This seems to be the winter that never ends, even though spring doesn't technically begin until next Thursday.
At this point in time on Friday morning, just about every model run is depicting a storm developing in the southern Plains and pushing east into the Mid-Atlantic by Sunday. Today and Saturday should be fantastic, so enjoy the mild temperatures around 60 degrees and plenty of sunshine. By Sunday, changes will be likely.
Chance of 4"+ of snow accumulating in the next 72 hours, from the WPC: pic.twitter.com/PmT1rjM366— Paul Anderson (@paulythegun) March 14, 2014
The tweet above shows what the Weather Prediction Center's chances of 4" or more of snow falling in the next 72 hours in the D.C. area. This is sitting between 50-80% for parts of the region. While, 4" is possible, predicting exact snowfall amounts at this current time is very difficult.
What kind of set up?
Conditions are definitely favorable for wintry precipitation across the D.C. area. At least PARTS of the D.C. area, as a Miller Type B pattern cyclogenesis sets up with the primary area of low pressure moving into the Appalachians and a new area of low pressure developing along the North Carolina coastline by early Monday morning.
The problem is there is the potential for a warm layer aloft in areas, particularly south and east of D.C. Some guidance even places the warm layer farther north into the D.C. Metro, mixing in sleet and possibly freezing rain to the region. The majority of the modeling depicts snow beginning after sunset Sunday and continuing through Monday. Here are some of the latest soundings from @AdamCaskey on Twitter.
High pressure located over the Midwest and Northeast will help push cooler air into the region starting Sunday and continuing through the storm. The problem is, there is no real arctic air source. This isn't like the last winter scenario where D.C. dropped 40 degrees and rain changed to snow with no problem.
- Our in-house RPM model depicting snow for the majority of the area by Sunday night
Precipitation is expected to start as rain late in the day before changing to snow overnight. Snow is expected to be the predominant precipitation type Sunday night into the day Monday, with high temperatures Monday only in the 30s.
Questions to be answered
This does lead to some thoughts about how warm it will be Sunday. If temperatures reach the mid 40s Sunday, road temperatures will be closer to the upper 40s or 50s, thus harder for snow to accumulate. There is also a considerable amount of salt and sand down on the roads, and if it doesn't rain heavily on Sunday prior to the changeover to snow, this should also help limit accumulations on the roads.
Another factor is temperatures themselves. If lows only fall into the low 30s Sunday night, roads may not be that bad. We would have to get some pretty high snow rates for it to overcome melting on the roadways.
Finally, there's also the thought of how far north the precipitation shield will be and how far north the rain-snow line will be. This will have major implications on where the heaviest snow will be. Adam Caskey displayed this graphic above via Twitter of the different 500mb Vorticity Plots. It basically is showing where the main troughing and energy is located between the models. For instance, the GFS is much farther south than the NAM, which is allowing for more colder air and thus more snow. Still a lot of time to go with this system.
As of now, the best chance for snow appears to be west of D.C. over the higher elevations in the mountains, such as the Blue Ridge and Appalachians. I additionally think there is a better chance for snow northwest of D.C. than the D.C. Metro.
The lower chances for snow exist in the southern portions of the viewing area such as Stafford and Fredericksburg east to Southern Maryland. Regardless, delays and cancellations will be possible Monday morning, so be prepared.
We'll surely have more updates this weekend. Until then, enjoy the warmer weather while it lasts!