© 2019 Terry Swails

THE TABLE IS SET FOR SOME ACTIVE MIDWEST WEATHER...

February 6, 2020

Some parts of my area and the central Midwest are scooping up some fresh snow while others, as expected NW of the Quad Cities, didn't even see a flake. From the looks of things we are now going into what has the potential to be an active period for much of the next 10 days. 

 

One thing that is interesting and points to that possibility, is the MJO (Madden Julien Oscillation). The EURO is forecasting it to go into phase 5 and wander around there for an extended period of up to 10 days. See the dotted green lines below.

In the graphic above I also inserted the phase 5 precipitation analog which shows above normal amounts all around my area and the central Midwest. It makes sense that such a prolonged stay in 5 would yield the potential for significant amounts, with the heaviest totals dependent on the precise position of the storm track.

 

Something that always plays and important role in the development of storms and where they travel is the storm track. Below you can see the 500mb flow February 13th is aligned in a strong southwest flow. A big ridge in the Atlantic and a deep trough over the west.

If you know anything about weather you know that's going to do 2 things. One draw moisture. Two, it's going to create a sharp baroclinic boundary right over the Midwest where the fight for supremacy will be on between cold air to the NW and warm moist air to the SE. Here's a perfect example of what I'm talking about. These are the temperature departures forecast off the GFS February 13th. The largest negative departure is -50 and the greatest positive departure is +25.   

Notice too the alignment is north south from Wisconsin and Iowa into Arkansas. That means the boundary is not moving much. That could allow multiple systems to travel along it  each with abundant moisture to work with. In this graphic you can see that water vapor over the SE is 325% above normal levels.

The end result is likely to be above normal precipitation as the MJO analog suggests. The GFS shows this for total precipitation the next 16 days.Some places in northern Iowa into SW Wisconsin are shown with up to 2.5".

These are the departures which in my are are 1/2 to 1" above normal for that 16 day period. That would not be that big in summer but for the first half of February those are substantial deviations. Some places in the southeast actually have an anomaly of 10.9". I can tell you right now that if that verifies serious flooding would be the end result and that part of the country could be headed for a high end flood event.

The other factor which will come into play are temperatures at 5,000 feet. (850mb). We care about that level because that's where we determine the critical thickness levels for snow, mixed precip, or rain. An 850 temperature of 0 or colder usually gets you snow. In the graphic below the freezing line (0 degree temperature) February 13 is cutting from NW Missouri through SE Iowa and across northern Illinois. At that time snow would be be the dominate precipitation type to the NW, rain to the SE and mixed types along that border.

For my area that implies the potential for a variety of precipitation types depending on location. That's something that will need to be determined with each individual system as that line is going to vacillate back and forth. For those that can stay below the zero 850 threshold this could be a very snowy period for some part of the upper Midwest.

 

In the 4 panel graphic below you can see over the next 16 days precipitation by type. In my area all 4 varieties of rain, ice pellets, snow, and freezing rain are shown at some point in the period.

This is of course all predicated on the models being right but they have exhibited good consistency in their depiction of the overall pattern. I will be very interested to see how the MJO precip analog works out for phase 5.

 

Going forward there are a couple systems in the works for the weekend. The first one is likely to have little to no impact in my area but some light snow showers or flurries are possible Friday as it scoots southeast. The GFS shows this for accumulations at a 10:1 ratio. They will be much higher so double what you are seeing.

The second system late Saturday night/Sunday looks more impressive with the potential for some significant accumulations, especially north of HWY 20 in NE Iowa and into southern Minnesota and Wisconsin. Further south, some light snow or a rain snow mix is possible but amounts will be much lighter. The track is still in doubt so it will take another day or so to hash it out. These are the raw preliminary model numbers which will likely decrease in future runs. I think the northern solution of the EURO will ultimately win the day.

 

The EURO.

The GFS

The Canadian GEM...by far the outlier being so far south!

Again, the numbers on the late weekend system is very preliminary and subject to change. Just wanted to give you a glimpse of what is currently on the table. Have a fine day and roll weather...TS

Share on Facebook
Share on Twitter
Please reload

ARCHIVED POSTS
Please reload

RECENT POSTS
Please reload