SWODY2
SPC AC 011729
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 PM CDT WED JUN 01 2011
VALID 021200Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS THU/THU NIGHT ACROSS PARTS OF
THE NRN PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS THU ACROSS PARTS OF THE
SOUTHERN APPALACHIANS AND ADJACENT PIEDMONT...
...SYNOPSIS...
MODELS SUGGEST THAT SOME FURTHER AMPLIFICATION OF THE UPPER FLOW MAY
OCCUR ACROSS THE U.S. DURING THIS FORECAST PERIOD. A VIGOROUS SHORT
WAVE IMPULSE...NOW TO THE SOUTHEAST OF THE ALEUTIANS...IS PROGGED TO
DIG TOWARD THE PACIFIC COAST AND CONTRIBUTE TO THE NORTHEASTWARD
ACCELERATION OF ANOTHER STRONG IMPULSE OUT OF BROADER WESTERN U.S.
UPPER TROUGHING. AS THIS OCCURS...RIDGING NORTH OF A LINGERING
SUBTROPICAL HIGH CENTER OVER THE SOUTH CENTRAL U.S. APPEARS LIKELY
TO BUILD TOWARD HUDSON BAY...WITH DOWNSTREAM TROUGHING DIGGING OFF
THE NORTH ATLANTIC COAST.
WHILE DRY STABLE CONDITIONS PREVAIL ACROSS MUCH OF THE NORTHEASTERN
STATES IN THE WAKE OF A SIGNIFICANT COLD FRONT...MUCH OF THE
SOUTHEAST WILL REMAIN SEASONABLY MOIST. AND SIGNIFICANT MOISTURE
RETURN WILL CONTINUE NORTHWARD AND EASTWARD OUT OF THE PLAINS
THROUGH THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES REGION BY 12Z
FRIDAY.
...NORTHERN PLAINS...
UNCERTAINTIES LINGER CONCERNING THE EXTENT OF THE CONVECTIVE
POTENTIAL ACROSS THE REGION THURSDAY. THIS INCLUDES THE DETAILS OF
SURFACE CYCLONE EVOLUTION FROM THE LEE OF THE NORTHERN ROCKIES INTO
THE CANADIAN PRAIRIES AND NORTHERN U.S. PLAINS...AND THE STRENGTH OF
MID-LEVEL CAPPING ASSOCIATED WITH VERY WARM ELEVATED MIXED LAYER AIR
ADVECTING OFF THE PLATEAU AND ROCKIES. STRONG MID-LEVEL HEIGHT
FALLS ARE PROGGED TO DEVELOP NORTHEASTWARD ACROSS THE NORTHERN
ROCKIES INTO SASKATCHEWAN/MANITOBA...ASSOCIATED WITH THE STRONG
SHORT WAVE IMPULSE EMERGING FROM THE INTERMOUNTAIN WEST. BUT THIS
MAY REMAIN MOSTLY TO THE NORTHWEST OF THE WARM SECTOR OF THE SURFACE
CYCLONE.
DAYTIME HEATING IS EXPECTED TO CONTRIBUTE TO MODERATELY LARGE CAPE
IN THE WARM SECTOR BY LATE AFTERNOON...AS HIGH AS 3000+ J/KG ALONG
AND EAST OF THE DRY LINE ACROSS PARTS OF WESTERN NORTH DAKOTA INTO
CENTRAL SOUTH DAKOTA...WHERE LOW-LEVEL CONVERGENCE SEEMS LIKELY TO
BECOME SUPPORTIVE OF AT LEAST ISOLATED TO SCATTERED STORM
DEVELOPMENT. VERTICAL SHEAR...NEAR THE PERIPHERY OF A 70-90 KT
SOUTHWESTERLY 500 MB JET ACCOMPANYING THE UPPER IMPULSE...WILL BE
SUFFICIENT FOR SUPERCELLS...WHICH LIKELY WILL PERSIST AND GRADUALLY
SPREAD EASTWARD THROUGH THE EVENING HOURS.
UPSCALE CONVECTIVE GROWTH INTO AN ORGANIZED SEVERE MESOSCALE
CONVECTIVE SYSTEM ACROSS THE CENTRAL/EASTERN DAKOTAS THURSDAY
EVENING DOES NOT APPEAR OUT OF THE QUESTION. THIS COULD POSE A
BROADER SCALE DAMAGING WIND AND HAIL THREAT WHICH MAY CONTINUE INTO
PARTS OF MINNESOTA OVERNIGHT.
...SOUTHERN APPALACHIANS AND ADJACENT PIEDMONT...
UPPER RIDGING APPEARS LIKELY TO REMAIN STRONG ACROSS THE REGION
...WITH NEGLIGIBLE HEIGHT FALLS EXPECTED IN ASSOCIATION WITH THE
TROUGH DIGGING OFF THE NORTH ATLANTIC COAST. HOWEVER...MODELS ARE
SUGGESTIVE THAT AN AREA OF BROADER SCALE UPWARD VERTICAL MOTION MAY
DEVELOP IN ASSOCIATION WITH LOWER/MID-LEVEL WARM ADVECTION. THIS
MAY AID OROGRAPHIC FORCING OF CONVECTIVE DEVELOPMENT IN THE PRESENCE
OF A VERY WARM AND MOIST... MODERATELY UNSTABLE AIR
MASS...CHARACTERIZED BY STEEP LOW-LEVEL LAPSE RATES AND CAPE OF
2000-3000+ J/KG. IT APPEARS THAT STRONGER PULSING STORMS COULD
BECOME RELATIVELY NUMEROUS AS LIGHT NORTHERLY FLOW CONTRIBUTES TO
PROPAGATION OFF THE HIGHER TERRAIN INTO THE PIEDMONT AND PERHAPS
PORTIONS OF THE UPPER TENNESSEE VALLEY LATE THURSDAY AFTERNOON.
..KERR.. 06/01/2011
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