Wednesday Night Update: Snow & Ice on Track

Some of the data tonight is suggesting the storm for Thursday and Friday may track slightly south of what the models had suggested before.  Both the NAM and the RPM computer models are hinting at that.  I haven't completely bought in to that just yet.  I want to see what some of the other models decide to do tonight.

The slight jog to the south greatly affects numbers for both snow and sleet/snow accumulation.  That is why you often hear meteorologists say "If the storm moves 50 miles one way or the other it can make a difference."

Here is what the evening run of the RPM (0z) computer is suggesting for ice/sleet accumulation and snow accumulation.  As of now I am not tweaking my numbers just yet.  However, don't be surprised to see the numbers change tomorrow as more data becomes available.

RPM Ice/Sleet Accumulation:

0z RPM Ice Accumulation through Friday afternoon.
(Click the image to see larger version.)

RPM Snow Accumulation:

0z RPM Snow Accumulation through Friday afternoon.
(Click the image to see larger version.)

0z RPM Snow Accumulation through Friday afternoon.
(Click the image to see larger version.)

This will be my last update for tonight.  I'll look at the data in the morning and hopefully have something posted by early afternoon.

Ice & Snow Projections: Wednesday Evening Update

A quick update to let you see what the latest 12km RPM computer model is projecting for freezing rain/sleet and snow accumulations for parts of Missouri, Illinois, Kentucky, Tennessee, Arkansas and Indiana.

This is the afternoon RPM's projection of ice accumulation.

18z RPM Ice Accumulation
(Click image to see larger version.)

This is the afternoon RPM's projection of snow accumulation.

18z RPM Snow Accumulation
(Click image to see larger version.)

Finally, here is the model's snow projection for central/southern Indiana.

18z RPM Snow Accumulation
(Click image to see larger version.)

I suspect we will see these numbers bouncing around over the next 12-18 hours while the models try to fine tune their numbers.  I suspect we will see the numbers going up a bit more for southern/central Indiana.  To see my latest snowfall projections, check out my blog post from earlier today.

Significant Snow & Ice

Looking over the morning weather data and one word keeps coming out of my mouth.  "Wow!"  Computer models are narrowing in on a target for winter weather Thursday through Friday for southeast Missouri, southern Illinois, western Kentucky and central/southern Indiana.

Let me start by saying there are many facets to this storm.  There will be rain changing over to sleet/freezing rain and then changing over to snow.  Travel could be a MAJOR headache for week's end.

The critical part of the forecast is trying to determine when things change over.  There is going to be PLENTY of moisture to work with.  In fact, the morning computer model runs are very aggressive with the moisture.

Here is a look at the profile for Cape Girardeau from this morning's run of the NAM computer model.

12z NAM for Cape Girardeau
(Click the image to see larger version.)

Green = rain | Orange = sleet | Red = freezing rain | Blue = snow

As you can see from the model, a little bit of everything is showing up.  It does appear that this is going to start out for rain in most locations.  As the colder air arrives at the surface the change will begin to happen.  As the layer of cold air at the surface is shallower, freezing rain will be the concern.  As the layer "thickens" it will eventually change over to sleet.  Once the column is large enough with cold air, it will change over to all snow.  Often times this happens at the tail end of the moisture, but that doesn't appear to be the case this time.

Ice is going to be a concern for several areas.  For places like Cape Girardeau and Poplar Bluff there could be 0.25" of ice before changing over to snow.  In Paducah, 0.5"-0.75" of ice accumulation before changing over to snow isn't out of the question.  Right now, Columbus, Indiana and Bloomington, Indiana look to stay away from any ice.  I do think there will be quite a bit of sleet contamination, which will cut down on the freezing rain accumulation, for areas north of a line from Poplar Bluff to Cairo, IL to Owensboro, KY.

Here is a look at how much freezing rain and sleet accumulation the NAM and the GFS are suggesting.

12z NAM Sleet Accumulation through 6pm CT Friday.
(Click image to see larger version.)

12z GFS Sleet Accumulation through 6pm CT Saturday.
(Click image to see larger version.)

