Winter Storm Regis a Weekend Nor'easter as Spring Arrives; Snow from Rockies to Mid-Atlantic, New England (FORECAST)

March 18,2016

Winter Storm Regis has already brought locally heavy snow to parts of the Rockies. Its "second phase" will be a nor'easter bringing snow to parts of New England and the mid-Atlantic states just as spring officially arrives this weekend.
(MORE: Latest Impacts/News)

Phase I: Rockies/High Plains

Regis was named just after midnight Friday when winter storm warnings were issued for the Denver metro area, meeting The Weather Channel population requirement for named winter storms.
(MORE: How Winter Storms are Named)
A roughly west-to-east band of heavy snow has shifted south along the High Plains, currently stretching from the Palmer Divide south of Denver east into the High Plains.

Current Radar and Conditions

Some snowfall totals so far, as of Friday morning include:

• 10.5 inches just east of Boulder, Colorado
• 5.8 inches just east of Ft. Collins, Colorado
• 4.2 inches at Denver International Airport

Storm-prone Interstate 80 was once again shut down due to snow and wind from Rawlins to Laramie, Wyoming Thursday night into early Friday, but has since reopened.
(INTERACTIVE: Radar | Storm Reports)
Below are the forecast details for Regis.

• Timing: Snow continues in Wyoming, Colorado and west Kansas Friday, ending first in the High Plains Friday afternoon, but lingering in the foothills and Front Range corridor of Colorado and southeast Wyoming into Friday evening.
• How Much Snow: The heaviest additional snow amounts will be along the Palmer Divide between Denver and Colorado Springs, as well as the foothills west of Denver and Boulder. Lighter additional snowfall is expected in most other areas.

Additional Snowfall through Friday Evening: Rockies

Phase II: Nor'easter

If it wasn't for the near record-setting snowfall from Winter Storm Jonas, New York's Central Park would be on pace for its least snowy season in 14 years. Only 4.8 inches of snow has fallen outside of that late January snowstorm.
It only stands to reason, then, that a chance of snow moves into the East this weekend.
(MORE: The Science Behind the First Day of Spring)
As can sometimes happen in East Coast snow events, there remains a sizable degree of uncertainty this far out.
First, colder air will gradually work its way into the East by Saturday, a pattern change led by a gyre of low pressure is slowly spinning down over the Great Lakes.
One of the reasons for the uncertainty is a complicated upper-level pattern. Exactly how the interaction of (A) a digging shortwave trough from the Rockies, (B) a remnant circulation from the aforementioned Midwest gyre and (C) a sharp southward dip in the jet stream nosediving southeastward from Canada will help determine how this potential East Coast system evolves.

In response to all this, low pressure should develop and intensify somewhere near or off the East Coast Sunday and Monday.
The $64,000 question then is, "Where will the center of low pressure track?"

The Setup This Weekend Into Monday

A closer track to the East Coast would bring a better chance of heavy snow, or perhaps even a period of rain closer to the coast, from parts of Virginia to New England, including a sizable swath of the heavily-populated I-95 Boston to Washington corridor.
However, a track farther offshore might confine the heaviest snow closer to coastal New England, leaving lighter snow for most other Northeast locations, except the Appalachians.
Here is our general forecast thinking for Sunday into Monday:

• Best potential for at least 6 inches of snow: Eastern New England, from eastern Long Island to Downeast and northern Maine; central Appalachians (W.V., western Maryland panhandle)
• Light to moderate snow totals most likely, but can't completely rule out locally heavy snow: I-95 corridor from New York City metro to northern Virginia. 
• An inch or two at best most likely: Upstate, central, western New York, western Pennsylvania.

(FORECAST: Boston | New York | Philadelphia | Washington D.C. | Bangor, Maine)
Our latest forecast maps for Sunday and Monday are shown below.
If the snowier East Coast scenario would come to pass, this could pose travel headaches including flight delays out of some major Northeast hubs and a challenging Monday morning commute in parts of New England.
In the meantime, some light snow accumulations, generally under 1 inch, are possible from Friday into Saturday from parts of the central Plains to the Ohio Valley.
(MAPS: 10-Day Forecast Highs/Lows | Weekly Planner)
Fortunately, this system should move rather quickly, either out to sea or into Atlantic Canada by Monday night.

Sunday's Outlook

Monday's Outlook

Big Change in the East After a Warm Stretch

If you needed any more reminders of how changeable the weather can be this time of year, this is your exhibit A.

A man rollerblades near the Bethesda Terrace in Central Park, Manhattan, New York City, March 9,2016 as people take advantage of the warm weather in the city.
(TIMOTHY A. CLARY/AFP/Getty Images)

Consider what we've seen recently in the East:

• A record warm December-February in New England, and one of the warmest on record in much of the East. 
• A rash of severe thunderstorms as far north as Maine in late February.
• The warmest temperatures so early in the season on March 9 in the Northeast, including low 80s in Albany, New York.
• Through March 16, this has been the least snowy season-to-date in both Albany, New York (10.3 inches), and Binghamton, New York (22.3 inches).

Check back with us at weather.com for the latest on this potential storm and any likely forecast changes ahead.

MORE: Winter Storm Regis (PHOTOS)