An expansive winter storm will spread snow, ice, and even rain in some northern locations of the East, South and Midwest through the Presidents' Day holiday, and Tuesday. Winter storm watches have been issued by the National Weather Service from parts of northern Georgia into the Appalachians and mid-Atlantic states, ahead of the storm.

More than 38 million people over a broad area from the Plains into the Midwest and East Coast were under a winter storm warning, watch or advisory as of Saturday night, as confidence increases that a large swath of snow and ice will affect parts of the country in the coming days.

Winter Weather Alerts

(Watches, warnings and advisories, as issued by the National Weather Service.)

The first ingredient in this wintry setup is the Arctic air being ushered in by strong high pressure. This is bringing the coldest temperatures of the winter so far to the Northeast this weekend.

(FORECAST:)

Southerly wind flow on the western flank of that high-pressure system in combination with upper-level energy and surface low pressure to its west will help pull moisture north into the cold air, resulting in snow and ice in the Midwest and South first.

Then a low-pressure system will track up the East Coast, bringing wintry weather to parts of the mid-Atlantic and Northeast, but also changing precipitation to rain for some, as well.

Latest Radar

(Blue indicates snow, while pink is a wintry mix and rain is shown in green.)

Let's first look atour latest forecast timeline. Keep in mind, however, that the forecast you see on weather.com or on your mobile app will likely change the next day or so, so be sure to check back often for the latest updates.

Sunday-Sunday Night

Areas to watch:A broad area of light to moderate snow will fall from the Upper Midwest into the Lower Ohio Valley. Some sleet or freezing rain is possible in southern Missouri, northern Arkansas, western Kentucky and west Tennessee. That area of snow then spreads into the rest of the Ohio Valley, Appalachians and Piedmont of the Carolinas Sunday night. Some freezing rain is possible on the southern end of that precipitation shield Sunday night in the southern Appalachians and parts of the Carolinas.Potential impacts:Slick roads (particularly bridges/overpasses) are possible due to sleet/ice accumulations in Missouri/Arkansas. Ice accumulations look light enough to avoid widespread power outage, tree damage impacts. Typical slippery roads in light/moderate snow areas.FORECAST: | |

Sunday's Forecast

Sunday Night's Forecast

Monday

Areas to watch: Snow spreads into the mid-Atlantic states, Lower Hudson Valley and southern New England. Moisture may overrun subfreezing air near the surface, leading to the potential of freezing rain and sleet for a period of time from parts of southern New Jersey and southeast Pennsylvania to Virginia to most of North Carolina. How far south and how long the sufficient cold remains in place will dictate the extent of this icing potential.Potential impacts: Accumulating snow possible in the Ohio Valley, Appalachians and mid-Atlantic will lead to slippery roads. The possibility of icing in the above-mentioned areascould at least cause slick travel conditions and, if subfreezing surface temperatures persist longer, could lead to some sporadic downed tree limbs and power outages.FORECAST: | |

Monday's Forecast

Monday Night-Tuesday

The greatest chance for significant snowfall accumulations will be well west and northwest of the I-95 corridor in the Northeast, from the Appalachians to western Pennsylvania, western, central and Upstate New York.Locations from Boston to Washington, D.C. may see a mixture of precipitation types before transitioning to plain rain.Some ice may linger in the Piedmont of Virginia and the Carolinas before possibly changing to rain, and may also occur, for a time into northern New Jersey and parts of western/northern New England.With low pressure expected to take a track near the coast or just inland, warmer air will penetrate much of the I-95 corridor, preventing this storm from being a major snow maker along the coastal plain.FORECAST: | |

Monday Night's Forecast

Tuesday's Forecast

How Much Snow, Ice?

For the Northeast and Midwest, this will be a modest snow event, by mid-February standards.

Except for parts of the Dakotas Saturday, most areas of the Midwest should pick up less than 6 inches of total snowfall.

In the South, the heaviest snow accumulation may occur in a swath from Kentucky to Tennessee and the southern Appalachians, where some totals could approach or locally top 6 inches.

In the Northeast, the heaviest accumulations will likely occur in a swath from the Appalachians to central New York.

Lighter snow accumulations, before the change over to rain, will occur along the I-95 corridor from Maine to Virginia. Some parts of the I-95 corridor could then pick up over an inch of rain Tuesday.

Additional Snowfall Tuesday

(A look at the additional snowfall expected Tuesday.)

In general, ice accumulations in southern Missouri, northern Arkansas, western Kentucky and west Tennessee, and also in a swath from north Georgia to parts of southern New England should be enough to make roads slick for a time, but less than the threshold for producing widespread power outages and downed trees.

Except for a few, isolated valley locations where cold air may get trapped longer, such as the Shenandoah Valley, most of these areas are expected to see temperatures rise near or slightly above freezing, also mitigating the effects of any freezing rain or sleet that would fall.

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(Ken Libbrecht/SnowCrystals.com)