A system which developed over the southern plains, fuelled by Pacific as well as Gulf moisture is now producing heavy snow across Illinois, Missouri and the Ohio Valley and will continue to snow further north and east through today.

Here’s the latest radar from weather.com showing the heaviest snows right now over Missouri, Illinois and Indiana but this swath becomes more organised and intense as today progresses. Note the heavy rains streaming north, as this bumps into the cold air, precip quickly changes to snow with a high change of thundersnow and intense snow rates.

As the low tracks ENE across the Ohio Valley, it’s drawing north warm, moist air and as it bumps up against the colder air being pulled south, the band of snow turns heavy with the potential for thundersnow and snow rates of 1-3 inches per hour, especially once the Atlantic’s moisture and warmth gets involved later Saturday.

Here’s the latest snow cover chart off the ECMWF through the next 48 hrs.

Notice the heavy accumulations expected by the ECMWF over the Northeast. The models picking up on some deepening and we could well see that widespread area of 12 inches over a large swath of the Northeast. While 3-6 inches is a safe bet from DC up to Boston, that heavier band could well go west or east of I-95. The heavy stuff arrives later today into Sunday morning over the Northeast.

Here’s a close look…

Here’s a look at the surface charts and notice the precip significantly increases over the Tri-State area as the low deepens and feedsback on the warm Atlantic moisture which if enough cold air is available, it could bring heavy bands of snow even to the Major Cities.

Note the plume of moisture rich air streaming north from the Gulf while a lobe of arctic air gets drawn southeast over the Lakes, this setup is perfect for thunderstorm and intense bands of snow right over the Major Cities.

By 36 hrs the system is hammering southern New England and likely producing the heaviest snow and snow bands while things should be gradually clearing to the south over DC, Philly, even NYC. Notice the lower thickness values pushing in.

Heaviest snows fall today across Chicago (3-5″) and particularly points south (8-10″) so tomorrow will be coldest with highs stuck in the mid-teens with a low tomorrow night likely approaching or dropping below 0 again. Heaviest snows in the Northeast fall tonight into tomorrow and while cold and likely right around freezing from DC to Boston, Monday is coldest with highs stuck in the mid to upper 20s again. With fresh arctic air over fresh snow, perfect for maximum heat loss by night and so expect 20s DC, 10s NYC, 0s Boston Monday night.

Here’s chilly 850 temps.

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It stays cold across the Northern Tier and Northeast through much of the upcoming week but a warming trend kicks in later in the week as another blast of potentially the coldest air yet, dives into the Northern Plains, this pumps an eastern ridge for a time, but any warming, make the most of it as that arctic surge will slide east with time. When? Probably right around Christmas.

Here’s the AccuWeather snow chart for the Midwest and Northeast.

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