Snow on My Radar, But Not in My Window?

Blog reader Dave from eastern PA left a Comment on this morning's blog:

Below I've pinpointed the county seat of Northampton County so you can see which county Dave's in. This is the standard Snow/Ice/Rain radar that Dave was looking at, seen through the eyes of our new Enhanced Radar which is now available on AccuWeather.com.

It looks like he's pretty socked-in alright. This is a real problem in the winter (something I have talked about before in my "Radar, Lies & Videotape" series), especially with "composite" radars that combine data from all radars together. The root of the problem is that the radar beam angles up from the Doppler radar itself, so after a few dozen miles out, it's looking into the clouds, or looking at precipitation that is not reaching the ground (virga) due to evaporation.

During those trying times I recommend using the Single-Site (local) radar which shows data from only one radar site, although this only works if you're close to the radar center. The KPHL radar, shown above, should be more accurate in those situations. Remember, the lightest levels on any radar may not mean there is actually precipitation reaching the ground. In this case its much more clear that there was little precip in Dave's area. (If you look at the State College (Central PA) radar, you can see that it's riding so high that it thinks Northampton county is covered). Just remember though, this type of radar does not provide the delineation between Snow, Ice and Rain.

A more "honest" Composite Radar is always something that we're looking to do here, but making the determination (whether or not precipitation is reaching the ground) is more difficult than you might think. With higher resolution may come a more accurate picture, and in fact I think you see some of that with the new from our Hi-Res Radar (available now to Premium & Pro users, soon for free). Below is a shot from the same time as the Snow/Ice/Rain shot above. Dave's still in the precipitation, but not as heavy as the "old" radar insists.