Bill Schintler
EF4
Winter Weather Discussion - Iowa
A strong winter storm will bring significant snowfall to much of eastern Iowa starting late Sunday morning and lasting into Monday morning. Snowfall will remain light until late Sunday afternoon. Rain will mix in with the snow in southeastern IA, during the first half of the storm during the day Sunday, reducing snowfall totals there. This will be a “wet, heavy†snow in most areas, which should not blow around much compared to other recent snowfalls as the storm departs and winds increase. Below are forecasts for specific locations in central and eastern IA:
Cedar Rapids, IA (Eastern IA Airport):
Snow will start at 12:30 PM Sunday. Total accumulation by Monday morning: 4.8 inches.
Iowa City, IA:
Snow will start at 11:30 AM Sunday. Total accumulation by Monday morning: 5.5 inches.
North Linn Co., IA (Paris and Coggon):
Snow will start at 12:45 PM Sunday. Total accumulation by Monday morning: 4.0 inches.
Marengo, IA:
Snow will start at noon Sunday. Total accumulation by Monday morning: 5.0 inches.
Union, IA:
Snow will start at 2:45 PM Sunday. Total accumulation by Monday morning: 3.7 inches.
Discussion:
UA analysis indicates a shortwave over NM and eastern AZ. This energy was poorly sampled by the earlier 12Z soundings, leading to larger then usual uncertainty in the track of the system over recent runs of most models. The northern stream long-wave trough axis was centered over ID, with southwesterly H5 flow over much of the central CONUS and terminating into a low amplitude ridge over the Great Lakes. These features phase over the Upper-Midwest between 00Z-12Z, To further complicate things, various other compact pieces of energy were pin wheeling around the main trough. Of lesser consequence was an H7 shortwave over western lake Superior. Radar at 03:24Z indicated elevated returns S of I-80 over IA, with no IA SFC stations reporting precipitation… At the SFC, light snow had expanded N to only Kansas City. 00Z UA charts indicated weak isentropic upglide along roughly the 292-297K surfaces.
Isentropic lift increases tonight, with snow expanding across northern MO; further north in IA, dry northerly mid-level flow (5-8 kft) will keep precipitation at bay through Sunday morning. Models indicate the H85 low will slowly deepen as it tracks E through northern MO. Recent models have trended towards a more southerly track of the SFC and H85 lows.
Ample moisture is available, with precipitable water currently in excess of 0.8 inches from northeastern TX and eastern OK; well above normal for this time of year. The 00Z H85 chart indicates 6-8C dewpoints over much of the TX Red River area. This moisture will advect north with time as a LLJ increases to 40 kts E of the H85 low Sunday. A negating factor heavy snowfall totals will be low snow-water ratios, especially south of I-80 until CAA increases Sunday afternoon.
Looking ahead, an arctic front will drop northeast into the area Tuesday. An associated mid-level shortwave will bring light snow, with limited moisture.
- bill s
9:33 PM CST, 02/20/10
A strong winter storm will bring significant snowfall to much of eastern Iowa starting late Sunday morning and lasting into Monday morning. Snowfall will remain light until late Sunday afternoon. Rain will mix in with the snow in southeastern IA, during the first half of the storm during the day Sunday, reducing snowfall totals there. This will be a “wet, heavy†snow in most areas, which should not blow around much compared to other recent snowfalls as the storm departs and winds increase. Below are forecasts for specific locations in central and eastern IA:
Cedar Rapids, IA (Eastern IA Airport):
Snow will start at 12:30 PM Sunday. Total accumulation by Monday morning: 4.8 inches.
Iowa City, IA:
Snow will start at 11:30 AM Sunday. Total accumulation by Monday morning: 5.5 inches.
North Linn Co., IA (Paris and Coggon):
Snow will start at 12:45 PM Sunday. Total accumulation by Monday morning: 4.0 inches.
Marengo, IA:
Snow will start at noon Sunday. Total accumulation by Monday morning: 5.0 inches.
Union, IA:
Snow will start at 2:45 PM Sunday. Total accumulation by Monday morning: 3.7 inches.
Discussion:
UA analysis indicates a shortwave over NM and eastern AZ. This energy was poorly sampled by the earlier 12Z soundings, leading to larger then usual uncertainty in the track of the system over recent runs of most models. The northern stream long-wave trough axis was centered over ID, with southwesterly H5 flow over much of the central CONUS and terminating into a low amplitude ridge over the Great Lakes. These features phase over the Upper-Midwest between 00Z-12Z, To further complicate things, various other compact pieces of energy were pin wheeling around the main trough. Of lesser consequence was an H7 shortwave over western lake Superior. Radar at 03:24Z indicated elevated returns S of I-80 over IA, with no IA SFC stations reporting precipitation… At the SFC, light snow had expanded N to only Kansas City. 00Z UA charts indicated weak isentropic upglide along roughly the 292-297K surfaces.
Isentropic lift increases tonight, with snow expanding across northern MO; further north in IA, dry northerly mid-level flow (5-8 kft) will keep precipitation at bay through Sunday morning. Models indicate the H85 low will slowly deepen as it tracks E through northern MO. Recent models have trended towards a more southerly track of the SFC and H85 lows.
Ample moisture is available, with precipitable water currently in excess of 0.8 inches from northeastern TX and eastern OK; well above normal for this time of year. The 00Z H85 chart indicates 6-8C dewpoints over much of the TX Red River area. This moisture will advect north with time as a LLJ increases to 40 kts E of the H85 low Sunday. A negating factor heavy snowfall totals will be low snow-water ratios, especially south of I-80 until CAA increases Sunday afternoon.
Looking ahead, an arctic front will drop northeast into the area Tuesday. An associated mid-level shortwave will bring light snow, with limited moisture.
- bill s
9:33 PM CST, 02/20/10
