Weekend Storm: Snow Numbers

A significant winter storm is still in the cards for Missouri, Illinois, Kentucky, and Indiana.  If you have plans to travel, you should read this and then reconsider your plans.

Dry air is currently infiltrating the central United States following a passing cold front.  Dew points have dropped below zero, hinting at the arctic origins of the air.

It will take a small amount of time to saturate the atmospheric column, but it should not take long for precipitation to reach the ground as snow.

TIMING:

• Missouri: Snow will start to enter southeast Missouri from the southwest Saturday morning.
• Illinois: Snow will enter Illinois late Saturday morning/early afternoon.
• Kentucky: Snow will enter the extreme southwest corner of Kentucky Saturday mid-morning.
• Indiana: Snow will enter the southwest corner of the state Saturday afternoon.  It should enter central Indiana late Saturday afternoon.

HOW MUCH:

Computer models have been extremely consistent on how much water will be available in the atmosphere.  There is one computer model that has been consistent with lower water amounts - the GFS.

All that being said, there is copious amounts of water available and there will also be cold air in place.  Snow to Liquid ratios will be higher than normal due to the cold.  Normally, we look at 10 to 1.  For this storm, the ratio could range from 12 to 1 to as much as 18 to 1.

After looking over the Friday morning computer model runs (and the last several days worth of data) these are the numbers I think could fall as snow through Sunday night.

INDIANA 

• Bloomington: 8"-12"
• Columbus: 10"-14"
• Indianapolis: 7"-10"
• Shelbyville: 8"-11"

MISSOURI

• Cape Girardeau: 8"-11"
• St. Louis: 7"-11"

ILLINOIS

• Carbondale: 10"-15"

KENTUCKY

• Paducah: 7"-12"

These numbers could still fluctuate as more data comes in over the next 24 hours.  If there is any sleet mixed in, especially in western Kentucky and the Missouri bootheel, it could have significant impact to snowfall amounts.

The attached map may not exactly match what I have forecast above.  It is a display of a blend of computer model snowfall through 7am ET Monday.

Winter Storm Update

I have been monitoring data coming in from Wednesday night's and Thursday morning's computer model runs and it still looks like a winter storm will have a significant impact on the Ohio River Valley.

The upper-level energy for the storm is still located off the southwest coast of California.  It will be better once it is overland and models can get a better sampling of what is happening in atmosphere.  That being said, the NOAA Hurricane Hunters - the pilots and scientists that fly in to hurricanes to collect data - started to fly missions in to the storm over the Pacific earlier this week.  Another mission is scheduled for Thursday evening.  I can't emphasize enough how important is that they collect.  The data goes straight in to the computer models we use to forecast weather.

In Wednesday's update I talked about how much water there will be to work with over the region.  Wednesday night's computer model runs, and Thursday morning's, increased the projected water available.

A 34-computer model average suggests the following liquid equivalent 7am ET Saturday - 7am ET Monday along with the range in data.

INDIANA 

• Bloomington: 0.82" (0.58" - 1.02")
• Columbus: 0.86" (0.61" - 1.05")
• Indianapolis: 0.67" (0.47" - 0.86")
• Shelbyville: 0.76" (0.58" - 0.91"

MISSOURI

• Cape Girardeau: 1.01" (0.82" - 1.22")
• St. Louis: 0.63" (0.43" - 0.83")

ILLINOIS

• Carbondale: 0.91" (0.70 - 1.10"

KENTUCKY

• Paducah: 1.16 (0.88" - 1.55")

Needless to say, that is a LOT of water for a winter storm.  Especially when most locations - north of the Ohio River - will be mainly all snow.

Having enough cold air to create snow will not be a problem with this storm.  (There will be some, mainly along and south of the Ohio River, that may have a little bit of warm air in the atmospheric column which would create sleet, at times.)

