Saturday, March 26, 2011

Weather Update - Saturday Afternoon

This is my latest forecast for the area. Again, there are no major changes. One thing to note - a lot of the snow will melt in the afternoon, so these numbers can be deceiving. Also, most of the accumulation will remain on grassy surfaces and other things detached from the ground. Temperatures will drop below freezing Monday night, though ground temperatures will remain well above freezing. Most of the major roads will remain wet, while untreated bridges and overpasses could become icy or dangerous.

Midnight to 4 AM
Rain with a few ice pellets will overspread central VA. It will be snowing in northwest VA.

4 AM to 10 AM
This will be the peak of the storm. Central VA will see cold rain and wet snow with a few ice pellets mixed in. It will be all snow for the northern half of the state.

10 AM to 2 PM
Precip will slowly taper - mix in central VA, rain farther south.

Here are several things to consider before this storm hits tonight and early tomorrow:

1) Duration of event

This storm system will race past the area, which will shrink the window of opportunity to see an accumulating snow. In fact, the best chances for Richmond to see an accumulating snow will be during the peak of the storm from 5 AM to 9 AM.

2) Intensity of precip

Most of the precip will be light to moderate, though we could see an occasional burst of rain or snow. This will also impact our accumulations.

3) Surface temperatures

Temperatures will hover around the freezing point in central VA during the peak of the storm (upper 20s in northern VA and mid 30s southern VA). Remember, the magic number is typically 35 for the rain/snow line. Most of the precip will be gone by early afternoon, so we could see temps rise to near 40, which will melt a lot of the snow.

4) Ground temperatures

Ground temps will remain well above freezing for the entire event. This means that most accumulations will stay on things detached from the ground: grassy surfaces, cars, rooftops. Ground temps will stay well above freezing Sunday night, so most roads should remain wet. However, bridges and overpasses could quickly become icy/dangerous.

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