Monday, November 28, 2011

Eyes Watching Snow

A spoke of energy is spinning around an area of low pressure that is currently centered over south central Kentucky.

Just ahead and along the spoke precipitation should begin to pick up in intensity.

The Storm Prediction Center has also taken notice of the current environment. They have recently issued a Mesoscale Discussion for western Tennessee, southeast Missouri and northeast Arkansas concerning snow rates picking up.


Laura Wibbenmeyer, former co-worker of mine at KFVS-TV, is in Portageville, Missouri and is reporting that it is all falling as snow. Nothing is sticking to the roads but snow is covering grass and car roofs.

The National Weather Service in Memphis is going a little higher than me with snow totals. They have mentioned that the freezing level has dropped further and is approximately 800-1,000 feet above the surface. If that is the case, more snow is likely to fall. Unfortunately, I don't have access to all the hi-res temperature profile data right now. (That is all located on my laptop at home.) However, I still think the snow will only accumulate on grassy and elevated surfaces.

Interesting to note the the NWS in Memphis has noticed that the rain is changing over to snow once the surface air temperature hits 36°-37°.


- Posted from my iPhone

Winter Weather Advisory

The National Weather Service in Memphis has issued a Winter Weather Advisory for the Missouri bootheel, northeast Arkansas and northwest Tennessee. The Advisory is in effect from 6pm through noon Tuesday.

The following is from the text of the Advisory.

NATIONAL WEATHER SERVICE MEMPHIS TN 222 PM CST MON NOV 28 2011
...EARLY SEASON WINTER STORM BECOMING MORE LIKELY ACROSS MUCH OF THE MIDSOUTH....
A POWERFUL UPPER LEVEL LOW WILL MOVE SOUTH OF THE AREA THIS AFTERNOON
AND TONIGHT. RAIN WILL CONTINUE ACROSS THE AREA TODAY AND GRADUALLY MIX
WITH AND CHANGE TO SNOW THIS EVENING AND TONIGHT AS COLDER AIR MOVES OVER
THE REGION. THE HEAVIEST SNOW SHOULD FALL ACROSS SOUTHERN WEST TENNESSEE
AND NORTHEAST MISSISSIPPI LATER TONIGHT. PRECIPITATION WILL TAPER OFF
TOMORROW MORNING AS THE SYSTEM LIFTS TO THE NORTHEAST.
ARZ009-018-MOZ113-115-TNZ001-290430-
CLAY-GREENE-DUNKLIN-PEMISCOT-LAKE-
INCLUDING THE CITIES OF...PARAGOULD...KENNETT...CARUTHERSVILLE
222 PM CST MON NOV 28 2011
...WINTER WEATHER ADVISORY IN EFFECT FROM 6 PM THIS EVENING TO NOON CST TUESDAY...
THE NATIONAL WEATHER SERVICE IN MEMPHIS HAS ISSUED A WINTER WEATHER ADVISORY
FOR SNOW...WHICH IS IN EFFECT FROM 6 PM THIS EVENING TO NOON CST TUESDAY.
* SNOW ACCUMULATIONS...1 TO 3 INCHES.
* TIMING...6 PM CST THIS EVENING TO NOON CST TUESDAY.
THE PERIOD OF HEAVIEST SNOW WILL OCCUR FROM MIDNIGHT CST TONIGHT UNTIL 6AM CST
 TUESDAY.
* IMPACTS...SNOW ACCUMULATIONS WILL OCCUR MAINLY ON GRASSY AREAS OR ELEVATED
SURFACES. HOWEVER IF SNOW COMES DOWN HEAVY FOR A PERIOD OF TIME THEN DRIVING
COULD BECOME HAZARDOUS.
PRECAUTIONARY/PREPAREDNESS ACTIONS...  A WINTER WEATHER ADVISORY FOR SNOW
MEANS THAT PERIODS OF SNOW WILL CAUSE SOME TRAVEL DIFFICULTIES. BE PREPARED
FOR POSSIBLE SNOW COVERED ROADS AND LIMITED VISIBILITIES...AND USE CAUTION
WHILE DRIVING.
&&
$$


How Much We Talking?

