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Winter Precipitation » Weather Or Not! | Weather or Not!
Feb 212013
 

Snapshot Around 11:30 a.m.

Areas east of Springfield still have some shots of sleet and ice accumulation possible, a back edge to the worst of it is in sight!

The Storm So Far

We have had reports of up to .25″ of ice (not sleet) on some surfaces.  But a lot of what fell changed into sleet.  The reason for this had to do with the unstable air existing over the cold air at the surface. This lead to more convection (hence the lightning and thunder) which features rapidly rising air. This air cools as it rises, it converts a freezing rain layer into a sleet layer. This cut down on a lot of potential ice accumulation!

Small Hail in Willard (Austin Houp)

To complicate matters, some small hail was also included in some of the thunderstorms!  I enclosed a picture from Willard today of some pea-sized hail.

Hail looks smoother while sleet is more grainy.

Another tenth of on inch of ice accumulation is possible with the band of showers east of Springfield over the next few hours. Sleet will be mixed with much of this.

As for Springfield, stick a fork in it, we’re essentially done with the heavy stuff!

Feb 212013
 

Radar/Temperatures at 7 a.m.

Overnight, a wave of lighter snow and sleet moved north over the Ozarks.

At this hour, convective bands (with some lightning and thunder) are organizing over northwest Arkansas and southwest Missouri. This represents heavier precipitation rates and with temperatures in the upper twenties, freezing rain and ice accumulation will continue for a few hours.

There might be sleet in the core of some of the heavier bands, reducing ice accumulations somewhat but overall, expect conditions to worsen through mid-morning, especially north and east of Springfield.

The real question for the day is: how much warming will occur at the surface and where?  My belief is that Springfield will see a recovery to near 32 degrees, still icy but more manageable.

Winter Advisories

The concern all along has been the persistent below freezing situation which will set up for areas of northern Arkansas and perhaps south-central Missouri later this morning and afternoon.  An ice storm warning is still in affect for a portion of that area.

Icy Table/Deck in Lakeview, AR (Erica Schultz)

Feb 202013
 

Possible Precipitation Type at 9 a.m. Thursday

Everything is progressing at about the same pace as this morning’s forecast.

One exception is the development of a light snow band out ahead of the main band expected later this evening.  This has produced some minor accumulations in portions of Barry, McDonald and Stone Counties in Missouri and Boone County in Arkansas.  It will remain light and weaken as it moves northeast.

The main show is still tonight and Thursday. Remember that many, including folks in Springfield, will go through a progression of precipitation types. It will start as snow later this evening, change over to sleet late tonight and then go to freezing rain by Thursday morning.

So waking up in Springfield, there will be several inches of snow/sleet on the ground with a glaze of ice on top of that.  Some icing of trees and wires will occur in Springfield however I don’t believe we will see the worst of it.

The heaviest icing should occur over areas of north-central Arkansas and south-central Missouri. I still feel as if coatings of near .40″ of an inch of ice are possible in these areas by tomorrow afternoon.

Pure snow accumulations will be reserved for areas about an hour north drive from Springfield during this storm.

I will have more updates later today.  This will include my video blog and a live web show at 6 p.m.

 

Feb 202013
 

Main Precipitation Threat Tonight/Thursday

All of the Ozarks are under some short of winter storm warning this morning for later tonight and Thursday. Ice accumulation is still a concern.

A huge amount of humidity is being lifted over a dome of cold air which will result in lots of rain aloft, which will transition to a mess in the Ozarks on the ground in the form of sleet and freezing rain.

Layout of Precipitation

There is an expected transition of precipitation type for many in the Ozarks. When the initial wave comes in tonight, it’s expected to be snow and some sleet.  This will probably stay snow in areas from let’s say Lamar to Camdenton northward.

As for Springfield, snow will give way to sleet and eventually freezing rain (ice) by dawn on Thursday.

Freezing Rain vs. Sleet: What’s the Difference?

 

Areas of northern Arkansas and south-central Missouri will hold on to freezing rain the longest and have the biggest threat of significant ice accumulations.

Totals

I expect Springfield will see several inches of snow/sleet overnight tonight with a glaze of ice on top of that starting sometime in the early morning hours of Thursday.

The snow up north could amount to 1-3″.  This of course will become a major snowstorm north and northwest of the Ozarks.

Ice accumulations will be between .10 and .40″ I think with the higher amounts in the area specified on the graphic.

