Bill Schintler
EF4
Two winter storms will affect much of Iowa over the next few days. The first will begin by early evening today and bring one to three inches of “light fluffy†snow to much of Iowa before ending Monday morning, with heaviest amounts generally occurring north of a line bisecting the state from Southwest to Northeast. Blowing snow will not be an issue given light winds. After a quiet day Monday, the “main event†arrives during the day Tuesday. Some areas may see a foot of snow, in addition to gusty winds resulting in blowing and drifting of the snow. Updates for that system will be forthcoming. Below is time of arrival and total snow accumulation for tonight’s event for specific locations in central and eastern IA:
Cedar Rapids, IA (Eastern IA Airport):
Snow will start after 5:30 PM and accumulate to 1.7 inches.
Iowa City, IA:
Snow will start after 6:20 PM and accumulate to 1.0 inches.
North Linn Co., IA (Paris and Coggon):
Snow will start after 5 PM and accumulate to 2.0 inches.
Marengo, IA:
Snow will start after 5 PM and accumulate to 2.0 inches.
Union, IA:
Snow will start after 4 PM and accumulate to 2.5 inches.
Discussion:
A surface boundary has been slowly sliding through central IA from the NW, and has pushed through all but the southeast corner of the state as of 16Z. This feature will slow as a wave approaches from KS. Isentropic lift will increase throughout the day as moisture pushes northward ahead of the developing system. The column saturates from top down by late afternoon, and by Sunday evening snow will be widespread across the area with strongest Q-vector convergence and isentropic lift persisting between 00 and 09 Z. A zone of H7 UVM in excess of -10ub/s travels across the southern half of the state between 21Z and 03Z. During the same period, a zone of mid-level frontogenesis develops along and N of US-30. Snow ratios should range from 12 to 15/1 given SREF guidance and surface temperatures in the mid-20’s.
Models have come into decent agreement with the 12Z runs. Earlier output, especially the NAM, had suffered from latent heat feedback issues which appears to be resolved. The H7 shortwave will travel across the area fairly quickly, which may impact the width of heaviest snowfall axis. One or more bands of enhanced snowfall may result, most likely between US-20 and US-30 across eastern IA.
- bill s
11:05 AM CST, 12/06/09
Cedar Rapids, IA (Eastern IA Airport):
Snow will start after 5:30 PM and accumulate to 1.7 inches.
Iowa City, IA:
Snow will start after 6:20 PM and accumulate to 1.0 inches.
North Linn Co., IA (Paris and Coggon):
Snow will start after 5 PM and accumulate to 2.0 inches.
Marengo, IA:
Snow will start after 5 PM and accumulate to 2.0 inches.
Union, IA:
Snow will start after 4 PM and accumulate to 2.5 inches.
Discussion:
A surface boundary has been slowly sliding through central IA from the NW, and has pushed through all but the southeast corner of the state as of 16Z. This feature will slow as a wave approaches from KS. Isentropic lift will increase throughout the day as moisture pushes northward ahead of the developing system. The column saturates from top down by late afternoon, and by Sunday evening snow will be widespread across the area with strongest Q-vector convergence and isentropic lift persisting between 00 and 09 Z. A zone of H7 UVM in excess of -10ub/s travels across the southern half of the state between 21Z and 03Z. During the same period, a zone of mid-level frontogenesis develops along and N of US-30. Snow ratios should range from 12 to 15/1 given SREF guidance and surface temperatures in the mid-20’s.
Models have come into decent agreement with the 12Z runs. Earlier output, especially the NAM, had suffered from latent heat feedback issues which appears to be resolved. The H7 shortwave will travel across the area fairly quickly, which may impact the width of heaviest snowfall axis. One or more bands of enhanced snowfall may result, most likely between US-20 and US-30 across eastern IA.
- bill s
11:05 AM CST, 12/06/09
