A LITTLE DAB WILL DO YOU...
Some fantastic fall weather enveloped the Midwest the past two days with Indian Summer in full swing. Monday was especially nice with highs in the low to mid 70s areawide. I was driving around the bluffs of Galena Monday and I could tell where the combines were active by the clouds of distant dust in the air. Didn't even need to see the tractors but I knew they were there. Make no mistake about it though, the dust clouds are proof much of my area really needs a good rain.
Speaking of proof, here in Dubuque we have measured just .07" of rain over the past 29 days. The past 40 days have produced just .64"
As you would expect in a pattern like this the air is extremely dry. Relative humidity levels in the afternoon the past couple of days have been bouncing around in the 25 to 35 percent range
That dry air really cools at night then quickly warms during the day once the sun goes to work on it. In Cedar Rapids the low went from 39 Monday to a high of 76 Monday. That's a pretty good range. In the graphic below, the black line shows solar radiation and the red line temperatures. You can see the correlation between daytime heating and sunshine. As solar radiation increases during the day temperatures rise accordingly. Around 3:00pm readings reach their peak but there is a lag before they start to fall and catch up with the decreased radiation at that time. However, once that sun fades around 6:00 temperatures quickly tail off in the ensuing darkness of the night ahead.
The dry air will be an issue with our next system which brings a couple periods of rain potential Tuesday through Wednesday. The first crack comes later Tuesday morning and extends into early afternoon. Most of this will be quite light and the way the moisture fields are aligned, it would seem the area SE of the Quad Cities has the best chance of seeing anything worthwhile.
Another opportunity arises later Tuesday night and Wednesday morning along a cold front that advances southeast. By then the best moisture has veered to the east and instability is limited with daytime heating long gone when forcing for rain arrives. That means the front will have challenges as a precipitation producer. Scattered showers and perhaps a thundershower can be expected but the rains look broken and again light, not the soakers we all could use.
Between the two windows for rain, here's what models are suggesting for totals ending Wednesday night. The NW, where rain is currently need the most appears to be the region that ends up getting the least. Maybe 1/10th of an inch in spots. The southeast third could catch 1/3rd of an inch but that's the high end potential. Most areas will likely end up with less than that.
The national model blend
The 3k NAM
Highs Tuesday should reach the upper 60s to low 70s despite increased cloud cover and some showers. The far SE could be cooler, 63-67 where the overcast is thicker and showers are more common. It also looks to be a blustery day with brisk SW winds.
Wednesday will be a transition day as winds turn to the W/NW behind the cold front. Deep mixing will rev up the winds later in the afternoon into Wednesday night. A strong cyclonic flow and pressure gradient holds into Friday meaning breezy conditions Thursday and Friday as well. This could set up the north for some hit and miss instability showers late Wednesday and Thursday afternoon that would be very much on the light side.
After highs in the range of 65 to 70 Wednesday, much cooler readings return for Thursday and Friday with most areas remaining in the 50s.
Saturday should see some moderation ahead of another cold front that re-amplifies the eastern U.S. trough Sunday into Tuesday of next week. That will see to it that below normal temperatures dominate the pattern Thursday through at least Tuesday of next week. The temperature departure for the period October 12th through 19th looks like this.
In general, our dry pattern appears to hold much of the next 2 weeks. The EURO shows this for 15 day rainfall departures through October 25th. Man, I'm hoping we get this turned around before snow season.
Well, if nothing else, Tuesday will have a different look to it with clouds and perhaps some showers, especially SE of the Quad Cities. A little dab will do you. With that, I will call it a wrap and move on to fight another day. Roll weather...TS