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Snow and Cold

7:44 am in Forecast Discussion, Winter Weather by Ted Keller

Get ready for more arctic air, led in by some snow this weekend.

The overall picture hasn’t changed too much since yesterday.  There is still a disturbance diving into the central U.S. this weekend from the northwest.  It still looks like it will rev up a storm which gets stronger as it moves east of us.  There is enough cold air to produce snow on its backside in the Ozarks late Saturday. 

There seems to be an accumulation track setting up from just northeast of Springfield, east-north eastward to around St. Louis and on into Illinois and points east.  As is always the case, storms at this distance need to be monitored carefully.  My feeling is that accumulating snow will track through the Ozarks late Saturday.

Then, cold air slams in!  This is easily the coldest air so far this season.  There are hints at single-digit low temperatures Monday morning with highs barely clearing twenty.  Brrrr!

Snow Possible

7:42 am in Forecast Discussion, Winter Weather by Ted Keller

When arctic air finds it easy to roost in the heartland of the U.S., watching for snow possibilities becomes my favorite past-time.  Here’s the latest…

Long-range computer models have been sending some signals as to the possibility of a snow-producing storm around December 11-12th (Saturday-Sunday) for about a week now.  As usual, such chances are taken with a grain of salt until we get a bit closer to the actual forecast time.

The arctic air now in place will be lifting out of here by late in the week.  A small disturbance that I hinted at late last week will be sliding into Oklahoma late tonight and early Tuesday on the edge of this cold air with some light snow potential.  This does not appear threatening to the Ozarks.

By Saturday night, a low pressure area has been showing up swinging near Missouri.  The track and intensity of this feature has been all over the dial as they say.  A more southerly track would bring us greater snow potential.  At this writing, this seems to be the outlying possibility.

I would say the most likely scenario would be a shot of snow Saturday night as the storm intensifies while moving east.  It’s an old joke but I’ll know more on Monday the 13th!  Stay tuned to KOLR/KSFX for the latest.

Today’s Winter Junk

9:23 am in Forecast Discussion by Ted Keller

9 am Temperatures

After hours of tornado warnings yesterday with possible touchdowns, we have been flung into the icebox today!

Area temperatures have fallen to right around freezing or just below in portions of the Ozarks.  Meanwhile, precipitation echoes are still showing up on radar.  Since the arctic air has undercut warmer air aloft, the precipitation is falling as rain or freezing rain if the temperature is at or below freezing.

So, technically, ice could form on surfaces this morning.  But because of recent warm temperatures, marginal cold and light precipitation, a major accumulation of ice is not expected.

As the cold air gets deeper, a transition to more of a sleet or snow will occur.  Again, totals are expected to be light, under half an inch.

A winter weather advisory is in effect for much of the Ozarks.  I’ll bring you the latest tonight on KOLR and KSFX!

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!

Latest Thanksgiving Weather Outlook

10:51 am in Forecast Discussion by Ted Keller

Computer Model Temperature Plots

Cold weather is coming!  This isn’t in question really as the cold front has been very consistent showing up on the long range computer models.

While it still appears an arctic front will progress through the Ozarks in short order late Wednesday or early Thursday, it is always worth watching carefully especially since enough cold air is in supply to produce winter precipitation.

Experience dictates watching to see if “waves” of precipitation will develop along this cold front. A wave essentially means a slowing and kinking of a front.

In the meantime, there is a weaker front forecast to slip through on Monday.  This feature may support some showers or perhaps even a thunderstorm as it passes through.

Warm air returns on Wednesday with the arctic front due in Wednesday night.  As you can see on the inserted graph, lows will be dipping down close to twenty degrees by Friday morning!  The high temperature is expected to be just above freezing on Thanksgiving day.

The Perils of Long-Range Forecasting

6:15 pm in Forecast Discussion by Ted Keller

I thought you might enjoy looking at these maps.  Each shows surface highs and lows (black lines, isobars), precipitation areas (green) and a rough approximation of temperature (dashed lines).  Each is a forecast or projection valid on noon Wednesday.  The difference is each computer model ran at different times with different input.  There are four over a 24 period run at 6pm last night, Midnight, 6am today and noon today.

Notice that a radically different weather pattern is painted over Missouri and Arkansas on each “run”. One has high pressure and no precipitation, two have us in chilly air with a hint of light precipitation and still another has low over St. Louis!

It is no wonder that trying to get an exact handle on the forecast for the days leading up to and including Thanksgiving is very challenging indeed.  Which model run is right, if any?

From Thursday Noon Run

Thursday 6am Run

Thursday Midnight Run

Wednesday 6pm Run

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