Aug 12, 2014 0600 UTC Day 1 Convective Outlook

SPC AC 120600

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0100 AM CDT TUE AUG 12 2014

   VALID 121200Z - 131200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE UPPER OH
   VALLEY AND NORTHEAST/MID-ATLANTIC STATES...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE PACIFIC
   NORTHWEST/NORTHERN INTERMOUNTAIN REGION...

   ...SUMMARY...
   SCATTERED STRONG TO SEVERE STORMS ARE EXPECTED ACROSS PARTS OF THE
   UPPER OHIO VALLEY AND NORTHEAST AND MIDDLE-ATLANTIC REGION. CLUSTERS
   OF SEVERE STORMS ALSO APPEAR POSSIBLE ACROSS PARTS OF THE WESTERN
   UNITED STATES.

   ...SYNOPSIS...
   A HIGHLY AMPLIFIED LONGWAVE REGIME WILL REMAIN OVER THE CONUS TODAY
   THROUGH EARLY WEDNESDAY. AN UPPER RIDGE CENTERED OVER THE EASTERN
   SLOPES OF THE ROCKIES AND HIGH PLAINS WILL BE FLANKED BY DUAL
   TROUGHS...ONE OVER THE WESTERN STATES AND THE OTHER OVER THE GREAT
   LAKES/MIDWEST AND APPALACHIANS.

   ...UPPER OH VALLEY AND NORTHEAST/MID-ATLANTIC STATES...
   WHILE A SURFACE LOW CONTINUES TO DEEPEN ACROSS
   ONTARIO...SHOWERS/EMBEDDED THUNDERSTORMS WILL ACCOMPANY AN
   EASTWARD-SPREADING COLD FRONT/NARROW WARM SECTOR ACROSS THE REGION
   TODAY. THE GENERAL PREVALENCE OF CLOUD COVER AND THE MOIST NATURE OF
   THE THERMODYNAMIC PROFILES WILL GENERALLY KEEP BUOYANCY RELATIVELY
   MODEST...ALTHOUGH CLOUD BREAKS AND WESTERN-PERIPHERAL HEATING IN
   VICINITY OF UPPER DRY SLOT SHOULD ALLOW FOR MUCH AS 500-1250 J/KG OF
   MLCAPE THIS AFTERNOON ACROSS THE UPPER OH VALLEY/DELMARVA VICINITY.

   DIURNALLY INTENSIFYING THUNDERSTORMS IN THE PRESENCE OF A
   STRENGTHENING CYCLONIC WIND FIELD...WITH 30-45 KT OF EFFECTIVE
   SHEAR...WILL SUPPORT SUSTAINED MULTICELLS AND A LEAST A CONDITIONAL
   SUPERCELL POTENTIAL WITH DAMAGING WINDS/SEVERE HAIL POSSIBLE.
   PROVIDED SUFFICIENT CLOUD BREAKS/HEATING...A BRIEF TORNADO OR TWO
   MAY BE POSSIBLE IN VICINITY OF THE SURFACE OCCLUSION/WARM FRONT
   WHERE WIND PROFILES WOULD SUPPORT LOW-LEVEL
   MESOCYCLONES...PARTICULARLY THIS AFTERNOON/EARLY EVENING IN A
   CORRIDOR INCLUDING PA/WESTERN NY AND THE DELMARVA VICINITY.

   ...CAROLINAS/GA...
   A SECONDARY IMPULSE EMBEDDED WITHIN THE BASE OF THE UPPER TROUGH
   WILL APPROACH THE REGION LATER TODAY/TONIGHT...WHILE WEAK HEIGHT
   FALLS AND AN ATTENDANT ZONE OF 20-30 KT MID-LEVEL SOUTHWESTERLY
   WINDS OVERSPREAD THE REGION. ALTHOUGH MID-LEVEL LAPSE RATES WILL BE
   WEAK...DIURNALLY STEEPENING LOW-LEVEL LAPSE RATES WITH AS MUCH AS
   1000-1500 J/KG OF MLCAPE WILL SUPPORT THE
   DEVELOPMENT/INTENSIFICATION OF MULTICELLS/LINE SEGMENTS CAPABLE OF
   LOCALLY DAMAGING WINDS THIS AFTERNOON/EARLY EVENING.

   ...PACIFIC NORTHWEST/NORTHERN INTERMOUNTAIN REGION/GREAT BASIN...
   A STRENGTHENING SOUTHERLY DEEP-LAYER WIND FIELD WILL ACCOMPANY
   APPRECIABLE DPVA OVER THE PACIFIC NORTHWEST/NORTHERN INTERMOUNTAIN
   REGION TODAY VIA THE NORTHEASTWARD ACCELERATION OF AN UPPER LOW
   CURRENTLY NEAR THE NORTHERN CA COAST. THIS SCENARIO...IN THE
   PRESENCE OF ABOVE-NORMAL PRECIPITABLE WATER VALUES /0.75-1.20
   INCHES/...WILL LIKELY LEAD TO THE DEVELOPMENT OF STRONGER
   THUNDERSTORMS ACROSS THE REGION THIS AFTERNOON. THE STRONGEST STORMS
   WILL BE CAPABLE OF SEVERE HAIL...WITH STRONG DOWNDRAFTS/LOCALLY
   DAMAGING WINDS LIKELY TO BE THE MORE PREVALENT CONCERN. BY MID/LATE
   AFTERNOON...SUFFICIENT FORCING FOR ASCENT/COLD POOL GENERATION MAY
   ALLOW NORTHWARD-MOVING CLUSTERS TO EVOLVE WITH A SOMEWHAT MORE
   CONCENTRATED WIND POTENTIAL INTO THE EVENING.

   ...AZ/LOWER CO RIVER VALLEY...
   A STEADY NORTHWARD INCREASE OF MOISTURE SHOULD ACCOMPANY A
   DISTURBANCE MOVING OUT OF NORTHWEST MEXICO THROUGH TONIGHT. THE
   MAGNITUDE OF DESTABILIZATION LATER TODAY WILL LIKELY BE HINDERED BY
   THE INFLUENCE OF PRIOR OUTFLOWS/CONVECTION ASIDE FROM MOISTENING
   MID-LEVEL PROFILES. THAT SAID...POCKETS OF STRONGER HEATING AND
   MODERATELY STRONG MID-LEVEL WINDS MAY ALLOW THE DEVELOPMENT OF
   WEST/NORTHWESTWARD MOVING CONVECTIVE SEGMENTS WITH STRONG
   THUNDERSTORM OUTFLOWS/SMALL HAIL THIS AFTERNOON/EARLY EVENING.

   ...SOUTH TX...
   AT LEAST ISOLATED THUNDERSTORMS SHOULD DEVELOP/INTENSIFY THIS
   AFTERNOON NEAR/SOUTH OF A FRONTAL BOUNDARY ACROSS THE REGION...A
   SCENARIO WELL-SUPPORTED BY GUIDANCE SUCH AS THE 00Z WRF-NSSL.
   VERTICAL SHEAR WILL BE WEAK IN THE PRESENCE OF NORTH-NORTHERLY WINDS
   THROUGH THE LOWER/MIDDLE TROPOSPHERE...BUT STEEP LOW-LEVEL LAPSE
   RATES/MODERATE BUOYANCY MAY ACCOUNT FOR LOCALIZED DOWNBURSTS THIS
   AFTERNOON/EARLY EVENING.