12z NAM Freezing Rain Accumulation through 6pm CT Friday.
(Click image to see larger version.)

12z GFS Freezing Rain Accumulation through 6pm CT Saturday.
(Click image to see larger version.)

As you can see, the models are much more bullish on sleet than freezing rain.  However, even a tiny bit of ice can cause HUGE problems.

Let's take a look at how much moisture will be available during the time the computer models suggest it will be all snow falling.  To be honest, I was a little surprised to see the consistency and the amount across the board.

Here is a matrix of quantitative precipitation forecasts (QPF) for various locations in Missouri, Illinois, Kentucky and Indiana.

Through Friday Afternoon

Through Friday AFternoon

The amounts shown above indicate how much moisture will be available while the atmospheric column is supportive of snow generation.  Yeah, there's a LOT!

Simple snow formulas suggest a 10:1 ratio.  It doesn't look SUPER cold in any of the locations (St. Louis will be a little colder) so I don't think this cause the ratio to slide too much.

Here's another look at some of the data from the computer models.  This is looking at snow accumulation from both this morning's run of the GFS and the NAM.

12z NAM Snow Accumulation through 6pm CT Saturday.
(Click image to see larger version.)

12z GFS Snow Accumulation through 6pm CT Saturday.
(Click image to see larger version.)

As to how much snow I think could fall?

INDIANA:

• Bloomington: 7"-10"
• Columbus: 8"-12"
• Evansville: 9"-14"
• Indianapolis: 4"-6"

ILLINOIS:

• Marion: 8"-13"

KENTUCKY:

• Paducah: 5"-8"

MISSOURI:

• Cape Girardeau: 7"-12"
• Poplar Bluff: 6"-10"
• St. Louis: 1"-2" (maybe 3)

Hope you have the snow shovels ready!  But PLEASE be careful if you are in places that could get ice first.  If you go out to shovel and hit some of the ice, your day may not be overly joyful.

Bottom line...

• There will be rain, freezing rain, sleet and snow.
• This will NOT be a repeat of 2009's historic ice storm.
• Temperatures get much colder.
• Significant snow will fall over parts of the Ohio/Mississippi River valleys.
• There could be another round of snow coming through Sunday/Monday. Let's first get past Thursday and Friday before dealing with Sunday/Monday.

FREAK-OUT-METER: (Scale of 0 to 10)
Time to break down the Freak-Out-Meter a little more.  If you've been paying attention to it over the last couple days, it is has been slowly inching up.

INDIANA:

• Columbus/Bloomington: 6/7
• Evansville: 7
• Indianapolis: 5

ILLINOIS:

• Marion: 6

KENTUCKY:

• Paducah: 7 (because of freezing rain)

MISSOURI:

• Bootheel: 7 (because of freezing rain)
• Cape Girardeau: 6
• Poplar Bluff: 6
• St. Louis: 3

Reminder:  To get more weather information throughout the day and night, follow me on Twitter (@johndissauer) where I put out lots of information and thoughts that don't necessarily make it in to my blog.

Colorado Deep Freeze

It is going to get cold.  Let me rephrase that, it is going to get VERY cold in southern and eastern Colorado starting in less than 24 hours.

As of last night's forecast, temperatures were forecast to stay at or below freezing Wednesday through late Monday morning for Colorado Springs and Pueblo.  New data this morning is suggesting temperatures could stay at or below freezing all the way through December 18.  Brrr!

The prolonged period of temperatures at or below freezing got me wondering how common is prolonged periods of cold temperatures for Colorado Springs and Pueblo.  Just looking back over the last five years of data for Colorado Springs shows that only six times has the temperature stayed at or below freezing for four consecutive days or more.

With the help of some of the meteorologists at the National Weather Service office in Pueblo I was able to get historical perspective.  Below are the records and Top 5 number of days below freezing (31° or less).