Everyone wants to know "How much?". That is not an easy question to answer. The reason being that it will be difficult to accurately measure the amount of snow we could see. A lot of this snow is going to melt as it falls through the sky. A lot of it is going to melt as it hits the ground.

I am still feeling pretty good about my projection as to where there could be snow. If anything, I might need to drop my line a little further south. Perhaps something along the lines of "south and east of a line from Murray, KY to New Madrid, MO to Malden, MO to Jonesboro, AR.

Rain is going to continue to fall. Forecast models are still on to that solution. The problem is the temperature profile of the atmosphere. In other words, if you go outside and look straight up, I am looking at the temperatures at different altitudes. In my previous post I went through and showed you what the models were indicating temperatures would be like at the surface and at 5,000 feet. The short range models, specifically the Rapid Update Cycle, are keeping the temperatures pretty close to what I mentioned before.

Cold air is on the move through Missouri. At 2pm CT, it is 33° F in Rolla, Missouri. Temperatures in southeast Missouri, western Kentucky, northwest Tennessee and northeast Arkansas are hovering in the upper 30's.

The tricky part is determining how much moisture will there be to interact with the strengthening cold air later this evening and tonight. Models are indicating that ss the colder air moves in the moisture will begin to move out.

Temperatures at the surface should be a degree or two above freezing as we go through the late night hours. So anything that falls is going to start to melt as it approaches the surface. That is why I don't think we will see any accumulation on roadways. The ground is just too warm. However, we could see a little snow accumulate on elevated surfaces (deck railings) and on grass.

I've extrapolated the following data from a recent run of the RUC model. I am going to use a snow to liquid ratio of 4:1. That is a low ratio as normally, you will see snow to liquid ratios of 10:1. Although, we can see snow ratios as high as 30:1 and as low as 1:1.

CITY | Rainfall amount interacting with below freezing air aloft | Snow
Blytheville, AR | 0.2" | 0.8"
Dyersburg, TN | 0.18" | 0.7"
Jackson, TN | 0.06" | .25"
Jonesboro, AR | .29" | 1.1"
Murray, KY | 0.02" | 0.1"
Walnut Ridge, AR | 0.17" | 0.7"

Keep in mind that the above numbers are if we were able to squeeze out every little bit of moisture and make it in to snow. I just don't think that's going to be the case tonight.

My "Freak Out Meter" is still pretty low with this system. I'm still giving it a 1 out of 10.

Light Snow Tonight

UPDATE Below: It appears like there is a chance for some light snow today and tonight across parts of southeast Missouri, western Kentucky, northwest Tennessee and northeast Arkansas.

As first mentioned 7 days ago, cold air is wrapping in behind the cold front/surface low pressure that initially brought rain to the region Sunday. Temperatures at 10am CT are in the upper 30's across southeast Missouri, western Kentucky, northwest Tennessee and northeast Arkansas. Temperatures are likely to hold steady in the upper 30's through the day.

Cold air aloft (a few thousand feet) will be between -1° and -3° Celsius. This will allow moisture to freeze in the form of snow. As the moisture drops to near the surface it will encounter temperatures that will be a couple degrees above freezing. This will allow for the snow to melt slightly. That's what we mean when we talk about a "wet snow". It is falling in to an environment that allows it to start the melting process.

The areas I think have the best chance at seeing accumulation, mainly on grassy and elevated surfaces, will be south and east of a line from Mayfield, Kentucky -- New Madrid, Missouri -- Malden, Missouri -- Jonesboro, Arkansas. That's not to say we couldn't see a little north of that line, but the bulk should be south and east of of that line. (I wouldn't be surprised to hear some reports of snow around Doniphan, Mo, Poplar Bluff, Mo, Van Buren, Mo or even Sikeston, Mo or Charleston, Mo.)

At this point, I don't think it will be a big deal. My "Freak-Out-Meter" is around a 1. (That's on a 10 point scale.) Soil/ground temperatures are still warm so that will allow for snow to quickly melt, especially on roads.
--------------------------------------------------------

11:42am CT Update:

To give a little more perspective as to the temperature profile of the atmosphere I wanted to show you what temperatures are forecast to be at the surface and at 5,000 feet (850mb).

The following is from NOAA's morning run (12z) Global Forecast model (GFS). All tempertaures listed in Celsius.

