Joe’s Weather World: Winter storm heads towards KC (THU-1/16)
This storm is going to be complicated to figure out…when you get 4 different types of precipitation…all coming over the course of less than 12 hours…and really everything revolving around a layer of above 32° air between roughly 5,000 and 10,000 feet above us. We call this the “warm” layer.
So why are things a bit in doubt about when exactly things transition from snow to sleet to freezing rain (the most impactful parts of this winter storm ahead) because we get VERY little data from this “warm” layer. There are dozens of temperature sensors on the ground around KC that we rely on for information…yet once you go above the ground…where in this situation temperatures are most critical to what actually falls…we get data 2 times per day…2 times.
Oh and that data comes to us from a balloon launch out in Topeka at 6AM and 6PM. The balloon goes where the winds blow right? Well tomorrow AM the balloon will be traveling quickly from the Topeka area to the north! Away from KC. Lovely. There is some good news though…the balloon launch in Springfield, MO will travel northbound and sample the air closer to us…but by the time it gets to the layer of warmth that we need to probe…it will still be too far south of KC.
These are just a couple of complications that we face as meteorologists for this storm.
Today: Variable clouds…lots of filtered sunshine out there with highs today in the 25-30° range.
Tonight: Clouds gradually lower and thicken…temperatures hold pretty steady around 25°
Tomorrow: Some snow…then sleet (lots of sleet) then freezing rain…then rain in the afternoon. Snow amounts could be 1″ or more…sleet amounts could match that. We transition to freezing rain then rain in the afternoon after lunch. Highs gradually getting to 35° by evening.
Friday night: Scattered rain showers…slowly warming into the lower 40s before daybreak Saturday:
Saturday: Turning colder in the morning with temperatures recovering into the 30° range later in the day
Sunday: Variable clouds with highs 25-30°.
This is one of the few ways we get weather data above the surface…it’s not the only way but we rely on this data tremendously. The issue is typically, with rare exception, here in the Plains we only get this data 2 times per day. The upper air balloon network isn’t that comprehensive.
The ones closest to us are Topeka and Springfield. As the balloon goes higher into the atmosphere it sends back weather information before eventually the balloon expands so much because of air pressure changes that it explodes and the weather instruments fall back to earth. Sometimes they’re found in farmer’s fields and returned to be reconditioned.
Other ways of use getting this important data is through satellite observations and aircraft sensors as the ascend after takeoff.
Why is this important?
Well let me show you…this is a forecast sounding for tomorrow morning off the latest NAM model. This is valid at 9AM. Note the area that I’ve circled…that is the “warm” layer which in reality is FORECAST to be around 40° at it’s warmest.
The red line is the temperature forecast going up in the atmosphere and the green line is the dew point. Where the 2 lines overlap…the air is fully saturated.
The white numbers at the very bottom are the temperatures in Celsius or °C.
So that layer of “warmth” prevents snowflakes from reaching the ground…the go through that layer…melt…then either refreeze as ice pellets (sleet) or don’t freeze fast enough and freeze on contact with the cold ground (freezing rain).
Again we get VERY little data for that “warm” layer…and that layer isn’t consistent everywhere. Some areas it’s not as thick…other areas it’s thicker.
Here is a conceptualized upper air profile of sleet…
and freezing rain…
The depth of the “warm” layer is very important in what actually happens and falls to the ground as you see from the images above.
So there are a lot of variables for tomorrow.
The data today shows that there is also a good fetch of dry air that will take a bit of time overnight to saturate. This isn’t that uncommon really. The dew points here at the surface this morning are the green numbers…
Near 0° dew points. Tonight the winds will be from the east also bringing in dry surface air…and dry air above us too for a few thousand feet or so..so it may take a bit of time to saturate the lower part of the atmosphere with various weak areas of lift coming this way in the morning tomorrow. This may hold off on whatever falls for a couple of extra hours…perhaps to just before daybreak.
Regardless we should have snow or sleet around (or both) during rush hour tomorrow morning. Obviously this will impact the roads quite a bit. Then this continues into the early afternoon until we get the surface temperatures above 32°.
The data this morning has more sleet than snow from this…and also slows things down a couple of hours…that’s the dry air going to work I think…it will be overcome in time during the morning though.
The slowdown, by a few hours, in the arrival time of the precip means that the atmosphere above us has a better chance of firming up this “warm” layer…this cuts the snow accumulations down a bit…but increases the sleet potential and the heaviness of the sleet tomorrow morning.
Like I said lots of moving parts on this one and again another complicated forecast.
The bottom line is that I would expect a snow/sleet combo developing after 4 or 5AM or so…maybe a few snow showers before hand…and that the roads get worse and worse between 6/7AM and 10AM tomorrow. Hi res NAM model data shows about 1/4″-1/2″ of “liquid” equivalent happening in the morning before Noon. This would be snow/sleet and some freezing rain. It will be messy.
We try and transition over to rain in fits and starts near or after lunch tomorrow.
Then we warm up into the lower 40s overnight Friday into Saturday in the wee hours before dropping into the 20s and then modifying into the 30-35° range Saturday afternoon. There may be a few slick areas on exposed surfaces Saturday AM as what wet may freeze back up a bit. There will be some decent wind though so that will help the drying process a lot towards daybreak on Saturday.
Then we should be OK on Sunday…cold but OK. Typical January cold really but temperatures will be in the 20s.
The specifics for various areas will be handled on the air tonight…
OK that’s a wrap for now…our feature photo comes from Nattapong Assalee of a Dark-eyed junco…I had no idea what kind of bird it was…that’s from Nattapong!