WEATHER

NJTV News Weather: Bitter Cold to Give Way to Wintry Precipitation

20150131_SnowMapBy Meteorologist John Cifelli

At 6 p.m. Saturday evening as I write, there is nary a reading above 30 degrees to be found across New Jersey. In fact, you have to go all the way to Virginia to find a temperature above freezing! As winds continue to relax overnight, we will chase the single digits even in southern and coastal New Jersey. It will be a frigid night. Tomorrow we will wake to increasing clouds, and temperatures gradually on the rise on southwest winds ahead of the storm approaching from the Ohio Valley. It is moisture laden, with both Pacific and Gulf of Mexico moisture streaming toward New Jersey. Some parts of the forecast are are going to get a lot of snow. Others will be dealing with a fair amount of rain. A stripe of freezing rain may be a high impact for a belted area in central New Jersey as well.

Yesterday I mentioned that the track was still unclear for this storm. Today there is a much better idea of the path the storm will take, and it has crept northward in the last 24 hours. As a result, rain and freezing rain have been more generously introduced into the forecast. The area of snow is likewise being truncated, but those who get snow are going to get a lot of it. One of the mechanisms that enhances lift and heavy banding of precipitation is called frontogenesis. Literally, the birth of a front, which is enhanced by a tightening of the temperature gradient. Tomorrow’s storm will be drawing temperatures in the 30s and 40s, both at the surface and aloft, into southern and central New Jersey. When that air pinches against the cold dome of Arctic air in place, it’s like throwing gasoline on a fire. Except it’s a fire that produces snow. Stay with me here.

Light precipitation will start early evening. South of the Atlantic City Expressway, you might not see more than a few flakes. There could be a coating at best here but by the time you wake on Monday morning, it’s been washed away. Philadelphia and points east will get a couple of inches of snow and sleet before the changeover to rain here. For the Route 1, 202, 22 and 78 corridors, things become a bit more tricky. The cold air at the surface is forecast to hold tight everywhere north of the surface low path, which should be through Pennsylvania and across southern New Jersey. This makes sense, with upper level confluence encouraging the surface high in southeast Canada to hold its position and strength, reinforcing the cold over the northern half of the state and New York City. Aloft, things are a different story, as warm air will surge northward, forced by the upper level lows that will travel along the Pennsylvania/New York border before hitting the Atlantic well to our north.

So sleet or freezing rain? That is now the question. If the cold air is very shallow and subzero just about the surface, the answer will be freezing rain. If the warm air aloft makes less of a surge and the layer below freezing is deeper in the column over your head, rain will freeze on its way down and fall as sleet. Sleet is easier to drive in than snow and is the least dangerous of the winter weather precipitation varieties, while freezing rain destroys trees, wrecks power lines and causes the worst travel conditions. With brutally cold air coming behind this system, we really don’t want to see the forecast for freezing rain materialize. Let’s hope that I’m wrong, but while 78 and 22 may escape with more sleet and snow and less ice, I am worried that the Route 1 and 202 corridors could see enough icing to cause some serious issues. Anyone in the ice band could see up to a quarter inch accrual. Especially given the fact that the surfaces — your driveway, roads, railings — are all very, very cold from this stretch of below average temperatures, icing may steal the show here.

North of the ice area, expect less sleet and more snow, so the accumulations go up — way up! I think the northern tier of New Jersey jackpots with over a foot of snow.

Things will be winding down around midday, west to east. The damage at that point will have been done, as the Route 1 corridor and points north can expect snow overnight transitioning to a wintry mix in central New Jersey, with snow continuing through the morning north. Monday night, temperatures will approach zero in places. Nasty cold. Let’s hope the power is on statewide.