SPC AC 240729
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0229 AM CDT WED JUN 24 2009
VALID 261200Z - 271200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
MODELS GENERALLY INDICATE THAT SEVERAL SIGNIFICANT SHORT WAVE
TROUGHS WILL CONTINUE TO PROGRESS THROUGH THE STRONGER BELT OF
WESTERLIES...WHICH ARE LIKELY TO LINGER NEAR THE CANADIAN/U.S.
BORDER AREA THROUGH THIS PERIOD. AT THE SAME TIME...SUBTROPICAL
RIDGING WILL REMAIN PROMINENT ACROSS THE SOUTH CENTRAL U.S...WITH
REMNANT WEAK UPPER TROUGHING OVER THE SOUTHEASTERN STATES...AND
ACROSS CALIFORNIA INTO THE INTERMOUNTAIN WEST. OF CONSIDERABLE
CONCERN TO THIS FORECAST...IS PERSISTENT LARGE SPREAD AMONG THE
MODELS AND NCEP SREF/MREF MEMBERS CONCERNING THE SHORT WAVE
DEVELOPMENTS AND DETAILS OF THE EVOLVING PATTERN WHICH WILL HAVE
CONSIDERABLE IMPACT ON THE CONVECTIVE POTENTIAL FOR FRIDAY/FRIDAY
NIGHT. THIS UNCERTAINTY/VARIABILITY IS JUST TOO LARGE TO JUSTIFY
SLIGHT RISK PROBABILITIES AT THE PRESENT TIME.
...NORTH CENTRAL STATES...
SEVERE THREAT ACROSS THE NATION APPEARS POTENTIALLY GREATEST FRIDAY
ACROSS PARTS OF THE NORTH CENTRAL PLAINS INTO THE UPPER MISSISSIPPI
VALLEY. THIS IS WHERE CONDITIONAL AND CONVECTIVE INSTABILITY ARE
EXPECTED TO BE LARGEST...ASSOCIATED WITH SEASONABLE BOUNDARY LAYER
MOISTURE BENEATH A PLUME OF VERY STEEP MID-LEVEL LAPSE RATES
EMANATING FROM THE PLATEAU/ROCKIES REGION. VERY WARM LOWER MID
TROPOSPHERIC TEMPERATURES WILL PROVIDE CONSIDERABLE INHIBITION
THROUGH MUCH OF THE DAY. BUT...MODELS INDICATE THAT IT IS POSSIBLE
THAT THIS COULD BECOME SUPPRESSED IN TIME FOR VIGOROUS LATE
AFTERNOON/EVENING CONVECTIVE DEVELOPMENT. THIS COULD OCCUR WITH
EITHER A RELATIVELY WEAK WAVE MIGRATING AROUND THE NORTHERN
PERIPHERY OF THE SUBTROPICAL RIDGE THROUGH THE NORTH CENTRAL PLAINS
INTO THE MID MISSOURI VALLEY...OR WITH A MUCH STRONGER POLAR IMPULSE
MORE PROMINENTLY IMPACTING PARTS OF THE DAKOTAS INTO MINNESOTA. IT
IS NOT OUT OF THE QUESTION THAT BOTH FEATURES COULD CONTRIBUTE TO
ONE OR MORE SIZABLE CONVECTIVE CLUSTERS WITHIN A PRE-FRONTAL SURFACE
TROUGH AND AHEAD OF A SURFACE FRONT ADVANCING SOUTHEASTWARD INTO THE
REGION FRIDAY NIGHT. IF THIS OCCURS...THERMODYNAMIC PROFILES WILL
TEND TO BE FAVORABLE FOR STRONG DOWNBURSTS AND THE EVOLUTION OF
CONVECTIVELY GENERATED COLD POOLS CAPABLE OF PRODUCING DAMAGING WIND
GUSTS. HOWEVER...LARGE HAIL AND ISOLATED TORNADOES...PARTICULARLY
WITH INITIALLY DISCRETE DEVELOPMENT...MAY ALSO BE POSSIBLE.
..KERR.. 06/24/2009
CLICK TO GET WUUS03 PTSDY3 PRODUCT
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z
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