Superbowl Sunday Snow

 

Good afternoon everyone! Today is going to be a very nice day, with highs in the 50s to the2 lower-mid 60s. But as a cold front moves through, and a storm moves behind it, we will be tracking the threat for some snow. The NWS has most of the region(except for the southern part of the region, and western MD) in a winter weather advisory for 1-2" of snow, with local amounts up to 4" of snow. The onset of the storm will start out as rain/mix, but it will turn to snow quickly. Everyone will be snow by the time sunrise happens on Sunday. This will be a light event, and after noon you should be fine to travel. However there might be a refreeze after 4 PM, which could cause some slick spots. Most accumulations will be on grassy surfaces, however there could be accumulation on paved surfaces too. Minor travel issues and slushy spots are not out of the question. High resolution models are starting to pick up on an FGEN band that may occur at the start of the event, that would bring moderate-heavy snow rates. It would dynamically cool the atmosphere and combat warm surface temperatures. I'll look at 2 high-resolution models: NAM NEST & HRRR.

HRRR:

The HRRR shows precip onset as rain, quickly turning over to snow. At 1-3 AM you can see a moderate-heavy snow band in parts of the region. By 3 PM, snow is done for almost all of the region, but I skipped some timeframes at the end to show a backend snow band that the HRRR gives. 

 

This is the total accumulated snow that the HRRR gives. Remember, not all of it will stick, so actual totals will be a bit lower than this. Gives a widespread 1-3", but I'm skeptical of the widespread 3"+ in parts of north central MD.

This HRRR sounding at 2 AM Sunday shows something interesting. In the sounding, there is intense lift in the DGZ, which allows for moisture and moderate-heavy precipitation rates. This is an FGEN band because you can see the wind barb directions rapidly changing. If you are a snow lover you want to see this happen for more accumulation. This is important because this will dynamically cool the atmosphere to be cold enough to support snow, and would help to quickly overtake the warm surface temps.

NAM NEST:

The NAM shows the inital onset as rain before quickly changing over to heavy snow. It also shows the heavy FGEN band between 1-4 AM, and is actually a bit more robust with the onset of precip compared to the HRRR. It also has the backend snow band, but not as robust as the HRRR.

 

The snow accumulations are bit more robust compared to the HRRR, but around the same. 

The NAM NEST also shows a nice FGEN band setting up around 1-4 AM, with more lift in the DGZ than the HRRR, creating heavy snow rates. You can see the FGEN banding on the map below setting up, and on the sounding too. I explained what this means while talking about the HRRR sounding. 

Snow Forecast:

More detailed view of the map and interactive map:

 

The bullseye of this storm will be western central VA, where a FGEN band will drop 3-6" of snow. The FGEN band looks to be better supported there with longer duration leading to more totals. I expect a general 1-3" for most of the region, with C-1" for western MD and C-1" for the southern part of our region. Most accumulations will be in the grass, but there could be some accumulations on paved surfaces too, especially where the FGEN band sets up. Some travel issues and slushy spots on paved surfaces is not out of the question.