MICRO-CLIMATE 101...

Thursday was another one of those unique days when several types of weather were found across my region. The variability was found in both temperatures and precipitation. Let me start with a satellite loop showing the system that caused the local microclimates.

What you can see in the animation is energy diving southeast in the NW flow that prevailed at 500mb. A closer inspection reveals 3 distinctively different areas of weather. The first is along a line from Waterloo to Iowa City and Galesburg. From that line west, there was enough heating from mixed morning sunshine to destabilize the atmosphere, allowing scattered showers and storms to develop there. To the right of that, there was another area where the air was more stable and a fair amount of sunshine prevailed and sent highs into the mid 60s (without any rain). Lastly, from west of Dubuque southeast into NW Illinois, low stratus and fog prevailed all day. The heavy overcast stunted temperatures, which never got out of the 40s and produce a raw, dreary day.

Just in terms of temperatures alone, this hodgepodge of sun and clouds created quite a thermal spread. Around 2:00PM. readings ranged from 44 in Dubuque to 67 in Keokuk.

Then there was the element of precipitation. Most of the NE half of my area avoided rain entirely. The SW half did not, although the rains were hit-and-miss. You can see the pop corn nature of the showers and storms as they randomly fell in SE Iowa and parts of WC Illinois late afternoon.

Doppler rainfall estimates indicate some places in a triangle extending from Mt. Pleasant to Wapello, and back to Mediapolis may have seen up to 1/2 inch of rain.

In the end, there were 3 distinctly different brands of weather, one cloudy and cold, one fairly sunny and pleasant, another mild but wet. As a side note, forecasts like this are honestly some of the hardest I make. I spent a lot of time the night before trying to break down the delineations. It's every bit as challenging as forecasting a snow event, aside from the fact you don't have to shovel the 3 different worlds of weather you end up with. I was in the ballpark, and that's about all a forecaster can hope for in that scenario.

Following the disturbance, Friday looks uneventful. However, some low level moisture may linger that fosters some pockets of low clouds and fog, especially in the morning. Hopefully, most of us will get into a mixture of sun and clouds by afternoon. For now, I'll play temperatures conservatively, with highs of 53 north to 58 south.

THE WEEKEND

Both Saturday and Sunday appear dry, but the amount of sunshine is still a bit in question for Saturday, which again dictates how warm temperatures get. We should see enough of it to add a few degrees, getting us into the range of 58-63. Sunday, with the approach of the next cold front, a stiff southerly wind should bump temperatures into the 66-73 category, coolest in the NE. It does look breezy, with gusts up to 30. A few models try and kick up a brief shower or sprinkle in the north ahead of a warm front at some point. If the warm front is slower, and it is a possibility, and it could lead to somewhat cooler conditions north of HWY 30. I debated whether to mention the potential and decided it was worth a sentence. More on that trend Friday

DOWN AGAIN EARLY NEXT WEEK

The warming trend does not last long, as another feisty cold front arrives Sunday night. With minimal moisture, it should largely be a dry passage, but I can't rule out a few brief showers in the SE late Sunday night or early Monday. The primary impact looks to be windy and colder weather early next week, with falling temperatures Monday into the 50s. Tuesday will be even cooler, with highs possibly remaining in the upper 40s across the north.

PALM SUNDAY TORNADO OUTBREAK, (60th ANNIVERSARY)

A historic outbreak of severe thunderstorms occurred on the afternoon and evening of April 11, 1965, across the Midwestern United States. I find this particularly interesting because one of the thirty-seven tornadoes that formed that day was high end and occurred in eastern Iowa.

The event coincided with the Christian observance of Palm Sunday, giving it the well-known name of the Palm Sunday tornado outbreak. While the 1965 Palm Sunday outbreak proved costly to both lives and property, it played a pivotal role in changing the United States Weather Bureau's (now National Weather Service) understanding and approach to forecasting severe thunderstorms and tornadoes.

