Weekend Winter Storm to have big impacts on Central United States

Chatter about a winter storm for the upcoming weekend is in full throat on the inter-webs.  I am just starting to dig in to the data and see what might be coming.

The good news... For most of the people that follow me on here - Missouri, Illinois, Indiana - the thermal profile of the atmosphere suggests this looks to be mainly a snow event, at the moment.  (This does not mean there could not be sleet involved for some.)  It looks to start in eastern Missouri pre-dawn Saturday and exit Indiana Sunday night.

Everyone wants to know how much.  Yes, people are throwing out numbers, but that is all it is at this moment.  Numbers.  To be honest, it is too early to talk specific snow amounts, snow no you will not see me giving snowfall amounts yet.  However, I will show you how much liquid precipitation computer models are suggesting for a few locales.

A 32-computer model average for 7am ET Saturday through 7 am ET Monday:

INDIANA

• Bloomington: 0.47"
• Columbus: 0.48"
• Indianapolis: 0.36"
• Shelbyville: 0.42"

MISSOURI

• Cape Girardeau: 0.79"
• St. Louis: 0.41"

ILLINOIS:

• Carbondale: 0.66"

Yes, at this distance it appears this storm has a hefty supply of water.

We can also look at ensemble computer models.  Instead of a single forecast run, an ensemble uses multiple model runs (often 20–50+).  Each run starts with slightly different initial conditions (temperature, pressure, wind, moisture).  The ensembles can give us a range of how things could happen.

Today, I want to show you how many members of five global ensemble models suggest there will be measurable snow on the ground Sunday evening.

Columbus, IN: 94% - 170 out of 180 members
Indianapolis, IN: 94% - 170 out of 180 members
St. Louis, MO: 94% - 170 out of 180 members

It does make me chuckle that out of 180 members, all three locations have identical numbers.

We know it will be cold, which will allow for some of the snow to be fluffed up, resulting in a higher snow to water ratio.

Winter Storm Watches have been hoisted from New Mexico to North Carolina.  As more data comes in, the forecast will be refined and the picture will become more clear.  As it becomes more clear, we will have a better idea for snow totals and impacts.  I suspect a Freak-Out-Meter will be issued before the weekend gets here.

BOTTOM LINE:  This will be a good weekend to stay indoors and watch the storm through the window.

What are you hoping for from the storm?

End of Week Winter Storm

Things could start getting active this week in the winter weather department.  Bitterly cold air will be on the move from Alaska/Canada and moisture could be coming north through the Mississippi River/Ohio River valleys.

Before I get too far in to this I want to remind you that the items I am going to discuss are still MANY days away.  Things can and likely will change in the forecast.  The data I am going to show you is not the actual forecast but instead a weather computer model projection of what could happen.

Ok, now that all of that is out of the way lets talk about later this week, specifically in Missouri, Illinois, Kentucky and Indiana.

One basic concept we need to discuss before going any further.  Cold air is denser/heavier than warm air.  Hence, hot air balloons rise.

All computer forecast data is indicating COLD air will be on the move through the central United States late Wednesday and Thursday.

Projected Surface Temperature - 6am CT Thursday
(Click image to see larger version.)

The cold front will be somewhere near the Ohio River by Thursday morning.  Again, keep in mind that cold air sinks, so the cold air will undercut warmer air, which will reside a few thousand feet in the sky.

Temperatures at the surface will be dropping and it will be cold at the end of the week and cold for the weekend.  Here is a look at forecast temperatures from the European forecast agency's computer model for Friday afternoon.

Projected Surface Temperature - 12pm CT Friday
(Click image to see larger version.)

Computer models also project a couple waves of energy riding up and over the cold front.  The moisture will be riding in the warmer layer above the ground.  As the moisture falls it will encounter the below freezing air.  Depending on how thick the layer of warm layer and cold layer is will determine what type of precipitation it could be.  In other words, we could be talking a cold rain, freezing rain, sleet and/or snow.

