WRAL WeatherCenter Blog

What whitened Wake Forest?

Posted January 28, 2013

On Sunday morning, we got a couple of reports of possible snow in the Wake Forest and north Raleigh areas, while there was nothing on radar and no indication from computer models that the atmosphere would support a typical snowfall scenario. Nonetheless, Sloane Heffernan drove in from the area and said it appeared there was snow on the ground and crystals in the air, and since that time we've received a couple of photos from the area (shown above) that were taken early Sunday, and the area was impressively whitened during the night and had a very wintry appearance in these shots.

For most of us on Sunday morning, there was a very low deck of shallow clouds and/or some fairly thick fog, with that fog mainly composed of tiny supercooled water droplets. Sometimes in a situation like that, "freezing fog" can occur, in which the tiny droplets freeze on contact with surfaces and create a fairly smooth white icy coating. The appearance in the photos above, however, looks much more like ice crystals settled on the ground, trees, deck railings and so on, and implies that either a slightly deeper cloud capable of producing a light period of snow (yet still shallow enough that weather radar beams passed over top of it undetected), or, perhaps more likely, that the combination of humidity and temperature within the fog in the area led to an "ice fog," with the fog itself composed of tiny ice crystals that accumulated into the coating we see here.

In order to form the classic dendritic, six-sided complex snow crystals that fall in our more typical snows (sometimes as individual small crystals, often as a collection of crystals clumped together into a snowflake), temperatures usually need to be around 14 degrees F or colder, but reports from our viewing area were not that cold yesterday. Instead, they were in the low to mid 20s, a temperature range where the correct amount of water vapor and the right kind of suspended particles of dust, minerals and salt or smoke (called ice nuclei) would more likely lead to crystals shaped like six-sided columns and needles, and possibly some six-sided plate-like crystals. If these formed within the fog and shallow low clouds over a sufficient period, they could have produced the nice-looking effects seen here.

I mentioned to Sloane yesterday that she may have seen ice fog or "diamond dust," which is a similar phenomenon in which tiny suspended ice crystals form in the absence of other precipitation. However, after seeing these photos, I think the "diamond dust" description was probably not the most appropriate, since it classically refers to situations where there are some tiny crystals in the air, but skies are otherwise fair and visibility is not very restricted, and it would be unlikely under those conditions that enough crystals would settle out to give the appearance we see here.

If anyone reading this was in that area early yesterday morning and saw this all occur in process, let me know if it had the appearance of a typical snowfall, or if it was more in the "ice fog" category with crystals floating around and gently settling - also if you noticed the shape of any crystals that fell, it would be interesting to know if they matched the description I gave above for the temperature range that was in place. These kinds of slight mysteries are always interesting to look into!

8 Comments

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  • Mike Moss Jan 30, 11:49 a.m.

    Just wanted to thank you all for the comments. Based on what a couple of you said and some reports I got Sunday morning, the ice fog with settling crystals theory seems to have held for at least some of the affected locations. I did also get a couple of photos from the area that showed hoar frost growth rather than a layer of settled crystals, so there were possibly localized areas with both or either phenomena. Thanks again! Mike

  • frankensteiner Jan 30, 9:59 a.m.

    I saw it in Durham in the woodcroft area. It looked like a very light falling snow.

  • thestella2 Jan 30, 9:05 a.m.

    I saw it in Granville County early Sunday morning around 6ish

  • packfan27 Jan 29, 10:25 a.m.

    I noticed what appeared to be an abnormally heavy frost on Sunday morning in Wake Forest. I did not see it occur, I think. When I woke up around 830, I noticed it and went outside. There were a very very few 'flakes' falling at that time, but I believe they were just falling off of tree limbs and not from the atmosphere.

    This 'frost' collected on trees, grass and remaining ice from the Friday event. It did appear as a light snow at a glance. But if you looked closely, it seemed to have 'grown' from the grass blades/tree limbs and not blanketed them.

    It did seem isolated to around Wake Forest. I did a short hike by Falls Lake off of Creedmoor Rd later in the morning and did not notice any abnormally heavy frost there. Indeed a strange event.

  • bobrobapex Jan 28, 12:19 p.m.

    A friend of mine called this "hoar frost" and I saw it Sunday morning at The Factory in Wake Forest.

    http://www.weatheronline.co.uk/reports/wxfacts/Hoar-Frost.htm

  • WF Dad Jan 28, 9:12 a.m.

    My daughter and I observed this in two other locations yesterday - along Durant Rd. at 7:30am, and along New Falls of Neuse Rd. around 11:30am. It was very pretty to see, but did leave us wondering just what had happened!

  • Red Bird Jan 28, 8:59 a.m.

    No matter what the phenomenon yesterday, the result was so beautiful and almost "other worldly"! What a special gift as my husband and I were driving home from our early church service! It seemed to center around the Wake Forest Middle School area.

  • solly93 Jan 28, 8:16 a.m.

    At first it looked like a very light snowfall, but upon closer inspection it seemed as if it was a "mist" of tiny frozen particles. It sounds most like ice fog as you describe it. I was surprised at how much white stuff actually settled to the ground.