Question of the Week

Today in Richmond, we are experiencing a messy and somewhat hazardous mix of snow, sleet and freezing rain. 

Do you know what atmospheric conditions cause each kind of frozen precipitation?



Answer:  Winter precipitation types generally depend on the vertical temperature profile of the atmosphere.

• Snow falls when the temperature of the entire depth of the atmosphere from the cloud to the ground is below freezing (32 F or 0 C).
• Sleet falls when there is a fairly shallow layer of warmer air (above freezing) between the cloud and the ground but the temperature at the ground is below freezing.  Snow falls from the cloud, then partially melts in the warmer layer and then refreezes in the colder layer near the surface, forming pellets of ice.
• Freezing rain falls when there is a deep layer of warmer air (above freezing) but the temperature is below freezing at the ground.  Snow falls from the cloud, melts completely in the warm layer and then refreezes either just before hitting the ground or on contact with the cold surface.

Question of the Week

It's snowing!  Snow showers are also predicted for Thursday and a winter storm might hit us this weekend.  Remember last December? 

Now for the Question of the Week:
What is the percent chance of a white Christmas in Richmond (in any given year)?

Answer:  In Richmond, there is a less than 10% chance that measurable snow will fall on Christmas Day.  There's about a 13% chance that at least a trace of snow will be on the ground and about a 7% chance that at least 1" will be on the ground.

Several inches of snow are predicted for today (Thursday, December 16), and a coastal storm this weekend has a 50-50 chance of bringing us more snow.  Will we see snow on the ground for Christmas?  We might...

Tis the Season… for Nor’easters?

What will this winter be like? If the current weather pattern continues, the East Coast will certainly be stormy. Friday night through Saturday (December 18-19), Virginia experienced yet another intense Nor’easter (see blog of November 12). This one dumped huge amounts of snow over the central and western parts of the state.
Whether Virginia gets rain or snow from a winter Nor’easter depends largely on the track of the storm. A more westerly inland track will pull in warmer ocean air and Virginia will usually get rain. If the center of the storm stays just off the coast, cold air is often pulled in behind the storm and Virginia can get snow, sometimes lots of it. Nor’easters can intensify to hurricane strength and bring extremely high winds, coastal flooding, beach erosion, and heavy rain or snow to the mid-Atlantic and Northeast states. In the satellite picture above, note the hurricane-like eye in the center of this intense storm.
In addition to the heavy snow and gusty winds, this storm also included thundersnow. Thundersnow occurs only rarely and is basically a winter thunderstorm with falling snow instead of the usual rain. The lightning is nearly blinding due to its reflection off the white snowflakes, and the sound of the thunder is acoustically suppressed by the snowfall. Normally, thunder can be heard many kilometers away from a thunderstorm, but the thunder from thundersnow can only be heard 2 or 3 kilometers away. We had thundersnow at my house just after midnight on the 19th with at least two very bright lightning strikes and accompanying thunder.
How much snow did you get from this storm? I had 1 foot at my house in Midlothian, about 15 miles west of Richmond.