SPC AC 121730

   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1230 PM CDT TUE AUG 12 2014

   VALID 131200Z - 141200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS WED AFTN AND EVE ACROSS THE
   NORTHERN INTERMOUNTAIN REGION...

   ...SUMMARY...
   A FEW SEVERE STORMS CAPABLE OF PRODUCING LARGE HAIL AND POTENTIALLY
   DAMAGING WIND GUSTS ARE POSSIBLE WEDNESDAY ACROSS THE NORTHERN
   INTERMOUNTAIN REGION.  STRONG STORMS MAY NOT BE COMPLETELY OUT OF
   THE QUESTION ACROSS PARTS OF SOUTHERN NEW ENGLAND...ACCOMPANIED BY
   SOME RISK FOR POTENTIALLY DAMAGING WIND GUSTS AND PERHAPS AN
   ISOLATED TORNADO.

   ...SYNOPSIS...
   MODELS SUGGEST THAT A CLOSED MID-LEVEL LOW NOW FORMING WITHIN THE
   SOUTHERN BRANCH OF THE SPLIT POLAR WESTERLIES WILL ONLY SLOWLY
   MIGRATE INLAND ACROSS THE OREGON COAST AND CASCADES ON WEDNESDAY. 
   THIS MOVEMENT APPEARS LIKELY TO BE LARGELY IN RESPONSE TO THE
   PROGRESSION OF A SIGNIFICANT EMBEDDED PERTURBATION AROUND ITS
   SOUTHERN AND EASTERN PERIPHERY...AS UPPER RIDGING WITHIN THE MORE
   PROMINENT NORTHERN BRANCH AMPLIFIES ACROSS MUCH OF THE NORTHEASTERN
   PACIFIC INTO WESTERN NORTH AMERICA...AND THE CYCLONIC CIRCULATION
   BECOMES INCREASINGLY CUT-OFF FROM THE WESTERLIES.

   MEANWHILE...DOWNSTREAM...THE PROGRESSION OF A MID-LEVEL CLOSED LOW
   NOW FORMING OVER THE UPPER GREAT LAKES REGION WILL BE HINDERED BY
   BLOCKING OFF THE NORTH ATLANTIC COAST.  HOWEVER...A SERIES OF
   SIGNIFICANT IMPULSES PIVOTING AROUND ITS PERIPHERY MAY CONTRIBUTE TO
   SOME EASTWARD REDEVELOPMENT ACROSS SOUTHERN ONTARIO INTO
   SOUTHWESTERN QUEBEC BY THE END OF THE PERIOD.

   IT APPEARS THAT THIS LATTER FEATURE COULD SUPPORT WEAK SURFACE
   CYCLOGENESIS TO THE SOUTH OF THE PRIMARY CYCLONE...ALONG A FRONTAL
   ZONE ACROSS THE NORTHERN MID ATLANTIC COAST REGION THROUGH SOUTHERN
   NEW ENGLAND LATER TONIGHT THROUGH WEDNESDAY.  WHILE THE TRAILING
   COLD FRONT PROBABLY WILL CLEAR MUCH OF THE MID ATLANTIC COAST EARLY
   IN THE PERIOD...IT MAY NOT ADVANCE MUCH FARTHER SOUTH THAN SOUTH
   ATLANTIC AND GULF COASTAL AREAS BEFORE STALLING.

   WITH SEASONABLY HIGH MOISTURE CONTENT AIR GENERALLY CONFINED TO THE
   WARM SECTOR OF THE LOW...AND SOUTH OF THE COLD FRONT...THUNDERSTORM
   POTENTIAL ACROSS MOST AREAS EAST OF THE ROCKIES IS EXPECTED TO BE
   RELATIVELY LOW WEDNESDAY.  HOWEVER... MOISTURE RETURN FROM THE LOWER
   LATITUDE EASTERN PACIFIC WILL CONTINUE THROUGH MUCH OF THE EASTERN
   GREAT BASIN AND ROCKIES INTO THE NORTHERN INTERMOUNTAIN
   REGION...WHICH SHOULD SUPPORT CONSIDERABLE THUNDERSTORM ACTIVITY.

   ...NORTHERN INTERMOUNTAIN REGION...
   FORCING FOR UPWARD VERTICAL MOTION...COOL MID-LEVEL TEMPERATURES AND
   ENHANCED VERTICAL SHEAR ASSOCIATED WITH THE INLAND MIGRATING
   MID-LEVEL CLOSED LOW ARE EXPECTED TO CONTRIBUTE TO THE RISK FOR
   SEVERE STORM DEVELOPMENT WEDNESDAY AFTERNOON AND EVENING.  MIXED
   LAYER CAPE BY THE AFTERNOON HOURS IS GENERALLY EXPECTED ON THE ORDER
   OF 500-1000 J/KG...BUT COULD BE LOCALLY HIGHER...AND SHOULD BE
   SUFFICIENT FOR SUPERCELLS BENEATH 30-50 KT CYCLONIC 500 MB FLOW. 
   INITIATION SEEMS PROBABLE BY AROUND 21Z...PARTICULARLY ACROSS PARTS
   OF NORTHEASTERN OREGON/SOUTHEASTERN WASHINGTON... WITH ADDITIONAL
   DEVELOPMENT PROBABLE THROUGH THE REMAINDER OF THE AFTERNOON ACROSS
   THE MOUNTAINS OF CENTRAL IDAHO INTO PARTS OF THE SNAKE RIVER VALLEY.
   THE CONSOLIDATION OF STORMS INTO AN UPSCALE GROWING MESOSCALE
   CONVECTIVE SYSTEM DOES NOT APPEAR OUT OF THE QUESTION ACROSS PARTS
   OF NORTHERN/CENTRAL IDAHO INTO WESTERN MONTANA BEFORE CONVECTION
   WEAKENS WEDNESDAY NIGHT.

   ...SOUTHERN NEW ENGLAND...
   UNCERTAINTY REMAINS CONCERNING THE STRENGTH AND TRACK OF THE
   DEVELOPING SURFACE LOW...AND ASSOCIATED POTENTIAL FOR INLAND
   BOUNDARY LAYER DESTABILIZATION DURING THE DAY WEDNESDAY. 
   HOWEVER...GIVEN THE LIKELY SEASONABLY HIGH MOISTURE CONTENT WITHIN
   THE WARM SECTOR OF THE LOW...IT DOES NOT APPEAR OUT OF THE QUESTION
   THAT CONDITIONS MAY BECOME AT LEAST MARGINALLY SUFFICIENT FOR THE
   DEVELOPMENT OF AN ISOLATED SUPERCELL OR TWO WITH SOME RISK FOR
   DAMAGING WIND GUSTS OR A TORNADO.

   ..KERR.. 08/12/2014

   CLICK TO GET WUUS02 PTSDY2 PRODUCT

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z