SPC AC 230730
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CDT WED MAY 23 2007
VALID 251200Z - 261200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
MODELS CONTINUE TO INDICATE THAT THE UPPER FLOW PATTERN WILL BECOME
MORE ZONAL LATE THIS WEEK...WITH THE STRONGER WESTERLIES GENERALLY
BECOMING CONFINED TO PARTS OF THE NORTHERN TIER STATES AND SOUTHERN
CANADA. A SIGNIFICANT LOW/MID-LEVEL CYCLONE...LIKELY TO DEVELOP
OVER ONTARIO IN RESPONSE TO POLAR TROUGH LIFTING OUT OF THE
ROCKIES...IS PROGGED TO LIFT NORTHEAST OF THE UPPER GREAT LAKES
FRIDAY/FRIDAY NIGHT. AS THIS OCCURS...ANOTHER SIGNIFICANT UPSTREAM
SHORT WAVE IMPULSE IS EXPECTED TO TURN EAST OF THE NORTHERN
ROCKIES...AS ANOTHER APPROACHES THE BRITISH COLUMBIA/PACIFIC
NORTHWEST COAST. LOWER/MID TROPOSPHERIC RIDGING IS FORECAST TO
REMAIN STRONG FROM MID/SOUTH ATLANTIC COASTAL AREAS THROUGH THE
LOWER MISSISSIPPI VALLEY. BUT...GRADUAL MID-LEVEL HEIGHT FALLS ARE
EXPECTED TO CONTINUE ACROSS THE LOWER GREAT LAKES INTO NEW
ENGLAND...WHILE BROAD TROUGHING IN THE SUBTROPICAL STREAM PROGRESSES
ACROSS THE SOUTHERN U.S. PLATEAU/ROCKIES AND MEXICAN PLATEAU.
...LOWER GREAT LAKES...
MODELS ARE SUGGESTIVE THAT THE PRIMARY MID/UPPER CLOSED LOW/SHORT
WAVE IMPULSE AND ASSOCIATED FLOW FIELDS WILL PROGRESS WELL NORTH OF
REGION. HOWEVER...A BELT OF MODERATE FLOW ON ITS SOUTHERN
PERIPHERY...PROGRESSING AROUND THE CREST OF FLATTENING RIDGE...
COULD ENHANCE CONVECTIVE DEVELOPMENT ALONG/AHEAD OF FRONT PROGGED TO
ADVANCE EAST OF THE GREAT LAKES THROUGH MUCH OF THE NORTHEAST LATE
FRIDAY AFTERNOON/FRIDAY NIGHT. THE MAIN THUNDERSTORM ACTIVITY SEEMS
LIKELY TO OCCUR ACROSS PARTS OF SOUTHERN ONTARIO BEFORE SPREADING TO
THE LEE OF THE LOWER GREAT LAKES BY EARLY FRIDAY EVENING. ALTHOUGH
WEAK MID-LEVEL LAPSE RATES WILL LIMIT INSTABILITY...GUSTY
WINDS/ISOLATED MARGINAL SEVERE HAIL COULD OCCUR BEFORE STORMS
DIMINISH WITH LOSS OF DAYTIME HEATING.
...PARTS OF CENTRAL/NORTHERN PLAINS...
A LEE SURFACE LOW/TROUGH IS FORECAST TO DEVELOP ACROSS THE NORTH
CENTRAL HIGH PLAINS IN RESPONSE TO UPSTREAM SHORT WAVE TROUGH.
AND...LAPSE RATES ARE EXPECTED TO BECOME QUITE STEEP NEAR THESE
FEATURES...AND DEVELOPING WARM FRONT ACROSS CENTRAL/EASTERN SOUTH
DAKOTA. HOWEVER...IN THE WAKE OF UPPER SYSTEM LIFTING THROUGH
EASTERN CANADA...SIGNIFICANT MOISTURE RETURN FROM THE SOUTHERN
PLAINS IS NOT PROGGED TO OCCUR UNTIL LATE FRIDAY NIGHT. WHILE THIS
WILL TEND TO MINIMIZE DESTABILIZATION...VERTICAL SHEAR PROFILES WILL
BE SUPPORTIVE OF UPDRAFT ROTATION IN SCATTERED STORMS EXPECTED TO
DEVELOP LATE FRIDAY AFTERNOON/EVENING FROM PARTS OF EASTERN
COLORADO/WESTERN NEBRASKA INTO SOUTHWEST/CENTRAL SOUTH DAKOTA. THIS
SUPPORTS AT LEAST SOME RISK FOR HAIL/GUSTY WINDS IN STORMS...WHICH
MAY DEVELOP NORTHEASTWARD IN STRENGTHENING WARM ADVECTION REGIME
ACROSS THE NORTH CENTRAL PLAINS FRIDAY NIGHT INTO EARLY SATURDAY.
..KERR.. 05/23/2007
CLICK TO GET WUUS03 PTSDY3 PRODUCT
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 1100Z
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