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Mesoscale Discussion 20
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   MESOSCALE DISCUSSION 0020
   NWS STORM PREDICTION CENTER NORMAN OK
   1127 AM CST SAT JAN 11 2014

   AREAS AFFECTED...WA...OR

   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

   VALID 111727Z - 111930Z

   PROBABILITY OF WATCH ISSUANCE...20 PERCENT

   SUMMARY...DEEP OCCLUDED LOW PRESSURE SYSTEM WILL MOVE ACROSS NRN
   VANCOUVER ISLAND LATER TODAY. STRONG PRESSURE GRADIENT WITH THIS
   SYSTEM WAS ALREADY CONTRIBUTING TO 35-45KT GUSTS ALONG THE PAC NW
   COAST. A FEW TSTMS WILL MOVE ACROSS THE COASTAL AREAS/OLYMPIC
   PENINSULA WITH THE POSSIBILITY OF LOCALLY HIGHER WIND GUSTS AND
   PERHAPS SMALL HAIL. WEAK INSTABILITY SHOULD LIMIT MORE WIDESPREAD
   SEVERE WEATHER POTENTIAL...ESPECIALLY WITH INLAND EXTENT.

   DISCUSSION...STRONG DECREASE IN STATIC STABILITY WAS UNDERWAY OFF
   THE PAC NW COAST AS COLD CORE MID/UPPER LOW MOVES EAST. WITH -30C
   AIR AT MID-LEVELS EXPECTED TO SPREAD INLAND OVER THE NEXT FEW
   HOURS...WEAK DESTABILIZATION IS EXPECTED IN MARGINALLY MOIST
   POST-FRONTAL AIRMASS WHERE SFC DEWPOINTS WERE IN THE LOW TO MID 40S.
   FORCING FOR DEEP-LAYER ASCENT WILL BE MAXIMIZED IN LEFT EXIT REGION
   OF 90KT MID-LEVEL JET AND SHOULD SPUR LOW-TOPPED CELLULAR
   CONVECTION. WITH 50-60KT WSW FLOW JUST ABOVE 1KM...SHEAR IN THE
   STORM UPDRAFT LAYER SHOULD CONTRIBUTE TO SUPERCELL POTENTIAL AND
   BETTER-ORGANIZED/LONGER-LIVED STORM UPDRAFTS. IN FACT...WEAK
   ROTATION AND LINE/LEWP STRUCTURES HAVE ALREADY BEEN OBSERVED IN TSTM
   CELLS NOW TRACKING TOWARD THE OLYMPIC PENINSULA. EXPECT AN
   INCREASING PROBABILITY OF STRONG/SEVERE STORMS WITH ISOLD SVR WIND
   AND POSSIBLY SMALL HAIL. GREATEST WIND POTENTIAL WILL LIKELY EXIST
   ALONG AND JUST INLAND FROM THE COAST AS ANY SFC-BASED INSTABILITY
   DECREASES MARKEDLY WITH INLAND EXTENT. A WATCH IS NOT ANTICIPATED.

   ..CARBIN/THOMPSON.. 01/11/2014


   ATTN...WFO...MFR...SEW...PQR...

   LAT...LON   48162369 46992279 45622268 43872363 43622432 44822408
               46762415 47912464 48402472 48162369 

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Page last modified: January 11, 2014
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