HIGH IMPACT STORMS?

HIGH IMPACT STORMS A THREAT TODAY

It's always a a challenge to predict a high impact severe weather event but less than 12 hours away there are concerning signs that some part of the area will see very large hail with a chance of a strong tornado or two. Early indications are the area north of I-80 is most susceptible to supercells, rotating mesocyclones with significant severe weather capability. The majority of the area is under a high end enhanced outlook for severe weather.

The tornado threat is certainly one to watch with SPC indicating a level 2 of 3 intensity threat, espcially north of I-80. Odds of a strong tornado in that area within 25 miles of a point are 10-14 percent, which is significant. Know what to do if a warning is issued for your local area.

Odds of severe hail (2" diameter plus) are listed at a level 2 risk of 2. Odds are 30-44 percent of severe hail within 25 miles of a point.

Probability of severe wind is generally in the 30-44 percent range within 25 miles of a given point in my area.

The culprit is a low pressure and associated cold front that that enteres eastern Iowa mid to late afternoon. In advance of it a warm front lifts into EC Iowa and far northern Illinois by 3:00pm, forcing dew points into the mid to upper 60s. With cold air advection aloft arriving at that time, a highly unstable air mas is anticipated. Conditions appear ripe for all modes of severe weather with substantial shear and steep lapse rates. On paper Thursday night , there is a lot of positives for intense thunderstorms

Most troubling is the tornado potential mid afternoon into early evening. CAPE (instability) is shown on the HRRR over eastern Iowa of 3,000 to 4,000 j/kg. (that is big for mid April)!

In the virtual sounding below for Dubuque at 3:00pm Friday, a PDS (particularly dangerous tordado sounding) is indicated with a very impressive hodograph. That's to be expected with 0-1 shear in the low levels of 30 kts. At 0-3 levels reach 50 kts, which implies stretching and rotation well into the mesoscylone. The sig. tor. parameter is near 8, quite high, and the supercell composite around 27, big too! Having said this, it's all virtual based on models. The position of instability can vascilate due to heating, instability, and outflow boundaries. Those mesoscale parameters should be more obvious by late morning, several hours before storm initiation. At the very least, I expect much of the area will go under tornado watches by early afternoon. It appears storms could initiate by mid afternoon with minimal capping, an early show.

There are some impressive updraft helicity tracks where one would expect them in the north, espcially near HWY 20 all across northern Illinois. At the time of this post, conditional tornado probabilities have been increased by SPC to indicate a stronger tornado potential locally.

Before any storms, it will be very warm and humid with highs ranging from 78 north to 84 south. Much like early June.

Friday night much cooler and drier air will end any rain and the remainder of the weekend will be significantly cooler with highs in the upper 40s to low 50s Saturday with a brisk NW wind. Sunday should be a tad warmer but still well below normal in the low to mid 50s in most spots.

Stand tand by for what could be and active afternoon in spots. If nothing else it will be nice and toasty until the action begins. Roll weather...TS

ON THE HEALTH FRONT...

Also, on the health front I am HOME, After 10 nights in the hospital! The first thing I did was stop at Finley hospital where I had an infusion of antibiotics. I was given a pump that runs 24 hours a day to destroy bacteria. Every day until June, I will go there for an infusion. It's kind of like having a tail as I have to have it near me all the time to keep me firing on all cylinders. So far so good and I am looking forward to my own bed with two cats (Emma and Frank), a dog (Nimbus), and a wife Carolyn. Just like old times. Thank you all sincerely for you well wishes and prayers. You have no idea how much they are appreciated and help. Same to all the doctors, nurses, and medical personel who put so much of their heart into my recovery. You are all special!!!