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Mesoscale Discussion 1720
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   MESOSCALE DISCUSSION 1720
   NWS STORM PREDICTION CENTER NORMAN OK
   0457 PM CDT TUE SEP 16 2014

   AREAS AFFECTED...A SMALL PART OF SOUTHERN CALIFORNIA

   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

   VALID 162157Z - 170000Z

   PROBABILITY OF WATCH ISSUANCE...5 PERCENT

   SUMMARY...THE RISK FOR ISOLATED STRONG THUNDERSTORMS WILL PERSIST
   INTO THE LATE AFTERNOON HOURS...AND AN ISOLATED SEVERE STORM CANNOT
   BE ENTIRELY RULED OUT. HOWEVER...THE ISSUANCE OF A WW IS NOT NEEDED.

   DISCUSSION...LATEST MOSAIC RADAR IMAGERY INDICATES A ROBUST
   CONVECTIVE CLUSTER AFFECTING WRN SECTIONS OF RIVERSIDE COUNTY.
   ADDITIONAL CONVECTION CONTINUES TO BLOSSOM OVER THE COASTAL RANGES
   NWD INTO SWRN SAN BERNARDINO AND ERN LOS ANGELES COUNTIES. WITH A
   LACK OF STRONGER DEEP-LAYER FORCING FOR ASCENT PER WATER VAPOR
   LOOPS...OROGRAPHIC CIRCULATIONS WILL BE THE PRIMARY MEANS FOR
   INCIPIENT CONVECTIVE FORMATION DURING THE NEXT FEW HOURS...ALONG
   WITH ASCENT ASSOCIATED WITH THE ELSINORE CONVERGENCE ZONE. IN
   FACT...RELATED CONVERGENCE COULD BE ENHANCING THE ONGOING CONVECTION
   AT PRESENT IN RIVERSIDE COUNTY.

   CONVECTION COULD GRADUALLY SPREAD TOWARD THE URBAN
   INTERFACE...ESPECIALLY TOWARD ORANGE COUNTY AND VICINITY. THE NKX
   VWP SAMPLES MODEST /10-20 KT/ ELYS IN THE LOWER 4 KM AGL. THIS WILL
   CONTRIBUTE TO STEERING COLD POOLS IN THE GENERAL DIRECTION OF THE
   COAST...WITH THE POTENTIAL FOR UPDRAFT REGENERATION ON THEIR LEADING
   EDGES IN THE MODERATELY UNSTABLE AIR FOUND E OF A SEA BREEZE
   BOUNDARY ANALYZED JUST INLAND FROM THE COAST. WITH MLCAPE AROUND
   1000-1500 J/KG...AND 35-40 KT OF HIGH-LEVEL FLOW CONTRIBUTING TO
   CONVECTIVE VENTILATION...A FEW ROBUST UPDRAFTS/DOWNDRAFTS MAY OCCUR.
   AND...WITH 30F-40F SFC TEMPERATURE-DEWPOINT SPREADS AND DCAPE IN
   EXCESS OF 1400 J/KG...A FEW STRONG MICROBURSTS COULD PRODUCE A DMGG
   WIND GUST OR TWO.

   ..COHEN/HART.. 09/16/2014


   ATTN...WFO...SGX...LOX...

   LAT...LON   33191721 33511761 34161810 34311715 33461659 33071694
               33191721 

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Page last modified: September 17, 2014
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