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?

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.

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.

One Word: "Mess!"

By now you should be aware of the winter storm headed for the Ohio River Valley of the United States. There is only one way to describe how this is going to turn out. This is going to be a mess!

The National Weather Service offices in Memphis, Paducah, and St. Louis have upgraded our Winter Storm Watches to Winter Storm Warnings and Ice Storm Warnings. Further east, Winter Storm Watches are being upgraded as the system gets closer.

Around the Heartland (Southeast Missouri, Southern Illinois, Western Kentucky, and Northwest Tennessee) it looks as though we are going to see a mix of heavy snow, heavy sleet, and heavy icing in the form of freezing rain. It appears that this will start to move in from the west starting around 7:00pm - 8:00pm give or take a couple of hours.

Over the last couple of days, all but one of the models had been indicating copious amounts of moisture in the atmosphere to work with. Late last night the one lone model came in line with all the others. The models are suggesting there could be 1" to 2.5" of moisture to work with. That is a LOT of moisture for a winter storm!

If you look at my blog post from yesterday, we had some questions that had to be answered before we could figure out how bad this storm will be. We needed to figure out how much moisture there would be. We needed to determine what the temperatures going up in the atmosphere would be. We then could start to figure out what kind of precipitation we would be getting.

Lets take a look at the temperatures going up. Here is one of the forecast models cross section over Cape Girardeau.

Remember that the time reads from right to left. Notice the large area of 0°+ temps sitting around 5,000 feet off the ground. To me, this is hinting more at sleet than snow or freezing rain. What we see falling out of the sky will depend on how thick that layer of warmer air is. If it remains similar to this, we will see sleet. If it thickens, or drops closer to the surface, we will see freezing rain as the frozen precip falls in to the warm layer and melts. Then once it gets near the surface it refreezes as ice.

I have had a feeling that this biggest problem with this storm would be ice and my feeling is still the same. Some folks will get some heavy snow, but the ice is flat out crippling as many remember from last February.

Here is a look at one of the forecast views from Farmington, Missouri.

Notice that it is mainly all snow. (Blue = snow) With the amount of moisture in the atmosphere and it all falls as snow, it isn't out of the question to see a 7"-10" of snow.

Further south here is the view of Paducah, Kentucky.

Notice all the freezing rain. (Red=freezing rain) For people in Western Kentucky, Northwest Tennessee, and southern sections of Southeast Missouri (Benton, Mo and south) this could be a HUGE ice storm. With all the moisture the computer models are spitting out, it is possible we could be talking over 1" of ice.

For friends further to the east in Indiana... I think there is going to be a band of heavy snow of 6"-8" of snow that runs from Columbus, IN to Indianapolis. If you are south of Seymour (getting closer to Louisville), it is going to be more of an icing issue.

Snowfall Accumulation Map (from computer model):

Sleet Accumulation Map (from computer model):

Remember... The images I have put on here are computer models. Not reality. There is a lot more that goes in to forecasting than just taking numbers straight from the computer model. We will be fine tuning the forecast as the event nears.

So are you ready for this one?

"Snowfall, Sleet & Ice Oh My!"

It never can be an easy forecast around here. Why can't it just be all snow? It would sure make forecasting this storm much easier.

By now, you might have heard about a winter storm headed our direction. It still indeed is. The National Weather Service (NWS) in Memphis, St. Louis, and Paducah has issued a Winter Storm Watch for the entire Heartland (Southeast Missouri, Southern Illinois, Western Kentucky, Northwest Tennessee). The watch is in effect Monday evening through Tuesday evening.

There are still a lot of uncertainties with the storm.

1. What will temperatures be at different heights of the atmosphere?
2. How much moisture is there to work with?
3. What type of precipitation will we have?
   

Looking at temperature profiles are interesting at times. Basically, I am talking about taking a slice of the air above the ground and looking at it from the side. Think about it this way. When you are looking at an aquarium, you can look down at the water just above the bottom. Then you can move up the glass until you see the waterline. It is just a cross section of the water in the aquarium. That is what we have to do when determining what type of precipitation we will have.

Here is an example of what one of the computer models is suggesting for Monday/Tuesday. It allows us to see the cross section over Cape Girardeau.

If you click on the graphic you can see a larger version. I want you to notice the yellow lines on the screen. At around 5k to 10k (5,000 feet to 10,000 feet) see the 0 line? That is the freezing line at different heights above the ground. Notice all around the outside of the 0° line there is colder air. Inside there is warmer air. That means that anything falling through that area of the atmosphere will warm up and probably melt to liquid.

Also notice how it then gets below 0° near the surface. That is when the moisture would refreeze. In that situation we would probably be talking about freezing rain. Freezing rain = ice = yuck!

When you look at the graphic, you see different colored vertical bars. That is how much precipitation and the precipitation type. Green=rain Red=freezing rain Orange=sleet Blue=snow. (Also, when looking at the graphic, the time runs from right to left. I know it is backwards, but I didn't write the program. haha)

This particular model is indicating mainly freezing rain. Not just a little freezing rain, but a lot! On the order of over an inch. That would definitely not be good!

When I look at one of the cross sections from this model for Farmington, Missouri it indicates mainly snow. And a lot of it! This specific model is trying to suggest 8.1" of snow.

Again, this is just a model. A suggestion. When I forecast I look at a minimum 5 computer models. For major snow storms, I might take a look at 8 models.

If you were watching Heartland News at 10pm Saturday night you might have heard me say that I had a gut feeling this could be a bigger ice storm than snow storm. My gut still feels that way. (Although, I am also hungry, so it could be telling me to eat something.) As is usually the case, we are going to see the dividing line between freezing rain, sleet, and snow over the top of us. I think some people could get some heavy snowfall out of this. I think some could get a decent amount of freezing rain.

Here is a map showing what one of the computer models is calling for with regards to freezing rain.

Here is what the forecasters at the Hydrometeorological Prediction Center (or HPC) are forecasting. (This forecast was updated Sunday morning.)

Like I mentioned before, there are still a lot of uncertainties with the storm. Some of the models are trying to bring only a tiny bit of moisture through the area. If that were to be the case, then the numbers would be held down drastically.

I'll be looking over the models this afternoon while I try to put together my forecast. Hopefully, I'll feel strongly enough about a snow/sleet/freezing rain amount forecast to have it on TV tonight at 10pm.

I now need to go find my colored markers. Even though we have all kinds of computer technology to do things, I still like to take out a map (on paper) and mark it up with the colored markers while putting together the forecast.

So all of that said, what are you hoping for out of the storm?