Sunday, January 29, 2012

The Week Ahead; Weekend Storm?

I've been looking over weather data today and there are some hints that we could see some "interesting" weather for the weekend.

Before I get too far ahead, I should mention what we're going to see at the beginning of the week. The jet stream is flattening out and becoming zonal. This will allow temperatures to climb on southwesterly winds. Highs will be in to the 60's for parts of the Midwest Monday, Tuesday and maybe Wednesday.

As you can see from the above graphic, temperatures are going to be 15 to 30 degrees above normal. A weak cold front will eventually come through late Tuesday night and early Wednesday morning that will drop temperatures 10 degrees. Also, ahead of the front we could see showers and a few thunderstorms develop in Missouri, Illinois, Kentucky and Indiana. At this point I am not expecting severe weather, but whenever you have temperatures in the 60's and strong southwesterly winds at the surface you always need to keep an eye on it.

Interesting that we are going to see mild if not warm weather for a couple of days. Our neighbors to the north are seeing the flip-side. Take a look at this picture taken around 11:00am this morning in Fairbanks, Alaska.

The picture was taken by my college meteorology professor, Dr. David Arnold. He said the overnight low was -51 degrees. It appears we may get a chunk of that colder air coming down for the lower 48 later this week or early next week. However, long range data is indicating the cold air will continue to pool over Alaska and temperatures will go back up for the lower 48 through the beginning of February.

Now back to what I was talking about off the top of this post. There are some hints that we could see a surface low develop and move up through the Mississippi Valley this weekend. I should say that not all computer models are agreeing with this. However, the European forecast agency's model and the Canadian forecast agency's computer model are suggesting this.

Here's a look at the Canadian model's output for 6am CT Saturday, February 4. The image shows surface pressure and precipitation.

(Click the image to see a larger version.)

Both models bring the surface low over the confluence of the Mississippi River and Ohio River. Models are also suggesting cold air diving south on the north side of the storm. If these models are correct (that remains to be seen), the big question will be how much cold air will be at the surface.

Potentially, this could bring snow to places like St. Louis to Effingham, IL to Indianapolis. Of course, the actual storm track will be key to determining who sees what and who sees how much. As I like to say, "Stay tuned..."

Sunday, January 22, 2012

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.

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

Saturday, January 21, 2012

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.

Friday, January 20, 2012

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.

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.

Thursday, January 12, 2012

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

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.

  • 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.

  • 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.

  • 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.

Wednesday, January 11, 2012

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.

Wednesday Afternoon Update

Still looking like an accumulating snow for much of the Midwest. As is usually the case, some will get much more than others. Totals could range from a dusting to as much as 10”.

In my last post I mentioned that I was waiting for the European forecast agency’s computer model to come in. The data is in and it is keeping in line with the GFS model.

Here is a breakdown of the amount of liquid is available to produce snow according to the European model. I am still looking at ratios generally being around 14:1 to 16:1. Some places could be as high as 18:1.

  • Cape Girardeau, MO: 0.08” | 1.1” - 1.3”
  • Carbondale, IL: 0.08” | 1.1” – 1.3”
  • Champaign, IL: 0.25” | 3.5” - 4.25”
  • Chicago, IL: 0.52” | 8.3” – 9.4”
  • Columbus, IN: 0.11” | 1.5” – 1.9”
  • Harrisburg, IL: 0.08” | 1.1” – 1.3”
  • Indianapolis, IN: 0.18” | 2.7” – 3”
  • Mt. Vernon, IL: 0.11” | 1.5” – 1.8”
  • Paducah, KY: 0.09” | 1.2” – 1.4”
  • Poplar Bluff, MO: 0.03” | 0.4” – 0.5”
Those are a lot of numbers to dissect, but you can see that the range could be from a dusting to 10”+.

Here’s a couple of graphical maps indicating snowfall amounts from two computer models, the North American Model (NAM) and the global forecast model (GFS).



I want to stress that this isn’t my final forecast as to how much snow will fall. The numbers listed/represented above come straight from a computer model. I am still going with the numbers I had mentioned earlier (Cape Girardeau: 0.75" - 1.5" | Indianapolis: 2"-4" | St. Louis: 2"-3") but I will likely be putting out a more detailed snow forecast later this evening.

Winter Weather Advisories are now posted for much of central Indiana and central/northern Illinois. Remember you can get the latest winter advisories, warnings and watches on my blog by clicking on the “Warnings & Watches” tab at the top of the page.

You can also get the latest by following me on Twitter as I'll be posting updates through the evening and tomorrow. Follow @johndissauer.

- Posted from my iPhone

Wednesday Morning Update

The next round of computer model data is coming in this morning and the models are keeping the upward trend. Last night I mentioned it would be interesting to see how this morning’s runs handle the moisture. Do they take it up, keep it the same or drop it?
I look at several computer forecast models when putting together the forecast. During snow storms I’ll look at upwards of eight different models from various worldwide forecast agencies. So far this morning, NOAA’s global forecast model (GFS) is in along with the RPM.

Let’s take a look at the breakdown of how much water the models are suggesting will be available for snow production.

  • Cape Girardeau: 0.10” | +0.03”
  • Indianapolis: 0.22” | +0.06”
  • St. Louis: 0.16” | +0.03”
Looking at the change from last night it may not look like a big change. However, when forecasting snow, it doesn’t take much to make more snow. For Cape Girardeau and St. Louis the 0.03” difference could add an additional half inch and for Indianapolis the additional 0.06” could add an additional inch of snow.

