A deep upper-level trough over the Great Lakes and anomalously strong surface low pressure system expected to swing from the Mid-Atlantic into the Northeast tonight are forecast to produce unsettled weather into the start of May from the Midwest to the East Coast.
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Heavy rain is likely tonight for much of the Northeast as the strong low pressure system ushers in a plentiful amount of atmospheric moisture from the Atlantic Ocean.
1 to 3 inches of rain over saturated ground could lead to scattered instances of flash, urban, and small stream flooding.
The greatest chances for flooding concerns overnight reside over parts of New Hampshire and southern Maine, where a Slight Risk (level 2/4) of Excessive Rainfall is in effect.
Heavy rain is also possible across eastern Pennsylvania, New Jersey, the Delmarva Peninsula, and parts of southern New York State into this evening.
As this system pushes into southeast Ontario, Canada on Monday, breezy, cool, and cloudy conditions are expected throughout the Northeast into Wednesday.
Additional showers are also possible, with the higher upslope elevations of the central and northern Appalachians experiencing at least a few inches of snow.
Speaking of snow, a significant spring snowfall event has begun across parts of the Upper Great Lakes and is expected to continue through Tuesday.
Cold northerly winds on the western side of the powerful low pressure system combined with a deep upper-level low supplying plenty of cold air aloft will support additional bursts of heavy-wet snow throughout the central/western U.P.
of Michigan and far northern Wisconsin.
Over 6 inches of snow has already accumulated through this morning, with a few more feet of snow possible by Tuesday.
Snow load and gusty winds could lead to broken tree limbs and power outages.
Winter Storm Warnings are in effect.
Other weather conditions associated with this powerful Eastern U.S.
spring storm include gusty winds across the Midwest and well below average temperatures throughout much of the eastern half of the Nation.
Wind gusts as high as 45 mph are possible this afternoon and again on Monday across the Upper Midwest from Minnesota to western Illinois.
Meanwhile, the core of the below average temperatures on Monday and Tuesday is forecast across the Great Lakes, Ohio Valley, and Interior Northeast.
With numerous clouds, showers, and breezy conditions in place, high temperatures will struggle to reach out of the 40s in this region (20+ degrees below the climatological average for the date).
For the western U.S., a cool and unsettled weather pattern is currently spreading into the West Coast as an upper-level low is forecast to slide into the region early this week.
This will lead to shower and high elevation snow chances, along with below average temperatures.
Further inland, gusty southerly winds and well above average temperatures are anticipated for much of the Intermountain West, with warm weather also spreading into the northern/central Rockies and northern High Plains.
Regions experiencing river flooding due to snow melt across the Great Basin can expect more significant snowmelt into this week.
Additionally, scattered shower and thunderstorm chances will overspread much of the Rockies by Tuesday as well. ■