SPC AC 200730
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CDT TUE JUN 20 2006
VALID 221200Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS THU/THU NIGHT ACROSS MUCH OF
THE NORTHEASTERN U.S...THROUGH THE LOWER OHIO AND MIDDLE MISSISSIPPI
VALLEYS....
MODELS INDICATE THAT SOUTHERN BRANCH OF HIGHER LATITUDE SPLIT FLOW
PATTERN WILL REMAIN GENERALLY ZONAL NEAR OR JUST SOUTH OF THE
CANADIAN/U.S. BORDER THROUGH THIS FORECAST PERIOD. HOWEVER...
SIGNIFICANT AMPLIFICATION IS FORECAST TO BE UNDERWAY IN THE NORTHERN
STREAM BY 12Z THURSDAY...WHEN A STRONG SHORT WAVE TROUGH IS FORECAST
TO BE IN THE PROCESS OF DIGGING THROUGH SOUTHERN HUDSON BAY/NORTHERN
ONTARIO. THIS WILL OCCUR IN THE WAKE OF A SIGNIFICANT SOUTHERN
BRANCH IMPULSE.
WHILE SOUTHERN SYSTEM IS PROGGED TO CONTINUE LIFTING ACROSS QUEBEC
THROUGH THE CANADIAN MARITIMES...UPSTREAM NORTHERN BRANCH TROUGH IS
FORECAST TO TURN EASTWARD ACROSS ONTARIO INTO WESTERN QUEBEC LATE
THURSDAY/THURSDAY NIGHT. THIS WILL CONTRIBUTE TO STRENGTHENING
MID-LEVEL FLOW EAST OF THE UPPER GREAT LAKES...MAINLY THROUGH AREAS
NORTH OF THE CANADIAN/U.S. BORDER. HOWEVER...NEAR OR JUST SOUTH AND
EAST OF THE LOWER GREAT LAKES/ST. LAWRENCE VALLEY...MID-LEVEL FLOW
MAY BE ENHANCED BY ANOTHER PERTURBATION IN THE SOUTHERN STREAM.
...UPPER OHIO VALLEY INTO NORTHEAST...
LOW-LEVEL FLOW IS EXPECTED TO WEAKEN CONSIDERABLY EARLY THURSDAY
ACROSS MUCH OF THE NORTHEAST IN WAKE OF INITIAL SOUTHERN BRANCH
SHORT WAVE TROUGH. ALTHOUGH CONVECTIVE CLUSTER ASSOCIATED WITH THIS
SYSTEM PROBABLY WILL BE IN PROCESS OF WEAKENING...A SUBSTANTIAL
RESIDUAL SURFACE COLD POOL SEEMS LIKELY TO ADVANCE TOWARD NEW
ENGLAND AND NORTHERN MID ATLANTIC COASTAL AREAS BY EARLY THURSDAY
AFTERNOON. MOISTURE RETURN AHEAD OF THIS BOUNDARY IS NOT EXPECTED
TO BE SUFFICIENT FOR SIGNIFICANT CONVECTIVE DEVELOPMENT ACROSS
COASTAL NORTHERN NEW ENGLAND. HOWEVER... MOISTENING/DESTABILIZATION
ACROSS SOUTHERN NEW ENGLAND THROUGH THE URBAN CORRIDOR FROM NEW YORK
THROUGH BALTIMORE/WASHINGTON D.C...INTO THE NORTH CENTRAL
APPALACHIANS...APPEARS LIKELY TO BE SUPPORTIVE OF VIGOROUS
CONVECTIVE DEVELOPMENT. THIS ACTIVITY MAY BE CAPABLE OF PRODUCING
DAMAGING WIND GUSTS AND SOME HAIL...BUT THIS WILL GENERALLY BE SOUTH
OF THE STRONGER WESTERLIES.
AIR MASS RECOVERY THROUGH THE DAY FROM THE LOWER GREAT LAKES INTO
NORTHERN NEW ENGLAND IS UNCERTAIN. BUT...IT APPEARS PROBABLE THAT
AT LEAST A NARROW CORRIDOR OF MODERATE DESTABILIZATION WILL OCCUR
AHEAD OF A SEASONABLY STRONG COLD FRONT ASSOCIATED WITH THE NORTHERN
BRANCH TROUGH. THIS IS EXPECTED TO GENERATE STRENGTHENING
THUNDERSTORM ACTIVITY BY THURSDAY AFTERNOON ACROSS PARTS OF SOUTHERN
QUEBEC/ONTARIO...POSSIBLY INTO PARTS OF LOWER MICHIGAN. THIS COULD
POSE A DAMAGING WIND/HAIL THREAT AS IT DEVELOPS SOUTH/EAST OF THE
ST. LAWRENCE VALLEY AND LOWER GREAT LAKES LATE THURSDAY AFTERNOON
AND EVENING.
...EAST CENTRAL PLAINS INTO LOWER OHIO VALLEY...
STRONGER WESTERLIES WILL BEGIN TO SHIFT NORTH/EAST OF REGION...BUT
BOUNDARY LAYER WILL REMAIN MOIST BENEATH STEEP MID-LEVEL LAPSE
RATES...IN CONFLUENT LOW-LEVEL FLOW REGIME SHIFTING EAST OF THE
CENTRAL PLAINS. PERHAPS AIDED BY FORCING ASSOCIATED WITH WEAK
TROUGING IN THE SUBTROPICAL STREAM...ONE OR MORE SMALL CONVECTIVE
CLUSTERS APPEAR POSSIBLE THURSDAY/THURSDAY NIGHT. THERMODYNAMIC
ENVIRONMENT IS EXPECTED TO BE FAVORABLE FOR POTENTIALLY DAMAGING
WIND GUSTS AND HAIL IN STRONGER ACTIVITY.
..KERR.. 06/20/2006
CLICK TO GET WUUS03 PTSDY3 PRODUCT
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 1100Z
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