© 2019 Terry Swails

LOTS OF ACTION, JUST AS MUCH UNCERTAINTY...

February 7, 2020

In my post yesterday I talked about how the potential was increasing for active winter weather in the Midwest in the coming 2 weeks. The general tends have been leaning that way but for every solid model run in favor, it seems the following one has evidence against it. The constant flip flopping is frustrating and  a long standing issue for guys like me this winter. One of the things I've noticed today is that forecasters at the Climate Prediction Center have issued a high risk of hazardous temperatures February 14-20th just to our northwest.

A point I've been pounding home the past 2 weeks is that the models have been pushing the idea of a ridge forming near Alaska that would send the EPO (Eastern Pacific Oscillation) negative. To me that's the only way to get cold air of any magnitude into the Midwest.  A second bonus would be if the AO (Arctic Oscillation) also goes negative. Together, that strongly stacks the deck for Arctic air to make a push. Look what the GFS ensembles show. A negative EPO and AO. Mmmm, that is very interesting and part of what CPS is seeing with its risk assessment of cold.

 

The EPO

The AO

I cant recall the last time I saw those two teleconnections in sync in a negative way. So does this actually happen? I will say that many times something like this has been advertised and never really comes to fruition. I am skeptical of how cold it ever gets based on the amount of false alarms this year and the MJO's reluctance to get out of warm phases.

 

Clearly the 18Z GFS is running with the bulls when it comes to cold. The GFS ensemble shows temperature departures from normal that look like this February 14th.

That shot comes and goes and seeds the the way for a second blast out 16 days. The departures with that are even worse as they surge toward the Midwest February 22nd.

All I can say is that there is plenty of evidence to introduce significant cold in the 5-15 day period. However, I'm not ready to get on the wagon yet. Nothing seems reliable or stable regarding pattern recognition, teleconnections, or short term trends this year. It's one of the toughest in recent memory for me to get a handle on.

 

Enough of that! There are a couple issues on the table this weekend and here's what we have to look forward to.

 

1. Late Friday light snow event in the far southwestern parts of my area.

 

A weak system is set to move southeast across the area Friday/Friday evening. It's moisture starved but has the potential to kick up 1/2 (to perhaps 1") of snow in a few spots. The main potential seems to be west of a line running from near Waterloo to Burlington. Little if any snow is expected northeast of there as dry air wins the war.. Again this is just another nickle and dime event that's more of a nuisance than anything else for those of you who see it. Here's what the EURO shows for snow accumulations Friday/Friday night.

2. A stronger snow/rain system late Saturday night and parts of Sunday.

 

A strong clipper like system is shown arriving late Saturday night and especially Sunday morning into early afternoon. The big question with this is track. The EURO is the furthest north and keeps accumulations in the 1-3" range near and north of HWY 20. 1 inch amounts closer to HWY 30. Much heavier than that in far northern Iowa. I prefer this track of the 3 major models. By the way, the EURO did shift a bit further south on the latest run,.

The GFS is further south (as it has been) and gets the 4" line to HWY 30. It shows 6" and up HWY 20 north. All I can say is it's the GFS, Hard to put much stock in that model.

Last but not least the Canadian. It's the furthest south and dumps on much of the area north of I-80. It did show some movement north in its latest run. Few times does this model rule the day but in recent weeks its skill scores are actually higher than the GFS. I still don't trust it.

Interesting enough, all of these models have been fairly consistent on their solutions the past several runs. I like the fact the EURO did a little shift south and the Canadian made a nudge north. Maybe the EURO is still a bit far north but in the end it makes the most sense and I suspect it is the winner. It's the king for a reason.That's the model I'm leaning on.

 

So, what I am saying with this system is that at this point in the game there could be some light accumulations down to HWY 30, that's about where the 1" line seems most realistic. I think the worst of it starts close to HWY 20 (1-3" there) and quickly gets progressively heavier going north. Hopefully we'll get some tighter consistency by tomorrow. Who knows, maybe it goes even further north which really eases the burden on my immediate area. That's possible too.

 

Needless to say this is a fluid situation and at the very least subtle changes will take place. Anywhere north of HWY 30 late this weekend needs to keep an eye on the trends. For sure there will be Winter Storm Watches out at some point Friday for northern Iowa and southern Minnesota and Wisconsin, More to come. Roll weather...TS

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