The map shows the distribution of smoke from wildfires in the United States and Canada at 12:18 MDT, July 28, 2013
More details from NOAA:
“DESCRIPTIVE TEXT NARRATIVE FOR SMOKE/DUST OBSERVED IN SATELLITE IMAGERY THROUGH 1730Z July 28, 2013
-A broad area of light remnant smoke stretches over much of central and northern Canada stemming from several active wildfires in Northwest Territories, Saskatchewan, and Manitoba. Light density smoke is seen from Saskatchewan east over the northern portion of Hudson Bay and then it wraps down over Newfoundland, while the moderate to dense smoke is concentrated mainly over Nunavut and the immediate surrounding provinces/waters.
-Smoke that originated from Canadian wildfires has dropped south into the central US and wraps east over the Ohio River Valley.
-Wildfires in the Pacific Northwest states of Oregon, Washington, Idaho, and western Montana are collectively producing a light density smoke mass that is moving east northeast and covers the said regions plus southern Alberta, Saskatchewan, Manitoba, and also the Dakotas and Minnesota.”