Some Feathery Frost
Posted February 5, 2010
Some of you who were with us for the coverage of our winter storm after-effects last Sunday morning may have heard me mention the potential for some especially picturesque frost formations on Monday morning due to a combination of some water vapor in the air (from evaporation of melted snow and sublimation of snow directly to vapor on Sunday afternoon) and very cold temperatures Monday morning. At the time, we expected lows to dip into the upper single digits to mid teens. When combined with enough moisture, this can lead to some unusual and fun to look at frost patterns, including some that look like partial snow flakes, plates, columns and star-like dendrites.
There may well have been some pockets around the area with that type of frost Monday morning, although probably not as many as there could have been. As it turned out, temperatures bottomed out a little warmer than forecast, with most of us falling into the mid teens to low 20s, although we did manage to drop as low as 10 at Roxboro, 13 at Roanoke Rapids and 16 at a couple of other locations, while RDU recorded a low of 18.
While not quite cold enough for the snow crystal patterns I had in mind to form on a widespread basis, it was a little colder than we often get with enough moisture on hand for frost, and at this combination of temperature and humidity there were at least some displays of intricate window frost patterns, still a good deal more photogenic than your typical fuzzy coating of frost that we often see with lows in the mid 20s to mid 30s.
One of our viewers shot a couple of nice photos of the Monday morning display in the Holly Springs area, and was mind enough to send them in. I've included them here as the first two images, and we extend our thanks to Ruffin Blackard for the nice shots! The third and fourth images are some I took on two different days of the mailbox in front of my house, one with a pretty common frost covering for these parts, and a second showing frost on a morning where we dropped into the low teens with enough moisture to form the six-sided "dendritic" crystals. You can read more about what goes into forming those, and see a couple more of the photos, by entering "moss fancy frost" into our search form...