Dec. 19 — Meteorologists expect the cold air to linger in the wake of the storm that brought up to a few feet of snow to the northeastern United States, but as episodes of melting and freezing will gradually reduce the snowpack, there is the potential for injury and accidents as well.
It may take crews a couple of days or more to clear off secondary roads and city streets following the storm that dumped from about an inch of snow along Interstate 95 in northern Virginia to 44 inches of powder on Newark Valley in the southern tier of New York state. Even though the snow will rapidly disappear in northern Virginia, it may be many days for the snow cover to melt where a few feet fell. The mountains of snow from cleanup operations could be around for many weeks.
Forecasters are warning motorists and pedestrians to exercise caution at intersections and in parking lots where massive piles of snow may block the view around the corner. Property owners should take some time after clearing their driveways and sidewalks to shovel out fire hydrants.
Cold air following the storm won’t likely help those working to clear the snow.
“The atmosphere is not likely to be in a hurry to warm up in the days following the storm. In fact, we expect temperatures to average below normal in most areas through at least the first part of next week,” AccuWeather senior meteorologist Brett Anderson said.
Highs typically range from the middle 20s F over northern New England to the upper 40s in southeastern Virginia.
“Through Saturday, high temperatures are likely to range from near 20 over northern New England to the lower 40s in northern Virginia, or about 5-10 degrees below average,” Anderson said.
“The reflective nature of deep fresh snow cover tends to reflect the sun’s rays back up into the atmosphere and prevents the air near the ground from warming up, but even the overall weather pattern still looks chilly for several days,” Anderson added.
When conditions are clear and calm at night, the temperatures can plummet, and cold air can collect near the ground, especially over the valleys where there is deep snow cover.
In the cities, especially the major metro areas along the I-95 corridor, the large urban heat island effect will allow some natural melting to take place during the daytime hours each day into next week.
However, sometimes the most dangerous part of a winter storm is a result of the natural melting that follows.
This melting will create runoff onto parking lots, sidewalks, city streets and secondary roads over the countryside. As the temperature plummets during the evening hours, the runoff is expected to freeze and that ice will linger into the morning commute the following day. This condition creates a thin sheen of clear ice that is sometimes called “black ice” and may appear to be wet rather than icy. Slip and falls and vehicle accidents could be a risk during this setup.
Icy patches can form on milder nights even when the air temperature is above freezing. This is due to the “freezer effect” of the large piles of snow that can help to chill the ground nearby. Areas that are shaded from the sun during the day are most prone, but this phenomenon can occur anywhere under the right conditions at night. The temperature right near the ground can be several degrees lower than at waist or eye level.
“The thaw and freeze cycles are likely to continue through next week in areas where there is a deep snow cover and/or massive piles of snow, even though temperatures may trend to and above average for a couple of days,” Anderson said.