Air will be cold enough for higher than normal snow to liquid ratios.  A good rule of thumb is for a 10 to 1 (10:1) ratio.  With the cold air expected to be in place, ratios could go from 12:1 to as much as 18:1.  

This is when the fun begins.  You - or your kids that know how to multiply - can start doing the math on how much snow that could potentially produce.  Multiply the water amount to the snow to liquid ratio.  Example:  0.86 x 14 = 12.0"

Areas that have sleet mixed in will drastically reduce the numbers.  Sometimes by as much as 40%+.

There is a little more massaging of the data that goes in to producing the snow forecast, but this can give you a rough idea.

If the models don't come in overnight/tomorrow suggesting much lower water amounts, this will likely be a "doozy" of a winter storm for many in Missouri, Illinois, Indiana, and Kentucky.  And that isn't talking about the BIG ice storm that will happen further south.

Let's see what Friday's information brings and that could warrant me issuing Freak-Out-Meters for several locations in Missouri, Illinois, Kentucky, and Indiana.  Stay tuned...

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?

Winter Storm for Mother's Day

Still need to get mom a gift for Mother's Day?  Well, Mother Nature may be able to help you get something useful.  If you're in eastern Colorado you could get her a shovel.  She may need it Sunday and Monday.

An area of low pressure is moving through the Gulf of Alaska off the northwest coast of the United States.  (See the satellite loop below taken Friday morning.)

Computer models project the low/energy will move southeast in to the Rocky Mountains Saturday.  Once in the mountains, a surface low is expected to develop over southeast Colorado Saturday afternoon.  As the low moves east, cold air will begin to filter in from the north/northwest.

Almost all of the data suggests moisture will begin to fall in the central mountains of Colorado Saturday.  The moisture is expected to move east and southeast over eastern Colorado Sunday afternoon.  Both medium-range computer models, the GFS and European forecast agency's model, suggest that moisture will remain in place over eastern Colorado through mid-day Monday.

Overall, the computer models are very bullish with the amount of moisture falling from this system.  Here is a look at a 27-computer model average of how much moisture will fall for locations in southeast Colorado through 6pm Monday MT.

• Colorado Springs: 0.70"
• Monument Hill: 1.03"
• La Junta: 0.48"
• Lamar: 0.37"
• Pueblo: 0.61"

Initially, moisture will likely fall as rain but in some locations it will change over to snow.  Places that get snow, could got a lot of snow.  Here is a look at the 27-computer model average of moisture that computer models project will fall as all snow through 6pm Monday MT.

• Colorado Springs: 0.52"
• Monument Hill: 0.76"
• La Junta: 0.08"
• Lamar: 0.01"
• Pueblo: 0.13"

As you can see, data is suggesting higher amounts across El Paso County and north.  This also likely suggests higher snow amounts in the higher elevations west of I-25 (Teller/Fremont counties).

Keep in mind this is still a couple days away from happening.  Computer models will get a better handle on the storm, the amount of moisture and the timing once it gets better sampling over the land.

Winter Storm Watch (in blue) Saturday night
through Monday morning.

In the meantime, the National Weather Service in Pueblo has issued a Winter Storm Watch for areas west of I-25 Saturday night through Monday morning.  I'll be in throughout the weekend and will have further updates on KOAA-TV, on Twitter, and time permitting, my blog.

Starting February with Snow & Ice

There has been a lot of talk in the one to two weeks about a colossal storm heading for the Midwest this week.  A lot of the talk and hype has been extremely irresponsible, but that is a discussion for a different day.  It does appear a storm will impact the Midwest Tuesday and Wednesday.

One of the reasons I have been relatively quiet about the storm and its potential is due to the many different solutions computer models were coming up with.  Some had it as a HUGE ice storm, others as a HUGE snow storm and most had it somewhere in between.

Patience is a virtue sometimes when it comes to weather forecasting.  Let the models battle it out for a while and then start to come up with a somewhat unified solution to what the storm could do.