HERE ARE SOME STATISTICS I GATHERED FROM A GREAT NATIONAL WEATHER SERVICE STORY BOARD REPORT

Six states were impacted by at least one tornado (Illinois, Indiana, Iowa, Michigan, Ohio, and Wisconsin).  17 violent tornadoes (EF3 or higher) were recorded on April 11, 1965. All 17 violent tornadoes were rated F4 on the Fujita Scale. This figure stands as the second-highest number of violent tornadoes recorded during a single day outbreak in United States history. Only the April 3, 1974, Super Outbreak saw more with 30.

The approximate distance (in miles) covered by the paths of the 37 tornadoes documented that day comes to 1,100 miles. The total path length is comparable to a drive between Chicago & Denver (1,004 miles).

The cost, in 1965 U.S. dollars, of total property damages resulting from the outbreak was $1,191,000,000. Adjusted to 2025, the total falls just shy of 12 billion dollars.

The outbreak resulted in over 260 deaths and numerous injuries, making it one of the deadliest tornado outbreaks in US history. The damage was extensive, with over 3,500 buildings destroyed and billions of dollars in losses. 

THE SELS OUTLOOK THE MORNING OF APRIL 11, 1965 (the Dept, of Commerce U.S. Weather Bureau)

The Severe and Local Storms Unit (SELS), the predecessor to today's Storm Prediction Center (SPC), issued a thunderstorm outlook above for the day. SELS indicated a large area of atmospheric instability expected from Texas northeastward into southern Illinois, and another area centered near Ohio and western Pennsylvania. They forecasted a large area as being favorable for thunderstorm activity, covering areas from the southern Great Plains states eastward to the Great Lakes and Appalachian states. They forecasted two areas as being favorable for severe thunderstorms, one from northeastern Texas northeastward into southern Illinois, and another from eastern Indiana eastward into western Pennsylvania and West Virginia. Ironically, many of the tornadoes occurred to the north of where the greatest risk was indicated.

Of note to me is the first tornado of the day---rated F4 on the Fujita Scale---which began near Lowden, Iowa. The tornado continued northeast toward the communities of Toronto, Elwood, Maquoketa, and Springbrook. My friend Steve Gottschalk, a weather historian and longtime weather observer for the NWS, remembers watching the tornado pass Lowden, where he lived as a young boy.

The track of the EF4 tornado that originated near Lowden. It narrowly missed the significant population base of Maquoketa to the southeast.

After Lowden, strong tornadoes were ongoing the remainder of the afternoon and evening of April 11th. This one produced extreme destruction near Crystal Lake, Illinois, killing 5 people.

Another powerful twister near Dunlap, Indiana. This was one of 2 EF4 tornadoes to hit the area around Dunlap. The storms there killed 36, with 33 of the deaths in a trailer park.

60 years later, this remains one of the worst tornado outbreaks in Midwest history. Following the event, a survey team learned that many people were confused about the terms used to alert people to the potential of tornadoes. At the time, Tornado Forecasts were issued if conditions were favorable for tornadoes. A Tornado Warning was implemented if a tornado had been positively identified. Many people felt that a warning was an “update” to the Tornado Forecast and did not realize how seriously the threat had been elevated. To help prevent confusion, the term “Tornado Forecast” was changed to “Tornado Watch”, a term still in use to this day.  

Additionally, Civil Defense sirens were repurposed to be used as a warning tool for those who may be outside or unable to access warnings provided by local media. That's proved to be an effective tool. Furthermore, radar advancements and technology such as weather radios and cell phones have dramatically improved lead time and more efficient ways of issuing and obtaining alerts. We've come a long way, and the National Weather Service and its people deserve great credit for the incredible work they do behind the scenes to protect lives and property. Our system of weather warnings and preparedness is first class and hands down the best in the world. The government should not privatize or take funding away funding from this essential organization. Make sure your local leaders and politicians keep the doors of the NWS open. Your life may depend on it. Roll weather...TS