It was virtually a year ago this week that brisk and raw conditions arrived in Deep South Texas, just in time for the Thanksgiving Day weekend (which began on November 22nd, 2007). On that day, morning drizzle gave way to a steely afternoon overcast, and temperatures leveled in the upper 40s to lower 50s. The change was a sharp contrast to the prior day, when afternoon highs were in the 80s on November 21st, plummeting more than 30 degrees between that afternoon and Thanksgiving Day!
Well, don’t look now, but here comes a similar situation. After a balmy, sunny day with temperatures in the upper 70s and lower 80s on Thursday, November 20th, 2008, Friday the 21st looks rather nippy, with a stiff north wind, a steely gray overcast, and intermittent light rain. While temperatures should be a little higher than on Thansgiving Day, 2007, the contrast will be similar, as daytime highs will likely hold somewhere in the 50s for most areas.
The culprits are similar this time, as well: Strong high pressure carrying modified Canadian air will plunge rapidly southward into Deep South Texas and northern Mexico after midnight. At the same time, south to southeast flow of warmer, moist air will continue a few thousand feet above the earth's surface, leading to a thick layer of clouds and some light precipitation. However, unlike the events of 2007, when the entire holiday weekend was unseasonably raw, conditions should gradually improve over the weekend, as winds should return to the southeast by Sunday the 23rd, bringing temperatures back well into the 70s.