Information Today/Tonight

I will post a winter storm update after the morning computer model runs come out, right around noon.

I will post a video review/blog by late afternoon.

Also, look for a live web show tonight to discuss the situation. Details coming up later today!

Feb 192013
 

Winter Precipitation Depends on Temperatures Above

When I use the phrase “winter mix”, it refers to some combination of snow, sleet or freezing rain (ice).

The term is used whenever any of these are possible over a certain time frame.

Both sleet and freezing rain require a layer of above freezing air aloft.  The difference is in the depth of the sub-freezing layer touching the ground (lower blue areas on diagram)

While the “general” layout is for snow to occur closest to the colder air with sleet, freezing rain and rain occurring in bands toward the warmer air (usually in a southerly direction), there are exceptions.

One is terrain. An increase in elevation means colder temperatures which can change the precipitation type.  Or the opposite, occasionally cold air becomes trapped in valleys and alters precipitation type.

Also, convective (rain/thunder) bands tend to cool a column of air near the ground and turning what might be a freezing rain situation into sleet.

Here are the definitions:

Sleet

This is liquid (rain) aloft which falls into subfreezing air near the surface deep enough to freeze the drops into ice balls.  Sleet “tings” when it strikes windows.  Sleet accumulates like snow but because it is essentially little ice pellets, it doesn’t accumulate nearly as fast. It actually offers some increased traction on roads when compared to snow.

Freezing Rain (Ice)

Nearly the same as sleet except that the drops stay liquid falling into a much shallower subfreezing layer at the ground. These “super-cooled” rain drops will then freeze on contact with surface objects, especially those off the ground such as trees and wires.  Freezing rain producing ice accumulations over a half inch can cause branches and wires to snap from the weight. An ice storm is born!

 

Feb 192013
 

Probability of >.10" of Ice Accumulation Wednesday Night

A mix of snow, sleet and freezing rain is expected in the Ozarks starting Wednesday evening and lasting into early Thursday.

Winter Storm

It’s a case of precipitation aloft running into cold and dry air only slowing retreating. This sets the stage for a mix of winter precipitation in the Ozarks.

The typical progression in systems like this is to start of with sleet (or snow), making a transition to freezing rain.  This will begin in the Ozarks sometime on Wednesday evening.

Freezing rain is otherwise referred to as ice and there is a possibility of ice accumulation  between .10″ and .40″ on elevated surfaces such as branches and wires.  There is a great amount of liquid available with this system (lots of rain if it were warm enough) so I’m concerned for potential significant ice accumulation.

Freezing Rain Area Late Wednesday Night/Thursday

While a transition to rain is possible in some areas on Thursday, it appears now that temperatures right around freezing might hang around in many areas.

Winter precipitation type depends on subtle changes in the entire profile of temperature overhead. Freezing rain by definition has to occur in surface temperatures below freezing. Timing and exact intensity of the precipitation is key.  The higher areas of northwest Arkansas might be more at risk as they are cooler.

I’ll have more on daily blogs and vblogs. Some special updates may be required.  Check in often!

Feb 182013
 

Winter Mix Spread Overnight Wednesday (3 a.m.)

Showers today will usher in colder air, setting up some winter precipitation Wednesday night.

Today’s Showers

No indication on radar early this morning but a sharp front will work with the humidity that’s out there to produce an area of light rain later today.

Light is the key word here. Most areas will have totals less than .20″. Perhaps a bit more east of Springfield.

Cold and Dry

Colder air replaces the mild stretch we’ve experienced Sunday and Monday.

Computer Model Temperature Trends

This wedge of winter air is being supplied by an area of high pressure.  Our temperature will average around forty degrees on both Tuesday and Wednesday.

Precipitation Meets Cold Air

As cold and dry air settles in the Ozarks the next few days, a deep area of low pressure will begin to develop out west. This is part of a pattern of winds aloft which will spread precipitation our way from the southwest. Trouble is, the cold air will still be in place near the surface!

This will set the stage for a band of sleet and freezing rain to develop Wednesday night into early Thursday.

The enclosed image shows the expected layout of the winter precipitation Wednesday night.  One source for concern is the “juiciness” of this system, lots of liquid aloft could translate into ice accumulations worth talking about by Thursday morning.

The other issue is of course any winter precipitation which occurs overnight often comes as a surprise to folks going to work and school the next morning.

It’s too early to try and estimate ice accumulations but I’ll be keeping a very close eye on this system as it develops.

