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Joe’s Weather Blog: Accumulating snow is April is rare…(SAT-3/31)

Good afternoon. A cold front is coming through the area this afternoon from north to south. Temperatures on the north side have topped off at 61° and have started to drop and that trend will spread to areas on the south side this afternoon. The north winds will be increasing as well this afternoon so a blustery evening with chillier temperatures are heading this way. It will be dry though. Tomorrow’s snow risk continues…including the potential for accumulating snow…but there are so many things that have to be considered including the higher April sun angle…the timing of the precipitation etc. Today’s data would suggest less of a road issue concern during the day…but perhaps a black ice scenario possible Sunday night. Lots of moving parts to this one.



Forecast:

Tonight: Variable clouds and cold with lows in the mid 20s

Sunday: Mostly cloudy in the morning then cloudy with a chance of rain>snow in the afternoon. Temperatures may try and warm up into the 30s in the morning but then start dropping in the afternoon. Let’s shoot for an approximate mid-day high of around 34° but dropping to about 30° later in the afternoon with snow.

Sunday night: Everything moves away except for the clouds…lows in the 20s

Monday: Cloudy and cold with highs near 40°. Could be a few patches of mist/drizzle later in the day/night.



Discussion:

Yesterday’s blog had all sorts of tidbits in in related to snow on 4/1 and April snow in general. The one I go back to is that of all the April days in KC weather history…close to 3900…only 64 of those days have we had 1/10″ or more of snow. So it’s a rare thing.

One reason is that typically you need temperatures to be below 32° which isn’t easy to do during the daytime in April. Still not hard to do at night…but during the day it’s tougher. Despite clouds…the higher April sun angle…does allow some solar warmth to develop…another thing is that the ground is “warm”. So what typically falls will melt when it hits the warmer ground. Another reason that it’s tough for it to happen is the atmosphere is typically “warmer” or at least above 32° for a few thousand feet…meaning what falls is usually more of that wet, sloppy type snow and that too melts rather easily.

So there are a lot of things working against any forecast of April snow accumulations. It’s happened before…but again it’s not common. It can certainly happen again but typically what it takes is for some serious moderate snowfall rates (or harder) to fall. This overwhelms any effects of warm ground…also the bands of heavier snow actually chill the atmosphere down allowing the “wet/sloppy” flakes to stick and not melt as easily.

Tomorrow some areas of our viewing area will get these moderate to heavier snow bands…the data today points to this happening more towards northern MO and NOT KC…BUT as we well know…can a shift of 50 miles south occur with these bands of heavier snow rates…absolutely.

So here is where I am at this point…the odds somewhat favor northern MO seeing upwards of 1-4″ of snow. In the KC Metro the odds favor a dusting to maybe 2″ of snow and areas farther south…perhaps just a dusting or nothing at all in terms of accumulations.

As far as timing goes…after 9AM into the afternoon for N MO…after 12PM>6PM for KC Metro. The timing plays a role in this because we’re going to warm up from the 20s in the morning to close to 35°. Then see falling temperatures in the afternoon with the snow falling. In KC proper there may be some rain to snow transition…perhaps even some sleet mixed in. Should this play out…the roads may not get bad at all. IF the snow comes down hard enough though…it will overwhelm the road “warmth” and slushy accumulations will start happening.

The issue then is what happens tomorrow night assuming we drop to about 25° or so…with little drying. Depending on any treatments…the roads may develop black ice…especially on the bridges and overpasses. It’s something worth monitoring.

As far as the nuts and bolts go…here is a look at the 1PM temperatures…the cold front coming through is the 1st step to the set-up tomorrow. The air is colder and also drier…with lower dew points. These lower dew points will have to be overcome with the “forcing” created by the incoming wave tomorrow.

Can you see the front in the above map. The temperatures are in RED. Notice the wind direction as well…shown by the black lines. The front is about at I-35 and behind the front the winds are blowing from the north to the south…ahead of the front from the SW to the NE.

Also notice the colder weather in Nebraska…20s/30s up there coming southwards. pretty impressive for April and some 20-30° below average per this next image from Penn State.

The air is drier as well…dew points are in the teens…so that’s the dry air that will need to be worked on to get snow for us tomorrow.

What usually happens in these situations is that the dry air mass puts up a fight for awhile tomorrow. It will be reinforced by a NE wind blowing in dry air as well. So the wave coming into the area needs to be strong enough to overcome those obstacles. Where the atmospheric lift is strongest…you get that to happen and you go from flurries to moderate snow (or more) very quickly. Where the lift is weaker this becomes a bigger hassle. When there isn’t a lot of time for snow to fall, due to the fast wave movement…that’s an issue.

Usually radar will display “banded” features…and the models will have a VERY tough time depicting those from a day+ out. Models today show this happening in N MO especially…but again could there be a secondary band of 2″+ snows out there (aside from northern MO)? Sure…could that happen in the KC Metro area? Sure. It will be a matter of tracking these features on radar tomorrow morning into the afternoon. Again within these bands, will be the areas that pick up the most accumulating snow. Their location is “to be determined” as they say.

A Winter Weather Advisory is in effect for northern MO…it may be extended farther south…but based on today’s data, aside from the EURO model which has these heavier bands in the KC Metro area…it’s questionable how far south the 2″ amounts will occur. The counties shaded in blue are under that advisory for Sunday

There is some pretty decent “lifting” coming in during the afternoon tomorrow…so let’s see how this exactly plays out.

Our feature photo comes from Jacob Allan…pretty sunrise from a week ago in KCK

Joe

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