Friday 9 a.m.
When National Weather Service meteorologist (Chicago area office) Gino Izzo mentioned the possibility of graupel in some of the showers this weekend, it led to this headline in the Chicago Sun-Times: "Weekend forecast: No snow, some graupel (We never heard of it either)" Graupel may look like small hail, but it crumbles when you touch it. It can look like pellets (as opposed to flakes) of snow.
Why use the term? First of all, it is difficult to explain. This means if a weather forecaster spends a long time on the explanation, there is less time to give a forecast that might turn partially erroneous. However, as to the issue itself, hailstones are solid balls of ice. The ice balls often have layers caused by the changing concentrations of water and ice in the cloud through which it travels. Sleet forms when snow melts on the way down, then freezes into small pellets of ice which bounce around on cars, rooftops, etc. Whereas many people tell me they've never heard of it when I talk about it, graupel is common enough to receive this entry on the first page after searching for it on Google:
In other words, graupel has been photographed numerous times.
In this video, we look at the forecast for this weekend and early next week. Whereas the major East Coast cities may have a round of showers with a frontal passage tomorrow night, places downwind from the Great Lakes (Buffalo, for example) may have persistent showers that can include narrow bands of heavy rain. Next week, colder air will invade the Northeast, and the area between the Great Lakes and Appalachians may be grappling with the first snow showers of the season.
Here is a Chicago area video:
A deck of clouds about a half-mile overhead spread westward from the Atlantic to much of the I95 corridor from DC to Boston early this morning. These cloud decks can be a forecaster's nightmare in the spring because ...
The map below the video is one of the GFS solutions for where the southeast storm will be early Saturday. The precipitation is predicted to be farther north than suggested by other models.
It is freezing cold in the Northeast this morning, but this map shows that much more mellow mildness has reached the Plains.
Extensive precipitation straddles both sides of the cold front that was moving through central New York and central Pennsylvania as of mid morning. This radar shows the distribution of rain and snow; some temperatures are added.
The cold front approaching the East shows up quite well in this pressure analysis. Several temperatures are plotted to give you a sense for how much the temperature changes behind the cold front. At Chicago, it went from 60 at 4 a.m. to 39 at 5:19, a 21-degree drop in little more than an hour.
Temperatures on Sunday and Monday will range from the 60s in parts of New England to near 80 in Maryland and Virginia. However, a strong cold front will then trigger and perhaps a few thunderstorms as it ushers in air that will be 30-40 degrees colder than it will be ahead of the cold front.