Thursday, February 3, 2011

A Look Ahead To Next Week's Storm

The computer data has been very consistent with a storm system approaching our area next Thursday (Feb 10th). However, the data is still inconsistent with the track of the low. Here are three different forecasts at 7 AM Thursday (ECMWF, CMC, GFS). The thick white line is a very crude forecast of the rain/snow line (rain is south of the line, snow is north). You can spot the low, which is indicated by a closed circle. The ECMWF low is right off the North Carolina coast, which would be more conducive to snow, where the CMC is farther north and west, which would bring more rain.

At 7 PM Thursday, all forecasts pull this low up the coast. ECMWF is a little farther out to sea, otherwise, the forecasts are in pretty good agreement. I think this is the first time this winter that the models actually show a similar scenario on a 7 day forecast!

Now, before you go out and buy a sled and snow shovel, you should realize that this track could easily shift farther west. In fact, the pattern does not look conducive for a major East Coast snow storm. The ridge, or Greenland block, is nonexistent. The blue/purple blob on the map below actually shows the opposite - a trough over Greenland.

Over the next couple days, we will probably see small shifts in the timing of this system. However, we could see some large shifts in its track, which would have a major impact on our forecast. This is something we will continue to watch. You can expect more updates in the coming days!

End of Week Rain Potential & Winter Weather Preview For Next Week

A storm system weaker than the one that just exited the U.S. will move through the Southeast through Saturday, bringing Virginia a good chance for rain beginning late Friday night into Saturday. The upper level vorticity for this system is currently over the desert Southwest, as shown here:

This upper support is also pulling moisture northward from the Gulf into the southern U.S. today, creating scattered light snow and rain showers. This moisture will spread toward the Mid-Atlantic Friday, which we will notice in the form of increasing cloud-cover from the south.
I do not expect rain to move into southern Virginia until after dark Friday.
Here's a Saturday time-line of the rain for you:

As you can see, we may get some breaks in the rain during the day Saturday, so don't expect a total washout. However, we could pick up anywhere from a quarter to a half inch of rain in the area from this system.

The rest of the weekend should be dry. There has been indication in the past couple of days of our weather pattern shifting back colder next week, much in the form we've experienced most of this Winter. There is the potential for two snow events next week. The first would be a quick, light snow on Tuesday as a result of a fast-moving clipper system. The second event is highly uncertain right now, but looks like it could affect Virginia sometime between Wednesday and Friday. That storm would be a coastal low pressure system developing in the Southeast, and then hugging the coastline up to the Mid-Atlantic. As we are well aware from prior storms this Winter (and last Winter, for that matter), that low's track will significantly impact our winter weather potential in the Commonwealth. The timing of this system will likely shift in the coming days, as will our expected impacts. But we are monitoring the data and looking for that pattern shift that would set us up for another coastal winter storm. We'll provide updates here on the blog! --Carrie

Spring Preview!

Yesterday was a rare treat for us this Winter with a high temperature at Richmond International Airport of 68 degrees. It was also on the heels of a temperature roller coaster since last weekend, where we've seen high temperatures range from the upper 30s to the upper 60s:

How rare was yesterday's warm-up? Well it was one of only three days since the meteorological start of Winter (December, January and February are considered to be the Winter weather months) with a high temperature of 60 degrees or warmer. Jan 1, 2011 had a high temperature of 61 degrees, and December 1, 2010 was 67 degrees. In fact, you have to go back to just before Thanksgiving to have a warmer day than yesterday!

But after a strong cold front swept through the Commonwealth last night, we experienced an abrupt end to the sweet taste of Spring as we now return to seasonable temperatures for the rest of the week. Check out the temperatures this morning across the eastern half of the U.S. (as of 8 a.m. Eastern) behind this storm system:

The purple to light pink colors in the nation's Heartland indicate temperatures this morning for them in the single digits to below zero (where the core of the Arctic high pressure is located). Here is a closer view of the low temperatures in Oklahoma, one of the hardest hit states by the snowstorm and the Arctic air:

The highest snowfall totals in Oklahoma were in the northeast corner, where 20" of snow accumulated in Miami, for example. Notice how the most of the coldest low temperatures in the state occurred there? That is the "ideal overnight cooling" result of clear skies, ample snowpack, light winds, and dry air.

I'll have an update on our next two storm systems in my next blog entry...stay tuned!