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Weekend Cold (and snow?)

12:09 pm in The Ozarks, Winter Weather by Ted Keller

Another arctic front will slam through our area on Saturday.  

While Minneapolis and parts of the upper Midwest are under a blizzard watch, our portion of the system consists of a cold front and very strong winds in the wake of the front.

Snow chances come in two forms: a brief changeover late Saturday as the front comes through and then some snow that may wrap around the upper Midwest storm which would affect central and eastern Missouri implying flurries in the Lake of the Ozarks area Saturday night.

Some computer models are outputing minor snow accumulations in the same areas I discussed earlier in the week to the northeast of Springfield and those chances remain as they were, outside the mainstream output.

The winds Saturday night and Sunday will be gusting over 25 mph!  This combined with temperatures in the teens will produce wind chill readings in near zero or even slightly below during this time!  Sunday’s high will only reach into the twenties.

Weekend Snow

8:07 am in The Ozarks, Winter Weather by Ted Keller

Weather Map at 6pm Saturday.

A weekend snow?  It seems more likely for a portion of the Ozarks as of this morning.

In yesterday’s blog, I was commenting on the reliability of the various runs of a long-range computer model I look at a lot.  Over the past 24 hours, four “runs” have come out and they all converge on a low track which is more southerly (the one that looked least likely yesterday!).  This means an accumulating snow is more likely, especially for the western, northern and central portion of Missouri. 

It is still way too early to nail down specifics.  And, at this distance, only one model has good output.  I’ll be watching this situation!  It looks like a late Saturday event.

NOTE: latest run still showing this feature!

Pre-Holiday Storm Threat

5:59 am in Forecast Discussion, Severe Storms, The Ozarks by Ted Keller

Dew Points at 5 am

Here’s the latest on the severe weather expected over the area later today.

A large storm at the jet stream level is progressing into the area today.  Upper level winds have increased and the surface winds are quite strong too.  This is a strong wind shear environment and is supportive of severe storms in the Ozarks.

As is typical in “cool season” set-ups like this, the amount of unstable air is in question.  But experience has shown that as long as the proportions of shear and instability are correct, severe storms can flurish.

At this point, it looks like storms will slowly develop over the Ozarks starting around 4 pm. Those with the greatest potential be become severe early on should be in the vicinity of the MO/KS/AR/OK borders where instability will be maximized.  This is also the area where the storms will start out isolated (discrete, non-linear)

Eventually, the storms will begin to form lines and progress eastward over the Ozarks.  With such strong winds near the surface, an isolated tornado threat is real with any supercell storms.

Tornado Probability Within a 25 mi Circle

Everyone should monitor the weather carefully today as small-scale changes in the timing of features and the development of pockets of unstable air could alter the intensity of these storms.

The strong cold front that everyone is aware of will begin to speed up this evening and slide through the Ozarks after the midnight hour.  I will have a separate post regarding this front and what it will do to our Thanksgiving Day weather!

Snow in Missouri Mid-Week?

9:36 am in Forecast Discussion, The Ozarks by Ted Keller

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Surface pressure and humidity at 6 pm Wednesday

A “clipper” low is one which comes out of the northwest over the central U.S.  Besides being fun to say, clipper lows are usually fast-moving (the name) and don’t normally produce a lot of precipitation.

We have a clipper coming toward Missouri/Arkansas by mid-week.  It’s main effect will be to spread light precipitation in the form of rain over the state.  It is not uncommon for such systems to lay down winter precipitation north of their track provided enough cold air is available.

Wednesday’s clipper might have enough chilly air coming in behind it to produce some light winter precipitation in northern Missouri.  It is unlikely to deliver a snow like last Saturdays’ in Iowa and Minnesota but a rain/snow mix is not impossible along with some minor snow accumulation.

Latest computer models suggest up to a half inch of rain may fall over portions of the Ozarks with most areas getting much less on Wednesday and Wednesday evening.

