- Mar 18, 2020

APRIL SHOWERS AND STORMS...EARLY!

A wet weather system is still slated to bring showers and yes, even thunderstorms to the area over the next 48 hours. The precipitation will come in two distinct waves. The first cuts through the region early Wednesday before exiting late afternoon or evening. This is what the surface pattern looks like at mid-day.

Here are some projected rain totals for the first event.

The second round of rain (and this time storms) arrives late Wednesday night and brings occasional showers and thunderstorms to the area through Thursday night. Here's the late afternoon surface pattern Thursday

The EURO shows this for additional precipitation with this wave.

Combined the EURO has this for 48 hour totals.

The 12k NAM does this.

Without a doubt the potential is there for significant rain with dew points on the EURO shown reaching 60 as far north as Cedar Rapids. The 3k NAM goes to 62. It's been some time since 60 degree dew points have been felt around here. If we get there you will feel the moisture.

You should also feel some warmth. These are the highs the EURO is projecting. It's painting mid to upper 60s into southern Iowa and much of Illinois.

The combination of spring warmth and moisture (if indeed it materializes) will generate significant instability, what's known as CAPE. For mid-March the 3k NAM is showing some very healthy buoyancy.

Last but not least there is directional shear present ahead of an advancing cold front. That enhances the chances of rotating thunderstorms known as supercells. The 3k NAM produces a supercell outlook that would be impressive even in May.

Supercell thunderstorms are also the type that can produce tornadoes. There are soundings that imply a tornado threat could develop if this scenario does indeed develop. The significant tornado parameter on the 3k hits 6 near Iowa City/Cedar Rapids. That would be quite robust if attained.

This virtual sounding taken near Iowa City shows 0-1 shear (the lowest levels) at significant thresholds of 42 kts. 0-6 shear of more than 75kts. That generates a healthy hodograph!

Of course this is all on paper and highly dependent on temperatures and moisture reaching the projected levels. If the warm front remains further south and we get into grunge that ruins the recipe with far less instability. The Storm Prediction Center has gone from no risk of severe weather to a slight risk across much of Iowa and my western counties Thursday.