NY NJ PA Weather Forecasts

Cold Front, Potential Coastal, And The Developing Deep Freeze

We are heading towards the finish line for November (wow, this month went fast), and all signs continue to point to some interesting potential for the forecast area through the Thanksgiving week.  

First lets deal with the end of the weekend, which will be dry yet very cold on Sunday.  Temperatures will continue to average 8 to 10 degrees below normal as Canadian high pressure slides through the forecast area.  

I know a lot of people are keeping an eye on the Monday/Tuesday time frame.  The GFS is starting to show what the ECMWF has been screaming for the past few model runs, which is coastal development along the Mid Atlantic coast. Let me be clear that I do not think that any coastal development with the pattern constituted and forecasted to set up in the fashion we are seeing would support a heavy precipitation event for the forecast area.  New England, possibly, but not the northern Mid Atlantic.  

The main issue is the type of blocking that sets up is that the cyclogenesis is usually too far north, which means that the forecast area will be under the influence of this coastal low during the development stages, where the precipitation shield is not matured.  As a result, the precipitation over the forecast area is usually unorganized and scattered.  

The other issue for those snow lovers is that we are depending on cold air to rush in at the same time as MAA from the Atlantic is developing at 700 and 850 MB, which is never a comfortable position to be in.  

Given all the data I am looking at, here is how I see Monday and Tuesday playing out.  Monday will start out much warmer than the past few days as southwesterly winds develop ahead of the cold front over the Ohio Valley.  A strong disturbance will be driving from the North Plains through the Ohio Valley on Monday as the cold front races towards the coast.  Monday evening is where the GFS and ECMWF camps split.  

The ECMWF develops the primary low pressure system along the coast, while the GFS camp keeps the primary  including the upper level low to the west over the Great Lakes.  I think the ECMWF is on to the right solution overall in terms of transitioning the primary low towards the coast.  The coastal plain after all will be the prime are for divergence and diffluence aloft along with a strong thermal gradient at the lower and mid levels of the atmosphere.  However, I think the ECMWF is a bit too fast and I expect this transition to unfold over New England coastal waters, not the Mid Atlantic coastal waters.  

As a result, the cold front will move through on Monday with scattered showers and falling temperatures in the evening.  The coastal low will develop on Monday night and Tuesday morning with the forecast area falling under increasing winds from the north and northwest along with additional rain and snow showers.  Eventually by Tuesday morning, most locations will have temperatures which support snow showers.  The brunt of this storm moves into New England from that point on.

High pressure will slowly build into the forecast area on Wednesday with partly cloudy skies, a few lingering snow showers, and likely windy conditions as the pressure gradient will mature and strengthen between the low and the high.  Temperatures will fall again with the potential for highs to struggle in the 30’s once again.