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:

Tuesday/Wednesday Update & Timeline

Precip will not start for another two days, so we can still see some shifts in the forecast. Generally speaking, this storm has been more "well-behaved" than previous storms. The computer data has been very consistent, so I haven't changed much from yesterday. Regardless, I encourage you to keep a close eye to the forecast tomorrow and Tuesday for any adjustments. Below you will find a timeline of what to expect with this storm.

1PM to 7PM Tuesday
Most of Tuesday looks cloudy and dry, though an isolated shower could sneak into Southern VA during this time.


7PM Tuesday to 1AM Wednesday
Precip will move into the area from the south at this time. It could briefly start as a wintry mix, especially along and west of I-95. As you can see below, temps will be above freezing in central VA, so I'm not expecting major problems on the roads.


1AM to 7AM Wednesday
Scattered rain showers likely across Central VA with a wintry mix still possible in Northern and Western VA. Accumulations will start in far Southwest VA.



7AM to 1PM
Periods of rain still likely in Central VA. Accumulations start building in Northern and Western VA.


1PM to 7PM Wednesday
Rain will briefly change over to wet snow in Central VA. With temps in the mid 30s, most snow will accumulate on grassy surfaces or anything detached from the ground (if at all). Accumulating snows will taper in Western and Northern VA.



Here is a map of vorticity, or spin, in the atmosphere for Wednesday afternoon. The red blob indicates a very potent upper-level storm system. These types of storms are notorious for creating a quick burst of snow, especially north of the vort max (red blob). The track of this vort max, along with surface temperatures, will be the keys to this forecast.



This is an early look at the accumulation potential. If anything will change with this forecast, it will be this map below. Be sure to check back tomorrow and Tuesday to get the very latest updates!

Update On Tuesday/Wednesday Storm

As always, I will start this discussion by saying that this is an early view of the upcoming storm. Things will change from now until Tuesday!

It's looking like things are slowing down with this upcoming system. We probably won't see precip in our area until Tuesday evening. It could initially start as a brief wintry mix, especially for areas west of I-95. Then we will see periods of rain through Tuesday night and into Wednesday. A few wet snow flakes could mix in with the rain as the storm system exits. For now, it appears that the best chances for any accumulations will stay well west of I-95 and into the Blue Ridge.

I'm only trusting one computer with this forecast - the ECMWF (European). It hasn't flip-flopped as much as the GFS, in addition, the operational forecast is closer to the ensemble mean, unlike the CMC.

I've posted some maps below. The first three are ECMWF precip, isobars (lines of constant pressure), and surface temps. Notice how the low (indicated by the isobar circles) tracks over SE VA and into the Atlantic. Also notice how surface temps stay in the upper 30s during most of the event.

This will be key to the forecast. From what I've learned from previous storms like this one, when the boundary layer (low levels of the atmosphere) is saturated, temps need to near or below 35 to get snow in central VA.

I've posted maps from the ECMWF ensemble for all you weather geeks (like myself) so that you can see how it stacks up with the operational forecast.