COLORADO SPRINGS:

1. 14 days ending January 9, 1970
2. 13 days ending January 10, 1979
3. 13 days ending January 11, 1973
4. 12 days ending March 4, 1960
5. 9 days ending February 7, 1985

PUEBLO:

1. 13 days ending January 11, 1974
2. 11 days ending March 3, 1960
3. 10 days ending January 9, 1988
4. 10 days ending January 9, 1979
5. 9 days ending December 25, 1983

Special thanks to the National Weather Service Pueblo office for helping dig up the stats.

Slip Slidin' - Tuesday Morning Update

Not a lot of time this morning to update the blog but I did get a few minutes to look over some of the new data trickling in from the morning computer model runs.

First take-away... The models are a little further north with the track of the system.  Which was expected.

There is a lot yet to be determined on placement/precipitation type.  As usual, the National Weather Service's NAM computer model is a little hyperactive with the amounts of precipitation.

Let me run you through several maps that can give you an idea of where the models are placing different types of precipitation.  Before I say anything else, PLEASE remember that this is not locked in stone.  These are just computer model projections and far from the actual forecast.

First, here is the NAM's projection of snow accumulation through 6pm CT Friday.

12z NAM - Snow Accumulation through 6pm CT Friday
(Click image to see larger version.)

 Now here is the NAM's projection of sleet accumulation through 6pm CT Friday.

12z NAM - Sleet Accumulation through 6pm CT Friday
(Click image to see larger version.)

Now the dread "ice" word.  Freezing rain accumulation through 6pm CT Friday.

12z NAM - Freezing Rain Accumulation through 6pm CT Friday
(Click image to see larger version.)

As you can see, the NAM is perhaps a little overzealous, especially with snow in the St. Louis metro.  (12"+?!?!)  The model is also heavy handed with the sleet for southeast Missouri and southern Illinois.  I could buy this scenario.

This event is at the edge of the model's projection view.  I have a feeling we will see these numbers dropping over the next 24-36 hours.

Now a look at the National Weather Service's Global Forecast model, the GFS.

Here is a look at what this morning's run of the GFS is suggesting for snowfall accumulation through 6pm CT Friday.

12z GFS - Snow Accumulation through 6pm CT Friday
(Click image to see larger version.)

 GFS sleet accumulation through 6pm CT Friday.

12z GFS - Sleet Accumulation through 6pm CT Friday
(Click image to see larger version.)

Finally, the GFS suggestion for freezing rain (ice) accumulation through 6pm CT Friday.

12z GFS - Freezing Rain Accumulation through 6pm CT Friday
(Click image to see larger version.)

Observation of the GFS... First, it is further south than the NAM.  It is also not as bullish with snow.  The GFS tries to hit the sleet and freezing rain a little harder.

Again, the models should start to line up better as we get closer to the event.

Bottom line... Cold air is expected to arrive later this week.  Moisture will be in place and there could be a mix of rain, freezing rain, sleet and snow across parts of southeastern/eastern Missouri, southern Illinois, western/northern Kentucky, northern Arkansas, northwest Tennessee and central/southern Indiana.  If you have travel plans Thursday-Saturday pay close attention to the forecast.

Reminder:  Follow me on Twitter for more information as it becomes available.  @johndissauer

Freak-Out-Meter:  4 out of 10

End of Week Winter Storm - Monday AM Update

The advertised cold front is still on its way to the southeast.  Temperatures this morning were -20° to -38° in western Canada.

As you can see from this image, temperatures are projected to drop well below normal by Friday afternoon.

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

Looking at morning data it is becoming clear there will be a storm to deal with Thursday and Friday in southeast Missouri, southern Illinois, western Kentucky, northern Arkansas and southern Indiana.

The new data from the National Weather Service’s Global Forecast model, the GFS, is hinting at the storm being perhaps a little warmer initially.  What does that mean?  The model suggests that things will start out as rain.  And there could be plenty of it initially.  As the cold air wedges in, things change over to freezing rain at the surface.  Eventually, the freezing rain would change over to a little sleet and then perhaps snow.

Here is a look at how much moisture two computer models are suggesting from 12pm Thursday through 6pm Friday.

2-computer model average quantitative precipitation forecast
(Click the image to see larger version.)

