Bill Schintler
EF4
Another in a series of winter weather systems will bring a mixture of precipitation to the Upper-Midwest towards the end of the weekend. The first wave will bring light snow and freezing rain to the east-central Iowa area. This will be followed by a lull in the precipitation during the morning hours on Monday, and then cold rain will fall Monday afternoon, possibly accompanied with thunder and small hail south of I-80. Following are specific point forecasts for locations in east-central Iowa:
Cedar Rapids:
Snowfall will start at 5:30 PM Sunday afternoon and accumulate to 0.8 inches before changing over to light freezing rain at 10 PM. Freezing rain will accumulate to a few hundredths of an inch before it ends at 11 PM and shouldn’t cause more then minor travel problems. On Monday, rain will develop during the mid-day hours and continue until after Midnight Tuesday. Expect 0.25 inches of rainfall.
Iowa City:
Snowfall will start at 4:00 PM Sunday afternoon and accumulate to 1.2 inches before changing over to light freezing rain at 8 PM. Freezing rain will accumulate to a few hundredths of an inch before it ends at 11 PM and shouldn’t cause more then minor travel problems. On Monday, rain and a few thunderstorms will develop during the mid-day hours and continue until after Midnight Tuesday. Expect 0.25 inches of rainfall.
Marengo:
Snowfall will start at 3:45 PM Sunday afternoon and accumulate to 1.0 inches before changing over to light freezing rain at 7:30 PM. Freezing rain will accumulate to a few hundredths of an inch before it ends at 10 PM and shouldn’t cause more then minor travel problems. On Monday, rain and a few thunderstorms will develop during the mid-day hours and continue until after Midnight Tuesday. Expect 0.25 inches of rainfall.
Paris/Coggon:
Snowfall will start at 5:45 PM Sunday afternoon and accumulate to 0.6 inches before changing over to light freezing rain at 10:30 PM. Freezing rain will accumulate to a few hundredths of an inch before it ends at 11 PM and shouldn’t cause more then minor travel problems. On Monday, rain will develop during the mid-day hours and continue until after Midnight Tuesday. Expect 0.25 inches of rainfall.
Synopsis:
UA charts indicated a number of disturbances ejecting ahead of a broad WRN CONUS trough. The first S/WV brought a few inches of SN to ERN IA earlier today, and this system appears to have been associated with forcing in the left-exit region of a 130kt H3 max and isentopic lift along the 290K SFC and had little in the way of a SFC reflection. Looking upstream, WV imagery and the H5 chart indicated disturbances over CO and WA/NRN CA. MDLS have a good handle on these features. The SFC map was relatively featureless, with moderating temperatures over IA despite weak NWRLY flow and high pressure. A pressure rise bulls-eye was noted over IL.
Discussion:
This is a difficult FCST due to uncertainty of timing and type of winter precipitation and possibly convective precipitation on Monday. The effect of the CO S/WV arrives in the area Sunday afternoon, with precipitation starting as SN from SW to NE. Forcing will be strong but brief as the left-exit region of a 90kt H3 speed max with attendant QG-forcing and isentropic up glide translates through the area. FCST soundings indicate a transition to FZ RA by mid evening, by which time the strongest forcing and QPF will have moved E of the area. ULVL ridging and subsidence will follow and then the main trough will arrive Monday afternoon, bringing a prolonged period of rain with isolated thunderstorms. Moisture will be plentiful as a 50kt LLJ noses into the area during this period. Elevated instability will result from steepening mid-level lapse rates to 7C/km. Small hail will be possible in any vigorous updrafts Monday afternoon in an environment consisting of impressive LLVL helicity and deep-layer shear, especially S of I-80.
- bill
10:00 PM CST, 02/02/08
Cedar Rapids:
Snowfall will start at 5:30 PM Sunday afternoon and accumulate to 0.8 inches before changing over to light freezing rain at 10 PM. Freezing rain will accumulate to a few hundredths of an inch before it ends at 11 PM and shouldn’t cause more then minor travel problems. On Monday, rain will develop during the mid-day hours and continue until after Midnight Tuesday. Expect 0.25 inches of rainfall.
Iowa City:
Snowfall will start at 4:00 PM Sunday afternoon and accumulate to 1.2 inches before changing over to light freezing rain at 8 PM. Freezing rain will accumulate to a few hundredths of an inch before it ends at 11 PM and shouldn’t cause more then minor travel problems. On Monday, rain and a few thunderstorms will develop during the mid-day hours and continue until after Midnight Tuesday. Expect 0.25 inches of rainfall.
Marengo:
Snowfall will start at 3:45 PM Sunday afternoon and accumulate to 1.0 inches before changing over to light freezing rain at 7:30 PM. Freezing rain will accumulate to a few hundredths of an inch before it ends at 10 PM and shouldn’t cause more then minor travel problems. On Monday, rain and a few thunderstorms will develop during the mid-day hours and continue until after Midnight Tuesday. Expect 0.25 inches of rainfall.
Paris/Coggon:
Snowfall will start at 5:45 PM Sunday afternoon and accumulate to 0.6 inches before changing over to light freezing rain at 10:30 PM. Freezing rain will accumulate to a few hundredths of an inch before it ends at 11 PM and shouldn’t cause more then minor travel problems. On Monday, rain will develop during the mid-day hours and continue until after Midnight Tuesday. Expect 0.25 inches of rainfall.
Synopsis:
UA charts indicated a number of disturbances ejecting ahead of a broad WRN CONUS trough. The first S/WV brought a few inches of SN to ERN IA earlier today, and this system appears to have been associated with forcing in the left-exit region of a 130kt H3 max and isentopic lift along the 290K SFC and had little in the way of a SFC reflection. Looking upstream, WV imagery and the H5 chart indicated disturbances over CO and WA/NRN CA. MDLS have a good handle on these features. The SFC map was relatively featureless, with moderating temperatures over IA despite weak NWRLY flow and high pressure. A pressure rise bulls-eye was noted over IL.
Discussion:
This is a difficult FCST due to uncertainty of timing and type of winter precipitation and possibly convective precipitation on Monday. The effect of the CO S/WV arrives in the area Sunday afternoon, with precipitation starting as SN from SW to NE. Forcing will be strong but brief as the left-exit region of a 90kt H3 speed max with attendant QG-forcing and isentropic up glide translates through the area. FCST soundings indicate a transition to FZ RA by mid evening, by which time the strongest forcing and QPF will have moved E of the area. ULVL ridging and subsidence will follow and then the main trough will arrive Monday afternoon, bringing a prolonged period of rain with isolated thunderstorms. Moisture will be plentiful as a 50kt LLJ noses into the area during this period. Elevated instability will result from steepening mid-level lapse rates to 7C/km. Small hail will be possible in any vigorous updrafts Monday afternoon in an environment consisting of impressive LLVL helicity and deep-layer shear, especially S of I-80.
- bill
10:00 PM CST, 02/02/08
