Now that the powerful winter storm has moved on to the Canadian Maritimes, the dome of Arctic air that fueled its wrath has dropped into the Heartland. Centered over eastern Kansas this morning, it has brought sub-zero temperatures to the Midwest and a freeze that extends to South Texas.
Beneath this high pressure dome, cold air is sinking, clouds cannot form and heat radiates into the upper atmosphere; in addition, the recent heavy snowfall refrigerates the surface air, counteracting the weak effects of a low February sun.
This sequence is common with winter storm systems. Precipitation, in the form of snow, sleet or freezing rain, occurs along the outer edge of the dome, where an atmospheric low is sweeping warm, humid air above the invading cold front. As the dome drops southward and eastward, the front pushes to the east and the storm spins its way along the front toward the northeast. The air along the edge of the dome is cold enough to produce snow and ice but generally much milder than the frigid air at its center. Once the storm moves off to the northeast, skies clear and temperatures drop; while the snowy landscape is illuminated by bright sunshine and the night sky is ablaze with stars, a deep chill grips the region.
Our next chance for snow will arrive as the Arctic dome moves off to the east and milder air flows in from the west and south; should a disturbance develop along the back edge of the dome, these air masses will mix and freezing rain or light snow will recoat the deep snow. Based on current forecasts, melting will be minimal over the next week and the prospects of an early spring seem to diminish with each passing day.
