11:00am Weather Update

If you step outside in the Midwest it may be hard to believe that we could be dealing with severe thunderstorms late tonight and early Monday morning.

Temperatures at 11am CT range from the 30°'s and 40°'s across Illinois, Indiana, Kentucky and Missouri. However, this will change later today as a warm front lifts through the Midwest. Behind the warm front, warmer, more moist air will begin to stream north on southerly winds. Temperatures are already beginning to climb in eastern Oklahoma, southeast Kansas and southwest Missouri.

The main threat for those of you in Indiana, Illinois and Missouri will be strong damaging winds with a line of storms that moves through late tonight and through the early AM hours Monday. The low-level jet stream is forecast to bring strong winds closer to the surface. The image below shows you a slice of the atmosphere.

(Click the image to see a larger version.)

The winds are forecast to hit 55 knots to 62 knots at 1,500 feet to 2,000 feet. Any thunderstorm moving through that environment will have the potential of tapping in to the wind and brining it down to the surface. (The above image is for Cape Girardeau, Missouri.)

Now there is going to be a larger threat for tornadoes for part of the Mississippi Valley. They could occur anywhere from northern Mississippi to western Kentucky and parts of southeast Missouri (towards the bootheel).

Often times I like to pick out an initial chase target of where I would go if I were storm chasing the event. Let me first say that tonight I AM NOT chasing nor do I recommend ANYONE chasing tonight as the conditions will not be safe. As for my target... After looking over weather data from the morning computer model runs, I am liking an area in eastern Arkansas. Somewhere between Searcy --> Newport --> Wynne.

Later today I am going to post a page that will allow you to look at radar images from the St. Louis radar, the Paducah radar and the Memphis radar. The images will update every 4-6 minutes as we go through the night.

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Threat of Storms Continues

The Storm Prediction Center has expanded the "Moderate Risk" and "Slight Risk" areas in the latest outlook.


Storms should arrive this evening for eastern Missouri and move east overnight. Damaging wind and tornadoes main threat.

Have a way to be alerted to severe weather warnings overnight. If you have a NOAA Weather Radio, be sure it is working and the batteries are still good.

Also remember to go over your severe weather plan with your kids in case of a tornado warning. Better to be prepared now than not being prepared when it happens.


- Posted from my iPhone

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Severe Thunderstorms Sunday

Looking over weather data for tomorrow evening. The potential exists for severe thunderstorms Sunday across southeast Missouri, southern Illinois, western Kentucky, northwest Tennessee, northeast Arkansas and southern Indiana.

The Storm Prediction Center has the area below shaded in yellow for a "Slight Risk" for seeing severe thunderstorms.

I wouldn't be surprised to see SPC upgrade parts of the "Slight Risk" to a "Moderate Risk" when their new forecasts come out tomorrow.

The best window of opportunity for severe storms appears to be from 5pm - 10pm for the KFVS viewing area.

Now is a good time to review your severe weather plan. What do you do if a Severe Thunderstorm Warning is issued? What do you do if a Tornado Warning is issued? Is your NOAA Weather Radio turned on? Do the batteries need replaced? It's always better to think about these things ahead of time instead of afterwards.

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2:00pm Weather Update

Warm air is beginning to transport northeast across Indiana. Yes, I said warm air, however you aren't likely to feel it. The warm air is around 3,000' - 5,000' feet above the surface of the earth.

(Click the image to see a larger version.)

Temperatures across Indiana at the surface are well below freezing. The freezing line is located from approximately Louisville to Mt. Vernon, Illinois.

(Click the image above to see a larger version.)

You can see the surface temps in the image above. The temperature is located to the upper left of the dot at each location. The lower left indicates the dew point temperature. The yellow lines are temperature contours that try to fill in "between the dots".

So far the "storm" is behaving as expected. There was a brief little burst of moisture for north central Indiana earlier. This is now waning and there will be a lull for several hours. I expect moisture to fill back in later this evening. For the Indianapolis area, I expect moisture to begin to move back in between 7:00pm and 10:00pm ET.

Contrary to what you may be hearing in some forecasts, I don't believe the Indianapolis metro area is going to see any snow. All of the moisture should fall as freezing rain. The mid-levels of the atmosphere will not have enough cold air to support snow. At best, it may change over to a little sleet but as I said, most, if not all, of it will fall as freezing rain.

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Freezing Rain Tonight

It is beginning to look more and more like parts of the Midwest will see freezing rain and/or freezing mist beginning later today.

At 11:00am CT, temperatures are cold across the Midwest with temperatures ranging from the single digits to the middle 20's. Dew points are very low ranging from below zero to the middle teens. Dew points that low indicates we are talking about an arctic air mass.

The above data shows that it is cold enough at the surface to freeze any kind of moisture falling out of the sky. However, the air a few thousand feet in the sky is something to note.

Right now, at 850mb, or 5,000', the temperature is -3° to -5° over central Indiana. However, forecast models are indicating warmer air will surge northeast and temperatures will go above freezing from Indianapolis south by 6:00pm ET to 8:00pm ET.
Having the warm air aloft is key as to what type of precipitation will fall. The warm layer will allow any snow to melt until it encounters the below freezing temperature. Since that below freezing air is at the surface, that usually means we are talking about freezing rain. Freezing rain is rain that freezes on contact with the ground.

