RAINDROPS FALLING ON OUR HEADS...
It's Memorial Day weekend, summer's last hurrah. From a weather perspective it's a good news bad news scenario. The bad news is that the weekend starts of unsettled with rain chances, lots of clouds, and cool temperatures. The good news is that as the weekend evolves. both the rain and clouds diminish early Saturday and the rest of the holiday period (Saturday afternoon-Monday) looks mighty fine.
The problems early in the weekend are associated with a developing wave that swings east across the Midwest Friday and Saturday. Rain should develop in much of the region Friday morning. Recently, models had come into better agreement that rain totals would be fairly light. However, Thursday night's runs show a more aggressive rainfall solution in my Iowa counties with some spots seeing amounts over 1/2 inch, especially west of the Mississippi in eastern Iowa. East of there amounts taper off in a hurry as dry air holds sway. Overall, I still think this looks like more of a stratiform event with only a few embedded thunderstorms and light to moderate rainfall, especially with limited cape and instability. That should keep most rainfall totals in the 1/4 to 1/2 inch range. However, with available water vapor approaching 2 inches, if storms can develop, especially in eastern Iowa there is the possibility of narrow heavier rain bands where an inch or more could be found. The EURO in particular shows this with warm advection frontogenesis in my central counties. Here's some of the latest rainfall forecasts through Saturday. The EURO is an outlier with its heavier QPF but I am not totally discounting it. Also you can see in most of the output the trend for the more significant amounts to be west of the Mississippi.
The 12K NAM
The 3K NAM
THE WPC blend
The window for the heavier rain Friday is greatest in the morning with intensity diminishing from west to east later in the afternoon as forcing advances across the region. Even where the rain is lightest clouds will be persistent most of the day leading to cool temperatures that end up a good 10-15 degrees below normal in the range of 65-70 degrees.
Saturday sees a cool front exit the south in the morning. That may bring some scattered light showers to that region early in the day, otherwise conditions will improve during the afternoon as skies begin to break out from NW to SE during the afternoon. Temperatures will be a bit warmer but still well below normal in the low to mid 70s.
The remainder of the holiday weekend high pressure and northwest flow aloft will bring some beautiful September weather to the central Midwest with mostly sunny skies and comfortable conditions with highs both days in the upper 70s north to the lower 80s south. Nighttime lows will be nice and fresh in the 50s.
Taking a peak at the future it appears as the pleasant temperatures should be with us into the middle of next week. Beyond that a ridge is forecast to build into the Midwest bringing above normal temperature during the 8-14 day period. The Climate Prediction Center shows the warmth September 10-16th.
I guess my closing statement would be to not be bummed by the slow start to the holiday weekend. Conditions will improve Saturday afternoon leaving us with some fine September weather Sunday and Monday. Friday is really the only day that constitutes a loser. Roll weather....TS