It overestimated the strength of the line of storms, but actually got them in pretty much the right place. It underestimated the breadth and strength of the northeast area of precip, but the radar is probably overestimating it - some of that precip is probably not reaching the ground.

ORIGINAL POST: Thunderstorms are heading towards the Northeast tonight and tomorrow... but how will you know when they arrive? What areas will they affect? This information is not only important to people planning outdoor activities, but also to local storm chasers who want to photograph the storms as they come in (which direction they are coming from is also crucial to photographers who may want to position themselves on nearby hills or fields without trees -- a unique problem that chasers don't have in the Plains). The SPC [JessePedia] has issued these cryptic maps:

While these maps tell the areas that are under the highest risks during the times specified (the highest risk is a Slight Risk for Severe Thunderstorms to the right of the green arrows, the brown is a General Thunderstorm risk), and are easily readable by meteorologists, they don't say where the storms will break out and how they will move. The most I can get out of these map is: Possibly have your camera ready between Sunday Morning and Tuesday Morning.
Although of course you can check your AccuWeather.com forecast, especially AccuPOP, for details on precipitation probabilities at each hour, I find it more helpful to envision what's happening on a map. On the AccuWeather.com Professional website (30-day free trial!), we have a new super-hi-res Weather Forecast Model [JessePedia] called the 4-KM WRF. This model is specific enough to pick out individual thunderstorms and squall lines through a product called "simulated radar" which basically does what it says - it simulates what the radar will look like every 3 hours for the next 2 days. This morning I requested a loop and looked at the image when the line of storms was approaching me here in Central PA:

I can even zoom in...

So, at 09Z (about 5 am) the line of storms should be near Johnstown, PA, home of Local storm chaser Ron "R-Factor" Shawley. I'm too old to be getting up that early so I will probably sleep through the storms. However, note that the area is never within the Slight Risk area outlined above, and overnight storms also generally have trouble keeping their strength so there might not even be any lightning to photograph. Without lightning, a storm in the night is no good to a photographer.

How about Philly and New York City? Well if I advance the loop I see this image...

...which shows the line of storms in between the two cities at 18Z (2 PM). Given that the storms are happening in the daytime, and based on the SPC Risk shown above, local storm chasers should bring their cameras with them to work on Monday, and be ready to deploy, unless they are lucky enough to have the day off, which in case they should position themselves somewhere high with a good view to the west-southwest. But again, the area is not within the Slight Risk, so this might not even be a great storm.

You can also look at a simulated winter radar to see the snow showers after the front goes through:

How close will this simulated radar come to reality? Well, the 4-KM WRF has some disadvantages. Because it is such high resolution, the government can only afford to run it twice a day, it only goes out 48 hours, and it takes 7 hours to run. So if the storms are going to hit me tonight at 5 AM, the last forecast I'll be able to check is from this morning, and it won't be available until dinnertime, which could not leave me enough time to plan. What we're looking at above is last night's forecast, which will be more inaccurate (because it had to predict farther out into the future).

I've found that the WRF 24-48 hour forecast is somewhat accurate, though it often misjudges the location or time of precip. The 12-24 hour forecast is better, but it still can be wrong, because, although it's an extremely high-res model, it's still relying on man-made algorithms and input. Still, if you're looking for an estimated simulated radar shot, it's all you've got.

If you're already a Pro member or you try our 30-day free trial, here's how you access these maps. Click on Forecast Models / North America / WRF-4km, then pick "Simulated Composite Radar" or "Combined Conditionals AND Amounts" (that's the winter radar) from the "Expanded Pick" dropdown menu. Then choose your hour or loop, and click Get Map.

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