THICK AS A BRICK...
The steam was rising again Tuesday as warm muggy air took another run at the region. Temperatures near and east of the Mississippi were held in check some by what's called convective debris, cloud remnants from a thunderstorm complex that grazed NE Iowa and SW Wisconsin. Where the clouds were a factor, highs remained in the mid 80s compared to the upper 80s to near 90 where sunshine was abundant. You can see what I'm talking about below.
Scattered storms (or their remnants) will continue to be a challenge the next couple of days as models depict development on the northeast fringe of the "ring of fire", a spot we'll be close to. Some are ongoing over NE Iowa Tuesday night as I write this. Unfortunately, there's not great agreement regarding the intensity and scope of the convection, or if it even penetrates my area Wednesday morning. That's problematic as a large cool pool associated with a thunderstorm complex can significantly lower temperatures and heat index values which are projected to be substantial. That is the fly in the ointment regarding the degree of heat we'll battle Wednesday.
As it stands now, even on the lower end of the spectrum dew points in the 70s and temperatures in the low 90s will be high enough to support the heat advisory the NWS has in place for heat index values of 100-105 degrees...perhaps 106-107 in a few local spots in SE Iowa if sunshine is maximized.
Wednesday night a front will descend on the area from the north bringing a chance of storms by morning. After dying off, storms may redevelop later Thursday afternoon in the far south. However, the warm air aloft presents a pretty stiff cap that may limit much in the way of storm coverage. If an MCS can fire up north Wednesday night or we can get some sort of outflow boundary Thursday, those factors combined with the overall forcing along the front may improve chances but it's too early to see those mesoscale details.
What will happen is cooler and drier air will invade the north during Thursday afternoon and spread southeast through the region Thursday night. That will effectively end this burst of heat but not before the area near and south of I-80 has another very steamy day. The north, especially up around HWY 20 will see highs only in the low 80s while readings near 90 will be found in the south (with a heat index near 100).
Friday through the weekend some pretty decent weather is on the table with seasonal temperatures and humidity. The primary forcing for any storms looks to be primarily SW of the area although there is at least a small shot at a shower or storm Saturday as another cool front approaches.
For many of us, Wednesday dawns as the 13th consecutive day with no rain. We need a good soaker. Here's the daily precipitation plots in Cedar Rapids for July. Only 5 days this month with measurable rain and a July total of 0.79". That's pretty brutal.
One thing I've been harping about for at least a week is that with phase 6 of the MJO in place we should be seeing cooler weather to close out the month. Then, as we transition into August the EURO quickly barrels the MJO into phase 8 to start it.
Notice the temperature analogs for phase 6 in July and phase 8 in August. Not a hot appearance to be sure.
Now look at the 7 day temperature departures the GFS shows for July 30th through August 5th. That's a pretty good blend with regards to what the MJO is signaling.
It's no wonder the GFS is depicting so much cool air with a 500mb pattern that looks like this August 3rd.
I have high confidence that once our little heat burst departs Thursday we are in for at least a good week of below normal temperatures. If it's gonna happen this is the time of year to do it!
Unfortunately, phases 6 and 8 are not what I would consider wet ones and over the next 10 days the GFS confirms that with rain departures that look like this. The EURO is in pretty good agreement.
We'll, there's no way to sugar coat the fact today is going to be a burner. However, you can take heart in the fact the end is already in sight. That helps a bunch. Roll weather....TS