Monday, January 24, 2011

Rain to Snow Looks Likely for the Metro

The storm system that will move into the area this week will be mostly rain (by duration), but will end as snow. I expect to see rain arriving after dark Tuesday night. Here's how I think things will look at 11 PM Tuesday (It's likely the rain will arrive a little earlier):

I expect to see all rain in central VA during the day Wednesday. We'll see a transition from rain to snow occur across the area close to sunset. Here's how things should look around 5 PM:

By 9 PM Wednesday, the metro should be seeing a wet snow that could be heavy at times. This snow will be due to the upper-level low that will be very intense. It wouldn't surprise me to hear a rumble of thunder or two as it is snowing, especially in areas to our east. The snow will be falling into surface temps that are still a few degrees above freezing, so although I think we could see a couple of inches of accumulation, it will occur on grassy surfaces, rooftops, etc. Roads might still be slick for the Thursday AM commute as the roads will be wet and temps will likely fall below freezing by sunrise. Here's a look at the way things should look at 9 PM Wed, followed by the temps at 7 AM Thursday:

Update on Approaching Storm: Monday 6:30 AM

A weak upper-level impulse will pass over the Commonwealth today, producing more clouds from mid-day through the afternoon. There may be a few flurries as a result, which I've shown here in this snapshot of late this afternoon:

There is light snow falling in the mountains of southwest Virginia early this Monday morning, so I do think it's feasible to get some of those flurries surviving into central Virginia later. However, those chances are slim, and any flurries that do fall would only briefly stick on the grass or other elevated objects. This would not be disruptive for travel today.

So now our attention turns to the developing low pressure system in the southern Mississippi Valley region that will impact the Commonwealth late Tuesday night through pre-dawn Thursday as the low tracks through the eastern Carolinas and Virginia. I've taken snapshots of the precipitation type for you during this time-frame, shown below. The green is rain, the pink is wet snow mixing with rain, and the blue/white is snow.

Because of the mixing and "wet" potential of this snowfall, it's difficult to nail down expected snowfall accumulations amidst the rain, but our working map still looks like a legitimate estimate for now: