Joe’s Weather Blog: An ‘interesting’ week of weather (SUN-12/27)

Weather

As 2020 winds down (thank goodness)…Mother Nature is starting to throw in some curveballs towards us. How well they curve and dip and do a few other things will determine the accuracy of the forecasts this week. There are some things with our early week system that seem pretty locked in including a wintry mix…turning to rain.

There will be the potential of some slick conditions developing depending on the timing of the mix…because there might be some sort of snow>sleet>freezing rain thing for awhile on Tuesday…then there will be a chance of something else on Wednesday…but that depends on how quickly the system progresses along.

Finally there is the issue for New Years Day, some model data is showing a unique set-up for a snowstorm locally…or very close by. The set-up is something that I don’t recall seeing in the past…a storm coming up from the due south. So I’m skeptical right now.

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Forecast:

Today: Sunny skies through early afternoon then turning cloudy with perhaps a few sprinkles after 1PM, especially from KC northwards. Temperatures will max out in the lower 50s before dropping this afternoon with increasing NW winds as colder air moves into the area. Temperatures SE of the Metro could be even warmer.

Tonight: Variable clouds and colder with lows in the 20° area

Tomorrow: Sunny but chilly with highs typical for late December…upper 30s

Tuesday: Messy with a wintry mix developing at some point during the morning…perhaps snow>sleet…then freezing rain>rain. Roads may be affected depending on the timing of the moisture. Highs rising from the 20s to the mid>upper 30s by later Tuesday night.

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Discussion:

I won’t be diving into the end of the week system at this point…too much other stuff happening.

This morning we’re starting out mild…the low at KCI was 40°. That won’t be the low for the day though…it will be whatever it is just before 12AM tonight.

A cold front will be coming through the region later this morning. It’s not necessarily the strongest of cold fronts…really all it’s going to do in inject seasonable December air into area…but the winds with the change will certainly be more of a thing this afternoon and evening as gusts may approach 25-30 MPH. The 10 AM surface map shows the front to the west of the Metro.

See those numbers in RED behind the solid blue line (the front)…those are the temperatures. They’re in the 30s in Nebraska which isn’t too bad for December really. So yeah…we come back to a bit of reality tonight and tomorrow.

There are a few showers with this transition. They may weaken though as they come closer to the state line. Odds are anything that falls may favor areas from KC northwards into northern MO.

Tomorrow is a typical late December day with seasonable highs well into the 30s.

By the way…today will go down as another above average day in the area. Yesterday highs nipped 60° in a few areas…especially from Downtown southwards. KCI hit 57°. For the month of December we’re running about 5.5° above average…and we’re so darn dry…only .06″ of moisture so far this month.

That last part will be changing. A storm is moving in the western US over the next 2 days. See the cloud mass off the Pacific NW?

That energy will come into CA tomorrow…and while it doesn’t per say come into the Plains…it will create a deep “U” or trough in the western US. That will place the region in a broad southwest flow aloft and make us susceptible to weak disturbances coming up from the southwest at various times. At first these will be coming into pretty dry air…but gradually the atmosphere will saturate on Tuesday morrning.

You can see that dip that I referred to by going up to about 18,000 feet and looking at what we refer to as the 500 millibar (mb) level. This is considered to be the “middle” part of the atmosphere. Roughly half the atmosphere is above this…going all the way up to about 100,000 feet…while the other half is below this…coming down to near the surface.

It’s a great way for us to track the various dips (troughs) and ridges.

See how the dip moves into the western US…and progresses across the Rockies. The bigger “U” sort of breaks up a bit…but again these small little waves come up from the southwest flow up the I-35 corridor.

As they do so they will be encountering cold air here at the bottom part of the atmosphere. They will also bring moisture with them…and create additional areas of lift in the Plains creasing more areas of precipitation.

This starts happening Monday night into Tuesday morning. Initially the air above us will be pretty dry…so it may take a bit of time to saturate the air. That in the end could be a saving grace because while the air is coldest…it’s also pretty dry. So the waves that come up from the SSW to the NNE will start to saturate the atmosphere. It remains to be seen really how much the air saturates while the cold air is holding firm.

What I find interesting is how the NAM and the higher res NAM gets the moisture to us…notice how the bulk of what falls is somewhat west of the State Line.

6AM TUE…18Z is Noon…0Z is 6PM

Now with that said…the blues are snow…the oranges are sleet…the purples are freezing rain and the green is rain.

We’re not out of the woods though. Temperatures before noon Tuesday will be in the mid>upper 20s and that could be problematic. While it may not be a LOT that falls…what does fall will ice things up it appears.

Why are we fighting sleet/ice instead of snow? Well the air above us is going to be rapidly warming up. Temperatures should be several degrees above freezing and as a matter of fact it will be warmer at 5,000 feet that it will be here on the ground.

So slick roads are a very possible issue on Tuesday through the middle of the day. The wintry mix may be somewhat persistent into the afternoon before we switch over to rain.

Then there is Wednesday. Colder air will return as the morning moves along. The moisture though may be moving east out of the area by the time the atmosphere is set up for snow again. The GFS/NAM are doing this and it looks reasonable. The EURO is hanging back just enough for us to switch back to snow. On the EURO at face value it would be an accumulating snow too from KC eastwards. There isn’t great support from the ensemble runs of the EURO for this solution with only about a 20-25% chance of at least 1″ of snow accumulating.

We should be OK on Thursday though for New Years Eve

The GFS has pushed the accumulating snows on Friday back westwards from St Louis to Central MO in the today’s run…and the EURO is even farther west. So it’s something to watch for but boy this would be a weird one.

Matt Golden has the feature photo of the day from up towards KCI.

Joe

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