SWODY1
SPC AC 291619
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1119 AM CDT THU APR 29 2010
VALID 291630Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE CENTRAL
PLAINS AND MID MO RIVER VALLEY....
...SYNOPSIS...
A BROAD...SLOW MOVING UPPER TROUGH COVERS MOST OF THE COUNTRY...WEST
OF THE ROCKIES...WITH A SERIES OF UPPER LEVEL IMPULSES ROTATING
CYCLONICALLY THROUGH THIS SYSTEM. WV IMAGERY SUGGESTS ONE OF THESE
IMPULSES...CURRENTLY LOCATED IN SRN CO... WILL SHIFT NEWD INTO
KS/NEB THIS AFTERNOON. THIS SHOULD AID STRONG TO SEVERE STORMS
DEVELOPING ACROSS PORTIONS OF THE CENTRAL PLAINS/MID MO RIVER VALLEY
LATE THIS AFTERNOON/EVENING. A SURFACE LOW WAS LOCATED WEST OF FSD
THIS MORNING...WITH COLD FRONT TRAILING SWWD INTO SWRN KS.
HOWEVER...APPROACHING IMPULSE IS LIKELY TO AID IN THE DEVELOPMENT OF
NEW SURFACE LOW ALONG FRONT IN NRN/NERN KS LATER THIS AFTERNOON.
COLD FRONT AND LOW WILL MOVE ONLY SLIGHTLY EWD THROUGH THE PERIOD
DUE TO THE SLOW MOTION OF THE UPPER TROUGH.
...PORTIONS OF THE CENTRAL PLAINS AND MID MO RIVER VALLEY...
ALTHOUGH SURFACE LOW PRESSURE OVER THE CENTRAL PLAINS WILL RESULT IN
STRONG SLY WINDS AND A SLOW INCREASE IN SURFACE DEWPOINTS INTO THE
MID AND UPPER 50S TODAY...GOES PW VALUES ONLY RANGE FROM 3/4 TO 1
INCH FROM THE TX COAST NWD INTO THE SLIGHT RISK AREA. DESPITE WEAK
MOISTURE RETURN...SUNNY SKIES AND CONSEQUENT STRONG HEATING WILL
LEAD TO STEEPENING LOW/MID LEVEL LAPSE RATES FROM ERN KS NEWD INTO
IA. THE COMBINATION OF INCREASING SURFACE DEWPOINTS AND STEEPENING
LAPSE RATES SHOULD YIELD MODERATE INSTABILITY BY LATE AFTERNOON EAST
OF THE SURFACE LOW/FRONT.
WHILE STORMS MAY INITIALLY DEVELOP BEHIND THE FRONT IN KS/NEB AROUND
MID AFTERNOON...STRONGER CONVECTION IS MOST LIKELY TO EVOLVE NEAR
AND NORTHEAST OF THE SURFACE LOW IN NERN KS/SERN NEB BY 00Z. THIS
CONVECTION SHOULD EXPAND INTO IA/MN AS THE FORCING SPREADS
NEWD...WITH STORMS ALSO DEVELOPING SWD ALONG THE FRONT INTO SRN KS.
WHILE A TORNADO OR TWO IS CERTAINLY POSSIBLE NEAR THE GREATER LOW
LEVEL SHEAR NEAR THE SURFACE LOW...THE POOR BOUNDARY LAYER MOISTURE
FAVORS SEVERE HAIL AS THE PRIMARY THREAT. STRONG WARMING THIS
AFTERNOON SHOULD SUSTAIN THE SEVERE THREAT INTO THE MID EVENING
HOURS...BUT NOCTURNAL COOLING SHOULD DECOUPLE THE BOUNDARY LAYER AND
DIMINISH THE SEVERE THREAT BY 06Z.
..IMY/GRAMS.. 04/29/2010
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