Periodic showers & storms are likely along the front boundary now & right into tonight. However, much of the shower/storm action will shift north of IN 18 by 1 a.m. & then north of the viewing area by 4 a.m.
The coverage may go down from 60% to 30% for a time this evening, then ramp back up rapidly to 70% tonight. Good enough for "periodic" wording for the forecast.
An isolated severe storm or two is possible with locally-heavy rainfall.
Temperatures won't change much tonight. In fact, they may even rise a bit late with the south wind. So, lows of 65-70 are likely with potential of rise to 66-72 late.
In the 7-10 a.m. tomorrow morning, we may have a couple showers & storms along outflow boundary (from Illinois storms) in our northwestern counties, otherwise, it looks mostly cloudy & muggy.
Tomorrow afternoon features sun/clouds with very warm to hot, muggy highs of 83-89 (coolest northwest) with southerly breezes & heat indices peaking at 85-94.
A few storms are possible in our northwestern counties with risk of an isolated severe storm or two in the afternoon-evening.
Other than an isolated storm or two, Wednesday looks dry with partly cloudy skies & highs of 82-89 (coolest northwest) with heat indices of 83-94.
Wind will turn variable at 5-10 mph with a surface high tending to migrate northwestward to our area with storm system & chilly air pushed west & northwestward.
Front should eventually pass Thursday with a few scattered showers & storms.
It does not look as cool as it looked last week for the end of the week.
Rather than highs 68-74, they look more like 75-80. Rather than lows 43-49, they look more like 50-56.
This is due to pattern that looks a lot like how this winter will unfold with our traditional La Nina developing.
The Southeast & East ridge protects us from the cold with the record cold diving into the Northern Rockies, Northern Plains & High Plains. Record-breaking frost & freezing is likely. While record-breaking temperature drop from 101 to 28 will occur in Denver with accumulating snowfall. The biggest drop in temperature in the early fall season prior to measurable snowfall (records back to 1873) occurred in September 12-13, 1993 with 92 to the upper 20s & an accumulating snowfall event. This one will beat them all!
Only difference in this pattern compared to Winter 2020-21 is that I think the Pacific Northwest will be much colder than normal, rather than the record EXTREME WILDFIRE DANGER & heat expected in this pattern. Also, I do not think the brutal cold this winter will go as far south as this particular cold wave (deep into Texas).
The main reason for the extreme nature of this cold wave & the extreme nature of the West heat & fires would be the two typhoons that hit South Korea only 50 miles apart. These caused a major, major change in the upper jet pattern as they combined with a deep upper trough west of Alaska in Siberia. This led to highly-significant upper trough there, which translates to extremes of upper ridge & upper trough downstream.
It looked cooler than normal anyway in mid-September with the Siberian trough, but this cold in the Front Range & Plains is EXTREME with the typhoons' effects!
Now to mid-September temperature anomalies:
Now, if this begins to turn into more of a La Nina Modoki with the greatest Pacific cold warmer anomaly more toward the middle between Australia & South American, then that would pull more of the very cold into our area with heavy snowfall.
Right now, that does not look to be the case.
Projected Winter 2020-21 temperatures anomalies:
Winter continues to look wetter than normal here with below normal snowfall. However, above to well-above normal snowfall is likely from the Pacific Northwest, through the Northern Rockies to the Northern Plains.
Dry weather with worsening drought is likely from California to Texas & through the Southeast to as far northeast as New Jersey, Connecticut, Rhode Island & southeastern Massachusetts.
In the mean time, the Southeast ridge pumps northward & brings warmer weather Saturday.
So, warm front moves through Saturday with some spotty showers & storms, followed by some scattered showers/storms on a warm, windy, humid Sunday.
It will turn a bit cooler Monday with lower humidity & highs 76-81.
Late September to early October looks warmer than normal.
Late September to early October also looks quite dry.