Our climate-guru and veteran National Weather Service observer Frank Wachowski reported late Wednesday that an average of 10" of snow was still ground at Midway Airport in the wake of Tuesday’s snowstorm. That's the deepest March 6 cover of snow at the South Side site since observations began there in 1928.
Forecasters carefully monitor the extent and depth of snow cover because it plays a critical role in determining the extent of daytime warming. Snow is, by its nature, incredibly reflective and able to send up to 90% of incoming sunlight back into space, thereby decreasing the speed at which warmer air is able to move into the area.
A cover of snow as extensive as the one currently in place across the Chicago area doesn't disappear overnight.
The appearance of comparatively strong March sunlight melts and compacts snow on the ground, something which will become more and more evident in coming days and contribute to this weekend's ability to generate temps in the 40s here and 50s and 60s downstate.
Snow-covered days have occurred at twice the pace of a year ago
There have been 22 days thus far this season at Midway Airport with 1" or more of snow on the ground in Chicago versus 11 days over the same period a year ago.
It's little wonder the count is running at nearly twice last season's pace. A trace or more of snow has fallen 25 of the past 36 days. The 26.7" of snow which has accumulated since late January is the 6th-snowiest such period on the books here since 1885.
In just the past week, the current snow season's ranking has dropped 40 slots---moving from a ranking of the city's 32nd-least snowy snow season 7 days ago to the 71st-least snowy season late Wednesday.
Soaking Saturday night/Sunday rains on the way; even some thunder could arrive in spots
Could there actually be a thunderstorm with this weekend's predicted move of mild, increasingly moist air into the Chicago area? To be sure, the chances for thunder aren't "off-the-charts" high---but that there's even a slight possibility with Saturday night and even Sunday speaks volumes. It's a sign more spring-like temperatures are on the move and edging ever- closer.
Were snow NOT still on the ground, we'd be forecasting 50s by Sunday for sure. It appears enough melting will transpire by Sunday that mid to upper 40s are a reasonable bet over the area. Should even more melting occur, readings might move into the 50s.
New storm behind warming weekend winds and the rain potential
A new storm is to organize over Colorado Friday, then move out into the Plains. Its expansive circulation is to deliver Chicago strengthening southerly this weekend which will bring moister air into the metro area, particularly Saturday night and Sunday. Nighttime temperatures remain elevated when the air is moist and this is likely to bring the melt-rate to a peak Saturday night into Sunday.
Snow from the storm which brought us snow Tuesday, moved off the East Coast Wednesday and is now intensifying. Its howling northeast winds are to gust to 50 and even 60 mph in the Boston and New York City areas Thursday.
Forecasters in that region face a real challenge with storms like this in pinning down the location of the critical rain/snow line. That feature plays a huge role in determining how much snow falls and where.
That much of Wednesday's precipitation which swept into Washington D.C. fell as liquid, cut into snow accumulations which had been predicted there. But the system's snow-producing capability may not be done.
Our RPM model is suggesting residents of both the Boston and New York City areas will have to monitor the windy storm and the threat of snow with it Thursday into Friday morning.