSIST INTO THE AFTN FROM CNTRL ND
NWD INTO SK/MB. FARTHER S...STRONGER SFC HEATING COUPLED WITH
MOISTURE INFLOW SHOULD BOOST SBCAPE TO AOA 2500 J/KG.
MAIN AREA OF FORCING WITH AFOREMENTIONED UPR IMPULSE WILL SKIRT THE
ND/CANADIAN BORDER...ALTHOUGH WEAKER FORCING FOR ASCENT LIKELY WILL
EXTEND SWD INTO SD. COMBINATION OF MODEST LARGE SCALE UVV... LOW
LVL CONVERGENCE ALONG COLD FRONT...AND INCREASING INSTABILITY SHOULD
SUPPORT SFC-BASED STORM DEVELOPMENT BY MID AFTN OVER CNTRL/ERN ND.
OTHER STORMS MAY FORM A BIT LATER SWD ALONG LEE TROUGH INTO CNTRL
SD. 35-40 KT DEEP W TO WSWLY SHEAR SHOULD ALLOW STORMS TO ASSUME
SUPERCELLULAR STRUCTURE...WITH DEEP EML AND STEEP BOUNDARY LAYER
LAPSE RATES FURTHER SUGGESTING GOOD LIKELIHOOD FOR BOTH LARGE HAIL
AND DMGG WINDS.
WITH THERMODYNAMIC SETUP FAVORING FAIRLY STRONG COLD POOLS...EXPECT
STORMS WILL EVOLVE INTO ONE OR TWO QLCSS THIS EVENING.
FORWARD-PROPAGATING SEGMENTS WITHIN THE SYSTEMS COULD POSE A RISK
FOR HIGH WINDS/HAIL E/SE INTO WRN MN AND ERN SD. THE SD STORMS MAY
PERSIST THROUGH SUNDAY MORNING AS STRENGTHENING/ VEERING LLJ ALLOWS
FOR POTENTIAL REDEVELOPMENT E/SE INTO SRN MN/WRN IA.
...CNTRL HI PLNS...
WEAKENING SWRN END OF NRN PLNS COLD FRONT WILL BACK DOOR S/SW INTO
NERN WY THIS AFTN. INCREASING UPSLOPE FLOW AND BOUNDARY LYR
MOISTURE /SFC DEWPOINTS IN THE MID-50S F/...AND STEEP LOW TO MID LVL
LAPSE RATES...WILL BE FAVORABLE FOR ISOLD TSTMS OVER THE HIGHER
TERRAIN. THESE MAY ASSUME SUPERCELLULAR STRUCTURE FOR A TIME AND
POSE A THREAT FOR LARGE HAIL THROUGH EARLY TONIGHT.
...LWR MS VLY E THROUGH THE DEEP S/SERN U.S...
WEAK QSTNRY FRONT ALONG SRN FRINGE OF AMPLIFYING UPR TROUGH WILL
REMAIN THE FOCUS FOR SCTD MAINLY DIURNAL TSTM CLUSTERS THIS PERIOD.
ONE PREFERRED AREA FOR DEVELOPMENT MAY EVOLVE FROM ERN AR E/SE INTO
NRN/CNTRL MS/AL...IN AREA OF 20-25 KT WNWLY MID LVL FLOW DOWNSTREAM
FROM DEEPENING TROUGH. MORE CONCENTRATED ACTIVITY MAY ALSO DEVELOP
ALONG DIFFERENTIAL HEATING BOUNDARIES OVER PIEDMONT NC/SC. MODEST
VERTICAL SHEAR AND HIGH PWS COULD YIELD ISOLD DMGG WIND GUSTS WITH
HEAVY RAIN.
...LWR MO VLY THIS MORNING...
SCTD...ELEVATED WAA STORMS MAY POSE A RISK FOR SVR HAIL OVER THE LWR
MO VLY UNTIL LLJ BACKS AND RE-COUPLES WITH THE BOUNDARY LAYER LATER
THIS MORNING.
..CORFIDI/HURLBUT.. 07/05/2008
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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