What happened?

After the fifth warmest fall on record in Richmond (September through November), the first freeze of the season came on the morning of November 29, and each of the following five nights have all been below freezing.

Regarding the daily average temperature, two of the last five days were more than 10 degrees colder than normal, and we probably have one or two more of those in the pipeline before the end of the weekend. 

But during the four weeks leading up to Thanksgiving, Richmond had 11 days that went the other way — more than 10 degrees warmer than normal.

For most of the fall, the jet stream winds over Virginia had been from the west or southwest, keeping the truly frigid air bottled up into Canada. But a surge northward in the jet stream over the West Coast late last week had ripple effects here in Richmond. Because air travels in waves, that surge north on the West Coast corresponded to a large surge south over the East Coast, and the flood gates to the Arctic opened wide.

Is it going to stay cold?

However, this does not mean the rest of winter will be so cold, as there are already signs of this weather pattern giving way before the first of next week. Plus, the temptation may be there to hope for snow after such a sudden stretch of cold weather, but the data tell another story. 

In the shorter term, the persistent flow of air from the cold Canadian prairies will finally subside this coming weekend, and Richmond will settle into a weather pattern more typical for December. The middle third of the month will have more swings in temperatures and at least a couple of chances at some soaking rain.

Aside from some small, renegade snow showers that may cross Richmond on Thursday, no precipitation is expected through the end of this weekend. And after the last of these cold surges of air settles in for Friday and Saturday, the temperature bounceback will begin.

As cold as it has been, we have been far from records.

During the first 10 days of December, record lows in Richmond are in the teens. The warmest of those is 19 degrees (12/2/1965), and the coldest is 10 degrees (12/4/1940).

This coming Friday night will likely return us to the low-to-mid 20s, but the record low for Saturday morning is 15 degrees (1954), which is probably out of reach. As a further testament to the warming climate, the last time we set any record low during December was 35 years ago, dropping to 9 degrees on the morning of December 23, 1989.

For the data curious, the coldest December temperature on record in Richmond came more than a century ago, dropping to -2 degrees on the morning of December 30, 1917.

Rain ahead, not snow

Back in the present, our temperature bounceback develops on Sunday as the jet stream shifts, coming more from the west and southwest, also allowing us to be on the lookout for larger soaking rains next week. Afternoons will average in the 50s next week, perhaps even squeeze into the 60s on Tuesday. Given that normal highs during that time are in the low to middle 50s, we could think of next week as a return to normalcy after the warm fall and the sudden shock to start December.

The first of two chances of rain arrives Monday or Tuesday next week, then a larger storm — at least in physical size — appears to push through around Wednesday or Thursday of next week.

Barring a big change in the data over the next few days, winds from the southwest will scour out the freezing air needed for snow, so both of these systems look like rain. However, some rain will be welcome, as we’ve only had about one-third of an inch of rain over the last two weeks. 

Between those two systems, expect about 0.5 to 1.5 inches of rain before the second one clears in time for the weekend of December 14. For the moment, that weekend appears to be dry with afternoons in the 50s and nights in the 30s.

White Christmas?

Statistically, a white Christmas in Richmond is rare (6 percent), and there is not much reason to deviate from that idea right now, but we should have a better idea in a couple of weeks.