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It was a noisy Friday morning across the eastern half of the state. Thunderstorms have been sweeping the area at regular intervals the last few days. They've been developing along the northern flank of a heat dome that is building and going to bring us the warmest weekend in several months.

Below is a GOES-East infrared satellite image taken at 10:05 am Friday courtesy of the College of DuPage weather website. The dark red colors just to the west of Cedar Rapids indicate very cold cloud tops and tallest thunderheads which produced some heavy downpours as they tracked south.

Since midnight Friday the heaviest rains have been confined mainly to southeast Minnesota in the dark reds. However, parts of northeast Iowa also had a good soaking with 1.5"-3" of rain with lesser amounts south to I-80. The image below courtesy of the National Weather Service.

Every once in a while these thunderstorms flare up in the high instability leading to occasional gusty winds and hail. While severe weather hasn't been widespread there have been a handful of warnings in my area. The chart below illustrates the time of day frequency of 351 warnings valid for Linn County since 1995. Less than 5% occur from midnight to about 5 pm. It's not until the late afternoon and evening during the peak heating when instability is maximized that thunderstorms tend to reach severe limits.

The storm track will generally lay out across the northern plains and upper Midwest this weekend with the well advertised heat locking in overhead. Various National Weather Service offices have already issued Heat Advisories for several locations across the nations midsection where heat index values will climb over 100° for several hours. It is certainly possible the advisory could get expanded further east into my local area.

Reserve your pool time now if you haven't already. Saturday high temperatures will range from the upper 80s to lower 90s in eastern Iowa with low to mid 90s further west.

Factor in the high humidity levels and the heat index will be well into the mid to upper 90s with triple digits likely further west.

Sunday high temperatures may be even a degree or two warmer.

Sunday heat index values approaching 100° in my local area.

Summer is here! Have a good weekend and stay cool.

Brandon (BMARSH)

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