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Welcome to June, the start of what's known as meteorological summer. While the calendar says the “Summer Solstice” isn't until June 20th, meteorologists consider summer to be June, July and August. Instead of using the astronomical calendar, whose dates vary from year to year, guys like me view the seasons a little differently. We consult the "calendar" to determine the start of a new season, rather than looking to Earth's orbit around the sun. We prefer to break the seasons down into groupings of three months based on the annual temperature cycle as well as our calendar.

Meteorological summer is exactly three months long, starting on June 1 and lasting through Aug. 31 of every single year. That way, the length of the meteorological seasons are more consistent, making it much easier to calculate seasonal statistics from monthly statistics, both of which are very useful for agriculture, commerce, and a variety of other purposes.

The way this spring has gone with so much rain, it's only appropriate that meteorological summer starts with additional chances of rain. More on that in a minute. Regarding the issue of rain and how wet it's been, this is how much has fallen the past 90 days (the equivalent of meteorological spring...March through May). Amounts of 13–15 inches are common! Notice too how widespread the rains have been east of the Rockies.

For the 3-month period beginning March 1st, most areas are 3–6 inches above normal.

In essence, this has finally put drought conditions to bed across the region. While there are still a few spots in Iowa where it's abnormally dry, this is the first time since the summer of 2020 (4 years) that no place in Iowa is experiencing drought conditions.

Look at the change in drought conditions since March 5th.

Saturday's rain chances hinge on a disturbance that swings east at a leisurely pace. Lift is not overly strong or focused, but today's guidance is definitely more bullish on rain west of the Mississippi. Overall, amounts will be manageable, with most areas seeing 1/4 inch or less. However, there does seem to be a localized area of convergence somewhere in SE or EC Iowa where somewhat higher amounts are possible over 1/2 inch. Take a look at the range of model rain solutions.




The 3k NAM

The extent and duration of cloud cover will determine how warm temperatures get Saturday. The latest trends are for little if any sunshine, especially east of the Mississippi, limiting highs to the range of 65-70 as the showers depart later in the afternoon.

Sunday looks to be a better day as a weak ridge of high pressure allows partly sunny skies and dry conditions. Highs look warmer, in the upper 70s to low 80s.

Monday and Tuesday appear rather summery, with dew points reaching the upper 60s, maybe 70 in a few spots. Highs are expected to reach the low 80s Monday and low to mid 80s Tuesday. There will be enough instability for scattered showers and storms both days. As it stands now, the storms would be confined to small windows and there are likely to be many dry hours. One time frame stands out when storm chances and coverage look greatest, and that is with the passage of a strong front Tuesday evening or night. Depending on mesoscale details yet unknown, strong thunderstorms are possible.

Behind the front, a strong NW flow develops that allows a closed upper air low to form over the Great lakes. This is a feature that has been hinted at for numerous days.

The cold core circulation is expected to bring unseasonably cool air and diurnal instability that could lead to afternoon and evening showers Thursday and perhaps even Friday afternoon. They are not expected to be heavy but should keep temperatures well below what's normal. The GFS is now the coldest model solution, showing temperature departures that are more than 20 degrees lower than typical levels next Friday.

Temperature departures, like the GFS shows above, translate to 1:00pm readings in the mid to upper 50s over much of my area next Friday. Gusty NW winds will no doubt make readings feel considerably colder than that!

The EURO, which 24 hours ago was just as cold as the GFS, has backed down some, showing less in the way of chill. Even so, it still has a fresh look late next week. I'm confident we are going to see below normal temperatures June 6th and beyond, the question is just how cool? That will be fine-tuned in the next couple of days.

The way it looks to me, the first week of meteorological summer is going to get off to a rather shaky start around the Midwest. Hopefully we get that issue straightened out in relatively short order! Have a terrific weekend and roll weather...TS


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