This is a storm that is going to develop over far southern New Mexico, western Texas and northern Mexico.  As it matures, moisture will become plentiful as it taps in to the Gulf of Mexico Tuesday.

Here is a solution the latest run of NOAA's Global Forecast model has come up with.  The image depicts 6pm CT Tuesday.

0z GFS - 6pm CT Tuesday
(Click image to see larger version.)

This is a classic winter storm for the Midwest.  The surface center of low pressure is tracking from around Monroe, Louisiana to just south of Nashville, Tennessee by Tuesday evening.  We're talking snow along and north of I-44 in Missouri and roughly along I-70 in Illinois.  This also means the rain/snow line is at play for southeast Missouri, southern Illinois and western Kentucky.

At this time, I do think all forms of winter precipitation will be possible for southeast Missouri, extreme southern Illinois and western Kentucky.  The primary nuisance will be rain, freezing rain and sleet.  There will probably be a change over to a little snow towards the end of the event.  The exact location of the rain/snow line is a little difficult to pinpoint this far out.  As you often hear meteorologists say, "The track of the storm will be extremely important." and this will be the case this time.  A change in just 40-miles will have a huge impact on what type of precipitation falls.

Right now, for places like Cape Girardeau, Paducah, and Poplar Bluff, I think rain, freezing rain and sleet will be the primary types of precipitation.  Icing could potentially be a concern, but let me say right now... This is NOT anything like the ice storm of 2009.  NO WHERE CLOSE.

TALKING SNOW

Let's talk a little snow for the Midwest.  I have gone through and looked at several computer model runs and have come up with a snow matrix.  Looking at the matrix can give you an idea of the range computer models are suggesting could happen through Wednesday night.  The data includes tonight's runs of the NAM and GFS and also Sunday morning's run of the European forecast agency's computer model as well as the 23-member SREF ensemble.

Missouri/Illinois Snow Matrix
(Click image to see larger version.)

Indiana Snow Matrix
(Click image to see larger version.)

Colorado Snow Matrix
(Click image to see larger version.)

As you can see, there is some variation between the computer models, but I must say, they are coming in to line with each other.

For many, the storm is still out 36 to 48 hours but I'll go ahead and throw out some ball park numbers.  I hope to update my blog tomorrow evening (time permitting) with fine tuned numbers.  Although, if you have followed my blog for a while, you know that my initially numbers usually only get slightly tweaked.  Think of it as a very time course correction.  But do know, these numbers can adjust as we get closer to the event.

COLORADO: (Monday night through Wednesday afternoon)

• Colorado Springs:  3"-5"
• Lamar:  5"-9"
• Pueblo:  2"-4"
• Springfield:  4"-6"

ILLINOIS: (Tuesday through Wednesday night)

• Mt. Vernon:  2"-5"

INDIANA: (Tuesday through Wednesday night)

• Columbus:  4"-8"
• Indianapolis:  6"-8"
• Lafayette:  5"-9"

MISSOURI: (Tuesday through Wednesday night)

• Cape Girardeau:  Up to 1"
• Poplar Bluff:  Up to 2"
• St. Louis:  3"-5"

FREAK-OUT-METER

COLORADO:

• Colorado Springs: 2
• Lamar: 5
• Pueblo: 2
• Springfield: 4

ILLINOIS:

• Mt. Vernon: 5

INDIANA:

• Columbus: 5
• Indianapolis: 5
• Lafayette: 5

MISSOURI:

• Cape Girardeau: 4
• Poplar Bluff: 4
• St. Louis: 3

For those that don't know what my Freak Out Meter is, it is a number I give out that attempts to quantify how big of a deal the upcoming weather event will be. It is based on a 0-10 scale. Zero being the lowest, "not a deal at all", and 10 being "get all the bread, milk and eggs and lock yourself in the basement". The score is 100% subjective and it's an attempt to have a little fun.

For more frequent updates, be sure to follow me on Twitter at @johndissauer.

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.