CITY | 1pm CT 2-meter/5,000' Temp | 7pm CT 2-meter/5,000' Temp | 1am (Tue) CT 2-meter/5,000' Temp

Cape Girardeau, MO | 3.6°/-0.7° | 2.3°/0.5° | 2.6°/1.6°
Dyersburg, TN | 3.7°/-2.1° | 1.5°/-2.5° | 0.7°/-1.5°
Jonesboro, AR | 4.8°/-4.0° | 3.3°/-3.2° | 1.3°/-1.0°
Murray, KY | 3.3°/0.8° | 2.7°/-0.8° | 2.0°/-2.0°
Paducah, KY | 3.2°/0.6° | 3.1°/1.2° | 3.8°/0.8°
Poplar Bluff, MO | 4.4°/-2.5° | 2.1°/-0.8° | 1.2°/1.6°

Looking at the above data you can see when the colder air aloft strengthens yet temperatures at the surface remain above freezing. You can also see areas where temperatures never get below freezing. Also notice the times when the temperature barely makes it below freezing (0° Celsius). Yes, a few tenths of a degree can make a BIG difference in what type of precipitation falls.

This gives you a look at some of the data forecasters look at when trying to determine what type of precipitation is going to fall. Keep in mind, this is only one model of several we look at. For big snow storms I may look at seven to eight models.

Monday, November 21, 2011

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..."

Monday, November 14, 2011

A Few Storms Possible

The Storm Prediction Center is monitoring southeast Missouri, southern Illinois, western Kentucky and northeast Arkansas for the need of issuing a tornado watch.


According to SPC the threat appears to be isolated. It will depend on how many storms can get fired up in the next couple hours as to whether a watch will be issued.

A Tornado Watch is currently in effect for most of Indiana. That watch is in effect until 9pm ET.


- Posted from my iPhone

Tuesday, November 8, 2011

Storms Tonight

The Storm Prediction Center has placed all of southeast Missouri and portions of southern Illinois, western Kentucky and Arkansas in a "Slight Risk" area for severe thunderstorms in their latest outlook.


It appears the best chance for severe storms in southeast Missouri and southern Illinois would be later tonight.

There are still a few question mark for severe thunderstorms to develop.

We need to see the atmosphere destabilize. Right now the air mass in place is relatively stable. As the surface low currently over Texas/Oklahoma tracks northeast the low will deepen (become stronger). Ahead of the low, southerly winds should tap in to more humid air to the south.

Forecast models are indicating instability should move back north and allow the atmosphere to become unstable by tonight.

If the air mass can become unstable there will likely see a few thunderstorms moving east across Arkansas and Missouri.

The main threat appears to be damaging wind. I can't rule out the chance of a quick spin up tornado, especially close to the track of the surface low. The good news is that if there is a tornado it won't be like the long lived tornadoes seen in Oklahoma yesterday.

A couple things bother me about the setup... Cloud cover. Missouri is pretty well socked in with cloud cover. This is going to limit instability somewhat.

Timing... The storms would likely move in well after sunset. This will take away some of the spark in the atmosphere. That's not to say we couldn't see something after dark, I just think that storms will be on the downward trend of severity.

Bottom line...
  • Will there be thunderstorms? Probably.
  • Will there be a watch? Possibly.
  • Will there be a severe weather outbreak? No.
  • Could there be warnings? Yes, there could be a few.
  • Should you freak out? No. Just keep an eye on the situation. Make sure you have your NOAA weather radio plugged in. Have a way to be alerted if a warning is issued for your location.


- Posted from my iPhone

Sunday, November 6, 2011

Threat of Storms

We are less than 25 days from the start of meteorological winter but we need to be thinking about spring... spring storms.

I have talked about the chance for colder air moving south out of the arctic in the next week and a half. Ahead of the colder air it appears we will have a chance for strong thunderstorms across the middle United States.

The Storm Prediction Center has included parts of Missouri, all of Arkansas and places further south in a "Slight Risk" for severe weather 7am Tuesday through 7am Wednesday.


An area of low pressure is going to develop over New Mexico and Texas over the next two and a half days.


