CHAMBER OF COMMERCE WEATHER...
If you were trying to sell weather this August chances are your wallet would be fat. Extremely pleasant conditions have blessed us at a time of year when conditions are typically stagnant, hot and humid. As you can see that's not been the case this year. Check out the temperatures so far in the Quad Cities and Cedar Rapids. Highs have been in the upper 70s and low 80s with lows in the low 50s (upper 40s in a few spots). Throw in sunny skies and very low humidity and you have yourself something to sell!
These are the temperature departures over the past 5 days. Parts of SE Iowa and central Illinois have been running 10-12 degrees below normal. If you are going to run deficits like that, now is the time to do it as opposed to winter.
Here's the 500mb jet stream flow which has brought us the chamber of commerce weather.
Holding onto a pattern like this for any period of time in early August is next to impossible and already signs of change are showing up. Notice on the satellite how return flow moisture is steaming into the Plains as our cool high pressure drifts off to the east. The southerly wins will bring warmer temperatures, much higher humidity, and even some rain chances in the days to come.
The first crack at rain reaches my area Thursday. While some models show a few showers reaching my counties in eastern Iowa by late day, I suspect the existing dry air will keep most of the rain up in the clouds. Saturation prospects are better Thursday night and that's when a few elevated showers or storms are possible. In general, amounts look to be very much on the light side with the best chances in my far western counties. The 3k NAM indicates amounts that look like this through Friday night. Not much shown east of the Mississippi.
If this fails to get the job done, chances will be better later in the weekend (especially Saturday night and Sunday) when better moisture, instability, and forcing comes into play. Models are still struggling with the overall timing so I'm not going to try and cute with specifics and will deal with that as we get closer to the event. That said, if the models are to be believed, some respectable rains are possible, especially when you include what could fall next week. I do caution this time of year rains tend to be scattered and our mid range models smooth the data so the gaps and banding that occur are often not indicate at this distance. That said, here's what the GFS and EURO show for total precipitation through next Wednesday. This includes what falls Thursday and Friday.
As for high temperatures, they will be dictated by the amount of cloud cover that results from debris clouds and any showers and storms that pop up. Models are a little bit cooler today than yesterday indicating highs in the mid 80s Friday and Saturday before climbing into the upper 80s to near 90 Sunday into the middle of next week. While highs may indeed be a few degrees cooler dew points by Sunday will be in the low to mid 70s and are likely to hold there for a few days after that. Heat index values of 95-100 are likely from Sunday through Wednesday if trends hold. This is the more typical weather we've come to expect in the dog days of summer.
Anyway, we've had a nice break and we'll pay the piper this weekend. Have yourself a fine Thursday and roll weather...TS