Archives

Share
RSS feed of this blog

Cold air damming now but beautiful later this week

As I pointed out in the last couple of posts the obnoxious cold air damming phenomenon is in place during the early part of this Thanksgiving week.  A strong high pressure system over eastern Canada – with its clockwise flow – coupled with a developing low pressure – with its counterclockwise flow – off the southeastern U.S. coastline have combined to turn our surface winds easterly, ushering in a very thin surface layer of cool moist air off the Atlantic Ocean.  That combination of weather factors “dams” the surface layer of air up against the Appalachians and keeps the Piedmont and coastal plain socked in under a low overcast which almost always lasts longer than the forecast models predict it will.

Thus our Monday morning gloominess will continue thru tomorrow (Tuesday) with the added factor of some overnight fogginess as the surface air cools down tonight and reaches the dew point, the temperature at which the rich water vapor in the moist air condenses into cloud droplets.  We won’t like see rain from these clouds although a light drizzle may occur in some widely scattered spots.

All this unpleasantness should end by Wednesday afternoon as both the high and low pressure systems move further to the east and we break out into bright sunshine and warmer temperatures for the trek toward our Thanksgiving celebrations.  The high temperature Wednesday will climb into the upper 50′s (F) while  Thanksgiving Day festivities will be conducted under bright blue skies amidst a high that should reach the 60 degree mark in the ‘Burg.

And in the spirit of Thanksgiving one thing we should be thankful for weather-wise in the ‘Burg is our lack of drought conditions.  Take a look at this graphic that depicts the drought situation in the “lower 48″ states:

I’ve circled Virginia to emphasize how well we are situated for moisture compared to spots further west which are overlain with the dark yellows and browns that indicate dry conditions.  (The green shading along the coastal regions undoubtedly reflects the precipitation totals from Sandy, whose rainbands did not reach the mountainous western parts of the Old Dominion.)  These conditions are relative to normal precipitation amounts for each area.  Having plenty of water available for our burgeoning population here in the East is a good thing - as long as it doesn’t mean floods!! – so having above normal moisture is something to be thankful for.

Post tags: |

Permalink: http://news.fredericksburg.com/weather/2012/11/19/cold-air-damming-now-but-beautiful-later-this-week/