SWODY1
SPC AC 150538
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1238 AM CDT FRI AUG 15 2008
VALID 151200Z - 161200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTN/EVE ACROSS PARTS OF
THE SOUTHERN PLAINS....
...THERE IS A SLGT RISK OF SVR TSTMS TODAY ACROSS MUCH OF THE URBAN
CORRIDOR OF THE NORTHEAST....
...SYNOPSIS...
CUT-OFF FROM THE STRONGER WESTERLIES...MODELS INDICATE THAT THE
INTERIOR U.S. CLOSED LOW WILL CONTINUE A SLOW SOUTHWARD/WESTWARD
MIGRATION FROM THE NORTHERN HIGH PLAINS INTO THE VICINITY OF THE
CENTRAL ROCKIES BY 12Z SATURDAY. THIS MOTION IS EXPECTED TO OCCUR
IN RESPONSE TO NORTHERLY STEERING FLOW TO THE LEE OF THE SHARP UPPER
RIDGE OVER THE WESTERN STATES...AND A COUPLE OF SIGNIFICANT SHORT
WAVE IMPULSES PIVOTING AROUND ITS NORTHERN/WESTERN PERIPHERY.
AT THE SAME TIME...A MID-LEVEL CIRCULATION...WHICH HAS DEVELOPED
WITHIN THE LARGER SCALE EASTERN U.S. UPPER TROUGH...IS PROGGED BY
MODELS TO ACCELERATED EAST NORTHEAST OF THE LOWER GREAT LAKES REGION
TODAY. THIS IS EXPECTED TO OCCUR IN RESPONSE TO THE APPROACH OF A
STRONG SHORT WAVE TOUGH...DIGGING WITHIN THE MAIN BELT OF POLAR
WESTERLIES...ACROSS THE HUDSON/JAMES BAY REGION.
OTHERWISE...SHARP CYCLONIC UPPER FLOW APPEARS LIKELY TO LINGER FROM
THE OHIO VALLEY INTO THE MID ATLANTIC STATES...WITH MORE BROADLY
CYCLONIC FLOW CONTINUING NORTH OF THE FOUR CORNERS INTO THE SOUTHERN
PLAINS...AND ACROSS THE GULF/SOUTH ATLANTIC COAST STATES.
COOL MID-LEVEL TEMPERATURES/WEAK INHIBITION ASSOCIATED WITH THIS
PATTERN IS EXPECTED TO ONCE AGAIN SUPPORT CONSIDERABLE THUNDERSTORM
ACTIVITY TODAY...DESPITE SOMEWHAT LOW MOISTURE LEVELS INLAND OF
GULF/SOUTH ATLANTIC COASTAL AREAS. THE BULK OF THIS ACTIVITY IS
EXPECTED WITH FORCING ACCOMPANYING THE SIGNIFICANT UPPER
FEATURES...FROM THE CENTRAL/SOUTHERN ROCKIES INTO THE SOUTHERN
PLAINS... AND ACROSS THE MID AND NORTHERN ATLANTIC COAST STATES.
...SOUTHERN ROCKIES INTO THE SOUTHERN PLAINS...
MOIST UPSLOPE FLOW TO THE NORTH OF THE CONVECTIVELY GENERATED/
ENHANCED SURFACE BOUNDARY SETTLING SOUTHWARD THROUGH THE SOUTHERN
PLAINS...COUPLED WITH STRONG DAYTIME HEATING...IS EXPECTED TO
CONTRIBUTE TO DESTABILIZATION ALONG AND TO THE LEE OF THE HIGHER
TERRAIN...FROM SOUTHEAST COLORADO INTO EASTERN NEW MEXICO. MIXED
LAYER CAPE OF 1000-2000 J/KG APPEARS POSSIBLE BY THIS AFTERNOON.
AND...IN THE PRESENCE OF MODERATELY STRONG DEEP LAYER SHEAR BENEATH
MODEST NORTHWESTERLY MID-LEVEL FLOW...A FEW SUPERCELLS ARE EXPECTED
AS STORMS DEVELOP OFF THE HIGHER TERRAIN. DIFLUENT/ DIVERGENT UPPER
FLOW SOUTHEAST OF THE APPROACHING CLOSED LOW MAY ENHANCE
CONVECTION...AND POTENTIAL EXISTS FOR CONSOLIDATION INTO AN
ORGANIZED STORM CLUSTER PROPAGATING ALONG THE BAROCLINIC ZONE
ASSOCIATED WITH THE REMNANT BOUNDARY ACROSS EASTERN NEW MEXICO INTO
THE TEXAS SOUTH PLAINS. IF THIS OCCURS...THERE ARE INDICATIONS
AMONG MODEL GUIDANCE THAT THERMODYNAMIC AND SYSTEM RELATIVE WIND
PROFILES COULD BECOME FAVORABLE FOR STRONG COLD POOL EVOLUTION BY
EARLY THIS EVENING...ACCOMPANIED BY A SWATH OR SWATHS OF POTENTIALLY
DAMAGING WIND GUSTS.
...NORTHEAST...
MODELS ARE SUGGESTIVE THAT AN AREA OF STRONGER FORCING AND WEAK TO
MODERATE DESTABILIZATION WILL OVERSPREAD THE URBAN CORRIDOR
NORTHEAST OF WASHINGTON/BALTIMORE INTO THE NEW YORK CITY AREA THIS
AFTERNOON...IN RESPONSE TO THE AFOREMENTIONED DEVELOPING UPPER FLOW
PATTERN. WHILE LOWER/MID TROPOSPHERIC WIND FIELDS ARE EXPECTED TO
REMAIN GENERALLY WEAK...SHEAR ASSOCIATED WITH STRONG AND
STRENGTHENING HIGH-LEVEL FLOW EAST OF THE UPPER TROUGH AXIS MAY
ENHANCE THUNDERSTORM ACTIVITY. AT LEAST A FEW SHORT LIVED
SUPERCELLS APPEAR POSSIBLE...PRIMARILY WITH THE RISK FOR LARGE HAIL
AND DAMAGING WIND GUSTS.
...SOUTHERN PLATEAU...
WITHIN OTHERWISE PREDOMINANTLY WESTERLY WIND PROFILES...MODELS
INDICATE A LINGERING EASTERLY MID-LEVEL FLOW COMPONENT
TODAY...GENERALLY TO THE SOUTH OF THE MOGOLLON RIM. THIS WILL
PROVIDE POTENTIAL FOR STORM PROPAGATION OFF THE MOUNTAINS OF
SOUTHEASTERN ARIZONA INTO THE LOWER DESERTS...WHERE THERMODYNAMIC
PROFILES PROBABLY WILL BE FAVORABLE FOR AT LEAST LOCALIZED
DOWNBURSTS AND COLD POOL DEVELOPMENT.
..KERR/CROSBIE.. 08/15/2008
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