Strong winds in the jet stream will rotate around and provide lift in the atmosphere. By mid to late afternoon Tuesday I expect to see thunderstorms developing over eastern Oklahoma, western Arkansas and western Missouri. The thunderstorms should develop in to a line of storms that will move east across Missouri, Arkansas and further south.

I have been looking over the morning run of the GFS and NAM computer models. There are a few subtle differences between the models but both appear to be pointing at diverging winds at the 300mb level over southeast Missouri by Tuesday evening/night. The NAM keeps winds a little more divergent over Arkansas and the GFS keeps winds a little more divergent over southern Illinois.

Here is a look at one of the computer models. This indicates winds at 300mb (approximately 30,000 feet) 7pm CT Tuesday.


I look for divergent winds at 300mb because that gives an indication if there will be lift in the atmosphere. Diverging winds create a void and wind from below lift in to fill the void.

All of the above said, it looks to me there could be strong to severe storms along the line of storms as it moves through Arkansas and Missouri. It is still a little early to nail down the main threat from the storms but it damaging winds, isolated tornadoes and hail all could be possible.

Stay tuned...
____________________________________

Daylight Saving has come to an end. Hopefully you remembered to change the times on your clock this morning.

Fire departments across the country use the time change as an opportunity to remind everyone to replace the batteries in your smoke detectors. This is good practice. I want to suggest you take it a step further and use the time change as an opportunity to replace the batteries in your NOAA weather radios.

Friday, November 4, 2011

ISS Sighting Tonight

There is another opportunity to see the space station tonight for part of the midwest. Unfortunately, it looks like areas in southeast Missouri, western Kentucky, Tennessee and Arkansas will have cloud cover obscuring the view.

The details:

Chicago:
  • When: 6:42pm (local) - The space station will be visible for 5 minutes.
  • Where: Look to the WNW sky. The space station will travel across the sky and exit to the SE. It will reach a height of 55° above the horizon.
Columbus, IN:
  • When: 7:42pm (local) - The space station will be visible for 6 minutes.
  • Where: Look to the NW sky. The space station will travel across the sky and exit to the SE. It will reach a height of 73° above the horizon.
Indianapolis:
  • When: 7:41pm (local) - The space station will be visible for 6 minutes.
  • Where: Look to the WNW sky. The space station will travel across the sky and exit to the SE. It will reach a height of 68° above the horizon.
Moline:
  • When: 6:40pm (local) - The space station will be visible for 6 minutes.
  • Where: Look to the WNW sky. The space station will travel across the sky and exit to the ESE. It will reach a height of 79° above the horizon.
St. Louis:
  • When: 6:41pm (local) - The space station will be visible for 6 minutes.
  • Where: Look to the NW sky. The space station will travel across the sky and exit to the ESE. It will reach a height of 65° above the horizon.
Skies will be clear for the areas listed above so it should be perfect conditions to see the ISS as it passes overhead.

It will initially look like a dim star but it will be moving like an aircraft.

Check it out and let me know if you see it. Leave a comment here on my blog. Enjoy!

Wednesday, November 2, 2011

Cold Air Building

It is the time of year when I like to start looking further out in the computer models. What am I looking for? I'm looking for cold air marching south through Canada and I am also looking for storms taking shape that can interact with the cold air. When the two play together, "fun things" develop.

For the last couple of days NOAA's Global Forecast model (GFS) has been advertising some cold air building and marching south out of Canada for mid-November. The latest run of the GFS (12z) continues to hint at the cold air coming.

Right now it looks like the cold air would come down in two shots. The first would arrive in the Midwest/Ohio River Valley sometime around November 13/14.


The second shot, and most likely the colder of the two, would arrive in around November 16/17. (The image above depicts the morning of November 16.) If the above image were to hold true, then I might have to use the "s" word for the first time this season. Yes, snow.

I should also add that the European Forecast Agency's computer model is also hinting at a shot of colder air coming down around November 12. At this point, it is splitting hairs between the two models. However, it is interesting that both models are hinting at something similar around the same time.

Don't get too excited just yet. This is a LONG way out in the computer models. There is a likely climatological bias in the models trying to bring in cold air to keep in mind. If I were a betting person, I would say the above scenario is not likely to happen this far in advance. However, it is something to keep an eye on. Especially if you enjoy colder weather.

Stay tuned...

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