American (GFS) model shows big dips in the jet stream arriving Saturday and late Tuesday over the eastern United States, allowing pools of cold air to dive south. (

Fall was delayed this year, not arriving until mid-October, when summer finally left the stage. Just three short weeks after the onset of this autumn-like weather, Washington faces its first two blasts of winter-like cold.

If you haven’t already broken out your winter coats, you’ll probably need to by Saturday.

Both this coming weekend and during the middle of next week, the jet stream will plunge south, delivering consecutive blasts of unseasonably chilly air. Highs in Washington are likely to only manage the 40s and lows will plunge into the 20s and 30s. Such temperatures are more characteristic of December and March.

Forecast temperature difference from normal at 7 a.m. between Thursday this week and Thursday next from American (GFS) model. (

In fact, the predicted temperatures are expected to be the coldest the region has witnessed since March — which was decidedly chilly.

The first wave of cold is entering the northern Rockies and Northern Plains. It will sink south into the Midwest by Friday and then arrive Saturday in the Mid-Atlantic.

The second blast will pour into the central United States by Monday and then ooze east, reaching our region by Tuesday night and Wednesday, in the wake of a possible coastal storm. The intensity of this second wave will ease some as it heads east, but still has a good chance to bring some of this season’s coldest air so far.

The cold this weekend

Forecast temperatures at 1 p.m. Saturday from American (GFS) model. (

High temperatures this weekend are only forecast to reach the mid- to upper 40s. On Saturday, in particular, winds will be gusty, producing wind chills in the 30s by evening.

Lows Sunday morning are likely to plummet into the 20s in our colder areas to the low 30s downtown. Reagan National Airport and downtown Washington have a chance (around 40 percent) to post their first freeze of the fall. If it happens, it would be about a week ahead of the recent 30-year average of Nov. 18.

Low temperature forecast from American (GFS) model Sunday morning. (

Weekend temperatures are likely to be the coldest since late March.

Cold during the middle of next week

A reinforcing shot of cold air will arrive by Tuesday night of next week, in the wake of rainy storm likely to come up the East Coast late Monday into Tuesday.

There is some uncertainty regarding the intensity of the cold. Models this week and last week had suggested unseasonably cold highs in the 30s but have backed off some and are now predicting highs in the low to mid-40s. Even so, such temperatures would be about 10 to 15 degrees below normal. In mid-November, the average high is in the upper 50s.

European modeling system average high and low temperature forecast for the next 15 days in Washington. (

Low temperatures Thursday may again dip into the 20s in our colder areas and flirt with freezing near the city.

After this second cold snap, long-range models suggest that temperatures will moderate into the third week of November, back to near-normal levels.