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An amazing (at times record breaking) stretch of award winning weather has finally run its course here in the Midwest. Thanks to a strong cold front the warmth, sunshine, and dry weather of the the past two weeks is in the process of doing an about face. Just to recap, here's the 10 day temperature departures going back to Halloween.

Throw in the 14 day rainfall, which in many areas was a trace or less, and it's clear to see we have won the lottery.

These are the highs the past 7 days in Cedar Rapids. My research indicates this is the first time with 7 consecutive days in the 70s during the month of November

The 7 day temperature departure averaged 20 degrees above normal per day!

That big arc of clouds on the satellite is the front that brings a reality check to all areas by late afternoon Tuesday.

The change was already well underway in NW Iowa Monday evening where snow was falling and temperatures were down in the low 30s. This graphic shows the wind chills at 6:00 PM ranging from 20 NW to 70 SE. In other words, it felt 50 degrees warmer in the southeast third of the state.

If you notice just off the NW tip of Iowa, temperatures Monday night are 40 degrees colder than just 24 hours earlier.

By now I'm sure you guessed where this is leading. However, of you are in the southeast half of my area you will have the morning and part of the afternoon to enjoy another day of warmth before the cold settles in. These are the forecast temperatures around 2:00 PM Tuesday afternoon.

The reason for the big contrast is a surface low riding the jet into EC Iowa. East of it you have spring like warmth and to the west you have winter.

This type of contrast combined with some healthy November shear could set the stage for some active thunderstorms Tuesday, especially over far southeast Iowa and western Illinois (roughly the Mississippi east). While SPC currently has only a slight risk they do show a 5% chance of a tornado. If instability ends up being higher than expected the threat could increase. We will need to keep an eye on morning trends.

As for rainfall, it will be heaviest NW of the low pressure track in my NW counties. However, if we can get some decent convection to pop heavier totals may be realized in swaths further east. Here's what the GFS shows for totals.

The EURO has this for the same time period.

Snow will pile up over NW Iowa into Minnesota and NW Wisconsin. Travel will be impacted if you are headed in that direction. As far as totals go, the GFS has this.

The EURO is similar with this.

It is a given that following the passage of the storm, readings will be much colder Wednesday with highs in the 40s areawide. A change of seasons for sure! Roll weather...TS

By the way, pre-sales continue for my new book Derecho 911, Iowa's Inland Hurricane. Order now and you can get yourself a discount on this historic Midwest storm. Click on the link below to get your copy or find out more about the content of this coffee table type book. It's color with more than 100 pictures and diagrams.