With temperatures at 43F and light rain falling, it’s another wet and dreary January day across the northeast. New Jersey is just upstream of the base of a weak negatively tilted trough. A vorticity maxima at 500mb is clearly present to our SW, and vorticity advection is allowing for enhanced uplift in the Maryland/Virginia area. West of this shortwave there exists mostly zonal flow across the entire southern United States. Even the trough associated with a strong vorticity maxima based in Minnesota is very flat.
At the jet level, we see a very broad, but strong feature overlaying a zonally oriented flow. A jet streak exists over Colorado at the base of the deamplified trough to the north. A secondary jet streak to the east of the northern trough is also present. The left exit region of the southern jet and the right entrance region of the northern jet come together over parts of Iowa and Wisconsin, indicating additional uplift support from the upper levels of the atmosphere here. However, with dewpoints of 10F and precipitable water <0.2, the atmosphere is bone dry and no precipitation is expected over this area.
A potent cold front is present at the surface, enhanced by the upper level features previously mentioned. A cyclone north of Minnesota can be seen forcing cold air southward across the Great Plains while creating a warm sector just north of the Great Lakes.
The main center of low pressure at the surface is northwest of Minnesota while a secondary low pressure has formed just south of Lake Erie. A tight pressure gradient between the cold, high pressure in the mountain west and the areas of low pressure moving to the east is allowing for very strong winds across the northern great plains into the midwest.
To understand the next few days, a gif of 500mb vorticity is most relevant. This is the 12Z NAM initialized on 1/3/17 showing the next 84 hours. The shortwave producing today’s rain passes through, which is followed by a great amount of energy from the deamplified trough that was north of Minnesota. The trough digs slightly into the Great Lakes region, looping as far south as the Mason Dixon Line before being propelled north again. Ridging in the western Atlantic prevents this trough from digging deep into the eastern United States and promoting cyclogenesis. Additionally, moisture is very limited with this air. Associated with this energy is an Arctic front which will drop temperatures on Thursday 1/4/17. As this front moves through, precipitable water across the northeast will drop below .2 in.
850 mb temperatures over the course of the next few days tell the whole temperature story. Cold air moves south with a more or less zonal orientation, meaning the line of coldest temperatures is more or less west to east. With a tight temperature gradient along the east coast, the chance of cyclogenesis increases from 0% to at least 15%. Clearly within the NAM’s scope of forecast, the temperature gradient remains along the east coast for some time, with the possibility of a shortwave moving in and introducing energy to promote development. In the last frame of the NAM 500mb map, you can see an area of energy moving through the south. This is where the hype for a southern states blizzard comes from. As of now, it is mostly hype as to the specifics of who gets what. However, the set up of this baroclinic zone will promote the development of a strong cyclone with access to not just cold air, but some cold air damming in southern Appalachia.
A summary of temperatures over the next few days at Rutgers is easily captured with the model’s raw output, as there is a consensus over the next few days of a passing cold front with cooler temperatures. The cold front moves through between Wednesday 1PM and 7PM, which prevents Thursday’s high from getting above 35F.
Short term, 1/3/17-1/4/17
Rain will become lighter by 4PM on 1/3/17 as an area of low pressure develops just off the NJ coast, rearranging precipitation around the NW and E of the center of low pressure. Scattered showers are possible again after 10PM on and off through 4AM. The 12Z NAM is depicting the heaviest rainfall moving through around 3-4PM as the low pressure that forms restructures its precipitation shield. The next timestep shows rain quickly moving out.
The moisture sticks around for Wednesday, keeping temperatures above 40, possibly reaching 50 as our warm sector receives additional heat and moisture from the south. Our warmest conditions will likely be just before the front moves in. Wednesday appears mostly dry in terms of precipitation as subsidence occurs from upper level mass convergence.
It is still far too early to mention specifics about any coastal storms that develop on the eastern United States. The GFS is including a rapidly developing storm that impacts eastern New England but there is no run to run consistency in this solution. As the energy associated with the potentially blockbuster storms moves onto the west coast of the United States, model consensus will likely become more apparent. At the very least, we will be able to come to an agreement about what is NOT possible.