Grasshopper’s Weekly Japan Forecast – January 2 – A Prolonged, Snowy W-NW Flow, Followed By a Warm, Wet Low

January 2nd, 2020

7-day ECMWF model forecast. Source:


Mountainwatch | The Grasshopper

A Prolonged, Snowy W-NW Flow, Followed By A Warm, Wet low

It’s a new year and a new decade; along with it comes a nice new load of Japow. W-NW winds will continue blowing over Japan into Sunday, with consistent snowfalls dropping up to 35-55cm+ over central Honshu and 10-25cm over northern Honshu and Hokkaido.

Then, after a little sunshine, a low-pressure system will steamroll over Honshu during Tuesday and Wednesday with warm temps and heavy rain likely. If we’re lucky, freezing N-NW following close behind may bring moderate-heavy snowfalls during Thursday.

Thursday, Jan 2 – Sunday, Jan 5 – A prolonged, snowy W-NW flow

Low pressure is expected to bounce around in the Sea of Okhotsk today through Sunday, leaving Japan in this snowy W-NW flow the entire time.

Snowfalls will mostly be light and consistent, but it may get a little slushy at times below 800m on central Honshu.

There will, however, be a break in snowfalls over northern Honshu later this afternoon into Friday morning. Then all of Honshu will take a breather on Saturday with only a few flurries, before things resume that night with a period of moderate-heavy falls.

Hokkaido hardly gets a mention here, as it barely strays from the “light and consistent” forecast. However, things will be rather sparse for most of Friday, with little or nothing falling over Niseko until that evening.

Snowfalls gradually peter out over Japan during the latter half of Sunday. Totals for this four-day period will be up around 35-55cm+ for central Honshu, and around 10-25cm for northern Honshu and Hokkaido.

Monday, Jan 6 – Thursday, Jan 9 – High pressure followed by a warm, wet low

 High pressure pushes over central Honshu during Monday, then northern Honshu and Hokkaido on Tuesday, with skies clearing briefly.

While this is happening, a low-pressure system extends into the Sea of Japan from the Yellow Sea. Warm S-SW winds will drag over Honshu during Tuesday and rain will set-in at some point, with heavy falls likely over central Honshu.

Luckily for Hokkaido, winds from the south don’t quite reach the island so temps remain cold, and light-moderate snowfalls should get underway late Tuesday or early Wednesday.

After the low has passed over Honshu late Wednesday, freezing N-NW winds will descend over Honshu and we could see a period of moderate-heavy snowfalls there on Thursday.