Boxing Day event

 

Most Of the precipitation shown on the leading edge on radar isn't reaching the ground due to the air being so dry. It will take a while for the air to moisten up enough for precipitation to reach the ground.

I want to clarify a little bit on the forecast I issued the other day. Generally the forecast still looks pretty good especially considering I issued it a few days ago. But the environment the clipper is moving into is complex and very volatile. So the forecast won't be perfect. In situations like this they never are. 

We are under the influence of a true arctic air mass with very cold temperatures and a lot of dry air. Coming in from the south, we are going to see the flow direct warmer and moisturized air push northward. That will come into conflict with the arctic air mass trying to push south. 

Most areas should fall generally within the parameters I've set out. But, the snow shield has expanded a little further north. When forecasting in this type of environment It's always a headache due to the likely event of mesoscale snowbands setting up. When we have two air masses like we're gonna have overhead; the two will battle it out, leading to a increase in the temperature gradient along parts of that frontal boundary. This is due to the warm air running into the cold air and lifting up and over the colder air mass. As the air rises it leads to increased and heavier precipitation. The mesoscale environment and setup means we could see several of these bands set up in various areas.  The areas that see banding could see more than I had originally thought. The very nature of this means that other areas also could see less snow accumulation than I had anticipated. The place most likely to be impacted by these changes looks to be Central New York State and areas a little north of the Mohawk Valley, over through the New York State capital district into Western Massachusetts including the Berkshires; These areas could end up seeing 3-7 inches of snow accumulation, with  locally higher amounts possible by Saturday morning. 

The models are similar in their appearance and the way they're handling the storm.

GFS

HRRR

NAM

Images credit tropical tidbits

This Boxing Day event Is going to see a large variety of different precipitation types across the region. Areas like extreme southwest New York State into northwest Pennsylvania Down into western Pennsylvania along the Appalachian ridge into central Pennsylvania will have a better chance of seeing an impactful freezing rain event. Areas that see the freezing rain It will be considered as rain as far as official measurement. Where is areas that see sleet the sleet will be considered snow. So an inch of sleet would be officially measured as an inch of snow. Also anyone who sees sleet will see their forecasted snow accumulations lowered by the sleet mixing in. The reason for this has to do with water ratios and molecular density. When sleet is made it becomes ice pellets Where the water molecules are much closer together. Meaning they're more tightly packed than they would be in a snow flake. Having to keep water ration between the two the same, means when measuring what fell to the ground; we end up with less sleet accumulation than we do snow accumulation when dealing with the same amount of water in each.

We're going to see another storm event later Saturday into  Sunday into early Monday this too looks to be quite impactful. Then we're going to have another storm move through as we get close to New Year's.  We are not done with cold air intrusions yet as there is still plenty of cold air in the pattern We are going to see the cold air reload up in northwest Canada And end up coming back down into the Great Lakes and Northeast, As we move through January into February. As I anticipated I have seen comments that the winter cold is done, and we're gonna be dealing with above average temperatures moving forward. But winter is only less than a week old and we still have plenty of time for more cold air intrusions and storms to impact our region.