LIVING ON THE EDGE, BUT NOT FOR LONG...
When I think back on the month of July my initial thoughts are that overall it was warm, and above the norm. However, spurts of amazing weather like we are enjoying right now have balanced out some pretty intense periods of heat and humidity. When you look at the numbers, it's basically a wash. Here's what the monthly temperature departures look like through July 28th
What the graphic tells us is that its been a tough summer for heat just west and south of us where a persistent heat dome has taken up residence since June. From time to time, tentacles of heat have attacked from the west but have been quickly beaten back by a weakness on the northeast fringe of the upper high. The heat comes, does its thing and quickly retreats after a 2-3 day stay. We've been fortunate not only to get breaks but our proximity to the ring of fire have brought most of us enough rain for an adequate growing season.
However, just to the west closer to the core of the heat its been hotter and drier allowing abnormally dry soils and moderate drought conditions to develop. Severe to extreme drought has crept into NW Iowa where it's been really hot.
IS IT OUR TURN TO FRY?
Looking at the players on the field, it's looking more and more likely that it may be our turn to fry as a subtle change in the pattern allows more ridging over the eastern U.S. That eliminates the weakness which has allowed ridge riding disturbances to bring regular respites from any heat that's tried to make inroads into the central Midwest.
As for the duration and intensity of the heat there are some minor details that could have major differences depending on how they unfold. Much of it is tied to convection. If the heat dome is strong enough to push the ring of fire north into Minnesota and Wisconsin thunderstorms are likely to be most focused there leading mainly to hot dry conditions in most of my area. If it ends up further south, thunderstorms (or at least debris clouds) could have a moderating effect on temperatures. As it stands now, scattered storms remain a possibility Sunday night or Monday morning as the nose of the heat pokes into my area. After that, the atmosphere gets so warm aloft that a cap develops keeping Tuesday through Thursday hot and dry. That could hold into Friday as well.
Using the NBM (national model blend) as a guide for temperatures you get this for readings through Tuesday August 9th. That's a big stretch of 90s with even a 100 degree day shown in the Quad Cities August 3rd.
Some models are even warmer, particularly the GFS. It shows deeper mixing which lowers dew points and allows hotter temperatures. This is an outlier and as I have said for days I just don't see highs of this magnitude. If nothing else, the GFS has come down 3-5 degrees getting it closer to reality but its still likely several degrees too hot.
The big take away is heat and humidity are coming and the hottest temperatures of the summer are possible next week. There is also high confidence above normal temperatures will continue well into the second week of August. The Climate Prediction Center indicates a high risk of excessive heat as far out as August 7th. with a moderate risk to August 9th.
The 6-10 day temperature outlook from CPC August 4-8
The 8-14 CPC outlook August 6-12.
Overall, thunderstorm activity at best is going to be widely scattered the next 10 days despite plenty of instability. From time to time a convective cluster may evolve if the heat dome induced cap can be broached. That's a big if and impossible to foresee due to mesoscale influences that are yet to be determined. Both the GFS and EURO show below normal rainfall the next 10 days which seems reasonable. Here's the departures.
Meantime, as we await the heat the rest of the weekend is shaping up to be sunny, dry, and seasonal. Highs of 80-85 are expected both days. The only discernable difference will be humidity. Dew points will go from comfortable levels in the upper 50s Saturday to more moderate levels in the mid 60s Sunday as winds return to the south. That's when the door opens for next weeks heat to enter. Have a solid weekend and roll weather...TS