It is looking like the moisture will start to reach the ground starting around 7:00pm ET - 8:00pm ET. This will coincide with the warm layer of air moving overhead. If by chance the moisture begins earlier, before the warm layer moves overhead, the precipitation will start as snow changing to sleet and eventually freezing rain.

Who will see what? I think from Indianapolis and south will be dealing mainly with freezing rain. Places around Carmel and Westfield will be near the line of where it will be a sleet/snow/freezing rain. North of that area, places like Lafayette, Muncie, Kokomo, should be all snow.

How much freezing rain am I talking about? Forecast models are suggesting anywhere from 0.02" to as much as 0.23". That will be enough to make roads slick and hazardous later tonight. If the higher side turns out to be true, I wouldn't be surprised if there were a few minor electrical grid problems.

It also appears we could see some light freezing rain/mist around the St. Louis area beginning late this afternoon or early this evening. The amount should be light. Probably less than 0.07" but nonetheless, it could put a small glaze over roads.

Be sure to follow me on Twitter (@johndissauer). Often times I will tweet out thoughts concerning weather events before composing a post for the blog.

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Thursday Afternoon Update

We still have several hours to go before the snow ends from west to east across the Midwest. I still feel pretty confident in the forecast that was posted last night.

• Cape Girardeau: 0.75” – 1.5”
• Columbus (IN): 1” – 2”
• Chicago: 7” – 9” (I think there can be localized 10”+ amounts.)
• Indianapolis: 2” – 4” (2” to 3” through the city. 3” to 4” on the north side near Carmel and Westfield.)
• St. Louis: 2” – 3”

In order for the snow to come to an end we need the upper-level low to move out of the Midwest.


You can see the upper-level low depicted in the image above. (Click on the image to see a larger version.) It is currently centered over northeast Missouri. The low and associated ripples of energy riding around it will help spark snow showers and snow bands through the evening and overnight hours (east of the Mississippi River).

As expected, temperatures are much colder than advertised by the computer models. The models were keeping temperatures in the lower to middle 20’s for today. Reality shows that temperatures are in the middle and upper teens over Missouri and central/northern Illinois as of 3:00pm CT.

Temperatures this cold will allow snow to come down as the result of high snow-to-liquid ratios. I think places in Missouri will now see ratios of 17:1 to 19:1. What does that mean? That means that the snow will be drier, fluffier and it won’t take much liquid to produce accumulations.

Again, snowfall amounts remain on track with what I’ve been forecasting for the last day or two.

- Posted from my iPhone

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Wednesday Night Update

Just getting a chance to look over the data from the evening computer model runs. A couple of the models are trying to back off (a little) on the moisture available to crank out snow. Could this impact snow amounts? Good question.

I continue to think that snow to liquid ratios should be above "normal" due to the strength of the cold air. I think we could see anywhere from a 15 to 1 ratio to as much as a 19 to 1 ratio.

Lets look at some of the numbers from the models. First, here is the North American forecast model, the NAM.

CITY: H20 | SNOW RANGE

• Cape Girardeau: 0.07" | 0.9" - 1.2"
  
• Columbus (IN): 0.09" | 1.3" - 1.6"
  
• Chicago: 0.50" | 7.5" - 9"
  
• Indianapolis: 0.12" | 1.8" - 2.2"
  
• St. Louis: 0.17" | 2.4" - 3.1"
  

Next, we take a look at NOAA's global forecast model, the GFS.

CITY: H20 | SNOW RANGE

• Cape Girardeau: 0.10" | 1.4" - 1.8"
  
• Columbus (IN): 0.20" | 3" - 3.6"
  
• Chicago: 0.46" | 7.3" - 8.3"
  
• Indianapolis: 0.22" | 3.3" - 4.0"
  
• St. Louis: 0.15" | 2.25" - 2.6"
  

Now lets take a look at the European forecast agency's model.

CITY: H20 | SNOW RANGE

• Cape Girardeau: 0.08" | 1.1" - 1.3"
  
• Columbus (IN): 0.11" | 1.6" - 2"
  
• Chicago: 0.58" | 9.2" - 11"
  
• Indianapolis: 0.13" | 1.8" - 2.3"
  
• St. Louis: 0.13" | 1.8" - 2.2"
  

In almost all cases, the numbers dropped slightly from earlier runs. However, that doesn't necessarily mean we are going to get less.

I am going to stay with what I was saying earlier today. The breakdown goes something like this...

• Cape Girardeau: 0.75" - 1.5"
• Columbus (IN): 1" - 2"
• Chicago: 7" - 9"
• Indianapolis: 2" - 4" (2" to 3" through the city. 3" to 4" on the northside near Carmel and Westfield.)
• St. Louis: 2" - 3"

As for timing... Check out my post from earlier today for the details on when the snow arrives.

My "Freak-Out-Meter" holds pretty much the same as earlier. For places like Cape Girardeau, St. Louis, Columbus (IN) it is a 3 out of 10. For Indianapolis it is a 4 out of 10 and in Chicago it is a 6 out of 10.

None the less temperatures will be much colder Thursday and Friday and winds will be gusty out of the west and northwest.

Be sure to leave your snowfall amounts in the comments section of this blog post.

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Live Radar Video Feed

I'm going to try something new for Thursday's snow. I am going to embed a live video stream of the radar for the St. Louis metro area. Please let me know what you think of this feature by leaving a comment in the "comment section" below.



I apologize in advance for the ads that run every 15 minutes.

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