This has been a 7-day stretch of consistently very warm to hot & often humid to even oppressive weather. Today was on-par with the intense heat of last Saturday.
Our peak heat index of 106 at our WLFI is the second highest of the year, only behind June 18 when it reached 107.
The highest dew points of the entire year were record at multiple sites in the viewing area today.
The number of observation sites reaching the extremely oppressive 80 today were the highest of the summer so far.
There has been a lot of severe weather since yesterday evening. The large amount was with congealing, bowing line of storms from Manitoba to D.C. It seems to decrease as it encountered some of, it not the, thickest wildfire smoke east of the Mississippi River in Ohio this morning.
To be classified as a derecho, widespread damaging wind with significant wind core & swaths of +75 mph for +250 miles have to occur. However, there is a proposal to require the path to be +400 miles. I agree with this. So, for the sake of new criteria, let's go with +400 miles.
Analysis shows that the most organized part was 568 miles. Although comma head (Bookend Vortex) & bow were clearly evident in Ohio & West Virginia, winds were very sporadic & certainly not widespread. It did not regain its strength until Pennsylvania to Maryland, New Jersey to Delaware, Maryland, D.C. & Virginia. So, there is a lapse in the track, otherwise it would be 1165-mile track. I did not include the Manitoba to west of Duluth parts as it lack a clear, concise bow with a well-sustained rear-inflow jet. Otherwise, you could then make it a 1453-mile track!
Regardless, it does qualify as a derecho with the wind & the +75 mph gusts in Wisconsin & northern Illinois at the very least.
It is a Progressive Derecho or "Ring of Fire" derecho that occurs on the periphery of significant heat waves. A massive amount of real estate from the Dakotas to Indiana to Georgia to Texas to Kansas was under either a Heat Advisory or Excessive Heat Warning. A huge territory saw heat indices exceed 105 & they reached +115 over parts of Minnesota & Iowa to Missouri & +120 from Oklahoma to Mississippi. Near-record dew points combined with temperatures around 100 produced some of the highest heat indices on record for the U.S. prior to the derecho with at least 126 in Mississippi & 125 in Arkansas.
Extreme, deadly heat wave will continue in the South for the next couple of days with highs around 100 & dew points to 84, leading to +120 heat indices & some places pushing 130.
Widespread Saharan dust is putting the kabosh on the hurricane season for now as it is especially thick in the Atlantic & extends all the way to the Caribbean. There has even been dust extending as far west as the Gulf of Mexico & southern Texas.
This air is dry, warm & the dust inhibits storm development by drying it out & causing a warm, heated subtropical ridge that limits any rising motion of the moisture to condense into clouds & storms.
Thick wildfire smoke plumes are similar in that the soot absorbs the sun's heat & heats that layer of the atmosphere, creating a warm, dry cap. This can inhibit storm develop, even here in our area. This was a factor in storms have trouble to get going today, despite boiling, explosive instability & up to 35 knots of Effective Shear on the tail end of the line of storms this morning.
Again, as said, the thick smoke may have also impacts the derecho as it entered Ohio.
Severe storms & locally heavy rainfall will occur southern Iowa & Missouri to southern Illinois & western Kentucky Friday-Saturday.
Here, we will see a few showers Saturday morning (best chance south of a Kentland to Brookston to Kokomo line) with mostly cloudy skies, then sunshine with highs near 80 to the mid 80s with east-southeast to south to southwest wind & an uptick in the humidity (dew points to mid 60s).
Saturday night after 7 pm north & after 11 p.m. in Greater Lafayette & south, a few spotty showers & t'showers are possible as a secondary cold front moves southward.
Severe storms may re-fire & move over the Lower Ohio Valley Saturday evening-night.
Few showers Saturday AM:
Few spotty showers & t'showers Saturday night:
With sun & clouds, a few spotty showers/t'showers are possible Sunday with 25-30% coverage before we completely clear out by Sunday as comfortable dew points in the 50s move in on north winds.
Highs of 77-83 are likely.
Monday-Thursday look good with sunshine, few clouds & a late-week warm-up.
The nights will be comfortably cool.
There will be considerable smoke at times turning the sky pale & hazy.
August 7-15 overall looks quite hot & muggy with many days upper 80s to lower 90s with heat indices 90s to 100s.
August 7 & 11 show potential of more widespread showers & storms. Anything in-between or after those dates looks nil or scattered in the heat & humidity.
Overall, August looks like quite a hot, humid month, with temperatures running above normal for much of the time. Semi-permanent horseshoe-shaped ridge will dominate with lots of heat from the Northwest U.S. (record heat wave possible again) to the Northern Plains, Midwest & the Northeast.
Parts of the Desert Southwest, Southern Plains will be cooler than normal.
I am still thinking rainfall will overall average a bit below normal for August,