This weekend has not been a washout, unless of course you are reading this from the Eastern Shore. But the weather has hardly been ideal, either. I think a lot of us who escaped significant rain Saturday will be getting wet over the next few hours. On the whole, I would describe this as nuisance rain, but some unlucky locations may get caught under a series of heavy downpours that create localized flash flooding. We will get a break in the precipitation later this evening, before yet another round of rain moves in overnight.
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Through tonight: Overcast skies will persist for the remainder of the day. There have been some breaks in the cloud cover over central and southern Virginia, helping to fuel the development of thunderstorms in that region. Locally, we will start to see pockets of rain pop up sometime after 5 p.m. These storms should be aligned in a northwest to southeast manner, developing generally parallel to the Potomac River. Some areas may get stuck under several regenerative storm cells capable of dropping a lot of rain in a short amount of time. Localized flash flooding is likely to result, especially toward the east/southeast of D.C. We should see a break in widespread precipitation right before midnight, before another batch of rain moves in overnight. Coverage with this batch will be more widespread, but generally less intense than the afternoon pop-up showers. It will be cool overnight, with lows in the upper 50s to low 60s and a northeast wind at 5-10 mph. Areas of patchy fog are likely to develop in the early-morning hours.
View the current weather at The Washington Post.
Tomorrow (Monday): Showers and fog will linger into the morning commute, probably causing some delays. Some isolated areas of heavy, slow-moving downpours will be around in the morning hours, which keeps alive the chance of localized flash flooding. We should begin to dry out in the early afternoon, although overcast skies are likely to linger for much of the day. Temperatures will be on the cool side, with highs in the upper 60s to low 70s and a northeast wind at 10 mph. I am hopeful that we will see a little bit of sunshine by tomorrow evening, especially north of D.C. Partly to mostly cloudy tomorrow night and remaining cool with lows in the upper 50s to low 60s.
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Behind the forecast: The people seem to enjoy these explanations, so who am I to deny the people what they want? Of course, I also like writing them, so it’s mutually satisfactory. Today’s weather is suffering from the same complexity as yesterday’s weather, namely, a whole lot of mesoscale (small-scale) influences creating a complicated surface map.
Essentially, where you see the fronts on the image above is where we are seeing precipitation develop this afternoon. Right now, much of our area is between the two frontal boundaries, hence the dry weather we’ve had for much of the day. However, the red arrow in the image above is focused on a “hitch” in the frontal boundary, which is probably related to the weak wave of low pressure that is riding along the front from west to east. That weak wave will push the entire front toward the south over the next few hours, which is why we will see a line of showers roll through.
The red circle is the source of our overnight and early-morning rain. This is a more traditional low-pressure system, coupled with upper-level support. However, it, too, will ride along the stalled frontal boundary, bringing with it a second round of precipitation. One slight concern I have with this second weather maker is that it will eventually collide with the northeast wind that we’ve been experiencing all day. Northeast winds come right off the ocean and are loaded with low-level moisture. Combined with the moisture that the low pressure will be bringing, we could see an area of high-moisture convergence (probably somewhere to the east of D.C.) where a lot of heavy rain will find a focal point.
I suppose time will tell on that one. In any case, expect Monday morning to be a soggy and foggy commute.
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