Transition

During the day on Thursday, enough warm air (above freezing) should spread into the area to convert the precipitation to rain. The totals should be good to us ranging from .50″ to perhaps as much as 1″ of liquid.

Weekend

This weekend looks dry and warmer. The next weather system should swing in by late Sunday and into Monday.

Feb 172013
 

Forecast for Noon Monday

This will be a fantastic Sunday in the Ozarks! Look forward to mild temperatures and mainly sunny skies.

A Few Mild Days

Both today and Monday will be warm for the season as high temperatures peak in the fifties. Southerly wind will remain in place until a cold front arrives on Monday.

Monday Front

By Monday afternoon, rain showers will begin to break out ahead of a cold front.  While many in the Ozarks will probably see some rain, meaningful rain totals will only be possible for areas to the east of Springfield.

Seasonal Chill

Tuesday and Wednesday will be chilly days, a tad lower than seasonal norms.  Highs in the forties.

Wintry Set-Up?

There is some possibility now of the next wave of precipitation, due in late Wednesday and Thursday, may run into enough cold air to cause a wintry mix in a portion of the Ozarks.

This appears most likely in areas to the north and northwest of Springfield either overnight Wednesday or early on Thursday.

This is part of a larger area of rain forecast to develop over a large area of the central U.S. as a storm deepens over Kansas.  I’ll watch this carefully as it comes down to very subtle changes in the temperature profile. More updates later in the week!

The Rain

HPC Projected Rain Wednesday-Friday

With or without wintry stuff, we’re hoping for a good soaking in the Ozarks.  Springfield may receive as much as an inch of rain late Wednesday-Thursday of all goes well.

Unsettled Pattern

The late week precipitation is one of two systems of some strength which will affect the Ozarks. Another appears around a week from now (late Sunday through Monday). It’s way out in time so the usual cautions apply for position and strength.

Feb 122013
 

Forecast for Snow Overnight

The Ozarks are still on track for some snow overnight tonight!

Snow Set Up

A system in the southwest is beginning to transport humidity, clouds and precipitation northward this morning.  The 4:30 a.m. radar image is shown. Green rain, blue snow.

This will start as a chilly rain in the Ozarks toward evening.  The temperature profile between rain and snow is right on the line for later tonight and into the overnight hours.

As is often the case in these borderline snow systems, additional cooling needed to keep the precipitation as snow for longer periods of time will come from either the core of heavier bands of precipitation or from higher elevations.

Weather Early This A.M.

Since temperatures will be right around freezing when it’s snowing, accumulations will mainly be seen in grassy areas.  But in areas of enhanced snow some sticking on roadways is possible. Take into consideration that you will be waking up to whatever falls on Wednesday morning!

Steady Wednesday and Thursday

Most of whatever snow the Ozarks receives will melt on Wednesday and Thursday with the return of sunshine and an above freezing daytime pattern.  Forties on Wednesday, right around fifty on Thursday.

Big Front

Colder than normal temperatures blast into the area Friday and Saturday.  Only thirties for maximum temperatures heading into the weekend.

Next System

The next “weather system of interest” comes our way on Monday. Looks like initially a rainmaker for the Ozarks with snow on its backside. Worth watching.

 

Jan 252013
 

Computer Temperature Trends

The freezing drizzle that has occurred has been light enough to prevent any major problems over southern Missouri and northern Arkansas this morning.

OK Friday and Saturday

A seasonably cool day this expected in the Ozarks today.  Temperatures are starting out in the twenties and will rise into the forties later today.

Clouds especially just to the south of Springfield will gradually move on by later today.

Saturday has even more potential with warmer conditions. Many folks will see a high right around fifty on Saturday.

Saturday Night/Sunday

As mentioned yesterday, a batch of needed rain will begin to approach the area Saturday night.  There is still a slight possibility that the leading edge of this precipitation will be freezing rain well to the east of Springfield Saturday night.  But the pattern is progressive and warmer air will win over from the southwest during the morning hours so the threat at this point looks minor.

Simulated Radar at 6 a.m. Sunday

Needed rain should fall across the Ozarks Saturday night, part of a pattern of slight wetter weather Sunday through Tuesday.

Wetter Weather

The Gulf of Mexico will be able to supply higher humidity values to the region Sunday through Tuesday.

Occasional rounds of rain and even some thunder will be possible during this period. 

 

It will be warmer too!  Sixties and possibly a seventy might be obtainable Monday or Tuesday before temperatures crash mid-week.