( CNN ) -- Six inches of snow in Chicago . A foot or so plastering the Upper Midwest . And up to 20 inches expected just west of Washington . Surely , there 's a silver lining to these snow clouds though , right ? Do n't they bring much-needed moisture to parched states ? Not quite . Snow is very fluffy , and it takes up to a foot of it to squeeze out an inch of rain , meteorologists say . Snowfall is `` definitely a benefit , but not a drought-buster , '' said CNN meteorologist Dave Hennen . Many drought-stricken states need a foot of rain , not snow . Frozen ground . When the ground is frozen , little of the moisture left by snow sinks into the soil . `` All of the snow that has fallen over the winter by and large remains on top of the landscape , '' said Minnesota 's state climatologist Greg Spoden . Winter storm moves in on D.C . When the sun comes out , it melts the snow first , while the ground remains hard , causing the water to flow off into lakes and rivers , or evaporating , instead of sinking in . Lake City , Minnesota , has received 11.5 inches of snow since Sunday morning , which amounts to about an inch of rain . Not much for a state with levels of soil moisture near all-time lows , according to Minnesota 's Department of Natural Resources . `` Even flooding at this point wo n't alleviate a drought , '' the agency said . But the recent snow will give river and lake levels a nice bump . The snow sent motorists sliding off of slick roads Tuesday , in spite of widespread coverage with salt spread by trucks . Plains states have it worst . Comparatively , Minnesota does n't have it that bad , according to U.S. Drought Monitor . About half of the United States is now `` abnormally '' to `` moderately '' dry , or worse . Things look particularly bad west of the Mississippi River . When 21 inches fell on Wichita , Kansas , in February , it broke a monthly snowfall record set in 1913 . But the state is still plagued by `` severe , '' `` extreme '' and `` exceptional '' drought , U.S. Drought Monitor said . Oklahoma and Kansas will keep more of the moisture the snow left behind , because the ground there is n't frozen , said meteorologist Joel Widenor . Only one state is drier , Nebraska , where U.S. Drought Monitor is located at the University of Nebraska in Lincoln . Most of the state is going through an `` exceptional '' drought . Climate change and snowfall . Record snow falls combined with record drought comes as no surprise to climatologists studying climate change . Total snowfall in the western half of the country is dropping , said Princeton climatologist Sarah Kapnick , which will mean less accumulation of moisture from snow . At the same time , the storms that sweep the United States should grow more intense , said meteorologist Marshall Shepherd from the University of Georgia . With global warming , `` we 're loading the dice or stacking the deck toward more intense blizzards , '' he said . River water levels . Snowfall has bolstered water levels on the Mississippi River , which had dropped due to drought , said Ann McCulloch , spokeswoman for American Waterways Operators . When high temperatures dried out much of the country last summer , barges were restricted to floating at a depth of nine feet instead of 12 feet . Recent snows have pushed water levels up enough to allow barges to run at 12 feet of depth again . McCulloch is afraid this might not hold , when the summer heat returns . Water where it 's not needed . As the current storm reaches the Atlantic coast , dumping snow on the nation 's capital , the white precipitation should become slushier and deliver more moisture per foot of snow , according to CNN 's Weather Center . The District of Columbia and Baltimore are bracing for potentially significant accumulations , according to the National Weather Service . Snow plows have been readied . Airlines have canceled flights to and from Washington 's Dulles airport ahead of the storm 's arrival : United 650 , U.S. Airways 350 , American 20 . But by the time the storm gets there , it could turn to rain . The Northeast does n't need it . It is already plenty moist , Drought Monitor said . In the parched Plains states , snow has n't helped enough . They could use that rain . CNN 's Mariano Castillo , Dana Ford and Phil Gast contributed to this report .
It takes up to a foot of snow to deliver an inch of rain . About half of the United States is too dry . Chicago sets snowfall record for the day .