When you see the numbers from the GFS you'll notice some hefty amounts.  A lot of that comes down as rain before things change over.  Having said that, freezing rain and then a couple inches of snow on top is not a fun situation.

Here is a closer look at this morning's GFS in a three dimensional sense.  Specifically, we are looking at Cape Girardeau.

12z GFS - Cape Girardeau
(Click the image to see larger version.)

Green vertical bars indicate rain.  Blue indicates snow.  Orange indicates sleet.  Red indicates freezing rain.  Notice the software and the computer model suggest freezing rain during the day Thursday and then changing over to a little snow Friday.

Go a little further north to St. Louis and see what the model is suggesting.

12z GFS - St. Louis
(Click the image to see larger version.)

Notice it is indicating all snow for St. Louis.  In fact, when looking at the 2-computer model average, the data would suggest a 2"-5" snow for the St. Louis area.

Here is a look at snow projections from last night's run of the European forecast agency's model.

0z ECMWF Projected snowfall through 6pm Friday.
(Click the image to see larger version.)

0z ECMWF Projected snowfall through 6pm Friday.
(Click the image to see larger version.)

I would say the Euro is a little more gung-ho with snow versus freezing rain.  Having said that, it still does suggest a little freezing rain for a line from Poplar Bluff to Cape Girardeau and up the Ohio River.  South of that line, the potential for freezing rain is higher.

Also... I am still looking at another chance for snow Sunday in to Monday.  We'll talk more about that as we get closer.

By the way, if you are on Twitter be sure to follow me as I send out many updates throughout the day I typically wouldn't put on the blog.  Follow me at @johndissauer.

Bottom line... No need to panic yet.  Know that there is a good chance of the area seeing something Thursday and Friday.  Know that this could be rain changing to freezing rain and/or sleet changing to snow.

Freak-Out-Meter: 3 out of 10

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.

Looking Over December

Hints of a mild Christmas in
 the forecast for 2013.

Just took a look at the experimental loooooong range European forecast computer model.  The model reaches out to December 29.

Before I get in to the observations, let me quickly touch on something coming for later this week.  COLD AIR!!!  This morning at 10am Central, the temperature was -38° in Eagle, Alaska.  Cold air is definitely recharging over interior Alaska.

Computer models have been advertising for days that cold air will be on the march in to the United States for mid to end of the week.  The question all along has been "Just how cold?".  The data has been suggesting VERY cold air but often times the models will start to moderate the temperatures as we get closer to it happening.  This appears to not be the case.

Some of the coldest air in four years could arrive in Colorado by Thursday.  The cold front will pass Wednesday but the brunt of the arctic air arrives a day later.  Ahead of the front, temperatures will be in the 60°s and perhaps 70°s in southern Colorado.  By Friday morning, temperatures could be 60° to 75° degrees colder.  Yes, temperatures look like they could go below zero.  And by Friday afternoon temperatures may struggle to get out of the single digits.

The cold air will push east and arrive in the upper-Midwest Friday and Saturday.  It looks very cold north of I-70 and very VERY cold along and north of I-80.

Now... On to the observations from the long range data...

Looking at 6pm CT December 25.

• Thunderstorms in the Midwest December 10.
• Warm-up in Colorado December 12-13.
• Quiet weather for the United States December 21.
• Mild temperatures for Colorado, Missouri, Illinois and Indiana.
• Christmas:
• Mild weather for Missouri, Illinois, Kentucky and Indiana.
• Normal to slightly above normal temperatures for Colorado.
• Snow moving through the Dakotas.

If you are hoping for a White Christmas in the Midwest, the way it looks right now it doesn't look likely.  In fact, there doesn't appear to be a need for winter coats during the afternoon.  Santa Claus may indeed be able to trade in the cold weather jacket for a Hawaiian shirt.

If you are traveling for Christmas, things look A-OK for much of the country on the 23rd and 24th.

As I like to remind... Keep in mind, the model is just that.  A computer model.  The farther out the model looks, the higher the possible error rate.  The key to look at this kind of data is not to look at specifics but instead trends and long wave patterns.