Blizzard warning issued for Hawaii with at least 12 inches of snow forecast

A blizzard warning has been issued for Hawaii, with at least 12 inches of snow forecast this weekend.

The warning is in effect for the Big Island summits from 6 p.m. Friday through 6 a.m. Sunday local time.

In addition to blizzard conditions, wind gusts over 100 mph are also expected, according to the alert issued by National Weather Service Honolulu.

"Travel could be very difficult to impossible," the alert said. "Blowing snow will significantly reduce visibility at times, with periods of zero visibility."

"The strong winds will likely cause significant drifting of snow," it added.

A blizzard warning for tropical Hawaii may come as a surprise, but snow is not uncommon; the summits of the Big Island's Mauna Kea and Mauna Loa volcanoes reach nearly 14,000 feet in elevation.

A flood watch has been also issued for all Hawaiian islands through Monday afternoon, as a prolonged period of heavy rainfall is anticipated over the weekend.

"Flash flooding caused by excessive rainfall continues to be possible," the alert said.

"Landslides may also occur in areas with steep terrain," it warned.

The "very active weather" in Hawaii is due to what's known as the kona low, a seasonal cyclone that pulls moisture from the south, according to Weather Channel meteorologist Ari Sarsalari.

"The coverage of the precipitation is going to get a little more intense into the weekend," Sarsalari said in a video update Friday. "This is going to be a lot of rain, so be prepared for some flooding issues."

The slow-moving kona low is expected to bring the "greatest potential for heavy rain" over Maui and the Big Island, NWS Honolulu said.

Elsewhere in the United States, a storm system is expected to sweep from the northern Rockies to northern Great Lakes, bringing a blast of snow and gusty winds later this weekend. Winter storm watches and warnings have been issued from Montana to northern Wisconsin, where more than a half a foot of snow is possible this weekend.

Strong, gusty winds will also impact parts of the northern Rockies later Saturday into Saturday night. High wind alerts are in effect from Great Falls, Montana, to Cheyenne, Wyoming.

ABC News' Dan Peck and Max Golembo contributed to this report.