*Flood watch in effect through tomorrow evening*

The first batch of rain has moved through the area and left us with anywhere from a half-inch to an inch of rain. We are in a rainfall lull over the next few hours, with just some scattered showers through the evening hours. The true soaking rains are poised to move in overnight, and there is a strong possibility we see anywhere from one to two inches of additional rain overnight and into tomorrow morning. That’s enough precipitation to warrant a flood watch for the entire region.

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Through tonight: Scattered showers will persist over the next several hours. You will certainly need an umbrella for evening plans, but Saturday night revelers should avoid the heaviest rains. Moderate to heavy rain moves into the area around midnight and will stick with us for pretty much the entire overnight period. Another one to two inches of rain is expected during this time frame. Temperatures will basically be stuck in the upper 40s and may actually start to rise toward dawn when we develop a southwest wind.

View the current weather conditions at The Washington Post.

It’s a muddy kind of weekend. (Wolfkann via Flickr)

Tomorrow (Sunday): Pockets of heavy rain will continue through Sunday morning. We should see the rain intensity begin to wane by late morning, and eventually, the rain will shut off entirely sometime after 1 p.m. Temperatures will be quite variable tomorrow depending on your location. Most of us spend the first half of the day in the upper 40s to low 50s, save for areas to the southeast of the District, where the temperature will quickly jump into the mid-60s. That warm pocket of air slowly spreads to the north in the afternoon, temporarily creating a sharp temperature gradient over a short distance before we all tap into the 60-degree air by the late afternoon. Skies will remain mostly cloudy with a light south wind at 10 mph. Showers and maybe even a rumble of thunder or two return tomorrow night as the cold front finally passes through the region. Lows tomorrow night will be in the mid-40s.

See Ian Livingston’s forecast through the weekend. And if you haven’t already, join us on Facebook and follow us on Twitter and Instagram. For related traffic news, check out Dr. Gridlock.

Blame the dry weather for the bad flu season: I found this blog post from Bob Henson to be extremely interesting — so much so that I am sharing it with you today. It turns out we are starting to see mounting evidence that atmospheric moisture is a powerful limiting factor in flu transmission. I encourage you to read Bob’s post, but here is the TL;DR version: More water in the atmosphere results in less flu floating around. Flu “droplets” that are coughed out by people are looking to latch onto something and are more likely when it’s relatively humid to attach themselves to atmospheric water droplets and fall out of the air rather than infect another person.

Statewide rankings for average precipitation during December 2017, as compared with each December since 1895. The entire country has seen below-average precipitation values this winter season. (Bob Henson)

That was an oversimplified explanation, and in reality, the mitigating factors in flu transmission and the severity of a flu season extend far beyond the antecedent weather conditions. That said, this year’s flu season has been historically bad during the United States’ driest winter in decades.

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