Not quite enough is the appropriate catch phrase for this weekend's weather. Today and tonight's clouds are brought to you by a series of upper level disturbances that are not quite strong enough to kick off any serious precipitation. If it does rain, or snow when it is colder at night, it will be not quite enough to dampen the dry soil. Two storms should move up the coast from the Carolinas over the weekend. They will be close enough to bring us clouds but not quite close enough for a serious rainfall. It is true that the temperatures have increased, but not quite enough to reach the lower-50s, which is normal for this time of year. So, we can expect cloudy conditions with a chance of light rain or snow through the weekend. Monday and Tuesday won't be much warmer, but they will be sunny as a high pressure system moves over us.
Whether we get rain or snow depends on how temperature and humidity vary with elevation in the atmosphere. Gothamist recently found the Precipitation Type applet that Tom Whittaker put online at the University of Wisconsin-Madison. The applet lets you specify initial temperature and humidity (wet bulb) conditions at four levels of the atmosphere. If you've chosen the right conditions a cloud forms and precipitation begins. Gothamist has wasted hours trying to simulate all sorts of precipitation types. Right now we've got water droplets turning into snow then turning into rain and snow grains. Fun! Maybe not for everyone, but it is fun for us.
MODIS visible satellite image from the Naval Research Labs.