Snow Covers Far and Wide

Amazing what four days can do to for a winter’s snow totals.  Two storms and in some cases more than 20” of snow has fallen across parts of the Midwest.

It all started last Tuesday/Wednesday as upwards of 18” of snow fell in parts of Missouri, Illinois and Indiana.  Then Friday night/Saturday morning another couple of inches of snow fell.

According to the National Operational Hydrologic Remote Sensing Center, 76.6% of the Midwest was covered with snow this morning.

(January 2, 2013 Snow Depth - Click image to see larger version)

Compare that to a year ago when only 0.6% of the Midwest was covered.

(January 2, 2012 Snow Depth - Click image to see larger version.)

Even a person not great at math can figure out that is a HUGE increase in snow.

Nationally, as of this morning 65.8% of the continental United States was covered by snow.  Whereas last year only 18.7% was covered.

(January 2, 2012 Snow Depth - Click image to see larger version.)

For those of you that do not like snow, you will like the next 6-8 days as forecast models suggest a quiet weather pattern.  Temperatures may even moderate a little early next week but winter is far from being done.

4:30pm Weather Update - Winter Weather

A quick look ahead at what a couple of national government forecast agencies are showing for Christmas Eve and the Post-Christmas Storm I mentioned in my previous blog post.

First Sunday night through Christmas Eve.  There is potential for parts of Missouri to central Indiana will encounter some light moisture being spread up from the south.  The moisture will encounter cold air near the surface.  Whenever you mix warm air a few thousand feet up and cold air at the surface you can get freezing rain.  This may be the case Sunday - Monday.

The Hydrometeorological Prediction Center has put out their probability forecast for freezing rain that covers 6pm CT Sunday through 6pm CT Monday.

(Click the image to see larger version.)

HPC indicates a heightened probability of freezing rain from roughly St. Louis to Indianapolis along and north of I-70.  Not great for travelers during that time period along a major interstate.

The one bit of "good" news is that it should be light.  Generally less than 0.10".  However, it doesn't take much to make driving "interesting".  This isn't set in stone so if you plan on traveling be sure to check the latest forecast.

Also want to show you what the Climate Prediction Center has highlighted in the Day 3-7 U.S. Hazardous Weather Outlook.

(Click image to see larger version.)

They are highlighting an area of "heavy snow" December 25 through December 26.  So it looks like they are on board with the Post-Christmas Snow Storm.  Although, this is subject to change and likely will wiggle around as computer models crunch the numbers.

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.

Signs of Snow

There are signs that snow may arrive to parts of the Midwest early next week.

For several days forecast models have been hinting at a storm developing over the southwest United States, eventually moving through the Midwest. The models haven't been jiving too well with each other to the course the storm will take. If you follow me on Facebook you might remember a status update that said, "Models are flip flopping around..."

Last night's runs started coming together and this morning's model runs are pretty similar in to the track of the surface low. (See graphic below.)

(Click image to see larger version.)

The above graphic was created by AccuWeather but is pretty close to what the models are showing regarding the track of the storm.

Northwest of the surface low cold air is expected to move in. This will allow for some significant snowfall in parts of the country.

It is interesting to compare the amount of moisture north of the surface low that could interact with the cold air and fall as snow. Models are not on the same page with this feature.

The European forecast agency's computer model is more bullish on the liquid amounts compared to NOAA's computer model. Here's a closer look at what the models are indicating for liquid available during the time it would fall as snow.

European Model:

• Kansas City - 0.77"
• Kirksville, Mo - 0.44"
• Columbia, Mo - 0.09"

GFS Model:

• Kansas City - 0.09"
• Kirksville, Mo - 0.03"
• Columbia, Mo - 0.00"

If the European model is correct, Kansas City could end up with 6"-9" of snow (maybe more). If the GFS is correct Kansas City could get 1" of snow. That is a pretty big difference.

I should mention that areas along and south of the track of the surface low will see good ole' rain.

Stay tuned...