At this point, it is too difficult to say with any certainty the form will be.  We are talking about trying to determine the temperature in a layer of air along with how thick the layer will be (A few hundred feet or thousands of feet?) for something that is 96-120 hours away.  That being said, at this time, I think there potential for snow and/or freezing rain.

What could make this interesting is there could be a couple waves of moisture and there could be ample moisture to work with.

Here is a look at the National Weather Service’s Global Forecast model, the GFS, using a program called BUFKIT.  Specifically, the data is for Cape Girardeau.  Keep in mind when looking at the data, the timeline runs from right to left.

12z Sunday GFS for Cape Girardeau
(Click the image for larger version.)

The colored bars indicate what the program is projecting what form the moisture will fall.  Green = rain | Orange = sleet | Red = freezing rain | Blue = snow.  See all the green and blue?  Right, neither do I.  It is showing up as red.  That means the software/computer model is suggesting it could be falling in the form of freezing rain.

I mentioned "ample moisture".  The GFS is projecting 0.4" to 0.8" of liquid Thursday through early Friday morning for much of southeast Missouri, southern Illinois and western Kentucky.  The European computer model is also putting down some decent moisture (0.5" to 0.8") for the same areas through Friday afternoon.  The one difference is the European model is suggesting it would fall as snow, especially north of the Missouri bootheel and western Kentucky

Also to note, there are hints of another round of moisture coming up through the area Sunday in to Monday.

At this point this is nothing to get concerned over.  My "Freak-Out-Meter" is at maybe a 2 out of 10.  However, I point out the possibilities for later in the week to try and get you to pay attention to the forecast over the coming days.  As more data becomes available, as the computer models are able to sample more of the atmosphere, we will start to get a better idea of what may happen.  As I like to say... Stay tuned.

Bottom line... It is going to turn much colder for the end of the week and the weekend.  There is potential for rain, snow, and freezing rain.

Wet and Slick Weather Ahead

Quite a few weather “things” coming to the Midwest over the next five to six days and there are still a lot of question marks as to what will hit the ground.  One thing is for sure, there will be a significant and beneficial amount of rain falling at least through Sunday.  In some instances, upwards of 6” of rain could fall in parts of Missouri, Illinois and Kentucky.

Here is the Hydrometeorological Prediction Center’s precipitation forecast for the next five days.

Click image to see larger version.

If the computer models are correct, the numbers on the map (above) might be on the low side of reality.  Just through Friday, a four computer model average for rainfall is:

• Cape Girardeau:  0.96”
• Indianapolis: 0.89”
• Paducah: 1.32”
• St. Louis: 0.96”

Considering much of the area is still well below normal (precipitation), the rains will definitely be beneficial.

CLEAR SLICK STUFF

Now  the main reason for writing this post… What comes Sunday/Monday.

In the next 24-48 hours I think you are going to start to hear television meteorologists/weather-peeps starting to mention “freezing rain” (a.k.a. ice).  Freezing rain isn’t fun as it only takes a very small amount to make things slick.

The temperature profile of the atmosphere will be a HUGE factor in determining what type of winter weather will reach the ground.  It is the changing temperatures with height that makes winter forecasting the most difficult.

Instead of going in to detail how each type of winter precipitation is formed, check out the following links for tutorials from the University of Illinois on how the various winter weather types are formed.

• Snow
• Sleet
• Freezing Rain

Ok, now that you have a better understanding of how the different precipitation types form, let’s take a look at what some of the computer models are advertising for a few select locations.  (Note:  This is just an overview of what a few locations could see.  The data used is coming straight from computer models and is not the forecast.  It is also subject to change, and likely will.)

For the last couple of runs, computer models are hinting at cold shallow air to be in much of the Midwest.  The cold air is scheduled to arrive late Saturday night through Sunday depending on your location.  The models have temperatures slightly above freezing at 5,000 feet and  how thick that “warm” layer is will determine the type of precipitation hitting the ground.

