This afternoon’s radar lit up in a hurry! The environment certainly was not lacking for moisture (dew points were in the low 70s), but it was always a bit questionable whether we would tap into some of that deep moisture and instability to kick start any storms. I think that question has been answered now. Be careful with these clusters of storms today, as they are going to be heavy on the cloud to ground lightning (due to lots of suspended, tiny ice particles above us). The storms should lose energy and move off to the south by sunset. But we are likely to face the same afternoon storm threat on Sunday.
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Through tonight: Scattered thunderstorms, with heavy rain and frequent cloud to ground lightning, will continue to rotate through the D.C. area from the west. The coverage of these storms is fairly widespread, but the intensity of each cell is pretty variable. Looking at the radar, there is a decent chance that all of us will see some raindrops before sunset, but not all of us will be subject to the same precipitation intensity. Where the stronger storms do develop, expect them to be slow-moving, dropping lots of rain in a short period of time. Storms around the D.C. area will die out rather quickly after sunset, with a secondary line of storms likely forming well to the south and east of our area later tonight. Locally, we stay mostly cloudy and warm overnight. Lows will be in the upper 60s to low 70s with high humidity values and a light southwest wind.
View the current weather at The Washington Post.
Tomorrow (Sunday): Sunday starts out warm and muggy, with pockets of haze/fog lingering in the early morning. We won’t see much in the way of sunshine, as skies should stay overcast for much of the day. That helps in the temperature department (highs in the mid-80s) but not in the humidity department, with dew point values in the upper 60s to low 70s. Similar to today, storms should start to pop up on the radar as soon as we hit the afternoon. Our area is in a more “favorable” position on Sunday for storm development, with the main hazards being heavy rainfall and frequent cloud to ground lightning. Based on Saturday’s storm characteristics, you should make your way inside as soon as one of these cells develops near your location, as the amount of lightning activity in these storms will make it extra dangerous to be outside. The storms may linger into the evening hours more so Sunday than they do on Saturday, but much of the activity should wane once again after sunset. It will be mostly cloudy, warm and humid at night with lows in the upper 60s.
Alberto update: Alberto has a name, but it isn’t much to look at. In fact, Alberto isn’t technically even a tropical storm by pure meteorological definitions. But the National Hurricane Center doesn’t seem to think that matters, and honestly, I agree with them. The storm system will probably become a tropical storm within the next 24 hours, but whether its subtropical or tropical doesn’t change the threats that the storm poses to those in its path.
The NHC began publishing “key messages” for tropical (or subtropical) storms a few years ago. It was a smart decision and a sure sign that the agency (NOAA) as a whole is more receptive to integrating social science with its public forecasts. And it’s an especially useful tool for a storm like Alberto, which won’t spark much fear from how it looks on satellite, but will still bring dangerous conditions to a wide swath of people on a holiday weekend.
As a side note, I’d be more than happy to answer questions (via the comments section or social media) on the differences between tropical and subtropical designations.
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