(Portland, OR)  --  Officials are working to confirm whether a tornado touched down in Multnomah and Clark counties during a storm that prompted two tornado warnings and a flood advisory yesterday.  The National Weather Service says they have confirmed that there were rotating funnel clouds in the area but that they won't know for sure whether a tornado touched down until sometime after daybreak today.  The agency issued tornado warnings in Burlington and in the Orchards and Walnut Grove areas of Clark County yesterday evening.  Both advisories expired shortly after they were issued.