We had a few showers/storms Saturday morning & Saturday night, mainly in our western counties, then much of the rainfall was south of us Sunday morning, before slow-moving storms Sunday afternoon-evening brought Flood Warning to Howard County. There was even some severe gusts reported just west of us in eastern Illinois Saturday.
It was interesting to watch the better, shorter-range model data this weekend. It had a hard time forecasting the clusters & just random scattered storms. This is the NAM projected out Saturday night, projecting Sunday 4 a.m. to 12 p.m. It put a cluster of torrential storms in the heart & southern half of the viewing area with up to 7" of rainfall in southwest Fountain County! It also projected 2-6" of rainfall for Montgomery County & anywhere from 0.25 to 3.25" for Tippecanoe County. This time of year, models can have a hard time with predicting where the bulk of storms will occur when there is not distinct, potent disturbance to trigger them. It is more like swirls of congealing suds in a bathtub of water when the strongest flow to guide things along is north of the area. Obviously, this didn't happen Sunday morning! Model data did better for afternoon-evening projections! It is a good lesson to never take just computer models at face value! Regardless, it has been hot & humid to very humid since Friday night with dew points as high as 77.
We will have quite a few to numerous showers & storms today (which develop into some broken lines & small linear clusters) with around 65-70% coverage for the area as cold front approaches & passes. Locally-heavy rainfall is possible in the heaviest cells with a quick +2" possible. Although the Marginal Risk of severe weather is northeast of us, given the potential of downdraft CAPE to reach 1400 J/kg & PWATs expected to reach 1.5" between near the surface & mid-levels, the potentail of a random wet microburst in the strongest cell or two cannot be ruled out.
We just have a lot of oppressive humidity & heat & these will go up quickly in a pulsey fashion, so they will also come down quickly & be loaded with water. The water-loading may tend to enhance the strongest downdrafts. This would only be one or two cells, though.
Also, it looks like there may be a lake breeze that merges with the cold the front later today & storms to even form a bit of a line with some forward momentum developing with that line, which could enhance a random rain-loaded gust.
Also, with it being so humid/tropical out, a random landspout funnel could briefly develop along outflow boundaries from nearby storms. They rarely touch down & if they do, tend to produce very brief EF0 damage. These rain-cooled boundaries prodouce localized areas of spin, especially where two merge, & it is easier to condense a column of air when it is so moist & unstable.
The cooler pattern will settle in, beginning Tuesday with sunshine (after some patchy fog & very low clouds in the morning). In fact, lows will drop well down into the 50s likely this week on a couple of nights! Highs will run 78-84 Tuesday-Wednesday.
It will turn humid later in the week. It will still be in the more-tolerable 80s, but with this pattern change, the stronger mid & upper winds will drop southward. In fact, at the end of the week a pretty impressive 90-knot core of upper level winds (jet streak will round the bend south of us. This could actually ignite a May-early June style severe weather episode from Missouri, through the southern half of Illinois, Indiana & over Kentucky. At this point, much of it looks to occur southwest & south of us. Moderate instability (with warmer temperatures), good shear & jet streak will promote organized severe weather potential there. We do need to monitor this, however. Any shift in the the placement of the jet streak, better instability, shear, etc. would increase or decrease any sort of storm risk here.
Right now, 50% coverage of showers/storms should suffice for the forecast wording for Friday after 30% wording Thursday.
The jet streak & potent upper trough:
Cooler pattern will continue right to early August with a night or two of lows at 49-55 with 70s & 80s dominating.
Keep an eye on Texas & Oklahoma & even the Desert Southwest, however. A dome of very intense heat will develop over that area with highs above to well-above normal with the very dry ground. Temperatures as high as 107 could occur in central Texas. This heat will be part of an area from Arkansas & Mississippi & southwest & westward that will see above normal temperatures during our cooler pattern & it will only expand northward to Kansas with time. By early August, temperatures to 109 may occur in Kansas. Meanwhile, we will be in the 70s & 80s.
With this gradient, pretty strong mid & upper flow & shear will be present from Missouri to Tennessee. Disturbances will be embedded in this, leading to the potential of organized severe weather events/episodes from Nebraska to Missouri, southern Illinois, southern Indiana to Kentucky & Tennessee late July-early August.
Here, the main threat zone is southwest & south of us. Also, the main corridor of heavy rainfall with some areas of flooding will set up there.
So, for us, it is more of a domination of the cooler weather with occasional bouts of some showers/storms as these severe episodes pass to our south & southwest.
With the cooler than normal temperature regime, I am still shooting toward precipitation running somewhat below normal for the period. This, unless that gradient corridor (severe corridor) shifts northeastward a bit.
Notice the cooler, drier domination here late July-early August via the CFSV2 ensembles (running the model over & over & over & over & then seeing what the majority of the outcomes show):
Temperatures (in relation to normal)(:
Rainfall (in relation to normal)...........I do think there will be a narrow corridor of heavier rainfall to our southwest & south that this model is not picking up on:
Around mid-August, I do think a lobe of this intense heat may elongate to the northeast ahead of a cold front & upper trough. That said, a brief spurt of intense humidity (as heat blows over wet ground to our southwest). This may only last two days, but 89-93 could occur with heat indices 97-107. We shall see if the upper winds & shear support severe. At this point, sufficient instability would support at least storms.
Cooler weather should follow, but I think the intense Plains/Texas ridge could really expand late August. In fact, we may end up with a round of intense heat from New England to the Plains with our temperatures pushing where they were on Memorial Day at 95-99. By that time, soils to our southwest may have dried out some, but humidity may still push the heat indices to advisory range at 100-109. This number will be influenced by just how much rainfall occurs to the southwest & if the soils do indeed really dry out well before late August.
This heat may last to just before Labor Day before abruptly ending.