Winter Weather

Dec 222017
 

Radar at 3:30 pm

A band of rain is sliding up into the Ozarks late this afternoon.

As temperatures begin to fall near the surface, the rain is expected to make a transition over to snow during the evening hours.

Accumulations will range between barely measurable to maybe as much as 2″. With a warm ground and temperatures above freezing, travel won’t be bad at first.

By later tonight as temperatures drop below freezing, roads make become slick in spots.

A Winter Weather Advisory is in effect for most of the area tonight.

 

Dec 192017
 

GFS Model Precipitation Type Sunday Morning (Image from COD)

It’s a hot topic for something cold!

Over the weekend, I hinted at the possibility of snow on Christmas Eve in the Ozarks. The chance for snow remains!

The funny thing about longer range forecasting is one looks for the general ingredients first: cold air and a disturbance.  Both of these continue to show up for Sunday but the details are still fuzzy.

It looks like light snow, not a major winter storms which is really the best kind for all concerned in that it looks nice without causing a travel problem.

Also, generally speaking, the last week of December and early January become more active meaning more precipitation chances and enough cold air to make winter precipitation a possibility.

Dec 172017
 

Sunday Morning Radar

What’s that sound?  Yes, it’s raining!

Welcome rain visited the Ozarks overnight and continues early today.

As of 7 am Sunday morning, Springfield picked up about a half inch of rain.  Morning radar shows showers in the Springfield area with the majority of the rain now northeast of the city.  The rain will end in the Ozarks early today.

The week heading into Christmas will be a mild one. Expect high temperatures in the fifties and even sixties!

However, a slam of arctic air will arrive on Friday.  Much colder air will be in place next weekend with highs in the forties and even thirties.

This leads me to a White Christmas comment.  The first ingredient is of course it has to be cold enough to snow which appears likely.

The second condition is a trigger for precipitation. Almost as exciting as Santa coming (a certainty!),  there has been a consistent signal for snow in or close to the Ozarks on Sunday.

A White Christmas is usually defined as snow on the ground not necessary snow on Christmas Eve so this could be an exciting development.  It will keep me watching the charts this week.

GFS Model of Precipitation Type Noon on Christmas Eve

More updates of course this week!

 

Dec 102017
 

Lake Effect on December 10th, 2017

I’ve watching lake-effect snow bands set up on the eastern end of Lake Erie today.

Lake-effect snow is the product of a warm lake and cold air. Because water cools more slowly than the air, this condition sets up starting in late fall and early winter.

It is essentially a very unstable set-up: the air in contact with the lake picks up a tremendous amount of heat energy and humidity below a winter-cold mass of air above.

The result, assuming temperatures support snow, is narrow and extremely efficient band of snow.

 Posted by at 7:26 pm
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!