Anybody have a guess where the national low temperature occurred Friday morning? Not that far away, Black River Falls, Wisconsin (just NE of La Crosse) plunged to 8 below zero. That is wicked but it is valley country and the light winds allowed the dense cold air to drain making it far colder there than in the surrounding high country.
Saturday the storm track levels off for a day allowing warmer air to make a quick return to the Midwest. For a change seasonal temperatures will take over and with mixed sun and clouds it should be a respectable November day. Highs should range from the mid 40s north to the mid 50s far south but it will be breezy. You can see the zonal nature of the jet allowing the moderation.
Here's the temperature departures Saturday. A nice tongue of warm air surging into western Iowa and Missouri.
Just about the time the really mild air arrives the jet sharply buckles and goes into this configuration Tuesday morning.
Look at the temperature departures that produces Tuesday.
In north-central Iowa readings are shown as much as 34 degrees below normal. In the graphic below you can see where the odds are near 100 percent that temperatures will be colder than 10 degrees Tuesday morning. These temperatures reflect little if any snow cover. If we can get an inch or two down, which some models suggest, record cold is a possibility.
Wind always makes the cold worse and the wind chills by Tuesday morning are projected zero to 10 below.
The cold does modify some mid-week but overall temperatures Monday-Friday will be well below normal. These are the 5 day departures ending next Saturday morning.
The other issue which is unfortunately still not well resolved is the prospect of some light snow behind the Arctic front Sunday night and Monday morning. Models seem to be having trouble keying on a specific short wave and are all over the board with snow amounts ranging from nothing to 2 to 4 inches. In all honestly I'm not seeing any impressive forcing that lasts for any period of time so QPF is likely going to be low, at the very best .15" of an inch in a narrow band. Here's the latest 0Z snowfall forecasts from Friday night.
The 12K NAM
As I was saying 24 hours ago I thought we would have better agreement in snow solutions Friday, Saturday at the latest. Well, we sure don't have much Friday night so I'm banking on Saturday to reveal the truth. My best guess now is more snow than what the US models show (basically flurries) but not as much as the EURO and Canadian. That leaves me with a 1 to perhaps 2" band of snow, most likely near and south of HWY 20 in my central and southern counties. We'll try and tighten it up for you by mid-day Saturday. Until then, roll weather...TS
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