With the amount of cold air coming in with the cold front, I am looking for snow to rain ratios of 14 to 1 or as high as 17 to 1. Going strictly from the GFS model that would put down:
  • Cape Girardeau: ¾” to 1.5” of snow
  • Indianapolis: 3”-4” of snow
  • St. Louis: 2”-3” of snow
I am still waiting to see what the European forecast agency’s computer model comes up with. All I have to look at right now are the numbers from last night’s run. They are fairly comparable to this morning’s GFS. Cape Girardeau – 0.09” | Indianapolis – 0.19” | St. Louis – 0.19”. Numbers from this morning’s European model will be in later this afternoon and I’ll try to give an update when they come out.

Timing: The snow should begin to fall in St. Louis during the pre-dawn hours (2am-4am CT), in Cape Girardeau during pre-dawn hours (5am-7am CT) and in Indianapolis by early afternoon (12pm-3pm ET).

As for my “Freak-Out-Meter”… I am going to keep it at a 3 out of 10 for St. Louis and Cape Girardeau and move it to a 4 out of 10 for Indianapolis. The “Freak-Out-Meter” is hard to score because there are two ways to do it. I could score it on how people’s reaction will be or how the reaction should be. I try to score it to how people’s reaction should be.

Remember you can follow me for more timely updates via Twitter @johndissauer and via my Facebook page.

-Posted from my iPhone

Tuesday, January 10, 2012

Numbers Going Up?

New data is streaming in as I type tonight. Interesting to note that on first look, it appears NOAA's global forecast model is coming in slightly wetter.

The time frame I am talking about is still Thursday in to Friday morning for parts of the Midwest.

A strong surge of cold air will blow in behind a cold front passing the Midwest Wednesday evening and Thursday morning. Th cold air will work very efficiently at changing the moisture to snow.

Earlier today I showed you what the GFS computer model was suggesting for moisture in Cape Girardeau (0.02"), Indianapolis (0.15") and St. Louis (0.07"). As of the time I am writing this, data is only available through Friday evening.

Here's a look at what the new run of the GFS is showing. Again, this is how much moisture is available, not snow.
  • Cape Girardeau - 0.07"
  • Indianapolis - 0.16"
  • St. Louis - 0.13"
Comparing that to this morning's numbers you can see the model is starting to increase the amounts.

The strength of the cold air is impressive. I think this could generate a 14:1 to 16:1 snow with a few locations seeing higher ratios. This would equate to around 1" in Cape Girardeau, 1.5" to 2.5" in Indianapolis and 1" to 2.5" in St. Louis. There could be a few locations upwards of 3" around central Indiana (likely north of Indianapolis).

It will be interesting to see what Wednesday morning's computer models are showing to see if they continue the trend of increasing the moisture, keeping it the same as tonight's runs or decreasing the moisture.

I am going to slightly increase the "Freak-Out-Meter" to a 3 out of 10. It won't be bad, but for some, this will be the first measurable snow of the season.

Stay tuned...

Light Snow Possible by Week's End

It is starting to look like we could see a little snow across parts of Missouri and Illinois within the next 72 hours. At this point, I want to stress the word “little”. I’m not talking about a major snowstorm. In fact, I’m not sure if the word “snow” or “storm” should even be included in this discussion.

A strong cold front is just beginning to move across the Canadian/United States border. Behind the front, cold air is on the march. At 1pm CT, temperatures were in the single digits in Alberta and British Columbia.

Forecast models are indicating the cold front will pass through Missouri and Illinois late Wednesday night into early Thursday morning. Behind the cold front, the previously mentioned cold air in Canada will spread over the Midwest.

It appears that the strength of the cold air will work on the little amount of moisture in the air and squeeze out a few snow showers Thursday. Both the European Agency’s forecast model and NOAA’s forecast model are suggesting light amounts of precipitation for the cold air to work with. What is “light amounts”? Let’s take a look.

Here is a breakdown of how much liquid water is forecast to fall by the models.

  • Cape Girardeau: 0.05” | 0.02”
  • Indianapolis: 0.15” | 0.12”
  • St. Louis: 0.06” | 0.07”
You can see what I mean by small amounts of liquid to work with. Typically, you can say there is a 10:1 ratio of snow to water. In this case, with the surge of cold air, I think we could see at most a 14:1 ratio. This would mean approximately a dusting to a half inch in Cape Girardeau, a half inch to 1” in St. Louis and 1” to 2” in Indianapolis.

Here is another view of what some of the models are indicating for Cape Girardeau and Chesterfield, Missouri.

Cape Girardeau:


The above are called meteograms. The ones I have posted indicate how much snow will fall according to various runs of forecast models and the forecast from the National Weather Service. Remember, a forecast model is just that… A model. It isn’t reality.

Bottom line… Could there be some snow? Yes. Will it be a lot? No. Where do I have my “Freak-Out-Meter”? I’ve currently got it at 2 out of 10.

- Posted from my iPhone

Thursday, January 5, 2012

Website Update

Made a small update to the design of the website today. I have added a recent satellite image from the University of Wisconsin and the latest forecast map for today from NOAA's Hydrometeorological Prediction Center (HPC).

You can view the images by scrolling down the site and looking in the right hand column.