A blocky weather pattern at high latitudes is going to make for a persistent push pull pattern the next couple of weeks. The end result will be a series of cool fronts that have the potential to produce rain, followed by several days of high pressure and cool temperatures. Preceding the fronts will be warm-ups accompanied by humid air masses. To be honest, the whole set-up looks very fallish and more typical of late September or even October. This is how the next 16 days look at 500mb, jet stream level.
Another way to look at the process is through the temperature departures. In this animation you are looking at 850 temperatures just above the surface....5,000 feet. Just look at the regularity of the cool pushes with the last surge the most significant at the end of August.
The next animation shows regular intervals of precipitation as the changing air masses wring out the available moisture.
The pattern supports the potential of significant precipitation in some part of the central Midwest. Smaller scale details impossible to see at this distance will determine where the heaviest rains set-up. As of late Friday the GFS shows this for 16 day total precipitation.
If the GFS were to verify it would be nearly perfect as it shows the most significant rains falling where moderate drought has developed over the past week. This is the latest drought monitor. as of Thursday August 15th.
It's amazing the Quad Cities is in the heart of the driest area considering the severe flooding that was experienced this spring. After the wettest 12 month period in Iowa history, you may recall the Mississippi River set an all-time record crest there in early May. The river was in major flood stage (above 18 feet) for 51 consecutive days from March 23 through May 12. The previous record was 31 days from mid-April to mid-May 2001, according to the NWS.
Needless to say, many of us were begging for the rain to go away back then. Now that it has, many of us are asking for it to return. There will be some chances this weekend but the best odds appear to be near and south of I-80. Here are the latest rain forecasts. This comes in two waves. One Friday night Saturday morning. The other late Saturday night early Sunday. Amounts are generally much lower north of I-80.
The 3k NAM
Even where rain falls, there will be plenty of dry hours to get out and about. Weekend temperatures and humidity will slowly climb with highs Saturday reaching the low 80s before building to the mid 80s Sunday. Whatever happens in your area, make it a good one! Roll weather...TS