The Lebanon, MO Tornado November 10th, 1995

9:14 pm in Severe Storms, Storm Summaries, The Ozarks by Ted Keller

Storm-Relative Velocity Showing the Couplet Near Lebanon at About 5 pm

This was an interesting storm for several reasons. 

First, it was a November tornado.  Actually, we shouldn’t be that surprised at this because the Ozarks have always had a significant “second season” of tornadoes which peaks in November and December, especially when it comes to outbreaks of tornadoes. 

November, and all of the months of winter too, are considered to be the “cool season” with regard to tornado development.  Most people don’t think of this period as being a particularly threatening time for tornadoes.  But the fact is that when tornado conditions develop during the cool season, the tornado threat is just as real as anything in the heart of May!

Cool season tornadoes are dangerous for reasons beyond just public apathy.  Because the length of daylight is very short, it is likely that cool season tornadoes will be nocturnal. (occurring at night)  Now, they may simply be late afternoon or evening storms which are nocturnal because of the time of year.  Or they may be storms which develop after the late news or worse after the majority of people of gone to bed.  Such overnight storms are often aided by the natural strong jet stream patterns found during the cool season which can force tornadic conditions anytime , not necessarily favoring the peak heating of late afternoon and evening.  This tornado touched down before sunset.

In the writing of this report, I requested the radar data archive for this date.  It showed a broken line of storms, many of which were taking on supercell characteristics.   I recorded a loop of these storms in the 5 o’clock hour.  The green triangle is a “scit” where the computer has tagged tight rotation in a storm.  It lasts for two frames or about eight minutes as it zips across south Lebanon.  This tornado tore apart Tracker Marine in Lebanon, throwing boats everywhere.  It crossed I-44 and did other damage to homes.

What I really find quite interesting in this post analysis of the event is the intensity of a storm immediately to the southwest of the Lebanon storm, also shown in the radar loop.  This storm had a more persistent and stronger rotation couplet associated with it reaching a peak near Twin Bridges south of Lebanon at around 5:24 pm!  Yet there were no tornado reports with this storm.  A curiosity.

One last note: this tornado occurred ahead of a powerful cold front!  I distinctly remember working this night and while trying to stay ahead of  the tornado warnings, I glanced over into eastern Kansas and saw what sure looked like a signature of snow on radar there!  In fact, it was snow and the area received a light accumulation of snow later that night and early in the morning!

Severe Storm Front

5:55 pm in Did You Know?, The Ozarks, Weather Education by Ted Keller

Me and the Rapid Scan DOW Radar

The Severe Local Storms (SLS) Conference is held once every two years.  It’s sponsored by the American Meteorological Society (AMS) and its purpose is to bring together scientists, researchers, forecasters and anyone else involved in severe local storms. 

This meeting, held in Denver this time around, comes on the heels of a huge tornado research project.  Vortex 2 was a multimillion dollar data collection extravaganza covering two storm seasons (2009/2010) and involving hundreds of people. 

I traveled here in hopes of learning some preliminary findings from Vortex 2 and also to get a sense for how the project went and whether the goal of a better understanding of tornadoes was realized, at least at this early stage.   There are other topics of research going on as well and I wanted to learn more about these too.

The conference is made up of of sessions in which presenters are given 12 minutes to talk about their subject using Power Point and sometimes video. There are also poster sessions where the information is printed and hung up along with all the other posters.  Attendees can then just walk up to the poster that interests them and at certain times have access to the author(s) of the poster to ask questions.  Finally, there are invited speakers and special sessions to round out the conference.

As is typical when I attend these conferences, there are papers presented which are FAR beyond my understanding.  But what does make it through helps me to understand severe storms just a bit more. It’s also just fascinating!  Researchers are doing some really exciting things in the areas of remote sensing and instrumentation, computer modeling and forecasting techniques.

I’ll blog in more detail here over the next few days as I collect my thoughts and notes and as time permits.

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