A strong trough of low pressure in the upper atmosphere moved into the southwest U.S. late on the 17th and early on the 18th.  The system was very fast moving with a strong jet of 165 kts streaming up the east side of the trough.  A short wave ejected out of the trough and raced northeast through the central U.S., reaching Illinois by the morning of the 19th.  Low pressure at the surface formed over western Kansas  during the afternoon of the 18th. It moved to northeast Kansas by evening, and to near Burlington, IA by sunrise on the 19th.  A strong low level jet pushed moisture over a polar airmass that was in place over Iowa.  In addition, the atmosphere became quite unstable for December over the state, resulting in the development of thunderstorms over a large part of Iowa during the overnight hours of the 18th into the 19th.  A variety of weather conditions developed over the northern two thirds of the state.  Thunder with snow and ice pellets was commonly reported, and resulted in some heavy amounts of each.  Over the central part of the state, ice pellets were predominant along the Interstate 80 corridor, with mostly snow falling north of U.S. Highway 30.  Over the central sections, many areas reported ice pellet accumulations in excess of an inch.  The heaviest amount was around 3 inches in Dallas County south of Perry.  One and one half to two inches was common across the Metropolitan Des Moines area as well.  Most other areas along the I-80 corridor were in the three quarters to one inch range.  Snowfall amounts increased rapidly as you headed north with six inch or greater snowfall amounts common from near U.S. Highway 30 north.  Seven to eight inch snow amounts were very common in a 50 mile wide band stretching east-west along the U.S. Highway 20 corridor.  There were two areas of heavier snow.  Over 10 inches of snow fell in Pocahontas County as thunderstorms moved through the area.  Another pocket of heavy snow was over the northeast part of the CWA.  The greatest amount fell in Butler County at Aplington, with 13.4 inches.  In Bremer County, 10 inches was reported in Plainfield, with 9.7 inches in Denver.  Roads became icy and snow packed, and by the early morning hours, travel was not recommended north of U.S. Highway 30.  Though damage was not all that great, the storm did cause considerable disruption.  Nearly all schools were closed on the 19th, and most other activities were canceled or delayed.  The heavy ice pellet accumulation caused the closing of the Des Moines Airport for a period, canceling several flights and causing numerous delays.

Winter Storm in TAMA, IOWA
From 18-DEC-08 19:00:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in CRAWFORD, IOWA
From 18-DEC-08 20:00:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in CARROLL, IOWA
From 18-DEC-08 20:00:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in BOONE, IOWA
From 18-DEC-08 20:00:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in STORY, IOWA
From 18-DEC-08 20:00:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in MARSHALL, IOWA
From 18-DEC-08 20:00:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in SAC, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in CALHOUN, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in WEBSTER, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in HAMILTON, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in HARDIN, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in GRUNDY, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in BLACK HAWK, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in POCAHONTAS, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in HUMBOLDT, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in WRIGHT, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in FRANKLIN, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in BUTLER, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in AUDUBON, IOWA
From 18-DEC-08 19:00:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in GUTHRIE, IOWA
From 18-DEC-08 19:00:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in GREENE, IOWA
From 18-DEC-08 19:00:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in DALLAS, IOWA
From 18-DEC-08 19:00:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Winter Storm in WARREN, IOWA
From 18-DEC-08 19:00:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Winter Storm in POLK, IOWA
From 18-DEC-08 19:00:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 20.00K
Crop damage: 0.00K
Reported by: NWS Employee

Winter Storm in MARION, IOWA
From 18-DEC-08 19:00:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Winter Storm in JASPER, IOWA
From 18-DEC-08 19:00:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in POWESHIEK, IOWA
From 18-DEC-08 19:00:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in BREMER, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in PALO ALTO, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in KOSSUTH, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in HANCOCK, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in CERRO GORDO, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in EMMET, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in WINNEBAGO, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Winter Storm in WORTH, IOWA
From 18-DEC-08 21:30:00 to 19-DEC-08 08:00:00 (CST-6)
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Official NWS Observations