SATURDAY, IN THE PARK
If you are planning to enjoy your Saturday in the park, you might want to accomplish your mission in the morning. After an absolutely gorgeous day Friday, clouds are rapidly increasing as our next weather maker draws a beeline for the area. Showers and a few thunderstorms are already into western Iowa Saturday morning, on a track that will take them across my area during the afternoon and evening. The system is fighting some dry air but should intercept enough moisture to get scattered showers to the ground. While the rain appears light in most spots, clouds and rain cooled air will see to it that temperatures remain in the mid 60s NW to the low to mid 70s east. The HRRR shows this for readings at 4:00pm, with 50s in central Iowa, low 80s in eastern Illinois, and my area situated in the middle.
Rainfall amounts remain low confidence, with models all over the board with their respective solutions. I just wonder if we can get enough moisture and instability to reach the higher levels some models indicate. Personally, I prefer lighter amounts of 1/4 inch or less, an amount similar to what the EURO shows. However, that's just a hunch. Here's what models are indicating, hard to nail a hard trend with so much variance.
The EURO
The GFS
The HRRR
The 3k NAM
Sunday, the weekend ends with substantial improvement thanks to another surge of dry air behind the system. Dew points will be slashed into the 40s, and the dry air advection leads to a nice clear out and temperatures in the range of 65-70. That's just a bit below normal, but with a light wind regime it should be a pleasant spring day. Beyond that, there's more unsettled conditions to deal with before a shot of late season cold arrives next weekend. More on that part of the weather story below.
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DOWN WITH TEMPERATURES...
Before we get to the cooling trend ahead, we do have several days of mild weather next week that will take us through at least Wednesday. During that period, highs should generally be in the low to mid 70s. However, there is plenty of energy to navigate which is somewhat unresolved, especially Tuesday and Wednesday. It does appear we get through Monday dry, but showers and thunderstorms return late Monday night and at least part of Tuesday. That disturbance passes and another is possible Wednesday night or Thursday, when a strong cold front dips in from the northwest with the ability to pop additional storms. That's the part of the long range forecast that remains uncertain.
I'm still getting strong signals that the pattern change I've alluded to for several days is set to arrive late next week. The "change" occurs as a series of short waves carve out a stout trough that looks like this, May 13th. Nothing good can come from NW flow like that.
To that point, temperature departures on the GFS are well below normal for the entire central U.S. May 15th.
The potential change arrives with a cold front less than a week from today. If timing and intensity holds, we should keep highs in the upper 50s to low 60s Thursday through Saturday of next week, which is well below normal. Mother's Day, a short reprieve is expected with highs back in the low to mid 60s thanks to a brief return of southerly winds.
One thing about the newly developing pattern is that after the middle of next week, NW flow should restrict moisture. As a result, the above normal precipitation of recent weeks should come to an end in most of my area. The GFS shows this for 10 day rainfall departures May 9-19th.
There's still some question about the duration of the cool-down and its intensity, especially with the change still nearly a week away. Some revisions are likely as details become clearer over the next 24–48 hours. Meantime, have a fine weekend. Roll weather TS...