- Posted from my iPhone

Turn up the Thermostat

November has been warm across much of the Midwest compared to what is "normal". I'd be willing to bet your electricity bill reflects the milder temperatures. I know mine has!

Temperature departure from normal across the Midwest.

Indiana:

• Bloomington +4.4°
• Indianapolis +4.6°
• Lafayette +4.6°

Illinois:

• Carbondale +3.0°
• Chicago +3.5°
• Moline +1.8°

Kentucky:

• Louisville +2.3°
• Paducah +2.9°

Missouri:

• Cape Girardeau +3.6°
• Chesterfield +3.9°
• Poplar Bluff +3.8°
• St. Louis +4.8°

We're getting close to the end of Meteorological Fall (September 1 - November 30) and the start of Meteorological Winter (December 1 - February 28). Temperatures in Fall 2011 will go in to the books above normal for just about everyone in the Midwest. But it appears that Mother Nature is aware that meteorological winter is just around the corner as it looks like colder air is on the way.

Forecast models are hinting at a change in the weather pattern starting as early as this weekend. The change in the pattern should bring a prolonged period of colder air to much of the country.

Before we get too excited about the cold air coming for the weekend, let me say that Thanksgiving and the day after Thanksgiving look to be nice. Winds will begin to turn out of the south Friday (it will be breezy) and temperatures will climb under mainly sunny skies.

A strong cold front is projected to move through the central United States starting Friday. Along the front, showers and thunderstorms will develop. Some of the rain could be heavy at times Saturday/Sunday (depending on where you live).

Once the front passes, winds will shift and temperatures will plunge. Here's a view of the weather setup for Sunday evening as advertised by NOAA's global forecast computer model (GFS).

According to the GFS, cold air will dive all the way to the gulf coast by Sunday evening. (Hint: Look at the blue 540 line.) This also indicates an upper-level low will develop and center over Missouri by Sunday.

With the low, low clouds will hang around. The clouds are indicated by the gray shading. Along with the clouds notice the model keeps some precipitation around Illinois, extreme eastern Missouri and western Kentucky. IF this precipitation lags behind the cold front and IF the temperatures drop as much as advertised much of this moisture would fall in the way of light snow.

The European Forecast Agency's computer forecast model is also hinting at something very similar. (See above) The slight difference in the European model holds off the moisture until Monday afternoon/evening. At this point, it is splitting hairs between the two models. The key is to see the trend of what the two models are showing and the trend is very similar.

At this point I'm not concerned with the amounts as it should be relatively light. But yes, there could be snow flurries and snow showers Sunday night through Tuesday morning. Again, this is nothing to get excited about. My "Freak-Out-Meter" is pretty low, less than a 1 (on a scale of 1-10).

The models keep the cold air in place all next week. Yes, the temperatures might warm up a little but I think we will likely be below normal during the stretch. This would make sense with my belief in the "Law of Averages". November was very mild, relatively speaking, so we are due for some below normal temperatures.

Let's have some fun now... Look waaaay out in to the future. The GFS allows us to look 384 hours in to the future (16 days). At the end of the forecast run it is hinting at a decent storm developing along the gulf coast.

Over running the storm is a moisture plume that extends as far north as Kansas City. The model also brings down some colder air on the back side of the storm that would likely interact with the moisture plume spreading north. IF this storm were to pan out this way, that's a BIG IF, southeast Missouri, southern Illinois and western Kentucky would likely start out as rain December 7 and eventually change over to a rain and/or snow mix by that night or early December 8. This would definitely bare watching if the model is right.

I should say that the model is not very good at depicting what is going to happen that far out in its run. The model is likely to take the storm out of the equation over the next several runs. In fact, what usually happens is the storm will show up once and then go away on all subsequent model runs. I just wanted to give you a "behind the scenes" look at some of the data meteorologists look at but don't always mention because we know it isn't likely to happen. But, as I like to say, "Stay tuned..."