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?
It may not seem like it this morning, but warmer days are just ahead! Enjoy them while you can.
The turn to a south wind and milder conditions begins tomorrow. Sixties are in the bag for Friday and through the weekend and into early next week. A rouge seventy or two could be lurking in the mix as well!
Large temperature swings, as always, are dictated by changes in the jet stream flow. Generally, when the flow dips over the western U.S. while rising over us, we experience warmer conditions.
The question is will the dip in the jet result in an eventual storm for us? The latest computer model guidance suggests the pattern will shift dramatically toward Thanksgiving, with much colder air replacing the warm. Depending on the nature of smaller disturbances in the flow, a cold front may simply advance through or may stall and develop “waves” or bumps of disturbed weather, some of these can occasionally go on to produce deep storms.
The latest computer models keep hinting at waviness in the arctic front sometime around Wednesday and Thursday, followed by a substantial drop in temperature. Lows could dip below twenty by Black Friday morning!
Since the models have been doing some waffling regarding the timing and position of the frontal waves, I still can’t determine whether winter precipitation of any consequence is possible on Wednesday or Thursday. As always, I will have the latest look at the situation on KOLR/KSFX tonight.
It’s about a week out but I can start making some reasonable speculations regarding the weather starting on Wednesday and going through the Thanksgiving holiday.
In the period leading up to Wednesday, a big travel day, warm conditions will prevail over the Ozarks. It appears as if a cool front does try to nudge its way into the area on Tuesday. Computer models want to stall this front just south of the area by Wednesday. There will be a large zone of temperature change north-south over the Ozarks on Wednesday. While we will be on the cool side of the front, it doesn’t look like the coldest of the arctic air will be in our area. Read: the front or any precipitation that forms behind it or as it advances back to the north should remain liquid.
Now, an upper air storm is forecast to move over this front by Thanksgiving. This has the effect of producing low pressure and also drawing down arctic air. The placement and arrival of arctic air has been in speculation for quite some time. Presently, waves along the front as it lies to the south and east of the Ozarks may be enough to spread precipitation into the Ozarks. There might be enough cold air in place by then to support winter precipitation.
My view of it now is to prepare for some showers or even a thunderstorm Monday/Tuesday, followed by cooler conditions through Thanksgiving. We should keep an eye on how far south the cold air penetrates and on the details of the upper levels on Thanksgiving and Black Friday.
These are all based on long range forecasts which have varying degrees of reliability. I’ll keep you posted. FYI: it is way to early to confirm any type of storm!
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.
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!
The 19th named storm of the season “Tomas” has formed!
This is a late-season tropical storm. Nevertheless, it is forecast as of today to strengthen to major hurricane status by Tuesday afternoon and be positioned in the Caribbean, south of Jamaica, Haiti and the Dominican Republic.
The storm will immediately impact the southern Leeward Islands between St. Johns and St. Georges’ islands from now until Saturday afternoon.
Tomas has good outflow meaning the air at the top of the storm is diverging away quite nicely. This will allow for rapid intensification of the storm as air will be removed from the center faster than it can be replaced.
It’s about a week out but I can start making some reasonable speculations regarding the weather starting on Wednesday and going through the Thanksgiving holiday.
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