Thursday, March 14, 2013

Windy and Colder...or Warmer

Colder air began pouring into the Fairbanks area Wednesday afternoon. The 4am Thursday surface analysis shows big high pressure extending from the Beaufort Sea southeast through the Yukon and western Northwest Territories, and broad low pressure in the Gulf of Alaska. Northeast winds gusted to  41 mph at the Fairbanks area during the late afternoon and early evening Wednesday.
Courtesy of Environment Canada
The winds diminished mid-evening but never went calm overnight. This prohibited any inversion from forming, as seen in the sounding plotted on the left. The wind speeds above the ground, plotted on the right side of the lower chart, are not excessive. Rather, with enough sunshine now to completely break the valley based inversion, once the winds started up Wednesday afternoon the winds were strong enough (enough momentum transport) to keep an inversion from developing, even under completely clear skies.

The result was that temperatures on the valley floor were considerably higher than the last couple of nights even as hills were much cooler. At Fairbanks International, the low temperature Thursday morning was 9 below, which was 13 degrees warmer than Wednesday. At Keystone Ridge, the low Thursday morning of  11 below was 17 degrees colder than the morning before. 

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