A strong upper level low pressure area moved into the central U.S. from the southwestern states during the night of the 20th into the morning of the 21st.  The system came out as a closed upper low, which passed over Iowa.  Surface low pressure developed over the Texas Panhandle and moved northeast across Kansas, and into west central Illinois by the afternoon of the 21st. Strong theta-e advection spread into the state during the evening of the 20th, and worked slowly north with the negative tilt trough ahead of the upper low through the night into early on the 21st.  Snow fell at a steady rate with the heaviest snow falling at the rate of one half to one inch per hour at times.  The storm produced little in the way of wind, but did cause travel problems in that the roads became snow packed.  Snowfall from the system was quite uniform in the 6 to 7 inch range with a few higher reports.  The greatest report received was 7.8 inches in Bremer County at Tripoli, and also in Cerro Gordo County at Clear Lake.

Heavy Snow in SAC, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in CALHOUN, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in WEBSTER, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in MARSHALL, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in BREMER, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 12:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in GRUNDY, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 12:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in WAPELLO, IOWA
From 20-JAN-07 17:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in APPANOOSE, IOWA
From 20-JAN-07 17:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in HAMILTON, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in AUDUBON, IOWA
From 20-JAN-07 17:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in GUTHRIE, IOWA
From 20-JAN-07 17:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in JASPER, IOWA
From 20-JAN-07 17:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in HARDIN, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in CRAWFORD, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in ADAIR, IOWA
From 20-JAN-07 17:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in TAMA, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 12:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in STORY, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in DECATUR, IOWA
From 20-JAN-07 17:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in WAYNE, IOWA
From 20-JAN-07 17:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in HANCOCK, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in CARROLL, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in CASS, IOWA
From 20-JAN-07 17:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in ADAMS, IOWA
From 20-JAN-07 17:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in UNION, IOWA
From 20-JAN-07 17:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in CLARKE, IOWA
From 20-JAN-07 17:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in GREENE, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in BOONE, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in WORTH, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 12:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in CERRO GORDO, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 12:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in FRANKLIN, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 12:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in TAYLOR, IOWA
From 20-JAN-07 17:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in RINGGOLD, IOWA
From 20-JAN-07 17:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in BUTLER, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 12:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in POCAHONTAS, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in HUMBOLDT, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Snow in WRIGHT, IOWA
From 20-JAN-07 23:00:00 to 21-JAN-07 11:00:00 (CST-6)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter