MORE SNOW, THIS TIME FURTHER SOUTH...

April 15, 2020

Before I get to the potential snow I wanted to briefly touch in the cold. Tuesday was another raw spring day around the region with temperatures at early March levels. In Cedar Rapids things started bad with a reading of 20 degrees. That tied the record low for the date set in 1950!

In northwest Iowa at Rock Rapids with a healthy snow cover, the low reached 7 degrees. That my friends is dang cold for April 14th.

On this enhanced satellite imagery you can see in red where snow is on the ground. What a difference that makes.

Here's some more record reports from NE Iowa, SE Minnesota, and a bit of SW Wisconsin.

During the day Tuesday temperatures all around the Midwest were 18-25 degrees below normal. In some parts of Iowa snowflakes have been seen for 3 consecutive days. Here's Tuesday's departures.

This impressively cold air mass will be with us the rest of the week. In some areas, especially near and south of HWY 30 you are waking up to a dusting to nearly 1" of snow that fell overnight. That's just chump change to what looks to be ahead for my southern counties Thursday night.

 

The latest trends in models have been to take channeled vorticity (energy) Thursday night and move it along an east/west boundary near the Missouri border. That results in a fairly lengthy period of forcing or ascent that generates a band of over-running snow. Recent model runs have shifted the snow band slightly further north into at least the southern half of my area,(roughly near and  south of HWY 30.

 

All the models are cranking out some decent QPF of up to an inch wherever the best forcing sets up. That could lead to heavy wet totals of 4-8" somewhere over southern Iowa and perhaps parts of far northern Missouri. The high resolution 3k NAM and NAM are now furthest north and in my opinion outliers. I also think the totals are very inflated, especially considering how compact and heavy the snow will be. I'm discarding their solution.

 

So, having said that, I am going to show you what I have with regards to snowfall output but want to STRESS, these are not forecasts, just model output which help us make the final call. We call it guidance and you need to be very careful with it this early in the game. More than anything, I'm just interested in trends and whether there is consistency among models...which are now in two camps. I"ll show you the raw models to give you an idea what we as forecasters are looking at and then point you in the direction I think is correct. Here we go.

 

The 3k NAM

The 12K NAM

The GFS

The SREF mean snowfall.

The Canadian GEM

The EURO

In summation, with plenty of time for revision. I like what the EURO and GEM are selling. I think the dry air in the northern part of my area will play a key role in keeping the worst of the snow in the southern half to one third of my area, especially near and south of I-80. It seems reasonable that 3-7" could pile up in that region with the heaviest near the HWY 34 corridor if current trends hold. Initially the snow could start as rain or a mix before turning over Thursday afternoon or evening. The snow in the south could last much of Thursday night. More to come. Until the next update, roll weather...TS

 

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© 2019 Terry Swails