February 14 9:45 PM Update: The one good thing about this storm, is that it arrives on a holiday… With schools closed. With that out of the equation, we still need to consider everybody else that has to drive or go to work. Most of our area is under a Winter Storm Watch or Winter Weather Advisory Monday. As I was working with my clients this evening I realize there are two main questions: 1) when will the snow start? 2) When will the changeover? Toss in the total snow and ice, and we can round this out below. If you remember what I wrote yesterday and this morning, the location of the High Pressure around New England at 7 AM Monday will help determine the track of the storm. I will revisit that point when plotted.
Onset: Snow Starting:
Here is the HRRR model timeline. Notice A) One band of snow between 1 AM and 4 AM. B) The main snow will be in southern Maryland and Virginia all morning and slowly push north. The morning will show more snow for the south and it will pile up, so roads will be trouble there. My concern for the first batch is virga (showing up on radar but sublimating before reaching the ground). But that will be gone before daybreak. That batch arrives in Washington and Annapolis later in the morning and Baltimore by lunchtime.
Notes:
- It will snow all day.
- Travel will be worse all around mid day through afternoon.
- Changeover to Sleet/Freezing rain from south to north during the evening.
- If you have snow at sunrise (east of the mountains) there is a good chance for change over by evening.
Cold Air Damming
My main concern is that this weekend arctic blast has chilled and frozen some of the Bay. There will be delayed warming at the surface, but the strong wind aloft will warm cloud level. So extended sleet and freezing rain will last into Tuesday morning.
Frozen Ground:
Air temperature is measured about 5 to 6 Ft above the ground. But the ground itself may take longer to thaw. So a temperature of 33°F might still have ice on the ground. Thus, Tuesday morning ice set up is far from easy to pin down.
My Final Call For Snowfall
Click here to compare to latest models and NWS Forecast snow maps
My thinking: More snow will fall in southern Maryland and Virginia in the morning. When the push of warmer air moves north, there may be a fast mix over to ice farther north. So the longer duration of snow Monday morning will help these totals. Especially for southern Maryland and parts of the Delmarva.
Many models show less snow north of Baltimore in York and Lancaster Counties due to delayed snow into the afternoon and then change over to ice at night. But the mountains to the west will see uplift snow build them into the 3″ or more range.
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