SPC AC 290723
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0223 AM CDT SAT AUG 29 2009
VALID 311200Z - 011200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
MODELS INDICATE A CONTINUED WEAKENING OF MID/UPPER WIND FIELDS
ACROSS THE EASTERN U.S. DURING THIS PERIOD...AS A SIGNIFICANT POLAR
IMPULSE LIFTS NORTHEAST OF THE EASTERN CANADIAN PROVINCES... AHEAD
OF ANOTHER DIGGING TOWARD HUDSON BAY. BUT...FLOW IS EXPECTED TO
REMAIN GENERALLY CYCLONIC EAST OF THE MISSISSIPPI VALLEY THROUGH THE
ATLANTIC SEABOARD...WITH PERHAPS A SLIGHT EASTWARD SHIFT TO THE
ELONGATED UPPER TROUGH AXIS. MEANWHILE... WEAK...BROADLY
ANTICYCLONIC UPPER FLOW IS EXPECTED TO PERSIST ACROSS MUCH OF THE
WEST INTO THE PLAINS...DOWNSTREAM OF A LARGE CLOSED LOW DIGGING OFF
THE NORTHERN PACIFIC/BRITISH COLUMBIA COAST ...SOUTH OF THE MAIN
BELT OF WESTERLIES. EMBEDDED WITHIN THIS REGIME...A WEAKENING
MID-LEVEL CLOSED LOW IS EXPECTED TO GRADUALLY SHIFT EASTWARD ACROSS
THE NORTHERN ROCKIES.
...NORTH CENTRAL HIGH PLAINS...
WHILE DISCREPANCIES AMONG THE MODELS EXIST...IT APPEARS A
POSSIBILITY THAT A NOCTURNALLY STRENGTHENING LOWER/MID TROPOSPHERIC
WARM ADVECTION REGIME COULD BECOME THE FOCUS FOR CONSOLIDATING
STORMS ACROSS PARTS OF EASTERN WYOMING INTO PARTS OF SOUTHWESTERN
SOUTH DAKOTA/WESTERN NEBRASKA MONDAY NIGHT. IF THIS
OCCURS...ENHANCED SHEAR ASSOCIATED WITH A MID-LEVEL SPEED MAXIMUM
ACCOMPANYING THE CLOSED LOW MAY BE SUPPORTIVE OF AN ORGANIZED STORM
CLUSTER CAPABLE OF PRODUCING HAIL...PERHAPS STRONG SURFACE
GUSTS...IN THE PRESENCE OF STEEP MID-LEVEL LAPSE RATES AND WEAK TO
MODERATE POTENTIAL INSTABILITY.
..KERR.. 08/29/2009
CLICK TO GET WUUS03 PTSDY3 PRODUCT
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z
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