This storm has the potential to be the second largest snowstorm of the 2018/2019 winter. Then again that is not saying much since most cities biggest snowfall happened back in November and dropped a widespread 4-8” across the region. Since then winter has been relatively quiet with a general lack of any snowfall across the region. This has the potential to be a significant storm along I-95 and points northwest. A mix of snow, ice, sleet and rain will spread from south to north starting early morning on Tuesday.
A low pressure across the great lakes will be transferring its energy to a developing coastal low that will throw precipitation into the northeast. As the low develops and move north it will flood the mid levels with warm Pacific air from the strong Pacific jet that has largely contributed to a lackluster winter. However, there is a strong high pressure to the north that will funnel cold air southward and create sleet and ice. Models tend to underdue mid-level warming and overdue lower level warming. If this trend stays true there will be a lot of sleet and freezing rain that will have to be dealt with.
Models have continually pointed to a stronger cold press and stronger mid level warming which will in turn create a lot of sleet and ice. The NAM has a large 850-mb frontogenesis band which I believe will pass after mid level warming has already occurred. It may be strong enough to turn some areas that are seeing sleet back to snow however for the majority of the area, it will be very heavy sleet and it goes through.
The extended HRRR is interesting as it warms the mid levels much slower allowing for more snow and less sleet. Notice the pinks over northern New Jersey, Long Island, eastern Pennsylvania and southern Connecticut. This is freezing rain and I believe these areas will see extended periods of it. Snow below sleet below freezing rain will create an absolute mess o the roadways for tomorrow's commute.
I believe all regions across the area will experience a period of at least a few hours of snow before everyone inevitably changes over to sleet, freezing rain and eventually plain rain. Below is my snowfall accumulations map, I am still going slightly aggressive and it remains largely unchanged from yesterday. The further north and west the higher chance for larger impacts in terms of frozen precipitation.
I also included my dominant precipitation type map which also remains unchanged. I believe that everyone will start out as snow. The further north the more snow and the slower the changeover. Southern New Jersey will stay mostly rain after a quick shoot of snow. Philadelphia up north of coastal areas will have a burst of heavy snow before prolonged periods of sleet and ice and eventually rain. Areas away from the coast will predominantly stay snow sleet and ice with also a touch of rain in some areas.