WE INTERRUPT THIS PROGRAM...
Things are still a bit stuffy but we have interrupted this program to bring you a scaled back version of our recent brush with oppressive heat. Gone are the 110 degree heat index's, gone are highs in the 90s. but we are not out of the woods as far as rain is concerned. We'll cancel that channel starting Friday!
As modeling had indicated over a week ago, (and I pushed vigorously on this site), this recent period was expected to be a wet one for many. Virtually every time in recent memory (at least the past ten years) that this area has experienced dew points near 80, they've been accompanied by heavy rain events and flash flooding. The past few days were no exception with a swath of 3-6 inch rains arching from NE Iowa through northern Illinois. Another heavy band of 2-4 inches has observed near I-80 from western Iowa into central Illinois.
Much of what fell up north came Monday night and Tuesday.
Tuesday's storms, associated with a mild derecho produced many severe weather reports from South Dakota into NW Iowa. 249 were associated with damaging winds.
Despite all the recent rain in July, over the past 30 days rainfall has averaged near normal (100% of the mean). A few spots slightly above at 125% and some in the south below at 75%.
For those in the south who could use more rain, Thursday could very well be your day as most models are indicating another MCS will bring a healthy rain event to at least the southern 1/2 of the region, roughly I-80 south. Before that arrives, some lingering showers and storms may fester Thursday morning in my southernmost counties, generally south of HWY 34 closer to Ft. Madison and Keokuk.
After that the focus turns towards a wave which cuts along a nearly stationary boundary across the southern Iowa border. Deep moisture is pooled along the front with water vapor on the 3K NAM pushing 2.4 inches.
Eventually, as the wave lifts E/NE Thursday night and interacts with the right entrance region of the jet (as well as an intensifying low level jet), the stage is set for what could be a heavy rain producing system for some. The question models are struggling with right now is precisely where the heaviest rain falls. Some are even suggesting two heavy bands. One would be near the warm front stretched out over southern Iowa. The other would be further north tied to more elevated storms within a deformation wing. These would also have the ability to be efficient rain producers. It's a rather complex set-up and has the potential to warrant a flood watch. The NWS has not done that yet due to some uncertainties it's monitoring. Here's what Thursday night's models are suggesting for rain totals. The general consensus is for the heavier rains to be confined to the area near and south of I-80. The northern third of my region (HWY 30 north) may see little if any rain. For sure, the 12k NAM is an outlier and I discount its wet look over my northern counties..
The GFS
The EURO
The 3k NAM
The 12K NAM...clearly an outlier!
One positive in this scenario is that instability is marginal in all but the far south Thursday and shear is less than impressive too. That means the overall severe weather threat is low aside from the torrential rain potential in the south.
By Friday the system is departing with only a slight chance of some widely scattered showers. Temperatures will go from the low 80s Thursday to the upper 70s Friday. Over the weekend, dry conditions are anticipated with seasonal temperatures and humidity (highs generally in the low 80s). What I would call an excellent July weekend!
Our next chance at showers or thunderstorms comes Monday out ahead of another cold front. Preceding it south winds will send in a quick shot of heat and humidity. Highs may reach 90 in the south with mid to upper 80s elsewhere. I do see strong signals that it will be a very sultry day with dew points reaching the mid 70s. However, as the front goes through with its rain chances later Monday, cooler drier air will follow on Tuesday.
With that I will call it a post, Make it a fine day and roll weather...TS
