Well it has almost been a month since our last event. As per usual this storm will be a fun one to forecast as it includes a switchover to snow. The timing of this switchover and its corresponding snow rates will determine which areas get snow, how much will fall, and if schools will be impacted.
Event Summary
HRRR Model simulation Midnight to 11 AM Tuesday
The storm center will move northeastward across southern Maryland and will bring rain to our region this evening into the overnight hours. As the cold air aloft moves in, the rain will switchover to a heavy snow in regions north and west (Southern PA, and northern portions of Frederick and Carroll Counties). The snow will then spread southward. Snow will be seen across the whole of Maryland and Delaware barring areas of southern Maryland and the eastern shore.
The areas where the snow begins earlier in the morning will be the most likely to see stickage and travel impacts. Although, for areas closer to Baltimore and/or to the ocean, heavy snow rates that are expected are more than enough to support accumulation on untreated roads or less traveled streets.
Overall, accumulations on grassy surfaces look to be a blanket 1-3 inches across the general region. I suspect areas that are north of Baltimore and between the PA line and 95 will see the most accumulation as this is a colder area and will be closer to the center of the storm which should provide a longer period of accumulating snow. Maximum snow accumulations will be 4 inches in these colder areas.
Range of Snow Totals
Snow totals range from around an inch to over 7 inches between the models due to varying timing of switchover and then the snow intensity. Some models are producing snow rates of 2 inches an hour which seems unrealistic. Some models have a later switchover and a shorter and weaker period of snow. All of these variables are a product of storm strength, speed of cold air moving in aloft, and the depth of this cold air in the atmosphere.
My job is to synthesize this information and give a realistic and comprehensive understanding of the storm which outlies what is expected and how the results could stray as I have outlined above. Now, below is my snowfall forecast.
My Forecast
Rain will switchover to snow before or around sunrise in areas north and west (promoting stickage) in Carroll and Frederick counties. Snow will move south and eastward and the switchover should reach Baltimore just after sunrise (8 AM, limiting stickage). Snow will come down at fast rates and can accumulate fast. These heavy snow rates could really skew totals higher, an hour or two difference in period of snow could mean and inch or two difference in accumulation. Snow should exit late morning before noon.
I would advise schools in Frederick, Howard, Carroll, Baltimore and Harford counties to place a two hour delay this evening with reevaluation in the morning to monitor whether snow is sticking and if the rest of the morning will be affected.
This Snowfall Map below is for snow accumulation on grassy surfaces, only areas in the counties mentioned above could see stickage on roads, but it is dependent on start time and snow intensity.
A few things to note
Warm temperatures leading up to the event - This will keep roads warm through the event and make it tougher for snow to stick on roads
Increasing sun angle - As we approach spring the sun is getting higher in the sky and even with cloudy skies, it can heat the roads during the day; limiting stickage.
If snow begins before sunrise in some areas, travel will be affected there
Temperatures throughout the event will be right around freezing - Making it tough for stickage
Updates to come as needed
Thank you! Great forecast :)