This is a meteogram for St. Louis.  Each line is a representation of a different run of a computer model’s prediction of freezing rain accumulation.

Click image to see larger version.

The light blue line shows the amount of freezing rain accumulation from this morning’s run of NOAA’s global forecast model, the GFS.  Disregard the dark blue line (comes from the 6z GFS which I hold little faith in).

Not shown in the above meteogram is the European forecast agency’s computer model, the ECMWF.  The Euro is suggesting 0.59” of rain may fall while temperatures at the surface are below 32°F.  (Keep in mind that not all precipitation falling accumulates.  That is a reason for difference in numbers.)

Here are meteograms for a few other locations along with how much precipitation is projected to fall by the Euro.

Cape Girardeau, Mo:   Euro – 0.63”

Click image to see larger version.

Indianapolis, In:  Euro – 0.60”

Click image to see larger version.

As we get closer to Sunday the models should get better at predicting the minute details needed for determining precipitation type. 

Bottom Line… What I want you to take away from all of this is that there is a chance we could see freezing rain Sunday in to early Monday morning (timing varies by location).  It could also fall as all rain or sleet.  There are still considerable uncertainty as to what will fall.

I know many are skittish after the 2009 ice storm but as of today I do not think this will be anywhere near that storm.  As you will see below in my “Freak-Out-Meter”, I don’t think you should be freaking out nor should you be stocking up supplies to go weeks without power.  Instead, what I think you should do is keep an eye on the forecast over the next couple of days, maybe beat the lines and grab a can of deicer and a few batteries.  Worst case (for me anyway), this doesn’t pan out and you’ve got an extra can of deicer and batteries.

FREAK-OUT-METER:

• Southeast Missouri: 2
• Southern Illinois: 2
• Western Kentucky: 2
• Northeast Arkansas: 2
• St. Louis Metro: 3
• Central Indiana: 2

9:00pm Weather Update - Winds of Concern

Seems like I've been talking about a lot of different type of weather the last two days.  Thunderstorms, tornadoes, snow and wind.  I want to take a minute and talk about the wind for Thursday.  It is going to be strong.

In the St. Louis area they could be sustained 30-35mph with gusts to 45-50mph tomorrow afternoon.  Indianapolis they could be 30-40mph with gusts to 50mph.

At times tomorrow the wind is going to be hauling just a few thousand feet up in the atmosphere.  Here is a cross section of what the 18z NAM computer model is projecting winds to look like at different altitudes tomorrow for St. Louis.  To give a frame of reference, each colored line indicates what the wind speed will be doing.  The white horizontal lines are indicators of height in thousands of feet.  Look to the right of the image to see the altitude.  (1k = 1,000 feet)  Finally, time goes from right to left.  Yes, backwards.  I didn't write the program. ;)

(Click the image to see larger version.)

Notice the area pointed marked with the "Strong Winds Aloft!" arrow.  Those are winds that will be 70-75 mph 2,300 feet above the ground.  Go lower in the atmosphere and they are 46mph at 500 feet.  That is pretty close to the surface.  There will be times that we can mix down some of the stronger winds aloft.  That is why there has been talk of strong winds in the Midwest tomorrow.

Here is another graphic I want to show you.  This is off the high resolution 4km RPM computer model.  I have used this product several times in the past with some success (ice storm 2009 in southeast Missouri and western Kentucky).  This uses alogrithms developed for energy companies and energy traders.  This shows potential power outage areas due to weather elements.  This can caused be a mixture of wind, snow, hurricane, ice, etc.

(Click the image to see larger version.)

Special thanks to Brian Wilkes at FOX59 in Indianapolis for passing this along.

