Minneapolis weather: 60 degrees possible Sunday - KMSP-TV

FACT OR FICTION: 60 degrees possible Sunday

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Meteorologist Cody Matz Meteorologist Cody Matz

You read that right -- we have a chance to hit 60 degrees for the first time this weekend since October 13 (for those counting that's nearly 6 months ago or 168 days).

Let's just agree it's been a long time. But will we actually get there?

Conditions look favorable for some warm temperatures Sunday, but there are a few concerning variables that may keep us from getting to that coveted mark.

Now let me be clear, it's not going to be cold on Sunday, and it looks like it is pretty much a lock for the warmest day we have seen since early November when temperatures were in the low to mid 50's. But lack of mixing, cloud cover, and a Monday storm shift, could all prevent us from hitting 60 and just keeping us in the that 53 or 54 degree area.

Let me explain...

First off, it's likely a mystery to many of you how we even know what the temperature will be like on a day to day basis. Sure there's climatology to tell us what the average temperatures are like on any given day, but where do we begin?

Well, we begin with MOS. It's an acronym that stands for Model Output Statistics. Super computers run their programs to forecast the weather for the next 48 hours. From those, numerical statistics are spewed out of these supercomputers with 3 hour time slots of temperature, dewpoint, cloud cover, precipitation, and a host of other variables.

These are what we call climatologically based data that takes into account the current season, ground temperature, snow cover, etc...and influences the raw model data to spew out a forecast based on the information that comes from the computer model combined with data on current conditions and time of year. This is where we start to analyze just how warm or cold our days will be.

The actual data from the 12Z model run is listed below from 2 separate computer models.

There is a lot of data here so let me direct your eyes to the information I want you to focus on. The five numbers circled in both images are the 12 hour highs and lows (our daily highs and lows).

For example, the first number is 21 on the top image with the number 22 on the bottom image. So these 2 models think that our low Friday night will be 21 and 22 degrees. But look at 4 numbers in...one model says 54 and the other says 55. That means these models think the high temperature on Sunday will be 54 and 55 degrees...surprisingly similar.

Model opinions can vary wildly. I have seen them as much as 25 degrees apart… which to say the least leads to a very tough forecast. So if these 2 models think that the high will be either 54 or 55 degrees, why is there a possibility of hitting 60? There are several reasons;

1. Model Output Statistics do very well with "normal" conditions for any given time of the year which involve small temperature changes and climatologically average temperatures. Since the average temperature this time of year is 48°, it will sway anticipated warmer highs cooler and anticipated cooler highs warmer.

2. "Junk in gets junk out". MOS data have been having a really rough time the last couple of months because initial conditions have been off with the models thinking we have too little snow on the ground, and now that it has mostly melted, too much. The typical meteorological saying is "if you put junk into the model, you will get junk to come out of it." This just basically means that if the initial conditions going into the model are incorrect, then your product coming out of your model will likely be incorrect as well.

3. You can often judge a model run by how far off it is by comparing it to the first conditions that are listed. The first conditions are located on the far left column starting with 18, which stands for 18Z, or 1pm CDT. If you look at the number directly below that one it is the temperature. The first image shows a temperature of 32° and the second one shows 34°, but the actual air temperature at 1pm today was 37°. It doesn't take a genius to realize those number are different and that both models are too cold. This is an indicator of how this particular model run will lean. In this case, likely too cold, which means those 54's and 55's might just be 58's or 59's on Sunday.

I know all of us would like a nice warm sunny and calm day this time of year, but in reality, that just doesn't happen. The nice warm and sunny part can, but it often comes with a bunch of wind. But what you may not realize is it's the wind that's actually allowing the temperatures to be so warm. Mixing is an important part of how temperatures at the surface warm. It allows compression of air flowing down to the surface to heat up the air parcel and give us a warmer day. Without these winds, temperatures can fall 5, 10, or even 25 degrees short of what otherwise would occur if winds were strong enough. Well, the winds may not be strong enough to maximize mixing Sunday which would ultimately keep us cooler than we otherwise would be. Check out the temperatures and wind speeds 5000 feet above the surface early Sunday morning.

You can see mild temperatures and those wind barbs show a southwest wind of nearly 50 knots. That's perfect! But as the day progresses, a strong low pressure begins to develop in Colorado (our next storm for Monday) which forces winds to calm and turn around out of the north.

You can see that late in the afternoon, temperatures at 5000 feet are cooler, and the wind barbs are just simple lines and are going in every direction meaning they have slacked AND are starting to shift northerly. This would effectively cutoff any potential mixing with warmer air aloft and could prevent us from getting to 60.

Our next storm will also start producing cloud cover sometime on Sunday. IF the clouds roll in a few hours early, this would cool off our very warm day as well. So there are many things working toward a warm day, but also just as many working against. Who wins?? I guess we will know on Sunday. Enjoy!!

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