Winter Storm (Dec. 18) Update #2

The National Weather Service offices that cover the state of Iowa were busy last night, issuing several different winter weather advisories/warnings. A quick overview of these warnings: A Winter Weather Advisory is in effect for a few of the far western Iowa counties, a Winter Storm Warning is in effect for areas north of I-80 throughout much of central and eastern Iowa; and finally a Ice Storm Warning is in effect for much of the state that is south of I-80. These advisories and warnings go into effect this afternoon and will continue into Friday morning while precipitation falls throughout this period.

The latest models are in very good agreement for this winter storm with both positioning and QPF amounts, along with precipitation type. The heaviest band of snowfall is expected to fall from a line just south of Sioux City, northeastward to near Webster City, and then just south of LaCrosse, WI. Areas along and north/south of this line are likely to see greater than 6 inches of snow, with isolated amounts near one foot. These heavier snow amounts may likely occur within areas of embedded thunder, in fact, several areas in the southern half of the state may see embedded thundershowers with this system. These thunderstorms will have the potential to put down several inches of snow, or significant amounts of sleet or freezing rain within a short period of time.

This system has the potential to be extremely hazardous, producing over a half inch of freezing rain for the southern third of the state; significant sleet and freezing rain mixtures; and very heavy snowfall amounts. Des Moines NWS once again has a very good graphic depiction of the events likely to occur this afternoon and through the overnight hours. Thanks to a reader that posted a comment in the previous update, indicating that freezing drizzle is already beginning over parts of the state.