Typhoon Lan is growing more powerful in the very warm waters of the tropical Pacific. It has more than enough energy to draw from over the next 48 hours, and will in all likelihood reach Category 4 strength Friday or Saturday.

The storm is tracking north, and although forecasts are calling for a slight turn to the right, coastal Japan — including Tokyo — will probably experience this storm’s effects, possibly even a direct landfall, on Sunday and Monday.

Lan is looking more formidable on satellite Friday, with a large area of rain bands and a clear eye. The environment around this typhoon is particularly favorable for strengthening. Warm water and calm upper-level winds will allow the storm’s maximum winds to reach nearly 140 mph Saturday.

Typhoon Lan is not going to strike the Philippines, but the storm is so large that its outer rain bands are lashing the country. This rain will “continue to trigger moderate to heavy rain in Bicol, Mimaropa, and the Visayas,” according to Philippines news site Rappler. “Residents in these areas should remain on alert for flash floods and landslides.”

In Japan, typhoon winds will reach the southern prefectures Saturday and continue to lash the country as it tracks north through the weekend.

Gale-force winds, along with stronger gusts, will affect Okinawa first this weekend. Rain will be torrential and the surf will be high, but direct landfall is not expected in Okinawa.

On Sunday or Monday, the storm’s center will have reached the Japan mainland. Although Typhoon Lan is expected to weaken by that time, its wind field will be enormous. Thousands of power outages are possible along with heavy rain, flash flooding and mudslides.

Landfall is possible near or south of Tokyo on Monday. Given the typhoon’s large wind area, storm surge could be damaging north of where the center comes ashore. Fortunately, Typhoon Lan will be moving very fast at that point, so direct impacts will be short-lived.

It’s been a relatively quiet typhoon season in the Pacific — just half the activity of a normal year — according to the Capital Weather Gang’s Phil Klotzbach.