A BIG STORM IN THE MAKING....

April 10, 2020

Snow showers and wind gusts of 50 mph made for a not so lovely spring day Thursday. Very cold air aloft at 5,000 feet was responsible for the instability that created the unpleasant conditions. Here's the high resolution satellite imagery showing the cellular nature of the snow showers which in a few spots dusted the ground. Once the sun set the atmosphere stabilized, skies cleared, and that was that!

Temperatures though were at a minimum 10-20 degrees cooler that 24 hours earlier during the late afternoon. In parts of central Illinois readings were down by 30-35 degrees!  

Friday will be a better day but still on the cool side. With sunshine highs will remain in the upper 40s north to the low to mid 50s south. A good 10 degrees below average.

 

After that a complex storm is set to bring an unsettled weekend to the region, one that could even end wintry Sunday night and Monday, especially in the NW fringe of my area. Things get cooking Saturday when the first of two waves of energy arrives. A healthy return flow will bring warm moist air up and over the top of the cool air now in place. The over-running will generate clouds, rain, and chilly temperatures Saturday afternoon and the first part of Saturday night. The rain should hold off long enough Saturday for most areas to reach well into the 50s for highs.

 

After a break in precipitation late Saturday night and Sunday morning, a potent spring storm starts cranking up and things get much more interesting!

 

As I've been pounding home the past few days there are some factors that will make this system a formidable one with the potential for a significant snowstorm over some part of the western and northern Midwest. Ample cold air for mid-April and extremely warm sea surface temperatures and latent heat off the Gulf of Mexico will be the fuel that feeds the beast.

 

Here is the available water vapor for the storm to work with Sunday evening surging northward into the storm centered in Missouri..

 Water vapor in eastern Iowa is greater than an inch and that's about 200 percent above what's normal.

At the same time you can see a digging trough merging with a short wave in the southern stream.

That phasing of energy will act as a steroid to vent and intensify a surface low. You can see it deepening here in the EURO in east central Illinois. The pressure has gone from 994 to 984 and eventually it dips to 977mb, That's a very robust storm. The GFS just came in and it bombs the low to 968mb in MIchigan. That's the mega storm scenario the EURO was showing earlier in the week! It's baaaack....

 

The EURO around Midnight Sunday.

This is the GFS Monday morning at 7:00 am

A major severe weather outbreak is expected over the south Sunday with strong long tracked tornadoes expected. It could be a deadly and damaging day down that way.

 

Further north, on the NW side of the deepening low cold air is changing rain to snow, and is some places it is likely to be heavy and accompanied by winds that could reach 50 mph. Thundersnow is also a good bet with the exceptional dynamics. The verdict is still out where the snow will be heaviest but I certainly could see a band of 6-12" somewhere if the storm attains the strength models are trending towards. 

 

The ground is warm and how soon dynamic cooling can change the rain to snow will be important factors in determining how much snow can accumulate. The track will determine where it falls. I will show you what models are hinting at but it is far too early to talk specifics. All we are looking at here are trends from model output. These are not hard forecasts.

 

The GFS which is an outlier, shows the snow further south than the EURO and Canadian. I doubt it. 

The EURO, further northwest is a more likely depiction..

The Canadian GEM agrees with the EURO in principal.

Total precipitation is likely to be significant with plenty of places picking up at least and inch, maybe as much as 2" in others. The GFS shows this for total precipitation.

The EURO shows this for totals.

The next 24-48 hours will be telling as data gets better sampled along the west coast and the track is better defined. I suspect the worst of the snow stays northwest of my area like the EURO shows. Close, but no cigar. The pieces are slowly coming together. Roll weather...TS 

 

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© 2019 Terry Swails