Snow Threat This Weekend? Split Jet Issues Suppressed or Phased?
Looking ahead to the rest of this week, if you were waiting for winter cold you will have that thanks to a cold high to the northwest north of the Great Lakes and a strengthening storm to the east in the Canadian Maritimes. The weather pattern has changed this week to some degree as the northern part of the jet stream has strengthened enough and we have cold Canadian air coming into the Northeast & Middle Atlantic States beginning Wednesday and carrying us into early next week.
Also an important change in the pattern is in the Pacific where the unrelenting jet stream from west to east across the Pacific has relaxed somewhat. This was a key change in the pattern and we look ahead to see how long it lasts. Meanwhile as we move along this week as energy comes into the west the southern portion of the jet stream will be active and a system will move across the Southern States. All this while the northern part of the jet in this "split" flow sends along its own short wave troughs southeastward. This will be key to whether we see snow here Saturday night and Sunday or will the snow be suppressed southward again like it was back in the December Middle Atlantic storm.
The European and GFS models today boil down to a matter of timing in an active northern jet with a southern stream shortwave that lies in between. The European timing is completely different in the East though the models are more in lock step in the west. Were the European correct we would be looking at a flat wave that passes off the North Carolina coast and heads east northeast and good bye. Perhaps some snow for the Middle Atlantic for Virginia and North Carolina and that would be pretty much it.
The GFS on the other hand times it all out differently in the north and while the short waves don't phase they would produce a significant snowfall further north into Southeastern NY & Southern New England southward. All of this is coming on what looks like a terrific surface set up with a big cold high in Quebec and cold air wedged southward into the MIddle Atlantic states.
Before snow weenies salivate here we have issues here with regards to the split north and southern jet that we need to resolve. So much for the long range. Let us look at what is going on for late this afternoon and evening.
The regional radar has a stick of what looks like impressive precipitation moving east but the air is so bone dry that a lot of this isn't even reaching the ground. The yellow bands on the radar are actually sleet as warm air aloft is pushing northeastward. This narrow band is in view of the regional and local radars right now. Dew points are in the teens and single digits. Look for this band to narrow further as it moves through New Jersey to Southern New England between 4pm and 8pm.
LOCAL RADAR NEW YORK CITY
LOCAL RADAR PHILADELPHIA
A second band follows later tonight between 1am and 8am which is what the Winter Weather Advisories are posted for. This is going to create some slick spots tonight in the areas to the north and west of the coast. I don't see too much change in the outlook for tonight into Tuesday morning. Temperatures tonight will hold for awhile in the upper 20s and lower 30s and then slowly rise later tonight into Tuesday morning. Much of the area should be above freezing for the Tuesday morning commute. Certainly along the coast this should be the case though some cold air could still be trapped inland.
Much of Tuesday will be cloudy and milder with highs in the 40s with a few more rain showers around tomorrow evening before the cold air begins to move in for later this week and this weekend.