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Winter Storm warning

posted Feb 20, 2011, 5:58 AM by Brian Donahoe
The National Weather Service has issued a Winter Storm Warning for Lake County from 3 a.m. Sunday, February 20, through Sunday afternoon.
Because of the warmer temperatures during the past several days and the expected precipitation over the next few days, the Lake County Stormwater Management Commission (SMC) has issued a "green flood alert," meaning that minor flooding is occurring or possible across Lake County.
Additionally, as follow-up to the February 1st and 2nd blizzard, the Illinois Emergency Management Agency (IEMA) requested that all public entities affected by the storm submit a report of specific excess costs using guidance and a form that they provided. Lake County entities were asked to submit their reports through the Lake County Emergency Management Agency (EMA), and we received a total of 125 reports documenting excess snow emergency costs in excess of $4.4 million dollars. Federal Emergency Management Agency (FEMA) and IEMA personnel will be contacting entities during the week of February 21 - 25 to verify and clarify the initial cost estimates submitted by those entities. Detailed information about this ongoing preliminary damage assessment process has been provided via separate email to those entities from whom reports were received.
A Winter Storm Warning is in effect from early Sunday morning through Sunday afternoon for Lake County. Travel may become difficult, particularly early Sunday morning through mid-day Sunday. Several different kinds of winter precipitation are likely, including some accumulating snow, sleet, freezing rain, and rain. Since very specific atmospheric temperature conditions are necessary for freezing rain to form, slight variations in the track or strength of a forecast storm may result in more or less icing than expected. Precipitation across Lake County is forecast to begin sometime after midnight tonight as snow. The snow could be intense at times, with accumulations of up to several inches of snow possible before the precipitation changes to sleet and freezing rain. This changeover is expected in the hours around daybreak, generally moving from southwest to northeast across Lake County. Some accumulation of freezing rain is possible, perhaps up to two or three tenths of an inch in some places, before surface temperatures warm sufficiently for the precipitation to become just rain during the day on Sunday. Ice accumulations on sidewalks, driveways, and porches, particularly elevated surfaces, may make walking somewhat hazardous on Sunday morning. Significant ice accumulation, generally from a quarter to a half inch of ice, can also cause some tree limbs, branches, and utility wires to fall, but widespread problems are not forecast with this storm. Winds of up to 30mph are also expected during the day on Sunday, which may increase the chances for minor damage to trees and utility lines. As the storm moves off to the east later on Sunday, winds from the northeast may produce some lake-effect snow enhancement in areas within several miles of Lake Michigan, and falling temperatures are expected to cause the rain to transition back to snow before ending overnight Sunday.
Lake County SMC and EMA personnel have been monitoring river and stream conditions across the county, and on Friday SMC issued a green flood alert, to remind people that flood conditions are possible over the next several days. River levels across Lake County have risen because of snowmelt cause by the relatively warm temperatures of the past several days. The Des Plaines River is below its action stage of 6.5' on gauges at Russell and Gurnee, and below the action stage of 10.5' at Lincolnshire. The expected precipitation over the next two days may cause further rises on the Des Plaines, but forecasts don't currently suggest that levels will exceed flood stage or cause any widespread problems. The Fox River upstream of Lake County at the New Munster gauge in Wisconsin is at just over 11.5', roughly halfway between the flood and moderate-flood stages. This water level doesn't generally produce any significant flooding in Lake County, but we will continue to carefully monitor the situation. Since forecasts suggest that more of the precipitation in the upper Fox River watershed will fall as snow rather than rain, significant increases are not expected on the Fox. The Illinois Department of Natural Resources (IDNR) is monitoring conditions and will manage water levels on the Fox River and Chain O' Lakes to the extent possible through adjustment of gate settings at the dams in McHenry and Algonquin. With lake levels at winter pool stage (low), the capacity of the Fox River channel has more impact than dam operations at McHenry in regulating the flow of water out of the Chain O' Lakes. Some rise in lake stages is expected.
While no areas of widespread flooding are forecast, the mix of different kinds of precipitation over the next few days may lead to some minor localized flooding, particularly in areas where there are still piles of snow that can obstruct storm drains, ditches, and floodways. Lake County SMC and EMA will continue to monitor the situation, and will provide additional updates only if conditions are expected to or do significantly worsen.
If you have any questions or need assistance, please feel free to contact us, during office hours (Monday through Friday 8:00 a.m. to 5:00 p.m.) at 847-377-7100, or after hours through the Lake County Sheriff's 9-1-1 center at 847-549-5200.