Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 162157
SWOMCD
SPC MCD 162157
CAZ000-170000-

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

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

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

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




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