After a hot weekend, there is no heat to be found over the next 7 days. We reached a high of 90° on Saturday and were in the 80s yesterday, but a comfortable week is ahead. Today, we still have some showers and thunderstorms around the area with high temperatures in the upper-70s. Once the cold front responsible for the rain today moves far enough to the southeast tonight, we will dry out and clear out heading into Tuesday. A second cold front will move through Wednesday into Wednesday night, which will enhance the cooler air moving in for the second half of this week. This cold front is moisture-starved, so while we are likely to see some clouds as it goes by, mid-week rain from this feature is unlikely. Low temperatures Friday and Saturday morning look to be in the lower-50s. Friday morning looks the chilliest right now as High Pressure sets up nearly over the top of us, so a temperature in the upper-40s is possible. Looking at our Almanac section at the end of this article, the normal low temperature for August 12th is 60°, so upper-40s to lower-50s is chilly for mid-August. It is not record breaking, though, as that would require us to drop to 37°. We should turn slightly warmer for the weekend, but even then, still looking at lower-80s for highs at best.
Overall, a mainly dry and comfortable week is ahead that should be great for giving the air conditioner a rest. You may notice some low-end humidity hanging around through Wednesday, but not as intense as yesterday or Saturday. All the humidity will be knocked out Wednesday night with the second cold front. There is one last risk I would like to make you aware of relating to the weekend forecast. While I think there is dry time, we’ll have to watch the mid-levels of the atmosphere closely because we may be on the edge of a favorable flow in the pattern that would support thunderstorms. For now, there is enough uncertainty in the positioning of thunderstorms to keep our chances low this far out, but this is something to keep in mind and something that will need to be fine-tuned in the forecast as the week goes on. Here is our graphic for this week showing the upper-70s and lower-80s for highs and low temperatures comfortably in the 50s:
One of the interesting pieces of weather news this last week was multiple funnel clouds being reported across the middle of the state last Thursday afternoon. How did these happen, even though the severe weather was focused on Wednesday? First off, we had hot and humid weather at the surface but it was cooler aloft at around 50° 1.5 miles above the ground. We then had what are called outflow boundaries, which are winds coming off of weak showers and thunderstorms that were occurring. The rising air in these thunderstorms can catch these boundaries and cause them to tilt vertically causing weak rotation and a funnel cloud. These funnel clouds often don’t show up on radar as you don’t have strong storm rotation like in a severe weather tornado. These rarely touch down and if they do they’ll be a bit weaker or as intense as an EF0 tornado. Since they aren’t visible on radar the NWS usually doesn’t issue a tornado warning. If you see one, shelter immediately and call your local NWS office or reach out to them on twitter to let them know.
Straight-line winds or a tornado?
This summer there’ve been a few tornadoes reported on the eastern side of the state but nothing in the Central Michigan region. What has caused the tree damage and power outages with the storms this summer? Every thunderstorm has what’s called a downdraft, which is where winds as well as rain descend from the clouds to the surface. If a storm has a strong downdraft then winds of over 60 mph can descend to the ground and cause areas of damage. For small pockets you may hear the term microburst while larger areas may be called a downburst or macroburst. These winds can also move out ahead of or along the leading edge of storms as they move through called a gust front. The National Weather Service trains their meteorologists to tell the difference between these winds and those of a tornado as damage looks like a line, hence the term straight line winds, rather than rotating. Thunderstorm winds can do as much damage as an EF1 tornado in the strongest storms so shelter immediately if you are in a severe thunderstorm warning.
July temperature and rainfall recap
Overall, it was pretty much a typical July across central MI. The concern we had was drier than normal weather leading to abnormally dry to moderate drought status on the drought monitor. As a matter of fact, the most recent drought monitor as of August 2nd maintains abnormally dry conditions for Isabella and Clare counties while a moderate drought is ongoing in Midland and Gratiot counties. In general across central MI, 75%-100% of the normal rainfall occurred, which would indicate near to somewhat below normal. Interestingly, I believe the conditions varied quite a bit over short distances – meaning the amount of rainfall you saw in your backyard could have been quite a bit different than what your friend a few blocks or a couple miles away experienced. This is because of the hit or miss and localized nature of thunderstorms. Rain does not fall evenly from thunderstorms, so very large differences in rainfall amounts are often observed over very short distances. The normal rainfall for July in or near Mount Pleasant and Central Michigan University is 3.22 inches. The CMU weather station measured 4.19”, so that is almost 1 inch more than normal, or 130% of normal. In contrast, the Mt. Pleasant Municipal airport only measured 1.76 inches of rain during July, which is 55% of normal. For reference, the CMU weather station near Kelly-Shorts Stadium and the Mt. Pleasant Municipal Airport are only roughly 4 miles apart and the observed rainfall totals are quite different. The bottom line is, on average, it was close to a bit drier than normal, but variable by location. This is where it becomes a huge help to have a rain gauge in your backyard so we can observe these differences more thoroughly.
What about temperatures? They were near/slightly below normal for the month of July. The average observed high was 82° compared to a normal average high of 84°. We had some hot days and some cooler days throughout the month that averaged together to give us a typical July in the end. The average low is 61°, and 58° was observed this year, so temperatures did come in slightly below normal.
Mt. Pleasant almanac for this week
Almanac Information is a way to look at normal and record high and low temperatures for this time of year. The normal temperatures are based on the 30-year average high and low for that date between 1991 and 2020. For example, if you take the high temperature for every August 8th between 1991 and 2020 and calculate the average of all 30 values, the result would be 83°. Therefore, the normal high for today is 83°. Record high and low temperature data goes back to 1895. Sunrise and sunset data is also provided. All information is valid for Mount Pleasant.
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– Weather Forecast by CMU Student Forecasters Isaac Cleland and Scott Thomas