HEAT'S A COMING...
Before we get to the coming heat, which will get your attention, we have some housekeeping to attend to. The first item, is what to do with Friday's rain system. There's been a significant discrepancy between the GFS and EURO for days regarding where rain falls and how heavy it is. I have been of the mindset that the area southwest of the Quad Cities was the most likely spot to see the lions share of the rain. I've also felt the GFS was just plain overdone on the amounts, what we call QPF. Despite my thinking the GFS continues to come in hot with a nice swath of rain (1/2 to 1 inch) through my central counties before it fades entering central Illinois.
The EURO is further southwest with the primary rain band and lighter on amounts. Personally I like its portrayal of the set-up better.
The 3k NAM falls into the camp of the EURO
The 12K NAM mirrors the higher resolution 3K.
Two trends are apparent. First is the fact there is moderate to high confidence the southwest half of my area (roughly the Quad Cities southwest), sees the majority of the rain Friday...the further southwest, the higher the amounts. Second, there remains low confidence on just how heavy amounts will be in the primary band. I'm leaning towards amounts of 1/4 to perhaps 1/2 inch in my southwest counties. Northeast of the Quad Cities, little if any rain is a distinct possibility. I don't see much in the way of thunderstorms either as this is more of a stratiform event. Temperatures may hold in the upper 60s where rain is more prevalent while reaching at least the low 70s where lower amounts and thinner clouds are anticipated in the northeast.
The weekend could have a few trouble spots as well due to the warm advection generated by a slow moving warm front. Best chances seem to be late Saturday or Saturday night, especially north of I-80. Instability will actually increase Sunday but the lack of a pronounced trigger should keeps storms scattered with many areas avoiding storms altogether. However, where they do fire, some good downpours are likely with dew points pushing 70. While Saturday appears seasonal with moderate humidity and highs in the upper 70s to lows 80s, Sunday will be warmer and quite steamy. Highs should be in the low to mid 80s.
HERE COMES THE HEAT
Monday the warm front surges edges north of the region as a stout heat dome expands and sticks its nose into the central Midwest. Very warm temperatures are shown at 850mb (5,000ft.) reaching as high as +27 C. The question is how much mixing takes place in this elevated layer. The EURO is bullish on mixing this layer out allowing the heat just above the surface to reach the ground. That provides some big-time sizzle Monday and Tuesday, and most likely Wednesday. Tuesday the EURO shows highs in most spots in the mid to upper 90s. A couple 100 degree highs are still indicated in southeast Iowa.
On the other hand, the GFS significantly limits the mixing and keep highs as much as 10 degrees cooler, generally in the upper 80s to low 90s. It also indicates a fair amount of cirrus which could hold readings back as well.
Both models have been staunch in their respective depictions for days with little deviation. I think playing this in the middle is the prudent thing to do for now and a compromise would result in low to mid 90s Monday, Tuesday, and probably Wednesday. With dew points in the low to mid 70s, heat index values could get into the range of 100-105 degrees. The EURO shows these values. That's easily heat advisory or even warning territory if the EURO verifies
A front is expected to break the siege Wednesday night, potentially producing storms. Readings will fall to much more seasonal levels for a couple days. However, there are signs the ridge rebuilds next weekend offering another round of heat and humidity. That period also has the potential to be active with the central Midwest close to the ring of fire.
Here's what the Climate Prediction Center shows for temperatures in the 6-10 and 8-14 day period confirming that potential in the central U.S.
That's a wrap for what is a tricky and challenging week of forecasting ahead. Hopefully I'm up to it. Happy Friday everybody and roll weather....TS