Take a look over Missouri and you will see that the model is indicating "widespread" to "extensive" power outages over north central and west central Missouri to northeast Missouri.  It also shows "scattered" power outages over parts of southeast Missouri, extreme southern Illinois and all of western Kentucky.  If you live in any of these areas, this might be something you have to deal with.  That being said, this is definitely not a guarantee.  The model can be wrong and sometimes is.  Also, don't get too hung up on the lowest threshold "scattered".  This means there could be a "heightened" threat.

12pm Weather Update - Talking Snow

Let’s get a little more in to the snow discussion.  Specifically, how much and for who.  I’ve put together a matrix of cities and various computer models’ snow output.

To begin with, here is the 12z snow accumulation projection from the high resolution RPM forecast model.  The model run covers snow through 6am CT Saturday.

(Click the image to see larger version.)

Heaviest snows will fall from southern Nebraska, central Iowa, southern Wisconsin and northern Michigan.

Now to the matrix.  These are for various locations across the Midwest.

CITY	12z NAM	12z GFS	12z RPM	12z EURO	AVG
Cedar Rapids, IA	8.2”	10.3”			9.3”
Columbus, IN			0.3”		0.3”
Bloomington, IN	2.2”		1.3”		1.8”
Indianapolis	1.4”	0.6”	0.7”		0.9”
Lafayette, IN	1.4”	0.9”	0.2”		0.8”
Moline, IL	3.8”	2.3”			3.1”
Muncie, IN	1.7”	1.5”	0.8”		1.3”
St. Louis	0.0”	0.1”	0.1”		0.1”

I will continue to update the matrix as more model data comes in.  This way, you can see what the various models are indicating.

4:30pm Weather Update

The morning run of both NOAA’s global forecast model (GFS) and the European agency’s (ECMWF) is in.  Both continue to indicate an area of low pressure developing early next week in the mid-Mississippi Valley.

We start our journey with the ECMWF (the Euro).  Generally, this is my preferred computer model for forecasting, especially beyond 48 hours.  The Euro develops an area of low pressure  initially over Oklahoma and Texas Monday afternoon.  The low then moves east.  Below is look at the Euro’s projection of Mean Surface Level Pressure and precipitation at 6am CT Tuesday, December 18.

(Click the image to see a larger version.)

You can see the area of low pressure centered over NW Mississippi.  That is a perfect location for measurable snow in parts of southeast Missouri, western Kentucky and extreme southern Illinois.  The big thing to note, look at the lack of moisture.  The storm doesn’t draw up a lot of moisture.

I also want you to note the grey and blue area in SW Missouri.  This is likely generated by the upper-level low coming in on the NW side of the storm.  Upper-level lows can and often do produce snow.  Usually it isn’t the BIG amounts of snow you see in snow storms, but more of a drier/fluffier snow.

The next image is from 12pm CT Tuesday.

(Click the image to see a larger version.)

The upper-level low is located over SW Missouri/NW Arkansas.  Notice the moisture the model tries to develop on the NW side of the surface low over the “Heartland”.

Just a quick view of the model would suggest 1”-3” of snow in parts of southeast Missouri, extreme southern Illinois, western Kentucky and northwest Tennessee.

The GFS on the other hand is a little quicker with moving the storm through the Midwest.  It is also much drier.  Below is the GFS for 12pm CT Monday.

(Click the image to see a larger version.)

Note it has the area of low pressure over NW Alabama and SW Tennessee.  The location is good but look on the north/northwest side of the storm.  It is dry.  Also notice that we are talking about the storms location 24-36 hours earlier than the Euro.

Here is the GFS for 6pm CT Monday.

(Click the image to see a larger version.)

It is quickly moving east to the coast.  In fact, beyond 6pm CT Monday, it develops are large storm for the east coast.

At this point it is entirely too early to be talking about specific snowfall amounts.  Heck, at this point it is too early to know if this storm will develop for sure.  As I mentioned in my earlier post from today, I want to see the models continue to show the storm on Thursday and Friday’s runs before I get too excited.  I am keeping my “Freak-Out-Meter” at 0.5 out of 10.